Abstract:
A zoom lens having a plurality of lens groups, includes: a first lens group including a plurality of lenses, provided closest to an object side, wherein a first lens made of a plastic lens having a positive refracting power is located closest to the object side among the plurality of lenses in the first lens group.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a zoom lens which has a high aperture ratio and a high variable magnification ratio, and which is a low cost and appropriate for sill cameras or video cameras. 
     Conventionally, a means in which a plastic lens is used for a high variable magnification ratio zoom lens, and thereby its cost is reduced, is widely known and many patent applications are made. A zoom lens in which 3 plastic lenses are used in 12 lens elements for cost reduction and which attains a high variable magnification ratio of 10-12 times, is disclosed in Japanese Patent Publication Open to Public Inspection No. 264902/1993. In Japanese Patent Publication Open to Public Inspection No. 106046/1996, a zoom lens is disclosed, in which further cost reduction is promoted, and even when 4 plastic lenses are used in 10 lens elements, the high variable magnification ratio of 12 times is attained. However, in any example, no plastic lens is used in the first lens group, and room to promote further cost reduction is left. 
     Incidentally, when a plastic lens is used for the first lens, there is a problem of damage caused by an impulse from the outside. As one means to solve the problem, there is a method to equip a protective glass on the object side of the first lens. However, the protective glass contributes to increase a cost, and therefore, it prevents the object of cost reduction. As another means, there is a means to conduct special coating (hereinafter, called hard coat) on the plastic lens surface to protect the surface. However, the hard coat to protect the plastic lens surface can be coated on only material having very good moisture resistance. 
     There are few types of plastic which can be used as optical materials, and types of high dispersion material are specifically fewer. Therefore, there is almost no room to select the material having very good moisture resistance, and the present status is that it is very difficult to conduct the hard coat on the high dispersion plastic lens. Comparing to this, recently, types of low dispersion plastic are relatively, gradually increasing, and material having highly excellent moisture resistance such as polyolefin, or the like, is put into practical use, thereby, the hard coat can be conducted on the low dispersion plastic lens. 
     Examples in which plastic lens is used in the first lens group, are disclosed in Japanese Patent Publication Open to Public Inspection Nos. 53718/1982, 13211/1984, and 34882/1994. 
     However, in the example of Japanese Patent Publication Open to Public Inspection No. 53718/1982, the first lens is a negative plastic lens, and high dispersion material is used, therefore, it is difficult to conduct the hard coat in order to protect the lens surface. Further, an example is disclosed in Japanese Patent Publication Open to Public Inspection No. 13211/1984, in which the composition of the first lens group is sequentially in the order of a positive lens, a negative lens, and a positive lens from the object side, and the first lens is made of glass lens, and the second and third lenses are made of plastic lenses. In such the composition, circumstantial characteristics of the first lens and that of the second lens are very different, and the first lens and the second lens can not be cemented; the decentering sensitivity of the first lens and the second lens becomes high; and disused light tends to totally reflect on the second surface of the first lens, and there is a possibility that ghost is generated. Further, in Japanese Patent Publication Open to Public Inspection No. 34882/1994, a plastic lens is used for only the third lens of the first lens group, therefore, room for further cost reduction is left. 
     Above-mentioned conventional examples disclosed in Japanese Patent Publication Open to Public Inspection Nos. 264902/1993 and 106046/1996, have 4 lens groups in the order of positive, negative, positive and positive lenses from the object side, and the second lens group has the variable magnification function, and the fourth lens group has a correction function to correct the focal plane movement according to the variable magnification, which are well known as a zoom lens having above functions. 
     However, in any of conventional examples, more than half of lens components are glass lenses, and therefore, room to promote the more cost reduction is left. 
     SUMMARY OF THE INVENTION 
     The present invention is considered to solve the above problems. That is, the object of the present example is to provide a zoom lens in which many plastic lenses are used and thereby, cost is greatly reduced as compared to the conventional one, whereas the zoom lens has a high aperture ratio and a high variable magnification ratio appropriate for still cameras or video cameras. 
     The object of the present invention can be attained by any one of the following structures. 
     That is, a zoom lens having at least 3 lens groups, is characterized in that the first lens group has a positive refracting power, the second lens group has a negative refracting power; the composition of the first lens group is in the order of the first positive lens, the second negative lens, and the third positive lens; both the first and the second lenses are formed of plastic; and the first lens and the second lens are cemented to each other, and the concave surface of the cemented surface of the first lens and the second lens faces to the object side. 
     A zoom lens is characterized in that the third lens of the first lens group is formed of inorganic glass. 
     A zoom lens is characterized in that the third lens of the first lens group is formed of plastic. 
     A zoom lens is characterized in that the first lens group has at least one aspherical surface. 
     A zoom lens is characterized by satisfying the following relationships: 
     
         ν.sub.1 -ν.sub.2 &gt;15                                 (1) 
    
     
         ν.sub.3 &gt;45                                             (2) 
    
     
         0.5&lt;|r.sub.2 /f.sub.1 |&lt;1.2              (3) 
    
     where, ν 1  is Abbe&#39;s number of the first lens in the first lens group, ν 2  is Abbe&#39;s number of the second lens in the first lens group, ν 3  is Abbe&#39;s number of the third lens in the first lens group, r 2  is a radius of curvature of the cemented surface of the first lens and the second lens in the first lens group, and f 1  is a focal length of the first lens group. 
     Herein, the operation of the zoom lens of the present invention will be described. 
     When the first lens group of the zoom lens of the present invention is structured as described above, low dispersion plastic material is used for the first lens, and therefore material having excellent moisture resistance can be selected and thereby, the hard coat to protect the lens surface can be conducted. Incidentally, it is preferable that the low dispersion plastic mentioned above has an Abbe&#39;s number of more than 40, and more preferably an Abbe&#39;s number of not less than 50. To be concrete, polyolefins or acrylic resins. On the other hand, the high dispersion plastic mentioned above has an Abbe&#39;s number of not more than 40. To be concrete, polycarbonate may be listed up. Further, by cementing the first lens and the second lens to each other, the decentering sensitivity of the first lens and the second lens can be suppressed lower, and a ghost due to total reflection of the unused light on the second surface of the first lens can be prevented from being generated. 
     Further, in order to prevent the out-of-focus due to temperature variation, it is advantageous to use a glass lens as the third lens. Thereby, the influence of the temperature variation can be cancelled by the first lens formed of a positive plastic lens and the second lens formed of a negative plastic lens. 
     However, a plastic lens can be used as the third lens and thereby, further cost reduction can be attained in the following cases: where the zoom lens is not required to have so high aperture ratio, or so high variable magnification ratio; or where the out-of-focus due to temperature variation is not needed to be so strictly considered in a system in which the out-of-focus in a zooming operation is allowed, and the focus may be adjusted at the time of the completion of zooming, when the zoom lens is used for still cameras, or the like. 
     In order to attain the high aperture ratio and high variable magnification ratio, it is preferable to use at least one aspherical surface in the first lens group, which is effective to finely correct the distortion on the wide angle side and the spherical aberration on the telephoto side. 
     The above-described relationships (1)-(3) will be described below. 
     Relationships (1) and (2) are necessary to finely correct the chromatic aberration generated in the first lens group. When Abbe&#39;s number is out of ranges of relationships (1) and (2), correction of the longitudinal chromatic aberration specifically on the telephoto side is difficult. 
     Incidentally, it is more preferable that the relationship (1) has the value of the following relationship (1-1). 
     
         ν.sub.1 -ν.sub.2 &lt;22                                 (1-1) 
    
     Further, it is more preferable that the relationship (2) has the value of the following relationship (2-1). 
     
         ν.sub.3 &gt;54                                             (2-1) 
    
     The relationship (3) compensates for the relationships (1) and (2), and more finely corrects the chromatic aberration. When |r 2  /f 1  | is smaller than the lower limit of the relationship (3), the longitudinal chromatic aberration on the telephoto side is excessively corrected, and the lateral chromatic aberration on the wide angle side is insufficiently corrected. When |r 2  /f 1  | is larger than the upper limit of the relationship (3), the longitudinal chromatic aberration on the telephoto side is insufficiently corrected. 
     Incidentally, it is more preferable that the relationship (3) has the value of the following relationship (3-1). 
     
         0.6&lt;|r.sub.2 /f.sub.1 |&lt;1.0              (3-1) 
    
     Further, the above object is attained by any one of the following structures. 
     That is, a zoom lens having the first lens group (the object side lens group) having the positive refracting power, the second lens group which has the negative refracting power and moves for variable magnification, the third lens group which has the positive refracting power and is fixed, and the fourth lens group (the image side lens group) which has the positive refracting power and corrects the change of the position of the image plane at variable magnification, the zoom lens is characterized in that one positive lens of lenses constituting the first lens group is formed of inorganic glass and all of the other lenses are formed of plastic; one negative lens of lenses constituting the second lens group is formed of inorganic glass and all of the other lenses are formed of plastic; all lenses constituting the third lens group are formed of plastic; and one positive lens of lenses constituting the fourth lens group is formed of inorganic glass and all of the other lenses are formed of plastic. 
     Further, a zoom lens satisfying the following conditional relationships: 
     
         |fw·Σ{1/f.sub.p(1) }|&lt;0.10(4) 
    
     
         |fw·Σ{1/f.sub.p(2) }|&lt;0.25(5) 
    
     
         |fw·Σ{1/f.sub.p(3,i) }|&lt;0.10(6) 
    
     where, fw is a focal length on the wide angle side of the entire system, 
     Σ{1/f p (1) } is the sum of inverse numbers of the focal length of each plastic lens in the first lens group, 
     Σ{1/f p (2) } is the sum of inverse numbers of the focal length of each plastic lens in the second lens group, 
     Σ{1/f p (3,i) } is the sum of inverse numbers of the focal length of each plastic lens in the third and image side lens groups. 
     Further, a zoom lens characterized in that the first lens group is composed of 2 positive lens and one negative lens, and in lenses constituting the first lens group, one positive lens and one negative lens are formed of plastic, and the remaining one positive lens is formed of inorganic glass. 
     Further, a zoom lens characterized in that the second lens group is composed of a negative single lens whose concave surface, having larger curvature on the image side than that on the object side, faces the image side, and the cemented lens of negative and positive lenses, in order from the object side, and the negative single lens is formed of inorganic glass, and both of 2 lenses constituting the cemented lens are formed of plastic. 
     Still further, a zoom lens characterized in that the third lens group is composed of one positive lens formed of plastic. 
     Furthermore, a zoom lens characterized in that the fourth lens group has the cemented lens of positive and negative or negative and positive lenses, and a positive single lens, and both of 2 lenses constituting the cemented lens are formed of plastic, and the positive single lens is formed of inorganic glass. 
     Herein, the operation of the zoom lens of the present invention will be described. 
     Generally, in the case where plastic lenses are used in a zoom lens, when temperature compensation is strictly conducted on the entire zoom range, the temperature compensation is necessary for each lens group of the zoom lens, that is, at least one glass lens is necessary for each lens group. 
     In the present invention, one glass lens having positive refracting power is placed in the first lens group having the positive refracting power, the other lenses in the first lens group are formed of plastic lenses, and the refracting power of the first lens group is mainly borne on one glass lens, thereby the temperature compensation of the first lens group is conducted; and one glass lens having negative refracting power is placed in the second lens group having negative refracting power, the other lenses in the second lens group are formed of plastic lenses, and the refracting power of the second lens group is mainly borne on one glass lens, thereby the temperature compensation of the second lens group is conducted. 
     In both of the third and fourth lens groups, variation of the magnification ratio due to zooming is small. Accordingly, even when temperature compensation is not conducted for each lens group, temperature compensation can be sufficiently conducted on the composition system of the third and fourth lens groups. Therefore, the third lens group is composed of only plastic lens, one glass lens having positive refracting power is placed in the fourth lens group, all of the other lenses in the fourth lens group are formed of plastic lenses, and temperature compensation is conducted on these lenses and plastic lenses in the third lens group. 
     More concrete structure of the above-described zoom lens of the present invention will be described below. 
     It is preferable that the first lens group is structured by positive and negative or negative and positive plastic lenses and a positive single lens formed of inorganic glass. The chromatic aberration can be finely compensated by the positive plastic lens and the negative plastic lens, and when the positive single lens is formed of a glass lens and main refracting power of the first lens group is borne on the glass lens, temperature compensation of the first lens group can be finely conducted. 
     It is preferable that the second lens group is structure by a negative single lens formed of inorganic glass and the cemented lens of a negative plastic lens and a positive plastic lens. The cemented lens has a negative lens and a positive lens, and thereby, the chromatic aberration can be finely compensated, and when a negative single lens is formed of a glass lens and main refracting power of the second lens group is borne on the glass lens, the temperature compensation in the second lens group can be finely conducted. Further, when plastic lenses are cemented to each other, the decentering sensitivity can be suppressed, and the number of lens surfaces is reduced and the transmissivity can be increased. 
     In order to suppress the number of lenses of the glass lens group minimum, the third lens group is preferably structured by one positive plastic lens. Temperature compensation of the third and fourth lens groups may be conducted on the composition system, and therefore, one glass lens may only be placed in the third and fourth lens groups. However, in the case where the third lens group is structured by one lens, which is the minimum number of lens, when the glass lens is used for the third lens group, and all lenses of the fourth lens group are formed of plastic lenses, temperature compensation can not be conducted, and therefore, a glass lens is necessary for also the fourth lens group. When the third lens group is composed of one positive plastic lens, a glass lens is placed in the fourth lens group, and when the composition refracting power of plastic lenses in the fourth lens group is negative, temperature compensation can be conducted. 
     It is preferable that the fourth lens group is structured by the cemented lens of positive and negative plastic lenses or negative and positive plastic lenses and a positive single lens formed of inorganic glass. The chromatic aberration is corrected by the cemented lens, and in order to eliminate variation of refracting power at the time of temperature variation generated in the positive plastic lens of the third lens group, it is necessary that the composition refracting power of the plastic lens in the fourth lens group is negative, and a positive glass lens is necessary in the fourth lens group. Further, when plastic lenses are cemented in the same manner as in the second lens group, the decentering sensitivity can be suppressed and the number of lens surfaces is reduced and the transmissivity can be increased. 
     Conditional relationships (4) to (6) will be described below. 
     Relationship (4) relates to the refracting power of the plastic lens in the first lens group. The first lens group eliminates variation of the refracting power due to temperature variation by forming one positive lens and one negative lens in 3 lenses constituting the first lens group, of plastic lenses. Within the range of the relationship, the variation of the refracting power due to temperature variation can be fully cancelled, and an amount of variation of the focus position can be more reduced. 
     Incidentally, it is more preferable that the relationship (4) has a value of the following relationship (4-1). 
     
         |fw·Σ{1/f.sub.p(1) }|&lt;0.05(4-1) 
    
     The relationship (5) relates to the refracting power of the plastic lens in the second lens group. The second lens group eliminates variation of the refracting power due to temperature variation by forming one negative lens and one positive lens in 3 lenses constituting the second lens group, of plastic lenses. Within the range of the relationship, the variation of the refracting power due to temperature variation can be fully cancelled, and an amount of variation of the focus position can be more reduced. 
     Incidentally, it is more preferable that the relationship (5) has a value of the following relationship (5-1). 
     
         |fw·Σ{1/f.sub.p(2) }|&lt;0.22(5-1) 
    
     The relationship (6) relates to the refracting power of the plastic lens in the third and image side lens groups. In the lens system of the present invention, the third lens group is structured by only plastic lenses, and the composition refracting power of the plastic lens in the image side lens group is made negative so that the variation of the refracting power due to temperature variation can be cancelled. Within the range of the relationship (6), an amount of variation of the focus position can be more reduced. 
     Incidentally, it is more preferable that the relationship (6) has a value of the following relationship (6-1). 
     
         |fw·Σ{1/f.sub.p(3,i) }|&lt;0.05(6-1) 
    
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view of lenses of Example 1. 
     FIGS. 2(a)-1 to 2(c)-3 are views showing aberration of lenses in Example 1. 
     FIG. 3 is a sectional view of lenses in Example 2. 
     FIGS. 4(a)-1 to 4(c)-3 are views showing aberration of lenses in Example 2. 
     FIG. 5 is a sectional view of lenses in Example 3. 
     FIGS. 6(a)-1 to 6(c)-3 are views showing aberration of lenses in Example 3. 
     FIG. 7 is a sectional view of lenses in Example 4. 
     FIGS. 8(a)-1 to 8(c)-3 are views showing aberration of lenses in Example 4. 
     FIG. 9 is a sectional view of lenses in Example 5. 
     FIGS. 10(a)-1 to 10(c)-3 are views showing aberration of lenses in Example 5. 
     FIG. 11 is a sectional view of lenses in Example 6. 
     FIGS. 12(a)-1 to 12(c)-3 are views showing aberration of lenses in Example 6. 
     FIG. 13 is a sectional view of lenses in Example 7. 
     FIGS. 14(a)-1 to 14(c)-3 are views showing aberration of lenses in Example 7. 
     FIG. 15 is a sectional view of lenses in Example 8. 
     FIGS. 16(a)-1 to 16(c)-3 are views showing aberration of lenses in Example 8. 
     FIG. 17 is a sectional view of lenses in Example 9. 
     FIGS. 18(a)-1 to 18(c)-3 are views showing aberration of lenses in Example 9. 
     FIG. 19 is a sectional view of lenses in Example 10. 
     FIGS. 20(a)-1 to 20(c)-3 are views showing aberration of lenses in Example 10. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Examples 1 to 10, which satisfy the above-described conditions, will be shown below. 
     Herein, r is the radius of curvature of each lens surface, d is the lens thickness or lens interval, n d  is a refractive index, and ν d  is Abbe&#39;s number. Further, * shown in Examples 1-4 means a plastic lens. 
     When x axis is set in the direction of the optical axis and y axis is set in the direction perpendicular to the optical axis, and κ, A2, A4, A6, A8, A10, A12 are aspherical coefficients, the shape of the aspherical surface is expressed by the following equation. ##EQU1## 
     Initially, Examples 1-4 will be shown below. 
     FIG. 1 is a sectional view of lenses in Example 1. FIGS. 2(a)-1 to 2(c)-3 are aberration curves of lenses in Example 1, and FIGS. 2(a)-1 to 2(a)-3 are aberration curves at the wide angle end, FIGS. 2(b)-1 to 2(b)-3 are those in the intermediate area, and 2(c)-1 to 2(c)-3 are those at the telephoto end. FIG. 3 is a sectional view of lenses in Example 2. FIGS. 4(a)-1 to 4(c)-3 are aberration curves of lenses in Example 2, and FIGS. 4(a)-1 to 4(a)-3 are aberration curves at the wide angle end, FIGS. 4(b)-1 to 4(b)-3 are those in the intermediate area, and 4(c)-1 to 4(c)-3 are those at the telephoto end. FIG. 5 is a sectional view of lenses in Example 3. FIGS. 6(a)-1 to 6(c)-3 are aberration curves of lenses in Example 3, and FIGS. 6(a)-1 to 6(a)-3 are aberration curves at the wide angle end, FIGS. 6(b)-1 to 6(b)-3 are those in the intermediate area, and 6(c)-1 to 6(c)-3 are those at the telephoto end. FIG. 7 is a sectional view of lenses in Example 4. FIGS. 8(a)-1 to 8(c)-3 are aberration curves of lenses in Example 4, and FIGS. 8(a)-1 to 8(a)-3 are aberration curves at the wide angle end, FIGS. 8(b)-1 to 8(b)-3 are those in the intermediate area, and 8(c)-1 to 8(c)-3 are those at the telephoto end. Symbols L1, L2, L3, and L4 shown in FIGS. 1, 3, 5, 7 respectively show the first, second, third, and fourth lens groups. 
     EXAMPLE 1 
     Focal length: f=4.16-56.49 
     F-number: F1.24-2.05 
     Angle of view: 2ω=61.2°-4.6° 
     
                       TABLE 1______________________________________Surface No.      r        d         n.sub.d                                ν.sub.d______________________________________1          56.516   10.60     1.54100*                                53.02          -28.352  2.00      1.58300*                                30.03          89.820   0.204          27.897   4.90      1.69680                                55.55          -326.707 A6          67.765   0.55      1.81600                                46.67          5.583    3.508          -9.349   1.65      1.49700*                                56.09          7.664    3.10      1.58300*                                30.010         -31.321  B11         17.459   3.50      1.51823                                59.012         -96.837  0.8013         30.000   1.50      1.58300*                                30.014         -32.443  C15         16.522   4.60      1.49700*                                56.016         -19.990  1.80      1.58300*                                30.017         30.139   0.5018         18.857   0.60      1.84666                                23.819         10.550   3.85      1.69680                                55.520         -29.102  D21         ∞  4.48      1.51633                                64.122         ∞______________________________________ 
    
     
                                           TABLE 2__________________________________________________________________________Aspherical coefficient               Aspherical coefficient__________________________________________________________________________1st surface  κ =       2.46870 × 10.sup.0               14th surface                      κ =                          -8.90200 × 10.sup.-2  A.sub.2 =       0              A.sub.2 =                           0  A.sub.4 =      -6.18830 × 10.sup.-6                      A.sub.4 =                           8.15400 × 10.sup.-6  A.sub.6 =       3.47790 × 10.sup.-8                      A.sub.6 =                           1.51040 × 10.sup.-6  A.sub.8 =      -1.71320 × 10.sup.-10                      A.sub.8 =                          -2.41610 × 10.sup.-8  A.sub.10 =       4.26970 × 10.sup.-13                      A.sub.10 =                           1.27010 × 10.sup.-10  A.sub.12 =      -3.88800 × 10.sup.-163rd surface  κ =       7.8590 × 10.sup.0               15th surface                      κ =                          -1.31200 × 10.sup.0  A.sub.2 =       0              A.sub.2 =                           0  A.sub.4 =      -3.10500 × 10.sup.-6                      A.sub.4 =                           3.87700 × 10.sup.-6  A.sub.6 =       7.12200 × 10.sup.-8                      A.sub.6 =                           2.51090 × 10.sup.-6  A.sub.8 =      -4.36400 × 10.sup.-10                      A.sub.8 =                          -1.07160 × 10.sup.-8  A.sub.10 =       1.45020 × 10.sup.-12                      A.sub.10 =                          -5.86230 × 10.sup.-10  A.sub.12 =      -1.74920 × 10.sup.-15                      A.sub.12 =                           7.30500 × 10.sup.-128th surface  κ =      -1.16130 × 10.sup.0               17th surface                      κ =                           1.55960 × 10.sup.0  A.sub.2 =       0              A.sub.2 =                           0  A.sub.4 =       2.39670 × 10.sup.-4                      A.sub.4 =                           1.24110 × 10.sup.-4  A.sub.6 =      -1.37990 × 10.sup.-5                      A.sub.6 =                          -3.72950 × 10.sup.-6  A.sub.8 =      -1.94700 × 10.sup.-8                      A.sub.8 =                           3.47200 × 10.sup.-7  A.sub.10 =       7.39500 × 10.sup.-8                      A.sub.10 =                          -1.01240 × 10.sup.-8  A.sub.12 =      -3.47220 × 10.sup.-9                      A.sub.12 =                           1.03180 × 10.sup.-1010th surface  κ =      -8.38910 × 10.sup.-2  A.sub.2 =       0  A.sub.4 =       8.15370 × 10.sup.-5  A.sub.6 =      -5.98240 × 10.sup.-6  A.sub.8 =       2.40320 × 10.sup.-7  A.sub.10 =      -6.96690 × 10.sup.-9__________________________________________________________________________ 
    
     
                       TABLE 3______________________________________Variable intervalFocal length      A       B          C     D______________________________________4.16       0.50    25.60      5.08  6.3315.33      14.94   11.16      2.06  9.3556.49      22.78   3.32       5.02  6.39______________________________________ |r.sub.2 /f.sub.1 | = 0.77 
    
     EXAMPLE 2 
     Focal length: f=4.28-49.36 
     F-number: F1.66-2.42 
     Angle of view: 2ω=59.6°-5.2° 
     
                       TABLE 4______________________________________Surface No.      r        d         n.sub.d                                ν.sub.d______________________________________1          48.744   7.10      1.49700*                                56.02          -24.682  2.00      1.58300*                                30.03          67.371   0.204          20.579   4.50      1.69680                                55.55          -107.073 A6          ∞  0.55      1.72916                                54.77          4.571    2.758          -8.232   1.54      1.49700*                                56.09          7.771    2.47      1.58300*                                30.010         -22.535  B11         21.663   1.73      1.48749                                70.212         -61.979  C13         9.268    4.00      1.49700*                                56.014         -16.346  1.90      1.58300*                                30.015         9.435    0.4616         11.563   4.20      1.48749                                70.217         -11.563  D18         ∞  4.30      1.51633                                64.119         ∞______________________________________ 
    
     
                                           TABLE 5__________________________________________________________________________Aspherical coefficient               Aspherical coefficient__________________________________________________________________________1st surface  κ =       5.76650 × 10.sup.0               10th surface                      κ =                          -2.44220 × 10.sup.-2  A.sub.2 =       0              A.sub.2 =                          0  A.sub.4 =      -1.06110 × 10.sup.-5                      A.sub.4 =                           1.66120 × 10.sup.-4  A.sub.6 =      -2.11190 × 10.sup.-7                      A.sub.6 =                          -1.59600 × 10.sup.-5  A.sub.8 =      -1.54700 × 10.sup.-9                      A.sub.8 -                          -9.44430 × 10.sup.-7  A.sub.10 =       4.65120 × 10.sup.-12                      A.sub.10 =                           7.07510 × 10.sup.-8  A.sub.12 =      -1.96110 × 10.sup.-153rd surface  κ =       2.60970 × 10.sup.1               13th surface                      κ =                           2.64940 × 10.sup.-2  A.sub.2 =       0              A.sub.2 =                           0  A.sub.4 =      -1.57910 × 10.sup.-6                      A.sub.4 =                           2.85290 × 10.sup.-5  A.sub.6 =       2.94500 × 10.sup.-7                      A.sub.6 =                          -3.19010 × 10.sup.-6  A.sub.8 =      -2.66800 × 10.sup.-9                      A.sub.8 =                          -7.91230 × 10.sup.-8  A.sub.10 =       9.00400 × 10.sup.-12                      A.sub.10 =                           2.17680 × 10.sup.-9  A.sub.12 =      -7.49340 × 10.sup.-158th surface  κ =      -1.04240 × 10.sup.0               15th surface                      κ =                           2.03100 × 10.sup.0  A.sub.2 =       0              A.sub.2 =                           0  A.sub.4 =       7.13290 × 10.sup.-4                      A.sub.4 =                           1.63430 × 10.sup.-4  A.sub.6 =      -5.52080 × 10.sup.-5                      A.sub.6 =                          -1.40390 × 10.sup.-5  A.sub.8 =       2.16380 × 10.sup.-6                      A.sub.8 =                           9.91920 × 10.sup.-10                      A.sub.10 =                          -1.28950 × 10.sup.-8__________________________________________________________________________ 
    
     
                       TABLE 6______________________________________Variable intervalFocal length      A       B          C     D______________________________________4.28       0.50    19.64      4.80  6.2114.54      10.75   9.39       2.47  8.5449.36      16.82   3.32       6.77  4.24______________________________________ |r.sub.2 /f.sub.1 | = 0.90 
    
     EXAMPLE 3 
     Focal length: f=4.59-52.9 
     F-number: F1.66-2.95 
     Angle of view: 2ω=55.8°-5.0° 
     
                       TABLE 7______________________________________Surface No.      r        d         n.sub.d                                ν.sub.d______________________________________1          63.127   5.20      1.52470*                                56.02          -29.046  1.42      1.58300*                                30.03          79.642   0.194          21.656   3.31      1.58913                                61.25          -65.096  A6          29.255   0.55      1.77250                                49.67          4.712    2.708          -7.285   0.55      1.58144                                40.79          7.285    2.30      1.84666                                23.810         -130.838 B11         15.517   2.55      1.49700*                                56.012         -36.276  C13         17.295   3.20      1.49700*                                56.014         -14.000  1.50      1.58300*                                30.015         9.694    0.3516         12.558   4.10      1.58913                                61.217         -12.558  D18         ∞  4.48      1.51633                                64.119         ∞______________________________________ 
    
     
                       TABLE 8______________________________________Aspherical coefficient            Aspherical coefficient______________________________________1st   κ = 9.96090 × 10.sup.0                12th    κ -3.62780 × 10.sup.-1surface A.sub.2 = 0    surface A.sub.2 = 6.43790 × 10.sup.-6 A.sub.4 = -1.30064 × 10.sup.-5                        A.sub.4 = -4.20640 × 10.sup.-4 A.sub.6 = 5.00198 × 10.sup.-8                        A.sub.6 = 4.86500 × 10.sup.-5 A.sub.8 = 7.70810 × 10.sup.-11                        A.sub.8 = -2.46740 × 10-6 A.sub.10 = -1.82634 × 10.sup.-12                        A.sub.10 = 6.16579 × 10.sup.-8 A.sub.12 = 7.25944 × 10.sup.-16                        A.sub.12 = -6.14960 × 10.sup.-103rd   κ = 3.17790 × 10.sup.1                13th    κ = 1.92580 × 10.sup.0surface A.sub.2 = 0    surface A.sub.2 = 0 A.sub.4 = -1.31921 × 10.sup.-6                        A.sub.4 = -3.69060 × 10.sup.-4 A.sub.6 = 6.63602 × 10.sup.-8                        A.sub.6 = 3. 39130 × 10.sup.-5 A.sub.8 = 1.21266 × 10.sup.-10                        A.sub.8 = -2.07930 × 10.sup.-6 A.sub.10 = -2.95560 × 10.sup.-12                        A.sub.10 = 5.43390 × 10.sup.-8 A.sub.12 = 1.70625 × 10.sup.-15                        A.sub.12 = -5.64120 × 10.sup.-1011th  κ = 9.77120 × 10.sup.-1                15th    κ = -1.39580 × 10.sup.0surface A.sub.2 = 0    surface A.sub.2 = 0 A.sub.4 = -4.73960 × 10.sup.-4                        A.sub.4 = 9.19140 × 10.sup.-5 A.sub.6 = 4.25190 × 10.sup.-5                        A.sub.6 = 2.84430 × 10.sup.-5 A.sub.8 = -2.26610 × 10.sup.-6                        A.sub.8 = -2.14730 × 10.sup.-6 A.sub.8 = 5.90820 × 10.sup.-8                        A.sub.10 = 6.66750 × 10.sup.-8 A.sub.12 = -6.09030 × 10.sup.-10                        A.sub.12 = -8.02360 × 10.sup.-10______________________________________ 
    
     
                       TABLE 9______________________________________Variable intervalFocal length      A       B          C     D______________________________________4.59       0.55    19.72      7.89  7.6316.09      11.86   8.41       3.28  12.2452.92      18.55   1.72       5.68  9.84______________________________________ |r.sub.2 /f.sub.1 | = 0.98 
    
     EXAMPLE 4 
     Focal length: f=4.59-44.10 
     F-number: F1.66-2.92 
     Angle of view: 2ω=56.2°-6.0° 
     
                       TABLE 10______________________________________Surface No.      r        d         n.sub.d                                ν.sub.d______________________________________1          111.985  5.50      1.52470*                                56.02          -18.152  1.50      1.58300*                                30.03          -130.078 0.204          21.285   3.70      1.52470*                                56.05          -138.844 A6          59.909   0.55      1.77250                                49.67          4.992    2.608          -6.829   1.00      1.49700*                                56.09          6.442    2.20      1.58300*                                30.010         -27.611  B11         15.495   2.55      1.49700*                                56.012         -36.512  C13         17.312   3.20      1.49700*                                56.014         -13.390  1.50      1.58300*                                30.015         9.756    0.3516         12.575   4.10      1.58913                                61.217         -12.575  D18         ∞  4.48      1.51633                                64.119         ∞______________________________________ 
    
     
                       TABLE 11______________________________________Aspherical coefficient            Aspherical coefficient______________________________________1st   κ = 7.36690 × 10.sup.0                11th    κ = 4.01940 × 10.sup.-1surface A.sub.2 = 0    surface A.sub.2 = 0 A.sub.4 = -1.25644 × 10.sup.-6                        A.sub.4 = -5.62660 × 10.sup.-4 A.sub.6 = -5.93197 × 10.sup.-9                        A.sub.6 = 5.16250 × 10.sup.-5 A.sub.8 = 1.37858 × 10.sup.-10                        A.sub.8 = -2.57580 × 10.sup.-6 A.sub.10 = 6.36718 × 10.sup.-13                        A.sub.10 = 6.44420 × 10.sup.-8 A.sub.12 = -1.88541 × 10.sup.-15                        A.sub.12 = -6.44530 × 10.sup.-103rd   κ = 3.13193 × 10.sup.1                12th    κ = -2.70210 × 10.sup.-1surface A.sub.2 = 0    surface A.sub.2 = 6.43790 × 10.sup.-6 A.sub.4 = 7.69046 × 10.sup.-6                        A.sub.4 = -5.19030 × 10.sup.-4 A.sub.6 = -1.45473 × 10.sup.-8                        A.sub.6 = 5.40960 × 10.sup.-5 A.sub.8 = 1.575.36 × 10.sup.-10                        A.sub.8 = -2.58200 × 10.sup.-6 A.sub.10 = 2.29179 × 10.sup.-12                        A.sub.10 = 6.24290 × 10.sup.-8 A.sub.12 = -1.14979 × 10.sup.-14                        A.sub.12 = -6.10980 × 10.sup.-108th   κ = -1.04120 × 10.sup.0                13th    κ = 7.37050 × 10.sup.-1surface A.sub.2 = 0    surface A.sub.2 = 0 A.sub.4 = 1.45290 × 10.sup.-4                        A.sub.4 = -3.39590 × 10.sup.-4 A.sub.6 = -1.10710 × 10.sup.-5                        A.sub.6 = 2.68820 × 10.sup.-5 A.sub.8 = -3.97450 × 10.sup.-6                        A.sub.8 = -1.63710 × 10.sup.-6 A.sub.10 = 3.93160 × 10.sup.-7                        A.sub.10 = 4.24050 × 10.sup.-8 A.sub.12 = -1.07720 × 10.sup.-8                        A.sub.12 = -4.34370 × 10.sup.-1010th  κ = 2.34960 × 10.sup.-1                15th    κ = -4.55930 × 10.sup.0surface A.sub.2 = 0    surface A.sub.0 = 0 A.sub.4 = 7.62730 × 10.sup.-5                        A.sub.4 = 5.18640 × 10-4 A.sub.6 = -4.46300 × 10.sup.-6                        A.sub.6 = 1.47350 × 10.sup.-5 A.sub.8 = -3.18290 × 10.sup.-7                        A.sub.8 = -1.74760 × 10.sup.-6 A.sub.10 = 1.74360 × 10.sup.-8                        A.sub.10 = 6.16470 × 10.sup.-8                        A.sub.12 = -8.02360 × 10.sup.-10______________________________________ 
    
     
                       TABLE 12______________________________________Variable intervalFocal length      A       B          C     D______________________________________4.59       0.55    18.92      8.32  7.6514.67      11.36   8.11       3.83  12.1444.10      17.75   1.72       3.62  13.35______________________________________ |r.sub.2 /f.sub.1 | = 0.61 
    
     The results of above Examples show that in all Examples 1 to 4, there can be obtained a zoom lens having small aberration and excellent optical performance with the zoom lens in which the first lens in the first lens group is made plastic lens and many plastic lenses are used. Incidentally, the distortion at wide angle end to the extent shown in the present Examples does not offer big problem. 
     Next, Examples 5-10 will be described. 
     Numerals *1-*4 shown in Examples 5-10 express plastic lenses, and changes of their refractive indexes due to respective temperature variation are as follows. 
     
                       TABLE 13______________________________________  Refractive index at             Refractive index at  normal temperature             normal temperature +30° C.______________________________________*1       1.5247       1.5211*2       1.583        1.5788*3       1.497        1.4934*4       1.5122       1.5092______________________________________ 
    
     FIG. 9 is a sectional view of lenses in Example 5. FIGS. 10(a)-1 to 10(c)-3 are aberration curves of lenses in Example 5, and FIGS. 10(a)-1 to 10(a)-3 are aberration curves at the wide angle end, FIGS. 10(b)-1 to 10(b)-3 are those in the intermediate area, and 10(c)-1 to 10(c)-3 are those at the telephoto end. FIG. 11 is a sectional view of lenses in Example 6. FIGS. 12(a)-1 to 12(c)-3 are aberration curves of lenses in Example 6, and FIGS. 12(a)-1 to 12(a)-3 are aberration curves at the wide angle end, FIGS. 12(b)-1 to 12(b)-3 are those in the intermediate area, and 12(c)-1 to 12(c)-3 are those at the telephoto end. FIG. 13 is a sectional view of lenses in Example 7. FIGS. 14(a)-1 to 14(c)-3 are aberration curves of lenses in Example 7, and FIGS. 14(a)-1 to 14(a)-3 are aberration curves at the wide angle end, FIGS. 14(b)-1 to 14(b)-3 are those in the intermediate area, and 14(c)-1 to 14(c)-3 are those at the telephoto end. FIG. 15 is a sectional view of lenses in Example 8. FIGS. 16(a)-1 to 16(c)-3 are aberration curves of lenses in Example 8, and FIGS. 16(a)-1 to 16(a)-3 are aberration curves at the wide angle end, FIGS. 16(b)-1 to 16(b)-3 are those in the intermediate area, and 16(c)-1 to 16(c)-3 are those at the telephoto end. FIG. 17 is a sectional view of lenses in Example 9. FIGS. 18(a)-1 to 18(c)-3 are aberration curves of lenses in Example 9, and FIGS. 18(a)-1 to 18(a)-3 are aberration curves at the wide angle end, FIGS. 18(b)-1 to 18(b)-3 are those in the intermediate area, and 18(c)-1 to 18(c)-3 are those at the telephoto end. FIG. 19 is a sectional view of lenses in Example 10. FIGS. 20(a)-1 to 20(c)-3 are aberration curves of lenses in Example 10, and FIGS. 20(a)-1 to 20(a)-3 are aberration curves at the wide angle end, FIGS. 20(b)-1 to 20(b)-3 are those in the intermediate area, and 20(c)-1 to 20(c)-3 are those at the telephoto end. Symbols L1, L2, L3, and L4 shown in FIGS. 9, 11, 13, 15, 17, 19 respectively show the first, second, third, and fourth lens groups. 
     Incidentally, in Examples other than Example 9, the first lens in the first lens group, which is a plastic lens, and the second lens in the first lens group, which is a plastic lens, are cemented together. Further, in Examples 6, 7, 9, and 11, the first lens in the first lens group, which is a low dispersion plastic lens, and the second lens in the first lens group, which is a high dispersion plastic lens, are cemented together. 
     EXAMPLE 5 
     Focal length: f=4.59-52.92 
     F-number: F1.66-2.92 
     Angle of view: 2ω=56.2°-5.0° 
     
                       TABLE 14______________________________________Surface No.      r        d         n.sub.d                                ν.sub.d______________________________________1          57.398   5.50      1.52470*1                                56.02          -29.272  1.50      1.58300*2                                30.03          98.352   0.204          20.901   3.50      1.62299                                58.25          -750.168 A6          107.432  0.55      1.77250                                49.67          5.084    2.758          -7.591   1.00      1.49700*3                                56.09          7.087    2.30      1.58300*2                                30.010         -23.452  B11         17.778   2.55      1.49700*3                                56.012         -42.863  C13         18.167   3.20      1.49700*3                                56.014         -16.636  1.50      1.58300*2                                30.015         10.696   0.2516         11.448   4.10      1.58913                                61.217         -17.879  D18         ∞  4.48      1.51633                                64.119         ∞______________________________________ 
    
     
                       TABLE 15______________________________________Aspherical coefficient            Aspherical coefficient______________________________________1st   κ = 1.69160 × 10.sup.1                11th    κ = -3.35040 × 10.sup.-2surface A.sub.l = 0    surface A.sub.0 = 0 A.sub.4 = 1.40470 × 10.sup.-7                        A.sub.4 = -5.24460 × 10.sup.-4 A.sub.6 = -3.60300 × 10.sup.-8                        A.sub.6 = 4.99900 × 10.sup.-5 A.sub.8 = 2.99340 × 10.sup.-10                        A.sub.8 = -2.57100 × 10.sup.-6 A.sub.10 = -2.48610 × 10.sup.-12                        A.sub.10 = 6.48340 × 10.sup.-8 A.sub.12 = -1.35710 × 10.sup.-15                        A.sub.12 = -6.34030 × 10.sup.-103rd   κ = 3.14300 × 10.sup.1                12th    κ = -2.19300 × 10.sup.-1surface A.sub.2 = 0    surface A.sub.l = 6.43790 × 10.sup.-6 A.sub.4 = 1.52700 × 10.sup.-5                        A.sub.4 = -5.20420 × 10.sup.-4 A.sub.6 = 5.11360 × 10.sup.-9                        A.sub.6 = 5.54180 × 10.sup.-5 A.sub.8 = 3.57330 × 10.sup.-10                        A.sub.8 = -2.75530 × 10.sup.-6 A.sub.10 = -2.27070 × 10.sup.-12                        A.sub.10 = 6.74250 × 10.sup.-8 A.sub.12 = 6.70920 × 10.sup.-15                        A.sub.12 = -6.44190 × 10.sup.-108th   κ = -1.12650 × 10.sup.0                13th    κ = 5.96260 × 10.sup.-2surface A.sub.l = 0    surface A.sub.l = 0 A.sub.4 = 1.44610 × 10.sup.-4                        A.sub.4 = -8.88510 × 10.sup.-5 A.sub.6 = -3.51320 × 10.sup.-6                        A.sub.6 = 1.82250 × 10.sup.-5 A.sub.8 = -4.44430 × 10.sup.-6                        A.sub.8 = -9.51540 × 10.sup.-7 A.sub.10 = 3.90890 × 10.sup.-7                        A.sub.10 = 2.18850 × 10.sup.-8 A.sub.12 = -1.03120 × 10.sup.-8                        A.sub.12 = -1.97480 × 10.sup.-1010th  κ = -1.19460 × 10.sup.-2                5th     κ = -4.36400 × 10.sup.0surface A.sub.l = 0    surface A.sub.l = 0 A.sub.4 = 4. 01450 × 10.sup.-5                        A.sub.4 = 5.36810 × 10.sup.-4 A.sub.6 = -3.95310 × 10.sup.-6                        A.sub.6 = 8.84490 × 10.sup.-6 A.sub.8 = -5.49740 × 10.sup.-7                        A.sub.8 = -9.27240 × 10.sup.-7 A.sub.10 = 2.24830 × 10.sup.-8                        A.sub.10 = 2.96870 × 10.sup.-8                        A.sub.12 = -3.53420 × 10.sup.-10______________________________________ 
    
     
                       TABLE 16______________________________________Variable intervalFocal length      A       B          C     D______________________________________4.59       0.55    22.42      8.20  8.7615.87      12.86   10.11      3.62  13.3452.92      20.15   2.82       5.06  11.90______________________________________ 
    
     
                       TABLE 17______________________________________The change of back focus at normal temperature +30° C.:Δ f.sub.B value  Focal length          Δ f.sub.B______________________________________  4.59    +0.052  15.87   +0.029  52.92   +0.018______________________________________ |fw · Σ {1/f.sub.p(1) }| = 0.00 |fw · Σ {1/f.sub.p(2) }| = 0.16 |fw · Σ {1/f.sub.p(3,i) }| = 0.01 
    
     EXAMPLE 6 
     Focal length: f=4.59-52.92 
     F-number: F1.66-2.76 
     Angle of view: 2ω=56.0°-5.0° 
     
                       TABLE 18______________________________________Surface No.      r        d         n.sub.d                                ν.sub.d______________________________________1          50.600   5.50      1.52470*1                                56.02          -30.702  1.50      1.58300*2                                30.03          79.293   0.204          20.392   3.50      1.62299                                58.25          -415.082 A6          63.888   0.55      1.77250                                49.67          5.319    2.708          -6.987   1.00      1.49700*3                                56.09          5.819    2.30      1.58300*2                                30.010         -35.331  B11         16.321   2.55      1.49700*3                                56.012         -39.845  C13         16.859   3.20      1.49700*3                                56.014         -16.636  1.50      1.58300*2                                30.015         9.744    0.3516         12.820   4.10      1.58913                                61.217         -12.820  D18         ∞  4.48      1.51633                                64.119         ∞______________________________________ 
    
     
                       TABLE 19______________________________________Aspherical coefficient            Aspherical coefficient______________________________________1st   κ = 7.82770 × 10.sup.0                11th    κ = 2.09080 × 10.sup.-1surface A.sub.2 = 0    surface A.sub.2 = 0 A.sub.4 = 4.17950 × 10.sup.-6                        A.sub.4 = -5.69160 × 10.sup.-4 A.sub.6 = 2.32090 × 10.sup.-8                        A.sub.6 = 5.31130 × 10.sup.-5 A.sub.8 = -8.21950 × 10.sup.-11                        A.sub.8 = -2.62430 × 10.sup.-6 A.sub.10 = 3.51610 × 10.sup.-13                        A.sub.10 = 6.52780 × 10.sup.-8 A.sub.12 = -1.35710 × 10.sup.-15                        A.sub.12 = -6.53650 × 10.sup.-103rd   κ = 3.14390 × 10.sup.1                12th    κ = -2.45760 × 10.sup.-1surface A.sub.2 = 0    surface A.sub.2 = 6.43790 × 10.sup.-6 A.sub.4 = 1.42020 × 10.sup.-5                        A.sub.4 = -5.49090 × 10.sup.-4 A.sub.6 = 5.95460 × 10.sup.-9                        A.sub.6 = 5.61640 × 10.sup.-5 A.sub.8 = 4.52140 × 10.sup.-10                        A.sub.8 = -2.63390 × 10.sup.-6 A.sub.10 = -3.81740 × 10.sup.-12                        A.sub.10 = 6.27520 × 10.sup.-8 A.sub.12 = 8.47670 × 10.sup.-15                        A.sub.12 = -6.10980 × 10.sup.-108th   κ = -9.79280 × 10.sup.-1                13th    κ = 4.48400 × 10.sup.-1surface A.sub.2 = 0    surface A.sub.2 = 0 A.sub.4 = 6.74700 × 10.sup.-5                        A.sub.4 = -3.16780 × 10.sup.-4 A.sub.6 = -1.57080 × 10.sup.-6                        A.sub.6 = 2.29990 × 10.sup.-5 A.sub.8 = -4.29520 × 10.sup.-6                        A.sub.8 = -1.32470 × 10.sup.-6 A.sub.10 = 3.83010 × 10.sup.-7                        A.sub.10 = 3.22380 × 10.sup.-8 A.sub.12 = -1.07720 × 10.sup.-8                        A.sub.12 = -3 15760 × 10.sup.-1010th  κ = -2.92560 × 10.sup.-2                15th    κ = -4.06930 × 10.sup.0surface A.sub.2 = 0    surface A.sub.2 = 0 A.sub.4 = 1.25190 × 10.sup.-4                        A.sub.4 = 4.61000 × 10.sup.-4 A.sub.6 = -2.96480 × 10.sup.-6                        A.sub.6 = 1.19660 × 10.sup.-5 A.sub.8 = -2.01450 × 10.sup.-7                        A.sub.8 = -1.36730 × 10.sup.-6 A.sub.10 = 1.66480 × 10.sup.-8                        A.sub.10 = 4.54130 × 10.sup.-8                        A.sub.12 = -5.60400 × 10.sup.-10______________________________________ 
    
     
                       TABLE 20______________________________________Variable intervalFocal length      A       B          C     D______________________________________4.59       0.55    20.32      7.75  7.9015.96      12.24   8.63       3.38  12.2752.92      19.15   1.72       5.37  10.28______________________________________ 
    
     
                       TABLE 21______________________________________The change of back focus at normal temperature +30° C.:Δ f.sub.B value  Focal length          Δ f.sub.B______________________________________  4.59    +0.047  15.96   +0.017  52.92   -0.001______________________________________ |fw · Σ {1/f.sub.p(1) }| = 0.00 |fw · Σ {1/f.sub.p(2) }| = 0.21 |fw · Σ {1/f.sub.p(3,i) }| = 0.01 
    
     EXAMPLE 7 
     Focal length: f=4.28-49.42 
     F-number: F1.66-2.53 
     Angle of view: 2ω=59.8°-5.4° 
     
                       TABLE 22______________________________________Surface No.      r        d         n.sub.d                                ν.sub.d______________________________________1          73.376   2.00      1.58300*2                                30.02          18.465   6.50      1.49700*3                                56.03          267.738  0.204          21.765   4.20      1.60311                                60.75          -1961.821               A6          79.651   0.55      1.77250                                49.67          5.259    3.058          -8.246   1.65      1.49700*3                                56.09          8.513    2.60      1.58300*2                                30.010         -27.280  B11         19.254   2.50      1.49700*3                                56.012         -41.687  C13         17.308   3.40      1.49700*3                                56.014         -17.714  2.10      1.58300*2                                30.015         9.933    0.3016         10.888   4.10      1.58913                                61.217         -16.960  D18         ∞  4.48      1.51633                                64.119         ∞______________________________________ 
    
     
                       TABLE 23______________________________________Aspherical coefficient            Aspherical coefficient______________________________________1st   κ = 2.00040 × 10.sup.1                11th    κ = -1.05620 × 10.sup.-1surface A.sub.0 = 0    surface A.sub.2 = 0 A.sub.4 = -5.28680 × 10.sup.-6                        A.sub.4 = -5.40500 × 10.sup.-4 A.sub.6 = -3.75670 × 10.sup.-8                        A.sub.6 = 5.06310 × 10.sup.-5 A.sub.8 = 2.91080 × 10.sup.-10                        A.sub.8 = -2.55010 × 10.sup.-6 A.sub.10 = -1.44570 × 10.sup.-12                        A.sub.10 = 6.49280 × 10.sup.-8 A.sub.12 = 1.39080 × 10.sup.-15                        A.sub.12 = -6.53380 × 10.sup.-103rd   κ = 3.14850 × 10.sup.1                12th    κ = -2.44450 × 10.sup.-1surface A.sub.2 = 0    surface A.sub.2 = 0 A.sub.4 = 6.22070 × 10.sup.-6                        A.sub.4 = -5.55910 × 10.sup.-4 A.sub.6 = -2.03160 × 10.sup.-8                        A.sub.6 = 5.71840 × 10.sup.-5 A.sub.8 = 3.52770 × 10.sup.-10                        A.sub.8 = -2.77510 × 10.sup.-6 A.sub.10 = -1.15230 × 10.sup.-12                        A.sub.10 = 6.81600 × 10.sup.-8 A.sub.12 = 1.62960 × 10.sup.-15                        A.sub.12 = -6.67650 × 10.sup.-108th   κ = -6.04500 × 10.sup.-1                13th    κ = -5.81410 × 10.sup.-2surface A.sub.2 = 0    surface A.sub.2 = 0 A.sub.4 = 2.31970 × 10.sup.-4                        A.sub.4 = -1.28300 × 10.sup.-4 A.sub.6 = 6.63100 × 10.sup.-6                        A.sub.6 = 1.99630 × 10.sup.-5 A.sub.8 = -4.30100 × 10.sup.-6                        A.sub.8 = -1.00750 × 10.sup.-6 A.sub.10 = 3.88670 × 10.sup.-7                        A.sub.10 = 2.24500 × 10.sup.-8 A.sub.12 = -1.23870 × 10.sup.-8                        A.sub.12 = -1.99070 × 10.sup.-1010th  κ = -6.63060 × 10.sup.-2                15th    κ = -4.16750 × 10.sup.0surface A.sub.2 = 0    surface A.sub.2 = 0 A.sub.4 = 2.64550 × 10.sup.-5                        A.sub.4 = 5.93560 × 10.sup.-4 A.sub.6 = -4.12230 × 10.sup.-6                        A.sub.6 = 8.52820 × 10.sup.-6 A.sub.8 = -1.56720 × 10.sup.-7                        A.sub.8 = -9.72590 × 10.sup.-7 A.sub.10 = 5.33450 × 10.sup.-9                        A.sub.10 = 3.17410 × 10.sup.-8                        A.sub.12 = -3.89120 × 10-10______________________________________ 
    
     
                       TABLE 24______________________________________Variable intervalFocal length      A       B          C     D______________________________________4.28       0.60    23.87      7.41  8.0414.54      13.83   10.64      3.40  12.0549.42      21.65   2.82       4.18  11.27______________________________________ 
    
     
                       TABLE 25______________________________________The change of back focus at normal temperature +30° C.:Δ f.sub.B value  Focal length          Δ f.sub.B______________________________________  4.28    +0.046  14.54   +0.026  49.42   +0.037______________________________________ |fw · Σ {1/f.sub.p(1) }| = 0.01 |fw · Σ {1/f.sub.p(2) }| = 0.15 |fw · Σ {1/f.sub.p(3,i) }| = 0.01 
    
     EXAMPLE 8 
     Focal length: f=4.28-49.42 
     F-number: F1.66-2.53 
     Angle of view: 2ω=59.8°-5.4° 
     
                       TABLE 26______________________________________Surface No.      r        d         n.sub.d                                ν.sub.d______________________________________ 1         88.502   6.70      1.51220*4                                57.0 2         -26.689  2.00      1.58300*2                                30.0 3         -1873.298               0.20 4         23.460   4.00      1.58913                                61.2 5         -498.501 A 6         79.651   0.55      1.77250                                49.6 7         5.259    3.05 8         -8.246   1.65      1.49700*3                                56.0 9         8.513    2.60      1.58300*2                                30.010         -27.280  B11         19.254   2.50      1.49700*3                                56.012         -41.687  C13         17.308   3.40      1.49700*3                                56.014         -17.714  2.10      1.58300*2                                30.015         9.933    0.3016         10.888   4.10      1.58913                                61.217         -16.960  D18         ∞  4.48      1.51633                                64.119         ∞______________________________________ 
    
     
                       TABLE 27______________________________________Aspherical coefficient            Aspherical coefficient______________________________________1st   κ = 2.10540 × 10.sup.1                11th    κ = -1.05620 × 10.sup.-1surface A.sub.2 = 0    surface A.sub.2 = 0 A.sub.4 = 2.42970 × 10.sup.-7                        A.sub.4 = -5.40500 × 10.sup.-4 A.sub.6 = -2.26890 × 10.sup.-8                        A.sub.6 = 5.06310 × 10.sup.-5 A.sub.8 = 3.13450 × 10.sup.-10                        A.sub.8 = -2.55010 × 10.sup.-6 A.sub.10 = -1.47720 × 10.sup.-12                        A.sub.10 = 6.49280 × 10.sup.-8 A.sub.12 = 2.75070 × 10.sup.-15                        A.sub.12 = -6.53380 × 10.sup.-103rd   κ = 3.14910 × 10.sup.1                12th    κ = -2.44450 × 10.sup.-1surface A.sub.2 = 0    surface A.sub.2 = 0 A.sub.4 = 8.26900 × 10.sup.-6                        A.sub.4 = -5.55910 × 10.sup.-4 A.sub.6 = -1.45650 × 10.sup.-8                        A.sub.6 = 5.71840 × 10.sup.-5 A.sub.8 = 3.27430 × 10.sup.-10                        A.sub.8 = -2.77510 × 10.sup.-6 A.sub.10 = -1.27350 × 10.sup.-12                        A.sub.10 = 6.81600 × 10.sup.-8 A.sub.12 = 2.10020 × 10.sup.-15                        A.sub.12 = -6.67650 × 10.sup.-108th   κ = -6.04500 × 10.sup.-1                13th    κ = -5.81410 × 10.sup.-2surface A.sub.2 = 0    surface A.sub.2 = 0 A.sub.4 = 2.31970 × 10.sup.-4                        A.sub.4 = -1.28300 × 10.sup.-4 A.sub.6 = 6.63100 × 10.sup.-6                        A.sub.6 = 1.99630 × 10.sup.-5 A.sub.8 = -4.30100 × 10.sup.-6                        A.sub.8 = -1.00750 × 10.sup.-6 A.sub.10 = 3.88670 × 10.sup.-7                        A.sub.8 = 2.24500 × 10.sup.-8 A.sub.12 = -1.23870 × 10.sup.-8                        A.sub.12 = -1.99070 × 10.sup.-1010th  κ = -6.63060 × 10.sup.-2                15th    κ = -4.16750 × 10.sup.0surface A.sub.l = 0    surface A.sub.2 = 0 A.sub.4 = 2.64550 × 10.sup.-5                        A.sub.4 = 5.93560 × 10.sup.-4 A.sub.6 = -4.12230 × 10.sup.-6                        A.sub.6 = 8.52820 × 10.sup.-6 A.sub.8 = -1.56720 × 10.sup.-7                        A.sub.8 = -9.72590 × 10.sup.-7 A.sub.10 = 5.33450 × 10.sup.-9                        A.sub.10 = 3.17410 × 10.sup.-8                        A.sub.12 = -3.89120 × 10.sup.-10______________________________________ 
    
     
                       TABLE 28______________________________________Variable intervalFocal length A      B          C    D______________________________________ 4.28         0.60  23.87      7.41  8.0414.54        13.83  10.64      3.40 12.0549.42        21.65   2.82      4.18 11.27______________________________________ 
    
     
                       TABLE 29______________________________________The change of back focus at normal temperature +30° C.:Δ f.sub.B value  Focal length          Δ f.sub.B______________________________________   4.28   +0.045  14.54   +0.022  49.42   -0.012______________________________________ |fw · Σ {1/f.sub.p(1) }| = 0.01 |fw · Σ {1/f.sub.p(2) }| = 0.15 |fw · Σ {1/f.sub.p(3, i) }| = 0.01 
    
     EXAMPLE 9 
     Focal length: f=4.28-49.46 
     F-number: F1.66-2.53 
     Angle of view: 2ω=59.2°-5.4° 
     
                       TABLE 30______________________________________Surface No.      r        d         n.sub.d                                ν.sub.d______________________________________ 1         56.524   2.00      1.58300*2                                30.0 2         17.052   0.30 3         17.723   6.50      1.49700*3                                56.0 4         173.283  0.20 5         21.766   4.20      1.60311                                60.7 6         -2009.441               A 7         79.651   0.55      1.77250                                49.6 8         5.259    3.05 9         -8.246   1.65      1.49700*3                                56.010         8.513    2.60      1.58300*2                                30.011         -27.280  B12         19.254   2.50      1.49700*3                                56.013         -41.687  C14         17.308   3.40      1.49700*3                                56.015         -17.714  2.10      1.58300*2                                30.016         9.933    0.3017         10.888   4.10      1.58913                                61.218         -16.960  D19         ∞  4.48      1.51633                                64.120         ∞______________________________________ 
    
     
                       TABLE 31______________________________________Aspherical coefficient            Aspherical coefficient______________________________________1st   κ = 9.20470 × 10.sup.0                12th    κ = -1.05620 × 10.sup.-1surface A.sub.2 = 0    surface A.sub.2 = 0 A.sub.4 = -2.98060 × 10.sup.-6                        A.sub.4 = -5.40500 × 10.sup.-4 A.sub.6 = -4.16820 × 10.sup.-8                        A.sub.6 = 5.06310 × 10.sup.-5 A.sub.8 = 2.70550 × 10.sup.-10                        A.sub.8 = -2.55010 × 10.sup.-6 A.sub.10 = -9.45890 × 10.sup.-13                        A.sub.10 = 6.49280 × 10.sup.-8 A.sub.12 7.42810 × 10.sup.-17                        A.sub.12 = -6.53380 × 10.sup.-104th   κ = 3.12980 × 10.sup.1                13th    κ = -2.44450 × 10.sup.-1surface A.sub.2 = 0    surface A.sub.2 = 0 A.sub.4 = 5.96490 × 10.sup.-6                        A.sub.4 = -5.55910 × 10.sup.-4 A.sub.6 = -4.96930 × 10.sup.-8                        A.sub.6 = 5.71840 × 10.sup.-5 A.sub.8 = 4.40660 × 10.sup.-10                        A.sub.8 = -2.77510 × 10.sup.-6 A.sub.10 = -1.29910 × 10.sup.-12                        A.sub.10 = 6.81600 × 10.sup.-8 A.sub.12 = -2.14820 × 10.sup.-15                        A.sub.12 = -6.67650 × 10.sup.-109th   κ = -6.04500 × 10.sup.-1                14th    κ = -5.81410 × 10.sup.-2surface A.sub.2 = 0    surface A.sub.2 = 0 A.sub.4 = 2.31970 × 10.sup.-4                        A.sub.4 = -1.28300 × 10.sup.-4 A.sub.6 = 6.6310.sup.0 × 10.sup.-6                        A.sub.6 = 1.99630 × 10.sup.-5 A.sub.8 = -4.3010.sup.0 × 10.sup.-6                        A.sub.8 = -1.00750 × 10.sup.-6 A.sub.10 = 3.88670 × 10.sup.-7                        A.sub.10 = 2.24500 × 10-8 A.sub.12 = -1.23870 × 10.sup.-8                        A.sub.12 = -1.99070 × 10.sup.-1011th  κ = -6.63060 × 10.sup.-2                15th    κ = -4.16750 × 10.sup.0surface A.sub.2 = 0    surface A.sub.2 = 0 A.sub.4 = 2.64550 × 10.sup.-5                        A.sub.4 = 5.93560 × 10.sup.-4 A.sub.6 = -4.12230 × 10.sup.-6                        A.sub.6 = 8.52820 × 10.sup.-6 A.sub.8 = -1.56720 × 10.sup.-7                        A.sub.8 = -9.72590 × 10.sup.-7 A.sub.10 = 5.33450 × 10.sup.-9                        A.sub.10 = 3.17410 × 10.sup.-8                        A.sub.12 = -3.89120 × 10.sup.-10______________________________________ 
    
     
                       TABLE 32______________________________________Variable intervalFocal length A      B          C    D______________________________________ 4.28         0.60  23.87      7.41  8.0414.55        13.83  10.64      3.40 12.0449.46        21.65   2.82      4.19 11.25______________________________________ 
    
     
                       TABLE 33______________________________________The change of back focus at normal temperature +30° C.:Δ f.sub.B value  Focal length          Δ f.sub.B______________________________________   4.28   +0.046  14.55   +0.026  49.46   -0.041______________________________________ |fw · Σ {1/f.sub.p(1) }| = 0.01 |fw · Σ {1/f.sub.p(2) }| = 0.15 |fw · Σ {1/f.sub.p(3, i) }| = 0.01 
    
     EXAMPLE 10 
     Focal length: f=4.28-49.47 
     F-number: F1.66-2.39 
     Angle of view: 2ω=59.8°-5.4° 
     
                       TABLE 34______________________________________Surface No.      r        d         n.sub.d                                ν.sub.d______________________________________ 1         130.398  6.90      1.52470*1                                56.0 2         -29.159  2.00      1.58300*2                                30.0 3         1342.071 0.20 4         24.371   4.50      1.60311                                60.7 5         -423.607 A 6         72.533   0.55      1.71300                                53.9 7         5.337    3.35 8         -8.268   1.65      1.49700*3                                56.0 9         8.603    2.70      1.58300*2                                30.010         -28.810  B11         20.448   2.50      1.49700*3                                56.012         -41.618  C13         17.320   3.40      1.49700*3                                56.014         -17.714  2.10      1.58300*2                                30.015         9.942    0.3016         10.897   4.10      1.58913                                61.217         -16.975  D18         ∞  4.48      1.51633                                64.119         ∞______________________________________ 
    
     
                       TABLE 35______________________________________Aspherical coefficient            Aspherical coefficient______________________________________1st   κ = 2.14460 × 10.sup.1                11th    κ = -1.02840 × 10.sup.-1surface A.sub.2 = 0    surface A.sub.l = 0 A.sub.4 = 3.94740 × 10.sup.-6                        A.sub.4 = -5.39700 × 10.sup.-4 A.sub.6 = -1.52860 × 10.sup.-8                        A.sub.6 = 5.05500 × 10.sup.-5 A.sub.8 = 2.04710 × 10.sup.-10                        A.sub.8 = -2.54470 × 10.sup.-6 A.sub.10 = -7.56630 × 10.sup.-13                        A.sub.10 = 6.49020 × 10.sup.-8 A.sub.12 = 1.15350 × 10.sup.-15                        A.sub.12 = -6.57850 × 10.sup.-103rd   κ = 3.14850 × 10.sup.1                12th    κ = -2.43700 × 10.sup.-1surface A.sub.2 = 0    surface A.sub.2 = 0 A.sub.4 = 9.65540 × 10.sup.-6                        A.sub.4 = -5.60900 × 10.sup.-4 A.sub.6 = -1.15050 × 10.sup.-8                        A.sub.6 = 5.73830 × 10.sup.-5 A.sub.8 = 2.21930 × 10.sup.-10                        A.sub.8 = -2.77800 × 10.sup.-6 A.sub.10 = -6.85650 × 10.sup.-13                        A.sub.10 = 6.81240 × 10.sup.-8 A.sub.12 = 7.67880 × 10.sup.-16                        A.sub.12 = -6.69890 × 10.sup.-108th   κ = -8.36850 × 10.sup.-1                13th    κ = -5.43750 × 10.sup.-2surface A.sub.2 = 0    surface A.sub.2 = 0 A.sub.4 = 2.31970 × 10.sup.-4                        A.sub.4 = -1.27960 × 10.sup.-4 A.sub.6 = 6.20760 × 10.sup.-6                        A.sub.6 = 2.00240 × 10.sup.-5 A.sub.8 = -4.30100 × 10.sup.-6                        A.sub.8 = -1.01170 × 10.sup.-6 A.sub.10 = 3.86300 × 10.sup.-7                        A.sub.10 = 2.23560 × 10.sup.-8 A.sub.12 = -1.19710 × 10.sup.-8                        A.sub.12 = -1.95620 × 10.sup.-1010th  κ = -6.84560 × 10.sup.-2                15th    κ = -4.17320 × 10.sup.0surface A.sub.2 = 0    surface A.sub.2 = 0 A.sub.4 = 6.55630 × 10.sup.-5                        A.sub.4 = 5.88090 × 10.sup.-4 A.sub.6 = -4.40020 × 10.sup.-6                        A.sub.6 = 8.51510 × 10.sup.-6 A.sub.8 = -1.45310 × 10.sup.-7                        A.sub.8 = -9.83690 × 10.sup.-7 A.sub.10 = 5.55040 × 10.sup.-9                        A.sub.10 = 3.20330 × 10.sup.-8                        A.sub.12 = -3.89120 × 10.sup.-10______________________________________ 
    
     
                       TABLE 36______________________________________Variable intervalFocal length A      B          C    D______________________________________ 4.28         0.60  25.37      7.20  8.0514.56        14.77  11.20      3.38 11.8749.47        23.15   2.82      4.06 11.19______________________________________ 
    
     
                       TABLE 37______________________________________The change of back focus at normal temperature +30° C.:Δ f.sub.B value  Focal length          Δ f.sub.B______________________________________   4.28   +0.041  14.56   +0.019  49.47   -0.009______________________________________ |fw · Σ {1/f.sub.p(1) }| = 0.01 |fw · Σ {1/f.sub.p(2) }| = 0.15 |fw · Σ {1/f.sub.p(3, i) }| = 0.01 |r.sub.2 / f.sub.1 | = 0.61 
    
     The results of the foregoing show that in all Examples, there can be obtained a zoom lens having small aberration, the change in focal point due to temperature change is small and excellent optical performance with the zoom lens in which many plastic lenses are used. Incidentally, the distortion at wide angle end to the extent shown in the present Examples does not offer big problem. 
     According to the present invention, a zoom lens which is appropriate for still cameras or video cameras can be provided whose cost is greatly reduced compared to the conventional one by using many plastic lenses, even if the aperture ratio is high and variable magnification ratio is high. Moreover, it is possible to obtain the zoom lens which is not liable to be affected by temperature, even though many plastic lens are used thereby reducing the production cost thereof.