Image reading lens, image reading device using the same and image forming device

Abstract

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. 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 is [Sigma]d, 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> / [Sigma]d<0.6, and (2) 0.6f<[Sigma]d<0.8f are satisfied.

Description

technical field [0001] The present invention relates to an image reading lens, an image reading device, and an imaging device, and in particular to an image reading lens used in an imaging device such as a digital copier or a facsimile machine. image information of the original image on the imaging element, and forms an image based on the read image information. Background technique [0002] In an imaging device such as a digital copier or a facsimile, an image reading unit or an image scanner uses an image reading lens to reduce the image to be read, which is used for imaging and signal processing by an imaging element such as a CCD. [0003] In order to read a color original, for example, a so-called three-line CCD is used, that is, three columns of imaging elements with red, green, and blue filters are arranged on a substrate, and the image is imaged on each imaging element surface, and then decomposed into three primary colors. Color originals are converted to signals. ...

AI Technical Summary

Problems solved by technology

[0010] Patent Document 1 (JP Laid-Open No. 2008-275783) and the like disclose a telephone-type image reading lens, in which the focal length ratio of the four-lens structure is F6, and it is difficult to obtain optical performances such as sufficient brightness and a wide viewing angle.

[0011] In addition, Patent Document 2 (JP Unexamined Publication No. 2005-234068), Patent Document 3 (JP Unexamined Publication No. 2005-266771), etc. also disclose reading lenses with a large viewing angle composed of five lenses, but the brightness of these lenses It is also F6, and there is no difference in lightness from the reading lens of the four-lens structure.

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