Space Target Atmospheric Non-isoplanatic Imaging Simulation Using Ray Trajectory

The earth atmosphere is a typical heterogeneous media where light propagates in will be subject to random perturbations. This effect major reflects in random fluctuation of the wave front of the light, named atmospheric non-isoplanatic effect, and result in greatly reducing of imaging resolution which will inevitably appear in atmospheric optical system such as telescope and aerial mapping system.This thesis considered the atmospheric non-isoplanatic effect and used numerical simulation methods to analysis telescope imaging process under conditions of atmospheric turbulence. The main steps are as follows:Firstly, research the statistical properties of the atmospheric turbulence, and use Fourier transform in frequency-domain and Zernike polynomials expansion in spatial-domain to simulate the mathematical models of atmospheric turbulence phase screen. Moreover take some technical improvements to this two methods.Secondly, analysis the mathematical models of the phase screens, and contrast the similarities of the phase structure function curves to verify the correctness of the resulting phase screens. The results show that both phase screens simulated by different methods conform the statistical properties of Kolmogorov spectrum. Furthermore, both technologies of improved harmonic compensation and increasing the number of Zernike polynomials can improve the performance of simulated phase screen as can be seen from the phase structure function curves.Thirdly, establish the Fresnel diffraction imaging model of ideal telescope system by combining scalar diffraction theory, multi-layer random phase screen theory and ray trajectories equations. Where use scalar diffraction theory to calculate Fresnel diffraction integral formula, and multi-layer phase screen to the atmospheric coherent length, and ray trajectories equations to correspondence of each point on object plane to respective phase screen. This three parts form the research of atmospheric non-isoplanatic effect in this thesis.Fourth, simulate the Fresnel diffraction imaging model of ideal telescope imaging system and analyze the simulation results. Results analysis:1) the results of the diffraction imaging showed simulation parameters can ensure the system diffraction limit;2) speckle imaging results show that atmospheric non-isoplanatic effect of multi-layer phase screen is lower than the single phase screen.