Photodetector-amplifier circuit and optical pickup device

• US 20060054789A1
• Filed: 09/01/2005
• Published: 03/16/2006
• Est. Priority Date: 09/13/2004
• Status: Active Grant

• Current Assignee: Panasonic Semiconductor Solutions Co., Ltd. (Winbond Electronics Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Miyamoto, Shinichi, Fukuda, Hideo
• Granted Patent: US 7,470,885 B2
• Time in Patent Office: Days
• US Class Current: 250/214.A
• CPC Class Codes: G01J 1/44 Electric circuits for command of an exposure part G03B7/02
• CPC Class Codes: G11B 7/13 Optical detectors therefor

Abstract

The present invention provides a photodetector-amplifier circuit capable of eliminating an influence of noise due to stray light entering a non-selected photodetector to stably select and switch a photodetector. The photodetector-amplifier circuit of the present invention comprises photodetectors 12 and 13. The photodetector 12 is connected via a switch 16 between an inverting input terminal of an operational amplifier 11 and GND, and is also connected via a switch 18 to a voltage source Vcc. The photodetector 13 is connected via a switch 17 to the inverting input terminal of the operational amplifier 11 and GND, and is also connected via a switch 19 to the voltage source Vcc.

Claims

1. A photodetector-amplifier circuit for outputting a voltage, depending on an intensity of incident light, comprising:

a plurality of photo-detecting sections;

an amplifying circuit;

a plurality of first switches of connecting the corresponding respective photo-detecting sections and an input terminal of the amplifying circuit; and

a plurality of second switches of connecting corresponding respective connection points between the first switches and the photo-detecting sections, and a predetermined voltage supplying point.

2. The photodetector-amplifier circuit according to claim 1, wherein the first and second switches connected to the same connection point are operated in a complementary manner so that one of the switches is ON while the other is OFF, and the one is OFF while the other is ON.

3. The photodetector-amplifier circuit according to claim 1, wherein a potential of the voltage supplying point is set to be equal to an output offset voltage of the amplifying circuit.

4. The photodetector-amplifier circuit according to claim 1, wherein a potential of the voltage supplying point is a ground potential.

5. The photodetector-amplifier circuit according to claim 1, wherein each of the first and second switches includes any of a bipolar transistor, an analog MOS transistor, and a junction FET.

6. An optical pickup device for outputting a voltage, depending on an intensity of reflected light from an optical disc medium, comprising:

a light source;

a plurality of photo-detecting sections of receiving returning light which is output from the light source and is then reflected from the optical disc medium;

an amplifying circuit;

a plurality of first switches of connecting the corresponding respective photo-detecting sections and an input terminal of the amplifying circuit; and

a plurality of second switches of connecting corresponding respective connection points between the first switches and the photo-detecting sections, and a predetermined voltage supplying point.

7. The optical pickup device according to claim 6, wherein the light source emits two or more light beams having different wavelengths.

8. The optical pickup device according to claim 7, wherein at least a portion of the returning light enters a different position, depending on a wavelength of the returning light.

9. The optical pickup device according to claim 6, wherein the first and second switches connected to the same connection point are operated in a complementary manner so that one of the switches is ON while the other is OFF, and the one is OFF while the other is ON.

10. The optical pickup device according to claim 6, wherein a potential of the voltage supplying point is set to be equal to an output offset voltage of the amplifying circuit.

11. The optical pickup device according to claim 6, wherein a potential of the voltage supplying point is a ground potential.

12. The optical pickup device according to claim 6, wherein each of the first and second switches includes any of a bipolar transistor, an analog MOS transistor, and a junction FET.