AbstractIn this review paper, conventional non-destructive testing (NDT) methods are briefly introduced and compared with selected examples for applications of optical coherence tomography (OCT) for NDT. The contactless, non-destructive and purely optical method enables multi-dimensional imaging for tomographic real-time evaluation in various fields of application. Depending on the material, penetration depths of several millimeters can be achieved, thus providing an attractive solution that can be used both as a stand-alone and as a process-integrated solution.

Surface laser structuring of electrical steel sheets can be used to manipulate their magnetic properties, such as energy losses and contribute to a more efficient use. This requires a technology such as low coherence interferometry, which makes it possible to be coupled directly into the existing beam path of the process laser and enables the possibility for an 100% inspection during the process. It opens the possibility of measuring directly in the machine, without removing the workpiece, as well as during the machining process. One of the biggest challenges in integrating an LCI measurement system into an existing machine is the need to use a different wavelength than the one for which the optical components were designed. This results in an offset between the measurement and processing spot. By integrating an additional scanning system exclusively for the measuring beam and developing a compensation model for the non-linear spot offset, this can be adaptively corrected by up to 98.9% so that the ablation point can be measured. The simulation model can also be easily applied to other systems with different components and at the same time allows further options for in-line quality assurance.

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