Illumination system particularly for microlithography

An illumination system, comprising:

• a source of light having a wavelength of less than or equal to 193 nm;
• a first optical element in a path of said light, having a plurality of field raster elements;
• a second optical element in said path, downstream of said first optical element, having a plurality of pupil raster elements;
• wherein said plurality of pupil raster elements receive said light from said plurality of field raster elements, and
• wherein said plurality of pupil raster elements are arranged in an irregular pattern on said second optical element.

An illumination system, comprising

• a source of light source having a wavelength of less than or equal to 193 nm;
• a first optical element having a plurality of field raster elements that receive said light from said source and provide a plurality of secondary light sources;
• a second optical element having a plurality of pupil raster elements that receive said light from said plurality of field raster elements, and redirect said light;
• and
• an optical component that receives said light from said second optical element, and images said secondary light sources into a plurality of tertiary light sources in an exit pupil of said illumination system,
• wherein said plurality of pupil raster elements are arranged to compensate for a distortion of said optical component, such that said tertiary light sources have a regular distribution.