Noise reduction system for optical record and reproduction apparatus using auto-power controlled semiconductor laser device
US5475210A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 8, 1993 |
| Grant date | Dec 12, 1995 |
| Priority date | — |
| Expiry date | Jun 8, 2013 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N5/85
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.