JPH11132849A - Method for correcting colorimetry value and colorimetery machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To output a measurement value by one colorimetry machine after correcting the measurement value to that by another reference colorimetry machine according to a simple correction calculation. SOLUTION: A colorimetry machine 10 outputs a colorimetry value being corrected to a colorimetry value according to another non-contact type colorimetry machine by performing measurement using essentially the same device body 12 as a contact type colorimetry machine. In this case, at least one of primary color constituents C, M, and Y is included, a color chart consisting of a plurality of colors that are adjusted by changing the ratio of at least one constituent in steps is measured by the device body 12 and another colorimetry machine in advance, and the difference of the colorimetry values between both of them is obtained. Further, a correction operation part 32 or the like for correcting the colorimetry value of an arbitrary color being measured by the device body 12 to a colorimetry value according to another colorimetry machine in the above is provided at the device body 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting a colorimetric value and a colorimeter, and more particularly, a colorimetric value which is equivalent to a case where one colorimeter is used and another standard colorimeter is used. The present invention relates to a colorimetric value correction method and a colorimeter which are preferably applied when obtaining the colorimetry.

[0002]

2. Description of the Related Art In recent years, in order to realize color reproduction in an output image by a color image output device such as a multi-color printer or a color printer, the output color is actually measured as a color value. ing.

However, for example, when the same color patch (measurement target) output by a color printer is measured by different spectral colorimeters, the same color patch is measured due to a difference in the spectral method of the colorimeter, a difference in the measurement environment, and the like. In many cases, colorimetric values cannot be obtained. Therefore, if the color to be measured is measured with a different colorimeter (including the case where the measurement environment is different), it cannot be accurately determined whether or not the same color has been reproduced from the obtained colorimetric values. become.

Therefore, in order to accurately determine the reproduction of the same color, it is necessary to perform measurement using the same colorimeter and under the same measurement environment. However, there is a case where measurement cannot be performed using the same colorimeter because the measurement place is different, for example, when a printed matter (color image) newly planned by the development department is printed on site.

As a technique applicable in such a case,
Colorimetric means for measuring the color of the object to be measured to obtain a color value,
A color value correcting means configured by a neural network for correcting the color value from the color measuring means in accordance with a predetermined characteristic to obtain a color value presented by a different color measuring device. Japanese Patent Application Laid-Open No. Hei 6-281501 discloses a technique for performing a correction at a spectral level by performing the analysis of the above and correcting the measured values between different colorimeters.

[0006]

However, in the correction technique disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 6-281501,
In order to correct the color values, complicated calculations are performed using the neural network as described above, so a high-performance large-scale computer is required, and complicated work such as learning is required. There is.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described conventional problems, and corrects a colorimetric value of one colorimeter to a colorimetric value of another colorimeter by a simple correction calculation. It is a first object to provide a colorimetric value correction method capable of performing the following.

Another object of the present invention is to provide a colorimeter capable of correcting a colorimetric value by another colorimeter by a simple correction calculation and automatically outputting the colorimetric value upon measurement. Make it an issue.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a colorimetric value correction method for correcting a colorimetric value by one colorimeter to a colorimetric value by another colorimeter. , Y, and a color chart composed of a plurality of colors adjusted by changing the ratio of at least one component stepwise is measured by the one colorimeter and the other colorimeter, respectively. A colorimetric value difference between the two is obtained, and a colorimetric value of an arbitrary color measured by the one colorimeter is measured by the other colorimeter based on the obtained colorimetric value difference. The first problem has been solved by correcting the color value.

The present invention is a colorimeter which outputs a colorimetric value corrected to a colorimetric value of another colorimeter when measured by the same apparatus main body as one of the colorimeters. Components C, M,
A color chart comprising at least one of Y and a plurality of colors adjusted by changing the ratio of at least one component in a stepwise manner is measured in advance by the apparatus main body and another colorimeter, and is measured by both. Correction means for calculating a color value difference and correcting a colorimetric value of an arbitrary color measured by the apparatus main body into a colorimetric value by the other colorimeter based on the obtained colorimetric value difference; However, the second problem has been solved by being attached to the apparatus main body.

According to the present invention, in the colorimetric value correcting method and the colorimeter, when the color chart is a gray chart created by superimposing the respective primary color components equally, Since the primary color components are evenly contained, the spectral reflectance can be uniformly distributed over the entire visible wavelength range, so that a colorimetric value suitable for correction calculation can be obtained. Correction can be made with high accuracy.

According to the present invention, in the colorimetric value correcting method and the colorimeter, the colorimetric value is a color value comprising three elements, and for each element, a quadratic value is obtained from the colorimetric value difference. When a correction formula is created and the colorimetric value is corrected for each element using the correction formula, an appropriate correction formula can be used for each element, so that the correction can be performed with high accuracy.

According to the present invention, in the colorimeter correcting method and the colorimeter, when the one colorimeter is a contact type and the other colorimeter is a non-contact type, With a simple contact colorimeter, it can be measured as a colorimetric value by a non-contact colorimeter that is usually used as a reference.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram including a block diagram showing a colorimeter according to an embodiment of the present invention.

The colorimeter 10 of the present embodiment includes an apparatus body (substantially the same as one colorimeter) 12 composed of a contact type colorimeter. In the apparatus main body 12, when light from a built-in light source is incident on a sample (color patch) at 45 ° by a ring lens system disposed around the light source, the reflected light in the vertical direction is received by a light receiving unit. (Optical fiber), the received light is split by the diffraction grating, and then the reflected light intensity for each wavelength is measured by the photodiode, and the measured value is input to the color value calculation unit 14 for colorimetry. The value is calculated.

The colorimeter 10 is provided with the device main body 12.
And a correction operation unit 30 for executing an operation for correcting the colorimetric value obtained by the above into a colorimetric value by another non-contact type colorimeter (other colorimeter) not shown. A memory 32 for holding calculation results, data for calculation, and the like;
Data or the like is input to the memory 32 and the operation unit 30
And an input / setting unit 34 for setting a correction condition to be described later, and the whole is housed in a case (not shown) and integrally formed.

The contact colorimeter and the non-contact colorimeter are both spectral colorimeters. A non-contact type colorimeter measures a measurement object at a distance, and can measure under a measurement environment using a standard light source or the like, so that a colorimetric value close to the perception of the human eye can be obtained. However, the whole equipment tends to be large-scale, and the measurement is troublesome. On the contrary,
The contact type colorimeter is easy to carry and easy to handle because it comes in contact with the object to be measured, blocks out ambient light, and emits specific light from the attached light source for measurement. There is a feature that is.

In this embodiment, the correction operation section 30 includes at least one of the primary color components C, M, and Y, and is a color chart composed of a plurality of colors adjusted by changing the ratio of at least one of the components stepwise. Was measured in advance by the apparatus main body 12 and another colorimeter, and the difference between the colorimetric values between the two was determined, and the measurement was performed by the apparatus main body 12 based on the calculated colorimetric value difference. An operation of correcting a colorimetric value of an arbitrary color to a colorimetric value of the other colorimeter is executed. Therefore, when the measurement is performed using the colorimeter 10 based on the contact colorimeter described above, the colorimetric value is automatically corrected to the colorimetric value obtained by the non-contact colorimeter and output.
The value can be displayed on the display unit.

First, a description will be given of a colorimetric value correction formula used in the calculation performed by the correction calculation unit 30 of the colorimeter 10 according to the present embodiment.

A colorimetric value obtained when the same color patch output by a predetermined color printer is measured by the apparatus body 12 constituting the colorimeter of this embodiment and a reference non-contact type colorimeter. Find the difference between At this time, a gray chart, which will be described later, which is generated by superimposing three primary color components C (cyan), M (magenta), and Y (yellow) is prepared as the color patch, and is used for the two colorimetric measurements. 3D color values (XYZ tristimulus values, L * a * b * by CIE (International Commission on Illumination)
Etc.) respectively.

Next, for example, a difference between colorimetric values (color values) measured for each of the X, Y, and Z elements is determined, and the colorimeter (the main unit 1) is measured.
The horizontal axis indicates the color value obtained in 2), and the vertical axis indicates the difference between the measured values with other non-contact colorimeters. Is calculated. Although a specific example will be described later, the approximate curve thus obtained is stored in the memory 32 by the input / setting unit 34 as a correction equation.

Since the above-mentioned approximate curve differs depending on the ink or paper quality used, the difference in ink or paper quality is used as a measurement condition, and an approximate curve (correction formula) is obtained by the above-described method for each different measurement condition. These are similarly stored in the memory 3
2 can be stored. When the measurement is performed, the input / setting unit 34 indicates the measurement condition, and the correction formula corresponding to the condition is read from the memory 32 into the correction calculation unit 30 and set. The correction calculation can be automatically performed.

Therefore, in the present embodiment, when there are a plurality of measurement conditions, one of them is set, and when the color is measured for an arbitrary measurement object by the colorimeter 10, the three-dimensional color value obtained is By performing correction independently for each element using the approximate curve (correction formula), the corrected colorimetric value of the non-contact type colorimeter is output.

Next, the operation of the present embodiment will be described in detail.

FIG. 2 is a flow chart showing a procedure for correcting using color values of XYZ tristimulus values as colorimetric values. For convenience, here, under one certain measurement condition,
A case where the measurement value of the colorimeter B (corresponding to the reference non-contact type colorimeter) is approximately determined from the measurement value of the colorimeter A (corresponding to the device main body 12 which is the contact-type colorimeter). explain.

First, in step 1, a gray chart created by superimposing three primary colors of C, M and Y by a predetermined color printer is output. This gray chart is paper white and C,
It is created with about 10 levels of gradation, including black, which is a combination of solid M and Y colors. FIG. 3 shows an example of a gray chart having 11 levels, together with the ratio of input values when the input values for obtaining solid colors of C, M, and Y are set to 100%.

Next, in step 2, the XYZ tristimulus values are measured by the colorimeter A and the colorimeter B for each gradation of the gray chart, and (Xa, Ya, Za), (Xb,
Yb, Zb). At that time, XYZ was measured in the same manner for the reference white plate, and the Y value of
Assuming 0, the measured values of the gray chart are normalized.

Next, in step 3, the difference between the measured values obtained for each gradation of the gray chart: (Xa-X
b), (Ya-Yb) and (Za-Zb) are obtained. The horizontal axis is the value of each element of (Xa, Ya, Za) of the colorimeter A, and the vertical axis is the difference between the value and the measurement value of the colorimeter B: (X
a-Xb), (Ya-Yb) and (Za-Zb) as
The data is plotted on a graph for each of X, Y, and Z elements. This graph will be described later with a specific example.

Next, in step 4, an approximate curve representing the difference between each of the elements X, Y, Z is obtained from the created graph. Here, a quadratic approximation curve is used. This 2
The following curve shows the difference between the measured values Xa, Ya, and Za measured by the colorimeter A and the colorimetric values measured by the colorimeter B as Dx (Xa),
Assuming that Dy (Ya) and Dz (Za), the following (1) to
It is expressed by equation (3).

[0031] ^{Dx (Xa) = αXa 2 +} βXa + γ ... (1) Dy (Ya) = αYa 2 + βYa + γ ... (2) Dz (Za) = αZa 2 + βZa + γ ... (3)

The values of α, β, and γ are determined by the least squares method for each of the X, Y, and Z elements of the above approximate curve, and correction equations of the following equations (4) to (6) are determined. .

Xa ′ = Xa− (Dx (Xa)) (4) Ya ′ = Ya− (Dy (Ya)) (5) Za ′ = Za− (Dz (Za)) (6)

Thereafter, in step 5, any C, M, Y
The color patch (arbitrary color) obtained by superimposing is measured by the colorimeter A, and the obtained (Xa, Ya, Za) is calculated for each element using the above-described correction formula. (X
a ′, Ya ′, Za ′), it is possible to approximately obtain a measured value when the same patch is measured by the colorimeter B.

In the colorimeter 10 of the present embodiment, the correction formulas (4) to (6) obtained in advance for each of the measurement conditions are stored in the memory 32. By performing the measurement, the correction calculation is executed by the above-described correction formula read by the correction operation unit 30, and the value measured by the colorimeter B is automatically output.

Next, a more specific embodiment will be described.

In this embodiment, PR-704 (trade name, Pho) is used as a non-contact type colorimeter which is a colorimeter B (other colorimeter).
Spectrolino (trade name, GRETA) as a contact type colorimeter which is a colorimeter A (device main body 12)
A case in which the colorimetric value is corrected by using G (manufactured by Company G) will be described as a specific example.

A color chart output by a sublimation type printer is used as a measurement object. When the color chart is measured by a contact type colorimeter A, the measured value is automatically converted to a measured value by a non-contact type colorimeter B. A case in which the output is corrected and output will be described.

First, the gray chart of 11 gradations shown in FIG. 3 is output by a sublimation printer, and the gray chart is measured by a contact type colorimeter A and a non-contact type colorimeter B, respectively. The value is normalized by the above-described reference white, and the difference between the measured values for each gradation is obtained. FIG. 4 is a table showing the measurement results and the errors by both.

FIG. 5 shows an image output by an ink jet printer.
As for the gray chart of the color (11 gradations), as shown in the colorimetric value of the spectral reflectance of each color, the reflectance is substantially averaged over the entire visible wavelength range. It is understood that the use of such a gray chart is effective for performing the calculation.

Next, a graph is created by plotting the difference between the measured value of the contact colorimeter A and the measured value of the non-contact colorimeter B on the horizontal axis and the measured value of the non-contact colorimeter B. In FIG.
Each graph for X, Y, and Z is shown.

From the graph created in this way, a quadratic approximate curve is obtained for the difference between each of the elements X, Y, and Z. The difference between the measured value (Xa, Ya, Za) of the contact type colorimeter A and the measured value of the non-contact type colorimeter B is Dx (Xa), Dy.
(Ya) and Dz (Za), by the least square method,
It can be obtained as in the following equations (1) 'to (3)'.

[0043] ^{Dx (Xa) = - 0.00008Xa 2} + 0.1390Xa -1.9022 ... (1) 'Dy (Ya) = - 0.00010Ya 2 + 0.1046Ya -1.8835 ... (2)' Dz (Za) = 0.00060Za 2 +0 .0323 Za -1.1390… (3) '

Accordingly, the measured values (Xa, Xa,
The correction formula for Ya, Za) is given by (1) 'to
It is obtained by substituting the calculated value of (3) 'into the above equations (4) to (6).

Thereafter, C, M, Y
Output a color patch of 10 ³ , that is, 1000 points, which are different from each other.
(4)-(6), the calculated values of the above-mentioned correction formulas (1) '-(3)' were substituted from (Xa, Ya, Za) measured in (4).
(Xa ', Ya', Za ') was determined using the equation. (Xa, Ya, Za) before correction and (Xa ', Ya) after correction.
', Za') and the color difference between the XYZ tristimulus value and the value (Xb, Yb, Zb) measured by the non-contact colorimeter B were determined. The color difference ΔE _xyz was calculated by the following equation: ΔE _xyz = {(Xa−Xb) ² + (Ya−Yb) ² + (Za−Zb) ² } ^1/2 (7) The results are shown in Table 1 below.

[0046]

[Table 1]

According to Table 1, it can be confirmed that the color difference between the contact type colorimeter and the non-contact type colorimeter is smaller than before correction by using the colorimetric value correction method according to the present embodiment. .

Therefore, in the colorimeter 10 of the present embodiment shown in FIG. 1, the correction formula is stored in the memory 32 and read into the correction operation unit 30 to be read by the apparatus main unit 1.
By performing a correction calculation on the measurement value obtained in Step 2, the measurement value can be automatically output as a measurement value obtained by a non-contact type colorimeter even though the colorimeter is a contact type colorimeter.

According to the colorimetric value correction method of the present embodiment described in detail above, it is possible to reduce errors in colorimetric values when the same object is measured by a plurality of colorimeters. For example, XYZ of a color chart measured with a contact-type colorimeter
From the values, XYZ values measured by a non-contact colorimeter can be approximately calculated. This makes it possible to manage / evaluate the same reference value even when different colorimeters are used, for example, when trying to manage / evaluate printed matter or printer output by colorimetric values.

Further, according to the colorimeter of the present embodiment, the value measured by the non-contact type colorimeter can be automatically output while being a contact type colorimeter. Management / evaluation based on colorimetric values such as printer output can be easily performed.

Although the present invention has been specifically described above, the present invention is not limited to the above-described embodiment, and can be variously modified without departing from the gist thereof.

For example, in the above-described embodiment, the case where the measurement value obtained by the contact type colorimeter is corrected to the measurement value obtained by the non-contact type colorimeter, but the present invention is not limited to this. The direction may be corrected, or the correction may be performed between contact colorimeters having different spectral systems or the like.

The case where the XYZ tristimulus values are used as the color values has been described. However, the present invention is not limited to this.
* B *, L * u * v *, etc.

In the above embodiment, the output from the sublimation type printer is used as the gray chart. However, the output device is not limited, and the graph corresponding to FIG. As shown in FIGS. 7 and 8, respectively, an approximate curve can be obtained in the same manner, so that the present invention is similarly applicable.

Further, a gray chart containing the three primary colors C, M, and Y equally is preferable, but is not necessarily limited to this. At least one of the three primary colors is included, and at least two is included. Any color chart can be used as long as it is a color chart composed of a plurality of colors in which one component ratio is changed stepwise and the rest are constant.

[0056]

As described above, according to the colorimetric value correction method of the present invention, the measurement value of one colorimeter is corrected to the measurement value of another colorimeter by a simple correction calculation. Can be.

According to the colorimeter of the present invention, when an arbitrary color is measured, a colorimetric value equivalent to the value measured by another colorimeter is automatically output by the same simple correction calculation. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a colorimeter according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a procedure of a correction calculation according to the embodiment;

FIG. 3 is a diagram showing an example of a gray chart by a sublimation printer used for creating a correction formula;

FIG. 4 is a chart showing a difference between measured values by a contact colorimeter and a non-contact colorimeter.

FIG. 5 is a diagram illustrating an example of a spectral reflectance of a gray chart;

FIG. 6 is a diagram showing an approximate curve representing a difference in colorimetric values in XYZ when a gray chart is measured by a sublimation printer.

FIG. 7 is a diagram illustrating an approximate curve representing a difference in colorimetric values of XYZ when a gray chart is measured by an inkjet printer.

FIG. 8 is a diagram showing an approximate expression representing a difference in colorimetric values of XYZ when a gray chart is measured by a gravure printing machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Colorimeter 12 ... Device main body 30 ... Correction calculation part 32 ... Memory 34 ... Input / setting part

Claims (8)

[Claims] 1. A colorimetric value correction method for correcting a colorimetric value by one colorimeter to a colorimetric value by another colorimeter, comprising at least one of primary color components C, M, and Y. A color chart composed of a plurality of colors adjusted by changing the ratio of at least one component stepwise is measured by the one colorimeter and another colorimeter, and the difference between the colorimetric values by the two is measured. Calculating, based on the obtained colorimetric value difference, correcting a colorimetric value of an arbitrary color measured by the one colorimetric device to a colorimetric value by the other colorimetric device. Colorimetric correction method. 2. The colorimetric value correction method according to claim 1, wherein the color chart is a gray chart created by equally overlapping each primary color component. 3. The colorimetric value according to claim 1, wherein the colorimetric value is a color value composed of three elements, and for each element, a secondary correction formula is created from the colorimetric value difference, and the correction formula is used. A colorimetric value correction method, wherein the colorimetric value is corrected for each element. 4. The colorimetric value correction method according to claim 1, wherein said one colorimeter is a contact type and said another colorimeter is a non-contact type. 5. A colorimeter which outputs a colorimetric value corrected to a colorimetric value of another colorimeter when measured by an apparatus body substantially the same as that of one colorimeter. , M, Y, including at least one component, a color chart composed of a plurality of colors adjusted by changing the ratio of at least one component stepwise is measured in advance by the apparatus main body and another colorimeter, A colorimetric value difference between the two is obtained, and a colorimetric value of an arbitrary color measured by the apparatus main body is converted to a colorimetric value by the other colorimeter based on the obtained colorimetric value difference. A colorimeter characterized in that correction means for correcting is provided in the apparatus main body. 6. The colorimetric correction method according to claim 5, wherein the color chart is a gray chart created by superimposing the respective primary color components equally. 7. The colorimetric value according to claim 5, wherein the colorimetric value is a color value composed of three elements, and for each element, a secondary correction formula is created from the colorimetric value difference, and the correction formula is used. A colorimetric value correction method, wherein the colorimetric value is corrected for each element. 8. The colorimeter according to claim 5, wherein said colorimeter main body is a contact type, and said another colorimeter is a non-contact type.