3-D shape measurement of a free surface from a single image produced using multiple laser spots

By setting a refractor at an angle relative to the optical axis of a CCD camera lens, the image of a measurement point recorded on the image plane is displaced by an amount that corresponds to the distance between the camera and the measurement point. When the refractor is rotated at high speed while the camera is operating, the image of the measurement point appears as an annular streak. Since the size of the annular streak is inversely proportional to the distance between the camera and measurement point, the 3-D position of the measurement point can be obtained by extracting data from the streak. In this paper, this system is applied to measure a moving surface. To do this, multiple laser spots are projected onto the surface. The position of each laser spot reflected from the surface is measured using a circular dynamic stereo system.