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:
Dec. 01, 1998
Filed:
Aug. 13, 1997
Takeshi Mizuno, Kanagawa, JP;
Sony Corporation, Tokyo, JP;
Abstract
There is provided an optical device which comprises a light-emitting portion for emitting a laser light, a light-receiving portion for receiving the light emitted from the light-emitting portion, and a converging portion for converging the light emitted from the light-emitting portion to thereby irradiate a portion to be irradiated and for converging a light reflected on and returned from the irradiated portion, wherein the light-receiving portion is located in the vicinity of a confocal point of the converging portion with respect to the light returned from the irradiated portion, the light emitted from the light-emitting portion is received by the light-receiving portion along a path which is coaxial before and after being reflected by the irradiated portion, a push-pull signal is detected by the light-receiving portion, and the push-pull signal is subjected to partial differentiation with the amount of defocus to obtain a coefficient which is used to detect a tracking error signal.