We report the use of backscatter sensors used to provide proactive laser safety protection as well as providing real-time process control potential in a laser welding process. Rather than use a single optical channel we have used multiple backscatter detectors each with a narrow bandwidth filter to examine the behaviour of backscatter in different spectral regions giving information concerning the state and stability of the laser process. As well as describing the stability of the laser process the backscatter also provides quantitative information concerning the absorption of the laser beam by the industrial process. Any rapid departure from this expected process condition can also be fed back to a laser safety management system to form the basis of a proactive control strategy to detect the onset of beam delivery failure and the possibility of an errant beam condition.
The proactive safety approach described here has significant technical and commercial advantages with regard to producing compact localised guarding systems which only need to provide protection from the errant laser by shutting down the process prior to the full laser beam escaping from its intended location. The protection system now need only provide protection from the laser using a time-based which is based on the shutdown response time of the sensor/management system. Here we seek to investigate the potential benefits and cost saving of the active sensing of the beam to reduce the unnecessary burden of excessive guarding as well as providing a useful laser welding process control system. Laser power sensor information defining the output at the laser aperture combined with backscatter detection from the irradiated component means that the laser safety management system is tracking the performance of the industrial process. Any significant departure from the expected outputs indicates a likely fault condition and the laser can be shut down immediately. Here we wish to define the next level of protection strategy as being proactive control stopping a hazardous situation from developing. Here we will provide results from a fibre laser welding installation using suitable multispectral backscatter detection for process control and a further laser safety management system which provides the necessary proactive laser safety control. This may have useful applications for the expanding use of handheld fibre laser processing systems which currently are proving difficult to adequately control with existing passive or active/reactive guarding strategies.