| 摘要 |
PROBLEM TO BE SOLVED: To secure an excellent optical performance practically non-susceptible to birefringence even when a material having characteristic birefringence is in use, such as fluorite. SOLUTION: The projection optical system comprises a plurality of transmissive members, wherein an image of a first plane is projected onto a second plane. The transmissive members includes crystalline transmissive members made of a crystalline material. Provided that the effective diameter of a crystalline transmissive member is ED and that the outer diameter of the same is LD, then at least one of the crystalline transmissive members satisfies a formula: 0.3<ED/LD<0.95. COPYRIGHT: (C)2004,JPO
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