Abstract:
A zoom lens for capturing images that enhances the image aberration correction rate to achieve high resolution and zooming ratio. The zoom lens includes, in sequence from an object side to an image side, a first lens group with positive refraction power, a second lens group with negative refraction power, a third lens group with positive refraction power, a fourth lens group with positive refraction power, a fifth lens group with positive refraction power and a sixth lens group with positive refraction power. The positions of first and sixth lens groups are fixed during photographing. When the zoom lens is made to zoom from a wide-angle end to a telephoto end thereof, the second lens group moves toward the image side while the fourth and fifth lens groups move toward the object side. In addition, the zoom lens has a reflection element so as to fold the image light entering thereof.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a zoom lens, and particularly to a small-size and high-zooming ratio zoom lens having a reflective element therein. 
         [0003]    2. Description of Prior Art 
         [0004]    In recent years, most electronic devices, such as mobile phones, personal digital assistants (PDAs), notebook computers, have been integrated with a zoom lens. Differing from the digital zoom, the zoom lens can vary zoom ratio without deteriorating the image quality. 
         [0005]    For example, U.S. Pub. No. 2005/0099700A1 disclosed a positive-negative-positive-positive 4-group zoom lens. When the zoom lens changes from a wide-angle end state to a telephoto end state, the first lens group and the third lens group are fixed in a predetermined position in an optical axis direction, and the second lens group moves towards the image side. The prior art disclosed an optical zooming structure, but it cannot achieve high zoom ratio. 
         [0006]    Then, as a configuration of a zoom lens to provide compatibility between slimming down and strong durability, in a four-group configuration of first positive, second negative, third positive and fourth positive groups, a right-angle prism is placed in the first lens group for bending the optical path approximately 90.degree. at midpoint to form a refractive optical system, thereby shortening the length of the optical system in the thickness direction thereof (Refer to JP-A-8-248318, JP-A-2000-131610 and JP-A-2003-202500). In the configuration, the first lens group is fixed when zoomed and focused and thus a structure wherein the entire lens barrel can be housed in the imaging apparatus main body can be produced, making it possible to increase the durability as compared with the zoom lens made up of three groups described above. 
         [0007]    However, the zoom lens described in JP-A-8-248318 is inappropriate for slimming down because the first lens group is large and the overall number of lenses is also large although the zoom lens has a large zoom ratio and a bright F value. The zoom lens described in JP-A-2000-131610 has a small number of lenses and a large angle of field at a wide angle end, but the first lens group is large and the right-angle prism has a low refractive index and is hard to totally reflect and thus reflecting coat becomes necessary on the reflection face of the right-angle prism, resulting in lowering of transmittance in the whole system and an increase in the cost. The zoom lens described in JP-A-2003-202500 involves various examples, which contain some examples of compact zoom lenses with a small number of lenses, but high-refractive index and high-dispersion material is used for the right-angle prism in every example and the transmittance on the short wavelength side of a visible light beam lowers. That is, in JP-A-2003-202500, a right-angle prism of a material with the refractive index at the d-line exceeding 1.8 and the Abbe number less than 30 is adopted as an example; under present circumstances, however, such a high-refractive index and high-dispersion material having sufficiently high transmittance does not exist and is not practical. 
       SUMMARY OF THE INVENTION 
       [0008]    An object of the present invention is to provide a zoom lens with a reflective element to provide a high zoom ratio and high level of image performance. Thus, the camera installed the zoom lens also shortens the operating timing. 
         [0009]    To achieve the above object, the present invention provides a zoom lens including, in order from an object side to an image side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power, a fifth lens group having positive refractive power and a sixth lens group having positive refractive power. The first and sixth lens groups are fixed when the zoom lens varies a power thereof. During zooming, the second lens group moves toward the first lens group along the optical axis, and the fourth and fifth lens groups move toward the sixth lens group. 
         [0010]    The first lens group further includes an optical-path bending member for folding the optical axis at least approximately ninety degrees. 
         [0011]    During zooming, the displacement of the second lens group moving along the optical axis is ΔX2 and the displacement of the fifth lens group moving along the optical axis is ΔX5, and then the zoom lens of the present invention satisfies the following condition (1): 
         [0000]      0.7 ×ΔX 2=Δ X 5   (1). 
         [0012]    During zooming, the zoom lens of the present invention further satisfies the following condition (2): 
         [0000]    
       
         
           
             
               
                 
                   
                     2.17 
                     &lt; 
                     
                       TTL 
                       f 
                     
                     &lt; 
                     8.7 
                   
                   , 
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where TTL represents a distance between the most object side lens surface of the zoom lens and an image plane and f represents a focal length of the zoom lens. 
         [0013]    Each of the at least three lenses of the zoom lens has an aspheric surface, and the first lens of the first lens group has an aspheric surface. 
         [0014]    In the zoom lens of the present invention, the first lens of the first lens group is a negative meniscus lens having an aspheric surface and has the functions of receiving light in wide angle and reducing the aberration. 
         [0015]    In first lens group of the zoom lens of the present invention, the optical-path bending member for folding the optical axis is located between the first and second lenses. 
         [0016]    In the present invention, the lens of the sixth lens group adjacent to the image side can be finely moved along the optical axis to compensate the focus of the zoom lens. 
         [0017]    In the zoom lens of the present invention, the second lens group includes, in order from an object side to an image side, a fourth negative lens, a fifth negative lens and a sixth positive lens. The fifth negative lens and the sixth positive lens are cemented. 
         [0018]    In the zoom lens of the present invention, the fourth lens group includes, in order from an object side to an image side, an eighth positive lens and a ninth negative lens, and the ninth negative lens is meniscus. 
         [0019]    When the zoom lens changes from a wide-angle end state to a telephoto end state, the second, fourth and fifth lens groups move toward the third lens group. 
         [0020]    The present zoom lens has a plurality of movable lens groups, but the displacement of each movable lens group is tiny. Thus, the present zoom lens provides the advantages of small size and low cost as compared to the conventional designs, while ensuring a high level of image performance. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The present invention may be best understood through the following description with reference to the accompanying drawings, in which: 
           [0022]      FIG. 1  is a schematic view illustrating lens positions of a zoom lens of the present invention at a telephoto end state; 
           [0023]      FIG. 2A  is a graphic representation of spherical aberration according to the zoom lens of the present invention at the telephoto end state; 
           [0024]      FIG. 2B  is a graphic representation of astigmatism aberration according to the zoom lens of the present invention at the telephoto end state; 
           [0025]      FIG. 2C  is a graphic representation of distortion aberration according to the zoom lens of the present invention at the telephoto end state; 
           [0026]      FIG. 2D  is a graphic representation of lateral chromatic aberration according to the zoom lens of the present invention at the telephoto end state; 
           [0027]      FIG. 3  is a schematic view illustrating lens positions of a zoom lens of the present invention at a intermediate position; 
           [0028]      FIG. 4A  is a graphic representation of spherical aberration according to the zoom lens of the present invention at the intermediate position; 
           [0029]      FIG. 4B  is a graphic representation of astigmatism aberration according to the zoom lens of the present invention at the intermediate position; 
           [0030]      FIG. 4C  is a graphic representation of distortion aberration according to the zoom lens of the present invention at the intermediate position; 
           [0031]      FIG. 4D  is a graphic representation of lateral chromatic aberration according to the zoom lens of the present invention at the intermediate position; 
           [0032]      FIG. 5  is a schematic view illustrating lens positions of a zoom lens of the present invention at a wide-angle end state; 
           [0033]      FIG. 6A  is a graphic representation of spherical aberration according to the zoom lens of the present invention at the wide-angle end state; 
           [0034]      FIG. 6B  is a graphic representation of astigmatism aberration according to the zoom lens of the present invention at the wide-angle end state; 
           [0035]      FIG. 6C  is a graphic representation of distortion aberration according to the zoom lens of the present invention at the wide-angle end state; 
           [0036]      FIG. 6D  is a graphic representation of lateral chromatic aberration according to the zoom lens of the present invention at the wide-angle end state; 
           [0037]      FIG. 7  is a sectional view showing a zoom lens according to the present invention together with the movement of each lens group upon zooming from a wide-angle end state to a telephoto end state. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0038]    The above-mentioned and other technical contents, features and effects of the present invention will become apparent from the hereinafter set forth detailed description of preferred numerical embodiments of the present invention in combination with the drawings. 
         [0039]      FIG. 1  is a schematic view illustrating lens positions of a zoom lens of the present invention at a telephoto end state,  FIG. 3  is a schematic view illustrating lens positions of a zoom lens of the present invention at a intermediate position, and  FIG. 5  is a schematic view illustrating lens positions of a zoom lens of the present invention at a wide-angle end state. The present invention provides a zoom lens, which is used in an image pickup device or a photographic device for forming an image of an object onto an image sensor or a film. The lens construction of the present zoom lens is illustrated in  FIGS. 1 ,  3  and  5 , in which symbol “OBJ” denotes the object side, symbol “IMA” denotes the image side, symbol “TTL” denotes a distance between the most object side lens surface of the zoom lens and an image plane, symbol “OA” denotes an optical axis of the zoom lens, and symbol “S” denotes an aperture stop. As shown in  FIGS. 1 ,  3  and  5 , the present zoom lens comprises, in order from the object side OBJ to the image side IMA, a first lens group  10  having positive refractive power, a second lens group  20  having negative refractive power, a third lens group  30  having positive refractive power, a fourth lens group  40  having positive refractive power, a fifth lens group  50  having positive refractive power and a sixth lens group having positive refractive power. 
         [0040]    When the present zoom lens varies a power thereof, the positions of the first lens group  10 , third lens group  30  and sixth lens group  60  are fixed, and the second lens group  20 , fourth lens group  40  and fifth lens group  50  are moved along the optical axis OA. The first lens group  10  includes an optical-path bending member L 2  for folding the optical axis at least approximately ninety degrees, such as a prism for folding the optical path for the first lens group  10 . 
         [0041]    When the present zoom lens varies a power thereof, the present zoom lens satisfies the following condition: 
         [0000]      0.7×Δ X 2=Δ X 5   (1) 
         [0000]    where ΔX 2  represents the displacement of the second lens group  20  moving along the optical axis OA and ΔX 5  represents the displacement of the fifth lens group  50  moving along the optical axis OA. 
         [0042]    When the present zoom lens varies a power thereof, the present zoom lens satisfies the following condition: 
         [0000]    
       
         
           
             
               
                 
                   2.17 
                   &lt; 
                   
                     TTL 
                     f 
                   
                   &lt; 
                   8.7 
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where TTL represents a distance along the optical axis OA from an object-side surface OBJ of the first lens L 1  of first lens group  10  to an image forming surface and f represents the focal length of the present zoom lens. 
         [0043]    The first lens group  10  with a focal length f 1 =3.987148 mm includes, in order from the object side OBJ to the image side IMA, a first negative lens L 1 , an optical-path bending member L 2 , a second positive lens L 3  and a third positive lens L 4 . The first negative lens L 1  is a negative meniscus lens whose convex surface R 11  is oriented toward the object side, and has two aspheric surfaces. Thus, the first lens L 1  has the functions of receiving light in wide angle and reducing the distortion aberration. 
         [0044]    The second lens group  20  with a focal length f 2 =−1.2975 mm includes, in order from the object side OBJ to the image side IMA, a fourth negative lens L 5 , a fifth negative lens L 6  and a sixth positive lens L 7 . The fifth negative lens L 6  and the sixth positive lens L 7  are combined to form a cemented lens. 
         [0045]    The third lens group  30  with a focal length f 3 =3.5675 mm includes a seventh positive lens L 8 . The seventh positive lens L 8  having two aspheric surfaces R 81 , R 82  is a positive meniscus lens whose convex surface R 81  is oriented toward the object side OBJ. 
         [0046]    The fourth lens group  40  with a focal length f 4 =3.8279 mm includes, in order from the object side OBJ to the image side IMA, an eighth positive lens L 9  and a ninth negative lens L 10 , and the eighth positive lens L 9  and the ninth negative lens L 10  are combined to form a cemented lens. The object side surface R 91  of the eighth positive lens L 9  which does not adhere to the ninth negative lens L 10  is aspheric. In addition, the ninth negative lens L 10  is a negative meniscus lens whose convex surface R 102  is oriented toward the image side IMA. 
         [0047]    The fifth lens group  50  with a focal length f 5 =20.18135 mm includes a tenth positive lens L 11 . 
         [0048]    The sixth lens group  60  with a focal length f 6 =14.8341 mm includes, in order from the object side OBJ to the image side IMA, an eleventh negative lens L 12 , a twelfth positive lens L 13  and a thirteenth positive lens L 14 . The eleventh negative lens L 12  and the twelfth positive lens L 13  are combined to form a cemented lens. The thirteenth positive lens L 14  adjacent to the image side IMA can be finely moved along the optical axis OA to compensate the focus of the zoom lens. 
         [0049]    The aperture stop S is located between the third lens group  30  and the fourth lens group  40 . 
         [0050]    Refer to  FIG. 7 , it shows that the zoom lens is at a wide-angle end state (Wide End) or at a telephoto end state (Tele End). The second lens group  20  is mainly involved with zooming and moves from the object side OBJ to the image side IMA along the optical axis OA at the time of zooming from a wide-angle end state to a telephoto end state. The fourth lens group  40  and the fifth lens group  50  are also mainly involved with zooming and move from the image side IMA to the object side OBJ along the optical axis OA at the time of zooming from a wide-angle end state to a telephoto end state. In other words, the second, fourth and fifth lens groups  20 ,  40 ,  50  move toward the third lens group  30  at the time of zooming from a wide-angle end state to a telephoto end state. 
         [0051]    Numerical values of the component lenses of the present zoom lens according to the embodiment of the invention are shown in Data Table 1 given below. In Data Table 1 and other similar data tables provided hereinafter, “i” represents the order of the surface from the object side (including lens surfaces, the aperture stop S and the glass element PL), “Ri” represents the radius of curvature (mm) of the ith surface, “D” represents the ith member thickness or the distance (mm) between the ith surface and the (i+1)th surface, and “Nd” and “Vd” respectively represent the refractive index (d-line) and Abbe number (d-line) of the ith member. 
         [0000]    
       
         
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
                 DATA TABLE 1 
               
               
                   
                   
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
               
               
                   
                 (i) 
                 Lens 
                 Ri (mm) 
                 D (mm) 
                 Nd 
                 Vd 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                  1 
                 L1 
                 8.2622 
                 0.15 
                 1.84666 
                 23.83 
               
               
                   
                  2 
                   
                 3.0148 
                 0.545 
               
               
                   
                  3 
                 L2 
                 ∞ 
                 2.3 
                 1.883 
                 40.77 
               
               
                   
                  4 
                   
                 ∞ 
                 0.05 
               
               
                   
                  5 
                 L3 
                 8.66 
                 0.325 
                 1.58913 
                 61.14 
               
               
                   
                  6 
                   
                 −8.227 
                 0.025 
               
               
                   
                  7 
                 L4 
                 2.58 
                 0.3625 
                 1.60311 
                 60.64 
               
               
                   
                  8 
                   
                 10.9555 
                 A 
               
               
                   
                  9 
                 L5 
                 −24.125 
                 0.1125 
                 1.7495 
                 35.28 
               
               
                   
                 10 
                   
                 1.48725 
                 0.2125 
               
               
                   
                 11 
                 L6 
                 −3.102 
                 0.1125 
                 1.6935 
                 50.81 
               
               
                   
                 12 
                 L7 
                 1.76325 
                 0.275 
                 1.92286 
                 20.88 
               
               
                   
                 13 
                   
                 8.5705 
                 B 
               
               
                   
                 14 
                 L8 
                 2.525 
                 0.2875 
                 1.8061 
                 40.95 
               
               
                   
                 15 
                   
                 19.5704 
                 0.2 
               
               
                   
                 16 
                 S 
                 ∞ 
                 C 
               
               
                   
                 17 
                 L9 
                 4.5285 
                 0.95 
                 1.48749 
                 70.21 
               
               
                   
                 18 
                 L10 
                 −1.26025 
                 0.125 
                 1.7552 
                 27.51 
               
               
                   
                 19 
                   
                 −1.99675 
                 D 
               
               
                   
                 20 
                 L11 
                 19.822 
                 0.195 
                 1.48749 
                 70.21 
               
               
                   
                 21 
                   
                 19.602 
                 E 
               
               
                   
                 22 
                 L12 
                 −4.3025 
                 0.125 
                 1.7552 
                 27.51 
               
               
                   
                 23 
                 L13 
                 4.0355 
                 0.3425 
                 1.43875 
                 94.95 
               
               
                   
                 24 
                   
                 −28.9865 
                 F 
               
               
                   
                 25 
                 L14 
                 2.24375 
                 0.5075 
                 1.6393 
                 44.87 
               
               
                   
                 26 
                   
                 6.8625 
                 G 
               
               
                   
                 27 
                 PL 
                 ∞ 
                 0.2 
                 1.51633 
                 64.14 
               
               
                   
                 28 
                   
                 ∞ 
                 0.6425 
               
               
                   
                 IMA 
                   
                 ∞ 
                 0 
               
               
                   
                   
               
             
          
         
       
     
         [0052]    According to the embodiment of the present zoom lens, with reference to  FIGS. 1 ,  3  and  5 , surfaces  1  and  2  of the first lens L 1 , surfaces  14  and  15  of the seventh lens L 8  and surface  17  of the eighth lens L 9  are all configured to be aspheric surfaces. Aspheric coefficients for these aspheric surfaces are given in following Data Table 2, wherein Conic represents a cone constant, and E 4 , E 6 , E 8 , E 10 , E 12  and E 14  are aspheric coefficients for fourth, sixth, eighth, tenth, twelfth and fourteenth order terms. During zooming operation, the first lens group  10 , third lens group  30  and sixth lens group  60  may also be kept stationary. That is, the first lens group  10 , third lens group  30  and sixth lens group  60  do not contribute to the zooming action. 
         [0000]    
       
         
               
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
                 DATA TABLE 2 
               
             
             
               
                   
                   
               
               
                   
                 Surface 
               
             
          
           
               
                   
                 1 
                 2 
                 14 
                 15 
                 17 
               
               
                   
                   
               
             
          
           
               
                 Conic 
                 19.3173 
                 1.1293 
                 0.6505 
                 43.7583 
                 −1.985 
               
               
                 E4 
                  8.810304E−3 
                  6.797632E−3 
                 −2.6771904E−3 
                 1.0758016E−2 
                 −1.5812672E−2 
               
               
                 E6 
                 −9.9815526E−4   
                 −2.006016E−4 
                 −6.3158784E−4 
                 3.0704845E−3 
                   2.8153139E−3 
               
               
                 E8 
                 −1.523789E−3 
                 −2.2965944E−3   
                   7.2800993E−3 
                 3.3796588E−3 
                    5.295358E−3 
               
               
                 E10 
                  5.18762E−5 
                 2.6212539E−4 
                 −1.9097217E−2 
                 3.2808632E−3 
                 −9.3548446E−3 
               
               
                 E12 
                 2.0126326E−4 
                 2.9033056E−5 
                   8.7762456E−2 
                  7.094833E−3 
                   8.7517089E−3 
               
               
                 E14 
                 −4.2061957E−5   
                 4.7887476E−5 
                 −5.5675124E−2 
                 5.0608271E−2 
                 −2.0410691E−3 
               
               
                   
               
             
          
         
       
     
         [0053]    Data Table 3 provided below shows variable spacings A, B, C, D and E between the six lens groups at the respective wide-angle end state (W), the intermediate position (M) and the telephoto end state (T) according to the embodiment, wherein A denotes a first variable spacing along the optical axis between the image-side surface  8  of the third positive lens L 4  of the first lens group  10  and the object-side surface  9  of the fourth negative lens of the second lens group  20 , B denotes a second variable spacing along the optical axis between the image-side surface  13  of the sixth positive lens L 7  of the second lens group  20  and the object-side surface  14  of the seventh positive lens L 8  of the third lens group  30 , C denotes a third variable spacing along the optical axis between the aperture stop S and the object-side surface  17  of the eighth positive lens L 9  of the fourth lens group  40 , D denotes a fourth variable spacing along the optical axis between the image-side surface  19  of the ninth negative lens L 10  of the fourth lens group  40  and the object-side surface  20  of the tenth positive lens L 11  of the fifth lens group  50 , and E denotes a fifth variable spacing along the optical axis between the image-side surface  21  of the tenth positive lens of the fifth lens group  50  and the object-side surface  22  of the eleventh negative lens L 12  of the sixth lens group  60 . In addition, the focal lengths f of the present zoom lens at the respective wide-angle end state (W), the intermediate position (M) and the telephoto end state (T) are also provided in Data Table 3. 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                   
               
               
                 Data Table 3 
               
             
          
           
               
                   
                 W (f = 1.737 mm) 
                 M (f = 3.37662 mm) 
                 T (f = 6.55332 mm) 
               
               
                   
                   
               
             
          
           
               
                 A 
                 0.1595 
                 1.208 
                 1.9365 
               
               
                 B 
                 1.90075 
                 0.8525 
                 0.12375 
               
               
                 C 
                 1.66675 
                 0.955 
                 0.17875 
               
               
                 D 
                 0.16325 
                 0.141 
                 0.40725 
               
               
                 E 
                 0.33525 
                 1.069 
                 1.57925 
               
               
                   
               
             
          
         
       
     
         [0054]    Data Table 4 provided below shows variable spacing F between the twelfth positive lens L 13  and the thirteenth positive lens L 14  six lens at the respective wide-angle end state (W), the intermediate position (M) and the telephoto end state (T) according to the embodiment. It also shows variable spacing G between the thirteenth positive lens L 14  and the flat glass PL at the respective wide-angle end state (W), the intermediate position (M) and the telephoto end state (T) according to the embodiment. Thus, F denotes a sixth variable spacing along the optical axis between the image-side surface  24  of the twelfth positive lens L 13  of the sixth lens group  60  and the object-side surface  25  of the thirteenth positive lens L 14  of the sixth lens group  60 , and G denotes a seventh variable spacing along the optical axis between the image-side surface  26  of the thirteenth positive lens L 14  of the sixth lens group  60  and the object-side surface  27  of the flat glass PL. Therefore, the thirteenth positive lens L 14  can be finely moved along the optical axis to compensate the focus of the zoom lens. 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                   
               
               
                 Data Table 4 
               
             
          
           
               
                   
                 W (f = 1.737 mm) 
                 M (f = 3.37662 mm) 
                 T (f = 6.55332 mm) 
               
               
                   
                   
               
             
          
           
               
                 F 
                 2.0586725 
                 2.0546725 
                 2.0604225 
               
               
                 G 
                 0.3483275 
                 0.3523275 
                 0.3465775 
               
               
                   
               
             
          
         
       
     
         [0055]      FIGS. 2A to 2D  are illustrations showing various aberration diagrams at the telephoto end state of the present invention. As shown in  FIG. 2A , the spherical aberration of the present zoom lens at the telephoto end state is less than 0.1 mm. As shown in  FIG. 2B , the astigmatism of the present zoom lens at the telephoto end state is less than 0.1 mm. As shown in  FIG. 2C , the distortion of the present zoom lens at the telephoto end state is less than 0.3%. As shown in  FIG. 2D , the lateral chromatic aberration of the present zoom lens at the telephoto end state is less than 0.03 mm. 
         [0056]      FIGS. 4A to 4D  are illustrations showing various aberration diagrams at the intermediate position of the present invention. As shown in  FIG. 4A , the spherical aberration of the present zoom lens at the intermediate position is less than 0.1 mm. As shown in  FIG. 4B , the astigmatism of the present zoom lens at the intermediate position is less than 0.12 mm. As shown in  FIG. 4C , the distortion of the present zoom lens at the intermediate position is less than 0.6%. As shown in  FIG. 4D , the lateral chromatic aberration of the present zoom lens at the intermediate position is less than 0.04 mm. 
         [0057]      FIGS. 6A to 6D  are illustrations showing various aberration diagrams at the wide-angle end state of the present invention. As shown in  FIG. 6A , the spherical aberration of the present zoom lens at the telephoto end state is less than 0.08 mm. As shown in  FIG. 6B , the astigmatism of the present zoom lens at the wide-angle end state is less than 0.08 mm. As shown in  FIG. 6C , the distortion of the present zoom lens at the wide-angle end state is less than 1%. As shown in FIG.  6 D, the lateral chromatic aberration of the present zoom lens at the wide-angle end state is less than 0.06 mm. 
         [0058]    As described above, the present zoom lens satisfies the following condition. 
         [0000]      0.7×Δ X 2=Δ X 5   (1) 
         [0000]    where ΔX 2  represents the displacement of the second lens group  20  moving along the optical axis OA and ΔX 5  represents the displacement of the fifth lens group  50  moving along the optical axis OA. 
         [0059]    From Data Table 3 as provided above, it can be obtained that, for zooming from the wide-angle end state to the intermediate position, the displacement ΔX 2  of the second lens group  20  moving along the optical axis OA with respect to the first lens group  10  is 1.0485 mm; and the displacement ΔX 5  of the fifth lens group  50  moving along the optical axis OA with respect to the sixth lens group  60  is 0.73375 mm. It can also be obtained that, for zooming from the intermediate position to the telephoto end state, the displacement ΔX 2  of the second lens group  20  moving along the optical axis OA with respect to the first lens group  10  is 0.7285 mm; and the displacement ΔX 5  of the fifth lens group  50  moving along the optical axis OA with respect to the sixth lens group  60  is 0.51025 mm. It is apparent that all these values for the embodiment satisfy the above condition (1). 
         [0060]    As described above, the present zoom lens satisfies the following condition. 
         [0000]    
       
         
           
             
               
                 
                   2.17 
                   &lt; 
                   
                     TTL 
                     f 
                   
                   &lt; 
                   8.7 
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where TTL represents a distance along the optical axis OA from an object-side surface OBJ of the first lens L 1  of first lens group  10  to an image forming surface and f represents the focal length of the present zoom lens. 
         [0061]    According to the present invention, the focal length f of the zoom lens at the wide-angle end state is 1.737 mm, the focal length f of the zoom lens at the intermediate position is 3.37662 mm, and the focal length f of the zoom lens at the telephoto end state is 6.55332 mm. In addition, the distance TTL along the optical axis OA from an object-side surface OBJ of the first lens L 1  of first lens group  10  to an image forming surface is 14.6775 mm, and the f-number of the zoom lens varying from a wide-angle end state to a telephoto end state is between 3.5 and 5.15. Thus, it is apparent that all these values for the embodiment satisfy the above condition (2). 
         [0062]    The present zoom lens has a plurality of movable lens groups, but the displacement of each movable lens group is tiny. Thus, the present zoom lens provides the advantages of small size and low cost as compared to the conventional designs, while ensuring a high level of image performance. Further, from  FIGS. 2A-2D ,  4 A- 4 D and  6 A- 6 D that illustrate various aberrations generated by the present zoom lens according to the different zooming variation, it can be seen that various aberrations have been well corrected by the combination of aspheric lenses and spherical lenses of the present invention. Therefore, a high level of image performance has been obtained by the present zoom lens while providing a compact configuration. 
         [0063]    It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.