Electronic influences on an infrared detector signal: nonlinearity and amplification

For mercury-cadmium-telluride detectors, frequently used in Fourier transform IR spectroscopy, the recorded signal is a nonlinear function of the light intensity. This behavior depends on a series resistor in the electronic circuit and thus the illumination of the detector. This nonlinearity must be accounted for to avoid spectroscopic errors. The results of theoretically calculating the effect permit a correction that can be applied, with corresponding lower accuracy, even after a phase correction. Also the use of the amplification stages does influence the phase of the signal electronically. For an accurate nonlinearity correction, compensation of the amplification of the analog signal is advisable.