SWIR imaging for facial image capture through tinted materials

Abstract

The use of short wave infrared (SWIR) imaging and illumination technology is at the forefront of system development for military and law enforcement in both night and daytime operational scenarios^{1 2 3 4}. Along with enabling nighttime operations, a secondary benefit of SWIR imaging is that it offers the possibility to capture images through tinted materials, such as tinted architectural or automotive glass and sunglass lenses⁵. The use of SWIR technology introduces challenges to facial recognition when comparing cross-spectrally from a visible gallery to images captured in the SWIR⁶. The challenges of SWIR facial recognition are further compounded by the presence of tinted materials in the imaging path due to varying material types, lighting conditions, and viewing angle. The paper discusses material and optical characterization efforts undertaken to understand the effects of temperature, interior and exterior light sources, and viewing angle on the quality of facial images captured through tinted materials. Temperature vs. spectrum curves are shown for tinted architectural, automotive, and sunglass materials over the range of -10 to 55C. The results of imaging under various permutations of interior and exterior lighting, along with viewing angle, are used to evaluate the efficacy of eye detection for cross-spectral facial recognition under these conditions.