Gonioreflectometer for measuring spectral diffuse reflectance.
Gonioreflectometric determination of reflectance factors that involves hemispherical collection of reflected flux, which is an alternative to integrating sphere-based methods, is discussed. A detailed description of a gonioreflectometer built at the Helsinki University of Technology is presented. The instrument is used to establish an absolute scale of total diffuse reflectance factors throughout the spectral range 360-830 nm. The hemispherical reflectance factors are obtained through integration of the gonioreflectometric measurement results. The reflectance factors of white high-quality artifacts can be determined with a combined standard uncertainty of 0.20%. Results of test measurements were found to be in agreement with values traceable to other absolute scales based on integrating-sphere methods.
Nevas
Saulius
S
Metrology Research Institute, Helsinki University of Technology, PO Box 3000, FIN-02015 HUT, Finland. saulius.nevas@hut.fi
Manoocheri
Farshid
F
Ikonen
Erkki
E