SCExAO is the premier high-contrast imaging platform for the Subaru Telescope. It offers high Strehl ratios at near-IR wavelengths (y-K band) with stable pointing and coronagraphs with extremely small inner working angles, optimized for imaging faint companions very close to the host. In the visible, it has several interferometric imagers which offer polarimetric and spectroscopic capabilities. A recent addition is the RHEA spectrograph enabling spatially resolved high resolution spectroscopy of the surfaces of giant stars, for example. New capabilities on the horizon include post-coronagraphic spectroscopy, spectral differential imaging, nulling interferometry as well as an integral field spectrograph and an MKID array. Here we present the new modules of SCExAO, give an overview of the current commissioning status of each of the modules and present preliminary results.

L'imagerie par rayons X est fortement développée dans notre société et notamment dans les domaines industriels, médicaux ou sécuritaires. L'utilisation de cette méthode d'imagerie des structures internes (pour la détection d'irrégularité, de contrôle non destructif de pièces ou de menaces) est quotidienne. En radiographie, le contraste produit sur les images est relié à la variation de l'atténuation du flux de rayons X, qui est fonction de la densité, de l'épaisseur du matériau étudié ainsi que de la longueur d'onde utilisée. Ainsi par exemple, des gaines métalliques, des os ou des armes amènent du contraste sur l'image. Mais en plus de leur atténuation, les rayons X vont subir un déphasage qui est d'autant plus important que le matériau est peu atténuant. Ce phénomène va amener du contraste, dit de phase, permettant d'imager des matériaux peu denses tels que des plastiques, composites, tissus mous ou explosifs. Ce travail de thèse présente le développement et l'adaptation, dans le domaine des rayons X, de méthodes d'imagerie par contraste de phase sur des équipements de laboratoire. Le but est de compléter, d'une manière plus accessible et quotidienne, les demandes d'évaluation non destructives. Ce manuscrit se découpe suivant deux axes portant sur la simulation d'une part et sur le développement instrumental d'autre part. Un outil de simulation a été développé portant sur une description hybride alliant optique géométrique et optique ondulatoire. Les limites du modèle et des validations sont présentées. La partie instrumentale se focalise sur l'étude de deux techniques d'imagerie différentielle de phase. La première technique est de l'interférométrie à décalage multilatéral, dont l'adaptation sur tube à rayons X est réalisée pour la première fois. Une exploitation intéressante de la redondance de la mesure que produit la technique sera notamment introduite. La deuxième approche est une technique d'interférométrie de suivi de tavelure, dont nous présenterons une nouvelle exploitation. / X-ray imaging is widely used in non-destructive testing dedicated to industry, medical or security domain. In most of the radiographic techniques, the image contrast depends on the attenuation of the X-ray beam by the sample. This attenuation is function of the density and thickness of the object and of the wavelength. Therefore, objects like metal covers, bones or weapons bring contrast on the image. In addition to attenuation, phase shifting happens, in particular for low-attenuating material. This phenomenon brings contrast, called phase contrast, and allows a X-ray image of low-attenuating material as plastics, composites, soft tissues or explosives. This work presents development and adaptation, in the X-ray domain, of phase contrast imaging techniques on laboratory equipment. The goal is to bring phase contrast imaging in daily use. This manuscript is split in two parts, simulation and instrumentation. A simulation tool has been developed, mixing geometrical optic and wave optic. Limits of the model and validation are presented. For the instrumental part, two interferometric techniques have been considered. The first one is multi-lateral interferometry where adaptation on X-ray tube is presented for the first time. Interesting use of the measurement recurrence will be introduced. The second one is speckle tracking interferometry, recently adapted on X-ray tube, for which we present new advancements.

The initiation of high explosives (HEs) under shock loading lacks a comprehensive understanding: particularly at the particle scale. One common explanation is hot spot theory, which suggests that energy in the material resulting from the impact event is localized in a small area causing an increase in temperature that can lead to ignition. This study focuses on the response of HMX particles (a common HE) within a polymer matrix (Sylgard-184^®), a simplified example of a polymer bonded explosive (PBX). A light gas gun was used to load the samples at impact velocities ranging from 370 to 520 m/s. The impact events were visualized using X-ray phase contrast imaging (PCI) allowing real-time observation of the impact event. The experiments used three subsets of PBX samples: multiple particle (production grade and single crystal), drilled hole, and milled slot. Evidence of damage and deformation occurred in all of the sample types. While the necessary impact velocity for consistent hot spot formation leading to reactions was not reached, the damage (particularly cracking) that occurred provides a useful indication of where hot spots may occur when higher velocities are reached. With the multiple particle samples, evidence of cracking and debonding occurred throughout. One sample showed significant volume expansion due to possible reaction. The samples containing drilled holes demonstrated the expected pore collapse behavior at these velocities, as well as damage downstream from the holes under various two-hole arrangements. Milled slot samples were tested to simulate existing cracks in the HMX. These samples showed increased damage at the site of the milled slot, as well as unique cracking behavior in one of the samples.

With the advent of high-power lasers in recent decades, a unique source of hard X-ray radiation has become availible. This source of collimated, broadband, femtosecond, incoherent and hard X-ray radiation is produced when a focused laser with intensity above 10^18 W/cm^2 collides with a gas target. The strong electric field of the laser pulse ionizes the gas and interacts with the plasma generating a strong plasma wake wave. This space charge separation inside the target generates longitudal electric fields of the order of 100 GV/m. This resulting electrostatic wakefield accelerates the electrons to relativistic velocities and causes them to travel in oscillatory motion behind the laser pulse, producing hard and collimated X-ray radiation. This thesis is focused on a theoretical evaluation and an experimental design of this laser-plasma X-ray source. Furthermore, we consider the source's unique properties for novel imaging applications.

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No description available.

Laser speckle contrast imaging (LSCI) is a non-invasive method for assessment of microcirculatory blood flow. The technique is based on analysis of speckle patterns to build 2D maps of perfusion with high spatial and temporal resolution. A drawback of the method is that it is highly sensitive to motion artifacts since the perfusion estimates are based on quantification of the motion blurring in the images. The camera is today limited to a bulky stand for good measurements, but even as it is fixed, it does not ensure that the patient is completely still. In many clinical settings, it would be advantageous to have a more flexible camera and to be able to detect if an image is influenced by external motion. Multi-exposure laser speckle contrast imaging (MELSCI) is an extension to LSCI that utilizes the contrast from multiple exposure times. The gain in information has paved way for more accurate perfusion estimates. The technique has been limited due to its computational complexity, but recently a real time system has been developed. The goals of this thesis was twofold, firstly find a quantifiable measure of motion artifacts to be able to evaluate and compare LSCI and MELSCI. Secondly, propose an algorithm that detects movements in LSCI recordings. Motion artifacts in LSCI and MELSCI were investigated by developing a setup where repeatable movements could be made. Measurements of a hand influenced by motions of different speeds and directions were acquired and the relative difference between motion and static states were calculated and compared for the two systems. The relative difference of the MELSCI measurements were lower for all speeds above 0.57 mm/s, indicating more robustness to motion artifacts. A detection algorithm using image registration to calculate the instantaneous speed in each frame of the recording was developed. The method successfully detects movements perpendicular to the camera and shows that the intensity images of an LSCI recording can be used to give a direct indication of when movement has occurred.

Laser speckle contrast imaging (LSCI) and its extension, multi-exposure laser speckle contrast imaging (MELSCI) are non-invasive techniques to monitor peripheral blood perfusion. One of the main drawbacks of LSCI and MELSCI in clinical use is that the techniques are sensitive to tissue movement. Moreover, the image background contributes to unnecessary data. The aim of this project was to develop and evaluate different methods to detect local motion artifacts and image backgrounds in LSCI and MELSCI. In this project, three different methods were developed: one using statistical analysis and two using machine learning. The method based on classical statistics was developed in MATLAB with a dataset made up of 1797 frames of 256 x 320 images taken from a recording of a hand where the thumb and middle finger were taking turns making small movements while the middle finger was the subject of three different states made by an occlusion cuff (baseline, occlusion, and reperfusion). The main filter that was used in the first method was the Hampel filter. Furthermore, networks for the machine learning method were developed in Python using the same dataset but with 20,000 small patches extracted from the dataset of sizes 3 x 3 to 21 x 21 pixels. The first machine learning method was based on two-dimensional data patches, hence no time dimension was included, while the second machine learning method used three-dimensional data patches where the time dimension was included (from 1s to 10s). The generation of ground truth for the dataset was manually created frame by frame in a ground truth generation graphical user interface (GUI) in MATLAB. To assess the three methods, the Dice coefficient was used. The statistical method resulted in a Dice coefficient of 0.7557. The highest Dice coefficient for the machine learning method with a 2D dataset was 0.2902 (patch size 13 x 13) and the lowest was 0.2372 (patch size 7 x 7). For the machine learning method with 3D datasets, the patch size of 21 x 21 x 4 resulted in the highest Dice coefficient (0.5173), and the 21 x 21 x 40 model had the lowest Dice coefficient (0.1782). Since the two methods based on temporal data proved to be performing best in this project, one conclusion for further development of an improved model is the usage of temporal data in the training of a model. However, one important difference between the statistical method and the three-dimensional machine learning method is that the statistical method does not handle fast perfusion changes as well as the machine learning method and can not detect image background and static tissue. Therefore, the overall most useful method to further develop is the three-dimensional machine learning method.

Conventional phase-contrast imaging entails stepping an analyser grating across the detector to resolve the interference pattern caused by the x-rays after passing through a series of gratings in a so-called Talbot-Lau interferometer. However, the analyser grating in the interferometer poses a challenge, not only due to the machinery and alignment required but also due to each exposure delivering a dose to the subject. Another downside of the analyser grating is that whilst the phase-step length can be adjusted, the x-rays allowed through the grating depend on its slit-width ratio, which cannot be changed without changing the whole grating.This thesis evaluates if the analyser grating can be removed by instead using a deep silicon photon-counting detector which can determine the photon interaction position with an uncertainty of around one micrometre. It is concluded that such a high-resolution detector will not only be able to remove the need for an analyser grating and its associated challenges, but the results also imply a three-fold increase in the contrast-to-noise ratio when dose-matching the grating-based approach with the grating-less approach. Furthermore, the conventional absorption image, which is lost when using an analyser grating, will still be available using a high-resolution detector. Finally, the removal of the analyser grating shifts most of the system conditions to the source grating and the phase grating, making it possible to design a compact unit of the two gratings for integration into a CT scanner. / Konventionell faskontrast involverar att stega ett analysgitter över detektorn för att detektera interferensmönstret som skapas av röntgenstrålarna efter att de passerat genom en serie gitter i en så kallad Talbot-Lau interferometer. Analysgittret introducerar en utmaning, inte enbart på grund av maskineriet och kalibreringen som krävs, utan även då varje steg utsätter det röntgade föremålet för strålning. Ytterligare en begränsning är att även om längden på stegen kan justeras beror mängden röntgenstrålar som passerar genom analysgittret på gittrets slitsbredd, vilken inte går att ändra på utan att byta hela gittret.Den här uppsatsen utvärderar om analysgittret kan tas bort genom att istället använda en högupplöst fotonräknande djup kiseldetektor som har förmågan att uppskatta positionen av en fotoninteraktion inom en mikrometer. Slutsatsen är att en sådan detektor kommer att kunna ersätta analysgittret och resultaten tyder på en trefaldig ökning av contrast-to-noise ratio vid dosmatchning mellan metoden med analysgitter och metoden med en högupplöst detektor. Vidare behålls den konventionella absorptionsbilden då man använder en högupplöst detektor, någonting som annars går förlorat vid användandet av analysgittret. Slutligen skiftas de flesta villkoren på systemet till källgittret och fasgittret, vilket tyder på att en kompakt konstruktion av dessa två gitter skulle kunna integreras i en CT-skanner.

Tendo em vista experimentos envolvendo o estudo da dinâmica de gases quânticos aprisionados, visando a simulação quântica de sistemas complexos, este trabalho discute a implementação e o estudo da técnica de imagem dispersiva, por contraste de fase, e a compara com o método de imagem por absorção óptica. A implementação da nova técnica foi feita em um regime não convencional de dessintonia, explorando a região proxima da ressonância atômica, onde se deve levar em conta o efeito da absorção, além da mudança de fase, do campo elétrico do laser de prova, após interagir com os átomos. Portanto, este trabalho apresenta não só a implementação de uma nova técnica experimental, mas também um modelo simples para interpretar os dados obtidos nesse novo regime. / Envisioning experiments involving the dynamics of trapped quantum gases, towards the quantum simulation of complex systems, this work presents the implementation and study of a dispersive imaging technique, by phase contrast, and compares it to absorption imaging. The implementation of this new technique in our laboratory was done in a non conventional range of detunings, exploring the region near atomic resonance, where absortion effecs need to be taken into account, in addition to the phase shift, introduced in the electric field of the probing laser, after interacting with the atoms. Therefore, this work presents not only the implementation of a new experimental technique, but also a simple model to interpret the dada obtained in this new regime.