Influence of sampling on target recognition and identification

Two perception experiments are conducted to quantify the relationship betwe en imager sampling artifacts and target recognition and identification perf ormance using that imager. The results of these experiments show that in-ba nd aliasing (aliasing that overlaps the baseband signal) does not degrade t arget identification performance, but out-of-band aliasing (such as Visible display raster) degrades identification performance significantly. Aliasin g had less impact on the recognition task than the identification task, but both in-band and out-of-band aliasing moderately degrades recognition perf ormance. Based on these experiments and other results reported in the liter ature, it appears that in-band aliasing has a strong effect on low-level di scrimination tasks such as point (hot-spot) detection; out-of-band aliasing has only a minor impact on these tasks. For high-lever discrimination task s such as target identification, however, out-of-band aliasing has a signif icant impact on performance, whereas in-band aliasing has a minor affect, F or intermediate-level discrimination tasks such as target recognition, both in-band and out-of-band aliasing have a moderate impact on performance. Ba sed on data from the perception experiments, the modulation transfer functi on (MTF) squeeze model is developed. The degraded performance due to unders ampling is modeled as an effective increase in system blur or, equivalently , a contraction or "squeeze" in the MTF. An equation is developed that quan tifies the amount of MTF squeeze or contraction to apply to the system MIF to account for the performance degradation caused by sampling. (C) 1999 Soc iety of Photo-Optical Instrumentation Engineers. [S0091-3286(99)00605-4].