Method for determining the luminance of traffic signs and device for implementing same
First Claim
1. A determination procedure of luminance of traffic signs comprising the following stages:
- a) obtaining a sequence of images at a frequency corresponding to a frequency of an electric grid such that the sequence of images are obtained at an identical point of a sine wave that characterizes an electric grid supply voltage, the sequence of images including a first image with a first illumination level and a second image with a second illumination level, the firsst illumination level corresponding to a stabilized base illumination and the second illumination level corresponding to the stabilized base illumination and an additional illumination, the sequence of images being obtained at a frequency of an electric grid such that the first and second images are obtained at an identical point of a sine wave characterizing a supply voltage from the electric grid;
b) extracting a first region of the image corresponding to a sign represented in the image and extracting a second region of the second image, the second region corresponding to the sign represented in the second image;
c) calculating a first luminance value of the sign using the first region, the first luminance value being the sum of luminance due to the stabilized base illumination La, luminance due to the additional illumination Lb and luminance due to uncontrolled ambient illumination Lc, whereby the first luminance value L1 is
L1=La+Lb+Lc,d) calculating a second luminance value of the sign using the second region, the second luminance value being the sum of luminance due to the stabilized base illumination La and luminance due to the ambient illumination Ld, the second luminance value L2 is;
L2=La+Ld,e) obtaining a luminance difference value of the sign corresponding to the first luminance value and the second luminance value L2,wherein, the luminance difference value Δ
L obtained is the luminance corresponding to the additional illumination Lb,
Δ
L=L1−
L2=Lb,such that, the effect of the ambient illumination and the stabilized base illumination have been suppressed.
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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.
21 Citations
9 Claims
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1. A determination procedure of luminance of traffic signs comprising the following stages:
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a) obtaining a sequence of images at a frequency corresponding to a frequency of an electric grid such that the sequence of images are obtained at an identical point of a sine wave that characterizes an electric grid supply voltage, the sequence of images including a first image with a first illumination level and a second image with a second illumination level, the firsst illumination level corresponding to a stabilized base illumination and the second illumination level corresponding to the stabilized base illumination and an additional illumination, the sequence of images being obtained at a frequency of an electric grid such that the first and second images are obtained at an identical point of a sine wave characterizing a supply voltage from the electric grid; b) extracting a first region of the image corresponding to a sign represented in the image and extracting a second region of the second image, the second region corresponding to the sign represented in the second image; c) calculating a first luminance value of the sign using the first region, the first luminance value being the sum of luminance due to the stabilized base illumination La, luminance due to the additional illumination Lb and luminance due to uncontrolled ambient illumination Lc, whereby the first luminance value L1 is
L1=La+Lb+Lc,d) calculating a second luminance value of the sign using the second region, the second luminance value being the sum of luminance due to the stabilized base illumination La and luminance due to the ambient illumination Ld, the second luminance value L2 is;
L2=La+Ld,e) obtaining a luminance difference value of the sign corresponding to the first luminance value and the second luminance value L2, wherein, the luminance difference value Δ
L obtained is the luminance corresponding to the additional illumination Lb,
Δ
L=L1−
L2=Lb,such that, the effect of the ambient illumination and the stabilized base illumination have been suppressed. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification