A new luminous flux calibration facility using a 2.5 m integrating sphere has been developed at NIST. The Absolute Integrating-Sphere Method, developed for realization of the lumen in 1995, has been applied to routine calibration measurements of luminous flux. The measurement of an external source is automated so that the responsivity of the sphere is calibrated every time a test lamp is measured. The new method based on illuminance measurement of the external source using standard photometers allows for calibration of test lamps with no need for luminous flux standard lamps. This brings the luminous flux calibration into detector-based measurement procedures, thereby eliminating the uncertainties associated with the use of working standard lamps. Lower uncertainties are achieved by shortening the calibration chain. Further, a new technique employing a chopper and a lock-in amplifier has been introduced to the external source, which allows for calibration of the sphere while the internal lamp is burning in the sphere avoiding the errors due to the effect of heat on the sphere and other nonlinearities.
Proceedings of the 24th Session of the CIE (Commission Internationale de l'Eclairage)
and Zong, Y.
Detector-Based Integrating Sphere Photometry, Proceedings of the 24th Session of the CIE (Commission Internationale de l'Eclairage), Warsaw, PL, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=841338
(Accessed December 3, 2023)