JPS6262233A - Color sensor - Google Patents

Abstract

PURPOSE:To simplify a color sensor dispensing infrared ray filter, by building up an active color filter with a polarizer, a ferroelectric material, first and second electrodes and an analyzer while material with the spectroscopic characteristic roughly coinciding a luminosity factor curve is sued in a photoelectric conversion layer forming a part of a photo sensor. CONSTITUTION:An electrode 12, a photoelectric conversion layer 13 and a transparent electrode 14 are formed sequentially on a substrate 11 of a color sensor to form a photosensor. An analyzer 15 is formed in contact with the transparent electrode 14 and a ferroelectric material layer 16 having an electrooptic effect and a polarizer 19 are laminated sequentially on an analyzer 15 to make a color filter. First and second electrodes 17 and 18 are provided to apply a voltage to the material layer 16 and a material with the spectroscopic characteristic roughly coinciding a luminosity factor curve is used in the photoelectric conversion layer 13 of the photo sensor section. This unnecessitates any infrared ray filter, thereby simplifying the color sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a color sensor using an active color filter that performs wavelength separation of transmitted light by an applied electric field.

(Prior Art) Conventionally, a color sensor that discriminates the color of incident light has generally added a color filter for separating three colors onto each element to discriminate the color of the incident light.

Recently, it has become possible to perform color discrimination with a single color sensor using active color filters that utilize the electro-optic effect of ferroelectric materials.

Lead lanthanum zirconate titanate (PLZT) exhibits electro-optic effects such as the Pockels effect, Kerr effect, and memory effect in an appropriate composition, and its electro-optic coefficient is large, making it an attractive material from the perspective of application to optical devices. It is a very attractive material. FIG. 5 shows the principle of an active color filter using the PLZT board 1. Comb-shaped electrodes 2.3 are provided on the PLZT plate 1 to a depth C (a cross section is shown in FIG. 6), and a driving power source 4 is connected between the electrodes 2 and 3. on the other hand,
A polarizer 5 and an analyzer 6 are placed on both sides of the PLZT plate l. The polarization directions of the polarizer 5 and the analyzer 6 are made perpendicular to each other. If an electric field E is applied between the electrodes 2.3, the letter direction r is expressed as r-Δn-ρ. Here, Δn---n3·Rc-E2, n is the refractive index of PLZT, and Rc is a constant number. Therefore, the transmittance 1/Io is expressed by the following formula.

I/I o=sin'(2yr I'/λ)-s
in2(πn3RoE'Q/λ), that is, I/1. is a function of E, L λ.

In Fig. 7 (a), (b), and (c), Q is 20, respectively.
μm.

The wavelength dependence of transmittance at 30 μm and 40 μm is shown. In addition, Fig. 8(a), (b), and (c) show 3 when σ is 20 μm, 30 μm, and 40 μm, respectively.
The voltage dependence of transmittance of color (430° 550.640 nm) is shown.

Based on these optical characteristics, using appropriate values of E and Q,
It is also understood that a plurality of filters can be arranged in series and used as various filters such as a bandpass filter, if necessary. Further, by variably controlling E, it is possible to change the transmission wavelength and sweep the wavelength.

Active color filters using such electro-optic materials have already been disclosed in Japanese Patent Laid-Open Nos. 57-198434 and 60-103330.

A color sensor that combines an active color filter and a light-receiving element can distinguish colors with a single light-receiving element.
It is possible to make the incident light beam uniform, and the accuracy of color discrimination is improved.

The wavelength of transmitted light can be arbitrarily selected within the visible light range by changing the voltage applied to the active color filter.
It can also be used as a single color sensor, and one sensor can handle multiple colors.

(Problems to be Solved by the Invention) FIG. 19 of Japanese Unexamined Patent Publication No. 57-198434 discloses a color sensor that combines an active color filter using an electro-optic effect and a photoelectric conversion element.

On the incident side of this color sensor, in addition to a lens for condensing light, a filter is provided to cut out wavelengths of light not to be measured. (Although no specific explanation is given, if a single crystal silicon photodiode, for example, is used as a photoelectric conversion element, an infrared cut filter is required.) As an active color filter, the transmitted wavelength is determined by sweeping the applied voltage. A variable type is used.

By the way, if a filter that cuts off light of wavelengths other than those to be measured can be omitted, a color sensor with a simpler configuration can be provided.

An object of the present invention is to provide a color sensor with a simple configuration.

(Means for Solving the Problems) A color sensor according to the present invention includes, on a substrate, an electrode layer, a photoelectric conversion layer, a transparent electrode layer, an analyzer, a ferroelectric material layer having an electro-optic effect, and a polarizer. A material formed by sequentially laminating the above-mentioned ferroelectric material layers, provided with a first electrode and a second electrode for applying a voltage to the above-mentioned ferroelectric material layer, and having the above-mentioned photoelectric conversion layer having spectral characteristics that substantially match the luminous efficiency curve. It is characterized by consisting of.

(Function) The polarizer, ferroelectric material, first electrode, second electrode, and analyzer constitute an active color filter. The electrode layer, photoelectric conversion layer, and transparent electrode layer constitute a photosensor. This photosensor has spectral characteristics that approximately match the visibility curve. Therefore, an infrared cut filter becomes unnecessary, and the configuration of the color sensor can be simplified.

(Example) Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a schematic cross-sectional view of an embodiment of a color sensor according to the present invention. On the substrate II, an electrode 12, an amorphous silicon (a-8t) layer 13 and a transparent electrode (ITO
) 14 are sequentially stacked. This forms an a-Si photosensor (photodiode). a-8t
The photo sensor may be of the photovoltaic or photoconductive type.

Furthermore, a PLZT color filter is laminated.

The PLZT color filter includes an analyzer 15 in contact with the transparent electrode 14, a PLZT plate 16 in contact with the analyzer 15, and a plate-shaped 6ZT
Plate 16 Plate-shaped electrode 17.18 and PLZT plate 16
It consists of a plate-shaped polarizer 19.

FIG. 2 shows the spectral sensitivity characteristics of this sensor.

The spectral sensitivity is 17°18° for the electrodes of the PLZT color filter.
It is obtained by applying a predetermined voltage to the a-8i photodiode, transmitting monochromatic light, and measuring the value of the current flowing through the a-8i photodiode with an ammeter. Here, the broken line is the spectral sensitivity of the a-8i photodiode itself. (The spectral sensitivity of a-8i almost matches the visual sensitivity.) From this result, it is possible to separate the three colors by suppressing the voltage applied to the PLZT electrode, and it can be used as a color sensor. Recognize.

FIGS. 3 and 4 are system diagrams when the color sensor of this embodiment is applied to color discrimination of incident light.

In FIG. 3, a photovoltaic a-S+ photodiode 21
In FIG. 4, a photoconductive type a-3i photocell 22 is used. A bias power supply 23 is connected to the photocell 22 . PLZT board 1 which is an active color filter
6, an appropriate voltage is applied by the applied voltage control section 24.

The signal calculation unit 25 determines the color from the output signal of the color sensor and outputs the result. In either system, color discrimination can be performed by varying the voltage applied to the electrodes of the active color filter, selectively controlling the transmitted wavelength, and comparing and calculating the photocurrents for each applied electrode.

(Effects of the Invention) Since a photoelectric conversion element such as a-Si whose spectral sensitivity is close to the visual sensitivity is used, an infrared cut filter is not required, and the configuration of the color sensor is simplified. Therefore, the manufacturing process can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a sectional view schematically showing the configuration of a color sensor. FIG. 2 is a graph of the spectral sensitivity characteristics of the color sensor. FIGS. 3 and 4 are block diagrams of color discrimination systems using color sensors, respectively. FIG. 5 is a diagram showing the principle of an active color filter using the electro-optic effect. FIG. 6 is a cross-sectional view of the PLZT layer. Figures 7(a), (b), and (c) are, respectively,
It is a graph showing the E dependence of transmittance. Figures 8(a), (b), and (c) are, respectively,
It is a graph showing wavelength dependence of transmittance. II... Substrate, 12... Electrode, 13... Photoelectric conversion layer, 14... Transparent electrode, 15 - Analyzer, 16
... Ferroelectric material layer, 17.18... Electrode, 19.
...Polarizer. Patent applicant Representative of Minolta Camera Co., Ltd. Patent attorney Mr. Aoki and 2 others = 8- Figure 1 Figure 2 Person + nm +

Claims (1)

[Claims] (1) An electrode layer, a photoelectric conversion layer, a transparent electrode layer, an analyzer, a ferroelectric material layer having an electro-optic effect, and a polarizer are sequentially laminated on a substrate, and a voltage is applied to the ferroelectric material layer. 1. A color sensor, comprising: a first electrode and a second electrode for applying a voltage, and wherein the photoelectric conversion layer is made of a material having spectral characteristics substantially matching a visibility curve.