JPH0690088B2 - Color sensor circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a color sensor circuit for determining the color of an object, and more particularly to a color sensor circuit applied to a colorimeter or a color identification circuit.

[Prior Art] FIG. 2 is a basic configuration example of a color identification circuit using a conventional color sensor circuit. Explaining this, the light emitted from the white light source 1 such as a halogen lamp or a xenon lamp is
The light is guided to a monitor light guide 3 whose end is branched into three and an illumination light guide 2 to split the light into two. The light guided to the illumination light guide 2 is applied to the object 9, and its reflected light or transmitted light (hereinafter, simply referred to as “reflected light”) ends at 3
It is guided to the branched light guide 4.

The monitor light and the object reflected light, which are guided to the monitor light guide 3 and the guide light guide 4 and are respectively divided into three lights, have monitor-side color filters F1 (R), F2 ( G), F3 (B) and object side color filter
F4 (R), F5 (G), and F6 (B) are used to separate into three primary color components of red (R), green (G), and blue (B).

These three primary color components are the monitor side photocurrent I _R1 , which is proportional to the incident light amount, due to the photovoltaic effect of the monitor side light receiving elements D ₁ , D ₂ , D ₃ and the object side light receiving elements D ₄ , D ₅ , D ₆ . I _G1 , I _B1
And the object-side photocurrents I _R2 , I _G2 , and I _B2 .

The monitor-side photocurrent and the object-side photocurrent thus converted for each color are amplified by the monitor-side proportional amplifiers OA1, OA2, OA3 and the object-side proportional amplifiers OA4, OA5, OA6 to the amplitude necessary for the subsequent processing. , Monitor side analog voltage signal V _R1 , V _G1 , V _B1
And object-side analog voltage signals V _R2 , V _G2 , and V _B2 .

These analog voltage signals are output by the multiplexer 5.
It is sequentially selected and sent to the A / D converter 6, where it is converted into digital values, and the monitor side 3 primary color outputs R ₁ , G ₁ and B ₁ and the object side 3 primary color outputs R ₂ , G ₂ and B ₂ are output. can get.

These monitor side 3 primary color output and object side 3 primary color output are CP
It is input to the arithmetic circuit 7 composed of U and the like, and the ratio of the corresponding components is taken here to perform normalization for the illuminance change of the light source 1. That is, a standardized value (reference value) based on the following equation is obtained.

The reference values R _S , G _S , and B _S obtained by the equation 1 are the values R _R , which are the standard values of the three primary color components of the object, which are obtained in advance and stored in the memory 10.
The object 9 which is the result of comparison between G _R and B _R by the arithmetic circuit 7
The corresponding color, and if necessary, the reference value of the object 9 which is the display parameter value of the corresponding color is displayed on the display device 8.

[Problems to be Solved by the Invention] However, the conventional color sensor circuit or color identification circuit configured as described above has the following problems.

(1) When the illuminance of the light source 1 is decreased, the measurement resolution is also decreased in proportion to the decrease of the illuminance.

That is, the measurement resolution is determined by the number of bits of the A / D converter 6, but this resolution is the resolution assigned to the maximum amplitude of the analog voltage signal input to the A / D converter 6 until the user gets tired of it. As the signal gets smaller, its resolution cannot be maintained. For example, when the illuminance of the light source does not decrease, if a resolution of 1/1000 is given between the analog voltage signals 3V and 0V, the object side caused by the low reflectance or transmittance of the object When the analog voltage signal has a fluctuation range of 10 times due to a decrease in the amount of light incident on the light receiving elements D ₄ , D ₅ , and D _6, and when it fluctuates between 3 V and 0.3 V, There is no problem because the resolution of 900 increments remains. However, when the illuminance of the light source decreased and the analog voltage signal dropped all over and fluctuated between 1 V and 0.1 V, only 300 steps of resolution remained during that time, and as a result , The resolution is significantly reduced.

(2) In the case of an object having a low reflectance (transmittance), the resolution is reduced as in (1).

In order to compensate for this, there is a method in which the gains of the proportional amplifiers OA1 to OA6 can be switched over several stages to perform the measurement. That is, the gains are sequentially switched so that the output having the optimum magnitude is obtained so that the analog voltage signal, which is the output of the proportional amplifier, is taken out with a sufficiently large value before the saturation.

However, according to this method, since the arithmetic circuit 7 must determine the optimum output, the number of digital conversions by the A / D converter 6 increases, and the determination speed in the arithmetic circuit 7 is significantly reduced. In addition, since a switching circuit having several stages is required for each amplifier, the circuit becomes complicated and the cost,
It is disadvantageous in terms of reliability.

(3) In order for the arithmetic circuit 7 to execute the calculation of the equation 1 performed for the standardization with respect to the illuminance change of the light source, the division needs to be performed three times digitally, so that the determination speed is reduced.

As described above, the conventional one has various drawbacks.

The object of the present invention is to eliminate the drawbacks of the above-mentioned conventional techniques by performing analogization for the illuminance change of the light source, enable high-speed determination, are not affected by the light source or the object, and are always constant. An object of the present invention is to provide a color sensor circuit which retains resolution and is excellent in cost and reliability.

[Means for Solving the Problems] A color sensor circuit of the present invention irradiates light emitted from a light source onto an object to be subjected to color discrimination to obtain reflected light or transmitted light, and Part is taken out as direct light. Then, the reflected light or the transmitted light and the direct light for monitoring are each decomposed into predetermined wavelength components in the visible wavelength range, for example, three primary colors, which are photoelectrically converted into the object side decomposed wavelength output and the monitor side decomposed. The wavelength output is obtained, and the ratio between the corresponding components of the object-side resolved wavelength output and the monitor-side resolved wavelength output is taken to normalize the illuminance change of the light source, and based on these normalized values, the object In the color sensor circuit for judging the color, the means for normalizing the illuminance change of the light source is a means for logarithmically converting the object-side resolved wavelength output and the monitor-side resolved wavelength output for each component, and the logarithmically converted object-side resolved wavelength. And a means for obtaining a difference between the corresponding decomposed wavelength components of the output and the monitor-side decomposed wavelength output.

[Operation] When the components of the monitor-side decomposed wavelength output directly extracted from the light source and the object-side decomposed wavelength output indirectly extracted by reflection or transmission at the object are guided to the logarithmic conversion means, each component Is logarithmically converted and output. The corresponding logarithmically converted corresponding decomposed wavelength component outputs are respectively supplied to the means for obtaining the difference, so that the difference in the logarithmic function is obtained.

Since the difference in the logarithmic function is nothing but the calculation of the logarithm of the ratio of the decomposed wavelength components, the standardization for the illuminance change of the light source is performed by this.

In this way, since the standardization of the measured value with respect to the illuminance change of the light source is all performed by the analog circuit, the determination speed is remarkably increased. Further, since the obtained value is logarithmically compressed, even if the illuminance of the light source is reduced or the reflectance or the transmittance of the object is low, the degradation of the resolution is prevented.

[Embodiment] An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a block diagram showing an embodiment of a color identification circuit to which the color sensor circuit of the present invention is applied.

In the figure, the same parts as those in FIG. 2 are designated by the same reference numerals, and the description thereof will be omitted.

Monitor-side photocurrents I _R1 , I _C1 , I _B1 and object-side photocurrents I _R2 , I _G2 converted by the monitor-side photodetectors D ₁ , D ₂ , D ₃ and the object-side D ₄ , D ₅ , D ₆ , I _B2 for each component of the monitor side logarithmic amplifiers LA1, LA2, LA3 and the object side logarithmic amplifiers LA4, LA5, L
Supply to A6, logarithmically converted monitor side 3 primary color output log
R ₁ , logG ₁ , logB ₁ and object side three primary color output logR ₂ , logG ₂ ,
Get logB ₂ .

Then, among these three corresponding primary color components, that is,
LogR ₁ and logR ₂ , logG ₁ and logG ₂ , logB ₁ and logB ₂ are added to the differential amplifiers DA1, DA2, DA3, respectively, and the difference between the components is obtained. This can be expressed by the following formula.

As is clear from the equation (2), taking the difference between the components of the monitor-side three-primary color output and the object-side three-primary color output by the differential amplifier DA is to standardize the illuminance change of the light source 1. , It is nothing but to get it with a logarithmically compressed analog voltage.

The three analog voltages R _S , G _S , obtained in this way,
B _S is sequentially supplied to the A / D converter via the multiplexer 5, converted into a digital value, and then taken into the arithmetic circuit 7. The values R _S , G _S , and B _S fetched by the arithmetic circuit 7 are the standard object values R _R , which are stored in advance in the memory 10.
G _R and B _R are compared, and the comparison result is the allowable range ΔR _R and Δ
It is assumed that the color is equal to the color of the standard object in the case of G _R and ΔB _R , and that color is regarded as the color of the object 9 by the display device 8.
To display.

As described above, according to this embodiment, since the analog signal supplied to the A / D converter 6 is logarithmically compressed, the light source 1
The measurement resolution does not decrease even when the illuminance decreases. For example, the output voltage from the differential amplifier DA is
If there is a change in voltage of 1V with respect to a 10-fold change in reflected light or transmitted light, the change in voltage from 3V to 2V, 2V to 1V, 1V to 0V is the same as the conventional 3V to 0.3V, 0.3V. V to 0.03V,
It means that it is equal to the change of voltage from 0.03V to 0.003V, and if the A / D converter 6 gives a resolution of 1/1000 between 3V and 0V, the above 10 Therefore, a constant resolution of 333 steps can be obtained for each fluctuation range of reflected light or transmitted light.

What has been described above is also applied to the case of an object having a low reflectance (transmittance), and similarly, a reduction in resolution is prevented. Therefore, since it is not necessary to switch the gain according to the reflectance of the object, the circuit becomes simple, and the cost and reliability are excellent. In addition, since the number of input lines to the multiplexer 5 is reduced from the conventional 6 to half, three lines can be simplified.

In addition, the logarithmically converted three primary color output components are output to a differential amplifier DA.
By taking the difference and taking the difference, the reference to the illuminance change of the light source is performed in an analog manner, so the time required for the reference becomes equal to the propagation delay time of the differential amplifier DA, and this time is Digitally divides 3 by arithmetic circuit 7
It is much shorter than the time required by the conventional circuit that performs the operation.

By the way, as described above, in the example of the present invention, not only the output of the three primary colors is simply logarithmically converted, but also the difference between the components of the output of logarithmically converted is taken at the stage before being input to the arithmetic circuit 7. There is a feature of. However, it is also possible in principle to use the arithmetic circuit 7 to take the difference between the logarithmically converted output components, and in this case, the differential amplifier can be omitted and the configuration can be further simplified. However, doing so is not preferable because the determination speed becomes low.

Although the logarithmic amplifier and the differential amplifier are used to logarithmically compress the standardization of the illuminance change in the above embodiment, a differential logarithmic amplifier in which the logarithmic amplifier and the differential amplifier are integrated is used. Is also possible.

Although the case where the reflected light and the direct light are separated into the three primary colors has been described, the present invention is not limited to this, and if the color of the object can be specified, it can be decomposed into arbitrary wavelength components in the visible wavelength range. Good.

[Effects of the Invention] The present invention has the following effects.

(1) Since the standardization for the illuminance change of the light source is performed in an analog manner, the color determination of the object can be speeded up.

(2) Since the determination is made based on the logarithmically compressed value, the measurement resolution becomes constant, and even if the illuminance of the light source is reduced, or the object with low reflectance or transmittance, accurate color measurement or color identification is performed. It can be performed.

(3) Since the gain switching of the photoelectric conversion unit is not necessary, the circuit is simplified, and the cost and reliability are particularly excellent as compared with the conventional technology that requires the gain switching.

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing an embodiment in which the color sensor circuit of the present invention is applied to a color identification circuit, and FIG. 2 is a block configuration diagram showing an example of a conventional color identification circuit. In the figure, 1 is a light source, 9 is an object, LA1 to LA6 are logarithmic amplifiers, DA
1~DA6 is a differential amplifier, D ₁ to D ₆ is the light-receiving element, F ₁ to F ₆ filter.

Claims (1)

[Claims] 1. A reflected light or a transmitted light emitted from a light source to an object and a direct light emitted from the same light source are each decomposed into predetermined wavelength components in a visible wavelength range, and these are photoelectrically converted to be decomposed on the object side. Obtain the wavelength output and the resolution wavelength output on the monitor side,
A color sensor for determining the color of an object based on the normalized values of the illuminance of the light source by taking the ratio of the corresponding components of the object-side resolved wavelength output and the monitor-side resolved wavelength output. In the circuit, means for normalizing the illuminance change of the light source, means for logarithmically converting the object-side decomposition wavelength output and monitor-side decomposition wavelength output, and logarithmically converted object-side decomposition wavelength output and monitor side A color sensor circuit, comprising: means for obtaining a difference between the decomposition wavelength components corresponding to the decomposition wavelength output.