What Exactly is the “2 POINT Scanning” Method?

This method is used in reflection light barriers with auto collimation in order to increase the operating range. Within reflection light barriers, the power of the light radiated from the transmitter and detected by the receiver is evaluated. If a certain threshold of the light detected by the receiver is exceeded, the light barrier switches. If an object is positioned between sensor and reflector, the amount of the light received is significantly lower; the threshold value not reached and the sensor switches again. A lot of light is reflected by highly reflective or mirror like objects to the receiver and the light reflected by the reflector decreases with increasing distance to the sensor. The maximum distance from the sensor to the reflector is limited because the amount of light reflected by the reflector must exceed the threshold value.

“2 POINT Scanning” is referred to as the introduction of an additional transmitter, which shows a difference between the object in the near field and the reflector in the far field. It can be recognized by means of a logical link between the different luminous power values, which are received by the different transmitters, whether an object is in the near field. The set threshold described above can thus be lowered and the operating range of the devices can be increased.

General internal setup of the ML7-54-G with two transmitters (2 point scanning)

Explanations: M = semitransparent mirror, L = Lens, R = Receiver, T1/2 = Transmitters, O = Object to be detected, RR = Reflector