| 摘要 |
A lens for reading an original has first to fifth lens groups sequentially arranged from an object side of a lens system to an image side thereof. The first lens group is constructed by a first lens composed of a negative meniscus lens having a convex face directed on the object side. The second lens group is constructed by a second lens composed of a positive lens. The third lens group is constructed by a third lens composed of a biconcave lens. The fourth lens group is constructed by a fourth lens composed of a positive lens. The fifth lens group is constructed by a fifth lens composed of a positive meniscus lens having a convex face directed on the object side. A combined focal length f of the entire lens system, a focal length f1 of the first lens group, and a combined focal length f24 of the second to fourth lens groups satisfy the following conditions. -2.4<(f1/f)<-1.2 (I) 0.85<(f24/f)<1.5 (II).
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