A new Standard Reference Material set has been developed at the National Office of Measures Hungary. The set includes six neutral absorbing glass filters for linearity measurements having optical densities 0.5 - 4.0, one cut-off filter for checking stray light and a didymium filter for wavelength calibration. A new method has been developed for high accuracy (< 0.06 nm) wavelength calibration. This accuracy was demonstrated at eight wavelengths during the past five years. The method is practically independent of bandwidth for spectrophotometer with bandwidths less than 10 nm.
"Standard reference material set for spectrophotometer calibration", Proc. SPIE 1712, 14th Symposium on Photonic Measurement, (9 February 1993); doi: 10.1117/12.140160; https://doi.org/10.1117/12.140160