Recent works have demonstrated non-line of sight (NLOS) reconstruction by using the time-resolved signal frommultiply scattered light. These works combine ultrafast imaging systems with computation, which back-projects the recorded space-time signal to build a probabilistic map of the hidden geometry. Unfortunately, this computation is slow, becoming a bottleneck as the imaging technology improves. In this work, we propose a new back-projection technique for NLOS reconstruction, which is up to a thousand times faster than previous work, with almost no quality loss. We base on the observation that the hidden geometry probability map can be built as the intersection of the three-bounce space-time manifolds defined by the light illuminating the hidden geometry and the visible point receiving the scattered light from such hidden geometry. This allows us to pose the reconstruction of the hidden geometry as the voxelization of these space-time manifolds, which has lower theoretic complexity and is easily implementable in the GPU. We demonstrate the efficiency and quality of our technique compared against previous methods in both captured and synthetic data.



@Article{Arellano2017fast, Title = {Fast Back-Projection for Non-Line of Sight Reconstruction}, Author = {Victor Arellano and Diego Gutierrez and Adrian Jarabo}, Journal = {Optics Express}, Volume = {25} Number = {10}, Year = {2017}, }




We want to thank Andreas Velten for providing the captured data, as well as the reconstruction code from [Velten2012], and Julio Marco for his help setting up the figures. This work has been funded by the Defense Advanced Research Projects Agency - DARPA (HR0011-16-C-0025); the European Research Council (ERC Consolidator Grant 682080), and the Spanish Ministerio de Economía y Competitividad (TIN2016-78753-P, TIN2014-61696-EXP).