A visual perception approach for accurate segmentation of light profiles

In this paper we describe the first industrial prototype to characterize automatically the headlamp beam properties using computer vision. The European commission for transportation provides strict regulations that have to be fulfilled as far as headlamp orientations, luminous and geometrical beam properties are concerned. To test the headlamps, the test system has to be properly aligned to the vehicle in order that the measures achieved on brightness and geometrical beam profile can be reliable. The system we present is composed of two integral subsystems. The first consists of a fixed stereo vision system capable of estimating automatically, in real time and with a very high accuracy, the longitudinal axis of the vehicle while it is approaching the stereo rig. The outcome is used to accurately align the second subsystem with respect to the vehicle. This subsystem is composed of a classic optical projection endowed with a CCD camera used to perform automatically radiometric and geometric assessments of the beam projected by the headlamps. Experiments carried out for both the subsystems prove how the high accuracy achieved by our method makes the prototype compliant with current regulations. It is worth remarking that the technology employed is low cost, thus making our approach suitable for commercial headlight tester.