Search results for "Computer vision"
showing 10 items of 2353 documents
Extraction de primitives à partir d'images de lumière structurée
2013
National audience; Les attributs géométriques tels que la courbure ou la normale constituent des informations complémentaires aux points 3D obtenus suite à la numérisation d'une surface ou d'un objet. Dans la chaine 3D classique, présentant une structure séquentielle, ces informations sont déterminées à partir du nuage de points dense (issus par exemple d'un scanner 3D). Par la suite, elles sont utilisées pour diminuer la quantité d'information et permettre ainsi d'aboutir à un modèle simplifié (compressé ou modélisé sous forme de primitives). Dans cet article, nous nous intéressons à la possibilité d'extraire certains des attributs mentionnés plus haut, directement à partir des images 2D o…
Using Visual Saliency for Object Tracking with Particle Filters
2010
International audience; This paper presents a robust tracking method based on the integration of visual saliency information into the particle filter framework. While particle filter has been successfully used for tracking non-rigid objects, it shows poor performances in the presence of large illumination variation, occlusions and when the target object and background have similar color distributions. We show that considering saliency information significantly improves the performance of particle filter based tracking. In particular, the proposed method is robust against occlusion and large illumination variation while requiring a reduced number of particles. Experimental results demonstrate th…
A NEW POTENTIAL FUNCTION FOR SELF INTERSECTING GIELIS CURVES WITH RATIONAL SYMMETRIES
2009
International audience; We present a new potential field equation for self-intersecting Gielis curves with rational rotational symmetries. In the literature, potential field equations for these curves, and their extensions to surfaces, impose the rotational symmetries to be integers in order to guarantee the unicity of the intersection between the curve/surface and any ray starting from its center. Although the representation with natural symmetries has been applied to mechanical parts modeling and reconstruction, the lack of a potential function for Rational symmetry Gielis Curves (RGC) remains a major problem for natural object representation, such as flowers and phyllotaxis. We overcome thi…
Estimation des Cartes du Temps de Collision (TTC) en Vision Para-catadioptrique
2013
National audience; Le temps de contact ou le temps de collision (TTC) est une information importante pour la navigation et l'évitement d'obtacles. Son estimation a largement été étudiée dans le cas des caméras perspectives. Par contre, très peu de travaux ont été effectués sur ce sujet pour les caméras catadioptriques, alors qu'elles sont très utiles, notamment, en navigation des robots mobiles. L'objectif de cet article, est de proposer un nouveau modèle d'estimation du TTC pour les caméras paracatadioptriques basé sur le flot optique, en adaptant celui développé pour les caméras perspectives. Le calcul du TTC en chaque pixel permet d'obtenir la carte des temps de collision. Nous avons val…
Etude de caméras sphériques : du traitement des images aux applications en robotique
2012
La vision omnidirectionnelle permet de percevoir l'environnement sur 360◦. C'est un atout considérable pour un robot mobile puisque grâce à cette particularité, il peut tirer parti d'une information globale de la scène à tout moment. Les premières recherches allant dans ce sens remontent en 1990 avec les travaux de Yasushi Yagi qui a proposé d'utiliser un dispositif nommé COPIS en associant une caméra perspective et un miroir conique pour obtenir une vue panoramique de la scène. En 1995, Mouaddib et Pégard présentent un procédé similaire pour localiser un robot dans son environnement. Bien que ce système possède des avantages pour la localisation, il se révèle peu adéquat pour reconstruire …
Estimation de mouvement d'un système stéréoscopique hybride à partir des droites
2010
We present a motion estimation approach for hybrid stereo rigs using line images. The proposed method can be applied to a hybrid system built up from any single view point (SVP) cameras such as perspective, central catadioptric and fisheye cameras. Such configuration combines advantageous characteristics of different types of cameras. Images captured by SVP imaging devices may be mapped to spherical images using the unified projection model. It is possible to recover the camera orientations using vanishing points of parallel line sets. We then estimate the translations from known rotations and line images on the spheres. The algorithm has been validated on simulated data and real images tak…
Multiple Structured Light-Based Depth Sensors for Human Motion Analysis: A Review
2012
Human motion analysis is an increasingly important active research domain with various applications in surveillance, human-machine interaction and human posture analysis. The recent developments in depth sensor technology, especially with the release of the Kinect device, have attracted significant attention to the question of how to take advantage of this technology in order to achieve accurate motion tracking and action detection in marker-less approaches. In this paper, we review the benefits and limitations deriving from the adoption of structured light-based depth sensors in human motion analysis applications. Surveying the relevant literature, we have identified in calibration, interf…
Evolutionary-based 3D reconstruction using an uncalibrated stereovision system: application of building a panoramic object view
2010
In this paper, we propose an original evolutionary-based method for 3D panoramic reconstruction from an uncalibrated stereovision system (USS). The USS is composed of five cameras located on an arc of a circle around the object to be analyzed. The main originality of this work concerns the process of the calculation of the 3D information. Actually, with our method, 3D coordinates are directly obtained without any prior estimation of the fundamental matrix. The method operates in two steps. Firstly, points of interest are detected in pairs of images acquired by two consecutive cameras of the USS are matched. And secondly, using evolutionary algorithms, we jointly compute the transformed matr…
On Keyframe Positioning for Pose Graphs Applied to Visual SLAM
2013
International audience; In this work, a new method is introduced for localization and keyframe identification to solve a Simultaneous Localization and Mapping (SLAM) problem. The proposed approach is based on a dense spherical acquisition system that synthesizes spherical intensity and depth images at arbitrary locations. The images are related by a graph of 6 degrees-of-freedom (DOF) poses which are estimated through spherical registration. A direct image-based method is provided to estimate pose by using both depth and color information simultaneously. A new keyframe identification method is proposed to build the map of the environment by using the covariance matrix between raletive 6 DOF…
Performance evaluation of Wireless Sensor Networks based on ZigBee technology in smart home
2013
International audience; Wireless Sensor Networks (WSNs) has diverse application domains such as smart home, smart care, industrial, etc. In this paper, we present a WSN system based on the ZigBee technology (IEEE 802.15.4) in Smart Home. To have a good sensor networks communication implanted in a smart home, studies of operating performance on this network is important. In this work, we investigate the performance of our ZigBee sensor networks. The study of performance is based on measurements of the Received Signal Strength Indicator (RSSI) in different parts of the Home. We will also discuss the impact of electromagnetic noise on the communication performance of a ZigBee Sensor Network in…