Realization of a spectral radiance scale at KRISS

The KRISS spectral radiance standards have been realized from 250 nm to 2.5 mum with reference to the radiance temperature scale. Based on the definition of the ITS-90, the temperature scale has been realized using a copper and silver point blackbody. This paper briefly describes the calibration facility, which consists of the variable temperature blackbody, the standard radiation pyrometer and the spectroradiometer. All of the radiating sources and the measurement system were fully controlled automatically and operated by two personal computers. The stabilities, noise characteristics, linearity and size of source effect of the spectroradiometer have been measured. Using two sheets of polarizer, the degree of linear polarization induced by the spectroradiometer and the Mueller matrix elements of the polarizer have also been simultaneously measured. For a tungsten strip lamp to be used as a spectral radiance transfer source, the current coefficient of spectral radiance, the stability in conjunction with the power supply and the degree of polarization have been measured to yield correction values at the reference condition after calibration. A mathematical model for the correction procedure and uncertainty analysis of the calibration is proposed. The relative standard uncertainty of the KRISS spectral radiance scale is determined to be 0.83% at 250 nm, 0.49% at 300 nm and less than 0.3% from 650 nm to 2.5 mum.