Effects of Errors in the Viewing Geometry on Shape Estimation

A sequence of images acquired by a moving sensor contains information about the three-dimensional motion of the sensor and the shape of the imaged scene. Interesting research during the past few years has attempted to characterize the errors that arise in computing 3D motion (egomotion estimation) as well as the errors that result in the estimation of the scene's structure (structure from motion). Previous research is characterized by the use of optic flow or correspondence of features in the analysis as well as by the employment of particular algorithms and models of the scene in recovering expressions for the resulting errors. This paper presents a geometric framework that characterizes the relationship between 3D motion and shape in the presence of errors. We examine how the three-dimensional space recovered by a moving monocular observer, whose 3D motion is estimated with some error, is distorted. We characterize the space of distortions by its level sets, that is, we characterize the systematic distortion via a family of iso-distortion surfaces, which describes the locus over which the depths of points in the scene in view are distorted by the same multiplicative factor. The framework introduced in this way has a number of applications: Since the visible surfaces have positive depth (visibility constraint), by analyzing the geometry of the regions where the distortion factor is negative, that is, where the visibility constraint is violated, we make explicit situations which are likely to give rise to ambiguities in motion estimation, independent of the algorithm used. We provide a uniqueness analysis for 3D motion analysis from normal flow. We study the constraints on egomotion, object motion, and depth for an independently moving object to be detectable by a moving observer, and we offer a quantitative account of the precision needed in an inertial sensor for accurate estimation of 3D motion.     

Incrementally improving dataspaces based on user feedback

One aspect of the vision of dataspaces has been articulated as providing various benefits of classical data integration with reduced up-front costs. In this paper, we present techniques that aim to support schema mapping specification through interaction with end users in a pay-as-you-go fashion. In particular, we show how schema mappings, that are obtained automatically using existing matching and mapping generation techniques, can be annotated with metrics estimating their fitness to user requirements using feedback on query results obtained from end users.     

Ethische Leitlinien der GI

Seit Ihrer Verabschiedung im Jahr 1994 waren die Ethischen Leitlinien der Gesellschaft für Informatik Gegenstand zuweilen kontroverser Diskussionen. Einerseits wurde begrüßt, dass sich die GI verbindlich an ein ethisches Regelwerk bindet und dadurch ihren Mitgliedern einen Leitfaden an die Hand gibt, um in Konfliktsituationen besser entscheiden zu können. Andererseits wurde bemängelt, dass die Ethischen Leitlinien Forderungen stellten, die für professionelles Handeln unabdingbar seien und deshalb keine ethischen Ansprüche darstellten. Des Weiteren wurde kritisiert, dass die Ethischen Leitlinien zu sehr im Abstrakten verharrten und deshalb keine konkrete Handlungsanweisung geben könnten. Die fachlichen und überfachlichen Anforderungen wurden zuweilen als zu anspruchsvoll empfunden. Einige dieser Kritikpunkte sind sicherlich berechtigt.Im November 2001 begann der Arbeitskreis Informatik und Verantwortung im Fachbereich Informatik und Gesellschaft (IuG) mit der Überarbeitung der Ethischen Leitlinien. Der hier vorgelegte Entwurf greift einige dieser Kritikpunkte auf. Seine Publikation soll eine breitere Diskussion innerhalb der GI ermöglichen. Die Autorinnen und Autoren dieses Entwurfs freuen sich auf diese Auseinandersetzung, die in der letzten Sitzung des Arbeitskreises durch den Vertreter der Selbständigen in der GI mit dem Hinweis begonnen wurde, dass den Leitlinien ein Berufsbild zugrunde liegt, in dem die Selbständigen nicht vorkommen.Die anlässlich der Informatik 2003 gegründete Fachgruppe Informatik und Ethik wird sich zu ihrer ersten Aufgabe machen, die Ergebnisse dieser Diskussion in die endgültige Version einfließen zu lassen. Entsprechende Diskussionsbeiträge und Anregungen sollten an Karl-Heinz Rödiger (E-Mail: roediger@informatik.uni-bremen.de), kommissarischer Sprecher der Fachgruppe, gerichtet werden.     

Plenoptic video geometry

More and more processing of visual information is nowadays done by computers, but the images captured by conventional cameras are still based on the pinhole principle inspired by our own eyes. This principle though is not necessarily the optimal image-formation principle for automated processing of visual information. Each camera samples the space of light rays according to some pattern. If we understand the structure of the space formed by the light rays passing through a volume of space, we can determine the camera, or in other words the sampling pattern of light rays, that is optimal with regard to a given task. In this work we analyze the differential structure of the space of time-varying light rays described by the plenoptic function and use this analysis to relate the rigid motion of an imaging device to the derivatives of the plenoptic function. The results can be used to define a hierarchy of camera models with respect to the structure from motion problem and formulate a linear, scene-independent estimation problem for the rigid motion of the sensor purely in terms of the captured images.     

Influence of hot-rolling conditions on texture development in deep-drawing steels

As the textures of deep-drawing sheet steels are important for certain material properties the purpose of this paper was to take a closer look at the hot-rolling, cold-rolling and annealing textures of different deep-drawing steel grades. Several Al-killed mild steels and vacuum-degassed Ti-IF steels have been hot rolled in the mill varying the finishing temperature (FT). After coiling, cold rolling and short-time annealing the textures at different thickness levels have been measured by means of (110)-pole figures and orientation distribution functions (ODFs). For both steel groups the textures at the surface of the hot strip exhibit a more or less pronounced shear type character. Towards the mid-thickness level (with lower FT more clearly) typical (cold-) rolling textures exist characterized by a strong {001}<110> orientation and in the Ti-IF steels additionally by a significant {112}<110> orientation density. In the case of high FT cold rolling and annealing lead to favourable {111}-textures where deep-drawing application is concerned. For the Al-killed steels lowering FT results in diffuse recrystallization textures whereas in the Ti-IF steels a sharp texture with near {223}<582> orientations can be observed which have not been known for these steels before. The results prove that the hot strip textures can be of great importance for the resulting annealing textures and the according material properties.     

On the compatibility of polystyrene/acrylonitrile-butadiene-g-styrene copolymer/solvent system

Summary Influence of the temperature on the compatibility of the polystyrene / AB-g-S graft copolymer / cyclohexanone have been studied by light scattering and viscosity measurement. It was established that the compatibility of components is changed in the temperature range where the conformational transitions take place.     

基于差频激光源的微量气体光声光谱检测系统

在周期极化的铌酸锂晶体中混合1．5－1．6μm可调谐半导体激光和1.064μmNd,YAG调Q脉冲激光,得到3．35－3．66μm的连续可调谐窄线宽激光脉冲,平均输出功率达0.2mW,实验装置比OPO相对简单,紧凑,无振荡阈值,根据该差频发生器的输出特性,设计了共振频率可调的光声池和光声光谱检测系统,并首次利用该系统对低浓度的CH4样品气体进行了光声谱测量,实验结果显示了系统在微量气体测量方面的优越性。