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. 17, 1985
Filed:
Nov. 03, 1982
Masahiro Takasago, Odawara, JP;
Takeshi Maeda, Odawara, JP;
Motoo Uno, Kokubunji, JP;
Yasumitsu Mizoguchi, Odawara, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
An optical information disc apparatus includes a laser source, a recording medium with an information track, an optical system for emitting a laser beam from the laser source onto the information track, a photodetector detecting the focus error of the optical system using the light reflected from the information track, and an auto-focusing servo system operating the optical system to make the focus of the system follow the upward and downward movement of the recording medium, the optical information disc apparatus being further provided with a control circuit to make the auto-focusing servo system effective only when the optical system is in a position equivalent to the linear region of a defocusing signal having an S-curve characteristic.