JPH10157206A - Method for calculating color in color printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for calculating color in a color printer which can implement color adjustment simply and surely. SOLUTION: A printing sample including an area from the minimum energy to the maximum energy which can be charged into a printing means is printed, the relationships between the spectral reflectance and the energy of three primary colors of yellow, magenta, and cyan of the printed sample are measured, and the approximation of an n-order equation is obtained assuming the spectral reflectance of every wavelength as the function of energy. Lambert-Beer's law is applied to the spectral reflectances of three primary colors, the coordinate value of a rectangular coordinate system is obtained using an isochromatic function, the difference between the measured spectral reflectance of the color tone obtained by printing three primary colors by the energy of an equal gradation and the spectral reflectance of the color tone obtained by calculation is obtained as a correction factor, and by correcting using the correction factor as the function of the energy of three primary colors, a color space coordinate of the color obtained corresponding to charged energy is calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of calculating colors in a color printer which obtains the same color tone on a display device that expresses a plurality of color tones by additive color mixing, for example, by mixing primary colors.

[0002]

2. Description of the Related Art As an output device of a computer and a printing device of a video monitor, there is a color printer, and a printing method such as a thermal transfer type, a thermal type, an ink jet type or an electrophotographic type has been developed.

In any of the above-mentioned methods, Y (yellow: yellow), which is the three primary colors (three primary colors of subtractive color mixing),
M (magenta: magenta) and C (cyan: light blue) are sequentially colored on the printing paper, and all the colors are expressed by changing the ratio of the density (color development amount) of each of the three primary colors.

[0004] In each of the above-described printing methods, the control method of the color development amount is different. This will be described below. a. Thermal transfer type / thermal type In the thermal transfer type and thermal type, the temperature is controlled by the number of pulses applied to the thermal head to change the amount of coloring. Therefore, the amount of color development is changed by the number of pulses applied to the thermal head.

B. Ink-jet type In the ink-jet type, the amount of color development is changed depending on the appropriate amount of liquid of the ejected ink. c. Electrophotography In the electrophotography, the amount of color development is controlled by the amount of charge on the photosensitive drum.

However, in either method, the amount of color development is controlled by the amount of energy applied to the printing unit. However, in any method, the hue, saturation, lightness, and the like used in the color printer are obtained by subtractive color mixing as described above, and thus cannot be directly calculated from the coordinate values in the color space. .

Therefore, there is no other means to confirm the color obtained when the energy is applied as described above, except to measure the color of the actually printed one and obtain the result. Therefore, in order to obtain a target color, an experiment for determining the energy input condition has to be repeated, which requires an enormous amount of time.

A conventional procedure for determining a gradation pulse in a sublimation type thermal transfer color printer will be described below.
FIG. 22 is a flowchart illustrating a conventional procedure for determining a gradation pulse.

In FIG. 22, a case where the color printer has eight gradations will be described as an example. The eight gradations are equally spaced for each value of L ^* , and the gray obtained by printing the gradations of Y, M, and C in an overlapping manner is achromatic (a ^* = 0, b ^* =
0).

FIG. 23 is a configuration diagram showing an example of the configuration of an evaluation pattern used when determining a gradation pulse. Note that, in the example shown in FIG. 23, 16 levels of energy gradation are measured, but the finer this step is, the better.

In FIG. 22, first, a test pattern at a certain energy level is printed for each of the Y, M, and C color ribbons using the evaluation pattern shown in FIG. 23, and L ^* is measured by a colorimeter. I do.

FIGS. 24 (a), 24 (b) and 24
(C) is a diagram showing an example of the relationship between L ^* and energy measured by a colorimeter. FIG. 24A,
In (b) and (c), L ^* is shown on the vertical axis, and energy (number of pulses) is shown on the horizontal axis.

Here, as shown in FIG. 24A, the energy E _MAX corresponding to the maximum concentration D _MAX is obtained based on the measurement result.
Is determined (Step St1). Next, as shown in FIG. 24 (b), determining the energy E _MIN corresponding to the lowest concentration D _MIN (step St2).

Thereafter, L ^* is divided into seven equal parts at equal intervals between the maximum density D _MAX and the minimum density D _NIM, and the energies E _{1 to} E ₈ of eight gradations as shown in FIG. Is obtained (Step St3). Such processing is performed for each of the colors Y, M, and C, and the energy of each is determined as follows. For yellow (Y): E _{Y1 to} E _{Y8 For} magenta (M): E _{M1 to} E _{M8 For} cyan (C): E _{C1 to} E _C8

Next, using the evaluation pattern shown in FIG. 23, three colors of Y, M, and C are superimposed, and eight gray levels are printed (Step St4). Further, the evaluation pattern printed in step St4 is measured by a colorimeter,
L ^* , a ^*, and b ^* are measured (Step St5).

FIG. 25 shows the measurement results in step St5. FIG. 25 (a) shows an example of the measured values of a ^* and b ^* , and FIG. 25 (b) shows an example of the measured values of L ^*. Is shown. In the next step St6, it is determined whether or not the measured value is appropriate.

In the example shown in FIGS. 25 (a) and 25 (b), the value of a ^* or b ^* is far from the target value of 5, and each point is scattered. Is not appropriate. On the other hand, L ^* is almost linearly arranged, and can be said to be good.

After that, the pulse condition of each level is adjusted within a range of ± 10 pulses, and the energy condition is corrected so that the measured value is optimized (Step St7). In addition, as the adjustment, the process of returning to the process of Step St4 and performing the test printing after the process of Step St7 is completed includes:
Usually it requires more than 100 times.

FIG. 26 shows the measurement results of the evaluation pattern after the energy condition has been corrected in step St7. FIG. 26 (a) shows an example of the measured values of a ^* and b ^* . b) shows an example of the measured value of L ^* .

In the example shown in FIG. 26A, the values of a ^{* and} b ^* converge within approximately 5 and it can be said that the gray balance is good. However, FIG.
As shown in (b), L ^* is inferior in linearity to the above-mentioned FIG. 25 (b). This is an adverse effect on giving priority to gray balance. In the above description, the case of eight gradations has been described as an example.
56 gradations are common.

[0021]

As described above, in the adjustment of the gray balance, it is usually impossible to converge all the gradations to the origin. Moreover, before the adjustment, the re-adjacent point to the finally reachable origin is unknown, and there is no choice but to judge from the adjustment result. That is, there is no guarantee that the final result considered to have been converged by the adjustment is the closest point, and there is no verification means.

Further, in order to experimentally accurately determine the closest point described above, an enormous amount of experiments are required, which is practically impossible. That is, for example, each pulse of Y, M and C is
If the experiment is performed under 0 conditions, the number of experiments is 1 for each gradation.
O ³ = about 1000 times is required. Even if only 16 gradations out of 256 gradations are executed, 16,000
This means that zero experiments are required.

As described above, the prior art has a problem that the number of experiments increases, the development period becomes long, and the development cost increases. The present invention has been made under such a background, and an object of the present invention is to provide a color calculation method in a color printer that can easily and reliably perform color adjustment.

[0024]

In order to solve the above-mentioned problems, according to the first aspect of the present invention, a print sample including a region from a minimum energy to a maximum energy which can be input to a printing unit is printed. A first step, and three of yellow, magenta, and cyan in the visible region of the printed print sample.
A second step of measuring the relationship between the spectral reflectance and energy of each primary color, a third step of obtaining an n-order approximation of the spectral reflectance for each wavelength as a function of the energy, A fourth step of applying Lambert-Beer's law to the spectral reflectance and obtaining coordinate values in a rectangular coordinate system using a color matching function; and a method of printing a color tone obtained by printing the three primary colors with equal gradation energy. A fifth step of obtaining the difference between the measured spectral reflectance and the spectral reflectance of the color tone obtained by calculation as a correction coefficient, and a sixth step of correcting using the correction coefficient as a function of the energy of each of the three primary colors. And calculating the color space coordinates of the color obtained corresponding to the input energy based on According to a second aspect of the present invention, in the color calculation method in the color printer according to the first aspect, the three primary colors of yellow, magenta, and cyan having the same gradation energy are printed by overlapping. Optimum gray balance based on the processing from the first process to the sixth process in which the energy condition closest to the color coordinate saturation and chromaticity spatial coordinate origin is sequentially set as the gray balance point of the gradation. It is characterized in that
According to a third aspect of the present invention, in the color calculation method of the color printer according to the first aspect, the three primary colors of yellow, magenta, and cyan having equal chromaticity and the same gradation are overlapped. The tone energy is determined such that the distance between the coordinate point of the color saturation and the chromaticity of the color tone obtained by printing on the space coordinates and the origin of the space coordinates is minimized. In the invention according to claim 4,
A first step of printing a print specimen containing an area from a minimum energy to a maximum energy that can be applied to the printing means;
Yellow, magenta, in the visible region of the printed print specimen,
A second step of measuring the relationship between the spectral reflectance and energy of each of the three primary colors of cyan, a third step of obtaining the n-order approximation of the spectral reflectance for each wavelength as a function of the energy, A fourth step of applying Lambert-Beer's law to the spectral reflectances of the three primary colors and obtaining coordinate values in a rectangular coordinate system using color matching functions; and printing the three primary colors with energy of the same gradation. A fifth step of obtaining, as a correction coefficient, a difference between each measured actual spectral reflectance and each calculated spectral reflectance, and a step of correcting using the correction coefficient as a function of each energy of the three primary colors. The color space coordinates of the color obtained corresponding to the input energy are calculated on the basis of the steps of (6).

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below. FIG. 1 is a flowchart illustrating a processing procedure in a color calculation method in a color printer according to an embodiment of the present invention. Note that the present embodiment is applied to, for example, adjustment (setting) of a gray balance of a sublimation type color printer. FIG. 2 is a diagram showing a print pattern used in the present embodiment, and FIG. 3 is a diagram showing print pulse conditions when determining the number of pulses.

In the present embodiment, as shown in FIG.
For each of the colors M, C and the black (K) color obtained by superimposing them, the entire range from the minimum 1 pulse to the maximum 1020 pulses is divided into 16 substantially equal intervals, and shown in FIG. 2 under each condition. Print the print pattern (step Sa
1). That is, for each of the colors Y, M, and C, a print sample is printed according to the print pattern shown in FIG. 2 under the 17 types of pulse conditions shown in FIG.

Next, using the colorimeter, the above-described step Sa is performed.
The spectral spectrum in the visible region of the print sample printed in step 1 is measured (step Sa2). In the present embodiment, the wavelength between 400 nm and 700 nm is
Measurements are taken at 10 nm intervals.

FIGS. 4 and 5 show the step Sa2 in which the horizontal axis (X axis) is the pulse number and the vertical axis (Y axis) is the spectral reflectance.
It is a figure which shows the measurement result in. Thus, the measurement result in step Sa2 is graphed (step S2).
a3).

Here, FIGS. 4 (a), 4 (b),..., 4 (n) and 4 (o) show wavelengths of 400 nm and 41, respectively.
5 (a), FIG. 5 (b)... FIG. 5 (o), FIG.
(P) indicates wavelengths of 550 nm, 560 nm,.
The case of 90 nm and 700 nm is shown. 4 and 5, the solid line indicates yellow (Y), the broken line indicates magenta (m), and the dashed line indicates cyan (C).

Next, the range of the number of pulses in the measurement result of step Sa2 is defined as region 1 from 0 to 252, region 2 from 124 to 700, and region 3 from 636 to 1020. Divided into Further, the relationship between each spectral reflectance and the number of pulses is approximated by an n-th order regression equation (fifth-order regression equation in the present embodiment) by the least squares method (step Sa4). When this regression equation is expressed by a general equation, it is expressed as follows.

T _Y (r) = A _5r E ⁵ + A _4r E ⁴ + A _3r E ³ + A _2r E ² + A _1r E + A _0r T _M (r) = B _5r E ⁵ + B _4r E ⁴ + B _3r E ³ + B _2r E ² + B _1r E + B _0r T _C (r) = C _5r E ⁵ + C _4r E ⁴ + C _3r E ³ + C _2r E ² + C _1r E + C _0r (1)

In the equation (1), r represents a wavelength, and A, B and C each represent a regression coefficient. E indicates the number of print pulses (energy).
That is, in the present embodiment, since the number of wavelengths is 31, the color is 3, and the area is 3, the number of regression equations is 31 × 3 × 3.

FIGS. 6 and 7 are graphs showing the calculation results in step Sa4. When these FIGS. 6 and 7 are compared with the corresponding FIGS. 4 and 5 described above, it can be seen that the measured values and the regression values almost completely match (FIG. 4A and FIG. wavelength 400 shown in a)
In the case of nm, they do not partially match, but this does not pose a problem in practical use).

Next, the reflected light obtained by superimposing the three colors of Y, M and C is modeled (step Sa5).
FIG. 8 is an explanatory diagram illustrating an example of a state of reflected light when three colors of Y, M, and C are printed.

Here, assuming that the spectral reflectance of each color of Y, M, and C at the wavelength r is T _Y (r), T _M (r), and T _C (r), the spectral reflection of the three-color superimposed printing is Lambert-Beer's law is applicable, and the spectral reflectance is expressed as:

Spectral reflectance at wavelength r = T _Y (r) · T _M (r) · T _C (r) (2) Further, for a color having a spectral reflectance represented by equation (2), The tristimulus values X _F , Y _F and Z _F are calculated using color matching functions as follows.

X _F = ΣT _Y (r) · T _M (r) · T _C (r) · P (r) · x (r) Y _F = ΣT _Y (r) · T _M (r) · T _C (r) · P (r) · y (r) Z F = ΣT Y (r) · T M (r) · T C (r) · P (r) · z (r) ··· (3) where And Σ indicates the sum of the spectral spectra in the visible region, and P
(R) shows the spectral distribution of the illumination light at the wavelength r,
Although it depends on the type of light source, a numerical value unique to the colorimeter is used. Further, x (r), y (r) and z (r) are X, Y or Z color matching functions, respectively.

Of the values necessary for the color mixture calculation using the equation (3), T _Y (r), T _M (r) and T _C (r) are the wavelengths calculated by the regression equation obtained in step Sa3. 400nm ~
The spectral reflectance at 700 nm. Further, x (r), y
(R) and z (r) are "C" defined by the International Commission on Illumination.
IE · 1931 · XYZ color system 10 ° visual field color matching function ”.

Thereafter, the coordinate values in the X, Y, Z color system of the equation (2) are converted into L ^* a ^* b ^* uniform color space coordinates as follows.

(Equation 1)

(Equation 2)

(Equation 3)

FIG. 9 shows actual measured values of a ^* and b ^* (FIG. 9).
(A)) and a calculated value (FIG. 9 (b)). FIG. 10 is a diagram showing an actually measured value and a calculated value of L ^* . next,
The discrepancy between the measured value and the calculated value is corrected by a correction coefficient. Here, a correction coefficient is obtained as described below (step Sa6).

(Equation 4)

Here, SP (...) Is a spectral reflection spectrum, and α means a correction factor, and usually 1 is used. R is a wavelength, and E _Y , E _M and E _C are Y,
M or C indicates the number of pulses, and E _AV indicates the average value of the numbers of Y, M, and C pulses.

FIG. 11 is a diagram showing correction coefficients when α is 1 and the wavelength r of the Y color (yellow) is 410 nm. Here, the obtained corrected count value is regressed by a quintic equation as a function of the number of pulses. In FIG. 11, a thick solid line indicates a correction count value, and a thin solid line indicates a regression value.

FIGS. 12 and 13 show the results of correcting the calculated values shown in FIG. 10 by the equation (5) and comparing the corrected values with the actually measured values. In FIG. 12, FIG. 12 (a) shows measured values and FIG. 12 (b) shows calculated values. Also in these figures, it is recognized that the two coincide.

FIG. 14 is a diagram showing the measured values of L ^* for each of the colors Y, M and C measured in step Sa2.
FIG. 14A shows the Y color, and FIG. 14B shows the M color. FIG. 14C shows C color.

As shown in this figure, the maximum density (L
^* Minimum value) and the minimum density (L ^* maximum value) are determined as a range shown in the figure (step Sa7), the maximum density and the minimum density are divided into 15 equal parts, and the number of pulses of 16 gradations is determined. Is determined (step Sa8), and is shown at the same time.

Here, K colors are printed by superimposing three colors with the number of gradation pulses determined in step Sa8 (step Sa8).
9) This is measured (step Sa10) and graphed (step Sa11).

FIG. 15 is a diagram showing the measured L ^* values by printing three colors in a superimposed manner with the number of gradation pulses determined in step Sa8. The solid line shows the measured value, the broken line shows the calculated value, and An alternate long and short dash line indicates a reset value described later. On the other hand, FIG.
Is a diagram showing similar a ^* and b ^* .

The a shown in FIG.^*And b^*The value of
The target a^*<5 and b ^*<5 is extremely
Judgment that the gray balance is broken
be able to.

Here, the pulse value of each gradation of Y, M and C
Is varied within a range of ± 20 pulses, and all combinations are
(40 × 40 × 40 × 16 ways) K color a^*, B^*And
And L ^*Is calculated. The specific calculation method is as follows.
Spectral spectrum of pulse of each gradation of Y, M, C by the method of 4.
Is calculated by the method of step Sa5.^*, B^*And L
^*Is calculated. However, steps in this course
The correction shown in Sa5 is added (step Sa12).

Next, the number of pulses for minimizing (a ^{* 2} + b ^{* 2} ) ^1/2 and L ^* at each gradation are obtained (step Sa13).
Display a graph. In FIG. 15, L ^* for minimizing (a ^{* 2} + b ^{* 2} ) ^1/2 is indicated by a dashed line as described above. FIG. 17 is a diagram showing a ^* b ^* in this case. According to FIG. 17, the target a ^* <5 and b ^* <
5 is not always satisfied, but it can be said that it is quite close to the target value.

FIG. 18 is a diagram showing pulse values of each floor length of the C color satisfying the condition of the closest approach to the origin obtained in step Sa13. In FIG. 18, there is no inconsistency in the relationship between the gradation and the number of pulses, but in rare cases, a reversal phenomenon occurs in which the number of pulses decreases while the number of gradations increases.

In order to eliminate such extreme contradictions, the plot points are regressed by a quadratic equation, and the number of pulses obtained by substituting the number of gradations into the regression equation is adopted as a reset value (step Sa14). The solid line shown in FIG. 18 is such a quadratic regression curve.

Next, a gradation pattern is printed again with the reset values obtained in step Sa14, and colorimetry is performed (step S14).
a15). The colorimetric result of L ^* in this case is as shown in FIG. 15, and FIG. 19 is a diagram showing an example of the colorimetric result of a ^* b ^* .

In FIG. 19, as a whole, the convergence is closer to the origin than in the diagram shown in FIG. 18. However, usually, the distance from the origin often increases due to the reset value, and the example shown in FIG. An example.

Next, the distance from the origin is L = (a ^{* 2} +
b ^{* 2} ) ^1/2 , and it is compared whether or not this value is equal to or less than a specified value (step Sa16).
It is determined that the gray balance has been achieved. It should be noted that the specified value is not always determined, but includes variations in the manufacture of the color ribbon to be used.

In this embodiment, a^*<5 and b^*<
5 as a condition, L = (5 ^Two+5^Two)^1/2Tona
L is about 7.1, and the value shown in FIG.
Then, this value is almost satisfied. Therefore, step S
Determine the reset value determined in a14 as the final pulse value
Then, the process ends.

On the other hand, in step Sa16 described above, L
Is greater than the specified value, step Sa12
Then, the calculation is repeatedly performed using the data of the spectral reflection spectrum measured in step Sa14.

FIG. 20 is a block diagram showing an example of a specific configuration to which the present embodiment is applied. In FIG. 20, reference numeral 1 denotes a colorimeter for measuring a spectrum of a test pattern, and 2 denotes a data conversion computer for digitally converting a measurement result output from the colorimeter.

Reference numeral 3 denotes a magnetic storage device such as a floppy disk for temporarily storing data output from the data conversion computer, and reference numeral 4 denotes a data calculation computer for calculating a set pulse number based on measured data.

FIGS. 21 (a) and 21 (b) correspond to FIG.
7 is a flowchart showing a rough flow of processing in the configuration shown in FIG. Since the contents of the processing in each step of FIGS. 21A and 21B are the same as those shown in FIG. 1, detailed description will be omitted.

In this case, the data calculation computer 4 shown in FIG. 20 first performs the processing shown in FIG. 21A, and then performs the processing shown in FIG. 21B. Further, the processing shown in FIG. 21B is repeated as necessary.

In this embodiment, as described above, the print density of each color in a color printer is calculated, and for example, a CRT (Cathode Ray Tube: cathode ray tube, cathode ray tube)
Adjust the color consistency with the screen display.

In the above embodiment, the adjustment of the gray balance in the sublimation type color printer has been described by way of example.
The present invention can be applied to all types of color printers, such as an ink jet type or an electrophotographic type, in which a color tone corresponding to input energy is a problem.

The application field of this embodiment is as follows.
Examples include the following: (1) Prediction of colors (L ^* , a ^*, and b ^* values) obtained corresponding to the print pulse energy conditions of Y, M, and C colors. (2) Determination of gradation pulse conditions. (3) Optimization of gray balance. (4) Examination of heat history control method.

[0065]

As described above, according to the present invention, a print sample including an area from the minimum energy to the maximum energy which can be input to the printing means is printed, and the yellow color in the visible area of the printed print sample is printed. , Magenta, and cyan, the relationship between the spectral reflectance and the energy of each of the three primary colors is measured, and the spectral reflectance for each wavelength is approximated by an n-order expression as a function of energy, and the Lambert-Beer spectral reflectance of the three primary colors is calculated. Apply the law of と と も に and calculate the coordinate value of the rectangular coordinate system using the color matching function. The measured spectral reflectance of the color tone obtained by printing the three primary colors with the energy of the same gradation and the spectral reflectance of the color tone obtained by calculation The difference from the ratio is obtained as a correction coefficient, and the correction is performed using the correction coefficient as a function of the energy of each of the three primary colors to calculate the color space coordinates of the color obtained corresponding to the input energy. The energy condition closest to the spatial coordinate origin of the saturation and chromaticity of a color tone obtained by printing three primary colors of yellow, magenta, and cyan with the same gradation energy as the gray balance point of the gradation is defined as the gray balance point of the gradation. Optimize gray balance. Further, coordinate points in spatial coordinates of saturation and chromaticity of a color tone obtained by printing three primary colors of yellow, magenta, and cyan at equal intervals and at the same gradation and superimposed,
Since the gradation energy is determined such that the distance from the origin of the spatial coordinates is minimized, an effect is obtained that a color calculation method in a color printer that can easily and reliably perform color adjustment can be realized.

That is, according to the present invention, the spectral reflection spectra of the three primary colors obtained according to the print energy are faithfully simulated for each color based on the measured values. 3
In calculating the colors obtained by mixing the primary colors, the current color mixing theory, which is the most faithful to the physical phenomenon, is used.

Although a difference occurs between the value obtained from the pure subtractive color mixing theory and the result obtained by actual printing, a correction method using a correction coefficient has been established. Therefore, when the colorimeter having the calculation function performs the processing in the present invention, the color simulation can be performed only by the mechanical operation.

This makes it possible to use a computer or the like to perform all the work conventionally relying on experiments, thereby improving the accuracy of color adjustment and greatly reducing labor and material costs at the time of development. became.

In addition, regarding the gray balance, since the limit of the balance point that can be finally reached can be calculated by calculation, it is possible to effectively avoid entering into an infinite loop which is likely to fall by an experimental method. It will be easier.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating a processing procedure in a color calculation method in a color printer according to an embodiment of the present invention.

FIG. 2 is a print pattern used in the embodiment.

FIG. 3 is a diagram showing print pulse conditions when determining the number of pulses.

FIG. 4 is a diagram showing a result of measuring a spectral spectrum of a print sample with the horizontal axis representing the number of pulses and the vertical axis representing the spectral reflectance.

FIG. 5 is a diagram showing a result of measuring a spectral spectrum of a print sample with the horizontal axis representing the number of pulses and the vertical axis representing the spectral reflectance.

FIG. 6 is a diagram in which the relationship between the spectral reflectance and the number of pulses is approximated by a fifth-order regression equation based on the least squares method and is represented by a graph.

FIG. 7 is a diagram in which the relationship between the spectral reflectance and the number of pulses is approximated by a fifth-order regression equation based on the least squares method and is graphed.

FIG. 8 is an explanatory diagram illustrating an example of a state of reflected light when three colors of Y, M, and C are printed.

FIG. 9 is a diagram showing actual measured values and calculated values of a ^* and b ^* .

FIG. 10 is a diagram showing measured values and calculated values of L ^* .

FIG. 11 is a diagram illustrating correction coefficients when α is 1 and the wavelength r of the Y color is 410 nm.

12 is a diagram illustrating a result of correcting the calculated value illustrated in FIG. 10 and comparing the corrected value with an actually measured value.

13 is a diagram showing a result of correcting the calculated value shown in FIG. 10 and comparing the corrected value with an actually measured value.

FIG. 14 is a diagram showing actual measured values of L ^* for each of the measured colors Y, M, and C.

FIG. 15 is a diagram showing L ^* values measured by printing three colors in a superposed manner with the number of gradation pulses equally dividing the maximum density and the minimum density of each color.

FIG. 16 is a diagram showing a ^* and b ^* measured by printing three colors in an overlapping manner with the number of gradation pulses equally dividing the maximum density and the minimum density of each color.

FIG. 17 is a diagram showing a ^* b ^* that minimizes (a ^{* 2} + b ^{* 2} ) ^1/2 .

FIG. 18 is a diagram showing the number of pulses and L ^* for minimizing (a ^{* 2} + b ^{* 2} ) ^1/2 at each gradation, and showing the pulse value of each floor length of C color that satisfies the condition of closest approach to the origin. It is.

FIG. 19 is a diagram illustrating an example of a colorimetric result of colorimetric a ^* b ^* in a gradation pattern printed with reset values.

FIG. 20 is a block diagram illustrating an example of a specific configuration to which the embodiment is applied.

FIG. 21 is a flowchart showing a rough processing flow in the configuration shown in FIG. 20;

FIG. 22 is a flowchart illustrating a conventional procedure for determining a gradation pulse.

FIG. 23 is a configuration diagram showing an example of the configuration of an evaluation pattern used when determining a gradation pulse in the related art.

FIG. 24 is a diagram showing an example of the relationship between L ^* and energy measured by a colorimeter.

FIG. 25 is a diagram showing an example of measured values of a ^* , b ^*, and L ^* measured by a colorimeter.

FIG. 26 is a diagram showing a measurement result of an evaluation pattern after an energy condition is corrected so that a measurement value is optimized.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Colorimeter 2 Computer for data conversion 3 Magnetic storage device 4 Computer for data operation

Claims (4)

[Claims] A first step of printing a print sample including an area from a minimum energy to a maximum energy that can be input to a printing means; and yellow, magenta, and yellow in a visible area of the printed print sample.
A second step of measuring the relationship between the spectral reflectance and energy of each of the three primary colors of cyan; a third step of obtaining an approximation of the n-th order expression using the spectral reflectance for each wavelength as a function of the energy; A fourth step of applying Lambert-Beer's law to the spectral reflectances of the three primary colors and obtaining coordinate values in a rectangular coordinate system using a color matching function; A fifth step of obtaining, as a correction coefficient, a difference between the measured spectral reflectance of the obtained color tone and the spectral reflectance of the color tone obtained by calculation, and a step of correcting using the correction coefficient as a function of the energy of each of the three primary colors. 6. A color calculation method for a color printer, wherein color space coordinates of a color obtained corresponding to input energy are calculated based on steps 6 and 7. 2. An energy condition closest to a spatial coordinate origin of saturation and chromaticity of a color tone obtained by superimposing and printing the three primary colors of yellow, magenta, and cyan having the same gradation energy, 2. The color calculation method according to claim 1, wherein the gray balance is optimized based on the processing from the first step to the sixth step in order as a gray balance point. 3. A coordinate point in spatial coordinates of chroma and chromaticity of a color tone obtained by superimposing and printing the three primary colors of yellow, magenta, and cyan having equal chromaticity and the same gradation, and the spatial coordinates. 2. The color calculating method according to claim 1, wherein the gradation energy is determined so that a distance from the origin of the color printer becomes minimum. 4. A first step of printing a print sample including a region from a minimum energy to a maximum energy that can be input to a printing means, and a yellow, magenta, and yellow portion in a visible region of the printed print sample.
A second step of measuring the relationship between the spectral reflectance and energy of each of the three primary colors of cyan; a third step of obtaining an approximation of the n-th order expression using the spectral reflectance for each wavelength as a function of the energy; A fourth step of applying Lambert-Beer's law to the spectral reflectances of the three primary colors and obtaining coordinate values in a rectangular coordinate system using a color matching function; A fifth step of obtaining, as a correction coefficient, a difference between each measured actual spectral reflectance and each calculated spectral reflectance, and a step of correcting using the correction coefficient as a function of each energy of the three primary colors. 6. A color calculation method for a color printer, wherein color space coordinates of a color obtained corresponding to input energy are calculated based on steps 6 and 7.