Wide angle zoom lens system having shortened closeup focal length

Claim 2

A wide angle zoom lens system capable of photographing objects from infinity to a close distance while maintaining an improved image-forming performance, said system comprising: a first divergent lens group including a divergent forward portion and a convergent rearward portion disposed with a predetermined spacing from said forward portion, the forward and rearward portions being movable relative to each other for focusing; and a second convergent lens group disposed rearwardly of said first group, said first and second groups being movable relative to each other to effect a magnification change.

Claim 3

The zoom lens system according to claim 1, satisfying the following conditions: 1.2|f.sub.1 |<f.sub.12 <2.8|f.sub.1 | and 0.07<d/|f.sub.1 |<0.2, where f 1 is the focal length of said first group, f 12 is the focal length of the rearward portion of said first group, and d is the spacing between the image side principal plane of the forward portion of said first group and the object side principal plane of the rearward portion of said first group during the focusing condition with respect to an infinite object.

Claim 4

The zoom lens system according to claim 2, wherein the rearward portion of said first group includes a positive meniscus lens having its convex surface facing the object side.

Claim 5

The zoom lens system according to claim 3, wherein the forward portion of said first group includes two negative meniscus lenses, each having its convex surface facing the object side.

Claim 6

The zoom lens system according to claim 3, wherein the forward portion of said first group includes, in order from the object side, a positive lens having its more sharply curved surface facing the object side, a negative lens having its more sharply curved surface facing the image side, and a negative meniscus lens having its convex surface facing the object side.

Claim 7

The zoom lens system according to claim 3, wherein the forward portion of said first group includes, in order from the object side, a negative meniscus lens having its convex surface facing the object side, a positive lens, and a negative lens having its more sharply curved surface facing the image side.

Claim 8

The zoom lens system according to claim 4 having the following numerical data: ______________________________________ Total focal length of the entire system: f = 36.0˜68.6 Angle of view: 2ω = 31°˜17.6° F-number: ______________________________________ 3.5 r.sub.1 = 43.640 d.sub.1 = 1.5 n.sub.1 = 1.71300 ν.sub.1 = 53.9 r.sub.2 = 25.862 d.sub.2 = 4.9 r.sub.3 = 97.646 d.sub.3 = 2.3 n.sub.2 = 1.69680 ν.sub.2 = 55.6 r.sub.4 = 34.089 d.sub.4 = close distance correcting spacing r.sub.5 = 32.807 d.sub.5 = 3.8 n.sub.3 = 1.80518 ν.sub.3 = 25.5 r.sub.6 = 43.313 d.sub.6 = variable spacing r.sub.7 = 38.800 d.sub.7 = 8.6 n.sub.4 = 1.62041 ν.sub.4 = 60.3 r.sub.8 = -118.771 d.sub.8 = 2.5 r.sub.9 = 21.150 d.sub.9 = 4.9 n.sub.5 = 1.62041 ν.sub.5 = 60.3 r.sub.10 = 67.565 d.sub.10 = 2.7 r.sub.11 = -111.186 d.sub.11 = 4.2 n.sub.6 = 1.80518 ν.sub.6 = 25.5 r.sub.12 = 20.265 d.sub.12 = 3.0 r.sub.13 = -100.634 d.sub.13 = 3.2 n.sub.7 = 1.62588 ν.sub.7 = 35.6 r.sub.14 = -29.367 d.sub.14 = 0.1 r.sub.15 = 50.024 d.sub.15 = 2.5 n.sub.8 = 1.62588 ν.sub.8 = 35.6 r.sub.16 = 110.281 ______________________________________ Back focal distance: βf = 42.7˜65.2 Close distance correction spacing: d.sub.4 = 10.7(∞)˜11.3 (β = 0.25) Variable spacing: d.sub.6 = 32.85˜0.05

Claim 9

The zoom lens system according to claim 5 having the following numerical data: ______________________________________ Total focal length of the entire system: f = 36.0˜68.8 Angle of view: 2ω = 31°˜17.4° F-number: ______________________________________ 3.5 r.sub.1 = 61.849 d.sub.1 = 8.2 n.sub.1 = 1.60323 ν.sub.1 = 42.5 r.sub.2 = -1037.164 d.sub.2 = 0.7 r.sub.3 = 1000.000 d.sub.3 = 1.5 n.sub.2 = 1.67790 ν.sub.2 = 55.5 r.sub.4 = 23.900 d.sub.4 = 6.8 r.sub.5 = 178.734 d.sub.5 = 1.5 n.sub.3 = 1.71300 ν.sub.3 = 53.9 r.sub.6 = 42.672 d.sub.6 = close distance correcting spacing r.sub.7 = 34.110 d.sub.7 = 3.9 n.sub.4 = 1.59507 ν.sub.4 = 35.6 r.sub.8 = 81.925 d.sub.8 = variable spacing r.sub.9 = 72.840 d.sub.9 = n.sub.5 = 1.62041 ν.sub.5 = 60.3 r.sub.10 = -72.840 d.sub.10 = 1.0 n.sub.6 = 1.80518 ν.sub.6 = 25.5 r.sub.11 = -144.173 d.sub.11 = 0.1 r.sub.12 = 26.644 d.sub.12 = 4.9 n.sub.7 = 1.51118 ν.sub.7 = 50.9 r.sub.13 = 246.000 d.sub.13 = 0.1 r.sub.14 = 20.743 d.sub.14 = 4.5 n.sub.8 = 1.51680 ν.sub.8 = 64.2 r.sub.15 = 27.990 d.sub.15 = 3.9 r.sub.16 = -370.855 d.sub.16 = 1.5 n.sub.9 = 1.80518 ν.sub.9 = 25.5 r.sub.17 = 18.700 d.sub.17 = 5.2 r.sub.18 = 64.660 d.sub.18 = 3.8 n.sub.10 = 1.64831 ν.sub.10 = 33.8 r.sub.19 = -39.168 ______________________________________ Back focal distance: βf = 43.7˜66.3 Close distance correction spacing: d.sub.6 = 5.7(∞)˜6.2(.beta = -0.25) Variable spacing: d.sub.8 = 33.45˜0.65

Claim 10

The zoom lens system according to claim 6 having the following numerical data: ______________________________________ Total focal length of the entire system: f = 36.0˜68.8 Angle of view: 2ω = 31°˜17.4° F-number: ______________________________________ 3.5 r.sub.1 = 50.379 d.sub.1 = 1.3 n.sub.1 = 1.74443 ν.sub.1 = 49.4 r.sub.2 = 27.469 d.sub.2 = 6.3 r.sub.3 = 670.373 d.sub.3 = 3.5 n.sub.2 = 1.51680 ν.sub.2 = 64.2 r.sub.4 = -114.009 d.sub.4 = 0.1 r.sub.5 = ∞ d.sub.5 = 1.8 n.sub.3 = 1.71300 ν.sub.3 = 53.9 r.sub.6 = 32.531 d.sub.6 = close distance correcting spacing r.sub.7 = 35.195 d.sub.7 = 3.4 n.sub.4 = 1.76182 ν.sub.4 = 26.5 r.sub.8 = 57.902 d.sub.8 = variable spacing r.sub.9 = 101.102 d.sub.9 = 3.0 n.sub.5 = 1.51680 ν.sub.5 = 64.2 r.sub.10 = -763.611 d.sub.10 = 0.1 r.sub.11 = 28.387 d.sub.11 = 6.4 n.sub.6 = 1.52000 ν.sub.6 = 70.1 r.sub.12 = -449.780 d.sub.12 = 0.1 r.sub.13 = 19.335 d.sub.13 = 5.9 n.sub.7 = 1.52000 ν.sub.7 = 70.1 r.sub.14 = 37.463 d.sub.14 = 4.0 r.sub.15 = -564.061 d.sub.15 = 1.4 n.sub.8 = 1.80518 ν.sub.8 = 25.5 r.sub.16 = 16.279 d.sub.16 = 3.85 r.sub.17 = 44.719 d.sub.17 = 4.1 n.sub.9 = 1.67270 ν.sub.9 = 32.2 r.sub.18 = -56.453 ______________________________________ Back focal distance: βf = 43.8˜68.7 Close distance correction spacing: d.sub.6 = 8.4(∞ )˜9.0(β = -0.25) Variable spacing: d.sub.8 = 28.93˜0.77