Printer, and color correction method therefor

Abstract

To reduce difference in mixed colors due to change of a distance in a raster line direction of nozzle arrays for discharging inks with different colors in a print head.SOLUTION: When a distance between a first nozzle array and a second nozzle array in a raster line direction is represented by L1, there are, in a plurality of first nozzle arrays and a plurality of second nozzle arrays, a first area in which the distance L1 is a first distance and a second area in which the distance L1 is a longer second distance in a nozzle arrangement direction. A control part performs control for forming a single color density correction pattern indicating a single color density of an ink on a medium, performs density correction of the single color of the ink on the basis of the single color density correction pattern, performs control for forming a mixed color correction pattern including mixed colors of the first color ink and the second color ink on the medium, and performs mixed color correction so as to match the mixed color of a portion corresponding to the first area with the mixed color of a portion corresponding to the second area in the medium on the basis of the mixed color correction pattern.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a printing apparatus that forms a printed image on a medium using a plurality of colors of ink from a print head, and a color correction method therefor.

Background Art

[0002] As a printing apparatus, a color inkjet printer that ejects a plurality of colors of ink droplets from a print head onto a medium is known. In an inkjet printer, the ejection characteristics of ink droplets, such as the amount and flight direction of ink droplets, vary from nozzle to nozzle. The inkjet printer shown in Patent Document 1 prints a correction pattern on a sheet for each color of ink, measures the density of the correction pattern for each pixel, and obtains a density correction value for each line. The inkjet printer forms dots of the corresponding line so as to have a density corrected based on the density correction value for each color.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a printed image is formed by a print head having a bridging area where the interval between nozzle rows is wider than the normal area, it has been found that a difference may occur in a streak shape between the color mixture in the normal portion corresponding to the normal area and the color mixture in the bridging portion corresponding to the bridging area on the medium. Therefore, if such uneven color mixture can be reduced, it will lead to an improvement in the image quality of the printed image.

Means for Solving the Problems

[0005] The printing apparatus of the present invention is a printing apparatus that forms a printed image on a medium using a plurality of colors of ink including ink of a first color and ink of a second color, A printing head having a plurality of first nozzle rows in which a plurality of first nozzles capable of discharging the ink of the first color are arranged in a nozzle arrangement direction, and a plurality of second nozzle rows in which a plurality of second nozzles capable of discharging the ink of the second color are arranged in the nozzle arrangement direction, a control unit that controls relative movement between the printing head and the medium in a raster line direction intersecting the nozzle arrangement direction, and ejection of the ink from the printing head, wherein a distance between the first nozzle row and the second nozzle row in the raster line direction is L1, the plurality of first nozzle rows and the plurality of second nozzle rows are arranged such that in the nozzle arrangement direction, there exist a first region where the distance L1 is a first distance and a second region where the distance L1 is a second distance longer than the first distance, the control unit performs control to form a single-color density correction pattern indicating the density of a single color of the ink on the medium, performs single-color density correction of the ink based on the single-color density correction pattern, performs control to form a color mixture correction pattern including color mixture of the ink of the first color and the ink of the second color on the medium, and has an aspect of performing color mixture correction so as to combine the color mixture of a portion corresponding to the first region and the color mixture of a portion corresponding to the second region on the medium based on the color mixture correction pattern.

[0006] Further, a color correction method of the present invention is a color correction method for a printing apparatus that relatively moves a printing head capable of discharging a plurality of colors of ink including ink of a first color and ink of a second color and a medium in a raster line direction intersecting a nozzle arrangement direction to form a printed image with the ink on the medium, wherein the printing head has a plurality of first nozzle rows in which a plurality of first nozzles capable of discharging the ink of the first color are arranged in the nozzle arrangement direction, and a plurality of second nozzle rows in which a plurality of second nozzles capable of discharging the ink of the second color are arranged in the nozzle arrangement direction, Let the distance between the first nozzle row and the second nozzle row in the raster line direction be L1. The plurality of first nozzle rows and the plurality of second nozzle rows are arranged such that in the nozzle arrangement direction, there exist a first region where the distance L1 is a first distance and a second region where the distance L1 is a second distance longer than the first distance. The color correction method includes: a single-color density correction pattern forming step of forming, on the medium, a single-color density correction pattern indicating the density of a single color of the ink; a single-color density correction step of performing single-color density correction of the ink based on the single-color density correction pattern; a mixed-color correction pattern forming step of forming, on the medium, a mixed-color correction pattern including the mixing of the ink of the first color and the ink of the second color; a mixed-color correction step of performing mixed-color correction so as to combine the mixing of the portion corresponding to the first region and the mixing of the portion corresponding to the second region on the medium based on the mixed-color correction pattern. It has an aspect including these.

Brief Description of the Drawings

[0007]

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DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described. Of course, the following embodiments are merely illustrative of the present invention, and not all of the features shown in the embodiments are necessarily essential to the solution means of the invention.

[0009] (1) Outline of aspects included in the present invention: First, an outline of aspects included in the present invention will be described with reference to the examples shown in FIGS. 1 to 11. Note that the figures in the present application are diagrams schematically showing examples, and the scales of each part may be different from the actual ones in order to make each part of these figures recognizable, the magnification ratios in each direction shown in these figures may be different, and the figures may not be consistent. Of course, each element of this aspect is not limited to the specific examples indicated by the reference numerals. In the "outline of aspects included in the present invention", the content in parentheses means a supplementary explanation of the immediately preceding word.

[0010] [Aspect 1] As illustrated in FIG. 1, a printing apparatus 1 according to one aspect is a printing apparatus 1 that forms a printed image IM0 by a plurality of colors of ink 36 including ink of a first color (e.g., C, i.e., cyan) and ink of a second color (e.g., Y, i.e., yellow) on a medium ME0, and includes a print head 30 and a control unit U1. As illustrated in FIGS. 2 and 3, the print head 30 has a plurality of first nozzle rows (e.g., C nozzle row 33c) in which a plurality of first nozzles capable of discharging the ink of the first color (C) onto the medium ME0 are arranged in a nozzle arrangement direction D1, and a plurality of second nozzle rows (e.g., Y nozzle row 33y) in which a plurality of second nozzles capable of discharging the ink of the second color (Y) onto the medium ME0 are arranged in the nozzle arrangement direction D1. The control unit U1 controls the relative movement between the print head 30 and the medium ME0 in a raster line direction D2 intersecting the nozzle arrangement direction D1, and the discharge of the ink 36 from the print head 30. Here, let the distance between the first nozzle row (33c) and the second nozzle row (33y) in the raster line direction D2 be L1. The plurality of first nozzle rows (33c) and the plurality of second nozzle rows (33y) are arranged such that in the nozzle arrangement direction D1, there are a first region (e.g., normal region A1) where the distance L1 is a first distance L11, and a second region (e.g., bridging region A2) where the distance L1 is a second distance L12 longer than the first distance L11. As illustrated in FIGS. 4 and 5, the control unit U1 performs control to form a single-color density correction pattern P1 indicating the density of a single color of the ink 36 on the medium ME0. The control unit U1 performs single-color density correction of the ink 36 based on the single-color density correction pattern P1. The control unit U1 performs control to form a color mixture correction pattern P10 including color mixture of the ink of the first color (C) and the ink of the second color (Y) on the medium ME0. The control unit U1 performs color mixture correction so as to combine the color mixture of the portion corresponding to the first region (A1) (e.g., normal portion B1) and the color mixture of the portion corresponding to the second region (A2) (e.g., bridging portion B2) on the medium ME0 based on the color mixture correction pattern P10.

[0011] When color mixing correction is not performed, as in the case of the provisional printed image IM1 illustrated in FIG. 4, the hues may be stripe-like different between the normal portion B1 and the bridging portion B2. In the above-described aspect 1, after the monochromatic density correction of the ink 36 is performed based on the monochromatic density correction pattern P1, the color mixing correction is performed based on the color mixing correction pattern P10. As a result, as in the printed image IM0 illustrated in FIG. 4, the color mixing of the portion (B1) corresponding to the first region (A1) and the color mixing of the portion (B2) corresponding to the second region (A2) on the medium ME0 are matched. Therefore, the above-described aspect 1 can provide a printing apparatus capable of reducing the difference in color mixing due to the change in the distance in the raster line direction between the nozzle rows that eject inks of different colors in the print head.

[0012] Here, the medium includes various things such as paper, cloth, film, and the like. The relative movement between the print head and the medium includes the case where the medium moves while the print head does not move, the case where the print head moves while the medium does not move, and the case where both the print head and the medium move. In the present application, "first", "second",... are terms for identifying each component included in a plurality of components having similar points, and do not mean an order. Which component among the plurality of components corresponds to "first", "second",... is determined relatively. For example, assume that inks of a plurality of colors include C (cyan) ink, M (magenta) ink, Y (yellow) ink, and K (black) ink. For example, the C ink may be applied as the ink of the first color and the Y ink may be applied as the ink of the second color, or the Y ink may be applied as the ink of the first color and the C ink may be applied as the ink of the second color. Note that the above-mentioned remarks are also applicable to the following aspects.

[0013] [Aspect 2] As illustrated in FIGS. 2 and 3, the inks 36 of the plurality of colors may include an ink of a third color (e.g., M). The print head 30 may have a plurality of third nozzle rows (e.g., M nozzle row 33m) in which a plurality of third nozzles capable of discharging the ink of the third color (M) onto the medium ME0 are arranged in the nozzle arrangement direction D1. Each of the third nozzle rows (33m) may be at a certain distance from the first nozzle row (33c) in the raster line direction D2. Here, let the distance between the third nozzle row (33m) and the second nozzle row (33y) in the raster line direction D2 be L2. The plurality of third nozzle rows (33m) and the plurality of second nozzle rows (33y) are arranged in the nozzle arrangement direction D1 such that there are a third region (e.g., normal region A3) where the distance L2 is a third distance L21 and a fourth region (e.g., bridging region A4) where the distance L2 is a fourth distance L22 longer than the third distance L21. As illustrated in FIG. 11, the control unit U1 may perform control to form the color mixture correction pattern P10 including the color mixture of the ink of the third color (M) and the ink of the second color (Y) on the medium ME0, and not including the color mixture of the ink of the first color (C) and the ink of the third color (M).

[0014] In the example shown in FIGS. 2 and 3, in the raster line direction D2, the M nozzle row is at a certain distance from the C nozzle row, and the K nozzle row is at a certain distance from the Y nozzle row. In this case, for the color mixture of C and M and the color mixture of Y and K, there is no difference in color mixture between the normal region and the bridging region, so the correction has little effect. By forming the color mixture correction pattern P10 that does not include the color mixture of C and M and the color mixture of Y and K, it is possible to avoid forming unnecessary patterns and avoid wasting ink and the medium ME0 for forming the patterns. As exemplified above, in the above-described aspect 2, since there is no correction pattern for unnecessary color mixture, it is possible to form a color mixture correction pattern that efficiently uses ink and the medium.

[0015] [Aspect 3] As illustrated in FIGS. 2 and 3, the plurality of color inks 36 may include black (K) ink. The print head 30 may have a plurality of black nozzles capable of discharging the black (K) ink onto the medium ME0. As illustrated in FIG. 11, the control unit U1 may perform control to form the color mixing correction pattern P10 that does not include the black (K) ink on the medium ME0. Since the frequency of expressing color mixing including black (K) ink is low, by not using black (K) ink in the color mixing correction pattern P10, a color mixing correction pattern that efficiently uses ink and the medium can be formed.

[0016] The low frequency of expressing color mixing using K is due to, for example, the following reasons. (Reason 1) K can be expressed by mixing C, M, and Y, and it is possible to express dark-colored chromatic colors using C, M, and Y. (Reason 2) When K is mixed with chromatic colors, the color tone of K becomes strong, and in some cases, it may be more convenient to use C, M, and Y than to use K when expressing colors other than K by mixing multiple colors. Based on the above, the above-described aspect 3 is preferable.

[0017] [Aspect 4] The control unit U1 may perform control to form the color mixing correction pattern P10 that shows discrete color mixing over at least one of the entire hue range and the entire density range on the medium ME0. For example, the control unit U1 can perform control to form the color mixing correction pattern P10 that shows discrete color mixing over at least one of the entire hue range and the entire density range on the medium ME0 according to the color mixing correction pattern data PD10 illustrated in FIGS. 8A and 8B. In the above case, the color mixing correction pattern P10 is formed on the medium ME0 over at least one of the entire hue range and the entire density range for the expressible colors provided in the printing apparatus 1. Therefore, the above aspect can reduce the color mixing difference caused by the change in the distance in the raster line direction between nozzle rows over at least one of the entire hue range and the entire density range.

[0018] [Aspect 5] The control unit U1 may perform control to form the color mixing correction pattern P10, in which at least one of the hue and density change factors changes stepwise, on the medium ME0. As illustrated in FIGS. 4 and 5, the control unit U1, for a portion where the difference (for example, ΔFi) between the color mixing of the portion (B1) corresponding to the first region (A1) and the color mixing of the portion (B2) corresponding to the second region (A2) in the medium ME0 exceeds a reference (for example, a threshold value THF) in the color mixing correction pattern P10, may perform control to form a second color mixing correction pattern (for example, high-resolution color mixing correction pattern data PD20) on the medium ME0, in which the change factor changes more finely than in the color mixing correction pattern P10. The control unit U1 may perform the color mixing correction based on the second color mixing correction pattern (P20). In the color mixing correction pattern P10 including a large number of color combinations, due to the space of the medium ME0, one pattern becomes small. Therefore, there is a possibility of being affected by the color pattern of another color when detecting the color of each pattern. In the above aspect, a second color mixing correction pattern (P20) in which the change factor changes more finely than the color mixing correction pattern P10 is formed at a location where it is found that color mixing unevenness has occurred in the color mixing correction pattern P10. Therefore, the above aspect can perform color mixing correction accurately based on the second color mixing correction pattern. Here, since the second color mixing correction pattern (P20) is generated based on the color mixing correction pattern P10, performing color mixing correction based on the second color mixing correction pattern (P20) is included in performing color mixing correction based on the color mixing correction pattern P10. This comment also applies to the following aspects.

[0019] [Aspect 6] Incidentally, a color correction method according to one aspect includes a print head 30 capable of discharging a plurality of colors of ink 36 including ink of a first color (C) and ink of a second color (Y), and a medium ME0, which are relatively moved in a raster line direction D2 intersecting a nozzle array direction D1 to form a printed image IM0 by the ink on the medium ME0. As illustrated in FIGS. 2 and 3, the print head 30 has a plurality of first nozzle arrays (33c) in which a plurality of first nozzles capable of discharging the ink of the first color (C) onto the medium ME0 are arranged in the nozzle array direction D1, and a plurality of second nozzle arrays (33y) in which a plurality of second nozzles capable of discharging the ink of the second color (Y) onto the medium ME0 are arranged in the nozzle array direction D1. Here, the distance between the first nozzle array (33c) and the second nozzle array (33y) in the raster line direction D2 is defined as L1. The plurality of first nozzle arrays (33c) and the plurality of second nozzle arrays (33y) are arranged such that in the nozzle array direction D1, there are a first region (A1) where the distance L1 is a first distance L11 and a second region (A2) where the distance L1 is a second distance L12 longer than the first distance L11. The present color correction method includes the following steps as illustrated in FIGS. 4 and 5. (a1) A single-color density correction pattern forming step ST1 of forming a single-color density correction pattern P1 indicating the density of a single color of the ink 36 on the medium ME0. (a2) A single-color density correction step ST2 of performing single-color density correction of the ink 36 based on the single-color density correction pattern P1. (a3) A mixed-color density correction pattern forming step ST3 of forming a mixed-color density correction pattern P10 including a mixture of the ink of the first color (C) and the ink of the second color (Y) on the medium ME0. (a4) A mixed-color density correction step ST4 of performing mixed-color density correction so as to combine the mixture of the portion (B1) corresponding to the first region (A1) and the mixture of the portion (B2) corresponding to the second region (A2) on the medium ME0 based on the mixed-color density correction pattern P10.

[0020] The above aspect can provide a color correction method capable of reducing the color mixing difference caused by the change in the distance in the raster line direction between nozzle rows that eject inks of different colors in the print head.

[0021] Furthermore, the above-described aspect is applicable to a printing system including the above-described printing apparatus, a control method of the above-described printing apparatus, a control method of the above-described printing system, a control program of the above-described printing apparatus, a control program of the above-described printing system, a computer-readable recording medium recording any of the above-described control programs, and the like. Also, the above-described printing apparatus may be composed of a plurality of distributed parts.

[0022] (2) Specific example of the printing apparatus: FIG. 1 schematically illustrates a printing apparatus 1. The printing apparatus 1 in this specific example is assumed to be the printer 2 itself, but the printing apparatus 1 may be a combination of the printer 2 and the host device HO1. The printer 2 may have an image reading unit 60 that reads a print image IM0. The printer 2 shown in FIG. 1 is an inkjet printer that ejects ink 36 as ink droplets 37, and is a line printer in which the medium ME0 moves in the feeding direction D3 without the print head 30 moving. The feeding direction D3 is the raster line direction D2 in which dots 38 are repeatedly formed from the same nozzle 34. Note that the printer 2 may be a serial printer, and the printing apparatus 1 may include additional elements not shown in FIG. 1. FIG. 2 schematically illustrates the print head 30 and the dot pattern. FIG. 3 schematically illustrates the G portion of FIG. 2. FIG. 4 schematically illustrates the color correction method of the printing apparatus 1.

[0023] The printer 2 shown in Fig. 1 includes a controller 10, a RAM (Random Access Memory) 21 which is a semiconductor memory, a communication I / F (Interface) 22, a storage unit 23, an operation panel 24, a print head 30, a driving unit 50, a reading unit 60, etc. The controller 10 and the driving unit 50 are examples of the control unit U1. The controller 10, the RAM 21, the communication I / F 22, the storage unit 23, and the operation panel 24 are connected to a bus and are capable of inputting and outputting information to each other.

[0024] The controller 10 includes a CPU (Central Processing Unit) 11 which is a processor, a color conversion unit 12, a halftone processing unit 13, a drive signal transmission unit 15, etc. The controller 10 controls the driving unit 50 and the print head 30 so that a print image IM0 is formed on a medium ME0 based on original image data DA1 acquired from any of a host device HO1, a memory card (not shown), etc. The original image data DA1 can be applied with RGB data having, for example, integer values of 2 8 tones and 2 16 tones. The controller 10 can be configured by an SoC (System on a Chip) or the like.

[0025] The CPU 11 is a device that mainly performs information processing and control in the printer 2. The color conversion unit 12 refers to, for example, a color conversion LUT (Look-Up Table) in which the correspondence between the tone values of R, G, and B and the tone values of C, M, Y, and K is defined, and converts the RGB data into ink amount data DA2 having integer values of 2 8 tones and 2 16 tones. The ink amount data DA2 represents the usage amounts of inks 36 of C, M, Y, and K in units of pixels PX0. Also, when the resolution of the RGB data is different from the print resolution, the color conversion unit 12 first converts the resolution of the RGB data to the print resolution or converts the resolution of the ink amount data DA2 to the print resolution.

[0026] The halftone processing unit 13 performs halftone processing on the gradation value of each pixel PX0 constituting the ink amount data DA2 by any one of a dither method, an error diffusion method, etc., to reduce the number of gradations of the gradation value and generate dot data DA3. The dot data DA3 represents the formation state of the dots 38 of the ink droplets 37 in units of the pixels PX0. The dot data DA3 may be binary data representing the presence or absence of dot formation, or may be multi-valued data of three or more gradations capable of corresponding to dots of different sizes such as large, medium, and small dots.

[0027] The drive signal transmission unit 15 generates a drive signal SG1 from the dot data DA3 and outputs it to the drive circuit 31 of the print head 30. The drive signal SG1 corresponds to the voltage signal applied to the drive element 32 of the print head 30. For example, if the dot data DA3 is "dot formation", the drive signal transmission unit 15 outputs a drive signal SG1 for discharging ink droplets for dot formation. Also, when the dot data DA3 is data of three or more values, the drive signal transmission unit 15 outputs a drive signal SG1 for discharging large ink droplets if the dot data DA3 is "large dot formation", and outputs a drive signal SG1 for discharging small ink droplets if the dot data DA3 is "small dot formation".

[0028] Each of the above units 11, 12, 13, 15 may be configured by an ASIC (Application Specific Integrated Circuit), and may directly read data to be processed from the RAM 21 or directly write the processed data to the RAM 21.

[0029] As shown in FIG. 3, the print head 30 has a nozzle array 33 on the nozzle surface 30a in which a plurality of nozzles 34 capable of discharging ink droplets 37 onto the medium ME0 are arranged at a predetermined nozzle pitch intervals in the nozzle array direction D1. Here, a nozzle means a small hole from which an ink droplet is ejected, and a nozzle array means an arrangement of a plurality of nozzles. The nozzle surface 30a is the ejection surface of the ink droplets 37. Each ink droplet 37 is ejected from the nozzle 34 aiming at the pixel PX0 of the medium ME0. Of course, a dot 38 of C is formed on the medium ME0 from the C ink droplet 37, a dot 38 of M is formed on the medium ME0 from the M ink droplet 37, a dot 38 of Y is formed on the medium ME0 from the Y ink droplet 37, and a dot 38 of K is formed on the medium ME0 from the K ink droplet 37. The print head 30 shown in FIG. 2 includes three or more chips CH0 in which a plurality of nozzles 34 are arranged continuously over the entire width direction D4 orthogonal to the feed direction D3 of the medium ME0. The longitudinal direction of each chip CH0 is oriented in the nozzle array direction D1 that intersects both the feed direction D3 and the width direction D4. Each chip CH0 includes, as the nozzle array 33, a C nozzle array 33c, an M nozzle array 33m, a Y nozzle array 33y, and a K nozzle array 33k.

[0030] In the C nozzle row 33c, a plurality of nozzles 34 capable of discharging C ink onto the medium ME0 are arranged in the nozzle arrangement direction D1. In the M nozzle row 33m, a plurality of nozzles 34 capable of discharging M ink onto the medium ME0 are arranged in the nozzle arrangement direction D1. In the Y nozzle row 33y, a plurality of nozzles 34 capable of discharging Y ink onto the medium ME0 are arranged in the nozzle arrangement direction D1. In the K nozzle row 33k, a plurality of nozzles 34 capable of discharging K ink onto the medium ME0 are arranged in the nozzle arrangement direction D1. In this specific example, C is fitted to the first color, Y is fitted to the second color, and M is fitted to the third color. In this case, the C nozzle row 33c is an example of the first nozzle row, the Y nozzle row 33y is an example of the second nozzle row, the M nozzle row 33m is an example of the third nozzle row, and the K nozzle row 33k is an example of the black nozzle row. The nozzles 34 of the C nozzle row 33c are an example of the first nozzle, the nozzles 34 of the Y nozzle row 33y are an example of the second nozzle, the nozzles 34 of the M nozzle row 33m are an example of the third nozzle, and the nozzles 34 of the K nozzle row 33k are an example of the black nozzle. It can be said that the print head 30 has a plurality of C nozzle rows 33c, a plurality of M nozzle rows 33m, a plurality of Y nozzle rows 33y, and a plurality of K nozzle rows 33k. The printer 2 can be said to be a color printer that forms a printed image IM0 on the medium ME0 with a plurality of colors of ink 36 including C ink, M ink, Y ink, and K ink.

[0031] In each chip CH0, the C nozzle row 33c and the Y nozzle row 33y are arranged at intervals in the nozzle arrangement direction D1, and the M nozzle row 33m and the K nozzle row 33k are arranged at intervals in the nozzle arrangement direction D1. In other words, it can be said that the C nozzle row 33c is on the extension line of the Y nozzle row 33y, and the M nozzle row 33m is on the extension line of the K nozzle row 33k. The C nozzle row 33c and the M nozzle row 33m are parallel to each other at a certain interval in the raster line direction D2. The Y nozzle row 33y and the K nozzle row 33k are parallel to each other at a certain interval in the raster line direction D2.

[0032] The above-described three or more chips CH0 are arranged in the width direction D4 while partially overlapping in the raster line direction D2 and the width direction D4, so that the nozzles 34 for C, M, Y, and K are arranged in the print head 30 so as to be continuous in the width direction D4, respectively. Each M nozzle row 33m is at a certain distance from the C nozzle row 33c in the raster line direction D2. Each K nozzle row 33k is at a certain distance from the Y nozzle row 33y in the raster line direction D2. On the other hand, in the raster line direction D2, the intervals between the C nozzle row 33c and the Y nozzle row 33y, between the C nozzle row 33c and the K nozzle row 33k, between the M nozzle row 33m and the Y nozzle row 33y, and between the M nozzle row 33m and the K nozzle row 33k are not constant. In the print head 30 shown in FIG. 3, for example, a bridging region A2 where the interval between the C nozzle row 33c and the Y nozzle row 33y in the raster line direction D2 is wider than the normal region A1 occurs. The normal region A1 is an example of the first region, and the bridging region A2 is an example of the second region. Also, a bridging region A4 where the interval between the M nozzle row 33m and the Y nozzle row 33y in the raster line direction D2 is wider than the normal region A3 occurs. The normal region A3 is an example of the third region, and the bridging region A4 is an example of the fourth region.

[0033] Here, let the distance between the C nozzle row 33c and the Y nozzle row 33y in the raster line direction D2 be L1, and the distance between the M nozzle row 33m and the Y nozzle row 33y in the raster line direction D2 be L2. The plurality of C nozzle rows 33c and the plurality of Y nozzle rows 33y are arranged in the nozzle arrangement direction D1 such that there are a normal region A1 where the distance L1 is the first distance L11 and a bridging region A2 where the distance L1 is the second distance L12 longer than the first distance L11. The plurality of M nozzle rows 33m and the plurality of Y nozzle rows 33y are arranged in the nozzle arrangement direction D1 such that there are a normal region A3 where the distance L2 is the third distance L21 and a bridging region A4 where the distance L2 is the fourth distance L22 longer than the third distance L21.

[0034] The drive unit 50 controlled by the controller 10 sends the medium ME0 in the feed direction D3 along the transport path 59 by driving the roller drive unit 55. The roller drive unit 55 includes a pair of transport rollers 56 and a pair of discharge rollers 57. The roller drive unit 55 is composed of a servo motor, and in accordance with the control of the controller 10, it rotates the drive transport rollers of the pair of transport rollers 56 and the drive discharge rollers of the pair of discharge rollers 57 at a constant speed to send the medium ME0 in the feed direction D3 at a constant speed. Therefore, it can be said that the drive unit 50 relatively moves the print head 30 and the medium ME0 in the raster line direction D2. It can be said that the control unit U1 controls the relative movement between the print head 30 and the medium ME0 in the raster line direction D2. The medium ME0 is the object to be printed that holds the printed image. The material of the medium ME0 is not particularly limited, and various materials such as paper, resin, metal, etc. can be considered. The shape of the medium ME0 is also not particularly limited, and various shapes such as rectangular, roll-shaped, etc. can be considered, and it may also be a three-dimensional shape.

[0035] The platen 58 is located below the transport path 59 and supports the medium ME0 by contacting the medium ME0 in the transport path 59. The print head 30 controlled by the controller 10 is provided with a drive circuit 31, a drive element 32, etc., and deposits the ink 36 on the medium ME0 by discharging the ink droplets 37 toward the medium ME0 supported by the platen 58. Therefore, it can be said that the control unit U1 controls the discharge of the ink droplets 37 from the print head 30. The drive circuit 31 applies a voltage signal to the drive element 32 in accordance with the drive signal SG1 input from the drive signal transmission unit 15. The drive element 32 may be a piezoelectric element that applies pressure to the ink 36 in the pressure chamber communicating with the nozzle 34, or may be a drive element that generates bubbles in the pressure chamber by heat to eject ink droplets 37 from the nozzle 34. Ink 36 is supplied to the pressure chamber of the print head 30 from an ink cartridge 35. The ink 36 in the pressure chamber is ejected as ink droplets 37 from the nozzle 34 toward the medium ME0 by the drive element 32. Thereby, dots 38 of the ink droplets 37 are formed on the medium ME0, and a print image IM0 represented by the pattern of the dots 38 is formed on the medium ME0. Here, the ink cartridge 35 refers to a member that can hold the ink 36 supplied to the pressure chamber. Therefore, the supplied ink is not necessarily limited to that supplied from the ink cartridge. For example, an ink tank type in which the ink tank of the printer 2 is interpreted as an ink cartridge and ink is directly supplied to the ink tank may be used.

[0036] The RAM 21 stores original image data DA1 and the like received from the host device HO1 or a memory (not shown). The communication I / F 22 is connected to the host device HO1 by wire or wirelessly, and inputs and outputs information to and from the host device HO1. The host device HO1 includes computers such as personal computers and tablet terminals, mobile phones such as smartphones, digital cameras, digital video cameras, and the like. The storage unit 23 stores correction pattern data PD0 and the like used for forming the correction pattern. The storage unit 23 may be a non-volatile semiconductor memory such as a flash memory, or may be a magnetic storage device such as a hard disk. The operation panel 24 includes an output unit 25 such as a liquid crystal panel for displaying information, an input unit 26 such as a touch panel for receiving operations on the display screen, and the like.

[0037] As shown in FIG. 4, the reading unit 60 can read a single-color density correction pattern P1, a color mixture correction pattern P10, a high-resolution color mixture correction pattern P20 as a second color mixture correction pattern, and the like. The reading unit 60 may be an image sensor using a CIS (Contact Image Sensor) method or a CCD (Charge Coupled Devices) method, or may be a solid-state imaging device such as a CMOS (Complementary Metal-Oxide Semiconductor) image sensor, a line sensor or an area sensor composed of a CCD, and the like. An external scanner may be connected to the printer 2 as the reading unit 60. The reading unit 60 of this specific example includes an analog / digital conversion circuit that converts the analog amount of the detection voltage of each pixel PX0 into a digital value, and converts the analog density amount corresponding to each detection voltage into a digital density value by the analog / digital conversion circuit and outputs it to the controller 10.

[0038] By the way, since a large number of nozzles 34 are formed on the print head 30 at a fine pitch, the ejection characteristics of the ink droplets 37 vary for each nozzle 34. The printer 2 of this specific example can print the single-color density correction pattern P1 on the medium ME0 for each color of the ink 36, measure the density of the single-color density correction pattern P1 for each pixel PX0, and obtain a density correction value for each raster line RL. The printer 2 performs single-color density correction based on the density correction values of each raster line RL for each color, and forms a corrected printed image IM0 on the medium ME0. When the distance in the raster line direction D2 between the nozzle rows ejecting different colors of ink is constant, color mixture is also generally corrected by performing single-color density correction.

[0039] Actually, as in the case of the temporary printed image IM1 shown in FIG. 4, there may be a case where the color tone is stripe-like different between the normal part B1 corresponding to the normal regions A1, A3 of the print head 30 and the bridging part B2 corresponding to the bridging regions A2, A4 of the print head 30 on the medium ME0. Since such color unevenness occurs after single-color density correction, it can be said to be color mixture unevenness. FIG. 4 shows that the bridging part B2 is darker than the normal part B1 in the temporary printed image IM1. Color unevenness occurs because the distances between nozzle rows 33 are different between the normal regions A1 and A3 and the bridging regions A2 and A4, resulting in a difference in the landing times of ink droplets 37 of different colors and a difference in color development. For example, when the medium ME0 easily absorbs the ink 36, the time for the ink droplets 37 that land first to be absorbed inside the medium ME0 is longer in the bridging portion B2 than in the normal portion B1. For this reason, it is considered that the degree of color mixing is different between the normal portion B1 and the bridging portion B2.

[0040] The printer 2 of this specific example performs color mixing correction based on at least the color mixing correction pattern P10 after single-color density correction. As a result, as in the printed image IM0 shown in FIG. 4, the color mixing in the normal portion B1 and the color mixing in the bridging portion B2 in the medium ME0 are adjusted.

[0041] (3) Outline of color correction method: First, with reference to FIG. 4, the outline of the color correction method will be described. The color correction method includes a single-color density correction pattern formation step ST1, a single-color density correction step ST2, a color mixing correction pattern formation step ST3, and a color mixing correction step ST4.

[0042] In the single-color density correction pattern formation step ST1, the control unit U1 performs control to form a single-color density correction pattern P1 indicating the single-color density of the ink 36 on the medium ME0. The single-color density correction pattern P1 includes a C density correction pattern P1c indicating the density of C ink on the medium ME0, an M density correction pattern P1m indicating the density of M ink on the medium ME0, a Y density correction pattern P1y indicating the density of Y ink on the medium ME0, and a K density correction pattern P1k indicating the density of K ink on the medium ME0. Each density correction pattern (P1c, P1m, P1c, P1k) includes a plurality of individual patterns P2 in which the density changes stepwise. The individual pattern P2 is an elongated pattern extending across all the nozzles 34 that eject the ink 36 with the longitudinal direction oriented in the width direction D4.

[0043] In the next single-color density correction step ST2, the control unit U1 performs single-color density correction of the ink 36 based on the single-color density correction pattern P1. For example, the control unit U1 causes the reading unit 60 to read the single-color density correction pattern P1 to obtain the single-color density of each raster line RL, and performs single-color density correction of each raster line RL based on the single-color density. FIG. 4 shows a temporary printed image IM1 to which single-color density correction has been applied. As described above, streak-like color mixing unevenness may occur in the printed image IM1. The printed image IM1 shown in FIG. 4 shows a normal part color F1 indicating color mixing in the normal part B1 and a bridging part color F2 indicating color mixing in the bridging part B2.

[0044] In the next color mixing correction pattern formation step ST3, the control unit U1 controls to form a color mixing correction pattern P10 including color mixing of C ink and Y ink and color mixing of M ink and Y ink on the medium ME0. The color mixing correction pattern P10 includes a plurality of individual patterns P11 in which at least one of the hue and density change elements changes stepwise. The individual pattern P11 is an elongated pattern extending over all the nozzles 34 that eject the ink 36 with the longitudinal direction facing the width direction D4. It is preferable that the color mixing correction pattern P10 includes a plurality of individual patterns P11 that discretely show color mixing over all hues, because color unevenness in color mixing over all hues is corrected. It is preferable that the color mixing correction pattern P10 includes a plurality of individual patterns P11 that discretely show color mixing over the entire density range, because color unevenness in color mixing over the entire density range is corrected.

[0045] The control unit U1 may further control to form a high-resolution color mixing correction pattern P20 on the medium ME0 for a portion where the difference between the color mixing in the normal part B1 and the color mixing in the bridging part B2 in the color mixing correction pattern P10 exceeds a reference. The high-resolution color mixing correction pattern P20 includes a plurality of individual patterns P21 in which the change elements change more finely than in the color mixing correction pattern P10. The individual pattern P21 is an elongated pattern extending over all the nozzles 34 that eject the ink 36 with the longitudinal direction facing the width direction D4.

[0046] In the final color mixing correction step ST4, the control unit U1 performs color mixing correction so as to combine the color mixing of the normal part B1 and the bridging part B2 in the medium ME0 based on the color mixing correction pattern P10. For example, the control unit U1 causes the reading unit 60 to read the color mixing correction pattern P10 to obtain the normal part color F1 and the bridging part color F2, and performs color mixing correction to match the printing location corresponding to the bridging part color F2 to the normal part color F1 when forming the printed image IM0. Even when the high-resolution color mixing correction pattern P20 is printed, since the high-resolution color mixing correction pattern P20 is formed based on the reading result from the color mixing correction pattern P10, it can be said that the control unit U1 performs color mixing correction based on the color mixing correction pattern P10. The control unit U1 may also cause the reading unit 60 to read the high-resolution color mixing correction pattern P20 to obtain the normal part color F1 and the bridging part color F2, and perform color mixing correction to match the printing location corresponding to the bridging part color F2 to the normal part color F1 when forming the printed image IM0. The color mixing correction can be performed by any of pixel value conversion referring to a color conversion LUT, adjustment of the ink amount data DA2, adjustment of the original image data DA1, and the like. FIG. 4 shows the printed image IM0 in which the color mixing of the bridging part B2 is adjusted to the normal part color F1 of the normal part B1, that is, the printed image IM0 in which color mixing unevenness is suppressed.

[0047] In addition, in the print head 30 shown in FIG. 3, in the nozzle array direction D1, the C nozzle rows 33c partially overlap each other, the M nozzle rows 33m partially overlap each other, the Y nozzle rows 33y partially overlap each other, and the K nozzle rows 33k partially overlap each other. Since these partially overlapping regions include the elements of the bridging regions A2 and A4, they may be treated as the bridging regions A2 and A4. However, since the partially overlapping regions are extremely narrow regions, they may be treated as the normal regions A1 and A3.

[0048] (4) Specific example of color correction processing: FIG. 5 schematically illustrates the color correction process performed by the controller 10. FIG. 6 schematically illustrates the single-color density correction pattern P1 and the acquired density. FIG. 7 schematically illustrates how the single-color density correction value E3i is acquired. FIGS. 8A and 8B schematically illustrate the multicolor correction pattern data PD10. FIG. 8C schematically illustrates the high-resolution multicolor correction pattern data PD20. FIG. 9A schematically illustrates the multicolor correction pattern P10 and the acquired density. FIG. 9B schematically illustrates the high-resolution multicolor correction pattern P20 and the acquired density. The color correction process shown in FIG. 5 includes the correction value acquisition process of steps S102 to S120 and the print control process of step S122. The correction value acquisition process and the print control process may be performed separately. In FIG. 5, step S102 corresponds to the single-color density correction pattern formation step ST1. Steps S104 to S108 correspond to the single-color density correction step ST2. Steps S110 to S116 correspond to the multicolor correction pattern formation step ST3. Steps S118 to S122 correspond to the multicolor correction step ST4. Hereinafter, the description of "step" may be omitted, and the step number may be indicated in parentheses.

[0049] When the color correction process shown in FIG. 5 starts, the controller 10 controls the movement of the medium ME0 and the ejection of the ink 36 so that the single-color density correction pattern P1 is formed on the medium ME0 according to the single-color density correction pattern data PD1 (see FIG. 6) (S102). FIG. 6 shows the C density correction pattern P1c as one of the single-color density correction patterns P1. The C density correction pattern P1c includes a plurality of individual patterns P2 in which the density of the C ink changes step by step. The same applies to the other density correction patterns (P1m, P1c, P1k). The single-color density correction pattern data PD1 indicates the single-color density E1i of the plurality of individual patterns P2. The variable i here is a variable for identifying the individual pattern P2.

[0050] Next, the controller 10 causes the reading unit 60 to read the single-color density correction pattern P1, and acquires the single-color density E2i of each raster line RL from the reading unit 60 (S104). The single-color density E2i includes the reading density of each individual pattern P2 of the C density correction pattern P1c, the reading density of each individual pattern P2 of the M density correction pattern P1m, the reading density of each individual pattern P2 of the Y density correction pattern P1y, and the reading density of each individual pattern P2 of the K density correction pattern P1k.

[0051] Next, the controller 10 acquires the single-color density correction value E3i based on the single-color densities E1i and E2i for each color (S106). FIG. 7 illustrates the correspondence CO1 between the single-color densities E1i and E2i. In FIG. 7, the horizontal axis represents the single-color density E1i as the input (Input), and the vertical axis represents the single-color density E2i as the output (Output). The single-color density correction value E3i means a value for correcting the output for the single-color density E1i from the single-color density E2i to the single-color density E1i, and can also be said to be the input value at which the output value becomes the single-color density E1i. The controller 10 can acquire the single-color density correction value E3i at which the output value becomes the single-color density E1i according to the correspondence CO1 for each color.

[0052] Next, the controller 10 stores the single-color density correction value E3i in the storage unit 23 for each color so that the single-color density correction value E3i is applied when controlling the formation of the printed image IM0 (S108). In the above manner, single-color correction is performed.

[0053] Next, the controller 10 controls the movement of the medium ME0 and the ejection of the ink 36 so that the color mixing correction pattern P10 is formed on the medium ME0 according to the color mixing correction pattern data PD10 (see, for example, FIGS. 8A, 8B, and 9A) (S110). The color mixing correction pattern data PD10 indicates the input colors F0i of a plurality of individual patterns P11. The variable i here is a variable for identifying the individual pattern P11. The input color F0i is represented by, for example, the coordinate values (R, G, B) in the RGB color space. Here, the R value, the G value, and the B value are values corresponding to 0 to 100%, respectively. Incidentally, the input color F0i is the CIE (International Commission on Illumination) L * a * b * coordinate values in the color space (L * ,a * ,b * ) and may be represented by the like. Incidentally, in order to make it easier to identify the individual pattern P11, the controller 10 may perform control to print the identification information of the individual pattern P11, for example, the identification number, on the medium ME0 in association with each individual pattern P11.

[0054] The color mixing correction pattern data PD10 illustrated in FIG. 8A indicates the input colors F0i of a plurality of individual patterns P11 in which both the hue H and the chroma C* change stepwise. Here, the chroma C* is the chromaticity coordinate a in the CIE L * a * b * color space coordinate a * ,b * from which the chroma C is calculated *This means that it can be said that the higher the saturation C*, the higher the density. The color mixing correction pattern data PD10 shown in FIG. 8A shows the input color F0i in which the hue H and the saturation C* are combined, and shows the input color F0i of a plurality of individual patterns P11 that discretely show color mixing over both the entire hue and the entire saturation range. "The entire hue" means over the entire hue angle of 0 to 360°. "The entire saturation range" means over the entire saturation range (for example, 0.4 to 1.0) included in the color mixing correction pattern data PD10 because the C, M, and Y inks are not ejected when the saturation C* is 0.0. Therefore, "the entire density range" means over the entire density range included in the color mixing correction pattern data PD10 because the ink 36 is not ejected when the density is 0. The controller 10 performs control to form a color mixing correction pattern P10 that discretely shows color mixing over both the entire hue and the entire saturation range on the medium ME0 according to the color mixing correction pattern data PD10 shown in FIG. 8A. The color mixing correction pattern P10 can be said to be a correction pattern for comprehensively checking all hues and densities, and includes color mixing of the C ink and the Y ink, and color mixing of the M ink and the Y ink.

[0055] The color mixing correction pattern data PD10 illustrated in FIG. 8B shows the input color F0i of a plurality of individual patterns P11 in which the hue H changes step by step on the premise that the saturation C* is constant. The controller 10 can execute control to form a color mixing correction pattern P10 that discretely shows color mixing over the entire hue on the medium ME0 according to the color mixing correction pattern data PD10 shown in FIG. 8B. Although not shown, the color mixing correction pattern data PD10 may show the input color F0i of a plurality of individual patterns P11 in which the saturation C* changes step by step on the premise that the hue H is constant.

[0056] After printing the color mixture correction pattern P10, the controller 10 causes the reading unit 60 to read the color mixture correction pattern P10, obtains the output color of each raster line RL from the reading unit 60, and selects the color mixture to be corrected based on the output color (S112). Here, as shown in FIG. 9A, the average of the output colors in each normal portion B1 is defined as the normal portion color F1i, and the average of the output colors in each bridging portion B2 is defined as the bridging portion color F2i. The normal portion color F1i and the bridging portion color F2i are represented by, for example, coordinate values (R, G, B) in the RGB color space. If the coordinate values of the normal portion color F1i are (R1i, G1i, B1i) and the coordinate values of the bridging portion color F2i are (R2i, G2i, B2i), the difference ΔFi between the normal portion color F1i and the bridging portion color F2i is, for example, { (R2i - R1i) 2 +(G2i - G1i) 2 +(R2i - R1i) 2} 1 / 2 represented by. In addition, when normal portions B1 exist on both sides of one bridging portion B2 in the width direction D4, the coordinate values (R1i, G1i, B1i) of the normal portion color F1i are the average of the coordinate values of the normal portion colors in the normal portions B1 on both sides. When the threshold value for the difference ΔFi is THF, the controller 10 can select the input color F0i corresponding to the individual pattern for which ΔFi > THF among the plurality of individual patterns P11 as the color mixture to be corrected. When the identification information associated with each individual pattern P11 is printed on the medium ME0, the user can visually select the color mixture to be corrected, or the controller 10 can obtain the identification information corresponding to the color mixture to be corrected by OCR (optical character reading) processing. For example, the controller 10 may receive an input of the identification information corresponding to the color mixture to be corrected from the user and select the color mixture to be corrected corresponding to the identification information.

[0057] Next, the controller 10 generates high-resolution color mixing correction pattern data PD20 (see, for example, FIG. 8C) in which the range of change elements of the color mixing correction pattern P10 is narrowed with respect to the color mixing to be corrected as a reference, and the change elements are finely changed. The high-resolution color mixing correction pattern data PD20 indicates the input color F0i of a plurality of individual patterns P21. The variable i here is a variable for identifying the individual pattern P21 shown in FIG. 9B. As described above, the input color F0i is represented by, for example, the coordinate values (R, G, B) in the RGB color space. The high-resolution color mixing correction pattern data PD20 illustrated in FIG. 8C indicates the input color F0i of a plurality of individual patterns P21 in which the change elements change more finely than the color mixing correction pattern data PD10 with respect to the color mixing to be corrected as a reference. The high-resolution color mixing correction pattern data PD20 shown in FIG. 8C indicates the input color F0i of a plurality of individual patterns P21 that are printed when the combination of hue H = 45° and chroma C* = 0.8 included in the color mixing correction pattern data PD10 shown in FIG. 8A is selected as the color mixing to be corrected. The range of the hue H shown in FIG. 8C is a part of the entire hue, and the hue H changes step by step within the range shown in FIG. 8C. The range of the chroma C* shown in FIG. 8C is a part of the entire chroma range, and the chroma C* changes step by step within the range shown in FIG. 8C.

[0058] After generating the high-resolution color mixing correction pattern data PD20, the controller 10 controls the movement of the medium ME0 and the ejection of the ink 36 so that a high-resolution color mixing correction pattern P20 is formed on the medium ME0 according to the high-resolution color mixing correction pattern data PD20 (S116). When the controller 10 follows the high-resolution color mixing correction pattern data PD20 shown in FIG. 8C, it performs control to form a high-resolution color mixing correction pattern P20 on the medium ME0, which shows color mixing in which the hue and chroma are discrete but change finely. In addition, in order to facilitate identification of the individual pattern P21, the controller 10 may perform control to print the identification information of the individual pattern P21, for example, the identification number, on the medium ME0 in association with each individual pattern P21.

[0059] Although not shown, the high-resolution color mixing correction pattern data PD20 may indicate the input colors F0i of a plurality of individual patterns P21 in which the hue H changes step by step on the premise that the chroma C* is constant. In this case, the controller 10 can execute control to form a high-resolution color mixing correction pattern P20 that shows a discrete but finely changing color mixture for a part of the entire hue on the medium ME0 according to the high-resolution color mixing correction pattern data PD20. Also, the high-resolution color mixing correction pattern data PD20 may indicate the input colors F0i of a plurality of individual patterns P21 in which the chroma C* changes step by step on the premise that the hue H is constant. In this case, the controller 10 can execute control to form a high-resolution color mixing correction pattern P20 that shows a discrete but finely changing color mixture for a part of the entire chroma range on the medium ME0 according to the high-resolution color mixing correction pattern data PD20.

[0060] After printing the high-resolution color mixing correction pattern P20, the controller 10 causes the reading unit 60 to read the high-resolution color mixing correction pattern P20, obtains the output color of each raster line RL from the reading unit 60, and obtains the normal partial color F1i and the bridging partial color F2i based on the output color (S118). As shown in FIG. 9B, the average of the output colors in each normal part B1 is defined as the normal partial color F1i, and the average of the output colors in each bridging part B2 is defined as the bridging partial color F2i.

[0061] Next, the controller 10 obtains a color mixing correction value F3i based on the normal partial color F1i and the bridging partial color F2i, stores it in the storage unit 23, and causes the color mixing correction value F3i to be applied when controlling the formation of the printed image IM0 (S120). Here, let the coordinate values of the normal partial color F1i be (R1i, G1i, B1i), the coordinate values of the bridging partial color F2i be (R2i, G2i, B2i), and the color mixing correction value F3i be (R3i, G3i, B3i). The color mixing correction value (R3i, G3i, B3i) may be, for example, a value for correcting the bridging partial color F2i to the normal partial color F1i, so (R1i - R2i, G1i - G2i, B1i - B2i) may also be used. Here too, when the normal part B1 exists on both sides of one bridging part B2 in the width direction D4, the coordinate values (R1i, G1i, B1i) of the normal partial color F1i are the average of the coordinate values of the normal partial colors in the normal parts B1 on both sides.

[0062] As illustrated in FIG. 10, the color mixing correction value F3i may be included in a color conversion look-up table. FIG. 10 schematically illustrates how the printed image IM0 to which the color mixing correction value F3i is applied is formed. The LUT1 to LUT3 shown in FIG. 10 are color conversion look-up tables that can be referred to by the color conversion unit 12 shown in FIG. 1. The LUT1 shown in FIG. 10 has a correspondence relationship (Ri, Gi, Bi)-(C1i, M1i, Y1i, K1i) defined in accordance with the color development of the normal part B1. The variable i here is a variable for identifying the grid points of the LUT1. The grid points are represented by the coordinate values (Ri, Gi, Bi) in the RGB color space which is the input color space. The output coordinate values of the LUT1 are the coordinate values (C1i, M1i, Y1i, K1i) in the CMYK color space which is the output color space.

[0063] The LUT2 shown in FIG. 10 has a correspondence relationship (Ri, Gi, Bi)-(C2i, M2i, Y2i, K2i) defined according to the color development of a certain bridging portion B2. The correspondence relationship of LUT2 can also be said to be the correspondence relationship obtained by correcting the correspondence relationship of LUT1 according to the color mixing correction values (R3i, G3i, B3i). Incidentally, when the input coordinate values (Ri, Gi, Bi) of the original LUT2 copied from LUT1 are corrected according to the color mixing correction values (R3i, G3i, B3i), the output coordinate values (C2i, M2i, Y2i, K2i) corresponding to the coordinates of the original grid points can be calculated by interpolation. By associating the calculated output coordinate values (C2i, M2i, Y2i, K2i) with the input coordinate values (Ri, Gi, Bi), LUT2 is generated. As shown in FIG. 10, the color conversion look-up table may be provided for each bridging portion B2. The LUT3 shown in FIG. 10 has a correspondence relationship (Ri, Gi, Bi)-(C3i, M3i, Y3i, K3i) defined according to the color development of another bridging portion B2.

[0064] In the above manner, color mixing correction is performed. After the correction value acquisition process of S102 to S120, the controller 10 performs the print control process of the print image IM0 in a state where the color mixing correction value F3i is applied in addition to the single-color density correction value E3i (S122). In S122, the controller 10 controls the movement of the medium ME0 and the ejection of the ink 36 so that the print image IM0 formed by the plurality of color inks 36 is formed on the medium ME0. The printer 2 forms the print image IM0 corresponding to the original image data DA1 on the medium ME0.

[0065] In the color correction process shown in FIG. 5, after the single-color density correction of the ink 36 is performed based on the single-color density correction pattern P1, the color mixing correction is performed based on the color mixing correction pattern P10. As a result, as in the print image IM0 shown in FIGS. 4 and 10, the color mixing in the normal portion B1 and the color mixing in the bridging portion B2 on the medium ME0 are matched. Therefore, it is possible to reduce the difference in color mixing caused by the change in the distance in the raster line direction D2 between the nozzle rows 33 that eject different color inks 36 in the print head 30.

[0066] (5) Variation: Various variations of the present invention are conceivable. For example, the combination of ink colors is not limited to C, M, Y, and K, and may include orange, green, light cyan with a lower concentration than C, light magenta with a lower concentration than M, dark yellow with a higher concentration than Y, light black with a lower concentration than K, and the like. Of course, even when the printing apparatus 1 does not use any of the inks C, M, Y, and K, the aspects of the present application are applicable. The arrangement of the multi-color nozzle rows 33 with respect to the chip CH0 is not limited to the examples shown in FIGS. 2 and 3. For example, in the chip CH0, the C nozzle row 33c and the Y nozzle row 33y may be parallel to each other at a certain interval in the raster line direction D2, and the M nozzle row 33m and the K nozzle row 33k may be parallel to each other at a certain interval in the raster line direction D2. In this case, the C nozzle row 33c may be fitted to the first nozzle row, the M nozzle row 33m may be fitted to the second nozzle row, and the Y nozzle row 33y may be fitted to the third nozzle row.

[0067] The main body that performs the above-described processing is not limited to the CPU, and may be an electronic component other than the CPU, such as an ASIC. Of course, a plurality of CPUs may cooperate to perform the above-described processing, or the CPU and other electronic components (for example, ASIC) may cooperate to perform the above-described processing. A part of the above-described processing may be performed by the host device HO1. In this case, the combination of the controller 10, the driving unit 50, and the host device HO1 becomes an example of the control unit U1, and the combination of the printer 2 and the host device HO1 becomes an example of the printing apparatus 1. In the color correction process shown in FIG. 5, it is possible to omit the high-resolution color mixing correction pattern printing process of S112 to S116.

[0068] The color mixture correction pattern P10 formed by the ink 36 ejected from the print head 30 shown in FIGS. 2 and 3 only needs to include the color mixture of C ink and Y ink, and the color mixture of M ink and Y ink. Therefore, as illustrated in FIG. 11, the controller 10 may perform control to form a color mixture correction pattern P10 that does not include the color mixture of C ink and M ink on the medium ME0. As described above, for the color combinations in which the distance between the nozzle rows 33 is constant in the raster line direction D2, that is, the combination of C and M, and the combination of Y and K, there is no difference in color mixture between the normal region and the bridging region. Therefore, by forming a color mixture correction pattern P10 that does not include the color mixture of C and M or the color mixture of Y and K, the ink 36 and the medium ME0 can be used efficiently.

[0069] Further, as illustrated in FIG. 11, the controller 10 may perform control to form a color mixture correction pattern P10 that does not include K ink on the medium ME0. As described above, the frequency of expressing the color mixture including K ink is low. Therefore, by not using K ink in the color mixture correction pattern P10, a color mixture correction pattern P10 that efficiently uses the ink 36 and the medium ME0 can be formed.

[0070] (6) Conclusion: As described above, according to the present invention, it is possible to provide a configuration or the like that can reduce the difference in color mixture caused by the change in the distance in the raster line direction between the nozzle rows that eject inks of different colors in the print head in various ways. Of course, even in an aspect consisting only of the constituent elements according to the independent claims, the above-described basic operations and effects can be obtained. In addition, a configuration in which the respective configurations disclosed in the above-described examples are mutually replaced or the combination is changed, a known technique, and a configuration in which the respective configurations disclosed in the above-described examples are mutually replaced or the combination is changed, etc. are also implementable. The present invention also includes these configurations and the like.

Description of Reference Numerals

[0071] 1... Printing device, 2... Printer, 10... Controller, 23... Memory unit, 30... Print head, 33... Nozzle array, 34... Nozzle, 36... Ink, 37... Ink droplet, 38... Dot, 50... Driving unit, 60... Reading unit, A1, A3... Normal area, A2, A4... Crossing area, B1... Normal part, B2... Crossing part, CH0... Chip, D1... Nozzle alignment direction, D2... Raster line direction, D3... Feeding direction, D4... Width direction, HO1... Host device, IM0... Print image, ME0... Medium, L1, L2... Distance, L11... First distance, L12... Second distance, L21... Third distance, L22... Fourth distance, P1... Monochromatic density correction pattern, P2... Individual pattern, P10... Color mixing correction pattern, P11... Individual pattern, P20... High-resolution color mixing correction pattern, P21... Individual pattern, PD0... Correction pattern data, PD1... Monochromatic density correction pattern data, PD10... Color mixing correction pattern data, PD20... High-resolution color mixing correction pattern data, PX0... Pixel, RL... Raster line, ST1... Monochromatic density correction pattern formation process, ST2... Monochromatic density correction process, ST3... Color mixing correction pattern formation process, ST4... Color mixing correction process, U1... Control unit.

Claims

1. A printing apparatus for forming a printed image on a medium with multi-color inks including a first-color ink and a second-color ink, comprising: a print head having a plurality of first nozzle arrays in which a plurality of first nozzles capable of discharging the first-color ink onto the medium are arranged in a nozzle arrangement direction, and a plurality of second nozzle arrays in which a plurality of second nozzles capable of discharging the second-color ink onto the medium are arranged in the nozzle arrangement direction; a control unit configured to control relative movement between the print head and the medium in a raster line direction intersecting the nozzle arrangement direction and discharge of the ink from the print head; wherein a distance between the first nozzle array and the second nozzle array in the raster line direction is defined as L1; the plurality of first nozzle arrays and the plurality of second nozzle arrays are arranged such that in the nozzle arrangement direction, there exist a first region where the distance L1 is a first distance and a second region where the distance L1 is a second distance longer than the first distance; the control unit: performs control to form a single-color density correction pattern indicating a density of a single color of the ink on the medium; performs single-color density correction of the ink based on the single-color density correction pattern; performs control to form a color mixture correction pattern including a color mixture of the first-color ink and the second-color ink on the medium; and performs color mixture correction so as to combine a color mixture of a portion corresponding to the first region and a color mixture of a portion corresponding to the second region on the medium based on the color mixture correction pattern.

2. The multi-color inks include a third-color ink; the print head has a plurality of third nozzle arrays in which a plurality of third nozzles capable of discharging the third-color ink onto the medium are arranged in the nozzle arrangement direction; each of the third nozzle arrays is at a certain distance from the first nozzle array in the raster line direction; wherein a distance between the third nozzle array and the second nozzle array in the raster line direction is defined as L2; the plurality of third nozzle arrays and the plurality of second nozzle arrays are arranged such that in the nozzle arrangement direction, there exist a third region where the distance L2 is a third distance and a fourth region where the distance L2 is a fourth distance longer than the third distance. The control unit performs control to form, on the medium, the color mixture correction pattern that includes a color mixture of the third color ink and the second color ink and does not include a color mixture of the first color ink and the third color ink, the printing apparatus according to claim 1.

3. The inks of the plurality of colors include a black ink, The print head has a plurality of black nozzles capable of discharging the black ink onto the medium, The control unit performs control to form, on the medium, the color mixture correction pattern that does not include the black ink, the printing apparatus according to claim 1 or claim 2.

4. The control unit performs control to form, on the medium, the color mixture correction pattern that shows color mixture discretely over at least one of the entire hue and the entire density range, the printing apparatus according to claim 1 or claim 2.

5. The control unit, performs control to form, on the medium, the color mixture correction pattern in which at least one of the change elements of the hue and the density changes stepwise, for a portion where the difference between the color mixture of the portion corresponding to the first region and the color mixture of the portion corresponding to the second region in the medium exceeds a reference among the color mixture correction patterns, performs control to form, on the medium, a second color mixture correction pattern in which the change element changes more finely than the color mixture correction pattern, and performs the color mixture correction based on the second color mixture correction pattern, the printing apparatus according to claim 1 or claim 2.

6. A color correction method for a printing apparatus that relatively moves a print head capable of discharging a plurality of colors of inks including a first color ink and a second color ink and a medium in a raster line direction intersecting a nozzle array direction to form a printed image by the inks on the medium, the print head has a plurality of first nozzle rows in which a plurality of first nozzles capable of discharging the first color ink onto the medium are arranged in the nozzle array direction, and a plurality of second nozzle rows in which a plurality of second nozzles capable of discharging the second color ink onto the medium are arranged in the nozzle array direction, with a distance between the first nozzle row and the second nozzle row in the raster line direction being L1, the plurality of first nozzle rows and the plurality of second nozzle rows are arranged such that in the nozzle array direction, there exist a first region where the distance L1 is a first distance and a second region where the distance L1 is a second distance longer than the first distance, the color correction method includes A single-color density correction pattern forming step of forming a single-color density correction pattern indicating the density of the single color of the ink on the medium; A single-color density correction step of performing single-color density correction of the ink based on the single-color density correction pattern; A color mixture correction pattern forming step of forming a color mixture correction pattern including a color mixture of the first color ink and the second color ink on the medium; A color mixture correction step of performing color mixture correction so as to combine the color mixture of the portion corresponding to the first region and the color mixture of the portion corresponding to the second region on the medium based on the color mixture correction pattern; A color correction method comprising:

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