Made available in DSpace on 2015-05-14T12:14:16Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 5113295 bytes, checksum: 299112e42f72744b732d195da1230c13 (MD5) Previous issue date: 2015-05-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this thesis we address issues pertaining to the fluctuations of the electromagnetic field in the optical domain, both experimentally as well as theoretically and numerically. It was experimentally demonstrated the interdependence between the degree of polarization and the degree of coherence of thermal optical fields. We analyzed the results and explained them in light of a new unifying theory. We have shown a way to control the coerence of light through polarization manipulations, concluding with a proposal for a simple thermal light source with a tunable spectral electromagnetic degree of coherence. We expanded the concept of a tunable light source, suggesting a partially coherent and partially polarized light source with complete control of the so called generalized Stokes parameters by mixing polarized stochastic optical fields. We obtain theoretically the statistical properties of the resulting optical field and their dependence on the properties of the primary fields. We discuss fundamental properties of the mixture of stochastic fields and point out some peculiarities through examples. All results are demonstrated through numerical simulations. We suggest a method to investigate the spatial statistical properties of gaussian stochastic fields through the Hanbury Brown-Twiss (HBT) interferometer, an admittedly simple experimenal method. We show theoretically that it is possible to measure the generalized Stokes parameters, thus allowing one to rebuild the coherence matrix and the polarization matrix of the field, completely characterizing the optical field both statistically and locally in the observation plane. We suggest a technique for the automation of the method, and also some applications. These many studies on the statistical properties of optical fields led us to a deeper understanding of the physical meanings of the parameters for characterizing them. From this understanding we also discuss a change to the definition of the cross-polarization degree and the significance of optical coherence in terms of this new definition. / Nesta tese abordamos problemas concernentes às flutuações do campo eletromagnético no domínio ótico, tanto experimentalmente quanto teoricamente e numericamente. Demonstramos experimentalmente a interdependência entre o grau de polarização e o grau de coerência de campos óticos térmicos. Analizamos os resultados e os explicamos à luz de novas teorias unificadoras. Mostramos assim uma forma de controlar a coerência da luz através de manipulações na polarização, concluindo com uma proposta de fonte de luz térmica simples, com grau espectral de coerência eletromagnética sintonizável. Expandimos o conceito de fonte luz sintonizável, propondo uma fonte de luz parcialmente coerente e parcialmente polarizada com completa liberdade de controle dos chamados parâmetros de Stokes generalizados, através da mistura de campos óticos estocásticos polarizados. Obtemos teoricamente as propriedades estatísticas do campo ótico resultante e a dependência destas com as propriedades dos campos primários. Discutimos propriedades fundamentais da mistura de campos estocásticos e apontamos algumas peculiaridades através de exemplos. Demostramos todos os resultados através de simulações numéricas. Sugerimos um método para investigar as propriedades estatísticas espaciais de campos estocásticos gaussianos através do interferômetro de Hanbury Brown-Twiss, um método experimenal reconhecidamente simples. Mostramos teoricamente que é possível medir os parâmetros de Stokes generalizados, permitindo reconstruir a matriz de coerência e a matriz de polarização do campo, caracterizando completamente o campo ótico tanto estatisticamente quanto localmente. Apontamos ainda técnica para a automação do método, além de aplicações. Os diversos estudos realizados acerca das propriedades estatísticas de campos óticos nos levaram a um entendimento profundo dos significados físicos dos parâmetros utilizados para caracterizá-los. A partir deste entendimento, discutimos ainda uma modificação na definição do grau de polarização cruzado e da significância da coerência ótica em termo desta nova definição.

Les travaux présentés dans ce mémoire portent sur l'étude, la conception et le développement de deux nouveaux prototypes de reconstruction tridimensionnelle, spécifique aux objets transparents. La numérisation 3D d'objets opaques est abondamment traitée dans la littérature et de nombreux systèmes sont d'ailleurs commercialisés. Cependant, lorsqu'il s'agit de la numérisation 3D d'objets transparents, les publications se font rares et aucun système de scanning n'existe sur le marché. La technique de numérisation de surfaces transparentes demeure compliquée et non maîtrisée à l'heure actuelle. L'opacification de la surface avant le scanning s'avère être la solution retenue dans le domaine du contrôle qualité. Néanmoins, cette alternative n'est pas optimale en raison du coût de traitements et du manque de précision éventuellement engendré. Afin de solutionner les problèmes de la numérisation d'objets transparents, nous avons développé deux approches dites non conventionnelles en étendant les méthodes existantes (dans le visible) aux longueurs d'onde dans lesquelles les sujets apparaissent opaques (IR et UV). Les deux méthodes de mesure sans contact retenues sont : - la reconstruction par polarisation dans l'IR, en vue de s'affranchir des problèmes d'inter-réflexions; - le scanning par laser UV, pour satisfaire les contraintes industrielles (précision, rapidité et coût) tout en résolvant de manière efficace le problème de réfraction. La première approche est fondée sur la réflexion spéculaire de l'objet dans l'IR tandis que la seconde exploite la propriété de l'objet à fluorescer sous l'irradiation UV. L'inexistence des lentilles télécentriques dans l'IR nous a conduits à adapter la reconstruction par polarisation dans l'IR à l'aide d'une lentille non télécentrique. Pour ce faire, une méthode d'approximation du modèle orthographique a été développée et une méthode de validation visant à améliorer la précision des résultats a été en outre intégrée dans le processus de reconstruction après l'étape d'estimation des paramètres de Stokes. Nos résultats sont très satisfaisants et attestent la faisabilité de la reconstruction par polarisation dans l'IR. Quatre configurations de système de scanning par triangulation ont été déployées afin d'exploiter la propriété de fluorescence des objets transparents irradiés sous un rayonnement UV. Des expérimentations visant à caractériser la fluorescence induite à la surface des objets considérés et à vérifier l'éligibilité de notre approche ont été menées. Les mesures spectroscopiques nous ont permis d'élaborer des critères de "tracking" (détection et localisation) des points fluorescents en présence des bruits inhérents à l'acquisition. Nous avons également mis au point des méthodes de validation des paramètres du modèle de reconstruction 3D estimés lors de la calibration, permettant ainsi d'optimiser la configuration du système de scanning. Les méthodes de "tracking" et de validation ont contribué considérablement à l'amélioration de la précision des résultats. Par ailleurs, la précision obtenue n'a jamais été atteinte au regard de ce que l'on trouve dans la littérature. / Two non-conventional methods for the 3D digitization of transparent objects via non-contact measurement are reported in this thesis. 3D digitization is a well acknowledged technique for opaque objects and various commercial solutions based on different measurement approaches are available in the market offering different types of resolution at different prices. Since these techniques require a diffused or lambertian surface, their application to transparent surfaces fails. Indeed, rays reflected by the transparent surface are perturbed by diverse inter-reflections induced by the refractive properties of the object. Therefore, in industrial applications like quality control, the transparent objects are powder coated followed by their digitization. However, this method is expensive and can also produce inaccuracies. Among the rare methods suggested in the literature, shape from polarization provides reliable results even though their accuracy had to be improved by coping with the inter-reflections. The two proposed solutions handle the extension of the existing methods to wavelengths beyond visible ranges: - shape from polarization in Infra Red (IR) range to deal with the above-mentioned inter-reflections; - scanning by Ultra Violet (UV) laser (based on triangulation scheme) to overcome the refraction problem that can be feasibly applied in industrial applications. The characteristic physical properties of transparent objects led us to explore the IR and UV ranges; since, transparent glass has strong absorption bands in the IR and UV ranges and therefore has opaque appearance. The first approach exploits the specular reflection of the considered object surface in IR and the second one exploits the fluorescence property of the object when irradiated with UV rays. Shape from polarization traditionally based on telecentric lenses had to be adapted with non-telecentric lenses to be used in the IR range. Thus, an approximation of the orthographic model is developed in this thesis while a validation method is implemented and integrated in the reconstruction process after Stokes parameters estimation, in order to improve the accuracy of the results. Some results of digitized objects are presented, which prove the feasibility of the shape from polarization method in the IR range to be used for transparent objects. A total of four configurations of the triangulation system are implemented in this thesis to exploit fluorescence produced by the UV laser scanning of the second approach. Experimental investigations aimed at characterizing the fluorescence are done. A specific fluorescence tracking method is carried out to deal with the inherent noise in the acquisitions. The uniqueness of the method relies on the criteria that are derived from the analysis of spectroscopic results. A validation method is made to optimize the configuration system while reducing the accuracy of reconstruction error. The results of some object digitization are presented with accuracies better than previously reported works.