Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Patent
1982-12-28
1985-05-07
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
2502221, H01J 4014
Patent
active
045160201
ABSTRACT:
A light-operated proximity detector is described in which reflected light intensity from a surface whose proximity to the detector is to be gauged is translated directly into a signal proportional to the distance of the detector from the surface. A phototransistor is used to sense the reflected light and is connected in a detector circuit which maintains the phototransistor in a saturated state. A negative feedback arrangement using an operational amplifier connected between the collector and emitter of the transistor provides an output at the output of the amplifier which is linearly proportional to the proximity of the surface to the detector containing the transistor. This direct proportional conversion is true even though the light intensity is varying with the proximity in proportion to the square of the inverse of the distance. The detector may be used for measuring the distance remotely from any target surface.
REFERENCES:
patent: 3843880 (1974-10-01), Tsuchiyasu
patent: 4079331 (1978-03-01), Pinckaers et al.
patent: 4096382 (1978-06-01), Numata et al.
McNeilly David R.
Simpson Marc L.
Breeden David E.
Brophy Jere J.
Hamel Stephen D.
Hightower Judson R.
Nelms David C.
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