light barrier

A light barrier is an optical barrier formed by a light beam. The light beam is generated by an optical transmitter and received and detected by an optical receiver.

The light beam serves as a limitation protection for access to an object, a house, an entrance door or another facility. However, the light beam interruption can also be used for other purposes, such as counting objects in production. As soon as the light beam is interrupted by a person, animal or object, the receiver detects this and triggers a signal that can lead to an action - for example, opening a door, switching off a machine or turning on the water flush - or triggering an alarm. Photoelectric sensors used for burglary protection use infrared light to prevent intruders from looking at the light barriers.

Infrared LEDs are used as optical transmitters, and photodiodes and phototransistors as optical receivers. Extraneous light is filtered out by light bundling.

Light barriers can not only be reached between two points, but can also be reflected with mirrors or guided around corners. In the case of reflective light barriers, the transmitter and receiver form a single unit. The light beam is reflected back to the transmitter-receiver unit by a mirror on an opposite wall.