US Patent 7557855 Focus position detection apparatus and method

A focus position detection apparatus calculates a focus position of a focus lens using an image signal obtained from an image sensing element. The apparatus comprises an acquisition unit that acquires focus states for a predetermined distance range, a control unit that controls the acquisition unit to acquire focus states at first intervals and second intervals which is shorter than the first intervals, and a focus position detection unit that determines a focus position on the basis of the focus states obtained at the first or second intervals. The control unit changes whether to acquire focus states at the second intervals based on the focus states obtained at the first intervals.