Tracking servo apparatus of optical information recording and reproducing apparatus

• US 20010040844A1
• Filed: 03/22/2001
• Published: 11/15/2001
• Est. Priority Date: 03/27/2000
• Status: Active Grant

• Current Assignee: Pioneer Corporation
• Original Assignee: Pioneer Corporation
• Inventors: Nishiwaki, Hiroshi, Sato, Mitsuru, Takahashi, Kazuo, Furukawa, Junichi, Maeda, Takanori, Nomoto, Takayuki, Kikuchi, Ikuya
• Granted Patent: US 6,992,953 B2
• Time in Patent Office: Days
• US Class Current: 369/44.32
• CPC Class Codes: G11B 7/0901 for track following only G11B7/0925, G11B7/094, G11B7/0941, G11B7/0943, G11B7/0945, G11B7/0946, G11B7/0948 take precedence
• CPC Class Codes: G11B 7/0912 by push-pull method
• CPC Class Codes: G11B 7/094 Methods and circuits for servo offset compensation
• CPC Class Codes: G11B 7/0941 Methods and circuits for servo gain or phase compensation during operation for initialising servos G11B7/0945
• CPC Class Codes: G11B 7/0943 Methods and circuits for performing mathematical operations on individual detector segment outputs
• CPC Class Codes: G11B 7/1353 Diffractive elements, e.g. holograms or gratings diffraction gratings per se G02B5/18; holograms per se G02B5/32; grating systems G02B27/44
• CPC Class Codes: G11B 7/1381 Non-lens elements for altering the properties of the beam, e.g. knife edges, slits, filters or stops G11B7/1353 - G11B7/1369 take precedence

Abstract

A tracking servo apparatus in which reflection light obtained when a laser beam is irradiated onto a recording surface of an optical disc is photoelectrically converted, thereby obtaining a photoelectric conversion signal, a tracking error signal showing a deviation amount of an irradiating position of said laser beam for a track in a disc radial direction on the recording surface is generated by the photoelectric conversion signal, a spherical aberration occurring in an optical system is detected, a level of the tracking error signal is corrected on the basis of the detection result, and the irradiating position of the laser beam is moved in the disc radial direction in accordance with the level-corrected tracking error signal.

Claims

1. A tracking servo apparatus of an optical information recording and reproducing apparatus for recording and reproducing information by irradiating a laser beam onto an optical disc, comprising:

an optical system for obtaining a photoelectric conversion signal by photoelectrically converting reflection light which is obtained when said laser beam is irradiated onto a recording surface of said optical disc;

a tracking error signal generating portion for generating a tracking error signal indicative of a deviation amount of an irradiating position of said laser beam for a track in a disc radial direction on said recording surface by said photoelectric conversion signal;

a spherical aberration detecting portion for detecting a spherical aberration occurring in said optical system;

a level correcting portion for correcting a level of said tracking error signal on the basis of a detection result of said spherical aberration detecting portion; and

a driving portion for moving the irradiating position of said laser beam in the disc radial direction in accordance with the tracking error signal, the level of which has been corrected by said level correcting portion.

2. An apparatus according to

claim 1

, wherein

said spherical aberration detecting portion generates a voltage signal, as the detection result of the spherical aberration, indicative of an error of a thickness of a transparent layer at the irradiating position of said laser beam for a specified thickness, and

said level correcting portion includes:

a gain control signal generating portion for generating a gain control signal on the basis of said voltage signal; and

an amplifying portion for receiving the tracking error signal generated from said tracking error signal generating portion and amplifying the received tracking error signal by an amplification gain corresponding to said gain control signal.