title: Gonioreflectometer for measuring spectral diffuse reflectance.
abstract: 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.
authors.affiliation: Metrology Research Institute, Helsinki University of Technology, PO Box 3000, FIN-02015 HUT, Finland. saulius.nevas@hut.fi
authors.forename: Saulius
authors.initials: S
authors.lastname: Nevas
authors.forename: Farshid
authors.initials: F
authors.lastname: Manoocheri
authors.forename: Erkki
authors.initials: E
authors.lastname: Ikonen