NIR-camera-based online diagnostics of laser beam welding processes

We have developed an on-axis camera-based online sensor system for laser beam welding diagnostics that detects the thermal radiation in the near-infrared (NIR) spectral range between 1200 and 1700 nm. In addition to a sensor in the visible (VIS) range, our camera detects the thermal radiation of the weld pool more clearly, and it is also sensible to the radiation of the solidified weld seam. The NIR images are analyzed by real-time image processing. Features are extracted from the images and evaluated to characterize the welding process. Keyhole and weld pool analysis complement VIS diagnostics, whereas the observation of the weld seam and heat affected zone with an NIR camera allows online heat flux thermography. By this means we are able to detect bad joints in overlap weldings (false friends) online during the welding process.