| 摘要 |
A zoom lens includes, in order from an object side toward an image side: a first lens unit having a positive refractive power and provided with a positive lens; a second lens unit having a negative refractive power; a third lens unit having a positive refractive power and provided with a diffraction plane of a diffraction optical element; a fourth lens unit having a positive refractive power to perform focusing; and an aperture stop between the second lens unit and the third lens unit. According to a change of magnification from a short focal end to a long focal end, the first lens unit is stationary, the second lens unit is moved to the image side, the third lens unit is moved to the object side, and the fourth lens unit is moved, and the positive lens satisfies the following condition formulas:
1.45<nd<1.65; [1]60.0<νd<95.0; and [2]0.005<Pg,F−(−0.001802×νd+0.6483)<0.050 [3] |
| 代理机构 |
Oblon, McClelland, Maier & Neustadt, L.L.P. |
代理人 |
Oblon, McClelland, Maier & Neustadt, L.L.P. |
| 主权项 |
1. A zoom lens comprising, in order from an object side toward an image side:
a first lens unit having a positive refractive power and provided with a positive lens; a second lens unit having a negative refractive power; a third lens unit having a positive refractive power and provided with a diffraction plane of a diffraction optical element; a fourth lens unit having a positive refractive power and configured to perform focusing; and an aperture stop installed between the second lens unit and the third lens unit, wherein, according to a change of magnification from a short focal end to a long focal end, the first lens unit is stationary, the second lens unit is moved to the image side, the third lens unit is moved to the object side, and the fourth lens unit is moved, and wherein the positive lens of the first lens unit satisfies the following condition formulas:
1.45<nd<1.65; [1]60.0<νd<95.0; and [2]0.005<Pg,F−(−0.001802×νd+0.6483)<0.050, [3] in which, nd denotes a refractive index of a material of the positive lens, νd denotes an Abbe number of the material of the positive lens, and Pg,F denotes a partial dispersion ratio of the material of the positive lens, which is expressed by: Pg,F=(ng−nF)/(nF−nC), with nF, nC, and ng denoting refractive indexes of F-line, C-line, and g-line of the material of the positive lens, respectively, and the partial dispersion ratio Pg,F. |
