Colour-rendition properties of solid-state lamps

A Žukauskas (1) , R Vaicekauskas (2) , M S Shur (3)

1 Institute of Applied Research
2 Department of Computer Science
3 Department of Electrical, Computer, and System Engineering

The applicability of colour quality metrics to solid-state light sources is validated and the results of the assessment of colour rendition characteristics of various lamps are presented. The standard colour rendering index metric (CRI) or a refined colour quality scale metric (CQS) fail to distinguish between two principle colour rendition properties of illumination: the ability to render object colours with high fidelity and the ability to increase chromatic contrast, especially when the spectra of light sources contain a few narrow-band electroluminescence components. Supplementing these metrics by the known figures of merit that measure the gamut area of a small number of test colour samples does not completely resolve this issue. In contrast, the statistical approach, which is based on sorting a very large number of test colour samples with respect of just perceivable colour distortions of several kinds, offers a comprehensive assessment of colour rendition properties of solid-state light sources. In particular, two statistical indices, colour fidelity index (CFI) and colour saturation index (CSI), which are the relative numbers of object colours rendered with high fidelity and increased saturation, respectively, are sufficient to reveal and assess three distinct types of solid state light sources. These are (i) high-fidelity lamps, which cover the entire spectrum with the spectral components present in the wavelength ranges of both 530-610 nm and beyond 610 nm (e.g. trichromatic warm white phosphor converted LEDs, red-amber-green-blue LED clusters, complementary clusters of white and coloured LEDs) ; (ii) colour-saturating lamps, which lack power in the 530-610 nm wavelength range (e.g. red-green-blue or red-cyan-blue LED clusters) ; and (iii) colour dulling lamps, which lack power for wavelengths longer than 610 nm (dichromatic daylight phosphor converted LEDs and amber-green-blue LED clusters). Owing to a single statistical format, CSI and CFI can be used for design and optimization of multiwavelength LED clusters providing " smart " illumination with a trade-off between different colour rendition characteristics.

Mots clés: Physical Sciences

A Žukauskas, R Vaicekauskas, M S Shur. Colour-rendition properties of solid-state lamps. Journal of Physics D: Applied Physics, 2010, 43 (35), pp.354006. ⟨10.1088/0022-3727/43/35/354006⟩. ⟨hal-00629975⟩