No / To investigate the relationship between neuroretinal rim (NRR) differential light absorption (DLA, a measure of spectral absorption properties) and visual field (VF) sensitivity in primary open-angle glaucoma (POAG). atients diagnosed with (n = 22) or suspected of having (n = 7) POAG were imaged with a multispectral system incorporating a modified digital fundus camera, 250-W tungsten-halogen lamp, and fast-tuneable liquid crystal filter. Five images were captured sequentially within 1.0 second at wavelengths selected according to absorption properties of hemoglobin (range, 570–610 nm), and a Beer-Lambert law model was used to produce DLA maps of residual NRR from the images. Patients also underwent VF testing. Differences in NRR DLA in vertically opposing 180° and 45° sectors either side of the horizontal midline were compared with corresponding differences in VF sensitivity on both decibel and linear scales by Spearman's rank correlation. The decibel VF sensitivity scale showed significant relationships between superior–inferior NRR DLA difference and sensitivity differences between corresponding VF areas in 180° NRR sectors (Spearman ρ = 0.68; P < 0.0001), superior-/inferior-temporal 45° NRR sectors (ρ = 0.57; P < 0.002), and superior-/inferior-nasal 45° NRR sectors (ρ = 0.59; P < 0.001). Using the linear VF sensitivity scale significant relationships were found for 180° NRR sectors (ρ = 0.62; P < 0.0002) and superior–inferior–nasal 45° NRR sectors (ρ = 0.53; P < 0.002). No significant difference was found between correlations using the linear or decibel VF sensitivity scales. Residual NRR DLA is related to VF sensitivity in POAG. Multispectral imaging may provide clinically important information for the assessment and management of POAG. / College of Optometrists (UK) PhD Studentship (JD), Central Manchester NHS Foundation Trust Grant RO1180, the Manchester Academic Health Sciences Centre (MAHSC), and the NIHR Manchester Biomedical Research Centre.

The study departs from a technical examination of the panel painting Polyxena is Sacrificed in the Stockholm University Collection of Art, establishing the artistic process, level of ambition, and material choices by means of multispectral imaging techniques and elemental analysis. The artist, Jacob de Wet I, was both a well-reputed Haarlem-painter who specialized in small scale history paintings and headed a mass-producing workshop which supplied the low-end art markets of Haarlem and Amsterdam. The study places this artwork within the artist’s broad range of production. Further, the social and cultural contexts of the painting are investigated by comparing it to other artist’s versions of the subject, by means of an iconographical analysis of the image, and by examining its prominent theatrical features in relation to Dutch theatre traditions. By combining the technical, social, and cultural findings, the study aims to establish – and to delimit – a specific place in the art market and to suggest a possible type of customer for the painting. Confirming the work’s originality and authenticity, the results show an intuitive, thus likely time-consuming artistic process, a wide palette including expensive pigments – all indicative of a high level of ambition. In combination with the subject matter, these results suggest the painting to be a commissioned work. Further, the image and its social and cultural context, indicate the commissioner to be a person of some formal power within the Amsterdam society, seeking to communicate high erudition and to express liberal political views.  De Wet effectively expresses his message using a combination of painterly effects, including the materiality of the paint.

No description available.

No description available.

No description available.

A number of tests were conducted to determine the realizable accuracies of the Global Positioning System for natural resource conditions. The effects of terrain, forest canopy, number of consecutive position fixes, and PDOP on accuracy were evaluated. Position accuracies were determined for a total of 27 sites: three replicate sites selected for each of nine distinct conditions: three canopy (deciduous, coniferous, open) and three terrain (ridge, slope, valley) in all possible combinations. Each site was visited ten times over a span of eight months to collect position data, for ten replicates of 60, 100, 200, 300, and 500 position fixes. The mean differentially corrected positional accuracy for all sites was 4.35 meters with 95 percent of the positions estimated within 10.2 meters of the true value. The least accurate differential position data were observed at coniferous sites. Positional accuracy was higher for deciduous sites and the most accurate differential position data was collected at open sites. Accuracy increased with increasing number of position fixes. When the number of position fixes increased from 60 to 500, mean accuracy increased 46.7% at deciduous sites, 32.8% at coniferous sites, and 44.5% at open sites. The average time required by the GPS receiver to lock onto four satellites and begin collecting positions varied from one to two minutes. The most time was spent collecting position fixes at coniferous sites. No correlation was found between accuracy and the receiver's distance from the base-station. Nine replicates of 300 position fixes were averaged for six sites, which ranged from 43 kilometers to 247 kilometers from a Virginia Tech base-station. Mean accuracy ranged from 1.48 meters to 2.43 meters. GPS position data were evaluated for ease of conversion to GIS formats. Conversion was accomplished without problems. / Master of Science

In the previous years, 3D imaging has found his way into the world of Egyptology. This lecture will present two case studies where 3D technology is used for the documentation of hieratic inscriptions. The inscriptions, painted in (red) ochre or black paint, were applied on different carriers, and required a different methodology. The Egyptian collection of the Royal Museums of Art and History (RMAH Brussels) contains a large number of small decorated and/or inscribed objects. Some of these objects are currently in a bad condition - any operation carried on them can result in considerable material losses -, making it necessary to document them in such a way that it allows future scholars to study them in detail without handling them. The EES Project therefore aims to create multispectral 3D images of these fragile objects with a multispectral ‘minidome’ acquisition system, based on the already existing system of the multi-light Portable Light Dome (PLD). The texture/colour values on the created 2D+ and 3D models are interactive data based on a recording process with infrared, red, green, blue, and ultraviolet light spectra. Software tools and enhancement filters have been developed which can deal with the different wavelengths in real-time. This leads to an easy and cost-effective methodology which combines multispectral imaging with the actual relief characteristics and properties of the physical object. The system is transportable to any collection or excavation in the field. As a case study, the well-known Brussels “Execration Figurines” (Middle Kingdom, c. 1900 BC) were chosen. These figurines are made of unbaked clay and covered with hieratic texts, listing names of foreign countries and rulers. The study of this type of collections is mostly hampered by the poor state of conservation of the objects, but also by the only partial preservation of the ink traces in visible light. The method has also been applied to other decorated objects of the RMAH collection, such as a Fayoum portrait, ostraca and decorated objects made of stone, wood and ceramics. The final goal will be to publish the newly created multispectral 3D images on Carmentis (www.carmentis.be), the online catalogue of the RMAH collection, making them accessible to scholars all over the world. The second case study presents the quarry inscriptions of the New Kingdom limestone quarries at Dayr Abu Hinnis (Middle Egypt). These gallery quarries contain hundreds of hieratic inscriptions, written on the ceiling. The texts are mainly related to the general administration of the quarry area. In documenting the abundance of ceiling inscriptions and other graffiti, we had to decide upon a practice that would allow not only to capture the \"content\", but also to document the location and orientation of each record. Every inscription can be photographed in detail, but this is insufficient to provide the reader access to vital information concerning the spatial distribution of the inscriptions, which may, for instance, relate to the progress of work. After experimenting with a variety of other methods, we adopted a photogrammetric software for 3D modelling photographs of the quarry ceilings, AGISOFT PHOTOSCAN, which uses structure from motion (SFM) algorithms to create three-dimensional images based on a series of overlapping two-dimensional images. The ultimate goal of this whole labour-intensive process in the quarries is not the creation of pure threedimensional models, but rather to generate an orthophoto of the entire ceiling of a quarry. Based on these images, each graffito could be analysed in context.

Dans l'ouvrage [DBB06], Dutré et al. énumèrent dix problèmes d'Illumination Globale non résolus. Parmi ceux-ci, huit sont liés à la mesure et à l'intégration de données réelles dans les simulations. Cette thèse, en quatre parties et trois annexes, s'intéresse à cette problématique. Tout d'abord, les simulations de la propagation de la lumière dans les domaines du rendu physiquement réaliste, de l'éclairage, de la télédétection, de la conception de systèmes optiques... sont envisagées comme résolutions numériques d'un problème d'optique, fédérées par la notion de « photosimulation ». Dans le cadre de l'équation de rendu, les modèles réalistes de sources et le principe de la mesure goniophotométrique en champ lointain sont alors rappelés. La représentation des interactions lumière-matière est ensuite introduite par une exploration de l'apparence macroscopique, qui amène au rappel de la Fonction de Distribution de la Réflectance Bidirectionnelle et Spectrale (SBRDF), de ses principales propriétés et modèles. Le problème de la mesure pratique de la SBRDF d'une surface dans le visible est ensuite exploré. Id est, une taxonomie des méthodes de la littérature est établie ; qui allègue en faveur du développement de nouvelles approches. Un dispositif innovant, multispectral imageant, est alors présenté. Il se fonde sur la capture de la projection de la SBRDF sur un écran lambertien 3/4-sphérique, par une caméra multispectrale grand angle, assemblage d'un objectif fisheye, d'un filtre dynamique LCTF et d'une caméra CCD 12 bits. L'extraction des images capturées de l'information de la SBRDF repose sur un modéle radiométrique, qui explicite la transformation de la lumière en niveaux des pixels, dans le formalisme physique. Ce modèle soulève des problèmes de reconstruction multispectrale et d'interréflexions, pour lesquels de nouveaux algorithmes de résolution sont implantés. Les mesures de SBRDF produites semblent très prometteuses. Dans la troisième partie, le problème de la reconstruction d'une fonction directionnelle, identifié comme fondamental en photosimulation, est traité dans le cadre de la reconstruction de SBRDF discrètes. Pour cela, les propriétés mathématiques souhaitables des fonctions reconstruites sont envisagées. Puis, à l'aune de ce corpus, les approches de la littérature sont discutées ; justifiant la recherche d'algorithmes plus performants. Une nouvelle méthode est alors proposée, fondée sur une double triangulation sphérique des échantillons, et une généralisation à la surface d'un triangle sphérique de l'interpolant spline cubique de Hermite. La fonction reconstruite est interpolante, dérivable, quasi-déterministe, ne présente pas l'artéfact bidirectionnel, intègre la métrique sphérique non euclidienne, et prend en compte le difficile problème du masquage. Qualitativement comme quantitativement, les résultats obtenus semblent plaider en faveur du surcroît de complexité théorique qu'induit cette approche. Dans la dernière partie, cet algorithme de reconstruction est appliqué au problème de la « photométrie en champ proche », ou, la caractérisation d'une source réelle par un solide photométrique étendu. La supériorité théorique du modèle étendu est d'abord démontrée. Puis, un état de l'art de la photométrie en champ proche est réalisé ; justifiant la mise en œuvre d'une nouvelle approche. Un nouveau dispositif est alors présenté. Il repose sur le déplacement d'un vidéoluminancemètre, couplage original d'une caméra CCD 12 bits avec un luxmètre, le long d'une trajectoire hémisphérique relative à la source. Les procédures de calibrage de l'instrument – géométrique, radiométrique, et photométrique – sont explicitées. Les sources de lumière caractérisées par cette approche ont été jugées suffisamment probantes pour être intégrées aux photosimulations spectrales du CSTB / Pas de résumé en anglais

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

Water resources play an important role in society and fulfill various functions such as providing drinking water, supporting industrial production and enhancing the overall landscape. Water bodies, such as rivers and lakes, are particularly important in this context. However, as societies and economies develop, the demand for water increases significantly. This also leads to the release of domestic, agricultural and industrial wastewater, which often exceeds the self-purification capacity of water bodies. Consequently, rivers and lakes are getting more and more polluted, endangering the safety of drinking water and causing ecological damage, affecting human health and biodiversity.  Water quality monitoring plays a crucial role in evaluating the state of water bodies. Traditional monitoring methods involve labor-intensive field sampling and expensive construction and maintenance of automatic stations. Although these methods provide accurate results, they are limited to specific sampling points and struggle to meet the demands of monitoring water quality across entire surfaces of rivers and lakes. This degree project aim at developing a method that can predict absorbance in water with the aim of remote sensing. Along with multispectral imaging and machine learning this work proves that this is possible. The result from multivariate analysis is an optimal model that can predict absorbance at 420 nm with RSQ of 0,996 and RMSE of 0,00081.