Optical proximity sensors

Optical proximity sensors always have a transmitter and a receiver. They use optical (red or infrared light) and electronic components and modules to detect an object located between the transmitter and receiver.

Particularly reliable transmitters of red and infrared light are semiconductor light emitting diodes (LEDs). They are small, robust, inexpensive, reliable, durable and easy to install. Red light has the advantage that it can be seen with the naked eye when aligning (adjusting) the optical axes of the proximity sensors. Photodiodes or phototransistors are used as the receiver component in optical proximity sensors.

A distinction is made between three types of optical proximity sensor:

• through-beam sensors,

• retro-reflective sensors,

• diffuse sensors.