1. Optoelectronics and Measurement Techniques, University of Oulu, 90570 Oulu, Finland
2. VTT Technical Research Centre of Finland, Kaitovayla 1, 90590 Oulu, Finland
3. Department of Histology, Cytology and Embryology, Institute of Clinical Medicine N.V. Sklifosovsky, I.M. Sechenov First Moscow State Medical University, Trubetskaya Street 8, 119991 Moscow, Russia
4. Institute of Engineering Physics for Biomedicine (PhysBio), National Research Nuclear University (MEPhI), Kashirskoe Shosse, 31, 115409 Moscow, Russia
5. CNRS, LP3, Aix-Marseille University, 163 Av. de Luminy, 13009 Marseille, France
6. College of Engineering and Physical Sciences, Aston University, Birmingham B4 7ET, UK