Hello,

I am building a non-sequential model and have observed unexpectedly high back reflection from a surface with an I.98 coating.

I have attached the Zemax file for reference. Two detectors were placed just before the surface: one records rays propagating toward the surface, and the other records the back-reflected rays. Based on the I.98 coating, I would expect only ~2% reflection. However, the results show that nearly 50% of the light is being reflected.

Has anyone encountered a similar issue? Could there be a reason why the coating appears to be ignored in this setup?

Any insights would be greatly appreciated.

Regards,
Hugh