Occluded Imaging with Time-of-Flight Sensors

Abstract

We explore the question of whether phase based Time of Flight (ToF) range cameras can be used for looking around corners and through scattering diffusers. By connecting time of flight measurements with theory from array signal processing we conclude that performance depends on two primary factors: camera modulation frequency and the width of the specular lobe (“shininess”) of the wall. For purely Lambertian walls, commodity time of flight sensors achieve resolution on the order of meters between targets. For seemingly diffuse walls, such as posterboard, the resolution is drastically reduced, to the order of ten centimeters. In particular, we find that the relationship between reflectance and resolution is nonlinear—a slight amount of shininess can lead to a dramatic improvement in resolution. Since many realistic scenes exhibit a slight amount of shininess we believe that off-theshelf ToF cameras can look around corners.