Based on the framework of the curve extraction algorithm developed in Ref.

and using the convergence mapping from the tripe point subset to the elliptical parameter set provided by the geometric properties on the pole and polar line of an ellipse

a new method to robustly and directly extract the ellipses of targets is presented. Compared to the old indirect method developed in Ref.

the new method has the attractive advantage of making sure the results of every mapping to be the valid elliptical parameters. The extensive experiments for the images exactly simulated by PC computer and for the real images have demonstrated that the method is very robust

fast and exact.