Robust Evaluation of Long-Term Stability of an InAs/GaSb Type II Superlattice Midwave Infrared Focal Plane Array

The temporal stability of the image quality of an infrared focal plane array (FPA) is one key parameter to consider for high-performance imaging applications. It is generally evaluated through residual fixed pattern noise (RFPN) measurements realized after a two-point correction (TPC) and bad pixels exclusion. However, the effect of random telegraph signal (RTS) on temporal stability has never been quantified, the intermittent blinking of RTS pixels making measurements inherently complicated. In this article, we propose a novel protocol and a novel data processing technique to fully characterize the temporal stability of an infrared FPA, thanks to simultaneous RFPN and RTS noise measurements. Using a robust statistics based on median absolute deviation (MAD) leads to a more trustful RFPN evaluation, unaffected by the bad pixels exclusion step. This new protocol can be applied to any FPA technology, cooled or uncooled, operating in the [3, 14] μm spectral domain. We chose to use a type-II superlattice (T2SL) midwave infrared FPA integrated in a cryocooler at 80 K. We show that the long-term stability of this 320 × 256 pixels FPA is excellent. The RFPN only slightly increases over 77 days, using a TPC that has been calculated on the first day of the measurements campaign. A simple offset update, compatible with operational contingencies, can further improve the temporal stability of this FPA. Only 0.3% of the pixels were affected by RTS noise at some moment. Those blinking pixels do not affect the RFPN evolution, which is a very encouraging result for T2SL detector technology.