Abstract
Non-line-of-sight (NLOS) imaging utilizes the full 5D
light transient measurements to reconstruct scenes beyond
the camera’s field of view. Mathematically, this requires
solving an elliptical tomography problem that unmixes the
shape and albedo from spatially-multiplexed measurements
of the NLOS scene. In this paper, we propose a new approach for NLOS imaging by studying the properties of
first-returning photons from three-bounce light paths. We
show that the times of flight of first-returning photons are
dependent only on the geometry of the NLOS scene and
each observation is almost always generated from a single
NLOS scene point. Exploiting these properties, we derive
a space carving algorithm for NLOS scenes. In addition,
by assuming local planarity, we derive an algorithm to localize NLOS scene points in 3D and estimate their surface
normals. Our methods do not require either the full transient measurements or solving the hard elliptical tomography problem. We demonstrate the effectiveness of our methods through simulations as well as real data captured from
a SPAD sensor.