Research On Transient Multi-frame Volume Holography Technology Of High-speed Particle Field

Particle field is an important research object in the fields of biology,aerospace,chemical engineering,medicine,national defense,material dynamic response,etc.It has different features in different fields.In the field of material dynamic response,particle field generally have the characteristics of high speed,small particle size and wide spatial distribution.In response to these characteristics,the film-type pulsed laser holography has long been used in high-speed particle field diagnosis due to its advantages of high spatial resolution,large field of view,three-dimensional diagnosis,and transient exposure.The main recording material used is silver halides dry plate.However,it is difficult to use silver halides dry plate to get multi?holograms for ultrafast processes.Silver halides dry plates for high-speed multi-frame holography mainly include wavelength multiplexing and angular multiplexing.Since the silver halides dry plate can only record thin hologram,it is difficult to completely separate multiple images in the angular multiplexing,which limits the number of frames and the SNR of reconstructions.Similarly,because the silver halides dry plate is a thin holographic material,wavelength multiplexing requires a very large spectral span to achieve,which in turn limits the number of frames and the SNR of reconstructions.In order to solve the problem of frame number limitation,this paper finds inspiration from the field of volume holography.Volume holography is regarded as the core technology of the next generation of read-only storage.Compared with surface storage and two-dimensional recording technology such as thin holography,its biggest advantage lies in the use of depth(volume).Volume holography combined with multiple multiplexing techniques enables very high density storage in the same recording volume.However,the use of the volume holography for high-speed particle field multiple holographic recording has faced many problems,such as insufficient sensitivity of the volume holographic material,single pulse exposure response is not obvious,and the scheme has insufficient applicability.These problems linit the combination of volume holography and high-speed particle field multi-holographic diagnosis.This dissertation is devoted to the combination of particle field holographic diagnosis and volume holography to solve the problem of frame number limitation in high-speed particle field holographic diagnosis.In order to achieve this goal,research has been carried out from theoretical simulation,sensitivity improvement of volume holographic materials,research on influencing factors of volume holographic image recording,design and experimental realization of transient multi-frame volume holographic scheme.In terms of theoretical simulation,this paper draws on Kogelnki's classical coupled wave theory(solving the diffraction of two-dimensional single volume grating)derivation process,re-derives and establishes the coupled wave theory of three-dimensional multi volume gratings which can realize parametric coupling with angular spectrum theory.The numerical solution method and the parametric coupling method with angular spectrum theory are given,and the feasibility of the theory is proved by examples.In terms of sensitivity improvement of volume holographic materials,this paper proposes a new sensitivity test method for testing samples of 49 kinds of volume holographic materials-Through the iterative optimization of the volume holographic formula,three kinds of volume holographic formulations which can achieve high response under single pulse exposure are obtained.The sensitivity test method in this paper is a real-time test method based on dual photo diodes and time division multiplexing.This method can avoid the shortcomings of the existing methods such as installation error,inter-area error and detection light absorption.In the research on the influencing factors of volume holographic image recording,this dissertation analyzes the exposure amount,the divergence angle and the scattering factors after material exposure.Studies have shown that proper exposure to form lower diffraction efficiency is more conducive to accurate reproduction of the image than near the highest diffraction efficiency;when the reproduced light divergence angle is inconsistent with the reference light,it mainly affects the light-dark distribution of the light field,and does not affect the resolution of the reproduction.The scattering factor is one of the factors affecting the contrast of the image reconstruction.The scattering factor requires the minimum diffraction efficiency of each hologram.Through scattering analysis,we finally identified two material formulations that are more suitable for transient multi-frame volume holographic recording.In the aspect of scheme design and experimental implementation,this dissertation designs a particle field transient multi-frame volume holographic recording scheme based on sequential pulsed laser,Pockels cell array and volume holographic angle multiplexing technology.The scheme takes into account the angular multiplexing characteristics of the volume holographic material,the characteristics of the particle field recording,the rapid debugging method of the system and the precise synchronization of the system.Finally,for the high-speed particle field generated by pulsed laser loading,a transient multi-frame volume holographic recording experiment is carried out,and the transient volume holograms of four moments are obtained.The experimental results fully verify the feasibility of the scheme.Through the analysis of the experimental results,the scheme has a large multiplexing potential in the angular space,and more transient holographic recordings can be realized under the condition of sufficient laser energy.