This paper deals with 3-D object reconstruction using a structured light system (SLS). The SLS is composed of a camera and a laser projector that illuminates spots on the scene of interest. The basic problem of such a system is the correspondence problem. If the correct correspondence between the imaged spots and the projected laser rays is found, the 3-D coordinates of the physical points associated with these spots can be calculated. We propose a method that automatically provides SLS configurations (i.e., the relative positions of both camera and laser projector with respect to the object to be analyzed) that allow performing an unambiguous and direct correspondence procedure. Experimental results are presented that show the validity and the effectiveness of the proposed method.
KEYWORDS: Motion estimation, 3D image processing, 3D modeling, 3D acquisition, 3D image reconstruction, Cameras, Genetic algorithms, Image processing, 3D metrology, Binary data
This paper proposes a method for estimating the three-dimensional (3D) rigid motion parameters from an image sequence of a moving object. The 3D surface measurement is achieved using an active stereovision system composed of a camera and a light projector, which illuminates the objects to be analyzed by a pyramid-shaped laser beam. By associating the laser rays with the spots in the two-dimensional image, the 3D points corresponding to these spots are reconstructed. Each image of the sequence provides a set of 3D points, which is modeled by a B-spline surface. Therefore, estimating the 3D motion between two images of the sequence boils down to matching two B-spline surfaces. We consider the matching environment as an optimization problem and find an optimal solution using genetic algorithms. A chromosome is encoded by concatenating seven binary coded parameters, the angle, and the three components of the rotation vector axis, and the three translation vector components. We have defined an original fitness function for calculating the similarity measure between two surfaces. Experimental results with real and synthetic image sequences are presented to show the effectiveness and the robustness of the method.
KEYWORDS: 3D image processing, Motion estimation, 3D modeling, 3D image reconstruction, 3D acquisition, Genetic algorithms, Cameras, 3D metrology, Projection systems, Imaging systems
This paper proposes a method for estimating 3D rigid motion parameters from an image sequence of a moving object. The 3D surface measurement is achieved using an active stereovision system composed of a camera and a light projector, which illuminates objects to be analyzed by a pyramid-shaped laser beam. By associating the laser rays and the spots in the 2D image, the 3D points corresponding to these spots are reconstructed. Each image of the sequence provides a set of 3D points, which is modeled by a B-spline surface. Therefore, estimating the motion between two images of the sequence boils down to matching two B-spline surfaces. We consider the matching environment as an optimization problem and find the optimal solution using Genetic Algorithms. A chromosome is encoded by concatenating six binary coded parameters, the three angles of rotation and the x-axis, y-axis and z-axis translations. We have defined an original fitness function to calculate the similarity measure between two surfaces. The matching process is performed iteratively: the number of points to be matched grows as the process advances and results are refined until convergence. Experimental results with a real image sequence are presented to show the effectiveness of the method.
This paper deals with the estimation of a dense displacement vector field between two successive images in a sequence using the markovian modelization. The optical flow is processed in two different hierarchical frameworks with the regularized constraint model we proposed. This model is derived from the potential function introduced by Geman and MacClure, in which we integrate the local motion amplitude obtained by Fourier analysis. It enables adaptive smoothness and then preserves motions discontinuities. First we apply a coarse-to-fine strategy in a standard multiresolution pyramid. We use the ICM algorithm only on the finest resolution scale of the pyramid, and the simulated annealing on the other scales. Secondly, we work with the multiscale scheme which allows only one resolution for the observations and a pyramidal structure for the primitives (the estimated optical flow). The results obtained on synthetic and real images sequences show that the estimation is efficiency increased. In our second contribution in this paper, we define a criterion for the determination of the regularization hyperparameter which controls the weight of the regularization term in the energy function. It is based on the entropy of the estimated motion vectors. An experimental study of this entropy allows to find the value of the hyperparameter which best fits a given sequence.
This paper presents a fast approach to the problem of velocity field estimation with Markov random fields. First, we propose to estimate the unknown velocity field by using a joint Markov random field through a convex markovian model which is called the energy function. Secondly, the estimated velocity field is determined explicitly by calculating the minimum of this energy function. The result obtained are compared in terms of CPU time and estimation quality to those obtained with the ICM.
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