A relational approach to zoom tracking for digital still cameras

Zoom tracking is becoming an integral part of any digital still camera. Zoom tracking involves the automatic adjustment of the focus motor in response to the zoom motor movements for the purpose of keeping an object of interest in focus. In this paper, we have introduced a new zoom tracking approach, named relational zoom tracking, where an estimate of a trace curve is obtained by using so called relational curves. A trace curve denotes focus motor positions versus zoom motor positions for a given object distance, whereas a relational curve denotes focus motor positions versus object distances for a given zoom motor position. The hardware implementation of this algorithm on a digital still camera is also provided in this paper. The obtained results show that the developed zoom tracking approach provides higher tracking accuracies as compared to the conventional zoom tracking methods while generating comparable or better tracking speeds.