STARING IMAGER MINIMUM RESOLVABLE TEMPERATURE-MEASUREMENTS BEYOND THESENSOR HALF SAMPLE RATE

It is a well-known phenomenon that three-and four-bar patterns can som etimes be resolved with staring sensors even when the bar pattern freq uency is beyond the half sample rate of the sensor. When performing a minimum resolvable temperature (MRT) test, for example, the modulation of the target bars can be significant even when the fundamental frequ ency of the four-bar target is higher than the half sample rate of the sensor. We show that the modulation of a four-bar target goes to zero at 0.6 times the sample rate of the sensor (1.2 times the half sample rate) if the sample phasing is optimized. If the bar pattern contains a larger number of bars, the modulation cutoff approaches the half sa mple rate of the sensor. Further, we illustrate that, when the sample phase is optimized during the MRT measurement, the MRT performance of a sampled imager can exceed the measured MRT performance of an analog sensor with the same system and component modulation transfer function s. (C) 1998 Society of Photo-Optical Instrumentation Engineers. [S0091 -3286(98)01506-2].