黒体放射に基づく分光放射照度標準の実現に関する調査研究

Abstract

The most fundamental and important quantity in optical radiometry is spectral irradiance, which is the irradi-ance per unit wavelength, where irradiance is defined as the density of radiant power with respect to area at a point on the irradiated surface. Spectral irradiance is widely used to characterize source properties, to calibrate optical measurement devices and to quantitatively evaluate optical phenomena on the irradiating surface. The primary standard of the spectral irradiance is generally realized by means of a blackbody radiator according to the Planck's law. This paper surveys the measurement techniques, implemented in world-leading national metrology institutes including National Metrology Institute of Japan (NMIJ), to realize the spectral irradiance based on the blackbody radiator and their uncertainty evaluation. There are two major approaches to determine blackbody temperature, using an absolute radiometer traceable to the electric standard, and a fixed-point black-body radiation traceable to the temperature standard. By reviewing technical progress and key issues in each approach, the future direction to improve the uncertainty of spectral irradiance scale in NMIJ is also discussed, especially by focusing on the uncertainty due to temperature determination of the blackbody radiator.