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. 17, 1990
Filed:
Mar. 28, 1988
Willem G Opheij, Eindhoven, NL;
Louis-Marie H Cobben, Eindhoven, NL;
U.S. Philips Corporation, New York, NY (US);
Abstract
Optical record carrier scanning apparatus including a source of radiation which is tunable to produce different wavelengths of a radiation beam and an optical assembly for forming the radiation beam into a spot for scanning information tracks on the record carrier. The optical assembly includes a diffraction grating which diffracts the beam so that only a selected diffraction order sub-beam thereof is formed into the scanning spot, the diffraction angle of such sub-beam and consequently the position of the scanning spot relative to the track being scanned being variable by variation of the wavelength of the radiation beam. A periodic transverse variation of spot position can thus be produced entirely optoelectronically, for producing a tracking error signal to control the scanning spot to remain centered on the information track.