Precise perimeter measurement for 3D object with a light-pen vision measurement system

A novel measurement scheme for a three-dimensional (3D) object's surface boundary perimeter is proposed. This scheme consists of three steps. First, a light-pen single-camera 3D coordinate vision measurement system is devised to obtain the 3D coordinates of a detected object's 3D surface boundary. Second, a novel 3D B-spline active contour is applied to converge to the object's 3D surface boundary accurately. Finally, for the convergent active contour, its true contour length is computed as the detected object's true perimeter. An experiment on a bent surface's perimeter measurement indicates that this scheme's measurement repetition error decreases to 0.6%.