Compact zoom objective

Claim 2

A compact zoom lens comprising: a movable first lens group having a positive power; a movable second lens group having a negative power and arranged to the rear of said first lens group; a third lens group having a positive power and arranged to the rear of said second lens group; and a fixed fourth lens group for image formation having a negative power and arranged to the rear of said third lens group, said fourth lens group consisting of a positive first lens of convex forward surface counting from the front, negative second lens of concave forward surface, a positive third lens, a biconvex positive fourth lens, and a negative fifth lens of concave forward surface and satisfying the following conditions: (1) 0.75F IV <r 15 <0.95F IV (2) 0.85F IV <|r 17 |<1.2F IV ,r 17 <0 (3) 2F IV <|r 22 |<3.5F IV ,r 22 <0 (4) 0.8F IV <|r 23 |<1F IV , r 23 <0 (5) 20<ν 18 21 30 (6) 20<ν 24 <30 where F IV is the focal length of the fourth lens group; r 15 is the radius of curvature of the front surface of the positive first lens; r 17 is the radius of curavature of the front surface of the negative second lens; r 22 is the radius of curvature of the rear surface of the positive fourth lens; r 23 is the radius of curavature of the front surface of the negative fifth lens; ν 18 is the Abbe number of the negative second lens; and ν 24 is the Abbe number of the negative fifth lens.

Claim 3

A zoom lens as described in claim 1, wherein said first lens group has a focusing function of causing difference in the object distance, said second lens group is axially movable to vary the focal length, and said third lens group is axially movable simultaneously with said second lens group to compensate for the image shift.

Claim 4

A zoom lens as described in claim 1, wherein said second lens group is axially movable to vary the focal length, said first lens group is axially movable simultaneously with said second lens group to compensate for the image shift and has a focusing function of causing difference in the object distance, and said third lens group is fixed to collimate the exiting rays of light.

Claim 5

A zoom lens as in claim 1, and having the following numerical data wherein the radius of curvature of the i-th lens surface is ri, the i-th axial separation between successive lens surfaces is di, the refractive index of the medium of the i-th lens is ni, the Abbe number of the medium of the i-th lens is νi, the i-th variable air separation is li, the focal lengths of the first, second, third and fourth lens groups are F I , F II , F III , and F IV respectively, and i=1, 2, 3, . . . ______________________________________ Focal length f = 9.228-43.805 F.No. 1: 1.26-1.45 ______________________________________ r[γ].sub.1 = 84.146 d.sub.1 = 2.0 n.sub.1 = 1.0 r[γ].sub.2 = 35.583 d.sub.2 = 7.87 n.sub.2 = 1.80518 ν.sub.2 = 25.4 r[γ].sub.3 = -103.996 d.sub.3 = 0.1 n.sub.3 = 1.58913 ν.sub.3 = 61.1 r[γ].sub.4 = 27.917 d.sub.4 = 4.07 n.sub.4 = 1.0 r[γ].sub.5 = 95.165 d.sub.5 = l.sub.1 n.sub.5 = 1.58913 ν.sub.5 = 61.1 r[γ].sub.6 = 363.049 d.sub.6 = 0.9 n.sub.6 = 1.0 r[γ].sub.7 = 12.195 d.sub.7 = 2.61 n.sub.7 ν.sub.7 = 53.2 r[γ].sub.8 = -16.671 d.sub.8 = 0.9 n.sub.8 = 1.0 r[γ].sub.9 = 13.785 d.sub.9 = 2.79 n.sub.9 = 1.69350 ν.sub.9 = 53.2 r[γ].sub.10 = -7680.848 d.sub.10 = l.sub.2 n.sub.10 = 1.80518 ν.sub.10 = 25.4 r[γ].sub.11 = 34.169 d.sub.11 = 0.9 n.sub.11 = 1.0 r[γ].sub.12 = 16.119 d.sub.12 = 4.82 n.sub.12 = 1.80518 ν.sub.12 = 25.4 r[γ].sub.13 = -52.155 d.sub.13 = l.sub.3 n.sub.13 = 1.62374 ν.sub.13 = 47.1 r[γ].sub.14 Diaphragm d.sub.14 = 1.68 n.sub.14 = 1.0 r[γ].sub.15 = 16.283 d.sub.15 = 4.35 n.sub.13 = 1.0 r[γ].sub.16 = 214.442 d.sub.16 = 3.63 n.sub.16 = 1.6968 ν.sub.16 = 55.5 r[γ].sub.17 = -18.519 d.sub.17 = 3.14 n.sub.17 = 1.0 r[γ].sub.18 = 46.639 d.sub.18 = 2.67 n.sub.18 = 1.7552 ν.sub.18 = 27.5 r[γ].sub.19 = 103.505 d.sub.19 = 3.63 n.sub.19 = 1.0 r[γ].sub.20 = -18.965 d.sub.20 = 0.54 n.sub.20 = 1.65844 ν.sub.20 = 50.9 r[γ].sub.21 = 18.834 d.sub.21 = 3.7 n.sub.21 = 1.0 r[γ].sub.22 = -47.131 d.sub.22 = 1.78 n.sub.22 = 1.883 ν.sub.22 = 40.8 r[γ].sub.23 = -18.952 d.sub.23 = 0.8 n.sub.23 = 1.0 r[ γ].sub.24 = 1068.979 n.sub.24 = 1.92286 ν.sub.24 = 20.9 n.sub.25 = 1.0 ______________________________________ f 9.228 20.090 43.805 ______________________________________ l.sub.1 1.495 14.229 20.085 l.sub.2 21.057 15.225 2.495 l.sub.3 14.215 7.313 14.187 ______________________________________

Claim 6

A zoom lens as in claim 1, and having the following numerical data wherein the radius of curvature of the i-th lens surface is ri, the i-th axial separation between successive lens surfaces is di, the refractive index of the medium of the i-th lens is ni, the Abbe number of the medium of the i-th lens is νi, the i-th variable air separation is li, the focal lengths of the first, second, third, and fourth lens groups are F I , F II , F III , and F IV respectively and i=1, 2, 3, . . . ______________________________________ Focal length f = 9.228-43.805 F.No.1:1.26-1.45 ______________________________________ r.sub.1 = 84.146 d.sub.1 = 2.0 n.sub.1 = 1.0 r.sub.2 = 35.583 d.sub.2 = 7.87 n.sub.2 = 1.80518 ν.sub.2 = 25.4 r.sub.3 = -103.996 d.sub.3 = 0.1 n.sub.3 = 1.58913 ν.sub.3 = 61.1 r.sub.4 = 27.917 d.sub.4 = 4.07 n.sub.4 = 1.0 r.sub.5 = 95.165 d.sub.5 = l.sub.1 n.sub.5 = 1.58913 ν.sub.5 = 61.1 r.sub.6 = 363.049 d.sub.6 = 0.9 n.sub.6 = 1.0 r.sub.7 = 12.195 d.sub.7 = 2.61 n.sub.7 = 1.69350 ν.sub.7 = 53.2 r.sub.8 = -16.671 d.sub.8 = 0.9 n.sub.8 = 1.0 r.sub.9 = 13.785 d.sub.9 = 2.79 n.sub.9 = 1.69350 ν.sub.9 = 53.2 r.sub.10 = -7680.848 d.sub.10 = l.sub.2 n.sub.10 = 1.80518 ν.sub.10 = 25.4 r.sub.11 = 47.713 d.sub.11 = 5.14 n.sub.11 = 1.0 r.sub.12 = -16.242 d.sub.12 = 0.9 n.sub.12 = 1.62374 ν.sub.12 = 47.1 r.sub.13 = -35.945 d.sub.13 = l.sub.3 n.sub.13 = 1.80518 ν.sub.13 = 25.4 r.sub.14 = Diaphragm d.sub.14 = 1.68 n.sub.14 = 1.0 r.sub.15 = 17.896 d.sub.15 = 3.85 n.sub.15 = 1.0 r.sub.16 = 176.591 d.sub.16 = 3.22 n.sub.16 = 1.834 ν.sub.16 = 37.2 r.sub.17 = -23.005 d.sub.17 = 3.01 n.sub.17 = 1.0 r.sub.18 = 74.537 d.sub.18 = 3.08 n.sub.18 = 1.92286 ν.sub.18 = 20.9 r.sub.19 = 100.572 d.sub.19 = 4.52 n.sub.19 = 1.0 r.sub.20 = -19.100 d.sub.20 = 0.21 n.sub.20 = 1.65844 ν.sub.20 = 50.9 r.sub.21 = 18.186 d.sub.21 = 3.77 n.sub.21 = 1.0 r.sub.22 = -58.998 d.sub.22 = 1.75 n.sub.22 = 1.67000 ν.sub.22 = 57.4 r.sub.23 = -17.527 d.sub.23 = 0.8 n.sub.23 = 1.0 r.sub.24 = -75.122 n.sub.24 = 1.7552 ν.sub.24 = 27.5 n.sub.25 = 1.0 ______________________________________ f 9.228 20.091 43.805 l.sub.1 1.495 14.229 20.085 l.sub.2 20.591 14.760 2.029 l.sub.3 14.215 7.313 14.187 ______________________________________

Claim 7

A zoom lens as in claim 1, and having the following numerical data wherein the radius of curvature of the i-th lens surface is ri, the i-th axial separation between successive lens surfaces is di, the refractive index of the medium of the i-th lens is ni, the Abbe number of the medium of the i-th lens is νi, the i-th variable air separation is li, the focal lengths of the first, second, third, and fourth lens groups are F I , F II , F III , and F IV respectively and i=1, 2, 3, . . . ______________________________________ Focal length f = 9.228-43.839 F.No.1:1.26-1.45 ______________________________________ r.sup.1 = 84.146 d.sub.1 = 2.0 n.sub.1 = 1.0 r.sup.2 = 35.583 d.sub.2 = 7.87 n.sub.2 = 1.80518 ν.sub.2 = 25.4 r.sup.3 = -103.996 d.sub.3 = 1.0 n.sub.3 = 1.58913 ν.sub.3 = 61.1 r.sup.4 = 27.917 d.sub.4 = 4.07 n.sub.4 = 1.0 r.sup.5 = 95.165 d.sub.5 = l.sub.1 n.sub.5 = 1.58913 ν.sub.5 = 61.1 r.sup.6 = 363.049 d.sub.6 = 0.9 n.sub.6 = 1.0 r.sup.7 = 12.195 d.sub.7 = 2.61 n.sub.7 = 1.69350 ν.sub.7 = 53.2 r.sup.8 = -16.671 d.sub.8 = 0.9 n.sub.8 = 1.0 r.sup.9 = 13.785 d.sub.9 = 2.79 n.sub.9 = 1.69350 ν.sub.9 = 53.2 r.sup.10 = -7680.848 d.sub.10 = l.sub.2 n.sub.10 = 1.80518 ν.sub.10 = 25.4 r.sup.11 = 40.338 d.sub.11 = 5.19 n.sub.11 = 1.0 r.sup.12 = -18.085 d.sub.12 = 0.9 n.sub.12 = 1.62374 ν.sub.12 = 47.1 r.sup.13 = -42.664 d.sub.13 = l.sub.3 n.sub.13 = 1.80518 ν.sub.13 = 25.4 r.sup.14 = Diaphragm d.sub.14 = 1.68 n.sub.14 = 1.0 r.sup.15 = 17.194 d.sub.15 = 3.77 n.sub.15 = 1.0 r.sup.16 = 198.428 d.sub.16 = 3.27 n.sub.16 = 1.7725 ν.sub.16 = 49.6 r.sup.17 = -20.139 d.sub.17 = 3.01 n.sub.17 = 1.0 r.sup.18 = 68.329 d.sub.18 = 3.11 n.sub.18 = 1.80518 ν.sub.18 = 25.4 r.sup.19 = 100.766 d.sub.19 = 4.56 n.sub.19 = 1.0 r.sup.20 = -19.422 d.sub.20 = 0.21 n.sub.20 = 1.65844 ν.sub.20 = 50.9 r.sup.21 = 18.996 d.sub.21 = 3.68 n.sub.21 = 1.0 r.sup.22 = -50.617 d.sub.22 = 1.81 n.sub.22 = 1.7725 ν.sub.22 = 49.6 r.sup.23 = -17.626 d.sub.23 = 0.8 n.sub.23 = 1.0 r.sup.24 = -181.929 n.sub.24 = 1.84666 ν.sub.24 = 23.9 n.sub.25 = 1.0 ______________________________________ f 9.228 20.111 43.839 l.sub.1 1.495 14.240 20.089 l.sub.2 20.976 15.134 2.396 l.sub.3 7.32 7.32 7.32 ______________________________________