JP2003177317A5 - - Google Patents

Claims (3)

In order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having positive refractive power,
When the lens position state changes from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group increases, and the distance between the second lens group and the third lens group increases. At least the first lens group and the fourth lens group are moved to the object side so that the distance between the third lens group and the fourth lens group decreases,
The third lens group includes, in order from the object side, three lenses, a first positive lens, a second positive lens, and a negative lens, and the fourth lens group includes a positive lens disposed closest to the image side, A negative lens disposed on the object side,
A zoom lens satisfying the following conditional expressions (1) to (3):
(1) 0.015 <D3P / ft <0.100
(2) 0.10 <Yo / (Bfw-Rlast) <0.25 (Rlast <0)
(3) 0.4 <Δ4 / (ft · fw) ^1/2 <1.0
However,
D3P: the center thickness of the second positive lens disposed in the third lens group,
ft: focal length in the telephoto end state,
Yo: half the diagonal length of the screen
Rlast: radius of curvature of the lens surface closest to the image side of the fourth lens group,
Bfw: the distance from the lens surface closest to the image side to the image plane in the fourth lens group in the wide-angle end state;
[Delta] 4: you the amount of movement toward the object side and positive at the moving amount of the fourth lens group when the lens position state to the telephoto end state changes from the wide-angle end state,
fw: focal length in the wide-angle end state. The zoom lens according to claim 1.
A zoom lens that satisfies at least one of the following conditional expressions (4) and (5):
(4) 0.1 <| f3N | / ft <0.7
(5) 0.2 <| r31 | / f3 <2.0
However,
f3N: focal length of the negative lens arranged in the third lens group,
ft: focal length in the telephoto end state,
r31: radius of curvature of the object-side lens surface of the negative lens disposed in the third lens group,
f3: focal length of the third lens group. The zoom lens according to claim 1 or 2,
The second lens group includes, in order from the object side, a first negative lens having a concave surface facing the image side, a second negative lens having a concave surface facing the object side, and a positive lens having a convex surface facing the object side. A zoom lens characterized by satisfying the following conditional expression (6):
(6) -0.7 <(r21 + r22) / (r21-r22) <0
However,
r21: radius of curvature of the image side lens surface of the first negative lens disposed in the second lens group,
r22: radius of curvature of the object-side lens surface of the second negative lens disposed in the second lens group.