A COMPARISON OF ROTATING-WIRE- AND ROTATING-PINHOLE-TYPE LASER BEAM ANALYSERS WHEN USED TO MEASURE PULSED ND-YAG LASER BEAMS

摘要

The increased use of lasers for cutting, drilling and welding in industrial applications has accentuated the need for effective laser beam diagnostic techniques. In this paper, results are presented of a comparative study of the performance of two commercially available laser beam analysers, a rotating-wire type (LBA) and a rotating-pinhole type (Prometec Laserscope). Both laser beam analysers were modified and used to measure the spatial distributions of power density, beam 'diameters' and M(2) beam quality values of converging/diverging laser beams at and about the focal point of a 350 W pulsed Nd:YAG laser welder. Although similar in basic concept, there were many differences in functionality noted between these two beam analysers. The Prometec is easy to use and to understand, but affords no direct access to the measured data. Alternatively, the LBA can be assembled from a few inexpensive electro-optical components, but is conceptually more complex and its operation is more difficult. It does, however, allow the user direct access to the measured data. in spite of these differences, there was good qualitative agreement between the multi-mode power density distributions measured using both devices at various positions about the focus of the Nd:YAG laser beam. In addition, the measured beam spot sizes and M(2) values were found to be in good agreement. [References: 20]