Dissertations / Theses on the topic 'Unwrapping'

In the field of optical interferometry, two-dimensional projections of light interference patterns are often analysed in order to obtain measurements of interest. Such interference patterns, or interferograms, contain phase information which is inherently wrapped onto the range -t to it. Phase unwrapping is the processes of the restoration of the unknown multiple of 2ir, and therefore plays a major role in the overall process of interferogram analysis. Unwrapping phase information correctly becomes a challenging process in the presence of noise. This is particularly the case for speckle interferograms, which are noisy by nature. Many phase unwrapping algorithms have been devised by workers in the field, in order to achieve better noise rejection and improve the computational performance. This thesis focuses on the computational efficiency aspect, and picks as a starting point an existing phase unwrapping algorithm which has been shown to have inherent noise immunity. This is, namely, the tile-based phase unwrapping method, which attains its enhanced noise immunity through the application of the minimum spanning tree concept from graph theory. The thesis examines the problem of finding a minimum spanning tree, for this particular application, from a graph theory perspective, and shows that a more efficient class of minimum spanning tree algorithms can be applied to the problem. The thesis then goes on to show how a novel algorithm can be used to significantly reduce the size of the minimum spanning tree problem in an efficient manner.

In the field of optical interferometry, two-dimensional projections of light interference patterns are often analysed in order to obtain measurements of interest. Such interference patterns, or interferograms, contain phase information which is inherently wrapped onto the range -t to it. Phase unwrapping is the processes of the restoration of the unknown multiple of 2ir, and therefore plays a major role in the overall process of interferogram analysis. Unwrapping phase information correctly becomes a challenging process in the presence of noise. This is particularly the case for speckle interferograms, which are noisy by nature. Many phase unwrapping algorithms have been devised by workers in the field, in order to achieve better noise rejection and improve the computational performance. This thesis focuses on the computational efficiency aspect, and picks as a starting point an existing phase unwrapping algorithm which has been shown to have inherent noise immunity. This is, namely, the tile-based phase unwrapping method, which attains its enhanced noise immunity through the application of the minimum spanning tree concept from graph theory. The thesis examines the problem of finding a minimum spanning tree, for this particular application, from a graph theory perspective, and shows that a more efficient class of minimum spanning tree algorithms can be applied to the problem. The thesis then goes on to show how a novel algorithm can be used to significantly reduce the size of the minimum spanning tree problem in an efficient manner.

This licentiate thesis is devoted to shape measurements using two different optical methods. The first one is a classical triangulation method, which uses projected fringes. The second one is a new interferometric method, which uses wavelength scanning. Both are whole field measuring methods. The main goal of the project has been to analyse the performance of an analysis scheme for absolute shape measurements called temporal phase unwrapping. This method permits the user to determine the absolute distance from the detector (usually a CCD-detector) to the object. A generalised version of the temporal phase unwrapping scheme is called reduced temporal phase unwrapping. The scheme uses an arbitrary number of fringe maps with varied fringe pitch, to calculate phase (shape). A thorough investigation is made of the performance of this algorithm. A single channel and a multi channel approach is considered. Expressions are found that relates the physical quantities to phase errors. In these simulations the single channel approach was found to be the most robust one. Expressions that relate the measurement accuracy and the unwrapping reliability, respectively, to the reduction of the fringe sequence were also found. As expected the measurement accuracy is not affected by a shorter fringe sequence while a significant reduction in the unwrapping reliability is found, as compared to the complete negative exponential sequence. The strength of reduced temporal phase unwrapping is demonstrated experimentally, in a projected fringe three-channel system. Instead of letting each channel carry phase-stepped images each channel can carry images with a change in fringe pitch. This significantly reduces noise, but at least three images needs to be acquired. It is also shown that the temporal phase unwrapping analysis scheme can be used to evaluate experimental data from wavelength scanning interferometry. Two unwrapping strategies are considered: fitting to a reversed exponential sequence and complex Fourier-transform ranging. The achievable accuracy for both methods ultimately depend on the tuning width, the speckle correlation, and random noise in the optical setup.
Godkänd; 2000; 20070318 (ysko)

The reconstruction of a phase surface from the observed principal values is required for a number of applications, including synthetic aperture radar (SAR) and magnetic resonance imaging (MRI). However, the process of reconstruction, called

This thesis investigates how David Bohm’s idea of dialogue could function as means to prompt awareness of hidden assumptions, and how this impacts communication for people involved. This is explored through the research question: "Can dialogue be a leverage to prompt awareness of underlying assumptions? And by extension: Would people experience this to benefit their communication?" To answer this question a dialogical workshop with four participants was conducted in the business environment. The project utilized a qualitative methodology, and data was gathered by the use of semi-structured interviews with the four participants’ from the workshop. Data from these interviews were analyzed by using the constant comparative method, which led to the categories "views on communication", "impact", "the workshop" and "time". The discussion of these categories are mainly grounded in the ideas of David Bohm, which is supported and extended by amongst Chris Argyris, Thomas Jordan, Jack Mezirow and Michael Poutiane. Findings in this suggest dialogue to hold the potential of being a leverage to prompt awareness of underlying assumptions, while also proposing that more extensive research is needed to say something substantial on how this impact peoples communication. Based on the findings there is also presented a model of how such processes plays out.

The development of a quantitative phase microscope (QPM) has allowed the ability to acquire real-time phase movies of biological processes. The image processing of the data is critical to the system's ability to measure relative changes. The phase data must be consistent throughout a measurement and background fluctuations must be minimized. The research presented in this work discusses methods to effectively process sequences of phase data such that it can be used to quantify changes within real-time studies of living cells. This work begins by exploring two-dimensional phase unwrapping to determine the most effective ways to estimate the measured phase surface. Conventional methods of comparing unwrapping performance will be used. In addition, a novel method will be introduced that can characterize accuracy using continuity of derivatives. It will be shown that the most accurate phase estimates are made using modulation data with quality-guided phase unwrapping. After two-dimensionally unwrapping all frames of data within a measurement, there are background fluctuations due to residual surface shape as well as mean phase value fluctuations. Traditionally, manual background removal methods are implemented. Due to the large streams of data that need to be analyzed for the QPM, an automated background removal method is introduced that automatically discriminates the background from features of interest and characterizes and removes the background shape from all frames within a sequence of data. No user intervention is required and the performance rivals manual methods. The final step in processing data from a QPM is to ensure consistent phase unwrapping over an entire dataset. This is a previously undiscussed topic within the field of quantitative phase microscopy. The two-dimensional phase unwrapping methods result in reasonable phase estimates of the measured sample however there are often inconsistencies in local regions amongst sequential frames of data. This work introduces a new method, Smart Temporal unwrapping that minimizes temporal inconsistencies. The image processing methods presented in this work combine to allow phase data acquired using a QPM to quantify relative changes in biological samples. These processing steps effectively minimize errors due to system vibration, residual measurement aberration, and phase unwrapping inconsistencies.

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Mecânica, Florianópolis, 2014.
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O correto funcionamento de tubulações subterrâneas para o transporte de gás e petróleo depende de um monitoramento frequente e correto dos estados de tensões. Avanços recentes na medição de tensões residuais têm aplicado métodos ópticos em conjunto com o alívio de tensões de maneira a avaliar o campo de tensões no componente. Estes métodos requerem uma etapa de remoção do salto de fase para interpretar corretamente os dados adquiridos. Esta remoção do salto de fase tem sido um desafio para diversas aplicações metrológicas. Este trabalho tem por objetivo propor uma abordagem original para a solução deste problema. Neste trabalho é apresentado o algoritmo proposto assim como diversos resultados com diferentes imagens comparados com métodos consagrados.A luz, comportando-se como onda, obedece ao princípio de superposição que por sua vez dá lugar ao fenômeno de interferência. Este fenômeno pode ser utilizado de diversas maneiras para a medição de superfícies e formas geométricas. No entanto, várias dessas aplicações, como interferometria speckle e shearografia, fornecem os valores de interesse restringidos a um intervalo de ?p a p. Assim, faz-se necessária uma operação para retomar os valores reais que produziram o resultado obtido. Esta operação é chamada de remoção do salto de fase.Por décadas tem-se estudado diversas técnicas para realizar a remoção do salto de fase. Elas podem ser divididas em duas categorias principais: métodos que seguem caminhos e métodos independente de caminhos. Métodos que seguem caminhos aplicam uma simples equação de comparação e adição de múltiplos de 2p por toda a imagem. Elas diferem nos caminhos de pixels escolhidos. Para que o resultado seja confiável, é necessário que esse caminho evite pixels de baixa qualidade ou corrompidos. As técnicas de branch-cut identificam esses pixels através da teoria de resíduos e conectando resíduos de sinais opostos, ela é capaz de traçar caminhos confiáveis para a remoção do salto de fase. Técnicas baseadas em qualidade atribuem notas relativas a diferentes critérios de qualidade para cada pixel, excluindo da análise aqueles que se encontram abaixo de um limiar arbitrário.Técnicas independentes de caminhos, como os métodos de norma mínima, assemelham-se a métodos de otimização. Estes são iterativos e procuram por um mínimo na diferença entre as derivadas da solução proposta e as derivadas da imagem original. Estes métodos são considerados bastante robustos e confiáveis. No entanto, estes tambémdemandam maior tempo de processamento para encontrar a resposta correta.Em paralelo aos desenvolvimentos na área de remoção do salto de fase, cientistas têm desenvolvido técnicas computacionais baseadas no comportamento de animais sociais. O campo de Inteligência de Enxame é inspirado por insetos como formigas, abelhas e cupins e outros animais como peixes e pássaros. Estes animais têm em comum o fato de criarem sistemas organizados embora compostos de elementos simples e a ausência de uma liderança clara. O comportamento de formigas e abelhas na busca por comida e os movimentos em grupo de peixes e pássaros são os exemplos mais claros do conceito de comportamento emergente: um comportamento que, embora não explícito na descrição de seus elementos individuais, surge com a interação entre diversos desses elementos. Este comportamento emergente pode ser explicado em termos de agentes simples e independentes, regras simples e um comportamento descentralizado.Este fenômeno tem inspirado as ciências da computação por décadas. Diversas soluções computacionais para problemas matemáticos ou operacionais têm sido propostas a partir das soluções elegantes encontradas na natureza. Exemplos dessas soluções são os algoritmos de otimização baseados no comportamento de formigas e abelhas. No entanto, pouco deste conceito tem sido aplicado na área de processamento de imagem. Quanto ao problema de remoção do salto de fase, mais especificamente, não foi encontrado nenhum trabalho que propusesse uma solução baseada em Inteligência de Enxame.Assim, o presente trabalho propõe uma solução baseada nestes conceitos. Por causa da natureza imprevisível do comportamento emergente, o desenvolvimento do algoritmo proposto foi pouco convencional. Em primeiro lugar, foi necessário o desenvolvimento de um ambiente de testes onde o enxame pudesse ser observado em tempo real durante a sua operação. Em segundo lugar, a criação do algoritmo se deu de maneira iterativa até que fosse encontrado um conjunto de regras satisfatório.Uma primeira solução foi encontrada modelando os agentes como máquinas de estados finitos. Este modelo de agente foi implementado com dinâmicas de comunicação indireta através de estigmergia e comunicação direta em casos de necessidade. Este método, apesar de ter apresentado bons resultados em termos de qualidade da remoção do salto de fase, necessitava ainda de um critério de parada independente do usuário. Na criação deste critério de parada, novas regras deram espaço para a criação de um algoritmo completamente diferente.Esta segunda solução modela o agente a partir de cinco regras simples que permitem, entre outras coisas, a criação e desativação de novos agentes. Uma vez que todos os agentes são desativados, o programa chega ao fim e retorna a imagem com o salto de fase removido. A primeira destas regras afirma que se há um ou mais pixels que podem ter seu salto removido na vizinhança do agente, um deles será escolhido aleatoriamente para a operação. O agente então se move para o pixel escolhido e ganha um ponto de energia. Se não há pixels aptos a serem trabalhados, um pixel já trabalhado na vizinhança é escolhido aleatoriamente, de acordo com a segunda regra. O agente se move para o pixel escolhido e perde um ponto de energia. A terceira regra faz com que agentes que encontram dois pixels vizinhos já trabalhados mas inconsistentes entre si, marcarem estes pixels como defeituosos e desativarem-se. As duas últimas regras fazem com que agentes com energia excedente repliquem-se e aqueles sem energia desativem-se.O comportamento esperado é que os agentes de distribuam pela imagem de maneira eficiente, aproveitando ao máximo os ciclos de processamento. Além disso, a regra de marcação de remoções duvidosas faz com que problemas de ambiguidade na remoção do salto de fase não sejam propagados por grandes regiões da imagem. Este algoritmo foi testado em diversas condições e comparado com outros métodos estabelecidos.Os primeiros resultados foram gerados aplicando-se o enxame em imagens sintéticas sem quaisquer erros. Assim, foi possível avaliar a influência de diferentes parâmetros escolhidos pelo usuário no comportamento do enxame e qualidade dos resultados. Foi possível observar o impacto dos parâmetros de energia na densidade do enxame que, por sua vez, é importante para a correção de ambiguidades propagadas.Em seguida, foram testadas imagens sintéticas com erros artificiais. Os resultados foram comparados com um algoritmo baseado em qualidade e um algoritmo de norma mínima. Foi observado que o algoritmo proposto foi extremamente capaz de contornar as dificuldades das imagens de maneira, produzindo resultados confiáveis. Para certas condições, os resultados foram ainda melhores que os obtidos pelo outro algoritmo baseado em qualidade.Foram testadas ainda imagens provenientes de aplicações metrológicas reais: projeção de franjas, interferometria speckle e shearografia. Os resultados obtidos pelo algoritmo baseado em Inteligência de Enxame foram bastante satisfatórios, comparáveis aos métodos mais robustos. Ainda, o algoritmo proposto apresentou melhoresresultados para imagens muito ruidosas quando comparado com o outro algoritmo baseado em qualidade testado. Estes resultados atestam do potencial do método proposto em obter resultados rápidos e confiáveis.Por fim, este trabalho foi concluído com um breve resumo destes resultados e a validação dos objetivos originais, afirmando assim o sucesso do método proposto. Foram listadas ainda algumas sugestões para avanços futuros como os testes com imagens e parâmetros de qualidade novos, a implementação de processamento paralelo e a criação de novas abordagens baseadas em Inteligência de Enxame para a solução deste problema e outros semelhantes.

Abstract : The proper functioning of underground oil and gas pipelines depend on the frequent and correct monitoring of stress states. Recent developments on residual stress measurement techniques have employed optical methods allied with stress relief in order to assess the underlying stress field. These optical methods require a phase unwrapping step to interpret the acquired data correctly. Phase unwrapping has posed a challenge for many optical metrology applications for decades and saw the development of many different solutions. For the past decades, the field of Swarm Intelligence, based on the behavior observed among ants, bees and other social insects, has been studied and many algorithms have been designed to perform a variety of computational tasks. Swarm Intelligence is commonly regarded as robust and fast, which are desirable features in a phase unwrapping algorithm. This work proposes a novel approach to phase unwrapping based on Swarm Intelligence, assessing its applicability, comparing it to existing methods and evaluating its potential to future developments. The proposed algorithm is thoroughly explained and the results for several different images are presented. These results show a great potential of the proposed method, performing better than some established techniques in specific situations. This potential is assessed and suggestion for future advancements are given.

Thesis (M.A.)--Wake Forest University. Dept. of Communication, 2008.
Title from electronic thesis title page. Thesis advisor: Mary M. Dalton. Vita. Includes bibliographical references (p. 102-108).

This thesis describes a new technique, absolute distance contouring, and a phase unwrapping algorithm for phase maps with discontinuities. Absolute distance contouring, which is based on the shadow moire method, using the rotation of a grating, is a technique which can be used for the measurement of absolute distance from the grating to the object and the determination of an object's height. By the selection of suitable rotation angles, images are captured at different positions of the grating to obtain the required data. The technique is divided into three different methods, according to the number of images required for each measurement and the rotation angles. These are known as: the absolute distance contouring method, the four-image method, and the three-image method. Using these methods, the three-dimensional shape of the object can be obtained directly and it is not necessary to determine the absolute moire fringe order nor to judge the hills and valleys of the object's surface. Some of the problems of the previous shadow moire methods can be solved and some inconvenience can be overcome by the proposed methods. The techniques have been verified by experimental work which was carried out on a specially designed system. The results show that the methods are fast and the accuracy is better than 10μm. The maximum measurable range is related to the geometry of the optical system and the rotation angles. The phase unwrapping algorithm is a technique to obtain the correct phase distribution for a phase map with discontinuities. A crossed grating, which has two sets of lines in two different directions, is projected onto the surface to be measured. The modulated grating image, which is equal to the superposition of two separate modulated images, is captured and Fourier transformed. The two images are separated in the Fourier domain. After filtering and frequency shifting, they are inverse transformed to obtain two phase maps with different precisions. Phase unwrapping at each pixel is carried out independently and the correct phase values can be obtained in the presence of discontinuities caused by a surface with steps or noise. This fast algorithm has been verified experimentally by measuring the shapes of objects with height steps, and it only requires a single image for each measurement. The methods of absolute distance contouring and the new phase unwrapping algorithm are new techniques for the measurement of three-dimensional object profile, which will find application in many areas.

This thesis regards the method of full field time-of-flight depth imaging by way of amplitude modulated continuous wave signals correlated with step-shifted reference waveforms using a specialized solid state CMOS sensor, referred to as photonic mixing device. The specific focus deals with the inherent issue of depth ambiguity due to a fundamental property of periodic signals: that they repeat, or wrap, after each period, and any signal shifted by a whole number of wavelengths is indistinguishable from the original. Recovering the full extent of the signal’s path is known as phase unwrapping. The common, accepted solution requires the imaging of a series of two or more signals with differing modulation frequencies to resolve the ambiguity, the time delay of which will result in erroneous or invalid measurements for non-static elements of the scene. This work details a physical model of the observable illumination of the scene which provides priors for a novel probabilistic framework to recover the scene geometry by imaging only a single modulated signal. It is demonstrated that this process is able to provide more than adequate results in a majority of representative scenes, and that it can be accomplished on typical computer hardware at a speed that allows for the range imaging to be utilized in real-time, interactive applications.

One such real-time application is presented: alpha-matting, or foreground segmentation, for background substitution of live video. This is a generalized version of the common technique of green-screening that is utilized, for example, by every local weather reporter. The presented method, however, requires no special background, and is able to perform on high resolution video from a lower resolution depth image.

The notion of tapu in eighteenth century Polynesia was all-pervasive: a system of fluid boundaries and thresholds in the landscape pertaining to islands, bodies and objects. The thesis aims to isolate a body of Austral god images from within the London Missionary Society collection and think through this corpus in terms of its materiality - complex assemblages of whalebone and ivory, wood, feathers, hair, tapa and sinnet bindings. Approaching these god images as tapu vessels which trap potency and confer mana, an analysis oftheir assembly and use by ritual' experts or tahu 'a, allows us to explore the way in which they were specifically designed to breach thresholds during ritual procedure. The collection is also significant as amaterial index of the dramatic sociopolitical and cultural shifts which followed the establishment of the London Missionary Society in the region. Critical analysis of missionary sources within the archive allows us to recover aspects of the complex encounters between islanders and missionaries which were often fraught, tense and certainly volatile. Details ofthe acquisition of these god images by London missionaries in the first two decades ofthe nineteenth century allows us to reconfigure the parameters of a series of accepted assumptions about idolatry and iconoclasm in central Polynesia and contests the notion that the conversion of the Austral Islands in particular was a straightforward transition to Christianity. Having established a set ofhistorical and contemporary frameworks for understanding these objects, the thesis finally explores the series of distinct thresholds through which these objects have moved since they were collected and sent to England and thinks about how contemporary display can be used as a critical means of recovery. In this way objects, their histories and display become a means ofre-addressing the missionary encounter in all its rich complexity allowing us to re-assess its resonance for Polynesians and Europeans today.

Noise, vibration and harshness (NVH)levels in the luxury automotive industry are used by customers as a subjective method of determining the vehicle quality. This can be achieved by adjusting the vehicle design, where simulations are used to predict the NVH behaviour. Changes can be expensive and time consuming when made after the design stage has been completed, so it is important to produce accurate simulations of the product. Variability exists to some extent in all products, even those just off the production line, however, if a high level of variability exists then only a small portion of products will meet the predicted behaviour. The aim of the project is to provide information that may lead to the reduction of variability in an automotive vehicle. This is achieved by quantifying the statistical spread of FRFs (frequency response function) in a set of nominally identical vehicles. Once overall levels have been calculated, the location of the most variable sources can be identified. Project also seeks to develop new methods of analysis for the system phase response to determine whether further information may be extracted compared to the magnitude response. There are three main themes that run throughout this thesis, with the first being the quantification of variability due to the measurement taking process which is covered in chapter 3. A novel application of a method to separate the measurement variability from the overall system uncertainty was achieved as well as the quantification of the vehicle to- vehicle variability. The second theme that runs through the study concerns the identification of variability sources. This is realised in chapter 4 and chapter 6 as a set of structural and acoustic tests on a luxury sedan door. The trim was found to be held to the door panel by a series of 11 polymer clips and 4 metal screws. The variability of small changes to a significant boundary condition at the door trim was quantified, showing that the removal of rigid clips had a more significant effect on the overall variability that if a loose clip has been removed. It was also found that clips at the corners were the most sensitive to change. The final theme outlines and tests new analysis methods on the phase and compares the statistical spread of the phase with the equivalent spread of the magnitude. Data taken from the same tests was used and for most of the cases the two results were found to be approximately the same.

This thesis is concerned with (a) the development of full-field, multi-axis and phase contrast wavelength scanning interferometer, using an electronically tuned CW Ti:Sa laser for the study of depth resolved measurements in composite materials such as GFRPs and (b) the development of temporal phase unwrapping algorithms for depth re-solved measurements. Item (a) was part of the ultimate goal of successfully extracting the 3-D, depth-resolved, constituent parameters (Young s modulus E, Poisson s ratio v etc.) that define the mechanical behaviour of composite materials like GFRPs. Considering the success of OCT as an imaging modality, a wavelength scanning interferometer (WSI) capable of imaging the intensity AND the phase of the interference signal was proposed as the preferred technique to provide the volumetric displacement/strain fields (Note that displacement/strain fields are analogous to phase fields and thus a phase-contrast interferometer is of particular interest in this case). These would then be passed to the VFM and yield the sought parameters provided the loading scheme is known. As a result, a number of key opto-mechanical hardware was developed. First, a multiple channel (x6) tomographic interferometer realised in a Mach-Zehnder arrangement was built. Each of the three channels would provide the necessary information to extract the three orthogonal displacement/strain components while the other three are complementary and were included in the design in order to maximize the penetration depth (sample illuminated from both sides). Second, a miniature uniaxial (tensile and/or compression) loading machine was designed and built for the introduction of controlled and low magnitude displacements. Last, a rotation stage for the experimental determination of the sensitivity vectors and the re-registration of the volumetric data from the six channels was also designed and built. Unfortunately, due to the critical failure of the Ti:Sa laser data collection using the last two items was not possible. However, preliminary results at a single wavelength suggested that the above items work as expected. Item (b) involved the development of an optical sensor for the dynamic monitoring of wavenumber changes during a full 100 nm scan. The sensor is comprised of a set of four wedges in a Fizeau interferometer setup that became part of the multi-axis interferometer (7th channel). Its development became relevant due to the large amount of mode-hops present during a full scan of the Ti:Sa source. These are associated to the physics of the laser and have the undesirable effect of randomising the signal and thus preventing successful depth reconstructions. The multi-wedge sensor was designed so that it provides simultaneously high wavenumber change resolution and immunity to the large wavenumber jumps from the Ti:Sa. The analysis algorithms for the extraction of the sought wavenumber changes were based on 2-D Fourier transform method followed by temporal phase unwrapping. At first, the performance of the sensor was tested against that of a high-end commercial wavemeter for a limited scan of 1nm. A root mean square (rms) difference in measured wavenumber shift between the two of ~4 m-1 has been achieved, equivalent to an rms wavelength shift error of ~0.4 pm. Second, by resampling the interference signal and the wavenumber-change axis onto a uniformly sampled k-space, depth resolutions that are close to the theoretical limits were achieved for scans of up to 37 nm. Access of the full 100 nm range that is characterised by wavelength steps down to picometers level was achieved by introducing a number of improvements to the original temporal phase unwrapping algorithm reported in ref [1] tailored to depth resolved measurements. These involved the estimation and suppression of intensity background artefacts, improvements on the 2-D Fourier transform phase detection based on a previously developed algorithm in ref [2] and finally the introduction of two modifications to the original TPU. Both approaches are adaptive and involve signal re-referencing at regular intervals throughout the scan. Their purpose is to compensate for systematic and non-systematic errors owing to a small error in the value of R (a scaling factor applied to the lower sensitivity wedge phase-change signal used to unwrap the higher sensitivity one), or small changes in R with wavelength due to the possibility of a mismatch in the refractive dispersion curves of the wedges and/or a mismatch in the wedge angles. A hybrid approach combining both methods was proposed and used to analyse the data from each of the four wedges. It was found to give the most robust results of all the techniques considered, with a clear Fourier peak at the expected frequency, with significantly reduced spectral artefacts and identical depth resolutions for all four wedges of 2.2 μm measured at FWHM. The ability of the phase unwrapping strategy in resolving the aforementioned issues was demonstrated by successfully measuring the absolute thickness of four fused silica glasses using real experimental data. The results were compared with independent micrometer measurements and showed excellent agreement. Finally, due to the lack of additional experimental data and in an attempt to justify the validity of the proposed temporal phase unwrapping strategy termed as the hybrid approach, a set of simulations that closely matched the parameters characterising the real experimental data set analysed were produced and were subsequently analysed. The results of this final test justify that the various fixes included in the hybrid approach have not evolved to solve the problems of a particular data set but are rather of general nature thereby, highlighting its importance for PC-WSI applications concerning the processing and analysis of large scans.

Three-dimensional reconstruction of small objects has been one of the most challenging problems over the last decade. Computer graphics researchers and photography professionals have been working on improving 3D reconstruction algorithms to fit the high demands of various real life applications. In this thesis, we implemented a 3D scanner system based on fringe projection method. Two different methods have been implemented and used as the unwrapping solution in fringe projection method. A parameterization tool has been created in order to generate different fringe patterns for distinctive needs in the fringe projection method. Considering our first practical implementation (based on phase shifting and multi wavelength techniques) the number of pictures used in phase shifting method has been decreased and the effects of reducing the fringe patterns on the level of precision of the 3D model have been investigated. Optical arrangement and calibration of the system (fringe projection method) have been studied, and numerous suggestions have been proposed to improve the precision of the system. Also, an evaluation method has been implemented based on calibration techniques. The error rate on both surface and height of the 3D model compare with the object has been calculated.

In the history of intercultural relationships, no country has exercised so great an influence on the English geographical imagination as Russia. From its humble beginnings as the kingdom of Muscovy, to the sprawling expanse of the U.S.S.R., Winston Chruchill’s famous “riddle, wrapped in a mystery, inside an enigma” both captivated and repulsed English audiences. Cartographically split between Europe and Asia, the ambiguous nature of Russian culture not only undermined absolute “Orientalist” binaries separating East from West, but also contributed, through the epoch-making fin de siècle influx of Slavic aesthetic forms, to the birth of English modernism. The idea of “Russianess,” for pre-war audiences, proved crucial to unsettling received notions of art, ideology, and identity. This destabilizing effect is especially evident in the work of Wyndham Lewis, T.S. Eliot, and D.H. Lawrence. Despite having largely been dismissed as “reactionary” and “xenophobic” in their political stances, the complex and variegated way in which each author engages with Russia, as this study demonstrates, suggests an underlying ambivalence in their writing. Rather than reflecting a geographic reality, Slavic society, in their hands, appears as a collective fantasy, an external manifestation of their own internal doubts, anxieties, and pre-occupations concerning “Englishness,” which serves to elucidate the conflicted and uncertain politics of twentieth-century avant-garde art.

Orientador: Cláudio Kitano
Banca: Ricardo Tokio Higuti
Banca: Ronny Calixto Carbonari
Resumo: Interferômetros ópticos de saída única são muito sensíveis quando operam nas proximidades do ponto de quadratura de fase da sua curva característica de entrada e saída. Entretanto, as flutuações ambientais de baixa frequência produzem derivas aleatórias entre os caminhos ópticos do interferômetro que desviam o ponto quiescente da quadratura, levando ao fenômeno de desvanecimento de sinal. Através de processamento eletrônico de dois sinais interferométricos de saída, defasados a 90º entre si, consegue-se demodular o sinal independentemente das derivas ambientais. Esses interferômetros chamados de interferômetros de quadratura são amplamente utilizados em laboratórios de metrologia, porém, devido à grande quantidade de componentes ópticos normalmente envolvidos, são de difícil alinhamento e de elevado custo. Neste trabalho estuda-se a interferometria homódina de dois feixes em quadratura e as suas complexidades inerentes. Propõe-se uma nova arquitetura, baseada na configuração de Michelson, de alinhamento mais simples e de baixo custo. Descreve-se matematicamente o processo de obtenção dos sinais em quadratura deste arranjo. Também, se explora uma técnica capaz de obter dois sinais interferométricos em quadratura através da configuração tradicional de Michelson explorando-se a distribuição espacial do padrão de franjas. Desenvolve-se, ainda, um novo algoritmo de phase unwrapping aplicável como método de detecção de fase óptica, capaz de reconstruir a forma de onda de sinais de modulação e fornecer a diferença de fase estática entre os braços do interferômetro, quando o sinal de modulação possui valor médio nulo. Testes computacionais são realizados para corroborar na tarefa de evidenciar o potencial da técnica. Por meio do método de demodulação apresentado, em adição com o interferômetro proposto e da técnica explorada, realiza-se testes experimentais em um atuador piezoelétrico...
Abstract: Optical interferometers with single outputs are very sensitive when operating close to the phase quadrature point of their input-output characteristic curves. However, low frequency environmental fluctuations generate random drifts between the optical paths of the interferometer that deviate the quiescent point from the quadrature condition. This problem causes the phenomenon called signal fading. By electronically processing these two interferometry output signals, shifted by 90º, it is possible to demodulate the signal regardless of environmental drift. These kinds of interferometers, known as quadrature interferometers, are widely used in metrology laboratories, but, due to the large amount of optical components, they are expensive and difficult to design. In this work a low cost homodyne interferometer with two output quadrature beams based on the Michelson configuration is studied, and the procedure to achieve the quadrature signals is mathematically described. Also, a recent technique, not widely known in the literature and that is able to obtain two quadrature signals by using the standard configuration of the Michelson interferometer is explored, exploiting the spatial distribution of the fringe pattern. A new method for optical phase shift demodulation based on phase unwrapping is developed. This approach is able to recover not only the modulation signal waveform, but can also calculate the static phase shift between the interferometer arms when the modulation signal has an average value equal to zero. The method also has the ability to demodulate signals which vary arbitrarily in time. Computational test were done aiming to demonstrate the technique potential. By using this new optical phase shift demodulation method, combined with the proposed interferometer and exploiting the spatial distribution of the fringe pattern, a piezoelectric flextensional actuator is characterized. Displacement versus drive voltage and frequency ...
Mestre

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Interferômetros ópticos de saída única são muito sensíveis quando operam nas proximidades do ponto de quadratura de fase da sua curva característica de entrada e saída. Entretanto, as flutuações ambientais de baixa frequência produzem derivas aleatórias entre os caminhos ópticos do interferômetro que desviam o ponto quiescente da quadratura, levando ao fenômeno de desvanecimento de sinal. Através de processamento eletrônico de dois sinais interferométricos de saída, defasados a 90º entre si, consegue-se demodular o sinal independentemente das derivas ambientais. Esses interferômetros chamados de interferômetros de quadratura são amplamente utilizados em laboratórios de metrologia, porém, devido à grande quantidade de componentes ópticos normalmente envolvidos, são de difícil alinhamento e de elevado custo. Neste trabalho estuda-se a interferometria homódina de dois feixes em quadratura e as suas complexidades inerentes. Propõe-se uma nova arquitetura, baseada na configuração de Michelson, de alinhamento mais simples e de baixo custo. Descreve-se matematicamente o processo de obtenção dos sinais em quadratura deste arranjo. Também, se explora uma técnica capaz de obter dois sinais interferométricos em quadratura através da configuração tradicional de Michelson explorando-se a distribuição espacial do padrão de franjas. Desenvolve-se, ainda, um novo algoritmo de phase unwrapping aplicável como método de detecção de fase óptica, capaz de reconstruir a forma de onda de sinais de modulação e fornecer a diferença de fase estática entre os braços do interferômetro, quando o sinal de modulação possui valor médio nulo. Testes computacionais são realizados para corroborar na tarefa de evidenciar o potencial da técnica. Por meio do método de demodulação apresentado, em adição com o interferômetro proposto e da técnica explorada, realiza-se testes experimentais em um atuador piezoelétrico ...
Optical interferometers with single outputs are very sensitive when operating close to the phase quadrature point of their input-output characteristic curves. However, low frequency environmental fluctuations generate random drifts between the optical paths of the interferometer that deviate the quiescent point from the quadrature condition. This problem causes the phenomenon called signal fading. By electronically processing these two interferometry output signals, shifted by 90º, it is possible to demodulate the signal regardless of environmental drift. These kinds of interferometers, known as quadrature interferometers, are widely used in metrology laboratories, but, due to the large amount of optical components, they are expensive and difficult to design. In this work a low cost homodyne interferometer with two output quadrature beams based on the Michelson configuration is studied, and the procedure to achieve the quadrature signals is mathematically described. Also, a recent technique, not widely known in the literature and that is able to obtain two quadrature signals by using the standard configuration of the Michelson interferometer is explored, exploiting the spatial distribution of the fringe pattern. A new method for optical phase shift demodulation based on phase unwrapping is developed. This approach is able to recover not only the modulation signal waveform, but can also calculate the static phase shift between the interferometer arms when the modulation signal has an average value equal to zero. The method also has the ability to demodulate signals which vary arbitrarily in time. Computational test were done aiming to demonstrate the technique potential. By using this new optical phase shift demodulation method, combined with the proposed interferometer and exploiting the spatial distribution of the fringe pattern, a piezoelectric flextensional actuator is characterized. Displacement versus drive voltage and frequency ...

Time series analysis of Synthetic Aperture Radar Interferometry (InSAR) data has become an important scientific tool for monitoring and measuring the displacement of Earth’s surface due to a wide range of phenomena, including earthquakes, volcanoes,landslides, changes in ground water levels, and wetlands. Time series analysis is a product of interferometric phase measurements, which become ambiguous when the observed motion is larger than half of the radar wavelength. Thus, phase observations must first be unwrapped in order to obtain physically meaningful results. Persistent Scatterer Interferometry (PSI), Stanford Method for Persistent Scatterers (StaMPS), Short Baselines Interferometry (SBAS) and Small Temporal Baseline Subset (STBAS)algorithms solve for this ambiguity using a series of spatio-temporal unwrapping algorithms and filters. In this dissertation, I improve upon current phase unwrapping algorithms, and apply the PSI method to study subsidence in Mexico City. PSI was used to obtain unwrapped deformation rates in Mexico City (Chapter 3),where ground water withdrawal in excess of natural recharge causes subsurface, clay-rich sediments to compact. This study is based on 23 satellite SAR scenes acquired between January 2004 and July 2006. Time series analysis of the data reveals a maximum line-of-sight subsidence rate of 300mm/yr at a high enough resolution that individual subsidence rates for large buildings can be determined. Differential motion and related structural damage along an elevated metro rail was evident from the results. Comparison of PSI subsidence rates with data from permanent GPS stations indicate root mean square(RMS) agreement of 6.9 mm/yr, about the level expected based on joint data uncertainty.The Mexico City results suggest negligible recharge, implying continuing degradation and loss of the aquifer in the third largest metropolitan area in the world. Chapters 4 and 5 illustrate the link between time series analysis and three-dimensional (3-D) phase unwrapping. Chapter 4 focuses on the unwrapping path.Unwrapping algorithms can be divided into two groups, path-dependent and path-independent algorithms. Path-dependent algorithms use local unwrapping functions applied pixel-by-pixel to the dataset. In contrast, path-independent algorithms use global optimization methods such as least squares, and return a unique solution. However, when aliasing and noise are present, path-independent algorithms can underestimate the signal in some areas due to global fitting criteria. Path-dependent algorithms do not underestimate the signal, but, as the name implies, the unwrapping path can affect the result. Comparison between existing path algorithms and a newly developed algorithm based on Fisher information theory was conducted. Results indicate that Fisher information theory does indeed produce lower misfit results for most tested cases. Chapter 5 presents a new time series analysis method based on 3-D unwrapping of SAR data using extended Kalman filters. Existing methods for time series generation using InSAR data employ special filters to combine two-dimensional (2-D) spatial unwrapping with one-dimensional (1-D) temporal unwrapping results. The new method,however, combines observations in azimuth, range and time for repeat pass interferometry. Due to the pixel-by-pixel characteristic of the filter, the unwrapping path is selected based on a quality map. This unwrapping algorithm is the first application of extended Kalman filters to the 3-D unwrapping problem. Time series analyses of InSAR data are used in a variety of applications with different characteristics. Consequently, it is difficult to develop a single algorithm that can provide optimal results in all cases, given that different algorithms possess a unique set of strengths and weaknesses. Nonetheless, filter-based unwrapping algorithms such as the one presented in this dissertation have the capability of joining multiple observations into a uniform solution, which is becoming an important feature with continuously growing datasets.

Modern optical measurement techniques have  developed rapidly in recent years. One of the  measurement technologies  is polarization interferometry that can be used  for roughness evaluation, deformation measurement,  and vibration analysis of objects. based on LabVIEW and MATLAB, this project  introduces the technique of virtual  instruments into the field of modern optical  measurements. The optical phase images  have been captured by LabVIEW and processed  by MATLAB to acquire the surface structures. The main research work in the project involves:  (1) Introduction of the virtual instrument  technique to capture and process optical phase  images; (2) Processing of phase  images acquired with different wavelengths using  MATLAB to reveal show the 2D and 3D  surface structures.

"3D shape measurements are critical in a range of fields, from manufacturing for quality measurements to art conservation for the everlasting archival of ancient sculptures. The most important factor is to gather quantitative 3D information from measurement devices. Currently, there are limitations of existing systems. Many of the techniques are contact methods, proving to be time consuming and invasive to materials. While non-contact methods provide opportunities, many of the current systems are limited in versatility. This project focuses on the development of a fringe projection based system for 3D shape measurements. The critical advantage of the fringe projection optical technique is the ability to provide full field-of-view (FOV) information on the order from several square millimeters to several square meters. In the past, limitations in speed and difficulties achieving sinusoidal projection patterns have restricted the development of this particular type of system and limited its potential applications. For this reason, direct coding techniques have been incorporated to the developed system that modulate the intensity of each pixel to form a sinusoidal pattern using a 624 nm wavelength MEMS based spatial light modulator. Recovered phase data containing shape information is obtained using varying algorithms that range from a single image FFT analysis to a sixteen image, phase stepping algorithm. Reconstruction of 3D information is achievable through several image unwrapping techniques. The first is a spatial unwrapping technique for high speed applications. Additionally, the system uses an optimized Temporal Phase Unwrapping (TPU) algorithm that utilizes varying fringe frequencies ranging from 4 to 512 pixels per fringe to recover shape information in the time domain. This algorithm was chosen based on its robustness and accuracy for high resolution applications [Burke et al., 2002]. Also, unwrapping errors are minimized by approximately 90% as the number of images used is increased from the minimum to maximum fringe density. Cxoontrary to other systems, the 3D shape measurement system developed in the CHSLT laboratories has unprecedented versatility to accommodate a variety of applications with the z-depth resolution of up to 25.4 µm (0.001 inches) and speeds close to 200 frames per second. Hardware systems are integrated into user-friendly software that has been customized for fringe projection. The system has been tested in two extreme environments. The first is for quantification of cracks and potholes in the surface of roads under dynamic conditions. The second application was digitization of an art sculpture under static conditions. The system shows promising results and the potential for high quality images via algorithm optimization. Most importantly, there is potential to present real time 3D information at video speeds."

This thesis deals with the development of the user interface for the application of the method Phase shifting profilometry. First deals with the theoretical approach of this method, and describes the process of image segmentation and data processing using morphological operations. In the practical part of the user interface is designed for acquiring and processing data received in Matlab.

This paper deals with the chemical identification of artefacts correlated with the process of ancient Egyptian mummification dating to the Graeco-Roman period. The samples were harvested from two artefacts belonging to the Museum of Mediterranean and Near Eastern Antiquities in Stockholm. The original description of the said samples defined them, as natron filled linen bags and bee product (honey?). To identify the true nature of the samples, advanced methods such as Fourier transform infrared spectrometry (FTIR), gas chromatography/mass spectrometry and powder X-ray Diffractometry were used. The results were correlated with previous made analyses regarding embalming materials to discover similarities. Furthermore, the research revealed that the previous sample identifications were false, while providing hypotheses based on the new results.

L’olografia può essere pensata come un metodo di imaging tridimensionale, che non richiede un contatto con l’oggetto della misura e permette di delinearne il profilo nello spazio. La tecnica dell’olografia fuori asse è presentata nel quadro della teoria della comunicazione e del processamento ottico dell’informazione. Essa permette di risolvere il problema del disturbo portato dalla sovrapposizione dell’ordine zero di diffrazione e delle immagini gemelle. In questo modo, sarà possibile estrarre le informazioni della fase portate dall’oggetto per una sua ricostruzione nello spazio. Il metodo è basato sull’analisi nel dominio della frequenza delle frange di interferenza con l’implementazione in Matlab della trasformata di Fourier in due dimensioni. Matlab sarà anche lo strumento per la sintesi digitale degli ologrammi su cui verranno svolte le misure oppure per la ricostruzione di ologrammi digitali acquisiti in laboratorio con un sensore CCD. A tal proposito, vengono presentati alcuni algoritmi di unwrapping della fase. Questo tipo di algoritmi è molto usato negli ambiti più svariati, dai radar ad apertura sintetica alla tomografia a risonanza magnetica.

A method for measuring the thickness and surface profiles of soft contact lenses while submerged in a saline solution has been implemented utilizing a low coherence Twyman-Green Interferometer. Although the original measurements demonstrated that features on the contact lens surfaces could be accurately determined, it was believed that the layout of the system also induced surface profile distortions. A new opto-mechanical layout has been implemented which eliminates many of these low frequency distortions. Improvements to the original phase unwrapping algorithms have also been developed to overcome the low visibility output inherent to the measurement allowing for a more complete analysis of the two surfaces of a contact lens.

This qualitative study was designed to explore the experiences and perceptions of a group of mothers whose elementary school-aged children met the criteria for intellectual giftedness in an Ontario school board. Guided by Beach and Mitchell’s image theory and Bronfenbrenner’s ecological systems theory, the study sought to identify (a) the meanings mothers ascribed to the concept of giftedness, (b) their experiences of the assessment, identification and placement process, and (c) the factors deemed important to educational decision making. A postpositivist orientation and rigorous qualitative research methods were employed. Data were collected in two phases: an internet-based survey comprised of demographic items and open ended questions, followed by in-depth interviews with five purposefully selected participants. Resultant data from 45 surveys and 15 interviews were coded and organized according to the survey questions and central elements of the theoretical framework. Eight research findings revealed that the experience of mothering gifted children was complex, challenging, emotional, and at times, isolating. Many mothers struggled with the concept of giftedness and how it pertained to their children. As mothers navigated the assessment, identification and placement process, the lack of accessible, timely, and consistent information from the school board posed a considerable barrier, prompting many to reach out to other parents of gifted children for information and support. Factors deemed important to decision making about educational placement included maternal perceptions related to the various options, child specific and practical considerations, and the attainability of specialized gifted programming. Educational decision making was identified as the most difficult aspect of the maternal experience. Given that the study participants were unusually well educated and well resourced, the findings were particularly revealing. The study findings add to a small but growing body of research that furthers our understanding of image theory in real life decision making. In addition, the findings give voice to the experience of mothering children identified as gifted, thus making a valuable and original contribution to the literature.

A three-by-three polarization ray tracing matrix method is developed to calculate the polarization transformations associated with ray paths through optical systems. The relationship between the three-by-three polarization ray tracing matrix P method and the Jones calculus is shown in Chapter 2. The diattenuation, polarization dependent transmittance, is calculated via a singular value decomposition of the P matrix and presented in Chapter 3. In Chapter 4 the concept of retardance is critically analyzed for ray paths through optical systems. Algorithms are presented to separate the effects of retardance from geometric transformations. The parallel transport of vectors is associated with non-polarizing propagation through an optical system. A parallel transport matrix Q establishes a proper relationship between sets of local coordinates along the ray path, a sequence of ray segments. The proper retardance is calculated by removing this geometric transformation from the three-by-three polarization ray trace matrix. Polarization aberration is wavelength and spatial dependent polarization change that occurs as wavefrontspropagate through an optical system. Diattenuation and retardance of interfaces and anisotropic elements are common sources of polarizationaberrations. Two representations of polarization aberrationusing the Jones pupil and a polarization ray tracing matrix pupil, are presentedin Chapter 5. In Chapter 6 a new class of aberration, skew aberration is defined, as a component of polarization aberration. Skew aberration is an intrinsic rotation of polarization states due to the geometric transformation of local coordinates; skew aberration occurs independent of coatings and interface polarization. Skew aberration in a radially symmetric system primarily has the form of a tilt plus circular retardance coma aberration. Skew aberration causes an undesired polarization distribution in the exit pupil. A principal retardance is often defined within (-π, + π] range. In Chapter 7 an algorithm which calculates the principal retardance, horizontal retardance component, 45° retardance component, and circular retardance component for given retarder Jones matrices is presented. A concept of retarder space is introduced to understand apparent discontinuities in phase unwrapped retardance. Dispersion properties of retarders for polychromatic light is used to phase unwrap the principal retardance. Homogeneous and inhomogeneous compound retarder systems are analyzed and examples of multi-order retardance are calculated for thick birefringent plates. Mathematical description of the polarization properties of light and incoherent addition of light is presented in Chapter 8, using a coherence matrix. A three-by-three-by-three-by-three polarization ray tracing tensor method is defined in order to ray trace incoherent light through optical systems with depolarizing surfaces. The polarization ray tracing tensor relates the incident light’s three-by-three coherence matrix to the exiting light’s three-by-three coherence matrix. This tensor method is applicable to illumination systems and polarized stray light calculations where rays at an imaging surface pixel have optical path lengths which vary over many wavelengths. In Chapter 9 3D Stokes parameters are defined by expanding the coherence matrix with Gell-Mann matrices as a basis. The definition of nine-by-nine 3D Mueller matrix is presented. The 3D Mueller matrix relates the incident 3D Stokes parameters to the exiting 3D Stokes parameters. Both the polarization ray tracing tensor and 3D Mueller matrix are defined in global coordinates. In Chapter 10 a summary of my work and future work are presented followed by a conclusion.

The Ground-Based Synthetic Aperture Radar (GB-SAR) is a relatively new technique, which in the last ten years has gained interest as deformation measurement and monitoring tool. The GB-SAR technique is based on an imaging radar-based sensor, which o ers high sensitivity to small displacements, in the region of sub-millimetres to millimetres, long-range measurements, which can work up to some kilometres, and massive deformation measurement capability. These features confer to the GB-SAR technique interesting advantages with respect to other point-wise deformation measurement techniques. The process of estimating deformation from the GB-SAR data is not straightforward: it requires complex data processing and analysis tools. This dissertation is focused on these tools, covering the whole deformation estimation process. This thesis collects the main research results achieved on this topic during my work at the Active Remote Sensing Unit of the Institute of Geomatics. Two di erent approaches for measuring deformation with GB-SAR data are described and discussed. The irst one is the interferometric approach, based on the exploitation of the phase component of the GB-SAR data, which is the commonly used GB-SAR method. The second one is a non-interferometric approach, which exploits the amplitude component of the GB-SAR data, o ering an interesting alternative way to exploit the GB-SAR data. This dissertation has two main objectives. The first one is presenting, step by step, a complete interferometric GB-SAR procedure for deformation measuring and monitoring. The second one is presenting two new algorithms, which represent the most innovative part of this thesis. The first algorithm faces the phase unwrapping problem, providing an automatic solution for detecting and correcting unwrapping errors, which is called 2+1D phase unwrapping. The second algorithm is the base of the above mentioned non- interferometric approach, which overcomes some of the most critical limitation of GB-SAR interferometry, at the expense of getting less precise deformation estimates. The dissertation is divided in 6 chapters. The first one is the introduction, while the second one provides an overview of GB-SAR interferometry, introducing the main aspects that are the basics of the subsequent chapters. Chapter 3 describes a complete GB-SAR processing chain. Chapters 4 and 5 contain the most original part of the dissertation, i.e. the 2D+1 phase unwrapping algorithm, and the non-interferometric approach. Finally, in Chapter 6 the conclusions are discussed and further research is proposed.
El radar terrestre d’obertura sintètica (GB-SAR) és una tècnica relativament nova que, en els últims deu anys, ha guanyat interès com a eina per a mesurar i monitorar deformacions. La tècnica GB-SAR es basa en un sistema radar amb capacitat per proporcionar imatges, que ofereix una alta sensibilitat a petits desplaçaments, d’ordre mil·limètric o submil·limètric, que és capaç de mesurar a llargues distàncies (alguns km) i que té una alta capacitat per fer mesures massives. Aquestes característiques donen a la tècnica interessants avantatges respecte a altres tècniques clàssiques de mesura de deformacions, típicament basades en mesures puntuals. Derivar mesures de deformació a partir de dades GB-SAR no és un procés senzill, ja que requereix uns procediments complexos de processat i anàlisi de dades. Aquesta tesi es centra en aquests processos. Aquesta tesi recull alguns dels resultats més destacats de la investigació que he desenvolupat sobre aquest tema a la unitat de Teledetecció Activa de l'Institut de Geomàtica. Al llarg del document es descriuen dues aproximacions diferents per mesurar deformacions amb GB-SAR. Una es basa en la explotació de la tècnica de la interferometria, és a dir explotant la component de la fase de les imatges GB-SAR: és la tècnica GB-SAR usada habitualment. La segona, anomenada tècnica no-interferomètrica, es basa en la component de l’amplitud de les dades GB-SAR i ofereix una interessant alternativa a la primera. La tesi acompleix dos objectius principals. En primer lloc presenta un procediment complet per la mesura i monitoratge de deformacions mitjançant interferometria GB-SAR. En segon lloc, descriu dos nous algorismes que resolen problemes específics de la interferometria clàssica aplicada al GB-SAR i que representen la part més innovadora d’aquesta tesi. El primer algorisme aborda un dels problemes oberts de la interferometria, el phase unwrapping, proposant un mètode automàtic per detectar-ne i corregir-ne els errors. El segon algorisme proposa un nou mètode per a l'explotació de les dades GB-SAR per mesurar deformacions sense utilitzar la interferometria. La estructura de la tesi consisteix en sis capítols. Després de la introducció, el Capítol 2 proporciona una visió general de la interferometria GB-SAR, introduint els conceptes principals utilitzats en la tesi. En el tercer capítol es descriu una cadena de processament basada en GB-SAR interferomètric. Els capítols quart i cinquè contenen la part més original de la tesi: l'algorisme de phase unwrapping i el mètode no-interferomètric per la mesura de deformacions. Finalment, es discuteixen les conclusions principals i es proposen futures línies d’investigació.

In this dissertation, improved techniques in digital holography, that have produced high-resolution, high-fidelity images, are discussed. In particular, the angular spectrum method of calculating holographic optical field is noted to have several advantages over the more commonly used Fresnel transformation or Huygens convolution method. It is observed that spurious noise and interference components can be tightly controlled through the analysis and filtering of the angular spectrum. In the angular spectrum method, the reconstruction distance does not have a lower limit, and the off-axis angle between the object and reference waves can be lower than that of the Fresnel requirement, while still allowing the zero-order background to be cleanly separated. Holographic phase images are largely immune from the coherent noise commonly found in amplitude images. With the use of a miniature pulsed laser, the resulting images have 0.5um diffraction-limited lateral resolution and the phase profile is accurate to about several nanometers of optical path length. Samples such as ovarian cancer cells (SKOV-3) and mouse-embryo fibroblast cells have been imaged. These images display intra-cellular and intra-nuclear organelles with clarity and quantitative accuracy. This technique clearly exceeds currently available methods in phase-contrast opticalmicroscopy in both resolution and detail and provides a new modality for imaging morphology of cellular and intracellular structures that is not currently available. Furthermore, we also demonstrate that phase imaging digital holographic movies provide a novel method of non-invasive quantitative viewing of living cells and other objects. This technique is shown to have significant advantages over conventional microscopy.

Of the wide variety of existing optical techniques for non-contact 3D surface mapping, Fourier Transform Interferometry (FTI) is the method that most elegantly combines simplicity with high speed and high resolution. FTI generates continuous-phase surface maps from a projected optical interference pattern, which is generated with a simple double-pinhole source and collected in a single snapshot using conventional digital camera technology. For enhanced stability and reduced system size, the fringe source can be made from a fiber optic coupler. Unfortunately, many applications require mapping of surfaces that contain challenging features not ideally suited for reconstruction using FTI. Rough and discontinuous surfaces, commonly seen in applications requiring imaging of rock particles, present a unique set of obstacles that cannot be overcome using existing FTI techniques. This work is based on an original analysis of the limitations of FTI and the means in which errors are generated by the particular features encountered in the aggregate mapping application. Several innovative solutions have been developed to enable the use of FTI on rough and discontinuous surfaces. Through filter optimization and development of a novel phase unwrapping and referencing technique, the Method of Multiple References (MoMR), this work has enabled surface error correction and simultaneous imaging of multiple particles using FTI. A complete aggregate profilometry system has been constructed, including a MoMR-FTI software package and graphical user interface, to implement these concepts. The system achieves better than 22µm z-axis resolution, and comprehensive testing has proven it capable to handle a wide variety of particle surfaces. A range of additional features have been developed, such as error correction, particle boundary mapping, and automatic data quality windowing, to enhance the usefulness of the system in its intended application. Because of its high accuracy, high speed and ability to map varied particles, the developed system is ideally suited for large-scale aggregate characterization in highway research laboratories. Additionally, the techniques developed in this work are potentially useful in a large number of applications in which surface roughness or discontinuities pose a challenge.
Ph. D.

The phase and amplitude gradient estimator (PAGE) method has proven successful in improving the accuracy of measured energy quantities over the p-p method, which has traditionally been used, in several applications. One advantage of the PAGE method is the use of phase unwrapping, which allows for increased measurement bandwidth above the spatial Nyquist frequency. However, phase unwrapping works best for broadband sources in free-field environments with high coherence. Narrowband sources often do not have coherent phase information over a sufficient bandwidth for a phase unwrapping algorithm to unwrap properly. In fact, phase unwrapping processing can cause significant error when there is no coherent signal near and above the spatial Nyquist frequency. However, for signals at any frequencies up to the spatial Nyquist frequency, the PAGE method provides correct intensity measurements regardless of the bandwidth of the signal. This is an improved bandwidth over the traditional method. For narrowband sources above the spatial Nyquist frequency, additional information is necessary for the PAGE method to provide accurate acoustic intensity. With sufficient bandwidth and a coherence of at least 0.1 at the spatial Nyquist frequency, a relatively narrowband source above the spatial Nyquist frequency can be unwrapped accurately. One way of using extra information, called the extrapolated PAGE method, uses the phase of a tone below the spatial Nyquist frequency and an assumption of a propagating field, and therefore linear phase, to extrapolate the phase above the spatial Nyquist frequency. Also, within certain angular and amplitude constraints, low-level broadband noise can be added to the field near a source emitting a narrowband signal above the spatial Nyquist frequency. The low-level additive broadband noise can then provide enough phase information for the phase to be correct at the frequencies of the narrowband signal. All of these methods have been shown to work in a free-field environment.

Dans cette thèse, nous nous sommes intéressés aux systèmes intelligents pour des applicationsmédicales et cosmétiques. Ainsi, nous avons conçu et réalisé trois instruments. Le premier estdédié à la mesure de la mouillabilité de la peau. L’originalité de ce dispositif réside en sa capacité àdonner une image 3D de la goûte de la surface de la peau explorée et de donner le comportementdynamique de la goûte. Cette stratégie nous donnera la possibilité de créer de nouvelles basesde données relatives à la mouillabilité de tout le corps humain. En effet, nous disposons que desdonnées sur la mouillabilité de l’avant-bras. Le deuxième instrument intelligent concerne la mesurede la réflectance d’une surface. Ce dispositif assure une mesure de très haute résolution angulairede la BRDF et une très bonne répétabilité de la mesure. Il a été validé sur la peau pour la mesurede l’ éclat. Et enfin le troisième instrument, basé sur une méthode originale de mesure de vibrationà l’aide d’un système de stéréo-vision associée à un motif périodique. Il a été appliqué pour lamesure du mouvement thoracique et abdominal lors de la respiration. Notre principale motivationpour développer ce système fut la réduction des artefacts, dus aux mouvements d’un patient lorsd’un examen radiologique
Smart Devices have been widely used by health care and cosmetics professionals. Indeed, they helpin many aspects of clinical practice by providing an efficient way for medical diagnosis, supportingbetter clinical decision-making and improving patient outcomes. In this thesis, we have beeninterested in three applications. The first one is related to the wettability measurement, especially forthe human skin. So we propose, a held-hand device that is based on the contact angle measurementto determine skin wettability. Besides, the device allows the visualization of the liquid dropletspreading in both dynamic and static modes. Moreover, it can measure the top and the left views ofthe droplet and provides the 3D droplet and the skin explored area profiles. The second applicationpermits the skin radiance measurement. For this purpose, we propose a miniaturized device havingan original method for the BRDF measurement associated with 3D profile measurement of the areastudied. As regards the third application, it is a non-invasive method for breath measurement that usesa stereovision system and a pseudo-periodic pattern. This system allows a high-resolution threedimensionaldisplacement measurement for the recording of the thoracoabdominal wall respiratorymovement. The devices developed during this research gives us a high accuracy, a good resolutionand repeatability of measurements

La mission SWOT (Surface Water and Ocean Topography), menée par le CNES et le JPL et dont le lancement est prévu pour 2020, marque un tournant majeur pour l'altimétrie spatiale, à la fois en océanographie et en hydrologie continentale. Il s'agit de la première mission interférométrique SAR dont l'objectif spécifique est la mesure de la hauteur des eaux. L'instrument principal de la mission, KaRIn, un radar interférométrique en bande Ka, présente des caractéristiques particulières : angle de visée proche du nadir (0.6 à 3.9°), faible longueur d'onde (8.6 mm) et courte base stéréoscopique (10 m). Ces spécificités techniques entrainent des particularités propres à SWOT, à la fois en termes de phénoménologie et de traitement des données. Par ailleurs, du fait de la nature et du grand volume des données, de nouvelles méthodes de traitement sont envisagées, qui se distinguent de celles des missions interférométriques antérieures. Pour le mode " Low Rate " (LR) dédié à l'océanographie, une grande partie du traitement se déroulera à bord pour limiter le volume de données à transmettre au sol. Le mode " High Rate" (HR) visant principalement l'hydrologie continentale, présente lui aussi des originalités en termes de traitement, essentiellement réalisé au sol, de par la grande diversité de structure des surfaces d'eau qui seront observées. Pour les deux modes, la stratégie d'inversion de la phase en hauteurs géolocalisées ne peut être calquée sur celles des missions antérieures, fondées sur le déroulement spatial de la phase interférométrique. L'approche retenue est d'utiliser, autant que possible, un modèle numérique de terrain (MNT) de référence pour lever l'ambiguïté de phase et procéder directement à l'inversion de hauteur. Ceci permet à la fois de gagner en temps de traitement et de s'affranchir de l'utilisation des points de contrôle, difficiles à obtenir sur les océans comme sur les continents, du fait des variations de niveau d'eau et un rapport signal à bruit très faible sur les zones terrestres. Dans les cas où la précision du MNT de référence n'est pas suffisante pour assurer correctement le déroulement de la phase, des méthodes visant à détecter et réduire les erreurs sont proposées. Afin de faciliter l'utilisation des hauteurs géolocalisées issues de la phase l'interférométrique en mode HR, nous proposons une méthode qui permet d'améliorer considérablement la géolocalisation des produits, sans dégrader l'information de hauteur d'eau
The SWOT mission (Surface Water and Ocean Topography), conducted by CNES and JPL, and scheduled for launch in 2020, is a major step forward for spaceborne altimetry, both for oceanography and continental hydrology. It is the first interferometric SAR mission whose specific objective is the measurement of water surface height. The main instrument of the mission, KaRIn, a Ka-band Radar Interferometer, has particular characteristics: very low incidence angle (from 0.6 to 3.9°), short wavelength (8.6 mm), and short baseline (10 m). This technical configuration leads to properties that are specific to SWOT, both in terms of phenomenology and data processing. Moreover, due to the nature and the huge volume of data, new processing methods, different from those used in previous interferometric mission, are considered. For the Low Rate (LR) mode dedicated to oceanography, a large part of the processing will take place onboard to limit the data volume transmitted to ground. The High Rate (HR) mode, mainly targeting continental hydrology, also present original characteristics in terms of processing, essentially conducted on ground, due to the large diversity in the structure of the observed water surfaces. In both modes, the strategy for conversion of phase into geolocated heights cannot be directly based on those of previous missions, relying on spatial phase unwrapping. The approach retained here is to use, as far as possible, a reference Digital Terrain Model (DTM) to remove the phase ambiguity and proceed directly to height inversion. This allows both to reduce the computing time and to avoid the need for ground control points, which are difficult to obtain both over oceans and continental surfaces, due to varying water level and very low signal-to-noise ratio over land. For cases where the precision of reference DTM is not good enough to ensure a correct phase unwrapping, methods to detect and reduce the errors are proposed. To facilitate the use of the geolocated heights derived from the interferometric phase in HR mode, we propose a method that permits to significantly improve the geolocation of the products, without degrading the water height information

Persistent Scatterer Interferometry (PSI) is a group of advanced differential interferometric SAR techniques that are used to measure and monitor terrain deformation. Different PSI techniques have been proposed in the last two decades. In this thesis, the two PSI chains implemented and used at the Geomatics division of CTTC are described: the local area PSI and the PSIG chains. The first part of the thesis is devoted to the local area PSI chain, used to analyse the deformations over small areas. The chain includes a linear deformation model to directly deal with interferometric wrapped phases. Moreover, it does not directly involve the estimation of the APS, thus simplifying the procedure and its computational cost. The chain has been tested using different types of SAR data. The availability of high resolution X-band SAR data has led to an improvement of the PSI results with respect to C-band data. The higher image resolution and phase quality implies an increase of the PS density, an improvement in the estimation precision of the residual topographic error and a higher sensibility to very small deformations, including the displacements caused by thermal dilation. An extension of the classical PSI linear deformation model has been proposed, to account for the thermal dilation effects. This allows obtaining a new PSI outcome, the thermal dilation parameter, which opens new interesting applications since it provides information on the physical properties of single objects, i.e. the coefficient of thermal expansion, and the static structures of the same objects. The second part of the thesis describes the PSIG chain, whose aim was to extend the interferometric processing to wider areas. The ability to cover wide areas is essential to obtain a unique and consistent deformation monitoring for the available SAR image full scenes, i.e. typically 30 by 50 km for TerraSAR-X, 40 by 40 km for CosmoSkyMed and 100 by 100 km for ASAR ENVISAT and ERS. This is particularly important for the forthcoming C-band Sentinel SAR data that will cover 250 by 250 km with a single image scene. The key steps of the PSIG procedure include a new selection of candidate PSs based on a phase similitude criteria and a 2+1D phase unwrapping algorithm. The procedure offers different tools to control the quality of the processing steps. It has been successfully tested over urban, rural and vegetated areas using X-band PSI data. The performance of the PSIG chain is illustrated and discussed in detail, analysing the procedure step by step.
Persistent Scatterer Interferometry (PSI) és un grup de tècniques avançades d'interferometria diferencial SAR que s'utilitzen per mesurar i monitoritzar deformacions del terreny. Durant les últimes dues dècades s’han proposat diverses tècniques PSI. En aquesta tesi es descriuen les dues cadenes PSI implementades i utilitzades en la divisió de Geomàtica del CTTC: la cadena PSI d’àrea local i la cadena PSIG. La primera part de la tesi està dedicada a la cadena PSI d’àrea local, que s'utilitza per analitzar deformacions en zones d’extensió limitada. La cadena inclou un model de deformació lineal per tractar directament amb les fases interferomètriques wrapped. En canvi, no estima directament la component atmosfèrica, cosa que simplifica el procediment i el seu cost computacional. La cadena s’ha provat sobre diferents tipus de dades SAR. La disponibilitat de dades SAR d’alta resolució en banda X ha donat lloc a una millora dels resultats del PSI respecte a les dades en banda C. La resolució més gran de la imatge i la qualitat de la fase impliquen un augment de la densitat de PS, una millora en la precisió de l'estimació de l'error topogràfic residual i una sensibilitat més alta a deformacions subtils, incloent-hi els desplaçaments causats per la dilatació tèrmica. Per tenir en compte els efectes de la dilatació tèrmica, s'ha proposat una extensió del model PSI clàssic que ens permet obtenir un nou producte PSI: el paràmetre de dilatació tèrmica. Aquest paràmetre obre noves aplicacions interessants: proporciona informació relacionada amb les propietats físiques dels objectes mesurats –com el coeficient d'expansió tèrmica– i amb la seva pròpia estructura estàtica. La segona part de la tesi descriu la cadena PSIG, l'objectiu de la qual és estendre el processament interferomètric a àrees més extenses. La capacitat de cobrir àrees grans és fonamental per obtenir un únic mapa global de deformacions que sigui consistent i cobreixi l’extensió sencera de les imatges SAR disponibles, de 30 km per 50 km per TerraSAR-X, de 40 km per 40 km per CosmoSkyMed i de 100 km per 100 km per ASAR-ENVISAT i ERS. Això és particularment important tenint en compte la propera disponibilitat de les dades del satèl•lit Sentinel, que opera en banda C i cobrirà 250 km per 250 km amb una sola imatge. Els passos clau del procediment PSIG són una nova selecció de PS candidats en base a un criteri de similitud de fase i un algoritme de 2+1D phase unwrapping. El procediment ofereix diferents eines per controlar la qualitat dels diferents passos del processament. La cadena PSIG s’ha utilitzat amb èxit en àrees urbanes, rurals i amb vegetació utilitzant dades PSI en banda X. El funcionament de la cadena PSIG s'il•lustra i es descriu en detall, analitzant el procediment pas a pas.

This dissertation thesis deals with the methods for processing image data in X-ray microtomography and digital holographic microscopy. The work aims to achieve significant acceleration of algorithms for tomographic reconstruction and image reconstruction in holographic microscopy by means of optimization and the use of massively parallel GPU. In the field of microtomography, the new GPU (graphic processing unit) accelerated implementations of filtered back projection and back projection filtration of derived data are presented. Another presented algorithm is the orientation normalization technique and evaluation of 3D tomographic data. In the part related to holographic microscopy, the individual steps of the complete image processing procedure are described. This part introduces the new orignal technique of phase unwrapping and correction of image phase damaged by the occurrence of optical vortices in the wrapped image phase. The implementation of the methods for the compensation of the phase deformation and for tracking of cells is then described. In conclusion, there is briefly introduced the Q-PHASE software, which is the complete bundle of all the algorithms necessary for the holographic microscope control, and holographic image processing.