Dissertations / Theses: 'Adaptative field of view'

1

Ducrocq, Julien. "Vision catadioptrique pour favoriser la perception d'environnements hétérogènes." Electronic Thesis or Diss., Amiens, 2022. http://www.theses.fr/2022AMIE0067.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Cette thèse présente les méthodes de conception de deux caméras catadioptriques capables de capturer des images exploitables d'environnements hétérogènes. Ces caméras s'inscrivent dans le domaine de la vision adaptative, qui rassemble les caméras dont la partie optique ou le capteur ont des propriétés hétérogènes qui peuvent varier au cours du temps. Les caméras adaptatives sont capables, entre autres, de capturer des environnements hétérogènes dont les propriétés physiques ou la géométrie varient dans l'espace. La thèse propose une revue de l'état de l'art des caméras adaptatives qui permettent de capturer certains types d'environnements hétérogènes. Dans un premier temps, on considère les scènes caractérisées par une variation spatiale de luminances, d'une gamme dynamique de l'ordre de 120 décibels. Ces scènes mettent en difficulté les caméras conventionnelles, dont les images ont des pixels d'intensité saturée et d'autres trop sombres, à cause de leur dynamique plus faible. Dans les deux cas, ces zones d'image n'apportent pas d'informations visuelles sur la scène, elles ne sont pas exploitables. Afin de capturer les luminances associées à ces zones claires et sombres, les caméras à large gamme dynamique (HDR) sont employées. Néanmoins, à l'heure actuelle, aucune caméra HDR n'est panoramique. C'est l'objet de la première contribution de cette thèse : concevoir une caméra panoramique HDR, afin d'améliorer la navigation de robots en extérieur par la perception visuelle seule dans des environnements à luminances variées. Montée sur un robot mobile, elle accroît le domaine de convergence et la précision en positionnement du robot en extérieur par asservissement visuel direct. Dans un second temps, on s'intéresse aux scènes dont le niveau de détail est non-uniforme dans l'espace : certains éléments de la scène présentent sont plus riches en informations visuelles que les autres. Afin de capturer de tels environnements hétérogènes, la deuxième contribution de cette thèse est une caméra adaptative. Elle s'appuie sur un nouveau miroir déformable dont les courbures locales permettent d'accroître ou de réduire le nombre de pixels qu'occupent les régions de la scène dans l'image. Cette caméra, surnommée Visadapt, capture des images multi-résolution selon le contenu de la scène. D'une scène à l'autre, il est possible de changer la forme du miroir afin d'optimiser la résolution des images qu'elle capture à cette nouvelle scène. La surface du miroir est constituée d'un matériau à la fois réfléchissant et déformable, le mylar et se déforme par une grille d'actionneurs linéaires placés sous sa surface. Ce miroir, plan à l’état initial, peut se déformer afin que les régions de la scène soient capturées par Visadapt à la résolution désirée. Une étude en simulation a permis de fixer les caractéristiques de Visadapt, notamment les dimensions et les matériaux des différents éléments qui la constituent, ainsi que l'espacement inter-actionneurs. Un prototype a été réalisé à partir des paramètres fixés en simulation. Les expérimentations réalisées ont montré que ce prototype est capable de magnifier jusqu'à quatre zones de la scène à la fois. Cette thèse se conclut sur des perspectives de travail qui proposent d'améliorer les prototypes des deux caméras conçues afin d'améliorer leurs performances et la variété des images qu'elles peuvent capturer. De plus, elle propose des pistes de recherche afin d'aller plus loin sur ces deux concepts de caméras et même sur la vision adaptative en général
This thesis presents the conception methods of two catadioptric cameras capable of recording usable images of heterogeneous environments. These cameras belong to the adaptive vision field, which gathers the cameras of which the optics or sensor have heterogeneous properties which can vary across time. Adaptive cameras abilities include capturing heterogenous environments which physical or geometrical properties change across space. This thesis proposes a survey of the state of the art on adaptive cameras which are able to capture specific types of heterogenous environments. On the one hand, we consider the scenes characterized by a spatial variation of radiances, with a dynamic range around 120 decibels. These scenes put conventional cameras in difficulty, their images have some pixels saturated and others to dark, because of their low dynamic range. In both casses, these image regions does not carry any visual information about the scene, they are not usable. In order to capture the radiances corresponding to these bright and dark areas, the high dynamic range cameras (HDR) are used. Nonetheless, there is no available HDR panoramic camera yet. Therefore, the first contribution of this thesis is the conception of an HDR panoramic camera in order to improve robots navigation, with only visual perception, in outdoor scenes with various. Mounted on a mobile robot, this camera enlarges the convergence domain and the positioning accuracy of a robot by direct visual servoing, outdoors. On the other hand, we consider the scenes which have a non-uniform level of details across space : some scene elements carry more visual information than the others. To capture such heterogeneous environments, the second contribution of this thesis is an adaptive camera. This camera is based on a new deformable mirror of local curvatures allowing to enlarge or reduce the number of pixels occupied by scene regions in the image. This camera, nicknamed Visadapt, capture multi-résolution images which depend on scene content. From one scene to another, the shape of the mirror may be changed to optimise the resolution of the images captured to this new scene. The surface of the mirror is made of material both reflective and deformable, the mylar, and changes of shape thanks to a grid of linear actuators placed underneath. This mirror, plan as an initial state, is able to change shape to give to the scene regions captured by Visadapt the desired resolution in the image. The characteristics of Visadapt, particularly the dimensions, the materials of its different elements and the actuators pitch, have been defined thanks to a simulation study. A real prototype have been built to respect the parameters defined by the simulation. The experiments shown that this prototype is able to magnify up to four scene regions at once. This thesis ends with a conclusion presenting future works to upgrade the prototypes of the two cameras, in order to enhance their performances and the diversity of images they can capture. Furthermore, this conclusion proposes research tracks to improve even further these two cameras and even adaptive vision in general

2

Pace, Brian A. "Physiology, Photochemistry, and Fitness of Mexican Maize Landraces in the Field." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1545421491370678.

Full text

APA, Harvard, Vancouver, ISO, and other styles

3

Iversen, Katarina. "Virtuella vägmarkeringar för att påverka hastighetsval vid bilkörning : Effekt och upplevelse hos bilförare med respektive utan ADHD." Thesis, Linköpings universitet, Institutionen för datavetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-166321.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Tidigare forskning har visat att bilförare tenderade att underskatta hastigheten de färdas i med ca 20%. Forskning har även visat att hastighetsupplevelse hos bilförare kan påverkas av ett utökat Field of View (FoV) vilket resulterar i lägre hastighetsval (Pretto et al., 2009; Schütz et al., 2015; Lidestam, Eriksson & Eriksson, 2019). Utöver FoV har även virtuella vägmarkeringar (VRM), visats ha potentialen att påverka hastighetsval genom att bistå bilförare med ytterliggare visuell information kring dennes omgivning (Lidestam, Eriksson & Eriksson, 2019). Attityder gentemot system som syftar till att påverka bilförares hastighetsval har studerats (Wall et al., 2013), med det finns luckor i forskning gällande hur dessa upplevs av bilförare med ADHD. Vidare har även upprepning av körningar med samma konstellationer av visuella stimuli har visats påverka hastighetsval vilket skulle tyda på perceptuell inlärning sker under bilkörning (Lindestam, Eriksson & Eriksson, 2019). Syftet med den aktuella studien var att undersöka huruvida VRM påverkade hastighetsval samt hur de upplevs av bilförare med respektive utan ADHD. Studien ämnade att göra detta genom att besvara följande frågeställningar 1. a. Hur upplevdes VRM? b. Finns det en skillnad i upplevelsen av VRMs mellan bilförare med ADHD och utan ADHD? 2. Vilken effekt har ADHD, FoV, VRM och replikat på självvald hastighet? Resultaten visade att upplevelsen av VRM inte skiljde sig signifikant mellan de två guppen, trots detta skattades samtliga frågor kring upplevelsen av VRM högre av bilförare med ADHD än bilförare utan ADHD. Körningarna rapporterades som signifikant mer koncentrationskrävande av bilförare utan ADHD. Replikat och FoV uppvisade en signifikant interaktionseffekt på hastighetsval. Framtida forskning kan med fördel studera hur VRM kan utformas för att upplevas som mer hjälpsamma samt hur de bör implementeras för att bilförare ska vilja använda dem vid körningar. Det är viktigt att framtida forskning i området även inkluderar bilförare med ADHD för att säkerställa att system som utformas även är gynnsamma för dessa bilförare.

4

Mateus, Forero Andrea D. "DESIGN IN ADAPTATION TO DROUGHTS AND HEAT WAVES CAUSED BY CLIMATECHANGE IN RICE FARMS IN LERIDA, TOLIMA, COLOMBIA." Miami University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=miami151213167340772.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Schrinner, Martin. "Mean-field view on geodynamo models." Doctoral thesis, [S.l.] : [s.n.], 2005. http://webdoc.sub.gwdg.de/diss/2005/schrinner.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

Hansen, Jeremy Roger. "Wide field of view satellite tracking." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0031/MQ65844.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

Cao, Shaohong. "Large field of view electron ptychography." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/19405/.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Electron ptychography can overcome the limits of the conventional electron microscopy in terms of both resolution and phase quantitative measurements. There are two ways to implement ptychography with electrons. One employs a focused probe and the other uses a large probe. The advantage of focused probe electron ptychography is allowing to analyse spectrum while collecting the data. The biggest advantage of large probe electron ptychography is much larger field of view with the same scanning positions. In this thesis, we investigate the applications of the large probe ptychography in three modes, which are a transmission electron microscope in the selected area diffraction mode (SAD ptychography), a scanning electron microscope in the transmission mode (SEM ptychography), and a scanning transmission electron microscope (STEM ptychography). The thesis includes the detailed experimental procedures to collect ptychographic data in the three modes, as well as the investigation and evaluation of the experimental parameters. It presents extensive experimental data and results, which includes the decomposition of a partially coherent electron source via the modal decomposition ptychography with the SAD ptychography, the improvement of the delocalization issue with the SEM ptychography, and the atomic resolution reconstruction with the STEM ptychography. The challenges of the implementation and the reconstruction of ptychography in the three modes are also discussed. The main achievement of the thesis is the modal decomposition of matter wave, which has never been done before.

8

Hansen, Jeremy Roger. "Wide field of view satellite tracking." Ottawa : National Library of Canada = Bibliothèque nationale du Canada, 2002. http://www.nlc-bnc.ca/obj/s4/f2/dsk1/tape3/PQDD%5F0031/MQ65844.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

9

Takami, Kuya. "Non-Field-of-View Acoustic Target Estimation." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/56892.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

This dissertation proposes a new framework to Non-Field-of-view (NFOV) sound source localization and tracking in indoor environments. The approach takes advantage of sound signal information to localize target position through auditory sensors combination with other sensors within grid-based recursive estimation structure for tracking using nonlinear and non-Gaussian observations. Three approaches to NFOV target localization are investigated. These techniques estimate target positions within the Recursive Bayesian estimation (RBE) framework. The first proposed technique uses a numerical fingerprinting solution based on acoustic cues of a fixed microphone array in a complex indoor environment. The Interaural level differences (ILDs) of microphone pair from a given environment are constructed as an a priori database, and used for calculating the observation likelihood during estimation. The approach was validated in a parametrically controlled testing environment, and followed by real environment validations. The second approach takes advantage of acoustic sensors in combination with an optical sensor to assist target estimation in NFOV conditions. This hybrid of the two sensors constructs observation likelihood through sensor fusion. The third proposed model-based technique localizes the target by taking advantage of wave propagation physics: the properties of sound diffraction and reflection. This approach allows target localization without an a priori knowledge database which is required for the first two proposed techniques. To demonstrate the localization performance of the proposed approach, a series of parameterized numerical and experimental studies were conducted. The validity of the formulation and applicability to the actual environment were confirmed.
Ph. D.

10

Chen, Xin. "Analytical Path to Improved RF Field Homogeneity for High Field MRI." Cleveland, Ohio : Case Western Reserve University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1237482374.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Spinks, Katie Rose. ""Factors that influence successful field placements" student and field instructor perspectives /." Columbus, Ohio : Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1243955704.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Yahya, Farouk. "Approche couplée discrète - continue adaptative pour la mise en forme des métaux." Electronic Thesis or Diss., Valenciennes, Université Polytechnique Hauts-de-France, 2023. http://www.theses.fr/2023UPHF0042.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

La mise au point des procédés de mise en forme passe généralement par la simulation numérique, et en particulier par la Méthode des Eléments Finis, afin de détecter, entre autres, d'éventuels risques de fissuration et leur propagation, à la fois dans la pièce forgée et les outillages.La méthode classique des éléments finis, ainsi que des variantes spécifiques appliquées à la modélisation de la fissuration, présentent des limitations lorsqu’il s’agit de simuler des problèmes de multi-fissuration dus aux non-linéarités materielles, géométriques et de contact. La nature même d'une fissure – une discontinuité – est contradictoire avec le cadre de la Mécanique des Milieux Continus. En revanche, la Méthode des Éléments Discrets se distingue par sa capacité à gérer efficacement les discontinuités. Elle est utilisée pour modéliser des milieux granulaires ou cohésifs fragiles. Cependant, cette approche présente également des limites, notamment en ce qui concerne la prise en compte des non-linéarités matérielles et les temps de calculs, qui peuvent nécessiter d’importantes capacités de calcul pour simuler des problèmes complexes.L'objectif de ces travaux de thèse est développer une méthode de remaillage dynamique, permettant de passer d'une méthode à l'autre afin de bénéficier des avantages des deux approches. Cet objectif sera atteint en trois étapes.Dans un premier temps, une méthode de couplage sans recouvrement, basée sur la méthode des multiplicateurs de Lagrange, a été développée. Cette méthode vise à assurer une condition de compatibilité des vitesses entre les sous-domaines éléments discrets et éléments finis, afin d’assurer la communication des quantités physiques entre les deux sous-domaines.Dans un second temps, il s'agit d'assurer la continuité des quantités physiques au sein d'une même zone lors de son remaillage. Cette étape est réalisée en utilisant une interpolation polynomiale des déplacements. Cette approche permet déterminer les champs au sein des éléments discrets au moment de la transition entre un sous-domaine des éléments finis et un sous-domaine des éléments discrets. Pour valider ces deux approches, des cas de test ont été mis en place.Enfin, une méthode a été développée pour automatiser la gestion des opérations de couplage et de transfert des champs. Cette approche implique l’utilisation d’une technique de remaillage qui génère automatiquement des sous-domaines discrets à partir de la géométrie de l’ensemble des éléments finis à remplacer.La méthode de remaillage dynamique mise en place dans ces travaux thèse est appliquée sur un cas test de type Kalthoff et validée par comparaison de l'angle de propagation de fissure avec des expériences issues de la bibliographie
The development of forming processes generally involves numerical simulation, particularly using the Finite Element Method, to detect, among other things, potential risks of cracking and their propagation, both in the forged piece and in the tooling.The classical Finite Element Method, as well as specific variants applied to crack modeling, have limitations when it comes to simulating multi-cracking problems due to material, geometric, and contact nonlinearities. The very nature of a crack – a discontinuity – is in opposition to the framework of Continuum Mechanics. On the other hand, the Discrete Element Method distinguishes itself by its ability to effectively handle discontinuities. It is used to model granular or brittle cohesive materials. However, this approach also has limitations, especially regarding the consideration of material nonlinearities and computation times, which may require significant computing resources to simulate complex problems.The objective of this thesis work was to develop a dynamic remeshing method that allowed transitioning between the two methods to leverage the advantages of both approaches. This objective was be achieved in three steps.Firstly, a non-overlapping coupling method based on the Lagrange multiplier method was developed. This method aimed at ensuring the compatibility of velocities between the discrete elements and finite elements subdomains to facilitate the communication of physical quantities between the two subdomains.Secondly, it was necessary to ensure the continuity of physical quantities within the same zone during its remeshing. This step was achieved by using polynomial interpolation of displacements. This approach allowed determining the fields within the discrete elements when the transition between a finite element subdomain and a discrete element subdomain took place. Test cases were set up to validate these two approaches.Finally, a method was developed to automate the management of coupling and field transfer operations. This approach involved the use of a remeshing technique that automatically generated discrete subdomains from the geometry of the entire finite elements to be replaced.The dynamic remeshing method implemented in this thesis work was applied to a Kalthoff test case and validated by comparing the crack propagation angle with experiments from the literature

13

Xiao, Peng. "Optique adaptative et interférométrie spatialement incohérente plein champ pour l’imagerie de la rétine." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLET015/document.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Cette thèse traite de l’étude et du développement d’un système d’optique adaptative pour la tomographie par cohérence optique plein champ (AO-FFOCT en anglais) appliquée à l’imagerie haute résolution de la rétine. L’analyse de l’effet des aberrations géométriques sur les performances en FFOCT a montré que pour une illumination spatialement incohérente, la résolution transverse est insensible aux aberrations et ne fait que diminuer le niveau du signal. Comme ce sont des aberrations de bas ordres comme la myopie et l’astigmatisme qui prédominent pour l’œil humain, une méthode d’optique adaptative avec une configuration sans conjugaison qui utilise une correction de front d’onde en transmission est suggérée, puis appliquée à la correction de ces ordres afin de simplifier le système d’AO-FFOCT. Des corrections de front d’onde sont effectuées sans analyseur de surface d’onde, en utilisant le niveau du signal de FFOCT comme métrique. Des expériences avec des échantillons diffusants et un œil artificiel sont menées pour démontrer la faisabilité d’un système d’AO-FFOCT conçu pour la correction d’aberration. Afin de résoudre les problèmes posés par les mouvements oculaires et de compenser en temps réel la différence de chemin optique entre les deux bras de l’interféromètre, l’instrument de FFOCT est couplé à un système d’OCT spectral. Avec cette combinaison de systèmes, l’imagerie FFOCT in vivo cellulaire de la rétine à haute résolution a été réalisée pour la première fois sur l’œil humain
This thesis follows the study and development of an adaptive optics full-field optical coherence tomography (AO-FFOCT) system, aiming for high resolution en face human retinal imaging. During the quantification of the effects of geometrical aberrations on the FFOCT system performance, it is shown that, with spatially incoherent illumination, the lateral resolution of FFOCT is insensitive to aberrations, which only cause the FFOCT signal reduction. Since low order aberrations like myopia and astigmatism dominate in human eye, a non-conjugate AO configuration by using transmissive wavefront corrector is suggested and applied for low order aberrations correction to simplify the AO-FFOCT system. Wavefront corrections are done with a wavefront sensorless method by using FFOCT signal level as the metric. Experiments with scattering samples and artificial eye model are conducted to demonstrate the feasibility of the customized AO-FFOCT system for aberration correction. In order to resolve the eye motion effects and employ real-time matching of the optical path lengths of the two interferometric arms in FFOCT, a system combination of traditional spectral-domain OCT (SDOCT) with FFOCT is adopted. With this combined system, high resolution FFOCT cellular retinal imaging is achieved in human eye in vivo for the first time

14

Ozkalayci, Burak Oguz. "Multi-view Video Coding Via Dense Depth Field." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607517/index.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Emerging 3-D applications and 3-D display technologies raise some transmission problems of the next-generation multimedia data. Multi-view Video Coding (MVC) is one of the challenging topics in this area, that is on its road for standardization via ISO MPEG. In this thesis, a 3-D geometry-based MVC approach is proposed and analyzed in terms of its compression performance. For this purpose, the overall study is partitioned into three preceding parts. The first step is dense depth estimation of a view from a fully calibrated multi-view set. The calibration information and smoothness assumptions are utilized for determining dense correspondences via a Markov Random Field (MRF) model, which is solved by Belief Propagation (BP) method. In the second part, the estimated dense depth maps are utilized for generating (predicting) arbitrary (other camera) views of a scene, that is known as novel view generation. A 3-D warping algorithm, which is followed by an occlusion-compatible hole-filling process, is implemented for this aim. In order to suppress the occlusion artifacts, an intermediate novel view generation method, which fuses two novel views generated from different source views, is developed. Finally, for the last part, dense depth estimation and intermediate novel view generation tools are utilized in the proposed H.264-based MVC scheme for the removal of the spatial redundancies between different views. The performance of the proposed approach is compared against the simulcast coding and a recent MVC proposal, which is expected to be the standard recommendation for MPEG in the near future. These results show that the geometric approaches in MVC can still be utilized, especially in certain 3-D applications, in addition to conventional temporal motion compensation techniques, although the rate-distortion performances of geometry-free approaches are quite superior.

15

Hough, Petrina. "The useful field of view, driving, and dementia." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ40011.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Katkam, Rajender. "Dual field of view optical system for colonoscope." Thesis, The University of Arizona, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1564291.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

The present dual field of view flexible colonoscope can provide both forward view and radial or backward view of the colon to improve detection of cancerous polyps. The colonoscope has its own illumination that illuminates the parts of the colon viewed by imaging optics. The optical system, limited only by the diffraction effects at the exit pupil over the entire visible spectrum, can provide high resolution and is suitable for color imaging. The flexible colonoscope has an on-board sensor at the proximal end of the colonoscope to improve resolution. The proximal end of colonoscope measures only 8 mm in diameter and 20 mm in length. The present colonoscope has the potential to be scaled down to as small as 6 mm inner diameter from the present 8 mm.

17

Patel, Kruti D. "Neuropsychological Factors Associated with Useful Field of View." Ohio University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1395411154.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Yang, Fan S. M. Massachusetts Institute of Technology. "Achromatic and wide field-of-view metalens design." Thesis, Massachusetts Institute of Technology, 2021. https://hdl.handle.net/1721.1/130677.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Thesis: S.M., Massachusetts Institute of Technology, Department of Materials Science and Engineering, February, 2021
Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 47-50).
Achromatic and wide field-of-view (WFOV) optical functionalities are desired for various imaging applications. Conventional methods use complicated design approaches or assemble multiple optical components to form achromatic and WFOV lenses. They are bulky and have limited focusing quality. Here a novel metalens design is presented which shows extraordinary achromatic and WFOV focusing quality simultaneously. The metalens is composed of all-dielectric meta-atoms selected from a large meta-atoms library with diverse dispersion behavior. The metalens and an aperture are integrated on opposite sides of the substrate to separate areas with different angle-of- incidents (AOIs). A theoretical analysis and a direct search algorithm are combined to obtain optimum phase profile of metalens. This design concept is generic and can be applied to lenses with different parameters to meet the demands of various applications.
by Fan Yang.
S.M.
S.M. Massachusetts Institute of Technology, Department of Materials Science and Engineering

19

Sharma, Arvindh R. "Liquid Jet in Oscillating Crossflow: Characterization of Near-Field and Far-Field Spray Behavior." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439281517.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

Cassel, Adrienne M. "Field Guide to the Heart." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1307320455.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Rapin, Kathryn. "Do laboratory syndromes predict field behavior? Comparison of laboratory based syndromes and field based measurements." Bowling Green State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1459776389.

Full text

APA, Harvard, Vancouver, ISO, and other styles

22

Ljung, Kenth. "Effects of Field-of-View in First-Person Video Games : A Study on Camera Field-of-View in Relation to Game Design." Thesis, Uppsala universitet, Institutionen för speldesign, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-254330.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Field of view in virtual environments such as games is the angular cone-of-vision a camera uses to display content on screen, and is subject to various characteristics and effects. Some of these effects have been documented based on simulation. However little to no research is readily available regarding video games. This paper set out to document and verify if field of view can reliably be used to affect potential game design aspects, particularly for first-person cameras. Several factors were identified and tests constructed which had participants play through a virtual first-person environment on regular computer hardware (no head-mounted display or other viewing mediums). The measured properties were distance, scale and speed as a function of field of view. According to the results, distances appear longer, objects appear smaller and movement faster at higher field of view, however at varying amounts depending on the context, scenario and viewing angle of the camera. In addition it was also shown that text readability and peripheral vision were significantly affected. It was concluded that field of view can be used within games and virtual applications to enable certain game design elements, and that field of view also should be a consideration in designing a game as it may be interpreted differently given a different field of view.

23

Hart, David Marvin. "Light-Field Style Transfer." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/7763.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

For many years, light fields have been a unique way of capturing a scene. By using a particular set of optics, a light field camera is able to, in a single moment, take images of the same scene from multiple perspectives. These perspectives can be used to calculate the scene geometry and allow for effects not possible with standard photographs, such as refocus and the creation of novel views.Neural style transfer is the process of training a neural network to render photographs in the style of a particular painting or piece of art. This is a simple process for a single photograph, but naively applying style transfer to each view in a light field generates inconsistencies in coloring between views. Because of these inconsistencies, common light field effects break down.We propose a style transfer method for light fields that maintains consistencies between different views of the scene. This is done by using warping techniques based on the depth estimation of the scene. These warped images are then used to compare areas of similarity between views and incorporate differences into the loss function of the style transfer network. Additionally, this is done in a post-training fashion, which removes the need for a light field training set.

24

Grönqvist, Helena. "Vision Enhancement Systems : The Importance of Field of View." Thesis, Linköping University, Department of Computer and Information Science, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-1370.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

The purpose of the project, which led to this thesis, was to investigate the possible effects different horizontal Fields of View (FoV) have on driving performance when driving at night with a Vision Enhancement System (VES). The FoV chosen to be examined were 12 degree and 24 degree FoV, both displayed on a screen with the horizontal size of 12 degree FoV. This meant that the different conditions of FoV also had different display ratios 1:1 and 1:2. No effort was made to separate these parameters.

A simulator study was performed at the simulator at IKP, Linköping University. Sixteen participants in a within-group design participated in the study. The participants drove two road sections; one with a 12 degree FoV and the other with a 24 degree FoV. During each section four scenarios were presented in which the participants passed one of three types of objects; a moose, a deer or a man. In each section, two of the objects stood right next to the road and two were standing seventeen meters to the right of the road. As the drivers approached the objects standing seventeen meters to the right of the road, the objects moved out of the VES when the vehicle was 200 meters in front of the object with a 12 degree FoV. The objects could be seen with the naked eye when the vehicle was 100 meters in front of the object. When the drivers approached the objects with a 24degree FoV the objects moved out of the VES display when it was possible to see them unaided.

Results show that a 24 degree FoV displayed with a 1:2 ratio gives the drivers improved anticipatory control, compared to a 12 degree FoV displayed with a 1:1 ratio. The participants with a broader FoV were able to make informed decisions whereas with a narrow FoV some participants started to reaccelerate when they could not see an object. Results also show that any difference in recognition distance that may exist between a 12 degree and a 24 degree camera angle displayed in a 12 degree FoV display do not seem to have any adverse effect on the quality of driving.

25

Edwards, Jerri. "The Useful Field of View of Reading Disabled Children." TopSCHOLAR®, 1995. http://digitalcommons.wku.edu/theses/908.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Recent research suggests that some reading disabled children process visual information differently due to a transient system or magnocellular pathway deficit. In light of this hypothesis, the present study represents an investigation of the visual processing abilities of both good and poor readers using a new technique which taps several aspects of transient visual input by presenting brief masked targets with varying attentional demand. Sixteen subjects' reading capabilities were assessed by the Woodcock Reading Mastery Test-Revised. The subjects were classified as reading disabled if they had a two or more year lag in reading skill (n=7) or as non-reading disabled if they showed reading capabilities at or above their expected age level (n=9). Subjects performed on the Visual Attention Analyzer in order to assess their UFOV™ the area of the visual field in which information can be acquired in a brief glance without head or eye movements. The UFOV™ protocol involves subtest measures of processing speed, divided attention, and selective attention. The first subtest requires subjects to identify a target at varying durations. The second subtest requires identification of a central target simultaneously with localization of a peripheral target at eccentricities of 10, 20, or 30 degrees. The third subtest requires the same responses but adds visual distractors with the peripheral target. The reading disabled subjects required longer durations to achieve equivalent performance in both the divided and selective attention tasks. This group demonstrated a more drastic reduction in UFOV^M than did normal readers when distractors were added in task 3. Furthermore, reading disabled individuals processed information in the right vs left half of the visual field differently than did non-reading disabled children. The reading disabled subjects made more localization errors overall and missed a significantly higher proportion of targets presented in the right half of the visual field. Reading disabled individuals processed visual information more slowly, were more easily distracted, and made more localization errors than did normal readers resulting in a reduction of the UFOV™. This pattern of results fits within the framework of the transient system deficit hypothesis for reading disabled children. Therefore, such differences in processing between normal and disabled readers may be the result of a transient system deficit in visual processing in reading disabled children.

26

Koopman, Marjolein. "Nanoscale cell membrane organization a near-field optical view /." Enschede : University of Twente [Host], 2006. http://doc.utwente.nl/55930.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Fahmi, Kamal Hanna. "Participatory action research (PAR) : a view from the field." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84506.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

The phenomenon of street children is world-wide and on the increase despite numerous programs aiming at its eradication. The failure to adequately address this complex and very diverse phenomenon is the result of conceptual confusion with respect to defining who a street child is. The dominant discourse on street children defines them as victims or deviants to be rescued and rehabilitated. As such, the capacity of many of these children for human agency is occluded by excluding them from participation in the construction of solutions to their problems. I argue that, far from being mere victims and deviants, these kids, in running away from alienating structures and finding relative freedom in the street, often become autonomous and are capable of actively defining their situations in their own terms. They are able to challenge the roles assigned to children, make judgements and develop a network of niches in the heart of the metropolis in order to resist exclusion and chronic repression. I further argue that for research and action with street kids to be emancipatory, it is necessary to acknowledge and respect the human agency the kids display in changing their own lives and to capitalize on their voluntary participation in non-formal educational activities as well as in collective advocacy.
The thesis draws on a participatory action research (PAR) methodology spanning eight years of fieldwork with street kids in Cairo, which eclectically combined street ethnography, street work and action science. I critically review the historical development of these methodologies, and I argue for a conception of PAR as an open-ended process of action and reflective participatory research incorporated into everyday activities and work with excluded, marginalized and oppressed groups such as street kids. As such, I pay special attention to the ethical dilemmas that arise in day-to-day PAR practice.

28

Prinsloo, David Schalk Van der Merwe. "Multi-mode antennas for hemispherical field-of-view coverage." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/97008.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Thesis ((PhD)--Stellenbosch University, 2015.
ENGLISH ABSTRACT: This dissertation proposes a multi-mode antenna element excited through a multiconductor feed. It is shown that each of the orthogonal transverse electromagnetic modes supported by the antenna feed results in a unique radiated far-field pattern that collectively allow for nearhemispherical field-of-view coverage. Three multi-mode antenna designs are presented: a dual-mode antenna, integrating a single linearly polarised dipole antenna with a co-located monopole, as well as two quad-mode antenna designs integrating two dual-polarised dipole elements with a co-located monopole element. The dual-mode antenna is excited through a balanced transmission line feed supporting both differential- and common-mode signals that, respectively, result in typical dipole-over-ground and monopole radiated far-field patterns. The quad-mode antennas are each fed through a quadraxial transmission line allowing for excitation through four orthogonal transverse electromagnetic port modes. To characterise the multi-mode response of the multi-mode antennas, generalised transformations are derived by which the multi-mode S-parameters and radiated far-fields can be calculated from the S-parameters and far-fields corresponding to single-ended excitations. These transformations are implemented to validate the response of a dual-mode and quad-mode antenna design through measurements. An equivalent network representation for active multi-mode antennas is presented, including generalised transformations relating the multi-mode signal and noise response of the low-noise amplifiers to the two-port S-parameters and noise parameters of the low-noise amplifiers. Through the use of classical beamforming algorithms, the performance of an active dual-mode and quadmode antenna is presented. In the case of the active dual-mode antenna, it is shown that through the added use of common-mode signals, a variation in sensitivity of less than 50% is achieved in the E-plane. Similarly, the additional excitation modes supported by the active quad-mode antenna is shown to result in a significant improvement in the polarimetric capabilities over the field-of-view coverage.
AFRIKAANSE OPSOMMING: Hierdie proefskrif stel ’n multimodale antenna element voor wat deur ’n multi-geleier transmissielyn gevoer word. Dit word gewys dat elk van die ortogonale transversale elektromagnetiese opwekkingsmodusse wat deur die antenna voer ondersteun word, ’n unieke vêrveld stralingspatroon skep, wat gesamentlik lei tot ’n hemisferiese gesigsveld. Drie multimodale antenna ontwerpe word voorgestel: ’n dubbelmodale antenna, waarin ’n enkel lineêrgepolariseerde dipool antenna en monopool mede-geleë word, asook twee viermodale antenna ontwerpe waarin twee dubbelgepolariseerde dipool elemente geïntegreer word met medegeleë monopool antenna elemente. Die dubbelmodale antenna word gevoer deur ’n gebalanseerde transmissielyn wat beide differensiële- en gemene-modus seine ondersteun, waar elk onderskeidelik dipool-oor-aardvlak en monopool stralingspatrone voortbring. Die viermodale antennas word elk gevoer deur vier-as transmissielyne wat vier ortogonale transversale elektromagnetiese opwekkingsmodusse ondersteun. Om die multimodale gedrag van die drie multimodale antennas te karakteriseer, word veralgemeende transformasies afgelei waardeur die multimodale strooiingsparameters asook die vêrveld stralingspatrone vanaf enkelpoort strooiingsparameters en vêrvelde bereken word. Hierdie transformasies word toegepas om die gedrag van ’n dubbel- en viermodale antenna ontwerp te karakteriseer deur metings. Ekwivalente netwerkvoorstellings vir aktiewe multimodale antennas word voorgestel, insluitend veralgemeende transformasies om die multimodale sein asook ruis gedrag van die lae-ruis versterkers betreklik te maak tot die tweepoort strooiingsparameters en ruisparameters van die laeruis versterkers. Deur gebruik te maak van klasieke bundelvormingsalgoritmes, word die gedrag van aktiewe dubbelmodale en viermodale antennas voorgestel. Vir die aktiewe dubbelmodale antenna word daar aangedui dat die gesamentlike gebruik van differensiële- en gemene-modus seine, ’n variasie in sensitiwiteit onder 50% tot gevolg het in die E-vlak. Soortgelyk word daar aangedui dat die addisionele opwekkingsmodusse wat deur die aktiewe viermodale antenna ondersteun word, tot ’n beduidende verbetering in die polarisasievermoë oor die gesigsveld lei.

29

Odom, Garret, and Garret Odom. "Diffusers in Coherently Illuminated, Wide Field of View Applications." Thesis, The University of Arizona, 2016. http://hdl.handle.net/10150/620709.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Diffusers are devices that are designed to spread or scatter light. Many different types of diffusers are readily available in the commercial and scientific industries, but most are designed with a specific application in mind. Thus, when attempting to use a diffuser in an unconventional way, it is important to understand how it will behave in the system it will be used in. One example is a diffuser in a coherently illuminated, wide field of view system such as a laser spot tracker. For some diffusers, coherent illumination and/or off-axis illumination can have a major impact on their diffusing properties, which may or may not be acceptable to system performance. This project evaluates the pros and cons of several types of diffusers in order to identify the most effective solution based on the parameters of a system, using a laser spot tracker as an example. First, three diffusers are down selected from the list based on their refractive and diffractive properties. Next, the candidates are evaluated analytically and/or experimentally to characterize their behavior when illuminated by a collimated laser over a wide range of incident angles. Results suggest that a computer generated diffractive diffuser is the most flexible design option for the described laser spot tracker, but some drawbacks such as diffraction efficiency and maximum diffusion angle do need to be considered. This selection method can be extended to serve as a guide for making the proper diffuser choice in many different applications.

30

Mazin, Samuel R. "A Wide field-of-view inverse geometry CT system /." May be available electronically:, 2007. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

Hsu, Fang-Chi. "Electric field effect in "metallic" polymers." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1127229727.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Thesis (Ph. D.)--Ohio State University, 2005.
Title from first page of PDF file. Document formatted into pages; contains xxi, 177 p.; also includes graphics (some col.). Includes bibliographical references (p. 167-177). Available online via OhioLINK's ETD Center

32

Zhang, Cheng. "Far field ultrasonic welding of thermoplastics." Connect to resource, 1988. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1156875186.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

Eswaran, Raman V. "Near field ultrasonic welding of thermoplastics." Connect to resource, 1988. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1157565798.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

Fletcher, Kerra Rose. "Low field modulation of complex species." Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1197912416.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

DURHAM, PHILIP R. "Force Field Development for Calbindin D9k." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1218547540.

Full text

APA, Harvard, Vancouver, ISO, and other styles

36

Chrisman, James Atticus. "Marsh's Field: A Novella and Introduction." Ohio University Honors Tutorial College / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1429799538.

Full text

APA, Harvard, Vancouver, ISO, and other styles

37

Wesolowski, Sarah. "Bayesian Methods for Effective Field Theories." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1500037172071861.

Full text

APA, Harvard, Vancouver, ISO, and other styles

38

Brucker, Margaret. "The Binocular Visual Field in Glaucoma." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1523998138093264.

Full text

APA, Harvard, Vancouver, ISO, and other styles

39

Khakshoor, Morteza. "Like the Beasts of the Field." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524072853367268.

Full text

APA, Harvard, Vancouver, ISO, and other styles

40

Liu, Shiyi. "Understanding Doped Organic Field-Effect Transistors." Kent State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=kent1574127009556301.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Aleman-Nieto, Alberto E. "Commande adaptative vectorielle d'un moteur asynchrone en utilisant un processeur de signal numérique." Université Joseph Fourier (Grenoble ; 1971-2015), 1996. http://www.theses.fr/1996GRE10141.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Dans cette thèse, une étude en simulation a été effectuée afin de mettre en évidence l'effet de la température sur les performances de l'asservissement, et de chercher une solution pour y pallier. Deux solutions sont proposées, l'une effectuée en simulation et l'autre implémentée en temps réel: la première suppose l'existence d'une sonde de température permettant la mesure directe de la variation de la température. Sa compensation se fera alors en temps réel en adaptant le modèle de flux, la pulsation de glissement et les coefficients du régulateur de flux. La seconde fait une estimation de la variation de la constante de temps rotorique. Cette méthode consiste à injecter une séquence binaire pseudo-aléatoire (SBPA). Ensuite la variation de #R est estimée en utilisant la méthode d'intercorrélation entre le signal et son effet recueilli sur l'erreur de la vitesse. L'implémentation de la méthode d'identification pour adapter la constante de temps rotorique est faite en trois étapes: d'abord la méthode a flux oriente indirecte est mis en œuvre. Ceci permet aussi de mettre au point la structure matérielle de la commande. Ensuite, la méthode a flux oriente directe est implémentée. Ceci a permis d'une part, de valider les simulations et d'autre part de mettre au point la section qui fait l'estimation du flux rotorique. Enfin l'implémentation de la méthode d'injection de signal binaire pseudo-aléatoire et corrélation est expliquée. Ces trois étapes sont accompagnées d'une explication détaillée concernant leur mise en œuvre

42

Goldberg, Benjamin M. "Picosecond Electric Field CARS; A Diagnostic Technique to Measure the Electric Field Development within Nanosecond Repetitively Pulsed Plasmas." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1354303147.

Full text

APA, Harvard, Vancouver, ISO, and other styles

43

Espe-Sherwindt, Marilyn. "The Individualized Family Service Plan (IFSP) in the field of early intervention: how level is the playing field? /." The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487931993468819.

Full text

APA, Harvard, Vancouver, ISO, and other styles

44

Compaleo, Jacob D. "Impact of Near-field-to-far-field Transformation on SAR Images Formed in an Indoor Non-anechoic Environment." Wright State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=wright1533206365760924.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

Jackson, Lauren M. "The Effects of Decreased Uncertainty and Telescopic Versus Full Field Training on The Useful Field of View." TopSCHOLAR®, 1990. http://digitalcommons.wku.edu/theses/1698.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

The “Useful Field of View” (UFOV) is the entire area in which information can be gathered without moving the eyes or head (Ball, Beard, Roenker, Miller & Griggs, 1998). Previous research has demonstrated that the UFOV shrinks with age (Scialfa, Kline & Lyman, 1987; Plude & Doussard-Roosevelt, 1987: Ball et al., 1988). With decrement in the UFOV, everyday activities, such as driving and walking can be limited. If the area in which information is received is smaller, then objects seem to appear suddenly and here is little time to react to them. One example of an everyday activity that would be affected by this decrement is driving. Driving involved simultaneously attending to a number of different elements at the same time, for example, speed, oncoming traffic, traffic signals and signs and pedestrians. A decrement of the UFOV would adversely affect driving performance. Only two studies have looked at training to increase the deficit in the UFOV (Sekuler & Ball, 1986: Ball, et al., 1988). Given this paucity of data, many questions have been left unanswered. This study addresses three of these questions: (a) Does target uncertainty affect older adults more adversely than younger adults?, (b) Does a recognizable pattern affect UFOV? and (c) What is the most effective training method to increase the UFOV? Two experiments were conducted to answer these questions. In the first experiment, a reduced presentation field was designed to test the uncertainty question. Along with this reduction in the presentation, two patterns (organized pattern vs. unorganized pattern) were designed to test the effects of a restricted presentation pattern on the UFOV. These two reduced patterns were compared with the full field presentation. Although the UFOV, in general, was smaller for older participants than younger individuals, there was no effect for full field versus reduced field presentation nor an organized versus unorganized condition effect. The second experiment addressed the efficacy of two training methods: Full field or telescoping rings. The telescoping ring training method began with presenting the targets on the edge of the field. As the participant improved his/her performance in locating the targets, the presentation ring was moved outward. The full field presentation presented targets in a full 30° radius. Analyses indicated a significant relationship between training method and UFOV. Specifically, both training method were effective in increasing the UFOV. However, no significant difference between the two training methods was observed. Both training conditions increased the field size; however, individuals in the ringer condition were more willing to continue the training. This seems to demonstrate that the telescoping method may cause less frustration for the participants than the full field.

46

Dai, Zhenwen, and 戴振文. "A Markov random field approach for multi-view normal integration." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B4308588X.

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

Van, der Westhuizen Christo Carel. "Efficient registration of limited field of view ocular fundus imagery." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/85633.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Thesis (MScEng)-- Stellenbosch University, 2013.
ENGLISH ABSTRACT: Diabetic- and hypertensive retinopathy are two common causes of blindness that can be prevented by managing the underlying conditions. Patients suffering from these conditions are encouraged to undergo regular examinations to monitor the retina for signs of deterioration. For these routine examinations an ophthalmoscope is used. An ophthalmoscope is a relatively inexpensive device that allows an examiner to directly observe the ocular fundus (the interior back wall of the eye that contains the retina). These devices are analog and do not allow the capture of digital imagery. Fundus cameras, on the other hand, are larger devices that o er high quality digital images. They do, however, come at an increased cost and are not practical for use in the eld. In this thesis the design and implementation of a system that digitises imagery from an ophthalmoscope is discussed. The main focus is the development of software algorithms to increase the quality of the images to yield results of a quality closer to that of a fundus camera. The aim is not to match the capabilities of a fundus camera, but rather to o er a cost-e ective alternative that delivers su cient quality for use in conducting routine monitoring of the aforementioned conditions. For the digitisation the camera of a mobile phone is proposed. The camera is attached to an ophthalmoscope to record a video of an examination. Software algorithms are then developed to parse the video frames and combine those that are of better quality. For the parsing a method of rapidly selecting valid frames based on colour thresholding and spatial ltering techniques are developed. Registration is the process of determining how the selected frames t together. Spatial cross-correlation is used to register the frames. Only translational transformations are assumed between frames and the designed algorithms focuses on estimating this relative translation in a large set of frames. Methods of optimising these operations are also developed. For the combination of the frames, averaging is used to form a composite image. The results obtained are in the form of enhanced grayscale images of the fundus. These images do not match those captured with fundus cameras in terms of quality, but do show a signi cant increase when compared to the individual frames that they consists of. Collectively a set of video frames can cover a larger region of the fundus than what they do individually. By combining these frames an e ective increase in the eld of view is obtained. Due to low light exposure, the individual frames also contain signi cant noise. In the results the noise is reduced through the averaging of several frames that overlap at the same location.
AFRIKAANSE OPSOMMING: Diabetiese- en hipertensiewe retinopatie is twee algemene oorsake van blindheid wat deur middel van die behandeling van die onderliggende oorsake voorkom kan word. Pasiënte met hierdie toestande word aangemoedig om gereeld ondersoeke te ondergaan om die toestand van die retina te monitor. 'n Oftalmoskoop word gebruik vir hierdie roetine ondersoeke. 'n Oftalmoskoop is 'n relatiewe goedkoop, analoë toestel wat 'n praktisyn toelaat om die agterste interne wand van die oog the ondersoek waar die retina geleë is. Fundus kameras, aan die ander kant, is groter toestelle wat digitale beelde van 'n hoë gehalte kan neem. Dit kos egter aansienlik meer en is dus nie geskik vir gebruik in die veld nie. In hierdie tesis word die ontwerp en implementering van 'n stelsel wat beelde digitaliseer vanaf 'n oftalmoskoop ondersoek. Die fokus is op die ontwikkeling van sagteware algoritmes om die gehalte van die beelde te verhoog. Die doel is nie om die vermoëns van 'n fundus kamera te ewenaar nie, maar eerder om 'n koste-e ektiewe alternatief te lewer wat voldoende is vir gebruik in die veld tydens die roetine monitering van die bogenoemde toestande. 'n Selfoonkamera word vir die digitaliserings proses voorgestel. Die kamera word aan 'n oftalmoskoop geheg om 'n video van 'n ondersoek af te neem. Sagteware algoritmes word dan ontwikkel om die videos te ontleed en om videogrepe van goeie kwaliteit te selekteer en te kombineer. Vir die aanvanklike ontleding van die videos word kleurband drempel tegnieke voorgestel. Registrasie is die proses waarin die gekose rame bymekaar gepas word. Direkte kruiskorrelasie tegnieke word gebruik om die videogrepe te registreer. Daar word aanvaar dat die videogrepe slegs translasie tussen hulle het en die voorgestelde registrasie metodes fokus op die beraming van die relatiewe translasie van 'n groot versameling videogrepe. Vir die kombinering van die grepe, word 'n gemiddeld gebruik om 'n saamgestelde beeld te vorm. Die resultate wat verkry word, word in die vorm van verbeterde gryskleur beelde van die fundus ten toon gestel. Hierdie beelde is nie gelykstaande aan die kwaliteit van beelde wat deur 'n fundus kamera geneem is nie. Hulle toon wel 'n beduidende verbetering teenoor individuele videogrepe. Deur dat 'n groot versameling videogrepe wat gesamentlik 'n groter area van die fundus dek gekombineer word, word 'n e ektiewe verhoging van data in die area van die saamgestelde beeld verkry. As gevolg van lae lig blootstelling van die individuele grepe bevat hul beduidende ruis. In die saamgestelde beelde is die ruis aansienlik minder as gevolg van 'n groter hoeveelheid data wat gekombineer is om sodoende die ruis uit te sluit.

48

Dai, Zhenwen. "A Markov random field approach for multi-view normal integration." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B4308588X.

Full text

APA, Harvard, Vancouver, ISO, and other styles

49

Modoran, Georgia C. "Intense field electron excitation in transparent materials." Columbus, Ohio : Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1133273960.

Full text

APA, Harvard, Vancouver, ISO, and other styles

50

Marinov, Toma M. "Field Emission and Scattering From Conducting Nanofibers." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1217614626.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Adaptative field of view'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles