Guillaume Caron

Direct model based visual tracking and pose estimation using mutual information

This paper deals with model-based pose estimation (or camera localization). We propose a direct approach that takes into account the image as a whole. For this, we consider a similarity measure, the mutual information. Mutual information is a measure of the quantity of information shared by two signals (or two images in our case). Exploiting this measure allows our method to deal with different image modalities (real and synthetic). Furthermore, it handles occlusions and illumination changes. Results with synthetic (benchmark) and real image sequences, with static or mobile camera, demonstrate the robustness of the method and its ability to produce stable and precise pose estimations.

Photometric visual servoing for omnidirectional cameras

Abstract2D visual servoing consists in using data provided by a vision sensor for controlling the motions of a dynamic system. Most of visual servoing approaches has relied on the geometric features that have to be tracked and matched in the image acquired by the camera. Recent works have highlighted the interest of taking into account the photometric information of the entire image. This approach was tackled with images of perspective cameras. We propose, in this paper, to extend this technique to central cameras. This generalization allows to apply this kind of method to catadioptric cameras and wide field of view cameras. Several experiments have been successfully done with a fisheye camera in order to control a 6 degrees of freedom robot and with a catadioptric camera for a mobile robot navigation task.

3D model based pose estimation for omnidirectional stereovision

Robot vision has a lot to win as well with wide field of view induced by catadioptric cameras as with redundancy brought by stereovision. Merging these two characteristics in a single sensor is obtained by combining a single camera and multiple mirrors. This paper proposes a 3D model tracking algorithm that allows a robust tracking of 3D objects using stereo catadioptric images given by this sensor. The presented work relies on an adapted virtual visual servoing approach, a non-linear pose computation technique. The model take into account central projection and multiple mirrors. Results show robustness in illumination changes, mistracking and even higher robustness with four mirrors than with two.

Multiple camera types simultaneous stereo calibration

Calibration is a classical issue in computer vision needed to retrieve 3D information from image measurements. This work presents a calibration approach for hybrid stereo rig involving multiple central camera types (perspective, fisheye, catadioptric). The paper extends the method of monocular perspective camera calibration using virtual visual servoing. The simultaneous intrinsic and extrinsic calibration of central cameras rig, using different models for each camera, is developed. The presented approach is suitable for the calibration of rigs composed by N cameras modelled by N different models. Calibration results, compared with state of the art approaches, and a 3D plane estimation application, allowed by the calibration, show the effectiveness of the approach. A cross-platform software implementing this method is available1.

Tracking planes in omnidirectional stereovision

Omnidirectional cameras allow direct tracking and motion estimation of planar regions in images during a long period of time. However, using only one camera leads to plane and trajectory reconstruction up to a scale factor. We propose to develop dense plane tracking based on omnidirectional stereovision to answer this issue. The presented method estimates simultaneously the parameters of several 3D planes along with the camera motion in a spherical model formulation. Results show the efficiency of the approach.

Vertical line matching for omnidirectional stereovision images

We are investigating the mobile robot indoor localization and environment mapping using an omnidirectional stereovision sensor. It uses four parabolic mirrors and an orthographic camera, giving four images of the same scene. At least, only two mirrors are needed. Using four mirrors gives redundancy. We propose to exploit the images of vertical lines. This paper presents a new method in order to match these lines in the four images. Contrary to existing approaches, we took into account the four sub-images existence in the design of this method, in order to exploit redundancy. This brought an original algorithm combining matching and pose estimation of vertical lines from the 3D environment. Experimental results will be presented to validate this approach.

A Serious Game for 3D cultural heritage

The research of this paper focuses on a context of cultural heritage through the use of Serious Games. It presents 3D serious game, dedicated to cultural heritage including a first prototype of a Tangible User Interface. This Serious Game focuses on the Gothic cathedral of Amiens in France, in the context of the e-cathedral research program that faces the preservation challenge.

A serious game for 3D cultural heritage digital world

The research of this paper focuses on a context of cultural heritage through the use of Serious Games. It presents 3D serious game, dedicated to cultural heritage including a first prototype of a Tangible User Interface. This Serious Game focuses on the Gothic cathedral of Amiens in France, in the context of the e-cathedral research program that faces the preservation challenge.

Single viewpoint stereoscopic sensor calibration

Calibration is a classical issue in computer vision. This work presents a camera calibration approach for single viewpoint cameras which can be modeled by the unified spherical projection. The paper extends the method of perspective camera calibration using virtual visual servoing, to central cameras and particularly to omnidirectional cameras. The contribution is the development of simultaneous intrinsic and extrinsic calibration of N central cameras stereo rig.

Omnidirectional photometric visual servoing

Visual servoing has been based on geometric features for a long time. Recent works have highlighted the interest of taking into account the photometric information of the entire image. This approach was tackled with images of perspective cameras. We propose, in this paper, to adapt this technique to central cameras. This generalization allows to apply this kind of method to wide field of view cameras. We also propose to adapt gradient computation to take into account distorsions of such cameras. Several experiments have been successfully done with a fisheye camera.