Research On Imaging Characteristics And Image Quality Enhancement Of High Resolution Pupil Rotation Optical Sensing System

Pupil rotation optical imaging system can realize the equivalent aperture imaging of rectangular long side with different angles by rotating through the center of rectangular pupil.It is a new imaging system to realize ultra-high resolution and ultra-large aperture optical load in space.Compared with the traditional system,it is light in weight,short in processing cycle,easy to carry and low in cost.So it is an important development direction of imaging payloads of ultra high resolution optical satellites in geostationary orbit.However,the degradation characteristics of the optical remote sensing imaging system with large aperture pupil rotation are complicated due to the coupling effects of pupil rotation,detector sampling,satellite platform motion and vibration during in-orbit imaging.Therefore,it is necessary to study the in-orbit imaging quality degradation characteristics of large aperture pupil rotation optical system and propose the image quality enhancement method.The main research work is as follows:(1)This thesis proposes an imaging characteristics analysis of high-resolution pupil rotation optical imaging system.Firstly,starting from the principle of system imaging,the imaging mechanism of the optical system is analyzed,and the Point Spread Function(PSF)characteristics of the rectangular optical pupil of the optical imaging system are analyzed by using the pupil autocorrelation theory.Secondly,the influence of platform vibration on the in-orbit imaging quality of the system is considered,and the image shift of the system is analyzed.Finally,combining the coupling relationship between the image shift generated by the platform vibration and the PSF of the rectangular pupil,an analysis model of the influence of image shift on the in-orbit imaging quality of the system is established.It provides theoretical basis for the establishment of system image simulation model and the study of image quality lifting method.(2)This thesis establishes the image simulation model and method for simulating the high-resolution optical pupil rotation imaging system.Based on image quality degradation mechanism,in orbit around the image link in platform vibration,optical system imaging detector and photoelectric transformation and sampling link of detector,on-orbit imaging features of the system to establish high resolution pupil rotating geometric quality of optical imaging system simulation model and the radiation quality simulation model,and using the simulation model to carry out the on-orbit imaging simulation,analyzed the platform vibration amplitude,vibration frequency and rotating velocity of pupil,the influence of parameters on the system imaging quality.By comparing the simulation results with the theoretical analysis of imaging characteristics,the correctness and effectiveness of the simulation model and method are illustrated,and a priori input is provided for the subsequent research on image quality improvement methods.(3)This thesis establishes the image quality lifting model and method of pupil rotation optical imaging system.Based on the analysis of the imaging characteristics of the system,an image registration model is established to restore the spatial correlation of the degraded image information of the system under different rotation angles of the rectangular pupil.On this basis,the high-resolution information of all directions of the target scene obtained by the system within one rotation period of the rectangular pupil is used to establish the image restoration model incorporating the prior regular term of the gradient distribution of the direction of the scene,so as to realize the restoration of the degraded image of the system during the single rotation period of the rectangular pupil.Furthermore,based on the convex set projection principle,an image super-resolution reconstruction method is established,and the sub-pixel sampling information between the images is restored by using multiple rotation cycles of rectangular pupil to realize the super-resolution processing of the image.(4)This thesis proposes experimental verification and analysis.To accurately assess high-resolution pupil rotating optical imaging system as qualitative methods for performance,like mass ascension method validation experiment scheme design system,choose the peak signal-to-noise ratio(PSNR)and visual information fidelity(VIF),structural similarity(SSIM),spatial frequency(SF),enhance resolution ratio before and after the evaluation of image quality evaluation indexes such as improve image quality.Experimental results show that the method proposed in this paper can improve the image quality of high-resolution pupil rotation optical imaging system.Under the condition of 0.2 pixel image registration accuracy,the image PSNR index can be improved by more than 12%,SSIM index can be improved by more than 11% and VIF index can be improved by more than 20%.The image resolution can be improved by more than 1.5 times.The experiment verifies the effectiveness of the image quality lifting method for the high resolution optical remote sensing system with pupil rotation.It provides support for the practical space application of high-resolution pupil rotation optical imaging technology in geostationary orbit.