Polarization In Light Scattering By Single Particle And Its Application In Interference Particle Imaging

Property of light scattering by a single particle is foundation of measuring particles using optical method.Polarization is an inherent parameter of light and is important in light scattering by particles.Property of polarization in light scattering by particles relates to particle size,refractive index,shape and anisotropy,and has wide applications in two-phase-flow particle measurement,biological tissue detection,and aerosol particle survey,demonstrating its important significance.To study and apply the polarization in light scattering by particles,this dissertation focuses on the polarization property of overall and various orders scattered light using Mie theory and Debye series expansion,and apply it in particle measurement based on interferometric particle imaging(IPI).The main works and innovations are as follows:1.A new organization method is proposed in Debye series expansion(DSE)of a coated particle,using the total times of reflections(N),reflection time on outer interface(M),and the number of chords in the core(X).With this organization,for a coated particle with a highly absorbing core,only one number(M)is necessary for reorganizing the Debye terms.Besides,we found that the coating size has important effects on the intensity distributions of M=0 and M=1 terms.2.For the two polarizations of incident light,i.e.,natural polarized and linear polarized,the polarizations of scattered light are studied.In the former situation,scattered light of droplets has high degree of polarization in side-direction and first rainbow angle,while that in the latter situation is generally elliptical polarized.The polarization degree in the former situation and the elliptical ratio in the latter situation are simulated and analyzed.3.A single-droplet generator(SDG)based on piezoelectric inkjet is developed,and the effects of pulse parameters on single droplets generation are analyzed.The SDG is easy set-up and low-cost,with the advantage of generating various size single droplets under different pulse parameters.The coefficient variation of droplet size is 1.43%,and the stable length of single droplets spray is not shorter than 4.62 mm,demonstrating single droplets are high-quality and expected to be used as a kind of standard liquid particles in the study of light scattering by small particles.4.Effects of polarization on visibility of fringes in IPI are analyzed,and an IPI system with adjustable scattering angle and polarization is set up for experimental verification.For the IPI fringes of the droplets generated by the SDG,the scattering angle of 70° with perpendicular polarization and that 90° with parallel polarization both have good visibility.5.Fringe qualities of wide size range particles in IPI are analyzed,and an extended IPI method with multiple scattering angles and different polariztions is proposed to enlarge the measurable size range.For measuring the water droplets,the measurable size range can be extended to 10?m-1mm using two scattering angles of 70° and 85°,with perpendicular and parallel polarization respectively.Experimental results of standard particles show that,when the refractive index changes,scattering angle of the IPI system should be carefully chosen to keep away from the high intensity rainbows.