IMAGING OPTICAL SYSTEM AND PROJECTION ALIGNER

摘要

PROBLEM TO BE SOLVED: To provide an imaging optical system of high performance capable of surely suppressing the birefringence arising when wavelengths are made shorter to a lower level and a projection aligner of high performance. SOLUTION: This imaging optical system has at least one refractive member consisting of a crystalline material SrF2. COPYRIGHT: (C)2003,JPO