Abstract:
A zoom lens system comprising a first, second, third and fourth lens groups, the first lens group being a focusing lens group and having positive refractive power, the second lens group being a variator and having negative refractive power, the third lens group being a compensator and having positive refractive power, the first, second and third lens groups constituting a varifocal subsystem, the fourth lens group being a relay lens, which comprises a first lens component comprising a positive lens and a negative lens and having positive refractive power as a whole, a second lens component comprising a positive lens, a third lens component comprising a negative lens, and a fourth lens component comprising a positive lens, the zoom lens system being small in size, light in weight and arranged that aberrations are corrected favourably.

Description:
BACKGROUND OF THE INVENTION 
     (a) Field of the Invention 
     The present invention relates to a zoom lens system and, more particularly, to a zoom lens system comprising four lens group and having comparatively simple lens configuration. 
     (b) Description of the Prior Art 
     There are known zoom lens systems comprising four lens groups, i.e., a first, second, third and fourth lens groups, in which the first, second and third lens groups constitute a varifocal subsystem, the first lens group being a focusing lens group and having positive refractive power, the second lens group being a variator and having negative refractive power, the third lens group being a compensator and having positive refractive power, the fourth lens group being a relay lens arranged in rear of the varifocal subsystem. Among known zoom lens systems comprising four lens groups as described in the above, there are such known zoom lens systems in which the fourth lens group, i.e., the relay lens, is arranged to have simplified lens configuration in order to simplify the lens configuration of the lens system as a whole. Japanese published unexamined patent application No. 126819/81 discloses an example of known zoom lens systems in which the relay lens is arranged to have simplified lens configuration as described in the above. The relay lens of the known zoom lens system disclosed in the abovementioned Japanese published unexamined patent application comprises a lens component, which comprises a positive lens and negative lens arranged in the order from the object side (varifocal subsystem side) and has positive refractive power as a whole, a biconvex lens arranged by leaving a comparatively large airspace in respect to said lens component, and a negative meniscus lens arranged to be convex toward the image side. The relay lens of said known zoom lens system has a disadvantage that positive distortion caused by the negative meniscus lens, which is arranged on the image side, cannot be satisfactorily corrected on the long focal length side. 
     Another example of the above-mentioned known zoom lens systems is disclosed in Japanese published unexamined patent application No. 131852/78. The relay lens of the known zoom lens system disclosed in the above-mentioned Japanese published unexamined patent application comprises a lens component, which comprises a positive lens and negative lens and has positive refractive power as a whole, a negative meniscus lens arranged by leaving a comparatively large airspace in respect to said lens component and arranged to be convex toward the image side, and a positive lens. Said zoom lens system has a disadvantage that coma caused by the negative meniscus lens is large because the converging action in the position in rear of the relay lens is insufficient and, therefore, it is difficult to obtain favourable contrast of image. 
     SUMMARY OF THE INVENTION 
     It is, therefore a primary object of the present invention to provide a compact zoom lens system comprising a first lens group arranged as a focusing lens group and having positive refractive power, a second lens group arranged as a variator and having negative refractive power, a third lens group arranged as a compensator and having positive refractive power, said first, second and third lens groups constituting a varifocal subsystem, and a fourth lens group arranged as a relay lens and located in rear of said varifocal subsystem, said relay lens having comparatively simple lens configuration, said zoom lens system being small in size and light in weight and, at the same time, being arranged that aberrations, especially coma flare, are corrected favourably. 
     The zoom lens system according to the present invention comprises, as shown in FIG. 1 or FIG. 2, the first lens group I having positive refractive power, the second lens group II having negative refractive power, the third lens group III having positive refractive power, and the fourth lens group IV, the first, second and third lens groups constituting a varifocal subsystem, and the fourth lens group constituting a relay lens. The fourth lens group IV which is the relay lens comprises, in the order from the object side, a first lens component IV a  comprising a positive lens and a negative lens and having positive refractive power as a whole, a second lens component IV b  comprising a positive lens and arranged by leaving a certain airspace in respect to the first lens component IV a , a third lens component IV c  comprising a negative lens, and a fourth lens component IV d  comprising a positive lens. Here, by arranging the second lens component IV b  on the object side of and with a certain airspace in respect to the third lens component IV c , heights of rays incident on the third lens component IV c  are made small so that coma is prevented from occurring. Besides, by arranging the fourth lens component IV d  on the image side of and at a certain distance from the third lens component IV c , distortion especially positive distortion on the long focal length side is prevented from occurring. 
     The zoom lens system according to the present invention is arranged that the fourth lens group, i.e., the relay lens, is simplified by arranging that the fourth lens group has the lens configuration as described in the above, and aberrations of the lens system as a whole is thereby corrected favourably. 
     When, however, the fourth lens group IV is arranged to fulfill the conditions (1) and (2) shown below, it is possible to correct aberrations more favourably: 
     
         0.3&lt;f.sub.4a /f.sub.4 &lt;3.0                                 (1) 
    
     
         0.03&lt;f.sub.4c /f.sub.4bcd &lt;0.3                             (2) 
    
     where, reference symbol f 4  represents the focal length of the fourth lens groups IV, reference symbol f 4a  represents the focal length of the first lens component IV a  in the fourth lens group, reference symbol f 4c  represents the focal length of the third lens component IV c  in the fourth lens group, and reference symbol f 4bcd  represents the total focal length of the second lens component IV b , the third lens component IV c  and the fourth lens component IV d  which constitute the fourth lens group. 
     When f 4a  /f 4  become smaller than the lower limit of the condition (1), it is possible to make the telephoto ratio small. However, aberrations to be caused become large and it is difficult to correct them, especially spherical aberration, favourably. When f 4a  /f a  becomes larger than the upper limit of the condition (1), the fourth lens group IV becomes large and it is impossible to make the zoom lens system as a whole compact. 
     When f 4c  /f 4bcd  becomes smaller than the lower limit of the condition (2), refractive power of the third lens component IV c  in the fourth lens group becomes strong, and it is difficult to correct coma favourably. When f 4c  /f 4bdc  becomes larger than the upper limit of the condition (2), it is difficult to correct curvature of field favourably. 
     For correction of curvature of field, the shape of the third lens component IV c  in the fourth lens group has large influence. Therefore, to correct curvature of field more favourably, it is preferable to fulfill the condition (3) shown below in additional to the conditions (1) and (2): ##EQU1## where, reference symbols r 4c1  and r 4c2  respectively represent radii of curvature of the surface on the object side and surface on the image side of the third lens component IV c  in the fourth lens group. 
     When the value defined by the condition (3) becomes smaller than the lower limit thereof, curvature of field becomes unfavourable on the short focal length side. When the value defined by the condition (3) becomes larger than the upper limits thereof, negative curvature of field occurs on the long focal length side. In either case, it is difficult to correct curvature of field favourably. 
     To correct distortion more favourably, it is preferable to fulfill the condition (4) shown below: 
     
         0.01&lt;D/f.sub.W &lt;0.3                                        (4) 
    
     where, reference symbol D represents the airspace between the third lens component IV c  and the fourth lens component IV d  in the fourth lens group, and reference symbol f W  represents the focal length of the zoom lens system as a whole on the short focal length side. 
     When D/f W  becomes smaller than the lower limit of the condition (4), it is difficult to correct positive distortion. When D/f W  becomes larger than the upper limit of the condition (4), the diameter of the fourth lens component IV d  becomes larger, and it is impossible to obtain a compact zoom lens system which is one of objects of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a sectional view of Embodiments 1 and 2 of the zoom lens system according to the present invention; 
     FIG. 2 shows a sectional view of Embodiments 3 through 6 of the zoom lens system according to the present invention; 
     FIGS. 3A, 3B and 3C respectively show graphs illustrating aberration curves of Embodiment 1 of the present invention; 
     FIGS. 4A, 4B and 4C respectively show graphs illustrating aberration curves of Embodiment 2 of the present invention; 
     FIGS. 5A, 5B and 5C respectively show graphs illustrating aberration curves of Embodiment 3 of the present invention; 
     FIGS. 6A, 6B and 6C respectively show graphs illustrating aberration curves of Embodiment 4 of the present invention; 
     FIGS. 7A, 7B and 7C respectively show graphs illustrating aberration curves of Embodiment 5 of the present invention; and 
     FIGS. 8A, 8B and 8C respectively show graphs illustrating aberration curves of Embodiment 6 of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Now, preferred embodiments of the zoom lens system according to the present invention described so far are shown below. 
     
         ______________________________________Embodiment 1______________________________________r.sub.1 =  144.9108  d.sub.1 = 2.8000                 n.sub.1 = 1.80518                             ν.sub.1 = 25.43r.sub.2 =  68.2361  d.sub.2 = 6.6000                 n.sub.2 = 1.61272                             ν.sub.2 = 58.75r.sub.3 =  -5481.9920  d.sub.3 = 0.2000r.sub.4 =  89.3518  d.sub.4 = 4.7000                 n.sub.3 = 1.61272                             ν.sub.3 = 58.75r.sub.5 =  11352.4996  d.sub.5 = D.sub.1 (variable)r.sub.6 =  648.1213  d.sub.6 = 1.5000                 n.sub.4 = 1.713000                             ν.sub.4 = 53.84r.sub.7 =  40.1579  d.sub.7 = 4.2000r.sub.8 =  -45.2768  d.sub.8 = 1.5000                 n.sub.5 = 1.71300                             ν.sub.5 = 53.84r.sub.9 =  45.7879  d.sub.9 = 3.4000                 n.sub.6 = 1.84666                             ν.sub.6 = 23.88r.sub.10 =  -6737.4941  d.sub.10 = D.sub.2 (variable)r.sub.11 =  112.8992  d.sub.11 = 5.8000                 n.sub.7 = 1.51633                             ν.sub.7 = 64.15r.sub.12 =  -32.3291  d.sub.12 = 1.5000                 n.sub.8 = 1.75520                             ν.sub.8 = 27.51r.sub.13 =  -57.1632  d.sub.13 = D.sub.3 (variable)r.sub.14 =  ∞ (stop)  d.sub.14 = 1.0000r.sub.15 =  24.5802  d.sub.15 = 5.6126                 n.sub.9 = 1.50048                             ν.sub.9 = 68.70r.sub.16 =  185.4000  d.sub.16 = 2.2118r.sub.17 =  -118.4028  d.sub.17 = 2.0078                 n.sub.10 = 1.80610                             ν.sub.10 = 35.22r.sub.18 =  -1060.6686  d.sub.18 = 19.216r.sub. 19 =  148.6683  d.sub.19 = 3.6148                 n.sub.11 = 1.51742                             ν.sub.11 = 52.41r.sub.20 =  -38.3100  d.sub.20 = 5.2560r.sub.21 =  -18.8457  d.sub.21 = 3.0815                 n.sub.12 = 1.77250                             ν.sub.12 = 49.66r.sub.22 =  -146.5229  d.sub.22 = 13.4117r.sub.23 =  90.1033  d.sub.23 = 4.1132                 n.sub.13 = 1.51112                             ν.sub.13 = 60.48r.sub.24 =  -194.4020f = 70.019˜136.124˜203.770f.sub.4a = 79.944,  f.sub.4 = 112.031f.sub.4a /f.sub.4 = 0.7136,               f.sub.4c = -28.294f.sub.4bcd = -176.874,               f.sub.4c /f.sub.4bcd = 0.160 ##STR1##f     70.019         136.124 203.770______________________________________D.sub.1  3.253          32.663 43.108D.sub.2 34.766          17.756 0.186D.sub.3 16.055          3.655  10.780______________________________________ 
    
     
         ______________________________________Embodiment 2______________________________________r.sub.1 =  142.9968  d.sub.1 = 2.8000                 n.sub.1 = 1.80518                             ν.sub.1 = 25.43r.sub.2 =  67.9794  d.sub.2 = 6.6000                 n.sub.2 = 1.61272                             ν.sub.2 = 58.75r.sub.3 =  -6530.3523  d.sub.3 = 0.2000r.sub.4 =  94.0605  d.sub.4 = 4.7000                 n.sub.3 = 1.61272                             ν.sub.3 = 58.75r.sub.5 =  12155.0599  d.sub.5 = D.sub.1 (variable)r.sub.6 =  454.0262  d.sub.6 = 1.5000                 n.sub.4 = 1.71300                             ν.sub.4 = 53.84r.sub.7 =  40.3500  d.sub.7 = 4.2000r.sub.8 =  -45.1046  d.sub.8 = 1.5000                 n.sub.5 = 1.71300                             ν.sub.5 = 53.84r.sub.9 =  46.0978  d.sub.9 =  3.4000                 n.sub.6 = 1.84666                             ν.sub.6 = 23.88r.sub.10 =  -2104.2705  d.sub.10 = D.sub.2 (variable)r.sub.11 =  111.8042  d.sub.11 = 5.8000                 n.sub.7 = 1.51633                             ν.sub.7 = 64.15r.sub.12 =  -32.3806  d.sub.12 = 1.5000                 n.sub.8 = 1.75520                             ν.sub.8 = 27.51r.sub.13 =  -56.6383  d.sub.13 = D.sub.3 (variable)r.sub.14 =  ∞ (stop)  d.sub.14 = 1.0000r.sub.15 =  29.2023  d.sub.15 = 5.5711                 n.sub.9 = 1.50048                             ν.sub.9 = 68.86r.sub.16 =  -12111.2296  d.sub.16 = 2.1862r.sub.17 =  -102.6169  d.sub.17 = 1.9800                 n.sub.10 = 1.80610                             ν.sub.10 = 38.27r.sub.18 =  771.0715  d.sub.18 = 19.2054r.sub.19 =  138.6019  d.sub.19 = 3.5882                 n.sub.11 = 1.51742                             ν.sub.11 = 52.41r.sub.20 =  -64.0731  d.sub.20 = 14.8972r.sub.21 =  -20.3040  d.sub.21 = 1.6732                 n.sub.12 = 1.77250                             ν.sub.12 = 49.66r.sub.22 =  -91.1372  d.sub.22 = 5.2036r.sub.23 =  120.8274  d.sub.23 = 4.0093                 n.sub.13 = 1.51112                             ν.sub.13 = 60.48r.sub.24 =  -90.7416f = 70.019˜136.124˜203.77f.sub.4a = 108.832, f.sub.4 = 115.886f.sub.4a /f.sub.4 = 0.9391,               f.sub.4c = -34.169f.sub.4bdc = -306.646,               f.sub.4c /f.sub.4bdc = 0.1114 ##STR2##f     70.019         136.124 203.77______________________________________D.sub.1  1.141          32.722 43.856D.sub.2 34.231          17.360 0.058D.sub.3 18.913          4.203  10.371______________________________________ 
    
     
         ______________________________________Embodiment 3______________________________________r.sub.1 =  127.9700  d.sub.1 = 2.6000                 n.sub.1 = 1.78472                             ν.sub.1 = 25.68r.sub.2 =  58.4160  d.sub.2 = 6.8000                 n.sub.2 = 1.62280                             ν.sub.2 = 57.06r.sub.3 =  ∞  d.sub.3 = 0.1500r.sub.4 =  86.2160  d.sub.4 = 4.6000                 n.sub.3 = 1.62299                             ν.sub.3 = 58.14r.sub.5 =  ∞  d.sub.5 = D.sub.1 (variable)r.sub.6 =  -212.4540  d.sub.6 = 1.7000                 n.sub.4 = 1.74320                             ν.sub.4 = 49.31r.sub.7 =  24.1010  d.sub.7 = 3.4000                 n.sub.5 = 1.78472                             ν.sub.5 = 25.68r.sub.8 =  35.6490  d.sub.8 = 4.0000r.sub.9 =  -53.1720  d.sub.9 =  1.6000                 n.sub.6 = 1.77250                             ν.sub.6 = 49.66r.sub.10 =  95.6530  d.sub.10 = 0.6400r.sub.11 =  68.3100  d.sub.11 = 3.2000                 n.sub.7 = 1.78472                             ν.sub.7 = 25.68r.sub.12 =  -233.9170  d.sub.12 = D.sub.2 (variable)r.sub.13 =  117.3390  d.sub.13 = 5.8000                 n.sub.8 = 1.51112                             ν.sub.8 = 60.48r.sub.14 =  -30.7220  d.sub.14 = 2.0000                 n.sub.9 = 1.78472                             ν.sub.9 = 25.68r.sub.15 =  -52.8370  d.sub.15 = D.sub.3 (variable)r.sub.16 =  ∞ (stop)  d.sub.16 = 1.7000r.sub.17 =  26.1193  d.sub.17 = 5.6000                 n.sub.10 = 1.51112                             ν.sub.10 = 60.48r.sub.18 =  470.2221  d.sub.18 = 1.9600r.sub. 19 =  -125.9016  d.sub.19 = 1.6000                 n.sub.11 = 1.83400                             ν.sub.11 = 37.16r.sub.20 =  154.9461  d.sub.20 = 19.9900r.sub.21 =  63.8585  d.sub.21 = 3.5300                 n.sub.12 = 1.51742                             ν.sub.12 = 52.41r.sub.22 =  -54.7038  d.sub.22 = 10.9200r.sub.23 =  -20.1245  d.sub.23 = 2.0600                 n.sub.13 = 1.77250                             ν.sub.13 = 49.66r.sub.24 =  -81.2528  d.sub.24 = 9.3286r.sub.25 =  61.1383  d.sub.25 = 4.0000                 n.sub.14 = 1.51112                             ν.sub.14 = 60.48r.sub.26 =  118.9530f = 66.922˜113.933˜194.051f.sub.4a = 126.251, f.sub.4 = 117.668f.sub.4a /f.sub.4 = 1.0729,               f.sub.4c = -35.144f.sub.4bcd = -547.444,               f.sub.4c /f.sub.4bcd = 0.0642 ##STR3##f     66.922         113.933 194.051______________________________________D.sub.1  2.191          24.467 37.535D.sub.2 36.355          23.260 0.975D.sub.3 10.982          1.800  11.017______________________________________ 
    
     
         ______________________________________Embodiment 4______________________________________r.sub.1 =  125.0059  d.sub.1 = 2.6000                 n.sub.1 = 1.78472                             ν.sub.1 = 25.68r.sub.2 =  58.4160  d.sub.2 = 6.8000                 n.sub.2 = 1.62299                             ν.sub.2 = 58.14r.sub.3 =  ∞  d.sub.3 = 0.1500r.sub.4 =  88.0510  d.sub.4 = 4.6000                 n.sub.3 = 1.62299                             ν.sub.3 = 58.14r.sub.5 =  ∞  d.sub.5 = D.sub.1 (variable)r.sub.6 =  -212.4540  d.sub.6 = 1.7000                 n.sub.4 = 1.74320                             ν.sub.4 = 49.31r.sub.7 =  24.1010  d.sub.7 = 3.4000                 n.sub.5 = 1.78472                             ν.sub.5 = 25.68r.sub.8 =  35.6490  d.sub.8 = 4.0000r.sub.9 =  -53.1720  d.sub.9  = 1.6000                 n.sub.6 = 1.77250                             ν.sub.6 = 49.66r.sub.10 =  95.6530  d.sub.10 = 0.6400r.sub.11 =  68.3100  d.sub.11 = 3.2000                 n.sub.7 = 1.78472                             ν.sub.7 = 25.68r.sub.12 =  -233.9318  d.sub.12 = D.sub.2 (variable)r.sub.13 =  117.3390  d.sub.13 = 5.8000                 n.sub.8 = 1.51112                             ν.sub.8 = 60.48r.sub.14 =  -30.7220  d.sub.14 = 2.0000                 n.sub.9 = 1.78472                             ν.sub.9 = 25.68r.sub.15 =  -52.8370  d.sub.15 = D.sub.3 (variable)r.sub.16 =  ∞ (stop)  d.sub.16 = 1.7000r.sub.17 =  26.4827  d.sub.17 = 5.6000                 n.sub.10  1.50048                             ν.sub.10 = 65.99r.sub.18 =  ∞  d.sub.18 = 2.2000r.sub.19 =  -128.0029  d.sub.19 = 2.0000                 n.sub.11 = 1.80610                             ν.sub.11 = 40.95r.sub.20 =  199.5243  d.sub.20 = 19.9834r.sub.21 =  100.7291  d.sub.21 = 3.6000                 n.sub.12 = 1.51742                             ν.sub.12 = 52.41r.sub.22 =  -63.4132  d.sub.22 = 10.9209r.sub.23 =  -19.6359  d.sub.23 = 1.8000                 n.sub.13 = 1.77250                             ν.sub.13 = 49.66r.sub.24 =  -81.8964  d.sub.24 = 8.5646r.sub.25 =  113.1923  d.sub.25 = 4.0000                 n.sub.14 = 1.51112                             ν.sub.14 = 60.48r.sub.26 =  -132.6134f = 66.923˜113.941˜194.149f.sub.4a = 102.258, f.sub.4 = 117.565f.sub.4a /f.sub.4 = 0.8698,               f.sub.4c = -33.862f.sub.4bcd = -271.117,               f.sub.4c /f.sub. 4bcd = 0.1249 ##STR4##f     66.923         113.941 194.149______________________________________D.sub.1  2.128          24.404 37.471D.sub.2 36.355          23.260 0.976D.sub.3 10.982          1.800  11.017______________________________________ 
    
     
         ______________________________________Embodiment 5______________________________________r.sub.1 =  127.9700  d.sub.1 = 2.6000                 n.sub.1 = 1.78472                             ν.sub.1 = 25.68r.sub.2 =  58.4160  d.sub.2 = 6.8000                 n.sub.2 = 1.62280                             ν.sub.2 = 57.06r.sub.3 =  ∞  d.sub.3 = 0.1500r.sub.4 =  86.2160  d.sub.4 = 4.6000                 n.sub.3  1.62299                             ν.sub.3 = 58.14r.sub.5 =  ∞  d.sub.5 = D.sub.1 (variable)r.sub.6 =  -212.4540  d.sub.6 = 1.7000                 n.sub.4 = 1.74320                             ν.sub.4 = 49.31r.sub.7 =  24.1010  d.sub.7 = 3.4000                 n.sub.5 = 1.78472                             ν.sub.5 = 25.68r.sub.8 =  35.6490  d.sub.8 = 4.0000r.sub.9 =  -53.1720  d.sub.9 =  1.6000                 n.sub.6 = 1.77250                             ν.sub.6 = 49.66r.sub.10 =  95.6530  d.sub.10 = 0.6400r.sub.11 =  68.3100  d.sub.11 = 3.2000                 n.sub.7 = 1.78472                             ν.sub.7 = 25.68r.sub.12 =  -233.9170  d.sub.12 = D.sub.2 (variable)r.sub.13 =  117.3390  d.sub.13 = 5.8000                 n.sub.8 = 1.51112                             ν.sub.8 = 60.48r.sub.14 =  -30.7220  d.sub.14 = 2.0000                 n.sub.9 = 1.78472                             ν.sub.9 = 25.68r.sub.15 =  -52.8370  d.sub.15 = D.sub.3 (variable)r.sub.16 =  ∞(stop)  d.sub.16 = 1.8494r.sub.17 =  26.7721  d.sub.17 = 5.6000                 n.sub.10 = 1.50048                             ν.sub.10 = 65.99r.sub.18 =  5065.7532  d.sub.18 = 2.2000r.sub.19 =  -117.1642  d.sub.19 = 2.0000                 n.sub.11 = 1.80610                             ν.sub.11 = 40.95r.sub.20 =  190.9331  d.sub.20 = 19.9824r.sub.21 =  72.4887  d.sub.21 = 3.6000                 n.sub.12 = 1.51742                             ν.sub.12 = 52.41r.sub.22 =  -57.4998  d.sub.22 = 10.9196r.sub.23 =  -20.2962  d.sub.23 = 1.8000                 n.sub.13 = 1.77250                             ν.sub.13 = 49.66r.sub.24 =  -108.8218  d.sub.24 = 8.4955r.sub.25 =  89.8728  d.sub.25 = 4.0000                 n.sub.14 = 1.51112                             ν.sub.14 = 60.48r.sub.26 =  -447.2719f = 66.923˜113.901˜194.091f.sub.4a = 113.799, f.sub.4 = 117.616f.sub.4a /f.sub.4 = 0.9675,               f.sub.c = -32.586f.sub.4bcd = -358.677,               f.sub.4c /f.sub.4bcd  = 0.0909 ##STR5##f     66.923         113.901 194.091______________________________________D.sub.1  2.208          24.448 37.516D.sub.2 36.355          23.260 0.975D.sub.3 10.982          1.800  11.017______________________________________ 
    
     
         ______________________________________Embodiment 6______________________________________r.sub.1 =  127.9700  d.sub.1 = 2.6000                 n.sub.1 = 1.78472                             ν.sub.1 = 25.68r.sub.2 =  58.4160  d.sub.2 = 6.800                 n.sub.2 = 1.62280                             ν.sub.2 = 57.06r.sub.3 =  ∞  d.sub.3 = 0.1500r.sub.4 =  86.2160  d.sub.4 = 4.6000                 n.sub.3 = 1.62299                             ν.sub.3 = 58.14r.sub.5 =  ∞  d.sub.5 = D.sub.1 (variable)r.sub.6 =  -212.4540  d.sub.6 = 1.7000                 n.sub.4 = 1.74320                             ν.sub.4 = 49.31r.sub.7 =  24.1010  d.sub.7 = 3.4000                 n.sub.5 = 1.78472                             ν.sub.5 = 25.68r.sub.8 =  35.6490  d.sub.8 = 4.0000r.sub.9 =  -53.1720  d.sub.9 = 1.6000                 n.sub.6 = 1.77250                             ν.sub.6 = 49.66r.sub.10 =  95.6530  d.sub.10 = 0.6400r.sub.11 =  68.3100  d.sub.11 = 3.2000                 n.sub.7 = 1.78472                             ν.sub.7 = 25.68r.sub.12 =  -233.9170  d.sub.12 = D.sub.2 (variable)r.sub.13 =  117.3390  d.sub.13 = 5.8000                 n.sub.8 = 1.51112                             ν.sub.8 = 60.48r.sub.14 =  -30.7220  d.sub.14 = 2.0000                 n.sub.9 = 1.78472                             ν.sub.9 = 25.68r.sub.15 =  -52.8370  d.sub.15 = D.sub.3 (variable)r.sub.16 =  ∞ (stop)  d.sub.16 = 1.7000r.sub.17 =  26.7709  d.sub.17 = 5.6000                 n.sub.10 = 1.51112                             ν.sub.10 = 60.48r.sub.18 =  ∞  d.sub.18 = 2.2000r.sub.19 =  -118.1771  d.sub.19 = 2.0000                 n.sub.11 = 1.83400                             ν.sub.11 = 37.16r.sub.20 =  178.9330  d.sub.20 = 19.9892r.sub.21 =  71.6571  d.sub.21 = 3.6000                 n.sub.12 = 1.51742                             ν.sub.12 = 52.41r.sub.22 =  -56.5196  d.sub.22 = 10.9200r.sub.23 =  -20.1562  d.sub.23 = 1.8000                 n.sub.13 = 1.77250                             v.sub.13 = 49.66r.sub.24 =  -129.7039  d.sub.24 = 8.4593r.sub.25 =  84.9757  d.sub.25 = 4.0000                 n.sub.14  1.51112                             v.sub.14 = 60.48r.sub.26 =  -266.5989f = 66.923˜113.901˜194.090f.sub.4a = 114.146, f.sub.4 = 117.603f.sub.4a /f.sub.4 = 0.9706,               f.sub.4c = -31.116f.sub.4bcd = -386.461,               f.sub.4c /f.sub. 4bcd = 0.0805 ##STR6##f     66.923         113.901 194.090______________________________________D.sub.1  2.208          24.448 37.516D.sub.2 36.355          23.260 0.975D.sub.3 10.982          1.800  11.017______________________________________ 
    
     In embodiments shown in the above, 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&#39;s numbers of respective lenses, and reference symbol f represents the focal length of the lens system as a whole. 
     Out of respective embodiments shown in the above, Embodiments 1 and 2 respectively have the lens configuration shown in FIG. 1. That is, in the zoom lens systems according to Embodiments 1 and 2, the first lens groups I comprises a positive cemented doublet and a positive lens, the second lens group II comprises a negative lens and a negative cemented doublet, and the third lens group III comprises a positive cemented doublet. The fourth lens group IV comprises, as described before, the first lens component IV a  comprising a positive lens and a negative lens and having positive refractive power as a whole, the second lens component IV b  comprising a positive lens, the third lens component IV c  comprising a negative lens, and the fourth lens component IV d  comprising a positive lens. In these embodiments, the focal length is varied by varying the airspaces d 5  =D 1 , d 10  =D 2  and d 13  =D 3  as shown in the numerical data of said embodiments. 
     Embodiments 3 through 6 respectively have the lens configuration shown in FIG. 2. That is, in these embodiments, the second lens group comprises a negative cemented doublet, a negative lens and a positive lens. The lens configuration of the other lens groups is substantially the same as that of the lens system shown in FIG. 1. In these embodiments, the focal length is varied by varying the airspaces d 5  =D 1 , d 12  =D 2  and d 15  =D 3  as shown in the numerical data of said embodiments. 
     Out of graphs illustrating aberration curves of respective embodiments, FIGS. 3A, 4A, 5A, 6A, 7A and 8A respectively show the aberration curves on the short focal length side, FIGS. 3B, 4B, 5B, 6B, 7B and 8B respectively show the aberration curves at the intermediate focal length, and FIGS. 3C, 4C, 5C, 6C, 7C and 8C respectively show the aberration curves on the long focal length side.