1. Department of Basic and Applied Sciences for Engineering, SAPIENZA Università di Roma, via A. Scarpa, 16, 00161 Roma, Italy
2. Department of Mechanical and Aerospace Engineering, SAPIENZA Università di Roma, via Eudossiana, 18, 00184 Roma, Italy
3. Fraunhofer Institute for Applied Optics and Precision Engineering, A.-Einstein-Str. 7, 07745 Jena, Germany