Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Patent
1996-02-29
1998-07-28
Tran, Thang V.
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
369 54, 369118, 369110, 369 4424, 369 4436, G11B 700, G11B 7135
Patent
active
057870616
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 blocking a peripheral portion of the laser beam depending on the 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 characteristic at its peripheral portion.
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Ichiura Shuichi
Kajiyama Seiji
Kanou Yasuyuki
Tsuchiya Yoichi
Sanyo Electric Co,. Ltd.
Tran Thang V.
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