Optical head

Details Optical head Optical head

1985-06-13

1988-02-09

Faber, Alan

Dynamic information storage or retrieval

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

Mechanism control by the control signal

369 46, 369 44, 250201, 250202, G11B 709

Patent

active

047245336

ABSTRACT:
An optical head in which the light emitted from a light source is narrowed to a minute spot of light and applied to a recording medium such as a disk thereby to effect recording and reproduction, or reproduction alone. A focusing plate or prism is provided in the optical path for forming the image of the light reflected from the recording medium. The focusing plate or prism has a first surface which reflects and transmits the reflected light and a second surface which is located closer to the image-forming position than the first surface and reflects the reflected light which is transmitted or reflected by the first surface. The optical head is further provided with a photodetector which is divided into at least two portions which individually receive the light rays which are respectively reflected from the first and second surfaces. A focusing servo control signal is obtained from the difference between the respective outputs of the divided photodetector portions. Moreover, a tracking servo control signal is obtained from the difference between the respective outputs of the peripheral portions among the divided photodetector portions.

REFERENCES:
patent: 4464741 (1984-08-01), Compaan
patent: 4507763 (1985-03-01), Kato
patent: 4612437 (1986-09-01), Ohsata

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