High precision x-ray stereo for automated 3-D CAD-based inspection

An important challenge in industrial metrology is to provide rapid measurement of critical three-dimensional (3-D) internal object geometry for either inspecting high volume parts or controlling a machining process. Existing metrological techniques are typically too slow to meet this need or can not measure small features with high precision. In this paper, we present a new method that achieves fast, accurate, internal 3-D geometry measurement based on 3-D reconstruction from a few X-ray views of a part. Our approach utilizes an accurate camera model for the X-ray sensor, calibration using in situ ground truth and geometry-guided X-ray feature extraction to achieve this goal and has been fully implemented in a prototype 3-D measurement system. We describe a novel application of the system to CAD-based verification of drilled hole positioning. Experimental results are given to illustrate the precision of the system and 3-D measurement on real industrial parts. Index Terms - CAD-based measurement, inspection, 3-D metrology, X-ray imaging.