US Patent 7860385 Autofocus system

When it is detected that a tracking target disappears in an image range in the course of tracking the tracking target, which is a registration pattern selected as a target to be tracked from among registration patterns, an autofocus is disabled. Thereafter, the autofocus is kept being disabled even if it is detected that the tracking target having the selected registration pattern appears in the image range. Alternatively, when the tracking target disappears in the image range in the course of tracking the tracking target, the autofocus is disabled, and thereafter when the tracking target having the registration pattern appears in the image range, it is started to track the tracking target having the registration pattern.