JP5157872B2 - Print control apparatus, print system, and print control program - Google Patents

Description

  The present invention relates to a printing control apparatus, a printing system, and a printing control program, and more particularly to a printing control apparatus, a printing system, and a printing control program for reproducing a target.

A printing method focusing on spectral reproducibility has been proposed (see Patent Document 1). In this document, a printer color (CMYKOG) is used so as to fit a spectral reflectance (target spectrum) of a target using a printing model in order to perform printing that spectrally and colorimetrically matches a target image. The combination of is optimized. In this way, by performing printing based on the printer color (CMYKOG), the target image can be spectrally reproduced, and as a result, a highly reproducible printing result can be obtained.
Special table 2005-508125 gazette

  According to the printing model, it is possible to predict the printing result without actually performing printing, but there may be a case where the prediction result of the printing model deviates from the actual printing result. For example, if the printing model itself is inaccurate, if the printing model has high accuracy but the printer reproduction characteristics change over time, or if the individual printer reproduction characteristics vary, the printing model There was a problem that the reproduction result as expected could not be obtained.

  The present invention has been made in view of the above problems, and provides a print control apparatus, a print control system, and a print control program that can efficiently achieve highly accurate reproduction.

  In order to solve the above-described problem, the printing control apparatus of the present invention refers to a specified index by referring to a lookup table in which a correspondence relationship between an index for specifying information indicating color and a color material amount set is defined. The color material amount set corresponding to is designated by the printing apparatus and printed. In the look-up table, an index that specifies information indicating the color of the object, and a color material amount set that maximizes the approximation to the object when attached to the recording medium by the printing apparatus. Correspondence is defined.

  The color material amount set defined in the look-up table is calculated by the following procedure so that the deviation is minimized. First, when a color material amount set to be corrected is attached to the recording medium by the printing apparatus using a method for predicting information indicating the color of a reproduction reproduced based on an arbitrary color material amount set. The information indicating the color of the confirmation patch printed based on the color material amount set to be corrected is acquired. Information indicating the color of the confirmation patch is acquired by colorimetry or the like. This may be acquired in advance, or the color may be measured after the confirmation patch is actually printed. Then, the plurality of color materials are grouped on the basis of the ability to finely adjust the color, a group is selected in ascending order of the ability to finely adjust the color, and the color material near the color material amount set to be corrected is selected. The difference between the information indicating the predicted color and the information indicating the color of the confirmation patch is calculated by calculating a Jacobian matrix based on the result of partial differentiation with the amount of use of each color material constituting the group as a differential variable. The correction amount is calculated based on the Jacobian matrix so as to eliminate the above. At this time, the deviation minimized by the color material amount of the selected group is set as the deviation to be eliminated in the next selected group, and the deviation is eliminated and the correction amount is changed until all the groups are selected. Calculation is repeated. An ink amount set to which the correction amount calculated in this way is applied is defined in the lookup table.

  An apparatus for calculating a color material amount set defined in such a lookup table includes a plurality of units such as a prediction unit, a Jacobian matrix calculation unit, a confirmation patch printing unit, a measurement value acquisition unit, and a correction unit. The predicting means predicts information indicating the color of a reproduction to be reproduced based on an arbitrary color material amount set. The Jacobian matrix calculating unit calculates a Jacobian matrix based on a result of partial differentiation of information indicating the color predicted by the prediction unit based on the usage amount of each color material, in the vicinity of the color material amount set to be corrected. The confirmation patch printing means designates the color material amount set to be corrected to the printing apparatus and prints the confirmation patch. The measurement value acquisition means acquires a measurement value obtained by measuring information indicating the color of the confirmation patch. Then, the correcting unit corrects the color material amount set so as to eliminate a deviation between the measured value and information indicating the color of the object based on the Jacobian matrix.

  Note that it is sufficient that the printing apparatus can attach at least a plurality of the color materials to the recording medium, and the present invention can be applied to various printing apparatuses such as an ink jet printer, a laser printer, and a sublimation printer. As a specific method of correcting the color material amount set so that the correction means eliminates the deviation, the deviation vector configured by the deviation of a plurality of components is multiplied by an inverse matrix of the Jacobian matrix. A correction amount for each color material in the correction can be calculated. That is, for the local region in the vicinity of the predicted color material amount set, it can be considered that the state value varies linearly, and by multiplying the deviation vector by the inverse matrix of the Jacobian matrix, the deviation It is possible to calculate a correction amount of the color material usage amount that eliminates the problem. In the present invention, the correction amount is calculated by multiplying the deviation vector by the Jacobian matrix based on the result of partial differentiation of the state value predicted by the prediction means with the usage amount of each color material. A case where a similar correction amount is obtained by performing an equivalent operation is also included in one embodiment of the present invention. For example, an equivalent correction amount may be calculated by calculating a vector element of the deviation vector and a matrix element of the Jacobian matrix without generating the Jacobian matrix.

  The Jacobian matrix type is not necessarily a square matrix because it is defined by the number of color materials and the number of components of the state value. Even in such a case, an inverse matrix of the Jacobian matrix can be obtained by performing singular value decomposition on the Jacobian matrix and obtaining a pseudo inverse matrix. Further, by setting the target value as the spectral reflectance of the target, it is possible to cause the printing apparatus to perform printing with good spectral reflectance reproducibility. In this case, the predicting unit predicts a spectral reflectance when printing is performed with an arbitrary color material amount set. In this configuration, the Jacobian matrix is configured by partial differentiation of the spectral reflectance in each wavelength section.

  Furthermore, by setting the target value as a color value under a plurality of light sources of the target, it is possible to cause the printing apparatus to execute printing with good color reproducibility under the plurality of light sources. In this case, the prediction means predicts color values under a plurality of light sources when printing is performed with an arbitrary color material amount set. In this configuration, the Jacobian matrix is configured by partial differentiation of each component constituting the color value under each light source. Furthermore, when the deviation between the measured value of the confirmation patch and the target value exceeds a predetermined threshold, the printing of the confirmation patch and the correction of the color material amount set may be repeatedly executed. . In this way, a certain accuracy can be obtained.

  Furthermore, the technical idea of the present invention can be realized not only by a specific printing control apparatus but also by a method thereof. That is, the present invention can also be specified as a method having steps corresponding to the respective units performed by the above-described print control apparatus. Of course, when the above-described printing control apparatus reads the program and realizes each means described above, the technical features of the present invention can be applied to a program for executing a function corresponding to each means and various recording media on which the program is recorded. It goes without saying that the idea can be embodied. Needless to say, the print control apparatus of the present invention can be distributed not only by a single apparatus but also by a plurality of apparatuses. For example, each means for indicating the state of the print control apparatus can be distributed in both the printer driver executed on the personal computer and the printer. In addition, each unit of the print control apparatus of the present invention can be included in a printing apparatus such as a printer.

Hereinafter, embodiments of the present invention will be described in the following order.
1. Configuration of print control device:
2. Print data generation processing:
3. Print control processing:
3-1.1 D-LUT creation processing:
3-2. Print control data generation processing:
4). Calibration process:
5. Spectral printing model:
6). Variations:
6-1: Modification 1:
6-2: Modification 2:
6-3: Modification 3:
6-4: Modification 4:
6-5: Modification 5:
6-6: Modification 6:
6-7: Modification 7:

1. Configuration of Print Control Device FIG. 1 shows a hardware configuration of a print control device according to an embodiment of the present invention. In FIG. 1, the print control apparatus is mainly composed of a computer 10, and the computer 10 includes a CPU 11, a RAM 12, a ROM 13, a hard disk drive (HDD) 14, a general-purpose interface (GIF) 15, a video interface (VIF) 16, and an input interface. (IIF) 17 and a bus 18. The bus 18 implements data communication between the elements 11 to 17 constituting the computer 10, and communication is controlled by a chip set (not shown). The HDD 14 stores program data 14a for executing various programs including an operating system (OS), and the CPU 11 executes calculations according to the program data 14a while expanding the program data 14a in the RAM 12. . The GIF 15 provides an interface conforming to the USB standard, for example, and connects the external printer 20 and the spectral reflectometer 30 to the computer 10. The VIF 16 connects the computer 10 to an external display 40 and provides an interface for displaying an image on the display 40. The IIF 17 connects the computer 10 to an external keyboard 50a and a mouse 50b, and provides an interface for the computer 10 to acquire input signals from the keyboard 50a and the mouse 50b.

  FIG. 2 shows a software configuration of a program executed by the computer 10 together with a schematic data flow. In the figure, the computer 10 mainly includes an OS P1, a sample printing application (APL) P2, a 1D-LUT generation application (LUG) P3a, a printer driver (PDV) P3b, a spectral reflectometer driver (MDV) P4, and a display driver ( (DDV) P5 is being executed. The OS P1 provides an image equipment interface (GDI) P1a and a spooler P1b as one of APIs that can be used by each program. The GDI P1a is called in response to a request from the APL P2, and further in response to a request from the GDI P1a. PDV P3b and DDV P5 are called. The GDI P1a provides a general-purpose mechanism for the computer 10 to control image output in an image output device such as the printer 20 or the display 40, while the PDV P3b or DDV P5 is a process specific to the model of the printer 20 or the display 40. Etc. The spooler P1b is interposed between the APL P2, the PDV P3b, and the printer 20 and executes job control and the like. APL P2 is an application program for printing the sample chart SC, generates print data PD in the RGB bitmap format, and outputs the print data PD to the GDI P1a. In generating the print data PD, the target spectral reflectance data RD is acquired from the MDV P4. The MDV P4 controls the spectral reflectometer 30 in response to a request from the APL P2, and outputs the spectral reflectance data RD obtained by the control to the APL P2.

  The print data PD generated by the APL P2 is output to the PDV P3b via the GDI P1a and the spooler P1b, and the PDV P3b executes processing for generating print control data CD that can be output to the printer 20 based on the print data PD. . The print control data CD generated by the PDV P3b is output to the printer 20 via the spooler P1b provided by the OS P1, and the printer 20 prints the sample chart SC on the printing paper by performing an operation based on the print control data CD. Let The overall processing flow has been schematically described above, but the processing executed by each of the programs P1 to P4 will be described in detail below using a flowchart.

2. Print Data Generation Processing FIG. 3 shows the flow of print data generation processing executed by APL P2. As shown in FIG. 2, the APL P2 includes a UI unit (UIM) P2a, a measurement control unit (MCM) P2b, and a print data generation unit (PDG) P2c. These modules P2a, P2b, and P2c are shown in FIG. Each step shown in 3 is executed. In step S100, the UIM P2a displays a UI screen for accepting a print instruction to print the sample chart SC via the GDI P1a and the DDV P5. On the UI screen, a display showing a template of the sample chart SC is provided.

FIG. 4 shows an example of the UI screen. In the figure, the template TP is displayed, and the template TP is provided with 12 frames FL1 to FL12 for laying out color patches. Each frame FL1 to FL12 can be selected by clicking the mouse 50b on the UI screen, and a selection window for instructing whether or not to start the spectral reflectance measurement when the frames FL1 to FL12 are clicked. W is displayed. The UI screen is also provided with a button B for instructing whether or not to print the sample chart SC. In step S110, the UIM P2a detects a click on each frame FL1 to FL12 by the mouse 50b, and if it is detected, a selection window W for instructing whether or not to start spectral reflectance measurement in step S120. Is displayed. In step S130, a click on the mouse 50b in the selection window W is detected. If cancel is clicked, the process returns to step S110. On the other hand, when the spectral reflectance measurement execution is clicked, in step S140, the MCM P2b sends the target spectral reflectance R _t (the spectral reflectance R (λ) of the target TG to the spectral reflectance meter 30 via the MDV P4. (λ) is measured, and spectral reflectance data RD storing the target spectral reflectance R _t (λ) is acquired. The target spectral reflectance R _t (λ) corresponds to a state value and a target value indicating the state of the target of the present invention.

When the measurement of the target spectral reflectance R _t (λ) in step S140 is completed, the color value (L ^* a ^* b ^* value) in the CIELAB color space when the most standard light source D65 light source is irradiated is calculated. . Then, the L ^* a ^* b ^* value is converted into an RGB value using a predetermined RGB profile, and the RGB value is acquired as a display RGB value. The RGB profile is a profile that defines a color matching relationship between the CIELAB color space as an absolute color space and the RGB color space of the present embodiment. For example, an ICC profile can be used.

FIG. 5 schematically shows how the display RGB values are calculated from the spectral reflectance data RD in step S140. As a result of measuring the target spectral reflectance R _t (λ) for the target TG, it is assumed that spectral reflectance data RD indicating the distribution of the target spectral reflectance R _t (λ) is obtained as illustrated. Note that the target TG means an object surface that is a target for spectral reproduction, and corresponds to, for example, an artificial object surface formed by another printing apparatus or a coating apparatus, a natural object surface, or the like. On the other hand, the D65 light source has a non-uniform distribution of spectral energy P (λ) in the visible wavelength region as shown in the figure, and the spectral energy of reflected light of each wavelength when the target TG is irradiated with the D65 light source is This is a value obtained by multiplying the target spectral reflectance R _t (λ) and the spectral energy P (λ) for each wavelength. Further, the spectral energy spectrum of the reflected light is convolved with the color matching functions x (λ), y (λ), z (λ) corresponding to the human spectral sensitivity characteristics, and normalized by the coefficient k. Thus, tristimulus values X, Y, and Z are obtained. The above is expressed by the following equation (1).

By converting the tristimulus values X, Y, and Z according to a predetermined conversion formula, an L ^* a ^* b ^* value indicating the color when the target TG is irradiated with the D65 light source can be obtained, and an RGB profile is used. By doing so, RGB values for display can be obtained. In step S145, the clicked frames FL1 to FL12 in the template TP are updated to a display filled with the display RGB values. As a result, the color of the target TG with the D65 light source, which is a standard light source, can be sensed on the UI screen. When step S145 is completed, a unique index is generated in step S150, and the index, position information of the frames FL1 to FL12 clicked in step S110, and display RGB values are associated with the spectral reflectance data RD. Store in the RAM 12. When step S150 is completed, the process returns to step S110, and steps S120 to S150 are repeatedly executed. Thereby, the other frames FL1 to FL12 can be selected, and the target spectral reflectance R _t (λ) of the other target TG can be measured for the other frames FL1 to FL12.

In the present embodiment, 12 different types of targets TG1 to TG12 are prepared, and the target spectral reflectance R _t (λ) for each of the targets TG1 to TG12 is acquired as spectral reflectance measurement data RD. And Accordingly, in step S150, data in which the spectral reflectance measurement data RD and the unique index for each frame FL1 to FL12 are associated with each other are sequentially stored in the RAM. The index only needs to be generated so that each value is unique. The index may be generated by increment or by a random number that does not overlap.

  In step S110, if a click on each of the frames FL1 to FL12 is not detected, a click on button B for executing printing of sample chart SC is detected in step S160, and if not detected, the process returns to step S110. On the other hand, if it is detected that the button B for executing printing of the sample chart SC is detected, the PDG P2c generates print data PD in step S170.

  FIG. 6 schematically shows the configuration of the print data PD. In the figure, the print data PD is composed of a large number of pixels arranged in a dot matrix, and each pixel has 4 bytes (8 bits × 4) of information. The print data PD shows an image similar to the template TP shown in FIG. 4, and the pixels other than the regions corresponding to the frames FL1 to FL12 of the template TP have RGB values of colors corresponding to the template TP. ing. The gradation value of each RGB channel is expressed by 8 bits (256 gradations), and 3 bytes out of the 4 bytes described above are used to store the RGB values. For example, when colors other than the frames FL1 to FL12 of the template TP are expressed by uniform intermediate gray of (R, G, B) = (128, 128, 128), the frames FL1 to FL12 in the print data PD. Pixels other than the region corresponding to 有 す る have color information of (R, G, B) = (128, 128, 128). The remaining 1 byte is not used.

  On the other hand, the pixels corresponding to the frames FL1 to FL12 of the template TP also have 4-byte information, and the index is usually stored using 3 bytes in which RGB values are stored. This index is unique for each of the frames FL1 to FL12 in step S150, and the PDG P2c acquires the index from the RAM 12 and stores the index corresponding to the pixel corresponding to each of the frames FL1 to FL12. For the pixels corresponding to the frames FL1 to FL12 in which the indexes are stored instead of the RGB values in this way, the flag indicating that the indexes are stored is set using the remaining 1 byte. This makes it possible to determine whether each pixel stores an RGB value or an index. In this embodiment, since 3 bytes can be used to store the index, it is necessary to generate an index that can be expressed with an information amount of 3 bytes or less in step S150. When the bitmap format print data PD can be generated as described above, the PDG P2c generates the index table IDB in step S180.

FIG. 7 shows an example of the index table IDB. In the figure, for each unique index generated corresponding to each of the frames FL1 to FL12, the target spectral reflectance R _t (λ) obtained by measurement and the L ^* a ^* b ^* value in the D65 light source. RGB values for display corresponding to are stored. When the generation of the index table IDB is completed, the print data PD is output to the PDV P3b via the GDI P1a and the spooler P1b. Since the print data PD is not different from the normal RGB bitmap format in appearance, the GDI P1a and the spooler P1b provided by the OS P1 can be processed in the same manner as a normal print job. On the other hand, the index table IDB is directly output to the PDV P3b. In this embodiment, the index table IDB is newly generated. However, a new correspondence relationship between the index, the target spectral reflectance R _t (λ), and the display RGB value is added to the existing index table IDB. You may make it do. The print data generation process and the print control process described later do not necessarily have to be executed consecutively in the same apparatus, and the print data generation process and the print control process are connected by a communication line such as a LAN or the Internet. It may be executed individually on a plurality of computers.

3. Print Control Process FIG. 8 shows the overall flow of the print control process executed by the LUG P3a and the PDV P3b. The LUG P3a takes charge of the 1D-LUT generation process (step S200), and the PDV P3b takes charge of one print control data generation process (step S300). The 1D-LUT generation process may be performed prior to the print control data generation process, or the 1D-LUT generation process and the print control data generation process may be performed in parallel.

3-1.1 D-LUT Creation Processing FIG. 9 shows the flow of 1D-LUT creation processing. As shown in FIG. 2, the LUG P3a includes an ink amount set calculation module (ICM) P3a1, a spectral reflectance prediction module (RPM) P3a2, an evaluation value calculation module (ECM) P3a3, and an LUT output module (LOM) P3a4. ing. In step S210, ICM P3a1 acquires the index table IDB. In step S220, one index is selected from the index table IDB, and spectral reflectance data RD associated with the index is acquired. In step S230, the ICM P3a1 performs a process of calculating an ink amount set that can reproduce the spectral reflectance R (λ) similar to the target spectral reflectance R _t (λ) indicated by the spectral reflectance data RD. At that time, the above-described RPM P3a2 and ECM P3a3 are used.

FIG. 10 schematically shows a flow of processing for calculating an ink amount set that can reproduce a spectral reflectance R (λ) similar to the target spectral reflectance R _t (λ) indicated by the spectral reflectance data RD. Yes. In response to the input of the ink amount set φ from the ICM P3a1, the RPM P3a2 predicts the spectral reflectance R (λ) when the printer 20 ejects ink onto a predetermined print sheet based on the ink amount set φ. The spectral reflectance R (λ) is output to the ECM P3a3 as the predicted spectral reflectance R _s (λ).

The ECM P3a3 calculates the difference D (λ) between the target spectral reflectance R _t (λ) and the predicted spectral reflectance R _s (λ) indicated by the spectral reflectance data RD for each wavelength λ, and weights each wavelength λ. Is multiplied by the difference D (λ). The square root of the mean square of this value is calculated as the evaluation value E (φ). The above calculation can be expressed by the following equation (2).

In the above equation (2), N means the finite number of sections of wavelength λ. In the above equation (2), the smaller the evaluation value E (φ), the smaller the difference between the target spectral reflectance R _t (λ) and the predicted spectral reflectance R _s (λ) at each wavelength λ. it can. That is, the smaller the evaluation value E (φ) is, from the spectral reflectance R (λ) reproduced on the recording medium when the printer 20 prints with the input ink amount set φ, and the corresponding target TG. It can be said that the obtained target spectral reflectance R _t (λ) is approximate. Further, according to the above equation (1), although the absolute color value indicated by the target TG corresponding to the recording medium when the printer 20 prints with the ink amount set φ according to the fluctuation of the light source both fluctuates. If the spectral reflectance R (λ) is approximated, it can be said that the same color is perceived relatively regardless of the variation of the light source. Therefore, according to the ink amount set φ in which the evaluation value E (φ) is small, it can be said that a print result perceived in the same color as the target TG can be obtained in any light source.

前記の（３）式においては、等色関数ｘ（λ），ｙ（λ），ｚ（λ）を加算することにより、重み関数ｗ（λ）が定義されている。なお、前記の（３）式の右辺全体に所定の係数を乗算して、重み関数ｗ（λ）の値の範囲を正規化してもよい。前記の（１）式によれば、等色関数ｘ（λ），ｙ（λ），ｚ（λ）が大きい波長域ほど、色彩値（Ｌ^*ａ^*ｂ^*値）に大きく影響するということができる。従って、等色関数ｘ（λ），ｙ（λ），ｚ（λ）を加算した重み関数ｗ（λ）を使用すれば、色への影響が大きい波長域を重視した二乗誤差が評価可能な評価値Ｅ（φ）を得ることができる。例えば、人間の目に知覚されない近紫外波長域においてはｗ（λ）が０となり、当該波長域における差分Ｄ（λ）は評価値Ｅ（φ）の増大に寄与しないこととなる。 In the present embodiment, the weighting function w (λ) uses the following equation (3).

In the above equation (3), the weighting function w (λ) is defined by adding the color matching functions x (λ), y (λ), and z (λ). The range of the value of the weighting function w (λ) may be normalized by multiplying the entire right side of the equation (3) by a predetermined coefficient. According to the above equation (1), the wavelength range where the color matching functions x (λ), y (λ), and z (λ) are larger greatly affects the color value (L ^* a ^* b ^* value). Can do. Therefore, if a weighting function w (λ) obtained by adding the color matching functions x (λ), y (λ), and z (λ) is used, a square error that emphasizes a wavelength region that has a large influence on the color can be evaluated. An evaluation value E (φ) can be obtained. For example, w (λ) is 0 in the near ultraviolet wavelength region that is not perceived by human eyes, and the difference D (λ) in the wavelength region does not contribute to the increase in the evaluation value E (φ).

That is, even if the difference between the target spectral reflectance R _t (λ) and the predicted spectral reflectance R _s (λ) is not necessarily small in the entire visible wavelength range, If the reflectance R _t (λ) and the predicted spectral reflectance R _s (λ) are similar, a small evaluation value E (φ) can be obtained, and the spectral reflectance R in accordance with the perception of the human eye. The evaluation value E (φ) can be used as an index of the closeness of (λ). The calculated evaluation value E (φ) is returned to ICM P3a1. That is, the ICMP 3a1 outputs an arbitrary ink amount set φ to the RPM P3a2 and the ECM P3a3, whereby the evaluation value E (φ) is finally returned to the ICM P3a1. The ICM P3a1 repeatedly executes to obtain the evaluation value E (φ) corresponding to an arbitrary ink amount set φ, so that the evaluation value E (φ) as the objective function is minimized. Calculate the optimal solution. As a method for calculating the optimum solution, for example, a nonlinear optimization method such as a gradient method can be used.

FIG. 11 schematically shows how the ink amount set φ is optimized in step S230. In the figure, as the ink amount set φ is optimized, the predicted spectral reflectance R _s (λ) when printing is performed with the ink amount set φ approaches the target spectral reflectance R _t (λ). . Further, by using the weighting function w (λ), the target spectral reflection of the predicted spectral reflectance R _s (λ) is increased in the wavelength region where the color matching functions x (λ), y (λ), and z (λ) are larger. The constraint on the rate R _t (λ) is stronger, and the difference between the predicted spectral reflectance R _s (λ) and the target spectral reflectance R _t (λ) is smaller. In this way, the predicted spectral reflectance R _s (λ) is preferentially applied to the target spectrum of the target TG in the wavelength range where the color matching functions x (λ), y (λ), and z (λ) are large and have a large effect on vision. Since it can be constrained to the reflectance R _t (λ), it is possible to calculate the ink amount set φ that makes the appearance close when irradiated with an arbitrary light source. As described above, it is possible to calculate the ink amount set φ that can be reproduced by the printer 20 with an appearance similar to the target TG in any light source. Note that the optimization termination condition may be the number of repetitions of the ink amount set φ update or the threshold value of the evaluation value E (φ).

  As described above, when the ICM P3a1 calculates the ink amount set φ that can reproduce the same spectral reflectance R (λ) as that of the target TG in step S230, all the indexes described in the index table IDB in step S240 are obtained. In step S220, it is determined whether or not all items have been selected. If not all items have been selected, the process returns to step S220 to select the next index. In this way, it is possible to calculate an ink amount set φ that can reproduce the same color as the target TG for all indexes. That is, an ink amount set φ that can reproduce the same spectral reflectance R (λ) as that of the targets TG1 to TG12 is calculated for all the targets TG1 to TG12 subjected to colorimetry in step S140 of the print data generation process (FIG. 2). can do. When it is determined in step S240 that the optimal ink amount set φ has been calculated for all indexes, in step S250, the LOM P3a4 generates a 1D-LUT and outputs the 1D-LUT to the PDV P3b.

  FIG. 12 shows an example of the 1D-LUT. In the figure, an optimum ink amount set φ is stored corresponding to each index. That is, for each target TG1 to TG12, a 1D-LUT describing an ink amount set φ that can be reproduced by the printer 20 with an appearance similar to each target TG1 to TG12 can be prepared. When the 1D-LUT is output to the PDV P3b, the 1D-LUT generation process is completed, and the next print control data generation process (step S300) is executed.

3-2. Print Control Data Generation Processing FIG. 13 shows the flow of print control data generation processing. As shown in FIG. 2, the PDV P3b includes a mode discrimination module (MIM) P3b1, an index separation module (ISM) P3b2, an RGB separation module (CSM) P3b3, a halftone module (HTM) P3b4, and a rasterization module (RTM). P3b5. In step S310, the mode determination module (MIM) P3b1 acquires the print data PD. In step S320, the MIM P3b1 selects one pixel from the print data PD. In step S330, the MIM P3b1 determines whether or not a flag indicating that the index is stored in the selected pixel is set. If it is determined that the flag is not raised, the CSM P3b3 refers to the 3D-LUT in step S340 and executes color conversion (separation) for the pixel.

FIG. 14 shows an example of a 3D-LUT. In the figure, the 3D-LUT has a plurality of representative relationships in the color space in which the RGB value and the ink amount set φ (d _C , d _M , d _Y , d _K , d _lc , d _lm , d _lk ) The table describes the coordinates, and the CSM P3b3 refers to the 3D-LUT and acquires the ink amount set φ corresponding to the RGB value of the pixel. At that time, the corresponding ink amount set φ is acquired by performing interpolation calculation for RGB values not directly described in the 3D-LUT. As a method for creating a 3D-LUT, JP 2006-82460 A or the like can be employed. In this publication, a 3D-LUT in which color reproducibility in a specific light source, gradation of reproducible color, graininess, light source independence of reproducible color, gamut, and ink duty are comprehensively improved. Is created.

  On the other hand, if it is determined in step S330 that the flag indicating that the index has been stored in the selected pixel is set, ISM P3b2 refers to the 1D-LUT in step S350, and the color for the pixel is determined. Perform conversion (separation). That is, the index is acquired from the pixel on which the flag indicating that the index is stored, and the ink amount set φ associated with the index is acquired by the 1D-LUT. In step S340 or step S350, if the ink amount set φ for the pixel can be acquired, it is determined in step S360 whether the ink amount set φ has been acquired for all the pixels. If there remains a pixel for which the ink amount set φ has not been acquired, the process returns to step S320 to select the next pixel.

  By repeatedly executing the above processing, the ink amount set φ can be obtained for all the pixels. When the ink amount set φ can be obtained for all the pixels, all the pixels are converted into the print data PD expressed by the ink amount set φ. As described above, by determining which one of the 1D-LUT and 3D-LUT is used for each pixel, with respect to the pixels corresponding to the frames F1 to F12 in which the index is stored, the respective light sources have the respective targets TG1 to TG12. Can be obtained, and color reproduction based on a 3D-LUT creation guideline (for example, emphasizing graininess) is performed for pixels storing RGB values. A possible ink amount set φ can be acquired.

  In step S370, the HTM P3b4 acquires print data PD in which each pixel is expressed by an ink amount set φ, and executes halftone processing. The HTM P3b4 can use a known dither method, error diffusion method, or the like for halftone processing. In the print data PD for which the halftone process has been completed, each pixel has an ejection signal indicating whether or not each ink is ejected. In step S380, the RTM P3b5 acquires the print data PD for which the halftone process is completed, and executes a process of assigning the ejection signal in the print data PD to each scan pass and each nozzle of the print head of the printer 20. As described above, the print control data CD that can be output to the printer 20 can be generated, and the print control data CD to which signals necessary for controlling the printer 20 are attached is output to the spooler P1b and the printer 20. As a result, the printer 20 ejects ink onto the printing paper to form a sample chart SC.

In the region corresponding to the frames FL1 to FL12 of the sample chart SC formed on the printing paper as described above, the target spectral reflectances R _t (λ) of the targets TG1 to TG12 can be reproduced. That is, the areas corresponding to the frames FL1 to FL12 are printed with an ink amount set φ that follows the colors of the targets TG1 to TG12 under a plurality of light sources, and thus similar to the targets TG1 to TG12 under each light source. Such colors can be reproduced. For example, when the sample chart SC is viewed indoors, the colors of the areas corresponding to the frames FL1 to FL12 reproduce the colors when the targets TG1 to TG12 are viewed indoors, and the sample chart SC is viewed outdoors. The colors of the regions corresponding to the frames FL1 to FL12 can be reproduced when the targets TG1 to TG12 are visually recognized outdoors.

Ultimately, if the sample chart SC having the same spectral reflectance R (λ) as the targets TG1 to TG12 is reproduced, the same color as the targets TG1 to TG12 can be reproduced with any light source. . However, since the ink (color material type) that can be used by the printer 20 is limited to CMYKlclmlk, an ink amount set φ that can reproduce the spectral reflectance R (λ) completely the same as the targets TG1 to TG12 is obtained. Is virtually impossible. In addition, even when the ink amount set φ that can reproduce the spectral reflectance R (λ) similar to the targets TG1 to TG12 is obtained in the wavelength range that does not affect the perceived color, it is useless in realizing the visual reproduction accuracy. . On the other hand, in the present invention, the target spectral reflectance R _t (λ is obtained by using the evaluation value E (φ) weighted based on the color matching functions x (λ), y (λ), z (λ). ) Is evaluated, it is possible to obtain the ink amount set φ that can achieve visually sufficient accuracy.

  On the other hand, in the region corresponding to the frames FL1 to FL12 of the sample chart SC formed on the printing paper, printing is performed with the ink amount set φ based on the 3D-LUT described above. For this reason, the printing performance for the area is based on the 3D-LUT. As described above, in the present embodiment, the area other than the frames FL1 to FL12 shows a uniform image of intermediate gray, but the printing performance targeted by the 3D-LUT can be satisfied in the area. That is, it is possible to realize printing in which the gradation of reproduced color, graininess, light source independence of reproduced color, gamut, and ink duty are comprehensively improved.

4). Calibration process:
In the frames FL1 to FL12 of the sample chart SC printed by the above processing, the target spectral reflectances R _t (λ) of the targets TG1 to TG12 can be reproduced. However, in some cases, an error may occur between the actual spectral reflectance R (λ) of the frames FL1 to FL12 of the sample chart SC and the target spectral reflectance R _t (λ) of each of the targets TG1 to TG12. . Since the ink amount set φ is predicted by the RPM P3a2 using the prediction model (spectral printing model), the printer that has constructed the spectral printing model (created the spectral reflectance database RDB) and the printer that actually performs printing This is because it is unavoidable that 20 aircrafts are different, or even if the same aircraft, errors occur due to changes over time.
Therefore, in this embodiment, calibration processing is performed, and the target spectral reflectance R _t (λ) in the result (frames FL1 to FL12 of the sample chart SC) printed on the printing paper by the ink amount set registered in each index. The color reproducibility is confirmed, and further processing for improving the reproducibility is performed. This process is roughly calculated as a process for minimizing the deviation between the spectral reflectance of the check patch and the target spectral reflectance, and a process for minimizing the error that occurs in the fractional process that is performed in accordance with the arithmetic process. And a process for minimizing the total amount of ink deposited in the ink set.

  FIG. 15 shows the flow of calibration processing. In this embodiment, the calibration process is executed by the confirmation patch measurement unit (KPM) P3a5 and the ink amount set correction unit (IMM) P3a6 of the LUG P3a shown in FIG.

  When the process is started, in step S400, the value n of the update number counter indicating the number of times the calibration process is repeated and the value m of the ink group counter for counting the number of ink groups described later are reset to 1. .

  In step S402, the sample chart SC is printed. More specifically, a sample chart printing instruction is issued as in step S160 described above, print data is generated as in step S170, and print control data generation processing is performed as in step S300. A sample chart SC is printed. Of course, if there is a printed sample chart SC, it may be used. However, in the printing of the sample chart SC that is executed after the condition is not satisfied in step S485, the printing result by the updated 1D-LUT is necessary, so the printing is always executed.

In step S405, the spectral reflectance R (λ) is measured for each frame FL1 to FL12 of the printed sample chart SC. Specifically, for example, the MDV P4 controls the spectral reflectometer 30 in response to a request from the confirmation patch measurement unit (KPM) P3a5, and the KPM P3a5 acquires the spectral reflectance data RD obtained by the control. Each frame FL1 to FL12 of the sample chart SC measured in step S405 corresponds to a confirmation patch. Note that the spectral reflectance R (λ) measured in step S405 will be referred to as a confirmed spectral reflectance R _c (λ) in the following description.

FIG. 16 is a graph for explaining a state in which a deviation occurs between the target spectral reflectance R _t (λ) and the confirmed spectral reflectance R _c (λ) of the target TG1 (frame FL1). In the figure, confirmed the spectral reflectance R _c (λ) is roughly follow the target spectral reflectance R _t (λ), but confirmed overall the low reflectance side spectral reflectance R _c (λ) Has shifted. Such a shift is a phenomenon that can occur when, for example, the amount of each ink ejected by the printer 20 increases over time as described above. Therefore, in steps S410 to S470, processing for correcting this deviation is performed.

  In step S410, the ink amount set correction unit (IMM) P3a6 selects one of the targets TG1 to TG12 (frames FL1 to FL12).

In step S420, the IMM P3a6 calculates a deviation ΔR (λ) between the confirmed spectral reflectance R _c (λ) and the target spectral reflectance R _t (λ). Specifically, for the target TG selected in step S410, the deviation ΔR (λ) of each wavelength is calculated by subtracting the target spectral reflectance R _t (λ) from the confirmed spectral reflectance R _c (λ). . The deviation ΔR (λ) can be expressed by a deviation vector ΔR composed of the deviation ΔR (λ) for each wavelength section, for example, as in the following equation (4). In the following formula (4), ΔR _a indicates an average deviation ΔR (λ) between wavelength sections λ = (a−5) to (a + 5) [nm] (a is, for example, 10 nm at a visible wavelength) Cycle value).

In step S430, the IMM P3a6 acquires the ink amount set φ (d _C , d _M , d _Y , d _K , d _lc , d _lm , d _lk ) used when the frame FL1 is printed. This ink amount set φ is obtained from the 1D-LUT set in advance by the above-described 1D-LUT creation processing (or the 1D-LUT updated in step S470 described later). Here, the ink amount set φ obtained from the 1D-LUT corresponds to the color material amount set to be corrected in the present invention.

In step S440, the IMM P3a6 calculates a Jacobian matrix J related to a minute section near the ink amount set φ with respect to the predicted spectral reflectance R _s (λ) predicted by the spectral printing model. However, instead of calculating the Jacobian matrix for all of the inks constituting the ink amount set φ, the matrix component corresponding to the ink of the ink group corresponding to the ink group counter m is calculated.

  Here, the ink group will be described. The ink group in the present embodiment is a group of the ink sets in the present embodiment according to the ability to finely adjust the color (density separation ability). The ability to finely adjust the color expresses whether or not fine color adjustment can be performed. For example, when only one drop of ink is attached to the printing paper, the smaller the density change that occurs on the printing paper, the higher the ability to fine-tune the color. The ability to do is low. In other words, it can be expressed as the ability to finely adjust the density. The higher the colorant density in the ink, the lower the color adjustment density (the density separation ability is low) and the lower the colorant density. The higher the ability to adjust the color (the higher the density resolution ability).

  For example, if the ink density of each ink is expressed by 256 gradations, and the dark ink has a density three times that of the light ink, in order to generate a density change for one gradation of the dark ink, the light ink Then, the ink amount for three gradations must be used. In other words, the light ink has a relatively small density fluctuation amount generated on the recording medium when the same amount of ink is attached to the recording medium. Can express the difference in density. In view of the characteristics of such dark and light inks, from the viewpoint of color reproducibility, when determining an ink set for reproducing a certain color, after preferentially assigning ink with low ability to finely adjust the color It is preferable to make fine adjustments with ink that has a high ability to finely adjust colors. From the viewpoint of ink placement limit (total amount of ink that can be deposited per unit area), an ink set for reproducing a certain color should be used. When deciding, it is better to use a lot of low ability to fine-tune the color.

  Specific examples of the ink group satisfying the above conditions include those in which K ink, CMY ink, and lclmlk ink are grouped, and those in which CMYKlclmlk is grouped in CMYK ink and lclmlk ink. These groups are associated with numerical values of the ink group counter m in ascending order of ability to finely adjust the color. That is, in the former case, if the numerical value associated with K ink is m = 1, C = 2 is associated with CMY ink, m = 3 is associated with lclmlk ink, and CMYK ink is associated with the latter. If the numerical value to be associated is m = 1, m = 2 is associated with lclmlk ink. In the present embodiment, the former ink grouping (how to divide into three groups of K ink, CMYK ink, and lclmlk ink) will be described as an example. When the ink set is an ink configuration in which the hue is not secured in all directions (no degree of freedom in the yellow direction) only with the light color ink (lclm), such as CMYKlclm ink, The Ylclm ink group may be configured by incorporating a Y ink having a degree of freedom into an ink group having a high ability to finely adjust the color. This is because an optimum solution cannot be calculated unless the degree of freedom in all directions of the hue is secured when finely adjusting the color. In the above example, the groups are grouped without duplication, but it is needless to say that there may be duplication of ink between the groups.

  By the way, in the process of calculating the ink amount set according to the present embodiment, the optimum solution is searched while changing by an amount smaller than the minimum ink amount that can be ejected onto the printing paper by the printer 20. For example, if the printer 20 can express 256 gradations by changing the ink discharge amount, an optimal ink amount set is searched while changing the gradation by 0.01. By reducing the search step in this way, vibration in the vicinity of the optimal solution in the search process is suppressed and it is easy to reach the optimal solution. However, the ink amount after the decimal point is reduced before actually setting the 1D-LUT. Rounded. However, the fraction of the ink amount of the ink having a low ability to finely adjust the color may be an amount that can be expressed by the ink amount of the ink having a high ability to finely adjust the color. In addition, as a result of the fraction processing being performed on both the dark ink and the light ink by assigning fractional ink amounts in the search process, an error from the optimum solution may be increased. In this embodiment described later, the influence of this rounding error is also minimized. In the following description, a numerical value having the minimum ejectable ink amount as a unit amount is described as an integer value, and a numerical value smaller than the unit amount is described as a decimal value.

The Jacobian matrix J calculated in step S440 is expressed by the following equation (5a). In the following equation (5a), R _sa represents an average predicted spectral reflectance R _s (λ) in the wavelength interval λ = (a−5) to (a + 5) [nm]. That is, the Jacobian matrix J is a matrix having a type of the number of wavelength sections (rows) × the number of inks (columns).

However, in step S440, since only the Jacobian matrix of the ink corresponding to the ink group counter m is calculated, in practice, for example, the Jacobian matrix J _{m = 1} calculated when _{m = 1} is j (5b ), The Jacobian matrix J _{m = 2} calculated when _{m = 2} is expressed by the above equation (5c), and the Jacobian matrix J _{m = 2} calculated when m = 3 is Equation (5d) is obtained. Hereinafter, the Jacobian matrix composed of an ink component corresponding to the ink group to as J _m.

FIG. 17 shows how the Jacobian matrix J is calculated. Here, description will be given by taking as an example the calculation of a Jacobian matrix (first column of the matrix) for C ink in the ink set. First, ink amounts (d _C + h) and (d _C −h) obtained by adding and subtracting a minute amount h to the ink amount d _C used when the frame FL1 is printed are calculated. Next, while maintaining the ink amount (d _M , d _Y , d _K , d _lc , d _lm , d _lk ) used when printing the frame FL1 for other inks, the ink amount set φ ^{+ h} ( d _C + h, d _M , d _Y , d _K , d _lc , d _lm , d _lk ) and ink amount set φ- ^h (d _C −h, d _M , d _Y , d _K , d _lc , d _lm , d _lk ). Then, the ink amount sets φ ^{+ h} and φ ^−h are respectively input to the RPM P3a2, thereby calculating predicted spectral reflectances R _s ^{+ h} (λ) and R _s ^−h (λ) based on the spectral printing model (each wavelength). The average of the sections R _s365 , R _s375 , R _s385 ...

Here, the difference between the predicted spectral reflectances R _s ^{+ h} (λ) and R _s ^-h (λ) is the predicted spectral reflectance corresponding to the minute interval (d _C + h) to (d _C −h) of the C ink amount. It can be considered as a fluctuation amount of R _s (λ). Accordingly, assuming the linearity of the fluctuation of the predicted spectral reflectance R _s (λ) in the minute section (d _C + h) to (d _C -h), {R _s ^{+ h} (λ) −R _s ^−h ( λ)} / 2h, the partial differential for C ink can be obtained. By performing the above calculation in the same manner for each wavelength section, the first column (C ink component) of the Jacobian matrix J can be obtained. Consists of components corresponding to the ink group in the Jacobian matrix J in the vicinity of the ink amount set φ used when the frame FL1 is printed by paying attention to the other inks that make up the ink group sequentially. The obtained Jacobian matrix J _m can be obtained. As described above, the Jacobian matrix _{J m} is obtained, the process proceeds to step S450.

上記（６）式においてＪ_ｍ ^-1はヤコビ行列Ｊ_ｍの逆行列を意味しており、逆行列Ｊ_ｍ ^-1の算出においては下記（７）式に示す特異値分解を利用する。

In step S450, the IMM P3a6 calculates a correction amount vector Δφ _m of the ink amount set φ in the ink group m by the following equation (6). If m = 1, the correction amount vector is Δφ _{m = 1} = (0, 0, 0, Δd _K , 0, 0, 0). If m = 2, the correction amount vector is Δφ _{m = 2} = (Δd _C , Δd _M , Δd _Y , 0, 0, 0, 0), and if m = 3, the correction amount vector is Δφ _{m = 3} = (0, 0, 0, 0, Δd _lc , (Δd _lm , Δd _lk ), the correction amount of the component corresponding to the corresponding ink.

In the above equation (6), J _m ⁻¹ means an inverse matrix of the Jacobian matrix J _m , and the singular value decomposition shown in the following equation (7) is used in calculating the inverse matrix J _m ⁻¹ .

In the above equation (7), the Jacobian matrix J is first decomposed into matrices U, Σ, and V ^T to calculate an inverse matrix (pseudo inverse matrix) J ⁻¹ . Note that the Jacobian matrix J is a matrix having a non-square type of the number of wavelength sections (rows) × the number of inks (columns), but by the singular value decomposition, the number of wavelength sections (rows) × the number of wavelength sections (columns). The matrix U, the number of inks (rows) × the number of inks (columns) V ^T, and the number of wavelength sections (rows) × the number of inks (columns), except for diagonal components, are decomposed into a matrix Σ. Further, the inverse matrix Σ ⁻¹ of the matrix Σ is obtained by taking the diagonal component of the matrix Σ as an inverse. For convenience of processing, when the reciprocal is smaller than a predetermined threshold, it is desirable to treat the reciprocal as 0.

  When the correction amount vector Δφ of the ink amount set φ can be calculated as described above, the correction amount vector is converted into an integer. That is, fraction processing of each element constituting the correction amount vector is performed. In the rounding process, the numerical value after the decimal point is rounded, and the rounding error (basically, the decimal value is rounded down) from the optimal solution calculated in step S450 occurs in the correction amount vector after the rounding process. When the same amount of rounding error occurs between the dark ink amount and the light ink amount, the dark ink has a greater influence on the reproduced color. For example, if the dark ink is an ink having a density three times that of the light ink, the density fluctuation when the 0.5 gradation is rounded with the dark ink is the case where the 1.5 gradation of the light ink is rounded. It corresponds to the concentration fluctuation. That is, the density fluctuation rounded as a decimal value in dark ink may be expressed as an integer value in light ink. Therefore, as in this embodiment, by performing ink amount correction in the order of the ability to fine-tune the color, the rounding error generated in the process of calculating the ink correction amount of the ink group with the low ability to fine-tune the color is It can be converted into an integer value in the ink amount of the ink group having a high ability to finely adjust the color. The correction amount vector of each ink group is temporarily rounded and stored in a storage medium such as a RAM.

  In step S460, it is determined whether or not the ink amount set has been updated for all ink groups. That is, it is determined whether or not the ink group counter m has reached m = 3. If the ink group counter has reached m = 3, the process proceeds to step S467. If the ink group counter has not reached m = 3, the process proceeds to step S462.

図３０は、上記（８）式や（９）式により、ステップＳ４６２の繰り返しによって偏差が更新されていく様子を示した図である。同図に示すように、算出されたＫインクの補正量が端数処理によって整数化され、Ｋインクによる偏差の解消量の算出に使用される。そしてＫインクによる偏差の解消量を減じた量を新たな偏差とし、ＣＭＹインクの補正量を算出する際に解消すべき偏差とするのである。 In step S462, the IMM P3a6 updates the deviation. That is, the deviation ΔR ′ eliminated by the ink corresponding to the ink group m is calculated by the following equation (8), and the eliminated deviation ΔR ′ is subtracted from the deviation ΔR as in the following equation (9). A deviation ΔR to be eliminated in the next ink group is set.

FIG. 30 is a diagram showing how the deviation is updated by repeating step S462 according to the above equations (8) and (9). As shown in the figure, the calculated K ink correction amount is converted to an integer by fraction processing and used to calculate the deviation cancellation amount due to K ink. Then, an amount obtained by subtracting the amount of cancellation of the deviation due to the K ink is set as a new deviation, which is to be eliminated when calculating the correction amount of the CMY ink.

When the update of the deviation is completed, the process proceeds to step S465, 1 is added to the ink group counter m, the process returns to step S440, and the processes of steps S440 to S460 are executed. For example, when m is counted up to 2 in step S465, the Jacobian matrix of the above equation (5c) is calculated based on the deviation ΔR updated in step S462 and the ink amount set φ acquired in step S430. Then, after calculating the correction amount vector Δφ ₂ by performing the calculations of the above equations (8) and (9) and fraction processing, the correction amount vector is temporarily stored in the RAM or the like, and the deviation ΔR is updated. Will be counted up to 3.

In step S467, the IMM P3a6 is based on each component of the ink amount set φ corresponding to the index used when the frame FL1 is printed, and the correction amount vector Δφ _m calculated corresponding to each ink group. Then, the corrected ink amount set φ _M is calculated by calculating the following equation (10).

  FIG. 31 is a diagram illustrating the ability to adjust the color in each ink group. As shown in the figure, when correction is performed with an ink group having a low ability to finely adjust the color, the spectral reflectance that can be obtained after correction can be selected only with a large interval, as indicated by the two-dot chain line shown in the left-hand enclosure. . On the other hand, when the correction is performed with an ink group having a high ability to adjust the color, the spectral reflectance that can be obtained after correction can be selected at a smaller interval as indicated by a two-dot chain line shown in the right-side enclosure. However, the number of steps until reaching the target spectral reflectance is smaller in the ink group having a lower ability to adjust the color, and it is possible to reach the vicinity of the target spectral reflectance with a small amount of ink. Therefore, after eliminating the maximum deviation with an ink group with a low ability to finely adjust the color, fine adjustment is made sequentially with an ink group with a high ability to finely adjust the color, and the total ink placement amount of the ink amount set φ Is minimized.

In step S470, it updates the 1D-LUT the correction ink amount set phi _M. That, 1D-LUT output unit (LOM) P3a4, the ink amount set phi for the corresponding index in the 1D-LUT, and updates the correction ink amount set phi _M calculated in step S450. If the ink amount set φ can be updated, the process proceeds to step S480.

In step S480, it is determined whether or not all the targets TG1 to TG12 (frames FL1 to FL12) have been selected. If the selection has been completed, the process proceeds to step S485. If the selection has not been completed, step S410 is performed. Return to. Returning to step S410, to select the next target TG1~TG12 (frame FL1~FL12), with all of the ink amount set corresponding to the target TG1~TG12, S410~S470 until the update to the correction ink amount set φ _M Repeat the process.

As described above, in the sample chart SC printed based on the corrected ink amount set φ _M after the condition is satisfied in step S480, printing that compensates for the above-described deviation ΔR (λ) can be realized, and the target spectral reflection can be realized. The rate R _t (λ) can be accurately reproduced. Hereinafter, the principle will be described with reference to FIG. Predicted spectral reflectance R _s (λ) slope characteristics by the spectral printing model in the vicinity of the correction target ink amount set φ used when the frame FL1 is printed, and the confirmed spectral reflectance R actually obtained by measuring the confirmation patch _c It can be considered that the slope characteristics of (λ) are similar. In many cases, although the absolute value of the confirmation spectral reflectance R _c (λ) when actually printed due to the change with time of the printer 20 or individual differences is shifted, the relative value between the approximate ink amount sets φ is shifted. This is because the fluctuation characteristics are considered not to fluctuate greatly. Further, it can be assumed that the fluctuation in the minute section is linear.

As shown in FIG. 17, the correction ink amount set φ _M that can actually reproduce the target spectral reflectance R _t (λ) has a curve (shown by a solid line) passing through the confirmed spectral reflectance R _c (λ) This is a value indicating the spectral reflectance R _t (λ). However, since the confirmation spectral reflectance R _c (λ) is obtained only for the correction target ink amount set φ used when the frame FL1 is printed, the confirmation spectral reflectance R _c (λ) is arbitrary. It is not obtained for the ink amount set φ. Accordingly, it is not possible to directly calculate the correction ink amount set φ _M that can actually reproduce the target spectral reflectance R _t (λ) based on the confirmed spectral reflectance R _c (λ). Therefore, first determine the curve of the predicted spectral reflectance prediction spectral reflectances R _s (lambda), based on the spectral printing model which can obtain for any ink amount set φ R _s (λ) (shown in phantom). Then, a Jacobian matrix J indicating the inclination in the vicinity of the correction target ink amount set φ used when the frame FL1 is printed on the curve is calculated.

As described above, the absolute value of the curve of the actual confirmation spectral reflectance R _c (λ) indicated by the broken line and the curve of the predicted spectral reflectance R _s (λ) based on the spectral printing model are shifted. However, since it can be considered that the relative fluctuation characteristics are similar, it can be estimated that the curve of the actual confirmation spectral reflectance R _c (λ) has the same slope. If the inclination of the actual confirmation spectral reflectance R _c (λ) can be estimated in this way, the deviation ΔR (λ), the correction amount vector Δφ necessary to compensate for the deviation ΔR (λ), and the Jacobian indicating the inclination It can be considered that the linear relationship of the above equation (6) is established with the matrix J. Then, by solving the above equation (6) with respect to the correction amount vector Δφ and subtracting the correction amount vector Δφ from the original ink amount set φ, the correction ink that can actually reproduce the target spectral reflectance R _t (λ). A quantity set φ _M can be obtained. Note that the Jacobian matrix J is composed of row components for each of a plurality of wavelength sections, but solves the above equations (6) and (7) (however, the equations that limit ink groups are calculated for all inks). Thus, it is possible to obtain a correction ink amount set φ _M that reduces the deviation ΔR (λ) of each wavelength in a least square manner. In the above description, the idea of the present invention is embodied by a determinant operation. However, the above-described equations (5a) and (6) to (10) (however, all the equations that limit ink groups are used). An operation equivalent to that calculated for ink) may be performed. Further, the Jacobian matrix J is not necessarily limited to that according to the above equation (5a), and an operation equivalent to the above operation may be performed using a mathematical expression or an array equivalent to the Jacobian matrix J.

Furthermore, in the present embodiment, it is possible to reproduce the spectral reflectance R (λ) with higher accuracy by repeatedly executing the above calibration process.
In step S485, it is determined whether or not the counter n indicating the number of repetitions of the calibration process has become 3. If not, the update number counter n is incremented by 1 (step S490). The process returns to step S402. Thereby, the printing of the confirmation patch in step S402 is executed again. Here, in order to print the confirmation patch based on the ink amount set φ updated by the calibration process of the previous loop, the target spectral reflectance R _t (λ) and the confirmed spectral reflectance R _c (λ ) And the magnitude of the deviation vector ΔR is predicted to decrease. In step S450, the correction amount vector Δφ is calculated for the new confirmation spectral reflectance R _c (λ). In step S470, the deviation vector ΔR whose magnitude has been reduced is updated to a correction ink amount set φ _M that further cancels out. Can do. Such calibration processing is repeated until the update counter n reaches 3, so that the deviation vector ΔR can be made extremely small during that time, and more accurate spectral reflectance reproduction can be realized. be able to. In the above, the number of repetitions is not limited to three. The calibration process as described above is preferably executed when the printer 20 of the same machine is not used for a long time or when the sample chart SC is printed by a printer of a different machine.

  In the present embodiment described above, the ink amount set defined in the 1D-LUT is the actual color indicated when the ink amount set associated with the predetermined color is attached to the printing paper by the printer 20 and the predetermined amount. In order to minimize the deviation from the color, based on the ability to finely adjust the color, the ink of the ink set is divided into a plurality of groups, and the predetermined amount is used as a differential variable in order from the ink amount of the group having the lower ability to adjust the color. Calculation is performed by sequentially eliminating the deviation based on a Jacobian matrix obtained by partial differentiation of information indicating color in the vicinity of the same ink amount set. Therefore, highly accurate reproduction is efficiently realized.

5. Spectral Printing Model FIG. 18 schematically shows the printing method of the printer 20 of this embodiment. The printer 20 includes a print head 21 having a plurality of nozzles 21a, 21a,... For each CMYKlclmlk ink, and the amount of ink for each CMYKlcmlk ink ejected by the nozzles 21a, 21a,. ink amount set φ mentioned above _{(d c, d m, d} y, d k, d lc, d lm, d lk) is controlled to an amount specified by performed based on the print control data CD a. Each nozzle 21a, the ink droplets 21a · · · is discharged becomes fine dots on the printing paper, a number of dots of ink amount set by a collection _{φ (d c, d m,} d y, d k, d lc, d A print image having an ink coverage corresponding to _lm , d _lk ) is formed on the printing paper.

Prediction model RPM P3a2 uses (spectral printing model), any ink amount set phi (d _c that may be used in the printer 20 of this _{embodiment, d m, d y, d} k, d lc, d lm, d _lk ) is a prediction model for predicting the spectral reflectance R (λ) when printing is performed as the predicted spectral reflectance R _s (λ). In the spectral printing model, a spectral reflectance database RDB obtained by actually printing color patches at a plurality of representative points in the ink amount space and measuring the spectral reflectance R (λ) with a spectral reflectance meter is used. prepare. An arbitrary ink amount set φ (d _c , d _m , d _y , d _k , d _lc , d _lm , d _lk ), and the spectral reflectance R (λ) when printing is predicted.

FIG. 19 shows the spectral reflectance database RDB. As shown in the figure, the spectral reflectance database RDB has an ink amount set φ (d) of a plurality of lattice points in the ink amount space (in this embodiment, it is 7-dimensional, but only the CM plane is shown for simplification). _c , d _m , d _y , d _k , d _lc , d _lm , d _lk ) are look-up tables in which spectral reflectances R (λ) obtained by actual printing / measurement are described. . For example, five grid points that divide each ink amount axis are generated. Here 5 ⁷ also lattice points are generated, it is necessary to print / measuring huge amount of color patches, since there is actually a time capable of ejecting ink duty limitation in the printer 20, The number of grid points to be printed / measured is reduced.

  Further, only some of the lattice points are actually printed / measured, and the other lattice points are spectrally reflected R (λ) based on the spectral reflectance R (λ) of the actually printed / measured lattice points. Thus, the number of color patches that are actually printed / measured may be reduced. The spectral reflectance database RDB needs to be prepared for each printing sheet that can be printed by the printer 20. Strictly speaking, the spectral reflectance R (λ) is determined by the spectral transmittance of the ink film (dot) formed on the printing paper and the reflectance of the printing paper, and the surface physical properties of the printing paper (depending on the dot shape). ) And reflectivity. Next, prediction by the cell division Yule-Nielsen spectral Neugebauer model using the spectral reflectance database RDB will be described.

  The RPM P3a2 executes prediction based on the cell division Yule-Nielsen spectral Neugebauer model using the spectral reflectance database RDB in response to a request from the ICM P3a1. In this prediction, a prediction condition is acquired from ICM P3a1, and this prediction condition is set. Specifically, printing paper and ink amount set φ are set as printing conditions. For example, when prediction is performed using glossy paper as a printing paper, a spectral reflectance database RDB created by printing color patches on glossy paper is set.

When it is set in the spectral reflectance database RDB, applying ink amount set φ input from _{ICM P3a1 (d c, d m} , d y, d k, d lc, d lm, d lk) to the spectral printing model . The cell splitting Yule-Nielsen spectroscopic Neugebauer model is based on the well-known spectroscopic Neugebauer model and the Yule-Nielsen model. In the following description, for simplification of description, a model in the case of using three types of CMY inks will be described. However, a similar model is used as a model using an arbitrary ink set including CMYKlclmlk according to the present embodiment. It is easy to expand. For cell division Yule-Nielsen spectral Neugebauer model, Color Res Appl 25, 4-19, 2000 and R Balasubramanian, Optimization of the spectral Neugebauer model for printer characterization, J. Electronic Imaging 8 (2), 156- See 166 (1999).

FIG. 20 is a diagram showing a spectral Neugebauer model. The spectral Neugebauer model, optional ink amount sets _{(d c, d m, d} y) predicted spectral reflectance of the printed matter when printed with R _s (lambda) is given by the following equation (11).

Here, a _i is the area ratio of the i-th region, and R _i (λ) is the spectral reflectance of the i-th region. The subscript i includes an area without ink (w), an area only with cyan ink (c), an area only with magenta ink (m), an area only with yellow ink (y), magenta ink and yellow ink. A region (r) where yellow ink and cyan ink are ejected, a region (b) where cyan ink and magenta ink are ejected, and a region where three inks CMY are ejected (region) (r) k) respectively. Further, f _c , f _m , and _fy are the proportions of the area covered with only one CMY ink when it is ejected (referred to as “Ink area coverage”).

The ink coverages f _c , f _m , and _fy are given by the Murray-Davis model shown in FIG. In the Murray-Davies model, for example, the ink area coverage f _c of the cyan ink is a nonlinear function of the ink amount d _c of the cyan, be converted to the ink amount d _c in the ink coverage f _c, for example by one-dimensional lookup table Can do. Ink coverage f _c, f _m, f _y is the ink amount d _c, d _m, reason for the non-linear function of d _y is spread enough ink in the case where a small amount of ink ejected to the unit area, This is because, when a large amount of ink is ejected, the ink is overlapped and the area covered with the ink does not increase so much. The same applies to other types of MY inks.

ここで、ｎは１以上の所定の係数であり、例えばｎ＝１０に設定することができる。前記の（１２ａ）式および（１２ｂ）式は、ユール・ニールセン分光ノイゲバウアモデル(Yule-Nielsen Spectral Neugebauer Model)を表す式である。 When the Yule-Nielsen model relating to spectral reflectance is applied, the equation (11) can be rewritten as the following equation (12a) or (12b).

Here, n is a predetermined coefficient of 1 or more, and can be set to n = 10, for example. The above equations (12a) and (12b) are equations representing the Yule-Nielsen Spectral Neugebauer Model.

  The Cellular Yule-Nielsen Spectral Neugebauer Model used in the present embodiment is obtained by dividing the ink amount space of the above-described Yule-Nielsen Spectral Neugebauer Model into a plurality of cells. is there.

FIG. 21A shows an example of cell division in the cell division Yule-Nielsen spectroscopic Neugebauer model. Here, for simplification of description depicts the cell division in a two-dimensional ink amount space including two axes of the ink amount d _c, d _m of the CM inks. Note that it for ink coverage f _c, is f _m with at Murray-Davis model described above the ink amount d _c, a unique relationship with d _m, the ink coverage f _c, also be considered as an axis indicating the f _m . White circles are cell division grid points (called “lattice points”), and a two-dimensional ink amount (coverage) space is divided into nine cells C1 to C9. The ink amount set (d _c , d _m ) corresponding to each lattice point is an ink amount set corresponding to the lattice point defined in the spectral reflectance database RDB. That is, the spectral reflectance R (λ) of each lattice point can be obtained by referring to the above-described spectral reflectance database RDB. Therefore, the spectral reflectances R (λ) ₀₀ , R (λ) ₁₀ , R (λ) ₂₀ ... R (λ) ₃₃ of each lattice point can be acquired from the spectral reflectance database RDB.

In fact, performs at seven-dimensional ink amount space of even the cell division CMYKlclmlk In this embodiment, the ink amount set phi (d _c coordinates also the six-dimensional lattice _{points, d m, d y, d} k, d lc , D _lm , d _lk ). Then, the ink amount set _{φ (d c, d m,} d y, d k, d lc, d lm, d lk) of the grid points corresponding to the spectral reflectance R (lambda) is the spectral reflectance database of each grid point It is acquired from RDB (for example, glossy paper).

FIG. 21 (B) shows the relationship between the ink area coverage f _c and the ink amount d _c which are used in the cell division model. Here, one kind of the ink amount in the range 0 to D _cmax of ink is also divided into three sections, the virtual used in the cell division model by non-linear curve which increases monotonically from 0 for each section to the 1 A typical ink coverage _fc is determined. For other inks, the ink coverages f _m and f _y are obtained in the same manner.

ここで、（１３）式におけるインク被覆率ｆ_c，ｆ_mは図２１（Ｂ）のグラフで与えられる値である。また、セルＣ５を囲む４つの格子点に対応する分光反射率Ｒ（λ）₁₁，（λ）₁₂，（λ）₂₁，（λ）₂₂は分光反射率データベースＲＤＢを参照することにより取得することができる。これにより、（１３）式の右辺を構成するすべての値を確定することができ、その計算結果として任意のインク量セットφ（ｄ_c，ｄ_m）にて印刷を行った場合の予測分光反射率Ｒ_s（λ）を算出することができる。波長λを可視波長域にて順次シフトさせていくことにより、可視波長域における予測分光反射率Ｒ_s（λ）を得ることができる。インク量空間を複数のセルに分割すれば、分割しない場合に比べて予測分光反射率Ｒ_s（λ）をより精度良く算出することができる。以上のようにして、ＲＰＭ Ｐ３ａ２がＩＣＭ Ｐ３ａ１の要請に応じて予測分光反射率Ｒ_s（λ）を予測することができる。 FIG. 21C shows the predicted spectral reflectance R _s (λ) when printing is performed with an arbitrary ink amount set (d _c , d _m ) in the center cell C5 of FIG. The calculation method is shown. The spectral reflectance R (λ) when printing is performed with the ink amount set (d _c , d _m ) is given by the following equation (13).

Here, the ink coverages f _c and f _m in the equation (13) are values given in the graph of FIG. The spectral reflectances R (λ) ₁₁ , (λ) ₁₂ , (λ) ₂₁ , and (λ) ₂₂ corresponding to the four lattice points surrounding the cell C5 are acquired by referring to the spectral reflectance database RDB. Can do. As a result, all values constituting the right side of the equation (13) can be determined, and the predicted spectral reflection when printing is performed with an arbitrary ink amount set φ (d _c , d _m ) as the calculation result. The rate R _s (λ) can be calculated. By sequentially shifting the wavelength λ in the visible wavelength region, the predicted spectral reflectance R _s (λ) in the visible wavelength region can be obtained. If the ink amount space is divided into a plurality of cells, the predicted spectral reflectance R _s (λ) can be calculated more accurately than when the ink amount space is not divided. As described above, the RPM P3a2 can predict the predicted spectral reflectance R _s (λ) according to the request of the ICM P3a1.

前記の（１４）式においては、ターゲットＴＧから得られたターゲット分光反射率Ｒ_t（λ）との相関が高い等色関数ｘ（λ），ｙ（λ），ｚ（λ）ほど線形結合の際の重みが大きくなるようにされている。以上のようにして得られた重み関数ｗ（λ）においては、ターゲットＴＧのターゲット分光反射率Ｒ_t（λ）が大きい波長域についての重みを強調することができる。従って、各光源下での反射光の分光エネルギーのスペクトルが強くなりがちな波長域を重視した評価値Ｅ（φ）を得ることができる。すなわち、特にターゲットＴＧのターゲット分光反射率Ｒ_t（λ）が大きい波長域については、ターゲットＴＧのターゲット分光反射率Ｒ_t（λ）と予測分光反射率Ｒ_s（λ）とのずれを許容しないようなインク量セットφの最適解を得ることができる。むろん、重み関数ｗ（λ）は各等色関数ｘ（λ），ｙ（λ），ｚ（λ）に由来しているため、人間の知覚に適合した評価値Ｅ（φ）を得ることができる。 6). Modification 6-1: Modification 1
FIG. 22 schematically shows the weighting function w (λ) set by the ECM P3a3 in the modification. In the figure, the target spectral reflectance R _t (λ) obtained from the target TG is shown, and the target spectral reflectance R _t (λ) and the color matching functions x (λ), y (λ), Correlation coefficients c _x , c _y and c _z with z (λ) are calculated by ECM P3a3. Then, the weighting function w (λ) according to this modification is calculated by the following equation (14).

In the above equation (14), the color combination functions x (λ), y (λ), z (λ) having a higher correlation with the target spectral reflectance R _t (λ) obtained from the target TG are linearly coupled. The weight at the time is made large. In the weight function w (λ) obtained as described above, it is possible to emphasize the weight for the wavelength region where the target spectral reflectance R _t (λ) of the target TG is large. Therefore, it is possible to obtain an evaluation value E (φ) that emphasizes the wavelength range where the spectrum of the spectral energy of the reflected light under each light source tends to be strong. That is, especially in the wavelength region where the target spectral reflectance R _t (λ) of the target TG is large, a deviation between the target spectral reflectance R _t (λ) of the target TG and the predicted spectral reflectance R _s (λ) is not allowed. Such an optimal solution of the ink amount set φ can be obtained. Of course, since the weight function w (λ) is derived from each color matching function x (λ), y (λ), z (λ), an evaluation value E (φ) suitable for human perception can be obtained. it can.

6-2: Modification 2
FIG. 23 schematically shows the weighting function w (λ) set by the ECM P3a3 in another modification. In the figure, the target spectral reflectance R _t (λ) obtained from the target TG is applied as it is as the weighting function w (λ). By doing so, in particular a deviation of the spectral reflectance of the target TG for target spectral reflectance R _t (λ) is larger wavelength range of the target TG R and (lambda) and the target spectral reflectance R _t (λ) An optimum solution of the ink amount set φ that is not allowed can be obtained.

6-3: Modification 3
FIG. 24 schematically shows the weighting function w (λ) set by the ECM P3a3 in another modification. In the figure, spectral energy P _D50 (λ), P _D55 (standard light source D50 light source, D55 light source, D65 light source, incandescent light bulb A light source, fluorescent lamp F11 light source). λ), P _D65 (λ), P _A (λ), and P _F11 (λ) are shown. In this modification, these spectral energies P _D50 (λ), P _D55 (λ), P _D65 (λ), P _A (λ), and P _F11 (λ) are linearly combined by the following equation (15). Thus, the weight function w (λ) is calculated.

In the above equation (15), w _{1 to} w ₅ are weighting factors for setting the weight for each light source. Thus, the weighting function w (λ) derived from the spectral energy distributions P _D50 (λ), P _D55 (λ), P _D65 (λ), P _A (λ), and P _F11 (λ) of the light source is set. As a result, it is possible to obtain an evaluation value E (φ) that places importance on the wavelength range in which the spectrum of the spectral energy of the reflected light under each light source tends to be strong. It is also possible to adjust the weighting coefficients w ₁ to w _5. For example, w ₁ = w ₂ = w ₃ = w ₄ = w ₅ may be used to ensure a good balance of color reproducibility for all light sources, and w may be used if importance is attached to color reproducibility for artificial light sources. ₁ , w ₂ , w ₃ <w ₄ , w ₅ may be set.

6-4: Modification 4
FIG. 25 shows a UI screen displayed on the display 40 in the modified example. In the figure, a graph of a plurality of target spectral reflectances R _t (λ) is displayed on the UI screen. By displaying such a UI screen, instead of the user measuring the target spectral reflectance R _t (λ) of the target TG in step S140, a graph of a desired waveform is displayed on the target spectral reflectance R _t ( λ) can be selected. In this way, the target spectral reflectance R _t (λ) can be set without actually measuring the spectral reflectance. Of course, the waveform of the graph may be directly editable by the user. For example, if editing the target spectral reflectances R _t (λ) of the target in the development of new of the object surface, without actually prototyping the object surface, the target spectral reflectance targeted R _t A sample chart SC having (λ) can be printed by the printer 20.

前記の（１６）式において、ｗ₁〜ｗ₅は各光源の重みを設定する重み係数であり、上述した変形例３の重み係数ｗ₁〜ｗ₅とほぼ同様の性質を有する。ここでも全光源における色の再現性をバランスよく確保したい場合にはｗ₁＝ｗ₂＝ｗ₃＝ｗ₄＝ｗ₅とすればよいし、人工光源における色の再現性を重視したい場合にはｗ₁，ｗ₂，ｗ₃＜ｗ₄，ｗ₅とすればよい。 6-5: Modification 5
FIG. 26 schematically illustrates the evaluation value (φ) according to the modification. In the figure, the color values (target color values) when the five types of light sources are irradiated to the target spectral reflectance R _t (λ) of the target TG are calculated by the above-described equation (1) and FIG. On the other hand, the color values (predicted color values) when the five types of light sources are applied to the predicted spectral reflectance R _s (λ) predicted by the RPM P3a2 are also expressed by the above-described equation (1) (R _t (λ)). R _s (λ) is used) and calculated according to FIG. Then, the color difference ΔE (ΔE ₂₀₀₀ ) between the target color value (L _t ^* , a _t ^* , b _t ^* ) and the predicted color value (L _s ^* , a _s ^* , b _s ^* ) in each light source is determined as the color difference of CIE DE2000. Calculate based on the formula. Then, the color difference ΔE for each light source is set to ΔE _D50 , ΔE _D55 , ΔE _D65 , ΔE _A , ΔE _F11, and the evaluation value E (φ) is calculated by the following equation (16).

In the above equation (16), w _{1 to} w ₅ are weighting factors for setting the weight of each light source, and have substantially the same properties as the weighting factors w _{1 to} w _{5 of} the above-described modification 3. Here too, w ₁ = w ₂ = w ₃ = w ₄ = w ₅ should be used to ensure a good balance of color reproducibility for all light sources, and when color reproducibility for artificial light sources should be emphasized. It may be set as w ₁ , w ₂ , w ₃ <w ₄ , w ₅ .

なお、上記の（１７）式において、（ΔＬ_a ^*，Δａ_a ^*，Δｂ_a ^*）は光源ａについての偏差（ΔＬ^*，Δａ^*，Δｂ^*）を示している。そして、前実施形態と同様に現在のインク量セットφの近傍に区間幅２ｈを有する微小区間を設定し、当該微小区間における分光プリンティングモデルによる予測色彩値（Ｌ_s ^*，ａ_s ^*，ｂ_s ^*）の線形的な傾きからヤコビ行列Ｊを算出する。本変形例におけるヤコビ行列Ｊは、下記の（１８）式によって表すことができる。

When calibration is performed in this modification, a sample chart SC as a confirmation patch is printed, and the spectral reflectance R (λ) is measured as the confirmation spectral reflectance R _c (λ). The target color values (L _t ^* , a _t ^* , b _t ^* ) when the five types of light sources are irradiated to the target spectral reflectance R _t (λ) of the target TG are _expressed by the above-described equation (1). 5, and the confirmation color values (L _c ^* , a _c ^* , b _c ^* ) when the confirmation patch is irradiated with the five types of light sources are expressed by the above-described equation (1) (R _t (λ ) Is used in place of R _c (λ)). For each light source, the deviation (ΔL ^* , Δa ^* , Δb ^* ) between the target color value (L _t ^* , a _t ^* , b _t ^* ) and the confirmation color value (L _c ^* , a _c ^* , b _c ^* ) is determined ^. ) Is calculated. Then, a deviation vector ΔC in which deviations at the respective light sources are sequentially arranged as in the following equation (17) is acquired. The confirmation color values (L _c ^* , a _c ^* , b _c ^* ) are not limited to those calculated based on the confirmation spectral reflectance R _c (λ), and the target TG is actually irradiated with the five types of light sources. Then, it may be obtained by performing colorimetry.

In the above equation (17), (ΔL _a ^* , Δa _a ^* , Δb _a ^* ) indicates a deviation (ΔL ^* , Δa ^* , Δb ^* ) with respect to the light source a. Similarly to the previous embodiment, a minute section having a section width 2h is set in the vicinity of the current ink amount set φ, and predicted color values (L _s ^* , a _s ^* , b _s) based on the spectral printing model in the minute section are set. ^{* The} Jacobian matrix J is calculated from the linear slope of ⁽ ). The Jacobian matrix J in this modification can be represented by the following equation (18).

本変形例においても、色彩値の偏差ΔＣを補償するような補正量ベクトルΔφを得ることができる。従って、式（１８），（１９）で表されるヤコビ行列や補正量ベクトルを上記実施形態のインクグループ毎に算出して、上記実施形態と同様に偏差を解消していく。なお、本変形例のヤコビ行列Ｊは各光源のＬ^*ａ^*ｂ^*成分についての偏微分の行要素で構成されるが、上記の（１９）式を解くことにより、各光源のＬ^*ａ^*ｂ^*成分についての偏差ΔＣを最小二乗法的に減少させるような補正量ベクトルを得ることができる。 As shown in the above equation (18), the Jacobian matrix J is a matrix having a type of total number (rows) × number of inks (columns) of the three components of L ^* a ^* b ^* of each light source. When the Jacobian matrix J is obtained as described above, the correction amount vector Δφ (Δd _C , Δd _M , Δd _Y , Δd _K , Δd _lc , Δd _lm , Δd _lk ) is calculated by the following equation (19). be able to.

Also in this modification, it is possible to obtain a correction amount vector Δφ that compensates for the deviation ΔC of the color value. Accordingly, the Jacobian matrix and the correction amount vector represented by the equations (18) and (19) are calculated for each ink group in the above embodiment, and the deviation is eliminated as in the above embodiment. Note that the Jacobian matrix J of this modification is composed of partial differential row elements for the L ^* a ^* b ^* components of each light source, but by solving the above equation (19), the L ^* a of each light source. It is possible to obtain a correction amount vector that reduces the deviation ΔC for the ^* b ^* component in a least square manner.

By the way, in this modification, when the target color values (L _t ^* , a _t ^* , b _t ^* ) and the confirmation color values (L _c ^* , a _c ^* , b _c ^* ) for each light source are obtained. These color differences ΔE (ΔE ₂₀₀₀ ) may be calculated for each light source. The color difference ΔE here is expressed as Δe _D50 , Δe _D55 , Δe _D65 , Δe _A , Δe _F11 for each light source. According to the color differences Δe _D50 , Δe _D55 , Δe _D65 , Δe _A , and Δe _{F 11} , it is possible to grasp how accurately the sample chart SC is reproduced by the color difference ΔE ₂₀₀₀ . Further, according to the average color difference Δe obtained by averaging the color differences Δe _D50 , Δe _D55 , Δe _D65 , Δe _A , Δe _F11 with respect to the light source as shown in the following equation (20), the reproduction accuracy of each target TG of a plurality of light sources is comprehensive. Can be judged.

FIG. 27 shows the flow of calibration processing according to this modification. Here, when the sample chart SC is printed (step S402), the confirmation spectral reflectance R _c (λ) of each confirmation patch (frames FL1 to FL12) is measured in step S405. In step S402, the average color difference Δe between the target color value (L _t ^* , a _t ^* , b _t ^* ) and the confirmation color value (L _c ^* , a _c ^* , b _c ^* ) is calculated for each frame FL1. Calculate for FL12. Then, it is determined in step S404 whether or not the average color difference Δe for all the frames FL1 to FL12 exceeds a predetermined threshold Th (for example, ΔE = 1.0), and the average of any of the frames FL1 to FL12 is determined. If the color difference Δe exceeds the threshold Th, the calibration process after step S410 is executed. When the calibration process is completed, the process returns to step S402 again, the sample chart SC is printed again based on the updated 1D-LUT, and the same process is repeatedly executed. In this way, the calibration process can be repeated until the average color difference Δe satisfies the threshold Th.

  In the above, an example of correcting the optimum ink amount set φ predicted by the spectral printing model has been exemplified, but the present invention can be applied to correcting any correction target ink amount set φ. The correction target ink amount set φ is not limited to the predicted one. For example, the present invention can also be applied when correcting the ink amount set φ of lattice points set in advance in the 3D-LUT illustrated in FIG. For example, when the accuracy of the reproduced color (under a single light source) when printing using the 3D-LUT is deteriorated due to a change with time of the printer 20, the ink amount set φ at each grid point described in the 3D-LUT Can also be corrected by the method of the present invention. Similarly, the ink amount set φ of the 3D-LUT can be corrected by the method of the present invention in order to compensate for the deviation of the reproduction color (under a single light source) between the individual printers 20.

6-6: Modification 6
In addition, what is necessary is just to make it print with the same color as area | regions other than the frame F about the area | region corresponding to the frame F which is not selected in embodiment mentioned above. Of course, it is not necessary to request spectral reproducibility for the region corresponding to the unselected frame F, so that color conversion using a 3D-LUT is performed in the same manner as the region other than the frame F. That's fine. Furthermore, a pattern, characters, marks, or the like may be printed in a region other than the region corresponding to the frame F in which the target TG is designated. For example, characters indicating what the target TG is may be written near the frame F in which the target TG is designated.

6-7. Modification 7
28 to 29 show a software configuration of the printing system according to the modification of the present invention. As shown in FIG. 28, a configuration corresponding to the LUG P3a of the above-described embodiment may be provided as an internal module (1D-LUT creation unit) of the PDV P3b. Also, as shown in FIG. 29, a configuration corresponding to the LUG P3a of the above-described embodiment may be executed in another computer 110. In this case, the computer 10 and the computer 110 are connected by a predetermined communication interface CIF, and the 1D-LUT generated by the LUG P3a of the computer 110 is transmitted to the computer 10 via the communication interface CIF. The communication interface CIF may intervene via the Internet. In this case, the computer 10 can perform color conversion with reference to the 1D-LUT acquired from the computer 110 on the Internet. Further, the printer 20 may execute the software configurations P1 to P5. Of course, the present invention can also be realized when hardware that executes processing equivalent to the software configurations P1 to P5 is incorporated in the printer 20.

2 is a block diagram illustrating a hardware configuration of a printing control apparatus. FIG. 2 is a block diagram illustrating a software configuration of a print control apparatus. FIG. 6 is a flowchart illustrating a flow of print data generation processing. It is a figure which shows an example of UI screen. It is a figure explaining the calculation for calculating a color value based on a spectral reflectance. It is a figure which shows print data. It is a figure which shows an index table. 5 is a flowchart illustrating an overall flow of print control processing. It is a flowchart which shows the flow of 1D-LUT creation processing. It is a schematic diagram showing a flow of processing for optimizing the ink amount set. It is a schematic diagram which shows a mode that an ink amount set is optimized. It is a figure which shows 1D-LUT. 6 is a flowchart illustrating a flow of print control data generation processing. It is a figure which shows 3D-LUT. It is a flowchart which shows the flow of a calibration process. It is a graph explaining a deviation. It is a graph explaining a Jacobian matrix. It is a schematic diagram which shows the printing system of a printer. It is a figure which shows a spectral reflectance database. It is a figure which shows a spectral Neugebauer model. It is a figure which shows a cell division | segmentation Yule-Nielsen spectroscopic Neugebauer model. It is a schematic diagram which shows the weight function concerning a modification. It is a schematic diagram which shows the weight function concerning a modification. It is a schematic diagram which shows the weight function concerning a modification. It is a figure which shows UI screen concerning a modification. It is a schematic diagram which shows the evaluation value concerning a modification. It is a flowchart which shows the flow of the calibration process concerning a modification. It is a figure which shows the software structure of the printing system concerning a modification. It is a figure which shows the software structure of the printing system concerning a modification. It is a figure explaining a mode that a deviation is canceled. It is a figure explaining the capability to adjust the color in each ink group.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Computer, 11 ... CPU, 12 ... RAM, 13 ... ROM, 14 ... HDD, 15 ... GIF, 16 ... VIF, 17 ... IIF, 18 ... Bus, P1 ... OS, P1a ... GDI, P1b ... Spooler, P2 ... APL, P2a ... UIM, P2b ... MCM, P2c ... PDG, P3a ... LUG, P3b ... PDV, P3a1 ... ICM, P3a2 ... RPM, P3a3 ... ECM, P3a4 ... LOM, P3a5 ... KPM, P3a6 ... IMM, P4 ... MDV, P5 ... DDV

Claims (9)

When printing is performed by attaching a plurality of color materials to a recording medium in a printing apparatus, a color material amount set that is a combination of the usage amounts of the color materials is designated to the printing apparatus, and based on the color material amount set A printing control device for executing printing,
The color material amount set corresponding to the specified index is designated in the printing apparatus by referring to a lookup table in which the correspondence between the index specifying the color information and the color material amount set is defined. Printing means for printing,
The color material amount set defined in the lookup table is:
Ability to fine-tune the color so that the deviation between the actual color and the predetermined color shown when the color material amount set associated with the predetermined color is attached to the recording medium by the printing apparatus is minimized. A Jacobian matrix in which the information indicating the predetermined color is partially differentiated in the vicinity of the same color material amount set as a differential variable in order from the color material amount of a group having a low ability to adjust the color by dividing the plurality of color materials into a plurality of groups The printing control apparatus according to claim 1, wherein the printing control apparatus is calculated by sequentially eliminating the deviation based on the method. The color material amount set predicted to indicate the predetermined color is:
2. The color material amount set according to claim 1, wherein a color predicted by a predetermined prediction model that predicts a color when an arbitrary color material amount set is attached to the recording medium is a color material amount set that is closest to the predetermined color. Print control device. In calculating a color material amount set that minimizes the deviation, for each color material amount of the color material amount set, the color material amount is changed while being smaller by a smaller amount than the minimum unit amount that can be attached by the printing apparatus. Predict
The printing control apparatus according to claim 1, wherein the corrected color material amount set is subjected to a fraction processing using the minimum unit amount as a rounding width.   The group having the highest ability to finely adjust the color among the plurality of groups can change the color in the entire hue direction by changing the amount of the color material constituting the group. The printing control apparatus according to any one of the above. Wherein the plurality of color material is configured to include a dark and light inks having different concentrations at the same hue,
Among the plurality of groups, a group having a low ability to finely adjust the color includes the dark ink, and a group having a high ability to finely adjust the color includes the light ink but does not include the dark ink. The printing control apparatus according to claim 1, comprising:   6. The information according to claim 1, wherein the information indicating the color is a spectral reflectance, and the Jacobian matrix is configured by partial differentiation of the spectral reflectance in each wavelength section. The printing control apparatus described.   The information indicating the color is a color value indicated by a predetermined object under a plurality of light sources, and the Jacobian matrix is configured by partial differentiation of each component constituting the color value under each light source. The printing control apparatus according to any one of claims 1 to 6. When printing is performed by attaching a plurality of color materials to a recording medium in a printing apparatus, a color material amount set that is a combination of the usage amounts of the color materials is designated to the printing apparatus, and based on the color material amount set A printing system comprising a print control device for executing printing,
The print control apparatus refers to a look-up table in which a correspondence relationship between an index for specifying information indicating color and a color material amount set is defined, so that the color material amount set corresponding to the specified index is determined as the color material amount set. A printing means for specifying and printing on the printing apparatus is provided.
The color material amount set defined in the lookup table is:
Ability to fine-tune the color so that the deviation between the actual color and the predetermined color shown when the color material amount set associated with the predetermined color is attached to the recording medium by the printing apparatus is minimized. A Jacobian matrix in which the information indicating the predetermined color is partially differentiated in the vicinity of the same color material amount set as a differential variable in order from the color material amount of a group having a low ability to adjust the color by dividing the plurality of color materials into a plurality of groups The printing system according to claim 1, wherein the deviation is eliminated and calculated sequentially. When printing is performed by attaching a plurality of color materials to a recording medium in a printing apparatus, a color material amount set that is a combination of the usage amounts of the color materials is designated to the printing apparatus, and based on the color material amount set A computer-readable print control program for causing a computer to execute a function of executing printing,
The color material amount set corresponding to the specified index is designated in the printing apparatus by referring to a lookup table in which the correspondence between the index specifying the color information and the color material amount set is defined. It has a print function to print,
The color material amount set defined in the lookup table is:
Ability to fine-tune the color so that the deviation between the actual color and the predetermined color shown when the color material amount set associated with the predetermined color is attached to the recording medium by the printing apparatus is minimized. A Jacobian matrix in which the information indicating the predetermined color is partially differentiated in the vicinity of the same color material amount set as a differential variable in order from the color material amount of a group having a low ability to adjust the color by dividing the plurality of color materials into a plurality of groups The printing control program is calculated by sequentially performing the elimination of the deviation based on the above.

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