Bhandari Anak, Hamre Børge, Frette Øvynd, Zhao Lu, Stamnes Jakob J, Kildemo Morten
Department of Physics and Technology, University of Bergen, Bergen, Norway.
Appl Opt. 2011 Jun 1;50(16):2431-42. doi: 10.1364/AO.50.002431.
A Lambert surface would appear equally bright from all observation directions regardless of the illumination direction. However, the reflection from a randomly scattering object generally has directional variation, which can be described in terms of the bidirectional reflectance distribution function (BRDF). We measured the BRDF of a Spectralon white reflectance standard for incoherent illumination at 405 and 680 nm with unpolarized and plane-polarized light from different directions of incidence. Our measurements show deviations of the BRDF for the Spectralon white reflectance standard from that of a Lambertian reflector that depend both on the angle of incidence and the polarization states of the incident light and detected light. The non-Lambertian reflection characteristics were found to increase more toward the direction of specular reflection as the angle of incidence gets larger.
朗伯表面在所有观察方向上看起来亮度相同，与照明方向无关。然而，随机散射物体的反射通常具有方向变化，这可以用双向反射分布函数（BRDF）来描述。我们测量了Spectralon白色反射标准在405和680纳米非相干照明下，来自不同入射角的非偏振光和平面偏振光的BRDF。我们的测量结果表明，Spectralon白色反射标准的BRDF与朗伯反射器的BRDF存在偏差，这种偏差既取决于入射角，也取决于入射光和检测光的偏振状态。随着入射角增大，非朗伯反射特性在镜面反射方向上的增加更为明显。
