Author:

Keywords:

appearance measurement, BSDF, BRDF and BTDF

Abstract:

To expedite colour and gloss measurements, the CIE and ASTM have recommended some basic geometries regarding illumination and viewing angles. There are, however, many surfaces that cannot be adequately measured using such limited conditions. Any gloss and colour measurement can be related to some particular value of the general spectral Bidirectional Scatter Distribution Function (BSDF). In our laboratory, we have built a goniospectroradiometer which allows us to determine the absolute BSDF of an object. Spectral properties can be measured at any spherical angle of illumination and at almost any spherical viewing angle using a detector circulating around the sample with two degrees of freedom. Absolute spectral BSDF values can be calculated from dark current corrected CCD readings (counts) according to ASTM E1392. Spectral and spatial characteristics of the instrument are determined and some measurement results on different kind of samples are reported.