Digital image restoration requires some knowledge of the degradation phenomena in order to attempt an inversion of that degradation. Typically, degradations which are included in the restoration process are those resulting from the optics and electronics of the imaging device. Occasionally, blurring caused by an intervening atmosphere, uniform motion or defocused optics is also included. Recently it has been shown that sampling, the conversion of the continuous output of an imaging system to a discrete array, further degrades or blurs the image. Thus, incorporating sampling effects into the restoration should improve the quality of the restored image. The system transfer function (the Fourier transform of the point spread function), was derived for the Landset Multi-Spectral Scanner and Thematic Mapper systems. Sampling effects were included, along with the relevant optical, instantaneous field of view and electronic filter data, in the system analysis. Using the system transfer function, a least squares (Wiener) filter was then derived. A Wiener filter requires the ratio of the power spectra of the scene and noise, which is often, for simplicity, assumed to be a constant over frequency. The restoration method used here includes models for the power spectra which are based on the study of several different types of Landsat scenes. The Wiener filter is then inverse Fourier transformed to find a restoration filter which is spatially windowed to suppress ringing. Qualitative and quantitative evaluations are made of the restored imagery. Comparisons are made to the approaches taken by other investigators, in particular, to one who has had success restoring the same type of imagery. It is found that the restoration method used here compares favorably with this previous work.

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Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 73-77). Also available via the Internet.

Thesis (M.S)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 100-104). Also available via the Internet.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 167-176). Also available via the Internet.

Coded-aperture systems are indirect imaging systems that have been used to image x-ray and (gamma)-ray sources. Coded aperture systems are also capable of recording tomographic information and because they involve no detector motion they are natural candidates for use in dynamic studies in nuclear medicine. Computer simulations suggest that an orthogonal-view coded-aperture system, which circumvents the problem of limited angular view, is capable of restoring clinically useful tomographic information. The restoration is performed with the aid of the iterative back-projection algorithm which is shown to yield the Moore-Penrose generalized inverse in the limit of many iterations. The convergence behavior of this algorithm is also examined. In order to improve reconstructions, the problems of optimizing coded aperture design is addressed. The concept of "alignment" is introduced in which the aperture parameters are adjusted until the system is tuned to measure well the object class of interest. A mean-square error figure of merit is derived that indicates the degree of alignment of a system. Aperture design may then be seen as a multidimensional optimization problem in which system parameters are adjusted in order to find a global minimum value for the figure of merit. The figure of merit presumes the use of an optimum restoration filter in the reconstruction process. Various restoration algorithms are suggested which fulfill this requirement. Finally, simple proof-of-principle simulations are given that demonstrate a degree of plausibility to the alignment approach.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisors: Alan C. Bovik and Lawrence K. Cormack. Vita. Includes bibliographical references.

Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, Dec. 2004. / Thesis Advisor(s): Philip A. Durkee. Includes bibliographical references (p. 35-36). Also available online.

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