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Title: Studies of indirect methods in high-resolution electron microscopy
Author: Chang, L.-Y.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2004
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Since accurate image restoration relies on a detailed understanding of imaging models, this thesis commences with a discussion of the partial coherence effects in an electron microscopy. The various approximations which have been developed to describe the effects of partial coherence in image formation are reviewed, and the validity of these expressions when applied to imaging at high resolution is examined. Accuracies and efficiencies of different calculation approaches, are also compared. Hence a computationally efficient alternative algorithm for incorporating the effects of partial coherence in calculations of high-resolution electron images has been developed. Both linear (the Wiener filter) and nonlinear (the MAL algorithm) image restoration methods are then discussed and compared. The significance of the nonlinear contributions to image intensities in a linear restoration is firstly investigated and the performance of the linear Wiener filter in dealing with the nonlinear contribution is assessed. Finally, the nonlinear image restoration method of the MAL algorithm has been developed using a general underlying imaging model. The performance of the MAL restoration method is then investigated through both qualitative and quantitative comparisons. Comparisons between a linear restoration and a nonlinear MAL restoration are also discussed for both simulated and experimental defocus series.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available