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1
Fu, Bo. "A configurable real-time adaptive imaging and illumination system". Thesis, University of Nottingham, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.582595.
Testo completoAbstract (sommario):
Research on information processing in neuronal networks may lead to a better understanding of many brain diseases and disorders and could inform potential future treatments. It may also lead to the development of more intelligent electronic technology. To understand how the brain processes information we need to study the patterns of action potentials (APs) in a neuronal network over the long-term. The aim of this project, therefore, is to develop an optical system to both detect and stimulate APs in a small neuronal network. A closed-loop system has been developed that consists of a signal detection tool (a camera system), a signal analysis tool (a real-time computer) and a signal delivery tool (a spatially modulated light source). The conventional techniques for measuring APs, using patch clamp electrodes or multi electrode arrays for example, are limited by the spatial extent, or the spatial resolution, that can be achieved. Alternatively, optical imaging systems can be used to monitor APs. Imaging systems can achieve high-resolution across a wide field-of-view. To record network-wide neuronal activity a high- speed camera is necessary. Ideally imaging needs to be performed continuously over long periods of time. However, continuous high-speed imaging is typically not possible using commercially available systems due to restrictions in bandwidth.
2
Panayiotou, Stephen. "A domain independent adaptive imaging system for visual inspection". Thesis, University of Greenwich, 1995. http://gala.gre.ac.uk/8696/.
Testo completoAbstract (sommario):
Computer vision is a rapidly growing area. The range of applications is increasing very quickly, robotics, inspection, medicine, physics and document processing are all computer vision applications still in their infancy. All these applications are written with a specific task in mind and do not perform well unless there under a controlled environment. They do not deploy any knowledge to produce a meaningful description of the scene, or indeed aid in the analysis of the image. The construction of a symbolic description of a scene from a digitised image is a difficult problem. A symbolic interpretation of an image can be viewed as a mapping from the image pixels to an identification of the semantically relevant objects. Before symbolic reasoning can take place image processing and segmentation routines must produce the relevant information. This part of the imaging system inherently introduces many errors. The aim of this project is to reduce the error rate produced by such algorithms and make them adaptable to change in the manufacturing process. Thus a prior knowledge is needed about the image and the objects they contain as well as knowledge about how the image was acquired from the scene (image geometry, quality, object decomposition, lighting conditions etc,). Knowledge on algorithms must also be acquired. Such knowledge is collected by studying the algorithms and deciding in which areas of image analysis they work well in. In most existing image analysis systems, knowledge of this kind is implicitly embedded into the algorithms employed in the system. Such an approach assumes that all these parameters are invariant. However, in complex applications this may not be the case, so that adjustment must be made from time to time to ensure a satisfactory performance of the system. A system that allows for such adjustments to be made, must comprise the explicit representation of the knowledge utilised in the image analysis procedure. In addition to the use of a priori knowledge, rules are employed to improve the performance of the image processing and segmentation algorithms. These rules considerably enhance the correctness of the segmentation process. The most frequently given goal, if not the only one in industrial image analysis is to detect and locate objects of a given type in the image. That is, an image may contain objects of different types, and the goal is to identify parts of the image. The system developed here is driven by these goals, and thus by teaching the system a new object or fault in an object the system may adapt the algorithms to detect these new objects as well compromise for changes in the environment such as a change in lighting conditions. We have called this system the Visual Planner, this is due to the fact that we use techniques based on planning to achieve a given goal. As the Visual Planner learns the specific domain it is working in, appropriate algorithms are selected to segment the object. This makes the system domain independent, because different algorithms may be selected for different applications and objects under different environmental condition.
3
Trumbull, Tara. "Simulation and Analysis of an Adaptive SPECT Imaging System for Tumor Estimation". Thesis, The University of Arizona, 2011. http://hdl.handle.net/10150/144580.
Testo completoAbstract (sommario):
We have developed a simulation of the AdaptiSPECT small-animal Single Photon Emission Computed Tomography (SPECT) imaging system. The simulation system is entitled SimAdaptiSPECT and is written in C, NVIDIA CUDA, and Matlab. Using this simulation, we have accomplished an analysis of the Scanning Linear Estimation (SLE) technique for estimating tumor parameters, and calculated sensitivity information for AdaptiSPECT configurations.SimAdaptiSPECT takes, as input, simulated mouse phantoms (generated by MOBY) contained in binary files and AdaptiSPECT configuration geometry contained in ASCII text files. SimAdaptiSPECT utilizes GPU parallel processing to simulate AdaptiSPECT images. SimAdaptiSPECT also utilizes GPU parallel processing to perform 3-D image reconstruction from 2-D AdaptiSPECT camera images (real or simulated), using a novel variant of the Ordered Subsets Expectation Maximization (OSEM) algorithm. Methods for generating the inputs, such as a population of randomly varying numerical mouse phantoms with randomly varying hepatic lesions, are also discussed.
4
Chan, Lok-sang, e 陳樂生. "Adaptive flow detector and estimator for ultrasound high frame rate vector flow imaging". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47753043.
Testo completoAbstract (sommario):
Cardiovascular diseases is a leading cause of death worldwide and improvement of the
corresponding screening tool is the best way to deal with this clinical problem. In this thesis
we attempted to develop a framework of ultrasound high frame rate vector flow imaging
(VFI) by emphasizing on the design of corresponding flow detector and flow estimator. We
believe that the high temporal resolution and the complex blood flow visualization ability of
high frame rate VFI enables it to be further developed as a reliable flow imaging modality
for cardiological examination.
In order to achieve high temporal resolution, fast data acquisition algorithm was applied
in the framework. Doppler signals acquired using this acquisition algorithm have two
unique characteristics comparing with conventional data acquisition algorithm: (1) widen
spectral bandwidth and (2) greater clutter to blood signal ratio. These signal characteristics
give rise to unique signal processing. In addition, complex blood flow pattern, which
is common in cardiological examination, induces extra challenges in implementing high
frame rate VFI. In this thesis, flow detector which is adaptive to different flow scenarios
and high dynamic range 2D flow estimator were presented.
The proposed flow detector employes K-means++ clustering algorithm to classify clutter
components from acquired Doppler signals. As a performance analysis, Field II simulation
studies were performed by a parabolic flow phantom (flow velocity: 10mm/s to
200mm/s; tissue motion: 10mm/s; beam-flow angle: 60?). The post-filtered Doppler power
map and BCR were used as qualitative and quantitativemeasures of detectors performance.
Analyzed result has indicated that, as compared with clutter downmixing detector and
eigen-based detector, the proposed flow detector could classify and suppress clutter component
more effectively. Results also suggested that the proposed flow detector is more
adaptive to slow flow scenarios where existing flow detectors failed to distinguish between
blood and clutter components.
For the proposed flow estimator, it was characterized by the interpolation of speckle
tracking results in Lagrangian reference frame. The estimation bias and RMS error were
calculated for different flow scenarios (flow velocity: 100mm/s to 500mm/s; beam-flow
angle: 15? to 60?). It was found that the proposed flow estimator provides higher dynamic
range than conventional speckle tracking-based flow estimator. Nonetheless, it is also observed
that the estimation variances and errors increases in slow flow scenarios.
In order to demonstrate the medical potential of the proposed high frame rate VFI
framework. A carotid bifurcation simulation model with realistic blood flow pattern calculated
using computational fluid dynamic software was applied in the performance evaluation
study. In the VFI image obtained, complex blood flow pattern was readily visualized.
In contrast, conventional ultrasound flow imaging was only able to estimate axial velocity
map and thus lead to many ambiguities in analyzing the complex blood flow pattern. It
proved that ultrasound high frame rate VFI has the potential to be further developed into a
new cardiological examination technique.published_or_final_version
Electrical and Electronic Engineering
Master
Master of Philosophy
5
Pazder, John Stanley. "The optical design of an adaptive optics system imaging two selectable atmospheric layers". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ32673.pdf.
Testo completo
6
Elgort, Daniel Robert. "Real-Time Catheter Tracking and Adaptive Imaging for Interventional Cardiovascular MRI". Case Western Reserve University School of Graduate Studies / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=case1111437062.
Testo completo
7
Bai, Yu. "Characterization of an Adaptive Optics System for Vision Studies". University of Dayton / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1461796856.
Testo completo
8
Kasper, Markus Erdmann. "Optimization of an adaptive optics system and its application to high-resolution imaging spectroscopy of T Tauri". [S.l. : s.n.], 2000. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB8986347.
Testo completo
9
Almotiri, Jasem. "A Multi-Anatomical Retinal Structure Segmentation System for Automatic Eye Screening Using Morphological Adaptive Fuzzy Thresholding". Thesis, University of Bridgeport, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10975223.
Testo completoAbstract (sommario):
Eye exam can be as efficacious as physical one in determining health concerns. Retina screening can be the very first clue to detecting a variety of hidden health issues including pre-diabetes and diabetes. Through the process of clinical diagnosis and prognosis; ophthalmologists rely heavily on the binary segmented version of retina fundus image; where the accuracy of segmented vessels, optic disc and abnormal lesions extremely affects the diagnosis accuracy which in turn affect the subsequent clinical treatment steps. This thesis proposes an automated retinal fundus image segmentation system composed of three segmentation subsystems follow same core segmentation algorithm. Despite of broad difference in features and characteristics; retinal vessels, optic disc and exudate lesions are extracted by each subsystem without the need for texture analysis or synthesis. For sake of compact diagnosis and complete clinical insight, our proposed system can detect these anatomical structures in one session with high accuracy even in pathological retina images.
The proposed system uses a robust hybrid segmentation algorithm combines adaptive fuzzy thresholding and mathematical morphology. The proposed system is validated using four benchmark datasets: DRIVE and STARE (vessels), DRISHTI-GS (optic disc), and DIARETDB1 (exudates lesions). Competitive segmentation performance is achieved, outperforming a variety of up-to-date systems and demonstrating the capacity to deal with other heterogenous anatomical structures.
10
Namroud, Iman. "An Analysis of Aliasing and Image Restoration Performance for Digital Imaging Systems". University of Dayton / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1399046084.
Testo completo
11
Krug, Sarah Elaine. "Digital Phase Correction of a Partially Coherent Sparse Aperture System". University of Dayton / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1437476352.
Testo completo
12
Ren, Lan. "Integrated process planning for a hybrid manufacturing system". Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/Ren_09007dcc8046714a.pdf.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Missouri University of Science and Technology, 2008.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 18, 2008) Includes bibliographical references.
13
Powell, Keith. "Next generation wavefront controller for the MMT adaptive optics system: Algorithms and techniques for mitigating dynamic wavefront aberrations". Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/222838.
Testo completoAbstract (sommario):
Wavefront controller optimization is important in achieving the best possible image quality for adaptive optics systems on the current generation of large and very large aperture telescopes. This will become even more critical when we consider the demands of the next generation of extremely large telescopes currently under development. These telescopes will be capable of providing resolution which is significantly greater than the current generation of optical/IR telescopes. However, reaching the full resolving potential of these instruments will require a careful analysis of all disturbance sources, then optimizing the wavefront controller to provide the best possible image quality given the desired science goals and system constraints. Along with atmospheric turbulence and sensor noise, structural vibration will play an important part in determining the overall image quality obtained. The next generation of very large aperture telescopes currently being developed will require assessing the effects of structural vibration on closed loop AO system performance as an integral part of the overall system design. Telescope structural vibrations can seriously degrade image quality, resulting in actual spot full width half maximum (FWHM) and angular resolution much worse than the theoretical limit. Strehl ratio can also be significantly degraded by structural vibration as energy is dispersed over a much larger area of the detector. In addition to increasing telescope diameter to obtain higher resolution, there has also been significant interest in adaptive optics systems which observe at shorter wavelength from the near infrared to visible (VNIR) wavelengths, at or near 0.7 microns. This will require significant reduction in the overall wavefront residuals as compared with current systems, and will therefore make assessment and optimization of the wavefront controller even more critical for obtaining good AO system performance in the VNIR regime.
14
Savidis, Nickolaos. "Application and System Design of Elastomer Based Optofluidic Lenses". Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/255155.
Testo completoAbstract (sommario):
Adaptive optic technology has revolutionized real time correction of wavefront aberrations. Optofluidic based applied optic devices have offered an opportunity to produce flexible refractive lenses in the correction of wavefronts. Fluidic lenses have superiority relative to their solid lens counterparts in their capabilities of producing tunable optical systems, that when synchronized, can produce real time variable systems with no moving parts. We have developed optofluidic fluidic lenses for applications of applied optical devices, as well as ophthalmic optic devices. The first half of this dissertation discusses the production of fluidic lenses as optical devices. In addition, the design and testing of various fluidic systems made with these components are evaluated. We begin with the creation of spherical or defocus singlet fluidic lenses. We then produced zoom optical systems with no moving parts by synchronizing combinations of these fluidic spherical lenses. The variable power zoom system incorporates two singlet fluidic lenses that are synchronized. The coupled device has no moving parts and has produced a magnification range of 0.1 x to 10 x or a 20 x magnification range. The chapter after fluidic zoom technology focuses on producing achromatic lens designs. We offer an analysis of a hybrid diffractive and refractive achromat that offers discrete achromatized variable focal lengths. In addition, we offer a design of a fully optofluidic based achromatic lens. By synchronizing the two membrane surfaces of the fluidic achromat we develop a design for a fluidic achromatic lens.The second half of this dissertation discusses the production of optofluidic technology in ophthalmic applications. We begin with an introduction to an optofluidic phoropter system. A fluidic phoropter is designed through the combination of a defocus lens with two cylindrical fluidic lenses that are orientated 45° relative to each other. Here we discuss the designs of the fluidic cylindrical lens coupled with a previously discussed defocus singlet lens. We then couple this optofluidic phoropter with relay optics and Shack-Hartmann wavefront sensing technology to produce an auto-phoropter device. The auto-phoropter system combines a refractometer designed Shack-Hartmann wavefront sensor with the compact refractive fluidic lens phoropter. This combination allows for the identification and control of ophthalmic cylinder, cylinder axis, as well as refractive error. The closed loop system of the fluidic phoropter with refractometer enables for the creation of our see-through auto-phoropter system. The design and testing of several generations of transmissive see-through auto-phoropter devices are presented in this section.
15
Bailey, Vanessa Perry. "Adaptive Optics for Directly Imaging Planetary Systems". Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/577514.
Testo completoAbstract (sommario):
In this dissertation I present the results from five papers (including one in preparation) on giant planets, brown dwarfs, and their environments, as well as on the commissioning and optimization of the Adaptive Optics system for the Large Binocular Telescope Interferometer. The first three Chapters cover direct imaging results on several distantly-orbiting planets and brown dwarf companions. The boundary between giant planets and brown dwarf companions in wide orbits is a blurry one. In Chapter 2, I use 3–5 μm imaging of several brown dwarf companions, combined with mid-infrared photometry for each system to constrain the circum-substellar disks around the brown dwarfs. I then use this information to discuss limits on scattering events versus in situ formation. In Chapters 3 and 4, I present results from an adaptive optics imaging survey for giant planets, where the target stars were selected based on the properties of their circumstellar debris disks. Specifically, we targeted systems with debris disks whose SEDs indicated gaps, clearings, or truncations; these features may possibly be sculpted by planets. I discuss in detail one planet-mass companion discovered as part of this survey, HD 106906 b. At a projected separation of 650 AU and weighing in at 11 Jupiter masses, a companion such as this is not a common outcome of any planet or binary star formation model. In the remaining three Chapters, I discuss pre-commissioning, on-sky results, and planned work on the Large Binocular Telescope Interferometer Adaptive Optics system. Before construction of the LBT AO system was complete, I tested a prototype of LBTI's pyramid wavefront sensor unit at the MMT with synthetically-generated calibration files. I present the methodology and MMT on-sky tests in Chapter 5. In Chapter 6, I present the commissioned performance of LBTIAO. Optical imperfections within LBTI limited the quality of the science images, and I describe a simple method to use the adaptive optics system to correct for the science camera's optical aberrations. Finally, in Chapter 7, I discuss the status of a more sophisticated method for correcting these optical aberrations in LBTI.
16
Bigelow, Bruce Charles. "Deformable secondary mirrors for adaptive optics". Thesis, University College London (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243988.
Testo completo
17
Aggarwal, Vikas. "Remote sensing and imaging in a reconfigurable computing environment". [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0012171.
Testo completo
18
Moore, Jared William. "Adaptive X-ray Computed Tomography". Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/145396.
Testo completoAbstract (sommario):
An adaptive pre-clinical x-ray computed tomography system, named "FaCT" was designed, built, and tested at the University of Arizona's Center for Gamma-Ray Imaging (CGRI). The FaCT system possesses the unique ability to change its magnification and dynamically mask the x-ray beam profile. Using these two abilities, the FaCT system can adapt its configuration to the object being imaged, and the task being performed, while achieving a reduction in the radiation dose applied for imaging.Development of the system included the design of all mechanical components, motion systems, and safety systems. It also included system integration of all electronics, motors, and communication channels. Control software was developed for the system and several high-performance reconstruction algorithms were implemented on graphics processing units for reconstructing tomographic data sets acquired by the system. A new geometrical calibration method was developed for calibrating the system that makes use of the full image data gathered by the system and does not rely on markers.An adaptive imaging procedure consisting of a preliminary scout scan, human guidance, and a diagnostic quality scan was developed for imaging small volumes of interest in the interior of an object at substantially reduced dose. The adaptive imaging procedure makes use of FaCT's adjustable magnification, beam-masking capability, and high-performance reconstruction software to achieve high-quality reconstruction of a volume of interest with less dose than would be required by a traditional x-ray computed tomography system without adaptive capabilities.To address ongoing research into mathematical rules for adapting an imaging system, such as FaCT, to better perform a given estimation task, a method of quantifying a system's ability to estimate a parameter of interest in the presence of nuisance parameters based on the Fisher Information was proposed. The method requires a statistical model of object variability. Possible strategies for increasing the performance of an estimation task, given an adaptive system, were suggested.
19
Fu, Deng Yuan. "ADAPTIVE DIGITAL IMAGE DATA COMPRESSION BY RECURSIVE IDPCM". Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275350.
Testo completo
20
Bagwell, Brett Edward. "Liquid Crystal Active Optics for Military Imaging Systems". Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/193576.
Testo completoAbstract (sommario):
There are inherent tradeoffs in size, weight, and adaptability for many military imaging systems. In some cases, active optical devices provide new alternatives external to the traditional trade-space. Applications of interest include remote wide-area surveillance, tactical use of high altitude and space-based sensors, remote navigation of unmanned ground and air vehicles, and night vision systems.My goal is to demonstrate that by augmenting or replacing static dioptric, catatropic, or catadioptric optical designs, mechanical complexity can be reduced while either maintaining or increasing performance in three areas:(1). Spectral Resolution(2). Spatial Resolution(3). MagnificationI present here three different imaging systems to showcase these capabilities.
21
Page, Kelly A. "Applications of linear predictors in adaptive optics". Laramie, Wyo. : University of Wyoming, 2005. http://proquest.umi.com/pqdweb?did=888858341&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
Testo completo
22
Reddy, Manoj Kumar M. "A new adaptive edge enhancement algorithm for color laser printers /". Online version of thesis, 2007. http://hdl.handle.net/1850/5535.
Testo completo
23
Huang, Hanyang. "Adaptive Elastomer-liquid Lenses for Advancing the Imaging Capability of Miniaturized Optical Systems". The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1562076808810062.
Testo completo
24
Pathak, P., O. Guyon, N. Jovanovic, J. Lozi, F. Martinache, Y. Minowa, T. Kudo, H. Takami, Y. Hayano e N. Narita. "A High-precision Technique to Correct for Residual Atmospheric Dispersion in High-contrast Imaging Systems". IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/622414.
Testo completoAbstract (sommario):
Direct detection and spectroscopy of exoplanets requires high-contrast imaging. For habitable exoplanets in particular, located at a small angular separation from the host star, it is crucial to employ small inner working angle (IWA) coronagraphs that efficiently suppress starlight. These coronagraphs, in turn, require careful control of the wavefront that directly impacts their performance. For ground-based telescopes, atmospheric refraction is also an important factor, since it results in a smearing of the point-spread function (PSF), that can no longer be efficiently suppressed by the coronagraph. Traditionally, atmospheric refraction is compensated for by an atmospheric dispersion compensator (ADC). ADC control relies on an a priori model of the atmosphere whose parameters are solely based on the pointing of the telescope, which can result in imperfect compensation. For a high-contrast instrument like the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system, which employs very small IWA coronagraphs, refraction-induced smearing of the PSF has to be less than 1 mas in the science band for optimum performance. In this paper, we present the first on-sky measurement and correction of residual atmospheric dispersion. Atmospheric dispersion is measured from the science image directly, using an adaptive grid of artificially introduced speckles as a diagnostic to feedback to the telescope's ADC. With our current setup, we were able to reduce the initial residual atmospheric dispersion from 18.8 mas to 4.2 in broadband light (y- to H-band) and to 1.4 mas in the H-band only. This work is particularly relevant to the upcoming extremely large telescopes (ELTs) that will require fine control of their ADC to reach their full high-contrast imaging potential.
25
Ernst, Eric Gerard. "Architecture design of a scalable adaptive deblocking filter for H.264/AVC /". Online version of thesis, 2007. http://hdl.handle.net/1850/5390.
Testo completo
26
Perry, Stuart William. "Adaptive image restoration perception based neural network models and algorithms /". Connect to full text, 1998. http://hdl.handle.net/2123/389.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Sydney, 1999.Title from title screen (viewed Apr. 16, 2008). Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the School of Electrical and Information Engineering, Faculty of Engineering. Degree awarded 1999; thesis submitted 1998. Includes bibliography. Also available in print form.
27
Garcia, E. Victor, Thayne Currie, Olivier Guyon, Keivan G. Stassun, Nemanja Jovanovic, Julien Lozi, Tomoyuki Kudo et al. "SCExAO AND GPI Y JH BAND PHOTOMETRY AND INTEGRAL FIELD SPECTROSCOPY OF THE YOUNG BROWN DWARF COMPANION TO HD 1160". IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/623097.
Testo completoAbstract (sommario):
We present high signal-to-noise ratio, precise Y JH photometry and Y band (0.957-1.120 mu m) spectroscopy of HD 1160 B, a young substellar companion discovered from the Gemini NICI Planet Finding Campaign using the Subaru Coronagraphic Extreme Adaptive Optics instrument and the Gemini Planet Imager. HD 1160 B has typical mid-M dwarf-like infrared colors and a spectral type of M5.5(-0.5)(+1.0), where the blue edge of our Y band spectrum rules out earlier spectral types. Atmospheric modeling suggests HD 1160 B has an effective temperature of 3000-3100 K, a surface gravity of log g - 4-4.5, a radius of. 1.55 +/- 0.10 R-J, and a luminosity of log L/L circle dot - 2.76 +/- 0.05. Neither the primary's Hertzspring-Russell diagram position nor atmospheric modeling of HD 1160 B show evidence for a subsolar metallicity. Interpretation of the HD 1160 B spectroscopy depends on which stellar system components are used to estimate the age. Considering HD 1160 A, B and C jointly, we derive an age of 80-125 Myr, implying that HD 1160 B straddles the hydrogen-burning limit (70-90 M-J) If we consider HD 1160 A alone, younger ages (20-125 Myr) and a brown dwarf-like mass (35-90 M-J) are possible. Interferometric measurements of the primary, a precise Gaia parallax, and moderate-resolution spectroscopy can better constrain the system's age and how HD 1160 B fits within the context of (sub) stellar evolution.
28
Abad, Alexis. "Ιmagerie interférοmétrique de particules irrégulières pοur l'étude d'écοulements : dévelοppement d'un dispοsitif adaptatif et de méthοdes d'analyse par apprentissage prοfοnd". Electronic Thesis or Diss., Normandie, 2024. http://www.theses.fr/2024NORMR067.
Testo completoAbstract (sommario):
L’imagerie interférométrique de particules (IIP) en défaut de mise au point est une technique de granulométrie optique permettant de déterminer la forme et la taille de particules micrométriques : 20 µm − 2 000 µm. Elles peuvent être de nature différentes, par exemple, des cristaux de glace en suspension dans l’atmosphère, des cendres volcaniques, des nuages de grains de sable ou encore des particules de charbon disséminées autour de centrales thermiques. Les exemples précédents ont tous un point commun, ce sont des particules rugueuses, de formes irrégulières et les résultats de ces travaux de thèse s’appuient sur ces caractéristiques. L’acquisition d’images avec cette technique repose sur un principe de fonctionnement simple. Une particule rugueuse est illuminée avec un laser ; celle-ci diffuse une partie du rayonnement incident dans toutes les directions due aux aspérités à sa surface. Ces aspérités créent des sources secondaires du rayonnement incident. Un système d’imagerie en défaut de mise au point, enregistre les images des interférences issues de ces sources secondaires. Le développement et l’amélioration des programmes permettant de reconstruire la forme de la particule à partir de son image interférométrique est réalisé avec un banc expérimental équipé d’une matrice de micro-miroirs (DMD). La particule est "programmée" sur le DMD. Les micro-miroirs qui simulent les sources secondaires de la particule réfléchissent une partie du faisceau incident en direction du système d’imagerie. Ces travaux de thèse se concentrent d’une part sur la création d’un réseau de neurones permettant de classer la forme d’une particule à partir de son image interférométrique. Ce réseau de neurones a montré une reconnaissance dans 100% des cas. D’autre part, l’élaboration d’un autre réseau de neurones permettant de reconstruire l’enveloppe de particules irrégulières à partir de leurs images expérimentales a montré une très bonne qualité de reconstruction entre les formes programmées et les formes reconstruites. Dans les deux cas, des bases de données constituées de plusieurs milliers d’images expérimentales ont été acquises avec un montage expérimental équipé d’une matrice de micro-miroirs pour "simuler" les particules rugueuses. De plus, dans le cadre de cette technique, deux travaux supplémentaires ont été effectués : (i) d’abord une première méthode de correction de l’aberration sphérique, par passage de la base cartésienne à la base polaire, et une seconde de simulation de l’aberration sphérique en IIP, par décomposition du terme de phase en fonction gaussiènnes ; et (ii) la réalisation d’un système d’imagerie interférométrique adaptatif à base de lentille liquide a été mis au point permettant de réduire le recouvrement des interférogrammes par réglage instantané de la défocalisation du système d’imagerieOut-of-focus interferometric particle imaging (IPI) is an optical particle sizing technique used to determine the shape and size of micrometric particles: 20 µm − 2,000 µm. They can be of different natures, for example, ice crystals suspended in the atmosphere, volcanic ash, clouds of sand grains or coal particles scattered around thermal power plants. The previous examples all have one thing in common, they are rough particles, with irregular shapes and the results of this thesis work are based on these characteristics. Image acquisition with this technique is based on a simple operating principle. A rough particle is illuminated with a laser; it diffuses part of the incident radiation in all directions due to the asperities on its surface. These asperities create secondary sources of the incident radiation. An out-of-focus imaging system records interference images from these secondary sources. The development and improvement of programs to reconstruct the shape of the particle from its interferometric image is carried out with an experimental bench equipped with a micro-mirror matrix (DMD). The particle is "programmed" on the DMD. The micro-mirrors that simulate the secondary sources of the particle reflect part of the incident beam towards the imaging system. This thesis work focuses on the one hand on the creation of a neural network to classify the shape of a particle from its interferometric image. This neural network has shown recognition in 100% of cases. On the other hand, the development of another neural network to reconstruct the envelope of irregular particles from their experimental images has shown very good reconstruction quality between the programmed shapes and the reconstructed shapes. In both cases, databases consisting of several thousand experimental images were acquired with an experimental setup equipped with a micro-mirror matrix to "simulate" rough particles. In addition, within the framework of this technique, two additional works were carried out: (i) first a first method of correction of spherical aberration, by passage from the Cartesian basis to the polar basis, and a second of simulation of spherical aberration in IPI, by decomposition of the phase term into Gaussian functions; and (ii) the realization of an adaptive interferometric imaging system based on a liquid lens was developed to reduce the overlap of interferograms by instantaneous adjustment of the defocus of the imaging system
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Dhanantwari, Amar C. "Synthetic aperture and adaptive processing to track and correct for motion artifacts in x-ray CT imaging systems". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0015/NQ58122.pdf.
Testo completo
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Laag, Edward Aric. "Observations of starburst galaxies science and supporting technology /". Diss., [Riverside, Calif.] : University of California, Riverside, 2009. http://proquest.umi.com/pqdweb?index=0&did=1957320791&SrchMode=2&sid=2&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1268854875&clientId=48051.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of California, Riverside, 2009.Includes abstract. Available via ProQuest Digital Dissertations. Title from first page of PDF file (viewed March 16, 2010). Includes bibliographical references. Also issued in print.
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Ménigot, Sébastien. "Commande optimale appliquée aux systèmes d'imagerie ultrasonore". Phd thesis, Université François Rabelais - Tours, 2011. http://tel.archives-ouvertes.fr/tel-00657980.
Testo completoAbstract (sommario):
Les systèmes d'imagerie médicale ultrasonore ont considérablement amélioré le diagnostic clinique par une meilleure qualité des images grâce à des systèmes plus sensibles et des post-traitements. La communauté scientifique de l'imagerie ultrasonore a consenti à un très grand effort de recherche sur les post-traitements et sur le codage de l'excitation sans s'intéresser, outre mesure, aux méthodes de commande optimale. Ce travail s'est donc légitimement tourné vers les méthodes optimales basées sur l'utilisation d'une rétroaction de la sortie sur l'entrée. Pour rendre applicable ces méthodes, ce problème complexe de commande optimale a été transformé en un problème d'optimisation paramétrique sous-optimal et plus simple. Nous avons appliqué ce principe au domaine de l'imagerie ultrasonore : l'échographie, l'imagerie harmonique native et l'imagerie harmonique de contraste avec ou sans codage de la commande. La simplicité de l'approche nous a permis, par une modification de la fonction de coût, de l'adapter à l'imagerie harmonique. Cette adaptation montre que la méthode peut être appliquée à l'imagerie ultrasonore en générale. Aujourd'hui, les enjeux de l'imagerie ultrasonore portent non seulement sur les traitements des excitations ou des images mais aussi sur les capteurs. Ce point nous a conduit naturellement à rechercher la commande optimale des transducteurs capacitifs (cMUT) afin de les adapter à une utilisation plus large en imagerie ultrasonore codée. Nos méthodes de compensation et de codage par commande optimale procurent des résultats très prometteurs qui vont au delà de nos espérances. Le champ d'applications de nos méthodes de codage optimal est large et nous n'en voyons pas forcément encore toutes les limites. L'atout majeur de nos approches est leur simplicité d'utilisation et d'implémentation. En effet, elles ne nécessitent pas d'informations a priori difficilement accessibles sur les outils utilisés ou milieux explorés. Notre système s'adapte automatiquement aux variations qui peuvent être liées au vieillissement du capteur ou à la modification du milieu exploré.
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Mendes, da Costa Rodrigues Gonçalo. "Adaptive optics with segmented deformable bimorph mirrors". Doctoral thesis, Universite Libre de Bruxelles, 2010. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210166.
Testo completoAbstract (sommario):
The degradation of astronomical images caused by atmospheric turbulence will be much more severe in the next generation of terrestrial telescopes and its compensation will require deformable mirrors with up to tens-of-thousands of actuators.Current designs for these correctors consist of scaling up the proven technologies of flexible optical plates deformed under the out-of-plane action of linear actuators. This approach will lead to an exponential growth of cost with the number of actuators, and in very complex mechanisms.
This thesis proposes a new concept of optical correction which is modular, robust, lightweight and low-cost and is based on the bimorph in-plane actuation.
The adaptive mirror consists of segmented identical hexagonal bimorph mirrors allowing to indefinitely increase the degree of correction while maintaining the first mechanical resonance at the level of a single segment and showing an increase in price only proportional to the number of segments.
Each bimorph segment can be mass-produced by simply screen-printing an array of thin piezoelectric patches onto a silicon wafer resulting in very compact and lightweight modules
and at a price essentially independent from the number of actuators.
The controlled deformation of a screen-printed bimorph mirror was experimentally achieved with meaningful optical shapes and appropriate amplitudes; its capability for compensating turbulence was evaluated numerically. The generation of continuous surfaces
by an assembly of these mirrors was numerically simulated and a demonstrator of concept consisting of 3 segments was constructed.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
33
Oscanoa1, Julio, Marcelo Mena e Guillermo Kemper. "A Detection Method of Ectocervical Cell Nuclei for Pap test Images, Based on Adaptive Thresholds and Local Derivatives". Science and Engineering Research Support Society, 2015. http://hdl.handle.net/10757/624843.
Testo completoAbstract (sommario):
Cervical cancer is one of the main causes of death by disease worldwide. In Peru, it holds the first place in frequency and represents 8% of deaths caused by sickness. To detect the disease in the early stages, one of the most used screening tests is the cervix Papanicolaou test. Currently, digital images are increasingly being used to improve Pap test efficiency. This work develops an algorithm based on adaptive thresholds, which will be used in Pap smear assisted quality control software. The first stage of the method is a pre-processing step, in which noise and background removal is done. Next, a block is segmented for each one of the points selected as not background, and a local threshold per block is calculated to search for cell nuclei. If a nucleus is detected, an artifact rejection follows, where only cell nuclei and inflammatory cells are left for the doctors to interpret. The method was validated with a set of 55 images containing 2317 cells. The algorithm successfully recognized 92.3% of the total nuclei in all images collected.Revisón por pares
34
Rodriguez, Colmeiro Ramiro German. "Towards Reduced Dose Positron Emission Tomography Imaging Using Sparse Sampling and Machine Learning". Thesis, Troyes, 2021. http://www.theses.fr/2021TROY0015.
Testo completoAbstract (sommario):
Cette thèse étudie le problème de dose de radiation dans les études de Tomographie par Émission de Positons (PET). Trois aspects du PET-scan sont analysées. La première partie de cette thèse est dédiée à la technologie PET-scan. Deux techniques sont développées pour le PET-scan à faible dose : l’AR-PET. Une première stratégie de sélection et de placement de photomultiplicateurs est proposée, augmentant la résolution énergétique. Une technique de localisation d’impacts des photons gamma dans les cristaux solides de scintillation est développé. Cette technique est basée sur des réseaux de neurones artificiels et sur une acquisition unique de champ. Nous montrons qu’une augmentation de la sensibilité du détecteur est obtenue. Dans la deuxième partie de cette thèse, la reconstruction de l’image PET avec l’aide de maillages est étudiée. Un algorithme de reconstruction qui utilise une série de maillages 2D pour décrire la distribution 3D du radiotraceur est proposé, résultant en une diminution du nombre de points d’échantillonnage et rendant possible l’optimisation et la parallélisation des maillages. Enfin, la génération de l’image d’atténuation au moyen de réseaux de neurones artificiels profonds est explorée. L’apprentissage du réseau de neurones se fait à travers une transformation d’images PET FDG sans correction d’atténuation pour produire une image de tomodensitométrie (CT) synthétique. La conclusion des travaux de cette thèse pose la base pour l’usage de PET-scan à bas coût et a faible dose, via l’usage d’une image d’atténuation artificielleThis thesis explores the reduction of the patient radiation dose in screening Positron Emission Tomography (PET) studies. It analyses three aspects of PET imaging, which can reduce the patient dose: the data acquisition, the image reconstruction and the attenuation map generation. The first part of the thesis is dedicated to the PET scanner technology. Two optimization techniques are developed for a novel low-cost and low-dose scanner, the AR-PET scanner. First a photomultiplier selection and placement strategy is created, improving the energy resolution. The second work focuses on the localization of gamma events on solid scintillation crystals. The method is based on neural networks and a single flood acquisition, resulting in an increased detector’s sensitivity. In the second part, the PET image reconstruction on mesh support is studied. A mesh-based reconstruction algorithm is proposed which uses a series of 2D meshes to describe the 3D radiotracer distribution. It is shown that with this reconstruction strategy the number of sample points can be reduced without loosing accuracy and enabling parallel mesh optimization. Finally the attenuation map generation using deep neural networks is explored. A neural network is trained to learn the mapping from non attenuation corrected FDG PET images to a synthetic Computerized Tomography. With these approaches, this thesis lays a base for a low-cost and low-dose PET screening system, dispensing the need of a computed tomography image in exchange of an artificial attenuation map
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Zurlo, Alice. "Characterization of exoplanetary systems with the direct imaging technique: towards the first results of SPHERE at the Very Large Telescope". Doctoral thesis, Università degli studi di Padova, 2015. http://hdl.handle.net/11577/3424178.
Testo completoAbstract (sommario):
In the year of the 20th anniversary of the discovery of the first extrasolar planet we can count more than 1800 companions found with different techniques. The majority of them are indirect methods that infer the presence of an orbiting body by observing the parent star (radial velocity, transits, astrometry). In this work we explore the technique that permits to directly observe planets and retrieve their spectra, under the conditions that they are bright and far enough from their host star.
Direct imaging is a new technique became possible thanks to a new generation of extreme adaptive optics instruments mounted on 8m class telescopes. On the Very Large Telescope two instruments dedicated to the research for exoplanets with direct imaging are now operative: NACO and SPHERE.
This thesis will describe the development and results of SPHERE from its predecessor NACO to its integration in laboratory and the final on sky results.
Chapter 1 gives a presentation of the exoplanet research, the formation mechanisms, and the characterization of planet atmospheres. Chapter 2 gives a general frame of the two instruments used for the results presented in this thesis: NACO and SPHERE. In Chapter 3 I describe an example of a false positive in the direct imaging technique, found during the survey NACO-Large Program. This work have been published in Zurlo et al. 2013. In Chapter 4 I present the performance of SPHERE, in particular of the subsystems IRDIS and IFS, deeply tested in the laboratory before the shipping to Paranal. This work has been published in Zurlo et al. 2014. Chapter 5 presents a work done to find special targets for the NIRSUR survey, these object are radial velocity long period planets which are observable with SPHERE. In Chapter 6 I present one of the first on sky result, the observations and analysis of the multi-planetary system HR\,8799. In Chapter 7 I give the conclusions and future prospects.Al giorno d'oggi più di 1800 pianeti sono stati scoperti orbitare attorno a stelle al di fuori del sistema solare. Le tecniche utilizzate per la ricerca di pianeti extrasolari sono molteplici: alcune, dette metodi indiretti, si basano sull'osservazione della perturbazione indotta dal pianeta orbitante sulla stella ospite, mentre altre si basano sull'osservazione diretta del pianeta stesso. La maggior parte dei pianeti scoperti attualmente é stata rivelata grazie ai primi. Specialmente il metodo delle velocità radiali e dei transiti hanno fornito il più alto numero si scoperte. Lo svantaggio di questo tipo di tecniche é che la caratterizzazione del pianeta non può essere completa a meno che non vengano usate simultaneamente più tecniche. Inoltre, per ottenere lo spettro del pianeta, quest'ultimo deve transitare e anche in questo caso il segnale é difficilmente estrapolabile. L'osservazione diretta di questi oggetti, detta “direct imaging”, é oggi possibile grazie ad avanzati sistemi di ottica adattiva installati su telescopi della classe 8m. Il direct imaging permette l'osservazione diretta di pianeti sufficientemente luminosi e distanti dalla stella ospite grazie ad una maschera che oscura la luce di quest'ultima. Questa tecnica quindi é particolarmente efficiente su sistemi giovani e vicini, dato che la luminosità intrinseca del pianeta diminuisce con l'età e che la separazione effettiva del pianeta dipende dalla distanza del sistema stesso. Sul Very Large Telescope a Paranal (Chile) due strumenti sono dedicati a questo tipo di ricerca: NACO e SPHERE. NACO é stato pensato come predecessore e prototipo di SPHERE, ma viene mantenuto grazie alle sue performance ancora competitive ed ad alcune caratteristiche che non sono presenti in SPHERE. SPHERE ha visto la sua prima luce in Maggio 2014 ed é ora pronto per cominciare una survey dedicata alla scoperta di pianeti attorno a sistemi giovani e vicini, NISUR. Questo strumento é composto da tre sottosistemi: IRDIS, IFS e ZIMPOL. IRDIS é una camera infrarossa cui detector é suddiviso in due porzioni uguali per sfruttare l'immagine simultanea del target in due filtri adiacenti. IFS é lo spettrografo di SPHERE, permette di estrarre lo spettro del pianeta con risoluzioni di 30 e 50 a seconda della banda spettrale utilizzata. ZIMPOL é l'unico sottosistema che lavora nel visibile, viene utilizzato per osservare la polarizzazione dei sistemi planetari. In questo lavoro viene presentato lo strumento SPHERE e il suo predecessore NACO, focalizzando sui risultati e sulle performance nella caratterizzazione dei sistemi planetari.
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Zurlo, Alice. "Characterization of exoplanetary systems with the direct imaging technique : towards the first results of SPHERE at the Very Large Telescope". Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4721/document.
Testo completoAbstract (sommario):
Aujourd’hui, plus de 1800 planètes qui orbitent autour d’étoiles en dehors du système solaire ont été découvertes. La plupart des planètes découvertes actuellement a été révélée grâce aux méthodes indirectes. Par contre, avec ce type de techniques, la caractérisation des planètes ne peut pas être complète si on n’utilise pas plusieurs techniques simultanément. Aussi, pour obtenir le spectre de la planète, il doit y avoir un transit et même dans ce cas là,le signal est très faible par rapport au signal de l’étoile. L’observation directe de ces objets, appellée imagerie directe, est maintenant possible grâce à des systèmes très avancés d’optique adaptative installés sur des télescopes de classe 8m. L’imagerie directe permet l’observation des planètes sufisamment lumineuses et éloignées de l’étoile principale en utilisant un masque qui cache la lumière de la dernière. Cette technique est donc efficace en particulier pour des systèmes jeunes et voisins car la luminosité intrinsèque de la planète diminue avec l’âge et la séparation réelle de la planète dépend de la distance du système. Dans le VLT au Paranal (Chili), deux instruments sont dédiés à ce type de recherche : NACO et SPHERE. SPHERE a vu sa première lumière en Mai 2014, et est maintenant prêt à commencer une enquête consacrée à la découverte de planètes autour de systèmes jeunes et voisins, NIRSUR. Cet instrument se compose de trois sous-systèmes : IRDIS, IFS et ZIMPOLIn the year of the 20th anniversary of the discovery of the first extrasolar planet we can count more than 1800 companions found with different techniques. The majority of them are indirect methods that infer the presence of an orbiting body by observing the parent star (radial velocity, transits, astrometry). In this work we explore the technique that permits to directly observe planets and retrieve their spectra, under the conditions that they are bright and far enough from their host star. Direct imaging is a new technique became possible thanks to a new generation of extreme adaptive optics instruments mounted on 8m class telescopes. On the Very Large Telescope two instruments dedicated to the research for exoplanets with direct imaging are now operative: NACO and SPHERE. This thesis will describe the development and results of SPHERE from its predecessor NACO to its integration in laboratory and the final on sky results
37
Huisman, Maximiliaan. "Vision Beyond Optics: Standardization, Evaluation and Innovation for Fluorescence Microscopy in Life Sciences". eScholarship@UMMS, 2019. https://escholarship.umassmed.edu/gsbs_diss/1017.
Testo completoAbstract (sommario):
Fluorescence microscopy is an essential tool in biomedical sciences that allows specific molecules to be visualized in the complex and crowded environment of cells. The continuous introduction of new imaging techniques makes microscopes more powerful and versatile, but there is more than meets the eye. In addition to develop- ing new methods, we can work towards getting the most out of existing data and technologies. By harnessing unused potential, this work aims to increase the richness, reliability, and power of fluorescence microscopy data in three key ways: through standardization, evaluation and innovation.
A universal standard makes it easier to assess, compare and analyze imaging data – from the level of a single laboratory to the broader life sciences community. We propose a data-standard for fluorescence microscopy that can increase the confidence in experimental results, facilitate the exchange of data, and maximize compatibility with current and future data analysis techniques.
Cutting-edge imaging technologies often rely on sophisticated hardware and multi-layered algorithms for reconstruction and analysis. Consequently, the trustworthiness of new methods can be difficult to assess. To evaluate the reliability and limitations of complex methods, quantitative analyses – such as the one present here for the 3D SPEED method – are paramount.
The limited resolution of optical microscopes prevents direct observation of macro- molecules like DNA and RNA. We present a multi-color, achromatic, cryogenic fluorescence microscope that has the potential to produce multi-color images with sub-nanometer precision. This innovation would move fluorescence imaging beyond the limitations of optics and into the world of molecular resolution.
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Ficocelli, Maurizio. "Distributed control of a retinal imaging adaptive optics system /". 2008. http://proquest.umi.com/pqdlink?did=1659920911&sid=9&Fmt=2&clientId=12520&RQT=309&VName=PQD.
Testo completo
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Chaix, Cécile, Stephen Kovalsky, Matthew A. Kupinski, Harrison H. Barrett e Lars R. Furenlid. "Design and fabrication of a preclinical adaptive SPECT imaging system : AdaptiSPECT". 2014. http://hdl.handle.net/10150/337235.
Testo completo
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Hsu, Kuo-chan, e 徐國展. "Adaptive optics-assisted imaging system for roughness measurement of metal surface". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/29742131088526566655.
Testo completoAbstract (sommario):
碩士國立中央大學
光機電工程研究所
99
The aim of this study is using a newly-developed method of intensity distribution of binary image (SdBD) for measuring surface roughness under dynamic turbulence with adaptive optics (AO) system. The focus of the study is (1) roughness measurement based on spatial average analysis of binary speckle image, (2) adaptive optics system for correcting aberrations induced by under dynamic turbulence and combinative interfaces of refractive-index-mismatch, (3) Adaptive optics-assisted imaging system for roughness measurement of metal surface. (1) The speckle image was obtained by illuminating a laser beam and the reflected laser pattern image from a surface was binarizd and examined. The intensity distribution of binary image utilizes the combined effects of speckle and scattering phenomena. A new parameter of intensity distribution of binary image, SdBD has been proposed and the surface roughness parameter Ra of machined surfaces (ground) was correlated experimentally. Measurement results demonstrate an excellent correlation between the SdBD and Ra with correlation coefficient of 0.9706. The practicality of the proposed method In-situ roughness measurement was applied to six samples from roughness Ra 0.2 to 6.25μm (0.3 λ and 10 λ, where λ is diode laser wavelength) of steel through grinding process. (2). This study experimentally demonstrate the capability of adaptive optics (AO) correction on aberrations induced by dynamic turbulence and combinative effects of multiple layers with convex/concave interfaces as well as Refractive-Index-Mismatch (RIM). A deformable mirror (DM) was used as a wavefront corrector, the wavefront aberration was detected by a Shack-Hartmann wavefront sensor. In the absence of AO correction scheme, induced low temporal turbulences can severely degrade the residual RMS (root-mean-square) errors of 0.26 μm. After real time closed-loop AO correction, we can improve wavefront to RMS of 0.07 μm, which not only compensate aberration error from induced disturbances, but also overall optical system. In addition, AO was found to be able to steadily compensate wavefront errors in less than 3 seconds. For Refractive-Index-Mismatch, we consider the aberration introduced by interfaces of RIM between water/oil and glass. After adaptive optics correction, we can improve wavefront with root mean square (RMS) of 2.17 to 0.17 μm for an interface between water and glass. As for the interface between oil and glass, we are capable of improving RMS of 0.24 to 0.10 μm. The benefits of AO correction are facilitated by removing low order of Zernike modes such as defocus and tip/tilt, which are found to be the two main contributing factors in serial arrangement of convex/concave interfaces and RIM. Adaptive optics system shows correction capability for multiple layers of different geometrical interfaces with RIM. (3).This study proposes an integrated roughness measurement system based on adaptive optics (AO) and binarized analysis of speckle pattern images. The main purpose of this study is to demonstrate the necessity of AO compensation where disturbances of both heat and fluid flow exist. The speckle image was first obtained by illuminating a laser beam and the reflected laser pattern image from a surface was binarized to experimentally correlate with the intensity. In the absence of AO correction scheme, induced turbulences can severely degrade the residual RMS errors from 0.14 to 1.4 μm. After real time closed-loop AO correction, we can improve wavefront with RMS of 0.12 μm, which not only compensate aberration error from induced disturbances, but also overall optical system. In addition, AO with various gains in control system was investigated and a threshold gain value was found to be able to steadily compensate wavefront errors in less than 2 seconds. Measurement results of five steel samples from roughness Ra =0.2 to 3.125μm (0.3 λ and 5 λ, where λ is diode laser wavelength) demonstrate an excellent correlation between the SdBD and Ra with correlation coefficient of 0.9982. We have developed an in-process measurement of surface roughness by combining an optical probe of laser scattering phenomena and adaptive optics for aberration corrections. The aim of this study is to demonstrate the necessity for AO compensation in regions containing turbulence of fluid flow. In the absence of the AO correction scheme, induced turbulence can severely increase the residual root mean square (RMS) error to 1.5 μm. After a real-time closed-loop AO correction, we can reduce the wavefront RMS error to 0.14 μm. Measurement results of five steel samples having roughness ranging from 0.2 to 3.125 μm (0.3λ and 5λ, where λ is the diode laser wavelength) demonstrate an excellent correlation between the peak power and average roughness with a correlation coefficient (R2) of 0.9967. The results were verified by the stylus method using three samples of steel (AISI 304) under various mechanical grinding conditions. The proposed AO-assisted system is in good agreement with less than 8.7% error values. Therefore, the developed system can be used as a rapid in-process roughness monitor/estimator to further increase the precision and stability of manufacturing processes in-situ.
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Tsai, Ming-Chia, e 蔡銘嘉. "Low-Complexity Adaptive Beamformer Engine in High Frame Rate Ultrasound Imaging System". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/90988686213995572358.
Testo completoAbstract (sommario):
碩士臺灣大學
電子工程學研究所
98
Medical imaging system is to provide a visual representation of anatomical structures, blood flow velocity, and other diagnostic information. Currently, the mainly three applications in ultrasound system are B-mode image processing, color Doppler, or spectral Doppler. B mode image represents the power of the received echo. The Doppler mode is used for blood flow estimation and cardiac muscle observation. In this thesis, we focus on B mode imaging. Since the natural characteristics of the propagation wave, beamforming thus play a vital role in array signal processing, whose functionality is to focus the received echoes. Beamforming can be performed by real aperture and synthetic aperture with corresponding ways of delay calculation to focus echoes. The oldest but the most popular method is to delay and sum for received echoes alignment, which we adopt in this work. Real aperture use full array, which consumes more power and computation complexity to form an image. Synthetic aperture uses less hardware overhead in trade of image quality. High frame rate imaging system (HFR) is just composed of synthetic transmit aperture and broad transmit beams (plane wave, defocused beams, and diffraction beams). The techniques of digital signal processing can overcome this problem by weighting adjustment on channels. Methods of constant weighting are often used to beam shaping; however, adaptive methods are also applied to medical signal processing recently. For example, CFMVDR aims to enhance terrible image quality in HFR system. The problem is the high complexity of weighing calculation. In this thesis, we propose a new method of low complexity adaptive imaging. This method has little hardware overhead without performance loss. We have built the proposed model on Matlab to test the efficacy by both synthetic data using Field II and clinical data of breast from female patients. Still, we implement the proposed adaptive beamforming on CUDA (Compute Unified Device Architecture, new platform of multi-core computing) and propose some methods of modification. In the assistance of multi-core platform, the proposed adaptive imaging can be proven to approach the requirement of real time application, which is ever published. Through this thesis, we offer the new concepts combined with adaptive algorithms and implementations for future research in this domain.
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Leung, Erich Tak-Him. "Adaptive enhancement of cardiac magnetic resonance (MR) images /". 2005.
Cerca il testo completoAbstract (sommario):
Thesis (M.Sc.)--York University, 2005. Graduate Programme in Computer Science.Typescript. Includes bibliographical references (leaves 186-196). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url%5Fver=Z39.88-2004&res%5Fdat=xri:pqdiss &rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR11837
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Shain, William Jacob. "Solutions to linear problems in aberrated optical systems". Thesis, 2018. https://hdl.handle.net/2144/31761.
Testo completoAbstract (sommario):
Linear problems are possibly the kindest problems in physics and mathematics. Given sufficient information, the linear equations describing such problems are intrinsically solvable. The solution can be written as a vector having undergone a linear transformation in a vector space; extracting the solution is simply a matter of inverting the transformation. In an ideal optical system, the problem of extracting the object under investigation would be well defined, and the solution trivial to implement. However, real optical systems are all aberrated in some way, and these aberrations obfuscate the information, scrambling it and rendering it inextricable. The process of detangling the object from the aberrated system is no longer a trivial problem or even a uniquely solvable one, and represents one of the great challenges in optics today. This thesis provides a review of the theory behind optical microscopy in the presence of absent information, an architecture for the modern physical and computational methods used to solve the linear inversion problem, and three distinct application spaces of relevance. I hope you find it useful.
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Iqbal, Azhar. "Modeling and Control of a Magnetic Fluid Deformable Mirror for Ophthalmic Adaptive Optics Systems". Thesis, 2009. http://hdl.handle.net/1807/24310.
Testo completoAbstract (sommario):
Adaptive optics (AO) systems make use of active optical elements, namely wavefront correctors, to improve the resolution of imaging systems by compensating for complex optical aberrations. Recently, magnetic fluid deformable mirrors (MFDM) were proposed as a novel type of wavefront correctors that offer cost and performance advantages over existing wavefront correctors. These mirrors are developed by coating the free surface of a magnetic fluid with a thin reflective film of nano-particles. The reflective surface of the mirrors can be deformed using a locally applied magnetic field and thus serves as a wavefront corrector. MFDMs have been found particularly suitable for ophthalmic imaging systems where they can be used to compensate for the complex aberrations in the eye that blur the images of the internal parts of the eye. However, their practical implementation in clinical devices is hampered by the lack of effective methods to control the shape of their deformable surface.
The research work reported in this thesis presents solutions to the surface shape control problem in a MFDM that will make it possible for such devices to become integral components of retinal imaging AO systems. The first major contribution of this research is the development of an accurate analytical model of the dynamics of the mirror surface shape. The model is developed by analytically solving the coupled system of fluid-magnetic equations that govern the dynamics of the surface shape. The model is presented in state-space form and can be readily used in the development of surface shape control algorithms. The second major contribution of the research work is a novel, innovative design of the MFDM. The design change was prompted by the findings of the analytical work undertaken to develop the model mentioned above and is aimed at linearizing the response of the mirror surface. The proposed design also allows for mirror surface deflections that are many times higher than those provided by the conventional MFDM designs. A third contribution of this thesis involves the development of control algorithms that allowed the first ever use of a MFDM in a closed-loop adaptive optics system. A decentralized proportional-integral (PI) control algorithm developed based on the DC model of the wavefront corrector is presented to deal mostly with static or slowly time-varying aberrations. To improve the stability robustness of the closed-loop AO system, a decentralized robust proportional-integral-derivative (PID) controller is developed using the linear-matrix-inequalities (LMI) approach. To compensate for more complex dynamic aberrations, an Hinf controller is designed using the mixed-sensitivity Hinf design method. The proposed model, design and control algorithms are experimentally tested and validated.
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Rosenberg, Luke. "Multichannel synthetic aperture radar". 2007. http://hdl.handle.net/2440/37884.
Testo completoAbstract (sommario):
"In this thesis, the two problems of image formation for a Multichannel Synthetic Aperture Radar (MSAR) and suppressing interferences while forming a good quality image have been addressed. For the first problem, three wavefront reconstruction algorithms were presneted based on the multichannel Matched Filter (MF) imagining equation which demonstrated differing levels of performance and accuracy. A fourth algorithm known as multichannel backprojection was also presented to provide comparative quality with a reduced computational load. To address the second problem, a detailed jammer model was described and tested with a multichannel imaging algorithm to demonstrate the effect of hot-clutter on a SAR image. Multi-channel imaging and optimal slow-time Space Time Adaptive Processing (STAP) were shown to only partially suppress the hot-clutter interference, while optimal fast-time STAP demonstrated a much greater performance." --p. 185 of source document.Thesis (Ph.D.)--School of Electrical and Electronic Engineering, 2007.
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Kriske, Jeffery Edward Jr. "A scalable approach to processing adaptive optics optical coherence tomography data from multiple sensors using multiple graphics processing units". Thesis, 2014. http://hdl.handle.net/1805/6458.
Testo completoAbstract (sommario):
Indiana University-Purdue University Indianapolis (IUPUI)Adaptive optics-optical coherence tomography (AO-OCT) is a non-invasive method of imaging the human retina in vivo. It can be used to visualize microscopic structures, making it incredibly useful for the early detection and diagnosis of retinal disease. The research group at Indiana University has a novel multi-camera AO-OCT system capable of 1 MHz acquisition rates. Until this point, a method has not existed to process data from such a novel system quickly and accurately enough on a CPU, a GPU, or one that can scale to multiple GPUs automatically in an efficient manner. This is a barrier to using a MHz AO-OCT system in a clinical environment. A novel approach to processing AO-OCT data from the unique multi-camera optics system is tested on multiple graphics processing units (GPUs) in parallel with one, two, and four camera combinations. The design and results demonstrate a scalable, reusable, extensible method of computing AO-OCT output. This approach can either achieve real time results with an AO-OCT system capable of 1 MHz acquisition rates or be scaled to a higher accuracy mode with a fast Fourier transform of 16,384 complex values.
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Shafer, Brandon Andrew. "Real-time adaptive-optics optical coherence tomography (AOOCT) image reconstruction on a GPU". Thesis, 2014. http://hdl.handle.net/1805/6105.
Testo completoAbstract (sommario):
Indiana University-Purdue University Indianapolis (IUPUI)Adaptive-optics optical coherence tomography (AOOCT) is a technology that has been rapidly advancing in recent years and offers amazing capabilities in scanning the human eye in vivo. In order to bring the ultra-high resolution capabilities to clinical use, however, newer technology needs to be used in the image reconstruction process. General purpose computation on graphics processing units is one such way that this computationally intensive reconstruction can be performed in a desktop computer in real-time. This work shows the process of AOOCT image reconstruction, the basics of how to use NVIDIA's CUDA to write parallel code, and a new AOOCT image reconstruction technology implemented using NVIDIA's CUDA. The results of this work demonstrate that image reconstruction can be done in real-time with high accuracy using a GPU.