Method for determining the luminance of traffic signs and device for implementing same

摘要

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.

主权项

1. A computer-implemented method for determining luminance of a traffic sign, comprising the steps of:
a) obtaining a first image using a first illumination level at a first point in time, the first illumination level being based on a first base illumination and a first ambient illumination; b) obtaining a second image using a second illumination level at a second point in time, the second illumination level being based on a second base illumination, a second ambient illumination and an additional illumination, the second illumination level being different from the first illumination level, a difference between the first point in time and the second point in time being an interval of time corresponding to a frequency of an electric grid such that the first image and the second image are obtained at a same point of a sine wave of a supply voltage from the electric grid; c) extracting a first array of pixels in the first image, the first array of pixels being representative of the traffic sign; d) extracting a second array of pixels in the second image, the second array of pixels being representative of the traffic sign; e) calculating a first luminance value of the traffic sign using the first array of pixels, the first luminance value being based on the first base illumination and the first ambient illumination; f) calculating a second luminance value of the traffic sign using the second array of pixels, the second luminance value being based on the second base illumination, the second ambient illumination and the additional illumination; and g) calculating a luminance difference value of the traffic sign corresponding to a difference between the first luminance value and the second luminance value.