US Patent 12022590 Illumination device, illumination system, and illumination control method

An illumination device includes a light emitter configured to emit illumination light and a controller configured to control the light emitter. The controller controls the illumination light such that a first decrease ratio of melanopic illuminance of illumination light during night-time illumination to melanopic illuminance of illumination light during daytime illumination is higher than a second decrease ratio of illuminance of the illumination light during the night-time illumination to illuminance of the illumination light during the daytime illumination.