Patent ID: 8493670
Filing Date: 2013-07-23
Classification: G02B,G03F

Abstract:
1. A unit-magnification optical system having a longitudinal system axis, comprising: a minor located on the system axis; an aperture stop located at the minor and defining a numerical aperture (NA) of the system; a first lens group including at least one optical element and having negative optical power located on the system axis and spaced apart from the mirror; a second lens group including at least one lens element and having positive optical power located on the system axis and spaced apart from the first lens group; an object plane located spaced apart by a first working distance from the second lens group; an image plane spaced apart from the second lens group by a second working distance; and wherein the object plane and image plane lie on opposite sides of the system axis and wherein the first and second working distances are the same and the object and image planes are coplanar in a plane perpendicular to the system axis.