| 摘要 |
A reading lens system, such as may be used in a facsimile machine or the like, having a small size, low cost, high performance and a large aperture ratio of 1:3.2 to 1:3.5 and a half angle of 22.5 DEG or more. The lens includes, in order from the object side, a first lens element which is a positive meniscus lens having its convex surface directed toward the object side, a second lens element which is a positive meniscus lens having its convex surface directed toward the object side, a third lens element which is a negative meniscus lens having its convex surface directed toward the object wide, a fourth lens element which is a negative meniscus lens having its concave surface directed toward the object side, a fifth lens element having its concave surface directed toward the object side, and a sixth lens element which is a positive lens. The second and third lens elements are cemented to make the overall system a five-unit six-element lens configuration. The lens system satisfies 0.6<¦f4¦/f<1.20, (f4<0), where f is the composite focal length of the overall system and f4 is the focal length of the fourth lens element.
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