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.