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Khan, Haris Ahmad. « Multispectral constancy for illuminant invariant representation of multispectral images ». Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCK028/document.
Texte intégralRésumé :
En imagerie couleur, un système d’acquisition capture une scène avec une haute résolution spatiale mais une résolution spectrale limitée. L’imagerie hyperspectrale permet d’acquérir la scène avec une grande résolution spectrale. Un système d’acquisition hyperspectrale est un ensemble complexe et il est difficile de l’utiliser pour acquérir des données dans une situation où les conditions d’imageries ne sont pas contrôlées. De plus, ces systèmes sont chers et souvent encombrants ou difficiles à manipuler. À cause de ces problèmes, l’utilisation de l’imagerie hyperspectrale n’a pas encore été beaucoup utilisée en vision assistée par ordinateur, et la plupart des systèmes de vision utilise l’imagerie couleur.L’imagerie multispectrale propose une solution intermédiaire, elle permet de capturer une information moins résolue selon la dimension spectrale, comparée à l’hyperspectrale, tout en préservant la résolution spatiale. Ces systèmes sont moins encombrants et moins difficiles à maitriser grâce aux récentes avancées technologiques, et arrivent sur le marché en tant que produits commerciaux. On peut citer les matrices de filtres spectraux (spectral filter arrays) qui permettent l’acquisition en temps réel d’images multispectrales grâce à l’utilisation d’unecaméra de complexité similaire à une caméra couleur. Jusqu’ici, les informations capturées par ces systèmes étaient considérées de la même manière que les imageurs hyperspectraux en champ proche, c’est à dire que pour utiliser l’information au mieux, les conditions d’acquisitions devaient être connues et le système calibré, en particulier pour l’éclairage de la scène et la dynamique de la scène.Afin d’élargir l’utilisation de l’imagerie multispectrale pour la vision par ordinateur dans des conditions générales, je propose dans cette thèse de développer les méthodes calculatoires en imagerie couleur (computational color imaging) et de les adapter aux systèmes d’imagerie multispectraux. Une caractéristique très puissante de l’imagerie couleur est de proposer un rendu constant des couleurs de la surface d’un objet à travers différentes conditions d’acquisition via l’utilisation d’algorithmes et divers traitements de l’information.Dans cette thèse, j’étends la notion de constance des couleurs et de balance des blancs de l’imagerie couleur à l’imagerie multispectrale. J’introduis le terme de constance de l’information spectrale (multispectral constancy).Je propose la construction d’un ensemble d’outils permettant la représentation constante de l’information spectrale à travers le changement d’éclairage. La validité de ces outils est évaluée à travers la reconstruction de la réflectance spectrale des objets lorsque l’éclairage change. Nous avons également acquis de nouvelles images hyperspectrales et multispectrales mises à disposition de la communauté.Ces outils et données permettront de favoriser la généralisation de l’utilisation de l’imagerie multispectrale en champ proche dans les applications classiques utilisant traditionnellement l’imagerie couleur et de sortir ce mode d’imagerie des laboratoires. L’avantage en vision par ordinateur est une meilleure analyse de la réflectance de la surface des objets et donc un avantage certain dans les tâches de classification et d’identification de matériauxA conventional color imaging system provides high resolution spatial information and low resolution spectral data. In contrast, a multispectral imaging system is able to provide both the spectral and spatial information of a scene in high resolution. A multispectral imaging system is complex and it is not easy to use it as a hand held device for acquisition of data in uncontrolled conditions. The use of multispectral imaging for computer vision applications has started recently but is not very efficient due to these limitations. Therefore, most of the computer vision systems still rely on traditional color imaging and the potential of multispectral imaging for these applications has yet to be explored.With the advancement in sensor technology, hand held multispectral imaging systems are coming in market. One such example is the snapshot multispectral filter array camera. So far, data acquisition from multispectral imaging systems require specific imaging conditions and their use is limited to a few applications including remote sensing and indoor systems. Knowledge of scene illumination during multispectral image acquisition is one of the important conditions. In color imaging, computational color constancy deals with this condition while the lack of such a framework for multispectral imaging is one of the major limitation in enabling the use of multispectral cameras in uncontrolled imaging environments.In this work, we extend some methods of computational color imaging and apply them to the multispectral imaging systems. A major advantage of color imaging is the ability of providing consistent color of objects and surfaces across varying imaging conditions. In this work, we extend the concept of color constancy and white balancing from color to multispectral images, and introduce the term multispectral constancy.The validity of proposed framework for consistent representation of multispectral images is demonstrated through spectral reconstruction of material surfaces from the acquired images. We have also presented a new hyperspectral reflectance images dataset in this work. The framework of multispectral constancy will make it one step closer for the use of multispectral imaging in computer vision applications, where the spectral information, as well as the spatial information of a surface will be able to provide distinctive useful features for material identification and classification tasks
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Adams, Andrew J. « Multispectral persistent surveillance / ». Online version of thesis, 2008. http://hdl.handle.net/1850/7070.
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Wahham, Atheer. « Multispectral Image Acquisition ». Thesis, Linköpings universitet, Institutionen för teknik och naturvetenskap, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-97053.
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The purpose of this project was to develop control software for a multi-spectral imaging system. The multi-spectral imaging system used by the colour Lab consists of a camera (Alta USB camera) and a filter (VariSpec liquid crystal tuneable filter). The camera and the filter were delivered by two different manufacturers and therefore have two separate stand-alone control programs. The fact that the hardware had to be controlled by two separate pieces of software meant that the image capturing procedure was very time-consuming and needed an unrealistic amount of user input. The project resulted in a C++ console program with all the required and necessary functionsas those provided by the individual software, camera and filter; and operated both the camera and the filter simultaneously and conveniently. The project was performed at the Norwegian colour Laboratory in Gjøvik University College.
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Jia, Jie. « Fourier Multispectral Imaging ». University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1494159492377494.
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Isoz, Wilhelm. « Calibration of Multispectral Sensors ». Thesis, Linköping University, Department of Electrical Engineering, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-5202.
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This thesis describes and evaluates a number of approaches and algorithms for nonuniform correction (NUC) and suppression of fixed pattern noise in a image sequence. The main task for this thesis work was to create a general NUC for infrared focal plane arrays. To create a radiometrically correct NUC, reference based methods using polynomial approximation are used instead of the more common scene based methods which creates a cosmetic NUC.
The pixels that can not be adjusted to give a correct value for the incomming radiation are defined as dead. Four separate methods of identifying dead pixels are used to find these pixels. Both the scene sequence and calibration data are used in these identifying methods.
The algorithms and methods have all been tested by using real image sequences. A graphical user interface using the presented algorithms has been created in Matlab to simplify the correction of image sequences. An implementation to convert the corrected values from the images to radiance and temperature is also performed.
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Unsalan, Cem. « Multispectral satellite image understanding ». The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1061903845.
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Ünsalan, Cem. « Multispectral satellite image understanding ». Columbus, Ohio : Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc%5num=osu1061903845.
Texte intégralRésumé :
Thesis (Ph. D.)--Ohio State University, 2003.Title from first page of PDF file. Document formatted into pages; contains xix, 235 p. : ill. (some col.). Advisor: Kim L. Boyer, Department of Electrical Engineering. Includes bibliographical references (p. 216-235).
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Vivone, Gemine. « Multispectral and hyperspectral pansharpening ». Doctoral thesis, Universita degli studi di Salerno, 2014. http://hdl.handle.net/10556/1604.
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2012-2013Remote sensing consists in measuring some characteristics of an object from a distance. A key example of remote sensing is the Earth observation from sensors mounted on satellites that is a crucial aspect of space programs. The first satellite used for Earth observation was Explorer VII. It has been followed by thousands of satellites, many of which are still working. Due to the availability of a large number of different sensors and the subsequent huge amount of data collected, the idea of obtaining improved products by means of fusion algorithms is becoming more intriguing. Data fusion is often exploited for indicating the process of integrating multiple data and knowledge related to the same real-world scene into a consistent, accurate, and useful representation. This term is very generic and it includes different levels of fusion. This dissertation is focused on the low level data fusion, which consists in combining several sources of raw data. In this field, one of the most relevant scientific application is surely the Pansharpening. Pansharpening refers to the fusion of a panchromatic image (a single band that covers the visible and near infrared spectrum) and a multispectral/hyperspectral image (tens/hundreds bands) acquired on the same area. [edited by author]
XII ciclo n.s.
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Von, chong echevers Alejandro. « Nouvelle approche pour l'estimation de la saturation en oxygène du sang artériel en utilisant un capteur multispectrale ». Thesis, Cergy-Pontoise, 2019. http://www.theses.fr/2019CERG1023.
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Ce manuscrit présente les travaux réalisés pour la mise au point d’un système d’estimation du taux d’oxygénation connu aussi sous le nom d’oxymètre de pouls. Ledit outil est indispensable, notamment dans le domaine médical, pour la surveillance des patients lors des interventions anesthésiques, pour les soins post-opératoires et aux urgences puisqu’il fournit de l’information relative à l’efficacité respiratoire et au rythme cardiaque. Le principe d’opération de ce dernier est basé sur la différence en absorption optique entre le sang oxygéné et le sang désoxygéné à l’aide d’une photodiode simple comme moyen de détection. Dans ce travail de recherche, nous introduisons une nouvelle méthode basée sur la différence des spectres d’absorption entre le sang oxygéné et le sang désoxygéné en utilisant un photodétecteur multispectrale.En premier lieu, une introduction et une analyse de l’état de l’art sont faites afin de mieux comprendre la théorie derrière l’oxymétrie de pouls et de mettre en évidence les limitations des méthodes actuelles, ce qui nous permettra de positionner scientifiquement et techniquement les contributions. Ensuite, une explication détaillée du système conçu, concernant l’électronique, l’acquisition et traitement des signaux est décrite.Finalement, nous présentons les résultats obtenus avec la méthode proposée. D’abord, une preuve de concept à plusieurs longueurs d’onde a été faite avec un spectromètre comme moyen de détection afin de valider le principe de fonctionnement de notre méthode. Pour ce faire, nous avons effectué des tests de désoxygénation par rétention de la respiration conjointement avec un oxymètre de haute gamme comme moyen de comparaison. Une fois le principe validé, nous avons remplacé le spectromètre par un capteur multispectrale. Nous avons alors montré que les estimations faites avec notre méthode, en régime stable, tombaient dans la tolérance permise par la norme ISO régulant les oxymètres de pouls.Ces travaux ouvrent une voie alternative et complémentaire à l’étude de l’oxymétrie de pouls capable de surmonter plusieurs limitations présentes dans la technique conventionnelle, en particulier dans le cadre du design d’implants autonomes. Des essais cliniques à venir permettront d’approfondir sur l’utilité de cette méthode et ses limitationsThis manuscript presents the work done to develop an alternative system for the estimation of the oxygen saturation of blood, also known as pulse oximeter. It is an essential tool, especially in the medical field, for patient monitoring during anesthesia procedures, post-operative care and emergencies, since it provides information related to the respiratory efficiency and heart rate. The principle of operation of the latter is based in the difference in optical absorption between oxygenated blood and deoxygenated blood using a simple photodiode as the sensor. In this research work, we introduce a new method based on the difference between the absorption spectrum between oxygenated blood and deoxygenated blood using a multispectral photodetector.In the first place, an introduction and analysis of the state of the art are made to better understand the theory behind pulse oximetry and highlight the limitations of current methods, which will allow us to position ourselves scientifically and technologically, for our contribution. Then, a detailed explanation of the designed system, concerning the electronics, the acquisition and signal processing is described.Finally, we present the results obtained with our proposed method. First, a proof of concept at several wavelengths was made with a spectrometer as a means of detection to validate the principle of operation. To accomplish deoxygenation, breath holding tests were carried out in conjunction with a high-end oximeter as a means of comparison. Once the principle was validated, we replaced the spectrometer with a multispectral sensor. We found that the estimates made with our method, under stable state conditions, fell within the tolerance allowed by the ISO standard regulating pulse oximeters.Since this is a new principle, we consider that with this work, we open an additional path to the study of pulse oximetry which might allow to overcome several limitations present in the conventional technique. Future clinical trials will explore the usefulness of this method and its limitations
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Nyström, Daniel. « Multispectral Color Reproduction Using DLP ». Thesis, Linköping University, Department of Science and Technology, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-1291.
Texte intégralRésumé :
The color gamut, i.e. the range of reproducible colors, is in most conventional display systems not sufficient for accurate color reproduction of highly saturated colors. Any conventional three-primary display suffers from a color gamut limited within the triangle spanned by the primary colors. Even by using purer primaries, enlarging the triangle, there will still be a problem to cover all the perceivable colors. By using a system with more than three primary colors, in printing denoted Hi-Fi color, the gamut will be expanded into a polygon, yielding a larger gamut and better color reproduction.
Digital Light Processing (DLP) is a projection technology developed by Texas Instrument. It uses a chip with an array of thousands of individually controllable micromirrors, each representing a single pixel in the projected image. A lamp illuminates the micromirrors, and by controlling the amount of time each mirror reflect the light, using pulse width modulation, the projected image is created. Color reproduction is achieved by letting the light pass through color filters, corresponding to the three primaries, mounted in a filter wheel.
In this diploma work, the DLP projector InFocus® LP™350 has been evaluated, using the Photo Research® PR®-705 Spectroradiometer. The colorimetric performance of the projector is found to be surprisingly poor, with a color gamut noticeably smaller then that of a CRT monitor using standardized phosphors. This is due to the broad banded filters used, yielding increased brightness at the expense of the pureness of the primaries.
With the intention of evaluating the potential for the DLP technology in multi- primary systems, color filters are selected for additional primary colors. The filters are selected from a set of commercially available filters, the Kodak Wratten filters for science and technology. Used as performance criteria for filter selection is the volume of the gamut in the CIE 1976 (L*u*v*) uniform color space.
The selected filters are measured and evaluated in combination with the projector, verifying the theoretical results from the filter selection process. Colorimetric performance of the system is greatly improved, yielding an expansion of the color gamut in CIE 1976 (L*u*v*) color space by 79%, relative the original three-primary system. These results indicate the potential for DLP in multiprimary display systems, with the capacity to greatly expand the color gamut, by using carefully selected filters for additional primary colors.
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Nyström, Daniel. « Colorimetric and Multispectral Image Acquisition ». Licentiate thesis, Linköping University, Linköping University, Department of Science and Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-8866.
Texte intégralRésumé :
The trichromatic principle of representing color has for a long time been dominating in color imaging. The reason is the trichromatic nature of human color vision, but as the characteristics of typical color imaging devices are different from those of human eyes, there is a need to go beyond the trichromatic approach. The interest for multi-channel imaging, i.e. increasing the number of color channels, has made it an active research topic with a substantial potential of application.
To achieve consistent color imaging, one needs to map the imaging-device data to the device-independent colorimetric representations CIEXYZ or CIELAB, the key concept of color management. As the color coordinates depend not only on the reflective spectrum of the object but also on the spectral properties of the illuminant, the colorimetric representation suffers from metamerism, i.e. objects of the same color under a specific illumination may appear different when they are illuminated by other light sources. Furthermore, when the sensitivities of the imaging device differ from the CIE color matching functions, two spectra that appear different for human observers may result in identical device response. On contrary, in multispectral imaging, color is represented by the object’s physical characteristics namely the spectrum which is illuminant independent. With multispectral imaging, different spectra are readily distinguishable, no matter they are metameric or not. The spectrum can then be transformed to any color space and be rendered under any illumination.
The focus of the thesis is high quality image-acquisition in colorimetric and multispectral formats. The image acquisition system used is an experimental system with great flexibility in illumination and image acquisition setup. Besides the conventional trichromatic RGB filters, the system also provides the possibility of acquiring multi-channel images, using 7 narrowband filters. A thorough calibration and characterization of all the components involved in the image acquisition system is carried out. The spectral sensitivity of the CCD camera, which can not be derived by direct measurements, is estimated using least squares regression, optimizing the camera response to measured spectral reflectance of carefully selected color samples.
To derive mappings to colorimetric and multispectral representations, two conceptually different approaches are used. In the model-based approach, the physical model describing the image acquisition process is inverted, to reconstruct spectral reflectance from the recorded device response. In the empirical approach, the characteristics of the individual components are ignored, and the functions are derived by relating the device response for a set of test colors to the corresponding colorimetric and spectral measurements, using linear and polynomial least squares regression.
The results indicate that for trichromatic imaging, accurate colorimetric mappings can be derived by the empirical approach, using polynomial regression to CIEXYZ and CIELAB. Because of the media-dependency, the characterization functions should be derived for each combination of media and colorants. However, accurate spectral data reconstruction requires for multi-channel imaging, using the model-based approach. Moreover, the model-based approach is general, since it is based on the spectral characteristics of the image acquisition system, rather than the characteristics of a set of color samples.
Report code: LiU-TEK-LIC- 2006:70
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Riseby, Emil, et Alexander Svensson. « Multispectral Imaging for Surveillance Applications ». Thesis, Linköpings universitet, Medie- och Informationsteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-115731.
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Silicon based sensors is a commonly used technology in digital cameras today. That has made such cameras relatively cheap and widely used. Unfortunately they are constructed to capture and represent image quality for humans. Several image applications work better without the restrictions of the visible spectrum. Human visual restrictions are often indirectly put on technology by using images showing only visible light. Thinking outside the box in this case is seeing beyond the visible spectrum.
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Huang, Jiwei. « Multispectral Imaging of Skin Oxygenation ». The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1356637098.
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Davenport, Carolyn Marie Connor. « Multispectral fluorescence imaging of atherosclerosis ». Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/186077.
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Multispectral fluorescence imaging is a new diagnostic technique with the potential to provide improved detection and classification of atherosclerotic disease. This technique involves imaging the fluorescence response of a tissue region through a tunable band-pass filtering device. The result is a set of images in which each individual image is composed of the fluorescence emission within a specified band of wavelengths. Multispectral imaging combined with angioscopic technology allows direct access to important spectral information and spatial attributes providing the potential for more informed clinical decisions about which, if any, treatment modality is indicated. In this dissertation, the system requirements for an angioscopic system with multispectral imaging capability are identified. This analysis includes a description of the necessary optical components and their characteristics as well as the experimental determination of spectral radiance values for the fluorescence response of human aorta specimens and the estimation of anticipated signal-to-noise ratios for the spectral images. Other issues investigated include the number of spectral images required to provide good classification potential and the best normalization method to be utilized. Finally, the potential utility of the information contained within a multispectral data set is demonstrated. Two methods of utilizing the multispectral data are presented. The first method involves generating a ratio-image from the ratio of the intensities of two spectrally filtered images. The second method consists of using histologically verified training data to train a projector and then applying that projector to a set of spectral images. The result (a weighted sum of the spectral images) provides improved contrast between normal and diseased tissue, and is called an optimized-contrast image. White-light images (generated using an incandescent light source), total-fluorescence images (the fluorescence response without spectral filtering), ratio-images, and optimized contrast images are compared. The results indicate that angioscopic fluorescence imaging appears to be a feasible and potentially useful technique in terms of providing improved detection of atherosclerotic disease. This technique warrants further investigation to further define the system requirements and to evaluate its clinical usefulness including the collection of a more extensive data set and the development of a prototype system.
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Tobin, Brendan. « Automatic Registration of Multispectral Images ». Thesis, The University of Arizona, 2013. http://hdl.handle.net/10150/297771.
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Multispectral imaging is an important tool in art conservation because it allows researchers to view under-drawing and restoration efforts on a painting. It is necessary to precisely align various images of the same painting using digital image processing techniques, however this is complicated by inconsistencies in image contents and the use of multiple cameras. This paper seeks to develop an effective method to automatically align and rescale multispectral images of paintings. Key point identification using the Speeded-Up Robust Feature detection algorithm with refinement by Random Sample Consensus fitting was determined to be an accurate and efficient method for aligning visible and infrared multispectral images.
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Pradhan, Pushkar S. « Multiresolution based, multisensor, multispectral image fusion ». Diss., Mississippi State : Mississippi State University, 2005. http://library.msstate.edu/etd/show.asp?etd=etd-07082005-140541.
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Alex, Aneesh. « Multispectral three-dimensional optical coherence tomography ». Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/54164/.
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A spectral-domain OCT system operating at 1300 nm wavelength region, capable of acquiring 47,000 A-lines/s, was designed and developed. Its axial and transverse resolutions were ∼ 6 µm and ∼15 µm respectively. OCT images of human skin were obtained in vivo using three OCT systems, in order to find the optimal wavelength region for dermal imaging. 800 nm OCT system provided better image contrast over other two wavelength regions. Meanwhile, 1300 nm wavelength region was needed to obtain information from deeper dermal layers. To determine the effect of melanin pigmentation on OCT, images were taken from subjects with different ethnic origins. Interestingly, melanin pigmentation was found to have little effect on penetration depth in OCT. In vitro tumour samples, comprising samples with different degrees of dysplasia, were imaged at 800 nm, 1060 nm and 1300 nm wavelength regions to find the capability of OCT to diagnose microstructural changes occurring during tumour progression. 800 nm OCT system was capable to detect the malignant changes with higher contrast than other wavelength regions. However, higher wavelength regions were required to penetrate deeper in densely scattering tumour samples at advanced stages. OCT system operating at 1060 nm was combined with a photoacoustic imaging (PAT) system to obtain complementary information from biological tissues. This multimodal OCT/PAT system demonstrated its potential to deliver microstructural information based on optical scattering and vascular information based on optical absorption in living mice and human skin. The results indicate OCT as a promising imaging modality that can have profound applications in several areas of clinical diagnostic imaging.
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Choate, Laura, Kevin Lundstrom, Kevin Pounds, Garrett Richards et Eli Vinal. « Remote Imaging System Acquisition Multispectral Imager ». International Foundation for Telemetering, 2011. http://hdl.handle.net/10150/595725.
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ITC/USA 2011 Conference Proceedings / The Forty-Seventh Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2011 / Bally's Las Vegas, Las Vegas, NevadaThe National Aeronautics and Space Administration's (NASA) Remote Imaging System Acquisition (RISA) camera will integrate the functionalities of existing space cameras. The system operates between 350nm and 1050nm wavelengths, with a MATLAB user interface, uses a CS-mount standard with a CMOS detector, and has a fixed focal plane. The implementation of a liquid lens uses electrical focus adjustments to image from infinity down to one foot. This will allow wireless operation and reduces mechanical failure. All images and video captured will be transmitted wirelessly to a MATLAB program. This data is then processed and stored, allowing for remote imaging.
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Ni, Chuan. « Spectral Filter Array for Multispectral Imaging ». University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1492374218701675.
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Krishnan, Nitya. « Multispectral segmentation of whole brain MRI ». Morgantown, W. Va. : [West Virginia University Libraries], 2004. https://etd.wvu.edu/etd/controller.jsp?moduleName=documentdata&jsp%5FetdId=3753.
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Thesis (M.S.)--West Virginia University, 2004.Title from document title page. Document formatted into pages; contains vii, 89 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 56-59).
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Chen, Ke. « Reconstruction algorithms for multispectral diffraction imaging ». Thesis, Boston University, 2014. https://hdl.handle.net/2144/10963.
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Thesis (Ph.D.)--Boston UniversityIn conventional Computed Tomography (CT) systems, a single X-ray source spectrum is used to radiate an object and the total transmitted intensity is measured to construct the spatial linear attenuation coefficient (LAC) distribution. Such scalar information is adequate for visualization of interior physical structures, but additional dimensions would be useful to characterize the nature of the structures. By imaging using broadband radiation and collecting energy-sensitive measurement information, one can generate images of additional energy-dependent properties that can be used to characterize the nature of specific areas in the object of interest. In this thesis, we explore novel imaging modalities that use broadband sources and energy-sensitive detection to generate images of energy-dependent properties of a region, with the objective of providing high quality information for material component identification. We explore two classes of imaging problems: 1) excitation using broad spectrum sub-millimeter radiation in the Terahertz regime and measure- ment of the diffracted Terahertz (THz) field to construct the spatial distribution of complex refractive index at multiple frequencies; 2) excitation using broad spectrum X-ray sources and measurement of coherent scatter radiation to image the spatial distribution of coherent-scatter form factors. For these modalities, we extend approaches developed for multimodal imaging and propose new reconstruction algorithms that impose regularization structure such as common object boundaries across reconstructed regions at different frequencies. We also explore reconstruction techniques that incorporate prior knowledge in the form of spectral parametrization, sparse representations over redundant dictionaries and explore the advantage and disadvantages of these techniques in terms of image quality and potential for accurate material characterization. We use the proposed reconstruction techniques to explore alternative architectures with reduced scanning time and increased signal-to-noise ratio, including THz diffraction tomography, limited angle X-ray diffraction tomography and the use of coded aperture masks. Numerical experiments and Monte Carlo simulations were conducted to compare performances of the developed methods, and validate the studied architectures as viable options for imaging of energy-dependent properties.
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Griffiths, Trace A. « Enhancing Multispectral Imagery of Ancient Documents ». DigitalCommons@USU, 2011. https://digitalcommons.usu.edu/etd/907.
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Multispectral imaging (MSI) provides a wealth of imagery data that, together with modern signal processing techniques, facilitates the enhancement of document images. In this thesis, four topic areas are reviewed and applied to ancient documents. They are image fusion, matched filters, bleed-through removal, and shadow removal. These four areas of focus provide useful tools for papyrologists studying the digital imagery of documents. The results presented form a strong case for the utility of MSI data over the use of a single image captured at any given wavelength of light.
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Mihoubi, Sofiane. « Snapshot multispectral image demosaicing and classification ». Thesis, Lille 1, 2018. http://www.theses.fr/2018LIL1I062/document.
Texte intégralRésumé :
Les caméras multispectrales échantillonnent le spectre du visible et/ou de l'infrarouge selon des bandes spectrales étroites. Parmi les technologies disponibles, Les caméras snapshot équipées d'une mosaïque de filtres acquièrent des images brutes à cadence vidéo. Ces images brutes nécessitent un processus de dématriçage permettant d'estimer l'image multispectrale en pleine définition. Dans ce manuscrit nous examinons les méthodes de dématriçage multispectrale et proposons une nouvelle méthode basée sur l'image panchromatique. De plus, nous mettons en évidence l'influence de l'illumination sur les performances de dématriçage, puis nous proposons des étapes de normalisation rendant ce dernier robuste aux propriétés d'acquisition. Les résultats expérimentaux montrent que notre méthode fournit de meilleurs résultats que les méthodes classiques.Afin d'effectuer une analyse de texture, nous étendons les opérateurs basés sur les motifs binaires locaux aux images de texture multispectrale au détriment d'exigences de mémoire et de calcul accrues. Nous proposons alors de calculer les descripteurs de texture directement à partir d'images brutes, ce qui évite l'étape de dématriçage tout en réduisant la taille du descripteur. Afin d'évaluer la classification sur des images multispectrales, nous avons proposé la première base de données multispectrale de textures proches dans les domaines spectraux du visible et du proche infrarouge. Des expériences approfondies sur cette base montrent que le descripteur proposé a à la fois un coût de calcul réduit et un pouvoir de discrimination élevé en comparaison avec les descripteurs classiques appliqués aux images dématriçéesMultispectral cameras sample the visible and/or the infrared spectrum according to narrow spectral bands. Available technologies include snapshot multispectral cameras equipped with filter arrays that acquire raw images at video rate. Raw images require a demosaicing procedure to estimate a multispectral image with full spatio-spectral definition. In this manuscript we review multispectral demosaicing methods and propose a new one based on the pseudo-panchromatic image. We highlight the influence of illumination on demosaicing performances, then we propose pre- and post-processing normalization steps that make demosaicing robust to acquisition properties. Experimental results show that our method provides estimated images of better objective quality than classical ones.Multispectral images can be used for texture classification. To perform texture analysis, we extend local binary pattern operators to multispectral texture images at the expense of increased memory and computation requirements. We propose to compute texture descriptors directly from raw images, which both avoids the demosaicing step and reduces the descriptor size. In order to assess classification on multispectral images we have proposed the first significant multispectral database of close-range textures in the visible and near infrared spectral domains. Extensive experiments on this database show that the proposed descriptor has both reduced computational cost and high discriminating power with regard to classical local binary pattern descriptors applied to demosaiced images
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Matanga, Jacques. « STUDY AND REALIZATION OF A MULTISPETRAL DETECTOR(FILTER) BY NON DESTRUCTIVE SPECTRAL DISPERSION THROUGH TE NANOSTRUCTURE FILM ». Thesis, Bourgogne Franche-Comté, 2020. http://www.theses.fr/2020UBFCK019.
Texte intégralRésumé :
Le développement des techniques d’imageries multispectral, d’holographie et de lithographie permet d’exploiter les propriétés des réseaux diffractant dans une grande variété de composants photoniques. Ils sont incorporés dans des diodes laser comme réflecteurs de Bragg distribués, dans différentes fonctions d’optique intégrée pour le multiplexage en longueur d’onde ou les interconnexions optiques, ou inscrits au sein même des fibres, conduisant à une grande variété de capteurs pour la détection d’éléments chimiques, la mesure des températures, des pressions, des accélérations d’acquisition et ou de restitution d’images multispectrales etc... [Lee et al. 2007] [Pagnoux et al. 2005].Parmi ces dispositifs, les réseaux résonnants suscitent un très vif intérêt car ils permettent d’obtenir des filtres ultra-sélectifs à partir d’une structure relativement simple. Cette structure est constituée par un guide diélectrique sur lequel est gravé un réseau sub-longueur d’onde de faible profondeur et ou épaisseur. Hors résonance, la structure réfléchit et transmet la lumière selon les propriétés de réflectivité et transmission très proches de celles du dioptre constitué par l’empilement de couches diélectriquesThe development of multispectral imaging, holography and lithography techniques exploits the properties of diffracting arrays in a wide variety of photonic components. They are incorporated in laser diodes as distributed Bragg reflectors, in various integrated optical functions for wavelength division multiplexing or optical interconnections, or inscribed within the fibers themselves, leading to a wide variety of sensors for detection of chemical elements, measurement of temperatures, pressures, accelerations of acquisition and or restitution of multispectral images, etc. [Lee et al. 2007] [Pagnoux et al. 2005].Among these devices, the resonant networks arouse a great interest because they allow to obtain ultra-selective filters from a relatively simple structure. This structure consists of a dielectric guide on which is etched a subwavelength network of shallow depth and thickness. Except resonance, the structure reflects and transmits the light according to the properties of reflectivity and transmission very close to those of the diopter constituted by the stack of dielectric layers.This work presents the experimental and theoretical studies carried out to overcome the technological obstacles inherent to the realization of thin-film multispectal optical filters.The aim of this thesis is to study and design ultra-selective optical filters based on nanoscale thin films, by exploiting a resonant network structure conceived by depositing multilayer nanowires of metamaterials to surpass the performances of the current filters. Particular in the field of their spectral characteristics and their sensitivity to polarization. An issue of the study is to develop the associated manufacturing process, to identify the technological limitations imposed by the state of the art, to propose a reproducible process and if possible compatible with a collective technological development and low cost.The second was to use the samples from the fabrication of the diffraction gratings to associate it with a tri-CCD transistor-based sensor in the LE2I laboratory, in order to design a sharp acquisition device in multispectral imaging and of vision.The analysis of experimental performances, confronted with theoretical predictions and technological limitations, must lead to a realistic estimate of the potentialities of the proposed filters. To do this we began our study with a literature review on all the key elements of the subject, Nanotechnology, nanoscience these advantages these disadvantages, these possibilities. A review of the literature on multispectral imaging and these ascendants
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Lesmanne, Emeline. « Approche photonique de la détection multispectrale ». Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAY097/document.
Texte intégralRésumé :
Cette thèse a pour objet l'étude des surfaces sélectives en fréquence comme filtres pour l'imagerie multispectrale infrarouge. Les surfaces sélectives en fréquence en transmission sont composées d'une couche métallique percée d'ouvertures périodiques résonantes. La longueur d'onde de résonance et le gabarit du filtre (transmission, largeur à mi-hauteur) dépendent de paramètres géométriques latéraux, ce qui permet d'envisager la conception de matrices multispectrales de pixels. Un modèle théorique utilisant la théorie temporelle des modes couplés sera utilisé pour mettre en évidence les mécanismes du fonctionnement de ces structures dans le domaine de l'infrarouge (λ=1-12 µm), où les métaux sont absorbants. Dans le cadre de cette théorie, des taux de pertes radiatifs et par absorption métallique seront calculés et commentés. Des simulations en FDTD (Finite Difference Time Domain) seront effectuées pour comparaison avec le modèle. De plus, des empilements prenant en compte les contraintes technologiques seront simulés et analysés et permettront de définir les composantes d'un empilement optimal en terme de géométrie et de paramètres matériau (choix des indices optiques). La tolérance à l'angle d'incidence de ces filtres sera également étudiéeThis thesis investigates frequency selective surfaces as filters for infrared multispectral imaging. Frequency selective surfaces for the transmission of light are made of a metallic layer etched with periodic resonant apertures. The resonance wavelength and the filter's parameters (transmission, full width at half maximum) depend on lateral geometrical parameters, facilitating the design and integration of filters on the focal plane array of the detector. A theoretical model using the temporal coupled mode theory will be used to highlight key parameters of the physics of these structures at infrared wavelengths (λ=1-12 µm), where metals are absorbing. Radiative and absorptive loss rates will be calculated and commented. FDTD (Finite Difference Time Domain) simulations will be made and compared with the model. Furthermore, optical stacks taking into account technological constraints will be simulated and analyzed and will allow us to define an optimal optical stack, considering geometrical and material parameters (choice of optical indexes). The filters' angular tolerance will be considered
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Rhoul, Camill. « Simulation de la fluorescence de la végétation mesurée depuis une orbite géostationnaire ». Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLX097/document.
Texte intégralRésumé :
Le travail de cette thèse porte sur l’étude de la télédétection de la fluorescence chlorophyllienne avec un instrument imageur passif depuis une orbite géostationnaire pour le suivi de l’état physiologique de la végétation. Le concept instrumental est étudié théoriquement pour aboutir à la création d’uninstrument et à sa validation. La possibilité de mesurer des cycles diurnes de la fluorescence végétale depuis une orbite géostationnaire est évaluée à l’aide de simulations qui permettent de dresser les spécifications d’un instrument spatial.L’instrument imageur passif mesure dans la bande O 2 -A d’absorption atmosphérique. Il utilise une roue à filtres interférentiels dont la fonction de transmittance varie avec l’angle d’incidence des rayons les traversant. L’étude théorique a permis d’optimiser le placement spectral des filtres en vuede minimiser l’incertitude liée à la mesure de fluorescence.Grâce à la comparaison des mesures de l’instrument imageur avec d’autres instrument de mesure de la fluorescence, l’instrument et son concept instrumental ont été validés. Néanmoins, à cause d’effets de structure de la végétation intervenant sur le transfert radiatif de la fluorescence et de la lumière solaire au sein du couvert végétal, ces mesures ont confirmé la difficulté d’estimer le rendement de fluorescence de la végétation à partir des flux de fluorescence mesurés.Une étude théorique menée grâce à une modélisation du transfert radiatif de la fluorescence dans le couvert végétal jusqu’au capteur a permis d’expliquer la difficulté à retrouver le rendement de fluorescence à partir des flux. Cette étude a mis en avant l’accessibilité du rendement pour des couverts à fortedensité de feuilles et lorsque la distribution de l’orientation des feuilles est centrée sur l’horizontale.Cette modélisation a été étendue pour simuler des mesures spatiales dans le but d’étudier la possibilité de mesurer la fluorescence depuis une orbite géostationnaire dans les bandes O 2 -A et O 2 -B. Les résultats de ces simulations montrent la possibilité de mesurer préférentiellement dans la bandeO 2 -A avec une faible incertitude sur les flux de fluorescence et une bonne répétabilité temporelle pour le suivi des cycles diurnes de la fluorescence de la végétationLe travail de cette thèse porte sur l’étude de la télédétection de la fluorescence chlorophyllienne avec un instrument imageur passif depuis une orbite géostationnaire pour le suivi de l’état physiologique de la végétation. Le concept instrumental est étudié théoriquement pour aboutir à la création d’uninstrument et à sa validation. La possibilité de mesurer des cycles diurnes de la fluorescence végétale depuis une orbite géostationnaire est évaluée à l’aide de simulations qui permettent de dresser les spécifications d’un instrument spatial.L’instrument imageur passif mesure dans la bande O 2 -A d’absorption atmosphérique. Il utilise une roue à filtres interférentiels dont la fonction de transmittance varie avec l’angle d’incidence des rayons les traversant. L’étude théorique a permis d’optimiser le placement spectral des filtres en vuede minimiser l’incertitude liée à la mesure de fluorescence.Grâce à la comparaison des mesures de l’instrument imageur avec d’autres instrument de mesure de la fluorescence, l’instrument et son concept instrumental ont été validés. Néanmoins, à cause d’effets de structure de la végétation intervenant sur le transfert radiatif de la fluorescence et de la lumière solaire au sein du couvert végétal, ces mesures ont confirmé la difficulté d’estimer le rendement de fluorescence de la végétation à partir des flux de fluorescence mesurés.Une étude théorique menée grâce à une modélisation du transfert radiatif de la fluorescence dans le couvert végétal jusqu’au capteur a permis d’expliquer la difficulté à retrouver le rendement de fluorescence à partir des flux. Cette étude a mis en avant l’accessibilité du rendement pour des couverts à fortedensité de feuilles et lorsque la distribution de l’orientation des feuilles est centrée sur l’horizontale.Cette modélisation a été étendue pour simuler des mesures spatiales dans le but d’étudier la possibilité de mesurer la fluorescence depuis une orbite géostationnaire dans les bandes O 2 -A et O 2 -B. Les résultats de ces simulations montrent la possibilité de mesurer préférentiellement dans la bandeO 2 -A avec une faible incertitude sur les flux de fluorescence et une bonne répétabilité temporelle pour le suivi des cycles diurnes de la fluorescence de la végétation
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Fernàndez, i. Ubiergo Gabriel. « Multispectral imaging : acquisition, analysis, compression and applications / ». Lausanne : EPFL, 1997. http://library.epfl.ch/theses/?nr=1673.
Texte intégral
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Hjartarson, Örn. « Separation of lobes in Multispectral Digital Holography ». Thesis, Umeå universitet, Institutionen för fysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-64314.
Texte intégralRésumé :
Through a holographic recording a property from the third dimension, the depth, is obtained in the form of a phase map of the incident light. One wavelength holography will have a unique phase for the depth range corresponding to the wavelength of the light and outside this range the real depth can not be resolved. By introducing more wavelengths to the measurement the unique phase combination of the waves will have a wider range and larger objects can be resolved. Up to six wavelengths can be simultaneous recorded by making them occupy different spatial frequencies. A set of spatial frequencies together describing a property of the wave is referred to as a lobe. For more than 6 wavelengths and a larger depth range produced by a more seldom repeated unique phase combination the individual waves will occupy the same frequencies, i.e. the lobes overlap. The separation of overlapping lobes is essential in order to make precise and time independent measurements of large and/or moving objects. To separate the lobes the complex fields, i.e. the phases together with the amplitudes, were simulated to propagate a distance and again recorded. The propagation leads to a phase shift of the spatial frequencies which reveals the complex fields in the case of two overlapping wavelengths. For three overlapping wavelengths the resolution, i.e spatial frequencies describing the object, has to be reduced in order to determine the individual complex fields. Since the propagation is a linear transformation for the frequencies that do not overlap, only the overlapping elements whose propagation is nonlinear produce new information. The new information gained is therefore independent of the number of wavelengths used which limits the exact determination of the fields to two wavelengths. Through the holographic recording another property of the complex field is obtained which is the superimposed individual intensities. This bounds the complex fields to certain values, i.e. restricts the possible amplitude of the waves. The recording in the two planes produces two intensity distributions which both must be satisfied by the complex fields. The optimization model for this was formulated and a simple optimization algorithm was implemented. Instead of an equality constraint of the intensities the inequality constraint was implemented, mainly due to that the optimization process was out of the scope of the thesis and the inequality constraint resulted in a simple implementation. The result pointed out important properties even though the optimization could not separate the fields satisfactorily for more than three wavelengths. The inequality constraint contains enough information to solve the case of three overlapping wavelengths.
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Carmody, James Daniel Physical Environmental & Mathematical Sciences Australian Defence Force Academy UNSW. « Deriving bathymetry from multispectral and hyperspectral imagery ». Awarded by:University of New South Wales - Australian Defence Force Academy. School of Physical, Environmental and Mathematical Sciences, 2007. http://handle.unsw.edu.au/1959.4/38654.
Texte intégralRésumé :
Knowledge of water depth is a crucial for planning military amphibious operations. Bathymetry from remote sensing with multispectral or hyperspectral imagery provides an opportunity to acquire water depth data faster than traditional hydrographic survey methods without the need to deploy a hydrographic survey vessel. It also provides a means of collecting bathymetric data covertly. This research explores two techniques for deriving bathymetry and assesses them for use by those involved in providing support to military operations. To support this aim a fieldwork campaign was undertaken in May, 2000, in northern Queensland. The fieldwork collected various inherent and apparent water optical properties and was concurrent with airborne hyperspectral imagery collection, space-based multispectral imagery collection and a hydrographic survey. The water optical properties were used to characterise the water and to understand how they affect deriving bathymetry from imagery. The hydrographic data was used to assess the performance of the bathymetric techniques. Two methods for deriving bathymetry were trialled. One uses a ratio of subsurface irradiance reflectance at two wavelengths and then tunes the result with known water depths. The other inverts the radiative transfer equation utilising the optical properties of the water to derive water depth. Both techniques derived water depth down to approximately six to seven metres. At that point the Cowley Beach waters became optically deep. Sensitivity analysis of the inversion method found that it was most sensitive to errors in vertical attenuation Kd and to errors in transforming the imagery into subsurface irradiance reflectance, R(0-) units. Both techniques require a priori knowledge to derive depth and a more sophisticated approach would be required to determine water depth without prior knowledge of the area of interest. This research demonstrates that water depth can be accurately mapped with optical techniques in less than ideal optical conditions. It also demonstrates that the collection of inherent and apparent optical properties is important for validating remotely sensed imagery.
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Wakeham, Steve. « Protective, antireflection coatings for multispectral zinc sulphide ». Thesis, University of Reading, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402630.
Texte intégral
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Cabrera-Mercader, Carlos R. (Carlos Rubén). « Robust compression of multispectral remote sensing data ». Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9338.
Texte intégralRésumé :
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.Includes bibliographical references (p. 241-246).
This thesis develops efficient and robust non-reversible coding algorithms for multispectral remote sensing data. Although many efficient non-reversible coding algorithms have been proposed for such data, their application is often limited due to the risk of excessively degrading the data if, for example, changes in sensor characteristics and atmospheric/surface statistics occur. On the other hand, reversible coding algorithms are inherently robust to variable conditions but they provide only limited compression when applied to data from most modern remote sensors. The algorithms developed in this work achieve high data compression by preserving only data variations containing information about the ideal, noiseless spectrum, and by exploiting inter-channel correlations in the data. The algorithms operate on calibrated data modeled as the sum of the ideal spectrum, and an independent noise component due to sensor noise, calibration error, and, possibly, impulsive noise. Coding algorithms are developed for data with and without impulsive noise. In both cases an estimate of the ideal spectrum is computed first, and then that estimate is coded efficiently. This estimator coder structure is implemented mainly using data-dependent matrix operators and scalar quantization. Both coding algorithms are robust to slow instrument drift, addressed by appropriate calibration, and outlier channels. The outliers are preserved by separately coding the noise estimates in addition to the signal estimates so that they may be reconstructed at the original resolution. In addition, for data free of impulsive noise the coding algorithm adapts to changes in the second-order statistics of the data by estimating those statistics from each block of data to be coded. The coding algorithms were tested on data simulated for the NASA 2378-channel Atmospheric Infrared Sounder (AIRS). Near-lossless compression ratios of up to 32:1 (0.4 bits/pixel/channel) were obtained in the absence of impulsive noise, without preserving outliers, and assuming the nominal noise covariance. An average noise variance reduction of 12-14 dB was obtained simultaneously for data blocks of 2400-7200 spectra. Preserving outlier channels for which the noise estimates exceed three times the estimated noise rms value would require no more than 0.08 bits/pixel/channel provided the outliers arise from the assumed noise distribution. If contaminant outliers occurred, higher bit rates would be required. Similar performance was obtained for spectra corrupted by few impulses.
by Carlos R. Cabrera-Mercader.
Ph.D.
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Lu, Nadine Chi-mei 1965. « Radiometric sensitivity comparisons of multispectral imaging systems ». Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277036.
Texte intégralRésumé :
Multispectral imaging systems provide much of the basic data used by the land and ocean civilian remote sensing community. There are numerous multispectral imaging systems which have been and are being developed. A common way to compare the radiometric performance of these sensors is to examine their noise equivalent change in reflectance, NEDeltarho. The NEDeltarho of a sensor is the reflectance difference that is equal to the noise in the recorded signal. In order to directly compare the sensors, calculations of the parameter being compared need to have a common basis. This thesis compares the noise equivalent change in reflectance of seven different multispectral imaging systems (AVHRR, AVIRIS, ETM, HIRIS, MODIS-N, SPOT-1/HRV, and TM) for a set of three atmospheric conditions (continental aerosol with 23 km visibility, continental aerosol with 5 km visibility, and a Rayleigh atmosphere), five values of ground reflectance (0.01, 0.10, 0.25, 0.50, and 1.00), a nadir viewing angle, and a solar zenith angle of forty-five degrees.
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Yan, Bolin 1954. « Multispectral analysis on a computer vision system ». Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277229.
Texte intégralRésumé :
A procedure of multispectral analysis was developed to classify a two category image. The procedure utilized pattern recognition and feature extraction techniques. Images were acquired using a computer vision system with a series of interference filters to limit the wavelength band of the images. The procedure developed for multispectral analysis is: (1) Filter selection and image acquisition. (2) Pattern recognition. (3) Bayes minimum error rate classification. (4) Feature extraction by Fisher transformation or by Hotelling transformation. The analytical procedure was programmed in Microsoft C computer language and implemented on an IBM AT computer. The system was tested by identifying an apple against a Formica background. The classified images and histograms indicated that the separation was possible.
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MacKenzie, Lewis Edward. « In vivo microvascular oximetry using multispectral imaging ». Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/7732/.
Texte intégralRésumé :
This thesis describes the application of multispectral imaging to several novel oximetry applications. Chapter 1 motivates optical microvascular oximetry, outlines oxygen transport in the body, describes the theory of oximetry, and describes the challenges associated with in vivo oximetry, in particular imaging through tissue. Chapter 2 reviews various imaging techniques for quantitative in vivo oximetry of the microvasculature, including multispectral and hyperspectral imaging, photoacoustic imaging, optical coherence tomography, and laser speckle techniques. Chapter 3 describes a two-wavelength oximetry study of two microvascular beds in the anterior segment of the eye: the bulbar conjunctival and episcleral microvasculature. This study reveals previously unseen oxygen diffusion from ambient air into the bulbar conjunctival microvasculature, altering the oxygen saturation of the bulbar conjunctiva. The response of the bulbar conjunctival and episcleral microvascular beds to acute mild hypoxia is quantified and the rate at which oxygen diffuses into bulbar conjunctival vessels is measured. Chapter 4 describes the development and application of a highly novel non-invasive retinal angiography technique: Oximetric Ratio Contrast Angiography (ORCA). ORCA requires only multispectral imaging and a small perturbation of blood oxygen saturation to produce angiographic sequences. A pilot study of ORCA in human subjects was conducted. This study demonstrates that ORCA can produce angiographic sequences with features such as sequential vessel filling and laminar flow. The application and challenges of ORCA are discussed, with emphasis on comparison with other angiography techniques, such as fluorescein angiography. Chapter 5 describes the development of a multispectral microscope for oximetry in the spinal cord dorsal vein of rats. Measurements of blood oxygen saturation are made in the dorsal vein of both healthy rats, and in rats with the Experimental autoimmune encephalomyelitis (EAE) disease model of multiple sclerosis. The venous blood oxygen saturation of EAE disease model rats was found to be significantly lower than that of healthy controls, indicating increased oxygen uptake from blood in the EAE disease model of multiple sclerosis. Chapter 6 describes the development of video-rate red eye oximetry; a technique which could enable stand-off oximetry of the blood-supply of the eye with high temporal resolution. The various challenges associated with video-rate red eye oximetry are investigated and their influence quantified. The eventual aim of this research is to track circulating deoxygenation perturbations as they arrive in both eyes, which could provide a screening method for carotid artery stenosis, which is major risk-factor for stroke. However, due to time constraints, it was not possible to thoroughly investigate if video-rate red eye can detect such perturbations. Directions and recommendations for future research are outlined.
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Howard, Matthew David. « Fourier Multispectral Imaging in the Shortwave Infrared ». University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1507560319244019.
Texte intégral
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Lafrique, Pierre. « Lidar multispectral pour la caractérisation des aérosols ». Thesis, Toulouse, ISAE, 2015. http://www.theses.fr/2015ESAE0033/document.
Texte intégralRésumé :
Cette thèse vise à montrer rapport d'un lidar multispectral, en particulier en ajoutant des longueurs d'onde dans le proche infrarouge proche, pour la caractérisation des aérosols. En effet par rapport à un lidar mono-longueur d'onde, l'information contenue dans les profils multispectraux permet de remonter aux propriétés microphysiques des aérosols (distribution en aille et composition). Pour cela un simulateur de signaux lidar multispectraux a été adapté à notre étude afin de pouvoir développer et tester deux méthodes permettant de retrouver les propriétés microphysiques des aérosols le long de la ligne e visée à partir de signaux lidar synthétiques. La première méthode, basée sur l'inversion des signaux lidar, permet de retrouver la répartition en taille des aérosols et donc d'en déduire notamment leur concentration et leur rayon modal. Cette méthode nécessite des informations a priori sur les aérosols. Un bilan d'erreur a été réalisé en introduisant des incertitudes sur ces paramètres a priori et montre que les résultats obtenus sur la concentration et le rayon modal sont précis (respectivement 16% et 17% d'erreur). Cette méthode présente l'avantage de ne pas nécessiter d'étalonnage absolu de l'instrument. La deuxième méthode est basée sur la minimisation de l'écart entre des signaux simulés et les signaux que l'on étudie. Même si la précision obtenue sur la répartition en taille retrouvée est plus faible (35% et 40 % d'erreur sur la concentration t le rayon modal) et que la constante d'étalonnage de l'instrument doit être connue, cette méthode a l'avantage de retrouver la composition des aérosols dans 74 % des casThe purpose of this thesis is to show the contribution of a multispectral Iidar for the characterisation of aerosols, in particular hen wavelengths in near infrared are added. Indeed, compared with a mono-wavelength Iidar, the information contained in multispectral profiles allow to retrieve the microphysical properties of aerosols (particule size distribution and composition). To this end, we adapted a multispectral Iidar signal simulator to our study in order to develop and test two methods which objective is to obtain the microphysical properties of aerosol along the line-of-sight from synthetic lidar signals. The first method, based on the inversion of lidar signals, enables to find the length distribution of aerosols and therefore to educe their concentration and their modal radius. This method requires a priori information about the aerosols. An error budget was made by introducing uncertainties on the a priori parameters. It shows that the results obtained regarding the concentration and modal radius are accurate (respectively 16% and 17% uncertainty). The advantage of this method is that it does not require absolute calibration of the instrument. The principle of the second method is to minimize the difference between the studied and the simulated signals. Even if the accuracy on the size distribution is lower (35% and 40% on the concentration and modal radius) and the calibration constant of the instrument has to be known, this method has the advantage to find the concentration of the aerosols in 74% of the cases. Finally, the first method was validated on real data, coming from a collaboration with the RSLab (Barcelona), by comparing ur results with those obtained by this team (7% difference on the modal radius)
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Pronti, Lucilla. « Multispectral imaging of painting : potentialities and limitations of the technique in relation with the chemical and optical proprierties of the pictorial materials ». Thesis, Avignon, 2016. http://www.theses.fr/2016AVIG0262/document.
Texte intégralRésumé :
Cette thèse porte sur l’application des images multispectrales pour l’analyse des matériaux utilisés dans une peinture par comparaison avec la photographie traditionnelle de fluorescence induite par rayons UV et la réflectoraphgie infrarouge. L’application des images multispectrales à l'étude des matériaux picturaux a été appuyée par d'autres techniques analytiques telles que la spectroscopie de réflectance et de fluorescence, la spectroscopie de fluorescence X, la spectroscopie d'absorption UV-visible et la spectroscopie infrarouge transformée de Fourier en réflectance totale atténuée. L’imagerie multispectrale a été testée comme outil de laboratoire d’identification des matériaux picturaux. Ainsi, des couches de peinture constituées de pigments (anciens et modernes), de liants (œufs et l’huile de lin) et de vernis naturels ont été analysées. Pour les matériaux organiques, des expériences de vieillissement accéléré (photodégradation et dégradation thermique) ont permis de modéliser les changements optiques et chimiques intervenant au cours de la vie d’un tableau. De plus, une analyse diagnostique a été réalisée sur deux tableaux conservés à « Accademia di San Luca » (Rome) par photographie de fluorescence induite par rayonnement UV, radiographie, spectroscopie de réflectance, spectroscopie de fluorescence X, images de fluorescence UV et réflectance multispectrale, réflectographie infrarouge multispectrale. Par rapport aux techniques traditionnelles, les images multispectrales permettent d’analyser de nombreuses régions spectrales qui, dans certains cas, permettent d’identifier le pigment et/ou des zones non homogènes de la couche superficielle picturale. Certaines gammes de longueurs d’onde infrarouge permettent notamment de voir les détails des différentes couches préparatoires, amenant à une analyse plus précise de la technique d’exécution. Cependant, une des limites des images multispectrales concerne l’identification des mélanges complexes et/ou des différentes strates de matériaux en fonction du type de filtre utiliséThis thesis focus on the application of multispectral images for the analysis of pictorial materials in comparison with the traditional UV-fluorescence photography and infrared reflectography. The assessment of multispectral imaging for the study of pictorial materials was supported by other analytical techniques such as reflectance and fluorescence spectroscopy, X-Ray Fluorescence (XRF), UV-visible absorption spectroscopy and Total Attenuated Reflectance - Fourier Transform Infrared Spectroscopy (ATR-FTIR). The multispectral imaging was tested on swatches of pictorial layers (constituted by ancient and modern pigment), binders (egg and linseed oil) and natural varnishes. For the organic materials, accelerated ageing methods (photo-chemical and thermal degradation) were used to model the optical and chemical changes occurring during the lifetime of a painting. In addition, a diagnostic investigation was performed on two paintings placed in "Accademia di San Luca" (Rome) by means of UV-fluorescence photography, radiography, reflectance spectroscopy, X-ray fluorescence spectroscopy, UV-VIS-NIR multispectral imaging. Multispectral images, comparing to traditional techniques, permit to individuate specific spectral behaviors, and, in some cases, identify the pigment and/or non-homogeneous areas of the pictorial or varnish layers. The possibility to select some infrared wavelengths allows to see details of the preparatory layers, leading to a more accurate analysis of the technique of execution. However, the limitations of multispectral images for the identification of complex mixtures and/or different layers of materials depending on the type of filter used
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Duan, Jun Wei. « New regional multifocus image fusion techniques for extending depth of field ». Thesis, University of Macau, 2018. http://umaclib3.umac.mo/record=b3951602.
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Höök, Josef. « Multispectral auroral imager and optical flow in aurora ». Thesis, KTH, Rymd- och plasmafysik, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-91893.
Texte intégralRésumé :
”Auroral Structure and Kinetics” (ASK) is a multispectral auroral imager,developed and built by University of Southampton, UK, and Royal Institute ofTechnology, Sweden. The scientific objective of the instrument include characterisationof both high and low energy electron precipitation in aurora with highspatial and temporal resolution, and direct observation of plasma drifts in theionosphere. ASK consists of three cameras taking images in different spectrallines. One part of this thesis deals with the development of the data acquisitionsystem for the instrument. This included the hardware part (computers controllingthe cameras)and the software for operation of ASK. ASK was installedon Svalbard in November 2005, and examples of first data are presented. Thesecond part of the thesis treats the problem of estimation of motions from theauroral sequences. Robust optical flow estimation algorithm has been applied toauroral sequences, and new formulations specific to the imaging of metastableions (carried out by ASK) are suggested.
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Viau, Claude. « Multispectral Image Analysis for Object Recognition and Classification ». Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34532.
Texte intégralRésumé :
Computer and machine vision applications are used in numerous fields to analyze static and dynamic imagery in order to assist or automate some form of decision-making process. Advancements in sensor technologies now make it possible to capture and visualize imagery at various wavelengths (or bands) of the electromagnetic spectrum. Multispectral imaging has countless applications in various field including (but not limited to) security, defense, space, medical, manufacturing and archeology. The development of advanced algorithms to process and extract salient information from the imagery is a critical component of the overall system performance.
The fundamental objectives of this research project were to investigate the benefits of combining imagery from the visual and thermal bands of the electromagnetic spectrum to improve the recognition rates and accuracy of commonly found objects in an office setting. The goal was not to find a new way to “fuse” the visual and thermal images together but rather establish a methodology to extract multispectral descriptors in order to improve a machine vision system’s ability to recognize specific classes of objects.A multispectral dataset (visual and thermal) was captured and features from the visual and thermal images were extracted and used to train support vector machine (SVM) classifiers. The SVM’s class prediction ability was evaluated separately on the visual, thermal and multispectral testing datasets. Commonly used performance metrics were applied to assess the sensitivity, specificity and accuracy of each classifier.
The research demonstrated that the highest recognition rate was achieved by an expert system (multiple classifiers) that combined the expertise of the visual-only classifier, the thermal-only classifier and the combined visual-thermal classifier.
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Kale, Mehmet Cemil. « Multispectral co-occurrence analysis for medical image processing ». Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1195500453.
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Mineart, Gary M. « Multispectral satellite analysis of marine stratocumulus cloud microphysics ». Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/23321.
Texte intégralRésumé :
Variations in marine stratocumulus cloud microphysics during FIRE IFO 1987 are observed and analyzed through the use of NOAA-9/10 AVHRR satellite data and aircraft in-cloud measurements. The relationships between channel 3 reflectance and cloud microphysical properties are examined through model reflectances based on Mie theory and the delta-Eddington approximation, and reveal a channel 3 reflectance dependence on cloud droplet size distribution. Satellite observations show significant regions of continental influence over the ocean through higher channel 3 reflectances resulting from the injection of continental aerosols and the associated modification of cloud droplet characteristics. Channel 3 reflectance gradients across individual cloud elements correspond to radially varying cloud droplet size distributions within the elements. Various mesoscale and microscale features such as ship stack effluent tracks and pollution sources are observed in the data. Correlations between reflectance values and aircraft measurements illustrate the potential of estimating cloud droplet size distribution and marine atmospheric boundary layer aerosol composition and concentration through use of satellite data. Such an estimation technique may prove useful in determining climatic implications of cloud reflectance changes due to the influence of natural and man-made aerosol sources, and provide a means to assess the performance of boundary layer electro-optic systems. Keywords: Radiometry; Cloud physics. Theses. (edc) 24u
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Ravagli, Andrea. « Development of Visible-to-LWIR multispectral chalcogenide glasses ». Thesis, University of Southampton, 2018. https://eprints.soton.ac.uk/428036/.
Texte intégralRésumé :
In the last four decades, Gallium Lanthanum Sulphide (GLS) glasses have been studied and proposed as material for active and passive applications. In this thesis, the effect of Se, Te, In and Cs on GLS is described presenting a new class of chalcogenide glasses with transparency from Visible to Long Wave IR range (500 nm - 16 μm). The addition of the new component was done by exchanging S with Se and Te, Ga with In and La with Cs in a variety of combinations to probe the glass forming ability of the new systems. The glasses were prepared mixing the precursors in a dry-N2 glovebox and adopting a melt-quench method in a Ar-purged furnace. The powders were melted at 1150 °C for 24 hours and then annealed at 490 °C for 24 hours. Glass formation in Se, Te and In samples was observed and the optical, thermal and mechanical properties of these samples were characterised. The addition of the new components resulted in an extension of the transmission towards the LWIR. Particularly, the largest improvement was observed for the sample containing 60 mol% Ga2Se3 which transmitted light up to 15 μm. This sample also exhibited transmission in the visible range up to 550 nm. Although modest improvements were observed for Te-GLS and In-GLS, these compositions exhibited phase separation and large losses in mass during the melting process. The thermal and mechanical properties of the samples were studied to investigate the possibility to produce optical components such as multispectral lenses. The results obtained showed superior properties than the commercial chalcogenide glasses. Indeed, higher characteristic temperatures, mechanical strength and comparable thermal expansion were observed. The effect of the temperature on the optical properties was studied up to 500 °C for high temperature applications. The properties in the THz spectrum were studied to study the dielectric properties of the glasses. The n2 was measured for supercontinuum generation and other applications in non-linear optics. The spectral properties of Nd3+ and Er3+ were studied for applications as amplifiers and middle-IR lasers. For these samples, mathematical models supported the experimental results to better understand the mechanism of light emission.
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Peyret, Remy. « Automated classification of cancer tissues using multispectral imagery ». Thesis, Northumbria University, 2017. http://nrl.northumbria.ac.uk/36221/.
Texte intégralRésumé :
Automated classification of medical images for colorectal and prostate cancer diagnosis is a crucial tool for improving routine diagnosis decisions. Therefore, in the last few decades, there has been an increasing interest in refining and adapting machine learning algorithms to classify microscopic images of tumour biopsies. Recently, multispectral imagery has received a significant interest from the research community due to the fast-growing development of high-performance computers. This thesis investigates novel algorithms for automatic classification of colorectal and prostate cancer using multispectral imagery in order to propose a system outperforming the state-of-the-art techniques in the field. To achieve this objective, several feature extraction methods based on image texture have been investigated, analysed and evaluated. A novel texture feature for multispectral images is also constructed as an adaptation of the local binary pattern texture feature to multispectral images by expanding the pixels neighbourhood to the spectral dimension. It has the advantage of capturing the multispectral information with a limited feature vector size. This feature has demonstrated improved classification results when compared against traditional texture features. In order to further enhance the systems performance, advanced classification schemes such as bag-of-features - to better capture local information - and stacked generalisation - to select the most discriminative texture features - are explored and evaluated. Finally, the recent years have seen an accelerated and exponential rise of deep learning, boosted by the advances in hardware, and more specifically graphics processing units. Such models have demonstrated excellent results for supervised learning in multiple applications. This observation has motivated the employment in this thesis of deep neural network architectures, namely convolutional neural networks. Experiments were also carried out to evaluate and compare the performance obtained with the features extracted using convolutional neural networks with random initialisation against features extracted with pre-trained models on ImageNet dataset. The analysis of the classication accuracy achieved with deep learning models reveals that the latter outperforms the previously proposed texture extraction methods. In this thesis, the algorithms are assessed using two separate multiclass datasets: the first one consists of prostate tumour multispectral images, and the second contains multispectral images of colorectal tumours. The colorectal dataset was acquired on a wide domain of the light spectrum ranging from the visible to the infrared wavelengths. This dataset was used to demonstrate the improved results produced using infrared light as well as visible light.
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Lins, Sergio Augusto Barcellos. « Multispectral analysis of Nuragic metallic samples (Sardinia, Italy) ». Master's thesis, Universidade de Évora, 2018. http://hdl.handle.net/10174/27727.
Texte intégralRésumé :
ABSTRACT:
In this investigation, a protocol combining the use of Monte Carlo simulations
together with energy-dispersive X-ray fluorescence (ED-XRF) analysis was used to
determine the chemical composition of a set of nine objects from a private collection,
apprehended by Carabinieri and without archaeological context. The artefacts are thought to
belong to the nuragic period from Sardinia, Italy. The protocol employed is a powerful and
non-destructive method useful for cultural heritage applications where usually no sampling
is allowed and was applied here with the objective of attesting the authenticity of the objects.
The samples were simulated as multilayered structures composed of bulk material and outer
corrosion layer so the patina thickness and composition could be estimated as well by the Xray Monte Carlo (XRMC) package. The method proved useful and powerful, capable of
efficiently determining the composition and structure of most of the objects in a total nondestructive approach, attesting the existence of at least one fake in the set. Nevertheless, for
a more throughout evaluation and a better estimation of the patina composition, the use of
complementary analytical techniques has shown required.
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Teresi, Michael Bryan. « Multispectral Image Labeling for Unmanned Ground Vehicle Environments ». Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/53998.
Texte intégralRésumé :
Described is the development of a multispectral image labeling system with emphasis on Unmanned Ground Vehicles(UGVs). UGVs operating in unstructured environments face significant problems detecting viable paths when LIDAR is the sole source for perception. Promising advances in computer vision and machine learning has shown that multispectral imagery can be effective at detecting materials in unstructured environments [1][2][3][4][5][6]. This thesis seeks to extend previous work[6][7] by performing pixel level classification with multispectral features and texture. First the images are spatially registered to create a multispectral image cube. Visual, near infrared, shortwave infrared, and visible/near infrared polarimetric data are considered. The aligned images are then used to extract features which are fed to machine learning algorithms. The class list includes common materials present in rural and urban scenes such as vehicles, standing water, various forms of vegetation, and concrete. Experiments are conducted to explore the data requirement for a desired performance and the selection of a hyper-parameter for the textural features. A complete system is demonstrated, progressing from the data collection and labeling to the analysis of the classifier performance.Master of Science
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Kale, Mehmet Cemil. « Multispectral co-occurence analysis for medical image processing ». The Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=osu1195500453.
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Holmberg, Andreas. « Combination analysis of multispectral and radar satellite data ». Thesis, Umeå universitet, Institutionen för fysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-185506.
Texte intégralRésumé :
Remote sensing technologies, such as satellite imagery, have proven to be a powerful tool for land cover classification when combined with machine learning algorithms. Depending on which type of sensor is used for the imagery, different properties of land cover classes may be distinguished. Because of this, a data set containing a combination of data from different sensors could potentially further improve the classification accuracy. To determine if adding data from the radar sensor on the satellite constellation Sentinel-1 to data from the multispectral optical sensor on the satellite constellation Sentinel-2 could improve the accuracy of land cover classification, a tool for combining data from both satellites was developed. The classification accuracy using the combined data was then compared to using non-combined Sentinel-2 data with a neural network and a random forest classifier. We found that the random forest classifier produced a higher accuracy than the neural network for both the combined data and non-combined data. The combined data increased the accuracy further compared to the non-combined data. However, the increase produced by the combined data was small and most likely not worth the extra computational power required to implement Sentinel-1 data to Sentinel-2 data.
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Koh, Kevin Rongsheng. « Multimodal multispectral optical endoscopic imaging for biomedical applications ». Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/6330.
Texte intégralRésumé :
Optical imaging is an emerging field of clinical diagnostics that can address the growing medical need for early cancer detection and diagnosis. Various human cancers are amenable to better prognosis and patient survival if found and treated during early disease onset. Besides providing wide-field, macroscopic diagnostic information similar to existing clinical imaging techniques, optical imaging modalities have the added advantage of microscopic, high resolution cellular-level imaging from in vivo tissues in real time. This comprehensive imaging approach to cancer detection and the possibility of performing an ‘optical biopsy’ without tissue removal has led to growing interest in the field with numerous techniques under investigation. Three optical techniques are discussed in this thesis, namely multispectral fluorescence imaging (MFI), hyperspectral reflectance imaging (HRI) and fluorescence confocal endomicroscopy (FCE). MFI and HRI are novel endoscopic imaging-based extensions of single point detection techniques, such as laser induced fluorescence spectroscopy and diffuse reflectance spectroscopy. This results in the acquisition of spectral data in an intuitive imaging format that allows for quantitative evaluation of tissue disease states. We demonstrate MFI and HRI on fluorophores, tissue phantoms and ex vivo tissues and present the results as an RGB colour image for more intuitive assessment. This follows dimensionality reduction of the acquired spectral data with a fixed-reference isomap diagnostic algorithm to extract only the most meaningful data parameters. FCE is a probe-based point imaging technique offering confocal detection in vivo with almost histology-grade images. We perform FCE imaging on chemotherapy-treated in vitro human ovarian cancer cells, ex vivo human cancer tissues and photosensitiser-treated in vivo murine tumours to show the enhanced detection capabilities of the technique. Finally, the three modalities are applied in combination to demonstrate an optical viewfinder approach as a possible minimally-invasive imaging method for early cancer detection and diagnosis.
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Rose, Robert A. « The generation and comparison of multispectral synthetic textures / ». Online version of thesis, 1994. http://hdl.handle.net/1850/11731.
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