1. CLI Department, University of Paris 8, 93200 Saint-Denis, France
2. Laboratoire Analyse, Géométrie et Applications, University of Sorbonne Paris Nord, 93430 Villetaneuse, France
3. Fondation Hopale, 62608 Berck, France
4. Laboratory for Integration of Systems and Technology, CEA, 91120 Palaiseau, France