Patent ID: 7712905

Claim:
An imaging system comprising: a plurality of optical elements configured to image an off-axis object field arranged outside an optical axis of the imaging system in an object surface of the imaging system onto an off-axis image field arranged outside the optical axis in an image surface of the imaging system and creating at least one intermediate image; the optical elements comprising at least one mirror group having an object side mirror group entry and an image side mirror group exit, the mirror group including: a first mirror having a first mirror surface configured to receive radiation from the mirror group entry in a first reflecting area; at least one second mirror having a second mirror surface facing the first mirror surface and configured to receive radiation from the first mirror in a second reflecting area; at least one of the first and second mirrors being a concave mirror having a concave mirror surface having a surface of curvature defining a mirror axis on the optical axis; wherein the mirrors of the mirror group are arranged such that radiation from the mirror group entry is reflected at least twice on given ones of the concave mirror surfaces of the mirror group prior to exiting the mirror group at the mirror group exit, and wherein the mirror group has at least one multiply reflecting mirror arranged such that a mirror surface of the multiply reflecting mirror is used twice at reflecting areas overlapping at least partially.