License plate recognition system based on computer vision technology usually includes five steps: license plate image acquisition, license plate location, character segmentation and optical character recognition. License plate image acquisition determines the vehicle route recognition technology. The two main technical routes in the world are the acquisition and recognition of natural light and infrared images. Natural light and infrared light will not have a negative psychological impact on the human body, nor will they produce new electronic pollution to the environment. They belong to green environmental protection technology
natural light path refers to the method of using natural light, night auxiliary lighting source and color camera to collect the real color image of the vehicle during the day, and identifying the license plate through the color image analysis and processing method. The technical route of natural light true color recognition is consistent with the photosensitive habit of human eyes. The true color image can reflect the image information of the vehicle and its surrounding environment. It can not only be used to identify the license plate, but also be used to identify the color of the license plate, vehicle and several vehicle models, such as color features
use the camera to collect images, and realize the collection and recognition of all front-end basic video information and manual image forensics and discrimination, which can reserve prospects for the engineering interface of intelligent transportation system in the future
the infrared light path uses the reflection and infrared optical characteristics of the license plate and the infrared camera to collect the gray image of the vehicle. Due to the infrared characteristics, the vehicle can only see the license plate in the image, and then use the black-and-white image processing method to identify the license plate. At 950nm, the infrared lighting device can capture a good reflective license plate image. Because infrared light is not visible light, it will not have a visual impact on the driver
in addition, the infrared illuminator provides constant light, and the captured image is the same, whether it is the brightest day or the darkest hour day. The only exception is during the day, when you sometimes see some details of the license, because of the influence of sunlight on sunny days. The disadvantage of using infrared light is that the captured license plate image is not color, and the vehicle image cannot be obtained, which seriously depends on the reflective material of the license plate< br/>