Patent ID: 7733574

Claim:
An illumination optical apparatus comprising: a light-emitting section; a lens system for converting a diverging beam emitted from the light-emitting section into a beam of collimated light; an afocal optical system for adjusting the cross-sectional area of the beam of collimated light obtained by the lens system; a fly-eye lens for forming a plurality of light-source images from the collimated light whose cross-sectional area is adjusted by the afocal optical system; and a Koehler illumination optical system that uses the plurality of light-source images formed by the fly-eye lens as a light source, wherein a plurality of the light-emitting sections is arranged such that optical axes thereof are parallel with each other, and the lens system is a lens array that includes a lens element corresponding to each of the plurality of light-emitting sections to convert light emitted from each of the light-emitting sections into collimated light with the corresponding lens element.