| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a reading lens that consists of the small number of lens elements or five lens elements, has telecentricity on an image side, further excellently corrects a longitudinal chromatic aberration in a wide range from the C-line to the g-line, and on top of that, to attain miniaturization and reduction in costs.SOLUTION: A reading lens is composed of a three-group five-element configuration consisting of, in order from an object side toward an image side,: a first lens group G1 that has a positive refractive power as a whole bounded by a first lens L1 of a double convex lens and a second lens L2 of a negative meniscus lens with a concave surface arranged to be directed toward the object side; a second lens group G2 that has a negative refractive power as a whole bounded by a third lens L3 of a double concave lens and a fourth lens L4 of a positive meniscus lens with a convex surface arranged to be directed toward the object side; and a third lens group G3 that is composed of a fifth lens L5 of the double convex lens. The reading lens has an aperture diaphragm AD between the first lens group G1 and the second lens group G2, and is disposed so as to be telecentric on the image side. On an imaging plane side of the third lens group G3, dummy glass DG is disposed that is composed of a parallel flat plate.</p> |
