Design of lighting window in a confined space

The daylighting illumination system is used to guide the natural light indoors for illumination. In this paper, we present a novel design of a lighting window to be used in the day lighting system. The lighting window consists of two freeform microstructures which allow the natural light passing through to a confined space such as an underground basement. Integrating with a compensating LED lighting, our design steadily provides 85% indoor illumination efficiency with 70 % uniformity.