In this paper we describe a focus control system for Nd:YAG laser welding based on an optical sensor incorporated into the fibre delivery system to detect light generated by the process. This broadband light is separated into two wavelength bands, and simple electronic processing gives a signal proportional to focal error, as a result of chromatic aberrations in the optical delivery system. Focus control is demonstrated for bead-on-plate welds in different thicknesses of titanium alloy, aluminium alloy, mild steel and stainless steel. The control system works for both pulsed and continuous laser radiation.
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© 1996 Laser Institute of America.
1996
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