Determination procedure of the luminance of traffic signs and device for its embodiment
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. A luminance detection system connectable to a vehicle and operable while the vehicle is moving along a roadway, the luminance detection system comprising:
a light source configured to illuminate a road marking positioned along the roadway, the light source being separate and distinct from a pair of headlights of the vehicle;
a first camera configured to obtain first image data, the first image data including the road marking, the first image data having first color characteristics;
a second camera configured to obtain second image data, the second image data including the road marking also included in the first image data, the second image data having second color characteristics, wherein the first color characteristics are separate and distinct from the second color characteristics;
a processor configured to:
calculate a distance between the vehicle and the road marking based on the first image data and the second image data;
apply one or more luminance transforms to convert one or more pixel values of the first image data and the second image data to obtain corresponding luminance levels representative of at least a portion of the road marking;
after applying the one or more luminance transforms, compare the first image data, and the second image data to minimize ambient light information; and
calculate a luminance value representative of a luminance of the road marking based on (i) the distance between the vehicle and the road marking (ii) the luminance levels representative of the road marking and (iii) the comparison of the first image data, after applying the luminance transform, and the second image data to minimize ambient light information.
2. The luminance detection system of claim 1 , wherein at least one of the first camera and the second camera is a color camera.
3. The luminance detection system of claim 1 , wherein the processor is configured to:
extract pixel values representative of the road marking from the first image data and the second image data.
4. The luminance detection system of claim 1 , further comprising a geo-referenced positioning device configured to generate vehicle position data representative of a position of the vehicle along the roadway, wherein the processor is configured to calculate the distance between the vehicle and the road marking based on the vehicle position data.
5. The luminance detection system of claim 1 , wherein the light source is positioned at the front of the vehicle.
6. The luminance detection system of claim 1 , wherein the first camera and the second camera are positioned at the front of the vehicle.
7. The luminance detection system of claim 1 , further comprising:
a light illumination adjustment sub-system including:
a light source external to the vehicle and separate and distinct from dipped headlights of the vehicle,
a sensor configured to measure an amount of light from the light source, and
a controller configured to adjust the amount of light emitted by the light source as a function of the amount of light measured by the sensor.