Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1995-05-30
1996-07-02
Allen, Stephone
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
2502015, 359494, G01J 120, G02F 101
Patent
active
055324770
ABSTRACT:
In an optical pickup apparatus, a laser beam is generated from a laser source toward a lens group for reading out information written on an information recording medium. The lens group determines paths of an incident beam to the information recording medium and a reflected beam from it. The lens group includes a polarization converting element such as a .lambda./4 plate, a .lambda./8 plate, or a 80/16 plate for polarizing a beam transmitted therethrough and a birefringent prism to refract the beam depending on the polarized state and an objective lens through which the beam is transmitted to be focused on the information recording medium. The laser source generates an ordinary ray composed of a linearly polarizing component to be refracted ordinarily in the birefringent prism. A photodetector receives the beam polarized and refracted by the lens group. The lens group is arranged in the order of the diffraction grating, the birefringent means, and the polarization converting means from the bottom. After the beam emitted from the laser source is transmitted through the diffraction grating, the birefringent prism and the polarization converting element in that order, the beam is incident on the recording medium and then reflected from it, and inversely transmitted therethrough, and then the beam is received by the photodetector so that an information reading operation, and a tracking and focusing control operations are performed.
REFERENCES:
patent: 4564631 (1986-01-01), O'Hara et al.
patent: 5272550 (1993-12-01), Dickson et al.
patent: 5404490 (1995-04-01), Matsubayashi et al.
Allen Stephone
Daewoo Electronics Co. Ltd.
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