Patent ID: 7838836

Claim:
A method of detection for detecting a phenomenon affecting visibility generated by an automotive vehicle, said method comprising the steps of: emitting a first beam of light, which beam of light can be reflected by an obstacle to provide a reflected beam of light; emitting a second reference beam of light using a second emitting source; receiving on a receiver the reflected beam of light resulting from the first beam of light being reflected by an obstacle, and said second reference beam of light sent directly to the receiver input; generating one or more detection signals as a function of a combination of said reflected beam of light if there is an obstacle and said second reference beam of light; and comparing the modulation of one or more detection signals generated with reference data; wherein said first beam of light and said second reference beam of light are infra-red beams, and said first beam of light is directed rearward of the vehicle; wherein said combination of the reflected beam of light and said second reference beam of light comprises a summation of said first beam of light and said second reference beam of light; said preceding method steps being conducted during movement of the vehicle and said receiver being located on the vehicle such that it directs said first beam of light rearward.