JP4564979B2 - Data processing apparatus, recording apparatus, and mask pattern manufacturing method - Google Patents

Description

  The present invention relates to a data processing apparatus, a recording apparatus, and a mask pattern manufacturing method. More specifically, the present invention relates to a process of converting image data into dot data using a dot arrangement pattern and dividing the dot data into dot data used for each of a plurality of scans of a print head using a mask.

  With the recent spread of information processing equipment such as personal computers, recording devices as image forming terminals have rapidly developed and become popular. In particular, among various recording apparatuses, an ink jet recording apparatus that performs recording on a recording medium such as paper, cloth, a plastic sheet, and an OHP sheet by ejecting ink from an ejection port is becoming a mainstream for personal use. This is a non-impact recording system with low noise, high-density and high-speed recording operation, easy compatibility with color recording, and low cost. Because it is.

  Advances in ink jet recording technology have promoted higher image quality, higher speed, and lower cost of recording, thereby contributing to the spread of recording devices to personal users. The spread of personal computers and digital cameras also contributes to the spread of recording devices. This digital camera includes not only a single camera that fulfills its function, but also a device that is integrated with another device, such as a mobile phone. However, with such widespread use, personal users are required to further improve image quality. In particular, in recent years, there has been a demand for a printing system that allows easy printing of photos at home and image quality suitable for silver halide photography.

  When compared with a silver salt photograph, the graininess is conventionally regarded as a problem in the ink jet recording apparatus. Various measures for reducing the graininess have been proposed. For example, an ink jet recording apparatus is known that includes an ink system in which light cyan or light magenta having a lower colorant density is added to normal cyan, magenta, yellow, and black. In such an apparatus, the graininess is reduced by using light cyan or light magenta ink in a low image density region. Further, in a region where the image density is high, recording using ordinary cyan ink or magenta ink makes it possible to realize a wider color reproduction range and smooth gradation.

  There is also a method for reducing graininess by designing the size of dots formed on a recording medium to be smaller. This is generally realized by reducing the amount of ink droplets ejected from the ejection port of the recording head. In this case, it is possible not only to reduce the amount of ink droplets but also to form a higher resolution image without lowering the recording speed by configuring more ejection openings with a higher arrangement density.

  By the way, many methods have been proposed for so-called binarization processing in which multi-value data representing an image to be recorded is converted into binary data indicating whether or not to form dots on a recording medium by ejecting ink droplets. ing. Among these, for example, the binarization process is first performed in a two-stage configuration in which a quantization process for reducing the level of the number of gradations to several stages is performed, and final quantization is performed on the quantized data. Many recording devices have been provided in recent years. In this case, since one pixel output from the host device is expressed by gradation using a plurality of levels of density, it can be said that this method is suitable for applications in which gradation is important, such as photographic image quality. This also allows the data processing burden to be divided into two steps or processes. As a result, even if the amount of data to be processed increases due to an increase in recording resolution and ink color type, the processing speed decreases. It is also possible to suppress this.

  Several methods for converting data once quantized into multilevel data at several levels into binary data have been proposed and implemented. For example, Patent Document 1 uses a dot arrangement pattern in which recording / non-recording of four dots is defined for each 2 × 2 area for one input pixel that can have five gradation values. Describes a method of binarization. In the same document, a plurality of dot arrangement patterns for each 2 × 2 area are prepared for the same gradation value, and the plurality of dot arrangement patterns are used sequentially or randomly. A method is also described. According to this, the dot arrangement pattern for each gradation is not fixed, and it is possible to reduce the so-called “break-off phenomenon” that appears in the pseudo contour or the edge portion of the image. Further, the use of a plurality of recording elements provided in the recording head can be averaged.

  Patent Document 2 uses a recording head having two ejection port arrays having different characteristics while ejecting ink droplets of the same color, and uses these two ejection port arrays. It is described that the recording time is shortened by adopting a method (column thinning) for switching between recording / non-recording every time. Furthermore, it is also disclosed that a plurality of dot arrangement patterns having different dot arrangements for the same gradation value are periodically arranged corresponding to each of various harmful effects.

  By the way, in an inkjet recording apparatus, particularly a serial type inkjet recording apparatus for personal users, a recording method called multi-pass recording is often employed.

  FIG. 1 is a diagram for explaining multi-pass printing, and schematically shows a print pattern by a print head and its scanning. Reference numeral 1001 denotes a recording head, which is shown here as having 16 nozzles (discharge ports) for the sake of simplicity. The 16 nozzles are divided into first to fourth nozzle groups, and each nozzle group includes four nozzles. Reference numeral 1002 denotes a mask pattern. Pixels that can be recorded by each nozzle in the pattern (printable pixels; that is, an area of mask data in which data “1” to be ejected is output without masking the data) Is shown in black. The patterns corresponding to the four nozzle groups are complementary to each other. When these patterns are overlapped, the recording of the area corresponding to the 4 × 4 pixels can be completed.

  Each pattern indicated by reference numerals 1003 to 1006 indicates a state in which an image is completed by overlapping recording scans. When each recording scan is completed, the recording medium is conveyed by the width of the nozzle group in the direction of the arrow in the figure. In this way, the image recording is completed in the same area of the recording medium (area corresponding to the width of each nozzle group) by four recording scans.

  In an inkjet recording head, it is difficult to avoid slight variations in the direction and amount of ink ejected between a plurality of nozzles due to the manufacture thereof. Further, in a serial type recording apparatus, the paper feed amount performed between each recording scan may include a structural error. Such variations and errors cause image defects such as streaks and density unevenness when ink is ejected onto a recording medium. However, by adopting multi-pass printing as described above, this image adverse effect can be reduced. Even if there is a variation in the ejection characteristics and the transport amount of each nozzle, these variations are distributed over a plurality of scans, and streaks and density unevenness are not noticeable. FIG. 1 shows an example of 4-pass printing in which the same image area is scanned four times, but multi-pass printing is not limited to this. Two-pass printing in which an image is completed by two recording scans or an image may be completed by five or more recording scans.

  In multi-pass printing, by devising the arrangement of the mask pattern, the number of dots printed in each printing scan can be adjusted, and the frequency of nozzles that are likely to cause problems can be reduced. That is, in addition to eliminating the streaks and density unevenness, it is possible to adopt forms according to various purposes. For example, Patent Document 3 describes an arrangement pattern of print permitting pixels in a mask having excellent dispersibility. In multi-pass printing, it is known that when the printing position of one scan deviates from the normal position determined with respect to the printing position of another scan, the pattern (texture) of the printable pixel of the applied mask pattern is visible. Yes. According to the mask pattern described in Patent Document 3, even in such a case, a visually preferable pattern having excellent dispersibility is used. Therefore, the same texture as the mask pattern is not visually obstructive, that is, is not easily noticeable. And the influence on the image quality is suppressed.

  By the way, when multi-pass printing is performed using dot data binarized by the dot arrangement pattern described in Patent Document 1 or Patent Document 2, density unevenness may occur depending on the recorded image, or the pattern of the mask pattern may be textured. There is a problem of appearing.

  FIG. 2 shows a process for creating dot data for each of two scans using image data binarized by a dot arrangement pattern using a mask. In the figure, the pattern (a) shows four input pixels binarized by the dot arrangement pattern by the dot arrangement pattern itself used for the binarization. One dot arrangement pattern composed of 4 × 2 pixels represents one gradation value depending on the number of arranged dots. In the example shown in the figure, four dot arrangement patterns having the same gradation value (five dots) are shown, and it is shown that these are constituted by two types of dot arrangement patterns 401 and 402.

  When mask processing is performed on the recorded image indicated by this dot arrangement pattern using the two-pass multi-pass masks (b) and (c), the dot patterns formed in the respective scans are respectively Patterns (d) and (e) are obtained. As can be seen from this figure, the formed dots are biased toward one scan, and density unevenness may occur in the completed image. This is because the dot arrangement pattern and the mask pattern constituting the recording image are synchronized or interfere with each other. Further, if there is such interference, the effect of reducing variations and streaks due to multi-pass recording cannot be fully exhibited.

  Japanese Patent Application Laid-Open No. 2004-228561 discloses one countermeasure for the same problem. In this document, in order to distribute dots almost evenly for each of a plurality of scans that complete an image, the same that does not synchronize with the arrangement of specific gradation values of a dot arrangement as a binary image obtained by the area gradation method It describes that dots are thinned out using a duty thinning pattern. This suppresses interference between the dot arrangement pattern constituting the image and the mask pattern, thereby preventing the dots from being distributed unevenly in a certain scan.

JP-A-9-46522 JP 2002-29097 A JP 2002-144552 A JP-A-5-031922

  However, although the configuration for suppressing interference described in Patent Document 4 can make the number of dots formed in each of a plurality of scans equal, it is formed in each of the plurality of scans. It does not consider the relationship between the arrangement of dots. For this reason, for example, the pattern of dots to be formed has a certain geometric shape, which may cause lines or the like to be noticeable.

  In this regard, as described above, Patent Document 3 discloses a mask pattern that increases the dispersibility of dot arrangement by mask processing. That is, a mask pattern in which the above-described streaks are not conspicuous is disclosed. However, the mask pattern described in Patent Document 3 does not consider the dot arrangement of image data processed by the mask. That is, only the dispersion between the print permitting pixels in the mask is considered. For this reason, particularly when the image to be masked has a certain dot arrangement pattern as described in Patent Document 1 or Patent Document 2, the influence of the dot arrangement pattern is affected by a plurality of scans. It may appear. In that case, although it is possible to obtain a dispersed dot arrangement according to the mask in each scan, it is difficult to realize an even arrangement of the number of dots between scans.

  Furthermore, in the configuration of Patent Document 4, when the gradation of the image is expressed in a simple unit of pixels, for example, 4 × 4 pixels, the mask pattern is asynchronous with the dot arrangement of the image. Is easy to form. However, when gradations are expressed in units of a relatively large number of pixels, the types of dot arrangements increase accordingly, making it difficult to form an asynchronous mask pattern. Further, when there are a plurality of types of patterns for expressing the same duty, it is difficult to cope with the method described in Patent Document 4.

  An object of the present invention is to provide a data processing apparatus, a recording apparatus, and a mask manufacturing method that reduce the interference between a dot arrangement pattern and a mask pattern that processes the dot arrangement pattern and improve the dispersibility of the dot arrangement using the mask. It is in.

Therefore, in the present invention, mask processing is performed on binary image data representing an image to be recorded in the same area of the recording medium using a plurality of mask patterns corresponding to a plurality of scans of the recording head for the same area. the row Ukoto, wherein a plurality of data processing apparatus for generating a thinned-out binary image data representing a thinned image to be recorded by scanning each, one other than the last scan of the plurality of scans Obtained by the logical product of the data indicating the print allowable pixels in the mask pattern corresponding to the scan of the image and the data indicating the print dots in the dot arrangement pattern used in the binarization process for generating the binary image data. The characteristic of the logical product pattern satisfies the following (a) and (b). Here, (a) represents the frequency components in the low frequency range in the logical product pattern is less than the frequency components of the high frequency range, that characteristic, (b) is from the low frequency half of the low frequency range area This is a characteristic that there is no frequency component peak.

In another embodiment, the binary image data representing an image to be recorded in the same area of the recording medium is subjected to mask processing using a plurality of mask patterns corresponding to a plurality of scans of the recording head for the same area. Thus , a data processing device for generating binary thinned image data representing a thinned image to be recorded in each of the plurality of scans, wherein the data processing device performs one time other than the last scan of the plurality of scans. Logic obtained by logical product of data indicating print allowable pixels in a mask pattern corresponding to scanning and data indicating print dots in a dot arrangement pattern used in the binarization processing for generating the binary image data The characteristics of the product pattern satisfy the following (a) and (b). Here, (a) represents the frequency components in the low frequency range in the logical product pattern is less than the frequency components of the high frequency range, that characteristic, (b) is to a lower frequency than 1/4 of the low frequency range This is a characteristic that there is no frequency component peak in a certain region.

In still another embodiment, mask processing is performed on binary image data representing an image to be recorded in the same area of the recording medium using a plurality of mask patterns corresponding to a plurality of scans of the recording head for the same area. the row Ukoto, wherein a plurality of data processing apparatus for generating a thinned-out binary image data representing a thinned image to be recorded by scanning each, one other than the last scan of the plurality of scans Obtained by the logical product of the data indicating the print allowable pixels in the mask pattern corresponding to the scan of the image and the data indicating the print dots in the dot arrangement pattern used in the binarization process for generating the binary image data. The characteristic of the logical product pattern satisfies the following (a) and (b). Here, (a) represents the frequency components in the low frequency region in the logical product pattern is less than the frequency components of the high frequency range, that characteristic, (b) does not exist peak frequency components in the low frequency range, It is a characteristic.

In still another embodiment, binarization means for performing binarization processing for converting multivalued image data having gradation values into binary image data, and the binary obtained by the binarization means In order to generate binary thinned-out image data used for each of the plurality of scans of the recording head from the image data, a plurality of mask patterns corresponding to the plurality of scans are applied to the binary image data. using a mask processing unit for performing mask processing and, the data representing the print permitting pixels in a mask pattern corresponding to the first scan of the plurality of scans, can be used in the binarization logical product patterns obtained by the logical product of the data indicating the recording dots in the dot arrangement pattern corresponding to one gradation values of a plurality of dot arrangement patterns corresponding respectively such a plurality of gradation values Properties and satisfies the following (a) and (b). Here, (a) represents the frequency components in the low frequency range in the logical product pattern is less than the frequency components of the high frequency range, that characteristic, (b) is to a lower frequency than 1/4 of the low frequency range This is a characteristic that there is no frequency component peak in a certain region.

Further, binary thinning representing a thinned image to be recorded in one scan of a plurality of scans of the recording head for the same region from binary image data representing an image to be recorded in the same region of the recording medium. a method of manufacturing a mask pattern used to generate the image data has a determination step of determining an arrangement of print permitting pixels in the mask pattern, said determining step, data indicating the print permitting pixels in the mask pattern And data indicating dot arrangement determined based on a plurality of dot arrangement patterns corresponding to a plurality of gradation levels usable in the binarization processing for generating the binary image data. as the low frequency components of the resulting logical product pattern is reduced, the serial in the mask pattern based on the plurality of dot arrangement patterns Characterized in that it comprises a change step of Ru by changing the arrangement of the permitted pixels.

In another embodiment, 2 representing a thinned image to be recorded in one scan of a plurality of scans of the recording head for the same region from binary image data representing an image to be recorded in the same region of the recording medium. A mask pattern manufacturing method used for generating thinned-out image data, and a plurality of gradation levels corresponding to a plurality of gradation levels usable in binarization processing for generating the binary image data A determination step of determining an arrangement of print-allowable pixels in the mask pattern based on a dot arrangement pattern, wherein the determination step includes a first step of setting the arrangement of the print-allowable pixels as a first arrangement; Based on the plurality of dot arrangement patterns, the arrangement of the print permitting pixels is changed from the first arrangement to the second arrangement so that low frequency components in the pixel arrangement pattern are reduced. Characterized in that it comprises a second step of reduction.

Further, in the mask pattern manufacturing method, the first binary image data representing an image to be recorded in the same area of the recording medium by the first nozzle group for ejecting the first color ink is used. Print-allowable pixels in the first mask pattern used to generate binary thinned-out image data representing a thinned image to be printed in one scan of a plurality of scans of the first nozzle group for the same region A first determination step for determining the arrangement of the second and second images representing an image to be recorded in the same area of the recording medium by a second nozzle group for ejecting ink of a second color different from the first color. Used to generate binary thinned image data representing a thinned image to be recorded in one of a plurality of scans of the second nozzle group with respect to the same region. A second determining step for determining the arrangement of the print permitting pixels in the second mask pattern, and the first determining step can be used in a binarization process for generating the first binary image data. Data indicating recording dots in the first dot arrangement pattern corresponding to one gradation value among a plurality of dot arrangement patterns respectively corresponding to a plurality of gradation values, and recording allowable pixels in the first mask pattern Print permitting in the first mask pattern based on the first dot arrangement pattern and the second mask pattern so that the low frequency component of the logical product pattern obtained by the logical product of A step of changing a pixel arrangement, wherein the second determination step includes a plurality of levels usable in the binarization processing for generating the second binary image data. A logical product obtained by a logical product of data indicating a recording dot in the second dot arrangement pattern among a plurality of dot arrangement patterns corresponding to each value and data indicating a print allowable pixel in the second mask pattern Including a step of changing the arrangement of print permitting pixels in the second mask pattern based on the second dot arrangement pattern and the first mask pattern so that the low frequency component of the pattern is reduced. To do.

  The arrangement of the print-allowable pixels of the mask pattern used in the mask processing of the present invention is manufactured in consideration of the overlap (logical product) with the dot pattern. That is, the distribution of the print-allowable pixels in the mask pattern when overlapped with the dot pattern is well dispersed with few low frequency components. Therefore, the dot data for each scan generated by the mask process is well distributed within a certain area without the number of the scan being biased to a specific scan. The good dispersibility suppresses the influence on the image quality because the texture that may be caused by various factors is hardly visually disturbed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 3 is a block diagram mainly showing hardware and software configurations of a personal computer (hereinafter also simply referred to as a PC) as an image processing apparatus according to an embodiment of the present invention.

  In FIG. 3, a PC 3000 that is a host computer operates application software 3001, a printer driver 3003, and a monitor driver 3005 by an operating system (OS) 3002. The application software 3001 performs processing related to a word processor, spreadsheet, Internet browser, and the like. The monitor driver 3005 executes processing such as creating image data to be displayed on the monitor 3006.

  The printer driver 3003 draws various drawing command groups (image drawing command, text drawing command, graphics drawing command, etc.) issued from the application software 3001 to the OS 3002, and finally generates image data used by the printer 3004. Specifically, by executing image processing described later in FIG. 4 and later, five values are obtained for each of the cyan (C), magenta (M), yellow (Y), and black (K) color components of the ink used in the printer 3004. Generate index data for. The printer 3004 outputs a dot arrangement pattern corresponding to each of the five values (levels) based on the index data.

  The host computer 3000 includes a CPU 3008, a hard disk (HD) 3007, a RAM 3009, a ROM 3010, and the like as various hardware for operating the above software. That is, the CPU 3008 executes the process in accordance with the software program stored in the hard disk 3007 or the ROM 3010, and the RAM 3009 is used as a work area when the process is executed.

  A printer 3004 as a recording apparatus is a so-called serial type printer that performs recording by scanning a recording medium for ejecting ink with respect to a recording medium and ejecting ink during that time. The recording head is prepared corresponding to each of the C, M, Y, and K inks, and can be scanned with respect to a recording medium such as a recording sheet by being mounted on the carriage. Each recording head has an ejection port array density of 1200 dpi, and ejects 2 picoliter (pl) of ink droplets from each ejection port. Further, the number of ejection ports of each recording head is 512. The multi-pass recording method of this embodiment performs recording of the number of passes according to each embodiment described later.

  FIG. 4 is a block diagram illustrating the flow of image data conversion processing in the recording system of the present embodiment. As described above with reference to FIG. 3, the printer (recording apparatus) according to the present embodiment includes the respective recording heads J0010 for ejecting four colors of C, M, Y, and K. Each process shown in FIG. 4 is executed by a printer and a personal computer (PC) as a host device.

  The application J0001 executes processing for creating image data to be recorded by the printer. When recording, image data created by the application is passed to the printer driver. The printer driver includes pre-processing J0002, post-processing J0003, γ correction J0004, halftoning J0005, and print data creation J0006 as processing. Below, each process is demonstrated easily.

  The pre-stage process J0002 performs color gamut mapping. This process performs data conversion for mapping the color gamut reproduced by the image data R, G, B of the sRGB standard into the color gamut reproduced by the printer. Specifically, by using a three-dimensional LUT (look-up table), data of 256 gradations in which each of R, G, and B is represented by 8 bits is used, so that each of R, G, Convert to B data.

  The post-stage processing J0003 obtains 8-bit color separation data Y, M, and C, which are combinations of inks that reproduce the colors represented by the data, based on the R, G, and B data on which the color gamut is mapped. Here, as in the previous process, conversion is performed using a three-dimensional LUT together with an interpolation operation.

  The γ correction J0004 performs density value (gradation value) conversion for each color component of the color separation data obtained by the post-processing J0003. Specifically, conversion is performed using a one-dimensional LUT so that the color separation data is linearly associated with the gradation characteristics of the printer.

  Halftoning J0005 performs quantization on each of the 8-bit color separation data Y, M, and C, and quantizes the data into 4-bit data. In the present embodiment, 256-bit 8-bit data is converted into 4-bit data representing 5 gradations using a multi-level error diffusion method. The 4-bit data is gradation value information that serves as an index for conversion processing to a dot arrangement pattern, which is binarization processing in the printer.

  The print data creation process J0006 creates print data by adding print control information to the print image information containing the 4-bit index data.

  When the print data is sent to the printer by the above processing by the host device, the printer performs dot arrangement patterning processing J0007 and mask data conversion processing J0008 on the input print data.

  The dot arrangement patterning process J0007 performs a binarization process by outputting a dot arrangement pattern based on five-valued index data. As a result, binary information indicating whether or not to eject ink, which is used when the printer performs recording, can be obtained.

  FIG. 5 is a diagram showing a dot arrangement pattern according to the present embodiment corresponding to five-value index data. The dot arrangement pattern is determined for each of the five values of gradation level 0 to gradation level 4 indicated by the index data of C, M, Y, and K.

  The 2 × 2 output pixel composed of two vertical pixels and two horizontal pixels shown in the figure corresponds to one input pixel output by halftone processing, and this input pixel is 600 dpi (dots in both vertical and horizontal directions). / Inch) is a size corresponding to the pixel density. Each of the plurality of pixels constituting one input pixel is an area where dot recording / non-recording (ink ejection / non-ejection) is defined. An area filled with “black” indicates a pixel in which dot recording is allowed (recording allowable pixel), and a “white” area indicates a pixel in which dot recording is not allowed (non-recording allowable pixel). Then, the number of print permitting pixels in which dot printing is defined is determined according to any value of level 0 to level 4 indicated by the index data.

  One pixel of these dot arrangement patterns corresponds to a recording density of 1200 dpi in the vertical direction and 1200 dpi in the horizontal direction in the printer of this embodiment. That is, the printer according to the present embodiment has a specification in which one dot is formed by ejecting 2 pl of ink droplets one by one from the recording head of each color to one pixel of about 20 μm in length and about 10 μm in width. ing. The dot arrangement patterning process J0007 performs a process of binarizing the quinary data using the above dot arrangement pattern, and “1” or “0” 1 for the ejection port corresponding to each area and the recording column. Bit discharge data is generated.

  When actual dot arrangement patterning processing is performed, as will be described later with reference to FIG. 11 and the like, 2 × 2 in which the positions of the “black” areas in the dot arrangement patterns at the respective gradation levels shown in FIG. This pattern is applied according to the position and level of the input pixel.

  Next, the mask data conversion process J0008 performs a mask process on the dot arrangement of each color determined by the dot arrangement patterning process J0007 using a plurality of mask patterns that are complementary to each other. Thereby, ejection data for each scan constituting a multi-pass is generated for each color of C, M, Y, and K. The mask pattern used in this process has reduced interference with the dot arrangement pattern used in the dot arrangement patterning process J0007, as will be described in detail later with reference to FIG. The pattern has high dispersibility. Furthermore, the mask of the second embodiment of the present invention to be described later has a reduced pattern coherence between the masks in addition to the above points.

  The ejection data obtained by the mask process is supplied to the head drive circuit J0009 at an appropriate timing in each of a plurality of scans in multipass printing. The 1-bit data of each color input to the driving circuit J0009 is converted into a driving pulse for the recording head J0010, and ink is ejected from the recording head J0010 for each color at a predetermined timing. Thus, ink is ejected according to the ejection data, and an image is recorded on the recording medium. In the present embodiment, a plurality of mask data corresponding to a plurality of recording modes are stored in the memory of the printer. Further, it is assumed that the above-described dot arrangement patterning process and mask data conversion process in the printer are executed under the control of the CPU constituting the control unit of the printing apparatus using dedicated hardware circuits for them. A printer that mainly performs mask data conversion processing in the above-described printer constitutes a data processing apparatus.

  In the following, some embodiments of a mask pattern manufacturing method and a mask pattern used by or used in the above-described recording system will be described. Before that, a basic method of mask pattern manufacturing and a method therefor will be described. The concept of repulsive force calculation to be used will be described.

(Mask manufacturing method)
In the following description of the basic mask manufacturing method, for simplification of description, a mask in which printing allowable pixels are arranged and a dot arrangement pattern having the same size as the mask in which dots are arranged are commonly used. This is called “plane”. Also, the print permitting pixels and dots arranged in these patterns are simply referred to as “dots”.

  In the mask manufacturing method according to the embodiment of the present invention, for such a dot arrangement pattern and a mask plane, first, as shown in FIGS. 6A to 6D, for example, the planes A1, A2, and A3 Three planes are defined. In addition, a repulsive force is applied between dots in the same plane or between different planes, and overlapping of dots in different planes is recognized, and a repulsive force is also applied between such overlaps so that dots in each plane Determine the placement.

  The method for determining the arrangement of dots in a plane is roughly divided into one of two methods: a method for determining the arrangement of a plurality of planes simultaneously (simultaneous generation) and a method for sequentially determining each plane (generation for each plane). Furthermore, for each of the above two generation methods, as a way of specifically determining the dot arrangement, all the dots on the plane are pre-arranged in advance and moved while increasing the dispersibility over the entire generated plane. There is a way to go (hereinafter referred to as “placement movement method”). In addition, a method of arranging dots one by one while increasing dispersibility over the entire generated plane (hereinafter referred to as “sequential arrangement method”) can also be executed.

Summary of arrangement determination processing of a dot by the arrangement moving method arrangement moving method is as follows.

  For example, when a dot arrangement rate of 50% plane is determined, for each of the planes A1, A2, and A3, an initial arrangement in which dots with 1-bit data of “1” are arranged at 50% of the dot arrangement possible positions. For example, it is obtained by a binarization process such as an error diffusion method. The reason why the initial arrangement of dots is obtained by using this binarization technique is that an arrangement with good dispersibility in the initial state can be obtained to some extent according to the binarization technique used. This is because the calculation time or convergence time until the final placement determination can be shortened. In other words, the method for obtaining the initial arrangement is not essential in applying the present invention. For example, the initial arrangement may be such that dots whose 1-bit data is “1” are randomly arranged in the plane.

Next, the repulsive potential is calculated for all the dots of the planes A1, A2, and A3 obtained as described above. In particular,
(I) A repulsive force corresponding to the distance is applied between dots in the same plane.
(Ii) Furthermore, a repulsive force is also applied to dots between different planes.
(Iii) Apply different repulsive forces between the same plane and different planes.
(Iv) Recognizing the overlap of dots in different planes, the dot overlap (two dot overlaps, three dot overlaps,...) Also gives a repulsive force according to the combination.

  FIG. 7 is a diagram schematically showing a function of the basic repulsive potential E (r) according to the present embodiment.

  As shown in the figure, the repulsive force function defined in the present embodiment has a repulsive force range up to r = 16 (position where 16 dots are arranged). By using a potential that decays with such a distance, basically, when dots are placed close to each other, the energy is high, that is, an unstable state. As a result of convergence calculation, the close placement is not selected as much as possible. Can be. It is more desirable to determine the shape of this repulsive force based on the ratio of dots to the entire mask pixel.

  Further, when considering a dot arrangement in which a plurality of dots overlap, the dots are arranged so as to overlap more than positions where dots can be arranged (in the case of resolution 1200, there are 1200 × 1200 possible positions in one inch square). For this reason, when calculating the repulsive potential for each dot, it is considered that the dot overlaps on the dot. For this reason, a function is defined so as to have a finite repulsive potential at r = 0. Thereby, dispersion in consideration of dot overlap is possible.

  In this embodiment, calculation is performed by giving a repulsive potential of αE (r) for dots in the same plane, βE (r) for dots between different planes, and γs (n) E (r) for overlapping dots. In other words, the potential due to the presence of a certain dot is added to the repulsive potential of dots in the same plane, dots in different planes, and even overlapping dots in different planes within the distance r.

  In the above repulsive potential, coefficients α, β, and γ are weighting coefficients, and for example, values of α = 3, β = 1, and γ = 3 are used. The dispersion of dots is affected by the values of α, β, and γ. The values of α, β, and γ can be obtained, for example, by performing an experiment in practice and optimizing with reference to a recorded image recorded using a mask.

  The coefficient s (n) is a coefficient that is further integrated in addition to γ in order to disperse overlapping dots. This coefficient s (n) is set to a value corresponding to the number of overlaps so that the more overlaps, the more the dots are dispersed. According to experiments by the inventors of the present application, good results regarding dispersion can be obtained by using s (n) obtained by either of the following two expressions.

  That is, when n is the number of overlaps, the sum of the number of combinations is s (n). Specifically, a dot that overlaps with the target dot for calculating repulsive force (at the same position in the same plane or in a different plane) and a dot located at a distance r from the target dot are checked. In this case, the number of overlaps in common between the dot of interest and the dot of another plane that overlaps at the same position as the pixel and the dot that overlaps at the same position of each plane at the distance r is n. Consider the repulsive force caused by the overlapping dots between these two positions.

  In this case, for example, n = 3 when considering an example in which dots commonly exist in the first plane, the second plane, and the third plane between two certain positions. A repulsive force resulting from the overlap of three dots is applied between these positions. Here, when the repulsive force due to the overlap of three dots is considered, it is considered that the overlap of two dots and the repulsive force of one dot act in a multiplexed manner together with the overlap of three dots. In other words, if the third plane is not considered, it can be considered that two dots of the first plane and the second plane overlap, and if the second plane is not considered, the two of the first plane and the third plane are considered. It can also be thought of as overlapping dots. If the first plane is not considered, it is considered that the second plane and the third plane overlap. In order to calculate the multiple effect of overlapping such dots, the repulsive force due to the combination of overlaps is defined and s (n) as described above is used. According to this, it has been experimentally confirmed that a dot arrangement with good dispersibility can be obtained.

  When the total energy obtained by summing up the repulsive potentials of all dots is obtained as described above, a process for attenuating the total energy is performed.

  In this process, for all the dots, the dots are sequentially transferred to the pixel where the repulsive potential is the lowest among the positions where the distance r is 4 or less. By repeating such processing, the total energy, which is the total value of the repulsive potential of all dots, is reduced. That is, the process in which the total energy decreases sequentially is a process in which the dot arrangement sequentially increases the dispersibility, that is, a process in which the low frequency components of the dot arrangement decrease in sequence.

  Then, the rate of reduction of the total energy is calculated, and if it is determined that it is equal to or less than a predetermined value, the energy attenuation process is terminated. The predetermined value can be obtained as a reduction rate at which an image in which low frequency components are appropriately suppressed can be recorded based on the result of actual printing. Finally, the dot arrangement of each plane in a state where the reduction rate of the total energy is equal to or less than a predetermined value as described above is set as the final dot arrangement.

  FIGS. 6A to 6D schematically show the above-described repulsive potential calculation and total energy attenuation processing. Specifically, the three planes A1, A2, and A3 are shown in a perspective view, and in particular, the movement of dots is shown in a plan view. Here, the smallest square indicates the dot arrangement possible position, and the overlapping position in the overlap of the three planes corresponds to the same arrangement possible position between the planes.

  FIG. 6A is a diagram for explaining that potential is added (increased) by repulsive force between dots when dots exist in the same plane. The example shown in the figure is an example in which one dot exists at a position separated by a distance r on the same plane as the dot Do at the target position of the plane A1, and in this case, α = 3 is applied and the potential of the dot Do is 1 A potential of × αE (r) is added.

  FIG. 6B is a diagram for explaining the repulsive potential applied in relation to these two dots when dots exist on a plane (planes A2 and A3) different from the target dot Do. Because of the relationship with dots between different planes, β = 1 is applied and a potential of 2 × βE (r) corresponding to two dots is added as the potential of the dot Do.

  FIG. 6C is a diagram for explaining the repulsive potential applied in relation to the dots in the case where dots exist at the same position on different planes and there are overlapping dots in addition to the above two cases. It is. In this case, in addition to the cases of FIGS. 6A and 6B, dots exist at the same position on the plane A3 different from the plane A1 of the target dot Do. As a result, the repulsive potential 1 × αE (r) of the same plane, the repulsive potential 1 × βE (0) due to one dot in a different plane at the same position, and the repulsive potential 2 × βE due to two dots in a different plane (R) and a potential of repulsive force γs (2) × E (r) due to the overlap, where the overlapping number n = 2 and γ = 3 are applied. As a result, the total repulsive potential due to the presence of the dot of interest Do in the dot arrangement shown in FIG. 6C is 1 × βE (0) + 1 × αE (r) + 2 × βE (r) + γs (2) × E (r).

  FIG. 6D is a diagram illustrating that in the dot arrangement shown in FIG. 6C, when the dot Do is moved, the total repulsive potential of the dot changes. As shown in FIG. 6D, when the dot Do (dot of the plane A1) moves to the adjacent pixel of the same plane, the total repulsive potential due to the presence of the dot Do is as follows. That is, the total repulsive potential changes to βE (1) + 1 × αE (r2) + 2 × βE (r2) because the distance is r2 and the number n of overlaps is 0. The total repulsive potential in the case of the dot arrangement shown in FIG. 6C is 1 × βE (0) + 2 × βE (r) + 1 × αE (r) + γs (2) × E (r), and FIG. It is possible to know the change in the total repulsive potential before and after the movement by comparing the total repulsive force due to the movement of the dots Do in d).

  In the above description, the sum of the repulsive potentials is the sum of the energy of the dots at three positions or when the dots are moved. However, this is for simplifying the explanation, and in fact, it is obtained as an integral of the repulsive potential based on the relationship with dots including dots at other positions that may exist in addition to these dots. It is.

  As shown in FIGS. 6A to 6C, among the dots for which the total repulsive potential is calculated, for example, when the dot Do has the largest total repulsive potential, the description has been given with reference to FIG. Thus, the change in repulsive potential before and after the movement is obtained. Then, the dot Do is moved to a position where the total repulsive potential becomes the lowest before and after the movement. By repeating such processing, the total energy of all three planes can be reduced. That is, in the overlap of the three planes, the dot distribution has a low frequency component and is well distributed.

  Then, since the dots are dispersed well in the overlap of the three planes A1 to A3 in this way, for example, when these three planes are two-pass masks, respectively, these masks are complementary to each other. Also, the dots are well dispersed. In addition, the dot distribution in the overlap of an arbitrary number (2, 3, 4, or 5) of these six planes is also well distributed with few low frequency components.

  Note that the above-described arrangement movement method relates to a case where three planes correspond to a two-pass mask and are applied to a mask of three planes used for the first pass among these two-pass masks. However, this method is not limited to this mode, and may be applied to all planes to determine dot arrangement. For example, the arrangement movement method may be applied to a mask of six planes for two passes. In this case, it is assumed that the movement of exchanging the arranged pixels in relation to the dots of other planes is allowed without limiting the range in which the dots are moved to the vicinity position. Specifically, for example, a dot on a certain plane is moved to a pixel on which no dot on the same plane is arranged. At the same time, replacement is performed such that a dot arranged in a pixel of another plane corresponding to the moved pixel is moved to a pixel corresponding to the pixel having the former dot in the same plane. Thereby, the arrangement relationship of dots in all the planes related to the calculation of the repulsive potential is changed, and the replacement movement that minimizes the potential energy becomes possible.

Sequential Arrangement Method As described above, this method is a method in which dots are sequentially arranged in a portion of the mask plane where dots are not yet arranged. For example, for each of the three planes shown in FIGS. 6A to 6C, dots are sequentially arranged one by one, and each dot is repeated according to the dot arrangement rate of that plane. Perform placement. In this case, first, when a dot is to be arranged, the repulsive potential generated between the dot at that position and the dots already arranged in the planes A1, A2, and A3 is calculated. The calculation of the repulsive potential itself is the same as that described in the above-described arrangement movement method. The difference is that in the example shown in FIGS. 6A to 6C, the dot Do is not already placed at the position shown in FIG. 6 but is already arranged when the dot Do is newly placed. This is a point where the repulsive potential is calculated between A1 and dots of different planes A2 and A3. As is clear from the above, the repulsive potential has the same value everywhere in the dot at the first stage where no dot is arranged yet.

  Next, the position where the lowest potential energy is determined among the repulsive potentials calculated when placed at each plane position is determined. Then, when there are a plurality of positions having the minimum energy, for example, one position is determined from the plurality of positions using a random number. In the present embodiment, the position of the minimum energy is determined under the condition that the dots are not overlapped at the positions where dots are already arranged in the same plane. Depending on parameters such as a weighting coefficient and a repulsive potential function, energy may be minimized when overlapping on the same plane when calculating repulsive potential due to the relationship with dots of other planes. In this case, the plane is forbidden to overlap because only one dot is allowed at one position. A dot is placed at the position of the determined minimum potential energy. That is, the mask data of the pixel is set to “1”. Then, it is determined whether one dot is arranged for each of the three planes A1, A2, A3. If not, the above process is repeated.

  When the dots are arranged one by one in this order in the planes A1, A2, and A3, the above process is repeated until 50% of the dots are arranged with respect to all possible arrangement positions of the three planes, and 50% is arranged. And this processing is terminated.

  A plane having characteristics similar to those of the above-described placement movement method can also be obtained by the sequential placement method described above. That is, in the three planes by the sequential arrangement method, dots are well dispersed even when they overlap.

  Another feature of the above-described plane manufacturing method is that a periodic pattern in which the arrangement of dots is regularly repeated is not generated. For example, a pattern having periodicity that repeats a staggered pattern or a Bayer pattern is not generated. Even if it is generated, it can be converged to avoid the periodic pattern by resetting the repulsive potential parameter. Thus, the plane generated by the mask manufacturing method of the present embodiment is an aperiodic pattern.

  In the above description, in order to simplify the description, it has been described that the dot arrangement pattern plane and the mask plane are not distinguished. However, as will be described in the following embodiments, in the calculation of repulsive force, the plane corresponding to the dot arrangement pattern or the dots in the plane out of the planes are predetermined as the dot arrangement pattern. In other words, the dots of the plane corresponding to the dot arrangement pattern are treated as fixed, and are not determined by the movement of the dot arrangement or the dot arrangement according to the energy of the repulsive potential. That is, in the embodiment of the present invention, the target for determining the dot arrangement is a plane corresponding to the mask, and at that time, the plane corresponding to the dot arrangement pattern or the dot is the target of repulsive force calculation. Specifically, in determining the dot arrangement of the plane corresponding to the mask, the term of the weighting coefficient α in the repulsive potential calculation is applied to the plane corresponding to the mask. The terms of coefficients β and γ are applied between a plane corresponding to the mask and a plane corresponding to another mask or a plane corresponding to a dot arrangement pattern.

  As a result, the arrangement of the print permitting pixels in the manufactured mask reduces the mutual interference with the dot arrangement pattern, and the mask print permitting pixel arrangement pattern itself has high dispersibility.

  Next, a mask manufacturing method according to some embodiments of the present invention using the basic mask manufacturing method described above will be described.

<Embodiment 1: 100% uniform mask for 2-pass printing>
Outline of the present embodiment In this embodiment, a single print head having a nozzle array that discharges cyan (C) ink is used as a printing element, and two-pass multi-pass printing is performed in which an image is completed in two scans. About. The mask used for the two-pass printing has reduced interference with the dot arrangement pattern, and the mask pattern itself is well dispersed. As a result, the dots recorded in each of the two scans have no deviation in the number of dots. In addition, since dots are formed in a dispersed manner in each scan, for example, even if there is a shift in the recording position, the texture that can be caused by it is less likely to be visually obstructive, and the influence on the image quality is suppressed. .

  FIG. 8 is a diagram schematically showing mainly the positional relationship between the recording head, the mask pattern, and the recording medium in order to explain the two-pass recording. The recording head 801 includes a cyan nozzle row, and the nozzle row includes 512 nozzles arranged at an interval of 1200 dpi. In the case of two-pass printing, the print data is divided into a first group and a second group each including 256 nozzles. Each group is associated with a mask 802 (two masks C1, C2) whose manufacturing method will be described later, and the size of each mask C1, C2 in the sub-scanning direction (conveyance direction) is the nozzle of each group. This is the same 256 pixels as the number. The mask C1 and the mask C2 have a complementary relationship, and when they are overlapped, recording of an area corresponding to 256 (horizontal) pixels × 256 (vertical) pixels can be completed. As shown in FIG. 8, in the first scan, recording is performed on the area A of the recording medium 803 using the mask C1, and after the recording medium is fed by 256 pixels, the mask C2 is used for the area A. To record. The image recording is completed by these two passes.

Mask Manufacturing Method A mask manufacturing method according to this embodiment will be described using the sequential arrangement method described above.

  FIG. 9 is a flowchart showing the arrangement determination process of the print permission pixels by the sequential arrangement method of the present embodiment.

  In the process shown in FIG. 9, the print permitting pixels are sequentially arranged on one plane, and the print permitting pixels having an arrangement ratio of 50% are arranged. First, in step S701, the plane of the mask C and the dot arrangement pattern plane where the print permitting pixels are to be arranged are defined, and the repulsive potential is calculated for the arrangement of the print allowance pixels in these planes. At this time, as described above, dots are already arranged in the plane corresponding to the dot arrangement pattern, and the print-allowed pixels to be arranged in the plane of the dots and the mask C with the dots fixed. Calculate repulsive force between.

  FIG. 10 is a diagram showing a concept for calculating a repulsive force related to the arrangement of the print allowable pixels of the mask C. In calculating the repulsive force, each of the planes P1 to P4 of the dot arrangement pattern to be considered is a fixed pattern. The dot arrangement patterns of these planes P1 to P4 are predetermined for each level indicated by the index data. In the process of determining the arrangement of the print permitting pixels of the mask C, the repulsive potential between the print permitting pixels in the mask pattern C and the repulsive potential between the print permitting pixels in the mask pattern C and the dots in the planes P1 to P4 are calculated. Then, as described above, the arrangement of the print permitting pixels of the mask C is determined based on the result of the repulsive potential calculation.

  FIG. 11 is a diagram showing a dot arrangement pattern according to the present embodiment. The dot arrangement pattern shown in FIG. 11 is a collection of four minimum unit patterns of 2 pixels × 2 pixels described above in FIG. 5 in the vertical direction and four in the horizontal direction. Specifically, the pattern shown in FIG. 5 is a pattern having a relationship obtained by rotating or inverting the minimum unit pattern shown in FIG. 5 for each level of index data (level 0 is not shown; all pixels are “white”). They are arranged according to predetermined rules. In the dot arrangement patterning process J0007, this 8 pixel × 8 pixel arrangement pattern is obtained by repeating 64 times in the vertical direction and 64 times in the horizontal direction corresponding to the number of nozzles of the recording head, and 512 pixels × 512 are obtained. A pattern having a size of a pixel (256 minimum unit pattern × 256 minimum unit pattern) is used. This pattern is stored in the memory for each gradation level (0 to 4) of the index data, and at the time of patterning processing, a minimum unit pattern of 2 pixels × 2 pixels is read according to the gradation level indicated by the index data. . At this time, the minimum unit pattern to be read corresponds to the position of the index data. Then, the read pattern of the minimum unit is subjected to mask processing in the next mask data conversion processing J0008 (FIG. 4).

  Of the dot arrangement patterns for each level indicated by the index data described above, the dot arrangement pattern for a size of 256 pixels × 256 pixels corresponds to 256 pixels × 256 pixels of the mask C. The arrangement of the print permitting pixels of the mask C is determined in consideration of the planes P1 to P4 of the dot arrangement pattern for each gradation level. Specifically, the arrangement of the print permitting pixels is determined using the calculation of the repulsive potential described above. However, the dot arrangement pattern to be considered is not a repetition of the 8 × 8 pixel pattern shown in FIG. This is to remove the bias of repulsive potential in advance as will be described in detail later.

FIG. 12 is a diagram showing the dot arrangement of the planes P1 to P4 that are targets of calculation of the repulsive potential when determining the arrangement of the print allowable pixels of the mask C. The dot arrangement patterns of the planes P1 to P4 are patterns obtained by disassembling the dot arrangement patterns shown in FIG. 11 so as to be mutually exclusive. Specifically, the original dot arrangement pattern shown in FIG. 11, that is, the dot arrangement pattern used in the process J0007 of FIG. is there. The plane P1 is a pattern (L1-L0) obtained by excluding the dot (L0) of the dot arrangement pattern of gradation level 0 from the dot (L1) of the dot arrangement pattern of gradation level 1. Similarly, the plane P2 is a dot pattern of a difference between the gradation level 2 pattern (L2) and the gradation level 1 pattern (L1). The plane P3 is a dot pattern that is the difference between the gradation level 3 pattern (L3) and the gradation level 2 pattern (L2). Further, the plane 4 is a dot pattern of a difference between the gradation level 4 pattern (L4) and the gradation level 3 pattern (L3). Since the planes P1 to P4 are exclusive patterns, when all of them are overlapped, dots are arranged at the same 100% arrangement rate as that of the gradation level 4. Here, when calculating the repulsive potential, the dot arrangement pattern is exclusively used in order to prevent the repulsive potential value from being biased to a certain region, thereby preventing the deviation of the allowable number of recording pixels arranged and the deterioration of the dispersibility. It is. That is, the dot arrangement pattern shown in FIG. 11 preserves the dot arrangement of the previous level when the level increases. For this reason, when the dot arrangement pattern itself is used for calculation of the repulsive potential, the potential is calculated as overlapping dots between different planes in which the stored dots are different. However, the dot of the dot arrangement pattern to which the mask is applied in the mask processing is one dot among a plurality of levels, and does not have multiple relations or interference with the mask as described above. Therefore, when the dot arrangement pattern itself is used in the calculation of the repulsive potential, the calculated repulsive potential value is biased with respect to the actual relationship, and in return, the bias and dispersibility of the allowable number of recording pixels to be arranged are returned. Will be reduced.

  In the above example, the dot arrangement pattern in which the dot arrangement of the previous gradation level is saved when the gradation level is increased is shown. However, the present invention is not limited to this, and the dot arrangement pattern in which the dot arrangement is not preserved. The present invention can also be applied when using.

  FIG. 13 is a diagram illustrating an example of a dot arrangement pattern in which the dot arrangement of the previous gradation level is not stored as it is when the gradation level is increased. As shown in FIG. 13, in the level 1 arrangement pattern, for example, dots are arranged in pixels 1301 and 1302. In contrast to this arrangement, at level 2 where the level is increased by one, no dot is arranged in the pixel 1301, and the dot at the level 1 is not stored. On the other hand, in the pixel 1302, dots are arranged as in the level 1 arrangement. As described above, there is a dot arrangement pattern in which the dot arrangement of the previous level is not completely saved (as it is).

  As described above, when using a dot arrangement pattern in which the dot arrangement is not stored as it is when the level increases, the pattern used for calculating the repulsive potential uses the dot arrangement pattern and each exclusive pattern. A pixel (for example, the pixel 1301) in which the dot (arrangement) is not stored has the same influence on the print permitting pixel of the mask in the calculation of the repulsive potential unless the distance is taken into consideration. On the other hand, the pixel in which the dot is stored (for example, the pixel 1302) has an overlap in the repulsive force calculation, and has a multiplex relationship with the recording allowable pixel of the mask. From this point, a dot arrangement pattern and its exclusive pattern are used as a repulsive force calculation plane.

FIG. 14 shows eight planes used for calculation of the repulsive potential when the dot arrangement pattern is the one shown in FIG. 14, planes P1 has a dot arrangement pattern of level 1 shown in FIG. 13, the plane P 2 has the exclusive pattern of the dot arrangement pattern of the level one. Similarly, the plane P3 has a level 2 dot arrangement pattern, and the plane P4 has its exclusive pattern. The plane P 5 has a level 3 dot arrangement pattern, the plane P 6 has its exclusive pattern, the plane P 7 has a level 4 dot arrangement pattern, and the plane P 8 has its exclusive pattern.

  When the dot arrangement pattern shown in FIG. 13 is used, the calculation of the repulsive potential for determining the arrangement of the print permitting pixels of the mask C is performed by fixing the dot arrangement of the mask C plane and the above eight planes. This is done for the other plane.

  Referring to FIG. 9 again, after calculating the repulsive potential as described above, the minimum repulsive potential calculated among the repulsive potentials calculated when the print allowable pixel is placed at the arrangement position of the mask C in step S702. The position that becomes the potential energy of is determined. In step S703, it is determined whether there are a plurality of positions having the minimum energy. If there are a plurality of positions, one position is determined from the plurality of positions using a random number in step S707. In step S704, a recording allowable pixel is arranged at the position of the determined minimum potential energy.

  In step S705, it is determined whether or not print permitting pixels have been arranged up to 50% of the arrangement possible positions on the mask C plane. When the recordable pixels are not arranged up to 50%, the processing from step S701 is repeated. Then, when 50% recordable pixels are arranged, this process is terminated.

  As described above, when the first-pass mask C1 of the two-pass mask is set, the mask C2 having a complementary relationship with the mask C1 can be determined based on this.

  As described above, according to the mask manufacturing method of the present embodiment, according to the above-described weighting of α, β, and γ, first, the arrangement of the print permitting pixels in the manufactured mask C has good dispersibility. . Second, even in the overlap of the mask C and the planes P1 to P4 of the dot arrangement pattern considered in the manufacture of the mask, the print permitting pixels and the dots are well dispersed. That is, both the logical product and the logical sum of the print allowable pixels arranged on the mask C and the dots arranged on the planes P1 to P4 are dispersed. This logical product and logical sum is obtained, for example, between 256 pixels × 256 pixels of the mask and 256 pixels × 256 pixels of each of the planes P1 to P4, and between the print allowable pixels and the dots arranged in each. It is required.

  Because of the above dispersibility of the logical sum, the mask C1 and the mask C2 that is complementary to the mask C1 are distributed with respect to the dot arrangement pattern shown in FIGS. It is guaranteed that the sex is good. Thereby, it can suppress that a dot is formed biased to specific scanning. Further, since the dispersibility of the logical product is good, the dispersibility of the dot pattern obtained by masking the dot data based on the dot arrangement pattern shown in FIGS. 11 and 13 using the mask C1 (C2) is good. That is also guaranteed. Such an operation of the present invention is also applicable to each embodiment described below.

  As a result, when the dot pattern generated by the dot arrangement pattern shown in FIG. 11 or FIG. 13 is recorded, the number of dots formed for each scan is specified by using the mask according to the present embodiment. And well dispersed. The good dispersibility suppresses the influence on the image quality because the texture that may be caused by various factors is hardly visually disturbed.

Mask of Comparative Example a mask mask characteristic evaluation and the embodiment 15, the mask C1 of this embodiment is produced by method described above (hereinafter, also referred to as pattern considering layered mask) the arrangement pattern of print permitting pixels FIG. Further, FIG. 16 shows a calculation of the repulsive potential between two mask planes for 2-pass printing disclosed in Japanese Patent Application No. 2005-197873 filed by the present applicant. It is a figure which shows one arrangement pattern of the defined mask (henceforth a laminated mask). The mask pattern shown in FIGS. 15 and 16 has 256 × 256 pixels. Both masks have a good dispersibility of the layout pattern of the print-allowable pixels, and give an overall smooth impression.

  17, FIG. 18, and FIG. 19 show the arrangement of the print permitting pixels of the pattern-considered laminated mask C1 of this embodiment shown in FIG. 15, and the dot arrangement of each of level 1, level 2, and level 3 shown in FIG. It is a figure shown with the dot pattern of the result of AND operation with these. 20, FIG. 21, and FIG. 21 similarly show the logical product of the arrangement of the print permitting pixels of the stacked mask shown in FIG. 16 and the dot arrangement of level 1 to level 3 shown in FIG. It is a figure shown by. That is, the dot pattern of level 1 to level 3 corresponding to the dot pattern at the time of printing is represented by a dot pattern that is driven in the first pass (scanning) when mask processing is performed using the mask C1 of the two-pass mask.

  As shown in comparison with FIGS. 17 to 19 and FIGS. 20 to 22, the dot patterns (FIGS. 17 to 19) recorded using the pattern-considered laminated mask of this embodiment are shown in FIGS. 20 to 22. In comparison, it can be seen that there is little bias in the arrangement of dots to be formed. In particular, it can be seen that the lower the level, the greater the difference due to the mask.

Evaluation by Power Spectrum Next, the mask of the present embodiment is evaluated by the power spectrum indicating the frequency characteristics of the mask pattern. The power spectrum described below is obtained for a mask pattern having a size of 256 pixels × 256 pixels. Here, the power spectrum can be treated as a one-dimensional two-dimensional spatial frequency, “T. Mitsa and KJ Parker,“ Digital Halftoning using a Blue Noise Mask ”, Proc. SPIE 1452, pp. 47-56 (1991)”. It is described as a radially averaged power spectrum. Here, in the specification and claims of the present application, the “low frequency component” means a frequency component on the lower frequency side from the center of the spatial frequency region where the frequency component (power spectrum) exists. Say. On the other hand, the “high frequency component” refers to a frequency component located on the higher frequency side than the center of the region. Therefore, taking FIG. 24 as an example, the low frequency side (approximately 0 to 90) is the “low frequency region” and the high frequency side (approximately 91 to 180) is the “high frequency region, with the spatial frequency“ 90 ”vicinity as the eaves. "

  “Low frequency component is less than high frequency component” means that the integrated value of the frequency component (low frequency component) existing in the low frequency region is the integrated value of the frequency component (high frequency component) existing in the high frequency region. Less than that.

  FIG. 23 is a diagram for explaining the frequency characteristics of the pattern-considering laminated mask C1 of this embodiment and the laminated masks disclosed in Japanese Patent Application No. 2005-197873 (hereinafter referred to as related applications). In FIG. 23, each curve shows the power spectrum of each mask pattern with respect to the spatial frequency. A curve b represents the power spectrum of the mask pattern of the pattern-considering laminated mask of this embodiment, and a curve a represents the power spectrum of the mask pattern of the laminated mask disclosed in the related application. Comparing these two curves, it can be seen that both have less power in the low frequency region and a power peak exists in the high frequency region. As described above, the mask according to the present embodiment considering the dot arrangement pattern also realizes pattern characteristics with few low frequency components and no peak in the low frequency region.

  FIG. 24 shows a pattern formed in the first pass when a level 1 dot pattern is recorded using the pattern-considering laminated mask C1 of this embodiment and the laminated mask disclosed in the related application (FIGS. 17 and 17). It is a figure explaining the frequency characteristic of 20). A curve a represents a power spectrum of the logical product pattern (that is, the logical product pattern of FIG. 20) of the layered mask shown in the related application and the level 1 dot arrangement pattern of FIG. In this curve, a has a peak also in a low frequency region and has a relatively large amount of low frequency components. The presence of a peak in the low frequency region means that the dot arrangement within one scan is biased due to interference between the mask pattern and the dot arrangement pattern, which may be perceived as noise.

  On the other hand, the curve b in FIG. 24 shows the power spectrum of the logical product pattern (that is, the logical product pattern in FIG. 17) of the pattern-considering laminated mask C1 of this embodiment and the level 1 dot arrangement pattern in FIG. Yes. This curve b shows the characteristic that the low frequency component is smaller than the high frequency component, and in particular, there is no substantial peak in the low frequency region and the low frequency component is relatively small. The absence of a peak in the low frequency region means that there is almost no dot deviation caused by interference between the mask pattern and the dot arrangement pattern, and the dots are arranged in a well-distributed state in one scan. .

  The characteristics of the curve b in FIG. 24 will be further described in detail. In general, the human eye has a so-called low-pass filter characteristic in which the sensitivity to low frequency components is high and the sensitivity decreases as the frequency increases. Therefore, it is effective for reducing the noise feeling to suppress the low frequency component as low as possible so that there is no peak of the frequency component in the entire low frequency region as shown by the curve b.

  In the low frequency range, noise detection has a significant effect on noise detection, especially the frequency components on the low frequency side from the center (half) of the low frequency range, and more strictly speaking, the frequency component is lower than 1/4 of the low frequency range. This is the frequency component on the side. In other words, the frequency characteristics related to the sensitivity of the human eye depend on the distance between the recorded material and the human eye. For example, Dooley (“RP Dooley: Prediction Brightness Appearance at Edges Using Linear and Non-Liner Visual Describing Functions, SPES annual Meeting (1975) ”). From various experiments, it is said that components in a frequency region lower than about 9 to 10 cycles / mm are easily recognized by human eyes. In the example of FIG. 24, the spatial frequency “50” corresponds to approximately 10 cycles / mm, and the vicinity of the center of the low frequency region (spatial frequency “45”) corresponds to approximately 9 cycles / mm. Therefore, it is effective to reduce the noise sensation by keeping the frequency component low so that there is no frequency component peak in the frequency region of 9 cycles / mm or less (that is, the region on the lower frequency side than the center (half) of the low frequency region). The curve b satisfies this condition. The visual sensitivity gradually increases as the frequency decreases from 9 cycles / mm, and the visual sensitivity increases rapidly from around 4.5 cycles / mm (spatial frequency “22.5” in the figure). The visual sensitivity is maximized in the vicinity of 1 to 2 cycles / mm (spatial frequency “5 to 10” in the figure). Therefore, in the frequency region (region lower than ¼ of the low frequency region) of the frequency component below 4.5 cycles / mm (spatial frequency “22.5” in the figure), which is a point at which the visual sensitivity increases sharply, It is important to keep the frequency component low so that there are no peaks. This condition is also satisfied in the curve b.

  As described above, according to the present embodiment, as shown by the curve b in FIG. 24, in the region on the lower frequency side than the quarter of the low frequency region (region of about 4.5 cycles / mm or less), the low frequency The low frequency component is kept low to such an extent that no component peak exists. Therefore, it is possible to obtain an image with less noise. In the curve b in FIG. 24, no low frequency component peaks are observed in the entire region on the lower frequency side (region of 9 cycles / mm or less) than near the half of the low frequency region, so that there is almost no sense of noise.

  As is clear from the above, the mask of this embodiment has the following logical product patterns (a) and (b1) to (b1), which are obtained by the logical product of the arrangement of the print allowable pixels in the mask and the dot arrangement in the dot arrangement pattern. It satisfies any of (b3). In this embodiment, in addition to (a), at least (b1) needs to be satisfied, more preferably (b2) is satisfied, and still more preferably (b3) is satisfied.

(A) The frequency component in the low frequency region is less than the frequency component in the high frequency region.
(B1) There is no frequency component peak in a region on the lower frequency side than 1/4 of the low frequency region.
(B2) The peak of the frequency component does not exist in a region on the low frequency side from half of the low frequency region.
(B3) There is no frequency component peak in the entire low frequency region.

  In this way, the dot arrangement pattern consideration type laminated mask C1 has a low frequency component of the logical product pattern obtained by the logical product of the arrangement of the print allowable pixels in the mask C1 and the dot arrangement in the dot arrangement pattern less than the high frequency component. The pattern has a characteristic in which no low frequency component peak exists.

  By using such a pattern-considering laminated mask, interference with the dot arrangement pattern can be reduced to reduce the deviation in the number of dots, and mask processing with high dispersibility can be performed. In addition, since the low frequency component is kept low, the mask pattern unevenness depending on the mask cycle can also be reduced.

<Embodiment 2: 100% uniform mask for 4-pass printing>
Outline of the Present Embodiment The second embodiment of the present invention completes an image by performing four scans (two reciprocating scans) for each ink of cyan (C), magenta (M), and yellow (Y). The present invention relates to a pattern-considering laminated mask used for multi-pass printing. In the mask of this embodiment, each mask has reduced interference with the dot arrangement pattern obtained from the index data as in the first embodiment, and also reduced interference with other masks. It is. According to this, it becomes possible to reduce the occurrence of beading that is caused by the collection of ink droplets ejected during a plurality of scans.

  In the present embodiment, the order of printing is as follows: cyan first pass → magenta first pass → first yellow first pass → yellow second pass → magenta second pass → cyan second pass → cyan third pass → -The fourth cyan pass. Accordingly, the order of masks to be used is C1, M1, Y1, Y2, M2, C2, C3, M3, Y3, Y4, M4, and C4. In this embodiment, since the pattern is dispersed between the masks as described above, an image with high dispersibility of dots formed in the middle scanning is obtained, thereby reducing the occurrence of beading.

Mask Production Method In the mask production method of this embodiment, print permitting pixels are arranged in each mask by the above-described generation method and sequential arrangement method for each pass.

  FIG. 25 is a flowchart showing the mask creation processing of this embodiment. The basic process is the same as the process of the first embodiment described with reference to FIG. The difference is that there are a plurality of (C, M, Y) planes for determining the arrangement (S2105), and when the target recording allowable pixel is arranged in the pixel where the repulsive potential is the lowest, it has been created so far. The pass mask pattern is fixed (S2102). In addition, since it is a mask for four-pass printing, the above-described creation process is repeated for the masks for three passes (C1, C2, C3; Y1, Y2, Y3; M1, M2, M3) for each color. Of course.

  When there are a plurality of masks that determine the arrangement by calculating the repulsive force, as shown in FIG. 26, when generating the mask pattern of each color, the repulsive potential is calculated in consideration of the dot arrangement pattern corresponding to the color. . For example, when generating a Y mask, the repulsive potential is calculated between the Y dot arrangement pattern and the M and C mask patterns. That is, the repulsive force between the mask patterns is also calculated.

  When generating the Y mask, the repulsive potential may be calculated between the M, C, and Y dot arrangement patterns and the M and C mask patterns to determine the Y mask recording allowable pixels. . However, the suppression of interference between the generated Y mask and the Y dot arrangement pattern is less effective than the above method.

  The pattern considered in generating the mask pattern for each color is the dot arrangement pattern for each color as in the first embodiment. Therefore, it is clear that the present invention can be applied even when the dot arrangement pattern of each color is the same or different.

  FIG. 27 is a diagram showing a dot arrangement pattern used in the present embodiment. As shown in the figure, in this embodiment, a different dot arrangement pattern is used for each color. The pattern used for the actual repulsive potential calculation is shown in FIG. FIG. 28 shows the dot arrangement obtained by taking the difference in the dot arrangement pattern of each level shown in FIG. 27, as described above in the first embodiment, and the dot arrangement of each plane is exclusive. .

Mask Characteristic Evaluation FIGS. 29 to 31 show the layout patterns of the print-permitted pixels of the pattern-considered laminated masks C1, M1, and Y1 for one plane of this embodiment manufactured by the above-described manufacturing method of this embodiment. FIG. Each mask pattern has an area of 128 × 256 pixels. As shown in these figures, it can be seen that the print permitting pixels are arranged with good dispersibility in the mask of any plane.

  32 to 34 are diagrams showing dot patterns formed in the first pass when the level 1 pattern shown in FIG. 27 is recorded using the masks C1, M1, and Y1. That is, the logical product of the arrangement of the print-permitted pixels of the pattern-considered laminated masks C1, M1, and Y1 of the present embodiment and the level 1 dot arrangement shown in FIG. 27 is shown by a dot pattern.

  32 to 34, it can be seen that the logical product of each mask and the corresponding dot arrangement pattern, that is, the dispersibility of the dot pattern obtained by the mask process is good. Similarly, the second pass and the third pass masks C2, C3, Y2, Y3, M2, and M3 have high dispersibility. This is because the repulsive force is similarly calculated between these masks and the corresponding dot arrangement pattern.

  FIG. 35 is a diagram illustrating frequency characteristics of a logical product pattern of a dot arrangement pattern of a predetermined level and each mask C1. As shown in this figure, the logical product pattern is such that the low frequency component is less than the high frequency component and there is no substantial peak in the region on the lower frequency side than 1/4 of the low frequency region. Therefore, there is almost no dot deviation caused by interference between the mask pattern and the dot arrangement pattern, and the dots are arranged in a state of being well dispersed in one scan.

  The mask of the second embodiment is not limited to the mask in which the logical product pattern with the dot arrangement pattern is as shown in FIGS. 32 to 34, and the following characteristics (a) and ( It is only necessary to satisfy any of b1) to (b3). The same applies to Embodiments 3 to 5 described later.

(A) The frequency component in the low frequency region is less than the frequency component in the high frequency region.
(B1) There is no frequency component peak in the region on the lower frequency side than 1/4 of the low frequency region.
(B2) The peak of the frequency component does not exist in the lower frequency region than half of the low frequency region.
(B3) There is no frequency component peak in the entire low frequency region.

  Further, in the present embodiment, in determining the arrangement of the print permitting pixels of the mask, as in the form disclosed in Japanese Patent Application No. 2005-197873 by the applicant, the interference or dispersion with other masks should be taken into consideration. The repulsive potential is calculated even with the mask. According to this, the dispersibility of the dots formed in the scanning in the middle of completing the recording becomes high, thereby reducing the occurrence of beading.

  This beading is particularly likely to occur in recent inkjet recording systems. In recent inkjet recording, the speeding up, density increase, and diversification of ink types are remarkably progressing. Higher speed, higher density, and increased types of ink increase the amount of ink applied per unit time and per unit area of the recording medium. In such a situation, depending on the recording medium, even if all the applied ink can be absorbed, the absorption may not be able to correspond to the application speed. Specifically, even if all applied ink is absorbed as a result and does not cause problems such as fixability and smear, it is not yet absorbed on the surface of the recording medium in the middle of a plurality of scans. Ink drops contact each other, which can cause problems in the recorded image.

  For example, consider a case in which a blue image expressed by cyan ink and magenta ink is recorded on a recording medium having a glossy surface by two-pass multi-pass printing. In many serial type ink jet recording apparatuses, discharge ports of four basic colors of cyan, magenta, yellow and black are arranged in parallel in the main scanning direction of the recording head. Therefore, each color is given to the same area of the recording medium in the same recording scan. In other words, in the above case, a cyan recording dot that has been thinned by half of the image data and a magenta dot that has also been thinned by half of the same image data are extremely short in the same printing scan. It is given by. At this time, the recorded cyan dots and magenta dots are attracted by the surface tension of each other when both are recorded on the same recording pixel or adjacent pixels, and two (or more) large dots (hereinafter referred to as “dots”). , Referred to as grain). Once such a grain is generated, ink droplets applied to adjacent positions in another scan are easily attracted to the grain. That is, the first generated grain gradually grows as a nucleus and eventually produces large grains. Such a grain remarkably appears mainly in a high density region where a large amount of ink is applied. In a uniform image area, such grains are scattered in an irregular manner, which is confirmed as an image detrimental effect called so-called beading.

  The grain phenomenon is not caused only by the surface tension between different color inks. For example, when recording agents that react with each other are recorded in the same recording scan, the contacting droplets are combined by a stronger chemical reaction, which may form a grain nucleus. Also, in the case of a configuration in which ink of the same color is printed using two nozzle rows in the same printing scan, grain occurs between them.

  In contrast, in the present embodiment, it is possible to suppress the occurrence of such grains by considering dispersion between masks.

<Embodiment 3: 100% gradation mask for 2-pass printing>
The third embodiment of the present invention relates to a technique for reducing interference or improving dispersibility when a gradation mask is used. Specifically, as in each of the above embodiments, the repulsive potential is calculated for the gradation mask and the arrangement pattern of this embodiment, and the arrangement of the print permitting pixels is determined.

  FIGS. 36A and 36B show a printing rate corresponding to the position in the nozzle array of the gradation mask according to the present embodiment (ratio of printing allowable pixels arranged in a predetermined area), and a two-pass mask pattern. FIG. In the present embodiment, the number of print permitting pixels corresponding to the print rate that changes in the nozzle arrangement direction according to the nozzle number is arranged. The planes of the dot arrangement pattern considered in the calculation of the repulsive potential are the four planes P1, P2, P3, and P4 shown in FIG. 12, as in the first embodiment.

  36A and 36B, in each scan of two-pass printing, the nozzles numbered 0 to 255 correspond to the mask C2, and the nozzles numbered 256 to 511 correspond to the mask C1.

  The mask manufacturing method is basically the same as that of the first embodiment. The difference is that when placing the printable pixel on the pixel with the lowest energy, if the number of rasters that are determined according to the print ratio corresponding to the nozzle exceeds the number of rasters, the raster that is within the limit of the number of placements, The lower pixel is located at that pixel of the raster. As a result, it is possible to obtain a gradation mask with high dispersibility in consideration of the dot arrangement pattern while varying the recording ratio for each raster.

<Embodiment 4: 150% uniform mask for 2-pass printing>
The present invention can also be applied to a plurality of masks exceeding 100% when the recording ratios of a plurality of masks in a complementary relationship are combined. The fourth embodiment of the present invention relates to a mask in which two planes of the same color used for two-pass printing each have a printing ratio of 75% and a total printing ratio of 150%.

  The mask manufacturing method of this embodiment can be performed basically in the same manner as in the first embodiment. The difference is that after a mask pattern with a 75% printing rate for the first pass is created, a mask for the second pass is created by arranging print permitting pixels at the exclusive positions as in the first embodiment. It is. That is, for the second pass mask, the same process as the first pass mask creation is repeated to generate a 75% pattern.

  Details of mask fabrication will be described below using a sequential arrangement method. Basically, the same processing as that shown in FIG. 9 according to the first embodiment is performed. The difference is that in the same determination step as in step S705, it is determined whether or not up to 75% of the print permitting pixels are arranged. Further, in the mask creation for the second pass, in the same process as step S704 in FIG. 9, when the print permitting pixels are arranged, the overlap with the print permitting pixels of different planes of the same color is not prohibited. That is, when an attempt is made to arrange at a position where the energy is lowest, the arrangement is made even if it overlaps with a print permitting pixel of another plane of the same color at that position. As a result, it is possible to generate a mask having a recording rate of 150%, in which two masks are overlaid and the recording rate exceeds 100%.

  FIGS. 37A and 37B show the recording ratio and the actual mask pattern for each nozzle of the 2-pass 150% uniform mask in this embodiment. The pattern considered is the same pattern of FIG. 10 as in the first embodiment.

  FIG. 38 is a diagram illustrating a logical sum of the mask C1 and the mask C2 illustrated in FIG. In FIG. 38, a pixel expressed in black is a pixel formed by overlapping two dots, and a pixel expressed in gray is a pixel formed with one dot. Here, the pixel on which two dots are formed is designated in advance and the mask is manufactured.

  FIG. 39 is a dot arrangement of the logical product of the mask pattern shown in FIG. 37B and the level 1 dot arrangement pattern used in this embodiment, that is, formed in one pass when the image data is level 1. It is a figure which shows a dot pattern. From this figure, it can be seen that the dot pattern formed by one scan has no dot deviation and has a good dispersibility.

<Embodiment 5: Mask with Cluster Size of m × n>
The fifth embodiment of the present invention relates to the creation of a so-called cluster mask in which m × n recording allowable pixels are one unit. Here, m indicates the number of pixels continuous in the main scanning direction, and n indicates the number of pixels continuous in the sub-scanning direction.

  In the present embodiment, a case where the cluster size is 2 × 2 pixels in a 100% uniform mask for 2-pass printing will be described. The mask manufacturing method of this embodiment can be performed basically in the same manner as in the first embodiment.

  FIG. 40A is a diagram illustrating a dot arrangement pattern used in the present embodiment. Similar to the dot arrangement pattern shown in FIG. 11, the pattern shown in FIG. 40A repeatedly uses a pattern having a size of 8 × 8 pixels in units of 2 × 2 pixels. It differs from the pattern in the content of 2 × 2 pixel units and its arrangement pattern. Specifically, as shown in FIG. 40 (b), when any of level 1 to level 3 is classified into A, B, C, and D according to the dot arrangement therein, as shown in FIG. The arrangement order of is different.

  FIG. 41 is a diagram showing four planes to be considered in mask production of the present embodiment based on the dot arrangement pattern shown in FIG. As shown in the figure, each of the planes P1 to P4 has a 2 × 2 pixel area corresponding to the cluster size of the mask to be created. Also, the arrangement of these planes in dot units is mutually exclusive or complementary. Thereby, when determining the arrangement of the print permitting pixels in the cluster mask of the present embodiment by calculating the repulsive potential between these planes, it is possible to obtain an arrangement having no bias and excellent dispersibility.

  FIG. 42 is a diagram showing a mask C1 created in consideration of the four planes P1 to P4 and a complementary mask C2 thereof. FIG. 43 is a diagram showing a dot pattern formed when the level 1 dot arrangement pattern shown in FIG. 40A is masked using the mask C1 shown in FIG. As is apparent from this figure, the formed dot pattern has no uneven number of dots and has excellent dispersibility.

  As described above, also in the case of a cluster mask, by considering the dot arrangement pattern, the number of dots formed by scanning is not biased, and the dispersibility of the pattern is improved. Due to the high dispersibility, even if a texture is generated, it is hardly visually disturbed and the influence on the image quality is suppressed.

  In addition, although the description has been given of the mask with 2 × 2 pixels as one unit as the cluster mask with m × n pixels as one unit, the present embodiment is not limited to this. For example, a mask having 1 × 2 pixels as one unit, a mask having 2 × 4 pixels as one unit, or the like may be used. The values of m and n may be any number where m and n are both positive integers and at least one of m and n is an integer of 2 or more.

<Other embodiments>
In the above-described embodiment, the arrangement of the print permitting pixels in the mask pattern is determined in consideration of the dot arrangement pattern corresponding to all of the gradation levels 1 to 4, but the present invention is not limited to this. Absent. For example, among the four levels, the arrangement of the print permitting pixels in the mask pattern may be determined in consideration of the dot arrangement pattern corresponding to level 1 to 3, level 1 to 2, or level 1. In this case, the effect of dot dispersibility is reduced as compared with a case where all levels of dot arrangement patterns are considered, but the effect of dispersibility is greater than when no dot arrangement pattern is considered. As described above, any form in which the arrangement of the print permitting pixels in the mask pattern is determined in consideration of the dot arrangement pattern corresponding to at least one gradation level is included in the scope of the present invention.

  Further, although cases have been described with the above embodiments where dot arrangement patterns corresponding to gradation levels are used, the application of the present invention is not limited to this. For example, when recording data is formed by a pattern having a repeating cycle, a mask in consideration of this periodic pattern can be created to obtain the same effect.

  In the above-described embodiment, the description has been made on the second and fourth passes. However, it is apparent from the above description that the present invention can be applied to any number of passes corresponding to three or more scans. Further, the mask used in the two-pass printing has been described by taking only one color as an example, but it is needless to say that the mask is not limited thereto. For example, the present invention can also be applied to a mask for two-pass printing for each of C, M, and Y. This is apparent from, for example, the mask creation of the second embodiment described above with reference to FIG.

  Further, in each of the above-described embodiments, the recording apparatus (printer) functions as the data processing apparatus of the present invention to perform mask processing and related processing. However, the application of the present invention is not limited to this configuration. Of course. For example, a data supply device (for example, the host device in FIGS. 3 and 4) that supplies binary data for each scan generated by mask processing to the printer functions as the data processing device of the present invention. The configuration may be such that mask processing using the described mask is performed.

  Furthermore, the present invention can also be realized by a program code that realizes the functions of the above-described embodiments and that realizes the procedures of the flowcharts shown in FIGS. 9 and 25, or a storage medium that stores the program code. It can also be achieved by reading and executing the program code stored in the storage medium by the computer (or CPU or MPU) of the system or apparatus. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.

  As a storage medium for supplying the program code, for example, a floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD-R, magnetic tape, nonvolatile memory card, ROM, or the like is used. be able to.

  In addition, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also the OS running on the computer performs an actual process based on the instruction of the program code. Part or all may be performed.

FIG. 3 is a diagram schematically illustrating a recording head and a recording pattern for explaining multi-pass recording. It is a figure showing the dot recording pattern by 2 pass printing. 1 is a block diagram mainly showing hardware and software configurations of a personal computer as an image processing apparatus according to an embodiment of the present invention. It is a block diagram for demonstrating the flow of the image data conversion process in the recording system applied by this embodiment. It is a figure which shows the dot arrangement pattern based on index data in this embodiment. (A)-(d) is a figure which shows typically the calculation of the repulsive potential mentioned above, and the attenuation | damping process of total energy. It is a figure which shows typically the function of the basic repulsive potential E (r) which concerns on this embodiment. FIG. 3 is a diagram schematically illustrating a positional relationship among a recording head, a mask pattern, and a recording medium for explaining two-pass recording in the first embodiment of the present invention. 6 is a flowchart showing a process for arranging print-permitted pixels by a sequential arrangement method in the first embodiment. It is a conceptual diagram for calculating the mask C in the first embodiment. It is a figure which shows the dot arrangement pattern based on index data in 1st embodiment. It is a figure which shows the pattern considered in the case of mask preparation based on the dot arrangement pattern shown in FIG. It is a figure which shows the other example of the dot arrangement pattern based on index data in 1st embodiment. It is a figure which shows the pattern considered in the case of mask preparation based on the dot arrangement pattern shown in FIG. It is a figure which shows the arrangement pattern of the print permission pixel in the pattern consideration type mask which concerns on 1st embodiment. It is a figure which shows the arrangement | positioning pattern of the recording permissible pixel in the lamination | stacking mask relevant to this invention. FIG. 12 is a diagram showing a logical product pattern of the pattern-considering laminated mask C1 and the level 1 dot arrangement shown in FIG. FIG. 12 is a diagram showing a logical product pattern of the pattern-considering laminated mask C1 and the level 2 dot arrangement shown in FIG. 11 in the first embodiment. FIG. 12 is a diagram showing a logical product pattern of the pattern-considering laminated mask C1 and the level 3 dot arrangement shown in FIG. 11 in the first embodiment. FIG. 12 is a diagram illustrating a logical product pattern of the layered mask related to the present invention and the level 1 dot arrangement shown in FIG. 11. FIG. 12 is a diagram illustrating a logical product pattern of the layered mask related to the present invention and the level 2 dot arrangement shown in FIG. 11. FIG. 12 is a diagram illustrating a logical product pattern of the layered mask related to the present invention and the level 3 dot arrangement shown in FIG. 11. It is a figure explaining the frequency characteristic of the pattern consideration type lamination mask (C1) in the first embodiment, and the lamination mask relevant to the present invention. A dot pattern formed by one scan each time the mask processing of the level 1 dot arrangement pattern is recorded using the mask according to the first embodiment and the laminated mask related to the present invention (FIG. 17, FIG. It is a figure explaining the frequency characteristic of 20). It is a flowchart which shows the arrangement | positioning determination process of the printing permissible pixel by the sequential arrangement method in 2nd embodiment of this invention. It is a conceptual diagram which shows the mask pattern production | generation of each color in 2nd embodiment. It is a figure which shows the dot arrangement pattern in 2nd embodiment. It is a figure explaining the pattern considered in the case of mask generation in 2nd embodiment. It is a figure which shows the mask pattern of C by 2nd embodiment. It is a figure which shows the mask pattern of M by 2nd embodiment. It is a figure which shows the mask pattern of Y by 2nd embodiment. It is a pattern which shows the logical product dot of pattern consideration type lamination mask C1 and dot arrangement of cyan level 1 in a second embodiment. It is a pattern which shows the logical product dot of the pattern consideration type | mold laminated mask M1 and the dot arrangement | positioning of cyan level 1 in 2nd embodiment. It is a pattern which shows the logical product dot of pattern consideration type lamination mask Y1 and dot arrangement of cyan level 1 in a second embodiment. A dot pattern formed by a single scan when a mask of a dot arrangement pattern is printed using a mask according to the second embodiment (a logical product obtained by a logical product of a mask pattern and a dot arrangement pattern) It is a figure explaining the frequency characteristic of a pattern. (A) And (b) is a figure which shows the mask pattern of the printing rate corresponding to the nozzle position of the gradation mask, and 2 pass printing in 3rd embodiment of this invention. (A) And (b) is a figure which shows the printing ratio with respect to each nozzle of a 2-pass 150% uniform mask in the 4th Embodiment of this invention, and an actual mask pattern. It is a figure which shows the logical sum of C1 and C2 shown in FIG.37 (b) concerning 4th embodiment. FIG. 38 is a diagram illustrating a logical dot arrangement of the mask pattern shown in FIG. 37 and the level 1 dot arrangement pattern used in the present embodiment in the fourth embodiment. (A) And (b) is a figure explaining the dot arrangement pattern and its arrangement in the fifth embodiment of the present invention. It is a figure explaining the pattern considered in the case of mask generation in 5th embodiment. It is a figure which shows the mask pattern of cluster size 2x2 produced by 5th embodiment. It is a figure which shows the dot pattern recorded by one scan when the mask pattern shown in FIG. 42 produced by 5th embodiment is used.

Explanation of symbols

3000 Personal computer (PC: Host computer)
3004 Printer J0007 Dot arrangement patterning process J0008 Mask data conversion process J0009 Head drive circuit J0010 Print head

Claims (22)

To binary image data representing an image to be recorded on the same area of the recording medium, a masking process by a row Ukoto using a plurality of mask patterns corresponding to plural scans of the recording head relative to the same region, the A data processing apparatus for generating binary thinned image data representing a thinned image to be recorded in each of a plurality of scans,
Dots used in binarization processing for generating data indicating print-acceptable pixels in a mask pattern corresponding to one scan other than the last scan of the plurality of scans and the binary image data A data processing apparatus, wherein characteristics of a logical product pattern obtained by logical product with data indicating recording dots in an arrangement pattern satisfy the following (a) and (b):
(A) The frequency component in the low frequency region in the logical product pattern is less than the frequency component in the high frequency region .
(B) the absence of a peak of the frequency components in the region of from the low frequency half of the low frequency range. To binary image data representing an image to be recorded on the same area of the recording medium, a masking process by a row Ukoto using a plurality of mask patterns corresponding to plural scans of the recording head relative to the same region, the A data processing apparatus for generating binary thinned image data representing a thinned image to be recorded in each of a plurality of scans,
Dots used in binarization processing for generating data indicating print-acceptable pixels in a mask pattern corresponding to one scan other than the last scan of the plurality of scans and the binary image data A data processing apparatus, wherein characteristics of a logical product pattern obtained by logical product with data indicating recording dots in an arrangement pattern satisfy the following (a) and (b):
(A) The frequency component in the low frequency region in the logical product pattern is less than the frequency component in the high frequency region.
(B) there is no peak frequency components in the region of from 1/4 to the low frequency side of the low frequency range. To binary image data representing an image to be recorded on the same area of the recording medium, a masking process by a row Ukoto using a plurality of mask patterns corresponding to plural scans of the recording head relative to the same region, the A data processing apparatus for generating binary thinned image data representing a thinned image to be recorded in each of a plurality of scans,
Dots used in binarization processing for generating data indicating print-acceptable pixels in a mask pattern corresponding to one scan other than the last scan of the plurality of scans and the binary image data A data processing apparatus, wherein characteristics of a logical product pattern obtained by logical product with data indicating recording dots in an arrangement pattern satisfy the following (a) and (b):
(A) The frequency component in the low frequency region in the logical product pattern is less than the frequency component in the high frequency region.
(B) there is no peak frequency components in the low frequency range. Binarization means for performing binarization processing for converting multi-valued image data having gradation values into binary image data;
To generate the decimated image data for a plurality of times of 2 values used in scanning each of the binary recording head from image data obtained by said binarizing means, the plurality of the image data of the binary a mask processing unit for performing mask processing, the using a plurality of mask patterns corresponding to the times of the scanning,
And data indicating the print permitting pixels in a mask pattern corresponding to the first scan of the plurality of times of scanning, among the plurality of dot arrangement patterns corresponding to the plurality of tone values available in the binarization A data processing apparatus characterized in that the characteristics of a logical product pattern obtained by logical product of data indicating a recording dot in a dot arrangement pattern corresponding to one gradation value satisfy the following (a) and (b) .
(A) The frequency component in the low frequency region in the logical product pattern is less than the frequency component in the high frequency region .
(B) there is no peak frequency components in the region of from 1/4 to the low frequency side of the low frequency range.   Binarization means for performing binarization processing for converting multi-valued image data having gradation values into binary image data;
In order to generate binary thinned-out image data used in each of a plurality of scans of the recording head from the binary image data obtained by the binarization means, A mask processing means for performing mask processing using a plurality of mask patterns corresponding to a single scan,
Of the plurality of dot arrangement patterns respectively corresponding to the plurality of gradation values usable in the binarization processing, the data indicating the print allowable pixels in the mask pattern corresponding to the first scan of the plurality of scans A data processing apparatus characterized in that the characteristics of the logical product pattern obtained by the logical product of the data indicating the recording dots in the dot arrangement pattern corresponding to one gradation value satisfy the following (a) and (b): .
(A) The frequency component in the low frequency region in the logical product pattern is less than the frequency component in the high frequency region.
(B) There is no frequency component peak in the lower frequency region than half of the low frequency region. Binarization means for performing binarization processing for converting multi-valued image data having gradation values into binary image data;
In order to generate binary thinned-out image data used in each of a plurality of scans of the recording head from the binary image data obtained by the binarization means, A mask processing means for performing mask processing using a plurality of mask patterns corresponding to a single scan,
Of the plurality of dot arrangement patterns respectively corresponding to the plurality of gradation values usable in the binarization processing, the data indicating the print allowable pixels in the mask pattern corresponding to the first scan of the plurality of scans A data processing apparatus characterized in that the characteristics of a logical product pattern obtained by the logical product of data indicating a recording dot in a dot arrangement pattern corresponding to one gradation value satisfy the following (a) and (b): .
(A) The frequency component in the low frequency region in the logical product pattern is less than the frequency component in the high frequency region.
(B) There is no frequency component peak in the low frequency region. The arrangement of the print permitting pixels in the mask pattern corresponding to the first scan among the plurality of scans is determined based on the dot arrangement pattern. The data processing apparatus described . 7. The print permitting pixel arrangement in the mask pattern corresponding to the first scan is determined based on a plurality of dot arrangement patterns respectively corresponding to the plurality of gradation values. A data processing apparatus according to any one of the above . The arrangement of the printable pixels in the mask pattern corresponding to the first scan is a calculation dot pattern obtained based on the plurality of dot arrangement patterns corresponding to the plurality of gradation values, and the dot arrangement is mutually exclusive. 9. The data processing apparatus according to claim 8 , wherein the data processing apparatus is determined based on a dot arrangement of each of a plurality of dot patterns for calculation having the relationship. The recording head has a plurality of recording elements arranged in a direction crossing the scanning direction for discharging ink of the same color,
The mask pattern has a print-allowed pixel and a non-print-allowed pixel that are two-dimensionally arranged in the scanning direction and the array direction of the printing elements,
The ratio of the print allowable pixels constituting the mask pattern used for masking the binary image data corresponding to the printing element at the end of the plurality of printing elements is the ratio of the plurality of printing elements. 10. The data according to claim 1, wherein the data is smaller than a ratio of recording allowable pixels constituting a mask pattern used for masking binary image data corresponding to a central recording element. Processing equipment . The mask pattern data processing apparatus according to any one of claims 1 to 9, wherein the print permitting pixels m × n pixels as a unit is one that was placed. It said masking means includes a generating means generates a thinned binary image data that is used by people said plurality of scans husband performs logical product of the image data of each said binary of said plurality of mask patterns the data processing apparatus according to any one of claims 1 to 11. The binary image data representing an image to be recorded in the same area of the recording medium is subjected to mask processing using a plurality of mask patterns corresponding to a plurality of scans of the recording head with respect to the same area. A data processing device for generating binary thinned image data representing a thinned image to be recorded in each of the scans,
Dots used in binarization processing for generating data indicating print-acceptable pixels in a mask pattern corresponding to one scan other than the last scan of the plurality of scans and the binary image data The frequency component of the low frequency region of the characteristic of the logical product pattern obtained by the logical product with the data indicating the recording dots in the arrangement pattern is less than the frequency component of the high frequency region,
The data processing device according to claim 1, wherein the arrangement of the print permitting pixels in the mask pattern corresponding to one scan other than the last scan is determined based on the dot arrangement pattern. Binarization means for performing binarization processing for converting multi-valued image data having gradation values into binary image data;
In order to generate binary thinned-out image data used in each of a plurality of scans of the recording head from the binary image data obtained by the binarization means, A mask processing means for performing mask processing using a plurality of mask patterns corresponding to a single scan,
Of the plurality of dot arrangement patterns respectively corresponding to the plurality of gradation values usable in the binarization processing, the data indicating the print allowable pixels in the mask pattern corresponding to the first scan of the plurality of scans The frequency component of the low frequency region of the logical product pattern obtained by the logical product of the data indicating the recording dot in the dot arrangement pattern corresponding to one gradation value of the number is smaller than the frequency component of the high frequency region,
The data processing apparatus according to claim 1, wherein the arrangement of the print permitting pixels in the mask pattern corresponding to the first scan is determined based on the dot arrangement pattern. A program that causes a computer to function as the data processing device according to any one of claims 1 to 14. Binary thinned-out image data representing a thinned image to be recorded in one scan out of a plurality of scans of the print head for the same region from binary image data representing an image to be recorded in the same region of the recording medium A method of manufacturing a mask pattern used to generate
A determination step for determining an arrangement of the print-allowed pixels in the mask pattern;
It said determining step includes a data indicating the print permitting pixels in the mask pattern, a plurality of dot arrangement patterns corresponding to the plurality of gray levels available in the binarization processing for generating image data of the binary and data showing the arrangement of determined based dots, so that the low frequency components of the logical product patterns obtained by the logical product is reduced, and changes the arrangement of the print permitting pixels in the mask pattern based on the plurality of dot arrangement patterns mask pattern manufacturing method characterized by comprising the change step of Ru is. The determination step includes calculating dot patterns obtained based on the arrangement of the print-allowable pixels and the plurality of dot arrangement patterns, and each dot of the plurality of calculation dot patterns in which the dot arrangement is mutually exclusive. And calculating a repulsive potential based on the arrangement, and calculating a total potential that is a sum of the repulsive potentials ,
The mask pattern manufacturing method according to claim 16, wherein in the changing step, the arrangement of the print-allowed pixels is changed so that the total potential obtained in the calculating step is lowered . Binary thinned-out image data representing a thinned image to be recorded in one scan out of a plurality of scans of the print head for the same region from binary image data representing an image to be recorded in the same region of the recording medium A method of manufacturing a mask pattern used to generate
A determination step of determining an arrangement of print permitting pixels in the mask pattern based on a plurality of dot arrangement patterns corresponding to a plurality of gradation levels usable in the binarization process for generating the binary image data; Have
The determining step includes the first step of determining the arrangement of the print permitting pixels in the first arrangement, and the plurality of dot arrangement patterns based on the plurality of dot arrangement patterns so that low frequency components in the arrangement pattern of the print permitting pixels are reduced. And a second step of changing the arrangement of the print permitting pixels from the first arrangement to the second arrangement . A mask pattern manufacturing method comprising:
From the first binary image data representing the image to be recorded in the same area of the recording medium by the first nozzle group for ejecting the first color ink, the first nozzle group for the same area a plurality of times. A first determination step for determining an arrangement of print permitting pixels in a first mask pattern used for generating binary thinned image data representing a thinned image to be printed in one of the scans;
The second binary image data representing the image to be recorded in the same area of the recording medium by the second nozzle group for ejecting the ink of the second color different from the first color is applied to the same area. Arrangement of print-allowable pixels in the second mask pattern used to generate binary thinned image data representing a thinned image to be printed in one of the plurality of scans of the second nozzle group A second determining step for determining
The first determination step includes one gradation value among a plurality of dot arrangement patterns respectively corresponding to a plurality of gradation values that can be used in the binarization process for generating the first binary image data. The low frequency component of the logical product pattern obtained by the logical product of the data indicating the recording dots in the first dot arrangement pattern corresponding to the above and the data indicating the recording allowable pixels in the first mask pattern is reduced. And changing the arrangement of print permitting pixels in the first mask pattern based on the first dot arrangement pattern and the second mask pattern,
In the second determination step, a second dot arrangement among a plurality of dot arrangement patterns respectively corresponding to a plurality of gradation values that can be used in the binarization process for generating the second binary image data. The second dot arrangement pattern so that the low-frequency component of the logical product pattern obtained by the logical product of the data indicating the recording dot in the pattern and the data indicating the recording allowable pixel in the second mask pattern is reduced. And a step of changing an arrangement of print permitting pixels in the second mask pattern based on the first mask pattern.
The mask pattern manufacturing method characterized by the above-mentioned. 20. The mask according to claim 16, wherein one of the plurality of scans is one scan other than the last scan of the plurality of scans. Pattern manufacturing method . The mask pattern manufacturing method according to claim 16, wherein one of the plurality of scans is a first scan of the plurality of scans. A mask process is performed on binary image data representing an image to be recorded in the same area of a recording medium, using the mask pattern manufactured by the mask pattern manufacturing method according to claim 16. A data processing apparatus comprising: generating means capable of generating binary thinned image data representing a thinned image to be printed in one of a plurality of scans of the print head for the same region.

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