JP5528037B2 - Computer color matching method and computer readable recording medium recording computer color matching program - Google Patents

Description

  The present invention relates to a computer color matching method and a computer readable recording medium on which a computer color matching program is recorded, and more specifically, a computer color matching method capable of accurately calculating four or more kinds (colors) of compounding recipes, The present invention also relates to a computer-readable recording medium on which a computer color matching program is recorded.

  In order to combine a plurality of colorants such as dyes and pigments to obtain a desired color, it is necessary to select a colorant and accurately determine the amount and ratio of the colorant. Until now, engineers have tried and error to select a colorant and obtain the amount and ratio of the colorant so as to obtain the desired color. In recent years, optical data and computers for each colorant concentration have been used. Computer color matching (hereinafter referred to as CCM) for obtaining a desired colorant and determining its blending amount and blending ratio has been proposed (for example, Patent Documents 1, 2, and 3). This method is useful because color matching can be performed comparatively easily and appropriately even if not skilled in the preparation of colorants.

  The general CCM procedure is as follows. First, the spectral reflectance of the presented target color sample is measured. Subsequently, basic data corresponding to the type of the order material is specified from the basic data group of the colorant. Isomeric match or metameric match calculation is performed using the specified basic data, and the optimal combination of colorant and prescription are calculated. Test coloring is performed based on the calculated colorant and prescription. At this time, if there is a color difference between the color sample and the test color, a correction calculation is performed to calculate a corrected prescription. This operation is repeated until it falls within the predetermined allowable color difference, and if it falls within the allowable range, mass production is performed with the prescribed formula. In mass production, if the color is misaligned, the same correction calculation as the above operation is performed, and if it falls within the acceptable range, the final color management is performed.

  In CCM, samples with different concentrations and mixing ratios are prepared by changing the relative amount from the reference, and the optical density and staining density or mixing ratio are used as the basic data, based on the Kubelka-Munk color mixing theory. Calculate the tristimulus values of the predicted color using the equation (Equation 1), Duncan's color mixing theory equation (Equation 2), and further, Sanderson's reflectance correction equation (Equation 3) as necessary. The calculation is performed to match the colors by metameric matching that repeats the calculation until the color difference ΔE with the target color is within the convergence color difference. (Non-Patent Document 1)

  As described above, in the CCM, the initial blending is corrected by performing a calculation to match colors by a metameric match that reduces the difference between the obtained predicted tristimulus value and the tristimulus value of the target color. Since this technique uses tristimulus values, it uses a calculation formula that assumes that the initial formulation is composed of three colorants.

  Therefore, when four or more colorants are used, such as the target color cannot be obtained unless there are four or more colors, this method cannot be used simply, and in addition to the tristimulus values XYZ, reflection Calculations that match rate differences are often performed. However, this reflectivity is difficult to match without using the same colorant as the original sample, and it is very complicated to match the reflectivity using a different colorant than the original sample. It becomes work. For this reason, there was no choice but to repeat trials based on human experience.

Japanese Examined Patent Publication No. 6-98880 Japanese Patent Laid-Open No. 4-181129 JP-A-9-229773

New edition Color Science Handbook 2nd Edition 567-585

  The present invention solves the above-mentioned problem, and can be computer-readable recording a computer color matching method and a computer color matching program in which four or more kinds (colors) or more of compounding recipes can be easily and accurately calculated. It is an object to provide a simple recording medium.

A computer color matching method for performing color matching using four or more and five or less colorants for an arbitrary target color,
(A) measuring a color value in a predetermined color system for a target color;
(B) selecting n types ( 4 ≦ n ≦ 5 ) of colorants to be used;
(C) a step of selecting three types of colorants selected in step b;
(D) calculating the blending amount using the three kinds of colorants selected in step c;
(E) calculating a color difference between the predicted color and the target color obtained in step d and a metamerism index;
(F) repeating steps c to e for all colorant combinations;
(G) determining the combination and combination of the three colorants with the smallest metamerism index;
(H) A step of selecting (n-3) types of colorants out of the three types of colorants obtained in step g as fixed colorants and multiplying the blending amount by a fixed coefficient to fix as a provisional blending amount. ,
(I) For the three types of colorants not selected in step h, a step of calculating a blending amount and a metamerism index based on a provisional blending amount of the other colorants fixed in step h;
(J) changing the fixed colorant and repeating steps h and i;
A computer color matching method comprising: (k) changing the fixed coefficient and repeating steps h, i, and j; and (l) determining a combination and combination of n colorants that minimize the metamerism index.

A computer-readable recording medium storing a program for executing computer color matching for performing color matching using four or more and five or less colorants for an arbitrary target color,
(A) measuring a color value in a predetermined color system for a target color;
(B) selecting n types ( 4 ≦ n ≦ 5 ) of colorants to be used;
(C) a step of selecting three types of colorants selected in step b;
(D) calculating the blending amount using the three kinds of colorants selected in step c;
(E) calculating a color difference between the predicted color and the target color obtained in step d and a metamerism index;
(F) repeating steps c to e for all colorant combinations;
(G) determining the combination and combination of the three colorants with the smallest metamerism index;
(H) A step of selecting (n-3) types of colorants out of the three types of colorants obtained in step g as fixed colorants and multiplying the blending amount by a fixed coefficient to fix as a provisional blending amount. ,
(I) For the three types of colorants not selected in step h, a step of calculating a blending amount and a metamerism index based on a provisional blending amount of the other colorants fixed in step h;
(J) changing the fixed colorant and repeating steps h and i;
(K) A program for executing the steps of changing the fixed coefficient and repeating steps h, i, and j, and (l) determining the combination and combination of n colorants that minimize the metamerism index is recorded. Computer-readable recording medium.

  According to the present invention, it is possible to easily and accurately calculate four or more kinds (colors) of compounding prescriptions by performing automatic brute force combination calculation without depending on human experience.

It is a flowchart which shows the whole procedure of this invention.

The present invention
(A) measuring a color value in a predetermined color system for a target color;
(B) selecting n types (n ≧ 4) of colorants to be used;
(C) a step of selecting three types of colorants selected in step b;
(D) calculating the blending amount using the three kinds of colorants selected in step c;
(E) calculating a color difference between the predicted color and the target color obtained in step d and a metamerism index;
(F) repeating steps c to e for all colorant combinations;
(G) determining the combination and combination of the three colorants with the smallest metamerism index;
(H) A step of selecting (n-3) types of colorants out of the three types of colorants obtained in step g as fixed colorants and multiplying the blending amount by a fixed coefficient to fix as a provisional blending amount. ,
(I) For the three types of colorants not selected in step h, a step of calculating a blending amount and a metamerism index based on a provisional blending amount of the other colorants fixed in step h;
(J) changing the fixed colorant and repeating steps h and i;
(K) changing the fixed factor and repeating steps h, i and j, and (l) determining the formulation and combination of n colorants that minimizes the metamerism index.
A computer color matching method for performing color matching using four or more kinds of colorants for an arbitrary target color, and a computer-readable recording medium on which a program for executing this method is recorded.

Here, the color value is not limited to the color system values such as XYZ and L * a * b * based on the spectral reflectance, and any color value is targeted. The color difference is the XYZ color system. Not only ΔX, ΔY, ΔZ, and CIELAB color system ΔL *, Δa *, Δb *, but also any color difference of any color system such as ΔE * ab, ΔEcmc, CIEDE2000. In particular, it is preferable that the spectral reflectance is measured and the L ^* a ^* b ^* color system is used based on the spectral reflectance in terms of general and easy understanding.

In the present invention, in the CCM method, when calculating a blending amount that matches a target color using four or more (hereinafter referred to as n types) colorants, first, from among the selected n types of colorants. Choose 3 types and make all combinations ( _n C ₃ ). From these combinations, a blending result in which the color difference from the target color converges and the metamerism index with a plurality of light sources becomes the smallest is obtained. This is still the result of using only three colorants, and is a process to get an approximate idea.

  Next, among the three types selected by the above method, any (n-3) types are fixed, and the blending amount calculated in the previous process is multiplied by a fixed coefficient. Here, the fixed coefficient is set to take a value of 0.1 to 1.0. Since the blend obtained in the previous process is a result of using only three kinds of colorants as described above, this blend cannot be applied as it is when four or more kinds are used. Therefore, on the premise that the blending amount of each of the three selected colorants is not greater than the blending amount obtained in the previous process, (n-3) arbitrary colors from the three types are selected. A result obtained by multiplying the blending amount by a fixing coefficient of 0.1 to 1.0 is fixed as a provisional blending amount of the color. Here, in order to change this fixed coefficient at intervals of 0.1, first, 0.1 is multiplied. Note that the value and interval of the fixed coefficient are not particularly limited. For example, the value of 0.02 to 1.0 may be changed at intervals of 0.02.

  Among the n kinds of colorants, the color difference from the target color converges again by the CCM method for the (n-3) color that is multiplied by 0.1 to fix the provisional blending amount and the other three colors, The blending result with the smallest metamerism index with multiple light sources is obtained. Next, the color to be fixed is changed among the three colors selected above, and this is repeated for all. Further, the fixed coefficient is changed to 0.2, 0.3,... 1.0, and this is repeated for all combinations. Then, the blending result in which the metamerism index finally becomes the smallest is determined as the final blend.

  Here, by using the metamerism index with a plurality of light sources as a determinant of blending, it is possible to determine a blending recipe with the smallest metamerism.

  The method of the present invention will be specifically described in the case of blending four kinds of colorants according to the flowchart shown in FIG. In step 1, the reflectance of the target color is measured with a spectrophotometer in step 2, and the reflectance data is taken into the computer. In step 3, the tristimulus values XYZ of the target color are calculated. Four types of colorants (A, B, C, D) used in the procedure 4 are selected, and in the procedure 5, the K / S or the absorption coefficient / scattering coefficient of the colorant is calculated. In step 6, three colors are further selected from the selected colorants (for example, A, B, and C), and in step 7, the blending amount is calculated using the Allen method or Newton-Raphson method. In step 8, the tristimulus value of the predicted color of the combination obtained in step 7 is obtained. In step 9, a color difference between the target color and the predicted color and a metamerism index with a plurality of light sources are calculated. This is done for all combinations of the selected colorants (procedure 10). The number of combinations when selecting 3 colors from 4 colors is 4C3 = 4. In this case, there are four types of A · B · C, A · B · D, A · C · D, and B · C · D.

  In step 11, the calculation converges from the combination obtained in steps 6 to 10, and the combination having the smallest metamerism index with a plurality of light sources is determined. The combination is A, B, and C. In step 12, the fixed coefficient is set to 0.1. In step 13, one color (A) is selected from the combinations A, B, and C determined in step 11 as a fixed colorant, and the amount is determined in step 11. The provisional blending amount obtained is multiplied by the fixed coefficient. In step 14, the remaining three colorants (B, C, D) are recalculated, and in step 15, the tristimulus value of the predicted color is calculated according to the following equation 4. In step 16, a color difference from the target color and a metamerism index with a plurality of light sources are calculated. Procedures 13 to 16 so far are calculated in the same manner from the combinations A, B, and C selected in Procedure 11 with the colorants (B and C) excluding the previous A as fixed colorants. Next, procedures 12 to 16 are performed by changing the fixed coefficient to 0.2, 0.3... 1.0. In step 19, the calculation converges therein, and the combination having the smallest metamerism index with a plurality of light sources is output as the final calculation result.

  The method for calculating the tristimulus values XYZ can be calculated from the following calculation formula using the spectral reflectance.

Further, the L ^* a ^* b ^* value can be calculated from the obtained tristimulus values XYZ by the following calculation formula.

  Hereinafter, the present invention will be described more specifically with reference to examples.

1. Configuration of computer color matching system used Personal computer: CPU Pentium (registered trademark) D manufactured by Intel 2.8 GHz Memory 1 G
OS: Windows XP
Display: SXGA (resolution 1280 x 1024)
Spectrophotometer: Color i5 manufactured by X-rite

  This personal computer is equipped with a calculation mechanism capable of performing a blending calculation that matches the target color, a database reference mechanism, a colorant blending simulation mechanism, and a colorant database mechanism for executing the calculation mechanism as programs.

Example 1 (Color matching with dye)
Dye type: 4 types of disperse dyes YELLOW
BORDEAUX
BLUE
TURQUISE BLUE
Color matching light source: D65 (10)
Second light source: F6 (10)

(Initial blending amount calculation)
Using the four dye colors, a target color was prepared according to the formulation in Table 1. Next, the blending amounts were calculated for all four combinations in which three colors were selected from the four colors. As a result, the combinations of the dyes having the minimum metamerism index and the blending amounts thereof were as follows.

YELLOW 0.0536 (% owf)
BORDEAUX 0.0365 (% owf)
BLUE 0.5490 (% owf)

  Subsequently, the fixed colorant was set to YELLOW, a fixed coefficient of 0.02 was applied, and the provisional blending amount of YELLOW was set to 0.00107 (% owf). Here, the fixed coefficient is set to a value of 0.02 to 1.0 and is varied at intervals of 0.02. In consideration of this, the blending amounts of the remaining three colors BORDEAUX, BLUE, and TURQUOISE were calculated. Subsequently, the fixed colorant was changed to BORDEAUX and BLUE, and the blending amount was calculated in the same manner. Further, the fixed amount was changed to 0.04, 0.06,... 1.0, and the blending amount was similarly calculated. As a result, when the fixed coefficient was 0.86, the metamerism index value (MI value) was minimized with the following combination (first time).

It dye | stained according to the obtained initial compounding quantity, and measured the color difference ((DELTA) E ^* ) with respect to a target color, and MI value. The results are shown in Table 1. It can be seen that the blending ratio difference between the initial blending amount and the target color is small, and the color matching accuracy is high.

For reference, based on the initial blending amount, the blending amount was recalculated in the same manner as in the method of the present invention (one correction). It dye | stained according to this corrected 1 time compounding quantity, and measured the color difference with respect to a target color, and MI value. The results are shown in Table 1. It can be seen that both the color difference (ΔE ^* ) and the MI value are small and the colors are well matched. Based on the blending amount of the correction one time, recalculation was performed in the same manner (two corrections). The results are shown in Table 1.

Example 2 (Color matching with dye)
Dye type: 4 types of disperse dyes YELLOW
Y. BROWN
RED
BLUE
Color matching light source: D65 (10)
Second light source: F6 (10)

(Initial blending amount calculation)
Using the four dye colors, a target color was prepared according to the formulation in Table 2. Next, the blending amounts were calculated for all four combinations in which three colors were selected from the four colors. As a result, the combinations of the dyes having the minimum metamerism index and the blending amounts thereof were as follows.

YELLOW 0.1010 (% owf)
Y. BROWN 1.2700 (% owf)
BLUE 0.1940 (% owf)

  Next, the fixing colorant was set to YELLOW, a fixing coefficient of 0.1 was applied, and the provisional blending amount of YELLOW was set to 0.0101 (% owf). Here, the fixed coefficient was set to a value of 0.1 to 1.0, and was varied at 0.1 intervals. Taking this into account, the remaining Y.M. The blending amount was calculated for three colors of BROWN, RED, and BLUE. The fixed colorant is It changed into BROWN and BLUE and computed the compounding quantity similarly. Further, the fixed amount was changed to 0.2, 0.3... 1.0, and the blending amount was calculated in the same manner. As a result, when the fixed coefficient was 0.8, the metamerism index value (MI value) was minimized with the following combination (first time).

It dye | stained according to the obtained initial compounding quantity, and measured the color difference ((DELTA) E ^* ) with respect to a target color, and MI value. The results are shown in Table 2. It can be seen that the blending ratio difference between the initial blending amount and the target color is small, and the color matching accuracy is high.

For reference, based on the initial blending amount, the blending amount was recalculated in the same manner as in the method of the present invention (one correction). It dye | stained according to this corrected 1 time compounding quantity, and measured the color difference with respect to a target color, and MI value. The results are shown in Table 2. It can be seen that both the color difference (ΔE ^* ) and the MI value are small and the colors are well matched. Based on the blending amount of the correction one time, recalculation was performed in the same manner (two corrections). The results are shown in Table 2.

Example 3 (Color matching with dye)
Dye type: 5 disperse dyes YELLOW
RED
BORDEAUX
BLUE
TURQUISE BLUE
Color matching light source: D65 (10)
Second light source: F6 (10)

(Initial blending amount calculation)
Using the five dyes, a target color was prepared according to the formulation shown in Table 3. Next, the blending amounts were calculated for all 10 combinations in which 3 colors were selected from these 5 colors. As a result, the combinations of the dyes having the minimum metamerism index and the blending amounts thereof were as follows.

YELLOW 0.0449 (% owf)
RED 0.1940 (% owf)
BLUE 0.6410 (% owf)

  Next, the fixing colorant was set to YELLOW and RED, a fixing coefficient of 0.1 was applied, and the respective provisional blending amounts were 0.00449 (% owf) and 0.01940 (% owf). Here, the fixed coefficient was set to a value of 0.1 to 1.0, and was varied at 0.1 intervals. In consideration of this, the blending amounts of the remaining three colors BORDEAUX, BLUE, and TURQUOISE BLUE were calculated. Next, the fixed colorant was changed to YELLOW and BLUE, and the blending amount was calculated in the same manner. Further, the fixed amount was changed to 0.2, 0.3... 1.0, and the blending amount was calculated in the same manner. As a result, when the fixed coefficient was 0.8, the metamerism index value (MI value) was minimized with the following combination (first time). The results are shown in Table 3. It can be seen that the blending ratio difference between the initial blending amount and the target color is small, and the color matching accuracy is high.

Example 4 (Color matching with pigment)
5 types of pigments Target color (D65 (10))
L ^* 32.78 a ^* 11.7 b ^* 0.15

(Initial blending amount calculation)
A target color was prepared using five colors of pigments listed in Table 4. In general, since color matching of pigments is performed using basic data of chromatic colors with white as a reference, calculation is performed using only chromatic colors. The blending amount was calculated for all four combinations in which three colors were selected from the four chromatic colors. As a result, the combinations of the dyes having the minimum metamerism index and the blending amounts thereof were as follows.

CARAMEL 10.67 (%)
RED 67.61 (%)
BLUE 11.77 (%)
WHITE 9.95 (%)

  Next, the fixed colorant was CARAMEL, and a fixed coefficient of 0.1 was applied to make each provisional blending amount 1.067 (%). Here, the fixed coefficient was set to a value of 0.1 to 1.0, and was varied at 0.1 intervals. In consideration of this, the blending amount was calculated for the remaining three chromatic colors of BORDEAUX, BLUE, and RED. Subsequently, the fixed colorant was changed to RED and BLUE, and the blending amount was calculated in the same manner. Further, the fixed amount was changed to 0.2, 0.3... 1.0, and the blending amount was calculated in the same manner. As a result, when the fixed coefficient was 0.6, the metamerism index value (MI value) was minimized with the following combination (first time). The results are shown in Table 4. It can be seen that the blending ratio difference between the initial blending amount and the target color is small, and the color matching accuracy is high.

Claims (2)

A computer color matching method for performing color matching using four or more and five or less colorants for an arbitrary target color,
(A) measuring a color value in a predetermined color system for a target color;
(B) selecting n types ( 4 ≦ n ≦ 5 ) of colorants to be used;
(C) a step of selecting three types of colorants selected in step b;
(D) calculating the blending amount using the three kinds of colorants selected in step c;
(E) calculating a color difference between the predicted color and the target color obtained in step d and a metamerism index;
(F) repeating steps c to e for all colorant combinations;
(G) determining the combination and combination of the three colorants with the smallest metamerism index;
(H) A step of selecting (n-3) types of colorants out of the three types of colorants obtained in step g as fixed colorants and multiplying the blending amount by a fixed coefficient to fix as a provisional blending amount. ,
(I) For the three types of colorants not selected in step h, a step of calculating a blending amount and a metamerism index based on a provisional blending amount of the other colorants fixed in step h;
(J) changing the fixed colorant and repeating steps h and i;
A computer color matching method comprising: (k) changing the fixed coefficient and repeating steps h, i, and j; and (l) determining a combination and combination of n colorants that minimize the metamerism index. A computer-readable recording medium storing a program for executing computer color matching for performing color matching using four or more and five or less colorants for an arbitrary target color,
(A) measuring a color value in a predetermined color system for a target color;
(B) selecting n types ( 4 ≦ n ≦ 5 ) of colorants to be used;
(C) a step of selecting three types of colorants selected in step b;
(D) calculating the blending amount using the three kinds of colorants selected in step c;
(E) calculating a color difference between the predicted color and the target color obtained in step d and a metamerism index;
(F) repeating steps c to e for all colorant combinations;
(G) determining the combination and combination of the three colorants with the smallest metamerism index;
(H) A step of selecting (n-3) types of colorants out of the three types of colorants obtained in step g as fixed colorants and multiplying the blending amount by a fixed coefficient to fix as a provisional blending amount. ,
(I) For the three types of colorants not selected in step h, a step of calculating a blending amount and a metamerism index based on a provisional blending amount of the other colorants fixed in step h;
(J) changing the fixed colorant and repeating steps h and i;
(K) A program for executing the steps of changing the fixed coefficient and repeating steps h, i, and j, and (l) determining the combination and combination of n colorants that minimize the metamerism index is recorded. Computer-readable recording medium.

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