Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Patent
1979-10-22
1981-06-30
Smith, Alfred E.
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
250394, G01J 100, G01J 142
Patent
active
042764742
ABSTRACT:
Automatic responsivity control for an array of infrared photodetectors is provided without additional hardware such as a beam chopper or a reference object of known irradiance. The requisite modulated reference signal is provided instead by uniformly modulating the bias voltage applied to each of the plurality of photodetectors in the array. Photodetectors having different responsivities respond to the same bias modulation differently to produce a superimposed sinusoidal component in the photodetector output current which is used to compensate for differences in responsivities of the individual photodetectors. For this purpose, an automatic responsivity control circuit selects the superimposed sinusoidal component from the photodetector output current corresponding to the frequency of the reference signal modulating the bias voltage, and compares the amplitude of the selected sinusoidal component with a reference level to adjust the amplification at the photodetector output in accordance with this comparison, so that the amplified outputs from the plurality of photodetectors respond uniformly to the sinusoidal reference signal applied as a bias voltage to the photodetectors.
REFERENCES:
patent: 3535521 (1970-10-01), Levine
patent: 3700905 (1972-10-01), Parkin et al.
patent: 4013889 (1977-03-01), Fryer
Howell Janice A.
Hughes Aircraft Company
MacAllister William H.
Smith Alfred E.
Wallace Robert M.
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