Many biological specimens are transparent and in weak intensity contrast, making it invisible using conventional bright field microscopes. Therefore, the phase-based optical microscopy techniques play important roles in the development of the modern biomedical science. Furthermore, the ability to achieve quantitative phase measurement of the tiny structures of biomedical specimens is of great importance for many biomedical applications. Thus, quantitative phase imaging becomes an important technique to measure the phase variations due to the difference of refractive index and geometric thickness of various structures and materials within the biomedical specimens. In this thesis, a spectral modulation interferometry (SMI) is developed to achieve quantitative phase imaging. In SMI, the phase and amplitude information will simultaneously be modulated onto the interference spectrum of the broadband light. Full-field phase images can be obtained by scanning along the orthogonal direction only. SMI incorporates the advantages of low coherence from broadband light source, high sensitivity from spectral domain interferometry and the high speed from the spectral modulation technique to achieve quantitative phase measurement with free of speckle, high temporal sensitivity (~0.1nm) and fast imaging rate. The principles of SMI system and programming as well as some important image processing methods will be discussed in detail. Besides, the quantitative phase measurement of the reflective object (USAF resolution target) and the transmitted biological objects (Peranema, human cheek cells) will be shown. / Master of Science

The need for high resolution, continuously sustained imaging drives the interest in space-borne, distributed aperture, interferometric (amplitude, heterodyne, or intensity correlation) systems. This paper will discuss the maneuver controls for a system of multiple space-based telescopes to secure optimal image quality. Such distributed aperture systems eff ectively measure the Fourier Transform of the collected light so that the observed wave pattern is seen in the frequency plane. This Fourier Transform representation of physical spacecraft maneuvers may be interpreted as coverage regions (discs) in the frequency plane. Superior coverage of the frequency plane, which is directly related to image quality, is investigated for imaging distant objects using interferometric techniques where apertures are distributed on multiple space-based telescopes. The corresponding cost function is based on the optimality of the spacecraft maneuvers, which in turn is based on achieving a high image quality. This study builds on previous research wherein the first-order necessary conditions (FONC) were derived. The FONC are derived for specialized rectilinear motion and expanded to incorporate varying coverage disc velocities. These linearized equations are verifi ed to be consistent with those for the constant velocity case. Next, linearized first-order necessary conditions are shown to correspond closely with the fully nonlinear case. After that, the conditions for optimal overlap of the coverage paths will be given; these conditions lead to the optimal cost based on frequency plane parameters. Finally, a heuristic approach will be used to compare diff erent frequency plane coverage strategies. An analogy to painting will be presented to demonstrate adequate signal-to-noise ratio required for a desired image quality.

A broad near-infrared photometric survey is conducted of 1678 stars in the direction of the $\rho$ Ophiuchi ($\rho$ Oph) star forming region using data from the 2MASS Calibration Database. The survey involves up to 1584 photometric measurements in the \emph{J}, \emph{H} and \emph{K$_{s}$} bands with an $\sim$1 day cadence spanning 2.5 years. Identified are 101 variable stars with $\Delta$\emph{K$_{s}$} band amplitudes from 0.044 to 2.31 mag and $\Delta$(\emph{J}-\emph{K$_{s}$}) color amplitudes ranging from 0.053 to 1.47 mag. Of the 72 $\rho$ Oph star cluster members, 79$\%$ are variable; in addition, 22 variable stars are identified as candidate members. The variability is categorized as periodic, long timescale, or irregular based on the \emph{K$_{s}$} time series morphology. The dominant variability mechanisms are assigned based on the correlation between the stellar color and single band variability. Periodic signals are found in 32 variable stars with periods between 0.49 to 92 days. The most common variability mechanism among these stars is rotational modulation of cool starspots. Periodic eclipse-like variability is identified in 6 stars with periods ranging from 3 to 8 days; in these cases the variability mechanism may be warped circumstellar material driven by a hot proto-Jupiter. Aperiodic, long time scale variability is identified in 31 stars with time series ranging from 64 to 790 days. The variability mechanism is split evenly between either variable extinction or mass accretion. The remaining 40 stars exhibit sporadic, aperiodic variability with no discernible time scale or variability mechanism. Interferometric images of the active giant $\lambda$ Andromedae ($\lambda$ And) were obtained for 27 epochs spanning November. 2007 to September, 2011. The \emph{H} band angular diameter and limb darkening coefficient of $\lambda$ And are 2.777 $\pm$ 0.027 mas and 0.241 $\pm$ 0.014, respectively. Starspot properties are extracted via a parametric model and an image reconstruction program. High fidelity images are obtained from the 2009, 2010, and 2011 data sets. Stellar rotation, consistent with the photometrically determined period, is traced via starspot motion in 2010 and 2011. The orientation of $\lambda$ And is fully characterized with a sky position angle and inclination angle of 23$\degree$ and 78$\degree$, respectively.

Ces travaux de thèse proposent une amélioration du Scanning Microdeformation Microscope (SMM),un microscope à sonde locale, pour la caractérisation mécanique élastique des matériaux à l’échellelocale. Il est montré qu’en utilisant n > 2 modes de résonance du SMM, il est possible de découplerles mesures du module de Young et du coefficient de Poisson d’un matériau isotrope.Une étude des modes du résonateur a permis d’enrichir son modèle afin qu’il puisse modélisern > 2 modes. Des procédures ont été développées pour identifier les paramètres de ce modèle etles constantes élastiques des matériaux à partir de n > 2 fréquences de résonance. Enfin, ces procéduresont été appliquées à des exemples de caractérisation à l’échelle locale afin de valider laméthode et d’en exhiber les possibilités et les limites.Pour gagner en robustesse et se diriger vers la caractérisation des matériaux anisotropes, un systèmed’imagerie interférométrique en lumière polarisée, permettant la mesure du champ de rotationde surfaces réfléchissantes dans une direction particulière, a été développé pour être intégré auSMM. Son prisme biréfringent à gradient uniaxial d’indice lui confère sa sensibilité à la rotation. Cesystème est capable de mesurer un champ de rotation localisé comme c’est le cas au voisinage dela pointe du SMM. Il a aussi montré son intérêt dans les cas où l’effet d’échelle rend particulièrementintéressante la mesure de la rotation. / This work proposes an improvement of the Scanning Microdeformation Microscope (SMM), a scanningprobe microscope, for the mechanical elastic characterization of materials at local scale. It demonstratesthat using n > 2 SMM resonance frequencies allows to decouple Young’s modulus andPoisson’s ratio values for an isotropic material.The mechanical description of the resonator has been enriched in order to allow for an accuratemodeling over a wide frequency range. Procedures have been developed to identify the modellingparameters and the elastic constants of the materials from n > 2 resonant frequencies. Finally, theseprocedures have been applied to the characterization of various materials at local scale in order tovalidate the method and to present possibilities and limits.To improve robustness and move towards the characterization of anisotropic materials, a polarizedlightimaging interferometer was developed to measure the rotation field of reflecting surfaces in aparticular direction. The sensitivity to the rotation originates from a homemade birefringent prism withuniaxial gradient of refractive index. This system is able to measure a localized rotation field as it isinduced in the vicinity of the tip of the SMM. Its interest is also demonstrated in cases in which scaleeffects make the rotation measurement preferable to the out-of-plane displacement measurement.

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La présente thèse traite de méthodes en microscopie holographique numérique (MHN) en couleurs, avec un éclairage de cohérence spatiale partielle. Le principal inconvénient de la microscopie optique classique est sa faible profondeur de champ, rendant difficile l’observation de phénomènes dynamiques dans des échantillons épais. Au contraire, la MHN offre une reconstruction en profondeur grâce à la propagation numérique de l’hologramme. La MHN interférométrique donne aussi le contraste quantitatif de la phase, utile pour analyser des objets transparents. Un éclairage à plusieurs longueurs d’onde dans une configuration appropriée permet la MHN en couleurs. L’imagerie en flux et en couleurs de particules en MHN est ici développée, avec une méthode pour la correction automatique de la balance des couleurs et des défauts permanents. Elle est appliquée pour l’analyse du plancton dans des échantillons d’eau de surface et fournit des images de haute qualité pour les intensité et phase optiques. En outre, la réduction du bruit obtenue en diminuant la cohérence spatiale de l’éclairage en MHN est également étudiée, avec deux modèles évaluant quantitativement ce phénomène en fonction de la cohérence spatiale de la lumière et de la distance entre la source de bruit et le plan d’enregistrement. De plus, la MHN différentielle est aussi abordée. Celle-ci fournit les phases différentielles, la phase étant calculée par intégration. Cependant, les défauts présents conduisent à des aberrations lors du calcul de la phase, qui affectent sa qualité et empêchent la reconstruction holographique. Un traitement spécifique est développé, permettant la reconstruction numérique en profondeur. Enfin, en MHN, un critère est essentiel pour déterminer automatiquement la distance de netteté de l’objet. Deux critères de netteté sont ici mis au point, fonctionnant indépendamment de la nature de l’objet observé (amplitude, phase ou mixte). L’un, monochromatique, est basé sur l’analyse de l’amplitude et sur un filtrage passe-haut ;l’autre, qui détecte rapidement le plan de netteté en MHN en couleurs, compare la phase dans le domaine de Fourier entre les couleurs. Les méthodes développées dans la thèse montrent le potentiel élevé de la MHN en couleurs avec un éclairage partiellement cohérent spatialement, suggérant un avenir prometteur pour cette technique. / The thesis deals with methods and developments in color digital holographic microscopy (DHM), with a partial spatial coherence illumination. The principal drawback of classical optical microscopy is its poor depth of field, which makes difficult the observation of dynamic phenomena in thick samples. On the contrary, DHM provides reconstruction in depth thanks to numeric propagation of the recorded hologram. Another feature of interferometric DHM is the quantitative phase contrast imaging, useful for analyzing transparent objects. Usual DHM is limited to monochromatic case, but multispectral illumination in an appropriate setup leads to color DHM. Color in-flow imaging of particles in DHM is developed in the thesis, with a method for the automatic correction of color balance and permanent defects. It is applied to analyze plankton microorganisms in untreated pond water samples, and provides high quality images, for both optical phase and intensity. Moreover, noise reduction obtained when decreasing the spatial coherence of the illumination in DHM is also investigated in the thesis, with the development of two models that quantitatively assess the noise reduction as a function of both the spatial coherence of the illumination, and the defocus distance of the noise source. Furthermore, differential DHM (DDHM) is also studied in the thesis. As DHM gives the optical phase, DDHM provides differential phases, from which phase is retrieved by integration. However, misalignments and defects give some aberrations, which affect phase quality and hinder refocusing. A specific hologram processing is developed, giving an accurate phase image and enabling holographic reconstruction in depth. Finally, in DHM, a criterion is essential to automatically achieve the refocusing distance of the object. Two refocusing criteria are developed in the thesis, both working independently of the nature of the observed object (amplitude, phase, or both mixed). The first one, monochromatic, is based on amplitude analysis and on a high-pass filtering process. The second one, which gives fast refocusing in multispectral DHM, compares the phase in the Fourier domain among wavelengths. Methods developed in the thesis show the high potential of color DHM with a partial spatial coherence illumination, suggesting a promising future for this technique. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished