Role of Transients in Two-Bounce Non-Line-of-Sight Imaging

Siddharth Somasundaram, Akshat Dave, Connor Andrew Henley, Ashok Veeraraghavan, Ramesh Raskar

Abstract:

The goal of non-line-of-sight (NLOS) imaging is to image
objects occluded from the camera’s field of view using mul-
tiply scattered light. Recent works have demonstrated the
feasibility of two-bounce (2B) NLOS imaging by scanning
a laser and measuring cast shadows of occluded objects in
scenes with two relay surfaces. In this work, we study the
role of time-of-flight (ToF) measurements, i.e. transients, in
2B-NLOS under multiplexed illumination. Specifically, we
study how ToF information can reduce the number of mea-
surements and spatial resolution needed for shape recon-
struction. We present our findings with respect to trade-
offs in (1) temporal resolution, (2) spatial resolution, and
(3) number of image captures by studying SNR and recov-
erability as functions of system parameters. This leads to
a formal definition of the mathematical constraints for 2B
lidar. We believe that our work lays an analytical ground-
work for design of future NLOS imaging systems, especially
as ToF sensors become increasingly ubiquitous.