JPH04213033A - Color measuring apparatus for metal-based applied color - Google Patents

Abstract

PURPOSE:To utilize the light from a light source part effectively and to reduce the error between the measurement and visual evaluation by optimally forming the incident light of the light source part and the angle of the regular reflected light from each light receiving part. CONSTITUTION:A color measuring apparatus comprises the parts having the following functions. A light source part 4 emits light at the incident angle of 20-30 degrees. A first light receiving part 5 has the optical axis which is inclined to the side of the light source part at 20-30 degrees with respect to the optical axis of the regular reflected light of the light source part 4. A second light receiving part 6 receives the reflected light which is inclined to the side of the light source part 4 by 85-100 degrees with respect to the optical axis of the regular reflected light. A photoelectric converter part 2 converts the received reflected lights into the electric signals, respectively. A data processing part 3 computes the color values corresponding to the applied colors by operating the electric signals and displays the values, respectively. The incident angle of the light source part 4 and the angles from the regular reflected lights of the light receiving parts 5 and 6 are optimally set. Therefore, the light from the light source 4 can be effectively utilized. Since the first light receiving part 5 is set at 20-30 degrees with respect to the regular reflected light, the reflected light is hard to enter into the light receiving part 5 even if the surface whose color is to be measured is the curved surface, and the error between the measurement and the visual evaluation can be made small.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color measuring device for color measuring metallic paint colors.

0002

BACKGROUND OF THE INVENTION Until recently, evaluation of the difference between a paint color and a reference color has relied on visual evaluation by an expert. However, this type of sensory evaluation is highly influenced by individual differences and the observation environment, resulting in a problem of variation in evaluation results. Therefore, it is desired to quantify the paint color and make an absolute evaluation, and various color measuring devices such as an integrating sphere color measuring device have been developed and put into practical use in recent years.

By the way, metallic paint colors containing scaly powders such as aluminum powder and mica powder are often used as paint colors for automobiles and the like. This metallic coating color is characterized in that the color development differs depending on the viewing angle depending on the orientation of the scaly powder. However, this feature, which is an advantage in terms of design, is a disadvantage when it comes to quantifying by colorimetry, and with colorimeter devices that use an integrating sphere, it is necessary to measure the surface multiple times by changing the angle of light irradiation onto the surface to be measured. It is necessary to quantify it. However, in the case of metallic paint colors, colorimetric evaluations and visual evaluations rarely match, and these colorimetric devices have been mainly used to measure solid paint colors. To actually evaluate a metallic paint color, hold the panels of the evaluation paint color and the standard paint color side by side, and tilt the panel approximately 60 degrees from the horizontal with your back to the sun.
Currently, an expert visually evaluates the panel from two angles: tilting the panel from that position until it becomes horizontal and looking at the shade in a horizontal position. However, as mentioned above, there are individual differences, and it takes a lot of man-hours to decide on the evaluation. Therefore, it has been desired to develop a color measuring device or method with higher accuracy.

For example, in US Pat. No. 4,479,718, light is irradiated onto the surface to be measured at an incident angle of 45°, and the reflected light at positions tilted by 15°, 45°, and 110° from the optical axis of the specularly reflected light is received and calculated. A color measurement method is disclosed.

[0005]

[Problems to be Solved by the Invention] As described above, with the device that receives light at a plurality of light receiving angles and performs calculations, it is possible to simultaneously perform color measurements corresponding to highlights and shades, and to measure metallic paint colors. In many cases, the color evaluation matches the human visual evaluation, and it can be said that the method has reached a practical level. However, when the incident angle is 45°, the amount of incident light decreases, and the amount of reflected light to the light receiving section equivalent to the shade is often insufficient, resulting in a decrease in resolution and a decrease in colorimetric accuracy. Therefore, it is necessary to increase the output of the light source section and the lens of the light receiving section, making the device larger and more complicated, making it difficult to make it compact.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a compact color measuring device capable of measuring color that is highly consistent with human visual evaluation.

[0007]

[Means and effects for solving the problems] The color measuring device for metallic color coating of the present invention which solves the above problems has a color measuring device of 20 to 3
A light source unit that irradiates light onto the surface to be measured at an incident angle of 0°, and a light source unit that is 20 to 30 degrees with respect to the optical axis of the specularly reflected light from which the light emitted from the light source unit is specularly reflected on the surface to be measured. A first light receiving section that receives reflected light with an optical axis tilted to the side, and a second light receiving section that receives reflected light that has an optical axis tilted toward the light source by 85 to 100 degrees with respect to the optical axis of specularly reflected light. a photoelectric conversion section that converts the reflected light received by the first light receiving section and the second light receiving section into electrical signals, and a reflected light received by the first light receiving section and the second light receiving section by calculating from the electrical signals. and a data processing unit that calculates and displays color values corresponding to the respective color values.

[0008] As the light source section, a conventional one such as a xenon lamp or a halogen lamp can be used. In the present invention, the light source unit irradiates the surface to be measured with an incident angle of 20 to 30 degrees. If the incident angle is smaller than 20°, the amount of reflected light received by the second light receiving section will decrease, leading to an increase in the size of the device. Furthermore, if the angle exceeds 30°, the amount of incident light decreases, which also results in an increase in the size of the device. By setting it within this range, the amount of reflected light received by the second light receiving section can be increased while maintaining the amount of incident light.

[0009] The first light receiving section and the second light receiving section can be constructed from lenses, optical fibers, etc., as in the prior art. The first light receiving section receives reflected light equivalent to a highlight, and its optical axis is tilted 20 to 30 degrees toward the light source with respect to the optical axis of the specularly reflected light when the light from the light source is specularly reflected on the surface to be measured. It is arranged so as to receive reflected light having . There is a relationship as shown in FIG. 5 between the angle between the light-receiving axis of the light-receiving section and the optical axis of specularly reflected light and the reflectance, and when the angle becomes 30 degrees or more, the reflectance becomes extremely small. Therefore, when the angle is greater than 30°, the reflectance decreases, and the discrepancy between the colorimetric results corresponding to highlights and the visual results increases. Moreover, if the inclination of the light receiving axis of this first light receiving part is less than 20°,
When the surface to be irradiated is a curved surface, specularly reflected light tends to enter the first light receiving section, and the accuracy of colorimetry decreases.

Further, the second light receiving section is arranged to receive reflected light equivalent to a shade, and to receive reflected light having an optical axis inclined toward the light source section by 85 to 100 degrees with respect to the optical axis of the specularly reflected light. ing. If the inclination of the light-receiving axis is less than 85°, there will be a large discrepancy between the colorimetric results equivalent to the shade and the visual results, and if it is more than 100°, the amount of reflected light will decrease, leading to an increase in the size of the device.

The photoelectric conversion section has a function of converting the reflected light received by the first light receiving section and the second light receiving section into electrical signals, and can utilize a known photoelectric conversion element such as a photodiode. The data processing section calculates the first light receiving section and the second light receiving section from the electrical signal output from the photoelectric conversion section.
Each color value corresponding to the reflected light received by the light receiving section is calculated. This color value includes the reflectance of light at each wavelength,
Examples include tristimulus values (X, Y, Z), L* a* b* values, and the like. Then, the color value corresponding to the reflected light received by each light receiving section is displayed. As a data processing section, A/D
Converters, digital circuits using microcomputers, CRTs, printers, liquid crystal display devices, etc. can be used.

0012

[Examples] Hereinafter, the present invention will be explained in detail using examples. Figure 1
2 shows a block diagram of a colorimetric device according to an embodiment of the present invention. This color measurement device includes a color measurement section 1, a photoelectric conversion section 2, and a data processing section 3. The color measurement section 1 has an opening 10a.
It is composed of a mounting base plate 10 having a mounting base plate 10, a support frame 11 fixed to the mounting base plate 10, a light source section 4, a first light receiving section 5, and a second light receiving section 6 fixed to the support frame 11.

The light source section 4 includes a xenon lamp 41 that emits light by a light emitting circuit 40, an optical fiber 42 that carries light from the xenon lamp 41, a light projecting lens barrel 43 connected to the other end of the optical fiber 42, and a light projecting lens barrel 43 that is connected to the other end of the optical fiber 42. It consists of a light projecting lens 44 provided at the other end of the light projecting lens barrel 43.
is fixed to the support frame 11. Here, the light emitted from the projection lens 44 is a parallel light beam, and its optical axis is inclined by −30° with respect to the normal line from the aperture 10a. That is, the light emitted from the projection lens 44 is configured to be emitted onto the aperture 10a at an incident angle of 30°.

The first light receiving section 5 includes a light receiving lens barrel 50, a light receiving lens 51 held at one end of the light receiving lens barrel 50, and an optical fiber 52 coupled to the other end of the light receiving lens barrel 50. The light receiving lens barrel 50 is fixed to the support frame 11. Here, the optical axis of the light entering the light-receiving lens barrel 50 from the light-receiving lens 51 is on the same plane as the optical axis of the light emitted from the light-emitting lens 44, and is directed toward the aperture 10a and the normal line from the aperture 10a. It is tilted +5° to the opposite side to the light emitted from the light projecting lens 44. In other words, Figure 2
As shown in FIG. 2, the light source 4 is configured to receive reflected light having an optical axis inclined toward the light source 4 by 25 degrees with respect to the optical axis of the specularly reflected light from the light source 4.

The second light receiving section 5 includes a light receiving lens barrel 60, a light receiving lens 61 held at one end of the light receiving lens barrel 60, and an optical fiber 62 coupled to the other end of the light receiving lens barrel 60. The light receiving lens barrel 60 is fixed to the support frame 11. Here, the optical axis of the light entering the light-receiving lens barrel 60 from the light-receiving lens 61 is on the same plane as the optical axis of the light emitted from the light-emitting lens 44, and is directed toward the aperture 10a and the normal line from the aperture 10a. Toward the projection lens 44 side -6
It is tilted at 5°. That is, as shown in FIG. 2, it is configured to receive reflected light having an optical axis inclined toward the light source section 4 at 95 degrees with respect to the optical axis of specularly reflected light from the light source section 4.

In the colorimeter 1 configured as described above, the mounting plate 10 is brought into contact with the object 100 to be measured, and the light source 4 illuminates the surface of the object 100 exposed through the opening 10a. Light is irradiated. Note that a soft member such as rubber is adhered to the surface of the mounting base plate 10 facing the object 100 to be color measured.
00 is prevented from being scratched. The photoelectric conversion unit 2 includes optical filters F1 to F9 and photodiodes P1 to P9 arranged behind them. The photodiodes P4 to P6 receive light from the optical fiber 52 extending from the first light receiving section 5, the photodiodes P1 to P3 receive light from the optical fiber 62 extending from the second light receiving section 6, and the photodiodes P7 to P9 receive light from the optical fiber 62 extending from the second light receiving section 6. It receives light from the xenon lamp 41 of the light source section 4. These optical filters F1 to F9 and photodiodes P1 to P9 are configured to have spectral sensitivities that approximate CIE color matching functions X(λ), Y(λ), and Z(λ), respectively. The output currents of the photodiodes P1 to P9 are converted into electrical signals by the respective photoelectric conversion units E1 to E9, and are input to the data processing unit 3.

The data processing section 3 includes an A/D conversion section 30, a C
It is composed of a PU 31, an input/output port 32, a keyboard 33, a buzzer 34, a liquid crystal display section 35, a printer 36, and the like. The A/D converter 30 converts the amount of electricity corresponding to the optical signal into a digital signal, which is input to the CPU 31 . Here, the output value from the A/D converter 30 is
1, YS1, ZS1, X2 S2, YS2, ZS2, X2
If R, YR, ZR, then in CPU31, X2m1=
X2S1/X2R, Ym1=YS1/YR, Zm1=Z
S1/ZR, X2m2=X2S2/X2R, Ym2=Y
By calculating S2/YR, Zm2=ZS2/ZR, fluctuations in the amount of light from the light source section 4 are canceled and color values are calculated. From these values, the tristimulus values (X,
Y, Z) are determined, further converted to the L* a* b* color system, and the respective values are displayed on the liquid crystal display section 35 and printer 36.

The operation will be explained according to the flowcharts shown in FIGS. 3 and 4. First, press the calibration key on the keyboard 33 to enter the calibration mode. Then, in step S11, the tristimulus values (X0i, Y0i, Z0i (i=1,
2) Enter ). Next, the mounting plate 10 of the colorimeter 1 is brought into contact with the calibration reference sample, and the measurement key is turned on to cause the xenon lamp 41 to emit light. As a result, the CPU 31 has A
The digital output values from the /D converter 30 are input, and Xmi, Ymi, and Zmi are calculated in step S14. Then, in step S15, the calibration constants αi, βi, γ
Find i.

Next, replace the calibration reference sample with the measurement sample and press the measurement key. Then, in step S23, Xmi, Ymi
, Zmi are calculated and multiplied by the calibration constant obtained earlier in step S24 to obtain tristimulus values (Xi, Yi, Zi).
is required. Then, in step S25, the lightness index L*
, chromaticness index a*, b* (CIE-1
976 (L*a*b*)), and in step S26, the respective values are displayed on the liquid crystal display section 35 and the printer 36.
to be displayed.

[0020]

According to the color measuring device of the present invention, the incident angle of the light source section and the angle from the specularly reflected light of each light receiving section are configured optimally, so that the light of the light source section can be used effectively. Therefore, even if the output of the light source section is reduced compared to conventional devices, color measurement can be performed with the same accuracy as conventional devices, and energy consumption can be reduced. Furthermore, since the amount of reflected light increases, even if the lens of the light receiving section is made smaller, the same accuracy as before can be obtained. Therefore, these effects make it possible to make the colorimetric device more compact than in the past, and the degree of freedom in colorimetry is greatly improved.

Furthermore, when the shape of the surface to be measured is a curved surface, errors may occur due to variations in the angle of reflected light. In other words, in conventional devices that have a light receiving section tilted at a small angle of 15 degrees with respect to the optical axis of the specularly reflected light, there is a high possibility that the specularly reflected light will enter the light receiving section, making visual evaluation difficult. errors are likely to occur. However, in the present invention, this angle is set to 20 to 30 degrees, so even if the shape of the surface to be measured is a curved surface, it is difficult for the specularly reflected light to enter the first light receiving section compared to the conventional method, and evaluation can be done visually. The error can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a colorimetric device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the configuration of an optical system of a colorimetric device according to an embodiment of the present invention.

FIG. 3 is a flowchart showing the processing of the colorimetric device according to the embodiment of the present invention.

FIG. 4 is a flowchart showing the processing of the colorimetric device according to the embodiment of the present invention.

FIG. 5 is a graph showing the relationship between reflectance and the angle between specularly reflected light and the light receiving axis.

[Explanation of symbols]

1 Color measurement section 2 Photoelectric conversion section 3 Data processing section 4 Light source section 5 First light receiving section 6 Second light receiving section

Claims (1)

[Claims] 1. A light source unit that irradiates light onto a surface to be measured at an incident angle of 20 to 30 degrees, and an optical axis of specularly reflected light when the light irradiated from the light source unit is specularly reflected by the surface to be measured. against 2
a first light receiving section that receives reflected light having an optical axis inclined toward the light source section by 0 to 30 degrees;
a second light receiving section that receives reflected light having an optical axis inclined toward the light source section by 5 to 100 degrees, the first light receiving section and the second light receiving section;
a photoelectric conversion section that converts each of the reflected lights received by the light receiving section into an electrical signal;
A color measurement device for metallic coating, comprising a light receiving section and a data processing section that calculates color values corresponding to the reflected light received by the second light receiving section and displays the color values.