JPS6150246B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color difference measuring device that can handle color information having a wide wavelength range.

Photoelectric conversion elements have traditionally been used to measure color differences, but the spectral sensitivity characteristics of conventional photoelectric conversion elements can vary to some extent depending on the semiconductor material, impurities, impurity injection conditions, etc. It was not possible to obtain spectral sensitivity corresponding to the light source. Therefore, a filter that takes into account the wavelength of the projected light is attached to the light receiving surface of the photoelectric conversion element and used as a color sensor. For this reason, it has been impossible to obtain a color sensor output that corresponds to a wide range of color information because it is restricted by the color characteristics of the filter.

In contrast, the present invention provides a color difference measuring device that can respond to a wide range of color information with a simple configuration by using an optical semiconductor element with a new structure. Next, the present invention will be explained in detail using the drawings.

First, the optical semiconductor device 1 will be explained using FIG. In the figure, reference numeral 2 denotes a P-type silicon semiconductor substrate, and N-type impurities and P-type impurities are successively introduced into one main surface side of the substrate 2, which becomes the light-receiving surface, by diffusion or ion implantation. deep from the surface
A 1PN junction 3 and a second PN junction 4 are formed in layers so as to overlap each other at a position close to the surface. Note that the above-mentioned P and N-type conductivities can be reversed, and when the uppermost layer on the main surface side is an N ⁺ layer, an inversion layer formed by an oxide film covering the substrate surface can be used. In the optical semiconductor device 1 including the first and second PN junctions 3 and ₄ , as shown in the equivalent circuit diagram of FIG. It can be seen that two phototransistors PD ₂ are formed. When the main surface of the semiconductor substrate on which the first and second PN junctions are formed is irradiated with light, the second PN junction 4, which is shallow from the substrate surface, absorbs the short wavelength component of the light component and generates an optical output current I. Output _PD2 and deep
1PN junction 3 absorbs long wavelength components and outputs optical current I
Output _PD1 .

In FIG. 1, reference numerals 5, 6, and 7 are electrode terminals provided in each region for extracting the optical output current generated in each of the above-mentioned PN junctions.

The spectral sensitivity characteristics of the optical semiconductor element 1 are shown by the solid line in FIG. The curve with a peak on the long wavelength side shows the spectral sensitivity characteristics of the first photodiode PD ₁ , and the curve with a peak on the short wavelength side shows the spectral sensitivity characteristics of the second photodiode PD _2. Each characteristic depends on the impurity diffusion conditions, PN junction depth, etc. Although it may vary depending on the characteristics, it is obtained as a characteristic unique to the element.

Next, a color difference measuring device using the above optical semiconductor element 1 will be explained. As is clear from the spectral sensitivity characteristic diagram shown in FIG. 3 above, the point where the sensitivity of the first photodiode PD ₁ and the sensitivity of the second photodiode PD ₂ in the optical semiconductor element 1 match with respect to the irradiation light is at the wavelength λ ₀ and the sensitivity of the first photodiode PD ₁ >
It can be seen that if the sensitivity of the second photodiode is the same, the wavelength λ of the irradiated light is greater than the above λ ₀ , and if the sensitivity is reversed, the wavelength λ is smaller than the above λ ₀ .

FIG. 4 shows a method for measuring color difference using the sensitivity characteristics of the optical semiconductor element 1, in which the optical output currents respectively derived from the first photodiode PD ₁ and the second photodiode PD ₂ of the optical semiconductor element 1 are amplified. The temperature is input to amplifier circuits A _{1 and A 2 which can be varied by variable resistors R 1} , _{R 2 ,} etc., and the amplifier circuits A ₁ and A ₂
The optical output current is amplified to a preset amplification degree by A ₂ and output. Here, if the amplification degrees in the amplifier circuits A ₁ and A ₂ are the same for both optical output currents, the sensitivities of both photodiodes will match at the wavelength λ ₀ in FIG. 3 as described above. However, by changing the amplification degree of both amplifier circuits, the wavelength at the point where the sensitivities match changes. For example, the first photodiode
The broken line in Figure 3 shows the spectral sensitivity characteristics of the first photodiode PD ₁ , in which the amplification degree of the amplifier circuit A ₁ connected to PD ₁ is set to 1.5 times the amplification degree of _the amplifier circuit A 2. The same spectral sensitivity characteristics with the intensity set to 0.5 times are shown by the dashed-dotted line in Figure 3. When the amplification is 1.5, the wavelength λ′ ₀ at which the sensitivity matches is on the short wavelength side,
When the amplification degree is 0.5, the wavelength λ″ ₀ at which the sensitivity matches appears closer to the long wavelength side.In other words, the wavelength of the irradiated light can be detected by changing the amplification degree of one output to that of the other output. The area can be expanded.

In FIG. 4, B is a comparison circuit which inputs the outputs of both amplifier circuits amplified by the preset amplification degree, compares the relationship between both input signals, and outputs the comparison result as a color difference output signal. . The above optical output current amplification circuit also includes operational amplifiers OA ₁ and OA ₂ to which logarithmic compression diodes logD ₁ and logD ₂ are connected, as shown in FIG.
It is also possible to logarithmically compress the photodiode output to obtain comparison results.

When forming a color difference signal, the output signal can be obtained by a color difference measuring device using one of the above-mentioned optical semiconductor elements, but in order to further improve measurement accuracy, the amplification degree is different from each other, that is, the sensitivity is matched. This can be carried out by using a plurality of sets of color difference measurement circuits whose wavelengths are shifted, and it is possible to obtain more subdivided color difference signals by the output signals of each color difference measurement circuit.

As described above, according to the present invention, by using a novel optical semiconductor element and varying the spectral sensitivity characteristics of the optical semiconductor element, it is possible to easily obtain a color difference signal over a wide wavelength range without requiring a filter or the like. Therefore, it is possible to obtain a color difference measuring device that can respond to color information with a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an optical semiconductor device applied to the present invention, FIG. 2 is an equivalent circuit diagram of the optical semiconductor device, and FIG.
The figure is a spectral sensitivity characteristic diagram used to explain the present invention.
The figure is a circuit diagram showing one embodiment of the invention, and FIG. 5 is a circuit diagram showing another embodiment of the invention. 1: Optical semiconductor element, 3: 1st PN junction, 4: 1st
2PN junction, A ₁ A ₂ : Amplifier circuit, R ₁ R ₂ : Variable resistance.

Claims (1)

[Claims] 1. An optical semiconductor element that forms at least two layers of PN junctions at different depths with respect to a light receiving surface, and is provided with electrodes that individually take out the optical output current in each PN junction, and the optical semiconductor element Each PN of
The optical output currents at the junctions are input simultaneously, respectively,
A variable amplifier that changes the amplification degree of one optical output current with respect to the other optical output current, and a comparison circuit that compares the magnitude relationship between the two optical output currents output from the amplifier and outputs a color difference signal. A color difference measuring device comprising: