Microscope suffers from the problem of limited depth of focus, which precludes the observation of complete image of a three-dimensional object in a single view. In this paper, extending depth of focus by multi-focus image fusion is investigated. The principle of image fusion based on depth of focus is analyzed, and one spatial domain multi-focus algorithm is implemented. Then a multi-focus micro-image fusion algorithm based on area wavelet transform is presented, which offer improved performance over existi...