Imaging Method Of Digital Holography With Irregular Phase Aberration

Digital holography is a kind of modern computational imaging technology,which has the characteristics of fast and flexible,digital focusing,and can obtain the intensity image and quantitative phase image of the object simultaneously.It is a phase imaging technology with application prospect in many fields such as biomedicine,Marine biology,micro-nano materials and photonics.The research on digital holographic imaging mainly focuses on improving resolution,eliminating conjugate image and reducing speckle noise,etc.However,the effect of irregular phase aberration caused by the surrounding medium is seldom considered in the current digital holographic imaging.In practical applications,especially in large field of view imaging,the phase aberration caused by the surrounding medium will have a great impact on the quality of digital holographic imaging,and even can make the traditional digital holographic imaging method invalid.In this thesis,the high resolution large field of view digital holographic imaging method is developed for overcomeing the influence of irregular phase aberration,and improving its practicability.In this thesis,the principle,algorithms and performance characteristics of the digital holography are systematically studied,and the effects of irregular phase aberration on digital holographic imaging are studied through theoretical analysis and numerical simulation.The results show that the effect of the phase aberration on the reconstructed image is mainly concentrated in the conjugate image,and the recording distance of the imaging system should be minimized when there is irregular phase aberration.In-line digital holograms can be recorded at a smaller distance than off-axis digital holograms.Therefore,the elimination method of the conjugate image of in-line digital holographic is focused in this thesis for overcomeing the influence of irregular phase aberration.Fistly,the elimination method of the conjugate image based dual-plane recording is developed.In order to overcome the problem that traditional dual-plane digital holography is only suitable for on-axis interferometer,a generalized reconstruction algorithm is proposed based on the dual-plane recording and digital reference wave.The simulation and experiments show that this method is valid for both on-axis and slightly off-axis recording setup.The effect of eliminating conjugate image and the resolution are the same as the traditional dual-plane on-axis digital holography,which is equal to the pixel size of the image sensor.For imaging the object with irregular phase aberration,a stochastic dual-plane on-axis digital holographic imaging method is proposed.Base on the dual-plane digital holography,the object is illuminated by a stochastic beam that is a speckle wave produced by a ground glass,and then the imaging quality of the intensity image of the object with irregular phase aberration is greatly improved.Secondly,an in-line and off-axis hybrid digital holography is proposed by combing with the off-axis digital holography based on constrained optimization and in-line digital holography based on phase retrieve.The method requires recording an off-axis hologram and an in-line hologram.The approximate phase distribution of object waves in the recording plane is obtained from the off-axis hologram by the constrained optimization algorithm.The approximate phase and the intensity of the in-line hologram are synthesized into the initial value of the complex amplitude of the object wave in the recording surface.Then the phase retrieval iterative algorithm is used to realize the high resolution reconstruction of the intensity image and phase image.Two kind of reording setups and reconstruction algorithms for the hybrid digital holography are presented in the thesis.One is to record the in-line and off-axis holograms by two shots using a single wavelength light source.The other is to produce the in-line and offaxis holograms respectively by different color lasers,and record them simultaneously by a color digital camera.Numerical simulation and experimental results show that this method has both the advantages of in-line digital holography and off-axis digital holography.The low-frequency phase information can be reconstructed well as the offaxis digital holography,the resolution and the imaging field is the same as the in-line digital holography.High resolution and large field of view digital holographic imaging for dynamic objects can be realized by using dual wavelength recording setup.Finally,the in-line and off-axis hybrid digital holography is applied to the imaging of the objects with irregular phase aberration.The compensation method for irregular phase aberration is studied.A compensation method based on principal component analysis is proposed.Numerical simulation and experimental results show that,the inline and off-axis hybrid digital holographic imaging method combined with principal component analysis phase aberration compensation method can be used to imaging of the objects with irregular phase aberration.