| 摘要 |
PROBLEM TO BE SOLVED: To provide an endoscope illuminating optical system suitable for a small-diameter and small-quantity-produced endoscope and capable of obtaining wide light distribution at a very low cost. SOLUTION: This endoscope illuminating optical system is constituted of a light guide made of single or multiple optical fibers and arranged in the insertion section of an endoscope and a plano-convex lens having a convex face on the light guide side and arranged at the tip of the insertion section. The following conditions (1), (2), (3) are satisfied: (1) r-(r<2> -D<2> /4)<1/2> +0.2<=d<=r+(r<2> - D<2> /4<1/2> , (2) 0.4<=sin<-1> Dg(n-1)2r}/ω<=0.8, (3) n>=1.7, where (r) is the absolute value of the radius of curvature of the convex face of the plano-convex lens, (d) is the center thickness of the plano-convex lens, (n) is the refraction factor of the plano-convex lens, Dg is the effective diameter of the light guide, andωis the half field angle of an observation optical system.
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