Patent ID: 6606207
Filing Date: 2003-08-12
Classification: G02B

Abstract:
An image reading lens comprising, in succession from the object side, six lenses, i.e., a meniscus-shaped positive first lens having its convex surface facing the object side, a second lens of which the both lens surfaces are concave surfaces, a third lens of which the both lens surfaces are convex surfaces, a meniscus-shaped fourth lens having its concave surface facing the object side, a meniscus-shaped negative fifth lens having its concave surface facing the object side, and a meniscus-shaped negative sixth lens having its concave surface facing the object side, characterized in that when the focal length of the ith lens as counted from the object side is defined as fi and the lens thickness of the fourth lens is defined as d8 and the radius of curvature of the image plane side lens surface of the second lens is defined as r4 and the combined focal length of the fifth lens and the sixth lens is defined as fn and the focal length of the entire system is defined as f, the following conditions are satisfied:0.91<f5/f6<2.78 âˆ’0.27<d8/fn0.16 2.48<r4/f<10.75.