Healthy, natural, efficient and tunable lighting: four-package white LEDs for optimizing the circadian effect, color quality and vision performance

To date, most current reports on the development and optimization of artificial lighting sources have focused on the energy performance levels and limited color qualities of white light-emitting diodes (LEDs). However, these properties are insufficient in terms of representing all performance levels required when adjusting white LEDs for healthy and smart lighting. Here, we introduce essential and advanced figures of merit pertaining to circadian performance as well as vision performance and color quality. We compare all possible properties of commercialized artificial lighting, daylight and four-package white LEDs which consist of long-wavelength pass dichroic filter (LPDF)-capped, phosphor-converted red, amber and green LEDs (pc-LEDs) and a blue LED. We show that these tunable four-package white LEDs produce a tunable circadian effect for melatonin suppression/secretion, a high color quality for color perception/reproduction, high efficiency for energy savings and tunable figures of merit for the smart LED lighting market. Researchers in Korea have discovered that carefully designed white LEDs can help optimize an individual's circadian rhythm. Ji Hye Oh and co-workers from Kookmin University studied four-package white LEDs, which consist of phosphor-converted red, amber and green LEDs, a blue LED and a long-wavelength dichroic filter. They compared these devices with a variety of traditional forms of lighting, and found that such four-package LED designs yield a high luminous efficacy, excellent color rendering and a tunable circadian effect for regulating the secretion of melatonin. The figures of merit suggest that carefully designed white LEDs could play an important role in creating smart lighting systems that help maintain good health, bring energy savings and provide optimal visualization of colors.