Advantages of coaxial external illumination for monitoring and control of laser materials processing

Due to high demands on quality assurance and the necessity of permanent documentation of product quality forced by ISO 9000 and in-house regulations, the need for reliable online process control systems increases. State-of-the-art sensor systems for process monitoring analyze electromagnetic radiation out of the process zone. This paper reports on advantages using a different observation method. By an additional diode laser beam coaxial to the working laser the material surface is being illuminated; the reflected light is observed likewise coaxial by a CMOS camera. This setup offers new observation possibilities for research and process control.