Entwicklung von RF-Technologie für die Ultrahochfeld-MRT: Optimierung und Anwendung einer Self-Grounded-Bow-Tie-Dipolantenne

Magnetic resonance imaging (MRI) is an important diagnostic imaging modality free of ionizing radiation. Sensitivity gain, signal-to-noise ratio (SNR) considerations, and changes in the tissue dependent MRI properties. Together with technical and scientific developments further research into increasing the magnetic field strength is justified, culminating in human applications at ultrahigh magnetic field (UHF, B0 ≥ 7.0 T) MRI. Elevating the field strength results in an increased radiofrequency (RF) for signal transmission and reception in MRI (= Larmor frequency, f ≈ 298 MHz at B0 = 7.0 T). The wavelength of this RF signal becomes sufficiently short when passing through tissue relative to the size of the target anatomy of the brain, upper torso, or abdomen. This phenomenon leads to constructive and deconstructive interference of the electromagnetic field (EMF) distribution, which results in a high susceptibility for non-uniformities in the magnetic RF transmission field (B1+). This detrimental excitation field distribution can cause shading, massive signal drop-off or even signal voids, and potentially offset the benefits of UHF-MRI due to compromised image quality. UHF cardiovascular MR (CMR) benefits from SNR gains and changes in the tissue dependent MRI properties, but the B1+ distribution – in addition to the wavelength dependent non-uniformities – is further compromised by a dielectrically heterogeneous tissue environment. Research on UHF-CMR focuses on the improvement of the cardiac chamber morphology quantification, myocardial T1- and T2*-mapping, fat-water imaging, and vascular imaging (4D-flow). These applications benefit from a homogenous B1+ within the heart and the vascular structure. Several published reports on the development of RF antenna array technology tailored for UHF-CMR address this challenge with ideas and achievements to enable broad clinical UHF-CMR applications in the future. The primary objective of advancing this RF technology is to achieve a uniform B1+ distribution in the heart and the vascular structure with optimizing the magnetic field pattern. The second objective is the improvement of the RF antenna’s efficiency with the reduction of the specific absorption rate (SAR), which is achieved by an optimization of the electric field pattern. The control of the electric field is furthermore conceptually appealing beyond conventional MR imaging modalities and useful for localized and targeted RF induced thermal intervention. Combining MRI with a thermal intervention modality in an integrated Thermal MR system permits direct supervision of the treatment via MR-thermometry, as well as adapting and improving the focal point quality of the RF power deposition. The Thermal MR system is a platform for comprehensive investigation of the effects of temperature on molecular, biochemical, and physiological processes, ultimately yielding insights into temperature utilization for diagnosis and therapy in vivo. EMF control of an RF antenna array depends on the radiation pattern of the antenna elements. Electrical dipoles are promising for UHF-MRI due to a linear polarized current pattern and an energy deposition perpendicular to the antenna. However, the channel count and therefore the degree of freedom for EMF shaping of previously reported antenna concepts is limited by the geometric extent and the coupling between the elements. The first section of this work addresses the design, implementation, and validation of a novel small-sized Self-Grounded Bow-Tie (SGBT) antenna, in combination with a dielectrically filled housing. The narrowband SGBT antenna variant is used in a 32-channel transmit/receive array configuration for UHF-CMR at 7.0 T. The second section focuses on the development of a modified broadband SGBT concept for the Thermal MR system. The broadband antenna increases the degree of freedom with an adaptation of the intervention frequency to improve the focal point quality (size, homogeneity, and specificity). The third section presents the implementation and validation of a signal generator in conjunction with the broadband SGBT variant introduced in section two. The device allows the generation of the intervention signal with a time dependent, channel-wise adaptation of amplitude, phase, and frequency. The work of this thesis offers a technical and conceptual framework for an increased degree of freedom for EMF shaping for a multitude of applications ranging from UHF-MRI to interventional MRI.Die Magnetresonanztomographie (MRI) ist ein wichtiges bildgebendes Diagnoseverfahren mit der Anwendung in vielen medizinischen Disziplinen. Die Forschung zu ultrahohen Magnetfeldern (UHF, B0 ≥ 7.0 T) im humanen Bereich wird durch technische und wissenschaftliche Errungenschaften getrieben und basiert auf einer höheren Sensitivität, einem verbesserten Signal-Rausch-Verhältnisses (SNR) sowie eine Veränderung der gewebsspezifischen MR Eigenschaften. Die höhere Feldstärke resultiert auch in einer erhöhten Radiofrequenz (RF) für die MRI Signalübertragung (= Larmorfrequenz, f ≈ 298 MHz bei B0 = 7.0 T). Die Wellenlänge des RF Signals im Gewebe ist dabei bezogen zur Zielanatomie (e.g. Schädel, Oberkörper und Abdomen) verkürzt was zu konstruktiven und destruktiven Interferenzen des elektromagnetischen Feldes (EMF) führt. Diese Interferenzen ergeben ein heterogenes RF Transmissionsfeld (B1+) mit Abschattungen, massiven Signalabfällen oder Signalausfällen welche die Vorteile der UHF-MRI durch eine beeinträchtigte Bildqualität schmälert. Die UHF Herz MR (CMR) profitiert von einem SNR-Gewinn sowie von veränderten gewebsspezifischen MR Eigenschaften bei höheren Feldstärken. Jedoch wird die B1+ Verteilung, neben der gegebenen RF wellenlängenabhängigen Heterogenität, durch dielektrische Gradienten im Bereich des Thorax zusätzlich beeinträchtigt. Die anwendungsbezogene Forschung und Entwicklung auf dem Gebiet der UHF-CMR konzentriert sich auf die Verbesserung der Quantifizierung der Herzkammermorphologie, des myokardialen T1- und T2*-Mappings, der Fett-Wasser-Bildgebung und der Gefäßbildgebung inklusive der Flussbildgebung (4D-Flow). Die Weiterentwicklung dieser Methoden streben eine breite klinische Anwendung an und profitieren von einer homogenen B1+ Verteilung im Herzen und in der Gefäßstruktur. Das primäre Ziel der der Forschung und Entwicklung von RF Antennenarraytechnologie ist eine Optimierung der B1+ Verteilung. Das sekundäre Ziel ist die Verbesserung der Effizienz durch die Verringerung der spezifischen Absorptionsrate (SAR) mittels einer elektrischen Feldoptimierung. Die Kontrolle des elektrischen Feldes kann aber auch über die konventionelle MR Bildgebung hinaus genutzt werden und ermöglicht konzeptionell eine lokalisierte und gezielte RF induzierte thermische Intervention. Die Kombination von MRI und thermischen Interventionen in einem integrierten Thermal MR System ermöglicht die Anpassung und Verbesserung der lokalen Intervention durch eine Supervision der Behandlung mittels MR-Thermometrie. Das Thermal MR System stellt damit eine technologische Plattform dar, welche eine umfassende Untersuchung der Auswirkungen der Temperatur auf molekulare, biochemische und physiologische Prozesse erlaubt. Letztlich kann die Plattform Erkenntnisse darüber liefern, wie die Temperatur für Diagnosen und Therapien in vivo genutzt werden kann. Die Kontrolle der EMF Verteilung durch ein RF Antennen Array ist abhängig von den Abstrahlungseigenschaften der einzelnen Antennenelemente. Elektrische Dipole stellen durch eine linear polarisierte Stromverteilung und eine Abstrahlungsrichtung orthogonal zur Antenne eine vielversprechende Option dar. Allerdings ist die Kanalzahl und damit der Freiheitsgrad für die EMF Optimierung bei bisher vorgestellten Antennenkonzepten durch die Größe und die Kopplung zwischen den Elementen begrenzt. Der erste Abschnitt dieser Arbeit befasst sich mit dem Entwurf, der Implementierung und der Validierung einer Self-Grounded Bow-Tie (SGBT) Antenne in Kombination mit einem dielektrisch gefüllten Gehäuse. Eine schmalbandige Antennenvariante wird in einer 32-Kanal Sende-/Empfangs-Array Konfiguration für UHF-CMR bei 7,0 T vorgestellt. Der zweite Abschnitt befasst sich mit der Entwicklung eines modifizierten breitbandigen SGBT-Konzepts für das Thermal MR System. Diese Antennenvariante erhöht die Freiheitsgrade für die Optimierung der elektrischen Feldverteilung um die Interventionsfrequenz und erlaubt eine Verbesserung der lokalen Erwärmung (Größe, Homogenität und Spezifität). Im dritten Abschnitt dieser Arbeit wird die Implementierung und Validierung eines Signalgenerators in Verbindung mit der im zweiten Abschnitt vorgestellten Breitbandantennenvariante vorgestellt. Der Signalgenerator erzeugt einen Interventionssignal mit der zeitabhängigen Anpassung von Amplitude, Phase und Frequenz für jeden Kanal. Die Entwicklungen und Erkenntnisse dieser Arbeit bieten einen konzeptionellen Rahmen für eine Vielzahl von realen Anwendungen, welche von der konventionellen MRI bis zu einem integrierten interventionellen Thermal MR System reichen.EC/H2020/743077/EU/Thermal Magnetic Resonance: A New Instrument to Define the Role of Temperature in Biological Systems and Disease for Diagnosis and Therapy/ThermalM

Application of advanced technology to space automation

Automated operations in space provide the key to optimized mission design and data acquisition at minimum cost for the future. The results of this study strongly accentuate this statement and should provide further incentive for immediate development of specific automtion technology as defined herein. Essential automation technology requirements were identified for future programs. The study was undertaken to address the future role of automation in the space program, the potential benefits to be derived, and the technology efforts that should be directed toward obtaining these benefits

EPICURE : A Partitioning and CoDesign Framework For Reconfigurable Computing

This paper presents a new global design methodology capable to bridge the gap between an abstract specification level and a heterogeneous reconfigurable architecture level. The Epicure contribution is the result of a joint study on abstraction/refinement methods and a smart reconfigurable architecture within the formal Esterel design tools suite. The original points of this work are : i) a generic HW/SW interface model, ii) a specification methodology that handles the control, includes efficient verification and HW/SW synthesis capabilities, iii) a method for parallelism exploration based on abstract resources/performance estimation expressed in terms of area/delay tradeoffs, iv) a HW/SW partitioning approach that refines the specification into explicit HW configurations and the associated SW control. The Epicure framework shows how a cooperation of complementary methodologies and CAD tools associated with a relevant architecture can significantly improve the designer productivity, especially in the context of reconfigurable architectures

Design of LCOS microdisplay backplanes for projection applications

De evolutie van licht emitterende diodes (LED) heeft ervoor gezorgd dat het op dit moment interessant wordt om deze componenten als lichtbron te gebruiken in projectiesystemen. LED’s hebben belangrijke voordelen vergeleken met klassieke booglampen. Ze zijn compact, ze hebben een veel grotere levensduur en ogenblikkelijke schakeltijden, ze werken op lage spanningen, etc. LED’s zijn smalbandig en kunnen een groterekleurenbereik realiseren. Ze hebben momenteel echter een beperkte helderheid. Naast de lichtbron is het type van de lichtklep ook bepalend voor de kwaliteit van een projectiesysteem. Er bestaan verschillende lichtkleptechnologieën waaronder die van de reflectieve LCOS-panelen. Deze lichtkleppen kunnen zeer hoge resoluties hebben en wordenvaak gebruikt in kwalitatieve, professionele projectiesystemen. LED’s zijn echter totaal verschillend van booglampen. Ze hebben een andere vorm, package, stralingspatroon, aansturing, fysische en thermische eigenschappen, etc. Hoewel er een twintigtal optische architecturen bekend zijn voor reflectieve beeldschermen (met een booglamp als lichtbron), zijn ze niet geschikt voor LED-projectoren en moeten nieuwe optische architecturen en een elektronische aansturing ontwikkeld worden. In dit doctoraat werd er hieromtrent onderzoek gedaan. Er werd uiteindelijk een driekleurenprojector (R, G, B) met een efficiënt LED-belichtingssysteem gebouwd met twee LCOS-lichtkleppen. Deze LEDprojector heeft superieure eigenschappen (zeer lange levensduur, beeldkwaliteit, etc.) en een matige lichtopbrengst

Benchmarking of Embedded Object Detection in Optical and RADAR Scenes

A portable, real-time vital sign estimation protoype is developed using neural network- based localization, multi-object tracking, and embedded processing optimizations. The system estimates heart and respiration rates of multiple subjects using directional of arrival techniques on RADAR data. This system is useful in many civilian and military applications including search and rescue. The primary contribution from this work is the implementation and benchmarking of neural networks for real time detection and localization on various systems including the testing of eight neural networks on a discrete GPU and Jetson Xavier devices. Mean average precision (mAP) and inference speed benchmarks were performed. We have shown fast and accurate detection and tracking using synthetic and real RADAR data. Another major contribution is the quantification of the relationship between neural network mAP performance and data augmentations. As an example, we focused on image and video compression methods, such as JPEG, WebP, H264, and H265. The results show WebP at a quantization level of 50 and H265 at a constant rate factor of 30 provide the best balance between compression and acceptable mAP. Other minor contributions are achieved in enhancing the functionality of the real-time prototype system. This includes the implementation and benchmarking of neural network op- timizations, such as quantization and pruning. Furthermore, an appearance-based synthetic RADAR and real RADAR datasets are developed. The latter contains simultaneous optical and RADAR data capture and cross-modal labels. Finally, multi-object tracking methods are benchmarked and a support vector machine is utilized for cross-modal association. In summary, the implementation, benchmarking, and optimization of methods for detection and tracking helped create a real-time vital sign system on a low-profile embedded device. Additionally, this work established a relationship between compression methods and different neural networks for optimal file compression and network performance. Finally, methods for RADAR and optical data collection and cross-modal association are implemented

MediaSync: Handbook on Multimedia Synchronization

This book provides an approachable overview of the most recent advances in the fascinating field of media synchronization (mediasync), gathering contributions from the most representative and influential experts. Understanding the challenges of this field in the current multi-sensory, multi-device, and multi-protocol world is not an easy task. The book revisits the foundations of mediasync, including theoretical frameworks and models, highlights ongoing research efforts, like hybrid broadband broadcast (HBB) delivery and users' perception modeling (i.e., Quality of Experience or QoE), and paves the way for the future (e.g., towards the deployment of multi-sensory and ultra-realistic experiences). Although many advances around mediasync have been devised and deployed, this area of research is getting renewed attention to overcome remaining challenges in the next-generation (heterogeneous and ubiquitous) media ecosystem. Given the significant advances in this research area, its current relevance and the multiple disciplines it involves, the availability of a reference book on mediasync becomes necessary. This book fills the gap in this context. In particular, it addresses key aspects and reviews the most relevant contributions within the mediasync research space, from different perspectives. Mediasync: Handbook on Multimedia Synchronization is the perfect companion for scholars and practitioners that want to acquire strong knowledge about this research area, and also approach the challenges behind ensuring the best mediated experiences, by providing the adequate synchronization between the media elements that constitute these experiences

DragonflEYE: a passive approach to aerial collision sensing

"This dissertation describes the design, development and test of a passive wide-field optical aircraft collision sensing instrument titled 'DragonflEYE'. Such a ""sense-and-avoid"" instrument is desired for autonomous unmanned aerial systems operating in civilian airspace. The instrument was configured as a network of smart camera nodes and implemented using commercial, off-the-shelf components. An end-to-end imaging train model was developed and important figures of merit were derived. Transfer functions arising from intermediate mediums were discussed and their impact assessed. Multiple prototypes were developed. The expected performance of the instrument was iteratively evaluated on the prototypes, beginning with modeling activities followed by laboratory tests, ground tests and flight tests. A prototype was mounted on a Bell 205 helicopter for flight tests, with a Bell 206 helicopter acting as the target. Raw imagery was recorded alongside ancillary aircraft data, and stored for the offline assessment of performance. The ""range at first detection"" (R0), is presented as a robust measure of sensor performance, based on a suitably defined signal-to-noise ratio. The analysis treats target radiance fluctuations, ground clutter, atmospheric effects, platform motion and random noise elements. Under the measurement conditions, R0 exceeded flight crew acquisition ranges. Secondary figures of merit are also discussed, including time to impact, target size and growth, and the impact of resolution on detection range. The hardware was structured to facilitate a real-time hierarchical image-processing pipeline, with selected image processing techniques introduced. In particular, the height of an observed event above the horizon compensates for angular motion of the helicopter platform.

Persönliche Wege der Interaktion mit multimedialen Inhalten

Today the world of multimedia is almost completely device- and content-centered. It focuses it’s energy nearly exclusively on technical issues such as computing power, network specifics or content and device characteristics and capabilities. In most multimedia systems, the presentation of multimedia content and the basic controls for playback are main issues. Because of this, a very passive user experience, comparable to that of traditional TV, is most often provided. In the face of recent developments and changes in the realm of multimedia and mass media, this ”traditional” focus seems outdated. The increasing use of multimedia content on mobile devices, along with the continuous growth in the amount and variety of content available, make necessary an urgent re-orientation of this domain. In order to highlight the depth of the increasingly difficult situation faced by users of such systems, it is only logical that these individuals be brought to the center of attention. In this thesis we consider these trends and developments by applying concepts and mechanisms to multimedia systems that were first introduced in the domain of usercentrism. Central to the concept of user-centrism is that devices should provide users with an easy way to access services and applications. Thus, the current challenge is to combine mobility, additional services and easy access in a single and user-centric approach. This thesis presents a framework for introducing and supporting several of the key concepts of user-centrism in multimedia systems. Additionally, a new definition of a user-centric multimedia framework has been developed and implemented. To satisfy the user’s need for mobility and flexibility, our framework makes possible seamless media and service consumption. The main aim of session mobility is to help people cope with the increasing number of different devices in use. Using a mobile agent system, multimedia sessions can be transferred between different devices in a context-sensitive way. The use of the international standard MPEG-21 guarantees extensibility and the integration of content adaptation mechanisms. Furthermore, a concept is presented that will allow for individualized and personalized selection and face the need for finding appropriate content. All of which can be done, using this approach, in an easy and intuitive way. Especially in the realm of television, the demand that such systems cater to the need of the audience is constantly growing. Our approach combines content-filtering methods, state-of-the-art classification techniques and mechanisms well known from the area of information retrieval and text mining. These are all utilized for the generation of recommendations in a promising new way. Additionally, concepts from the area of collaborative tagging systems are also used. An extensive experimental evaluation resulted in several interesting findings and proves the applicability of our approach. In contrast to the ”lean-back” experience of traditional media consumption, interactive media services offer a solution to make possible the active participation of the audience. Thus, we present a concept which enables the use of interactive media services on mobile devices in a personalized way. Finally, a use case for enriching TV with additional content and services demonstrates the feasibility of this concept.Die heutige Welt der Medien und der multimedialen Inhalte ist nahezu ausschließlich inhalts- und geräteorientiert. Im Fokus verschiedener Systeme und Entwicklungen stehen oft primär die Art und Weise der Inhaltspräsentation und technische Spezifika, die meist geräteabhängig sind. Die zunehmende Menge und Vielfalt an multimedialen Inhalten und der verstärkte Einsatz von mobilen Geräten machen ein Umdenken bei der Konzeption von Multimedia Systemen und Frameworks dringend notwendig. Statt an eher starren und passiven Konzepten, wie sie aus dem TV Umfeld bekannt sind, festzuhalten, sollte der Nutzer in den Fokus der multimedialen Konzepte rücken. Um dem Nutzer im Umgang mit dieser immer komplexeren und schwierigen Situation zu helfen, ist ein Umdenken im grundlegenden Paradigma des Medienkonsums notwendig. Durch eine Fokussierung auf den Nutzer kann der beschriebenen Situation entgegengewirkt werden. In der folgenden Arbeit wird auf Konzepte aus dem Bereich Nutzerzentrierung zurückgegriffen, um diese auf den Medienbereich zu übertragen und sie im Sinne einer stärker nutzerspezifischen und nutzerorientierten Ausrichtung einzusetzen. Im Fokus steht hierbei der TV-Bereich, wobei die meisten Konzepte auch auf die allgemeine Mediennutzung übertragbar sind. Im Folgenden wird ein Framework für die Unterstützung der wichtigsten Konzepte der Nutzerzentrierung im Multimedia Bereich vorgestellt. Um dem Trend zur mobilen Mediennutzung Sorge zu tragen, ermöglicht das vorgestellte Framework die Nutzung von multimedialen Diensten und Inhalten auf und über die Grenzen verschiedener Geräte und Netzwerke hinweg (Session mobility). Durch die Nutzung einer mobilen Agentenplattform in Kombination mit dem MPEG-21 Standard konnte ein neuer und flexibel erweiterbarer Ansatz zur Mobilität von Benutzungssitzungen realisiert werden. Im Zusammenhang mit der stetig wachsenden Menge an Inhalten und Diensten stellt diese Arbeit ein Konzept zur einfachen und individualisierten Selektion und dem Auffinden von interessanten Inhalten und Diensten in einer kontextspezifischen Weise vor. Hierbei werden Konzepte und Methoden des inhaltsbasierten Filterns, aktuelle Klassifikationsmechanismen und Methoden aus dem Bereich des ”Textminings” in neuer Art und Weise in einem Multimedia Empfehlungssystem eingesetzt. Zusätzlich sind Methoden des Web 2.0 in eine als Tag-basierte kollaborative Komponente integriert. In einer umfassenden Evaluation wurde sowohl die Umsetzbarkeit als auch der Mehrwert dieser Komponente demonstriert. Eine aktivere Beteiligung im Medienkonsum ermöglicht unsere iTV Komponente. Sie unterstützt das Anbieten und die Nutzung von interaktiven Diensten, begleitend zum Medienkonsum, auf mobilen Geräten. Basierend auf einem Szenario zur Anreicherung von TV Sendungen um interaktive Dienste konnte die Umsetzbarkeit dieses Konzepts demonstriert werden

Visual Attention for Robotic Cognition: A Biologically Inspired Probabilistic Architecture

The human being, the most magnificent autonomous entity in the universe, frequently takes the decision of `what to look at' in their day-to-day life without even realizing the complexities of the underlying process. When it comes to the design of such an attention system for autonomous robots, all of a sudden this apparently simple task appears to be an extremely complex one with highly dynamic interaction among motor skills, knowledge and experience developed throughout the life-time, highly connected circuitry of the visual cortex, and super-fast timing. The most fascinating thing about visual attention system of the primates is that the underlying mechanism is not precisely known yet. Different influential theories and hypothesis regarding this mechanism, however, are being proposed in psychology and neuroscience. These theories and hypothesis have encouraged the research on synthetic modeling of visual attention in computer vision, computational neuroscience and, very recently, in AI robotics. The major motivation behind the computational modeling of visual attention is two-fold: understanding the mechanism underlying the cognition of the primates' and using the principle of focused attention in different real-world applications, e.g. in computer vision, surveillance, and robotics. Accordingly, we observe the rise of two different trends in the computational modeling of visual attention. The first one is mostly focused on developing mathematical models which mimic, as much as possible, the details of the primates' attention system: the structure, the connectivity among visual neurons and different regions of the visual cortex, the flow of information etc. Such models provide a way to test the theories of the primates' visual attention with minimal involvement from the live subjects. This is a magnificent way to use technological advancement for the understanding of human cognition. The second trend in computational modeling, on the other hand, uses the methodological sophistication of the biological processes (like visual attention) to advance the technology. These models are mostly concerned with developing a technical system of visual attention which can be used in real-world applications where the principle of focused attention might play a significant role for redundant information management. This thesis is focused on developing a computational model of visual attention for robotic cognition and, therefore, belongs to the second trend. The design of a visual attention model for robotic systems as a component of their cognition comes with a number of challenges which, generally, do not appear in the traditional computer vision applications of visual attention. The robotic models of visual attention, although heavily inspired by the rich literature of visual attention in computer vision, adopt different measures to cope with these challenges. This thesis proposes a Bayesian model of visual attention designed specifically for robotic systems and, therefore, tackles the challenges involved with robotic visual attention. The operation of the proposed model is guided by the theory of biased competition, a popular theory from cognitive neuroscience describing the mechanism of primates' visual attention. The proposed Bayesian attention model offers a robot-centric approach of visual attention where the head-pose of a robot in the 3D world is estimated recursively such that the robot can focus on the most behaviorally relevant stimuli in its environment. The behavioral relevance of an object determined based on two criteria which are inspired by the postulates of the biased competitive hypothesis of visual attention in the primates. Accordingly, the proposed model encourages a robot to focus on novel stimuli or stimuli that have similarity with a `sought for' object depending on the context. In order to address a number of robot-specific issues of visual attention, the proposed model is further extended to the multi-modal case where speech commands from the human are used to modulate the visual attention behavior of the robot. The Bayes model of visual attention, inherited from the Bayesian sensor fusion characteristic, naturally accommodates multi-modal information during attention selection. This enables the proposed model to be the core component of an attention oriented speech-based human-robot interaction framework. Extensive experiments are performed in the real-world to investigate different aspects of the proposed Bayesian visual attention model

Schätzung dichter Korrespondenzfelder unter Verwendung mehrerer Bilder

Most optical flow algorithms assume pairs of images that are acquired with an ideal, short exposure time. We present two approaches, that use additional images of a scene to estimate highly accurate, dense correspondence fields. In our first approach we consider video sequences that are acquired with alternating exposure times so that a short-exposure image is followed by a long-exposure image that exhibits motion-blur. With the help of the two enframing short-exposure images, we can decipher not only the motion information encoded in the long-exposure image, but also estimate occlusion timings, which are a basis for artifact-free frame interpolation. In our second approach we consider the data modality of multi-view video sequences, as it commonly occurs, e.g., in stereoscopic video. As several images capture nearly the same data of a scene, this redundancy can be used to establish more robust and consistent correspondence fields than the consideration of two images permits.Die meisten Verfahren zur Schätzung des optischen Flusses verwenden zwei Bilder, die mit einer optimalen, kurzen Belichtungszeit aufgenommen wurden. Wir präsentieren zwei Methoden, die zusätzliche Bilder zur Schätzung von hochgenauen, dichten Korrespondenzfeldern verwenden. Die erste Methode betrachtet Videosequenzen, die mit alternierender Belichtungsdauer aufgenommen werden, so dass auf eine Kurzzeitbelichtung eine Langzeitbelichtung folgt, die Bewegungsunschärfe enthält. Mit der Hilfe von zwei benachbarten Kurzzeitbelichtungen können wir nicht nur die Bewegung schätzen, die in der Bewegungsunschärfe der Langzeitbelichtung verschlüsselt ist, sondern zusätzlich auch Verdeckungszeiten schätzen, die sich bei der Interpolation von Zwischenbildern als große Hilfe erweisen. Die zweite Methode betrachtet Videos, die eine Szene aus mehreren Ansichten aufzeichnen, wie z.B. Stereovideos. Dabei enthalten mehrere Bilder fast dieselbe Information über die Szene. Wir nutzen diese Redundanz aus, um konsistentere und robustere Bewegungsfelder zu bestimmen, als es mit zwei Bildern möglich ist