The recognition principle of license plate recognition system Identification process Automatic license plate recognition is a pattern recognition technology that uses vehicle dynamic video or still images to automatically identify the license plate number and license plate color. The hardware infrastructure generally includes triggering equipment (monitoring whether the vehicle enters the field of vision), camera equipment, lighting equipment, image acquisition equipment, and processor (such as computer) for identifying the license plate number. Its software core includes license plate location algorithm, license plate character segmentation algorithm and Optical character recognition algorithms. Certain license plate recognition systems also have the function of judging whether there is a car through a video image or not, which is called video vehicle detection. A complete license plate recognition system should include vehicle detection, image acquisition, license plate recognition and other parts (as shown in Figure 1). When the vehicle detection section detects the arrival of the vehicle, the image acquisition unit is triggered to collect the current video image. The license plate recognition unit processes the image, locates the license plate position, and then separates the characters in the license plate for identification, and then composes the license plate number output. Vehicle inspection Vehicle detection can use buried coil detection, infrared detection, radar detection technology, video detection and other methods. The use of video detection can avoid damage to the road surface, no need for additional external inspection equipment, no need to correct the trigger position, cost savings, and is more suitable for mobile and portable applications. The system carries on the video vehicle detection, needs to have the very high processing speed and uses the *** algorithm, realizes the image acquisition, the processing in the basic situation that does not drop the frame. If the processing speed is slow, it will result in dropped frames, making it impossible for the system to detect a vehicle with a fast traveling speed. It is also difficult to ensure that recognition processing is started at a position that is favorable for recognition, and the system recognition rate is affected. Therefore, combining video vehicle detection with automatic license plate recognition has certain technical difficulties. Number identification For license plate recognition, the following basic steps are required: 1) License plate location, location of the license plate in the positioning picture; 2) The license plate character is divided and the characters in the license plate are separated; 3) Recognition of license plate characters, identifying the segmented characters and eventually composing the license plate number. In the license plate recognition process, the identification color of the license plate is based on different algorithms, which may be realized in the above-mentioned different steps, and usually cooperate with the license plate recognition to verify each other. 1) License plate location Under the natural environment, the background of the car image is complex and the illumination is uneven. How to accurately determine the license plate area in the natural background is the key to the entire recognition process. Firstly, the collected video images are searched in a wide range of related areas to find a number of areas that meet the characteristics of the automobile license plate as candidate areas. Then these candidate areas are further analyzed and judged, and a fairly good area is selected as the license plate area. Separate it from the image. 2) license plate character segmentation After completing the positioning of the license plate area, the license plate area is divided into individual characters and then recognized. Character segmentation generally adopts vertical projection method. Since the projection of a character in the vertical direction necessarily takes place near the local rather small value at the spaces between characters or within characters, this position should satisfy the character writing format, characters, size restrictions, and some other conditions of the license plate. Using vertical projection method has a good effect on character segmentation in car images under complex environments. 3) License plate character recognition methods mainly include template matching algorithm and artificial neural network algorithm. The template-based matching algorithm first binarizes the segmented characters and scales their size to the size of the template in the character database, then matches all the templates, and selects a fairly good match as a result. There are two kinds of algorithms based on the artificial neural network: one is to extract features from the characters first, and then use the obtained features to train the neural network distributor; the other method is to directly input the images into the network, and the features are automatically extracted 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 license plate quality and the shooting quality. The quality of the license plate can be affected by various factors such as rust, stain, paint peeling, font fade, license plate obstruction, license plate tilt, bright reflective, multiple license plates, fake license plates, etc.; the actual shooting process will also be subject to environmental brightness , shooting methods, vehicle speed and other factors. These influencing factors reduce the recognition rate of license plate recognition in different degrees. It 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, it should also find a way to overcome various lighting conditions, so that the acquired image is quite conducive to recognition. License plate recognition PTZ camera captures license plate through light suppression screen, electronic shutter adjustment, wide dynamic function, etc.: Strong light shielding: Based on the low-light color camera, through the function of the software, the relatively bright part of the image is blocked. In traffic monitoring, the headlights are generally blocked by strong light, so that the license plate can be captured more clearly. However, the considerable disadvantage of this camera is that the software is not clear, it is unclear about the very bright part of the image, it is possible to block the license plate number, and it is impossible to handle the capture of high-speed moving objects. At present, domestic cameras do more in the light shielding, and the results vary. Adjustable electronic shutter: For high-speed movement of objects to capture (the speed of the car on the highway is generally more than 70KM / hour), you can achieve a clear snapshot by reducing the electronic shutter speed, generally through manual adjustment. However, the considerable problem of this method is that during the day and night, the illumination is not the same. It is necessary to set two shutter speeds to adapt to daytime and nighttime monitoring respectively. Wide dynamic function: This is a very good way to solve the impact of the lights on the capture, the wide dynamics was brought forward by Matsushita. When the background light is too bright, ordinary cameras cannot solve the display problem of light and dark images. As a very important means of identifying vehicle identities in the field of intelligent transportation, license plate recognition technology has played a significant role in realizing the intelligent management of traffic. In each work, there is the penetration of license plate recognition technology. First, monitoring alarm For vehicles that are included in the "blacklist", such as vehicles that are wanted or reported missing, vehicles that are underpaid, vehicles that do not have annual inspections, accidents escaping, illegal vehicles, etc., simply enter their license plate number into the application system and license plate recognition equipment is installed. At designated junctions, bayonet or by law enforcement officers, they can be placed as required. The system will read all the vehicle's license plate numbers and compare them with the “black list†in the system. Once the designated vehicle is detected, it will immediately send an alarm message. The system can work uninterrupted throughout the day, without fatigue, with a very low error rate; it can adapt to high-speed vehicles; it can complete tasks in the vehicle without affecting normal traffic; the driver will not be aware of the entire monitoring process and high confidentiality. . Applying such a system will greatly increase the efficiency of law enforcement. Second, violation of speeding penalties The license plate recognition technology combined with the speed measuring device can be used for speeding violations of vehicles and is generally used in highways. The specific applications are: setting speed monitoring points on the road, capturing speeding vehicles and identifying license plate numbers, sending license plate numbers and pictures of illegal vehicles to various exits; setting penalties at each exit, using vehicle license plate recognition devices to identify passing vehicles and numbering Compare with the number of speeding vehicles that have been received. Once the numbers are the same, an alert device is activated to notify law enforcement officers. Compared with traditional speed monitoring methods, this application can save the police force, reduce the work intensity of law enforcement personnel, and it is safe, secure and hidden. The driver must always remind himself that he can not speed, which greatly reduces the accident caused by speeding. Third, vehicle access management The license plate recognition equipment is installed at the entrance and exit, record the license plate number and the access time of the vehicle, and combine it with the control equipment of automatic doors and barriers to realize the automatic management of the vehicle. Applied to the parking lot can realize automatic time-based charging, and can also automatically calculate the number of available parking spaces and give hints. The automatic parking fee management can save manpower and improve efficiency. The application to the smart community can automatically determine whether the entry vehicle belongs to the local community and implement automatic hourly charging for non-interior vehicles. In some units, this kind of application can also be combined with the vehicle dispatching system to automatically and objectively record the vehicle's outbound condition. H3 Smart uses the license plate recognition technology in the traffic management system to achieve no parking and exemption from cards. Improve the efficiency of vehicle access. Fourth, automatic release The designated license plate information is entered into the system, and the system automatically reads the license plate of the passing vehicle and queries the internal database. For vehicles that need to be automatically released to drive electronic gates or barriers to allow them to pass, warnings will be given to other vehicle systems and handled by on-duty personnel. Can be used for special units (such as military administrative areas, confidential units, key protection units, etc.), road and bridge charge bayonet, residential areas. Fifth, highway toll management License plate recognition equipment is installed at each entrance of the expressway. When the vehicle enters, it recognizes the vehicle license plate and stores the entrance data in the charging system. When the vehicle arrives at the exit, it recognizes its license plate again and invokes the entrance data according to the license plate information. It combines the entrance and exit data to realize the charge management. This application can achieve automatic billing and prevent cheating and avoid the loss of receivables. Expressway has begun to implement networking fees. With the expansion of the scope of networking, the difference between the price of different models is also increasing. The problem of drivers using the loopholes in the existing charging system through the midway exchange for card evasion will become more and more prominent. License plate recognition technology is the fundamental method to solve such problems. Six, calculate the vehicle travel time In the traffic management system, the average travel time of a vehicle on a road can be used as a parameter for judging the road congestion condition. The license plate recognition equipment is installed at the start and end points of the road, and all the passing vehicles are read and the license plate number is transmitted back to the traffic command center. Based on these results, the command center management system can calculate the average travel time of the vehicle. VII. Automatic Registration of License Numbers The traffic supervision department handles a large number of images of illegal vehicles every day. Usually, the number of the license plate is manually identified and then input into the management system. This method has a large workload and is prone to fatigue and misjudgment. Using automatic identification can reduce the work intensity and can greatly improve the processing speed and efficiency. This feature can be used for electronic police systems, road monitoring systems, etc. The license plate recognition parking management system automatically recognizes and converts the vehicle license plate number image captured by the camera at the entrance into a digital signal. To achieve one card and one vehicle, the advantage of license plate recognition is that it can associate the card with the car, so that the management can be improved by one grade. The corresponding advantages of the card and the car are that the long-term card must be used in conjunction with the car to eliminate the use of one card and multiple vehicles. Vulnerabilities improve the benefits of property management; at the same time, they automatically compare incoming and outgoing vehicles to prevent theft. The upgraded camera system can collect clearer pictures and save them as files, which can provide strong evidence for disputes. It facilitates management personnel to compare the vehicles when they appear on the market, which greatly enhances the security of the system. Eight, license plate recognition has a wide application prospect With the continuous development of parking management systems, license plate recognition technology has also begun to apply to parking lots. However, according to investigations, as only a few companies in China have specially developed license plate recognition technology for parking lots, many of the license plate recognition technologies currently used in parking lots are copied from early license plate recognition technologies, and the two are in recognition environment and identification angles. The large differences in the lighting environment, vehicle speed, and other aspects have also led to the emergence of "acclimatization" in most of these license plate recognition systems. A lot of parking lot calls for "private custom" license plate recognition system. According to fairly new statistics, by the end of 2015, the market demand for parking lots in China will exceed 3.7 billion yuan, and the next five years will surely be the golden period for the intelligentization of parking lots. Automatic license plate recognition is a very valuable market in the future parking market. With the integration of high-definition and intelligence, license plate recognition can also help us solve more problems in our lives. License plate recognition integrated machine has excellent imaging control, can automatically track light changes, effectively inhibit the smooth light and backlight, especially at night to suppress the interference of the car headlights, thus clearly capturing the license plate; and for the temporary absence of license plates or serious damage to the license plate The situation can also realize intelligent traffic management; in addition, offline operation is also a unique advantage of the license plate recognition integrated machine, which can effectively improve the efficiency of vehicle access. In the future, with the acceleration of the development of China's urbanization process, traffic pressure will become more severe, so intelligent traffic management will be the general direction of future traffic development. As an important core in the intelligent traffic management system, the license plate recognition system will also be further supported and developed. Experts predict that the future license plate recognition technology will have broader applications. At that time, the license plate recognition system industry will also face a major reshuffle. Only companies with independent core technologies and product quality standards will be able to cross the border. This is also the process of license plate recognition technology moving toward rapid development. The only way to go. original: Blower Fan,Mini Blower Fan,Industrial Air Blower,Squirrel Cage Blower Foshan Shunde Josintech Electrical Appliance Technology Co.,Ltd , https://www.josintech.com