Multiple-sensor integration for rapid and high-precision coordinate metrology

Rapid acquisition of high-precision coordinate data from parts having complex geometry has many applications, including dimensional inspection, agile machining, and reverse engineering. Due to distinct characteristics of different coordinate digitizing sensors, a multiple-sensor integrated coordinate measurement system is developed in order to simultaneously achieve rapid and high-precision coordinate acquisition. The multiple-sensor integrated system consists of a multiple-sensor coordinate measuring machine (CMM), an information aggregation module, and a multiple-sensor planning module.; The multiple-sensor CMM is equipped with a motorized touch probe and a 3D active vision system. The 3D active vision system can simultaneously acquire thousands of data points over a large spatial range; therefore capturing the global surface information of an object in real time is possible. The 3D active vision system is composed of a CCD camera, a digital projector, and a personal computer with an image processing board. An automatic camera calibration scheme that utilizes the CMM and novel calibration algorithms is developed to perform automated and accurate camera calibration and support the sensor integration. A digital projector calibration method with a light beam model is developed to compensate projector lens distortions and to fully utilize the flexibility of the digital projector. A rigid body transformation calibration method is also developed for the digital projector such that re-calibrating all light beams is unnecessary.; The 3D active vision system along with intelligent information aggregation algorithms could provide the global surface information of the object. When only a part of the object surface is digitized, the missing information is estimated to approximate the unknown surface area. In order to extract high-level area, missing information extraction and reasoning algorithms are developed. The obtained surface information is subsequently used by the multiple-sensor planning module to locate the most informative viewpoints for the vision system, to automatically guide the touch probe for rapid surface acquisition, and to plan the next best coordinate digitizing strategy. Through the sensor integration and the developed information automation technologies, the multiple-sensor integrated coordinate measurement system is developed to perform automated, high-speed and high-precision 3D coordinate acquisition.