Surface scattering is an important effect to consider when analyzing both the illumination and stray light characteristics of a system. In many cases scattering is a desired effect. Surface scattering distributions which are built into ZEMAX include the Lambertian, Gaussian, and ABg models. More information on these distributions may be found in the chapter of the ZEMAX manual entitled “Non-Sequential Components”.

There may be cases when it is necessary to model surfaces whose scattering properties do not follow any of the built-in ZEMAX distributions. If the desired distribution is both analytic and integrable, a user-defined surface scattering model may be constructed, as described in the Knowledge Base article “How to Create a User-Defined Scattering Function”. However, in many cases the desired distribution is simply provided in terms of a table of measured data for the Bi-Directional Scatter Distribution Function (BSDF). An example of this is BSDF data that is measured by the Imaging Sphere for Scatter and Appearance (IS-SA) which has been developed by Radiant Imaging, Inc. (www.radimg.com).

To address this situation, a user-defined model has been constructed in which tabular BSDF data may be used to generate surface scattering properties. This article describes the model, and provides an example of how this model can be used to specify the scattering distribution on any component surface in the non-sequential mode of ZEMAX.