The measurement techniques for angular 3-D pinholes based on capacitive probe

Based on the measurement progress of straight through pinholes, the measuring for angular is challenging because the probe is inconvenient to stretch into the pinhole exactly. In the paper, an adjustable five-dimensional system, which is mainly composed of a three-coordinate measuring machine (CMM), a turntable, a visual sensor and a capacitive probe, is employed to accomplish the measurement for a circular workpiece with angular multi-pinholes. The CMM traces the coordinates while the capacitive probe moves, a precise turntable turns the workpiece at desired angle to guarantee the pinhole and the probe in the same orientation. A binocular visual sensor and a capacitive probe is for alignment and measuring, respectively. A comprehensive algorithm of combining projection and the least-squares fitting is put forward for fitting spatial axis equation of 3-D pinholes. Finally, a reliable and entire measurement system is set up and the optimal equation of the spatial axis is obtained.