Reversible and apparent ageing effects in infrared detectors

Infrared (IR) radiometric applications require the use of IR detectors having characteristics which are stable with time. Little has appeared in the scientific literature on the ageing effects of IR detectors. The purpose of this paper is to describe some effects that can be attributed to ageing and that were observed in some of the IR detectors studied, and to identify their origins. It was observed that some IR detectors exhibit stronger ageing effects than others and, furthermore, that the effects of some of the observed ageing processes can be reversed. Some ageing effects designated apparent ageing effects are not true manifestations of ageing but originate from the presence of atmospheric absorption bands. The measured apparent structure in the response of an IR detector arises due to changes in the conditions which prevail in the measurement facility, differences in path lengths during the characterization of the detectors, errors in the wavelength scale or radiation bandwidth used and, in some cases, due to nonlinearities in the response of some IR detection systems.