Optical tracking method based on geometric feature point of the extended target

Optical tracking systems need to measure the shift of target in real time so as to compensate the shift effect. For extended target, template matching techniques are usually used to estimate the image shift, in which the shift can be computed up to subpixel with the parabolic interpolation. In this paper, we propose a new method to estimate the shift accurately building on geometric feature point tracking. The method first extracts feature points from the reference image using Harris detector, and tracks the same feature point by correlating the small patch around it with that of each point detected in other images. The subpixel feature point position utilized to estimate the image shift is then determined by the modified Harris strength of the pixels around that point. Experimental results validates that the proposed method can accurately measure image shifts over large distance under noisy conditions, and that the mean of estimate error is less than 0.03 pixels. Moreover, the contrast of long exposure images before and after shift compensation is compared to evaluate our algorithm in the optical tracking system.