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:
Dec. 05, 1978
Filed:
Oct. 26, 1976
Gerald Roullet, Paris, FR;
Jean-Pierre Bortuzzo, Paris, FR;
Thomson-Brandt, Paris, FR;
Abstract
The invention relates to the exact focussing of a light beam on a track carried by an optically readable information support. The object of the invention is to provide in an optical reading device a dichotomic focussing error detection device of which the two states correspond to the absence and to the presence of the reading signal. In the absence of the reading signal, the lens of the optical reading device is moved at a uniform speed between two limit positions by means of a triangular control signal, the position control loop of the lens being open. In the presence of the reading signal, the lens is no longer controlled by the triangular control signal, but instead by an error signal emanating from the position control loop which is then closed.