JP2005231060A - Image processor and inkjet recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processor and an inkjet recording apparatus, which generate image data capable of suppressing a deviation (variation) in ejection characteristics of a lengthened recording head even if the deviation exists in the lengthened recording head, and capable of bringing about high-speed and high-image-quality printout. <P>SOLUTION: This inkjet recording apparatus has the recording head wherein a plurality of nozzles for ejecting ink are arranged. The inkjet recording apparatus performs multipass recording wherein an image is recorded in the same area of a recording medium by means of different nozzle groups split depending on the number of passes, by micromoving the recoding medium in the direction of the arrangement of the nozzles depending on the number of passes and making the recording head do a plurality of scans in a direction crossing the direction of the arrangement of the nozzles. The plurality of nozzles are split in a smaller split unit than a split unit depending on the number of the passes for the multipass recording; a thinning rate is set for each small split unit; a mask pattern depending on the set thinning rate is set for each small split unit; the set mask pattern is applied to the image data for each small split unit, so that the thinned-out image data recorded through the respective passes for the multipass recording can be generated; and the image is recorded according to the thinned-out image data. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image processing apparatus and an inkjet recording apparatus, and more particularly to an image processing apparatus and an inkjet recording apparatus that generate image data used in multipass recording.

  2. Description of the Related Art Currently, inkjet printers that record images by ejecting liquid ink droplets from a plurality of nozzles arranged in a recording head are widely used as small-sized printers. An ink jet printer has a simple structure and a low printing sound, and can record a multi-tone image such as a photographic image with high image quality. Recently, a printer having a relatively long recording head and capable of high-speed printing has been developed. While such a printer has the advantage of being capable of high-speed printing, it is difficult to maintain the uniformity of the ejection characteristics of each nozzle within the recording head due to the increase in length, and the quality of the image due to variations in nozzle characteristics. There is a problem that decreases.

  In order to prevent deterioration in image quality due to variations in nozzle characteristics, a multi-pass printing method has been proposed. In the multi-pass recording method, recording is performed with different nozzle groups by moving the recording medium minutely in the nozzle arrangement direction of the recording head and scanning the recording head a plurality of times (multi-pass) in a direction intersecting the nozzle arrangement direction. The image thinned in the same area of the medium is complementarily recorded to complete the image. As a result, variations in ejection characteristics for each nozzle of the recording head are dispersed, and deterioration in image quality is prevented.

  Hereinafter, the conventional multi-pass recording method will be described in detail with reference to FIGS. Here, a case where an image is recorded by scanning a recording head having 256 nozzles is taken as an example.

  If the image is completed by one-pass (collective) recording without performing multi-pass recording, the density of the recorded image is biased as indicated by M1 in FIG. This is because, as described above, the density of ink ejected from each nozzle varies due to the variation in ejection characteristics of each nozzle. The “density variation” in FIG. 5A shows the value of the nozzle discharge density when the nozzle discharge density in the design of the print head is set to 100. Here, the 256 nozzles are divided into 32 nozzle groups, the density of the droplets discharged for each nozzle group is averaged, and the averaged value is shown as the discharge density of each nozzle group. . As shown in the drawing, since there is a variation in the discharge density for each nozzle group, the density of the image is biased as indicated by M1 in FIG.

  On the other hand, in the 2-pass printing method, the 256 nozzles arranged in the print head are divided into two nozzle groups, and the first pass is printed by the lower half (1 to 128) nozzle groups, By recording the second pass with half (129 to 256) nozzle groups, the image of the recording target area is completed. The “thinning rate” is 50% for each nozzle group because of 2-pass printing. Further, as shown in “divided MASK” in FIG. 5A, a predetermined mask pattern “A” is applied to the image data recorded by the upper half nozzle, and the image recorded by the lower half nozzle. The mask pattern “A ′” having a relationship in which the exclusive OR with the mask pattern “A” is 1 is applied to the data. As a result, the thinned image data image is complementarily recorded in the recording target area by two passes, and the image is completed.

  FIG. 5B is a diagram illustrating a state in which the recording head moves in the nozzle arrangement direction by the print width for one pass. The numerical values shown are density values for each nozzle group ejected for each pass, obtained by multiplying the density variation of each nozzle group of the recording head by the thinning rate.

  As described above, when the recording head moves by the print width and is recorded in a complementary manner in the recording target area by two passes, the density variation is suppressed as shown in FIG. As indicated by M2 in 5 (D), the density deviation of the image is improved as compared with the one-pass printing. However, as shown in the figure, the density deviation still remains, and the influence due to the variation in the nozzle characteristics is not sufficiently eliminated.

  By the way, it is a technique related to a mask pattern of a multi-pass printing method, and it is an image quality deterioration due to a local variation in characteristics of nozzles of a print head, for example, shading unevenness / streak depending on variations in ejection directionality or drop amount (density). As a technique that can reduce, for example, a thinning mask pattern applied to image data generation for each pass of multipass printing is randomized, and a different mask pattern is used for each color, so that binarization There is known a method capable of efficiently suppressing variations in ejection directionality without interfering with a screen pattern (see, for example, Patent Documents 1 and 2). In addition, when recording at a higher resolution than the predetermined resolution using a mask pattern, in order to prevent unintentional concentration of recording pixels, not only the mask pattern is given randomness but also weighting according to the input data, further nozzle characteristics There is also known a method for reducing density unevenness and streaks due to variations in the number (for example, see Patent Document 3).

Although it is also related to the mask pattern, it is possible to reduce image quality deterioration due to variations in nozzle characteristics of the print head division unit (print width unit), for example, moire depending on how the divided print patterns overlap. As a technology, due to the use of different random mask patterns in the print area of the print width during multi-pass printing, the same mask pattern is used, resulting from the mask pattern misalignment for each pass. A method of reducing “regular moire” is known (for example, see Patent Document 4). A method for dynamically generating a mask pattern is also known (see, for example, Patent Document 5).
JP 7-52390 A Japanese Patent Laid-Open No. 10-235852 JP 2002-331650 A JP-A-7-125311 JP-A-10-235851

  However, the technology for reducing image quality degradation due to local characteristic variations in the nozzle unit of the printhead is effective when the nozzle characteristic variations are uniformly present in the printhead. Small if there is a bias across the width. For example, when the discharge density is low at the nozzle at the end of the recording head and the discharge density is high at the nozzle at the center, the effect of reducing this is small with the conventional technique. Therefore, it is not an effective improvement means for the deviation of the nozzle ejection characteristics in the recording head, which has been particularly problematic as the recording head becomes longer. Also, the method using a random mask pattern or the method of dynamically generating a mask pattern does not take into account the characteristics of each nozzle, and thus cannot be said to be an effective means for solving the conventional problems.

  Furthermore, in multi-pass printing, if the number of passes is increased, the image quality is improved. However, the problem is that the printing speed becomes slower as the number of passes is increased.

  The present invention has been made to solve the above-described problems. Even when there is a deviation in ejection characteristics in a long recording head, this deviation (variation) can be suppressed, and high-speed and high-quality printing can be achieved. An object of the present invention is to provide an image processing apparatus and an ink jet recording apparatus that generate image data from which output can be obtained.

  In order to achieve the above object, a first image processing apparatus according to the present invention is an inkjet recording apparatus having a recording head in which a plurality of nozzles for ejecting ink are arranged. An image is recorded in the same area of the recording medium by different nozzle groups divided according to the number of passes by finely moving the recording medium in the arrangement direction and scanning the recording head a plurality of times in a direction intersecting the arrangement direction of the nozzles. An image processing apparatus for generating thinned image data recorded in each pass in multi-pass printing, wherein the plurality of nozzles are divided into smaller division units smaller than a division unit corresponding to the number of passes of the multi-pass printing. A thinning rate setting means for dividing and setting a thinning rate for each small division unit, and a mask pattern corresponding to the thinning rate set by the thinning rate setting means for each small division Mask pattern setting means for setting each position, and the thinned image data recorded in each pass of the multi-pass recording by applying the mask pattern set by the mask pattern setting means to the image data for each subdivision unit Generating means for generating.

  That is, in the first image processing apparatus, the plurality of nozzles are divided into smaller division units smaller than the division unit corresponding to the number of passes of multi-pass printing, and a thinning rate is set for each of the smaller division units. A mask pattern corresponding to the thinning rate is set for each subdivision unit, and the set mask pattern is applied to the image data for each subdivision unit, so that the thinned image data recorded in each pass of multipass recording Is generated.

  As a result, the thinned-out image data is generated by adjusting the thinning rate more finely than the conventional method that generates the thinned-out image data by setting the thinning rate evenly for each division unit corresponding to the number of passes. Therefore, image quality deterioration (density deviation) due to variations in ejection characteristics of the nozzles arranged in the recording head can be suppressed, and high-speed and high-quality print output can be obtained.

  The thinning rate setting means can set the thinning rate according to the characteristics of the nozzles for each of the small division units. Further, the thinning rate setting means can further set the thinning rate according to the color of ink ejected from the nozzles for each of the small division units.

  The characteristics of the nozzles used for setting the thinning rate are not particularly limited as long as the characteristics affect the output result, and may be the ejection directionality of the nozzles or ink droplets ejected from the nozzles. It may be the amount, that is, the density of the formed image.

  Further, the mask pattern setting means can set a mask pattern generated by performing a predetermined calculation process according to the thinning rate set by the thinning rate setting means for each subdivision unit.

  The second image processing apparatus of the present invention is a micro-movement of the recording medium in the direction of nozzle arrangement according to the number of passes, which is performed by an ink jet recording apparatus having a recording head in which a plurality of nozzles for ejecting ink are arranged. Each pass in multi-pass printing, in which an image is recorded in the same area of the recording medium by different nozzle groups divided according to the number of passes by scanning the recording head a plurality of times in a direction crossing the nozzle arrangement direction. An image processing apparatus for generating thinned image data recorded in a step, wherein the plurality of nozzles are thinned for each division unit according to the characteristics of the nozzles for each division unit according to the number of passes of the multipass printing. A ratio is set, or the plurality of nozzles are divided into smaller division units smaller than the division unit corresponding to the number of passes of the multi-pass printing, and the characteristics of the nozzles for each smaller division unit are determined. A decimation rate setting means for setting a decimation rate for each subdivision unit, and a mask pattern for setting a mask pattern corresponding to the decimation rate set by the decimation rate setting unit for each subdivision unit or for each subdivision unit Applying the setting unit and the mask pattern set by the mask pattern setting unit to the image data for each division unit or each subdivision unit to generate thinned image data recorded in each pass of the multi-pass recording Generating means.

  That is, in the second image processing apparatus of the present invention, the thinning rate is set according to the characteristics of the nozzle. Also, the thinning rate is set for each division unit corresponding to the number of passes of multi-pass printing for a plurality of nozzles, or in a small division unit smaller than the division unit corresponding to the number of passes for multi-pass printing. It is divided and set for each small division unit. A mask pattern is set according to the set thinning rate, and the thinned image data is generated by applying the mask pattern to the image data.

  Thus, since the thinning rate is set according to the characteristics of the nozzle, not only when the thinning rate is set for each small division unit smaller than the division unit according to the number of passes, but also for each division unit according to the number of passes. Even when the thinning rate is set, it is possible to eliminate unevenness in density due to variations in nozzle characteristics and form a high-quality image.

  The thinning rate setting means can further set the thinning rate according to the color of ink ejected from the nozzles for each of the small division units.

  Further, the mask pattern setting means can set a mask pattern generated by performing a predetermined calculation process according to the thinning rate set by the thinning rate setting means for each subdivision unit.

  The first inkjet recording apparatus of the present invention has a recording head in which a plurality of nozzles for ejecting ink are arranged, and the recording medium is finely moved in the nozzle arrangement direction in accordance with the number of passes to arrange the nozzle in the arrangement direction. An inkjet recording apparatus for performing multi-pass recording in which an image is recorded in the same area of a recording medium with different nozzle groups divided according to the number of passes by scanning the recording head a plurality of times in a direction intersecting with the recording head, A plurality of nozzles are divided by a small division unit smaller than a division unit corresponding to the number of passes of the multi-pass printing, and a thinning rate setting unit that sets a thinning rate for each small division unit and a thinning rate setting unit are set. A mask pattern setting means for setting a mask pattern corresponding to the thinning rate for each subdivision unit, and a mask pattern set by the mask pattern setting means Is applied to the image data for each sub-division unit, the multipath generation means for generating a thinned-out image data to be recorded in each pass of the recording, it is configured to include a.

  Since the first ink jet recording apparatus operates in the same manner as the first image processing apparatus, image quality degradation (density deviation) due to variations in ejection characteristics of the nozzles arranged in the recording head can be suppressed. High-speed and high-quality print output can be obtained.

  In the first ink jet recording apparatus, the thinning rate setting means can set the thinning rate according to the characteristics of the nozzles for each of the small division units.

  The second inkjet recording apparatus of the present invention has a recording head in which a plurality of nozzles for ejecting ink are arranged, and the recording medium is finely moved in the arrangement direction of the nozzles according to the number of passes to arrange the nozzles An inkjet recording apparatus that performs multi-pass recording in which an image is recorded in the same area of a recording medium with different nozzle groups divided according to the number of passes by scanning the recording head a plurality of times in a direction intersecting with the recording head, Set a thinning rate for each division unit according to the characteristics of the nozzles for each division unit corresponding to the number of passes of the multipass printing, or set the plurality of nozzles to the number of passes for the multipass printing. A thinning rate setting unit that divides into smaller subdivision units smaller than the subdivision unit, and sets a thinning rate for each subdivision unit according to the nozzle characteristics for each subdivision unit; A mask pattern setting means for setting a mask pattern corresponding to the thinning rate set by the rate setting means for each division unit or each subdivision unit, and a mask pattern set by the mask pattern setting means for each division unit or each And generating means for generating thinned-out image data recorded in each pass of the multi-pass recording, applied to the image data for each subdivision unit.

  Since the second inkjet recording apparatus operates in the same manner as the second image processing apparatus, not only the thinning rate is set for each small division unit smaller than the division unit corresponding to the number of passes, but also according to the number of passes. Even when the thinning rate is set for each division unit, it is possible to eliminate density unevenness due to variations in nozzle characteristics and form a high-quality image.

  As described above, according to the present invention, even when there is a deviation in overall jetting characteristics in the elongated recording head, this deviation (variation) can be suppressed, and a high-speed and high-quality print output can be obtained. There is an excellent effect of being able to.

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

  FIG. 1 is a diagram showing a configuration of an ink jet recording apparatus according to an embodiment of the present invention. The ink jet recording apparatus according to the present embodiment is a recording apparatus that performs multi-pass printing (two-pass printing) with two passes. As illustrated, the color correction unit 10, the binarization unit 12, and the binary And a recording head information storage unit 16, a multi-pass print control unit 18, a recording head drive unit 20, and a recording head 22.

  The color correction unit 10 converts multi-value gradation image data in RGB format input from the outside into multi-value gradation image data in CMYK format, and outputs the converted data to the binarization unit 12. The binarization unit 12 binarizes the CMYK format multi-gradation image data input from the color correction unit 10 by a known method and outputs the binarized data storage unit 14. The binarized data storage unit 14 stores image data binarized by the binarizing unit 12 (binarized data).

  In the recording head 22, 256 nozzles for ejecting ink are arranged in a line. Note that the ink jet recording apparatus of the present embodiment is equipped with a recording head for ejecting ink of four colors of K (black), C (cyan), M (magenta), and Y (yellow). However, here, four recording heads are illustrated together. The recording head 22 is driven by a recording head driving unit 20 described later.

  The recording head information storage unit 16 stores information indicating the characteristics of each nozzle of the recording head 22. Here, information on the density of ink droplets ejected from the nozzles (hereinafter referred to as ejection density) is stored as information indicating the characteristics of the nozzles. Specifically, as shown in the items “Nozzle” and “density variation” in FIG. 3A, 256 nozzles are divided into 32 nozzle groups, and the discharge density of the designed nozzles is set. When 100 is set, the discharge density of each nozzle is averaged for each nozzle group, and the averaged value is stored as the discharge density of each nozzle group. The information stored in the recording head information storage unit 16 is information corresponding to each of the recording heads 22 of the ink jet recording apparatus. For example, the information of each nozzle can be obtained by performing experiments at the time of manufacturing or shipping the ink jet recording apparatus. Information on the discharge density is acquired and stored.

  The multipass print control unit 18 includes a mask pattern generation unit 18a, a multipass data generation unit 18b, and a thinning rate table 18c.

  The thinning rate table 18c stores a thinning rate according to the nozzle characteristics (here, the discharge density). In multi-pass printing, an image is completed by recording a thinned image that is thinned so as to complement each other in each pass, and thinned image data representing the thinned image is generated in the thinned table 18c. The optimum thinning rate is stored corresponding to both the difference between the nozzle discharge density and the designed nozzle discharge density “100” and the difference between the complementary nozzle discharge density and the nozzle discharge density in a complementary relationship. . This thinning rate is obtained and set in advance by experiments or the like.

  The mask pattern generation unit 18a stores the characteristics of the nozzles from the printhead information storage unit 16 for each of the smaller division units (in this case, 32 divided into eight) smaller than the division unit (128) according to the number of passes. Is obtained, and the thinning rate stored in the thinning rate table 18c is selected and set according to the obtained information. Further, the mask pattern generation unit 18a dynamically generates a mask pattern corresponding to the set thinning rate for each subdivision unit.

  The multipath data generation unit 18b generates thinned image data from the binarized data stored in the binarized data storage unit using the mask pattern generated by the mask pattern generation unit 18a.

  The multi-pass print control unit 18 is composed of a microcomputer including a CPU, a ROM, and a RAM. The thinning rate table 18c is stored in the ROM. The mask pattern generation unit 18a and the multipath data generation unit 18b are functions realized by a program stored in the ROM.

  The recording head drive unit 20 drives the recording head 22. The recording head drive unit 20 is supplied with power for driving the recording head 22 from a power source (not shown). The recording head drive unit 20 selectively energizes the elements provided corresponding to the respective nozzles of the recording head 22 at a timing according to the thinned image data generated by the multi-pass print control unit 18. Ink droplets are selectively ejected and the recording head 22 is moved in a direction orthogonal to the nozzle arrangement direction.

  The ink jet recording apparatus is also provided with a transport unit that transports a recording medium (such as paper) in the direction in which the nozzles in the recording head 22 are arranged.

  Next, processing for generating and printing thinned image data in the ink jet recording apparatus according to the present embodiment will be described with reference to FIGS. As described above, since the inkjet recording apparatus of the present embodiment performs two-pass printing, as shown in FIG. 3A, 256 nozzles arranged in the recording head 22 are divided into two nozzle groups. Divide and record the first pass with the lower half (1 to 128) nozzle group, and record the second pass with the upper half (129 to 256) nozzle group to complete the image of the recording target area Let Here, processing in a single color (one recording head) will be described.

  FIG. 2 is a flowchart showing the flow of processing performed by the multipass print control unit 18. In step 100, the mask pattern generation unit 18a prints the print head information storage unit 16 for each of the subdivision units (in this case, 32 divided into 8) smaller than the 256 nozzles according to the number of passes (128). The information indicating the characteristics of the nozzle is taken in from. That is, the information of the discharge density for every 32 nozzle groups as shown in the “density variation” item of FIG.

  In step 102, the mask pattern generation unit 18a selects and sets the thinning rate stored in the thinning rate table 18c for each subdivision unit.

  In this embodiment, since two-pass printing is performed, thinned images that are thinned so as to be complemented by different nozzle groups in the first pass and the second pass are recorded. Therefore, in each nozzle group, as shown in FIG. 3 (A), the 225th to 256th nozzle groups and the 97th to 128th nozzle groups are in a complementary relationship, and the 193rd to 224th nozzle groups are 65th to 65th. The 96th nozzle group has a complementary relationship, the 161st to 192nd nozzle groups and the 33rd to 64th nozzle groups have a complementary relationship, and the 129th to 160th nozzle groups and the 1st to 32nd nozzle groups Are complementary. As described above, in the thinning rate table 18c, the optimum thinning rate includes both the difference between the nozzle discharge density and the designed discharge density, and the difference between the complementary nozzle discharge densities. Correspondingly stored. Accordingly, the thinning rate of the 225th to 256th nozzle groups is complementary to the difference between the discharge density “90” of the 225th to 256th nozzle groups and the designed discharge density “100” to “−10”. The thinning rate (“35%” in FIG. 3A) stored corresponding to the difference “−30” from the discharge density “110” of the 97th to 128th nozzle groups in the relationship is the thinning rate table. 18c is selected and set. For the other nozzle groups, the thinning rate is similarly selected and set as shown in FIG.

  In step 104, the mask pattern generation unit 18a dynamically generates a mask pattern corresponding to the set thinning rate for each subdivision unit. For example, the mask pattern of the recording area of the lower half (1st to 128th) nozzle groups of the recording head 22 can be generated as follows. First, as shown in FIG. 4A, a random number table 1 “r1 (x)” (x is an x coordinate value in a recording area of a small divided unit (hereinafter referred to as a small divided area)), and a random number table 2 A random number is generated from a function “f (r1 (x), r1 (y))” using “r1 (y)” (y is a y-coordinate value in a small divided area). Subsequently, as shown in FIG. 4B, the x and y coordinate values of the subdivision areas are set to 0 from the multipath definition table in which either 0 or 1 is defined for each thinning rate according to the random number. Decide whether to set to 1 or 1. This process is repeated for all the x and y coordinate values of each subdivision area corresponding to the upper half nozzle group, thereby generating a mask pattern for each subdivision area and recording the upper half 128 nozzle groups. A mask pattern to be applied to the region is generated. Note that the mask pattern applied to the recording area of the lower half nozzle group is generated so that the exclusive OR with the generated mask pattern applied to the recording area of the upper half nozzle group is 1 (FIG. 3). (Refer to the item “Divided MASK” in (A)).

  Thereby, for example, a mask pattern as shown in FIG. 4C is generated. The generated mask pattern is set as a mask pattern for generating thinned image data. The shaded portion in FIG. 5C is “1”, and the white portion is “0”.

  By dynamically generating the mask pattern in this way, the required memory capacity can be reduced compared to the case where a large number of mask patterns are stored in advance.

  In step 106, the multi-pass data generation unit 18b takes in the binarized data corresponding to the print width of the recording head 22 from the binarized data storage unit 14, and in step 108 takes in the generated and set mask pattern. Applying to binarized data, thinned-out thinned image data is generated. Specifically, the binarized data is ANDed with a mask pattern (mask processing by logical product), and the binarized data is thinned out.

  In step 110, the generated thinned image data is output. Thereby, the recording head drive unit 20 drives the recording head 22 to perform printing.

  In step 112, it is determined whether or not the printing process of all binarized data has been completed. If it is determined that the printing process has not been completed, the process returns to step 106 and the above process is repeated. Note that the binarized data captured in step 106 is binarized data of an area shifted by the print width for one pass. The processing from step 106 to step 112 is repeated until it is determined in step 112 that the printing process for all binarized data has been completed.

  FIG. 3B is a diagram illustrating a state in which the recording head moves in the nozzle arrangement direction by the print width for one pass. The numerical values shown are density values for each nozzle group ejected for each pass, obtained by multiplying the density variation of each nozzle group of the recording head by the thinning rate. When the image is recorded in a complementary manner in the recording area by two passes, the combined density value falls within a predetermined range (between 102.8 and 103.0 in FIG. 3C). Variations are suppressed.

  As described above, in the case of the conventional one-pass printing, as shown in P1 of FIG. 3D, the density is uneven. However, as described above, the thinning rate is set according to the characteristics of the nozzle. It is set for each subdivision unit, a mask pattern is set according to each thinning rate, applied to the binarized data, thinned image data is generated, and two-pass printing is performed, as shown in P2 of FIG. As shown, the variation in the print image density is almost eliminated.

  Therefore, since the density variation can be sufficiently suppressed without increasing the number of passes, a high-quality printed image can be obtained at high speed.

  The present invention is not limited to the above-described embodiments, and various design changes can be made within the scope described in the claims.

  For example, in the above-described embodiment, an example in which the nozzles of the recording head are divided into sub-divided units of 1/4 of the multi-pass print unit, and the thinned-out image data is generated by setting the thinning rate for each sub-divided unit. However, it may be smaller than this, for example, may be divided into 1/8 to generate thinned image data. As a result, it becomes possible to cope with a finer nozzle characteristic profile, and the image quality is improved.

  Furthermore, in the above-described embodiment, the example in which the thinning rate is set by dividing the plurality of nozzles of the recording head into smaller division units smaller than the division unit according to the number of passes has been described. May be divided in the same division unit as the division unit corresponding to the number of passes, and a thinning rate may be set in accordance with the nozzle characteristics for each division unit to generate thinned image data. As a result, even if the division unit for setting the thinning rate is the same as the division unit corresponding to the number of passes, the thinned image data corresponding to the characteristics of the nozzle is generated, so that the image quality is sufficiently higher than the conventional method. Can be improved.

  In the above-described embodiment, the processing with a single color (one recording head) has been described as an example. However, when processing is performed with, for example, a four-color four-recording head, thinned image data is generated in the same manner as described above. By doing so, it is possible to suppress degradation of the image. When a four-color four-recording head is used, the above-described nozzle characteristic variation is superimposed, and image quality deterioration further increases. However, even in such a case, the plurality of nozzles of the print head are divided into smaller division units smaller than the division unit corresponding to the number of passes, and thinned image data is generated reflecting the nozzle characteristics of each print head. By doing so, it is possible to greatly improve the image deterioration due to the deviation of the nozzle characteristics of the recording head. In this case, the thinning rate stored in the thinning rate table may be different for each color. For example, for a color whose image quality is hardly improved even if the thinning rate is changed, a value can be stored so that the thinning rate is hardly changed even if the variation in ejection density is large.

  Furthermore, in the above-described embodiment, the example in which the thinning rate is set according to the discharge density of the nozzle has been described. However, the present invention is not limited to this, and for example, it is set according to the discharge direction of the nozzle. May be.

  In the above-described embodiment, the ink jet recording apparatus has been described as an example. However, the present invention is not limited to the ink jet recording apparatus. For example, the function of the multipass print control unit described above is provided, and the function is Thus, the present invention can also be applied to an image processing apparatus that generates thinned image data.

1 is a diagram illustrating a configuration of an ink jet recording apparatus according to an embodiment of the present invention. It is the flowchart which showed the flow of the process performed in a multipass printing control part. In the multi-pass printing of the embodiment, (A) is a diagram showing the relationship between each nozzle group, the variation in discharge density, and the thinning rate, and (B) is a print for one pass by the recording head. FIG. 6C is a diagram showing a state in which the nozzle moves in the nozzle arrangement direction by the width, and FIG. 8C shows a case where two-pass printing is performed by changing the thinning rate for each small division unit according to the nozzle characteristics. It is the figure which showed the synthetic density value, (D) with the same nozzle group, the printing result when 1 pass printing is done, 2 pass printing was done by changing the thinning rate every small division unit It is the figure which showed the printing result at that time. (A) is a diagram showing a function for generating a random number from the random number table 1 and the random number table 2, and (B) is a multi-function in which either 0 or 1 is defined for each thinning rate according to the random number. It is the figure which showed the path | pass definition table, (C) is an example of the produced | generated mask pattern. In the conventional multi-pass printing, (A) is a diagram showing the relationship between each nozzle group, the variation in discharge density, and the thinning rate according to the embodiment, and (B) is one pass for the print head. FIG. 5C is a diagram showing a state where the nozzle moves in the nozzle arrangement direction by the print width corresponding to the print width, and FIG. 5C shows a state in which the thinning rate is changed for each division unit corresponding to the number of passes according to the nozzle characteristics. It is the figure which showed the synthetic | combination density value when performing pass printing, (D) is the printing result when performing 1-pass printing with the same nozzle group, and the printing result when performing 2-pass printing FIG.

Explanation of symbols

16 recording head information storage unit 18 multi-pass print control unit 18a mask pattern generation unit 18b multi-pass data generation unit 18c thinning rate table 22 recording head

Claims (10)

In an ink jet recording apparatus having a recording head in which a plurality of nozzles for ejecting ink are arranged, the recording medium is finely moved in the nozzle arrangement direction according to the number of passes, and in a direction crossing the nozzle arrangement direction. In order to generate thinned image data recorded in each pass in multi-pass recording in which an image is recorded in the same area of a recording medium by different nozzle groups divided according to the number of passes by scanning the recording head a plurality of times. Image processing apparatus,
A thinning rate setting unit configured to divide the plurality of nozzles by a small division unit smaller than a division unit corresponding to the number of passes of the multipass printing, and to set a thinning rate for each small division unit;
Mask pattern setting means for setting a mask pattern corresponding to the thinning rate set by the thinning rate setting means for each subdivision unit;
Generating means for applying the mask pattern set by the mask pattern setting means to the image data for each subdivision unit to generate thinned image data recorded in each pass of the multi-pass recording;
An image processing apparatus.   The image processing apparatus according to claim 1, wherein the thinning rate setting unit sets the thinning rate according to a characteristic of a nozzle for each of the small division units.   The image processing apparatus according to claim 2, wherein the thinning rate setting unit further sets the thinning rate according to a color of ink ejected from a nozzle for each of the small division units.   The mask pattern setting unit sets a mask pattern generated by performing a predetermined arithmetic processing according to a thinning rate set by the thinning rate setting unit for each subdivision unit. The image processing apparatus according to claim 1. In an ink jet recording apparatus having a recording head in which a plurality of nozzles for ejecting ink are arranged, the recording medium is finely moved in the nozzle arrangement direction according to the number of passes, and in a direction crossing the nozzle arrangement direction. In order to generate thinned image data recorded in each pass in multi-pass recording in which an image is recorded in the same area of a recording medium by different nozzle groups divided according to the number of passes by scanning the recording head a plurality of times. Image processing apparatus,
A thinning rate is set for each division unit according to the characteristics of the nozzles for each of the plurality of nozzles according to the number of passes of the multipass printing, or the number of passes for the multipass printing is set for the plurality of nozzles. A thinning rate setting unit that divides the data into smaller subdivision units smaller than the subdivision unit, and sets a thinning rate for each subdivision unit according to the characteristics of the nozzle for each subdivision unit;
A mask pattern setting means for setting a mask pattern corresponding to the thinning rate set by the thinning rate setting means for each division unit or each small division unit;
Generating means for applying the mask pattern set by the mask pattern setting means to image data for each division unit or each subdivision unit, and generating thinned image data recorded in each pass of the multi-pass recording;
An image processing apparatus.   The image processing apparatus according to claim 5, wherein the thinning rate setting unit further sets the thinning rate in accordance with a color of ink ejected from a nozzle for each of the small division units.   7. The mask pattern setting unit sets a mask pattern generated by performing a predetermined arithmetic process according to a thinning rate set by the thinning rate setting unit for each subdivision unit. Image processing apparatus. A recording head having a plurality of nozzles that eject ink is arranged, and the recording medium is slightly moved in the nozzle arrangement direction according to the number of passes, and the recording head is moved a plurality of times in the direction intersecting the nozzle arrangement direction. An inkjet recording apparatus that performs multi-pass recording in which an image is recorded in the same area of a recording medium with different nozzle groups divided according to the number of passes by scanning,
A thinning rate setting unit configured to divide the plurality of nozzles by a small division unit smaller than a division unit corresponding to the number of passes of the multipass printing, and to set a thinning rate for each small division unit;
Mask pattern setting means for setting a mask pattern corresponding to the thinning rate set by the thinning rate setting means for each subdivision unit;
Generating means for applying the mask pattern set by the mask pattern setting means to the image data for each subdivision unit to generate thinned image data recorded in each pass of the multi-pass recording;
An ink jet recording apparatus.   The inkjet recording apparatus according to claim 8, wherein the thinning rate setting unit sets the thinning rate according to a characteristic of a nozzle for each of the small division units. A recording head having a plurality of nozzles that eject ink is arranged, and the recording medium is slightly moved in the nozzle arrangement direction according to the number of passes, and the recording head is moved a plurality of times in the direction intersecting the nozzle arrangement direction. An inkjet recording apparatus that performs multi-pass recording in which an image is recorded in the same area of a recording medium with different nozzle groups divided according to the number of passes by scanning,
A thinning rate is set for each division unit according to the characteristics of the nozzles for each of the plurality of nozzles according to the number of passes of the multi-pass printing, or the number of passes for the multi-pass printing is set for the plurality of nozzles. A thinning rate setting unit that divides into smaller subdivision units that are smaller than the subdivision unit, and sets a thinning rate for each subdivision unit according to the characteristics of the nozzle for each subdivision unit;
Mask pattern setting means for setting a mask pattern corresponding to the thinning rate set by the thinning rate setting means for each division unit or each small division unit;
Generating means for applying the mask pattern set by the mask pattern setting means to image data for each division unit or each subdivision unit, and generating thinned image data recorded in each pass of the multi-pass recording;
An ink jet recording apparatus.

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