Process monitoring of laser welding using chromatic filtering of thermal radiation

摘要

An innovative real-time weld monitoring technique using chromatic filtering of the thermal radiation from a weld pool is developed. The thermal radiation from the weld pool is focused onto an aperture and the transmitted thermal radiation is monitored at two wavelengths with high-speed single-element detectors. Owing to the chromatic aberration introduced in the focusing optics, the transmittance curve of thermal radiation varies according to the wavelength. Owing to this difference in the transmittance, the local variation of thermal radiation from the weld pool can be monitored by recording the two spectral signals from the two detectors. In this paper, the algorithms used to monitor the laser power on the weld specimen and the focus shift of the focusing optics are investigated and the performance of laser power and focus monitoring for pulsed Nd:YAG laser welding is shown.