<title>Location of focus of expansion from edges in an epipolar image of a scene</title>

Abstract

One of the tasks of a navigation autonoumous vision system is to determine his motion from the environment in a sequence of images. This information can be obtained from the focus of expansion (FOE) or the focus of contraction (FOC) due to the translational egomotion. We propose a simple method which allows to extract the FOE (or FOC) from time varying images. This algorithm uses neither the computation of the optical flow, nor image features tracking. It is based on a simplified Hough transform processing which is applied to the horizontal and vertical edges of the epipolar image captured by a translating camera, the optical axis of which is near from the motion direction. The epipolar image is obtained by a recursive operation between two images of a no dense sequence of a structuring or weakly structuring scene. This image stores the trajectory of the horizontal and vertical segments of the scene objects, because these edges have the particularity to have a size which linearly decreases until they are going out near the FOE. Then, by a simple analysis of the HOugh space in the horizontal and vertical direction, we deduce the FOE location. The FOE (or FOC) coordinate correspond to the Hough histogram minima. This methods can be implemented in hardware by a parallel pipelined image processing system.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.