JPH0526731A - Photoelectric tint meter - Google Patents

Abstract

PURPOSE:To enable measurement accuracy to be improved by calculating an amount of compensation according to saturation, hue and lightness of a measure ment value when measuring a title item and performing compensation which matches characteristics of an error. CONSTITUTION:In a photoelectric tint meter with a plurality of light-reception systems consisting of optical filters F1-F6 and photoelectric conversion elements P1-P6, a compensation coefficient for obtaining an amount of compensation according to a color element of saturation, hue, and lightness of a plurality of calibration colors which are measured by the light-reception systems is calculated and is stored in a compensation coefficient memory portion 8. Then, an amount of compensation is calculated by using the compensation coefficient and lightness compensation value calculation means 13, 14, and 15 according to the saturation, hue, and lightness of a value which is obtained by measuring an object to be measured and a measurement value is compensated by a means 16 for calculating amount of compensation, thus obtaining a measured value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric colorimeter having a plurality of light receiving systems composed of an optical filter and a photoelectric conversion element, and more particularly to a photoelectric colorimeter which performs correction for accurate color measurement.

[0002]

2. Description of the Related Art Today, there is a demand for a colorimeter capable of easily and quickly measuring the color value of a sample. By the way, regarding the spectral sensitivity of the colorimeter, the International Commission on Illumination (CIE) defines its color matching function, but it is extremely difficult to manufacture a colorimeter having a spectral sensitivity that exactly matches the color matching function. This discrepancy is the main cause of the absolute value error at the time of measurement. Further, even if the same model is used, there is variation in spectral sensitivity, so that an error between devices (hereinafter referred to as instrumental error) occurs.

Conventionally, various methods have been proposed in order to measure the color value of a sample more accurately. For example, by providing multiple calibration points, the color space is divided into multiple areas,
There are two types, one is that the correction coefficient for each area is calculated during calibration and the correction in that area is added to the measured value, and another is that the output of each light receiving system is adjusted by multiplying the sensitivity of the other light receiving system by a constant multiple. Proposed (Japanese Patent Laid-Open No. 62-142239)
Japanese Patent Laid-Open No. 2-45718).

[0004]

Problems to be Solved by the Invention JP-A-62-1422
In the colorimeter described in Japanese Patent Publication No. 39, the correction is completely performed at the calibration point, but the correction effect becomes weaker as the measured value of the sample becomes farther from the calibration point. That is, the accuracy of correction changes depending on the distance between the measured value and the calibration point. To improve this, it is sufficient to increase the number of calibration points and divide the color space into finer areas, but this leads to an increase in cost and an increase in the number of calibration operations.

Further, in the colorimeter described in Japanese Patent Application Laid-Open No. 2-45718, the accuracy of correction does not change depending on the distance between the measured value and the calibration point as described above, but an average effect over the entire color space. Since it is a correction for obtaining the above, it is impossible to perform a complete correction, and the correction accuracy is also low.

The present invention has been made in view of the above,
Provided is a photoelectric colorimeter capable of improving the measurement accuracy and reducing the instrumental error by calculating the hue, saturation, and lightness of a measurement target and calculating the correction amount in consideration of the characteristics of the error. The purpose is to

[0007]

According to the present invention, a plurality of light receiving systems each including an optical filter and a photoelectric conversion element, and at least one of color elements of saturation, hue and lightness based on the outputs of the light receiving systems. On the basis of the color element calculated from the output value of the measurement sample and the correction coefficient, a color element calculation means for calculating one of the two, a correction coefficient storage means for storing a correction coefficient for correcting the output error of the light receiving system, And a correction unit that corrects the output error of the measurement value of the light receiving system (claim 1).

Further, according to the present invention, a plurality of light receiving systems each including an optical filter and a photoelectric conversion element, and at least one of color elements of saturation, hue and lightness are calculated based on the outputs of the light receiving systems. Color element calculating means, error calculating means for measuring a plurality of calibration colors in the light receiving system in the calibration operation, and calculating an output error between the output value and the true value of the calibration colors, and the plurality of calibration color output values. Correction coefficient calculation means for calculating a correction coefficient for calculating the correction amount by the color element based on the plurality of color elements and the output error calculated from, and the sample output value during the measurement of the sample. According to a second aspect of the present invention, there is provided a correction unit that corrects the output error of the light receiving system based on the color element and the correction coefficient.

Further, according to the present invention, there is provided a light receiving system comprising an optical filter and a photoelectric conversion element, and a light receiving system to be corrected for correcting an output error thereof, and a long wavelength light receiving system having a sensitivity in a wavelength range longer than that of the light receiving system to be corrected. Based on the outputs of the wavelength-side light-receiving system, the short-wavelength-side light-receiving system having sensitivity in a shorter wavelength range than the corrected light-receiving system, and the corrected, long-wavelength-side, short-wavelength-side light-receiving system, the saturation and hue A color element calculation means for calculating at least one of the color elements corresponding to the brightness, a correction coefficient storage means for storing a correction coefficient for correcting the output error of the light receiving system to be corrected, and an output value of the measurement sample According to the third aspect of the present invention, there is provided a correction means for correcting the output error of the measured value of the light receiving system to be corrected based on the color element calculated from the above and the correction coefficient.

Further, the present invention is a light receiving system comprising an optical filter and a photoelectric conversion element, and a light receiving system to be corrected for correcting an output error thereof, and a long light receiving system having a sensitivity in a wavelength range longer than that of the light receiving system to be corrected. Based on the outputs of the wavelength-side light-receiving system, the short-wavelength-side light-receiving system having sensitivity in a shorter wavelength range than the corrected light-receiving system, and the corrected, long-wavelength-side, short-wavelength-side light-receiving system, the saturation and hue , A color element calculating means for calculating at least one of the color elements corresponding to the lightness, and a plurality of calibration colors are measured by the three light receiving systems in the calibration operation, and between the output value and the true value of the calibration color. Error calculation means for calculating an output error, and correction for calculating a correction coefficient for calculating a correction amount by a color element based on a plurality of color elements and output errors calculated from the output values of the plurality of calibration colors Coefficient calculation means and the sample output when measuring the sample Based on the correction coefficient computed color elements from the value, the a structure in which a correcting means for correcting the output error of the correcting light-receiving system (claim 4).

According to the present invention, the light receiving system to be corrected is a light receiving system having a spectral sensitivity characteristic y (λ) in a tristimulus value direct reading type photoelectric colorimeter, and the long wavelength side light receiving system is a spectral sensitivity characteristic x.
In the light receiving system having (λ), the light receiving system on the short wavelength side has the spectral sensitivity characteristic z (λ) (claim 5).

[0012]

According to the present invention having the above-described structure, the color element is calculated by the color element calculation means based on the output of the light receiving system, and the correction means is based on the correction coefficient stored in the correction coefficient storage means and the color element. Thus, the output error of the measured value of the light receiving system is corrected.

According to a second aspect of the invention, based on the outputs of the plurality of light receiving systems, the error calculating means calculates the output error between the plurality of calibration color output values and the true value of the calibration color, and the color element is calculated. A plurality of color elements of the calibration color are calculated by the calculation means, and a correction coefficient is calculated by the correction coefficient calculation means based on the plurality of color elements and the output error. Further, the color element of the sample is calculated by the color element calculation means, and the output error of the light receiving system is corrected by the correction means based on the correction coefficient and the color element of the sample.

According to the third aspect of the invention, the color element of the measurement sample is calculated by the color element calculating means based on the outputs of the light receiving system to be corrected, the long wavelength side and the short wavelength side, and is stored in the correction coefficient storing means. The correction means corrects the output error of the measured value of the light receiving system to be corrected based on the stored correction coefficient and the color element.

According to a fourth aspect of the present invention, the error calculating means calculates the difference between the output value of a plurality of calibration colors and the true value of the calibration color based on the outputs of the corrected, long wavelength side and short wavelength side light receiving systems. Of the calibration color is calculated by the color element calculation means, and the correction coefficient is calculated by the correction coefficient calculation means on the basis of the plurality of color elements and the output error. Further, the color element of the sample is calculated by the color element calculating means, and the output error of the light receiving system to be corrected is corrected by the correcting means based on the correction coefficient and the color element of the sample.

According to a fifth aspect of the invention, a light receiving system having a spectral sensitivity characteristic y (λ) and a light receiving system having a spectral sensitivity characteristic x (λ) and a spectral sensitivity characteristic z in a tristimulus value direct reading type photoelectric colorimeter are provided. Based on the output from the light receiving system having (λ), the error calculation means calculates the output error between the output values of the plurality of calibration colors and the true value of the calibration color, and the color element calculation means calculates the plurality of calibration colors. Are calculated, and the correction coefficient is calculated by the correction coefficient calculation means based on the plurality of color elements and the output error. Further, the color element calculation means calculates the color element of the sample, and the correction means corrects the output error of the light receiving system having the spectral sensitivity characteristic y (λ) based on the correction coefficient and the color element of the sample.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a photoelectric colorimeter according to the present invention. F1 to F6 are filters, and P1 to P6 are photoelectric conversion elements such as photodiodes. Light receiving systems F1P1 to F6P6 are formed by combining these filters and photoelectric conversion elements.

The light receiving systems F1P1 to F3P3 are light receiving systems for measuring the sample 1 (measurement object), and are arranged so that the reflected light from the sample 1 of the light source 2 enters. Each of these light receiving systems is x (λ) y (λ) z defined by CIE.
It has a spectral sensitivity characteristic that approximates (λ).

The light receiving systems F4P4 to F6P6 are light receiving systems for monitoring the fluctuation of the light source 2 and are arranged so that the light from the light source 2 directly enters (the reflected light from the sample 1 does not enter). There is. These F4P4 to F6P6 have the same spectral sensitivity characteristics as the light receiving systems F1P1 to F3P3.

Reference numeral 3 is a current-voltage conversion circuit for converting each output current of the light receiving systems F1P1 to F6P6 into a voltage.
Reference numeral 4 is an A / D conversion circuit for converting the output voltage of the current-voltage conversion circuit 3 into a digital value.

Reference numeral 5 denotes a first arithmetic unit, which is a light receiving system F1P1 to F3.
The output data from P3 and the light receiving systems F4P4 to F6P6 are taken to have the same sensitivity characteristic, and the influence ratio of the light source fluctuation is removed by taking the ratio of the two. Further, the first calculation unit 5 converts those data into tristimulus values XYZ. Reference numeral 7 denotes the tristimulus value XYZ obtained by the first calculation unit 5 as L * a * b *.
Is a second calculation unit for converting into a color space such as. This color space conversion is performed based on the color space conversion formula stored in the color information storage unit 6.

Reference numeral 9 denotes a correction calculation unit for making a correction which will be described later.
It has a saturation calculation means 10, a hue calculation means 11 and a lightness calculation means 12 for calculating each color element of saturation, hue and lightness from the output of the second operation unit 7. Furthermore, the above 10, 11, 1
Saturation correction value calculating means 13, hue correction value calculating means 14 for calculating correction values for saturation, hue, and lightness from the respective outputs of No. 2 and the correction coefficients obtained in advance stored in the correction coefficient storage section 8; It has a brightness correction value calculation means 15. Then, the correction amount calculation means 16 calculates the correction amount from each correction value and corrects the measured values X, Y, Z obtained by the first calculation section 5. Reference numeral 17 denotes a display unit for displaying the measured value as the measurement result obtained by the correction calculation unit 9.

Reference numeral 18 is a control unit for controlling the operation of the photoelectric colorimeter in a centralized manner, and is composed of, for example, a microcomputer. A keyboard 19 for inputting various data necessary for measurement is connected to the control unit 18. Two
1 is driven and controlled by the control unit 18 to turn on and off the light source 2.

The controller 18 may store the calculated correction coefficient instead of the program for calculating the correction coefficient.

Next, the principle of calculating the correction amount of the present invention will be described with reference to the drawings. FIG. 4 is a graph showing the error between the spectroscopic sensor of the photoelectric colorimeter and the color matching function. FIG. 5 shows the spectral reflectance characteristics of a highly saturated color target.
FIG. 6 is a graph showing an error that occurs when the color chart of FIG. 5 is measured using the light receiving system of FIG.

As can be seen from FIG. 6, the error appears on the long wavelength side of the spectroscopic sensor in red, on the medium long wavelength side of the spectroscopic sensor in yellow, and on the short wavelength side of the spectroscopic sensor in cyan.
Thus, the error is closely related to the change in color, that is, the change in hue.

FIG. 7 is a graph in which the vertical axis represents the error when measuring a plurality of color targets with a photoelectric colorimeter and the horizontal axis represents the hue of the sample. It should be noted that the quadrangle in the drawing indicates the magnitude of the saturation of the color target, and the larger the quadrangle, the greater the saturation of the sample. From FIG. 7, the magnitude of the error is the saturation,
It can be seen that it changes depending on the hue.

It is well known that the error increases as the saturation increases. Therefore, in order to clarify the relationship between the error and the saturation, a graph obtained by rewriting FIG. 7 with the value KC obtained by dividing the error by the saturation as the vertical axis is shown in FIG. KC = Error / Saturation (1) From FIG. 8, KC is not affected by saturation if the hue is the same,
It can be seen that they have almost the same KC and change like a cubic curve as the hue changes.

In FIG. 8, the measured values with constant brightness are displayed.
FIG. 9 is a graph showing the same contents as in FIG. 8 for each of the four brightness levels. It can be seen from FIG. 9 that the higher the lightness is, the larger the error is, and that the characteristics of KC with respect to the saturation and the hue are not affected even if the lightness changes.

FIG. 10 is a graph obtained by rewriting FIG. 9 with the vertical axis representing the value KL obtained by dividing KC by the lightness. KL = KC / lightness (2) From FIG. 10, it can be seen that KL does not change even if the lightness changes.

Since KL changes with the hue, if the function is F, it can be expressed by the following equation. KL = K1 × F (hue + K2) (K1 and K2 are coefficients) (3) From equations (2) and (3), KC = K1 × F (hue + K2) × lightness (4) (1), ( From equation (4), error = K1 × F (hue + K2) × lightness × saturation (5) As described above, the error of the photoelectric colorimeter can be expressed by using the saturation, hue, and lightness. . This means that the error can be corrected by using the saturation, hue, and brightness.

Since the influences on the errors of saturation, hue and lightness are independent of each other, each correction function can be described independently. When the correction formula is G (saturation, hue, lightness), the saturation correction function is C (saturation), the hue correction function is H (hue), and the lightness correction function is L (lightness), the following formula Can be expressed as G (saturation, hue, lightness) = C (saturation) x H (hue) x L (lightness) ... (6) C (saturation) = KC1 x saturation + KC2 ... (7) H (hue) = KH1 × Hue ³ + KH2 × Hue ² + KH3 × Hue + KH4 (8) L (lightness) = KL1 × lightness + KL2 (9) (KC1, KC2, KH1, KH2, KH3, KH4, KL1 and KL2 are correction factors) C ( Saturation), L (lightness) correction coefficient, KC1, KC2, KL
1 and KL2 are added to obtain a better correction effect.
Further, the reason that the cubic polynomial is used for the H (hue) correction function is to obtain a better correction effect.

C (saturation), L (brightness), H (hue)
The expression used for is not particularly limited, and an appropriate expression such as a trigonometric function, an exponential function, a polynomial can be used.

Next, the tristimulus value X, measured with a photoelectric colorimeter,
A procedure for obtaining X _C , Y _C , and Z _C by correcting Y and Z will be described with reference to FIGS. 2 and 3. Here, a procedure for obtaining Y _C from Y will be described as an example.

First, the procedure for obtaining the above-mentioned correction coefficient will be described with reference to the flowchart of FIG. First, a plurality of appropriate calibration colors are measured, and the error of the measurement value with respect to the calibration color, that is, the amount to be corrected is calculated from the obtained measurement value and the true value of the calibration color (# 1, # 2). . However, the correction amount =
True value-measured value. If the errors between the true values of the calibration colors 1 to N and the measured values are X _K , Y _K , and Z _K , respectively, for each calibration color, (X ₁ , Y ₁ , Z ₁ ), ………, (X _N , Y _N , Z _N ) is obtained. Also, the saturation, hue, and lightness of the calibration color are calculated (# 3). Therefore, (C * ₁ , H ° ₁ , L * ₁ ), ..., (C * _N , H ° _N , L * _N ) is obtained.

Then, in the equation (6), X _K , Y _K , Z _K and C
Substitute * _K , H ° _K , and L * _K. For example, the description of Y is as follows. _{Y 1 = G (C * 1} , H ° 1, L * 1) Y 2 = G (C * 2, H ° 2, L * 2) ......... ......... Y N = G (C * N, H ° _N , L * _N ) Correction coefficients (KC1, KC2, KH1, KH2, K) from these equations and the above equations (7) to (9) by an appropriate method such as the least squares method.
H3, KH4, KL1, KL2) are calculated (# 4). In addition, X,
A correction coefficient is similarly calculated for Z. Subsequently, the determined correction coefficients are stored in the correction coefficient storage unit 8 (# 5).

Next, the correction of the measured value at the time of actual measurement using this photoelectric colorimeter will be described with reference to the flowchart of FIG. First, the measurement target is measured, and the first calculation unit 5 calculates the tristimulus values X, Y, and Z (# 11, # 12). Next, the calculated tristimulus values X, Y, and Z are converted into L * a * b * by the second operation unit 7 (# 13), and the saturation calculation unit 10 and the hue calculation unit 1 are further converted.
1 and the lightness calculation means 12 obtain the saturation (C *), the hue (H °), and the lightness (L *) (# 14). Next, the correction factors prepared in advance (KC1, KC2, KH1, KH2, K
(H3, KH4, KL1, KL2) are read from the correction coefficient storage unit 8 (# 15).

At # 16, the saturation correction value calculating means 13 and the hue are calculated using these correction coefficients and the saturation (C *), hue (H °) and lightness (L *) obtained at # 14. The correction value calculation unit 14 and the brightness correction value calculation unit 15 perform the correction calculation shown in the following formula. C (C *) = KC1 × C * + KC2 (10) H (H °) = KH1 × H ° ³ + KH2 × H ° ² + KH3 × H ° + KH4 (11) L (L *) = KL1 × L * + KL2 (12) Further, the correction amount calculating means 16 performs the correction calculation shown in the following equation. G (C *, H °, L *) = C (C *) × H (H °) × L (L *) (13) Y _C = Y + G (C *, H °, L *) (14) The correction value Y _C of the tristimulus value Y is obtained as described above.

Similarly, correction calculation is performed for the tristimulus values X and Z to obtain the correction values X _C and Z _C.

Subsequently, the tristimulus values X _C , Y _C and Z _C are L
The value of * a * b * is converted to L _C *, a _C *, b _C * (# 1
7) is displayed on the display unit 17 (# 18).

By performing the correction as described above, the error of the photoelectric colorimeter can be corrected.

Although the L * a * b * space has been described as an example here, the present invention can be applied to any color space in which saturation, hue, and lightness can be calculated. Further, since the present invention relates to a photoelectric color correction method, its input form is not particularly limited. For example, the first calculation unit 5
Instead of the output of, the color data from another system may be input. Alternatively, a device without a light source may be used, in which light from a measurement sample is directly incident and measurement is performed.

Further, in this embodiment, the correction amount is obtained from the three values of saturation, hue and lightness.
When the lightness is constant or almost constant, the correction amount may be calculated only by the saturation. Further, when the saturation and lightness of the measurement target are constant or almost constant, the correction amount may be calculated using only the hue. Further, when the saturation and hue of the measurement target are constant or almost constant, the correction amount may be calculated only by the lightness. At this time, the correction amount calculating means may simply add the correction value to the obtained measurement value.

Further, when the lightness of the object to be measured is constant or almost constant, the correction amount may be calculated only by the saturation and the hue. Further, when the saturation of the measurement target is constant or almost constant, the correction amount may be calculated only by the hue and the lightness.
Further, when the hue to be measured is constant or almost constant, the correction amount may be calculated only by the brightness and the saturation.

Next, a second embodiment of the present invention will be described with reference to the drawings. The same parts as those in the first embodiment are designated by the same reference numerals, and the description of their operation will be omitted. FIG. 11 is a block diagram showing an embodiment of the photoelectric colorimeter according to the present invention. F11 to F20 are filters,
P11 to P20 are photoelectric conversion elements such as photodiodes. 10 light receiving systems F11P by each combination
11 to F20P20 are formed. Light receiving system F11P1
1 to F15P15 are light receiving systems for measuring the sample 1, and are arranged so that the reflected light from the sample 1 of the light source 2 enters. The light receiving systems F16P16 to F20P20 are
It is a light receiving system for monitoring the fluctuation of the light source 2, and is arranged so that the light of the light source 2 directly enters.

The light receiving systems F12P12 to F14P14 are light receiving systems X, Y and Z having spectral sensitivity characteristics approximate to the color matching function x (λ) y (λ) z (λ). F11P1
Reference numeral 1 is a light receiving system X'having a sensitivity on the long wavelength side of the light receiving system X, and F15P15 is a light receiving system Z'having a sensitivity on the short wavelength side of the light receiving system Z. FIG. 14 shows these five sensitivity characteristics. The light receiving systems F16P16 to F20P20 have the same spectral sensitivity characteristics as the light receiving systems F11P11 to F15P15, respectively.

Reference numeral 9 denotes a correction operation unit for making a correction. From the output of the second operation unit 7, a value corresponding to saturation, a value corresponding to hue,
Saturation equivalent calculation means 10 'for calculating a value corresponding to lightness,
It has a hue equivalent calculation means 11 'and a lightness equivalent calculation means 12'. Further, a saturation-equivalent correction for calculating a correction value corresponding to the saturation, the hue, and the lightness from the respective outputs 10 ', 11' and 12 'and the previously obtained correction coefficients stored in the correction-coefficient storage unit 8. It has a value calculation means 13 ', a hue equivalent correction value calculation means 14' and a lightness equivalent correction value calculation means 15 '. Then, the correction amount calculation means 16 calculates the correction amount from each correction value and corrects the measured values X, Y, Z, X ', Z'obtained by the first calculation section 5. .

Next, the principle of calculating the correction amount of the present invention will be described. The present invention performs correction by utilizing the fact that an error can be expressed by saturation, hue and lightness.
The reason why the error can be expressed by saturation, hue, and brightness is that the error changes depending on how the spectral characteristics of the measurement target are applied to the spectral distribution of the error of the light receiving system (the inclination of the spectral characteristics of the measurement target with respect to the spectral characteristics of the light receiving system). Because it does.

However, the saturation, hue, and lightness are values calculated from the tristimulus values XYZ centering on Y in order to match the sensitivity of the human eye, and the light receiving systems X and Z sandwiching the light receiving system Y are used. It can be said that the value expresses how the spectral characteristic of the measurement target is applied to the light receiving system Y. Therefore, the correction based on the saturation, hue, and lightness of the first embodiment is more effective for Y than for light receiving systems X and Z. Therefore, in order to obtain the same effect as Y for the light receiving systems X and Z, X and Z
It suffices if each has a light receiving system with sensitivity on both sides.

In the second embodiment, a long wavelength side sensitivity X'is provided on the long wavelength side of the light receiving system X, and values corresponding to saturation, hue and lightness are calculated from the outputs of the light receiving systems X ', X, Y. Then, the light receiving system X is corrected by using the saturation equivalent, the hue equivalent, and the brightness equivalent. The same applies to the light-receiving system Z. A light-receiving system Z'having a sensitivity on the short wavelength side of Z is provided, and saturation, hue, and lightness are calculated from the outputs of Y, Z, Z ', and Z Make a correction. FIG. 14 shows the sensitivity characteristics of the five light receiving systems X'to Z '.

Next, a correction method in the photoelectric colorimeter having the above five light receiving systems will be described. Tristimulus value Z as an example
Figure 1 shows the procedure for correcting (measured value) to obtain Z _C.
2, it demonstrates using FIG.

First, the procedure for obtaining the above-mentioned correction coefficient will be described with reference to the flowchart of FIG. at first,
A plurality of suitable calibration colors are measured, and the error with respect to Y, Z, Z ', that is, the amount to be corrected is calculated from the obtained measured values and the true values of the calibration colors (# 21, # 22). Calibration color 1
The error between the true value of N and its measured value is Y _K , Z _K ,
'When _K, for each calibration color _{(Y 1, Z 1, Z} ' Z 1), ........., (Y N, Z N, Z 'N) is obtained. Further, the saturation equivalent, the hue equivalent, and the brightness equivalent of the calibration color are calculated (# 23). Therefore, (C ₁ , H ₁ , L ₁ ), ..., (C _N , H _N , L _N ) is obtained.

Then, according to the equations (6) to (9), Y, Z,
Each correction coefficient for Z'is determined (# 24). For example, referring to Z, the following equation is obtained from the definition. _{Z 1 = G (C 1,} H 1, L 1) Z 2 = G (C 2, H 2, L 2) ......... ......... Z N = G (C N, H N, L N) of The correction coefficients (KC11, KC12, KH11, KH1) are calculated from the equations and the equations (6) to (9) by an appropriate method such as the least square method.
2, KH13, KH14, KL11, KL12) are calculated.

The same procedure is applied to X and Y.
The correction coefficient is calculated using equations (6) to (9). Subsequently, the determined correction coefficients are stored in the correction coefficient storage unit 8 (#
25).

Next, correction of the measured value at the time of actual measurement using this photoelectric colorimeter will be described with reference to the flowchart of FIG. First, the measurement target is measured, and the first calculation unit 5 measures the tristimulus values X ′, X,
Y, Z and Z'are calculated (# 31, # 32). Next, the calculated tristimulus values X ′, X, Y, Z, Z ′ are converted by the second operation unit 7 into L * a * b * color difference space values (# 3
3) Further, the saturation equivalent calculation means 10 ', the hue equivalent calculation means 11', and the brightness equivalent calculation means 12 'obtain saturation equivalent (C), hue equivalent (H), and brightness equivalent (L) (# 3).
4).

Next, the correction coefficient (KC1
1, KC12, KH11, KH12, KH13, KH14, KL11, KL1
2) is read from the correction coefficient storage unit 8 (# 35).

At # 36, these correction coefficients and the saturation equivalent (C), hue equivalent (H) and lightness equivalent (L) obtained at # 34 are used to calculate the saturation equivalent correction value calculating means 13 '. The correction calculation shown in the following equation is performed by the hue-equivalent correction value calculation means 14 'and the lightness-equivalent correction value calculation means 15'. C (C) = KC11 × C + KC12 ... (10 ') H (H) = KH11 × H 3 + KH12 × H 2 + KH13 × H + KH14 ... (11') L (L) = KL11 × L + KL12 ... (12 ') further The correction amount calculating means 16 performs the correction calculation shown in the following equation. G (C, H, L) = C (C) × H (H) × L (L) ... (13 ') Z C = Z + G (C, H, L) ... (14' to) above Then, the correction value Z _C of the tristimulus value Z is obtained.

The tristimulus values X and Y are similarly corrected. In the case of X, the X filter is the spectral sensor to be corrected, the X'filter is the long wavelength spectral sensor, the Y filter is the short wavelength spectral sensor, and in the case of Y, the Y filter is the spectral sensor to be corrected, X Using the filter as the long wavelength side spectroscopic sensor and the Z filter as the short wavelength side spectroscopic sensor, the correction calculation is performed in the same manner as in the case of Z, and the correction values X _C and Y _C are obtained.

Subsequently, the tristimulus values X _C , Y _C and Z _C are L
* A * b * is converted into values L _C *, a _C *, b _C * in the color-difference space (# 37), and the converted measurement result is displayed as it is or in another display form on the display unit 17. (# 3
8).

By performing the correction as described above, the error of the photoelectric colorimeter can be corrected.

Although the L * a * b * space has been described as an example here, the present invention can be applied to any color space in which saturation, hue, and lightness can be calculated. Further, since the present invention relates to a correction method for a photoelectric colorimeter, its input form is not particularly limited. For example, color data from another system may be input instead of the output of the first calculation unit 5. Alternatively, a device without a light source may be used, in which light from a measurement sample is directly incident and measurement is performed.

In this embodiment, the correction amount is obtained from three values corresponding to saturation, hue, and lightness. However, when the hue and lightness of the object to be measured are constant or almost constant, The correction amount may be calculated only by the degree equivalent. Further, when the saturation equivalent and the brightness equivalent of the measurement object are constant or almost constant, the correction amount may be calculated only by the hue equivalent. Further, when the saturation equivalent and hue equivalent of the measurement object are constant or almost constant, the correction amount may be calculated only by the brightness equivalent. At this time, the correction amount calculating means may simply add the correction value to the obtained measurement value.

When the lightness corresponding to the measurement target is constant or almost constant, the correction amount may be calculated only by the saturation and the hue. Further, when the saturation equivalent of the measurement object is constant or almost constant, the correction amount may be calculated only by the hue equivalent and the brightness equivalent. Further, when the hue equivalent of the measurement target is constant or almost constant, the correction amount may be calculated only by the lightness equivalent and the saturation equivalent.

In this embodiment, the X, Y, and Z filters whose characteristics are fixed have been described. However, in addition to this, it is effective for three filters arranged spectrally continuously. is there. For example, it can be applied to a filter of a measuring instrument in an infrared region or an ultraviolet region, or an individual filter of a spectrocolorimeter.

[0065]

As is apparent from the above embodiments, the present invention is based on a plurality of light receiving systems each including an optical filter and a photoelectric conversion element, and based on the outputs of the light receiving systems, the colors of saturation, hue and lightness. A color element calculation means for calculating at least one of the elements, a correction coefficient storage means for storing a correction coefficient for correcting the output error of the light receiving system, a color element calculated from the output value of the measurement sample, and Since the correction means for correcting the output error of the measurement value of the light receiving system is provided on the basis of the correction coefficient, the correction amount of the measurement value is calculated according to the characteristic of the error. realizable. Further, unlike the conventional case, the measurement accuracy does not change depending on the distance from the calibration point.

Further, according to the present invention, a plurality of light receiving systems each including an optical filter and a photoelectric conversion element, and at least one of color elements of saturation, hue and lightness are calculated based on the outputs of the light receiving systems. Color element calculating means, error calculating means for measuring a plurality of calibration colors in the light receiving system in the calibration operation, and calculating an output error between the output value and the true value of the calibration colors, and the plurality of calibration color output values. Correction coefficient calculation means for calculating a correction coefficient for calculating the correction amount by the color element based on the plurality of color elements and the output error calculated from, and the sample output value during the measurement of the sample. Since the correction means for correcting the output error of the light receiving system is provided on the basis of the color element and the correction coefficient, the correction amount of the measurement value is calculated according to the error characteristic, so that the photoelectric colorimeter with high measurement accuracy is provided. Can be realized. Further, unlike the conventional case, the measurement accuracy does not change depending on the distance from the calibration point.

Further, according to the present invention, there is provided a light receiving system comprising an optical filter and a photoelectric conversion element, and a light receiving system to be corrected for correcting an output error thereof and a long light receiving system having a sensitivity in a wavelength range longer than that of the light receiving system to be corrected. Based on the outputs of the wavelength-side light-receiving system, the short-wavelength-side light-receiving system having sensitivity in a shorter wavelength range than the corrected light-receiving system, and the corrected, long-wavelength-side, short-wavelength-side light-receiving system, the saturation and hue , A color element calculating means for calculating at least one of the lightness color elements, a correction coefficient storing means for storing a correction coefficient for correcting the output error of the light receiving system to be corrected, and a calculation from the output value of the measurement sample Based on the corrected color element and the correction coefficient, since the correction means for correcting the output error of the measured value of the light receiving system to be corrected is provided, the correction amount of the measured value is calculated according to the error characteristic. A photoelectric colorimeter with high measurement accuracy can be realized. Further, unlike the conventional case, the measurement accuracy does not change depending on the distance from the calibration point.

Further, according to the present invention, there is provided a light receiving system comprising an optical filter and a photoelectric conversion element, and a light receiving system to be corrected for correcting the output error thereof and a long light receiving system having a sensitivity in a wavelength range longer than that of the light receiving system to be corrected. Based on the outputs of the wavelength-side light-receiving system, the short-wavelength-side light-receiving system having sensitivity in a shorter wavelength range than the corrected light-receiving system, and the corrected, long-wavelength-side, short-wavelength-side light-receiving system, the saturation and hue , A color element calculating means for calculating at least one of the color elements corresponding to the lightness, and a plurality of calibration colors are measured by the three light receiving systems in the calibration operation, and between the output value and the true value of the calibration color. Error calculation means for calculating an output error, and correction for calculating a correction coefficient for calculating a correction amount by a color element based on a plurality of color elements and output errors calculated from the output values of the plurality of calibration colors Coefficient calculation means and the sample output when measuring the sample Since the correction means for correcting the output error of the light receiving system to be corrected is provided based on the color element calculated from the value and the correction coefficient, the correction amount of the measurement value is calculated according to the error characteristic. A photoelectric colorimeter with high measurement accuracy can be realized. Further, unlike the conventional case, the measurement accuracy does not change depending on the distance from the calibration point.

In the present invention, the light receiving system to be corrected is a light receiving system having a spectral sensitivity characteristic y (λ) in a tristimulus value direct reading type photoelectric colorimeter, and the long wavelength side light receiving system is a spectral sensitivity characteristic x.
Since the light receiving system having (λ) is the light receiving system having the spectral sensitivity characteristic z (λ), the light receiving system on the short wavelength side can be applied to a generally widely used tristimulus value direct reading photoelectric colorimeter. It is possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of a photoelectric colorimeter according to the present invention.

FIG. 2 is a flowchart illustrating a procedure for obtaining a correction coefficient according to the first embodiment.

FIG. 3 is a flowchart illustrating correction of a measurement value during actual measurement according to the first embodiment.

FIG. 4 is a graph showing an error between a spectral sensor of a photoelectric colorimeter and a color matching function.

FIG. 5 is a graph showing a spectral reflectance characteristic of a highly saturated color target.

6 is a graph showing an error that occurs when the color chart of FIG. 5 is measured using the light receiving system of FIG.

FIG. 7 is a graph in which the vertical axis represents the error when measuring a plurality of color targets with a photoelectric colorimeter and the horizontal axis represents the hue of the sample.

FIG. 8 is a graph in which the vertical axis represents the value KC obtained by dividing the error by the saturation.
Is a rewritten graph.

FIG. 9 is a graph showing the same contents as in FIG. 8 for each of four brightness levels.

FIG. 10 is a graph in which FIG. 9 is rewritten with the vertical axis representing a value KL obtained by dividing KC by lightness.

FIG. 11 is a block diagram showing a second embodiment of the photoelectric colorimeter according to the present invention.

FIG. 12 is a flowchart illustrating a procedure for obtaining a correction coefficient according to the second embodiment.

FIG. 13 is a flowchart illustrating correction of measured values during actual measurement according to the second embodiment.

FIG. 14 is a graph showing the characteristics of spectral sensors of X, Y, Z filters and X ′, Z ′ filters.

[Explanation of symbols]

1 sample (measurement target) 2 light sources 3 Current-voltage conversion circuit 4 A / D conversion circuit 5 First computing unit 6 color information storage 7 Second operation unit 8 Correction coefficient storage 9 Correction calculator 10 Saturation calculation means 10 'chroma equivalent calculation means 11 Hue calculation means 11 'hue equivalent calculation means 12 Brightness calculation means 12 'brightness equivalent calculation means 13 Saturation correction value calculation means 13 'Saturation equivalent correction value calculation means 14 Hue correction value calculation means 14 'hue equivalent correction value calculation means 15 Brightness correction value calculation means 15 'Brightness equivalent correction value calculation means 16 Correction amount calculation means 17 Display 18 Control unit 19 keyboard 21 Lighting circuit F1 to F6 filters F11 to F20 filters P1 to P6 photoelectric conversion element P11 to P20 photoelectric conversion element

Claims (5)

[Claims] 1. A plurality of light receiving systems each comprising an optical filter and a photoelectric conversion element, and saturation based on the outputs of the light receiving systems,
Color element calculation means for calculating at least one of hue and lightness color elements, correction coefficient storage means for storing a correction coefficient for correcting an output error of the light receiving system, and calculation from output values of the measurement sample. And a correction unit that corrects an output error of a measurement value of the light receiving system based on the color element and the correction coefficient. 2. A plurality of light receiving systems each comprising an optical filter and a photoelectric conversion element, and saturation based on the outputs of the light receiving systems,
A color element calculating means for calculating at least one of hue and lightness color elements, and a plurality of calibration colors are measured by the light receiving system in the calibration operation, and an output error between the output value and the true value of the calibration color is calculated. Error calculating means for calculating, and a correction coefficient calculating means for calculating a correction coefficient for calculating a correction amount by a color element based on a plurality of color elements and output errors calculated from the plurality of calibration color output values. A photoelectric colorimeter provided with a correction means for correcting an output error of the light receiving system based on a color element calculated from an output value of the sample and the correction coefficient when measuring the sample. 3. A light receiving system composed of an optical filter and a photoelectric conversion element, a light receiving system to be corrected for correcting an output error thereof, and a light receiving system on the long wavelength side having a sensitivity in a wavelength range longer than that of the light receiving system to be corrected. And corresponding to saturation, hue, and lightness based on the outputs of the short-wavelength side light-receiving system having sensitivity in a shorter wavelength range than the corrected light-receiving system and the corrected, long-wavelength side, short-wavelength side light-receiving system. Color element calculating means for calculating at least one of the color elements, a correction coefficient storing means for storing a correction coefficient for correcting the output error of the light receiving system to be corrected, and an output value of the measurement sample. Based on the color element and the correction coefficient,
A photoelectric colorimeter, comprising: a correction unit that corrects an output error of a measured value of the light receiving system to be corrected. 4. A light receiving system including an optical filter and a photoelectric conversion element, a light receiving system to be corrected for correcting an output error of the light receiving system, and a long wavelength side light receiving system having sensitivity in a wavelength range longer than that of the light receiving system to be corrected. And corresponding to saturation, hue, and lightness based on the outputs of the short-wavelength side light-receiving system having sensitivity in a shorter wavelength range than the corrected light-receiving system and the corrected, long-wavelength side, short-wavelength side light-receiving system. Color element calculating means for calculating at least one of the color elements, and a plurality of calibration colors are measured by the three light receiving systems in the calibration operation, and an output error between the output value and the true value of the calibration color is calculated. Error calculating means, and a correction coefficient calculating means for calculating a correction coefficient for calculating the correction amount by the color element based on the plurality of color elements and the output error calculated from the output values of the plurality of calibration colors. When measuring a sample, it is calculated from the output value of the sample. And a correction unit that corrects an output error of the light receiving system to be corrected based on the color element and the correction coefficient. 5. The light receiving system to be corrected is a light receiving system having a spectral sensitivity characteristic y (λ) in a tristimulus value direct reading type photoelectric colorimeter, and the long wavelength side light receiving system is a light receiving system having a spectral sensitivity characteristic x (λ). 5. The photoelectric colorimeter according to claim 4, wherein the light receiving system on the short wavelength side is a light receiving system having a spectral sensitivity characteristic z (λ).