Artistic Path Space Editing of Physically Based Light Transport

Die Erzeugung realistischer Bilder ist ein wichtiges Ziel der Computergrafik, mit Anwendungen u.a. in der Spielfilmindustrie, Architektur und Medizin. Die physikalisch basierte Bildsynthese, welche in letzter Zeit anwendungsübergreifend weiten Anklang findet, bedient sich der numerischen Simulation des Lichttransports entlang durch die geometrische Optik vorgegebener Ausbreitungspfade; ein Modell, welches für übliche Szenen ausreicht, Photorealismus zu erzielen. Insgesamt gesehen ist heute das computergestützte Verfassen von Bildern und Animationen mit wohlgestalteter und theoretisch fundierter Schattierung stark vereinfacht. Allerdings ist bei der praktischen Umsetzung auch die Rücksichtnahme auf Details wie die Struktur des Ausgabegeräts wichtig und z.B. das Teilproblem der effizienten physikalisch basierten Bildsynthese in partizipierenden Medien ist noch weit davon entfernt, als gelöst zu gelten. Weiterhin ist die Bildsynthese als Teil eines weiteren Kontextes zu sehen: der effektiven Kommunikation von Ideen und Informationen. Seien es nun Form und Funktion eines Gebäudes, die medizinische Visualisierung einer Computertomografie oder aber die Stimmung einer Filmsequenz -- Botschaften in Form digitaler Bilder sind heutzutage omnipräsent. Leider hat die Verbreitung der -- auf Simulation ausgelegten -- Methodik der physikalisch basierten Bildsynthese generell zu einem Verlust intuitiver, feingestalteter und lokaler künstlerischer Kontrolle des finalen Bildinhalts geführt, welche in vorherigen, weniger strikten Paradigmen vorhanden war. Die Beiträge dieser Dissertation decken unterschiedliche Aspekte der Bildsynthese ab. Dies sind zunächst einmal die grundlegende Subpixel-Bildsynthese sowie effiziente Bildsyntheseverfahren für partizipierende Medien. Im Mittelpunkt der Arbeit stehen jedoch Ansätze zum effektiven visuellen Verständnis der Lichtausbreitung, die eine lokale künstlerische Einflussnahme ermöglichen und gleichzeitig auf globaler Ebene konsistente und glaubwürdige Ergebnisse erzielen. Hierbei ist die Kernidee, Visualisierung und Bearbeitung des Lichts direkt im alle möglichen Lichtpfade einschließenden "Pfadraum" durchzuführen. Dies steht im Gegensatz zu Verfahren nach Stand der Forschung, die entweder im Bildraum arbeiten oder auf bestimmte, isolierte Beleuchtungseffekte wie perfekte Spiegelungen, Schatten oder Kaustiken zugeschnitten sind. Die Erprobung der vorgestellten Verfahren hat gezeigt, dass mit ihnen real existierende Probleme der Bilderzeugung für Filmproduktionen gelöst werden können

Contributions to the design of Fourier-optical modulation systems based on micro-opto-electro-mechanical tilt-mirror arrays

Spatial Light Modulators (SLMs) based on Micro-Opto-Electro-Mechanical Systems (MOEMS) are increasingly being used in various fields of optics and enable novel functionalities. The technology features frame rates from a few kHz to the MHz range as well as resolutions in the megapixel range. The field continues to make rapid progress, but technological advancements are always associated with high expenditure. Against this background, this dissertation addresses the question: What contribution can optical system design make to the further development of MOEMS-SLM-based modulation? A lens is a simple example of an optical system. This dissertation deals with system design based on Fourier optics in which the wave properties of light are exploited. On this basis, arrays of micromirrors can modulate light properties in a spatially resolved manner. For example, tilt-mirrors can control the intensity distribution in an image plane. In this dissertation variations of the aperture required for this are investigated. In addition to known absorbing apertures, phase filters in particular are investigated, which apply a spatially distributed delay effect to the light wave. This dissertation proposes the combination of MOEMS-SLMs with static, pixelated elements in the same system. These may be pixelated phase masks, also known as diffractive optical elements (DOEs). Analogously, pixelated polarizer arrays and absorbing photomasks exist. The combination of SLMs and static elements allows new degrees of freedom in system design. This thesis proposes new modulation systems based on MOEMS tilt-mirror SLMs. These systems use analog tilt-mirror arrays for the simultaneous modulation of intensity and phase as well as intensity and polarization. The proposed systems thus open up new possibilities for MOEMS-based spatial light modulation. Their properties are validated and investigated by numerical simulations. System properties and limitations are derived from these near and far field simulations. This dissertation shows that the modulation of different MOEMS-SLM types can be fundamentally changed by system design. Piston mirror arrays are classically used for phase modulation and tilt-mirror arrays for intensity modulation. This thesis proposes the use of subpixel phase structures. Their use approximately provides tilt-mirrors with the phase-modulating effect of piston-mirrors. In order to achieve this, a new optimization method is presented. Piston-mirror arrays are available only to a limited extent. By contrast, tilt-mirror arrays are well established. In combination with subpixel phase features, tilt-mirrors may replace piston-mirrors in some applications. These and other challenges of MOEMS-SLM technology can be adequately addressed on the basis of system design.Räumliche Lichtmodulatoren (Spatial Light Modulators, SLMs) auf Basis von Mikro-Opto-Elektro-Mechanischen Systemen (MOEMS) finden zunehmend Anwendung in verschiedensten Teilgebieten der Optik und ermöglichen neuartige Funktionalitäten. Die Technik ermöglicht Frameraten von einigen kHz bis in den MHz-Bereich sowie Auflösungen bis in den Megapixelbereich. Der Fachbereich macht nach wie vor rasche Fortschritte, technologische Weiterentwicklungen sind aber stets mit hohem Aufwand verbunden. Vor diesem Hintergrund widmet sich diese Arbeit der Frage: Welchen Beitrag kann optisches Systemdesign zur Weiterentwicklung der MOEMS-SLM-basierten Modulation leisten? Bereits eine Linse stellt ein Beispiel für ein optisches System dar. Diese Dissertation beschäftigt sich mit Systemdesign auf Basis der Fourier-Optik, bei der die Welleneigenschaften des Lichts genutzt werden. Auf dieser Basis können Arrays von Mikrospiegeln die flächige Verteilung von Licht einstellen. Beispielsweise können Kippspiegel die Intensitätsverteilung in einer Bildebene steuern. In dieser Dissertation werden Variationen der dafür nötigen Apertur untersucht. Neben bekannten absorbierenden Blenden werden insbesondere Phasenfilter untersucht, welche eine flächig verteilte Verzögerungswirkung auf die Lichtwelle aufbringen. Diese Dissertation schlägt die Kombination von MOEMS-SLMs mit statischen, pixelierten Elementen im selben System vor. Hierbei kann es sich um pixelierte Phasenmasken handeln, auch bekannt als diffraktive optische Elemente (DOEs). Analog existieren pixelierte Polarisatorarrays und absorbierende Fotomasken. Die Kombination von SLMs und statischen Elementen ermöglicht neue Freiheiten im Systemdesign. Diese Arbeit schlägt neue Modulationssysteme auf Basis von MOEMS-Kippspiegel-SLMs vor. Diese Systeme nutzen analoge Kippspiegelarrays für die simultane Modulation von Intensität und Phase sowie von Intensität und Polarisation. Die vorgeschlagenen Systeme eröffnen damit neue Möglichkeiten für die MOEMS-basierte Flächenlichtmodulation. Ihre Eigenschaften werden mithilfe von numerischen Simulationen validiert und untersucht. Aus diesen Nah- und Fernfeldsimulationen werden Systemeigenschaften und Limitierungen abgeleitet. Es wird in dieser Arbeit gezeigt, dass die Modulation verschiedener MOEMS-SLM-Typen auf Basis des Systementwurfs fundamental verändert werden kann. Senkspiegelarrays werden klassischerweise zur Modulation der Phase eingesetzt und Kippspiegelarrays zur Modulation der Intensität. Diese Arbeit schlägt die Nutzung von Subpixel-Phasenstrukturen vor. Diese verleihen Kippspiegeln näherungsweise die phasenmodulierende Wirkung von Senkspiegeln. Um dies zu erreichen, wird ein neuartiges Optimierungsverfahren vorgestellt. Senkspiegelarrays sind nur in geringem Umfang verfügbar. Im Gegensatz dazu sind Kippspiegelarrays gut etabliert. In Kombination mit Subpixel-Phasenstrukturen könnten Kippspiegel in einigen Anwendungen Senkspiegel ersetzen. Diese und andere Herausforderungen der MOEMS-SLM-Technologie lassen sich auf der Grundlage des Systemdesigns adäquat adressieren

LANDSAT-4/5 image data quality analysis

A LANDSAT Thematic Mapper (TM) quality evaluation study was conducted to identify geometric and radiometric sensor errors in the post-launch environment. The study began with the launch of LANDSAT-4. Several error conditions were found, including band-to-band misregistration and detector-to detector radiometric calibration errors. Similar analysis was made for the LANDSAT-5 Thematic Mapper and compared with results for LANDSAT-4. Remaining band-to-band misregistration was found to be within tolerances and detector-to-detector calibration errors were not severe. More coherent noise signals were observed in TM-5 than in TM-4, although the amplitude was generally less. The scan direction differences observed in TM-4 were still evident in TM-5. The largest effect was in Band 4 where nearly a one digital count difference was observed. Resolution estimation was carried out using roads in TM-5 for the primary focal plane bands rather than field edges as in TM-4. Estimates using roads gave better resolution. Thermal IR band calibration studies were conducted and new nonlinear calibration procedures were defined for TM-5. The overall conclusion is that there are no first order errors in TM-5 and any remaining problems are second or third order

Optimal prefilters for display enhancement

Creating images from a set of discrete samples is arguably the most common operation in computer graphics and image processing, lying, for example, at the heart of rendering and image downscaling techniques. Traditional tools for this task are based on classic sampling theory and are modeled under mathematical conditions which are, in most cases, unrealistic; for example, sinc reconstruction – required by Shannon theorem in order to recover a signal exactly – is impossible to achieve in practice because LCD displays perform a box-like interpolation of the samples. Moreover, when an image is made for a human to look at, it will necessarily undergo some modifications due to the human optical system and all the neural processes involved in vision. Finally, image processing practitioners noticed that sinc prefiltering – also required by Shannon theorem – often leads to visually unpleasant images. From these facts, we can deduce that we cannot guarantee, via classic sampling theory, that the signal we see in a display is the best representation of the original image we had in first place. In this work, we propose a novel family of image prefilters based on modern sampling theory, and on a simple model of how the human visual system perceives an image on a display. The use of modern sampling theory guarantees us that the perceived image, based on this model, is indeed the best representation possible, and at virtually no computational overhead. We analyze the spectral properties of these prefilters, showing that they offer the possibility of trading-off aliasing and ringing, while guaranteeing that images look sharper then those generated with both classic and state-of-the-art filters. Finally, we compare it against other solutions in a selection of applications which include Monte Carlo rendering and image downscaling, also giving directions on how to apply it in different contexts.Exibir imagens a partir de um conjunto discreto de amostras é certamente uma das operações mais comuns em computação gráfica e processamento de imagens. Ferramentas tradicionais para essa tarefa são baseadas no teorema de Shannon e são modeladas em condições matemáticas que são, na maior parte dos casos, irrealistas; por exemplo, reconstrução com sinc – necessária pelo teorema de Shannon para recuperar um sinal exatamente – é impossível na prática, já que displays LCD realizam uma reconstrução mais próxima de uma interpolação com kernel box. Além disso, profissionais em processamento de imagem perceberam que prefiltragem com sinc – também requerida pelo teorema de Shannon – em geral leva a imagens visualmente desagradáveis devido ao fenômeno de ringing: oscilações próximas a regiões de descontinuidade nas imagens. Desses fatos, deduzimos que não é possível garantir, via ferramentas tradicionais de amostragem e reconstrução, que a imagem que observamos em um display digital é a melhor representação para a imagem original. Neste trabalho, propomos uma família de prefiltros baseada em teoria de amostragem generalizada e em um modelo de como o sistema ótico do olho humano modifica uma imagem. Proposta por Unser and Aldroubi (1994), a teoria de amostragem generalizada é mais geral que o teorema proposto por Shannon, e mostra como é possível pré-filtrar e reconstruir sinais usando kernels diferentes do sinc. Modelamos o sistema ótico do olho como uma câmera com abertura finita e uma lente delgada, o que apesar de ser simples é suficiente para os nossos propósitos. Além de garantir aproximação ótima quando reconstruindo as amostras por um display e filtrando a imagem com o modelo do sistema ótico humano, a teoria de amostragem generalizada garante que essas operações são extremamente eficientes, todas lineares no número de pixels de entrada. Também, analisamos as propriedades espectrais desses filtros e de técnicas semelhantes na literatura, mostrando que é possível obter um bom tradeoff entre aliasing e ringing (principais artefatos quando lidamos com amostragem e reconstrução de imagens), enquanto garantimos que as imagens finais são mais nítidas que aquelas geradas por técnicas existentes na literatura. Finalmente, mostramos algumas aplicações da nossa técnica em melhoria de imagens, adaptação à distâncias de visualização diferentes, redução de imagens e renderização de imagens sintéticas por método de Monte Carlo

Three-dimensional reconstruction of individual helical nano-filament structures from atomic force microscopy topographs

Atomic force microscopy, AFM, is a powerful tool that can produce detailed topographical images of individual nano-structures with a high signal-to-noise ratio without the need for ensemble averaging. However, the application of AFM in structural biology has been hampered by the tip-sample convolution effect, which distorts images of nano-structures, particularly those that are of similar dimensions to the cantilever probe tips used in AFM. Here we show that the tip-sample convolution results in a feature-dependent and non-uniform distribution of image resolution on AFM topographs. We show how this effect can be utilised in structural studies of nano-sized upward convex objects such as spherical or filamentous molecular assemblies deposited on a flat surface, because it causes ‘magnification’ of such objects in AFM topographs. Subsequently, this enhancement effect is harnessed through contact-point based deconvolution of AFM topographs. Here, the application of this approach is demonstrated through the 3D reconstruction of the surface envelope of individual helical amyloid filaments without the need of cross-particle averaging using the contact- deconvoluted AFM topographs. Resolving the structural variations of individual macromolecular assemblies within inherently heterogeneous populations is paramount for mechanistic understanding of many biological phenomena such as amyloid toxicity and prion strains. The approach presented here will also facilitate the use of AFM for high-resolution structural studies and integrative structural biology analysis of single molecular assemblies

The Feasibility of Quantitatively Characterizing the Vehicle Motion Environment (VME)

https://deepblue.lib.umich.edu/bitstream/2027.42/154108/1/ervin1990.pd

Fast Super-resolution with Affine Motion Using an Adaptive Wiener Filter and Its Application to Airborne Imaging

Fast nonuniform interpolation based super-resolution (SR) has traditionally been limited to applications with translational interframe motion. This is in part because such methods are based on an underlying assumption that the warping and blurring components in the observation model commute. For translational motion this is the case, but it is not true in general. This presents a problem for applications such as airborne imaging where translation may be insufficient. Here we present a new Fourier domain analysis to show that, for many image systems, an affine warping model with limited zoom and shear approximately commutes with the point spread function when diffraction effects are modeled. Based on this important result, we present a new fast adaptive Wiener filter (AWF) SR algorithm for non-translational motion and study its performance with affine motion. The fast AWF SR method employs a new smart observation window that allows us to precompute all the needed filter weights for any type of motion without sacrificing much of the full performance of the AWF. We evaluate the proposed algorithm using simulated data and real infrared airborne imagery that contains a thermal resolution target allowing for objective resolution analysis

Detecting anomalies in remotely sensed hyperspectral signatures via wavelet transforms

An automated subpixel target detection system has been designed and tested for use with remotely sensed hyperspectral images. A database of hyperspectral signatures was created to test the system using a variety of Gaussian shaped targets. The signal-to-noise ratio of the targets varied from -95dB to -50dB. The system utilizes a wavelet-based method (discrete wavelet transform) to extract an energy feature vector from each input pixel signature. The dimensionality of the feature vector is reduced to a one-dimensional feature scalar through the process of linear discriminant analysis. Signature classification is determined by nearest mean criterion that is used to assign each input signature to one of two classes, no target present or target present. Classification accuracy ranged from nearly 60% with target SNR at -95dB without any a priori knowledge of the target, to 100% with target SNR at -50dB and a priori knowledge about the location of the target within the spectral bands of the signature

Spectral image utility for target detection applications

In a wide range of applications, images convey useful information about scenes. The “utility” of an image is defined with reference to the specific task that an observer seeks to accomplish, and differs from the “fidelity” of the image, which seeks to capture the ability of the image to represent the true nature of the scene. In remote sensing of the earth, various means of characterizing the utility of satellite and airborne imagery have evolved over the years. Recent advances in the imaging modality of spectral imaging have enabled synoptic views of the earth at many finely sampled wavelengths over a broad spectral band. These advances challenge the ability of traditional earth observation image utility metrics to describe the rich information content of spectral images. Traditional approaches to image utility that are based on overhead panchromatic image interpretability by a human observer are not applicable to spectral imagery, which requires automated processing. This research establishes the context for spectral image utility by reviewing traditional approaches and current methods for describing spectral image utility. It proposes a new approach to assessing and predicting spectral image utility for the specific application of target detection. We develop a novel approach to assessing the utility of any spectral image using the target-implant method. This method is not limited by the requirements of traditional target detection performance assessment, which need ground truth and an adequate number of target pixels in the scene. The flexibility of this approach is demonstrated by assessing the utility of a wide range of real and simulated spectral imagery over a variety ii of target detection scenarios. The assessed image utility may be summarized to any desired level of specificity based on the image analysis requirements. We also present an approach to predicting spectral image utility that derives statistical parameters directly from an image and uses them to model target detection algorithm output. The image-derived predicted utility is directly comparable to the assessed utility and the accuracy of prediction is shown to improve with statistical models that capture the non-Gaussian behavior of real spectral image target detection algorithm outputs. The sensitivity of the proposed spectral image utility metric to various image chain parameters is examined in detail, revealing characteristics, requirements, and limitations that provide insight into the relative importance of parameters in the image utility. The results of these investigations lead to a better understanding of spectral image information vis-à-vis target detection performance that will hopefully prove useful to the spectral imagery analysis community and represent a step towards quantifying the ability of a spectral image to satisfy information exploitation requirements