Fish eye lens is one of the most simple and effective methods to build panoramic vision. Its outstanding feature is that it can absorb all the information in a view angle of more than 180 degrees at one time, so as to achieve the effect of no blind area. In terms of characteristics, the fish eye lens is a special lens with super wide angle. The front lens of this kind of photographic lens is parabolic in diameter and protrudes towards the front of the lens. Its visual effect is similar to that of fish eye observing the scenery on the water. It is a kind of short focal length lens. Generally, the focal length is between F=6-16mm. According to the optical imaging principle, the short focal length can show the monitoring effect of large field of view.

There are two kinds of common fisheye lens, one is circular imaging, the other is rectangular imaging. The former has a larger 3D angle than the latter. At present, most panoramic cameras use fish eye lens as the first type, because its 3D angle of view can reach 360 degrees x 180 degrees, which is an ideal panoramic angle of view. Although the field angle provides unparalleled enjoyment, it is obtained at the expense of the original monitoring image. The distorted image of the fish eye lens is generally called barrel distortion, which will become serious with the expansion of the field angle. However, it is also a reasonable phenomenon.

Generally, the field of view of the monitoring probe is about 60 ° - 90 °. If all the monitoring needs of the monitoring field are large, if only a few more cameras are installed to cover the monitoring area, it will undoubtedly increase the camera cost and installation cost, as well as the display and storage cost of the back-end; Even though the ball machine can achieve 360 degree full range monitoring through the PTZ, it cannot achieve the 360 degree simultaneous monitoring range. In practical applications, most ball machines monitor the scene by setting preset positions, which is difficult to avoid the occurrence of "missing control" of important events.

In the current security market, as the blind spots of video surveillance are becoming more and more intolerable, the market demands more and more blind spot free video surveillance systems. The panoramic camera is to realize panoramic monitoring. Its appearance can eliminate the blind area of monitoring in a real sense, and ensure the reliability and integrity of video, which is of great significance to users and even to society. One type is a panoramic camera based on ultra wide angle fish eye lens. The fish eye panoramic camera is a modification and upgrade of the existing monitoring system. In the fish eye panoramic monitoring system, only one fish eye panoramic camera is required to achieve panoramic blind zone free monitoring, without any mechanical parts. The image is captured by the ultra wide angle fish eye lens to capture the panoramic image of the monitoring site. Depending on the different installation methods, it can reach a 180 degree or 360 degree panoramic image, and the elliptical or circular deformed image is corrected to a normal video image through embedded or external image processing software. If strictly speaking, the panoramic camera is not a camera, it is a "three in one" panoramic monitoring system composed of fish eye high-definition camera image processing software.