Study On The Auto-focus Algorithms Based On Image Processing And Its System Realization

The accurate focusing ability is the crucial factor that get high quality images forimage systems.In the deep space exploration domain, the auto-focusing technology has not beenapplied on the optical imaging payloads given the rigor environment. Traditionalmethods of auto-focusing has the limit application range. In this paper, the microscopeis as the object of study, the principle of the technology that implemention ofauto-focus based on image processing were studied and analyzed. The auto-focusexperiment plat was built based on a PC to test and verify the method.The auto-focusing technology procedure which based on image processing asfollows. First, the image systems obtain image, the sharpness of the image wascalculated. Then the moving direction and distance of focusing mechanism wasdecided under search strategy. Repeat the cycle until the focus position was found.Two key factors of the auto-focusing algorithm were function of image definition andthe strategy of searching in-focus position.Given the uncertainties of the edge of target image. In this paper, the revisedSobel operator was as the focus measurement to evaluate the image definition bydetection the image edges. The revised Sobel operator with a wider focus range,sensitive and real-time features by comparing other focus evaluate function. In otherhand, the paper prosed a improved searching strategy. First, coarse search the wholefocus range with large step; second, fine search with small step on the basics ofhill-climbing algorithm. It can avoid the disturbing of local extreme value, increasedthe search efficiency.In order to simplify structure,we design a microscope object len that imaging andilluminating function realization with the same light path. The gear transmissionmechanism that was driven by the stepper motor to move the lens for changing objectdistance, so the image systems would get auto-focusing ability. By the experiment, theimaging system can find the in-focus position fast and accurate. At last,we analyzedthe accuracy of the systems and the influencing factors of real-time features.With the development of modern electronic circuit technology, the focusingcircuit can be designed simple and high reliability. By the study of auto-focusing method based on image processing, we can make preparation for the application ofauto-focusing technology in the deep space exploration domain.