JPH0438428A - Method and apparatus for measuring color - Google Patents

Abstract

PURPOSE:To always correctly and highly accurately obtain color information inherent to a medium (specimen to be measured) in a non-contact state where an apparatus is separated from the medium not depending on external lighting environmental conditions by taking a difference in chromaticity signals between at the time of illuminating a light emitting source and at the time of not illuminating the source. CONSTITUTION:An apparatus for measuring color comprises a light source lamp 11, a slit 12 which emits light 30 from the light source lamp 11 to a medium 100 from a slant direction, a condenser plate 17 for condensing dispersed reflection light 32 from the medium 100, an optical fiber 16 which transmits the condensed light to a surface of a light receiver 18, the light receiver 18 for photoelectrically converting the light, a sample & hold circuit 19 which converts an output signal of the light receiver 18 into a digital amount and stores it, an A/D converter 20, a memory 21, a subtractor 23 which performs subtraction for subtracting the output signal of the light receiver 18 from a signal stored in the memory 21, an optical fiber 26, a photo cell 13 and a detection monitor unit 14 which detects light emission intensity and a fluctuation in color to output a compensation value of the fluctuation, and a signal processing unit which compensates the output signal of the subtractor 23 based on the fluctuation compensation value to calculate a color signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color measurement method and apparatus for measuring the color of automobile paint, ink, etc. in a non-contact manner.

[Conventional technology] In recent years, lighting and televisions in offices and department stores.

2. Description of the Related Art As the management of colors of signal lights, guide lights, automobile paints, plants, etc. becomes increasingly important, various color measuring devices for color management have been developed and put into practical use. Most of such color measuring devices conventionally operate in a mode in which the color is measured by contacting the medium surface. This means that when the wavelength and angle of incidence of external light change, the intensity of reflected light from the medium changes (i.e., the gloss changes).
, because the medium no longer exhibits its inherent color,
By bringing it into contact with the medium, the influence of external light is removed.

FIG. 3 shows an example of a conventional color measuring device.

The conventional device uses a light source lamp 11. A light shielding plate 41 that blocks direct light from the light source lamp in order to irradiate the sample with only diffused light. Diffusion plate 42. Optical fiber 16 for transmitting diffused light from sample 100. Optical sensor 18 that performs photoelectric conversion. and a signal processing circuit 43 that calculates a chromaticity signal,
A chromaticity signal is obtained by directly contacting the measurement sample 100, which is a medium, and shielding the measurement location from the outside with a cover 44 to prevent disturbance light from entering. in this case,
When external light enters, diffused light and specularly reflected light due to the external light are generated as signal components, so that the color is recognized as different from the color unique to the medium. That is why they are placed in contact to block external light. Of course, when calculating the chromaticity signal with the external environment unchanged and the external light taken in, it is possible to levitate the device, but this is a special category of usage and may cause inaccurate Color information will be available.

[Problem to be Solved by the Invention 1] However, if the color is managed in-line while the car is being painted, and the amount of material mixed in the spraying machine is accurately controlled, Such a contact-type color measuring device is not suitable. This is because if the measuring device adheres to the painted surface of an automobile, the paint may peel off or the painting process must be temporarily interrupted. Furthermore, when controlling the color of plants, etc., it is said that it is difficult to judge the growth status of the plant unless the color of the concave part at the base of the leaf is measured. When measuring by applying it to the surface, problems such as damaging the soft leaves occurred, making it unsuitable.

An object of the present invention is to provide a color measuring method and an apparatus therefor that eliminates such conventional drawbacks by using a non-contact method.

[Means for Solving the Problems] In order to achieve the above object, the color measurement method according to the present invention is a method of measuring the color specific to a medium by performing diffuse reflected light processing and signal processing. In the diffuse reflected light processing, the diffuse reflected light from the medium to be measured is received separately when the medium is irradiated with light and when the medium is not irradiated under the same environmental conditions, and each diffuse reflected light is The signal processing is performed by performing subtraction processing based on the two chromaticity signals obtained in the above processing, and calculating a medium-specific chromaticity signal based on the result. It is something.

Further, in the color measurement device according to the present invention, the color measurement device includes a light source lamp, a slit, a light condensing plate, an optical fiber, a light receiver, and a signal processing section, wherein the light source lamp is a device to be measured. The slit is used to irradiate the medium with light. The slit is used to diagonally irradiate the medium to be measured with the irradiated light from the light source lamp, and the condenser plate is used to collect the diffusely reflected light from the medium to be measured. Yes, the optical fiber is for transmitting the focused diffusely reflected light, the receiver is for photoelectrically converting the diffusely reflected light transmitted by the optical fiber, and the signal processing section is for converting the diffusely reflected light transmitted by the optical fiber into electricity. The signal is processed to calculate a chromaticity signal specific to the medium.

Further, in the color measurement device according to the present invention, the color measurement device includes a light source lamp, a slit, a lens, a photosensor, and a signal processing section, wherein the light source lamp irradiates light onto a medium to be measured. The slit allows the light from the light source lamp to obliquely irradiate the medium to be measured, the lens focuses the diffusely reflected light from the medium to be measured, and the photosensor It photoelectrically converts the diffusely reflected light collected by the lens, and the signal processing section processes the photoelectrically converted signal to calculate a chromaticity signal specific to the medium.

[Operation] According to the present invention, under the same environmental conditions, the diffuse reflected light from the medium is received separately when the light source lamp is not emitting light, and when the light source lamp is emitting light, and a signal is obtained, and the difference signal is obtained. It is extracted and used as a chromaticity signal. Therefore, all diffused disturbances and reflected light caused by various types of external light incident on the medium from the outside are removed. That is, the color unique to the medium determined by the wavelength of the light emitting source is measured under any environmental conditions. Therefore, for example, when painting a car body, the color of a painted surface can be monitored in-line and remotely from a certain distance from the painted surface.

This allows automation of painting.

[Example] Hereinafter, an example of the present invention will be described in detail using the drawings.

(Example 1) FIG. 1 is a diagram showing a schematic configuration of a color measuring device according to Example 1 of the present invention.

In the figure, this device includes a light source lamp 11, a slit 12 that allows light 30 from the light source lamp 11 to be irradiated onto a medium 100 from an oblique direction, and a diffusely reflected light 30 from the medium 100.
an optical fiber 16 that transmits the focused light to the surface of the light receiver 18; a light receiver I8 for photoelectrically converting the light; and a light receiver I8 that converts the output signal of the light receiver 18 into a digital quantity. Sample hold circuit 1 for converting and storing
9. From the A/D converter 20, the memory 21, and the signal stored in the memory 21 (the light reception signal when the light source lamp is irradiated), the output signal of the light receiver 18 (the light reception signal when the light source lamp is not irradiated) is obtained. a subtractor 23 that performs subtraction for subtracting;
An optical fiber 26, a photocell 13, a detection monitor section 14, and a detection monitor section 14 for detecting variations in the light emission intensity of the light source lamp II in nine colors and outputting a correction value for the variation, and an output signal of the subtracter 23 based on the variation correction value. and a signal processing section that corrects and calculates a chromaticity signal. Note that the optical fiber 26 for transmitting the light emitted from the light source lamp 11 is not necessarily required, and the photocell 13 may be placed directly near the light source lamp 11.

In the color measuring device of this embodiment, a fan-shaped light condensing plate 17 is provided on the light receiving surface in order to take in uniform and sufficiently strong diffused light even when floating a predetermined distance from the medium 100, and to enable detection. An optical fiber 16 is attached to this light condensing plate 17 to transmit light to a light receiver 18. The surface of the light condensing plate 17 is blackened to prevent light reflection.

The color measurement method will be described below. First, the light source lamp 11 made of a standard light source such as a xenon lamp is activated to obliquely irradiate the surface of the medium +00 with incident light 3o. This incident light 30 is absorbed inside the medium, causes specular reflection, or causes diffuse reflection. At this time, since the specularly reflected light 31 due to specular reflection travels in an oblique direction, the light condensing plate 17
It doesn't come inside. Diffuse reflected light 32 inside is scattered in random directions when viewed from the irradiation point of the incident light. This light is taken in by the condenser plate 17 uniformly at any position and with as high an intensity as possible. The diffusely reflected light 32 captured in this manner is transmitted through the plurality of optical fibers 16, hits the light receiving surface of the light receiver 18, and is photoelectrically converted. The resulting analog signal is sampled by a sample hold circuit 19, converted into a digital signal by an A/D converter 20, and a chromaticity signal corresponding to the diffusely reflected light from the medium is stored in a memory 21. The chromaticity signal information stored in the memory 21 in this way is based on not only the incident light from the light source lamp 11 but also the external irradiation light (for example, sunlight or other irradiation light) that is irradiated onto the medium. It is something that is observed in the state of being. Now, assuming that the chromaticity signal due to the incident light from the light source lamp 11 is ycs, and the chromaticity signal due to the external irradiation light is yci, the chromaticity signal information Y0 stored in the memory 21 is expressed by the following equation.

Yc = Yc s + Yc e
- (1) Next, under the same environmental conditions, without emitting light from the light source lamp 11, external irradiation light hits the medium, and as a result, reflected light due to diffuse reflection, specular reflection, etc. is transmitted to the optical fiber 16. The light is taken into the light receiver 18. A signal generated after this light is photoelectrically converted is converted into a digital quantity in the same manner as described above and sent to the subtracter 23. This subtracter 23 performs an operation of subtracting the chromaticity signal when the light source lamp is not irradiated from the chromaticity signal when the light source lamp is not irradiated. The signal Y obtained by this subtraction is: Y,1=Yc Yci=Ycs
Equivalent to (2), it is only the chromaticity signal specific to the medium when irradiated with light from a standard light source.In addition, in order to detect subtle changes such as variations in the luminous intensity of the light source lamp in 9 colors, , an optical fiber 26, a photocell 13, and a detection monitor section 14 are provided, and the correction value for the variation detected by the detection monitor section is sent to the signal processing section 15 to correct the chromaticity signal Y. Accurate chromaticity signals are obtained.

These operations such as photoelectric conversion, light emission operation of the light source lamp, digital conversion, storage operation in memory, subtraction, and signal processing are controlled by a pulse train from the timing generation system 22.

As described above, by capturing the chromaticity signals from the medium in time series and performing the subtraction operation, the brightness 1
It is possible to obtain a medium-specific chromaticity signal even under different environmental conditions. The color measurement device is equipped with a curved light condensing plate, and by keeping the light condensing position at a constant distance from the medium even in areas that are far from directly above the irradiation point of the medium, it can produce uniform and high-intensity light. Since the light is taken in, the light can be collected efficiently, and a sufficient chromaticity signal level can be obtained even in a non-contact state where the measuring device is separated from the medium.

(Example 2) FIG. 2 is a diagram showing a schematic configuration of a color measuring device according to Example 2 of the present invention.

In the figure, in the second embodiment, a lens 25. The configuration of the device was simplified by using the photo sensor 24 and the photo sensor 24. The other configurations are the same as those in FIG. 2, so they are omitted.

In this example, the lens 25 is floated a predetermined distance above the medium 100, the medium is obliquely irradiated with incident light 3o from the light source lamp 11, and the specularly reflected light 31 from the medium 100 is not taken in, but only the diffusely reflected light 32 is sent to the lens 25. to focus the light. By applying this focused light to the surface of the photosensor 24, photoelectrically converting it, and passing it through the same circuit block as in the first embodiment, the chromaticity signal can be stored in the memory in the same manner as in the first embodiment. A chromaticity signal unique to the medium can be obtained by performing the same calculation operations below. It goes without saying that the same effects as in Example 1 can be obtained by this.

Since this device does not use a light condensing plate or an optical fiber, it is simpler than the first embodiment, and the manufacturing cost is also lower. However, since lenses are used, it is difficult to construct a large-sized device.

[Effect of the invention 1] As explained in detail above, according to the present invention, by taking the difference in chromaticity signals between when the light emitting source is irradiated and when it is not irradiated, the device can be used without depending on external lighting environment conditions. Color information specific to the medium (sample to be measured) can always be obtained accurately and with high precision in a non-contact state where the color information is separated from the medium. In addition, the light condensing configuration uses lenses and curved light condensing plates, making it possible to condense light uniformly and with high efficiency.Even when the device is in a non-contact state, a sufficient amount of light can be obtained, making it possible to achieve high precision. Color identification becomes possible.

With such a configuration or measurement method, it becomes possible to perform in-line color monitoring (painting, etc.), which has not been possible in the past, and color viewing without damaging plant leaves. This means that the present invention realizes complete automation of painting, an automatic plant growth status monitoring system, and the like.

[Brief explanation of drawings]

1 is a diagram showing the configuration of a color measuring device according to Embodiment 1 of the present invention, FIG. 2 is a diagram showing the configuration of a color measuring device according to Embodiment 2 of the present invention, and FIG. 3 is a diagram showing the configuration of a color measuring device according to Embodiment 2 of the present invention. FIG. 2 is a diagram showing the configuration of the device. ■...Light source lamp 12...Slit 3.
...Photocell 14...Detection monitor section 5.
...Signal processing unit 16.26...Optical fiber 7...Light condensing plate 18...Light receiver 9...
・Sample hold circuit 20...A/D converter 21
...Memory 22...Timing generation system 23...Subtractor 24...Photo sensor 25...Lens 3o...Incoming light 31...Specular reflected light 32...Diffuse reflected light 100...・Measurement medium

Claims (3)

[Claims] (1) A method for measuring the unique color of a medium by performing diffuse reflected light processing and signal processing. and the diffusely reflected light on the medium in the case where no light irradiation is performed, are received separately, and each diffusely reflected light is photoelectrically converted into a chromaticity signal, and the signal processing is performed by converting the chromaticity signal obtained by the above processing into a chromaticity signal. A color measurement method characterized in that a subtraction process is performed based on two chromaticity signals, and a chromaticity signal specific to the medium is calculated based on the result. (2) A color measurement device that includes a light source lamp, a slit, a condenser plate, an optical fiber, a light receiver, and a signal processing section, where the light source lamp irradiates light onto a medium to be measured. The slit allows the light from the light source lamp to obliquely irradiate the medium to be measured, the condenser plate collects the diffusely reflected light from the medium to be measured, and the optical fiber allows the light to be condensed. The optical receiver converts the diffusely reflected light transmitted through the optical fiber into an electric signal, and the signal processing section processes the photoelectrically converted signal to determine the color specific to the medium. A color measuring device characterized in that it calculates a color signal. (3) A color measurement device having a light source lamp, a slit, a lens, a photosensor, and a signal processing section, where the light source lamp irradiates light onto the medium to be measured, and the slit serves as a light source. The light from the lamp is irradiated obliquely onto the medium to be measured, the lens is to collect the diffusely reflected light from the medium to be measured, and the photosensor is to collect the diffusely reflected light focused by the lens. What is claimed is: 1. A color measurement device that performs photoelectric conversion of a signal, and a signal processing unit that processes the photoelectrically converted signal to calculate a chromaticity signal specific to the medium.