Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1988-02-29
1989-09-05
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
369 46, 369111, G05B 100
Patent
active
048641189
ABSTRACT:
A scanning unit for an optical disc record carrier includes a radiation-sensitive detection system having a plurality of detection elements on which is formed a reflected image of the scanning spot on the track structure of the record carrier. A tracking error signal is derived by combining the output signals of detection elements situated on respective sides of a boundary line between two halves of the detection system, and comparing with each other the combined signals from both halves. Several different such tracking error signals are derived, for boundary lines having different orietations with respect to the direction of the track instantaneously being scanned. The tracking error signal corresponding to a boundary line most nearly parallel to the direction of such track will be of greatest amplitude, and is selected as the tracking error signal used for controlling the scanning unit to follow the center line of such track. This achieves improved tracking error sensitivity providing more accurate tracking over the entire track structure.
REFERENCES:
patent: 4123652 (1978-10-01), Bouhuis
patent: 4458144 (1984-07-01), Reilly et al.
patent: 4532522 (1985-07-01), Tsunoda et al.
patent: 4695992 (1987-09-01), Aoi
patent: 4747090 (1988-05-01), Yamashita et al.
Opheij Willem G.
Van Engelen Gerard
van Rosmalen Gerard E.
Eason Leroy
Messinger Michael
Nelms David C.
Tamoshunas Algy
U.S. Philips Corporation
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