Dynamic information storage or retrieval – Control of storage or retrieval operation by a control... – Mechanism control by the control signal
Patent
1982-03-03
1984-08-07
McElheny, Jr., Donald E.
Dynamic information storage or retrieval
Control of storage or retrieval operation by a control...
Mechanism control by the control signal
369 46, 369112, G11B 700
Patent
active
044647417
ABSTRACT:
An optical focusing error-detection device is disclosed which comprises a radiation-sensitive detector with four sub-detectors, and an astigmatic lens system arranged between the detector and the objective system whose focusing-error is to be detected. The astigmatic system is arranged in a non-collimated beam and comprises two cylindrical lenses having mutually perpendicular axes and having different powers so that the resulting focusing-error signal is symmetrical and linear around the zero point.
REFERENCES:
patent: 4011400 (1977-03-01), Simons et al.
patent: 4025949 (1977-05-01), Whitman
patent: 4123652 (1978-10-01), Bouwhuis
patent: 4344164 (1982-08-01), Bricot et al.
Mayer Robert T.
McElheny Jr. Donald E.
Tamoshunas Algy
U.S. Philips Corporation
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