This paper proposed a multi-scale measurement methodology for turbine blade, which is able to evaluate the geometrical features of turbine surface in different scales. A turbine blade measurement system is designed by using LED illuminators in this work. To ensure the efficiency and the accuracy of our system during the scale transition, a fast light source calibration method is introduced with a special designed calibration target, where with only one camera snapshot, the position and the orientation of a LED can be calibrated precisely and simultaneously. A surface reconstruction algorithm via iteration is improved by analyzing the LED radiant intensity distribution. The simulation is carried out with a synthetic hyperboloid structure, where the root mean square error (RMSE) of rebuilding is lower than 1.7 µm, and the mean angular error(MAE) of normal estimation is 0.5°. System calibration is performed by using a USAF 1951 calibration target with 3 different scales with the minimum deviation below 4 µm. Experiments are implemented on the concave and the tenon of a turbine blade from civil aero engine, where the profile, the size of the cooling hole and the roughness are retrieved successfully in different scales, which shows the great potential of the proposed methodology in blade inspection applications.

本文提出了一种涡轮叶片的多尺度测量方法，能够在不同尺度上评估涡轮表面的几何特征。在这项工作中使用LED照明器设计了涡轮叶片测量系统。为确保系统在尺度转换过程中的效率和准确性，引入了快速光源校准方法和特殊设计的校准目标，只需一个相机快照，即可精确校准LED的位置和方向同时。通过分析LED辐射强度分布改进了通过迭代的表面重建算法。模拟采用合成双曲面结构进行，其中重建的均方根误差 (RMSE) 低于 1.7 µm，法线估计的平均角度误差（MAE）为 0.5°。系统校准是通过使用具有 3 个不同刻度且最小偏差低于 4 µm 的 USAF 1951 校准目标来执行的。在民用航空发动机涡轮叶片的凹面和榫头上进行了实验，在不同尺度上成功地获取了轮廓、冷却孔尺寸和粗糙度，这表明所提出的方法在叶片检测中的巨大潜力应用程序。