20 May 2009 Auto-focusing technology for photoelectric measurement system
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Automatic focusing (AF) is a key technology of measuring TV capturing the clear objective image in photoelectric measurement system. It is viable to enhance the performance of measuring TV through focusing effectively and quickly. In the process of maneuvering target tracking, the background and the feature of targets change from time to time, and the reliability of AF is highly required. Firstly, conditions for starting AF need to be investigated. The relation between degree of definition and edge acutance is proved by experiments. Combined with the sharpness value, it decides whether to begin AF. Secondly, it needs focusing quickly and exactly after starting AF. The accuracy and efficiency of the sharpness function is another key factor of AF. By comparing some favorable sharpness functions, normalized variance and square-gradient functions are employed based on focus windows. Thirdly, the optimized mountain-climb searching algorithm based on the defocusing extents and the adaptive searching step size is proposed. Experiments show the algorithm proposed improves the speed and reliability of AF.
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Tao Lei, Tao Lei, Sihan Yang, Sihan Yang, Yong Zhang, Yong Zhang, Qinzhang Wu, Qinzhang Wu, } "Auto-focusing technology for photoelectric measurement system", Proc. SPIE 7283, 4th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment, 728346 (20 May 2009); doi: 10.1117/12.828804; https://doi.org/10.1117/12.828804

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