| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an image reading lens capable of satisfying a variety of requirements for an image reading lens and also reading a full-color document image even if formed of a small number of lenses, an image reading device, and an image forming device. <P>SOLUTION: An image reading device comprises an image reading lens. The image reading lens has a five-group six-lens configuration, in which there are arranged a first lens L1 which is a positive meniscus lens, a second lens L2 which is a negative meniscus lens, a cemented lens with positive refractive power in which a third lens L3 which is a negative lens with a biconcave shape, and a fourth lens L4 which is a positive lens with a biconvex shape are cemented together, a fifth lens L5 with negative refractive power, and a sixth lens L6 which is a negative meniscus lens in this order from the object side. There is a stop S between the second and third groups. At least the second lens L2 and the sixth lens L6 have aspherical surfaces. The image reading lens should satisfy the following formulas (1) to (4): (1) 0.9<f1/f<2.6, (2) -1.2<f6/f<-0.7, (3) -0.01<(n convex-n concave)<0.07, and (4) 10.0<(ν convex-ν concave)<11.5. <P>COPYRIGHT: (C)2013,JPO&INPIT |
