Approaches to solve inverse problems for optical sensing around corners

Optically non-line-of-sight sensing or seeing around the corner is a computational imaging approach describing a classical inverse problem where information about a hidden scene has to be reconstructed from a set of indirect measurements. In the last decade, this field has been intensively studied by different groups, using several sensory and reconstruction approaches. We focus on active sensing with two main concepts: The reconstruction of reflective surfaces by back-projection of time-of-flight data and a six degree-of-freedom tracking of a rigid body from intensity images using an analysis-by-synthesis method. In the first case, the inverse problem can be approximately solved by back-projection of the transient data to obtain a geometrical shape of the hidden scene. Using intensity images, only the diffusely reflected blurred intensity distribution and no time information is recorded. This problem can be solved by an analysis-of-synthesis approach.