Dispersed particle size measurement is crucial in a variety of applications,
be it in the sizing of spray droplets, tracking of particulate matter in
multiphase flows, or the detection of target markers in machine vision systems.
Further to sizing, such systems are characterised by extracting quantitative
information like spatial position and associated velocity of the dispersed
phase particles. In the present study we propose an imaging based volumetric
measurement approach for estimating the size and position of spherically
dispersed particles. The approach builds on the 'Depth from Defocus' (DFD)
technique using a single camera approach. The simple optical configuration,
consisting of a shadowgraph setup and a straightforward calibration procedure,
makes this method readily deployable and accessible for broader applications