Patent ID: 8363108

Claim:
An autofocus system comprising: an image pickup unit that takes an subject image formed by an optical system; an autofocus unit that performs focus adjustment of the optical system so as to bring into an subject in a predetermined auto focusing (AF) area in each of photographing images taken by the image pickup unit; a tracking unit that moves the AF area to follow a movement of the subject in a range of a photographing screen of the image pickup unit; a reference pattern registering unit that registers as a reference pattern, an image of the subject which is to be in focus in the photographing images taken by the image pickup unit; and a matched image detecting unit that detects an subject which is matched with the reference pattern in each of the photographing images taken by the image pickup unit, wherein, when an amount of movement of the subject detected by the matched image detecting unit in the photographing screen of the image pickup unit is less than a given value, the reference pattern is updated with the image of the subject that is currently detected, and an AF frame is updated to follow the moved subject, and when said amount of movement is equal to or more than the given value, the tracking unit stops a tracking operation.