ABSTRACT
Light scattering techniques using visible and near visible wavelengths are popular for studying particulate systems such as sprays, clouds and powders. Scattering techniques can be non-intrusive i .e . without physical probes that disturb the sometimes delicate hydra-and aero-dynamics of the system under investigation. For particles of size of order microns, choosing visible wavelengths makes the scattering efficient and strongly dependent on particle properties such as size. However the stronger the interaction the more likely that multiple scattering will be a problem. If each photon interacts with only one particle (i .e , single scattering) it arrives at the detector carrying unambiguous information about that particle. If on average it interacts with more than one particle (multiple scattering) the information it carries relates to all of these particles and may be ambiguous or difficult to interpret. Most popular techniques assume single scattering. As the particle concentration increases, at some level this assumption will become inadequate. This paper is concerned with estimating the error due to multiple scattering in planar Mie images of sprays,
In planar Mie imaging a laser beam is formed into a thin sheet which illuminates a plane in the particulate field. A camera, axis perpendicular to the light sheet, images the scattered light. The image yields information about the spatial distribution of particles in the illuminated plane. If the particle size is known the concentration can be quantified. The optical setup of planar Mie imaging is the basis of other imaging techniques which yield other quantities, e.g. planar laser induced fluorescence.
