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. 14, 1991
Filed:
Dec. 21, 1989
Ricoh Company, Ltd., Tokyo, JP;
Abstract
An optical information reading and writing device comprising a laser source which emits a laser beam for irradiating an optical recording disk to record an information therein and an optical signal detection system which receives a reflection beam reflected from the disk surface and controls position of the disk. The optical signal detection system comprises a condenser lens for converging the reflection beam and a dual grating element which has linear diffraction gratings formed on its both side surfaces. The incident side grating divides the reflection beam to two beams, one being a beam which is diffracted by the grating and the other being a beam which passes substantially straight through the grating without being diffracted thereby. The optical signal detection system further comprises a pair of three-segment light receiving detector elements for detecting the divided two beams. The two detector elements are disposed on a same plane.