| 摘要 |
In a four-sheet lens configuration composed of convex, concave, convex, and concave lenses, predetermined conditional expressions are satisfied so as to attain a compact size and a wider field angle in a lens system for reading out images, while correcting various kinds of aberration. Further, a bright lens system is obtained. Successively from the object side, a first lens (L1) comprising a positive meniscus lens with a convex surface directed onto the object side, a second lens (L2) comprising a biconcave lens, a third lens (L3)comprising a biconvex lens, and a fourth lens (L4) comprising a negative meniscus lens with a convex surface directed onto an imaging surface side are disposed, while the following conditional expressions (1) to (3) are satisfied:0.87<f(1/R8-1/R7)<2.75(1)0.23<R1/f<0.38(2)1.08<|N4xf4|/f<3.70(3)
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