JP5402339B2 - Image forming apparatus and program - Google Patents

Description

  The present invention relates to an image forming apparatus and a program.

  2. Description of the Related Art Conventionally, a recording apparatus having a recording density unevenness correction function that detects density unevenness of a pattern formed by a recording head in which a plurality of recording elements are arranged and corrects density data for each recording element is known (for example, Patent Document 1). In this recording apparatus, the position detection pattern of the recording element is printed in association with the density unevenness detection pattern, and the density data of the density unevenness detection pattern and each recording element are based on the address position of the position detection pattern. It corresponds.

Japanese Patent No. 317849

  In the present invention, the position of the recording element corresponding to the position where the density unevenness is detected can be accurately determined regardless of the angle of view of the optical system, as compared with the case where marks corresponding to the positions of the recording elements are formed at equal intervals. It is an object to provide an image forming apparatus and a program that can be specified.

In order to achieve the above object, an image forming apparatus according to the first aspect of the present invention is configured such that a plurality of recording elements are arranged along a direction orthogonal to a conveyance direction of a recording medium, and the recording elements are arranged according to image information. image forming means for forming an image on the recording medium by driving, reading the image formed on the recording medium by said image forming means through the optical system, a reading means for outputting the read data, by said reading means The density in the reading area is gradually narrowed in the direction perpendicular to the transport direction from the position of the optical axis of the reading means relative to the recording medium to the periphery, and is arranged in the direction perpendicular to the transport direction Control means for controlling the image forming means so that a reference image having a plurality of patterns for detecting unevenness is formed, and reading the reference image by the reading means. Based on the obtained read data by the formed uneven density from the pattern when it is detected, the position of the recording element corresponding to the position where density unevenness is detected, perpendicular to the conveying direction of the pattern Specifying means for specifying based on the position of the recording element determined in advance corresponding to the end of the direction.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect of the present invention, the plurality of patterns are arranged with their positions in the transport direction being shifted with respect to adjacent patterns. together, the position of both end portions in the direction perpendicular to the conveying direction, overlap in a direction perpendicular to the ordered pattern next to the transport direction.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect of the invention, the plurality of patterns are based on read data obtained by reading the reference image with the reading unit. And an end position detecting means for detecting the position of each end portion in a direction perpendicular to the transport direction, and the specifying means is detected by the end position detecting means at the position where the density unevenness is detected. Based on the position of the end portion and the position of the recording element obtained in advance corresponding to the end portion, the position of the recording element corresponding to the position where the density unevenness is detected is specified.

According to a fourth aspect of the present invention, there is provided a program for a computer, wherein a plurality of recording elements are arranged along a direction orthogonal to a conveyance direction of a recording medium, and the recording elements are driven according to image information to the recording medium. An image formed on the recording medium by an image forming means for forming an image is read from an optical axis position of the reading means with respect to the recording medium in a reading area by the reading means for reading the read data through an optical system. A reference image having a plurality of patterns for detecting density unevenness arranged in a direction orthogonal to the transport direction is formed by gradually narrowing the width in the direction orthogonal to the transport direction as going to the periphery. The control means for controlling the image forming means and the reading data obtained by reading the reference image by the reading means When the density unevenness from the pattern is detected with the position of the recording element corresponding to the position where density unevenness is detected, obtained in advance corresponding to the end portion in the direction perpendicular to the conveying direction of the pattern This is a program that functions as specifying means for specifying based on the position of the recording element.

As described above, according to the image forming apparatus of the first aspect and the program of the fourth aspect , the image of the optical system is compared with the case where the marks corresponding to the positions of the recording elements are formed at equal intervals. Regardless of the angle, there is an effect that the position of the recording element corresponding to the position where the density unevenness is detected can be specified with high accuracy.

  In addition, according to the image forming apparatus of the second aspect, it is possible to accurately detect the density of the portion where the pattern is adjacent as compared with the case where a plurality of patterns are arranged without overlapping. .

  In addition, according to the image forming apparatus of the third aspect, the positions of the end portions of the plurality of patterns are detected as compared with a case where a plurality of patterns having the same narrow width as the peripheral pattern are formed. It is possible to shorten the time required for this.

  In addition, according to the image forming apparatus of the fifth aspect, the time required for detecting the positions of the plurality of marks can be shortened as compared with the case where a plurality of marks having the same center interval as the periphery are formed. The effect of being able to be obtained.

1 is a schematic diagram illustrating an overall configuration of a droplet discharge device according to a first embodiment of the present invention. It is a figure which shows arrangement | positioning of an optical sensor and an optical system. It is a block diagram which shows the principal part of the control system of the droplet discharge apparatus which concerns on the 1st Embodiment of this invention. It is a graph which shows the relationship between the angle of view of an optical system, and lateral magnification. It is a figure which shows an example of reading data. It is a figure which shows an example of a test pattern. It is a block diagram which shows the function structure of the image data process part of the droplet discharge apparatus which concerns on the 1st Embodiment of this invention. It is a flowchart which shows the density | concentration nonuniformity detection processing routine in the 1st Embodiment of this invention. It is a figure which shows an example of a test pattern. It is a flowchart which shows the density nonuniformity detection processing routine in the 2nd Embodiment of this invention. It is a block diagram which shows the function structure of the image data process part of the droplet discharge apparatus which concerns on the 3rd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Hereinafter, the case where the image forming apparatus of the present invention is applied to an ink jet type droplet discharge apparatus will be described.

  FIG. 1 is a schematic diagram showing the overall configuration of an ink jet type droplet discharge apparatus 10 according to a first embodiment.

  The droplet discharge device 10 includes a recording head array 12. The recording head array 12 includes a cyan ink liquid (C), a magenta ink liquid (M), a yellow ink liquid (Y), a black ink liquid (K), and a processing liquid (T). Correspondingly, five recording heads 14C, 14M, 14Y, 14K, and 14T are provided.

  The recording heads 14C, 14M, 14Y, 14K, and 14T are recording heads whose printing width is equal to or larger than the width of the recording area. The recording heads 14 </ b> C, 14 </ b> M, 14 </ b> Y, 14 </ b> K, and 14 </ b> T are fixed, and eject the respective ink droplets and processing droplets from the ejection nozzles onto the recording paper 16 that is being conveyed. An image is formed based on the data. The treatment liquid is colorless or light-colored, and the ink liquid of each color is dropped on the recording paper 16 and then dropped so as to overlap, thereby reducing ink bleeding and improving the image quality.

  The recording heads 14C, 14M, 14Y, 14K, and 14T are connected to the ink cartridges 18C, 18M, 18Y, 18K, and 18T respectively storing the CMYK ink liquid and the processing liquid through pipes (not shown), and the ink liquid and the processing liquid. Are supplied to the recording heads 14C, 14M, 14Y, 14K, and 14T. As the ink, various known inks such as water-based ink, oil-based ink, and solvent-based ink may be used.

  In addition, the droplet discharge device 10 includes a conveyance belt 19 that is an endless belt below the recording head array 12. The conveyor belt 19 is wound around the drive rolls 20A and 20B, and is driven to rotate in the A direction, which is the clockwise direction in FIG. 1, by the rotational force of the drive rolls 20A and 20B. The conveying belt 19 when facing the recording head array 12 is flat, and the recording paper 16 is conveyed to the flat area, and ink droplets are applied to the recording paper 16 from the recording heads 14C, 14M, 14Y, and 14K. As a result, an image is formed. At this time, the recording heads 14C, 14M, 14Y, and 14K discharge ink droplets from the discharge nozzles to the recording paper 16 with a time difference. As a result, the ink droplets of the respective colors are superimposed on the recording paper 16, and an image is formed.

  Further, the droplet discharge device 10 includes a charging roll 22 on the upstream side in the driving direction from the region of the conveying belt 19 facing the recording head array 12. A predetermined voltage is applied to the charging roll 22, and the charging roll 22 is driven while sandwiching the conveyance belt 19 and the recording paper 16 with the drive roll 20 </ b> A, thereby applying a charge to the recording paper 16. The recording paper 16 that has been charged by the charging roll 22 is electrostatically attracted to the transport belt 19 and is transported along with the circumferential drive of the transport belt 19.

  The recording paper 16 is accumulated in a paper feed tray 24 provided on the lower side inside the droplet discharge device 10. The recording paper 16 is taken out from the paper feed tray 24 one by one by the pick-up roll 26, and is transported to the transport belt 19 by the recording paper transport unit 30 having a plurality of transport rollers 28.

  A peeling plate 32 is disposed on the downstream side in the driving direction of the conveying belt 19 in FIG. 1 from the portion facing the recording head array 12. The peeling plate 32 peels the recording paper 16 from the transport belt 19. The recording paper 16 peeled off from the transport belt 19 is transported by a plurality of discharge rollers 36 constituting a discharge transport section 34 and is discharged to a paper discharge tray 38 provided at the upper part of the droplet discharge device 10.

  A cleaning roll 40 that sandwiches the conveyance belt 19 with the drive roll 20B is disposed on the downstream side in the rotation direction of the conveyance belt 19 in FIG. The cleaning roll 40 cleans the surface of the conveyor belt 19.

  Further, the recording paper 16 having an image formed on one side is conveyed again to the conveyance belt 19 by the reverse conveyance unit 44 constituted by a plurality of reverse rollers 42, and an image is formed on the other side. The reverse conveying unit 44 branches from the discharge conveying unit 34 and is arranged to convey the recording paper 16 to the recording paper conveying unit 30.

  An optical sensor 46 is disposed on the upstream side in the rotational direction from the position where the peeling plate 32 is disposed on the downstream side in the rotational direction of the conveyor belt 19 in FIG. 1 with respect to the portion facing the recording head array 12. The optical sensor 46 is composed of, for example, a CCD line sensor or a CCD area sensor, and reads, for example, a test pattern image for correcting the density of the ink ejected by the ejection nozzle at a predetermined reading resolution. In the present embodiment, as shown in FIG. 2, a lens (optical system) 71 is provided between the optical sensor 46 and a reading area having substantially the same width as the printing width of the recording head 14 of the recording paper 16 being conveyed. The light is emitted from the reading area of the conveyed recording paper 16 and is converged by the lens 71 and enters the light receiving surface of the optical sensor 46. When the recording paper 16 is conveyed, an image of the entire surface of the recording paper 16 is read by the optical sensor 46 through the lens 71. In addition, the lens 71 is arranged so that the position on the recording paper 16 that is conveyed passes through the optical axis of the lens 71 is the center position in the width direction of the recording paper 16.

  FIG. 3 is a diagram illustrating a main part of a control system of the droplet discharge device 10.

  The droplet discharge device 10 includes a CPU 50 that controls the entire droplet discharge device 10. The CPU 50 includes a ROM 52, a RAM 54, a hard disk storage device 56, an image data input unit 58, an operation display unit 60, an image formation control unit 62, an image data processing unit 64, an optical sensor 46, a control bus, a data bus, and the like. Connection is made via a bus 116.

  The ROM 52 stores a control program for controlling the droplet discharge device 10. The RAM 54 is used as a work space for processing various data. The hard disk storage device 56 stores image data, test pattern data for forming a test pattern image, various data relating to image formation, and the like. The hard disk storage device 56 stores nozzle characteristic data (such as a correction LUT described later) for each ejection nozzle.

  The image data input unit 58 receives input of image data from a personal computer (not shown). The input image data is transmitted to the hard disk storage device 56.

  The operation display unit 60 includes an operation button for a user to perform various operations in addition to a touch panel in which an operation function and a display function are integrated. The operation display unit 60 receives an operation such as start of image formation on the recording paper 16 and notifies the user of the control state of the droplet discharge device 10 and the like.

  The image forming control unit 62 forms heads on the recording paper 16 based on image data, a head driver 68 that drives the recording heads 14C, 14M, 14Y, 14K, and 14T, and various roll motors (not shown). The motor driver 70 and the like for driving are controlled.

  The image data processing unit 64 performs image processing such as ink density adjustment on the image data stored in the hard disk storage device 56. The image data processing unit 64 processes read data obtained by reading the test pattern with the optical sensor 46 and corrects the ink density of the image formed on the recording paper 16. A table (hereinafter referred to as “correction LUT”) is generated.

  Next, test patterns used in the first embodiment will be described. The density unevenness correction processing executed in the present embodiment is the same processing for each of the recording heads 14C, 14M, 14Y, 14K, and 14T. Therefore, hereinafter, a test pattern for one recording head 14 is used. Will be described.

  As shown in FIG. 4, due to the aberration of the lens 71, the lateral magnification increases as the angle of view with respect to the optical axis of the lens 71 increases, and the lateral magnification decreases at the end of the lens 71. That is, as the angle of view of the lens 71 with respect to the optical axis increases, the amount of change in lateral magnification corresponding to the aberration of the lens 71 increases. The relationship between the position of the data read through the lens 71 and the actual position of the reading area is distorted in the direction in which the ejection nozzles are arranged as the angle of view with respect to the optical axis of the lens 71 increases.

  As shown in FIG. 5, the actual width of the read data with respect to the same width of the read data differs between the vicinity a of the optical axis of the lens 71 and the peripheral portion b. For example, for a and b of the same width, a corresponds to 400 elements and b corresponds to 380 elements.

  Therefore, in this embodiment, as shown in FIG. 6, the test pattern 72 is configured by arranging a plurality of density patterns 74 for detecting density unevenness. The density pattern 74 is formed to have a width substantially the same as the print width of the recording head by arranging a plurality of divided patterns 76 in the discharge nozzle arrangement direction for each density pattern of different densities. In the divided pattern 76, the width in the arrangement direction of the discharge nozzles gradually decreases from the position where the optical axis of the lens 71 passes in the reading region to the periphery. The division patterns 76 are arranged so as to be shifted from the adjacent division patterns in the paper conveyance direction. In addition, the positions of both end portions of the divided pattern 76 in the arrangement direction of the discharge nozzles overlap with the adjacent divided pattern 76 in the arrangement direction of the discharge nozzles.

  The division pattern 76 is recorded by the ejection nozzle group corresponding to the range of the division pattern 76 of the recording head 14. Both ends (edges) of the divided pattern 76 are recorded by the discharge nozzles at both ends of the corresponding discharge nozzle group.

  Note that information indicating the number of discharge nozzles (discharge nozzle positions) from the left end of the recording head 14 is stored in the hard disk storage device 56 in advance in association with the discharge nozzles that record the edges at both ends of the divided pattern 76. .

  Each density pattern 74 is arranged at a predetermined interval in the paper conveyance direction, and is assigned a number from the top as density pattern 74 (1), density pattern 74 (2),... Density pattern 74 (n). To do. n is the number of steps of the density pattern, and is an arbitrary number, for example, 8 steps or 16 steps. Each density pattern 74 includes, for example, the density pattern 74 (1) as an input pixel value d1, the density pattern 74 (2) as an input pixel value d2,..., And the density pattern 74 (n) as an input pixel value dn. Furthermore, it corresponds to a predetermined input pixel value.

  When the image data processing unit 64 is represented by functional blocks, as shown in FIG. 7, a read image acquisition unit 80, an edge detection unit 82, a nozzle position correspondence determination unit 84, a density unevenness detection unit 86, a correction data generation unit 88, An input image acquisition unit 92, an image correction unit 94, and a test image generation unit 96 are provided.

  The read image acquisition unit 80 acquires read data obtained by reading the test pattern with the optical sensor 46. The edge detection unit 82 detects the positions of the edges at both ends of each divided pattern of the density pattern 74 of the test pattern 72 based on the read data representing the read test pattern. The nozzle position correspondence determination unit 84 determines the both ends of each divided pattern 76 of the density pattern 74 of the test pattern 72 represented by the read data based on the relationship between the edges of the both ends of each divided pattern obtained in advance and the positions of the ejection nozzles. The correspondence relationship between the position of the edge and the position of the discharge nozzle is determined.

  The density unevenness detection unit 86 inputs the input pixel value for each discharge nozzle based on each density pattern 74 of the test pattern 72 represented by the read data and the correspondence relationship between the positions of the edges at both ends of the divided pattern 76 and the positions of the discharge nozzles. The output density corresponding to n stages is measured, density unevenness is detected, and the discharge nozzle corresponding to the position where the density unevenness is detected is specified.

  The correction data generation unit 88 determines the output density of the discharge nozzle corresponding to the position where the uneven density is detected based on the discharge nozzle specified corresponding to the position where the uneven density is detected and the measured output density. Then, a correction lookup table (hereinafter referred to as “correction LUT”) for correcting the input pixel value to approximate the target density is generated. The correction data generation unit 88 outputs the generated correction LUT to the hard disk storage device 56 for storage.

  The input image acquisition unit 92 reads out and acquires the image data input by the image data input unit 58 from the hard disk storage device 56. The image correction unit 94 corrects the input pixel value of the image data using the correction LUT stored in the hard disk storage device 56. The image correction unit 94 outputs the corrected image data to the image formation control unit 62.

  The test image generator 96 generates image data representing the test pattern 72 based on the test pattern data stored in the hard disk storage device 56 and outputs the image data to the image formation controller 62.

  Next, the density unevenness detection processing routine in the first embodiment will be described with reference to FIG. When an instruction signal for instructing density unevenness correction is input, the CPU 50 executes the density unevenness correction program stored in the ROM 52 to start this routine.

  First, in step 100, a test pattern 72 is generated, and the test pattern 72 is formed on the recording paper 16 by the recording head array 12 and the image formation control unit 62. In step 101, when the recording paper 16 on which the test pattern 72 is formed is conveyed to the reading position of the optical sensor 46, the entire surface of the test pattern 72 formed on the recording paper 16 is detected by the optical sensor 46. The image is read and read data based on the test pattern 72 is output. In the next step 102, a variable R indicating the stage of the density pattern 74 is set to an initial value of 1, and a variable C for identifying the division pattern 76 (for example, a variable indicating the number from the left) is initialized. Set the value to 1.

  In step 104, the position of the right edge of the C-th divided pattern 76 from the left of the density pattern 74 (R) is detected. In step 106, the position of the left edge of the divided pattern 76 is detected.

  In the next step 108, it is determined whether or not the variable C is a constant C_MAX indicating the number of division patterns 76. If the variable C is not the constant C_MAX, the variable C is incremented in step 110, and the process returns to step 104 above. On the other hand, when the variable C reaches the constant C_MAX, it is determined that the edges of all the divided patterns 76 of the density pattern 74 (R) have been detected, and the process proceeds to step 112.

  In step 112, it is determined whether or not the variable R is a constant R_MAX indicating the number of steps of the density pattern 74. If the variable R is not the constant R_MAX, in step 114, the variable R is incremented, the variable C is set to 1, and the process returns to step 104. On the other hand, when the variable R reaches the constant R_MAX, it is determined that the edge of each divided pattern 76 has been detected for all density patterns 74 (R), and the process proceeds to step 116.

  In step 116, based on the correspondence relationship between the positions of the discharge nozzles obtained in advance and the edges of the divided patterns 76, the positions of the edges at the both ends of each divided pattern 76 detected in steps 104 and 106, and the discharge nozzles Find the correspondence with the position.

  In step 118, based on the test pattern 72 represented by the read data acquired in step 100 and the correspondence between the positions of the edges at both ends of each divided pattern 76 and the position of the discharge nozzle obtained in step 116. Then, the output density at the position of each discharge nozzle is measured. In the next step 120, density unevenness is detected based on the output density at the position of each discharge nozzle measured in step 118, and the position of the discharge nozzle corresponding to the position where the density unevenness is detected is specified.

  In step 122, a correction LUT is generated so that the output density at the position of the ejection nozzle corresponding to the position where the density unevenness specified in step 120 is detected, and the hard disk storage device 56 is generated. And the density unevenness detection processing routine is completed.

  When the droplet discharge device 10 receives input of image data from a personal computer or the like, the image data is temporarily stored in the hard disk storage device 56, and the image data is read from the hard disk storage device 56. Then, the input pixel value of the image data is converted into a converted pixel value by the correction LUT stored in the hard disk storage device 56, and the image data is corrected. Then, the recording heads 14C, 14M, 14Y, 14K, and 14T are driven based on the corrected image data, and an image based on the image data is formed on the recording paper 16.

  Next, a second embodiment will be described. Note that the configuration of the liquid droplet ejection apparatus according to the second embodiment is the same as that of the first embodiment, and therefore, the same reference numerals are given and description of the configuration is omitted.

  The second embodiment is different from the first embodiment in that the test pattern has a density pattern and a plurality of marks provided along the arrangement direction of the discharge nozzles.

  A test pattern used in the second embodiment will be described. The density unevenness correction processing executed in the present embodiment is the same processing for each of the recording heads 14C, 14M, 14Y, 14K, and 14T. Therefore, hereinafter, a test pattern for one recording head 14 is used. Will be described.

  As shown in FIG. 9, the test pattern 272 includes a plurality of density patterns 274 for detecting density unevenness, and a plurality of test patterns 272 that are formed for each density pattern 274 and serve as a reference when calculating the individual discharge nozzle positions. Mark 276.

  The density pattern 274 is formed in a band shape having a width that is the same as the print width of the recording head with respect to the ejection nozzle arrangement direction and a width that is predetermined with respect to the paper conveyance direction, for each density pattern with different densities. . Each density pattern 274 is arranged at a predetermined interval in the paper transport direction, and is assigned a number such as density pattern 274 (1), density pattern 274 (2), and density pattern 274 (3) from the top.

  The mark 276 divides the discharge nozzles of the recording head 14 into a plurality of groups, and is recorded by the first discharge nozzle (for example, the left end) in each discharge nozzle group. The mark 276 is a straight line having a predetermined length extending in the paper conveyance direction, and the interval in the arrangement direction of the discharge nozzles gradually decreases from the position where the optical axis of the lens 71 in the reading region passes to the periphery. Formed as follows. Further, the group of marks 276 arranged in the arrangement direction of the discharge nozzles is formed on the sheet conveyance direction side (upper side in FIG. 9) from each density pattern 274, respectively. The mark 276 includes a mark 276 (1), a mark 276 (2), a mark 276 (3) corresponding to the density pattern 274 (1), the density pattern 274 (2), and the density pattern 274 (3) from above. Give a number.

  Note that information indicating the number of discharge nozzles (discharge nozzle positions) from the left end of the recording head 14 is stored in the hard disk storage device 56 in advance in association with each other.

  The read image acquisition unit 80 of the image data processing unit 64 acquires read data obtained by reading the test pattern 272 with the optical sensor 46. The edge detection unit 82 detects the positions of the marks 276 formed on the upper side of the density patterns 274 of the test pattern 272 based on the read data representing the read test pattern 272. The nozzle position correspondence determining unit 84 determines the position of each mark 276 of the test pattern 272 represented by the read data and the position of the discharge nozzle based on the relationship between each mark 276 obtained in advance and the position of the discharge nozzle. Determine the correspondence.

  The density unevenness detection unit 86 has n stages corresponding to the input pixel values for each discharge nozzle based on the density patterns 274 of the test pattern 272 represented by the read data and the correspondence between the positions of the marks 276 and the discharge nozzles. The output density of the minute is measured to detect the density unevenness, and the discharge nozzle corresponding to the position where the density unevenness is detected is specified.

  The test image generator 96 generates image data representing the test pattern 272 and outputs the image data to the image formation controller 62.

  Next, the density unevenness detection processing routine in the second embodiment will be described with reference to FIG. In addition, about the process similar to 1st Embodiment, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  When an instruction signal for instructing density unevenness correction is input, the CPU 50 executes the density unevenness correction program stored in the ROM 52 to start this routine.

  First, in step 100, a test pattern 272 is generated, and the test pattern 272 is formed on the recording paper 16 by the recording head array 12 and the image formation control unit 62.

  In step 101, when the recording paper 16 on which the test pattern 272 is formed is conveyed to the reading position of the optical sensor 46, the entire surface of the test pattern 272 formed on the recording paper 16 is detected by the optical sensor 46. The image is read and read data based on the test pattern 272 is output. In the next step 200, a variable R indicating the stage of the density pattern 274 is set to 1 which is an initial value.

  In step 202, the positions of all marks 276 (R) above the density pattern 274 (R) are detected. In the next step 112, it is determined whether or not the variable R is a constant R_MAX indicating the number of steps of the density pattern 274. If the variable R is not the constant R_MAX, the variable R is incremented in step 204 and the process returns to step 202. On the other hand, when the variable R reaches the constant R_MAX, it is determined that the positions of all the marks 276 (R) corresponding to all the density patterns 274 (R) have been detected, and the process proceeds to step 206.

  In step 206, the correspondence between the position of each mark 276 detected in step 202 and the position of the discharge nozzle is obtained based on the correspondence between the position of the discharge nozzle and the mark 276 obtained in advance.

  In step 118, the position of each discharge nozzle is determined based on the test pattern 272 represented by the read data acquired in step 100 and the correspondence between the position of each mark 276 and the position of the discharge nozzle obtained in step 206. Measure the output density at. In the next step 120, density unevenness is detected based on the output density at the position of each discharge nozzle measured in step 118, and the position of the discharge nozzle corresponding to the position where the density unevenness is detected is specified.

  In step 122, a correction LUT is generated so that the output density at the position of the ejection nozzle corresponding to the position where the density unevenness specified in step 120 is detected, and the hard disk storage device 56 is generated. And the density unevenness detection processing routine is completed.

  Note that other configurations and operations of the droplet discharge device according to the second embodiment are the same as those of the first embodiment, and thus the description thereof is omitted.

  Next, a third embodiment will be described. In addition, about the part which becomes the structure similar to 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The third embodiment differs from the first embodiment in that the driving waveform of the head driver is corrected in order to correct the density unevenness.

  When the image data processing unit 364 of the droplet discharge device according to the third embodiment is represented by functional blocks, as shown in FIG. 11, a read image acquisition unit 80, an edge detection unit 82, and a nozzle position correspondence determination unit 84. , A density unevenness detection unit 86, a correction data generation unit 388, and a test image generation unit 96 are provided.

  The correction data generation unit 388 determines the output density of the discharge nozzle corresponding to the position where the density unevenness is detected based on the discharge nozzle specified corresponding to the position where the density unevenness is detected and the measured output density. Then, the ejection nozzle drive waveform corrected to approach the target density is generated. The correction data generation unit 388 sets the generated drive waveform in the head driver 68 via the image formation control unit 62.

  A drive waveform is generated and set in the head driver 68 by correcting the output density at the position of the discharge nozzle corresponding to the position where the specified density unevenness is detected by the density unevenness detection processing routine so as to approach the target density. To do.

  When the droplet discharge device 10 receives input of image data from a personal computer or the like, the droplet discharge device 10 is temporarily stored in the hard disk storage device 56, and the image data is read from the hard disk storage device 56. Based on the image data, the ejection nozzles of the recording heads 14C, 14M, 14Y, 14K, and 14T are driven by the head driver 68 using the corrected drive waveform, and an image based on the image data is displayed on the recording paper 16. It is formed.

  Note that other configurations and operations of the droplet discharge device according to the third embodiment are the same as those of the first embodiment, and thus the description thereof is omitted.

  In the first to third embodiments, the case where there is one optical system has been described as an example. However, the present invention is not limited to this, and there are two or more optical systems. May be. For example, each of two optical sensors arranged in the arrangement direction of the discharge nozzles may read through each of the two optical systems. In this case, the density pattern is divided according to the two optical systems, and the density pattern corresponding to each optical system is moved closer to the periphery from the optical axis position of the optical system in the reading region via the optical system. A plurality of divided patterns whose widths in the arrangement direction of the discharge nozzles are gradually narrowed may be arranged.

  Further, the case where the droplet discharge device forms an image (including characters) on the recording paper has been described as an example, but the recording medium is not limited to the recording paper, and the liquid to be discharged is ink. The present invention is not limited to the liquid, and is also applied to other liquid droplet ejection recording apparatuses such as a pattern forming apparatus that ejects liquid droplets onto a sheet-like substrate for pattern formation such as a semiconductor or a liquid crystal display. .

  Further, although the case where the image forming apparatus of the present invention is applied to a droplet discharge device has been described as an example, it may be applied to an LED printer or a thermal printer. An LED printer to which the present invention is applied has a plurality of light emitting elements arranged in a predetermined direction as recording elements, and emits an electrostatic latent image on a photosensitive member by causing the light emitting elements to emit light according to an input pixel value. It has an exposure part to be formed and a developing part for developing an electrostatic latent image formed on the exposure part to form an image. Then, by converting the input pixel value into the converted pixel value based on the correction LUT, the light emission amount for each light emitting element is changed, and the density of the image formed by the developing unit is corrected. A thermal printer to which the present invention is applied has a plurality of thermal heads arranged in a predetermined direction as recording elements, applies a voltage to the recording elements in accordance with an input pixel value, and records the recording elements on thermal paper. An image is formed by pressing. Then, by converting the input pixel value to the converted pixel value based on the correction LUT, the voltage applied to the recording element is changed, and the density of the formed image is corrected.

  In the specification of the present application, the embodiment has been described in which the program is installed in advance. However, the program may be provided by being stored in a storage medium such as a CDROM.

DESCRIPTION OF SYMBOLS 10 Droplet discharge device 12 Recording head array 14 Recording head 16 Recording paper 46 Optical sensor 56 Hard disk storage device 62 Image formation control part 64, 364 Image data processing part 72, 272 Test pattern 71 Lens 74, 274 Density pattern 76 Division pattern 80 Read image acquisition unit 82 Edge detection unit 84 Nozzle position correspondence determination unit 86 Density unevenness detection unit 88, 388 Correction data generation unit 94 Image correction unit 96 Test image generation unit 276 Mark

Claims (4)

A plurality of recording elements arranged along a direction orthogonal to the conveyance direction of the recording medium, and driving the recording elements according to image information to form an image on the recording medium ;
A reading unit that reads an image formed on the recording medium by the image forming unit via an optical system and outputs read data;
The width of the reading area by the reading means gradually narrows in the direction perpendicular to the transport direction from the position of the optical axis of the read means relative to the recording medium to the periphery, and in the direction perpendicular to the transport direction. Control means for controlling the image forming means so that a reference image having a plurality of patterns for detecting the arranged density unevenness is formed;
Based on the read data obtained by reading the reference image by the reading unit, when density unevenness is detected from the formed pattern, the position of the recording element corresponding to the position where the density unevenness is detected is determined. Specifying means for specifying based on the position of the recording element obtained in advance corresponding to the end of the pattern in the direction orthogonal to the transport direction ;
An image forming apparatus including: The plurality of patterns are arranged by shifting the positions in the transport direction with respect to the patterns arranged next to each other, and the positions of both end portions in the direction orthogonal to the transport direction are arranged next to the patterns The image forming apparatus according to claim 1, wherein the image forming apparatus overlaps in a direction orthogonal to the transport direction . Further comprising end position detecting means for detecting the positions of the end portions of each of the plurality of patterns in the direction orthogonal to the transport direction based on read data obtained by reading the reference image by the reading means. ,
The specifying means is based on the position where the density unevenness is detected, the position of the end detected by the end position detecting means, and the position of the recording element obtained in advance corresponding to the end. The image forming apparatus according to claim 1, wherein the position of the recording element corresponding to the position where the density unevenness is detected is specified. Computer
A plurality of recording elements are arranged along a direction perpendicular to the conveying direction of the recording medium, the image forming means for forming an image on the recording medium by driving the recording elements in accordance with image information is formed on the recording medium The width of the reading area by the reading means that reads the image through the optical system and outputs the read data in the direction orthogonal to the transport direction as it goes from the position of the optical axis of the reading means to the recording medium. Control means for controlling the image forming means so that a reference image having a plurality of patterns for detecting density unevenness that is gradually narrowed and arranged in a direction perpendicular to the transport direction is formed; and If density unevenness is detected from the formed pattern based on the read data obtained by reading the reference image with the reading means, the density unevenness is detected. The position of the recording element corresponding to the detected position is made to function as specifying means for specifying the position based on the position of the recording element obtained in advance corresponding to the end of the pattern in the direction orthogonal to the transport direction . program.