Abstract
The accuracy of the acrylic burn pattern method, widely used for observing a beam intensity profile of high power CO2 laser, has been studied by comparing the burn patterns with corresponding beam intensity profiles measured by the computer controlled pinhole scan method. It is found that the shape of burn pattern is determined by beam irradiation time, beam intensity and beam size, owing to the differences in reflectivity at various incident angles and in threshold energy for evaporation of acrylic piastics. Thcs, it is considered that the acrylic burn pattern method is not reliable and that a more accurate method, such as the pinhole scanning method, must be used for studying precise beam qualities.
