Neste trabalho são apresentados os resultados obtidos no desenvolvimento de um sistema especificado para realizar testes na caracterização de dispositivos fotodetectores como fotodiodos de avalanche. O sistema de ensaios elaborado pretende auxiliar com na caracterização da fotodetecção em dispositivos de acoplamento de cargas com multiplicação de elétrons (EMCCD). O objetivo deste trabalho é avaliar o desempenho dos dispositivos fotodetectores para caracterizar os parâmetros mais significativos no processo da transdução óptica de modo a colaborar no projeto da eletrônica embarcada de controle e leitura da informação contida no EMCCD. A tecnologia da multiplicação dos elétrons em dispositivos CCD e diodos de avalanche têm aplicações importantes na vigilância de ambiente de luminosidade reduzida, astronomia, além de outras aplicações de imagens científicas incluindo as de baixo nível de bioluminescência para identificação de drogas e aplicações da engenharia genética. Para efeito de avaliação do desempenho do sistema fotodetector foi necessário desenvolver uma infra-estrutura para ter controle adequado da temperatura de operação do EMCCD. Foram nomeadas as opções com uma montagem de resfriamento com células Peltier e uma opção por criogenia resfriada com nitrogênio líquido. Os resultados obtidos são úteis na detecção de sinais luminosos ultrafracos minimizando o ruído do detector na aquisição de imagens com o auxilio da instrumentação de um filtro óptico sintonizável que será integrado no telescópio SOAR de 4 metros, instalado no Chile, para observações melhoradas com óptica adaptativa. / This work presents the results obtained in the development of a system specified to perform tests in the characterization of photo-detectors devices such as avalanche photodiodes. The test system is prepared to contribute to the characterization of the photo-detection in charge-coupled devices with electron multiplication (EMCCD). The objective of this study is to evaluate the performance of photo-detectors devices to characterize the most significant parameters in the optic transduction in order to collaborate in the project of an embedded electronic system for controlling and reading the information contained with the EMCCD. The technology of the electron multiplication in CCD devices and avalanche diodes has important applications in monitoring the environment of low light, astronomy and other scientific imaging applications including the low level of bioluminescence for the identification of drugs and applications of genetic engineering. For purposes of assessing the performance of the photo-detector it was necessary to develop an infrastructure to have proper control of the operating temperature of the EMCCD. Options were named with a montage of Peltier cell cooling and a choice of cryogenically cooled with liquid nitrogen. The results are useful in the detection of ultra weak light signals while minimizing detector noise during the acquisition of images from instrument comprising an optical tunable filter, that will be integrated into SOAR 4 meters telescope, installed in Chile, for observations improved with adaptive optics.

The development of a chip-based sensor array composed of individually addressable polystyrene-polyethylene glycol and agarose microspheres has been demonstrated. The microspheres are selectively arranged in micromachined cavities localized on silicon wafers. These cavities are created with an anisotropic etch and serve as miniaturized reaction vessels and analysis chambers. The cavities possess pyramidal pit shapes with trans-wafer openings that allow for both fluid flow through the microreactors/analysis chambers as well optical access to the chemically sensitive microspheres. Identification and quantification of analytes occurs via colorimetric and fluorescence changes to receptor and indicator molecules that are covalently attached to termination sites on the polymeric microspheres. Spectral data is extracted from the array efficiently using a charge-coupled device (CCD) allowing for the near-real-time digital analysis of complex fluids. The power and utility of this new microbead array detection methodology is demonstrated here for the analysis of complex fluids containing a variety of important classes of analytes including acids, bases, metal cations, sugars and antibody reagents. The application of artificial neural network analyses to the microbead array is demonstrated in the context of pH measurements. To assess the utility of the analysis and gain an understanding of the molecular level design of the sensor, parameters such as the choice of the indicator dyes, array size, data pre-processing techniques, as well as different network types and architectures were evaluated. Additionally, the development of miniaturized chromatographic systems localized within individual polymer microspheres and their incorporation into an array is reported. The integrated chromatographic and detection concept is based on the creation of distinct functional layers within the microspheres. Such beads have been incorporated into the array platform and used for speciation and concentration determination of aqueous metal cation solutions. / text

This thesis describes an investigation into the suitability of complementary metal oxide semiconductor (CMOS) active pixel sensor (APS) devices for scientific imaging applications. CMOS APS offer a number of advantages over the established charge-coupled device (CCD) technology, primarily in the areas of low power consumption, high-speed parallel readout and random (X-Y) addressing, increased system integration and improved radiation hardness. The investigation used a range of newly designed Test Structures in conjunction with a range of custom developed test equipment to characterise device performance. Initial experimental work highlighted the significant non-linearity in the charge conversion gain (responsivity) and found the read noise to be limited by the kTC component due to resetting of the pixel capacitance. The major experimental study investigated the contribution to dark signal due to hot-carrier injection effects from the in-pixel transistors during read-out and highlighted the importance of the contribution at low signal levels. The quantum efficiency (QE) and cross-talk were also investigated and found to be limited by the pixel fill factor and shallow depletion depth of the photodiode. The work has highlighted the need to design devices to explore the effects of individual components rather than stand-alone imaging devices and indicated further developments are required for APS technology to compete with the CCD for high-end scientific imaging applications. The main areas requiring development are in achieving backside illuminated, deep depletion devices with low dark signal and low noise sampling techniques.

This thesis presents the characterization process of an imaging device for a satellite. The camera system was built by the Space Dynamics Laboratory (SDL) and will be used in the Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) instrument for National Aeronautics and Space Administration's (NASA) Ionospheric Con- nection Explorer (ICON) satellite. This mission will further scientists' understanding of the connection between the Earth's weather and ionospheric conditions. The ionosphere, a part of the atmosphere, interferes with satellite communications, causing disturbances and disruptions. By learning more about the ionosphere through the data collected by this instrument, scientists will better understand its effects on our communications.

La tomographie optique diffuse (TOD) est une technique d’imagerie médicale relativement récente qui utilise la lumière dans le proche infrarouge pour acquérir des images in vivo de façon non invasive. Cette technique est en utilisation croissante par de nombreux chercheurs et biologistes et plusieurs équipes dans le monde travaillent sur le développement de scanners par TOD y compris notre groupe de recherche (groupe TomOptUS). Le Centre d’imagerie moléculaire de Sherbrooke dispose d’un appareil pour imagerie optique sur petit animal développé par la compagnie Quidd, soit le QOS (Quidd Optical imaging System). Cet appareil est utilisé par des biologistes et chercheurs pour diverses études précliniques sur modèles animaux (souris) de maladies humaines comme le cancer. Le QOS est entièrement contrôlé par ordinateur à l’aide d’un logiciel sophistiqué (le QOSoft) qui permet d’obtenir des images en fluorescence et en bioluminescence. Il est toutefois limité en ne permettant d’acquérir que des images planaires de la lumière sortant d’un animal ; il ne permet pas la tomographie, à savoir obtenir des images tridimensionnelles (3D) des sources fluorescentes ou bioluminescentes situées en profondeur à l’intérieur de l’animal. Bien que le QOS offre une grande flexibilité en terme d’angle d’acquisition d’images autour de l’animal avec sa caméra montée sur un bras rotatif, il a une sensibilité limitée pour de l’imagerie en profondeur, notamment parce qu’il fonctionne en mode épiillumination (détection de la lumière du même côté que l’injection de la lumière excitatrice dans l’animal) et aussi à cause de la sensibilité limitée de sa caméra. Afin d’augmenter les capacités tomographiques et la sensibilité du QOS, ainsi que le contraste des images qu’il fournit, le présent projet propose des développements logiciels intégrés au QOSoft. Ces ajouts logiciels au niveau du contrôle d’instrumentation et de l’interface graphique permettent d’intégrer une caméra EMCCD à ultra-haute sensibilité et ultra-faible bruit pour remplacer la caméra CCD refroidie existante ainsi qu’un module d’illumination laser rotatif. Ce module d’illumination, développé par le groupe TomOptUS, permet l’imagerie en mode transillumination ainsi que toutes les configurations intermédiaires jusqu’à l’épi-illumination. Ce module permet en outre d’injecter une densité de puissance lumineuse supérieure à celle possible avec la configuration actuelle du QOS. Le QOS et son logiciel mis à jour avec les ajouts faisant l’objet du présent projet sont validés par des expériences de fluorescence et de bioluminescence sur fantômes et animaux vivants.

Salinity and turbidity are two important seawater properties for the physical oceanography. The study of physical oceanography requires a compact high-resolution in-situ salino-turbidi-meter. The main objective of this work is to propose, design and implement an optical solution to simultaneously measure the seawater salinity and turbidity. Our first study is carried out to design a high-resolution refractometer based on a laser beam deviation measurement by a Position Sensitive Device (PSD). The refractive index measurements obtained by the voltage value delivered by PSD have been evaluated to quantify the performances of the sensor. According to the obtained results, it is clear that this PSD-based refractometer is attractive for innovative applications in metrology. However, PSD lacks the capability to retrieve the power distribution information of laser beam, which is related to the turbidity measurements. On the contrary, Charge-Coupled Device (CCD) gives much more information of laser beam than PSD. In the second part of the thesis, a performance comparison between PSD and CCD combined with a centroid algorithm are discussed with special attention paid to the CCD-based refractometer. According to the operating principle of CCD-based system, five factors of CCD-based system: image window size, number of processed images, threshold, binning and saturation are evaluated to optimize the CCD-based refractometer. By applying the optimized parameters, the performance of CCD-based refractometer is better than PSD-based refractometer in measuring the refractive index. Furthermore, by applying different post-processing algorithms, CCD-based system possesses the capability of measuring the power distribution sensitive quantities. To show this advantage of CCD-based system, the attenuation measurement method is used to measure turbidity without modifying the refractometer configuration. The turbidity measurement and salinity measurements influence each other in a refractometer. To overcome these influences, a CCD combined with a new location algorithm is used to measure both the refractive index and the attenuation. Several simulations and experiments are carried out to evaluate this new method. According to the results, the way to improve the resolution is discussed as well. Comparing to the nephelometer specified by the NTU standard, our method has been proved as a valid method to measure turbidity. By studying the performances of CCD-based refracto-turbidi-meter, 3 new prototypes are proposed to improve the salinity and turbidity measurement performance at the end of this thesis.

The BRIght Target Explorer (BRITE) constellation is revolutionary in the sense that the same scientific objectives can be achieved smaller (cm3 versus m3 ) and lighter (< 10kg versus 1, 000kg). It is a space astronomy mission, observing the variations in the apparent brightness of stars. The work presented herein focuses on the assembly, integration and test of the instrument used on-board six nanosatellites that form the constellation. The instrument is composed of an optical telescope equipped with a Charge Coupled Device (CCD) imager and a dedicated computer. This thesis provides a particular in-depth look into the inner workings of CCD. Methods used to characterize the instrument CCD in terms of its bias level stability, gain factor determination, saturation, dark current and readout noise level evaluation are provided. These methodologies are not limited to CCDs and they provide the basis for anyone who wishes to characterize any type of imager for scientic applications.

The BRIght Target Explorer (BRITE) constellation is revolutionary in the sense that the same scientific objectives can be achieved smaller (cm3 versus m3 ) and lighter (< 10kg versus 1, 000kg). It is a space astronomy mission, observing the variations in the apparent brightness of stars. The work presented herein focuses on the assembly, integration and test of the instrument used on-board six nanosatellites that form the constellation. The instrument is composed of an optical telescope equipped with a Charge Coupled Device (CCD) imager and a dedicated computer. This thesis provides a particular in-depth look into the inner workings of CCD. Methods used to characterize the instrument CCD in terms of its bias level stability, gain factor determination, saturation, dark current and readout noise level evaluation are provided. These methodologies are not limited to CCDs and they provide the basis for anyone who wishes to characterize any type of imager for scientic applications.

High power Gallium Nitride (GaN) based field effect transistors are used in many high power applications from RADARs to communications. These devices dissipate a large amount of power and sustain high electric fields during operation. High power dissipation occurs in the form of heat generation through Joule heating which also results in localized hot spot formation that induces thermal stresses. In addition, because GaN is strongly piezoelectric, high electric fields result in large inverse piezoelectric stresses. Combined with residual stresses due to growth conditions, these effects are believed to lead to device degradation and reliability issues. This work focuses on studying these effects in detail through modeling of Heterostructure Field Effect Transistors (HFETs) and metal oxide semiconductor hetero-structure field effect transistor (MOSHFETs) under various operational conditions. The goal is to develop a thorough understanding of device operation in order to better predict device failure and eventually aid in device design through modeling. The first portion of this work covers the development of a continuum scale model which couples temperature and thermal stress to find peak temperatures and stresses in the device. The second portion of this work focuses on development of a micro-scale model which captures phonon-interactions at the device scale and can resolve local perturbations in phonon population due to electron-phonon interactions combined with ballistic transport. This portion also includes development of phonon relaxation times for GaN. The model provides a framework to understand the ballistic diffusive phonon transport near the hotspot in GaN transistors which leads to thermally related degradation in these devices.

Indiana University-Purdue University Indianapolis (IUPUI) / Accurate determination of working length during endodontic therapy is a crucial step in achieving a predictable outcome. This is determined by the use of electronic apex locators, tactile perception, and knowledge of average tooth lengths and/or dental radiography whether digital or conventional is utilized. It is the aim of this study to determine if there is a difference between Schick digital radiography and Kodak Insight conventional film in accurately determining working lengths when modifying exposure time and source-film/sensor distance. Twelve teeth with size 15 K-flex files at varying known lengths from the anatomical apex were mounted in a resin-plaster mix to simulate bone density. Each tooth was radiographed while varying the source-film/sensor distance and exposure 122 time. Four dental professionals examined the images and films independently. Ten images and 10 films were selected at random and re-examined to determine each examiner?s repeatability. The error in working length was calculated as the observed value minus the known working length for each tooth type. A mixed-effects, full-factorial analysis of variance (ANOVA) model was used to model the error in working length. Included in the ANOVA model were fixed effects for type of image, distance, exposure time, and all two-way and three-way interactions. The repeatability of each examiner for each film type was assessed by estimating the intra-class correlation coefficient (ICC). The repeatability of each examiner on digital film was good with ICCs ranging from 0.67 to 1.0. Repeatability on the conventional film was poor with ICCs varying from -0.29 to 0.55.We found there was an overall difference between the conventional and digital films (p < 0.001). After adjusting for the effects of distance and exposure time, the error in the working length from the digital image was 0.1 mm shorter (95% CI: 0.06, 0.14) than the error in the working length from the film image. There was no difference among distances (p = 0.999) nor exposure time (p = 0.158) for film or images. Based on the results of our study we conclude that although there is a statistically significant difference, there is no clinically significant difference between digital radiography and conventional film when exposure time and source-film/sensor distance are adjusted.