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
11 results
Search Results
Now showing 1 - 10 of 11
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 Sampled hard edge reconstruction: Definition of frequency modulation function for a sampling-reconstructing system (not quantized)(17th Congress of the International Commission for Optics: Optics for Science and New Technology, Pts 1 and 2, 1996) Sanz, Inmaculada; Calvo Padilla, María Luisa; Chevalier Del Río, MargaritaItem Applications Of Optical Image Processing For The Determination Of The Optical Properties Of The Cellular Membranes.(10th International Optical Computing Conference, 1984) Carreras Béjar, Carmen; Chevalier Del Río, Margarita; Calvo Padilla, María LuisaIn this paper, we present a theoretical model for the transmission function of a biological cell. Three different cases have been considered: a) Real transmission function, b) Pure phase Object, c) Mixed case where both, real and complex terms are present in the transmission function. We have studied in all those cases the response in the Fourier plane. The comparison of the models proposed above allow us to conclude that the most correct treatment would come from c). Even if the cytoplasm gives the most important contribution, neither the nucleus nor the membrane can be neglected.Item Optical image processing to determine the optical properties of cellular membranes(Applied Optics, 1984) Carreras Béjar, Carmen; Chevalier Del Río, Margarita; Calvo Padilla, María LuisaIn this paper we present a theoretical model for the transmission function of a biological cell. Three different cases are considered: real transmission function, pure phase object, general case, where both real and complex terms are present in the transmission function. In all cases we studied the response in the Fourier plane. Comparison of the proposed models leads us to conclude that the most correct treatment would come from the general case, where it was found that the membrane contribution predominates in the total diffracted amplitude distribution.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 Resolution criterion and contrast factor for resolving two-line images under coherent and incoherent illumination(Optics in Complex Systems, 1990) Mondal, Pronab Kumar; Chevalier Del Río, Margarita; Calvo Padilla, María LuisaWe define a resolution criterion for the case of two narrow line images. For doing so, we have considered the two lines as superposition of gradients of two Heaviside step-functions.Item Digitally generated soft edges with predetermined luminance: An analysis of its influence on image degradation.(Sixth International Workshop on Digital Image Processing and Computer Graphics: Applications in Humanities and Natural Sciences, 1998) Sanz, Inmaculada; Calvo Padilla, María Luisa; Chevalier Del Río, MargaritaThe presence of degraded or soft edges on a scene or digital image may cause ambiguities in depth perception(1,2). This kind of edges has been analyzed by introducing a mathematical model to digitally implement a large category of degraded edges. This model has accounted the origin of degradation, the performance of psychophysical test for measuring the degradation perception, and image characteristics currently used in artificial vision as momenta, number of gray scale level per pixels, etc. It is the subject of current researches to be applied to artificial reproduction of human visual perception.Item Influence of Small Phase Variations in the Diffraction Pattern of a Biological Cell(Application of optical instrumentation in medicine XIII: medical image production, processing, and display, 1985) Carreras Béjar, Carmen; Calvo Padilla, María Luisa; Chevalier Del Río, Margarita; Dwyer, Samuel J. III; Schneider, Roger H.In preceding works, a theoretical model has been introduced for the transmission function of a biological cell, in which the physical effects of the three transmission functions for the cytoplasm, the nucleus and the cellular membrane have been considered and studied1. Since biological cells are generally objects having small phase variations, we introduce this specific characteristic in the proposed theoretical model, in the present work, Its Fourier transform is numerically analyzed.