Optical Recognition of Motor Vehicle License Plates

In this paper a system for the recognition of car license plates is presented. The aim of the system is to read automatically the Italian license number of a car passing through a tollgate. A TV camera and a frame grabber card are used to acquire a rearview image of the vehicle. The recognition process consists of three main phases. First, a segmentation phase locates the license plate within the image. Then, a procedure based upon feature projection estimates some image parameters needed to normalize the license plate characters. Finally, the character recognizer extracts some feature points and uses template matching operators to get a robust solution under multiple acquisition conditions. A test has been done on more than three thousand real images acquired under different weather and illumination conditions, thus obtaining a recognition rate close to 91%.