Abstract
A model for light scattering by rough surfaces is presented. It is based on the Kirchhoff approximation of the electromagnetic field. In particular, the approach of Beckmann is extended and developed to meet the requirements of lighting engineers. The intensity scattered by a normally distributed rough surface is derived for any angles of incidence and scattering. It is then analysed and transformed into photometric quantities such as radiance and radiance factors. The final expression of the model is fairly concise, with only a few parameters. It is compared with measurements of the intensity scattered by a rough surface. Frosted glass has been chosen for the surfaces because it is homogeneous and transparent, such that no volume scattering was present. When shadowing effects are taken into account, it is shown that the relative deviation from measured intensities is less than 30% for significant values.
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