Study On Imaging Characteristics And Restoration Methods Of Spatial Large-aperture Mosaic Optical System

With the increasing demand for high resolution and high quality optical remote sensing satellite images,it is urgent to develop very large aperture optical remote sensing imaging load.The splicing optical system has a folding/expansion structure and is flexible in the process of installation and adjustment.It has become an important development direction of large aperture and high resolution optical remote sensing imaging load.Space,however,large diameter splicing imaging system imaging quality acceptor splice lens error and the force of on-orbit thermal environment affect together,its degradation properties than traditional single aperture imaging system is more complex,result in image quality can meet the actual demand,objective interpretation and therefore need to intensify the large-diameter stitching for space optical system imaging features of the study,and on this basis put forward the corresponding method of image restoration.At present,although scholars at home and abroad have carried out partial studies on the imaging characteristics of the splicing optical system,the influence of splicing error and in-orbit degradation coupling factors has not been fully considered,and there are few reports on the study of image restoration methods for the above characteristics.To solve this problem,this paper studies the imaging characteristics and image restoration methods of large aperture optical system,and carries out corresponding experimental verification.The main research contents include:(1)Imaging simulation modeling and characteristic analysis of space large-aperture splicing optical system.Based on the mathematical modeling of the special entrance pupil structure of the mirror splicing optical system,the imaging characteristics of the ideal large-aperture splicing optical system are analyzed,and the variation rules of the point diffusion function and the modulation transfer function of the optical system under the action of three splicing errors,namely piston error,tilt error and sub-mirror gap,are also analyzed.On this basis,based on optical remote sensing of the link,the atmospheric transmission,detector signal sampling,electronics,satellite platform vibration and random noise on image quality and the influence of large caliber splicing coupling optical system imaging features,establish large caliber splicing on-orbit optical system imaging quality degradation model,and analysis the space of large diameter splicing imaging system with image MTF and high frequency information loss serious,texture detail fuzzy,imaging features,such as the high frequency noise,large diameter splicing imaging system for subsequent space prior input image restoration method research.(2)Establishment of image restoration model and method for spatial large-aperture stitching optical system.In view of the imaging quality degradation characteristics of large aperture optical system,ESRGAN is generated based on enhanced super resolution to achieve a balance between the generated network G and the discriminant network D through confrontation training,and the middle and high frequency information of the image is restored.At the same time,for a real recovery image texture details,will be generated by wavelet transform is introduced into the network,through the characteristic figure of degraded image wavelet decomposition,and set the wavelet threshold function to remove high frequency noise,so as to put forward a kind of integrated into the wavelet decomposition and ESRGAN image restoration method of neural network,improve image MTF and restore the image of high frequency information at the same time,guarantee the texture details,the purpose of effectively restrain the high frequency noise.(3)Experimental verification and analysis.Combined with the simulation experiment,the effectiveness of the image restoration method is verified and compared with the processing results of existing restoration methods.At the same time,different image quality evaluation indexes are selected to evaluate the processing results of the restoration method and analyze the processing performance of the restoration method to degraded images under different types and different degrees of stitching errors.Proved through the experiment in this paper,the establishment of a rehabilitation method can effectively restore the texture details of image and edge structures,large diameter splicing imaging system can effectively solve the space image MTF curve that exist in the fall,middle and high frequency texture details such as fuzzy image quality problem,for large caliber splicing optical system of space applications to provide technical support in the future.