Eye-to-Eye Calibration: Extrinsische Kalibrierung von Mehrkamerasystemen mittels Hand-Auge-Kalibrierverfahren

The problem addressed in this thesis is the extrinsic calibration of embedded multi-camera systems without overlapping views, i.e., to determine the positions and orientations of rigidly coupled cameras with respect to a common coordinate frame from captured images. Such camera systems are of increasing interest for computer vision applications due to their large combined field of view, providing practical use for visual navigation and 3d scene reconstruction. However, in order to propagate observations from one camera to another, the parameters of the coordinate transformation between both cameras have to be determined accurately. Classical methods for extrinsic camera calibration relying on spatial correspondences between images cannot be applied here. The central topic of this work is an analysis of methods based on hand-eye calibration that exploit constraints of rigidly coupled motions to solve this problem from visual camera ego-motion estimation only, without need for additional sensors for pose tracking such as inertial measurement units or vehicle odometry. The resulting extrinsic calibration methods are referred to as "eye-to-eye calibration". We provide solutions based on pose measurements (geometric eye-to-eye calibration), decoupling the actual pose estimation from the extrinsic calibration, and solutions based on images measurements (visual eye-to-eye calibration), integrating both steps within a general Structure from Motion framework. Specific solutions are also proposed for critical motion configurations such as planar motion which often occurs in vehicle-based applications.Diese Arbeit beschäftigt sich mit der extrinsischen Kalibrierung von Mehrkamerasystemen ohne überlappende Sichtbereiche aus Bildfolgen. Die extrinsischen Parameter fassen dabei Lage und Orientierung der als starr-gekoppelt vorausgesetzten Kameras in Bezug auf ein gemeinsames Referenzkoordinatensystem zusammen. Die Minimierung der Redundanz der einzelnen Sichtfelder zielt dabei auf ein möglichst großes kombiniertes Sichtfeld aller Kameras ab. Solche Aufnahmesysteme haben sich in den letzten Jahren als hilfreich für eine Reihe von Aufgabenstellungen der Computer Vision erwiesen, z. B. in den Bereichen der visuellen Navigation und der bildbasierten 3D-Szenenrekonstruktion. Um Messungen der einzelnen Kameras sinnvoll zusammenzuführen, müssen die Parameter der Koordinatentransformationen zwischen den Kamerakoordinatensystemen möglichst exakt bestimmt werden. Klassische Methoden zur extrinsischen Kamerakalibrierung basieren in der Regel auf räumlichen Korrespondenzen zwischen Kamerabildern, was ein überlappendes Sichtfeld voraussetzt. In dieser Arbeit werden alternative Methoden zur Lagebestimmung von Kameras innerhalb eines Mehrkamerasystems untersucht, die auf der Hand-Auge-Kalibrierung basieren und Zwangsbedingungen starr-gekoppelter Bewegung ausnutzen. Das Problem soll dabei im Wesentlichen anhand von Bilddaten gelöst werden, also unter Verzicht auf zusätzliche Inertialsensoren oder odometrische Daten. Die daraus abgeleiteten extrinsischen Kalibrierverfahren werden in Anlehnung an die Hand-Auge-Kalibrierung als Eye-to-Eye Calibration bezeichnet. Es werden Lösungsverfahren vorgestellt, die ausschließlich auf Posemessdaten basieren und den Prozess der Poseschätzung von der eigentlichen Kalibrierung entkoppeln, sowie Erweiterungen, die direkt auf visuellen Informationen der einzelnen Kameras basieren. Die beschriebenen Ansätze führen zu dem Entwurf eines Structure-from-Motion-Verfahrens, das Poseschätzung, Rekonstruktion der Szenengeometrie und extrinsische Kalibrierung der Kameras integriert. Bewegungskonfigurationen, die zu Singularitäten in den Kopplungsgleichungen führen, werden gesondert analysiert und es werden spezielle Lösungsstrategien zur partiellen Kalibrierung für solche Fälle entworfen. Ein Schwerpunkt liegt hier auf Bewegung in der Ebene, da diese besonders häufig in Anwendungsszenarien auftritt, in denen sich das Kamerasystem in oder auf einem Fahrzeug befindet

Implementación de un módulo didáctico para la instalación, comprobación y funcionamiento de medidores de baja tensión para el laboratorio de la carrera de Electromecánica Extensión La Maná

This research work aims at the development of a didactic module for the installation, verification, and operation of low voltage meters, which facilitates the understanding of the behavior of low voltage distribution networks, both in normal operation and in case of failures, in the system. The test module consists of three single-phase, two-phase, and three-phase meters, it has its respective phase and neutral electric power redistribution lines and also has its respective tools for its manipulation. Allowing us to understand that electricity is considered today as an essential basic service for the population, since the use of the electricity allows the operation of our appliances, industries, and service networks, among other things. Due to the importance and impact of the use of electric meters in all homes, businesses, companies, for this reason, this research has as its main aim the implementation of a didactic module for the laboratory of the electromechanical major in Universidad Técnica de Cotopaxi Extensión “La Maná”, for compliance of the purpose, the various components that will be essential for the development and implementation of the module were considered; resulting in the study of the elements that make it up and how each of them works and how it would affect if a correct installation were not carried out, allowing that university students obtain experiences. In conclusion, this didactic module can be used as a practice tool where the knowledge obtained in a classroom is put into operation. Moreover, when observing the performance of the module, it was possible to appreciate that it is in accordance with the stated aims, by demonstrating that it will be of great help to Universidad Técnica de Cotopaxi.El presente trabajo de investigación tiene como objetivo implementar un módulo didáctico para la instalación, comprobación y funcionamiento de medidores de baja tensión, el mismo que facilita la comprensión del comportamiento de las redes de distribución en baja tensión, tanto en operación normal como en caso de fallas, en el sistema. El módulo de pruebas consta de tres medidores monofásico, bifásico y trifásico, cuenta con sus respectivas líneas de redistribución de energía eléctrica fase y neutro, y también con las respectivas herramientas para su manipulación. Permitiendo comprender que la electricidad es considerada hoy en día como un servicio básico indispensable para la población, ya que mediante el uso de esta permite el funcionamiento de nuestro electrodoméstico, industrias, las redes de servicio, entre un sinnúmero de cosas. Debido a la importancia e impacto que tiene el uso de medidores en todos los hogares, negocios, empresas, se encamino esta investigación, y para el cumplimiento del propósito, se tomó en cuenta los diversos componentes que serán indispensables para la construcción e implementación del módulo; dando como resultado el estudio de los elementos que la conforman y cuál es el funcionamiento de cada uno de ellos y de qué forma afectaría si en caso no se realizara una instalación adecuadamente, permitiendo que los jóvenes universitarios obtengan experiencias. Concluyendo que este módulo didáctico sirva como una herramienta de práctica donde se ponga en funcionamiento los conocimientos adquiridos dentro de una aula. Así mismo, al observar el rendimiento del módulo se pudo apreciar que se encuentra en concordancia con los objetivos planteados, al demostrar que servirá de gran ayuda a la Universidad Técnica de Cotopaxi

Histopathological effects of silver nanoparticles in Rhamdia quelen after oral exposure

The studies about silver nanoparticles (AgNP) increased in the last years but few is known about their effects in Brazilian neotropical freshwater fish species. The current study investigated the effects of AgNP on adult silver catfish Rhamdia quelen after subchronic oral exposure. After nanoparticle (NP) size and area characterization fish were administrated with three different doses for 15 days (0.03, 0.3 and 3 μg g-1). The concentration of silver in liver and kidney was measured to evaluate the bioaccumulation and discuss its effects in the target organs. Liver bioaccumulated 15, 1.7 and 0.2 % of administered doses while kidney bioaccumulated 1.33, 0.33 and 0.9 % (respectively for 0.03, 0.3 and 3 μg g-1). The histopathological findings were considered in both organs to evaluate the effects of AgNP, according to Bernet’s Lesion Index (BLI). Also were included the melano-macrophages center (MMC) and new nephrons (NN) counting respectively in liver and posterior kidney. The results revealed morphological injuries as inflammation in both studied organs and vascular congestion and steatosis in liver, in a concentration dependent way. The presence of AgNP in the tissues revealed the bioavailability of the nanoparticle while the damages and morphological disturbs showed the potential risk of exposure in R. quelen, even under environmental relevant concentrations

Estimation and Post-Capture Compensation of Synchronization Error in Unsynchronized Multi-Camera Systems

Multi-camera systems are used in entertainment production, computer vision, industry and surveillance. The benefit of using multi-camera systems is the ability to recover the 3D structure, or depth, of the recorded scene. However, various types of cameras, including depth cameras, can not be reliably synchronized during recording, which leads to errors in depth estimation and scene rendering. The aim of this work is to propose a method for compensating synchronization errors in already recorded sequences, without changing the format of the recorded sequences. We describe a depth uncertainty model for parametrizing the impact of synchronization errors in a multi-camera system, and propose a method for synchronization error estimation and compensation. The proposed method is based on interpolating an image at a desired timeframe based on adjacent non-synchronized images in a single camera's sequence, using an array of per-pixel distortion vectors. This array is generated by using the difference between adjacent images to locate and segment the recorded moving objects, and does not require any object texture or distinguishing features beyond the observed difference in adjacent images. The proposed compensation method is compared with optical-flow based interpolation and sparse correspondence based morphing, and the proposed synchronization error estimation is compared with a state-of-the-art video alignment method. The proposed method shows better synchronization error estimation accuracy and compensation ability, especially in cases of low-texture, low-feature images. The effect of using data with synchronization errors is also demonstrated, as is the improvement gained by using compensated data. The compensation of synchronization errors is useful in scenarios where the recorded data is expected to be used by other processes that expect a sub-frame synchronization accuracy, such as depth-image-based rendering