Patent ID: 7277158

Claim:
A lithographic projection apparatus, comprising: an illumination system configured to provide a beam of radiation; a support configured to support a patterning device, the patterning device configured to impart the beam of radiation with a pattern in its cross section; a substrate table configured to hold a substrate; and a projection system configured to project the patterned beam of radiation onto a target portion of the substrate, wherein the illumination system comprises a pupil facet mirror; and a plurality of field facet mirrors, each field facet mirror being associated with one of a plurality of radiation sources and each field facet of a given field facet mirror being configured to image the associated source onto one of a plurality of pupil facets of the pupil facet mirror, each pupil facet being adapted to direct the source image received to a predetermined area to form the beam of radiation, wherein an optical path length between each field facet and its corresponding pupil facet is substantially the same for all field facet and pupil facet pairs, all the field facets have substantially the same optical power and all the pupil facets have substantially the same optical power.