JP2023091484A - Information processing device, image forming device, image forming system, method and program - Google Patents

Abstract

To determine an area in which color unevenness is caused out of a multicolor area and a primary color nozzle that corrects the color unevenness.SOLUTION: A ruler having primary colors is detected from a scan image obtained by scanning a recording medium on which an image including a patch having multi colors having two or more primary colors mixed and the ruler having primary colors constituting multi-colors. Based on the position of the ruler having the primary colors in the scan image, an area where there is color unevenness in the patch having the multi-colors in the scan image and a nozzle having primary colors that correct the multi-colors in the area where there is the color unevenness.SELECTED DRAWING: Figure 7A

Description

The present invention relates to an information processing device, an image forming device, an image forming system, a method, and a program.

2. Description of the Related Art An inkjet printer forms an image by ejecting colorants onto a paper surface from nozzles of a plurality of nozzle rows having colorants (inks) of primary colors different from each other. 2. Description of the Related Art In an inkjet printer, color unevenness (non-uniformity in ink concentration and color) may occur in an image on paper due to variations in ejection characteristics of a plurality of nozzles in a nozzle row, and print quality may be degraded.

Japanese Patent Application Laid-Open No. 2002-200000 describes the correlation between the gradation value (amount of color material) of the primary color and the color information (RGB value) of the image (printed matter) in which the color material is recorded, and acquires the data for each predetermined region of the image in the nozzle row direction. Disclosed is a technique for correcting the gradation value of the primary color based on the data (pixel value) obtained by the correction. The nozzle row direction refers to the direction in which a plurality of nozzles are aligned in a straight line. This technology is hereinafter referred to as head shading technology. The head shading technology can correct the gradation value of the primary color by using the gradation value of the primary color as an input value and referring to the 1D-LUT for each predetermined area of the image, thereby improving the color unevenness of the primary color. . Note that the head shading technique may not be able to improve color unevenness of multi-order colors.

Japanese Patent Application Laid-Open No. 2002-200000 describes the correlation between the gradation value (amount of color material) of a multi-order color and the color information (RGB value) of an image (printed matter) in which the color material is recorded, and for each predetermined region of the image in the direction of the nozzle row. Disclosed is a technique for correcting gradation values of multinary colors based on acquired data (pixel values). This technology is hereinafter referred to as color shading technology. Color shading technology can correct multinary color gradation values by using multinary color gradation values as input values and referring to a multidimensional LUT for each predetermined area of an image, thereby reducing color unevenness in multinary colors. can be improved.

JP 2012-066516 A Japanese Patent No. 5780734

In Patent Document 2, a ruler (detection mark) of the same color as the multinary color patch is used in order to obtain color information of an area with color unevenness from the multinary color patch. The multinary color ruler forms a single line in the same way as the primary color ruler when the registrations between the primary colors forming the multinary color (hereinafter referred to as intercolor registration) match. For this reason, Japanese Patent Laid-Open No. 2002-200000 discloses a method for correcting an area with color unevenness and multinary color gradation values from a multinary color patch by detecting a multinary color ruler when color registration matches. A primary color nozzle can be determined.

However, even if there is no color misregistration, color misregistration may occur due to changes in the nozzle array over time, meandering during paper transport, and the like. When an inter-color misregistration occurs, the multinary color ruler appears on the image as two or more rulers of the primary colors that make up the multinary color. In this case, Japanese Patent Application Laid-Open No. 2002-200000 may not be able to determine the area with color unevenness and the primary color nozzles for correcting the color unevenness.

As described above, there is a problem that a region with color unevenness and a primary color nozzle for correcting color unevenness cannot be determined from a multi-color region.

An object of the present invention is to determine an area with color unevenness and primary color nozzles for correcting color unevenness from a multi-color area.

In order to achieve the object of the present invention, an information processing apparatus according to one embodiment of the present invention has the following configuration. That is, the information processing apparatus scans a recording medium on which an image including a multinary color patch obtained by mixing two or more primary colors and a ruler of primary colors forming the multinary color is formed by an image forming apparatus. and a detection means for detecting the primary color ruler from the scanned image obtained by the above, and based on the position of the primary color ruler in the scanned image, color unevenness in the multicolor patch in the scanned image. and a determining means for determining the primary color nozzles for correcting the multinary color in the area with the color unevenness.

According to the present invention, it is possible to determine an area with color unevenness and a primary color nozzle for correcting color unevenness from a multi-color area.

2 is a diagram showing an example of the hardware configuration of an image forming apparatus; FIG. FIG. 2 is a diagram for explaining an example of the hardware configuration of an image forming system; FIG. 3 is a diagram illustrating an example of functions of an information processing apparatus; An example of a test image used for creating a 4D-LUT is shown. An example of a test image used to create a cyan 1D-LUT is shown. An example of a test image used to create a 1D-LUT in blue is shown. FIG. 4 is a diagram for explaining a method of obtaining primary color correction values using a 1D-LUT; FIG. 4 is a diagram for explaining a method of obtaining correction values for primary colors that form multinary colors using a 1D-LUT; FIG. 4 is a diagram showing the positional relationship between a test image and nozzle rows when forming the test image; FIG. 4 is a diagram showing the positional relationship between a test image and nozzle rows when forming the test image; FIG. 4 is a diagram showing the positional relationship between a test image and nozzle rows when forming the test image; FIG. 4 is a diagram showing the positional relationship between a test image and nozzle rows when forming the test image; 6 is a flowchart for explaining the flow of detecting an area of color unevenness; FIG. 7B is a flowchart showing the details of the processing of S703 in FIG. 7A; FIG. FIG. 7B is a flowchart showing the details of the processing of S705 in FIG. 7A; FIG. FIG. 10 is a diagram showing an example of a test image when the ruler is placed above the patch; FIG. 10 is a diagram showing an example of a test image when rulers are arranged above and below the patch; FIG. 4 is a diagram showing an example of a test image composed of multiple pages; The figure which shows an example of the test image which arranged several patches and rulers on the same page. 4A and 4B are diagrams for explaining misalignment between colors; FIG. FIG. 10 is a diagram showing an example of a test image when rulers are arranged above and below the patch; FIG. 10 is a diagram showing an example of a test image when rulers are arranged above and below the patch; FIG. 10 is a diagram showing an example of a test image when rulers are arranged above and below the patch; FIG. 10 is a diagram showing an example of a test image when rulers are arranged above and below the patch; FIG. 10 is a diagram showing an example of a test image when rulers are arranged above and below the patch; The figure which shows an example of the test image which arranged the ruler in consideration of SN ratio. The figure which shows an example of the test image which concerns on 2nd Embodiment. FIG. 5 is a diagram showing an example of a test image corresponding to the paper transport speed; 7B is a flowchart showing detailed processing in S701 of FIG. 7A;

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. In addition, the following embodiments do not limit the invention according to the scope of claims. Although multiple features are described in the embodiments, not all of these multiple features are essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same or similar configurations are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment)
The information processing apparatus scans a recording medium on which an image including a multinary color patch obtained by mixing two or more primary colors and a ruler of primary colors forming the multinary color is formed by an image forming apparatus. A primary color ruler is detected from the resulting scanned image. Based on the position of the ruler of the primary color in the scanned image, the information processing apparatus corrects an area with color unevenness in a patch of multinary colors in the scanned image and a primary color that corrects the multinary color in the area with color unevenness. Determine the nozzle of the

Here, a scanned image (synonymous with a test image) is an image that includes multicolor patches and a ruler located at a position that does not overlap the patches in the print medium conveying direction (direction perpendicular to the print head). It is an image obtained by scanning an image formed on a recording medium by a forming device. A patch is a multicolor (e.g., blue) area formed on a recording medium (e.g., paper) by an image forming apparatus using nozzle arrays that eject different primary colors (CMYK). say. The ruler (detection mark) refers to the position at which the nozzles of the primary color nozzle array eject the coloring material onto the recording medium. Used to determine the nozzles in the color nozzle row. Inter-color registration refers to aligning the left or right ends of the nozzle arrays of the primary colors (eg, cyan and magenta) with respect to the recording medium. Hereinafter, the misalignment of the primary color nozzle arrays is defined as the misalignment between colors.

FIG. 1 is a diagram showing an example of the hardware configuration of an image forming apparatus. The image forming apparatus 10 is a device that receives image data and forms the image data on a recording medium (for example, paper), and includes, for example, an inkjet printer. The image forming apparatus 10 includes a recording head 100 , conveying rollers 105 and an in-line sensor 107 .

The printhead 100 is a full-line type printhead and includes nozzle arrays 101-104. The nozzle row 101, nozzle row 102, nozzle row 103, and nozzle row 104 correspond to black, cyan, magenta, and yellow ink colors, respectively. In the nozzle rows 101 to 104, a plurality of nozzles for ejecting ink are arranged in the x direction at regular intervals. For example, in the case of a nozzle array with a print head length of 15 inches and a print resolution of 1200 dpi, approximately 18000 (=15×1200) nozzles are arranged in the x direction.

The transport roller 105 has a motor (not shown), and transports the recording medium 106 in the y direction by the driving force of the motor. A recording medium 106 is a sheet of paper on which ink ejected by the recording head 100 is recorded. While the conveying roller 105 conveys the recording medium 106 in the y direction, a plurality of nozzles provided in the nozzle arrays 101 to 104 eject coloring material (ink) according to recording data, thereby forming an image on the recording medium 106. It is formed. It is assumed that the print resolution in the conveying direction (y direction) of the print medium 106 is 1200 dpi.

The in-line sensor 107 has a plurality of optical reading elements arranged at regular intervals in the x-direction, and is positioned below the recording head 100 in the y-direction. The in-line sensor 107 optically reads RGB values of an image (printed matter) using an optical reading element. The in-line sensor 107 outputs (notifies) the external device as a scanned image representing the RGB values read from the image in the RGB color space. It is assumed that the in-line sensor 107 has a reading resolution of 1200 dpi in the conveying direction (y direction) of the recording medium 106 .

FIG. 2 is a diagram illustrating an example of the hardware configuration of the image forming system. The image forming system 20 includes an information processing device 30 and an image forming device 40 .

The information processing device 30 is a device that controls the image forming device 40 and includes, for example, a smart phone, a tablet, a PC, and the like. Information processing apparatus 30 includes CPU 201 , RAM 202 , storage unit 203 , ROM 204 and I/F 205 .

The CPU 201 is a microprocessor that controls each part of the information processing device 30, and performs various processes by executing programs and data in the RAM 202, the storage part 203, and the ROM 204. FIG. Although the CPU 201 performs all image processing, the CPU 211 of the image forming apparatus 40 may perform all or part of the image processing performed by the CPU 201 .

The RAM 202 is a readable/writable random access memory and temporarily stores various data used by the information processing device 30 . The RAM 202 stores various work areas for storing data necessary for processing and various data whose values are changed during processing.

The storage unit 203 is a device that stores various data and programs for the information processing device 30, and includes, for example, non-volatile storage including removable media such as a hard disk (HDD), SD card, and CF card.

The ROM 204 is a read-only non-volatile memory and stores a boot program and the like executed by the CPU 201 . When the CPU 201 executes the boot program, the operating system to be booted from the storage unit 203 and various control programs are loaded into the RAM 202 . The CPU 201 executes programs in the RAM 202 .

The I/F 205 is an interface that controls display on a display (not shown) such as a liquid crystal monitor provided in the information processing apparatus 30 . The I/F 205 also controls HIDs (Human Interface Devices) such as a keyboard and a mouse provided in the information processing apparatus 30 . Furthermore, the I/F 205 controls transmission and reception of data between the information processing device 30 and the image forming device 40 . Connection methods for data transmission/reception include, for example, USB and wired or wireless LAN.

The image forming device 40 is a device that forms recording data on the recording medium 106, and includes, for example, an inkjet printer. Image forming apparatus 40 includes CPU 211 , RAM 212 , ROM 213 , control section 214 and I/F 215 .

The CPU 211 is a microprocessor that controls each part of the image forming apparatus 40, and performs various processes by executing programs and data in the RAM 212 and ROM 213. FIG.

A RAM 212 is a readable/writable random access memory, and temporarily stores various data used by the image forming apparatus 40 . The RAM 212 stores various work areas for storing data necessary for processing and various data whose values are changed during processing.

The ROM 213 is a read-only non-volatile memory and stores a boot program and the like executed by the CPU 211 . When the CPU 211 executes the boot program, the operating system to be booted from the ROM 213 and various control programs are loaded into the RAM 212 . The CPU 211 executes programs in the RAM 212 .

A control unit 214 is a device that controls the print head 100 and the in-line sensor 107 shown in FIG. The control unit 214 controls the ink ejection operation of each nozzle of the nozzle arrays 101 to 104 of the print head 100 based on, for example, a binary quantized halftone image stored in the RAM 212 . Also, the control unit 214 controls each optical reading element of the in-line sensor 107 .

The I/F 215 is an interface that controls transmission and reception of data between the information processing device 30 and the image forming device 40 . Connection methods for data transmission/reception include, for example, USB and wired or wireless LAN. The I/F 215 corresponds to receiving means for receiving image data.

FIG. 3 is a diagram illustrating an example of functions of the information processing apparatus. The information processing device 30 includes a color conversion section 301, a color separation section 302, a color shading section 303, head shading sections 305-308, and quantization sections 313-316.

The color conversion unit 301 converts an image expressed in an RGB color space (hereinafter referred to as an RGB image) as recording data into the color reproduction range of the image forming apparatus 40 using a three-dimensional lookup table (hereinafter referred to as a 3D-LUT). Convert to the corresponding R'G'B' image. The color conversion section 301 outputs the R'G'B' image to the color separation section 302 . The resolution of the RGB image and the R'G'B' image is assumed to be 1200 dpi, which is the same as the recording resolution of the recording head 100 shown in FIG. The bit depth of each color component of the above image is all 16 bits, except for the halftone images (images expressed in intermediate tones of light and shade formed by halftone dots) output by the quantization units 313 to 316. .

The color separation unit 302 converts the R'G'B' image into a color image (hereinafter referred to as a CMYK image) corresponding to the primary colors used by the image forming apparatus 40 using a 3D-LUT. The color separation section 302 outputs the CMYK image to the color shading section 303 . When the image forming apparatus 40 uses CMYK color materials (inks), the color separation unit 302 converts the R'G'B' image into a CMYK image including four CMYK channels.

The color shading unit 303 uses the CMYK image as an input value, refers to a four-dimensional lookup table (hereinafter referred to as a 4D-LUT 304) for each region of the CMYK image, and adjusts the multidimensional colors on the CMYK image to a predetermined color. , to correct multinary color tone values. Color shading section 303 then outputs the C'M'Y'K' image after correcting the CMYK image to head shading sections 305-308. Processing by the color shading unit 303 and creation of the 4D-LUT 304 are performed by a known method (Patent Document 2 and Japanese Patent No. 5762497). A method for creating the 4D-LUT 304 will be described with reference to FIG. 4A.

The head shading units 305-308 refer to the 1D-LUTs 309-312 with the gradation value (color material amount) of each primary color in the C'M'Y'K' image as an input value, and The gradation value is corrected for each area of the CMYK image. Then, the head shading units 305-308 output the C''M''Y''K'' images corrected for the gradation value (color material amount) for each primary color to the quantization units 313-316. The method described in Patent Document 1 is used for the processing by the head shading units 305-308 and the creation of the 1D-LUTs 309-312.

The quantization units 313 to 316 apply quantization processing by the dither method to the C''M''Y''K'' image to obtain binary values (printing of color material dots with "1"). , non-recording is represented by "0") to generate a halftone image (C'''M'''Y'''K''' image).

FIG. 4A shows an example of test images used to create the 4D-LUT 304. FIG. A total of 625 (=5.times.5.times.5.times.5) multinary color patches are formed on the paper 401 by changing the gradation value (amount of color material) of each of CMYK in five stages. The test image is an image (scanned image) obtained by scanning the paper 401 with the inline sensor 107 by the image forming apparatus 40 . A multi-color patch is represented as a belt-like portion with different shades of color. In-line sensor 107 obtains RGB values for each patch from the test image at the intervals of arrow 402 . The in-line sensor 107 creates the 4D-LUT 304 by obtaining information representing the relationship between the CMYK gradation values (color material amounts) and the RGB values obtained for each patch at the intervals of the arrow 402 . The color shading unit 303 applies the 4D-LUT 304 to a predetermined area of each patch of the CMYK image (the area where the RGB values are read at the intervals of the arrow 402), thereby improving color unevenness of multi-order colors.

FIG. 4B shows an example of a test image used to create the 1D-LUT 309 in cyan. Five multi-color patches are formed on the paper 401 with the gradation value (amount of color material) of cyan (C) changed in five steps. The in-line sensor 107 acquires RGB values for each patch from the test image at intervals of arrows 402 . As a result, the in-line sensor 107 obtains the correlation between the C gradation value and the RGB values of the test image, and uses it to correct the C gradation value (color material amount). - LUT 309 can be created.

FIG. 4C shows an example of a test image used to create the 1D-LUT 309 in blue. Five blue patches with cyan (C) and magenta (M) gradation values (color material amounts) changed in five steps are formed on the paper 401 . In-line sensor 107 obtains RGB values for each patch from the test image at the intervals of arrow 402 . As a result, the in-line sensor 107 obtains the correlation between the C and M tone values and the RGB values of the test image, and uses it to correct the C and M tone values. A LUT 309 can be created.

FIG. 5A is a diagram for explaining a method of obtaining primary color correction values using a 1D-LUT. In FIG. 5A, the horizontal axis indicates the cyan (C) gradation value, and the vertical axis indicates the R (=complementary color of cyan (C)) value among the RGB values acquired from the test image by the inline sensor 107 . Paper white refers to a state where cyan (C) is not recorded in the area of the paper 401 (halftone dot area ratio of 0%). Solid refers to a state in which cyan (C) is printed in the area of the paper 401 (halftone dot area ratio of 100%).

The head shading unit 305 uses the 1D-LUT 309 to correct the input value (C′) of C, from the intersection of the upward extension of the input value (C′) and the straight line 501, the input value ( A target value (R (=complementary color of cyan (C)) value) corresponding to C') is obtained. The head shading unit 305 calculates a correction value for C (C'' ). It is assumed that the in-line sensor 107 has acquired the curve 502 using the test image in which cyan (C) in FIG. 4B is printed. The head shading unit 305 can improve the color unevenness of cyan (C) by obtaining a correction value for the input value of cyan (C) for each predetermined region of the patch. An example of obtaining the correction value for the input value of cyan (C) has been described, but the correction values for the input values of other ink colors (MYK) are obtained by the same method as for cyan (C).

FIG. 5B is a diagram for explaining a method of obtaining correction values for primary colors forming multinary colors using a 1D-LUT. In FIG. 5B, the horizontal axis indicates the gradation value of cyan (C) or magenta (M), and the vertical axis indicates the B value among the RGB values acquired by the inline sensor 107 from the test image. Paper white refers to a state in which C and M are not recorded in the area of the paper 401 (halftone dot area ratio of 0%). Solid refers to the state where C and M are printed in the area of the paper 401 (halftone dot area ratio 100%).

Japanese Patent No. 4661376 discloses a technique for improving multi-color unevenness using head shading units 305 to 308, as described below. For example, when the inline sensor 107 improves the color unevenness of blue (B), from the uniform patch of B (FIG. 4C), the gradation values of C and M and the B value among the RGB values obtained from the test image Determine the correlation (curve 504). A common 1D-LUT 309 is used for C and M. In order to correct the input value of C (C'), the head shading unit 305 calculates a target value corresponding to the input value (C') from the intersection of the upward extension line of the input value (C') and the straight line 503. find the value. The head shading unit 305 calculates a correction value (C ''). Note that the head shading unit 305 has obtained the curve 504 using the test image in FIG. 4C.

Next, in order to correct the input value of M (M'), the head shading unit 305 corrects the input value (M') from the intersection of the upward extension line of the input value (M') and the straight line 503. Find the corresponding target value. The head shading unit 305 calculates the correction value (M'') from the intersection of the right extension line from the target value and the curve 504 representing the correlation between the gradation value of M and the B value measured from the test image. demand. Note that the head shading unit 305 has obtained the curve 504 using the test image in FIG. 4C. Each of the head shading units 305 and 306 obtains a correction value for the input value (C') and the input value (M') for each predetermined region of each patch, thereby improving color unevenness of blue (B).

In this manner, the head shading units 305 to 308 correct the input values of the primary colors that make up the multinary color using the 1D-LUT 309, thereby improving the color unevenness of the multinary color. Therefore, the CPU 201 of the information processing device 30 can omit the color shading unit 303 when using the method of correcting the input value of the primary color as described above.

FIG. 6A is a diagram showing the positional relationship between the test image and the nozzle rows when forming the test image. A nozzle row 601 is a cyan (C) nozzle row, and a nozzle row 602 is a magenta (M) nozzle row. A blue (B) patch 604 and a patch 605 obtained by mixing cyan (C) and magenta (M) are printed on paper 603 .

Patent Document 2 describes that when obtaining an area with blue (B) color unevenness from patches 604 to 605, the same multi-color (blue (B)) ruler as patches 605 to 605 is used. . The multi-color rulers 607-609 are represented in the same color (blue) as the patches 604-605, and are displayed above the patches 604-605 at positions spaced apart from the left ends of the nozzle rows 601-602. be done. Rulers 607 to 609 are used to detect misalignment in the x direction between nozzle row 601 and nozzle row 602 .

The rulers 607 to 609 form one line when there is no misalignment between colors (the left ends of the nozzle row 601 and the nozzle row 602 match). Therefore, the CPU 201 can refer to the multinary color rulers 607 to 609 to determine a region 610 for acquiring color unevenness and a nozzle group 606 for correcting an input value in the patch 604, for example.

FIG. 6B is a diagram showing the positional relationship between the test image and the nozzle rows when forming the test image. Here, unlike FIG. 6A, FIG. 6B shows that the nozzle row 602 is shifted from the nozzle row 601 by two nozzles in the x direction. The inter-color registration deviation 611 is caused by changes in the nozzle array over time, meandering when the paper 603 is conveyed in the y direction, and the like. In this way, the blue (B) ruler 607 in FIG. 6A is separated into a cyan ruler 612 and a magenta ruler 615 when an inter-color misregistration 611 occurs. Ruler 608 in FIG. 6A is separated into ruler 613 representing cyan and ruler 616 representing magenta. Ruler 609 in FIG. 6A is separated into ruler 614 indicating cyan and ruler 617 indicating magenta. In Japanese Patent Application Laid-Open No. 2004-200001, since multi-color rulers disappear when misregistration occurs between colors, a primary color nozzle group for correcting an area with color unevenness and an input value is determined from a patch on a test image. Can not.

Therefore, the first embodiment provides a method of determining a primary color nozzle group for correcting an area of color unevenness and an input value from a patch on a test image even when color misregistration occurs. FIG. 6C shows the positional relationship between a test image used when acquiring a color unevenness area from multinary color patches and the nozzle arrays used when forming multinary color patches. FIG. 6C is a diagram showing the positional relationship between the test image and the nozzle rows when forming the test image. FIG. 6C, unlike FIGS. 6A-6B, illustrates the use of primary color rulers rather than multi-color rulers when multi-color patches are being recorded. Multi-color (blue (B)) patches 604 and 605 in FIG. 6C are formed by mixing cyan (C) and magenta (M). Therefore, rulers 618, 619 and 620 for cyan, and rulers 621, 622 and 623 for magenta are used as the primary color rulers. Note that FIG. 6C shows a state where there is no misalignment between colors, so the cyan (C) rulers 618 to 620 and the magenta (M) rulers 621 to 623 are aligned in the y direction. .

FIG. 6D is a diagram showing the positional relationship between the test image and the nozzle rows when forming the test image. FIG. 6D shows that, unlike FIG. 6C, nozzle row 602 is offset from nozzle row 601 by two nozzles in the x-direction. A right arrow indicates an inter-color misregistration 611 . The CPU 201 detects the primary color rulers 618 to 623 and executes processing shown in FIGS. can decide. Further, the CPU 201 can determine the nozzle group 625, nozzle group 626, nozzle group 628, and nozzle group 629 for correcting the input value.

FIG. 7A shows a flowchart for explaining the flow of detecting an area of color unevenness. The flowchart of FIG. 7A will now be described with reference to FIG. 6D.

In S701, the in-line sensor 107 scans the recording medium (paper 603) on which recording data is recorded to generate a test image (scanned image).

In step S<b>702 , the CPU 201 sets the uppermost patch among the plurality of patches on the test image as a target patch (hereinafter referred to as target patch). The CPU 201 compares the positional relationship between the patches 604 and 605 on the test image, and determines the patch 604 located at the uppermost position on the test image as the patch of interest.

In step S<b>703 , the CPU 201 selects a primary color ruler to refer to, based on the information on the primary colors forming the patch of interest. For example, the CPU 201 determines the color of the patch of interest based on the pixel values of the patch of interest. The CPU 201 selects cyan rulers 618 to 620 and magenta rulers 621 to 623 because the patch 604 is formed with blue (B), which is a mixture of cyan (C) and magenta (M). Here, FIG. 8A is a diagram showing an example of a test image when a primary color ruler is arranged above the patch. When the patch of interest is the blue (B) patch 803B in FIG. 8A, the CPU 201 selects the cyan (C) ruler 802C and the magenta (M) ruler 802M. If the patch of interest is a process gray (gray mixed with CMYK) patch 803P, the CPU 201 selects rulers 802C, 802M, 802Y, and 802K.

Here, FIG. 7B is a flowchart showing the details of the processing of S703 in FIG. 7A. In S710, the CPU 201 acquires color information (primary color information) representing the primary colors forming the patch of interest based on the pixel values of the patch of interest. The primary color information refers to pixel values (RGB values) obtained by image analysis of the patch of interest.

In S711, the CPU 201 determines whether or not the target patch (patch 604) includes cyan (C) based on the primary color information (pixel value (RGB value)). If the CPU 201 determines that the patch of interest (patch 604) contains cyan (C) (Yes in S711), the process proceeds to S712. When the CPU 201 determines that the patch of interest (patch 604) does not include cyan (C) (No in S711), the process proceeds to S713.

In S712, the CPU 201 adds a cyan (C) ruler as a primary color ruler to be referenced.

In step S713, the CPU 201 converts the patch of interest (patch 604) into magenta (M ) is included. If the CPU 201 determines that the patch of interest (patch 604) contains magenta (M) (Yes in S713), the process proceeds to S712. When the CPU 201 determines that the patch of interest (patch 604) does not include magenta (M) (No in S713), the process proceeds to S714.

In S714, the CPU 201 adds a magenta (M) ruler as a primary color ruler to be referenced.

In S715, the CPU 201 determines whether the patch of interest (patch 604) includes yellow (Y) based on the information on cyan (C) and magenta (M). If the CPU 201 determines that the patch of interest (patch 604) contains yellow (Y) (Yes in S715), the process proceeds to S716. If the CPU 201 determines that the patch of interest (patch 604) does not include yellow (Y) (No in S715), the process proceeds to S717.

In S716, the CPU 201 adds a yellow (Y) ruler as a primary color ruler to be referenced.

In S717, the CPU 201 determines whether the patch of interest (patch 604) includes black (K) based on the information on cyan (C) and magenta (M). If the CPU 201 determines that the patch of interest (patch 604) includes black (K) (Yes in S717), the process proceeds to S718. If the CPU 201 determines that the patch of interest (patch 604) does not include black (K) (No in S717), the process ends.

In S718, the CPU 201 adds a black (K) ruler as a primary color ruler to be referred to, and ends the process.

Returning to the description of FIG. 7A, in S704, the CPU 201 detects the position of the ruler of the primary color selected in S703 based on the type of primary color forming the patch of interest. Specifically, the CPU 201 obtains the coordinates of the C and M rulers 618 to 623 on the scanned image in FIG. 6D.

In S705, the CPU 201 detects an area with color unevenness from the patch of interest (patch 604) based on the detected positions of the primary color rulers 618 to 623, and selects the nozzle group used to form that area. decide. It is assumed that areas 624 and 627 have color unevenness. It is assumed that the area of the patch 605 where there is color unevenness is the area 630 .

Here, FIG. 7C is a flowchart showing the details of the processing of S705 in FIG. 7A. In S719, the CPU 201 determines a color of interest (hereinafter referred to as a color of interest) from among the primary color rulers 618 to 623 to be referred to. For example, in FIG. 6D, the CPU 201 determines magenta (M) among cyan (C) and magenta (M) as the color of interest. At this time, since the left ends of the patches 604 and 605 are aligned, for example, the CPU 201 detects the ruler 618 located on the extension of the left ends in the y direction. Next, the CPU 201 determines the primary color of the ruler 621 shifted from the ruler 618 in the x direction as the color of interest. Note that the CPU 201 may determine the first determined primary color of the ruler 618 as the target color.

In S720, the CPU 201 sets the leftmost ruler 621 on the test image among the magenta (M) rulers 621 to 623 as the ruler of interest.

In S<b>721 , the CPU 201 obtains the difference in x-direction coordinates between the position (coordinates) of the ruler of interest (ruler 621 ) and the position (coordinates) of the ruler 622 . Here, it is assumed that the widths of the regions 624 and 627 in the y direction are set in advance as the difference in coordinates in the y direction. Accordingly, the CPU 201 can detect the area 624 from the patch 604 based on the difference in the coordinates in the x direction and the difference in the coordinates in the y direction. Similarly, the CPU 201 obtains the difference in x-direction coordinates between the position (coordinates) of the ruler 622 of interest and the position (coordinates) of the ruler 623 . Accordingly, the CPU 201 can detect the area 627 from the patch 604 based on the difference in the coordinates in the x direction and the difference in the coordinates in the y direction. On the other hand, a method of detecting an area 630 (an area with uneven color) when the patch of interest is 605 and the ruler of interest is 621 will be described. Similar to the above, it is assumed that the y-direction coordinate difference of the area 630 is set in advance. The CPU 201 can detect the area 630 from the patch 605 based on the x-direction coordinate difference and the y-direction coordinate difference between the positions (coordinates) of the ruler 621 and the ruler 622 .

At S<b>722 , the CPU 201 integrates the pixel values of the area 624 on the patch 604 to obtain the RGB values of the area 624 .

In S<b>723 , the CPU 201 determines the positions (coordinates) of some nozzles (hereinafter referred to as nozzle groups) of the color of interest (magenta (M)) used to form the regions 624 and 627 . When the CPU 201 forms the regions 624 and 627 based on the relationship between the positions (coordinates) of the rulers 621 to 623 of the color of interest (M) determined in S719 and the position (coordinates) of the nozzle row 602 of M, Determine the nozzle group 626 and the nozzle group 629 used for . For example, the CPU 201 can determine the position (coordinates) of the nozzle group 626 in the nozzle row 602 corresponding to the x-direction coordinate difference based on the difference from the left end to the right end of the region 624 (x-direction coordinate difference). .

In S724, the CPU 201 determines the positions (hereinafter referred to as nozzle groups) of some nozzles (hereinafter referred to as nozzle groups) of the color (cyan (C)) that is not the color of interest (magenta (M)) used to form the regions 624 and 627. coordinates). Here, the positions (coordinates) of the rulers 621 to 623 for the color of interest (M) and the positions (coordinates) of the rulers 618 to 620 for the color (C) that is not the color of interest are known. Further, the positions (coordinates) of the nozzles in the C nozzle row 601 corresponding to the positions (coordinates) of the C rulers 618 to 620 are known. Therefore, the CPU 201, based on the difference from the left end to the right end of the M nozzle group 626 (difference in coordinates in the x direction) and the difference in the x direction (deviation 611) between the nozzle row 601 and the nozzle row 602, The position (coordinates) of the C nozzle group 625 can be calculated by interpolation. Similarly, the CPU 201 calculates the difference based on the difference from the left end to the right end of the M nozzle group 629 (difference in coordinates in the x direction) and the difference in the x direction (deviation 611) between the nozzle row 601 and the nozzle row 602. , C can be calculated by interpolation.

In S<b>725 , the CPU 201 increments (switches) the ruler of interest to the ruler 622 . In S726, the CPU 201 terminates the process based on whether or not the currently selected ruler of interest is the rightmost ruler in the x direction. If the CPU 201 determines that the currently selected ruler of interest is the ruler located on the rightmost side in the x direction (Yes in S726), the CPU 201 ends the process. If the CPU 201 determines that the currently selected ruler of interest is not the rightmost ruler in the x direction (No in S726), the process returns to S721.

Returning to the description of FIG. 7A, in S706, the CPU 201 stores the data acquired in S705 (area 624, area 627, nozzle group 625, nozzle group 626, nozzle group 628, nozzle group 629) in the storage unit 203. In S<b>707 , the CPU 201 increments (switches) the target patch to the patch 605 .

In S<b>708 , the CPU 201 determines whether or not the currently selected patch of interest is the lowest patch of interest on the test image. If the CPU 201 determines that the currently selected patch of interest is the lowest patch of interest on the test image (Yes in S708), the process proceeds to S709. If the CPU 201 determines that the patch of interest that is being selected is not the patch of interest located on the lowest side on the test image (No in S708), the process returns to S703.

In S709, a table (4D-LUT or 1D-LUT) for correcting color unevenness of multi-color patches is generated based on data acquired from all patches on the test image.

As described above, according to the first embodiment, even if misregistration occurs between colors, a primary color that corrects an area with color unevenness from a patch of multinary colors and a multinary color in the area with color unevenness of nozzles (nozzle group) can be determined.

(Modification 1)
The placement of patches and rulers on the test image is not limited to FIGS. 6C and 8A. However, even if misalignment between colors occurs due to meandering of paper transport, etc., the following conditions are required in order to normally perform the processing of FIG. 7A. Specifically, the ruler selected for each patch of interest must be positioned at least either above or below the patch in the y direction within a predetermined distance from the patch. The predetermined distance is the maximum distance that allows the CPU 201 to normally detect the ruler of the primary color from the patch of interest even if misalignment (difference) in color registration occurs due to meandering of paper transport. refers to distance. Further, the predetermined distance is such that the difference between the position of the ruler of the primary color and the position of the ruler of the other primary color is less than the threshold value, and the position of the ruler of the primary color and the ruler of the other primary color. position is the farthest distance from the multinary color patch. Note that the threshold value (permissible value for misalignment between colors) may be an arbitrary value representing the difference in x-direction coordinates within a range in which the CPU 201 can normally detect the primary color ruler.

FIG. 9 is a diagram for explaining misalignment between colors. A patch 903B, a patch 904B, a patch 905B, a patch 907B, a patch 908B, a patch 909B, a ruler 902C, a ruler 906C, a ruler 902M and a ruler 906M are formed on the paper 901. FIG. Hereinafter, the paper 901 means a test image (scanned image) scanned by the image forming apparatus 40 . Also, the trajectory of a cyan (C) ruler 902C (illustrated by a dotted line) and the trajectory of a magenta (M) ruler 902M (illustrated by a broken line) are shown on the paper 901 . The distance between the trajectory of the ruler 902C and the trajectory of the ruler 902M is numerically indicated on each patch as the color registration deviation. For example, the misregistration between colors on the patch 903B is 5px. At a position above patch 903B, there is a deviation of 5px between the trajectory of ruler 902C and the trajectory of ruler 902M, so 5px is used as a deviation reference. The amount of change in deviation relative to the reference deviation when the paper 901 is conveyed in the y direction will be described below.

Here, the misalignment between colors is 0px (=|5px-5px|) for patch 903B, 2px (=|3px-5px|) for patch 904B, and 3px (=|2px-5px|) for patch 905B. . The misalignment between colors is 5px (=|0px-5px|) for 907B, 7px (=|-2px-5px|) for 908B, and 8px (=|-3px-5px|) for 909B. For this reason, the amount of change in color misregistration increases as the patch is positioned lower in the y direction from the ruler 902M.

In other words, when the amount of change in color misregistration is large, the CPU 201 can determine the nozzle groups 625 and 626 used to form the area 624 and the area 624 in FIG. 6D based on the primary color ruler. color unevenness cannot be improved. Therefore, the CPU 201 needs to determine the ruler to be selected for each patch of interest by setting a threshold value for the amount of change in color misregistration. For example, when the threshold value is set to 3px in FIG. 9, the CPU 201 determines that the patches capable of detecting the ruler 902C and the ruler 902M are the patch 903B, the patch 904B, and the patch 905B.

Also, the amount of change in color misregistration between the rulers 906C and 906M will be described using 0px as a reference for the color misregistration between the rulers 906C and 906M. The misregistration between colors is 5px (=|5px-0px|) for patch 903B, 3px (=|3px-0px|) for patch 904B, and 2px (=|2px-0px|) for patch 905B. The misalignment between colors is 0px (=|0px-0px|) for 907B, 2px (=|-2px-0px|) for 908B, and 3px (=|-3px-0px|) for 909B. Therefore, when the threshold is set to 3px, the CPU 201 determines that the patches capable of detecting the ruler 906M and the ruler 906C are the patch 904B, the patch 905B, the patch 907B, the patch 908B, and the patch 909B. The CPU 201 can detect the ruler 902C, the ruler 902M, the ruler 906C, and the ruler 906M when either the patch 904B or the patch 905B is set as the patch of interest. When the CPU 201 detects a plurality of primary color rulers from the patch of interest (patch 904B and patch 905B), the CPU 201 calculates the position of the ruler obtained by averaging the positions of the plurality of rulers obtained from the respective patches of interest and determines the position of the ruler in the area of color unevenness or the like. May be used for decision making.

Note that the transport distance of the paper in the y direction corresponding to the threshold value of the misregistration between colors is obtained based on the amplitude and period of the misregistration between colors. For example, as shown in FIG. 9, the CPU 201 can reduce the misregistration between colors to less than the threshold within the paper transport distance from the patch 903B to the patch 905B in the y direction with the position of the ruler 902M as a reference. In this manner, the CPU 201 may determine the ruler to be detected from each patch of interest by using the paper transport distance in the y direction from the ruler of interest as a constraint condition. Next, an example of a test image in which the ruler selected for each patch of interest is located above or below the patch of interest and within a predetermined distance from the patch of interest will be described.

FIG. 8B is a diagram showing an example of a test image when rulers are arranged above and below the patch. In the test image of FIG. 8B, a cyan (C) ruler 802C and a magenta (M) ruler 802M are formed above and below a blue (B) patch 804B. By arranging the rulers above and below the patch in this way, the influence of misalignment between colors can be reduced.

FIG. 8C is a diagram showing an example of a test image composed of multiple pages. The test image consists of multiple pages (eg, 3 pages). The CPU 201 can reduce the influence of misregistration between colors by detecting the ruler on the same page as the patch of interest. The CPU 201 detects the cyan ruler 805C from the cyan patch 806C and detects the cyan ruler 807C from the cyan patch 808C in the uppermost test image. The CPU 201 detects a cyan ruler 809C and a magenta ruler 809M from the blue patch 810B in the second test image from the top, and detects a cyan ruler 811C and a magenta ruler 811M from the blue patch 812B. To detect.

The CPU 201 detects a cyan ruler 813C, a yellow ruler 813Y, and a black ruler 813K from a green patch 814G in which cyan, yellow, and black are mixed in the third test image from the top. The CPU 201 detects a cyan ruler 815C, a yellow ruler 815Y, and a black ruler 815K from a green patch 816G obtained by mixing cyan, yellow, and black. Here, the order of the primary colors arranged on the upper side of the patch 814G (order of K, Y, C) and the order of the primary colors arranged on the lower side of the patch 814G (order of C, Y, K) are It becomes asymmetric with the patch 814G as the axis. In this way, the CPU 201 can reduce the influence of misregistration between colors by detecting the ruler on the same page as the patch of interest. In addition, the area of the test image can be saved by not arranging a ruler of a color not detected from the patch (for example, when there is a black ruler for a blue patch) on the same page as the patch of interest.

FIG. 8D is a diagram showing an example of a test image in which multiple patches and rulers are arranged on the same page. The test image is a scan of a roll of paper with a length of several meters or more in the paper transport direction. For each patch of interest, a ruler located above or below the patch of interest and within a predetermined distance from the patch of interest is detected. For example, the CPU 201 detects the cyan ruler 817C from the cyan patch 818C. CPU 201 detects cyan ruler 819C and magenta ruler 819M from blue patch 820B. The CPU 201 detects a cyan ruler 821C, a yellow ruler 821Y, and a black ruler 821K from a green patch 822G obtained by mixing cyan, yellow, and black. On the other hand, although the patch 822G contains cyan, the rulers 817C and 819C of cyan from the patch 822G are not within the predetermined distance from the patch 822G, so the CPU 201 does not detect the rulers 817C and 819C.

As described above, by detecting the ruler within a predetermined distance from the patch of interest, even if misalignment of color registration occurs due to meandering of the paper conveyance, the area of uneven color and the area of uneven color can be detected from the patch of interest. A primary color nozzle (nozzle group) for correcting the next color can be determined.

(Modification 2)
Even if misalignment between colors occurs due to meandering of paper conveyance, the CPU 201 performs primary correction for correcting uneven color areas and multinary colors in the uneven color areas as long as the position of the ruler is close to the patch. Color nozzles (nozzle groups) can be determined. Therefore, in Modification 2, a test image will be described in which a primary color ruler, which has a large effect on image quality, is placed near the patch of interest.

FIG. 10A shows an example of a test image with primary color rulers placed above and below the patch. A patch 1003 of process gray mixed with CMYK is formed on the paper 1001 . When magenta has a greater effect on image quality (color reproducibility when reproducing patch colors) than cyan, a ruler 1002M for magenta is placed near the patch 1003, and a ruler 1002M for cyan is placed farther from the patch 1003. 1002C is placed. If black has a greater effect on image quality (color reproducibility when patch colors are reproduced) than yellow, a black ruler 1002K is placed near the patch 1003, and a yellow ruler 1002K is placed farther from the patch 1003. , the ruler 1002Y is arranged.

FIG. 10B shows an example of a test image with primary color rulers placed above and below the patch. It is assumed that black, magenta, cyan, and yellow have a greater effect on image quality (color reproducibility when reproducing patch colors) in that order. Patches 1004K, 1004M, 1004C, and 1004Y are arranged in order from the patch 1005 on the upper side of the patch 1005 of process gray mixed with CMYK. Also, below the patch 1005, the patch 1006K, the patch 1006M, the patch 1006C, and the patch 1006Y are arranged in order from the patch 1005 in order of position.

FIG. 10C shows an example of a test image with primary color rulers placed above and below the patch. Patches 1007K, 1007M, 1007C, and 1007Y are arranged in order from the patch 1008 on the upper side of the patch 1008 of process gray mixed with CMYK. Also, on the lower side of the patch 1008, the patch 1009Y, the patch 1009C, the patch 1009M, and the patch 1009K are arranged in the order of position closer to the patch 1008. FIG.

The arrangement of the rulers for the primary colors shown in FIG. 10C makes it possible to uniformly correct the gradation values of the primary colors, and thus has the effect of uniformly improving the color unevenness of the multi-primary colors. Furthermore, by arranging the primary color rulers in the order of position closer to the patch 1008 based on the priority of the ruler colors, the effect of improving color unevenness can be controlled. In addition, the primary color that greatly affects the image quality (color reproducibility when reproducing the color of the patch) changes depending on the color of the patch. Therefore, by changing the arrangement order of the primary color ruler with respect to the patch according to the color of the patch, color unevenness in the patch area can be improved.

FIG. 10D shows an example of a test image with primary color rulers placed above and below multiple patches. The patch 1011 is assumed to be a color with a strong blue color (the pixel value of B is high), which is a mixture of CMYK colors. In that case, since cyan and magenta constituting blue have a great influence on the image quality, the cyan and magenta rulers should be arranged near the patch 1011 . That is, the cyan ruler 1010C is placed above the patch 1011, and the magenta ruler 1010M is placed below the patch 1011. FIG. Also, the yellow ruler 1010Y is arranged above the ruler 1010C, and the black ruler 1010K is arranged below the ruler 1010M.

The patch 1013 is assumed to be a mixed color of CMYK, in which yellow (Y) and black (K) are strong (the pixel values of R and G are high). In that case, yellow and black have a large effect on the image quality, so the yellow and black rulers should be arranged near the patch 1013 . That is, the yellow ruler 1012Y is arranged above the patch 1013, and the black ruler 1012K is arranged below the patch 1013. FIG. Also, the cyan ruler 1012C is arranged above the ruler 1012K, and the magenta ruler 1012M is arranged below the ruler 1012K.

Note that in FIG. 10D , the CPU 201 detects separate primary color rulers from the patches 1011 and 1013 , respectively, but may detect a common primary color ruler from the patches 1011 and 1013 .

FIG. 10E shows an example of a test image with primary color rulers placed above and below the patch. The CPU 201 detects rulers 1017M and 1018K of common primary colors from the patches 1016 and 1020. FIG. The patch 1016 is assumed to have a strong blue (high B pixel value) color in which CMYK is mixed, similarly to the patch 1011 in FIG. 10D. Here, a cyan ruler 1015C and a magenta ruler 1017M are placed directly above and below patch 1016, respectively. Ruler 1014Y and ruler 1018K are arranged directly above ruler 1015C and directly below ruler 1017M, respectively. CPU 201 detects ruler 1014 Y, ruler 1015 C, ruler 1017 M, and ruler 1018 K from patch 1016 .

On the other hand, the patch 1020 is assumed to have a strong green (high G pixel value) color obtained by mixing CMYK. In that case, yellow and cyan, which form green, have a large effect on the image quality, so rulers for yellow and cyan should be arranged near the patch 1020 . A yellow ruler 1019Y and a cyan ruler 1021C are arranged directly above and below the patch 1020, respectively. A magenta ruler 1017M and a black ruler 1018K are positioned away from the patch 1020 . CPU 201 detects ruler 1017M, ruler 1018K, ruler 1019Y, and ruler 1018C from patch 1020 . CPU 201 detects ruler 1017M and ruler 1018K from both patch 1016 and patch 1020. FIG.

As described above, by changing the order of the rulers of the primary colors to be arranged at positions close to the patch according to the color of the patch, it is possible to obtain the effect of improving color unevenness.

(Modification 3)
When the ruler of the primary color is detected by the in-line sensor 107, the higher the contrast of the ruler of the primary color, the higher the SN ratio (Signal to Noise ratio), and the longer the ruler, the higher the SN ratio. The SNR is used as an evaluation index of image quality in test images. The higher the SN ratio, the less the image is affected by noise, and the higher the image quality. On the other hand, the lower the SN ratio, the more susceptible the image is to noise, resulting in lower image quality. Here, FIG. 11 is a diagram showing an example of a test image in which rulers are arranged in consideration of the SN ratio of primary colors.

FIG. 11(a) shows a test image in which rulers are placed in consideration of the SN ratio. The arrangement of the primary color rulers shown in the test image of FIG. 11A can reduce variations in image quality due to the SN ratio of the primary colors. A patch 1103 of process gray mixed with CMYK is formed on the paper 1101 . Assume that the signal-to-noise ratios of the primary colors increase in the order black, magenta, cyan, and yellow. In this case, the y-direction lengths of the rulers 1102C, 1102M, 1102Y, and 1102K are lengthened in order of decreasing SN ratio.

FIG. 11(b) shows a test image in which rulers are placed in consideration of the SN ratio. The effect of the SN ratio in detecting the ruler on the improvement of color unevenness (color reproducibility in reproducing the color of the patch) varies depending on the color of the patch. For example, compared to the dark blue patch 1105, the light blue patch 1107 has less effect on image quality even if the SN ratio is poor. Therefore, the length of ruler 1106C and ruler 1106M detected from light blue patch 1107 can be made shorter than the length of ruler 1104C and ruler 1104M detected from dark blue patch 1105. FIG. As a result, the length of the ruler formed in the test image in the y direction can be compressed, so that the area of the test image can be reduced.

FIG. 11(c) shows a test image in which the ruler is arranged considering the SN ratio of the primary colors. A blue patch 1111 in which cyan and magenta are equally mixed has less effect on image quality even if the cyan SN ratio is poor compared to a blue patch 1109 in which magenta is stronger than cyan (B pixel value is high). . Therefore, the length of the cyan ruler 1110C detected from the patch 1111 can be made shorter than the length of the cyan ruler 1108C detected from the patch 1109. FIG. As a result, the length of the ruler formed in the test image in the y direction can be compressed, so that the area of the test image can be reduced.

(Embodiment 2)
In the first embodiment, an M ruler 1203M is placed directly above the multicolor patch (illustrated in FIG. 12A) on the test image, and a C ruler 1202C is placed directly above the ruler 1203M. placed. In other words, in the first embodiment, rulers of primary colors different from each other are not arranged in a mixed manner either directly above the patch or directly above the patch. Here, the position closest to the patch in the y direction is directly above or below the patch as the "first stage", and the second closest position from the patch in the y direction is directly above or directly below the first stage as the "second stage". Define.

On the other hand, in the second embodiment, in the test image (illustrated in FIG. 12B) in which patches are formed, primary color rulers of different colors are mixedly arranged in the first stage immediately above the patches. FIG. 12 is a diagram showing an example of a test image according to the second embodiment;

FIG. 12A shows an example of a test image in which blue patches 1203 are formed on paper 1201 according to the first embodiment. Blue is a mixture of cyan and magenta. A cyan ruler 1202C is arranged on the first stage immediately above the patch 1203, and a magenta ruler 1202M is arranged on the second stage immediately above the first stage. Therefore, as the number of types of primary colors forming the patch color increases, the length of the primary color ruler arranged in the y direction from the patch increases, resulting in an increase in the area of the test image.

FIG. 12B shows an example of a test image in which blue patches 1205 are formed on paper 1201 according to the second embodiment. Blue is a mixture of cyan and magenta. A cyan ruler 1204</b>C and a magenta ruler 1204</b>M are mixedly arranged in the first stage just above the patch 1205 . In addition, the ruler 1204C and the ruler 1204M are arranged alternately in the x direction on the first stage just above the patch. The placement of the primary color ruler as shown in FIG. 12B reduces the accuracy of determining the positions (coordinates) of the primary color nozzles (nozzle group) that correct the multi-primary colors in the uneven color area. deteriorates. However, even if the number of primary colors that make up the patch color increases, the length of the primary color ruler arranged in the y direction from the patch does not become longer than in FIG. can be reduced.

(Modification 1)
Influence of the accuracy of determining the primary color nozzles (nozzle group) for correcting multi-color patches from areas with color unevenness in multi-color patches on improvement of color unevenness (color reproduction when patch colors are reproduced) degree) depends on the type of primary colors that make up the color of the patch. For example, a decrease in the accuracy of determining the nozzle group of the black nozzle row causes deterioration in image quality compared to other primary colors (CMY). Here, FIG. 12C shows an example of a test image in which process gray patches 1208 are formed on the paper 1201 . Process gray is a mixture of CMYK colors. Only the black ruler 1207K is placed on the first stage directly above the process gray patch 1208, and no other primary color (MYK) rulers are placed. A ruler 1206C, a ruler 1206M, and a ruler 1206Y are arranged on the second stage immediately above the first stage. Also, the ruler 1206C, the ruler 1206M, and the ruler 1206Y are alternately arranged in the x direction on the second stage. As a result, by arranging only the ruler for the primary color (for example, black) that causes deterioration in image quality due to a decrease in the determination accuracy of the nozzles (nozzle group), the color unevenness improvement effect can be maintained. Also, since the length of the primary color ruler in the y direction from the patch can be compressed, the area of the test image can be reduced.

In addition, the influence of the nozzle (nozzle group) determination accuracy on the improvement of color unevenness (color reproducibility when reproducing the color of a patch) varies depending on the color of the patch. Here, FIG. 12D shows an example of a test image in which dark blue patches 1210 and light blue patches 1212 are formed on paper 1201 . The accuracy of determining the nozzle group from the patch 1212 may be lower than the accuracy of determining the nozzle group from the patch 1210 because it has less impact on image quality. Therefore, ruler 1211C and ruler 1211M detected from patch 1212 are mixedly arranged in the first stage just above patch 1212 . On the other hand, rulers 1209C and 1209M detected from patch 1210 are arranged as follows. The ruler 1209M is arranged on the first stage directly above the patch 1210, and the ruler 1209C is arranged on the second stage directly above the first stage. That is, the ruler 1209M and the ruler 1209C are arranged in different stages (first stage or second stage). As a result, the length of the ruler of the primary color in the y direction from the patch can be shortened while maintaining the effect of improving color unevenness, so the area of the test image can be reduced.

FIG. 12E shows an example of a test image in which dark blue patches 1214 and light blue patches 1216 are formed on paper 1201 . The accuracy of nozzle group determination from a blue patch 1214 in which M is stronger than C (the pixel value of B is high) is higher than that from a blue patch 1216 in which C and M are mixed to the same extent. Since there is little effect on the image quality, it may be low. Therefore, in the first stage directly above the patch 1216, the ruler 1215C and the ruler 1215M are arranged at a ruler number ratio of 1:3. On the other hand, on the first stage directly above the patch 1214, the ruler 1213C and the ruler 1213M are arranged at a ruler number ratio of 1:1. In this way, when arranging rulers of different primary colors in the same row based on the characteristics of the color of the patch, by changing the ratio of the number of arranged rulers for each primary color, color unevenness can be reduced. The improvement effect can be maximized.

(Modification 2)
When the inline sensor 107 reads (scans) an image recorded on paper, the length of the scanned image (test image) read by the inline sensor 107 in the paper transport direction (y direction) changes depending on the paper transport speed. do. FIG. 13 is a diagram showing an example of a test image corresponding to the paper transport speed. FIG. 13A is a diagram showing an example of a test image obtained by scanning paper 1301 on which blue patches 1303 are formed. In-line sensor 107 reads paper 1301 on which patch 1303, cyan ruler 1302C, and magenta ruler 1302M are formed. At this time, if the transport speed for transporting the paper 1301 in the y direction is the "low speed mode", a scanned image (same as the paper 1301) shown in FIG. 13A is obtained. On the other hand, when the transport speed for transporting the paper 1301 in the y direction is the "high speed mode", a scanned image 1304 in FIG. 13B is obtained. FIG. 13B shows a scanned image 1304 obtained by scanning the paper 1301 by the inline sensor 107. FIG. The scanned image 1304 has a smaller size in the y direction than the scanned image (paper 1301) scanned in the low speed mode.

If the sampling period when the in-line sensor 107 scans the paper 1301 is constant regardless of the speed at which the paper 1301 is conveyed, the sampling points decrease as the speed at which the paper 1301 is conveyed increases. As a result, the patch 1306, ruler 1305C, and ruler 1305M in FIG. 13B are smaller in size in the y direction than the patch 1303, ruler 1302C, and ruler 1302M in FIG. 13A. As described in Modification 3 of the first embodiment, when the length of the primary color ruler is shortened, the SN ratio of the primary color ruler deteriorates. Therefore, when scanning the paper 1301 in the high-speed mode, the length of the ruler for the primary color should be increased, but the area of the test image increases by the length of the ruler.

Here, FIG. 13C is a diagram showing an example of image data before scanning the paper 1301 on which the blue patch 1308 is formed. On the first stage directly above the paper 1301, cyan rulers 1307C and magenta rulers 1307M are alternately arranged in the x direction. In FIG. 13C, the lengths of the patch 1308, the ruler 1307C, and the ruler 1307M are increased, and the rulers of different colors are mixedly arranged on the first stage just above the patch 1308. FIG.

FIG. 13(d) shows a scanned image 1304 obtained by scanning the paper 1301 on which the image data shown in FIG. 13(c) has been printed in high-speed mode. The lengths of patch 1310, ruler 1309C, and ruler 1309M on scanned image 1304 are approximately the same as the lengths of patch 1303, ruler 1302M, and ruler 1302C on the scanned image scanned in the slow mode shown in FIG. Become. As a result, the SN ratios of the rulers 1309C and 1309M on the scanned image 1304 obtained by scanning the paper 1301 in the high speed mode are approximately the same as the primary color rulers on the scanned image in the low speed mode. Note that the process of changing the length of the patch and ruler according to the paper transport speed is performed in S701 of FIG. 7A. FIG. 14 is a flowchart showing detailed processing in S701 of FIG. 7A. Processing for generating image data for the “low-speed mode” and the “high-speed mode” (referring to image data to be printed on the printing medium (paper 1301)) by the CPU 201 will be described below.

In S<b>1401 , the CPU 201 determines whether or not the set value of the transport speed of the paper 1301 input via the I/F 205 exceeds the threshold. Here, the CPU 201 may determine whether the input transport speed setting for the paper 1301 is the “low speed mode” or the “high speed mode”. When the CPU 201 determines that the input set value of the transport speed of the paper 1301 does not exceed the threshold value (No in S1402), the process proceeds to S1402. On the other hand, if the CPU 201 determines that the input set value of the conveying speed of the paper 1301 exceeds the threshold value (Yes in S1402), the process proceeds to S1404.

In S1402, the CPU 201 determines that the lengths of the rulers 1307C and 1307M in FIG. 13C are shorter than the lengths of the rulers 1307C and 1307M in FIG. Place ruler 1302M. In addition, the CPU 201 arranges a ruler 1302C having approximately the same length as the ruler 1302M in the second stage immediately above the first stage in the image data for "low speed mode" (FIG. 13(a)). At this time, the CPU 201 arranges the ruler 1302M and the ruler 1302C in the image data for the "low speed mode" without mixing them in the same row (first row and second row) (FIG. 13A).

In S1403, the CPU 201 arranges a patch 1303 having a shorter length in the y direction than the patch 1308 shown in FIG. 13C in the image data for "low speed mode" (FIG. 13A).

In S1404, the CPU 201 determines that the length of the rulers 1302C and 1302M in FIG. 13A is longer than the length of the ruler 1302C and the ruler 1302M in FIG. Place rulers 1307C and 1307M. At this time, the CPU 201 arranges the ruler 1307C and the ruler 1307M alternately in the x-direction on the first stage in the image data for the "high-speed mode" (FIG. 13(c)).

In S1405, the CPU 201 arranges a patch 1308 longer in the y direction than the patch 1303 shown in FIG. 13(a) in the "high speed mode" image data (FIG. 13(c)).

In S1406, the CPU 201 outputs image data for "low speed mode" (shown in FIG. 13A) in which the ruler 1302M, ruler 1302C, and patch 1303 set in S1402-1403 are arranged. On the other hand, the CPU 201 outputs image data for "low speed mode" (illustrated in FIG. 13C) in which the ruler 1307C, ruler 1307M and patch 1308 set in S1404 to S1405 are arranged. Then, the in-line sensor 107 scans the recording medium on which the image data for the "low speed mode" or "high speed mode" is recorded to obtain a scanned image.

As described above, a test image (scanned image) with good image quality is generated by changing the length and arrangement of the rulers of the primary colors that make up the multicolor and the patch length according to the paper transport speed. can be used to save test image area.

(Other examples)
The present invention supplies a program that implements one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in the computer of the system or apparatus reads and executes the program. It can also be realized by processing to It can also be implemented by a circuit (for example, ASIC) that implements one or more functions.

The invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the claims are appended to make public the scope of the invention.

20: Image forming system, 30: Information processing device, 40: Image forming device, 201: CPU, 202: RAM, 203: Storage unit, 204: ROM, 205: I/F

Claims (22)

A scanned image obtained by scanning a recording medium on which an image including a multinary color patch obtained by mixing two or more primary colors and a ruler of the primary colors forming the multinary color is formed by an image forming apparatus. detection means for detecting the ruler of the primary color from
Based on the position of the ruler of the primary color in the scanned image, the primary color that corrects the multinary color in an area with uneven color in the patch of multinary colors in the scanned image and the multinary color in the area with uneven color. a determining means for determining a nozzle of
An information processing device comprising: obtaining means for obtaining color information representing the primary colors forming the multinary color from the multinary color patch in the scanned image;
The information processing apparatus according to claim 1, characterized by: The acquiring means acquires color information representing the multinary color of the area with the color unevenness from the area with the color unevenness in the multinary color patch in the scanned image.
3. The information processing apparatus according to claim 2, characterized by: the detection means detects a ruler for a primary color different from the ruler for the primary color from the scanned image based on color information representing the primary colors that form the multi-primary color;
The determining means corrects the multi-nary color in the area with the uneven color based on the difference between the position of the ruler of the primary color in the scanned image and the position of the ruler of the other primary color. determine the primary color nozzle for
4. The information processing apparatus according to any one of claims 1 to 3, characterized by: The detecting means further detects a primary color ruler that constitutes the other multinary color from another multinary color patch that is different from the multinary color patch in the scanned image.
The information processing apparatus according to any one of claims 1 to 4, characterized in that: further comprising generating means for generating an image including a multinary color patch obtained by mixing the two or more primary colors and a ruler of the primary colors forming the multinary color;
The information processing apparatus according to any one of claims 1 to 5, characterized in that: The generating means arranges the primary color ruler that constitutes the multinary color in the image at a position within a predetermined distance from the multinary color patch.
7. The information processing apparatus according to claim 6, characterized by: When the image forming apparatus forms the image on the recording medium, the predetermined distance is the position of the ruler of the primary colors forming the multi-primary color and the position of the ruler of the primary colors different from the ruler of the primary colors. A difference between the position of the ruler and the position of the ruler is less than a threshold, and the position of the ruler of the primary color and the position of the ruler of the other primary color are the farthest distance from the multi-color patch.
8. The information processing apparatus according to claim 7, characterized by: The generating means generates any one of the rulers of the primary colors forming the multinary color based on the degree of influence of the primary colors forming the multinary color on the multinary color in the image. placed closest to the color patch,
The information processing apparatus according to any one of claims 6 to 8, characterized by: The generating means arranges the rulers of the primary colors forming the multinary color in the image at positions asymmetrical with respect to the patch of the multinary color.
10. The information processing apparatus according to any one of claims 6 to 9, characterized by: The generating means changes the position of the ruler of the primary colors forming the multinary color based on the color information representing the multinary color in the image.
The information processing apparatus according to any one of claims 6 to 10, characterized in that: The generation means changes the length of the ruler of the primary colors that make up the multinary color based on the SN ratio of the primary colors that make up the multinary color in the image.
The information processing apparatus according to any one of claims 6 to 11, characterized in that: The generation means changes the length of the ruler of the primary colors forming the multinary color based on the color information representing the multinary color in the image.
The information processing apparatus according to any one of claims 6 to 12, characterized in that: The generation means places a ruler of a primary color forming the multinary color in the image and a ruler of another primary color different from the ruler of the primary color at positions at the same distance from the patch of the multinary color. Deploy,
14. The information processing apparatus according to any one of claims 6 to 13, characterized by: The generating means generates any one of the rulers of the primary colors forming the multinary color based on the degree of influence of the primary colors forming the multinary color on the multinary color in the image. locating at a position closer to the multi-color patch than at a position at the same distance from the color patch;
15. The information processing apparatus according to claim 14, characterized by: The generating means changes the number of rulers arranged in the primary colors that make up the multinary color in the image, based on a mixing ratio of the primary colors that make up the multinary color.
16. The information processing apparatus according to any one of claims 6 to 15, characterized by: Based on whether or not the conveying speed at which the image forming apparatus conveys the recording medium exceeds a threshold value, the generation means generates a ruler for primary colors that form the multinary colors in the image, and a ruler for the primary colors. Placing a ruler of another primary color different from the ruler at the same distance from the patch of the multi-primary color, and changing the length of the ruler of the primary color and the ruler of the other primary color;
17. The information processing apparatus according to any one of claims 6 to 16, characterized by: The generating means changes the length of the multinary color patch in the image based on whether or not the conveying speed at which the image forming apparatus conveys the recording medium exceeds a threshold value.
18. The information processing apparatus according to any one of claims 6 to 17, characterized by: An image forming apparatus comprising a recording head having nozzle arrays for ejecting different primary color materials, and conveying a recording medium in a direction orthogonal to the recording head to form an image on the recording medium,
receiving means for receiving image data;
Based on the image data received by the receiving means, an image is formed on the recording medium including a multinary color patch obtained by mixing two or more primary colors and a ruler of primary colors forming the multinary color. a forming means for
acquisition means for scanning the recording medium on which the image is formed to acquire a scanned image;
notification means for notifying an external device of the scanned image;
An image forming apparatus comprising: an image forming apparatus;
an information processing apparatus according to any one of claims 1 to 18;
An image forming system comprising: A method executed by an information processing device, comprising:
A scanned image obtained by scanning a recording medium on which an image including a multinary color patch obtained by mixing two or more primary colors and a ruler of the primary colors forming the multinary color is formed by an image forming apparatus. a detecting step of detecting the ruler of the primary color from
Based on the position of the ruler of the primary color in the scanned image, the primary color that corrects the multinary color in an area with uneven color in the patch of multinary colors in the scanned image and the multinary color in the area with uneven color. a determining step of determining the nozzle of
A method comprising: A program for causing a computer to function as each means of the information processing apparatus according to any one of claims 1 to 18.

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