Dynamic information storage or retrieval – Control of storage or retrieval operation by a control... – Mechanism control by the control signal
Patent
1982-02-19
1984-11-13
Richardson, Robert L.
Dynamic information storage or retrieval
Control of storage or retrieval operation by a control...
Mechanism control by the control signal
G11B 700, G11B 2700
Patent
active
044829892
ABSTRACT:
An apparatus for optically reading a disc-shaped record carrier, which apparatus comprises a radial tracking control system which employs a radial error signal obtained by comparing two signals supplied by two radially adjacent detectors. In order to stabilize the loop gain of the control loop at a constant value, a measuring signal of predetermined frequency is injected into the control loop. The response of the control loop to said injected signal is compared with the injected signal, which comparison results in a control signal for a controllable amplifier circuit. Suitably, said comparison is a phase comparison. The injected measuring signal causes the scanning beam to oscillate relative to the track to be followed. By measuring the correlation between said oscillation signal and the amplitude of the information signal being read, a signal can be obtained which is a measure of deviations, not caused by tracking errors, between the signals supplied by the two detectors and which may be used for correction purposes.
REFERENCES:
patent: 3932700 (1976-01-01), Snopko
patent: 4337534 (1982-06-01), Basilico et al.
patent: 4338682 (1982-07-01), Hosaka et al.
Mayer Robert T.
Richardson Robert L.
Tamoshunas Algy
U.S. Philips Corporation
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