Visual servoing of mobile robots using non-central catadioptric cameras

This paper presents novel contributions on image-based control of a mobile robot using a general catadioptric camera model. A catadioptric camera is usually made up by a combination of a conventional camera and a curved mirror resulting in an omnidirectional sensor capable of providing 360° panoramic views of a scene. Modeling such cameras has been the subject of significant research interest in the computer vision community leading to a deeper understanding of the image properties and also to different models for different types of configurations. Visual servoing applications using catadioptric cameras have essentially been using central cameras and the corresponding unified projection model. So far only in a few cases more general models have been used. In this paper we address the problem of visual servoing using the so-called radial model. The radial model can be applied to many camera configurations and in particular to non-central catadioptric systems with mirrors that are symmetric around an axis coinciding with the optical axis. In this case, we show that the radial model can be used with a non-central catadioptric camera to allow effective image-based visual servoing (IBVS) of a mobile robot. Using this model, which is valid for a large set of catadioptric cameras (central or non-central), new visual features are proposed to control the degrees of freedom of a mobile robot moving on a plane. In addition to several simulation results, a set of experiments was carried out on Robot Operating System (ROS)-based platform which validates the applicability, effectiveness and robustness of the proposed method for image-based control of a non-holonomic robot

Vision-based Navigation and Mapping Using Non-central Catadioptric Omnidirectional Camera

Omnidirectional catadioptric cameras find their use in navigation and mapping, owing to their wide field of view. Having a wider field of view, or rather a potential 360 degree field of view, allows the user to see and move more freely in the navigation space. A catadioptric camera system is a low cost system which consists of a mirror and a camera. A calibration method was developed in order to obtain the relative position and orientation between the two components so that they can be considered as one monolithic system. The position of the system was determined, for an environment using the conditions obtained from the reflective properties of the mirror. Object control points were set up and experiments were performed at different sites to test the mathematical models and the achieved location and mapping accuracy of the system. The obtained positions were then used to map the environment

Visual servoing of mobile robots using non-central catadioptric cameras

This paper presents novel contributions on image-based control of a mobile robot using a general catadioptric camera model. A catadioptric camera is usually made up by a combination of a conventional camera and a curved mirror resulting in an omnidirectional sensor capable of providing 360° panoramic views of a scene. Modeling such cameras has been the subject of significant research interest in the computer vision community leading to a deeper understanding of the image properties and also to different models for different types of configurations. Visual servoing applications using catadioptric cameras have essentially been using central cameras and the corresponding unified projection model. So far only in a few cases more general models have been used. In this paper we address the problem of visual servoing using the so-called radial model. The radial model can be applied to many camera configurations and in particular to non-central catadioptric systems with mirrors that are symmetric around an axis coinciding with the optical axis. In this case, we show that the radial model can be used with a non-central catadioptric camera to allow effective image-based visual servoing (IBVS) of a mobile robot. Using this model, which is valid for a large set of catadioptric cameras (central or non-central), new visual features are proposed to control the degrees of freedom of a mobile robot moving on a plane. In addition to several simulation results, a set of experiments was carried out on Robot Operating System (ROS)-based platform which validates the applicability, effectiveness and robustness of the proposed method for image-based control of a non-holonomic robot

Calibrage et modélisation d’un système de stéréovision hybride et panoramique

Dans cette thèse nos contributions à la résolution de deux problématiques rencontrées en vision numérique et en photogrammétrie, qui sont le calibrage de caméras et la stéréovision, sont présentées. Ces deux problèmes font l’objet de très nombreuses recherches depuis plusieurs années. Les techniques de calibrage existantes diffèrent beaucoup suivant le type de caméras à calibrer (classique ou panoramique, à focale fixe ou à focale variable, ..). Notre première contribution est un banc de calibrage, à l’aide des éléments d’optique diffractive, qui permet de calibrer avec une bonne précision une très grande partie des caméras existantes. Un modèle simple et précis qui décrit la projection de la grille formée sur l’image et une méthode de calibrage pour chaque type de caméras est proposé. La technique est très robuste et les résultats pour l’ensemble des caméras calibrées sont optimaux. Avec la multiplication des types de caméras et la diversité des modèles de projections, un modèle de formation d'image générique semble très intéressant. Notre deuxième contribution est un modèle de projection unifié pour plusieurs caméras classiques et panoramiques. Dans ce modèle, toute caméra est modélisée par une projection rectiligne et des splines cubiques composées permettant de représenter toutes sortes de distorsions. Cette approche permet de modéliser géométriquement les systèmes de stéréovision mixtes ou panoramiques et de convertir une image panoramique en une image classique. Par conséquent, le problème de stéréovision mixte ou panoramique est transformé en un problème de stéréovision conventionnelle. Mots clés : calibrage, vision panoramique, distorsion, fisheye, zoom, panomorphe, géométrie épipolaire, reconstruction tridimensionnelle, stéréovision hybride, stéréovision panoramique.This thesis aims to present our contributions to the resolution of two problems encountered in the field of computer vision and photogrammetry, which are camera calibration and stereovision. These two problems have been extensively studied in the last years. Different camera calibration techniques have been developed in the literature depending on the type of camera (classical or panoramic, with zoom lens or fixed lens..). Our first contribution is a compact and accurate calibration setup, based on diffractive optical elements, which is suitable for different kind of cameras. The technique is very robust and optimal results were achieved for different types of cameras. With the multiplication of camera types and the diversity of the projection models, a generic model has become very interesting. Our second contribution is a generic model, which is suitable for conventional and panoramic cameras. In this model, composed cubic splines functions provide more realistic model of both radial and tangential distortions. Such an approach allows to model either hybrid or panoramic stereovision system and to convert panoramic image to classical image. Consequently, the processing challenges of a hybrid stereovision system or a panoramic stereovision system are turned into simple classical stereovision problems. Keywords: Calibration, panoramic vision, distortions, fisheye, zoom, panomorph, epipolar geometry, three-dimensional reconstruction, hybrid stereovision, panoramic stereovision