Optical head device and optical information apparatus using a li

Details Optical head device and optical information apparatus using a li Optical head device and optical information apparatus using a li

1997-01-03

1997-11-11

Young, W. R.

Dynamic information storage or retrieval

Specific detail of information handling portion of system

Radiation beam modification of or by storage medium

369 4423, 369112, G11B 700

Patent

active

056871538

ABSTRACT:
An optical head device includes: a light source for emitting a light beam; an objective lens for converging the light beam on an information storage medium; a hologram for receiving the light beam reflected by the information storage medium and generating diffracted light from the light beam, the hologram having such a polarization anisotropy that it diffracts light in a second polarization state more strongly than light in a first polarization state which is different from the second polarization state; and a photodetector including a plurality of photodetective sections for receiving a part of the diffracted light and outputting a photocurrent in accordance with the intensity of the part of the diffracted light. The optical head device further include a quarter-wave plate disposed between the objective lens and the hologram for causing the polarization state of the light beam reflected by the information storage medium to be the second polarization state; and the hologram is disposed so that the distance between the hologram and the objective lens is shorter than the distance between the hologram and the photodetector.

REFERENCES:
patent: 5013107 (1991-05-01), Biles
patent: 5062098 (1991-10-01), Hori et al.
patent: 5293038 (1994-03-01), Kadowaki et al.
patent: 5301182 (1994-04-01), Komma et al.
patent: 5361244 (1994-11-01), Nakamura et al.

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