Focus acquisition and maintenance for optical disk system

Details Focus acquisition and maintenance for optical disk system Focus acquisition and maintenance for optical disk system

1984-07-06

1987-06-30

Richardson, Robert L.

Dynamic information storage or retrieval

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

Mechanism control by the control signal

250201, 369 46, G11B 700

Patent

active

046776052

ABSTRACT:
Apparatus and methods are disclosed for acquiring and maintaining focus of a coherent light source used to read and write data in an optical disk data storage device. The system uses a conventional astigmatic focus system in conjunction with a signal processor to detect proximity of focus. After proximity of focus is detected, the signal processor enables a fine focus servo system to maintain focus of the coherent light on the disk surface. The system includes a coherent light source for reading and writing data on the optical disk storage medium, a condenser lens for focusing the coherent light on the recording surface of the disk, a cylindrical lens for passing light reflected from the recording surface, a quad light detector responsive to the reflected light from the cylindrical lens for providing an output signal, a controller responsive to the quad detector output signal for providing a control signal when proximity of focus is detected, and a fine servo system for controlling the position of the condenser lens. The system also includes a method of avoiding a false focus on any transparent overcoat layer placed over the recording surface of the optical disk storage medium.

REFERENCES:
patent: 4290132 (1981-09-01), Kotaka
patent: 4358774 (1982-11-01), Wilkinson
patent: 4425043 (1984-01-01), Rosmalen
patent: 4495407 (1985-01-01), Kodama et al.

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