Optical head device

Details Optical head device Optical head device

1990-06-05

1993-10-12

Envall, Jr., Roy N.

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

369 4412, 369 4442, G11B 700

Patent

active

052532372

ABSTRACT:
The invention discloses an optical head device having a diffraction grating element divided into a plurality of diffraction gratings have a substantially equal diffraction angle, a substantially equal optical utilization efficiency, and different focal distances of first order diffracted lights, each of the first order diffracted lights being produced from a reflected light from the recording medium, at the respective diffraction gratings and a photodetector positioned at a mid-position between two focal points produced when there occurs no focusing error, the photo-detecting means having a plurality of photo-detecting parts juxtaposed in a direction substantially orthogonal to an average diffracting direction of the diffraction grating element. The above arrangement enables to produce a small size optical head device and improve the detecting of focusing errors and tracking errors.

REFERENCES:
patent: 4654838 (1987-03-01), Sugiki
patent: 4695158 (1987-09-01), Kotaka et al.
patent: 4817074 (1989-03-01), Yamanaka
patent: 4897828 (1990-01-01), Yoshitoshi et al.
patent: 4904856 (1990-02-01), Nagahama et al.
patent: 4924079 (1990-05-01), Opheij et al.
patent: 4929823 (1990-05-01), Kato et al.
patent: 5060217 (1991-10-01), Kume

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