Optical head comprising a diffraction grating for directing two

Details Optical head comprising a diffraction grating for directing two Optical head comprising a diffraction grating for directing two

1986-12-10

1990-07-31

Stephan, Steven L.

Dynamic information storage or retrieval

Specific detail of information handling portion of system

Radiation beam modification of or by storage medium

250237G, 369 46, 369110, 369120, 369 4411, G01J 120, G11B 2110, G11B 713

Patent

active

049455290

ABSTRACT:
For use in combination with an optical source for generating a coherent beam along a main optical axis, an optical head device comprises a diffraction grating having a plurality of grating regions which are responsive to the coherent beam for directing a zeroth-order diffracted beam to a focussing lens and are responsive to an optical beaem reflected from an optical recording medium for directing sidewards diffracted beams to an optical detector assembly. An effective area of a diameter of about 5 mm is sufficient for the diffraction grating. Each sidewards diffracted beam may form an angle of 20.degree. with the main optical axis. The optical detector assembly is used in detecting focussing and tracking errors for the recording medium and can be used in reproducing optical information from the recording medium. A six-partitioned optical detector assembly is preferred when the grating regions are four in number. Either a four-partitioned or a three-partitioned optical detector assembly is preferred when the grating regions are two in number. Depending on the grating regions, the optical detector assembly preferably has two optical detector elements which are placed on different levels relative to the diffraction grating.

REFERENCES:
patent: 3876842 (1975-04-01), Bouwhuis
patent: 4498159 (1985-02-01), Daimon
patent: 4624526 (1986-11-01), Tsukoi
patent: 4665310 (1987-05-01), Heemskerk
patent: 4731772 (1988-03-01), Lee
patent: 4733065 (1988-03-01), Hoshi
M. G. Carasso et al., "The Compact Disc Digital Audio System", Phillips Tech., Rev. 40, 151-155, 1982, No. 6.
"Techniques for Mastering CD Digital Audios", May 15, 1985, Seibundo Sinkosya, pp. 19-36.

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