2018 Volume 41 Pages 40-52
With the advance of medium and high power light-emitting diodes (LED), tuneable light sources with sophisticated spectral power distributions have been emerging. The increasing variety of LEDs and their spectral behaviour complicates their design as well. Most notably, many different parameters have to be taken into account to describe the quality of light. This paper introduces a new characteristic, Spectral Deviation, which both combines various light quality parameters into one single value and correlates with the most commonly used quality parameters. Our Spectral Deviation allows a more time efficient quality assessment of a designed spectral power distribution without complex calculations or colour space transformations. The parameter is derived directly from the spectral power distribution of a test illuminant as the sum of absolute differences to a standardized reference distribution. A weighting function is used to take the characteristic of human perception into account. An upper limit for the parameter is proposed for the design of new spectral power distributions. Our parameter can be used during the selection process of single-emitter LED for tuneable luminaires as a preselector. It eliminates undesired solutions before even calculating detailed quality parameters, allowing more possible combinations to be checked in the same time.