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:
Nov. 24, 1998
Filed:
Dec. 13, 1996
Josephus J Braat, Eindhoven, NL;
U.S. Philips Corporation, New York, NY (US);
Abstract
A device for optically scanning an information layer by means of a focused radiation beam. Radiation reflected from the information layer is made astigmatic by an oblique plane parallel plate and subsequently detected by a detection system. An electronic circuit 26 derives two focus error signals, each representing the distance between the focal point of the radiation beam and the information plane. The first focus error signal is formed from the high-frequency components in the electrical detector signals, and the second focus error signal is formed from the low-frequency components in the same detector signals. A second electronic circuit combines the two focus error signals to a combined focus error signal.