Morphological Estimation of the Optimal Subject Region for an Affordable Auto-Focusing System

We present a novel, morphological image processing method for selecting the optimal subject region for fully automatical focusing (AF). The proposed approach aims at fully digital realization of the intelligent AF system for an affordable imaging system such as a mobile phone. The proposed region selection algorithm consists of; i) the morphological erosion of the input image, ii) estimation of the subject region by the difference of the input and the eroded images, and iii) computation of the maximum focus value in the estimated region. The experimental results shows that the AF system with the proposed subject region selection method provides the well-focused subject without human interaction.