Three-dimensional measurement of moving objects using a multiple-camera vision system

Machine vision systems utilizing lighting triangulation technique are often used for the depth measurement or profiling. The surface depth information is extracted from a 2D image and require the object in stationary form. For most of the industrial gauging applications, several measurements of a large moving object must be done simultaneously from different perspectives with high accuracy. This requires a system with multiple cameras that can provide the true 3D measurements in a world coordinate system. A unique solution based on IDAS vision system has been designed and developed for measuring large fast-moving objects with high accuracy. The vision system developed consists of three camera systems. Each camera system is calibrated to obtain the information in all three dimensions through a very detail calibration procedure using a common reference jig. Information obtained from each of the three cameras can be converted into a world coordinate system that is created during the calibration. Because of the unified coordinate system, objects can be accurately measured independent of their orientation and position. This enables the system to perform the 3D measurement of the objects moving at a high speed without the occlusion problem. The technique can be expanded to n-camera system to support the measurement of complex objects. The details of the system configuration, optics selections, calibration procedure, and the image processing algorithms will be included in this paper.