Zoom lens

Claim 2

A zoom lens including a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power and a fourth lens group having a positive refractive power, which are arranged in the mentioned order from the objective side of the zoom lens, said third lens group having therein an air lens, and said fourth lens group having therein at least one joint surface, wherein upon zooming from the short focal length side to the long focal length side, said first-lens group moves at first to the image side and then is reversed to move toward the objective side, while said second, third and fourth lens group monotonously move toward the objective side by different distances, respectively, and further the following conditions are satisfied: ##EQU2## where f 2 : shortest focal length; f i : focal length of i-th lens group; l i : moving distance of i-th lens group upon zooming; r 20 , r 21 : radii of curvature of objective and image side surfaces of air lens in third lens group: r 26 : radius of curvature of joint surface in fourth lens group; and n 14 , n 15 : refractive indexes of lens materials on both sides of joint surface in fourth lens group, with respect to d-ray.

Claim 3

A zoom lens as set forth in claim 1, wherein said first lens group comprises a negative meniscus single lens having its convex surface directed to the objective side, a positive single lens, a negative meniscus single lens having its convex surface directed to the objective side and a jointed lens including a double-concave lens and a positive meniscus lens having its convex surface directed to the objective side which are jointed together, said those lenses being arranged in the mentioned order from the objective side.

Claim 4

A zoom lens as set forth in claim 1 or 2, wherein said second lens group comprises a positive single lens, a jointed lens including a negative meniscus lens having its convex surface directed to the objective side and a positive lens which are jointed together, and a positive single lens, said those lens being arranged in the mentioned order from the objective side, and said third lens group comprises a jointed lens including a positive meniscus lens having its convex surface directed to the image side and a double-concave single lens which are jointed together, and a negative single lens.

Claim 5

A zoom lens as set forth in claim 1, or 2, wherein said second, and third and fourth lens groups can be moved toward the objective side in accordance with the following conditions: 0<l.sub.3 /l.sub.2 <l.sub.4 /l.sub.2 <1 thereby, macro-photography can be made.

Claim 6

A zoom lens as set forth in claim 1 as shown by the following data: ______________________________________ 25.7 < f < 73 F.sub.NO = 4 83.2° > 2ω > 32° r.sub.1 = 94.156 d.sub.1 = 1.6 n.sub.1 = 1.67003 ν.sub.1 = 47.2 r.sub.2 = 33.236 d.sub.2 = 7.8 r.sub.3 = 220.768 d.sub.3 = 4.4 n.sub.2 = 1.75500 ν.sub.2 = 52.33 r.sub.4 = -128.656 d.sub.4 = .1 r.sub.5 = 99.691 d.sub.5 = 1.4 n.sub.3 = 1.69680 ν.sub.3 = 55.46 r.sub.6 = 45.897 d.sub.6 = 4.7 r.sub.7 = -110.865 d.sub.7 = 1.3 n.sub.4 = 1.75500 ν.sub.4 = 52.33 r.sub.8 = 25.117 d.sub.8 = 5.5 n.sub.5 = 1.84666 ν .sub.5 = 23.83 r.sub.9 = 78.553 d.sub.9 = variable r.sub.10 = 99.482 d.sub.10 =2.3 n.sub.6 = 1.71300 ν.sub.6 = 53.94 r.sub.11 = -161.832 d.sub.11 = .1 r.sub.12 = 76.169 d.sub.12 = .9 n.sub.7 = 1.84666 ν.sub.7 = 23.83 r.sub.13 = 20.565 d.sub.13 = 5.0 n.sub.8 = 1.75500 ν.sub.8 = 52.33 r.sub.14 = 445.917 d.sub.14 = .1 r.sub.15 = 29.76 d.sub.15 = 3.7 n.sub.9 = 1.62041 ν.sub.9 = 60.34 r.sub.16 = -364.194 d.sub.16 = variable r.sub.17 = -83.25 d.sub.17 = 1.8 n.sub.10 = 1.84666 ν.sub.10 = 23.83 r.sub.18 = -25.292 d.sub.18 = .9 n.sub.11 = 1.71300 ν.sub.11 = 53.94 r.sub.19 = 57.893 d.sub.19 = 2.3 r.sub.20 = -32.375 d.sub.20 = .9 n.sub.12 = 1.69680 ν.sub.12 = 55.46 r.sub.21 = 435.585 d.sub.21 = variable r.sub.22 = -235.012 d.sub.22 = 3.1 n.sub.13 = 1.69680 ν.sub.13 = 55.46 r.sub.23 = -24.932 d.sub.23 = .1 r.sub.24 = 121.076 d.sub.24 = 7.5 n.sub.14 = 1.58913 ν.sub.14 = 61.25 r.sub.25 = -15.903 d.sub.25 = 1.0 n.sub.15 = 1.83400 ν.sub.15 = 37.34 r.sub.26 = -58.017 ______________________________________ Variable space distance: f 25.7 43.314 73 ______________________________________ d.sub.9 31.908 12.109 1.221 d.sub.16 4.542 10.517 19.425 d.sub.21 8.969 5.856 1.528 ______________________________________ where f: synthetic focal length of total system w: half image angle r: radius of curvature of refractive surface d: space distance between refractive surfaces n: refractive index ν: abbe's number.

Claim 7

A zoom lens as set forth in claim 5, wherein said second, third and fourth lens groups are moved respectively by said second lens: 4.084 said third lens: 1.43 said fourth lens: 3.028 thereby macro-photography is made.

Claim 8

A zoom lens as set forth in claim 1 as shown by the following data: ______________________________________ 24.8 ≦ f ≦ 70 F.sub.NO = 4 85.4° > 2ω > 33.2° r.sub.1 = 90.049 d.sub.1 = 1.6 n.sub.1 = 1.66672 ν.sub.1 = 48.30 r.sub.2 = 33.900 d.sub.2 = 7.6 r.sub.3 = 218.528 d.sub.3 = 4.5 n.sub.2 = 1.71300 ν.sub.2 = 53.94 r.sub.4 = -144.319 d.sub.4 = .1 r.sub.5 = 102.913 d.sub.5 = 1.4 n.sub.3 = 1.64000 ν.sub.3 = 60.15 r.sub.6 = 41.332 d.sub.6 = 5.0 r.sub.7 = -149.196 d.sub.7 = 1.3 n.sub.4 = 1.75500 ν.sub.4 = 52.33 r.sub.8 = 25.242 d.sub.8 = 5.5 n.sub.5 = 1.84666 ν .sub.5 = 23.83 r.sub.9 = 73.930 d.sub.9 = variable r.sub.10 = 99.221 d.sub.10 = 2.3 n.sub.6 = 1.71300 ν.sub.6 = 53.94 r.sub.11 = -176.043 d.sub.11 = .1 r.sub.12 = 98.353 d.sub.12 = .9 n.sub.7 = 1.84666 ν.sub.7 = 23.83 r.sub.13 = 22.340 d.sub.13 = 5.0 n.sub.8 = 1.75500 ν.sub.8 = 52.33 r.sub.14 = -2907.673 d.sub.14 = .1 r.sub.15 = 29.376 d.sub.15 = 3.7 n.sub.9 = 1.62041 ν.sub.9 = 60.34 r.sub.16 = -380.375 d.sub.16 = variable r.sub.17 = -76.959 d.sub.17 = 1.9 n.sub.10 = 1.84666 ν.sub.10 = 23.83 r.sub.18 = -26.088 d.sub.18 = .9 n.sub.11 = 1.71300 ν.sub.11 = 53.94 r.sub.19 = 86.694 d.sub.19 = 2.3 r.sub.20 = -34.298 d.sub.20 = .9 n.sub.12 = 1.69680 ν.sub.12 = 55.46 r.sub.21 = 144.605 d.sub.21 = variable r.sub.22 = -228.816 d.sub.22 = 3.0 n.sub.13 = 1.69680 ν.sub.13 = 55.46 r.sub.23 = -24.460 d.sub.23 = .1 r.sub.24 = 126.483 d.sub.24 = 7.2 n.sub.14 = 1.58913 ν.sub.14 = 61.25 r.sub.25 = -15.949 d.sub.25 = 1.1 n.sub.15 = 1.83400 ν.sub.15 = 37.34 r.sub.26 = -57.092 ______________________________________ Variable space distance f 24.8 41.665 70 ______________________________________ d.sub.9 30.884 11.715 1.208 d.sub.16 4.002 10.287 19.613 d.sub.21 9.33 6.092 1.525 ______________________________________

Claim 9

A zoom lens as set forth in claim 1 as shown by the following data; ______________________________________ 24.8 ≦ f ≦ 72.8 F.sub.NO = 4 85.4° ≧ 2ω ≧ 32.2° r.sub.1 = 95.222 d.sub.1 = 1.6 n.sub.1 = 1.66672 ν.sub.1 = 48.30 r.sub.2 = 35.025 d.sub.2 = 7.6 r.sub.3 = 188.753 d.sub.3 = 4.5 n.sub.2 = 1.69680 ν.sub.2 = 55.46 r.sub.4 = -147.207 d.sub.4 = .1 r.sub.5 = 105.648 d.sub.5 = 1.4 n.sub.3 = 1.62041 ν.sub.3 = 60.34 r.sub.6 = 40.548 d.sub.6 = 5.1 r.sub.7 = -191.182 d.sub.7 = 1.3 n.sub.4 = 1.75500 ν.sub.4 = 52.33 r.sub.8 = 24.566 d.sub.8 = 5.5 n.sub.5 = 1.84666 ν .sub.5 = 23.83 r.sub.9 = 66.528 d.sub.9 = variable r.sub.10 = 86.785 d.sub.10 = 2.3 n.sub.6 = 1.71300 ν.sub.6 = 53.94 r.sub.11 = -311.359 d.sub.11 = .1 r.sub.12 = 78.584 d.sub.12 = .9 n.sub.7 = 1.84666 ν.sub.7 = 23.83 r.sub.13 = 21.564 d.sub.13 = 5.0 n.sub.8 = 1.75500 ν.sub.8 = 52.33 r.sub.14 = 541.895 d.sub.14 = .1 r.sub.15 = 29.638 d.sub.15 = 3.7 n.sub.9 = 1.62041 ν.sub.9 = 60.34 r.sub.16 = -436.795 d.sub.16 = variable r.sub.17 = -103.359 d.sub.17 = 1.9 n.sub.10 = 1.84666 ν.sub.10 = 23.83 r.sub.18 = -288.864 d.sub. 18 = .9 n.sub.11 = 1.71300 ν.sub.11 = 53.94 r.sub.19 = 62.037 d.sub.19 = 2.3 r.sub.20 = -31.025 d.sub.20 = .9 n.sub.12 = 1.71300 ν.sub.12 = 53.94 r.sub.21 = 1800.352 d.sub.21 = variable r.sub.22 = -157.739 d.sub.22 = 3.0 n.sub.13 = 1.71300 ν.sub.13 = 53.94 r.sub.23 = -24.981 d.sub.23 = .1 r.sub.24 = 104.923 d.sub.24 = 7.2 n.sub.14 = 1.58913 ν.sub.14 = 61.25 r.sub.25 = -16.230 d.sub.25 = 1.1 n.sub.15 = 1.83400 ν.sub.15 = 37.34 r.sub.26 = -57.580 ______________________________________ Variable space distance f 24.8 42.49 72.8 ______________________________________ d.sub.9 31.949 12.018 1.433 d.sub.16 3.708 9.876 19.311 d.sub.21 9.259 5.946 1.457 ______________________________________

Claim 10

A zoom lens as set forth in claim 1 as shown by the following data: ______________________________________ 25.7 ≦ f ≦ 73 F.sub.NO = 4 83.4° > 2ω > 31.8° r.sub.1 = 84.928 d.sub.1 = 1.6 n.sub.1 = 1.67003 ν.sub.1 = 47.20 r.sub.2 = 31.837 d.sub.2 = 8.1 r.sub.3 = 256.904 d.sub.3 = 4.2 n.sub.2 = 1.71300 ν.sub.2 = 53.94 r.sub.4 = -127.262 d.sub.4 = .1 r.sub.5 = 113.601 d.sub.5 = 1.4 n.sub.3 = 1.62041 ν.sub.3 = 60.34 r.sub.6 = 49.737 d.sub.6 = 4.6 r.sub.7 = -131.053 d.sub.7 = 1.3 n.sub.4 = 1.71300 ν.sub.4 = 53.94 r.sub.8 = 22.236 d.sub.8 = 6.0 n.sub.5 = 1.80518 ν .sub.5 = 25.46 r.sub.9 = 63.486 d.sub.9 = variable r.sub.10 = 96.464 d.sub.10 = 2.3 n.sub.6 = 1.71300 ν.sub.6 = 53.94 r.sub.11 = -167.838 d.sub.11 = .1 r.sub.12 = 63.858 d.sub.12 = .9 n.sub.7 = 1.84666 ν.sub.7 = 23.83 r.sub.13 = 20.058 d.sub.13 = 5.2 n.sub.8 = 1.75500 ν.sub.8 = 52.33 r.sub.14 = 196.304 d.sub.14 = .1 r.sub.15 = 30.338 d.sub.15 = 3.9 n.sub.9 = 1.62041 ν.sub.9 = 60.34 r.sub.16 = -274.039 d.sub.16 = variable r.sub.17 = -71.458 d.sub.17 = 2.1 n.sub.10 = 1.80518 ν.sub.10 = 25.46 r.sub.18 = -22.061 d.sub. 18 = .9 n.sub.11 = 1.71300 ν.sub.11 = 53.94 r.sub.19 = 65.142 d.sub.19 = 2.3 r.sub.20 = -35.803 d.sub.20 = .9 n.sub.12 = 1.69680 ν.sub.12 = 55.46 r.sub.21 = 259.242 d.sub.21 = variable r.sub.22 = -294.242 d.sub.22 = 3.1 n.sub.13 = 1.69680 ν.sub.13 = 55.46 r.sub.23 = -25.251 d.sub.23 = .1 r.sub.24 = 165.577 d.sub.24 = 7.0 n.sub.14 = 1.58913 ν.sub.14 = 61.25 r.sub.25 = -15.718 d.sub.25 = 1.0 n.sub.15 = 1.83400 ν.sub.15 = 37.34 r.sub.26 = -52.669 ______________________________________ Variable space distance f 25.7 43.314 73 ______________________________________ d.sub.9 31.928 12.154 1.242 d.sub.16 4.16 10.107 19.043 d.sub.21 8.635 5.47 1.194 ______________________________________

Claim 11

A zoom lens as set forth in claim 3, wherein said second, third and fourth lens groups can be moved toward the objective side in accordance with the following conditions: 0<l.sub.3 /l.sub.2 <l.sub.4 /l.sub.2 <1 thereby, macro-photography can be made.