Study Of Scattering Imaging Methods Based On Transmission Matrix And Memory Effect

The disordered media leads to distortion of beam,which makes wavefront distribution completely unpredictable and limits the ability of light to transmit energy and information greatly.In recent years,optical focusing and imaging technologies based on disordered scattering media have developed,overcame some shortcomings of traditional optical systems such as low resolution and limited observation depth when imaging through scattering media.These technologies have shown important value in the fields of biomedicine,life science and materials science.However,these studies are still relatively few,including the theoretical basis of light propagation characteristics,transmission and scattering characteristics.Therefore,in order to further study the modulation methods of disordered media using different control technologies,explore transmission characteristics of light and tap the potential of optical information processing,this paper launches research focused on these issues from the theoretical and experimental perspectives.The theoretical research on the propagation of light through a disordered scattering media is taken from the wave equation.Based on the point source scattering model,the form of space-frequency domain Green's function is studied.The field and intensity transmission characteristics of light in finite and infinite media are discussed by introducing boundary conditions.After that,the idea of using Green's function to solve the wave equation in homogeneous media is improved and the propagation of light in disordered media has been discussed as well.A method for modeling disordered scattering media as a set of scattered light points is introduced to simplify the calculation.According to the concept of coherent transmission,a solution to the global average Green's function of light field propagation in a disordered scattering media is introduced,with this,the transmission of a light passing through a media can be defined.This thesis discussed the statistical characteristics of optical speckles with a large number of composed random walking in optical speckles.The statistical analysis of the phasor sum shows that the joint probability density of the speckle's real part and the imaginary part satisfies the "circular" complex gaussian distribution,and meanwhile the speckle's intensity distribution satisfies the negative exponential probability density distribution.The optical transmission matrix plays an important role in describing the transmission characteristics of light in a scattering media.In this paper,by combining the full-field phaseshift interference method and the Hadamard optical multi-channel measurement technology,an experiment is designed to realize the measurement of the transmission complex matrix of disordered media samples made of zinc oxide particles.The thesis achieved the light field control of disordered media with transmission matrix theory and digital optical phase conjugation theory,thus the pure phase pattern can be recovered from the disordered speckle image.At the same time,the beam can be focused and imaging at any specified position on the detection plane.In the experiment,by analyzing the media channel information contained in the transmission matrix,the wavefront optimization method is used to increase the signal-to-noise ratio of the adjusted outgoing light.In addition,the relationship between the light fields transmitted and reflected by the disordered media is explored from the perspective of the transmission channel,and the mutual mapping coefficients between the channels are also calculated to reflect the negative correlation between the transmittance and the reflectance.This paper exploits the optical memory effect to recovery the objects hidden by a thin scattering media.Which the optical memory effect makes the scattering imaging system linearly invariant within a certain range.If a system's point spread function is obtained in advance,imaging recovery after the scattering media can be achieved through deconvolution.In this paper,it starts with the iterative recovery imaging method using multi speckle patterns' cross-correlation based on the optical memory effect.And then it has been proposed the measurement of point spread function of the full-field scattering imaging system based on the correlated imaging method.Aiming at the time-consuming disadvantage of multi speckle patterns or the measurement the PSFs,this paper optimized the recovery algorithm model and improved the iterative process.With the help of GPU hardware and CUDA computing architecture,the image recovery with only one speckle pattern is realized,and the goal of real-time imaging through disordered scattering media is achieved as well.