La question de l'eau constitue à l'heure actuelle un enjeu majeur pour nos sociétés. Bien qu'il s'agisse d'une ressource renouvelable, son cycle naturel est soumis à de fortes pressions issues tant de l'activité humaine que des modifications climatiques.Le débit des fleuves constitue une des variables clefs du cycle de l'eau. Sa quantification implique des mesures in situ lourdes. De ce fait, son suivi à l'échelle globale reste problématique, et les techniques de télédétection peuvent représenter un atout majeur. Les techniques satellitaires optiques et radar ne peuvent actuellement que mesurer les variables de surface et n'accèdent pas aux paramètres de fond des cours d'eau. Ce travail propose une méthode d'estimation de ces paramètres hydrauliques de fond à partir des seules mesures des variables de surface, en vue de l'estimation du débit. Cette méthode a été validée sur des données simulées exactes et une étude de sensibilité au bruit de mesure a été menée sur des données simulées bruitées et sur des données réelles.Le second volet de ce travail porte sur le potentiel de l'interférométrie radar temporelle à mesurer la variable de vitesse de surface des fleuves. Une campagne de mesure aéroportée a été réalisée sur le Rhône (ONERA-Cemagref) et a montré des résultats concordants avec les mesures de vitesses réalisées in situ par ADCP. En revanche, le modèle de rétrodiffusion M4S, testé dans le cadre de cette thèse, est apparu peu adapté aux scènes fluviales : il s'avère extrêmement sensible aux conditions de vent, ce qui peut s'expliquer par une faiblesse dans la modélisation des caractéristiques des surfaces de fleuves. Dans le cadre du programme SWOT (NASA-CNES), nous avons développé une méthode de mesure in situ de la rugosité des surfaces fluviales. Validée lors de mesures en laboratoire, cette méthode a été mise en œuvre sur le Rhône, et a ainsi permis de caractériser la surface et l'influence de l'intensité du vent sur les paramètres de rugosité. / The water issue is currently a major challenge for our societies. Even if water is a renewable resource, its natural cycle supports great stresses, both human activity and climate change.River discharge is a key variable of the water cycle, whose quantification requires heavy field measurements. Therefore the global monitoring of river discharge remains problematic and satellite remote sensing techniques could be a major asset. Earth Observation radar techniques are currently limited to the measurement of surface variables and cannot measure river bottom hydraulic parameters. The current study proposes a method to estimate these parameters from surface variables, in order to estimate the river discharge. This method has been validated on exact simulated data and its robustness to measurement noise has been studied on noisy simulated data and on real data.The second part of this work explores the abilities of radar along-track interferometry to measure river surface velocity. Velocity measurements carried out on the Rhône river during an airborne campaign (ONERA-Cemagref) show a strong consistency with ADCP field measurements. M4S backscattering model, tested in the framework of this study, is poorly adapted to river scenes : it appears to be extremely sensitive to wind intensity which could be explained by a poor modeling of surface roughness. As part of the SWOT mission program (NASA-CNES) a method allowing in situ characterization of river surface roughness has been developed. It was validated under laboratory controlled conditions. It was implemented on the Rhône river to characterize water surface and quantify the influence of wind intensity on the water surface roughness parameters.

Cette thèse présente les travaux de recherche effectués dans le but de concevoir et optimiser un instrument de métrologie du front d’onde et d’imagerie de phase sur faisceau synchrotron dans la gamme des rayonnements X durs. L’étude s’est focalisée sur la conception d’un interféromètre à réseau unique dont l’extraction des informations associées à l’analyse du front d’onde s’effectue par démodulation Fourier. Ces choix ont été déterminés par la volonté de concevoir un instrument robuste pouvant fonctionner sur une large gamme de conditions expérimentales sans avoir à modifier et accorder les paramètres et éléments constitutifs fondamentaux de l’instrument à chaque expérience. Ceci se résume par la contrainte forte de pouvoir réaliser une calibration absolue du système de façon à garantir la prise de mesure ultérieure par acquisition d’un interférogramme unique tout en s’affranchissant des erreurs de mesure déterministes de l’instrument.La variable expérimentale la plus importante correspond à l’énergie de travail; par conséquent la conception de l’interféromètre s’est organisée autour de la recherche de performances constantes sur une large bande spectrale pour des énergies entre 10 à 30keV, et a conduit à l’étude et à la mise en œuvre d’une configuration interférométrique innovante. Celle-ci exploite un régime diffractif particulier du réseau permettant d’accéder à la propriété d’achromaticité (non rigoureuse) par repliement des performances de mesure sur cette bande spectrale, et ce, pour un instrument reposant pourtant sur un composant diffractif fondamentalement chromatique.D’autre part, afin de garantir l’analyse quantitative de l’information portée par les modulations interférométriques générées par le réseau, nous avons également optimisé les traitements numériques et abouti au développement d’un algorithme de pré-traitement des interférogrammes permettant de s’affranchir des effets de bord lors de l’analyse d’images à support fini. Les artefacts rencontrés sont connus sous le nom de phénomènes de Gibbs et apparaissent dans le cas général de la transformée de Fourier d’un signal discontinu. Ainsi, annuler ces effets de bord permet également de gérer les problèmes d’éclairement partiel de la pupille de l’analyseur dont la gestion est essentielle en métrologie de front d’onde.Enfin nous présenterons les résultats expérimentaux de validation du concept interférométrique et de mesures applicatives en métrologie optique et en imagerie de phase sur des échantillons d’intérêt issus de domaines variés, de la biologie à la paléontologie. / This PhD dissertation presents the optimization and design of a wavefront analyzer dedicated to optical metrology and phase imaging on synchrotron sources in the hard X-ray regime. We chose to develop a single grating interferometer combined with a phase retrieval algorithm based on Fourier analysis. The main purpose here is to conceive a bulk instrument able to work in a great variety of experimental conditions without having to tune the parameters of the instrument in between experiments. This is thus related to the key constraint that is to calibrate the wavefront analyzer so that any further measurements could be corrected from any deterministic errors and allow single shot measurements of any sample.The key varying parameter in synchrotron experiments is the radiation energy (or wavelength). Therefore, the design of the interferometer aimed at minimizing the discrepancies of its performances over a broad spectral range from 10 to 30keV . This research lead in one hand to the description and implementation of an innovative interferometric configuration based on the achromatization of the instrument performances over this spectral range, despite the chromatic nature of the grating.On the other hand, in order to guaranty the quantitative analysis of interferograms, we also optimized the numerical approach to extract and treat the information they contain. This lead to the development of a conditioning procedure for a subsequent phase retrieval by Fourier demodulation. It fulfills the classical boundary conditions imposed by Fourier transform techniques and allows a nearly artifact-free extraction of the information.At last, experimental results demonstrate first, the viability of the grating achromatization concept, and then, the possibility to realize the metrology of grazing incidence optics at different wavelengths. The instrument was then used for phase imaging purposes of biological and archaeological samples.

In Earth remote sensing precise characterization of the backscatter coefficient is important to extract valuable information about the observed target. A system that eliminates platform motion during near-nadir airborne observations is presented in this thesis, showing an improvement on the accuracy of measurements for a Ka- band scatterometer previously developed at Microwave Remote Sensing Laboratory (MIRSL). These very same results are used to simulate the reflectivity of such targets as seen from a spaceborne radar and estimate height errors based on mission-specific geometry. Finally, data collected from a dual-frequency airborne interferometer com- prised by the Ka-band system and an S-band radar is processed and analyzed to estimate forest heights.

Over the last 20 years, Gregory G. Zilliac of the NASA AMES Research Center has been in continuous development of a fringe-imaging skin friction PC application used in oil interferometry analysis. This application, CXWIN5G, allows users to analyze propagation of oil smears across an aerodynamic surface using photogrammetry. The purpose of this thesis is to investigate the feasibility of increasing the level of automation currently found in CXWIN5G by developing a MATLAB solver capable of determining oil smear geometry with minimal user input. There are two main automation goals of this thesis that are reflected in the core of the MATLAB solver: the determination of oil smear centerline propagation without user input and the calculation of fringe spacing without the use of fiduciary markings on the test surface. In CXWIN5G, oil smear propagation centerlines must be drawn by a user with their computer mouse. The MATLAB solver removes the necessity for this by utilizing the centroid location of each fringe as a reference for centerline propagation. The solver’s ability to calculate fringe spacing without the use of fiduciary markings is a result of its ability to accurately determine the physical dimensions captured in an image. This is done by separating the camera’s field of view into its pixel components and calculating the horizontal and vertical object length captured in each pixel. Validation of the MATLAB solver’s ability to define fringe propagation and fringe spacing is performed at multiple different camera positions. When the camera location is not directly overhead an oil smear the camera is in a state of skew. Camera skew is measured in degrees, and can occur in the horizontal or vertical direction. Images analyzed in this thesis feature representative hand-drawn oil smears, as well as oil smears created in the Cal Poly 3’ x 4’ low speed wind tunnel. The MATLAB solver’s ability to create accurate centerlines is accessed by comparing pixel coordinates of the MATLAB centerlines with pixel coordinates of centerlines created on an identical image in Microsoft Paint. During experimentation, 18 images were analyzed under both horizontal (X) and vertical (Y) skew camera conditions, with skew angles ranging from zero to 13.2 degrees. Under X-skew camera conditions the average position error between MATLAB and hand drawn centerlines is 0.6 %, while average position error under Y-skew camera conditions is 1.0 %. Fringe spacing accuracy is defined by how closely fringe spacing determined by the MATLAB solver is to fringe spacing measured by hand with a 1/16th inch ruler. Spacing analysis is performed on the same photos used in centerline determination. For X-skew camera positions, the average fringe spacing error is 6.1 %, while the average spacing error in Y-skew conditions is 4.3 %. As is discussed in later sections of this text, the X-skew fringe spacing error is artificially inflated due to human error during data collection.

This diploma thesis deals with the algorithms for signal processing in a field of a low-coherence interferometry. The introductory part is devoted to the basic principle of the low-coherence interferometry and to presenting its field of applications. The second part contains a list of selected algorithms supplemented by a description of their functionality. The procedure of experimental measurement of known surface with Michelson interferometer is described in the third part and the results obtained for particular algorithms are presented. Finally, algorithms are compared on the basis of measurement results.

Aim of this thesis is the design of experimental equipment for studying the formation of lubricating films in contacts lubricated machine parts Liquid gases with the following parameters: experimental device to operate on the principle of optical tribometer, the design will be modified so that it can be used to deleting contacts liquid gases.

Cette thèse s’inscrit dans le contexte des travaux visant à réduire la durée d’impulsion des lasers XUV générés dans des plasmas au domaine femtoseconde. La bande spectrale très étroite du milieu amplificateur limite la durée minimum accessible (limite de Fourier). Le milieu amplificateur des lasers XUV sont des plasmas denses et chauds qui peuvent être créés aussi bien par décharge électrique rapide que par différents types de lasers de puissance. Il existe ainsi 4 types de sources lasers XUV distinctes dont les paramètres du plasma (densité, température) dans la zone de gain diffèrent. Or, les propriétés spectrales et temporelles du rayonnement émis sont fortement liées à ces paramètres. L’ensemble des 4 types de lasers XUV opèrent en mode d'amplification de l'émission spontanée (ASE) et 2 d'entre eux peuvent opérer en mode « injecté ». Cette technique consiste à injecter une impulsion harmonique d'ordre élevé femtoseconde, résonante avec la transition laser, à l'une des extrémités du plasma amplificateur. L'important désaccord entre la largeur spectrale du plasma et celle de l'harmonique ne permet pas de conserver la durée fs de cette dernière au cours de l'amplification. Les simulations (code Bloch-Maxwell COLAX) montrent que l'amplification est fortement non-linéaire dans ces systèmes, avec notamment l'apparition d’oscillations de Rabi. La génération d'oscillations de Rabi dans des lasers XUV en mode injecté est actuellement considérée comme un moyen prometteur de produire des lasers XUV fs, mais la manifestation de ces dernières n’a toutefois encore jamais été mise en évidence expérimentalement. Ainsi, une méticuleuse caractérisation expérimentale des propriétés spectrales des 4 types de lasers XUV en relation avec les conditions du plasma, associée à une meilleure compréhension des mécanismes d’amplification sous différentes conditions plasma basée sur des études théoriques et des simulations, sont nécessaires pour atteindre notre objectif. Une large campagne expérimentale visant à caractériser spectralement l'ensemble des différents types de lasers XUV a été menée par notre groupe sur la dernière décennie. La résolution spectrale nécessaire n'étant pas accessible avec les spectromètres actuels, la méthode employée consiste à mesurer la cohérence temporelle du laser XUV par autocorrélation du champ électrique à l'aide d'un interféromètre à division de front d'onde, spécifiquement conçu pour ces mesures, à partir desquelles la largeur spectrale peut être déduite. Le dernier type de laser XUV (PALS, Prague) a été caractérisé dans le cadre de cette thèse. Le temps de cohérence mesuré est de 0,68 ps, significativement inférieur aux valeurs mesurées sur les autres types de lasers XUV. L'analyse de l'ensemble des mesures a fait apparaître un comportement différent suivant que la durée d’impulsion est longue devant le temps de cohérence ou proche de celui-ci. Dans le premier cas les largeurs spectrales déduites sont en bon accord avec les calculs, dans le second l’accord est moins bon et la forme des traces d'autocorrélation n'était pas comprise. Ces observations ont motivé une étude détaillée de l'influence des propriétés temporelles de l'émission ASE des lasers XUV sur la méthode interférométrique employée pour caractériser leur largeur spectrale. Cette étude, basée sur un modèle emprunté aux lasers à électrons libres, a révélé un effet de la cohérence temporelle partielle sur les mesures d'autocorrélation en champ de ces sources. Elle ouvre des perspectives sur l'utilisation de notre méthode pour une mesure simultanée de la largeur spectrale et de la durée d'impulsion de la source. Enfin, une étude basée sur un modèle Bloch-Maxwell a été réalisée pour tenter de mieux comprendre les conditions d'apparition des oscillations de Rabi au cours de l'amplification de l'harmonique dans le plasma de laser XUV. Deux régimes d'amplification, adiabatique et dynamique, autour d'un seuil d'inversion de population ont été mis en évidence. / The work of this thesis was made in the context of the efforts made to reduce the pulse duration of plasma-based XUV lasers down to the femtosecond domain. The very narrow spectral width of the amplifier medium (~ 1E10 - 1E11 Hz) limits the minimum achievable pulse duration (Fourier limit). The amplifier medium of XUV lasers pumped by collisional excitation are dense and hot plasmas that can be created both by rapid electrical discharge and by different types of power lasers. There are thus 4 distinct types of XUV laser sources with different plasma parameters (density, temperature) in the gain region. Yet, the spectral and temporal properties of the emitted radiation are strongly linked to these parameters. All 4types of XUV lasers operate in amplification of spontaneous emission (ASE) mode, and 2 of them, for a few years, can operate in "seeded" mode. This technique consists in injecting a femtosecond high order harmonic pulse (the seed), resonant with the lasing transition, at one extremity of the plasma amplifier. Because of the major mismatch between the spectral width of the plasma and that of the seed the femtosecond duration of the latter is not preserved during amplification. Simulations (COLAX Maxwell-Bloch code) show that the amplification is highly non-linear in such systems, including the appearance of Rabi oscillations. Generating Rabi oscillations in seeded XUV lasers is currently considered a promising way to produce femtosecond XUV lasers. However Rabi oscillations have yet never been experimentally demonstrated. Thus, a meticulous experimental characterization of the spectral properties of the 4 types of XUV lasers in connection with the plasma conditions, combined with a better understanding of amplification mechanisms under different theoretical plasma conditions based on studies and simulations are needed to reach our goal. A wide experimental campaign aiming to spectrally characterize all different types of XUV lasers was conducted by our group over the past decade. The required spectral resolution is not available with the best current spectrometers, so the method we used consists on the measurement of the temporal coherence of the XUV laser through an electric field autocorrelation, using a wave front-division interferometer that was specifically designed for these measures, from which the spectral width can be deduced. The latter type of the four XUV laser types (PALS, Prague) was characterized during this thesis, closing this experimental campaign. The measured coherence time was 0.68 ps, which is significantly lower than the coherence times measured on the other XUV laser types. Analysis of the overall results revealed two different behavior whether the XUV laser has a long pulse duration compared to its coherence time or if the two durations are close. In the first case the inferred spectral widths are in good agreement with theoretical predictions, while in the second case the agreement was not as good and the shape of the electric field autocorrelation traces was not understood. This observation has prompted a detailed study of the influence of temporal properties of ASE XUV lasers on the interferometric methodology used to determine the spectral width of XUV lasers. The study, based on a model developed for X-free electron lasers, revealed an effect of partial temporal coherence in electric field autocorrelation measures of these sources. This study offers perspectives on a simultaneous measure of the spectral width and the duration of theses sources with our method. Finally, a study based on Maxwell-Bloch equations was carried out in order to understand better the conditions of apparition of Rabi oscillations. This study highlighted two amplification regimes, adiabatic and dynamic, around a population inversion threshold.

The brightness and proximity of many classical Be stars makes them perfect laboratories for studying the physics of astrophysical disks. They are also among the most popular targets for optical/IR interferometers, which are able to fully resolve their circumstellar disks, to which much of the recent progress in our understanding of these enigmatic objects is owed. The current consensus is that classical Be stars eject material from the stellar surface into Keplerian orbits, thus forming a disk, whose subsequent evolution is governed by turbulent viscosity, which is the basis of the so-called viscous decretion disk (VDD) model. Among the main results of the present work is arguably the best-constrained model of a particular Be star β CMi. The VDD predictions were confronted also with radio observations, which allowed for the first determination of the physical extent of a Be disk. This result subsequently led to the detection of a binary companion, which is truncating the disk by tidal forces. Extending the sample to include five more targets led to revealing a similar outer disk structure in all of them. The range of explanations includes the most plausible scenario, in which the truncation of Be disks by (unseen) companions is much more common than previously thought.

[pt] Neste trabalho são apresentados os resultados referentes ao desenvolvimento de um sistema interferométrico primário, o interferômetro Linnik, para medidas de comprimento de amostras na escala micrométrica e nanométrica. O sistema experimental foi caracterizado e otimizado para prover rastreabilidade a degraus de altura, usados como referência na escala de comprimento. As principais fontes de incerteza foram avaliadas, sendo a planicidade do artefato o parâmetro com o maior valor de contribuição para a incerteza final. A estabilidade do sistema de referência pode ser mostrada através da alta reprodutibilidade apresentada ao longo de algumas semanas de medição. Este também serviu como base para prover a rastreabilidade no SI, para instrumentos ópticos tais como OCT, AFM e microscópios confocais, sendo os dois últimos usados na área de nanotecnologia. Estes instrumentos foram calibrados usando como padrão de transferência os degraus de altura, previamente avaliados no interferômetro Linnik. Com isto, foi estabelecida a rastreabilidade na escala de comprimento para alguns institutos no país. / [en] In this work are presented the results related to the development of a primary interferometric system, the Linnik interferometer for length measurements of samples in the micrometer and nanometer scales. The experimental system has been characterized and optimized to provide traceability to step height, used as the reference standards in length scale. The main sources of uncertainty were evaluated, and the flatness of the artifact was the parameter with the highest contribution to the final uncertainty. The stability of the reference system can be demonstrated through the reproducibility that was evaluated over several weeks. This system also served as the basis to provide traceability to the SI for optical instruments such as OCT and confocal microscopes AFM, the latter two being used in the field of nanotechnology. These instruments were calibrated using step heights, as transfer standards, that were previously evaluated in Linnik interferometer. Therefore, it was established the traceability in length scale for some institutes in the country.

[pt] A maioria dos métodos de avaliação de ondas vibratórias é realizada através do contato entre o sensor e o objeto a ser analisado. Esse requisito de contato impõe algumas limitações de quais objetos podem ser avaliados, como por exemplo, o tamanho do mesmo. Uma técnica que expandiu a capacidade de medição se comparado aos sensores tradicionais de vibração é a vibrometria laser doppler. Ela possibilita medições não intrusivas com alta resolução espacial e tempo de teste reduzido. Dentre as várias aplicações que se beneficiam das aquisições com o vibrômetro laser doppler, o imageamento fotoacústico se encontra no centro do objetivo deste trabalho. O imageamento fotoacústico é uma tecnologia emergente que supera o alto espalhamento óptico em amostras biológicas utilizando o efeito fotoacústico. Ele combina aspectos de imageamento óptico e ultrassom e, consequentemente, algumas de suas vantagens: imagear certos componentes biológicos em profundidades de alguns centímetros e com alto contraste. A técnica mais direta de obter imagens em um sistema fotoacústico é a excitação pontual da amostra e a detecção por varredura. O foco deste trabalho é analisar e implementar uma técnica óptica para detecção das vibrações ultrassonoras em um sistema fotoacústico. Foram avaliados diferentes sistemas interferométricos experimentais, tanto por mapeamento pontual quanto por campo pleno. O princípio da interferometria e a teoria das medições quantitativas são apresentados para explicar as técnicas experimentais utilizadas para aquisição das ondas vibratórias. Igualmente, a técnica de processamento do sinal vibratório é discutida. Dentre as técnicas testadas experimentalmente, duas foram implementadas, analisadas e discutidas em detalhe e seus resultados foram apresentados e comparados entre si. A primeira técnica discutida é o Laser Optical Feedback Imaging (LOFI), um interferômetro heteródino que utiliza a dinâmica do laser e a sua grande sensibilidade ao fenômeno de reinjeção óptica para realizar medições de alta precisão do sinal retroespalhado da amostra. Essa técnica realiza suas aquisições ponto a ponto, através do do escaneamento do feixe do laser na superfície da amostra. Esse modo de aquisição possui um tempo de teste e processamento elevado, mas com alta resolução espacial e com a possibilidade de medir a região transitória. A segunda técnica utilizada para a aquisição de medidas de vibrações ultrassonoras é o estroboscópio Mach-Zehnder, um interferômetro de campo pleno que possibilita a aquisição do padrão de speckle de toda a região de interesse da amostra com baixo tempo de aquisição e processamento. Dessa forma, essa técnica tem um grande potencial para aplicações em tempo real. Os resultados experimentais de ambos os sistemas são apresentados e discutidos em detalhe. Um transdutor piezoelétrico é utilizado para as medições com os dois sistemas, com as mesmas características de teste. Adicionalmente, são apresentados os resultados com a técnica LOFI quando o ganho não-linear é compensado. Esse tipo de teste não é possível no sistema estroboscópico Mach-Zehnder campo pleno, considerando que apenas o LOFI é capaz de realizar medidas transitórias. Para concluir o trabalho, são discutidos e comparados os principais parâmetros para as técnicas testadas: ruído, potência do laser, resolução espacial, resolução temporal, e tempo de aquisição. / [en] Photoacoustic imaging combines aspects of optical and ultrasound imaging and, consequently, combines some of their particular advantages: imaging of specific tissue components in a depth up to several centimeters becomes possible with a high image contrast. The most straightforward strategy to produce photoacoustic images is point-wise excitation and detection in a scanning mode. The main focus of this work is to analyze and implement optical techniques to detect ultrasound vibrations in a photoacoustic system. We evaluate different interferometric systems, both point scanning and full field. Two techniques that were implemented and further discussed are the Laser Optical Feedback Imaging (LOFI), which is a sensitive, point scanning, heterodyne interferometer that uses the dynamics of the laser, and a full field, stroboscopic Mach-Zehnder to acquire ultrasound vibration measurements.We discuss the results from each system and its advantages with the intended application.