Study On Technology Of Optical Sighting Auto-Focusing Based On Image Processing Method

Auto-focusing technique, one of the key technologies in digital imaging system is developed rapidly which is employed in the cameras of all grades. The technique is updated and improved continually.However, the technique has some limitations in the measurement instruments. In the small arm optical sighting performance parameter testing system, the focus will be blurred when the CCD camera system magnification is high and the focal length is short. So the focusing accurately is very important, which is the first step of the testing to obtain the clear reticule pattern and guarantee the precision measurement.On the basis of a large number of domestic and international documents on auto-focusing technique, the paper fully explores the basic principle of the optical imaging system, carefully analyzes each link of the auto-focusing which is based on image processing and deeply researches the three key techniques, focusing evaluation function, focusing window selection and auto-focusing feedback control.On the basis of full research on the working principle of the photoelectric auto-focusing system, an auto-focusing system based on image processing is designed in this paper according to the basic requirements of the optical sighting performance parameter testing of small weapons. In this system, through the performance comparison of some image analysis operators, the maximum gradient squares algorithm based on threshold is improved. As a result,the computational accuracy is raised greatly. Through the analysis of Depth From Defocus and Depth From Focus,a new auto-focusing algorithm combining both algorithm is presented. It fully uses the high speed of Depth from defocus and the high accurate of Depth from Focus. The effect of Auto-focusing has a statistically significant increase.The conclusions of above researches are applied in the optical sighting performance parameter testing of small weapons for the first time. Experiments have repeatedly established that this auto-focusing system has stable performance,high precision and good real-time property. The precision and efficiency of the optical sighting performance parameter testing of small weapons are improved greatly. So this system has high practice value.