With the rapid development of information technology and computer image processing technology and the improvement of people's safety awareness, real-time video surveillance systems have gradually become an indispensable part of people's lives and have been widely used in production, transportation, social security and other aspects. However, due to severe weather (fog, rain, wind, light, etc.) conditions and the technical conditions of the monitoring system itself, video images often fail to achieve the desired results. Under the influence of these conditions, the image will be degraded and blurred, which will lead to difficulties in identification, forensics, event analysis and other operations and the system will not be applied normally. Therefore, the research and application of fuzzy image processing technology has a very important meaning in the field of security.
1. Analysis of the causes of blurred images
The presentation of images is the result of the cooperation of the entire system. A complete video surveillance system is a very large and complex system. From the front end to the back end, all links may cause the loss of video image signals and blur the image. It can be analyzed from the following aspects.
1.1 The system itself
A complete video surveillance system consists of these parts from front to back. In the full simulation monitoring system, from the front end to the back end is composed of several links such as image acquisition, image transmission, image storage, image display and so on. In every link, there will be a loss of video information, that is, the image quality will be deteriorated or blurred.
From the front-end lens, camera, video BNC connector, transmission cable, monitor image presentation and other links, each link will cause image blur. The lens, which affects the light entering the camera and the accuracy of the imaging, will directly cause the image to be blurred. The photosensitive sensor in the camera affects the collection of optical signals and the photoelectric conversion effect, which will directly lead to blurred images. The BNC connectors at both ends of the video transmission cable will cause signal loss due to the gap of the signal shielding. The transmission of the video transmission cable over a long distance, the resistance, shielding, and impedance matching of the transmission cable will cause signal attenuation and directly lead to image quality The variation becomes blurred, and there is also a certain signal loss at the display end of the monitor image. Therefore, every node and link in the entire monitoring system may cause the image to be blurred.
In an all-digital video monitoring system, network transmission is adopted. The video signal on the transmission line is digitally encoded. The transmission and storage of digital signals can effectively avoid image damage due to signal attenuation. However, the loss of image signals during lens, image acquisition, and back-end rendering is still inevitable. In addition, in the digital video surveillance system, the A / D conversion of the video signal and the video coding compression link are added, and these links will also lead to the direct loss of information. Existing video compression coding algorithms are lossy compression, which will directly cause the loss of video information and affect the video clarity.
1.2 Natural environment
In addition to the factors of the system itself, the natural environment also has a great influence on the clarity of the video image. Natural weather such as windy, rainy, snowy, foggy, etc., will cause the image quality to drop sharply or blurry.
In addition, there are insufficient illumination, backlight, backlighting, low or high temperature, etc., which will affect the image restoration system and affect the image clarity. Under the condition of insufficient light, the sensor imaging of the camera will generate a lot of noise. These noises will affect the image clarity, and will greatly increase the code stream of the image encoding.
1.3 Man-made environment
The power supply of the power supply system is not "clean", that is, a relatively strong interference signal enters, which specifically means that the interference signal is superimposed on the 50Hz sine wave. If there is a high-power thyristor frequency and speed control device, thyristor rectifier, thyristor AC-DC converter in the power grid, it will pollute the power supply.
There is a strong source of electromagnetic interference or electromagnetic radiation near the TV monitoring system. Electromagnetic interference sources, such as welding, radio transmission, large motors, and large relay interference, can also cause video signal interference. Electromagnetic interference will cause the image to have vertical bars with equal spacing or the image will flash regularly, etc., which will cause the image to be blurred.
There is also the cause of man-made destruction, such as license plates that are made difficult to recognize, so that the camera cannot capture the license plate number.
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