In this paper we describe a method to compute the collineation matrix between two unmatched images of an unknown planar contour described using a B-spline snake. The two images of the contour are matched and the collineation matrix is used to servo a camera mounted on the robot end-effector using a 2 1/2 D visual servoing technique. The experimental results, obtained using common planar objects, show that our method give very good results and allow the robot end-effector to be positioned with a great precision.