Catadioptric lens barrel structure having a support structure to maintain alignment of a plurality of sub-barrels

1. Field of the Invention A catadioptric lens barrel structure for a projection exposure apparatus includes a pair of lens barrels. Each lens barrel has an optical axis and comprises a plurality of sub-barrels which are serially aligned along the corresponding optical axis. The optical axes of the lens barrels run substantially parallel to each other. A reticle is placed in front of an entrance end of a first one of the lens barrels and a wafer is placed in front of an exit end of the second lens barrel. A support structure supports each sub-barrel. A plurality of adjustment articles may be provided to correct the substantially parallel alignment of the optical axes. Each sub-barrel is spaced apart from the others in the series so that each sub-barrel can slide in and out of alignment with the corresponding optical axis and each sub-barrel can be individually attached to or detached from the support structure. The support structure is made of a material having a low coefficient of thermal expansion and is designed to minimize errors due to temperature changes, vibrational motion, or other external forces.