Inline surface topography measurements of ultrashort laser pulsed manufactured micro structures based on low coherence interferometry

In view of ever-increasing demands on process accuracies and increasingly narrow tolerance windows in laser micro structuring, the monitoring of laser processes and the subsequent quality assurance of the laser-structured products are becoming more and more important. Functional surface structures to be manufactured by laser micro structuring are nowadays in the range of 50 μm down to 10 μm regarding their surface geometries. To cover this demand, this paper deals with the development of a holistic approach to scanner-based, coaxial topography measurement by the integration of a highly accurate inline measuring system into the existing optics of a laser micro machining system. The combination and implementation of the laser processing beam and the measuring beam by the same optics is intended to open up the possibilities of real-time process feedback of the measurement data for the realization of an adaptively controlled laser micro structuring process. Therefore, the influence of the individual system components of the laser beam path on the measurement beam and induced optical aberrations gets evaluated and explained. Resulting from this, solutions for improving the system against these aberrations are developed and evaluated in a demonstrator setup, implementing the measurement system coaxially into a laser micro machining beam path.