TWI Industrial Member Report Summary 540/1996
P A Hilton and J R Tyrer
Almost all CO2 and ND:YAG lasers used in materials processing use a focused laser beam, invariably produced either by refractive optical techniques, eg simple lenses or reflective optical techniques, eg paraboloidal mirrors. These techniques give the high intensity, symmetric energy distributions used in a wide range of laser welding and cutting applications. For laser surface engineering and some welding applications, the ability to produce two- and three-dimensional energy profiles is a requirement. This type of energy distribution tends to be difficult and costly to produce using conventional refractive and reflective optical techniques, but it is possible using computer- generated holographic optical elements. Such optical elements are used in the telecommunications industry, and in headsets for virtual reality presentations. However, these devices have not yet been effectively demonstrated for use with high power laser sources. This briefing presents results of a feasibility study conducted by TWI and the Department of Mechanical Engineering at Loughborough University of Technology, into the possibility of producing such optical elements for use with high power CO2 lasers.
To produce a diffractive holographic optical element with a uniform energy distribution in the form of a rectangular 'box' 8 x 6mm, when irradiated with the typical 'Gaussian' energy distribution available from a high power CO2 laser.