Vehicle License Plate RecogniTIon (VLPR) is an application of computer video image recognition technology in vehicle license plate recognition. License plate recognition is widely used in highway vehicle management. In the electronic toll collection (ETC) system, it is also the main means to identify the identity of vehicles in combination with DSRC technology.
The license plate recognition technology requires that the sports license plate can be extracted and recognized from the complex background, and the vehicle license plate, image pre-processing, feature extraction, license plate character recognition and other technologies are used to identify the vehicle grade, color and other information, and the latest technical level. The recognition rate for letters and numbers can reach 99.7%, and the recognition rate for Chinese characters can reach 99%.
In parking lot management, license plate recognition technology is also the main means of identifying vehicle identity. In the "Technical Requirements for Vehicle Image and Number Plate Information Collection and Transmission System of Parking Garage (Field)" constructed by Shenzhen Public Security Bureau, license plate recognition technology has become the main means of vehicle identification.
The license plate recognition technology is combined with the electronic non-stop toll collection system (ETC) to identify the vehicle. When the passing vehicle passes through the crossing, there is no need to stop, that is, the vehicle identity can be automatically recognized and automatically charged. In the management of the yard, in order to improve the traffic efficiency of the entry and exit vehicles, the license plate recognition is for vehicles that do not need to collect parking fees (such as monthly trucks, free internal vehicles), and build an unattended fast-track, free of access and non-stop access experience. Change the management mode of access to the parking lot.
Principle of license plate recognition system
Automatic license plate recognition is a pattern recognition technology that uses the dynamic video or static image of the vehicle to automatically identify the license plate number and license plate color. The hardware foundation generally includes a trigger device (monitoring whether the vehicle enters the field of view), a camera device, a lighting device, an image acquisition device, a processor (such as a computer) that recognizes the license plate number, and the software core includes a license plate location algorithm, a license plate character segmentation algorithm, and Optical character recognition algorithms, etc. Some license plate recognition systems also have a function of judging whether or not there is a car through a video image, which is called video vehicle detection. A complete license plate recognition system should include several parts such as vehicle detection, image acquisition, and license plate recognition (as shown in Figure 1). The image acquisition unit is triggered when the vehicle detection portion detects that the vehicle arrives, and the current video image is acquired. The license plate recognition unit processes the image, locates the license plate position, and then divides the characters in the license plate for identification, and then forms a license plate number for output.
License plate recognition system vehicle detectionVehicle detection can use buried coil detection, infrared detection, radar detection technology, video detection and other methods. Video detection can avoid damage to the road surface, no need to attach external testing equipment, no need to correct the trigger position, save money, and is more suitable for mobile and portable applications.
The system performs video vehicle detection, and needs to have a high processing speed and an excellent algorithm to achieve image acquisition and processing without substantially dropping frames. If the processing speed is slow, the frame is lost, so that the system cannot detect the vehicle with a faster traveling speed, and it is also difficult to ensure that the recognition processing is started at the position favorable for recognition, which affects the system recognition rate. Therefore, combining video vehicle detection with automatic license plate recognition has certain technical difficulties.
License plate recognition system number identificationIn order to carry out license plate recognition, the following basic steps are required:
1) Position the license plate and locate the license plate position in the picture;
2) Separate the license plate characters and divide the characters in the license plate;
3) License plate character recognition, identifying the divided characters and finally forming the license plate number.
In the license plate recognition process, the license plate color is identified according to different algorithms, which may be implemented in the above different steps, and usually cooperate with the license plate recognition to verify each other.
1) License plate positioning
In the natural environment, the background image of the car is complicated and the illumination is uneven. How to accurately determine the license plate area in the natural background is the key to the whole identification process. Firstly, a large-scale correlation search is performed on the captured video images, and a plurality of regions meeting the characteristics of the license plate are found as candidate regions, and then the candidate regions are further analyzed and judged, and finally an optimal region is selected as the license plate region, and Separate it from the image.
2) License plate character segmentation
After the positioning of the license plate area is completed, the license plate area is divided into individual characters and then identified. Character segmentation generally uses vertical projection. Since the projection of the character in the vertical direction necessarily takes the vicinity of the local minimum between the characters or the gaps within the characters, this position should satisfy the character writing format, character, size limit and some other conditions of the license plate. The vertical projection method has a good effect on character segmentation in car images in complex environments.
3) License plate character recognition methods are mainly based on template matching algorithm and artificial neural network based algorithm. Based on the template matching algorithm, the segmented characters are first binarized and scaled to the size of the template in the character database, and then matched with all the templates to select the best match as the result. There are two kinds of algorithms based on artificial neural network: one is to extract the characters first, and then use the obtained features to train the neural network allocator; the other method is to directly input the image into the network, and the feature extraction is automatically realized by the network until Identify the result.
In practical applications, the recognition rate of the license plate recognition system is also closely related to the quality of the license plate and the quality of the shooting. The quality of the license plate will be affected by various factors, such as rust, stain, paint peeling, font fading, license plate occlusion, license plate tilt, high-gloss reflective, multi-license, fake license plate, etc.; the actual shooting process will also be subject to environmental brightness , the way of shooting, vehicle speed and other factors. These influencing factors reduce the recognition rate of license plate recognition to different extents, which is also the difficulty and challenge of the license plate recognition system. In order to improve the recognition rate, in addition to constantly improving the recognition algorithm, we should also find ways to overcome various lighting conditions, so that the collected images are most conducive to recognition.
The license plate recognition system LPR is an important part of the Intelligent Transportation System (ITS). The main task of the license plate recognition system is to analyze and process the vehicle images in the complex background, to locate the split license plate, and finally to automatically recognize the characters on the license plate. The license plate recognition uses the uniqueness of the license plate to identify and count the vehicles. In the development of modern transportation, the license plate recognition system is an important factor restricting the intelligent and modernization of the transportation system. The license plate recognition system should be able to automatically extract the vehicle image from an image, whitely split the license plate image, and correctly identify the characters, thus reducing traffic. Manage the complexity of the work. The license plate recognition system performs a series of processing on the acquired vehicle image, and outputs the result in the form of a string, so that not only the data amount is small, but also the storage is convenient, and the operation is also easier. Therefore, the convenience of the license plate recognition system is the manual license plate recognition system. Unmatched, it contains a lot of economic value and development space, and the research on license plate recognition technology is very meaningful.
For vehicles that are included in the “blacklistâ€, such as vehicles that are wanted or lost, vehicles that are underpaid, vehicles that are not inspected, accidents, and illegal vehicles, simply enter their license plate number into the application system, and license plate identification equipment is installed. At the designated intersection, bayonet or by law enforcement personnel, it will be placed as needed. The system will read all the license plate numbers of the passing vehicles and compare them with the “blacklist†in the system. Once the designated vehicle is found, it will immediately send out an alarm message. The system can work uninterrupted all day, without fatigue, and the error rate is extremely low; it can adapt to high-speed vehicles; it can complete tasks during the exercise of the vehicle without affecting normal traffic; the driver will not be aware and confidential during the whole monitoring process. . Applying such a system will greatly improve the efficiency of law enforcement.
Speeding violation punishment The license plate recognition technology combined with the speed measuring device can be used for vehicle speeding violation punishment, generally used for highways. The specific application is: set the speed monitoring point on the road, capture the overspeed vehicle and identify the license plate number, send the license plate number and picture of the illegal vehicle to each exit; set the penalty point at each exit, identify the passing vehicle and the number with the license plate recognition device Compared with the number of overspeed vehicles that have been received, once the numbers are the same, the warning device is activated to notify the law enforcement personnel to handle the problem. Compared with the traditional overspeed monitoring method, this application can save the police force and reduce the work intensity of law enforcement personnel. It is safe, efficient and concealed. The driver needs to remind himself that he can not overspeed, greatly reducing the accident caused by speeding.
Female Header Connector,0.80Mm Female Header Connector,2.54Mm Female Header Connector,3.96Mm Female Header Connector
Shenzhen CGE Electronic Co.,Ltd , https://www.cgeconnector.com