"An illustration of a polarized retro-reflective photoelectric sensor application. The image shows a can on a pallet on a conveyor. On either side of the conveyor are the retro-reflector and the combined emitter/receiver photo eye module. The ""effective beam"" of light is shown transmitting from the emitter, bouncing off the reflector, and then traveling back to the receiver. A polarizing filter on the emitter only permits light oscillating in a certain direction to be emitted. The retro-reflector causes the polarization of the beam to be rotated by 90° before bouncing back towards the receiver. The receiver also has a polarized filter which only permits light oscillating opposite to the emitter's filter. This ensures that the light received bounced off of the retro-reflector."
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