Intercomparison of industrial near-infrared diffuse reflectance measurements

Abstract

An intercomparison of diffuse reflectance measurements in the near-infrared region was carried out. Fourteen participants from industry and academia measured a number of different reflectance standards, calibrated at the NPL, over the wavelength range from 800 to 2500 nm. Measurements were made in the integrating sphere geometries, i.e. specular included and specular excluded and in the 0/45 geometry. The results of the intercomparison are presented. The raw data results showed significant variations in the value of diffuse reflectance measured across industry, in excess of 80% difference from NPL reflectance values in some cases. Renormalisation of the data to the NPL near-infrared diffuse reflectance scale significantly improved the agreement in measured values between participants, most being within 5% of the NPL values. Integrating sphere errors were present in many of the instruments used.