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:
Feb. 06, 1996
Filed:
Oct. 07, 1991
Shigeru Nakamura, Tachikawa, JP;
Mariko Umeda, Tokyo, JP;
Takeshi Nakao, Sgamihara, JP;
Akira Arimoto, Kodaira, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
An optical information processing apparatus comprising a diffraction grating for producing a zero-order beam which is a beam emitted by a light source and allowed to pass therethrough and two plus and minus first-order sub-beams respectively having positive and negative astigmatisms, radiated in directions at slight angles different from the main beam, wherein said two sub-beams are focused at opposite positions across said main beam, wherein focusing control is performed by a focusing error signal detected from a difference of signal amplitudes obtained from the respective reflected light quantities of said two sub-beams and wherein tracking control is performed by an off-track signal obtained from a signal according to a reflected light quantity of said main beam. In an apparatus for magneto-optically reproducing information, above all else, a wave plate is inserted between the focusing lens and the separating optical system, thereby increasing the reflected light quantities and stabilizing the magneto-optical signal, focusing signal and tracking signal.