Superresolution imaging through atmospheric turbulence

The angular resolution of an imaging system is ultimately limited by diffraction effects related to the size of the image pupil once imperfections such as aberrations in the optical surfaces, grainy film, and noisy electronics have been eliminated. However, because of scatterings by turbulence, aerosols, and other inhomogeneities, the atmosphere diminishes the spatial coherence of propagating radiation and reduces the achievable resolution. Improving our ability to see through the atmosphere is of unmeasurable usefulness in astronomy, satellite imaging, remote detection, and all other areas in which high-resolution is desirable.; Methods such as wave front correction via adaptive optics and techniques like the Knox-Thompson speckle interferometry method have already shown good improvement in compensating for resolution loss due to the turbulent atmosphere.{dollar}sp{lcub}1-5{rcub}{dollar} Although these techniques are having revolutionary effects on astronomic imaging, they are by no means a complete solution for atmospheric imaging. Adaptive optics requires complicated and expensive equipment and necessitates that the viewed object be either within close proximity of a bright star or that a laser guide star be generated.{dollar}sp{lcub}6-8{rcub}{dollar} Likewise, Knox-Thompson-type techniques also need a bright point source in order to obtain the ensemble average of the squared Fourier transform of the point-spread function. There is such a vast and diverse need for atmospheric imaging that the development of complimentary tools in this area is of undeniable importance.; The research described in this dissertation was aimed at developing improved methods of seeing through atmospheric turbulence. In specific the use of the turbulence induced and Fourier extrapolation superresolution effects were investigated for their potential in improving achievable image resolution of reconstructed images. These effects allow the possibility of achieving resolution beyond the imaging system's diffraction limit via post-processing of the captured images. Incorporating statistical knowledge of the stochastic nature of the atmosphere's effect on short- and long-exposures into the restoration techniques was also examined as a method of increasing resolution performance beyond current restoration capabilities. The research introduction presented in Chapter 1 gives a more in depth description of the research content of this dissertation presented in Part ?? of this work and how it is broken up into chapters.; Background information relevant to this dissertation is covered in Part I. Included is a description of the model used for both the local turbulent inhomogeneities of the atmosphere and the atmosphere's gross structure. A brief overview is given of the methods used to describe wave propagation through the atmosphere in a statistical sense and specifically how the extended Huygen-Fresnel principle and structure functions can be used to describe imaging problems. Methods of phase screen generation and their use in computer simulation of atmospheric imaging are described. Finally a description of the principles behind the predominant image restoration methods in current use is given. (Abstract shortened by UMI.)...