Optical EngineeringIdentification and estimation of nonlinearity in constant-voltage-biased infrared sensor detected signals
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In mercury-cadmium-telluride (HgCdTe) photoconductive detectors, the recorded signal is usually a nonlinear function of the incident photon flux. This nonlinear behavior must be taken into account when used in precision hardware applications such as IR radiometers. We investigate the effects of nonlinearity contributed by the illuminated and nonilluminated detector areas, which to our knowledge was not investigated earlier. The effects of wire resistance and detector preamplifier loading as well as the impact of off-centered detector illumination compared to the centered detector illumination on the nonlinearity are also investigated. Finally, it is shown that the nonlinearity can be estimated using a third-order polynomial. Computer simulation results that estimate the effect of nonlinearity are presented for a constant-voltage-biased detector circuit that minimizes the nonlinearity as compared to alternate detector bias and readout methods.