Zoom lens system

Claim 2

A zoom lens system comprising, in the order from the object side, a first lens group having a positive refractive power and comprising a positive cemented doublet, a second lens group having negative refractive power and comprising two negative lens components and a positive lens component, a third lens group having positive refractive power and comprising a cemented doublet, and a fourth lens group having a positive refractive power, and said fourth lens group, which is arranged to be the rearmost lens group, consisting of a positive lens element, a positive lens element and a negative lens element, the airspaces between said lens elements constituting the fourth lens group being constant, and the airspace between said third lens group and fourth lens group being variable at the time of zooming.

Claim 3

A zoom lens system according to claim 1 wherein said fourth lens group consists of a positive meniscus lens convex toward the object side, a biconvex lens spaced a distance from said positive meniscus lens, and a negative meniscus lens convex toward the image side.

Claim 4

A zoom lens system according to claim 1 wherein said first lens group further comprises a positive lens component, said second lens group comprises a negative lens component, a negative lens component and a positive cemented doublet, and said third lens group comprises a positive lens component and a positive cemented doublet.

Claim 5

A zoom lens system according to claim 2 wherein said first lens group further comprises a positive lens component, said second lens group comprises a negative lens component, a negative lens component and a positive cemented doublet, and said third lens group comprises a positive lens component and a positive cemented doublet.

Claim 6

A zoom lens system comprising, 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, said fourth lens group comprising a positive lens element, a positive lens element and a negative lens element in the order from the object side, said first lens group comprising a positive cemented doublet and a positive lens component, said second lens group comprising a negative lens component, a negative lens component and a positive cemented doublet and said third lens group comprising a positive lens component and a positive cemented doublet, said system fulfilling the conditions (1) through (4) shown below: ##EQU2## where, reference symbol f T represents the focal lengths of the lens system as a whole in the teleposition, references symbols f 2 and f 4 respectively represent the focal lengths of the second lens group and the fourth lens group, reference symbol d 9 represents the airspace between the negative lens component and the image side and positive cemented doublet in the second lens group, reference symbol r 22 represents the radius of curvature of the surface on the object side of the negative lens component in the fourth lens group.

Claim 7

A zoom lens system comprising, 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, said fourth lens group comprising a positive lens element, a positive lens element and a negative lens element in the order from the object side, said first lens group comprising a positive cemented doublet and a positive lens component, said second lens group comprising a negative lens component, a negative lens component and a positive cemented doublet and said third lens group comprising a positive lens component and a positive cemented doublet, said system fulfilling the conditions (1) through (4) shown below: ##EQU2## where, reference symbol f T represents the focal lengths of the lens system as a whole in the teleposition, references symbols f 2 and f 4 respectively represent the focal lengths of the second lens group and the fourth lens group, reference symbol d 9 represents the airspace between the negative lens component and the image side and positive cemented doublet in the second lens group, reference symbol r 22 represents the radius of curvature of the surface on the object side of the negative lens component in the fourth lens group.

Claim 8

A zoom lens system according to claim 5 which fulfills the condition (5) through (7) shown below: ##EQU3## where, reference symbol r 11 represents the radius of curvature of the cemented surface of the positive cemented doublet in the second lens group, reference symbols n 9 and n 10 respectively represent refractive indices of respective lens elements constituting the positive cemented doublet in the third lens group, and reference symbol ν 11 represents Abbe's number of the positive lens component on the object side in the fourth lens group.

Claim 9

A zoom lens system according to claim 6 which has the following numerical data: ______________________________________ f = 51.50˜242.50, F/5.0 ______________________________________ r.sub.1 = 128.727 d.sub.1 = 2.50 n.sub.1 = 1.84666 ν.sub.1 = 23.88 r.sub.2 = 68.205 d.sub.2 = 7.50 n.sub.2 = 1.48749 ν.sub.2 = 70.15 r.sub.3 = -299.373 d.sub.3 = 0.10 r.sub.4 = 69.486 d.sub.4 = 5.20 n.sub.3 = 1.52310 ν.sub.3 = 50.84 r.sub.5 = ∞ d.sub.5 = D.sub.1 (variable) r.sub.6 = -261.031 d.sub.6 = 1.50 n.sub.4 = 1.77250 ν.sub.4 = 49.66 r.sub.7 = 39.500 d.sub.7 = 5.40 r.sub.8 = -53.505 d.sub.8 = 1.50 n.sub.5 = 1.77250 ν.sub.5 = 49.66 r.sub.9 = 62.712 d.sub.9 = 2.33 r.sub.10 = 61.045 d.sub.10 = 5.50 n.sub.6 = 1.78472 ν.sub.6 = 25.71 r.sub.11 = -57.198 d.sub.11 = 1.51 n.sub.7 = 1.77250 ν.sub.7 = 49.66 r.sub.12 = ∞ d.sub.12 = D.sub.2 (variable) r.sub.13 = 165.028 d.sub.13 = 3.80 n.sub.8 = 1.66892 ν.sub.8 = 44.98 r.sub.14 = -75.553 d.sub.14 = 0.10 r.sub.15 = 35.272 d.sub.15 = 7.80 n.sub.9 = 1.48749 ν.sub.9 = 70.15 r.sub.16 = -62.293 d.sub.16 = 1.50 n.sub.10 = 1.74077.sup. ν.sub.10 = 27.79.sup. r.sub.17 = 79.705 d.sub.17 = D.sub.3 (variable) r.sub.18 = 34.235 d.sub.18 = 4.88 n.sub.11 = 1.48749.sup. ν.sub.11 = 70.15.sup. r.sub.19 = 97.153 d.sub.19 = 28.30 r.sub.20 = 86.089 d.sub.20 = 5.39 n.sub.12 = 1.54072.sup. ν.sub.12 = 47.20.sup. r.sub.21 = -81.160 d.sub.21 = 3.00 r.sub.22 = -24.571 d.sub.22 = 1.50 n.sub.13 = 1.77250.sup. ν.sub.13 = 49.66.sup. r.sub.23 = -70.469 ______________________________________ f D.sub.1 D.sub.2 D.sub.3 ______________________________________ wide position 51.50 2.073 36.245 14.985 standard position 100.00 17.720 20.598 8.210 teleposition 242.50 37.918 0.400 6.996 ______________________________________ overall length of the lens system = 181.60 (W)˜218.20 (T) |f.sub.2 /f.sub.T | = 0.11, f.sub.4 /f.sub.T ______________________________________ = 0.68 where, reference symbols r 1 through r 23 respectively represent radii of curvature of respective lenses, reference symbols d 1 through d 22 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 13 respectively represent refractive indices of respective lenses, and reference symbols ν 1 through ν 13 respectively represent Abbe's numbers of respective lenses.

Claim 10

A zoom lens system according to claim 6 which has the following numerical data: ______________________________________ f = 51.50˜242.50, F/5.0 ______________________________________ r.sub.1 = 128.395 d.sub.1 = 2.50 n.sub.1 = 1.84666 ν.sub.1 = 23.88 r.sub.2 = 68.149 d.sub.2 = 7.50 n.sub.2 = 1.48749 ν.sub.2 = 70.15 r.sub.3 = -478.561 d.sub.3 = 0.10 r.sub.4 = 61.404 d.sub.4 = 6.00 n.sub.3 = 1.51742 ν.sub.3 = 52.41 r.sub.5 = 1197.293 d.sub.5 = D.sub.1 (variable) r.sub.6 = -2114.022 d.sub.6 = 1.50 n.sub.4 = 1.77250 ν.sub.4 = 49.66 r.sub.7 = 35.576 d.sub.7 = 5.40 r.sub.8 = -51.140 d.sub.8 = 1.50 n.sub.5 = 1.77250 ν.sub.5 = 49.66 r.sub.9 = 59.878 d.sub.9 = 2.04 r.sub.10 = 60.660 d.sub.10 = 5.50 n.sub.6 = 1.78472 ν.sub.6 = 25.71 r.sub.11 = -57.198 d.sub.11 = 1.50 n.sub.7 = 1.77250 ν.sub.7 = 49.66 r.sub.12 = -713.043 d.sub.12 = D.sub.2 (variable) r.sub.13 = 147.275 d.sub.13 = 3.80 n.sub.8 = 1.64328 ν.sub.8 = 47.85 r.sub.14 = -85.306 d.sub.14 = 0.10 r.sub.15 = 37.347 d.sub.15 = 7.40 n.sub.9 = 1.48749 ν.sub.9 = 70.15 r.sub.16 = -62.692 d.sub.16 = 1.50 n.sub.10 = 1.72825.sup. ν.sub.10 = 28.46.sup. r.sub.17 = 89.560 d.sub.17 = D.sub.3 (variable) r.sub.18 = 32.932 d.sub.18 = 5.27 n.sub.11 = 1.48749.sup. ν.sub.11 = 70.15.sup. r.sub.19 = 95.696 d.sub.19 = 26.39 r.sub.20 = 60.343 d.sub.20 = 6.79 n.sub.12 = 1.54072.sup. ν.sub.12 = 47.20.sup. r.sub.21 = -126.559 d.sub.21 = 3.62 r.sub.22 = -24.279 d.sub.22 = 1.50 n.sub.13 = 1.80400.sup. ν.sub.13 = 46.57.sup. r.sub.23 = -72.053 ______________________________________ f D.sub.1 D.sub.2 D.sub.3 ______________________________________ wide position 51.50 1.180 36.211 15.241 standard position 100.00 16.827 20.564 8.867 teleposition 242.50 37.025 0.366 4.523 ______________________________________ overall length of the lens system = 181.71 (W)˜215.18 (T) |f.sub.2 /f.sub.T | = 0.12, f.sub.4 /f.sub. T = ______________________________________ 0.61 where, reference symbols r 1 through r 23 respectively represent radii of curvature of respective lenses, reference symbols d 1 through d 22 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 13 respectively represent refractive indices of respective lenses, and reference symbols ν 1 through ν 13 respectively represent Abbe's numbers of respective lenses.

Claim 11

A zoom lens system according to claim 6 which has the following numerical data: ______________________________________ f = 51.75˜241.25, F/5.0 ______________________________________ r.sub.1 = 111.361 d.sub.1 = 2.80 n.sub.1 = 1.8666 ν.sub.1 = 23.88 r.sub.2 = 67.753 d.sub.2 = 7.00 n.sub.2 = 1.48749 ν.sub.2 = 70.15 r.sub.3 = ∞ d.sub.3 = 0.10 r.sub.4 = 88.370 d.sub.4 = 5.70 n.sub.3 = 1.51742 ν.sub.3 = 52.41 r.sub.5 = -1294.543 d.sub.5 = D.sub.1 (variable) r.sub.6 = -178.326 d.sub.6 = 1.50 n.sub.4 = 1.77250 ν.sub.4 = 49.66 r.sub.7 = 36.631 d.sub.7 = 5.00 r.sub.8 = -53.997 d.sub.8 = 1.50 n.sub.5 = 1.78590 ν.sub.5 = 44.18 r.sub.9 = 78.310 d.sub.9 = 1.84 r.sub.10 = 66.355 d.sub.11 = 5.40 n.sub.6 = 1.78470 ν.sub.6 = 26.22 r.sub.11 = -50.596 d.sub.11 = 1.60 n.sub.7 = 1.77250 ν.sub.7 = 49.66 r.sub.12 = -202.724 d.sub.12 = D.sub.2 (variable) r.sub.13 = 146.837 d.sub.13 = 3.80 n.sub.8 = 1.67003 ν.sub.8 = 47.25 r.sub.14 = -80.269 d.sub.14 = 0.10 r.sub.15 = 34.080 d.sub.15 = 7.60 n.sub.9 = 1.48749 ν.sub.9 = 70.15 r.sub.16 = -60.335 d.sub.16 = 1.70 n.sub.10 = 1.71736.sup. ν.sub.10 = 29.51.sup. r.sub.17 = 70.612 d.sub.17 = D.sub.3 (variable) r.sub.18 = 37.699 d.sub.18 = 5.0 n.sub.11 = 1.48749.sup. ν.sub.11 = 70.15.sup. r.sub.19 = 107.992 d.sub.19 = 28.76 r.sub.20 = 72.285 d.sub.20 = 5.00 n.sub.12 = 1.53172.sup. ν.sub.12 = 48.90.sup. r.sub.21 = -63.118 d.sub.21 = 3.00 r.sub.22 = -26.315 d.sub.22 = 1.50 n.sub.13 = 1.77250.sup. ν.sub.13 = 49.66.sup. r.sub.23 = -112.160 ______________________________________ f D.sub.1 D.sub.2 D.sub.3 ______________________________________ wide position 51.75 2.733 35.896 13.443 standard position 100.00 24.335 20.406 7.299 teleposition 241.25 50.233 0.535 5.002 ______________________________________ overall length of the lens system = 180.64 (W)˜225.64 (T) |f.sub.2 /f.sub.T | = 0.13, f.sub. 4 /f.sub.T = ______________________________________ 0.71 where, reference symbols r 1 through r 2 respectively represent radii of curvature of respective lenses, reference symbols d 1 through d 22 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 13 respectively represent refractive indices of respective lenses, and reference symbols ν 1 through ν 13 respectively represent Abbe's numbers of respective lenses.