| 摘要 |
PURPOSE: A micro lithography reduction-projection objective is provided to use supremely a material in connection with acromat. CONSTITUTION: A micro lithography reduction-projection objective comprises first to sixth lens groups(LG1-LG6). The first, third and fifth lens groups(LG1,LG3,LG5) are a positive lens group, and the second, fourth and sixth lens groups(LG2,LG4,LG6) are a negative lens group. The sixth lens group(LG6) comprises an apparatus iris(AP). Lenses(18,23,26) in the fourth to sixth lens groups(LG4-LG6) have a negative refraction force, and are comprised of a quartz glass(SiO2), respectively.
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