Unit-magnification catadioptric and catoptric projection optical systems
View Patent ↗Ring-field, catoptric and catadioptric, unit-magnification, projection optical systems having non-concentric optical surfaces are disclosed. Each system has a system axis with object and image planes on opposite sides of the system axis. The non-concentric surfaces allow for working distances of the object and image planes in excess of 100 millimeters to be achieved, with a ring-field width sufficient to allow a rectangular object-field having a long dimension in excess of 100 mm to be projected.
1. A unit-magnification optical system having a longitudinal system axis, comprising:
a concave mirror located on the system axis;
a convex mirror located on the system axis and spaced apart from the concave mirror;
a lens including at least one optical element and having positive optical power located on the system axis and spaced apart from the convex mirror on the opposite side thereof from the concave mirror;
an object plane located spaced apart by a first working distance from the lens;
an image plane located spaced apart by a second working distance from the lens; and
wherein the object plane and image plane lie on opposite sides of the system axis; and
wherein the lens consists of first and second air-spaced elements and wherein the first element is a negative meniscus element and the second element is a bi-convex element.
2. The optical system of claim 1 , wherein the mirrors and lens are arranged such that a light ray propagating from the object plane to the image plane is transmitted twice through the lens, reflected twice from the concave mirror, and reflected once from the convex mirror.
3. The optical system of claim 1 , wherein the first and second working distances are the same.
4. The optical system of claim 3 wherein object and image planes are coplanar in a plane perpendicular to the system axis.
5. The optical system of claim 1 wherein the centers of curvature of the convex surface of the bi-convex element, the convex mirror, and the concave mirror are not concentric.
6. A unit-magnification optical system having a longitudinal system axis, comprising:
a concave mirror located on the system axis;
a convex mirror located on the system axis and spaced apart from the concave mirror;
a lens including at least one optical element and having positive optical power located on the system axis and spaced apart from the convex mirror on the opposite side thereof from the concave mirror;
an object plane located spaced apart by a first working distance from the lens;
an image plane located spaced apart by a second working distance from the lens, wherein the object plane and image plane lie on opposite sides of the system axis; and an aperture stop located at the convex mirror and defining a numerical aperture (NA) of the optical system.
7. The optical system of claim 6 , wherein the lens consists of first and second air-spaced elements.
8. The optical system of claim 7 , wherein the first element is a negative meniscus element and the second element is a bi-convex element.
9. The optical system of claim 6 , wherein the lens consists of only one element and that one element is selected from the group consisting of a plano-convex element and a bi-convex element.
10. A unit-magnification optical system having a longitudinal system axis, comprising:
a concave mirror located on the system axis;
a convex mirror located on the system axis and spaced apart from the concave mirror;
first and second plane mirrors spaced apart from the convex mirror, located on opposite sides of the system axis, and inclined to the system axis; and
first and second positive lenses, each thereof including at least one lens element, the first positive lens being spaced apart from the first plane mirror and defining an object plane spaced apart from the first positive lens, the second positive lens being spaced apart from the second plane mirror and defining an image plane spaced apart from the second positive lens, whereby the object plane and the image plane lie on opposite sides of the system axis and wherein the first and second positive lenses are identical and wherein each of the positive lenses consists of first and second air-spaced elements and wherein the first element is a negative meniscus element and the second element is a bi-convex element.
11. The optical system of claim 10 , wherein the mirrors and lenses are arranged such that a light ray propagating from the object plane to the image plane is transmitted once through the first positive lens, reflected twice from the concave mirror, reflected once from the convex mirror, then transmitted through the second positive lens.
12. The optical system of claim 10 wherein each of the plane mirrors are inclined at 45 degrees to the system axis such that the object and image planes are parallel to the system axis.
13. A unit-magnification optical system having a longitudinal system axis, comprising:
a concave mirror located on the system axis;
a convex mirror located on the system axis and spaced apart from the concave mirror;
first and second plane mirrors spaced apart from the convex mirror, located on opposite sides of the system axis, and inclined to the system axis;
first and second positive lenses, each thereof including at least one lens element, the first positive lens being spaced apart from the first plane mirror and defining an object plane spaced apart from the first positive lens, the second positive lens being spaced apart from the second plane mirror and defining an image plane spaced apart from the second positive lens, whereby the object plane and the image plane lie on opposite sides of the system axis; and
an aperture stop located at the system axis and defining a numerical aperture (NA) of the optical system.
14. The optical system of claim 13 , wherein the first and second positive lenses are identical.
15. The optical system of claim 14 , wherein the each of the positive lenses consists of only one element and that element is selected from the group consisting of a plano-convex element and a bi-convex element.
16. The optical system of claim 12 , wherein each of the positive lenses consists of first and second air-spaced elements.
17. The optical system of claim 16 , wherein the first element is a negative meniscus element and the second element is a bi-convex element.
18. A unit-magnification optical system having a longitudinal system axis, comprising:
a first concave mirror located on the system axis;
a convex mirror located on the system axis and spaced apart from the concave mirror;
a second concave mirror smaller than the first concave mirror, located on the system axis between the first concave mirror and the convex mirror
an object plane located spaced apart by a first working distance from the first concave mirror;
an image plane located spaced apart by a second working distance from the first concave mirror; and
wherein the object plane and image plane lie on opposite sides of the system axis.
19. The optical system of claim 18 wherein the mirrors are arranged such that a light ray propagating from the object plane to the image plane is reflected twice from the first concave mirror, twice from the convex mirror and once from the second concave mirror.
20. The optical system of claim 18 , further including at least one plane reflecting surface immediately adjacent the convex mirror, inclined to the optical axis, and arranged to spatially separate the object and image planes.