1. Optoelectronics and Measurement Techniques Unit, University of Oulu, 90570 Oulu, Finland
2. Research Unit of Sustainable Chemistry, University of Oulu, 90570 Oulu, Finland
3. Fibre and Particle Engineering Research Unit, University of Oulu, 90570 Oulu, Finland
4. Research Unit of Medical Imaging, Physics and Technology, University of Oulu, 90570 Oulu, Finland