Confocal non-line-of-sight imaging based on the light-cone transform

A confocal scanning technique solves the reconstruction problem of non-line-of-sight imaging to give fast and high-quality reconstructions of hidden objects. Shining light on the out of sight The ability to accurately reconstruct objects that are hidden from view is of great importance in several fields, including remote sensing, autonomous vehicles and robotics. Unlike light detection and ranging methods, non-line-of-sight (NLOS) imaging relies on multiply scattered light to reconstruct macroscopic objects from their shape and albedo. So far, experimental demonstrations of NLOS imaging have been considered to have limited applicability because of the computational demands of existing reconstruction algorithms. Here, Matthew O'Toole and colleagues show that a confocal scanning technique leads to fast and high-quality reconstructions of macroscopic hidden objects. This is made possible by a computationally more efficient inverse method based on a closed-form solution to the NLOS reconstruction problem, which the authors refer to as the light-cone transform. With suitable improvements to the current technique, the authors expect real-time frame rates to become accessible in the future. How to image objects that are hidden from a camera’s view is a problem of fundamental importance to many fields of research 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , with applications in robotic vision, defence, remote sensing, medical imaging and autonomous vehicles. Non-line-of-sight (NLOS) imaging at macroscopic scales has been demonstrated by scanning a visible surface with a pulsed laser and a time-resolved detector 14 , 15 , 16 , 17 , 18 , 19 . Whereas light detection and ranging (LIDAR) systems use such measurements to recover the shape of visible objects from direct reflections 21 , 22 , 23 , 24 , NLOS imaging reconstructs the shape and albedo of hidden objects from multiply scattered light. Despite recent advances, NLOS imaging has remained impractical owing to the prohibitive memory and processing requirements of existing reconstruction algorithms, and the extremely weak signal of multiply scattered light. Here we show that a confocal scanning procedure can address these challenges by facilitating the derivation of the light-cone transform to solve the NLOS reconstruction problem. This method requires much smaller computational and memory resources than previous reconstruction methods do and images hidden objects at un