JP5968288B2 - Patch chart, calibration method, and chart data generation apparatus - Google Patents

Description

  The present invention relates to a patch chart, a calibration method, and a chart data generation device.

  In a certain calibration method, a patch chart is printed on an image forming apparatus to be calibrated, the printed patch chart is color-measured, and calibration is performed based on the color measurement result (see, for example, Patent Document 1). .

  In such a chart, a method has been proposed in which a reference patch is arranged around the measurement patch, and the colorimetric value of the measurement patch is corrected based on the colorimetric value of the reference patch (see, for example, Patent Document 2).

JP 2009-213055 A JP 2009-219090 A

  However, in the above-described method using the reference patch, there is a gap between the reference patch and the measurement patch, and the area of the reference patch is large, so the number of measurement color patches that can be included in one patch chart. Will decrease. Further, in the electrophotographic image forming apparatus, the edge effect becomes large at both ends of the gap (that is, the edges of the measurement patch and the reference patch), and the calibration accuracy is lowered. In particular, in an image forming apparatus in which in-plane unevenness occurs due to the use environment or the like, the density variation of the in-plane unevenness is not corrected, and the calibration accuracy is lowered.

  The present invention has been made in view of the above problems, and can effectively suppress the influence of density fluctuations due to in-plane unevenness while increasing the number of measurement color patches. It is an object of the present invention to obtain a patch chart with good accuracy, a calibration method using the patch chart, and a chart data generation device that generates data of the patch chart.

  The patch chart according to the present invention includes a plurality of blocks arranged two-dimensionally. The block has N (N> 1) patches arranged without gaps in the main scanning direction and the sub-scanning direction, respectively. The plurality of blocks all have only one reference patch for correcting the measurement value by the measurement color patch at the same position, and the reference patch is one of the patches located at the four corners of the block. The patches other than the reference patch in the block are measurement color patches.

  In the calibration method according to the present invention, the patch chart is printed on an image forming apparatus to be calibrated, the measurement color patch and the reference patch in the patch chart are measured, and a plurality of peripherals around the measurement color patch are measured. An interpolated value of the colorimetric value of the reference patch at the position of the measurement color patch is determined from the colorimetric value of the reference patch, and the amount of variation in the colorimetric value of the reference patch and the position of the measurement color patch are determined. The colorimetric value at the position of the measurement color patch corresponding to the error between the interpolated value and the standard colorimetric value of the reference patch based on the conversion data indicating the relationship between the colorimetric value variation amount of The variation amount is specified, the colorimetric value of the measurement color patch is corrected by the specified variation amount, and calibration is performed with the corrected colorimetric value of the measurement color patch.

  The chart data generation apparatus according to the present invention generates chart data for causing the image forming apparatus to be calibrated to print the patch chart.

  According to the present invention, it is possible to satisfactorily suppress the influence of density fluctuations caused by in-plane unevenness while increasing the number of measurement color patches, and consequently, a patch chart with good calibration accuracy, and the patch A calibration method using a chart and a chart data generation device for generating data of the patch chart can be obtained.

FIG. 1 is a block diagram showing the configuration of a system including a chart data generation device that generates patch chart data and an image forming device to be calibrated according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of a patch chart according to the embodiment of the present invention. FIG. 3 is a flowchart illustrating calibration of the image forming apparatus 2 using the patch chart according to the embodiment of the present invention. FIG. 4 is a diagram illustrating a part of an example of a patch chart according to the second embodiment. FIG. 5 is a diagram illustrating a part of another example of the patch chart according to the second embodiment.

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

Embodiment 1 FIG.

  FIG. 1 is a block diagram showing the configuration of a system including a chart data generation device that generates patch chart data and an image forming device to be calibrated according to an embodiment of the present invention.

  In FIG. 1, a chart data generation device 1 includes a chart data generation unit 11 that generates patch chart data, a chart data storage unit 12 that stores patch chart data generated by the chart data generation unit 11, and a communication device 13. Is provided. The chart data generation unit 11 is configured by a computer or the like, and the chart data storage unit 12 is configured by a volatile memory or a nonvolatile memory. The communication device 13 is a network interface or a peripheral device interface, and is used to transmit patch chart data to the image forming apparatus 2.

  The patch chart data generated by the chart data generation unit 11 is patch chart printing data according to the embodiment of the present invention. FIG. 2 is a diagram showing an example of a patch chart according to the embodiment of the present invention. As shown in FIG. 2, the patch chart includes a plurality of blocks arranged two-dimensionally, and each block has N blocks (N> 1, N> 1, respectively) arranged without gaps in the main scanning direction and the sub-scanning direction. Here, N = 2) patches are provided. Further, the plurality of blocks all have the same position (the position of the upper left corner in FIG. 2) at the same position (reference patch in FIG. 2) for correcting the measurement value by the measurement color patch (white patch in FIG. 2). The reference patch is any one of the patches located at the four corners of the block. Further, patches other than the reference patch in each block are measurement color patches.

  For example, a patch chart is generated for each toner color of the image forming apparatus 2 to be calibrated.

  Further, the density of the plurality of reference patches is constant and 50% of the maximum density. For example, when the pixel value of the maximum density is 255, the pixel value of the reference patch is 128.

  The density of the plurality of measurement color patches is a predetermined gradation value, for example, obtained by dividing the minimum density from 0% to the maximum density of 100% into N equal parts (32 equal parts, 64 equal parts, 255 equal parts, etc.). It is done. One density may be assigned to one measurement color patch, or may be assigned to a plurality of measurement color patches.

  The plurality of measurement color patches may be arranged at random, or may be arranged in descending or increasing order of density along the main scanning direction and the sub scanning direction, or along the main scanning direction and the sub scanning direction. Alternatively, the descending order and the ascending order of the concentration may be alternately selected and arranged.

  For example, the chart data generation unit 11 has coordinates {x, y} (x indicating the position of the patch in units of a predetermined number of pixels along the main scanning direction and the sub scanning direction along the main scanning direction and the sub scanning direction. , Y are integers), a reference patch is arranged at a position where both x and y are odd numbers (mod (x, N) = mod (y, N) = N−1), and other positions The patch chart data is generated by arranging the measurement color patches.

  (1) A reference patch is placed at a position where both x and y are even numbers (position where mod (x, N) = mod (y, N) = 0), and the measurement color is located at other positions. Patch chart data may be generated by arranging patches, or (2) a position where x is an odd number and y is an even number (mod (x, N) = N−1, mod (y, The patch chart data may be generated by arranging the reference patch at the position N) = 0) and the measurement color patch at the other positions, or (3) x is an even number. Yes, a reference patch is placed at a position where y is an odd number even (mod (x, N) = 0, mod (y, N) = N−1), and a measurement color patch is placed at any other position. The patch chart data may be generated by arranging them.

  The image forming apparatus 2 includes a printing device 21, a controller 22, a communication device 23, a storage device 24, and the like that print an image on paper using an electrophotographic method. The controller 22 generates image data of the print image from the print data based on the characteristic data 25 (color conversion table or the like) stored in the non-volatile storage device 24, and sends the image data to the printing device 21. Print the image based on. The communication device 23 is a network interface or a peripheral device interface, and is used to receive printing data such as patch chart data.

  The measurement value correction device 3 includes an input / output unit 31, a measurement value correction unit 32, a storage device 33, and the like. The input / output unit 31 is a network interface, a peripheral device interface, and the like, and inputs and outputs various data. The input / output unit 31 is used to input the color measurement result of the patch chart printed by the image forming apparatus 2 and to output the color measurement data obtained by correcting the color measurement result. The measurement value correction unit 32 is configured by a computer or the like, and corrects the color measurement result of the patch chart printed by the image forming apparatus 2 using the conversion data 34 stored in the non-volatile storage device 33.

  The conversion data 34 is data indicating the relationship between the amount of change in the colorimetric value of the reference patch due to in-plane unevenness and the amount of change in the colorimetric value at the position of the measurement color patch, and image formation without in-plane unevenness. It is derived in advance from the color measurement result by the apparatus and the color measurement result by the image forming apparatus having in-plane unevenness.

  Here, the derivation of the conversion data 34 will be described.

  In coordinates {x, y} (x and y are integers) indicating the position of the patch in units of a predetermined number of pixels along the main scanning direction and the sub scanning direction, one of x and y is an odd number and the other is an even number. The above-mentioned reference patch is arranged at a certain position, and the respective charts in which the density of an area other than the reference patch (hereinafter referred to as a non-reference patch portion) is set discretely from 0% to 100% Printing is performed by an image forming apparatus having no unevenness and an image forming apparatus having in-plane unevenness. It should be noted that the density of the non-reference patch portion may be changed at equal intervals, for example, at different intervals such as 0%, 10%, 20%, 40%, 60%, 80%, 90%, and 100%. It may be changed.

  For each density, the amount of change in the colorimetric value of the reference patch due to in-plane unevenness, and the colorimetric value at the position of the measurement color patch adjacent to the reference patch in the above-mentioned patch chart in the non-reference patch part Conversion data that specifies the amount of variation and expresses the correspondence between the amount of variation in the colorimetric value of this reference patch and the amount of variation in the colorimetric value at the position of the measurement color patch, using a lookup table, formula, etc. 34.

  In this way, the conversion data 34 is generated.

  At this time, a chart in which only the reference patch is arranged on the entire surface only at the reference patch arrangement position of the above-described patch chart or only at the reference patch arrangement position of the conversion data 34 creation chart described above Printing is performed with an image forming apparatus having no internal unevenness, and the standard colorimetric value is specified from the colorimetric result of the reference patch in the chart. For example, the standard colorimetric value is an addition average, geometric average, mode value in a histogram of colorimetric values, or the like of the reference patches in the chart.

  Here, the chart data generation device 1 and the measurement value correction device 3 are different devices from the image forming device 2, but the functions of the chart data generation device 1 and the measurement value correction device 3 are as follows. You may make it incorporate in the image forming apparatus 2. FIG.

  Next, calibration of the image forming apparatus 2 using the above-described patch chart will be described. FIG. 3 is a flowchart illustrating calibration of the image forming apparatus 2 using the patch chart according to the embodiment of the present invention.

  First, the chart data generation device 1 described above generates patch chart data (step S1), the patch chart data is transmitted to the image forming device 2, and the image forming device 2 prints a patch chart based on the patch chart data. (Step S2).

  Next, the printed patch chart is measured by a colorimeter (not shown) (spectral colorimeter, density system, etc.) (step S3). Thereby, the density value, CIEXYZ value, LAB value, spectral spectrum, etc. of each patch are obtained.

  This color measurement result is input to the measurement value correction device 3 and corrected by the color measurement value correction unit 32 (step S4).

  Specifically, based on the color measurement result, the color measurement value correction unit 32 interpolates the color measurement value of the reference patch at the position of the measurement color patch from the color measurement values of the plurality of reference patches around the measurement color patch. The value is specified, and based on the conversion data 34, the amount of change in the colorimetric value at the position of the measurement color patch corresponding to the error between the interpolated value and the standard colorimetric value of the reference patch is specified and specified. The colorimetric value of the measurement color patch is corrected by the amount of variation.

  For example, when the color measurement result is three-dimensional data, and the reference patch is adjacent to the upper and lower sides of the measurement color patch, the above-described interpolation value is calculated by the following equation.

{Xa, Ya, Za} = ({Xup, Yup, Zup} + {Xdown, Ydown, Zdown}) / 2

  When the reference patch is adjacent to the left and right sides of the measurement color patch, the above-described interpolation value is calculated by the following equation.

{Xa, Ya, Za} = ({Xleft, Yleft, Zleft} + {Xright, Yright, Zright}) / 2

  Further, when the reference patch is not adjacent to any of the upper, lower, left, and right sides of the measurement color patch, the above-described interpolation value is calculated by the following equation.

{Xa, Ya, Za} = ({Xleft-up, Yleft-up, Zleft-up} + {Xright-up, Yright-up, Zright-up} + {Xleft-down, Yleft-down, Zleft-down} + {Xright-down, Yright-down, Zright-down)} / 4

  In the above formula, {Xa, Ya, Za} are interpolation values, {Xright, Yright, Zright} are colorimetric values of the reference patch on the right side of the measurement color patch, and {Xleft, Yleft, Zleft } Is the colorimetric value of the reference patch on the left side of the measurement color patch, {Xup, Yup, Zup} is the colorimetry value of the reference patch above the measurement color patch, and {Xdown, Ydown, Zdown} is the measurement color This is a colorimetric value of the reference patch below the patch. Further, {Xleft-up, Yleft-up, Zleft-up} is a colorimetric value of a reference patch adjacent to the upper left of the measurement color patch, and {Xright-up, Yright-up, Zright-up} is a measurement color patch. , {Xleft-down, Yleft-down, Zleft-down} are the colorimetric values of the reference patch adjacent to the lower left of the measurement color patch, {Xright-down, Yright-down, Zright-down)} is a colorimetric value of a reference patch adjacent to the lower right of the measurement color patch.

  Further, the interpolated value may be other than the addition average. For example, when the color measurement result is all positive data such as the CIEXYZ value, it may be a geometric average.

  Then, the color measurement data including the color measurement values of the corrected measurement color patch is output from the measurement value correction apparatus 3, and the characteristic data 25 of the image forming apparatus 2 is updated based on the color measurement data (step S5). . The controller 22 of the image forming apparatus 2 may update the characteristic data 25 based on the colorimetric data, or new characteristic data is generated from the colorimetric data by an apparatus other than the image forming apparatus 2, The characteristic data 25 in the image forming apparatus 2 may be updated with the generated characteristic data.

  As described above, the patch chart according to Embodiment 1 includes a plurality of blocks arranged two-dimensionally. Each block has N (N> 1) patches arranged without gaps in the main scanning direction and the sub-scanning direction. The plurality of blocks have only one reference patch for correcting the measurement value by the measurement color patch at all the same positions, and the reference patch is one of the patches located at the four corners of the block. The patches other than the reference patch in the block are measurement color patches.

  Accordingly, it is possible to satisfactorily correct the density fluctuation caused by the in-plane unevenness while increasing the number of measurement color patches in the patch chart, and the calibration accuracy of the image forming apparatus is improved.

Embodiment 2. FIG.

  FIG. 4 is a diagram illustrating a part of an example of a patch chart according to the second embodiment.

  As shown in FIG. 4, in the patch chart according to the second embodiment, the measurement color patch 101 in which all the adjacent patches 111 to 114 adjacent in the main scanning direction and the sub scanning direction are measurement color patches, and the adjacent patches 111 to 114 are displayed. An intermediate density region 121 is provided at the boundary between the two.

  The intermediate density region 121 has a predetermined width, and here has a density of 50%.

  Of the above-mentioned boundaries, the intermediate density region may not be provided for those whose density change at the boundary is smaller than a predetermined threshold.

  FIG. 5 is a diagram illustrating a part of another example of the patch chart according to the second embodiment. When the density of the measurement color patch gradually changes along the main scanning direction, the intermediate density region 121 is not provided at the boundary between the measurement color patches arranged in the main scanning direction as shown in FIG. It may be.

  Note that the patch chart, the calibration method, and the other configuration of the chart data generation device 1 according to the second embodiment are the same as those of the first embodiment, and thus the description thereof is omitted.

  As described above, according to the second embodiment, the density change at the boundary between the measurement color patch and the measurement color patch is reduced, and the edge effect at the boundary is reduced.

Embodiment 3 FIG.

  In the patch chart according to the third embodiment, the density of the above intermediate density region is the average of the density of the measurement color patches on both sides of the boundary where the intermediate density region is provided.

  Note that the patch chart, the calibration method, and the other configuration of the chart data generation device 1 according to the third embodiment are the same as those of the second embodiment, and thus the description thereof is omitted.

  As described above, according to the third embodiment, the density change at the boundary between the measurement color patch and the measurement color patch is reduced, and the edge effect at the boundary is reduced.

  Each of the above-described embodiments is a preferred example of the present invention, but the present invention is not limited thereto, and various modifications and changes can be made without departing from the scope of the present invention. It is.

  For example, in the above embodiment, the above N is 2, but it may be 3 or more.

  The present invention is applicable to, for example, calibration of density and color in an image forming apparatus.

1 Chart Data Generation Device 2 Image Forming Device 25 Characteristic Data 34 Conversion Data

Claims (7)

A plurality of blocks arranged two-dimensionally,
The block has N (N> 1) patches arranged without gaps in the main scanning direction and the sub-scanning direction, respectively.
The plurality of blocks all have only one reference patch for correcting a measurement value by a measurement color patch at the same position,
The reference patch is any one of patches located at four corners of the block;
Patches other than the reference patch in the block are measurement color patches,
A patch chart characterized by   The patch chart according to claim 1, wherein the density of the reference patch is constant and 50%.   An intermediate density region is provided at a boundary between the measurement color patch in which all adjacent patches adjacent in the main scanning direction and the sub-scanning direction are the measurement color patch and the adjacent patch. Item 3. The patch chart according to item 1 or item 2.   4. The patch chart according to claim 3, wherein the intermediate density region is not provided for a boundary whose density change at the boundary is smaller than a predetermined threshold value.   5. The patch chart according to claim 3, wherein the density of the intermediate density region is an average of the densities of the measurement color patches on both sides of the boundary where the intermediate density region is provided. The patch chart according to any one of claims 1 to 5 is printed on a calibration target image forming apparatus,
Measuring the measurement color patch and the reference patch in the patch chart;
Identifying the interpolated value of the colorimetric value of the reference patch at the position of the measurement color patch from the colorimetric values of the plurality of reference patches around the measurement color patch,
Based on the conversion data indicating the relationship between the amount of change in the colorimetric value of the reference patch and the amount of change in the colorimetric value at the position of the measurement color patch, the interpolated value and the standard colorimetric value of the reference patch The amount of change in the colorimetric value at the position of the measurement color patch corresponding to the error of
Correct the colorimetric value of the measurement color patch by the specified variation amount,
Performing calibration with the colorimetric values of the corrected measurement color patches;
A calibration method characterized by   6. A chart data generating apparatus for generating chart data for causing the image forming apparatus to be calibrated to print the patch chart according to any one of claims 1 to 5.

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