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:
Mar. 23, 1999
Filed:
Sep. 05, 1996
Teruo Fujita, Tokyo, JP;
Mitsubishi Denki Kabushiki Kaisha, Tokyo, JP;
Abstract
To achieve a tracking error detection, a device for use in a simple optical system is disclosed which reduces offset resulting from the lateral movement of an objective lens or a tilt of an information recording medium. The disclosed device maintains the maximum amplitude of a tracking error signal irrespective of variations in track pitch of the information recording medium. The device produces a light beam having substantially-half portions about 180 degrees out of phase with each other, and another light beam which are directed and focused via an objective lens to an information recording medium. The light spots formed by the two light beams are disposed on the information recording medium with a spacing of substantially an integral multiple of the track pitch in the direction perpendicular to the tracks on the information recording medium. Each light beam returning from the information recording medium is received by a pair of split photodetectors, and a tracking error signal is obtained from the difference between the differential outputs.