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An Auto-Focusing Method for Different Object Distance Situation


Quan Feng, Ke Han, Xiu-chang Zhu


Vol. 7  No. 6  pp. 31-35


The auto-focusing system is an important factor to determine the imaging quality of digital camera. Currently, many auto focusing methods have been proposed, most of which are suitable for the long-object-distance situation, but ignore the long-short-object-distance situation. So this paper analyses the imaging relation and the properties of image clarity evaluation function under long-short-object-distance situation, and finds that the curve of the image clarity evaluation function always has multiple peaks, not the single peak. And according to this property, image clarity evaluation function based on Sobel operator is proposed in this paper. Experimental results indicate that the proposed method can effectively focus the images both under the long-short-object-distance situation and under the long-object-distance situation.


Auto-focusing, Image processing, Evaluation function, Gray gradient