Light sensing and emitting devices with a safelight

Details Light sensing and emitting devices with a safelight Light sensing and emitting devices with a safelight

1988-07-29

1990-03-06

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

356443, G01J 350

Patent

active

049068350

ABSTRACT:
A light sensor for use to detect only light above a given frequency uses as its light sensitive element a light emitting diode. The L.E.D. is one which, if it were arranged to emit light, would emit light having a maximum frequency equal to the said given frequency.
In combination with such a sensor another L.E.D. can be used having a maximum emission frequency below the said given frequency to illuminate an area without affecting the light sensor.

REFERENCES:
patent: 4199252 (1980-04-01), Vermeulen
patent: 4673807 (1987-06-01), Kobayashi et al.
patent: 4804833 (1989-02-01), Matsubara
"Solid State Dark Room Lighting", from Elektor (GB) vol. 9, No. 10, Oct. 1983 (pp. 36-37).
"LED Flashlight", Research Disclosure No. 19107 (Mar. 1980), pp. 105-106.

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