Vehicle license plate recognition is an important research topic in the intelligent traffic fields in which computer vision and pattern recognition technology is applied. This technology has a wide range of applications. The systematic studies of vehicle license plate abroad have achieved some progress, but they do not best fit China's national conditions. In China, the hanging position of vehicle license plate is not fixed. Besides, some vehicle license plates are seriously polluted due to environmental, road or human factors. In this case, these vehicles are not allowed to hit the road in foreign developed countries, but in China, they can still be on the road.
Based on these, if an automatic recognition system is developed to rapidly and accurately recognize the vehicle license plates in public places, it will be of great significance to the improvement of vehicle safety management level and management efficiency.
License Plate Recognition difficulty:
1 ) Since the license plate image more outdoor collection, will be affected lighting conditions , weather conditions , the image will appear fuzzy , low contrast, the target area is too small , color distortion and other effects , and will be accompanied by a complex background image , which will affect the license plate positioning and identification .
2 ) Every time acquisition target location is not the same, there will be great changes in the acquisition perspective , and because the license plate hanging correct, will cause the license plate appear distorted.
3 ) license persity. Car license plate format in other countries , such as the size, arrangement of characters on the license , usually only one . In China, according to different models, use , provides a variety of license formats, such as into military vehicles, police cars, ordinary cars. Our standard car license plate is composed of Chinese characters , English letters and Arabic numerals , the identification and recognition of letters and numbers are very different characters , increasing the difficulty of identification .
4 ) the color of the background and character of the perse vehicle license , blue white, black on yellow , white on black , black on red , green and white variety .
5 ) Due to the environment or human factors road vehicle license pollution , in this case in developed countries are not allowed on the road, but in our country is still on the road. Such plates reduce the contrast characteristic is not obvious, even in the case of accurate positioning , character recognition will be greatly affected.
A variety of existing licenses in the country format , and there are all these difficulties and peculiarities of automatic license plate recognition has increased the difficulty of making the Chinese vehicle license plate recognition far more difficult to vehicle license plate recognition abroad. So how to improve the timeliness and usefulness of recognition rate and processing has become an urgent task .
1.2    Current status of license plate recognition technology at home and abroad
    The study of license plate recognition technology based on image processing started earlier in foreign countries. In America, Italy, Germany, Israel, Singapore and other countries, relatively mature products have been put into use, such as AUTOSCOF 2003 System in America, See/Vehicle System developed by Hi-Tech Corporation in Israel, ARTEM7S System developed by Siemens in Germany and VLPRS System by Optasa Corporation in Singapore. However, due to the persity in license plate styles and colors and the Chinese characters in these plates, these license recognition systems are not suitable for China's national conditions. Android-based Vehicle License Plate Recognition Software(2):http://www.751com.cn/jisuanji/lunwen_15765.html