Hi,

I need to model both forward and back scattering from each surface in a lens system using ABg values.

For the sake of this example I set the ABg values to be the same. 

The scatter forward/back is scaled to the specularly transmitted and reflected components. In this case, the surface Coating is set to I.99, so the back-scatter is 1% of the forward-scatter.

My problem: 

I have been working under the assumption that AR coatings will not reduce the scatter - AR coatings can change the scatter profile, but the TIS tends to increase as coat layers only add to Rq*. However, simple coatings (6-layers or less) tend to the TIS of the uncoated substrate.

*Stray Light Analysis and Control, Eric C. Fest, Section 4.2

Therefore my scattering predictions are for uncoated substrates - giving me TIS values. I then scale them to the incident ray. So I ideally want the scatter of the surface to be independent of the AR coating. 

Is there a way to tell Zemax to scale the scatter to the incident ray? Or do I need to upscale my ABg values to factor out the AR coatings?