Optical reproducing apparatus

Details Optical reproducing apparatus Optical reproducing apparatus

1983-09-26

1986-05-27

Richardson, Robert L.

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

369 46, 369121, 369118, 369112, G11B 700, G11B 2110

Patent

active

045920389

ABSTRACT:
In an optical reproducing apparatus a divergent beam from a semiconductor laser light source is collimated to form a parallel light beam that is converged by an objective lens and focussed on an optical record medium. The light beam is reflected by the optical record medium and introduced into a signal photodetector so as to provide a reproduced signal. A phase type diffraction grating between the semiconductor laser light source and a beam splitter separates the laser beam from the semiconductor laser light source into zero, plus first and minus first order diffracted beams. A pair of tracking photodetectors receive reflected beams of the plus first and minus first order diffracted beams reflected by the optical record medium and then by the beam splitter. A concave lens located between the photodetectors and the beam splitter facilitates convenient positioning of the photodetectors so that a tracking error signal can be obtained by calculating the difference between the outputs of the first and second tracking photodetectors.

REFERENCES:
patent: 4462095 (1984-07-01), Di Chen

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