Spectral design for potential health lighting based on combined circadian and visual effects

Light, as a basic need of human being, provides not only vision, but also non-visual effects such as regulating the circadian system. While the traditional lighting design only focuses on the visual aspect, we recently proposed a novel health-lighting design space that takes consideration of both visual and circadian aspects. It allows the exploration of combinations of circadian stimulus and visual brightness appearance. In this work, we first demonstrate that with monochromatic LEDs, almost any combination of circadian & visual impacts can be achieved; with the color constraints from the requirement of general illumination and the purpose of adjusting the lighting's circadian effect during the day, an LED color mixing and tuning solution is shown to optimize the achievable gamut in the circadian-versus-visual lighting design space. As an example of applying this concept, we demonstrate that our RGBW LED color-mixing solution can be used to mimic both visual and circadian characteristics of the measured dynamic daylight for both sunny and cloudy weather conditions.