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 AmericaFull Article | PDF Article
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