Graduate theses
Current Record: 1272 of 1665
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Identifier |
000341167 |
Title |
Επίδραση της ανομοιομορφίας του πλέγματος των φωτοϋποδοχέων στη διακριτική ικανότητα |
Alternative Title |
The effect of asymmetry in the photoreceptor mosaic on visual resolution |
Author
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Θεοδωράκης, Μ.
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Thesis advisor
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Παλλήκαρης, Ιωάννης
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Abstract |
It is known that the packing geometry and density of photoreceptors have an
effect on the spatial resolution of the human visual system. The primary
objective of this work is to evaluate the effects of deviations in the spatial
symmetry of the photoreceptor mosaic on spatial resolution.
To this end, the reported shape and spacing of cone photoreceptors are
examined in the foveal, parafoveal and peripheral retina and compared against
the normally perceived spatial resolution.
Especially in the fovea, this is done assuming a symmetrical hexagonal
photoreceptor mosaic and alternative models of retina tiling that result in
quasi-symmetrical patterns of photoreceptors, without change in the mean
cone density.
It is verified that there is uniformly less aliasing reported for high spatial
frequency stimuli, than would be expected if the sole limitation were the cone
Nyquist frequency.
In the fovea, when the optics as a limiting factor is bypassed, aliasing is
produced only slightly above the Nyquist limit.
Parafoveally, where the departure from symmetry is significant, the cone
Nyquist limit is more easily overcome.
In the periphery, aliasing never appears, but this is due to the scarcity of cones
and great increase in receptive field size and neural undersampling.
Therefore, it is assumed that the asymmetry in cone packing is a significant
factor in detecting and understanding stimuli exceeding the Nyquist limit,
along with ocular movements and higher processing in the visual cortex.
Research that would help elucidate its exact effect should encompass
alternative asymmetrical models of retina tiling, the effective application of
blind deconvolution techniques in real time experiments and the evaluation of
natural imagery, whose power spectrum seems to be more efficiently rendered
on asymmetrical mosaics.
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Language |
Greek |
Subject |
Ophthalmology |
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Vision physiology |
Issue date |
2006-08-04 |
Collection
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School/Department--School of Medicine--Department of Medicine--Post-graduate theses
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Type of Work--Graduate theses
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Notes |
Διατμηματικό-μεταπτυχιακό πρόγραμμα σπουδών: "Οπτική και Όραση" |
Permanent Link |
https://elocus.lib.uoc.gr//dlib/6/3/d/metadata-dlib-d140e3c969f8a418eb4324db5eb9975a_1236844797.tkl
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Views |
181 |