PROBLEM TO BE SOLVED: To provide a small sized image reading lens, an image reader and an image forming apparatus obtaining a high quality image by matching an image surface position in the optical axis direction of the sagittal beam and the meridional beam and correcting the chromatic aberration.;SOLUTION: The image reader includes: a first group composed of a first lens of a negative meniscus shape with a convex surface facing the object side; a second group composed of a second lens of a positive meniscus shape with a convex surface facing the object side; a third group composed of a third lens of a negative meniscus shape with a concave surface facing the object side; a fourth group composed by joining a fourth lens which is convex on both surfaces and a fifth lens of a negative meniscus shape with a convex surface facing the image side; and a fifth group composed of a sixth lens of a negative meniscus shape with a convex surface facing the image side, in this order from the object side. In this case, it is characteristic that following expressions (1) and (2) are satisfied. However, f expresses the focal distance of the total image reading lens system, f1 expresses the focal distance of the first lens, Σd expresses the thickness of the total image reading lens system: expression (1) 0.7Σd/f1.0, expression (2) 0.8-f1/f2.3.;COPYRIGHT: (C)2012,JPO&INPIT
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机译:要解决的问题:为了提供小型的图像读取透镜,图像读取器和图像形成装置,其通过使矢状光束和子午光束的光轴方向上的像面位置匹配并校正色度来获得高质量的图像。解决方案:图像读取器包括:第一组,该第一组由负弯月形的第一透镜构成,该第一透镜具有面向物侧的凸面;第二组由具有弯月形形状的第二透镜构成,该第二透镜具有面向物侧的凸面。第三组由弯月形负透镜构成,其第三透镜的凹面朝向物侧。第四组,其特征在于,将两面均为凸面的第四透镜和弯月面形状为负的弯月状的第五透镜的凸面朝向像侧,将第四组接合。第五组由负弯月形状的第六透镜构成,该透镜具有从物侧开始依次面对像侧的凸面。在这种情况下,特征在于满足以下表达式(1)和(2)。但是,f表示整个图像读取镜头系统的焦距,f 1 Sub>表示第一个透镜的焦距,&Sigma; d表示整个图像读取镜头系统的厚度:表达式(1 )0.7 <&Sigma; d / f <1.0,表达式(2)0.8 <-f 1 Sub> / f <2.3 .;版权:(C)2012,JPO&INPIT
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