Automation technology can no longer be imagined without photoelectric sensors as "artificial eyes". They are used where a reliable and non-contact detection of the exact position of objects is required. The material of the object to be detected is of no importance. Compared to inductive sensors, photoelectric sensors have a much greater sensing zone.
Through-beam sensors are distinguished by a long range. The system consists of two separate components: a transmitter and a receiver. The light only covers one way (from the transmitter to the receiver). Adverse effects in the applications, such as dust in the air, dirt on the lenses, steam or mist do not immediately interfere with the system.
For retro-reflective sensors the transmitter and receiver are incorporated into one housing. By means of a reflector the transmitted light is returned to the receiver. Retro-reflective sensors without polarisation filter operate with infrared light, systems with polarisation filter with visible red light.
Diffuse reflection sensors are used for the direct detection of objects. The transmitter and receiver are integrated into one housing. The transmitter emits light which is reflected by the object to be detected and seen by the receiver. The light reflection from an object is evaluated. Therefore additional functional components (such as reflectors for retro-reflective sensors) are not needed for the operation of a diffuse reflection sensor.