NATIONAL-INSTITUTE-OF-STANDARDS-AND-TECHNOLOGY DETECTOR-BASED PHOTOMETRIC SCALE

The Systeme International base unit for photometry, the candela, has b een realized by using absolute detectors rather than absolute sources. This change in method permits luminous intensity calibrations of stan dard lamps with an expanded uncertainty of 0.46%, almost a factor-of-2 improvement. A group of eight reference photometers has been construc ted with silicon photodiodes, matched with filters to mimic the Commis sion Internationale de I'Eclairage spectral luminous efficiency functi on for photopic vision.The design, characterization, calibration, eval uation, and further application of the photometers are discussed.