JP2015104921A - Correction value calculation method, printer controller, and printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in which it is necessary to suppress density unevenness especially becoming the problem when a line printer is used.SOLUTION: A correction value calculation method comprises: a printing control step of causing liquid to be discharged from a plurality of nozzles of a line type print head having the plurality of nozzles arranged side-by-side in a first direction onto an object to be printed transported in a second direction intersection with the first direction and a test pattern to be printed; a colorimetric value acquisition step of acquiring a colorimetric value of the test pattern printed; and a correction value calculation step of calculating a correction value for correcting image data corresponding to a region directed toward the second direction in which the liquid is discharged from a predetermined number of nozzles on the basis of the colorimetric value corresponding to the region. The correction value is the correction value for reducing a value of the image data.

Description

  The present invention relates to a correction value calculation method, a print control apparatus, and a printer.

  In the field of an inkjet printer having a nozzle for ejecting liquid, a step of printing a test pattern by ejecting liquid onto an area on a medium corresponding to pixel data from a first nozzle and a second nozzle, and a test pattern And reading a scanner to obtain a read value, and calculating a correction value for correcting pixel data corresponding to the region ejected from the first nozzle and the second nozzle based on the read value. A correction value calculation method is known (Patent Document 1).

JP 2009-274232 A

  Even if you try to eject ink droplets of the same size (same weight) by design from the multiple nozzles of the printer, it is not possible to accurately unify the size (ink weight) per ink droplet that is actually ejected between the nozzles It is difficult to manufacture the printer. That is, the ink weight for each nozzle varies. When such variation exists, streaky unevenness (density unevenness) may occur in an image printed by a printer depending on the difference in nozzles used for ink ejection, leading to image quality deterioration.

  Here, as a kind of ink jet printer, a line type print head that has a plurality of nozzles arranged in the first direction and discharges liquid from the nozzles to a substrate to be conveyed in a second direction intersecting the first direction is provided. A so-called line printer is known. Unlike the so-called serial printer, in which the print head reciprocates along the direction intersecting the direction in which the substrate is transported, the line printer prints the same area on the substrate with a plurality of different nozzles. I can't. Accordingly, in the line printer, if there is a variation in the ink weight for each nozzle, there is a problem that the variation is likely to appear remarkably as density unevenness (as compared to a serial printer) in the printing result.

  The present invention has been made to solve at least the above-described problem, and a correction value calculation method capable of accurately obtaining a correction value for eliminating density unevenness that easily occurs when a line type print head is used. A print control device and a printer are provided.

  One of the aspects of the present invention is that the correction value calculation method is performed on a substrate to be conveyed from a nozzle of a line type print head having a plurality of nozzles arranged in the first direction in a second direction intersecting the first direction. A printing control step of discharging a liquid to print a test pattern; a colorimetric value acquisition step of acquiring a colorimetric value of the printed test pattern; and the second of discharging the liquid from a predetermined number of the nozzles A correction value calculating step of calculating a correction value for correcting the image data corresponding to the area facing the direction based on the colorimetric value corresponding to the area, and the correction value is defined by the image data. This is a correction value for reducing the amount of the liquid to be performed.

  According to this configuration, it is possible to accurately calculate a correction value for eliminating density unevenness that tends to occur when a line-type print head is used, based on the colorimetric value. Further, since the calculated correction value is a correction value for reducing the amount of the liquid defined by the image data, it is possible to reliably correct the image data in all gradation ranges.

  One aspect of the present invention uses a line-type print head having a configuration in which a plurality of heads each having a nozzle row including a plurality of nozzles arranged in the first direction are arranged in the first direction in the print control step. That is, the line type print head is configured by connecting a plurality of heads in the first direction. In such a configuration, variation in ink weight for each nozzle is not so large within one head, and variation in ink weight between different heads tends to increase. Therefore, by setting the predetermined number of nozzles to one or more nozzles belonging to the common head, it is possible to obtain a correction value that accurately eliminates density unevenness due to variations in ink weight between heads. .

In one aspect of the present invention, the correction value calculating step calculates the correction value according to a difference between a reference value common to a plurality of printers for the colorimetric value and the colorimetric value.
According to this configuration, a correction value that not only eliminates density unevenness due to ink weight variations among nozzles in a printer having a line-type print head, but also eliminates color reproducibility variations between printers. Can be obtained.

  The technical idea of the present invention may be realized by an object or method different from the correction value calculation method as described above. As an example, print control for printing a test pattern by discharging liquid from a nozzle of a line-type print head having a plurality of nozzles arranged in the first direction onto a substrate to be conveyed in a second direction intersecting the first direction. A colorimetric value acquisition unit that acquires a colorimetric value of the printed test pattern, and corrects image data corresponding to a region facing the second direction in which the liquid is ejected from a predetermined number of the nozzles A correction value calculation unit that calculates a correction value for the image based on the colorimetric value corresponding to the area, and the correction value is a correction value that decreases the amount of the liquid defined by the image data. The print control apparatus can be regarded as one invention.

Further, a printer comprising a line-type print head having a plurality of nozzles arranged in a first direction and capable of discharging liquid from the nozzles to a substrate to be conveyed in a second direction intersecting the first direction, The liquid is ejected from a predetermined number of the nozzles calculated based on a printing unit that ejects the liquid from the nozzles onto the substrate and prints a test pattern, and a colorimetric value of the printed test pattern. A correction value holding unit that holds a correction value for correcting image data corresponding to the region facing the second direction, and the correction value is a correction that reduces the amount of the liquid defined by the image data. A printer that is a value can be regarded as one invention.
Furthermore, the present invention may be realized by a program that causes hardware (a computer installed in a print control apparatus or a printer) to execute the above-described method, or a computer-readable recording medium that records the program.

It is a figure showing roughly the device composition concerning this embodiment. It is a block diagram which shows each function which a control part implement | achieves. It is a figure which illustrates a part of print head. It is a flowchart which shows a correction table calculation process. It is a figure which illustrates a test pattern. It is a figure which illustrates the colorimetric value for every belt area | region of a test pattern. It is a figure which illustrates the colorimetric value etc. corresponding to the position of the nozzle with a test pattern. It is a figure which illustrates a correction table. 6 is a flowchart illustrating print control processing. 4 is a flowchart illustrating details of ink amount data correction processing.

Embodiments of the present invention will be described in the following order.
1. 1. Outline of device configuration 2. Calculation of correction table 3. Flow of print control process with correction Summary 5. Other

1. FIG. 1 schematically shows a configuration of a print control system 1 according to the present embodiment. The print control system 1 includes a printer 20 and a print control device (control device 10) for controlling the printer 20. The control device 10 is a device in which a program for controlling the printer 20 is installed, and is an execution subject of the correction value calculation method. The control apparatus 10 is typically a desktop or laptop personal computer (PC), but may be a tablet terminal or a mobile terminal. The print control system 1 may include a color measurement device 50. The color measurement device 50 is a device for measuring the color of a printed material on which an image is printed, and corresponds to a colorimeter, an image reading device (scanner), or the like.

  The control device 10, the printer 20, and the like that constitute the print control system 1 may be individual devices connected so as to be communicable, or may constitute a single product. For example, the printer 20 may include the control device 10 in a part of the machine body. In this case, the printer 20 itself that includes the print control 10 in the machine body corresponds to the print control system 1 or the print control apparatus, and becomes the execution subject of the correction value calculation method. Further, the printer 20 may be a multi-function machine that further includes the scanner. The print control system 1 may be called a print control apparatus.

  The print control system 1 may further include a standard machine 40. The standard machine 40 is a printer of the same type as the printer 20, and is a machine body that serves as a correction reference for the printer 20. In the correction value calculation method of the present embodiment, a correction table T that calculates the color reproducibility of the printer 20 to be equivalent to the color reproducibility of the standard machine 40 is calculated. The calculation of the correction table T may be performed by the manufacturer before the printer 20 is shipped, or may be performed by the user who owns the printer 20 after shipment. When the correction table T is calculated before the shipment of the printer 20, the printer 20 after the correction table T is calculated (the printer 20 after shipment) is controlled separately from the control device 10 used for calculating the correction table T. Therefore, a control device for doing so exists on the user side. In the following, for simplicity of explanation, not only the control device used for calculating the correction table T but also the control device for controlling the printer 20 after the correction table T is calculated is the control device 10. Assume that

  In the control device 10, the CPU 12 that is the center of the arithmetic processing controls the entire control device 10 via the system bus. A ROM 13, a RAM 14, and various interfaces (I / F 19 a, 19 b, etc.) are connected to the bus, and a hard disk (HD) 16 as storage means is connected via a hard disk drive (HD DRV) 15. The HD 16 can store a correction target value TG, a colorimetric value V, a correction table T, and the like. The HD 16 stores an operating system, application programs, a printer driver PD, and the like. These programs are read by the CPU 12 to the RAM 14 as appropriate and executed. The CPU 12, the ROM 13, and the RAM 14 are collectively referred to as a control unit 11. The I / F 19 a is connected to the printer 20 and the standard machine 40, and the I / F 19 b is connected to the color measuring device 50. The control device 10 further includes a display unit 17 configured by, for example, a liquid crystal display, an operation unit 18 configured by, for example, a keyboard, a mouse, a touch pad, and a touch panel.

  FIG. 2 shows each function realized by the control unit 11 by performing processing according to the printer driver PD. According to FIG. 2, the control unit 11 has functions such as a print control unit F1, a colorimetric value acquisition unit F2, a correction value calculation unit F3, and an ink amount data correction unit F4. Each of these functions will be described later.

  In the printer 20 (and the standard machine 40, the same applies to the description of FIG. 1 below), the I / F 25 is connected to the I / F 19a on the control device 10 side so as to be wired or wirelessly communicable, and the control unit 21 or the like is connected. Connected via system bus. In the control unit 21, the CPU 22 appropriately reads a program (firmware) stored in the ROM 23 or the like to the RAM 24 and executes predetermined arithmetic processing. The control unit 21 is connected to each unit of the print head 26, the head driving unit 27, and the feeding mechanism 28 to control each unit.

  The print head 26 supplies various inks from an ink cartridge (not shown) for each of a plurality of types of ink (for example, cyan (C) ink, magenta (M) ink, yellow (Y) ink, black (K) ink, etc.). Receive. The print head 26 can eject (discharge) ink droplets from a plurality of ink discharge holes (nozzles) provided corresponding to various inks. Of course, the specific types and number of liquids used by the printer 20 are not limited to those described above. For example, various inks and liquids such as light cyan, light magenta, orange, green, gray, light gray, white, metallic, etc. Can be used.

  FIG. 3 illustrates a part of the print head 26. The print head 26 is a line type print head having a plurality of nozzles Nz arranged in the longitudinal direction (first direction). That is, the printer 20 (and the standard machine 40) is a line printer. The print head 26 has a plurality of heads 29. Since the print head 26 is a set of a plurality of heads 29, it may be expressed as a head unit or the like. Each head 29 has a plurality of nozzle rows parallel to each other (two rows in the example of FIG. 3). The nozzle row is composed of a plurality of nozzles Nz arranged at regular intervals in the first direction. The nozzle rows in the head 29 are shifted from each other in the first direction, whereby all the nozzles Nz in the head 29 are arranged at equal intervals along the first direction. In FIG. 3, the second direction intersecting the first direction indicates the direction in which the substrate is conveyed by the feeding mechanism 28. The term “intersection” here means basically orthogonal. However, in this specification, even when the directions and positions of the components inside and outside the print head 26 are expressed as parallel, equally spaced, orthogonal, etc., they mean only strictly parallel, equally spaced, orthogonal. It does not mean that it includes errors that are acceptable in terms of product performance and errors that may occur during product manufacturing.

  In FIG. 3, for the sake of convenience, the plurality of heads 29 are divided into a plurality of groups (head groups) depending on the presence / absence of hatching and the difference in density and direction of lines due to the hatching. It expresses that the ejected ink is different. As an example, in FIG. 3, the plurality of heads 29 are divided into four head groups, and as a result, the print head 26 can eject ink of four colors (for example, C, M, Y, K). . Here, for convenience, the term head row is defined. The head row refers to a row composed of a plurality of heads 29 arranged linearly in the first direction. In the example of FIG. 3, the head group corresponding to one ink color is composed of two head rows. More specifically, in one head group, the heads 29 belonging to one head row and the heads 29 belonging to the other head row are alternately arranged along the first direction. With such an arrangement, the nozzles Nz for ejecting the same color ink are present at equal intervals in the first direction within one head group. In each head group, the nozzles Nz are arranged at equal intervals over at least the width in the first direction of the printable area of the substrate.

  Returning to the description based on FIG. The feeding mechanism 28 is controlled by the control unit 21 and transports the printing material in a predetermined feeding direction (second direction) by a roller (not shown) or the like. A printing substrate (print substrate) is a material that holds a printed image. The shape is generally rectangular, but there are round shapes (for example, optical disks such as CD-ROM and DVD), triangles, quadrangles, polygons, etc., and at least Japanese Industrial Standard “JIS P0001: 1998 Paper / Board and Pulp” Includes all paper and board varieties and processed products described in "Terminology".

  The head drive unit 27 is provided corresponding to each nozzle Nz of the print head 26 based on print data (print data will be described later) acquired from the control device 10 by the control unit 21 via the I / F 25. A drive voltage for driving the piezoelectric element is generated. The head drive unit 27 outputs the drive voltage to the print head 26. As a result, ink droplets of each ink type are ejected from the nozzles Nz of the print head 26 onto the conveyed printed material. The ejected ink droplets adhere to the substrate and dots are formed on the substrate, so that an image based on the print data is reproduced on the substrate.

  In the printer 20 including such a line type print head (print head 26), the nozzle density in the first direction (number of nozzles per inch (npi)) is equivalent to the print resolution in the first direction. Further, the printing resolution in the second direction mainly depends on the conveyance speed of the printing material by the feeding mechanism 28. Furthermore, the printer 20 includes a display unit 30 configured by, for example, a liquid crystal display, and an operation unit 31 configured by, for example, a button or a touch panel. In the printer 20, the means for ejecting ink droplets from the nozzles Nz is not limited to the piezoelectric element, and a configuration in which ink is heated by a heating element and ink droplets are ejected from the nozzles Nz may be employed.

2. Calculation of Correction Table FIG. 4 is a flowchart showing a correction table calculation process (correction value calculation method).
In step S <b> 100, the print control unit F <b> 1 (FIG. 2) causes the printer 20 to print the test pattern TP on the substrate S based on the test pattern data representing the predetermined test pattern TP. The test pattern data is bitmap data in which each pixel has gradation values (for example, 256 gradations from 0 to 255) equivalent to the ink amount, and is prepared in advance. Step S100 corresponds to a print control process for printing a test pattern.

  In step S100, the print control unit F1 performs halftone processing (halftoning) on the test pattern data. The specific method of halftone processing is not particularly limited. For example, the print control unit F1 may execute halftone processing by dithering using a predetermined dither mask, or may execute halftone processing by an error diffusion method. The halftone process generates halftone data that defines ejection (dot formation) or non-ejection (dot non-formation) of each color ink of CMYK for each pixel. Halftone data corresponds to print data. The print control unit F1 rearranges the generated print data in the order to be transferred to the print head 26. By the rearrangement process, it is determined at which timing the nozzles of the ink defined by the print data are ejected by which nozzle Nz according to the pixel position and the ink color. The print control unit F1 transmits the print data after the rearrangement process to the printer 20 via the I / F 19a together with information defining other printing conditions. As a result, the printer 20 prints the test pattern TP based on the transmitted print data.

  FIG. 5 illustrates the test pattern TP printed on the substrate S in step S100. The test pattern TP shown in FIG. 5 is a single color pattern printed with only one color ink (for example, C ink) among the inks (for example, CMYK inks) used by the printer 20. Such a test pattern TP has a plurality (four in the example of FIG. 5) of band regions in which the direction perpendicular to the second direction is the longitudinal direction along the second direction. As shown in FIG. 5, it is printed at different densities. That is, the plurality of band regions constituting the test pattern TP using one color ink have a plurality of densities (tone values) at predetermined intervals between the lowest density (tone value 0) and the highest density (tone value 255). It is expressed by. In the test pattern data, all the pixels in one band region have the same gradation value for a certain ink color. Such a test pattern TP is printed for each ink color CMYK used by the printer 20.

  In FIG. 5, a region that faces the second direction (the second direction is the longitudinal direction) and is printed by a predetermined number m (m = 1) of nozzles Nz is illustrated by reference symbol A. For example, when the test pattern TP shown in FIG. 5 is printed with C ink, the region A is printed by any nozzle Nz belonging to the head group corresponding to the C ink in the print head 26. In other words, the image printed by the print head 26 is formed by bundling the region A for each nozzle Nz.

In step S110, the colorimetric value acquisition unit F2 (FIG. 2) acquires the colorimetric values of the test pattern TP printed in step S100. That is, the test pattern TP printed on the substrate S is color-measured by the color measuring device 50, and the color measurement result is input from the color measuring device 50. For example, the color measuring device 50 measures each band area constituting the test pattern TP at a predetermined reading frequency along the longitudinal direction of the band area (and by changing the position in the second direction a plurality of times). The colorimetric value acquisition unit F2 performs colorimetry on color values represented by L ^* , a ^* , b ^* components of the CIE L ^* a ^* b ^* color space defined by the International Lighting Commission (CIE), for example. Enter as a value. The colorimetric value of the test pattern TP acquired in step S110 is referred to as a colorimetric value V for convenience. Of course, the colorimetric value acquisition unit F2 acquires the colorimetric value V of each test pattern TP printed for each ink color used by the printer 20. The colorimetric value V is temporarily stored in a predetermined storage area (for example, HD 16; see FIG. 1). Step S110 corresponds to a colorimetric value acquisition step.

FIG. 6 exemplifies the colorimetric value V for each band region (for each tone value of the band region) obtained from the test pattern TP with one ink color using a graph. In the graph shown in FIG. 6, the vertical axis represents the colorimetric value V, and the horizontal axis represents the position P (first to Nth positions). The colorimetric value V (and a correction target value TG described later) is, for example, lightness (L ^* ). However, a value obtained by linearly adding L ^* , a ^* , and b ^* may be used as the colorimetric value V (or the correction target value TG). The position P is a reading position along the longitudinal direction of the belt region when the color of the belt region is measured, and is equivalent to the position in the first direction of the nozzles Nz belonging to the head group corresponding to the ink color of the test pattern TP. There is a one-to-one correspondence between one position P and one region A. The colorimetric value V for each band region shown in FIG. 6 is an average value for each position P of colorimetry performed a plurality of times for each band region. The reason why the colorimetric value V for each position P with respect to the same band region is not constant is that the ink weight for each nozzle Nz is not constant.

  In step S120, the correction value calculation unit F3 (FIG. 2) corrects correction values (correction table T) for correcting image data (ink amount data described later) corresponding to the region (region A) facing the second direction. Is calculated based on the colorimetric value V corresponding to the area. That is, the correction table T is calculated for each position P. Step S120 corresponds to a correction value calculation step.

  In calculating the correction table T, the correction value calculation unit F3 acquires a correction target value TG. The correction target value TG is a colorimetric value obtained by printing the test pattern TP based on the test pattern data on the substrate S by the standard machine 40 and causing the colorimetric device 50 to measure the color of the test pattern TP. is there. The only difference in the process of acquiring the correction target value TG and the colorimetric value V is that the printer used for printing the test pattern TP is the standard machine 40 or the printer 20. The correction target value TG is a common value used when generating the correction table T required for each of the mass-produced printers 20, and corresponds to the “reference value” in the claims. The correction target value TG is measured in advance and stored in a predetermined storage area (for example, HD16), and the correction value calculation unit F3 reads the correction target value TG from the storage area.

The correction value calculation unit F3 calculates a correction table T for each position P according to the difference between the correction target value TG and the colorimetric value V.
FIG. 7 shows, as an example, the colorimetric values (colorimetric values V) of the test pattern TP printed with C ink by the printer 20, and the colorimetric values V at the Pn-th position Pn (FIG. 6) are represented by white circles. Is plotted. The gradation values Cn1, Cn2, Cn3... Shown on the horizontal axis in FIG. 7 are gradation values for each band area in the test pattern data representing the test pattern TP. In FIG. 7, a straight line (or a curved line) obtained by interpolating such a colorimetric value V is illustrated by a solid line L1.

  Here, in FIG. 7, it is assumed that the colorimetric value V corresponding to the gradation value Cn2 of one band region is “Vn2”. Further, the color measurement value (correction target value TG) of the test pattern TP printed by the C ink by the standard machine 40, and the gradation value Cn2 of the color measurement value (correction target value TG) at the position Pn. Assume that the corresponding colorimetric value (corrected target value TG) is “TGn2”. In this case, the correction value calculation unit F3 specifies the gradation value of C ink necessary for the printer 20 to realize a color value equivalent to the correction target value TGn2 as a value after correction of the gradation value Cn2. . Specifically, the gradation value Cn2 ′ for realizing the correction target value TGn2 on the solid line L1 is a value after the correction of the gradation value Cn2. The correction value calculation unit F3 specifies such a gradation value correction relationship for the gradation values Cn1, Cn2, Cn3,... Of all band regions, and further, the gradation values Cn1, Cn2, Cn3,. The correction relationship specified every time is interpolated over all gradations 0 to 255.

  FIG. 8 illustrates a straight line (or a curved line) obtained by such interpolation as a solid line L2. The solid line L2 corresponds to the correction table T for C ink at the position Pn. The correction table T is a table in which input gradation values over all gradations 0 to 255 are associated with corrected gradation values (output gradation values). The correction value calculation unit F3 similarly calculates the correction table T for every position P (first to Nth) and for each ink color CMYK used by the printer 20.

  In step S130, the correction value calculation unit F3 stores the correction table T calculated in step S120 as described above in association with the corresponding position P and ink color information. The storage destination is a predetermined storage area (for example, HD16) on the control device 10 side or a predetermined storage area (for example, memory in the control unit 21) on the printer 20 side. This is the end of the correction table calculation process. The means for holding the correction table T on the printer 20 side corresponds to the correction value holding unit. Further, the configuration in the printer 20 that operates for printing an arbitrary image (such as the test pattern TP) corresponds to a printing unit.

3. Flow of Print Control Process with Correction FIG. 9 is a flowchart showing a process (print control process) in which the control apparatus 10 causes the printer 20 to execute printing in accordance with the printer driver PD. This process involves a correction process using the correction table T calculated as described above.
In step S200, the print control unit F1 (FIG. 2) acquires image data arbitrarily selected by the user from a predetermined input source. That is, the user can arbitrarily select image data representing an image to be printed by operating the operation unit 18 or the like while viewing the user interface screen (UI screen) displayed on the display unit 17 or the like. The input source of the image data is not particularly limited, and for example, any image input device that is communicably connected to the control device 10 in addition to the HD 16, a memory card (not shown) inserted from the outside into the control device 10 and the like corresponds to this. .

  The format of the image data acquired in step S200 is, for example, a bitmap format, and has R (red), G (green), and B (blue) gradation values for each pixel. Further, when the acquired image data does not correspond to the RGB color system, the print control unit F1 converts the acquired image data into data of the color system. Furthermore, the print control unit F1 appropriately performs resolution conversion processing and the like on the image data to match the print resolution of the printer 20 (the print resolution in the first direction and the second direction).

  In step S210, the print control unit F1 performs a color conversion process on the image data after step S100. That is, the color system of image data is converted into an ink color system used by the printer 20 for printing. As described above, when the image data expresses the color of each pixel in RGB with gradation, the RGB gradation value is converted into a gradation value for each CMYK for each pixel. Hereinafter, the image data expressed by the CMYK gradation value for each pixel is referred to as “ink amount data”. The color conversion process can be executed by referring to an arbitrary color conversion lookup table.

  In step S220, the ink amount data correction unit F4 (FIG. 2) corrects the ink amount data obtained in step S210 using the correction table T. The ink amount data correction unit F4 reads the correction table T from a predetermined storage area on the print control 10 side (for example, HD16) or a predetermined storage area on the printer 20 side (for example, a predetermined memory in the control unit 21). be able to. As described above, since the correction table T is also stored on the printer 20 side, the control device for controlling the printer 20 after the correction table T is calculated is the control used to calculate the correction table T. Even if it is different from the apparatus, the correction table T can be obtained with certainty.

  FIG. 10 is a flowchart showing details of the correction process in step S220. The ink amount data correction unit F4 selects one pixel to be corrected from a plurality of pixels constituting the ink amount data (step S221). Next, the ink amount data correction unit F4 selects one gradation value of the ink color to be corrected from the gradation values for each CMYK that the correction target pixel has (step S222). Next, the ink amount data correction unit F4 reads the correction table T corresponding to the correction target ink color of the correction target pixel, and stores the correction target ink color level of the correction target pixel in the read correction table T. By inputting the tone value, the tone value of the input ink color is corrected (step S223).

  As described above, the correction table T is generated for each position P. Further, the position P is a coordinate (X coordinate) in a direction (for example, the X direction) equivalent to the first direction among the biaxial directions (X and Y directions orthogonal to each other) of the ink amount data that is bitmap data. It is synonymous. Therefore, in step S223, the ink amount data correction unit F4 reads the correction table T corresponding to the position P corresponding to the X coordinate of the pixel to be corrected, and corresponding to the ink color to be corrected. The ink amount data correction unit F4 includes a table in which the position P and the X coordinate are associated one to one, and the correction table T related to the position P corresponding to the X coordinate of the correction target pixel with reference to the table. May be read out. A pixel row composed of pixels having the same X coordinate in the ink amount data (a row of pixels arranged in the Y direction equivalent to the second direction) corresponds to one of the regions A facing the second direction, and The gradation values of the same ink color in the pixel row are corrected by the same correction table T.

  The ink amount data correction unit F4 determines whether or not the correction in step S223 has been completed for the gradation values of all ink colors CMYK included in the pixel to be corrected (step S224), and there is an ink color that has not been corrected. In step S222, the tone value relating to the uncorrected ink color is newly selected. On the other hand, if the correction in step S223 has been completed for the gradation values of all ink colors CMYK, the process proceeds to step S225. In step S225, the ink amount data correction unit F4 determines whether or not the correction has been completed for all the pixels constituting the ink amount data. If there is a pixel that has not been corrected, the process returns to step S221 and the uncorrected data is returned. A new pixel is selected. On the other hand, when all the pixels have been corrected, the correction process is ended.

In step S230 (FIG. 9), the print control unit F1 performs halftone processing on the ink amount data after the correction processing described above to generate halftone data (print data).
In step S240, the print control unit F1 performs the above-described rearrangement process on the print data generated in step S230, and transmits the print data after the rearrangement process to the printer 20 side via the I / F 19a. Accordingly, the printer 20 performs printing based on the transmitted print data (printing of an image represented by the image data acquired in step S200).

4). Summary As described above, the present embodiment is based on the assumption that the printer 20 including the line-type print head (print head 26) having the plurality of nozzles Nz arranged in the first direction is used, and a predetermined number m (m = 1). A correction value (correction table T) for correcting image data (ink amount data) corresponding to a region facing the second direction in which liquid is ejected from the nozzle Nz is used as a colorimetric value V (printer) corresponding to the region. 20 is a colorimetric value of the test pattern TP printed), and is stored in the printer 20. In other words, even if there is a variation in the ink weight for each nozzle Nz of the print head 26, printing is performed for each nozzle Nz by adjusting the ink amount data that defines the amount of ink ejected by each nozzle Nz. The difference in color for each region A is suppressed. As a result, the density unevenness of the printing result that is remarkable in a printer having a line type print head is suppressed.

  In the present embodiment, the correction target value TG serving as a correction reference is a reference value that is commonly used for correction of each of a plurality of mass-produced printers 20. Therefore, when calculating the correction table T for each printer 20, the correction table T not only eliminates density unevenness due to ink weight variation between nozzles Nz of one printer 20, but also between printers 20. This also eliminates variations in printing results.

  Here, the two-dot chain line shown in FIG. 8 is a straight line with an inclination “1” indicating that the input gradation value = the output gradation value of the correction table T. As can be seen from FIG. 8, the value after correction (output gradation value) defined by the correction table T is lower than the value before correction (input gradation value). With such a configuration, a situation in which the value before correction cannot be substantially corrected is avoided. That is, if the correction table T has a characteristic of increasing the input value, if the input value is a value close to the maximum value 255 or the maximum value 255, the corrected value cannot take a value exceeding the maximum value 255. For this reason, the value after correction does not change or hardly changes from that before correction. For this reason, correction to the extent necessary originally (correction necessary to approximate the color reproducibility of the printer 20 to the color reproducibility of the standard machine 40) may not be possible. On the other hand, if the correction table T has a characteristic of decreasing the input value, even when the input value is the maximum value 255 or a value close to the maximum value 255, the necessary correction is surely executed. .

  Therefore, as described above, the correction table T is supposed to decrease the value of the ink amount data. In order to realize such a correction table T, the standard machine 40 has an ink weight of ink droplets ejected by the nozzles Nz that is about the same as that of the printer 20 of the category with the smallest ink weight among the mass-produced printers 20. It is set to become. With this setting, when the correction table calculation process (FIG. 4) is performed for a certain printer 20, the correction table T (the color reproducibility of the printer 20) is always corrected to reduce the value of the input ink amount data. Thus, a correction table T) that can realize correction necessary to approximate the color reproducibility of the standard machine 40 is obtained.

5. Others In the foregoing, the case where the predetermined number m = 1 has been described as an example, but the predetermined number m may be a number greater than one. That is, the correction table T may be generated for each area wider (thick in the first direction) than the area A printed by one nozzle Nz in the head group. Specifically, in step S120 (FIG. 4), the correction value calculation unit F3 performs printing for each area printed by m (m> 1) nozzles Nz arranged continuously in the first direction in the common head 29. Based on the comparison between the average value of the colorimetric values V and the correction target value TG, a correction table T for correcting image data (ink amount data) corresponding to the area is calculated. However, when the maximum value of the number of nozzles Nz arranged in the first direction in one head 29 is M, the predetermined number m is M or less. That is, in the present embodiment, the predetermined number m of nozzles Nz means one or more nozzles Nz that are continuous in the first direction within the common head 29.

  According to such a configuration, the generated correction table T is the maximum number of nozzles Nz arranged in the first direction in the head group × the number of ink colors used by the printer 20, and the minimum is the first in the head group. The number of heads 29 arranged in the direction × the number of ink colors. In particular, variation in the ink weight for each nozzle Nz is small in the same head 29, but tends to increase between different heads 29. Therefore, by generating the correction table T for each area corresponding to the head 29 (and the correction table T for each ink color), density unevenness that is particularly noticeable between areas printed by different heads 29 with as few correction tables as possible. And the variation in print results with other printers 20 can be eliminated.

  In the print head 26 illustrated in FIG. 3, each head 29 constituting the head group is disposed so as to partially overlap the end of the other head 29 at both ends or one end in the first direction. In the example of FIG. 3, when the range (overlap range) where the end portions of the head 29 overlap in this way is viewed along the second direction, the two nozzles Nz overlap in the head group. However, in the present embodiment, the print data generated corresponding to the position of the overlap range is allocated at a predetermined ratio to one of the two overlapping nozzles Nz in the rearrangement process described above. Therefore, regarding the generation process of the correction table T and the correction process of the ink amount data described so far, the existence of the overlap range is not particularly considered, and the two overlapping nozzles Nz in the overlap range are regarded as one. It does not matter.

DESCRIPTION OF SYMBOLS 1 ... Print control system, 10 ... Control apparatus, 11 ... Control part, 12 ... CPU, 13 ... ROM, 14 ... RAM, 15 ... HD DRV, 16 ... HD, 17 ... Display part, 18 ... Operation part, 19a, 19b ... I / F, 20 ... Printer, 21 ... Control part, 22 ... CPU, 23 ... ROM, 24 ... RAM, 25 ... I / F, 26 ... Print head, 27 ... Head drive part, 28 ... Feed mechanism, 29 ... Head 30. Display unit 31 Operation unit 40 Standard machine 50 Color measuring device F 1 Print control unit F 2 Color measurement acquisition unit F 3 Correction value calculation unit F 4 Ink amount data correction Part, Nz ... nozzle, PD ... printer driver, S ... substrate, T ... correction table, TG ... correction target value, TP ... test pattern, V ... colorimetric value

Claims (5)

A print control step of printing a test pattern by discharging liquid from a nozzle of a line-type print head having a plurality of nozzles arranged in a first direction to a substrate to be conveyed in a second direction intersecting the first direction;
A colorimetric value acquisition step of acquiring a colorimetric value of the printed test pattern;
Correction value calculation for calculating a correction value for correcting image data corresponding to an area facing the second direction in which the liquid is ejected from a predetermined number of nozzles based on the colorimetric value corresponding to the area A process,
The correction value calculation method, wherein the correction value is a correction value for reducing the amount of the liquid defined by the image data. In the printing control step, a line type print head having a configuration in which a plurality of heads each having a nozzle row including a plurality of nozzles arranged in the first direction are arranged in the first direction,
The correction value calculation method according to claim 1, wherein the predetermined number of nozzles is one or more nozzles belonging to the common head.   3. The correction value calculating step calculates the correction value according to a difference between a reference value common to a plurality of printers for the colorimetric value and the colorimetric value. The correction value calculation method described in 1. A print control unit that prints a test pattern by discharging liquid from a nozzle of a line-type print head having a plurality of nozzles arranged in a first direction to a printing material that is transported in a second direction that intersects the first direction;
A colorimetric value acquisition unit for acquiring a colorimetric value of the printed test pattern;
Correction value calculation for calculating a correction value for correcting image data corresponding to an area facing the second direction in which the liquid is ejected from a predetermined number of nozzles based on the colorimetric value corresponding to the area With
The print control apparatus according to claim 1, wherein the correction value is a correction value for decreasing the amount of the liquid defined by the image data. A line-type print head having a plurality of nozzles arranged in a first direction and capable of discharging liquid from the nozzles to a substrate to be conveyed in a second direction intersecting the first direction,
A printing unit that prints a test pattern by discharging the liquid from the nozzle onto the substrate;
A correction value for correcting image data corresponding to a region facing the second direction in which the liquid is ejected from a predetermined number of the nozzles, which is calculated based on the colorimetric values of the printed test pattern, is stored. A correction value holding unit to
The printer according to claim 1, wherein the correction value is a correction value that decreases the amount of the liquid defined by the image data.