Patent ID: 7957069

Claim:
A projection optical system for imaging a first object into a region of a second object, the projection optical system comprising: a plurality of lenses disposed along an optical axis of the projection optical system; wherein the plurality of lenses is dividable into a plurality of non-overlapping groups of lenses, such that a total refractive power of each group of lenses is one of a negative refractive power and a positive refractive power; wherein a first group of lenses has a negative refractive power; wherein a lens closest to the first object of the plurality of lenses is included in the first group of lenses; wherein a refractive power of each lens of the first group of lenses is a negative refractive power; wherein a second group disposed directly adjacent to the first group has a positive refractive power; wherein a third group disposed directly adjacent to the second group has a negative refractive power; wherein a fourth group disposed directly adjacent to the third group has a positive refractive power; wherein the fourth group of lenses is that group of lenses among all groups of lenses that is disposed closest to the second object; wherein a refractive power of each lens of the fourth group of lenses is equal to or greater than 0, wherein a lens of the third group of lenses which is disposed directly adjacent to a lens of the fourth group of lenses has a concave surface facing towards the second object, and wherein the fourth group of lenses further comprises an aperture stop.