Recognition Of License Plate Characters Based On Projective Invariant

Recognition of license plate characters is the last step in the license plate recognition system, and it requests that recognizing single character rapidly and accurately. The result of characters recognition shows the success or failure of the whole license plate recognition system. However, license plate images are easily impacted by the shooting angle, so characters on them will inevitably be deflective and deformative. General characters recognition algorithms can't offer a good way to recognize characters of deflective license plate, and before they recognize deflective characters, a step named deflection rectifying must be progressed, but the effect of this step is a big influence on the result of characters recognition. This paper provides a new recognition algorithm based on the projective invariant, it can effectively recognize 3D objects from their 2D images and will not be affected by visual angles. It means that this algorithm can recognize deflective characters directly. The algorithm extracts feature points by using the geometric shapes of characters, and then calculates the projective invariant of each character by coordinates of each point as the recognition feature, and it can recognize characters accurately. The experimental result shows that the proposed approach is feasible and effective.