La polarimétrie de Mueller est une technique optique qui mesure la réponse polarimétrique complète d’un milieu sous la forme d’une seule matrice de Mueller afin de remonter à ses propriétés optiques comme le dichroïsme, la biréfringence et la dépolarisation. Le couplage avec la microscopie non-linéaire (SHG par exemple) permet d’avoir accès à des informations précises sur un milieu biologique (structure, organisation, . . .). Cela impose de passer à une modalité d’imagerie à balayage laser, qui nécessite de mesurer la réponse polarimétrique du milieu pixel-par-pixel en des temps relativement courts (de l’ordre de la microseconde). Le but de cette thèse est de mettre en oeuvre un polarimètre de Mueller dont les cadences d’acquisition sont compatibles avec l’imagerie à balayage laser. Dans un premier temps, un polarimètre de Mueller inédit est proposé, basé sur le codage spectral de la polarisation dont toute l’information polarimétrique de l’échantillon est mesurée sous la forme d’un seul signal d’intensité en un temps record (10 μs). Ce dispositif est constitué d’une source à balayage rapide en longueur d’onde à 100 kHz (ou swept-source), de lames de phase d’ordre élevé et d’un détecteur monocanal. Les erreurs systématiques qui entachent la mesure sont évaluées et des méthodes de correction permettent de les prendre en compte dans une étape d’étalonnage qui utilise la réponse de deux milieux étalons.Ensuite, le polarimètre est implémenté dans un microscope commercial à balayage laser, utilisé initialement pour réaliser de l’imagerie non-linéaire (SHG). Cela requiert un redimensionnement du montage, ainsi que la synchronisation entre les deux systèmes. Par ailleurs, un protocole de calibration du dispositif est développé et permet de tenir compte de l’ensemble des erreurs systématiques du polarimètre indépendamment des anisotropies optiques engendrées par le microscope. Enfin, les premières images polarimétriques de Mueller en microscopie à balayage laser ont été acquises sur des échantillons inhomogènes spatialement (rubans adhésifs et cristaux de roches). La potentialité de la microscopie multimodale est démontrée sur des échantillons de fibroses de foie, en couplant l’imagerie polarimétrique de Mueller et la microscopie non-linéaire au sein d’un seul instrument. / Mueller polarimetry is an optical technique allowing the acquisition of the full polarimetric signature of a medium with a single Mueller matrix, and leading to its polarimetric parameters such as dichroism, birefringence and depolarization. Coupling Mueller polarimetry with nonlinear microscopy techniques (SHG for example), more precise information about the medium could be obtained (structure, organization . . .). This imaging technique uses a laser scanning system to measure the Mueller matrix of a medium point-to-point quickly (of the order of the microsecond). The aim of this thesis is to develop a Mueller polarimeter compatible with the laser scanning system. First, a new Mueller polarimeter is proposed using spectral encoding of the polarization and measuring the full polarimetric signature of a sample with a single channeled spectrum in a fast way (10 μs). This setup is composed of a 100 kHz swept-source laser, high order retarders and a single channel detector. Systematic errors on the Mueller matrix measurement are evaluated and correction methods take into account these errors in a calibration step that uses polarimetric signature of two references medium. Then, the polarimeter is implemented on a commercial laser scanning microscope that usually images non-linear contrasts (SHG). The update needs to reduce the dimension of the polarimeter and ensure an electronic synchronization between these two systems. However, a new calibration step is proposed and takes into account all the systematic errors of the polarimeter, independently of the optical anisotropy induced by the microscope. Finally, the images with the first Mueller scanning microscope are obtained with spatially inhomogeneous samples (cellophane tapes, rocks). The potentiality of the multimodal scanning microscopy Mueller/SHG on the same instrument is demonstrated in the case of hepatic fibrosis.

La polarisation de la lumière est très souvent utilisée en imagerie pour caractériser certaines propriétés de la matière, ou pour mettre en évidence des zones qui ne seraient peu ou pas contrastées avec des caméras d'intensité classiques. Nous explorons le potentiel d'une nouvelle technique de polarimétrie, dite de « brisure d'orthogonalité », pour réaliser des acquisitions de manière simple, directe et à haute cadence. Cette technique d'imagerie par balayage laser repose sur l'emploi d'une source de lumière bi-fréquence bi-polarisation pour sonder les caractéristiques polarimétriques (notamment le dichroïsme ou anisotropie d'absorption) des échantillons imagés.Nous explorons la possibilité du déport de la mesure de « brisure d'orthogonalité » par fibre optique faiblement multimode pour le développement d'endoscopes polarimétriques. Un tel dispositif vise à fournir une méthode de diagnostic rapide pour analyser des tissus biologiques profonds tout en évitant le recours aux biopsies. Nous démontrons, théoriquement et expérimentalement, la compatibilité de cette approche avec un dispositif d'endoscopie commercial (fibre ou bundle multicœurs, légèrement multimodes) pourvu que le nombre de modes guidés soit inférieur à une dizaine. D'autre part, nous présentons la conception, la réalisation, la validation et l'exploitation d'un démonstrateur d'imagerie active par brisure d'orthogonalité dans le proche infrarouge. Ce dernier vise des applications défense de détection et/ou décamouflage de cibles. Après caractérisation des bruits dominants les signaux acquis, nous illustrons l'apport du démonstrateur pour la mise en évidence d'éléments dichroïques. Enfin, nous démontrons que la technique de brisure d'orthogonalité peut être avantageusement, et très simplement, adaptée pour mesurer sélectivement le dichroïsme, la biréfringence, et la dépolarisation, paramètres essentiels à la détection d'objets manufacturés (cibles). Ces trois modalités, lorsqu'elles sont conjuguées, offrent au démonstrateur des capacités d'identification. / Polarimetric imaging is a useful tool to characterize some matter properties, or to highlight regions slightly or not contrasted with intensity cameras. We investigate the capability of a novel polarimetric technique, namely the “orthogonality breaking technique”, to perform direct and straightforward measurements at high speed. Relying on the use of a dual-frequency dual-polarization light source, this imaging modality probes polarimetric features (dichroism, or absorption anisotropy) in imaged samples.We explore the potential to perform orthogonality breaking measurements through few mode optical fibers towards polarimetric endoscopy. Such an imaging device would greatly improve the diagnosis efficiency to analyze in-depth biologic tissues without biopsy surgery. We show, theoretically and experimentally, the compatibility of our approach with a commercial flexible endoscope (slightly multimode multicore fibers or bundle) provided that the number of guided modes remains inferior to a dozen.On the other hand, we describe the design, the development, the validation and the exploitation of an active near infrared imaging demonstrator based on the orthogonality breaking technique for defense target detection applications. After characterization of the acquired signals noise, we illustrate the imager capability to reveal dichroic elements. Finally, we demonstrate that the orthogonality breaking technique can be advantageously and straightforwardly tailored to address selectively the dichroism, the birefringence and the depolarization, which are core parameters for the detection of manufactured objects (targets). The combination of these three modalities grants an identification capability to the demonstrator.

Disertační práce pojednává o polarizačních nedokonalostech optických komponentů, které jsou využívány ke kontrole a k transformaci polarizačního stavu světla. Získané teoretické výsledky jsou pak využity ve vybraných aplikacích, jež ke své činnosti využívají právě polarizace světla. Konkrétně se jedná o zařízení měřící vibrace oscilujících objektů, dále o interferenční měření dvojlomu v transparentních materiálech a konečně, o vybraná témata z optické kvantové komunikace.

PURPOSE. Confocal laser scanning ophthalmoscopy (HRT; Heidelberg retinal tomograph II) and scanning laser polarimetry (GDx-variable corneal compensator [VCC]) were used to investigate whether early indicators of retinal nerve fiber layer (RNFL) thickness loss could be observed in patients infected with the human immunodeficiency virus (HIV) that had no associated retinopathy or optic neuropathy and were concomitantly receiving antiretroviral medications. METHODS. HRT and GDx-VCC parameters obtained from a group of 13 HIV-positive subjects (n = 26 eyes) on antiretroviral therapy examined with HRT, with a subgroup of six subjects (n = 12 eyes) examined with both HRT and GDx-VCC, were compared with those of a matched HIV-negative control cohort (13 subjects, n = 26 eyes) examined with HRT, with a subgroup of five subjects (n = 10 eyes) examined with both HRT and GDx-VCC. We employed generalized estimating equations for statistical analysis. RESULTS. Reduced mean values for the HRT height variation contour (p < 0.045) and HRT mean RNFL thickness (p < 0.023) were observed in HIV-positive subjects controlling for age, sex, and race. A significantly reduced mean value corresponding to the GDx-VCC superior maximum (p < 0.014) and inferior maximum (p < 0.016) were also observed for the HIV-positive cohort analyzed controlling for age, sex, and race. CONCLUSION. HRT and GDx-VCC indicators of RNFL thickness appear to be significantly reduced in HIV-positive subjects without retinopathy or optic nerve disease using antiretroviral medication, suggesting RNFL loss occurs in this population of HIV-positive patients. The lack of correlation between CD4 counts, viral load, number of antiretroviral medications used, or years from diagnosis of HIV and RNFL thinning, suggests that possibly other factors associated with HIV infection may contribute to the apparent RNFL thickness loss.

No description available.

Ziel der Dissertation: Ziel ist die Weiterentwicklung und Charakterisierung eines nichtionisierenden Diagnoseverfahrens für die Detektion von Okklusalkaries auf Basis von polarisationssensitiver optischer Kohärenztomografie (PS OCT). Die Einführung eines erweiterten polarisationsmikroskopischen Verfahrens (Depolarisationsmikroskopie, DLM) ermöglicht erstmals die Visualisierung der Pathohistologie der Karies durch Depolarisationsbildgebung am Dünnschliff. Material und Methode: Insgesamt wurden 17 Zähne mit klinisch auffälligen Okklusalflächen in-vitro mit fünf Bildgebungsverfahren untersucht: digitale Bissflügelaufnahmen, µCT, PS-OCT und konventionelle sowie erweiterte Polarisationsmikroskopie (Depolarisationsmikroskopie). Die optischen Verfahren wurden an intakten Zähnen und histologischen Dünnschliffen angewendet. Die kariösen Läsionen konnten nach räumlicher Registrierung der verschiedenen Datensätze in Schnittebenen vergleichend visualisiert werden. Ergebnisse: Die vergleichende Darstellung der verschiedenen Verfahren in einer Schnittebene liefert einen Beitrag zum Grundverständnis der optischen Eigenschaften kariöser Läsionen. Die konventionelle zahnmedizinische Histologie wurde um zwei neue optische Bildgebungsverfahren ergänzt: PS-OCT und Depolarisationsmikroskopie. Die erstmalige Auswertung des DOP im histologischen Dünnschliff ermöglicht die Quantifizierung der pathohistologischen Zonen der Karies. Demineralisierte Schmelzareale sowie demineralisiertes, sklerosiertes und gesundes Dentin können farbunabhängig visualisiert werden. Die Ursache der Depolarisation in Schmelz und Dentin ist unterschiedlich. Die Studie liefert Erkenntnisse für die Auswertung von PS-OCT Daten in-vivo. Schlussfolgerung: Für die valide Interpretation zukünftiger klinischer PS-OCT Daten ist es erforderlich, die polarisationsoptischen Eigenschaften von Zahnhartsubstanzen genauer zu untersuchen. Dies wurde mit der Auswertung des Polarisationsgrades (Degree of Polarization, DOP) mit Polarisationsmikroskopie und PS-OCT im histologischen Präparat erzielt und dient dem Grundverständnis von PS-OCT Volumendaten für die zukünftige zahnärztliche Praxis. Die vorgestellten Verfahren sind eine relevante Ergänzung der klassischen zahnmedizinischen Histologie bei der wissenschaftlichen Charakterisierung kariöser Läsionen. / Objective: The aim of this doctoral thesis is the advancement and characterization of a non-invasive, non-ionizing diagnostic method for the detection of occlusal caries based on polarization-sensitive optical coherence tomography (PS-OCT). By introducing an expanded polarization microscopic technique (depolarized light microscopy, DLM), enables, for the first time, the visualization of the pathohistology of caries through depolarization imaging on thin sections. Material and Methods: A total of 17 teeth with clinically suspicious occlusal surfaces were examined in vitro using five imaging techniques: digital bitewing radiographs, µCT, PS-OCT, and conventional as well as expanded polarized light microscopy (depolarized light microscopy). The optical methods were applied to intact teeth and histological thin sections. After spatial registration of the different datasets, carious lesions were comparably visualized in sectional planes. Results: The comparative representation of various optical imaging methods within the same sectional plane contributes to the fundamental understanding of the optical properties of carious lesions. Traditional dental histology was supplemented by the inclusion of two innovative optical imaging methods: PS-OCT and depolarized light microscopy. The preliminary assessment of the degree of polarization (DOP) in histological thin sections enables the quantification of the pathohistological zones of caries. Demineralized areas in enamel as well as demineralized, sclerotic, and healthy dentin can be visualized color-independently. The cause of depolarization in enamel and dentin is different. The study provides insights for the evaluation of PS-OCT data in-vivo. Conclusion: For the valid interpretation of future clinical PS-OCT data, it is necessary to investigate the polarization-optical properties of dental hard tissues more closely. This was achieved by the evaluation of the degree of polarization (DOP) with polarized light microscopy and PS-OCT in histological preparations, contributing to the fundamental understanding of PS-OCT volumetric data for future dental practice. The presented methods are also a relevant addition to classical dental histology for characterizing carious lesions.

This thesis is devoted to the experimental quantitative characterization of the shape and orientation distribution of ice particles in clouds. The characterization is based on measured and modeled elevation dependencies of the polarimetric parameters differential reflectivity and correlation coefficient. The polarimetric data is obtained using a newly developed 35-GHz cloud radar MIRA-35 with hybrid polarimetric configuration and scanning capabilities. The full procedure chain of the technical implementation and the realization of the setup of the hybrid-mode cloud radar for the shape determination are presented. This includes the description of phase adjustments in the transmitting paths, the introduction of the general data processing scheme, correction of the data for the differences of amplifications and electrical path lengths in the transmitting and receiving channels, the rotation of the polarization basis by 45°, the correction of antenna effects on polarimetric measurements, the determination of spectral polarimetric variables, and the formulation of a scheme to increase the signal-to-noise ratio. Modeling of the polarimetric variables is based on existing backscattering models assuming the spheroidal representation of cloud scatterers. The parameters retrieved from the model are polarizability ratio and degree of orientation, which can be assigned to certain particle orientations and shapes. In the thesis the first quantitative estimations of ice particle shape at the top of liquid-topped clouds are presented. Analyzed ice particles were formed in the presence of supercooled water and in the temperature range from -20 °C to -3 °C. The estimation is based on polarizability ratios of ice particles measured by the MIRA-35 with hybrid polarimetric configuration, manufactured by METEK GmbH. For the study, 22 cases observed during the ACCEPT (Analysis of the Composition of Clouds with Extended Polarization Techniques) field campaign were used. Polarizability ratios retrieved for cloud layers with cloud-top temperatures of about -5, -8, -15, and -20 °C were 1.6, 0.9, 0.6, and 0.9, respectively. Such values correspond to prolate, quasi-isotropic, oblate, and quasi-isotropic particles, respectively. Data from a free-fall chamber were used for the comparison. A good agreement of detected shapes with well-known shape{temperature dependencies observed in laboratories was found.

L’étude de la structure du nucléon est un sujet actif de la recherche et un des objectifs majeurs du Thomas Jefferson National Accelerator Facility (Jefferson Lab). Dans cette optique et afin d’obtenir des résultats statistiquement significatifs, il est essentiel d’avoir une cible polarisée ayant à la fois une haute polarisation et une densité de matériel polarisé élevée. Cette thèse présente les principes et utilisations d’une cible de deutérure d’hydrogène (ou cible de HD) qui remplit les deux conditions précédemment énoncées. Bien qu’il ait été prouvé que la cible de HD pouvait être utilisée avec succès sous un faisceau de photons de haute intensité, il restait à montrer si elle pouvait résister un faisceau d’électrons de courant relativement élevé (nA). Dans ce but, la cible de HD a été testée pour la première fois dans son mode de “spin gelé” sous un faisceau d’électrons pendant l’expérience g14 dans le Hall B de Jefferson Lab en 2012. Deux méthodes de polarimétrie sont également décrites dans cette thèse : une par Resonance Magnétique Nucléaire appliquée à la cible de HD pendant les tests sous un faisceau d’électrons, et une autre utilisant la réaction de diffusion élastique d’un faisceau d’électrons sur une cible en utilisant des données élastiques sur l’hélium-3 prises en 2003 pendant l’expérience E97-110 dans le Hall A de Jefferson Lab. / The study of the nucleon structure has been a major research focus in fundamental physics in the past decades and still is the main research line of the Thomas Jefferson National Accelerator Facility (Jefferson Lab). For this purpose and to obtain statistically meaningful results, a highly efficient polarized target is essential. This means high polarization and high relative density of polarized material. This dissertation presents the principles and usage procedures of a Hydrogen Deuteride (HD) target that presents both such characteristics. Although the HD target has been shown to work successfully under a high intensity photon beam, it remained to be seen if the target could stand an electron beam of reasonably high current (nA). In this perspective, the HD target was tested for the first time in its “frozen spin” mode under an electron beam during the g14 experiment in the Jefferson Lab’s Hall B in 2012. Two methods of polarimetry are also discussed in this dissertation : one with Nuclear Magnetic Resonance of this HD target during the electron beam tests, and another with the elastic scattering of electrons off a polarized target by using data taken on helium-3 during the E97-110 experiment that occurred in Jefferson Lab’s Hall A in 2003.

Neste trabalho apresentamos uma nova técnica para a medida da rotação da polarização da luz por uma substância que possui atividade óptica. O sistema utiliza um LED, dois polarizadores, um prisma de vidro semicilíndrico, uma cubeta, uma CCD e um computador para análise de dados. Luz proveniente do LED passa pelo primeiro polarizador, cujo eixo de transmissão se encontra a 45&deg;, e incide no prisma pelo lado semicilíndrico, ocorrendo reflexão na sua base, num ângulo próximo do ângulo crítico. Devido ao tamanho finito do feixe e o formato curvo da superfície do prisma, vários ângulos de incidência são observados na base da lente semicilíndrica. A luz refletida passa então pela cubeta e depois por um analisador, cujo eixo se encontra paralelo ao primeiro polarizador, e então o sinal é captado pela CCD. De forma alternativa, a cubeta pode ser posicionada após o primeiro polarizador, antes do prisma. Quando a cubeta é preenchida com água, observa-se na CCD uma interferência destrutiva exatamente no ângulo crítico caracterizado por um mínimo de intensidade nesse ângulo. Se uma substância opticamente ativa é utilizada para preencher a cubeta, a posição desse mínimo é alterada dependendo do ângulo de rotação da polarização imposto pela substância. Uma calibração é necessária e pode ser feita utilizando-se soluções de concentração conhecida de sacarose ou frutose, por exemplo. O aparato obtido foi utilizado para medir a rotação causada por uma amostra normal (0,26 g/ml) de soluções de sacarose e frutose e apresenta uma precisão de 0,04&deg;. Equivalentemente, a precisão em concentração é de 0,001 g/ml ou aproximadamente 0,1% (m/m). Isso corresponde a uma precisão que é uma ordem de grandeza acima dos aparelhos comerciais e técnicas mais comuns utilizadas atualmente. Em contrapartida, o custo da montagem experimental é duas ordens de grandeza menor que os mesmos aparelhos comerciais. A produção de uma gama de ângulos de incidência devido à focalização na superfície cilíndrica do prisma substitui a necessidade de se produzir rotação no eixo de polarização do analisador após a passagem da luz pela amostra opticamente ativa, como ocorre em alguns aparelhos comercializados. Este dispositivo, por ser de baixo custo, compacto e de fácil manuseio, é de grande importância porque pode ser utilizado na indústria sucroalcooleira para a medida da quantidade de sacarose em cana e também na indústria farmacêutica para a identificação de substâncias opticamente ativas dextrogiras ou levógiras. / In this thesis we present a novel technique for measuring light polarization rotation caused by an optically active substance. The system is composed by a LED, two polarizers, a semi cylindrical glass prism, a cuvette, a linear CCD camera and a computer for data analysis. Light from the LED passes through the first polarizer, whose transmission axis is set at 45&deg;. After that, the linear polarized light enters the prism by the semi cylindrical face, occurring reflection in the flat face at critical angle approximately. Several incidence angles are accessed due to the beams finite size and the shape of the semi cylindrical lens. The reflected light passes through the cuvette and then through the analyzer, whose transmission axis is set parallel to the first polarizer. Finally, the light is detected by the CCD. When the cuvette is filled up with water, a destructive interference at the critical angle is observed, characterized by a narrow valley centered at this angle. If the cuvette is filled up with an optically active substance, the center of this valley is shifted depending on the substance, its concentration and the optical path travelled by the light in the substance. A calibration is needed and is performed using a set of solutions of known concentrations. Our apparatus was used to measure the angle rotation caused by a normal solution (0,26 g/ml) of sucrose and fructose solutions and has a precision of 0,04&deg;. It corresponds to a precision that is one order of magnitude above most used commercial apparatus and developed techniques. In contrast, the cost of our experimental setup is two orders of magnitude less than the same commercial devices. The production of a range of angles of incidence due to focusing on the cylindrical surface of the prism replaces the need of producing a rotation of the analyzer polarization axis after the light passes through the optically active sample, as it happens in some commercial devices. Since this device has a low cost, is compact and easy to handle, it may be of great importance for applications in the pharmaceutical industry to identify enantiomers, and in the sugar industry for measuring sugar content in sugar cane juice.

Los Radares de Apertura Sintética, o sistemas SAR, representan el mejorejemplo de sistemas activos de teledetección por microondas. Debido a su naturaleza coherente, un sistema SAR es capaz de adquirir información dedispersión electromagnética con una alta resolución espacial, pero por otro lado, esta naturaleza coherente provoca también la aparición de speckle.A pesar de que el speckle es una medida electromagnética, sólo puede ser analizada como una componente de ruido debido a la complejidad asociadacon el proceso de dispersión electromagnética.Para eliminar los efectos del ruido speckle adecuadamente, es necesario un modelo de ruido, capaz de identificar las fuentes de ruido y como éstasdegradan la información útil. Mientras que este modelo existe para sistemasSAR unidimensionales, conocido como modelo de ruido speckle multiplicativo,éste no existe en el caso de sistemas SAR multidimensionales.El trabajo presentado en esta tesis presenta la definición y completa validación de nuevos modelos de ruido speckle para sistemas SAR multidimensionales,junto con su aplicación para la reducción de ruido speckle y la extracción de información.En esta tesis, los datos SAR multidimensionales, se consideran bajo una formulación basada en la matriz de covarianza, ya que permite el análisisde datos sobre la base del producto complejo Hermítico de pares de imágenesSAR. Debido a que el mantenimiento de la resolución especial es un aspectoimportante del procesado de imágenes SAR, la reducción de ruido speckleestá basada, en este trabajo, en la teoría de análisis wavelet.