Scales of spectral irradiance are disseminated from NIST by assignment of values to FEL-type lamp standards for defined conditions. These lamp standards can be used for absolute calibration of irradiance radiometers, or more typically, be used in conjunction with a diffuse reflectance standard to establish a scale of spectral radiance and subsequent absolute calibration of radiance radiometers. The NIST FEL standards are valuable artifacts requiring special care. Many users optimize resources by in-house transfer of their primary standard to working standards. There are a number of sources of uncertainty in utilizing FEL lamps, e.g., lamp current, alignment, distance setting, instrument aperture size, drift, scattered light, and interpolation in the wavelength grid for the specified irradiance values. In this work, we validated this type of transfer activity by ITT of their primary, NIST-traceable FEL lamp standards. A portable irradiance bench that had kinematic mounts for an FEL lamp, on-axis baffle, and three different irradiance radiometers was built, tested, and deployed to ITT in Rochester, NY. We report the results of this comparison activity. An uncertainty budget for the NIST bench was developed, and, in combination with the ITT estimated uncertainties, it was found that the results agreed well within the combined activities.
Proceedings Title: SPIE Proceedings Vol 8510 (2012)
Conference Dates: August 13-17, 2012
Conference Location: San Diego, CA
Conference Title: SPIE Optics and Photonics
Pub Type: Conferences
Irradiance standard lamps, spectral irradiance scales, traceability, uncertainty estimates, validation