Hybrid linear compensation and improved Hermite interpolation for optical measurement of 3D airfoil surface

Non-contact optical measurement systems such as laser scanner have been widely used to measure 3D profiles. In the case of measuring a polished turbine airfoil, however, specular reflection on the surface causes "non-measurable" gaps in each optical scan. Conventional techniques like linear interpolation and spline interpolation become ineffective in reconstructing the surface from such "corrupted" measurement data sets. This work develops a hybrid technique that combines piecewise cubic Hermite interpolation with linear compensation. The technique preserves the shape well, and generates smooth curvature in the specular reflection gap. In comparison with spline interpolation, it achieves better and more accurate profile fitting.