Experimental Study On Focusing Of Light Through Scattering Medium Using Optimization Algorithm

Multiple scattering occurs when light passes through the scattering medium.This phenomenon severely impairs the penetration depth and imaging resolution of light in the medium,especially in some important applications where light is transmitted through the scattering medium for focusing and imaging.Photodynamic therapy,optogenetics,aperture and fluorescence imaging.Emerging wavefront shaping technology is expected to solve thisproblem.It uses a spatial light modulator and an optimization algorithm to control the amplitude and phase of the light wavefront,thereby overcoming the effects of multiple scattering.However,the current research on this technology is still in its infancy in China,and it still lacks detailed basic experimental research.Based on extensive literature research on wavefront shaping technology,this dissertation focuses on the basic research contents of the following two aspects:First,increase the focus depth study.As we all know,longer wavelength lasers have deeper penetrating depth.Therefore,we use a 1550nm wavelength laser as a light source,DMD as a light modulation device,a genetic algorithm,and a binary amplitude modulation method to perform the experiment of focusing light through a strong scattering medium,and obtain a light transmission thickness of 456?m of zinc oxide sample.That is,the light is focused on the other side of the strong scattering medium.This is the maximum thickness of a light-diffusing medium that can be achieved using the wavefront shaping method reported in the literature at the same time,and it also realizes focusing of light at any position and multi-point focusing.Second,iterative optimization algorithm is developed with better anti-noise performance.Although the genetic algorithm has better anti-noise performance than otheralgorithms,such as sequence optimization algorithms,the effect of noise in the laboratory environment is still very serious,so we have researched and developed a particle swarmalgorithm with better anti-noise performance.And conducted an experimental study.Inexperiments,the anti-noise performance of particle swarm optimization and geneticalgorithm was compared.It was found that the improved particle swarm optimizationalgorithm has obvious advantages in anti-noise performance compared to genetic algorithm.