Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1989-08-15
1991-04-16
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
250221, 250214R, G01V 904, H01J 4014
Patent
active
050085310
ABSTRACT:
A light identifying system includes a photoelectric conversion unit for receiving a pulsed light from a light emitting part on a light receiving part to generate a light reception signal that varies in magnitude according to the quantity of the received light. A peak holding circuit has a time constant that is long compared with the pulse interval of the pulsed light. The peak holding circuit stores a peak value of the light reception signal for its time constant. The peak value is divided by a constant for application to a comparator. The comparator compares it with the light reception signal as a threshold. A peak value of the light reception signal is held, and the peak value thus held is specified as a threshold to the light reception signal, therefore in the unlikely event of decrease in the quantity of emitted light due to a secular change or of decrease in the quantity of received light due to mist and oil film, the threshold decreases accordingly.
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patent: 4851689 (1989-07-01), Hasegawa
Kobayashi Atsuhito
Ono Shoichi
Chinon Kabushiki Kaisha
Messinger Michael
Nelms David C.
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