The Research On Light Control And Imaging Through Scattering Medium

Light undergos multiple scattering when passing through a scattering'medium,resulting in a strong speckle,which has caused great obstacles to the application of many optical technologies.In recent study,although the scattering medium disrupts the incident light wave,the light information is not lost.The scattering medium can be used to manipulate the light wave and even image.This paper studied the light control and imaging through the scattering medium.Based on the transmission matrix of the scattering medium,it is possible to realize precisely manipulation of the light through the scattering medium,and to reconstruct the image hidden in front of the scattering medium.The specific research contents are as follows:This paper introduced the principle of multiple scattering and wavefront shaping,then modeled the transmission of light through a scattering medium.The scattering medium was modeled as a multi-layer random phase template,and the distance between each layer was expressed by the mean free path of the scattering medium.This paper used the method of angular spectrum to represent the propagation between two layers.Based on the mathematical model,this paper had completed the simulation of the method of three-step phase shift for measuring the transmission matrix of the scattering medium.In the simulation,the inline interferometric device was used to collect the speckle data,and finally calculated the transmission matrix.The method of light control based on the transmission matrix of scattering medium was studied.The derivation of theoretical formula shows that the virtual transmission matrix is calculated by convolving the transmission matrix with the virtual input wavefront.Using the virtual transmission matrix,arbitrary patterns can be generated at different positions behind the scattering medium,so as to realize light control,and the method was analyzed in the simulation.Building an experimental device,this paper had verified that the virtual transmission matrix can be used to generate donuts,crosses and letters behind the scattering medium.The method studied in this paper does not depend on the memory effect of the scattering medium,and is also effective for strong scattering medium.Based on the transmission matrix of the scattering medium,to recover the objects hidden before the scattering medium,the imaging method of through scattering medium was studied.Since the intensity image loses the phase information,the forward model as a non-linear mapping was constructed,and then a generalized phase retrieval algorithm was employed to recover the hidden object.The method was verified and analyzed by simulation.Building an experimental device,this paper had reconstructed a phase object with a size of 32*32 from 150*150 speckle particles in the experiment.