# Patent

## Title
High magnification zoom lens

## Abstract

A high magnification zoom lens system includes a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having positive refractive power, which are arranged in order from an object side. The third lens group includes three lens elements respectively having positive, positive, and negative refractive powers in order from the object side. The fourth lens group includes at least two positive lens elements and a doublet lens having positive refractive power as a whole, each lens group moves independently during magnification change. The high magnification zoom lens system satisfies the conditions that




  
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where fw is the focal length of the overall lens system at a wide-angle end, fbw is the back focal length of the lens system at the wide-angle position, β3,4w is the combined magnification ratio of the third and fourth lens groups at the wide-angle position, and β3,4T is the combined magnification ratio of the third and fourth lens groups at the telephoto position.

## Background
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
This application claims the benefit of Korean Patent Application No. 10-2006-0108367, filed on Nov. 3, 2006, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a compact and thin high magnification zoom lens.
2. Description of the Related Art
Digital still cameras (DSCs) are widely used as a photographing device. Some DSCs use, a three-group zoom lens of negative-positive-positive refractive powers having a half viewing angle at a wide angle position of 29 to 32 degrees and a magnification of 3×. The three-group zoom lens is widely used because the diameter or entire length of a lens can be miniaturized. In contrast, a typical silver halide single lens reflex uses 35 mm film and has a photographing lens which is changeable but results in a relatively large photographing device to accommodate changing lenses that are separately available in the market. However, a photographing device having a size smaller than 35 mm is in demand. In this case, since the viewing angle is narrow, an exchange lens having a short focal length is needed. Changing lenses, however, introduces the risk of dust or other debris entering the camera and damaging it or degrading performance. Thus, a high magnification zoom lens capable of photographing without changing lenses is desired.
FIG. 1 illustrates a four-group type zoom lens disclosed in Japanese Laid-open Patent Publication No. 2003-241,097. Referring to FIG. 1, the zoom lens includes a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, and a fourth lens group G4 having positive refractive power, in order from the object side. When the magnification changes from the wide-angle position to the telephoto position, the distance between the first and second lens groups decreases and the distance between the first, third, and fourth lens groups decrease. Also, the first, third, and fourth lens groups move toward the object. Focusing is performed by movement of only the second lens group. Reference numerals in FIG. 1 show surface numbers of each lens. Although the zoom lens has a high magnification of about 10 times, the viewing angle is too narrow.
SUMMARY OF THE INVENTION
To solve the above and/or other problems, the present invention provides a zoom lens having a short focal length and provides both a wide angle viewing and high magnification.
According to an aspect of the present invention, a high magnification zoom lens includes a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having positive refractive power, which are arranged respectively in order from an object side, wherein the third lens group comprises three lens elements respectively having positive, positive, and negative refractive powers in order from the object side, the fourth lens group comprises at least two positive lens elements and a doublet lens having positive refractive power as a whole, each lens group moves independently during magnification change, and the high magnification zoom lens satisfies the conditions that



  
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where fw is a focal length of an overall lens system at a wide-angle end, fbw is a back focal length of a lens system at the wide-angle end, β3,4w is a combined magnification ratio of the third and fourth lens groups at the wide-angle end, and β3,4T is a combined magnification ratio of the third and fourth lens groups at a telephoto end.

According to another aspect of the present invention, a high magnification zoom lens includes a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having positive refractive power, which are arranged in order from an object side, wherein the third lens group comprises three lens elements respectively having positive, positive, and negative refractive powers in order from the object side, each lens group moves independently during magnification change, and the high magnification zoom lens satisfies the conditions that




  
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where fw is a focal length of an overall lens system at a wide-angle end, fbw is a back focal length of a lens system at the wide-angle end, β3,4w is a combined magnification ratio of the third and fourth lens groups at the wide-angle end, β3,4T is a combined magnification ratio of the third and fourth lens groups at a telephoto end, and fT is a focal length of the overall lens system at the telephoto end.




BRIEF DESCRIPTION OF THE DRAWINGS
The above and other features and advantages of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings in which:
FIG. 1 illustrates the lens system and magnification change of the zoom lens disclosed in Japanese Laid-open Patent Publication No. 2003-241,097;
FIGS. 2A, 2B, and 2C respectively illustrate the configurations at a wide-angle position, a middle angle position, and a telephoto position of a high magnification zoom lens according to an embodiment of the present invention;
FIGS. 3A, 3B, and 3C respectively illustrate the spherical aberration, astigmatic field curvature, and distortion at the wide-angle end of the high magnification zoom lens of FIGS. 2A, 2B, and 2C;
FIG. 4 illustrates the lateral color at the wide-angle end of the high magnification zoom lens of FIGS. 2A, 2B, and 2C;
FIGS. 5A, 5B, and 5C respectively illustrate the spherical aberration, astigmatic field curvature, and distortion at the middle end of the high magnification zoom lens of FIGS. 2A, 2B, and 2C;
FIG. 6 illustrates the lateral color at the middle end of the high magnification zoom lens of FIGS. 2A, 2B, and 2C;
FIGS. 7A, 7B, and 7C respectively illustrate the spherical aberration, astigmatic field curvature, and distortion at the telephoto end of the high magnification zoom lens of FIGS. 2A, 2B, and 2C;
FIG. 8 illustrates the lateral color at the telephoto end of the high magnification zoom lens of FIGS. 2A, 2B, and 2C;
FIGS. 9A, 9B, and 9C respectively illustrate the configurations at a wide-angle position, a middle angle, and a telephoto position of a high magnification zoom lens according to another embodiment of the present invention;
FIGS. 10A, 10B, and 10C respectively illustrate the spherical aberration, astigmatic field curvature, and distortion at the wide-angle position of the high magnification zoom lens of FIGS. 9A, 9B, and 9C;
FIG. 11 illustrates the lateral color at the wide-angle position of the high magnification zoom lens of FIGS. 9A, 9B, and 9C;
FIGS. 12A, 12B, and 12C respectively illustrate the spherical aberration, astigmatic field curvature, and distortion at the middle angle position of the high magnification zoom lens of FIGS. 9A, 9B, and 9C;
FIG. 13 illustrates the lateral color at the middle angle position of the high magnification zoom lens of FIGS. 9A, 9B, and 9C;
FIGS. 14A, 14B, and 14C respectively illustrate the spherical aberration, astigmatic field curvature, and distortion at the telephoto position of the high magnification zoom lens of FIGS. 9A, 9B, and 9C;
FIG. 15 illustrates the lateral color at the telephoto position of the high magnification zoom lens of FIGS. 9A, 9B, and 9C;
FIGS. 16A, 16B, and 16C respectively illustrate the configurations at a wide-angle position, a middle angle position, and a telephoto position of a high magnification zoom lens according to yet another embodiment of the present invention;
FIGS. 17A, 17B, and 17C respectively illustrate the spherical aberration, astigmatic field curvature, and distortion at the wide-angle position of the high magnification zoom lens of FIGS. 16A, 16B, and 16C;
FIG. 18 illustrates the lateral color at the wide-angle position of the high magnification zoom lens of FIGS. 16A, 16B, and 16C;
FIGS. 19A, 19B, and 19C respectively illustrate the spherical aberration, astigmatic field curvature, and distortion at the middle angle position of the high magnification zoom lens of FIGS. 16A, 16B, and 16C;
FIG. 20 illustrates the lateral color at the middle angle position of the high magnification zoom lens of FIGS. 16A, 16B, and 16C;
FIGS. 21A, 21B, and 21C respectively illustrate the spherical aberration, astigmatic field curvature, and distortion at the telephoto position of the high magnification zoom lens of FIGS. 16A, 16B, and 16C;
FIG. 22 illustrates the lateral color at the telephoto position of the high magnification zoom lens of FIGS. 16A, 16B, and 16C;
FIGS. 23A, 23B, and 23C respectively illustrate the configurations at a wide-angle position, a middle angle position, and a telephoto position of a high magnification zoom lens according to another embodiment of the present invention;
FIGS. 24A, 24B, and 24C respectively illustrate the spherical aberration, astigmatic field curvature, and distortion at the wide-angle position of the high magnification zoom lens of FIGS. 23A, 23B, and 23C;
FIG. 25 illustrates the lateral color at the wide-angle position of the high magnification zoom lens of FIGS. 23A, 23B, and 23C;
FIGS. 26A, 26B, and 26C respectively illustrate the spherical aberration, astigmatic field curvature, and distortion at the middle angle position end of the high magnification zoom lens of FIGS. 23A, 23B, and 23C;
FIG. 27 illustrates the lateral color at the middle angle position of the high magnification zoom lens of FIGS. 23A, 23B, and 23C;
FIGS. 28A, 28B, and 28C respectively illustrate the spherical aberration, astigmatic field curvature, and distortion at the telephoto position of the high magnification zoom lens of FIGS. 23A, 23B, and 23C;
FIG. 29 illustrates the lateral color at the telephoto position of the high magnification zoom lens of FIGS. 23A, 23B, and 23C;
FIGS. 30A, 30B, and 30C respectively illustrate the configurations at a wide-angle position, a middle angle position, and a telephoto position of a high magnification zoom lens according to another embodiment of the present invention;
FIGS. 31A, 31B, and 31C respectively illustrate the spherical aberration, astigmatic field curvature, and distortion at the wide-angle position of the high magnification zoom lens of FIGS. 30A, 30B, and 30C;
FIG. 32 illustrates the lateral color at the wide-angle position of the high magnification zoom lens of FIGS. 30A, 30B, and 30C;
FIGS. 33A, 33B, and 33C respectively illustrate the spherical aberration, astigmatic field curvature, and distortion at the middle angle position of the high magnification zoom lens of FIGS. 30A, 30B, and 30C;
FIG. 34 illustrates the lateral color at the middle angle position of the high magnification zoom lens of FIGS. 30A, 30B, and 30C;
FIGS. 35A, 35B, and 35C respectively illustrate the spherical aberration, astigmatic field curvature, and distortion at the telephoto position of the high magnification zoom lens of FIGS. 30A, 30B, and 30C;
FIG. 36 illustrates the lateral color at the telephoto position of the high magnification zoom lens of FIGS. 30A, 30B, and 30C;
FIGS. 37A, 37B, and 37C respectively illustrate the configurations at a wide-angle position, a middle angle position, and a telephoto position of a high magnification zoom lens according to another embodiment of the present invention;
FIGS. 38A, 38B, and 38C respectively illustrate the spherical aberration, astigmatic field curvature, and distortion at the wide-angle position of the high magnification zoom lens of FIGS. 37A, 37B, and 37C;
FIG. 39 illustrates the lateral color at the wide-angle position of the high magnification zoom lens of FIGS. 37A, 37B, and 37C;
FIGS. 40A, 40B, and 40C respectively illustrate the spherical aberration, astigmatic field curvature, and distortion at the middle angle position of the high magnification zoom lens of FIGS. 37A, 37B, and 37C;
FIG. 41 illustrates the lateral color at the middle angle position of the high magnification zoom lens of FIGS. 37A, 37B, and 37C;
FIGS. 42A, 42B, and 42C respectively illustrate the spherical aberration, astigmatic field curvature, and distortion at the telephoto position of the high magnification zoom lens of FIGS. 37A, 37B, and 37C;
FIG. 43 illustrates the lateral color at the telephoto position of the high magnification zoom lens of FIGS. 37A, 37B, and 37C;
FIGS. 44A, 44B, and 44C respectively illustrate the configurations at a wide-angle position, a middle angle position, and a telephoto position of a high magnification zoom lens according to another embodiment of the present invention;
FIGS. 45A, 45B, and 45C respectively illustrate the spherical aberration, astigmatic field curvature, and distortion at the wide-angle position of the high magnification zoom lens of FIGS. 44A, 44B, and 44C;
FIG. 46 illustrates the lateral color at the wide-angle position of the high magnification zoom lens of FIGS. 44A, 44B, and 44C;
FIGS. 47A, 47B, and 47C respectively illustrate the spherical aberration, astigmatic field curvature, and distortion at the middle angle position of the high magnification zoom lens of FIGS. 44A, 44B, and 44C;
FIG. 48 illustrates the lateral color at the middle angle position of the high magnification zoom lens of FIGS. 44A, 44B, and 44C;
FIGS. 49A, 49B, and 49C respectively illustrate the spherical aberration, astigmatic field curvature, and distortion at the telephoto position of the high magnification zoom lens of FIGS. 44A, 44B, and 44C;
FIG. 50 illustrates the lateral color at the telephoto position of the high magnification zoom lens of FIGS. 44A, 44B, and 44C;
FIGS. 51A, 51B, and 51C respectively illustrate the configurations at a wide-angle position, a middle angle position, and a telephoto position of a high magnification zoom lens according to another embodiment of the present invention;
FIGS. 52A, 52B, and 52C respectively illustrate the spherical aberration, astigmatic field curvature, and distortion at the wide-angle position of the high magnification zoom lens of FIGS. 51A, 51B, and 51C;
FIG. 53 illustrates the lateral color at the wide-angle position of the high magnification zoom lens of FIGS. 51A, 51B, and 51C;
FIGS. 54A, 54B, and 54C respectively illustrate the spherical aberration, astigmatic field curvature, and distortion at the middle angle position of the high magnification zoom lens of FIGS. 51A, 51B, and 51C;
FIG. 55 illustrates the lateral color at the middle angle position of the high magnification zoom lens of FIGS. 51A, 51B, and 51C;
FIGS. 56A, 56B, and 56C respectively illustrate the spherical aberration, astigmatic field curvature, and distortion at the telephoto position of the high magnification zoom lens of FIGS. 51A, 51B, and 51C; and
FIG. 57 illustrates the lateral color at the telephoto position of the high magnification zoom lens of FIGS. 51A, 51B, and 51C.



DETAILED DESCRIPTION OF THE INVENTION
Referring to FIGS. 2A, 2B, and 2C, the high magnification zoom lens includes a first lens group Gr1, a second lens group Gr2, a third lens group Gr3, and a fourth lens group Gr4 which are arranged respectively in order from the object side. During magnification change, the first through fourth lens groups Gr1 through Gr4 move independently.
The first lens group Gr1 has positive refractive power, the second lens group Gr2 has negative refractive power, the third lens group Gr3 has positive refractive power, and the fourth lens group Gr4 has positive refractive power. The second, third, and fourth lens groups Gr2, Gr3, and Gr4 each have at least one aspherical surface.
The first lens group Gr1 includes, for example, first, second, and third lens elements 101-1, 102-1, and 103-1. The second lens group Gr2 includes fourth, fifth, sixth, and seventh lens elements 104-1, 105-1, 106-1, and 107-1. The fourth lens element 104-1 that is the first lens element of the second lens group Gr2 from the object side may have an aspherical surface. In FIG. 2, an aspherical surface is provided at the first lens element of the second lens group Gr2 from the object side. The lens element having the aspherical surface may be formed of a hybrid lens. The hybrid lens is an aspherical lens having an aspherical surface formed by coating at least one glass lens with resin.
The third lens group Gr3 includes three lens elements, for example, an eighth lens element 108-1 having positive refractive power, a ninth lens element 109-1 having positive refractive power, and a tenth lens element 110-1 having negative refractive power which are arranged respectively in order from the object side. The first lens element of the third lens group Gr3 from the object side, that is, the eighth lens element 108-1, may have an aspherical surface. The aspherical surface may be formed of a hybrid lens. An aperture stop ST is provided between the second lens group Gr2 and the third lens group Gr3 and is moved together with the third lens group Gr3.
The fourth lens group Gr4 includes at least two positive lens elements and a doublet lens, and has a positive refractive power as a whole. In FIG. 2, the fourth lens group Gr4 includes, for example, an eleventh lens element 111-1 having positive refractive power, a twelfth lens element 112-1 having positive refractive power, and a positive doublet lens 113-1 and 114-1. Also, the fourth lens group Gr4 may include, as shown in FIG. 16, a positive eleventh lens element 111-3, a positive twelfth lens element 112-3, a negative thirteenth lens element 113-3, and a positive doublet lens 114-3 and 115-3 which are arranged respectively in order from the object side. The fourth lens group Gr4 may include at least one aspherical surface. For example, an aspherical surface may be formed at the first lens element from the object side. The aspherical surface may be formed of a hybrid lens.
The relationship between the overall focal length and the back focal length at the wide-angle position of the zoom lens is shown below.




  
    
      
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In Inequality 1, fw is the focal length of the overall lens system at the wide-angle position and fbw is the back focal length of the lens system at the wide-angle position. Above the upper limit of Inequality 1, the back focal length to the focal length decreases. This is advantageous in the wide-angle position but fringe back used for a single lens reflex camera cannot be secured. Under the lower limit of Inequality 1, the fringe back can be secured but the zoom lens has a strong back focus so that greater negative distortion and astigmatic field curvature are generated.
The following is the magnification of the third and fourth lens groups. The zoom lens according to the present embodiment satisfies the following conditions.




  
    
      
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In Inequality 2, β3,4w is a combined magnification ratio of the third and fourth lens groups at the wide-angle position and β3,4T is a combined magnification of the third and fourth lens groups at the telephoto position. The third and fourth lens groups serve to maintain good astigmatism throughout the entire area of the zoom lens system by changing the interval therebetween during magnification change. Under the lower limit of Inequality 2, it is not possible to achieve high magnification change while maintaining good aberration of the overall lens system. In particular, the refractive power of the third and fourth lens groups become strong so that acceptable astigmatism cannot be maintained. Above the upper limit of Inequality 2, since the third and fourth lens groups have sufficient refractive power, high magnification can be achieved and the astigmatism is easily maintained in the overall lens system. However, when the refractive power increases, eccentricity sensitivity increases to an extent that manufacture of the lens system is difficult.
The zoom lens of the present embodiment has the following high magnification.




  
    
      
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In Inequality 3, fT is the focal length of the overall lens system at the telephoto position and fw is the focal length of the overall lens system at the wide-angle position.
Preferably, the first lens group Gr1 satisfies the following condition.




  
    
      
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In Inequality 4, f1 is the focal length of the first lens group. Inequality 4 shows the refractive power of the first lens group. Under the lower limit of Inequality 4, the refractive power of the first lens group is weak and the focal length increases so that the magnification of the lens groups other than the first lens group at the telephoto end decreases. Thus, aberration is not increased and it is easy to correct aberration. However, when the back focal length is secured at the wide-angle position while maintaining a relatively short overall length, the negative refractive power of the second lens group, which is mainly responsible for the magnification change, decreases so that the amount of movement during the magnification change increases. Also, since the overall length at the telephoto position increases, the structure of the barrel becomes complicated. Above the upper limit of Inequality 4, the refractive power of the first lens group increases and the refractive power of the second lens group increases as well so that the amount of movement during the magnification change decreases. Thus, although it is advantageous to make a compact zoom lens and form a barrel, since the refractive power of the second lens group is too strong, significant aberration is generated in the second lens group. As a result, it is impossible to maintain good aberration throughout the overall area of the lens system.
The refractive power of the fourth lens group is shown below and the zoom lens according to the present embodiment satisfies the following condition.




  
    
      
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In Inequality 5, f4 is the focal length of the fourth lens group. Under the lower limit of Inequality 5, the refractive power of the fourth lens group decreases so that it is advantageous to secure the back focal length at the wide-angle position. Also, the relative eccentricity sensitivity of the third and fourth lens groups decrease. Thus, the effect of correcting astigmatism in the overall area of the lens system is insufficient with the relatively small amount of zoom movement. Above the upper limit of Inequality 5, the refractive power of the fourth lens group increases so that the correction of the astigmatism is advantageous. However, it is difficult to secure the back focal length at the wide-angle position and maintain the relative eccentricity sensitivity of the third lens group small.
The fourth lens group includes a lens element having positive refractive power, another lens element having positive refractive power, a lens element having negative refractive power and a strong concave surface facing the image side, and a doublet lens having positive refractive power as a whole which are arranged respectively in order from the object side. Since the fourth lens group is separated from the aperture stop toward the image side, a burden of correction of aberration changing in a viewing angle direction is great compared to the third lens group. Thus, the fourth lens group includes more lens elements than those of the third lens group. The lens having positive refractive power at the object side is formed of two lens units so that the flux of light divergent from the second lens group having negative refractive power is concentrated by the third lens group having positive refractive power and the flux of light accessing the fourth lens group parallel to each other is concentrated again on an image surface. Therefore, the generation of spherical aberration and coma aberration is mainly reduced, the lens having negative refractive power corrects spherical aberration, and the lens having positive refractive power at the image surface is formed of a doublet lens to correct lateral chromatic aberration.
Also, in the present embodiment, an aspherical lens is adopted in each of the second, third, and fourth lens groups. In the high magnification lens, the amount of zoom movement needed to achieve high zoom magnification increases and the size thereof increases. However, by adopting the aspherical surface, the number of lens elements of each lens group and the thickness of each lens group can be reduced to avoid increasing the overall size of the high magnification lens system. However, in the first lens group, even when the aspherical lens is adopted, it is difficult to correct all of the astigmatism, spherical aberration, and coma aberration. Also, in the high magnification zoom, since it is difficult to decrease the number of lens elements of the second lens group to less than three, the present embodiment does not adopt the aspherical lens.
In the present embodiment, focusing of an object at a short distance is performed by moving the second lens group. In general, in the zoom lens in which the first lens group has positive refractive power, focusing is usually performed by the first lens group. However, greater movement of the first lens group is required in a high magnification system, which results in greater consumption of energy and reduction in the amount of peripheral light and the change in aberration during movement of lens, in an auto-focus camera in which a focus lens group is moved by a motor. In contrast, when the focusing operation is performed by the second lens group, since the lens group for the magnification change is moved, the viewing angle is changed. However, since the second lens group is smaller than the first lens group, energy consumption is small and the reduction of the amount of peripheral light is small. Also, even when the zoom lens moves significantly during magnification change, aberration changes are small so that the aberration change in the focusing operation is small.
In the meantime, the aspherical surface in the present embodiment is defined as follows. Assuming that an optical axis direction is an X axis, a direction perpendicular to the optical axis direction is a Y axis, and the direction in which a light ray proceeds is positive, the shape of the aspherical surface of the zoom lens according to the present embodiment can be expressed by the following equation.




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In Equation 6, x is the distance from the apex of the lens in the optical axis direction, h is the distance in the direction perpendicular to the optical axis, K is a conic constant, A4, A6, and A8, and A10 are aspherical coefficients, and c is a reciprocal (1/R) of the radius of curvature at the apex of a lens.
The present invention is related to a zoom lens suitable for a photographing device of a camera which has a high magnification ratio of about 9-12 times. Also, a common focal length from wide-angle to telephoto of 28 mm to 300 mm converted in terms of a 35 mm photo lens is embodied by a single camera lens.
The present invention includes lenses according to optimal conditions to embody the miniaturization of a zoom lens according to embodiments through the following various designs. Detailed lens data of various embodiments of a zoom lens according to the present invention are described below. In the following description, f is a combined focal length of the overall zoom lens system, FNO is an F number, 2w is a viewing angle, fb is a back focal length, R is a radius of curvature, D is a thickness of the center of a lens or an interval between lenses, an Nd is refractive power, and Vd is an Abbe number. Also, St is an aperture stop and D5, D14, D22, D30, and D32 are variable distances. In drawings illustrating the embodiments, numerals of each embodiment correspond to reference numerals of each lens.
EMBODIMENT 1
FIGS. 2A, 2B, and 2C respectively illustrate a wide-angle position, a middle angle position, and a telephoto position of a high magnification zoom lens system according to an embodiment of the present invention. Reference numeral 115-1 denotes a filter.











TABLE 1






Radius of
Thickness or
Refractive
Abbe



Curvature
Distance
Power
Number


Surface
(R)
(D)
(Nd)
(vd)



















1
119.139
1.30
1.84666
23.8


2
69.935
6.75
1.49700
81.6


3
−6256.068
0.10


4
65.908
5.18
1.72916
54.7


5
212.268
D5


6
923.887
0.03
1.53610
41.2


7
125.002
1.00
1.83500
43.0


8
15.334
6.39


9
−32.817
1.00
1.80420
46.5


10
51.486
0.10


11
36.593
4.70
1.84666
23.8


12
−36.593
2.24


13
−18.995
1.00
1.77250
49.6


14
−32.495
D14


15
Inf.(ST)
0.60


16
34.600
0.15
1.53610
41.2


17
36.544
3.16
1.49700
81.6


18
−655.923
0.10


19
21.362
5.02
1.48749
70.4


20
−44.594
0.67


21
−27.873
1.00
1.83400
37.3


22
258.467
D22


23
56.957
0.14
1.53610
41.2


24
150.404
3.54
1.54072
47.2


25
−31.968
0.10


26
90.189
3.46
1.51742
52.2


27
−40.231
0.10


28
71.520
1.00
1.83400
37.3


29
15.133
3.15
1.51680
64.2


30
23.842
D30


31
Inf.(FILTER)
4.00
1.51680
64.2


32
Inf.









Table 2 shows the aspherical coefficients of the zoom lens according to the present embodiment.













TABLE 2







K
A4
A6
A8
A10





















6
−1.000
2.28361E−05
−4.47122E−08
9.92250E−11
7.16140E−14


16
−1.000
1.10863E−05
−7.06322E−09
5.21498E−10
0.00000E+00


23
−1.000
−4.96143E−05  
  3.47894E−08
−3.06711E−11  
−1.15546E−12  









Table 3 shows the F numbers, variable distances D5, D14, D22, and D30, and the back focal lengths at the wide-angle position, the middle angle position, and the telephoto position.











TABLE 3







Wide-angle End
Middle End
Telephoto End





















f
18.609
60.040
193.925



FNO
3.61
5.21
5.77



D5
2.760
30.833
59.564



D14
30.740
12.199
1.001



D22
6.475
2.695
1.741



D30
34.404
60.818
75.600



fb
1.000
1.000
1.000










FIGS. 3A, 3B, 3C, and 4 respectively illustrate the spherical aberration, astigmatic field curvature, distortion, and lateral color at the wide-angle position of the high magnification zoom lens of FIGS. 2A, 2B, and 2C. FIGS. 5A, 5B, 5C, and 6 respectively illustrate the spherical aberration, astigmatic field curvature, distortion, and lateral color at the middle angle position of the high magnification zoom lens of FIGS. 2A, 2B, and 2C. FIGS. 7A, 7B, 7C, and 8 respectively illustrate the spherical aberration, astigmatic field curvature, distortion, and lateral color at the telephoto position of the high magnification zoom lens of FIGS. 2A, 2B, and 2C. The astigmatic field curvature is tangential astigmatic field curvature T and sagittal astigmatic field curvature S. In the following embodiments, the descriptions about the drawings and tables which are the same as those of the present embodiment are omitted.
EMBODIMENT 2











TABLE 4







Thickness
Refractive




Radius of Curvature
or Distance
Power
Abbe Number


Surface
(R)
(D)
(Nd)
(vd)



















1
103.514
1.30
1.84666
23.8


2
63.226
7.10
1.49700
81.6


3
2650.078
0.10


4
63.216
5.35
1.72916
54.7


5
208.604
D5


6
156.037
0.02
1.53610
41.2


7
83.049
1.00
1.83500
43


8
14.093
6.62


9
−31.291
1.00
1.80420
46.5


10
45.045
0.10


11
32.289
4.91
1.84666
23.8


12
−32.289
1.29


13
−19.978
1.00
1.77250
49.6


14
−53.299
D14


15
Inf.(STOP)
0.60


16
37.477
0.20
1.53610
41.2


17
46.674
3.27
1.49700
81.6


18
−77.808
0.10


19
21.948
5.41
1.48749
70.4


20
−29.775
0.67


21
−28.540
1.00
1.83400
37.3


22
63.945
D22


23
40.092
0.03
1.53610
41.2


24
49.878
3.94
1.54072
47.2


25
−36.201
0.10


26
84.390
3.04
1.51742
52.2


27
−63.425
0.56


28
−163.676
1.00
1.83400
37.3


29
24.273
1.76


30
329.972
3.34
1.51680
64.2


31
−37.663
D31


32
Inf.(FILTER)
4.00
1.51680
64.2


33
Inf.









Table 5 shows the aspherical coefficients of the zoom lens according to the present embodiment.













TABLE 5







K
A4
A6
A8
A10





















6
−1.000
1.88758E−05
−4.51670E−08
1.61416E−10
−1.44849E−13


16
−1.000
2.92148E−06
−1.27437E−07
2.17029E−09
−1.22897E−11


23
−1.000
−2.85933E−05  
  3.00245E−08
1.02213E−11
−9.76324E−13




















TABLE 6







Wide-angle End
Middle End
Telephoto End





















f
18.599
60.058
193.962



FNO
3.61
5.40
5.77



D5
2.515
30.107
56.056



D14
26.990
10.923
1.000



D22
7.716
2.772
1.600



D31
34.400
61.690
76.538



fb
1.000
1.000
1.000










EMBODIMENT 3











TABLE 7







Thickness
Refractive




Radius of Curvature
or Distance
Power
Abbe Number


Surface
(R)
(D)
(Nd)
(vd)



















1
116.292
1.30
1.84666
23.8


2
66.116
7.41
1.49700
81.6


3
−737.336
0.10


4
58.421
5.47
1.72916
54.7


5
171.519
D5


6
191.658
0.02
1.53610
41.2


7
92.634
1.00
1.83500
43


8
14.069
6.60


9
−31.652
1.00
1.80420
46.5


10
40.913
0.10


11
30.882
5.08
1.84666
23.8


12
−30.882
1.64


13
−19.594
1.00
1.77250
49.6


14
−63.415
D14


15
Inf.(STOP)
0.60


16
42.742
0.20
1.53610
41.2


17
55.950
3.14
1.49700
81.6


18
−67.808
0.10


19
23.237
4.87
1.48749
70.4


20
−36.957
0.60


21
−33.264
1.00
1.83400
37.3


22
73.583
D22


23
35.984
0.20
1.53610
41.2


24
50.645
3.88
1.58267
46.5


25
−37.235
0.10


26
59.720
2.76
1.58267
46.5


27
−195.429
1.04


28
−194.587
1.00
1.83400
37.2


29
23.289
1.50


30
104.381
1.00
1.75520
27.5


31
31.057
4.56
1.54814
45.8


32
−38.977
D32


33
Inf.(FILTER)
4.00
1.51680
64.2


34
Inf.





















TABLE 8





Surface
K
A4
A6
A8
A10




















6
−1.000
1.94570E−05
−4.86659E−08
1.82542E−10
−2.80721E−13


16
−1.000
2.94083E−06
−1.50163E−07
2.52438E−09
−1.45167E−11


23
−1.000
−2.42694E−05  
  6.53243E−08
−5.05050E−10  
  1.50844E−12




















TABLE 9







Wide-angle End
Middle End
Telephoto End





















f
18.598
60.059
193.907



FNO
3.6
5.40
5.77



D5
2.387
29.293
53.974



D14
24.214
10.021
1.000



D22
8.147
2.991
1.600



D32
34.413
61.771
76.124



fb
1.000
1.000
1.000










EMBODIMENT 4











TABLE 10







Thickness
Refractive




Radius of Curvature
or Distance
Power
Abbe Number


Surface
(R)
(D)
(Nd)
(vd)



















1
111.458
1.30
1.84666
23.8


2
64.301
7.46
1.49700
81.6


3
−943.418
0.10


4
58.051
5.52
1.72916
54.7


5
173.390
D5


6
207.725
0.02
1.53610
41.2


7
94.222
1.00
1.83500
43


8
13.999
6.61


9
−31.219
1.00
1.80420
46.5


10
39.255
0.10


11
30.356
5.13
1.84666
23.8


12
−30.356
1.73


13
−19.325
1.00
1.77250
49.6


14
−60.302
D14


15
Inf.(STOP)
0.60


16
39.252
0.20
1.53610
41.2


17
49.693
3.13
1.49700
81.6


18
−80.102
0.10


19
23.346
4.93
1.48749
70.4


20
−34.273
0.69


21
−30.598
1.00
1.83400
37.3


22
72.621
D22


23
35.402
0.20
1.53610
41.2


24
50.956
4.01
1.57099
50.9


25
−33.910
0.10


26
87.874
2.88
1.54814
45.8


27
−76.004
1.24


28
−171.585
1.00
1.83400
37.3


29
22.760
1.59


30
120.663
4.58
1.54814
45.8


31
−20.146
1.00
1.69895
30.1


32
−37.636
D32


33
Inf.(FILTER)
4.00
1.51680
64.2


34
Inf.





















TABLE 11





surface
K
A4
A6
A8
A10




















6
−1.000
2.07374E−05
−4.59433E−08
1.61187E−10
−2.39484E−13


16
−1.000
1.81996E−06
−1.59424E−07
2.72262E−09
−1.54147E−11


23
−1.000
−2.31917E−05  
  7.10315E−08
−6.82249E−10  
  2.55080E−12




















TABLE 12







Wide-angle End
Middle End
Telephoto End





















f
18.602
60.053
193.945



FNO
3.61
5.40
5.77



2w
74.91
26.70
8.40



D5
2.400
29.728
53.839



D14
24.206
10.217
1.000



D22
7.427
2.877
1.600



D32
34.402
60.581
75.564



fb
1.000
1.000
1.000










EMBODIMENT 5











TABLE 13







Thickness
Refractive




Radius of Curvature
or Distance
Power
Abbe Number


Surface
(R)
(D)
(Nd)
(vd)



















1
111.458
1.30
1.84666
23.8


2
64.301
7.46
1.49700
81.6


3
−943.418
0.10


4
58.051
5.52
1.72916
54.7


5
173.390
D5


6
207.725
0.02
1.53610
41.2


7
94.222
1.00
1.83500
43


8
13.999
6.61


9
−31.219
1.00
1.80420
46.5


10
39.255
0.10


11
30.356
5.13
1.84666
23.8


12
−30.356
1.73


13
−19.325
1.00
1.77250
49.6


14
−60.302
D14


15
Inf.(STOP)
0.60


16
39.252
0.20
1.53610
41.2


17
49.693
3.13
1.49700
81.6


18
−80.102
0.10


19
23.346
4.93
1.48749
70.4


20
−34.273
0.69


21
−30.598
1.00
1.83400
37.3


22
72.621
D22


23
35.402
0.20
1.53610
41.2


24
50.956
4.01
1.57099
50.9


25
−33.910
0.10


26
87.874
2.88
1.54814
45.8


27
−76.004
1.24


28
−171.585
1.00
1.83400
37.3


29
22.760
1.59


30
120.663
4.58
1.54814
45.8


31
−20.146
1.00
1.69895
30.1


32
−37.636
D32


33
Inf.(FILTER)
4.00
1.51680
64.2


34
Inf.





















TABLE 14





Surface
K
A4
A6
A8
A10




















6
−1.000
2.06855E−05
−5.38985E−08
1.95853E−10
−2.96967E−13


16
−1.000
3.41143E−06
−1.49099E−07
2.45487E−09
−1.38191E−11


23
−1.000
−2.79691E−05  
  6.98254E−08
−5.05665E−10  
  1.45373E−12




















TABLE 15







Wide-angle End
Middle End
Telephoto End





















f
18.598
60.051
193.912



FNO
3.61
5.40
5.77



D5
2.376
29.289
53.248



D14
23.912
10.050
1.000



D22
7.504
2.916
1.600



D32
34.411
61.254
75.899



fb
1.000
1.000
1.000










EMBODIMENT 6











TABLE 16







Thickness
Refractive




Radius of Curvature
or Distance
Power
Abbe Number


Surface
(R)
(D)
(Nd)
(vd)



















1
111.321
1.30
1.84666
23.8


2
64.506
7.42
1.49700
81.6


3
−1012.345
0.10


4
57.981
5.49
1.72916
54.7


5
170.001
D5


6
179.214
0.02
1.53610
41.2


7
85.755
1.00
1.83500
43.0


8
13.801
6.32


9
−29.987
1.00
1.80420
46.5


10
42.487
0.10


11
31.348
4.90
1.84666
23.8


12
−31.348
2.14


13
−18.793
1.00
1.77250
49.6


14
−51.216
D14


15
Inf.(STOP)
0.60


16
40.097
0.20
1.53610
41.2


17
51.832
3.32
1.43875
94.9


18
−49.648
0.10


19
23.243
5.04
1.51742
52.2


20
−30.167
1.00
1.83400
37.3


21
56.344
D21


22
33.426
0.20
1.53610
41.2


23
44.636
3.83
1.58913
61.3


24
−42.765
0.10


25
68.985
3.10
1.58144
40.9


26
−90.275
1.12


27
−191.78
1.00
1.83400
37.3


28
21.191
1.73


29
135.373
4.55
1.58144
40.9


30
−19.524
1.00
1.76182
26.6


31
−36.336
D31


32
Inf.(FILTER)
4.00
1.51680
64.2


33
Inf.





















TABLE 17





Surface
K
A4
A6
A8
A10




















6
−1.000
2.12877E−05
−5.34987E−08
2.00628E−10
−2.84803E−13


16
−1.000
2.01794E−06
−1.40982E−07
2.44151E−09
−1.40006E−11


22
−1.000
−2.02994E−05  
  6.13913E−08
−5.64655E−10  
  1.95935E−12




















TABLE 18







Wide-angle End
Middle End
Telephoto End





















f
18.595
60.069
193.923



FNO
3.61
5.40
5.77



D5
2.368
30.147
53.678



D14
23.835
10.120
1.000



D21
8.123
2.983
1.600



D31
34.423
60.439
76.004



fb
1.000
1.000
1.000










EMBODIMENT 7











TABLE 19







Thickness
Refractive




Radius of Curvature
or Distance
Power
Abbe Number


Surface
(R)
(D)
(Nd)
(vd)



















1
111.743
1.30
1.84666
23.8


2
65.150
7.34
1.49700
81.6


3
−1083.310
0.10


4
58.682
5.44
1.72916
54.7


5
171.718
D5


6
269.978
0.02
1.53610
41.2


7
95.628
1.00
1.83500
43.0


8
14.081
6.21


9
−29.358
1.00
1.80420
46.5


10
41.488
0.10


11
31.601
5.07
1.84666
23.8


12
−31.601
2.86


13
−18.208
1.00
1.77250
49.6


14
−41.239
D14


15
Inf.(STOP)
0.60


16
46.135
0.16
1.53610
41.2


17
56.324
3.37
1.43875
94.9


18
−42.910
0.10


19
21.523
5.32
1.51742
52.2


20
−27.127
1.00
1.83400
37.3


21
48.546
D21


22
26.135
0.02
1.53610
41.2


23
27.872
4.34
1.56883
56.0


24
−47.251
0.10


25
67.651
2.93
1.61310
44.4


26
−85.508
0.56


27
−884.005
1.00
1.83400
37.3


28
18.397
1.78


29
82.030
4.94
1.60562
43.9


30
−17.056
1.00
1.83400
37.3


31
−39.619
D31


32
Inf.(FILTER)
4.00
1.51680
64.2


33
Inf.





















TABLE 20





Surface
K
A4
A6
A8
A10




















6
−1.000
2.37306E−05
−6.70281E−08
2.53625E−10
−3.77265E−13


16
−1.000
2.94368E−06
−1.10467E−07
1.96479E−09
−1.07803E−11


22
−1.000
−1.67855E−05  
  6.46721E−08
−7.49482E−10  
  2.94548E−12




















TABLE 21







Wide-angle End
Middle End
Telephoto End





















f
18.594
60.057
193.984



FNO
3.61
5.40
5.77



D5
2.398
30.162
54.412



D14
24.235
10.248
1.000



D21
7.722
2.826
1.600



D31
34.411
60.575
75.309



fb
1.000
1.000
1.000










EMBODIMENT 8











TABLE 22







Thickness
Refractive




Radius of Curvature
or Distance
Power
Abbe Number


Surface
(R)
(D)
(Nd)
(vd)



















1
77.623
1.30
1.84666
23.8


2
52.595
7.25
1.49700
81.6


3
286.202
0.10


4
57.978
5.38
1.72916
54.7


5
161.599
D5


6
267.543
0.02
1.53610
41.2


7
79.502
1.00
1.83500
43.0


8
13.481
6.83


9
−29.358
1.00
1.80420
46.5


10
44.272
0.10


11
33.111
4.76
1.84666
23.8


12
−33.111
1.71


13
−17.870
1.00
1.77250
49.6


14
−33.587
D14


15
Inf.(STOP)
0.60


16
47.424
0.02
1.53610
41.2


17
48.245
3.46
1.43875
94.9


18
−65.481
0.10


19
37.015
4.21
1.51742
52.1


20
−42.024
1.00
1.83400
37.3


21
154.123
D21


22
16.674
0.02
1.53610
41.2


23
16.505
5.48
1.48749
70.4


24
−65.020
0.10


25
2371.342
2.51
1.48749
70.4


26
−61.171
0.10


27
67.542
1.00
1.83400
37.3


28
14.954
1.71


29
34.518
6.04
1.59551
39.2


30
−13.550
1.00
1.83400
37.3


31
−55.649
D31


32
Inf.(FILTER)
4.00
1.51680
64.2


33
Inf.





















TABLE 23





Surface
K
A4
A6
A8
A10




















7
−1.000
2.98624E−05
−6.74560E−08
1.60510E−10
1.10978E−13


17
−1.000
−2.16915E−06  
−4.77683E−09
1.20000E−12
0.00000E+00


23
−1.000
8.30812E−06
−1.17966E−08
0.00000E+00
0.00000E+00




















TABLE 24







Wide-angle End
Middle End
Telephoto End





















F
18.649
60.059
193.710



FNO
3.61
5.40
5.80



2w
74.77
26.70
8.41



D5
2.482
28.921
53.626



D14
25.205
10.119
1.000



D21
11.034
3.839
1.600



D31
34.393
62.163
80.940



Fb
1.000
1.000
1.000










The following tables show that the above-described embodiments satisfy the conditions of the above Inequalities 1, 2, 4, and 5.















TABLE 25












Embodiment
Embodiment


Inequality
Embodiment 1
Embodiment 2
Embodiment 3
Embodiment 4
Embodiment 5
Embodiment 6
7
8























0.4 < fW/fbW < 0.55
0.489
0.489
0.489
0.489
0.489
0.489
0.489
0.490


0.35 < β3.4W/
0.380
0.397
0.406
0.406
0.409
0.409
0.410
0.372


β3.4T < 0.43


0.15 < fW/f1 < 0.22
0.183
0.196
0.204
0.204
0.207
0.206
0.203
0.199


0.28 < fW/f4 < 0.47
0.338
0.371
0.393
0.405
0.418
0.390
0.403
0.375


fW
18.609
18.599
18.598
18.602
18.598
18.595
18.594
18.649


fbW
38.041
38.037
38.050
38.040
38.048
38.060
38.048
38.030


β3W
−8.541
−16.043
28.692
12.256
9.521
24.405
12.338
14.004


β4W
0.104
0.062
−0.037
−0.086
−0.112
−0.044
−0.085
−0.072


β3T
3.612
3.194
2.838
2.636
2.494
2.861
2.645
2.705


β4T
−0.646
−0.778
−0.917
−0.982
−1.044
−0.915
−0.971
−1.007


f1
101.420
94.926
91.013
91.016
89.887
90.486
91.469
93.776


f4
54.974
50.162
47.376
45.943
44.517
47.727
46.196
49.788









Table 26 shows the focal length and magnification at the telephoto end for each embodiment.









TABLE 26









Embodiment
















1
2
3
4
5
6
7
8



















Ft
193.9251
193.9623
193.9068
193.9451
193.9124
193.9229
193.9836
193.7097


fT/fw
10.421
10.429
10.426
10.426
10.427
10.429
10.433
10.387









Referring to Table 26, it can be seen that the zoom lens system according to the present invention exhibits a high magnification ratio of about 10 times.
As described above, the high magnification zoom lens system according to the present invention provides a zoom lens system having a short focal lens and satisfying both the wide angle and high magnification change with a single lens system. No changing of lenses is necessary and the disadvantages of changing lenses is avoided.
While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

## Claims

1. A high magnification zoom lens system including a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having positive refractive power, which are arranged respectively in order from an object side, wherein the third lens group comprises three lens elements respectively having positive, positive, and negative refractive powers in order from the object side, the fourth lens group comprises at least two positive lens elements and a doublet lens and has a positive refractive power as a whole, each lens group moves independently during magnification change, and the high magnification zoom lens system satisfies the following conditions,



  
    0.40
    <
    
      
        f
        w
      
      
        f
        bw
      
    
    <
    
      0.55
      ⁢
      
        
      
      ⁢
      and
    
  




  
    
      0.35
      <
      
        
          β
          
            3
            ,
            
              4
              ⁢
              
                
              
              ⁢
              W
            
          
        
        
          β
          
            3
            ,
            
              4
              ⁢
              
                
              
              ⁢
              T
            
          
        
      
      <
      0.43
    
    ,
  


where fw is the focal length of the overall lens system at the wide-angle position, fbw is the back focal length of the lens system at the wide-angle position, β3,4w is the combined magnification of the third and fourth lens groups at the wide-angle position, and β3,4T is the combined magnification ratio of the third and fourth lens groups at the telephoto position.

2. The high magnification zoom lens system of claim 1, wherein the fourth lens group comprises three lens having positive, positive, and negative refractive powers, respectively, in order from the object side, and a positive doublet lens.

3. The high magnification zoom lens system of claim 1, wherein the zoom lens system satisfies the following condition,




  
    0.15
    <
    
      
        f
        W
      
      
        f
        1
      
    
    <
    0.22
  
  ,



where f1 is the focal length of the first lens group.

4. The high magnification zoom lens system of claim 1, wherein the zoom lens system satisfies the following condition,




  
    0.28
    <
    
      
        f
        W
      
      
        f
        4
      
    
    <
    0.47
  
  ,



where f4 is the focal length of the fourth lens group.

5. The high magnification zoom lens system of claim 1, wherein each of the second through fourth lens groups has at least one aspherical surface.

6. The high magnification zoom lens system of claim 5, wherein at least one the aspherical surface is formed of a hybrid lens.

7. The high magnification zoom lens system of claim 1, wherein focusing is performed by moving the second lens group when an object located at a short distance is photographed.

8. A high magnification zoom lens system including a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having positive refractive power, which are arranged respectively in order from an object side, wherein the third lens group comprises three lens elements respectively having positive, positive, and negative refractive powers in order from the object side, each lens group moves independently during magnification change, and the high magnification zoom lens system satisfies the following conditions,



  
    
      
        0.40
        <
        
          
            f
            w
          
          
            f
            bw
          
        
        <
        0.55
      
      ,
      
        

      
      ⁢
      
        0.35
        <
        
          
            β
            
              3
              ,
              
                4
                ⁢
                
                  
                
                ⁢
                W
              
            
          
          
            β
            
              3
              ,
              
                4
                ⁢
                
                  
                
                ⁢
                T
              
            
          
        
        <
        0.43
      
      ,
      
        
      
      ⁢
      and
    
    ⁢
    
      
    
  




  
    
      9
      <
      
        
          f
          T
        
        
          f
          W
        
      
      <
      12
    
    ,
  


where fw is the focal length of the overall lens system at the wide-angle position, fbw is the back focal length of the lens system at the wide-angle position, β3,4w is the combined magnification of the third and fourth lens groups at the wide-angle position, β3,4T is the combined magnification of the third and fourth lens groups at the telephoto position, and fT is the focal length of the overall lens system at the telephoto position.

9. The high magnification zoom lens system of claim 8, wherein the fourth lens group comprises three lens elements having positive, positive, and negative refractive powers, respectively, in order from the object side, and a positive doublet lens.

10. The high magnification zoom lens system of claim 8, wherein the zoom lens system satisfies the following condition,




  
    0.15
    <
    
      
        f
        W
      
      
        f
        1
      
    
    <
    0.22
  
  ,



where f1 is the focal length of the first lens group.

11. The high magnification zoom lens system of claim 8, wherein the zoom lens system satisfies the following condition,




  
    0.28
    <
    
      
        f
        W
      
      
        f
        4
      
    
    <
    0.47
  
  ,



where f4 is the focal length of the fourth lens group.

12. The high magnification zoom lens system of claim 8, wherein each of the second through fourth lens groups has at least one aspherical surface.

13. The high magnification zoom lens of claim 12, wherein at least one of the aspherical surfaces is formed of a hybrid lens.

14. The high magnification zoom lens system of claim 8, wherein focusing is performed by moving the second lens group when an object located at a short distance is photographed.