Optical system for tracking an information recording medium

Details Optical system for tracking an information recording medium Optical system for tracking an information recording medium

1985-03-19

1987-09-15

McElheny, Jr., Donald

Dynamic information storage or retrieval

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

Mechanism control by the control signal

250201, G11B 700

Patent

active

046944435

ABSTRACT:
In an optical system for tracking an optical disk with multiple beams, recording, reproduction and guide laser beams are converged by an objective lens onto a tracking guide formed by a light reflecting surface of the optical disk. The laser beams reflected from the light reflecting surface are transferred to a half mirror and are split into a first and a second set of laser beams. The first set of laser beams are also converged by a projection lens onto a first photodetector. A knife edge is located in the optical path of the first set of laser beams. Accordingly, a part of the first set of laser beams are shielded by the knife edge, and the other part of the first set of laser beams are incident on the first photodetector. The photodetector has first and second photosensitive region, regions, a photosensitive region and a third photosensitive region. The reproduction laser beam of the first set of laser beams is detected by the first and second photosensitive region to generate a focusing signal, the recording beam of the first set of laser beams is attenuated by the photoinsensitive region, and the guide beam of the first set of laser beams is detected by the third photosensitive region.

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