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. 07, 1993
Filed:
Jan. 03, 1992
Isao Hoshino, Yokohama, JP;
Yoshinori Honguh, Yokohama, JP;
Kabushiki Kaisha Toshiba, Kawasaki, JP;
Abstract
In an optical head, a converging lens and a holographic optical element are arranged in the optical path of light reflected by the recording surface of an optical memory recording medium and passing through an objective lens. The holographic optical element has a hologram formed in at least one of two regions split by a region splitting line crossing the optical axis of the converging lens. A photodetector is arranged on the extension line of the optical axis. The photodetector has a plurality of detection surfaces which are respectively split along the region partition line of the holographic optical element to detect light beams diffracted by the hologram. The optical head also includes a detecting system for detecting a focusing error of the objective lens of the optical head by performing predetermined arithmetic operations using an incorporated processing circuit on the basis of output signals obtained by the plurality of detection surfaces of the photodetector.