Patent Publication Number: US-11036059-B2

Title: Imaging lens and imaging apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2018-035613 filed on Feb. 28, 2018. The above application is hereby expressly incorporated by reference, in its entirety, into the present application. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an imaging lens, which is particularly suitable for imaging apparatuses such as a digital camera, a lens interchangeable type digital camera, and a movie imaging camera, and an imaging apparatus comprising the imaging lens. 
     2. Description of the Related Art 
     In imaging lenses used in imaging apparatuses such as a digital camera, a lens interchangeable type digital camera, and a movie imaging camera, a super telephoto type imaging lens having an angle of view of 10° or less has been proposed in order to capture an image of a further distant object (for example, JP2016-161643A and JP2017-215491A). 
     SUMMARY OF THE INVENTION 
     In order to capture an image of a moving object with such a super telephoto type imaging lens, it is necessary to correct camera shaking more effectively by focusing at a higher speed. However, in a super telephoto type imaging lens in which the rays passing through the lens system becomes large, it is difficult to reduce the weight of both the focus lens group and the vibration reduction lens group. Further, in order to increase the shutter speed, it is necessary for a lens to have a small F number. However, in a case of using a lens with a small F number, the diameter of rays becomes large. As a result, it becomes further difficult to reduce the weight. In the imaging lenses of Examples 1 and 2 of JP2016-161643A, the reduction in weight of the vibration reduction lens group is not sufficient. 
     The present invention has been made in consideration of the above-mentioned situations, and an object of the present invention is to provide an imaging lens which has a small F number and in which weights of both the focus lens group and the vibration reduction lens group are reduced, and an imaging apparatus comprising the imaging lens. 
     An imaging lens of the embodiment of the present invention comprises, in order from an object side: a first lens group that has a positive refractive power; an aperture stop; a second lens group that has a positive refractive power; and a third lens group that has a refractive power. The second lens group consists of two or less lenses, and moves to the object side during focusing from an object at infinity to an object at a closest distance. The third lens group includes, successively in order from at a position closest to an image side, a rear lens group that has a positive refractive power and a vibration reduction lens group that has a negative refractive power and moves in a direction intersecting with an optical axis during image blur correction. In addition, assuming that a focal length of the vibration reduction lens group is f3ois, and a focal length of the rear lens group is f3r, Conditional Expression (1) is satisfied.
 
−1.5&lt; f 3 ois/f 3 r&lt;− 0.85  (1)
 
     It is more preferable to satisfy Conditional Expression (1-1).
 
−1.2&lt; f 3 ois/f 3 r&lt;− 0.88  (1-1)
 
     In the imaging lens of the embodiment of the present invention, assuming that a focal length of a whole system is f, and a focal length of the third lens group is f3, it is preferable to satisfy Conditional Expression (2). It is more preferable to satisfy Conditional Expression (2-1).
 
−0.32&lt; f/f 3&lt;0.3  (2)
 
−0.3&lt; f/f 3&lt;0.1  (2-1)
 
     Further, assuming that a distance on the optical axis from a surface closest to the image side in the second lens group to a surface closest to the object side in the vibration reduction lens group is D2o, and a distance on the optical axis from a surface closest to the object side in the first lens group to an image plane is L, it is preferable to satisfy Conditional Expression (3). It is more preferable to satisfy Conditional Expression (3-1).
 
0.04&lt; D 2 o/L&lt; 0.1  (3)
 
0.05&lt; D 2 o/L&lt; 0.08  (3-1)
 
     Further, the vibration reduction lens group includes a positive lens and a negative lens. Assuming that an Abbe number of the positive lens included in the vibration reduction lens group at a d line is νdop, it is preferable that at least one positive lens of the positive lens included in the vibration reduction lens group satisfies Conditional Expression (4). It is more preferable to satisfy Conditional Expression (4-1).
 
ν dop&lt; 20  (4)
 
10&lt;ν dop&lt; 20  (4-1)
 
     Further, it is preferable that at least one negative lens is provided between the second lens group and the vibration reduction lens group. 
     Further, it is preferable that the rear lens group includes at least four lenses. 
     Further, it is preferable that the rear lens group includes, successively in order from at a position closest to the object side, a positive lens and a negative lens. 
     Further, it is preferable that the first lens group includes, successively in order from at the position closest to the image side, a negative lens and a positive lens with an air gap interposed therebetween. 
     Further, it is preferable that the first lens group includes, successively in order from at a position closest to the object side, a positive lens, a positive lens, and a cemented lens in which a positive lens and a negative lens are cemented in order from the object side. 
     Further, assuming that an Abbe number of the lens closest to the object side in the first lens group at a d line is νd1, it is preferable to satisfy Conditional Expression (5). It is more preferable to satisfy Conditional Expression (5-1).
 
10&lt;ν d 1&lt;43  (5)
 
15&lt;ν d 1&lt;38  (5-1)
 
     An imaging apparatus of the embodiment of the present invention comprises the above-mentioned imaging lens of the embodiment of the present invention. 
     It should be noted that the term “consists of ˜” means that the imaging lens may include not only the above-mentioned elements but also lenses substantially having no powers (refractive powers), optical elements, which are not lenses, such as a stop, a mask, a cover glass, and a filter, and mechanism parts such as a lens flange, a lens barrel, an imaging element, and a camera shaking correction mechanism. 
     Further, the focal length in each conditional expression is set as a value during focusing on the object at infinity. Further, surface shapes, signs of refractive powers, radii of curvature of the lenses are assumed as those in paraxial regions in a case where some lenses have aspheric surfaces. 
     The imaging lens of the embodiment of the present invention consists of, in order from an object side: a first lens group that has a positive refractive power; an aperture stop; a second lens group that has a positive refractive power; and a third lens group that has a refractive power. The second lens group consists of two or less lenses, and moves to the object side during focusing from an object at infinity to an object at a closest distance. The third lens group comprises, successively in order from at a position closest to an image side, a rear lens group that has a positive refractive power and a vibration reduction lens group that has a negative refractive power and moves in a direction intersecting with an optical axis during image blur correction. In addition, assuming that a focal length of the vibration reduction lens group is f3ois, and a focal length of the rear lens group is f3r, Conditional Expression (1) is satisfied. Therefore, it is possible to provide an imaging lens which has a small F number and in which weights of both the focus lens group and the vibration reduction lens group are reduced, and an imaging apparatus comprising the imaging lens.
 
−1.5&lt; f 3 ois/f 3 r&lt;− 0.85  (1)
 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view illustrating a lens configuration of an imaging lens (common to Example 1) according to an embodiment of the present invention. 
         FIG. 2  is a cross-sectional view illustrating a lens configuration of an imaging lens of Example 2 of the present invention. 
         FIG. 3  is a cross-sectional view illustrating a lens configuration of an imaging lens of Example 3 of the present invention. 
         FIG. 4  is a cross-sectional view illustrating a lens configuration of an imaging lens of Example 4 of the present invention. 
         FIG. 5  is a diagram of aberrations of the imaging lens of Example 1 of the present invention. 
         FIG. 6  is a diagram of aberrations of the imaging lens of Example 2 of the present invention. 
         FIG. 7  is a diagram of aberrations of the imaging lens of Example 3 of the present invention. 
         FIG. 8  is a diagram of aberrations of the imaging lens of Example 4 of the present invention. 
         FIG. 9  is a perspective view illustrating the front side of an imaging apparatus according to an embodiment of the present invention. 
         FIG. 10  is a perspective view illustrating the rear side of the imaging apparatus of  FIG. 9 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawing.  FIG. 1  is a cross-sectional view illustrating a lens configuration of an imaging lens according to an embodiment of the present invention. The exemplary configuration shown in  FIG. 1  is the same as the configuration of the imaging lens of Example 1 to be described later. In  FIG. 1 , the left side is an object side, and the right side is an image side. In addition, an aperture stop St shown in the drawing does not necessarily show its real size and shape, but show a position on an optical axis Z. The upper side of  FIG. 1  shows a state where the object at infinity is in focus, and additionally shows on-axis rays Ia and rays with the maximum angle of view Ib. The lower side of  FIG. 1  shows a state where the close-range object is in focus, and additionally shows on-axis rays Ca and rays with the maximum angle of view Cb. 
     In order to mount the imaging lens on an imaging apparatus, it is preferable to provide various filters and/or a protective cover glass based on specification of the imaging apparatus. Thus,  FIG. 1  shows an example where a plane-parallel-plate-like optical member PP, in which those are considered, is disposed between the lens system and the image plane Sim. However, a position of the optical member PP is not limited to that shown in  FIG. 1 , and it is also possible to adopt a configuration in which the optical member PP is omitted. 
     The imaging lens of the present embodiment is composed of, in order from the object side, a first lens group G 1  having a positive refractive power, an aperture stop St, a second lens group G 2  having a positive refractive power, and a third lens group G 3  having a refractive power. 
     The second lens group G 2 , which is a focus lens group, consists of two or less lenses, and moves toward the object side during focusing from an object at infinity to an object at the closest distance. 
     The third lens group G 3  comprises, successively in order from at a position closest to an image side, a rear lens group G 3   r  that has a positive refractive power and a vibration reduction lens group G 3   ois  that has a negative refractive power and moves in a direction intersecting with an optical axis during image blur correction. 
     By disposing the aperture stop St at a position closer to the image side than the first lens group G 1  in this manner, the diameter of the aperture stop St can be reduced. As a result, there is an advantage in reducing the overall diameter of the lens barrel. 
     In addition, by forming the first lens group G 1  as a group having a positive refractive power, the diameter of the lens at a position closer to the image side than the first lens group G 1  can be made small. As a result, there is an advantage in reducing the weight. 
     In addition, by forming the second lens group G 2  as a group having a positive refractive power, it is possible to reduce the diameter of the lens at a position closer to the image side than the second lens group G 2 . As a result, there is an advantage in reducing the weight. In addition, by making the second lens group G 2  composed of two or less lenses, it is possible to reduce the weight of the second lens group G 2 . As a result, there is an advantage in increasing the focusing speed. Furthermore, by moving the second lens group G 2  to the object side during focusing from the object at infinity to the object at the closest distance, the second lens group G 2  is located on the image side during focusing on the object at infinity. Therefore, the diameter of the rays passing through the second lens group G 2  during focusing on the object at infinity becomes small. As a result, there is an advantage in reducing the weight of the second lens group G 2 . 
     Further, by disposing the vibration reduction lens group G 3   ois  at a position closer to the image side than the second lens group G 2  having a positive refractive power in the third lens group G 3 , the diameter of the rays passing through the vibration reduction lens group G 3   ois  can be reduced. As a result, there is an advantage in reducing the weight of the vibration reduction lens group G 3   ois . Further, by disposing the rear lens group G 3   r  having a positive refractive power on the image side of the vibration reduction lens group G 3   ois , the negative refractive power of the vibration reduction lens group G 3   ois  can be increased. 
     Therefore, it is possible to suppress an amount of movement during the vibration reduction operation. 
     Further, assuming that a focal length of the vibration reduction lens group G 3   ois  is f3ois and a focal length of the rear lens group G 3   r  is f3r, the imaging lens of the present embodiment is configured to satisfy Conditional Expression (1).
 
−1.5&lt; f 3 ois/f 3 r&lt;− 0.85  (1)
 
     By not allowing the result of Conditional Expression (1) to be equal to or greater than the upper limit, it is possible to ensure the refractive power of the rear lens group G 3   r  and suppress the height of the off-axis ray passing through the surface closest to the image side in the vibration reduction lens group G 3   ois . As a result, there is an advantage in reducing the effective diameter and reducing the weight of the vibration reduction lens group G 3   ois . Further, it is possible to increase the effective diameters of the first lens group G 1  and the second lens group G 2  while reducing the size of the vibration reduction lens group G 3   ois . As a result, there is an advantage in reducing the F number. By not allowing the result of Conditional Expression (1) to be equal to or less than the lower limit, it is possible to ensure the refractive power of the vibration reduction lens group G 3   ois  and to suppress the amount of movement during the vibration reduction operation. Therefore, a driving mechanism therefor can be miniaturized. In addition, in a case where Conditional Expression (1-1) is satisfied, it is possible to obtain more favorable characteristics.
 
−1.2&lt; f 3 ois/f 3 r&lt;− 0.88  (1-1)
 
     In the imaging lens of the present embodiment, assuming that a focal length of a whole system is f and a focal length of the third lens group G 3  is f3, it is preferable to satisfy Conditional Expression (2). By not allowing the result of Conditional Expression (2) to be equal to or greater than the upper limit, the positive refractive power of the third lens group G 3  can be suppressed, and the positive refractive power of the second lens group G 2  can be increased. Therefore, it is possible to suppress the amount of movement of the second lens group G 2  during focusing. As a result, there is an advantage in shortening the total length of the lens system and achieving reduction in size. By not allowing the result of Conditional Expression (2) to be equal to or less than the lower limit, it is possible to suppress the negative refractive power of the third lens group G 3  and suppress the diameter of the rays passing through the second lens group G 2 . Therefore, there is an advantage in reducing the weight of the second lens group G 2 . In addition, in a case where Conditional Expression (2-1) is satisfied, it is possible to obtain more favorable characteristics.
 
−0.32&lt; f/f 3&lt;0.3  (2)
 
−0.3&lt; f/f 3&lt;0.1  (2-1)
 
     Further, assuming that a distance on the optical axis from a surface closest to the image side in the second lens group G 2  to a surface closest to the object side in the vibration reduction lens group G 3   ois  is D2o and a distance on the optical axis from a surface closest to the object side in the first lens group G 1  to the image plane Sim is L, it is preferable to satisfy Conditional Expression (3). By not allowing the result of Conditional Expression (3) to be equal to or greater than the upper limit, it is possible to prevent the space between the second lens group G 2  and the vibration reduction lens group G 3   ois  from being excessively increased. Therefore, it is possible to shorten the total length of the lens system and achieve reduction in size. By not allowing the result of Conditional Expression (3) to be equal to or less than the lower limit, the rays emitted from the focus lens group (the second lens group G 2 ) having the positive refractive power sufficiently converges and then enters the vibration reduction lens group G 3   ois . Therefore, it is possible to suppress the diameter of the rays passing through the vibration reduction lens group G 3   ois . As a result, there is an advantage in reducing the weight of the vibration reduction lens group G 3   ois . Further, it is possible to increase the effective diameters of the first lens group G 1  and the second lens group G 2  while reducing the size of the vibration reduction lens group G 3   ois . As a result, there is an advantage in reducing the F number. In addition, in a case where Conditional Expression (3-1) is satisfied, it is possible to obtain more favorable characteristics.
 
0.04&lt; D 2 o/L&lt; 0.1  (3)
 
0.05&lt; D 2 o/L&lt; 0.08  (3-1)
 
     Further, the vibration reduction lens group G 3   ois  comprises a positive lens and a negative lens. Assuming that an Abbe number of the positive lens included in the vibration reduction lens group G 3   ois  at a d line is νdop, it is preferable that at least one positive lens of the positive lens included in the vibration reduction lens group G 3   ois  satisfies Conditional Expression (4). By disposing both the positive lens and the negative lens in the vibration reduction lens group G 3   ois , fluctuation in chromatic aberration during the vibration reduction operation can be suppressed. By not allowing the result of Conditional Expression (4) to be equal to or greater than the upper limit, there is an advantage in correcting chromatic aberration during the vibration reduction operation. In addition, in a case where Conditional Expression (4-1) is satisfied, it is possible to obtain more favorable characteristics. By not allowing the result of Conditional Expression (4-1) to be equal to or less than the lower limit, it is possible to suppress occurrence of the secondary chromatic aberration.
 
ν dop&lt; 20  (4)
 
10&lt;ν dop&lt; 20  (4-1)
 
     Further, it is preferable that at least one negative lens is provided between the second lens group G 2  and the vibration reduction lens group G 3   ois . With such a configuration, there is an advantage in suppressing fluctuation in spherical aberration during focusing. 
     Further, it is preferable that the rear lens group G 3   r  comprises at least four lenses. With such a configuration, there is an advantage in suppressing field curvature. 
     Further, it is preferable that the rear lens group G 3   r  comprises, successively in order from at a position closest to the object side, a positive lens and a negative lens. With such a configuration, there is an advantage in correcting lateral chromatic aberration. 
     Further, it is preferable that the first lens group G 1  comprises, successively in order from at the position closest to the image side, a negative lens and a positive lens with an air gap interposed therebetween. With such a configuration, the curvatures of the image side surface of the positive lens and the object side surface of the negative lens can be appropriately set. As a result, there is an advantage in suppressing the spherical aberration. 
     Further, it is preferable that the first lens group G 1  comprises, successively in order from at the position closest to the object side, a positive lens, a positive lens, and a cemented lens in which a positive lens and a negative lens are cemented in order from the object side. With such a configuration, it is possible to suppress longitudinal chromatic aberration while converting the rays into convergent light. 
     Further, assuming that an Abbe number of the lens closest to the object side in the first lens group G 1  at the d line is νd1, it is preferable to satisfy Conditional Expression (5). By satisfing Conditional Expression (5), secondary chromatic aberration can be appropriately corrected. In addition, in a case where Conditional Expression (5-1) is satisfied, it is possible to obtain more favorable characteristics.
 
10&lt;ν d 1&lt;43  (5)
 
15&lt;ν d 1&lt;38  (5-1)
 
     In the example shown in  FIG. 1 , the optical member PP is disposed between the lens system and the image plane Sim. However, various filters such as a lowpass filter and a filter for cutting off a specific wavelength region may not be disposed between the lens system and the image plane Sim. Instead, such various filters may be disposed between the lenses, or coating for functions the same as those of various filters may be performed on a lens surface of any lens. 
     Next, numerical examples of the imaging lens of the embodiment of the present invention will be described. First, the imaging lens of Example 1 will be described.  FIG. 1  is a cross-sectional view illustrating a lens configuration of the imaging lens of Example 1. In  FIG. 1  and  FIGS. 2 to 4  corresponding to Examples 2 to 4 to be described later, left sides thereof are the object side, and right sides thereof are the image side. In addition, the aperture stop St shown in the drawings does not necessarily indicate its size or shape, and indicates a position thereof on the optical axis Z. The upper side of  FIG. 1  shows a state where the object at infinity is in focus, and additionally shows on-axis rays Ia and rays with the maximum angle of view Ib. The lower side of  FIG. 1  shows a state where the close-range object is in focus, and additionally shows on-axis rays Ca and rays with the maximum angle of view Cb. 
     The imaging lens of Example 1 is composed of, in order from the object side, a first lens group G 1  composed of eight lenses L 1   a  to L 1   h , an aperture stop St, a second lens group G 2  composed of two lenses L 2   a  and L 2   b , and a third lens group G 3  composed of nine lenses L 3   a  to L 3   i . In the third lens group G 3 , the vibration reduction lens group G 3   ois  is composed of three lenses L 3   b  to L 3   d , and the rear lens group G 3   r  is composed of five lenses L 3   e  to L 3   i.    
     Table 1 shows basic lens data of the imaging lens of Example 1, Table 2 shows data about specification, and Table 3 shows data about variable surface distances. Hereinafter, meanings of the reference signs in the tables are, for example, as described in Example 1, and are basically the same as those in Examples 2 to 4. 
     In the lens data of Table 1, the column of the surface number shows surface numbers. The surface of the elements closest to the object side is the first surface, and the surface numbers sequentially increase toward the image plane side. The column of the radius of curvature shows radii of curvature of the respective surfaces. The column of the surface distance shows distances on the optical axis Z between the respective surfaces and the subsequent surfaces. Further, the column of n shows a refractive index of each optical element at the d line (a wavelength of 587.6 nm (nanometers)), the column of ν shows an Abbe number of each optical element at the d line (a wavelength of 587.6 nm (nanometers)), and the column of θgF shows a partial dispersion ratio of each optical element. 
     It should be noted that a partial dispersion ratio θgF is represented by the following expression.
 
θ gF =( ng−nF )/( nF−nC )
 
     Here, ng is a refractive index at the g line, 
     nF is a refractive index at the F line, and 
     nC is a refractive index at the C line. 
     In addition, the sign of the radius of curvature is positive in a case where a surface has a shape convex toward the object side, and is negative in a case where a surface has a shape convex toward the image plane side. In the basic lens data, the aperture stop St and the optical member PP are additionally noted. In a place of a surface number of a surface corresponding to the aperture stop St, the surface number and a term of (stop) are noted. Further, in the lens data of Table 1, in each place of the surface distance which is variable during focusing, DD[surface number] is noted. Numerical values each corresponding to the DD[surface number] are shown in Table 3. 
     In the data about the specification of Table 2, values of the focal length f, the F number FNo, and the total angle of view 2ω(°) are noted. 
     In the basic lens data, the data about specification, and the data about variable surface distances, “°” is used as a unit of an angle, and mm (millimeters) is used as a unit of a length, but appropriate different units may be used since the lens system can be used even in a case where the system is enlarged or reduced in proportion. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Example 1 • Lens Data (n and ν are based on d line) 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                 Radius of 
                 Surface 
                   
                   
                   
               
               
                 Number 
                 Curvature 
                 Distance 
                 n 
                 ν 
                 θgf 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                  1 
                 430.7013 
                 7.0700 
                 1.67270 
                 32.10 
                 0.59891 
               
               
                  2 
                 −727.3321 
                 0.4562 
               
               
                  3 
                 165.9720 
                 10.7500 
                 1.43875 
                 94.66 
                 0.53402 
               
               
                  4 
                 −1120.2835 
                 20.2132 
               
               
                  5 
                 105.9369 
                 13.9100 
                 1.49700 
                 81.54 
                 0.53748 
               
               
                  6 
                 −218.3400 
                 3.1600 
                 1.83481 
                 42.74 
                 0.56490 
               
               
                  7 
                 775.7212 
                 1.6106 
               
               
                  8 
                 91.4829 
                 11.0200 
                 1.49700 
                 81.54 
                 0.53748 
               
               
                  9 
                 −267.5300 
                 2.7200 
                 1.91082 
                 35.25 
                 0.58224 
               
               
                 10 
                 141.8275 
                 22.2150 
               
               
                 11 
                 266.7587 
                 4.1100 
                 1.80809 
                 22.76 
                 0.63073 
               
               
                 12 
                 −266.7587 
                 0.3002 
               
               
                 13 
                 266.7635 
                 2.0000 
                 1.80000 
                 29.84 
                 0.60178 
               
               
                 14 
                 47.2925 
                 9.4871 
               
               
                 15 (Stop) 
                 ∞ 
                 DD[15] 
               
               
                 16 
                 61.1684 
                 1.8100 
                 1.54814 
                 45.78 
                 0.56859 
               
               
                 17 
                 39.3800 
                 6.6000 
                 1.69680 
                 55.53 
                 0.54341 
               
               
                 18 
                 ∞ 
                 DD[18] 
               
               
                 19 
                 36.1305 
                 2.3000 
                 1.60342 
                 38.03 
                 0.58356 
               
               
                 20 
                 23.9164 
                 7.9000 
               
               
                 21 
                 415.3848 
                 2.2800 
                 1.95906 
                 17.47 
                 0.65993 
               
               
                 22 
                 −91.4760 
                 1.5100 
                 1.73400 
                 51.47 
                 0.54874 
               
               
                 23 
                 42.9219 
                 1.8900 
               
               
                 24 
                 −217.2372 
                 1.4000 
                 1.80100 
                 34.97 
                 0.58642 
               
               
                 25 
                 66.6268 
                 3.2077 
               
               
                 26 
                 51.5518 
                 3.1100 
                 1.90366 
                 31.31 
                 0.59481 
               
               
                 27 
                 ∞ 
                 1.0602 
               
               
                 28 
                 −77.9583 
                 1.4000 
                 1.80809 
                 22.76 
                 0.63073 
               
               
                 29 
                 145.8634 
                 4.4301 
               
               
                 30 
                 133.6002 
                 4.2800 
                 1.80610 
                 40.93 
                 0.57141 
               
               
                 31 
                 −60.7409 
                 0.6043 
               
               
                 32 
                 53.2520 
                 8.6300 
                 1.65412 
                 39.73 
                 0.57369 
               
               
                 33 
                 −53.2520 
                 1.9000 
                 1.80000 
                 29.84 
                 0.60178 
               
               
                 34 
                 154.3014 
                 28.1625 
               
               
                 35 
                 ∞ 
                 2.8500 
                 1.51680 
                 64.20 
                 0.53430 
               
               
                 36 
                 ∞ 
                 1.1000 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Example 1 • Specification (d Line) 
               
            
           
           
               
               
               
            
               
                   
                   
                 Close Range 
               
               
                   
                 Infinity 
                 (1.57 m) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 f 
                 194.01 
                 181.53 
               
               
                   
                 FNo. 
                 2.06 
                 2.33 
               
               
                   
                 2ω [°] 
                 9.0 
                 8.2 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Example 1 • Variable Surface Distance 
               
            
           
           
               
               
               
            
               
                   
                   
                 Close Range 
               
               
                   
                 Infinity 
                 (1.57 m) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 DD[15] 
                 18.63 
                 7.08 
               
               
                   
                 DD[18] 
                 4.92 
                 16.47 
               
               
                   
                   
               
            
           
         
       
     
       FIG. 5  shows a diagram of aberrations of the imaging lens of Example 1. In  FIG. 5 , spherical aberration, astigmatism, distortion, and lateral chromatic aberration during focusing the object at infinity are shown in order from the upper left side, and spherical aberration, astigmatism, distortion, and lateral chromatic aberration during focusing on the close-range (1.57 m (meters)) object are shown in order from the lower left side. Each aberration diagram shows aberration at the d line (a wavelength of 587.6 nm (nanometers)) which is set as a reference wavelength. In the spherical aberration diagram, aberrations at the d line (a wavelength of 587.6 nm (nanometers)), the C line (a wavelength of 656.3 nm (nanometers)), and the F line (a wavelength of 486.1 nm (nanometers)) are respectively indicated by the solid line, the long dashed line, and the short dashed line. In the astigmatism diagram, aberrations in sagittal and tangential directions are respectively indicated by the solid line and the short dashed line. In the lateral chromatic aberration, aberrations at the C line (a wavelength of 656.3 nm (nanometers)) and F line (a wavelength of 486.1 nm (nanometers)) are respectively indicated by the long dashed line and the short dashed line. In addition, in the spherical aberration diagram, FNo. means an F number. In the other aberration diagrams, ω means a half angle of view. 
     Next, an imaging lens of Example 2 will be described.  FIG. 2  is a cross-sectional view illustrating a lens configuration of the imaging lens of Example 2. The group configuration of the imaging lens of Example 2 is the same as the imaging lens of Example 1 except that the second lens group G 2  is composed of only one lens L 2   a . Further, Table 4 shows basic lens data of the imaging lens of Example 2, Table 5 shows data about specification, and Table 6 shows data about variable surface distances.  FIG. 6  shows aberration diagrams thereof during focusing on the object at infinity and aberration diagrams thereof during focusing on the close-range (1.58 m (meters)) object. 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Example 2 • Lens Data (n and ν are based on d line) 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                 Radius of 
                 Surface 
                   
                   
                   
               
               
                 Number 
                 Curvature 
                 Distance 
                 n 
                 ν 
                 θgf 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                  1 
                 281.2593 
                 6.3629 
                 1.75520 
                 27.51 
                 0.61033 
               
               
                  2 
                 2438.6986 
                 0.1998 
               
               
                  3 
                 179.0364 
                 11.8394 
                 1.43875 
                 94.66 
                 0.53402 
               
               
                  4 
                 −467.3399 
                 16.4487 
               
               
                  5 
                 112.9579 
                 15.2533 
                 1.49700 
                 81.54 
                 0.53748 
               
               
                  6 
                 −158.2489 
                 3.1692 
                 1.83481 
                 42.72 
                 0.56486 
               
               
                  7 
                 3858.0241 
                 1.4998 
               
               
                  8 
                 75.7081 
                 11.5198 
                 1.49700 
                 81.54 
                 0.53748 
               
               
                  9 
                 −472.5613 
                 2.6713 
                 1.91082 
                 35.25 
                 0.58224 
               
               
                 10 
                 117.3523 
                 19.0647 
               
               
                 11 
                 386.2243 
                 3.9211 
                 1.80809 
                 22.76 
                 0.63073 
               
               
                 12 
                 −228.3100 
                 0.2998 
               
               
                 13 
                 510.7042 
                 1.9998 
                 1.80000 
                 29.84 
                 0.60178 
               
               
                 14 
                 50.4368 
                 9.1114 
               
               
                 15 (Stop) 
                 ∞ 
                 DD[15] 
               
               
                 16 
                 57.4626 
                 4.8476 
                 1.67790 
                 55.34 
                 0.54726 
               
               
                 17 
                 ∞ 
                 DD[17] 
               
               
                 18 
                 38.4414 
                 2.6103 
                 1.80809 
                 22.76 
                 0.63073 
               
               
                 19 
                 25.7549 
                 7.5893 
               
               
                 20 
                 ∞ 
                 2.3072 
                 1.95906 
                 17.47 
                 0.65993 
               
               
                 21 
                 −80.7940 
                 1.5098 
                 1.73400 
                 51.47 
                 0.54874 
               
               
                 22 
                 49.5562 
                 1.5195 
               
               
                 23 
                 1271.6918 
                 1.3999 
                 1.84666 
                 23.78 
                 0.62054 
               
               
                 24 
                 75.2976 
                 3.1998 
               
               
                 25 
                 48.2673 
                 5.6809 
                 1.75700 
                 47.82 
                 0.55662 
               
               
                 26 
                 −45.8385 
                 1.4098 
                 1.48749 
                 70.44 
                 0.53062 
               
               
                 27 
                 34.1075 
                 0.9999 
               
               
                 28 
                 41.4424 
                 3.6327 
                 1.85026 
                 32.27 
                 0.59299 
               
               
                 29 
                 −1307.3710 
                 1.5401 
               
               
                 30 
                 −64.3145 
                 1.9999 
                 1.80518 
                 25.42 
                 0.61616 
               
               
                 31 
                 90.1776 
                 4.6289 
               
               
                 32 
                 79.7092 
                 5.0240 
                 1.65412 
                 39.68 
                 0.57378 
               
               
                 33 
                 −67.0533 
                 28.4110 
               
               
                 34 
                 ∞ 
                 2.8500 
                 1.51680 
                 64.20 
                 0.53430 
               
               
                 35 
                 ∞ 
                 1.1000 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Example 2 • Specification (d Line) 
               
            
           
           
               
               
               
            
               
                   
                   
                 Close Range 
               
               
                   
                 Infinity 
                 (1.58 m) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 f 
                 194.00 
                 182.57 
               
               
                   
                 FNo. 
                 2.05 
                 2.32 
               
               
                   
                 2ω [°] 
                 9.0 
                 8.0 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 Example 2 • Variable Surface Distance 
               
            
           
           
               
               
               
            
               
                   
                   
                 Close Range 
               
               
                   
                 Infinity 
                 (1.58 m) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 DD[15] 
                 19.50 
                 7.03 
               
               
                   
                 DD[17] 
                 4.90 
                 17.37 
               
               
                   
                   
               
            
           
         
       
     
     Next, an imaging lens of Example 3 will be described.  FIG. 3  is a cross-sectional view illustrating a lens configuration of the imaging lens of Example 3. The group configuration of the imaging lens of Example 3 is the same as the imaging lens of Example 1. Further, Table 7 shows basic lens data of the imaging lens of Example 3, Table 8 shows data about specification, and Table 9 shows data about variable surface distances.  FIG. 7  shows aberration diagrams thereof during focusing on the object at infinity and aberration diagrams thereof during focusing on the close-range (1.57 m (meters)) object. 
     
       
         
           
               
             
               
                 TABLE 7 
               
             
            
               
                   
               
               
                 Example 3 • Lens Data (n and ν are based on d line) 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                 Radius of 
                 Surface 
                   
                   
                   
               
               
                 Number 
                 Curvature 
                 Distance 
                 n 
                 ν 
                 θgf 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                  1 
                 252.0494 
                 9.8962 
                 1.62588 
                 35.70 
                 0.58935 
               
               
                  2 
                 −515.9847 
                 0.1998 
               
               
                  3 
                 181.5973 
                 8.4802 
                 1.43387 
                 95.18 
                 0.53733 
               
               
                  4 
                 3607.5955 
                 8.5933 
               
               
                  5 
                 124.9313 
                 14.0837 
                 1.49700 
                 81.54 
                 0.53748 
               
               
                  6 
                 −215.0537 
                 3.3343 
                 1.83481 
                 42.72 
                 0.56486 
               
               
                  7 
                 840.9410 
                 2.7045 
               
               
                  8 
                 83.3042 
                 11.9492 
                 1.49700 
                 81.54 
                 0.53748 
               
               
                  9 
                 −400.8617 
                 2.8416 
                 1.91082 
                 35.25 
                 0.58224 
               
               
                 10 
                 119.6849 
                 21.4964 
               
               
                 11 
                 −324.6320 
                 3.5998 
                 1.80809 
                 22.76 
                 0.63073 
               
               
                 12 
                 −168.4377 
                 0.3000 
               
               
                 13 
                 105.1594 
                 2.0001 
                 1.83481 
                 42.74 
                 0.56490 
               
               
                 14 
                 50.6766 
                 10.0397 
               
               
                 15 (Stop) 
                 ∞ 
                 DD[15] 
               
               
                 16 
                 52.2700 
                 2.2077 
                 1.51742 
                 52.43 
                 0.55649 
               
               
                 17 
                 39.7936 
                 8.0002 
                 1.48749 
                 70.44 
                 0.53062 
               
               
                 18 
                 −399.3433 
                 DD[18] 
               
               
                 19 
                 42.8701 
                 1.6998 
                 1.80809 
                 22.76 
                 0.63073 
               
               
                 20 
                 27.2242 
                 8.5002 
               
               
                 21 
                 2006.0214 
                 2.5511 
                 1.95906 
                 17.47 
                 0.65993 
               
               
                 22 
                 −81.5346 
                 1.5098 
                 1.73400 
                 51.47 
                 0.54874 
               
               
                 23 
                 54.0462 
                 1.8541 
               
               
                 24 
                 −649.2442 
                 1.4000 
                 1.85478 
                 24.80 
                 0.61232 
               
               
                 25 
                 97.5423 
                 3.1999 
               
               
                 26 
                 37.4736 
                 5.7159 
                 1.89190 
                 37.13 
                 0.57813 
               
               
                 27 
                 −116.6064 
                 0.3851 
               
               
                 28 
                 −81.2653 
                 4.9385 
                 1.64769 
                 33.79 
                 0.59393 
               
               
                 29 
                 31.4083 
                 5.0526 
               
               
                 30 
                 45.6062 
                 7.0002 
                 1.85026 
                 32.27 
                 0.59299 
               
               
                 31 
                 −47.2286 
                 0.3000 
               
               
                 32 
                 −53.8124 
                 6.6472 
                 1.51742 
                 52.43 
                 0.55649 
               
               
                 33 
                 −27.5720 
                 1.9002 
                 1.75520 
                 27.51 
                 0.61033 
               
               
                 34 
                 −541.8644 
                 28.4187 
               
               
                 35 
                 ∞ 
                 2.8500 
                 1.51680 
                 64.20 
                 0.53430 
               
               
                 36 
                 ∞ 
                 1.1000 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 8 
               
             
            
               
                   
               
               
                 Example 3 • Specification (d Line) 
               
            
           
           
               
               
               
            
               
                   
                   
                 Close Range 
               
               
                   
                 Infinity 
                 (1.57 m) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 f 
                 193.99 
                 179.01 
               
               
                   
                 FNo. 
                 2.06 
                 2.38 
               
               
                   
                 2ω [°] 
                 9.0 
                 8.2 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 9 
               
             
            
               
                   
               
               
                 Example 3 • Variable Surface Distance 
               
            
           
           
               
               
               
            
               
                   
                   
                 Close Range 
               
               
                   
                 Infinity 
                 (1.57 m) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 DD[15] 
                 20.36 
                 7.03 
               
               
                   
                 DD[18] 
                 4.90 
                 18.22 
               
               
                   
                   
               
            
           
         
       
     
     Next, an imaging lens of Example 4 will be described.  FIG. 4  is a cross-sectional view illustrating a lens configuration of the imaging lens of Example 4. The group configuration of the imaging lens of Example 4 is the same as the imaging lens of Example 1 except that the third lens group G 3  is composed of eight lenses L 3   a  to L 3   h . In the third lens group G 3 , the vibration reduction lens group G 3   ois  is composed of three lenses L 3   b  to L 3   d , and the rear lens group G 3   r  is composed of four lenses L 3   e  to L 3   h . Further, Table 10 shows basic lens data of the imaging lens of Example 4, Table 11 shows data about specification, and Table 12 shows data about variable surface distances.  FIG. 8  shows aberration diagrams thereof during focusing on the object at infinity and aberration diagrams thereof during focusing on the close-range (1.57 m (meters)) object. 
     
       
         
           
               
             
               
                 TABLE 10 
               
             
            
               
                   
               
               
                 Example 4 • Lens Data (n and ν are based on d line) 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                 Radius of 
                 Surface 
                   
                   
                   
               
               
                 Number 
                 Curvature 
                 Distance 
                 n 
                 ν 
                 θgf 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                  1 
                 411.1910 
                 7.0788 
                 1.59270 
                 35.31 
                 0.59336 
               
               
                  2 
                 −783.9622 
                 0.1998 
               
               
                  3 
                 157.9844 
                 11.3824 
                 1.43387 
                 95.18 
                 0.53733 
               
               
                  4 
                 −979.8539 
                 29.1491 
               
               
                  5 
                 109.1871 
                 13.7051 
                 1.49700 
                 81.54 
                 0.53748 
               
               
                  6 
                 −162.8971 
                 2.9998 
                 1.81600 
                 46.62 
                 0.55682 
               
               
                  7 
                 561.4165 
                 1.4998 
               
               
                  8 
                 71.1159 
                 12.2734 
                 1.49700 
                 81.54 
                 0.53748 
               
               
                  9 
                 −252.4552 
                 2.6000 
                 1.90366 
                 31.31 
                 0.59481 
               
               
                 10 
                 152.4778 
                 12.9485 
               
               
                 11 
                 329.2005 
                 3.9241 
                 1.85896 
                 22.73 
                 0.62844 
               
               
                 12 
                 −281.5785 
                 0.3001 
               
               
                 13 
                 201.5251 
                 1.9998 
                 1.83481 
                 42.74 
                 0.56490 
               
               
                 14 
                 45.6609 
                 9.8306 
               
               
                 15 (Stop) 
                 ∞ 
                 DD[15] 
               
               
                 16 
                 50.4067 
                 1.8100 
                 1.51742 
                 52.43 
                 0.55649 
               
               
                 17 
                 40.5884 
                 7.0158 
                 1.51633 
                 64.14 
                 0.53531 
               
               
                 18 
                 −527.3168 
                 DD[18] 
               
               
                 19 
                 40.0225 
                 1.6998 
                 1.80809 
                 22.76 
                 0.63073 
               
               
                 20 
                 26.1519 
                 5.6749 
               
               
                 21 
                 −2449.0499 
                 2.7887 
                 2.00272 
                 19.32 
                 0.64514 
               
               
                 22 
                 −67.3353 
                 1.5098 
                 1.73400 
                 51.47 
                 0.54874 
               
               
                 23 
                 55.2906 
                 1.4783 
               
               
                 24 
                 496.4175 
                 1.4001 
                 1.85896 
                 22.73 
                 0.62844 
               
               
                 25 
                 68.8324 
                 3.2000 
               
               
                 26 
                 40.8755 
                 6.9154 
                 1.73400 
                 51.47 
                 0.54874 
               
               
                 27 
                 −43.8133 
                 1.4098 
                 1.51742 
                 52.43 
                 0.55649 
               
               
                 28 
                 29.5881 
                 2.4117 
               
               
                 29 
                 37.4505 
                 3.7408 
                 1.85150 
                 40.78 
                 0.56958 
               
               
                 30 
                 3119.6621 
                 2.2407 
               
               
                 31 
                 −55.8576 
                 7.0002 
                 1.62588 
                 35.70 
                 0.58935 
               
               
                 32 
                 −65.7215 
                 33.8550 
               
               
                 33 
                 ∞ 
                 2.8500 
                 1.51680 
                 64.20 
                 0.53430 
               
               
                 34 
                 ∞ 
                 1.1000 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 11 
               
             
            
               
                   
               
               
                 Example 4 • Specification (d Line) 
               
            
           
           
               
               
               
            
               
                   
                   
                 Close Range 
               
               
                   
                 Infinity 
                 (1.57 m) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 f 
                 193.99 
                 178.01 
               
               
                   
                 RNo. 
                 2.06 
                 2.33 
               
               
                   
                 2ω [°] 
                 9.0 
                 8.0 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 12 
               
             
            
               
                   
               
               
                 Example 4 • Variable Surface Distance 
               
            
           
           
               
               
               
            
               
                   
                   
                 Close Range 
               
               
                   
                 Infinity 
                 (1.57 m) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 DD[15] 
                 18.28 
                 5.03 
               
               
                   
                 DD[18] 
                 3.75 
                 17.00 
               
               
                   
                   
               
            
           
         
       
     
     Table 13 shows values corresponding to Conditional Expressions (1) to (5) of the imaging lenses of Examples 1 to 4. It should be noted that, in the above-mentioned examples, the d line is set as the reference wavelength, and the values shown in Table 13 are values at the reference wavelength. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 13 
               
               
                   
               
               
                 Expression 
                 Conditional 
                 Exam- 
                   
                   
                   
               
               
                 Number 
                 Expression 
                 ple 1 
                 Example 2 
                 Example 3 
                 Example 4 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 (1) 
                 f3ois/f3r 
                 −0.904 
                 −1.012 
                 −1.126 
                 −1.104 
               
               
                 (2) 
                 f/f3 
                 −0.149 
                 0.025 
                 −0.262 
                 −0.294 
               
               
                 (3) 
                 D2o/L 
                 0.069 
                 0.072 
                 0.069 
                 0.051 
               
               
                 (4) 
                 νdop 
                 17.47 
                 17.47 
                 17.47 
                 19.32 
               
               
                 (5) 
                 νd1 
                 32.10 
                 27.51 
                 35.70 
                 35.31 
               
               
                   
               
            
           
         
       
     
     As can be seen from the above-mentioned data, all the imaging lenses of Examples 1 to 4 satisfy the conditional expressions (1) to (5), and are imaging lenses each of which has a small F number of about 2 and in which weights of both the focus lens group and the vibration reduction lens group are reduced. 
     Next, an embodiment of the imaging apparatus according to the embodiment of the present invention will be described with reference to  FIGS. 9 and 10 . In  FIGS. 9 and 10 , a camera  30 , which is obliquely viewed respectively on the front side and the rear side, is a non-reflex (so-called mirrorless) type digital camera on which an interchangeable lens  20  housing the imaging lens  1  according to the above-mentioned embodiment of the present invention in a lens barrel is detachably mounted. 
     The camera  30  comprises a camera body  31 , and a shutter button  32  and a power button  33  are provided on an upper surface thereof. Further, operation sections  34  and  35  and a display section  36  are provided on a rear surface of the camera body  31 . The display section  36  is for displaying a captured image and an image within an angle of view before imaging. 
     An imaging aperture, through which light from an imaging target is incident, is provided at the center on the front surface of the camera body  31 . A mount  37  is provided at a position corresponding to the imaging aperture. The interchangeable lens  20  is mounted on the camera body  31  with the mount  37  interposed therebetween. 
     In the camera body  31 , there are provided an imaging element (not shown in the drawing), a signal processing circuit, a recording medium, and the like. The imaging element such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) outputs a captured image signal based on a subject image which is formed through the interchangeable lens  20 . The signal processing circuit generates an image through processing of the captured image signal which is output from the imaging element. The recording medium records the generated image. The camera  30  is able to capture a still image or a moving image by pressing the shutter button  32 , and is able to store image data, which is obtained through imaging, in the storage medium. 
     The present invention has been hitherto described through embodiments and examples, but the present invention is not limited to the above-mentioned embodiments and examples, and may be modified into various forms. For example, values such as the radius of curvature, the surface distance, the refractive index, and the Abbe number of each lens component are not limited to the values shown in the examples, and different values may be used therefor. 
     In the above-mentioned embodiment of the imaging apparatus, the non-reflex type digital camera is taken as an example and described with the drawings. However, the imaging apparatus of the embodiment of the present invention is not limited to this. For example, the present invention may be applied to imaging apparatuses such as video cameras, digital cameras which are not the non-reflex type, movie imaging cameras, broadcast cameras. 
     EXPLANATION OF REFERENCES 
     
         
         
           
               1 : imaging lens 
               20 : interchangeable lens 
               30 : camera 
               31 : camera body 
               32 : shutter button 
               33 : power button 
               34 ,  35 : operation section 
               36 : display section 
               37 : mount 
             Ca: on-axis rays during focusing on close-range object 
             Cb: rays with maximum angle of view during focusing on close-range object 
             G 1 : first lens group 
             G 2 : second lens group (focus lens group) 
             G 3 : third lens group 
             G 3   ois : vibration reduction lens group 
             G 3   r : rear lens group 
             Ia: on-axis rays during focusing on object at infinity 
             Ib: rays with maximum angle of view during focusing on object at infinity 
             L 1   a  to L 3   i : lens 
             PP: optical member 
             Sim: image plane 
             St: aperture stop 
             Z: optical axis