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L'atmosphère et la surface terrestre interagissent en permanence par le biais des échanges d'énergie et de matière. Ces flux jouent un rôle important dans l'étude de l'hydrologie des surfaces ou de l'écologie terrestre, ou bien encore l'étude des phénomènes météorologiques et climatiques. En effet, ils représentent les conditions aux limites des différents compartiments du système Terre et la quantification de ces échanges à différentes échelles spatiales est indispensable pour les modèles de prévision. Les mesures de flux d'énergie sont très répandues pour des mesures très localisées, in situ et au sol. Cependant, peu d'instruments de mesures permettent d'obtenir des flux intégrés sur des distances de l'ordre de la centaine de mètres à quelques kilomètres, c'est-à-dire des distances correspondant à la représentativité des pixels des images satellitaires. On compte parmi eux les scintillomètres, instrument de mesure optique, permettant de calculer les flux intégrés de chaleur sensible à partir des mesures de paramètres caractérisant l'intensité turbulente de l'atmosphère tels que le paramètre de structure de l'indice de réfraction de l'air Cn². La présence de vapeur d'eau dans l'atmosphère peut cependant perturber le signal de ces instruments. L'objectif de ce travail est le développement et la mise en oeuvre d'un scintillomètre optique permettant de mettre en évidence la contribution de l'absorption par la vapeur d'eau sur les scintillations. Les études menées à partir du développement instrumental ne s'orienteront qu'autour de la bande d'absorption à 940nm, longueur d'onde d'émission de certains scintillomètres LAS (Large Aperture Scintillometer). Au début de ma thèse, un prototype de scintillomètre, type LAS, a été conçu de façon à maitriser complètement la technologie : partie optique électronique et le traitement du signal reçu. Celui-ci a ensuite été installé au-dessus d'un site de cultures dans les environs de Toulouse, au cours des années 2007 et 2008. Les résultats obtenus avec ce prototype ont permis d'optimiser le choix de la méthode de calcul H à partir du Cn², en fonction du rapport de Bowen (rapport du flux de chaleur sensible sur le flux de chaleur latente). Les variations de l'intensité lumineuse de l'onde, menant au Cn², sont principalement dues à des effets de réfraction et de dispersion, maissont aussi sensibles à l'absorption de la vapeur d'eau. Afin de quantifier l'influence de 'absorption sur le signal Cn², j'ai utilisé 2 approches : une première approche par filtrage numérique (‘Gabor Transform'), et une seconde, par méthode chromatique. Cette dernière a nécessité de modifier considérablement le système optique du prototype LAS. Les résultats obtenus expérimentalement montrent que la contribution de l'absorption à la mesure du Cn² est en moyenne assez faible, mais qu'elle peut prendre de forte valeur, principalement lors de faibles flux H. La quantification de l'absorption par méthode hromatique est pour l'instant limité au développement technique de l'instrument. / Atmosphere, soil and vegetation are in interactions by the bias of energetic or matter exchanges. This latters have an important impact on hydrology, ecology, meteorology. Actually, they represent the boundary conditions of the Earth-Atmosphere system. Then, the quantification of these exchanges or fluxes is necessary to understand large scales phenomena and to improve forecasting models. Numerous devices are able to quantify these fluxes at local scales, but few are available to measure them over kilometres, which mean at the resolution of remote sensing datas. Amongst them, we can notice the scintillometers that are able to calculate sensible heat fluxes over distances from hundred meters to few kilometres. Actually, these devices are sensitive to variations of the refractive index of air, mainly due to turbulent eddies, defined by the structure parameter of refractive index : Cn². However, this measurement can be altered by the presence of water vapour in the air. Thus, the aim of this work is to design and make a scintillometer which is able to quantify the water vapour contribution on the Cn² measurement. In this thesis, we will focus on this contribution in the 940nm band which is the wavelength of various scintillometers LAS (Large Aperture Scintillometers). At the beginning of my PhD thesis, un scintillometer prototype has been realised in order to master the technology : optics, electronics, signal processing…This latter has been set up over crops at a few kilometres from Toulouse, between 2007 and 2008. Thanks to the results of this scintillometer, we optimize the choice on the Cn² to H algorithm, according to the Bowen ratio ß (ratio of sensible to latent heat flux). Variations of the light beam, leading to the Cn², are mainly due to refraction and dispersion effect. However, absorption can be important. In order to quantify the contribution of absorption on the Cn², 2 methods are suggested : one based on signal processing aspect (Gabor filtering), and the second one on two wavelengths propagation. To realize this latter the optics and electronics of the device have been really modified. Results show that absorption contribution is small, but can be important for low H values. Finally, the quantification of absorption by two wavelengths approach is nowadays bounded to instrumental development.

<p>Face detection is a preprocessing step for face recognition algorithms. It is the localization of face/faces in an image or image sequence. Once the face(s) are localized, other computer vision algorithms such as face recognition, image compression, camera auto focusing etc are </p><p>applied. Because of the multiple usage areas, there are many research efforts in face processing. Face detection is a challenging computer vision problem because of lighting conditions, a high degree of variability in size, shape, background, color, etc. To build fully </p><p>automated systems, robust and efficient face detection algorithms are required. </p><p> </p><p>Numerous techniques have been developed to detect faces in a single image; in this project we have used a classification-based face detection method using Gabor filter features. We have designed five frequencies corresponding to eight orientations channels for extracting facial features from local images. The feature vector based on Gabor filter is used as the input of the face/non-face classifier, which is a Support Vector Machine (SVM) on a reduced feature </p><p>subspace extracted by using principal component analysis (PCA). </p><p> </p><p>Experimental results show promising performance especially on single face images where 78% accuracy is achieved with 0 false acceptances.</p>

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Face detection is a preprocessing step for face recognition algorithms. It is the localization of face/faces in an image or image sequence. Once the face(s) are localized, other computer vision algorithms such as face recognition, image compression, camera auto focusing etc are applied. Because of the multiple usage areas, there are many research efforts in face processing. Face detection is a challenging computer vision problem because of lighting conditions, a high degree of variability in size, shape, background, color, etc. To build fully automated systems, robust and efficient face detection algorithms are required. Numerous techniques have been developed to detect faces in a single image; in this project we have used a classification-based face detection method using Gabor filter features. We have designed five frequencies corresponding to eight orientations channels for extracting facial features from local images. The feature vector based on Gabor filter is used as the input of the face/non-face classifier, which is a Support Vector Machine (SVM) on a reduced feature subspace extracted by using principal component analysis (PCA). Experimental results show promising performance especially on single face images where 78% accuracy is achieved with 0 false acceptances.

Thesis (Ph.D.)--City University of Hong Kong, 2009. / "Submitted to the Department of Electronic Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy." Includes bibliographical references.

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains ix, 76 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 71-76).

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains xvii, 158 p.; also includes graphics (some col.). Includes bibliographical references (p. 150-158). Available online via OhioLINK's ETD Center

Since 1962, a photographic invention by Gabriel Lippmann (1845-1921), his Nobel Prize winning interference colour photograph of 1891, has been cited by physicists as the antecedent of the three-dimensional hologram. However, Dennis Gabor (1900-1979) in his original publications on the hologram of 1948 and 1949 did not cite Lippmann’s work. This thesis explores how the hologram that featured in Gabor’s original theory, as an imaging technique to improve the electron-microscope, was significantly different from the hologram for which Gabor was awarded the Nobel Prize for Physics in 1971. The citation of Lippmann’s work as the antecedent to the hologram confirmed that the hologram was to be seen as a three-dimensional photograph, and attempted to give the invention a progressive historical lineage that would conform to photography’s existing history. This popular narrative, as demonstrated in this text, could overlook the pursuit of the hologram for Cold War surveillance by researchers at the University of Michigan on behalf of the United States military. This technology was, from 1955, engaged with aerial radar image processing, a significant application that was classified and hidden from the public, and initially from Gabor himself. Two researchers at the University of Michigan, Emmett Leith (1927–) and Juris Upatnieks (1936–) attracted the attention of the popular press for their development of a three-dimensional laser hologram. This thesis reveals the fragmented nature of the new discipline at the peak of holography’s popularity. This analysis explores some of the historical traits between the two Nobel Prize winning inventions, the Lippmann photograph and the hologram, that were exploited to promote a new imaging medium to the public. In presenting these technologies as images the text also reviews devices and papers––some cited within the popular Lippmann-to Gabor historical narrative––by father and son Frederic (1856-1937) and Herbert Ives (1882-1953), that have competed to produce a three-dimensional full-colour image.

Ingeniero Civil Eléctrico / Un sistema de identificación facial consiste en un método que toma una imagen del rosto de un individuo desconocido y un banco de imágenes de personas conocidas, con el objetivo de identificar a este individuo y decidir si está presente o no en el banco de imágenes conocidas. Este Trabajo de Titulo se propone como objetivo estudiar el uso de escalas de alta resolución y combinaciones de las mismas en el problema de reconocimiento frontal de rostros. Para esto se utiliza la base de datos XM2VTS que contiene imágenes de rostros de individuos a una resolución de 720x576 píxeles. Se propone generar imágenes a escalas del 50 % y 25% de escala de resolución mediante el método de Pirámides de Gauss, obteniendo tres distintas resoluciones. Luego son procesadas mediante LBP y Filtros Gabor para realizar combinaciones de la información extraída por estos métodos en distintas escalas de resolución. Finalmente se utiliza este vector de información en un clasificador K-NN y se logra el reconocimiento de cada individuo. Se realizan pruebas de reconocimiento para realizar el ajuste de parámetros de los métodos de extracción de características en distintas escalas de resolución y pruebas para detectar las combinaciones de información de estas últimas que entreguen los mejores resultados. Por separado los métodos LBP y Filtros Gabor obtuvieron como máximos desempeños un 97,96% y un 94,12% de reconocimiento exitoso respectivamente. Sin embargo, al fusionar la información obtenida a través de estas técnicas de extracción de características, se obtiene un método de reconocimiento frontal de rostros que logra un 98,9% de reconocimiento exitoso, con un tiempo de procesamiento total de 21 minutos y 1,26 segundos por cada individuo como resultado final. Comparando con trabajos similares realizados con las mismas muestras se posiciona a la par de estos, demostrando ser un método competente y eficiente, además de entregar pautas para seguir el estudio del problema del reconocimiento facial.