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Lasers which operate at both high average power and energy are in demand for a wide range of applications such as materials processing, directed energy and EUV generation. Presented in this dissertation is a high-power 1 μm ytterbium-based hybrid laser system with temporally tailored pulse shaping capability and up to 62 mJ pulses, with the expectation the system can scale to higher pulse energies. This hybrid system consists of a low power fiber seed and pre-amplifier, and a solid state thin-disk regenerative amplifier. This system has been designed to generate high power temporally tailored pulses on the nanosecond time scale. Temporal tailoring and spectral control are performed in the low power fiber portion of the system with the high pulse energy being generated in the regenerative amplifier. The seed system consists of a 1030 nm fiber-coupled diode, which is transmitted through a Mach-Zehnder-type modulator in order to temporally vary the pulse shape. Typical pulses are 20-30 ns in duration and have energies of ~0.2 nJ from the modulator. These are amplified in a fiber pre-amplifier stage to ~100 nJ before being used to seed the free-space Yb:YAG thin-disk regenerative amplifier. Output pulses have maximum demonstrated pulse energies of 62 mJ with 20 ns pulse after ~250 passes in the cavity. The effects of thermal distortion in laser and passive optical materials are also. Generally the development of high power and high energy lasers is limited by thermal management strategies, as thermally-induced distortions can degrade laser performance and potentially cause catastrophic damage. Novel materials, such as optical ceramics, can be used to mitigate thermal distortions; however, thorough analysis is required to optimize their fabrication and minimize thermal distortions. iv Using a Shack-Hartmann wavefront sensor (SHWFS), it is possible to analyze the distortion induced in passive and doped optical elements by high power lasers. For example, the thin-disk used in the regenerative amplifier is examined in-situ during CW operation (up to 2 kW CW pump power). Additionally, passive oxide-based optical materials and Yb:YAG optical ceramics are also examined by pumping at 2 and 1 μm respectively to induce thermal distortions which are analyzed with the SHWFS. This method has been developed as a diagnostic for the relative assessment of material quality, and to grade differences in ceramic laser materials associated with differences in manufacturing processes and/or the presence of impurities. In summation, this dissertation presents a high energy 1 μm laser system which is novel in its combination of energy level and temporal tailoring, and an analysis of thermal distortions relevant to the development of high power laser systems.

Optical testing in adverse environments, ophthalmology and applications where characterization by curvature is leveraged all have a common goal: accurately estimate wavefront shape. This dissertation investigates wavefront sensing techniques as applied to optical testing based on gradient and curvature measurements. Wavefront sensing involves the ability to accurately estimate shape over any aperture geometry, which requires establishing a sampling grid and estimation scheme, quantifying estimation errors caused by measurement noise propagation, and designing an instrument with sufficient accuracy and sensitivity for the application. Starting with gradient-based wavefront sensing, a zonal least-squares wavefront estimation algorithm for any irregular pupil shape and size is presented, for which the normal matrix equation sets share a pre-defined matrix. A Gerchberg–Saxton iterative method is employed to reduce the deviation errors in the estimated wavefront caused by the pre-defined matrix across discontinuous boundary. The results show that the RMS deviation error of the estimated wavefront from the original wavefront can be less than λ/130~ λ/150 (for λ equals 632.8nm) after about twelve iterations and less than λ/100 after as few as four iterations. The presented approach to handling irregular pupil shapes applies equally well to wavefront estimation from curvature data. A defining characteristic for a wavefront estimation algorithm is its error propagation behavior. The error propagation coefficient can be formulated as a function of the eigenvalues of the wavefront estimation-related matrices, and such functions are established for each of the basic estimation geometries (i.e. Fried, Hudgin and Southwell) with a serial numbering scheme, where a square sampling grid array is sequentially indexed row by row. The results show that with the wavefront piston-value fixed, the odd-number grid sizes yield lower error propagation than the even-number grid sizes for all geometries. The Fried geometry either allows sub-sized wavefront estimations within the testing domain or yields a two-rank deficient estimation matrix over the full aperture; but the latter usually suffers from high error propagation and the waffle mode problem. Hudgin geometry offers an error propagator between those of the Southwell and the Fried geometries. For both wavefront gradient-based and wavefront difference-based estimations, the Southwell geometry is shown to offer the lowest error propagation with the minimum-norm least-squares solution. Noll’s theoretical result, which was extensively used as a reference in the previous literature for error propagation estimate, corresponds to the Southwell geometry with an odd-number grid size. For curvature-based wavefront sensing, a concept for a differential Shack-Hartmann (DSH) curvature sensor is proposed. This curvature sensor is derived from the basic Shack-Hartmann sensor with the collimated beam split into three output channels, along each of which a lenslet array is located. Three Hartmann grid arrays are generated by three lenslet arrays. Two of the lenslets shear in two perpendicular directions relative to the third one. By quantitatively comparing the Shack-Hartmann grid coordinates of the three channels, the differentials of the wavefront slope at each Shack-Hartmann grid point can be obtained, so the Laplacian curvatures and twist terms will be available. The acquisition of the twist terms using a Hartmann-based sensor allows us to uniquely determine the principal curvatures and directions more accurately than prior methods. Measurement of local curvatures as opposed to slopes is unique because curvature is intrinsic to the wavefront under test, and it is an absolute as opposed to a relative measurement. A zonal least-squares-based wavefront estimation algorithm was developed to estimate the wavefront shape from the Laplacian curvature data, and validated. An implementation of the DSH curvature sensor is proposed and an experimental system for this implementation was initiated. The DSH curvature sensor shares the important features of both the Shack-Hartmann slope sensor and Roddier’s curvature sensor. It is a two-dimensional parallel curvature sensor. Because it is a curvature sensor, it provides absolute measurements which are thus insensitive to vibrations, tip/tilts, and whole body movements. Because it is a two-dimensional sensor, it does not suffer from other sources of errors, such as scanning noise. Combined with sufficient sampling and a zonal wavefront estimation algorithm, both low and mid frequencies of the wavefront may be recovered. Notice that the DSH curvature sensor operates at the pupil of the system under test, therefore the difficulty associated with operation close to the caustic zone is avoided. Finally, the DSH-curvature-sensor-based wavefront estimation does not suffer from the 2π-ambiguity problem, so potentially both small and large aberrations may be measured.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

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Este trabalho apresenta um sistema computacional que utiliza técnicas de Aprendizado de Máquina (AM) para auxiliar o diagnóstico oftalmológico. Trata-se de um sistema de medidas objetivas e automáticas dos principais vícios de refração ocular, astigmatismo, hipermetropia e miopia. O sistema funcional desenvolvido aplica técnicas convencionais de processamento a imagens do olho humano fornecidas por uma técnica de aquisição chamada Hartmann-Shack (HS), ou Shack-Hartmann (SH), com o objetivo de extrair e enquadrar a região de interesse e remover ruídos. Em seguida, vetores de características são extraídos dessas imagens pela técnica de transformada wavelet de Gabor e, posteriormente, analisados por técnicas de AM para diagnosticar os possíveis vícios refrativos presentes no globo ocular representado. Os resultados obtidos indicam a potencialidade dessa abordagem para a interpretação de imagens de HS de forma que, futuramente, outros problemas oculares possam ser detectados e medidos a partir dessas imagens. Além da implementação de uma nova abordagem para a medição dos vícios refrativos e da introdução de técnicas de AM na análise de imagens oftalmológicas, o trabalho contribui para a investigação da utilização de Máquinas de Vetores Suporte e Redes Neurais Artificiais em sistemas de Entendimento/Interpretação de Imagens (Image Understanding). O desenvolvimento deste sistema permite verificar criticamente a adequação e limitações dessas técnicas para a execução de tarefas no campo do Entendimento/Interpretação de Imagens em problemas reais. / This work presents a computational system that uses Machine Learning (ML) techniques to assist in ophthalmological diagnosis. The system developed produces objective and automatic measures of ocular refraction errors, namely astigmatism, hypermetropia and myopia from functional images of the human eye acquired with a technique known as Hartmann-Shack (HS), or Shack-Hartmann (SH). Image processing techniques are applied to these images in order to remove noise and extract the regions of interest. The Gabor wavelet transform technique is applied to extract feature vectors from the images, which are then input to ML techniques that output a diagnosis of the refractive errors in the imaged eye globe. Results indicate that the proposed approach creates interesting possibilities for the interpretation of HS images, so that in the future other types of ocular diseases may be detected and measured from the same images. In addition to implementing a novel approach for measuring ocular refraction errors and introducing ML techniques for analyzing ophthalmological images, this work investigates the use of Artificial Neural Networks and Support Vector Machines (SVMs) for tasks in Image Understanding. The description of the process adopted for developing this system can help in critically verifying the suitability and limitations of such techniques for solving Image Understanding tasks in \"real world\" problems.

Este trabalho apresenta um sistema computacional que utiliza técnicas de Aprendizado de Máquina (AM) para auxiliar o diagnóstico oftalmológico. Trata-se de um sistema de medidas objetivas e automáticas dos principais vícios de refração ocular, astigmatismo, hipermetropia e miopia. O sistema funcional desenvolvido aplica técnicas convencionais de processamento a imagens do olho humano fornecidas por uma técnica de aquisição chamada Hartmann-Shack (HS), ou Shack-Hartmann (SH), com o objetivo de extrair e enquadrar a região de interesse e remover ruídos. Em seguida, vetores de características são extraídos dessas imagens pela técnica de transformada wavelet de Gabor e, posteriormente, analisados por técnicas de AM para diagnosticar os possíveis vícios refrativos presentes no globo ocular representado. Os resultados obtidos indicam a potencialidade dessa abordagem para a interpretação de imagens de HS de forma que, futuramente, outros problemas oculares possam ser detectados e medidos a partir dessas imagens. Além da implementação de uma nova abordagem para a medição dos vícios refrativos e da introdução de técnicas de AM na análise de imagens oftalmológicas, o trabalho contribui para a investigação da utilização de Máquinas de Vetores Suporte e Redes Neurais Artificiais em sistemas de Entendimento/Interpretação de Imagens (Image Understanding). O desenvolvimento deste sistema permite verificar criticamente a adequação e limitações dessas técnicas para a execução de tarefas no campo do Entendimento/Interpretação de Imagens em problemas reais. / This work presents a computational system that uses Machine Learning (ML) techniques to assist in ophthalmological diagnosis. The system developed produces objective and automatic measures of ocular refraction errors, namely astigmatism, hypermetropia and myopia from functional images of the human eye acquired with a technique known as Hartmann-Shack (HS), or Shack-Hartmann (SH). Image processing techniques are applied to these images in order to remove noise and extract the regions of interest. The Gabor wavelet transform technique is applied to extract feature vectors from the images, which are then input to ML techniques that output a diagnosis of the refractive errors in the imaged eye globe. Results indicate that the proposed approach creates interesting possibilities for the interpretation of HS images, so that in the future other types of ocular diseases may be detected and measured from the same images. In addition to implementing a novel approach for measuring ocular refraction errors and introducing ML techniques for analyzing ophthalmological images, this work investigates the use of Artificial Neural Networks and Support Vector Machines (SVMs) for tasks in Image Understanding. The description of the process adopted for developing this system can help in critically verifying the suitability and limitations of such techniques for solving Image Understanding tasks in \"real world\" problems.

Master Hartmann and the Swabian Woodcarving at the Beginning of the 15th Century The stonemason Master Hartmann from Ulm is known to art historians already long time, but his role in Swabian woodcarving at the beginning of the 15th century, however, still evokes numerous questions. Although Hartmann is believed to work simultaneously in the hut and the woodcarving workshop, the average quality of his works, and the fact, that he was accepted as a citizen only in the year 1928, more than ten years after we encounter him in Ulm records for the first time, indicates certain complications of this hypothesis. In this doctoral thesis, Master Hartmann is studied from the perspective of social and cultural situation in Ulm at the beginning of the 15th century. Attention is given to his position in the hut organization on the construction of Ulm Minster and his artistic activity on the western façade, which in its iconographical concept reflects also the historical background. The second part of the thesis focuses on the woodcarving workshop, where the Altarpiece of Dornstadt was made, and on the phenomenon of wide distribution of this style around the entire Swabia. The Ulm workshop is presented in the context of the city and its minster hut, former local centers and even more distant regions. Around 1415,...

Für den mittelalterlichen Menschen ist die Verwandtschaft von zentraler Bedeutung. Demensprechend wird das zeitgenössische Denken weit über das Konzept von Personenbeziehungen hinaus vom Prinzip der Genealogie bestimmt. Es erstaunt deshalb wenig, dass nicht nur historiographische, sondern auch literarische Texte von dieser Denkform bestimmt sind. Zahlreiche wissenschaftliche Arbeiten haben dies inzwischen gezeigt. Mit der vorliegenden Dissertation wird eine Lücke geschlossen, die trotz des großen Interesses am Thema bis heute geblieben ist, indem der Frage nachgegangen wird, welche Bedeutung der Thematik in den deutschsprachigen Artusromanen des Mittelalters zukommt. Da die Protagonisten der Romane als Einzelkämpfer erscheinen, von deren Verwandten man nur wenig erfährt, und zudem die erzählte Welt besonders wirklichkeitsentrückt wirkt, scheint die Genealogie auf den ersten Blick in diesen Texten keine Rolle zu spielen. Die Fiktionalität der Artusromane ermöglicht es aber im Gegenteil, Möglichkeiten und Grenzen von dynastisch bedingtem Herrschaftsgewinn und persönlichem Leistungsstreben frei auszuloten. Die konkurrierenden Konzepte werden in den beiden ersten deutschsprachigen Artusromanen Hartmanns von Aue in ihrer Gegensätzlichkeit aufgegriffen: Erec, der Titelheld von Hartmanns erstem Roman, folgt dem Vater als einziger Sohn auf den Thron. Der Protagonist des ‚Iwein‘ hingegen erkämpft sich Ehe und Herrschaft im ritterlichen Zweikampf. Beide Artusritter verlieren aber ihre Herrschaft bis sie gelernt haben, die Schwächen dauerhaft zu überwinden, die aus ihrer dynastischen Selbstsicherheit bzw. ihrer leistungsorientierten Übermotivation erwachsen. Während in den Artusromanen Hartmanns eine Form der Herrschaftsübertragung von zentraler Bedeutung für den Weg des Protagonisten ist, wird in den nachklassischen Artusromanen ‚Wigalois‘ Wirnts von Grafenberg und ‚Wigamur‘ durchgespielt, wie sinnvolle Verknüpfungen einer erfolgreichen Herrschaft nützlich sind. / For medieval man, kinship is of central importance. Accordingly, contemporary thought was determined by the principle of genealogy far beyond the concept of personal relationships. It is therefore hardly surprising that not only historiographical but also literary texts are characterised by this form of thought. Numerous academic works have shown this in the meantime. This dissertation fills a gap that has remained despite the great interest in the subject to this day by investigating the significance of the topic in the German-language Arthurian novels of the Middle Ages. Since the protagonists of the novels appear to be lone warriors whose relatives we learn little about, and since the narrated world seems particularly removed from reality, genealogy does not appear to play a role in these texts at first glance. On the contrary, the fictional nature of the Arthurian romances makes it possible to freely explore the possibilities and limits of dynastic rule and personal ambition. The competing concepts are taken up in Hartmann von Aue's first two German-language Arthurian novels in their contradictory nature: Erec, the title hero of Hartmann's first novel, succeeds his father as the only son on the throne. The protagonist of 'Iwein', on the other hand, fights for marriage and rule in a knightly duel. However, both Arthurian knights lose their rule until they have learnt to permanently overcome the weaknesses that arise from their dynastic self-assurance and their performance-oriented over-motivation. While in Hartmann's Arthurian romances a form of transfer of rule is of central importance for the protagonist's path, the post-classical Arthurian romances 'Wigalois' Wirnt’s von Grafenberg and 'Wigamur' play out how meaningful connections are useful for successful rule.

Les écoulement confinés soumis à un fort champ magnétique vertical et les écoulements en rotation autour d'un axe vertical présentent au moins deux caractéristiques communes marquantes : d'une part, le champ de vitesse est quasi-bidimensionnel loin des parois, et d'autre part, une couche limite de structure simple se développe le long des parois perpendiculaires à la direction du champ magnétique (couche de Hartmann) ou à l'axe de rotation (couche d'Ekman). Nous présentons ici une étude de ces propriétés remarquables dans des cas où les autres forces qui agissent sur l'écoulement (inertie, viscosité,...) ne sont plus négligeables devant la force de Laplace ou de Coriolis. Il est montré que la combinaison des couplages verticaux et horizontaux conduit d'une part, à une dépendance quadratique du champ de vitesse en fonction de la verticale (effet tonneau), et d'autre part à la présence de jet dans les couches de Hartmann ou d'Ekman. Une loi de paroi analytique pour diverses configurations des couches de Hartmann est construite (présence d'effets inertiels, présence d'une composante horizontale du champ magnétique, parois conductrices...) dans le but d'éviter le maillage fin que requiert le calcul numérique direct d'une telle couche. Les propriétés remarquables des écoulements quasi-2D sont ensuite utilisées pour construire trois modèles 2D différents, à partir de la moyenne verticale des équations du mouvement. Ces modèles simples, ne reposent que sur les hypothèses physiques et ne nécessitent en particulier aucun étalonnage numérique. Le modèle PSM2000 pour les écoulements MHD avec inertie et sous fort champ vertical conduit à des résultats très proches de l'expérience et met notamment en évidence le fait que le pompage d'Ekman dans les couches de Hartmann se traduit approximativement par une diffusion du champ de vorticité le long des lignes de courant de l'écoulement moyen. Un modèle analogue, mais sans effets inertiels et avec un champ non homogène et instationnaire permet en premier lieu de déterminer dans quel cas les couches de Hartmann contrôlent l'écoulement global et en second lieu, d'étudier la possibilité de contrôler un écoulement d'acier liquide par un champ glissant dans un procédé de coulée continue. Finalement, un modèle quasi-géostrophique modifié fournit une base théorique pour l'étude du comportement des couches parallèles lors des expériences de Spin-Up et Spin-Down d'une cuve tournante.