A Direct Visual Servoing Scheme for Automatic Nanopositioning

This paper demonstrates an accurate nanopositioning scheme based on a direct visual servoing process. This technique uses only the pure image signal (photometric information) to design the visual servoing control law. With respect to traditional visual servoing approaches that use geometric visual features (points, lines ...), the visual features used in the control law is the pixel intensity. The proposed approach has been tested in term of accuracy and robustness in several experimental conditions. The obtained results have demonstrated a good behavior of the control law and very good positioning accuracy. The obtained accuracies are 89 nm, 14 nm, and 0.001^° in the x-, y -, and θ-axes of a positioning platform, respectively.