Broad-band BRDF measurement and analysis of weak scatterers

Complex wave-optics scattering phenomenon exists on the surfaces of the weak scatterers. With the increase of the incidence angle, the light scattering from such a surface varies from directional diffuse scattering to mirror reflection, while the magnitude of mirror reflections varies with the wavelengths. To study the phenomenon, a broad-band gonioreflectometer was used to measure the bidirectional reflectance distribution functions (BRDFs) of two weak scatterer at various wavelengths; on the other hand, a stylus profilometer was used to obtain the surface height data and, furthermore, the statistical characteristics of the rough surfaces. A wave-optics BRDF model was fitted to the measured data with Quasi-Newton optimization algorithm, and accurately predicted the correlation of the scattered light with the angles and the wavelengths. By comparing the fitting results and the measured data, we prove that the phenomena can be predicted accurately with the wave-optics based model.