Research On Scattering Focusing And Imaging By Digital Optical Phase Conjugation

Digital optical phase conjugation technology originated from the optical phase conjugation technology in holographic technology,which is an optoelectronic technology that uses spatial light modulators to produce phase conjugate light.Digital optical phase conjugation technology can focus through the scattering media,so it has widespread application in many fields such as holographic recording,scattering imaging,and biological imaging.There is a hot research topic in this field that using of digital optical phase conjugation technology to achieve scatter-focused imaging and improve its performance indicators.The current research mainly focuses on the speed of focus,imaging through scattering media and imaging quality of digital optical phase conjugation technology.However the optical depolarization introduced by the scattering medium is usually not considered in the existing technical methods,which results in errors of focus and imaging.In addition,the errors of alignment between the modulation surface and the measuring surface also result in errors of experimental result.To resolve above problems,this paper proposes theories and methods for improving the performance of focus and imaging through scattering media based on digital optical phase conjugation experiments,the specific methods are as follows:1.Based on the scalar and vector scattering matrix theory,the scattering effect of the scattering medium on the light is analyzed.Through theoretical calculation and analysis,it is concluded that the part of scattering medium will affect the polarization direction of the scattered light.On this basis,the realization process of digital optical phase conjugation is calculated,and computer simulation is used to verify the realization of imaging through scattering media.The theoretical calculation and simulation results show that based on the digital optical phase conjugation technology,it is possible to realize focusing or imaging,and the alignment error in the experimental system will have a great impact on the experimental results.2.Designed an experimental setup based on digital optical phase conjugation to achieve focusing through scattering media,analyzed the effect of optical elements in the experimental system on the experimental results,and it is concluded that errors of alignment between the modulation surface and the measuring surface result from the lens and reflector.Then,this paper proposed to use Zernike polynomial to fit the error between the modulation surface and the measurement surface of the system.In the experiment,firstly,the focusing through scattering media is realized based on the DOPC technology,and on this basis,the QPSO algorithm is used to reduce the size of the optimized focal spot by about 33% compared with the unoptimized one.The experimental results show that the alignment problem of DOPC system can be optimized based on QPSO algorithm.3.Based on the vector scattering matrix,the optical depolarization caused by scattering medium is analyzed,and the conclusion is that,because of optical depolarization,scattering media will change the polarization state of the linearly polarized light into the elliptically polarized light.In order to recover the information of scattered light maximally,an experimental system based on DOPC for imaging through the scattering medium is designed to realize the holographic recording and conjugate playback of the scattered light with two orthometric polarization.The experimental results show that imaging through scattering media with two orthometric linearly polarized light performs better.In summary,this article has intensive researched on the field of digital optical phase conjugation theory based on scattering matrix,analysis and solution of error of experimental alignment,focus through scattering media,and extensively discussing the DOPC technology in the perspective imaging theory and experimental system.The above results have positive effects on the further development and application of digital optical phase conjugation technology.