Inversion algorithm for estimating particle size information from scattering properties. Keywords: Particle size distribution, scattering, Vis/NIR spectroscopy, inversion algorithm, fitting Major/minor: Biosysteemtechniek – Agrovoeding/Nanotechnologie; Statistiek Abstract Microstructure properties are very important quality parameters for materials in industry, medicine and agriculture. The forward relation between the physical microstructure of materials and their scattering properties can be well described with for instance Mie scattering theory. Nowadays, it is possible to measure the scattering properties of various materials with accurate, non-destructive and fast techniques. Therefore, the inversion of Mie theory would clear the way for the in-line estimation of physical microstructure information from measured scattering properties. As scattering measurements are typically performed over a range of wavelengths (e.g. Vis/NIR), and the effect of wavelength on the scattering properties is inversely proportional to the effect of particle size, the scattering spectra can be consulted to estimate the particle size distribution (PSD) of the scattering particles. In this thesis, an analytical approximation of Mie theory will be consulted to relate the size of a spherical scattering particle with its scattering properties. An inversion algorithm will be developed based on the promising Philips-Twomey regularization in combination with a non-negative least squares fitting approach to estimate the PSD from measured scattering spectra. Initially, this approach will be followed to estimate predefined PSD’s (Weibull, lognormal, normal, …). Later on, it will be extended to also include a shapeindependent model based on spline functions. This approach will be validated on an available set of simulated and measured scattering spectra for fat-in-water emulsions (milk, intralipid, …) and nanoparticle suspensions. Promotor: Prof. Wouter Saeys BIOSYST - MeBioS (Mechatronics, Biostatistics and Sensors), KU Leuven Kasteelpark Arenberg 30 Box 2456, B-3001 Leuven, Belgium Tel: +32 16 328527 e-mail: [email protected] website: http://www.biw.kuleuven.be/biosyst/mebios/biophotonics Supervisor: Dr. Ben Aernouts BIOSYST - MeBioS (Mechatronics, Biostatistics and Sensors), KU Leuven Kasteelpark Arenberg 30 Box 2456, B-3001 Leuven, Belgium Tel: +32 16 321470 e-mail: [email protected] Contact: [email protected]