A NEW METHOD OF WAVELENGTH SCANNING INTERFEROMETRY FOR INSPECTING SURFACES WITH MULTI-SIDE HIGH-SLOPED FACETS

With the development of modern advanced manufacturing technologies, the requirements for ultra-precision structured surfaces are increasing rapidly for both high value-added products and scientific research. Examples of the components encompassing the structures include brightness enhancement film (BEF), optical gratings and so forth. Besides, specially designed structured surfaces, namely metamaterials can lead to specified desirable coherence, angular or spatial characteristics that the natural materials do not possess. This promising field attracts a large amount of funding and investments. However, owing to a lack of effective means of inspecting the structured surfaces, the manufacturing process is heavily reliant on the experience of fabrication operators adopting an expensive trial-and-error approach, resulting in high scrap rates up to 50-70% of the manufactured items. Therefore, overcoming this challenge becomes increasingly valuable. The thesis proposes a novel methodology to tackle this challenge by setting up an apparatus encompassing multiple measurement probes to attain the dataset for each facet of the structured surface and then blending the acquired datasets together, based on the relative location of the probes, which is achieved via the system calibration. The method relies on wavelength scanning interferometry (WSI), which can achieve areal measurement with axial resolutions approaching the nanometre without the requirement for the mechanical scanning of either the sample or optics, unlike comparable techniques such as coherence scanning interferometry (CSI). This lack of mechanical scanning opens up the possibility of using a multi-probe optics system to provide simultaneous measurement with multi adjacent fields of view. The thesis presents a proof-of-principle demonstration of a dual-probe wavelength scanning interferometry (DPWSI) system capable of measuring near-right-angle V-groove structures in a single measurement acquisition. The optical system comprises dual probes, with orthogonal measurement planes. For a given probe, a range of V-groove angles is measurable, limited by the acceptance angle of the objective lenses employed. This range can be expanded further by designing equivalent probe heads with varying angular separation. More complicated structured surfaces can be inspected by increasing the number of probes. The fringe analysis algorithms for WSI are discussed in detail, some improvements are proposed, and experimental validation is conducted. The scheme for calibrating the DPSWI system and obtaining the relative location between the probes to achieve the whole topography is implemented and presented in full. The appraisal of the DPWSI system is also carried out using a multi-step diamond-turned specimen and a sawtooth brightness enhancement film (BEF). The results showed that the proposed method could achieve the inspection of the near-right-angle V-groove structures with submicrometre scale vertical resolution and micrometre level lateral resolution

DEVELOPMENT AND CHARACTERIZATION OF A HIGH-ENERGY IN-LINE PHASE CONTRAST TOMOSYNTHESIS PROTOTYPE

Phase sensitive 3D imaging techniques have been an emerging field in x-ray imaging for two decades. Among them, in-line phase contrast tomosynthesis has been investigated with great potential for translation into clinical applications in the near future, due to combining the advantages of configuration simplicity, structural noise elimination and potentially low radiation dose delivery. The high-energy in-line phase contrast tomosynthesis technique developed and presented in this dissertation initiates this translational procedure by optimizing the imaging conditions, performing phase retrieval, offering opportunities to further reduce radiation dose delivery, improving detectability and specificity with the employment of auxiliary phase contrast agents, and potentially performing quantitative imaging. First, the high-energy in-line phase contrast tomosynthesis prototype was developed and characterized in this dissertation as the first of its kind following a number of engineering trade-off considerations. The quantitative results as well as the imaging results of tissue-simulating phantoms and biology-related phantoms demonstrate the extensive capability of this imaging prototype in improving tumor detectability. In addition, the optimization of the x-ray prime beam toward the PAD phase retrieval method proved the potential of high-energy imaging and predicated the solution toward imaging time reduction by employing photon counting based imaging techniques. In the past several years, applications of microbubbles as a phase contrast agent have shown the capability for image quality improvement in quantitative imaging. In this dissertation, a preliminary study of quantitative imaging of microbubbles using the in-line phase contrast projection mode imaging prototype, which is a system without tomosynthesis capability, provided a discussion on how the materials of the bubble shells and gas infills could impact the imaging capabilities and resulting image detectability. In addition, the results of the study provided a guideline for microbubble selections for in-line phase contrast mode imaging modalities. Based on this criterion discussed in the study, the albumin-shell microbubbles were selected as the phase contrast agent for the imaging prototype presented in this dissertation. The imaging results showed the feasibility of performing quantitative imaging by employing microbubbles as the auxiliary phase contrast agent. Clinical conditions were simulated by distributing microbubbles on the interface between two tissue-like phantom structures. The quantitative imaging results provided clinical motivation for translating phantom studies into more biology-related investigations providing radiation dose reductions in the future

Image Stitching

Projecte final de carrera fet en col.laboració amb University of Limerick. Department of Electronic and Computer EngineeringEnglish: Image processing is any form of signal processing for which the input is an image, such as a photograph or video frame; the output of image processing may be either an image or, a set of characteristics or parameters related to the image. Most image processing techniques involve treating the image as a two-dimensional signal and applying standard signal processing techniques to it. Specifically, image stitching presents different stages to render two or more overlapping images into a seamless stitched image, from the detection of features to blending in a final image. In this process, Scale Invariant Feature Transform (SIFT) algorithm can be applied to perform the detection and matching control points step, due to its good properties. The process of create an automatic and effective whole stitching process leads to analyze different methods of the stitching stages. Several commercial and online software tools are available to perform the stitching process, offering diverse options in different situations. This analysis involves the creation of a script to deal with images and project data files. Once the whole script is generated, the stitching process is able to achieve an automatic execution allowing good quality results in the final composite image.Castellano: Procesado de imagen es cualquier tipo de procesado de señal en aquel que la entrada es una imagen, como una fotografía o fotograma de video; la salida puede ser una imagen o conjunto de características y parámetros relacionados con la imagen. Muchas de las técnicas de procesado de imagen implican un tratamiento de la imagen como señal en dos dimensiones, y para ello se aplican técnicas estándar de procesado de señal. Concretamente, la costura o unión de imágenes presenta diferentes etapas para unir dos o más imágenes superpuestas en una imagen perfecta sin costuras, desde la detección de puntos clave en las imágenes hasta su mezcla en la imagen final. En este proceso, el algoritmo Scale Invariant Feature Transform (SIFT) puede ser aplicado para desarrollar la fase de detección y selección de correspondencias entre imágenes debido a sus buenas cualidades. El desarrollo de la creación de un completo proceso de costura automático y efectivo, pasa por analizar diferentes métodos de las etapas del cosido de las imágenes. Varios software comerciales y gratuitos son capaces de llevar a cabo el proceso de costura, ofreciendo diferentes alternativas en distintas situaciones. Este análisis implica la creación de una secuencia de comandos que trabaja con las imágenes y con archivos de datos del proyecto generado. Una vez esta secuencia es creada, el proceso de cosido de imágenes es capaz de lograr una ejecución automática permitiendo unos resultados de calidad en la imagen final.Català: Processament d'imatge és qualsevol tipus de processat de senyal en aquell que l'entrada és una imatge, com una fotografia o fotograma de vídeo, i la sortida pot ser una imatge o conjunt de característiques i paràmetres relacionats amb la imatge. Moltes de les tècniques de processat d'imatge impliquen un tractament de la imatge com a senyal en dues dimensions, i per això s'apliquen tècniques estàndard de processament de senyal. Concretament, la costura o unió d'imatges presenta diferents etapes per unir dues o més imatges superposades en una imatge perfecta sense costures, des de la detecció de punts clau en les imatges fins a la seva barreja en la imatge final. En aquest procés, l'algoritme Scale Invariant Feature Transform (SIFT) pot ser aplicat per desenvolupar la fase de detecció i selecció de correspondències entre imatges a causa de les seves bones qualitats. El desenvolupament de la creació d'un complet procés de costura automàtic i efectiu, passa per analitzar diferents mètodes de les etapes del cosit de les imatges. Diversos programari comercials i gratuïts són capaços de dur a terme el procés de costura, oferint diferents alternatives en diverses situacions. Aquesta anàlisi implica la creació d'una seqüència de commandes que treballa amb les imatges i amb arxius de dades del projecte generat. Un cop aquesta seqüència és creada, el procés de cosit d'imatges és capaç d'aconseguir una execució automàtica permetent uns resultats de qualitat en la imatge final

Recent Advances in Signal Processing

The signal processing task is a very critical issue in the majority of new technological inventions and challenges in a variety of applications in both science and engineering fields. Classical signal processing techniques have largely worked with mathematical models that are linear, local, stationary, and Gaussian. They have always favored closed-form tractability over real-world accuracy. These constraints were imposed by the lack of powerful computing tools. During the last few decades, signal processing theories, developments, and applications have matured rapidly and now include tools from many areas of mathematics, computer science, physics, and engineering. This book is targeted primarily toward both students and researchers who want to be exposed to a wide variety of signal processing techniques and algorithms. It includes 27 chapters that can be categorized into five different areas depending on the application at hand. These five categories are ordered to address image processing, speech processing, communication systems, time-series analysis, and educational packages respectively. The book has the advantage of providing a collection of applications that are completely independent and self-contained; thus, the interested reader can choose any chapter and skip to another without losing continuity