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. 20, 1983
Filed:
Aug. 14, 1981
Applicant:
Inventors:
Assignee:
Olympus Optical Co. Ltd., , JP;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
G01J / ; G11B / ;
U.S. Cl.
CPC ...
369 45 ; 250204 ;
Abstract
A method and apparatus for detecting a focussing error signal of an objective lens with respect to a video disc on which a light beam emitted from a laser light source is to be focussed as a light spot by the objective lens. A light flux reflected by the video disc is made incident upon a detection prism surface which is set substantially at a critical angle with respect to peripheral light fluxes reflected by the video disc, and the peripheral light fluxes reflected by the reflection surface are separately received by two light receiving regions which are spaced apart from each other. The focussing error signal is derived as a difference between output signals from the two light receiving regions.