The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 07, 2004
Filed:
Jun. 14, 1999
Josephus J. M. Braat, Eindhoven, NL;
Koninklijke Philips Electronics N.V., Eindhoven, NL;
Abstract
A device scans an optical record carrier having optically detectable marks along a track. The device includes a radiation source for emitting a radiation beam, an objective system for guiding the radiation beam to the record carrier, and a radiation-sensitive detection system for receiving radiation from the record carrier. The detection system includes at least two detectors on both sides of a dividing line. Each detector has an output for providing a detector signal. An electronic circuit forms a focus error signal from the detector signals. The electronic circuit determines a time or phase difference between corresponding parts of the detector signals relating to passage of the radiation beam over patterns of the marks having a spatial frequency in a first range and in a different, second range, and forms a focus error signal in dependence on the time or phase difference.