JP6582787B2 - Image forming apparatus and program - Google Patents

Description

  The present invention relates to an image forming apparatus and a program.

  In an image forming apparatus such as a printer, a Lab value may be acquired by reading a printing result of the image forming apparatus with a colorimeter in order to periodically check whether or not a color misregistration is in a normal state. However, since color measurement is a manual operation, it becomes complicated. Therefore, it has been proposed to automatically read the print result with an in-line sensor or the like of the image forming apparatus instead of the colorimeter to acquire RGB values and convert the RGB values into Lab values.

  Japanese Patent Laid-Open No. 2004-228867 has an object to improve the generation efficiency of color conversion information used for color conversion while reducing the influence on the accuracy of color conversion, and obtain RGB values by printing color patches. It is described that the patch data is deleted so that the number of images becomes a predetermined number, the remaining patches are color-measured to obtain Lab values, and a color prediction model is generated using the obtained RGB and Lab values. Has been.

JP 2012-248934 A

  Color patches for reading RGB values with an in-line sensor, etc., will be printed over multiple sheets due to mounting and technical constraints, and the same multiple color patches when acquiring Lab values with a colorimeter Therefore, there is a problem that the color measurement man-hour is large. Although deleting the number of patch data reduces the labor of color measurement, there is a limit to the number of patches that can be deleted, so further improvement is desired.

  On the other hand, it may be possible to reduce the color measurement man-hour by arranging the color value acquisition color patch and the Lab value acquisition color patch separately on the paper (chart). Disturbing the patches as separate ones can cause disturbances, specifically in-plane unevenness and differences between jobs, which can reduce the colorimetric accuracy, that is, the color conversion profile accuracy.

  An object of the present invention is to provide an apparatus and a program that suppress in-plane unevenness and differences between jobs.

Invention according to claim 1, reading and printing unit for printing by arranging a plurality of color patches for evaluation of the same color values in the color patch on the paper, the color values of the printed color patches the evaluation, the color And a control unit that creates color conversion profile data using a color patch of a paper whose color value difference is equal to or less than an allowable value, and the printing unit has the evaluation color patch at the same position on different papers Is an image forming apparatus that arranges and prints .

According to a second aspect of the present invention, there is provided a printing unit that places a plurality of evaluation color patches having the same color value on a color patch and prints them on a sheet, reads the color value of the printed evaluation color patch, A color conversion profile data using color patches of paper whose color value difference is equal to or less than an allowable value, and the printing unit has different positions on the same paper and the same on different paper In the image forming apparatus, the evaluation color patch is arranged at a position and printed .

The invention according to claim 3, wherein the printing unit, as the different positions of the same sheet, the longitudinal direction, transverse direction, to claim 2 for printing by arranging the evaluation color patch in at least one of a diagonal direction The image forming apparatus described.

According to a fourth aspect of the present invention, the control unit is configured such that the smallest color value difference among all possible combinations of the evaluation color patches arranged at the same position on the different sheets is an allowable value. The image forming apparatus according to claim 1 , wherein the color conversion profile data is created by using a color patch of the following paper .

The invention according to claim 5, wherein the printing unit, when the color value difference is not less than the allowable value, the color patch repeated until the allowable value or less in any one of claims 1 to be printed on paper The image forming apparatus described.

According to a sixth aspect of the present invention, a plurality of evaluation color patches having the same color value are arranged in a color patch and printed on a sheet, and the color value of the printed evaluation color patch is read, and the color A color conversion profile data using a color patch of a paper whose color value difference is equal to or less than an allowable value, and the printing unit uses a first color space value as the color patch. The color patch for acquisition and the color patch for acquiring the second color space value are printed, and the control unit reads the first color space for acquiring the first color space value. An image forming apparatus that creates the color conversion profile data from a value and a second color space value obtained by measuring the color patch for obtaining the second color space value .

According to a seventh aspect of the present invention, the printing unit prints the first color space value acquisition color patch and the second color space value acquisition color patch on the same sheet, and a plurality of sheets. The image forming apparatus according to claim 6 , wherein the image forming apparatus prints over the paper .

The invention according to claim 8 is the image forming apparatus according to claim 7 , wherein the evaluation color patch is arranged in the color patch for obtaining the first color space value .

The invention according to claim 9 is the image forming apparatus according to claim 7 , wherein the printing unit further prints an identification patch for identifying each of the plurality of sheets .

The invention according to claim 10, the first color space is a device dependent color space, the second color space in the image forming apparatus according to any one of claims 6-9 apparatus is independent color space is there.

The invention according to claim 11 is the image forming apparatus according to claim 10 , wherein the first color space is RGB, and the second color space is Lab .

The invention according to claim 12 is a step of arranging a plurality of evaluation color patches having the same color value on a color patch and printing them on a sheet of paper, and arranging the evaluation color patch at the same position on different sheets of paper. And printing the color value of the printed evaluation color patch, and creating color conversion profile data using the color patch of the paper whose color value difference, which is the difference between the color values, is less than or equal to the allowable value Is a program that executes a step to be executed .

According to a thirteenth aspect of the present invention, a plurality of evaluation color patches having the same color value are arranged on a color patch and printed on a sheet by a computer, and the same sheet is printed at different positions and at different positions on the same sheet. The step of arranging and printing the evaluation color patch, reading the color value of the printed evaluation color patch, and using the color patch of the paper whose color value difference, which is the difference between the color values, is less than or equal to an allowable value And a step of generating color conversion profile data .

According to the invention described in claims 1 and 12 , color conversion profile data can be created while suppressing in-plane unevenness and differences between jobs. In particular, color conversion profile data can be created while suppressing differences between jobs.

According to the invention described in claims 2 and 13 , color conversion profile data can be created while suppressing in-plane unevenness and differences between jobs. In particular, color conversion profile data can be created while suppressing in- plane unevenness and differences between jobs .

According to the third aspect of the invention, in particular, color conversion profile data can be created while suppressing at least one of vertical, horizontal, and oblique unevenness as in- plane unevenness .

According to the fourth aspect of the present invention, color conversion profile data that minimizes the difference between jobs can be created.

According to the fifth aspect of the invention, in particular, color conversion profile data can be created by using a color patch of a paper whose color value difference is equal to or smaller than an allowable value .

According to the invention described in claim 6, in particular, the first color space value obtained by reading the color patch for acquiring the first color space value and the color patch for acquiring the second color space value are obtained. Color conversion profile data can be created from the second color space value obtained by colorimetry .

According to the seventh aspect of the invention, in particular, the first color space value obtained by reading the color patch for acquiring the first color space value and the color patch for acquiring the second color space value are obtained. Color conversion profile data can be created from the second color space value obtained by colorimetry .

According to the eighth aspect of the invention, in particular, the evaluation color patch can be arranged by effectively utilizing the space .

According to the ninth aspect of the invention, in particular, each of a plurality of sheets can be identified .

According to the invention described in claim 10 , color conversion profile data can be created from a specific type of color patch .

According to the eleventh aspect , color conversion profile data can be created from a specific type of color patch.

1 is a configuration diagram of an image forming apparatus according to an embodiment. It is explanatory drawing of the color patch of embodiment. It is arrangement | positioning explanatory drawing of the evaluation color patch and the identification patch. It is evaluation explanatory drawing of in-plane nonuniformity. It is a graph which shows the change of the in-plane nonuniformity of a vertical direction, a horizontal direction, and a diagonal direction. It is evaluation explanatory drawing of the difference between jobs. It is a table figure which shows the difference between jobs calculated brute force. It is a processing flowchart of an embodiment. It is a processing flowchart of other embodiments.

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

<Basic principle>
The basic principle of this embodiment is that a plurality of evaluation color patches having the same color value are arranged in a color patch, and in-plane unevenness is obtained using the color value difference obtained by reading the color values of the plurality of evaluation color patches. Or the difference between jobs is evaluated, and color conversion profile data is created by using a color patch of the paper such that the color value difference is equal to or less than the allowable value. Even if a plurality of evaluation color patches having the same color value are printed and arranged, if there are in-plane unevenness or differences between jobs, the color values obtained by reading these will vary, resulting in color value differences. In the present embodiment, this color value difference is used.

  Here, the same color value means a color in which the first color space value such as RGB or the second color space value such as Lab is the same. Therefore, the color value difference also means a first color space value difference such as RGB or a second color space value difference such as Lab. Note that the first color space is a color space (device-dependent color space) depending on the image forming apparatus, and corresponds to, for example, RGB. The second color space is a color space that does not depend on the image forming apparatus (apparatus-independent color space), and corresponds to, for example, Lab. In the following embodiments, the first color space will be described as RGB, and the second color space will be described as Lab. In the following embodiments, in-plane unevenness and differences between jobs are evaluated by RGB differences (ΔRGB), but the present invention is not limited to this. Further, “in-plane unevenness” means a change in the same color value at different positions in the same sheet (chart), and “difference between jobs” means the same color value at the same position in different sheets (chart). Means change. Therefore, if a plurality of evaluation color patches are arranged at different positions on the same paper, the in-plane unevenness in the paper can be evaluated, and if a plurality of evaluation color patches are arranged at the same position on different papers, the papers, that is, jobs You can evaluate the difference. Since the in-plane uneven directions can be roughly divided into a vertical direction, a horizontal direction, and an oblique direction, the evaluation color patches may be arranged in the vertical direction, the horizontal direction, and the oblique direction.

  Even if in-plane unevenness or differences between jobs occur, the accuracy of the color conversion profile data can be ensured by creating the color conversion profile data using a color patch whose color value difference is equal to or less than the allowable value.

  As color patches, a color patch for acquiring RGB values and a color patch for acquiring Lab values are arranged separately on a plurality of sheets. The color patch for acquiring RGB values and the color patch for acquiring Lab values may have the same number of patches but different sizes. For example, the patch size of the color patch for acquiring Lab values may be the same as that for acquiring RGB values. You may make it smaller than the patch size of a color patch. When arranging RGB value acquisition color patches on a plurality of sheets, Lab value acquisition color patches are also arranged on the same plurality of sheets. The color patches for acquiring RGB values arranged on a plurality of sheets have different patterns, but the color patches for acquiring Lab values arranged on a plurality of sheets may overlap each other. In the following embodiment, 18 color patches for acquiring RGB values are arranged and 18 color patches for acquiring Lab values are arranged on the same 18 sheets. However, the present invention is not limited to this.

  Further, a plurality of evaluation color patches are arranged in the RGB value acquisition color patch, and in-plane unevenness and differences between jobs are evaluated using these evaluation color patches. If the in-plane unevenness or the difference between jobs evaluated using the evaluation color patch is within the allowable value, the RGB value and the Lab value are obtained using the color patch for acquiring the RGB value and the color patch for acquiring the Lab value, respectively. Acquire and generate a color conversion profile.

  On the other hand, if the in-plane unevenness or the difference between jobs evaluated using the evaluation color patch exceeds the allowable value, the color for acquiring RGB values is the same as before without using the color patch for acquiring Lab values. Using the patch, not only RGB values but also Lab values are acquired, and a color conversion profile is generated.

  Select the combination of RGB color acquisition color patches and Lab value acquisition color patches that can be within the allowable value even if the in-plane unevenness or difference between jobs exceeds the allowable value evaluated using the evaluation color patch. It is also possible to obtain RGB values and Lab values to generate a color conversion profile.

  In the following embodiments, the evaluation color patches for evaluating the in-plane unevenness are arranged in the vertical direction, the horizontal direction, and the oblique direction. However, the present invention is not limited to this, and only the vertical direction is the horizontal direction. Only in an oblique direction, only in a vertical direction, and in a horizontal direction, etc.

  In the following embodiments, any one of the evaluation color patches for evaluating the in-plane unevenness is used as an evaluation color patch for evaluating the difference between jobs, but is not limited thereto. Instead, different evaluation color patches may be used.

  In the following embodiments, both in-plane unevenness and differences between jobs are evaluated, but color conversion profile data may be created by evaluating only in-plane unevenness or only differences between jobs.

<Configuration>
Next, the configuration of the present embodiment will be specifically described.

  FIG. 1 is a configuration diagram of an image forming apparatus according to the present embodiment. Note that the image forming apparatus 10 may be connected to a management server via a network.

  The image forming apparatus 10 is a printer, a multifunction peripheral, or the like, and includes a color conversion unit 101, a print engine 102, a color patch reading unit 103, a storage unit 104, a control unit 105, and a user interface unit 106. The colorimeter 107 may be a part of the image forming apparatus 10 or may exist separately.

  The image forming apparatus 10 executes a process for printing out the input print image data. The print image data is, for example, bitmap image data or image data described in PDL (page description language). When the image forming apparatus 10 includes a scanner, image data read by the scanner may be used as print image data. The print image data is converted into a raster image that can be processed by the print engine 102 by an interpreter (not shown) or other image processing unit.

  The color conversion unit 101 performs color conversion on the raster image according to the profile data. The profile data is data including information indicating the correspondence between the color coordinates of each grid point in the input side color space and the color coordinates in the output side color space corresponding to the grid point. The output side color space is a color space of the print engine 102 and is typically expressed by a combination of four colors of cyan (C), magenta (M), yellow (Y), and black (K). The profile data is generated by the control unit 105 and stored in the storage unit 104. For example, profile data may be generated for each paper type and stored in the storage unit 104, and the user may select and use data suitable for the paper to be used from a plurality of profile data. For each pixel of the raster image, the color conversion unit 101 calculates the color coordinate of the output side color space according to the profile data when the value (color coordinate) of the pixel is the color coordinate of the input side color space.

  The print engine 102 prints an image of the color conversion result output from the color conversion unit 101 on paper.

  The color patch reading unit 103 reads a color patch printed by the print engine 102 under the control of the control unit 105, acquires RGB values, and outputs the RGB values to the control unit 105. The color patch reading unit 103 includes an inline sensor or the like. The in-line sensor has substantially the same configuration as a known image reading scanner, and specifically includes an imaging unit, an illumination unit, an image processing unit, and a sensor calibration unit. The mounting position in the image forming apparatus 10 is preferably in the vicinity of the paper discharge portion where the color development of the printed color patch is completed and the paper curl is removed and the posture is stabilized. The image processing unit is provided with a three-color CCD, and reads color correction in real time to calculate color information of the color patch.

  The control unit 105 controls the entire image forming apparatus 10 according to a processing program stored in the program memory. The control unit 105 receives a print instruction from the user via the user interface unit 106, and controls the color conversion unit 101, the print engine 102, and the like to print a target image of the print instruction. In addition, the control unit 105 executes a process for generating color conversion profile data. The color conversion profile data is obtained by printing a color patch serving as a color reference on the print engine 102, reading the print result by the color patch reading unit 103, and measuring the color by the colorimeter 107, and RGB obtained from these measurement results It generates based on a data group of values and Lab values. The generated color conversion profile data is stored in the storage unit 104. The color patch is an image pattern in which color patches having different densities in a plurality of stages are arranged for each color of CMYK. The color patch data is stored in the storage unit 104 as a chart pattern, and the control unit 105 reads out the data and causes the print engine 102 to print it in accordance with the processing program.

  A known algorithm can be used as a method for calculating a color conversion profile indicating conversion from RGB values to Lab values. For example, it may be composed of a first step for performing lightness conversion by a lookup table (LUT) and a second step for performing linear conversion by matrix calculation (for example, 3 × 10 matrix calculation). It is calculated from a large number of color patch reading values by a certain arithmetic algorithm. These LUTs and determinant coefficients are stored in the storage unit 104 as parameters.

  The user interface unit 106 notifies the user of the state of the image forming apparatus 10 and receives an instruction input from the user. The user interface unit 106 may include a display device such as a liquid crystal touch panel and an input button such as a keypad.

  Here, the chart pattern stored in the storage unit 104 is data that defines the arrangement of color patches printed by the print engine 102 in order to acquire RGB values and Lab values. Due to the above restrictions, only half of the printing paper can be arranged with color patches, and the light emitted from the light source is reflected not only by the color patch to be measured but also by the adjacent color patch. The light that has returned to the light source is further reflected and applied to the color patch to be measured, so that the reflected light affected by the reflectance of the adjacent color patch is received by the image reading element. Considering this, since it is necessary to secure the patch area, the number of color patches is, for example, 18 sheets. In this case, in order to obtain RGB values, reading must be performed when 18 color patches are output, and furthermore, the color patches of 18 color patches must be measured by the colorimeter 107, which takes time for the color measurement process.

  Therefore, in accordance with the processing program, the control unit 105 uses the same combination (however, the size is small) as the RGB value acquisition color patch for acquiring the Lab value separately from the color patch for acquiring the RGB value. A color patch is set, and the Lab value acquisition color patch is arranged on the same sheet as the RGB value acquisition color patch.

  Next, the color patch of this embodiment will be described.

  FIG. 2 schematically shows a color patch for acquiring RGB values and a color patch for acquiring Lab values according to the present embodiment. In the drawing, the color patch is shown as a rectangular area without filling, but in actuality, it is a patch in which the density is changed in a plurality of stages for each color of CMYK.

<Color patch for RGB value acquisition>
As described above, RGB color acquisition color patches are printed over a plurality of sheets under the technical restrictions of mounting the color patch reading unit (inline sensor) 103 and the cavity effect. Specifically, only half of one sheet of patches can be arranged, and if the area of one color patch is 2 cm × 2 cm or more and the number of patches is 1584, the number of color patches is 18 sheets. Become. These 18 sheets of RGB value acquisition color patches (charts) are 20-1, 20-2, 20-3,..., 20-18 (in the figure, 20-1, 20 Only -2, 20-3, 20-4 are shown). A color patch 22 for obtaining RGB values is printed on the upper half of these 18 sheets 20-1, 20-2, 20-3,..., 20-18. Of course, the pattern of the color patch 22 printed on the paper 20-1 and the pattern of the color patch 22 printed on the paper 20-2, 20-3,... Are different from each other.

<Color patches for obtaining Lab values>
On the other hand, the color patch for acquiring the Lab value is not affected by the cavity effect as much as the color patch reading unit (inline sensor) 103, so the area of one color patch is smaller than the color patch 22 for acquiring the RGB value. For example, it can be reduced to about 0.7 cm × 0.7 cm.

  Therefore, using the fact that the area of one patch is small while having the same number of patches (1584) as the RGB value acquisition color patch 22, the Lab value acquisition color patch 24 is divided into two Lab values. The color patches 24a and 24b for acquisition are used, the color patch 24a for acquiring the Lab value is printed on the lower half of the paper 20-1 on which the color patch 22 is printed, and the color patch 24b for acquiring the Lab value is colored. The patch 22 is printed on the lower half of the paper 20-2 on which the upper half is printed.

  Similarly, the color patches 24a and 24b for acquiring Lab values are printed on the other sheets 20-3, 20-4,..., 20-18.

  Therefore, if a total of 18 sheets (charts) are 20-i (i = 1, 2, 3,..., 18), i is an odd number of 1, 3, 5,. An acquisition color patch 22 and a Lab value acquisition color patch 24a are arranged, and i is an even number of 2, 4, 6,..., An RGB value acquisition color patch 22 and a Lab value acquisition color. A patch 24b is arranged.

<Color patch for evaluation>
FIG. 3 shows an evaluation color patch.

  The evaluation color patches 30 are embedded in four locations of the RGB value acquisition color patch 22. Taking the paper 20-1 as an example, the evaluation color patch 30 is located at each vertex of the rectangle among the color patches 22 for obtaining RGB values, and has two color patches in the vertical, horizontal and diagonal directions. Are spaced apart. The evaluation color patches 30 arranged at the four locations all have the same color value. Although it does not specifically limit about an arrangement position, It is preferable to have separated in the vertical direction, the horizontal direction, and the diagonal direction to such an extent that it meets the objective of evaluating in-plane nonuniformity.

  The same applies to the other sheets 20-2, 20-3,..., 20-18, and the evaluation color patch 30 is a predetermined position of the color patch 22 for obtaining RGB values, that is, the sheet 20-1. It is arranged at the same position as the arrangement position in.

  Further, in this embodiment, apart from the evaluation color patch 30, an identification patch 32 for identifying the sheets 20-1, 20-2,. The identification patch 32 is for identifying each sheet, and corresponds to the page number of the sheet, so it is not necessarily a color patch. The identification patch 32 may be arranged at a position different from the color patch 22 for acquiring RGB values and the color patches 24a and 24b for acquiring Lab values. As shown in the figure, the color patch 24a for acquiring Lab values is used. , 24b.

<Evaluation of in-plane unevenness>
FIG. 4 shows a method for evaluating in-plane unevenness.

  In the paper 20-1, the in-plane unevenness, specifically the in-plane unevenness in the vertical direction, the in-plane unevenness in the horizontal direction, and the in-plane unevenness in the oblique direction are evaluated using four evaluation color patches. One of the four evaluation color patches 30, for example, the evaluation color patch 30 arranged in the upper left is used as a reference, and the reference patch and the color patch arranged in the vertical direction with respect to the reference patch are used as the vertical patches. Evaluate the in-plane unevenness of the direction, evaluate the in-plane unevenness in the horizontal direction using the reference patch and the color patch arranged in the direction transverse to the reference patch, and obliquely inspect the reference patch and the reference patch. The in-plane unevenness in the oblique direction is evaluated using the color patches arranged in the area. The above evaluation is also performed for all the other sheets 20-2, 20-3,..., 20-18, and in-plane unevenness in the vertical direction, the horizontal direction, and the oblique direction is evaluated.

  FIG. 5 shows an example of in-plane unevenness. FIG. 5A shows in-plane unevenness in the vertical direction, the horizontal axis indicates the number of sheets (charts), and the sheet 20-1 corresponds to the first sheet and the sheet 20-18 corresponds to the 18th sheet. The vertical axis represents the difference ΔRGB between the RGB values of two evaluation color patches 30 arranged in the vertical direction. The ΔRGB value is 0 because it is originally the same color value, but if there is in-plane unevenness, the ΔRGB value becomes a finite value other than 0.

  FIG. 5B shows in-plane unevenness in the horizontal direction, the horizontal axis is the number of sheets (charts), and the vertical axis is the difference ΔRGB between the RGB values of two evaluation color patches 30 arranged in the horizontal direction. The ΔRGB value is 0 because it is originally the same color value, but if there is in-plane unevenness, the ΔRGB value becomes a finite value other than 0.

  FIG. 5C shows the in-plane unevenness in the oblique direction, the horizontal axis is the number of sheets (charts), and the vertical axis is the difference ΔRGB between the RGB values of the two evaluation color patches 30 arranged in the oblique direction. The ΔRGB value is 0 because it is originally the same color value, but if there is in-plane unevenness, the ΔRGB value becomes a finite value other than 0.

  If the ΔRGB values in the vertical, horizontal, and diagonal directions are within the allowable values, that is, within the allowable values when colorimetry is performed by the colorimeter 107, in-plane unevenness can be ignored. Even if the color patches 24a and 24b for acquiring Lab values are arranged separately from the color patch 22 for acquiring RGB values, the accuracy of the color conversion profile is affected.

  In the case of FIGS. 5A, 5B, and 5C, the in-plane unevenness in the vertical direction is not more than the allowable value in all sheets (charts), but there is no problem in the in-plane unevenness in the horizontal and oblique directions. The permissible value is exceeded, and in-plane unevenness can be a problem. One of the correspondences in such a case is that the colorimeter 107 performs color measurement using the RGB value acquisition color patch 22 without using the Lab value acquisition color patches 24a and 24b.

<Evaluation of differences between jobs>
FIG. 6 shows a method for evaluating a difference between jobs.

  One of the four evaluation color patches 30 arranged on each of the sheets 20-1, 20-2,..., 20-18, for example, the upper left color patch is set as a reference patch, and these 18 references. The ΔRGB value between patches is evaluated as a brute force.

  Specifically, ΔRGB values of the reference patch of the paper 20-1 and the reference patch of the paper 20-2, ΔRGB values of the reference patch of the paper 20-1 and the reference patch of the paper 20-3,. ΔRGB values of the reference patch of the paper 20-18 and the reference patch of the paper 20-2, ΔRGB values of the reference patch of the paper 20-2 and the reference patch of the paper 20-3,... This is the ΔRGB value of the reference patch.

FIG. 7 shows a table of ΔRGB values evaluated brute force, that is, for all possible combinations. In the figure, the ΔRGB value of the reference patch of the sheet 20-1 (first sheet) and the sheet 20-2 (second sheet) is denoted as ΔRGB _1-2 . A combination of two sheets having the smallest ΔRGB value is extracted from the ΔRGB values evaluated by the round robin. However, the extracted color patches for the Lab value acquisition of the combination of the two sheets must be one of the color patches 24a for acquiring the Lab value, and the other one must be the color patch 24b for acquiring the Lab value. I must. The reason for this is that if the color patches for acquiring Lab values of the two extracted combinations are both the color patches 24a for acquiring Lab values, sufficient Lab values cannot be acquired even if they are measured. is there. Accordingly, when the ΔRGB value evaluated as a brute force is ΔRGB _i−j , it can be said that a combination having the smallest ΔRGB value is extracted from a combination in which one of i and j is an odd number and the other is an even number. i and j correspond to page numbers and can be specified by the identification patch 32.

For example,
ΔRGB _1-3 <ΔRGB _2-4 <ΔRGB _1-2 <.
In this case, ΔRGB _1-3 and ΔRGB _2-4 are not selected, ΔRGB1-2 is selected, and measurement is performed using the color patches 24a and 24b for acquiring Lab values of the paper 20-1 and the paper 20-2. Color is measured by the color device 107.

  Note that such processing is processing that results from the Lab value acquisition color patch 24 being divided into Lab value acquisition color patches 24a and 24b and printed on different sheets. When the color patch 24 is printed on one sheet of paper, such processing is not necessary, and it is only necessary to extract the one having the smallest ΔRGB value. Even when the color patch 24 for acquiring the Lab value is divided into the color patches 24a and 24b for acquiring the Lab value and printed on different papers, the Lab value is acquired when calculating the total RGB values. If it is limited to all possible combinations including the color patches 24a and 24b, the one having the smallest ΔRGB value may be extracted.

  Since the in-plane unevenness and the difference between jobs both affect the colorimetry in the colorimeter 107, it is preferable that the in-plane unevenness is within an allowable value and the difference between jobs is also within an allowable value. . Therefore, for the combination of two sheets having the smallest difference between jobs, it is preferable to finally adopt the combination of the two sheets if the in-plane unevenness is within the allowable value.

  However, if there is a situation where either the in-plane unevenness or the difference between jobs can be ignored, it is sufficient to evaluate either the in-plane unevenness or the difference between jobs.

<Overall processing>
Next, the overall processing of this embodiment will be described. This is a case where both in-plane unevenness and differences between jobs are required to be within allowable values.

  FIG. 8 is a processing flowchart of the embodiment. First, the control unit 105 controls the print engine 102 to output a total of 18 sheets, that is, charts. At this time, the color patch reading unit (inline sensor) 103 reads the RGB value acquisition color patch 22 to acquire RGB values (S101).

Next, the control unit 105 calculates ΔRGB values indicating differences between jobs using the acquired RGB values and calculates ΔRGB indicating in-plane unevenness (S102, S103). For the difference between jobs, ΔRGB _i−j is calculated omnidirectionally using the reference patch. In-plane unevenness calculates ΔRGB in the vertical direction, the horizontal direction, and the diagonal direction using the reference patch.

  Next, the control unit 105 determines whether or not the calculated ΔRGB indicating in-plane unevenness and ΔRGB indicating the difference between jobs are smaller than the threshold value X (S104). This determination is for determining whether the in-plane unevenness and the difference between jobs are both equal to or less than an allowable value. A method for setting the threshold value X will be described later. Regarding a difference between jobs, a combination having the smallest ΔRGB value among the combinations in which one of i and j is an odd number and the other is an even number is determined.

  If the in-plane unevenness and the difference between jobs are both smaller than the threshold value X, the papers 20-i and 20-j specified by i and j to be determined are set as a colorimetric chart (S105). At this time, the control unit 105 specifies the paper 20-i and the paper 20-j using the identification patch 32.

  Next, the control unit 105 measures the color patch for acquiring the Lab value of the paper 20-i and the color patch for acquiring the Lab value of the paper 20-j, which are set color measurement charts, by the colorimeter 107. Then, the Lab value is acquired (S106).

  Next, the control unit 105 creates profile data using the RGB value acquired in S101 and the Lab value acquired in S106 (S107). The color conversion profile is composed of a first step for performing lightness conversion by a look-up table (LUT) and a second step for performing linear conversion by matrix calculation (eg, 3 × 10 matrix calculation). It is calculated from the data pair of the value and the Lab value by an arithmetic algorithm. The LUT and the determinant coefficient are stored in the storage unit 104 as parameters.

  On the other hand, when at least one of the in-plane unevenness and the difference between jobs is equal to or greater than the threshold value X (NO in S104), the color patches for acquiring RGB values without using the color patches 24a and 24b for acquiring Lab values. Profile data is created using the Lab value obtained by measuring the color 22 with the colorimeter 107 (S108, S107).

Here, the threshold value X used in the determination process of S104 is determined in consideration of the color difference factor. In other words, as a cause of color difference,
-Profile accuracy-Image forming device (IOT) variation-Color patch reading unit (ILS) variation is considered, so the average color difference ΔE _ave is
ΔE _ave = {(profile accuracy) ² + (IOT variation) ² + (ILS variation) ² } ^0.5
It becomes. For example,
・ Profile accuracy = 1.5
Image forming apparatus (IOT) variation = 2.0
-Color patch reading unit (ILS) reading variation = x
When the threshold value of ΔEave is 3.0,
ΔE _ave = {(1.5) ² + (2.0) ² + x ² } <3.0
Because
x <1.66
It becomes. At this time, the threshold value X of the in-plane unevenness and the difference between jobs is 1.66.

In this embodiment, if YES in S104, that is, if the in-plane unevenness and the difference between jobs are both smaller than the threshold value X, two sheets set as the colorimetric chart, for example, the sheet 20-1 and the sheet 20- Since the color conversion profile data is created by performing color measurement using 2, the color measurement man-hour is greatly reduced. That is, when performing RGB value acquisition and Lab value acquisition using only the RGB color patch 22 without using the Lab value acquisition color patch 24,
18 images for RGB acquisition 18 images are required for Lab value acquisition. In this embodiment,
18 sheets for RGB value acquisition Only 2 sheets for Lab value acquisition are required, and the color measurement man-hour is greatly reduced from 18 sheets to 2 sheets. In addition, in the present embodiment, it is ensured that the in-plane unevenness of two selected sheets and the difference between jobs are within allowable values, so that the accuracy of the color conversion profile data can be ensured.

  FIG. 9 is an overall process flowchart of another embodiment. The difference from FIG. 8 is processing when at least one of the in-plane unevenness and the difference between jobs is equal to or greater than a threshold value.

  S201 to S204 are the same as S101 to S104 in FIG. 8, acquire RGB values, calculate ΔRGB indicating in-plane unevenness and differences between jobs, and compare this with a threshold value X. If the in-plane unevenness and the difference between jobs are smaller than the threshold value X, a colorimetric chart is set in the same manner as in FIG. 8, and the color patch for obtaining the Lab value is measured, and profile data is created (S205 to S207). ).

  On the other hand, if at least one of the in-plane unevenness and the difference between jobs is greater than or equal to the threshold value X in S204 (NO in S204), the process returns to S201 again to output the chart and re-acquire the RGB values. And the difference between jobs is calculated. Then, the in-plane unevenness and the difference between jobs are compared with the threshold value again. If it is smaller than the threshold value X, the processing from S205 is executed, and if not, the processing returns to S201 again. That is, the chart output is repeated until the in-plane unevenness and the difference between jobs become smaller than the threshold value X. Of course, it is useless to repeat the process indefinitely, so it is preferable to set the upper limit of the chart to be output and repeat until the upper limit is reached. If it is equal to or greater than the threshold value, the Lab value is acquired using the color patch 22 for acquiring the RGB value as in FIG. 8, and profile data is created.

  Although the embodiment of the present invention has been described above, the image forming apparatus 10 of the present embodiment is connected to a color management server via a network, and the image forming apparatus 10 outputs a color patch to perform color measurement, and performs color measurement. The present invention can also be applied to a system that transmits data to a color management server and periodically and remotely manages the state of the image forming apparatus 10 on the color management server side.

  DESCRIPTION OF SYMBOLS 10 Image forming apparatus, 22 RGB value acquisition color patch, 24, 24a, 24b Lab value acquisition color patch, 30 Evaluation color patch, 32 Identification patch, 101 Color conversion part, 102 Print engine, 103 Color patch Reading unit, 104 storage unit, 105 control unit, 106 user interface unit, 107 colorimeter.

Claims (13)

A printing unit that arranges a plurality of evaluation color patches of the same color value on a color patch and prints them on paper;
Read the color values of the printed the evaluation color patches, and a control unit that creates a color conversion profile data using the color patches of the paper color value difference which is a difference between the color value is less than the allowable value,
Equipped with a,
The printing unit is an image forming apparatus that prints by arranging the evaluation color patch at the same position on different sheets . A printing unit that arranges a plurality of evaluation color patches of the same color value on a color patch and prints them on paper;
A controller that reads the color value of the printed evaluation color patch and creates color conversion profile data using a color patch of a paper whose color value difference is equal to or less than an allowable value;
With
The image forming apparatus that arranges and prints the evaluation color patch at different positions on the same sheet and at the same position on different sheets . The image forming apparatus according to claim 2 , wherein the printing unit arranges and prints the evaluation color patch in at least one of a vertical direction, a horizontal direction, and an oblique direction as different positions on the same sheet . The control unit uses a color patch of a sheet in which the smallest color value difference among all possible combinations of the evaluation color patches arranged at the same position of the different sheets is equal to or less than an allowable value. The image forming apparatus according to claim 1 , wherein the color conversion profile data is created . The printing unit, when the color value difference is not less than the allowable value, the image forming apparatus according to any one of claims 1 to print the color patch repeated until the allowable value or less in the paper. A printing unit that arranges a plurality of evaluation color patches of the same color value on a color patch and prints them on paper;
A controller that reads the color value of the printed evaluation color patch and creates color conversion profile data using a color patch of a paper whose color value difference is equal to or less than an allowable value;
With
The printing unit prints a first color space value acquisition color patch and a second color space value acquisition color patch as the color patch,
The control unit is obtained by measuring the first color space value obtained by reading the color patch for acquiring the first color space value and the color patch for acquiring the second color space value. An image forming apparatus that creates the color conversion profile data from the second color space value . The printing unit includes a color patch of the first color space values for obtaining, in claim 6, wherein the second color patches of the color space values for the acquired print on the same sheet, and to print across multiple sheets of paper The image forming apparatus described. The image forming apparatus according to claim 7 , wherein the evaluation color patch is arranged in the color patch for obtaining the first color space value . The image forming apparatus according to claim 7 , wherein the printing unit further prints an identification patch for identifying each of the plurality of sheets . The first color space is a device dependent color space;
The image forming apparatus according to claim 6 , wherein the second color space is an apparatus-independent color space . The first color space is RGB;
The image forming apparatus according to claim 10 , wherein the second color space is Lab . On the computer,
A step of arranging a plurality of evaluation color patches having the same color value on a color patch and printing them on a sheet, and a step of arranging and printing the evaluation color patches on the same position on different sheets; and
Reading the color value of the printed evaluation color patch, and creating color conversion profile data using a color patch of the paper whose color value difference is equal to or less than an allowable value;
A program that executes On the computer,
A step of arranging a plurality of evaluation color patches having the same color value on a color patch and printing them on a paper, and placing and printing the evaluation color patches at different positions on the same paper and at the same positions on different papers. When,
Reading the color value of the printed evaluation color patch, and creating color conversion profile data using a color patch of the paper whose color value difference is equal to or less than an allowable value;
A program that executes