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:
Aug. 07, 1984
Filed:
Mar. 03, 1982
Applicant:
Inventor:
Klaas Compaan, Eindhoven, NL;
Assignee:
U.S. Philips Corporation, New York, NY (US);
Attorneys:
Primary Examiner:
Int. Cl.
CPC ...
G11B / ;
U.S. Cl.
CPC ...
369 45 ; 369 46 ; 369112 ;
Abstract
An optical focusing error-detection device is disclosed which comprises a radiation-sensitive detector with four sub-detectors, and an astigmatic lens system arranged between the detector and the objective system whose focusing-error is to be detected. The astigmatic system is arranged in a non-collimated beam and comprises two cylindrical lenses having mutually perpendicular axes and having different powers so that the resulting focusing-error signal is symmetrical and linear around the zero point.