Light receiving amplification element

• US 20030231574A1
• Filed: 06/12/2003
• Published: 12/18/2003
• Est. Priority Date: 06/14/2002
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Ohnishi, Masaya, Okuda, Takanori
• Granted Patent: US 7,002,881 B2
• Time in Patent Office: Days
• US Class Current: 369/124.12
• CPC Class Codes: G11B 2007/0006 adapted for scanning different types of carrier, e.g. CD & DVD
• CPC Class Codes: G11B 7/005 Reproducing G11B7/0065 takes precedence
• CPC Class Codes: G11B 7/1275 Two or more lasers having different wavelengths
• CPC Class Codes: G11B 7/131 Arrangement of detectors in a multiple array

Abstract

The object of the invention is to provide a light receiving amplification element applicable to an optical pickup apparatus comprising a semiconductor two-wavelength laser element and one condensing lens. The light receiving amplification element is provided with a plurality of light receiving portions corresponding to different wavelengths, a plurality of trans-impedance type amplifiers connected to the light receiving portions according to the different wavelengths and adaptable to the different wavelengths and switching portion for switching output from the trans-impedance type amplifier according to each of the wavelengths.

Claims

1. A light receiving amplification element which is used for an optical pickup apparatus including a semiconductor laser having a plurality of light emitting points from which different wavelength light is emitted each other, and an optical element for irradiating an optical disk with emitting light from the semiconductor laser and guiding reflecting light on the optical disk to the light receiving amplification element, the light receiving amplification element comprising:

a plurality of light receiving portions corresponding to the different wavelengths;

a plurality of trans-impedance type amplifiers connected to the light receiving portions according to the different wavelengths and corresponding to the different wavelengths; and

switching means for switching outputs from the trans-impedance type amplifiers according to each of the wavelengths.

2. The light receiving amplification element of claim 1, wherein the plurality of trans-impedance type amplifiers comprise a first trans-impedance type amplifier having a feedback constant adapted to a first wavelength and a second trans-impedance type amplifier having a feedback constant adapted to a second wavelength.

6. The light receiving amplification element of claim 2, wherein the first and second trans-impedance type amplifiers comprise:

first and second differential elements;

a single current mirror circuit in which output of the differential elements is electrically connected to each other and which acts as an active load;

an emitter follower output circuit; and

two feedback circuits,

an output terminal is provided with respect to the first and second trans-impedance type amplifiers.

9. The light receiving amplification element of claim 6, wherein the switching means operates to bias emitter connecting points of the first and second differential elements in first and second current sources comprising a constant current source, a switching circuit-and a current mirror circuit;

to switch the first and second current sources by an external switching signal; and

to switch the first and second differential elements in an active state.

12. The light receiving amplification element of claim 1, wherein the plurality of light receiving portions and the plurality of trans-impedance type amplifiers are formed on a single chip and a distance between the plurality of light receiving portions is equal to a distance between the plurality of emitting points.

3. A light receiving amplification element which is used for an optical pickup apparatus including a semiconductor laser having a plurality of light emitting points from which different wavelength light is emitted each other and an optical element for irradiating an optical disk with emitting light from the semiconductor laser and guiding reflecting light on the optical disk to the light receiving amplification element, the light receiving amplification element comprising:

a plurality of light receiving portions corresponding to the different wavelengths;

a plurality of trans-impedance type amplifiers connected to the plurality of light receiving portions and corresponding to a plurality of optical disks with different reflectance; and

switching means for switching outputs from the trans-impedance type amplifiers according to the optical disk,

the light receiving amplification element being commonly connected between outputs from the plurality of light receiving portions and inputs to the plurality of trans-impedance type amplifier.

4. The light receiving amplification element of claim 3, wherein the plurality of trans-impedance type amplifiers comprise a first trans-impedance type amplifier having a first feedback constant adapted to reflectance of a reproduction only optical disk and a second trans-impedance type amplifier having a second feedback constant adapted to reflectance of a rewritable optical disk.

5. The light receiving amplification element of claim 4, wherein a clamp circuit comprising a diode and a resistance is connected in parallel to a second feedback circuit which sets the second feedback constant.

7. The light receiving amplification element of claim 4, wherein the first and second trans-impedance type amplifiers comprise:

first and second differential elements;

a single current mirror circuit in which output of the differential elements is electrically connected to each other and which acts as an active load;

an emitter follower output circuit; and

two feedback circuits,

an output terminal is provided with respect to the first and second trans-impedance type amplifiers.

8. The light receiving amplification element of claim 5, wherein the first and second trans-impedance type amplifiers comprise:

first and second differential elements;

a single current mirror circuit in which output of the differential elements is electrically connected to each other and which acts as an active load;

an emitter follower output circuit; and

two feedback circuits,

an output terminal is provided with respect to the first and second trans-impedance type amplifiers.

10. The light receiving amplification element of claim 7, wherein the switching means operates to bias emitter connecting points of the first and second differential elements in first and second current sources comprising a constant current source, a switching circuit and a current mirror circuit;

to switch the first and second current sources by an external switching-signal; and

to switch the first and second differential elements in an active state.

11. The light receiving amplification element of claim 8, wherein the switching means operates to bias emitter connecting points of the first and second differential elements in first and second current sources comprising a constant current source, a switching circuit and a current mirror circuit;

to switch the first and second current sources by an external switching signal; and

to switch the first and second differential elements in an active state.

13. The light receiving amplification element of claim 3, wherein the plurality of light receiving portions and the plurality of trans-impedance type amplifiers are formed on a single chip and a distance between the plurality of light receiving portions is equal to a distance between the plurality of emitting points.

14. An optical pickup apparatus comprising:

a semiconductor laser having a plurality of light emitting points from which different wavelength light is emitted each other;

a light receiving amplification element including;

a plurality of light receiving portions corresponding to the different wavelengths;

a plurality of trans-impedance type amplifiers connected to the light receiving portions according to the different wavelengths and corresponding to the different wavelengths; and

switching means for switching an output from the trans-impedance type amplifier according to each of the wavelengths; and

an optical element for irradiating an optical disk with emitting light from the semiconductor laser and guiding reflecting light on the optical disk to the light receiving amplification element.

15. An optical pickup apparatus comprising:

a semiconductor laser having a plurality of light emitting points from which different wavelength light is emitted each other;

a light receiving amplification element including;

a plurality of light receiving portions corresponding to the different wavelengths;

a plurality of trans-impedance type amplifiers connected to the plurality of light receiving portions and corresponding to a plurality of optical disks with different reflectance; and

switching means for switching an output from the trans-impedance type amplifier according to the optical disk,

the light receiving amplification element being commonly connected between outputs from the plurality of light receiving portions and inputs to the plurality of trans-impedance type amplifier; and

an optical element for irradiating an optical disk with emitting light from the semiconductor laser and guiding reflecting light on the optical disk to the light receiving amplification element.