Statistical evaluation method to determine the laser welding depth by optical coherence tomography

A statistical filtering method to determine the depth of laser-welded seams from signals recorded by means of optical coherence tomography (OCT) is proposed and discussed. The measured data points are initially classified into noise and significant data by means of a noise probability, which was defined based on the normalized Poisson distribution. A percentile filter is then applied to the significant data to obtain the depth of the weld seam. It is shown that the depth determined by this approach corresponds to the real seam depth, as obtained from longitudinal sections, to within an average error of less than 5%. The method can be applied to different laser welding situations without having to adjust the filter parameters.