Zoom lens

Claim 2

A compact 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 and a fourth lens group similarly having a positive focal length in the order from the object side, wherein a partial system consisting of the first lens group and the second lens group has a negative resultant focal length over the entire range of zooming, and when zooming is carried out from the wide position to the tele position, the first lens group and the fourth lens group are moved towards the object, the second lens group is moved towards the image, and the third lens group is arranged so that an airspace formed between the third lens group and the second lens group is decreased and an airspace formed between the third lens group and the fourth lens group is also decreased, and further wherein a fifth positive lens group is arranged on the image side of the fourth lens group, said lens system satisfying the following conditions: 0.4fw<t.sub.1.2T <1.5fw 0.4fw<t.sub.2.3w <1.5fw 0.4fw<|f.sub.2 |<1.5fw, f.sub.2 <0 0.3<K.sub.4(f) <3 0.5f.sub.T <f.sub.5 <5.0f.sub.T -0.5f.sub.T <X.sub.5(f) <0.5f.sub.T where: f: focal length as a whole at a suitable zooming position. fw: f at the wide position fT: f at the tele position fi: focal length of the i lens group Xi(f): amount of movement of the i lens group where focal length is f with the wide position as a reference; movement towards the object being positive, movement towards the image being negative Ki(f): coefficient indicative of the ratio of amount of movement of the i lens group at the focal length f to the amount of movement Xl(f) of the first lens group, Ki(f)=Xi(f)/Xl(f) t 1 .2T : Airspace between the first and second lens groups at the tele position t 2 .3w : Air space between the second and third lens groups at the wide position, and t 3 .4w : Airspace between the third and fourth lens groups at the wide position.

Claim 3

The zoom lens system according to claim 1, which satisfies the following condition: -0.3fw<X.sub.2(fT) <0.3fw.

Claim 4

The zoom lens system according to claim 1, which satisfies the following conditions: 0.5f.sub.T <f.sub.1 <1.5f.sub.T 1.7<NN.sub.2 40<ν.sub.p1 40<ν.sub.N2 0.3fw<γ.sub.A <0.9fw where NN 2 : average value of refractive index of the negative lens of the second lens group. ν p1 : average value of Abbe number of the positive lens of the second lens group. νN 2 : average value of Abbe number of the negative lens of the second lens group. γ A : radius of curvature on the image side of the head negative lens on the object side of the second lens group.

Claim 5

The zoom lens system according to claim 3, which is illustrated by data as follows: ______________________________________ R d n ν ______________________________________ 1 117.842 2.00 1.80518 25.0 2 59.774 8.00 1.62299 58.2 3 1 519.689 0.20 4 46.841 6.00 1.69680 55.5 5 107.461 dI 6 190.981 1.20 1.81600 46.6 7 18.527 6.55 8 -55.368 2.30 1.80518 25.4 9 2 -33.225 1.20 1.81600 46.6 10 181.151 0.20 11 40.259 2.50 1.80518 25.4 12 300.512 dII 13 49.561 4.50 1.62299 58.2 14 -21.215 1.00 1.80518 25.4 15 -49.873 0.20 16 28.701 3.00 1.69680 55.5 17 -99.568 2.66 3 18 -906.891 2.50 1.80518 25.4 19 -30.319 1.20 1.81600 46.6 20 130.557 2.60 21 -35.388 1.00 1.78590 44.2 22 37.388 dIII 23 -49.083 3.00 1.71300 53.8 24 -25.651 1.00 1.80518 25.4 25 -28.457 0.20 26 353.178 1.00 1.83400 37.2 4 27 23.128 6.50 1.51633 64.1 28 -40.087 0.20 29 32.778 7.00 1.51633 64.1 30 57.268 ______________________________________ f dI dII dIII FNo. ______________________________________ T 104.999 34.090 3.000 2.000 4.5 M 59.656 19.266 15.666 4.158 4.0 W 35.105 2.000 27.224 9.866 3.5 ______________________________________

Claim 6

The zoom lens system according to claim 3, which is illustrated by data as follows: ______________________________________ R d n ν ______________________________________ 1 132.460 2.00 1.80518 25.0 2 62.879 8.00 1.62299 58.2 3 1 1225.753 0.20 4 47.762 6.50 1.69680 55.5 5 125.777 dI 6 244.168 1.20 1.81600 46.6 7 18.416 6.55 8 -44.997 2.30 1.80518 25.4 9 2 -30.179 1.20 1.81600 46.6 10 257.320 0.20 11 44.107 2.50 1.80518 25.4 12 -10693.06 dII 13 54.186 4.50 1.62299 58.2 14 -21.736 1.00 1.80518 25.4 15 -49.065 0.20 16 30.704 3.00 1.69680 55.5 17 -119.983 3.13 3 18 -408.511 2.50 1.80518 25.4 19 -30.544 1.20 1.81600 46.6 20 352.213 2.60 21 -38.525 1.00 1.78590 44.2 22 36.959 dIII 23 -63.042 3.00 1.71300 53.8 24 -24.461 1.00 1.80518 25.4 25 -30.822 0.20 4 26 155.475 1.00 1.83400 37.2 27 25.073 6.50 1.51633 64.1 28 -42.383 dIV 29 34.121 7.00 1.51633 64.1 5 30 45.516 ______________________________________ f dI dII dIII dIV FNo. ______________________________________ T 104.993 32.617 3.000 2.000 9.168 4.5 M 59.663 18.590 15.094 3.034 7.233 4.0 W 35.098 2.000 24.651 10.967 0.200 3.5 ______________________________________

Claim 7

The zoom lens system according to claim 3, which is illustrated by data as follows: ______________________________________ R d n ν ______________________________________ 1 1685.046 2.00 1.80518 25.0 2 137.358 5.00 1.62230 53.2 3 -546.643 0.20 4 56.914 5.00 1.69680 55.5 5 391.533 dI 6 335.982 1.20 1.81600 46.6 7 19.658 6.55 8 -65.425 2.30 1.80518 25.4 9 -42.732 1.20 1.81600 46.6 10 -355.394 0.20 11 35.932 2.50 1.80518 25.4 12 91.601 dII 13 41.828 4.50 1.62299 58.2 14 -21.388 1.00 1.80518 25.4 15 -48.271 0.20 16 29.922 3.00 1.69680 55.5 17 -109.384 2.43 18 1809.543 2.50 1.80518 25.4 19 -29.369 1.20 1.81600 46.6 20 66.894 2.60 21 -32.694 1.00 1.78590 44.2 22 39.471 dIII 23 -60.366 3.00 1.71300 53.8 24 -25.579 1.00 1.80518 25.4 25 -28.919 0.20 26 754.056 1.00 1.83400 37.2 27 23.608 6.50 1.51633 64.1 28 -53.665 dIV 29 41.426 7.00 1.51633 64.1 30 221.545 ______________________________________ d dI dII dIII dIV FNo. ______________________________________ T 104.93 30.00 3.00 5.86 32.06 4.5 M 61.73 16.50 16.50 5.00 19.42 4.0 W 35.13 2.00 31.00 9.72 0.20 3.5 ______________________________________

Claim 8

The zoom lens system according to claim 3, which is illustrated by data as follows: ______________________________________ R d n ν ______________________________________ 1 -364.082 2.00 1.80518 25.0 2 204.616 6.00 1.62230 53.2 I 3 -139.245 0.20 4 55.304 4.00 1.69680 55.5 5 211.080 dI 6 866.035 1.20 1.81600 46.6 7 20.213 6.55 8 -80.752 2.80 1.80518 25.4 II 9 -41.601 1.20 1.81600 46.6 10 -631.263 0.20 11 34.746 3.00 1.80518 25.4 12 76.396 dII 13 39.771 4.50 1.62299 58.2 14 -21.599 1.00 1.80518 25.4 15 -49.836 0.20 16 29.467 3.50 1.69680 55.5 17 -98.677 1.79 III 18 3426.221 3.00 1.80518 25.4 19 -29.843 1.20 1.81600 46.6 20 71.973 2.60 21 -33.904 1.00 1.78590 44.2 22 33.574 dIII 23 -61.746 4.00 1.71300 53.8 24 -28.572 1.00 1.80518 25.4 25 -32.942 0.20 IV 26 2488,937 1.00 1.83400 37.2 27 23.668 6.80 1.58913 61.0 28 -59.078 dIV 29 43.954 5.80 1.56873 63.1 30 160.040 ______________________________________ f dI dII dIII dIV FNo. ______________________________________ T 104.93 30.0 3.00 5.90 32.06 4.5 M 61.48 16.5 16.5 5.50 18.96 4.0 W 35.16 2.0 31.00 9.76 0.20 3.5 ______________________________________

Claim 9

The zoom lens system according to claim 3, which is illustrated by data as follows: ______________________________________ R d n ν ______________________________________ 1 -519.654 2.00 1.80518 25.0 2 179.756 6.00 1.62230 53.2 I 3 -184.513 0.20 4 57.973 4.00 1.69680 55.5 5 322.429 dI 6 -2191.042 1.20 1.81600 46.6 7 22.133 6.55 8 -87.250 2.80 1.80518 25.4 II 9 -41.868 1.20 1.81600 46.6 10 1326.117 0.20 11 38.360 3.00 1.80518 25.4 12 94.963 dII 13 42.106 4.50 1.62299 58.2 14 -22.222 1.00 1.80518 25.4 15 -50.884 0.20 16 27.161 3.50 1.69680 55.5 17 -107.726 1.75 III 18 515.712 3.00 1.80518 25.4 19 -31.917 1.20 1.81600 46.6 20 65.113 2.60 21 -34.928 1.00 1.78590 44.2 22 31.051 dIII 23 -51.728 4.00 1.71300 53.8 24 -26.680 1.00 1.80518 25.4 25 -34.046 0.20 IV 26 480.267 1.00 1.83400 37.2 27 24.973 6.80 1.58913 61.0 28 -55.606 dIV 29 64.267 5.80 1.56873 63.1 30 -367.464 ______________________________________ f dI dII dIII dIV FNo. ______________________________________ T 104.83 30.00 3.00 5.02 32.98 4.5 M 61.38 16.50 16.50 5.00 19.50 4.0 W 35.13 2.0 31.00 9.80 0.20 3.5 ______________________________________

Claim 10

The zoom lens system according to claim 3, which is illustrated by data as follows: ______________________________________ R d n ν ______________________________________ 1 1546.649 2.00 1.80518 25.0 2 115.765 5.00 1.62230 53.2 3 1 -293.700 0.20 4 53.459 6.00 1.69680 55.5 5 241.557 dI 6 384.404 1.20 1.81600 46.6 7 18.799 6.55 8 -71.048 2.30 1.80518 25.4 9 2 -38.523 1.20 1.81600 46.6 10 24025.370 0.20 11 34.507 2.50 1.80518 25.4 12 90.541 dII 13 42.406 4.50 1.62299 58.2 14 -21.548 1.00 1.80518 25.4 15 -58.909 0.20 16 29.656 3.00 1.69680 55.5 17 -112.680 3.32 3 18 5325.193 2.50 1.80518 25.4 19 -29.859 1.20 1.81600 46.6 20 68.876 2.60 21 -31.877 1.00 1.78590 44.2 22 41.754 dIII 23 -57.355 3.00 1.71300 53.8 24 -26.480 1.00 1.80518 25.4 25 -29.914 0.20 4 26 268.952 1.00 1.83400 37.2 27 22.095 6.50 1.51633 64.1 28 -54.400 dIV 29 41.811 7.00 1.51633 64.1 5 30 228.144 ______________________________________ f dI dII dIII dIV FNo. ______________________________________ T 104.97 30.00 6.50 5.02 28.20 4.5 M 58.72 16.50 20.29 4.74 14.70 4.0 W 35.12 2.0 31.67 7.86 0.20 3.5 ______________________________________