Seeing around corners with edge-resolved transient imaging

Abstract

Non-line-of-sight (NLOS) imaging is a rapidly growing field seeking to form images of objects outside the field of view, with potential applications in autonomous navigation, reconnaissance, and even medical imaging. The critical challenge of NLOS imaging is that diffuse reflections scatter light in all directions, resulting in weak signals and a loss of directional information. To address this problem, we propose a method for seeing around corners that derives angular resolution from vertical edges and longitudinal resolution from the temporal response to a pulsed light source. We introduce an acquisition strategy, scene response model, and reconstruction algorithm that enable the formation of 2.5-dimensional representations—a plan view plus heights—and a 180∘ field of view for large-scale scenes. Our experiments demonstrate accurate reconstructions of hidden rooms up to 3 meters in each dimension despite a small scan aperture (1.5-centimeter radius) and only 45 measurement locations.

Stray light characterization with ultrafast time-of-flight imaging

“…Recent improvements of 2D fast sensors based on single-photon avalanche diodes (SPADs) make them an interesting candidate technology for ultrafast ToF imaging, with increasing numbers of pixels 7,8 . Latest works with SPADs also involve occluded scene reconstruction [9][10][11] . Nevertheless, the reported temporal resolution (a few tens of picoseconds) remains too small for our application.…”

Edge-Resolved Transient Imaging: Performance Analyses, Optimizations, and Simulations

“…Planar surfaces with a certain reflectivity, height and orientation about the floor-to-ceiling axis are fit via parametric estimation to the difference histogram for each wedge separably, thus providing a 2.5-dimensional recovery of the hidden area. An approximate, closed form solution to the temporal response from such surfaces (including occlusions between them) is derived in [15] and allows efficient evaluation of the forward model. The fitting of these planar surfaces is achieved in the original ERTI paper using Bayesian inference through a Markov chain Monte Carlo (MCMC) sampling approach that accounts for prior beliefs about scene structure and only requires evaluations of the forward model [18,19].…”

“…Edge-resolved transient imaging (ERTI) [15] uses aspects of these approaches to achieve NLOS imaging through a small aperture using a small number of illumination positions. The most analogous previous works estimate only moving parts of the hidden scene [16] or projections thereof [17].…”

Ground Moving Target Imaging via SDAP-ISAR Processing: Review and New Trends

“…Last but not least, this method only leads to a detection that cannot be related to a real-time event but can only confirm that a target has moved in or out of a certain position in the time between the two passages. Additional ideas are proposed in [ 7 ], where the motion of moving targets is exploited for improving resolution and enhance their detectability, and in [ 8 ] where the motion of controllable illumination is exploited to obtain high-resolution imaging through a small effective aperture and therefore enhance signal to clutter ratio. When spatial Degrees of Freedom (DoFs) are available, such as in the case of multi-channel radar systems, more powerful techniques can be devised.…”