Computer-controlled gonioreflectometer for the measurement of spectral reflection characteristics.

A computer-controlled apparatus-the gonioreflectometer-is described, which was designed and manufactured at the Physikalisch-Technische Bundesanstalt. It enables the spectral radiance coefficient to be measured for all relevant angles of incidence and viewing. From basic considerations about the relationship between reflection characteristics it is shown that, e.g., the reflectance or the radiance factor for standardized geometries can be calculated from the measured radiance coefficient. This makes it required instrumentation for the calibration of reflection standards.