Dual-imaging optical system
AssigneeNikon Corporation
InventorTomowaki Takahashi
Life of this patent
Estimating the term…
Abstract
An optical imaging system especially for microlithography includes a first imaging system forming an intermediate image of an object, and a second imaging system forming, on a surface, an image of the intermediate image. A reflective surface directs light from the first imaging system to the second imaging system. An aspherical corrective optical surface is located at or near the location of the intermediate image for correcting aberrations such as high-order distortion, aberrations due to accumulation of manufacturing tolerances, and spherical aberration. The first imaging system comprises a positive power refractive element and a concave mirror. The second imaging system comprises refractive elements and no concave mirror.
Claims19
An optical imaging system for forming an image of an object on a surface, comprising on an optical axis:
- (a) a first imaging system that forms an intermediate image of the object;
- (b) a second imaging system that forms an image, of said intermediate image, on said surface;
- and
- (c) a first corrective aspheric optical surface, located at or near the location of the intermediate image.
A catadioptric imaging system for forming an image of an object on a surface, comprising:
- (a) a first imaging system that forms an intermediate image of the object, the first imaging system comprising
- (i) a concave mirror, and
- (ii) at least one convex lens arranged such that light from the object propagates through the convex lens to the concave mirror and light reflected from the concave mirror propagates back through the convex lens;
- and
- (b) a second imaging system that forms an image of the intermediate image on the surface, the second imaging system comprising one or more refractive lenses;
- (c) a reflective surface arranged to guide light flux returning from the first imaging system toward the second imaging system;
- and
- (d) a corrective aspheric optical surface, located at or near the location of the intermediate image.
Dependencies are inferred from the claim text.