You can fool an ordinary IR-based proximity sensor with an unreflective dark object — but not LightRanger click. Nothing will escape its notice; it has a sensor that can detect individual photons.
LightRanger click carries the VL6180X IC from STMicroelectronics. The chip combines a IR emitter, an ambient light sensor, and a range detector into one powerful whole that can detect anything short of a black hole.
Based on ST’s patented FlightSense™ technology, VL6180X IC calculates distance by measuring the time it takes for a photon to travel from the sensor to the nearest object and back. This breakthrough technology makes the sensor much more reliable compared to alternatives.
See, ordinary infrared based proximity sensors derive the same distance by measuring the amount of reflected light, a variable that changes significantly depending on the reflectivity or color of an object that needs detection.
Within a 10cm range, LightRanger click can measure the range fairly precisely; at a longer range it isn’t as precise but it can still act as a detector (up to about 20cm, or so).