In this paper a system for the recognition of car license plates is pr
esented. The aim of the system is to read automatically the Italian li
cense number of a car passing through a tollgate. A TV camera and a fr
ame grabber card are used to acquire a rearview image of the vehicle.
The recognition process consists of three main phases. First, a segmen
tation phase locates the license plate within the image. Then, a proce
dure based upon feature projection estimates some image parameters nee
ded to normalize the license plate characters. Finally, the character
recognizer extracts some feature points and uses template matching ope
rators 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%.