Reflection of a laser beam from a surface depends on the optical properties of the surface, and can have components that are diffuse (in all directions) or specular (in one direction). Hazard distances tend to be short and easily calculated for diffuse reflections. However, specular reflections have longer hazard distances and their calculation poses challenges due to the spatial and temporal characteristics of the reflected beam. We have developed and refined a methodology to calculate hazard distances from specular reflections. This methodology uses analytical expressions to determine the irradiance and exposure time of the reflected beam, from which hazard distances are calculated. The method accounts for the properties of the incident beam, the material reflecting properties, and the shape of the surface.
The motivations and concepts of the specular methodology are presented, along with the equations resulting from this approach. The spatial and temporal characteristics of the reflected beam for a specific laser and surface are calculated from the application of these equations. These characteristics are then used to determine either localization of hazardous regions in the surrounding space or a description of possible hazards at specific locations. Examples of the application of the specular methodology are presented with their corresponding hazardous conditions.