Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1982-03-22
1984-11-13
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
369 45, G01J 120
Patent
active
044828039
ABSTRACT:
An optical sensor for delivering error signals in order to control focusing of a lens on a movable recording medium or optical memory and more particularly a videodisk comprises a laser for producing a beam which is focused at a point S.sub.1. The divergent beam which proceeds from the point S.sub.1 is reflected from the face AB of a prism and is focused at a point S.sub.2. If the point S.sub.2 is located in the plane of the movable recording medium or so-called memory plane, the beam reflected from the memory plane is autocollimated and passes back through the focusing lens. A part of the beam enters the prism through the face AB, then emerges through the face AC and a circular light spot is formed in the plane corresponding to the circle of least confusion. If the point S.sub.2 is not located in the memory plane, the light spot is deformed and these deformations are detected by four juxtaposed cells placed in the plane of the circle of least confusion.
REFERENCES:
patent: 3983317 (1976-09-01), Glorioso
patent: 4025949 (1977-05-01), Whitman
patent: 4079247 (1978-03-01), Bricot et al.
Fichot Bernard
Lacotte Jean-Pierre
Troude Gilles
"Thomson-CSF"
Austin II Ernest
Nelms David C.
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