JP2007055013A - Color correcting device, color correction method and color correction program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and the like for acquiring an ink correction factor whereby information necessary for performing color correction of data which expresses a printing image can be correctly acquired, and a good color reproducibility in the printing image can be achieved in the case where a plurality of drive signal generating circuits are equipped. <P>SOLUTION: The device for acquiring the ink correction factor comprises a printing head in which an ID indicating a gap between an ink amount of dots ejected and a reference ink amount of the dots is recorded in a predetermined recording region, and the plurality of drive signal generating circuits each capable of generating a drive signal that includes a driving pulse and feeding the signal to the printing head. The comprises a patch output means which makes the printing head eject the dots of a predetermined size by supplying the drive signal of a predetermined waveform from the drive signal generating circuit to the printing head, thereby printing a patch in a state with the gap of the ink amounts indicated by the ID being compensated, and a correction factor calculating means which calculates a correction factor corresponding to the gap of the ink amounts caused by driving errors of the drive signal generating circuits for every drive signal generating circuit by subjecting the patch to colorimetry and comparing a colorimetric value acquired by the colorimetry with a predetermined standard value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a color correction apparatus, a color correction method, and a color correction program.

Conventionally, for each print head corresponding to the ink type (for example, cyan (C), magenta (M), yellow (Y), black (K)) used in the color printing apparatus, it corresponds to the deviation of the ink weight to be ejected. A technique is known in which the acquired ID is acquired and the color image data for printing is corrected using this ID during printing (for example, Patent Document 1).
Japanese Patent Laid-Open No. 10-278360

In the above prior art and the like, the ID to be written in the recording area of the print head is determined based on the ink ejection performance of the print head alone. However, when printing is actually performed, the print head is supplied with a drive signal from a drive signal generation circuit called a digital-analog converter (DAC) circuit, and is driven in accordance with the drive signal to generate dots of a predetermined size. Discharge. In the drive signal generation circuit, there is a fine drive error for each product, and the generated drive signal waveform varies.
That is, even if the image data is corrected in consideration of only the ID reflecting the ink ejection performance of the print head alone as in the prior art, such correction does not reflect the variation of the drive signal generation circuit, As a result, it was difficult to say that accurate color correction was achieved.

There is also a printing apparatus that includes a plurality of drive signal generation circuits and that can eject dots of a plurality of types of sizes by a combination of drive pulses generated by each drive signal generation circuit.
In such a printing apparatus, since there are a plurality of drive signal generation circuits, the characteristics of the drive error in each drive signal generation circuit are also different. Color reproduction becomes very difficult.

  The present invention has been made in view of the above problems, and in particular, when a plurality of drive signal generation circuits are provided, information necessary for color correction of data representing a print image is obtained accurately, and the print image is excellent. An object of the present invention is to provide a color correction apparatus, a color correction method, and a color correction program capable of realizing excellent color reproducibility.

  In order to achieve the above object, in the color correction apparatus according to the present invention, the patch output unit prints an ID indicating a deviation between the ink amount of the ejected dots and the reference ink amount of the dots in a predetermined recording area. And a plurality of drive signal generation circuits that can respectively generate drive signals including drive pulses and supply them to the print head. Then, by supplying a drive signal having a predetermined waveform from the drive signal generation circuit to the print head, specific dots are ejected from a plurality of dot types that can be ejected by the print head, and a patch is printed. The patch to be printed at this time is in a state in which the deviation of the ink amount indicated by the ID is compensated. Specifically, when printing a patch, the density of patch image data representing a patch image is corrected according to the ID, and the drive signal generation circuit is driven based on the corrected patch image data.

  Here, the patch is printed at a density that compensates for the deviation of the ink discharge amount of the print head alone, but the amount of ink caused by the drive error that the drive signal generation circuit has potentially. The concentration does not compensate for the deviation. Therefore, the correction coefficient calculation unit performs colorimetry on the printed patch and compares the colorimetric value acquired by the colorimetry with a predetermined standard value, thereby causing a drive error of the drive signal generation circuit. A correction coefficient corresponding to the ink amount deviation is calculated for each drive signal generation circuit. The ink data correction unit corrects the ink data for each dot type that can be ejected by the print head by using a correction coefficient in addition to the ID. At this time, the ID and the correction coefficient are applied in the correction of the ink data relating to the specific dot, and the ink data relating to the dot type other than the specific dot is also corrected using the ID and the correction coefficient.

  As described above, according to the present invention, it is possible to acquire a correction coefficient representing a deviation in ink amount due to the drive error for each of the plurality of drive signal generation circuits. Then, by correcting the ink data using such a correction coefficient, it is possible to achieve good color reproducibility in a print image when the print head is driven using a plurality of drive signal generation circuits. The correction coefficient represents a deviation in the ink amount due to the drive error of the drive signal generation circuit, and its value does not change greatly depending on the dot type used for printing the patch. Therefore, in the present invention, the patch is printed with specific dots for the sake of convenience, and the obtained correction coefficient is also applied to correction of ink data relating to dot types other than the specific dots. That is, patch printing and colorimetry work are greatly simplified.

As another configuration of the present invention, the patch is printed corresponding to each drive signal generation circuit, and each patch is printed by supplying only a drive signal generated by a single drive signal generation circuit to the print head. It is good also as what was done.
In the case of having a plurality of drive signal generation circuits, it is possible to eject dots of a certain size from the print head by generating a drive pulse at a predetermined timing in each circuit. However, when printing the patch to be colorimetrically measured, one patch is printed using one drive signal generation circuit. As a result, based on the color measurement result of the patch, it is possible to reliably calculate the correction coefficient corresponding to the deviation of the ink amount caused by the drive error in the drive signal generation circuit used for printing the patch.

  As another configuration of the present invention, the ink data correction unit is configured to change a distribution rule in a dot distribution table that distributes ink data into ink data for a plurality of dot types having different dot sizes according to the density, the ID, and the correction. The ink data may be corrected by changing the coefficient. Each drive signal generation circuit generates the drive signal for ejecting dots of each size based on the ink data after the distribution process by the dot distribution table. A printing result that compensates for variations in can be obtained.

  Here, when the dot corresponding to the ink data to be corrected is ejected by the drive pulse generated by the plurality of drive signal generation circuits, the ink data correction unit weights the correction coefficient as follows. It is good. That is, the ratio of the ink amount corresponding to the drive pulse generated by each of the plurality of drive signal generation circuits in order to eject the dots corresponding to the ink data to be corrected is specified, and each drive signal generation circuit according to the ratio The correction coefficients are weighted and integrated. As a result, by correcting the ink data to be corrected using the correction coefficient after the weighted integration, the color misregistration caused in the printing result due to the drive error in the plurality of drive signal generation circuits can be appropriately compensated. Can do.

  Further, the patch output means may print the patch using only one print head among a plurality of print heads corresponding to the ink type. This is because each drive signal generation circuit can supply a drive signal to each print head even when there are a plurality of print heads. In other words, by comparing the colorimetric result of a patch printed using any one of the print heads with the standard value, a correction coefficient corresponding to the ink amount deviation caused by the drive error of the drive signal generation circuit can be calculated. The correction coefficient calculated in this way can be applied to the correction of ink data corresponding to each ink type (each print head). Therefore, when the ink data correction means corrects the ink data for each ink type, the ink data corresponding to the print head used for printing the patch is the correction coefficient and the ID of the print head used for printing the patch. Will be corrected using. When correcting ink data corresponding to a print head other than the print head used for printing the patch, the correction coefficient and the ID of a print head other than the print head used for printing the patch are used.

  The technical idea relating to the color correction apparatus described above can also be grasped as an invention of the method, and the invention according to claim 5 exhibits the same operations and effects as the color correction apparatus. Similarly, the technical idea of the color correction apparatus can be grasped as an invention of a color correction program that causes a computer to execute the procedure, and the invention according to claim 6 has the same operations and effects as the color correction apparatus. Have

Embodiments of the present invention will be described in the following order.
(1) Schematic configuration of the present invention (2) Correction coefficient calculation process (3) Ink data correction process (4) Summary

(1) Schematic Configuration of the Present Invention FIG. 1 shows a computer 10 and a printer 20 corresponding to a color correction apparatus according to the present invention.
In the computer 10, the CPU 11 which is the center of the arithmetic processing controls the entire computer 10 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, and the like. And a hard disk (HD) 14 that is a magnetic disk is also connected via a hard disk drive.

  The HD 14 stores an operating system (OS), an application program (APL), and the like, which are appropriately transferred to the RAM 13 by the CPU 11 and executed. In the present embodiment, the HD 14 is an ink correction coefficient acquisition program, a color correction program, a color adjustment ID (hereinafter simply referred to as ID) 14a acquired from the printer 20, a plurality of color correction data 14b, a color conversion look. The predetermined storage area stores an up table (LUT), a dot distribution table 14d, a color component conversion table TB, and the like.

The colorimeter 40 is connected to the I / F 17a (for example, USB I / F). The colorimeter 40 directs the color detection unit 40a to the object to be colorimetrically measured so that a plurality of color components L ^* , a based on the L ^* a ^* b ^* color system defined by the International Commission on Illumination (CIE). ^{* And} b ^* can be acquired as color component amounts (color values), and the acquired color component amounts can be output to the computer 10. Here, the L ^* a ^* b ^* color space is a uniform color space that does not depend on the device. Of course, color space colorimetry, CIE defines the L ^* u ^* v ^* color space, XYZ color space of the CIE defined, it may be an RGB color space or the like. Hereinafter, “ ^* ” will be omitted.

  A display 18a for displaying an image corresponding to the data based on color image data is connected to the I / F 17b, and 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 is a printer to be mass-produced. In the present embodiment, the print head 29a supplies four types of ink filled in four ink cartridges 28 respectively corresponding to the colors C, M, Y, and K. The print image corresponding to the print data is printed by forming dots by ejecting from ~ 29d and adhering ink to the print paper (print medium). Of course, a printer using light cyan, light magenta, light black, dark yellow, red, violet, uncolored ink, or the like may be employed, and the number of ink types is not limited. In addition, various printing apparatuses such as a bubble printer that generates bubbles in the ink passage and ejects ink, and a laser printer that prints a print image on printing paper using toner ink can be employed. The ink used by the printing device may be liquid or solid. 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 29 a to 29 d and a nonvolatile semiconductor memory 31 provided for each ink type. The memory 31 can be an EEPROM or the like, and an ID or the like used for correcting ink data on the computer 10 side is recorded. 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 computer 10, and the printer 20 receives raster data for each color transmitted from the computer 10 via the communication I / O 24. The ASIC 26 generates applied voltage data (digital data) corresponding to the raster data while transmitting / receiving a predetermined signal to / from the CPU 21, and outputs the applied voltage data to the head driving unit 26a. The applied voltage data is data defining the size (dot type) of the dots to be ejected for each pixel, and the head drive unit 26a is based on the applied voltage data and the piezo elements incorporated in the print heads 29a to 29d. An applied voltage pattern (drive signal) is generated, and the generated drive signal is supplied to each of the print heads 29a to 29d, thereby ejecting ink of each color 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 the printing paper while performing a page break operation as appropriate, thereby performing sub-scanning.

Each of the print heads 29a to 29d is provided with a plurality of inkjet nozzles, and piezo elements are arranged corresponding to the respective nozzles.
As shown in FIG. 2, 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 pulse waveform drive signal is applied between the electrodes provided at both ends of the piezo element PE. As shown in the lower part of the figure, the signal is extended for the application time, and one side wall of the ink passage 25b is deformed. As a result, the volume of the ink passage 25b contracts in accordance with 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 penetrates into the printing paper. Dots are formed and printing is performed.

  Here, the head drive unit 26a includes a first drive signal generation circuit (DAC circuit) 26a1 that can generate the first drive signal COM1, and a second drive signal generation circuit (DAC circuit) that can generate the second drive signal COM2. 26a2. Both the DAC circuit 26a1 and the DAC circuit 26a2 can supply drive signals to the print heads 29a to 29d, respectively. The types of dots ejected by the print heads 29a to 29d vary depending on the waveform of the drive signal supplied from the head drive unit 26a. In the present embodiment, from the order of decreasing ink amount per dot, small one dot, Five types of dots, small 2 dots, medium 1 dot, medium 2 dots, and large dots, can be ejected.

FIG. 3 shows the relationship between the waveforms of the first drive signal COM1 and the second drive signal COM2 and the dot type.
As shown in the figure, the first drive signal COM1 basically includes a first small dot drive pulse PS11, a first middle dot drive pulse PS12, and a first large dot drive pulse PS13. The second drive signal COM2 basically includes a second small dot drive pulse PS21, a second middle dot drive pulse PS22, and a second large dot drive pulse PS23. The generation period TP of the first drive signal COM1 and the second drive signal COM2 is a period for generating a drive signal for ejecting one drop of dots from the print head, and this generation period TP is divided into three periods T1 to T3. Is done.

  The DAC circuit 26a1 can generate the driving pulse PS11 in the period T1, the driving pulse PS12 in the period T2, and the driving pulse PS13 in the period T3. On the other hand, the DAC circuit 26a2 can generate the drive pulse PS21 in the period T1, the drive pulse PS22 in the period T2, and the drive pulse PS23 in the period T3. The amplitude of each drive pulse corresponds to the amount of ink to be ejected.

  That is, the DAC circuit 26a1 and the DAC circuit 26a2 determine the drive pulse to be generated according to the dot type indicated by the applied voltage data, and supply the drive signal including the determined drive pulse to the print head to which each is supplied. To send. However, both the DAC circuit 26a1 and the DAC circuit 26a2 do not simultaneously generate drive pulses in each of the periods T1 to T3. Therefore, in each of the periods T1 to T3, there can be three states that the drive pulse is generated by the DAC circuit 26a1, the drive pulse is generated by the DAC circuit 26a2, and none of the drive pulses are present. The number of drive signal patterns that can be supplied to the print heads 29a to 29d is theoretically the third power of 3, that is, 27 patterns.

  In the present embodiment, as described above, five types of dots, small 1 dot, small 2 dot, medium 1 dot, medium 2 dot, and large dot, can be ejected. The state is realized by using appropriate 6 patterns among the above 27 patterns.

  The table in the lower part of the figure shows an example of how each drive pulse is generated to realize each of the above six states. In the table, “0” indicates that there is no drive pulse, and “1” indicates that there is a drive pulse. For example, the drive signal corresponding to one small dot is composed of a first drive signal COM1 that generates only the drive pulse PS11 and a second drive signal COM2 that does not generate any drive pulse, and this waveform is the DAC circuit 26a1. By supplying to the print head from the DAC circuit 26a2, one small dot is ejected from the print head. In the example shown in the figure, the drive signal for ejecting one of the dots from the print head is the first drive signal COM1 that generates only the drive pulse PS11 and the second drive signal that generates only the drive pulse 22. The drive signal for ejecting two middle one dots from the print head is a combination of the COM2 and the first drive signal COM1 that generates only the drive pulse PS11 and the second drive signal COM2 that generates only the drive pulse 23. It becomes a combination.

  On the other hand, in the computer 10, a printer driver 14 e for controlling the printer I / F 17 e is incorporated in the OS, and various controls are executed. APL exchanges data with hardware via the OS. The printer driver 14e is operated when the APL printing function is executed, can perform bidirectional communication with the printer 20 via the printer I / F 17e, and expresses a print target image from the APL via the OS. Print data is received, converted into raster data, and sent to the printer 20.

Processing by the printer driver 14e will be described.
As the print control process, the printer driver 14e executes the color conversion process, the halftone process, and the rasterization process after acquiring the print data. The print data is dot matrix data in which each pixel color of RGB is expressed in multiple gradations to define the color of each pixel, and a color system according to the sRGB standard is adopted. Of course, various data such as JPEG image data using the YCbCr color system and image data using the CMYK color system can also be used.

  In the color conversion process, the color conversion LUT recorded in the HD 14 is referred to as appropriate, and the print data (RGB data) is converted into ink data expressed by gradation values for each CMYK used by the printer 20 for each pixel. To do. Here, the gradation value of the ink data corresponds to the ink recording amount of the corresponding ink color (for example, the ink recording rate indicating the ratio of the number of formed dots to the total number of pixels in a predetermined area on the printing medium). For example, gradation values 0 to 255 correspond linearly to ink recording rates 0 to 100%.

  As described above, the printer 20 can eject five types of dots from each of the print heads 29a to 29d. For this reason, in the color conversion process, the dot distribution table 14d recorded in the HD 14 is referred to, and the ink data converted as described above is distributed to the ink data for each dot type for each ink type. By this sorting process, basically, for each ink color, small 1-dot ink data indicating a small 1-dot ink recording amount, small 2-dot ink data indicating a small 2-dot ink recording amount, and medium 1 Medium 1-dot ink data indicating a dot ink recording amount, medium 2-dot ink data indicating a medium 2-dot ink recording amount, and large-dot ink data indicating a large dot ink recording amount are generated. .

In the halftone process, the ink data after the sorting process is converted into halftone data that specifies ink ejection / non-ejection for each CMYK and for each dot type in each pixel. For the halftone processing, a so-called error diffusion method, dither method, or the like can be employed.
In the rasterizing process, the halftone data is received, rearranged in the order used by the printer 20, raster data for each CMYK is generated, and output to the printer 20. Thereafter, the printer 20 executes print processing based on the raster data as described above.

  As described above, an ID is recorded in the memory 31 provided in the print head unit 29 of the printer 20. The ID is acquired and recorded for each of the print heads 29a to 29d at the factory when the print head unit 29 is manufactured, and indicates a deviation from the ink ejection amount reference in each of the print heads 29a to 29d. The method for acquiring the ID will be described as follows. First, a print head that is an ID acquisition target is assembled to a predetermined inspection jig, a predetermined number of dots are ejected by a predetermined number of shots, the ink weight is measured, and this measurement result is divided by the number of shots. Find the ink weight per dot. Then, an ID for the print head is determined according to a comparison between the obtained ink weight per dot (measured weight) and the ideal ink weight (reference weight) of the dot of the specific size.

  FIG. 4 shows an example of the relationship between the result of the comparison and the determined ID. The ID can be expressed by, for example, an integer of 1 to 21, and when the measured weight substantially matches the reference weight, 11 as an intermediate value is set as the print head ID. When the measured weight is smaller than the reference weight, a numerical value larger than the intermediate value 11 is set as ID according to the value. Conversely, when the measured weight is larger than the reference weight, the intermediate value 11 is set according to the value. A numerical value smaller than that is defined as ID. When the IDs for the print heads 29a to 29d are determined in this way, the determined IDs are recorded in the memory 31.

(2) Correction coefficient calculation processing In the above configuration, the ID of each print head 29a to 29d is recorded in the memory 31 of the print head unit 29. Therefore, the computer 10 passes the printer I / F 17e during print control. The ID can be acquired from the printer 20. Then, by correcting the ink data for each ink color according to the value of the ID, it is possible to output a print image that compensates for variations in the ink ejection performance of the print heads 29a to 29d.
However, factors affecting the ink ejection amount include not only the ink ejection performance of the print heads 29a to 29d but also the drive errors of the DAC circuit 26a1 and the DAC circuit 26a2 that supply drive signals to the print heads 29a to 29d. is there. The drive error here means that an error is generated in the waveform of the drive pulse to be generated, for example.
Therefore, in the present embodiment, as shown below, the drive error of each of the DAC circuit 26a1 and the DAC circuit 26a2 is grasped, and the ink data is corrected including this error.

FIG. 5 is a flowchart showing the content of the correction coefficient calculation process executed by the computer 10. This process is executed in a state where the printer 20 is connected to the computer 10.
The computer 10 acquires the IDs of the print heads 29 a to 29 d from the printer 20 in step S (hereinafter, description of steps is omitted) 110. Specifically, the computer 10 creates an ID acquisition request and transmits it to the printer 20. Then, the printer 20 receives the acquisition request, reads the ID from the memory 31 of the print head unit 29, and transmits it to the computer 10. The computer 10 acquires the ID and stores it in the HD 14 as ID 14a.

In S120, the computer 10 acquires patch image data from the HD 14 or the like. The patch image data is data in which a patch having a specific density of one color is expressed by a number of pixels, and a correction coefficient calculation patch P is printed based on the patch image data, as will be described later. Here, as an example, the patch image data represents a K-color patch. Of course, the color of the patch represented by the patch image data is not limited to K, and may be any of CMY.
In S130, the patch image data is corrected according to the ID 14a corresponding to the color of the patch, in this case, the ID 14a corresponding to K. In the present embodiment, the color correction data 14b associated with each ID is stored in the HD 14.

  FIG. 6 is a diagram schematically showing the structure of a plurality of color correction data 14b recorded on the HD 14. As shown in FIG. As shown in the figure, each color correction data 14b is stored in the HD 14 in association with a predetermined ID value. As shown in the lower part of the figure, the color correction data 14b shows the correspondence between the input gradation value i (i is an integer from 0 to 255) and the output gradation value for all gradations of the input gradation value i. It is a defined information table. An output tone value Ci with respect to the input tone value i is defined as a solid line in the upper part of the figure.

The computer 10 reads the ID 14a corresponding to K, that is, the ID 14a of the print head 29d, from the HD 14, specifies the color correction data 14b corresponding to the ID 14a from the plurality of color correction data 14b stored in the HD 14, and specifies the specified The patch image data is corrected by the color correction data 14b.
If the ID is a value greater than 11, the amount of ink ejected by the print head is less than the design standard. Therefore, as shown in FIG. 6, color correction is performed so as to increase the degree of color development of the printed image. The data 14b has an output tone value larger than the input tone value as a whole tendency. By referring to such color correction data 14b, the ink data of the color corresponding to the print head whose ID is larger than 11 is corrected so that the gradation value becomes larger as a whole.

  On the other hand, when the ID is a value smaller than 11, the amount of ink ejected by the print head is larger than the design standard, and as shown in FIG. The color correction data 14b has an output gradation value smaller than the input gradation value as a whole tendency. By referring to such color correction data 14b, the ink data of the color corresponding to the print head whose ID is smaller than 11 is corrected so that the gradation value becomes smaller as a whole. It should be noted that the degree of correction by the color correction data, such as how much the output gradation value is made smaller or smaller than the input gradation value, may be set in advance according to the magnitude of the ID value.

In S140, the computer 10 prints the correction coefficient calculation patch P1 on the printing paper by one dot type that can be ejected only by the drive signal generated by the DAC circuit 26a1 based on the corrected patch image data. The control to be executed is executed.
Further, in S150, the computer 10 applies the correction coefficient calculation patch P2 on the printing paper by one dot type that can be ejected only by the drive signal generated by the DAC circuit 26a2 based on the corrected patch image data. Execute control to print.

FIG. 7 shows the correction coefficient calculation patch P1 and the correction coefficient calculation patch P2 printed on the printing paper B.
Each of the patches P1 and P2 is a K-colored patch, and is printed using only the print head 29d corresponding to K. Further, the patch P1 is recorded only by dots (for example, small one dot) ejected only by the drive signal generated by the DAC circuit 26a1, and the patch P2 is only the drive signal generated by the DAC circuit 26a2. Are recorded only by the dots ejected at (for example, small 2 dots).
That is, the patches P1 and P2 recorded by the dots ejected from one print head when the DAC circuit 26a1 and the DAC circuit 26a2 are independently driven are acquired by the processing from S110 to S150. The patches P1 and P2 are printed based on the ink data corrected according to the ID indicating the variation in ejection performance of the print head used for printing.

In S160, the printed patches P1 and P2 are measured using the colorimeter 40, and the computer 10 obtains the color component amounts Lab of the patches P1 and P2. Here, the color component amount of the patch P1 is represented as L1a1b1, and the color component amount of the patch P2 is represented as L2a2b2.
In S <b> 170, the computer 10 compares the color component amounts of the patches P <b> 1 and P <b> 2 with the corresponding standard color component amounts, and performs a process of converting the comparison result into the ink weight ratio. Here, the standard color component amount L01a01b01 to be compared with the color component amount L1a1b1 of the patch P1 is determined based on the patch image data in a printer (standard printer) as a design standard machine of the same type as the printer 20. This is a colorimetric result of a K-color patch recorded with only dots (small one dot) ejected by only the drive signal generated by the DAC circuit corresponding to the circuit 26a1. The standard color component amount L02a02b02 to be compared with the color component amount L2a2b2 of the patch P2 is only a drive signal generated by the DAC circuit corresponding to the DAC circuit 26a2 based on the patch image data in the standard printer. This is a colorimetry result of a K-color patch recorded only with the dots ejected in (2 small dots).

  The standard color component amount L01a01b01 and the standard color component amount L02a02b02 are information recorded in advance on the HD 14. Here, if there is no difference between the standard color component amount L01a01b01 and the color component amount L1a1b1, and there is no difference between the standard color component amount L02a02b02 and the color component amount L2a2b2, the printer 20 uses the above-mentioned ID for the ink data. It can be said that ideal color reproducibility can be realized only by correction, and conversely, if there is a difference, correction using only ID is not sufficient, and driving errors in the DAC circuits 26a1 and 26a2 are also taken into consideration. It is necessary to perform the correction.

FIG. 8 shows the color component conversion table TB.
The color component conversion table TB is a color measurement result of K patches printed by the standard printer and a plurality of printers in which the ink weight of the ejected dots varies compared to the standard printer, based on the patch image data. And a correspondence relationship between the ink weights q of common dot types ejected by the printers. The conversion table TB converts the color component amount L of the color component amount Lab into ink weight. As shown in the figure, even when the K patch is printed with the same patch image data, the color component amount L as the color measurement result is large in the airframe in which the ink weight of the ejected dots tends to be small, In the airframe in which the ink weight of the ejected dots tends to be large, the color component amount L as the color measurement result is small.

Here, the conversion result of the color component amount L1 of the patch P1 is the ink weight q1, the conversion result of the color component amount L2 of the patch P2 is the ink weight q2, the conversion result of the standard color component amount L01 is the ink weight q01, and the standard color component amount. When the conversion result of L02 is an ink weight q02, an ink weight ratio q1 / q01 and an ink weight ratio q2 / q02 are obtained.
It can be said that the ink weight ratio q1 / q01 indicates the degree of drive error relative to the design standard of the DAC circuit 26a1 in the printer 20, and the ink weight ratio q2 / q02 indicates the degree of drive error relative to the design standard of the DAC circuit 26a2. It can be said that.

In S180, the computer 10 determines the correction coefficient α of the DAC circuit 26a1 and the correction coefficient β of the DAC circuit 26a2 according to the ink weight ratio.
The correction coefficients α and β are numerical values expressed in increments of 0.01 with a minimum value of 0.9 to a maximum value of 1.1 with 1 as the center value, for example. When the ink weight ratios q1 / q01 and q2 / q02 are 1, the DAC circuits 26a1 and 26a2 of the printer 20 can be said to have no driving error with respect to the design standard, and therefore the correction coefficients α and β are also 1. . On the other hand, when the ink weight ratio is greater than 1, the corresponding DAC circuit can be said to eject dots having a larger amount of ink than the design standard. Under the principle that a correction coefficient lower than 1 is given, an appropriate numerical value of 0.9 or more and less than 1 is given as a correction coefficient. In addition, when the ink weight ratio is smaller than 1, the corresponding DAC circuit can be said to eject dots having a smaller amount of ink than the design standard. Therefore, for such an ink weight ratio, the ink weight ratio is Under the principle that a smaller correction coefficient is given as a value smaller than 1, an appropriate numerical value higher than 1 and up to 1.1 is given as a correction coefficient.

In S190, the computer 10 records the correction coefficients α and β determined as described above on the HD 14.
As described above, in the present embodiment, based on the ink data after correction according to the ID of the print head used for printing the patch, only the DAC circuit 26a1 is driven out of the DAC circuits 26a1 and 26a2, and the patch P1 is driven. Similarly, based on the ink data after correction according to the ID of the print head used for printing the patch, only the DAC circuit 26a2 of the DAC circuits 26a1 and 26a2 is driven to print the patch P2. . As a result, by comparing the colorimetric results of the patches P1 and P2 with a predetermined standard value (standard color component amount), a correction coefficient for compensating for the drive error that each of the DAC circuit 26a1 and the DAC circuit 26a2 has independently. α and β can be acquired.

(3) Ink Data Correction Processing After calculating the correction coefficient α of the DAC circuit 26a1 and the correction coefficient β of the DAC circuit 26a2 as described above, the computer 10 corrects the ink data using the correction coefficients α and β and the ID 14a. To do. In this embodiment, the ink data is corrected by correcting the gradation value conversion relationship in the dot distribution table 14d.
As shown in the upper part of FIG. 9, the dot distribution table 14d includes ink data (input gradation value i) for each CYMK after color conversion, and output gradation values Di (dots) representing the dot formation amount for each type of dot. This is an information table that defines a correspondence relationship with ink data after distribution. The table 14d is provided for each ink color.

FIG. 10 is a flowchart showing the contents of the dot assignment table correction process executed by the computer 10.
In S210, the computer 10 reads the ID corresponding to each ink color from the HD 14, and similarly reads the correction coefficients α and β from the HD 14 in S220.
Next, the computer 10 corrects the dot allocation table 14d for a certain ink color with the ID and the correction coefficients α and β (S230). Here, first, a description will be given of a case where the dot distribution table 14d corresponding to K for which a patch has been actually printed is corrected when calculating the correction coefficients α and β.

FIG. 11 is a flowchart showing details of the correction process for the dot distribution table 14d. The correction of the dot allocation table 14d referred to in the present embodiment means that the gradation value itself on the output side defined in the table is corrected.
In S310, first, one dot type to be corrected is specified. That is, one of small 1 dot, small 2 dot, medium 1 dot, medium 2 dot, and large dot is set as the dot type to be corrected.

  In S320, the drive pulse included in the drive signal supplied to the print head in order to eject the dots to be corrected is specified. Referring to FIG. 3, when the correction target is one small dot, the drive pulse included in the drive signal is only the drive pulse PS11 generated by the DAC circuit 26a1. When the correction target is medium 1 dot, the drive pulse included in the drive signal is the drive pulse PS11 generated by the DAC circuit 26a1 and the drive pulse PS22 generated by the DAC circuit 26a2. The included drive pulses are a drive pulse PS11 generated by the DAC circuit 26a1, and a drive pulse PS22 and a drive pulse PS23 generated by the DAC circuit 26a2.

In S330, it is determined whether the drive signal for ejecting the dots to be corrected includes either the drive pulse generated by the DAC circuit 26a1 or the drive pulse generated by the DAC circuit 26a2.
If the drive pulse from both DAC circuits is not included, in the example of FIG. 3, if the dot type to be corrected is small 1 dot or small 2 dot, in step S370, ID and The dot distribution table 14d is corrected using the correction coefficient. Specifically, among the output gradation values stored for each dot type in the table 14d, the output gradation value for the dot type to be corrected is corrected by the color correction data 14b corresponding to the ID, Further, the corrected output gradation value is multiplied by a correction coefficient (either α or β) applied to the DAC circuit used for ejection of the dot type to be corrected.

  In other words, since only one DAC circuit is operated for discharging small 1 dot or small 2 dots, in addition to the variation in the discharge performance of the print head used for printing, the same operation is performed in correcting the variation in the ink discharge amount. Only the drive error of one DAC circuit needs to be considered. The ID used for correcting the output tone value is, of course, the ID corresponding to the ink color applied to the dot allocation table 14d to be corrected. In this example, the ID of the print head 29d corresponding to the K ink Become.

On the other hand, when it is determined in S330 that the drive signal for ejecting the dots to be corrected includes both the drive pulse generated by the DAC circuit 26a1 and the drive pulse generated by the DAC circuit 26a2. Advances to the process of S340.
In S340, the ink amount corresponding to the drive pulse by the DAC circuit 26a1 and the ink amount corresponding to the drive pulse by the DAC circuit 26a2 are specified. For example, when one medium dot is to be corrected, the ink amount corresponding to the drive pulse PS11 generated by the DAC circuit 26a1 and the ink amount corresponding to the drive pulse PS22 generated by the DAC circuit 26a2 are specified. Even when there are a plurality of drive pulses supplied to the print head, the number of dots ejected from the nozzles of the print head is one drop per generation period TP. In this sense, there is an ink amount corresponding to each drive pulse.

In S350, the correction coefficients α and β are weighted according to the ratio between the ink amount corresponding to the drive pulse by the DAC circuit 26a1 specified in S340 and the ink amount corresponding to the drive pulse by the DAC circuit 26a2, and the weighted integration is performed. A new correction factor is calculated. Here, when the ink amount corresponding to the drive pulse generated by the DAC circuit 26a1 is s1, the ink amount corresponding to the drive pulse generated by the DAC circuit 26a2 is s2, and the sum of s1 and s2 is S, the new correction coefficient A is represented by the following equation.
A = α (s1 / S) + β (s2 / S)

  In S360, the dot allocation table 14d is corrected using the new correction coefficient A and ID calculated as described above. Specifically, among the output gradation values stored for each dot type in the table 14d, the output gradation value for the dot type to be corrected is corrected by the color correction data 14b corresponding to the ID, Further, the new correction coefficient A is multiplied to the output gradation value after the correction. That is, it is necessary to correct the output gradation values corresponding to the types of dots ejected by operating both the DAC circuit 26a1 and the DAC circuit 26a2 using the correction coefficients of both DAC circuits. Therefore, in the present embodiment, the degree of influence of both DAC circuits on dot formation is specified by the ratio of the ink amount corresponding to the drive pulse generated by both DAC circuits, and correction is performed according to this ratio. The degree of correction by the coefficients α and β is changed.

  In S380, it is determined whether the output tone values have been corrected for all the dot types. If there are any dot types that have not been corrected, the process returns to S310, and after changing the dot types to be corrected, Repeat the process. On the other hand, when the correction of the output gradation values has been completed for all the dot types, the flow of FIG. 11 is terminated, and the process proceeds to the determination of S240 of FIG.

In S240, it is determined whether the dot allocation table 14d corresponding to all ink colors has been corrected. If the dot allocation table 14d for the ink color that has not been corrected remains, the dot allocation table to be corrected remains. The above process is repeated after changing the table 14d. Here, the ID used for correcting the dot allocation table 14d is an ID corresponding to the ink color applied to the newly allocated dot allocation table 14d, but the correction coefficient is a print head corresponding to K ink. The correction coefficients α and β acquired from the color measurement results of the patches P1 and P2 printed using 29d are used.
On the other hand, when the dot allocation table 14d for all ink colors has been corrected, the dot allocation table correction process ends.

Information specifying which drive pulse each of the DAC circuit 26a1 and DAC circuit 26a2 generates when ejecting each dot type, and information specifying the ink amount corresponding to each drive pulse are stored in the computer 10. Are previously stored in a recording area such as HD14.
In the lower part of FIG. 9, the tone value on the output side corresponding to each dot type is corrected by the ID (actually, the color correction data 14b corresponding to the ID) and the correction coefficient (or new correction coefficient). The dot allocation table in the state rewritten by the output gradation value Ei is shown.

(4) Summary As described above, according to the present invention, the DAC circuit 26a1 has the DAC circuit 26a1 and the DAC circuit 26a2 that can supply drive signals to the print heads 29a to 29d corresponding to the ink colors. A correction coefficient α for correcting an error in the ink discharge amount caused by the drive error and a correction coefficient β for correcting an error in the ink discharge amount caused by the drive error of the DAC circuit 26a2 can be calculated. . Then, by correcting the conversion relationship in the dot allocation table 14d using the correction coefficient and the ID representing the variation in the ink ejection amount of the print head alone, the error in the ink ejection performance in the print head and each DAC circuit are corrected. Therefore, it is possible to output a print image with extremely high color reproducibility that compensates for variations in the amount of ink discharged due to the drive error of the printer.

  Further, when obtaining the correction coefficient α corresponding to the DAC circuit 26a1 and the correction coefficient β corresponding to the DAC circuit 26a2, the patch P made of dots that can be ejected by driving only one DAC circuit is the number of DAC circuits. Since it is sufficient to print only as much as it is, there is very little labor for printing patches and measuring colors. The correction coefficient obtained in this way is not used for printing the patch P in addition to correcting the output gradation value in the dot distribution table 14d corresponding to the dot type when the patch P is printed. The present invention can also be applied to correction of output tone values in the dot allocation table 14d corresponding to other dot types.

  Furthermore, each DAC circuit 26a1, 26a2 is configured to supply a drive voltage to each of the print heads 29a-29d corresponding to each ink color, and the influence of the drive error in each DAC circuit 26a1, 26a2 is different from each other. It extends in substantially the same way for the print heads 29a-29d. Therefore, the correction coefficient obtained from the color measurement results of the patches P1 and P2 printed using one print head among a plurality of print heads is applied when correcting the dot distribution table 14d corresponding to each print head. Thus, high color reproducibility can be realized for each color in the subsequent printing results.

The block diagram which shows a computer and a printer. The figure which expands and shows a nozzle and its internal structure. The figure which shows the relationship between the waveform of a 1st drive signal and a 2nd drive signal, and a dot kind. The figure which shows the relationship between ink weight and ID. The flowchart which shows the content of the correction coefficient calculation process. The figure which shows the structure of color correction data typically. The figure which shows the patch for correction coefficient calculation. Diagram showing color component conversion table The figure which shows the structure of a dot allocation table typically. The flowchart which showed the content of the dot allocation table correction process. The flowchart which showed the detail of the correction process with respect to a dot allocation table.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Computer, 11 ... CPU, 12 ... ROM, 13 ... RAM, 14 ... Hard disk (HD), 14a ... Color adjustment ID, 14b ... Color correction data, 14d ... Dot allocation table, 14e ... Printer driver, 20 ... Printer , 26a ... head drive unit, 26a1, 26a2 ... DAC circuit, 29 ... print head unit, 29a-29d ... print head, 31 ... non-volatile semiconductor memory, 40 ... colorimeter, TB ... color component conversion table

Claims (6)

A print head in which an ID indicating a deviation between the ink amount of the ejected dot and the standard ink amount of the dot is recorded in a predetermined recording area, and a plurality of drive signals including a drive pulse that can be generated and supplied to the print head. An ink indicated by the ID by ejecting specific dots out of a plurality of dot types that can be ejected by the print head by supplying a drive signal of a predetermined waveform from the drive signal generation circuit to the print head. Patch output means for printing a patch in a state in which a deviation in amount is compensated;
By measuring the color of the patch and comparing the colorimetric value acquired by the colorimetry with a predetermined standard value, each correction coefficient corresponding to the deviation of the ink amount due to the drive error of the drive signal generation circuit is obtained. Correction coefficient calculation means for calculating for each drive signal generation circuit;
An ink data correction unit that performs correction using the ID and the correction coefficient for ink data relating to dot types other than the specific dot when correcting ink data for each dot type that can be ejected by the print head;
A color correction apparatus comprising:   The patch is printed corresponding to each drive signal generation circuit, and each patch is printed by supplying only a drive signal generated by a single drive signal generation circuit to the print head. The color correction apparatus according to claim 1.   The ink data correction means changes the distribution rule in the dot distribution table that distributes the ink data to the ink data of a plurality of dot types having different dot sizes according to the density using the ID and the correction coefficient. The color correction apparatus according to claim 2, wherein the correction of the ink data is realized.   The ink data correction unit specifies a ratio of ink amounts corresponding to drive pulses generated by each of a plurality of drive signal generation circuits in order to eject dots corresponding to ink data to be corrected, and according to the ratio 4. The color correction according to claim 1, wherein the correction coefficient of each drive signal generation circuit is weighted and integrated, and the ink data is corrected using the correction coefficient after the weighted integration. apparatus.   A print head in which an ID indicating a deviation between the ink amount of the ejected dot and the standard ink amount of the dot is recorded in a predetermined recording area, and a plurality of drive signals including drive pulses that can be generated and supplied to the print head. By using a drive signal generation circuit and supplying a drive signal having a predetermined waveform from the drive signal generation circuit to the print head, a specific dot is ejected from a plurality of dot types that can be ejected by the print head, and the ID indicates Generate a drive signal by printing a patch in a state in which the deviation of the ink amount is compensated, and measuring the color of the patch and comparing the colorimetric value acquired by the colorimetry with a predetermined standard value A correction coefficient calculation step for calculating a correction coefficient corresponding to a deviation in the amount of ink caused by a circuit drive error for each drive signal generation circuit, and dots that can be ejected by the print head In correcting the ink data for each kind, a color correction method characterized by comprising the ink data correction step of the ink data according to a dot type other than the specific dot performing correction using the ID and the correction coefficient.   A print head in which an ID indicating a deviation between the ink amount of the ejected dot and the standard ink amount of the dot is recorded in a predetermined recording area, and a plurality of drive signals including a drive pulse that can be generated and supplied to the print head. By using a drive signal generation circuit and supplying a drive signal having a predetermined waveform from the drive signal generation circuit to the print head, a specific dot is ejected from a plurality of dot types that can be ejected by the print head, and the ID indicates Generates a drive signal by printing a patch in a state in which the deviation of the ink amount is compensated, and measuring the color of the patch and comparing the colorimetric value acquired by the colorimetry with a predetermined standard value. A correction coefficient calculation function for calculating a correction coefficient corresponding to a deviation in ink amount caused by a circuit drive error for each drive signal generation circuit, and dots that can be ejected by the print head A color which causes a computer to execute an ink data correction function for correcting ink data relating to dot types other than the specific dot using the ID and the correction coefficient when correcting ink data for each class. Correction program.

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