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High-resolution, high-speed inline optical topography measurement system for laser micro-machining process control

 
: Folkersma, K.G.P.; Woldering, L.A.; Voss, K.H.J.; Pohl, R.; Resink, S.G.; Kunze, Rouwen; Schmitt, Robert; Klein, M.E.; Borreman, A.; de Hoon, C.J.A.

European Society for Precision Engineering and Nanotechnology -EUSPEN-:
17th International Conference & Exhibition of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2017 : 29th May – 2nd June 2017, Hannover, Germany
Bedford: Euspen, 2017
ISBN: 978-0-9957751-0-7
S.417-418
European Society for Precision Engineering and Nanotechnology (EUSPEN International Conference & Exhibition) <17, 2017, Hannover>
European Commission EC
H2020; 637045; ADALAM
Sensor based adaptive laser micromachining using ultrashort pulse lasers for zero-failure manufacturing
Englisch
Konferenzbeitrag
Fraunhofer IPT ()
topography measurement; laser micro-machining; FD-OCT; FD-LCI; optical coherence tomography; low-coherence interferometry

Abstract
An in situ topography measurement system for monitoring and controlling laser micromachining processes is presented in this paper. A frequency-domain low-coherence interferometry (FD-LCI) system is used to generate high-resolution, high-speed topographic data that will enable an automatically adaptive micro-machining process with increased machining precision. To provide the topographic data directly in machine coordinates, the measurement beam has to be co-axial with the ultra-short pulse machining laser (wavelength 515 nm). A camera sensor-based module was developed to measure offset and angle between both beams, which can be corrected by fine-adjustment of the measurement beam. The reflectivity of the workpiece can vary over a very wide range. To maintain an optimal strength of the interferometry signal while scanning the workpiece surface, the feedback light power from the reference path is adapted with a high-speed beam shutter, such that it always matches the return light levels from the measurement path. Preliminary tests indicate that the FD-OCT system can provide topographic measurement points at varying rates of up to 20 kHz, with a depth measurement range of zrange = 1 mm and a depth resolution better than 4 μm.

: http://publica.fraunhofer.de/dokumente/N-487613.html