Wide magnification-variable range zoom lens system

Claim 2

In a zoom lens system comprising a first lens group having a positive focal length, a second lens group having a negative focal length, a third lens group having a positive focal length, a fourth lens group having a negative focal length and a fifth lens group having a positive focal length in the order from the object side, a wide magnification-variable range zoom lens system characterized in that over the entire range of focal length: a partial lens system consisting of said first and second lens groups has a negative focal length and another partial lens system consisting of said third through fifth lens groups has a positive focal length; when focal length of the entire zoom lens system is varied from the shortest to the longest length, said first lens group is moved toward the object side to accelerate increase of imaging magnification of said second lens group; said second and third lens groups are moved in the direction to increase imaging magnification levels of their own; said fourth lens group is moved to accelerate increase of the imaging magnification level of said partial lens system consisting of said third through fifth lens groups; said fifth lens group is moved in the direction to increase the imaging magnification level of its own; and the airspaces reserved between the individual lens groups satisfy the following conditions: dT.sub.1.2 (f)/df>0 dT.sub.2.3 (f)/df<0 dT.sub.3.4 (f)/df>0 dT.sub.4.5 (f)/df<0 wherein the reference symbols are defined as follows: f: focal length of the entire zoom lens system Tij(f): airspace reserved between the ith lens group and the jth lens group when the entire zoom lens system has a focal length f dTij(f)/df: variation ratio of Tij(f) relative to f.

Claim 3

A wide magnification-variable range zoom lens system according to claim 1 satisfying the following conditions: ______________________________________ 0.7f.sub.t < f.sub.1 < 1.2f.sub.t 0.5f.sub.w < |f.sub.2 | < 1.3f.sub.w 0.6f.sub.w < f.sub.3 < 1.4f.sub.w 0.5f.sub.w < |f.sub.4 | < 1.3f.sub.w f.sub.w < f.sub.5 < 1.7f.sub.w 0.8√v < V.sub.2 < 1.3√v 0.7√v < V.sub.3.4.5 < 1.2√v ______________________________________ wherein the reference symbols are defined as follows: fi: focal lengt of the ith lens group f w : focal length of the entire zoom lens system at its wide position f t : focal length of the entire zoom lens system at its tele position V: zooming ration (=f t /f w ) V 2 : imaging magnification ratio of the second lens group between the wide position and tele position V 3 4 5 : imaging magnification ratio of the partial lens system consisting of said third through fifth lens groups between the tele position and wide position.

Claim 4

A wide magnification-variable range zoom lens system according to claim 2 wherein said second lens group comprises at least two negative lens components and a positive lens component, said third lens group comprises at least two positive lens components one of which is a doublet consisting of a positive lens element and a negative lens element and, said fourth lens group comprises at least two negative lens components one of which is a doublet consisting of a positive lens element and a negative lens element, said zoom lens system satisfying the following conditions: ______________________________________ 1.7 < N.sub.P2 1.7 < N.sub.N2 40 < ν.sub.N2 N.sub.P3 < 1.6 50 < ν.sub.P3 1.7 < N.sub.N4 40 < ν.sub.N4 ______________________________________ wherein the reference symbols are defined as follows: N Pi : mean value of refractive indices of the positive lenses arranged in the ith lens group N Ni : mean value of refractive indices of the negative lenses arranged in the ith leng group ν Pi : mean value of Abbe's numbers of the positive lenses arranged in the ith lens group ν Ni : mean value of Abbe's numbers of the negative lenses arranged in the ith lens group.

Claim 5

A wide magnification-variable range zoom lens system according to claim 3 where in said first lens group comprises at least a positive lens component which is a doublet consisting of a positive lens element and a negative lens element and said fifth lens group comprises at least two positive lens components at least one of which is a doublet consisting of a positive lens element and a negative lens element, said zoom lens system having the following numerical data: ______________________________________ Dwg. No. R D nd ν ______________________________________ 1 154.085 2.00 1.80518 25.4 2 1st lens 71.160 7.00 1.62299 58.2 3 group -408.750 0.10 4 50.885 4.50 1.62299 58.2 5 82.750 variable 6 133.870 1.20 1.77250 49.6 7 17.125 6.44 8 2nd lens -119.741 2.50 1.80518 25.4 9 group -37.040 1.00 1.77250 49.6 10 73.977 0.10 11 27.602 2.20 1.80518 25.4 12 39.973 variable 13 3rd lens 65.439 4.75 1.58913 61.1 14 group -20.400 1.00 1.80518 25.4 15 -29.765 0.10 16 21.416 3.46 1.51633 64.1 17 65.918 variable 18 119.573 3.76 1.71736 29.5 19 4th lens -17.128 1.00 1.77250 49.6 20 group 41.633 1.49 21 -34.680 1.00 1.77250 49.6 22 140.021 variable 23 -129.801 4.95 1.71300 53.9 24 -16.485 1.00 1.80518 25.4 25 5th lens -27.188 0.30 26 group -97.088 1.00 1.80610 40.9 27 24.597 7.50 1.58913 61.1 28 -45.921 0.30 29 42.314 4.16 1.51633 64.1 30 312.792 ______________________________________ wherein the reference symbols are defined as follows: R represents radius of curvature on the lens surface D designates the airspace between lens surfaces nd denotes the refractive index for the d line ν represents the Abbe number.

Claim 6

A wide magnification-variable range zoom lens system according to claim 3 wherein said first lens group comprises at least a positive lens component which is a doublet consisting of a positive lens element and a negative lens element and said fifth lens group comprises at least two positive lens components at least one of which is a doublet consisting of a positive lens element and a negative lens element, said zoom lens system having the following numerical data: ______________________________________ Dwg. No. R D nd ν ______________________________________ 1 116.691 2.00 1.80518 25.4 2 1st lens 61.756 7.60 1.62299 58.2 3 group 2363.005 0.10 4 52.223 4.50 1.62299 58.2 5 83.794 variable 6 88.470 1.20 1.77250 49.6 7 19.354 6.55 8 2nd lens -94.460 2.80 1.80518 25.4 9 group -35.285 1.20 1.77250 49.6 10 87.810 0.20 11 33.119 2.40 1.80518 25.4 12 40.708 variable 13 55.135 4.00 1.58913 61.1 14 3rd lens -36.777 1.00 1.80518 25.4 15 group -45.243 0.10 16 25.142 3.80 1.51633 64.1 17 756.094 variable 18 458.443 3.00 1.71736 29.5 19 4th lens -21.726 1.00 1.77250 49.6 20 group 54.509 1.25 21 -38.471 1.00 1.77250 49.6 22 88.589 variable 23 -81.678 5.00 1.71300 53.9 24 -16.168 1.00 1.80518 25.4 25 5th lens -27.256 0.10 26 group -1253.462 1.00 1.80610 40.9 27 24.851 7.00 1.58913 61.1 28 -66.642 0.10 29 41.868 7.00 1.51633 64.1 30 213.165 ______________________________________ wherein the reference symbols are defined as follows: R represents radius of curvature on the lens surface D designates the airspace between lens surfaces nd denotes the refractive index for the d line ν represents the Abbe number.