Optical element, illumination apparatus, and projective display apparatus

An illumination apparatus, comprising:

• a light source;
• an optical member including a first surface on which light from the light source is incident and a second surface facing the first surface;
• and
• an integrator on which light emitted from the optical member is incident, wherein
• the optical member is rotatable around a rotation axis extending parallel to a direction in which light from the light source is incident and is emitted,
• a planar shape of the optical member is annular around the rotation axis,
• multiple recessed and protruding structure units each having a fan-surface-like planar shape and including a recessed and protruding portion are consecutively formed on the first surface or the second surface of the optical member,
• an extended line of a boundary between adjacent recessed and protruding structure units intersects the rotation axis,
• when the boundary between the adjacent recessed and protruding structure units is a mirror plane, the adjacent recessed and protruding structure units are in a mirror symmetry relation, and recessed and protruding portions of the adjacent recessed and protruding structure units are smoothly connected together,
• recessed portions and protruding portions of the recessed and protruding portion of each recessed and protruding structure unit are smoothly connected together, and
• an area occupied by the recessed and protruding portion of each recessed and protruding structure unit is larger in size than incident light from the light source.