Non-Line of Sight Terahertz Imaging from a Single Viewpoint

We present a novel method for imaging objects hidden around occlusions by exploiting the scattering properties of terahertz (THz) waves. Most building surfaces reflect THz waves strongly in a single direction (specular scattering) and behave as lossy mirrors that allow imaging of non-line-of-sight (NLOS) objects from a single observation location. Interestingly, mirror surfaces can be directly imaged by capturing the backscattered waves due to diffusion scattering. We demonstrate the NLOS THz imaging capability using a backpropagation synthetic aperture radar (SAR) imaging algorithm that corrects the cluttered raw data and acquires accurate THz images of the occluded areas. The new imaging approach is verified through imaging examples in the 220–330 GHz band using common building materials.