Showing papers by "Nicholas Ayache published in 1988"
TL;DR: It is shown how visual maps corresponding to different positions of the robot can be registered to compute a better estimate of its displacement between the various viewpoint positions, as suming an otherwise static environment.
Abstract: This paper deals with the problem of building three-dimen sional descriptions (we call them visual maps) of the environ ment of a mobile robot using passive vision. These maps are local (i.e., attached to specific frames of reference). Since noise is present, they incorporate information about the ge ometry of the environment and about the uncertainty of the parameters defining the geometry. This geometric uncertainty is directly related to its source (i.e., sensor uncertainty). We show how visual maps corresponding to different positions of the robot can be registered to compute a better estimate of its displacement between the various viewpoint positions, as suming an otherwise static environment. We use these esti mates to fuse the different visual maps and reduce locally the uncertainty of the geometric primitives which have found correspondents in other maps. We propose to perform these three tasks (building, registrating, and fusing visual maps) within the general framework of extended Kalman filter...
215 citations
Proceedings Article•
01 May 1988
TL;DR: In this paper, the authors present a tool called Extended Kalman Filter (EKF) for the problem of building and updating 3D representations of the environment of a mobile robot using passive vision as its main sensory modality.
Abstract: A description is given of current ideas related to the problem of building and updating three-dimensional representations of the environment of a mobile robot that uses passive vision as its main sensory modality. The authors attempt to represent both geometry and uncertainty. The authors motivate their approach by defining the problems they are trying to solve and then give some simple didactic examples. They then present a tool they think is extremely well adapted to solving most of these problems: the extended Kalman filter (EKF). The authors discuss the notions of minimal geometric representations for three-dimensional lines, planes, and rigid motions. They show how the EKF and the representations can be combined to provide solutions for some of the problems. A number of experimental results on real data are given. >
199 citations
14 Nov 1988
TL;DR: A technique is presented for calibrating and rectifying in a very efficient and simple manner pairs or triplets of images taken for binocular or trinocular stereovision systems, allowing for simpler and more efficient matching algorithms.
Abstract: A technique is presented for calibrating and rectifying in a very efficient and simple manner pairs or triplets of images taken for binocular or trinocular stereovision systems. After the rectification of images, epipolar lines are parallel to the axes of the image coordinate frames. Therefore, potential matches between two or three images satisfy simpler relations, allowing for simpler and more efficient matching algorithms. Experimental results obtained with a binocular and a trinocular stereovision system are presented, and a complexity analysis is provided. >
189 citations
05 Dec 1988
TL;DR: An innovative method for the reconstruction of 3-D seginents which provides better results and a new validation technique based on the observation that neighbors in the image should be neighbors in space are developed.
Abstract: We present recent advancements in our passive trinocular stereo system. These include a technique for calibrating and rectifying in a very eficient and simple manner the triplets of images taken for trinocular stereovision systerns. After the rectification of images, epipolar lines are parallel to the axes of the image coordinate frames. Therefore, potential matches between the three images satisfy simpler relations, allowing for a less complicated and more efficient matching algorithm. We also describe a more robust and general control strategy now employed in our trinocular stereo system. We have also developed an innovative method for the reconstruction of 3-D seginents which provides better results and a new validation technique based on the observation that neighbors in the image should be neighbors in space. Experiments are presented demonstrating these advancements. 2 Rectification of the images
19 citations
14 Nov 1988
TL;DR: The technique proposed is based on matching 3-D tokens computed from stereo at different time instants based on the standard paradigm of hypothesis prediction and testing and exploits the constraint that objects and environment are rigid.
Abstract: The following problem is addressed: given a stereo rig moving in an unknown environment where an arbitrary number of rigid mobile objects might be present, it is required to segment the various mobile objects from the background and determine the motions of the stereo rig and of the mobile objects. The technique proposed is based on matching 3-D tokens computed from stereo at different time instants. The matching uses the standard paradigm of hypothesis prediction and testing and exploits the constraint that objects and environment are rigid. The uncertainty about the position and velocity of the tokens is explicitly taken into account in the matching process through an extended Kalman filter. Preliminary results are presented. >
14 citations