In-Process Measurement System for Radiation Spectrum in Laser Welding

Abstract This paper presents an in-process measurement system for radiant light spectrum during laser welding process. The measurement system is composed of a spectrum detecting unit and a spectral data processing computer. The detecting unit is a multichannel spectrophotometer with an image intensifier tube, and separates radiant light into spectral components, intensifies, and detects spectral intensities in a CCD type photodiode array. Then, the detecting unit controller constructs a complete spectrum and transfers to the computer, which finds a specified number of wavelengths indicating peak intensities in the spectrum. Using the measurement system, in-process spectrum measurements of radiant light during evaporating in a vacuum chamber and during welding under various control parameters were performed. Experimental results show that these wavelengths are invariable and constituent material-specific, and peak intensities at these wavelengths can be used as in-process indices of plasma forming, evaporating or melting state of constituent materials during welding.