Spectral Optimization of Three-Primary LEDs by Considering the Circadian Action Factor

For humans, nonvisual biological effects, which can be parameterized by the circadian action factor (CAF), are important for their health and work performance. In this paper, an approach by adjusting electrical currents of three-primary light-emitting diodes (RGB-LEDs) to tune the CAF and color coordinates to be close to those of the standard light with various correlated color temperature (CCT) (2700 K–6500 K) has been reported. This approach is based on deriving an empirical formula between the optical power and the electrical current. In order to meet the requirement of both high color rendering index (CRI) and better CAF, we theoretically perform further spectral optimization on RGB-LEDs and have found that peak wavelengths of 466, 547, and 615 nm for the blue, green, and red color component, respectively, turn out to be the best peak wavelength combination for obtaining both high CRI and high luminous efficacy of radiation of RGB-LEDs, while the CAF, CCT, and color coordinates of RGB-LEDs approach those of the standard light.