Patent ID: 8350910

Claim:
An optical device for a motor vehicle, designed to detect the condition of a road surface, comprising: a unit for an emission of electromagnetic radiation in the direction of the road surface to be detected; a receiving unit coupled to an optical element for focusing the electromagnetic radiation back-diffused by the road surface; an electronic control and processing unit, designed to receive signals at output from said receiving unit and to process the signals in order to determine the condition of the road surface, wherein: said unit for emission is able to emit electromagnetic radiation in a spectral region of the visible and/or the near infrared; said control and processing unit is provided for detecting: both an intensity I ref of the electromagnetic radiation back-reflected at a first wavelength, considered as reference wavelength, and an intensity I of the electromagnetic radiation back-reflected at at least one second wavelength, said control and processing unit being programmed in such a way that, to a given pair of values of the intensity of electromagnetic radiation I, I ref thus detected there is made to correspond a given condition of the road surface on a basis of a reference-map; wherein said first wavelength is a wavelength at which the intensity of the back-diffused light from the road is invariant to a change of road condition, wherein said second wavelength is a wavelength at which the intensity of the back-diffused light from the road varies between different road conditions, wherein said reference is a reference map, in a form of a cartesian plane in which values of the intensity of electromagnetic radiation I ref back-reflected at the reference wavelength appear on a first cartesian axis, the values of the intensity of electromagnetic radiation I back-reflected at the second wavelength appear on a second cartesian axis, wherein said cartesian plane is divided into subareas identified beforehand as corresponding to different conditions of the road surface, and wherein boundary lines that divide said subareas from one another comprise both: portions of a straight line converging radially towards a common origin of the cartesian plane, and portions of a straight line oriented transversely with respect to said portions of a straight line converging radially and wherein one of said portions of a straight line which are oriented transversely with respect to said portions of a straight line converging radially separates a region of the map corresponding to presence of ice on the road surface from regions corresponding to the presence of water or snow on the road surface.