EFFECTS OF NON-LAMBERTIAN SURFACES ON INTEGRATING SPHERE MEASUREMENTS

The effects of non-Lambertian scattering of the interior wall of an in tegrating sphere are examined through a sphere simulation model. The m odel employs Monte Carlo techniques. A sphere used for measurement of directional-hemispherical reflectance is modeled. The simulation allow s sphere wall scattering to vary from perfectly Lambertian to perfectl y specular in steps. The results demonstrate that significant measurem ent error can result as the scattering deviates from the Lambertian id eal. The error is found to be a strong function of the wall reflectanc e value as well: it is minimized for reflectances approaching 1.0 and increases as the reflectance value decreases to the minimum value exam ined of 0.5. The magnitudes of the errors associated with non-Lamberti an scattering are also shown to be relatively independent of the speci fic field of view of the detector used in the measurement.