Aiming at the effect of converge laser light scattering caused by subsurface micro-defect, and the change rule of laser scattering modulation was studied. First, the geometry model is built by defect type; then, by finite element method based on electromagnetic theory, the scattering light intensity distribution and variation curve with different detection defect depth, which convergence light spot focus on, were researched by numerical simulation. Finally, simulation model was verified by comparing experiment. This research results are important to setup the mathematical relation between subsurface defect and light scattering, and realize quantitative detection for the subsurface defect of optical element.
It is important for particle detection technology to research the polarization properties of particle’s scattered light and explore the relationship between particle size and polarization degree of its scattered light. Particle scattering model was established and polarization properties of spherical particle’s scattered light with different sizes and different scattering angles was simulated using the finite element method. The polarization degree of particle scattered light were explored with different sizes, also were the polarization degree with different scattering angles. Results show that relationship curves between polarization degree and scattering angles can be described as parabolas. Polarization degree increases when scattering angles increase in the range of 0°-90° and reached the maximum value at 90°. Polarization degree decreases when the size of particle increase and this change more obvious gradually. The polarization degree of particle scattered light reached 1 at 90°when the particle size is much smaller than the wavelength and the maximum value of polarization degree decreases gradually when particle size increase further. In order to verify the correctness of the finite element simulation model, the polarization degrees were calculated in different particle sizes and different scattering angles by classical Mie scattering theory. Polarization simulation model of particle scattered light is proved to be correct and effective by making comparisons between simulation results and theoretical calculation results. This model lays a foundation for the further research on polarization characteristics of particle scattered light with different morphology and distribution.