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. 24, 1988
Filed:
Jul. 14, 1986
Masanori Doi, Akishima, JP;
Olympus Optical Co., Ltd., Tokyo, JP;
Abstract
A semiconductor laser drive device is adopted in an optical disk read/write unit for writing/reading data in/from an optical disk. The device has driver for modulating the laser beam of the intensity corresponding to a drive current value in accordance with write data WDATA, photodiode for detecting the light-emitting intensity of semiconductor laser, and APC circuit for comparing the detected light-emitting intensity of photodiode with a desired light-emitting intensity and changing the drive current value for semiconductor laser until the detected light-emitting intensity coincides with the desired light-emitting intensity. APC circuit has battery backup memory. A drive current value obtained at the start of the device is stored in memory. Thereafter, APC circuit starts APC from the stored drive current value. After APC is completed, when the drive current value calculated by APC circuit is different from the stored drive current value, the drive current value stored in battery backup memory is updated to the drive current value calculated by APC circuit. After APC is completed, when the difference between the drive current value calculated by APC circuit and the stored drive current value exceeds a predetermined value, APC circuit determines that the service life of semiconductor laser is exhausted.