Diffraction grating using birefringence and optical head in whic

Details Diffraction grating using birefringence and optical head in whic Diffraction grating using birefringence and optical head in whic

1987-07-20

1989-12-05

Stephan, Steven L.

Dynamic information storage or retrieval

Control of storage or retrieval operation by a control...

Mechanism control by the control signal

250237G, 3501622, 35016223, 369 46, 369109, 369112, 369120, G11B 709, G11B 1210, G01J 120

Patent

active

048857343

ABSTRACT:
A diffraction grating comprises a birefractive sheet (11) having a corrugated surface with at least each groove filled with a mass (12) of a material of a refractive index which is substantially equal to one of ordinary and extraordinary indices of the birefractive sheet. The diffraction grating is effective in an optical head device when made to have a plurality of grating regions of different patterns of corrugations. In this event, a linearly polarized beam should be supplied to the diffraction grating with electric vectors directed parallel to those of ordinary and extraordinary components when the refractive index is substantially equal to the ordinary and extraordinary indices, respectively. Alternatively, such an optical head device may comprise a reflection grating in which reflective corrugations are substantially parallel in the respective grating regions. In this event, a linearly polarized beam is supplied from an optical source to the reflective corrugations as a p-polarized beam. When either the birefringence grating or the reflection grating is used, the optical head device should further comprise a quarterwave plate for receiving the linearly polarized beam which is exited from the grating.

REFERENCES:
patent: 3876842 (1975-04-01), Bouwhuis
patent: 4665310 (1987-05-01), Heemskerk
patent: 4733065 (1988-03-01), Hoshi et al.
patent: 4733277 (1988-03-01), Kokado
patent: 4733943 (1988-03-01), Suzwki et al.
patent: 4753513 (1988-06-01), Shikama
patent: 4771411 (1988-09-01), Greve

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