Compact zoom lens system

Claim 2

A zoom lens system consisting of, in order from the object side, a first lens group located in the foremost position and having positive refractive power, a second lens group located in a position subsequent to said first lens group and having negative refractive power, and a third lens group located subsequent to said second lens group and having positive refractive power, said zoom lens system being zoomed from a wide position to a teleposition by keeping said second lens group fixed with respect to an image surface, and moving said first lens group and said third lens group respectively toward the direction away from the image surface independently of each other by individually different amounts of movements, said zoom lens system being focused on an object at an infinite distance up to an object at a short distance by moving only said first lens group toward the direction away from the image surface.

Claim 3

A zoom lens system according to claim 1, further comprising: an aperture stop located between said second lens group and said third lens group, said stop arranged to be moved during zooming independently of the movements of said respective lens groups.

Claim 4

A zoom lens system according to claim 2, wherein said aperture stop is moved to a position approximately in the middle of said second lens group and said third lens group.

Claim 5

A zoom lens system according to claim 3, wherein said zoom lens system is arranged to fulfill the following conditions: (1) 1.5<f 1 f W <2.5 (2) -0.65<f 2 /f W <-0.39 (3) -1.6<1/β 2W -1/β 2T <-0.7 1.8<β 2T /β 2W <2.2 (4) 0.75<f 3 /f W <1.1 (5) 0.2<1/β 3T -1/β 3W <0.3 1.2<β 3T /β 3W <1.6 wherein, reference symbol f W represents the focal length of the lens system as a whole in the wide position, reference symbols f 1 , f 2 and f 3 respectively represent focal lengths of the first, second and third lens groups, reference symbols β 2T and β 2W respectively represent magnifications of the second lens group in the teleposition and wide position, and reference symbols β 3T and β 3W respectively represent magnifications of the third lens group in the teleposition and wide position.

Claim 6

A zoom lens system according to claim 4, wherein said third lens group at least comprises a negative meniscus lens arranged to be concave toward the object side and a negative meniscus lens arranged to be convex toward the object side and located adjacent to and on the image side of said negative meniscus lens concave toward the object side, and wherein said zoom lens system is arranged to further fulfill the following conditions: (6) 0.7<R/f 3 <1.2 (7) 0.25<D/f 3 <0.35 wherein, reference symbol R represents the radius of curvature of the surface on the image side of said negative meniscus lens arranged to be convex toward the object side, and reference symbol D represents the total thickness of said two negative meniscus lenses.

Claim 7

A zoom lens system according to claim 5, wherein said first lens group comprises a cemented doublet and a positive meniscus lens, said second lens group comprises a negative meniscus lens and two cemented doublets, and said third lens group comprises three positive lenses, a negative meniscus lens arranged to be concave toward the object side, a negative meniscus lens arranged to be convex toward the object side, and two positive lenses, said zoom lens system having the following numerical data: ______________________________________ r.sub.1 = 136.988 d.sub.1 = 2.5 n.sub.1 = 1.80518 ν.sub.1 = 25.43 r.sub.2 = 53.184 d.sub.2 = 9 n.sub.2 = 1.51633 ν.sub.2 = 64.15 r.sub.3 = -104.043 d.sub.3 = 0.1 r.sub.4 = 30.479 d.sub.4 = 4.8 n.sub.3 = 1.65160 ν.sub.3 = 58.67 r.sub.5 = 56.486 d.sub.5 = l.sub.1 (0.764˜9.901˜17.377) r.sub.6 = 52.644 d.sub.6 = 1.5 n.sub.4 = 1.77250 ν.sub.4 = 49.66 r.sub.7 = 16.297 d.sub.7 = 3.2 r.sub.8 = 152.848 d.sub.8 = 3 n.sub.5 = 1.72825 ν.sub.5 = 28.46 r.sub.9 = -40.125 d.sub.9 = 1 n.sub.6 = 1.72 ν.sub.6 = 50.25 r.sub.10 = 76.052 d.sub.10 = 2.8 r.sub.11 = -17.423 d.sub.11 = 1 n.sub.7 = 1.66671 ν.sub.7 = 57.33 r.sub.12 = 27.345 d.sub.12 = 3.2 n.sub.8 = 1.83400 ν.sub.8 = 37.16 r.sub.13 = -55.989 d.sub.13 = l.sub.21 (7.673˜2.376˜0.548) r.sub.14 = ∞ (stop) d.sub.14 = l.sub.22 (10.418˜7.184˜0.293) r.sub.15 = 31.182 d.sub.15 = 5.14 n.sub.9 = 1.48749 ν.sub.9 = 70.15 r.sub.16 = -80.213 d.sub.16 = 2 r.sub.17 = 957.849 d.sub.17 = 3.3 n.sub.10 = 1.48749 ν.sub.10 = 70.15 r.sub.18 = -61.412 d.sub.18 = 0.11 r.sub.19 = 100.245 d.sub.19 = 3 n.sub.11 = 1.617 ν.sub.11 = 62.79 r.sub.20 = -131.354 d.sub.20 = 4.25 r.sub.21 = -22.878 d.sub.21 = 2 n.sub.12 = 1.84666 ν.sub.12 = 23.88 r.sub.22 = -35.645 d.sub.22 = 0.2 r.sub.23 = 68.089 d.sub.23 = 8.05 n.sub.13 = 1.80518 ν.sub.13 = 25.43 r.sub.24 = 30.546 d.sub.24 = 3.47 r.sub.25 = 15585.232 d.sub.25 = 4 n.sub.14 = 1.61921 ν.sub.14 = 60.27 r.sub.26 = -45.091 d.sub.26 = 0.11 r.sub.27 = 51.892 d.sub.27 = 5.08 n.sub.15 = 1.55960 ν.sub.15 = 58.63 r.sub.28 = 133.727 f = 36.235˜101.295, F 4.1 f.sub.1 = 62.433, f.sub.1 /f.sub.W = 1.717 f.sub.2 = -17.786, f.sub.2 /f.sub.W = -0.491 f.sub.3 = 32.417, f.sub.3 /f.sub.W = 0.895 β.sub.2 W = -0.5091, β.sub.2 S = -0.6894, β.sub.2 T = -0.9707 β.sub.3 W = -1.1401, β.sub.3 S = -1.4033, β.sub.3 T = -1.6723 1/β.sub.2 W - 1/β.sub.2 T = -0.994, β.sub.2 T/β.sub.2 W = 1.907 1/β.sub.3 T - 1/β.sub.3 W = 0.279, β.sub.3 T/β.sub.3 W = 1.467 r.sub.24 /f.sub.3 = 0.942, (d.sub.21 + d.sub.23)/f.sub.3 ______________________________________ = 0.31 wherein reference symbols r 1 through r 28 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 27 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 15 respectively represent refractive indices of respective lenses, reference symbols ν 1 through ν 15 respectively represent Abbe's numbers of respective lenses, and reference symbols β 2 S and β 3 S respectively represent magnifications of the second and third lens groups in the standard position.

Claim 8

A zoom lens system according to claim 5, wherein said first lens group comprises a cemented doublet and a positive meniscus lens, said second lens group comprises a negative meniscus lens and two cemented doublets, and said third lens group comprises three positive lenses, a negative meniscus lens arranged to be concave toward the object side, a negative meniscus lens arranged to be convex toward the object side, and two positive lenses, said zoom lens system having the following numerical data: ______________________________________ r.sub.1 = 325.502 d.sub.1 = 2.5 n.sub.1 = 1.81379 ν.sub.1 = 35.4 r.sub.2 = 50.724 d.sub.2 = 9 n.sub.2 = 1.51633 ν.sub.2 = 68.96 r.sub.3 = -85.321 d.sub.3 = 0.1 r.sub.4 = 35.934 d.sub.4 = 5.2 n.sub.3 = 1.834 ν.sub.3 = 40.62 r.sub.5 = 56.505 d.sub.5 = l.sub.1 (1.531˜16.459˜27.537) r.sub.6 = 65.784 d.sub.6 = 1.5 n.sub.4 = 1.834 ν.sub.4 = 47.72 r.sub.7 = 16.446 d.sub.7 = 3.2 r.sub.8 = -93.764 d.sub.8 = 3.6 n.sub.5 = 1.48749 ν.sub.5 = 46.35 r.sub.9 = -44.124 d.sub.9 = 1 n.sub.6 = 1.83481 ν.sub. 6 = 46.83 r.sub.10 = -77.685 d.sub.10 = 2.8 r.sub.11 = -18.935 d.sub.11 = 1 n.sub.7 = 1.66259 ν.sub.7 = 61.89 r.sub.12 = 27.100 d.sub.12 = 3 n.sub.8 = 1.83481 ν.sub.8 = 36.61 r.sub.13 = -45.231 d.sub.13 = l.sub.21 (6.82˜1.522˜0.25) r.sub.14 = ∞ (stop) d.sub.14 = l.sub.22 (10.418˜7.707˜0.6) r.sub.15 = 28.716 d.sub.15 = 5.14 n.sub.9 = 1.48749 ν.sub.9 = 70.15 r.sub.16 = -161.540 d.sub.16 = 2.3 r.sub.17 = 558.626 d.sub.17 = 3.3 n.sub.10 = 1.56873 ν.sub.10 = 68.78 r.sub.18 = -64.622 d.sub.18 = 0.11 r.sub.19 = 92.049 d.sub.19 = 3 n.sub.11 = 1.63306 ν.sub.11 = 63.26 r.sub.20 = -137.918 d.sub.20 = 4.25 r.sub.21 = -24.097 d.sub.21 = 2 n.sub.12 = 1.82889 ν.sub.12 = 20.34 r.sub.22 = -42.366 d.sub.22 = 0.2 r.sub.23 = 100.979 d.sub.23 = 8.16 n.sub.13 = 1.83641 ν.sub.13 = 31.52 r.sub.24 = 30.921 d.sub.24 = 3.47 r.sub.25 = 345.629 d.sub.25 = 4 n.sub.14 = 1.62026 ν.sub.14 = 59.37 r.sub.26 = -56.495 d.sub.26 = 0.1 r.sub.27 = 63.594 d.sub.27 = 5.08 n.sub.15 = 1.56873 ν.sub.15 = 57.74 r.sub.28 = -291.508 f = 36.22˜101.307, F 4.1 f.sub.1 = 80.018, f.sub.1 /f.sub.W = 2.209 f.sub.2 = -20.157, f.sub.2 /f.sub.W = -0.557 f.sub.3 = 35.169, f.sub.3 /f.sub.W = 0.971 β.sub.2 W = -0.3876, β.sub.2 S = -0.5436, β.sub.2 T = -0.7752 β.sub.3 W = -1.1678, β.sub.3 S = -1.3929, β.sub.3 T = -1.6339 1/β.sub.2 W - 1/β.sub.2 T = -1.29, β.sub.2 T/β.sub.2 W = 2 1/β.sub.3 T - 1/β.sub.3 W = 0.244, β.sub.3 T/β.sub.3 W = 1.399 r.sub.24 /f.sub.3 = 0.896, (d.sub.21 + d.sub.23)/f.sub.3 ______________________________________ = 0.295 wherein reference symbols r 1 through r 28 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 27 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 15 respectively represent refractive indices of respective lenses, reference symbols ν 1 through ν 15 respectively represent Abbe's numbers of respective lenses, and reference symbols β 2 S and β 3 S respectively represent magnifications of the second and third lens groups in the standard position.

Claim 9

A zoom lens system according to claim 5, wherein said first lens group comprises a cemented doublet and a positive meniscus lens, said second lens group comprises a negative meniscus lens and two cemented doublets, and said third lens group comprises three positive lenses, a negative meniscus lens arranged to be concave toward the object side, a negative meniscus lens arranged to be convex toward the object side, and two positive lenses, said zoom lens system having the following numerical data: ______________________________________ r.sub.1 = 148.501 d.sub.1 = 2.5 n.sub.1 = 1.80518 ν.sub.1 = 25.43 r.sub.2 = 58.233 d.sub.2 = 9 n.sub.2 = 1.51633 ν.sub.2 = 64.15 r.sub.3 = -106.930 d.sub.3 = 0.1 r.sub.4 = 31.261 d.sub.4 = 5.2 n.sub.3 = 1.72916 ν.sub.3 = 54.68 r.sub.5 = 56.152 d.sub.5 = l.sub.1 (0.55˜10.49˜16.62) r.sub.6 = 53.077 d.sub.6 = 1.5 n.sub.4 = 1.7725 ν.sub.4 = 49.66 r.sub.7 = 15.712 d.sub.7 = 3.2 r.sub.8 = 139.937 d.sub.8 = 3.4 n.sub.5 = 1.60342 ν.sub.5 = 38.01 r.sub.9 = -29.521 d.sub.9 = 1 n.sub.6 = 1.804 ν.sub.6 = 46.57 r.sub.10 = 207.838 d.sub.10 = 2.8 r.sub.11 = -18.409 d.sub.11 = 1 n.sub.7 = 1.66687 ν.sub.7 = 57.33 r.sub.12 = 28.284 d.sub.12 = 3.2 n.sub.8 = 1.834 ν.sub.8 = 37.16 r.sub.13 = -54.062 d.sub.13 = l.sub.21 (7.4˜1.402˜0.274) r.sub.14 = ∞ (stop) d.sub.14 = l.sub.22 (10.42˜7˜0.4) r.sub.15 = 31.123 d.sub.15 = 5.14 n.sub.9 = 1.48749 ν.sub.9 = 70.15 r.sub.16 = -76.631 d.sub.16 = 2.02 r.sub.17 = 1490.2 d.sub.17 = 3.3 n.sub.10 = 1.48749 ν.sub.10 = 70.15 r.sub.18 = -60.161 d.sub.18 = 0.1 r.sub.19 = 109.458 d.sub.19 = 3 n.sub.11 = 1.617 ν.sub.11 = 62.79 r.sub.20 = -140.632 d.sub.20 = 4.25 r.sub.21 = -22.961 d.sub.21 = 2 n.sub.12 = 1.84666 ν.sub.12 = 23.88 r.sub.22 = -35.748 d.sub.22 = 0.2 r.sub.23 = 67.841 d.sub.23 = 8.15 n.sub.13 = 1.80518 ν.sub.13 = 25.43 r.sub.24 = 30.118 d.sub.24 = 3.47 r.sub.25 = -1582.82 d.sub.25 = 4 n.sub.14 = 1.61941 ν.sub.14 = 60.27 r.sub.26 = -43.736 d.sub.26 = 0.11 r.sub.27 = 45.619 d.sub.27 = 5.08 n.sub.15 = 1.56101 ν.sub.15 = 58.63 r.sub.28 = 108.887 f = 36.22˜101.35, F 4.1 f.sub.1 = 60.207, f.sub.1 /f.sub.W = 1.662 f.sub.2 = -17.331, f.sub.2 /f.sub.W = -0.478 f.sub.3 = 32.637, f.sub.3 /f.sub.W = 0.901 β.sub.2 W = -0.5204, β.sub.2 S = -0.7419, β.sub.2 T = -1.0057 β.sub.3 W = -1.156, β.sub.3 S = -1.440, β.sub.3 T = -1.674 1/β.sub.2 W - 1/β.sub.2 T = -0.927, β.sub.2 T/β.sub.2 W = 1.933 1/β.sub.3 T - 1/β.sub.3 W = 0.268, β.sub.3 T/β.sub.3 W = 1.448 r.sub.24 /f.sub.3 = 0.923, (d.sub.21 + d.sub.23)/f.sub.3 ______________________________________ = 0.31 wherein reference symbols r 1 through r 28 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 27 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 15 respectively represent refractive indices of respective lenses, reference symbols ν 1 through ν 15 respectively represent Abbe's numbers of respective lenses, and reference symbols β 2 S and β 3 S respectively represent magnifications of the second and third lens groups in the standard position.