Optical head having a grating with a doubly periodic structure

Details Optical head having a grating with a doubly periodic structure Optical head having a grating with a doubly periodic structure

1991-06-26

1993-09-14

Sniezek, Andrew L.

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

369112, 369109, 359569, 359900, 2502015, G11B 700, G02B 518

Patent

active

052455963

ABSTRACT:
An optical head is disclosed in which a beam from a diode laser is directed onto an optical disc, and a beam reflected from the optical disc is passed through an optical device which forms a plurality of discrete beams of different orders. The beams from the optical device are focussed onto photodetectors, and signals from the photodetectors are used for error detection, tracking, and signal detection. The optical device comprises two diffraction gratings which are supported on a substrate and are separated from each other by a thin film. In order to obtain the advantages of a doubly-periodic structure, the thickness of the thin film between the two gratings is very accurately controlled to be on the order of the wavelength of the incident beam of radiation.

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patent: 5101389 (1992-03-01), Ohuchida et al.
"A High Density Dual Type Grating for Magneto-Optical Disk Head", Journal of Applied Physics, vol. 28, Supplement 28-3 pp. 193-195, 1989.
"Rigorous Analysis of Guided Waves in Doubly Periodic Structures", Journal Optical Society of Americas, A7, 1448 (1990).

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