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Description:
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Three -dimensional surface recovery based on a pair of stereoscopic images is a very well -known ill -posed problem with solutions depending mainly on the correct measures of the shifts between corresponding points (disparities ) in the images acquired by a known imaging system . Noise , occlusions , and distortion present in the pair of images make the task of finding precise disparities difficult and very time consuming .
This work presents a three -dimensional surface restoration method based on the recovery of the optimum surface within a 3 -D cross -correlation coefficient volume via a two -stage dynamic programming technique . This procedure is applied to a set of optic nerve head (ONH ) images , which are used for finding clinical measures of progression of glaucoma . Registration of these types of images is performed through a two -step coarse -to - fine procedure using power cepstrum and cross -correlation operations , while a local registration based on the weighted mean of second -degree polynomials is used for image fitting .
Variations in topography of the ONH can be measured through cup -to -disc ratios which are computed from the 3 -D surface generated from longitudinal stereo disc photographs of glaucoma patients spanning several years . These computer -generated measures of cup -to -disc volume ratios correlate well with the traditional stereo cup -to -disc ratios manually computed from clinical interpretations .
Such algorithmic approach to semi -automated computation of cup -to -disc volume ratios may potentially provide a more precise and repeatable measure of progression of glaucoma than the existing clinical measures . Moreover , the 3 -D surface recovery technique developed in this thesis may provide a general technique for visualizing 3 -D objects in a natural scene . |