Abstract
This paper describes an effective approach for the optimization of multiband spectra to produce prospective white-light spectra having specific color temperatures. The optimization process employs a genetic algorithm known as differential evolution, which aims to minimize the color rendering differences between a prospective white-light spectrum and its corresponding reference illuminant. Color rendering is assessed by calculating the CIEDE2000 color difference (ΔE00) for 14 CIE test colors under the two sources. Optimized white-light spectra were matched to three CIE standard illuminants, that is, A (2856 K), D50 (5003 K), and D65 (6504 K). Optimal solutions for three- and four-band 25 and 50 nm Gaussian spectra are presented and analyzed, together with mixed 4-LED spectra that were optimized in the same way. In all cases, the simulated sources were shown to provide color rendering of such quality that ΔE00av ≤ 2.24 units. Such white-light sources would likely find wide acceptance in numerous lighting applications.
Highlights
It is firmly established that, by tuning the spectral intensities of light-emitting diodes (LEDs) which emit different bands of radiation, a white-light spectrum characterized by good color rendering and efficacy can be designed
The color rendering properties of the white-light spectrum are expressed using the color rendering index (CRI) recommended in Commission Internationale de l’Eclairage (CIE) publication 13.3 [9], and efficacy in terms of the luminous efficacy of radiation which is the ratio of luminous flux to radiant flux (LER, lm/rad-W)
We have demonstrated that it is possible to simulate the CIE standard illuminants A, D50, and D65 by mixing multiband LED and Gaussian spectra
Summary
It is firmly established that, by tuning the spectral intensities of light-emitting diodes (LEDs) which emit different bands of radiation, a white-light spectrum characterized by good color rendering and efficacy can be designed. The performance of any given mixture is governed by the number of bands [7] and their shape [10], as well as the peak emission wavelengths (λi) and bandwidths (Δ i) of each of the bands used [5, 6]. Starting with a trichromatic mixture of “Red,” “Green,” and “Blue” bands, the color rendering can be improved by the addition of an “Amber” band. It is shown that if the peak wavelengths and bandwidths of available LEDs could be freely manipulated, it would be possible to produce three-LED sources with excellent white-light spectra [5]
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