Person: Chevalier Del Río, Margarita
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First Name
Margarita
Last Name
Chevalier Del Río
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Medicina
Department
Radiología, Rehabilitación y Fisioterapia
Area
Radiología y Medicina Física
Identifiers
5 results
Search Results
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Item Theoretical approach to hyperacuity tests based on resolution criteria for two-line images(Proceedings of Holography, Interferometry, and Optical Pattern Recognition in Biomedicine, 1991) Mondal, Pronab Kumar; Calvo Padilla, María Luisa; Lakshminarayanan, Vasudevan; Chevalier Del Río, MargaritaResolution criteria for resolving two line images under coherent and incoherent illumination are presented. This technique has been used to interpret psychophysical data obtained from hyperacuity paradigms.Item Edge image processing: An analysis of modified heaviside functions as degraded edge generators(17th Congress of the International Commission for Optics: Optics For Science And New Technology, Pts 1 And 2, 1996) Manzanares Ituarte, Ana; Calvo Padilla, María Luisa; Chevalier Del Río, Margarita; Lakshminarayanan, VasudevanItem Line spread function formulation proposed by W. H. Steel: A revision(Applied Optics, 1997) Manzanares Ituarte, Ana; Calvo Padilla, María Luisa; Chevalier Del Río, Margarita; Lakshminarayanan, VasudevanA revised formulation of the image Light distribution of an incoherent line source proposed by Steel [Rev. Opt. 31, 334-340 (1952)] is presented. Analytical and numerical results based on this new representation are given. We explicitly show that a major error in Steel's final expression generates singularities, thereby preventing convenient numerical computation.Item Edge image quality assessment: a new formulation for degraded edge imaging(Image and Vision omputing, 1998) Manzanares Ituarte, Ana; Calvo Padilla, María Luisa; Chevalier Del Río, Margarita; Lakshminarayanan, VasudevanWe discuss a formalism to characterize degraded edge images formed in a diffraction limited system (with circular pupil of unit radius) under conditions of incoherent illumination. We introduce a novel definition of degraded edges and consider this approach to model a basic optical mechanism involved in the perception of visual depth and edge detection. We introduce a degradation parameter to quantize the degree of edge blur. We present a generalization of such a procedure by assuming the Heaviside function to be a systematic generator of degraded edges. We reproduce experimentally the predictions made by the formalism proposed herein.Item Perception of high-contrast blurred edges(Journal of Visual Communication and Image Representation, 2001) Sanz, Iván; Chevalier Del Río, Margarita; Lakshminarayanan, VasudevanObserver sensitivity to edge blur has been examined by experimental measurements of threshold blur as a function of contrast. An extension of previous results from Watt and Morgan for high-contrast blur edges is discussed and analyzed. We propose a psychophysical test based on a two-alternative forced choice test. The results found for three adult observers show a comparable behavior. A tendency for the blur threshold to reach an average value as contrast increases is mainly discussed. These results complement previous ones from other authors for which low- and intermediate-contrast ranges were analyzed. The observed behavior suggests a need to improve algorithms for image quality assessment, extending the actual range of contrast values to high-contrast ones.