Catadioptric lens barrel structure

Abstract

A catadioptric lens barrel structure for a projection exposure apparatus includes first and second lens barrels. Each of the lens barrels has an optical axis. The optical axes run parallel to each other. The lens barrel structure also includes a third lens barrel transversely connecting the first lens barrel to the second lens barrel. A reticle is placed in front of an entrance end of the first lens barrels and a wafer is placed in front of an exit end of the second lens barrel. Each lens barrel has a center plane perpendicular to the corresponding optical axis at a position half-way along the length of the corresponding lens barrel. A lens barrel support structure firmly secures the plurality of lens barrels. The lens barrel support structure is made of a material having a low coefficient of thermal expansion. The support structure includes first and second support platforms to support the first and second lens barrels, respectively, near the corresponding center planes to minimize errors due to temperature changes, vibrational motion, or other external forces.

Dependencies are inferred from the claim text.