In this paper we face the problem of positioning a camera attached to the end-effector of a robotic manipulator so that it gets parallel to a planar object. Such problem, so-called plane-to-plane positioning, has been treated for a long time in visual servoing. Our approach is based on linking to the camera a structured light emitter composed of four parallel laser pointers so that its distribution is aimed to produce a suitable set of visual features. The aim of using structured lighting is not only for easing the image processing and allowing low-textured objects to be treated, but also for producing a control scheme with nice properties like decoupling, stability and good camera trajectory. This paper proposes several sets of visual features and analyzes their performance and robustness against different types of calibration errors both analytically and experimentally.
