Product Code: ICA10_101

Online Focus Shift Measurement in High Power Fiber Laser Welding
Authors:
Daniel Reitemeyer, BIAS - Bremer Institut fuer angewandte Strahltechnik GmbH; Bremen Germany
Thomas Seefeld, BIAS - Bremer Institut fuer angewandte Strahltechnik GmbH; Bremen Germany
Frank Vollertsen, BIAS - Bremer Institut fuer angewandte Strahltechnik GmbH; Bremen Germany
Presented at ICALEO 2010

The occurrence of focus shift in high power fiber laser welding has been reported. The small percentage of laser light absorbed in the optical elements of the welding head leads to a thermal focus shift. Contaminations on the optical surfaces are enhancing the absorption and thus the focus shift. So, one of the main influencing on focus shift factors is the condition of the optics of the head. The topic of this paper is the development of a novel method to measure the shift of the focal plane during processing. This method allows considering the shift caused by every optical element within the path of the beam. The online focus shift measurement is the missing part for a closed loop focus shift control during high power fiber laser welding.