We describe the development of a real-time nonintrusive monitor to detect degradation of a gas shield condition during laser welding by use of on-axis spectrally resolved detection of light emitted from the workpiece. Failure of gas shielding to the point at which there is a risk of contamination from the air is revealed by the marked increase in the intensity of a spectral feature around 426 nm. To avoid unwanted sensitivity to the overall intensity of the radiation, the intensity at 426 nm is normalized by that at 835 nm, where the spectrum is insensitive to gas shielding. We collected the radiation by using the same optics as are used to deliver the processing beam, and thus the detection process is entirely nonintrusive. We demonstrate successful operation for welding stainless steel and titanium under both helium and argon gas shielding.
© 2001 Optical Society of America
Original Manuscript: February 6, 2001
Revised Manuscript: July 18, 2001
Published: December 20, 2001
Mahlen D. T. Fox, Chris Peters, Ian J. Blewett, Duncan P. Hand, and Julian D. C. Jones, "Real-time, nonintrusive oxidation detection system for the welding of reactive aerospace materials," Appl. Opt. 40, 6606-6610 (2001)