Guiding 3D coordinate measurement with an integrated video camera

An experimental measurement system for dimensional quality control is described in which laser radar based 3D coordinate measurements are guided to given points using information from video imagery. The system is controlled by a measurement model file that contains the measurement program and the nominal data of the interesting features in the target object. Because the real world objects differ from the nominal model due to, e.g., changes in their shape, dimensions and position, the measurement system must be adaptive. This adaptivity is provided by using video imagery for guiding the 3D coordinate measurements to the position indicated in the measurement program. At the moment the system is capable of finding points that are marked with circular tags and guiding the laser range finder beam into these points. The linearity and repeatability of the image analysis based feature finding system is better than 0.5 mm at 11 m. Tag finding in a 512 by 574 image takes ca. 2.5 second using a low cost frame grabber and a PC.