| 摘要 |
PROBLEM TO BE SOLVED: To provide optical systems for avoiding the influence of a temperature even the inside of a device under high-temperature conditions. SOLUTION: Optical systems 2, 3, 4 are provided with a cover member 12 for enveloping air-tightly an optical element group including at least a lens system. The cover member 12 comprises an introducing port 13 for introducing cooling air; a passage for cooling 15 for passing through the cooling air; and an exhausting port 14 for discharging the cooling air. COPYRIGHT: (C)2004,JPO
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