JPH0698880B2 - Computer color matching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a computer color matching method.

(Prior Art) Computer Color Matching (hereinafter referred to as CCM)
The method is to dye an object to be dyed with individual dyes at several levels of density, and use optical density calculated from the spectral reflectance of the sampling sample as basic data, and use this basic data as an option for any combination of dyes. This is a method of matching the optical density of the target color by adding the optical density values of the dye density of.
This method is convenient because even an unskilled person can easily perform color matching in a short time.

The procedure when this CCM method is used at the time of manufacturing a product will be described with reference to the flowchart of FIG.

Step: Measure the spectral reflectance of the target color and calculate the optical density.

Step: If you instruct the computer to calculate the color combination with this value as the target value, the computer will calculate the optical density of each dye at all the dye densities, and then how much each dye will be mixed to obtain the optical color of the target color. It is calculated whether it matches the density and the calculation result is output to the display device.

Step: Based on this calculation formula, the dye is weighed and added to dye the article to be dyed.

Step: The spectral reflectance of the sampling sample of the first dyeing of this dyed product is measured.

Step: Target color and sampling sample eg CIEΔL
Color difference values such as ^* , Δa ^* , and Δb ^* are calculated, and the distance of the color difference in the color space ΔE = ((ΔL ^* ) ² + (Δa ^* ) ² + (Δ
b ^* ) ² ) Calculate ^0.5 .

Step: Judge pass or fail depending on whether the color difference ΔE is within a preset tolerance range.

Step: If the result is unacceptable, the difference between the optical density of the target color and the optical density after the first dyeing is newly regarded as the target color, the step is calculated, and the dye prescription to be additionally added is output to the display device.

Step: After the additional addition of dye, re-staining is performed, the process returns to step, and the above steps are performed. If the step passes, the process proceeds to the next step.

(Problems to be Solved by the Invention) However, although the CCM method described above can be applied in steps, there is a problem that it cannot be applied in steps when the sampling sample is visually darker than the target color. That is, the reason why the color is darker than the target color is apparently because the dye was added in excess of a predetermined amount,
It is necessary to newly dye the dyed product with a smaller mixing ratio than the dye prescription at the first dyeing. However, conventional CCM
This is because the method forcibly sets the minimum value of the additional dye prescription to 0 when the density is darker than the target color, which causes an error in theoretical calculation and does not improve the accuracy of CCM.

Therefore, in such a case, the dyed product is decolorized so that it becomes lighter than the target color, and then the conventional CCM method is applied to calculate the dye prescription to be additionally added. However, the work form accompanied by such a decolorization step is inefficient, and there are further problems such as the occurrence of decolorization spots and the detrimental effect of the decolorizing agent on the material to be dyed, and its solution is desired. Was there.

The present invention has been made in view of the above-mentioned problems, and even when the sample sample is visually dark with respect to the target color, it is possible to easily and efficiently perform color correction by additionally adding a dye. It is intended to provide a method.

(Means for Solving Problems) The above-described object is a computer that performs color matching with a target color having an arbitrary spectral reflectance by using a specific combination of dyes.
A color matching method, which comprises (a) a first step in which individual dyes are individually prepared into several density-dependent samples and the optical density thereof is used as basic data; Based on the basic data
A second step of virtualizing virtual optical density when the staining density is negative; (c) arbitrary using the basic data obtained in the first step and the virtual data obtained in the second step The third step of obtaining the density of each dye so as to match the target color having the spectral reflectance of, and (d) the density of all the dyes is shifted when the dye density obtained in the third step is a negative amount. And a fourth step of eliminating the negative amount. The computer color matching method is achieved.

Next, the present invention will be described in more detail. Here, A
The case of using dyes, B dyes, and C dyes will be described as an example.

(1) A first step in which individual dyes are individually used to prepare several density-dependent samples and the optical density thereof is used as basic data.

A dye of A, B, C dye alone is made into several levels of density, the color of the sample of the dyed product is measured, and the optical density (K / S) of the material to be dyed is measured from the spectral reflectance R. Obtain and use as basic data (the optical density can be calculated by (K / S) = (1-R) ² /2R...(1)).

Usually, the purpose of creating this basic data is to obtain the ratio of the change in K / S to the change in the dyeing concentration of each dye from the existing dyed product, and to calculate the K / S value at an unknown dyeing concentration in the known dyeing concentration. This is so that it can be calculated from the proportional relationship with K / S. Further, the reason for creating a dyeing material having a concentration of several levels is to increase the accuracy of the measurement by providing a large amount of actual measurement data. This can be expressed by the formula: dyeing density of A dye C _AX optical density (K / S)
_{AX looks} like this:

(K / S) _AX = ∂ (K / S) _Ai / ∂C _Ai × C _AX (2) However, (K / S) _Ai : K / S measured value at dyeing density C _Ai Similarly, dyeing density of B dye Optical density (K / S) of C _{BX BX} is as follows.

(K / S) _BX = ∂ (K / S) _Bi / ∂C _Bi × C _BX (2) However, (K / S) _Bi : K / S measured value in C _Bi The dye density of C dye similarly C _CX optical density (K / S) _CX is as follows.

(K / S) _CX = ∂ (K / S) _Ci / ∂C _Ci × C _CX (2) However, (K / S) _Ci : K / S measured value at staining density C _Ci (2) First step above Based on the basic data obtained in
A second step in which the optical density when the dyeing density is negative is assumed to be virtual data.

In the above formula (2), when the values of C _AX , C _BX , and C _CX are negative values, (K / S) _AX , (K / S) _BX , and (K / S) _CX are also negative, so this minus The optical density of is used as virtual data.

That is, the basic data and the virtual data are drawn symmetrically with 0 being point symmetry, and the above formula (2) is expressed by the staining densities C _AX , C
_{When BX} and C _CX are positive, it becomes the basic data and the staining density
When C _AX , C _BX , and C _CX are negative, it becomes virtual data.

(3) A third step of obtaining the density of each dye so as to match a target color having an arbitrary reflectance using the basic data obtained in the first step and the virtual data obtained in the second step.

If the optical density of the target color is (K / S) _S , for example, the optical density of the sampling sample after the first dyeing is (K / S) _M , then the difference Δ
(K / S) ＝ (K / S) _S − (K / S) _Create a Duncan color mixture formula for _M.

However, (K / S) _W : optical density of undyed fabric C _AX when both sides are equal in the above formula (3),
C _BX and C _CX are obtained by a successive approximation method such as Newton-Raphson method and used as additional input prescription.

Since this iterative approximation method is a mathematical method, C _AX , C _BX ,
It is _{quite possible} that C _CX becomes a negative amount. For example,
The frequency is especially high when the sample sample is visually dark with respect to the target color such that Δ (K / S) on the left side becomes negative. In that case, the virtual data minus the optical density obtained in step (2) is used.

(4) The fourth step of shifting the density of all dyes to eliminate the negative amount when the dye concentration obtained in the third step is obtained in the negative amount.

If the prescription C _{AX of the} dye A reaches the maximum negative amount, the negative amount is replaced with the positive amount of another dye by the following formula (4). For example, C ′ _AX = C _AX + | C _AX | = 0 (4) C ′ _BX = C _BX + | C _AX | (4) C ′ _CX = C _CX + | C _AX | , | | Indicates an absolute value.

The C ′ _AX , C ′ _BX , and C ′ _CX are additionally charged and additional dyeing is performed to match the optical density of the target color.

(Operation) Since the present invention is configured as described above, for example, when the sampling sample is visually dark with respect to the target color, the dye density of the dark hue is displayed as a negative value, and therefore the density of all dyes is shifted. By doing so, for example, the dye density of a dark hue can be made 0, and the density of another dye that is a complementary color for canceling this dark hue can be increased, so that the dark hue is canceled as a whole and the light hue is Since they are added, the target color as a whole is approached.

(Examples) Hereinafter, the present invention will be described in detail based on Examples.

FIG. 1 shows an apparatus for implementing the computer color matching method of the present invention. (1) is a spectrophotometer for measuring the spectral reflectance and spectral transmittance of a sampling sample, and is an apparatus capable of measuring at least a visible light region having a wavelength of 400 nm to 700 nm. (2) is a storage device such as a ROM, a RAM, and a magnetic disk, which stores basic data obtained from several levels of optical density of each dye alone and virtual data that is a virtual optical density when the dye density is negative. Has been done. Reference numeral (3) is a computing device such as a microcomputer, which is used for obtaining an optical density by using the data of the sampling sample measured by the spectrophotometer (1) and a storage device (2).
Using the basic data and virtual data stored in, obtain the density of each dye so as to match the target color with any spectral reflectance, and when the dye density is negative, shift the density of all dyes. The work is done to eliminate the negative amount. (4) is a display device such as a display or a printer, which displays the calculated additional calculation prescription and the like.

Next, the present invention will be specifically described with reference to specific examples.

(1) First Step A panty stocking using the following yarn was dyed with the following dye to obtain a sampling sample.

i) Dyeing object Kanebo nylon pantyhose knitted with nylon thread ii) Dye Acid dye Yellow Acid dye Rubin Acid dye Blue Acid dye Orange Acid dye Red iii) Density 0.005,0.01,0.05,0.1% owf The color of the sampled sample was measured, and the optical density (K / S) was calculated from the spectral reflectance using the above formula (1), which was used as basic data.

(2) Second step Further, the negative optical density (K / S) when the staining density is negative was hypothesized using the above-mentioned formula (2), and made into virtual data.

Figure 3 shows the results of the acid dye Yellow.

(3) Third Step In the conventional method, the computer color matching method of the present invention was applied to three sets of sample samples in the case where the color matching to the target color was made only by the decoloring means.

i) The same dyeing material as in the first step was used and dyed according to the following formulation to obtain a dyed material (FIG. 2, step).

First dyeing recipe Example 1 Acid dye Yellow 0.19681% owf 〃 Rubin 0.07721% owf 〃 Blue 0.13088% owf Example 2 Acid dye Orange 0.00997% owf 〃 Red 0.01177% owf 〃 Blue 0.03432% owf Example 3 Acid dye Orange 0.02952% owf 〃 Red 0.02340% owf 〃 Blue 0.02828% owf ii) The color of the sampling sample after the first dyeing was measured (step), and the color difference between the target color and the sampling sample after the first dyeing was calculated (step).

iii) The color difference ΔE at this time was judged to be larger than 1 and failed (step).

iv) Applying the above formula (3) to the difference Δ (K / S) between the optical density (K / S) _{S of the} target color and the optical density (K / S) _M of the sampling sample after the first dyeing, The dye concentrations C _AX , C _BX and C _CX were obtained. As a result, a negative amount of prescription was calculated, and as a case, all three dyes were used in Example 1, Or-ange dyes in Example 2, and red and blue dyes in Example 3.

(4) Fourth step i) The above formula (4) is applied to the negative amount of dye concentration obtained in the third step, other dyes are shifted, and the negative amount is replaced with the positive amount of other dyes (step ).

ii) The dyed product after the initial dyeing was dyed by the additional calculation prescription obtained in the step (step) to obtain the dyed product (the dyeing method is the same as in the first step).

iii) The color of the sample sample after additional dyeing was measured (step), and the color difference between the target color and the sample of sample after additional dyeing was calculated (step).

iv) The color difference ΔE at this time was less than 1 in all three cases and was judged to be acceptable (step).

Table 1 shows the results obtained in the third step and the fourth step.

As can be seen from Table 1, the color difference ΔE after additional dyeing is 1.0
Below, it can be seen that the CCM method according to the present invention has practical accuracy (CI for gray and beige stockings).
The color acceptance value in the ELAB colorimetric value is empirically determined to be ΔE <1.0).

(Effects of the Invention) As described in detail above, according to the computer color matching method of the present invention, the procedure of color matching can be performed accurately and quickly, and the productivity is further improved. Is extremely prominent.

[Brief description of drawings]

FIG. 1 is a block diagram showing an apparatus for carrying out the method of the present invention, FIG. 2 is a flow chart when the method of the present invention is used in manufacturing a product, and FIG. This is a result of creating a sample, imagining the optical density when the dyeing density is negative based on the optical density, and obtaining virtual data. Explanation of symbols (1) ... spectrophotometer, (2) ... storage device, (3) ... computing device, (4) ... display device.

Claims (1)

[Claims] 1. A computer for color matching a target color having an arbitrary spectral reflectance with a specific combination of dyes.
A color matching method, which comprises (a) a first step in which individual dyes are individually prepared into several density-dependent samples and the optical density thereof is used as basic data; Based on the basic data
A second step of virtualizing virtual optical density when the staining density is negative; (c) arbitrary using the basic data obtained in the first step and the virtual data obtained in the second step The third step of obtaining the density of each dye so as to match the target color having the spectral reflectance of, and (d) the density of all the dyes is shifted when the dye density obtained in the third step is a negative amount. And a fourth step of eliminating the negative amount, the computer color matching method.