DAYLIGHTING OPTICAL ELEMENT AND DAYLIGHTING DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a practical structure that eliminates excessive entry of sunlight indoors and lets in necessary amount of sunlight as needed. SOLUTION: The daylighting optical element 1 of plate shape which is installed at the opening part 20 of a building comprises a plurality of prisms 10 compactly provided on the same plane. One side 13 of the slant faces of each prism 10 has an angle which transmits sunlight when the elevation angleθS of the sun is smaller than the critical elevation angle and totally reflects sunlight when it is larger than the critical elevation angle. The total daylighting amount when the elevation angleθS of the sun is larger than the critical elevation angle is smaller than that when it is smaller than the critical elevation angle. The critical elevation angle is larger than the elevation angleθS at the time when the sun is at the meridian transit in winter. The daylighting device is equipped with a sun following mechanism 4 that follows the movement of the sun and controls the attitude of the daylighting optical element 1 so that the extending direction of each prism 10 and the direction of the line that connects a point on the center axis of the daylighting optical element 1 and the sun S cross orthogonally in the plan view.