Method of providing modulated illumination of a road, and a vehicle headlight for performing the said method

Abstract

The invention relates to a method of lighting a road with a vehicle headlight, in which the projected light is modulated in response to the presence of any persons on the road. The method comprises the following operations: detecting in the road scene at least one person, pinpointing the location of the person in the road scene, creating on an imager a mask having dimensions and position corresponding to the person, and lighting the road through the imager, to create a projected shadow around the person. The invention also provides a headlight for performing this method and having a first light source, an imager, a light guide for carrying the light from the light source towards the imager, and an electronic system for generating light-occulting masks on the imager.

What is claimed is:  
     
         1 . A method of lighting a road scene with a vehicle headlight, including the following operations: 
 detecting in the road scene at least one person,    pinpointing the location of this person in the road scene,    creating, on an imager, a mask having dimensions and position corresponding to the person, and    illuminating the road through the imager, so creating a projected shadow around the person.    
     
     
         2 . A method of lighting according to  claim 1  which illuminates a zone of the road scene situated above a cut-off line.  
     
     
         3 . A method of lighting according to  claim 1 , wherein the detection of the person comprises taking an image of the road scene with thermal detection of the person.  
     
     
         4 . A method of lighting according to  claim 1 , wherein detection of the person comprises taking an image of the road scene with detection of movement of the person.  
     
     
         5 . A method of lighting according to  claim 1 , wherein the pinpointing of location, and mask creation, are obtained by image processing.  
     
     
         6 . A method of lighting according to  claim 1 , wherein the pinpointing of location consists in applying a threshold-value technique to the image of the road scene.  
     
     
         7 . A method of lighting according to  claim 6 , wherein the application of threshold value comprises forming an image at two levels, black and white, of the image of the road scene.  
     
     
         8 . A method of lighting according to  claim 7 , wherein the creation of the mask comprises applying, in inverse video on the imager, the image to which the threshold-value technique has been applied.  
     
     
         9 . A method of lighting according to  claim 6 , wherein the creation of the mask includes convolution, by means of a convoluting element, of the image to which the threshold-value technique has been applied.  
     
     
         10 . A method of lighting according to  claim 1 , wherein creation of the mask is performed in real time.  
     
     
         11 . A main beam headlight for a vehicle, comprising a first light source and a system for modulating the light therefrom, wherein the modulating system comprises an imager, a light guide for transporting the light from the light source to the imager, and an electronic system for generating masks on the imager for blocking light.  
     
     
         12 . A headlight according to  claim 11 , wherein the imager comprises a matrix of liquid crystal systems which are electrically controllable, or a matrix of lenses, the focal length of which is capable of being modulated by electrical control.  
     
     
         13 . A headlight according to  claim 11 , wherein the light guide comprises at least one matrix of optical fibres or an optical fibre of large cross section.  
     
     
         14 . A headlight according to  claim 11 , wherein the light guide comprises a first light path for guiding the light towards the imager, and a second light path for guiding the light towards an optic adapted for diffusing the light.  
     
     
         15 . A main beam headlight for a vehicle, comprising a first light source and a system for modulating the light therefrom, wherein the modulating system comprises an imager comprising a matrix of lenses, the focal length of which is able to be modulated by electrical control, and an electronic system for generating masks on the imager for blocking light.  
     
     
         16 . A headlight according to  claim 11 , including a second light source independent of the first light source and providing main beam or cruising illumination.  
     
     
         17 . A headlight according to  claim 11 , wherein the electronic system is controlled by a means for detecting persons.  
     
     
         18 . A headlight according to  claim 17 , wherein the detection means is a thermal camera.  
     
     
         19 . A headlight according to  claim 17 , wherein the detection means is an infrared camera.  
     
     
         20 . A headlight according to  claim 11 , wherein the light guide includes, upstream of the imager, means for making the distribution of the light in the imager homogeneous.  
     
     
         21 . A headlight according to  claim 20 , wherein the means for making the light homogeneous is a block or bar of quartz or glass.  
     
     
         22 . A headlight according to  claim 11 , including a lens for diffusing the light downstream of the imager.  
     
     
         23 . A headlight according to  claim 11 , wherein the first light source is located in a housing outside the modulating system.