I take it that you to understand the fisheye camera from many aspects

What is the fisheye camera?

When it comes to the fisheye camera, we have to start with the name of the fisheye to find out. Scientific research has shown that the structure of the fisheye is similar to that of the human eye. Still, its crystal is spherical, and the human eye is oblate. Therefore, the fisheye can only see relatively close objects, but it has a viewing angle of about 180 degrees. With the enhancement of optical technology, optical engineers have simulated and produced a lens with a viewing angle of 180 degrees.

The diameter of the front lens is very short and parabolic, the front of the lens is convex, and the viewing angle is 180 degrees or even more significant, which is quite similar to the eyes of fish, so it is called "fisheye lens". Conventional cameras have a viewing angle of 80 degrees to 120 degrees, but a small viewing angle means that the monitoring range is small, and there are blind spots that cannot be monitored. It is necessary to increase the number of cameras, to achieve large-scale monitoring,

On the one hand, it increases the hardware cost, on the other hand. On the one hand, because the video images captured by multiple cameras need to be stitched together, it brings specific difficulties to the continuous monitoring of a moving object within the monitoring range. The image stitching technology also has very high requirements on the relative positions of multiple cameras. At the micron level, the difficulty of production and assembly is significantly increased.

The demand for full-scene monitoring is increasing day by day. Engineers have manufactured a fisheye camera based on the 180-degree viewing angle of the fisheye lens. Its structure is also simple. On the basis of a conventional camera board, an optical 180-degree fisheye lens is installed. In this fisheye camera, the focal length is 1.6mm or even shorter, and the viewing angle is close to or greater than or equal to 180°. Imitation of fish eye imaging, it realizes a single camera for large-scale viewing without dead angle.

It provides the possibility to establish a monitoring system with small size, lightweight, low power consumption and large viewing angle.

Technical difficulties of the fisheye camera

1. Serious optical distortion:The fisheye camera has an ultra-wide angle, but it is accompanied by serious visual distortion, such as the picture on the left below, the picture is almost circular, and the image distortion is serious, which does not meet the Normal visual perception; the original image needs to be corrected by the distortion correction algorithm before its effect can be accepted by the user. As the image correction algorithm matures, the impact of this camera distortion becomes less and less obvious.

2. Insufficient performance of details:The optical characteristics of the lens determine that a large viewing angle will inevitably have a smaller focal length and depth of field, resulting in a fisheye camera that cannot see distant scenes. It is necessary to use a high-resolution sensor to ensure that the target object has more pixels to represent; at the same time, the resolution and depth of field of the fisheye lens are improved as high as possible to improve the clarity of distant objects.   
3. The cost is higher than that of ordinary cameras:due to the high requirements of fisheye cameras for sensors and lenses, the price is bound to rise. However, for application scenarios with panoramic monitoring needs, fisheye cameras are better than multiple cameras in terms of price. Realize panoramic monitoring.

Development and application of fisheye camera

In the initial stage of use of the fisheye camera: the product only has the function of outputting distorted panoramic images and quad-screen images. At the intermediate stage: the image output by the fisheye camera can be subjected to certain deformation correction and virtual PTZ, but the effect of deformation and correction is unsatisfactory. In addition, the lower resolution (less than 3 megapixels) makes the image processing sharpness effect. It is not good, and the application of traditional compression coding algorithms also makes the video processing consume too many resources of the main control server.

Now at the advanced stage: fisheye camera products have a resolution of 3 million or even 12 million pixels and can flexibly perform image distortion correction and virtual PTZ as needed. At present, the government has installed a lot of fisheye cameras on occasions that do not require details but need to grasp the whole situation of the whole place, such as public places, traffic hubs, and traffic intersections. Scope of civil places, panoramic VR equipment, police or special fields are favoured by users, and fisheye cameras can be seen everywhere.

CK vision cam has developed a 12-megapixel fisheye lens for customers: 12-megapixel high-definition image output, ensuring that the distant view also has a high definition; H.265/H.264/MJPEG encoding format is optional, on the premise of ensuring image quality, which can greatly reduce coding power consumption and memory usage; Mainstream/sub-stream dual-stream configuration, high and low resolution can be switched at will; Digital noise reduction, digital wide dynamic, strong light suppression, make fisheye cameras clearer and more reliable High-quality picture quality; Support two-way intercom, provide necessary two-way communication in real-time; Support SD card local storage, built-in pickup to realize audio and video recording; Fisheye, 360 panoramas, 180 panoramas, 1+3, 1+5, 1+7, etc. A variety of output modes are optional; Support I/O alarm, SD card full alarm, motion detection alarm; Support ONVIF protocol, CGI, GB28181 protocol; Infrared fill light distance of 15 meters; IP66 waterproof and dustproof, outdoor support installation.