Systems and methods to achieve an auto-focus camera with a movable lens barrel having a mechanic shock detection capability combined with a re-initialization of the camera module have been disclosed. This re-initialization may comprise moving the lens barrel displaced by the shock to a home position. In a preferred embodiment of the invention a motor with integrated position detection has been used. In a normal operation the position detection feature senses the actual position of the lens, e.g. during auto-focusing of the lens barrel, and provides this position information to a control unit which is controlling the movement of the lens barrel to a target position. In case of a mechanic shock, e.g. if the camera module drops to ground, the control unit detects an extreme rapid displacement of the lens barrel and initiates a re-initialization of the camera module.