Optical device for motor vehicles, for detecting the condition of the road surface

An optical device for motor vehicles, designed to detect the condition of the road surface, comprising:

• a unit for the 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 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 them in order to determine the condition of the road surface,
• said optical device being characterized in that:
• said emission unit is able to emit radiation in the spectral region of the visible and/or the near infrared;
• said control and processing unit is provided for detecting:
• both the intensity Iref of the radiation back-reflected at a first wavelength, considered as reference wavelength,
• and the intensity of the radiation back-reflected 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 radiation I,Iref thus detected there is made to correspond a given condition of the road surface on the basis of a reference map;
• where said reference map is a cartesian plane in which the values of the intensity of radiation back-reflected at the reference wavelength appear on a first cartesian axis, the values of the intensity of 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 the boundary lines that divide said subareas from one another comprise both portions of straight line converging radially towards a common origin of the cartesian plane and portions of straight line oriented transversely with respect to said radial portions of straight line.