Theoretical and experimental investigation of precise and dynamic beam shaping for laser materials processing
Production Automation and Assembly Technology
Final Report Abstract
Laser material processing is established in industry due to its non-contact and precise control. For higher feed speeds and quality, the beam shape of the laser must be adapted to the application in order to achieve optimum processing results. However, technologies for the dynamic change of beam shapes often have design deficits such as low damage thresholds and design algorithms do not yet allow real-time adaptation. The overall goal of the project is the realization of a precise and dynamic laser beam shaping with subsequent amplification. The first goal of this project is to reduce the pixel crosstalk effect (acts like a high-pass filter on beam manipulation) when using LCoS beam shaping elements. Liquid-Crystal-on-Silicon (LCoS) is a pixel-based beam shaping technology, which allows the beam profile to be adjusted with high spatial and temporal resolution. Overall, the flatter the gradients in the phase masks used (local adaptation of the phase of the electric field), the lower the influence of the crosstalk. This can be achieved by avoiding lenses or shaping the beam outside the focal plane. Furthermore, it has been possible to train an artificial neural network (NN) that generates phase masks for different intensity distributions and reduces the calculation time of phase masks by over 40% compared to the iterative wave propagation algorithm (IWPA) developed in the previous project and further developed in this project. However, the quality of the generated phase masks is lower than that of iterative algorithms such as IWPA. The third objective involves the coupling of IWPA and an algorithm to solve the inverse heat conduction problem so that a temperature distribution can be used as a target for the generation of phase masks and the deviation from the target temperature distribution can be reduced by over 40%. The decisive factor here is that minimizing the deviation from the target intensity distribution does not simultaneously lead to a minimization of the deviation from the target temperature distribution. The fourth objective, from the previous project, involves beam shaping with subsequent amplification. Through rigorous modelling, it is possible to consider an amplifier in the design of phase masks and thus experimentally demonstrate an amplification factor of 1.3.
Publications
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Verfahren zur Einstellung und/oder dynamischen Anpassung der Leistungsdichteverteilung von Laserstrahlung (DE 10 2020 134 416), erteilt (2020)
O. Hofmann & G. König
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Application of machine learning to overcome challenges of generating phase masks for dynamic beam shaping in complex optical systems. High-Power Laser Materials Processing: Applications, Diagnostics, and Systems XII, 28. SPIE.
Kurth, Robin; Hofmann, Oskar; Stollenwerk, Jochen & Holly, Carlo
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Hochdynamische Multistrahl- und Strahlformungssysteme für die Werkstoffbearbeitung mit Laserstrahlung, Dissertation, RWTH Aachen University
Hofmann, O.
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Kompensation von Dezentrierung und Rotation bei der Vermessung von mittels SLM erzeugten Intensitätsverteilungen. Deutsche Gesellschaft für angewandte Optik (DGaO), Erlangen
Kurth, R.
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Iterative algorithm for the generation of phase masks for spatial laser beam shaping in arbitrary optical systems. International Optical Design Conference 2023, 58. SPIE.
Hofmann, Oskar; Stollenwerk, Jochen & Holly, Carlo
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Modellbasierte Strahlformung mittels diffraktiver optischer Elemente für die Lasermaterialbearbeitung, Erlangen Ausgabe 2024.
Kurth, R.; Hofmann, O. & Colak, Y.
