US 7,031,233 B2Granted

Optical recording/reproduction device and focal point control method

AssigneeSony Corporation

InventorIsao Ichimura

Life of this patent

Estimating the term…

Loading patent…

Abstract

An optical recording/playback apparatus of the present invention achieves proper focus control on a target recording layer of a single-layer disk or a multilayer disk. When the focus control is performed on the target information-recording layer of a recording medium, spherical-aberration compensation is first adjusted with respect to the thickness of a transmissive protection layer (cover layer) for the target information-recording layer. Alternatively, the adjustment may be made with respect to the average thickness of transmissive protection layers for the corresponding multiple information-recording layers. An objective lens is then moved along the optical axis to perform a focus-searching operation. In that case, the polarity of a focusing error signal and the level of a reflected-beam intensity signal generated as reflected-beam information are observed so as to perform the focusing operation.

Claims20

Dependent claims

An optical recording/playback apparatus that records and plays back information by projecting a laser beam onto a recording medium having a single information-recording layer or multiple information-recording layers, comprising:

objective-lens means having a predetermined numerical aperture, the objective lens means being provided as an output end for the laser beam;
compensation optical means for compensating for spherical aberrations caused by the thickness of a transmissive protection layer provided for the information-recording layer of the recording medium;
moving means for moving the objective lens along the optical axis;
reflected-beam detecting means for detecting the laser beam reflected by the recording medium and for outputting reflected-beam information;
determination means for determining the polarity of a focusing error signal generated as the reflected-beam information and the level of a reflected-beam intensity signal generated as the reflected-beam information;
and
focus control means for performing a focusing operation based on the determination information from the determination means by using the moving means to move the objective-lens means along the optical axis in a state where the compensation optical means is optimized with respect to the thickness of a certain transmissive protection layer,
wherein the focus control means performs the focusing operation on the target information-recording layer based on the direction in which the objective-lens means is moved by the moving means and based on the order of occurrences of the polarity information of the focusing error signal obtained by the determination means.

5 more elements

A focus-control method for performing a focusing operation on a target information-recording layer in an optical recording/playback apparatus that records and plays back information by projecting a laser beam onto a recording medium having a single information-recording layer or multiple information-recording layers, comprising:

adjusting the setting of compensation optical means for optimization with respect to the thickness of a certain transmissive protection layer, the compensation optical means being provided for compensating for spherical aberrations caused by the thickness of the transmissive protection layer for the information-recording layer of the recording medium;
determining the polarity of a focusing error signal and the level of a reflected-beam intensity signal while moving an objective lens having a predetermined numerical aperture along the optical axis, the focusing error signal being obtained as reflected-beam information of the laser beam from the recording medium, the reflected-beam intensity signal being generated as the reflected-beam information, the objective lens being provided as an output end for the laser beam;
and
performing the focusing operation based on the determination information obtained by the determination,
wherein the focusing operation is performed on the target information-recording layer based on the moving direction of the objective lens and based on the order of occurrences of the polarity information of the focusing error signal obtained by the determination.

2 more elements

Dependencies are inferred from the claim text.

Facts

Application: 10/487,051Filed 3 Jul 2003
Priority: JP 2002-1957454 Jul 2002
Published: US 2004/0207944 A121 Oct 2004
Granted: 18 Apr 2006
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

G11B 7/13925
Means for controlling the beam wavefront, e.g. for correction of aberration: active, e.g. controlled by electrical or mechanical means
G11B 7/08511
Methods for track change, selection or preliminary positioning by moving the head: with focus pull-in only
G11B 7/0945
With provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record…
G11B 7/1369
Separate or integrated refractive elements, e.g. wave plates: active plates, e.g. liquid crystal panels or electrostrictive elements