| 摘要 |
A zoom lens substantially consists of, in order from the object side, a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group. During magnification change from the wide-angle end to the telephoto end, the first and third lens groups are fixed in the optical axis direction, the second lens group is moved toward the image side, and the fourth lens group is moved along the optical axis. The second lens group includes an air space formed between a convex surface and a concave surface, and a cemented surface between a negative lens and a positive lens. The third lens group consists of, in order from the object side, a fixed front group, and a positive rear group being able to be shifted in directions intersecting with the optical axis to shift the image formed on the reduced side. |
| 主权项 |
1. A zoom lens consisting of, in order from an object side:
a first lens group having a positive refractive power; a second lens group having a negative refractive power; a third lens group having a positive refractive power; and a fourth lens group having a positive refractive power, wherein, during magnification change from a wide-angle end to a telephoto end, the first lens group and the third lens group are fixed in an optical axis direction relative to an image plane, the second lens group is moved toward an image side along the optical axis relative to the image plane, and the fourth lens group is moved in the optical axis direction relative to the image plane, the second lens group comprises an air space formed between a convex surface and a concave surface facing each other, and a cemented surface between a negative lens and a positive lens, the third lens group consists of, in order from the object side, a front group that is fixed, and a rear group that has a positive refractive power and is able to be shifted in directions intersecting with the optical axis to thereby shift an image formed on the image side, and the condition expressions (1) to (3) below are satisfied:
2.0<|f12w/fw|<3.0 (1),2.5<|(Rz1+Rz2)/(Rz1−Rz2)|<5.0 (2), and8.6<Mz/fw<12.0 (3),where f12w is a combined focal length of the first lens group and the second lens group at the wide-angle end, fw is a focal length of the entire system at the wide-angle end, Rz1 and Rz2 are radii of curvature forming the air space in the second lens group, and Mz is an amount of movement of the second lens group during magnification change from the wide-angle end to the telephoto end. |
