The disclosure relates to measuring devices that are particularly suited
for the purpose of in-situ characterization of particles present in fluid
substances or in air using a low-coherence interferometer. Specifically,
the characterization includes average size, size distribution, volumetric
density, and composition. The low-coherence interferometer utilizes a
split band of radiation to illuminate a sample probe and a reference probe
then combines the reflected radiation from both probes to determine the
photon pathlength distribution of the tested particulate or colloidal
containing stream and from this information determine the size
characteristics of said stream. The methodology is relevant to possible
spatially distributed control of chemical processes such as emulsion
polymerization to produce paints, coatings, synthetic rubbers, or
crystallization processes in pharmaceuticals, food, and bulk chemicals
industries. Another application relates to on-line control of particle
size and volumetric density is in combustion for diagnostics. The
invention can be used for the characterization of coal particles, dense
sprays and solid propellants or any other system, which is too dense for
conventional optical measurement techniques. Beside the intrinsic
particulate nature of these systems, random index of refraction variations
are also created due to turbulence/temperature interactions. The remote
optical characterization of systems with high-concentration of suspended
solids is also important for water quality control and pollution
monitoring.
