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Dissertations / Theses on the topic 'Optics, Geometrical'
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Gauvin, Alain. "Geometrical distortion of magnetic resonance images." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60675.
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The problem of geometrical distortion in MR images is addressed in the context of the applicability of stereotactic techniques. For this purpose, the distortion of phantom images is measured at various readout bandwidths and the spatial linearity is evaluated in view of the use of a stereotactic frame. The presence of a contribution to the overall distortion of non-linear magnetic gradients is shown from the data, although the distortion observed seems to be mostly attributable to the main field inhomogeneity. The specific problems of distortion of the fiducial markers due to bulk magnetic susceptibility effects is addressed. The occurrence of such effects is characterized with the help of imaging, and the role of the phenomenon on proper target localization is demonstrated. In addition, a method of bypassing the detrimental aspect of these effects is presented.Various distortion correction approaches are discussed, and their benefits and drawbacks are evaluated. In the light of this discussion, a recently reported correction method is then presented. This method allows the calculation of an image free from geometrical and intensity distortion from the combined effect of main field inhomogeneity, susceptibility effects and chemical shift.
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Van, Brunt Bruce. "Functional differential equations and lens design in geometrical optics." Thesis, University of Oxford, 1989. http://ora.ox.ac.uk/objects/uuid:d56090fc-b360-492b-9bd9-c6f36c30db86.
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The subject of this thesis is lens design using a system of functional differential equations arising from Fermat's Principle in geometrical optics. The emphasis is primarily on existence, uniqueness, and analyticity, properties of solutions to these equations, but some asymptotic methods are developed for special cases. Three specific lens problems are considered in detail: the first is an axial lens having two pairs of foci on the optical axis, the second is an axial lens which focuses light at two different frequencies to two distinct points, the third is a lens symmetric about an axis having foci not on said axis.
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Abbas, Syed A. (Syed Aun) Carleton University Dissertation Engineering Systems and Computer. "Microcellular mobile radio channel simulation: a geometrical optics approach." Ottawa, 1993.
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Wosilait, Karen. "Research as a guide for the development of tutorials to improve student understanding of geometrical and physical optics /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/9652.
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Rakich, Andrew. "Simple four-mirror anastigmatic systems with at least one infinite conjugate." Thesis, University of Canterbury. Physics and Astronomy, 2007. http://hdl.handle.net/10092/1463.
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This thesis describes an analytical approach to the optical design of four-mirror anastigmatic optical systems. In all cases investigated here the object is at infinity. In the introduction the field of reflecting, or "catoptric", optical system design is discussed and given some historical context. The concept of the "simplest possible reflecting anastigmat" is raised in connection with Plate Diagram analysis. It is shown that four-plate systems are in general the simplest possible anastigmats, and that four-plate systems comprised of four spherical mirrors are the last family of "simplest possible reflecting anastigmats" for which the complete solution set remains unknown. In chapter 2 third-order aberration coefficients in wavefront measure are derived in a form that is particularly suitable for Plate Diagram analysis. These coefficients are subsequently used to describe the Plate Diagram, and to detail the application of the Plate Diagram to the survey of all possible solutions for four-spherical-mirror anastigmats. The Plate Diagram technique is also generalized to investigate its use as an optical design tool. In the example given a generalized Plate Diagram approach is used to determine solutions for four-mirror anastigmats with a prescribed first-order layout and a minimum number of conicoids. In chapter 3 results are presented for the survey of four-spherical-mirror anastigmats in which all elements are required to be smaller than the primary mirror. Two novel families of four-spherical-mirror anastigmats are presented and these are shown to be the only examples of four-spherical-mirror systems that exist under the given constraints. Chapter 4 gives an example of the application of Plate Diagram analysis to the design of an anastigmatic system with a useful first-order layout and a minimum number of conicoid mirrors. It is shown that systems with useful first-order layouts and only one conicoid mirror can be obtained using this method. In chapter 5 results are presented of the survey of all remaining four-spherical-mirror anastigmatic systems: that is systems in which elements are allowed to exceed the diameter of the entrance pupil, which includes systems with concave and convex primary mirrors. A wide variety of solutions are presented and classified according to both the underlying geometry of the solutions and the first-order layouts. Of these systems only one has been reported in previously published literature. The results presented in this thesis complete the set of "four-plate" reflecting anastigmats, and it can now be said that all possible solutions for four-spherical-mirror anastigmatic systems have been determined.
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Sullivan, Christopher Charles. "The application of biquaternion analysis to the transformation of the electromagnetic field and geometrical optics." Thesis, University of Surrey, 1993. http://epubs.surrey.ac.uk/810773/.
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The addition of the laws of reflection and refraction to basic Euclidean geometry gives rise to an optical geometry which extends into non-Euclidean spaces with the inclusion of non-uniform, isotropic media, for which the ray paths are curved. Transformation theorems arise which are stranger than can be expected from the mere addition of the laws of optics to ordinary geometry. A common characteristic of these transformations is their dependence on the concept of geometrical inversion; such inversions have otherwise been largely ignored in theoretical physics. Given that the geometrical optic field is the infinite frequency approximation of the exact electromagnetic field representation, it is anticipated that any transformations which apply to a geometrical optic system should also apply to the equivalent electromagnetic field system. The work of this thesis introduces the effects of transformations arising from geometrical optics by considering the effects of conformal transformation of the underling electromagnetic field. The geometrical optic transformations to be considered include, among others, Budden's and Bateman's inversion theorems and an inversion theorem applicable within a spherically symmetrical medium. The approach adopted is to proceed in the same manner as in the analogous two dimensional electrostatic/hydrodynamic case, where the conformal properties of complex variable theory are exploited. This approach anticipates that a similar process applies to the four dimensional case of electromagnetism through the use of functions of a hypercomplex variable. These arise in the form originally discovered by Hamilton as quaternion variables, which have been extended in this work through the inclusion of complex i to biquaternion variables. It is also demonstrated that biquaternion variables possess holomorphic properties which are highly relevant to the representation of the electromagnetic field, so that the complete set of Maxwell's electromagnetic field equations can be formulated algebraically and without reference to any physical entities. Most importantly, it is shown how the required transformations of the electromagnetic field arise immediately from biquaternion similarity transformations. Functions of a biquaternion variable are studied in much the same manner as functions of a complex variable. The work of this thesis investigates and makes extensive use of such biquaternion functions. It is necessary then to be able to generate such biquaternion functions. The generation of such functions is based on a technique attributable to Fueter who, for the case of quaternions, defined a generating function which produces a series of polynomials, commonly referred to as Fueter Polynomials. This technique has been extended to biquaternion in this work. The biquaternions used are also descriptive of physical entities, describing for example distance, velocity, force and potentials. These biquaternions are termed physical biquaternions. This work has defined and made use of a number of physical biquaternions which are particularly relevant to describing geometrical optics and electromagnetism. The customary potential descriptions of the electromagnetic field in terms of field vectors or in any of the usual potential descriptions have proved inadequate for applications analogous with the transformations of geometrical optics. An alternative representation of the electromagnetic field has been developed that allows such an association. This has been achieved through the introduction and reformulation of the electromagnetic field in terms of two scalar potentials. This reformulation of the electromagnetic field results in certain conditions being placed on these scalar potentials, which must be met if realisable electromagnetic fields are to be obtained. The two examples of plane wave and dipole generated fields are considered in this thesis. This reformulation has also shown, that, for the spherically symmetrical medium, it provides the orthogonal transformation (the inversion) for rays and for the medium refractive index.
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Constantinides, Evagoras D. "A uniform geometrical optics and an extended uniform geometrical theory of diffraction for evaluating high frequency EM fields near smooth caustics and composite shadow boundaries /." The Ohio State University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487843314694902.
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Ma, Donglin. "Exploration of Ray Mapping Methodology in Freeform Optics Design for Non-Imaging Applications." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/594394.
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This dissertation investigates various design metrologies on designing freeform surfaces for LED illumination applications. The major goal of this dissertation is to study designing freeform optical surfaces to redistribute the radiance (which can be simplified as intensity distribution for point source) of LED sources for various applications. Nowadays many applications, such as road lighting systems, automotive headlights, projection displays and medical illuminators, require an accurate control of the intensity distribution. Freeform optical lens is commonly used in illumination system because there are more freedoms in controlling the ray direction. Design methods for systems with rotational and translational symmetry were well discussed in the 1930's. However, designing freeform optical lenses or reflectors required to illuminate targets without such symmetries have been proved to be much more challenging. For the simplest case when the source is an ideal point source, the determination of the freeform surface in a rigorous manner usually leads to the tedious Monge-Ampère second order nonlinear partial different equation, which cannot be solved with standard numerical integration techniques. Instead of solving the differential equation, ray mapping is an easier and more efficient method in controlling one or more freeform surfaces for prescribed irradiance patterns. In this dissertation, we investigate the ray mapping metrologies in different coordinate systems to meet the integrability condition for generating smooth and continuous freeform surfaces. To improve the illumination efficiency and uniformity, we propose a composite ray mapping method for designing the total internal reflective (TIR) freeform lens for non-rotational illumination. Another method called "double pole" ray mapping method is also proposed to improve system performance. The ray mapping designs developed for the point source do not work well for extended sources, we have investigated different design methodologies including optimization method, deconvolution method and feedback modification method to design freeform optical surfaces for extended sources.
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Andersson, Roger. "Teaching and learning geometrical optics with computer assisted instruction : changing conceptions about vision, image and ray." Licentiate thesis, Karlstad University, Faculty of Technology and Science, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-720.
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The information and communication technology, ICT, is opening new possibilities for the educational arena. Previous research shows that achieving positive educational outcomes requires more than simply providing access to computer hardware and software. How does this new technology affect the teaching and learning of physics? This thesis focuses on the field of geometrical optics. It reports two studies, both in Swedish upper secondary school. Important for the use of the ICT in physics education is the teaching strategy for using the new technology. The first study investigates with a questionnaire, how 37 teachers in a region of Sweden use computers in physics education and what intentions they follow while doing so. The results of this study show that teachers’ intentions for using ICT in their physics teaching were to increase students' interest for physics, to increase their motivation, to achieve variation in teaching, and to improve visualization and explanation of the phenomena of physics. The second study investigates students’ conceptual change in geometrical optics during a teaching sequence with computer-assisted instruction. For this purpose we choose the computer software "Constructing Physics Understanding (CPU)", which was developed with a base in research on students conceptions in optics. The thesis presents the teaching sequence developed together with the teacher. The study is based on a constructivist view of learning. The concepts analysed in this study were vision, image, ray and image formation. A first result of this study is a category system for conceptions around these concepts, found among the students. With these categories we found that students even at this level, of upper secondary school, have constructed well-known alternative conceptions before teaching, e.g. about a holistic conception of image. The results show also some learning progress: some alternative conceptions vanish, in some cases the physics conceptions are more often constructed after teaching. The students and the teacher also report that the CPU program gave new and useful opportunities to model multiple rays and to model vision.
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Sasaki, Katsuhiro, and Hiroyasu Saka. "A simple method of the electric/magnetic field observation by a conventional transmission electron microscope." Trans Tech Publications Inc, 2005. http://hdl.handle.net/2237/5299.
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Hellman, Brandon, Erica Bosset, Luke Ender, Naveed Jafari, Phillip McCann, Chris Nguyen, Chris Summitt, Sunglin Wang, and Yuzuru Takashima. "3D visualization of optical ray aberration and its broadcasting to smartphones by ray aberration generator." SPIE-INT SOC OPTICAL ENGINEERING, 2017. http://hdl.handle.net/10150/627182.
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The ray formalism is critical to understanding light propagation, yet current pedagogy relies on inadequate 2D representations. We present a system in which real light rays are visualized through an optical system by using a collimated laser bundle of light and a fog chamber. Implementation for remote and immersive access is enabled by leveraging a commercially available 3D viewer and gesture-based remote controlling of the tool via bi-directional communication over the Internet.
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Fournier, Florian. "FREEFORM REFLECTOR DESIGN WITH EXTENDED SOURCES." Doctoral diss., University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3146.
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Reflector design stemmed from the need to shape the light emitted by candles or lamps. Over 2,000 years ago people realized that a mirror shaped as a parabola can concentrate light, and thus significantly boosts its intensity, to the point where objects can be set afire. Nowadays many applications require an accurate control of light, such as automotive headlights, streetlights, projection displays, and medical illuminators. In all cases light emitted from a light source can be shaped into a desired target distribution with a reflective surface. Design methods for systems with rotational and translational symmetry were devised in the 1930s. However, the freeform reflector shapes required to illuminate targets with no such symmetries proved to be much more challenging to design. Even when the source is assumed to be a point, the reflector shape is governed by a set of second-order partial non-linear differential equations that cannot be solved with standard numerical integration techniques. An iterative approach to solve the problem for a discrete target, known as the method of supporting ellipsoids, was recently proposed by Oliker. In this research we report several efficient implementations of the method of supporting ellipsoids, based on the point source approximation, and we propose new reflector design techniques that take into account the extent of the source. More specifically, this work has led to three major achievements. First, a thorough analysis of the method of supporting ellipsoids was performed that resulted in two alternative implementations of the algorithm, which enable a fast generation of freeform reflector shapes within the point source approximation. We tailored the algorithm in order to provide control over the parameters of interest to the designers, such as the reflector scale and geometry. Second, the shape generation algorithm was used to analyze how source flux can be mapped onto the target. We derived the condition under which a given source-target mapping can be achieved with a smooth continuous surface, referred as the integrability condition. We proposed a method to derive mappings that satisfy the integrability condition. We then use these mappings to quickly generate reflector shapes that create continuous target distributions as opposed to reflectors generated with the method of supporting ellipsoids that create discrete sets of points on the target. We also show how mappings that do not satisfy the integrability condition can be achieved by introducing step discontinuities in the reflector surface. Third, we investigated two methods to design reflectors with extended sources. The first method uses a compensation approach where the prescribed target distribution is adjusted iteratively. This method is effective for compact sources and systems with rotational or translational symmetry. The second method tiles the source images created by a reflector designed with the method of supporting ellipsoids and then blends the source images together using scattering in order to obtain a continuous target distribution. This latter method is effective for freeform reflectors and target distributions with no sharp variations. Finally, several case studies illustrate how these methods can be successfully applied to design reflectors for general illumination applications such as street lighting or luminaires. We show that the proposed design methods can ease the design of freeform reflectors and provide efficient, cost-effective solutions that avoid unnecessary energy consumption and light pollution.Ph.D.
Optics and Photonics
Optics and Photonics
Optics PhD
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Clerici, Giancarlo. "Geometrical optics design of a compact range Gregorian subreflector system by the principle of the central ray /." The Ohio State University, 1988. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487588249825016.
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Marcum, Frank. "Design of an image radiation monitor for ILS glide slope in the presence of snow." Ohio : Ohio University, 1995. http://www.ohiolink.edu/etd/view.cgi?ohiou1174609165.
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Borrajo, Thiago Balacó. "Atividades investigativas para o ensino de óptica geométrica." reponame:Repositório Institucional da UFC, 2017. http://www.repositorio.ufc.br/handle/riufc/23546.
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BORRAJO, T. B. Atividades investigativas para o ensino de óptica geométrica. 2017.117 f. Dissertação (Mestrado Nacional Profissional em Ensino de Física) - Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2017.Submitted by francisco lima (admir@ufc.br) on 2017-06-21T18:09:56Z No. of bitstreams: 1 2017_dis_tbborrajo.pdf: 2234935 bytes, checksum: 28fb00441f75e93f7465f2b7b75ff5ed (MD5)
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In the face of a scene of dissatisfaction and indifference in the process of teaching/learning of science in basic education, we present a proposal for teaching some fundamentals topics of geometrical optics, based on investigative activities that require reflection and reasoning. In it, the students are divided into groups and they need to discuss about ideas, make hypotheses and find ways for prove them. At the end of each class, the group conclusions are confronted with formal knowledge. Making it possible to analyze discrepancies and concordances with the know theory. The methodology is based on the concepts of active learning, sociointeractionism and inquiry based learning. The main focus of the proposal is increase student interest, make him more receptive to new knowledges by problematization and discussion with colleagues and teacher. With this method, it is possible to transform student into an agent in his own process of learning, developing his skills and capabilities in a science education process.
Diante de um cenário de insatisfação e desinteresse no processo de ensino/aprendizagem de ciências na educação básica, apresentamos uma proposta para o ensino de alguns tópicos fundamentais de óptica geométrica, baseada em atividades investigativas que exigem reflexão e raciocínio. Nela, os estudantes são divididos em grupos e precisam debater ideias, construir hipóteses e encontrar meios para comprová-las. Ao final de cada aula, as conclusões dos grupos são confrontadas com o conhecimento formal, possibilitando a análise de discordâncias e concordâncias com a teoria já estabelecida. A metodologia é baseada nos conceitos de aprendizagem ativa, sociointeracionismo e ensino por investigação. O grande foco da proposta é despertar o interesse do aluno, torná-lo mais receptivo aos novos conhecimentos através da problematização e do debate com os colegas e com o professor. A partir de entrevistas com os alunos, observação da sala durante as práticas e análise de relatórios elaborados pelos próprios estudantes, foi possível constatar que eles conseguiram desenvolver, efetivamente, uma atitude científica ao longo das investigações. Com esse método, é possível fazer do estudante um agente no seu próprio processo de aprendizagem, desenvolvendo suas habilidades e capacidades em um processo de educação científica.
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Isik, Hakan. "Relationship of college student characteristics and inquiry-based geometrical optics instruction to knowledge of image formation with light-ray tracing." Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1201718813.
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Camelo, Midori Hijioka. "O espelho e a janela: as investigações ópticas de Filippo Brunelleschi (1377-1446) e Leon Battista Alberti (1404-1472) para a "costruzione legittima"." Pontifícia Universidade Católica de São Paulo, 2009. https://tede2.pucsp.br/handle/handle/13444.
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Previous issue date: 2009-10-16This work tried to identify the contributions of Filippo Brunelleschi and Leon Battista Alberti to the geometrical optics study. Tradicinally, seen by the history of arts and architecture study as inventors of the perspective, in this history of science study, the issue of genealogy was left behind, so they could find in the investigations about costruzione legittima , contributions for the geometrical optics. The period lived by Brunelleschi and Albert, the Renaissance one, shows many changing elements that made the transition from the Medieval and the Modern History. Specially about the perspective study, it s an incorporating moment, with a different meaning to the word. What used to be the synonym of optics throughout Middle Age, thanks largely to the investigations of architects and painters started then, has now the idea of the representation way , keeping it though the time, like we understand it today. Along with the complex movement of approaching of the heavenly thing to the ones here on Earth, witch in canvas mean the introduction of elements of the real world in representations, we can also see an approach of mathematics to the useful things of life, and geometry becomes equally important to the costruzione legittima of visual reality. In the arts and science knowledge and duties meetings, brought to you by the humanism, the spirit of modern science blends together, In the history of geometrical and experimental optics, the art of painting is show more present than it was traditionally thought to. At the time of seeing, the birth of modern science, the connections of Brunellesch and Alberti revealed how artificial the limit of art and science, the duties and the knowledge
Esta pesquisa buscou identificar as contribuições de Filippo Brunelleschi e Leon Battista Alberti para o estudo da óptica geométrica. Tradicionalmente, disputados pelos estudiosos da história da arte e arquitetura como inventores da perspectiva, neste estudo em história da ciência, deixaram-se de lado a questão de genealogia para encontrar, no interior das investigações para a costruzione legittima , contribuições para a óptica geométrica. O período vivido por Brunelleschi e Alberti, o Renascimento, apresenta muitos elementos de transformações que marcaram historicamente a transição entre o Medieval e o Moderno. Particularmente para o estudo da perspectiva, trata-se de um momento de formação de um novo significado para o termo. O que era sinônimo de óptica durante toda Idade Média, passa a incorporar, graças às investigações dos pintores e arquitetos iniciada ali, a idéia de modo de representação , ficando no decorrer do tempo somente com esta última, tal como entendemos hoje. Juntamente com o complexo movimento de aproximação de elementos do mundo real para a pintura, vemos ocorrer uma aproximação da geometria à forma de representação. No encontro de saberes e fazeres, de arte e ciência, plasma-se o espírito da ciência moderna. Na história da óptica geométrica e experimental, a arte da pintura mostra-se mais presente que tradicionalmente se pensa. Ao vislumbrar, no alvorecer da ciência moderna, as conexões entre Brunelleschi e Alberti revelou-se a artificialidade da fronteira entre a arte e a ciência, o fazer e o saber
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Petkov, Theodor. "Statics and dynamics of ellipsoidal particles in laser beams." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0878/document.
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Ce travail de thèse est une contribution au projet national AMOCOPS, financé par l’ANR. Le thème central du projet est la diffusion de lumière par des particules de formes complexes et de grandes tailles (plusieurs dizaines de µm au moins), domaine où les méthodes de simulation numérique existantes trouvent leurs limites d’applicabilité. Nous abordons le problème par le biais des effets mécaniques de la lumière, autrement dit les forces et couples créés par la pression de radiation. Etant la conséquence du transfert d’impulsion entre l’onde et la matière, ces effets sont directement liés à la diffusion de lumière. La thèse comprend une partie expérimentale –majoritaire- concernant les réponses mécaniques de particules de polystyrène de forme ellipsoïdale et d’allongement variable sous illumination par un ou deux faisceaux laser. Les cas de faisceaux faiblement focalisés (lévitation optique) et d’un faisceau très fortement focalisé (pincette optique) sont examinés successivement. Nous caractérisons différents types d’équilibre statique, certains d’entre eux non décrits auparavant, obtenus dans les deux géométries. Par ailleurs nous confirmons l’existence de réponses purement dynamiques, où la particule oscille en permanence. Trois nouveaux modes sont observés, deux dans la géométrie lévitation optique et un autre sous pincette optique. Cette étude nous permet de distinguer les oscillations dites de Simpson-Hanna dans le régime linéaire de celles non linéaires mises en évidence avant nous par Mihiretie et al..Les résultats de nos expériences sont comparés à ceux obtenus par les simulations de J.C. Loudet, sur la base de la simple optique géométrique (OG) et limitées à 2 dimensions (2d). Nous montrons que ces simulations permettent de reproduire qualitativement et comprendre physiquement la plupart des comportements observés dans nos expériences. La principale limitation de ces calculs tient à ce que l’OG ignore le caractère ondulatoire de la lumière. Pour faire mieux et aller vers des simulations fiables quantitativement, il faut développer un modèle alliant optique géométrique et optique ondulatoire. C’est la fonction du modèle VCRM (Vectorial Complex Ray Model) développé récemment par K.F. Ren en 2d. Le but du projet Amocops est de mettre au point la version 3d de la méthode et de la valider sur la base d’expériences comme celles que nous avons conduites. La deuxième partie de la thèse est consacrée à la méthode VCRM. Nous en exposons les principes, et nous présentons quelques résultats des travaux en cours avec une version intermédiaire entre 2d et 3d, dite « 2d+ ». Quelques illustrations sont proposées sur des exemples impliquant des sphères et ellipsoïdes de grandes taillesThis work is a contribution to the “AMOCOPS” project, funded by Agence Nationale de la Recherche. AMOCOPS is dedicated to the development of new computation schemes to simulate the light scattering patterns of large complexly shaped particles. Particle sizes are of the order of several 10s of micrometres, which is at the limit, or beyond the capabilities of currently available computation techniques.Our work indirectly deals with light scattering through the corresponding mechanical effects of light. Light scattering is the source of momentum transfer between light and matter, and therefore of the forces and torques acting on the exposed particles. The majority of Part A of this thesis is about the mechanical responses of ellipsoidal polystyrene particles of varying aspect ratios, under illumination by one or two laser beams. We investigate the case of weakly focused beams (optical levitation), and that of a single large aperture beam (optical tweezers). Different types of static equilibria, some of which are new, are observed and characterized in both geometries. We confirm the existence of dynamic states, whereby the particle permanently oscillates within the laser beam(s). Three new oscillation modes are observed, two of them in the conditions of optical levitation, and another one in the optical tweezer geometry. The study allows us to make a distinction between noise-driven oscillations in the linear regime, of the type predicted by Simpson and Hanna, and nonlinear oscillations such as those evidenced prior to this work, by Mihiretie et al..Results from our experiments are compared to simulations by J.C. Loudet, using simple ray-optics (RO) in two dimensions (2D). We show that results from 2D-RO qualitatively match most of our observations, and allow us to physically understand the main mechanisms at work in the observed phenomena. The simulations cannot be quantitatively exact, due to the 2D limitation, and because RO essentially ignores the wave nature of light. In Part B of the manuscript, we present the principles of the Vectorial Complex Ray Model (VCRM), which was recently developed by K.F. Ren in 2d. The goal of AMOCOPS is to develop a full 3D version of VCRM, able to simulate light scattering by particles of any shape with a smooth surface. We explain the basics of the model, as well as the “2D+” version, which is an extension of the basic 2D-VCRM. A few illustrative examples of light scattering patterns computed with 2d+-VCRM for large-sizes spheres and ellipsoids are presented
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Rushton, Elliott C. "Predicting the effects of shadowing and scattering from planar surfaces on localizer course structure using geometrical optics and the uniform theory of diffraction as implemented in the near zone basic scattering code." Ohio : Ohio University, 1994. http://www.ohiolink.edu/etd/view.cgi?ohiou1178731752.
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Ciydem, Mehmet. "Ray Based Finite Difference Method For Time Domain Electromagnetics." Phd thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606633/index.pdf.
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In this study, novel Ray Based finite difference method for Time Domain electromagnetics(RBTD) has been developed. Instead of solving Maxwell&rsquos hyperbolic partial differential equations directly, Geometrical Optics tools (wavefronts, rays) and Taylor series have been utilized. Discontinuities of electromagnetic fields lie on wavefronts and propagate along rays. They are transported in the computational domain by transport equations which are ordinary differential equations. Then time dependent field solutions at a point are constructed by using Taylor series expansion in time whose coefficients are these transported distincontinuties. RBTD utilizes grid structure conforming to wave fronts and rays and treats all electromagnetic problems, regardless of their dimensions, as one dimensional problem along the rays. Hence CFL stability condition is implemented always at one dimensional eqaulity case on the ray. Accuracy of RBTD depends on the accuracy of grid generation and numerical solution of transport equations. Simulations for isotropic medium (homogeneous/inhomogeneous) have been conducted. Basic electromagnetic phenomena such as propagation, reflection and refraction have been implemented. Simulation results prove that RBTD eliminates numerical dispersion inherent to FDTD and is promising to be a novel method for computational electromagnetics.
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Le, Bouteiller Philippe. "Approche eulérienne de l'équation de Hamilton-Jacobi par une méthode Galerkine discontinue en milieu hétérogène anisotrope : Application à l'imagerie sismique." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAU035/document.
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Pouvoir déterminer la structure et la composition de l’intérieur de la Terre est un enjeu scientifique fondamental, pour la compréhension de l’organisation de la Terre profonde, des mécanismes des séismes et leur localisation en lien avec la prévention du risque sismique, pour la détection et l’exploitation des ressources naturelles telles que l’eau ou les hydrocarbures, ou encore pour toutes les activités de construction et de prévention associées au génie civil. Pour cela, les ondes sismiques sont un outil de choix. L’utilisation d’une approximation haute fréquence pour la modélisation de la propagation des ondes est avantageuse en termes de coût de calcul dès lors que plusieurs centaines, voire milliers, ou plus de longueurs d’ondes doivent être propagées. À la place de l’équation des ondes linéaire, l’approximation haute fréquence fournit trois équations aux dérivées partielles fondamentales. L’équation Eikonal, non linéaire, permet d’obtenir le temps de trajet. Une deuxième équation fournit l’angle d’émergence. L’équation Eikonal et l’équation des angles appartiennent toutes deux à la grande famille des équations de Hamilton-Jacobi. Enfin, l’équation de transport permet de calculer l’amplitude.Le tracé des rais sismiques est une technique lagrangienne qui utilise la méthode des caractéristiques pour obtenir un ensemble d’équations différentielles ordinaires à partir de ces équations aux dérivées partielles. Ces équations peuvent être intégrées facilement, donnant ainsi accès au temps de trajet et à l’amplitude le long des rais. Très largement utilisés dans la communauté géophysique du fait de leur simplicité, les outils de tracé de rais ne sont pas pour autant les plus efficaces et les plus robustes en pratique pour des applications d’imagerie et d’inversion haute résolution. En lieu et place, il peut être utile de résoudre directement les équations aux dérivées partielles par une méthode eulérienne. Durant les trois dernières décennies, une multitude de solveurs ont été développés pour l’équation Eikonal, la plupart utilisant la méthode des différences finies. Ces différents travaux visent à obtenir le meilleur compromis entre précision, coût de calcul, robustesse, facilité d’implémentation et souplesse d’utilisation.Dans cette thèse, je développe une approche différente, se basant principalement sur une méthode Galerkine discontinue. Dans le champ des mathématiques, cette méthode a été largement utilisée pour résoudre les lois de conservation et les équations de Hamilton-Jacobi. Très peu de travaux ont porté sur l'utilisation de cette méthode pour la résolution de l’équation Eikonal statique dans un contexte géophysique, et ce malgré le haut niveau de précision qu'elle apporte. C’est pourquoi, en me basant sur des travaux mathématiques, je propose un nouveau solveur Eikonal adapté au contexte géophysique. Les milieux hétérogènes complexes, anisotropes, et incluant des variations topographiques sont correctement pris en compte, avec une précision sans précédent. En y intégrant de manière robuste une stratégie de balayage rapide, je montre que ce solveur présente une très grande efficacité en deux comme en trois dimensions.J'utilise également ce solveur pour calculer l’angle d’émergence. Je développe par ailleurs un solveur voisin en volumes finis pour la résolution de l’équation de transport, permettant ainsi le calcul de l’amplitude. La variable d’état adjoint pour la tomographie sismique des temps et des pentes vérifiant une équation de transport semblable, je montre qu'on peut également la calculer à l'aide de ce solveur en volumes finis. En conséquence, je propose et analyse un ensemble consistant de solveurs pour la communauté géophysique. Ces outils devraient s’avérer utiles pour une large palette d’applications. Finalement, en guise d’illustration, je les utilise dans des schémas d’imagerie sismique, dans le but de démontrer le bénéfice apporté par une approximation haute fréquence dans ce type de schémasRecovering information on the structure and the composition of the Earth's interior is a fundamental issue for a large range ofapplications, from planetology to seismology, natural resources assessment, and civil engineering. Seismic waves are a very powerful tool for that purpose. Using a high-frequency approximation for the numerical modeling of seismic wave propagation is computationally advantageous when hundreds, thousands, or more of wavelengths have to be propagated. Instead of the linear wave equation, the high-frequency approximation yields three fundamental partial differential equations. The nonlinear Eikonal equation leads to traveltime. A second equation is derived for the take-off angle. Both Eikonal and angle equations belong to the wide Hamilton-Jacobi family of equations. In addition, the transport equation leads to the amplitude.As a Lagrangian approach, seismic ray tracing employs the method of characteristics to derive a set of ordinary differential equations from these partial differential equations. They can be easily integrated, thus yielding traveltime and amplitude along rays. Widely used in the geophysical community for their simplicity, the ray-tracing tools might not be the most efficient and robust ones for practical high-resolution imaging and inversion applications. Instead, it might be desirable to directly solve the partial differential equations in an Eulerian way. In the three last decades, plenty of Eikonal solvers have been designed, mostly based on finite-difference methods. Successive works try to find the best compromise between accuracy, computational efficiency, robustness, ease of implementation, and versatility.In this thesis, I develop a different approach, mainly based on the discontinuous Galerkin method. This method has been intensively used in the mathematical field for solving conservation laws and time-dependent Hamilton-Jacobi equations. Only few investigations have been done regarding its use for solving the static Eikonal equation in a geophysical context, despite the high level of accuracy allowed by this method. Therefore, improving upon mathematical studies, I propose a new Eikonal solver suitable for the geophysical context. Complex heterogeneous anisotropic media with non-flat topographies are correctly handled, with an unprecedented accuracy. Combined with a fast-sweeping strategy in a robust way, I show that this new solver exhibits a high computational efficiency, in two dimensions as well as in three dimensions.I also employ this solver for the computation of the take-off angle. I design an additional finite-volume solver for solving the transport equation, leading to the computation of amplitude. With this solver, I also consider the computation of the adjoint-state variable for seismic tomography, since it satisfies a similar transport equation. Eventually, I propose a whole set of consistent solvers to the geophysical community. These tools should be useful in a wide range of applications. As an illustration, I finally use them in advanced seismic imaging schemes, in order to demonstrate the benefit brought by the high-frequency approximation in this kind of schemes
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Sen, Saffet Gokcen. "Investigation Of Electromagnetic Wave Propagation In Double Negative Materials." Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609748/index.pdf.
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This thesis analyzes some aspects of electromagnetic wave propagation in double negative materials. Double negative materials have negative refractive indices. They are backward-wave materials. Plane waves undergo negative refraction at interfaces between double positive and double negative media. Causality principle implies these properties. High frequency plane wave scattering from a double negative infinitely long cylinder has been analyzed by using modified Watson transform, geometrical optics and Mie series. Mie series results and the modified Watson transform results have been found to be in good agreement. Hence, the physical mechanism of the scattering has been revealed.
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Neves, Juliano César Silva. "Mundos Brana: Buracos negros e buracos de minhoca." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-10012013-235659/.
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Neste trabalho, construímos novas soluções com simetria esférica ou axial para as equações do campo gravitacional induzido num cenário brana do tipo Randall-Sundrum, onde uma 3-brana com constante cosmológica está imersa num espaço-tempo 5-dimensional conhecido como bulk. Para o caso esfericamente simétrico, com constante cosmológica negativa, obtivemos uma família de soluções numa brana assintoticamente anti-de Sitter, sendo que cada membro desta é diferenciado de outro por uma constante integração C, que fixada proveu-nos soluções de buracos negros ou buracos de minhocas. Com a mesma simetria, geometrias que descrevem buracos de minhoca foram encontradas numa brana assintoticamente de Sitter. Para o caso axialmente simétrico, métricas assintoticamente anti-de Sitter e de Sitter foram construídas no contexto citado. Propriedades óticas, como a rotação do vetor de polarização, foram estudadas, mostrando-nos algumas diferenças entre os mundos brana, tratados como uma teoria de gravitação modificada, e a relatividade geral.In this work we have constructed new solutions, with axial or spherical symmetry, to the induced gravitational field equations within a Randall-Sundrum type brane world scenario, where a 3-brane with cosmological constant is embedded in a 5-dimensional space-time called bulk. For the spherical case with negative cosmological constant, we have found a family of solutions in an anti-de Sitter brane, where each member of the family is different from another when C is fixed. With a fixed C we have black holes or wormholes. In this same case, with spherical symmetry, we have obtained wormhole solutions in a de Sitter brane. In the same context, for the axially symmetric case, metrics asymptotically anti-de Sitter and de Sitter were built. Optics features, like rotation of polarization vector, have been studied. These features showed some differences between brane worlds, a theory of modified gravity, and the General Relativity.
24
Hultin, Harald. "Investigation of Near-Field Contribution in SBR for Installed Antenna Performance." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-260077.
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To investigate near-eld contributions for installed antennas, an in-house code iswritten to incorporate near-eld terms in Shooting and Bouncing Rays (SBR). SBRis a method where rays are launched toward an object and scatter using GeometricalOptics (GO). These rays induce currents on the object, from which the totalscattered eld can be found.To gauge the eect of near-eld terms, the in-house code can be set to excludenear-eld terms. Due to this characteristic, the method is named SBR Includingor Excluding Near-eld Terms (SIENT). The SIENT implementation is thoroughlydescribed. To make SIENT more exible, the code works with triangulated meshesof objects. Antennas are represented as near-eld sources, allowing complex antennasto be represented by simple surface currents. Further, some implementedoptimizations of SIENT are shown.To test the implemented method, SIENT is compared to a reference solution andcomparable commercial SBR solvers. It is shown that SIENT compares well to thecommercial options. Further, it is shown that the inclusion of near-eld terms actsas a small correction to the far-eld of the installed antenna.För att undersöka närfältsbidrag för installerade antenner, har en kod skrivits föratt ta med närfältstermer i Shooting Bouncing Rays (SBR). SBR är en metod där strålar (”rays”) skjuts mot ett object och sprids via Geometrisk Optik (GO). Dessa strålar inducerar strömmar på objectet, från vilka det totala sprida fältet kan hittas. För att undersöka bidraget från närfältstermer, så kan koden exkludera dessa. På grund av denna karaktär, kallas koden SBR Including or Excluding Near-field Terms (SIENT). Implementationen av SIENT beskrivs utförligt. För att göra SIENT mer flexibel, arbetar SIENT med triangulerade nät av objekt. Antenner representeras av närfältskällor, vilket låter komplexa antenner representeras med enkla yt-strömmar.Implementerade optimeringar av SIENT visas också.För att testa den implementerade metoden, jämförs SIENT med en referenslösning och jämförbara kommerciella SBR-lösare. Det visas att SIENT överensstämmer bra med kommerciella alternativ. Det visas också att närfältstermer agerar som enmindre korrektion till fjärrfältet av den installerade antennen.
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Kaltakci, Derya. "Development And Application Of A Four-tier Test To Assess Pre-service Physics Teachers'." Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614699/index.pdf.
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The main purpose of this study was to develop and administer a four-tier test for assessing Turkish pre-service physics teachers&rsquomisconceptions about geometrical optics. Sixteen pre-service physics teachers, who were selected by maximum variation and convenience sampling methods from three state universities in Ankara, were interviewed in the contexts of plane mirrors, spherical mirrors, and lenses. From these interviews and the studies in the literature, the Open-Ended Geometrical Optics Test was developed. It was administered to 52 pre-service physics teachers from three state universities selected by purposive and convenience sampling. The responses of each subject for each item were categorized in order to determine the alternatives of the multiple-tier multiple-choice misconception test. The initial form of the test, the Three-Tier Geometrical Optics Test (TTGOT), was administered to 53 pre-service physics teachers from three state universities selected by purposive and convenience sampling as a pilot study. The analysis of the results of the TTGOT was used to revise the test items. Finally, the Four-Tier Geometrical Optics Test (FTGOT) was developed and administered to 243 pre-service physics teachers from 12 state universities in Turkey. The validity of the FTGOT scores was established by means of some qualitative and quantitative methods. The Cronbach alpha reliability coefficients were calculated for different test scores. Those for the total correct scores and standardized misconception scores (SUMM4) were found to be .59 and .42, respectively. Some misconceptions, which were held by more than 10 % of the pre-service teachers, were identified and considered to be significant.
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Sefi, Sandy. "Computational electromagnetics : software development and high frequency modeling of surface currents on perfect conductors." Doctoral thesis, KTH, Numerisk Analys och Datalogi, NADA, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-590.
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In high frequency computational electromagnetics, rigorous numerical methods be come unrealistic tools due to computational demand increasing with the frequency. Instead approximations to the solutions of the Maxwell equations can be employed to evaluate th electromagnetic fields. In this thesis, we present the implementations of three high frequency approximat methods. The first two, namely the Geometrical Theory of Diffraction (GTD) and th Physical Optics (PO), are commonly used approximations. The third is a new invention that will be referred to as the Surface Current Extraction-Extrapolation (SCEE). Specifically, the GTD solver is a flexible and modular software package which use Non-Uniform Rational B-spline (NURBS) surfaces to model complex geometries. The PO solver is based on a triangular description of the surfaces and includes fas shadowing by ray tracing as well as contribution from edges to the scattered fields. GTD ray tracing was combined with the PO solver by a well thought-out software architecture Both implementations are now part of the GEMS software suite, the General ElectroMag netic Solvers, which incorporates state-of-the-art numerical methods. During validations both GTD and PO techniques turned out not to be accurate enough to meet the indus trial standards, thus creating the need for a new fast approximate method providing bette control of the approximations. In the SCEE approach, we construct high frequency approximate surface currents ex trapolated from rigourous Method of Moments (MoM) models at lower frequency. T do so, the low frequency currents are projected onto special basis vectors defined on th surface relative to the direction of the incident magnetic field. In such configuration, w observe that each component displays systematic spatial patterns evolving over frequenc in close correlation with the incident magnetic field, thus allowing us to formulate a fre quency model for each component. This new approach is fast, provides good control of th error and represents a platform for future development of high frequency approximations. As an application, we have used these tools to analyse the radar detectability of a new marine distress signaling device. The device, called "Rescue-Wing", works as an inflatabl radar reflector designed to provide a strong radar echo useful for detection and positionin during rescue operations of persons missing at sea.QC 20101004
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Nordblad, Erik. "Opening New Radio Windows and Bending Twisted Beams." Doctoral thesis, Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-158797.
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In ground based high frequency (HF) radio pumping experiments, absorption of ordinary (O) mode pump waves energises the ionospheric plasma, producing optical emissions and other effects. Pump-induced or natural kilometre-scale field-aligned density depletions are believed to play a role in self-focussing phenomena such as the magnetic zenith (MZ) effect, i.e., the increased plasma response observed in the direction of Earth's magnetic field. Using ray tracing, we study the propagation of ordinary (O) mode HF radio waves in an ionosphere modified by density depletions, with special attention to transmission through the radio window (RW), where O mode waves convert into the extraordinary (X, or Z) mode. The depletions are shown to shift the position of the RW, or to introduce RWs at new locations. In a simplified model neglecting absorption, we estimate the wave electric field strength perpendicular to the magnetic field at altitudes normally inaccessible. This field could excite upper hybrid waves on small scale density perturbations. We also show how transmission and focussing combine to give stronger fields in some directions, notably at angles close to the MZ, with possible implications for the MZ effect. In a separate study, we consider electromagnetic (e-m) beams with helical wavefronts (i.e., twisted beams), which are associated with orbital angular momentum (OAM). By applying geometrical optics to each plane wave component of a twisted nonparaxial e-m Bessel beam, we calculate analytically the shift of the beam's centre of gravity during propagation perpendicularly and obliquely to a weak refractive index gradient in an isotropic medium. In addition to the so-called Hall shifts expected from paraxial theory, the nonparaxial treatment reveals new shifts in both the transverse and lateral directions. In some situations, the new shifts should be significant also for nearly paraxial beams.
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Evans, Jonathan W. "Beam Switching of an Nd:YAG Laser Using Domain Engineered Prisms in Magnesium Oxide Doped Congruent Lithium Niobate." University of Dayton / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1281366442.
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Roberto, Edson Valentim. "Aprendizagem ativa em ótica geométrica: experimentos e demonstrações investigativas." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-05072009-203744/.
Full textAbstract:
Atualmente existe, praticamente, um consenso entre os pesquisadores de Ensino de Física, de que a metodologia tradicional não é a mais efetiva por não promover um real engajamento dos estudantes durante o processo de ensino/aprendizagem. Muitos pesquisadores denominam Aprendizagem Ativa (AA), os métodos que requerem tal engajamento e as pesquisas indicam que esta abordagem é mais efetiva. Ou seja, verifica-se um aumento da compreensão dos conceitos básicos de Física. Entretanto, ainda há pouca aplicação de novas metodologias em sala de aula, tanto no ensino médio quanto no superior. No nosso entender, as atividades experimentais (de laboratório ou demonstração) são as mais adequadas para a aplicação de metodologias de AA. Entretanto, particularmente no Brasil, existe pouco material didático experimental disponível que utilize essa metodologia. Este trabalho visa sanar tal necessidade no campo da Ótica Geométrica, oferecendo uma série de roteiros comentados para experimentos e demonstrações interativas. Estes roteiros usam a idéia de investigação orientada onde se pretende que os conhecimentos prévios dos alunos sejam expostos e confrontados com os conceitos científicos. Este material foi aplicado a estudantes do ensino médio (escolas públicas) e do curso de Licenciatura em Ciências Exatas do IFSC. Para a avaliação do mesmo foram realizados testes escritos e monitoramentos em sala de aula.There is nowadays consensus among the physics education researchers that the traditional teaching methods are not the most effective in promoting real engagement of the students in the teaching/learning process. Several researchers named Active Learning (AL), methods that require this engagement and research evidences indicate that this approach is the most effective, a better comprehension of the basic physics concepts is verified. However, particularly in Brazil, there are few didactic materials available using AL approaches. This works aims to fulfill this need in the field of Geometrical Optics, offering a series of tutorials (guides) for experiments and interactive demonstrations. These tutorials are based in the idea of guided investigation where the students previous beliefs are exposed and confronted with the scientific concepts. This material was applied to high school students (in public schools) and college students (science teacher preparation course of IFSC). In order to evaluate this material, written tests were performed as well as observation of classrooms.
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Sigal-Pauchard, Marie. "Application de la théorie de l'optimisation à certains problèmes de relativité générale." Rouen, 1986. http://www.theses.fr/1986ROUES004.
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Dans le problème de commande considérée, le système dynamique est un point matériel issu d'une source donnée dans l'espace-temps physique ; le vecteur tangent à la trajectoire du point matériel, aux points où il existe, doit appartenir à chaque instant au cône de lumière introduit par la théorie de la relativité au point correspondant de l'espace-temps ; l'ensemble des contraintes sur la commande dépend ainsi à chaque instant de l'état du système, et il est défini par un champ de cônes. L'ensemble accessible associé à une source ponctuelle admet pour frontière une hypersurface semi-perméable, tangente en chacun de ces points au cône correspondant du champ donné. L'étude est centrée sur les trajets de l'optique géométrique, caractérisés par le fait que chacun d'eux est contenu dans une hypersurface semi-perméable. On utilise la théorie de la commandabilité en boucle fermée pour aborder l'optique géométrique en relativité. Propriétés des rayons lumineux dans l'espace; problèmes de réfraction, liés à l'influence du milieu matériel et à la présence de gravitation; transformation d'un indice optique de réfraction dans un changement de coordonnées
31
Matalgah, Mustafa M. "Geometric theory for designing optical binary amplitude and binary phase-only filters /." free to MU campus, to others for purchase, 1996. http://wwwlib.umi.com/cr/mo/fullcit?p9717158.
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Miskiewicz, Matthew Nile. "Computer Generated Geometric Phase Holograms." Thesis, North Carolina State University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3710731.
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This dissertation concerns the fabrication, analysis, and simulation of computer generated geometric phase holograms (CGHs). The current knowledge of CGHs is advanced to enable the creation of new sophisticated optical elements with unique characteristics. These elements enable new technologies related to displays, astronomy, sensing, beam-steering, beam-shaping, and more.
First, a novel direct-write system for CGH creation is presented. A mathematical description of the system is developed which allows the result of a given scan pattern to be predicted. The accuracy of the model is validated with various scan patterns, then a high-quality direct-write polarization grating and q-plate are fabricated for the first time.
With a system capable of creating CGHs, the most common and useful CGHs are explored in depth: the polarization grating, the geometric phase lens, and the Fourier geometric phase hologram. For each element, the possible scan patterns and parameters and their effect on the resulting element's quality are studied. Ultimately, the optimal scan patterns and parameters are found, then best-quality elements of each type are created and characterized.
Finally, a new tool for simulating periodic CGHs is developed. This begins with the derivation of the algorithm, which is based on the finite-difference time-domain (FDTD) method. Next tool's capabilities are verified by simulating many test structures and comparing the results to known solutions. The tool is used to simulate, for the first time, a CGH multiple beam splitter and a GPL array.
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Pěchotová, Barbora. "Lokalizace optického disku na snímcích sítnice." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-219943.
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This thesis deals with the analysis of retinal images from digital fundus camera, especially with structure of optic disc (OD). The theoretic part describes main features of the human visual system and princip of eyeground examination. The paper discussed sevaral available methods that have been used for localization of the optic disc. In the second part is proposed the automatic detector of the optic disc based on the principle of genetic algorithm by using the method of segmentation of vessels by matched filtering. Original images are tested with this automatic method.
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Honel, Jorge. "Métodos geométricos para a avaliação de sistemas ópticos centrados." Universidade de São Paulo, 1991. http://www.teses.usp.br/teses/disponiveis/54/54132/tde-28052009-094815/.
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Três métodos geométricos de traçado de raios são desenvolvidos e aplicados num programa de avaliação de sistema ópticos para microcomputadores padrão IBM-PC. O primeiro método corresponde ao traçado paraxial construído a partir do Invariante de Abbe; o segundo método corresponde ao traçado meridional proposto por Rudolf Kingslake; e o terceiro método corresponde ao traçado espacial proposto por Hainz Haferkorn e Volker Tautz. Dentro do programa estão incluídas algumas das representações das aberrações ópticas que caracterizam um sistema óptico centrado.Three methods of ray tracing are development for use on IBM PC/XT personal computer. The first method is a paraxial ray tracing derived from the invariant Abbe; the second is a meridional ray tracing proposed by Rudolf Kingslake; and the third is a skew ray tracing proposed by Heinz Haferkorn and Volker Tautz . Based on these three methods some optical aberrations are employed to exemplify an optical centered system.
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Saiz, Ipiña Juan Antonio. "Análisis de sistemas radiantes sobre geometrías arbitrarias definidas por superficies paramétricas." Doctoral thesis, Universidad de Cantabria, 1995. http://hdl.handle.net/10803/10678.
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En esta tesis se presenta un método para analizar antenas montadas sobre estructuras arbitrarias. La Optica Geométrica (GO) y la Teoría Uniforme de la difraccion (UTD), han sidoempleadas para analizar los efectos que la estructura produce sobre el diagrama de radiación de la antena emisora. Para la descripción geométrica de la estructura, han sido utilizados parches NURBS (Non Uniform Rational B-Spline), por lo que el método presentado, es compatible con la mayoría de los programas gráficos disponibles en el mercado.EL tratamiento de geometrías arbitrarias requiere un código eficiente en el análisis de tres dimensiones.Por otro lado, para obtener resultados satisfactorios, la descripción de la superficie de la estructura, debe ser muy próxima al modelo real, sin embargo, esto complica el tratamiento computacional. Aquí la estructura es modelada mediante un conjunto de parches NURBS, que unidos entre sí, describen el modelo completo. Esta descripción permite manipular superficies arbitrarias con un bajo numero de parches, lo que significa un volumen de información reducido.La descripción inicial por NURBS del modelo, es acompañada con información complemetaria como por ejemplo: la tipología de las superficies, las curvas frontera, el tipo de material, etc. Esto es imprescindible para la aplicación de criterios de selección dedicados a la aceleración del proceso.El método tras leer la descripción del modelo, descompone los parches NURBS en superficies racionales de Bezier. Un parche de Bezier es también una superficie paramétrica definida en términos de una combinación lineal de los polinomios de Bernstein.Las antenas son modeladas usando modelos numéricos simples basados en agrupaciones de dipolos infinitesimales eléctricos y magnéticos. Esta caracterización de la antena es muyventajosa ya que con un numero reducido de datos de entrada, la fuente queda definida para cualquier dirección del espacio y el valor del campo radiado puede ser calculado fácilmente.El análisis electromagnético de los efectos que contribuyen al campo dispersado por la geometría comienza con una selección rigurosa de la geometría iluminada desde la fuente.Unicamente los parches de Bezier iluminados serán almacenados por el ordenador durante el análisis. La filosofía de este proceso es descartar aquella parte de la geometría que no contribuye a los efectos de dispersión.El campo total calculado es la superposición de los siguientes efectos pertenecientes a la GO y a la UTD: campo directo procedente de la fuente, campo reflejado por los parches de Bezier, campo difractado por las aristas del modelo definidas como curvas de Bezier, ondas de superficie, dobles reflexiones, reflexione-difraccion y difraccion-reflexión. El método ha sido diseñado para analizar campo cercano y lejano. El mayor gasto computacional se debe a la búsqueda de los puntos de dispersión, por lo que antes de emplear los algoritmos de intersección es necesario aplicar un conjunto de criterios rápidos dependientes de la dirección de observación.El principio de Fermat en combinación con el Gradiente Conjugado (CGM) es usado para obtener de manera eficiente los puntos de dispersión sobre la estructura. Para cada efecto, laposible ocultación de la trayectoria completa del rayo es examinada, por ello, si el rayo corta alguno de los parches de Bezier su contribución será descartada. Los dobles efectos son tratados como una generalización de los simples efectos.El método desarrollado es eficiente ya que precisa de un numero reducido de superficies para modelar objetos complejos lo que se traduce en bajos requerimientos de memoria y reducidos tiempos de calculo.In this thesis a method to analyze antennas on board of complex bodies is presented. The Geometrical Optics (GO) and Uniform Theory of Diffraction (UTD) have been used to analyze the effect of the structure in the radiation pattern of the antennas. The bodies are geometrically modelled by using NURBS (Non Uniform Rational B-Spline) surfaces. In addition to be accurate and efficient, the method is compatible with most of the modern CAGD (Computer Aided Geometric Design) available programs.The treatment of arbitrary geometries requires a code which can carry out an efficient 3D analysis. To obtain accurate results the description of the surface must be close to the real model, however this complicates the computational procedure. Here the structure is modeled by a collection of individual N.U.R.B.S. surface patches joined to form a complete description of the surface model. The NURBS description is able to manipulate free form surfaces with a low number of patches, and therefore, with a low amount of information. The initial description of the model by NURBS surfaces is accompanied with other complementary data for example : the topology of the surfaces, the boundary curves, the types of material and other inputs. It is very interesting to apply criteria to make the complete analysis faster.The method reads the NURBS description of the model and transforms the NURBS into the rational BEZIER surfaces. A rational BEZIER patch is also a parametric surface defined in terms of a linear combination of Bernstein polynomials.The antennas are modelled using simple numerical models based on arrays of electric and magnetic infinitesimal dipoles. This antenna modelization is very advantageous because with a little input data, the source is defined in any direction and the field value is readily accessible.The electromagnetic analysis of the contributive effects to the scattering field by the geometry, starts with the rigorous selection of the geometry illuminated from the source. Only the Bezier patches illuminated will be in memory of the computer during the analysis. The philosophy of this previous process is to discard in the process the part of the geometry which does not contribute to the scattering effects.The total field is the superposition of the following GO and UTD field components: direct field from the source, reflected fields from the Bezier patches of the model, diffracted fields from the arbitrary edges defined as a Bezier curves, creeping waves, double reflected field and diffracted-reflected and reflected-diffracted fields. The search of specular and diffraction points are the most CPU time consuming, thus before using the intersection algorithms it is necessary to apply a set of fast selection criteria which depend on the observation direction.The Fermat principle in conjunction with the Conjugate Gradient Method (CGM) is used for obtaining efficiently the reflection points and diffraction points on the structure. For each effect the complete ray path is examined to see whether or not it is interrupted by any Bezier patch of the model, in this case the field component is not computed. The double effects are treated using a generalization of the single effects algorithms. The method has been developed to analyze the near and far field cases for different frequencies.The developed method is quite efficient because it makes use of a small number of surfaces to model complex bodies, so it requires few memory and low computing time.
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Doucet, François. "Continuous parallel plate waveguide lenses for future low-cost and high-performances multiple beams antennas." Thesis, Rennes 1, 2019. http://www.theses.fr/2019REN1S004/document.
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Les travaux présentés dans cette thèse portent sur l’étude et la conception de lentilles continues en guide d’ondes à plans parallèles (PPW) pour des applications multi-faisceaux. La conversion du front d'onde est assurée par une lentille formée d’une lame et d'une cavité transversale. Ce concept, proposant une approche mécanique simplifiée et possiblement purement métallique, est particulièrement attractif pour les futurs systèmes de communications par satellites (GEO/LEO) requérants des solutions à moindre coût tout en maintenant de hautes performances. La première partie de cette thèse présente la réalisation d’un outil d’analyse numérique basée sur l’optique géométrique (GO). Une prédiction rapide et précise des performances en rayonnement est obtenue. En combinant cet outil avec des processus d’optimisation, des performances en dépointage sur un large secteur angulaire sont ensuite démontrées, incluant une stabilité des diagrammes en rayonnement (ouverture à mi-puissance, niveaux de lobes secondaires et pertes en dépointage). Un prototype fonctionnant dans la bande Ka est réalisé, validant les performances précédemment obtenues. De hautes efficacités de rayonnement sont également mises en avant sur l’ensemble de la plage de fréquence. Enfin un second prototype plus compact basé sur de multiples lentilles est proposé et étudié, démontrant des performances similaires à la première solution fabriquée et mesuréeThe activities presented in this PhD focus on the study and development of continuous parallel plate waveguide (PPW) lenses for multiple beam applications. The wave front conversion is ensured by a PPW transversal ridge and cavity. The proposed concept, based on a simplified mechanical approach and possibly full-metal, is particularly suitable for future satellite communication systems (GO/LEO) requiring low-cost antennas while maintaining high performances. The first part of the thesis deals with the development of a numerical analysis tool based on geometrical optics (GO). A fast and accurate prediction of the radiation performance is provided.Combining the tool with optimization processes, large scanning performances have been demonstrated, including a stability of the radiation pattern performance (HPBW, SLL, scan loss). A prototype working at Ka band has been manufactured, validating the performances demonstrated previously. High radiation efficiencies are also proved over the entire frequency range. Finally, a second prototype targeting performances in compactness and based on multiple lenses is proposed and studied, showing similar performances as the first solution fabricated and measured
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L'hour, Charles-Antoine. "Modélisation de la propagation électromagnétique en milieux inhomogènes basée sur les faisceaux gaussiens : application à la propagation en atmosphère réaliste et à la radio-occultation entre satellites." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30069/document.
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La thèse, dont le sujet est "Modélisation de la propagation électromagnétique en milieux à gradient d'indice basée sur les faisceaux gaussiens - Application à la propagation en atmosphère réaliste et à la radio-occultation entre satellites" a été commencée le 2 décembre 2013, au Département ÉlectroMagnétisme et Radar (DEMR) de l'Onera de Toulouse et avec le laboratoire LAPLACE de l'Université Paul Sabatier. Elle est co-financée par l'ONERA et par la Région Midi-Pyrénées. L'encadrement a été assuré par Jérôme Sokoloff (Laplace/UPS, directeur de thèse), Alexandre Chabory (ENAC, co-directeur) et Vincent Fabbro (ONERA). L'École Doctorale est l' "École Doctorale Génie Électrique, Électronique, Télécommunications : du système au nanosystème". Le faisceau gaussien a été principalement utilisé dans la recherche scientifique afin d'étudier les systèmes optiques tels que les lasers. Des études plus rares et plus récentes ont proposé de l'utiliser pour modéliser la propagation des ondes sismiques. Ses propriétés spatiales et spectrales ont amené certains auteurs à étudier son utilisation dans des modèles de propagation atmosphériques. Cette thèse a consisté à développer un modèle, appelé GBAR (Gaussian Beam for Atmospheric Refraction), de propagation troposphérique réaliste et déterministe en utilisant le formalisme des faisceaux gaussiens. La démarche adoptée a consisté à reprendre les équations fondamentales introduites par Cerveny et Popov décrivant de façon itérative la propagation d'un faisceau gaussien en milieu inhomogène, sous hypothèse de haute fréquence (modèle asymptotique). De nouvelles équations ont été développées à partir d'elles pour obtenir une description analytique de la propagation d'un faisceau gaussien dans un milieu troposphérique décrit par les variations spatiales de l'indice de réfraction. L'hypothèse de base pour l'obtention de la formulation analytique est que le gradient de l'indice de réfraction peut être considéré vertical et constant au voisinage du faisceau. Les équations analytiques pour la description de la propagation d'un seul faisceau ont ensuite été étendues à la modélisation d'un champ quelconque dans un milieu troposphérique pouvant contenir de fortes variations du gradient d'indice, y compris des inversions de gradient. Ceci a été réalisé en couplant les équations analytiques avec la procédure de décomposition multi-faisceaux développée dans sa thèse pas Alexandre Chabory. Le modèle GBAR a été validé dans des milieux troposphériques réalistes issus de simulations du modèle météo méso-échelle WRF (Weather Research and Forecasting). Dans un troisième temps, le modèle a été utilisé pour simuler des inversions de données de radio-occultation. Des outils existent pour fournir un modèle d'interprétation de ces données pour estimer les propriétés physiques de l'atmosphère à partir des mesures en phase, amplitude, Doppler et délai des signaux GNSS transmis entre satellites en orbite autour de la TerreThe subject of this PhD thesis is " Electromagnetic propagation modeling in inhomogeneous media with refractive index gradients based on Gaussian beams - Application to realistic atmospheric propagation and radio occultation between satellites ". The study started on december 2nd, 2013 at the DEMR (Département Électromagnétisme et Radar) department of the ONERA research laboratory, in Toulouse, France. It was funded both by the ONERA and Région Midi-Pyrénées. It was supervised by Jérôme Sokoloff (LAPLACE/UPS, thesis director), Alexandre Chabory (ENAC, thesis co-director) and Vincent Fabbro (ONERA). The doctoral school was "École Doctorale Génie Électrique, Électronique, Télécommunications : du système au nanosystème ". The Gaussian beam was mostly used in scientific investigations to study optical systems such as lasers. Rarer and more recent works suggested the use of the Gaussian beam formalism in order to model the propagation of seismic waves. The properties of the Gaussian beam also led some authors to develop models for atmospheric propagation. In this thesis a model based on Gaussian beams called GBAR (Gaussian Beam for Atmospheric Refraction) was developped for tropospheric propagation in realistic and deterministic conditions. The scientific approach consisted in rewritting the fundamental equations introduced by Cerveny and Popov describing iteratively the propagation of a Gaussian beam in inhomogeneous media, under the high-frequency assumption (asymptotic model). New equations were derived from them in order to get analytical equations of the propagation of a Gaussian beam in inhomogeneous media described by the variations of the refractive index. The basic assumption under to get the analytical equations is to consider that the refractive index gradient is vertical and constant around the beam axis. The analytical equations that describe the propagation of a Gaussian beam were extended to model the propagation of an arbitrary field in a tropospheric medium with strong variations and inversions of the refractive index. This was done by coupling the analytical equations with the multibeam expansion procedure developped by Alexandre Chabory in his PhD thesis. The GBAR model was validated in tropospheric conditions, using refractive index grids from the WRF (Weather Research and Forecasting) mesoscale meteorological model. In the third and final phase, the GBAR model was used to simulate Radio Occultation data inversions. Tools exist to allow for interpretations of Radio Occultation data in order to estimate the physical properties of the atmosphere from measured phased, amplitude, Doppler shift and delay of GNSS signals transmitted between satellites orbiting around the Earth
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Mignon, Hervé. "Anémométrie phase Doppler et particules non sphériques : cas des cylindres et des ellipsoïdes." Rouen, 1997. http://www.theses.fr/1997ROUES004.
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L'anémométrie phase Doppler est une technique de mesure optique utilisée pour évaluer la taille et la vitesse de particules sphériques et homogènes en mouvement. Ce mémoire est dédié à l'extension de cette technique aux particules non sphériques. En raison de leurs importances tant fondamentales qu'appliquées, ce manuscrit se focalise sur les cylindres infiniment longs et les particules ellipsoïdes. La géométrie dite plane est employée pour déterminer la taille d'une particule cylindrique arbitrairement orientée. La réponse des géométries dites planes et standard est étudiée pour des particules ellipsoïdes, déformées ou en cours de déformation. L'influence d'un écart à la sphéricité sur une mesure phase Doppler est quantifiée. Ces configurations sont évaluées numériquement par l'optique géométrique puis validées expérimentalement.
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Díaz, José Antonio, and Virendra N. Mahajan. "Diffraction and geometrical optical transfer functions: calculation time comparison." SPIE-INT SOC OPTICAL ENGINEERING, 2017. http://hdl.handle.net/10150/626488.
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In a recent paper, we compared the diffraction and geometrical optical transfer functions (OTFs) of an optical imaging system, and showed that the GOTF approximates the DOTF within 10% when a primary aberration is about two waves or larger [Appl. Opt., 55, 3241-3250 (2016)]. In this paper, we determine and compare the times to calculate the DOTF by autocorrelation or digital autocorrelation of the pupil function, and by a Fourier transform (FT) of the point-spread function (PSF); and the GOTF by a FT of the geometrical PSF and its approximation, the spot diagram. Our starting point for calculating the DOTF is the wave aberrations of the system in its pupil plane, and the ray aberrations in the image plane for the GOTF. The numerical results for primary aberrations and a typical imaging system show that the direct integrations are slow, but the calculation of the DOTF by a FT of the PSF is generally faster than the GOTF calculation by a FT of the spot diagram.
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Yang, Chang. "Ultra-Compact Grating-Based Monolithic Optical Pulse Compressor for Laser Amplifier Systems." Research Showcase @ CMU, 2016. http://repository.cmu.edu/dissertations/731.
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Ultra-short and high-peak-power laser pulses have important industrial and scientific applications. While direct laser amplification can lead to peak powers of several million watts, higher values than these cannot be achieved without causing damage to the amplifier material. Chirped pulse amplification technique is thus invented to break this barrier. By temporally stretching pulses before entering amplifier, the pulse peak power is significantly reduced and thus becomes safe to be passed through the amplifier. After amplification, a compressor is used to recover the pulse width, and high-power ultra-short laser pulses are produced. Chirped pulse amplification technology increases the pulse energy by transferring the damaging effects of high-peak power laser pulses from the vulnerable amplifier to a relatively robust compressor system. The compressor is therefore a crucial device for producing high peak powers. However, there are some major drawbacks associated with it. First, compressors in high-energy laser system are usually over 1 cubic meter in size. For many applications, this large and cumbersome size is a limiting factor. Second, compressors are sensitive to outside disturbances; a little misalignment can lead to failure of pulse compression process. Third, gratings with large uniformly ruled area are difficult to fabricate, which impose a limit on achievable peak powers and pulse durations of laser pulses through the use of conventional compressors. In this project, we present a grating-based monolithic optical compressor that offers a way around some of the major problems of existing compressors. By integrating the key optical components, one can make a robust and monolithic compressor that requires no alignment. In the new scheme, folding the optical path with reflective coatings allows one to design a compressor of significantly reduced size by minimizing both the longitudinal and transverse dimensions of the device. The configuration and operation mechanism of this novel compressor are described. A method for calculating the volume of the compressor is investigated. This is validated by computing the size of a specific monolithic compressor. Simulation results obtained through finite-difference time-domain method are presented, proving that the new compressor provides a compact, portable, and robust means for temporally compressing long duration pulses.
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Kobayashi, Hirokazu. "Geometric phases in optical interferometry." 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/142564.
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Gao, Kun. "OPTICAL SIMULATION AND FABRICATION OF PANCHARATNAM (GEOMETRIC) PHASE DEVICES FROM LIQUID CRYSTALS." Kent State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=kent1490805847205484.
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Poliak, Juraj. "Difrakční jevy ve vysílaném optickém svazku." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-233653.
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Dizertačná práca pojednáva o vlnových a elektromagnetických javoch, ku ktorým dochádza pri zatienení eliptického Gausovského zväzku kruhovou apretúrou. Najprv boli z Huygensovho-Fresnelovho princípu odvodené dva modely Fresnelovej difrakcie. Tieto modely poskytli nástroj pre zavedenie kontrastu difrakčného obrazca ako veličiny, ktorá kvantifikuje vplyv difrakčných javov na prevádzkové parametre optického spoja. Následne, pomocou nástrojov elektromagnetickej teórie svetla, boli odvodené štyri výrazy (dva presné a dva aproximatívne) popisujúce geometrický útlm optického spoja. Zároveň boli skúmané tri rôzne prípady odsmerovania zväzku - priečne posunutie a uhlové odsmerovanie vysielača, resp. prijímača. Bol odvodený výraz, ktorý tieto prípady kvantifikuje ako útlm elipticky symetrického Gausovského zväzku. Všetky vyššie uvedené modely boli overené v laboratórnych podmienkach, aby sa vylúčil vplyv iných javov. Nakoniec práca pojednáva o návrhu plne fotonického optického terminálu. Najprv bol ukázaný návrh optického vysielača nasledovaný vývojom optomechanickej sústavy prijímača. Pomocou nástrojov geometrickej a maticovej optiky boli vypočítané parametre spoja a odhad tolerancie pri zamierení spoja.
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Sabra, Ahmad. "Nonlinear PDE and Optical Surfaces Design." Diss., Temple University Libraries, 2015. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/345398.
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MathematicsPh.D.
We introduce two models to design near field reflectors in R^3 that solve an inverse problem in radiometry, taking into account the inverse square law of irradiance. The problem leads to a Monge-Ampere type inequality. The surfaces in the first model are strictly convex and require to be far from the source to avoid obstruction. In the second model, the reflectors are neither convex nor concave and do not block the rays even if they are close to the source.
Temple University--Theses
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Yagdjian, Karen. "Geometric optics for the nonlinear hyperbolic systems of Kirchhoff-type." Universität Potsdam, 2001. http://opus.kobv.de/ubp/volltexte/2008/2605/.
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Contents:
1 Introduction
2 Main result
3 Construction of the asymptotic solutions
3.1 Derivation of the equations for the profiles
3.2 Exsistence of the principal profile
3.3 Determination of Usub(2) and the remaining profiles
4 Stability of the samll global solutions. Justification of One Phase Nonlinear Geometric Optics for the Kirchhoff-type equations
4.1 Stability of the global solutions to the Kirchhoff-type symmetric hyperbolic systems
4.2 The nonlinear system of ordinary differential equations with the parameter
4.3 Some energies estimates
4.4 The dependence of the solution W(t, ξ) on the function s(t)
4.5 The oscillatory integrals of the bilinear forms of the solutions
4.6 Estimates for the basic bilinear form Γsub(s)(t)
4.7 Contraction mapping
4.8 Stability of the global solution
4.9 Justification of One Phase Nonlinear Geometric Optics for the Kirchhoff-type equations
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Hashemi, Hila. "Geometric manipulation of light : from nonlinear optics to invisibility cloaks." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/73365.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mathematics, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 189-203).
In this work, we study two different manipulations of electromagnetic waves governed by macroscopic Maxwell's equations. One is frequency conversion of such waves using small intrinsic material nonlinearities. We study conversion of an input signal at frequency w1 to frequency Wk due to second or third harmonic generation or four-wave mixing using coupled-mode theory. Using this framework, we show there is a critical input power at which maximum frequency conversion is possible. We study in depth the case of third harmonic generation, its solutions, and their stability analysis. Based on the dynamics of the system, we propose a regime of parameters that 100%- efficient frequency conversion is possible and propose a way of exciting this solution. We also look at same analysis for the case of degenerate four-wave mixing and come up with 2d and 3d designs of a device that exhibits high-efficiency second-harmonic generation. Second, we consider proposals for invisibility cloaks to change the path of electromagnetic waves in a certain way so that the object appears invisible at a certain frequency or a range of frequencies. Transformation-based invisibility cloaks make use of the coordinate invariance of Maxwell's Equations and require complex material configuration e and p in the cloak. We study the practical limitations of cloaking as a function of the size of the object being cloaked. Specifically, we study the bandwidth, loss, and scattering limitations of cloaking as the object gets larger and show that cloaking of objects many times larger than the wavelength in size becomes practically impossible.
by Hila Hashemi.
Ph.D.
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Bennani, Yacine. "Signature électromagnétique bi-statique d'une cible complexe intégrée dans son environnement : Application à l'imagerie ISAR d'une scène maritime." Thesis, Brest, 2012. http://www.theses.fr/2012BRES0065/document.
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Le travail réalisé dans le cadre de cette thèse s’intègre bien dans le domaine de la télédétection de l’environnement maritime. Il porte notamment, d’une part sur l’étude de l’interaction d’une onde électromagnétique avec une surface maritime en présence d’une cible complexe et observée en configuration bi-statique. D’autre part l’étude est complétée par l’étude et l’analyse de l’influence des différents paramètres à la fois liés à la cible et aussi à l’environnement. Dans ce contexte d’étude, le présent travail s’articule autour de deux volets importants. Le premier vise l’étude et la simulation de la Surface Equivalente Radar(SER) d’une cible complexe placée dans son environnement maritime. Et un deuxième volet applicatif traite l’imagerie radar ISAR d’une scène observée, avec prise en compte des cibles présentes sur la surface. Afin de traiter le premier point, le modèle électromagnétique retenu est basé sur une combinaison de méthodes asymptotiques (Optique Physique (OP), Optique Géométrique (OG), Méthode des courants équivalents (MCE)). Pour l’étude de l’influence de la surface de mer sur la réponse électromagnétique de la cible, nous avons opté pour une représentation de la scène (cible+surface de mer) par un ensemble de facettes triangulaires. Dans ce cadre, la cible discrétisée par un maillage triangulaire est générée à l’aide d’un outil de CAO (CATIA V5), quant à la surface de la mer, elle est générée en utilisant le spectre de mer d’Elfouhaily (et le modèle de Debye pour la prise en compte des paramètres diélectriques de l’eau de mer). Enfin, pour l’application de l’imagerie radar ISAR, le calcul de la SER de la cible navale a été effectué en considérant une nouvelle représentation de la cible en parallélépipèdes. La méthodologie proposée a été évalué via des simulations ainsi que des expérimentations sur un modèle générique d’un navireThe work presented here interset with remote sensing of the maritime environment.It espacially carried with the study of electromagnetic scattering by sea surface with the presence of the target. This study is done in bistatic configuration. So, it is completed by the analysis of the influence of various parameters related to the target and also to the environment. In this context, this work focuses on two important parts. The first is the study and simulation of Radar Cross Section (RCS) of a complex target placed in the maritime environment.And the second part deals with the application of ISAR radar imagery of an observed scene, with consideration of target on the sea surface. We have opted for a combination between Physical Optics (PO), Geometrical Optics (GO) and Equivalent Edge Currents (ECM) (POGO/ EMC) to estimate the RCS. In order to take into account the infuence of sea surface, we have genereted a 2D sea surface from the Elfouhaily spectrum. In order to integrate the target into the scenario (the target in its environment, radar imagery), we propose a parallelepiped representation of the naval taget and RCS calculation. The proposed methodology was evaluated through simulations and measurements on a generic model of a ship
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Bistrý, Jan. "Registrace obrazu pomocí metody Optical Flow." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-219258.
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Registration of medical images is technique, which is developing with new hybrid diagnostic imaging systems. Nowadays is a trend in image registration focused on monomodality and multimodality images registration. The first part of this master’s thesis is intent on present basic information about image registration. Concretely is intending on image transformation, interpolation, criteria function and at optimalization. Further part present realized Optical Flow technique and used “Demon” algorithm for image registration. The next part is focused on presentation of program solution and GUI. In the last section of this master’s thesis is verifying of created program on usual images and real CT images.
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Pereira, Erms Rodrigues. "Física dos cristais líquidos e gravitação : pontos de encontro." Universidade Federal da Paraíba, 2011. http://tede.biblioteca.ufpb.br:8080/handle/tede/9546.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Aspects of the physics of nematic liquid crystals are studied in this thesis from the viewpoint of riemannian geometry through analogue models of gravitation. The topics chosen for study were: geometric and wave optics, elastic waves, hydrodynamics and heat conduction. The main analogue model used is based on the interpretation of Fermat’s principle as a process to obtain null geodesics, where the liquid crystalline material is seen as a riemannian manifold. This approach predicts that the metric effectively felt by the light ray depends on the configuration of molecules in the liquid crystal and on the parallel and perpendicular refractive indexes to the axis of symmetry of the liquid-cristal molecule. It is known that, for the particular case of the existence of topological defects within the material, effective metric similar to cosmological defects (like global monopoles and cosmic strings) are obtained. This thesis develops itself on the situation where there are topological defects of hedgehog type and (k = 1, c = 0) disclination type in the nematic phase of the liquid crystalline material. The first problem studied, as a review, deals with the wave optics, with respect to the light diffracted by the cited defects. Since plane waves of small wavelength have identical trajectories to light rays, the use of analog model is therefore justified. Thus, we show that light scattered by these defects generates a characteristic diffraction pattern, being the location given by an algebraic expression dependent on the parallel and perpendicular refractive indexes to the axis of symmetry of the molecule. We also show how theses patterns depend on the temperature of the material. The second studied problem deals with the geometrical optics and hydrodynamics of the nematic liquid crystals. From a molecular configuration similar to a (k = 1, c = 0) disclination, we let the material flow radially towards the axis of the defect. Then, using the hydrodynamic fact that velocity gradients in the material locally change the refractive index of the molecule, we find the velocity profile that must exist around the defect so that the metric actually experienced by light traveling in the plane perpendicular to the axis the defect is the Schwarzschild one in the equatorial plane, with the Schwarzschild radius interior to the object. We found that the absolute values of the velocity of liquid crystalline fluid can be order of a few meters per second, differing greatly from the values obtained by Gordon metric for an isotropic fluid under identical conditions. The third studied problem deals with the elastic oscillations in the presence of topological defects. Similarly to the first problem, the trajectory of the sound is obtained by an elastic version of Fermat’s principle and, then, compared with a null geodesic. We show how topological defects influence the sound trajectories and the sound diffracted by them. The fourth problem deals with the heat conduction in the vicinity of defects. Considering that the defects come from an addition or removal of portion of the material, letting the medium relaxes elastically, effective metric of the space disturbed by the defect are found, with expressions similar to those obtained by the analogous model based on Fermat’s principle. These metrics generate a modified thermal conductivity tensor, allowing the study of the temperature field in this situation. We show that, depending on the values of parallel and perpendicular thermal conductivity to the axis of symmetry of the molecule and on the defect in question, the temperature gradient can be accentuated or attenuated on the defect, allowing control of the response thermal temperature of the material, according to the presence of defects. Encouraging a greater understanding of the physics of liquid crystals and its use as a background in analogue models of gravity is the main theme of each analyzed problem.
Aspectos da física dos cristais líquidos nemáticos são estudados nesta tese do ponto de vista da geometria riemannina, por meio de modelos análogos de gravitação. Os tópicos escolhidos para estudo foram: óptica geométrica e ondulatória, ondas elásticas, hidrodinâmica e condução de calor. O principal modelo análogo empregado baseia-se na interpretação do princípio de Fermat como um processo de obtenção de geodésicas nulas, onde o material líquido-cristalino é visto como sendo uma variedade riemanniana. Esta abordagem prevê que a métrica efetivamente sentida pelo raio luminoso dependa da configuração das moléculas dentro do cristal líquido e dos índices de refração paralelo e perpendicular ao eixo de simetria da molécula líquido-cristalina. É sabido que, para o caso especial da existência de defeitos topológicos dentro do material, métricas efetivas semelhantes às de defeitos cosmológicos (como monopolos globais e cordas cósmicas) são obtidas. Esta tese desenrola-se sobre a situação onde existem defeitos topológicos do tipo ouriço e do tipo desclinação (k = 1, c = 0) na fase nemática do material líquido-cristalino. O primeiro problema estudado, em caráter de revisão, trata da óptica ondulatória, no que concerne a difração de luz pelos defeitos citados. Uma vez que ondas planas de comprimento de onda pequeno possuem trajetórias idênticas aos raios luminosos, o emprego do modelo análogo é justificado. Assim, mostramos que a luz espalhada por esses defeitos gera padrões de difração bem característicos, sendo a localização dada por expressão algébrica dependente dos índices de refração paralelo e perpendicular ao eixo de simetria da molécula líquido-cristalina. Também mostramos de que forma esses padrões dependem da temperatura do material. O segundo problema estudado trata da óptica geométrica e da hidrodinâmica dos cristais líquidos nemáticos. A partir de uma configuração de moléculas semelhantes à de uma desclinação (k = 1, c = 0), permitimos que o material flua radialmente na direção do eixo do defeito. Em seguida, fazendo uso do fato hidrodinâmico de que gradientes de velocidade no material modificam localmente os índices de refração da molécula, encontramos o perfil de velocidade que deve existir em torno do defeito para que a métrica efetivamente sentida pela luz, que viaja no plano perpendicular ao eixo do defeito, seja a de Schwarzschild no plano equatorial, com raio de Schwarzschild interior ao objeto. Encontramos que os valores absolutos da velocidade de fluido líquido-cristalino podem ser da ordem de alguns metros por segundo, diferindo enormemente dos valores obtidos pela métrica de Gordon para um fluido isotrópico em condições idênticas. O terceiro problema estudado aborda as oscilações elásticas na presença de defeitos. Semelhantemente ao primeiro problema, a trajetória do som é obtida por uma versão elástica do princípio de Fermat e, então, comparada com uma geodésica nula. Mostramos como defeitos topológicos influenciam nas trajetórias sonoras, assim como no som difratado por eles. O quarto problema trata da condução de calor na vizinhança de defeitos. Considerando que os defeitos são resultantes de uma adição ou remoção de porção de material, dando-se seguimento a uma relaxação elástica do meio, métricas efetivas do espaço perturbado pelo defeito são encontradas, com expressões semelhantes às obtidas pelo modelo análogo baseado no princípio de Fermat. Essas métricas geram um tensor condutividade térmica modificado, dando cabo ao estudo do campo de temperatura nessa situação. Mostramos que, dependendo dos valores da condutividade térmica perpendicular e paralela ao eixo de simetria da molécula líquido-cristalina e do defeito em questão, o gradiente de temperatura pode ser acentuado ou atenuado sobre o defeito, permitindo o controle da resposta térmica do material à temperatura, de acordo com a presença de defeitos. Suscitar um entendimento maior da física dos cristais líquidos e de seu emprego como background em modelos análogos de gravitação é o tema principal de cada um dos problemas analisados.
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Zhu, Zixu James. "Graphene geometric diodes for optical rectennas." Thesis, University of Colorado at Boulder, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3635957.
Full textAbstract:
Optical rectennas, which are micro-antennas to convert optical-frequency radiation to alternating current combined with ultrahigh-speed diodes to rectify the current, can in principle provide high conversion efficiency solar cells and sensitive detectors. Currently investigated optical rectennas using metal/insulator/metal (MIM) diodes are limited in their RC response time and poor impedance matching between diodes and antennas. A new rectifier, the geometric diode, can overcome these limitations. The thesis work has been to develop geometric diode rectennas, along with improving fabrication processes for MIM diode rectennas. The geometric diode consists of a conducting thin-film, currently graphene, patterned into a geometry that leads to diode behavior. In contrast with MIM diodes that have parallel plate electrodes, the planar structure of the geometric diode provides a low RC time constant, on the order of 10-15 s, which permits operation at optical frequencies. Fabricated geometric diodes exhibit asymmetric DC current-voltage characteristics that match well with Monte Carlo simulations based on the Drude model. The measured diode responsivity at DC and zero drain-source bias is 0.012 A/W. Since changing the gate voltage changes the graphene charge carrier concentration and can switch the majority charge type, the rectification polarity of the diode can be reversed. Furthermore, the optical rectification at 28 THz has been measured from rectennas formed by coupling geometric diodes with graphene and metal bowtie antennas. The performance of the rectenna IR detector is among the best reported uncooled IR detectors. The noise equivalent power (NEP) of the rectenna detector using geometric diode was measured to be 2.3 nW Hz-1/2. Further improvement in the diode and antenna design is expected to increase the detector performance by at least a factor of two. Applications for geometric diodes and graphene bowtie antennas include detection of terahertz and optical waves, ultra-high speed electronics, and optical power conversion.