JP4375041B2 - Color correction method - Google Patents

Description

The present invention relates to a color correction method for compensating for color misregistration in a printing apparatus that prints an image corresponding to print data on a print medium using a print head.

  2. Description of the Related Art Conventionally, mass-produced ink jet printers are provided with a print nozzle row for each ink color (type), and an ID (error information) is recorded to compensate for a deviation in the weight of ink ejected from each print nozzle row. A non-volatile semiconductor memory is provided. When performing print control for each printer, color correction data such as a calibration LUT (lookup table) corresponding to the ID is created and stored in advance, and the color correction data corresponding to the ID is referred to. Thus, the ink weight error is compensated so that the weight of the ink ejected from the print head matches the reference printer (reference body) (for example, see Patent Document 1).

In a printer production factory, when a print head is not assembled to a printer, a predetermined number of inks are ejected from the print head, the ink weight is measured, and the difference from the ink weight of the reference printer is made to correspond to the ID, and a nonvolatile semiconductor memory Calibration work to be recorded.
Japanese Patent Laid-Open No. 10-278360

While it takes a certain amount of time to measure the weight of the ink ejected from the print head, it has been desired to quickly perform a calibration operation in order to reduce costs when mass-producing printers .

SUMMARY An advantage of some aspects of the invention is that it provides a color correction method capable of speeding up a calibration operation of a printing apparatus .

Means for Solving the Problems and Effects of the Invention

In order to achieve the above object, the present invention provides a color correction method for compensating for color misregistration in a printing apparatus that prints a print image corresponding to print data on the print medium using a print head that deposits ink on the print medium. A standard image having an ink recording amount with the largest variation in colorimetric data due to variation in the amount of ink adhering to the printing medium generated for each printing apparatus is printed on the printing medium by the printing apparatus. colorimetric data and control as line cormorants Engineering acquires colorimetric data of color measurement to the standard image standard image of the variation printed on the printing medium has the largest ink recording amount in a predetermined color space An acquisition step, color measurement data of the standard image, and a standard measurement obtained by measuring the standard image of the ink recording amount printed on the print medium with the largest variation in the predetermined color space. Color day And the error information indicating the comparison result is obtained, and the obtained error information is used to compensate for the deviation of the colorimetric data of the standard image from the reference colorimetric data. And a color correction process for correcting the print data .
Calibrate the printing device more quickly by correcting the print data based on the comparison result between the standard image of the ink recording amount and the standard image with the largest variation in colorimetric data due to variations in the amount of ink adhering to the print medium. Work can be performed.
A print control apparatus that performs print control on a printing apparatus that prints a print image corresponding to print data on a print medium using a print head that deposits ink on the print medium, the error acquisition unit, In the case of providing the printing control means, error information is obtained by the error obtaining means. The error information includes color measurement data obtained by measuring a standard image of a standard recording amount of the ink printed on a print medium with a printing apparatus in a predetermined color space, reference color measurement data, , And is the information that represents the comparison result. By using this error information, the print control means corrects the print data representing the image into print data that compensates for the color shift of the print image printed by the printing apparatus. Then, control for causing the printing apparatus to print a print image corresponding to the corrected print data is performed. Then, the printing apparatus causes the ink to adhere to the print medium from the print head, and prints the print image in which the color misregistration is compensated on the print medium.

  The color misregistration of the printing device is compensated based on the error information indicating the comparison result between the colorimetric data of the standard image and the reference colorimetric data actually printed on the printing medium by the printing device to be controlled. Therefore, there is no subtle error in the color of the printed image due to subtle variations in the voltage applied to the print head. Therefore, it is possible to improve the color reproducibility of the print image with respect to the reference color as compared with the conventional case where only the ink weight is compensated.

The ink recording amount may be a dot recording amount that represents the number of ink dots formed per unit area on the printing medium, or a dot recording rate that represents the ratio of the number of ink dots. In the case of using a printing apparatus capable of forming a plurality of types of dots, an ink record indicating the number of ink dots formed per unit area on the print medium when converted to a predetermined type of dot such as a large dot It may be a density or an ink recording rate representing a ratio of the number of the ink dots.
The standard image may be an image formed with one type of ink or an image formed with two or more types of ink. Here, if the standard image is a solid image that is uniform throughout, the colorimetric data can be obtained more accurately, so that a good color reproducibility with respect to the reference color can be obtained for the printing apparatus.
One standard recording amount is preferable in that a calibration operation can be performed more quickly on the printing apparatus. However, a plurality of standard recording amounts can be provided.

The predetermined color space can be a color space having a plurality of color components as color component amounts. The color space and the color component and the color component amounts, if CIE L ^* a ^* b ^* color space defined by International Commission on Illumination ^{(CIE) L *, a *} , each of the color components of b ^* In the case of CIE L ^* u ^* v ^* color space, each color component of L ^* , u ^* , v ^* and their values, and in the case of CIE XYZ color space, each color component of X, Y, Z and each of these In the case of a value and RGB color space, various combinations such as R, G, and B color components and their respective values can be considered. Here, L ^* is an element color representing lightness (brightness), and a ^* , b ^* , u ^* , and v ^* are element colors representing hue and saturation. Hereinafter, “ ^* ” is omitted.

Various data can be considered as the print data. For example, the print data may be data expressing the image with gradation data for each pixel. The gradation data may be 256 gradations before halftone processing or the like, or 2 gradations after halftone processing. The number of pixels may be any number as long as it can represent an image, and may have a plurality of pixels. For example, a small image such as 4 × 4 pixels or 8 × 8 pixels may be represented.
The color misregistration of the printing apparatus can be a color misregistration with respect to a reference color. For example, if the color misregistration with respect to a reference printing apparatus (reference machine) is used as a reference, the color misregistration of a printed image can be more reliably compensated. It becomes possible. Of course, the reference color measurement data may be reference color measurement data or color measurement data other than the reference color.

  When printing a standard image on a print medium, dot amount data for printing the standard image is generated from the standard recording amount, and the standard image is output to the printing apparatus using the dot amount data. If the control for printing on the print medium is performed, the standard image can be printed using a part of the process of printing the print image using the print data, so that it is easy to create error information. Become.

  The printing control means uses the error information to perform printing that compensates for an error with respect to the reference colorimetric data in the colorimetric data of the standard image printed by the printing apparatus from the print data representing the image. It is good also as a structure corrected to data. Then, the color misregistration of the print image is compensated on the basis of the state printed on the print medium, so that the color reproducibility of the print image with respect to the reference color can be improved more reliably.

The error information may be recorded in the printing apparatus, and the error acquisition unit may acquire the error information from the printing apparatus. Since the error information is integrated with the printing apparatus, even if the user of the printing control apparatus changes the printing apparatus, the error information is acquired from the printing apparatus and does not need to be input separately. Therefore, convenience can be improved.
Further, the print control means specifies a color correction correspondence relationship between the print data before correction and the print data after correction for compensating for the color shift of the print image based on the error information acquired by the error acquisition means. The print data expressing the image may be corrected with the specified color correction correspondence.

  Compensation for color shift between the print data before correction and the print image for each of a plurality of stages of the comparison result between the colorimetric data obtained by measuring the standard image in the predetermined color space and the reference colorimetric data. A storage area storing a plurality of color correction data defining a color correction correspondence relationship with the corrected print data is provided, and the print control means includes the error information among the plurality of color correction data stored in the storage area. May be specified, and the print data may be corrected with reference to the color correction data. The print data can be corrected so as to compensate for the color shift of the print image with a simple configuration, and good color reproducibility with respect to the reference color can be obtained for the print image. Here, the color correction data may be a color correction table in an information table format or data for performing calculations, such as a calibration LUT, a calibration conversion equation, a color conversion LUT (color conversion table), and the like. Various data can be considered.

When the color information obtained by measuring the standard image in the predetermined color space is compared with the reference colorimetric data, the error information is recorded from the plurality of color component amounts. It may be information indicating a comparison result in which only the color component amount having the largest change with respect to the change in amount is compared. The print control unit may correct the print data so as to compensate for an error with respect to the reference colorimetric data in the color component amount having the largest change in the standard image printed by the printing apparatus.
The error information is the color component selection image printed on the print medium. The color component amount that has the largest change with respect to the change in the ink recording amount in the colorimetric data is displayed. It is possible to obtain good color reproducibility with respect to the reference color. Also, when creating error information, using the comparison result of only the color component amount that has the greatest change with respect to the change in the ink recording amount from among the multiple color component amounts in the color space that is the standard for colorimetry, Since information only needs to be created, it is not necessary to perform complicated calculations during the calibration operation of the printing apparatus to be printed. Therefore, it is possible to speed up the calibration work.

Here, with respect to the reference printing apparatus used as a reference, the color component selection image is printed on the print medium with the first recording amount and the second recording amount having different recording amounts in the ink, and each printed color component The color of the selection image is measured in the predetermined color space, and the color measurement data including the plurality of color component amounts is acquired for the color selection image, and both color components are selected for each color component of the predetermined color space. When the color component amount difference for the image for use is obtained and the selected color component amount of the color component having the largest difference is specified from the plurality of color component amounts, the standard image is measured in a predetermined color space. When the colorimetric data obtained in this way and the reference colorimetric data are compared, information representing a comparison result obtained by comparing only the same selected color component amount may be used as error information. The print control unit may correct the print data so as to compensate an error with respect to the reference colorimetric data in the selected color component amount of the standard image printed by the printing apparatus by using the error information. . Then, with a simple configuration, the calibration operation of the printing apparatus can be speeded up, and good color reproducibility with respect to the reference color can be obtained for the printed image more reliably.
The difference between the color component amounts for the color component selection image may be a value that increases as the difference between the two color component amounts increases.
Here, when the combination of the first recording amount and the second recording amount is the minimum and maximum of the ink recording amount changed as described above, it is possible to obtain a good color reproducibility with respect to the reference color with a simple configuration. It becomes.

In the ink, the ink recording amount that causes the largest variation in colorimetric data due to the variation in the amount of ink adhering to the printing medium that occurs for each printing device is set as the standard recording amount on the printing medium with respect to the printing device. Information representing a comparison result between the color measurement data obtained by measuring the printed standard image in the predetermined color space and the reference color measurement data may be used as error information. The printing control means uses the error information to compensate for an error with respect to the reference colorimetric data in the colorimetric data of the standard image of the ink recording amount with the largest variation printed by the printing apparatus. The print data may be corrected.
The error information indicates the comparison result of the color measurement data obtained by measuring the standard image of the ink recording amount with the largest variation in the color measurement data due to the variation in the amount of ink adhering to the print medium. The color reproducibility with respect to can be obtained more reliably. Further, by generating error information using the selected color component amount of only the standard image of the ink recording amount having the largest variation, it is possible to perform the calibration operation of the printing apparatus more quickly.

First and second (first and second) printing apparatuses having different ink amounts are caused to print a plurality of recording amount determination images with different ink recording amounts on a print medium. Each of the recording amount determination images printed by the second printing device is color-measured in the predetermined color space to obtain first and second colorimetric data for each recording amount determination image, Variations in colorimetric data due to variations in the amount of ink adhering to the print medium that occurs for each printing device, based on the second colorimetric data and the recorded amount of ink on which a plurality of recording amount determination images are printed When the ink recording amount with the largest ink is determined as the standard recording amount, the colorimetric data obtained by measuring the standard image of the determined ink recording amount in the predetermined color space is compared with the reference colorimetric data. Information representing the result may be error information. By using the error information, the print control unit corrects the print data so as to compensate for an error with respect to the reference color measurement data in the standard image color measurement data having the determined ink recording amount. Good.
The error information indicates the comparison result of the color measurement data obtained by measuring the standard image of the ink recording amount determined from the color measurement data of the recording amount determination image printed on the printing medium. The color reproducibility with respect to can be obtained more reliably.

  If the first and second printing apparatuses are apparatuses that deposit ink on the print medium with the lower limit and upper limit of the variation in the ink amount, the color reproducibility of the print image with respect to the reference color can be further improved.

In the above ink, the recording amount of the standard image dot printed with the second dot having a larger amount of ink than the first dot is set to be smaller than the recording amount of the standard image dot printed with the first dot. Information representing a comparison result between the colorimetric data obtained by measuring the standard image of each type of dot printed on the printing medium on the printing medium in the predetermined color space and the reference colorimetric data. May be error information. In addition, in the ink, the dot recording amount of the standard image to be printed is reduced as the ink amount of the dot is increased, and the standard image according to the type of dot printed on the printing medium is printed on the printing medium by the printing device. Information representing the comparison result between the color measurement data obtained by color measurement in the color space and the reference color measurement data may be used as error information. The print control means may correct the print data so as to compensate for the color shift of the print image printed by the printing apparatus by using the corresponding error information for each type of dot.
Since the amount of colorimetric data that varies greatly due to variations in the amount of ink adhering to the printing medium that occurs for each printing device decreases as the ink amount of dots increases, color reproducibility of the printed image with respect to the reference color can be achieved with the above configuration. Can be further improved.

  Error information is provided for each type of ink, and the print control means uses the corresponding error information for each type of ink so that the print data is compensated for color misregistration of a print image printed by the printing apparatus. May be modified. Then, it becomes possible to further improve the color reproducibility of the print image with respect to the reference color.

The above-described printing control apparatus includes various modes such as being implemented together with other methods in a state where the printing control apparatus is incorporated in a certain device. For example, the present invention can be applied as a printing system including a printing apparatus. Further, since it is also possible to proceed with the processing according to a predetermined procedure which corresponds to the configuration of the print control apparatus, the print control apparatus is applicable as a control method, has the action of Similarly, the effects. Furthermore, since there is a case of executing the control program in the apparatus, and program, it is also applicable as a computer-readable recording medium recorded with the program, having similar actions and effects.

Hereinafter, embodiments of the present invention will be described in the following order.
(1) Configuration of printing system and color correction system:
(2) Explanation of error information creation method:
(3) Print control processing:
(4) Modification:

(1) Configuration of printing system and color correction system:
FIG. 1 is a diagram schematically showing the configuration of a print control apparatus U0 according to an embodiment of the present invention. FIG. 2 is a personal computer (PC) that is the print control apparatus and color correction apparatus of the present invention in this embodiment. 10 shows a printing system including an inkjet printer 20 capable of color printing as a printing apparatus (printing means). FIG. 3 is a diagram schematically showing a color correction method, and FIG. 4 is a block diagram showing an outline of a color correction system suitable for carrying out this color correction method. Of course, the computer used in the present invention is not limited to a PC.

  In the PC 10, the CPU 11 serving as the center of the arithmetic processing controls the entire PC via the system bus 10a. The bus 10a includes a ROM 12 which is a non-rewritable semiconductor memory, a RAM 13 which is a rewritable semiconductor memory, a CD-ROM drive 15, a flexible disk (FD) drive 16, various interfaces (I / F) 17a to 17e, etc. And a hard disk (HD) 14 that is a magnetic disk is also connected via a hard disk drive. In the case of a printing system including a color correction device, the RAM 13 temporarily stores colorimetric data 13a, data 13b representing the specified selected color component amount, determined ink recording amount 13c, standard dot amount data 13d, and the like. Is done.

The HD 14 stores an operating system (OS), an application program (APL), and the like, and is appropriately transferred to the RAM 13 and executed by the CPU 11 at the time of execution. In the case of a printing system including the printing control apparatus of the present invention, the HD 14 includes the printing control program of the present invention, the ID 14a acquired from the printer, a plurality of color correction data 14b made into a one-dimensional LUT, a color conversion LUT (color conversion table). ) 14c, a dot allocation table (dot type correspondence data) 14d, various threshold values, and the like, and a predetermined storage area. A digital camera 50 or the like can be connected to the I / F 17a (for example, USB I / F).
In the case of a printing system including a color correction device, the HD 14 stores a color correction program, recording amount data 14g and 14h, various threshold values, and the like. In this case, the color measuring device 40 is connected to the I / F 17a. The color measuring device 40 directs the color detection unit 40a to the object to be measured, whereby a plurality of color components L, a, and b based on the Lab color system in the CIE (1976) standard are color component amounts (color values). The acquired color component amounts L, a, and b can be output to the PC 10. Here, the CIE Lab color space (predetermined color space) is a uniform color space that does not depend on a device having a plurality of color components L, a, and b as color component amounts. Note that L represents lightness (brightness), and a and b are color coordinates representing hue and saturation. Of course, the color space for color measurement may be a CIE XYZ color space, a CIE Luv color space, an RGB color space, or the like.
A display 18a for displaying an image corresponding to the data based on the color image data is connected to the CRTI / F 17b. A keyboard 18b and a mouse 18c are connected to the input I / F 17c as operation input devices, and a printer I / F 17e. For example, the printer 20 is connected via a serial I / F cable.

The printer 20 discharges six colors of ink filled in six ink cartridges 28 corresponding to each color of CMYRVK (cyan, magenta, yellow, red, violet, black) from the print head, A print image corresponding to print data representing a color image is printed by forming dots by attaching ink to print paper (print medium). Of course, a printer that uses light cyan, light magenta, light black, dark yellow, non-colored ink, or the like may be employed, or a printer that does not use any of CMYRVK inks may be employed. Various printing apparatuses such as a bubble printer that generates bubbles in the ink passage and discharges the ink and a laser printer that prints a print image on a print medium using toner ink can be employed. The ink used by the printing device may be liquid or solid. Each ink of the present embodiment is an ink in which a color material composed of a fine pigment is mixed in an aqueous solvent, but may be an ink in which a colorant composed of a dye is mixed, or an ink using an oil-based solvent It is good.
In the printer 20, a CPU 21, a ROM 22, a RAM 23, a communication I / O 24, a control IC 25, an ASIC 26, an I / F 27, and the like are connected via a bus 20 a, and the CPU 21 controls each unit according to a program written in the ROM 22.

Each ink cartridge 28 is mounted on a carriage that reciprocates in the main scanning direction by the carriage mechanism 27a, and a print head unit (print head assembly) 29 is mounted. The unit 29 includes print heads 29a to 29f and a nonvolatile semiconductor memory 31 provided for each of six types of CMYRVK inks. The memory 31 can be an EEPROM or the like, and is recorded with a color adjustment ID (error information) 31a used for correcting print data on the PC side. Each of the print heads 29a to 29f installed in the printer can eject ink of a corresponding color and adhere to the print paper, and the printer 20 uses the corresponding print head 29a to f for each type of ink. The dots are formed on the printing paper to print the print image.
Each cartridge 28 is provided with a memory chip 28a made of, for example, RAM, and each memory chip 28a is electrically connected to the control IC 25.

  The communication I / O 24 is connected to the printer I / F 17e of the PC 10, and the printer 20 receives raster data for each color transmitted from the PC 10 via the communication I / O 24. The ASIC 26 outputs applied voltage data corresponding to the raster data to the head driving unit 26a while transmitting / receiving a predetermined signal to / from the CPU 21. The head drive unit 26a generates an applied voltage pattern to the piezo elements incorporated in the print heads 29a to 29f from the applied voltage data, and causes the print heads 29a to 29f to eject six colors of ink in dot units. The carriage mechanism 27a and the paper feed mechanism 27b connected to the I / F 27 cause the print head unit 29 to perform main scanning, and sequentially feed print sheets while performing a page break operation as appropriate, thereby performing sub-scanning.

The print heads 29a to 29f are provided with a plurality of ink jet nozzles for each color, and piezo elements are arranged corresponding to the respective nozzles.
As shown in FIG. 5, the piezo element PE is installed at a position in contact with the ink passage 25b that guides ink to the nozzle Nz, and when a voltage having a predetermined time width is applied between the electrodes provided at both ends of the piezo element PE. Then, the voltage is extended for the time of voltage application, and one side wall of the ink passage 25b is deformed. As a result, the volume of the ink passage 25b contracts according to the expansion of the piezo element PE, and the ink corresponding to the contraction becomes ink droplets Ip and is ejected from the tip of the nozzle Nz at a high speed and soaks into the printing medium. Dots are formed and printing is performed.

  In the figure, driving waveforms for forming a predetermined number of types of dots having different ink amounts are shown, and dots having different ink amounts are formed by the driving waveforms V1 and V2 in a predetermined period. Since the degree of expansion and contraction of the piezo element increases as the voltage difference between the drive waveforms increases, the dot becomes larger. As shown in the lower part of the figure, this printer 20 can form three types of dots of large, medium, and small sizes on a print medium. Each dot can further form three types of dots with different ink amounts on the print medium. Accordingly, the printer ejects ink of different levels of ink from the same print head for each color, and forms dots having a size corresponding to the levels of ink of the multiple levels. The raster data transmitted from the PC to the printer is added with identification information for identifying nine types (predetermined number) of dot types, and the printer forms the types of dots corresponding to the identification information. When raster data composed of dot data representing the type of dot is input for each raster, the printer forms a plurality of types of dots having different ink amounts on the print medium in accordance with the raster data.

In the PC 10, a printer driver and the like for controlling the printer I / F 17e are incorporated in the OS, and various controls are executed. APL exchanges data with hardware via the OS. The printer driver is operated when the APL printing function is executed, and can perform bidirectional communication with the printer 20 via the printer I / F 17e. The printer driver receives print data from the APL via the OS and converts it into raster data. The data is converted and sent to the printer 20.
The print control program of the present invention may be configured by any of OS, APL, OS and APL. In addition to the HD 14, the medium on which these programs are recorded may be a CD-ROM 15a, FD, semiconductor memory, or the like. Further, the communication I / F 17d may be connected to the Internet network, and the program of the present invention may be downloaded from a predetermined server and executed.

  The printing control apparatus U0 shown in FIG. 1 includes an error acquisition unit U1 that is an error acquisition unit, and units U21 to U26 that are print control units. In the memory 31 of the print head unit of the printer, color correction patches (standard recording amount printed on a print medium for a total of 54 types of all six colors of ink and nine types of dots) ( An ID (error information) 31a representing a comparison result between the color measurement data obtained by measuring the color of the standard image) in the Lab color space and the reference color measurement data is recorded. The error acquisition unit U1 acquires all 54 types of IDs 31a from the printer 20 and stores them in the HD 14.

  The image input unit U22 receives the image data DA1 and converts the image into RGB data DA2 in which gradation is expressed by a plurality of pixels for each of RGB (red, green, and blue). The color conversion unit U23 color-converts the RGB data DA2 into CMYRVK data DA3 in which an image is expressed by a plurality of pixels for each CMYRVK. The dot distribution unit U3 refers to the dot distribution table 14d stored in the HD, and converts the CMYRVK data DA3 into dot amount data (print data) representing a plurality of types of dot formation amounts with different ink amounts by the same type. . Here, the dot amount compensation unit U21 uses the ID acquired by the error acquisition unit U1 to cause the dot distribution unit U24 to print the dot amount data representing the image on the printer. The dot amount data DA4 for compensating the color misregistration is corrected.

  The halftone processing unit U25 performs predetermined halftone processing on the corrected dot amount data DA4 to generate halftone data DA5. The rasterization processing unit U26 performs predetermined rasterization processing on the halftone data DA5, generates raster data DA6, and sends it to the printer. By the processing performed by these units U25 and U26, control is performed to cause the printer to print a print image corresponding to the corrected dot amount data DA4.

(2) Explanation of error information creation method:
The color correction system shown in FIG. 4 is assumed to be used in a printer production factory. A color colorimeter (colorimeter) 40 is connected to the PC 10 and a printer to be calibrated (hereinafter referred to as an object). The printer is also connected sequentially. In addition, a reference printer (reference printing device) as a reference, a first printer (first printing device) with a relatively small amount of ink adhering to the printing medium, and a printing medium that is more than the first printer. A second printer (second printing apparatus) with a large amount of ink adhering thereto is connected. Then, the calibration of the target printer is performed using the color of the print image reproduced on the print medium by the reference printer as the reference color.
In the color correction method of this embodiment shown in FIG. 3, the color correction patch (standard image) is printed by correcting the print data in which the color image is represented by sequentially performing steps S1 to S5. Color compensation of the target printer.

  Here, as shown in FIGS. 6 and 7, a description will be given together with a calibration process performed by a PC as a color correction apparatus.

In the color component selection step S1, first, a reference printer is connected to the PC 10, and the predetermined printer stored in the HD 14 for each ink color and each dot size, that is, for each combination of ink color and dot type. A plurality of color component selection patches (color component selection images) P1 in which the dot recording amount is changed from a plurality of dot recording amounts (a kind of ink recording amount) included in the color component selection recording amount data 14g. Is generated, and the PC 10 is caused to execute control for causing the reference printer to print each color component selection patch P1 corresponding to the standard dot amount data on the print medium (step S205, hereinafter “ “Step” is omitted). The standard dot amount data is data in which color component selection patches for each ink color and dot type are expressed by gradation data for each of a number of pixels in a dot matrix form. A predetermined halftone process and a predetermined rasterization process are performed on the standard dot amount data to generate raster data, and the raster data is sent to the printer, thereby printing a plurality of color component selection patches P1. These patches P1 are printed for each color and each ink size (for each type). Each patch P1 is a printed image composed of a primary color using only one type of ink, and the entire printed image is a plain image. Here, the dot recording amount can be, for example, the number of dots formed per unit area on the print medium. In this case, if the ink recording density (a kind of ink recording amount) is the ink weight deposited per unit area on the printing medium, the dot recording amount multiplied by the dot drop weight gives the ink recording density. Become.
Glossy paper such as photo paper is preferable as a print medium from the viewpoint of obtaining stable ink color and highly accurate color compensation, but it is more glossy than glossy paper from the viewpoint of reducing the cost of calibration work. Plain plain paper is preferred.

Next, using the colorimeter 40, each color component selection patch P1 printed on the printing medium is color-measured in the Lab color space, and the colorimetric data composed of a plurality of color component amounts L, a, and b are converted into color components. Obtained for each selection patch P1 (S210). Here, the color component amounts L, a, and b are the L amount, a amount, and b amount that define the CIE (1976) Lab color space defined in JIS Z8105. Of course, the L amount, the a amount, and the b amount may be converted by a linear equation or the like to obtain gradation values having the same predetermined number of gradations (for example, 256 gradations). Each gradation value is also a plurality of color component amounts, and the color reproducibility of the target printer with respect to the reference color can be obtained more reliably by setting all the plurality of color component amounts in the color space to the same gradation number. .
Further, based on the acquired colorimetric data and the recorded amount of dots printed with a plurality of color component selection patches P1, a change in the recorded amount of dots from among the plurality of color component amounts L, a, and b is detected. Then, the selected color component amount having the largest change is specified as the color component amount for correcting the print data (S215).

FIG. 8 shows the ratio of the number of dots formed with respect to the total number of pixels in a predetermined area on the print medium for a large Y dot 1, that is, a dot recording rate (a kind of ink recording amount) that is a relative value of the dot recording amount. 10 shows an example of a result obtained by printing nine color component selection patches of 10 to 90% in 10% increments on glossy paper and performing color measurement in the Lab color space. Here, the horizontal axis represents the dot recording rate (% unit), and the vertical axis represents the L amount, a amount, and b amount that define the Lab color space. In the example of the figure, among the color component amounts L, a, and b, the b amount having the largest change with respect to the change in the dot recording rate is set as the selected color component amount and specified as the color component amount for correcting the print data.
For example, in colors and dot types that specify the selected color component amount, the color component selection patches with different dot recording rates R1 (first recording amount), R2 (second recording amount), and dot recording rate R1 are measured. Color component amounts L, a, and b are L1, a1, and b1, respectively, and color component amounts L, a, and b are measured when a color component selection patch having a dot recording rate R2 (R2> R1) is measured. Are L2, a2, and b2, respectively. When ΔL = | L2−L1 |, Δa = | a2−a1 |, and Δb = | b2−b1 | are calculated as the difference in color component amount for both color component selection patches of the recording ratios R1 and R2, ΔL and Δa , Δb are values that increase as the difference in color component amount between the two color component selection patches of the recording ratios R1 and R2 increases. Therefore, the color component amount of the color component corresponding to the maximum calculated value from ΔL, Δa, and Δb can be specified as the selected color component amount. If the minimum dot recording rate and the maximum dot recording rate among the changed dot recording rates are the recording rates R1 and R2, good color reproducibility with respect to the reference color can be obtained for the target printer.

  When the selected color component amount is specified, in the recording amount determination step S2, first, the first printer that has a relatively small amount of ink adhering to the print medium and the second ink that has a relatively large amount of ink adhering to the print medium. With the printer connected to the PC 10, for each ink color and dot type, dot recording is performed from a plurality of dot recording amounts included in the predetermined recording amount determination recording amount data 14h stored in the HD. The PC 10 is caused to execute control for causing the first and second printers to print a plurality of recording amount determination patches (recording amount determination images) P2 with different amounts on a predetermined print medium (S220 to S225). . The standard dot amount data is data in which a recording amount determination patch is expressed by gradation data for each of a number of pixels in the form of a dot matrix for each ink color and dot type, and when the plurality of patches P2 are printed. In this case, halftone processing and rasterization processing are performed on the standard dot amount data, and the generated raster data is sent to the printer. These patches P2 are also printed for each color and each ink size (for each type). Each patch P2 is a printed image composed of a primary color using only one type of ink, and the entire printed image is a uniform solid image. Here, when the first print head having a relatively large weight of ink to be ejected is attached to the reference printer, the first printer can be obtained, and the second ink having a larger weight of ink to be ejected than the first print head. When the print head is attached to the reference printer, the second printer can be obtained.

Next, using the colorimeter 40, each recording amount determination patch P2 printed by the first printer is measured in the Lab color space, and the selected color component amount selected in step S1 is determined as the recording amount. For each patch P2 (S230). The selected color component amount acquired here is the first selected color component amount. Further, the color measuring device 40 is used to measure each recording amount determination patch P2 printed by the second printer in the Lab color space, and the selected color component amount selected in step S1 is used to determine the recording amount. Obtained for each patch P2 (S235). The selected color component amount acquired here is the second selected color component amount.
Further, from the first and second selected color component amounts and the recorded amount of dots printed with the plurality of recording amount determination patches P2, the amount of ink attached to the print medium generated for each printer with respect to the selected color component amount is determined. The recording amount with the largest fluctuation due to variation is determined as the standard recording amount and stored in the RAM 13 (S240). The stored same recording amount 13c is determined for each color and for each dot type, and is the recording amount of dots of each color correction patch P3 used for correcting the color of the target printer.
The process shown in FIG. 6 is performed for all colors and dot types.

For the Y large dot 1 described above, since the b amount is the selected color component amount, the b amounts of the plurality of recording amount determination patches P2 printed by the first and second printers are acquired. The dot recording amount of each color correction patch P3 is determined using the b amount and the dot recording amount.
Fig. 9 shows the Lab color space by printing 9-level recording rate determination patches on glossy paper with a dot recording rate of 10% in 10% increments for Y large dot 1, medium dot 1 and small dot 1 1 shows an example of the result of measuring the color and calculating the variation amount of the selected color component amount (b amount) for each dot recording rate. Here, the horizontal axis represents the dot recording rate (% unit), and the vertical axis represents the fluctuation amount (Vb) of the b amount. In the example shown in the figure, in the case of large dot 1, the dot recording rate 30% has the largest fluctuation amount Vb, so the dot recording amount (determined recording amount) of the color correction patch P3 is determined to be 30%. Similarly, in the case of medium dot 1, the dot recording amount of the color correction patch P3 is determined to be 50%, and in the case of small dot 1, the dot recording amount of the color correction patch P3 is determined to be 90%.

Generally, when each dot recording rate is Ri (i is an integer of 2 or more) and the first and second selected color component amounts at each recording rate Ri are S1i and S2i, respectively, the selection is made at each recording rate Ri. The color component amount variation amount VSi can be calculated from, for example, VSi = | S2i−S1i |. The dot recording rate Ri corresponding to the maximum VSi among the plurality of VSi can be determined as the dot recording rate DR of the color correction patch P3.
Of course, the amount of selected color components at each dot recording rate Ri may be acquired for three or more printing apparatuses, and the variation amount VSi at each recording rate Ri may be a value obtained by statistical processing such as dispersion or standard deviation.

  Note that the first printer is a printer that measures the weight (ink amount) of ink ejected from the print head for a plurality of printers and ejects ink at the lower limit of ink weight variation, and ink at the upper limit of ink weight variation. The printer that discharges the ink may be a second printer. In other words, the first printer is a printer that deposits ink on the print medium at the lower limit of variation in ink weight, and the second printer is a printer that deposits ink on the print medium at the upper limit of variation in ink weight. . As a result, the dot recording amount that maximizes the variation due to the variation in the amount of ink adhering to the print medium can be determined more reliably with respect to the selected color component amount. Can do.

  When the dot recording rate of the color correction patch P3 is determined, in the standard image printing control step S3, first, the reference printer is connected to the PC 10, and the recording amount 13c determined from the recording amount 13c determined in step S2 is set. Standard dot amount data 13d that expresses a reference color correction patch (reference standard image) for each ink color and each dot type is generated (S245) and corresponds to the standard dot amount data 13d for the reference printer. The PC 10 is caused to execute control for printing each reference color correction patch P4 on the printing medium (S250). Further, standard dot amount data for expressing a color correction patch (standard image) of the recording amount for each ink color and for each dot type from the recording amount 13c with the printer to be calibrated connected to the PC 10. 13d is generated, and the PC 10 is caused to execute control for causing the printer to print each patch P3 corresponding to the standard dot amount data 13d on the print medium (S255). The standard dot amount data 13d is data in which patches for color correction are expressed by gradation data for each of a number of pixels in the form of a dot matrix for each ink color and dot type. When printing the plurality of patches, Halftone processing and rasterization processing may be performed on the standard dot amount data, and the generated raster data may be sent to the printer.

  FIG. 10 shows a calibration sheet in which a plurality of color correction patches P3 are printed on the printing paper. A calibration sheet obtained by printing a plurality of reference color correction patches P4 on the same type of printing paper has the same configuration. Each patch P3 is a printed image composed of a primary color using only one type of ink, and the entire printed image is a plain image. Of course, a print image composed of at least a secondary color using two or more types of ink may be used as a color correction patch or a reference color correction patch. The plurality of patches P3 are images having only one standard dot recording amount for each ink color and each dot type. In the example of the figure, it is shown that 54 patches P3 obtained by multiplying the number of ink types 6 and the number of dot types 9 are printed. By printing only one type of color correction patch for each condition and using it for color correction of the target printer, the calibration operation can be performed quickly. Here, each patch P3 is printed with the dot recording amount determined in step S2. That is, each color correction patch has a variation due to variations in the amount of ink adhering to the print medium that occurs for each printer with respect to the selected color component amount specified from the color component amounts L, a, and b in the color component selection step. Printing is performed with the largest dot recording amount.

If each patch P4 having the above-mentioned conditions is printed on the print medium by the reference printer in advance, the step of causing the reference printer to print the color correction patch can be omitted in step S3.
As described above, in step S3, the target printer is controlled to print a standard image having a standard recording amount for each ink on the print medium.

When the color correction patch P3 is printed, in the colorimetric data acquisition step S4, first, each color correction patch printed on the print medium from the reference printer is measured in the Lab color space by the colorimeter 40, and the ink Colorimetric data of a color correction patch is acquired for each color and each dot type (S260). This is reference colorimetric data that is colorimetric data that is the reference of the colorimetric data. Further, each color correction patch P3 printed on the printing medium from the target printer is measured in the Lab color space by the colorimeter 40, and the color measurement data of the patch P3 is acquired for each ink color and each dot type. (S265). In the present embodiment, since the colorimeter 40 outputs all the color component amounts L, a, and b to the PC, the PC will be described as acquiring all the L amount, a amount, and b amount of each patch. Only the selected color component amount may be acquired from the L amount, the a amount, and the b amount. Then, the configuration of the program and apparatus for performing the present color correction method is simplified.
If the color measurement data of each color correction patch printed on the printing medium from the reference printer is prepared in advance, the step of obtaining the color measurement data of each patch P4 of the reference printer can be omitted in step S4. .

When the color measurement data of the color correction patch is acquired, in the color correction step S5, the color measurement data of both patches P4 and P3 are compared for each ink color and for each dot type, and the ID indicating the comparison result is displayed. Then, the color adjustment ID 31a is generated (S270), and the ID 31a is stored in the memory 31 of the print head unit (S275). When the memory 31 is a PROM or the like, the ID 31a may be recorded in the memory 31 using a ROM writer or the like. The ID may be recorded in the ROM 22 of the printer.
When comparing the colorimetric data of both patches P3 and P4, the comparison is made using only the selected color component amount specified in step S1. Then, the generated ID 31a is information representing a comparison result of only the color component amount (color value) having the largest change with respect to the change in the dot recording amount among the plurality of color component amounts. Of course, it can be said that the ID 31a is a comparison result of the color component amount with the largest change. In the example of FIG. 3, since the b amount is selected as the selected color component amount, the value of Δb is obtained by comparing the b amount of the reference color correcting patch P4 with the b amount of the color correcting patch P3. It is shown that the comparison result ID is generated based on the value of Δb.
If the selected color component amount of the reference color correction patch is S0, the selected color component amount of the color correction patch is SS, and the predetermined coefficient is c (c> 0), the value of the comparison result ID is, for example, ID = C · (SS−S0).
Note that the processing of S255, S265 to S275 is performed for all target printers.

FIG. 11 shows how the ID is determined. The upper part of the figure shows the selected color component amounts S0, SS obtained by measuring the patches P4, P3 for each color when the dot type is the small dot 1. In the case of the small dot 1, when the ink is C, the selected color component amount is L amount, when M is the selected color component amount is a amount, and when Y is Y, the selected color component amount is b amount and K. In some cases, the selected color component amount is L and the like, and the selected color component amount is specified for each color. Therefore, the selected color component amount obtained by color measurement is the color component amount corresponding to the ink color. Yes.
The selected color component amounts S0 and SS in both patches P4 and P3 are acquired for each color and for each dot size, and the ID value is calculated using the above formula ID = c · (SS−S0). . The middle part of the figure shows the ID value for each color in the case of the small dot 1. Here, ID values are calculated for 54 types of all combinations of all six colors of ink and all nine types of dots. Examples of calculated values of all IDs are shown in the lower part of the figure.
In this way, an ID can be generated for each color and each dot type. Each generated ID is recorded in a predetermined area in the memory 31.

The generated ID contrasts only the selected color component amount specified in step S1 as the color component amount having the greatest change with respect to the change in the dot recording rate from among the color component amounts L, a, and b in the Lab color space. This is error information representing the comparison result. The ID indicates that only the color correction patch printed on the print medium with the dot recording amount having the largest variation in the colorimetric data due to the variation in the amount of ink adhering to the print medium generated for each printer is the Lab color. It is also error information representing a comparison result obtained by comparing colorimetric data obtained by colorimetry in space.
When the ID is recorded in the memory 31, the ID 31 is read from the memory 31, and by using the ID 31, the print data that represents the color image is changed to print data that compensates for the color shift of the print image printed by the target printer. Correct it. As a result, the print data can be corrected so as to compensate the color of the printer on which the color correction patch is printed.

(3) Print control processing:
FIG. 12 is a flowchart illustrating a process of correcting print data using the ID 31a and performing print control based on the corrected print data. FIG. 13 is a diagram schematically showing the processing. FIG. 14 is a diagram schematically showing the structure of a plurality of color correction data 14b stored in the HD 14. As shown in FIG. The color correction data 14b is stored in the HD corresponding to the ID of each stage of the ID value.
First, the PC 10 determines whether or not the ID 31a has been acquired from the printer 20 by the error acquisition unit U1 (S105). If the condition is satisfied, it is determined that it is not necessary to acquire an ID from the printer, and the process proceeds to S120. Even when the printer connected to the PC 10 is changed, it is determined that there is no ID corresponding to the printer, and the process proceeds to S120.
If the condition is not satisfied, a request for obtaining the color adjustment ID is created and transmitted to the printer 20 (S110). Then, the printer 20 receives the acquisition request, reads out 54 types of IDs 31a including all 6 types of ink and 9 types of dots from the memory 31 of the print head unit, and transmits them to the PC. Therefore, the PC acquires all IDs 31a and stores them in the HD 14 (S115). As described above, since the color adjustment ID is integrated with the printer, the user of this printing system does not need to input the color adjustment ID separately even if the printer is changed. Therefore, this printing control apparatus is convenient.

  In S120, the image input unit U22 inputs image data D1 composed of gradation data corresponding to a plurality of element colors for each of a large number (predetermined number) of pixels, and the image is composed of a plurality of pixels for each RGB. Conversion into RGB data in a wide-range RGB color space expressed by gradation. At this time, data may be partially read, or only a pointer indicating a buffer area used for data transfer may be transferred. The input image data D1 is data in which an image is expressed by gradation data for each of a number of pixels in the form of a dot matrix. The image data is composed of RGB defined in the sRGB color space, or in the YUV color system. Image data composed of YUV, and the like. Of course, data conforming to the Exif 2.2 standard (Exif is a registered trademark of the Japan Electronics and Information Technology Industries Association), data corresponding to Print Image Matching (PIM: PIM is a registered trademark of Seiko Epson Corporation), and the like may be used. Since each component of the image data has various gradation numbers, the image data is converted into RGB data of 256 gradations of RGB in the wide RGB color space according to the definition of sRGB or YUV color system. The RGB data is print data representing an image with a plurality of element colors RGB.

Next, the color conversion unit U23 refers to the color conversion LUT 14c while sequentially moving the target pixel using the gradation data of each pixel constituting the RGB data as the conversion target, and converts the RGB data into the respective CMYRVK inks. Color conversion is performed to CMYRVK data D2 including gradation data corresponding to the usage amount (S125). The color conversion LUT 14c is an information table that defines a correspondence relationship between the RGB data and CMYRVK data in which an image is expressed in gradation by the same number of pixels for each CMYRVK for a plurality of reference points. When CMYRVK data that matches the input RGB data is not stored in the color conversion LUT, CMYRVK data corresponding to a plurality of RGB data close to the input RGB data is acquired, and RGB data is obtained by interpolation such as volume interpolation. To CMYRVK data corresponding to. The CMYRVK data D2 is print data in which an image is expressed by gradation data for each of a large number (predetermined number) of pixels in a dot matrix like RGB data, and represents the amount of ink used by the printer 20 ejected from the print head. It is assumed that the data is 256 gradations for each CMYRVK.
Thereafter, the dot distribution unit U24 configures the CMYRVK data after color conversion by referring to the dot distribution table 14d while sequentially moving the target pixel using the gradation data of each pixel constituting the CMYRVK data as the conversion target. A dot distribution process is performed to convert gradation data (input gradation data) for each CMYRVK color into dot amount data (output gradation data) representing a plurality of types of dot formation amounts with different ink amounts by the same type (S130). . In this embodiment, color misregistration is compensated by correcting dot amount data (print data) using ID.

  As shown in the upper part of FIG. 15, the dot allocation table 14d is a correspondence relationship between input gradation data representing the amount of ink used in the printer and output gradation data representing the amount of dot formation for each type of dot. Is an information table that defines The table 14d is provided for each color, and stores output gradation values representing the dot formation amount at each gradation of the input gradation values for each dot type. In FIG. 13, the horizontal axis represents the input tone value, and the vertical axis represents the relative value of the output tone value, and the dot amount data of small, medium, and large dots with respect to the input tone value is schematically shown. In the present embodiment, three types of dot size setting modes are provided. Therefore, in the dot distribution table 14d, the output gradation data D11, the small dot 2, and the medium dot that are referred to when forming the small dot 1, the medium dot 1, and the large dot 1 corresponding to each setting mode 1 to 3. Output gradation data D12 referred to when forming the dot 2 and the large dot 2, and output gradation data D13 referred to when forming the small dot 3, the medium dot 3, and the large dot 3 are stored. .

  In the dot allocation process, the gradation data constituting the CMYRVK data is allocated to the usage amounts of a plurality of types of dots corresponding to the setting modes 1 to 3 with reference to the dot allocation table, and for small dots as shown in FIG. Dot amount data D3, medium dot amount data D4, and large dot amount data D5 are generated. Similar to the CMYRVK data, these dot amount data D3 to D5 are data representing the image with gradation data for a large number (predetermined number) of pixels in a dot matrix, and for each dot ejected from the print head by the printer 20. It is assumed that CMYRVK data representing each ink usage amount is 256 gradation data.

  However, even if the printer performs printing using the dot amount data at this stage, there may be a slight error in the color of the image printed on the print medium. This is due to a deviation in the weight of the ink ejected from each print nozzle row, a slight variation in the voltage applied to the print head when the print head is assembled to the printer, and the like. In addition, depending on the variation in voltage and the assembled state of the print head, the dots formed on the print medium may be broken, resulting in a non-circular shape. As a result, the color of the printed image may vary slightly. Therefore, the dot amount data is corrected so as to compensate for such color variations.

When each dot amount data is generated, the dot amount compensation unit U21 sets the color and dot type to be corrected for the dot amount data (S135). For example, if different numerical values are associated with 54 types of all inks and all dots and the value of the pointer for storing the numerical values is sequentially updated, the target color and dot type are set from among all 54 types. Good. Next, the ID 14a of the set color and dot type is read from the HD, the color correction data corresponding to the value of the ID 14a is specified from the plurality of color correction data 14b stored in the HD, and the color correction data is read. (S140). Here, since the color correction data is data defining the color correction correspondence between the dot amount data before correction and the dot amount data after correction, the color correction correspondence relationship of the dot amount data is specified based on the ID. Will be. Then, the target pixel is referred to by referring to the color correction data read in S140 while sequentially moving the target pixel with the gradation data of each pixel constituting the dot amount data corresponding to the set color and dot type as the conversion target. Are corrected, and corrected dot amount data D6 to D8 are generated (S145).

  When the ID is a negative value, the target printer has a smaller degree of color development on the print medium than the reference printer. Therefore, as shown in FIG. 14, the degree of color development of the print image is increased. As a whole, the color correction data has an output tone value larger than the input tone value. Thus, by referring to such color correction data, the tone value of the color and dot type dot amount data having a negative ID is greatly corrected as a whole. On the other hand, when the ID is a positive value, the target printer has a higher degree of color development on the print medium than the reference printer, and as shown in FIG. As a result, the color correction data has an output gradation value smaller than the input gradation value as an overall tendency. Therefore, by referring to such color correction data, the tone value of the color and dot type dot amount data having a positive ID is corrected to be small as an overall tendency. As a result, the color compensation of the printing apparatus on which the color correction patch is printed can be performed.

Thereafter, it is determined whether or not all colors and dot types have been set (S150). If the condition is not satisfied, S135 to S150 are repeated, and if the condition is satisfied, the process proceeds to S155.
In S155, the halftone processing unit U25 performs predetermined halftone processing such as an error diffusion method, a dither method, and a density pattern method on the dot amount data for each dot size, and the same number of pixels as the number of pixels of the CMYRVK data. The halftone data for each CMYRVK is generated. The halftone data is data representing the dot formation status as the presence / absence of dot formation. For example, the gradation value “1” is binarized by corresponding to dot formation and the gradation value “0” corresponding to no dot formation. Two-level binary data can be obtained. Of course, it is good also as data of 4 gradations.

  Further, the rasterization processing unit U26 performs a predetermined rasterization process on the generated halftone data and rearranges the generated halftone data in the order used by the printer to generate raster data for each CMYRVK (S160). Output (S165), the flow ends. Then, the printer 20 obtains raster data representing the image, drives the print head based on these data, ejects ink, and deposits it on the print paper, thereby forming a print image corresponding to the RGB data. . Since the raster data is data in which color misregistration is compensated for each CMYRVK, the print image is an image in which color misregistration is compensated. Here, the target printer is color-compensated based on the color adjustment ID representing the comparison result between the color measurement data of the color correction patch actually printed on the print medium by the target printer and the reference color measurement data. Therefore, there is no subtle error in the color of the printed image due to subtle variations in the voltage applied to the print head. Therefore, the color reproducibility with respect to the reference color is improved for the printed image as compared with the conventional case where only the ink weight is compensated.

In this way, when RGB data is input and converted into dot amount data, an error with respect to the reference colorimetric data in the colorimetric data of the color correction patch actually printed on the print medium by the target printer is compensated. Control that specifies the color correction correspondence of dot amount data before and after correction based on the ID, converts it to dot amount data corrected by the color correction correspondence, and causes the printer to print a high-quality print image after color compensation It can be performed. Dot amount data to be corrected, so is modified to shift disappears with respect to the reference colorimetric data definitive color measurement data of color correction patch that is printed on a print medium, the color reproducibility with respect to the reference color for the print image Will be very good. If the printer can execute halftone processing, multi-tone CMYRVK data may be sent to the printer to correct the dot amount data.

Here, the color correction correspondence relationship of the dot amount data before and after correction can be specified as follows.
That is, the target printer is controlled to print a standard color correction patch for each ink color and each dot type on the print medium, and a plurality of color components as in the Lab color space are color component amounts. The color correction patch printed on the same print medium in the predetermined color space is measured to obtain color measurement data of the same color correction patch. Then, the obtained color measurement data is compared with the reference color measurement data, and the color correction correspondence relationship before and after the correction of the dot amount data for color compensation of the target printer is specified using the comparison result comparison result.
Then, the PC 10 that performs the print control process corrects the dot amount data according to the color correction correspondence relationship, and performs printing that controls the target printer to print a print image corresponding to the corrected dot amount data on the print medium. It becomes a control device.

  Note that print data to be corrected at the time of color compensation can be halftone data, raster data, or the like in addition to the dot amount data. In the case of these data, the print image can be color-compensated by increasing or decreasing the number of dots formed on the print medium at a ratio corresponding to the ID value. Further, when the dot size is one kind, the CMYRVK data immediately after the color conversion can be used as the print data to be corrected. In the case of the CMYRVK data, the color of the print image can be compensated by referring to the color correction data corresponding to the ID value as in the case of the correction for the dot amount data. Of course, even for RGB data before color conversion, a color correction LUT that defines the correspondence between the RGB data before correction and the RGB data after correction is prepared in correspondence with each value of the ID, and the ID value By correcting the RGB data with reference to the corresponding color correction LUT, the print image can be color compensated.

  In addition, when the dot size is one type, in addition to the dot recording rate, the ink recording density, which is the weight of ink deposited per unit area on the print medium, all pixels in a predetermined area on the print medium The ratio of the ink weight deposited on the print medium in the same area with respect to the ink weight when the ink dots are formed on the print medium, that is, the ink recording rate may be used as the ink recording amount. Then, the selected color component amount is specified, and the selected color component amount is printed with a color correction patch with the ink recording amount having the largest variation due to variation in the amount of attached ink as a standard recording amount. By correcting the print data using the comparison result of only the selected color component amount, the printer can be color compensated.

As described above, the color of the printer based on the error information indicating the comparison result between the color measurement data of the color correction patch on the print medium printed by the printer to be controlled and the reference color measurement data. Since the deviation is compensated, there is no subtle error in the color of the printed image due to subtle variations in the voltage applied to the print head. Accordingly, it is possible to improve the color reproducibility of the print image with respect to the reference color. In addition, the error information represents the comparison result of the selected color component amount having the largest change with respect to the change in the ink recording amount among the plurality of color component amounts in the color space used as the colorimetric reference, and printing. Since the colorimetric data comparison results of the color correction patch with the ink recording amount with the largest variation in the colorimetric data due to variations in the amount of ink adhering to the medium are shown, the print image is also excellent with respect to the reference color for this point. Color reproducibility can be obtained.
Furthermore, the error information is obtained by using the comparison result for only the selected color component amount having the largest change with respect to the change in the ink recording amount from among the plurality of color component amounts in the color space used as a colorimetric reference when creating the error information. Therefore, complicated calculation is not necessary in the calibration operation of the printing apparatus to be printed. Therefore, it is possible to speed up the calibration work. Further, since the color measurement data of only the color correction patch having the ink recording amount with the largest variation in the color measurement data is used when the error information is created, the calibration operation can be speeded up in this respect as well.

(4) Modification:
By the way, various configurations are possible for the computer and the peripheral device that can be used in carrying out the present invention. For example, the printing apparatus may be integrated with a computer. A printing apparatus that prints only a single color image may be used. A part or all of the above-described flow may be executed by a printing apparatus or a dedicated image processing apparatus.

In addition, as shown in FIG. 16, when correcting the dot amount data, the dot distribution table 14d itself may be corrected, and the dot amount data may be corrected with reference to the corrected table. Note that S105 to S130 and S155 to S165 are almost the same as those in FIG. 12, but after the ID is stored in the HD 14 in S115, the process proceeds to S405.
In S405, all the dot distribution table 14d provided for each color is read from the HD. Next, the target color and dot type to be corrected in the data of the table 14d are set (S410), the set color and dot type ID 14a is read from the HD, and the plurality of color correction data 14b stored in the HD is stored. Then, the color correction data corresponding to the value of the ID 14a is specified, and the color correction data is read (S415). Further, referring to the read color correction data, the data in the table 14d corresponding to the set color and dot type is corrected (S420).

As shown in the lower part of FIG. 14, the color correction data 14b indicates the correspondence between the input gradation value Ai (i is an integer from 0 to 255) and the output gradation value for each color and for each dot type. The information table defines each gradation (all gradations) of the value Ai. In the case of the gradation value in the small dot 1 of C, the output gradation value ACi with respect to the input gradation value Ai is defined as a solid line in the upper part of the figure. Such a correspondence relationship is defined for types of dots other than the small dot 1, and MYRVK is also defined for each dot type.
As shown in FIG. 15, both dot allocation tables before and after correction refer to the output gradation value corresponding to the dot type from the address corresponding to the value of each gradation data constituting the CMYRVK data, and the CMYRVK data is color-coded. It can be converted into dot amount data for each dot type. When correcting the reference dot distribution table 14d before correction, the corrected dot distribution table can be created by replacing the output gradation value of the table 14d with the output gradation value of the color correction data 14b. For example, when the output gradation value of the C small dot 1 in the reference table 14d is Ai, the output gradation value ACi is stored in the color correction LUT of FIG. 14 corresponding to the input gradation value Ai. Therefore, the output gradation value Ai of the C small dot 1 is corrected by replacing Ai with ACi for the output gradation value of the table 14d.

When the corrected dot distribution table is generated, it is determined whether or not all colors and dot types have been set (S425). If the condition is not satisfied, S410 to S425 are repeated, and if the condition is satisfied, the process proceeds to S120. Image data is input, color conversion is performed, and dot amount data is generated with reference to the corrected dot assignment table (S120 to S130). Then, the printer can print the color-compensated print image using the dot amount data (S155 to S165).
As described above, once the dot distribution table is corrected and stored, the processing for correcting the print data can be speeded up, and the processing speed of print control for the printer can be improved.

  When creating the error information, the standard recording rate table D21 shown in FIG. 17 is stored in advance in the HD of the PC used as the color correction device, and by using the table D21, the color to be printed as the ink amount of dots increases. It is also possible to reduce the dot recording amount of the correction patch and cause the printer to print a color correction patch with a standard recording amount on the print medium for each dot type. As shown in FIG. 9, the maximum value of the selected color component amount variation amount VSi for the dot recording rate of a certain color is because the dot recording rate decreases as the ink amount of dots increases. The standard recording rate table D21 is provided for each color and for each setting mode (dot size setting mode). FIG. 17 shows an example for the Y setting mode 1.

FIG. 18 shows a calibration process performed by the color correction apparatus used for performing the calibration work using the standard recording rate table.
In this modification, instead of performing the processing of FIG. 6, first, the standard dot recording rate SR for each color and dot type is acquired from the standard recording rate table D21 stored in the HD, and temporarily stored in the RAM. (S605). That is, the standard dot recording rate SR, which is reduced as the ink amount of dots increases, is specified as the standard dot recording amount for correcting print data. Next, standard dot amount data 13d representing a plurality of corresponding solid color correction patches is generated from the dot recording amount acquired in S605 for each color and each dot type, and is temporarily stored in the RAM ( S610). Thereafter, a plurality of reference color correction patches P4 are printed on the reference printer (S615), colorimetric data of each reference color correction patch P4 is acquired (S620), and a plurality of color correction patches P3 are applied to the target printer. Printing is performed (S625), and colorimetric data of each color correction patch P3 is acquired (S630). By the processing of S615 and S625, the dot recording amount of the color correction patch to be printed is reduced as the ink amount of the dot is increased, and the color correction patch of the standard recording amount is printed for each type of dot to the printer. Can be printed on top. Then, an ID value c · (SS−S0) corresponding to the difference only in the selected color component amount is calculated for each color and for each dot type (S635), and the determined ID is recorded in the memory 31 of the target printer (S640). ), S625 to S645 are repeated until the IDs are recorded in the memories 31 of all the target printers (S645).

Thereafter, when the print control process shown in FIG. 12 is performed, the dot amount data (print data) for each ink color and each dot type can be corrected so as to compensate the color of the print image in the target printer. The print image corresponding to the print data can be controlled to be printed on the print medium.
If the small dot is the first dot according to the present invention and at least one of the medium dot and the large dot is the second dot according to the present invention, the dot recording of the color correction patch to be printed with the second dot is performed. The color correction patch with the standard dot recording amount for each of the first and second dots is printed on the print medium by making the amount smaller than the dot recording amount of the color correction patch to be printed with the first dot. Will be printed. The same applies to the case where the large dot is the second dot and at least one of the small dot and the medium dot is the first dot.

Since the dot recording amount with a large variation in the selected color component amount due to the variation in the amount of ink adhering to the print medium that occurs for each printer becomes smaller as the ink amount of the dot increases, the color reproduction of the print image with respect to the reference color is performed by the above processing. It is possible to improve the property.
As described above, according to the present invention, it is possible to obtain good color reproducibility with respect to the reference color for a printed image according to various aspects.

FIG. 2 is a block diagram schematically illustrating a configuration of a print control apparatus. 1 is a block diagram showing a configuration of a printing system. The figure which shows the color correction method typically. The block diagram which shows the outline of a color correction system. The figure which expands and shows a nozzle and its internal structure. The flowchart which shows a calibration process. The flowchart which shows a calibration process. FIG. 6 is a diagram illustrating an example of color measurement results of color component amounts L, a, and b with respect to dot recording rates. The figure which shows an example of the variation amount of the selection color component amount with respect to a dot recording rate according to dot type. The figure which shows a calibration sheet | seat. The figure which shows a mode that color adjustment ID is determined typically. 6 is a flowchart showing print control processing. The figure which shows a printing control process typically. The figure which shows typically the structure of several color correction data. The figure which shows the structure of a dot allocation table typically. 9 is a flowchart showing print control processing in a modification. The figure which shows typically the structure of a standard recording rate table in a modification. The flowchart which shows a calibration process in a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Personal computer (PC), 11 ... CPU, 12 ... ROM, 13 ... RAM, 14 ... Hard disk (HD), 14a ... Color adjustment ID (error information), 14b ... Color correction data, 14d ... Dot distribution table, 20 DESCRIPTION OF SYMBOLS ... Inkjet printer, 29 ... Print head unit, 29a-f ... Print head, 31 ... Non-volatile semiconductor memory, 31a ... Color adjustment ID (error information), 40 ... Color colorimeter, D1 ... Image data, D2 ... CMYRVK data D3 to D5 ... Dot amount data (print data) before correction, D6 to D8 ... Dot amount data (print data) after correction, D11 to D13 ... Output gradation data, D21 ... Standard recording rate table, P1 ... Color Component selection patch (color component selection image), P2... Recording amount determination patch (recording amount determination image), P3. Fixed patch (standard image), P4 ... reference color correction patch, U0 ... print control unit, U1 ... error acquisition unit (error acquisition unit), U21~U26 ... print control means

Claims (2)

A color correction method for compensating for color misregistration of a printing apparatus that prints a print image corresponding to print data on a print medium using a print head that deposits ink on the print medium,
It intends row control to print on the printing medium to the ink amount of variation above printing apparatus standard image change is largest ink recording amount of colorimetric data by adhering onto the printing medium caused for each of the printing device and as Engineering,
A colorimetric data acquisition step of measuring the standard image of the ink recording amount printed on the print medium with the largest variation in a predetermined color space and acquiring colorimetric data of the standard image;
Color measurement data of the standard image; reference color measurement data obtained by measuring the standard image of the ink recording amount printed on the print medium with the largest variation in the predetermined color space; and The print data is acquired so as to compensate for the deviation of the colorimetric data of the standard image with respect to the reference colorimetric data by using the acquired error information. And a color correction step of correcting the color . The step of controlling the printing apparatus to print the standard image of the ink recording amount with the largest fluctuation on the printing medium ,
A plurality of recording amounts in which the recording amount of the ink is changed with respect to the first printing device and the second printing device having a larger amount of ink adhering to the printing medium than the first printing device. The determination image is printed on the printing medium, and each recording amount determination image printed by the first printing apparatus is color-measured in the predetermined color space, and the first recording amount determination image The second colorimetric data for each recording amount determination image obtained by measuring each recording amount determination image printed by the second printing apparatus in the predetermined color space. The amount of ink adhering to the printing medium generated for each printing device from the first and second selected color component amounts and the recording amount of the ink on which the same plurality of recording amount determination images are printed The ink recording amount with the largest variation in colorimetric data due to variations in color is determined as the standard recording amount. Has that record amount determining step,
The color correction method according to claim 1 , wherein the standard image of the ink recording amount determined in the recording amount determination step is printed on the printing medium by the printing apparatus.

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