We describe a three-dimensional measurement system which can acquire not only three-dimensional shapes of target objects but also these surface reflectance parameters. The system is constructed by one or some digital cameras, digital projector, and a computer which controls
cameras and projectors. For 3-D geometrical reconstruction, we use well known gray code structured light method. The method projects gray code light patterns from the projector and obtain illuminated scenes by cameras. We add additional light patterns for surface reflectance measurement. These patterns are all white and gray light pattern. To recover complete shape of the target object, the object is measured from various viewpoints repeatedly, or measured repeatedly from fixed viewpoint while be moving by hand or turn table. To end the measurement, relative positions of each obtained range data are calculated by ICP algorithm. For each small region of the target object surface, we calculate reflectance parameters from surface normals, viewpoint (camera viewpoint), and light position (the projector viewpoint). Enough sampling of these three information
sources are obtained for each small surface, we estimate reflectance parameters for each surface points. We demonstrate this geometrical and reflectance measurement method by experiments for fewer objects.
We developed a 3D measurement system consists of a camera and a projector which can be calibrated easily at short times. In this system, the camera and the projector are calibrated in advance with Zhang's calibration method. The measurement procedure in this system is as follows. A calibrated camera and a calibrated projector are put in front of the calibration plane. Then the relative pose between the camera and the projector can be computed by projecting a number of light patterns from the projector onto the calibration plane and taking those images with the camera. And this system performs a 3D measurement with the gray code pattern projection. Since this system can be calibrated easily, this system does not need to be fixed exactly and the configuration of this system, which is the baseline and the measurement range, can be changed freely depending on the target and the purpose. This system can obtain a range data in a high accuracy of an error about 0.1% in spite of the
fact that this system can be calibrated easily.
In this research, the recognition of gesture in 3D space is examined by using serial range images obtained by a real-time 3D measurement system developed in our laboratory. Using this system, it is possible to obtain time sequences of range, intensity and color data for a moving object in real-time without assigning markers to the targets. At first, gestures are tracked in 2D space by calculating 2D flow vectors at each points using an ordinal optical flow estimation method, based on time sequences of the intensity data. Then, location of each point after 2D movement is detected on the x-y plane using thus obtained 2D flow vectors. Depth information of each point after movement is then obtained from the range data and 3D flow vectors are assigned to each point. Time sequences of thus obtained 3D flow vectors allow us to track the 3D movement of the target. So, based on time sequences of 3D flow vectors of the targets, it is possible to classify the movement of the targets using continuous DP matching technique. This tracking of 3D movement using time sequences of 3D flow vectors may be applicable for a robust gesture recognition system.
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