Proximity Sensor

A sensor that detects whether something is nearby, and how close, without needing to touch it.

A proximity sensor detects the presence or distance of a nearby object without contact, using principles that include capacitive sensing (a nearby object changes an electric field), inductive sensing (sensitive only to metal), infrared and other optical methods, time-of-flight (measuring how long light takes to travel out and back), and ultrasonic sensing. The sensor that turns off a phone’s screen when it’s held to your ear works this way. In robotics, proximity sensing fills the gap between vision and touch: a camera is often blocked at close range by the arm or the object itself, while touch sensing needs actual contact to produce a signal. There are two common uses: mounting sensors on a robot arm’s housing as a “sensing skin” that slows or steers the arm away when a person gets close, supporting safety in human-robot collaboration; and mounting them on gripper fingertips to fine-tune finger position in the last small gap before contact. A 2021 survey by Navarro and colleagues systematically reviews these systems.

ExampleA collaborative robot arm’s housing is ringed with capacitive proximity sensors; when a worker’s hand gets within a set distance, the arm automatically slows down and stops.

Also called

Proximity Sensing, Near-Field Sensing

Related

Tactile Sensor · Electronic Skin · Time of Flight · Ultrasonic Sensor · Human-Robot Collaboration · Speed and Separation Monitoring

Sources

Proximity sensor - Wikipedia
Proximity Perception in Human-Centered Robotics: A Survey on Sensing Systems and Applications (arXiv 2108.07206)