Optical Disc cd recording/reproducing apparatus recording/reprod

Details Optical Disc cd recording/reproducing apparatus recording/reprod Optical Disc cd recording/reproducing apparatus recording/reprod

1999-12-29

2000-12-26

Tran, Thang V.

Dynamic information storage or retrieval

Specific detail of information handling portion of system

Radiation beam modification of or by storage medium

369118, 369110, G11B 700

Patent

active

061670197

ABSTRACT:
An optical disc reproducing apparatus includes a semiconductor laser, an objective lens converging a laser beam from the semiconductor laser on a recording surface of an optical disc, a polarization plane rotating unit selectively rotating the plane of polarization of the laser beam according to the thickness of a substrate of the optical disc, and a polarizing filter selectively shading a peripheral portion of the laser beam having the rotated plane of polarization. In one embodiment, a numerical aperture changing unit includes a non-patterned twisted nematic liquid crystal, and the polarizing filter includes a polarizing film having a polarization characteristics at its peripheral portion.

REFERENCES:
patent: 4225873 (1980-09-01), Winslow
patent: 5150234 (1992-09-01), Takahashi et al.
patent: 5281797 (1994-01-01), Tatsuno et al.
patent: 5621719 (1997-04-01), Nomoto
patent: 5807498 (1998-09-01), Gibbons et al.

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