This paper is about a control law design closed by vision, to allow a mobile robot to maintain itself in front of the observed object with an imposed distance. The proposed application rests on the use of the stereoscopic vision system embedded on the mobile robot which provides informations on the distance and the direction of the observed object compared to the mobile robot. The proposed state feedback control law is based on a linearized model that separates distance and direction controls thanks to longitudinal and angular velocities.