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:
Mar. 17, 1992
Filed:
Feb. 06, 1990
Daniel R Marshall, Boise, ID (US);
Hewlett-Packard Company, Palo Alto, CA (US);
Abstract
A method and apparatus for detecting the focus of a beam of light directed onto grooved optical media, wherein light reflected from said media has a number of orders of reflection forming a sheared interferogram, and wherein overlapping regions are generated between said orders of reflection in said interferogram, is shown to include a light receiving member for receiving light reflected from the media and for directing the light onto a detector member for detecting differences in the brightness of light across the overlapping regions. The detecting member is shown to include, a first photosensitive member for detecting the brightness of light in a portion of the overlap region between the zeroth and first order reflections, a second photosensitive member for detecting the brightness of light in the remainder of the overlap region between the zeroth and first order reflections, and a comparator for comparing the brightness detected between the portion and the remainder of the overlap region.