Optical disc reproducing apparatus

Details Optical disc reproducing apparatus Optical disc reproducing apparatus

1982-04-05

1985-01-15

Richardson, Robert L.

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

358342, 358907, H04N 576, G11B 1700

Patent

active

044942257

ABSTRACT:
In an optical video disc player, a still picture mode reproduction is effected by returning a light spot on a disc by one track pitch in its radial direction after each revolution of the disc. The displacement of the light beam is carried out by supplying a returning signal to a moving coil coupled with an objective lens. An amplitude of the returning signal is automatically adjusted by means of a negative feedback loop to such a value that the light spot is shifted accurately by one track pitch. The negative feedback loop includes an envelope detector for detecting a descent of a reproduced signal, a sampling pulse generator for producing a sampling pulse in response to a first descent during the displacement of the light spot, a pulse generator for producing a returning pulse having a constant amplitude, a sawtooth generator actuated by the returning pulse to produce a sawtooth signal, a phase comparator for sampling the sawtooth signal by the sampling signal to produce a control signal and a pulse level modulator for modifying the level of the returning pulse with the control signal.

REFERENCES:
patent: 3911211 (1975-10-01), Rennick
patent: 3973080 (1976-08-01), Dickopp et al.
patent: 4340907 (1982-07-01), Hirata et al.

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