Patent ID: 8917334

Claim:
An image tracking device, comprising: an image sensor that acquires image information in an image field formed by an imaging optical system; a tracking subject detector that detects a position of a tracking subject in the image field based upon reference image information related to an image of the tracking subject and the image information acquired by the image sensor; an acquisition unit that acquires focal distance information and photographic distance information with regard to the imaging optical system from the imaging optical system; and a magnification detector that calculates a magnification of the imaging optical system based upon a ratio of the focal distance information to the photographic distance information acquired by the acquisition unit, wherein the tracking subject detector determines whether or not the calculated magnification of the imaging optical system is greater than a predetermined value, starts operation to detect the position of the tracking subject when determining that the calculated magnification of the imaging optical system is greater than the predetermined value, and does not start the operation to detect the position of the tracking subject when determining that the calculated magnification of the imaging optical system is smaller than the predetermined value.