Measurements and Predictions of Light Scattering by Clear Coatings.
Measurements and Predictions of Light Scattering by
McKnight, M. E.; Vorburger, T. V.; Marx, E.; Nadal, M.
E.; Barnes, P. V.; Galler, M. A.
Applied Optics, Vol. 40, No. 13, 2159-2168, May 1,
light scattering; coatings; appearance; BRDF; modeling
Comparisons are made between calculated and measured
angle-resolved light-scattering distributions from clear
dielectric isotropic epoxy coatings over a range of rms
roughness conditions, resulting in strongly specular
scattering to diffuse scattering characteristics.
Calculated distributions are derived from topography
measurements performed with interferometric microscopes.
Two methods of calculations are used. One determines the
intensity of scattered light waves using a phase
integral in the Kirchoff approximation. The other is
based on the reflection of light rays by locally flat
surfaces. The angle-resolved scattering distributions
for the coatings are measured with the spectral
trifunction automated reference reflectometer (STARR)
developed by National Institute of Standards and
Technology. Comparisons between measured and calculated
results are shown for three surfaces with rms roughness
values of approximately 3, 150 and 7800 nm for an angle
of incidence of 20 deg.