Optical detection system for motor-vehicles having multiple functions, including detection of the condition of the road surface
An optical detection system per motor-vehicles, suitable to detect the condition of the road surface on which the vehicle is travelling, comprising a photodetector unit composed of a camera having a matrix of pixels composed of photodetectors based on a photosensitive material suitable to detect both radiations in the visible and near infrared, i.e. having a wavelength comprised between 380 and 900 nanometres, and radiations in the short wavelength infrared, i.e. having a wavelength comprised between 900 and 1700 nanometres.
1. Optical detection system for motor-vehicles, able to detect the condition of a road surface on which a vehicle is travelling, said system comprising:
a photodetector unit mounted on board the motor-vehicle, for receiving a 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, said system being characterised in that said photodetector unit is a chamber having a matrix of pixels composed of photodetectors based on a material, preferably InGaAs or Ge/Si, suitable to detect both radiations that are visible and near infrared, wherein the radiation has a wavelength comprised between 380 and 900 nanometres, and radiations in the short wavelength infrared (SWIR), has a wavelength comprised between 900 and 1700 nanometres,
wherein the optical detection system comprises a matrix of filters arranged before at least one part of the matrix of pixels in such a manner that each filter transmits the radiation to one and only one pixel of the matrix, and
in that the matrix of filters comprises four-positions subgroups, wherein two positions are occupied by band-pass filters with respective wavelengths centred on values at which the radiation is respectively absorbed by water and ice, and two positions are without filters, to allow complete passage of a spectral band.
2. System according to claim 1 , wherein said control and processing electronic unit is programmed to control and addressing of the pixels of the matrix 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.
3. System according to claim 2 , wherein said control and processing electronic unit is programmed to process a first image, a second image and a third image for each pixel of the matrix and hence detect the condition of the road surface.
4. System according to claim 3 , wherein said control and processing electronic unit is programmed to calculate, each pixel of the matrix, a ratios between a intensity of said first image and said second image with respect to a intensity of said third image and to detect the condition of the road surface according to a reference map.
5. System according to claim 4 , wherein 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.
6. System according to claim 5 , wherein in said reference map the border lines that divide such subareas from each other comprise both line portions converging radially towards the origin of the cartesian axes, and line portions directed transversely with respect to said radial line portions, one of said transverse line portions separating a region of the map corresponding to the presence of ice on the road surface from regions corresponding to presence of water or snow on the road surface.
7. System according to claim 2 , wherein said control and processing electronic unit is programmed to use said third image in such a manner to meet one or more further preventive safety functions selected from among:
lane departure warning or LDW,
high beam alignment,
traffic signal recognition,
night vision,
collision avoidance and mitigation, and
pre-crash warning and intervention.
8. System according to claim 1 , wherein said matrix of filters is placed in front of an entire extension of said matrix of photodetectors.
9. System according to claim 1 , wherein said matrix of filters is placed only in front of a portion of said matrix of photodetectors which is dedicated to the detection of the condition of the road surface.
10. System according to claim 1 , wherein said matrix of filters is placed only in front of one line, or some lines, of said matrix of photodetectors which are dedicated to the detection of the condition of the road surface, complete information regarding the condition of the road surface being obtained when the vehicle is moving.
11. System according to claim 7 , wherein said control and processing electronic unit is programmed to provide information regarding the condition of the road surface to the algorithms of the CAM and PCWI functions.
12. System according to claim 7 , wherein said control and processing electronic unit is programmed to provide information regarding the condition of the road for estimating the grip of the vehicle against the road in systems for controlling a lateral and longitudinal dynamic of the vehicle.
13. System according to claim 1 , wherein said control and processing electronic unit is programmed to provide information regarding the condition of the road in correlation with a value of an environmental temperature sensor.