Method for Determining the Articulation Angle of a Combination

The invention relates to a method and to a device for determining the articulation angle of a combination, consisting of a towing vehicle and a trailer attached using a tongue, by identifying the hitch tongue using a digital back-up camera with variable exposure times, the following steps being carried out: a) recording a first color image of the rear environment of the towing vehicle, the color image being based on the HSY color space, b) analyzing the hue values, saturation values and brightness values of adjacent surfaces of a vehicle-environment region that is to be evaluated, c) determining the tongue from the first color image using an edge detection method in order to determine the articulation angle if the hue values, saturation values and brightness values of adjacent surfaces in the region that is to be evaluated are substantially equal, "substantially equal" meaning that the values of hue, saturation and brightness of adjacent surfaces differ by at most a first threshold in percent, d) recording a second color image in the HSY color space if in the first color image the hue values and saturation values of adjacent surfaces in the region that is to be evaluated are substantially equal while the brightness values of the adjacent surfaces deviate greatly from each other, "deviate greatly from each other" meaning that the brightness values of adjacent surfaces differ from each other by more than a second threshold in percent, the exposure time of the second color image being selected in such a way that the brightness values of the adjacent surfaces within the vehicle-environment region that is to be evaluated are substantially equal, e) determining the tongue from the second color image by means of an edge detection method in order to determine the articulation angle.