Search results for "Computer Vision and Pattern Recognition"

Scanning From Heating : extension pour la numérisation 3D de surfaces métalliques spéculaires

2011

National audience; En raison des difficultés liées à la réflexion spéculaire de certaines surfaces, peu de méthodes répétables ont été proposées pour mesurer la forme en trois dimensions des objets métalliques polis. Nous présentons l'application sur ce type de matériau d'une nouvelle approche appelée " Scanning From Heating ". Cette méthode a été initialement développée pour la numérisation 3D d'objets transparents. Du fait des nombreuses différences de propriétés physiques entre métaux et diélectriques, le principe de fonctionnement de la méthode SFH doit être modifié. Une simulation des échanges thermique grâce à un logiciel de calcul par éléments finis a permis de déterminer comment ada…

Calibration et Rectification

2013

PROCEDE DE NUMERISATION TRIDIMENSIONNELLE AUTOMATIQUE

2012

Special Issue on Community Structure in Complex Networks

2013

International audience; Network science is a powerful paradigm to better understand the complex systems encountered in many different disciplines such as physics, sociology, biology and computer science. One of the most relevant features of networked systems is community structure. Despite the tremendous efforts of a large interdisciplinary community of scientists working on this subject over the past few years to characterise, model and analyse communities in complex network, it is still a very hard problem that needs further investigation. Therefore, the primary goal of this special issue is to showcase the cutting edge research advances in community structures in complex networks, in ord…

Application du Scanning From Heating à la numérisation 3D de surfaces métalliques spéculaires

2011

Because of the difficulty of dealing with specularity of several surfaces, few methods have been proposed to measure three-dimensional shapes of specular metallic objects. In this paper we present an application on this kind of material of an approach called "Scanning From Heating". This approach has been developed initially for 3D reconstruction of transparent objects. This article presents an application of the working principle of SFH method on material with high thermal conductivity and low absorptivity.

Filtrage physiquement admissible des images codées en polarisation moyennant un parcours fractal de type Peano-Hilbert

2009

International audience; L'existence du bruit est inhérente aux systèmes imageurs. Causé par différents mécanismes, sa présence dégrade en général l'interprétation des données et peut dans le cas de l'imagerie polarimétrique nuire au caractère physique des mesures. Il convient donc de l'éliminer de manière à garder présente l'admissibilité physique des images polarimétriques afin de tirer pleinement profit de leur richesse informationnelles. Une méthode de filtrage paramétrique est proposée dans ce papier. Cette méthode repose sur une combinaison de deux techniques fréquemment utilisées en filtrage d'images multispectrales ; le Scatter plot est le masquage des données, sur lesquelles une vec…

Calcul de pose d'un réseau de caméras hybrides à partir de droites

2011

We present a pose estimation approach for a setup of multiple hybrid cameras using line features. From line images across at least three single viewpoint cameras such as perspective, central catadioptric or fish-eye ones, the camera poses are recovered by a decoupling of rotations and translations : rotations are estimated from vanishing points of parallel lines and translations are calculated from known rotations and line images. The 3D lines are reconstructed by the triangulation of projective planes passing through line correspondences. The camera poses and 3D scene are finally refined by bundle adjustment. This technique can be used to recover the topology of a multiple hybrid camera sy…

Estimation de mouvement d'un drone à partir d'un capteur stéréo hybride

2011

Motion and velocity are two of the most important parameters to be known for an Unmanned Aerial Vehicle (UAV) especially during critical maneuvers such as landing or steady flight. In this paper, we present mixed stereoscopic vision system made of a fish-eye camera and a perspective camera for motion estimation. Contrary to classical stereoscopic systems based on feature matching between cameras, we propose an algorithm which tracks and exploits points in each camera independently. The omnidirectional view estimates the orientation of the motion while the perspective view contribute to estimate the scale of the translation and brings accuracy. By fusing points tracked in each camera and kno…

Extraction et analyse automatiques des sinus de Valsalva à partir de séquences IRM

2011

MRI appears to be particularly attractive for the study of the Sinuses of Valsalva (SV), however there is no global consensus on their suitable measurements. In this paper, we propose a new method to automatically evaluate the SV from cine-MRI in a cross-sectional orientation. It consists in the extraction of the shape, the detection of relevant points (commissures, cusps and the centre of the SV), the measure of associated distances and in a classification of the SV as bicuspid or tricuspid. Our method was tested on 23 patient examinations and radii calculations were compared with manual processing. The classification of the valve as tricuspid or bicuspid was correct for all the cases. Mor…

Numérisation 3D intelligente : deux algorithmes automatiques et progressifs

2011

This paper presents two methods for the digitization of 3D objects without prior knowledge on their shape. The first method is based on the bounding box of the object during the acquisition steps. The second method is a combination of two concepts : the Mass Vector Chains (MVC) to define the orientation of the scanned part and the Mesurability Matrix to determine the coverage rate for each view point. Tests with simulated objects were performed and results of digitization are provided.