No description available.

No description available.

Quantitative phase Imaging(QPI) has emerged as a valuable tool for imaging specimens with weak scattering and absorbing abilities such as cells and tissues. It is complementary to fluorescence microscopy, as such, it can be applied to unlabelled specimens without the need for fluorescent tagging. By quantitatively mapping the phase changes induced in the incident light field by the optical path length delays of the specimen, QPI provides objective measurement of the cellular dynamics and enables imaging the specimen with high contrast. Transport of Intensity Equation(TIE) is a powerful computational tool for QPI because of its experimental and computational simplicity. Using TIE, the phase can be quantitatively retrieved from defocused intensity images. However, the resolution of the phase image computed using TIE is limited by the diffraction limit of the imaging system used to capture the intensity images. In this thesis, we have developed a super resolution phase imaging technique by applying the principles of Structured Illumination Microscopy(SIM) to Transport of Intensity phase retrieval. The modulation from the illumination shifts the high frequency components of the phase object into the system pass-band. This enables phase imaging with resolutions exceeding the diffraction limit. The proposed method is experimentally validated using a custom-made upright microscope. Because of its experimental and computational simplicity, the method in this thesis should find application in biomedical laboratories where super resolution phase imaging is required / Master of Science / Transport of Intensity Equation is a quantitative phase microscopy technique that enables imaging thin transparent specimens with high phase contrast using a through focus intensity stack. It provides speckle free imaging, compatibility with bright field microscopes and valid under partial coherence. However, the Optical Transfer Function(OTF) of the imaging system or the microscope acts a low pass filter, effectively limiting the maximum spatial frequency that can pass through the system. This reduces the spatial resolution of the computed phase image to the spatial diffraction limit. There has been a continuous drive to develop Super resolution techniques that will provide sub-diffraction resolutions because it will provide better insight into the cellular structure, morphology and composition. Structured Illumination Microscopy(SIM) is one such established technique. Existing work in super resolution phase imaging using SIM is exclusively limited to holography and interferometry based techniques. However, such methods require two-beam interference, illumination sources with high coherence, high experimental stability and phase unwrapping in the postprocessing step to retrieve the true object phase. In this work, we demonstrate a single beam propagation based super resolution phase imaging technique by applying structured illumination to Transport of Intensity Equation. It is valid under partial coherence, and does not require interference, simplifying the experimental and computational requirement. We have designed an upright microscope to demonstrate high resolution phase imaging of human cheek cells.

No / We present a numerical analysis of rendered pairs of rooms, in which the spectral power distribution of the illuminant in one room matched the surface reflectance function in the other room, and vice versa. We ask whether distinction between the rooms is possible and on what cues this discrimination is based. Using accurately rendered three-dimensional (3D) scenes, we found that room pairs can be distinguished based on indirect illumination, as suggested by A. L. Gilchrist and A. Jacobsen (1984). In a simulated color constancy scenario, we show that indirect illumination plays a pivotal role as areas of indirect illumination undergo a smaller appearance change than areas of direct illumination. Our study confirms that indirect illumination can play a critical role in surface color recovery and shows how computer rendering programs, which model the light¿object interaction according to the laws of physics, are valuable tools that can be used to analyze and explore what image information is available to the visual system from 3D scenes.

No / Image gradients - smooth changes in color and luminance - may be caused by intrinsic surface reflectance properties or extrinsic illumination phenomena, including shading, shadowing, and inter-reflections. In turn, image gradients may provide the visual system with information concerning the origin of these factors, such as the orientation of surfaces with respect to the light source. Color gradients induced by mutual illumination (MI) may play a similar role to that of luminance gradients in shape-from-shading algorithms; it has been shown that 3D shape perception modulates the influence of MI on surface color perception (M. G. Bloj, D. Kersten, & A. C. Hurlbert, 1999). In this study, we assess human sensitivity to changes in color and luminance gradients that arise from changes in the light source position, within a complex scene. In Experiment 1, we tested whether observers were able to discriminate between gradients due to different light source positions. We found that observers reliably detected a change in the gradient information when the light source position differed by only 4 deg from the reference scene. This sensitivity was mainly based on the luminance information in the gradient (Experiments 2 and 3). Some observers make use of the spatial distribution of chromaticity and luminance values within gradients when discriminating between them (Experiment 4). The high sensitivity to gradient differences supports the notion that gradients contain information that may assist in the recovery of 3D shape and scene configuration properties.

A significant portion of severe crashes and severe crashes involving vulnerable road users, 29 percent and 39 percent respectively, occur at night in Utah, despite roughly only 25 percent of traffic occurring at night. Nighttime crash causes are less understood than daytime crashes as there are fewer nighttime crashes, but it is generally assumed that increasing street lighting can help mitigate these crashes. To test this assumption, the Utah Department of Transportation was interested in developing Crash Modification Factors (CMFs) specific to the state of Utah which correlate the quantity and quality of light to crash outcomes, to observe how specific light quantities and qualities might reduce nighttime crashes. Average illuminance and light uniformity metrics were measured for several arterial roads in Utah and statistical models were used to build models for estimating CMFs. CMFs indicated that average illuminance was not correlated to a significant change in crashes except when increasing illuminance above 3.2 lux. This indicates that some light is better than none, but the benefit of increasing existing light levels may not be significant. However, CMFs for the uniformity of light indicated that less uniformity correlated to fewer crashes at lower average illuminance, and more crashes at higher illuminance. This may show that it is more important to light specific locations than to light entire road segments evenly, unless light levels are already high. Despite the possible benefit of increasing uniformity on roadways with high light levels, most uniformity CMFs suggested that future research should be focused on locations like crosswalks where lighting is most important.

No description available.

L'imagerie terrestre urbaine se développe grâce à la diffusion grand public de visualisateurs immersifs au niveau de la rue. L'objectif de cette thèse est de proposer une méthode physique d'estimation de la réflectance des matériaux d'une scène urbaine à partir des images d'un système mobile d'acquisition, comme par exemple le véhicule d'acquisition Stereopolis, développé au laboratoire MATIS de l'Institut National de l'Information Géographique et Forestière (IGN).Pour cela, on considère que l'on dispose d'un modèle 3D de la scène, segmenté en zones de réflectance homogène (décrite par un modèle paramétrique), d'un jeu d'images géoréférencées corrigées radiométriquement. On propose une méthode d'estimation des réflectances par minimisation de l'écart entre les images réelles acquises par le capteur et des images simulées depuis le même point de vue. Après une modélisation phénoménologique des différentes composantes de la luminance arrivant au niveau d'un capteur imageur dans le domaine visible, une méthode utilisant le lancer de rayons sert à simuler cette luminance. Cela constitue ici le problème direct. Cet outil de simulation nécessite la connaissance de l'illumination de la scène, i.e. la répartition et la puissance des sources de lumière. Pour une acquisition avec Stereopolis, on ne réalise généralement pas de mesures atmosphériques et/ou radiométriques permettant de déterminer l'illumination avec des codes de transfert radiatif ; c'est pourquoi on propose une méthode d'estimation de la luminance du ciel à partir des images, en utilisant les pixels qui voient le ciel. L'éclairement solaire direct, non accessible directement dans les images, est estimé par une méthode ombre-soleil grâce à une plaque de référence placée sur le toit du véhicule. L'algorithme d'inversion du système se fait par minimisation d'une fonction coût constituée par la différence pixel à pixel entre les images simulées avec certains paramètres de réflectance et les images réelles. Cela nécessite de nombreuses simulations par lancer de rayons, car l'algorithme est itératif en raison des réflexions multiples entre les objets qui doivent être calculées avec des paramètres de réflectances initiaux. Afin d'éviter ces très coûteux lancers de rayons, on propose un algorithme de lancer de rayons formel qui stocke la luminance simulée comme des fonctions des paramètres de réflectances au lieu d'une valeur numérique. Cela permet de mettre à jour les images de luminance simulées par simple évaluation de ces fonctions avec le jeu de paramètres courant. La minimisation elle-même est effectuée par la méthode du gradient conjugué. Des résultats sur des scènes synthétiques permettent de faire une première validation de la méthode. Cependant, l'application sur un jeu d'images issues de Stereopolis pose plusieurs difficultés, notamment liées l'étalonnage radiométrique et à la segmentation du modèle 3D utilisé en entrée / Urban terrestrial imagery is widely used through online viewers of street-level images. The MATIS of the French National Geographical and Forester Data Institute (IGN) has developed its own mobile-mapping vehicle, Stereopolis, dedicated to research purposes. In this thesis, we develop a physically-based method to retrieve the reflectance of urban materials from a set of images shot by a mobile-mapping vehicle. This method uses a 3D model of the scene (segmented in areas of homogeneous reflectance, modeled by a parametric formula) and a set of georeferenced and radiometrically corrected images. We present a method for the estimation of the reflectances of the materials by minimizing the difference between real acquired images and simulated images from the same point of view. A modelisation of the physical phenomena leading to the formation of optical images is presented. A code using ray-tracing algortihm is used to compute the radiance at the sensor level. This is the direct problem for our estimation of reflectances. The illumination of the scene must be an input of this simulation tool; now, in a typical urban mobile-mapping acquisition neither atmospheric nor radiometric measurements are performed, that could be used to determine the illumination with a radiative transfer code. We propose an estimation of the illumination using directly the sky pixels in the acquired images. The direct solar irradiance cannot be estimated from the images because of overexposure, but we can use a shadows casted on a dedicated reference plate placed on top of the vehicle. The reflectances estimation is performed by minimizing a cost function; this cost function is the pixel-wise difference between simulated images (with current reflectances parameters) and acquired images. This leads to numerous ray-tracing simulations as the algorithm is iterative due to interreflections between the objects of the scene, that are computed using initial parameters. In order to prevent these costly ray-tracing simulations, we propose a symbolic ray-tracing algorithm that computes the radiance as a symbolic function of the reflectances parameters instead of a numerical value. Then, each iteration of the minimization algorithm is only an evaluation of a symbolic function. Results are shown on synthetic scenes to perform a first validation the estimation method. Using this method on real Stereopolis images remains difficult, mainly due to the radiometric calibration of cameras and the segmentation on the 3D model

Este trabalho faz um levantamento dos Sistemas de Iluminação Automáticos (SIA) utilizados atualmente, das tecnologias empregadas e das linhas de pesquisas que vêm surgindo neste tema. É analisada também a relação dos sistemas de controle distribuído (SCD) com os SIA e com a automação predial. Um estudo de caso de um SIA que utiliza um SCD como plataforma tecnológica também é analisado. Ao final da dissertação, propõe-se uma tese, fruto das análises feitas durante este trabalho, que visa aumentar a modularidade, a flexibilidade e a interoperabilidade dos sistemas de automação predial baseados em SCD. Durante a dissertação são descritas: as características da luz; a relação entre a luz e o ser humano; os principais componentes de um SIA; as características básicas de um SCD; e a tecnologia Lonworks. / This work describes the Illumination Automatic Systems (IAS) used nowadays, the used technologies and the research lines that arise in this knowledge area. It\'s also analyzed the relation between Distributed Control Systems (DCS), IAS and building automation. A case study is done with a system that uses IAS and DCS. In the end of this work, it\'s suggested a thesis, result of analyses done during this work, with the objective of increasing the modularity, flexibility and interoperability of buildings automation systems based on DCS technologies. During this dissertation is described: the light characteristics; the relation between light and the human being; the main components of IAS; the characteristics of a DCS; and the Lonworks technology.

Este trabalho faz um levantamento dos Sistemas de Iluminação Automáticos (SIA) utilizados atualmente, das tecnologias empregadas e das linhas de pesquisas que vêm surgindo neste tema. É analisada também a relação dos sistemas de controle distribuído (SCD) com os SIA e com a automação predial. Um estudo de caso de um SIA que utiliza um SCD como plataforma tecnológica também é analisado. Ao final da dissertação, propõe-se uma tese, fruto das análises feitas durante este trabalho, que visa aumentar a modularidade, a flexibilidade e a interoperabilidade dos sistemas de automação predial baseados em SCD. Durante a dissertação são descritas: as características da luz; a relação entre a luz e o ser humano; os principais componentes de um SIA; as características básicas de um SCD; e a tecnologia Lonworks. / This work describes the Illumination Automatic Systems (IAS) used nowadays, the used technologies and the research lines that arise in this knowledge area. It\'s also analyzed the relation between Distributed Control Systems (DCS), IAS and building automation. A case study is done with a system that uses IAS and DCS. In the end of this work, it\'s suggested a thesis, result of analyses done during this work, with the objective of increasing the modularity, flexibility and interoperability of buildings automation systems based on DCS technologies. During this dissertation is described: the light characteristics; the relation between light and the human being; the main components of IAS; the characteristics of a DCS; and the Lonworks technology.