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:
Apr. 18, 1995
Filed:
Apr. 28, 1993
Applicant:
Inventors:
Assignee:
Sharp Kabushiki Kaisha, Osaka, JP;
Attorney:
Primary Examiner:
Assistant Examiner:
Int. Cl.
CPC ...
G11B / ;
U.S. Cl.
CPC ...
369 4412 ; 369 4424 ; 369 4432 ; 369103 ; 369112 ;
Abstract
An optical pickup apparatus for reproducing information from an optical recording medium such as a compact disc comprising: a laser device; one or more diffraction devices; and a photodetector receiving a laser beam diffracted by the diffraction device. The surfaces of the diffraction device are provided with an antireflection coating. When the apparatus is used for the three-beam method, the two photodetecting areas in the photodetector for producing the tracking error signal are different in size and in positional relation to the laser device.