This thesis discusses the application of Slab Coupled Optical Fiber Sensors (SCOS) in a railgun. The specific goal of these sensors is to create an electric field profile at a specific point in the gun as the armature passes. The thesis explores the theory that powers the railgun as well as the principles of the SCOS sensors. It also elaborates on the various noise sources found throughout the detection system and concludes with a summary of the various field tests that were performed throughout this project. There are many benefits to using a railgun over traditional weapons in the field. These benefits not only include both safety and cost, but also greater overall defense capabilities. Unfortunately, the velocity skin effect (VSE) causes the current railgun designs to have limited life span through wear on the rails. In order to develop superior railguns and railgun armatures, the accurate detection of the VSE through measuring the electric field is of great interest. We used a SCOS, a small directionally precise dielectric sensor, as a small sensing area is required to be able to measure the electric fields inside of the rail gun. The actual usage of the SCOS within the railgun produced an additional set of problems that are not commonly encountered in the lab. The chief amongst these was noise from strain, RF pickup, and phase noise. This thesis also reports various methods used to reduce each of these noise sources.

Proposed are novel sensors for extreme environment power plants, laser beam analysis and biomedicine. A hybrid wireless-wired extreme environment temperature sensor using a thick single-crystal Silicon Carbide (SiC) chip embedded inside a sintered SiC probe design is investigated and experimentally demonstrated. The sensor probe employs the SiC chip as a Fabry-Perot (FP) interferometer to measure the change in refractive index and thickness of SiC with temperature. A novel temperature sensing method that combines wavelength-tuned signal processing for coarse measurements and classical FP etalon peak shift for fine measurements is proposed and demonstrated. This method gives direct unambiguous temperature measurements with a high temperature resolution over a wide temperature range. An alternative method using blackbody radiation from a SiC chip in a two-color pyrometer configuration for coarse temperature measurement and classical FP laser interferometry via the same chip for fine temperature measurement is also proposed and demonstrated. The sensor design is successfully deployed in an industrial test rig environment with gas temperatures exceeding 1200 C. This sensor is proposed as an alternate to all-electrical thermocouples that are susceptible to severe reliability and lifetime issues in such extreme environments. A few components non-contact thickness measurement system for optical quality semi-transparent samples such as Silicon (Si) and 6H SiC optical chips such as the one used in the design of this sensor is proposed and demonstrated. The proposed system is self-calibrating and ensures a true thickness measurement by taking into account material dispersion in the wavelength band of operation. For the first time, a 100% repeatable all-digital electronically-controlled pinhole laser beam profiling system using a Texas Instruments (TI) Digital Micro-mirror Device (DMD) commonly used in projectors is experimentally demonstrated using a unique liquid crystal image generation system with non-invasive qualities. Also proposed and demonstrated is the first motion-free electronically-controlled beam propagation analyzer system using a TI DMD and a variable focus liquid lens. The system can be used to find all the parameters of a laser beam including minimum waist size, minimum waist location and the beam propagation parameter M2. Given the all-digital nature of DMD-based profiling and all-analog motion-free nature of the Electronically Controlled Variable Focus Lens (ECVFL) beam focus control, the proposed analyzer versus prior-art promises better repeatability, speed and reliability. For the first time, Three Dimensional (3-D) imaging is demonstrated using an electronically controlled Liquid Crystal (LC) optical lens to accomplish a no-moving parts depth section scanning in a modified commercial 3-D confocal microscope. The proposed microscopy system within aberration limits has the potential to eliminate the sample or objective motion-caused mechanical forces that can distort the original sample structure and lead to imaging errors. A signal processing method for realizing high resolution three dimensional (3-D) optical imaging using diffraction limited low resolution optical signals is also proposed.

This dissertation demonstrates the first of its kind distributed magnetic field sensor based on a fiber optic distributed acoustic sensing (DAS) scheme. Ferromagnetic nickel and Metglas® were dispersed internally within a fiber optic preform and then drawn on an in-house fiber optic draw tower to lengths in the kilometers. Due to the close proximity of the ferromagnetic metals and fiber optic core, the magnetostrictive strain response of the ferromagnetic materials when exposed to a magnetic field would perturbate within the fiber cladding and transfer that strain, internally, to the fiber optic core. Strain resulting from the magnetostrictive effect allows the DAS based sensor to accurately translate strain into readable magnetic field data. Due to the high sensitivity seen in this sensor design, multiparameter sources, acoustic and magnetic fields, were tested and validated and a three dimensional magnetic-field vector sensor was proposed. Numerical analysis of the novel sensor design was first implemented using COMSOL Multiphysics, where inputs such as magnetostrictive element shape, size, distance, and number were first investigated. Upon optimizing system constraints, the sensor design was further modified such that single mode operation was consistent across multiple fiber draws while retaining high strain transfer from the ferromagnetic elements to the fiber optic core. Ferromagnetic material selection was evaluated as a function of the saturation magnetostriction constants and a total of 4 modules were used to fully characterize the complex physics involved in this sensor design. All fabrication and testing were performed in-house using a full scale 3-story fiber draw tower and custom environmental testing stations to imitate naturally occurring events such as magnetic or acoustic point sources. A unique stacking method was used to embed ferromagnetic nickel and Metglas® into a fiber optic preform which when combined with a custom fiber draw process resulted in consistent multi-material fibers drawn to lengths of 1-km. In-house testing facilities included different types of electromagnetic generators, in addition to a soil test bed, and an outdoor test bed which allowed 100 meters of fiber to be tested simultaneously. All tested sensors demonstrated high strain transfer capabilities on the order of 0.01-10 μϵ depending on the materials used, ferromagnetic rod number, and core to metal spacing. Due to the sensitivity of the system the difference between AC and DC was distinct, and directional magnetostriction was studied. Transverse and longitudinal magnetic wave propagation was controlled through a solenoid and rectangular Helmholtz coil, both built in-house. A three-dimensional magnetic field vector sensor was proposed due to the success of the magnetic field sensor, and a design was proposed and initially tested to validate direction as a function of field strength and distance. To summarize, this dissertation explores the first fully distributed magnetic field sensor using DAS based techniques and one of the first multi-material fiber draw processes which can produce consistent single mode fiber up to 1-km. Due to extensive FEA modeling, multiple iterations of the magnetic sensor were fully characterized and an equation describing the relationship between sensor design and strain transfer has been created and validated experimentally. Multi-parameter tests including acoustic and magnetic fields were implemented and an algorithm was developed to separate the mixed signals. Finally, a test was performed to demonstrate the feasibility of sensing magnetic fields directionally. Cumulative results demonstrate a high-quality sensor alternative to current designs which may surpass other magnetic sensors due to innate multi-parameter capabilities, in addition to the inexpensive production cost and extremely long operating lengths. / Doctor of Philosophy / This dissertation demonstrates the first of its kind distributed magnetic field sensor based on a fiber optic distributed acoustic sensing (DAS) scheme. Ferromagnetic nickel and Metglas® were dispersed internally within a fiber optic preform and then drawn on an in-house fiber optic draw tower to lengths in the kilometers. Due to the close proximity of the ferromagnetic metals and fiber optic core, the magnetostrictive strain response of the ferromagnetic materials when exposed to a magnetic field would perturbate within the fiber cladding and transfer that strain, internally, to the fiber optic core. Strain resulting from the magnetostrictive effect allows the DAS based sensor to accurately translate strain into readable magnetic field data. Due to the high sensitivity seen in this sensor design, multiparameter sources, acoustic and magnetic fields, were tested and validated and a three dimensional magnetic-field vector sensor was proposed. Numerical evaluation of the sensing structure was perused before experimental testing using COMSOL Multiphysics. Experimental and numerical evaluations were compared and showed a high degree of certainty which allowed expedited design modifications. Sensor characterization included scanning electron microscopy, and electron diffraction spectroscopy, which provided insight into material composition and fiber polishing quality. Due to the high-quality results attained in the combined acoustic and magnetic field tests, a final design was proposed to gather magnetic field data as a vector, showing both magnitude and direction. The 3D magnetic field vector sensor was partially validated based on a test which compared intensity with distance and a design and methodology was proposed to fully test and characterize this design. To summarize, a novel magnetic field sensor, capable of multi-parameter sensing, was proposed and tested experimentally and numerically resulting in a robust and highly sensitive design. The work presented here provides some of the first insights into multi-material fiber fabrication, an equation which provides an estimated relationship between magnetostrictive strain transfer onto a fiber optic core and the perceived DAS based sensor results, as well as a first of its kind multi-parameter distributed acoustic and magnetic field sensor.

This research serves to evaluate the ability of optical detection techniques to ascertain the lubricity of revenue service track from a moving platform for railroad applications. A literature review is presented that covers the rail vehicle dynamics that drive the need of Top-of-Rail lubrication and directly affect the manner in which the Top-of-Rail Friction Modifiers (TORFM) and flange grease both spread down rail and eventually wear away. This literature review also highlights previous research in the field of rail lubrication and the benefits that rail lubricants, specifically TORFM, provide for the railroads. Finally, the literature review covers the governing optical principals inherent to the synchronous spot radiometer that has been developed for use in the research as a gloss ratio instrument and also addresses the drawbacks and challenges inherent to applying this type of instrument in the railroad industry. The research then overviews previous rail lubricity sensors developed by the Railway Technologies Laboratory (RTL) at Virginia Tech and the lessons learned from their application. The preceding field testing conducting with a modified second generation rail lubricity sensor and a rail push car is briefly summarized with emphasis on the drawbacks and issues that were used to develop the third generation sensor used for this research. The development of the third generation sensor is covered, including the issues that it attempts to solve from its predecessor and the governing optical principals that govern the operation of the sensor. The laboratory evaluations conducting to commission the sensor are also covered in preparation for deploying the new third generation sensor in medium speed, medium distance revenue service testing. This includes a shakedown run on a siding in Riverside, VA prior to conducting mainline in-service testing. Finally, this research thesis covers the in-service testing on revenue track conducted with the new third generation rail lubricity sensor and the accompanying remote-controlled (RC) rail cart. The two components, when combined, create a Lubricity Assessment System which is capable of being operated at speeds upwards of 10 mph remotely from a follow hy-rail truck. The data collected from this field test is analyzed for the lubricity assessments that are able to be drawn from this initial phase of field service testing. The conclusions from this testing affirm the ability of optical methods to determine and evaluate Top-of-Rail (TOR) lubricity from a moving platform. Specifically, the new sensor is able to identify several local phenomena that demonstrate the high potential for errant evaluation of rail lubricity evaluation from spot check based methods that are solved by evaluating the track in a continuous, moving fashion. Based on the continuous moving data collected for this test, several new signal traits such as the spatial frequency (wavenumber) associated with the passing freight cart wheels in the lubricity signal and the phantom applicator effect of transient lubricity conditions at the entrances and exits of curves can be detected and investigated. The success of this research indicates the continued evaluation of lubricity signals from a moving platform is warranted and suggests the potential for introducing one of these systems to various track metrology cars deployed throughout the United States railroads. / Master of Science / The United States railroads have been employing rail lubricants to the rails since the beginning of the industry and have recently, in the past 20 years, introduced another type of lubricant: Top-of-Rail Friction Modifiers (TORFM). TORFM creates a third body layer between the train wheels and the Top-of-Rail surface to minimize asset wear of both the wheel and rail and to increase the train efficiency. As the United States railroads embrace Precision Scheduled Railroading (PSR), increased train efficiency can allow the railroads to run longer trains with fewer locomotives. This increases the efficiency and capability of the rail network and also decreases the fuel burned and the amount of rail and wheel wear. TORFM has been proven to be effective and is widely adopted, but the railroads are still in need of tools to determine the presence and absence of these thin and often nearly invisible layers of lubricant on the rail surface. This research uses lasers as tool to quantify the level of lubrication of the rail surface. The presence of rail lubricants, such as TORFM, on the rail surface change the amount of light that is reflected and scattered off the shiny steel surface. These changes are often small but can be captured by photodetectors housed in the instrument. By plotting the detected sensor values, trends in the lubricity signal can be tracked and evaluated to determine the presence or absence of rail lubricants and assess the overall quality of lubrication on the rail at specific locations down track. The research in this thesis takes existing methods that were used for single spot inspections and adapts them to a moving platform. The moving platform is able to continuously scan the Top-of-Rail surface as the instrument moves along and generates continuous moving evaluations of rail lubricity. This can be especially important when the lubricity is not uniform and allows for trends in the data to be analyzed to provide more consistent and precise evaluations of the lubricity trends down rail. Optical tools like this sensor, which are by nature non-contact sensors, can easily be adapted to existing track measurement railcars and deployed system wide. This solves a strong need for railroad engineers: to be able to identify the presence of rail lubricants and evaluate the effectiveness of their lubrication practices.

Biosensors have a multitude of important applications in basic research, environmental monitoring, biodefense, and medicine. This research aims to show that Ionic Self-Assembled Multilayers (ISAMs) adsorbed on Long Period Gratings (LPGs) can serve as a highly sensitive, robust, inexpensive optical-based biosensor platform. The ISAM technique is a layer-by-layer deposition method that builds nanometer-thick films based on the principle of Coulomb attraction between oppositely charged polyelectrolyte solutions while LPGs cause strong attenuation bands that enable an optical fiber to be extremely sensitive to changes in the surrounding environment. LPGs have been shown to be highly sensitive to the adsorption of nanoscale self-assembled films on the optical fiber cladding surface. In this work, we utilize Turnaround Point (TAP) LPGs, which possess even greater sensitivity than standard LPGs. This thesis focuses on evaluation of approaches to increasing the sensitivity of the sensor platfom, implementation of a biosensor for detection of several biomolecules, and preliminary evaluation of the potential for pH sensing. For a thin-film coated TAP LPG, we have demonstrated that shifts in the transmitted light intensity at the resonant wavelength of the LPG can result from the variation in film thickness and/or refractive index. We have observed decreases in intensity as large a 7 dB for one bilayer of ISAM film (~1 nm), which corresponds to an 80% decrease in the transmitted light intensity at the resonant wavelength. We have also shown that the sensitivity of the TAP LPG sensor can be increased by implementing nm-thick ISAM films that have a refractive index greater than silica. Furthermore, it is shown that incorporation of silica nanoparticles into the ISAM films significantly increases sensitivity through increased surface area and thickness. The biotin-streptavidin system was used as a model for implementaion and optimization of the ISAM-coated TAP LPG biosensor platform. Through evaluation of various biotin derivatives to maximize the amount functionalized onto the ISAM film, optimization of the ISAM film properties, and use of LPGs designed for higher sensitivity, the minimum detectable concentration of streptavidin was decreased from 0.0125 mg/ml to 12.0 ng/ml. The biosensor platform was then tested on prostate specific antigen (PSA), which is used as a clinical marker for early diagnosis of potential prostate cancer. Using a direct crosslinking approach of the monoclonal antibody to PSA into the ISAM film, a sensitivity level of 11.64 ng/ml PSA was obtained through combined optimization of the ISAM film and antibody surface coverage. Finally, the potential of ISAM TAP LPGs as pH sensors was examined based on the pH dependent swelling of ISAM films. / Ph. D.

Biosensors have widespread applications in many areas. Currently the Surface Plasmon Resonance (SPR) biosensor is one of the most prevalent types of biosensor. However, it has several disadvantages such as being delicate, expensive, and non-portable. Ionic Self-Assembled Multilayers (ISAMs) adsorbed on Long Period Fiber Gratings (LPGs) provides an attractive platform for building optical sensors, which could potentially overcome the disadvantages of SPR biosensors. The ISAM technique is a type of layer-by-layer deposition technique for building nanoscale thin films. An LPG is a type of fiber device that is sensitive to physical property changes of the ambient environment. LPGs have been extensively investigated for use as optical sensors. We have carried out a study on combining these two techniques to build efficient biosensors. In this thesis, we demonstrate ultra-sensitive LPGs whose attenuation can be changed by 25 dB (~99.7%) over a 48-nm spectral band, with ambient-index changes of only 2.7E-4. The device schematic allows arbitrarily high index sensitivities to be achieved, which makes it an attractive platform for realizing sensors and modulators that respond to small index changes. For a thin-film coated LPG, we find theoretically that the resonant wavelength shift of the LPG can result from either the variation of the thickness of the film and/or the variation of its refractive index. Furthermore, results illustrate that the sensitivity of the sensor could be enhanced using a nm-thick thin-film (e.g. ISAM films) whose refractive index is greater than silica. Experimentally, we demonstrate the fabrication of nm-thick ISAM films deposited on LPGs, which induces dramatic shifts in the resonant wavelength. The refractive index and the thickness of the ISAM film was precisely controlled by altering the relative fraction of the anionic and cationic materials combined with layer-by-layer deposition. Finally, we demonstrate that ISAM-coated LPGs can function effectively as biosensors by using the biotin-streptavidin system. These demonstrations confirm that the ISAM-LPG scheme provides a thermally-stable, reusable, and robust platform for building efficient optical sensors. / Ph. D.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2010. / Thesis submitted in partial fulfilment of the requirements for the degree of MASTER OF SCIENCE IN ENGINEERING (MINERAL PROCESSING) in the Department of Processing Engineering at the University of Stellenbosch / ENGLISH ABSTRACT: This work evaluates the use of inverse least squares (ILS) and classical least squares (CLS) models for calibration of a diffuse reflectance spectrophotometer for on-line monitoring of the aqueous phase in a flotation cells. Both models use a Beer's law for the quantification of the metals. The formulated statistical models are compared to a proprietary Blue Cube model in terms of prediction ability to determine the potential applicability of the models. A diffuse reflectance spectrophotometry was used for simultaneous analysis of copper (Cu), cobalt (Co) and zinc (Zn) in the solutions. The laboratory set-up of Blue Cube instrument was used for the experimental analysis. The concentrations and matrix compositions of the samples are simulated according to Skorpion zinc mine plant conditions. The calibration samples were prepared using a simplex-centroid mixture design with the triplicates of the centroid run. The unknown or test samples were prepared randomly within the same concentration of the calibration samples. The effects of temperature and nickel concentration on absorption of the metals were evaluated in the following range, 20 - 80 °C and 125 - 400 ppm, respectively. The statistical models (ILS and CLS) were calibrated from visible and near infrared (VNIR) spectra data of the calibration samples. A modified Beer's method was used as a preprocessing technique to convert the raw data into absorbance values. The manual wavelength selection procedure was used to select the wavelengths to be used in both models. The quality of the models was evaluated based on Rª and % root mean squared error (RMSE) values with 0.90 and 10% used as the guideline for the respective statistical parameters. Both ILS and CLS models showed good results for all three metals (Cu, Co and Zn) during their calibration steps. It was further shown that both models give worse predictions for Zn as compared to other metals due to its low relative intensity in the mixture. The derivative orders of absorbance spectra that were used to enhance the prediction results of Zn had no positive effect but they rather lowered accuracy of predictions. An increase in temperature was found to increase the intensities of the absorption spectra of all the metals while an increase in nickel concentration decreases the prediction ability of model. The developed statistical models were compared to a Blue Cube model in terms of prediction ability using analysis of variance (ANOVA) test. The ANOVA results revealed that there is no statistical difference between the developed models and Blue Cube model since the F-values for all the metals were below the critical F-value. Furthermore, the partial least squares (PLS) model shows an increased accuracy results for prediction of zinc metal as compared to both the ILS and CLS models. Finally, good comparisons of the statistical models results with atomic absorption spectroscopy (AAS) analyses were establish for the unknown samples. The study demonstrates that chemometric models (ILS and CLS) developed here can be used for quantification of several metals in real hydrometallurgical solutions as samples were simulated according to a plant conditions. However, in order to have confidence in the results of the models, a factorial-mixture design must be used to study the effect of temperature and nickel concentration. Moreover the models must be further tested and validated on the real samples from a plant. / AFRIKAANSE OPSOMMING: Hierdie werkstuk evalueer die gebruik van inverse kleinste kwadraatmetodes (IKK) en klassieke kleinste kwadraatmetodes (KKK) vir die kalibrasie van 'n diffuse reflektansiespektrofotometer vir die aanlyn monitering van die waterige fase in flottasieselle. Beer se wet word vir die kwantifisering van metale vir albei modelle gebruik. Die omskrewe data-gebaseerde modelle is op grond van voorspellingsvermoë vergelyk met'n. Blue Cube model, sodat die moontlike toepaslikheid van hierdie modelle bepaal kan word. 'n Diffuse reflectantie spektrofotometrie is ingespan vir die gelyktydige analise van koper (Cu), kobalt (Co) en sink (Zn) in oplossing. Eksperimentele analises is met behulp van 'n laboratoriumopstelling met 'n Blue Cube instrument uitgevoer. Die konsentrasies en matriks-samestellings van monsters is gesimuleer om Skorpion sinkmyn aanlegkondisies na te boots. Kalibrasie monsters is voorberei volgens . simpleks-sentroïed mengselontwerp met drievoudige sentroïede lopies. Onbekende (toets) monsters is ewekansig voorberei binne dieselfde konsentrasie spesifikasies as die kalibrasie monsters. Die invloed van temperatuur en nikkelkonsenstrasie op die absorpsie van die metale is in die bestek van 20 - 80 °C en 125 - 400 dpm, onderskeidelik, bepaal. Die data-gebaseerde modelle (IKK en KKK) is met sigbare en naby infrarooi (SNIR) spektra data van die kalibrasie monsters gekalibreer. 'n Gewysigde Beer metode is vir data voorbereiding benut om rou data na absorbansie waardes om te skakel. Die handgolflengte-seleksieprosedure is vir beide modelle gebruik om die golflengtes te kies. Die kwaliteit van die modelle is op grond van Rª en % wortel gemiddelde kwadratiese fout (WGKF) geevalueer, met waardes van 0.90 en 10% (onderskeidelik) as riglyne vir hierdie statistiese parameters. Beide IKK en KKK modelle het vir hul kalibrasie stappe vir al drie metale (Cu, Co en Zn) goeie resultate getoon. Dit is verder getoon dat albei modelle die slegste voorspellings lewer vir Zn (vergeleke met die ander metale) as gevolg van Zn se lae relatiewe intensiteit in die mengsel. Afgeleide ordes van absorbansie spektra is gebruik om die Zn voorspellings te versterk, maar het geen positiewe effek gehad nie; inteendeel, voorspellingakkuraatheid is verlaag. ʼn Verhoging in temperatuur het die intensiteite van die absorpsie spektra van alle metale verhoog, terwyl ʼn verhoging in nikkelkonsentrasie die voorspellingakkuraatheid van die modelle verlaag het. Die ontwikkelde data-gebaseerde modelle is met ʼn Blue Cube model vergelyk in terme van voorspellingsvermoë met behulp van variansie-analise (ANOVA). Die ANOVA resultate toon dat daar geen statistiese verskil tussen die ontwikkelde modelle en die Blue Cube model is nie, aangesien die F-waardes vir al die metale onder die kritiese F-waarde is. Die gedeeltelike kleinste kwadraatmodel (GKK) toon verder verhoogde voorspellingakkuraat-heid vir sinkmetaal tenoor beide die IKK en KKK modelle. Ten slotte, goeie ooreenstemming van die data-gebaseerde modelresultate met atoomabsorpsie spektroskopie (AAS) analise is vir die onbekende monsters gevind. Hierdie werkstuk toon dat die chemometriese modelle (IKK en KKK) wat hier ontwikkel is, gebruik kan word vir die kwantifisering van verskeie metale in werklike hidrometallurgiese oplossings, aangesien monsters gesimuleer is volgens aanlegkondisies. Om egter verdere vertroue te hê in die modelresultate, sal ʼn faktoriaal-mengselontwerp toegepas moet word om die effek van temperatuur en nikkelkonsentrasie te ondersoek. Voorts moet die modelle verder getoets en gevalideer word op werklike monsters van ʼn aanleg.

La mesure de distance et la détection d'objets sont devenues essentielles dans de nombreux domaines tels que l'automobile ou la robotique, les applications médicales, les procédés industriels et agricoles, les systèmes de surveillance et de sécurité, etc. Dans le but d'améliorer les performances des dispositifs de télémétrie laser en terme de bruit et de diaphonie, une technique hétérodyne par mélange optoélectronique doit être utilisée. Par ailleurs, l'aspect système embarqué nécessite une réduction de l'encombrement et de la consommation à performances égales. L'intégration de mélangeurs optoélectroniques en technologie CMOS apporte donc une solution optimale à cette approche grâce à ses multiples avantages (intégration du circuit d'instrumentation sur la même puce, modèles bien connus, coût raisonnable, performances élevées,…). Ainsi cette thèse traitera de l'étude de mélangeurs optoélectroniques en technologie CMOS pour la télémétrie embarquée haute résolution. Le premier chapitre de ce manuscrit présente les diverses technique de mesure de distance par télémétrie laser par et justifie le choix de la télémétrie laser par déphasage ainsi que le gain en performances lié à l'hétérodynage. Le second chapitre décrit les mélangeurs électriques et optoélectroniques ainsi que les propriétés nécessaires à leur réalisation. Quelques photodétecteurs y sont présentés au vu de la possibilité de les utiliser en mélangeurs optoélectroniques et d'une intégration potentielle en technologie CMOS. Les principales contraintes liées à l'intégration en technologie CMOS de photocapteurs utilisables en mélangeurs optoélectroniques, sont exposés dans la troisième partie. Les travaux de conception et d'optimisation des structures ainsi que les phases de simulations et de test y sont détaillés. Enfin, pour valider expérimentalement les études précédentes, le dernier chapitre présente la conception d'une chaîne de mesure multivoies pour une tête de photoréception CMOS matricée pour un télémètre laser embarqué haute résolution. / Distance measurement and object detection has become essential in many fields such as automotive and robotics, medical applications, industrial processes and farming systems, surveillance and security, etc.. In order to improve the performance of laser ranging devices in terms of noise and crosstalk, an optoelectronic heterodyne technique of mixing should be used. Moreover, the aspect of embedded system requires a reduction in the size and power consumption for the same performance. The integration of optoelectronic mixers in CMOS technology will provide an optimal solution to this approach through its many advantages (integrated instrumentation circuit on the same chip, well-known models, reasonable cost, high performance, ...). Thus this thesis will focus on the study of optoelectronic mixers in CMOS technology for high resolution, embedded laser range finding systems. The first chapter of this thesis discusses the various technique of distance measurement by laser ranging and justifies the choice of phase shift technique and the gain in performance related to heterodyning. The second chapter describes the electrical and optoelectronic mixers and the properties needed to develop them. Some photodetectors are presented given the opportunity to use optoelectronic mixers and a potential integration with CMOS technology. The main constraints to the integration of CMOS photosensors used in optoelectronic mixers are set out in Part III. The work of design and optimization of structures and phases of simulations and testing are detailed. Finally, to experimentally confirm the earlier studies, the final chapter presents the design of a measuring head for a multichannel photoreceptor CMOS for a high resolution laser range finder.

A complexidade na dinâmica do nitrogênio é resultado de suas interações com o ambiente. Embora muito já tenha sido estudado, a adubação nitrogenada em cana-de-açúcar ainda pode ser considerada um desafio. Entre os esforços para melhorar o manejo do nitrogênio em cana-de-açúcar está o uso de sensores ativos de dossel. Para que um sensor de dossel se preste à adubação nitrogenada ele deve atingir requisitos fundamentais. Com base nisto, o objetivo deste trabalho foi avaliar se o sensor de dossel GreenSeekerTM é uma ferramenta de auxílio na recomendação da adubação nitrogenada em cana-de-açúcar, através da avaliação dos requisitos: capacidade de identificar a resposta radiométrica às diferentes condições de nutrição por nitrogênio e de se correlacionar com a produtividade final da cultura. A produtividade e os dados de índice de vegetação da diferença normalizada (NDVI) foram coletados em cinco experimentos de resposta ao nitrogênio, ao longo do ano safra 2011-12. Os tratamentos se constituíram de doses de nitrogênio variando entre 0 e 240 kg ha-1. Para determinação do NDVI foi utilizado o sensor ativo de dossel GreenSeekerTM, modelo RT200 (Trimble Navigation Ltda., Sunyvaley, CA, EUA). As avaliações com o sensor foram guiadas pela altura média dos colmos. Apenas 50% dos experimentos avaliados foram responsivos ao nitrogênio. O sensor se mostrou capaz de identificar significativamente a resposta da cultura ao suprimento diferenciado de N, tanto em experimentos responsivos quanto na ausência de resposta, com R2 de até 0,997. Além disso, o sensor foi capaz de se correlacionar com a produtividade final da cultura, através do índice NDVI medido no início do ciclo com R2 significativos variando entre 0,466 e 0,666. Quando o método do índice de resposta (RI) modificado foi utilizado para estimar produtividade, foram obtidos melhores ajustes, proporcionando aumento nos valores de R2, até três vezes maiores do que os obtidos com dados brutos de NDVI e produtividade, o que resultou na possibilidade de englobar no mesmo modelo dados referentes a experimentos heterogêneos quanto a ambientes variedades e tratamentos, porém com relações inferiores ao esperado. O sensor foi altamente eficiente na determinação da resposta da cultura ao suprimento diferencial de nitrogênio e foi capaz de se correlacionar com a produtividade final, caracterizando-se, portanto, como uma ferramenta útil no manejo da adubação nitrogenada em cana-de-açúcar. / The complexity in the nitrogen dynamics is due the range of iterations it has in the environment. Even though much has been studied already, sugarcane nitrogen fertilization is still considered a challenge. Among the efforts to better manage nitrogen in sugarcane is the use of active crop canopy sensors. In order to be valuable for nitrogen management, a sensor must fulfill fundamental requirements. Based on that, the objective of this study was to evaluate if the canopy sensor GreenSeekerTM is a valuable tool in the process of nitrogen recommendation in sugarcane, through the following requirements: capacity of identifying the crop radiometric response to differentiated conditions of nitrogen supply and to correlate with crop final yield. The yield and the normalized difference vegetative index (NDVI) data were collected from 5 different nitrogen response trials during the harvest season of 2011-12. The treatments consisted of nitrogen rates ranging from 0 to 240 kg ha-1. A GreenSeekerTM, active crop canopy sensor, model RT200 (Trimble Navigation Ltda., Sunyvaley, CA, EUA) was used to obtain the NDVI data. The sensor readings were guided by the average crop stalk height. Just 50% of the evaluated trials were responsive to nitrogen. The sensor has shown to be able to significantly identify the crop response to nitrogen supply in either responsive or nonresponsive conditions with a maximum R2 of 0,997. In addition, the sensor was also able to correlate with final yield, using early NDVI readings with significant R2 values ranging from 0,466 to 0,666. When the modified response index (RI) yield prediction method was used, better fits were found, which translated into an increase in the R2 values of up three times fold when compared to the estimation made with raw NDVI and yield data, resulting in the possibility to address in the same model data from trials heterogeneous in conditions, varieties and treatments even though the relations found were weaker than expected. The sensor was highly effective in identifying crop response to nitrogen supply and to correlate to final yield, hence it was characterized as a valuable tool for nitrogen management in sugarcane.

No presente trabalho é apresentada uma nova abordagem para medida de potenciais em altos níveis de tensão que utilizam sensores eletro-ópticos Pockels. Também descreve a aplicação da técnica de interferometria de luz branca em sistemas de alta tensão por fibras ópticas. Neste sistema a informação é codificada no espectro da luz, permitindo assim que a medida seja independente da potência óptica transmitida pelo link de fibras ópticas. Um protótipo foi construído e testado sob excitação de tensão a.c. até 20 kV em 60 Hz mostrando boa resposta e demonstrando a viabilidade deste método. / A new approach to perform measurement of potentials in high voltage levels using electrooptical Pockels sensors is presented here. This work describes an application of the White Light Interferometry technique to a high voltage optical fiber measurement system. In this system the information is encoded in the spectrum of the light, allowing the measurement to be independent of the optical power transmitted by the optical fiber link. A prototype was built and tested under excitation of a.c. voltages up to 20 kV in 60 Hz showing good response and demonstrating the feasibility of this method.