TWI Industrial Member Report Summary 669/1999
P A Hilton
Almost all high power lasers used for materials processing applications use a focused laser beam, invariably produced either by refractive optical techniques, eg simple lenses, or reflective optical techniques, eg paraboloidal mirrors. These techniques produce the high intensity, symmetric energy distributions used in a wide range of laser welding and cutting applications. Energy distributions other than symmetric spots are not easy to produce using reflective and refractive optical systems. However, the use of diffractive or holographic optical techniques enables any required energy distribution in the beam to be reproduced from the surface of either reflective or transmissive optics. In an earlier TWI report (540/1996), Hilton and Tyrer describe the results of a feasibility study into the use of diffractive optical elements for manipulation of CO2 laser radiation. In this work, a circular Gaussian energy distribution from a 5kW CO2
The work reported here describes how the computation of the diffractive patterns, the optic manufacturing techniques and the efficiency of the process, have all been improved to the extent that several optical elements specifically tailored to industrial processes have been developed to demonstrate the application of diffractive optical techniques to laser materials processing.
The objectives of the work were:
- To improve the efficiency of diffractive optics used for manipulation of CO2 laser energy.
- To produce diffractive optics capable of producing asymmetric energy distributions.
- To demonstrate materials processing applications using diffractive optics which provide advantages which would not be possible using conventional beam focusing optics.