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:
Feb. 12, 1991
Filed:
Dec. 05, 1989
Hitoshi Okada, Chiba, JP;
Sony Corporation, Tokyo, JP;
Abstract
This invention relates to a focusing error detection circuit employed in an optical pickup of an optical disk apparatus or the like. The laser light received from the recording medium is detected by a photodetector and processed in a focusing error computing device to form a first focusing error signal. The first focusing error signal is sampled and held at the timing of periodic turn-off of the laser beam and the sampled-and-held signal is subtracted from the first focusing error signals to produce a second focusing error signal. The second focusing error signal is freed of adverse effects caused by factors, such as temperature changes of the focusing error computing device thereby enabling the accurate focusing servo control of the optical pickup device.