Target Discrimination in the Extended SWIR (eSWIR) Band (2-2.5 mu m) Compared to Vis, NIR, and SWIR in Degraded Visual Environments

Abstract

Long-range target identification is well studied in the Visible (Vis) and near-infrared (NIR) bands, and more recently in the shortwave infrared (SWIR). The longer wavelength of SWIR (1-1.7 mu m) improves target detection for both long ranges and under challenging atmospheric conditions because it is less limited by scattering and absorption in the atmosphere. For these reasons, SWIR sensors are proliferating on military platforms. The extended shortwave infrared (eSWIR) band spanning from 2 to 2.5 mu m is not typically limited by diffraction, and, as a result, the band benefits target acquisition both at long ranges and for degraded visual environments. Theoretical and experimental data compare eSWIR to Vis, NIR, and SWIR for atmospheric transmission, reflectivity, illumination, and sensor resolution and sensitivity. The experimental setup includes two testbeds, each with four cameras. The first is a wide field of view (FOV) testbed matching FOV at 20 degrees for each camera. The second is a narrow FOV telescope testbed to match instantaneous FOV (IFOV) for consistent resolution across all four bands at long ranges. Both the theory and experiment demonstrate advantages of using eSWIR for long-range target identification under degraded visual environments.