JP2005271353A - Color chart, color chart forming device and method of forming color chart - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a color chart with good color reproducibility without wastefully consuming a printing paper or an ink. <P>SOLUTION: As a color patch of a color having a small saturation is disposed in this color chart at a central section in a main scanning direction of a print head, the color patch having the small saturation can be reproduced to be in an accurate color. As a result, it is possible to perform calibration with good reproducibility, particularly in a low-saturation region. As it is unnecessary to form a dummy patch, it is possible to prevent a printing paper or an ink from being wastefully consumed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a color chart, a color chart creation device, and a color chart creation method.

Conventionally, this type of color chart is known in which dummy patches are formed at both ends in the scanning direction of the print head (see, for example, Patent Document 1).
According to such a configuration, the color reproducibility of the evaluation color patch can be stabilized because the evaluation color patch is not created at both ends in the scanning direction where the print head is accelerated and decelerated and the print head scan is not stable. It was possible. Further, since the ink can be ejected to some extent when the dummy patch is printed, the ink ejection system can be driven in advance. That is, the evaluation color patch can be prevented from being printed at the rise when ink ejection becomes unstable, and in this respect also, the color reproducibility of the evaluation color patch can be stabilized.
JP 2003-1810 A

However, there is a problem that the ink for printing the dummy patch is wasted and the entire print medium cannot be effectively used for printing the dummy patch.
SUMMARY An advantage of some aspects of the invention is that it provides a color chart, a color chart creation apparatus, and a color chart creation method that do not waste ink and a print medium.

Means and actions / effects for solving the problems

  In order to achieve the above object, the invention according to claim 1 forms a color patch by causing a print head capable of ejecting ink to scan on a recording medium. A color chart is created by forming the color patch on the recording medium. The color patches with low saturation are concentrated on the central portion of the print head in the scanning direction on the recording medium. Since the end of the print head in the scanning direction on the recording medium is a portion where the print head performs acceleration / deceleration, the ink discharge amount per unit area may not be stable. That is, the color reproducibility is deteriorated at the end portion in the scanning direction of the print head on the recording medium as compared with the central portion in the scanning direction. Immediately after the start of scanning of the print head, the ink ejection system rises, so the ink ejection state is not stable. Accordingly, the color reproducibility is further deteriorated at the end portion of the print head in the scanning direction through which the print head passes immediately after the start of scanning of the print head.

  On the other hand, since it is easy to feel a slight hue shift in a low-saturation color, it is necessary to accurately reproduce the color in the color chart. Therefore, by disposing concentrated colors with low color saturation, which require high color reproducibility, at the central portion in the scanning direction of the print head on the recording medium with good color reproducibility, overall hue shift is achieved. This makes it possible to create the above color chart. Note that even if the color patch having high saturation has a slightly poor color reproducibility, a hue shift is hardly felt. Therefore, there is no problem even if the color patch having high saturation is formed on the end of the print head in the scanning direction on the recording medium. Further, by disposing a high saturation color patch at the end of the print head in the scanning direction, the ink ejection system can be stably operated while reproducing the high saturation color patch. It is not necessary to separately form dummy patches for starting up the ink ejection system in a stable state.

  That is, since the color chart can be formed using the entirety of the recording medium, the recording medium is not wasted and ink is not wasted. In addition, since the above-described color chart in which hue deviation is hardly felt can be created as a whole, calibration with good color reproducibility can be performed using the color chart. For example, when creating a color conversion table using this color chart, it is possible to create a highly accurate color conversion table in which hue deviation is not noticeable.

  Furthermore, it can be said that the above-described apparatus for creating a color chart also uses the technical idea of the present invention, and a color chart creating apparatus corresponding to claim 1 can be configured as in claim 2.

  According to a third aspect of the present invention, the color data acquisition means acquires color data indicating the color of each color patch. The saturation calculation means calculates the saturation of the color indicated by the color data from the acquired color data. Then, the arrangement means determines the position on the recording medium of the color patch reproduced by the color data based on the calculated saturation. That is, the color data indicating a color with low saturation can be specified, and the color patch reproduced by the color data can be concentrated on the central portion in the scanning direction of the print head on the recording medium.

In the invention according to claim 4, the saturation calculation unit calculates the saturation of the color indicated by the color data, and determines whether the saturation is below a predetermined threshold. If the color patch is less than the threshold value, the arrangement means arranges the color patch reproduced by the color data whose saturation of the indicated color is smaller than the threshold value at the central portion in the scanning direction of the print head on the recording medium. To do. That is, a predetermined threshold value is provided for saturation, and the arrangement position on the recording medium can be limited for color patches with lower saturation. Therefore, the color patch whose saturation exceeds the threshold value can be arranged at an arbitrary position on the recording medium. The threshold value can be set to be equal to or lower than the saturation of a color used when reproducing a sepia-like photograph, for example. In this case, in the Lab color space (usually this space is expressed as L ^* a ^* b ^* , but in this specification, * is omitted for simplicity; the same applies hereinafter), the saturation is about 10 above the threshold value. Will be set as Of course, other values may be set as the threshold value, and the threshold value is not limited to the threshold value set as the saturation in the Lab color space.

  Further, according to the invention of claim 5, the color stable area setting means obtains color reproduction accuracy information on the recording medium in advance, and a color on which the color patch whose saturation is below the threshold value can be arranged based on the information. Set the stable region. That is, by previously setting a color stable area on the recording medium with good color reproduction accuracy, it is possible to arrange the color patch whose saturation is below the threshold only in the same color stable area.

  As an example of a specific mode of the color reproduction accuracy information, the invention according to claim 6 is that the color stable area setting means prints the color patch based on the same color data over the entire surface of the recording medium. Do. Then, the color difference from the reference color patch reproduced at the central portion in the scanning direction of the print head on the recording medium is calculated from the color measurement result of the color patch printed on the entire surface. Furthermore, an area where the color patch having the same color difference is present on the recording medium can be specified as the color stable area. That is, the area where the speed of the print head is stabilized and the color patch of the same color as the reference color patch reproduced in the stable operation state of the ink ejection system in the print head is reproduced as the color stable area. Identify.

  The method of creating a color chart as described above is not necessarily limited to a substantial apparatus, and is effective as a method invention as in the invention described in claim 7. Of course, a configuration corresponding to claims 3 to 6 is also possible. By the way, Claim 1 which specified invention as a color chart can also be set as the structure corresponding to Claims 3-6. In addition, such a color chart creation apparatus may be implemented alone, or may be implemented together with other apparatuses and methods in a state of being incorporated in a certain device. However, it includes various aspects, and can be changed as appropriate, such as software or hardware.

  For example, when a color chart is used to create a color conversion table, the color chart creation apparatus of the present invention may be incorporated in the color conversion table color conversion table creation apparatus. In the case of software that implements the apparatus, the software naturally functions as an invention and is used. Therefore, the present invention can also be realized as a color chart creation program. The recording medium may be a magnetic recording medium, a magneto-optical recording medium, or any recording medium that will be developed in the future. Furthermore, the duplication stages such as the primary replica and the secondary replica are equivalent without any question. .

  In addition, even when the communication method is used as a supply method, the present invention is not used. Further, even when a part is software and a part is realized by hardware, the idea of the invention is not completely different, and a part is stored on a recording medium and is appropriately changed as necessary. It may be in the form of being read. In addition, all functions may not be realized by the program itself, but may be realized by an external program or the like. Even in such a case, it is only necessary that each function can be realized by a computer.

Here, embodiments of the present invention will be described in the following order.
(1) Apparatus and process for creating a color chart:
(2) Other embodiments:
(3) Summary:

(1) Apparatus and process for creating a color chart:
FIG. 1 is a flowchart showing a process for creating a color chart according to the present invention, and FIG. 2 is a block diagram showing a configuration of a computer for executing the process. In the present embodiment, processing for creating a color chart used for creating a color conversion table will be described as an example. The computer 10 includes an arithmetic processing unit 11 that executes arithmetic processing and an HDD 12 that stores data. Further, it is connected to the printer 20 via an interface (not shown), and print data can be output from the computer 10 to execute printing.

  Further, the computer 10 can capture colorimetric data obtained by colorimetry by the colorimeter 30. This color measurement data can be input using a predetermined input device, input via a recording medium, or input by connecting and transferring data via a predetermined interface. It is. The printer 20 uses cyan (C) ink, magenta (M) ink, yellow (Y) ink, black (K) ink, light cyan (lc) ink, and light magenta (lm) ink. Can be used.

  The arithmetic processing unit 11 can execute arithmetic processing by executing a predetermined program for creating a color chart and a color conversion table. On the other hand, the separation function data 12a, the area definition data 12b, the threshold value 12c, and the color conversion table (LUT) 12d can be stored in the HDD 12. In step S100, it is determined whether or not the area definition data 12b is stored. The The area definition data 12b is data that defines a color stable area and a non-color stable area, and is not stored at a stage where a color chart has not been output before. The following description will be made assuming that the area definition data 12b is not stored at this stage.

  In step S105, the color separation processing unit 11a acquires one CMY value for area definition. This area defining CMY value is indicated by an integer gradation of 0 to 255. Further, assuming three colors of CMY ink, the ink amount and the gradation value are considered to correspond linearly. The calculated area definition CMY values acquired in step S105 are input to the color separation processing unit 11a in step S110, and the color separation processing is performed. The separation process is performed by substituting the area definition CMY values into a predetermined separation function. This separation function is defined by separation function data 12 a stored in the HDD 12.

  Of course, the color separation processing may be performed by interpolation processing using LUT instead of assignment to a function. In color separation, although it is not strict, it is assumed that colors before and after color separation coincide with each other, and the value of CMYKlclm data after color separation is an integer value of 0 to 255. Further, it is considered that the magnitude of the value of CMYKlclm data after color separation and the ink amount correspond linearly. As a result, the CMY values for area definition are expressed by the gradation of CMYKlclm ink that can be used in the printer 20. When the color separation processing unit 11a generates CMYKlclm data by the color separation processing, in step S115, the arrangement processing unit 11d specifies the position of the color patch that reproduces the color-separated CMYKlclm data.

FIG. 3 shows a layout of color patches (sometimes simply referred to as patches; the same shall apply hereinafter) in the color chart. One section shown in a square cell shape corresponds to one color patch. In this embodiment, the printing paper on which the color chart is reproduced is A4 size, and no margin is formed in the width direction (main scanning direction of the print head), so the width of the color chart is 210 mm. Yes. Moreover, since in order to create the LUT, it is necessary to colorimetric normally 10 ^three color patches, 50 rows (1 to 50) × 20 columns (R1 to R10, L1 to L10) of 10 ^three color The basic layout allows patches to be placed. In step S115, CMYKlclm data based on the CMY values for area definition is assigned to all of them. In other words, the color chart at this stage is formed with one color corresponding to the CMY value for region definition (referred to as the same color chart; the same applies hereinafter).

In step S120, the halftone processing unit 11e performs a halftone process for identifying the ink droplets discharged from the printer 20 based on the amount of each color ink of CMYKlclm. In this halftone process, intermediate data specifying whether or not to eject ink droplets for each pixel in the printer 20 is generated. The print data generation / output unit 11f performs print data for printing a color chart corresponding to the CMYKlclm data by performing processing such as arranging the data after the halftone processing in the order of ink droplet ejection at each nozzle of the printer 20. Generate and output to the printer 20. As a result, the printer 20 prints the same color chart composed of 10 ³ color patches of the same color (step S125). Hereinafter, a configuration for performing the printing will be described.

  FIG. 4 is a block diagram showing the hardware configuration of the printer 20. In FIG. 2, a CPU 21, ROM 22, RAM 23, ASIC 24, control IC 25, USB I / O 26, interface (I / F) for transmitting image data, driving signals, and the like are connected to a bus 20 a provided inside the printer 20. 27, etc. are connected. And CPU21 controls each part according to the program written in ROM22, using RAM23 as a work area. The ASIC 24 is an IC customized for driving a print head (not shown), and performs processing for driving the print head while transmitting / receiving a predetermined signal to / from the CPU 21. The applied voltage data is output to the head drive unit 29.

  The control IC 25 is an IC that controls a cartridge memory that is a non-volatile memory mounted on each of the ink cartridges 28a to 28f. Under the control of the CPU 21, the information on the color and remaining amount of ink recorded in the cartridge memory is read out. Ink remaining amount information is updated. The USB I / O 26 is connected to the computer 10, and the printer 20 receives data transmitted from the computer 10 via the USB I / O 26. A carriage mechanism 27 a and a paper feed mechanism 27 b are connected to the I / F 27. The paper feed mechanism 27b includes a paper feed motor, a paper feed roller, and the like, and sequentially feeds a print recording medium such as a printing paper to perform sub-scanning. The carriage mechanism 27a includes a carriage on which the print head is mounted, and causes the print head to perform main scanning by reciprocating the carriage.

  FIG. 5 shows the carriage and its operation. The carriage can reciprocate in the main scanning direction orthogonal to the paper feeding direction (sub-scanning direction) by the paper feeding mechanism 27b by the carriage mechanism 27a, and includes a print head 29a below. The print head 29a is connected to a cartridge holder 28 on which ink cartridges 28a to 28f filled with six colors of ink can be mounted, and is supplied with each ink. Then, the piezo element is driven in an ink chamber communicating from the tube to the ejection port, thereby ejecting ink. The head drive unit 29 generates an applied voltage pattern to the piezo elements built in the print head 29 a based on the applied voltage data input from the ASIC 24.

  In the ink discharge portion of the print head 29a, six sets of nozzle arrays that discharge each of the six colors of ink are formed so as to be aligned in the main scanning direction of the print head 29a, and each nozzle array has a plurality of nozzles in the sub-scanning direction. Are arranged at regular intervals. The ink in the ink cartridges 28a to 28f and the ink chamber communicate with each other via a tube (not shown) so that each color ink can be ejected from the nozzle. In the figure, the state in which ink is ejected from each nozzle is schematically shown by arrows.

  After printing the same color chart as described above, the colorimeter 30 measures the color of each patch in the same color chart (step S130). The colorimeter 30 is a device that acquires Lab coordinate values to be measured as colorimetric data, and the acquired colorimetric data is taken into the area definition unit 11 b of the computer 10. The area defining unit 11b uses patches belonging to the columns L1, L2, and R1 in the same color chart shown in FIG. 3 as reference color patches, and calculates an average color from these color measurement results as a reference color. Further, an average color is calculated for each of the columns (R1 to R10, L1 to L10). Then, the color difference ΔE between the average color and the reference color for each column is calculated. In the Lab color space, the color difference ΔE can be calculated from the linear distance between colors.

  FIG. 6 is a graph showing the relationship (color reproduction accuracy information) between the main scanning position and the color difference of each column. In the figure, the horizontal axis indicates the main scanning position, and the vertical axis indicates the color difference ΔE. As can be seen from the figure, although the same color is reproduced for the entire region, color misregistration occurs at both ends in the main scanning direction as compared with the central portion. In general, color misregistration is perceived when a low-saturation image such as a monochrome photograph or a sepia tone photograph is printed under the condition that the color misregistration ΔE exceeds 0.5. The reason why the color reproducibility deteriorates at the end portion in the main scanning direction of the print head 29a is as follows.

  In principle, since the ink ejection timing is controlled by controlling the voltage pattern applied to the piezo element in accordance with the main scanning speed of the print head 29a, the dot pitch in the main scanning direction is constant. However, when the acceleration / deceleration of the print head 29a is performed, the main scanning speed of the print head 29a becomes complicated, an appropriate ejection timing cannot be realized, and the dot pitch may not be constant. That is, in FIG. 5, when the main scanning of the print head 29a is at a constant speed, the dot pitch in the main scanning direction is constant, whereas at both ends in the main scanning direction where the print head 29a performs acceleration / deceleration, dots are printed. The pitch is sparse and dense. In particular, in the present embodiment, since no margin is formed in the main scanning direction of the printing paper, ink is ejected onto the printing paper before the print head 29a enters the stable scanning state. On the other hand, the ink ejection is stopped outside the printing paper so as not to contaminate the inside of the printer 20 at both ends of the print head 29a in the main scanning direction. Accordingly, the ink ejection system from the ink cartridges 28a to 28f to the nozzles is stopped once, the main scanning is started again, and the operation is restarted.

  That is, the ink discharge system is in a rising state at the beginning of each main scan, and the ink discharge system is in a continuous drive state at the middle and end of each main scan. Since the normal ink state and the piezo element state behave differently in the rising state and the continuous drive state, even if the ink discharge system is driven under the same conditions, the amount of ink discharged between the two will be different. . In general, the ink ejection system is set in accordance with the continuous drive state in which the majority of the printed image is formed, so the ink ejection amount is not stable in the rising state of the ink ejection system, and the hue shifts to a reproduced color. Etc. occur. That is, if one-way printing is performed, hue deviation or the like occurs at one end of the print head 29a in the main scanning direction, and if bidirectional printing is performed, hue deviation or the like occurs at both ends in the main scanning direction of the print head 29a. Occur.

  Returning to FIG. 6, the color difference ΔE <0.5 is satisfied in the region inside the row L5 and the row R5, and the low saturation color used for the low saturation image such as a monochrome photograph or a sepia tone photograph is reproduced. It is possible to create a color patch without any problem. On the other hand, even if a color patch having a low saturation color as described above is reproduced in the region outside the columns L5 and R5, reliable colorimetric data cannot be acquired in LUT creation. Furthermore, if a LUT is created using a color chart in which color patches of low saturation are reproduced in the area outside the rows L5 and R5, a low saturation image such as a monochrome photograph or a sepia tone photograph can be obtained. It cannot be reproduced in detail. Therefore, in step S135, the region inside the row L5 and the row R5 is defined as a color stable region, and the other region is defined as a non-color stable region to distinguish between them.

  FIG. 7 shows the layout of the color patch in the color chart, and shows the color stable region and the non-color stable region by hatching. When the color stable region and the non-color stable region are defined in step S135, the region definition data 12b for the same region is stored in the HDD 12. Therefore, if the processing from step S105 to S135 has been performed previously, it is determined in step S100 that there is region definition data 12b, and step S140 is executed. Note that the change in the ink ejection characteristics due to the main scanning of the print head 29a depends on the model and specification of the printer 20. Therefore, once the color stable region and the non-color stable region are defined in the printer 20, the printer 20 Thus, it is not necessary to perform steps S105 to S135 each time a color chart is created. In this embodiment, the same color chart of 50 rows × 20 columns is reproduced. However, it is only necessary to compare the reproduced colors in the main scanning direction, and the number of rows to be sampled may be reduced. .

In step S140, the color separation processing unit 11a acquires a colorimetric virtual CMY value. That is, CMY gradation data that can represent one colorimetric color patch is acquired. In this embodiment, the colorimetric virtual CMY values correspond to the values of 10 ³ grid points that are evenly arranged in the virtual CMY space, and correspond to the colors reproduced in each color patch of the color chart. Note that the gradation value range of the virtual CMY is 0 to 255, and the gradation value is defined by an integer. Further, assuming three colors of CMY ink, the ink amount and the gradation value are considered to correspond linearly. The colorimetric virtual CMY values are input to the color separation processing unit 11a, and the color separation processing is executed in step S145. Since the separation process is the same as that described above, the description thereof is omitted here. In step S145, in parallel with the color separation processing, the saturation calculation unit 11c calculates the saturation from the colorimetric virtual CMY values.

  FIG. 8 schematically shows the saturation of the colorimetric virtual CMY values in the virtual CMY color space. Note that the virtual CMY color space is composed of axes in which the components of CMY are orthogonal to each other. In the figure, the gray axis h indicated by a broken line indicates a trajectory in which the CMY values are equal, and corresponds to an axis that can virtually reproduce an achromatic color. That is, it can be said that the colorimetric virtual CMY values located farther from the gray axis h have higher saturation. In the present embodiment, in order to quantify the saturation, first, an auxiliary straight line p that is orthogonal to the gray axis h and passes the colorimetric coordinate T indicated by the colorimetric virtual CMY value to be calculated is calculated. When the auxiliary straight line p is calculated, an orthogonal coordinate Q between the auxiliary straight line p and the gray axis h is calculated. Then, the linear distance between the orthogonal coordinate Q and the colorimetric coordinate T is calculated as the saturation S.

  In the present embodiment, the index indicating saturation is simply specified by the above method, but the saturation index may be specified by other methods. For example, the color may be converted into coordinates in the Lab color space, and saturation in a strict sense may be calculated from the Lab coordinates. The arrangement processing unit 11d compares the saturation S with the threshold value 12c in step S150. The threshold 12c is preset and stored in the HDD 12. The threshold value 12c can be set to an upper limit saturation (for example, S = 10) that can be used for a low saturation image such as a monochrome photograph or a sepia photograph. If the saturation S is smaller than the threshold value 12c, it is determined in step S155 whether there is a remainder in the color stable region. As shown in FIG. 7, the color stable region is a region from columns L4 to R4, and the number of colorimetric color patches that can be formed in the region is limited to 8 columns × 50 rows = 400. That is, if the color stable area is completely filled with the colorimetric color patches arranged before that, a new colorimetric color patch cannot be arranged in the same color stable area.

  Therefore, in step S155, it is examined whether or not the color measurement color patch can be formed in the color stable region. If it can be formed, in step S165, the CMYKlclm data of the color measurement color patch is added to the remaining region in the color stable region. Assign. On the other hand, if there is no remaining color stable area and the colorimetric color patch cannot be formed in the color stable area, a color chart print area is added for one line in step S160. As a result, eight colorimetric color patches can be formed at the main scanning position equivalent to the color stable region, so that the colorimetric color patch is added to the color stable region expanded in step S165. Of CMYKlclm data can be allocated.

  On the other hand, if it is determined in step S150 that the saturation S is greater than the threshold value 12c, it is determined in step S170 whether there is a remainder in the non-color stable region. In other words, since the number of colorimetric color patches arranged in the non-color stable region is limited, it is determined whether or not the colorimetric color patch can be assigned. If possible, the non-color stable region is assigned to the non-color stable region in step S175. CMYKlclm data of color patches for colorimetry is assigned. On the other hand, if there is no remainder in the non-color stable region, the CMYKlclm data of the colorimetric color patch is assigned to the color stable region in step S165. The high saturation color patch may be arranged in any region, and there is no problem even if it is arranged in the color stable region. That is, in steps S150 to S165, a process is performed in which a low-saturation colorimetric color patch whose saturation S is smaller than the threshold value 12c is always arranged in the color stable region.

In step S180, it is determined whether or not the placement process has been completed for all colorimetric color patches. If not, the next colorimetric virtual CMY value is acquired in step S140. On the other hand, if the arrangement processing has been completed for all colorimetric color patches, halftone processing is executed in step S185. Since CMYKlclm data is generated for all colorimetric color patches at this time, halftone processing can be performed based on the CMYKlclm data. Since the halftone process is the same as that described above, the description thereof is omitted. When the halftone process is completed, a color chart composed of 10 ³ colorimetric color patches can be printed in step S190.

  Then, the LUT 12d that defines the correspondence between the CMYKlclm data and the RGB data by measuring the color of the printed color chart and associating the color measurement result with the RGB data in the Lab color space as the device-independent color space. Can be created. In this way, the low-saturation color patch is arranged in the central portion of the print head 29a in the main scanning direction and concentrated in the color stable region that satisfies the predetermined color reproduction accuracy. The color reproducibility can be improved. That is, the speed of the print head 29a is stabilized while reaching the central portion of the print head 29a in the main scanning direction, and the ink ejection system can be continuously driven while printing the non-color stable region. Accordingly, it is possible to accurately reproduce the low saturation color patch, and to improve the color reproducibility of the low saturation region of the LUT 12d created based on this color chart. In addition, once the area definition data 12b is stored, the same color chart need not be output, and it is not necessary to form dummy patches or the like, so that consumption of printing paper and ink can be reduced.

(4) Other embodiments:
FIG. 9 is a flowchart showing an operation for creating a color chart according to another embodiment of the present invention. In step S1100, virtual CMY values for all colorimetry (10 ³ ) are acquired. Thereafter, a color separation process and a saturation calculation process are performed for all the colorimetric virtual CMY values. (Steps S1110, S1120) The color separation process and the saturation calculation process are the same as those described above, and a description thereof will be omitted. In step S1130, the colorimetric color patches corresponding to the colorimetric virtual CMY values having the low saturation S calculated in step S1120 are arranged in order from the central portion in the main scanning direction of the print head 29a.

  FIG. 10 shows the arrangement order at this time. In the figure, the order of the saturation S is shown inside the cell indicating each colorimetric color patch. For example, it means that the color patch for colorimetry with the smallest saturation S is assigned to the cell in the first row: L1 column, and the saturation S1000 is the smallest in the 50th row: R10 column (the smallest). This means that color patches for colorimetry are assigned. Also by doing this, the color patches for colorimetry with low saturation can be concentrated and arranged at the center of the print head 29a in the main scanning direction. In addition, it is not necessary to print the same color chart, and it is possible to further reduce consumption of ink and printing paper. In this embodiment, when there are many colorimetric color patches with low saturation S, colorimetric color patches with low saturation are arranged in the area corresponding to the non-color stable area in the previous embodiment. It is also conceivable. However, it is effective when it is known that the virtual CMY values for colorimetry exist uniformly in the virtual CMY color space and the number of color patches for colorimetry with low saturation is not large as in the case of creating an LUT. Means.

  In the above description, the color chart of the present invention is used as an example for LUT creation. However, the color chart of the present invention may be used for other calibrations. For example, even when an ink ejection system is adjusted or an ink component is adjusted, the color chart of the present invention makes it possible to accurately adjust the low saturation region. . Accordingly, it is possible to obtain a print result that hardly causes color misregistration in any adjustment.

  Further, the color reproducibility has a tendency in the main scanning direction of the print head 29a, and has no particular tendency in the sub-scanning direction. Therefore, even if the arrangement of the colorimetric color patches is changed in the same column, the color reproducibility of the color chart does not become a problem. Therefore, for example, when the arrangement processing is completed in step S1130, the colorimetric color patches may be rearranged in the sub-scanning direction based on the CMYKlclm data. For example, the sum for each ink component of the CMYKlclm data arranged at both ends (about three columns) of each row is calculated, and rearranged so that the sum does not have a component with a predetermined value or less (not 0). For example, all the ink can be ejected once before the print head 29a reaches the central portion in the main scanning direction. That is, all the ink discharge systems can be started up before reproducing the color patch for colorimetry with low saturation at the center in the main scanning direction. Accordingly, it is possible to accurately reproduce the color patch for colorimetry with low saturation at the center in the main scanning direction. In particular, when expressing achromatic colors in CMY composite gray, the CMY ejection balance is important, which is an effective means.

(3) Summary:
According to the color chart of the present invention, since the color patch having a low saturation is arranged at the center of the print head in the main scanning direction, the color patch having a low saturation can be reproduced with an accurate color. Therefore, it is possible to perform calibration with good color reproducibility, particularly in the low chromatic region. Further, since there is no need to form dummy patches, it is possible to prevent wasteful consumption of printing paper and ink.

It is a flowchart which shows a color chart creation process. It is a block diagram of a computer. It is a figure which shows a color chart. FIG. 2 is a diagram illustrating a schematic hardware configuration of a printer. It is a figure explaining operation | movement of a print head. It is a graph which shows the relationship between a main scanning position and a color difference. It is a figure which shows a color chart. It is a figure explaining a saturation calculation process. It is a flowchart which shows a color chart creation process. It is a figure which shows a color chart.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Computer, 11 ... Arithmetic processing part, 11a ... Separation processing part, 11b ... Area definition part, 11c ... Saturation calculation part, 11d ... Arrangement processing part, 11e ... Halftone processing part, 11f ... Print data generation / output 12 ... HDD, 12a ... Separation function data, 12b ... area definition data, 12c ... threshold, 12d ... LUT, 20 ... printer, 20a ... bus, 21 ... CPU, 22 ... ROM, 23 ... RAM, 24 ... ASIC , 25 ... control IC, 27a ... carriage mechanism, 27b ... paper feed mechanism, 28 ... cartridge holder, 28a-28f ... ink cartridge, 29 ... head drive unit, 29a ... print head, 30 ... colorimeter

Claims (7)

In a color chart consisting of a plurality of color patches formed on the recording medium by scanning a printing head capable of ejecting ink on the recording medium,
A color chart in which the color patches having low saturation are concentrated and arranged at a central portion in the scanning direction of the print head on the recording medium. In a color chart creating apparatus for creating a color chart composed of a plurality of color patches formed on a recording medium by scanning a print head capable of ejecting ink on the recording medium,
A color chart creating apparatus, wherein the color patches with low saturation are concentrated and arranged at a central portion in the scanning direction of the print head on the recording medium. Color data acquisition means for acquiring color data indicating the color of each color patch;
Saturation calculating means for calculating the saturation of the color indicated by the color data from the color data;
3. The apparatus according to claim 2, further comprising an arrangement unit that determines a position on the recording medium of the color patch reproduced by the color data based on the saturation calculated by the saturation calculation unit. Color chart creation device.   When the saturation of the color indicated by the color data calculated by the saturation calculation means is below a predetermined threshold, the arrangement means uses the color data at the center of the print head in the scanning direction on the recording medium. The color chart creating apparatus according to claim 3, wherein the color patch to be reproduced is arranged.   Color stability area setting means is provided for previously setting a color stable area on the recording medium on which the color patch whose color saturation is less than the threshold value can be arranged from color reproduction accuracy information on the recording medium. The color chart creating apparatus according to claim 4.   The color stable area setting means prints the color patch based on the same color data over the entire surface of the recording medium, and the print head on the recording medium from the colorimetric result of the printed color patch. 6. The color chart creating apparatus according to claim 5, wherein an area where the color patch having a small color difference from the reference color patch reproduced in the center in the scanning direction is specified as the color stable area. In a color chart creating method for creating a color chart composed of a plurality of color patches formed on a recording medium by scanning a printing head capable of ejecting ink on the recording medium,
A color chart creation method comprising: concentrating and arranging color patches with low saturation at a central portion in the scanning direction of the print head on the recording medium.

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