Three-Dimentional Imaging Based On Interferenceless Coded Aperture Correlation Digital Holography

Incoherent holography enables the recording and 3D reproduction of holograms from incoherent light sources or self-emitting objects,breaking the traditional holography requirement of high coherence of light sources and extending the application of digital holographic 3D imaging in the field of incoherent imaging such as fluorescent biological sample imaging and natural scenes imaging.Aperture-encoded incoherent correlation digital holography based on phase mask modulation is a three-dimensional computational imaging technique that does not require scanning of the sample.Three incoherent digital holography techniques have been developed based on different coded phase masks,Fresnel Incoherent Correlation Holography(FINCH),Coded Aperture Correlation Holography(COACH)and Interferenceless Coded Aperture Correlation Holography,(I-COACH).I-COACH is a new incoherent digital holography technique proposed in recent years,with the advantages of high axial resolution(compared FINCH),wide spectrum and 3D fast imaging.I-COACH technique uses the GS algorithm to obtain a pseudo-random coded phase mask(CPM)to modulate the object field and obtain point spread hologram(PSH)and object hologram(OH),and then reconstructs the 3D object information by the PSH and OH cross-correlation method.However,the CPM obtained by the iterative GS algorithm does not satisfy the bandwidth constraint of the spatial spectral domain well and causes a large degree of background noise in the hologram cross-correlations of the COACH system.Meanwhile,the existing reconstruction methods such as pure phase filtering and nonlinear reconstruction methods are unable to suppress the hologram reconstruction noise and result in serious background noise in the reconstructed image.Therefore,this paper focuses on the acquisition method of high signal-to-noise ratio reconstructed images of I-COACH system and the improvement of the imaging performance of the system,and the main research contents and results are summarized as follows:1.Research on reconstruction image quality improvement method based on phase encoding mask optimization.The relationship between the sparsity of the randomly sparse CPM and the high-quality reconstructed image at different axial planes is studied through simulations and experiments。Then,the CPM with an annular sparse system response is further obtained through the modified GS algorithm.The modulation transfer function characteristics of annular sparse CPM and random sparse CPM with the same sparse points are experimentally investigated.In order to avoid the problem of stagnation caused by the initial phase of the traditional GS algorithm,the random phase with band-limit constraint and the special quadratic phase are set as the initial phase of the GS algorithm,and the amplitude iteration constraint is added to approximately satisfy the GS algorithm spectral bandwidth condition,so that the algorithm can converge fast and the root mean square error of the CPM obtained is greatly reduced.The hologram of the I-COACH system with high signal-to-noise ratio is obtained,which improves the quality of the hologram reconstruction.2.High quality 3D reconstruction method for single exposure holograms.Firstly,by analyzing the frequency domain modulation characteristics of different modulation parameters of the I-COACH single exposure nonlinear imaging method and introducing noise suppression parameters in the optimized reconstruction algorithm to improve the reconstruction model,a nonlinear optimized reconstruction method is proposed,and an improvement of more than 20% in the peak signal-to-noise ratio of the reconstructed image is obtained.Through the theoretical analysis of the pure phase filter reconstruction method of I-COACH system hologram and the problem of this reconstruction method is pointed out.A new single-exposure hologram phase filter reconstruction method is constructed by combining the wiener filter method,and the special parameter reconstruction image in the nonlinear reconstruction is determined as the modified phase filter adaptive parameter ξ.In this way,a fast and adaptive I-COACH single-exposure hologram reconstruction method with high quality is obtained synthetically.Combining the application of compression perception in non-coherent digital hologram imaging,the compressive sensing model of I-COACH system is theoretically established for the first time under compression perception theory system,By compressed reconstruction of single-exposure holograms,the highest quality reconstructed image of single-exposure holograms in the current I-COACH system is obtained experimentally.3.Research on depth-of-field extension method for interferenceless coded aperture correlation holography imaging system.Based on the foundation of the previous work,we try to develop the application demand research of I-COACH technology for endoscope and telescope.Through the theoretical calculation of the I-COACH imaging system,the source of the axial aberration of objects in the image sensor plane at different axial positions in the system is determined.Combined with the principle of wavefront encoding imaging technology,a annular multifocal phase mask with large depth of field,low scatter,and high energy efficiency is theoretically synthesized and used as an optical pupil function for the I-COACH system,and the effectiveness of the proposed method for depth of field expansion of the I-COACH system is demonstrated in simulation and experiment.Further,the imaging depth problem of the radial quartic phase function(RQPF)is optimized,and a modifiedquartic phase function(M-RQPF)phase mask design method is derived,and the M-RQPF has a continuous depth-of-field expansion capability,and the simulations and experiments demonstrate the capability of the M-RQPF method for I-COACH system depth-of-field expansion.The simulations and experiments demonstrate the ability of M-RQPF method to expand the depth-of-field of I-COACH system.