Orientador: Clesio Luis Tozzi / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-10T17:08:02Z (GMT). No. of bitstreams: 1 Nogueira_FernandoMarquesdeAlmeida_D.pdf: 5973806 bytes, checksum: ec2975af264084ab2665aa65eca49541 (MD5) Previous issue date: 2007 / Resumo: Este trabalho apresenta uma nova abordagem iterativa e hierárquica para a obtenção de mapas densos de disparidade, a partir de um par de imagens estereoscópicas retificadas, na qual oclusões são explicitamente identificadas. Esta abordagem se fundamenta num processo de busca hierárquica onde são determinados pares homólogos prioritários sobre os quais é aplicada a Injunção de Ordem. Pares homólogos prioritários consistem nos pontos que apresentam a propriedade de Correspondência Bidirecional para o maior número de janelas de busca organizadas em ordem crescente de tamanho. A aplicação da Injunção de Ordem aos pares homólogos prioritários elimina, já nas primeiras iterações, uma grande quantidade de correspondências ambíguas aumentando o índice de acertos e reduzindo o tempo de processamento. A abordagem proposta destaca-se pela utilização de apenas dois parâmetros que devem ser fornecidos a priori de maneira empírica: o tamanho inicial da janela e o número de níveis hierárquicos. A eficiência do algoritmo proposto foi avaliada a partir de imagens reais e simuladas e os resultados comparados com outras abordagens descritas na literatura / Abstract: This work presents a new hierarchical and iterative approach to obtain dense disparity maps from a pair of rectified stereoscopic images in which occlusions are explicitly identified. This approach is based on a process of hierarchical searching where priority matches are determined and upon which is applied the Order Constraint. Priority matches consist of points that present a property of Bidirectional Correspondence for the greatest number of searching windows, these ones organized in a size ascending order. The Order Constraint application on the priority matches eliminates, usually after the first iterations, a lot of ambiguous matches, increasing the rate of true matches and reducing the execution time. The proposed approach stands out by using only two parameters that must be provided a priori in an empirical way: the initial window size and the number of hierarquical levels. The efficiency of the proposed algorithm was evaluated using real and simulated images and the results were compared to other approaches described in the literature / Doutorado / Automação / Doutor em Engenharia Elétrica

O desenvolvimento da realidade virtual permitiu experimentos psicofísicos inéditos, como o aqui descrito, cujo objetivo foi investigar a microgênese da percepção visual de profundidade decorrente de disparidade binocular. Tais processos ocorrem em etapas, com construção gradual do percepto. Experimentos já indicavam a percepção da profundidade em etapas precoces do processamento visual. Isso é confirmado neste trabalho, realizado com tecnologia que garante a estimulação visual exclusivamente por disparidade binocular. Para isso, foram desenvolvidos hardware e software específicos que permitem o controle preciso dos tempos de estimulação binocular e a medida confiável de tempos de reação. Resultado significativo deste trabalho foi também a validação dessas ferramentas, possibilitando estudos futuros de psicofísica em realidade virtual. Finalmente, são sugeridas as cautelas necessárias em experimentos dessa natureza, tanto para a proteção dos participantes contra condições desconfortáveis ou aversivas, como para a seleção de participantes sem déficits funcionais de estereopsia. / Virtual reality technology opened up the possibility of novel psychophysiscal investigations. This work describes a research on the microgenesis of depth perception, as induced exclusively by binocular disparity. Such processes occur in early stages, whereby the percept is gradually built. Previous experiments indicated that depth perception is perceived in early stages of visual processing. This conclusion is now confirmed by the present work, carried out with a technology that guarantees visual stimulation exclusively by binocular disparity. Specific hardware and software were developed, to permit accurate timing of binocular stimulation and reliable measurements of reaction time. A significant result of the present work was the validation of these new tools. Finally, the results also allow suggesting the precautions necessary in the execution of experiments of this type, both to protect participants from possibly uncomfortable or aversive situations, and also to select participants without functional stereopsis deficits.

Objective of this master's thesis is developing and describing of human vision process and anaglyph production. The text contains individual possibilities of achieving spatial sensation from two two-dimensional images. This thesis contains an application for the anaglyph creation developed in the Matlab 2008b interface and description of its functions and properties. Created anaglyphs and the source code sample are attached. The electronic version of the thesis and application are available on the attached DVD.

This thesis concern physiology of binocular vision, tools for recording, processing and reproduction of stereoscopic dynamic records. The thesis describes design and realization of recording tool which uses couple of digital still video cameras as stereoscopic video recorders. The thesis deals with the software capabilities of image processing in Matlab and presents possible solutions in the form of a program for creating stereoscopic video in various formats. In the thesis is presented in detail passive projection techniques O anaglyph and polarization method. Has been designed and constructed projection tool uses the light polarization to obtain stereoscopic vision and then has been objectively and subjectively evaluated qualities of both methods in survey with group of observers.

This paper follows up theme of binocular vision and his working in daily life. The individual chapters contain anatomy and physiology of visual organ. In detail are discussed physical principles of binocular vision. Discussed are also development, eventual pathologies and examination methods of human binocular vision. Theoretical introduction defines the concept of stereoscopy and states overview of stereoscopic imaging methods. Paper also includes approaches to recording of three dimensional image and camera settings. Practical part of work is dedicated to the selection of shooting methods and design of dynamic scenes from daily traffic. Introduced is also the projection method of captured scenes to the group of viewers. The last chapter analyzes the method and evaluation of the experiment itself and the resulting conclusions.

Purpose: It is unknown whether individuals with two balanced eyes show quicker response and lower threshold in fine stereoscopic detection. Previous methods to measure ocular dominance were primarily qualitative, which do not quantify the degree of dominance and show limitation in identifying the dominant eye. In this study, we aimed at quantifying the difference of ocular strength between the two eyes with ocular dominance index (ODI) and studying the association of ocular balance between the two eyes with stereoscopic detection. Methods: Stereoscopic threshold was measured in thirty-three subjects. Stereopsis was measured with random dot stimuli. The minimal detectable disparity (Dmin) and the minimal time needed to acquire the best stereoacuity (Tmin) were quantified. Ocular dominance was measured by a continuous flashing technique with the tested eye viewing a titled Gabor patch increasing in contrast and the fellow non-tested eye viewing a Mondrian noise decreasing in contrast. The log ratio of Mondrian to Gabor’s contrasts was recorded when a subject just detected the tilting direction of the Gabor during each trial. The t-value derived from a t-test of the 50 values obtained in each eye was used to determine a subject’s ODI (ocular dominance index) to quantify the degree of ocular dominance. A subject with ODI ≥ 2 (p < 0.05) was defined to have clear dominance and the eye with larger mean ratio was the dominant eye. Results: The Dmin (55.40 arcsec) in subjects with two balanced eyes were not significantly different from the Dmin (43.29 arcsec) in subjects with clear ocular dominance (p = 0.87). Subjects with two balanced eyes had significantly (p = 0.01) shorter reaction times on average (Tmin = 138.28 msec) compared to subjects with clear dominance (Tmin = 1229.02 msec). Tmin values were highly correlated with ocular dominance (p = 0.0004). Conclusion: Subjects with two relatively balanced eyes take shorter reaction time to achieve optimal level of stereoacuity. Keywords: Ocular Dominance, Local Stereopsis, Binocular, Balanced Eyes, Anisometropia

No description available.

Yes / Motion in depth (MID) can be cued by high-resolution changes in binocular disparity over time (CD), and low-resolution interocular velocity differences (IOVD). Computational differences between these two mechanisms suggest that they may be implemented in visual pathways with different spatial and temporal resolutions. Here, we used fMRI to examine how achromatic and S-cone signals contribute to human MID perception. Both CD and IOVD stimuli evoked responses in a widespread network that included early visual areas, parts of the dorsal and ventral streams, and motion-selective area hMT+. Crucially, however, we measured an interaction between MID type and chromaticity. fMRI CD responses were largely driven by achromatic stimuli, but IOVD responses were better driven by isoluminant S-cone inputs. In our psychophysical experiments, when S-cone and achromatic stimuli were matched for perceived contrast, participants were equally sensitive to the MID in achromatic and S-cone IOVD stimuli. In comparison, they were relatively insensitive to S-cone CD. These findings provide evidence that MID mechanisms asymmetrically draw on information in precortical pathways. An early opponent motion signal optimally conveyed by the S-cone pathway may provide a substantial contribution to the IOVD mechanism. / Supported by the Biotechnology and Biological Sciences Research Council Grants BB/M002543/1 (to A.R.W.), BB/M001660/1 (to J.M.H.), and BB/M001210/1 (to M.B.). / Research Development Fund Publication Prize Award winner, May 2019.

Impairment of stereoacuity is common in the elderly population and is found to be a risk factor for falls. The purpose of these experiments was to extend knowledge regarding impairment of binocular vision and adaptive gait. Firstly using a 3D motion analysis system to measure how impairment of stereopsis affected adaptive gait during a negotiation of a step, secondly by determining which clinical stereotest was the most reliable for measuring stereoacuity in elderly subjects and finally investigating how manipulating the perceived height of a step in both binocular and monocular conditions affected negotiation of a step. In conditions of impaired stereopsis induced by acutely presented monocular blur, both young and elderly subjects adopted a safety strategy of increasing toe clearance of the step edge, even at low levels of monocular blur (+0.50DS) and the effect was greater when the dominant eye was blurred. The same adaptation was not found for individuals with chronic monocular blur, where vertical toe clearance did not change but variability of toe clearance increased compared to full binocular correction. Findings indicate stereopsis is important for accurately judging the height of a step, and offers support to epidemiological findings that impaired stereoacuity is a risk for falls. Poor agreement was found between clinical stereotests. The Frisby test was found to have the best repeatability. Finally, a visual illusion that caused a step to be perceived as taller led to increased toe elevation. This demonstrates a potential way of increasing toe clearance when stepping up and hence increase safety on stairs. / The Study data files are unavailable online.

Impairment of stereoacuity is common in the elderly population and is found to be a risk factor for falls. The purpose of these experiments was to extend knowledge regarding impairment of binocular vision and adaptive gait. Firstly using a 3D motion analysis system to measure how impairment of stereopsis affected adaptive gait during a negotiation of a step, secondly by determining which clinical stereotest was the most reliable for measuring stereoacuity in elderly subjects and finally investigating how manipulating the perceived height of a step in both binocular and monocular conditions affected negotiation of a step. In conditions of impaired stereopsis induced by acutely presented monocular blur, both young and elderly subjects adopted a safety strategy of increasing toe clearance of the step edge, even at low levels of monocular blur (+0.50DS) and the effect was greater when the dominant eye was blurred. The same adaptation was not found for individuals with chronic monocular blur, where vertical toe clearance did not change but variability of toe clearance increased compared to full binocular correction. Findings indicate stereopsis is important for accurately judging the height of a step, and offers support to epidemiological findings that impaired stereoacuity is a risk for falls. Poor agreement was found between clinical stereotests. The Frisby test was found to have the best repeatability. Finally, a visual illusion that caused a step to be perceived as taller led to increased toe elevation. This demonstrates a potential way of increasing toe clearance when stepping up and hence increase safety on stairs.