| 摘要 |
A Keplerian zoom finder optical system having a zoom power variable objective lens, the Keplerian zoom finder optical system comprising: a zoom objective lens including a first lens group having a negative refracting power and a second lens group including at least a positive meniscus lens whose convex surface faces an image and having a positive refracting power, the lens group being moved for the purpose of conducting the zoom power variation; and an ocular used for enlarging and observing the image formed by the zoom objective lens, wherein when a focal length of the first lens group is f1, a focal length of the second lens group is f2, and a curvature radius of the convex surface of the positive meniscus lens is ra, the following conditions are met: <IMAGE> <IMAGE>
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