JP2016072763A - Dot filter generation device, image recording device, correction information acquisition method, dot filter generation method and test chart - Google Patents

Abstract

PROBLEM TO BE SOLVED: To acquire correction information to be utilized for high-accuracy correction of a dot filter.SOLUTION: In a dot filter generation device 43, a plurality of temporary threshold matrices which are obtained for each dot size on the basis of recording rates of a plurality of dot sizes are stored. Continuously, a temporary meshing processing part 432 performs meshing processing of a test image using the plurality of temporary threshold matrices to generate temporary halftone image. Next, when recording a test chart on a recording medium on the basis of the temporary halftone image data in which the plurality of dot sizes are mixed, dots of only one dot size are recorded. Filter correction information corresponding to selected one dot size is acquired by a correction information acquisition part 433. Thus, regarding the one dot size, the filter correction information to be utilized for high-accuracy correction of the threshold matrix can be acquired without being influenced by varying sizes or the like of dots in the other dot sizes.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a technique for acquiring correction information used for correcting the density of an image in an image recording apparatus, and a technique for generating a halftone dot filter used for shading processing using the correction information.

  2. Description of the Related Art Conventionally, an image recording apparatus that records an image on a recording medium by an ink jet method by moving an ejection unit that ejects micro droplets of ink from a plurality of ejection ports relative to the recording medium has been used. Yes. In the image recording apparatus, an image is recorded by forming ink dots at each pixel position on the recording medium based on the halftone image data generated by the shading process.

  In the line printer of Patent Document 1, in order to suppress deterioration in print image quality due to a characteristic difference between a plurality of small heads arranged in the width direction, the dither mask width is set to an ejection port used in each small head. 1 / N of the arrangement width of the group (N is an integer of 1 or more) so that the dither mask does not straddle the boundary between adjacent small heads.

  In the printing apparatus of Patent Document 2, the dot size of ink formed on a recording medium can be switched between S size, M size, and L size. In the printing apparatus, the element value of the basic dither matrix is corrected based on the variation in the print density in the width direction due to the discharge from the plurality of discharge ports, and printing is performed using the corrected dither matrix, so that a plurality of Image unevenness due to variations in the discharge amount of the minute droplets from the discharge port is suppressed. The modified dither matrix is generated by dividing each element value of the basic dither matrix by the corresponding correction coefficient. The correction dither matrix is a set of a sub correction matrix for S size, a sub correction matrix for M size, and a sub correction matrix for L size.

JP 2009-18480 A JP 2007-196472 A

  By the way, in an apparatus like patent document 1, in order to adjust the attachment position of a small head, a part of small head may be shifted in the width direction. In this case, since the number of discharge ports used in each head is different, the width of the dither mask is different from 1 / N (N is an integer of 1 or more) of the arrangement width of the discharge port group used in each small head. End up.

  In the printing apparatus of Patent Document 2, the element values corresponding to the sub correction matrixes for S size, M size, and L size are obtained by division by one correction coefficient. If the size differs, there is a possibility that appropriate density correction is not performed. For example, in one small head, a droplet forming an S size dot may be ejected larger than a specification value, and a droplet forming an L size dot may be ejected smaller than a specification value. In this case, if the correction coefficient is to reduce the droplets, the density difference from other small heads is small on the highlight side where there are many S size dots, but on the shadow side where there are many L size dots, On the contrary, the density difference with other small heads becomes large, and density unevenness (that is, banding unevenness) or the like for each small head may occur, resulting in a decrease in print quality.

  The present invention has been made in view of the above problems, and an object of the present invention is to obtain correction information used for highly accurate correction of a halftone filter in an image recording apparatus in which the dot size can be switched. Another object of the present invention is to provide a halftone dot filter that is corrected based on the correction information.

  According to a first aspect of the present invention, there is provided a dot output unit for recording dots whose size can be switched at a plurality of dot recording positions arranged along the width direction on the recording medium, and the plurality of dots on the recording medium. A halftone image data used for image recording in an image recording apparatus including a moving mechanism that moves a recording position relative to the recording medium in a moving direction that intersects the width direction. A halftone dot filter generation device for generating a halftone dot filter used in a halftone process for generating the halftone image data in which a plurality of dot sizes are mixed from an image, each recording of the plurality of dot sizes A provisional halftone dot filter storage unit that stores a plurality of provisional halftone dot filters that are obtained for each dot size based on the rate and are used for image shading processing; Temporary halftone image data indicating the size of a plurality of dots respectively formed at a plurality of pixel positions arranged in a matrix in a halftone image region by performing a halftone image shading process using a temporary halftone dot filter When a test chart is recorded on the recording medium based on the temporary halftone processing unit to be generated and the temporary halftone image data in which the plurality of dot sizes are mixed, the plurality of the temporary halftone image data Only a dot of one dot size selected from the dot size is recorded in the target area of the test chart, and a correction information acquisition unit that acquires filter correction information corresponding to the one dot size from the target area; Temporary halftone dot filter corresponding to the one dot size among the plurality of temporary halftone dot filters using filter correction information Corrected, and a dot filter correction unit for generating a corrected dot filter corresponding to the one dot size.

  According to a second aspect of the present invention, there is provided a dot output section for recording dots whose size can be switched at a plurality of dot recording positions arranged along the width direction on the recording medium, and the plurality of dots on the recording medium. A halftone image data used for image recording in an image recording apparatus including a moving mechanism that moves a recording position relative to the recording medium in a moving direction that intersects the width direction. A halftone dot filter generation device for generating a halftone dot filter used in a halftone process for generating the halftone image data in which a plurality of dot sizes are mixed from an image, each recording of the plurality of dot sizes A provisional halftone dot filter storage unit that stores a plurality of provisional halftone dot filters that are obtained for each dot size based on the rate and are used for image shading processing; Temporary halftone image data indicating the size of a plurality of dots respectively formed at a plurality of pixel positions arranged in a matrix in a halftone image region by performing a halftone image shading process using a temporary halftone dot filter When the test chart is recorded on the recording medium based on the temporary halftone processing unit to be generated and the temporary halftone image data in which the plurality of dot sizes are mixed, the plurality of temporary halftone image data A correction information acquisition unit that converts all dots of dot size into dots of a single dot size, records them in the target area of the test chart, and acquires filter correction information corresponding to the one dot size from the target area And using the filter correction information, the temporary dot filter corresponding to the one dot size among the plurality of temporary halftone filters. Filter corrected, and a dot filter correction unit for generating a corrected dot filter corresponding to the one dot size.

  The invention according to claim 3 is the halftone filter generation device according to claim 1 or 2, wherein the correction information acquisition unit and the halftone filter correction unit are controlled to change the one dot size. Meanwhile, by repeating the acquisition of the filter correction information and the generation of the corrected halftone filter, a plurality of filter correction information respectively corresponding to the plurality of dot sizes is acquired and a plurality of corrected halftone filters are generated. A repetition control unit is further provided.

  The invention according to claim 4 is the halftone dot filter generation device according to claim 1, wherein the temporary halftone processing unit converts the temporary halftone dot filter corresponding to the one dot size to the corrected halftone dot. When the test image is shaded by changing to a filter, new temporary halftone image data is generated, and a test chart is recorded on the recording medium based on the new temporary halftone image data In the new provisional halftone image data, only the dots having the one dot size and the new one dot size are recorded in the target area of the test chart, and the correction information acquisition unit is configured to update the new one from the target area. New filter correction information corresponding to the new dot size is acquired, and the halftone dot filter correction unit uses the new filter correction information to obtain the new one dot size. Correcting the corresponding temporary halftone dot filter to generate a corrected dot filter corresponding to the new one dot size.

  The invention according to claim 5 is the halftone dot filter generation device according to claim 4, wherein the new one dot size is larger than the one dot size.

  According to a sixth aspect of the present invention, there is provided a dot output section for recording dots whose size can be switched at a plurality of dot recording positions arranged along the width direction on the recording medium, and the plurality of dots on the recording medium. A halftone image data used for image recording in an image recording apparatus including a moving mechanism that moves a recording position relative to the recording medium in a moving direction that intersects the width direction. A halftone dot filter generation device for generating a halftone dot filter used in a halftone process for generating the halftone image data in which a plurality of dot sizes are mixed from an image, each recording of the plurality of dot sizes A provisional halftone dot filter storage unit that stores a plurality of provisional halftone dot filters that are obtained for each dot size based on the rate and are used for image shading processing; The maximum halftone image is formed at a plurality of pixel positions arranged in a matrix in a halftone image area by performing a halftone image area using a temporary halftone filter corresponding to the maximum dot size. A provisional halftone processing unit that generates provisional halftone image data indicating the arrangement of dots of a dot size; and the maximum dot size from a target area of a test chart recorded on the recording medium based on the provisional halftone image data A correction information acquisition unit that acquires filter correction information corresponding to the image, and a corrected halftone dot filter corresponding to the maximum dot size by correcting the temporary dot filter corresponding to the maximum dot size using the filter correction information. A halftone dot filter correction unit that generates the corrected halftone dot processing unit corresponding to the maximum dot size. The test image is shaded using a point filter and a temporary halftone dot filter corresponding to the second largest dot size among the plurality of dot sizes, and the maximum dot size and the 2 in the halftone image region are processed. New temporary halftone image data indicating the arrangement of dots of the second largest dot size is generated, and the correction information acquisition unit generates new temporary halftone image data recorded on the recording medium based on the new temporary halftone image data. The filter correction information corresponding to the second largest dot size is acquired from the target area of the test chart, and the halftone dot filter correction unit utilizes the filter correction information corresponding to the second largest dot size. The temporary halftone dot filter corresponding to the second largest dot size is corrected, and the second largest dot size is corrected. A corrected halftone dot filter corresponding to the size is generated.

  A seventh aspect of the present invention is the halftone dot filter generation device according to any one of the first to sixth aspects, wherein the test image includes a plurality of test unit areas respectively corresponding to a plurality of designated gradation values. The target area in the test chart includes a plurality of chart unit areas respectively recorded corresponding to the plurality of test unit areas, and the correction information acquisition unit includes the density in each of the plurality of chart unit areas. Based on the above, the filter correction information corresponding to the one dot size is acquired.

  The invention according to claim 8 is the halftone dot filter generation device according to claim 7, wherein the plurality of chart unit regions are arranged in the movement direction, and each of the plurality of chart unit regions is in the width direction. The filter correction information corresponding to the one dot size includes a plurality of divided areas arranged along a set of divided areas arranged in the movement direction in the plurality of chart unit areas as a divided area group. , Including a plurality of division filter correction information corresponding to a plurality of division region groups arranged along the width direction, and the correction information acquisition unit is based on the density of the plurality of chart unit regions in each division region group The division filter correction information corresponding to each of the divided region groups is acquired.

  The invention according to claim 9 is the halftone filter generation device according to claim 8, wherein the dot output units are arranged along the width direction and respectively correspond to the plurality of divided region groups. A plurality of divided output units are provided.

  A tenth aspect of the present invention is the halftone dot filter generation device according to the eighth or ninth aspect, wherein the correction information acquisition unit includes the density of each chart unit region and each chart unit in each divided region group. Based on the relationship with the target density relating to each designated gradation value corresponding to the area, the division filter correction information corresponding to each divided area group is acquired, and the target density is equal to or more than two adjacent in the width direction. It is an average density of each chart unit region in the divided region group.

  An eleventh aspect of the invention is the halftone filter generation device according to any one of the first to tenth aspects, wherein the temporary halftone filter is corrected on the recording medium by the correction of the temporary halftone filter. The gradation value-recording rate information indicating the relationship between the recording rate indicating the ratio of the number of dots of the one dot size to the total number of pixel positions defined as recordable in the unit area and the gradation value is corrected. .

  A twelfth aspect of the present invention is the halftone dot filter generation device according to any one of the first to eleventh aspects, wherein the corrected halftone dot filter is a threshold value matrix.

  A thirteenth aspect of the present invention is an image recording apparatus for recording an image on a recording medium, the halftone dot filter generating apparatus according to any one of the first to twelfth aspects, and the halftone dot filter generating apparatus. A halftone image processing unit for generating halftone image data by performing a shading process on the original image using the corrected halftone dot filter, and a plurality of dot recording positions arranged in the width direction on the recording medium. A dot output section for recording dots whose size can be switched, and a moving mechanism for moving the plurality of dot recording positions on the recording medium relative to the recording medium in a moving direction intersecting the width direction; The dot output unit is controlled based on the halftone image data in parallel with the relative movement of the plurality of dot recording positions on the recording medium with respect to the recording medium. And a control unit.

  The invention described in claim 14 is the image recording apparatus according to claim 13, wherein the dot output unit is controlled based on the halftone image data by the output control unit, and the dot on the recording medium An ejection unit that ejects micro droplets of ink to a plurality of dot recording positions to record dots is provided.

  According to a fifteenth aspect of the present invention, there is provided a dot output section that records dots whose size can be switched at a plurality of dot recording positions arranged along the width direction on the recording medium, and the plurality of dots on the recording medium. A correction information acquisition method for acquiring correction information used for image density correction in an image recording apparatus including a moving mechanism that moves a recording position relative to the recording medium in a moving direction that intersects the width direction. A) A shading process for generating halftone image data obtained for each dot size based on the respective recording rates of a plurality of dot sizes and mixed with the plurality of dot sizes from a multi-tone original image. A step of preparing a plurality of temporary halftone filters to be used; and b) a halftone image region in which halftone image processing is performed using the plurality of temporary halftone filters. Generating temporary halftone image data indicating the size of a plurality of dots respectively formed at a plurality of pixel positions arranged in a matrix, and c) the temporary halftone image data in which the plurality of dot sizes are mixed When a test chart is recorded on the recording medium based on the above, only one dot size selected from the plurality of dot sizes of the temporary halftone image data is recorded in the target area of the test chart. And obtaining filter correction information corresponding to the one dot size from the target area.

  According to a sixteenth aspect of the present invention, there is provided a dot output unit for recording dots whose size can be switched at a plurality of dot recording positions arranged along the width direction on the recording medium, and the plurality of dots on the recording medium. A correction information acquisition method for acquiring correction information used for image density correction in an image recording apparatus including a moving mechanism that moves a recording position relative to the recording medium in a moving direction that intersects the width direction. A) A shading process for generating halftone image data obtained for each dot size based on the respective recording rates of a plurality of dot sizes and mixed with the plurality of dot sizes from a multi-tone original image. A step of preparing a plurality of temporary halftone filters to be used; and b) a halftone image region in which halftone image processing is performed using the plurality of temporary halftone filters. Generating temporary halftone image data indicating the size of a plurality of dots respectively formed at a plurality of pixel positions arranged in a matrix, and c) the temporary halftone image data in which the plurality of dot sizes are mixed When the test chart is recorded on the recording medium based on the test chart, all the dots of the plurality of dot sizes of the temporary halftone image data are converted into dots of one dot size, and then the test chart target And acquiring filter correction information corresponding to the one dot size from the target area.

  The invention according to claim 17 is the correction information acquisition method according to claim 15 or 16, wherein the plurality of dot sizes are obtained by repeating the step c) while changing the one dot size. A plurality of filter correction information corresponding to each is acquired.

  According to an eighteenth aspect of the present invention, a dot output unit that records dots whose size can be switched to a plurality of dot recording positions arranged in the width direction on the recording medium, and the plurality of dots on the recording medium A halftone image data used for image recording in an image recording apparatus including a moving mechanism that moves a recording position relative to the recording medium in a moving direction that intersects the width direction. 18. A halftone dot filter generation method for generating a halftone dot filter used in a halftone process for generating the halftone image data in which a plurality of dot sizes are mixed from an image. After the a) step to the c) step and d) the c) step of the halftone dot filter generation method described above, the plurality of the plurality of filter correction information are used using the filter correction information. Of halftone filter, and a step of correcting the temporary halftone dot filter corresponding to the one of the dot size, to produce a corrected dot filter corresponding to the one dot size.

  According to a nineteenth aspect of the present invention, there is provided a dot output section for recording dots whose size can be switched at a plurality of dot recording positions arranged along the width direction on the recording medium, and the plurality of dots on the recording medium. A halftone image data used for image recording in an image recording apparatus including a moving mechanism that moves a recording position relative to the recording medium in a moving direction that intersects the width direction. 16. A halftone filter generation method for generating a halftone filter used in a halftone process for generating the halftone image data in which a plurality of dot sizes are mixed from an image, the halftone filter according to claim 15. After the steps a) to c) and d) c) of the generation method, the filter correction information is used to correspond to the one dot size. Correcting a halftone dot filter to generate a corrected halftone dot filter corresponding to the one dot size; and e) changing a temporary halftone dot filter corresponding to the one dot size to the corrected halftone dot filter. A step of performing a shading process on the test image to generate new temporary halftone image data; and f) when a test chart is recorded on the recording medium based on the new temporary halftone image data. In the new provisional halftone image data, only the dots of the one dot size and the new one dot size are recorded in the target area of the test chart and correspond to the new one dot size from the target area. Obtaining new filter correction information to be performed; and g) provisional halftone dot fill corresponding to the new one dot size using the new filter correction information. Corrected, and a step of generating a corrected dot filter corresponding to the new one dot size.

  The invention described in claim 20 is the halftone dot filter generation method according to claim 19, wherein the new one dot size is larger than the one dot size.

  According to a twenty-first aspect of the present invention, there is provided a dot output section for recording dots whose size can be switched at a plurality of dot recording positions arranged along the width direction on the recording medium, and the plurality of dots on the recording medium. A halftone image data used for image recording in an image recording apparatus including a moving mechanism that moves a recording position relative to the recording medium in a moving direction that intersects the width direction. A halftone dot filter generation method for generating a halftone dot filter used in the halftone processing for generating the halftone image data in which a plurality of dot sizes are mixed from an image, and a) each of a plurality of dot sizes A halftone image that is obtained for each dot size based on a recording rate and generates halftone image data in which the plurality of dot sizes are mixed from an original image of multiple gradations A step of preparing a plurality of temporary halftone filters used for processing; and b) performing a halftone process on a test image using a temporary halftone filter corresponding to a maximum dot size among the plurality of temporary halftone filters. A step of generating provisional halftone image data indicating an arrangement of dots of the maximum dot size formed at a plurality of pixel positions arranged in a matrix in the halftone image area; and c) the provisional halftone image data Acquiring filter correction information corresponding to the maximum dot size from a target area of a test chart recorded on the recording medium based on the d, and d) using the filter correction information to correspond to the maximum dot size. Correcting a halftone filter to generate a corrected halftone filter corresponding to the maximum dot size; e) Performing halftone processing of the test image using the corrected halftone dot filter and the temporary halftone dot filter corresponding to the second largest dot size among the plurality of temporary halftone dot filters, and in the halftone image region Generating new temporary halftone image data indicating an arrangement of dots of the maximum dot size and the second largest dot size; and f) recording on the recording medium based on the new temporary halftone image data. Obtaining filter correction information corresponding to the second largest dot size from the target area of the new test chart, and g) using the filter correction information obtained in step f). The temporary halftone dot filter corresponding to the second largest dot size is corrected, and the corrected halftone dot size corresponding to the second largest dot size is corrected. Generating a point filter.

  The invention according to claim 22 is the halftone filter generation method according to any one of claims 18 to 21, wherein the test image includes a plurality of test unit areas respectively corresponding to a plurality of designated gradation values. And the target area in the test chart includes a plurality of chart unit areas respectively recorded corresponding to the plurality of test unit areas, and in the step c), the density in each of the plurality of chart unit areas is set. Based on this, the filter correction information corresponding to the one dot size is acquired.

  The invention according to claim 23 is the halftone filter generation method according to claim 22, wherein the plurality of chart unit regions are arranged in the movement direction, and each of the plurality of chart unit regions is in the width direction. The filter correction information corresponding to the one dot size includes a plurality of divided areas arranged along a set of divided areas arranged in the movement direction in the plurality of chart unit areas as a divided area group. , Including a plurality of divided filter correction information corresponding to a plurality of divided region groups arranged along the width direction, and in the step c), based on the density of the plurality of chart unit regions in each divided region group, Division filter correction information corresponding to each division region group is acquired.

  The invention according to claim 24 is the halftone dot filter generation method according to claim 23, wherein the dot output portions are arranged along the width direction and respectively correspond to the plurality of divided region groups. A plurality of divided output units are provided.

  The invention described in claim 25 is the halftone dot filter generation method according to claim 23 or 24, wherein in the step c), the density of each chart unit region in each divided region group and each chart unit region Division filter correction information corresponding to each of the divided region groups is acquired based on the relationship with the target density relating to each designated gradation value corresponding to, and the target density is divided into two or more divisions adjacent in the width direction. It is an average density of each chart unit region in the region group.

  The invention according to claim 26 is the halftone dot filter generation method according to any one of claims 18 to 25, wherein the unit area on the recording medium is obtained by correcting the temporary halftone filter in the step d). The gradation value-recording rate information indicating the relationship between the recording rate indicating the ratio of the number of dots of the one dot size to the total number of pixel positions defined as recordable in FIG.

  The invention according to claim 27 is the halftone filter generation method according to any one of claims 18 to 26, wherein the corrected halftone filter is a threshold value matrix.

  The invention described in claim 28 is a dot output section for recording dots whose size can be switched to a plurality of dot recording positions arranged in the width direction on the recording medium, and the plurality of dots on the recording medium. A halftone image data used for image recording in an image recording apparatus including a moving mechanism that moves a recording position relative to the recording medium in a moving direction that intersects the width direction. A test chart used to generate a halftone dot filter used in the halftone process for generating the halftone image data in which a plurality of dot sizes are mixed from an image, each corresponding to a plurality of specified gradation values Selected from the plurality of dot sizes scheduled to be recorded corresponding to each specified gradation value. Only the dot of dot size is recorded.

  The invention described in claim 29 is a dot output section for recording dots whose size can be switched at a plurality of dot recording positions arranged along the width direction on the recording medium, and the plurality of dots on the recording medium. A halftone image data used for image recording in an image recording apparatus including a moving mechanism that moves a recording position relative to the recording medium in a moving direction that intersects the width direction. A test chart used to generate a halftone dot filter used in the halftone process for generating the halftone image data in which a plurality of dot sizes are mixed from an image, each corresponding to a plurality of specified gradation values A plurality of chart unit areas, and in each chart unit area, all the dots of the plurality of dot sizes scheduled to be recorded corresponding to each designated gradation value are unified. It is recorded after having been converted to the dot of the dot size.

  In the present invention, correction information used for highly accurate correction of a halftone dot filter can be acquired. It is also possible to provide a halftone dot filter corrected based on the correction information.

1 is a diagram illustrating a configuration of an image recording apparatus according to an embodiment. It is a bottom view which shows a discharge unit. It is a figure which shows the structure of a control unit. It is a block diagram which shows the function of a control unit. It is a figure which shows gradation value-recording rate information. It is a figure which shows the flow of the production | generation of a matrix set. It is a figure which shows a test image. It is a figure which shows a test image and a temporary threshold value matrix. It is a figure which shows the object area | region of a 1st test chart. It is a figure which shows the object area | region of a 1st test chart. It is a figure which shows the object area | region of a 1st test chart. It is a figure which shows the object area | region of a 1st test chart. It is a figure which shows the object area | region of a 2nd test chart. It is a figure which shows the object area | region of a 2nd test chart. It is a figure which shows the object area | region of a 2nd test chart. It is a figure which shows the object area | region of a 3rd test chart. It is a figure which shows the flow of the production | generation of a matrix set. It is a figure which shows the flow of the production | generation of a matrix set. It is a figure which shows the object area | region of a 3rd test chart. It is a figure which shows the object area | region of a 3rd test chart. It is a figure which shows the flow of the production | generation of a matrix set. It is a figure which shows the flow of the production | generation of a matrix set. It is a figure which shows the object area | region of a 3rd test chart. It is a figure which shows the object area | region of a 3rd test chart. It is a figure which shows the object area | region of a 3rd test chart.

  FIG. 1 is a diagram showing a configuration of an image recording apparatus 1 according to an embodiment of the present invention. The image recording apparatus 1 is a sheet-fed printing apparatus (so-called inkjet printer) that sequentially records color images on a plurality of recording media 9 by ejecting micro droplets of ink onto the recording medium 9. The recording medium 9 is, for example, printing paper.

  In FIG. 1, two horizontal directions perpendicular to each other are shown as an X direction and a Y direction, and an up and down direction perpendicular to the X direction and the Y direction is shown as a Z direction. The X direction and the Y direction in FIG. 1 are not necessarily horizontal, and similarly, the Z direction is not necessarily vertical. That is, the upper side and the lower side in FIG. 1 do not necessarily need to coincide with the upper side and the lower side in the direction of gravity.

  As shown in FIG. 1, the image recording apparatus 1 includes a moving mechanism 2, a discharge unit 3, a supply unit 51, a discharge unit 52, and a control unit 4. The moving mechanism 2 moves the plurality of recording media 9 in the moving direction which is the (+ Y) direction in FIG. The discharge unit 3 is arranged above the moving mechanism 2 (on the (+ Z) side) and is fixed to a frame (not shown). The ejection unit 3 is a dot output unit that ejects micro droplets of ink toward the recording medium 9 being transported by the moving mechanism 2. The supply unit 51 supplies the recording medium 9 to the moving mechanism 2. The discharge unit 52 receives the recording medium 9 after printing from the moving mechanism 2. The control unit 4 controls mechanisms such as the moving mechanism 2, the discharge unit 3, the supply unit 51 and the discharge unit 52.

  The moving mechanism 2 includes a plurality of stages 21, an annular guide 22, and a belt driving mechanism 23. Each of the plurality of stages 21 sucks and holds one sheet-like recording medium 9. The guide 22 internally includes a belt to which a plurality of stages 21 are connected, and guides the plurality of stages 21. The belt drive mechanism 23 moves the belt in the guide 22 counterclockwise in FIG. 1 to move the stage 21 holding the recording medium 9 below the discharge unit 3 (that is, on the (−Z) side) ( Move in the + Y) direction.

  FIG. 2 is a bottom view showing the discharge unit 3. The discharge unit 3 includes a plurality of head assemblies 31 having a similar structure. Each of the plurality of head assemblies 31 ejects micro droplets of different colors toward the recording medium 9. The plurality of head assemblies 31 are arranged in the Y direction (that is, the moving direction) and attached to the attachment portion 30 of the discharge unit 3. In the example shown in FIG. 2, four head assemblies 31 are provided in the discharge unit 3.

  The most (−Y) side head assembly 31 in FIG. 2 ejects black (K) color ink. The head assembly 31 on the (+ Y) side of the black head assembly 31 ejects cyan (C) color ink. The head assembly 31 on the (+ Y) side of the cyan head assembly 31 ejects magenta (M) color ink. The most (+ Y) side head assembly 31 ejects yellow (Y) ink.

  Each head assembly 31 includes a plurality of ejection heads 32. The plurality of ejection heads 32 are arranged in a staggered manner along a predetermined direction that intersects the moving direction. In the example illustrated in FIG. 2, in each head assembly 31, four ejection heads 32 are arranged along the width direction (that is, the X direction) perpendicular to the movement direction. Each ejection head 32 is provided with a plurality of ejection openings arranged along the width direction. The plurality of discharge ports are not necessarily arranged along the width direction, and may be arranged along a direction intersecting the moving direction.

  In the image recording apparatus 1 shown in FIG. 1, each head assembly 31 is provided over the entire recording area on the recording medium 9 (for example, over the entire X direction of the recording medium 9) in the X direction. A plurality of ejection openings of each head assembly 31 are also provided over the entire width of the recording area in the X direction.

  The size of the micro droplets of ink ejected from each ejection port of each head assembly 31 can be switched. That is, each head assembly 31 can eject different amounts of fine ink droplets from each ejection port. The size of the ink droplets is switched, and when the droplets land on the recording medium 9, the size of the dots formed on the recording medium 9 is also switched. That is, in the image recording apparatus 1, dots whose size can be switched are recorded on the recording medium 9 by the ejection unit 3.

  In the image recording apparatus 1 shown in FIG. 1, the size of the micro droplets of ink ejected from each head assembly 31 is “small size”, “medium size” larger than the small size, and “larger than medium size”. It is possible to switch between the three "large size". The small-sized micro droplet is the smallest size of the micro droplets of ink ejected from each head assembly 31. The large-sized micro droplet is the largest size of the micro droplets of ink ejected from each head assembly 31. By switching the size of the fine ink droplets, the dot size of the ink formed on the recording medium 9 is switched between “small size”, “medium size”, and “large size”. In the following description, small, medium, and large dots are also referred to as “small dots”, “medium dots”, and “large dots”, respectively. A small dot is a dot having a minimum dot size among a plurality of dot sizes that can be switched in the image recording apparatus 1, and a large dot is a dot having a maximum dot size among a plurality of dot sizes that can be switched in the image recording apparatus 1. is there. The medium dot is a dot having a dot size that is the next largest (that is, the second largest) dot size among the plurality of dot sizes.

  In the image recording apparatus 1, the output unit 41 (see FIG. 4) of the control unit 4 controls the ejection unit 3 and the moving mechanism 2, and the recording medium 9 faces the plurality of head assemblies 31 of the ejection unit 3. Is passed only once in the (+ Y) direction, black, cyan, magenta, and yellow inks are sequentially ejected onto the recording medium 9 to complete image recording on the recording medium 9.

  In other words, in the image recording apparatus 1, a plurality of head assemblies 31 (see FIG. 2), which are ejection units, are disposed at a plurality of dot recording positions arranged in the width direction over the entire width on the recording medium 9. The ink droplets are ejected from the ejection port to record dots. Then, the plurality of dot recording positions on the recording medium 9 are moved only once relative to the recording medium 9 in the moving direction perpendicular to the width direction by the moving mechanism 2, thereby providing a single pass for the recording medium 9. Printing is performed. As described above, the direction in which the plurality of dot recording positions are arranged is not necessarily perpendicular to the movement direction, and may be a direction that intersects the movement direction.

  FIG. 3 is a diagram illustrating a configuration of the control unit 4. The control unit 4 has a general computer system configuration including a CPU 401 that performs various arithmetic processes, a ROM 402 that stores basic programs, and a RAM 403 that stores various information. The control unit 4 includes a fixed disk 404 for storing information, a display 405 for displaying various information such as images, a keyboard 406a and a mouse 406b for receiving input from an operator, an optical disk, a magnetic disk, a magneto-optical disk, and the like. A reading / writing device 407 that reads and writes information from the computer-readable storage medium 48 and a communication unit 408 that transmits and receives signals to and from other components of the image recording device 1.

  In the control unit 4, the program 480 is read from the storage medium 48 via the reading / writing device 407 in advance and stored in the fixed disk 404. The CPU 401 executes arithmetic processing while using the RAM 403 and the fixed disk 404 according to the program 480. The function of the control unit 4 may be realized by a dedicated electrical circuit, or a partially dedicated electrical circuit may be used.

  FIG. 4 is a block diagram illustrating functions of the control unit 4. FIG. 4 also shows a part of the configuration of the image recording apparatus 1 connected to the control unit 4. The control unit 4 includes the above-described output control unit 41, a shading processing unit 42, and a halftone filter generation device 43.

  The output control unit 41 includes a discharge control unit 411 and a movement control unit 412. The movement control unit 412 controls the relative movement of the recording medium 9 with respect to the ejection unit 3 by the moving mechanism 2. The ejection control unit 411 controls the ejection of ink from a plurality of ejection ports of each head assembly 31 (see FIG. 2) of the ejection unit 3 in synchronization with the relative movement of the recording medium 9.

  The halftone filter generation device 43 generates a halftone filter that is used when the original image is shaded. The shading processing unit 42 performs shading processing of the original image using a halftone filter (corrected halftone filter described later) generated by the halftone filter generating device 43, and from the multi-tone original image, Halftone image data in which a plurality of dot sizes (that is, small size, medium size and large size dots) are mixed is generated. The output control unit 41 performs output control of the ejection unit 3 that is a dot output unit based on the halftone image data in parallel with the relative movement of the plurality of dot recording positions on the recording medium 9 with respect to the recording medium 9. As a result, the image recording apparatus 1 records an image using the halftone image data. In the example shown in FIG. 4, a threshold matrix is used as a halftone filter.

  The shade processing unit 42 includes an image memory 421, a plurality of matrix storage units 422 (also referred to as SPM (Screen Pattern Memory)), an image data generation unit 423 (halftoning circuit), and a color component image generation unit 424. With.

  The color component image generation unit 424 performs color separation processing while performing gray replacement (GCR (Gray Component Replacement)) on a multi-tone color image input from the outside. Gray replacement is a gray portion expressed by overlapping cyan, magenta, and yellow dots in each pixel by expressing the shade of black ink, thereby providing cyan, magenta, and yellow colors added to the gray portion. This is a process for reducing the amount of ink.

  By color separation processing by the color component image generation unit 424, a color component image that is a gradation image of a plurality of color components (that is, black, cyan, magenta, and yellow) included in the color image is generated. Data of the gradation image of each color component of black, cyan, magenta and yellow (hereinafter referred to as “color component image data”) is stored in the image memory 421. The color component image data indicating the gradation image of each color component is original image data indicating the original image of each color component. In the color separation processing in the color component image generation unit 424, gray replacement need not be performed.

  The plurality of matrix storage units 422 are memories that store threshold matrixes corresponding to black, cyan, magenta, and yellow color components, respectively. The threshold value matrix is generated in advance by the above-described halftone dot filter generation device 43. The generation of the threshold matrix by the halftone filter generation device 43 will be described later.

  Each matrix storage unit 422 includes a small dot matrix 811 that is a threshold matrix for small dots, a medium dot matrix 812 that is a threshold matrix for medium dots, and a large dot matrix that is a threshold matrix for large dots. 813 is stored. Each of the small dot matrix 811, the medium dot matrix 812, and the large dot matrix 813 is a threshold matrix used for FM (Frequency Modulated) screening that expresses gradation by changing the number of irregularly arranged dots. It is.

  In FIG. 4, the small dot matrix 811, the medium dot matrix 812, and the large dot matrix 813 stored in one matrix storage unit 422 are illustrated, but each of the other color component matrix storage units 422 is also illustrated. A small dot matrix 811, a medium dot matrix 812, and a large dot matrix 813 are stored. In the following description, the three threshold matrixes of the small dot matrix 811, the medium dot matrix 812, and the large dot matrix 813 are collectively referred to as a “matrix set”. At the same position of the three threshold matrixes, the small dot matrix 811 has the smallest threshold, and the large dot matrix 813 has the largest threshold. The threshold value of the medium dot matrix 812 is a value between the threshold values of the small dot matrix 811 and the large dot matrix 813.

  The image data generation unit 423 is a comparison unit that generates halftone image data by comparing the color component image data and the threshold matrix for each color component. In other words, the image data generation unit 423 performs a shading process on the multi-tone color image described above, and converts the halftone image data used for image recording in the image recording apparatus 1 into the plurality of color components. This is an image data generation device for generating The image data generation unit 423 may be realized by software.

  The halftone filter generation device 43 includes a plurality of temporary matrix storage units 431, a temporary halftone processing unit 432 (halftoning circuit), a correction information acquisition unit 433, a matrix correction unit 434, and a repetition control unit 435. Prepare. The temporary matrix storage unit 431 is a temporary halftone filter storage unit, and the matrix correction unit 434 is a halftone filter correction unit.

  The plurality of temporary matrix storage units 431 respectively correspond to the plurality of color components described above. Each temporary matrix storage unit 431 stores a plurality of temporary halftone filters used for the shading process of the corresponding color component image. In the example shown in FIG. 4, the plurality of temporary halftone dot filters are a small dot temporary matrix 831, a medium dot temporary matrix 832, and a large dot temporary matrix 833. In the following description, the three temporary threshold value matrices (that is, temporary halftone dot filters) of the temporary matrix 831 for small dots, the temporary matrix 832 for medium dots, and the temporary matrix 833 for large dots are collectively referred to as “temporary matrix set”.

  The small dot temporary matrix 831, the medium dot temporary matrix 832, and the large dot temporary matrix 833 are based on the recording rates of dots of a plurality of dot sizes (that is, small dots, medium dots, and large dots). Obtained for each size. The recording rate is a value indicating the ratio of the number of dots actually recorded by one head assembly 31 to the unit number on the recording medium 9 with respect to the reference number. The reference number is the total number of pixel positions where ink dots are defined as recordable in the unit area. The recording rate is normally 100% when the gradation value is 255 (that is, the maximum gradation value that can be expressed on the recording medium 9), and the gradation value is 0 (that is, it can be expressed on the recording medium 9). The minimum gradation value) is 0%. Specifically, the provisional matrix set is based on the gradation value-recording rate information indicating the relationship between the gradation value of the image and the recording rate when an image of uniform gradation is recorded by the image recording apparatus 1. can get.

  FIG. 5 is a diagram illustrating an example of gradation value-recording rate information. In FIG. 5, the recording rates of small droplets of small size, medium size, and large size ink are indicated by solid lines denoted by reference numerals A1, A2, and A3, respectively. In the following description, the recording rates of small droplets of small size, medium size, and large size ink are referred to as “small size recording rate”, “medium size recording rate”, and “large size recording rate”, respectively. A line A1 indicates the small size recording rate characteristic indicating the relationship between the small size recording rate and the gradation value. A line A2 indicates the medium size recording rate characteristic indicating the relationship between the medium size recording rate and the gradation value. A line A3 indicates the large size recording rate characteristic indicating the relationship between the large size recording rate and the gradation value.

  In the example shown in FIG. 5, the threshold range of the small dot temporary matrix 831 is 0 to 170. The threshold range of the medium dot temporary matrix 832 is 85 to 255. The threshold range of the large dot temporary matrix 833 is 170 to 255. In the threshold range of the large dot temporary matrix 833, the large size recording rate monotonously increases as the gradation value increases. Similar to the matrix set, the threshold value of the medium dot temporary matrix 832 is larger than the threshold value of the small dot temporary matrix 831 at positions corresponding to each other in the three temporary threshold matrixes of the temporary matrix set, and the medium dot temporary matrix. The threshold value of the large dot temporary matrix 833 is larger than the threshold value of 832. When a large dot is formed at one position, a small dot and a medium dot are not drawn even if the input pixel value exceeds the threshold value. When a medium dot is formed at one position, the small dot becomes an input pixel. Even if the value exceeds the threshold, it is not drawn.

  As shown in FIG. 5, when the gradation value of the image is in the range of 0 to 85, the small size recording rate increases linearly as the gradation value increases. The medium dot recording rate and the large size recording rate are 0%. When the gradation value is in the range of 0 to 85, the image is recorded with only small dots, and the medium dots and large dots are not used for image recording.

  When the gradation value of the image is in the range of 85 to 170, the small size recording rate decreases linearly and the medium size recording rate increases linearly as the gradation value increases. The large size recording rate is 0%. When the gradation value is in the range of 85 to 170, the image is recorded with small dots and medium dots, and the large dots are not used for image recording.

  When the gradation value of the image is in the range of 170 to 255, the medium size recording rate decreases linearly and the large size recording rate increases linearly as the gradation value increases. The small dot recording rate is 0%. When the gradation value is in the range of 170 to 255, the image is recorded with medium dots and large dots, and the small dots are not used for image recording.

  The small size recording rate characteristic, medium size recording rate characteristic, and large size recording rate characteristic illustrated in FIG. 5 may be changed as appropriate. For example, in a certain gradation value range, small dots, medium dots, and large dots may be recorded. May be used.

  When a temporary threshold value matrix corresponding to each dot size of the temporary matrix set is generated, for example, an original original threshold value matrix is created by a method disclosed in Japanese Patent Application Laid-Open No. 2008-199154. Then, the threshold range of the original threshold value matrix is narrowed as necessary, and an offset value is added to each threshold value so that the minimum threshold value matches the appearance gradation value of the dot of that size, so that the temporary matrix for small dots 831, a medium dot temporary matrix 832 and a large dot temporary matrix 833 are obtained.

  Next, the flow of generating a matrix set by the halftone filter generating device 43 will be described with reference to FIG. In the following description, generation of a matrix set of one color component will be described. In the halftone filter generation device 43, matrix sets of other color components are similarly generated.

  In the halftone filter generation device 43, first, the temporary matrix for small dots 831, the temporary matrix for medium dots 832 and the temporary matrix for large dots 833 (that is, a plurality of temporary threshold matrixes) obtained as described above are used as the temporary matrix. It is prepared by being stored in the storage unit 431 (step S11).

  Subsequently, a temporary dot processing unit 432 that is a halftone circuit uses the small dot temporary matrix 831, the medium dot temporary matrix 832, and the large dot temporary matrix 833 to generate a test image 94 shown in FIG. Shading processing is performed to generate temporary halftone image data (step S12). The provisional halftone image data indicates the sizes of a plurality of dots respectively formed at a plurality of pixel positions arranged in a matrix in the halftone image area. That is, in the temporary halftone image data, a plurality of dots of dot sizes are mixed.

  The test image 94 is a correction pattern used for correcting the threshold matrix in the halftone filter generation device 43. The test image 94 includes a plurality of test unit regions 941 that respectively correspond to a plurality of designated gradation values. Each of the plurality of test unit areas 941 is a substantially rectangular tint image having a corresponding designated gradation value. In the example shown in FIG. 7, the designated gradation values of the plurality of test unit areas 941 are 255 (100%), 204 (80%), 153 (60%), 102 (40%), in order from the (+ Y) side. 51 (20%) and 26 (10%). The numerical value in () attached to the designated gradation value indicates the ratio to the maximum gradation value 255 (the same applies to the following). The test image 94 may include many test unit areas 941 corresponding to more specified gradation values than those illustrated in FIG. Alternatively, the number of test unit regions 941 may be smaller than that illustrated in FIG. Further, the above-mentioned designated gradation value may be changed as appropriate. The test image 94 may include an area other than the plurality of test unit areas 941.

  The generation of the temporary halftone image data in step S12 may be performed by the image data generation unit 423, which is a halftoning circuit of the shading processing unit 42, using the temporary matrix set of the temporary matrix storage unit 431. In other words, one halftoning circuit may be shared by the halftone filter generation device 43 and the shading processing unit 42 as the provisional shading processing unit 432 and the image data generation unit 423.

  Here, the shading process of the test image 94 (that is, halftoning of the test image 94) will be described. FIG. 8 is a diagram abstractly showing the test image 94 and the provisional threshold matrix. In FIG. 8, the temporary matrix set is collectively indicated by a reference numeral 83 as one temporary threshold matrix. In the temporary threshold value matrix 83, a row direction corresponding to the width direction of the recording medium 9 (shown as x direction in FIG. 8) and a column direction corresponding to the moving direction (shown as y direction in FIG. 8). ) Are arranged in a matrix, and the test image 94 also has a plurality of pixels arranged in a matrix in the row direction and the column direction.

  When halftoning the test image 94, as shown in FIG. 8, the test image 94 is divided into a plurality of regions of the same size, and a repetitive region 71 serving as a unit of halftoning is set. . The temporary matrix storage unit 431 shown in FIG. 4 has a storage area corresponding to one repeating area 71, and stores a temporary threshold value matrix 83 by setting a threshold value for each address (coordinate) of this storage area. . Conceptually, the repeated regions 71 of the test image 94 and the temporary threshold value matrix 83 are overlapped, and the pixel values of the pixels in the repeated region 71 are compared with the corresponding threshold values of the temporary threshold value matrix 83. The comparison between the pixel value and the threshold value is performed for three temporary threshold value matrices corresponding to three types of dot sizes (that is, the small dot temporary matrix 831, the medium dot temporary matrix 832, and the large dot temporary matrix 833). Accordingly, whether or not to draw at the position of the pixel on the recording medium 9 and the size of the dot to be drawn are determined.

  In actual operation, the pixel value of one pixel of the test image 94 is read based on the address signal from the address generator included in the provisional shading processing unit 432 of FIG. On the other hand, the address generator also generates an address signal indicating the position in the repetitive area 71 corresponding to the pixel, and the three threshold values of the small dot temporary matrix 831, the medium dot temporary matrix 832, and the large dot temporary matrix 833 are set. It is identified and read from the temporary matrix storage unit 431. The pixel values and the three threshold values are compared by the provisional shading processing unit 432, so that a plurality of pixel positions (that is, a plurality of pixel positions arranged in a matrix in the halftone image region that is an output image region) are obtained. The size of a plurality of dots formed at each of the drawing positions is sequentially determined.

  Specifically, the pixel value of each pixel of the test image 94 (hereinafter referred to as “input pixel value”) and the threshold value of the large dot temporary matrix 833 at the pixel position corresponding to each pixel of the halftone image area are as follows. If the input pixel value is greater than the threshold value, the value “3” is assigned to the pixel position. Hereinafter, the value in the halftone image area is referred to as “halftone pixel value”. When the input pixel value is smaller than the threshold value of the large dot temporary matrix 833, the input pixel value is compared with the threshold value of the medium dot temporary matrix 832. When the input pixel value is larger than the threshold value of the medium dot temporary matrix 832, the halftone pixel value “2” is given to the pixel position. When the input pixel value is smaller than the threshold value of the medium dot temporary matrix 832, the input pixel value is compared with the threshold value of the small dot temporary matrix 831. When the input pixel value is larger than the threshold value of the small dot temporary matrix 831, the halftone pixel value “1” is assigned to the pixel position, and when the input pixel value is less than the threshold value, the halftone pixel value “0” is assigned. The

  At the pixel position of the halftone image area where the halftone pixel value is “3” (that is, the recording pixel on the recording medium 9), a large ink droplet is ejected to form a large dot. In addition, in the pixel position where the halftone pixel value is “2”, a medium droplet is formed by ejecting a small droplet of medium-sized ink, and in the pixel position where the halftone pixel value is “1”, Small dots of small size ink are ejected to form small dots. No dot is formed at the pixel position where the halftone pixel value is “0”.

  When the shading process of the test image 94 is completed, the output control unit 41 controls the moving mechanism 2 and the discharge unit 3 based on the temporary halftone image data of the test image 94, whereby the test chart 95 shown in FIG. Is recorded on the recording medium 9 (step S13). FIG. 9 shows a partial area of the test chart 95 (hereinafter referred to as “target area 950”). A target area 950 shown in FIG. 9 is an area corresponding to a small-sized dot. The test chart 95 also includes target areas 950 that respectively correspond to medium-sized and large-sized dots. The target area 950 includes a plurality of chart unit areas 951 respectively recorded corresponding to the plurality of test unit areas 941 (see FIG. 7). The plurality of chart unit areas 951 are arranged in the movement direction described above. Each chart unit area 951 is a substantially rectangular tint image having a substantially uniform density.

  In the plurality of chart unit areas 951 of the target area 950, only dots having one dot size selected from the plurality of dot sizes in the temporary halftone image data are recorded. In other words, in the temporary halftone image data, a dot of one dot size among small dots, medium dots, and large dots that are to be recorded in each chart unit area 951 (that is, to be recorded). Are recorded in each chart unit area 951. In the example shown in FIG. 9, only small dots are recorded in each chart unit area 951. That is, in the provisional halftone image data, dots are formed only at the pixel positions where the halftone pixel value is “1”, and at the pixel positions where the halftone pixel values are “0”, “2”, and “3”. Dots are not formed.

  For example, in the chart unit region 951 on the most (−Y) side where the designated gradation value of the corresponding test unit region 941 is 26 (10%), the temporary halftone image data includes only small dots as shown in FIG. Therefore, an image according to the provisional halftone image data is recorded on the recording medium 9. Therefore, the density of the chart unit area 951 is approximately equal to the specified density, which is an ideal density set for the corresponding designated gradation value. The same applies to the second chart unit region 951 from the (−Y) side where the specified gradation value of the corresponding test unit region 941 is 51 (20%).

  In the third chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 102 (40%), the provisional halftone image data is composed of small dots and medium dots. The image of only small dots among all the dots constituting the temporary halftone image data is recorded on the recording medium 9. Also, no dots are recorded at pixel positions where medium dots are to be recorded in the provisional halftone image data. Therefore, the density of the chart unit region 951 is lower than the specification density related to the corresponding designated gradation value. The same applies to the fourth chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 153 (60%).

  In the fifth chart unit region 951 from the (−Y) side where the specified gradation value of the corresponding test unit region 941 is 204 (80%), the temporary halftone image data is composed of medium dots and large dots, and small. Since no dots are included, no dots are recorded. Therefore, the density of the chart unit area 951 is naturally lower than the specification density related to the corresponding designated gradation value.

  In the most (+ Y) side chart unit area 951 in which the specified gradation value of the corresponding test unit area 941 is 255 (100%), the temporary halftone image data is composed of only large dots and does not include small dots. Because there is no dot, no dot is recorded. Therefore, the density of the chart unit area 951 is naturally lower than the specification density related to the corresponding designated gradation value.

  When the recording of the test chart 95 is completed, the correction information acquisition unit 433 (see FIG. 4) performs filter correction information corresponding to the small size that is the one dot size described above (that is, the dot recorded only in the target area 950). Filter correction information corresponding to the dot size) is acquired based on the density in each of the plurality of chart unit regions 951 of the target region 950 (step S14).

  Specifically, for example, in one chart unit region 951, an average value in the moving direction of the density at the pixel position corresponding to each ejection port (hereinafter referred to as “moving direction average density”) is obtained, and the moving direction average is obtained. The density and the target density on the recording medium 9 relating to the specified gradation value of the chart unit area 951 are compared. When the moving direction average density is higher than the target density, a correction coefficient for increasing the threshold value corresponding to the discharge port of the small dot temporary matrix 831 in order to reduce the discharge frequency of the small dots from the discharge port. Is acquired. On the other hand, when the moving direction average density is lower than the target density, in order to increase the ejection frequency of the small dots from the ejection port, the correction coefficient for decreasing the threshold value corresponding to the ejection port of the small dot temporary matrix 831 Is acquired. The target density is, for example, an average value of the density of the entire chart unit region 951 corresponding to the target density. Alternatively, the target density may be a specified density that is an ideal density set on the recording medium 9 with respect to a specified gradation value corresponding to the chart unit area 951.

  In the acquisition of the correction coefficient, for example, for each discharge port, a level indicating the relationship between the moving direction average density in each of the plurality of chart unit regions 951 and a plurality of specified gradation values corresponding to the plurality of chart unit regions 951 is obtained. The tone value-moving direction average density information is obtained. Subsequently, based on the gradation value-moving direction average density information and the target density, each designated floor of the gradation value-recording rate information (see FIG. 5) so as to realize the target density at each predetermined gradation value. The recording rate in the tone value is multiplied by the recording rate correction coefficient. The recording rate correction coefficient at each designated gradation value may be, for example, a value obtained by dividing the target density by the moving direction average density. Alternatively, based on the gradation value-moving direction average density information, a gradation value in which the moving direction average density is equal to the target density is obtained, and the gradation value is divided by a designated gradation value corresponding to the target density However, the recording rate correction coefficient at each designated gradation value may be used. Then, the correction coefficient is obtained based on the relationship between the threshold matrix for realizing the recording rate corrected by the recording rate correction coefficient and the temporary threshold matrix.

  In the correction information acquisition unit 433, filter correction information corresponding to a small size is obtained by collecting a set of correction coefficients related to each ejection port for the plurality of chart unit regions 951 (that is, for the plurality of specified gradation values). It is.

  Subsequently, the matrix correction unit 434 (see FIG. 4) uses the filter correction information corresponding to the small size acquired in step S14, and the plurality of temporary threshold value matrices (that is, the small dot temporary matrix 831). Among the medium dot temporary matrix 832 and the large dot temporary matrix 833), the small dot temporary matrix 831 corresponding to the small size which is the one dot size is corrected. Thereby, a small dot matrix 811 which is a corrected halftone dot filter corresponding to the small size is generated (step S15). Specifically, as illustrated in FIG. 8, a small dot temporary matrix 831 is arranged in each of a plurality of repeating regions 71 arranged in the x direction, and in each set of small dot temporary matrix 831, The small threshold value matrix 811 is generated by correcting the corresponding threshold value based on the correction coefficient relating to each of the ejection ports described above.

  When step S15 ends, the first dot size is changed to the medium size which is the next dot size (steps S16 and S17), and the process returns to step S14. Then, the correction information acquisition unit 433 and the matrix correction unit 434 are controlled by the iterative control unit 435 (see FIG. 4), so that filter correction information corresponding to the medium size is acquired, and medium dots which are corrected halftone filters. A matrix for use 812 is generated (steps S14 and S15). In step S14, another target area 950 corresponding to the medium size dot shown in FIG. In the target area 950 shown in FIG. 10, only medium-sized dots are recorded in the provisional halftone image data described above. Specifically, in the temporary halftone image data, dots are formed only at the pixel positions where the halftone pixel value is “2”, and the halftone pixel values are “0”, “1”, “3”. No dot is formed at the position.

  For example, in the chart unit region 951 on the most (−Y) side where the designated gradation value of the corresponding test unit region 941 is 26 (10%), the temporary halftone image data includes only small dots as shown in FIG. Since no medium dot is included, no dot is recorded. Therefore, the density of the chart unit area 951 is naturally lower than the specification density related to the corresponding designated gradation value. The same applies to the second chart unit region 951 from the (−Y) side where the specified gradation value of the corresponding test unit region 941 is 51 (20%).

  In the third chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 102 (40%), the provisional halftone image data is composed of small dots and medium dots. The image of only the medium dots among all the dots constituting the temporary halftone image data is recorded on the recording medium 9. Also, no dots are recorded at pixel positions where small dots are to be recorded in the provisional halftone image data. Therefore, the density of the chart unit region 951 is lower than the specification density related to the corresponding designated gradation value. The same applies to the fourth chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 153 (60%).

  In the fifth chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 204 (80%), the provisional halftone image data is composed of medium dots and large dots. The image of only the medium dots among all the dots constituting the temporary halftone image data is recorded on the recording medium 9. Also, no dots are recorded at pixel positions where large dots are to be recorded in the temporary halftone image data. Therefore, the density of the chart unit area 951 is lower than the specified density related to the corresponding designated gradation value.

  In the most (+ Y) side chart unit area 951 in which the specified gradation value of the corresponding test unit area 941 is 255 (100%), the temporary halftone image data is composed of only large dots and includes medium dots. Because there is no dot, no dot is recorded. Therefore, the density of the chart unit area 951 is naturally lower than the specification density related to the corresponding designated gradation value.

  When the medium dot matrix 812 is generated, one dot size is changed to a large size (steps S16 and S17), and filter correction information corresponding to the large size is acquired (step S14). Then, a large dot matrix 813 which is a corrected halftone filter is generated, and the generation of the matrix set in the halftone filter generation device 43 ends (steps S15 and S16). In step S14, in the test chart 95, another target area 950 corresponding to the large size dot shown in FIG. 11 is used. In the target area 950 shown in FIG. 11, only large-sized dots are recorded in the temporary halftone image data described above. Specifically, in the temporary halftone image data, dots are formed only at pixel positions where the halftone pixel value is “3”, and the halftone pixel values are “0”, “1”, and “2”. No dot is formed at the position.

  For example, in the chart unit region 951 on the most (−Y) side where the designated gradation value of the corresponding test unit region 941 is 26 (10%), the temporary halftone image data includes only small dots as shown in FIG. Since no large dot is included, no dot is recorded. Therefore, the density of the chart unit area 951 is naturally lower than the specification density related to the corresponding designated gradation value. The same applies to the second chart unit region 951 from the (−Y) side where the specified gradation value of the corresponding test unit region 941 is 51 (20%).

  In the third chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 102 (40%), the temporary halftone image data is composed of small dots and medium dots, and is large. Since no dots are included, no dots are recorded. Therefore, the density of the chart unit area 951 is naturally lower than the specification density related to the corresponding designated gradation value. The same applies to the fourth chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 153 (60%).

  In the fifth chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 204 (80%), the provisional halftone image data is composed of medium dots and large dots. The image of only large dots among all the dots constituting the temporary halftone image data is recorded on the recording medium 9. Also, no dots are recorded at pixel positions where medium dots are to be recorded in the provisional halftone image data. Therefore, the density of the chart unit area 951 is lower than the specified density related to the corresponding designated gradation value.

  In the chart unit region 951 on the most (+ Y) side where the designated gradation value of the corresponding test unit region 941 is 255 (100%), the provisional halftone image data is composed only of large dots, and therefore the provisional halftone image An image according to the data is recorded on the recording medium 9. Therefore, the density of the chart unit area 951 is approximately equal to the specified density, which is an ideal density set for the corresponding designated gradation value.

  As described above, in the halftone filter generation device 43, the correction information acquisition unit 433 and the matrix correction unit 434 are controlled by the iterative control unit 435, and the acquisition of the filter correction information and the corrected halftone dot are changed while one dot size is changed. The generation of a threshold matrix that is a filter is repeated. As a result, a plurality of pieces of filter correction information respectively corresponding to the plurality of dot sizes described above are acquired, and a plurality of corrected halftone dot filters 811, small dot matrix 812, medium dot matrix 812, and large dot matrix 813 That is, a matrix set) is generated.

  In the generation of the matrix set by the halftone dot filter generation device 43, the correction of the temporary matrix for small dots 831, the temporary matrix for medium dots 832 and the temporary matrix for large dots 833 by the matrix correction unit 434 results in the gradation value − It can also be understood that the recording rate information is corrected and new gradation value-recording rate information corresponding to the small dot matrix 811, the medium dot matrix 812, and the large dot matrix 813 is generated. When the total recording rate of small dots, medium dots, and large dots exceeds 100% by the above correction of the gradation value-recording rate information, the level of each dot is set so that the maximum value of the total recording rate is 100%. The tone value-recording rate information is corrected.

  In the halftone filter generation device 43, if steps S14 and S15 are substantially repeated for small-sized, medium-sized, and large-sized dots, for example, the test chart 95 is generated before the generation of the corrected halftone filter. A plurality of pieces of filter correction information respectively corresponding to the small size, the medium size, and the large size may be acquired in parallel or sequentially from the plurality of target regions 950 respectively corresponding to the small size, the medium size, and the large size. Thereafter, the small dot matrix 811, the medium dot matrix 812, and the large dot matrix 813 are generated in parallel or sequentially using a plurality of pieces of filter correction information respectively corresponding to the small size, medium size, and large size. Also good.

  The halftone dot filter generation device 43 generates a small dot matrix 811, a medium dot matrix 812, and a large dot matrix 813 for each of the plurality of color components described above. Then, the small dot matrix 811, the medium dot matrix 812, and the large dot matrix 813 (that is, the matrix set) of each color component are sent from the halftone dot filter generation device 43 to the halftone processing unit 42 and correspond to each color component. Stored in the matrix storage unit 422.

  In the shading processing unit 42, as described above, the matrix set of each color component stored in the matrix storage unit 422 (that is, the halftone dot filter generation device) with respect to the original image data of each color component stored in the image memory 421. The image data generation unit 423 performs a shading process using the matrix set generated by the process 43. Thereby, halftone image data of each color component is generated. In the image recording apparatus 1, the output mechanism 41 controls the moving mechanism 2 and the ejection unit 3 on the basis of the halftone image data of each color component generated by the shading processing unit 42, whereby the recording medium 9. The ink of each color component is ejected on the image recording is completed.

  As described above, in the halftone dot filter generation device 43 of the image recording device 1, in step S11, the provisional matrix storage unit 431 obtains a plurality of dot sizes obtained for each dot size based on the respective recording rates of the plurality of dot sizes. Is stored as a temporary threshold value matrix (that is, a temporary halftone dot filter). Subsequently, in step S12, the temporary shading processing unit 432 performs a shading process on the test image 94 using a plurality of temporary threshold value matrices to generate temporary halftone image data. Next, in step S13, when the test chart 95 is recorded on the recording medium 9 based on the provisional halftone image data in which a plurality of dot sizes are mixed, the plurality of dot sizes in the provisional halftone image data are extracted. Only the selected dot of one dot size is recorded in the target area 950. In step S <b> 14, the correction information acquisition unit 433 acquires filter correction information corresponding to the selected one dot size from the target area 950. As a result, the filter correction information used for highly accurate correction of the threshold matrix can be acquired for the one dot size without being affected by variations in the size of dots in other dot sizes.

  As described above, the test image 94 used for obtaining the filter correction information in the halftone filter generation device 43 includes a plurality of test unit regions 941 respectively corresponding to a plurality of specified gradation values, and is the target in the test chart 95. The area 950 includes a plurality of chart unit areas 951 that are respectively recorded corresponding to the plurality of test unit areas 941. Then, the correction information acquisition unit 433 acquires filter correction information corresponding to the one dot size based on the density in each of the plurality of chart unit regions 951. Thereby, the filter correction information over a wide gradation range can be acquired.

  In the halftone filter generation device 43, in step S15, the matrix correction unit 434 corrects the temporary threshold value matrix corresponding to the selected one dot size using the filter correction information, and the one dot size. A threshold matrix (ie, a corrected halftone filter) corresponding to is generated. Thereby, it is possible to provide a threshold value matrix in which the one dot size is corrected with high accuracy based on the filter correction information.

  In the image recording apparatus 1, dot processing is performed on the recording medium 9 using the threshold value matrix corrected with high accuracy by the halftone filter generation apparatus 43 for the one dot size. . Thereby, it is possible to perform highly accurate density correction for the one dot size without being affected by other dot sizes. As a result, the density of the image can be made close to a desired density in the range of gradation values in which the dot of the one dot size is used for image recording.

  In the halftone filter generation device 43, the repeat control unit 435 repeats steps S14 and S15, thereby acquiring a plurality of pieces of filter correction information respectively corresponding to the plurality of dot sizes described above. Thereby, for each of the plurality of dot sizes, filter correction information used for highly accurate correction of the threshold value matrix can be acquired without being affected by variations in dot size in other dot sizes. it can. Further, for each of the plurality of dot sizes, a threshold value matrix that is corrected with high accuracy can be provided by generating the threshold value matrix using the filter correction information.

  In the image recording apparatus 1, a dot process is performed on the plurality of dot sizes using the threshold value matrix corrected with high precision by the halftone filter generation apparatus 43, and dots are recorded on the recording medium 9. . As a result, it is possible to perform high-precision density correction for the plurality of dot sizes without being affected by other dot sizes. That is, the resolution for correcting the density of the image recorded on the recording medium 9 can be improved. As a result, the image density can be made close to a desired density over a wide range of gradation values.

  In the above description, the halftone dot filter generation device 43 corrects the temporary threshold value matrix to generate the threshold value matrix, so that the density at the pixel position corresponding to each ejection port of the head assembly 31 is individually corrected. On the other hand, as described above, each head assembly 31 with the discharge unit 3 includes a plurality of discharge heads 32 that are a plurality of divided output units arranged along the width direction (see FIG. 2). In the head assembly 31 including such a plurality of ejection heads 32, the small dots ejected from one ejection head 32 are smaller than the small dots ejected from the other ejection heads 32, and the one ejection head 32 is concerned. In some cases, a difference in density occurs in units of the ejection head 32, such as the large dots ejected from the nozzles being larger than the large dots ejected from the other ejection heads 32. In this case, the threshold matrix may be generated by performing correction on the temporary threshold matrix for each ejection head 32 without performing individual correction for each ejection port. Hereinafter, the correction for each discharge head 32 will be described.

  In the correction for each discharge head 32, processing similar to steps S11 to S13 shown in FIG. 6 is performed, and a test chart 95 is obtained. The target area 950 of the test chart 95 shown in FIG. 12 is an area corresponding to a small dot, which is one dot size, as in FIG. The target area 950 is divided into a plurality of divided area groups 952 that respectively correspond to the plurality of ejection heads 32. In FIG. 12, the boundaries of the four divided region groups 952 arranged along the width direction are indicated by two-dot chain lines. Each divided region group 952 is recorded by the corresponding ejection head 32. Each divided region group 952 is a set of a plurality (six in the example of FIG. 12) of divided regions 953 arranged in the moving direction recorded by the corresponding ejection head 32 in the plurality of chart unit regions 951. Each of the plurality of chart unit regions 951 includes a plurality of (four in the example of FIG. 12) divided regions 953 arranged along the width direction.

  In step S <b> 14, the correction information acquisition unit 433 acquires filter correction information corresponding to a small size that is one dot size based on the density in each of the plurality of chart unit regions 951 in the target region 950. Specifically, based on the density of the plurality of chart unit areas 951 in each divided area group 952 (that is, the density of the plurality of divided areas 953 included in each divided area group 952), the division corresponding to each divided area group 952 is performed. Filter correction information is acquired by the correction information acquisition unit 433.

  At this time, the division filter correction information corresponding to each divided region group 952 corresponds to the density of each chart unit region 951 in each divided region group 952 (that is, the density of each divided region 953) and each chart unit region 951. It is acquired based on the relationship with the target density relating to each designated gradation value. The target density relating to each designated gradation value is, for example, the average density of each chart unit region 951 corresponding to each designated gradation value in two or more divided region groups 952 adjacent in the width direction. The two or more divided region groups 952 may be all of the plurality of divided region groups 952 described above. Alternatively, some of the divided region groups 952 out of the plurality of divided region groups 952 may be the two or more divided region groups 952. In this case, the divided region group 952 from which the divided filter correction information is acquired is preferably included in the two or more divided region groups 952.

  In the correction information acquisition unit 433, a set of a plurality of divided filter correction information respectively corresponding to the plurality of divided region groups 952 is acquired as filter correction information corresponding to a small size. In other words, the filter correction information corresponding to the small size includes a plurality of divided filter correction information respectively corresponding to the plurality of divided region groups 952.

  In step S15, as described above, the small dot matrix 811 is generated by correcting the small dot temporary matrix 831 by the matrix correction unit 434 using the filter correction information corresponding to the small size. . Further, for the medium size and the large size, the acquisition of the division filter correction information for each ejection head 32 in step S14 and step S15 are repeated, and the medium dot matrix 812 and the large dot matrix 813 are generated.

  In the halftone filter generation device 43, even when correction is performed for each ejection head 32, similarly to the above, each of the plurality of dot sizes is affected by variations such as dot sizes in other dot sizes. Instead, it is possible to obtain filter correction information used for highly accurate correction of the threshold matrix. Further, for each of the plurality of dot sizes, a threshold value matrix that is corrected with high accuracy can be provided by generating the threshold value matrix using the filter correction information.

  In particular, by obtaining the divided filter correction information for each ejection head 32 by the halftone filter generation device 43, banding unevenness between the ejection heads 32 can be suppressed in image recording by the image recording apparatus 1. Further, when acquiring the division filter correction information, the average density of each chart unit area 951 in two or more divided area groups 952 adjacent in the width direction is used as the target density, so that each chart unit area 951 Even when the recording medium 9 for which the specified density (that is, the ideal density on the recording medium 9) is not set for the corresponding designated gradation value is used, banding unevenness between the ejection heads 32 is reduced. Can be suppressed.

  When the line sensor that reads the density of the target region 950 has a sensitivity error in the width direction (for example, when the sensitivity at the end in the width direction is lower than the sensitivity at the center), the target density is The average density of each chart unit region 951 in a part of the divided region group 952 including the divided region group 952 from which the divided filter correction information is acquired is preferable. Thereby, the division filter correction information capable of suppressing the density difference between the two adjacent ejection heads 32 can be obtained with high accuracy. Further, when the recording medium 9 in which the specification density for each designated gradation value is set is used, the target density may be made equal to the specification density.

  When the division filter correction information is acquired for each ejection head 32, the division filter correction information is different on both sides of the boundary between the two ejection heads 32 in the region of the temporary threshold value matrix straddling two adjacent ejection heads 32. Therefore, the mode of correction by the matrix correction unit 434 is also different.

  In the test chart 95, the plurality of divided region groups 952 of the target region 950 are not necessarily set corresponding to the plurality of ejection heads 32, and the head assembly 31 does not have the plurality of ejection heads 32. Even in some cases, a plurality of divided region groups 952 may be set as the target region 950. In this case, banding unevenness between a plurality of areas corresponding to the plurality of divided area groups 952 in the width direction on the recording medium 9 can be suppressed.

  Next, acquisition of filter correction information using a test chart different from the above-described test chart 95 (see FIGS. 9 to 11) will be described. FIG. 13 is a diagram showing a part of the second test chart 95a. FIG. 13 shows a target area 950a corresponding to a small dot in the second test chart 95a. Similar to the test chart 95 shown in FIGS. 9 to 11, the second test chart 95a also includes target areas 950a corresponding to medium-sized and large-sized dots, respectively. In the following description, the test chart 95 of FIG. 9 is also referred to as “first test chart 95”.

  The flow of obtaining filter correction information using the second test chart 95a and generating a matrix set is substantially the same as steps S11 to S17 described above (see FIG. 6). First, as in the case of using the first test chart 95, a small dot temporary matrix 831, a medium dot temporary matrix 832, and a large dot temporary matrix 833 are prepared (step S11), and a temporary shading processing unit 432 is prepared. Thus, the test image 94 is shaded to generate temporary halftone image data (step S12).

  Subsequently, the output control unit 41 controls the moving mechanism 2 and the discharge unit 3 based on the temporary halftone image data of the test image 94, thereby recording a second test chart 95a partially shown in FIG. It is recorded on the medium 9 (step S13). A target area 950a shown in FIG. 13 includes a plurality of chart unit areas 951 arranged in the moving direction described above. Each chart unit area 951 is a substantially rectangular tint image having a substantially uniform density.

  In the plurality of chart unit areas 951 of the target area 950a, all the dots of the plurality of dot sizes of the temporary halftone image data are converted into dots of one dot size and recorded. In other words, all of the small dots, medium dots, and large dots that are to be recorded in each chart unit area 951 in the temporary halftone image data (that is, to be recorded) are dots of one dot size. And then recorded in each chart unit area 951. In the example shown in FIG. 13, dots of all sizes scheduled to be recorded in each chart unit area 951 are converted into small dots, and only small dots are recorded in each chart unit area 951. That is, in the provisional halftone image data, small dots are formed at all pixel positions where the halftone pixel values are “1”, “2”, and “3”, and the pixel position where the halftone pixel value is “0”. No dot is formed on the.

  For example, in the chart unit region 951 on the most (−Y) side where the designated gradation value of the corresponding test unit region 941 is 26 (10%), the temporary halftone image data includes only small dots as shown in FIG. Therefore, an image according to the provisional halftone image data is recorded on the recording medium 9. Therefore, the density of the chart unit area 951 is approximately equal to the specified density, which is an ideal density set for the corresponding designated gradation value. The same applies to the second chart unit region 951 from the (−Y) side where the specified gradation value of the corresponding test unit region 941 is 51 (20%).

  In the third chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 102 (40%), the provisional halftone image data is composed of small dots and medium dots. The small dots are recorded on the recording medium 9 as they are, and the medium dots are recorded on the recording medium 9 after being converted into small dots. Therefore, the density of the chart unit region 951 is lower than the specification density related to the corresponding designated gradation value. The same applies to the fourth chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 153 (60%).

  In the fifth chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 204 (80%), the provisional halftone image data is composed of medium dots and large dots. Both medium dots and large dots are converted to small dots and then recorded on the recording medium 9. Therefore, the density of the chart unit region 951 is lower than the specification density related to the corresponding designated gradation value.

  In the chart unit region 951 on the most (+ Y) side where the designated gradation value of the corresponding test unit region 941 is 255 (100%), the provisional halftone image data is composed of only large dots, so that the large dots are small. It is recorded on the recording medium 9 after being converted into dots. Therefore, the density of the chart unit region 951 is lower than the specification density related to the corresponding designated gradation value.

  When the recording of the second test chart 95a is completed, the correction information acquisition unit 433 causes the filter correction information corresponding to the small size that is the one dot size described above (that is, the dot size of the dot recorded only in the target area 950a). Is obtained based on the density in each of the plurality of chart unit areas 951 of the target area 950a (step S14). A specific method for obtaining the filter correction information is, for example, substantially the same as when the first test chart 95 is used.

  Subsequently, the matrix correction unit 434 uses the filter correction information corresponding to the small size acquired in step S <b> 14 to store the small dot temporary matrix 831, the medium dot temporary matrix 832, and the large dot temporary matrix 833. Among them, the small dot temporary matrix 831 corresponding to the small size which is the one dot size is corrected. Thereby, a small dot matrix 811 which is a corrected halftone dot filter corresponding to the small size is generated (step S15).

  When step S15 ends, the first dot size is changed to the medium size which is the next dot size (steps S16 and S17), and the process returns to step S14. Then, filter correction information corresponding to the medium size is acquired, and a medium dot matrix 812 that is a corrected halftone filter is generated (steps S14 and S15). In step S14, in the second test chart 95a, another target area 950a corresponding to the medium size dot shown in FIG. 14 is used. In the target area 950a shown in FIG. 14, all the dots of the plurality of dot sizes of the provisional halftone image data described above are converted into medium dots, and then only the medium dots are recorded in each chart unit area 951. Specifically, in the provisional halftone image data, medium dots are formed at all pixel positions where the halftone pixel values are “1”, “2”, and “3”, and the halftone pixel value is “0”. No dot is formed at a certain pixel position.

  For example, in the chart unit region 951 on the most (−Y) side where the designated gradation value of the corresponding test unit region 941 is 26 (10%), the temporary halftone image data includes only small dots as shown in FIG. Therefore, small dots are converted into medium dots and recorded on the recording medium 9. Therefore, the density of the chart unit region 951 is higher than the specification density related to the corresponding designated gradation value. The same applies to the second chart unit region 951 from the (−Y) side where the specified gradation value of the corresponding test unit region 941 is 51 (20%).

  In the third chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 102 (40%), the provisional halftone image data is composed of small dots and medium dots. The medium dots are recorded on the recording medium 9 as they are, and the small dots are recorded on the recording medium 9 after being converted into medium dots. Therefore, the density of the chart unit region 951 is higher than the specification density related to the corresponding designated gradation value. The same applies to the fourth chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 153 (60%).

  In the fifth chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 204 (80%), the provisional halftone image data is composed of medium dots and large dots. The medium dots are recorded on the recording medium 9 as they are, and the large dots are recorded on the recording medium 9 after being converted into medium dots. Therefore, the density of the chart unit region 951 is lower than the specification density related to the corresponding designated gradation value.

  In the chart unit region 951 on the most (+ Y) side where the designated gradation value of the corresponding test unit region 941 is 255 (100%), the provisional halftone image data is composed of only large dots, so that the large dots are medium. It is recorded on the recording medium 9 after being converted into dots. Therefore, the density of the chart unit region 951 is lower than the specification density related to the corresponding designated gradation value.

  When the medium dot matrix 812 is generated, one dot size is changed to a large size (steps S16 and S17), filter correction information corresponding to the large size is acquired, and the corrected dot filter is a large dot filter. A matrix 813 is generated (steps S14 and S15). In step S14, in the second test chart 95a, another target area 950a corresponding to the large size dot shown in FIG. 15 is used. In the target area 950a shown in FIG. 15, all the dots of the plurality of dot sizes of the provisional halftone image data described above are converted into large dots, and then only the large dots are recorded in each chart unit area 951. Specifically, in the provisional halftone image data, large dots are formed at all pixel positions where the halftone pixel values are “1”, “2”, and “3”, and the halftone pixel value is “0”. No dot is formed at a certain pixel position.

  For example, in the chart unit region 951 on the most (−Y) side where the designated gradation value of the corresponding test unit region 941 is 26 (10%), the temporary halftone image data includes only small dots as shown in FIG. Therefore, small dots are converted into large dots and then recorded on the recording medium 9. Therefore, the density of the chart unit region 951 is higher than the specification density related to the corresponding designated gradation value. The same applies to the second chart unit region 951 from the (−Y) side where the specified gradation value of the corresponding test unit region 941 is 51 (20%).

  In the third chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 102 (40%), the provisional halftone image data is composed of small dots and medium dots. Both small dots and medium dots are converted to large dots and then recorded on the recording medium 9. Therefore, the density of the chart unit region 951 is higher than the specification density related to the corresponding designated gradation value. The same applies to the fourth chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 153 (60%).

  In the fifth chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 204 (80%), the provisional halftone image data is composed of medium dots and large dots. The large dots are recorded on the recording medium 9 as they are, and the medium dots are recorded on the recording medium 9 after being converted into large dots. Therefore, the density of the chart unit region 951 is higher than the specification density related to the corresponding designated gradation value.

  In the chart unit region 951 on the most (+ Y) side where the designated gradation value of the corresponding test unit region 941 is 255 (100%), the provisional halftone image data is composed only of large dots, and therefore the provisional halftone image An image according to the data is recorded on the recording medium 9. Therefore, the density of the chart unit area 951 is approximately equal to the specified density, which is an ideal density set for the corresponding designated gradation value.

  As described above, in the halftone filter generation device 43, the correction information acquisition unit 433 and the matrix correction unit 434 are controlled by the iterative control unit 435, and the acquisition of the filter correction information and the corrected halftone dot are changed while one dot size is changed. The generation of a threshold matrix that is a filter is repeated. As a result, a plurality of filter correction information respectively corresponding to the plurality of dot sizes described above is acquired, and a plurality of corrected halftone dot filters 811, a small dot matrix 811, a medium dot matrix 812, and a large dot matrix 813 (that is, , Matrix set) is generated. In the halftone dot filter generation device 43, the gradation value-recording rate information shown in FIG. 5 is corrected by correcting the temporary matrix for small dots 831, the temporary matrix for medium dots 832, and the temporary matrix for large dots 833 by the matrix correction unit 434. It can also be understood that new gradation value-recording rate information corresponding to the small dot matrix 811, the medium dot matrix 812, and the large dot matrix 813 is generated.

  In the halftone dot filter generation device 43, if steps S14 and S15 are substantially repeated for small, medium and large size dots, for example, the second dot filter is generated before the corrected halftone dot filter is generated. Even if a plurality of pieces of filter correction information respectively corresponding to the small size, medium size, and large size are acquired in parallel or sequentially from the plurality of target regions 950a corresponding to the small size, medium size, and large size of the test chart 95a. Good. Thereafter, the small dot matrix 811, the medium dot matrix 812, and the large dot matrix 813 are generated in parallel or sequentially using a plurality of pieces of filter correction information respectively corresponding to the small size, medium size, and large size. Also good.

  As described above, the first test chart 95 is used by acquiring the filter correction information corresponding to the selected one dot size from the target area 950a using the second test chart 95a. Similarly to the case, the filter correction information used for highly accurate correction of the threshold matrix can be obtained for the one dot size without being affected by variations in the dot size in other dot sizes. it can. In addition, since the second test chart 95a includes a plurality of chart unit regions 951 as in the first test chart 95, filter correction information over a wide gradation range can be acquired. Furthermore, by correcting the temporary threshold value matrix corresponding to the one dot size using the filter correction information, it is possible to provide a threshold value matrix that is corrected with high accuracy for the one dot size. As a result, in the image recording apparatus 1, it is possible to perform highly accurate density correction for the one dot size without being affected by other dot sizes.

  Even when the second test chart 95a is used, similarly to the case where the first test chart 95 is used, steps S14 and S15 are repeated to obtain a plurality of pieces of filter correction information corresponding to a plurality of dot sizes. Thus, for each of the plurality of dot sizes, filter correction information used for highly accurate correction of the threshold matrix is obtained without being affected by variations in the dot size in other dot sizes. Can do. Further, it is possible to provide a threshold value matrix corrected with high accuracy for each of a plurality of dot sizes. As a result, the image recording apparatus 1 can perform high-precision density correction for a plurality of dot sizes without being affected by other dot sizes. That is, the resolution for correcting the density of the image recorded on the recording medium 9 can be improved.

  Also in the second test chart 95a, as in the first test chart 95, a plurality of divided area groups 952 (see FIG. 12) are set in the target area 950a, and each of the divided area groups 952 is set by the correction information acquisition unit 433. Corresponding division filter correction information may be acquired. Thereby, banding unevenness between a plurality of areas corresponding to the plurality of divided area groups 952 in the width direction on the recording medium 9 can be suppressed. Further, when the plurality of divided region groups 952 correspond to the plurality of ejection heads 32 of the head assembly 31, banding unevenness between the plurality of ejection heads 32 can be suppressed.

  Next, acquisition of filter correction information using a test chart different from the first test chart 95 and the second test chart 95a described above will be described. FIG. 16 is a diagram showing a third test chart 95b. FIG. 16 shows a target area 950b corresponding to a small-sized dot in the third test chart 95b. Unlike the first test chart 95 and the second test chart 95a, the third test chart 95b does not include the target area 950b corresponding to the medium-sized and large-sized dots.

  The flow of obtaining filter correction information using the third test chart 95b and generating a matrix set is partially different from that shown in FIG. 6, as shown in FIGS. 17A and 17B. When the third test chart 95b is used, first, as in the case of using the first test chart 95, a small dot temporary matrix 831, a medium dot temporary matrix 832, and a large dot temporary matrix 833 are prepared. (Step S21), the temporary shading processing unit 432 performs shading processing of the test image 94 to generate temporary halftone image data (Step S22).

  Subsequently, one dot size for obtaining the filter correction information is selected (step S23). Hereinafter, the one dot size selected in step S23 is referred to as “selected dot size”. In the following description, it is assumed that the first selected dot size is a small size.

  When the selected dot size is selected, the output control unit 41 controls the moving mechanism 2 and the ejection unit 3 based on the temporary halftone image data of the test image 94, whereby the third test relating to the selected dot size is performed. A chart 95b (see FIG. 16) is recorded on the recording medium 9 (step S24). A target area 950b shown in FIG. 16 includes a plurality of chart unit areas 951 arranged in the moving direction described above. Each chart unit area 951 is a substantially rectangular tint image having a substantially uniform density.

  In the target area 950b of the third test chart 95b to be recorded first, one dot size (that is, selected dot) selected from a plurality of dot sizes of the provisional halftone image data in the plurality of chart unit areas 951. Only size dots are recorded. In this case, only the small dots are recorded in each chart unit area 951 among the small dots, medium dots, and large dots that are to be recorded in each chart unit area 951 in the temporary halftone image data. That is, in the provisional halftone image data, dots are formed only at the pixel positions where the halftone pixel value is “1”, and at the pixel positions where the halftone pixel values are “0”, “2”, and “3”. Dots are not formed. Therefore, the target area 950b recorded first in FIG. 16 is the same image as the target area 950 shown in FIG. Note that the medium size or large size may be selected as the first selected dot size. In this case, the target area 950b to be recorded first is an image different from the target area 950 shown in FIG.

  When the recording of the first third test chart 95b is completed, the correction information acquisition unit 433 causes the filter correction information corresponding to the small size that is the selected dot size to be the density in each of the plurality of chart unit regions 951 in the target region 950b. (Step S25). A specific method for obtaining the filter correction information is, for example, substantially the same as when the first test chart 95 is used. This makes it possible to acquire filter correction information used for highly accurate correction of the threshold matrix without being affected by variations in the dot size or the like in other dot sizes for the small size that is the selected dot size. it can.

  When step S25 is completed, the matrix correction unit 434 uses the filter correction information corresponding to the small size acquired in step S25 to generate a plurality of temporary threshold matrixes (that is, a small dot temporary matrix 831 and a medium dot matrix). Among the temporary matrix 832 and the large dot temporary matrix 833), the small dot temporary matrix 831 corresponding to the small size which is the selected dot size is corrected. Thereby, a small dot matrix 811 which is a corrected halftone dot filter corresponding to the small size is generated (step S26). As a result, it is possible to provide a threshold matrix that is corrected with high accuracy without being affected by variations in the size of dots in other dot sizes for a small size that is a selected dot size.

  Subsequently, in the temporary shading processing unit 432, the small dot temporary matrix 831 corresponding to the selected dot size among the plurality of temporary threshold value matrices is changed to the small dot matrix 811, and the small dot matrix 811 and the medium dot matrix are used. The test image 94 is shaded using the temporary matrix 832 and the large dot temporary matrix 833. Thereby, new temporary halftone image data is generated (step S27).

  Next, the selected dot size is changed from a small size to a medium size which is a new dot size (step S28). In other words, the medium size is selected as the new selected dot size. The small size for which filter correction information has already been acquired is the information acquired dot size.

  When a new selected dot size is selected, the output control unit 41 controls the moving mechanism 2 and the discharge unit 3 based on the new temporary halftone image data generated in step S27. As shown in FIG. 5, a new third test chart 95b relating to a new selected dot size is recorded on the recording medium 9 (step S29). The target area 950b of the third test chart 95b shown in FIG. 18 also includes a plurality of chart unit areas 951 arranged in the above moving direction, similarly to the target area 950b shown in FIG.

  In the target area 950b of the third test chart 95b shown in FIG. 18, the small size that is the information-acquired dot size of the temporary halftone image data generated in step S27, and the plurality of chart unit areas 951, and Only the medium size dots which are the new selected dot size are recorded. Specifically, in the temporary halftone image data, small dots are formed at pixel positions where the halftone pixel value is “1”, and medium dots are formed at pixel positions where the halftone pixel value is “2”. . Also, no dots are formed at pixel positions where the halftone pixel values are “0” and “3”.

  For example, in the chart unit region 951 on the most (−Y) side where the designated gradation value of the corresponding test unit region 941 is 26 (10%), the temporary halftone image data includes only small dots as shown in FIG. Therefore, an image according to the provisional halftone image data is recorded on the recording medium 9. Therefore, the density of the chart unit area 951 is approximately equal to the specified density, which is an ideal density set for the corresponding designated gradation value. The same applies to the second chart unit region 951 from the (−Y) side where the specified gradation value of the corresponding test unit region 941 is 51 (20%).

  In the fourth chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 102 (40%), the provisional halftone image data is composed of small dots and medium dots. The image according to the provisional halftone image data is recorded on the recording medium 9. Therefore, the density of the chart unit area 951 is approximately equal to the specified density, which is an ideal density set for the corresponding designated gradation value. The same applies to the fourth chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 153 (60%).

  In the fifth chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 204 (80%), the provisional halftone image data is composed of medium dots and large dots. The image of only the medium dots among all the dots constituting the temporary halftone image data is recorded on the recording medium 9. Also, no dots are recorded at pixel positions where large dots are to be recorded in the temporary halftone image data. Therefore, the density of the chart unit region 951 is lower than the specification density related to the corresponding designated gradation value.

  In the most (+ Y) side chart unit area 951 where the specified gradation value of the corresponding test unit area 941 is 255 (100%), the temporary halftone image data is composed of only large dots, and the small dots and medium dots are Since it is not included, no dot is recorded. Therefore, the density of the chart unit area 951 is naturally lower than the specification density related to the corresponding designated gradation value.

  When the recording of the third test chart 95b for the second time is completed, the correction information acquisition unit 433 causes the filter correction information corresponding to the medium size that is the selected dot size in each of the plurality of chart unit regions 951 of the target region 950b. Obtained based on the density (step S30). A specific method for obtaining the filter correction information is, for example, substantially the same as when the first test chart 95 is used. In this case, the target area 950b includes small dots in addition to the medium dots, but the density based on the small dots has been corrected based on the filter correction information acquired in step S25, and thus is the selected dot size. With respect to the medium size, it is possible to obtain filter correction information used for highly accurate correction of the threshold value matrix without being affected by variations in dot size and the like in other dot sizes.

  When step S30 ends, the matrix correction unit 434 corrects the medium dot temporary matrix 832 corresponding to the medium size that is the selected dot size using the filter correction information corresponding to the medium size acquired in step S30. Is done. As a result, a medium dot matrix 812 that is a corrected halftone dot filter corresponding to the medium size is generated (step S31). As a result, it is possible to provide a threshold matrix that is corrected with high accuracy without being affected by variations in the dot size of other dot sizes for the medium size that is the selected dot size.

  When step S31 is completed, the temporary dot processing unit 432 changes the medium dot temporary matrix 832 corresponding to the selected dot size to the medium dot matrix 812, and the small dot matrix 811, the medium dot matrix 812, and the large dot. The test matrix 94 is shaded using the temporary matrix 833. Thereby, new temporary halftone image data is generated (steps S32 and S33), and the process returns to step S28.

  Next, the selected dot size is changed from a medium size to a large size which is a new dot size (step S28). In other words, a large size is selected as the new selected dot size. Further, the medium size for which the filter correction information has already been acquired is the information acquired dot size, similarly to the small size.

  When a new selected dot size is selected, the output control unit 41 controls the moving mechanism 2 and the discharge unit 3 based on the new temporary halftone image data generated in step S33, so that FIG. As shown in FIG. 5, the third test chart 95b relating to the new selected dot size is recorded on the recording medium 9 (step S29). Similarly to the target area 950b shown in FIG. 16, the target area 950b of the third test chart 95b shown in FIG. 19 also includes a plurality of chart unit areas 951 arranged in the moving direction described above.

  In the target region 950b of the third test chart 95b shown in FIG. 19, the small and medium sizes of the information-acquired dot size in the temporary halftone image data generated in step S33 are displayed in the plurality of chart unit regions 951. A large size dot, which is a new selected dot size, is recorded. Specifically, in the temporary halftone image data, small dots are formed at pixel positions where the halftone pixel value is “1”, and medium dots are formed at pixel positions where the halftone pixel value is “2”. . Further, a large dot is formed at a pixel position where the halftone pixel value is “3”, and no dot is formed at a pixel position where the halftone pixel value is “0”. Accordingly, in the target area 950b of the third test chart 95b for the third time shown in FIG. 19, the density of each chart unit area 951 is a specified density that is an ideal density set for the corresponding designated gradation value. Is approximately equal to

  When the third recording of the third test chart 95b is completed, the correction information acquisition unit 433 causes the filter correction information corresponding to the large size that is the selected dot size to be received in each of the plurality of chart unit regions 951 of the target region 950b. Obtained based on the density (step S30). A specific method for obtaining the filter correction information is, for example, substantially the same as when the first test chart 95 is used. In this case, the target area 950b includes small dots and medium dots in addition to the large dots, but the density of the small dots and medium dots is based on the filter correction information acquired in step S25 and the first step S30. Therefore, the filter correction information used for high-precision correction of the threshold matrix is not affected by the variation of the dot size in other dot sizes for the large size that is the selected dot size. Can be acquired.

  When step S30 ends, the matrix correction unit 434 corrects the large dot temporary matrix 833 corresponding to the large size which is the selected dot size using the filter correction information corresponding to the large size acquired in step S30. Is done. As a result, a large dot matrix 813 which is a corrected halftone filter corresponding to a large size is generated, and generation of a matrix set in the halftone filter generation device 43 ends (steps S31 and S32). As a result, it is possible to provide a threshold value matrix that is corrected with high accuracy without being affected by variations in the size of dots in other dot sizes for a large size that is the selected dot size.

  Even when the third test chart 95b is used, as in the case of using the first test chart 95 and the second test chart 95a, the image recording apparatus 1 uses other dot sizes for a plurality of dot sizes. Highly accurate density correction can be performed without being affected. That is, the resolution for correcting the density of the image recorded on the recording medium 9 can be improved.

  In the above example, the small size is selected as the selected dot size in step S23, and the medium size is selected as the new selected dot size in the first step S28. In other words, the new one dot size in step S28 is larger than the one dot size in step S23. As a result, it is possible to acquire the medium-size filter correction information with higher accuracy in consideration of the density correction result relating to the small dots. As a result, the density correction in the intermediate gradation range (that is, the gradation range between the highlight side and the shadow side) in which the recording rate of medium dots is relatively high can be performed with higher accuracy. In general, since the unevenness is more noticeable in the intermediate gradation range than in the highlight side, it is preferable to improve the density correction accuracy in the intermediate gradation range.

  In the above example, the large size is selected as the new selected dot size in the second step S28. In other words, the new one dot size in the second step S28 is larger than the new one dot size in the first step S28. In other words, a plurality of dot sizes are selected as the selected dot size in ascending order. Thereby, the filter correction information for the large size can be obtained with higher accuracy in consideration of the density correction results relating to the small dots and the medium dots. As a result, the density correction in the gradation range on the shadow side where the recording rate of large dots is relatively high can be performed with higher accuracy. In general, unevenness is more noticeable in the shadow-side tone range than in the highlight-side tone range and intermediate tone range, so improving the accuracy of density correction in the shadow-side tone range Further preferred.

  Also in the third test chart 95b, as in the first test chart 95, a plurality of divided area groups 952 (see FIG. 12) are set in the target area 950b, and the correction information acquisition unit 433 assigns each divided area group 952 to each divided area group 952. Corresponding division filter correction information may be acquired. Thereby, banding unevenness between a plurality of areas corresponding to the plurality of divided area groups 952 in the width direction on the recording medium 9 can be suppressed. Further, when the plurality of divided region groups 952 correspond to the plurality of ejection heads 32 of the head assembly 31, banding unevenness between the plurality of ejection heads 32 can be suppressed.

  In the image recording apparatus 1, the matrix set may be generated by another generation method different from the above-described method using the third test chart 95b. As shown in FIGS. 20A and 20B, the flow of processing by the other generation method is partially different from that shown in FIGS. 17A and 17B. In the processing shown in FIGS. 20A and 20B, a plurality of dot sizes are selected as the selected dot size in descending order, and a threshold matrix that is a corrected halftone filter corresponding to the selected dot size is sequentially generated.

  In the image recording apparatus 1, first, similarly to step S 21, a small dot temporary matrix 831, a medium dot temporary matrix 832, and a large dot temporary matrix, which are a plurality of temporary threshold matrixes (that is, a plurality of temporary halftone filters). 833 is prepared (step S41). Subsequently, a large size that is the maximum dot size among the plurality of provisional threshold matrices is selected as the selected dot size (step S42). Then, the large dot temporary matrix 833 corresponding to the large size is used to perform the shading process of the test image 94, and the dot having the maximum dot size formed at a plurality of pixel positions in the halftone image region. Temporary halftone image data indicating the arrangement of dots is generated (step S43). The temporary halftone image data is composed only of large dots. Specifically, “3” or “0” is assigned as a halftone pixel value to each pixel position of the provisional halftone image data, and “2” and “1” are not assigned.

  Next, the output control unit 41 controls the moving mechanism 2 and the ejection unit 3 based on the provisional halftone image data of the test image 94, whereby the third test chart 95b relating to the large dot size (see FIG. 21). ) Is recorded on the recording medium 9 (step S44). The target area 950b shown in FIG. 21 includes a plurality of chart unit areas 951 arranged in the moving direction described above. Each chart unit area 951 is a substantially rectangular tint image having a substantially uniform density.

  As described above, since the provisional halftone image data is composed of only large dots, only the large dots are recorded in the plurality of chart unit regions 951 in the target area 950b of the third test chart 95b that is recorded first. Is done. Specifically, in the provisional halftone image data, a large dot is formed at a pixel position where the halftone pixel value is “3”, and no dot is formed at a pixel position where the halftone pixel value is “0”.

  For example, in the chart unit region 951 on the most (−Y) side where the designated gradation value of the corresponding test unit region 941 is 26 (10%), an image is originally recorded with only small dots as shown in FIG. Since this is an area to be printed, no dot is recorded. Therefore, the density of the chart unit area 951 is naturally lower than the specification density related to the corresponding designated gradation value. The same applies to the second chart unit region 951 from the (−Y) side where the specified gradation value of the corresponding test unit region 941 is 51 (20%).

  In the third chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 102 (40%), the image is originally recorded only with small dots and medium dots. As a result, no dots are recorded. Accordingly, the density of the chart unit region 951 is naturally lower than the specification density related to the corresponding designated gradation value. The same applies to the fourth chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 153 (60%).

  In the fifth chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 204 (80%), the image is originally recorded with medium dots and large dots. Therefore, large dots are recorded on the recording medium 9, and medium dots are not recorded on the recording medium 9. Therefore, the density of the chart unit region 951 is lower than the specification density related to the corresponding designated gradation value.

  The chart unit area 951 on the most (+ Y) side where the designated gradation value of the corresponding test unit area 941 is 255 (100%) is an area where an image is originally recorded with only large dots. Therefore, the density of the chart unit area 951 is approximately equal to the specified density, which is an ideal density set for the corresponding designated gradation value.

  When the recording of the first third test chart 95b is completed, the correction information acquisition unit 433 causes the filter correction information corresponding to the large size that is the selected dot size to be the density in each of the plurality of chart unit regions 951 in the target region 950b. (Step S45). A specific method for obtaining the filter correction information is, for example, substantially the same as when the first test chart 95 is used. This makes it possible to acquire filter correction information used for highly accurate correction of the threshold matrix without being affected by variations in the size of dots in other dot sizes for a large size that is the selected dot size. it can.

  When step S45 ends, the matrix correction unit 434 corrects the large dot temporary matrix 833 corresponding to the large size that is the selected dot size using the filter correction information corresponding to the large size acquired in step S45. Is done. Thereby, a large dot matrix 813 which is a corrected halftone filter corresponding to a large size is generated (step S46). As a result, it is possible to provide a threshold value matrix that is corrected with high accuracy without being affected by variations in the size of dots in other dot sizes for a large size that is the selected dot size.

  Subsequently, the selected dot size is changed from the large size which is the maximum dot size to the medium size which is the second largest dot size (step S47). In other words, the medium size is selected as the new selected dot size. Further, the large size for which the filter correction information has already been acquired becomes the information acquired dot size.

  Next, in the temporary shading processing unit 432, a large dot matrix 813 (that is, a corrected halftone filter) corresponding to a large size which is the information acquired dot size, and a selected dot among the plurality of temporary threshold matrixes. The test image 94 is shaded using the medium dot temporary matrix 832 corresponding to the size. Thus, new provisional halftone image data indicating the arrangement of large dots and medium dots in the halftone image area is generated (step S48). The provisional halftone image data includes only large dots and medium dots. Specifically, “3”, “2”, or “0” is assigned as the halftone pixel value to each pixel position of the provisional halftone image data, and “1” is not added.

  When step S48 ends, the output control unit 41 controls the moving mechanism 2 and the discharge unit 3 based on the new provisional halftone image data generated in step S48, as shown in FIG. A new third test chart 95b relating to the medium size which is the new selected dot size is recorded on the recording medium 9 (step S49). Similar to the target area 950b shown in FIG. 21, the target area 950b of the third test chart 95b shown in FIG. 22 also includes a plurality of chart unit areas 951 arranged in the moving direction described above.

  As described above, the provisional halftone image data is composed only of large dots and medium dots, and therefore, in the target area 950b of the third test chart 95b recorded for the second time, the large number of chart unit areas 951 are large. Only dots and medium dots are recorded. Specifically, in the provisional halftone image data, a large dot is formed at a pixel position where the halftone pixel value is “3”, and a medium dot is formed at a pixel position where the halftone pixel value is “2”. . Further, no dot is formed at a pixel position where the halftone pixel value is “0”.

  For example, in the chart unit region 951 on the most (−Y) side where the designated gradation value of the corresponding test unit region 941 is 26 (10%), an image is originally recorded with only small dots as shown in FIG. Since this is an area to be printed, no dot is recorded. Therefore, the density of the chart unit area 951 is naturally lower than the specification density related to the corresponding designated gradation value. The same applies to the second chart unit region 951 from the (−Y) side where the specified gradation value of the corresponding test unit region 941 is 51 (20%).

  In the third chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 102 (40%), the image is originally recorded only with small dots and medium dots. Therefore, medium dots are recorded on the recording medium 9, and small dots are not recorded on the recording medium 9. Therefore, the density of the chart unit region 951 is lower than the specification density related to the corresponding designated gradation value. The same applies to the fourth chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 153 (60%).

  In the fifth chart unit region 951 from the (−Y) side where the designated gradation value of the corresponding test unit region 941 is 204 (80%), the image is originally recorded with medium dots and large dots. . Therefore, the density of the chart unit area 951 is approximately equal to the specified density, which is an ideal density set for the corresponding designated gradation value.

  The chart unit area 951 on the most (+ Y) side where the designated gradation value of the corresponding test unit area 941 is 255 (100%) is an area where an image is originally recorded with only large dots. Therefore, the density of the chart unit area 951 is approximately equal to the specified density, which is an ideal density set for the corresponding designated gradation value.

  When the recording of the third test chart 95b for the second time is completed, the correction information acquisition unit 433 causes the filter correction information corresponding to the medium size that is the selected dot size in each of the plurality of chart unit regions 951 of the target region 950b. Obtained based on the density (step S50). A specific method for obtaining the filter correction information is, for example, substantially the same as when the first test chart 95 is used. In this case, the target area 950b includes large dots in addition to the medium dots, but the density based on the large dots has been corrected based on the filter correction information acquired in step S45, and thus is the selected dot size. With respect to the medium size, it is possible to obtain filter correction information used for highly accurate correction of the threshold value matrix without being affected by variations in dot size and the like in other dot sizes.

  When step S50 ends, the matrix correction unit 434 uses the filter correction information corresponding to the medium size acquired in step S50 to correct the medium dot temporary matrix 832 corresponding to the medium size that is the selected dot size. Is done. As a result, a medium dot matrix 812 that is a corrected halftone filter corresponding to the medium size is generated (step S51). As a result, it is possible to provide a threshold matrix that is corrected with high accuracy without being affected by variations in the dot size of other dot sizes for the medium size that is the selected dot size.

  Subsequently, the process returns to step S47 (step S52), and the selected dot size is changed from the medium size which is the second largest dot size to the small size which is the third largest dot size (also the minimum dot size). (Step S47). In other words, a small size is selected as a new selected dot size. Further, the medium size for which the filter correction information has already been acquired becomes the information acquired dot size together with the large size.

  Next, in the temporary shading processing unit 432, the large dot matrix 813 and the medium dot matrix 812 (that is, the corrected halftone dot filter) corresponding to the large size and medium size which are information acquired dot sizes, and the above The test image 94 is shaded using the small dot temporary matrix 831 corresponding to the selected dot size among the plurality of temporary threshold value matrices. Thereby, new provisional halftone image data indicating the arrangement of large dots, medium dots and small dots in the halftone image region is generated (step S48). The provisional halftone image data includes large dots, medium dots, and small dots (that is, all the dots having the plurality of dot sizes). Specifically, “3”, “2”, “1”, or “0” is assigned to each pixel position of the provisional halftone image data as a halftone pixel value.

  When step S48 ends, the output control unit 41 controls the moving mechanism 2 and the discharge unit 3 based on the new provisional halftone image data generated in step S48, as shown in FIG. A new third test chart 95b relating to the small size which is the new selected dot size is recorded on the recording medium 9 (step S49). Similarly to the target area 950b shown in FIG. 21, the target area 950b of the third test chart 95b shown in FIG. 23 also includes a plurality of chart unit areas 951 arranged in the moving direction described above.

  As described above, the provisional halftone image data is composed of large dots, medium dots, and small dots. Therefore, the target area 950b of the third test chart 95b recorded for the third time includes a plurality of chart unit areas 951. Large dots, medium dots and small dots are recorded. Specifically, in the provisional halftone image data, a large dot is formed at a pixel position where the halftone pixel value is “3”, and a medium dot is formed at a pixel position where the halftone pixel value is “2”. . Further, a small dot is formed at a pixel position where the halftone pixel value is “1”, and no dot is formed at a pixel position where the halftone pixel value is “0”. Therefore, in the target area 950b of the third test chart 95b for the third time shown in FIG. 23, the density of each chart unit area 951 is a specified density that is an ideal density set for the corresponding designated gradation value. Is approximately equal to

  When the recording of the third test chart 95b for the third time is completed, the correction information acquisition unit 433 causes the filter correction information corresponding to the small size that is the selected dot size in each of the plurality of chart unit regions 951 of the target region 950b. Obtained based on the density (step S50). A specific method for obtaining the filter correction information is, for example, substantially the same as when the first test chart 95 is used. In this case, the target area 950b includes large dots and medium dots in addition to small dots, but the density of the large dots and medium dots is based on the filter correction information acquired in step S45 and the first step S50. Therefore, the filter correction information used for high-precision correction of the threshold matrix is not affected by variations in the dot size of other dot sizes for the small size that is the selected dot size. Can be acquired.

  When step S50 ends, the matrix correction unit 434 corrects the small dot temporary matrix 831 corresponding to the small size, which is the selected dot size, using the filter correction information corresponding to the small size acquired in step S50. Is done. Thereby, a small dot matrix 811 which is a corrected halftone filter corresponding to the small size is generated, and the generation of the matrix set in the halftone filter generation device 43 is completed (steps S51 and S52). As a result, it is possible to provide a threshold matrix that is corrected with high accuracy without being affected by variations in the size of dots in other dot sizes for a small size that is a selected dot size.

  Even when the third test chart 95b is used in the method shown in FIGS. 20A and 20B, the image recording apparatus 1 is the same as the case where the third test chart 95b is used in the method shown in FIGS. 17A and 17B. In FIG. 5, high-precision density correction can be performed for a plurality of dot sizes without being affected by other dot sizes. That is, the resolution for correcting the density of the image recorded on the recording medium 9 can be improved.

  When the third test chart 95b is used in the method shown in FIGS. 20A and 20B, in step S43 and the first step S48, the temporary threshold value matrix or the threshold value matrix and the test image 94 are set for some dot sizes. There is no need to perform comparison (ie, shading). For this reason, the generation of the matrix set can be simplified, and the time required to generate the matrix set can be shortened.

  Various modifications can be made in the halftone filter generation device 43 and the image recording device 1.

  As described above, in the test image 94 illustrated in FIG. 7, the designated gradation values of the plurality of test unit areas 941 are distributed from the maximum gradation value to the vicinity of the minimum gradation value. There is no need. For example, when the gradation value range that requires correction of the temporary threshold value matrix is a partial gradation range between the minimum gradation value and the maximum gradation value, the designated floors of the plurality of test unit regions 941 are designated. The tone value may be determined within the partial tone range.

  The halftone dot filter generation device 43 does not necessarily need to generate a threshold value matrix by correcting the temporary threshold value matrix for all of a plurality of dot sizes (that is, small size, medium size, and large size). For example, when there are variations in the dot size etc. in some dot sizes among the plurality of dot sizes and there are no variations in other dot sizes, the temporary threshold is set for the some dot sizes. The matrix may be corrected as described above to generate a threshold matrix, and other dot sizes may be sent to the shading processing unit 42 as a threshold matrix without correcting the temporary threshold matrix.

  For example, when there is a variation in dot size or the like only on small dots on the recording medium 9 and there is no variation on medium dots and large dots, steps S14 and S15 are performed only once, and for small dots. The temporary matrix 831 is corrected to generate a small dot matrix 811. In this case, in the first test chart 95 and the second test chart 95a, only the target areas 950 and 950a corresponding to the small size need be recorded. The intermediate dot temporary matrix 832 and the large dot temporary matrix 833 are sent to the shading processing unit 42 as the medium dot matrix 812 and the large dot matrix 813 without being corrected.

  In the image recording apparatus 1 illustrated in FIG. 1, the dot size of each color ink does not necessarily need to be three types of small size, medium size, and large size, and may be two types or four or more types. In the image recording apparatus 1, ink of color components other than black, cyan, magenta, and yellow may be used for dot recording. Further, the above-described halftone dot filter generation device 43 may be applied to an image recording device that records an image with only one color of ink.

  The threshold value matrix generated by the halftone dot filter generation device 43 is used for AM (Amplitude Modulated) screening that expresses gradation by changing the size of a cluster that is a set of regularly arranged dots. May be. In the halftone filter generation device 43, a corrected halftone filter other than the threshold matrix may be generated. For example, a corrected halftone dot filter may be generated by correcting a temporary halftone dot filter used for the shading process by the error diffusion method.

  In the image recording apparatus 1, if the recording medium 9 moves relative to the ejection unit 3 in the Y direction, for example, the ejection unit 3 is moved by the moving mechanism 2 above the stopped recording medium 9. You may move in the Y direction. The structure of the image recording apparatus 1 may be applied to, for example, an image recording apparatus that performs interlaced printing, or may be applied to an image recording apparatus that records an image on a long roll paper. The recording medium 9 may be a film or a thin metal plate other than printing paper.

  The halftone dot filter generation device 43 may be used in an image recording device other than an ink jet printer. For example, the halftone filter generator 43 may be used in an electrophotographic image recording apparatus. In this case, the light emitting unit that irradiates light to the photosensitive drum to form a latent image and the rotation mechanism that rotates the photosensitive drum are the dot output unit and the moving mechanism that relatively moves the dot recording position, respectively.

  The halftone filter generation device 43, for example, records an image on the printing plate by scanning the light beam emitted from the light source unit on the printing plate as a recording medium via a polygon mirror or the like. It may be used in the apparatus. In this case, the light source that emits the light beam serves as a dot output unit, and the polygon mirror or the like serves as a moving mechanism that moves the dot recording position on the printing plate relative to the printing plate.

  The halftone filter generation device 43 is a halftone dot filter used for halftone image data that generates halftone image data in which a plurality of dot sizes are mixed from a multi-tone original image, independently of the image recording device. It may be used as a generating device.

  The configurations in the above-described embodiments and modifications may be combined as appropriate as long as they do not contradict each other.

DESCRIPTION OF SYMBOLS 1 Image recording apparatus 2 Moving mechanism 3 Discharge unit 9 Recording medium 31 Head assembly 32 Discharge head 41 Output control part 42 Shading process part 43 Halftone filter production | generation apparatus 83 Temporary threshold matrix 94 Test image 95, 95a, 95b Test chart 431 Temporary Matrix storage unit 432 Shading processing unit 433 Correction information acquisition unit 434 Matrix correction unit 435 Repetition control unit 811 Small dot matrix 812 Medium dot matrix 813 Large dot matrix 831 Small dot temporary matrix 832 Medium dot temporary matrix 833 Large Temporary dot matrix 941 Test unit area 950, 950a, 950b Target area 951 Chart unit area 952 Divided area group 953 Divided areas S11-S17, S21-S33 Steps

Claims (29)

A dot output unit for recording dots whose size can be switched to a plurality of dot recording positions arranged along the width direction on the recording medium, and the plurality of dot recording positions on the recording medium intersect the width direction. In relation to halftone image data used for image recording in an image recording apparatus provided with a moving mechanism that moves relative to the recording medium in a moving direction, a plurality of dot sizes are mixed from an original image with multiple gradations A halftone dot filter generating device for generating a halftone dot filter used in the halftone processing for generating the halftone image data,
A temporary halftone dot filter storage unit that stores a plurality of temporary halftone dot filters that are obtained for each dot size based on the respective recording rates of the plurality of dot sizes and are used for image halftone processing;
Temporary halftone indicating the size of a plurality of dots respectively formed at a plurality of pixel positions arranged in a matrix in a halftone image area by performing a shading process of a test image using the plurality of temporary halftone dot filters A temporary shading processing unit for generating image data;
When a test chart is recorded on the recording medium based on the provisional halftone image data in which the plurality of dot sizes are mixed, one selected from the plurality of dot sizes in the provisional halftone image data Only a dot size dot is recorded in the target area of the test chart, and a correction information acquisition unit that acquires filter correction information corresponding to the one dot size from the target area;
Using the filter correction information, among the plurality of temporary halftone filters, a temporary halftone filter corresponding to the one dot size is corrected to generate a corrected halftone dot filter corresponding to the one dot size. A halftone filter correction unit;
A halftone dot filter generation apparatus comprising: A dot output unit for recording dots whose size can be switched to a plurality of dot recording positions arranged along the width direction on the recording medium, and the plurality of dot recording positions on the recording medium intersect the width direction. In relation to halftone image data used for image recording in an image recording apparatus provided with a moving mechanism that moves relative to the recording medium in a moving direction, a plurality of dot sizes are mixed from an original image with multiple gradations A halftone dot filter generating device for generating a halftone dot filter used in the halftone processing for generating the halftone image data,
A temporary halftone dot filter storage unit that stores a plurality of temporary halftone dot filters that are obtained for each dot size based on the respective recording rates of the plurality of dot sizes and are used for image halftone processing;
Temporary halftone indicating the size of a plurality of dots respectively formed at a plurality of pixel positions arranged in a matrix in a halftone image area by performing a shading process of a test image using the plurality of temporary halftone dot filters A temporary shading processing unit for generating image data;
When a test chart is recorded on the recording medium based on the provisional halftone image data in which the plurality of dot sizes are mixed, all the dots of the plurality of dot sizes in the provisional halftone image data are one dot. A correction information acquisition unit that acquires the filter correction information corresponding to the one dot size recorded from the target area after being converted into dots of a size and recorded in the target area of the test chart;
Using the filter correction information, among the plurality of temporary halftone filters, a temporary halftone filter corresponding to the one dot size is corrected to generate a corrected halftone dot filter corresponding to the one dot size. A halftone filter correction unit;
A halftone dot filter generation apparatus comprising: A halftone dot filter generation device according to claim 1 or 2,
By controlling the correction information acquisition unit and the halftone dot filter correction unit and changing the one dot size, by repeating the acquisition of the filter correction information and the generation of the corrected halftone dot filter, the plurality of dots A halftone dot filter generation apparatus, further comprising: an iterative control unit that acquires a plurality of pieces of filter correction information corresponding to sizes and generates a plurality of corrected halftone dot filters. The halftone filter generation device according to claim 1,
The temporary halftone processing unit changes the temporary halftone dot filter corresponding to the one dot size to the corrected halftone dot filter, performs a halftone process on the test image, and generates new temporary halftone image data And
When a test chart is recorded on the recording medium based on the new temporary halftone image data, only the dots of the one dot size and the new one dot size of the new temporary halftone image data Is recorded in the target area of the test chart,
The correction information acquisition unit acquires new filter correction information corresponding to the new one dot size from the target area,
The halftone dot filter correction unit corrects the temporary halftone dot filter corresponding to the new one dot size using the new filter correction information, and the corrected halftone dot corresponding to the new one dot size. A halftone dot filter generation apparatus characterized by generating a filter. The halftone filter generation device according to claim 4,
The halftone dot filter generating apparatus, wherein the new one dot size is larger than the one dot size. A dot output unit for recording dots whose size can be switched to a plurality of dot recording positions arranged along the width direction on the recording medium, and the plurality of dot recording positions on the recording medium intersect the width direction. In relation to halftone image data used for image recording in an image recording apparatus provided with a moving mechanism that moves relative to the recording medium in a moving direction, a plurality of dot sizes are mixed from an original image with multiple gradations A halftone dot filter generating device for generating a halftone dot filter used in the halftone processing for generating the halftone image data,
A temporary halftone dot filter storage unit that stores a plurality of temporary halftone dot filters that are obtained for each dot size based on the respective recording rates of the plurality of dot sizes and are used for image halftone processing;
A test image is shaded using a temporary dot filter corresponding to the maximum dot size among the plurality of temporary dot filters, and formed at a plurality of pixel positions arranged in a matrix in a halftone image region. A provisional halftone processing unit for generating provisional halftone image data indicating an arrangement of dots of the maximum dot size,
A correction information acquisition unit that acquires filter correction information corresponding to the maximum dot size from a target area of a test chart recorded on the recording medium based on the temporary halftone image data;
A halftone dot filter correction unit that corrects a temporary halftone dot filter corresponding to the maximum dot size using the filter correction information, and generates a corrected halftone dot filter corresponding to the maximum dot size;
With
The temporary halftone processing unit uses the corrected halftone dot filter corresponding to the maximum dot size and the temporary halftone dot filter corresponding to the second largest dot size among the plurality of dot sizes. Performing a shading process to generate new provisional halftone image data indicating an arrangement of dots of the maximum dot size and the second largest dot size in the halftone image region;
The correction information acquisition unit acquires filter correction information corresponding to the second largest dot size from a target area of a new test chart recorded on the recording medium based on the new temporary halftone image data. ,
The halftone dot filter correction unit corrects the temporary halftone filter corresponding to the second largest dot size by using the filter correction information corresponding to the second largest dot size, and the second largest A halftone dot filter generation apparatus for generating a corrected halftone dot filter corresponding to a dot size. The halftone dot filter generation device according to any one of claims 1 to 6,
The test image includes a plurality of test unit areas respectively corresponding to a plurality of specified gradation values,
The target area in the test chart includes a plurality of chart unit areas respectively recorded corresponding to the plurality of test unit areas,
The halftone dot filter generation device, wherein the correction information acquisition unit acquires the filter correction information corresponding to the one dot size based on the density in each of the plurality of chart unit regions. The halftone dot filter generation device according to claim 7,
The plurality of chart unit regions are arranged in the movement direction,
Each of the plurality of chart unit regions includes a plurality of divided regions arranged along the width direction;
A set of divided areas arranged in the movement direction in the plurality of chart unit areas as a divided area group,
The filter correction information corresponding to the one dot size includes a plurality of divided filter correction information corresponding to a plurality of divided region groups arranged along the width direction,
The halftone dot filter generation apparatus, wherein the correction information acquisition unit acquires division filter correction information corresponding to each divided region group based on the density of the plurality of chart unit regions in each divided region group. The halftone dot filter generation device according to claim 8,
The halftone dot filter generation device, wherein the dot output unit includes a plurality of divided output units arranged along the width direction and respectively corresponding to the plurality of divided region groups. The halftone dot filter generation device according to claim 8 or 9,
The correction information acquisition unit assigns each divided region group to each divided region group based on the relationship between the density of each chart unit region in each divided region group and the target density related to each designated gradation value corresponding to each chart unit region. Get the corresponding split filter correction information,
The halftone dot filter generating apparatus, wherein the target density is an average density of each chart unit area in two or more divided area groups adjacent in the width direction. A halftone dot filter generation device according to any one of claims 1 to 10,
A recording rate indicating a ratio of the number of dots of the one dot size to the total number of pixel positions defined to be recordable in the unit area on the recording medium by the correction of the temporary halftone filter by the halftone dot filter correcting unit. And a tone value-recording rate information indicating a relationship between the tone value and the tone value is corrected. A halftone dot filter generation device according to any one of claims 1 to 11,
The halftone dot filter generating apparatus, wherein the corrected halftone dot filter is a threshold value matrix. An image recording apparatus for recording an image on a recording medium,
A halftone dot filter generation device according to any one of claims 1 to 12,
A halftone image processing unit that performs halftone image data processing using the corrected halftone dot filter generated by the halftone dot filter generation device, and generates halftone image data;
A dot output unit for recording dots whose size can be switched to a plurality of dot recording positions arranged along the width direction on the recording medium;
A moving mechanism that moves the plurality of dot recording positions on the recording medium relative to the recording medium in a moving direction that intersects the width direction;
An output control unit that controls the dot output unit based on the halftone image data in parallel with the relative movement of the plurality of dot recording positions on the recording medium with respect to the recording medium;
An image recording apparatus comprising: The image recording apparatus according to claim 13, wherein
The dot output unit is controlled based on the halftone image data by the output control unit, and has a discharge unit that records dots by discharging micro droplets of ink to the plurality of dot recording positions on the recording medium. An image recording apparatus comprising: A dot output unit for recording dots whose size can be switched to a plurality of dot recording positions arranged along the width direction on the recording medium, and the plurality of dot recording positions on the recording medium intersect the width direction. A correction information acquisition method for acquiring correction information used for image density correction in an image recording apparatus comprising: a moving mechanism that moves relative to the recording medium in a moving direction;
a) It is obtained for each dot size based on the recording rate of each of a plurality of dot sizes, and is used for halftone image data for generating halftone image data in which the plurality of dot sizes are mixed from a multi-tone original image. Preparing a plurality of temporary halftone filters;
b) A test image is shaded using the plurality of temporary halftone filters, and temporary sizes indicating the sizes of a plurality of dots respectively formed at a plurality of pixel positions arranged in a matrix in the halftone image region are displayed. Generating halftone image data;
c) when a test chart is recorded on the recording medium based on the provisional halftone image data in which the plurality of dot sizes are mixed, selected from the plurality of dot sizes in the provisional halftone image data Only the dots of one dot size are recorded in the target area of the test chart, and obtaining the filter correction information corresponding to the one dot size from the target area;
A correction information acquisition method comprising: A dot output unit for recording dots whose size can be switched to a plurality of dot recording positions arranged along the width direction on the recording medium, and the plurality of dot recording positions on the recording medium intersect the width direction. A correction information acquisition method for acquiring correction information used for image density correction in an image recording apparatus comprising: a moving mechanism that moves relative to the recording medium in a moving direction;
a) It is obtained for each dot size based on the recording rate of each of a plurality of dot sizes, and is used for halftone image data for generating halftone image data in which the plurality of dot sizes are mixed from a multi-tone original image. Preparing a plurality of temporary halftone filters;
b) A test image is shaded using the plurality of temporary halftone filters, and temporary sizes indicating the sizes of a plurality of dots respectively formed at a plurality of pixel positions arranged in a matrix in the halftone image region are displayed. Generating halftone image data;
c) When a test chart is recorded on the recording medium based on the temporary halftone image data in which the plurality of dot sizes are mixed, all the dots of the plurality of dot sizes in the temporary halftone image data are A step of acquiring the filter correction information corresponding to the one dot size from the target area, after being converted into dots of the dot size and recorded in the target area of the test chart;
A correction information acquisition method comprising: The correction information acquisition method according to claim 15 or 16,
A correction information acquisition method, wherein a plurality of pieces of filter correction information respectively corresponding to the plurality of dot sizes are acquired by repeating the step c) while changing the one dot size. A dot output unit for recording dots whose size can be switched to a plurality of dot recording positions arranged along the width direction on the recording medium, and the plurality of dot recording positions on the recording medium intersect the width direction. In relation to halftone image data used for image recording in an image recording apparatus provided with a moving mechanism that moves relative to the recording medium in a moving direction, a plurality of dot sizes are mixed from an original image with multiple gradations A halftone filter generation method for generating a halftone filter used in a halftone process for generating the halftone image data,
The a) step to the c) step of the halftone filter generation method according to any one of claims 15 to 17,
d) After the step c), the temporary dot filter corresponding to the one dot size is corrected among the plurality of temporary dot filters using the filter correction information to obtain the one dot size. Generating a corresponding corrected halftone filter;
A halftone dot filter generation method comprising: A dot output unit for recording dots whose size can be switched to a plurality of dot recording positions arranged along the width direction on the recording medium, and the plurality of dot recording positions on the recording medium intersect the width direction. In relation to halftone image data used for image recording in an image recording apparatus provided with a moving mechanism that moves relative to the recording medium in a moving direction, a plurality of dot sizes are mixed from an original image with multiple gradations A halftone filter generation method for generating a halftone filter used in a halftone process for generating the halftone image data,
The a) step to the c) step of the halftone filter generation method according to claim 15,
d) After the step c), the correction halftone filter corresponding to the one dot size is corrected using the filter correction information to generate a corrected halftone dot filter corresponding to the one dot size. Process,
e) changing the temporary halftone dot filter corresponding to the one dot size to the corrected halftone dot filter and performing a shading process on the test image to generate new temporary halftone image data;
f) When a test chart is recorded on the recording medium based on the new temporary halftone image data, the one dot size and the new one dot size of the new temporary halftone image data Only the dots are recorded in the target area of the test chart, and obtaining new filter correction information corresponding to the new one dot size from the target area;
g) correcting the temporary halftone dot filter corresponding to the new one dot size using the new filter correction information to generate a corrected halftone dot filter corresponding to the new one dot size; ,
A halftone dot filter generation method comprising: The halftone dot filter generation method according to claim 19,
The halftone dot filter generation method, wherein the new one dot size is larger than the one dot size. A dot output unit for recording dots whose size can be switched to a plurality of dot recording positions arranged along the width direction on the recording medium, and the plurality of dot recording positions on the recording medium intersect the width direction. In relation to halftone image data used for image recording in an image recording apparatus provided with a moving mechanism that moves relative to the recording medium in a moving direction, a plurality of dot sizes are mixed from an original image with multiple gradations A halftone filter generation method for generating a halftone filter used in a halftone process for generating the halftone image data,
a) It is obtained for each dot size based on the recording rate of each of a plurality of dot sizes, and is used for halftone image data for generating halftone image data in which the plurality of dot sizes are mixed from a multi-tone original image. Preparing a plurality of temporary halftone filters;
b) The test image is shaded using a temporary dot filter corresponding to the maximum dot size among the plurality of temporary dot filters, and a plurality of pixel positions arranged in a matrix in the halftone image region Generating temporary halftone image data indicating an arrangement of dots of the maximum dot size to be formed;
c) obtaining filter correction information corresponding to the maximum dot size from a target area of a test chart recorded on the recording medium based on the temporary halftone image data;
d) correcting the provisional halftone filter corresponding to the maximum dot size using the filter correction information to generate a corrected halftone filter corresponding to the maximum dot size;
e) The test image is shaded using the corrected halftone dot filter corresponding to the maximum dot size and the temporary halftone dot filter corresponding to the second largest dot size among the plurality of temporary halftone dot filters. Performing a step of generating new temporary halftone image data indicating an arrangement of dots of the maximum dot size and the second largest dot size in the halftone image region;
f) obtaining filter correction information corresponding to the second largest dot size from a target area of a new test chart recorded on the recording medium based on the new provisional halftone image data;
g) Using the filter correction information obtained in the step f), the temporary halftone filter corresponding to the second largest dot size is corrected, and the corrected corresponding to the second largest dot size. Generating a halftone filter;
A halftone dot filter generation method comprising: The halftone dot filter generation method according to any one of claims 18 to 21,
The test image includes a plurality of test unit areas respectively corresponding to a plurality of specified gradation values,
The target area in the test chart includes a plurality of chart unit areas respectively recorded corresponding to the plurality of test unit areas,
In the step c), the halftone dot filter generation method is characterized in that the filter correction information corresponding to the one dot size is acquired based on the density in each of the plurality of chart unit regions. A halftone dot filter generation method according to claim 22,
The plurality of chart unit regions are arranged in the movement direction,
Each of the plurality of chart unit regions includes a plurality of divided regions arranged along the width direction;
A set of divided areas arranged in the movement direction in the plurality of chart unit areas as a divided area group,
The filter correction information corresponding to the one dot size includes a plurality of divided filter correction information corresponding to a plurality of divided region groups arranged along the width direction,
In the step c), the halftone filter generation method is characterized in that division filter correction information corresponding to each divided region group is acquired based on the density of the plurality of chart unit regions in each divided region group. A halftone dot filter generation method according to claim 23,
The dot output unit includes a plurality of divided output units arranged along the width direction and corresponding to the plurality of divided region groups, respectively. A halftone dot filter generation method according to claim 23 or 24,
In the step c), corresponding to each divided region group based on the relationship between the density of each chart unit region in each divided region group and the target density related to each designated gradation value corresponding to each chart unit region. Division filter correction information to be acquired,
The halftone filter generating method, wherein the target density is an average density of each chart unit area in two or more divided area groups adjacent in the width direction. A halftone dot filter generation method according to any one of claims 18 to 25,
A recording rate indicating the ratio of the number of dots of the one dot size to the total number of pixel positions defined as recordable in the unit area on the recording medium by the correction of the temporary halftone dot filter in the step d); A halftone filter generation method characterized by correcting gradation value-recording rate information indicating a relationship with a gradation value. A halftone filter generation method according to any one of claims 18 to 26,
A halftone dot filter generation method, wherein the corrected halftone dot filter is a threshold matrix. A dot output unit for recording dots whose size can be switched to a plurality of dot recording positions arranged along the width direction on the recording medium, and the plurality of dot recording positions on the recording medium intersect the width direction. In relation to halftone image data used for image recording in an image recording apparatus provided with a moving mechanism that moves relative to the recording medium in a moving direction, a plurality of dot sizes are mixed from an original image with multiple gradations A test chart used for generating a halftone filter used in a halftone process for generating the halftone image data,
Including a plurality of chart unit areas respectively corresponding to a plurality of specified gradation values,
In each chart unit area, only a dot having one dot size selected from the plurality of dot sizes scheduled to be recorded corresponding to each designated gradation value is recorded. A dot output unit for recording dots whose size can be switched to a plurality of dot recording positions arranged along the width direction on the recording medium, and the plurality of dot recording positions on the recording medium intersect the width direction. In relation to halftone image data used for image recording in an image recording apparatus provided with a moving mechanism that moves relative to the recording medium in a moving direction, a plurality of dot sizes are mixed from an original image with multiple gradations A test chart used for generating a halftone filter used in a halftone process for generating the halftone image data,
Including a plurality of chart unit areas respectively corresponding to a plurality of specified gradation values,
In each chart unit area, all the dots of the plurality of dot sizes scheduled to be recorded corresponding to each specified gradation value are recorded after being converted into one dot size dot. chart.

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