Zoom lens system

Claim 2

A large relative aperture zoom lens system comprising a front lens group having negative refractive power and a rear lens group having positive refractive power and so designed as to change magnification level by varying an airspace reserved between said front and rear lens groups, wherein said rear lens group comprises, in the sequence from the object side, at least two positive lens components, a negative lens component having a surface with a small radius of curvature on the image side, a positive lens component and a negative meniscus lens component arranged on the extreme image side therein and having a surface with a small radius of curvature on the object side, a stop being arranged before said negative lens component arranged on the object side and the object side surface of said negative lens component arranged on the extreme image side being designed as a spherical surface whose center of curvature is located in the vicinity of said stop, said larger relative aperture zoom lens system satisfying the following condition (1): 0.75<|φ.sub.a |·f.sub.R <1.0 (1) where the reference sumbol φ a represents power of the image side surface of the negative lens component arranged on the object side in said rear lens group, and the reference symbol f R denotes focal length of said rear lens group.

Claim 3

A large relative aperture zoom lens system according to claim 1 satisfying the following condition (2): 0.6<|φ.sub.b |·f.sub.R <1.2 (2) wherein the reference symbol φ b designates power of the object side surface of the negative lens component arranged on the image side in said rear lens group.

Claim 4

A large relative aperture zoom lens system according to claim 1 wherein said front lens group comprises a negative meniscus lens component having a surface with a small radius of curvature on the image side, a biconcave lens component and a positive lens component arranged sequentially from the object side.

Claim 5

A large relative aperture zoom lens system according to claim 2 wherein said front lens group comprises a negative meniscus lens component having a surface with a small radius of curvature on the image side, a biconcave lens component and a positive lens component arranged sequentially from the object side.

Claim 6

A large relative aperture zoom lens system according to claim 4 safisfying the following conditions (3) through (6):

Claim 7

0<|f F |/f T <1.3 (3) 1.1<φ.sub.c ·f.sub.F <1.3 (4) ν.sub.1 <35 (5) (6) At least one of the two or more positive lens components arranged on the object side in said rear lens group has an Abbe's number of 60 or large. wherein the reference symbol f F represents focal length of said front lens gorup, the reference symbol f T designates focal length of said zoom lens system as a whole at its tele position, the reference symbol φ c denotes power of the image side surface of the negative lens component arranged on the object side in said front lens goup and the reference symbol ν 1 represents Abbe's number of the negative lens component arranged on the object side in said front lens group.

Claim 8

0<|f F |/f T <1.3 (3) 1.1<φ.sub.c ·f.sub.F <1.3 (4) ν.sub.1 <35 (5) (6) At least one of the two or more positive lens components arranged on the object side in said rear lens group has an Abbe's number of 60 or large. wherein the reference symbol f F represents focal length of said front lens gorup, the reference symbol f T designates focal length of said zoom lens system as a whole at its tele position, the reference symbol φ c denotes power of the image side surface of the negative lens component arranged on the object side in said front lens goup and the reference symbol ν 1 represents Abbe's number of the negative lens component arranged on the object side in said front lens group.

Claim 9

A large relative aperture zoom lens system according to claim 5 comprising a rear lens group consisting of two positive lens components, a negative lens component having a surface with a small radius of curvature on the image side, a positive lens component and a negative lens component having a surface with a small radius of curvature on the object side, and having the following numerical data: ______________________________________ f = 36˜67.9, F/2.8 r.sub.1 = 75.212 d.sub.1 = 2.27 n.sub.1 = 1.71736 ν.sub.1 = 29.51 r.sub.2 = 28.319 d.sub.2 = 9.57 r.sub.3 = -166.359 d.sub.3 = 1.61 n.sub.2 = 1.77251 ν.sub.2 = 49.66 r.sub.4 = 100.970 d.sub.4 = 2.72 r.sub.5 = 52.881 d.sub.5 = 5.56 n.sub.3 = 1.78471 ν.sub.3 = 26.22 r.sub.6 = 883.234 d.sub.6 = 51.81˜0.97 r.sub.7 = 102.616 d.sub.7 = 4.06 n.sub.4 = 1.61700 ν.sub.4 = 62.79 r.sub.8 = -110.285 d.sub.8 = 0.10 r.sub.9 = 25.653 d.sub.9 = 6.85 n.sub.5 = 1.62299 ν.sub.5 = 58.14 r.sub.10 = 308.903 d.sub.10 = 5.81 r.sub.11 = -71.429 d.sub.11 = 5.29 n.sub.6 = 1.71736 ν.sub.6 = 29.51 r.sub.12 = 23.314 d.sub.12 = 4.00 r.sub.13 = 110.651 d.sub.13 = 7.99 n.sub.7 = 1.71300 ν.sub.7 = 53.84 r.sub.14 = -23.289 d.sub.14 = 1.27 r.sub.15 = -21.858 d.sub.15 = 1.50 n.sub.8 = 1.74400 ν.sub.8 = 44.73 r.sub.16 = -40.239 f.sub.F = -80.754, f.sub.R = 48.248 |φ.sub.a |·f.sub.R = 0.86, |φ.sub.b |·f.sub.R = 0.94 φ.sub.c ·f.sub.F = 1.19 ______________________________________ wherein the reference symbols r 1 , r 2 , . . . represent radii of curvature on the surfaces of the respective lens components, the reference symbols d 1 , d 2 , . . . designate thicknesses of the respective lens component, and airspaces reserved therebetween, the reference symbols n 1 , n 2 , . . . denote refractive indices of the respective lens components, the reference symbols ν 1 , ν 2 , . . . represent Abbe's numbers of the respective lens components and the reference symbol f designates focal length of said zoom lens system as a whole.

Claim 10

A large relative aperture zoom lens system according to claim 5 comprising a rear lens group consisting of three positive lens components, a negative lens component having a surface with a small radius of curvature on the image side, a positive lens component and a negative lens component having a surface with a small radius of curvature on the object side, and having the following numerical data: ______________________________________ f = 36˜67.9, F/2.8 r.sub.1 = 95.636 d.sub.1 = 2.37 n.sub.1 = 1.78470 ν.sub.1 = 26.22 r.sub.2 = 30.107 d.sub.2 = 11.30 r.sub.3 = -96.301 d.sub.3 = 1.71 n.sub.2 = 1.77250 ν.sub.2 = 49.66 r.sub.4 = 117.179 d.sub.4 = 2.48 r.sub.5 = 65.123 d.sub.5 = 6.40 n.sub.3 = 1.78470 ν.sub.3 = 26.22 r.sub.6 = -159.522 d.sub.6 = 51.77˜1.05 r.sub.7 = 135.394 d.sub.7 = 3.70 n.sub.4 = 1.48750 ν.sub.4 = 70.15 r.sub.8 = -101.971 d.sub.8 = 0.10 r.sub.9 = 25.660 d.sub.9 = 6.85 n.sub.5 = 1.51633 ν.sub.5 = 64.15 r.sub.10 = 104.695 d.sub.10 = 0.10 r.sub.11 = 39.143 d.sub.11 = 4.50 n.sub.6 = 1.48750 ν.sub.6 = 70.15 r.sub.12 = 106.690 d.sub.12 = 5.76 r.sub.13 = -67.737 d.sub.13 = 5.66 n.sub.7 = 1.71736 ν.sub.7 = 29.51 r.sub.14 = 23.237 d.sub.14 = 3.17 r.sub.15 = 65.718 d.sub.15 = 7.49 n.sub.8 = 1.71300 ν.sub.8 = 53.84 r.sub.16 = -25.189 d.sub.16 = 2.21 r.sub.17 = -21.751 d.sub.17 = 1.50 n.sub.9 = 1.74400 ν.sub.9 = 44.73 r.sub.18 = -42.755 f.sub.F = -78.831, f.sub.R = 49.304 | φ.sub.a |·f.sub.R = 0.89, |φ.sub.b |·f.sub.R = 0.97 φ.sub.c ·f.sub.F = 1.15 ______________________________________ wherein the reference symbols r 1 , r 2 , . . . represent radii of curvature on the surfaces of the respective lens components, the reference symbls d 1 , d 2 , . . . designate thicknesses of the respective lens components and airspaces reserved therebetween, the reference symbols n 1 , n 2 , . . . denote refractive indices of the respective lens components, the reference symbols ν 1 , ν 2 , . . . represent Abbe's numbers of the respective lens components and the reference symbol f designates focal length of said zoom lens system as a whole.

Claim 11

A large relative aperture zoom lens system according to claim 5 comprising a rear lens groups consisting of three positive lens components, a negative lens component having a surface with a small radius of curvature on the image side, a positive lens component and a negative lens component having a surface with a small radius of curvature on the object side, and having the following numerical data: ______________________________________ f = 36˜67.9, F/2.8 r.sub.1 = 78.690 d.sub.1 = 2.37 n.sub.1 = 1.78472 ν.sub.1 = 25.71 r.sub.2 = 28.373 d.sub.2 = 11.30 r.sub.3 = -87.953 d.sub.3 = 1.71 n.sub.2 = 1.75700 ν.sub.2 = 47.87 r.sub.4 = 108.050 d.sub.4 = 1.69 r.sub.5 = 59.711 d.sub.5 = 6.40 n.sub.3 = 1.78470 ν.sub.3 = 26.22 r.sub.6 = -162.087 d.sub.6 = 51.43˜1.51 r.sub.7 = 158.847 d.sub.7 = 3.70 n.sub.4 = 1.51633 ν.sub.4 = 64.15 r.sub.8 = -117.834 d.sub.8 = 0.10 r.sub.9 = 25.974 d.sub.9 = 6.82 n.sub.5 = 1.51633 ν.sub.5 = 64.15 r.sub.10 = 97.653 d.sub.10 = 0.10 r.sub.11 = 41.687 d.sub.11 = 4.50 n.sub.6 = 1.54072 ν.sub.6 = 47.20 r.sub.12 = 147.910 d.sub.12 = 6.61 r.sub.13 = -59.973 d.sub.13 = 5.62 n.sub.7 = 1.78470 ν.sub.7 = 26.22 r.sub.14 = 25.362 d.sub.14 = 2.88 r.sub.15 = 64.385 d.sub.15 = 7.48 n.sub.8 = 1.77250 ν.sub.8 = 49.66 r.sub.16 = -25.689 d.sub.16 = 2.21 r.sub.17 = -21.628 d.sub.17 = 1.50 n.sub.9 = 1.71301 ν.sub.9 = 53.84 r.sub.18 = -43.593 f.sub.F = -78.16, f.sub.R = 48.949 |φ.sub.a |·f.sub.R = 0.85, |φ.sub.b |·f.sub.R = 0.94 φ.sub.c ·f.sub.F = 1.21 ______________________________________ wherein the reference symbols r 1 , r 2 , . . . represent radii of curvature on the surfaces of the respective lens components, the reference symbols d 1 , d 2 , . . . designate thicknesses of the respective lens components and airspaces reserved therebetween, the reference symbols n 1 , n 2 , . . . denote refractive indices of the respective lens components, the reference symbols ν 1 , ν 2 , . . . represent Abbe's numbers of the respective lens components and the reference symbol f designates focal length of said zoom lens system as a whole.