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:
Jul. 21, 1987
Filed:
Jun. 14, 1985
Atsushi Uejima, Kanagawa, JP;
Fuji Photo Film Co., Ltd., , JP;
Abstract
A focussing error detection device for use in a optical disk type recording system wherein a light beam is converged by objective lens means onto a recording surface of the disk and wherein the light beam reflected by said recording surface is divided by a first beam divider interposed between said objective lens means and a light beam source. The improvement comprises a second beam divider for further dividing the light beam divided by said first beam divider into central light beam fraction and a peripheral light beam fraction, a first photo detector for detecting the quantity of the central light beam fraction, a second photo detector for detecting the quantity of the peripheral light beam fraction, and a subtracter for indicating the difference between the output from the first photo detector and the second photo detector.