Time of flight sensor (Time of flight)
The Time Of Flight (TOF) sensor measures distances by measuring the time it takes for a light signal to return to the original light source via reflection.
The sensor consists of a light source, an infrared filter and a light sensitive sensor. The speed of the light is constant so by measuring the time between sending and receiving a light signal the distance can be determined. This method is many times more accurate than for example a brightness reflection measurement or a reflection angle measurement.
The time it takes for a photon to bridge 2 cm is 66.7 picoseconds. The object is then at a distance of 1 cm (the light has to go back and forth). So if you can measure the time in picoseconds and you have a sensor that reacts so fast, then the distance can be determined accurately.
The used sensors already react on 1 single photon! The sensors were initially developed for use in mobile phones, which is why the price of these sensors is low, as is the energy consumption.