JP2006292578A - Color difference evaluation method and colorimetric system for anisotropic sample - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quantitatively evaluate a color difference correlated sufficiently with visual observation evaluation, as to an anisotropic sample applied with metallic coating, pearl coating or the like. <P>SOLUTION: This colorimetric system S is provided with a reflected light measuring instrument 1 having a multiangle type geometry, a measurement control means 2, a photodetective data processing means 3, a color difference calculation means 4, a color difference expression/coefficient storage part 5, an operation means 6, an output part 71 and a display part 72. The color difference calculation means 4 receives setting of a coefficient in response to the geometry, and finds the color difference, using a color difference expression capable of setting optionally coefficients about lightness, saturation and hue. The coefficient is set to satisfy a relation of L1>L2, where L1 represents the lightness coefficient in the color difference expression applied to photodetective data of a highlight optical system, and L2 represents the lightness coefficient in the color difference expression applied to the photodetective data of a shade optical system. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for evaluating a color difference, which is a color shift with respect to a predetermined reference color, and a colorimetric system for an anisotropic sample having a different color sensation depending on the viewing direction, such as a sample subjected to metallic coating or pearl coating. It is about.

  Metallic coating and pearl coating, which are widely used for the coating of automobile bodies and exterior members of various home appliances, include flake-shaped aluminum pieces and mica pieces called glitter materials in the paint film, so-called metallic Has an effect and pearl effect. This is because the contribution of the glittering material to the reflection characteristics varies depending on the illumination and the viewing direction (viewing direction). The painted surface on which the metallic coating or the pearl coating is applied has a color sensation depending on the viewing direction. (In this specification, a sample having such a painted surface is referred to as an “anisotropic sample”).

Normally, color management is performed on a product that has been coated to check whether the coating color has a color shift with respect to a predetermined reference color. In this case, for example, a predetermined illumination light receiving optical system (geometry) as disclosed in Patent Document 1 is used to irradiate the coating surface with predetermined illumination light and receive the reflected light. In general, color difference evaluation is performed by applying a predetermined color difference formula. The L ^* a ^* b ^* color system recommended by the International Commission on Illumination (CIE) is mainly used at present as such a color difference formula. This CIEL ^* a ^* b ^* color difference formula is expressed as the following formula (1).

Furthermore, in order to complement that the L ^* a ^* b ^* color system does not necessarily match human visual judgment, CMC (l: c), which is a color difference formula including coefficients relating to lightness, saturation, and hue. ) Color difference formulas, CIE 1994 color difference formulas, CIE 2000 color difference formulas (these color difference formulas will be described in detail later) are known.

By the way, unlike solid color samples that do not vary in color depending on the viewing direction, anisotropic samples with metallic or pearl coating have different colors depending on the viewing direction. Color management is required. Conventionally, the color management of anisotropic samples ultimately depends on the visual evaluation of the inspector. This is because the numerical color difference value based on the currently used CIE L ^* a ^* b ^* color difference formula may differ from the result of human visual evaluation, especially in the case of anisotropic samples. Because there is a case to do. In other words, even if the color difference values are greatly different, there is a case where the color difference is not felt so much as the visual sense of the person.

In addition, there is an example in which the CMC (l: c) color difference formula capable of setting a coefficient that compensates for a defect in the L ^* a ^* b ^* color system is used for color management of textile products. However, what is actually used is CMC (1: 1) with lightness coefficient l = 1 and saturation coefficient c = 1, which are the initial setting values, and lightness to widen the allowable range at the time of acceptance inspection, etc. These are just two types of color difference formulas with CMC (2: 1) with coefficient l = 2 and saturation coefficient c = 1. That is, the monochromatic sample and the anisotropic sample as described above are not distinguished from each other, and the coefficient is alternatively set depending on whether or not the inspection with a wide allowable range is performed.

Further, in a measuring instrument having a so-called multi-angle geometry in which the angle of the light receiving direction relative to the illumination direction or the angle of the illumination direction relative to the light receiving direction can be changed, the CMC (l: c) color difference formula, CIE 1994 color difference formula, CIE 2000 color difference formula Etc. can be set as a color difference formula for obtaining a color difference value. However, a measuring instrument that can set coefficients relating to lightness, saturation, and hue in the color difference formula according to the geometry to be used and the sample to be measured has not been proposed yet. In the first place, it has not been sufficiently elucidated how to set the coefficient under what measurement conditions. Therefore, even if the above color difference formula is used, quantitative evaluation that is sufficiently correlated with visual evaluation cannot be performed on anisotropic samples that have been subjected to metallic coating, pearl coating, etc. It depends on visual evaluation by the eyes.
JP 2001-50817 A

  The present invention has been made in view of the current situation as described above, and uses a color difference formula in which a coefficient can be arbitrarily set, and an appropriate value according to a geometry, a sample to be measured, and the like using the coefficient of the color difference formula. By making it possible to set the color difference evaluation method and colorimetry of an anisotropic sample that can perform quantitative evaluation sufficiently correlated with visual evaluation of an anisotropic sample that has been subjected to metallic coating, pearl coating, etc. The purpose is to provide a system.

The color difference evaluation method for an anisotropic sample according to claim 1 of the present invention uses an illumination light receiving optical system in which the angle of the light receiving direction relative to the illumination direction or the angle of the illumination direction relative to the light receiving direction can be changed, and the color sensation depends on the viewing direction. A color difference evaluation method for performing a color difference evaluation by applying a predetermined color difference formula to received light data obtained by irradiating illumination light to different anisotropic samples and receiving the reflected light, wherein the color difference formula includes at least Using a color difference formula capable of arbitrarily setting a coefficient relating to brightness, the brightness coefficient of the color difference formula applied to the received light data obtained when the illumination light receiving optical system is set as a highlight optical system is L1, and the shade optical system When the lightness coefficient of the color difference formula applied to the received light data obtained when
L1> L2
The lightness coefficient is set so as to satisfy the above relationship.

  As shown in FIG. 1A, in an anisotropic sample in which a bright material 102 such as aluminum flakes or mica flakes is blended in a coating film 101, regular reflection of illumination light by an illumination light receiving optical system (geometry). The influence of the components will be greatly different. That is, as is apparent from FIG. 1B showing the light reflection characteristics of the anisotropic sample, in the highlight optical system in which the angle between the illumination direction and the light receiving direction is small, the influence of the specular reflection component from the surface of the glitter material 102. Becomes larger. For this reason, the light source color is strongly reflected in the metallic paint in which colorless aluminum flakes are blended, and the rainbow-colored coloring effect is remarkably confirmed in the pearl paint in which mica flakes are blended. On the other hand, in a shade optical system having a large angle between the illumination direction and the light receiving direction, diffused light components due to absorption and scattering by the pigment in the coating film 101 are mainly observed.

  The regular reflection component is evaluated as lightness among color components including lightness, saturation, and hue. In the visual evaluation by the human eye, as more regular reflection components are included, the influence of the brightness difference becomes smaller than other color components (saturation and hue). That is, even if the value of brightness is greatly different numerically, there is a tendency that it cannot be recognized as a great difference by human eyes. On the other hand, when the regular reflection component is not included so much, it is possible to relatively sense a numerical difference in brightness.

  In view of the visual characteristics with respect to the light reflection characteristics of the anisotropic sample as described above, in the invention according to claim 1, the color difference formula applied to the received light data obtained when the geometry is set to the highlight optical system. The lightness coefficient L1 is made relatively large to reduce the influence of the lightness difference in the color difference evaluation in the highlight optical system. On the other hand, by setting the lightness coefficient L2 of the color difference formula applied to the received light data obtained when the geometry is set to the shade optical system to be smaller than the L1, the influence of the lightness difference in the color difference evaluation is handled relatively large. It is a thing. Thereby, the color difference evaluation close to the visual feeling can be performed.

The anisotropic sample color difference evaluation method according to claim 2 of the present invention uses a predetermined illumination light receiving optical system, irradiates an anisotropic sample having a different color sense depending on the viewing direction, and receives the reflected light. A color difference evaluation method for performing color difference evaluation by applying a predetermined color difference formula to received light data obtained by using a color difference formula capable of arbitrarily setting coefficients relating to lightness, saturation, and hue as the color difference formula When the illumination light receiving optical system is set to an optical system having a predetermined reflection angle, the lightness coefficient of the color difference formula applied to the received light data is l, the saturation coefficient is c, and the hue coefficient is h.
l ≧ c ≧ h where l ≠ h
Or
l ≧ h ≧ c where l ≠ c
The lightness coefficient is set so as to satisfy any of the following relationships.

  The visual perception by human eyes has a characteristic that the difference is felt sensitively in the order of lightness difference <saturation difference <hue difference regardless of the geometry. In other words, the lightness difference cannot be distinguished very finely, but a slight difference in hue can be well identified. Therefore, by setting the coefficient of the color difference formula in the relationship of lightness coefficient l ≧ saturation coefficient c ≧ hue coefficient h (where l ≠ h), each effect of lightness difference, saturation difference and hue difference in the color difference evaluation. The degree can be matched to the visual feeling. However, depending on the type of anisotropic sample, there may be a case where the difference is felt sensitively in order of lightness difference <hue difference <saturation difference. In this case, it is possible to match the visual feeling by setting the coefficient of the color difference formula in the relationship of lightness coefficient l ≧ hue coefficient h ≧ saturation coefficient c (where l ≠ c).

The color difference evaluation method for an anisotropic sample according to claim 3 of the present invention uses an illumination light receiving optical system in which the angle of the light receiving direction relative to the illumination direction or the angle of the illumination direction relative to the light receiving direction can be changed, and the color sensation depends on the viewing direction. A color difference evaluation method for evaluating a color difference by applying a predetermined color difference formula to received light data obtained by irradiating illumination light to different anisotropic samples and receiving the reflected light. Using a color difference formula that can arbitrarily set coefficients relating to saturation and hue, the lightness coefficient of the color difference formula applied to the received light data obtained when the illumination light receiving optical system is set to a highlight optical system is L1. When the lightness coefficient of the color difference formula applied to the received light data obtained when the shade optical system is set is L2,
L1 ≧ L2
Set the brightness coefficient to satisfy the relationship, and
When the illumination coefficient of the color difference applied to the received light data obtained when the illumination light receiving optical system is set to an optical system having a predetermined reflection angle is l, the saturation coefficient is c, and the hue coefficient is h,
l ≧ c ≧ h where l ≠ h
Or
l ≧ h ≧ c where l ≠ c
The lightness coefficient is set so as to satisfy any of the following relationships.

  According to this configuration, it is possible to optimize the influence of the lightness difference in the color difference evaluation when the geometries are different, and to visually recognize the influences of the lightness difference, the chroma difference, and the hue difference in the color difference evaluation in an arbitrary geometry. Can be matched to.

  The colorimetric system according to claim 4 of the present invention can change the angle of the light receiving direction with respect to the illumination direction or the angle of the illumination direction with respect to the light receiving direction, and can irradiate a predetermined sample with illumination light and receive the reflected light. An illumination light receiving optical system configured as described above, and a color difference calculating means for calculating a color difference by applying a predetermined color difference formula to the received light data of the reflected light obtained by the illumination light receiving optical system, the color difference calculating means Set by the coefficient setting unit, a color difference formula storage unit that stores a predetermined color difference formula that can arbitrarily set coefficients relating to brightness, saturation, and hue, a coefficient setting unit that receives settings for the coefficient of the color difference formula, and the coefficient setting unit And calculating a color difference for the received light data of the reflected light by substituting the calculated coefficient into the color difference formula.

  According to this configuration, for example, in a color measuring device having a multi-angle geometry, it is possible to set coefficients relating to lightness, saturation, and hue in the coefficient setting unit according to the reflection angle of the geometry, etc. Thus, the color difference can be obtained by a predetermined color difference equation by the calculation unit.

  In the above-described configuration, it is preferable that a coefficient storage unit that stores the coefficient set in the coefficient setting unit is provided. According to this configuration, it is possible to store coefficients related to lightness, saturation, and hue set according to the reflection angle of the geometry or the material of the anisotropic sample in the coefficient storage unit. When color difference evaluation is performed on an anisotropic sample, the coefficient can be read from the coefficient storage unit and measured.

  In this case, a sample mode selection unit is provided for selecting whether the sample to be colorimetric is a first sample whose color sensation does not substantially differ depending on the viewing direction or a second sample whose color sensation differs depending on the viewing direction. The coefficient storage unit stores a first coefficient for the first sample and a second coefficient for the second sample, and the first sample is selected by the sample mode selection unit. It is desirable that the first coefficient is set in the coefficient setting unit when selected, and the second coefficient is set in the coefficient setting unit when a second sample is selected ( Claim 6). According to this configuration, for example, when either a monochromatic sample (first sample) or an anisotropic sample (second sample) is selected by the sample mode selection unit, a predetermined coefficient is used in each sample mode. Can be set in the coefficient setting section as a default value.

  In addition, a sample type selection unit that selects a sample type for the second sample is provided, and the coefficient storage unit stores coefficients corresponding to the sample types, and is selected by the sample type selection unit. It is desirable that a coefficient corresponding to the sample type is set in the coefficient setting unit (claim 7). According to this configuration, just by the user specifying the type of the anisotropic sample (second sample), a coefficient suitable for the anisotropic sample is set in the coefficient setting unit.

  The configuration according to claim 6 or 7, further comprising an operation unit for correcting a coefficient once set in the coefficient setting unit, wherein the coefficient storage unit is capable of storing the coefficient corrected by the operation unit. (Claim 8). According to this configuration, for example, a coefficient set as a default value can be finely adjusted to a coefficient more correlated with the visual feeling according to user tuning.

  Further, according to any one of claims 4 to 8, comprising: a predetermined display unit; and a display control unit that generates work guidance information related to selection of at least a sample to be colorimetric, selection of a color difference formula, and setting of a coefficient; The work guidance information generated by the display control unit can be displayed on the display unit (claim 9). According to this configuration, when performing the color difference evaluation of the anisotropic sample, the user can be navigated based on the work guidance information for at least the sample selection, the color difference formula selection, and the coefficient setting.

  According to the first aspect, since the lightness coefficient of the color difference formula is set according to the influence of the lightness difference received when the color difference evaluation of the anisotropic sample is visually performed for each geometry, the visual evaluation and the correlation High color difference evaluation can be performed. Therefore, the color management of the article on which the metallic coating or the pearl coating is applied can be accurately performed according to the visual feeling.

  According to the second aspect, since the brightness coefficient of the color difference formula is set according to the visual sensitivity for the color component difference of the brightness difference, the saturation difference, and the hue difference, the color difference evaluation having high correlation with the visual evaluation. The color management of the article can be performed accurately according to the visual feeling.

  According to the third aspect, the influence of the brightness difference in the color difference evaluation when the geometries are different can be optimized, and the influence of each of the brightness difference, the saturation difference, and the hue difference in the color difference evaluation in an arbitrary geometry can be obtained. Since it can be matched to the visual feeling, the color management of the article can be performed more accurately.

  According to claim 4, it is possible to set coefficients relating to lightness, saturation, and hue in the coefficient setting unit according to the reflection angle of each geometry, etc., and color management of articles subjected to metallic coating or pearl coating Can be accurately performed according to the visual feeling.

  According to the fifth aspect, since the coefficient of the color difference formula can be appropriately read from the coefficient storage unit and measured, the coefficient setting work can be simplified, and the color difference measuring work can be performed efficiently.

  According to the sixth aspect, in each sample mode, a predetermined recommended value as a coefficient, a value used in the past, or the like can be set as a default value in the coefficient setting unit, so that the coefficient setting work can be simplified and the color difference measurement work can be performed. Can be performed efficiently.

  According to the seventh aspect, since the coefficient suitable for the anisotropic sample is set in the coefficient setting section, the color difference measurement work can be performed more efficiently.

  According to the eighth aspect, since the coefficient having a correlation with the visual feeling can be finely adjusted according to the user tuning, it is possible to perform the color difference evaluation that accurately corresponds to the color management purpose for each user.

  According to the ninth aspect, by displaying the work guidance information on the display unit, it is possible to accurately navigate the coefficient setting work according to the sample to be measured.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
(Description of hardware configuration)
FIG. 2 is a block diagram schematically showing an overall configuration of the color measurement system S (an anisotropic sample color difference evaluation method) according to the embodiment of the present invention. This color measurement system S can be applied as a system for evaluating a color shift (color difference) from a reference color in each predetermined viewing direction for various anisotropic samples having different color sensations depending on the viewing direction. In the embodiment, a color measurement system S for quantitatively evaluating the color difference of the anisotropic sample 8 subjected to metallic coating or pearl coating will be described as an example. The color measurement system S includes a reflected light measuring device 1 having a multi-angle illumination light receiving optical system (geometry), a measurement control unit 2, a received light data processing unit 3, a color difference calculating unit 4, a color difference formula / coefficient storage unit 5, It comprises an operation means 6, an output unit 71 and a display unit 72.

  The reflected light measurement device 1 irradiates a predetermined measurement area of the anisotropic sample 8 to be measured with illumination light, photoelectrically converts the reflected light, and obtains reflected light reception data of the measurement area. The reflected light reception data includes at least a highlight optical system (an optical system that receives a large amount of specularly reflected light components of illumination light) and a shade optical system (illumination light). And an optical system that receives light containing almost no specularly reflected light component), and is acquired by each optical system.

  The measurement control means 2 controls the operation of the light source and the light receiving element provided in the reflected light measuring device 1 and performs control to acquire the reflected light reception data in a predetermined procedure. The light reception data processing means 3 gives amplification processing, A / D conversion processing, and other necessary calculation processing to the acquired reflected light reception data. The color difference calculation means 4 applies the light reception data given from the light reception data processing means 3 to the color difference formula in which the coefficients relating to lightness, saturation, and hue are set to predetermined values, and at least the highlight optical system and the shade optical system. Find the color difference in the system.

  The color difference formula / coefficient storage means 5 stores a predetermined color difference formula used in the color difference calculation means 4 in which coefficients relating to lightness, saturation, and hue can be arbitrarily set, and for each type of the anisotropic sample 8. Coefficient values (recommended coefficients or user-tuned coefficient values) are stored. The operation means 6 is used by the user to give predetermined processing commands, setting commands, etc. to the measurement control means 2, the color difference calculation means 4, and the like. The output unit 71 comprises a printer or the like, and outputs the color difference obtained by the color difference calculation means 4 as numerical data, a graph, or the like. The display unit 72 includes an LCD, a CRT, or the like, and displays the color difference or the like to the user.

The hardware configuration of the color measurement system S can be set as appropriate. For example,
(A) A reflected light measuring device 1 having a multi-angle type geometry (multi-directional illumination unidirectional light reception or unidirectional illumination multi-directional light reception) is prepared, and measurement control means 2, received light data processing means 3, color difference calculation means 4, A hardware configuration in which the color difference equation / coefficient storage means 5, the operation means 6 and the display unit 72 are configured by a personal computer or the like, and both are connected by a USB cable,
(B) In the configuration of (a) above, a hardware configuration in which the reflected light measurement device 1 includes the measurement control means 2 and the received light data processing means 3;
(C) The reflected light measuring apparatus 1 is integrated with the measurement control means 2, the received light data processing means 3, the color difference calculation means 4, the color difference formula / coefficient storage means 5, the operation means 6 and the display unit 72. Hard configuration,
Etc. can be illustrated.

  FIG. 3 is a configuration diagram showing an example of the color measurement system S having the hardware configuration (b). The color measurement system S is configured by connecting a reflected light measurement device 10 of multi-angle illumination type and a personal computer PC with a USB cable 10c. The reflected light measuring apparatus 10 includes a box-shaped outer body 10a, an illumination optical system 11, a light receiving optical system 14, a spectral light receiver 15 and a signal processing circuit 16 housed in the outer body 10a.

  A measurement opening 10b is provided in the bottom surface portion of the outer body 10a, and a sample surface 81 of an anisotropic sample 8 that is a measurement object is closely opposed to the measurement opening 10b. The anisotropic sample 8 is made of, for example, a metallic painted surface or a pearl painted surface of an automobile body.

  The outline of the geometry provided in the reflected light measurement device 10 is as shown in FIG. That is, the light receiving direction (light receiving axis n) is the normal direction of the sample surface 81 of the anisotropic sample 8, and the light source (1) in which the illumination direction is set in three different directions with respect to the light receiving axis n, A light source (2) and a light source (3) are provided. The illumination direction of the light source (1) is set to 25 ° with respect to the light receiving axis n, and the geometry received from the light source (1) through the sample surface 81 is a specular reflection component (FIG. 1 (FIG. 1)). b) is a highlight optical system that receives a relatively large amount of light. On the other hand, the illumination direction of the light source (3) is set to 75 ° with respect to the light receiving axis n, and the geometry received from the light source (3) through the sample surface 81 is mainly composed of relatively diffuse light components. The shade optical system receives a large amount of light. The illumination direction of the light source (2) is set to 45 ° with respect to the light receiving axis n, which is an intermediate geometry between the highlight optical system and the shade optical system.

  Returning to FIG. 3, the illumination optical system 11 includes a first illumination system 11a, a second illumination system 11b, and a second illumination system 11b arranged in directions of 25 °, 45 °, and 75 ° from the normal direction of the sample surface 81, respectively. It consists of a third illumination system 11c. That is, the illumination directions of the light sources (1) to (3) shown in FIG.

  The first illumination system 11a includes a light source 12a made of a tungsten lamp or the like, and a collimator lens 13a disposed in front of the light source 12a. The light emitted from the light source 12a is collimated by the collimating lens 13a into a parallel light beam, and illuminates the sample surface 81 of the anisotropic sample 8 from the direction of the normal angle of 25 °. Similarly, the second illumination system 11b and the third illumination system 11c have light sources 12b and 12c and collimating lenses 13b and 13c, respectively, and the sample surface 81 is viewed from directions of normal angles of 45 ° and 75 °, respectively. Illuminate. As a result, the illumination light can be individually irradiated with the parallel light beams from the directions of the normal angles of 25 °, 45 °, and 75 ° with respect to the sample surface 81. The configuration of the illumination optical system 11 may be set as appropriate. For example, a configuration including the first illumination system 11a and the third illumination system 11c (geometry only in the highlight direction and the shade direction), or four or more. It is good also as a structure which consists of an illumination system.

  Or as shown in FIG. 5, it is good also as a ring illumination system which arrange | positions several light sources concentrically centering on the light-receiving axis n. That is, for example, the emission ends 110a, 11b, and 110c of the illumination optical fiber are arranged in a ring shape in the illumination directions of the light sources (1) to (3) shown in FIG. A 75 ° annular light source may be formed to irradiate the sample surface 81 with illumination light. By adopting such an illumination system, measurement that is not affected by the orientation of the reflected light measurement device 1 can be performed.

  Next, the light receiving optical system 14 includes a plurality of light receiving lenses, a diaphragm plate, and the like, and is disposed in the normal direction of the sample surface 81 as described above, and the spectral light receiver 15 (light receiving element 152) disposed in the subsequent stage. Then, an optical image of the reflected light reflected from the sample surface 81 is formed.

  The spectral light receiver 15 outputs an electrical signal corresponding to the reflected light imaged by the light receiving optical system 14. The spectral light receiver 15 receives a spectral filter 151 that splits the reflected light into a predetermined wavelength, and receives light of each wavelength separated by the spectral filter 151, and an electric signal corresponding to the reflected light intensity for each wavelength. And a light receiving element 152 that outputs the light. In place of the spectral filter 151, a diffraction grating, a prism, or the like may be used. As the light receiving element 152, for example, a light receiving device in which silicon photodiodes are arranged in an array can be used.

  The signal processing circuit 16 includes an amplification circuit for an analog signal output from the light receiving element 152, an A / D conversion circuit, and the like. The amplification circuit includes a current-voltage conversion circuit, a variable gain amplifier, and the like, and converts a current generated by photoelectric conversion by the light receiving element 152 into a voltage and amplifies it to a predetermined voltage signal. The A / D conversion circuit converts the analog voltage signal output from the amplifier circuit into a digital signal. A signal output from the signal processing circuit 16 is transmitted to the personal computer PC via an unillustrated interface unit and the USB cable 10c.

(Explanation of color difference formula and coefficient setting)
In the present embodiment, a color difference evaluation for evaluating a color shift from the reference color is performed by applying a predetermined color difference formula to the light reception data acquired by the reflected light measurement device 10. As the color difference formula, a color difference formula that can arbitrarily set coefficients relating to lightness, saturation, and hue is used. Examples of such color difference formulas whose coefficients can be arbitrarily set include [a] CMC (l: c) color difference formula, [b] CIE1994 color difference formula, and [c] CIE2000 color difference formula.

[A] CMC (l: c) color difference formula This color difference formula is set in consideration of the difference between the scale of the L ^* a ^* b ^* color system recommended by the CIE in 1976 and human color sense. Color difference formula. That is, since the color difference obtained by the CIE L ^* a ^* b ^* color difference formula of the above formula (1) does not necessarily match the actual human visual feeling determination, the brightness is made more consistent with the human color feeling. The color difference formula gives a coefficient for correcting the saturation. The CMC (l: c) color difference formula is given by the following formula (2).

here,
S _L = 0.040975L ^* _{t / (1} + 0.01765L ^* _t )
However, when L ^* _t <16, S _L = 0.511
S _C = 0.0638C ^* _{t / (1} + 0.00131C ^* _t ) +0.638
S _H = S _C (fT + 1−f)
f = [(C ^* _t ) ⁴ / (C ^* _t ) ⁴ +1900] ^1/2
When 164 ° ≦ h <345 °, T = 0.56 + | 0.2 cos (h + 168 °) |
When 345 ° ≦ h <164 °, T = 0.36 + | 0.4 cos (h + 35 °) |
However,
L ^* _t : Metric brightness index of the reference sample (L ^* a ^* b ^* brightness index in the color system)
C ^* _t : Metric saturation of reference sample h: Metric color difference of reference sample ΔL ^* , ΔC ^* , ΔH ^* : L ^* a ^* b ^* Color difference value between reference color and sample in color system l: Constant (lightness coefficient) )
c: Constant (saturation coefficient)

  In the above equation (2), the lightness coefficient l and the saturation coefficient c can be set arbitrarily. Note that the coefficient h related to the hue is fixed in h = 1, and thus does not appear in the expression (2).

[B] CIE 1994 Color Difference Formula This color difference formula multiplies ΔL ^* , ΔC ^* , and ΔH ^* , which are color difference values based on the CIE L ^* a ^* b ^* color system, by constants called a weight coefficient and a parametric coefficient. By this, it is a color difference formula which enabled the weighting according to a color with _respect to (DELTA) E ^* _ab in said Formula (1). This CIE 1994 color difference formula is also a color difference formula set to make the difference between the color difference calculated by the CIE L ^* a ^* b ^* color difference formula and the actual human visual judgment as possible as follows. It is given by equation (3).

However,
^{ΔL *, ΔC *, ΔH *} : L * a * b * Table color difference values between the reference color and the sample in the color system _{K L, K C, K H} : Parametric coefficient _{(K L} = lightness coefficient, _{K C} = Saturation Coefficient, K _H = hue coefficient)
S _L , S _C , S _H : Weight coefficient where S _L = 1
S _C = 1 + 0.0045C ^*
S _H = 1 + 0.0015C ^*

In the above equation (3), the lightness coefficient K _L , the saturation coefficient K _C and the hue coefficient K _H are constants that can be arbitrarily set according to the purpose of the color difference determination. Incidentally, the heavy valence coefficient S _L, S _C, S _H is a defined value whether to extend the extent allowable range based on the lightness, is treated as a fixed value.

[C] CIE2000 Color Difference Formula This color difference formula is the CIE 1994 shown in the above formula (3) regarding the correlation between the color difference value and visual evaluation in the case of a minute color difference in the CIE L ^* a ^* b ^* color system. The color difference formula was further improved and developed as a more complete color difference formula. CIE2000 color difference formula is similarly ^L * ^a * ^{b *} color system of the color difference value [Delta] L ^*, [Delta] C ^*, with respect to [Delta] H ^*, but multiplies the weight value factor and parametric coefficients, especially ^{the a *} axis in the low saturation region It is a feature that the scale correction is performed. This CIE2000 color difference formula is given by the following formula (4).

However,
RT: Rotation function ΔL ^* , ΔC ^* , ΔH ^* : L ^* a ^* b ^* Color difference values between the reference color and the sample in the color system K _L , K _C , K _H : Parametric coefficients (K _L = lightness coefficient, K _C = saturation coefficient, K _H = hue coefficient)
S _L , S _C , _SH : Weight coefficient

In the above equation (4), the lightness coefficient K _L , the saturation coefficient K _C and the hue coefficient K _H are constants that can be arbitrarily set according to the purpose of the color difference determination. Incidentally, the weight value factor _{S L, S C, S H} is calculated with the following equation (5) is defined.

  Further, in the above equation (4), the rotation function RT is defined to be calculated by the following equation (6).

The above CMC (l: c) color difference formula, CIE 1994 color difference formula, and CIE 2000 color difference formula are all basically elliptical. As is clear from the above equations (2) to (4), the lightness coefficient (l or K _L ), the saturation coefficient (c or K _C ), and the hue coefficient (K _H ) are all items of the respective expressions. Therefore, the larger the coefficient is, the smaller the color difference in the color component is handled, and the permissible range in the color difference evaluation (the range determined to be acceptable in the color difference determination) is expanded.

FIG. 6 is a graph schematically showing the above points. Now, if the ellipse defined by the CMC (l: c) color difference formula, CIE1994 color difference formula or CIE2000 color difference formula is the ellipse 200 shown in FIG. Will be treated. The first axis 201 (long axis in the figure) of the ellipse 200 is an index in the saturation direction C. By setting the saturation coefficient (c or K _C ) to an arbitrary value, the arrow in the figure As shown, the area (allowable range) in the direction of the first axis 201 can be enlarged or reduced. Similarly, the second axis 202 is an index of the hue direction H, and the allowable range of the second axis 202 can be expanded or reduced by setting the hue coefficient (K _H ) to an arbitrary value. Further, the third axis 203 is an index in the brightness direction L, and the allowable range of the third axis 203 can be expanded or reduced by setting the brightness coefficient (l or K _L ) to an arbitrary value. is there.

  Next, a method for setting coefficients in the above color difference formula will be described. As described above with reference to FIG. 1, in a highlight optical system, the specular reflection component from the surface of the glitter material 102 (see FIG. 1B) is used in an anisotropic sample that has been subjected to metallic coating or pearl coating. On the other hand, in the shade optical system, a diffused light component due to absorption and scattering by the pigment in the coating film 101 is mainly observed. The specular reflection component is mainly evaluated as brightness, but in visual evaluation by the human eye, as more specular reflection components are included, the influence of the brightness difference is greater than other color components (saturation and hue). It becomes smaller (the discriminability of brightness difference decreases). On the other hand, when the regular reflection component is not included so much, the distinguishability of the brightness difference is relatively good.

In view of the visual characteristics of the anisotropic sample with respect to the light reflection characteristics, the brightness coefficient (l or K _L ) of the color difference formula applied to the received light data obtained when the geometry is set to the highlight optical system. When L1 is L2, and the lightness coefficient of the color difference formula applied to the received light data obtained when the shade optical system is set is L2,
L1> L2 (7)
The brightness coefficient is set so as to satisfy this relationship. That is, the lightness coefficient L1 in the case of the highlight optical system is made relatively large to reduce the influence of the lightness difference in the color difference evaluation in the highlight optical system, while the lightness coefficient L2 in the case of the shade optical system is set to the L1. By setting a smaller value, the influence of the brightness difference in the color difference evaluation is handled relatively large. Thereby, the color difference evaluation close to the visual feeling can be performed.

In addition, visual perception by human eyes has a characteristic that the difference is sensitive in the order of brightness difference <saturation difference <hue difference regardless of the geometry. In other words, the lightness difference cannot be distinguished very finely, but a slight difference in hue can be well identified. Therefore, the lightness coefficient (1 or K _L above) of the color difference formula applied to the received light data obtained when the geometry is set to an optical system having a predetermined reflection angle is 1 and the saturation coefficient (c or K _C ). Is c and the hue coefficient (K _H ) is h,
l ≧ c ≧ h where l ≠ h (8)
The brightness coefficient is set so as to satisfy this relationship. That is, by setting the coefficient of the color difference formula in the relationship of lightness coefficient l ≧ saturation coefficient c ≧ hue coefficient h (where l ≠ h), the influence of each of the brightness difference, saturation difference, and hue difference in the color difference evaluation. The degree can be matched to the visual feeling. In the case where the anisotropic sample is a metallic coating sample or a pearl coating sample, the relationship of the above equation (8) may be used, but as described in a modified embodiment described later, in a special anisotropic sample, The degree of influence on the visual feeling may be brightness difference <hue difference <saturation difference. In this case, the coefficient of the color difference formula is set in the relationship of lightness coefficient l ≧ hue coefficient h ≧ saturation coefficient c (where l ≠ c).

It is desirable to set the lightness coefficient according to the difference in the geometry of the above expression (7) and the coefficient according to the color component of the above expression (8) in combination. That is, in addition to the relationship of lightness coefficient L1 in the case of the highlight optical system> lightness coefficient L2 in the case of the shade optical system, in each optical system, the lightness coefficient l ≧ saturation coefficient c ≧ hue coefficient h (where l It is desirable to set each coefficient so as to satisfy the relationship of ≠ h). Thereby, the color difference evaluation closer to the visual feeling can be performed. In addition, when the relationship between the above formula (7) and the above formula (8) is used in combination, the above formula (7) is
L1 ≧ L2 (7) ′
It is also good.

(Explanation of electrical configuration)
Subsequently, the main electrical configuration of the color measurement system according to the present embodiment in which the coefficient setting of the color difference formula as described above can be performed will be described. FIG. 7 is a block diagram showing the main parts of the electrical functional configuration of the reflected light measurement device 10 and the personal computer PC. The reflected light measurement apparatus 10 includes a measurement control unit 20 in addition to the light sources 12a to 12c, the light receiving element 152, and the signal processing circuit 16 described above. The measurement control unit 20 controls the lighting operation of the light sources 12a to 12c provided in the illumination optical system 11 according to a predetermined measurement routine (for example, sequentially turns on the light having a smaller normal angle) and reflects the reflected light. Is controlled by the spectral light receiver 15.

  On the other hand, in addition to the display unit 72 described above, the personal computer PC is functionally provided with a color difference calculation unit 40, a storage unit 50, a coefficient operation unit 60, and a display control unit 73. In such a configuration, first, the color difference calculation unit 40 is a functional unit that calculates a color difference by applying a predetermined color difference formula to the received light data obtained by the reflected light measurement device 10, and includes a color difference formula setting unit 41, a coefficient setting. A unit 42, a calculation unit 43, and a determination unit 44.

  The color difference formula setting unit 41 sets a color difference formula in which a lightness coefficient, a saturation coefficient, and a hue coefficient can be arbitrarily set in order to calculate a color difference. Specifically, an appropriate color difference formula that matches the purpose of color difference evaluation is selected by the user from the color difference formulas shown in the above formulas (2) to (4) stored in the color difference formula storage unit 51 described later. Set by.

The coefficient setting unit 42 receives the setting of the coefficient used for the color difference formula set in the color difference formula setting unit 41. In the present embodiment, the lightness coefficient (1 or K _L described above), the saturation coefficient (c or K _C ), the hue coefficient (K) for each geometry according to the color difference formulas shown in the formulas (2) to (4). _H ) is accepted. That is, a coefficient that satisfies the relationship of the above formula (7) or the above formula (8), or satisfies the relationship of the above formula (7) or (7) ′ and the above formula (8). Accept the settings.

  The calculation unit 43 substitutes the coefficient set by the coefficient setting unit 42 into the color difference formula set by the color difference formula setting unit 41 and calculates the color difference for the received light data obtained by the reflected light measurement device 10. Do. The determination unit 44 compares a threshold value set in advance for the purpose of color difference evaluation with the color difference value obtained by the calculation unit 43, and determines whether or not the color difference is within a reference value range. It is a functional part that performs. This determination result is displayed on the display unit 72 or the like, and is notified to the user as a color difference evaluation result for the anisotropic sample.

  The storage unit 50 includes a color difference type storage unit 51, a coefficient storage unit 52, a reference value storage unit 53, a RAM (Random Access Memory) 54, and a ROM (Read Only Memory) 55. The color difference formula storage unit 51 stores a color difference formula in which the lightness coefficient, the saturation coefficient, and the hue coefficient can be arbitrarily set, for example, the above formulas (2) to (4). The coefficient storage unit 52 stores the lightness coefficient, the saturation coefficient, and the hue coefficient used in the equations (2) to (4) for each type of anisotropic material.

  FIG. 8 is a table format showing an example of the coefficient data table 520 stored in the coefficient storage unit 52. This data table 520 includes a color difference formula field 521 indicating the type of color difference formula, a type field 522 in which the type of anisotropic material is stored as a coating material type, manufacturer, and product number, and a lightness coefficient and a saturation coefficient for each geometry. And a coefficient field 523 in which the hue coefficient is stored, and an update date field 524 indicating the latest date in which these data are set. By holding such a data table 520, when selection information about the type of anisotropic material is given, a recommended value for the anisotropic material is used as a default value to the coefficient setting unit 42 for each geometry. The coefficient can be set. The coefficient value in the coefficient field 523 can be rewritten, and the rewrite date or the newly set date is input to the update date field 524.

In the reference value storage unit 53, the color difference values ΔL ^* , ΔC ^* , ΔH ^* between the reference color and the sample in a predetermined color system in the color difference formulas (2) to (4) above are calculated ^. The color value of the reference color is stored. The RAM 54 temporarily stores data such as arithmetic processing and control processing, as well as received light data provided from the reflected light measurement device 10, spectral reflectance (color value) data obtained from the received light data, or reflection. Data when the received light data stored in the memory unit provided in the light measurement device 10 is downloaded to the personal computer PC is temporarily stored. The ROM 55 stores a control program for operating the measurement system S and the like.

  Next, the coefficient operation unit 60 is a functional unit that accepts operations related to selection of the color difference formula and coefficient setting by the user, and includes a color difference formula selection unit 61, a sample mode selection unit 62, a sample type selection unit 63, and a manual setting unit 64. I have.

  The color difference formula selection unit 61 receives a selection as to which of the color difference formulas stored in the color difference formula storage unit 51 of the storage unit 50 is to be used. The sample mode selection unit 62 selects whether the sample to be colorimetric is a solid color sample (first sample) or the above-described anisotropic sample (second sample). Accept. In this case, when a monochromatic sample is selected, the coefficient set in the coefficient setting unit 42 is set as “lightness coefficient = saturation coefficient = hue coefficient = 1”, and when an anisotropic sample is selected, A predetermined coefficient value for the anisotropic sample stored in the coefficient storage unit 52 is set.

  The sample type selection unit 63 accepts selection as to which anisotropic sample is subjected to color difference evaluation when a plurality of types of anisotropic samples are subjected to colorimetry. In this case, when a specific anisotropic sample is selected based on the data table 520 as shown in FIG. 8, a coefficient set in advance for the sample is set in the coefficient setting unit 42.

  The manual setting unit 64 accepts setting of a coefficient by manual operation when tuning a coefficient for a specific anisotropic sample or inputting a coefficient setting value for a new anisotropic material. The coefficient value input here is set in the coefficient setting unit 42 and stored in the coefficient storage unit 52 (rewritten to a new coefficient value).

  The display control unit 73 converts the color difference data calculated by the color difference calculation unit 40 into a predetermined format and displays it on the display unit 72, and at least selects a sample to be colorimetric, selection of a color difference formula, coefficient The work guidance information related to the setting is generated, and the work guidance information is displayed on the display unit 72. That is, when evaluating the color difference of an anisotropic sample, information for navigating the user's work is provided by displaying predetermined work guidance information on the display unit 72 regarding at least sample selection, color difference formula selection, and coefficient setting. To do.

  FIG. 9 to FIG. 11 show examples of display drawings of the navigation information generated by the display control unit 73 on the display unit 72. FIG. 9 is a plan view showing a use object screen 81 for setting basic items for colorimetry. The used object screen 81 includes a color difference type selection window 811, a sample mode selection window 812, and a geometry selection window 813. The color difference formula selection window 811 displays a selectable color difference formula and accepts a selection for the color difference formula. The sample mode selection window 812 displays the classification of the sample to be measured and accepts selection for the classification. Here, an example is shown in which a solid color sample, a metallic paint sample, a pearl paint sample, and a special sample are displayed. The geometry selection window 813 accepts a selection regarding the configuration of the geometry used for the color measurement work. Here, an example is shown in which “CIE 1994” is selected in the color difference selection window 811, “pearl coating” is selected in the sample mode selection window 812, and “25 ° / 45 ° / 75 °” is selected in the geometry selection window 813. ing. When the OK key 814 is pressed in this state, a transition is made to the screen shown in FIG.

  FIG. 10 is a plan view showing an example of a sample type selection screen 82 for selecting a sample type for pearl coating. The sample type selection screen 82 is provided with a sample type selection window 821. The sample type selection window 821 displays types for selectable pearl coating and accepts selections for the types. In this example, “white pearl (1)” is selected as the type. When the OK key 822 is pressed in this state, a transition is made to the screen shown in FIG.

  FIG. 11 is a plan view showing an example of a coefficient setting screen 83 for setting coefficients according to a specific sample type and color difference formula. The coefficient setting screen 83 includes a sample type display window 831 for displaying the sample type selected on the sample type selection screen 82, and a color difference type display window 832 for displaying the color difference formula selected on the use object screen 81. And a coefficient display unit 833 that displays the coefficient used in the color difference formula and receives the setting.

  The coefficient display unit 833 displays the initial value, recommended value, value used in the previous measurement, or tuning value by the user as the default value of the coefficient for the specific sample type, color difference formula. When the OK key 834 is pressed in this state, the color difference formula displayed here is set in the color difference formula setting unit 41 and the coefficient as the default value is set in the coefficient setting unit 42. . On the other hand, when the user manually sets the coefficient, the input of a desired coefficient to the coefficient display unit 833 is accepted with the depression of the manual setting key 835 as an input start condition.

(Explanation of operation flow)
Next, the operation of the color measurement system S configured as described above will be described. FIG. 12 is a flowchart showing the operation of calculating the color difference by the colorimetry system S. First, the color difference formula and its coefficient used for the color difference evaluation are set in the color difference formula setting unit 41 and the coefficient setting unit 42 (see FIG. 7) (step S1). This operation will be described in detail later based on the flowchart of FIG.

  Hereinafter, the illumination receiving operation for each geometry is executed by the measurement control unit 20 of the reflected light measurement device 10. First, the light source 12a (see FIG. 3) of the first illumination system 11a is turned on, and the measurement light is irradiated to the sample surface 81 of the anisotropic sample 8 arranged in the measurement opening 10b (step S2). Then, the reflected light reflected by the sample surface 81 is received by the spectral light receiver 15 (light receiving element 152), and the reflected light is received in the direction of normal angle 25 ° (25 ° / 0 °) (highlight direction). Data is acquired. The received light data is temporarily stored in the memory unit (not shown) of the reflected light measurement device 10, the RAM 54 of the personal computer PC, or the like (step S3).

  Subsequently, the light source 12b of the second illumination system 11b is turned on, and the sample surface 81 is irradiated with measurement light (step S4). Then, the reflected light reflected by the sample surface 81 is received by the spectral light receiver 15, and the reflected light reception data in the direction of the normal angle 45 ° (45 ° / 0 °) is acquired and stored (step) S5). Further, the light source 12c of the third illumination system 11c is turned on, and the sample surface 81 is irradiated with measurement light (step S6). Then, the reflected light reflected by the sample surface 81 is received by the spectral receiver 15, and the reflected light reception data in the direction of the normal angle of 75 ° (75 ° / 0 °) is acquired and stored (step) S7).

  As described above, when the reflected light reception data is acquired for each of the 25 ° / 0 °, 45 ° / 0 °, and 75 ° / 0 ° geometries, the data is read from the RAM 54 or the like by the calculation unit 43, Spectral reflectance (color value) in each geometry is calculated (step S8). Subsequently, the color difference for each geometry is calculated by applying the color difference formulas and coefficients set in the color difference formula setting unit 41 and the coefficient setting unit 42 by the calculation unit 43 (step S9). At this time, while using the same color difference equation, the coefficient is calculated with different values set for each geometry. Thereafter, the determination unit 44 determines whether or not the color difference is within a predetermined threshold range, and the determination result, the obtained color difference value, and the like are displayed on the display unit 72 (step S10).

  FIG. 13 is a flowchart showing a detailed flow of the color difference formula and coefficient setting thereof in step S1. This flow is executed by being guided by the navigation screen as shown in FIGS. First, a selection instruction is accepted as to what kind of geometry is used in the color difference evaluation (what kind of reflection angle geometry 10 is used for the reflected light measurement device) (step S11). This selection instruction is performed, for example, by a geometry selection operation in the geometry selection window 813 shown in FIG.

  Subsequently, a color difference formula selection instruction is accepted (step S12). This selection instruction is performed, for example, by a color difference expression selection operation (selection operation by the color difference expression selection unit 61 shown in FIG. 7) in the color difference expression selection window 811 shown in FIG. The color difference formula selected here is set in the color difference formula setting unit 41. Further, a sample mode selection instruction is accepted (step S13). This sample mode is a selection between a single color sample (first sample) whose color sensation does not substantially differ depending on the viewing direction, or an anisotropic sample (second sample) whose color sensation varies depending on the viewing direction. This selection instruction is performed by, for example, a sample mode selection operation (selection operation by the sample mode selection unit 62) in the sample mode selection window 812 shown in FIG.

  When a single color sample is selected with the flag in step S13, it is not necessary to consider the color sensation in the illumination direction, so an initial value (for example, lightness coefficient = saturation coefficient = hue coefficient = 1) is automatically set as a coefficient. (Step S14). On the other hand, when an anisotropic sample is selected, a flag for selecting a sample type is executed (step S15). This selection instruction is performed by, for example, a sample type selection operation (selection operation by the sample type selection unit 63) in the sample type selection window 821 shown in FIG.

In the flag of step S15, any one of a sample that has been subjected to metallic coating (step S16), a sample that has been subjected to pearl coating (step S17), and a sample having other reflection characteristics (step S18) is selected. An example is shown. When these sample types are selected, a standard default coefficient (a preset recommended coefficient) corresponding to the sample type is read from the coefficient storage unit 52, and the coefficient is temporarily stored in the coefficient setting unit 42. Is set. Then, the temporarily set coefficient is displayed on the coefficient display unit 833, for example, in a mode like a coefficient setting screen 83 shown in FIG. 11 (step S20).

  As described above, in addition to the mode in which the coefficient is automatically set with the default value, the coefficient can be manually input from the manual setting unit 64. Specifically, the user tuning value customized according to the user's color difference evaluation purpose can be input (step S19). The formulation of such user tuning values is based on the progress of accumulation of evaluation data on the target anisotropic sample, analysis of color difference evaluation values, determination of optimum coefficients, and the like. The input operation of the user tuning value is, for example, an operation in which a manual setting key 835 is pressed on the coefficient setting screen 83 and a desired coefficient value is input to the coefficient display unit 833.

  Subsequently, the quality of the temporarily set coefficient is determined as described above. If the coefficient set value is not appropriate (NO in step S21), an operation for correcting the coefficient set value is accepted (step S22). Then, for example, the coefficient is determined by pressing the OK key 834 on the coefficient setting screen 83, the coefficient setting condition is stored in the coefficient storage unit 52 (step S23), and the process is completed. If the coefficient set value is appropriate (YES in step S21), the process skips to step S23, and the temporarily set coefficient is set as it is in the coefficient setting unit 42 and stored in the coefficient storage unit 52.

  CIE2000 color difference formula and CMC using the reflected light measuring device of three-way illumination one-way light reception set in the geometry of 25 ° / 0 °, 45 ° / 0 °, 75 ° / 0 ° as shown in FIG. The color difference of the anisotropic sample was evaluated using (l: c) color difference formula. The anisotropic samples used were exterior parts of automobiles, all of which were judged to be acceptable in both the highlight direction and shade direction in visual color difference evaluation (the deviation from the reference color was judged to be within the allowable range) ) Was used. As sample types, four colors with white pearl paint, silver paint, light color paint, and dark color paint were selected, and four samples (16 samples in total) were prepared for each color.

Specifically, the CIE 2000 color difference formula is used as Example 1, and the lightness coefficient K _L , the saturation coefficient K _C , and the hue coefficient K _H are 25 ° / 0 °, 45 ° / 0 °, and 75 ° / 0 °. Each geometry was set as shown in Table 1. Further, the CMC (l: c) color difference formula is used as Example 2, and the lightness coefficient l and the saturation coefficient c are shown in Table 1 for each geometry of 25 ° / 0 °, 45 ° / 0 °, and 75 ° / 0 °. Each was set as follows. In the CMC (l: c) color difference formula, the hue coefficient = 1 is fixed.

For comparison with this, as shown in Table 1 below, ΔE ^* a ^* b ^* color difference formula (Comparative Example 1) that does not use the coefficient shown in the above formula (1), and the lightness coefficient K _L for all geometries. CIE 2000 color difference formula set to 1 = saturation coefficient K _C = hue coefficient K _H = 1 (Comparative Example 2), and CMC (l: c) color difference formula set to 1 (Saturation coefficient c = 1) 3) was set.

  FIG. 14 shows the results of obtaining the color difference for the 16 samples using the color difference formulas set in Examples 1 and 2 and Comparative Examples 1 to 3. FIG. 14 shows the spectral reflectance of each of the 16 samples in the geometries of 25 ° / 0 °, 45 ° / 0 °, and 75 ° / 0 °, and the color difference formula shown in Table 1 above is applied thereto. Thus, the color difference obtained is represented as a line graph in one graph. There are three plots for each sample, which show the color difference in the geometry of 25 ° / 0 °, 45 ° / 0 °, and 75 ° / 0 ° in order from the left.

  As is clear from FIG. 14, those using the color difference formulas of Examples 1 and 2 are generally calculated with a low color difference (color difference = 1 or less), and are highly correlated with the visual color difference evaluation result. Is obtained. In Example 2, the color difference value is calculated to be high for the dark color sample. This is considered to be due to the fact that the same coefficient is adopted regardless of the sample type. It is possible to enhance the correlation with the visual color difference evaluation result by individually setting the coefficients suitable for

  On the other hand, those using the color difference formulas of Comparative Examples 1 to 3 are generally calculated as high values of the color difference, and have a low correlation with the visual color difference evaluation result. In particular, the color difference in the highlight direction (geometry of 25 ° / 0 °) tends to be high, and this is because the lightness difference that cannot be recognized as a significant difference by human vision is treated as a large value. This is thought to be caused by this.

(Description of Modified Embodiment)
Although the embodiments of the present invention have been described above, various modified embodiments other than the above can be adopted. For example, in the above-described embodiment, the metallic coating sample and the pearl coating sample are exemplified as the anisotropic sample, but the present invention can also be applied to a sample that changes in color different from these. As an example, an anisotropic sample having a multi-layered paint layer whose hue changes greatly depending on the viewing direction can also be a colorimetric object.

For example, a sample having a paint layer having a two-layer structure with different colors (hues), and in the highlight direction, the light reflected by both the first layer on the outer surface and the second layer below it can be visually recognized. However, since the film thickness of the first layer increases in the shade direction in the shade direction, the light reflected by the second layer is blocked by the first layer, and as a result, the reflected light from the second layer cannot be visually recognized. Sample. In the sample having the paint layer having such a two-layer structure, when the hues of the first layer and the second layer are different, the relationship of the above equation (8) is adopted while adopting the relationship of the above equation (7). The coefficient is set by transforming as in the following equation (8) ′.
l ≧ h ≧ c where l ≠ c (8) ′
In this case, since there are innumerable combinations of hues of the first layer and the second layer, it is desirable to change the coefficient value for each sample. This relationship is also applied to a sample having a coating layer having a number of layers higher than that of the two-layer structure and the color of the lower layer portion can be identified. However, when the first layer and the second layer are the same color, or when the colors are different in saturation, the relationship of the above equation (8) may be applied.

  Furthermore, a sample having a paint layer having a multilayer structure, and an anisotropic sample (for example, trade name “Majora” manufactured by Nippon Paint Co., Ltd.) whose hue changes greatly depending on the viewing direction due to the effect of the interference wavelength is applied. Sample) can also be a colorimetric object. In this case as well, in order to extend the tolerance of hue, it is desirable to set the coefficient according to the relationship of the above equation (8) 'while adopting the relationship of the above equation (7).

  Further, as specific examples of the geometries, the geometries of 25 ° / 0 °, 45 ° / 0 °, and 75 ° / 0 ° are illustrated, but other than this, for example, 15 ° / 0 °, 45 ° / 0 °, 65 ° A / 0 ° geometry or the like can also be employed. Further, instead of the three-way geometry, only the two-way geometry (for example, 25 ° / 0 ° and 75 ° / 0 °) between the highlight direction and the shade direction may be used, or a geometry having four or more directions may be used. Also good. Furthermore, in the said embodiment, although the geometry (multi-directional illumination unidirectional light reception) which can change the angle of the illumination direction with respect to a light reception direction was illustrated, the geometry (unidirectional illumination multi-direction) which can change the angle of the light reception direction with respect to an illumination direction Light reception).

(A) is a cross-sectional view schematically showing a cross section of an anisotropic sample, and (b) is a schematic view for explaining light reflection characteristics of the anisotropic sample. It is a block diagram which shows roughly the whole structure of the color measurement system S (color difference evaluation method of an anisotropic sample) concerning embodiment of this invention. 2 is a configuration diagram illustrating an example of a hardware configuration of a specific color measurement system S. FIG. It is explanatory drawing which shows the outline of the geometry with which the reflected light measurement apparatus of the colorimetry system S is equipped. It is explanatory drawing which shows other embodiment of an illumination system. It is a graph which shows typically the coefficient setting method of a color difference type | formula. It is a block diagram which shows the principal part of an electrical functional structure of a reflected light measuring apparatus and a personal computer. It is a table format figure which shows an example of the data table of the coefficient stored in a coefficient memory | storage part. It is a top view which shows an example of the display screen which provides the navigation information for a coefficient setting. It is a top view which shows an example of the display screen which provides the navigation information for a coefficient setting. It is a top view which shows an example of the display screen which provides the navigation information for a coefficient setting. 5 is a flowchart illustrating an operation of calculating a color difference by the colorimetry system S. It is a flowchart which shows the detailed flow of a color difference type | formula and its coefficient setting. It is a graph which shows the color difference calculation result by an Example and a comparative example.

Explanation of symbols

1, 10 Reflected light measuring device (illumination light receiving optical system / geometry)
4 Color difference calculation means PC Personal computer (color difference calculation means)
40 Color Difference Calculation Unit 41 Color Difference Formula Setting Unit 42 Coefficient Setting Unit 43 Calculation Unit 50 Storage Unit 51 Color Difference Formula Storage Unit 52 Coefficient Storage Unit 60 Coefficient Operation Unit 61 Color Difference Formula Selection Unit 62 Sample Mode Selection Unit 63 Sample Type Selection Unit 64 Manual Setting Part (operation part to correct the coefficient)
72 Display Unit 73 Display Control Unit 8 Anisotropic Sample

Claims (9)

Using an illumination light receiving optical system that can change the angle of the light receiving direction relative to the illumination direction or the angle of the illumination direction relative to the light receiving direction, illuminate the anisotropic sample with a different color sense depending on the viewing direction, and receive the reflected light A color difference evaluation method for performing a color difference evaluation by applying a predetermined color difference formula to the received light data obtained in the above,
As the color difference formula, a color difference formula that can arbitrarily set at least a coefficient relating to lightness is used,
The color difference applied to the received light data obtained when the illumination light receiving optical system is set to the highlight optical system is set to L1, and the lightness coefficient of the color difference formula applied to the received light data obtained when the shade optical system is set. When the brightness coefficient of the equation is L2,
L1> L2
A color difference evaluation method for anisotropic samples, characterized in that a lightness coefficient is set so as to satisfy the above relationship. Using a predetermined illumination light receiving optical system, illuminating an anisotropic sample with a different color sensation depending on the viewing direction, and applying the predetermined color difference formula to the received light data obtained by receiving the reflected light, color difference evaluation A color difference evaluation method for performing
As the color difference formula, a color difference formula that can arbitrarily set coefficients relating to lightness, saturation, and hue is used.
When the illumination coefficient of the color difference applied to the received light data obtained when the illumination light receiving optical system is set to an optical system having a predetermined reflection angle is l, the saturation coefficient is c, and the hue coefficient is h,
l ≧ c ≧ h where l ≠ h
Or
l ≧ h ≧ c where l ≠ c
A method for evaluating a color difference of an anisotropic sample, wherein a brightness coefficient is set so as to satisfy any one of the following relationships. Using an illumination light receiving optical system that can change the angle of the light receiving direction relative to the illumination direction or the angle of the illumination direction relative to the light receiving direction, illuminate the anisotropic sample with a different color sense depending on the viewing direction, and receive the reflected light A color difference evaluation method for performing a color difference evaluation by applying a predetermined color difference formula to the received light data obtained in the above,
As the color difference formula, a color difference formula that can arbitrarily set coefficients relating to lightness, saturation, and hue is used.
The color difference applied to the received light data obtained when the illumination light receiving optical system is set to the highlight optical system is set to L1, and the lightness coefficient of the color difference formula applied to the received light data obtained when the shade optical system is set. When the brightness coefficient of the equation is L2,
L1 ≧ L2
Set the brightness coefficient to satisfy the relationship, and
When the illumination coefficient of the color difference applied to the received light data obtained when the illumination light receiving optical system is set to an optical system having a predetermined reflection angle is l, the saturation coefficient is c, and the hue coefficient is h,
l ≧ c ≧ h where l ≠ h
Or
l ≧ h ≧ c where l ≠ c
A method for evaluating a color difference of an anisotropic sample, wherein a brightness coefficient is set so as to satisfy any one of the following relationships. An illumination light receiving optical system configured such that the angle of the light receiving direction with respect to the illumination direction or the angle of the illumination direction with respect to the light receiving direction can be changed, illuminates the predetermined sample with illumination light, and can receive the reflected light;
Color difference calculating means for calculating a color difference by applying a predetermined color difference formula to the received light data of the reflected light obtained by the illumination light receiving optical system,
The color difference calculating means includes
A color difference formula storage unit for storing a predetermined color difference formula capable of arbitrarily setting coefficients relating to lightness, saturation, and hue;
A coefficient setting unit for receiving settings for the coefficient of the color difference formula;
A colorimetric system comprising: an arithmetic unit for substituting the coefficient set by the coefficient setting unit into the color difference formula to obtain a color difference for the received light data of the reflected light.   The colorimetric system according to claim 4, further comprising a coefficient storage unit that stores a coefficient set in the coefficient setting unit. A sample mode selection unit for selecting whether the sample to be colorimetric is a first sample whose color sensation is not substantially different depending on at least the viewing direction or a second sample whose color sensation is different depending on the viewing direction;
The coefficient storage unit stores a first coefficient for the first sample and a second coefficient for the second sample,
When the first sample is selected by the sample mode selection unit, the first coefficient is set in the coefficient setting unit, and when the second sample is selected, the second coefficient is set in the coefficient setting unit. The colorimetric system according to claim 5, wherein the coefficient is set. A sample type selection unit for selecting a sample type for the second sample;
The coefficient storage unit stores a coefficient corresponding to the sample type,
The color measurement system according to claim 6, wherein a coefficient corresponding to the sample type selected by the sample type selection unit is configured to be set in the coefficient setting unit. An operation unit for correcting a coefficient once set in the coefficient setting unit;
The color measurement system according to claim 6 or 7, wherein the coefficient storage unit is capable of storing a coefficient corrected by the operation unit. A predetermined display section;
A display control unit that generates work guidance information related to at least selection of a sample to be colorimetric, selection of a color difference formula, and coefficient setting;
The colorimetric system according to claim 4, wherein work guidance information generated by the display control unit can be displayed on the display unit.

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