Autofocus System Designed Based On Integration Camera

With the development of information technology, video surveillance is widely used in highways, smart cities and other scenes. Pan-Tilt-Zoom integrated cameras have the functions of switching scenes and auto focusing, making it easier to achieve the goal of target detection, tracking and real-time analysing. Therefore studying autofocus is of great significance to make the video surveillance more automatically and intelligentize.Based on the current research of automatic focusing, this thesis developes an autofocus system on the plateform of the DaVinci. Measures designed to weaken the effect of noise are taken into account and the system is consisted of four parts:video capture module, user interactive module, drivers of stepped motor and autofocus algorithm. Autofocus algorithm is the key of this thesis while the other modules render services for the algorithm. Firstly the algorithm obtains the statistics of the gradient and variance of the image data captured by the video capture module to evaluate the image sharpness. Secondly according to the results, the algorithm determines whether it needs to adjust the focal length of the lens. If it is necessary, the algorithm will adjust the position of the focus motor to make the image clear using the drivers of stepped motor. User interactive module provides methods for users to set parameters and control motors. When users manually control the zoom motor to move, the algorithm will adjust the focus motor’s position using the zoom tracking method to achieve the purpose of image remaining clear during the entire operation.Experimental results show that the autofocuse system that this thesis developes can play an effective role in actual environment and can ensure video images remaining clear in all cases. It is proved that the system is valuable in engineering.