Optical attachment to vehicle windscreen for detecting dirt or stains on surface: comprises transmitter and receiver, parabolic lenses and reflector to produce parallel light paths with internal reflections

摘要

Light from a transmitter (18) passes through an optical unit (22) with parabolic lenses (32,34) at an angle that produces internal windscreen reflections. A reflector (24) returns the light along a parallel path with corresponding internal reflections to a receiver (20) linked to a processor. Dirt or stains on the outer surface (14) of the windscreen disturb the internal reflections such that the light received is diminished or extinguished