A memory colour quality metric for white light sources

Abstract

Over the past years, the tremendous progress in solid-state lighting technology, especially in terms of energy-efficiency, has increased the interest in solid-state lighting (SSL) as an alternative to conventional sources in general lighting applications. Colour quality is one of the key challenges for SSL, as lighting with a poor colour quality is often unacceptable in general lighting. For many lighting designers and architects, the CIE colour rendering index is the current standard to assess colour quality of a light source. Unfortunately, it correlates poorly with the visual appreciation of many SSL sources. In this paper a colour quality metric is presented that references to the memory colours of familiar objects. The basic idea is simple: the closer a light source renders colours to what is expected, the better will be the colour quality. A correlation analysis, based on data from several psychophysical studies described in literature, has shown that the metric correlates highly with the visual appreciation of white light sources. Some of the key differences between the memory colour quality metric and the CIE colour rendering index are shortly illustrated, as well as its potential for the design of more energy-efficient light source spectra showing good colour quality.