Introduction to Time-of-Flight Imaging

Time-of-flight imaging is a subset of imaging science interested in the detection of the time-of-flight of certain waves, usually light, to reconstruct the position of objects in a 3D scene. Optical time-of-flight imagers have existed for decades, but it is only with the introduction of solid-state sensors with fast (global) shutters, that they have become compact and prone to mass-production. In these sensors, light propagation can be frozen in time and space and its time-of-flight can be evaluated on the pixel-by-pixel basis to accurately reconstruct 3D scenes and volumes. Applications include gaming, gesture recognition, and virtual keyboards for short-range cameras, security, 3D video monitoring, and robotic operation for medium-range cameras, safety and pedestrian avoidance for long-range cameras, and LIDAR telemetry and landscape monitoring for ultra-long-range cameras. Also based on similar concepts are non-vision applications, such as time-of-flight positron emission tomography, fluorescence lifetime imaging microscopy, and time-resolved optical coherent tomography, to name a few.