| 摘要 |
PROBLEM TO BE SOLVED: To provide a photo-optical system tolerant to an autoclave sterilization and inconspicuous in ghost light. SOLUTION: The photo-optical system is composed of at least a cover glass which is exposed outside and an objective lens from object side to order, the cover glass is composed of a material which has ruggedness against the autoclave sterilization, the objective lens is composed by a pre-group which has a negative refraction, a brightness diaphragm and a back group which has a positive refraction from the object side to order, and the concave face of the pre-group which is closest to the object is directed to the object. COPYRIGHT: (C)2004,JPO
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