The purpose of the simulation was to find out how much of the optical signal actually comes from the target as opposed to the optical and mechanical structures of the measurement system.
In order to estimate the actual emissivity values of the critical optical and optomechanical structures used in the commercial measurement unit, the reflectivity (and transmissivity, in some cases) of these structures were measured at the wide optical band using a Biorad Fourier Transform Infrared (FTIR) spectrometer.
The average reflectivity (and transmissivity) at a band of 8–14m was used to deduce the emissivity value in the optical simulations.