Non-invasive Optical Imaging With Extended Fourier-domain Shower-curtain Effect

"Flowers in the fog are not flowers,and the moon in the water is not the moon." Those words describe something appears to be illusory,impenetrable,and unattainable due to the influence of the scattering medium.Occurring in daily life and scientific research,this kind of situation affects the quantity and quality of people's access to world information,such as deep-sea exploration,star observation,travel and telephoto in haze,and observation of lesions under biological tissues.When the photon transmits through the scattering medium,it will interact with the scattering particles,and its transmission direction will become randomized,therefore changing the information of the incident light field.This phenomenon is called "Light Scattering".How to realize optical imaging through scattering media is a very challenging and significant subject,which has important application value in the fields of medical diagnosis,military defense,and security monitoring.In recent years,some effective methods have been proposed to deal with scattering imaging tasks from specific scenarios,such as optical coherence tomography based on the selection of scattered photons,wavefront shaping based on phase conjugation,scattering transfer matrix method based on transmission matrix measurement,speckle autocorrelation method and speckle deconvolution method based on memory effect.These technologies have their own advantages and disadvantages,but they also have a difficulty in practical applications.It is difficult to deal with the problem that the spatial correlation of speckles and the quality of restored images is reduced because of the scattering of dynamic systems.In this thesis,the work mainly revolves around how to solve the scattering imaging in dynamic systems.First,for the scattering of static scattering media,two scattering imaging techniques based on the optical memory effect-speckle deconvolution and speckle autocorrelation are introduced to verify the efficiency of the former and introduce the latter's the core technology-Phase Recovery Algorithm.Then,theoretical derivation and experiments verified the speckle autocorrelation based on the Fourier-domain Shower-curtain Effect(FDSE).This method develops the classical Spatial-domain Shower-curtain effect(SDSE)to the spatial frequency domain and proposes the concept of the Fourier shower curtain effect.Taking advantage of shower curtain effect immunes to the dynamic scattering medium,this method well overcomes the problem of image quality degradation caused by the dynamic scattering medium.However,this method has specific limitations on the optical path device(requirements for the first scatterer)and limitations in the imaging distance.Based on the full demonstration of its optical path theoretical model,this paper exploits the Fourier transform characteristics of the positive lens to propose an improved strategy which can break through the original limitation.The new method has been verified theoretically and experimentally that it can realize the imaging recovery of objects at any distance behind/between the scattering mediums without any limitation of the first scatterer.Through the random translation of the diffuser and/or imaging target(simulating the dynamic situation),combining with the phase recovery algorithm can realize the non-invasive optical imaging of static/dynamic objects between dynamic/static scattering media.In addition,this paper firstly proposes a new integrated transceiver scheme to effectively image objects completely hidden by dynamic scattering media.Finally,this paper guesses a new scatter transmission model.Based on this new model,the original and improved FDSE-based speckle autocorrelation techniques have been derived and quantitatively analyzed by the scalar diffraction of the light field.The quantitative effect of the positive lens in the improved scheme is explained.In summary,this article proposes an improved FDSE-based speckle autocorrelation technique,which effectively realizes the imaging recovery of objects behind or between the scattering media in the dynamic scattering system.It has some advantages: non-invasive,low-cost,simple operation,high resolution and so on.This method will have an important value in the fields of medical diagnosis,security monitoring and military defense.