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:
May. 26, 1987
Filed:
Aug. 30, 1985
Jean-Louis Gerard, Paris, FR;
Pierre Berthet, Paris, FR;
Claude Bricot, Paris, FR;
Michel Audoin, Paris, FR;
Thomson-CSF, Paris, FR;
Abstract
A process and device for focussing a light energy beam on a data carrier comprising sites fromed of virgin areas free from any data recording provided along tracks and serving as reference plane for said focussing. In a preferred variation, these areas are preceded by flags associated with a specific code. Control is achieved by measuring the deviation between the plane of focussing of a beam into a spot scanning the tracks and the reference plane formed by the surface of the virgin areas. Between two passages of these areas of the measurements are stored. The focussing error signal is obtained by filtering these measurements.