Search results for " Pattern recognition"

A Multi-Projector Calibration Method for Virtual Reality Simulators with Analytically Defined Screens

2017

The geometric calibration of projectors is a demanding task, particularly for the industry of virtual reality simulators. Different methods have been developed during the last decades to retrieve the intrinsic and extrinsic parameters of projectors, most of them being based on planar homographies and some requiring an extended calibration process. The aim of our research work is to design a fast and user-friendly method to provide multi-projector calibration on analytically defined screens, where a sample is shown for a virtual reality Formula 1 simulator that has a cylindrical screen. The proposed method results from the combination of surveying, photogrammetry and image processing approac…

Stability of stochastic nonlinear systems with state-dependent switching

2013

In this paper, the problem of stability on stochastic systems with state-dependent switching is investigated. To analyze properties of the switched system by means of Itô’s formula and Dynkin’s formula, it is critical to show switching instants being stopping times. When the given active-region set can be replaced by its interior, the local solution of the switched system is constructed by defining a series of stopping times as switching instants, and the criteria on global existence and stability of solution are presented by Lyapunov approach. For the case where the active-region set can not be replaced by its interior, the switched systems do not necessarily have solutions, thereby quasi-…

Primitives extraction based on structured-light images

2013

International audience; Geometric attributes such as curvature or surface orientation are additional information of the 3D points obtained after the scanning of an object. In the classic 3D chain, characterized by a sequential structure, these information are determined from the dense point cloud (from a 3D scanner). Then, they are used to reduce the amount of information and allows to obtain a simplified model. In this paper, we investigate the possibility to extract some geometric attributes, directly from 2D images obtained by the camera of a structured-light system.

Towards a Guidance System to Aid in the Dosimetry Calculation of Intraoperative Electron Radiation Therapy

2015

In Intraoperative Electron Radiation Therapy (IOERT), the lack of specific planning tools limits its applicability, the need for accurate dosimetry estimation and application during the therapy being the most critical. Recently, some works have been presented that try to overcome some of the limitations for establishing planning tools, though still an accurate guidance system that tracks, in real-time, the applicator and the patient is needed. In these surgical environments, the acquisition of an accurate 3D shape of the patient’s tumor bed in real-time is of high interest, as current systems make use of a 3D model acquired before the treatment. In this paper, an optical-based system is pre…

Étude d'un système de stéréo-vision hybride

2013

National audience; On considère dans ce travail un système de vision hybride fixe composé d'une caméra fisheye et d'une caméra PTZ dans un environnement rigide. Nous souhaitons être en mesure d'orienter la caméra mécanisée sur une cible visible depuis l'image omnidirectionnelle de manière à obtenir une image de bonne définition de l'objet d'intérêt à partir de la caméra PTZ. Nous proposons dans cet article d'utiliser la modélisation sphérique des images ainsi que les propriétés de la géométrie épipolaire afin d'initialiser la localisation de la cible dans la caméra PTZ.

Variable fractional Fourier processor: a simple implementation: erratum

1997

Une nouvelle approche de classification de personnes à partir d'une plate-forme multi-kinect

2015

International audience; Dans ce papier nous présentons un descripteur 3D original pour la classification de personnes. Nous avons réalisé une plate-forme multi-kinect qui fait l'acquisition de nuages de points complets (c'est à dire selon une vue à 360°). Un post-traitement (suppression d'arrière-plan) isole les éléments qui sont candidats à représenter une personne. Notre descripteur exploite ces données et permet, au travers d'un classifieur SVM (Support Vector Machine), de classifier les personnes et de déterminer l'orientation du plan frontal de la personne. Il utilise la répartition spatiale et l'orientation des normales aux surfaces dans un procédé dérivé de celui des HOG (Histogram o…

Model selection using limiting distributions of second-order blind source separation algorithms

2015

Signals, recorded over time, are often observed as mixtures of multiple source signals. To extract relevant information from such measurements one needs to determine the mixing coefficients. In case of weakly stationary time series with uncorrelated source signals, this separation can be achieved by jointly diagonalizing sample autocovariances at different lags, and several algorithms address this task. Often the mixing estimates contain close-to-zero entries and one wants to decide whether the corresponding source signals have a relevant impact on the observations or not. To address this question of model selection we consider the recently published second-order blind identification proced…

Gear classification and fault detection using a diffusion map framework

2015

This article proposes a system health monitoring approach that detects abnormal behavior of machines. Diffusion map is used to reduce the dimensionality of training data, which facilitates the classification of newly arriving measurements. The new measurements are handled with Nyström extension. The method is trained and tested with real gear monitoring data from several windmill parks. A machine health index is proposed, showing that data recordings can be classified as working or failing using dimensionality reduction and warning levels in the low dimensional space. The proposed approach can be used with any system that produces high-dimensional measurement data. peerReviewed

Automatic dynamic texture segmentation using local descriptors and optical flow

2012

A dynamic texture (DT) is an extension of the texture to the temporal domain. How to segment a DT is a challenging problem. In this paper, we address the problem of segmenting a DT into disjoint regions. A DT might be different from its spatial mode (i.e., appearance) and/or temporal mode (i.e., motion field). To this end, we develop a framework based on the appearance and motion modes. For the appearance mode, we use a new local spatial texture descriptor to describe the spatial mode of the DT; for the motion mode, we use the optical flow and the local temporal texture descriptor to represent the temporal variations of the DT. In addition, for the optical flow, we use the histogram of orie…