This is the first of two papers which describe some of the advances over the last 20 years that have been made in primary scales and supporting techniques which have led to an order of magnitude improvement in the uncertainty of optical radiation measurement scales disseminated to industry and academia. In this paper we concentrate on cryogenic radiometry, laser radiometry and filter radiometry, the latter being the interface between the largely monochromatic primary realizations and the more useable polychromatic scales. The paper reviews some of the history of the underpinning current methodologies and some directions for the future, concentrating on those in which NPL has made a significant contribution.
Nigel P. Fox, Nigel P. Fox,
"Developments in optical radiation measurement at NPL: part I", Proc. SPIE 4450, Harnessing Light: Optical Science and Metrology at NIST, (18 June 2001); doi: 10.1117/12.431247; https://doi.org/10.1117/12.431247