Method for correcting influence of thickness unevenness of recording medium, information recording/reproducing apparatus using the same method and optical head unit

• US 20060092780A1
• Filed: 12/13/2005
• Published: 05/04/2006
• Est. Priority Date: 07/31/2001
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Ando, Hideo
• Granted Patent: US 7,274,628 B2
• Time in Patent Office: Days
• US Class Current: 369/44.26
• CPC Class Codes: G11B 2007/0013 for carriers having multiple discrete layers
• CPC Class Codes: G11B 2007/13727 Compound lenses, i.e. two or more lenses co-operating to perform a function, e.g. compound objective lens including a solid immersion lens, positive and negative lenses either bonded together or with adjustable spacing
• CPC Class Codes: G11B 7/0909 by astigmatic methods
• CPC Class Codes: G11B 7/0925 Electromechanical actuators for lens positioning G11B7/0857 takes precedence
• CPC Class Codes: G11B 7/094 Methods and circuits for servo offset compensation
• CPC Class Codes: G11B 7/0945 Methods for initialising servos, start-up sequences
• CPC Class Codes: G11B 7/0948 specially adapted for detection and avoidance or compensation of imperfections on the carrier, e.g. dust, scratches, dropouts G11B7/095 takes precedence
• CPC Class Codes: G11B 7/131 Arrangement of detectors in a multiple array
• 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 7/1378 Separate aberration correction lenses; Cylindrical lenses to generate astigmatism; Beam expanders
• 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
• CPC Class Codes: G11B 7/13927 during transducing, e.g. to correct for variation of the spherical aberration due to disc tilt or irregularities in the cover layer thickness

Abstract

An optical disk unit of this invention includes a defocus detecting system for detecting a defocus of an objective lens, a thickness unevenness detecting system for detecting a thickness unevenness of a transparent resin layer provided nearest the objective lens of a recording medium, and a thickness unevenness correcting mechanism for changing the focusing characteristic of light impinging upon the objective lens based on a change in the thickness of the transparent resin layer detected by the thickness detecting system.

Claims

1. An optical head unit comprising:

a light source supplies light of a predetermined wavelength;

an objective lens focus the light from said light source to the recording layer of the recording medium;

an objective lens moving mechanism moves the objective lens in the optical axis direction and in the direction intersecting a guide groove and a signal mark string formed in said recording medium preliminarily;

a defocus detecting system detects a defocus in said objective lens;

a thickness unevenness detecting system detects a thickness unevenness in a transparent resin layer of the recording medium provided nearest said objective lens; and

a thickness unevenness correcting mechanism changes a focusing characteristic of light impinging upon said objective lens from said light source based on a change in the thickness of said transparent resin layer of said recording medium detected by said thickness detecting system.