The Research and Application on Light Shape Detection of Car's Headlamp

Abstract

Light shape detection of headlamps is an important project of yearly check. In the aspect of lowbeam detection, it is necessary to not only accurately calculate the boundary between brightness and shade, but also optical axis intersection point. By the principle that the second derivative indicates the concavity and convexity of functions, a polynomial fitting is used to calculate the columns grayscale profile of a lowbeam figure, and then get the cut-off point through second derivative of a polynomial. The boundary between brightness and shade is consisted of these cut-off points. The optical axis intersection point is obtained by second order difference of the boundary. While fully extracting graphic features, the method precisely locates positions of the boundary and the intersection.