License Plate Recognition Technology Research And Implementation

The License Plate Identification System mainly depends on the computer vision technology and the pattern recognition technology, and it plays an important role in intelligent traffic control system, paking lot monitor system and automatic charging system.The algorithms of all steps for implementing a complete system include image preprocessing, license plate location, character segmentation and character recognition, and these are studied further in this thesis.Image preprocessing: The image is processed by several algorithms including gray level stretch, homomorphic processing and image smoothing, and then the quality of image gets better.License plate location: This aspect is an extremely important step in this system and is also emphased in this paper. Several algorithms proposed traditionally are compared with that in this thesis. Several common points are summarized, and a new location algorithm is then put forward. The location process consists of two stages: coarse location followed by exact location, and we take advantages of both gray character and color character.Character segmentation: First, the top and bottom frame of the license plate are cut off. Secondly, the corresponding connection region is used to divide up the isolate character. At the same time, some efficient methods are provided for conglutination treatment.Character recognition: Foley-Sammon Discriminant Vector is employed in this paper in order that a satisfactory recognition effect is ensured.The algorithm we adopted is not restricted by the location of the plate in the image, and it has strong anti-jamming ability to lean, distortion, pollution and blur. The algorithm is also adaptable to the varieties of circumstance light and image contrast. System test result: the veracity of plate location reaches above 96%, and character identification rate above 90%.