Investigating directional reflection characteristics of anisotropic machined surfaces using a self-designed scatterometer.
The directional reflection characteristics of anisotropic surfaces play an important role in the precise modeling of radiative heat transfer and target detection. Nevertheless, the directional reflection characteristics of anisotropic machined surfaces have not been fully understood. In this work, an accurate automated scatterometer was built to investigate the bidirectional reflectance distribution function (BRDF) of anisotropic machined surfaces produced by various kinds of machining methods, including plain milling, planer processing, and flat grinding. The effects of the incident angle, machining method, and surface roughness on the bidirectional reflectance properties were studied. The results indicate that the incident azimuthal angle affects the BRDF of a plain-milling surface in a vitally different way compared to planer processing and flat grinding. When the plane of incidence orients parallel to the macroscopic surface strips, the plain-milling surface displays diffuse dominated reflection (reflected energy distributed over 90°), whereas the other two show mirror-like properties, only distributed about 4° around the specular direction. Under the same surface roughness, the plain-milling surface shows the weakest reflected intensity, while the flat-grinding surface has the strongest.