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. 19, 1989
Filed:
Apr. 20, 1988
Fuji Photo Film Co., Ltd., Kanagawa, JP;
Abstract
A pickup apparatus for a magneto-optical recording medium comprises the first and second waveguides lying one upon the other for receiving a light beam reflected by a magneto-optical recording medium, and first and second focusing grating couplers disposed on the first waveguide for introducing the reflected light beam into the first waveguide in the same guided mode. A third focusing grating coupler is disposed for introducing the reflected light beam into the second waveguide in a different guided mode. First, second and third photodetectors are secured to the first or second waveguide for detecting the optical waves converged by the first, second and third focusing grating couplers. Tracking error and focusing error are detected based on the outputs of the first and second photodetectors, and recorded signals are detected based on a difference between the output of the first and/or second photodetector and an output of the third photodetector.