Maximizing the non-line-of-sight information content retrievable from passive scattered light fields: a comparison between visible, long wave infrared, and terahertz radiation

Abstract

We explore the use of plenoptic data for performing passive non-line-of-sight imaging using light scattered from interior hallways at visible, long-wave infrared, and terahertz frequencies. The use of longer wavelength radiation in the LWIR and THz bands can increase the retrievable NLOS image information in comparison to visible radiation. However, significant scattering effects at LWIR wavelengths and diffraction effects at the millimeter wavelengths of THz radiation present unique optical design challenges. In this paper, by assuming a general imaging system for light field capture, we provide a theoretical framework to describe measured NLOS information including scattering and diffraction effects. Our analysis combines a ray-based light field description of the plenoptic space with a Wigner distribution function formalism to provide an intuitive physical understanding of the limits of NLOS imaging. Further, based on the analysis, we provide a simple strategy to design optical measurement systems in the LWIR and THz wavelength ranges.