Vari-focal lens system

Claim 2

A vari-focal lens system comprising, in the order from the object side, a first lens group having a positive focal length and arranged to be always kept fixed, a second lens group having a negative focal length and arranged to be movable along the optical axis when varying the focal length of the lens system as a whole and to be kept fixed at the time of focusing, a third lens group having a positive focal length and arranged to be always kept fixed, and a fourth lens group with a positive focal length located by leaving a comparatively large airspace in respect to said third lens group and arranged to be movable for the purpose of compensation so as to eliminate the displacement of the focal point caused when varying the focal length of the lens system as a whole and, moreover, to integrally move said fourth lens group as a whole for the purpose of focusing, said vari-focal lens system being arranged that rays coming out from said third lens group become approximately afocal.

Claim 3

A vari-focal lens system according to claim 1 wherein said first lens group comprises a negative lens, a positive lens and a positive lens, said second lens group comprises a first negative lens, a second negative lens and a positive lens, said third lens group comprises at least one positive lens and a negative lens, and said fourth lens group comprises a negative lens, a first positive lens and a second positive lens, said vari-focal lens system being arranged to fulfill the conditions (1) through (10) shown below: ##EQU2## where, reference symbol f T represents the longest focal length of the lens system as a whole, reference symbol f AT represents the total focal length of the first, second and third lens groups in the position of the longest focal length, reference symbol f W represents the shortest focal length of the lens system as a whole, reference symbol f 4 represents the total focal length of the fourth lens group, reference symbol D T represents the airspace between the third and fourth lens groups when the lens system is focused on an object at the infinite distance in the position of the longest focal length, reference symbol t I represents the distance from the foremost surface to the rearmost surface of the first lens group, reference symbol f I represents the total focal length of the first lens group, reference symbol f II represents the total focal length of the second lens group, reference symbol n 5 represents the refractive index of the second negative lens in the second lens group, reference symbol n 6 represents the refractive index of the positive lens in the second lens group, reference symbol ν 5 represents Abbe's number of the second negative lens in the second lens group, reference symbol ν 6 represents Abbe's number of the positive lens in the second lens group, reference symbol n IVp represents the refractive index of the first positive lens in the fourth lens group, reference symbol n IVn represents the refractive index of the negative lens in the fourth lens group, reference symbol ν IVp represents Abbe's number of the first positive lens in the fourth lens group, and reference symbol ν IVn represents Abbe's number of the negative lens in the fourth lens group.

Claim 4

A vari-focal lens system according to claim 2 having the following numerical data: ______________________________________ f = 12˜ 72 F/1.2˜F/1.7 ______________________________________ r.sub.1 = 160.1139 d.sub.1 = 1.5000 n.sub.1 = 1.80518 ν.sub.1 = 25.43 r.sub.2 = 56.7068 d.sub.2 = 0.6000 r.sub.3 = 63.5411 d.sub.3 = 8.7000 n.sub.2 = 1.60311 ν.sub.2 = 60.70 r.sub.4 = -118.9448 d.sub.4 = 0.1500 r.sub.5 = 34.6640 d.sub.5 = 5.9000 n.sub.3 = 1.60311 ν.sub.3 = 60.70 r.sub.6 = 96.5475 d.sub.6 = D.sub.1 (variable) r.sub.7 = 56.5891 d.sub.7 = 1.0000 n.sub.4 = 1.83400 ν.sub.4 = 37.16 r.sub.8 = 14.1280 d.sub.8 = 5.8000 r.sub.9 = -16.8744 d.sub.9 = 1.0000 n.sub.5 = 1.69700 ν.sub.5 = 48.51 r.sub.10 = 21.7195 d.sub.10 = 3.8000 n.sub.6 = 1.84666 ν.sub.6 = 23.78 r.sub.11 = -80.2671 d.sub.11 = D.sub.2 (variable) r.sub.12 = 45.6568 d.sub.12 = 4.9000 n.sub.7 = 1.77250 ν.sub.7 = 49.66 r.sub.13 = -60.9922 d.sub.13 = 1.0000 r.sub.14 = ∞ (stop) d.sub.14 = 3.000 r.sub.15 = 27.0781 d.sub.15 = 3.6000 n.sub.8 = 1.69680 ν.sub.8 = 55.52 r.sub.16 = 158.3382 d.sub.16 = 1.8000 r.sub.17 = -55.6584 d.sub.17 = 1.1000 n.sub.9 = 1.84666 ν.sub.9 = 23.78 r.sub.18 = 67.4790 d.sub.18 = D.sub.3 (variable) r.sub.19 = 441.5308 d.sub.19 = 1.2000 n.sub.10 = 1.84666 ν.sub.10 = 23.78 r.sub.20 = 29.7156 d.sub.20 = 1.0000 r.sub.21 = 62.2357 d.sub.21 = 3.8000 n.sub.11 = 1.69680 ν.sub.11 = 55.52 r.sub.22 = -31.9184 d.sub.22 = 0.1500 r.sub.23 = 21.5326 d.sub.23 = 3.3000 n.sub.12 = 1.69680 ν.sub.12 = 55.52 r.sub.24 = 118.4843 d.sub.24 = D.sub.4 (variable) r.sub.25 = ∞ d.sub.25 = 14.0000 n.sub.13 = 1.51633 ν.sub.13 = 64.15 r.sub.26 = ∞ d.sub.26 = 1.0000 r.sub.27 = ∞ d.sub.27 = 6.0000 n.sub.14 = 1.51633 ν.sub.14 = 64.15 r.sub.28 = ∞ ______________________________________ f 12 29 72 ______________________________________ D.sub.1 1.000 18.453 30.158 D.sub.2 30.658 13.206 1.500 D.sub.3 14.494 9.838 12.332 D.sub.4 3.000 7.656 5.162 ______________________________________ f.sub.T /f.sub.AT = 0.238 ##STR73## ##STR74## ##STR75## ##STR76## n.sub.6 - n.sub.5 = 0.14966 ν.sub.5 - ν.sub.6 = 24.73 n.sub.IVn -n.sub.IVp = 0.14986 ν.sub.IVp - ν.sub.IVn = 31.74 ##STR77## ##STR78## s.sub.T = 4.224 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses, reference symbol f represents the focal length of the lens system as a whole, reference symbol f BW represents the back focal length in the wide position (position of the shortest focal length), and reference symbol S T represents the advancing amount of the fourth lens group when the lens system is to be focused on an object at the object distance of 1 m in the teleposition (position of the longest focal length).

Claim 5

A vari-focal lens system according to claim 2 having the following numerical data: ______________________________________ f = 12˜ 72 F/1.2˜F/1.7 ______________________________________ r.sub.1 = 135.4596 d.sub.1 = 1.5000 n.sub.1 = 1.80518 ν.sub.1 = 25.43 r.sub.2 = 53.4855 d.sub.2 = 0.4000 r.sub.3 = 57.1682 d.sub.3 = 8.5000 n.sub.2 = 1.60311 ν.sub.2 = 60.70 r.sub.4 = -156.9705 d.sub.4 = 0.1500 r.sub.5 = 36.1375 d.sub.5 = 5.5000 n.sub.3 = 1.60311 ν.sub.3 = 60.70 r.sub.6 = 113.9903 d.sub.6 = D.sub.1 (variable) r.sub.7 = 47.6409 d.sub.7 = 1.0000 n.sub.4 = 1.83400 ν.sub.4 = 37.16 r.sub.8 = 13.4748 d.sub.8 = 6.0000 r.sub.9 = -17.1192 d.sub.9 = 1.0000 n.sub.5 = 1.69700 ν.sub.5 = 48.51 r.sub.10 = 19.7618 d.sub.10 = 4.0000 n.sub.6 = 1.84666 ν.sub.6 = 23.78 r.sub.11 = -82.2933 d.sub.11 = D.sub.2 (variable) r.sub.12 = -303.1840 d.sub.12 = 2.7000 n.sub.7 = 1.77250 ν.sub.7 = 49.66 r.sub.13 = -50.3064 d.sub.13 = 1.0000 r.sub.14 = ∞ (stop) d.sub.14 = 3.0000 r.sub.15 = 38.9098 d.sub.15 = 4.0000 n.sub.8 = 1.69680 ν.sub.8 = 55.52 r.sub.16 = -343.4102 d.sub.16 = 1.6000 r.sub.17 = -56.3115 d.sub.17 = 1.1000 n.sub.9 = 1.84666 ν.sub.9 = 23.78 r.sub.18 = -274.6890 d.sub.18 = D.sub.3 (variable) r.sub.19 = -838.5286 d.sub.19 = 1.2000 n.sub.10 = 1.84666 ν.sub.10 = 23.78 r.sub. 20 = 33.5553 d.sub.20 = 0.3500 r.sub.21 = 40.3991 d.sub.21 = 5.3000 n.sub.11 = 1.69680 ν.sub.11 = 55.52 r.sub.22 = -40.8461 d.sub.22 = 0.1500 r.sub.23 = 26.1080 d.sub.23 = 4.1000 n.sub.12 = 1.69680 ν.sub.12 = 55.52 r.sub.24 = 200.0303 d.sub.24 = D.sub.4 (variable) r.sub.25 = ∞ d.sub.25 = 14.0000 n.sub.13 = 1.51633 ν.sub.13 = 64.15 r.sub.26 = ∞ d.sub.26 = 1.0000 r.sub.27 = ∞ d.sub.27 = 6.0000 n.sub.14 = 1.51633 ν.sub.14 = 64.15 r.sub.28 = ∞ ______________________________________ f 12 29 72 ______________________________________ D.sub.1 1.000 18.851 30.454 D.sub.2 30.645 12.794 1.192 D.sub.3 25.803 21.561 24.164 D.sub.4 3.000 7.242 4.638 ______________________________________ f.sub.T /f.sub.AT = 0.099 ##STR79## ##STR80## ##STR81## ##STR82## n.sub.6 - n.sub.5 = 0.14966 ν.sub.5 - ν.sub.6 = 24.73 n.sub.IVn - n.sub.IVp = 0.14986 ν.sub.IVp - ν.sub.IVn = 31.74 ##STR83## ##STR84## s.sub.T = 4.023 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses, reference symbol f represents the focal length of the lens system as a whole, reference symbol f BW represents the back focal length in the wide position (position of the shortest focal length), and reference symbol S T represents the advancing amount of the fourth lens group when the lens system is to be focused on an object at the object distance of 1 m in the teleposition (position of the longest focal length).

Claim 6

A vari-focal lens system according to claim 2 having the following numerical data: ______________________________________ f = 12˜ 72 F/1.2˜F/1.8 ______________________________________ r.sub.1 = 123.7332 d.sub.1 = 1.5000 n.sub.1 = 1.80518 ν.sub.1 = 25.43 r.sub.2 = 52.2449 d.sub.2 = 0.3000 r.sub.3 = 56.2238 d.sub.3 = 7.2000 n.sub.2 = 1.60311 ν.sub.2 = 60.70 r.sub.4 = -161.1663 d.sub.4 = 0.1500 r.sub.5 = 34.5295 d.sub.5 = 5.7000 n.sub.3 = 1.60311 ν.sub.3 = 60.70 r.sub.6 = 114.2507 d.sub.6 = D.sub.1 (vari- able) r.sub.7 = 50.8351 d.sub.7 = 1.0000 n.sub.4 = 1.83400 ν.sub.4 = 37.16 r.sub.8 = 13.7931 d.sub.8 = 6.8000 r.sub.9 = -16.1577 d.sub.9 = 1.0000 n.sub.5 = 1.67790 ν.sub.5 = 55.33 r.sub.10 = 22.2461 d.sub.10 = 3.7000 n.sub.6 = 1.84666 ν.sub.6 = 23.78 r.sub.11 = -161.9847 d.sub.11 = D.sub.2 (vari- able) r.sub.12 = -1356.9084 d.sub.12 = 3.7000 n.sub.7 = 1.83400 ν.sub.7 = 37.16 r.sub.13 = -44.0824 d.sub.13 = 1.0000 r.sub.14 = ∞ (stop) d.sub.14 = 3.0000 r.sub.15 = 41.3545 d.sub.15 = 4.5000 n.sub.8 = 1.69680 ν.sub.8 = 55.52 r.sub.16 = -136.6095 d.sub.16 = 1.3000 r.sub.17 = -51.0155 d.sub.17 = 1.1000 n.sub.9 = 1.84666 ν.sub.9 = 23.78 r.sub.18 = 351.8015 d.sub.18 = D.sub.3 (vari- able) r.sub.19 = 71.3423 d.sub.19 = 1.2000 n.sub.10 = 1.84666 ν.sub.10 = 23.78 r.sub.20 = 32.6618 d.sub.20 = 1.1000 r.sub.21 = 51.4512 d.sub.21 = 5.9000 n.sub.11 = 1.48749 ν.sub.11 = 70.20 r.sub.22 = -33.9160 d.sub.22 = 0.1500 r.sub.23 = 25.4014 d.sub.23 = 5.1000 n.sub.12 = 1.48749 ν.sub.12 = 70.20 r.sub.24 = -375.7640 d.sub.24 = D.sub.4 (vari-- able) r.sub.25 = ∞ d.sub.25 = 14.0000 n.sub.13 = 1.51633 ν.sub.13 = 64.15 r.sub.26 = ∞ d.sub.26 = 1.0000 r.sub.27 = ∞ d.sub.27 = 6.0000 n.sub.14 = 1.51633 ν.sub.14 = 64.15 r.sub.28 = ∞ ______________________________________ f 12 29 72 ______________________________________ D.sub.1 1.000 17.251 27.885 D.sub.2 31.380 15.129 4.495 D.sub.3 21.754 16.513 18.240 D.sub.4 3.000 8.241 6.513 ______________________________________ f.sub.T /f.sub.AT = 0.063 ##STR85## ##STR86## ##STR87## ##STR88## n.sub.6 - n.sub.5 = 0.16876 ν.sub.5 - ν.sub.6 = 31.55 n.sub.IVn - n.sub.IVp = 0.35917 ν.sub.IVp - ν.sub.IVn = 46.42 ##STR89## ##STR90## s.sub.T = 4.104 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses, reference symbol f represents the focal length of the lens system as a whole, reference symbol f BW represents the back focal length in the wide position (position of the shortest focal length), and reference symbol S T represents the advancing amount of the fourth lens group when the lens system is to be focused on an object at the object distance of 1 m in the teleposition (position of the longest focal length).

Claim 7

A vari-focal lens system according to claim 2 having the following numerical data: ______________________________________ f = 12˜ 72 F/1.2˜F/1.7 ______________________________________ r.sub.1 = 165.9365 d.sub.1 = 1.5000 n.sub.1 = 1.80518 ν.sub.1 = 25.43 r.sub.2 = 53.4205 d.sub.2 = 0.3000 r.sub.3 = 57.0057 d.sub.3 = 7.9000 n.sub.2 = 1.60311 ν.sub.2 = 60.70 r.sub.4 = -170.2011 d.sub.4 = 0.1500 r.sub.5 = 39.4171 d.sub.5 = 5.5000 n.sub.3 = 1.69680 ν.sub.3 = 55.52 r.sub.6 = 156.9904 d.sub.6 = D.sub.1 (variable) r.sub.7 = 46.4325 d.sub.7 = 1.0000 n.sub.4 = 1.83400 ν.sub.4 = 37.16 r.sub.8 = 13.9757 d.sub.8 = 6.0000 r.sub.9 = -18.4154 d.sub.9 = 1.0000 n.sub.5 = 1.67790 ν.sub.5 = 55.33 r.sub.10 = 21.9302 d.sub.10 = 3.5000 n.sub.6 = 1.84666 ν.sub.6 = 23.78 r.sub.11 = -117.8717 d.sub.11 = D.sub.2 (variable) r.sub.12 = 296.3316 d.sub.12 = 3.5000 n.sub.7 = 1.72000 ν.sub.7 = 50.25 r.sub.13 = -46.7165 d.sub.13 = 0.1500 r.sub.14 = 34.5044 d.sub.14 = 2.8000 n.sub.8 = 1.72000 ν.sub.8 = 50.25 r.sub.15 = 89.5454 d.sub.15 = 2.9000 r.sub.16 = -41.4221 d.sub.16 = 1.1000 n.sub.9 = 1.84666 ν.sub.9 = 23.78 r.sub.17 = -99.0301 d.sub.17 = 1.1500 r.sub.18 =∞ (stop) d.sub.18 = D.sub.3 (variable) r.sub.19 = -184.2482 d.sub.19 = 1.2000 n.sub.10 = 1.84666 ν.sub.10 = 23.78 r.sub.20 = 33.3380 d.sub.20 = 0.3500 r.sub.21 = 39.5733 d.sub.21 = 5.6000 n.sub.11 = 1.69680 ν.sub.11 = 55.52 r.sub.22 = -33.5001 d.sub.22 = 0.1500 r.sub.23 = 26.6392 d.sub.23 = 4.0000 n.sub.12 = 1.69680 ν.sub.12 = 55.52 r.sub.24 = 703.8247 d.sub.24 = D.sub.4 (variable) r.sub.25 = ∞ d.sub.25 = 14.0000 n.sub.13 = 1.51633 ν.sub.13 = 64.15 r.sub.26 = ∞ d.sub.26 = 1.0000 r.sub.27 = ∞ d.sub.27 = 6.0000 n.sub.14 = 1.51633 ν.sub.14 = 64.15 r.sub.28 = ∞ ______________________________________ f 12 29 72 ______________________________________ D.sub.1 1.000 18.238 29.856 D.sub.2 29.856 12.618 1.000 D.sub.3 20.227 17.009 20.933 D.sub.4 3.000 6.218 2.294 ______________________________________ f.sub.T /f.sub.AT = 0.120 ##STR91## ##STR92## ##STR93## ##STR94## n.sub.6 - n.sub.5 = 0.16876 ν.sub.5 - ν.sub.6 = 31.55 n.sub.IVn - n.sub.IVp = 0.14986 ν.sub.IVp - ν.sub.IVn = 31.74 ##STR95## ##STR96## s.sub.T = 4.048 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses, reference symbol f represents the focal length of the lens system as a whole, reference symbol f BW represents the back focal length in the wide position (position of the shortest focal length), and reference symbol S T represents the advancing amount of the fourth lens group when the lens system is to be focused on an object at the object distance of 1 m in the teleposition (position of the longest focal length).

Claim 8

A vari-focal lens system according to claim 1 wherein said first lens group comprises a negative lens, a positive lens and a positive lens, said second lens group comprises a first negative lens, a second negative lens and a positive lens, said third lens group comprises at least one positive lens and a negative lens, and said fourth lens group comprises a first positive lens, a second positive lens and a negative lens, said vari-focal lens system being arranged to fulfill the conditions (1) through (10) shown below: ##EQU3## where, reference symbol f T represents the longest focal length of the lens system as a whole, reference symbol f AT represents the total focal length of the first, second and third lens groups in the position of the longest focal length, reference symbol f W represents the shortest focal length of the lens system as a whole, reference symbol f 4 represents the total focal length of the fourth lens group, reference symbol D T represents the airspace between the third and fourth lens groups when the lens system is focused on an object at the infinite distance in the position of the longest focal length, reference symbol t I represents the distance from the foremost surface to the rearmost surface of the first lens group, reference symbol f I represents the total focal length of the first lens group, reference symbol f II represents the total focal length of the second lens group, reference symbol n 5 represents the refractive index of the second negative lens in the second lens group, reference symbol n 6 represents the refractive index of the positive lens in the second lens group, reference symbol ν 5 represents Abbe's number of the second negative lens in the second lens group, reference symbol ν 6 represents Abbe's number of the positive lens in the second lens group, reference symbol n IVp represents the refractive index of the second positive lens in the fourth lens group, reference symbol n IVn represents the refractive index of the negative lens in the fourth lens group, reference symbol ν IVp represents Abbe's number of the second positive lens in the fourth lens group, and reference symbol ν IVn represents Abbe's number of the negative lens in the fourth lens group.

Claim 9

A vari-focal lens system according to claim 7 having the following numerical data: ______________________________________ f = 12˜72 F/1.2˜F/1.8 ______________________________________ r.sub.1 = 144.0963 d.sub.1 = 1.5000 n.sub.1 = 1.80518 ν.sub.1 = 25.43 r.sub.2 = 55.0145 d.sub.2 = 0.1600 r.sub.3 = 56.7336 d.sub.3 = 7.2000 n.sub.2 = 1.60311 ν.sub.2 = 60.70 r.sub.4 = -163.8458 d.sub.4 = 0.1500 r.sub.5 = 39.2075 d.sub.5 = 5.1000 n.sub.3 = 1.60311 ν.sub.3 = 60.70 r.sub.6 = 130.5878 d.sub.6 = D.sub.1 (variable) r.sub.7 = 65.3930 d.sub.7 = 1.0000 n.sub.4 = 1.77250 ν.sub.4 = 49.66 r.sub.8 = 16.0137 d.sub.8 = 6.5000 r.sub.9 = -20.5600 d.sub.9 = 1.0000 n.sub.5 = 1.67790 ν.sub.5 = 55.33 r.sub.10 = 24.3845 d.sub.10 = 3.4000 n.sub.6 = 1.84666 ν.sub.6 = 23.78 r.sub.11 = -243.3111 d.sub.11 = D.sub.2 (variable) r.sub.12 = 239.6682 d.sub.12 = 2.4000 n.sub.7 = 1.77250 ν.sub.7 = 49.66 r.sub.13 = -104.3267 d.sub.13 = 1.0000 r.sub.14 = ∞(stop) d.sub.14 = 3.0000 r.sub.15 = 98.7511 d.sub.15 = 3.2000 n.sub.8 = 1.77250 ν.sub.8 = 49.66 r.sub.16 = -73.8104 d.sub.16 = 1.3000 r.sub.17 = -34.9115 d.sub.17 = 1.2000 n.sub.9 = 1.84666 ν.sub.9 = 23.78 r.sub.18 = -79.1788 d.sub.18 = D.sub.3 (variable) r.sub.19 = 236.7931 d.sub.19 = 3.7000 n.sub.10 = 1.77250 ν.sub.10 = 49.66 r.sub.20 = -49.2961 d.sub.20 = 0.1500 r.sub.21 = 36.8956 d.sub.21 = 7.4000 n.sub.11 = 1.69680 ν.sub.11 = 55.52 r.sub.22 = -28.4243 d.sub.22 = 1.2000 n.sub.12 = 1.84666 ν.sub.12 = 23.78 r.sub.23 = -740.9855 d.sub.23 = D.sub.4 (variable) r.sub.24 = ∞ d.sub.24 = 14.0000 n.sub.13 = 1.51633 ν.sub.13 = 64.15 r.sub.25 = ∞ d.sub.25 = 1.0000 r.sub.26 = ∞ d.sub.26 = 6.0000 n.sub.14 = 1.51633 ν.sub.14 = 64.15 r.sub.27 = ∞ ______________________________________ f 12 29 72 ______________________________________ D.sub.1 1.000 19.076 31.852 D.sub.2 31.852 13.776 1.000 D.sub.3 24.932 21.747 25.234 D.sub.4 3.000 6.185 2.698 ______________________________________ f.sub.T /f.sub.AT = -0.002 ##STR97## ##STR98## ##STR99## ##STR100## n.sub.6 - n.sub.5 = 0.16876 ν.sub.5 - ν.sub.6 = 31.55 n.sub.Ivn - n.sub.IVp = 0.14986 ν.sub.IVp - ν.sub.IVn = 31.74 ##STR101## ##STR102## s.sub.T = 4.132 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses, reference symbol f represents the focal length of the lens system as a whole, reference symbol f BW represents the back focal length in the wide position (position of the shortest focal length), and reference symbol S T represents the advancing amount of the fourth lens group when the lens system is to be focused on an object at the object distance of 1 m in the teleposition (position of the longest focal length).

Claim 10

A vari-focal lens system according to claim 7 having the following numerical data: ______________________________________ f = 12˜72 F/1.2˜F/1.8 ______________________________________ r.sub.1 = 238.5683 d.sub.1 = 1.5000 n.sub.1 = 1.80518 ν.sub.1 = 25.43 r.sub.2 = 59.6039 d.sub.2 = 0.1300 r.sub.3 = 61.5281 d.sub.3 = 7.1000 n.sub.2 = 1.60311 ν.sub.2 = 60.70 r.sub.4 = -150.6907 d.sub.4 = 0.1500 r.sub.5 = 42.2290 d.sub.5 = 4.7000 n.sub.3 = 1.72000 ν.sub.3 = 50.25 r.sub.6 = 119.9301 d.sub.6 = D.sub.1 (variable) r.sub.7 = 49.8486 d.sub.7 = 1.0000 n.sub.4 = 1.83400 ν.sub.4 = 37.16 r.sub.8 = 16.3739 d.sub.8 = 6.9000 r.sub.9 = -21.0451 d.sub.9 = 1.0000 n.sub.5 = 1.67790 ν.sub.5 = 55.33 r.sub.10 = 24.8249 d.sub.10 = 3.9000 n.sub.6 = 1.84666 ν.sub.6 = 23.78 r.sub.11 = -148.0327 d.sub.11 = D.sub.2 (variable) r.sub.12 = 199.9856 d.sub.12 = 2.4000 n.sub.7 = 1.80518 ν.sub.7 = 25.43 r.sub.13 = -84.5931 d.sub.13 = 1.0000 r.sub.14 = ∞ (stop) d.sub.14 = 3.0000 r.sub.15 = 50.2773 d.sub.15 = 3.7000 n.sub.8 = 1.77250 ν.sub.8 = 49.66 r.sub.16 = -107.1752 d.sub.16 = 1.2000 r.sub.17 = -42.6456 d.sub.17 = 1.2000 n.sub.9 = 1.84666 ν.sub.9 = 23.78 r.sub.18 = 129.7076 d.sub.18 = D.sub.3 (variable) r.sub.19 = 352.8759 d.sub.19 = 4.2000 n.sub.10 = 1.77250 ν.sub.10 = 49.66 r.sub.20 = -41.6555 d.sub. 20 = 0.1500 r.sub.21 = 33.3832 d.sub.21 = 7.8000 n.sub.11 = 1.69680 ν.sub.11 = 55.52 r.sub.22 = -29.8010 d.sub.22 = 1.2000 n.sub.12 = 1.84666 ν.sub.12 = 23.78 r.sub.23 = 540.8846 d.sub.23 = D.sub.4 (variable) r.sub.24 = ∞ d.sub.24 = 14.0000 n.sub.13 = 1.51633 ν.sub.13 = 64.15 r.sub.25 = ∞ d.sub.25 = 1.0000 r.sub.26 = ∞ d.sub.26 = 6.0000 n.sub.14 = 1.51633 ν.sub.14 = 64.15 r.sub.27 = ∞ ______________________________________ f 12 29 72 ______________________________________ D.sub.1 1.000 20.703 35.159 D.sub.2 35.159 15.456 1.000 D.sub.3 22.509 19.488 23.086 D.sub.4 3.578 6.598 3.000 ______________________________________ f.sub.T /f.sub.AT = -0.088 ##STR103## ##STR104## ##STR105## ##STR106## n.sub.6 - n.sub.4 = 0.16876 ν.sub.5 - ν.sub.6 = 31.55 n.sub.IVn - n.sub.IVp = 0.14986 ν.sub.IVp - ν.sub.IVn = 31.74 ##STR107## ##STR108## s.sub.T = 4.282 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thickness of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses, reference symbol f represents the focal length of the lens system as a whole, reference symbol f BW represents the back focal length in the wide position (position of the shortest focal length), and reference symbol S T represents the advancing amount of the fourth lens group when the lens system is to be focused on an object at the object distance of 1 m in the teleposition (position of the longest focal length).

Claim 11

A vari-focal lens system according to claim 7 having the following numerical data: ______________________________________ f = 12˜72 F/1.2˜F/1.7 ______________________________________ r.sub.1 = 239.9118 d.sub.1 = 1.5000 n.sub.1 = 1.80518 ν.sub.1 = 25.43 r.sub.2 = 59.3936 d.sub.2 = 0.1000 r.sub.3 = 60.8202 d.sub.3 = 7.2000 n.sub.2 = 1.60311 ν.sub.2 = 60.70 r.sub.4 = -142.9706 d.sub.4 = 0.1500 r.sub.5 = 41.7740 d.sub.5 = 4.5000 n.sub.3 = 1.72000 ν.sub.3 = 50.25 r.sub.6 = 109.6368 d.sub.6 = D.sub.1 (variable) r.sub.7 = 51.6613 d.sub.7 = 1.0000 n.sub.4 = 1.83400 ν.sub.4 = 37.16 r.sub.8 = 16.5840 d.sub.8 = 6.9000 r.sub.9 = -21.2063 d.sub.9 = 1.0000 n.sub.5 = 1.67790 ν.sub.5 = 55.33 r.sub.10 = 25.5470 d.sub.10 = 3.9000 n.sub.6 = 1.84666 ν.sub.6 = 23.78 r.sub.11 = -148.7898 d.sub.11 = D.sub.2 (variable) r.sub.12 = 134.9300 d.sub.12 = 2.9000 n.sub.7 = 1.80518 ν.sub.7 = 25.43 r.sub.13 = -78.1776 d.sub.13 = 1.0000 r.sub.14 = ∞ (stop) d.sub.14 = 3.0000 r.sub.15 = 51.7843 d.sub.15 = 3.3000 n.sub.8 = 1.77250 ν.sub.8 = 49.66 r.sub.16 = -156.2525 d.sub.16 = 1.3000 r.sub.17 = -44.4456 d.sub.17 = 1.2000 n.sub.9 = 1.84666 ν.sub.9 = 23.78 r.sub.18 = 115.7071 d.sub.18 = D.sub.3 (variable) r.sub.19 = 294.2054 d.sub.19 = 4.1000 n.sub.10 = 1.77250 ν.sub.10 = 49.66 r.sub.20 = -41.9683 d.sub.20 = 0.1500 r.sub.21 = 33.0844 d.sub.21 = 7.6000 n.sub.11 = 1.69680 ν.sub.11 = 55.52 r.sub.22 = -30.5175 d.sub.22 = 1.2000 n.sub.12 = 1.84666 ν.sub.12 = 23.78 r.sub.23 = 425.6829 d.sub.23 = D (variable) r.sub.24 = ∞ d.sub.24 = 14.0000 n.sub.13 = 1.51633 ν.sub.13 = 64.15 r.sub.25 = ∞ d.sub.25 = 1.0000 r.sub.26 = ∞ d.sub.26 = 6.0000 n.sub.14 = 1.51633 ν.sub.14 = 64.15 r.sub.27 = ∞ ______________________________________ f 12 29 72 ______________________________________ D.sub.1 1.000 20.896 35.388 D.sub.2 35.388 15.492 1.000 D.sub.3 23.161 20.053 23.468 D.sub.4 3.307 6.415 3.000 ______________________________________ f.sub.T /f.sub.AT = -0.091 ##STR109## ##STR110## ##STR111## ##STR112## n.sub.6 - n.sub.5 = 0.16876 ν.sub.5 - ν.sub.6 = 31.55 n.sub.Ivn - n.sub.IVp = 0.14986 ν.sub.IVp - ν.sub.IVn = 31.74 ##STR113## ##STR114## s.sub.T = 4.280 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses, reference symbol f represents the focal length of the lens system as a whole, reference symbol f BW represents the back focal length in the wide position (position of the shortest focal length), and reference symbol S T represents the advancing amount of the fourth lens group when the lens system is to be focused on an object at the object distance of 1 m in the teleposition (position of the longest focal length).

Claim 12

A vari-focal lens system according to claim 7 having the following numerical data: ______________________________________ f = 12˜72 F/1.2˜F/1.7 ______________________________________ r.sub.1 = 151.7233 d.sub.1 = 1.5000 n.sub.1 = 1.80518 ν.sub.1 = 25.43 r.sub.2 = 59.3632 d.sub.2 = 0.0800 r.sub.3 = 60.4104 d.sub.3 = 7.1000 n.sub.2 = 1.60311 ν.sub.2 = 60.70 r.sub.4 = -195.3134 d.sub.4 = 0.1500 r.sub.5 = 42.4112 d.sub.5 = 4.9000 n.sub.3 = 1.69680 ν.sub.3 = 55.52 r.sub.6 = 126.8250 d.sub.6 = D.sub.1 (variable) r.sub.7 = 74.3595 d.sub.7 = 1.0000 n.sub.4 = 1.83400 ν.sub.4 = 37.16 r.sub.8 = 16.6897 d.sub.8 = 6.9000 r.sub.9 = -21.4114 d.sub.9 = 1.0000 n.sub.5 = 1.67790 ν.sub.5 = 55.33 r.sub.10 = 26.0921 d.sub.10 = 3.9000 n.sub.6 = 1.84666 ν.sub.6 = 23.78 r.sub.11 = -132.3403 d.sub.11 = D.sub.2 (variable) r.sub.12 = 1504.2944 d.sub.12 = 2.5000 n.sub.7 = 1.83400 ν.sub.7 = 37.16 r.sub.13 = -64.5680 d.sub.13 = 0.1500 r.sub.14 = 65.3163 d.sub.14 = 3.0000 n.sub.8 = 1.77250 ν.sub.8 = 49.66 r.sub.15 = -152.0870 d.sub.15 = 1.3000 r.sub.16 = -44.1309 d.sub.16 = 1.2000 n.sub.9 = 1.84666 ν.sub.9 = 23.78 r.sub.17 = -299.7950 d.sub.17 = 1.7000 r.sub.18 = ∞ (stop) d.sub.18 = D.sub.3 (variable) r.sub.19 = 403.8921 d.sub.19 = 3.3000 n.sub.10 = 1.77250 ν.sub.10 = 49.66 r.sub.20 = -47.6736 d.sub.20 = 0.1500 r.sub.21 = 33.1981 d.sub.21 = 6.3000 n.sub.11 = 1.69680 ν.sub.11 = 55.52 r.sub.22 = -31.7379 d.sub.22 = 1.2000 n.sub.12 = 1.84666 ν.sub.12 = 23.78 r.sub.23 = 3541.3418 d.sub.23 = D.sub.4 (variable) r.sub.24 = ∞ d.sub.24 = 14.0000 n.sub.13 = 1.51633 ν.sub.13 = 64.15 r.sub.25 = ∞ d.sub.25 = 1.0000 r.sub.26 = ∞ d.sub.26 = 6.0000 n.sub.14 = 1.51633 ν.sub.14 = 64.15 r.sub.27 = ∞ ______________________________________ f 12 29 72 ______________________________________ D.sub.1 1.000 19.710 32.772 D.sub.2 32.772 14.062 1.000 D.sub.3 27.473 24.446 28.080 D.sub.4 3.607 6.634 3.000 ______________________________________ f.sub.T /f.sub.AT = -0.003 ##STR115## ##STR116## ##STR117## ##STR118## n.sub.6 - n.sub.5 = 0.16876 ν.sub.5 - ν.sub.6 = 31.55 n.sub.IVn - n.sub.IVp = 0.14986 ν.sub.Ivp - ν.sub.IVn = 31.74 ##STR119## ##STR120## s.sub.T = 4.096 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses, reference symbol f represents the focal length of the lens system as a whole, reference symbol f BW represents the back focal length in the wide position (position of the shortest focal length), and reference symbol S T represents the advancing amount of the fourth lens group when the lens system is to be focused on an object at the object distance of 1 m in the teleposition (position of the longest focal length).

Claim 13

A vari-focal lens system according to claim 7 having the following numerical data: ______________________________________ f = 12˜72 F/1.2˜F/1.4 ______________________________________ r.sub.1 = 172.1071 d.sub.1 = 1.5000 n.sub.1 = 1.80518 ν.sub.1 = 25.43 r.sub.2 = 58.7963 d.sub.2 = 10.3000 n.sub.2 = 1.60311 ν.sub.2 = 60.70 r.sub.3 = -182.7541 d.sub.3 = 0.1500 r.sub.4 = 42.7525 d.sub.4 = 6.7000 n.sub.3 = 1.69680 ν.sub.3 = 55.52 r.sub.5 = 116.4808 d.sub.5 = D.sub.1 (variable) r.sub.6 = 79.8595 d.sub.6 = 1.0000 n.sub.4 = 1.83400 ν.sub.4 = 37.16 r.sub.7 = 16.8977 d.sub.7 = 6.5000 r.sub.8 = -21.0692 d.sub.8 = 1.0000 n.sub.5 = 1.67790 ν.sub.5 = 55.33 r.sub.9 = 27.9713 d.sub.9 = 3.8000 n.sub.6 = 1.84666 ν.sub.6 = 23.78 r.sub.10 = -85.4768 d.sub.10 = D.sub.2 (variable) r.sub.11 = 93.5629 d.sub.11 = 3.4000 n.sub.7 = 1.83400 ν.sub.7 = 37.16 r.sub.12 = -58.2455 d.sub.12 = 0.1500 r.sub.13 = 42.6717 d.sub.13 = 2.5000 n.sub.8 = 1.83400 ν.sub.8 = 37.16 r.sub.14 = 263.3215 d.sub.14 = 2.0000 r.sub.15 = -47.0980 d.sub.15 = 1.2000 n.sub.9 = 1.84666 ν.sub.9 = 23.78 r.sub.16 = 89.1812 d.sub.16 = 1.8000 r.sub.17 = ∞(stop) d.sub.17 = D.sub.3 (variable) r.sub.18 = 218.8046 d.sub.18 = 3.8000 n.sub.10 = 1.77250 ν.sub.10 = 49.66 r.sub.19 = -37.4666 d.sub.19 = 0.1500 r.sub.20 = 28.8015 d.sub.20 = 6.6000 n.sub.11 = 1.69680 ν.sub.11 = 55.52 r.sub.21 = -27.3008 d.sub.21 = 1.2000 n.sub.12 = 1.84666 ν.sub.12 = 23.78 r.sub.22 = 144.0063 d.sub.22 = D.sub.4 (variable) r.sub.23 = ∞ d.sub.23 = 14.00000 n.sub.13 = 1.51633 ν.sub.13 = 64.15 r.sub.24 = ∞ d.sub.24 = 1.0000 r.sub.25 = 28 d.sub.25 = 6.0000 n.sub.14 = 1.51633 ν.sub.14 = 64.15 r.sub.26 = ∞ ______________________________________ f 12 29 72 ______________________________________ D.sub.1 1.000 20.175 34.097 D.sub.2 34.097 14.922 1.000 D.sub.3 18.710 16.296 20.330 D.sub.4 4.620 7.034 3.000 ______________________________________ f.sub.T /f.sub.AT = 0.063 ##STR121## ##STR122## ##STR123## ##STR124## n.sub.6 - n.sub.5 = 0.16876 ν.sub.5 - ν.sub.6 = 31.55 n.sub.IVn - n.sub.IVp = 0.14986 ν.sub.IVp - ν.sub.IVn = 31.74 ##STR125## ##STR126## s.sub.T = 4.076 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses, reference symbol f represents the focal length of the lens system as a whole, reference symbol f BW represents the back focal length in the wide position (position of the shortest focal length), and reference symbol S T represents the advancing amount of the fourth lens group when the lens system is to be focused on an object at the object distance of 1 m in the teleposition (position of the longest focal length).

Claim 14

A vari-focal lens system according to claim 7 having the following numerical data: ______________________________________ f = 12˜72 F/1.2˜F/1.4 ______________________________________ r.sub.1 = 146.6769 d.sub.1 = 1.5000 n.sub.1 = 1.80518 ν.sub.1 = 25.43 r.sub.2 = 59.8399 d.sub.2 = 9.9000 n.sub.2 = 1.60311 ν.sub.2 = 60.70 r.sub.3 = -158.8523 d.sub.3 = 0.1500 r.sub.4 = 44.0533 d.sub.4 = 5.2000 n.sub.3 = 1.69680 ν.sub.3 = 55.52 r.sub.5 = 89.2553 d.sub.5 = D.sub.1 (vari-) able) r.sub.6 = 74.9300 d.sub.6 = 1.0000 n.sub.4 = 1.83400 ν.sub.4 = 37.16 r.sub.7 = 18.2563 d.sub.7 = 6.3000 r.sub.8 = -22.3794 d.sub.8 = 1.0000 n.sub.5 = 1.67790 ν.sub.5 = 55.33 r.sub.9 = 28.2140 d.sub. 9 = 4.0000 n.sub.6 = 1.84666 ν.sub.6 = 23.78 r.sub.10 = -121.1135 d.sub.10 = D.sub.2 (vari-) able) r.sub.11 = 151.6487 d.sub.11 = 4.2000 n.sub.7 = 1.83400 ν.sub.7 = 37.16 r.sub.12 = -36.0357 d.sub.12 = 1.0000 r.sub.13 = -25.4309 d.sub.13 = 1.2000 n.sub.8 = 1.84666 ν.sub.8 = 23.78 r.sub.14 = -50.7361 d.sub.14 = 1.6000 r.sub.15 = ∞ (stop) d.sub.15 = D.sub.3 (vari- able) r.sub.16 = 265.2715 d.sub.16 = 3.9000 n.sub.9 = 1.77250 ν.sub.9 = 49.66 r.sub.17 = -43.6405 d.sub.17 = 0.1500 r.sub.18 = 37.6550 d.sub.18 = 7.2000 n.sub.10 = 1.69680 ν.sub.10 = 55.52 r.sub.19 = -29.0405 d.sub.19 = 1.2000 n.sub.11 = 1.84666 ν.sub.11 = 23.78 r.sub.20 = -4474.8116 d.sub.20 = D.sub.4 vari- able) r.sub.21 = ∞ d.sub.21 = 14.0000 n.sub.12 = 1.51633 ν.sub.12 = 64.15 r.sub.22 = ∞ d.sub.22 = 1.0000 r.sub.23 = ∞ d.sub.23 = 6.0000 n.sub.13 = 1.51633 ν.sub.13 = 64.15 r.sub.24 = ∞ ______________________________________ f 12 29 72 ______________________________________ D.sub.1 1.000 21.561 36.591 D.sub.2 36.591 16.030 1.000 D.sub.3 24.419 21.834 25.333 D.sub.4 3.915 6.499 3.000 ______________________________________ f.sub.T /f.sub.AT = -0.012 ##STR127## ##STR128## ##STR129## ##STR130## n.sub.6 - n.sub.5 = 0.16876 ν.sub.5 - ν.sub.6 = 31.55 n.sub.IVn - n.sub.Mp IVp = 0.14986 ν.sub.IVp - ν.sub.IVn = 31.74 ##STR131## ##STR132## s.sub.T = 4.128 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, reference symbols ν 1 , ν 2 , respectively represent Abbe's numbers of respective lenses, reference symbol f represents the focal length of the lens system as a whole, reference symbol f BW represents the back focal length in the wide position (position of the shortest focal length), and reference symbol S T represents the advancing amount of the fourth lens group when the lens system is to be focused on an object at the object distance of 1 m in the teleposition (position of the longest focal length).

Claim 15

A vari-focal lens system according to claim 7 having the following numerical data: ______________________________________ f = 12˜72 F/1.2˜F/1.7 ______________________________________ r.sub.1 = 194.2138 d.sub.1 = 1.5000 n.sub.1 = 1.80518 ν.sub.1 = 25.43 r.sub.2 = 59.5678 d.sub.2 = 0.1000 r.sub.3 = 61.2093 d.sub.3 = 7.3000 n.sub.2 = 1.60311 ν.sub.2 = 60.70 r.sub.4 = -184.1545 d.sub.4 = 0.1500 r.sub.5 = 44.0378 d.sub.5 = 5.000 n.sub.3 = 1.69680 ν.sub.3 = 55.52 r.sub.6 = 151.5499 d.sub.6 = D.sub.1 (variable) r.sub.7 = 74.2547 d.sub.7 = 1.0000 n.sub.4 = 1.77250 ν.sub.4 = 49.66 r.sub.8 = 17.1596 d.sub.8 = 6.9000 r.sub.9 = -22.7122 d.sub.9 = 1.0000 n.sub.5 = 1.67790 ν.sub. 5 = 55.33 r.sub.10 = 26.8421 d.sub.10 = 3.9000 n.sub.6 = 1.84666 ν.sub.6 = 23.78 r.sub.11 = -196.2969 d.sub.11 = D.sub.2 (variable) r.sub.12 = 88.2234 d.sub.12 = 3.8000 n.sub.7 = 1.77250 ν.sub.7 = 49.66 r.sub.13 = -48.8973 d.sub.13 = 1.3000 r.sub.14 = -27.5304 d.sub.14 = 1.2000 n.sub.8 = 1.84666 ν.sub.8 = 23.78 r.sub.15 = -42.9386 d.sub.15 = 1.5000 r.sub.16 = ∞ (stop) d.sub.16 = D.sub.3 (variable) r.sub.17 = 454.7542 d.sub.17 = 3.7000 n.sub.9 = 1.69680 ν.sub.9 = 55.52 r.sub.18 = -42.3595 d.sub.18 = 0.1500 r.sub.19 = 31.6599 d.sub.19 = 6.6000 n.sub.10 = 1.69680 ν.sub.10 = 55.52 r.sub.20 = -31.5807 d.sub.20 = 1.2000 n.sub.11 = 1.84666 ν.sub.11 = 23.78 r.sub.21 = 401.9241 d.sub.21 = D.sub.4 (variable) r.sub.22 = ∞ d.sub.22 = 14.0000 n.sub.12 = 1.51633 ν.sub.12 = 64.15 r.sub.23 = ∞ d.sub.23 = 1.0000 r.sub.24 = ∞ d.sub.24 = 6.0000 n.sub.13 = 1.51633 ν.sub.13 = 64.15 r.sub.25 = ∞ ______________________________________ f 12 29 72 ______________________________________ D.sub.1 1.000 20.518 34.647 D.sub.2 34.647 15.129 1.000 D.sub.3 25.673 22.821 26.471 D.sub.4 3.797 6.650 3.000 ______________________________________ f.sub.T /f.sub.AT = 0.000 ##STR133## ##STR134## ##STR135## ##STR136## n.sub.6 -n.sub.5 = 0.16876 ν.sub.5 - ν.sub.6 = 31.55 n.sub.IVn - n.sub.IVp = 0.14986 ν.sub.IVp - ν.sub.IVn = 31.74 ##STR137## ##STR138## s.sub.T = 4.147 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thickness of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses, reference symbol f represents the focal length of the lens system as a whole, reference symbol f BW represents the back focal length in the wide position (position of the shortest focal length), and reference symbol S T represents the advancing amount of the fourth lens group when the lens system is to be focused on an object at the object distance of 1 m in the teleposition (position of the longest focal length).

Claim 16

A vari-focal lens system according to claim 7 having the following numerical data: ______________________________________ f = 12˜72 F/1.2˜F/1.4 ______________________________________ r.sub.1 = 164.7468 d.sub.1 = 1.5000 n.sub.1 = 1.80518 ν.sub.1 = 25.43 r.sub.2 = 65.8749 d.sub.2 = 9.9000 n.sub.2 = 1.60311 ν.sub.2 = 60.70 r.sub.3 = -184.0637 d.sub.3 = 0.1500 r.sub.4 = 48.6323 d.sub.4 = 5.2000 n.sub.3 = 1.69680 ν.sub.3 = 55.52 r.sub.5 = 101.2168 d.sub.5 = D.sub.1 (variable) r.sub.6 = 57.6084 d.sub.6 = 1.0000 n.sub.4 = 1.77250 ν.sub.4 = 49.66 r.sub.7 = 18.9625 d.sub.7 = 7.3000 r.sub.8 = -24.9630 d.sub.8 = 1.0000 n.sub.5 = 1.67790 ν.sub.5 = 55.33 r.sub.9 = 28.1850 d.sub. 9 = 4.000 n.sub.6 = 1.84666 ν.sub.6 = 23.78 r.sub.10 = -260.2746 d.sub.10 = D.sub.2 (variable) r.sub.11 = 1399.3348 d.sub.11 = 4.2000 n.sub.7 = 1.77250 ν.sub.7 = 49.66 r.sub.12 = -29.8010 d.sub.12 = 1.1000 r.sub.13 = -22.4006 d.sub.13 = 1.2000 n.sub.8 = 1.85666 ν.sub.8 = 23.78 r.sub.14 = -39.0155 d.sub.14 = 1.5000 r.sub.15 = ∞ (stop) d.sub.15 = D.sub.3 (variable) r.sub.16 = 355.6424 d.sub.16 = 3.8000 n.sub.9 = 1.77250 ν.sub.9 = 49.66 r.sub.17 = -43.8189 d.sub.17 = 0.1500 r.sub.18 = 41.1951 d.sub.18 = 6.8000 n.sub.10 = 1.69680 ν.sub.10 = 55.52 r.sub.19 = -29.4069 d.sub.19 = 1.2000 n.sub.11 = 1.84666 ν.sub.11 = 23.78 r.sub.20 = -238.5031 d.sub.20 = D.sub.4 (variable) r.sub.21 = ∞ d.sub.21 = 14.0000 n.sub.12 = 1.51633 ν.sub.12 = 64.15 r.sub.22 = ∞ d.sub.22 = 1.0000 r.sub.23 = ∞ d.sub.23 = 6.000 n.sub.13 = 1.51633 ν.sub.13 = 64.15 r.sub.24 = ∞ ______________________________________ f 12 29 72 ______________________________________ D.sub.1 1.000 23.870 40.808 D.sub.2 40.808 17.938 1.000 D.sub.3 22.376 20.186 23.556 D.sub.4 4.181 6.371 3.000 ______________________________________ f.sub.T /f.sub.AT = -0.001 ##STR139## ##STR140## ##STR141## ##STR142## n.sub.6 - n.sub.5 = 0.16876 ν.sub.5 - ν.sub.6 = 31.55 n.sub.IVn - n.sub.IVp = 0.14986 ν.sub.IVp - ν.sub.IVn = 31.74 ##STR143## ##STR144## s.sub.T = 4.080 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, reference symbols ν 1 ,ν 2 , . . . respectively epresent Abbe's numbers of respective lenses, reference symbol f respresents the focal length of the lens system as a whole, reference symbol f BW represents the back focal length in the wide position (position of the shortest focal length), and reference symbol S T represents the advancing amount of the fourth lens group when the lens system is to be focused on an object at the object distance 1 m in the teleposition (position of the longest focal length).