We present new astrometric measurements from our ongoing monitoring campaign of the HR 8799 directly imaged planetary system. These new data points were obtained with NIRC2 on the W.M. Keck II 10 m telescope between 2009 and 2014. In addition, we present updated astrometry from previously published observations in 2007 and 2008. All data were reduced using the SOSIE algorithm, which accounts for systematic biases present in previously published observations. This allows us to construct a self-consistent data set derived entirely from NIRC2 data alone. From this data set, we detect acceleration for two of the planets (HR 8799b and e) at >3 sigma. We also assess possible orbital parameters for each of the four planets independently. We find no statistically significant difference in the allowed inclinations of the planets. Fitting the astrometry while forcing coplanarity also returns chi(2) consistent to within 1 sigma of the best fit values, suggesting that if inclination offsets of less than or similar to 20 degrees are present, they are not detectable with current data. Our orbital fits also favor low eccentricities, consistent with predictions from dynamical modeling. We also find period distributions consistent to within 1 sigma with a 1:2:4:8 resonance between all planets. This analysis demonstrates the importance of minimizing astrometric systematics when fitting for solutions to highly undersampled orbits.

We present new H (1.51.8 mu m) photometric and K-1 (1.92.2 mu m) spectroscopic observations of the young exoplanet HD 95086 b obtained with the Gemini Planet Imager. The Hband magnitude has been significantly improved relative to previous measurements, whereas the lowresolution K-1 (lambda/delta lambda approximate to 66) spectrum is featureless within the measurement uncertainties and presents a monotonically increasing pseudocontinuum consistent with a cloudy atmosphere. By combining these new measurements with literature L' photometry, we compare the spectral energy distribution (SED) of the planet to other young planetarymass companions, field brown dwarfs, and to the predictions of grids of model atmospheres. HD 95086 b is over a magnitude redder in K-1 - L' color than 2MASS J120733463932539 b and HR 8799 c and d, despite having a similar L' magnitude. Considering only the near-infrared measurements, HD 95086 b is most analogous to the brown dwarfs 2MASS J2244316+204343 and 2MASS J21481633+4003594, both of which are thought to have dusty atmospheres. Morphologically, the SED of HD 95086 b is best fit by low temperature (T-eff = 8001300 K), low surface gravity spectra from models which simulate high photospheric dust content. This range of effective temperatures is consistent with field L/T transition objects, but the spectral type of HD 95086 b is poorly constrained between early L and late T due to its unusual position the colormagnitude diagram, demonstrating the difficulty in spectral typing young, low surface gravity substellar objects. As one of the reddest such objects, HD 95086 b represents an important empirical benchmark against which our current understanding of the atmospheric properties of young extrasolar planets can be tested.

We present a new matched-filter algorithm for direct detection of point sources in the immediate vicinity of bright stars. The stellar point-spread function (PSF) is first subtracted using a Karhunen-Love image processing (KLIP) algorithm with angular and spectral differential imaging (ADI and SDI). The KLIP-induced distortion of the astrophysical signal is included in the matched-filter template by computing a forward model of the PSF at every position in the image. To optimize the performance of the algorithm, we conduct extensive planet injection and recovery tests and tune the exoplanet spectra template and KLIP reduction aggressiveness to maximize the signalto- noise ratio (S/N) of the recovered planets. We show that only two spectral templates are necessary to recover any young Jovian exoplanets with minimal S/N loss. We also developed a complete pipeline for the automated detection of point-source candidates, the calculation of receiver operating characteristics (ROC), contrast curves based on. false positives, and completeness contours. We process in a uniform manner more than 330 data sets from the Gemini Planet Imager Exoplanet Survey and assess GPI typical sensitivity as a function of the star and the hypothetical companion spectral type. This work allows for the first time a comparison of different detection algorithms at a survey scale accounting for both planet completeness and false-positive rate. We show that the new forward model matched filter allows the detection of 50% fainter objects than a conventional cross-correlation technique with a Gaussian PSF template for the same false-positive rate.

We present optical and near-infrared high-contrast images of the transitional disk HD 100546 taken with the Magellan Adaptive Optics system (MagAO) and the Gemini Planet Imager (GPI). GPI data include both polarized intensity and total intensity imagery, and MagAO data are taken in Simultaneous Differential Imaging mode at Ha. The new GPI H-band total intensity data represent a significant enhancement in sensitivity and field rotation compared to previous data sets and enable a detailed exploration of substructure in the disk. The data are processed with a variety of differential imaging techniques (polarized, angular, reference, and simultaneous differential imaging) in an attempt to identify the disk structures that are most consistent across wavelengths, processing techniques, and algorithmic parameters. The inner disk cavity at 15 au is clearly resolved in multiple data sets, as are a variety of spiral features. While the cavity and spiral structures are identified at levels significantly distinct from the neighboring regions of the disk under several algorithms and with a range of algorithmic parameters, emission at the location of HD 100546 "c" varies from point-like under aggressive algorithmic parameters to a smooth continuous structure with conservative parameters, and is consistent with disk emission. Features identified in the HD 100546 disk bear qualitative similarity to computational models of a moderately inclined two-armed spiral disk, where projection effects and wrapping of the spiral arms around the star result in a number of truncated spiral features in forward-modeled images.

The relationship between accommodation and myopia has been under investigation for many years, and the effort to understand it is ongoing. In this thesis, an introduction to the state of myopia research is given first, with particular reference to studies of accommodation and higher-order ocular aberrations, which feature in the subsequent chapters. Following a brief introduction to the general technique of aberrometry and visual stimulus control using adaptive optics, the development of a monocular adaptive optics instrument for this purpose is described. The instrument is used to vary a dioptric stimulus and record the accommodation response in pilot studies and a detailed experiment, which has also been published elsewhere. It is found, among other things, that accommodation can respond to more than one different input level during its latency period, and that such inputs can be stored until components of the accommodation control system are free to process them. Indications of a minimum halting time for accommodation, of around 0.6 s, are presented. In later chapters, the development and testing of a new, binocular adaptive optics apparatus will be found. As well as binocular aberrometry and adaptive optics control of stimulus aberrations, this instrument displaces images to allow for and stimulate ocular convergence in binocular accommodation experiments. It is the first instrument in the world with its combined functionalities. Finally, the contribution of this thesis is summarised, and further instrumentation development and experiments are put forward for the continuation of this branch of accommodation and myopia research.

Cette thèse étudie les aspects de contrôle d'applications optique adaptative, une technologie utilisée pour améliorer la performance des systèmes optiques en réduisant l'effet des distorsions de front d'onde, à l'imagerie haute résolution angulaire. Le problème Adaptive Optics contrôle est présenté à travers une revue de la littérature. Par conséquent, la conception d'un contrôleur de rétroaction est adressée, d'un point de vue moderne de contrôle, au moyen de la méthode de contrôle Linéaire Quadratique Gaussienne. L'approche proposée met l'accent sur la capacité de la boucle d'optique adaptative de rejeter l'aberration atmosphérique. On dérive un système de représentation diagonale état-espace qui sépare nettement la dynamique de la plante (miroir déformable et le capteur de front d'onde) de la dynamique des perturbations (modèle atmosphérique). Cette représentation facilite la résolution numérique du problème. Une analyse de fréquence est effectuée pour vérifier les spécifications de performance et de robustesse de la multiple-input multiple-système de rétroaction de sortie. De plus, nous analysons les performances et la robustesse de LQG contrôle basé par rapport au témoin intégrante classique, au moyen de bout en bout des simulations et en considérant les différents niveaux de bruit du capteur de front d'onde. Durant le-ciel observations, l'énergie turbulente et la vitesse relative de chaque couche de l'atmosphère peut changer rapidement dégrader l'estimation de front d'onde. Pour cette raison, un algorithme de modèle numérique de conception garantissant une performance satisfaisante rejet de perturbations, même dans le cas de variables dans le temps caractéristique de la turbulence est dérivé. Expériences numériques en utilisant les CAOS du progiciel ont été menées pour démontrer la robustesse de chaque approche proposée. Compte tenu de la conviction auteur que l'avenir de l'optique adaptative repose également sur le développement d'un plus sophistiqués (par exemple, non linéaire) des modèles, une quantité importante de travail a été consacrée à l'étude de deux classes de méthodes de reconnaissance des formes répandues. À savoir Support Vector Machines et méthodes du noyau, dont la régression des capacités sont exploitées dans la solution du problème non linéaire suivi optimal. En ce qui concerne Support Vector Machines, grâce à la théorie du contrôle optimal singulier, les contraintes se relâchent permettant une résolution plus facile et plus rapide numérique du problème d'optimisation. Alors que, dans le cas totalement déterministe du contrôleur Support Vector résulte plus simple à synthétiser. En référence aux méthodes du noyau, une tentative originale de réunir leurs forces de régression avec le concept de contrôle adaptatif inverse est présentée. Le noyau récursif des moindres carrés algorithme est utilisé pour mettre en œuvre un contrôleur adaptatif inverse capable de forcer une dynamique non linéaire appropriés pour suivre une sortie désirée. Cette méthode très peut également être utilisé pour vérifier si une trajectoire donnée arbitraire est une sortie admissible pour le système non linéaire à l'étude. Un tel algorithme innovant pourrait être utilement appliquée dans les travaux futurs, le contrôle de Tip-Tilt miroirs. Finalement, une première esquisse du cadre théorique soutenant l'utilisation du contrôle adaptatif inverse pour la solution du problème de suivi général est donné. Après l'introduction de la formulation mathématique du problème de suivi et les définitions nécessaires mathématiques, des conditions suffisantes et nécessaires (cas linéaire) et des conditions suffisantes (cas non-linéaire) de l'existence de la solution sont dérivés. / His thesis investigates the control aspects of Adaptive Optics applications, a technology used to improve the performance of optical systems by reducing the effect of wavefront distortions, to high angular resolution imaging. The Adaptive Optics control problem is presented through a survey of the literature. Consequently, the design of a feedback controller is addressed, from a modern control point of view, by means of the Linear Quadratic Gaussian control methodology. The proposed approach emphasizes the ability of the adaptive optics loop to reject the atmospheric aberration. We derive a diagonal state-space system representation which clearly separates the dynamics of the plant (deformable mirror and wavefront sensor) from the disturbance dynamics (atmospheric model). This representation facilitates the numerical resolution of the problem. A frequency analysis is carried out to check the performance and robustness specifications of the multiple-input multiple-output feedback system. Moreover, we analyze the performance and the robustness of LQG-based control compared to classic integral control, by means of end-to-end simulations and by considering different levels of wavefront sensor noise. During on-sky observations, the turbulent energy and relative speed of each atmospheric layer can change rapidly degrading the wavefront estimate. For this reason, a numerical model design algorithm guaranteeing satisfactory disturbance rejection performance even in the case of time-varying turbulence's characteristic is derived. Numerical experiments using the Software Package CAOS have been conducted to demonstrate the robustness of every proposed approach. Given the author firm belief that the future of Adaptive Optics also relies on the development of more sophisticated (i.e., nonlinear) models, a substantial amount of work was dedicated to the study of two classes of widespread pattern recognition methods. Namely Support Vector Machines and Kernel Methods, whose regression capabilities are exploited in the solution of the nonlinear optimal tracking problem. Concerning Support Vector Machines, thanks to the singular optimal control theory, constraints are loosened permitting an easier and faster numerical resolution of the optimization problem. So that, in the fully deterministic case the Support Vector controller results simpler to synthesize. With reference to Kernel Methods, an original attempt to bring together their regression strengths with the concept of Adaptive Inverse Control is presented. The Kernel Recursive Least-Square algorithm is used to implement an adaptive inverse controller capable of forcing a suitable nonlinear dynamics to follow a desired output. This very method can also be used to check if a given arbitrary trajectory is an admissible output for the nonlinear system under study. Such an innovative algorithm could be fruitfully applied, in future works, to the control of Tip-Tilt mirrors. Eventually, a first sketch of the theoretical framework supporting the use of Adaptive Inverse Control for the solution of the general tracking problem is given. After introducing the mathematical formulation of the tracking problem and the needed mathematical definitions, sufficient and necessary conditions (linear case) and sufficient (nonlinear case) conditions to the existence of the solution are derived.

Over the past few decades, fluorescence microscopy has proven to become the most widely used imaging technique in the field of life sciences. Unfortunately, all classical optical microscopy techniques have one thing in common: their resolution is limited by the diffraction. Thankfully, due to the very strong interest, development of fluorescent microscopy techniques is very intense, with novel solutions surfacing repeatedly. The major breakthrough came with the appearance of super-resolution microscopy techniques, enabling imaging well below the diffraction barrier and opening the new era of nanoscopy. Among the fluorescent super-resolution techniques, Stimulated Emission Depletion (STED) microscopy has been particularly interesting, as it is a purely optical technique which does not require post image processing. STED microscopy has proven to resolve structures down to the molecular resolution. However, super-resolution microscopy is not a cure to all the problems and it also has its limits. What has shown to be particularly challenging, was the super-resolution imaging of thick samples. With increased thickness of biological structures, the aberrations increase and signal-to-noise (SNR) decreases. This becomes even more evident in the super-resolution imaging, as the nanoscopic techniques are especially sensitive to aberrations and low SNR. The aim of this work is to propose and develop a 3D STED microscope that can successfully image thick biological samples with nanoscopic resolution. In order to achieve that, adaptive optics (AO) has been employed for correcting the aberrations, using the indirect wavefront sensing approach. This thesis presents a custom built 3D STED microscope with the AO correction and the resulting images of thick samples with resolution beyond diffraction barrier. The developed STED microscope achieved the resolution of 60nm in lateral and 160nm in axial direction. What is more, it enabled super-resolution imaging of thick, aberrating samples. HeLa, RPE-1 cells and dopaminergic neuron differentiated from human IPS cells were imaged using the microscope. The results shown in this thesis present 3D STED imaging of thick biological samples and, what is particularly worth to highlight, 3D STED imaging at the 80μm depth, where the excitation and depletion beams have to propagate through the thick layer of tissue. 3D STED images at such depth has not been reported up to date.

Adaptive optics work to reduce optical losses in the LIGO detectors, making them more sensitive to gravitational wave events. Mode-mismatch between the coupled optical cavities, caused by uncertainty in the radii of curvature and orientation of the interferometer optics, is one of the main sources of loss in Advanced LIGO. Thermal actuators are used to dynamically change the radius of curvature of certain interferometer optics, allowing mode mismatches to be reduced. Finely tunable astigmatic mirrors have the potential to be very useful in gravitational wave detectors for beam reflections at non-normal incidence, but have never been tested. These astigmatic composite mirrors are constructed by bonding a fused silica mirror to a non-axially-symmetric metal plate. When heated, the mirror is differentially distorted in the x- and y-directions due to its asymmetric design, resulting in an elliptical reflected beam profile. We model and test an initial mirror design, finding that it does, in fact, act as an astigmatic mirror. This finding opens a new avenue towards development of adaptive optics for current and next-generation gravitational wave detectors.

Adaptive optics (AO) systems make use of active optical elements, namely wavefront correctors, to improve the resolution of imaging systems by compensating for complex optical aberrations. Recently, magnetic fluid deformable mirrors (MFDM) were proposed as a novel type of wavefront correctors that offer cost and performance advantages over existing wavefront correctors. These mirrors are developed by coating the free surface of a magnetic fluid with a thin reflective film of nano-particles. The reflective surface of the mirrors can be deformed using a locally applied magnetic field and thus serves as a wavefront corrector. MFDMs have been found particularly suitable for ophthalmic imaging systems where they can be used to compensate for the complex aberrations in the eye that blur the images of the internal parts of the eye. However, their practical implementation in clinical devices is hampered by the lack of effective methods to control the shape of their deformable surface. The research work reported in this thesis presents solutions to the surface shape control problem in a MFDM that will make it possible for such devices to become integral components of retinal imaging AO systems. The first major contribution of this research is the development of an accurate analytical model of the dynamics of the mirror surface shape. The model is developed by analytically solving the coupled system of fluid-magnetic equations that govern the dynamics of the surface shape. The model is presented in state-space form and can be readily used in the development of surface shape control algorithms. The second major contribution of the research work is a novel, innovative design of the MFDM. The design change was prompted by the findings of the analytical work undertaken to develop the model mentioned above and is aimed at linearizing the response of the mirror surface. The proposed design also allows for mirror surface deflections that are many times higher than those provided by the conventional MFDM designs. A third contribution of this thesis involves the development of control algorithms that allowed the first ever use of a MFDM in a closed-loop adaptive optics system. A decentralized proportional-integral (PI) control algorithm developed based on the DC model of the wavefront corrector is presented to deal mostly with static or slowly time-varying aberrations. To improve the stability robustness of the closed-loop AO system, a decentralized robust proportional-integral-derivative (PID) controller is developed using the linear-matrix-inequalities (LMI) approach. To compensate for more complex dynamic aberrations, an Hinf controller is designed using the mixed-sensitivity Hinf design method. The proposed model, design and control algorithms are experimentally tested and validated.

Adaptive optics (AO) systems make use of active optical elements, namely wavefront correctors, to improve the resolution of imaging systems by compensating for complex optical aberrations. Recently, magnetic fluid deformable mirrors (MFDM) were proposed as a novel type of wavefront correctors that offer cost and performance advantages over existing wavefront correctors. These mirrors are developed by coating the free surface of a magnetic fluid with a thin reflective film of nano-particles. The reflective surface of the mirrors can be deformed using a locally applied magnetic field and thus serves as a wavefront corrector. MFDMs have been found particularly suitable for ophthalmic imaging systems where they can be used to compensate for the complex aberrations in the eye that blur the images of the internal parts of the eye. However, their practical implementation in clinical devices is hampered by the lack of effective methods to control the shape of their deformable surface. The research work reported in this thesis presents solutions to the surface shape control problem in a MFDM that will make it possible for such devices to become integral components of retinal imaging AO systems. The first major contribution of this research is the development of an accurate analytical model of the dynamics of the mirror surface shape. The model is developed by analytically solving the coupled system of fluid-magnetic equations that govern the dynamics of the surface shape. The model is presented in state-space form and can be readily used in the development of surface shape control algorithms. The second major contribution of the research work is a novel, innovative design of the MFDM. The design change was prompted by the findings of the analytical work undertaken to develop the model mentioned above and is aimed at linearizing the response of the mirror surface. The proposed design also allows for mirror surface deflections that are many times higher than those provided by the conventional MFDM designs. A third contribution of this thesis involves the development of control algorithms that allowed the first ever use of a MFDM in a closed-loop adaptive optics system. A decentralized proportional-integral (PI) control algorithm developed based on the DC model of the wavefront corrector is presented to deal mostly with static or slowly time-varying aberrations. To improve the stability robustness of the closed-loop AO system, a decentralized robust proportional-integral-derivative (PID) controller is developed using the linear-matrix-inequalities (LMI) approach. To compensate for more complex dynamic aberrations, an Hinf controller is designed using the mixed-sensitivity Hinf design method. The proposed model, design and control algorithms are experimentally tested and validated.