# US 4,394,570 A · Photoelectric conversion circuit

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- Number: US 4,394,570 A
- Document ID: US4394570A
- Status: Granted
- Kind: A
- Application number: 06/213,612
- Filed: 1980-12-05
- Granted: 1983-07-19
- Earliest claimed: 1979-12-25
- Assignees: Olympus Optical Co., Ltd.
- Inventors: Kazunori Mizokami
- Web page: https://patentgrep.com/patent/US4394570A

## CPC

- G01J 1/46: using a capacitor
- G01J 1/4214: {specially adapted for view-taking apparatus}
- G03B 7/099: Arrangement of photoelectric elements in or on the camera
- G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N)
- G03B: APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR (optical parts of such apparatus G02B; photosensitive materials or processes for photographic purposes G03C; apparatus for processing exposed photographic materials G03D)

## Abstract

A photoelectric conversion circuit comprises a pair of cascade connected semiconductor switching circuits, each of which is formed by a CMOS inverter. A pair of oppositely poled, series connected photodiodes define a photometric, photoelectric transducer element. A capacitor is arranged to be charged and discharged in response to a photocurrent from the transducer element. The combination of the transducer element and the capacitor form a feedback circuit which is connected across the switching circuits to cause the latter to oscillate.

## Claims

### Claim 1

A photoelectric conversion circuit comprising:
a pair of series connected photodiodes having first and second connection points;
a capacitor having one side thereof connected to said first connection point of said photodiodes and arranged to be charged and discharged in response to a photocurrent from said photodiodes;
first and second semiconductor switching circuits, wherein the output of said first switching circuit is connected to the input of said second switching circuit to form a junction, and wherein said second connection point of said photodiodes is connected to said junction; and
the combination of said photodiodes and said capacitor forming a feedback circuit connected across said first and second switching circuit, whereby the switching operation of said switching circuits is effected in response to charging and discharging of said capacitor by photocurrent from said photodiodes.

### Claim 2 (depends on 1)

A photoelectric conversion circuit in accordance with claim 1, wherein the other side of said capacitor is connected to the output of said second switching circuit, and wherein the first connection point of said photodiodes is also connected to the input of said first switching circuit.

### Claim 3 (depends on 1)

A photoelectric conversion circuit in accordance with claim 1, wherein each of said first and second semiconductor switching circuits includes a CMOS inverter.

### Claim 4 (depends on 1)

A photoelectric conversion circuit in accordance with claim 1, wherein said pair of series connected photodiodes are oppositely poled relative to each other.

### Claim 5 (depends on 1)

A photoelectric conversion circuit in accordance with claim 1, wherein said pair of series connected photodiodes have substantially equal characteristics.