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:
Jun. 12, 2001
Filed:
Oct. 29, 1998
Akihito Nakayama, UE Square, SG;
Kenji Shintani, Singapore, SG;
Shunsuke Kohama, Chiba, JP;
Yukari Hashimoto, Yokohama, JP;
Other;
Abstract
A device for measuring focusing characteristics of an optical pickup and/or an optical disc capable of measuring characteristics of focusing states with high accuracy by a simplified circuit. An arithmetic-logic unit,controls an offset supplying circuit,for applying an offset voltage to a focusing servo control signal. This arithmetic-logic unit,detects an error rate of the playback data in such a state in which the focusing position of the laser light is deviated by a pre-set offset amount. The arithmetic-logic unit,sequentially varies the offset voltage to repeat the above processing for detecting the error rate. The arithmetic-logic unit,approximates the relationship of the error rate to the offset amount by a quadratic curve based on detected data. The offset amount which minimizes the error rate is found from this equation of approximation.