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:
Feb. 13, 2007
Filed:
Oct. 06, 2003
Hiromichi Ishibashi, Ibaraki, JP;
Tetsuya Shihara, Kadoma, JP;
Hisashi Senga, Neyagawa, JP;
Toshio Matsumoto, Kyoto, JP;
Hiromichi Ishibashi, Ibaraki, JP;
Tetsuya Shihara, Kadoma, JP;
Hisashi Senga, Neyagawa, JP;
Toshio Matsumoto, Kyoto, JP;
Matsushita Electric Industrial Co., Ltd., Osaka, JP;
Abstract
In an optical disc drive, a laser light source emits a laser beam having an intensity changeable with the amount of drive current supplied. A first photodetector receives the laser beam reflected from an optical disc, thereby generating a readout signal. A second photodetector receives the laser beam, generates an electric signal representing the power of the laser beam received, and outputs the electric signal as a light quantity detection signal. A feedback control loop compares the level of the light quantity detection signal with a predetermined target value and regulates the drive current such that the level of the light quantity detection signal approaches the target value. In reading data from the optical disc, the target value is changed so as to compensate for a variation of the sensitivity of the second photodetector, thereby controlling the power of the laser beam emitted from the laser light source.