# Patent

## Title
Zoom lens and photographing apparatus including the same

## Abstract

A small-sized zoom lens having a high zooming rate and a high optical performance, the zoom lens including a first lens group 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 an iris diaphragm is disposed between the second lens group and the third lens group.

## Background
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
This application claims priority from Korean Patent Application No. 10-2010-0031879, filed on Apr. 7, 2010, in the Korean Intellectual Property Office, and Japanese Patent Application No. 2009-296050, filed on Dec. 25, 2009, in the Japan Patent Office, the disclosures of which are incorporated herein in their entireties by reference.
BACKGROUND
1. Field
Apparatuses consistent with exemplary embodiments relate to a zoom lens and a photographing apparatus including the same.
2. Description of the Related Art
Photographing apparatuses, such as surveillance cameras including a solid state imaging device, such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS), video cameras, digital cameras, or the like are widely used. Photographing apparatuses need to have a high performance and be small-sized. Thus, zoom lenses used in photographing apparatuses also need to have a high optical performance and be small-sized.
As an example of zoom lenses used in photographing apparatuses, a rear focusing zoom lens including a first lens group having a negative refractive power and including a negative lens and a positive lens and having at least one aspherical surface, a second lens group having a positive refractive power, a third lens group having a positive refractive power, and a fourth lens 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, and wherein, simultaneously, zooming is performed by moving the second lens group in an optical axis direction, a variation in an image plane caused by zooming is corrected by moving the fourth lens group in the optical axis direction, and focusing is performed, is widely used.
In the rear focusing zoom lens, an effective diameter of the first lens group may be made relatively small compared to that of a zoom lens that performs focusing by allowing the first lens group to move in the optical axis direction, and thus the entire lens system may be easily minimized. Also, since close focusing can be performed and a comparatively small and light-weight lens group is moved in the optical axis direction, the rear focusing zoom lens can quickly focus on a subject by using only a small amount of driving power.
As the sizes of pixels are greatly reduced due to a solid state imaging device having a small size and a large number of pixels, a small-sized zoom lens having high optical performance and a short overall length of a lens is required. However, in order to obtain high optical performance, the number of lenses needs to be increased, and the overall length of the lens needs to be increased. Thus, it is difficult to make a small-sized zoom lens.
Also, in order to make a small-sized zoom lens while increasing a zooming rate of the zoom lens, a variation in aberration caused by zooming increases, and thus it is difficult to obtain good optical performance from a wide angle end to a telephoto end. In particular, in a zoom lens having a high zooming rate, it is difficult to correct spherical aberration at the telephoto end. Also, as the size of the zoom lens becomes small and a zooming rate thereof increases, the amount of aberration of an actuating lens group increases.
SUMMARY
One or more of the exemplary embodiments provides a small-sized zoom lens with a high optical performance and a photographing apparatus including the zoom lens.
According to an aspect, there is provided a zoom lens comprising a first lens group 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 moving the second lens group in an optical axis direction and focusing is performed by moving the fourth lens group in the optical axis direction, and the zoom lens satisfies the following Equations: 1.4<|f2|/fW<2.0, 0.3<f1/fT<0.6, where a combined focal length of the first lens group is f1, a combined focal length of the second lens group is f2, a focal length of the zoom lens at a wide angle end is fw, and a focal length of the zoom lens at a telephoto end is fT.
An iris diaphragm is disposed between the second lens group and the third lens group.
The first lens group comprises a negative lens and three positive lenses sequentially arranged from the object side.
The three positive lenses comprise two positive lenses each having a convex surface on the object side.
The second lens group comprises at least three negative lenses and a positive lens sequentially arranged from the object side.
The third lens group comprises a positive lens having a convex surface on the object side and a negative meniscus lens having a concave surface on the image side.
When a lens surface of the object side of the meniscus lens has a curvature radius of R3W and a lens surface of the image side of the meniscus lens has a curvature radius of R3T, the zoom lens satisfies the following Equation: 1.5<R3W/R3T<3.0.
When a length of an optical axis from a vertex of the object side of the lens disposed closest to the object side of the first lens group to an image plane is ΣD, the zoom lens satisfies the following Equation: 0.6<(ΣD/fT)<1.3.
When an Abbe's number of a positive lens disposed closest to the object side of the first lens group is v1D, the zoom lens satisfies the following Equation: 80<ν1D.
The fourth lens group comprises a positive lens having at least one aspherical surface and two convex surfaces and a negative meniscus lens having a concave surface on the object side.
When a focal length of the third lens group is f3, the zoom lens satisfies the following Equation: 4.0<f3/fW<6.0.
When lateral magnification during focusing on an object at infinity e at the telephoto end is β4T, the fourth lens group satisfies the following Equation: 0.3<β4T<0.6.
The first lens group comprises a negative lens, a positive lens, and two positive lenses each having a convex surface on the object side, wherein the lenses are sequentially arranged from the object side to the image side, and the second lens group comprises at least three negative lenses and a positive lens, wherein the lenses are sequentially arranged from the object side to the image side, and the third lens group comprises a positive lens having a convex surface on the object side and a negative meniscus lens having a concave surface on the image side, wherein the lenses are sequentially arranged from the object side to the image side.
According to another aspect, there is provided a photographing apparatus comprising a zoom lens; and an imaging device for photoelectrically converting an image formed by the zoom lens, wherein the zoom lens comprises a first lens group 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 moving the second lens group in an optical axis direction and focusing is performed by moving the fourth lens group in the optical axis direction, and the zoom lens satisfies the following Equations: 1.4<|f2|/fW<2.0, 0.3<f1/fT<0.6, where a combined focal length of the first lens group is f1, a combined focal length of the second lens group is f2, a focal length of the zoom lens at a wide angle end is fw, and a focal length of the zoom lens at a telephoto end is fT.



BRIEF DESCRIPTION OF THE DRAWINGS
The above and/or other aspects will become more apparent by describing in detail exemplary embodiments with reference to the attached drawings in which:
FIG. 1 is a cross-sectional view of a zoom lens according to an exemplary embodiment;
FIG. 2 is a cross-sectional view of a zoom lens according to another exemplary embodiment;
FIG. 3 are charts of aberration showing spherical aberration, astigmatism, distortion aberration, and at a wide angle end of the zoom lens of FIG. 2, respectively;
FIG. 4 are charts of aberration showing spherical aberration, astigmatism, distortion aberration, and lateral chromatic aberration at a middle end of the zoom lens of FIG. 2, respectively;
FIG. 5 are charts of aberration showing spherical aberration, astigmatism, distortion aberration, and lateral chromatic aberration at a telephoto end of the zoom lens of FIG. 2, respectively;
FIG. 6 is a cross-sectional view of a zoom lens according to another exemplary embodiment;
FIG. 7 are charts of aberration showing spherical aberration, astigmatism, distortion aberration, and lateral chromatic aberration at a wide angle end of the zoom lens of FIG. 6, respectively;
FIG. 8 are charts of aberration showing spherical aberration, astigmatism, distortion aberration, and lateral chromatic aberration at a middle end of the zoom lens of FIG. 6, respectively;
FIG. 9 are charts of aberration showing spherical aberration, astigmatism, distortion aberration, and lateral chromatic aberration at a telephoto end of the zoom lens of FIG. 6, respectively;
FIG. 10 is a cross-sectional view of a zoom lens according to another exemplary embodiment;
FIG. 11 are charts of aberration showing spherical aberration, astigmatism, distortion aberration, and lateral chromatic aberration at a wide angle end of the zoom lens of FIG. 10, respectively;
FIG. 12 are charts of aberration showing spherical aberration, astigmatism, distortion aberration, and lateral chromatic aberration at a middle end of the zoom lens of FIG. 10, respectively;
FIG. 13 are charts of aberration showing spherical aberration, astigmatism, distortion aberration, and lateral chromatic aberration at a telephoto end of the zoom lens of FIG. 10, respectively;
FIG. 14 is a cross-sectional view of a zoom lens according to another exemplary embodiment;
FIG. 15 are charts of aberration showing spherical aberration, astigmatism, distortion aberration, and lateral chromatic aberration at a wide angle end of the zoom lens of FIG. 14, respectively;
FIG. 16 are charts of aberration showing spherical aberration, astigmatism, distortion aberration, and lateral chromatic aberration at a middle end of the zoom lens of FIG. 14, respectively;
FIG. 17 are charts of aberration showing spherical aberration, astigmatism, distortion aberration, and lateral chromatic aberration at a telephoto end of the zoom lens of FIG. 15, respectively;
FIG. 18 is a cross-sectional view of a zoom lens according to another exemplary embodiment;
FIG. 19 are charts of aberration showing spherical aberration, astigmatism, distortion aberration, and lateral chromatic aberration at a wide angle end of the zoom lens of FIG. 18, respectively;
FIG. 20 are charts of aberration showing spherical aberration, astigmatism, distortion aberration, and lateral chromatic aberration at a middle end of the zoom lens of FIG. 18, respectively;
FIG. 21 are charts of aberration showing spherical aberration, astigmatism, distortion aberration, and lateral chromatic aberration at a telephoto end of the zoom lens of FIG. 18, respectively;
FIG. 22 is a cross-sectional view of a zoom lens according to another exemplary embodiment;
FIG. 23 are charts of aberration showing spherical aberration, astigmatism, distortion aberration, and lateral chromatic aberration at a wide angle end of the zoom lens of FIG. 22, respectively;
FIG. 24 are charts of aberration showing spherical aberration, astigmatism, distortion aberration, and lateral chromatic aberration at a middle end of the zoom lens of FIG. 22, respectively;
FIG. 25 are charts of aberration showing spherical aberration, astigmatism, distortion aberration, and lateral chromatic aberration at a telephoto end of the zoom lens of FIG. 22, respectively; and
FIG. 26 is a schematic view of a photographing apparatus having a zoom lens, according to an exemplary embodiment.



DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
Exemplary embodiments will now be described more fully with reference to the accompanying drawings.
Lens data illustrated in the following description is only an example, and the present invention is not limited thereto and may be properly modified within the scope of the invention.
FIG. 1 is a cross-sectional view of a zoom lens according to an exemplary embodiment.
The zoom lens according to the current exemplary embodiment may be used as a photographing optical system of a photographing apparatus, such as a surveillance camera, a digital video camera, a digital still camera, or the like. The zoom lens includes a first lens group L1 having a positive refractive power, a second lens group L2 having a negative refractive power, a third lens group L3 having a positive refractive power, and a fourth lens group L4 having a positive refractive power. The lens groups L1, L2, L3, and L4 are sequentially arranged from an object side O to an image side I of the zoom lens, as illustrated in FIG. 1. An iris diaphragm SP may be disposed between the second lens group L2 and the third lens group L3, and an optical block G that corresponds to an optical filter, a faceplate, or the like may be disposed between the fourth lens group L4 and an image plane IP.
In the zoom lens, while the first and third lens groups L1 and L3, respectively, are fixed, zooming is performed by moving the second lens group L2 in an optical axis direction, and focusing is performed by moving the fourth lens group L4 in the optical axis direction. Also, in the zoom lens, when zooming is performed from a wide angle end to a telephoto end, the second lens group L2 is moved to the image side I according to an arrow a of FIG. 1, and simultaneously, the fourth lens group L4 may be moved according to an arrow b or c of FIG. 1. The arrows b and c each is convex toward the object side O, thereby correcting a variation in the image plane IP caused by zooming.
The arrow b indicated by a solid line and the arrow c indicated by a dotted line in FIG. 1 represent moving paths for correcting a variation in the image plane IP caused by zooming when an object at infinity and a near object are respectively focused on. The fourth lens group L4 is moved according to a moving path that is convex toward the object side O, thereby efficiently using a space between the third lens group L3 and the fourth lens group L4 and reducing the overall length of the zoom lens.
The photographing apparatus forms an image at a photographing plane of an imaging device (photoelectric conversion device), such as a charge coupled device (CCD), a complementary metal-oxide semiconductor device, or the like, that is, light incident on the object side O of the zoom lens is transmitted onto the image plane IP. The photographing apparatus photoelectrically converts light formed as an image on the imaging device into an electrical signal and generates a digital image corresponding to an image of a subject. Then, the photographing apparatus writes the digital image into a recording medium, such as a hard disk drive (HDD), a memory card, an optical disc, a magnetic tape, or the like. When the photographing apparatus is a film camera, the image plane IP corresponds to a film plane.
The first lens group L1 may include a negative lens 1, a positive lens 2, and two positive lenses 3 and 4 each having a convex surface on the object side O. The lenses 1, 2, 3, and 4 are sequentially arranged from the object side O to the image side I. Thus, light affected by a positive refractive power of the first lens group L1 is dispersed into each of the lenses 2, 3, and 4, thereby easily correcting spherical aberration at the telephoto end.
The second lens group L2 may include at least three negative lenses 5, 6, and 7 and a positive lens 8 sequentially arranged from the object side O to the image side I. Thus, distortion aberration of a wide angle may be prevented, and a variation in spherical aberration caused by zooming may be corrected.
The third lens group L3 may include a positive lens 9 having a convex surface on the object side O and a negative meniscus lens 10 having a concave surface on the image side I. The lenses 9 and 10 are sequentially arranged from the object side O to the image side I. Thus, a position of a main point of the third lens group L3 is moved to the object side O, and a distance between the third lens group L3 and the fourth lens group L4 is reduced, thereby miniaturizing the zoom lens.
The fourth lens group L4 may include a positive lens 11 that has at least one aspheric surface and two convex surfaces, and a negative meniscus lens 12 that has a concave surface formed on the object side O. The lenses 11 and 12 are sequentially arranged from the object side O to the image side I. Thus, a variation in aberration during focusing may be reduced.
In the zoom lens according to an exemplary embodiment, when a combined focal length of the first lens group L1 is f1 [mm], a combined focal length of the second lens group L2 is f2 [mm], a focal length of the zoom lens at the wide angle end is fw [mm], and a focal length of the zoom lens at the telephoto end is fT [mm], the zoom lens may satisfy the following Equations 1 and 2:

1.4<|f2|/fW<2.0  (1)

0.3<f1/fT<0.6

When |f2|/fW is less than the lower limit value of Equation 1, a variation in aberration from the wide angle end to the telephoto end during zooming may not be easily corrected. On the other hand, when |f2|/fW is greater than the upper limit value of Equation 1, the amount of movement from the wide angle end to the telephoto end during zooming increases, and thus, the overall length of the zoom lens increases. Also, when f1/fT is less than the lower limit value of Equation 2, spherical aberration at the telephoto end may not be properly corrected. On the other hand, when f1/fT is greater than the upper limit value of Equation 2, the focal length of the first lens group L1 increases, and allowance for miniaturization decreases, and thus, the overall length of the zoom lens increases.
The zoom lens according to the current exemplary embodiment may satisfy the following Equations 3 and 4:

1.45<|f2|/fW<1.7  (3)

0.32<f1/fT<0.55  (4).

In the zoom lens according to an exemplary embodiment, when a length from a vertex of the object side O of the lens 1, as the lens disposed closest to the object side O of the first lens group L1, to the image plane IP along the optical axis is ΣD (mm), the zoom lens may satisfy the following Equation 5:

0.6<(ΣD/fT)<1.3  (5).

When (ΣD/fT) is greater than the lower limit value of Equation 5, the overall length of the zoom lens decreases, but an astigmatic field curvature may not be easily corrected. On the other hand, when (ΣD/fT) is greater than the upper limit value of Equation 5, aberration correction is easily performed, but the overall length of the zoom lens increases.
Also, the zoom lens according to the current exemplary embodiment may satisfy the following Equation 6:

0.8<(ΣD/fT)<1.2  (6).

In the zoom lens according to an exemplary embodiment, when the Abbe's number of the lens 1, which is the lens disposed closest to the object side O of the first lens group L1, is v1D, the zoom lens may satisfy the following Equation 7:

80<ν1D  (7).

When ν1D is less than the lower limit value of Equation 7, axial chromatic aberration and lateral chromatic aberration at the telephoto end may not be properly corrected.
The third lens group L3 may include the positive lens 9 having at least one aspherical surface and the convex surface on the object side O and the negative meniscus lens 10 having the concave surface on the image side I. Thus, spherical correction and coma correction may be easily performed.
When the object side O of the meniscus lens 10 has a curvature radius of R3W (mm) and the image side I of the meniscus lens 10 has a curvature radius of R3T (mm), the zoom lens may satisfy the following Equation 8:

1.5<R3W/R3T<3.0  (8).

When R3W/R3T is less than the lower limit value of Equation 8, the position of the main point of the third lens group L3 is moved to the object side O, and the distance between the third lens group L3 and the fourth lens group L4 is small, and thus, the allowance for miniaturizing the zoom lens is reduced, and the overall length of the zoom lens increases. On the other hand, when R3W/R3T is greater than the upper limit value of Equation 8, the distance between the third lens group L3 and the fourth lens group L4 is very small. Thus, a space in which the fourth lens group L4 may move may not be sufficiently obtained.
The zoom lens according to the current exemplary embodiment may satisfy the following Equation 9:

2.0<R3W/R3T<2.5  (9)

In the zoom lens according to an exemplary embodiment, when the focal length of the third lens group L3 is f3 (mm), the zoom lens may satisfy the following Equation 10:

4.0<f3/fW<6.0  (10)

When f3/fW is less than the lower limit value of Equation 10, the positive refractive power of the third lens group L3 increases, while spherical aberration, coma aberration or astigmatism occurs, and the aforementioned aberration may not be easily corrected. On the other hand, when f3/fW is greater than the upper limit value of Equation 10, the positive refractive power of the third lens group L3 decreases, and the positive refractive power of the fourth lens group L4 increases. In this case, spherical aberration, coma aberration, astigmatism, and distortion aberration may not be properly corrected.
The zoom lens according to the current exemplary embodiment may satisfy the following Equation 11:

4.5<f3/fW<5.5  (11).

In an exemplary embodiment, when lateral magnification during focusing on an object at infinity at the telephoto end is β4T, the fourth lens group L4 may satisfy the following Equation 12:

0.3<β4T<0.6  (12).

When β4T is less than the lower limit value of Equation 12, a back focal length increases, and the zoom lens increases in size. On the other hand, when β4T is greater than the upper limit value of Equation 12, the moving distances of the fourth lens group L4 increase, and the distance between the third lens group L3 and the fourth lens group L4 may be relatively big. Thus, the zoom lens may not be easily miniaturized.
The zoom lens according to the current exemplary embodiment may satisfy the following Equation 13:

0.35<β4T<0.55  (13)

The zoom lens that satisfies the aforementioned conditions has a high zooming rate. For example, the zoom lens according to the current embodiment may have a zooming rate of 15× to 25×. Also, a variation in distortion aberration at the wide angle end, spherical aberration at the telephoto end, and spherical aberration caused by zooming, or the like may be easily corrected, and a good optical performance from the wide angle end to the telephoto end may be obtained, and the overall length of the zoom lens may be reduced, thereby realizing miniaturization of the zoom lens.
Since the zoom lens according to the current exemplary embodiment has a small size and may correspond to a solid state imaging device having a large number of pixels, when the zoom lens is employed in a photographing optical system of a photographing apparatus, such as a surveillance camera, a digital video camera, a digital still camera, or the like, a photographing apparatus having a small size and a high optical performance may be realized.
Hereinafter, the effect of exemplary embodiments will be clarified. However, the present invention is not limited thereto and may be properly modified within the scope of the invention.
A structure of the zoom lens based on design data of a first exemplary embodiment is illustrated in FIG. 2. The zoom lens of FIG. 2 has the same structure as that of the zoom lens of FIG. 1, and the following tables 1, 2, and 3 show the design data of the zoom lens of FIG. 1.












TABLE 1





Lens

Radius of
Thick-
Refractive
Abbe's


surface
Lens
curvature
ness
index
number


(i)
(GjRk)
(R)
(D)
(Nd)
(Vd)




















1
G1R1
118.64980
1.700
1.84666
23.78


2
G1R2/G2R1
40.03122
5.617
1.49700
81.61


3
G2R2
384.92901
0.200


4
G3R1
55.34000
3.807
1.72916
54.67


5
G3R2
979.81305
0.200


6
G4R1
30.88549
3.798
1.77250
49.62


7
G4R2
80.85718
D1


8
G5R1
67.13133
0.800
1.88300
40.80


9
G5R2
6.83834
3.918


10
G6R1
−25.32670
0.800
1.83481
42.72


11
G6R2
20.02199
0.200


12
G7R1
13.28255
3.620
1.84666
23.78


13
G7R2/G8R1
−27.50218
0.850
1.77250
49.62


14
G8R2
97.87753
D2


15
Iris
1.00E+18
0.350



diaphragm


16
G9R1
8.24439
4.691
1.69350
53.20


17
G9R2
−626.92898
1.015


18
G10R1
13.97634
1.000
1.84666
23.78


19
G10R2
6.14653
D3


20
G11R1
9.35247
4.167
1.51633
64.06


21
G11R2/G12R1
−10.04080
0.900
1.84666
23.78


22
G12R2
−17.66512
D4


23
Plane
1.00E+18
2.880
1.51680
64.20


24
Plane
1.00E+18
2.430




















TABLE 2







Wide angle
Middle
Telephoto



end
end
end





















Focal
4.63
20.39
83.00



length



F number
1.64
2.26
2.91



D1
0.65
17.95929
26.3735



D2
28.27627
10.96698
2.552771



D3
7.296295
3.465589
10.93191



D4
4.835614
8.66632
1.2



















TABLE 3









Number of surfaces











16
17
20
















C
0.121294563
−0.001595077
0.106923587



K
−0.5
0
0



A4
−2.8469E−05
4.5773E−05
−1.0425E−04



A6
1.5268E−08
0.0000E+00
−4.2529E−07



A8
0.0000E+00
0.0000E+00
0.0000E+00



A10
0.0000E+00
0.0000E+00
0.0000E+00










i of the lens surface column (where i is a natural number) in Table 1 represents the position of a lens surface when a first surface is a lens surface closest to the object side O and a last surface is a lens surface closest to the image side I. In a lens GjRk of the lens column in Table 1 (where j is a natural number and k is 1 or 2), j represents the position of a lens when a first lens is a lens closest to the object side O and a last lens is a lens closest to the image side I. k represents a lens surface of the object side O when set as 1 and a lens surface of the image side I when set as 2.
In Table 1, R represents a curvature radius (mm) of a lens surface.
In Table 1, D represents an axial surface distance (mm) between an i-th lens surface and an (i+1)-th lens surface at the object side O, and when D varies, D represents an axial surface distance (mm) at the wide angle end, the middle end, or the telephoto end. Meanwhile, the focal length and the F number of the zoom lens at the wide angle end, the middle end, and the telephoto end, respectively, are indicated in Table 2.
In Table 1, Nd represents a refractive index, and Vd represents an Abbe's number.
Table 3 shows the number of surfaces and an aspherical coefficient of an aspherical lens. The aspherical surface may be indicated using the following aspherical Equation x.




  
    x
    =
    
      
        
          
            (
            ch
            )
          
          2
        
        
          1
          +
          
            
              1
              -
              
                
                  (
                  
                    k
                    +
                    1
                  
                  )
                
                ⁢
                
                  c
                  2
                
                ⁢
                
                  h
                  2
                
              
            
          
        
      
      +
      
        
          ∑
          
            i
            =
            2
          
          6
        
        ⁢
        
          
        
        ⁢
        
          
            A
            
              2
              ⁢
              
                
              
              ⁢
              i
            
          
          ⁢
          
            h
            
              2
              ⁢
              
                
              
              ⁢
              i
            
          
        
      
    
  
  ,




where x is a distance from a vertex of a lens in optical axis direction, h is a distance in a direction perpendicular to the optical axis, K is a conic constant, Ai is an aspherical coefficient, and c is a reverse number (1/R) of a curvature radius at the vertex of the lens.

Spherical aberration, astigmatism, distortion aberration, and chromatic difference of magnification of the zoom lens having the above structure according to the first exemplary embodiment are shown in FIGS. 3, 4, and 5.
FIG. 3 illustrates aberrations at the wide angle end, and FIG. 4 illustrates aberrations at the middle end, and FIG. 5 illustrates aberrations at the telephoto end.
Spherical aberration for d-line is indicated by a solid line, and spherical aberration for g-line is indicated by a one-dot oblique line. Astigmatism is represented by a saggital ray ΔS and a meridional ray ΔM for each wavelength. Distortion aberration is represented for a wavelength of 587.56 nm. Lateral chromatic aberration for g-line of magnification is represented by a line.
The zoom lens according to the first exemplary embodiment has a zooming rate of about 17.9× and may properly correct each of the aforementioned aberration, as illustrated in FIGS. 3, 4, and 5.
A structure of a zoom lens based on design data of a second embodiment is shown in FIG. 6. The zoom lens of FIG. 6 according to the second exemplary embodiment has the same structure as that of the zoom lens of FIG. 1, and the following table 4 shows the design data of the zoom lens.
The variables and identifiers of table 4 are the same as that of table 1.












TABLE 4





Lens

Radius of
Thick-
Refractive
Abbe's


surface
Lens
curvature
ness
index
number


(i)
(GjRk)
(R)
(D)
(Nd)
(Vd)




















1
G1R1
108.39785
1.300
1.84666
23.78


2
G1R2/G2R1
38.80964
5.687
1.49700
81.61


3
G2R2
321.41392
0.200


4
G3R1
56.99701
3.705
1.72916
54.67


5
G3R2
809.02699
0.200


6
G4R1
30.82923
3.876
1.77250
49.62


7
G4R2
84.51211
D1


8
G5R1
53.28842
0.800
1.88300
40.80


9
G5R2
6.72058
4.192


10
G6R1
−21.75523
0.800
1.83481
42.72


11
G6R2
29.36278
0.200


12
G7R1
14.26015
3.653
1.84666
23.78


13
G7R2/G8R1
−24.07464
0.850
1.77250
49.62


14
G8R2
49.31345
D2


15
Iris
1.00E+18
0.350



diaphragm


16
G9R1
8.08558
4.700
1.69350
53.20


17
G9R2
−1066.85368
0.699


18
G10R1
12.97788
1.000
1.84666
23.78


19
G10R2
6.01215
D3


20
G11R1
9.34494
5.507
1.48749
70.20


21
G11R2/G12R1
−9.79114
0.900
1.84666
23.78


22
G12R2
−16.50220
D4


23
Plane
1.00E+18
2.880
1.51680
64.20


24
Plane
1.00E+18
2.430









Spherical aberration, astigmatism, distortion aberration, and chromatic aberration of magnification of the zoom lens according to the second exemplary embodiment are shown in FIGS. 7, 8, and 9. Illustrative representations of FIGS. 7 through 9 are similar to those of FIGS. 3 through 5.
The zoom lens of the second exemplary embodiment satisfies conditions, as illustrated in Table 4. The zoom lens of the second exemplary embodiment has a zooming rate of about 18.8× and may properly correct each of the aforementioned aberrations, as illustrated in FIGS. 7, 8, and 9.











TABLE 5







Wide angle
Middle
Telephoto



end
end
end





















Focal
4.62
20.39
87.00



length



F number
1.65
2.34
2.89



D1
0.65
17.8287
26.36515



D2
28.27627
11.09757
2.561119



D3
8.081343
3.618478
11.28494



D4
4.203596
8.66646
1





















TABLE 6







16
17
20





















C
0.123676907
−0.000937336
0.10700982



K
−0.5
0
0



A4
−2.8469E−05
4.5773E−05
−1.0425E−04



A6
1.5268E−08
0.0000E+00
−4.2529E−07



A8
0.0000E+00
0.0000E+00
0.0000E+00



A10
0.0000E+00
0.0000E+00
0.0000E+00










A structure of a zoom lens based on design data of a third exemplary embodiment is shown in FIG. 10. The zoom lens of FIG. 10 has the same structure as that of the zoom lens of FIG. 1, and the following tables 7, 8, and 9 show the design data of the zoom lens. The variables and identifiers of tables 7, 8, and 9 are the same as those of tables 1, 2, and 3.












TABLE 7





Lens

Radius of
Thick-
Refractive
Abbe's


surface
Lens
curvature
ness
index
number


(i)
(GjRk)
(R)
(D)
(Nd)
(Vd)




















1
G1R1
104.76570
1.300
1.84666
23.78


2
G1R2/G2R1
38.20108
5.824
1.49700
81.61


3
G2R2
276.67561
0.200


4
G3R1
55.95163
3.825
1.72916
54.67


5
G3R2
750.23130
0.200


6
G4R1
31.14282
3.885
1.77250
49.62


7
G4R2
87.13674
D1


8
G5R1
71.23104
0.800
1.88300
40.80


9
G5R2
6.68350
4.050


10
G6R1
−28.14992
0.800
1.83481
42.72


11
G6R2
22.41795
0.200


12
G7R1
12.78157
3.713
1.84666
23.78


13
G7R2/G8R1
−30.47981
0.850
1.77250
49.62


14
G8R2
45.02467
D2


15
Iris
1.00E+18
0.350



diaphragm


16
G9R1
8.01727
4.700
1.69350
53.20


17
G9R2
−704.05940
1.061


18
G10R1
13.07743
1.000
1.84666
23.78


19
G10R2
5.74667
D3


20
G11R1
8.85432
5.000
1.48749
70.20


21
G11R2/G12R1
−10.04982
0.900
1.84666
23.78


22
G12R2
−16.24472
D4


23
Plane
1.00E+18
2.880
1.51680
64.20


24
Plane
1.00E+18
2.430




















TABLE 8







Wide angle
Middle
Telephoto



end
end
end





















Focal
4.66
20.39
88.75



length



F number
1.66
2.33
2.93



D1
0.65
17.88103
26.36515



D2
28.27627
11.04524
2.561119



D3
8.653215
4.285486
11.95116



D4
4.297942
8.66567
1



















TABLE 9









Number of surfaces











16
17
20
















C
0.124730744
−0.001420335
0.112939278



K
−0.47
0
0



A4
−3.0048E−05
5.8845E−05
−1.0425E−04



A6
−1.0071E−07
0.0000E+00
−3.7396E−07



A8
2.3587E−09
0.0000E+00
0.0000E+00



A10
0.0000E+00
0.0000E+00
0.0000E+00










Spherical aberration, astigmatism, distortion aberration, and chromatic difference of magnification of the zoom lens having the above structure according to the third exemplary embodiment are shown in FIGS. 11, 12, and 13. The descriptions of FIGS. 11, 12, and 13 are similar to those above with respect to FIGS. 3 through 5.
The zoom lens of the third exemplary embodiment has a zooming rate of about 19.0× and may properly correct each of the aforementioned aberration, as illustrated in FIGS. 11, 12, and 13.
A structure of a zoom lens based on design data of a fourth exemplary embodiment is shown in FIG. 14. The zoom lens of FIG. 14 has the same structure as that of the zoom lens of FIG. 1, and the following tables 13 through 15 show the design data of the zoom lens of the fourth exemplary embodiment. Also, variables and identifiers of tables 13 through 15 are the same as those described above with respect to tables 1 through 3.












TABLE 10





Lens

Radius of
Thick-
Refractive
Abbe's


surface
Lens
curvature
ness
index
number


(i)
(GjRk)
(R)
(D)
(Nd)
(Vd)




















1
G1R1
127.86685
1.582
1.84666
23.78


2
G1R2/G2R1
41.01482
5.609
1.49700
81.61


3
G2R2
548.55597
0.200


4
G3R1
55.63303
3.738
1.72916
54.67


5
G3R2
782.60841
0.200


6
G4R1
30.54129
3.844
1.77250
49.62


7
G4R2
79.27478
D1


8
G5R1
67.49803
0.800
1.88300
40.80


9
G5R2
6.73144
3.616


10
G6R1
−27.45549
0.800
1.83481
42.72


11
G6R2
17.85686
0.200


12
G7R1
12.42626
4.035
1.84666
23.78


13
G7R2/G8R1
−32.76014
0.850
1.77250
49.62


14
G8R2
117.77246
D2


15
Iris
1.00E+18
0.350



diaphragm


16
G9R1
8.37333
4.700
1.69350
53.20


17
G9R2
−708.17294
0.489


18
G10R1
14.04082
1.000
1.84666
23.78


19
G10R2
6.64997
D3


20
G11R1
10.27168
4.110
1.51633
64.06


21
G11R2/G12R1
−9.75173
0.900
1.84666
23.78


22
G12R2
−17.86303
D4


23
Plane
1.00E+18
2.880
1.51680
64.20


24
Plane
1.00E+18
2.430




















TABLE 11







Wide angle
Middle
Telephoto



end
end
end





















Focal
4.65
20.39
80.00



length



F number
1.64
2.23
2.86



D1
0.65
18.07722
26.3735



D2
28.27627
10.84905
2.552771



D3
7.257847
3.534748
11.00108



D4
4.943229
8.666328
1.2



















TABLE 12









Number of surfaces











16
17
20
















C
0.119426759
−0.001412084
0.097355071



K
−0.5
0
0



A4
−2.8469E−05
4.5773E−05
−1.0425E−04



A6
1.5268E−08
0.0000E+00
−4.2529E−07



A8
0.0000E+00
0.0000E+00
0.0000E+00



A10
0.0000E+00
0.0000E+00
0.0000E+00










Spherical aberration, astigmatism, distortion aberration, and chromatic difference of magnification the zoom lens having the above structure according to the fourth exemplary embodiment are shown in FIGS. 15, 16, and 17. The illustrative representations of FIGS. 15, 16, and 17 are similar to those of FIGS. 3 through 5.
The zoom lens of the fourth exemplary embodiment has a zooming rate of about 17.2× and may properly correct each of the aforementioned aberration, as illustrated in FIGS. 15, 16, and 17.
A structure of a zoom lens based on design data of a fifth exemplary embodiment is shown in FIG. 18. The zoom lens of FIG. 18 has the same structure as that of the zoom lens of FIG. 1, and the following tables 13, 14, and 15 show the design data of the zoom lens of the fifth exemplary embodiment. The variables and identifiers of tables 13, 14, and 15 are the same as those of tables 1, 2, and 3.












TABLE 13





Lens

Radius of
Thick-
Refractive
Abbe's


surface
Lens
curvature
ness
index
number


(i)
((GjRk)
(R)
(D)
(Nd)
(Vd)




















1
G1R1
163.09425
1.200
1.84666
23.78


2
G1R2/G2R1
44.00423
5.821
1.49700
81.61


3
G2R2
−1000.00000
0.200


4
G3R1
63.34724
3.462
1.72916
54.67


5
G3R2
1000.00000
0.200


6
G4R1
30.27719
4.070
1.77250
49.62


7
G4R2
84.72659
D1


8
G5R1
66.47501
0.800
1.88300
40.80


9
G5R2
7.10296
4.265


10
G6R1
−19.72125
0.800
1.83481
42.72


11
G6R2
70.85877
0.200


12
G7R1
15.51835
3.639
1.84666
23.78


13
G7R2/G8R1
−23.27269
0.850
1.77250
49.62


14
G8R2
33.96808
D2


15
Iris
1.00E+18
0.350



diaphragm


16
G9R1
7.95404
4.700
1.69350
53.20


17
G9R2
1000.00000
0.611


18
G10R1
12.37741
1.000
1.84666
23.78


19
G10R2
5.90478
D3


20
G11R1
9.09761
4.246
1.51633
64.06


21
G11R2/G12R1
−9.76915
0.900
1.84666
23.78


22
G12R2
−17.05484
D4


23
Plane
1.00E+18
2.880
1.51680
64.20


24
Plane
1.00E+18
2.430




















TABLE 14







Wide angle
Middle
Telephoto



end
end
End





















Focal
4.60
20.39
76.00



length



F number
1.65
2.28
2.82



D1
0.65
17.84228
25.96043



D2
28.27627
11.08399
2.965845



D3
7.608525
3.480579
9.769246



D4
4.538654
8.6666
2.377933



















TABLE 15









Number of surfaces











16
17
20
















C
0.12572226
0.001
0.109919025



K
−0.5
0
0



A4
−2.8469E−05
4.5773E−05
−1.0425E−04



A6
1.5268E−08
0.0000E+00
−4.2529E−07



A8
0.0000E+00
0.0000E+00
0.0000E+00



A10
0.0000E+00
0.0000E+00
0.0000E+00










Spherical aberration, astigmatism, distortion aberration, and chromatic difference of magnification of the zoom lens having the above structure according to the fifth exemplary embodiment are shown in FIGS. 19, 20, and 21. The illustrative representations of FIGS. 19, 20, and 21 are similar to those of FIGS. 3 through 5.
The zoom lens of the fifth exemplary embodiment has a zooming rate of approximately 16.5× and may properly correct each of the aforementioned aberration, as illustrated in FIGS. 19, 20, and 21.
A structure of a zoom lens based on design data of a sixth exemplary embodiment is shown in FIG. 22. The zoom lens of FIG. 22 has the same structure as that of the zoom lens of FIG. 1, and the following tables 16, 17, and 18 show the design data of the zoom lens of the sixth embodiment. The variables and identifiers of tables 16, 17, and 18 are the same as those set forth above with respect to tables 1 through 3.












TABLE 16





Lens

Radius of
Thick-
Refractive
Abbe's


surface
Lens
curvature
ness
index
number


(i)
((GjRk)
(R)
(D)
(Nd)
(Vd)




















1
G1R1
341.81496
1.400
1.84666
23.78


2
G1R2/G2R1
50.54268
6.500
1.45650
90.27


3
G2R2
−221.50088
0.200


4
G3R1
60.89819
4.362
1.73400
51.05


5
G3R2
−926.25733
0.200


6
G4R1
30.81335
3.830
1.77250
49.62


7
G4R2
71.93096
D1


8
G5R1
60.17265
0.800
1.88300
40.80


9
G5R2
6.85760
3.872


10
G6R1
−17.96616
0.800
1.83481
42.72


11
G6R2
95.07716
0.200


12
G7R1
15.35510
4.404
1.84666
23.78


13
G7R2/G8R1
−25.21508
0.850
1.77250
49.62


14
G8R2
32.98076
D2


15
Iris
1.00E+18
0.350



diaphragm


16
G9R1
10.16590
6.500
1.69350
53.20


17
G9R2
−714.39840
1.273


18
G10R1
18.24725
1.000
1.84666
23.78


19
G10R2
8.13518
D3


20
G11R1
10.42112
5.000
1.48749
70.24


21
G11R2/G12R1
−8.99178
0.900
1.84666
23.78


22
G12R2
−14.33099
D4


23
Plane
1.00E+18
2.880
1.51680
64.20


24
Plane
1.00E+18
2.430




















TABLE 17







Wide angle
Middle
Telephoto



end
end
end





















Focal
4.65
20.39
115.00



length



F number
1.67
2.53
3.62



D1
0.65
18.29
27.88



D2
29.69
12.05
2.46



D3
9.31
4.05
14.99



D4
6.68
11.94
1.00



















TABLE 18









Number of surfaces











16
17
20
















C
0.098368104
−0.001399779
0.095958933



K
−0.409551138
0
0



A4
−2.0062E−05
5.7064E−05
−1.0418E−04



A6
8.2492E−08
0.0000E+00
−2.9081E−07



A8
−1.1343E−09
0.0000E+00
0.0000E+00



A10
0.0000E+00
0.0000E+00
0.0000E+00










Spherical aberration, astigmatism, distortion aberration, and chromatic difference of magnification of the zoom lens having the above structure according to the sixth exemplary embodiment are shown in FIGS. 23, 24, and 25. The illustrative representations of FIGS. 23, 24, and 25 are similar to those of FIGS. 3 through 5. The zoom lens of the sixth exemplary embodiment has a zooming rate of about 24.7× and may properly correct each of the aforementioned aberrations, as illustrated in FIGS. 23, 24, and 25.
The following table shows that the first through sixth exemplary embodiments satisfy conditions of Equations 1 through 13.













TABLE 19






First
Second
Third
Fourth
Fifth
Sixth


Equation
embodiment
embodiment
embodiment
embodiment
embodiment
embodiment





















|f2|/fw
1.58
1.51
1.5
1.61
1.55
1.475


f1/fT
0.48
0.452
0.443
0.493
0.515
0.347


ΣD/fT
1.01
0.98
0.97
1.04
1.1
0.818


ν1D
81.6
81.6
81.6
81.6
81.6
90.27


R3W/R3T
2.27
2.16
2.28
2.11
2.1
2.243


f3/fw
5.16
5
5.04
4.94
4.91
5.811


β4T
0.46
0.46
0.44
0.51
0.41
0.503









As described above, through the above-described lens configuration, a zoom lens having a high zooming rate (for example, 15 times or more), a small-size, and a high optical performance, and a photographing apparatus including the zoom lens can be provided.
FIG. 26 is a schematic view of a photographing apparatus 100 having a zoom lens 111, according to an exemplary embodiment. The photographing apparatus 100 includes the zoom lens 111, which may be one of the exemplary embodiments described above, and an imaging sensor 112 that converts light condensed by the zoom lens 111 into an electrical image signal. The photographing apparatus 100 may include a recording unit 113 in which information corresponding to an image of a subject that is photoelectrically converted by the imaging sensor 112 is recorded, and a view finder 114 that observes the image of the subject. A display unit 115 that may display the image of the subject may be provided. Although the view finder 114 and the display unit 115 are additionally provided, only an electronic finder in which a view finder and a display unit are used together without installing an additional view finder may be provided. The zoom lens 111 according to an exemplary embodiment may be employed in a single-lens reflex camera including a reflection mirror and an optical finder and a camera having an electronic finder.
The photographing apparatus of FIG. 26 is an example, and the present invention is not limited thereto and can be employed in various types of optical devices.
While exemplary embodiments have been particularly shown and described, 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 present invention as defined by the following claims.

## Claims

1. A zoom lens comprising:
a first lens group 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 moving the second lens group in an optical axis direction and focusing is performed by moving the fourth lens group in the optical axis direction, and
wherein the zoom lens satisfies the following Equations:


1.4<|f2|/fW<2.0,



0.3<f1/fT<0.6,


where a combined focal length of the first lens group is f1, a combined focal length of the second lens group is f2, a focal length of the zoom lens at a wide angle end is fw, and a focal length of the zoom lens at a telephoto end is fT.

2. The zoom lens of claim 1, wherein an iris diaphragm is disposed between the second lens group and the third lens group.

3. The zoom lens of claim 1, wherein the first lens group comprises a negative lens and three positive lenses sequentially arranged from the object side.

4. The zoom lens of claim 3, wherein the three positive lenses comprise two positive lenses each having a convex surface on the object side.

5. The zoom lens of claim 1, wherein the second lens group comprises at least three negative lenses and a positive lens sequentially arranged from the object side.

6. The zoom lens of claim 1, wherein the third lens group comprises a positive lens having a convex surface on the object side and a negative meniscus lens having a concave surface on the image side.

7. The zoom lens of claim 6, wherein, when a lens surface of the object side of the meniscus lens has a curvature radius of R3W and a lens surface of the image side of the meniscus lens has a curvature radius of R3T, the zoom lens satisfies a following Equation:


1.5<R3W/R3T<3.0.

8. The zoom lens of claim 1, wherein, when a length of an optical axis from a vertex of the object side of the lens disposed closest to the object side of the first lens group to an image plane is ΣD, the zoom lens satisfies a following Equation:


0.6<(ΣD/fT)<1.3.

9. The zoom lens of claim 1, wherein, when an Abbe's number of a positive lens disposed closest to the object side of the first lens group is v1D, the zoom lens satisfies the following Equation:


80<ν1D.

10. The zoom lens of claim 1, wherein the fourth lens group comprises a positive lens having at least one aspherical surface and two convex surfaces and a negative meniscus lens having a concave surface on the object side.

11. The zoom lens of claim 1, wherein, when a focal length of the third lens group is f3, the zoom lens satisfies the following Equation:


4.0<f3/fW<6.0.

12. The zoom lens of claim 1, wherein, when lateral magnification during focusing on an object at infinity e at the telephoto end is β4T, the fourth lens group satisfies a following Equation:


0.3<β4T<0.6.

13. The zoom lens of claim 1, wherein the first lens group comprises a negative lens, a positive lens, and two positive lenses each having a convex surface on the object side, wherein the lenses are sequentially arranged from the object side to the image side, and the second lens group comprises at least three negative lenses and a positive lens, wherein the lenses are sequentially arranged from the object side to the image side, and the third lens group comprises a positive lens having a convex surface on the object side and a negative meniscus lens having a concave surface on the image side, wherein the lenses are sequentially arranged from the object side to the image side.

14. A photographing apparatus comprising:
a zoom lens; and
an imaging device for photoelectrically converting an image formed by the zoom lens,
wherein the zoom lens comprises:
a first lens group 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 moving the second lens group in an optical axis direction and focusing is performed by moving the fourth lens group in the optical axis direction, and
wherein the zoom lens satisfies the following Equations:


1.4<|f2|/fW<2.0,



0.3<f1/fT<0.6,


where a combined focal length of the first lens group is f1, a combined focal length of the second lens group is f2, a focal length of the zoom lens at a wide angle end is fw, and a focal length of the zoom lens at a telephoto end is fT.

15. The photographing apparatus of claim 14, wherein an iris diaphragm is disposed between the second lens group and the third lens group.

16. The photographing apparatus of claim 14, wherein the first lens group comprises a negative lens and three positive lenses sequentially arranged from the object side.

17. The photographing apparatus of claim 16, wherein the three positive lenses comprise two positive lenses each having a convex surface on the object side.

18. The photographing apparatus of claim 14, wherein the second lens group comprises at least three negative lenses and a positive lens sequentially arranged from the object side.

19. The photographing apparatus of claim 14, wherein the third lens group comprises a positive lens having a convex surface on the object side and a negative meniscus lens having a concave surface on the image side.

20. The photographing apparatus of claim 19, wherein, when a lens surface of the object side of the meniscus lens has a curvature radius of R3W and a lens surface of the image side of the meniscus lens has a curvature radius of R3T, the zoom lens satisfies the following Equation:


1.5<R3W/R3T<3.0.

21. The photographing apparatus of claim 14, wherein, when a length of an optical axis from a vertex of the object side of the lens disposed closest to the object side of the first lens group to an image plane is ΣD, the zoom lens satisfies the following Equation:


0.6<(ΣD/fT)<1.3.