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:
Nov. 08, 1988
Filed:
Aug. 14, 1986
Shigeru Aoi, Kawasaki, JP;
Canon Kabushiki Kaisha, Tokyo, JP;
Abstract
An error signal detecting device is composed of means for irradiating an object with a concentrated light beam, a photosensor having a photoreceptor face divided into plural portions and adapted to receive the light reflected or transmitted by the object, a device for respectively dividing a first output and a second output obtained respectively from the first and second portions of the photoreceptor face of the photosensor, a first comparator for respectively comparing the outputs divided from the first output with the second output, a second comparator for respectively comparing the outputs divided from the second output with the first output, and a device for deriving a positional error signal indicating the positional error of the light beam spot with respect to the surface of the object, at least in one of the direction of optical axis and a direction perpendicular to the optical axis.