Patent ID: 7303291

Claim:
An illumination apparatus comprising: a light source including a group of light source segments arranged in an array; a lens array including a group of condenser lenses arrayed as opposed to the group of light source segments, and a group of lens elements arrayed as opposed to the group of condenser lenses, each of the lens elements converging a light ray that has been generated in the opposing light source segment and has been transmitted through the opposing condenser lens; and an illumination optical system which guides the rays that have been transmitted through the lens elements in such a manner that the rays fall an illumination plane at a predetermined angle of incidence, wherein the lens elements are arrayed in a rectangular effective area with a clearance from each other, the effective area being defined by the illumination optical system as an area capable of arranging the lens elements and having a shape of a rectangle whose one side extends along an X-axis, and each of the lens elements having a shape of a rectangle whose longitudinal axis intersects the X-axis at 45°, and an aspect ratio of each of the lens elements is less than 2, and the lens elements are arrayed along two sides of the effective area orthogonal to each other with a pitch of √2·V where V represents a length of a shorter side of each of the lens elements.