US 7,126,899 B2Granted

Optical recording medium processing device and focal point control method thereof

AssigneeSony Corporation

InventorsIsao Ichimura, Tsutomu Maruyama

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Abstract

The focus is moved from a first layer (L0) to a second layer (L1) of a double-layered optical disk by stopping a control loop operation and applying acceleration pulses for an interlayer jump to a two-axis electromagnetic actuator. Here, switching timing between acceleration and deceleration for an interlayer jump is generated based on the rate of change of a SUM signal obtained from a light-sensitive element (27), the SUM signal is distinguished by a specific threshold TH, and an S-shaped error signal is distinguished by thresholds THH and THL with different positive/negative level, thereby performing a pull-in operation of focus control. In addition, at the time of the interlayer jump, a liquid crystal element (23) for correcting the spherical aberration is optimized in advance for the cover layer thickness of the target layer L1.

Claims1

Dependent claims

An optical recording medium handling device comprising:

an objective lens unit focusing a spot of light onto an optical data-recording medium having a plurality of data-recording layers;
a driving unit moving the objective lens unit in the direction of the optical axis to move the focal point of the spot of light between the plurality of data-recording layers;
a spherical aberration correcting unit correcting the spherical aberration occurring in transparent cover layers provided for each data-recording layer and having different thicknesses;
a reflected-light detecting unit detecting the spot of light reflected by the optical data-recording medium;
and
a control unit switching between acceleration and deceleration of the driving unit based on the rate of change of a reflected-light intensity signal detected by the reflected-light detecting unit, when an interlayer movement is performed, the interlayer movement being the movement of the focal point of the spot of light from one data-recording layer to another data-recording layer, wherein the objective lens unit includes a two-group objective lens with high numerical aperture.

3 more elements

Dependencies are inferred from the claim text.

Facts

Application: 10/505,047Filed 26 Dec 2003
Priority: JP 2003-0007867 Jan 2003
Published: US 2005/0157614 A121 Jul 2005
Granted: 24 Oct 2006
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 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 7/1369
Separate or integrated refractive elements, e.g. wave plates: active plates, e.g. liquid crystal panels or electrostrictive elements
G11B 2007/0013
For carriers having data stored in three dimensions, e.g. volume storage: for carriers having multiple discrete layers