Indoor illumination imitating optical parameters of sunny summer daylight

Abstract Natural daylight has an essential effect on the human organism. It affects mood, emotion or the ability to sleep. For most people, a sunny summer day is the most pleasant day. For this reason, we propose an indoor lighting source which imitates sunny summer daylight. We collected a series of experimental measurements of days during the summer of 2018. We chose the sunniest day (minimum cloud, high temperature, high total time of sunshine) and we used its optical parameters as an example. The obtained parameters (colour coordinates x and y) served as the input parameters for LightTools simulations. Simulations in LightTools enabled to obtain power settings of individual colour chips. The power values were transformed into forward current values of individual colour chips. Subsequent, laboratory measurements of the optical parameters according the forward current values were done with a tetrachromatic RGBA LED. Suitable setting of forward currents of the RGBA LED enables to create sunny daylight from sunrise to sunset. The laboratory measurement confirmed our assumptions, the imitation of daylight was successful.