Method For Determining The Luminance Of Traffic Signs And Device For Implementing Same

• US 20100316252A1
• Filed: 04/08/2008
• Published: 12/16/2010
• Est. Priority Date: 02/12/2008
• Status: Active Grant

• Current Assignee: AMAC NORTH AMERICA, LLC
• Original Assignee: Fundación Cidaut
• Inventors: Mansilla Gallo, Alberto, Perales Garcia, Alberto Senen, Gutierrez Mendez, Jose Antonio, Burgoa Roman, Francisco Javier, Oritz de Lejarazu Machin, Diego
• Granted Patent: US 9,171,360 B2
• Time in Patent Office: Days
• US Class Current: 382/100
• CPC Class Codes: B60Q 1/085 due to special conditions, e.g. adverse weather, type of road, badly illuminated road signs or potential dangers B60Q1/10, B60Q1/12, B60Q1/1423 take precedence
• CPC Class Codes: B60Q 1/18 being additional front lights bracket mounted headlights B60Q1/0483
• CPC Class Codes: B60Q 2300/314 Ambient light
• CPC Class Codes: B60Q 2300/45 Special conditions, e.g. pedestrians, road signs or potential dangers
• CPC Class Codes: G01N 2021/551 Retroreflectance
• CPC Class Codes: G01N 21/55 Specular reflectivity
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction
• CPC Class Codes: G06V 20/582 of traffic signs
• CPC Class Codes: H04N 13/279 the virtual viewpoint locations being selected by the viewers or determined by tracking

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.

Claims

1-9. -9. (canceled)

10. A determination procedure of luminance of traffic signs comprising the following stages:

a) obtaining a sequence of images composed of at least two images with different illumination levels, one with a stabilized base illumination (5) and the other with the same base illumination (5) and an additional illumination (7);

b) extracting the region where the sign is on the image;

c) calculating the luminance values of the signs;

in one of the images, the luminance is the sum of that due to the base illumination (5) L_a, that due to the additional illumination (7) L_b and the uncontrolled ambient illumination L_c (other vehicles, public lighting, etc), whereby the measured luminance is

L1=L_a+L_b+L_c,

analogously, for the other image, the luminance will be due to the base illumination (5) L_a and the ambient illumination L_d, the measured luminance will be;

L2=L_a+L_d,

d) obtaining the difference in luminance of the sign corresponding to the two illumination levels,

as the difference between the images to process is minimum in terms of the ambient illumination, we can assume that;

L_c=L_d,

whereby, the differential luminance obtained is the luminance corresponding to the additional illumination (7),

Δ

L=L1−

L2=L_b,

such that, the effect of the ambient illumination and the base illumination (5) have been suppressed.

11. The determination procedure of the luminance of traffic signs in accordance with claim 10, wherein 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.