Illumination optical apparatus and optical apparatus

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.