Using both the scattering and coating capabilities in Non-Sequential ZEMAX, we can model a partially reflective (or optionally transmissive) surface which diffusely scatters only a fraction of the initial incident energy in a specific distribution. 

Assume that we wish to simulate a partially reflective (60% reflective) face of a rectangular volume which scatters 80% of this reflected light in a Lambertian distribution.  The other 20% is specularly reflected.  Using three Non-Sequential Objects, we may quickly and easily demonstrate how to apply Lambertian scattering and ideal coatings to produce the desired effects.

To avoid the redundancy of having to create the file from scratch, please download the attached Non-Sequential ZEMAX file on the very last page of this article.

FILE:  "Partial Reflection and Scattering.ZMX"

As the file currently exists, a single Source Ray is incident onto the front face of a Rectangular Volume made of material type MIRROR.  The ray from the source perfectly reflects back onto itself and is incident on the detector plane.  Currently, there are no coatings and/or scattering profiles defined on any single surface of the Rectangular Volume.

From a Monte Carlo Ray Trace without considering polarization, a single ray illuminates the centermost pixel of the detector with a total power of 1W.