ROR: Rejection of Outliers by Rotations in Stereo Matching

Abstract

We address the problem of rejecting false matches of points between two perspective views. Even the best algorithms for image matching make some mistakes and output some false matches. We present an algorithm for identification of the false matches between the views. The algorithm exploits the possibility of rotating one of the images to achieve some common behaviour of the correct matches. Those matches that deviate from this common behaviour turn out to be false matches. The statistical tool we use is the mean shift mode estimator. Our algorithm does not use in any way the image characteristics of the matched features. In particular it avoids problems that cause the false matches in the first place. The algorithm may be run as a post processing step on output from any point matching algorithm. Use of the algorithm may significantly improve the ratio of correct matches to incorrect matches. On real images our algorithm has improved the percentage of correct matches from an initial 20%-30% to a final 70%-80%. For robust estimation algorithms which are later employed, this is a very desirable quality since it reduces significantly their computational cost. We present the algorithm, identify the conditions under which it works, and present results of testing it on both synthetic and real images.