Proximity Switches - Background Suppressed
Different object colours and surfaces can heavily affect the detection behaviour of an energetic switch. With purely energetic evaluation, it is, for example, not possible to detect a black object in front of a white background. The white background reflects more light than the black object itself.
In order to deal with such applications consistently, the background suppression procedure was developed. In this procedure, both the light reflected by the background and by the object is evaluated. The light is captured by two different receiver elements. With this procedure, it is possible to reliably detect e.g. a dark object on a light colour conveyor belt.
There are two different procedures for the physical realisation of background suppression. In general, a distinction is made between a fixed and an adjustable background suppression. With a fixed background suppression, the transmitter and receiver elements are rigidly mounted.
One receiver element captures the light from the object, and the light from the background. Thus, it is not the returning energy which is evaluated but rather the geometric position of the object to be detected. The overlap of the transmitter and receiver angles fixes the field of detection.
Objects outside the field of detection cannot be detected. With adjustable background suppression, the parameters for detection of objects can be mechanically adjusted with an adjusting screw or electronically adjusted through a teach-in process.
This enables much greater flexibility of use.