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. 12, 1989
Filed:
Dec. 17, 1986
Masatoshi Ohtake, Ome, JP;
Seiji Yonezawa, Hachioji, JP;
Toshiaki Tsuyoshi, Kokubunji, JP;
Kazuo Ichino, Tokyo, JP;
Yukio Fukui, Machida, JP;
Takashi Takeuchi, Fujisawa, JP;
Takeshi Maeda, Kokubunji, JP;
Toshimitsu Kaku, Sagamihara, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
A tracking servo system includes in addition to a composite servo system composed of a push-pull track deviation detecting loop operative with pregrooves formed in an optical disc and a wobbling track deviation detecting loop operative with intermittently provided wobbled tracking marks, an offset correcting loop for detecting offset component possibly produced due to tilt, deformation and eccentricity of a recording medium or change in optical and mechanical parameters in the course of time lapse to drive forcibly a light spot by applying an electrical offset to cancel out the offset component. In the offset correcting loop, light reflected by wobbled tracking marks provided intermittently or mirror areas formed by interrupting intermittently the pregroove is utilized for detecting the offset component.