Affiliations: Department of Information Systems Science, Faculty of
Engineering, Soka University, 1-236, Tangi-cho, Hachioji, Tokyo 192-8577,
Japan.
Abstract: A visualization technique using an ultraviolet CCD camera has been
successfully applied to the non-contact monitoring of molten pools produced in
material processing by high power CO_2 lasers. This technique is based on the
principle that the temperature sensitivity of UV radiation emitted from molten
pools is much higher than visible or infrared region. Additionally, the target
area directly irradiated by a focused laser beam could be largely dominated by
UV radiation because of its highly energetic condition. In this experiment,
molten pools produced by a 100-W CO_2 laser were observed as 250-nm UV images
by means of an UV-CCD imaging system. It has been attractively demonstrated
that the developed technique could offer not only more realistic pictures of
actual laser focused area without the secondary effects due to heat conduction
around them, but also the intensity profiles of the incoming, invisible laser
beam. The 3-D representation of laser beam intensity profile has been
reconstructed through the contour maps of UV images captured at a laser
irradiated target region, with showing a very small deviation of 5% from the
ideal Gaussian distribution. The obtained results imply that this visualization
method could be an alternative beam profiling technique to conventional acrylic
burning method which has much larger deviations in beam profiling.
Keywords: visualization, ultraviolet image, temperature sensitivity, molten pool, beam profile