| 摘要 |
A zoom lens includes a first lens group with a diffraction optical element and having positive refractive power, a second lens group having negative refractive power, a third lens group having negative refractive power, and a fourth lens group having positive refractive power, which are sequentially arranged from an object side to an image side. The second lens group and the third lens group are moved in accordance with zooming between a wide angle end and a telephoto end such that the second lens group is positioned to the object-most side at the wide angle end, and the third lens group is positioned to the image-most side at the telephoto end. At least one of the second lens group and the third lens group includes a negative lens satisfying the conditional expressions: 1.50<nd<1.75; 60.0<νd<75.0; and θC,A′−0.0015×νd<0.2550. |
| 主权项 |
1. A zoom lens comprising:
a first lens group provided with a diffraction optical element and having positive refractive power, a second lens group having negative refractive power, a third lens group having negative refractive power, and a fourth lens group having positive refractive power, which are sequentially arranged, from an object side to an image side, wherein the second lens group and the third lens group are moved in accordance with zooming between a wide angle end and a telephoto end such that the second lens group is positioned to the object-most side at the wide angle end, and the third lens group is positioned to the image-most side at the telephoto end, wherein at least one of the second lens group and the third lens group includes a negative lens satisfying the following conditional expressions:
1.50<nd<1.75; [1]60.0<νd<75.0; and [2]θC,A′−0.0015×νd<0.2550, [3] in which nd denotes the refractive index of a material composing the negative lens, νd denotes the Abbe number of the material composing the negative lens, and θC,A denotes the partial dispersion ratio of the material composing the negative lens, and the partial dispersion ratio θC,A′ is represented as θC,A′=(nC−nA′)/(nF−nC) with the refractive indices of the material composing the negative lens for an F line, a C line, and an A′ line being denoted by nF, nC, and nA′. |
