Tele-photographic lens of large aperture ratio

Claim 2

A tele-photographic lens of a large aperture ratio comprising: a fixed first lens group which has a positive refracting power; a fixed second lens group which has a negative refracting power and is disposed on the image side of said first lens group; a third lens group which has a negative refracting power and is disposed on the image side of said second lens group, said third lens group being arranged to be movable in the direction of the optical axis of the lens for focusing it on an object to be photographed; and a fixed fourth lens group which has a positive refracting power and is disposed on the image side of said third lens group; wherein, when said tele-photographic lens is focused on an object located at infinity, the compound focal length of the first, second and third lens groups is f(I,II,III) and the focal length of the whole lens system is fT, said tele-photographic lens is arranged to satisfy the following condition: 2 fT<f(I, II, III)<2.6 fT

Claim 3

A tele-photographic lens according to claim 1, wherein said first lens group is composed of two positive lenses and one negative lens; said second lens group is composed of a meniscus lens having its convex face directed to an object to be photographed; said third lens group is a doublet lens composed by cementing together a positive lens and a negative lens; and, designating the radius of curvature of a lens surface located at an i-th position in the whole system as ri, the center thickness or the spatial interval of the i-th lens of the whole system as di, the refractive index of the i-th lens of the whole system as ni and the focal length of the positive third lens group as fIII, said tele-photographic lens is arranged to satisfy the following conditions: 0.35 fT<|fIII|<0.58 fT and fIII<0 0.125 fT<r8<0.15 fT 0.24 fT<r11<0.3 fT 0.1/fT<(n6-n5)/r10<1/fT

Claim 4

A tele-photographic lens according to claim 2 wherein, designating the Abbe number of the positive lens of said third lens group as ν5, the partial dispersion ratio thereof as θ5, the Abbe number of the negative lens of said third lens group as ν6 and the partial dispersion ratio thereof as θ6, said tele-photographic lens satisfies the following condition: -0.004<(θ6-θ5)/(ν6-ν5)<0.003

Claim 5

A tele-photographic lens according to claim 2, wherein said first lens group corresponds to r1-r6, said second lens group to r7 and r8, said third lens group to r9-r11 and said fourth lens group to r12-r14; and designating r as the radius of curvature, nd as the refractive index of the line d, d as the center thickness of the lens of a spatial interval and νd as the Abbe number of the line d and said lens, having a focal length f=100, a F number=1:2.8 and an image angle 2ω=8.24°, satisfies the following conditions: ______________________________________ r d νd nd ______________________________________ 1 46.022 5.613 81.60 1.49700 2 -198.074 0.170 1. 3 35.074 5.783 81.60 1.49700 4 -214.081 1.051 1. 5 -147.297 1.700 32.10 1.67270 6 69.040 10.307 1. 7 15.878 2.041 61.10 1.58913 8 13.769 5.517 1. 9 -85.014 2.041 27.50 1.75520 10 -23.328 0.850 47.10 1.62374 11 28.488 12.090 1. 12 58.660 0.850 53.30 1.58904 13 17.971 2.721 62.90 1.54771 14 -81.504 ______________________________________ b.f = 39.24

Claim 6

A tele-photographic lens according to claim 2, wherein said first lens group corresponds to r1-r6, said second lens group to r7 and r8, said third lens group to r9-r11 and said fourth lens group to r12 and r13; and designating r as the radius of curvature, d as the lens thickness on the axis or a spatial interval, nd as the refractive index of the line d and νd as the Abbe number of the line d and said lens, having a focal length f=100, a F number=1:2.8 and an image angle 2ω=8.24°, satisfies the following conditions: ______________________________________ r d νd nd ______________________________________ 1 47.975 5.109 81.60 1.49700 2 -578.939 0.170 1. 3 36.441 6.471 81.60 1.49700 4 -131.121 1.052 1. 5 -114.319 1.703 32.10 1.67270 6 102.753 10.320 1. 7 17.114 2.043 61.10 1.58913 8 14.526 5.524 1. 9 -89.834 2.043 27.50 1.75520 10 -28.832 0.851 45.60 1.54869 11 24.817 13.637 1. 12 54.096 1.703 60.30 1.51835 13 -132.637 ______________________________________ b.f = 39.60

Claim 7

A tele-photographic lens according to claim 2, wherein said first lens group corresponds to r1-r6, said second lens group to r7 and r8, said third lens group to r9-r11 and said fourth lens group to r12 and r13; and designating r as the radius of curvature, d as the lens thickness on the axis or a spatial interval, nd as the refractive index of the line d and νd as the Abbe number of the line d and said lens, having a focal length f=100, a F number=1:2.8 and an image angle 2ω=8.24°, satisfies the following conditions: ______________________________________ r d νd nd ______________________________________ 1 55.949 8.000 81.60 1.49700 2 -53.319 1.920 1. 3 -48.599 1.666 37.80 1.77551 4 -384.929 0.333 1. 5 34.351 5.333 81.60 1.49700 6 808.551 11.182 1. 7 15.225 1.931 61.10 1.58913 8 12.986 5.555 1. 9 127.952 1.666 27.50 1.75520 10 -64.236 0.666 41.90 1.66755 11 25.975 8.322 1. 12 108.111 1.333 41.10 1.70154 13 -823.619 ______________________________________ b.f = 42.21

Claim 8

A tele-photographic lens according to claim 1, wherein: said first lens group includes positive and negative lenses; the front lens surface of said second lens group is a convex face directed to an object to be photographed while the rear lens surface of said second lens group is a concave face directed to an image; said third lens group includes positive and negative lenses; said fourth lens group is a doublet lens formed by cementing negative and positive lenses together; and designating the Abbe number of the negative lens of the fourth lens group as ν7, the partial dispersion ratio thereof as θ7, the Abbe number of the positive lens of the fourth lens group as ν8 and the partial dispersion ratio thereof as θ8, said fourth lens group satisfies the following condition: -0.0005<(θ8-θ7)/(ν8-ν7)<+0.0035

Claim 9

A tele-photographic lens according to claim 7, wherein said first lens group corresponds to r1-r6, said second lens group to r7 and r8, said third lens group to r9-r11 and said fourth lens group to r12-r14; and designating r as the radius of curvature, d as the lens thickness on the axis or a spatial interval, nd as the refractive index of the line d and νd as the Abbe number of the line d and said lens, having a focal length f=100, a F number=1:2.8 and an image angle 2ω=8.24°, satisfies the following conditions: ______________________________________ r d νd nd ______________________________________ 1 42.819 6.123 81.60 1.49700 2 -165.112 0.170 1. 3 35.799 5.783 95.10 1.43387 4 -163.269 0.980 1. 5 -119.601 1.700 34.60 1.72047 6 89.689 10.915 1. 7 15.878 2.041 61.10 1.58913 8 13.799 5.532 1. 9 -71.830 2.041 25.40 1.80518 10 -24.673 0.850 43.80 1.61340 11 28.817 11.588 1. 12 60.563 0.850 55.50 1.69680 13 19.768 2.721 63.40 1.61800 14 -90.954 ______________________________________ b.f = 38.595

Claim 10

A tele-photographic lens according to claim 7, wherein said first lens group corresponds to r1-r6, said second lens group to r7 and r8, said third lens group to r9-r11 and said fourth lens group to r12-r14; and designating r as the radius of curvature, d as the lens thickness on the axis or a spatial interval, nd as the refractive index of the line d and νd as the Abbe number of the line d and said lens, having a focal length f=100, a F number=1:2.8 and an image angle 2ω=6.18°, satisfies the following conditions: ______________________________________ r d νd nd ______________________________________ 1 43.787 5.84 81.6 1.497 2 -169.35 0.13 1. 3 37.296 5.58 81.6 1.497 4 -155.24 0.97 1. 5 -115.08 1.63 34.6 1.72047 6 74.556 10.99 1. 7 15.672 2.13 61.1 1.58913 8 13.767 6.27 1. 9 -77.692 2.01 27.5 1.7552 10 -21.975 0.88 43.8 1.6134 11 28.891 9.59 1. 12 56.621 0.75 49.6 1.7725 13 19.999 2.33 55. 1.6175 14 -81.517 1. ______________________________________ b.f = 38.55

Claim 11

A tele-photographic lens according to claim 7, wherein said first lens group corresponds to r1-r6, said second lens group to r7 and r8, said third lens group to r9-r11 and said fourth lens group to r12-r14; and designating r as radius of curvature, d as the lens thickness on the axis or a spatial interval, nd as the refractive index of the line d and νd as the Abbe number of the line d and said lens, having a focal length f=100, a F number=1:2.8 and an image angle 2ω=8.24°, satisfies the following conditions: ______________________________________ r d νd nd ______________________________________ 1 44.980 5.39 81.60 1.49700 2 -166.553 0.13 1. 3 37.715 5.56 81.60 1.49700 4 -155.611 1.04 1. 5 -115.267 1.63 34.70 1.72047 6 78.877 12.24 1. 7 15.977 2.13 61.00 1.58913 8 13.989 6.65 1. 9 -80.934 2.01 25.70 1.78472 10 -20.879 0.88 39.70 1.65412 11 26.949 9.83 1. 12 55.810 0.75 54.70 1.72916 13 20.592 2.27 58.70 1.61272 14 -70.248 ______________________________________ b.f = 37.33

Claim 12

A tele-photographic lens according to claim 7, wherein said first lens group corresponds to r1-r6, said second lens group to r7 and r8, said third lens group to r9-r11 and said fourth lens group to r12-r14; and designating r as the radius of curvature, d as the lens thickness on the axis or a spatial interval, nd as the refractive index of the line d and νd as the Abbe number of the line d and said lens, having a focal length f=100, a F number=1:2.8 and an image angle 2ω=8.24°, satisfies the following conditions: ______________________________________ r d νd nd ______________________________________ 1 44.980 5.39 81.60 1.49700 2 -166.553 0.13 1. 3 37.715 5.56 81.60 1.49700 4 -155.611 1.04 1. 5 -115.267 1.63 34.70 1.72047 6 78.877 12.24 1. 7 15.977 2.13 61.00 1.58913 8 13.989 6.65 1. 9 -80.934 2.01 25.70 1.78472 10 -20.879 0.88 39.70 1.65412 11 26.949 9.83 1. 12 55.810 0.75 54.70 1.72916 13 20.592 2.27 58.70 1.61272 14 -70.248 ______________________________________ b.f = 37.33