Former To The Wide-angle Light Scattering Submicron Particle Size Test Methods

The problem of accurate measurement of micron-sub-micron particle size arosepeople's attention greatly in producing and science research, It has influence on the development of many fields, such as environmental protection, industrial production quality control, medical treatment etc.The measurement method by light scattering is advanced, widely used and prospective. The measurement results to used the instrument based on the principle of Fraunhofer diffraction are exact in the range of above 5 microns, but not of less than 5 microns. To solve the problem, one of the main research work is to find a method which improve system based on Fraunhofer diffraction.The measuring principle used light scattering of sub-micron particles, theory of light scattering and its algorithm are introduced in this paper. The sizing method based on Fraunhofer diffraction is limited. Because of the limitation of size parameter a ?1 and size of photodetector, it can't measure the particles less than 5 microns accurately. To extending lower limit of measurement, Inverse-Fourier- Transform technique is discussed. We find that the change of distance between lens and sample cell will result in the change of lower limit of measurement. Analysis of Mie theory indicate that, at the position of 7?angle relative to optical axis, normalization light scattering energy increases followed by the increase of particle size, but at the angle of 35?, the trend is opposite. So we using large-angle experiment system detect light scattering in side direction, the purpose is to study the problem of sub-micron particle size measurement.The system is composed of Inverse-Fourier-Transform system, optic fiber sensor and high sensitivity CCD. Its software system of signal acquisition and data processing used the platform of virtual instrument LabVIEW. We tested system stability and investigated latex particle size from 32nm to 123nm, several phenomenon below have been found:(1) The experiment result is consistent with the theoretical arithmetic result of the relation between particle size and normalization light scattering energy at the position of 7?and 35?angle. Maybe we can get the particle size by analysis of normalization light scattering energy at angle 7?and 35?.(2) Samples are measured in static state. At the angle of 7?, the smaller of particle size, the bigger of light scattering energy jumpiness, which reflectsJJE (% Hi})' '&' A'^ tjjij ri.'ff-'fe ift A' _ Abstractthat brownnian motion of small particle is more acute than big particle's. We can get information of particle size with the measuring jumpiness of light scattering energy. (3) There is a relation approximate to exponential function between particle sizeand jumpiness of light scattering energy.At last, we given several conceives for the follow-work, and hope to obtain more monodisperse standard samples which particle size is from 0. lum to 3um in the future, so we can find the relation between light scattering energy and energy jumpiness more accurately.fl no-Wi rfcce z^fiq Shec...