The quantitative analysis of transonic flows by holographic interferometry

This thesis explores the feasibility of routine transonic flow analysis by holographic interferometry. Holography is potentially an important quantitative flow diagnostic, because whole-field data is acquired non-intrusively without the use of particle seeding. Holographic recording geometries are assessed and an image plane specular illumination configuration is shown to reduce speckle noise and maximise the depth-of-field of the reconstructed images. Initially, a NACA 0012 aerofoil is wind tunnel tested to investigate the analysis of two-dimensional flows. A method is developed for extracting whole-field density data from the reconstructed interferograms. Fringe analysis errors axe quantified using a combination of experimental and computer generated imagery. The results are compared quantitatively with a laminar boundary layer Navier-Stokes computational fluid dynamics (CFD) prediction. Agreement of the data is excellent, except in the separated wake where the experimental boundary layer has undergone turbulent transition. A second wind tunnel test, on a cone-cylinder model, demonstrates the feasibility of recording multi-directional interferometric projections using holographic optical elements (HOE’s). The prototype system is highly compact and combines the versatility of diffractive elements with the efficiency of refractive components. The processed interferograms are compared to an integrated Euler CFD prediction and it is shown that the experimental shock cone is elliptical due to flow confinement. Tomographic reconstruction algorithms are reviewed for analysing density projections of a three-dimensional flow. Algebraic reconstruction methods are studied in greater detail, because they produce accurate results when the data is ill-posed. The performance of these algorithms is assessed using CFD input data and it is shown that a reconstruction accuracy of approximately 1% may be obtained when sixteen projections are recorded over a viewing angle of ±58°. The effect of noise on the data is also quantified and methods are suggested for visualising and reconstructing obstructed flow regions

Dual modality optical coherence tomography : Technology development and biomedical applications

Optical coherence tomography (OCT) is a cross-sectional imaging modality that is widely used in clinical ophthalmology and interventional cardiology. It is highly promising for in situ characterization of tumor tissues. OCT has high spatial resolution and high imaging speed to assist clinical decision making in real-time. OCT can be used in both structural imaging and mechanical characterization. Malignant tumor tissue alters morphology. Additionally, structural OCT imaging has limited tissue differentiation capability because of the complex and noisy nature of the OCT signal. Moreover, the contrast of structural OCT signal derived from tissue’s light scattering properties has little chemical specificity. Hence, interrogating additional tissue properties using OCT would improve the outcome of OCT’s clinical applications. In addition to morphological difference, pathological tissue such as cancer breast tissue usually possesses higher stiffness compared to the normal healthy tissue, which indicates a compelling reason for the specific combination of structural OCT imaging with stiffness assessment in the development of dual-modality OCT system for the characterization of the breast cancer diagnosis. This dissertation seeks to integrate the structural OCT imaging and the optical coherence elastography (OCE) for breast cancer tissue characterization. OCE is a functional extension of OCT. OCE measures the mechanical response (deformation, resonant frequency, elastic wave propagation) of biological tissues under external or internal mechanical stimulation and extracts the mechanical properties of tissue related to its pathological and physiological processes. Conventional OCE techniques (i.e., compression, surface acoustic wave, magnetomotive OCE) measure the strain field and the results of OCE measurement are different under different loading conditions. Inconsistency is observed between OCE characterization results from different measurement sessions. Therefore, a robust mechanical characterization is required for force/stress quantification. A quantitative optical coherence elastography (qOCE) that tracks both force and displacement is proposed and developed at NJIT. qOCE instrument is based on a fiber optic probe integrated with a Fabry-Perot force sensor and the miniature probe can be delivered to arbitrary locations within animal or human body. In this dissertation, the principle of qOCE technology is described. Experimental results are acquired to demonstrate the capability of qOCE in characterizing the elasticity of biological tissue. Moreover, a handheld optical instrument is developed to allow in vivo real-time OCE characterization based on an adaptive Doppler analysis algorithm to accurately track the motion of sample under compression. For the development of the dual modality OCT system, the structural OCT images exhibit additive and multiplicative noises that degrade the image quality. To suppress noise in OCT imaging, a noise adaptive wavelet thresholding (NAWT) algorithm is developed to remove the speckle noise in OCT images. NAWT algorithm characterizes the speckle noise in the wavelet domain adaptively and removes the speckle noise while preserving the sample structure. Furthermore, a novel denoising algorithm is also developed that adaptively eliminates the additive noise from the complex OCT using Doppler variation analysis

InSAR Deformation Analysis with Distributed Scatterers: A Review Complemented by New Advances

Interferometric Synthetic Aperture Radar (InSAR) is a powerful remote sensing technique able to measure deformation of the earth’s surface over large areas. InSAR deformation analysis uses two main categories of backscatter: Persistent Scatterers (PS) and Distributed Scatterers (DS). While PS are characterized by a high signal-to-noise ratio and predominantly occur as single pixels, DS possess a medium or low signal-to-noise ratio and can only be exploited if they form homogeneous groups of pixels that are large enough to allow for statistical analysis. Although DS have been used by InSAR since its beginnings for different purposes, new methods developed during the last decade have advanced the field significantly. Preprocessing of DS with spatio-temporal filtering allows today the use of DS in PS algorithms as if they were PS, thereby enlarging spatial coverage and stabilizing algorithms. This review explores the relations between different lines of research and discusses open questions regarding DS preprocessing for deformation analysis. The review is complemented with an experiment that demonstrates that significantly improved results can be achieved for preprocessed DS during parameter estimation if their statistical properties are used

Models of the η Corvi Debris Disk from the Keck Interferometer, Spitzer, and Herschel

Debris disks are signposts of analogs to small-body populations of the solar system, often, however, with much higher masses and dust production rates. The disk associated with the nearby star η Crv is especially striking, as it shows strong mid- and far-infrared excesses despite an age of ~1.4 Gyr. We undertake constructing a consistent model of the system that can explain a diverse collection of spatial and spectral data. We analyze Keck Interferometer Nuller measurements and revisit Spitzer and additional spectrophotometric data, as well as resolved Herschel images, to determine the dust spatial distribution in the inner exozodi and in the outer belt. We model in detail the two-component disk and the dust properties from the sub-AU scale to the outermost regions by fitting simultaneously all measurements against a large parameter space. The properties of the cold belt are consistent with a collisional cascade in a reservoir of ice-free planetesimals at 133 AU. It shows marginal evidence for asymmetries along the major axis. KIN enables us to establish that the warm dust consists of a ring that peaks between 0.2 and 0.8 AU. To reconcile this location with the ~400 K dust temperature, very high albedo dust must be invoked, and a distribution of forsterite grains starting from micron sizes satisfies this criterion, while providing an excellent fit to the spectrum. We discuss additional constraints from the LBTI and near-infrared spectra, and we present predictions of what James Webb Space Telescope can unveil about this unusual object and whether it can detect unseen planets

Urban Deformation Monitoring using Persistent Scatterer Interferometry and SAR tomography

This book focuses on remote sensing for urban deformation monitoring. In particular, it highlights how deformation monitoring in urban areas can be carried out using Persistent Scatterer Interferometry (PSI) and Synthetic Aperture Radar (SAR) Tomography (TomoSAR). Several contributions show the capabilities of Interferometric SAR (InSAR) and PSI techniques for urban deformation monitoring. Some of them show the advantages of TomoSAR in un-mixing multiple scatterers for urban mapping and monitoring. This book is dedicated to the technical and scientific community interested in urban applications. It is useful for choosing the appropriate technique and gaining an assessment of the expected performance. The book will also be useful to researchers, as it provides information on the state-of-the-art and new trends in this fiel

Phase extraction of non-stationary signals produced in dynamic interferometry involving speckle waves

It is now widely acknowledged, among communities of researchers and engineers of very different horizons, that speckle interferometry (SI) offers powerful techniques to characterize mechanical rough surfaces with a submicronic accuracy in static or quasi-static regime, when small displacements are involved (typically several microns or tens of microns). The issue of dynamic regimes with possibly large deformations (typically several hundreds of microns) is still topical and prevents an even more widespread use of speckle techniques. This is essentially due to the lack of efficient processing schemes able to cope with non-stationary AM-FM interferometric signals. In addition, decorrelation-induced phase errors represent an hindrance to accurate measurement when such large displacements and classical fringe analysis techniques are considered. This work is an attempt to address those issues and to endeavor to make the most of speckle interferometry signals. Our answers to those problems are located on two different levels. First of all, we adopt the temporal analysis approach, i.e. the analysis of the temporal signal of each pixel of the sensor area used to record the interferograms. A return to basics of phase extraction is operated to properly identify the conditions under which the computed phase is meaningful and thus give some insight on the physical phenomenon under analysis. Due to their intrinsic non-stationary nature, a preprocessing tool is missing to put the SI temporal signals in a shape which ensures an accurate phase computation, whichever technique is chosen. This is where the Empirical Mode Decomposition (EMD) intervenes. This technique, somehow equivalent to an adaptive filtering technique, has been studied and tailored to fit with our expectations. The EMD has shown a great ability to remove efficiently the random fluctuating background intensity and to evaluate the modulation intensity. The Hilbert tranform (HT) is the natural quadrature operator. Its use to build an analytical signal from the so-detrended SI signal, for subsequent phase computation, has been studied and assessed. Other phase extraction techniques have been considered as well for comparison purposes. Finally, our answer to the decorrelation-induced phase error relies on the well-known result that the higher the pixel modulation intensity, the lower the random phase error. We took benefit from this result – not only linked to basic SNR considerations, but more specifically to the intrinsic phase structure of speckle fields – with a novel approach. The regions within the pixel signal history classified as unreliable because under-modulated, are purely and simply discarded. An interpolation step with the Delaunay triangulation is carried out with the so-obtained non-uniformly sampled phase maps to recover a smooth phase which relies on the most reliable available data. Our schemes have been tested and discussed with simulated and experimental SI signals. We eventually have developed a versatile, accurate and efficient phase extraction procedure, perfectly able to tackle the challenge of dynamic behaviors characterization, even for displacements and/or deformations beyond the classical limit of the correlation dimensions

Three-dimensional geometry characterization using structured light fields

Tese de doutoramento. Engenharia Mecânica. Faculdade de Engenharia. Universidade do Porto. 200

Time Series Analysis of Surface Deformation Associated With Fluid Injection and Induced Seismicity in Timpson, Texas Using DInSAR Methods

In recent years, a rise in unconventional oil and gas production in North America has been linked to an increase in seismicity rate in these regions (Ellsworth, 2013). As fluid is pumped into deep formations, the state of stress within the subsurface changes, potentially reactivating pre-existing faults and/or causing subsidence or uplift of the surface. Therefore, hydraulic fracturing and/or fluid disposal injection can significantly increase the seismic hazard to communities and structures surrounding the injection sites (Barnhart et al., 2014). On 17th May 2012 an Mw4.8 earthquake occurred near Timpson, TX and has been linked with wastewater injection operations in the area (Shirzaei et al., 2016). This study aims to spatiotemporally relate, wastewater injection operations to seismicity near Timpson using differential interferometric synthetic aperture radar (DInSAR) analysis. Results are presented as a set of time series, produced using the Multidimensional Small Baseline Subset (MSBAS) InSAR technique, revealing two-dimensional surface deformation

Spatially multiplexed interferometric microscopy: from basic principles to advanced arrangements

La posibilidad de visualizar y analizar objetos microscópicos transparentes de una manera no invasiva ha sido uno de los principales retos de la microscopía óptica a lo largo del siglo XX. Para ello, se desarrollaron diversas técnicas de microscopía que convertían las variaciones en el índice de refracción de los objetos en variaciones de intensidad, haciendo estos objetos visibles a simple vista, entre las que destacan la microscopía de contraste de fase de Zernike o de contraste diferencial de Nomarski. Sin embargo, estas técnicas solamente proporcionan información cualitativa del objeto, por lo que su análisis se limita a la simple visualización. Por otro lado, existen otras técnicas de microscopía basadas en la interferometría, que proporcionan información cuantitativa de fase de un modo sencillo y directo. A partir de esta información de fase es posible obtener, de una manera precisa, información sobre la morfología y el índice de refracción del objeto bajo análisis. Este hecho hace que este tipo de técnicas sean muy interesantes en diversas áreas de conocimiento como la medicina, la biofotónica, o la biología, entre otras. Quizás la técnica interferométrica por excelencia para la obtención de imágenes cuantitativas de fase sea la microscopía holográfica digital. La microscopía holográfica digital surge de la combinación de holografía digital y la microscopía óptica. En los últimos años, se han llevado a cabo numerosos avances en el campo de la microscopía holográfica digital con el fin de introducir mejoras en términos de robustez, simplicidad, precisión y coste. En la misma línea de estos avances, esta tesis está centrada en el desarrollo y la mejora de una técnica llamada “microscopía interferométrica por multiplexado espacial”. Esta técnica se basa en la introducción de una serie de modificaciones sencillas en el cuerpo de un microscopio estándar de campo claro, con el objetivo de convertirlo en uno holográfico de una manera muy robusta, sencilla y económica. Todas las modificaciones realizadas están encauzadas a la implementación de un interferómetro de camino común empleando estrategias de multiplexado espacial en el microscopio. Estas modificaciones son principalmente tres: 1) la sustitución de la fuente de iluminación de banda ancha del propio microscopio por una fuente luminosa coherente que permita interferencias; 2) el multiplexado espacial del campo de visión mediante su división en dos o tres regiones para la transmisión de un haz de referencia; y 3) la inserción de un elemento interferométrico, tal como una red de difracción o un cubo divisor de haz, que produzca el patrón interferencial a registrar. Así pues, todas las técnicas desarrolladas en esta tesis están encaminados a la mejora de esta técnica en términos de: 1) ruido coherente, 2) diseño del campo de visión, 3) resolución espacial, 4) capacidad de análisis de objetos no transparentes, 5) caracterización del índice de refracción, y 6) capacidad de análisis a tiempo real. Todas las validaciones experimentales realizadas durante esta tesis demuestran que la técnica de microscopía interferométrica por multiplexado espacial es una técnica muy versátil, potente y económica que permite la obtención de imágenes cuantitativas de fase a partir de un microscopio de campo claro convencional.The possibility of visualizing and analysing transparent microscopic objects in a non-invasively manner was one of the addressed challenges in the microscopy field during 20th century. Several microscopy techniques were created for that purpose, including quantitative phase imaging. Quantitative phase imaging provides numerical information about the morphology and the refractive index of such objects, so that it can be very appealing in diverse fields of knowledge such as medicine, biophotonics or life science, just to cite a few. One of the easiest ways of achieving quantitative phase imaging is employing digital holographic microscopy techniques. Digital holographic microscopy arises from the combination of digital holography and optical microscopy. In recent years, many novel digital holographic microscopy approaches have been successfully developed in order to improve their capabilities in terms of robustness, simplicity, usability, accuracy, and price. In line with that, this thesis is focused on the development and improvement of the technique named "Spatially Multiplexed Interferometric Microscopy". This technique introduces minimal modifications in the embodiment of a conventional bright field microscope in order to convert it into a holographic one in an extremely simple, low-cost and highly-stable way. The modifications are aimed to implement a common-path interferometer by a spatially multiplexed approach in the embodiment of the microscope and are mainly three: 1) the replacement of the broadband illumination source of the microscope by a coherent one; 2) the spatial multiplexed of the input plane by dividing it into two or three regions; 3) and the insertion of an interferometric component such as a diffraction grating or a beam splitter cube. All performed arrangements and phase retrieval procedures are focused on the enhancement of such a technique regarding: 1) coherent noise; 2) spatial multiplexed input plane; 3) spatial resolution; 4) ability for reflective samples analysis; 5) refractive index characterization; and 6) real-time analysis. Experimental validations carried out during the thesis demonstrate that spatially multiplexed interferometric microscopy is a powerful, versatile, and low-cost technique for achieving quantitative phase images from a commercially available standard microscope