Influence of the beam diameter on the resistance of laser guards

Laser guards are critical components for ensuring safety in laser processing systems. While current safety standards and regulations establish general protection requirements, the existing correction functions for beam diameter effects have proven to be outdated. The findings of this study demonstrate that the established scaling model drastically overestimates the actual laser resistance. In this study, a standardized testing box was developed to systematically investigate the laser resistance of various plastic and mineral glass filter materials. Laser exposure tests were conducted using near-infrared and visible laser radiation across a wide range of beam diameters d86 from 1 to 100 mm. The results demonstrate that the maximum tolerable irradiance exhibits a power-law dependence on the laser beam diameter for all investigated materials. A significant finding of this work is that normalizing the irradiance to a beam diameter of 20 mm (E20), rather than the 1 mm diameter often used in standards, significantly reduces data scatter and enables a more reliable scaling. Based on these findings, a new material-independent, piecewise correction function, incorporating a plateau for small beam diameters, is proposed. This function allows the calculation of the protective exposure limit across the entire diameter range based on individual standard tests. This advancement provides a robust methodology to enhance the safety, practicality, and cost-efficiency of laser safety systems while reducing the need for extensive case-specific suitability testing.