| 摘要 |
<P>PROBLEM TO BE SOLVED: To exert favorable imaging performance by correcting various aberrations in an image reading lens. <P>SOLUTION: The image reading lens includes, in order from an object side, a front group GF, an aperture stop St, and a back group GB, and has a telecentricity in the object side. The front group GF is disposed with: a first group G1 of a positive or negative cemented lens; a second group G2 of a positive or negative cemented lens; a third group G3 of a positive cemented lens with its convex surface on the object side; and a fourth group G4 of a cemented lens with its concave surface on an image side. The back group GB comprises three or four lens groups, and includes a fifth group G5 of a negative cemented lens with its concave surface on the object side, and a positive sixth group G6 with its convex surface on the image side. Three or more positive lenses constituting the front group GF and two or more positive lenses constituting the back group GB are configured to satisfy a conditional expression (1): νd>60.0, and one or more positive lenses constituting the front group GF and two or more positive lenses constituting the back group GB are configured to satisfy a conditional expression (1): Δθ<SB POS="POST">g,d</SB>>0.015. <P>COPYRIGHT: (C)2013,JPO&INPIT |
