Application of Thin Plate Splines for Surface Reverse Engineering and Compensation for Femtosecond Laser Micromachining

The femtosecond laser micromachining (FLM) systems could potentially be used for the rapid prototyping of microstructures on the surface of a workpiece. However, surface scale characteristics or workpiece holding fixtures could introduce position and orientation errors of the workpiece surface. These errors must be accounted and compensated for during FLM such that the focused laser spot position is known in the coordinates of the measured and not of an ideal surface thus assuring the desired machining results. In this manuscript, an algorithm for offline surface topography reconstruction from measured scattered control points is introduced. The target machining points are interpolated by thin-plate splines (TPS), an approach based on minimizing a roughness cost function. The reverse engineered surface could then be interfaced and used with a CAD/CAM system such that the focal spot is fully compensated for based on the measured wafer surface