Influence of melanopsin-expressing retinal ganglion cells on spatial brightness in ante and post meridian periods of time

To clarify the effects of melanopsin cells on spatial brightness, we conducted an experiment in which the brightness of the space was evaluated using a magnitude estimation method during AM (9.00 to 10:00) and PM (18.00 to 19.00) periods by modulating the stimulus value of melanopsin cells while keeping the chromaticity values of a light environment constant. The light environment was constructed and installed on the ceiling of a windowless room model of a typical office space, using a 24-colour multispectral light source device with variable spectral distribution characteristics. The results showed that the influence of melanopsin cells under high-illuminance conditions depends on the time slot. The floor illuminance, at which the influence of melanopsin cells begins to emerge, was suggested to exist between 500 lx and 1000 lx. This study can contribute to the development of lighting design methods to balance energy efficiency and comfort by controlling melanopsin stimulation.