JP2003326768A - Apparatus and method for optimizing color material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily select an appropriate color material for precise reproduction of a target color. <P>SOLUTION: In an optimizing apparatus 1 for optimizing an assortment of ink to reproduce the set target color, the characteristics of a plurality of ink are stored in an ink characteristics storage section 16. An estimated result of a mixture of colors is gained corresponding to the assortment of ink selected from a plurality of ink stored in the storage section 16 and the prescribed input amount from an ink overprint correcting section 11. From a section for calculating a margin of error 17 and a section for judging a minimal margin of error 18, a minimum value of the difference between the estimated color mixture and the target color is obtained by repeating an estimation of the above color mixture while the prescribed input amount with respect to the selected assortment of ink is being changed. Then, the color material is optimized by changing the assortment of ink until the minimum value becomes smaller than the prescribed one. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique of predicting a color reproduced by multicolor reproduction processing using a special color ink, for example, multicolor printing or multicolor printing using a color printer, that is, a reproduced color. Regarding

[0002]

2. Description of the Related Art A general color printed matter is composed of three colors of cyan, magenta, and yellow generated from a color original through three primary color separations, and four colors of black (CMY).
It is printed by the process printing method using the ink of K). Also, when printing a large amount of the same image, such as magazines and posters, printing is performed with the addition of several types of special color ink that match the original image, resulting in subtle shades and gamuts that cannot be reproduced with process printing. Is reproduced. For example, when developing an ink jet or laser printer, CMYK ink is generally used. However, even if it is simply CMYK ink, there are inks with various characteristics, and many companies are Working on development. In addition to the CMYK ink, a technique of adding new ink and printing with more than four colors in order to perform more accurate color reproduction has also been studied. In order to improve the efficiency of such ink development, it is required to automatically optimize the ink.

Recently, a method for automatically and accurately performing color separation into each plate when a special color ink is used has been developed. For example, in Japanese Patent Laid-Open No. 2001-053976,
A special color separation method for separating an original image into a YMC plate and a special color plate is shown. On the other hand, as a technique for improving color reproduction accuracy, there is a technique called spectral color reproduction in which not only tristimulus values of colors but also spectral distributions themselves are matched.
It is disclosed in Japanese Patent Publication No. 296836. As described above, in order to accurately reproduce the target color, the method of using the special color ink (the special color separation method) and the method of making the spectral distribution characteristics as close as possible while the ink is the same as the conventional one There are two types of methods (spectral color reproduction).

[0004]

The conventional spot color separation method is to separate the given CMYK ink and spot color ink. For example, Japanese Patent Laid-Open No. 2001-2001
In Japanese Patent No. 053976, it is premised that the colorimetric data of the special color ink is required for color separation, and that the special color ink manually selected in advance is used. However, there is a problem that a clear method has not been established for the selection method of the ink itself, such as what kind of ink is used for optimal color reproduction for a certain original image or color. Therefore, in practice, a skilled technician
The special color ink was selected by trial and error.

On the other hand, also in the spectral color reproduction, it has been attempted to make the spectral distribution as close as possible to the color reproduction closest to the target color by using the given ink. However, there is a problem in that the spectral distribution characteristics of a target image or color cannot be reproduced only by using a given ink even if the spectral approximation is attempted.
Further, there is a problem that a technique has not been established as to what kind of ink having a spectral distribution characteristic can be used to reproduce the spectral distribution characteristic of a target color / image.

The present invention has been made to solve the above problems, and an object of the present invention is to make it possible to easily select an appropriate color material and an amount to be imprinted for reproducing a target color with high accuracy. .

[0007]

A color material optimizing apparatus according to the present invention for achieving the above object has the following constitution. That is, a device for optimizing a combination of color materials to reproduce a set target color, a holding unit that holds characteristics of a plurality of color materials, and a color material selected from the plurality of color materials. The color mixture obtained by the combination,
Predicting means for predicting based on the characteristics held in the holding means and the driving amount set for each color material, and the combination of the selected color material, by changing the driving amount for each color material, the prediction means Acquiring means for acquiring the minimum value of the difference between the predicted color mixture and the set target color that is repeatedly operated, and the combination of the color materials until the minimum value acquired by the acquiring means becomes smaller than a predetermined value. And a control unit that repeats the acquisition unit.

Further, a color material optimizing method according to the present invention for achieving the above object is a method of optimizing a combination of color materials for reproducing a set target color. The holding means for holding the characteristics of the holding means is accessed, and the color mixture obtained by the combination of the coloring materials selected from the plurality of coloring materials held by the holding means is added to the characteristics held by the holding means and the respective coloring materials. For the combination of the predicting step and the selected color material based on the set impact amount, the impact amount for each color material is changed, the predicting step is repeatedly executed, and the predicted color mixture is set. An acquisition step of acquiring the minimum value of the difference from the target color, and a control process in which the combination of the color materials is changed and the acquisition step is repeated until the minimum value acquired in the acquisition step becomes smaller than a predetermined value. Provided with a door.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

(First Embodiment) FIG. 1 is a block diagram showing the arrangement of an ink optimizing apparatus according to the first embodiment.

In FIG. 1, reference numeral 1 denotes an ink optimizing apparatus according to the first embodiment. An ink design unit 2 designs ink characteristics for a given target color.
Reference numeral 3 is a primary color dot gain estimation unit, and the ink design unit 2
The primary color dot gain of the ink designed by is estimated. A primary color dot gain LUT storage unit 4 stores the primary color dot gain LUT estimated by the primary color dot gain estimation unit 3. In the present embodiment, inks of a plurality of colors are used as the color material, but the optimization method of the present embodiment can be similarly applied when other color materials such as toner are used.

A colorimetric value data storage unit 5 stores the colorimetric values of the output patch of the printer used for the ink optimization process. 6 is an ink overlay correction coefficient calculation unit,
The ink overlay correction coefficient is calculated based on the colorimetric values stored in the colorimetric data storage unit 5. An ink overlay correction coefficient storage unit 7 stores the ink overlay correction coefficient calculated by the ink overlay correction coefficient calculation unit 6.

An ink ejection amount setting unit 8 sets the designed ink ejection amount. Reference numeral 9 denotes a primary color dot gain correction unit, which performs primary color correction in consideration of dot gain, which will be described later, with respect to the ink ejection amount set by the ink ejection amount setting unit 8 (note that in the present embodiment, 1
The term “next color correction” is used because, in general KM theory, the idea that the parameter (K / S) changes linearly with respect to the amount of imprinting is used, and the effect of non-linearity of dot gain is This is because the non-linearity of the dot gain is corrected in this embodiment, which is not taken into consideration). An estimated initial value calculation unit 10 calculates a color mixing result (estimated initial value of spectral reflectance) from the value of each primary color corrected by the primary color dot gain correction unit 9. Reference numeral 11 denotes an ink overlay correction unit, which uses the spectral reflectance estimation initial value calculated by the estimated initial value calculation unit 10 as the ink overlay correction coefficient and the ink ejection amount stored in the ink overlay correction coefficient storage unit 7. Correction is performed using the ink ejection amount stored in the storage unit 9 to obtain the spectral reflectance estimated value.

An output prediction data storage unit 12 stores an estimated output prediction value (estimation result obtained by the ink overlay correction unit 11, details will be described later with reference to the flowchart of FIG. 2). A target color data storage unit 13 stores the target color set by the user. A target color data setting unit 14 provides a user interface for the user to set a target color. An ink optimization result display unit 15 controls the display device 19 to display the optimized ink information. Reference numeral 16 denotes an ink characteristic storage unit that stores in advance the characteristics of the paper used for printing and the ink characteristics obtained by measuring the characteristics of some existing inks. An error calculator 17 calculates an error between the output prediction data and the target color data. A minimum error determination unit 18 determines the magnitude of the minimum value (error minimum value) of the error calculated by the error calculation unit 17 and the threshold value. A display device 19 displays a target color designated by the user and displays the ink optimization result under the control of the ink optimization result display unit 15. As the display device 19, a CRT, LCD or the like can be used.

<Ink Optimization Processing> FIG. 2 is a flow chart for explaining the ink optimization processing by the ink optimization device 1 of the first embodiment. 3 is a diagram showing an example of a user interface for the user to set the target color in the target color setting unit 14, and FIG. 4 is for displaying the ink optimization result on the ink optimization display unit 15. It is a figure which shows an example of the user interface of. Hereinafter, the ink optimization process according to the first embodiment will be described with reference to these drawings.

First, in step S201, the target color setting unit 14 sets a desired target color by the user, and the set target color is stored in the target color data storage unit 13. Here, the target color setting unit 14 provides a user interface as shown in FIG. 3, for example, and the user sets the target color via this interface (details will be described later). Succeedingly, in a step S202, it is determined whether or not the user has finished inputting all the target colors. This judgment is based on FIG.
In the interface shown in FIG.
This is done by detecting that 6 has been pressed. Three
The target color set using 01 or 302 is stored in the target color data storage unit 13 by pressing the target color addition button 305.

If the ink optimization button 306 is pressed, the process proceeds to step S203. In step S203, among the ink characteristics stored in the ink characteristic storage unit 16, for example, CMYK ink that is generally used,
The spectral reflectance when the amount of the spot color ink such as green or orange is 100% is set in the ink design unit 2 as an initial value. In this embodiment, ink design using six colors of ink is performed.

Next, in step S204, the dot with an arbitrary ejection amount is set in the primary color dot gain estimation unit 3 based on the spectral reflectance when the ink ejection amount set by the ink design unit is 100%. Estimate gain, LUT
Is stored in the primary color correction LUT (details will be described later).

Next, in step S205, the ink overlay correction coefficient calculation unit 6 reads the ink overlay colorimetric values stored in the colorimetric value data storage unit 5 and calculates the ink overlay correction coefficient. . The calculated ink overlay correction coefficient is stored in the ink overlay correction coefficient storage unit 7 (details will be described later). However, since the same value is used as the ink overlay correction coefficient for all ink combinations, the process of step S205 can be omitted after it has been executed once. Then, in step S206, the ejection amounts of all the inks are set to initial values (for example, 0% for all), and the process after step S207 is prepared.

In step S207, in the primary color dot gain correction unit 9, the ink ejection amount set in the ink ejection amount setting unit 8 and the primary color dot gain LUT are set.
The primary color dot gain LUT stored in the storage unit 4 is used to correct the primary color dot gain, and the spectral reflectance corresponding to the given ejection amount of each ink is calculated. In step S208, the estimated initial value calculation unit 10 sets 1
The spectral reflectance of each ink calculated by the next color dot gain correction unit 9 is represented by the following equations (1) to (3)
Color mixing is predicted using Munk theory (hereinafter, KM theory). Note that (K / S) at the wavelength λ of the paper is stored in the ink characteristic storage unit 16.

[0021]

[Equation 1]

In step S209, the ink overlay correction unit 11 stores the spectral reflectance estimation initial value estimated by the estimated initial value calculation unit 10 into the ink overlay correction coefficient stored in the ink overlay correction coefficient storage unit 7. Correction is performed using the coefficient, and the final spectral distribution estimation result is calculated (details will be described later).

In step S210, step S209
The final estimation result of the spectral distribution calculated in step S20
The error calculation unit 17 calculates an error from the target color set in 1. And if the error is less than the minimum value,
The error minimum value in the output prediction data storage unit 12 is updated with the error, and the ink characteristics and the ejection amount at that time are stored in the output prediction data storage unit 12. In step S211, it is determined whether or not all the combinations of ejection amounts have been tried for the currently set ink. If all combinations have been tried, the process proceeds to step S213. In step S212, the driving amount is changed by a constant change amount, and the process is returned to step S207. Note that the combination of the implantation amounts in the above processing is basically a full search. For example, when 6 color inks are used, all combinations from the case where all the ink ejection amounts are 0% to the case where all the field ink ejection amounts are 100% are tried. However, it is possible to determine by default the percentage of change from 0% to 100%, or to set a certain value by user operation.

In step S213, the minimum error determination unit 18 determines whether or not the minimum error value stored in the predicted output data storage unit 12 is larger than the set threshold value. If larger, the process proceeds to step S214, and if smaller. Step S
Proceed to 215. In step S214, at least one of the currently set inks is replaced with an ink having another characteristic. Ink having other characteristics is read from the characteristic storage unit 16.

If the minimum error value stored in the output prediction data storage unit 12 becomes smaller than the set threshold value, in step S215, the minimum error value stored in the output prediction data storage unit 12 and The ink characteristics and the ejection amount at that time are displayed, for example, in the form as shown in FIG. 4 (details will be described later). When a plurality of target colors are set in step S201, the process of FIG. 2 is repeated for all the set target colors. More precisely, the processes of steps S206 to S214 of FIG. 2 are repeated for each target color. Further, in the replacement with the ink having other characteristics in step S214, all the combinations for selecting a predetermined number of colors (for example, 6 colors) from the ink candidates stored in the ink characteristics storage unit 16 are the replacement targets. can do.

<Target Color Setting User Interface> The user interface provided by the target color setting unit 14 will be described. FIG. 3 is an example of a user interface for the user to set a target color in the target color data setting unit 14. Hereinafter, the method of setting the target color will be described in detail with reference to FIG.

The user can set the target color to be output by the printer by the tristimulus value or the spectral reflectance. When setting the target color by the tristimulus value, the user sets a desired light source in the light source setting unit 307, and the numerical value input unit 3
01 or slider bar 302 can be used to set the desired tristimulus value under that light source. In addition, the target color spectral reflectance input unit 30 is used for setting the spectral reflectance.
A user interface for changing the graph displayed in 4 with a pointing device such as a mouse is provided. The setting is made so as to obtain a desired spectral reflectance. The set target color is displayed on the target color confirmation unit 303. Here, if the user wants to add more target colors, the target color can be added by pressing the target color addition button 305 after setting the desired target color. If all the target colors are input and the ink is optimized using the input target colors, the ink optimization button 306 is pressed.

<Estimation of Primary Color Dot Gain> Normally, in printing, the relationship between the amount of ejected ink and the spectral reflectance is not linear, and the area of ink on the paper becomes larger than the theoretical area ratio. That phenomenon occurs. this is,
This is a well known phenomenon as dot gain. In this embodiment, the dot gain of the ink designed by the ink design unit 2 is estimated by the primary color dot gain estimation unit 3.

FIGS. 5 (a) and 5 (b) are diagrams showing the relationship between the impact amount of a certain cyan ink and the spectral reflectance. It can be seen from FIG. 5 that the spectral reflectance changes non-linearly with respect to the implantation amount. Therefore, the following estimation formula is used to estimate this dot gain.

[0030]

[Equation 2]

In the above estimation formula, the constants a and b can be the same for all inks. This constant can be determined by the least-squares method or the like using colorimetric data of any ink. Further, in the present embodiment, the spectral reflectance at each implantation amount is estimated based on the spectral reflectance at 100%, but it is also possible to use another implantation amount as a reference. However, it is considered that the estimation accuracy becomes better when the estimation is performed using the spectral reflectance at 100%. Using the above estimation formula, the estimated value when the ejection amount is changed is obtained for each ink for each wavelength, and LU is calculated.
It is stored as T in the primary color dot gain LUT storage unit 4. Note that the wavelength for which the estimated value is obtained is all wavelengths sampled in the visible wavelength range (for example, 380 nm
For 41 wavelengths in 10 nm increments up to 780 nm), an estimated value is obtained using the above equation (4).

<Calculation of Ink Overlay Correction Coefficient>
The details of the ink overlay correction coefficient calculation in step S205 will be described. In step S205, the colorimetric data of the ink overlay correction patch that has been output and colorimetrically measured using the target printer for which color reproduction prediction is to be performed is stored in the colorimetric value data storage unit 5. here,
An ink overlay correction patch as shown in FIG. 6 is used. That is, the ejection amount of each ink is changed from 0% to 100.
%, And the inks used are printed by superimposing 2 to 4 colors.

On the other hand, in the estimated initial value calculation unit 10,
Using the data of the overlay correction patch shown in FIG. 6, the spectral reflectance estimation initial value of the overlay correction patch is estimated by the equations (1) to (3). The initial value of the estimated spectral reflectance calculated here is obtained by actually measuring the color of the overlay correction patch, and an error occurs with respect to the actual measurement data stored in the colorimetric value data storage unit 5. . Therefore,
In order to correct the error from the measured data, the following (5)
The correction coefficients a _{h, λ} , b _{i, j, λ} and c _{k, l, m, λ} are determined by using the least square method or the like so that the error is minimized using the formula.

[0034]

[Equation 3] In the above equation (5), R _{p, λ} is the equation (1)
R _{mod, λ} is an inferred value after the primary color correction obtained by the KM theory of the equation (3), and R _{mod, λ} represents a corrected inferred value after the ink overlay correction. Then, the coefficients a _{h, λ} and b are set so that the error between R _{mod, λ} and the measured value of the color patch is reduced.
_{i, j, λ} and _{ck, l, m, λ} are determined. Also, in the second term
i, j and k, l, m in the third term represent arbitrary inks. For example, when four colors of C, M, Y and K are used as inks of n colors, i = C, M , Y, K, j = C, M, Y, K, ... (However, i ≠ j, k ≠ l ≠ m). Also, (K / S) is (1)
As defined in the formula. The ink overlay correction coefficient obtained as described above is stored in the ink overlay correction coefficient storage unit 7.

<Ink Overlay Correction> Next, the details of the ink overlay correction processing in step S209 will be described. In step S209, the ink overlay correction coefficient stored in the ink overlay correction coefficient storage unit 7 (calculated in step S205) with respect to the spectral reflectance estimation initial value calculated in step S208.
Using Eq. (4), the estimation error due to ink superposition is corrected by the above equation (4).

<Estimation Result Display User Interface> FIG. 4 shows an example of a user interface for displaying the ink optimization result on the ink optimization result display section 15. Hereinafter, a method of displaying the ink optimization result will be described in detail with reference to FIG.

In displaying the ink optimization result, the spectral reflectance of the target color set by the user is displayed on the target color spectral reflectance display section 401, and the tristimulus values thereof are displayed on the target color tristimulus value display section 403. To be done. Further, the spectral reflectance output estimated using ink optimized for reproducing the target color is displayed on the reproduced color spectral reflectance display unit 402,
The tristimulus values at that time are displayed on the reproduced color tristimulus value display portion 405.

Further, the ink ejection amount necessary for outputting the reproduced color is displayed on the ink ejection amount display portion 407. Then, the error (for example, color difference ΔE) between the target color and the reproduced color at this time is displayed on the error display unit 404. However, since the light source information is necessary to calculate the tristimulus value, the user selects the desired light source as the light source selection unit 40.
It can be selected at 6. When the optimized ink is selected by the user with the ink number selection unit 408, the spectral reflectance of the selected ink is displayed on the optimal ink spectral reflectance display unit 409.

As described above, according to the first embodiment, a candidate color material characteristic is set, a reproduced color using the set color material is estimated, and an error amount between the target color and the reproduced color is estimated. By determining, it is possible to determine the color material to be used.

(Second Embodiment) A second embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 7 is a block diagram showing the arrangement of a color reproduction prediction device according to the second embodiment. In FIG. 7, 7
Reference numeral 01 denotes an ink optimization device according to the second embodiment.

An ink designing unit 702 designs ink characteristics for a given target color. A primary color dot gain estimating unit 703 estimates the primary color dot gain of the ink designed by the ink designing unit 702. 7
A primary color dot gain LUT storage unit 04 stores the primary color dot gain LUT estimated by the primary color dot gain estimation unit 703.

A colorimetric value data storage unit 705 stores colorimetric values of output patches of a printer used for ink optimization. An ink overlay correction coefficient calculation unit 706 calculates an ink overlay correction coefficient from the colorimetric values stored in the colorimetric value data storage unit 705. An ink overlay correction coefficient storage unit 707 stores the ink overlay correction coefficient calculated by the ink overlay correction coefficient calculation unit 706.

Reference numeral 708 denotes an ink ejection amount setting unit,
Set the designed ink ejection amount. 709 is 1
The secondary color dot gain correction unit performs primary color correction on the ink ejection amount set by the ink ejection amount setting unit 708. An estimated initial value calculation unit 710 calculates a spectral reflectance estimated initial value as a color mixing result from the values of the respective primary colors corrected by the primary color dot gain correction unit 709. Reference numeral 711 denotes an ink overlay correction unit that uses the spectral reflectance estimation initial value calculated by the spectral reflectance estimation initial value calculation unit 710 as an ink overlay correction coefficient stored in the ink overlay correction coefficient storage unit 707. The estimated ink reflectance is calculated using the ink ejection amount stored in the ink ejection amount storage unit 709 to calculate the spectral reflectance estimated value.

An output prediction data storage unit 712 stores the estimated output prediction value. A target color data storage unit 713 stores the target color set by the user. 7
A target color measuring unit 14 provides an interface for the user to measure the target color. An ink optimization result display unit 715 displays optimized ink information on a display device 719. An ink characteristic storage unit 716 stores the characteristics of the paper used for printing in advance and the ink characteristics obtained by measuring some existing inks.
An error calculation unit 717 calculates an error between the output prediction data and the target color. A minimum error determination unit 718 determines the magnitude of the minimum error value and the threshold value. A display device 719 includes a CRT, an LCD, or the like. A spectral distribution measuring device 720 measures a target color such as a spectrophotometer.

<Ink Optimization Process> FIG. 8 is a flow chart for explaining the ink optimization process executed by the color reproduction prediction device 701 of the second embodiment. In addition, FIG.
FIG. 8 is a diagram showing an example of a user interface for a user to measure a target color with a target color measuring unit 714. The user interface for displaying the ink optimization result is displayed on the display device 719 under the control of the ink optimization result display unit 715, and the content thereof is the same as that of the first embodiment (FIG. 4). . Hereinafter, the ink optimization process according to the second embodiment will be described in detail.

First, in step S801, the target color measuring unit 714 measures the target color that the user wants to output,
It is stored in the target color data storage unit 713. Step S80
In step 2, it is determined whether the user has finished measuring all target colors, and if so, the process proceeds to step S803. Whether or not the measurement of the target color has been completed is determined by whether or not the ink optimization button 906 (FIG. 9) has been pressed to instruct the start of ink optimization. The target color measuring operation using the user interface provided by the target color measuring unit 714 will be described later.

When the start of ink optimization is instructed, in step S803, the ink characteristic storage unit 71 is started.
From the ink characteristics stored in No. 6, the spectral reflectance at the time of 100% of the ejection amount of the commonly used CMYK ink or special color ink such as green or orange is read out, and this is read by the ink design unit. In 702, it is set as an initial value.

Next, in step S804, the primary color dot gain estimation unit 703 sets the ink ejection amount at an arbitrary ejection amount based on the spectral reflectance when the ink ejection amount set by the ink design unit 702 is 100%. Estimate the dot gain,
Generate an LUT. Then, this LUT is stored in the primary color dot gain LUT storage unit 704.

In step S805, the ink overlay correction coefficient calculation unit 706 reads the ink overlay colorimetric values stored in the colorimetric value data storage unit 705,
The ink overlay correction coefficient is calculated. The calculated ink overlay correction coefficient is stored in the ink overlay correction coefficient storage unit 707. However, since the same value is used as the ink overlay correction coefficient for all ink combinations, the process of step S805 can be omitted after it has been executed once. In step S806, the ejection amounts of all inks are set to initial values (for example, all 0
%) To prepare for the processing from step S807.

In step S807, in the primary color dot gain correction section 709, the ink ejection amount setting section 70 is set.
The ink ejection amount set in step 8 and the primary color dot gain LUT stored in the primary color dot gain LUT storage unit 704 are used to correct the primary color dot gain, and ejection of each ink is given. The spectral reflectance corresponding to the quantity is calculated. In step S808, the estimated initial value calculation unit 7
10, the spectral reflectance of each ink calculated by the primary color dot gain correction unit 709 is subjected to color mixture prediction using the KM theory represented by the equations (1) to (3), and the spectral reflectance estimation initial stage Calculate the value. Further, in step S809, the ink overlay correction unit 711 sets the spectral reflectance estimation initial value estimated by the estimated initial value calculation unit 710 to the ink overlay correction coefficient stored in the ink overlay correction coefficient storage unit 707. Is used to calculate the final spectral distribution estimation result.

In step S810, the error calculation unit 717 calculates the error between the calculated spectral distribution final estimation result and the target color.
Calculate with. Then, when the calculated error is smaller than the minimum error value stored in the output prediction data storage unit 712 at that time, the minimum error value is updated with the calculated error, and the ink characteristic at that time is updated. , The driving amount is stored in the predicted output data storage unit 712.

In step S811, it is determined whether or not all the combinations of the ejection amounts have been tried for the currently set ink. If all the trials have been tried, the process proceeds to step S813, otherwise the process proceeds to step S812. In step S812, the driving amount is changed by a constant change amount.

In step S813, the minimum error determination unit 718 determines whether the minimum error value stored in the predicted output data storage unit 712 is larger than the set threshold value,
If it is larger, the process proceeds to step S814, and if it is smaller, the process proceeds to step S815. In step S814, for at least one of the currently set inks, ink having another characteristic is read from the ink characteristic storage unit 716 and replaced, and then the process returns to step S805 to perform the above-described process. repeat. In step S815,
The minimum error value stored in the predicted output data storage unit 712, the ink characteristic at that time, and the ejection amount are, for example, as shown in FIG.
The display method is as shown in.

<Target Color Measurement User Interface> FIG. 9
Is an example of a user interface for the user to measure a target color in the target color data setting unit 714. Hereinafter, the method for measuring the target color will be described in detail with reference to the drawings.

After the user selects a desired light source in the light source selection unit 902, the target color patch to be output by the printer is set in the target color measuring unit 714, and the color measurement start button 9
When 07 is pressed, the tristimulus value of the measured target color under the selected light source is displayed on the target color tristimulus value display unit 901, and the spectral reflectance is displayed on the target color spectral reflectance display unit 904. Is a file that describes the ICC profile (how to reproduce colors on a specific device (monitor, scanner, printer, etc.) (that is, a specific color space), and device-independent color information (L * a * b * in this case)) The RGB value of the monitor is converted into the RGB value of the monitor by the description of what kind of RGB value should be converted to reproduce the same color on the device, and the result is displayed on the target color confirmation unit 903. Here, if the user wants to add more target colors, he or she can add target colors by pressing the target color addition button 905, and if all target colors are input and ink optimization is desired. Is the ink optimization button 9
Press 06.

As described above, according to each of the above-described embodiments, the candidate color material characteristics are set in the color material setting for reproducing the target color, and the set color material is used. Since the reproduced color is estimated and the color material to be used is determined based on the determination result of the error amount between the target color and the reproduced color, the color material that best reproduces the target color can be automatically selected.

<Wavelength calculation range and sampling interval>
In each of the above embodiments, the spectral reflectance does not have to be a limited wavelength range or a sampling interval, and if it is desired to improve the accuracy of error evaluation, the wavelength range may be widened or the sampling interval may be narrowed. It doesn't matter. On the contrary, it is possible to reduce the calculation amount by narrowing the wavelength range and widening the sampling interval. That is, according to the accuracy desired by the user, the amount of calculation, the above wavelength range,
The sampling interval can be changed. Also, a user interface for setting them may be provided.

<Color Space> In each of the above embodiments, the color mixture prediction and the correction of the predicted value are performed using the spectral reflectance, but this may be performed using a physical quantity other than the reflectance. Absent. For example, the ink density, the tristimulus value of the ink (XYZ or L * a * b *), and the like can be mentioned. Even when these physical quantities are used, the influence of the dot gain can be treated in the same manner as in the above embodiment. However, the color mixture prediction based on the KM theory cannot be used, and the color mixture prediction suitable for the physical quantity will be used.

<Number and Type of Ink Used> In each of the above-described embodiments, the combination of inks of six colors was optimized, but this is not limited to six colors. For example, it is possible to optimize ink combinations of 5 colors or less, or 7 colors or more. Or the conventional C
When the MYK ink is used as the fixed ink and one or more inks are added, it is possible to optimize only the additional ink.

<Correction Patch> Further, the correction patch used in each of the above-described embodiments is 0% to 1 for each color of the imprinting amount.
The patch is formed by superposing two or more color inks with an interval of 20% up to 00%. However, the patch is not limited to the combination of the above patches. Alternatively, if it is desired to reduce the number of patches to be output, the interval for changing the implantation amount may be increased.

<Order of Ink Overlay Correction Equation> In each of the above-described embodiments, in the ink overlay correction equation (5) _, the m of the spectral reflectance R _{p, λ} estimated by the KM theory is used.
Consider the polynomials up to the next and the secondary and tertiary colors (K /
(K / S) _{i, j, λ} and (K / S) _{k, l, m, λ} which are S) are used, but R _{p, It} is also possible to change the order of _λ , use (K / S) only for secondary colors, or use information of quaternary colors or more.

<Ink Characteristic Used for Ink Optimization> In each of the above-described embodiments, the ink characteristic used as the optimization candidate is stored in advance in the ink characteristic storage unit 16 or 716 by storing the actual measurement result of the ink characteristic. ,
After performing ink optimization, ink having other characteristics may be added and stored, and recalculation may be performed. In addition, it is possible to set the ink having virtual characteristics by changing the characteristics of the actual ink, for example, the peak wavelength and the magnitude of the reflectance sequentially in the computer, and further, to set the ink characteristics desired by the user. It is also possible to freely specify and add to the ink candidates. That is, the characteristics of the ink used here may be real or virtual, and are not limited to either one.

<Amount of Change in Ink Strike Amount> In each of the above embodiments, the amount of ink strike is changed by a constant amount to search for the amount of strike that minimizes the error from the target color. The amount is not limited to any particular value, and it is not necessary to use the same value throughout the process. For example, it is possible to increase the change amount in a large error range and perform a search at coarse intervals, and as the error decreases, decrease the change amount and perform a fine search. In other words, when the error between the target color and the estimated output value is used as the evaluation function, it is a combination optimization problem that determines the optimum ink ejection amount of each ink
A method for solving a general combinatorial optimization problem such as the steepest descent method, simulated annealing, and genetic algorithm may be used.

<Storage Medium> Even when the present invention is applied to a system composed of a plurality of devices (for example, host computer, interface device, reader, printer, etc.), an apparatus (for example, a device composed of one device) It may be applied to a copying machine, a facsimile machine, etc.). Further, an object of the present invention is to supply a storage medium storing a program code of software that realizes the functions of the above-described embodiments to a system or apparatus, and the computer (or CPU or MPU) of the system or apparatus stores the storage medium. It is needless to say that this is also achieved by reading and executing the program code stored in.

In this case, the program code itself read from the storage medium realizes the function of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.

As a storage medium for supplying the program code, for example, a flexible disk, hard disk, optical disk, magneto-optical disk, CD-ROM,
CD-R, magnetic tape, non-volatile memory card, RO
M or the like can be used. Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system) running on the computer based on the instruction of the program code. It goes without saying that a case where a part of the actual processing is performed and the functions of the above-described embodiments are realized by the processing is also included.

Further, after the program code read from the storage medium is written in the memory provided in the function expansion board inserted into the computer or the function expansion unit connected to the computer, based on the instruction of the program code, The CPU provided in the function expansion board or function expansion unit performs some or all of the actual processing,
It goes without saying that the processing includes the case where the functions of the above-described embodiments are realized.

[0069]

As described above, according to the present invention,
It is possible to easily select an appropriate color material for reproducing the target color with high accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an ink optimizing device according to a first embodiment.

FIG. 2 is a flowchart illustrating an ink optimization process in the ink optimization device according to the first embodiment.

FIG. 3 is a diagram showing an example of a user interface presented in the ink optimizing apparatus of the first embodiment for setting a target color.

FIG. 4 is a diagram showing an example of a user interface for displaying an ink optimization result in the ink optimization apparatus of the first embodiment.

5A is a diagram showing a spectral reflectance with respect to each ejection amount of cyan ink, and FIG. 5B is a diagram showing a primary color correction LUT obtained from the spectral reflectance data of FIG. 5A.

FIG. 6 is a diagram illustrating an example of an ink overlay correction patch.

FIG. 7 is a block diagram showing a configuration of an ink optimizing device according to a second embodiment.

FIG. 8 is a flowchart illustrating an ink optimization process in the ink optimization device according to the second embodiment.

FIG. 9 is a diagram showing an example of a user interface for setting a target color in the second embodiment.

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Claims (22)

[Claims] 1. An apparatus for optimizing a combination of color materials for reproducing a set target color, comprising: holding means for holding characteristics of a plurality of color materials; and a plurality of color materials selected from the plurality of color materials. A color mixture obtained by a combination of color materials, a prediction unit that predicts based on the characteristics held in the holding unit and the driving amount set for each color material, and for the combination of the selected color materials, for each color material Obtaining the minimum value of the difference between the predicted color mixture and the set target color, the minimum value obtained by the obtaining means is more than the predetermined value. And a control means for repeating the acquisition means until the combination of the color materials is changed. 2. A combination of color materials when the minimum value becomes smaller than a predetermined value, and a display means for displaying the amount of each color when the minimum value is obtained are further provided. Item 1. The color material optimizing device according to Item 1. 3. The predicting means corrects the primary color of each color material according to the set amount of printing, and the primary color of each color material obtained by the primary color correcting means. The color material optimizing apparatus according to claim 1, further comprising: a color mixture predicting unit that predicts a color mixture by using. 4. The primary color correction means estimates the correspondence relationship between the imprinting amount and the spectral reflectance for each color material based on the spectral reflectance at a predetermined imprinting amount, and holds the correspondence relationship holding means for holding this. 4. The color material optimizing device according to claim 3, wherein the color material optimizing device corrects the spectral reflectance of the primary color of each color material based on the correspondence relationship held by the correspondence relationship holding means. 5. The color mixture predicting means obtains an estimating means for estimating a color mixture by using the primary color obtained by the primary color correcting means, and outputs a plurality of color materials with a set implantation amount. And a storage means for storing a correction coefficient determined on the basis of an error between the actual color obtained and the color mixture estimated by the estimation means with respect to the set ejection amount, and the ejection amount of the designated recording material. 4. The color material optimizing device according to claim 3, wherein the color mixture estimated by the estimating means is corrected based on the correction coefficient stored in the storing means to obtain a mixed color prediction result. 6. The color material optimizing apparatus according to claim 1, further comprising setting means for setting the target color. 7. The color material optimizing apparatus according to claim 6, wherein the setting unit specifies a tristimulus value of a target color. 8. The color material optimizing apparatus according to claim 6, wherein the setting unit specifies a spectral reflectance of a target color. 9. The color material optimizing apparatus according to claim 6, wherein the setting unit is a spectral reflectance obtained by measuring a spectral distribution of the target color sample. 10. A method for optimizing a combination of color materials for reproducing a set target color, comprising: accessing a holding means for holding characteristics of a plurality of color materials, and holding the holding means by the holding means. A predicting step of predicting a color mixture obtained by a combination of color materials selected from a plurality of color materials based on the characteristics held by the holding means and the driving amount set for each color material; For a combination of different color materials, an acquisition step of changing the driving amount for each color material and repeatedly performing the prediction step, and acquiring the minimum value of the difference between the predicted color mixture and the set target color, and the acquisition step. And a control step of changing the combination of the color materials and repeating the acquisition step until the minimum value acquired in step 1 becomes smaller than a predetermined value. 11. The display device further comprises a display step of displaying a combination of color materials when the minimum value is smaller than a predetermined value and an imprinting amount of each color when the minimum value is obtained. Item 10. The color material optimization method according to Item 10. 12. The prediction step comprises a primary color correction step of correcting a primary color of each color material according to a set amount of imprinting, and a primary color of each color material obtained in the primary color correction step. The color material optimizing method according to claim 10, further comprising: a color mixture predicting step of predicting a color mixture by using. 13. The primary color correction step estimates, for each color material, a correspondence relationship between an imprinting amount and a spectral reflectance based on a spectral reflectance at a predetermined imprinting amount, stores the correspondence in a memory, and holds the memory. The color material optimizing method according to claim 12, wherein the spectral reflectance in the primary color of each color material is corrected based on the correspondence relationship. 14. The color mixture predicting step is obtained by estimating a color mixture by using the primary color obtained in the primary color correcting step, and outputting a plurality of color materials with a set implantation amount. And a storage step of storing a correction coefficient determined on the basis of an error between the actual color obtained and the color mixture estimated in the estimation step with respect to the set ejection amount, and the ejection amount of the designated recording material. 13. The color material optimizing method according to claim 12, wherein the mixed color estimated in the estimating step is corrected based on the correction coefficient stored in the storing step to obtain a mixed color prediction result. 15. The color material optimizing method according to claim 10, further comprising a setting step of setting the target color. 16. The color material optimizing method according to claim 15, wherein the setting step specifies a tristimulus value of a target color. 17. The color material optimizing method according to claim 15, wherein the setting step specifies a spectral reflectance of a target color. 18. The color material optimizing method according to claim 15, wherein the setting step includes a measuring step of measuring a spectral distribution of the target color sample. 19. A control program for causing a computer to execute the color material optimizing method according to any one of claims 10 to 18. 20. A storage medium storing a control program for causing a computer to execute the color material optimizing method according to claim 10. 21. A method of determining a combination of color materials for reproducing a set target color, which holds characteristics of a plurality of color materials, and a combination of color materials selected from the plurality of color materials. The color mixture obtained by the above is predicted on the basis of the characteristics held by the holding means and the shot amount set for each color material, and the shot amount for each color material is changed for the combination of the selected color materials, And a target color that has been set, and the combination is changed by changing the combination of the color materials until the comparison result satisfies a predetermined condition. 22. The processing method according to claim 21, wherein the predetermined condition is a condition that a difference between the predicted color mixture and the set target color is smaller than a predetermined value.