MEASUREMENT OF SPECTRAL AND DIRECTIONAL REFLECTION CHARACTERISTICS OF BUILDING MATERIALS SEPARATED INTO BOUNDARY AND LAYER REFLECTION COMPONENTS

Recently various lighting designs have become required more than ever. In order to closely examine and appropriately design various lighting environments, highly accurate luminance predictive simulation techniques would be more required. In the most of conventional lighting environment prediction simulations it is often assumed that all the reflecting surfaces were uniformly diffusing surfaces. However, the actual surfaces usually have directional reflection characteristics between the uniform diffuse reflection and the specular reflection, which are different from the assumption in the conventional simulations. In more accurate luminance prediction simulations directional reflection characteristics of the building materials should be considered, so it is necessary to obtain directional reflection characteristic data to be incorporated into such simulations. Throughout the measurements made in this study, the followings were found. (1) The luminous intensity coefficients of the reflected light from the nineteen building materials with different finishes, such as PVC floorings, PVC sheet, granite and resin coated metal plates, were measured by being separated into the boundary reflection and the layer reflection component using a polarizer. By the measurements we obtained data set of directional reflection characteristics for the simulation. (2) From these measurements, we confirmed 1) the intensities of the boundary reflection component tends to increase as the incident angle increases, 2) the differences in color appear to be resulted from different properties of the layer reflection component, and 3) the difference in the surface finish may characterize the properties of the boundary reflection component. (3) The measured values of luminous intensity coefficients ρ was approximated well by the Uetani-Matsuura mathematical model, so it was suggested that these measurement values will be able to be incorporated into luminance simulation considering directional reflection characteristics. (4) Spectral reflection characteristics of the boundary reflection and the layer reflection components were obtained by the measurements using a polarizer. It was confirmed that the spectral structures of the light source is retained in the boundary reflection component, while the spectral reflection characteristics of the sample can be explained by the layer reflection component.