Development of a high-precision surface metrology system and its uncertainty analysis

In this paper, we present a high-precision surface metrology system based on structured light projection. Gray code patterns are projected onto the object surface by a DMD projection device and a CCD camera captures the distorted pattern images. For the purpose of precision measurement, a 3D mathematical model is proposed for the system and a calibration process is developed to obtain system parameters. The surface profile can be computed based on the calibrated model. In order to acquire higher measurement resolution, we propose a correspondence matching method which combines Gray codes encoding and sub-pixel edge detection. With a line-shifting procedure, the measurement resolution is elevated four times higher. Furthermore, an uncertainty analysis is performed to evaluate the performance of the developed system. Experiment results demonstrate the system has measurement area of 12 times 9 mm² with lateral resolution about 10mum and vertical resolution about 3mum.