JP2015080051A - Information processor and colorimetry chart creation method and colorimetry chart - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that one patch size is reduced when a number of patches required for calibration are arranged, and the operability degrades, in a color chart where a color patch for use in color calibration is arranged.SOLUTION: In a test chart for color calibration, patches are arranged in a grid. In the scanning direction of a colorimetry device, slits are provided between the patches. Furthermore, guides (1202, 1203) indicating the width of the colorimetry device, when scanning the patch line, are arranged in the slit. Preferably, each patch line is composed of patches of one color component of different density, and a guide for scanning the line is composed of the same color as that of the patch line.

Description

  The present invention relates to an information processing apparatus, a colorimetry chart creation method, and a colorimetry chart related to a technique for correcting the color of an image forming apparatus such as a printer.

  In an electrophotographic color image forming apparatus, a slight change in the environment causes a change in the output density. Therefore, it is necessary to have means for keeping the gradation of the output density constant. Therefore, as a means therefor, some conventional color image forming apparatuses are equipped with a calibration mechanism for performing color calibration (hereinafter simply referred to as calibration). In calibration, an image forming apparatus to be calibrated uses a chart composed of patches of data of different gradations corresponding to toners of C (cyan), M (magenta), Y (yellow), and K (black). The output chart is read using a measuring instrument such as a densitometer independent of the image forming apparatus. A LUT (Look Up Table) for correcting gradation independently of CMYK is created by comparing the read value with target data that is held in advance. The image forming apparatus forms an image by performing gradation correction using the created LUT. The LUT is a table indicating output data corresponding to input data divided at specific intervals, and can express non-linear characteristics that cannot be expressed by arithmetic expressions. The input signal values of C, M, Y, and K are converted into output signal values on the image forming apparatus side that can be expressed.

  Since the calibration technique uses a chart composed of a plurality of patches having different gradations, if the number of gradations of the LUT is larger than the number of patches to be arranged, intermediate gradation values that are not formed as patches are obtained by interpolation calculation. Calculated. When the number of patches is small, the halftone value calculated by interpolation increases, so that the calibration accuracy decreases. Therefore, it is ideal to place more patches on the chart in order to increase the calibration accuracy, but in order to place many patches on a limited size chart, the individual patch size must be reduced. There is a need to.

  In the process of performing the calibration, user work such as directly measuring the output chart with a densitometer is involved. Therefore, an artificial measurement error may occur. For example, when measuring each color patch of a color chart in which color patches are arranged in multiple columns using a measuring instrument in units of one column, the color patch in a column different from the original measurement column is measured incorrectly. May end up.

  In some cases, different patches cannot be distinguished because the scanning speed of the patches is too high. In the measuring device, the user scans the measuring device to read the patch, and the measuring device identifies the breaks between patches of different gradation values arranged in each column. In order to facilitate identification of patch breaks, it is necessary to arrange patches called slits between patches having different gradations in the scanning direction. The slit is composed of a color having a large density difference or color difference with respect to adjacent patches. In other words, the measuring device identifies that the patch has been switched if there is a large change in lightness or color difference during scanning. For this reason, if the scanning speed is too high, the slit cannot be identified, and a plurality of patches having different gradations are read as one patch. As a result, the number of patches to be read is insufficient, or a colorimetric value different from the gradation value (density value) of the patch to be read is obtained.

  As described above, if the patch size is reduced, the possibility of these artificial measurement errors increases. In addition, if a correction LUT is created using these measured values, the accuracy of the correction LUT is significantly reduced. When printing is performed using the correction LUT created here, the gradation property of the density and the stability of the color tone, which are the original purposes of calibration, are greatly impaired.

  As one of the methods for dealing with these problems, a gap image is arranged between the patches, and the measuring instrument is based on the colorimetric value when the gap image is read and the reference colorimetric data acquired in advance. A technique for determining whether or not the patch has passed has been proposed (Patent Document 1).

  In addition, a technique has been proposed in which a plurality of color samples are measured a plurality of times, state information indicating the state of the colorimeter is acquired from the acquired measurement data, and evaluation information for the colorimetric skill is generated from the acquired state information. (Patent Document 2).

JP 2012-205221 A JP 2012-37437 A

  However, in Patent Document 1, when the colorimetric value obtained by measuring the gap image is compared with the reference colorimetric data, and the comparison result determines that the colorimeter has not passed through the patch, Colorimetric values when measuring colors are excluded. As a result, it is possible to acquire only a smaller number of patches than the number of patches originally supposed to be arranged, and the calibration accuracy may be lowered.

  Further, in Patent Document 2, an evaluation result for colorimetry is generated and the user is notified of the colorimetry skill to be improved. However, when the colorimetric patch is small, it is not easy to reduce colorimetry errors. It was.

  Although the present invention has been made in view of the above-described conventional examples, it is possible to reduce the occurrence of scanning errors during calibration and improve the calibration accuracy without causing the problems of the conventional techniques described in these documents. It is an object of the present invention to provide an information processing apparatus, a colorimetry chart creation method, and a colorimetry chart capable of performing the above.

  In order to achieve the above object, the present invention has the following configuration.

An information processing apparatus for performing color calibration of an image forming apparatus that outputs an image formed on a sheet based on a colorimetric value obtained by measuring a colorimetric chart output by the image forming apparatus by a colorimetric device. There,
Generating means for generating image information of a colorimetric chart in which patches are arranged in a lattice pattern and guides are arranged along the rows of the patches;
Means for causing the image forming apparatus to output a color measurement chart based on image information of the color measurement chart;
The guide is disposed at least in a slit that is a gap between adjacent patches in the direction of the guide.

  According to another aspect, the present invention has the following configuration.

A color measurement chart for performing color calibration of an image forming apparatus that outputs an image formed on a sheet based on a color measurement value obtained by measuring a color measurement chart output by the image forming apparatus with a color measurement apparatus. There,
Grid-like patches and guides along the rows of the patches are arranged,
The guide is disposed at least in a slit that is a gap between adjacent patches in the direction of the guide.

  According to the present invention, it is possible to provide a color chart that can reduce the occurrence of scanning errors.

1 is an overall view of a calibration system. 1 is a block configuration diagram of an image forming apparatus. It is a block block diagram of PC. It is a block diagram of an image processing part. It is a block diagram of 1D-LUT. It is a control flow of PC at the time of calibration. It is a control flow at the time of chart information generation. 6 is a control flow of the image forming apparatus during calibration. It is an external view of a color measuring device. It is an example of the chart used for colorimetry. It is an example of the scanning mistake of a colorimetry apparatus. 3 is an example of installation of a scanning guide in Embodiment 1. FIG. 6 is an example of a patch size lower limit calculation method according to the first embodiment. 10 is a control flow at the time of a colorimetric error in the second embodiment. 10 is an example of a UI screen according to the second embodiment. 10 is a control flow at the time of a colorimetric error in the third embodiment. It is explanatory drawing of 1D-LUT.

[First Embodiment]
Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of a calibration system suitable for applying the present embodiment. A PC (Personal Computer) 101 that is an information processing apparatus is connected to a LAN 106 and causes a color measurement chart to be printed on a sheet by the image forming apparatus 105, and a color measurement value from a color measurement apparatus (also referred to as a measurement apparatus) 102. And a calibration process for transmitting the color measurement result to the image forming apparatus 105 is performed. On the OS (Operating System) of the PC 101, a calibration application for executing color calibration (hereinafter simply referred to as calibration) is operating. The internal configuration of the PC will be described later with reference to FIG. The input device 103 is a keyboard or a mouse, for example, and notifies the PC 101 of operation instructions from the colorimeter. The display device 104 is a display for the calibration application to display operation instructions for the colorimeter. These provide a user interface for the user. The colorimetric device 102 is a colorimeter such as a spectrophotometer or a densitometer, and each can acquire a density value or a Lab value directly or by calculating a measured value.

  FIG. 9A shows the appearance of the color measuring device 102 used in this embodiment. A colorimetric device 102 shown in the present embodiment can be operated by a colorimeter with one hand, and includes a sensor 901, a measurement switch 902, and a light source (not shown). A light source (not shown) is configured by an LED or the like, and irradiates light to a color chart disposed at the lower part of the color measuring device 102. The sensor 901 is disposed on the bottom surface of the color measuring device 102, receives reflected light with respect to the light irradiated on the color chart, and converts the reflected light into an analog signal. Further, the colorimetric device 102 is provided with an A / D conversion unit (not shown), which converts an analog signal measured by the sensor 901 into a digital signal and outputs it to the PC 101 via the USB cable 903. The color measurement device 102 outputs a color measurement value while the measurement switch 902 is pressed. Further, the color measuring device 102 has a line scan function for measuring the color patch while being slid on the color chart. That is, while the measurement switch 902 is being pressed, it is possible to specify the patch portion and measure the color of the patch portion by performing color measurement at a predetermined sampling interval. Note that the patches are arranged in a grid pattern on the chart.

  FIG. 9B shows an example of a color measuring device having a shape different from that of the color measuring device shown in FIG. The configuration of the color measurement device 102 shown in FIG. 9B is the same as that of the color measurement device shown in FIG.

<Image forming apparatus>
FIG. 2 is a diagram showing a system configuration of an image forming apparatus 105 suitable for applying this embodiment. The controller 201 is a controller that inputs and outputs colorimetric data, image data, and device information by connecting to a printer 202 that is an image output apparatus and on the other hand to a LAN 106. The CPU 203 functions as a controller that controls the entire image forming apparatus 105. A RAM (Random Access Memory) 204 is controlled by the CPU 203 and is used as a temporary storage of control data or a work memory. A ROM (Read Only Memory) 205 stores a program executed by the CPU 203. An HDD 206 is a hard disk drive that stores system software, image data, and the like. A network I / F 210 is connected to the LAN 106 and inputs / outputs information. The above configuration is arranged on the system bus 211. An image bus I / F 207 is a bus bridge that connects a system bus 211 and an image bus 212 that transfers image data at high speed and converts a data structure. The image bus 212 is configured by a high-speed bus such as a PCI bus or IEEE1394. A device I / F unit 209 connects the printer 202, which is an image output device, and the controller 201, and performs synchronous / asynchronous conversion of image data. The image processing unit 208 corrects, processes, and edits input image data, and performs processing suitable for subsequent print output or image transmission. The configuration of the image processing unit 208 will be described later with reference to FIG.

<Image processing unit>
FIG. 4 is a block diagram illustrating a configuration of the image processing unit 208 of the image forming apparatus 105. When print data is input to the image forming apparatus 105, a raster image is input to the image processing unit 208. The image processing unit 208 includes at least a color conversion unit 401, a 1D-LUT correction unit 402, and a halftone processing unit 403. The color conversion unit 401 converts the input RGB color space image data into the CMYK color space. When the input image data is in the CMYK color space, the color conversion unit 401 is skipped. The CMYK data subjected to color space conversion is subjected to gradation correction for each of C, M, Y, and K in the 1D-LUT correction unit 402, and converted to C2, M2, Y2, and K2, respectively. For example, when the input signal of the 1D-LUT is 8-bit data, the number of entries of the 1D-LUT is preferably 256 from 0 to 255. That is, it is preferable that one output value is stored for every input value. The correction LUT obtained as a result of color calibration is applied by the 1D-LUT correction unit 402. In the halftone processing unit 403, C2, M2, Y2, and K2 data are subjected to screen processing using a dither pattern or the like.

  Here, the 1D-LUT generation method will be described with reference to FIG. FIG. 17A shows the relationship between ideal target characteristics of the image forming apparatus 105 and density characteristics (engine characteristics) output from the image forming apparatus 105. Further, a relationship of a 1D-LUT (correction LUT) for correcting the density characteristic output from the image forming apparatus 105 to the target characteristic is shown. These characteristics indicate density values actually formed as an image with respect to the output signal value. Here, the more sampling points for measuring the engine characteristics, the more accurately the engine characteristics can be detected. Accordingly, the accuracy of the 1D-LUT for correction can be improved accordingly.

  FIG. 17B shows an example when the sampling points for measuring the engine characteristics are small, and FIG. 17C shows an example when the sampling points for measuring the engine characteristics are sufficiently large. When the number of sampling points is small as shown in FIG. 17B, the gradation value between the sampling points is calculated by, for example, linear interpolation, and thus deviates from the actually output engine characteristics. For this reason, the 1D-LUT generated from the measured engine characteristics is also low in accuracy. On the other hand, when the sampling points for measuring the engine characteristics are sufficient as shown in FIG. 17C, the engine characteristics can be accurately measured, and the accuracy of the generated 1D-LUT is increased.

  FIG. 5 is a schematic diagram showing the input / output relationship of the 1D-LUT correction unit 402. FIG. 5 shows that one output is made for one input. That is, four 1D-LUTs for each color component are independent for C input C2 output, M input M2 output, Y input Y2 output, and K input K2 output.

<Internal configuration of PC>
FIG. 3 is a diagram showing an internal configuration of the PC 101 suitable for applying this embodiment. The CPU 301 functions as a controller that controls the entire PC 101. A RAM 302 is controlled by the CPU 301 and is used as a temporary storage of control data or a work memory. The ROM 303 stores a program executed by the CPU 301. An HDD 304 is a hard disk drive that stores system software, colorimetric data, and the like. A network I / F 305 is connected to the LAN 106 and inputs / outputs information. A video card (VC) 306 controls display on the display device 104. A USB I / F 307 controls communication with a USB device. Here, an input device 103 such as a keyboard and a mouse, a color measurement device 102, and the like are connected to the PC 101 via the USB I / F 307. The above configuration is arranged on the system bus 308.

<Control flow>
Control by the CPU 301 in the PC 101 will be described. FIG. 6A is a diagram illustrating a control flow of the CPU 301 that controls the operation of creating a colorimetric chart from the PC 101 to the time of chart printing on the image forming apparatus 105. The operation in each step of this flowchart is realized by the CPU 301 developing and executing the program stored in the ROM 303 on the RAM 204.

  The CPU 301 receives a colorimetry device selection signal from the input device 103 (step S601). The CPU 301 determines the received colorimetric device selection signal (step S602). If the colorimetric device A is selected as a result of the determination, the colorimetric device A information is acquired (step S603). On the other hand, if the color measuring device B is selected, the color measuring device B information is acquired (step S604). It is assumed that the color measuring device A information and the color measuring device B information are stored in the HDD 304 in advance. Here, the color measurement device information is information including the color measurement device width of the color measurement device 102, the opening width 1005 of the color measurement device 102, and the color measurement sampling speed of the color measurement device 102. The color measuring device width is the width of the color measuring device 102 in the direction orthogonal to the scanning direction in which the color measuring device 102 is scanned. The opening width is a width in the same direction as the color measuring device width of the opening for receiving light by the sensor 901. For example, if the opening with respect to the sensor 901 is circular, the diameter is the same. The colorimetric sampling speed is the number of samplings per fixed time by the colorimetric device 102. These values are registered in advance in the PC 101 when the colorimetric device 102 is connected, stored in a nonvolatile memory or the like of the colorimetric device 102, or held in a server that can be connected via the Internet or the like. In this embodiment, the two color measuring devices A and B are taken as an example, but the present invention is not limited to this, and one or three or more color measuring devices can be selected. It's okay.

  Next, the CPU 301 generates chart information based on the colorimetric device information acquired in step S603 or step S604 (step S605). The chart information generation flow will be described later with reference to FIG. The CPU 301 makes a chart print request to the image forming apparatus 105 based on the chart information generated in step S605 (step S606). The chart information is image information such as vectors and images corresponding to the chart.

  FIG. 6B is a diagram illustrating a control flow of the CPU 301 that controls an operation from acquiring a colorimetric value from the colorimetric device 102 and transmitting a measurement result to the image forming apparatus 105. The CPU 301 acquires colorimetric values obtained by scanning the color patches on the color chart from the colorimetric device 102 (step S607). Next, the CPU 301 transmits the color measurement result obtained in step S607 to the image forming apparatus 105 (step S608). The color measurement result transmitted here is the density value of each color component measured by the color measurement device 102.

  FIG. 8 shows an operation procedure performed by the image forming apparatus 105 when a chart print request is received. FIG. 8A shows a control flow of the CPU 203 from receiving a print request to outputting a chart. The CPU 203 receives a chart print request from the PC 101 (step S801). The CPU 203 transmits a pre-calibration control execution instruction to the printer 202, and the printer 202 executes the pre-calibration control (step S802). The pre-calibration control is control for setting the internal state of the printer when outputting the chart to a certain target state. The state inside the printer refers to various potential settings in an electrophotographic process for forming a toner image on an intermediate transfer belt, for example. Then, a toner image is formed on the intermediate transfer belt, and various potential settings for determining the measured value of the toner image to a target value are determined while measuring with an internal sensor (not shown). When the pre-calibration control is completed, the CPU 203 generates chart image data according to the chart information received in step S801 (step S803), and then the CPU 203 outputs a chart to the printer 202 (step S804).

  FIG. 8B shows a control flow of the CPU 203 from when the measurement value is received until the calibration is completed. The CPU 203 receives the measurement result from the PC 101 (step S805). Next, the CPU 203 generates a 1D-LUT for converting the measured engine characteristic into the target characteristic based on the measurement result received in step S805 (step S806). Next, the CPU 203 sets the 1D-LUT generated in step S807 in the 1D-LUT correction unit 402 shown in FIG. 4 (step S807).

<Color measuring method>
FIG. 10A shows a color chart measurement method using the colorimetric device 102. FIG. 10B is an enlarged view of a region surrounded by a dotted line shown in FIG. As a reading method of the colorimetric device 102, a colorimeter performs colorimetry of a plurality of calibration patches 1002 arranged on the color chart 1001 in units of columns (vertical direction in the figure) while scanning the colorimetric device 102. . The colorimeter makes the bottom surface of the color measuring device 102 closely contact the color chart 1001 and scans the color measuring device 102 along the scanning direction 1004 so that the opening 1005 for receiving light by the sensor 901 passes over the color patch 1002. . Although FIG. 10 is monochrome, it cannot be represented, but one color component patch is arranged in one column, and different color component patches are arranged in the row direction (left-right direction in the figure). In FIG. 10, patches of one color component are arranged in a line, but they can be arranged in a plurality of lines. Further, patches of different color components may be arranged in one row.

  On the color chart 1001, a slit 1003, which is a gap for detecting switching to a patch, is arranged in addition to a color patch having a specific gradation value (that is, density). The slits 1003 are arranged between the color patches 1003 arranged along the scanning direction 1004 and are formed with gradation values having a large density difference or color difference with respect to the gradation values of the patches before and after the scanning direction 1004. For example, when the tone values of the front and rear patches are dark, a light tone value is formed. On the other hand, when the front and back tone values are light, a dark tone value is formed. By disposing the slits 1003 between patches, the colorimetric device 102 can identify that the patch has been switched at a sampling point where the colorimetric value difference is large while scanning in the scanning direction 1004.

  Here, when the colorimeter performs the color measurement while scanning the color patch 1002 of the color chart 1001 along the scanning direction 1004 using the color measurement device 102, the scanning direction may be misaligned depending on the colorimetry. In some cases, colorimetric values may be acquired. For example, in the example of FIG. 10, when the scanning direction is shifted, the color of a patch of another color component is measured. When the correction LUT is generated using the colorimetric values obtained here, the accuracy of calibration is lowered. Further, even if a patch that has acquired an erroneous colorimetric value is skipped, the number of samples is reduced and the calibration accuracy is reduced. Here, skipping a patch indicates that the sampling points for measuring the engine characteristics shown in FIG. 17 are reduced.

  On the other hand, in order to increase the calibration accuracy, it is ideal that a large number of patches are arranged and that many sample points are used for calibration. However, in order to arrange many patches on the color chart, it is necessary to reduce the patch size. FIG. 11 is a diagram illustrating that the difficulty level of operability varies depending on the patch size. In FIG. 11, since the opening 1005 is located on the bottom surface of the color measuring device 102, it cannot be seen from the upper part of the color measuring device. When the patch size is larger than the width of the color measuring device 102, scanning can be performed while confirming that the color measuring device can scan the patch, so that a scanning error hardly occurs. However, when the width of the color measuring device 102 is large, it is necessary to increase the patch size accordingly. For this reason, the number of patches that can be arranged is reduced and the calibration accuracy is lowered. In order to increase the calibration accuracy, it is necessary to increase the number of patches, and accordingly, the patch size may have to be made smaller than the color measuring device width. In this case, since the patch is hidden under the color measuring device 102 when the opening 1005 passes through the patch, scanning is performed while determining whether the opening 1005 of the color measuring device 102 has passed through the patch. It becomes difficult.

  Therefore, in this embodiment, based on the colorimetric device information of the colorimetric device 102 selected by the colorimeter, the color chart is displayed so that scanning can be performed while confirming the scanning line while ensuring the number of patches necessary for calibration. A color chart having a scanning guide is provided. The scanning line is a virtual line extending in the direction in which the color measuring device 102 is scanned, and indicates the scanning direction.

  12A, 12B, 12C, 12D, and 12E show an example in which scanning guides are arranged on the color chart when the patch size is reduced. FIG. 12A shows an example in which a scanning guide is arranged when scanning a scanning line composed of magenta tone values. Here, the positions where the scanning guides are arranged are arranged from the center position 1201 of the patch on the scanning line to a position 1202 of (−color measuring device width / 2) and a position 1203 of (+ color measuring device width / 2). The reason why the guide is arranged at the ± colorimetric device width / 2 on the basis of the center position of the patch is that the opening 1005 is assumed to be substantially at the center of the bottom of the measuring device 102. Therefore, if that is not the premise, the guide is arranged so that the guide is drawn at a position corresponding to the width of the measuring apparatus 102 with the sensor 901 (or the opening 1005) placed on the patch to be measured. Is done. Information such as the amount of deviation from the center of the opening is acquired from the colorimetric device information. FIG. 12B shows an example in which a scanning guide is arranged when scanning is performed along a scanning line composed of yellow gradation values. As in FIG. 12A, the positions where the guides are arranged are the positions of (−color measuring device width / 2) and (+ color measuring device width / 2) from the center position of the patch in the yellow scanning line. .

  FIG. 12C shows an example in which guides for all scanning lines are arranged. FIG. 12D shows an example in which guides configured with the same color as the patch of each scanning line are arranged. This is to prevent the scan guide for the scan line to be read from becoming unclear when guides are arranged in the same color (for example, only black) for each scan line. Here, although the scanning guide is configured with the same color as the scanning line, for example, the scanning guide for each scanning line may be formed by dotted lines having different point intervals. In this embodiment, the scanning guide is disposed only in the slit in the scanning line. This is because the visibility of the patch decreases if the scanning guide is also disposed on the patch. In this way, by arranging a guide associated with a color measurement target patch in color or shape on a chart, the possibility of human error can be further reduced.

  FIG. 12E shows a patch arrangement when toner unnecessary for the scanning line is reduced compared to FIGS. 12C and 12D. Here, the patch portion between the guide for the scanning line and the scanning guide of the adjacent patch is reduced. Thereby, not only the guides arranged in the slits but also the edges of the patches of the adjacent scanning lines can play the role of guides, and the visibility is further improved. In addition, the amount of toner used for calibration can be reduced. In this embodiment, the patch size and the scanning guide position with respect to the scanning line are generated based on the colorimetric device information.

<Chart information generation flow>
FIG. 7 shows details of the chart information generation flow in step S605 of FIG. The CPU 301 generates a patch size from the colorimetric device information acquired in step S603 or step S604 in FIG. 6, and calculates the number of patches that can be arranged on the color chart (step S701). For example, when the paper size to be used is A4 paper (width 210 mm × height 297 mm), the patch width is 35 mm (= color measurement device width), and the patch height is 20 mm, the number of patches that can be arranged is 5 × width 12 = 60 patches. That is, when the patches are composed of single colors of cyan, magenta, yellow, and black, the number of patches that can be arranged is 15 patches for each color.

  The CPU 301 compares the number of patches calculated in step S701 with the number of patches necessary for calibration (step S702). Here, the number of patches necessary for calibration is, for example, about 20 patches for each color when there is no engine characteristic inflection point (that is, when the characteristic curve is a simple convex curve or concave curve), and there is one inflection point. If the curve is S-shaped, about 40 patches for each color are required. Therefore, engine characteristics are obtained from the sampled measurement values, and it is determined whether or not the number of patches that can be arranged on the chart is insufficient based on a predetermined number of patches corresponding to the shape of the characteristic curve (S702). If it is determined that there is no shortage (NO in step S702), the colorimetric device width is set as the patch size, and chart information is generated (step S703). If it is determined that the patch is insufficient (YES in step S702), a patch size lower limit value that can be generated from the colorimetric device information acquired in step S603 or step S604 in FIG. 6 is calculated (step S704). The patch size lower limit calculation method will be described later with reference to FIG.

  The CPU 302 generates scanning guide information from the patch size calculated in step S704 and the color measurement device width (step S705). The scanning guide information generated here includes the position where the scanning guide is arranged, the formation color, and the guide shape.

  Then, the patch information having the determined patch size is arranged, and chart information in which a guide corresponding to the operation guide information is further arranged is created (step S706). This completes the chart information generation process shown in FIG.

<Patch lower limit calculation method>
Hereinafter, the patch size lower limit calculation method will be described with reference to FIG. FIG. 13 is a diagram showing the relationship between the patch and the scanning guide position when the patch size is reduced. In the figure, MW is the color measuring device width, and AW is the opening width. PW1, PW2, and PW3 indicate patch sizes when the patch size PW is changed, and MW = PW1>PW2>PW3> AW.

For example, when the patch size PW = PW1, the scanning guide is arranged at the boundary 1301 between the Nth and N + 1th patches. In this case, a guide indicating the width of the measuring device, which is arranged at the boundary between adjacent columns, can be shared between the columns, and does not necessarily indicate the relationship between the guide and the column. In this case, the guide may be disposed at least in the slit. However, since the guide passes through the boundary between adjacent patches in the row, it does not interfere with the patch boundary. When PW = PW2, the scanning guide for scanning the N columns is arranged in the slit 1302 in the (N + 1) th column. Similarly to the case of PW = PW2, PW = PW3 is arranged in the slit 1303 in the (N + 1) th row of the scanning guide when scanning the Nth row, and is positioned so as to be in contact with the opening position when scanning the (N + 1) th row. Become. That is, when the patch size is made smaller than PW3, the scanning guide for scanning the Nth column is disposed within the opening width for scanning the (N + 1) th column. As a result, the guide in the slit becomes an object to be measured, and the measurement apparatus may not be able to recognize that the patch on the scanning line, which is originally the role of the slit, has been switched. For this reason, the patch size (patch width) PW is calculated within a range that satisfies the following conditions.
When INT (MW / PW) is an odd number:
MW-PW × INT (MW / PW) <PW-AW
And PW> AW,
When INT (MW / PW) is an even number:
MW-PW × INT (MW / PW)> AW
And PW> AW.

  Here, INT () is a function for truncating the decimal part. For example, when MW = 3 and PW = 2, INT (3/2) = 1.

  For example, when MW = PW = 35 mm and AW = 6 mm, INT (35/35) = 1, 35-35 × INT (35/35) <35-6, 0 <29, and INT (MW / Inequalities hold when PW) is odd. On the other hand, when MW = 35 mm, PW20 mm, and AW = 6 mm, INT (35/20) = 1, 35-20 × INT (35/20) <20-6, and 15 <14, so INT (MW / PW) is not an inequality for odd numbers. When the inequality is not satisfied, the scanning guide is disposed at the position of the opening width, and therefore the patch size that satisfies the above expression is calculated. In addition, although AW is used as the opening width here, it is also possible that AW ′ = AW × N so as to allow a slight shift of the scanning line.

  In the above equation, when the measurement device width = 35 mm and the opening width AW ′ = 12 mm, the patch size is 23.5 mm, and the number of patches that can be arranged is horizontal 8 × vertical 12 = 96, which is 1.6 times larger. Patches can be placed. In the above formula, since MW and AW are determined by the measuring device, several values of PW satisfying the above conditions can be determined in advance for each measuring device, and the required number of patches can be formed on the chart. The maximum width may be selected.

  The meaning of the above formula will be described. The value of INT (MW / PW) means how many rows of patches fit within the width MW of the measuring apparatus. When INT (MW / PW) is an even number, the maximum is obtained under the condition that the central portion of the measuring device is coincident with the central portion of the patch, and the patch width PW is an even number of INT (MW / PW). Then, the end portion of the measuring device coincides with the central portion of the patch. The width MW of the measuring device at this time can be expressed as PW × INT (MW / PW). If a guide is arranged at the position of the width of the measuring device at this time, the guide is placed at the center of the opening 1005 of the measuring device that scans along the guide. The guide is removed from the opening 1005 when the width of the measuring device is wider than the width by AW / 2 on the left and right sides, and the AW is expanded. Therefore, the width MW of the measuring device is PW × INT (MW / PW) + AW needs to be greater (or may be equal). That is, MW−PW × INT (MW / PW)> AW. Even if the guide is arranged at the position of the width of the measuring device at this time, the guide is not applied to the opening 1005 of the measuring device that scans along the guide. If the patch width is minimum (that is, odd-numbered patch rows are almost within the width of the measuring device) under the condition that INT (MW / PW) is an even number, the ends of the measuring device are adjacent to each other. Will coincide with the boundary. If the guide is arranged at the position of the width of the measuring device at this time, the guide is not hung on the opening 1005 of the measuring device that scans along the guide. Therefore, when INT (MW / PW) is an even number, the patch width has only an upper limit and no lower limit.

  On the other hand, if INT (MW / PW) is an odd number, the central part of the measuring device is coincident with the central part of the patch, and the patch width PW is an odd number of INT (MW / PW). At maximum, the ends of the measuring device will coincide with the boundaries of adjacent patches. If the guide is arranged at the position of the width of the measuring device at this time, the guide is not hung on the opening 1005 of the measuring device that scans along the guide. If the patch width is the minimum (that is, even-numbered patch rows are almost within the width of the measuring device) under the condition that INT (MW / PW) is an odd number, the end of the measuring device is the center of the patch. Will match. The width MW of the measuring device at this time can be expressed as approximately PW × INT (MW / PW) + PW (if equal, INT (MW / PW) is an even number). If a guide is arranged at the position of the width of the measuring device at this time, the guide is placed at the center of the opening 1005 of the measuring device that scans along the guide. The guide is removed from the opening 1005 when the width of the measuring device is narrower than the width by AW / 2 inward, and the width MW of the measuring device is PW × INT (MW / PW). ) + PW−AW. That is, MW−PW × INT (MW / PW) <PW−AW. Even if the guide is arranged at the position of the width of the measuring device at this time, the guide is not applied to the opening 1005 of the measuring device that scans along the guide. Therefore, if INT (MW / PW) is an odd number, the patch width has only a lower limit and no upper limit.

As described above, in the first embodiment, the patch size is determined based on the color measurement device information of the color measurement device 102, and a chart for arranging the scanning guide is generated based on the determined patch size and the color measurement device information. Therefore, calibration of the image forming apparatus 105 was performed using the generated chart. Accordingly, it is possible to provide a color chart and a calibration system that can reduce scanning errors even when the number of patches necessary for calibration is read.
[Second Embodiment]
In the first embodiment, the patch size is determined based on the colorimetric device information, and the chart is generated by determining the position where the scanning guide is installed based on the determined patch size and the colorimetric device information. However, when the patch size is reduced, a scanning error may occur even when the scanning guide is arranged. When scanning mistakes occur frequently, if the patch in which the scanning mistake has occurred is skipped, the calibration accuracy is lowered. Further, when notifying the colorimeter that a color measurement error has occurred, if a number of color measurement errors occur, it takes a long time to complete calibration. That is, the calibration process itself cannot be completed, which is the original purpose. In the present embodiment, a method for prompting the colorimeter to change the chart when scanning mistakes frequently occur due to a small patch size will be described.

  FIG. 14 shows a control flow of the CPU 301 at the time of chart color measurement in the present embodiment. The CPU 301 initializes the number of measurement failures (step S1401). Next, the CPU 301 acquires a color measurement value of the Nth column from the color measurement device 102 (step S1402). Next, the CPU 301 determines whether the measurement has failed from the colorimetric values acquired in step S1402 (step S1403). Here, the measurement failure means whether or not the scanning line has shifted or the scanning speed is too high. As a method of detecting that the scanning line has shifted, for example, whether or not a color such as the color of an adjacent line (for example, cyan or yellow) is read while scanning a column composed of magenta color. Judgment can be made by As for the detection of the scanning speed, since the slit cannot be recognized if the scanning speed is too high, it may be determined whether or not the number of detected patches does not satisfy the number of arranged patches. Alternatively, it may be determined that a specified number of samples could not be obtained in the patch.

  If it is determined that the measurement is successful (NO in step S1403), the CPU 301 moves the measurement string to the next line (step S1404). Next, the CPU 301 determines whether or not the measurement for all the columns has been completed (step S1405). If it is determined that all columns have been measured, this flow ends (YES in step S1405). If it is determined that the measurement of all columns is not completed, the process returns to S1402 (NO in step S1405).

  If it is determined in step S1403 that the measurement has failed (YES in step S1403), the CPU 301 counts up the number of measurement failures (E_CNT) (step S1406). Next, the CPU 301 compares the number of measurement failures with a predetermined threshold value (Th) (step S1407). If it is determined that the threshold is not exceeded (NO in step S1407), the process returns to step S1402 without changing the measurement sequence. If it is determined in step S1407 that the threshold value has been exceeded (YES in step S1407), a message prompting re-output of the chart is displayed (step S1408).

  An example of the message displayed on the display device 104 is shown in FIG. Here, the output of a simple chart is prompted. Here, when the Yes button 1501 is pressed, a signal indicating that the simple chart is selected is transmitted to the CPU 301. On the other hand, when the NO button 1502 is pressed, a signal indicating that the detailed chart is selected is transmitted to the CPU 301.

  Next, the CPU 301 receives a signal for re-outputting the chart, and when output in the simplified chart is selected (YES in step S1409), the CPU 301 issues a chart printing request in the simplified chart to the image forming apparatus 105 (step S1410). ). Here, the simple chart refers to a chart in which the patch size calculated in the first embodiment is enlarged and patches are thinned out, that is, the number of columns is reduced or the number of gradation patches of each color is reduced.

  If output in the simplified chart is not selected in step S1409 (NO in step S1409), the CPU 301 acquires the paper feed stage information of the image forming apparatus 105, and there is a sheet having a size larger than the designated paper size. It is determined whether or not (step S1411). Here, the designated paper size is A4 paper, and a paper size larger than that is assumed to be A3 paper. If it is determined that there is A3 paper (YES in step S1411), the patch size of the detailed chart calculated in the first embodiment is enlarged and arranged at an enlargement ratio from A4 to A3 (S1412). When a guide is recorded on a chart as in the first embodiment, the enlarged patch size needs to satisfy the conditions related to PW described in the first embodiment. Then, a chart print request is made with the detailed chart to the image forming apparatus 105 (YES in step S1411). If it is determined in step S1411 that there is no A3 sheet (NO in step S1411), the detailed chart calculated in the first embodiment is divided into a plurality of A4 sheets and the number of sheets divided for the image forming apparatus 105 is obtained. Then, a chart print request is made (step S1413). Here, as a method of dividing the patch, there are a method of dividing by the number of columns and a method of dividing by the gradation value, but there is no particular limitation here. In step S1411, the paper feed stage information is acquired and automatically determined, but for example, a selection message may be displayed to the colorimeter as shown in FIG. If the selection button 1503 is pressed here, the CPU 301 is notified that the A3 sheet has been selected. On the other hand, when the selection button 1504 is pressed, the CPU 301 is notified that split printing on A4 paper has been selected.

  As described above, in the second embodiment, when a scanning error occurs, the chart is reprinted by prompting the colorimeter to change the chart. As a result, it is possible to reduce the occurrence of a scanning error due to the reduced patch size and the delay in the calibration work.

[Third Embodiment]
In the second embodiment, the method for prompting the colorimeter to change the chart when scanning mistakes frequently occur due to the patch size being reduced has been described. However, since there is not one cause of the scanning error, if the patch size is changed only by the presence or absence of the occurrence of the scanning error, the patch is enlarged in the direction not originally causing the scanning error, and the number of patches is reduced. It may decrease. Therefore, in the present embodiment, a method for changing the patch size according to the cause of the scanning error will be described.

  FIG. 16 shows a control flow of the CPU 301 when the patch size is changed according to the scanning error factor at the time of the scanning error in the present embodiment. The control flow of the CPU 301 in FIG. 16 is provided between the control in steps S1403 and S1406 in FIG. 14 shown in the second embodiment.

  If the CPU 301 determines that the measurement has failed in step S1403 in FIG. 14, the CPU 301 determines whether or not the measurement failure factor is a mistake due to a scan line shift (step S1601). If the measurement error is caused by a scanning line shift (YES in step S1601), a predetermined enlarged width WC is added to the patch width PW shown in FIG. 13 (step S1602). If it is determined in step S1601 that the scan line is not shifted (NO in step S1601), the process advances to step S1603. When recording a guide on a chart as in the first embodiment, PW + WC needs to satisfy the conditions related to PW described in the first embodiment.

  Next, the CPU 301 determines whether or not the measurement failure factor is a mistake due to the scanning speed (step S1603). If the measurement error is caused by the scanning speed (YES in step S1603), a predetermined enlargement width HC is added to the patch height PH shown in FIG. 13 (step S1604), and the process is terminated. If it is determined in step S1603 that there is no mistake due to the scanning speed (NO in step S1603), the process ends.

  In the above processing, the patch size is updated each time each measurement failure factor occurs. Therefore, based on the patch sizes (PW and PH) finally calculated by this processing, the processing after step S1406 shown in FIG. Do. That is, the simplified chart output in step S1410 shown in FIG. 14 is generated based on the patch size created in the present embodiment.

As described above, in the third embodiment, when a scanning error occurs, the patch size is changed according to the scanning error factor of the colorimeter. Thereby, it is possible to prevent the patch size from being changed in a direction in which no scanning error occurs, and to prevent the number of patches from being reduced more than necessary [Other Embodiments].
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

Claims (21)

An information processing apparatus for performing color calibration of an image forming apparatus that outputs an image formed on a sheet based on a colorimetric value obtained by measuring a colorimetric chart output by the image forming apparatus by a colorimetric device. There,
Generating means for generating image information of a colorimetric chart in which patches are arranged in a lattice pattern and guides are arranged along the rows of the patches;
Means for causing the image forming apparatus to output a color measurement chart based on image information of the color measurement chart;
The information processing apparatus according to claim 1, wherein the guide is disposed at least in a slit that is a gap between adjacent patches in the direction of the guide.   2. The information according to claim 1, wherein the generation unit generates the guide as a line indicating a width of the color measurement device when the color measurement device performs color measurement on a row of patches to be measured. Processing equipment.   The generation unit configures the patch row by arranging patches of the same color component and different densities, and configures a guide corresponding to the patch row in association with the color component of the patch row. The information processing apparatus according to claim 1 or 2.   The information processing apparatus according to claim 3, wherein the generation unit configures a guide corresponding to the row of patches with the same color component as a color component of the row of patches.   The said generation means arrange | positions the said guide in the position which is not measured by the said colorimetry apparatus, when scanning the row | line | column of a patch along the said guide by the said colorimetry apparatus. The information processing apparatus according to any one of 1 to 4.   The colorimetric device has an opening of a sensor, and the generation means places the guide at a position that does not hook the opening when the colorimetric device scans a row of patches along the guide. The information processing apparatus according to claim 5, wherein the information processing apparatus is arranged. Means for receiving a measurement result from the color measuring device and determining a measurement failure for each column of the patches;
The said generation | occurrence | production means produces | generates again the image information of the simple chart which thinned the patch of the said colorimetric chart when the said measurement failed, It is any one of Claim 1 thru | or 6 characterized by the above-mentioned. Information processing device. Means for receiving a measurement result from the color measuring device and determining a measurement failure for each column of the patches;
7. The information according to claim 1, wherein the generation unit generates the color measurement chart image information again by enlarging the patch when the measurement fails. 8. Processing equipment.   The information processing apparatus according to claim 8, wherein the generation unit generates image information of a color measurement chart obtained by enlarging the patch so as to be divided into a plurality of sheets.   The information processing apparatus according to claim 8, wherein the generation unit generates image information of a color measurement chart obtained by enlarging the patch so as to be formed on an enlarged sheet. Further comprising user interface means;
11. The user interface unit according to any one of claims 7 to 10, wherein when there is a failure in the measurement, the user interface unit displays the fact and receives designation of an output of the colorimetric chart thereafter. The information processing apparatus described. Means for receiving a measurement result from the colorimetric device and determining a measurement failure due to a shift of the colorimetric device from a patch row or a measurement failure due to the scanning speed; ,
The generating means enlarges the colorimetric chart patch when there is a measurement failure due to deviation from the patch row, and when there is a measurement failure due to the scanning speed, the slit The information processing apparatus according to any one of claims 1 to 6, wherein the image information of the color measurement chart is generated again by enlarging. A color measuring device;
A calibration system comprising: the information processing apparatus according to claim 1.   The calibration system according to claim 13, further comprising an image forming apparatus. The colorimetric chart for performing color calibration of an image forming apparatus that outputs an image formed on a sheet based on a colorimetric value obtained by measuring a colorimetric chart output by the image forming apparatus by a colorimetric device A program for creating
A step of generating a color measurement chart image information in which patches are arranged in a lattice pattern and guides are arranged along the rows of the patches;
A program for causing a computer to execute a step of outputting a color measurement chart to the image forming apparatus based on image information of the color measurement chart,
The program is characterized in that the guide is arranged at least in a slit which is a gap between patches adjacent to each other in the direction of the guide. Creation of a colorimetric chart for performing color calibration of an image forming apparatus that outputs an image formed on a sheet based on a colorimetric value obtained by measuring the colorimetric chart output by the image forming apparatus with a colorimetric device A method,
A step of generating a color measurement chart image information in which patches are arranged in a lattice pattern and guides are arranged along the rows of the patches;
A step of outputting a color measurement chart to the image forming apparatus based on image information of the color measurement chart,
The colorimetric chart creation method, wherein the guide is disposed at least in a slit that is a gap between adjacent patches in the direction of the guide. A color measurement chart for performing color calibration of an image forming apparatus that outputs an image formed on a sheet based on a color measurement value obtained by measuring a color measurement chart output by the image forming apparatus with a color measurement apparatus. There,
Grid-like patches and guides along the rows of the patches are arranged,
The colorimetric chart, wherein the guide is arranged at least in a slit which is a gap between adjacent patches in the direction of the guide.   18. The color measurement chart according to claim 17, wherein the guide is a line indicating a width of the color measurement device when the color measurement device performs color measurement on a row of patches to be measured.   The patch row is configured by arranging patches of the same color component and different densities, and the guide corresponding to the patch row is configured corresponding to the color component of the patch row. The colorimetric chart according to claim 17 or 18.   The colorimetric chart according to claim 19, wherein the guide corresponding to the row of patches is composed of the same color components as the color components of the row of patches.   18. The guide is arranged at a position where the colorimetric device does not perform colorimetry when the patch row is scanned along the guide by the colorimetry device. The colorimetric chart according to any one of 20.

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