Patent ID: 8905586

Claim:
A hybrid illumination system, comprising: a natural lighting apparatus, comprising: a first light condensing member comprising a concave mirror having a parabolic shape and reflecting incident sunlight to a focal region; and a second light condensing member comprising a convex mirror having a parabolic shape and provided in the focal region of the first light condensing member to convert sunlight condensed in the focal region through the first light condensing member into straight parallel light rays; an artificial illumination mechanism supplying artificial illumination via a lighting fixture; and a hybrid controller controlling natural illumination provided by the natural lighting apparatus and artificial illumination provided by the artificial illumination mechanism, the hybrid controller comprising: a luminance sensor measuring indoor luminance; a memory storing a minimum reference luminance for optimal luminance; and a hybrid control module controlling the artificial illumination mechanism to operate when a luminance measured by the luminance sensor is lower than the minimum reference luminance stored in the memory, wherein, when the luminance measured by the luminance sensor is lower than the minimum reference luminance stored in the memory, the hybrid control module sets operation of the lighting fixture based on each luminance level measured by the luminance sensor, and repeats a process of operating the lighting fixture by increasing stepwise a luminance level at which the lighting fixture is operated, from a lowest luminance level to a higher luminance level, until a measured luminance level is greater than or equal to the minimum reference luminance.