Optical disc recording/reproducing apparatus recording/reproduci

Details Optical disc recording/reproducing apparatus recording/reproduci Optical disc recording/reproducing apparatus recording/reproduci

1999-12-29

2000-10-24

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, G11B 700

Patent

active

061377643

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

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