Diffraction Analysis for Particle Sizing
The use of laser diffraction to measure a particle size distribution (PSD) is a mature technique that relies on the solution of an ill-posed problem. To calculating a PSD, an m×n scattering matrix A is generated using an appropriate scattering theory. The measured scattering data provides the right hand side b of an ill-posed problem Ax=b, the solution x gives the PSD. The calculation of x in the next generation of instrument requires two areas of study. Firstly, the suppression of background artifacts in b will help calculate a more accurate PSD. A recent development at Malvern has suggested that scattering pattern symmetry holds information which can allow scattering source identification. Methods for leveraging this information to both suppress unwanted artifacts and correct the parameters used in the matrix generating approximations should be developed. Secondly, the approximations by which A is generated will be investigated. Currently, Mie’s solution or the Fraunhofer approximation are used. Investigating novel modeling methods to expand the applicability of the diffraction sizing technique would be necessary. Finally, knowledge gained in these areas should be applied to solve problems with the current generation of sizing instrument and inform novel optical designs in the next.