| Size and the refractive index are two important parameters of particles,which have important influence on the physical and chemical properties.The precise measurement of the size and the refractive index,which can determine the particles scale and the composition simultaneously,have great significance in the industrial and agricultural production,scientific research,environmental monitoring and other fields,so it is a hotspot for researching.The particle size measurement by scattering method is widely used,which is based on the particle scattering distribution.But the particle scattering distribution is not only related to the particle size,but also related with the particle refractive index.Therefore,in order to accurately measure the particle size,to asure the refractive index of particle is needed to mearure the particle size.While there is no mature method to measure the particle refractive index.Therefore,this paper focuses on particle size and refractive index measurement.Based on Mie scattering theory and geometric light approximation theory(GOA),the particle size and refractive index methods of scattering spectral imaging of particles are studied in depth.The main work and innovation points are as follows:1.Based on Mie theory and GOA theory,the distribution of light intensity of particles is studied and analyzed.Considering the influence of diffracted light and surface wave,the scattering light intensity calculation method is proposed based on improved GOA theory.The results show that the calculation results are closer to Mie theory.The formula of intensity distribution of scattered light spectrum by Fourier transform is derived.Compared with the method based on GOA theory,the scope of application is larger.2.A new method of particle size measurement based on diffraction spectrum points distance is proposed.According to the Fourier transform of diffraction wavelet,the relationship between diffraction spectrum points distance and particle size is deduced.The proposed receiving parameters to obtain diffraction spectra are scattering angle 4 ? and receive half angle 3 ? obtained by numerical simulation.The experimental system is designed and constructed to measure the particle sizes of the national standard material polystyrene(PSL)particles and glass beads respectively.The error between the measurement results and the nominal value is less than 2.0%,which verified the effectiveness of the diffraction spectrum point method.This method does not need to know the refractive index of particles before and can accurately measure the particle size.3.A refractive index measurement method based on particle scattering spectral point imaging was proposed.The influence of receiving angle and magnification deviation of imaging system on the accuracy of particle refractive index measurement is analyzed.An experimental method for determining scattering angle and amplification ratio based on linear fitting is presented.Based on the autocorrelation method and gaussian interpolation,the spatial distance between two spectral point images is determined accurately.The measurement experiments of PSL particles,glass beads and water drops show that the measurement accuracy can be improved by data fitting.The effectiveness of the proposed method is verified by measuring the sum of standard PSL particles and glass beads.4.A method to measure the particle size and refractive index at the same time is proposed,which receive the scattered light at two scattering angles by the means of dual beams.The size is measured in the scattering angle 90 ? direction,using two spectral reflectance points distance;at the same time,the refractive index is measured using the reflection and refraction of lights' interference fringes in the scattering angle 65 ? direction.The optical experiment system is used to measure PSL particles,glass beads particles and single droplets of national standard substance respectively,which verified the effectiveness of the method. |
PDF Full Text Request