Measuring the Mueller matrix with optical coherence tomography (OCT) makes it possible to acquire the complete polarization properties of scattering media with three-dimensional spatial resolution. We first proved that the measured degree-of-polarization (DOP) of the backscattered light by OCT remains unity-a conclusion that validated the use of Jones calculus in OCT. A multi-channel Mueller-matrix OCT system was then built to measure the Jones-matrix, which can be transformed into a Mueller matrix, images of scattering biological tissues accurately with single depth scan. We showed that when diattenuation is negligible, the round-trip Jones matrix represents a linear retarder, which is the foundation of conventional PS-OCT, and can be calculated with a single incident polarization state although the one-way Jones matrix generally represents an elliptical retarder; otherwise, two incident polarization states are needed. We discovered the transpose symmetry in the roundtrip Jones matrix, which is critical for eliminating the arbitrary phase difference between the two measured Jones vectors corresponding to the two incident polarization states to yield the correct Jones matrix. We investigated the various contrast mechanisms provided by Mueller-matrix OCT. Our OCT system for the first time offers simultaneously comprehensive polarization contrast mechanisms including the amplitude of birefringence, the orientation of birefringence, and the diattenuation in addition to the polarization-independent intensity contrast, all of which can be extracted from the measured Jones or the equivalent Mueller matrix. The experimental results obtained from rat skin samples, show that Mueller OCT provides complementary structural and functional information on biological samples and reveal that polarization contrast is more sensitive to thermal degeneration of biological tissues than amplitude-based contrast. Finally, an optical-fiber-based multi-channel Mueller-matrix OCT was built and a new rigorous algorithm was developed to retrieve the calibrated polarization properties of a sample. For the first time to our knowledge, fiber-based polarization-sensitive OCT was dynamically calibrated to eliminate the polarization distortion caused by the single-mode optical fiber in the sample arm, thereby overcoming a key technical impediment to the application of optical fibers in this technology.

No description available.

Clinical guidelines dictate that frequent blood glucose monitoring in diabetic patients is critical towards proper management of the disease. Although, several different types of glucose monitors are now commercially available, most of these devices are invasive, thereby adversely affecting patient compliance. To this end, optical polarimetric glucose sensing through the eye has been proposed as a potential noninvasive means to aid in the control of diabetes. Arguably, the most critical and limiting factor towards successful application of such a technique is the time varying corneal birefringence due to eye motion artifact. In the first part of this research, we describe a birefringent ocular model along with a geometric ray tracing scheme to serve as a tool towards better understanding of the cornea’s birefringence properties. The simulations show that index-unmatched coupling of light is spatially limited to a smaller range when compared to index-matched situation. Polarimetric measurements on rabbits’ eyes indicate relative agreement between the modeled and experimental values of corneal birefringence. In addition, the observed rotation in the plane of polarized light for multiple wavelengths demonstrates the potential for using a dual-wavelength polarimetric approach to overcome the noise due to time-varying corneal birefringence. These results will ultimately aid in the development of an appropriate eye coupling mechanism for in vivo polarimetric glucose measurements. The latter part of the dissertation focuses on design and development of a dual wavelength optical polarimeter. The described system utilizes real-time closed-loop feedback based on proportional-integral-derivative (PID) control, which effectively reduced the time taken by the system to stabilize while minimizing the effect of motion artifact, which appears as common noise source for both the wavelengths. Glucose measurements performed in both in vitro and ex vivo conditions demonstrate the sensitivity of the current system. Finally, in vivo results in rabbits indicate that dual-wavelength polarimetry has the potential to noninvasively probe glucose through the anterior chamber of the eye.

Levels of carbon dioxide in the atmosphere have been steadily increasing since the beginning of the Industrial Revolution in the 1800s. The earth's climate is sensitive to alterations in these levels of carbon dioxide and other greenhouse gases (GHG), with significant changes in climate predicted long term. The adoption of the Kyoto Protocol in 1997 heralded a new age in terms of greenhouse gas accounting and emissions responsibility, for all nations. In Australia, carbon emissions from the Land Use and Land Use Change and Forestry sector are responsible for a large proportion of the national total emissions. Radar remote sensing has demonstrated considerable potential in the estimation and mapping of vegetation biomass and subsequently carbon. The aim of this research is to investigate the potential of airborne polarimetric radar for quantifying and mapping the biomass and structural diversity of woodlands in semi-arid Australia. Initial investigation focussed on the physical structure of the woodland, which revealed that despite a diversity of woodland associations, the species diversity was relatively low. Both excurrent and decurrent growth forms were present, which subsequently resulted in varying allocation of biomass to the components (i.e., branches, trunks). In view of this, both empirical and modelling methodologies were explored. Empirical relationships were established between SAR backscatter and the total above ground biomass. Considerable scatter was present in these relationships, which was attributed to the large range of species and their associated structures. Comparison of actual and model simulations for C-, L- and P-band wavelengths, reveal that no significant difference existed for these wavelengths, except at CHH, and the cross-polarised data at L- and P-band. The study confirmed that microwaves at C-band interacted largely with the leaves and small branches, with scattering at VV polarization dominating. Compared to the lower frequencies, the return from the ground surface (as expected) was significant. The differences in scattering mechanisms (i.e., branch-ground versus trunk-ground) between excurrent and decurrent structures were due largely to the larger angular branches associated with Eucalyptus and Angophora species, which were absent from Callitris glaucophylla.

Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2007. / Phillip Gibbs, Committee Member ; Rick Trebino, Committee Member ; Christoph Fahrni, Committee Member ; Donald Doyle, Committee Member ; Andreas Bommarius, Committee Chair.

Cette thèse est composée de deux axes de recherche. Le premièr, plutôt méthodologique, consiste de nos efforts pour répondre à des questions ouvertes dans la communauté de RSO polarimétrique, tandis que le second est plutôt lié à l'application spécifique - le télédétection du manteau neigeux.Suite à la modélisation statistique alternative des images RSO multivariées et haute- ment texturées, par le modèle SIRV, nous proposons d'abord une évaluation appropriée des paramètres de circularité et sphéricité, autrement à priori présumés. La dernière est accouplée avec le test de symétrie sphérique, ce qui forme une méthode pour l'évaluation de pertinence de modèle statistique SIRV dans le contexte de données RSO polarimétriques. Compte tenu du taux de réjection, cela parait justifié de mettre en question les hypothèses de circularité et sphéricité, alors que la pertinence de modèle SIRV doit être soupçonnée dans les régions caractérisées par la diffusion déterministe forte. En suite, comme le point culminant de cette thèse, nous proposons une décomposition incohérente de cible polarimétrique, basée sur l'ACI et fondée sur l'hypothèse de non-Gaussianité du clutter RSO polarimétrique. En exploitant l'information contenue dans les ordres statistiques supérieurs, cette décomposition donne à la sortie un ensemble de vecteurs de cible, qui sont mutuellement indépendants (plutôt que seule- ment décorrélés) et non-orthogonaux. Contrairement à la première composant dominante, qui parait presque identique à l'une estimée par le homologue conventionnel, la deuxième com- posante dominante diffère significativement, ce qui représente un potentiel additionnel pour l'interprétation des données RSO polarimétriques.Dans le contexte appliqué, la première contribution présentée serait une approche stochas- tique pour la cartographie du manteau neigeux au moyen de données RSO multi-temporelles. Les apports les plus notables de la méthode présentée à l'ensemble de techniques de la détec- tion de changements dans la cartographie du manteau neigeux, sont l'hypothèse modifiée du ratio de rétrodiffusion entre la neige sèche et la neige humide, aussi que la corrélation spatiale entre les régions de la neige humide, introduite en impliquant la statistique locale de speckle dans le processus de décision. Finalement, nous présentons la méthode non-autonome pour l'estimation spatiale de l'équivalent en eau de la neige (EEN), basée sur des données optiques. En utilisant avec succès des données de télédétection dans la calibration du modèle EEN externe, on essaie de démontrer l'utilité et la nécessite du télédétection dans la surveillance du manteau neigeux. / This thesis comprises two research axes. The first, being rather methodological, consists of our efforts to answer some of the open questions in the POLSAR community, while the latter is sooner related to the specific application - the remote sensing of snow.Following the alternative statistical modelling of highly textured multivariate SAR datasets by means of SIRV model, we propose the appropriate assessment of, otherwise assumed, cir- cularity and sphericity parameters. The last is coupled with the spherical symmetry test, forming a method for the evaluation of SIRV statistical model suitability in the context of POLSAR data. Given the rejection rate, challenging circularity and sphericity appears to be justified, while SIRV model pertinence must be doubted in the regions characterized by strong deterministic scattering. Further on, as the highlight of this thesis, we propose a po- larimetric incoherent target decomposition, based on ICA and founded on the hypothesis of non-Gaussianity of POLSAR clutter. By exploiting the information contained in the higher statistical orders, this decomposition provides at the output a set of mutually independent (rather than only decorrelated), non-orthogonal target vectors. Unlike the first dominant com- ponent, which is nearly identical to the one estimated by the conventional ICTD counterpart, the second dominant component differs significantly, which, as we anticipate, represents an additional potential for the POLSAR datasets interpretation.In the applied context, the first presented contribution would be a stochastic approach in snow mapping by means of multitemporal SAR datasets. The most notable supplements of the presented method to the ensemble of change detection techniques in snow mapping are the plausibly modified assumption of the wet/dry snow backscattering ratio and implicitly introduced spatial correlation between wet snow areas, achieved by directly implicating local speckle statistics in the decision process. Finally, we present the non-autonomous method for SWE spatial estimation, based on optical datasets. By successfully involving the remote sensing datasets in the calibration of the external SWE model, we seek to demonstrate the utility and the necessity of the former in the snow pack monitoring. / Ova teza podrazumijeva dva pravca istraživanja. Prvi, metodološki, predstavlja naše naporeda odgovorimo na neka od otvorenih pitanja u POLSAR zajednici, dok je drugi vezan zaspecifičnu aplikaciju - teledetekciju sniježnog pokrivača.Uzevši u obzir alternativno statističko modelovanje multivarijantnih SAR slika visoke rezolucijekoristeći SIRV model, mi predlažemo odgovarajuću estimaciju, uostalom pretpostavljenihparametara cirkularnosti i sfernosti. Integrišući posljednju u test sferne simetrije, formiranje metod za evaluaciju prikladnosti statističkog modela SIRV u kontekstu POLSAR slikavisoke rezolucije. Posmatrajući stopu odbacivanja, sumnja u opravdanost pretpostavke cirkularnostii sfernosti se čini opravdanom, dok pogodnost SIRV modela mora biti preispitana uregionima koje karakteriše jako determinističko elektromagnetno rasijanje. U nastavku, kaoprimarni doprinos ove teze, predlažemo polarimetrijsku nekoherentnu dekompoziciju mete,koja je bazirana na ICA metodu i zasnovana na hipotezi o otklonu od Gausove prirode POLSARclutter -a. Eksploatišući informaciju sadržanu u višim statističkim redovima, predloženadekompozicija daje na izlazu set međusobno nezavisnih (prije nego samo nekorelisanih), neortogonalnihvektora mete. Za razliku od prve dominante komponente, koja je skoro identičnakomponenti estimiranoj koristeći konvencionalnu ICTD metodu, druga dominanta komponentase značajno razlikuje, što predstavlja dodatan potencijal u interpretaciji POLSAR slika.Prvi prezentovani doprinos u primijenjenom kontekstu bio bi stohastički metod za mapiranjesniježnog pokrivača baziran na multitemporalnom setu SAR slika. Najznačajniji priloziprezentovane metode grupi tehnika "detekcije promjene" u mapiranju sniježnog pokrivača suopravdano promijenjena pretpostavka o količniku povratnog rasijanja djelimično otopljenog isuvog snijega, kao i implicitno uvedeno prostorna korelacija između regiona djelimično otopljenogsnijega, postignuta direktnim uvođenjem lokalne statistike speckle šuma u proces odlučivanja.Konačno, predlažemo neautonomni metod za prostornu estimaciju SWE parametra,zasnovan na optičkim slikama. Uspješno inflitrirajući teledetekciju u kalibraciju eksternogSWE modela, imamo za cilj demonstrirati njenu korisnost i neophodnost u monitoringu sniježnogpokrivača.

A linha de instabilidade (LI) pré-frontal que atingiu a Região Metropolitana de São Paulo em 26 de abril de 2007 foi monitorada e analisada por meio de medições de superfície, altitude, radar e satélite. As análises indicam que havia ambiente sinótico favorável para a formação e manutenção da LI. Na região de formação da LI havia ar relativamente quente e úmido em baixos níveis e ar relativamente frio e seco em níveis médios com convergência de massa em baixos níveis e divergência em altos níveis, além de gradiente de temperatura produzido pela aproximação do sistema frontal. A LI foi monitorada pelo radar meteorológico MXPOL e permitiu a avaliação dinâmica e microfísica do sistema. Esta última realizada por meio da classificação de hidrometeororos com as variáveis polarimétricas medidas com o MXPOL. Preliminarmente, os dados de refletividade diferencial (ZDR) e refletividade efetiva (Z) foram consistidos por meio do método da autoconsistência (Vivekanadan et al., 2003), entre essas duas variáveis e a fase diferencial específica (KDP). Removido os viéses de ZDR (-0,36 dB) e da refletividade efetiva (-0,46 dBZ), a classificação de hidrometeoros, em dezessete categorias (gotículas a granizo, insetos, ecos de terreno e de segunda viagem), foi realizada pelo método de lógica fuzzy (Vivekanadan et al., 2003). A classificação de hidrometeoros foi realizada em planos de elevação constante (PPI). Os tipos e estratificação de hidrometeoros são compatíveis com estudos anteriores. Por exemplo, a banda brilhante foi classificada com uma região de mistura de gelo e gotas líquidas com predominância de gotas abaixo e cristais de gelo acima desta. A dinâmica interna da LI foi avaliada por meio da velocidade radial e evidenciou um jato de baixos níveis, convergência ciclônica na dianteira do sistema, e divergência em altos níveis, entre outras características. O rápido deslocamento da LI resultou em precipitação de 7 mm e rajadas de vento de 18 m s-1. Assim, o impacto mais significativo desse sistema na RMSP foi produzido pelo vento. / A prefrontal squal line (LI) that reached tne metropolitan area of São Paulo on April 26 2007 was monitored and analyzed by means of of surface and upper air measurements, weather radar and satellite data. Analyses indicate a favorable synoptic environment to form and sustain the LI. In its genesis region there was relatively warm and moiture air near the surface and relatively cold and dry air aloft with mass convergence below and divergence aloft, as well as temperature gradient along its path induced by the associated cold front. This LI was measured with the MXPOL weather radar and allowed a mesoscale dynamic analysis as well as a microphysics of this weather system. The later was performed by means of a hydrometeor classification with the polarimetric data sets of MXPOL. Initially, the differential reflectivity (ZDR) and the efective reflectivity (Z) were corrected by the selfconsistency method (Vivekanandan et al., 2003) together with the specific diferrential phase (KDP). Ounce removed the ZDR (-0,36 dB) and Z (-0,46 dBZ) biases, the hydrometeoro classification (small drops to hail, insects, ground clutter and second trip echoes) was carrie out by the fuzzy logic method (Vivekanadan et al., 2003). The hydrometeor classification was made at constant elevation angles (PPI) across the LI. The hydrometeoro types are compatible to similar studies. For instance, the bright band was classified as a region mixed phase with drops below and ice crystals aboce it. The LI internal dynamics was analyzed with the help of the radial velocity and indicated a low level jet, cyclonic convergence at the leading edge and divergence aloft at the convective band, among other features. This fast moving LI produced 7 mm of rainfall and wind gust of 18 m s-1. Its most significant impact over RMSP was caused by the wind intensity.

Depuis 2007, une nouvelle génération de radar satellitaires imageurs plus performants permet de renouveler les approches cartographiques et ce, en particulier, sur les zones tropicales où l'acquisition des images optiques est difficile du fait de la présence quasi permanente de nuages. Ces radars opèrent en différentes longueurs d'onde (bande L, C, X), différentes polarisations et avec des résolutions spatiales variables (Très Haute Résolution à Moyenne Résolution Spatiale).Nos sites d'étude se situent en Guyane française et en Côte d'Ivoire en contexte climatique tropical humide. Sur la Guyane française de nombreuses études antérieures garantissent une connaissance géographique riche et détaillée, nos recherches porteront sur la méthodologie de traitement et d'analyse d'images radar multi-paramètres (longueur d'onde, polarisation, résolution) et de leur exploitation conjointe avec des images optiques très haute résolution spatiale en vue d'effectuer le suivi temporel des milieux rencontrés localement (forêt dense sur socle, plaine littorale, forêt de mangrove, zones humides…).Une fois ce bilan détaillé et argumenté, effectué sur la Guyane, les recherches se porteront sur des zones test en Côte d'Ivoire qui contrairement à la Guyane, ne disposent pas de connaissances géographiques de qualité mais où le climat tropical rend, comme en Guyane, l'usage des images radar incontournable. Le premier chapitre de ce travail décrit les milieux rencontrés sur nos zones d'étude ainsi que les données disponibles sur chacun d'entre eux. Le second chapitre porte sur la méthodologie de traitement et d'analyse d'images radar multi paramètres et de leur exploitation conjointe avec des images optiques très haute résolution spatiale. Deux approches d'évaluation des images y sont discutées. Une première approche, basée sur la photo-interprétation, s'appuie sur les documents cartographiques existants, les levés de terrain pour évaluer visuellement les images. Une seconde approche aborde l'évaluation grâce aux méthodes de classification supervisée pour lesquelles deux techniques ont été utilisées : la classification SVM et la classification orientée objet. Le troisième chapitre est consacré aux applications thématiques des images sur les zones test situées en Guyane française et en Côte d'Ivoire. Y sont abordées la cartographie de l'occupation du sol, le suivi des zones humides littorales et la dynamique côtière et toutes ces applications pouvant conduire à la mise à jour des documents cartographiques existants / Since 2007, the launch of fully polarimetric SAR sensors has significantly improved the potential of satellite SAR data for the vegetation cartography. These sensors allow to make a complete description of the polarization state of the backscattered wave whatever the polarization configuration of the incident wave. Polarimetric data are sensitive to the geometrical structure of the vegetation cover, bringing a significant contribution for vegetation cartography. Different fully polarimetric sensors have been launched since 2007: ComoSkyMed, RADARSAT-2, and PALSAR sensors allowing observations in X, C, and L bands, with spatial resolution ranging from 1 to 30 m. Pilote sites are French Guiana (French) and Ivory coast (West African country) in humid tropical zone. In French Guiana, many studies in the past years guarantee a rich and detailed geographical knowledge, our works concern the multi parameters radar image analysis method (wavelength, polarization, resolution) and their exploitation together with external mapping data in the aim of implementing the temporal survey of the locally encountered environment (dense forest, coastal plains, mangrove forests, wetlands,…). In fact, with 80% of forest cover, French Guyana needs an update of existing cartographic documents to quantify the evolution of his dynamic vegetation. Once this assessment made on the Guyana was detailed and argued, the researches will concern to test zones in Ivory Coast which contrary to the Guyana, do not have geographical quality knowledge but where the tropical climate makes the use of radar images necessary as in Guyana. The first chapter of this work describes the fields met on our areas of study as well as the data available on each of them. Second chapter focuses on the methodology of processing and analysis of multicriterias radar images and their joint exploitation with optical images of very high-spatial resolution. Then, two approaches of evaluation of the images are discussed. A first approach, based on photo-interpretation, relies on the existing cartographic documents and on the land surveys to estimate visually the images. A second approach stating the evaluation thanks to the supervised classification for which two techniques were used: the SVM classification and the object-oriented classification. The third chapter is dedicated to the thematic applications of images on the test areas situated in French Guyana and in Ivory Coast. The mapping of the land use, the follow-up (survey) of the littoral wetlands and the coastal dynamics, all these applications can lead to the update of the existing cartographic documents

The capability to map anthropogenic aerosol quantities and properties over land can provide significant insights for climate and environmental studies on global and regional scales. One of the primary challenges in aerosol information monitoring is separating two signals measured by downward-viewing airborne or spaceborne instruments: the light scattered from the aerosols and light reflected from the Earth's surface. In order to study the aerosols independently, the surface signal needs to be subtracted out from the measurements. Some observational modalities, such as multispectral and multiangle, do not provide enough information to uniquely define the Earth's directional reflectance properties for this task due to the high magnitude and inhomogeneity of albedo for land surface types. Polarization, however, can provide additional information to define surface reflection. To improve upon current measurement capabilities of aerosols over urban areas, Jet Propulsion Laboratory developed the Multiangle SpectroPolarimetric Imager (MSPI) that can accurately measure the Degree of Linear Polarization to 0.5%. In particular, data acquired by the ground-based prototype, GroundMSPI, is used for directional reflectance studies of outdoor surfaces in this dissertation. This work expands upon an existing model, the microfacet model, to characterize the polarized bidirectional reflectance distribution function (pBRDF) of surfaces and validate an assumption, the Spectral Invariance Hypothesis, on the surface pBRDF that is used in aerosol retrieval algorithms. The microfacet model is commonly used to represent the pBRDF of Earth's surface types, such as ocean and land. It represents a roughened surface comprised of randomly oriented facets that specularly reflect incoming light into the upward hemisphere. The analytic form of the pBRDF for this model assumes only a single reflection of light from the microfaceted surface. If the incoming illumination is unpolarized, as it is with natural light from the Sun, the reflected light is linearly polarized perpendicular to the plane that contains the illumination and view directions, the scattering plane. However, previous work has shown that manmade objects, such as asphalt and brick, show a polarization signature that differs from the single reflection microfacet model. Using the polarization ray-tracing (PRT) program POLARIS-M, a numerical calculation for the pBRDF is made for a roughened surface to account for multiple reflections that light can experience between microfacets. Results from this numerical PRT method shows rays that experience two or more reflections with the microfacet surface can be polarized at an orientation that differs from the analytical single reflection microfacet model. This PRT method is compared against GroundMSPI data of manmade surfaces. An assumption made regarding the pBRDF for this microfacet model is verified with GroundMSPI data of urban areas. This is known as the Spectral Invariance Hypothesis and asserts that the magnitude and shape of the polarized bidirectional reflectance factor (pBRF) is the same for all wavelengths. This simplifies the microfacet model by assuming some surface parameters such as the index of refraction are spectrally neutral. GroundMSPI acquires the pBRF for five prominent region types, asphalt, brick, cement, dirt, and grass, for day-long measurements on clear sky conditions. Over the course of each day, changing solar position in the sky provides a large range of scattering angles for this study. The pBRF is measured for the three polarimetric wavelengths of GroundMSPI, 470, 660, and 865nm, and the best fit slope of the spectral correlation is reported. This investigation shows agreement to the Spectral Invariance Hypothesis within 10% for all region types excluding grass. Grass measurements show a large mean deviation of 31.1%. This motivated an angle of linear polarization (AoLP) analysis of cotton crops to isolate single reflection cases, or specular reflections, from multiple scattering cases of light in vegetation. Results from this AoLP method show that specular reflections off the top surface of leaves follow the Spectral Invariance Hypothesis.

Polarization observations of the unique eclipsing binary, Epsilon Aurigae, are being carried out using a new dual beam imaging polarimeter on the 0.36m telescope of the Harry D. Powell Observatory. This bright binary system has a 27.1 year period with an eclipse duration of nearly two years. The primary is known to be a pulsating F0 supergiant with the secondary a large and essentially opaque disk. We report here on the characteristics of the polarimeter and on the status of V-band observations that are being obtained to better understand the system's geometry and the nature of its two components. In particular, the characteristics of the secondary disk remain a puzzle. Results are compared to polarization observations from the 1982-1984 eclipse.