Patent ID: 7746561
Filing Date: 2010-06-29
Classification: G02B,G03B,G03F

Abstract:
1. A projection optical system which projects an image of a first object onto a second object, the projection optical system comprising: a plurality of lenses; and a plurality of aperture stops for determining a numerical aperture, wherein said plurality of aperture stops include a first aperture stop having an opening whose size is configured to be changed, and a second aperture stop having an opening whose size is configured to be changed, wherein said first aperture stop and said second aperture stop are positioned nearer to the second object than a lens having a maximum effective diameter among lenses included in an imaging optical system nearest to the second object, wherein at least one of said first aperture stop and said second aperture stop is positioned at or near a pupil of the imaging optical system, and wherein a range of a numerical aperture determined by said first aperture stop is larger than a range of a numerical aperture determined by said second aperture stop.