JPH01260330A - Color recognizing apparatus - Google Patents

Abstract

PURPOSE:To facilitate the evaluation of metamerism and to measure a color with high accuracy, by constituting a spectroscope of a variable interference mechanism utilizing a Fabry-Perot interferometer having no mechanism part. CONSTITUTION:The spectroscope device of a spectroscopic color recognizing device comprises a variable interference mechanism having a Fabry-Perot interferometer capable of controlling an interference characteristic by an external signal. Said Fabry-Perot interferometer is constituted by opposing two transparent bases 1, 2 through a spacer 3 at a predetermined interval and forming reflecting films 4 to the opposed inner surfaces of said substrates. The Fabry- Perot interferometer has a unified structure formed of the parent substrates 1, 2 and the spacer 3.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a spectral color recognition device using a variable interference mechanism.

<Prior Art> Conventionally, color recognition devices that measure colors and accurately obtain tristimulus values, which are basic numerical values expressing colors, are broadly classified into three color separation methods and spectroscopic methods.

First, the three-color separation method will be explained. Figure 7 shows the conventional 3
1 shows an enlarged configuration diagram of a color sensor, which is a main part of a color separation type color recognition device. The color sensor is a silicon chip 51
The three-part photodiode 52 formed in
, 9 , : Three-color filter 5 of red, green, and blue corresponding to
It consists of 3.

The filter 53 is either an interference filter, a colored glass filter, or a resin color filter.

After the light to be measured passes through the three-color filter 53, it is photoelectrically converted by each photodiode 52, and its output value is the tristimulus value (
X, Y, Z) are bundled directly.

On the other hand, a spectral color recognition device mainly consists of a spectrometer, a light receiving element,
It consists of a white light source and a control/arithmetic processing unit that controls various devices and processes data.

Spectroscopic devices that use a diffraction grating or multiple filters are used. Tristimulus values (X, Y.

Z) is obtained by calculating the spectral distribution data of the light source obtained from the standard sample and the spectral distribution data obtained from the measurement sample.

<Problems to be Solved by the Invention> In order to accurately measure colors in a three-color separation type color recognition device, it is necessary to precisely reproduce the number of equal colors, and the spectral sensitivity and spectral sensitivity of the light receiving element, filter, and light source must be Spectral distribution must be precisely controlled. Therefore, the filter must be manufactured with high precision to match the color matching number, taking into account the spectral sensitivity of the photodiode and the spectral distribution of the light source.In particular, the spectral sensitivity of each photodiode element must be manufactured with high precision. Since the characteristics vary, it is necessary to create a filter with different characteristics for each photodiode. The light source also needs to be controlled so that it always emits stable white light. Furthermore, as can be seen from FIG. 7, the three color filters are slightly shifted in position, so if there is color unevenness in a fine pattern or if there is a distribution in the amount of light, measurement errors will occur. For a three-color separation type color recognition device, it is important to maintain the spectral sensitivity and accuracy and stability of the spectral distribution of the light source, filter, and light receiving element.In particular, if you want a highly accurate color recognition device, the filter Since it is not easy to manufacture, mass production is difficult. Furthermore, since the filter also deteriorates, reliability remains a problem. Furthermore, the three-color separation method has the problem that it is not easy to evaluate metamerism (evaluation of the degree of color change when the light source is changed).

On the other hand, the spectral color recognition device has solved most of the above-mentioned problems of the three-color separation color recognition device.

However, conventional spectral color recognition devices require a complex optical system, a mechanism that rotates a diffraction grating, or a mechanism that rotates a disk filter (a single disk has many filters). Since there are 3 parts, the device becomes large and 3 parts are required.
The advantages that color separation color recognition devices had, such as being small, lightweight, and easy to use, have been significantly lost.

<Means for Solving the Problems> The means for solving the problems according to the present invention mainly include a white light source (which may not be used in some cases), a spectrometer, a light receiving element, and control and calculation for controlling various devices and processing data. The spectroscopic device is composed of a processing section, and the spectroscopic device is composed of a variable interference mechanism having a Fapley-Bello interferometer whose interference characteristics can be controlled by an external signal.

The Fapley-Perot interferometer has two transparent substrates facing each other with a predetermined distance between them with a spacer interposed therebetween, and a reflective film is formed on the opposing inner surfaces. The interferometer has an integral structure with a transparent substrate and a spacer.

<Operation> In the above-mentioned means for solving the problem, the basic principle of the variable interference mechanism will first be explained. Consider the case where light is incident perpendicularly to the substrate surface and there is no phase jump in the reflective film.

When the distance between the reflective films is d, and the refractive index of the medium between them is n, the Fabry-Perot interference transmittance is maximized at a wavelength λm expressed by the following equation.

Here, consider the case where the medium in the space between the reflective films is air.

The refractive index of air is assumed to be l. Also consider the case where m=1. However, the medium in the space between the reflective films is not limited to air, and may be any other gas or liquid. λ at this time
1 scanning wavelength range from λa to λb (however, λb<2λa
), then the distance d between the reflective films is λa/2≦d≦λ
When b/2 is satisfied, light having a center wavelength of λ,=2d is transmitted.

That is, by arbitrarily changing d from λa/2 to λb/2, only light of an arbitrary wavelength in the wavelength range from λa to λb can be selectively transmitted.

For example, if the scanning wavelength range is 400 to 750 nm,
The distance d between the reflective films may be controlled within a range of 200 to 375 nm. Strictly speaking, since light with a wavelength shorter than λ1 is also transmitted, it is necessary to use a filter that removes light with a wavelength of λ1 or less, or to use a light receiving element that is insensitive to light with a wavelength of λ1 or less.

The variable interference mechanism according to the present invention is constructed by adding a displacement means to the Fapley-Bello interferometer to change the distance d between the reflective films in accordance with an external signal.

As a means for changing the distance d, a method of bending and deforming at least one of the transparent substrates is excellent in terms of controllability of the distance d.

Therefore, as a displacement means, a bimorph type piezoelectric element,
Electrostatic attraction between electromagnetic coils and electrodes is considered, and the generated force is controlled by the voltage applied to the piezoelectric element, the current flowing through the electromagnetic coil or the applied voltage, or the applied voltage between the electrodes, and by extension, the electrostatic attraction between the reflective films. control the distance d.

As described above, in the present invention, the variable interference mechanism as a spectroscopic device consists of a Farpley-Perot interferometer and a displacement means for changing its interference characteristics, so it is constructed in a very small size.

Since the measurement light passes through the Fabry-Perot interferometer in a straight line and enters the light receiving element, a complicated optical system is not required. In addition, the displacement means is a small electronically controlled driving element without a rotating mechanism, and is integrated with the Fapley-Perot interferometer, so the variable interference mechanism is resistant to vibration and easy to handle. becomes.

Furthermore, according to the present invention, the tristimulus values are obtained through arithmetic processing after the measurement light is spectrally divided, so there is no need for special high-precision filters as in a three-color separation type color recognition device, and metamerism can be easily evaluated. The spectral recognition device can be made compact and simple, which has advantages such as the ability to

<Example> First Example> Hereinafter, a first example of the present invention will be described in detail based on the drawings. FIG. 1 is an enlarged perspective view of a variable interference mechanism which is a main component of a spectral color recognition device according to the present invention.

As shown in the figure, the transparent substrates 1.2 are opposed to each other with a spacer 3 in between. A reflective film 4 is formed on the opposing inner surfaces to form a hollow structure.

The translucent substrate 1.2 may be joined via the spacer 3, or may be held from the outside with a jig or the like. Glass, transparent ceramics, or polymer resin is used for the transparent substrate 1.2.

The reflective film 4 is made of a metal film or a single-layer or multi-layer dielectric film. The spacer 3 and the reflective film 4 are manufactured by a thin film forming method such as a vapor deposition method, a sputtering method, or a CVD method. The space sandwiched between the reflective films 4 constitutes a Fapley-Perot interferometer. The transparent substrate 2 is fixed to a holder 6. Then, the bimorph 5 is fixed to the middle ruler 6 at the end of the bimorph 5 so that the bimorph 5 is in light contact with the translucent substrate 1 almost at the center or with a very small gap so that the movement of the bimorph 5 is not hindered. .

The measurement light 7 is perpendicularly incident on the transparent substrate 1.2, and the light transmitted through the transparent substrate 1.2 is received by a light receiving element (not shown). It is preferable to provide an optical system in which the measurement light 7 is always perpendicularly incident on the transparent substrate 1.2 by combining optical fibers and lenses as appropriate. Further, it is preferable to make a notch at the tip of the bimorph 5 so as not to obstruct the optical axis. Bimorph 5 is a device in which two types of piezoelectric materials with different expansion and contraction directions are pasted together and a voltage is applied using the transverse effect of the piezoelectric material (the direction of the electric field and the direction of expansion and contraction of the material are perpendicular). For example, it is a piezoelectric element that has the property of being curved. If the bimorph 5 is installed as shown in FIG. 1 and a voltage is applied to the bimorph 5 in the direction of convexly curving it upward, the bimorph 5 will push the transparent substrate l.

The transparent substrate (2) is pushed and curved, and as a result, the distance d between the reflective films decreases. In this way, d can be changed by the voltage applied to the bimorph, and the interference characteristics of the interference mechanism can be controlled.

FIG. 2 shows an example of the operation of this embodiment. When the voltage applied to the bimorph 5 is low, the load applied to the transparent substrate l is small and the distance d between the reflective films is large, so that light having a center wavelength at a long wavelength is transmitted. As the voltage applied to the bimorph 5 increases, the load applied to the transparent substrate 1 increases, and the distance d between the reflective films decreases, so that the center wavelength of transmission shifts toward the shorter wavelength side. In this way, the voltage applied to the bimorph 5 is controlled to scan the wavelength of the transmitted light.

Next, FIG. 3 shows a block diagram of a spectral color recognition apparatus according to a first embodiment of the present invention. The control/arithmetic processing unit 13 is the drive circuit 1
6, the drive circuit 16 sends a drive signal to the variable interference mechanism 10, and controls the variable interference mechanism 10.

The object to be measured 20 is vertically illuminated with white light from the white light source 12 . The scattered light (signal light) from the object to be measured passes through the slit 19, reaches the variable interference mechanism 10, and is separated into spectra.

The separated light enters the light receiving element 11 and is photoelectrically converted. An electric signal output from the light receiving element 11 is amplified by an amplifier 14 and converted into a digital signal by an A/D converter 15. Thereafter, the digital signal is input to a control/arithmetic processing unit 13 such as a microprocessor, and is subjected to arithmetic processing there. The results are displayed on the display 17.

A manual switch 18 for operating the control/arithmetic processing section 13 is connected to the control/arithmetic processing section 13 .

In addition to the method of capturing scattered light from the object to be measured as in this embodiment, there is also a method of capturing reflected light or transmitted light.

Furthermore, if the object to be measured is a light emitter, there is also a method of capturing the emitted light. In this case, no light source is required.

Next, the principle of color measurement will be explained using FIG. 4. The International Commission on Illumination (CIE) has defined the sensitivity of the standard human eye to the spectrum as the color equivalence number 5i,9,=. The color is determined by the tristimulus value (X,
Y, Z).

Here, P(λ) is the spectral distribution of the light source used for illumination (FIG. 4(a)), and ρ(λ) is the reflectance of the object (FIG. 4(b)). That is, it can be seen that the tristimulus values (X, Y, Z) are not determined only by the reflectance of the object but are influenced by the spectral distribution of illumination. In addition, the color matching function group, 9, = (Figure 4 (
C)) is the value under equal energy white light, but in reality there is no such ideal illumination light source, so the tristimulus values are calculated using reference light (standard light). demand. In other words, the original tristimulus values (X, Y, Z) of a certain standard light
means to seek.

Here, the difference between a three-color separation type and a spectral type color recognition device will be explained. The three color separation formula is a color matching function.

This method uses three types of filters with spectra corresponding to the intensity of the light and calculates tristimulus values directly from the amount of transmitted light of each filter. Equation (2) does not mention the spectral sensitivity of the light receiving element, but in order to actually configure a color recognition device, it is necessary to correct this, and this is done by subtly adjusting the spectral characteristics of the three types of filters. ing. The stability of the spectral characteristics of the light source used for illumination is also important.

On the other hand, the spectral formula begins with the spectral distribution P(λ
), then measure the reflectance ρ(λ) of the object, and then calculate (2
) formula to find the tristimulus values. The feature of this method is that various corrections can be easily made by knowing the spectral distribution. In other words, it is easy to correct the spectral distribution of the illumination light source, and illumination other than standard light can also be used. This means that the range of choices for illumination sources is widened and that their stability is not strictly required. Further, it is easy to correct the spectral sensitivity of the light receiving element. Another feature is that conditional color matching (metamerism) can be easily evaluated.

Conditional color matching means that even if two objects have different spectral reflectances, their colors match under certain illumination (tristimulus values (X, Y, Z)).
) appear to match). In this case, if you change the lighting, the two colors will appear different.

The degree of this color shift will be small if the spectral reflectance spectra of the two objects are similar, and conversely, the degree of color shift will be large if the spectra of the spectral reflectances of the two objects are significantly different. In order to perform highly accurate color measurements like this, it is necessary to change the lighting and examine changes in color.

In order to evaluate this conditional color matching, it is naturally necessary to prepare a plurality of illumination light sources in the three-color separation method. However, with the spectroscopic method, the tristimulus values when illuminated with various types of illumination can be determined by simply changing the correction value of the spectral distribution of the light source, that is, by simply calculating.

The tristimulus values obtained in this way can be compared with other data to determine color differences, compared with reference data to output judgment signals for color management, and converted to other display systems. Arithmetic processing is performed.

Second Embodiment FIG. 5 is an enlarged perspective view of a second embodiment of a variable interference mechanism which is a main component of a spectral color recognition device according to the present invention. As shown in the figure, the transparent substrates 1.2 are opposed to each other with a spacer 3 in between. A reflective film 4 is formed on the opposing inner surfaces to form a hollow structure, forming a Fapley-Bello interferometer.

The light-transmitting substrate 1.2 is set to be sandwiched between the magnetic core 31 and a plate-shaped magnetic body 33 having a light-transmitting window 33a. A coil 32 is formed in a part of the magnetic core 31 . The magnetic core 31 and the coil 32 constitute an electromagnet, and when a current is passed through the coil 32, an attractive force is generated between the magnetic core 31 and the magnetic body 33. This attractive force can be changed by changing the current flowing through the coil 32. By bending at least one of the transparent substrates 1.2 by this force, the distance d between the reflective films 4 can be controlled. In this way, a variable interference mechanism can be constructed. The principle and configuration of the spectral color recognition device are the same as in the first embodiment.

Third Embodiment FIG. 6 shows an enlarged sectional view of a third embodiment of a variable interference mechanism which is a main component of a spectral color recognition device according to the present invention.

As shown in the figure, the transparent substrates 1.2 are opposed to each other with a spacer 3 in between. A metal film 41 is formed on the opposing inner surfaces. The metal film 41 has a function as a reflective film and an electrode. That is,
A cavity is formed between the metal films 41 to constitute a Fapley-Perot interferometer. Here, when a voltage is applied to the metal film 41 from the power supply 42, electrostatic attraction is generated between the picture electrodes (metal film 41), and this force causes bending displacement of at least one of the transparent substrates 1.2. In this way,
By changing the voltage applied to the metal film 41, the metal film 41
(reflective films) can be controlled. Metal film 4
Films of Ag, Al, Au, etc. are suitable for No. 1.

Further, in this embodiment, the metal film 41 has both the functions of a reflective film and an electrode film, but since they are originally different, for example, the reflective film is used as a dielectric film, and the electrode film is used as a metal film. It may be composed of a film of

As described above, in this embodiment, the variable interference mechanism can be configured with an extremely simple structure. The principle and configuration of the spectral color recognition device are the same as in the first embodiment.

<Effects of the Invention> As is clear from the above description, according to the present invention, in a color recognition device, a spectroscopic device is configured with a variable interference mechanism using a Fapley-Bello interferometer or the like without a mechanical part, so that evaluation of metamerism is not possible. It is possible to realize a compact and easy-to-handle spectral color recognition device that facilitates color measurement with high accuracy. In addition, this spectroscopic color recognition device is easy to manufacture and the illumination spectrum can be easily corrected, so it has the characteristics of widening the range of choices for the illumination light source to be used and easing restrictions on the usage environment. It can be used not only as a controller but also as a control device.

[Brief explanation of the drawing]

FIG. 1 is an enlarged perspective view of a first embodiment of a variable interference mechanism which is a main component of a color recognition device according to the present invention, and FIG.
A characteristic diagram showing an example of the operation of the variable interference mechanism shown in FIG.
) (c) is a diagram for explaining the operating principle of the color recognition device according to the present invention, FIG. 5 is an enlarged perspective view showing the second embodiment of the variable interference mechanism, and FIG. 6 is a diagram showing the third embodiment of the variable interference mechanism. FIG. 7 is an enlarged sectional view showing an embodiment of the present invention, and FIG. 7 is an enlarged perspective view of a color sensor element which is a main component of a conventional three-color separation type color recognition device. l, 2: Transparent substrate, 3 varnish spacer, 4: Reflective film, 5:
Bimorph, 6: Holder, lO; Variable interference mechanism, 11
: Light receiving element, 12: White light source, 13: Control/arithmetic processing unit, 14: Amplifier, l 5 : A/D converter, 16: Drive circuit, 17: Display body, 18: Input switch, 19 Nislit, 20: Object to be measured, 31: Magnetic core, 32: Coil, 3
3: Magnetic material, 41: Metal film, 42: Power supply, 51: Silicon chip, 52: Photodiode, 53: Filter. Applicant Sharp Corporation

Claims (1)

[Claims] A spectroscopic device that separates light from an object to be measured, a light receiving element that receives the separated light transmitted through the spectroscopic device, and a control calculation that processes signals from the light receiving element to drive and control the spectroscopic device. a processing section, the spectroscopic device comprises a variable interference mechanism having a pair of opposing reflective films, a substrate supporting each of the reflective films, and a displacement means for displacing the distance between the two reflective films. A color recognition device comprising: