AUTOFOCUS DEVICE

PROBLEM TO BE SOLVED: To prevent degradation of focusing performance in low contrast. SOLUTION: The autofocus device includes an image pickup device which takes an image formed by a photographic optical system, evaluation value-calculation means which calculates a contrast evaluation value in a predetermined area in the image taken by the image pickup device, focusing means which carries out focusing of the photographic optical system, and control means which carries out focusing of the photographic optical system by the focusing means so that the contrast evaluation value calculated by the evaluation value-calculation means is maximum. In the evaluation value-calculation means, the predetermined area is divided into a plurality of areas. The ratio of the difference K between the maximum luminance and the minimum luminance in the every divided area to the difference S between the maximum luminance and the minimum luminance in the predetermined area, K/S is calculated, and the total value of the ratio K/S in the every divided area is the contrast evaluation value of the predetermined area. COPYRIGHT: (C)2010,JPO&INPIT