To overcome the drawbacks of the models of line and parabola when there is an inflection point on the edge

a novel approach to edge locating to sub-pixel accuracy is proposed in this paper. The Levenberg-Marquardt iterative method is utilized to obtain the control points of the cubic Bézier curve. Simulation results illustrate that the determination of the edges is much more accurate than that of the existing approaches when the shape of the fitted edge is close to a cubic with an inflection point on it. The proposed model is based on an ideal step edge; therefore

it will be improved to fit other kinds of edges.