Imager performance assessment with TRM4: recent developments

Model-based performance assessment is an important tool in the design of electro-optical and infrared imagers and their performance comparison. It alleviates the need for expensive field measurements and can be used for parameter trade studies. TRM4 serves this purpose and features a validated approach to consider aliasing in the range performance assessment of focal plane arrays. TRM4.v3 was released in October 2021 and came with a set of new model features. One of the new capabilities is the performance assessment of imagers used for aerial imaging by computing the National Imagery Interpretability Rating Scale (NIIRS) as performance measure. The NIIRS values are calculated in TRM4 using the latest version of the General Image Quality Equation. In this paper, the result of a recent validation effort for the NIIRS calculation is reported. Current TRM4 development focusses on performance modeling of subpixel target scenarios and color cameras. For subpixel targets, the calculation of the signal-to-noise ratio (SNR) for the additional target signal is presented considering different target locations with respect to the detector matrix. Best-case and worst-case detection ranges are derived from specified threshold SNRs of detection algorithms. First results are shown using the TRM4.v3 sky background scenario feature to model ground-to-air imaging of flying targets. A first step for modeling color cameras is the extension of AMOP (Average Modulation at Optimum Phase) calculation, which is used in TRM4 to describe the spatial signal transfer characteristics along the imaging chain. It is shown how the sampling by sensors with Bayer filter and demosaicing can be included into the AMOP calculation procedure.