PROCEEDINGS ARTICLE | May 8, 2012
Proc. SPIE. 8427, Biophotonics: Photonic Solutions for Better Health Care III
KEYWORDS: Refractive index, Optical spheres, Data modeling, Scattering, Calibration, Water, Particles, Light scattering, Laser scattering, Signal detection
A simple, dual wavelength, multiple-angle, light scattering system has been developed for detecting cryptosporidium
suspended in water. Cryptosporidium is a coccidial protozoan parasite causing cryptosporidiosis; a diarrheal disease of
varying severity. The parasite is transmitted by ingestion of contaminated water, particularly drinking-water, but also
accidental ingestion of bathing-water, including swimming pools. It is therefore important to be able to detect these
parasites quickly, so that remedial action can be taken to reduce the risk of infection. The proposed system combines
multiple-angle scattering detection of a single and two wavelengths, to collect relative wavelength angle-resolved
scattering phase functions from tested suspension, and multivariate data analysis techniques to obtain characterizing
information of samples under investigation. The system was designed to be simple, portable and inexpensive. It employs
two diode lasers (violet InGaN-based and red AlGaInP-based) as light sources and silicon photodiodes as detectors and
optical components, all of which are readily available. The measured scattering patterns using the dual wavelength
system showed that the relative wavelength angle-resolved scattering pattern of cryptosporidium oocysts was
significantly different from other particles (e.g. polystyrene latex sphere, E.coli). The single wavelength set up was
applied for cryptosporidium oocysts'size and relative refractive index measurement and differential measurement of the
concentration of cryptosporidium oocysts suspended in water and mixed polystyrene latex sphere suspension. The
measurement results showed good agreement with the control reference values. These results indicate that the proposed
method could potentially be applied to online detection in a water quality control system.
