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. 25, 2003
Filed:
Dec. 18, 2000
Steffen Lehr, Villingen-Schwenningen, DE;
Rüdiger Brunheim, Unterkirman, DE;
Thomson Licensing S.A., Boulogne, FR;
Abstract
The invention relates to a method and a circuit arrangement for a laser control loop with automatic adaptation to the monitoring signal polarity. Use is made of a single-phase method which consists in that a signal produced by the monitor during the starting phase of the laser control loop is compared with a reference value, and in accordance with the result of the comparison the signal produced by the monitor is fed directly or inverted to the comparator for controlling the light power of the laser during the starting phase of the laser control loop. A signal is produced which initially feeds the comparator for controlling the light power the inverted monitoring signal, or directly feeds the monitoring signal, in a fashion always independent of the monitoring signal polarity, but dependent on the polarity of a reference value, and feeds it in a non-inverted fashion in the case of a monitoring signal running up to the reference value. The laser control loop circuit according to the invention ensures that the monitoring signal is fed with a fixed polarity to the first comparator before the reference value for controlling the light power is reached. This is achieved by virtue of the fact that the monitoring signal is fed to a comparator which compares the monitoring signal with a reference value which is smaller than the reference value for controlling the light power. In the case of a monitoring signal not running up to the first reference value, the comparator for controlling the light power still continues to be fed the inverted monitoring signal. The laser control loop is provided, for example, for controlling the light power of a laser in optical scanning systems for recording or reproducing information independently of the monitoring signal polarity and/or the polarity of the monitor diode of the laser.