1. A defect detection system for identifying defects in weld seams comprising: a scanning apparatus which is fitted to a movement apparatus of a processing device, with the scanning apparatus being moveable by the movement apparatus over at least one weld seam to be examined, wherein the scanning apparatus scanning the weld seam at a predeterminable frequency, each scan being correlated with a time signal, with the time of the scanning of at least one defect location being recorded with the time signal; an analysis module for determining the coordinates of the defect locations from the scan signals obtained by the scans, the analysis module storing the coordinates of the defect locations; and a localization module for determining a distance between the defect locations along the weld seam by evaluation of a velocity profile of the movement apparatus during the scans, of the time signals associated with the defect locations, and of the coordinates of the defect locations produced by the analysis module.