Rongfang He, Weibin Zhang, Guofang Gao, Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang, Sichuan 621999, China
To realize the feature recognition and defects detection of the inner surface in the fine hole with diameter under 6mm, a special optical measurement system was designed. A special optical component is employed to import the external illumination light into the fine hole and export the corresponding image. A flexible light array is introduced to suit the narrow space, and the effective field of view is analyzed. Besides, the arc surface projection error, pixel equivalent calibration error and manufacturing assembly error of the device are analyzed, then compensated or ignored if small enough. In the test of the benchmark of the simulated circle defects with the diameter φ0.1mm, φ0.2mm, 0.4mm distance distribution and the engraved line defects with the width 0.3mm, the maximum measurement error standard deviation are all about 10μm. The minimum diameter of the measured fine hole is 4mm and the depth can reach 47mm. The experimental results show that the system is feasible and available for online feature recognition and defect detection.
Visual measurement, Machine vision, Defects detection, Fine hole inspection.