Self-calibration of turntable sequences from silhouettes

This paper addresses the problem of recovering both the intrinsic and extrinsic parameters of a camera from the silhouettes of an object in a turntable sequence. Previous silhouette-based approaches have exploited correspondences induced by epipolar tangents to estimate the image invariants under turntable motion and achieved a weak calibration of the cameras. It is known that the fundamental matrix relating any two views in a turntable sequence can be expressed explicitly in terms of the image invariants, the rotation angle, and a fixed scalar. It will be shown that the imaged circular points for the turntable plane can also be formulated in terms of the same image invariants and fixed scalar. This allows the imaged circular points to be recovered directly from the estimated image invariants, and provide constraints for the estimation of the imaged absolute conic. The camera calibration matrix can thus be recovered. A robust method for estimating the fixed scalar from image triplets is introduced, and a method for recovering the rotation angles using the estimated imaged circular points and epipoles is presented. Using the estimated camera intrinsics and extrinsics, a Euclidean reconstruction can be obtained. Experimental results on real data sequences are presented, which demonstrate the high precision achieved by the proposed method. © 2009 IEEE.published_or_final_versio

Smooth surface reconstruction and regularisation

In this paper, we address the problem of smooth surface reconstruction from image sequences obtained with known camera motion . An approach based on a local reconstruction method is presented . Previous works have shown that local shape estimation can b e achieved using the occluding contours . Several algorithms allow such a reconstruction and we present our approach . Recovered rim points are then used to compute a triangular mesh . Resulting meshes are regularised in order to correct noise perturbation s which affect the reconstruction . Experimentations on real data are shown to illustrate the whole process .Dans cet article, nous abordons le problème de la reconstruction de surface d'objets courbes à partir de séquences d'images. Nous présentons une approche basée sur une méthode de reconstruction locale. De précédents travaux ont montré qu'une reconstruction locale de la surface était possible à partir de ses contours occultants. Plusieurs algorithmes permettent une telle reconstruction et nous présentons notre approche. Les points ainsi reconstruits servent ensuite à construire un maillage triangulaire. Les maillages obtenus sont régularisés pour corriger les effets du bruit présent dansle processus de reconstruction. Des expérimentations réalisées sur des données réelles viennent illustrer l'ensemble de la méthode