| 摘要 |
PROBLEM TO BE SOLVED: To provide an image reading lens of a small diameter and a low cost that has a high contrast in a high spatial frequency area, enables a full color to be read, allows a light beam to be incident at a full stop even in a peripheral area, while a peripheral light amount is thereby secured.SOLUTION: The image reading lens comprises: a first positive meniscus lens 1 with a convex surface on the object side; a second negative lens 2 with a concave surface on an image side; a stop 6; a third positive lens 3 with the convex surface on the object side; a fourth positive lens 4 with the convex surface on the object side; and a fifth negative lens 5 with the convex surface on the image side; arranged in order from an object side. The image reading lens satisfies the following condition (1)&ngr;d3-&ngr;d4>25 and (2)0.3<f3/f4<3, where an Abbe number of the third lens 3 denotes &ngr;d3, an Abbe number of the fourth lens 4 denotes &ngr;d4, a focal length of the third lens 3 denotes f3, and a focal length of the fourth lens 4 denotes f4. |
