A detector-based spectral irradiance scale has been realized at the National Institute of Standards and Technology. Unlike the previousNIST spectral irradiance scales, the new scale is generated using filter radiometers calibrated for absolute spectral power responsivitytraceable to the NIST High-Accuracy Cryogenic Radiometer instead of using the gold freezing-point blackbody. The calibrated filterradiometers are then used to establish the radiance temperature of a high-temperature blackbody (HTBB) operating near 3000K. Thespectral irradiance of the HTBB is then deternidned using the knowledge of the geometric factors and is used to assign the spectralirradiances of a group of I 000 W FEL lamps. The detector-based spectral irradiance scale results in the reduction of the uncertaintiesfrom the previous, source-based, spectral irradiance scale by at least a factor of two in the ultraviolet and visible wavelength regions. Thenew detector-based, spectral irradiance scale also leads to a reduction in the uncertainties in the short-wave infrared wavelength region byat least a factor of two to ten, depending on the wavelength. Following the establishment of the spectral irradiance scale in the early1960's, the detector-based spectral irradiance scale represents a fundamental change in the way that the NIST spectral irradiance scale isrealized.
Citation: Applied Optics
Issue: No. 28
Pub Type: Journals
absolute radiometry, blackbody, filter radiometers, spectral irradiance