Shape from Stereo Using Fine Correlation: Method and Error Analysis

We are considering the problem of recovering the three-dimensional geometry of a scene from binocular stereo disparity. Once a dense disparity map has been computed from a stereo pair of images, one often needs to calculate some local differential properties of the corresponding 3-D surface such as orientation or curvatures. The usual approach is to build a 3-D reconstruction of the surface(s) from which all shape properties will then be derived without ever going back to the original images. In this paper, we depart from this paradigm and propose to use the images directly to compute the shape properties. We thus propose a new method, called \emph{fine correlation}, extending the classical correlation method to estimate accurately both the disparity and its derivatives directly from the image data. We then relate those derivatives to differential properties of the surface such as orientation and curvatures. We present the results of the reconstruction and of the estimation of the surface orientation and curvatures on some stereo pairs of real images. The performance and accuracy of both classical and fine correlation are analysed using synthetic images. By modeling the correlation error distribution as a mixture of Gaussian, we can compute the intrinsic accuracy of each method and the proportion of false matches, depending on the local disparity slope. The results show that the accuracy is almost constant with respect to slope using fine correlation, whereas it increases dramatically using classical correlation

Técnicas de visión estereoscópica para determinar la estructura tridimensional de la escena

En este trabajo se realiza un estudio sobre la efectividad de una serie de métodos de correspondencia estereoscópica. La correspondencia estereoscópica constituye uno de los pasos esenciales dentro de la visión estereoscópica en los sistemas robotizados, de ahí su importancia. El objetivo se centra en el estudio de la viabilidad de los mismos de cara a su implementación en sistemas estereoscópicos que han de operar en entornos de exterior y bajo condiciones del entorno adversas. La motivación del trabajo proviene de la necesidad derivada de una serie de proyectos de investigación dentro de las actividades del grupo ISCAR. En este trabajo se han realizado diversas pruebas experimentales orientadas a la identificación de los métodos más prometedores en el ámbito de la correspondencia estereoscópica con la finalidad indicada. Se han estudiado varias técnicas existentes en la literatura y se han establecido las pautas a seguir en el futuro a tenor de los resultados obtenidos para su implementación en sistemas reales. [ABSTRACT] In this work we have studied several stereovision matching approaches with the aim of testing its effectiveness. The main step in robotized systems, equipped with stereovision, is the correspondence, here is its relevance. The goal of this work is focused on the study of the viability of such methods with the aim that they can be implemented in stereoscopic vision-based systems working in adverse outdoor environmental conditions. This work is motivated because the ISCAR group is currently working in several research projects where the stereovision is a crucial system. In this work several experimental tests have been carried out oriented toward the identification of the most promising correspondence methods with the above expressed goal. Several existing approaches in the literature have been studied and, as a result, some guidelines have been established based on the results reported, so that the research is oriented toward future implementations in real systems