Abstract: A reduction projection system characterized by large numerical aperture has an unobscured optical path without the need to resort to truncated lens elements and provides locations for field and aperture stops. The system includes a first lens group, a first double-pass component group, a first concave mirror, a second lens group, a second double-pass component group, a second concave mirror, and a third lens group. The light encounters the first double-pass component group before and after it encounters the first concave mirror. Similarly, the light encounters the second double-pass component group before and after it encounters the second concave mirror. Together, the first lens group, the first double-pass component group, the first concave mirror, and the second lens group form an intermediate reduced image of the object at an intermediate image plane. The second double-pass component group, the second concave mirror, and the third lens group form a further reduced image at an image plane.