Bi-directional reflectance and Raman characterizations of Spectralons with varying albedos

We measured the spectral bi-directional reflectance distribution function (BRDF) of 8 Spectralon calibration plaques with nominal reflectance values of 2%, 5%, 10%, 20%, 40%, 60%, 80%, and 99%, across a wavelength range of 350 to 2150 nm. The measurements were taken at two incident zenith angles, 0° and 60°. At normal incidence, the BRDF of the 40% Spectralon exhibits the most Lambertian behavior, while all other Spectralons exhibit both backscattering and forward-scattering lobes. However, at 60° incidence, the 99% Spectralon shows the best Lambertian behavior. Additionally, several particulate samples with varying albedos were calibrated using these Spectralon standards. The results indicate that while the angular shapes of the BRDF are not influenced by the specific plaque used, the absolute REFF values calibrated by the 99% plaque are consistently the highest.