Definition of a spectral mismatch index for spectral power distributions

To investigate, select and publish an LED reference spectrum to complement the CIE Standard Illuminant A in photometric calibrations, a new technical committee has been recently created by CIE. This technical committee requires defining a spectral mismatch index to quantify the match of spectral power distributions (SPDs) of real sources to the selected reference spectrum. A proposal for such an index is given here, assuming that the spectral mismatch index of the SPD of a real source is directly related to the spectral mismatch systematic error introduced when the photometric quantity is measured using a photometer which is calibrated to a light source with the reference SPD. Finally, the value of this index is discussed and interpreted in photometric terms.