Directional Characteristics of Radiation Reflection on Rough Metal Surfaces with Description of Heat Transfer Parameters.

Directional distribution of bidirectional reflectance ρ for visible laser irradiation is investigated experimentally on rough metal surfaces. The reflection is found to be far from perfect-diffuse. Relationship of reflection characteristics and rms surface roughness Σ is not simple in case Σ is of an order of the wavelength of incident radiation. It is recommended to analyze the reflection characteristics on (ρ cos θR), where θR is the zenithal angle of reflection. What has been called 'off-specular' peak does not appear in this case. A reflection model for describing the directional distribution is presented for heat transfer applications. The model can evaluate the values of the specular component RS and the perfect-diffuse component Rd of the hemispherical reflectance RH for directional incidence. It is interesting that calculated values of the specularly reflected energy ratio (RS / RH) do not always fit with our impression on the specularity in the directional distribution of ρ.