| 摘要 |
PROBLEM TO BE SOLVED: To obtain an original reading lens which has an FNO showing the bright one though constitution is simple, whose aberration is well-balancedly corrected while maintaining a large numerical aperture to a peripheral viewing angle, and which has high resolving power, and an original reader using the lens. SOLUTION: This original reading lens for forming the image information of an original into an image on a reading means has four lenses, that is, a 1st positive lens being a meniscus whose convex surface faces an original surface side, a 2nd negative lens whose both surfaces are concave, a 3rd positive lens whose both surfaces are convex, and a 4th negative lens being a meniscus whose concave surface faces the original surface side in order from the original surface side. At least one lens surface is set so that its shape in a direction orthogonal to the optical axis is asymmetric to the optical axis and the lens satisfies respective conditional expressions.
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