Robust focus measure for unsupervised auto-focusing based on optimum discrete cosine transform coefficients

In this paper we present a robust focus measure for unsupervised au to-focusing b ased on op timum d iscrete cosine transform (DCT) c oefficients. The foc using window of an input image is divided into non-overl apping 8×8 sub-images, and the focusing measure is computed from the appropriately chosen mid frequency band. Be cause of low c omplexity in computing the DCT coefficients, the proposed focusing measure can be applied to the real-time auto-focusing. Experimental results show that the proposed method is more effective than the traditional methods based on comparison w ith well-known autofocusing uncertainty measure (AUM).