An intense laser or charged particle pulse propagating through matter excites light-speed refractive index structures in its wake via Kerr effect, ionization, or displacement of electrons from background ions. Examples include plasma wakes used to accelerate charged particles and self-guided filaments used for atmospheric analysis and micromachining. Such applications constrain the shape, size and evolution of the index structure, yet often these are known in detail only through intensive computer simulations based on estimated initial conditions. Here we develop and demonstrate three methods for visualizing evolving light-speed structures directly in the laboratory in a single shot : (1) frequency-domain streak camera, (2) frequency-domain tomography, and (3) multi-object-plane phase-contrast imaging. All three methods are based on analyzing phase perturbations that an evolving object imprints on one or more probe laser pulses that cross its path obliquely. The methods are tailored to different propagation lengths, material densities, and dimensionality of imaging. Using these techniques, evolving laser-driven filaments in glass and air and plasma wakes in helium gas driven by laser pulses up to petawatt peak power are visualized in one shot, revealing underlying nonlinear laser-plasma interaction physics that is compared in detail to computer simulations. / text

Pavement rutting is one of the major asphalt pavement surface distresses affecting pavement structure integrity and driving safety and is also a required performance measure specified in the Highway Performance Monitoring System (HPMS). Manual rutting measurement is still conducted by many state Departments of Transportation (DOTs), like Georgia DOT; however, it is time-consuming, labor-intensive, and dangerous. Although point-based rut bar systems have been developed and utilized by state DOTs to measure rutting conditions, they often underestimate rut depth measurements. There is an urgent need to develop an automated method to accurately and reliably measure rutting conditions. With the advance of sensing technology, emerging 3D line laser imaging technology is capable of collecting high-resolution 3D range data at highway speed (e.g., 100 km/h) and, therefore, holds a great potential for accurately and repeatedly measuring pavement rutting condition. The main contribution of this research includes a methodology, along with a series of methods and procedures, for the first time, developed utilizing emerging 3D line laser imaging technology to improve existing 1D rut depth measurement accuracy and repeatability and to measure additional 2D and 3D rutting characteristics. These methods and procedures include: (1) a threshold-based outlier removal method employing the multivariate adaptive regression splines (MARS) technique to remove outliers caused by non-rutting features, such as wide transverse cracks and potholes; (2) a modified topological-ordering-based segment clustering (MTOSC) method to optimally partition the continuous roadway network into segments with uniform rutting condition; (3) an overlapping-reducing heuristic method to solve large-scale segmentation problems; (4) a network-level rutting condition assessment procedure for analyzing 3D range data to statistically interpret the pavement rutting condition in support of network-level pavement management decisions; (5) an isolated rut detection method to determine the termini, maximum depth, and volume of isolated ruts in support of project-level maintenance operations. Comprehensive experimental tests were conducted in the laboratory and the field to validate the accuracy and repeatability of 1D rut depth obtained using the 3D range data. Experimental tests were also conducted in the laboratory to validate the accuracy of 3D rut volume. Case studies were conducted on one interstate highway (I-95), two state routes (SR 275 and SR 67), and one local road (Benton Blvd.) to demonstrate the capability of the developed methods and procedures. The results of experimental tests and case studies show that the proposed methodology is promising for improving the rutting measurement accuracy and reliability. This research is one of the initial effort in studying the applicability of this emerging sensing technology in pavement management. And the outcomes of this research will play a key role in advancing state DOTs’ existing pavement rutting condition assessment practices.

Asphaltenic crude oil is a complex fluid containing various components with different chemical properties. When it comes in contact with water, its polar components adsorb at the oil/water interface, reducing the interfacial tension and eventually developing viscoelastic films. The interfacial films impact emulsion stability and adhere to the oil-bearing reservoirs rocks, altering their wettability and thus hindering oil mobilization. Here, we investigate the formation of crude oil/water interfacial films. We measure both the time-dependent shear and extensional interfacial rheology moduli, and we relate it to the chemical composition of the films, highlighting the role of polar aromatic molecules in film formation. Varying chemical composition of the aqueous phase, we show that the properties of the interfacial films depend not only on the concentration of ionic species in water but also on their chemical nature. In particular, we highlight the role of sulfate salt in promoting interfacial viscoelasticity and in altering the composition of fully developed films. To study the rock/fluid interaction, we fabricate mixed-wet capillaries with angular cross-sections inspired by the naturally occurring primary drainage of pore-filling brine by invading crude oil. After employing our novel coating procedure, we experimentally investigate water invasion in mixed-wet capillaries and compare it with predictions of dynamic and quasi-static (Mayer-Stowe-Princen (MSP)) meniscus-invasion models. None of the dynamic models built for uniformly-wet pores can fully describe our experimental data in mixed-wet capillaries. However, the experimental results agree with predictions of MSP theory. To our knowledge, this is the first direct experimental validation of MSP theory under mixed-wet conditions. We confirm the possibility of spontaneous piston-type imbibition with high ($> 90^{\circ}$) advancing contact angles into mixed-wet pores, given that the contact angle is lowered below a critical value that is a function of pore geometry and residual water saturation. In oil reservoirs, injection of specific brines would be required to change the contact angle to values below the imbibition threshold. Finally, we extend our study and introduce a powerful 3D high-speed laser imaging of dynamic fluid flow in angular capillaries and investigate its capability to capture non-equilibrium shapes of fluid interfaces.

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Une nouvelle architecture d’Imagerie Flash Laser, appelée imagerie flash laser mosaïque (IFLM) consistant àvisualiser une scène par acquisition rapide de petites zones ou imagettes a été développée à l’ONERA. Par rapport àl’imagerie Flash laser traditionnelle qui acquiert en une seule fois toute la scène, cette technique permet d’augmenterle niveau de l’éclairement sur chaque imagette mais nécessite de couvrir l’ensemble de la scène d’étude avec unehaute cadence d’échantillonnage spatiale. Cette thèse a pour but d’évaluer les performances de ce nouveau conceptpuis de les comparer à l’imagerie flash laser classique. Dans une première étape, un simulateur complet d’IFLM (Modèle de formation d’image incluant les algorithmes de reconstruction de la scène) a été développé afin de synthétiser tous les phénomènes intervenant dans la formation des images acquises par la caméra puis de réaliser les traitements de restauration nécessaires afin de s’affranchir des artefacts introduits par cette technique. La simulation des images en entrée instrument prend en compte la formedu faisceau de la source, le type de balayage, le canal de propagation (transmission atmosphérique et turbulence) etenfin des bruits instrumentaux. Afin de reconstituer une image complète de la scène à partir des imagettes, trois méthodesde restauration ont été comparées montrant l’apport de notre méthode d’optimisation avec contrainte RL1L2.Dans une seconde étape, ce simulateur bout-en-bout a été utilisé afin de sélectionner le balayage optimal dufaisceau laser pour obtenir la meilleure qualité d’image. Nous avons montré qu’un balayage en quinconce était préférableà un balayage en ligne. Dans une troisième étape, les performances en termes de rapport signal-à-bruit et de contraste ont été évaluées et comparées à des images acquises par imagerie flash laser classique. Les résultats obtenus sur des images synthétiquesont montré que les performances entre ces deux techniques étaient comparables. Enfin, une analyse est menée sur l’étude des performances d’un tel système en tenant compte des technologies disponibles. Compte tenu des caractéristiques actuelles des sources laser et détecteurs, l’imagerie flash laser mosaïque montre son intérêt lorsqu’il faut couvrir un large champ de la scène présentant de faibles évolutions temporelles. / Flash active imaging can be used for surveillance or target identification at long range and Iow visibility conditions. Its principle is based on the illumination of a scene With a pulsed laser which is then backscattered to the sensor. The signal to noise ratio and contrast of the object over the background are increased in comparison With passive imaging. Even though, range and field of view (FOV) are limited for a given laser power. The new active imaging system presented here aims at vercoming this limitation. It acquires the entire scene With a high-speed scanning laser illumination focused on a limited region, whereas at each scan the full frame active image is acquired. The whole image is then reconstructed by mosaicking Il these successive images. A evaluation of the performance of this system is conducted by using a direct physical model of his so-called « mosaic active imaging ». This End to End model, realistic in terms of turbulence effects (scintillation, beam andering.. gives us a sequence of images a synthetic scenes. After describing this model, the reconstruction method will be described. It is based on a total-variation minimization scheme. Finally, the performances of this new concept are ompared to those of a conventional flash active camera by using usual metrics (Johnston's criteria, SNR, ...). For va rious mean laser powers, we quantify the gains expected in terms of range and field of view of this new concept.

L’imagerie thermique est largement utilisée dans le domaine militaire pour ses capacités de vision diurne etnocturne et sa longue portée d’observation. Cette technologie est basée sur la détection passive dans l’infrarouge.En conditions météorologiques dégradées ou quand la cible est partiellement dissimulée par du feuillage ou desfilets de camouflages militaires, elle devrait être à court terme de plus en plus complémentée par un systèmed’imagerie active. Cette technologie est essentielle pour l’imagerie à longue portée. La technique d’imagerie diteflash 2D est basée sur une source laser impulsionnel qui illumine la scène et sur une caméra rapide synchroniséequi constitue le système d’imagerie. Ces deux technologies sont bien éprouvées en présence de conditionsmétéorologiques claires. Les modèles TRM4 (imagerie thermique) et PERFIMA (imagerie active) sont capablesde prédire correctement les performances de tels systèmes par beau temps. En revanche, en conditions dégradéestelle que la pluie, le brouillard ou la neige, ces modèles deviennent non pertinents. Cette étude introduit denouveaux modèles pour compléter les codes TRM4 et PERFIMA, et les rendre aptes à prévoir les performancesdans ces conditions dégradées. Nous analysons ici plus particulièrement le temps de pluie pour l’imagerie activeet l’imagerie thermique. Dans un premier temps, nous répertorions l’impact possible de la pluie sur des paramètresphysiques connus (extinction, transmission, résolution spatiale, luminance de trajet, turbulence). Nous étudionsensuite les phénomènes physiques et les lois régissant les caractéristiques de la pluie. Nous avons développé desmodèles physiques permettant de calculer l’impact de la pluie sur le système global d’imagerie. Enfin, nous avonssimplifié et allégé ces modèles pour obtenir des modèles faciles à utiliser et à interfacer avec les codes TRM4 etPERFIMA qui sont couramment utilisés pour des applications industrielles. Ces modèles de prédiction del’imagerie active et de l’imagerie thermique ont été confrontés à la réalité (expérience avec l’imageur MILPATpar exemple) pour être validé sur des données réelles, comme la portée des systèmes. / Thermal imaging cameras are widely used in military contexts for their day and night vision capabilities andtheir observation range; there are based on passive infrared sensors (e.g. MWIR or LWIR range). Under badweather conditions or when the target is partially hidden (e.g. foliage, military camouflage) they will be more andmore complemented by active imaging systems, a key technology to perform target identification at long ranges.The 2D flash imaging technique is based on a high powered pulsed laser source that illuminates the entire sceneand a fast gated camera as the imaging system. Both technologies are well experienced under clear meteorologicalconditions; current models such as TRM4 (themal imaging) and PERFIMA (active imaging) codes are able topredict accurately the systems performances. However, under bad weather conditions such as rain, haze or snow,these models are not relevant. This study introduces new models to complete TRM4 and PERFIMA codesperformances predictions under bad weather conditions for both active and infrared imaging systems. We pointout rain effects on controlled physical parameters (extinction, transmission, spatial resolution, thermalbackground, turbulence). Then we develop physical models to describe their intrinsic characteristics and theirimpact on the imaging system performances. Finally, we approximate these models to have a “first order” modeleasy to deploy into TRM4 and PERFIMA already use for industrial applications. This theoretical work is validatedon real active and infrared data, as systems range.

L'imagerie laser 3D est une technique performante utilisée notamment pour cartographier l'environnement dans lequel évolue un aéronef, en mesurant la distance le séparant d'un objet, en plus des coordonnées (x,y). Le système est capable d'acquérir des mesures par tout temps (nuit, pluie, brouillard). Une nouvelle génération de capteurs, multi-pixels et ultra-sensibles, permet alors de répondre aux besoins identifiés pour cartographier avec précision une zone de grande superficie : haute résolution spatiale, longue portée avec précision centimétrique et rapidité d'acquisition. Il s'agit des plans focaux 3D Geiger. Avant leur utilisation en aéroporté, il était nécessaire de se familiariser avec leur fonctionnement, basé sur les probabilités de détection. Un simulateur reproduisant l'ensemble de la chaîne d'acquisition à été développé, puis validé sur des cas réels, au sol et en conditions statiques. Il a ensuite permis de démontrer l'intérêt des plans focaux Geiger pour la cartographie aéroportée à longue distance. / 3D laser imaging is a powerful technique used to recognize the environment around an aircraft, by measuring the distance between the system and an objet, in addition to its spatial coordinates. Also, it allows data acquisition under any weather condition (night, rain, fog). A new kind of sensors, multi-pixel arrays with high sensitivity, seems in line with the needs of an accurate 3D mapping of a big area : high spatial resolution, longe range detection with centimeter accuracy and low acquisition time. There are 3D Geiger-mode focal plane arrays. Before an onboard use, it was necessary to analyze the operation of such a sensor, based on probabilities of detection. An end-to-end simulator reproducing the entire acquisition process has been implemented, then experimentally validated on ground and static cases. It finally allowed to demonstrate the potential and contribution of Geiger-mode focal plane arrays for long distance and high spatial resolution airborne 3D mapping.