Research On Image Restoration Technology Of Synthetic Aperture Imaging System

With the continuous development of space science and technology,the resolution requirements of optical system in such fields as space observation and space remote sensing are becoming higher and higher.According to Rayleigh rule,when the wavelength of the optical system is fixed,the resolution can only be improved by increasing its aperture.However,the space system has strict restrictions on the volume and weight of its optical system,so the large aperture optical system is gradually developing towards the direction of small volume and light weight.In addition to the limitations of processing technology,materials,processing cost and other factors,scientists have proposed synthetic aperture technology,which has successfully overcome the complex processing technology,high processing cost,and volume and weight excess Major constraints.The characteristics of synthetic aperture imaging also determine its own defects.Because the system is to partially fill its equivalent large aperture,resulting in the reduction of the light area.When the filling factor is small,it will lead to a very serious decline in the medium and low frequency during the formation process,or even may be missing,resulting in a decrease in the contrast of the imaging results and image blur.In order to obtain a satisfactory imaging result,image restoration plays an indispensable role in SAR imaging.In this paper,the synthetic aperture system is studied in the following aspects:(1)Firstly,the basic principle of synthetic aperture imaging is analyzed,and the corresponding imaging model is established.The influence of some parameters of synthetic aperture,such as aperture arrangement,filling factor and cut-off frequency,on its imaging quality is analyzed.Using MATLAB to design the simulation software of synthetic aperture,the imaging simulation of the synthetic aperture system with different arrangement structure and filling factor is carried out,and the ideal point spread function and modulation transfer function are obtained.Then,the real point spread function is obtained by experiments and compared with the simulation results.(2)The synthetic aperture imaging system is to partially fill its equivalent single aperture,which leads to the reduction of its luminous area and the reduction of its ability to obtain image information.In order to obtain a larger field of view of the synthetic aperture system,it is necessary to reduce its filling factor.However,when the filling factor of the system is small,the modulation transfer function of the system is very serious in the low and medium frequency,and even the phenomenon of low and medium frequency loss occurs,which leads to a very serious degradation of image quality.General image restoration can not restore the low-frequency loss of the image,so this paper uses the characteristics of single aperture system which has a good response to the low-frequency,proposes a method based on the image fusion of single aperture system and synthetic aperture system to compensate the low-frequency loss of synthetic aperture system,and obtains the simulation results,which is effective for this method Verification of.(3)Finally,the traditional image restoration algorithm is applied to restore the image based on the compensation of medium and low frequency.Due to the influence of many noises on the imaging results of the synthetic aperture system,a proper filter is selected before the image restoration,which not only ensures that the image noise is well suppressed,but also ensures that the structure of the image is not damaged.Finally,after preprocessing,Wiener filter restoration,R-L restoration based on maximum likelihood and TV regularization restoration are applied to the image results.The restoration results of different algorithms are compared and analyzed,and the restoration quality is evaluated.