Optimising metameric spectra for integrative lighting to modulate the circadian system without affecting visual appearance

Babak Zandi; Oliver Stefani; Alexander Herzog; Luc J M Schlangen; Quang Vinh Trinh; Tran Quoc Khanh

doi:10.1038/s41598-021-02136-y

Optimising metameric spectra for integrative lighting to modulate the circadian system without affecting visual appearance

Sci Rep. 2021 Nov 30;11(1):23188. doi: 10.1038/s41598-021-02136-y.

Authors

Babak Zandi¹, Oliver Stefani², Alexander Herzog³, Luc J M Schlangen⁴, Quang Vinh Trinh³, Tran Quoc Khanh³

Affiliations

¹ Department of Electrical Engineering and Information Technology, Laboratory of Lighting Technology, Technical University of Darmstadt, Darmstadt, Germany. zandi@lichttechnik.tu-darmstadt.de.
² Transfaculty Research Platform Molecular and Cognitive Neurosciences (MCN), Centre for Chronobiology, University of Basel, Basel, Switzerland.
³ Department of Electrical Engineering and Information Technology, Laboratory of Lighting Technology, Technical University of Darmstadt, Darmstadt, Germany.
⁴ Department Human-Technology, Intelligent Lighting Institute, Eindhoven University of Technology, Eindhoven, The Netherlands.

Abstract

Smart integrative lighting systems aim to support human health and wellbeing by capitalising on the light-induced effects on circadian rhythms, sleep, and cognitive functions, while optimising the light's visual aspects like colour fidelity, visual comfort, visual preference, and visibility. Metameric spectral tuning could be an instrument to solve potential conflicts between the visual preferences of users with respect to illuminance and chromaticity and the circadian consequences of the light exposure, as metamers can selectively modulate melanopsin-based photoreception without affecting visual properties such as chromaticity or illuminance. This work uses a 6-, 8- and 11-channel LED luminaire with fixed illuminance of 250 lx to systematically investigate the metameric tuning range in melanopic equivalent daylight illuminance (EDI) and melanopic daylight efficacy ratio (melanopic DER) for 561 chromaticity coordinates as optimisation targets (2700 K to 7443 K ± Duv 0 to 0.048), while applying colour fidelity index R_f criteria from the TM-30-20 Annex E recommendations (i.e. R_f [Formula: see text] 85, R_f,h1 [Formula: see text] 85). Our results reveal that the melanopic tuning range increases with rising CCT to a maximum tuning range in melanopic DER of 0.24 (CCT: 6702 K, Duv: 0.003), 0.29 (CCT: 7443 K, Duv: 0) and 0.30 (CCT: 6702, Duv: 0.006), depending on the luminaire's channel number of 6, 8 or 11, respectively. This allows to vary the melanopic EDI from 212.5-227.5 lx up to 275-300 lx without changes in the photopic illuminance (250 lx) or chromaticity ([Formula: see text] [Formula: see text] 0.0014). The highest metameric melanopic Michelson contrast for the 6-, 8- and 11-channel luminaire is 0.16, 0.18 and 0.18, which is accomplished at a CCT of 3017 K (Duv: - 0.018), 3456 K (Duv: 0.009) and 3456 K (Duv: 0.009), respectively. By optimising ~ 490,000 multi-channel LED spectra, we identified chromaticity regions in the CIExy colour space that are of particular interest to control the melanopic efficacy with metameric spectral tuning.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Circadian Rhythm*
Equipment Design
Humans
Lasers
Light*
Lighting*
Materials Testing
Rod Opsins
Sleep*

Substances

Rod Opsins
melanopsin