Optical head device for reading information stored in a recordin

Details Optical head device for reading information stored in a recordin Optical head device for reading information stored in a recordin

1989-07-26

1991-01-08

Arnold, Bruce Y.

Dynamic information storage or retrieval

Information location or remote operator actuated control

Selective addressing of storage medium

35016211, 369 4411, 369109, 369 4421, G02B 518, G02B 2744

Patent

active

049830171

ABSTRACT:
An optical head device for reading information stored in a recording medium wherein a light beam from a light source converges onto an optical disk and a beam reflected from the optical disk is received by a light receiving element to read information stored on the optical disk. This device includes a diffraction element having first diffraction gratings for dividing the light beam from the light source into a zero order diffracted beam utilized for reading the information stored on the optical disk and a pair of first order diffracted beams utilized for reading tracking errors. The diffraction element also has second diffraction gratings for guiding the beam reflected from the optical disk to a light receiving element. The transmission factors of the zero order diffracted beam of the first and/or second diffraction gratings in the regions located in the vicinity of both ends of the diffraction element are lower than those of the first and/or second diffraction gratings in the regions located in the vicinity of the center of the diffraction element. The ends and center are set in a direction corresponding to the radial direction of the optical disk.

REFERENCES:
patent: 4458980 (1984-07-01), Ohki et al.
patent: 4695992 (1987-09-01), Aoi
patent: 4731772 (1988-03-01), Lee
patent: 4787076 (1988-11-01), Deguchi et al.
patent: 4885734 (1989-12-01), Yuzo

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