Maximization of the Average Color Rendering Index of Color Temperature and Illuminance Constraints

Recent studies have shown that improving the light environment in a room increases intellectual productivity, and studies have been carried out with a focus on light color in addition to illuminance and color temperature. This study therefore focuses on color rendering properties in addition to illuminance and color temperature, and is aimed at establishing a more comfortable room environment. In the experiments in this study, four-color full-color LED lighting units manufactured by Sharp were used, and a spectroscope manufactured by Ocean Photonics was used to measure the average color rendering index. The focus of the study was to enhance the average color rendering index using an optimization algorithm based on the steepest descent method in a controlled environment in which the color temperature and the illuminance were kept constant. The results of the experiments indicate that the average color rendering index was successfully enhanced by using the proposed lighting control method while maintaining the illuminance and color temperature in the room. The results of an experiment in which three-color lighting units were used also indicated that the average color rendering index could similarly be enhanced without altering the illuminance and color temperature. Therefore, the average color rendering index can be enhanced using the proposed lighting control method with lighting units with three or more different colors (which have a wide wavelength range), while still maintaining the illuminance and color temperature in the room or work environment.