Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1992-09-09
1993-10-05
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
369116, 250214C, G01J 132, G11B 700
Patent
active
052507963
ABSTRACT:
An optical disk apparatus includes a semiconductor laser for emitting a light beam, and an automatic power control or APC circuit for driving the laser. A compound prism structure is optically coupled to the laser in an optical head section, and defines a first optical path for causing a front laser light to be projected onto a rotating optical disk and guiding a reflected light therefrom toward a first photodetector, and a second optical path for guiding a part of the reflected light toward a second photodetector. An output signal of the first photodetector is used to generate a reproduced information signal. An output signal of the second photodetector is fed back to the APC circuit as a front light monitor signal. A part of a laser control signal internally generated in the APC circuit is supplied through a wiring line to a noise reduction circuit as a laser noise monitor signal. The noise reduction circuit subtracts this noise monitor signal from the reproduced information signal to provide a noise-suppressed information signal.
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Shimura Kei
Sugaya Toshihiro
Taguchi Toyoki
Yamada Hisashi
Kabushiki Kaisha Toshiba
Messinger Michael
Nelms David C.
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