OPTICAL DEVICE FOR MOTOR VEHICLES, FOR DETECTING THE CONDITION OF THE ROAD SURFACE

• US 20100141765A1
• Filed: 11/23/2009
• Published: 06/10/2010
• Est. Priority Date: 12/09/2008
• Status: Active Grant

• Current Assignee: C.R.F. Societa Consortile Per Azioni
• Original Assignee: C.R.F. Societa Consortile Per Azioni
• Inventors: Capello, Davide, Guglielmetto, Luca, Liotti, Luca, Pallaro, Nereo
• Granted Patent: US 8,350,910 B2
• Time in Patent Office: Days
• US Class Current: 348/149
• CPC Class Codes: B60Q 1/0023 the element being a sensor, e.g. distance sensor, camera
• CPC Class Codes: B60W 2420/40 Photo, light or radio wave sensitive means, e.g. infrared sensors
• CPC Class Codes: B60W 40/068 Road friction coefficient
• CPC Class Codes: G01N 21/3151 using two sources of radiation of different wavelengths G01N21/33 - G01N21/39 take precedence
• CPC Class Codes: G01N 21/359 using near infrared light
• CPC Class Codes: G01N 21/4738 Diffuse reflection precedence is given to G01N21/55 - G01N21/57 if specular component is taken into consideration, e.g. also for testing fluids, fibrous materials
• CPC Class Codes: G01N 2201/0627 Use of several LED's for spectral resolution
• CPC Class Codes: G01N 2201/0696 Pulsed

Abstract

An optical device for motor vehicles, designed to detect the condition of the road surface, comprises 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 and an electronic control and processing unit for receiving signals at output from said receiving unit and for processing them in order to determine the condition of the road surface, on the basis of a reference map. Appearing in said map are the values of the intensity of radiation I_ref back-reflected at a reference wavelength and at least one second wavelength. The map is divided into subareas identified beforehand as corresponding to the different conditions of the road surface.

Claims

1. 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 I_ref 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,I_ref 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.

2. The device according to claim 1, wherein said electronic control and processing unit is also designed to regulate said emission unit.

3. The device according to claim 1, wherein said reference map is pre-determined with subareas each corresponding to a condition of the road surface:

dry, wet, icy, and covered with snow.

4. The device according to claim 1, wherein said reference map is pre-determined with subareas respectively corresponding to a plurality of different ranges of values of the coefficient of friction of the road surface.

5. The device according to claim 1, wherein it is pre-arranged for being installed inside a front light assembly of a motor vehicle.

6. The device according to claim 1 wherein it constitutes a motor-vehicle headlight, said headlight being thus able to perform both the function of headlight and the function of detector of the condition of the road surface.

7. The device according to claim 6, wherein the source of light of the headlight constitutes at least part of said emission unit of the device.

8. The device according to claim 1, wherein it is pre-arranged for being installed within the body of an external rearview mirror of a motor vehicle.

9. The device according to claim 1, wherein it is pre-arranged for being installed within the engine compartment of a motor vehicle.

10. The device according to claim 5, wherein at least one of said sources is the same source dedicated to the function of lighting, and in that optical elements are provided, designed to shape part of the beam of radiation emitted by the source in order to direct it onto a portion of road.

11. The device according to claim 10, wherein it comprises an optical chopper positioned within the light assembly.

12. The device according to claim 1, wherein said emission unit comprises one or more light sources chosen from amongst LEDs, IRLEDs, laser diodes, incandescence sources, and halogen sources coupled to an optical chopper.

13. The device according to claim 1, wherein the sensitive element constituting the receiving unit is chosen from between:

a silicon photodiode with high spectral response in the near infrared or a silicon PIN photodiode characterized by a high sensitivity at high frequencies; and

an InGaAs PIN photodiode characterized by a high spectral response from 0.9 μ

m to 1.7 μ

m or else up to 2.5 μ

m.

14. The device according to claim 1, wherein the optical device is pre-arranged so as to supply the data on the condition of the road surface and/or on the coefficient of friction in correlation with the signal emitted by an ambient-temperature sensor.

15. The device according to claim 1, wherein the optical device is pre-arranged so as to supply the data on the condition of the road surface and/or on the coefficient of friction in correlation with the measurement of the temperature of the road surface made at a distance by means of thermoelectric or pyroelectric sensors.

16. The device according to claim 1, wherein the optical device is pre-arranged so as to supply the data on the condition of the road surface and/or on the coefficient of friction in correlation with the data supplied by a rain sensor installed on board the vehicle.

17. The device according to claim 1, wherein the optical device is pre-arranged so as to supply the data on the condition of the road surface and/or on the coefficient of friction in correlation with the data acquired by a telecamera for detecting the scene in front of the vehicle, in particular the data of estimation of the condition of wet road surface.

18. The device according to claim 1, wherein it comprises two sources of emission of radiation, associated to two distinct wavelengths, and a receiving unit able to receive and distinguish, by associating the intensity of the radiation back-diffused by the portion of asphalt, the corresponding source of emission, said measurement being made in a sequential mode, the contributions of the radiation back-diffused by the sources of emission in at least two successive instants of time being distinct.

19. The device according to claim 1, wherein it comprises two sources of emission of radiation and two receiving units, each designed to receive the radiation emitted by a source of emission of radiation, the measurements being made simultaneously.

20. The device according to claim 1, wherein it comprises a source of emission of radiation comprising the whole spectrum of wavelengths of interest and two radiation-receiving units, each associated to an optical filter, designed to select the pre-defined wavelength.

21. The device according to claim 1, wherein it comprises a source of emission of radiation comprising the whole spectrum of wavelengths of interest, associated to an optical element designed to separate into at least two optical channels the radiation of emission, said optical channels being characterized in that they are associated to optical filters for selection of the pre-defined wavelength and in that there is provided a single radiation-receiving unit operating in sequential mode, or else in that there are provided two receiving units operating simultaneously.

22. A method for detecting on board a motor vehicle the condition of the road surface on which the motor vehicle is travelling, which envisages:

emitting electromagnetic radiation in the direction of the road surface to be detected; and

receiving and analysing the radiation back-diffused by the road surface, in order to determine the condition of the road surface,

said method being characterized in that;

the radiation emitted towards the road surface is in the spectral region of the visible and/or near infrared;

said analysis of the back-reflected radiation is made by detecting;

both the intensity I_ref of the radiation back-reflected at a first wavelength, considered as reference wavelength;

and the intensity I of the radiation back-reflected at least one second wavelength; and

to a given pair of values of the intensity of radiation I,I_ref thus detected there is made to correspond a given condition of the road surface on the basis of a reference map,

wherein said reference map is a cartesian plane in which the values of the intensity of radiation I_ref back-reflected at the reference wavelength appear on a first cartesian axis, the values of the intensity of radiation back-reflected at the second wavelength appear on a second cartesian axis, in which said cartesian plane is divided into subareas identified beforehand as corresponding to different conditions of the road surface, and in which the boundary lines that divide said subareas from one another comprise both portions of straight line converging radially towards a common origin and portions of straight line oriented transversely with respect to said radial portions of straight line.

23. The method according to claim 22, wherein said reference map is pre-determined with subareas each corresponding to a condition of the road surface:

dry, wet, icy, and covered with snow.

24. The method according to claim 22, wherein said reference map is pre-determined with subareas respectively each corresponding to a plurality of different ranges of values of the coefficient of friction of the road surface.