Imaging Study Of Radial Multi-mirror Sparse Aperture Array

In order to meet application requirements and acquire high-resolution satellite images,it is necessary to develop a large-aperture,long-focal-length space optical system.However,the limitations of optical materials,processes,manufacturing costs,and volume and weight give the development and development of high-resolution spatial remote sensors.The launch caused great difficulties.Therefore,people have begun to seek new theories and methods to solve the above problems.Among them,the sparse aperture optical imaging system is one of the methods to achieve a large-caliber space optical system,and its research will open up new technical approaches for the realization of high-resolution optical remote sensing systems.In this paper,starting from discussing the imaging principle of the sparse aperture optical system,the sparse aperture array arrangement and sparse aperture image restoration research are carried out.A sparse aperture structure of a radial multi-sub-mirror(MSM)based on a liquid lens is proposed,and the specific structure of the MSM is given.Spatial arrangement,study its modulation transfer function characteristics and simulation imaging performance.Firstly,the problems studied in this thesis are introduced,and the status of research at home and abroad and the significance of selecting topics are introduced.Secondly,the simplified model,basic principle,array design,array optimization and characteristic index of the sparse aperture optical imaging system are discussed,and its modulation transfer function is studied.A sparse aperture structure of a radial MSM based on a liquid lens is proposed,and the mathematical expression of the modulation transfer function of the sparse aperture optical system is given.In order to obtain the universal law of MSM system imaging,the dimensionless method was used to reduce the structural parameters.According to the baseline length statistical distribution graph and the modulation transfer function curve graph,the characteristics and IF characteristics of the structure are analyzed.The sparse aperture array structure of the radial MSM is studied,and the type II radial multi-mirror array arrangement with the least redundancy is obtained by array optimization,which improves the imaging quality of the optical system.Detailed analysis and comparison of the modulation transfer function of the radial MSM and the annular composite sparse aperture structure.The structure and imaging characteristics of the sparse aperture system of a radial MSM based on a liquid lens are introduced.The MSM array structure is simulated and reconstructed.Using ZEMAX optical design software,the modulation transfer function analysis and simulation imaging research of sparse aperture structure and annular composite structure of multiple submirrors with different fill factors are performed.In order to reduce the IF characteristics of the sparse aperture system,the Wiener filter is used to restore the noise image.The standard deviation and the peak signal-to-noise ratio between the sparse aperture imaging system and the single-aperture imaging system are used to evaluate the image quality of the images under different fill factors.The restored images are compared and analyzed to obtain the fill factor and The relationship between image quality.The results show that: due to the uniform distribution of the sub-mirrors of the radial MSM array and the repeated number of each baseline length in the intermediate frequency region,the structure has good intermediate frequency response.The MSM structure(type II-312)has better actual equivalent aperture,actual cut-off frequency,average modulation transfer function,intermediate frequency characteristics,and imaging quality than the composite ring-shape structure.As the sub-aperture diameter increases,the imaging quality of the structure increases.After Wiener filtering,the image quality is improved,and the image restoration effect increases with the increase of the fill factor.