# Patent

## Title
Zooms lens system and photographing apparatus including the same

## Abstract

A zoom lens system and a photographing apparatus including the same, wherein the zoom lens system includes a first lens group including one or more lenses, and an optical member for changing a path of light, and having a positive refractive power; a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power, wherein zooming is performed by varying air gaps between the first through fourth lens groups.

## Background
CROSS-REFERENCE TO RELATED PATENT APPLICATION
This application claims priority from Korean Patent Application No. 10-2011-0001549 filed on Jan. 6, 2011 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
BACKGROUND
1. Field
Apparatuses consistent with exemplary embodiments relate to a zoom lens system and a photographing apparatus including the same.
2. Description of the Related Art
Recently, a zoom lens system used in photographing apparatuses such as digital cameras or digital camcorders having a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) needs to be small-sized and to have a high optical performance. However,it is difficult to simultaneously achieve a high performance and compactness, and if a high-refraction aspherical material is used for the compactness, manufacturing costs increase. Thus, it is difficult to simultaneously obtain a high optical performance and low manufacturing costs.
A photographing apparatus is classified as a retractable type or an inner-zoom type. With respect to the retractable type, a lens is outwardly projected from a camera when photographing is performed, and the lens is retracted into a camera body when the camera is not used. In this regard, since a lens group is projected from the camera and is externally exposed, a shock resistance function and a water-proof function of the camera may deteriorate. With respect to the inner-zoom type, an optical path is curved by using a reflective member so as to protect a photographing apparatus from an external environment. In a case of a lens system including a prism for reflection and/or refraction, the thickness of the lens system may be decreased by curving an optical path by 90°. In order to achieve compactness with a reflection member and/or a refraction member in which the thickness of a lens system is decreased by using a reflective member and/or a refractive member including a prism, a reflective mirror, or the like, various methods such as a method of limiting an overall length of the lens system, a method of restricting sensitivity, or the like have been presented.
SUMMARY
One or more exemplary embodiments provide a small zoom lens system.
One or more exemplary embodiments also provide a photographing apparatus including a small zoom lens system.
According to an aspect of an exemplary embodiment, there is provided a zoom lens system including a first lens group including one or more lenses, and an optical member for changing a path of light, and having a positive refractive power; a second lens group having a negative refractive power; a third lens group having a positive refractive power; and a fourth lens group having a positive refractive power, wherein the first lens group, the second lens group, the third lens group, and the fourth lens group are sequentially arranged from an object side to an image side, wherein zooming is performed by varying air gaps between the first through fourth lens groups, and wherein the zoom lens system satisfies the following expressions:




  
    1.8
    ≤
    
      
        f
        I
      
      
        
          
            f
            W
          
          ⁢
          
            f
            T
          
        
      
    
    ≤
    2.7
  
  ,
  
    

  
  ⁢
  
    
      and
      ⁢
      
        

      
      -
      1.0
    
    ≤
    
      
        f
        II
      
      
        
          
            f
            W
          
          ⁢
          
            f
            T
          
        
      
    
    ≤
    
      -
      0.7
    
  
  ,




where fW indicates an overall focal length at a wide angle end, fT indicates an overall focal length at a telephoto end, fl indicates a focal length of the first lens group, and fll indicates a focal length of the second lens group.

The third lens group may include an aperture.
The aperture may be disposed at the object side of the third lens group.
The optical member may include a prism and may satisfy the following expression:

nI(P)≧180,

where nI(P) indicates a refractive index of the optical member of the first lens group.

The first lens group may include a negative lens, the optical member for changing a path of light that has passed through the negative lens, and a positive lens.
The negative lens may be a meniscus lens having a convex surface toward the object side.
The fourth lens group may include a positive lens and a negative lens.
The fourth lens group may perform focusing.
The third lens group may include a positive lens, a positive lens, and a negative lens.
An F-number at the wide angle end may be equal to or less than 1.8.
The third lens group may include two or more lenses.
At least one of the first through fourth lens groups may include at least one aspherical lens.
At least one of the second through fourth lens groups may include at least one doublet lens.
The second lens group and the fourth lens group may move during zooming.
According to another aspect, there is provided a photographing apparatus including a zoom lens system; and an imaging sensor for converting an image formed by the zoom lens system into an electrical signal, wherein the zoom lens system includes a first lens group including one or more lenses, and an optical member for changing a path of light, and having a positive refractive power; a second lens group having a negative refractive power; a third lens group having a positive refractive power; and a fourth lens group having a positive refractive power, wherein the first lens group, the second lens group, the third lens group, and the fourth lens group are sequentially arranged from an object side to an image side, zooming is performed by varying air gaps between the first through fourth lens groups, and the zoom lens system satisfies the following expressions:




  
    1.8
    ≤
    
      
        f
        I
      
      
        
          
            f
            W
          
          ⁢
          
            f
            T
          
        
      
    
    ≤
    2.7
  
  ,
  
    

  
  ⁢
  
    
      and
      ⁢
      
        

      
      -
      1.0
    
    ≤
    
      
        f
        II
      
      
        
          
            f
            W
          
          ⁢
          
            f
            T
          
        
      
    
    ≤
    
      -
      0.7
    
  
  ,




where fW indicates an overall focal length at a wide angle end, fT indicates an overall focal length at a telephoto end, fl indicates a focal length of the first lens group, and fll indicates a focal length of the second lens group.




BRIEF DESCRIPTION OF THE DRAWINGS
The above and other aspects will become more apparent by describing in detail exemplary embodiments with reference to the attached drawings, in which:
FIG. 1 illustrates a zoom lens system at each of a wide angle end, a middle end, and a telephoto end according to an exemplary embodiment;
FIGS. 2A through 2C are graphs illustrating aberrations at the wide angle end, the middle end, and the telephoto end of the zoom lens system of FIG. 1, according to an exemplary embodiment;
FIG. 3 illustrates a zoom lens system at each of a wide angle end, a middle end, and a telephoto end according to another exemplary embodiment;
FIGS. 4A through 4C are graphs illustrating aberrations at the wide angle end, the middle end, and the telephoto end of the zoom lens system of FIG. 3, according to an exemplary embodiment;
FIG. 5 illustrates a zoom lens system at each of a wide angle end, a middle end, and a telephoto end according to another exemplary embodiment;
FIGS. 6A through 6C are graphs illustrating aberrations at the wide angle end, the middle end, and the telephoto end of the zoom lens system of FIG. 5, according to an exemplary embodiment;
FIG. 7 illustrates a zoom lens system at each of a wide angle end, a middle end, and a telephoto end according to another exemplary embodiment;
FIGS. 8A through 8C are graphs illustrating aberrations at the wide angle end, the middle end, and the telephoto end of the zoom lens system of FIG. 7, according to an exemplary embodiment;
FIG. 9 illustrates a zoom lens system at each of a wide angle end, a middle end, and a telephoto end according to another exemplary embodiment;
FIGS. 10A through 10C are graphs illustrating aberrations at the wide angle end, the middle end, and the telephoto end of the zoom lens system of FIG. 9, according to an exemplary embodiment;
FIG. 11 illustrates a zoom lens system at each of a wide angle end, a middle end, and a telephoto end according to another exemplary embodiment;
FIGS. 12A through 12C are graphs illustrating aberrations at the wide angle end, the middle end, and the telephoto end of the zoom lens system of FIG. 11, according to an exemplary embodiment;
FIG. 13 illustrates a zoom lens system at each of a wide angle end, a middle end, and a telephoto end according to another exemplary embodiment;
FIGS. 14A through 14C are graphs illustrating aberrations at the wide angle end, the middle end, and the telephoto end of the zoom lens system of FIG. 13, according to an exemplary embodiment;
FIG. 15 illustrates a zoom lens system at each of a wide angle end, a middle end, and a telephoto end according to another exemplary embodiment;
FIGS. 16A through 16C are graphs illustrating aberrations at the wide angle end, the middle end, and the telephoto end of the zoom lens system of FIG. 15, according to an exemplary embodiment; and
FIG. 17 is a diagram of a photographing apparatus including the zoom lens system, according to an exemplary embodiment.



DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
Hereinafter, exemplary embodiments will be described in detail with reference to the attached drawings. In the drawings, like reference numerals in the drawings denote like elements, and the size of each component may be exaggerated for clarity.
Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.
FIG. 1 illustrates a zoom lens system 1111 at each of a wide angle end, a middle end, and a telephoto end according to an exemplary embodiment. The zoom lens system 1111 includes a first lens group G1, a second lens group G2, a third lens group G3, and a fourth lens group G4 that are sequentially arranged from an object side O to an image side I. The first lens group GI has a positive refractive power. The first lens group G1 may include a first lens 1, optical members 2 and 3 for changing an optical path of light passing through the first lens 1 and a second lens 4. The first lens 1 may be a negative lens, and the second lens 4 may also be a negative lens. The optical members 2 and 3 may include a reflective mirror, a prism, or an optical fiber. For example, the reflective mirror may bend an optical path by reflecting light by 90°. The optical members 2 and 3 allow a space to be efficiently used by bending incident light by a predetermined degree such as 90° with respect to an optical axis, and thus a photographing apparatus including the zoom lens system 1111 may be small-sized.
The first lens 1 may be a meniscus lens having a convex surface toward the object side O. The second lens 4 may be a double-convex lens.
The second lens group G2 has a negative refractive power. For example; the second lens group G2 may include a third lens 5, a fourth lens 6, and a fifth lens 7. The third lens 5 and the fourth lens 6 may be double-concave lenses. The fifth lens 7 may be a meniscus lens having a convex surface toward the object side O.
The third lens group G3 has a positive refractive power. The third lens group G3 may include two lenses or three lenses. For example, the third lens group G3 may include a sixth lens 8, a seventh lens 9 and an eighth lens 10. The sixth lens 8 may be a double-convex lens, the seventh lens 9 may also be a double-convex lens, and the eighth lens 10 may be a double-concave lens. Also, the sixth lens 8 may be a positive lens, the seventh lens 9 may be a positive lens, and the eighth lens 10 may be a negative lens. The third lens group G3 may include an aperture ST. For example, the aperture ST may be disposed at the object side O of the sixth lens 8.
FIGS. 1, 3, and 5 correspond to a case in which the third lens group G3 of the zoom lens system 1111 includes three lenses. FIGS. 7, 9, 11, 13, and 15 correspond to a case in which the third lens group G3 of the zoom lens system 1111 includes two lenses. Referring to FIG. 7, the first lens group G1 may include a first lens 111, optical members 112 and 113, and a second lens 114. The second lens group G2 may include a third lens 115, a fourth lens 116, and a fifth lens 117. The third lens group G3 may include a sixth lens 118 and a seventh lens 119. The fourth lens group G4 may include an eighth lens 120 and a ninth lens 121. A reference numeral 122 indicates an optical filter. The sixth lens 118 and the seventh lens 119 may be bonded.
Referring back to FIG. 1, the fourth lens group G4 has a positive refractive power. For example, the fourth lens group G4 may include a ninth lens 11 and a tenth lens 12. The ninth lens 11 may be a double-convex lens. The tenth lens 12 may be a double-concave lens. The ninth lens 11 may be a positive lens, and the tenth lens 12 may be a negative lens.
In the zoom lens system 1111 according to the present exemplary embodiment, the second lens group G2 and the fourth lens group G4 may move during zooming. Also, during zooming, the first lens group G1 and the third lens group G3 may not move. Thus, an overall length of the zoom lens system 1111 is not changed during zooming. Also, the fourth lens group G4 may perform focusing so as to complement movement of an image plane due to a variation in an object length. Since the fourth lens group G4 performs both zooming and focusing, the zoom lens system 1111 may be driven by using only two motors to move the lens groups, and thus, the zoom lens system 1111 may be small-sized.
During zooming from the wide angle end toward the telephoto end, the second lens group G2 moves toward the image side I so as to be distant from the first lens group G1. Also, during zooming, the fourth lens group G4 moves toward the object side O so as to be close to the third lens group G3.
At least one of the first through fourth lens groups G1, G2, G3 and G4 may include at least one aspherical lens. Also, at least one of the second through fourth lens groups G2, G3 and G4 may include at least one doublet lens. In order to configure a bright lens system, an F-number of the zoom lens system 1111 at the wide angle end may be equal to or less than 1.8.
In the present exemplary embodiment, the fourth lens group G4 may satisfy Expression 1 and Expression 2 below:




  
    
      
        
          1.8
          ≤
          
            
              f
              I
            
            
              
                
                  f
                  W
                
                ⁢
                
                  f
                  T
                
              
            
          
          ≤
          2.7
        
        ,
        
          

        
        ⁢
        and
      
    
    
      
        〈
        
          Expression
          ⁢
          
            
          
          ⁢
          1
        
        〉
      
    
  
  
    
      
        
          
            -
            1.0
          
          ≤
          
            
              f
              II
            
            
              
                
                  f
                  W
                
                ⁢
                
                  f
                  T
                
              
            
          
          ≤
          
            -
            0.7
          
        
        ,
      
    
    
      
        〈
        
          Expression
          ⁢
          
            
          
          ⁢
          2
        
        〉
      
    
  




where fW indicates an overall focal length at the wide angle end, fT indicates an overall focal length at the telephoto end, fl indicates a focal length of the first lens group G1, and fll indicates a focal length of the second lens group G2.

Expression 1 defines a ratio of the focal length of the first lens group G1 with respect to the overall focal length at the wide angle end and the overall focal length at the telephoto end. If the ratio exceeds an upper limit value, the refractive power of the first lens group G1 decreases, and thus, an amount of movement of the second lens group G2 during zooming increases. By doing so, it may be difficult to make the zoom lens system 1111 small-sized. If the ratio exceeds a lower limit value, the positive refractive power of the first lens group G1 increases, and thus, coma correction may be difficult.
Expression 2 defines a ratio of the focal length of the second lens group G2 with respect to the overall focal length at the wide angle end and the overall focal length at the telephoto end, and in this regard, if a value of Expression 2 exceeds an upper limit value, the refractive power of the second lens group G2 increases and thus a focus position with respect to an error of a position with respect to zooming sharply varies, and thus it is difficult to achieve a desired performance. If the value of Expression 2 exceeds a lower limit value, an amount of movement of the second lens group G2 during zooming increases and thus it may be difficult to make the zoom lens system 1111 small-sized.
The optical member may satisfy Expression 3 below:

nI(P)≧1.80   <Expression 3>,

where ni(p) indicates a refractive index at a d-line of the optical member of the first lens group G1.

In the present exemplary embodiment, an aspherical surface is defined below.
An aspherical shape of a zoom lens according to the present exemplary embodiment may be defined by Equation 4 below, when an X-axis indicates an optical axis direction, a Y-axis indicates a direction perpendicular to the optical axis direction, and a forward direction of light is a positive direction. Here, x indicates a distance from a vertex of a lens in the optical axis direction, y indicates a distance in a direction perpendicular to the optical axis, k is a conic constant, A, B, C and D are aspherical coefficients, and c is a reciprocal number (1/R) of a curvature radius at the vertex of the lens.




  
    
      
        x
        =
        
          
            
              cy
              2
            
            
              1
              +
              
                
                  1
                  -
                  
                    
                      (
                      
                        K
                        +
                        1
                      
                      )
                    
                    ⁢
                    
                      c
                      2
                    
                    ⁢
                    
                      y
                      2
                    
                  
                
              
            
          
          +
          
            Ay
            4
          
          +
          
            By
            6
          
          +
          
            Cy
            8
          
          +
          
            Dy
            10
          
        
      
    
    
      
        〈
        
          Expression
          ⁢
          
            
          
          ⁢
          4
        
        〉
      
    
  




Design data of the zoom lens system 1111 according to the present exemplary embodiment will now be described.
Hereinafter, EFL indicates a focal length in mm, Fno indicates an F-number, 2ω indicates a viewing angle in degrees, and D1, D2, D3 and D4 indicate variable lengths in mm. Also, R indicates a curvature radius in mm, Dn indicates a center thickness of a lens or a distance in mm between lenses, Nd indicates a refractive index of a material, Vd indicates an Abbe's number of a material, and ASP indicates an aspherical surface.
<First Exemplary Embodiment>
Table 1 shows design data of the zoom lens system 1111 of FIG. 1. With respect to Table 1, an optical filter 13 such as an infrared-light blocking filter may be further disposed between the tenth lens 12 and an image sensor I, and S26 and S27 indicate two surfaces of the optical filter 13. Hereinafter, the image sensor I and the image side I will be described using the same reference numeral.













TABLE 1







Lens surface
R
Dn
Nd
Vd






















S1
12.6732
1.000
1.9227
20.8804



S2
7.1760
4.0736



S3
infinity
5.5000
1.8467
23.7848



S4
infinity
0.000



S5
infinity
5.5000
1.8467
23.7848



S6
infinity
0.1000



S7(ASP)
30.8083
3.8777
1.6097
57.7355



S8(ASP)
−11.6415
D1



S9
−68.7616
0.8000
1.8160
46.5719



S10
8.5179
1.4489



S11
−14.8099
0.8000
1.4875
70.4412



S12
6.7644
0.2572



S13
7.6112
1.6716
1.8467
23.7848



S14
20.9597
D2



S15(ST)
infinity
1.000



S16
11.3819
1.8858
1.8335
29.9705



S17
1052.1485
0.7741



S18
7.7982
2.5
1.4875
70.4412



S19
−16.0503
0.1628



S20
−14.7963
0.8000
1.8467
23.7848



S21
9.2144
D3



S22
4.2424
2.5000
1.4875
70.4412



S23
−14.6403
0.1000



S24(ASP)
−87.5227
1.5000
1.8086
40.4212



S25(ASP)
11.0513
D4



S26
infinity
2.1200
1.5168
64.1983



S27
infinity
2.5340



S28
IMG










Table 2 shows aspherical coefficients of the zoom lens system 1111 of FIG. 1, and Table 3 shows a focal length (EFL), an F-number (Fno), an entire viewing angle (2ω), and variable lengths (D1, D2, D3 and D4) at each of the wide angle end, the middle end, and the telephoto end.












TABLE 2







K
A
B
C




















S7
−4.7407
−3.6178e−005
6.6115e−007
−2.6382e−008


S8
−0.2933
−3.1789e−006
7.9968e−007
−2.8667e−008


S24
10.0000
−9.1322e−004
5.1745e−005
−1.5958e−006


S25
−1.4980
1.9915e−003
1.9889e−004
5.9864e−006



















TABLE 3





Variable length
Wide angle end
Middle end
Telephoto end


















EFL
3.8000
11.4000
19.000


Fno
1.7866
2.4309
2.4838


2ω
68.2202
23.5490
14.2100


D1
0.9000
9.4698
12.9000


D2
13.1500
4.5802
1.1500


D3
4.8626
1.7600
1.5000


D4
3.0440
6.1466
6.4066









FIGS. 2A through 2C are graphs illustrating aberrations at the wide angle end, the middle end, and the telephoto end of the zoom lens system 1111 of FIG. 1. Also, a tangential field curvature and a sagittal field curvature are shown as an astigmatic field curvature.
<Second Exemplary Embodiment>













TABLE 4







Lens surface
R
Dn
Nd
Vd






















S1
18.8089
0.8500
1.9229
20.8804



S2
8.9328
2.9262



S3
Infinity
5.5000
1.8052
25.4652



S4
Infinity
0.0000



S5
Infinity
5.5000
1.8052
25.4652



S6
Infinity
0.1000



S7(ASP)
23.9974
2.9663
1.6900
53.0000



S8(ASP)
−16.9212
D1



S9
−21.3869
0.6000
1.6204
60.3438



S10
7.9422
1.1620



S11
−40.9052
0.6000
1.6204
60.3438



S12
6.2125
1.7899
1.8052
25.4564



S13
21.9691
D2



S14(ST)
Infinity
1.0000



S15
11.6242
1.6156
1.8052
25.4564



S16
73.6349
0.1000



S17
10.0523
2.3866
1.4875
70.4412



S18
−14.9903
0.6000
1.8052
25.4564



S19
12.8026
D3



S20
4.9270
3.0000
1.5891
61.2526



S21
−31.2567
0.7200



S22(ASP)
−90.9231
1.5000
1.8170
24.2000



S23(ASP)
11.7861
D4



S24
infinity
2.1200
1.5168
64.1983



S25
infinity
2.6926



S26
IMG










Table 5 shows aspherical coefficients of the zoom lens system 1111 of FIG. 3, and Table 6 shows a focal length (EFL), an F-number (Fno), an entire viewing angle (2ω), and variable lengths (D1, D2, D3 and D4) at each of the wide angle end, the middle end, and the telephoto end of the zoom lens system 1111 of FIG. 3.












TABLE 5







K
A
B
C




















S7
−7.2927
−3.1055e−005
−3.9051e−006
1.2136e−007


S8
0.2562
−6.7689e−005
4.2881e−006
−1.2398e−007


S22
−10.0000
−0.0019
8.3980e−005
−3.5975e−006


S23
−6.5954
0.0009
0.0002
−4.6824e−006



















TABLE 6





Variable length
Wide angle end
Middle end
Telephoto end


















EFL
3.8000
11.3999
18.9998


Fno
1.7884
2.4501
2.7720


2ω
68.3388
34.6680
14.3364


D1
0.9000
9.9089
12.9000


D2
13.1000
4.0911
1.1000


D3
6.6233
3.1696
1.5000


D4
3.0320
6.4857
8.1553









FIGS. 4A through 4C are graphs illustrating aberrations at the wide angle end, the middle end, and the telephoto end of the zoom lens system 1111 of FIG. 3.
<Third Exemplary Embodiment>
FIG. 5 is a diagram of the zoom lens system 1111 at each of a wide angle end, a middle end, and a telephoto end according to another exemplary embodiment. Table 7 shows design data of the zoom lens system 1111 of FIG. 5.













TABLE 7







Lens surface
R
Dn
Nd
Vd






















S1
27.2366
0.8500
1.9229
20.8804



S2
10.6429
2.7232



S3
Infinity
5.5000
1.8467
23.7848



S4
Infinity
0.0000



S5
Infinity
5.5000
1.8467
23.7848



S6
Infinity
0.2095



S7(ASP)
19.3345
3.0048
1.6900
53.0000



S8
−19.6619
D1



S9
−37.0269
0.6500
1.8830
40.8054



S10
8.7365
1.3368



S11
−23.8758
0.6500
1.6178
63.3959



S12
8.4024
1.7899
1.9229
20.8804



S13
50.7436
D2



S14(ST)
Infinity
1.0000



S15
12.6607
1.6085
1.9229
20.8804



S16
40.5916
0.5131



S17
9.0557
2.5000
1.4875
70.4412



S18
−15.5636
0.8000
1.9229
20.8804



S19
19.0645
D3



S20
4.9174
2.5000
1.5638
60.8301



S21
−34.1644
1.4522



S22(ASP)
−24.7628
1.5000
1.8170
24.2000



S23(ASP)
17.4229
D4



S24
infinity
2.1200
1.5168
64.1983



S25
infinity
2.6926



S26
IMG










Table 8 shows aspherical coefficients of the zoom lens system 1111 of FIG. 5, and Table 9 shows a focal length (EFL), an F-number (Fno), an entire viewing angle (2ω), and variable lengths (D1, D2, D3 and D4) at each of the wide angle end, the middle end, and the telephoto end of the zoom lens system 1111 of FIG. 5.












TABLE 8







K
A
B
C




















S7
0.4910
−4.7146e−005
−8.1253e−008
−1.0108e−009


S22
−2.8114
−0.0030
1.1815e−004
−1.93658e−006


S23
−8.1184
−2.8784e−004
2.2236e−004
5.1839e−006



















TABLE 9





Variable length
Wide angle end
Middle end
Telephoto end


















EFL
3.8000
11.4000
18.9996


Fno
1.8207
2.4136
2.5571


2ω
68.1230
23.5578
14.3046


D1
0.9000
10.1770
13.7143


D2
13.9143
4.6373
1.1000


D3
5.1628
2.2335
1.5000


D4
2.1223
5.0516
5.7851









FIGS. 6A through 6C are graphs illustrating aberrations at the wide angle end, the middle end, and the telephoto end of the zoom lens system 1111 of FIG. 5.
<Fourth Exemplary Embodiment>
FIG. 7 is a diagram of the zoom lens system 1111 at each of a wide angle end, a middle end, and a telephoto end according to another exemplary embodiment.
Table 10 shows design data of the zoom lens system 1111 of FIG. 7.













TABLE 10







Lens surface
R
Dn
Nd
Vd






















S1
27.5841
0.6500
1.8467
23.7848



S2
10.0983
2.8426



S3
Infinity
5.5000
1.9229
20.8804



S4
Infinity
0.0000



S5
Infinity
5.5000
1.9229
20.8804



S6
Infinity
0.1000



S7(ASP)
19.7344
3.1723
1.6226
58.1640



S8
−17.4831
D1



S9
−26.2279
0.6500
1.6935
53.3430



S10
10.8619
0.8365



S11
758.7320
0.6500
1.7725
49.6243



S12
6.4056
1.8527
1.9229
20.8804



S13
16.8589
D2



S14(ST)
Infinity
0.2000



S15
8.8964
2.7535
1.6186
42.6334



S16
−8.8964
0.8000
1.8996
29.0446



S17
508.0817
D3



S18
4.8151
3.0000
1.6180
63.3959



S19
−38.4588
0.6754



S20(ASP)
37.6970
1.5000
1.8170
24.2000



S21(ASP)
6.1952
D4



S22
infinity
2.1200
1.5168
64.1983



S23
infinity
2.7417



S24
IMG










Table 11 shows aspherical coefficients of the zoom lens system 1111 of FIG. 7, and Table 12 shows a focal length (EFL), an F-number (Fno), an entire viewing angle (2ω), and variable lengths (D1, D2, D3 and D4) at each of the wide angle end, the middle end, and the telephoto end of the zoom lens system 1111 of FIG. 7.












TABLE 11







K
A
B
C




















S7
−1.0849
−1.5366e−005
−1.2527e−007
−1.6078e−009


S20
−5.4806
−2.9254e−003
2.7445e−005
1.7760e−006


S21
−0.3673
−2.2405e−004
1.9243e−004
1.4277e−005



















TABLE 12





Variable length
Wide angle end
Middle end
Telephoto end


















EFL
3.8000
11.4000
19.000


Fno
1.8000
2.4863
2.8871


2ω
68.3836
23.5586
14.3510


D1
0.9000
10.2523
13.2783


D2
13.4783
4.1260
1.1000


D3
6.6469
3.3660
1.5000


D4
2.4302
5.7111
7.5771









FIGS. 8A through 8C are graphs illustrating aberrations at the wide angle end, the middle end, and the telephoto end of the zoom lens system 1111 of FIG. 7.
<Fifth Exemplary Embodiment>
FIG. 9 is a diagram of the zoom lens system 1111 at each of a wide angle end, a middle end, and a telephoto end according to another exemplary embodiment.
Table 13 shows design data of the zoom lens system 1111 of FIG. 9.













TABLE 13







Lens surface
R
Dn
Nd
vd






















S1
20.2159
0.6500
1.8052
25.4564



S2
8.5749
3.1022



S3
Infinity
5.5000
1.9229
20.8804



S4
Infinity
0.0000



S5
Infinity
5.5000
1.9229
20.8804



S6
Infinity
0.1000



S7(ASP)
25.6673
2.8074
1.6226
58.1640



S8
−14.5433
D1



S9
−20.9081
0.6500
1.7880
47.4938



S10
11.6354
0.8023



S11
−1983.3472
0.6500
1.6180
63.3959



S12
7.3982
1.5035
1.9229
20.8804



S13
17.4359
D2



S14(ST)
Infinity
0.3500



S15
9.3194
2.6190
1.6237
47.0507



S16
−9.2643
0.8000
1.9037
31.3150



S17
433.2150
D3



S18
4.8836
3.5000
1.6180
63.3959



S19
−46.7906
0.8102



S20(ASP)
−66.5138
1.5000
1.8170
24.2000



S21(ASP)
8.4994
D4



S22
infinity
2.1200
1.5168
64.1983



S23
infinity
1.7758



S24
IMG










Table 14 shows aspherical coefficients of the zoom lens system 1111 of FIG. 9, and Table 15 shows a focal length (EFL), an F-number (Fno), an entire viewing angle (2ω), and variable lengths (D1, D2, D3 and D4) at each of the wide angle end, the middle end, and the telephoto end of the zoom lens system 1111 of FIG. 9.













TABLE 14







K
A
B
C
D





















S7
−1.0378
−1.8769e−005
−1.2055e−007
3.7602e−009
−3.5628e−011


S20
9.5920
−2.7118e−003
2.9174e−005
7.6110e−006
−5.7194e−007


S21
−0.8993
6.2694e−004
1.2819e−004
3.6054e−005
−1.1367e−006



















TABLE 15





Variable length
Wide angle end
Middle end
Telephoto end


















EFL
3.8000
11.4000
19.000


Fno
1.8000
2.5337
2.8882


2ω
68.3346
23.2890
14.2198


D1
0.6500
10.3651
13.7897


D2
14.2397
4.5246
1.1000


D3
6.0605
2.9765
1.5000


D4
3.3394
6.3933
7.8699









FIGS. 10A through 10C are graphs illustrating aberrations at the wide angle end, the middle end, and the telephoto end of the zoom lens system 1111 of FIG. 9.
<Sixth Exemplary Embodiment>
FIG. 11 is a diagram of the zoom lens system 1111 at each of a wide angle end, a middle end, and a telephoto end according to another exemplary embodiment.
Table 16 shows design data of the zoom lens system 1111 of FIG. 11.













TABLE 16







Lens surface
R
Dn
Nd
Vd






















S1
18.1450
0.6500
1.8467
23.7848



S2
8.9801
2.9078



S3
Infinity
5.5000
1.9229
20.8804



S4
Infinity
0.0000



S5
Infinity
5.5000
1.9229
20.8804



S6
Infinity
0.1000



S7(ASP)
21.2377
2.6221
1.6465
58.6331



S8
−16.0227
D1



S9
−19.3759
0.6500
1.8830
40.8054



S10
10.9427
0.8608



S11
−66.5819
0.6500
1.6180
63.3959



S12
7.0727
1.5623
1.9229
20.8804



S13
21.5794
D2



S14(ST)
Infinity
0.3500



S15
8.7878
2.6775
1.6465
47.2777



S16
−8.2350
0.8000
1.9037
31.3150



S17
−778.8869
D3



S18
4.4946
3.0677
1.6152
63.5041



S19
−72.2204
0.8777



S20(ASP)
−45.2213
0.9468
1.8170
24.2000



S21(ASP)
7.9930
D4



S22
infinity
2.1200
1.5168
64.1983



S23
infinity
1.4195



S24
IMG










Table 17 shows aspherical coefficients of the zoom lens system 1111 of FIG. 11, and Table 18 shows a focal length (EFL), an F-number (Fno), an entire viewing angle (2ω), and variable lengths (D1, D2, D3 and D4) at each of the wide angle end, the middle end, and the telephoto end of the zoom lens system 1111 of FIG. 11.













TABLE 17







K
A
B
C
D





















S7
−1.2080
−1.7649e−005
−1.9219e−007
4.4435e−009
−4.2123e−011


S20
10.0000
−2.7869e−003
1.6765e−004
−9.2097e−006
−2.0809e−007


S21
1.9975
1.1442e−003
3.4641e−004
2.7654e−005
−6.6340e−007



















TABLE 18





Variable length
Wide angle end
Middle end
Telephoto end


















EFL
3.8000
11.4000
19.000


Fno
1.8000
2.5337
2.8882


2ω
66.0952
22.2346
13.4948


D1
0.6500
9.2008
12.6780


D2
13.1280
1.5771
1.1000


D3
4.5474
1.9597
1.5000


D4
3.4124
6.0000
6.4598









FIGS. 12A through 12C are graphs illustrating aberrations at the wide angle end, the middle end, and the telephoto end of the zoom lens system 1111 of FIG. 11.
<Seventh Exemplary Embodiment>
FIG. 13 is a diagram of the zoom lens system 1111 at each of a wide angle end, a middle end, and a telephoto end according to another exemplary embodiment.
Table 19 shows design data of the zoom lens system 1111 of FIG. 13.













TABLE 19







Lens surface
R
Dn
Nd
Vd






















S1
18.9203
0.6500
1.8467
23.7848



S2
9.1660
2.8267



S3
Infinity
5.5000
1.9229
20.8804



S4
Infinity
0.0000



S5
Infinity
5.5000
1.9229
20.8804



S6
Infinity
0.1000



S7(ASP)
19.9057
2.6445
1.6226
58.1640



S8
−15.8959
D1



S9
−19.5232
0.6500
1.8830
40.8054



S10
11.0072
0.8189



S11
−101.3319
0.6500
1.6180
63.3959



S12
6.8637
1.5465
1.9229
20.8804



S13
18.8729
D2



S14(ST)
Infinity
0.3500



S15
8.7188
2.6620
1.6584
50.8546



S16
−8.2818
0.8000
1.9108
35.2500



S17
−5629.9446
D3



S18
4.2746
3.0969
1.6063
63.7110



S19
−49.8266
0.7960



S20
−12.1926
0.8627
1.8170
24.2000



S21(ASP)
13.4082
D4



S22
Infinity
2.1200
1.5168
64.1983



S23
Infinity
1.6372



S24
IMG










Table 20 shows aspherical coefficients of the zoom lens system 1111 of FIG. 13, and Table 21 shows a focal length (EFL), an F-number (Fno), an entire viewing angle (2ω), and variable lengths (D1, D2, D3 and D4) at each of the wide angle end, the middle end, and the telephoto end of the zoom lens system 1111 of FIG. 13.













TABLE 20







K
A
B
C
D





















S7
−1.2290
−1.8796e−005
−1.7095e−007
1.6655e−009
−1.4480e−012


S21
10.0000
4.2222e−003
3.1092e−004
−1.9492e−005
9.8502e−006



















TABLE 21





Variable length
Wide angle end
Middle end
Telephoto end


















EFL
3.8000
11.4000
19.000


Fno
1.8000
2.5142
2.7181


2ω
66.1660
22.2694
13.5480


D1
0.6500
9.1709
12.4784


D2
12.9284
4.4075
1.1000


D3
5.0638
2.2871
1.5000


D4
3.1464
5.9231
6.7102









FIGS. 14A through 14C are graphs illustrating aberrations at the wide angle end, the middle end, and the telephoto end of the zoom lens system 1111 of FIG. 13.
<Eighth Exemplary Embodiment>
FIG. 15 is a diagram of the zoom lens system 1111 at each of a wide angle end, a middle end, and a telephoto end according to another exemplary embodiment.
Table 22 shows design data of the zoom lens system 1111 of FIG. 15.













TABLE 22







Lens surface
R
Dn
Nd
Vd






















S1
17.4242
0.6500
1.9229
20.8804



S2
9.5668
2.6733



S3
Infinity
5.0000
1.9229
20.8804



S4
Infinity
0.0000



S5
Infinity
5.0000
1.9229
20.8804



S6
Infinity
0.1000



S7
23.4348
2.3264
1.7433
49.2216



S8
−21.1687
D1



S9
−21.7008
0.6500
1.8830
40.8054



S10
9.9678
0.9061



S11
−65.0492
0.6500
1.6779
55.5187



S12
6.8947
1.6276
1.9229
20.8804



S13
27.1274
D2



S14(ST)
Infinity
0.3500



S15
9.5398
2.4661
1.6180
63.3959



S16
−8.7436
0.7500
1.8830
40.8054



S17
−91.3766
D3



S18
4.5910
0.3500
1.6180
63.3959



S19
−34.7262
0.6383



S20
−13.6464
0.9783
1.8170
24.2000



S21(ASP)
14.6454
D4



S22
Infinity
2.1200
1.5168
64.1983



S23
Infinity
2.8776



S24
IMG










Table 23 shows aspherical coefficients of the zoom lens system 1111 of FIG. 15, and Table 24 shows a focal length (EFL), an F-number (Fno), an entire viewing angle (2ω), and variable lengths (D1, D2, D3, and D4) at each of the wide angle end, the middle end, and the telephoto end of the zoom lens system 1111 of FIG. 15:













TABLE 23







K
A
B
C
D





















S21
−6.1229
3.9437e−003
2.6557e−004
−2.2278e−005
6.4690e−006



















TABLE 24





Variable length
Wide angle end
Middle end
Telephoto end


















EFL
3.8065
11.4074
19.0113


Fno
1.8000
2.4663
2.8083


2ω
66.1404
22.3094
13.5480


D1
0.6500
9.3999
12.3755


D2
12.8255
4.0756
1.1000


D3
6.1675
3.0389
1.5000


D4
2.0934
5.2220
6.7609









FIGS. 16A through 16C are graphs illustrating aberrations at the wide angle end, the middle end, and the telephoto end of the zoom lens system 1111 of FIG. 15.
Table 25 shows that each of the first through eighth exemplary embodiments satisfies conditions of Expressions 1 and 2.
















TABLE 25







First
Second
Third
Fourth
Fifth
Sixth
Seventh
Eighth



embodiment
embodiment
embodiment
embodiment
embodiMent
embodiment
Embodiment
embodiMent
























Exp. 1
2.00492
2.35871
2.31793
2.60651
2.53950
2.24587
2.28026
2.54407


Exp. 2
−0.80037
−0.86158
−0.86801
−0.91875
−0.96071
−0.83694
−0.82863
−0.82068









The zoom lens system according to the exemplary embodiments has a high zooming rate, a small-size, and low costs of manufacturing. The zoom lens system according to the exemplary embodiments may be appropriately used in photographing apparatuses including a digital still camera, a single lens reflex camera, a video camera, a portable terminal, or the like using a solid-state imaging device such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS).
FIG. 17 is a diagram of a photographing apparatus 1100 including the zoom lens system 1111, according to an embodiment. The photographing apparatus 1100 includes the zoom lens system 1111 according to the above exemplary embodiments, and an imaging sensor 1112 for converting light collected by the zoom lens system 1111 into an electrical image signal. The photographing apparatus 1100 may include a recording means 1113 and a viewfinder 1114 for viewing a target object image, wherein information corresponding to the target object image that is photoelectrically converted by the imaging sensor 1112 is recorded to the recording means 1113. Also, the photographing apparatus 1100 may include a display unit 1115 for displaying the target object image. In the present exemplary embodiment of FIG. 17, the viewfinder 1114 and the display unit 1115 are separately arranged, but the display unit 1115 may be arranged without the viewfinder 1114. The photographing apparatus 1100 of FIG. 17 is an example, and thus, the above exemplary embodiments may be applied to various optical apparatuses other than a camera. As described above, by applying the zoom lens system 1111 to a photographing apparatus such as a digital camera, it is possible to provide an optical device having a small-size, a low cost, and a high zooming rate.
While the inventive concept has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the inventive concept as defined by the following claims.

## Claims

1. A zoom lens system comprising:
a first lens group comprising one or more lenses, and an optical member for changing a path of light, and having a positive refractive power;
a second lens group having a negative refractive power;
a third lens group having a positive refractive power; and
a fourth lens group having a positive refractive power,
wherein the first lens group, the second lens group, the third lens group, and the fourth lens group are sequentially arranged from an object side to an image side,
wherein zooming is performed by varying air gaps between the first through fourth lens groups, and
wherein the zoom lens system satisfies the following expressions:





  
    1.8
    ≤
    
      
        f
        I
      
      
        
          
            f
            W
          
          ⁢
          
            f
            T
          
        
      
    
    ≤
    2.7
  
  ,
  
    

  
  ⁢
  
    
      and
      ⁢
      
        

      
      -
      1.0
    
    ≤
    
      
        f
        II
      
      
        
          
            f
            W
          
          ⁢
          
            f
            T
          
        
      
    
    ≤
    
      -
      0.7
    
  
  ,




where fw indicates an overall focal length at a wide angle end, fT indicates an overall focal length at a telephoto end, fI indicates a focal length of the first lens group, and fII indicates a focal length of the second lens group,
wherein the fourth lens group performs focusing, and wherein an F-number at the wide angle end is equal to or less than 1.8.

2. The zoom lens system of claim 1, wherein the third lens group comprises an aperture.

3. The zoom lens system of claim 2, wherein the aperture is disposed at the object side of the third lens group.

4. The zoom lens system of claim 1, wherein the optical member satisfies the following expression:


nI(P)≧1.80


where nI(P) indicates a refractive index of the optical member.

5. The zoom lens system of claim 4, wherein the optical member comprises a prism.

6. The zoom lens system of claim 1, wherein the first lens group comprises a negative lens, the optical member for changing a path of light that has passed through the negative lens, and a positive lens.

7. The zoom lens system of claim 6, wherein the negative lens is a meniscus lens having a convex surface toward the object side.

8. The zoom lens system of claim 1, wherein the fourth lens group comprises a positive lens and a negative lens.

9. The zoom lens system of claim 1, wherein the third lens group comprises a positive lens, a positive lens, and a negative lens.

10. The zoom lens system of claim 1, wherein the third lens group comprises two or more lenses.

11. The zoom lens system of claim 1, wherein at least one of the first through fourth lens groups comprises at least one aspherical lens.

12. The zoom lens system of claim 1, wherein at least one of the second through fourth lens groups comprises at least one doublet lens.

13. The zoom lens system of claim 1, wherein the second lens group and the fourth lens group move during zooming.

14. A photographing apparatus comprising:
a zoom lens system; and
an imaging sensor for converting an image formed by the zoom lens system into an electrical signal,
wherein the zoom lens system comprises:
a first lens group comprising one or more lenses, and an optical member for changing a path of light, and having a positive refractive power;
a second lens group having a negative refractive power;
a third lens group having a positive refractive power; and
a fourth lens group having a positive refractive power,
wherein the first lens group, the second lens group, the third lens group, and the fourth lens group are sequentially arranged from an object side to an image side,
wherein zooming is performed by varying air gaps between the first through fourth lens groups, and
wherein the zoom lens system satisfies the following expressions:





  
    1.8
    ≤
    
      
        f
        I
      
      
        
          
            f
            W
          
          ⁢
          
            f
            T
          
        
      
    
    ≤
    2.7
  
  ,
  
    

  
  ⁢
  
    
      and
      ⁢
      
        

      
      -
      1.0
    
    ≤
    
      
        f
        II
      
      
        
          
            f
            W
          
          ⁢
          
            f
            T
          
        
      
    
    ≤
    
      -
      0.7
    
  
  ,




where fW indicates an overall focal length at a wide angle end, fT indicates an overall focal length at a telephoto end, fI indicates a focal length of the first lens group, and fII indicates a focal length of the second lens group,
wherein the fourth lens group performs focusing, and wherein an F-number at the wide angle end is equal to or less than 1.8.

15. The photographing apparatus of claim 14, wherein the third lens group comprises an aperture.

16. The photographing apparatus of claim 15, wherein the aperture is disposed at the object side of the third lens group.

17. The photographing apparatus of claim 14, wherein the optical member satisfies the following expression:


nI(P)≧1.80


where nI(P) indicates a refractive index of the optical member.

18. The photographing apparatus of claim 14, wherein the first lens group comprises a negative lens, the optical member for changing a path of light that has passed through the negative lens, and a positive lens.