JPH10142057A - Color discrimination sensitivity measurement device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To obtain color discrimination sensitivity characteristics with high accuracy using a small number of object surface color samples. SOLUTION: A plurality of samples of an object surface color are generated, and a color difference is measured (100, 102). Sensitivity ratios of adjacent two-color direction series are obtained from measured values measured from the operator's psychological experiment (104, 106). Based on the ratios, the entire color space is maintained while maintaining consistency using the measured color difference. The sensitivity ratio is corrected so as to obtain uniform sensitivity (108 to 112). The corrected sensitivity ratio for each color direction sequence is interpolated so as to be spatially continuous, and a color discrimination sensitivity characteristic is obtained (114, 116).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color discrimination sensitivity measuring apparatus, and more particularly to a color discrimination sensitivity measuring apparatus for measuring the sensitivity when measuring a difference in color.

[0002]

2. Description of the Related Art Quality inspection and quality control are important tasks for maintaining industrial products at a constant appearance quality. For example, in the molding of resin products with colors, even under the same molding conditions, the appearance of the finish may differ greatly due to slight changes in temperature, humidity, and the like. Further, when one molded product having the same color but different materials is connected to create one product, it is necessary to reduce the difference between adjacent colors so as not to make the user feel uncomfortable. As described above, in order to stably supply a product of high color quality, a management called “color matching” for evaluating the color of the article and the reference color based on the visual evaluation judgment of the operator (expert) is implemented. I have.

However, the judgment by the operator is
Since the guidelines for color correction are not quantified, the work of color correction has been inefficient and costly. In addition, the evaluation value may be unstable depending on the environment such as the time, place, and situation evaluated by the operator, the physical condition and mood at that time, and the evaluation value is unstable.

[0004] When an operator performs a visual evaluation, it
The entire color space is used for quantitative measurement and evaluation.
The distance between the perception and the distance in the space
There is a uniform color space. As an example, CIE (International Commission on Illumination)
The color space recommended by the member committee) is highly versatile and
It is a color space that can be used effectively. Two in this color space
The color difference between the object colors is generally the lightness index L^*And perception
Chromaticity (hereinafter referred to as chromaticity) a^*, B^*Using the three attributes
Expressed CIELAB color difference formula and lightness index L ^*, Chromaticity
u^*, V^*CIELUV color expressed using three attributes
It is calculated using the difference equation. To find such a color difference
The other color difference formulas are
Dams Nickerson color difference formula, Hunter color difference formula and
There is a CMC (l; c) color difference formula.

However, since these uniform color spaces are generalized so that the colors of the entire gamut can be handled in a unified system, they are used for the purpose where strict accuracy is required for each color. Not suitable for In recent years, the color quality required for industrial products has been increasing, and it has become impossible to accurately represent colors with the accuracy of conventional general-purpose formulas. Therefore,
There is a demand for a highly accurate uniform color space according to the purpose of use.

[0006] That is, the color difference which is an object in controlling the color quality of industrial products is a small level of about 0.1 to 1 in terms of ΔEab value. Therefore, the "uniform color space for an arbitrary color" is practically such that the perceived distance and the spatial distance coincide with each other in the vicinity of the center color (a range of about 2 to 3 in terms of ΔEab value). What is necessary is just to form a color space. If the range is limited to the vicinity of the center color, if one representative isochromic plane (a group of points perceived as having the same color difference) can be derived, a uniform color space can be formed as a similar space of that plane.

For this reason, a color discrimination sensitivity characteristic (hereinafter referred to as a color difference discrimination sensitivity characteristic), which is a sensitivity characteristic by which an operator can discriminate a color, is considered as a typical color difference difference surface.

[0008] However, it is known that the color difference discrimination sensitivity characteristic has a large individual difference (Brown, 195).
7) It is necessary to measure the color difference discrimination sensitivity characteristics according to the purpose. In addition, since the inspection and management of the object surface color always involves a texture, the stimulus used for measuring the color difference discrimination sensitivity characteristics includes a sample having the color and texture of the actual object surface color (hereinafter, referred to as a sample).
It is desired to use a “color chart”).

As an example of measuring such color difference discrimination sensitivity characteristics, a psychophysical measurement method for measuring human color difference discrimination sensitivity characteristics is known. A typical example is M
Experiment to find color discrimination ellipse by acAdam (MacAdam "
Visual Sensitivities to Color Differnces in Daylig
ht ", 1942).

In this experiment, the directional characteristics (shape and size of the discrimination ellipse) of each of the 25 colors scattered on the chromaticity diagram were determined using a color matching experiment using light. I'm checking. The discrimination limit of the difference is obtained from the standard deviation of the variation of the answer using an adjustment method which is a typical method of the psychophysical experiment.

However, the experimental stimulus used above is a color-matching experimental stimulus that can be presented by being continuously changed using light, and cannot be used when a discrete stimulus such as a color chart representing the surface color of an object is used.

The limit method, which is a typical method as another example, is a method for easily obtaining a discrimination area using discrete stimuli.

However, in the extreme method, it is necessary to intensively prepare a stimulus near a discrimination limit between visible and invisible, and it is difficult to control the toning at a minute difference level such as a sample of an object surface color. Not available to

As described above, the psychophysical measurement method is a method devised on the premise that an experimental stimulus can be freely synthesized using light, and has a problem that it is difficult to measure using an object surface color. is there. In addition, the number of required samples tends to increase because high-precision measurement is desired, and the manufacturing cost increases as the number of samples increases. For this reason, there is also a problem that the measurement operation is complicated and the cost is increased.

Recently, there has been an attempt to extract a color difference discrimination sensitivity characteristic using a neural network. This method is a simple and highly practical color difference discrimination method by preparing a large number of samples of peripheral colors with respect to the center color without spatial deviation and aligning the individual colorimetric data and sensory evaluation data as a set. Sensitivity characteristics can be extracted. In addition, since the experimental stimulus may be a discrete sample and it may be difficult to control the toning at a minute difference level, there are many applications for industrial products such as cloth, plastic surfaces, and metal surfaces.

However, in this method, it is necessary to produce a large number of samples (200 to 300 or more) without spatial deviation, and this method is applicable when a large number of samples cannot be produced technically or costly. Can not.

[0017]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and provides a color discrimination sensitivity measuring apparatus capable of measuring color discrimination sensitivity characteristics with high accuracy with a small number of object surface color samples. Is the purpose.

[0018]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is directed to a perceived chromaticity coordinate plane having a predetermined predetermined color as a center color and an image on said plane centered on said center color. Color difference measuring means for measuring a color difference between each of the plurality of color patches representing the object surface color generated in advance along the color direction sequence for each of the plurality of color direction sequences, with the direction as a color direction sequence, and the center color; And input means for previously obtaining a local sensitivity ratio between adjacent color direction series for the plurality of color patches, and inputting the obtained value; and obtaining a distortion degree using the local sensitivity ratio. Weighting each of the local sensitivity ratios based on the sensitivity ratio global correction means for correcting the local sensitivity ratio to a global sensitivity ratio, and correcting the corrected global sensitivity ratio to the perceived chromaticity. It is continuous on the coordinate plane Includes a sensitivity ratio correction means for interpolating, and output means for outputting the interpolation result as a color discrimination sensitivity, the.

In the color discrimination sensitivity measuring device,
As the color chart, a color chart which is generated along the color direction series and at a constant chromaticity interval from the center color can be used.

In the above-mentioned color discrimination sensitivity measuring device,
The value to be input to the input means is a local sensitivity between adjacent color direction sequences by determining a sensitivity ratio between adjacent sequences for all color chart pairs of adjacent color direction sequences on a color space. A value obtained by calculating the ratio may be used.

In the present invention, the color difference between each of the plurality of color patches representing the surface color of the object and the center color is measured by the color difference measuring means. On the perceived chromaticity coordinate plane, the plurality of color patches have a predetermined color as a center color and a direction on the plane centered on the center color as a color direction sequence. It is generated in advance so as to follow the color direction series. It is preferable that the color chart be generated along the color direction series and at a constant chromaticity interval from the center color. By generating in this way, it is possible to cover the perceived chromaticity coordinate plane evenly with the colors based on the color patches. For these color patches, the local sensitivity ratio between adjacent color direction series is determined in advance. This local sensitivity ratio is obtained by calculating the sensitivity ratio between adjacent series for all color chart pairs of adjacent color direction series on the color space, thereby obtaining the local sensitivity ratio between adjacent color direction series. Can be. For example, using a generated color chart (a test piece having the color and texture of the surface of an object), a sensitivity difference between two adjacent color direction series is obtained by a psychophysical experiment.
The obtained local sensitivity ratio is input from the input unit, and the sensitivity ratio global correction unit obtains the distortion degree using the local sensitivity ratio. The sensitivity ratio global correction means corrects the local sensitivity ratio to a global sensitivity ratio that is substantially uniform in the entire color space by weighting each of the local sensitivity ratios based on the distortion degree. The corrected global sensitivity ratio is interpolated by the sensitivity ratio correction means so as to be continuous on the perceived chromaticity coordinate plane. In other words, one color discrimination sensitivity characteristic is obtained by interpolating the corrected (spatially discrete) sensitivity ratio for each corrected color direction sequence into a spatially continuous surface. The result of the interpolation is output as color discrimination sensitivity characteristics by the output means.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In this embodiment, the present invention is applied to a color misregistration evaluation device. This color misregistration evaluation device determines whether the degree of color misregistration of an inspection component with respect to a reference component is within a tolerance.

As shown in FIG. 1, a color shift evaluation device 10
Is a device main body 12 for obtaining a color difference discrimination sensitivity characteristic in accordance with a program stored in advance, a keyboard 26 for inputting data, etc.
It comprises an RT 28 and a color measuring device 30 for measuring the color of the color chart.

The apparatus body 12 comprises a CPU 14, a RAM 1
6. It includes a ROM 18 and is connected by a bus 24 so that data and commands can be transmitted and received. Note that a program for obtaining a color difference discrimination sensitivity characteristic, which will be described in detail later, is stored in the ROM in advance. Further, the device main body 12 is connected to an input / output (I
/ O) device 22 and memory 20. The memory 20 stores in advance the chromaticity of the reference color, the correction coefficient, and the tolerance for determining the color shift (details will be described later).

The keyboard 26, the CRT 28, and the color measuring device 30 are connected to an input / output (I / O) device 22 of the device main body 12.

Next, the operation of the present embodiment will be described. First, with reference to FIG. 2, a description will be given of a pre-process for obtaining the color difference discrimination sensitivity characteristics.

In this embodiment, in order to use the interior material of the vehicle interior, the material is made of polypropylene and the surface has a specific "grain" (for example, an uneven pattern simulating the surface state of leather).
A description will be given of a case where the directional characteristic of the sensitivity on the chromaticity a ^* b ^* plane of the CIEL ^* a ^* b ^* color system when the skilled inspector evaluates the object surface on which is formed. The color of the object surface is determined in advance using the color of chromaticity a ₀ ^* b ₀ ^* measured by the integrating sphere colorimeter 30 as a reference color.

In step 100 of FIG. 2, a plurality of color samples prepared as follows are prepared. The color difference of the sample with respect to the reference color is set to be evenly spaced, that is, the reference color is set as the origin, and the color difference Δa from the reference color is set.
^*, △ b ^* on the axis and the a ^* b ^* color difference planes orthogonal to, the five stages of the chromaticity substantially equal intervals radially substantially equal 8 (arrow R ₁ to R ₈ in FIG. 3) A sample aiming at this is produced (see FIG. 3). 40 samples thus prepared are prepared. In the next step 102, the chromaticities a ^* and b ^* of each of the prepared samples are measured by an integrating sphere colorimeter. FIG. 3 shows the results of colorimetry of these samples. In addition, in the figure, the hit points are represented as samples D _ij . In the sample _Dij , i is the direction (arrow R in FIG. 3).
_{1 to} R ₈ ), and j corresponds to the rank from the point farthest from the reference color. In the following description, each direction (arrows R _{1 to} R _{8 in} FIG. 3) is referred to as a color direction sequence.

Next, steps 104 and 106
, The sensitivity ratio local measurement is performed. Step 1
In step 04, a sample pair whose color difference is identified between samples belonging to adjacent color direction series, which is determined as follows, is input.

First, as shown in FIG. 5, a visual experiment device 32 for an operator to conduct a visual experiment includes an artificial sun light 3.
4 is provided. The artificial sun light 34 is provided so that light is emitted at a predetermined angle α (for example, 50 °) with respect to the normal direction of the mounting table 36. The operator OP gazes at a predetermined angle β (for example, 20 °) from the optical axis of the artificial sunlight 34. At the gaze position of the operator OP, as shown in FIG. 4, a sample 38 including a color chart SS of a reference color, a reference sample PS, and a test sample TS is simultaneously presented so that the user can evenly gaze at each.

A sample pair whose color difference is identified between samples belonging to adjacent color direction series is determined as follows. For example, the sample and the second color direction series belonging to the first color direction sequence (arrow R ₁ direction in FIG. 3) (arrow R in FIG. 3
_{As an} example of the sample belonging to ₂ ), as shown in FIG. 6, the sample D ₂₅ of the second color direction sequence is used as a test sample TS, and the samples D ₁₁ and D ₁₁ of the first color direction sequence are used.
Using D ₁₂ , D ₁₃ , D ₁₄ , and D ₁₅ in order as reference samples PS, the operator selects a sample of the first color direction series corresponding to the color difference from the reference color to the test sample TS. This is executed for all adjacent color direction series. FIG. 7 shows a sample belonging to the first color direction sequence and a second color direction sequence.
The results of sample pairs identified with the samples belonging to the color direction series are indicated by a circle. FIG.
, The sample pairs identified on the a ^* b ^* color difference plane are indicated by dotted lines. When the sample pairs in which the color difference is identified between the samples belonging to the adjacent color direction series are connected to each other in this way, the sensitivity map shown in FIG. 12 can be generated, but since these connections remain incomplete, It is not enough to obtain accurate sensitivity characteristics.

For this reason, in step 106 of FIG. 2, an average sensitivity ratio between adjacent series is calculated as follows using the colorimetric values (step 102) measured above.

Based on the sample pairs identified between adjacent sequences and the colorimetric values of the corresponding samples, the average ratio of the sensitivities of the adjacent sequences is determined using the following equation (1). . Based on the colorimetric value of the sample,
This is because the reference sample used as the evaluation sensitivity (scale) of the test sample changes for each color direction sequence, so that it is necessary to standardize the evaluation scale. Further, obtaining the average ratio of the sensitivities is based on the fact that the discrimination limit of color misregistration by visual observation is ΔE =
Since the reliability for these becomes low near 0.1, it is assumed that the reliability increases in proportion to the color difference, and when obtaining an average sensitivity ratio (scale ratio), the drag differs depending on the color difference. That's because.

[0034]

(Equation 1)

Where Pi is the average sensitivity ratio between the i-th color direction sequence and the adjacent color direction sequence (i = 1,...,
8) ΔE _i1 to ΔE _i5 : Samples of the i-th color direction sequence _identified with adjacent color direction sequences, and colorimetric values of the samples ΔE _j1 to ΔE _j5 : i-th color direction A sample of the j-th color direction sequence adjacent to the sequence, and the colorimetric value of the sample

Next, the sensitivity ratio global measurement is performed by the processing of steps 108 to 112 in FIG. In step 108, in order to quantify the inconsistency due to visual instability, the distortion ratio η generated when the circuit makes a round in the Δa ^* b ^* plane using the sensitivity ratio obtained above is referred to by the following equation (2). Ask.

[0037]

(Equation 2)

However, the ideal value η = 1

In the next step 110, step 102
The average angle formed by the adjacent series in the Δa ^* b ^* plane is determined as follows based on the colorimetric values of First, for each color direction series, regression lines L1 to L8 passing through the reference point are obtained using the colorimetric values of the samples belonging to the color direction series (see FIG. 9). Next, the angle θi (i = 1,..., 8) formed by the regression lines of the adjacent color direction series is obtained (FIG. 10).
reference).

In the next step 112, the distortion degree η obtained in step 108 is calculated by referring to the following equation (3).
By assigning each color direction sequence according to the angle obtained in step 10, distortion of the local sensitivity ratio is corrected, and the corrected sensitivity ratio Qi is obtained. This step 11
In 2, it is assumed that the distortion occurs uniformly during one cycle,
The magnitude of the distortion is determined according to the magnitude of the angle between the series.

[0041]

(Equation 3)

Where i = 1,..., 8 Qi: sensitivity ratio after correction

In the next step 114, a sensitivity ratio interpolation process is performed. First, the eight sensitivity ratios obtained in step 112 are located elliptical with respect to the reference color (center) in the Δa ^* b ^* plane. Interpolation is performed so that the eight points are continuously connected as a continuous line. Thus, one sensitivity curve is generated using the corrected eight sensitivity ratios. That is, the sensitivity of one of the color direction series, in this embodiment, the sensitivity of another color direction series when the second color direction series is a reference (= 1) is calculated using the angle θi and the corrected sensitivity ratio Qi. (See FIG. 11). Here, instead of obtaining several contour lines from one visual result, only one line having high reliability is extracted.

In the next step 116, the sensitivity curve obtained as described above is output. For this output, a sensitivity curve, that is, a color difference discrimination sensitivity characteristic may be output as a diagram or as a numerical value. FIG. 13 (1) shows a specific “grain” on the surface (for example, a rugged pattern simulating the surface state of leather) made of polypropylene for the purpose of using a vehicle interior material, which is called a so-called gray color. Is a graph showing the sensitivity direction characteristics when a skilled inspector evaluates the object surface on which is formed on a △ a ^* b ^* color difference plane centered on a reference color. Similarly, FIG. 13 (2) shows the sensitivity direction characteristics of what is called a brown color. In the figure, Sδ represents sensitivity, and δ represents the angle in the counterclockwise direction for the color direction series.

In this embodiment, a sensitivity map is obtained from a sensitivity direction characteristic, that is, a sensitivity curve, in order to obtain a color shift degree described later, and the sensitivity map is stored in a memory as a correction coefficient. In this sensitivity map, the sensitivity is obtained for each predetermined angle from the sensitivity curve, and the correspondence between the angle and the sensitivity is represented.

Next, a determination process for determining whether or not the degree of color misregistration of the inspection component with respect to the reference component is within the tolerance is shown in FIG.
This will be described with reference to the flowchart of FIG. Here, the chromaticity of the reference color, which is the color of the reference component, and the correction coefficient (sensitivity map) obtained as described above are stored in the memory 20 of the apparatus body 12.
Sθ and the value Clim of the tolerance of the color misregistration of the reference component are stored.

In step 120 of FIG. 14, the color (chromaticity a ^* b ^* ) of the inspection component is measured by the integrating sphere colorimeter 30. In the next step 122, the reference color is read from the memory 20 and the color difference ΔC between the reference color and the color of the inspection component is read.
^{* Is obtained} by the following equation (4).

ΔC^*= (△ a^{* 2}+ △ b^{* 2})^1/2 ... (4) where Δa^*: Chromaticity a between the reference color and the color of the inspection part^*Difference of b^*: Chromaticity b between the reference color and the color of the inspection part^*In the next step 124, the correction coefficient Sθ
And the color shift ΔC in which the sensitivity characteristics have been corrected.
new is obtained by the following equation (5). Note that △ a ^*, △ b
^*From the angle θ and read the corresponding correction coefficient Sθ
You.

ΔCnew = ΔC ^* / Sθ (5)

In the next step 126, △ Cnew <Cli
By determining m, it is determined whether or not the degree of color misregistration △ Cnew is within the tolerance. When △ Cnew <Clim, the CRT 28 is displayed as OK in the next step 128, and △ Cnew ≧ C
When lim, NG is displayed.

A set of points perceived as having the same color difference with respect to an arbitrary color in a color space has an elliptical characteristic in the color space. Depends on. Therefore, in the present embodiment, a sample is prepared for each color direction sequence with respect to the reference color using this aggregate as a color difference discrimination sensitivity characteristic, and the color difference sensitivity difference is measured for two adjacent color direction sequences (sensitivity ratio locality). Measurement), the measured local sensitivity ratios are corrected based on the consistency of the entire color space (sensitivity ratio global correction), so that the color difference discrimination sensitivity in the visual evaluation of any operator for any object surface color Characteristics can be output with high efficiency and high accuracy.

Further, since it is only necessary to prepare a sample for each color direction series, it can be applied to a small number of samples. Further, since strict toning precision is not required for the production, the production cost can be reduced.

Furthermore, the number of experiments required to extract the color difference discrimination sensitivity characteristics is small, and the individual experiments are easy to judge by comparing adjacent directions, so that the burden on the operator is minimized. be able to.

In the above description, a sample as a color chart is prepared so as to have a constant interval from a position close to the reference color in each of the eight color direction series with respect to the reference color, but the present invention is not limited to this. Instead, the number of color direction series (the number of divisions in the color direction), the width of intervals in the series, the number of samples in the series, and the like are appropriately determined according to the properties of the object surface color to be evaluated. be able to.

[0055]

As described above, according to the present invention, for a color chart for each color direction series with respect to a reference color, the local sensitivity ratio between two adjacent color direction series is determined based on the consistency of the entire color space. Is corrected as a global sensitivity ratio based on the above, there is an effect that a color difference discrimination sensitivity characteristic measurement result for an arbitrary object surface color according to the purpose can be output with high efficiency and high accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a color misregistration evaluation apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a flow of a pre-processing routine for obtaining a color difference discrimination sensitivity characteristic.

FIG. 3 is a diagram showing a Δa ^* Δb ^* plane coordinate system centered on a reference color.

FIG. 4 is an image diagram showing an arrangement of a sample group watched by an operator.

FIG. 5 is a block diagram illustrating a schematic configuration of a visual test device.

FIG. 6 is an explanatory diagram for explaining that a sample pair in which color differences are identified between samples belonging to adjacent color direction series is determined.

FIG. 7 is an image diagram showing a result of a sample pair identified between samples belonging to adjacent color direction series.

FIG. 8 is a diagram showing, by dotted lines, sample pairs identified on a Δa ^* Δb ^* plane coordinate system centered on a reference color.

FIG. 9 is a diagram showing a color direction series as a regression line on a Δa ^* Δb ^* plane coordinate system centered on a reference color.

FIG. 10 is a diagram showing angles formed by regression lines of adjacent color direction series.

FIG. 11 is an explanatory diagram for explaining that a color difference discrimination sensitivity curve is generated.

FIG. 12 is a diagram in which a sample pair identified on a Δa ^* Δb ^* plane coordinate system centered on a reference color is simply indicated by a dotted line.

FIG. 13 is a diagram illustrating an example of a color difference discrimination sensitivity curve.

FIG. 14 is a flowchart illustrating a flow of a determination processing routine for determining whether or not the degree of color misregistration of an inspection component with respect to a reference component is within an allowable difference;

[Explanation of symbols]

 Reference Signs List 10 Color misregistration evaluation device 12 Main unit 30 Color measurement device

Continuing from the front page (72) Inventor Miyuki Yamakawa 41-Cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Institute, Inc. 41 No. 1 in Toyota Central Research Institute, Inc. (72) Inventor Hiroyoshi Tsuji Hirochi, Aichi-gun Aichi-gun, Nagakute-machi, Oji-cho, Yokomichi 41 No. 1 in Toyota Central Research Institute, Inc. No.Ichitaura Port Town Kanto Automobile Industry Co., Ltd. (72) Inventor Hiroyuki Ito No.Tapo Port Town Yokosuka City, Kanagawa Prefecture Kanto Automobile Industry Co., Ltd.

Claims (1)

[Claims] 1. On a perceived chromaticity coordinate plane, for each of a plurality of color direction sequences, a predetermined predetermined color is set as a center color, and a direction on the plane centered on the center color is set as a color direction sequence. A color difference measuring unit that measures a color difference between each of the plurality of color patches representing the object surface color generated in advance along the color direction series and the central color; and, for the plurality of color patches, between adjacent color direction series. Input means for obtaining the local sensitivity ratio in advance, and inputting the obtained value, obtaining a distortion degree using the local sensitivity ratio, and weighting each of the local sensitivity ratios based on the distortion degree. A sensitivity ratio global correction unit that corrects the local sensitivity ratio to a global sensitivity ratio; and a sensitivity ratio correction unit that interpolates the corrected global sensitivity ratio so as to be continuous on the perceived chromaticity coordinate plane. Color discrimination of interpolation result Color discrimination sensitivity measuring apparatus having an output means for outputting a degree, the.