  Passive non-line-of-sight imaging methods are often faster and stealthier
than their active counterparts, requiring less complex and costly equipment.
However, many of these methods exploit motion of an occluder or the hidden
scene, or require knowledge or calibration of complicated occluders. The edge
of a wall is a known and ubiquitous occluding structure that may be used as an
aperture to image the region hidden behind it. Light from around the corner is
cast onto the floor forming a fan-like penumbra rather than a sharp shadow.
Subtle variations in the penumbra contain a remarkable amount of information
about the hidden scene. Previous work has leveraged the vertical nature of the
edge to demonstrate 1D (in angle measured around the corner) reconstructions of
moving and stationary hidden scenery from as little as a single photograph of
the penumbra. In this work, we introduce a second reconstruction dimension:
range measured from the edge. We derive a new forward model, accounting for
radial falloff, and propose two inversion algorithms to form 2D reconstructions
from a single photograph of the penumbra. Performances of both algorithms are
demonstrated on experimental data corresponding to several different hidden
scene configurations. A Cramer-Rao bound analysis further demonstrates the
feasibility (and utility) of the 2D corner camera.
