Focusing error detecting apparatus

Details Focusing error detecting apparatus Focusing error detecting apparatus

1990-01-04

1992-11-03

Envall, Jr., Roy N.

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

369 4424, 369 4442, 369112, 2502015, G11B 700

Patent

active

051611392

ABSTRACT:
In an apparatus for detecting a focusing error of an objective lens, a light beam reflected from an optical disk passes the objective lens and is reflected from a beam splitter. The reflected light beam is incident on a cylindrical lens so that the light beam is converged in one direction by the cylindrical lens. The converged light beam is incident on first and second triangular prisms so that it is divided into two beams and the two beams are guided into different directions and form beam spots on photo-detectors, respectively. In the respective triangular prism, light rays of the light beam pass through different optical paths. Thus, an aberration is applied to the light beam from the prisms. Accordingly, the shape of each beam spot on the photo-detector is changed in accordance with a focusing error.

REFERENCES:
patent: 4023033 (1977-05-01), Bricot et al.
patent: 4513408 (1985-04-01), Nomura et al.
patent: 4712205 (1987-12-01), Smid et al.
patent: 4835378 (1989-05-01), Coops
patent: 4904856 (1990-02-01), Nagahama et al.
patent: 4929823 (1990-05-01), Kato et al.

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