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:
Dec. 03, 1991
Filed:
Apr. 03, 1989
Ricoh Company, Ltd., Tokyo, JP;
Abstract
An optical pickup device for optically reproducing an information recorded on a recording medium of a magneto-optical disc or a write-only-read-many optical disc, includes a semiconductor laser, an objective lens for converging the laser light emitted by the laser on the recording medium, a photo-detector for detecting a light reflected from the recording medium, a beam splitter for leading the emitted light from the laser to the objective lens and for leading said light reflected by the recording medium to the photodetector, a first phase plate disposed between the beam splitter and the objective lens, a second phase plate disposed between the beam splitter and the photo-detector, and a rotator for rotate the first phase plate in such a manner than the beam splitter forbids to transmit the light reflected by the recording medium into the laser in a case where the recording medium is said write-only-read-many optical disc, and that the beam splitter allows to transmit the light reflected by the recording medium into the laser in a case where the recording medium is the magneto-optical disc.