Self-calibration and motion recovery from silhouettes with two mirrors

LNCS v. 7724-7727 (pts. 1-4) entitled: Computer vision - ACCV 2012: 11th Asian Conference on Computer Vision ... 2012: revised selected papersThis paper addresses the problem of self-calibration and motion recovery from a single snapshot obtained under a setting of two mirrors. The mirrors are able to show five views of an object in one image. In this paper, the epipoles of the real and virtual cameras are firstly estimated from the intersection of the bitangent lines between corresponding images, from which we can easily derive the horizon of the camera plane. The imaged circular points and the angle between the mirrors can then be obtained from equal angles between the bitangent lines, by planar rectification. The silhouettes produced by reflections can be treated as a special circular motion sequence. With this observation, technique developed for calibrating a circular motion sequence can be exploited to simplify the calibration of a single-view two-mirror system. Different from the state-of-the-art approaches, only one snapshot is required in this work for self-calibrating a natural camera and recovering the poses of the two mirrors. This is more flexible than previous approaches which require at least two images. When more than a single image is available, each image can be calibrated independently and the problem of varying focal length does not complicate the calibration problem. After the calibration, the visual hull of the objects can be obtained from the silhouettes. Experimental results show the feasibility and the preciseness of the proposed approach. © 2013 Springer-Verlag.postprin

Hawaii Geothermal Project : environmental impact statement information meetings with Hawaii agencies on October 1991 in Hilo and Honolulu

An outline of the meeting with a cover letter.The meeting discussed the preparation of an EIS for large scale (up to 500 MW) of geothermal energy development on the island of Hawaii, and the U.S. Department of Energy served as the lead agency in preparing the EIS

Motion recovery for uncalibrated turntable sequences using silhouettes and a single point

LNCS v. 5259 is the conference proceedings of ACIVS 2008This paper addresses the problem of self-calibration and motion recovery for turntable sequences. Previous works exploited silhouette correspondences induced by epipolar tangencies to estimate the image invariants under turntable motion and recover the epipolar geometry. These approaches, however, require the camera intrinsics in order to obtain an Euclidean motion, and a dense sequence is required to provide a precise initialization of the image invariants. This paper proposes a novel approach to estimate the camera intrinsics, the image invariants and the rotation angles from a sparse turntable sequence. The silhouettes and a single point correspondence are extracted from the image sequence. The point traces out a conic in the sequence, from which the fixed entities (i.e., the image of the rotation axis, the horizon, the vanishing point of the coordinates, the circular points and a scalar) can be recovered given a simple initialization of the camera intrinsic matrix. The rotation angles are then recovered by estimating the epipoles that minimize the transfer errors of the outer epipolar tangents to the silhouettes for each pair of images. The camera intrinsics can be further refined by the above optimization. Based on a given range of the initial focal length, a robust method is proposed to give the best estimate of the camera intrinsics, the image invariants, the full camera positions and orientations, and hence a Euclidean reconstruction. Experimental results demonstrate the simplicity of this approach and the accuracy in the estimated motion and reconstruction. © 2008 Springer Berlin Heidelberg.link_to_subscribed_fulltextThe 10th International Conference on Advanced Concepts for Intelligent Vision Systems (ACIVS 2008), Juan-les-Pins, France, 20-24 October 2008. In Lecture Notes in Computer Science, 2008, v. 5259, p. 796-80

Motion Recovery for Uncalibrated Turntable Sequences Using Silhouettes and a Single Point

This paper addresses the problem of self-calibration and motion recovery for turntable sequences. Previous works exploited silhouette correspondences induced by epipolar tangencies to estimate the image invariants under turntable motion and recover the epipolar geometry. These approaches, however, require the camera intrinsics in order to obtain an Euclidean motion, and a dense sequence is required to provide a precise initialization of the image invariants. This paper proposes a novel approach to estimate the camera intrinsics, the image invariants and the rotation angles from a sparse turntable sequence. The silhouettes and a single point correspondence are extracted from the image sequence. The point traces out a conic in the sequence, from which the fixed entities (i.e., the image of the rotation axis, the horizon, the vanishing point of the coordinates, the circular points and a scalar) can be recovered given a simple initialization of the camera intrinsic matrix. The rotation angles are then recovered by estimating the epipoles that minimize the transfer errors of the outer epipolar tangents to the silhouettes for each pair of images. The camera intrinsics can be further refined by the above optimization. Based on a given range of the initial focal length, a robust method is proposed to give the best estimate of the camera intrinsics, the image invariants, the full camera positions and orientations, and hence a Euclidean reconstruction. Experimental results demonstrate the simplicity of this approach and the accuracy in the estimated motion and reconstruction