OPTICAL ELEMENT AND ILLUMINATION DEVICE

摘要

The optical element according to one embodiment is formed from a material that is transparent with respect to visible light, and is shaped so as to be rotationally symmetrical with respect to a central axis. A hole wherein the transparent material is not present is provided to the inside of the optical element. An inner surface of the hole is shaped so as to include a curved section wherein a hole boundary at which said inner surface intersects a plane that includes the central axis expands toward the outside of the optical element. When a starting point is set inside the hole and the forward direction is the direction clockwise along the boundary with respect to the starting point, and when a first tangent vector is set at a first point along the boundary and a second tangent vector is set at a second point that is next to the first point in the forward direction, the angle formed by the second tangent vector with respect to the first tangent vector, the clockwise direction being positive, is always equal to or greater than zero. In addition, the inner surface of the hole does not include a surface that is recessed to the inside.