Detection of faults in laser beam welds by near-infrared camera observation

We monitor thin disk laser beam welding processes coaxially through the welding optics with a camera that is sensitive in the near-infrared (NIR) spectrum (1200…1700 nm). With this sensor we detect the thermal radiation from the process zone and we can analyze it in real-time during the welding process. From the observed features we monitor the laser weld in respect to various welding faults.

In particular, we analyze the thermal trace of the weld seam and its vicinity. For lap joints the analysis of the thermal trace enables us to detect missing fusion immediately and in real-time. This in-situ online heat flow thermography is a unique method to detect “false friends” during the welding process itself.