Determination procedure of the luminance of traffic signs and device for its embodiment

Abstract

The method of the invention comprises: obtaining a sequence of at least two images, with different levels of illumination; extracting the region containing the sign in the image; calculating the luminance values of the signs; and obtaining the difference in luminance of the sign corresponding to the two levels of illumination. The value obtained is the luminance of the sign ( 11 ) corresponding to an illumination equal to the difference between the illuminations, or additional illumination. This result is based on the additive property of luminance, according to which the luminance of a sign is the sum of the luminance produced by each source of illumination. A basic illumination device ( 5 ), an additional illumination device ( 7 ), at least one camera for taking images, and image recording, positioning and synchronism systems are required to implement the method.

1 . Determination procedure of the luminance of traffic signs characterized in that it comprises the following stages:
 a) Obtaining a sequence of images composed of at least two images with different illumination levels.   b) Extracting the region where the sign is on the image.   c) Calculating the luminance values of the signs.   d) Obtaining the difference in luminance of the sign corresponding to the two illumination levels.   
     
     
         2 . Determination procedure of the luminance of traffic signs in accordance with  claim 1 , characterized in that the capturing of the two images with different illumination levels is done with an interval of time
   Δ t=p /(2* n*f )
   
       where “f” is the supply frequency of the public lighting network and “n” and “p” are whole numbers. 
     
     
         3 . Device for the determination of the luminance of traffic signs which, using the procedure of the above claims, is characterized by comprising the following, fitted on a vehicle:
 at least one camera for capturing the images,   a base illumination device,   an additional illumination device,   a positioning system,   a system for image and data recording and treatment,   a synchronism system.   
     
     
         4 . Device for the determination of the luminance of traffic signs in accordance with  claim 3 , characterized in that the cameras for capturing images are digital cameras. 
     
     
         5 . Device for the determination of the luminance of traffic signs in accordance with  claim 3 , characterized in that the base illumination device ( 5 ) comprises the dipped lights of the vehicle with a stabilizer system ( 6 ). 
     
     
         6 . Device for the determination of the luminance of traffic signs in accordance with  claim 3 , characterized in that the additional illumination device ( 7 ) comprises external lamps and an adjustment and control device ( 8 ) working in a closed loop which by means of some sensors ( 9 ) for the light intensity maintains a constant illumination level C modifiable by an operator. 
     
     
         7 . Device for the determination of the luminance of traffic signs in accordance with  claim 3 , characterized in that the positioning system comprises a GPS device. 
     
     
         8 . Device for the determination of the luminance of traffic signs in accordance with  claim 3 , characterized in that the image and data recording system comprises;
 a digital storage device,   a device that applies some transformation equations enabling the luminance of each pixel to be obtained from its characteristic values.   
     
     
         9 . Device for the determination of the luminance of traffic signs in accordance with  claim 3 , characterized in that the synchronism system comprises a local positioning device via the milometer of a vehicle on which it is installed.