Dissertations / Theses on the topic 'White Light Interferometry (WLI)'
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Bora, Ethem. "Cylindrical Surface Analysis with White Light Interferometry." Thesis, Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-15308.
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At present, one of the big challenges is to develop a precise surface measurement method for mechanical parts. Especially, to study cylindrical surface, the cause of many difficulties because of its geometry shape. This thesis presents a quite good solution for analyzing topography of cylindrical surface with White Light Interferometry optical system which is one of the important and suitable tools in optics. In the construction period, the aim was to build a system which can be easily mounted on the sample. This is done by a very simple and compact design that also enables us to use it in research laboratories. In the project, a cylindrical surface analysis is achieved by taking subsequent images with different nano-scale distance from the sample and stitched the acquired images. To achieve this implementation, subsequent images with the highest intensity are first determined and then located in a single image. In the stitching process, cross correlation method that is extremely useful to find out relative point of the images is used to merge the acquired images. Additionally, stitching process is helped us to extend the area where research can be done. In the project, MATLAB & LABVIEW are used for analyzing the images and controlling the motors, respectively.
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Sathiamoorthy, Karthick, and Tanjim Ahmed. "Construction and Validation of a White Light Interferometer." Thesis, Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-14378.
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White light interferometry is a well-developed and very old technique for optical measurements. The thesis describes the design of a vertical scan interferometer system to study the surface topography of surfaces down to nanometers. The desired properties of the system are its simplicity, portability and compact size, making it suitable for use in general labs and for educational purposes. By acquiring a sequence of images of the deformed fringe pattern, the surface topography can be observed, giving greater understanding of the surface roughness. The principle behind the system is coherence peak sensing where the resulting fringe pattern of the object gets changed in accordance with its surface topography. To accomplish this, individual components of the interferometer were studied and a prototype was built in the lab. A series of experiments were performed which validate the working of the system. The results of the validation which are produced in the report give the accuracy of the system. The output from the prototype interferometer is processed by MATLAB to decode the surface topography of the object under measurement. The design of the prototype is also discussed. Possible application of this device for sensing the surface topography of a cylindrical object is also put forward. Even-though the white light interferometer is more common, making them simple and cost effective will be more advantageous for the whole research community.
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Gianto, Gianto. "Multi-dimensional Teager-Kaiser signal processing for improved characterization using white light interferometry." Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAD026/document.
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L'utilisation de franges d'interférence en lumière blanche comme une sonde optique en microscopie interférométrique est d'une importance croissante dans la caractérisation des matériaux, la métrologie de surface et de l'imagerie médicale. L'Interférométrie en lumière blanche est une technique basée sur la détection de l'enveloppe de franges d'interférence. Il a été démontré antérieurement, la capacité des approches 2D à rivaliser avec certaines méthodes classiques utilisées dans le domaine de l'interférométrie, en termes de robustesse et de temps de calcul. En outre, alors que la plupart des méthodes tiennent compte seulement des données 1 D, il semblerait avantageux de prendre en compte le voisinage spatial utilisant des approches multidimensionnelles (2D/3D), y compris le paramètre de temps afin d'améliorer les mesures. Le but de ce projet de thèse est de développer de nouvelles approches n-D qui sont appropriées pour une meilleure caractérisation des surfaces plus complexes et des couches transparentesThe use of white light interference fringes as an optical probe in microscopy is of growing importance in materials characterization, surface metrology and medical imaging. Coherence Scanning Interferometry (CSI, also known as White Light Scanning Interferometry, WSLI) is well known for surface roughness and topology measurement [1]. Full-Field Optical Coherence Tomography (FF-OCT) is the version used for the tomographic analysis of complex transparent layers. Both techniques generally make use of some sort of fringe scanning along the optical axis and the acquisition of a stack of xyz images. Image processing is then used to identify the fringe envelopes along z at each pixel in order to measure the positions of either a single surface or of multiple scattering objects within a layer.In CSI, the measurement of surface shape generally requires peak or phase extraction of the mono dimensional fringe signal. Most of the methods are based on an AM-FM signal model, which represents the variation in light intensity measured along the optical axis of an interference microscope [2]. We have demonstrated earlier [3, 4] the ability of 2D approaches to compete with some classical methods used in the field of interferometry, in terms of robustness and computing time. In addition, whereas most methods only take into account the 1D data, it would seem advantageous to take into account the spatial neighborhood using multidimensional approaches (2D, 3D, 4D), including the time parameter in order to improve the measurements.The purpose of this PhD project is to develop new n-D approaches that are suitable for improved characterization of more complex surfaces and transparent layers. In addition, we will enrich the field of study by means of heterogeneous image processing from multiple sensor sources (heterogeneous data fusion). Applications considered will be in the fields of materials metrology, biomaterials and medical imaging
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Oliveira, Rafael Figueiredo de. "Evaluation of Proposed Natural Corrosion Inhibitors for X-52 Carbon Steel in Ethanol Media." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1448385629.
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Hissmann, Michael. "Bayesian estimation for white light interferometry." Berlin Pro Business, 2005. http://shop.pro-business.com/product_info.php?products_id=357.
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Ferri, Carlo. "White light interferometry in measurements of micro volumes." Thesis, Cardiff University, 2006. http://orca.cf.ac.uk/54574/.
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A procedure for measuring micro-volumes of solids with irregular and complex boundaries of both concave and convex forms has been developed. Advantages, limitations and potential applications of the developed procedure are identified and discussed. The precision of this procedure is demonstrated in the case of a con vex form. In the light of the key role of metrology in the current trend toward product miniaturisation, the need for dedicating resources and effort to assessing quantitatively the performances of measuring processes is most apparent. The developed procedure is based on white light interferometric microscopy. In order to enable the deployment of this measuring system in the developed procedure and in agreement with the centrality of metrology mentioned above, an investigation of white light interferometric microscopy has been carried out from a user perspective. In particular, two sources of variability were identified and experimentally quantified and the precision in repeatability conditions was estimated when measuring length along the z-axis in a pre-specified micro-metric range. A critical analysis of the calibration procedure built in the investigated microscope has also been conducted. In order to overcome the pitfalls discovered in such an analysis, a spline-based calibration procedure has been developed and demonstrated. In addition, the control methods needed for the practical usage of the proposed calibration procedure have been developed. Calibration studies are made possible by the provision of traceable reference materials. Therefore, a cost-effective and versatile procedure for the build ing of traceable reference samples of length in the micrometric range was developed. The proposed method used standard gauge blocks commonly found in metrology laboratories.
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Bhatia, Vikram. "Signal processing techniques for optical fiber sensors using white light interferometry." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-09192009-040440/.
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Yu, Bing. "Development of Tunable Optical Filters for Interrogation of White-Light Interferometric Sensors." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/27496.
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Interferometric fiber optic sensors have been extensively used to measure a large variety of physical, chemical and biomedical parameters due to their superior performance. At the Center for Photonics Technology of Virginia Tech, a variety of interferometric fiber optic sensors have been developed in recent years, for efficient oil recovery, partial discharge detection in high voltage transformers, pressure sensing in gas turbine engines, and temperature measurements in gasifiers and boilers. However, interrogating an interferometric sensor involves accurate recovery of a measurand from the phase-modulated lightwaves, and has been a challenge for high performance, high speed, and low-cost, to current white-light interferometry (WLI) techniques, such as the widely used scanning WLI (S-WLI) and spectral-domain WLI (SD-WLI). The performance of a white-light interferometric sensing system depends not only on the design of the probes, but also, to a great extent, on the interrogation strategy to be used.
In this Ph.D. research, a tunable optical filter based WLI (TOF-WLI) is proposed and validated as a low cost, yet high performance, solution to the interrogation of various types of interferometric sensors. In addition to the capability of linear/quadrature demodulation, TOF-WLI retains all the features of WLI, is compatible with the SD-WLI, and can be tailored for both static and wideband signals. It also has great potential in surface metrology and biomedical imaging as well as optical spectroscopy. The key, to the success of this new approach in competition with the other available WLI techniques, is that the tunable optical filter (TOF) must be specially designed for sensing and extremely low cost. Therefore, two novel TOFs, a diffraction grating tunable filter (DG-TOF) and an extrinsic Fabry-Perot tunable filter (EFP-TF), are proposed and demonstrated. Laboratory and field test results on using the DG-TOF WLI for partial discharge and thermal fault detection in high voltage power transformers, and the EFP-TF WLI in temperature sensor systems and a turbine engine monitoring system will also be presented to demonstrate the feasibility for efficient sensor interrogation.Ph. D.
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Li, Beinan. "Optical audio reproduction for stereo phonograph records by using white-light interferometry and image processing." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=103586.
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This dissertation presents an optical approach for reproducing stereo audio from the stereo disc phonograph records (LPs). Since the late nineteenth century, as one of the most influential recording technologies, the phonograph recording has enjoyed its popularity and produced numerous cylinders and discs that carry speeches, music, and all kinds of audio cultural heritage. The preservation of phonograph sound recordings is thus of world-wide concern. This research provides an alternative approach to digitizing the stereo disc phonograph records, potentially for long-term preservation, by optically acquiring the 3D disc record surface profile and extracting the audio signals from the record surface profile images by using software algorithms. The dissertation discusses the workflow of optically reproducing stereo audio from the stereo disc phonograph records by using the white-light interferometry technique. This workflow includes the acquisition of the 3D disc record surface profile by using a commercial white-light interferometry microscope, the extraction of the record groove undulations, which encodes the stereo audio information, by using our custom image processing algorithms, and finally the reproduction of the stereo audio signal from the groove undulations through signal processing. The workflow is evaluated with a test stereo record containing standard sinusoid signals and a musical record. The quality of the optically-reproduced audio is quantitatively evaluated and compared with that of the audio digitized by a turntable. The dissertation contains three main parts. The first include an introduction to the general background of the optical audio reproduction for the stereo disc phonograph records and the review of the phonograph recording technology, the previous efforts in optically reproducing audio from the cylinder and disc phonograph records, and the relevant optical techniques including the white-light interferometry. The second part focuses on our complete workflow for optically reproducing the stereo audio from the stereo disc phonograph records. This is followed by the evaluation of our workflow and the output audio quality. The dissertation concludes by introducing the challenges and the possible directions in the future development of our optical audio reproduction workflow.Cette thèse présente une nouvelle approche de reproduction optique d'enregistrements phonographiques stéréo. L'enregistrement phonographique s'est imposé, vers la fin du XIXème siècle, comme la technologie d'enregistrement de référence partout dans le monde. Il existe donc une pléthore de cylindres et autres disques où ont été gravés discours, morceaux de musique, et autres artefacts culturel sonores. La préservation de ces enregistrements sonores phonographiques est donc une préoccupation mondiale. Le présent travail de recherche propose une approche alternative de numérisation des enregistrements phonographiques stéréo en vue de leur éventuelle préservation. En effet, à partir de l'acquisition optique du profil (en trois dimensions) de la surface d'enregistrement du disque, les signaux audio peuvent être reconstruits grâce à nos algorithmes d'analyse d'images. Cette thèse examine les étapes de la reproduction optique audio stéréo à partir d'enregistrements phonographiques sur disques stéréo en utilisant l'interférométrie en lumière blanche. Ces étapes comportent: l'acquisition du profil de la surface d'enregistrement d'un disque 3D en utilisant un microscope commercial interférométrique en lumière blanche ; l'extraction des ondulations du sillon, qui encode l'information audio stéréo en utilisant nos algorithmes de traitement d'images ; et finalement, la reproduction du signal audio stéréo depuis les ondulations du sillon par des techniques de traitement du signal. Le processus complet est évalué sur un enregistrement stéréo test comprenant des signaux sinusoïdaux et un enregistrement musical. La qualité de l'audio reproduit par voie optique est évaluée de façon quantitative et comparée avec celle de l'audio numérisé de manière « traditionnelle », à l'aide d'une platine. Cette thèse s'articule en trois parties. La première comporte une introduction des principes nécessaires à la reproduction d'enregistrements phonographiques stéréo par voie optique. Plus précisément, les principes de la technologie d'enregistrement phonographique sont passés en revue ; l'état de l'art des efforts de reproduction optique des enregistrements phonographiques sur disques et cylindres est présenté ; et enfin, les techniques optiques pertinentes incluant l'interférométrie en lumière blanche sont décrites. La deuxième partie livre une présentation détaillée du processus de reproduction optique que nous avons développé. Dans la troisième partie, l'évaluation quantitative de la qualité de la restitution du signal audio obtenue par notre procédé est aussi décrite. La thèse se conclue sur un bilan des défis et des directions possibles dans le futur développement de notre approche de reproduction des signaux audio par voie optique.
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Wylde, Clarissa Eileen Kenney, and Clarissa Eileen Kenney Wylde. "The Art of Optical Aberrations." Thesis, The University of Arizona, 2017. http://hdl.handle.net/10150/624090.
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Art and optics are inseparable. Though seemingly opposite disciplines, the combination of art and optics has significantly impacted both culture and science as they are now known. As history has run its course, in the sciences, arts, and their fruitful combinations, optical aberrations have proved to be a problematic hindrance to progress. In an effort to eradicate aberrations the simple beauty of these aberrational forms has been labeled as undesirable and discarded. Here, rather than approach aberrations as erroneous, these beautiful forms are elevated to be the photographic subject in a new body of work, On the Bright Side. Though many recording methods could be utilized, this work was composed on classic, medium-format, photographic film using white-light, Michelson interferometry. The resulting images are both a representation of the true light rays that interacted on the distorted mirror surfaces (data) and the artist’s compositional eye for what parts of the interferogram are chosen and displayed. A detailed description of the captivating interdisciplinary procedure is documented and presented alongside the final artwork, CCD digital reference images, and deformable mirror contour maps. This alluring marriage between the arts and sciences opens up a heretofore minimally explored aspect of the inextricable art-optics connection. It additionally provides a fascinating new conversation on the importance of light and optics in photographic composition.
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Romare, Dario. "The application of adaptive linear and non-linear filters to fringe order identification in white-light interferometry systems." Thesis, City, University of London, 1998. http://openaccess.city.ac.uk/19993/.
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Conventional optical interferometry systems driven by highly coherent light sources have a very short unambiguous operating range, a direct consequence of the flatness of the interference fringes visibility profile at the output of the system. The range can be extended by using a white-light interferometer (WU), which is driven by a low-coherence source and produces a Gaussian visibility profile with a unique maximum in correspondence of the central fringe. Due to system and/or measurement noise, however, the position of the maximum (from which an accurate measurement of the measurand - displacement, temperature, pressure, flow, etc. - can be derived) is not easily detectable, and can lead to large measurement errors. This is especially true in a multiplexing scheme, where the source power is distributed evenly among various sensors, with a corresponding drop in the overall signal-to-noise ratio. The inclusion of a signal processing scheme at the receiver end is thus a necessity. As the fringe pattern at the output of a WLI system is basically a noisy sine wave amplitude modulated by a Gaussian envelope, it can be classified as a non-stationary, narrow-band, linear but non-Gaussian signa\. So far, no attempt has been made to apply digital filtering techniques, as understood in the signal processing community, to the output signal of a WLI system. This thesis constitutes a first step in that direction. Since the only measurable information given by the system is contained in the output signal, the system is modelled as a "black box" driven by the system and measurement noise processes and containing an unknown set of parameters. Standard least squares techniques can then be applied to estimate the parameters of the model, as is usually done in the field of system identification when only noisy output measurements are available. It is shown that identification of the model parameters is equivalent to finding a set of coefficients for an inverse filter which takes the WU signal at its input and delivers the unknown noise process at the output. The non-stationarity of the signal is accounted for by allowing for time variations of the model parameters; this justifies the use of adaptive filters with time-varying coefficients. A new central fringe identification scheme is proposed, based on a modification of the standard least mean square (LMS) adaptive filtering algorithm in combination with amplitude thresholding of the fringe pattern. The new scheme is shown to offer considerable improvement in the identification rate when tested against current schemes over comparable operating ranges, while retaining the computational simplicity and operational speed of the standard LMS. Its performance is also shown to be largely independent of the step-size parameter controlling the rate of convergence and tracking in the standard LMS, which is known to be the main obstacle for a successful application of the algorithm in a practical setting. The non-Gaussianity of the signal is explored and an attempt is made to apply higher-order statistics (HOS) algorithms to central fringe identification. The effectiveness of Gaussianity tests on pilot Gaussian data is seen to depend not only on the number and length of records available but, perhaps more importantly, on the bandwidth of the process. Violation of the stationarity assumption is shown to lead to mis-classification of a seemingly non-Gaussian signal into a Gaussian one, as the visibility profile may alter the distribution of the underlying sinusoid making it appear Gaussian, even when beam diffraction and wavefront aberrations combine to produce a nonGaussian profile. HOS-based adaptive algorithms may still be of some benefit, however, if processing is confined to that region of the fringe pattern where sufficient non-Gaussianity is allowed to develop. Non-linear adaptive filters based on the Volterra theories are finally applied to compensate for possible non-linearities introduced by mismatches in optical components, chromatic aberrations, and analogue-to-digital converters. It is shown that although a Volterra filter is able to reproduce the low-amplitude distortions of the fringe pattern better than a linear filter does, the identification rate does not improve. Reasons are given for such behaviour.
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Olszak, Artur G., and Chase Salsbury. "Spectrally controlled interferometry for measurements of flat and spherical optics." SPIE-INT SOC OPTICAL ENGINEERING, 2017. http://hdl.handle.net/10150/627191.
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Conventional interferometry is widely used to measure spherical and flat surfaces with nanometer level precision but is plagued by back reflections. We describe a new method of isolating the measurement surface by controlling spectral properties of the source (Spectrally Controlled Interferometry - SCI). Using spectral modulation of the interferometer's source enables formation of localized fringes where the optical path difference is non-zero. As a consequence it becomes possible to form white-light like fringes in common path interferometers, such as the Fizeau. The proposed setup does not require mechanical phase shifting, resulting in simpler instruments and the ability to upgrade existing interferometers. Furthermore, it allows absolute measurement of distance, including radius of curvature of lenses in a single setup with possibility of improving the throughput and removing some modes of failure.
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Otto, Marc-André [Verfasser], and Otmar [Gutachter] Loffeld. "Automated high-precision crack detection in airplane combustion chamber liners using white light interferometry / Marc-André Otto ; Gutachter: Otmar Loffeld." Siegen : Universitätsbibliothek der Universität Siegen, 2020. http://d-nb.info/122862707X/34.
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Han, Ming. "Theoretical and Experimental Study of Low-Finesse Extrinsic Fabry-Perot Interferometric Fiber Optic Sensors." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/27825.
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In this report, detailed and systematic theoretical and experimental study of low-finesse extrinsic Fabry-Perot interferometric (EFPI) fiber optic sensors together with their signal processing methods for white-light systems are presented. The work aims to provide a better understanding of the operational principle of EFPI fiber optic sensors, and is useful and important in the design, optimization, fabrication and application of single mode fiber(SMF) EFPI (SMF-EFPI) and multimode fiber (MMF) EFPI (MMF-EFPI) sensor systems. The cases for SMF-EFPI and MMF-EFPI sensors are separately considered.
In the analysis of SMF-EFPI sensors, the light transmitted in the fiber is approximated by a Gaussian beam and the obtained spectral transfer function of the sensors includes an extra phase shift due to the light coupling in the fiber end-face. This extra phase shift has not been addressed by previous researchers and is of great importance for high accuracy and high resolution signal processing of white-light SMF-EFPI systems. Fringe visibility degradation due to gap-length increase and sensor imperfections is studied. The results indicate that the fringe visibility of a SMF-EFPI sensor is relatively insensitive to the gap-length change and sensor imperfections.
Based on the spectral fringe pattern predicated by the theory of SMF-EFPI sensors, a novel curve fitting signal processing method (Type 1 curve-fitting method) is presented for white-light SMF-EFPI sensor systems. Other spectral domain signal processing methods including the wavelength-tracking, the Type 2-3 curve fitting, Fourier transform, and two-point interrogation methods are reviewed and systematically analyzed. Experiments were carried out to compare the performances of these signal processing methods. The results have shown that the Type 1 curve fitting method achieves high accuracy, high resolution, large dynamic range, and the capability of absolute measurement at the same time, while others either have less resolution, or are not capable of absolute measurement.
% Very different from SMF-EFPI sensors, MMF-EFPI sensors with high fringe visibility usually are more difficult to obtain in practice because the fringe visibility of a MMF-EFPI sensor is much more sensitive to gap-length change and sensor head imperfections. %Previously, only geometric-optics are available to analyze MMF-EFPI sensors which approximate the light in MMF as rays propagating in different directions. Geometric-optics theory has fundenmental limitations because it is approximate and only valid for limited conditions. Moreover, geometric-optics theory is not capable of poviding the exact fringe pattern which is important in the signal processing of white light MMF-EFPI sensor systems. In this report,
Previous mathematical models for MMF-EFPI sensors are all based on geometric optics; therefore their applications have many limitations. In this report, a modal theory is developed that can be used in any situations and is more accurate. The mathematical description of the spectral fringes of MMF-EFPI sensors is obtained by the modal theory. Effect on the fringe visibility of system parameters, including the sensor head structure, the fiber parameters, and the mode power distribution in the MMF of the MMF-EFPI sensors, is analyzed. Experiments were carried out to validate the theory. Fundamental mechanism that causes the degradation of the fringe visibility in MMF-EFPI sensors are revealed. It is shown that, in some situations at which the fringe visibility is important and difficult to achieve, a simple method of launching the light into the MMF-EFPI sensor system from the output of a SMF could be used to improve the fringe visibility and to ease the fabrication difficulties of MMF-EFPI sensors.
Signal processing methods that are well-understood in white-light SMF-EFPI sensor systems may exhibit new aspects when they are applied to white-light MMF-EFPI sensor systems. This report reveals that the variations of mode power distribution (MPD) in the MMF could cause phase variations of the spectral fringes from a MMF-EFPI sensor and introduce measurement errors for a signal processing method in which the phase information is used. This MPD effect on the wavelength-tracking method in white-light MMF-EFPI sensors is theoretically analyzed. The fringe phases changes caused by MPD variations were experimentally observed and thus the MFD effect is validated.Ph. D.
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Ivanov, Georgi Pavlov. "Fabry-Perot Sapphire Temperature Sensor for Use in Coal Gasification." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/32931.
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Sapphire fiber based temperature sensors are exceptional in their ability to operate at temperatures above 1000ºC and as high as 1800ºC. Sapphire fiber technology is emerging and the fiber is available commercially. Sapphire fiber has a high loss, is highly multi-mode and does not have a solid cladding, but it is nonetheless very useful in high temperature applications. Of the available interferometer configurations, Fabry-Perot interferometers are distinguished in their high accuracy and great isolation from sources of error.
In this thesis, improvements are reported to an existing design to enhance its reliability and to reduce possible modes of failure. The existing high temperature sensor design has shown a lot of potential in the past by continuously measuring the temperature in a coal gasifier for 7 months, but its true potential has not yet been realized. The goal of this work and the work of many others is to extend the working life and reliability of high-temperature optical sapphire temperature sensors in harsh environments by exploring a solid cladding for sapphire fiber, improved fringe visibility sapphire wafers and a new sensor design. This project is supported by the National Energy and Technology Laboratory of the Department of Energy.Master of Science
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Ma, Cheng. "Modeling and Signal Processing of Low-Finesse Fabry-Perot Interferometric Fiber Optic Sensors." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/77225.
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This dissertation addresses several theoretical issues in low-finesse fiber optic Fabry-Perot Interferometric (FPI) sensors. The work is divided into two levels: modeling of the sensors, and signal processing based on White-Light-Interferometry (WLI).
In the first chapter, the technical background of the low-finesse FPI sensor is briefly reviewed and the problems to be solved are highlighted.
A model for low finesse Extrinsic FPI (EFPI) is developed in Chapter 2. The theory is experimentally proven using both single-mode and multimode fiber based EFPIs. The fringe visibility and the additional phase in the spectrum are found to be strongly influenced by the optical path difference (OPD), the output spatial power distribution and the working wavelength; however they are not directly related to the light coherence.
In Chapter 3, the Single-Multi-Single-mode Intrinsic FPI (SMS-IFPI) is theoretically and experimentally studied. Reflectivity, cavity refocusing, and the additional phase in the sensor spectrum are modeled. The multiplexing capacity of the sensor is dramatically increased by promoting light refocusing. Similar to EFPIs, wave-front distortion generates an additional phase in the interference spectrogram. The resultant non-constant phase plays an important role in causing abrupt jumps in the demodulated OPD.
WLI-based signal processing of the low-finesse FP sensor is studied in Chapter 4. The lower bounds of the OPD estimation are calculated, the bounds are applied to evaluate OPD demodulation algorithms. Two types of algorithms (TYPE I & II) are studied and compared. The TYPE I estimations suffice if the requirement for resolution is relatively low. TYPE II estimation has dramatically reduced error, however, at the expense of potential demodulation jumps. If the additional phase is reliably dependent on OPD, it can be calibrated to minimize the occurrence of such jumps.
In Chapter 5, the work is summarized and suggestions for future studies are given.Ph. D.
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Zhu, Yizheng. "Miniature Fiber-Optic Sensors for High-Temperature Harsh Environments." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/27762.
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Measurement of physical parameters in harsh environments (high pressure, high temperature, highly corrosive, high electromagnetic interference) is often desired in a variety of areas, such as aerospace, automobile, energy, military systems, and industrial processes. Pressure and temperature are among the most important of these parameters. A typical example is pressure monitoring in jet engine compressors to help detect and control undesirable air flow instabilities, namely rotating stall and surge. However, the temperatures inside a compressor could reach beyond 600°C for today's large engines. Current fiber-optic sensor can operate up to about 300°C and even the most widely employed semiconductor sensors are limited below 500°C.
The objective of this research is to push the limit of fiber-optic sensing technology in harsh environment applications for both pressure and temperature measurements by developing novel sensing structures, fabrication techniques, and signal processing algorithms. An all-fused-silica pressure sensor has been demonstrated which is fabricated on the tip of a fiber with a diameter no larger than 125μm. The sensor was able to function beyond the current limit and operate into the 600~700°C range. Also a temperature sensor has been developed using sapphire fibers and wafers for ultra-high temperature measurement as high as 1600°C. This effort will generate more understanding regarding sapphire fiber's high temperature properties and could possibly lead to novel designs of pressure sensor for beyond 1000°C. Both sensors have been field tested in real-world harsh environments and demonstrated to be reliably and robust.
In this dissertation, the design, fabrication, and testing of the sensors are discussed in detail. The system and signal processing techniques are presented. The plan and direction for future work are also suggested with an aim of further pushing the operating limit of fiber-optic sensors.Ph. D.
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Zhao, Xin. "Study of Multimode Extrinsic Fabry-Perot Interferometric Fiber Optic Sensor on Biosensing." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/34534.
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The electrostatic self-assembly (ESA) method presents an effective application in the field of biosensing due to the uniform nanoscale structure. In previous research, a single mode fiber (SMF) sensor system had been investigated for the thin-film measurement due to the high fringe visibility. However, compared with a SMF sensor system, a multimode fiber (MMF) sensor system is lower-cost and has larger sensing area (the fiber core), providing the potential for higher sensing efficiency.
In this thesis, a multimode fiber-optic sensor has been developed based on extrinsic Fabry-Perot interferometry (EFPI) for the measurement of optical thickness in self-assembled thin film layers as well as for the immunosensing test. The sensor was fabricated by connecting a multimode fiber (MMF) and a silica wafer. A Fabry-Perot cavity was formed by the reflections from the two interfaces of the wafer. The negatively charged silica wafer could be used as the substrate for the thin film immobilization scheme. The sensor is incorporated into the white-light interferometric system. By monitoring the optical cavity length increment, the self-assembled thin film thickness was measured; the immunoreaction between immunoglobulin G (IgG) and anti-IgG was investigated.
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Al-Mamun, Mohammad Shah. "Development of a Miniature, Fiber-optic Temperature Compensated Pressure Sensor." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/71308.
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Since the invention of Laser (in 1960) and low loss optical fiber (in 1966) [1], extensive research in fiber-optic sensing technology has made it a well-defined and matured field [1]. The measurement of physical parameters (such as temperature and pressure) in extremely harsh environment is one of the most intriguing challenges of this field, and is highly valued in the automobile industry, aerospace research, industrial process monitoring, etc. [2]. Although the semiconductor based sensors can operate at around 500oC, sapphire fiber sensors were demonstrated at even higher temperatures [3].
In this research, a novel sensor structure is proposed that can measure both pressure and temperature simultaneously. This work effort consists of design, fabrication, calibration, and laboratory testing of a novel structured temperature compensated pressure sensor. The aim of this research is to demonstrate an accurate temperature measurement, and pressure measurement using a composite Fabry-Perot interferometer. One interferometer measures the temperature and the other accurately measures pressure after temperature compensation using the temperature data from the first sensor.Master of Science
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Blecha, Martin. "Pracoviště pro optickou interferometrii." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-217262.
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This thesis is specialized on composition of workplace for experiments flowing from optical interferometry. Here are described laboratory exercise servant for demonstration basic principles of interferometry. In more details is described method measurement of height profile objects with method white light interferometry.
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Klempner, Adam R. "Development of a modular interferometric microscopy system for characterization of MEMS." Link to electronic thesis, 2007. http://www.wpi.edu/Pubs/ETD/Available/etd-010407-173332/.
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Thesis (M.S.)--Worcester Polytechnic Institute.Keywords: vacuum; shape and deformation measurement; MEMS; vibrometry; scanning white light; Interferometry; thermal; vibration. Includes bibliographical references (136-139 leaves ).
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Ås, Sigmund. "Fatigue Life Prediction of an Aluminium Alloy Automotive Component Using Finite Element Analysis of Surface Topography." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-758.
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A 6082 aluminium alloy has been characterized with regard to the influence of surface roughness on fatigue strength.
Fatigue life testing of smooth specimens was used to establish reference curves for the material in extruded and forged T6 condition. The extruded material was found to have better fatigue strength than the forged material, although the cyclic stress-strain response was similar for both. The forged material was tested in T5, T6 and T7 tempers, showing no significant difference in fatigue strength.
Surface roughness was created by circumferential grinding of cylindrical test specimens, and the surface topography was measured using a white light interferometry microscope. The measurements proved to be accurate, although errors were observed for certain surface features. Residual stresses were quantified by X-ray diffraction. Compressive residual stresses of around 150 MPa were found in both rough and smooth specimens. Load cycling did not significantly alter the surface residual stresses.
Stress solutions ahead of all major surface grooves were found using a linear elastic material model. Estimates of cyclic stresses and strains were calculated in the notch roots using different Neuber corrections of the linear solution. The results were compared to finite element analysis employing a bilinear kinematic hardening model. A generalized version of the Neuber correction was found to be within 20% of the nonlinear finite element results.
Several empirical models for the notch sensitivity factor were investigated. These were found to be unable to describe the notch influence on fatigue life and initiation life. In order to follow this approach, it was recommended that different test specimens should be used where the short fatigue crack growth could be monitored.
It was shown that microstructural fracture mechanics theories could be used to estimate the fatigue limit of rough surfaces. In some cases, initiation from material defects or weaknesses would override the influence of surface geometry. In one specimen, the initiation appeared to have started as at a de-bonded grain, while in other cases, initiation was thought to have started at larger second phase particles embedded in notch roots. Further work in this area should focus on statistical descriptions of surface roughness, inherent material defects, and their interaction.
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Silva, Luiz Pinheiro Cordovil da. "Transformador óptico por interferometria de luz branca para medição de altas tensões." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-17042006-105554/.
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No presente trabalho é apresentada uma nova abordagem para medida de potenciais em altos níveis de tensão que utilizam sensores eletro-ópticos Pockels. Também descreve a aplicação da técnica de interferometria de luz branca em sistemas de alta tensão por fibras ópticas. Neste sistema a informação é codificada no espectro da luz, permitindo assim que a medida seja independente da potência óptica transmitida pelo link de fibras ópticas. Um protótipo foi construído e testado sob excitação de tensão a.c. até 20 kV em 60 Hz mostrando boa resposta e demonstrando a viabilidade deste método.A new approach to perform measurement of potentials in high voltage levels using electrooptical Pockels sensors is presented here. This work describes an application of the White Light Interferometry technique to a high voltage optical fiber measurement system. In this system the information is encoded in the spectrum of the light, allowing the measurement to be independent of the optical power transmitted by the optical fiber link. A prototype was built and tested under excitation of a.c. voltages up to 20 kV in 60 Hz showing good response and demonstrating the feasibility of this method.
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Silva, Luiz Pinheiro Cordovil da. "Interferômetros recuperadores de baixa tensão de meia onda para sistemas interferométricos de luz branca utilizando moduladores eletro-ópticos." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-08122011-153421/.
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O trabalho tem por objetivo o estudo e o desenvolvimento de interferômetros recuperadores com baixa tensão de meia onda utilizando moduladores eletro-ópticos para serem aplicados em sistemas Interferométricos de luz branca. Ele dá continuidade às pesquisas do autor em seu mestrado, em que foi desenvolvido e testado um sistema de sensoriamento eletro-óptico capaz de medir diretamente tensões de até 69,4 kVRMS. Desta forma aperfeiçoa-se o sistema de processamento de sinais ópticos desenvolvendo um novo interferômetro recuperador, baseado em óptica integrada. Para o desenvolvimento do tema proposto, inicialmente foi feito uma revisão da literatura/bibliografia, baseada em livros, artigos e teses, visando identificar o \"estado da arte\" relacionado aos moduladores eletro-ópticos para definir o tipo de modulador mais adequado à aplicação em vista. O estudo resultou na escolha de um componente em óptica integrada que foi aplicado numa configuração inédita em um protótipo de transformador de potencial óptico para medição de elevados níveis de tensão elétrica. As características de desempenho deste protótipo foram comparadas com as do protótipo previamente construído. Como resultado deste trabalho, amplia-se o conhecimento e fixa-se em âmbito nacional o domínio sobre as técnicas de construção de interferômetros recuperadores baseados em óptica integrada aplicáveis à recuperação de sinais ópticos em sistemas interferométricos para medição de altas tensões.This work has as objective the study and development of low half-wave voltage recovery interferometers using electro-optical modulators to be applied to white light interferometric systems. This work is a continuation in the research carried out by the author to obtain his master degree, in which it was developed and tested an electro- optic sensing system capable to measure direct voltage to 69.4 kVrms. In the present work the optical signals processing system is improved by developing a new recovery interferometer based on integrated optics. To develop the proposed subject, initially a review of the literature, based on books, articles and thesis, has been done aiming to identify the State of the Art related to electro-optic modulators and helping to define the most suitable type of modulator for the desired application. The study resulted in the selection of an integrated optical device arranged in an unpublished configuration that was applied to a prototype of optical voltage transformer, intended to measure high voltage levels. The performance of this prototype was compared with a previous version. The results of this work increase the knowledge of the construction techniques of recovery interferometers based on integrated optic devices applicable to the recovering of optical signals in interferometric systems for high voltage measurement.
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Huang, Chao-Nan, and 黃兆男. "Stress measurement with white light interferometry." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/32235889126077202596.
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碩士明新科技大學
電子工程研究所
97
Currently there is a need for optical interference filters coated on plastic and flexible substrates in high technology industry. Since Young’s modulus and thermal expansion coefficients of plastic and flexible substrates are quite different from the glass, the stress of coated films on plastic and flexible substrates is more complicate. We build a white-light vertical scanning Michelson interferometer to measure stress of optical thin films. The white-light interferometer is based on short white-light coherence length and measure surface profiles of plastic and flexible substrates by a vertical scanning method with zero-order interference fringe identification. Stress of thin films will be calculated by comparing the deflection of the substrates before and after film deposition. Besides, the relationship between applied voltages and displacement of piezoelectric transducer devices was also accurately measured by both using analyses of phase shifting interferometry algorithms and setting up a Twyman-Green interferometer.
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Chang, Chia-Yuan, and 張家源. "White Light Phase Shifting Interferometry for Surface Profilometry." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/72572170054195677152.
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Ling, Wei-Cheng, and 凌維成. "Surface Profilometry of Micro Device with White Light Interferometry." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/06364741933686812854.
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碩士國立中興大學
機械工程學系
93
This research uses white light illumination and two identical microscope objectives to build a Linnik interferometer and also use a objective which specially made for interferometer to build a Mirau interferometer., The surface profile of the sample can be reconstructed by phase shift interferometry, phase unwrap or zero order interference fringe identification. Because the usage of microscope objective, the measurement area and the height resolution are suitable for measuring micro devices. In this research, a flat mirror, standard sphere and a step height have been measured. The phase shift interferometry successfully measured samples that under the height difference limit ( ), between two adjacent pixels, and the step height can be measured correctly by zero order interference fringe identification. During the experiment, we found a phase shift which is not controlled by the interferometer has a long term influence of all our measurements. We found this phase shift correlates with the temperature. The phase shift caused by temperature will introduce measurement error and degrade the repeatability of the interferometer.
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Yeh, Yi-Lin, and 葉易霖. "Research on the Vertical Scanning of White-Light Interferometry." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/27921651596661531187.
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碩士國立臺灣大學
機械工程學研究所
92
This study aims to establish the 3D profile measurement techniques of white-light interferometry with large vertical and horizontal measuring ranges. The purpose includes a complete investigation of the SIS-1000 (SNU Precision Company) surface profilometer for its operation principles and component specifications. The core of the research is to develop an effective methodology for large-range and long-depth 3D profile measurement with nano-scale resolution and accuracy. The measuring method includes vertical scanning and image merging method (Geomagic Studio) by using SIOS laser interferometer for the purpose of precision positioning. The proposed “enhanced vertical scanning method” combines traditional vertical scanning with image merging method. Along with the outcome of experiments, this achieves the perfect ability for 3D reconstruction techniques.
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Hißmann, Michael [Verfasser]. "Bayesian estimation for white light interferometry / presented by Michael Hißmann." 2005. http://d-nb.info/976058693/34.
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Hong, Wen-Ming, and 洪文明. "White-light Phase Shifting Interferometry for Three Dimension Surface Measurement." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/93134633335835686657.
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碩士國立交通大學
光電工程所
91
In order to study the application of white-light phase-shifting interferometry (PSI) in three dimension surface measurement ,we use traditional PZT phase shifting and achromatic phase shifting .We compare and discuss the results from both the phase-shifting methods. The measurement system is a Linnik interferometer. The light source is a halogen lamp,which is a polychromatic light source,covering the visible spectral range . In the theory we assume that the polychromatic light source has a Gaussian power spectral density, so we use a narrow bandwidth filter with central wavelength 629.5nm and broad bandwidth filter with central wavelength 550nm, to satisfy the theoretical requirement. To verify our measurement results,we compare the surface profiles measured by our interferometer with that by Zygo instrument. By using phase shifting, we can achieve high vertical resolution, but have a limited vertical depth. If we consider the characteristics of the short coherence length of white-light and make a vertical scanning to find the location of maximum intensity, we can greatly improve the measurement of vertical range.
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SHEN, Ming-Sing, and 沈明興. "Design and Fabrication of Auto-Focusing Michelson White Light Interferometry." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/48447862422042706875.
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碩士國立成功大學
機械工程學系碩博士班
95
The white light interferometer which has characteristics of non-destruction and nanometer precision in vertical resolution is helpful for the development of precise nanometer measurement. This paper use Michelson white light interferometry and the technique of Auto-Focusing to develop a system of three dimensional surface measurement for Auto-focusing Michelson white light interferometry . In order to set up the three-dimensional profile of the sample, we search the range of interference by auto-focusing first, then search the position of highest intensity of light by analyzing interference fringe .In the Auto-Focusing method, we adopt passive auto-focusing. Passive auto-focusing has two important parts: sharpness measures, and rule search algorithms. In the analysis of interference fringes, we introduce Fourier Transform method, Peak detection, and phase-shifting in this paper. In the collocation of Michelson interferometer and the auto-focusing method, we use the corrected Rule-based algorithm to make PZT to scan the whole field interference fringes to obtain the three-dimensional profile. In the analysis of interference fringes, we found that the phase-shifting method has better accuracy and stability with different magnification. And we also found that with low different magnification, the limits of measurement is affected by the horizontal resolution.
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劉韋良. "Measuring Stress of Thin Films with Stitch of White-light Interferometry." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/97681934960482818006.
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碩士明新科技大學
電子工程研究所
98
The stress in thin films is well known to be very important in all optical coating applications, because film stress produces several undesirable phenomena, such as the cracking or peeling of the film and the bending of the substrate. In this study, stress is measured by a white-light Michelson interferometer, which is based on short white-light coherence length and measures surface profiles of substrates by a vertical scanning method with zero-order interference fringe identification. We used the stitch technology to expand the measurement area of the substrates with addition of tilt terms of X and Y axes when the stress was measured by using the white-light Michelson interferometer. By using the Zernike polynomials fitting for the wavefront being tested, surface contours for the uncoated and coated substrates are obtained. Stress is calculated by comparing the deflection of the substrates before and after film deposition. The results show the white-light Michelson interferometer with stitch technology is capable of measuring large scope on the substrates.
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Lin, Yi-Hsuan, and 林宜萱. "Innovative 3-D Surface Profilometer Using White Light Lateral Scanning Interferometry." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/6675nt.
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碩士國立臺北科技大學
機電整合研究所
97
An in-situ 3-D surface profilometer for reconstructing micro surface profiles with a long depth measuring range and a nano-scale resolution was developed using innovative white light lateral scanning interferometry (LSI). Current measuring field of view (FOV) of conventional white light interferometers is currently limited by microscopic views of the existing interferometric objectives, such as Michelson, Mirau or Linnik design. Moreover, vertical scanning operation required for acquiring volumetric interferometric data is extremerely time consuming and makes white light vertical scanning interferometry (VSI) infeasible for in-situ automatic optical inspection (AOI) on micro 3-D structures. The traditional LSI methods were mainly developed by tilting the whole optical axis with respect to the scanning direction of a sample’s surface underlying inspection, in which it has one inherent difficulty in effective collision avoidance between the optical objective and the object’s surface. To resolve this, a new white light LSI method was developed here by controlling the tilting angle of the reference mirror in the interferometric objective. With the proposed optical configuration, the surface is inspected at a tilting angle with respect to the maximum coherence plane of the interferometric system along its lateral scanning direction when the objective lies perpendicularly with the tested surface. In addition, a calibration method was developed to establish an accurate mathematical mapping model between the object depth and the lateral axis. To evaluate the feasibility of the methodology, a calibrated step height was measured for evaluating the accuracy and repeatability. Some industrial samples, such as photon spacers and other microstructures fabricated by -nano imprinting processes, were measured to verify the actual performance on real components. It was found that the measurement repeatability was controlled less than 60 nm within one standard deviation for a maximum measurable depth of 27.21 μm.
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Chen, Chien-Cheng, and 陳建丞. "White-light Achromatic Phase Shifting Interferometry for Three Dimension Surface Profile Measurement." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/12748259146553563444.
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碩士國立交通大學
光電工程系所
92
This work focuses on the abilities of white-light phase-shifting interferometry (WLPSI) in 3-D surface profile measurement. We set up a Linnik type interferometric microscope in which an achromatic phase-shifting method with rotating waveplate is used. A quartz tungsten-halogen(QTH) lamp, covering the visible spectral range 400~700 nm, is used as the white-light source. In this theory the light source is required to have a Gaussian spectral power distribution. However, the QTH lamp does not have a good Gaussian spectral distribution. Two narrowband band-pass filters with central wavelength at 589.5nm and 629.5nm are used in order to get better Gaussian distribution. The measured results are compared with those measured by a Zygo instrument(Newview5000). In this work, the phase-shifting module is placed at input and output ends for comparison. The comparison shows that the input end case has better performance than the output end case in the measurement accuracy, contrast and repeatability. In the input end case the shift of interference pattern at the image plane can be avoided when the waveplate rotates in the phase-shifting module. Although phase-shifting method usually gives very good vertical resolution, it still suffers from a limited measurement range in the vertical direction. If we consider the characteristics of the short coherence length of white-light, this method combined with a vertical scanning of maximum intensity position can increase the vertical depth measurement range greatly.
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Wang, Huai-Yi, and 王懷逸. "Application of White-light Scanning Interferometry on Localized Surface Plasmon Resonance Sensor." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/75478268426276217461.
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碩士國立中央大學
光電科學與工程學系
105
This article aims to set up a biosensor based on white-light scanning interferometry (WLSI) and applies to localized surface plasmon resonance (LSPR) sensor. In the WLSI system, the amplitude changes, as functions of wavelength, is retrieved by means of Fourier transform of the correlograms (interferograms in vertical direction). The Fourier amplitude method is capable to measure environmental changes in refractive index which results in a red shift of the amplitude (or spectrum) of gold nanoparticles (GNPs) solution. Meanwhile, the article shows that the performance of a spectrometer with poor spectral resolution is improved by the spectral centroid algorithm significantly because more data points (wavelengths) are considered for signal-to-noise ratio improvement Additionally, the sources of errors in the WLSI system, inclusive of the accuracy of wave-number and illumination non-uniformity, are improved. We use the spectrum of an edge filter as a check of the wavenumber accuracy. The result shows the best match with frame interval of 71 nm. In comparison to a spectrometer, the average spectrum error is 1.04 %. The illumination uniformity is also improved from 41.34 % to 92.49 % by the program correction. A method to measure the refractive index variation in the WLSI system is described in the article. The limit of detection (LOD) is 1.2"×" 10-3 RIU (Refractive Index Unit). The bio-applicability was investigated using the rs242557 tau gene, an Alzheimer's and Parkinson’s disease biomarker. The LOD was calculated as 15 pM.
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Yeh, Li-chi, and 葉力旗. "Stitching of White-Light Interferometry Profile by Applying Digital-Image-Correlation Method." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/46532213493711784816.
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碩士國立成功大學
機械工程學系碩博士班
95
This thesis aims to build a large horizontal range of white light interferometry techniques applied in the mirco-structure surface profile measurement. It particularly focuses on the surface profile of micro-eletro-mechanical to perform the non-destructiveness and high resolution profile measurement. Based on its frequency spectrum characteristics of continuous wavelength, the white light interferometry technique shortens coherence length significantly. In experiment setup, we adopt a Mirau objective which specifically designed for interferometer to build the white light interferometer, and work with phase shifting algorithm to find out the position of the maximum intensity of interference fringes and finally reconstruct the topography of sample. In addition, we compare the result of experiment with the Alpha-Step instruments, and evaluate 3 sigma of measurement system. As for the large horizontal measurement range, we stitch the image and 3D profile of different position by using digital-image-correlation method. Firstly, we capture the two images that have the same feature from different position to transact the Laplacian filter, and select the area to compare each other to find out the stitching position from overlapping area of the two images. Finally, this study applies image stitching position to stitch the 3D profile of the white light interferometry and confirm the research feasibility. The experiment results show that stitching precision will achieve 1 pixel when standard deviation of comparison area of image exceed 7.1,and the error of 3D profile stitching is under 20 nm.
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陳政儒. "Refractive Index and Thickness of Thin Films Measured by White Light Interferometry." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/30244495543722605760.
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碩士明新科技大學
電子工程研究所
99
A white-light vertical scanning Michelson interferometer has been successfully built to measure refractive index and thickness of optical thin films in the study. The white-light interferometer is based on short white-light coherence length and measure optical paths between both top and bottom faces of thin films by a vertical scanning method with zero-order interference fringe identification. Refractive index and thickness of thin films are determined by fitting interference patterns of white-light intensity with numerical analyses. The method of measuring refractive index and thickness of optical thin films has the advantages of inherently high sensitivity and accuracy.
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Lien, Chun-Tai, and 連俊泰. "Innovative Anti-vibration Technique for On-line White-light Vertical Scanning Interferometry (VSI)." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/3q3u7b.
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碩士國立臺北科技大學
自動化科技研究所
97
White light interferometer (WLI) has become a popular method for measuring micro surface profiles having a large height range with a nano-scale resolution. However, it is easily influenced by environmental vibration or noisy disturbances, which significantly restricts its usefulness and application for in-field inspection. Tremendous research effort has been invested to overcome the vibration-induced measurement problems. Thus, in this research, a novel white-light optical interferometric system was developed to minimize measurement errors potentially caused by environmental vibrations. The novel developed systemTM is composed of a white-light LED light source, a narrow bandpass filter, a Mirau objective, a PZT for vertical scanning and two image sensing devices. Using the development, the vibration displacement can be accurately monitored and compensated for accurate vertical scanning interferometry (VSI). From the preliminary experimental results, it is verified that nano-scale displacement detection for a vibration having a bandwidth of 20 Hz can be effectively achieved. The feasibility of the anti-vibration white-light VSI is further verified by performing an industrial in-field test.
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Bold, Geoffrey Terence. "White Light Feedback Interferometry for Aberration Correction, and Near-Real-Time Phase-Difference Amplification." 2002. http://hdl.handle.net/2292/855.
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There has recently been much interest in the use of adaptive optics systems for automatic aberration correction in applications such as astronomical and line-of-sight imaging. The background of aberration correction is presented, reviewing applications of adaptive optics systems, and commonly used wavefront sensing and correcting techniques. Aberration correction systems use a variety of correction elements including liquid crystal devices and segmented mirrors. Clearly, characteristics such as response time, phase vs. drive voltage, and sensitivity to wavelength and polarisation state of input light are important to system performance. The characteristics of two liquid crystal spatial light modulators, pertinent to aberration correction, are initially investigated. Research on a novel white light feedback interferometric technique that can be used for aberration correction is then presented. Using this technique, a phase proportional to the interferometer output intensity is applied to a modulator within the interferometer to achieve automatic phase correction. The interferometer operates in white light. A theoretical analysis of white light feedback interferometry is given along with simulated and experimental results. The results show that aberration correction can, in principle, be achieved using the technique. Liquid crystal spatial light modulators suffer from relatively slow response times and a limited phase modulation range. Segmented mirrors have much faster response times, and a much larger phase modulation range, but are prohibitively expensive. Therefore, we decided to construct a 3x3 segmented mirror for use in aberration correction systems. The construction, testing, housing and mounting of the segmented mirror purpose built for aberration correction is then discussed. Phase-difference amplification is a technique that can be used for high accuracy phase measurement. Using this technique a diffraction grating is constructed using the interferogram of a test wavefront. The ±n orders diffracted from the grating are interfered together to form a phase-amplified interferogram from which a phase map of the test wavefront can be recovered. In the future, phase-difference amplification may be a very useful technique for aberration correction systems. Conventional systems use time consuming and inconvenient photographic techniques to construct the grating. The second part of this thesis describes several phase-difference amplification systems where the diffraction grating is written on a liquid crystal spatial light modulator. The liquid crystal devices, which have a high resolution and much faster response times than the photographic development time, make the systems convenient and allow near-real-time operation. A phase map of the test object is retrieved using phase stepping techniques. Experimental results for each system are presented and compared. They show that amplification factors of up to 6 are easily achievable.
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Du, Jen-Wu, and 杜振武. "Refractive Index、Extinction Coefficient and Thickness of Thin Films Measured by White Light Interferometry." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/jxn48u.
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碩士明新科技大學
電子工程研究所
101
In this study, a white-light vertical scanning Michelson interferometer has been successfully built to measure refractive index, extinction coefficient, and thickness of optical thin films. The white-light interferometer, based on short white-light coherence length, measures the optical path between the top and bottom faces of a thin film by a vertical scanning method with zero-order interference fringe identification. Refractive index, extinction coefficient, and thickness of thin films are determined by fitting interference patterns of white-light intensity using a LabVIEW program with a simplex algorithm, made by ourselves. The differences of refractive index, extinction coefficient, and thickness of a dielectric film between measurements of the white-light interferometer and an ellipsometer are within 0.1, 0.01, and 5nm over the 400-700nm wavelength range. The differences of refractive index, extinction coefficient, and thickness of a thin metal film between measurements of the white-light interferometer and an ellipsometer are within 0.4, 0.2, and 1nm over the 400-700nm wavelength range. The method of measuring refractive index, extinction coefficient, and thickness of optical thin films has the advantages of inherently high sensitivity and accuracy.
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Wang, Pei-Syuan, and 王珮璇. "A New Approach to Calculate the Profile Measurement using White-Light Interferometry with Uneven Sampling Spacing." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/82d39q.
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碩士國立臺北科技大學
機電整合研究所
101
The white-light interferometry has been broadly used in micro/nano-structure in recent years. As environmental vibration affects the measurement accuracy, it is necessary to modulate offset-compensation of vibration. There are two methods for compensating the displacement of vibration. The first method is to use the PZT as feedback. The other method is to detect the displacement and use the appropriate algorithm to attenuate and correct adjustments. Of the two methods, the former relies on the accuracy of PZT. Its limitation is that the bandwidth of PZT stays low, causing delay to the compensatory system. The aim of this study is to use the embedded system in hope of achieving high-coherence by effectively mastering white-light interference fringe to calculate the offset with phase-shift algorithm. It focuses on signal processing with high-coherence interference fringe, which can be sampled in high and accurate resolution. According to the white-light interference principle, the highest peak of white-light interference fringe is the height of the object. Hence, it can be used as a method to estimate the peak using mathematical algorithm. White-light interferometry measurement assumes equidistant sampling condition, but the measurement is in aperiodic waveforms. This study estimated the peak of fringe which is sampled in unequal, aperiodic and asymmetric. In order to obtain the peak position of the white-light interference, the study uses white-light curve fitting algorithm for fitting sampling points, which can be applied to unequal, asymmetric signals. By using the algorithm to estimate the peak point of the white-light interference fringe, this study reconstructs the three dimension outlines of components to be analyzed. The algorithm developed by this study can calculate with the standard deviation of 2.22 nm, which is one of the better algorithms so far.
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Jen, Shu-yi, and 任書毅. "3-Dimensional Static and Dynamic Measurements by a White-Light Achromatic Phase-Shifting Interferometry on Microscope." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/32285247624249746459.
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碩士國立成功大學
機械工程學系碩博士班
95
A 3-Dimensional profilometer focuses on the measurement of microstructure surface profiles by using a new white-light phase-shifting interferometry was developed. This system originates from interferometric microscope with Mirau object lens. This kind of upright microscope differs from other interferometries, such as Linnik, Michelson, Fizeau interferometry, which were installed on optical table. The upright microscope can measure an item not only static but also kinematic specimen. Unlike the general kinematic microscopes, the setup uses a polarizer phase-shifter without using a PZT for a Mirau object lens. We combine Linnik interferometry on an upright microscope, and co-operate with a polarizer phase-shifter. The measurement with sub-wavelength scale resolution is achieved by measuring the fringe contrast function of the white-light interferogram. This non-destructive, non-contact optical interferometry can offer desirable depth measurement sensitivity and density of lateral resolution. This system is based on an available phase-shifters which employ a rotating polarization component at the light source end of the interferometry. In this new setup, a half-wave plate and a quarter-wave plate were used to modulate the phase difference of incident beams before entering microscope. The demanding precision of a polarization phase-shifter is not as high as the requirement in a traditional phase-shifting method with PZT for a Mirau object lens. Therefore, by using the technique, the speed of image processing will be faster than the speed of traditional phase-shifting method by PZT for a Mirau object lens. This new method has no problem like the noises caused by a PZT from the traditional one.
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Liao, Hsin-Hung, and 廖信宏. "A Micromirror Module using a MEMS Digital-to-Analog Converter and its Application for White-Light Interferometry System." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/67992207090398620449.
Full textAbstract:
博士國立臺灣大學
機械工程學研究所
99
In this work, we develop a microelectromechanical digital-to-analog converter mirror module (M-DACMM), and demonstrate its application for non-contact optical surface profiling systems. The proposed device generates nano-scale step motions that are proportional to input digital signals. The M-DACMM device, which consists of a large-area mirror, a digital-to-analog converter and 8 electrostatic parallel-plate actuators, can be monolithically fabricated by using a proposed micromachining process. Also, the process is suitable for releasing a large-area mirror (1mm in diameter) without the need of etching holes on the mirror surface. The transient responses of the mirror module are also measured and discussed. The switching time between two input binary states is less than 80 ms. The measured full-scale displacement is 1050 nm, and the motion step is 72 nm. The M-DACMM device has advantages of high position accuracy, high repeatability, and small size. Also, the device can be easily controlled by a simple actuation circuit. The M-DACMM is successfully installed on a white-light interferometry system as a reference mirror module. The surface-profiling results measured by the system are also presented.