Time of Flight

Measures how long light takes to bounce off an object and return, then converts that time into distance.

Time of flight measures distance from the round-trip travel time of light: distance equals the speed of light times the round-trip time, divided by two. A ToF camera carries its own near-infrared light source and measures a distance at every pixel, producing a depth map directly. Direct time of flight (dToF) sends short pulses and times them directly — most lidar uses this; indirect time of flight (iToF) sends modulated light and measures the phase shift of the returning signal to compute distance, which is how the Kinect for Xbox One and Azure Kinect work. ToF doesn’t depend on surface texture and the module is compact; common problems include multipath interference (light bouncing repeatedly in corners, inflating the measured distance), flying pixels at object edges, and weak returns under strong sunlight or from dark surfaces. Robots commonly use it for close-range obstacle avoidance and tabletop depth sensing.

ExampleAzure Kinect uses amplitude-modulated continuous-wave iToF: it emits modulated near-infrared light and computes depth from the phase of the returning signal; when it images a corner, the light bounces back and forth between the two walls, so those pixels get marked invalid with a depth of zero.

Also called

ToF, ToF Camera, Time-of-Flight Camera

Related

Direct Time of Flight · Indirect Time of Flight · LiDAR · Structured Light · Flying Pixels · Depth Camera

Sources

Wikipedia: Time-of-flight camera
Azure Kinect DK depth camera（Microsoft Learn）