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. 02, 1980
Filed:
Feb. 28, 1979
William R Roach, Rocky Hill, NJ (US);
Ping Sheng, Princeton, NJ (US);
RCA Corporation, New York, NY (US);
Abstract
An incident light beam illuminates the surface of a disc, having signal elements recorded therein in the form of a succession of spaced apart depressions, with a light spot that spans a plurality of depressions. The structure of the depressions serves as a diffraction grating which reflects the incident light beam into a plurality of substantially coplanar diverging fans of light. Polarizers are interposed between the light beam source and the surface to polarize the light beam in orthogonal directions. Photodetectors, positioned to intercept the reflected fans, provide outputs corresponding to the light power in the reflected fans. The photodetectors provide a first output of the reflected light power of the light beam polarized in a first direction and a second output of the light power of the reflected light beam polarized in a direction orthogonal to the first direction. The ratio of the first output to the second output is indicative of the depression depth.