| 摘要 |
PROBLEM TO BE SOLVED: To obtain a light and compact wide visual field ocular which is constituted of three groups having positive, negative and positive refractive indexes in order from an object side, where the 1st lens group is constituted of a positive meniscus lens having a concave surface facing the object side and the 2nd lens group is constituted of a combined lens consisting of a negative lens and a positive lens, whose angle of visibility is >=60 deg. and whose diameter is small. SOLUTION: This ocular is constituted of a 1st lens group G1 constituted of the positive meniscus lens whose concave surface faces the object side, a 2nd lens group G2 constituted of the combined lens consisting of a biconcave lens whose surface having a large curvature faces an eye side and a biconvex lens whose both surfaces have same curvature, and a 3rd lens group G3 having the positive refractive power in order from the object side; and satisfies expressions: 1.2<f1 /f<3.5, 3<-f2 /f, 0.010<ν2 N-1/ν2 P, 1<|R3 /f|(provided that f: the focal distance of an entire system, fn : the focal distance of an n-th lens group Gn ,ν2 N: the Abbe number of the negative lens of the 2nd lens group G2 ,ν2 P: the Abbe number of the positive lens of the 2nd lens group G2 , and R3 : the radius of curvature of the surface closest to the object side of the 2nd lens group G2 ).
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