Fourier Spectrum Analysis Of Space Dynamic Optical Imaging Influenced By Satellite Vibration

The proposal of new dynamic imaging model such as frame push imaging and scanning mirror imaging technology based on space-based optical system makes the realization of high-resolution large-width imaging technology possible.However,the inherent vibrations of the payload components are coupled with the perturbation properties of this new imaging modality,which creates new interference factors that lead to dramatic degradation of image quality and hinder the development of high-resolution remote sensing imaging technology.Therefore,it is necessary to systematically study the degradation influences of satellite vibrations on image quality in new imaging modes.Two parts of work are completed in this thesis: the frame push imaging of CMOS area scan camera and the TDI CCD scanning imaging process in the dynamic scanning mirror imaging process are modeled respectively,and the influence of multi-source vibration on the image quality in the dynamic imaging process is analyzed.In order to study the influence of the camera attitude angle and the error velocity caused by random vibration on the image quality during the frame push imaging process of the CMOS area array camera,the curvature mapping function between the object plane and the image plane is deduced,and singles frame image at different attitude angles are obtained.The frequency domain filtering templates of sub-satellite point imaging and dynamic frame push imaging are constructed,and high-resolution remote sensing images are used as input,the distorted images at different attitude angles and the degraded images interfered by random vibration are output.The simulation results show that:during the frame-by-frame imaging process of the area array camera,the attitude angle changes periodically,then the distorted images under different attitude angles are significantly different.The output image distortion degree increases obviously when the attitude angle increases to 50°,and the image mean square error increases by 5.1958,and the image sharpness decreases,which shows that the camera exposure time and error velocity caused by random vibration directly affect the image sharpness.In order to study the influence of vibration frequency and amplitude on image quality during the scan imaging process of TDI CCD camera,the motion scanning imaging equation of TDI camera is established,a filtering template that combines the amplitude and frequency of the disturbance source is designed,and the image quality degradation model of frequency domain perturbation filter template is proposed.The parameters of the vibration source from 1 Hz to 1000 Hz are obtained by data fitting,and the segmented function is divided according to the scanning line frequency to simulate the output image under multi-source disturbance.The simulation results show that: during the imaging process of the space-based payload scanning mirror,if the vibration frequency is close to the exposure frequency of the camera,the image will be greatly affected by superposition degradation.In the scanning imaging model with an orbit height of 500 km and the camera focal length of 0.5m,when the instantaneous swing angle is 50°,the exposure frequency of the camera is 110 Hz,the vibration whose frequency is close to 110 Hz will aggravate the image deterioration and transfer function curve decreases obviously.Therefore,when the disturbance frequency is close to the space-based scanning frequency,and it has a great influence on the imaging quality.On the basis of qualitative analysis,this paper quantitatively studies the influence of satellite vibration on spatial dynamic remote sensing imaging.The output process of satellite vibration disturbance degraded images in dynamic swing mirror scanning imaging is inverted,and the image degradation mechanism caused by multi-source vibration is analyzed.The research of this topic is of great significance for improving the quality of high-resolution imaging and developing new imaging technologies,in addition,it also provides a theoretical basis for spatial vibration suppression and image quality degradation assessment of new spatial imaging modes.