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Wittwer, Christian. "Fundamentals of digital imaging /." Online version of thesis, 1995. http://hdl.handle.net/1850/12257.
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Velasco, J. Cabello. "High throughput digital autoradiography imaging." Thesis, University of Surrey, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.510588.
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Walls, Kirsty. "Nanophotonic filters for digital imaging." Thesis, University of Glasgow, 2013. http://theses.gla.ac.uk/4514/.
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There has been an increasing demand for low cost, portable CMOS image sensors because of increased integration, and new applications in the automotive, mobile communication and medical industries, amongst others. Colour reproduction remains imperfect in conventional digital image sensors, due to the limitations of the dye-based filters. Further improvement is required if the full potential of digital imaging is to be realised. In alternative systems, where accurate colour reproduction is a priority, existing equipment is too bulky for anything but specialist use. In this work both these issues are addressed by exploiting nanophotonic techniques to create enhanced trichromatic filters, and multispectral filters, all of which can be fabricated on-chip, i.e. integrated into a conventional digital image sensor, to create compact, low cost, mass produceable imaging systems with accurate colour reproduction. The trichromatic filters are based on plasmonic structures. They exploit the excitation of surface plasmon resonances in arrays of subwavelength holes in metal films to filter light. The currently-known analytical expressions are inadequate for optimising all relevant parameters of a plasmonic structure. In order to obtain arbitrary filter characteristics, an automated design procedure was developed that integrated a genetic algorithm and 3D finite-difference time-domain tool. The optimisation procedure's efficacy is demonstrated by designing a set of plasmonic filters that replicate the CIE (1931) colour matching functions, which themselves mimic the human eye's daytime colour response. The best designs were fabricated and demonstrated a least-mean-square error, in comparison to the desired colour matching functions, of 6.37*10^3, 2.34*10^3 and 11.10*10^3 for the red, green, and blue filters respectively. Notably the spectrum for the red filter contained a double peak, as present in the corresponding colour matching function. Such dual peak behaviour cannot be achieved using a single current dye-based filter. The filters retain the same layer thickness for all structures so they can be defined in a single lithography step. A new approach to enable the fabrication of a multispectral filter array on a CMOS imager is also presented. This combines a Fabry-Perot filter with effective medium theory (EMT) to enable the fabrication of multiple filters in a single cavity length via lithographic tuning of the filter passband. Two approaches are proposed; air-filled nanostructures and dielectric backfilled nanostructures. The air-filled approach is demonstrated experimentally producing three filters with FWHM of 60 - 64 nm. Using the backfilled design, and incorporating a highindex cavity material, a set of twenty three narrowband filters, with a FWHM of 22 - 46nm is demonstrated. A virtual image reproduction process was developed to quantify the image reproduction performance of both the plasmonic and Fabry-Perot filter sets. A typical rgb dye-based filter set used in conventional imagers achieves a mean colour error of 2.711, whereas the experimental data from the plasmonic filters achieves an error of 2.222 which demonstrated a slight improvement in colour reproduction. The multispectral filter set developed in this work performed even better, with 4 filters giving an error of 0.906, 10 filters an error of 0.072 and continued improvement in the colour error reaching 0.047 for 23 filters. All the filter sets proposed are fully compatible with the CMOS process so as to enable direct integration onto CMOS image sensors in industrial foundries in future. The performance of the presented filters also suggest new compact applications in art reproduction, agricultural monitoring and medical imaging.
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Spencer, Timothy. "Digital imaging of the retina." Thesis, University of Aberdeen, 1992. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=124209.
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In this study, fluorescein angiograms of the ocular fundus have been digitised to enable them to be processed and analysed by computer. A fully automated technique for counting microaneurysms (MA) in these images was developed with a view to producing an objective, accurate and highly repeatable way of quantifying these lesions. Prior to any other image processing, a number of pre-processing stages were applied in order to compensate for non-uniformaties and to remove the background fluorescence component present in all the images. Matched filters modelled on two-dimensional Gaussian distributions were employed to detect MA in the 'shade-corrected' images. A binary image representation of the vascular network was constructed. This 'vessel mask', used in conjunction with the original match-filtered images, enabled MA to be detected by grey-level thresholding the filtered images. The resulting binary objects could then be counted by the computer as MA. The automated technique was assessed by comparing the computer's results for six fluorescein angiograms with MA counts obtained by ophthalmologists analysing both analogue and digital images. The performance of both man and machine were judged with respect to 'gold standards' compiled from prints of the original negatives. The best results were obtained by the clinicians analysing the analogue prints, although they differed greatly in their ability to detect microaneurysms. The computer performed better than the clinicians when they were counting MA in the digital images and produced highly repeatable results. To improve the performance of the automated technique, images were captured at approximately four times the previous spatial resolution and a smaller area of each image was analysed. Additionally, more complex image-processing techniques were employed to increase the accuracy of the computer analysis. Although the performance of the automated technique was improved, the computer results only matched those of the clinicians' analogue analyses for two of the images.
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Wolf, Michael Trevor. "Digital holographic imaging of microorganisms." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36684.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (leaf 25).
Imaging aquatic microorganisms in 3D space is of interest to biologists and ocean scientists seeking to understand the behavior of these organisms in their natural environments. In this research, digital holographic imaging (DHI), with a 4f system providing transverse magnification of 9.1, is used to study such microorganisms. To test the imaging technique, DHI was used to locate and track 10 micrometer Dunaliella freely swimming in a 30 milliliter tank of artificial ocean water. Multiple holograms were recorded onto one frame with laser pulsing to identify short algae trajectories. An automatic algae locating program was designed, but the signal to noise ratio was too low, and therefore the program could only locate algae reliably with manual confirmation. With refinement to the experimental setup, the signal to noise ratio could be increased, and this imaging technique could be used to analyze many systems of aquatic microorganisms interacting in a 3D space.
by Michael Trevor Wolf.
S.B.
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Amba, Prakhar. "Learning methods for digital imaging." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAS011/document.
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Pour produire des images couleurs nous devons obtenir l'information relative aux trois couleurs primaires (généralement Rouge, Vert et Bleu) à chaque pixels de l'image. Pour capturer cette information la plupart des caméras numériques utilisent une matrice de filtres couleurs (CFA – Color Filter Array en anglais), c'est-à-dire qu'une mosaïque de couleurs recouvre le capteur de manière à ce qu'une seule couleur soit mesurée à chaque position dans l'image.Cette méthode de mesure est similaire à celle du système visuel humain (HVS – Human Visual System en anglais) pour lequel les cônes LMS (sensibles aux longues L, moyenne M et courte S (short en anglais)) forment également une mosaïque à la surface de la rétine. Pour le système visuel, l'arrangement est aléatoire et change entre les individus alors que pour les caméras nous utilisons des arrangements réguliers. Dans les caméras, on doit interpoler les couleurs manquantes pour retrouver une image couleur totalement résolue, méthode appelée démosaïçage. A cause de l'arrangement régulier ou périodique des filtres couleurs, l'image démosaïçée peut faire apparaître des fausses couleurs ou des artefacts. Dans la littérature, les algorithmes de démosaïçage adressent principalement les mosaïques régulières.Dans cette thèse, nous proposons un algorithme de démosaïçage par apprentissage statistique, qui peut être utilisé avec n’importe quelle mosaïque régulière ou aléatoire. De plus, nous optimisons l’arrangement des couleurs dans la mosaïque et proposons des mosaïques qui, avec notre méthode, offrent des performances supérieures aux meilleures méthodes appliquées aux mosaïques régulières. Les images démosaïçées à partir de ces mosaïques ne présentent pas de fausses couleurs ou artefacts.Nous avons étendu l’algorithme pour qu’il ne soit pas limité à trois couleurs mais puisse être utilisé pour un arrangement aléatoire d’un nombre quelconque de filtres spectraux. Avoir plus de trois couleurs permet non seulement de mieux représenter les images mais aussi de mesurer des signatures spectrales de la scène. Ces mosaïques sont appelées matrice de filtres spectraux (SFA – Spectral Filter Array en anglais). Les technologies récentes nous offrent une grande flexibilité pour définir les filtres spectraux et par démosaïçage nous pouvons obtenir des couleurs plus justes et une estimation de la radiance spectrale de la scène. Le substrat silicium dans lequel les photodiodes du capteur sont réalisées est sensible aux radiations proche infra-rouge et donc des filtres visibles et proche infra-rouge peuvent-être combinés dans la même mosaïque. Cette combinaison est particulièrement utile pour le nouveau challenge des caméras numérique d’obtenir des images couleurs en vision de nuit à basse lumière.Nous démontrons l'application de notre algorithme pour plusieurs exemples de cameras récentes équipées d'une matrice de filtres spectraux. Nous montrons que notre méthode est plus performante que les algorithmes actuels en terme de qualité d'image et de vitesse de calcul. Nous proposons également d'optimiser les transmissions des filtres et leur arrangement pour améliorer les résultats selon des métriques ou applications choisies.La méthode, basée sur la minimisation de l'erreur quadratique moyenne est linéaire et par conséquent rapide et applicable en temps réel. Finalement, pour défier la nature linéaire de notre algorithme, nous proposons un deuxième algorithme de démosaïçage par réseaux de neurones qui à des performances légèrement meilleures mais pour un coût de calcul supérieurTo produce color images we need information of three primary colors (notably Red, Green and Blue) at each pixel point. To capture this information most digital cameras utilize a Color Filter Array (CFA), i.e. a mosaic arrangement of these colors is overlaid on the sensor such that only one color is sampled at one pixel.This arrangement is similar to the Human Visual System (HVS) wherein a mosaic of LMS cones (for sensitivity to Long, Medium and Short wavelength) forms the surface of the retina. For HVS, the arrangement is random and differs between individuals, whereas for cameras we use a regular arrangement of color filters. For digital cameras one needs to interpolate the missing colors to recover the full color image and this process is known as demosaicing. Due to regular or periodic arrangement of color filters the output demosaiced image is susceptible to false colors and artifacts. In literature, the demosaicing algorithms proposed so far cater mainly to regular CFAs.In this thesis, we propose an algorithm for demosaicing which can be used to demosaic any random or regular CFA by learning statistics of an image database. Further, we optimize and propose CFAs such that they outperform even the state of art algorithms on regular CFAs. At the same time the demosaiced images from proposed CFAs are free from false colors and artifacts.We extend our algorithm such that it is not limited to only three colors but can be used for any random arrangement of any number of spectral filters. Having more than three colors allows us to not only record an image but to record a spectral signature of the scene. These mosaics are known as Spectral Filter Arrays (SFAs). Recent technological advances give us greater flexibility in designing the spectral filters and by demosaicing them we can get more accurate colors and also do estimation of spectral radiance of the scene. We know that silicon is inherently sensitive to Near-Infrared radiation and therefore both Visible and NIR filters can be combined on the same mosaic. This is useful for low light night vision cameras which is a new challenge in digital imaging.We demonstrate the applicability of our algorithm on several state of the art cameras using these novel SFAs. In this thesis, we demonstrate that our method outperforms the state of art algorithms in image quality and computational efficiency. We propose a method to optimize filters and their arrangement such that it gives best results depending on metrics and application chosen.The method based on minimization of mean square error is linear in nature and therefore very fast and suitable for real time applications. Finally to challenge the linear nature of LMMSE we propose a demosaicing algorithm using Neural Networks training on a small database of images which is slightly better than the linear demosaicing however, it is computationally more expensive
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Datodi, Mark. "Digital imaging: Creating new realities." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 1999. https://ro.ecu.edu.au/theses/1253.
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More and more it is becoming increasingly difficult to discern photo reality from digital reality. Digital imagery is revolutionising photography and challenging preconceived notions of this art form. Over the years, photography has been viewed metaphorically as a window on the world and on the past. No longer however, is the creation of photographic imagery reliant upon its intrinsic relationship with reality. Using computer technology original photographic material can be altered, manipulated and seamlessly combined with other fictional imagery without obvious detection and with relative ease. The proliferation of digital imaging is producing two apparent crises for photography. The first is the perceived threat to photography, involving the fear that traditional photographic processes, methods and product will be superseded by manipulated digital images passing themselves off as real photographs. Added to these growing concerns for photography's longevity, is the prospect that viewers will no longer believe m photography as a deliverer of objective truth and that the medium itself will lose its power as a 'privileged conveyer of information'(Batchen, 1994,p.47). The second crisis pertains to ethical concerns that these digital simulations raise: copyright, moral rights and artistic integrity.
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Cabello, Velasco J. "High throughput digital beta autoradiography imaging." Thesis, University of Surrey, 2009. http://epubs.surrey.ac.uk/844626/.
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This thesis presents three main strands of work concerned with developing digital imaging for high throughput beta autoradiography. These three strands comprise work with the image sensor technology, Monte Carlo simulation and the use of post-acquisition image analysis based on image registration. In this way, the complete autoradiography imaging chain is addressed. CCD and CMOS imaging technologies are presented as potential imaging alternatives to using conventional film in autoradiography. These digital technologies exhibit enhanced sensitivity, dynamic range and linearity compared to film using imaging methods developed at Surrey. These imaging methods address the different sources of noise typically present in CCD and CMOS technologies. Tissue imaging using 3H, 35S and 121I, the typical radioisotopes used by the Drug Addiction Group in the School of Biomedical and Biological Sciences, is presented. The first successful images of 3H-labelled tissue sections using CCD and CMOS technologies operating at room temperature are presented as one of the main achievements of this work. To better understand the image creation process some preliminary Monte Carlo simulations, using the GEANT4 toolkit, have been undertaken, demonstrating intrinsic and extrinsic key parameters of these digital sensors that can be used to optimise spatial resolution. These simulations demonstrate that each radioisotope requires a different optimum detector architecture. In this work these optimum architectures are analysed. To support the high sensitivity (i.e. fast) imaging produced by the sensor technology, automated post-acquisition analysis is also considered, using an atlas-based image registration approach, by previously aligning automatically segmented biological landmarks using a feature-based extraction approach, region growing. This has the potential to speed up the post-acquisition analysis aspects of the imaging chain. Thus a computer-based tool designed to semi-automatically elastically register a radiogram with an atlas has been developed.
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Domínguez-Caballero, José Antonio. "Digital holographic imaging of aquatic species." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35655.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 160-174).
The aim of this thesis is to design, develop and implement a digital holographic imaging (DHI) system, capable of capturing three-dimensional (3D) images of aquatic species. The images produced by this system are used in a non-intrusive manner to characterize the abundance, morphology and 3D location of the aquatic species. The DHI system operates by recording the hologram produced by the interference between a reference wave and the wave scatter by a coherently illuminated object with a charge-couple-device (CCD). The recorded hologram contains information about the amplitude and phase of the optical field as modified by the object. This optical field is retrieved by numerical algorithms, which enable the reconstruction of the field at different distances relative to the detector from a single hologram. The recording of the holograms with the CCD allows the implementation of image post-processing techniques intended to enhance the reconstructed images. A description of the optimization of the reconstruction by means of an auto-scan algorithm and the reconstruction of large holograms are discussed. It is found that the in-line single-beam experimental set-up is the most suitable configuration for underwater imaging of aquatic species.
(cont.) This is experimentally verified by imaging brine shrimp and copepods under various conditions. Small, sub-10um features of the objects were successfully resolved. It is also found that by using configurations with a spherical reference wave, resolutions comparable to those obtained by a conventional optical microscope can be achieved in a "lens-free" approach with larger working distances.
by José Antonio Domínguez-Caballero.
S.M.
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Luo, Wen. "Assessment of Tooth Colour using Digital Imaging." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485749.
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As tooth whitening has become a popular and routine dental procedure, the measurement of tooth colour, especially for the evaluation of the efficacy of the tooth-whitening products, has become important. One of the instrumental methods of assessing tooth whiteness is digital photography. The aim of this study was to develop a digital imaging method in colorimetry of human teeth which could be used for evaluating the efficacy of tooth-whitening products. The successful use .of a tooth-imaging system for assessing tooth whiteness relies upon two things: precise and preferably accurate colour-rendering for teeth, and an appropriate whiteness scale or index for quantifying the tooth whiteness according to human perception. These two things are the main objectives needed to be achieved in this study. The development of the tooth-imaging system consists of two essential procedures: calibration and characterisation. The imaging system was firstly calibrated according to the requirements of clinical tooth-colour measurement, including accurate control of the intensity of the light source with the aid of software. For camera characterisation, besides the traditional methods, efforts were made by choosing training samples that are physically similar to real human teeth for the characterisation model to improve the accuracy of the system. Two cameras were evaluated and several characterisation models were compared. Moreover, uncertainties involved in the clinical tooth-colour measurement were investigated as a complementarity to the performance of the tooth-imaging system. In order to find the relationship between the objective measurements and visual assessments of tooth whiteness, psychophysical experiments were conducted in a controlled viewing condition as well as a typical clinical viewing condition. A whiteness index for quantifying tooth whiteness was proposed and its performance was compared with some existing whiteness/yellowness indices. Finally, the validation of the tooth-imaging system and the tooth-whiteness index were assessed under the conditions of clinical whitening trials. In addition to the tooth-whiteness study, the gloss of tooth, as one part of the tooth appearance, was investigated on a gonio-imaging system which was verified by results from the repeatability test and the tooth-etching experiments.
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Kunkel, Timo Daniel. "Colour appearance modelling for digital imaging pipelines." Thesis, University of Bristol, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.528097.
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Sindle, Timothy Grant. "An autonomous, omnidirectional, digital, borehole imaging system." Thesis, Stellenbosch : Stellenbosch University, 2005. http://hdl.handle.net/10019.1/50260.
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Thesis (MScEng)--University of Stellenbosch, 2005.ENGLISH ABSTRACT: This thesis documents the research, design, implementation and successful testing of a prototype camera probe to survey the inside of hard rock boreholes. Rock core images are intended to aid mine geologists in recording the borehole rock layers. The system consists of a wide-angle fisheye lens mounted onto a CMOS digital image sensor. The image data is read in and processed by an FPGA, then stored on a removable sn flash memory card. All of the aforementioned components are mounted inside a watertight Perspex tube. Application specific PC software is used to process the data to form strip images of the borehole wall. Using mathematical correlation, these images are stitched together into a virtual core that is a flattened representation of the rock inside the borehole. The probe contains its own power and light source which enables it to be deployed easily with no external wires needed for operation. The storage capacity, image quality, and lighting design can be improved in future design revisions.
AFRIKAANSE OPSOMMING: Die inhoud van hierdie tesis behels die navorsmg, ontwerp, implementering, en suksesvolle toetsing van 'n prototipe kameraprobe wat dit moontlik maak om die binnewand van boorgate in harde rots te besigtig. Beelde van die rotskern vergemaklik die taak van myngeoloë wat die rotslae, waardeur die boorgat strek, moet opteken. Die stelsel behels 'n wyehoek bollens wat op 'n CMOS digitale sensor gemonteer is. Die data gewerf vir die vorming van die beeld word deur 'n FPGA ingelees en verwerk, waarna dit op 'n verwyderbare SD flits geheuekaart gestoor word. Die bogenoemde komponente word alles binne 'n waterdigte Perspexbuis monteer. Gebruikerspesifieke sagteware vir persoonlik rekenaars word gebruik om die data te verwerk en sodoende strookbeelde van die binnewand van die boorgat te vorm. Met gebruik van wiskundige korrelasie word hierdie beelde aan mekaar gelas om 'n virtuele kern te vorm, wat 'n voorstelling is van die rots binne die boorgat. Die probe bevat self krag en ligbronne, wat toelaat dat dit maklik bruikbaar is sonder enige eksterne bedrading. Toekomstige hersienings van die ontwerp sal verbeterde data geheue, beeldgehalte en beligting kan bewerkstellig.
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Gonçalves, Bruno Filipe Pimparel. "Digital imaging processing tools for neuronal images." Master's thesis, Universidade de Aveiro, 2012. http://hdl.handle.net/10773/10584.
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Mestrado em Biomedicina MolecularOs neurónios são celulas especializadas do Sistema Nervoso, cujas funções se baseiam na correta formação de três compartimentos subcelulares primários – corpo celular, axónio e dendrites – e na rede neuronal que formam para passar a informação entre si. A análise quantitativa das características destas estruturas pode ser usada para estudar a relação entre a morfologia e função neuronal, e monitorizar alterações que ocorram em células individuais ou ao nível da rede, que se possam correlacionar com doenças neurológicas. Nesta tese foi efetuada uma pesquisa de ferramentas digitais disponíveis dedicadas ao processamento e análise de imagens neuronais, com enfoque na sua aplicabilidade para analisar as nossas bioimagens neuronais de fluorescência adquiridas no dia-a-dia. Nos programas selecionados (NeuronJ, NeurphologyJ e NeuriteQuant) foi primeiro avaliada a necessidade de preprocessamento, e os programas foram subsequentemente utilizados em conjuntos de imagens de culturas primárias de córtex de rato para comparar a sua eficácia no processamento destas bioimagens. Os dados obtidos com os vários programas foram comparados com a análise manual usando o ImageJ como ferramenta de análise. Os resultados demonstraram que o programa que aparenta funcionar melhor com as nossas imagens de fluorescência é o NeuriteQuant, porque é automático e dá resultados globalmente semelhantes aos da análise manual, especialmente na avaliação do Comprimento das Neurites por célula. Uma das desvantagens é que a quantificação da ramificação das neurites não dá resultados satisfatórios e deve continuar a ser realizada manualmente. Também realizamos uma pesquisa de ferramentas de processamento de imagem dedicada a imagens de contraste de fase, mas poucos programas foram encontrados. Estas imagens são mais fáceis de obter e mais acessíveis economicamente, contudo são mais difíceis de analisar devido às suas características intrínsecas. Para contornar esta lacuna, estabeleceu-se e otimizou-se uma sequência de processamento e análise para melhor extrair informação neuronal relevante de imagens de contraste de fase utilizando o programa ImageJ. A sequência desenvolvida, na forma de uma macro do ImageJ designada NeuroNet, foi aplicada a imagens de contraste de fase de culturas neuronais em diferentes dias de diferenciação, na presença ou ausência de um inibidor farmacológico, com o objetivo de responder a uma questão científica. A macro NeuroNet desenvolvida provou ser útil para analisar estas bioimagens, existindo contudo espaço para ser aperfeiçoada.
Neurons are specialized cells of the Nervous System, with their function being based on the formation of the three primary sub cellular compartments – soma, axons, and dendrites – and on the neuritic network they form to contact and pass information to each other. The quantitative analysis of the characteristics of these structures can be used to study the relation between neuronal morphology and function, and to monitor distortions occurring in individual cells or at the network level that may correlate with neurological diseases. In this thesis a survey of freely available digital tools dedicated to neuronal images processing and analysis was made with an interest in their applicability to analyse our routinely acquired neuronal fluorescent bioimages. The selected program´ (NeuronJ, NeurphologyJ and NeuriteQuant) preprocessing requirements were first evaluated, and the programs were subsequently applied to a set of images of rat cortical neuronal primary cultures in order to compare their effectiveness in bioimage processing. Data obtained with the various programs was compared to the manual analysis of the images using the ImageJ analysis tool. The result show that the program that seems to work better with our fluorescence images is NeuriteQuant, since it is automatic and gives overall results more similar to the manual analysis. This is particularly true for the evaluation of the Neurite Length per Cell. One of the drawbacks is that the quantification of neuritic ramification does not give satisfactory results and is better to be performed manually. We also performed a survey of digital image processing tools dedicated to phase contrast microphotographs, but very few programs were found. These images are easier to obtain and more affordable in economic terms, however they are harder to analyse due to their intrinsic characteristics. To surpass this gap we have established and optimized a sequence of steps to better extract relevant information of neuronal phase contrast images using ImageJ. The work-flow developed, in the form of an ImageJ macro named NeuroNet, was then used to answer a scientific question by applying it to phase contrast images of neuronal cultures at different differentiating days, in the presence or absence of a pharmacological inhibitor. The developed macro NeuroNet proved to be useful to analyse the images however there is still space to improvement.
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Brown, Carol Christy. "Plugged-in : 40 years of digital imaging /." Online version of thesis, 1994. http://hdl.handle.net/1850/11892.
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Parshall, Daniel. "Phase imaging digital holography for biological microscopy." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000285.
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Samsheerali, P. T. "Investigations on improved digital holographic imaging techniques." Thesis, IIT Delhi, 2015. http://localhost:8080/iit/handle/2074/6928.
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Liu, Changgeng. "Coherent Digital Holographic Adaptive Optics." Scholar Commons, 2015. https://scholarcommons.usf.edu/etd/5527.
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A new type of adaptive optics (AO) based on the principles of digital holography (DH) is proposed and developed for the use in wide-field and confocal retinal imaging. Digital holographic adaptive optics (DHAO) dispenses with the wavefront sensor and wavefront corrector of the conventional AO system. DH is an emergent imaging technology that gives direct numerical access to the phase of the optical field, thus allowing precise control and manipulation of the optical field. Incorporation of DH in an ophthalmic imaging system can lead to versatile imaging capabilities at substantially reduced complexity and cost of the instrument. A typical conventional AO system includes several critical hardware pieces: spatial light modulator, lenslet array, and a second CCD camera in addition to the camera for imaging. The proposed DHAO system replaces these hardware components with numerical processing for wavefront measurement and compensation of aberration through the principles of DH.
We first design an image plane DHAO system which is basically simulating the process the conventional AO system and replacing the hardware pieces and complicated control procedures by DH and related numerical processing. In this original DHAO system, CCD is put at the image plane of the pupil plane of the eye lens. The image of the aberration is obtained by a digital hologram or guide star hologram. The full optical field is captured by a second digital hologram. Because CCD is not at the conjugate plane of the sample, a numerical propagation is necessary to find the image of the sample after the numerical aberration compensation at the CCD plane. The theory, simulations and experiments using an eye model have clearly demonstrated the effectiveness of the DHAO. This original DHAO system is described in Chapter 2.
Different from the conventional AO system, DHAO is a coherent imaging modality which gives more access to the optical field and allows more freedom in the optical system design. In fact, CCD does not have to be put at the image plane of the CCD. This idea was first explored by testing a Fourier transform DHAO system (FTDHAO). In the FTDHAO, the CCD can directly record the amplitude point spread function (PSF) of the system, making it easier to determine the correct guide star hologram. CCD is also at the image plane of the target. The signal becomes stronger than the image plane DHAO system, especially for the phase aberration sensing. Also, the numerical propagation is not necessary. In the FTDHAO imaging system, the phase aberration at the eye pupil can be retrieved by an inverse Fourier transform (FT) of the guide star hologram and the complex amplitude of the full field optical field at the eye pupil can be obtained by an inverse FT of the full field hologram. The correction takes place at the eye pupil, instead of the CCD plane. Taking FT of the corrected field at the eye pupil, the corrected image can be obtained. The theory, simulations, and experiments on FTDHAO are detailed in chapter 3.
The successful demonstration of FTDHAO encourages us to test the feasibility of putting CCD at an arbitrary diffraction plane in the DHAO system. Through theoretical formulation by use of paraxial optical theory, we developed a correction method by correlation for the general optical system to perform the DHAO. In this method, a global quadratic phase term has to be removed before the correction operation. In the formulation, it is quite surprising to find that the defocus term can be eliminated in the correlation operation. The detailed formulations, related simulations, and experimental demonstrations are presented in Chapter 4.
To apply the DHAO to the confocal retinal imaging system, we first transformed the conventional line-scanning confocal imaging system into a digital form. That means each line scan is turned into a digital hologram. The complex amplitude of the optical field from each slice of the sample and aberration of the optical system can be retrieved by digital holographic process. In Chapter 5, we report our experiments on this digital line-scanning confocal imaging system. This digital line-scanning confocal image absorbs the merits of the conventional line-scanning confocal imaging system and DH. High-contrast intensity images with low coherent noise, and the optical sectioning capability are made available due to the confocality. Phase profiles of the samples become accessible thanks to DH. The quantitative phase map is even better than that from the wide field DH.
We then explore the possibility of applying DHAO to this newly developed digital line-scanning confocal imaging system. Since optical field of each line scan can be achieved by the DH, the aberration contained in this field can be eliminated if we are able to obtain the phase aberration. We have demonstrated that the phase aberration can be obtained by a guide star hologram in the wide field DHAO systems. We then apply this technique to acquire the aberration at the eye pupil, remove this aberration from the optical fields of the line scans and recover the confocal image. To circumvent the effect of phase aberration on the line illumination, a small collimated laser beam is shone on the cylindrical lens. Thus the image is solely blurred by the second passage through the aberrator. This way, we can clearly demonstrate the effect of DHAO on the digital line-scanning confocal image system. Simulations and experiments are presented in chapter 6, which clearly demonstrates the validity of this idea. Since line-scanning confocal imaging system using spatially coherent light sources has proven an effective imaging tool for retinal imaging, the presented digital adaptive optics line-scanning confocal imaging system is quite promising to become a compact digital adaptive optics laser scanning confocal ophthalmoscope.
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Tsang, Kwong Man. "A real-time acoustic imaging system using digital signal processor array." HKBU Institutional Repository, 1995. http://repository.hkbu.edu.hk/etd_ra/49.
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Basu, Ansu. "Diabetic retinopathy screening using advanced digital imaging technology." Thesis, University of Newcastle upon Tyne, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413265.
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Hobson, David Mark. "Characterisation of rice grains using digital imaging techniques." Thesis, University of Kent, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509657.
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Gomes, David Menotti. "Contrast enhancement in digital imaging using histogram equalization." Phd thesis, Université Paris-Est, 2008. http://tel.archives-ouvertes.fr/tel-00470545.
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Nowadays devices are able to capture and process images from complex surveillance monitoring systems or from simple mobile phones. In certain applications, the time necessary to process the image is not as important as the quality of the processed images (e.g., medical imaging), but in other cases the quality can be sacrificed in favour of time. This thesis focuses on the latter case, and proposes two methodologies for fast image contrast enhancement methods. The proposed methods are based on histogram equalization (HE), and some for handling gray-level images and others for handling color images As far as HE methods for gray-level images are concerned, current methods tend to change the mean brightness of the image to the middle level of the gray-level range. This is not desirable in the case of image contrast enhancement for consumer electronics products, where preserving the input brightness of the image is required to avoid the generation of non-existing artifacts in the output image. To overcome this drawback, Bi-histogram equalization methods for both preserving the brightness and contrast enhancement have been proposed. Although these methods preserve the input brightness on the output image with a significant contrast enhancement, they may produce images which do not look as natural as the ones which have been input. In order to overcome this drawback, we propose a technique called Multi-HE, which consists of decomposing the input image into several sub-images, and then applying the classical HE process to each one of them. This methodology performs a less intensive image contrast enhancement, in a way that the output image presented looks more natural. We propose two discrepancy functions for image decomposition which lead to two new Multi-HE methods. A cost function is also used for automatically deciding in how many sub-images the input image will be decomposed on. Experimental results show that our methods are better in preserving the brightness and producing more natural looking images than the other HE methods. In order to deal with contrast enhancement in color images, we introduce a generic fast hue-preserving histogram equalization method based on the RGB color space, and two instances of the proposed generic method. The first instance uses R-red, G-green, and Bblue 1D histograms to estimate a RGB 3D histogram to be equalized, whereas the second instance uses RG, RB, and GB 2D histograms. Histogram equalization is performed using 7 Abstract 8 shift hue-preserving transformations, avoiding the appearance of unrealistic colors. Our methods have linear time and space complexities with respect to the image dimension, and do not require conversions between color spaces in order to perform image contrast enhancement. Objective assessments comparing our methods and others are performed using a contrast measure and color image quality measures, where the quality is established as a weighed function of the naturalness and colorfulness indexes. This is the first work to evaluate histogram equalization methods with a well-known database of 300 images (one dataset from the University of Berkeley) by using measures such as naturalness and colorfulness. Experimental results show that the value of the image contrast produced by our methods is in average 50% greater than the original image value, and still keeping the quality of the output images close to the original
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MacLennan-Brown, Ken. "Quantification of artefacts inherent within digital imaging chains." Thesis, University of Westminster, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251717.
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Vettenburg, Tom. "Optimal design of hybrid optical digital imaging systems." Thesis, Heriot-Watt University, 2010. http://hdl.handle.net/10399/2438.
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Several types of pupil modulation have been reported to decrease the aberration variance of the modulation-transfer-function (MTF) in aberration-tolerant hybrid optical-digital imaging systems. It is common to enforce restorability constraints on the MTF, requiring trade of aberration-tolerance and noise-gain. In this thesis, instead of optimising specific MTF characteristics, the expected imaging-error of the joint design is minimised directly. This method is used to compare commonly used phase-modulation functions. The analysis shows how optimal imaging performance is obtained using moderate phasemodulation, and more importantly, it shows the relative merits of different functions. It is shown that the technique is readily integrable with off-the-shelf optical design software, which is demonstrated with the optimisation of a wide-angle reflective system with significant off-axis aberrations. The imaging error can also be minimised for amplitudeonly masks. It is shown that phase aberrations in an imaging system can be mitigated using binary amplitude masks. This offers a low-cost, transmission-mode alternative to phase correction as used in active and adaptive optics. More efficient masks can be obtained by the optimisation of the imaging fidelity.
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Wisby, C. "Real-time digital imaging techniques for flow visualization." Thesis, University of Surrey, 1989. http://epubs.surrey.ac.uk/848586/.
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A real-time digital imaging technique has been applied to smoke flow visualized turbulent flows to provide statistical data concerning bluff body wakes. The 'digital imaging technique' has been successfully applied to the wake of a two-dimensional flat plate, circular cylinder and a jet in a crossflow configuration. A detailed study of the two-dimensional flat plate model involved comparative hot-wire and pressure measurements combined with data from previously published experimental investigations. The results obtained included, intermittency measurements, vortex shedding spectral analyses (autocorrelations), spatial correlations, wake interface statistics and turbulence data. In the majority of cases, the digital imaging technique was found to provide excellent quantitative detail whilst also offering some unique wake interface statistics. The experiments conducted on the circular cylinder model revealed details of secondary vortex shedding and their base-bleed dependence, whilst the jet in a crossflow configuration enabled the imaging technique to be applied to a complex, three-dimensional flow model. The resulting iso-intermittency contour map was produced expediently, and within an experimental period far shorter than could be expected for single-location probe measurements. In addition to the above-outlined quantitative technique, real-time digital imaging was also applied more qualitatively to the study of dynamic stall on an aerofoil and to the enhancement of high-speed vapour-screen visualizations, both techniques offering the possibility for enhanced quantitative flow studies in future investigations. Finally, true-colour video digitisation has been exploited in a preliminary study of the quantification of global surface shear stress values using liquid crystal technology. Although in its infancy, the realisation of an experimental procedure along such lines would be of immense benefit to experimental aerodynamic research.
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Al, Sulaiman Rana. "Establishing A Quality Assurance Routine For Digital Imaging." Wright State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=wright1519232738854316.
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Manivannan, Ayyakkannu. "Digital fundus imaging with a scanning laser ophthalmoscope." Thesis, University of Aberdeen, 1993. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU602038.
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A prototype scanning laser ophthalmoscope was constructed based on the original principles of Webb et al (1987 and 1990). The basic design was, however, altered in a number of ways to give the flexibility needed for what was primarily a research instrument with a requirement to use lasers of various wavelengths and to carry out confocal imaging with a variety of slice thicknesses. Some of the performance characteristics of the prototype SLO, such as modulation transfer function, axial resolution and uniformity of illumination were measured and are presented. The SLO can operate in three different modes; direct, confocal and indirect. The direct mode imaging has a large depth of focus and collects light from all layers of the fundus. High contrast imaging is possible due to scattered light being significantly reduced as only a single spot is illuminated at a time. Confocal imaging further improves the contrast by collecting light only from a small slice of the fundus. The capacity to carry out confocal imaging is a significant advantage over fundus cameras. By moving the confocal aperture, light from different layers could be collected enabling the visualisation of various lesions. The indirect mode collects only the scattered light, avoiding the directly reflected light. The clinical value of the equipment was evaluated with a small number of patients with various pathological conditions from the Eye Out-patient Clinic of the Aberdeen Royal Infirmary. The images from the SLO were compared with fundus photographs. The confocal capability, together with the penetrating capacity of near infrared illumination, was utilised to demonstrate the ability to visualise deep lying structures such as choroidal vessels and intra- retinal abnormalities. Near infrared illumination was found useful for imaging through media opacities, such as cataracts. The indirect mode was found useful for visualising structures such as drusen and epiretinal membrane. It is concluded that near infrared monochromatic imaging with the SLO offers a 'new' picture of the fundus. The confocal capability provides the ability to produce 3-D images of the fundus. The near infrared reflective characteristics of many normal and pathological tissues appear to offer new clinical insights into fundal pathology. However, more work is needed to fully appreciate the clinical potential of this new imaging modality.
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Vilas, Boas Lenilson Lemos. "Identificação de pragas na agricultura utilizando APIs de visão computacional." Pontifícia Universidade Católica de São Paulo, 2018. https://tede2.pucsp.br/handle/handle/21763.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Systems that use Computer Vision Application Program Interfaces (APIs) can learn and identify patterns and thus perform associations to retrieve additional data. They are able to obtain results much faster than any human agent is. The study uses three computational vision APIs and evaluates their application in the identification of four plant leave diseases. Based on a corpus of fifty images, the API training was conducted in two stages, the first with thirty images and the second training with twenty more images. After the two trainings, the results of the diseases were collected for each API studied, which made it possible to evaluate the identification capacity and its evolution of learning after each training. The results corroborated the hypothesis. They gave evidence of the feasibility of identification of plant leaf diseases by means of computer vision APIs
Sistemas que utilizam APIs (Interfaces de Programação de Aplicação) de visão computacional têm a capacidade de aprender e identificar padrões, e assim realizar associações com outros resultados, sendo capaz de apresentar resultados mais rápidos do que uma pessoa. O trabalho identificou três APIs de visão computacional e avaliou sua aplicação na identificação de doenças em folhas de plantas, comparando os resultados de quatro diferentes doenças de plantas. Os treinamentos das APIs foram realizados em duas etapas, sendo o primeiro treinamento com uma quantidade de imagens e o segundo treinamento adicionando mais imagens. Após os dois treinamentos foram coletados os resultados das doenças para cada API estudada, sendo possível avaliar a capacidade de identificação e sua evolução de aprendizado após cada um dos treinamentos. Os resultados obtidos corroboram as expectativas, apontando para a viabilidade de identificação de doenças em folhas de plantas através de APIs de visão computacional
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Xue, R. G. "The image processing for the target centre detection in digital image." Master's thesis, University of Cape Town, 1992. http://hdl.handle.net/11427/21834.
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This thesis comprises of five chapters. Chapter one describes basic principles of the digital image, digital image construction and the present status of the digital photogrammetry system, named PHOENICS (PHOtogrammetric ENgineering and Industrial digital Camera System), as developed by H. Rüther (1989). The target's shape analysis in the digital image are presented in chapter two. Chapter three presents the algorithms to detect and locate target on the digital image. These are the least squares adjustment technique, moment method, moment-preserving for edge detection as well as test methods for the evaluation of the various alglorithms. The novel RG method is presented in chapter four. Chapter five introduces the theory of some image processing methods.
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Sivard, Seth A. "Digital radiography in the education of radiologic technology students." The Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1409229904.
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Tickhill, Justin D. "The virtual pig head digital imaging in cephalic anatomy /." Ohio : Ohio University, 2007. http://www.ohiolink.edu/etd/view.cgi?ohiou1187634238.
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Olson, J. A. "Digital imaging, leucocytes, gamma-linolenic acid and diabetic retinopathy." Thesis, University of Aberdeen, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.593242.
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The work for this thesis has been carried out in the Diabetic Clinic, Woolmanhill, the Eye Clinic, Foresterhill and the Departments of Bio-Medical Physics and Ophthalmology, University of Aberdeen. One hundred and twenty two patients with type 1 diabetes mellitus were recruited from the Diabetic Clinic, Woolmanhill, and attended a Research Clinic at the Eye Clinic, Foresterhill, on a three monthly basis for two years each between 1992 and 1995. Data was extensively collated relating to diabetic control and diabetic complications. Concentrations and activities of several serum factors were studied in an attempt to elucidate pathogenetic mechanisms in diabetic retinopathy. Serum levels of soluble leucocyte endothelial adhesion molecules were measured to see if there is indirect evidence for increase leucocyte adhesion in diabetic retinopathy. Similar studies were also performed looking at serum induced retinal endothelial capillary cell migration, a putative early feature in the development of sight-threatening new vessel formation. Computer image analysis methods, developed in the Department of Bio-Medical Physics, were modified and evaluated, leading to robust techniques suitable for quantifying lesions of diabetic retinopathy in large numbers of unselected fundal photographs and fluorescein angiograms. This latter work was completed in 1997. As it is known that essential fatty acid metabolism in diabetes is abnormal, leading to low levels of gamma-linolenic acid and its metabolites, the above techniques were used to assess the progress of diabetic retinopathy in a two year crossover trial of dietary gamma-linolenic acid supplementation.
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Zaharescu, Catalin A. "Wear-quantification of textured geomembranes using digital imaging analysis." Thesis, Loughborough University, 2018. https://dspace.lboro.ac.uk/2134/36244.
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During the past decades there has been an increase in the use of geosynthetics in construction due to their versatility in providing a wide array of functions such as reinforcement, containment, separation, filtration and drainage. Often, geosynthetics are used in conjunction with other geosynthetics to accomplish these functions. However, geosynthetics create possible planes of weakness which can lead to failures. Textured geomembranes are widely used within landfill and mining industries due to their containment and shear strength properties, however, there are subjected to a wide array of loads and environments which are potentially hazardous, as such is of utmost importance to retain their integrity in order to avoid ecological disasters. The challenge is to understand how geomembranes resist damage, wear and which of these factors control the development of wear on textured geomembranes. Digital imaging techniques have been used in order to develop a protocol that describes the quantification of wear on textured structured geomembranes. Direct shear tests were performed to induce wear on the geomembrane textures (asperities) to analyse the wear mechanisms and study the factors that induce wear on the asperities. The research showed that normal stress and shear displacement have a major role in the development of wear on interfaces. However, the geometrical characteristics of the geomembrane asperities control the amount of wear the geomembrane can sustain without significant shear strength loss. These outcomes help to better understand the behaviour of interfaces which have as component geomembranes, leading to more robust designs. This study also proposed new asperity texture shapes by using Rapid Prototyping (RP) techniques, such as Selective Laser Sintering and Fused Filament Fabrication. Using RP techniques to create new textures for the geomembrane, could allow the creation of textures which have increased shear strength thresholds and better withstand wear, allowing for more advanced and economical designs.
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Tickhill, Justin David. "The Virtual Pig Head: Digital Imaging in Cephalic Anatomy." Ohio University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1187634238.
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Chuirazzi, William C. "Combinatorial Optimization of Scintillator Screens for Digital Neutron Imaging." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1586903047809812.
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Mraz, Alex. "Evaluation of digital imaging systems used in highway applications." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000487.
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Yafuso, Eiji 1963. "Digital acquisition system for high-speed 3-D imaging." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/288777.
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High-speed digital three-dimensional (3-D) imagery is possible using multiple independent charge-coupled device (CCD) cameras with sequentially triggered acquisition and individual field storage capability. The system described here utilizes sixteen independent cameras, providing versatility in configuration and image acquisition. By aligning the cameras in nearly coincident lines-of-sight, a sixteen frame two-dimensional (2-D) sequence can be captured. The delays can be individually adjusted lo yield a greater number of acquired frames during the more rapid segments of the event. Additionally, individual integration periods may be adjusted to ensure adequate radiometric response while minimizing image blur. An alternative alignment and triggering scheme arranges the cameras into two angularly separated banks of eight cameras each. By simultaneously triggering correlated stereo pairs, an eight-frame sequence of stereo images may be captured. In the first alignment scheme the camera lines-of-sight cannot be made precisely coincident. Thus representation of the data as a monocular sequence introduces the issue of independent camera coordinate registration with the real scene. This issue arises more significantly using the stereo pair method to reconstruct quantitative 3-D spatial information of the event as a function of time. The principal development here will be the derivation and evaluation of a solution transform and its inverse for the digital data which will yield a 3-D spatial mapping as a function of time.
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Cherry, Shirley J. "Do Exposure Principles and ALARA Apply in Digital Imaging?" Digital Commons @ East Tennessee State University, 2012. https://dc.etsu.edu/etsu-works/2480.
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Li, Jia, and 李佳. "Computational imaging technologies for optical lithography extension." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206757.
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With the development and production of integrated circuits at the 22nm node, optical lithography faces increasing challenges to keep up with the specifications on its performance along various metrics, such as pattern fidelity and process window. The past few years saw the emergence of source mask optimization (SMO) as an important technique in computational lithography, which allows lithographers to rise to the challenges by exploiting a larger design space on both mask and illumination configuration, and integrates with methods such as inverse imaging. Yet, many methods that are used to tackle SMO problem arising in the inverse imaging involve heavy computation and slow convergence, making the technique unappealing for full-chip simulations or large circuits. Therefore, the purpose of this research is to take advantage of computational imaging technologies to solve source and mask design problems, extending the lifetime of optical lithography.
The computational burden results in part from identical optimization over the whole mask pattern, consequently, we propose a weighted SMO scheme which applies different degrees of correction in the corresponding regions so that the optimal solutions are reached with fewer iterations. Additionally, undesirably long time is also attributed to the algorithm adopted to solve SMO problem. A fast algorithm based on augmented Lagrangian methods is therefore developed, which use the quasi-Newton method to accelerate convergence, thereby shortening the overall execution time. However, as semiconductor lithography is pushed to even smaller dimensions, mask topography effects have to be taken into account for a more accurate solution of SMO. At this stage, intensive computation is spent mainly in rigorous 3D mask modeling and simulations. To address this issue, we devise an optimization framework incorporating pupil aberrations into SMO procedure, which is performed based on the thin mask model so as to ensure a faster speed.
We apply the above approaches to various mask geometries with different critical dimensions. Compared to conventional SMO, simulation results show that the proposed methods lead to better pattern fidelity and larger process window, especially in rigorous calculations. This demonstrates that the source and mask design generated through our algorithms are more practical. More importantly, the improved performance is not at the cost of speed. Instead, our methods take the least time to achieve it. This allows the advantages of computational imaging technologies to be worth exploring for further applications in optical lithography.published_or_final_version
Electrical and Electronic Engineering
Doctoral
Doctor of Philosophy
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Fu, Deng Yuan. "ADAPTIVE DIGITAL IMAGE DATA COMPRESSION BY RECURSIVE IDPCM." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275350.
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Wang, Rong. "Digital Stero Imaging and Reconstruction of Flame Dynamics and Structure." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508604.
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Phillips, Russell Picton. "Quantification of diabetic maculopathy by digital imaging of the retina." Thesis, University of Aberdeen, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359757.
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Diabetic retinopathy is the commonest cause of blindness in the working age population of the United Kingdom, with maculopathy being responsible for most of the visual impairment within this population. In this thesis, the application of digital imaging techniques to the quantification of diabetic maculopathy has been investigated. A suite of programs has been written which quantifies three major aspects of maculopathy, namely microaneurysms, exudates, and macular oedema. The accuracy, repeatability, and reproducibility of these techniques has been investigated in order to assess their potential for clinical use. For each of the three aspects of maculopathy the computer performed at least as well as experienced clinicians when images of comparable spatial resolution were analysed. The problems involved in computerised analysis of maculopathy are identified, and suggestions for improvements are made.
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Nguyen, Khoa Minh. "Key receiver circuits for digital beamforming in millimeter-wave imaging." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/64587.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 123-129).
Millimeter-wave (MMW) frequencies have wavelengths small enough to offer sufficient spatial resolution for certain imaging applications. Advances in silicon processes have developed devices that can operate at these frequencies, which has led to the potential for low cost MMW imaging, provided that the circuit design can meet the performance specifications for these applications. In this research, we investigate key components for an active phased array imaging system operating at 77GHz that performs purely digital beamforming. Each element in the phased array has an antenna and processor that measures the phase and amplitude of the received signal. The focus of this thesis is the quality of the phase measurement. Phase noise from the receiver's front-end circuits will degrade the spatial resolution and image integrity. The system requires a MMW phase-locked loop (PLL) to generate the local oscillator. The PLL is a significant contributor to phase noise. A MMW PLL was designed in a 0.13tm silicon-germanium BiCMOS technology for low phase noise and power consumption while maintaining enough output power to robustly drive a mixer load. Measurement results show a de-embedded single-ended output power of -2dBm, a phase noise of -8ldBc/Hz at 1MHz offset corresponding to ips of timing jitter at the carrier, and a total power dissipation of 107mW. A new technique called digital phase tightening reduces phase noise from receiver front-end circuits to allow precise phase estimation for digital beamforming. This technique leverages the large ratio between the MMW carrier frequency and the low frame rates in imaging applications. By mixing down to an intermediate frequency (IF) and then averaging over many samples, we reduce phase error caused by phase noise. A test chip demonstrating the phase tightening concept was designed and characterized. We show that we can reduce RMS error from 450ps to 1.4ps at a 175MHz IF which corresponds to reducing ips of jitter to 3fs at a 77GHz carrier.
by Khoa Minh Nguyen.
Ph.D.
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Konstantinidis, A. "Evaluation of digital X-ray detectors for medical imaging applications." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1322919/.
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Digital x-ray detectors are now the detector of choice in many X-ray examinations. They have been accepted into clinical practice over the past decade but there are still ongoing developments in the technology. Complementary metal oxide semiconductor (CMOS) active pixel sensors (APS) are a novel digital technology that offers advantages compared to some of the more established approaches (charge-coupled devices (CCD), thin film transistor arrays (TFT) and CMOS passive pixel sensors (PPS)). This thesis looks at the performance of these new sensors and attempts to identify their role in future medical imaging applications. Standard electro-optical and x-ray performance evaluations of two novel CMOS APS, namely the large Area Sensor (LAS) and Dexela CMOS x-ray detector, are presented. The evaluation was made in terms of the photon transfer curve (PTC), the modulation transfer function (MTF), the normalized noise power spectrum (NNPS) and the resultant detective quantum efficiency (DQE). Modifications were introduced to extend the standard methods to overcome technical limitations. The performance of these detectors was compared to three commercial systems (Remote RadEye HR (CMOS APS), Hamamatsu C9732DK (CMOS PPS) and Anrad SMAM (a-Se TFT)) at beam qualities (28 kV for mammography and 52 kV and 74 kV for general radiography) based on the IEC standards. Both the LAS and Dexela CMOS detectors demonstrate enhanced performance. The effect of the CMOS APS inherent nonlinearity on the x-ray performance was also evaluated. Finally, the measured performance parameters were used to simulate images for different mammographic imaging tasks in order to establish possible areas of application for the new sensors. Two software phantoms (one representing a 3-D breast and the other the CDMAM test tool) were used to simulate a range of mammographic conditions. The results show that both novel CMOS APS detectors offer high image quality compared to the commercial detector systems.
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MacIntosh, Michael J. "A CCD based camera for digital imaging of the nightglow." Thesis, University of Aberdeen, 1986. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU366584.
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This thesis deals with the development of a microprocessor controlled CCD based camera for digital imaging of the nightglow. A brief description of the techniques used to image the nightglow is given and the reasons for choosing a CCD as the detector are discussed. The fundamentals of CCD operation are then described with particular emphasis on buried channel CCD image sensors as the P8603 CCD used in the camera is of this type. A major part of the thesis is devoted to the detailed design of the camera electronics which consists of three main sections; (i) a MC6802 based microprocessor controller with 4 K of ROM and 64 K of dynamic RAM; (ii) a display interface which allows an on-line display of the images to be produced on an oscilloscope for monitoring purposes while observing; and (iii) the CCD interface which consists of the drive pulse buffers for the image, store and readout sections of the CCD, the bias voltage generators for the CCD on-chip charge amplifier, and the signal processing electronics which has a choice of four software selectable gains and uses correlated double sampling to achieve low noise levels. The design of a digital cassette system for recording the image data is also described. The system, which is based on a low cost stereo cassette recorder, accepts and produces data in the same RS232 serial format used by the camera and is capable of operating at up to 9600 baud on two channels. A further section deals with the optical, structural and cryogenic design. This includes a description of the camera optical system which is based on a commercial FI.4 CCTV lens, theoretical calculations of the expected response of the camera to a range of nightglow emissions, the design of the liquid nitrogen cryostat which is used to cool the CCD, the design of the camera chassis, and calculations to determine (i) the CCD temperature required to reduce the dark current to an acceptable level; and (ii) the capacity of the liquid nitrogen reservoir which is necessary to allow a whole night's observing without refilling. The detailed operation of the camera control program, which is written in 6800 assembly language, is then described with the aid of flowcharts. Currently the control program is set up to give a one minute integration period using half-frame imaging and a 3 x 2 pixel amalgamation. The final section of the thesis deals with the testing and performance of the camera. Several experiments were carried out including the measurement of the various possible ampilifier gains, the noise performance of the system, the angular response of the camera optics, and the calibration of the camera using a standard light to allow the absolute intensity of nightglow emissions to be calculated. Theoretical calculations of the expected noise levels and the expected response of the camera to the standard light are also included. A suite of image processing programs, written in Pascal for an Apple II microcomputer, are then described. These programs allow various operations to be performed such as scanning the images stored on tape, and correcting for the defective columns on the CCD and the angular response of the camera optics. Lastly, the performance of the camera in the field is discussed and the results of observations made locally, which include photographs of images believed to show hydroxyl airglow structure, are presented.
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Xu, Chen. "Low voltage CMOS digital imaging architecture with device scaling considerations /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202004%20XU.
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Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 131-136). Also available in electronic version. Access restricted to campus users.
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Campbell, Sydney. "Experiences of analogue-trained radiographers utilising digital imaging in projection radiography." Thesis, Nelson Mandela Metropolitan University, 2017. http://hdl.handle.net/10948/14796.
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The professional work of a radiographer encompasses both patient care and the use of technology. The technology employed could either be analogue or digital technology. Since 1973, the analogue imaging system has slowly been replaced by digital radiography imaging systems. Despite the many advantages of digital imaging it does present the radiographer with added responsibilities. Furthermore, analogue-trained radiographers have found adjusting to digital imaging especially challenging. The aim of the study was to explore and describe the experiences of analogue-trained radiographers utilising digital imaging in projection radiography with the intention of developing guidelines to equip radiography managers to assist analogue-trained radiographers to better utilise digital imaging. The researcher used Schlossberg’s Transition Theory as a lens to look at the experiences of analogue-trained radiographers using digital imaging to produce radiographs. The research study used a qualitative design which was explorative, descriptive and contextual in nature. The target population included all diagnostic radiographers (public and private) in the local municipality who were registered with the Health Professions Council of South Africa. Purposive sampling was employed to select the radiographers that represented all radiographers in the Nelson Mandela Bay Health District. The sample included all radiographers who fulfilled the identified selection criteria. The selected participants were recruited to take part in in-depth, semi-structured individual interviews. The data was analysed using a computer-aided qualitative data analysis software package, ATLAS.ti. The trustworthiness of this study was ensured by applying Guba’s model of trustworthiness that includes credibility, transferability, dependability and confirmability. The ethical principles of respect for persons, beneficence and justice, as espoused by the Belmont Report, were adhered to in order to ensure that the study was conducted in an ethical manner. Two themes emanated from the data, namely the evolution of the radiographer when faced with the advances in technology as well the role that the work environment played in the manner that the participants experienced the change. The experiences of the participants were described using direct quotations from the interviews and a literature control was used to verify the participants’ experiences. Evidence was found of radiographer indifference towards exposure selection, dose optimisation and placement of anatomical side markers when utilising digital imaging. Finally, guidelines were developed to equip radiography managers to assist analogue-trained radiographers to better utilise digital imaging. In addition, the guidelines will assist all other radiographers to better utilise digital imaging.
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Sechopoulos, Ioannis. "Investigation of physical processes in digital x-ray tomosynthesis imaging of the breast." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/22589.
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Teo, Chek Koon. "Digital enhancement of night vision and thermal images." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Dec%5FTeo%5FChek.pdf.
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Thesis (M.S. in Combat Systems Technology)--Naval Postgraduate School, December 2003.Thesis advisor(s): Monique P. Fargues, Alfred W. Cooper. Includes bibliographical references (p. 75-76). Also available online.
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Ekestorm, Stig R. T. "An all-digital image synthesizer for countering high-resolution imaging radars." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/ADA381835.
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Offiah, Amaka. "Optimisation of the digital radiographic imaging of suspected non-accidental injury." Thesis, University College London (University of London), 2005. http://discovery.ucl.ac.uk/1444875/.
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Aim: To optimise the digital (radiographic) imaging of children presenting with suspected non-accidental injury (NAI).;Objectives: (i) To evaluate existing radiographic quality criteria, and to develop a more suitable system if these are found to be inapplicable to skeletal surveys obtained in suspected NAI. (ii) To document differences in image quality between conventional film-screen and the recently installed Fuji5000R computed radiography (CR) system at Great Ormond Street Hospital for Children, (iii) To document the extent of variability in the standard of skeletal surveys obtained in the UK for suspected NAI. (iv) To determine those radiographic parameters which yield the highest diagnostic accuracy, while still maintaining acceptable radiation dose to the child, (v) To determine how varying degrees of edge-enhancement affect diagnostic accuracy. (vi) To establish the accuracy of soft compared to hard copy interpretation of images in suspected NAI.;Materials and Methods: (i) and (ii) Retrospective analysis of 286 paediatric lateral spine radiographs by two observers based on the Commission of European Communities (CEC) quality criteria, (iii) Review of the skeletal surveys of 50 consecutive infants referred from hospitals throughout the United Kingdom (UK) with suspected NAI. (iv) Phantom studies. Leeds TO. 10 and TO. 16 test objects were used to compare the relationship between film density, exposure parameters and visualisation of object details, (iv) Clinical study. Anteroposterior and lateral post mortem skull radiographs of six consecutive infants were obtained at various exposures. Six observers independently scored the images based on visualisation of five criteria, (v) and (vi) A study of diagnostic accuracy in which six observers independently interpreted 50 radiographs from printed copies (with varying degrees of edge-enhancement) and from a monitor.;Results: The CEC criteria are useful for optimisation of imaging parameters and allow the detection of differences in quality of film-screen and digital images. There is much variability in the quality and number of radiographs performed as part of skeletal surveys in the UK for suspected NAI. The Leeds test objects are either not sensitive enough (TO. 10) or perhaps over sensitive (TO. 16) for the purposes of this project. Furthermore, the minimum spatial resolution required for digital imaging in NAI has not been established. Therefore the objective interpretation of phantom studies is difficult. There is scope for reduction of radiation dose to children with no effect on image quality. Diagnostic accuracy (fracture detection) in suspected NAI is generally low, and is not affected by image display modality.;Conclusions: The CEC quality criteria are not applicable to the assessment of clinical image quality. A national protocol for skeletal surveys in NAI is required. Dedicated training, close supervision, collaboration and consistent exposure of radiologists to cases of NAI should improve diagnostic accuracy. The potential exists for dose reduction when performing skeletal surveys in children and infants with suspected NAI. Future studies should address this issue.