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:
May. 23, 1989
Filed:
Feb. 01, 1988
Fuji Photo Film Co., Ltd., Kanagawa, JP;
Abstract
A pickup apparatus for a magneto-optical recording medium comprises an optical waveguide for receiving a light beam reflected by a magneto-optical recording medium, and first and second focusing grating couplers disposed side by side on the optical waveguide for introducing the reflected light beam into the optical waveguide by exciting the same guided mode, and converging the guided optical waves. A third focusing grating coupler is disposed for introducing the reflected light beam into the optical waveguide in a different guided mode and converging the guided optical wave. First, second and third photodetectors are secured to the optical waveguide for respectively 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.