title: Calorimetric support of directional-hemispherical reflection measurements in the infrared spectral range.
abstract: Measurements of the directional-hemispherical reflectance ρ with the Physikalisch-Technische Bundesanstalt IR sphere reflectometer have been confirmed by calorimetric determination of the absorptance α in the same geometrical conditions (irradiation at 10°, hemispherical reflection). The good agreement of ρ with (1 - α) on both highly reflecting and low-reflecting surfaces indicates that in the mid-IR spectral range the integrating sphere reflectometer is capable of essentially correct reflectance measurements of diffusely reflecting surfaces, with an estimated uncertainty of 0.01 after correction for a small systematic deviation. This capability opens up the possibility of developing IR reflectance standards.
authors.forename: W
authors.initials: W
authors.lastname: Richter
authors.forename: S M
authors.initials: SM
authors.lastname: Sarge
authors.forename: F
authors.initials: F
authors.lastname: Kämmer