Filter radiometer based realization of photometric scale traceable to cryogenic radiometer at UME

Abstract

This work presents the progress made in primary level photometric measurements at the National Metrology Institute of Turkey (UME). A Cryogenic Radiometer (Oxford Instruments Radiox) was employed in the optics laboratory as an absolute primary standard. Temperature-controlled filter radiometer constructed from three-element silicon trap detector, band-pass filters and precision aperture. Filter radiometers were calibrated using the cryogenic radiometer at discrete laser wavelengths of vertically polarized tuneable Ar+, fixed He-Ne and Nd: YAG (with second harmonic) laser sources. Luminous intensity unit of candela was realized with an expanded uncertainty of 2.88x10-3 and photometric scale was re-established depending on this detector-based realization. Candela realization was performed on optical bench using traditional Osram Wi41/G type incandescent light source and an absolute filter radiometer. Other derived units of photometry that are luminous flux, illuminance, color temperature and luminance are derived from candela through various photometric measurements including some homemade devices of laboratory.