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.
© 1994 Optical Society of America
Original Manuscript: March 10, 1993
Revised Manuscript: July 21, 1993
Published: March 1, 1994
Wolfgang Richter, Stefan M. Sarge, and Frank Kämmer, "Calorimetric support of directional–hemispherical reflection measurements in the infrared spectral range," Appl. Opt. 33, 1270-1273 (1994)