Study On The Mechanism And Key Techniques Of Wide-field Scattering Imaging

When the traditional optical imaging system images the target through the scattering medium,the detector can only observe the speckle pattern and cannot obtain the morphological information of the target.In view of the difficulty of the traditional optical imaging in complex scattering environments,researchers have proposed a speckle correlation imaging method,which utilize the characteristics of similarity between the target autocorrelation and speckle autocorrelation.Only a single frame of the speckle can be measured to obtain a highperformance target Fourier amplitude information,combined with a phase retrieval technology to recover the Fourier phase information of the target.Then we can reconstruct the entire target field information.This method can not only observe the unknown target behind the scattering media,but also needn't to set a reference point.At the same time,the data processing time is short,and it has great practical application potential.However,when the imaging target range exceeds the optical memory effect range,the autocorrelation information of multiple targets in the field of view will be aliased in the Fourier domain,resulting in the inability to obtain accurate target Fourier amplitude information,thus limiting imaging field of view and depth of field.Aiming at the shortcomings of speckle correlation technology imaging with small field of view and short imaging depth,this paper proposes a dual-target imaging method based on the statistical characteristics of speckles.The autocorrelation distribution of speckles generated on the same target using the same statistical characteristics of the scattering media is also consistent.The characteristics of the final realization of a wide field of view and large depth of field imaging through the scattering media.The main work of this paper is listed as follows:(1)Firstly,the causes and statistical characteristics of the speckles are introduced,and the correlation functions of speckles in the horizontal and vertical directions are measured.According to the correlation between different speckle patterns,the optical memory effect range of the scattering medium in the horizontal and vertical directions is measured through experiments,and the corresponding optical memory effect curve is drawn,and the optical memory of the scattering medium is calculated by combining the experimental results and the calculated memory effect angle.(2)According to the strong similarity between different speckles in the range of optical memory effect,the convolution model in scattering imaging is described,and the establishment process of speckle correlation imaging theory is shown.Three commonly used phase recovery algorithms are introduced detailly,and the corresponding constraints are given.Combined with speckle correlation theory and phase retrieval algorithm,the reconstruction effect of speckle correlation imaging is tested from both simulation and experiment,respectively.(3)Study of the wide-field dual-target speckle correlation imaging method based on a priori target,proving the shortcomings of the direct phase retrieval method and the Gaussian kernel fitting method through simulation,and propose a target reconstruction method based on the statistical characteristics of speckle.The final experimental results show that when the a priori target size is between 0.3 to 3 times the unknown target,the proposed method can achieve the structure similarity of the reconstructed target greater than 0.5,and the peak signal-to-noise ratio is higher than 15 d B.(4)On the basis of speckle correlation imaging of dual-target with a wide field of view,a dual-target large depth of field imaging method is proposed.Simulations and experiments have demonstrated that when the center distance of any two target exceeds the range of the lateral memory effect of the scattering media,the imaging depth can be extended to at least13 times of the range of the longitudinal memory effect of the scattering media by using the proposed method in this paper,and the structural similarity of the reconstructed target can reach to 0.5,and we finally achieve speckle achieve imaging with wide field of view and large depth of field.