Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Patent
1976-03-29
1977-06-28
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
250205, 250214RC, 250221, H01J 3912
Patent
active
040327779
ABSTRACT:
A photometric monitoring device for detection and surveillance of objects entering and leaving a light field is provided wherein a monitored light source is compared with a reference light source in such a manner that abrupt or rapid changes in monitored light are detected and gradual changes are ignored. A first photo cell for monitoring a light source is coupled to the input of an operational amplifier having a feedback loop which includes a reference light source coupled to a second photocell. An RC network delays the reaction of the operational amplifier in balancing the voltage across both of said first and second photocells when abrupt changes occur, allowing a signal to be developed. Additional circuitry includes a comparator responsive to such developed signals which exceed predetermined limits, producing an output signal for use by a utilization device, such as a camera, recording device, alarm system, or the like.
REFERENCES:
patent: 3582661 (1971-06-01), Emmasingel
patent: 3775617 (1973-11-01), Dubauskas
patent: 3931513 (1976-01-01), Germain
Nelms David C.
Noe George T.
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