Modeling image center and feature trajectory under changing focal length

Camera calibration is an important task in a computer vision system. This step establishes the all important relationship between the 2D image coordinates and their 3D counterparts and vice versa. Image center is subject to many different definitions. Moreover, its location is subject to a drift in most variable parameter lenses. This drift has an adverse effect on algorithms that rely on the a fixed center of image. A geometric model is presented that describes the trajectory of feature points in response to changing focal length under a shifting image center