Effectiveness assessment of signal processing in the presence of smear

Abstract

Moving imagery from a static scene was recorded with an uncooled thermal imager at nine different angular velocities ranging from 0 (static) to 1 pixel/frame (3.75 deg/s) using a tilted rotating mirror. The scene contained a thermal acuity test chart with triangular test patterns based on the triangle orientation discrimination (TOD) test method. The imagery was processed with different types of image enhancement: dynamic super-resolution (DSR), local adaptive contrast enhancement (LACE), and combinations. DSR shows a significant performance improvement at low velocities, a moderate improvement at medium velocities where smear becomes apparent, and no benefit at high speed. Performance with LACE is close to optimized gain and level setting by hand. Static performance and dynamic performance at 0.57 pixel/frame containing significant smear were compared with earlier published identification performance data for two-hand held systems collected under a variety of signal processing conditions. It shows that the ratio M75 between the 75% correct threshold size for the two-hand held objects and the TOD triangle is preserved under all conditions measured. Thus, TA range prediction based on the TOD is robust against a complex combination of conditions, including motion, smear, and the types of image enhancement applied.