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:
May. 09, 1995
Filed:
Dec. 04, 1992
Junichi Iida, Chigasaki, JP;
Syohei Aoyama, Hiratsuka, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
Disclosed is a focusing search circuit to activate a focusing servo loop of an optical disc player for driving an objective lens and for focusing a laser beam onto a signal recording surface of an optical disc. The circuit has a DC bias applying circuit for applying a DC signal of a predetermined level to an output signal of a photodetector which is a fluctuation of an AC signal centering about a predetermined DC signal level in the focusing search operation. The output signal of the photodetector which has been shifted by the predetermined level is compared with a reference voltage having a predetermined DC level of the photodetector before it is shifted by a comparing circuit. When the laser beam is in almost the in-focus state, the comparing circuit detects the coincidence between both of the above signals and activates the servo loop.
Data source: USPTO (United States Patent and Trademark Office) public patent records. Weekly synchronization. How IDiyas builds this profile