New Photometric Calibration Programs at the National Institute of Standards and Technology

The NIST candela is maintained via standard photometers which have shown long-term stability better than 0.1% per year. The detector-based method has allowed us to reduce the uncertainties of calibrations and to expand the range of calibration capabilities. There have been several new developments in photometry at NIST. A high-illuminance calibration facility has been developed. Four temperature-controlled standard photometers, tested for linearity and effect of heat at high illuminances, are used with a high-pressure xenon arc source to provide the illuminance scale at levels up to 100 klx. A flashing light photometric unit (lx·s) has been realized using four standard photometers equipped with current integrators and two independent methods. Calibration services for illuminance meters at high illuminance levels and flashing-light photometers are now available at NIST. On-going new projects include the development of a detector-based luminous flux calibration facility using a 2.5 m integrating sphere, realization of the total spectral radiant flux scale, and the development of a reference spectroradiometer for colorimetry of displays. Calibration services are planned in these areas of photometry and colorimetry in the near future.