Photo-detecting device

Details Photo-detecting device Photo-detecting device

1991-02-08

1992-09-22

Envall, Jr., Roy N.

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

369 4441, 369 4442, G11B 700

Patent

active

051503425

ABSTRACT:
The light receiving element of the photo-detecting device of this invention has its light receiving area formed smaller than the diameter of a beam reflected from an optical information recorded disc. This makes it possible for the tracking error signal to be taken from a central area of the beam spot where the light intensity is high. This minimizes the dc offset caused by misalignment between the objective lens and the beam axis. The light receiving surface of the element is divided into at least four sections along a line at 45 degrees to the direction of tracking. A difference is taken between the light quantities received by two divided light receiving surfaces disposed perpendicular to the tracking direction. This differential signal allows adjustment to be made of an angle between the disc and the photo-detecting device in the direction perpendicular to the tracking direction.

REFERENCES:
patent: T953022 (1976-12-01), Firester
patent: 4425043 (1984-01-01), van Rosmalen
patent: 4475182 (1984-10-01), Hosaka
patent: 4866688 (1989-09-01), Ohtake et al.

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