A new method for three-dimensional shape recovery from image focus is proposed. The method is based on approximation of the focused-image surface (FIS) by a piecewise curved surface that tracks the realistic FIS in image space. The piecewise curved surface is estimated by interpolation using the Lagrangian polynomial. The new method has been implemented on a prototype camera system. Experiments and their results are described and discussed. The results show that the new method is more accurate than previous methods.