Optical detection system for motor-vehicles, able to detect the condition of the road surface on which the vehicle is travelling, said system comprising: - a photodetector unit mounted on board the motor-vehicle, for receiving the electromagnetic radiation diffused by the road surface, and - a control and processing electronic unit, suitable to receive signals output from said photodetector unit and to process them with the aim of detecting the condition of the road surface, wherein said photodetector unit is a camera having a matrix of pixels composed of photodetectors based on a material, preferably InGaAs or Ge/Si, suitable to detect radiations in the visible and near infrared, i.e. having a wavelength comprised between 380 and 900 nanometres, and wherein said camera comprises a matrix of filters arranged before at least one part of the matrix of pixels in such a manner that each filter (f 1,f 2) transmits the radiation to one and only one pixel of the matrix, said system being characterised in that: - said photodetectors are suitable to detect also radiations in the short wavelength infrared (SWIR), i.e. having a wavelength comprised between 900 and 1700 nanometres, and - the matrix of filters comprises four-positions subgroups, wherein two positions are occupied by band-pass filters (f 1,f 2) with respective wavelengths centred on values at which the radiation is respectively absorbed by water and ice, and two positions (c) are without filters, in such a manner to allow complete passage of the spectral band, - said control and processing electronic unit is programmed to control the addressing of the pixels of the matrix of the camera for the acquisition of at least three images: a first image and a second image corresponding to the wavelengths wherein the radiation is respectively absorbed by water and ice, and at least a third image with full or partial spectral content in the band from the visible to the SWIR, - said control and processing electronic unit is programmed to process the abovementioned images for each pixel of the matrix of the camera and hence detect the condition of the road surface, - said control and processing electronic unit is programmed to calculate, for each pixel of the camera matrix, the ratios between the intensity of said first image and said second image with respect to the intensity of said third image and to detect the condition of the road surface according to a reference map, and - said reference map is a cartesian plane wherein the intensity values of said third image are indicated on a first cartesian axis, the intensity values of said first image and said second image are indicated on a second cartesian axis, and wherein such cartesian plane is divided into subareas identified a priori as corresponding to different conditions of the road surface. - a photodetector unit mounted on board the motor-vehicle, for receiving the electromagnetic radiation diffused by the road surface, and - a control and processing electronic unit, suitable to receive signals output from said photodetector unit and to process them with the aim of detecting the condition of the road surface, wherein said photodetector unit is a camera having a matrix of pixels composed of photodetectors based on a material, preferably InGaAs or Ge/Si, suitable to detect radiations in the visible and near infrared, i.e. having a wavelength comprised between 380 and 900 nanometres, and - said photodetectors are suitable to detect also radiations in the short wavelength infrared (SWIR), i.e. having a wavelength comprised between 900 and 1700 nanometres, and - the matrix of filters comprises four-positions subgroups, wherein two positions are occupied by band-pass filters (f 1,f 2) with respective wavelengths centred on values at which the radiation is respectively absorbed by water and ice, and two positions (c) are without filters, in such a manner to allow complete passage of the spectral band, - said control and processing electronic unit is programmed to control the addressing of the pixels of the matrix of the camera for the acquisition of at least three images: a first image and a second image corresponding to the wavelengths wherein the radiation is respectively absorbed by water and ice, and at least a third image with full or partial spectral content in the band from the visible to the SWIR, - said control and processing electronic unit is programmed to process the abovementioned images for each pixel of the matrix of the camera and hence detect the condition of the road surface, - said control and processing electronic unit is programmed to calculate, for each pixel of the camera matrix, the ratios between the intensity of said first image and said second image with respect to the intensity of said third image and to detect the condition of the road surface according to a reference map, and - said reference map is a cartesian plane wherein the intensity values of said third image are indicated on a first cartesian axis, the intensity values of said first image and said second image are indicated on a second cartesian axis, and wherein such cartesian plane is divided into subareas identified a priori as corresponding to different conditions of the road surface.