Photoelectric sensors detect various objects by means of visible or invisible light.There are three different function principles.
Diffuse-reflective sensors detect the light reflected by a target. The sensing range of these sensors largely depends on the reflectivity of the target. Diffuse mode sensors with fixed or adjustable background suppression are capable of detecting dark objects in front of a light background.
Retro-reflective sensors detect the light reflected by a reflector. The sensor reacts to the interruption
of this light beam by the target. The reflectivity factor of the target is subordinate.
Through beam sensors operate on a similar principle. Two separate devices are used, an emitter and a receiver. Through beam sensors typically have a significantly larger sensing range than retro-reflective sensors.