| 摘要 |
PROBLEM TO BE SOLVED: To provide a compact objective optical system which excels in color reproducibility and where halation by guide light of a laser probe is reduced. SOLUTION: The objective optical system has a first group G1 having positive refractive power, and a second group G2 having positive refractive power. The first group G1 has a first parallel flat plate L1, a stop S, a second parallel flat plate L2, and a first plano-convex lens L3 turning its convex surface to an image side, wherein the first parallel flat plate L1, the second parallel flat plate L2 and the plane-convex lens L3 form a cemented lens. The second parallel flat plate L2 includes an infrared absorbing filter, and the second group G2 has a second plan-convex lens L4 turning its convex surface to an object side. COPYRIGHT: (C)2010,JPO&INPIT
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