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US 6,586,717 B2Granted
Optical scanning head
AssigneeKoninklijke Philips Electronics N.V.
InventorsJoris Jan Vrehen, Jeroen Wals, Sjoerd Stallinga
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AssigneeKoninklijke Philips Electronics N.V.
InventorsJoris Jan Vrehen, Jeroen Wals, Sjoerd Stallinga
Estimating the term…
An optical head scans the information layer (3) of an optical record carrier (1) by means of a radiation beam (13). Optical aberrations in the beam such as coma and spherical aberration, caused by tilt and thickness variations in the optical disc respectively, are compensated by an aberration compensator (27) arranged in the radiation beam. The tilt or thickness variation is measured by a detector (30) and used to control the aberration compensator. The radiation beam is focused onto the information layer by an objective system (11). A displacement of the objective system in the transverse direction (26) as used for radial tracking of the optical beam, causes a mismatch between the wavefront to be compensated and the wavefront introduced by the aberration compensator (27). The mismatch is reduced by using a position detector (33) for measuring the transverse position of the objective system and using the position signal (34) as input for the control of the aberration compensator.
An optical head for scanning an optical record carrier having an information layer and a transparent layer, comprising a radiation source for generating a radiation beam and an objective system for converging the radiation beam through the transparent layer to a focus on the information layer, an aberration detector for detecting an optical aberration in the radiation beam, an aberration compensator arranged in the optical path between the radiation source and the objective system, and a control circuit connected to an output of the aberration detector for controlling the aberration compensator, characterized in that the optical head comprises a position detector for determining a transverse position of the objective system and that the control circuit is connected to an output of the position detector, wherein the aberration compensator introduces an amount of a first optical aberration of the type as measured by the aberration detector and an amount of a second optical aberration of a lower radial order than the first aberration, wherein the control circuit is operatively connected such that the amount of the first aberration depends substantially on a signal at the output of the aberration detector and the amount of the second aberration depends substantially on a signal at the output of the position detector.
A device for scanning an optical record carrier having an information layer and a transparent layer, comprising an optical head and an information processing unit for error correction, said optical head comprising:
Dependencies are inferred from the claim text.