Laser marking of a laminated surface characterized by an optodynamic method

Marking plain surfaces using laser ablation is widely used in a serial production. However, during a laser marking of small laminated surfaces, a problem arises as a consequence of the gaps between the laminations; this tends to decrease the efficiency of the process. Therefore, a real-time measuring method that can be implemented in an industrial system for laser processing is required. In this contribution, we describe an optodynamic method for the on-line characterization of pulsed-laser marking of a laminated surface. The processing-laser beam generates an optodynamic response, i.e., the shock waves, which then spread into the surrounding gas. By using a laser-beam-deflection probe, the analysis of the obtained signals indirectly enables the real-time monitoring of the surface structure. Evaluation of the results obtained by our on-line measuring method is made by two techniques: non-destructive microscopy with extended depth of field and destructive cross-section measurements with optical microscopy. The performed experiments demonstrate that the established experimental system can simultaneously detect the changes in the laser-marking process. Furthermore, it can provide the position and the size of a gap as well as the orientation and the inclination of the samples.