| 摘要 |
PROBLEM TO BE SOLVED: To provide an image reading lens for reducing and imaging image information in a document on an imaging element formed by arraying elements linearly, and reading the image information by the imaging element. SOLUTION: In this image reading lens, a first group 1 is a meniscus lens having a convex face facing the object side; a second group 2 is a biconvex lens, a third group 3 is a cemented lens constituted of a plurality of lenses, wherein the face closest to the object side has a convex face on the object side, and the face closest to the image side has a convex face on the image side; and a fourth group 4 is a meniscus lens having a concave face facing the object side. When the focal length of the whole system of the image reading lens is f, the thickness of the whole system of the image reading lens isΣd, the thickness of the cemented lens of the third group is d<SB>3g</SB>, the following conditions: (1) 0.4<d<SB>3g</SB>/Σd<0.6, and (2) 0.6f<Σd<0.8f are satisfied. COPYRIGHT: (C)2011,JPO&INPIT |
