PATENT DOCUMENT

Abstract:
A telephoto lens includes a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit, and the first lens unit includes a front-side lens unit having a positive refractive power and a rear-side lens unit, and the second lens unit moves at the time of focusing, and the third lens unit has a positive lens and a negative lens, and the front-side lens unit includes lenses positioned closer to the object side than a predetermined negative lens that satisfies Conditional Expression (a), and the rear-side lens unit has the predetermined negative lens and a positive lens, and Conditional Expressions (1A) and (14) are satisfied: 
       0.5≦| f/fLn|   (a),
 
       0.015≦ DGFGR/f≦0.25    (1A), and
 
       0.19≦ DGF airmax/ DGF≦1.0    (14).

Full Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2016-004631 filed on Jan. 13, 2016; the entire contents of which are incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    The present invention relates to a telephoto lens and an image pickup apparatus using the same. 
       Description of the Related Art 
       [0003]    Photography using a telephoto lens or a super-telephoto lens (hereinafter referred to as “telephoto lens”) has the effect of making a distant subject or a small subject appear in front of the photographer. For this reason, telephoto lenses are widely used in various scenes such as taking photographs of sports scenes, taking photographs of wild animals such as wild birds, and astrophotography. 
         [0004]    Examples of telephoto lenses for use in taking photographs of such scenes are disclosed in Japanese Patent Application Laid-open Nos. 2009-139543, 2008-261969, 2013-250293, and H09-236742. 
       SUMMARY OF THE INVENTION 
       [0005]    A telephoto lens of the present invention comprises: 
         [0006]    in order from an object side, 
         [0007]    a first lens unit having a positive refractive power; 
         [0008]    a second lens unit having a negative refractive power; and 
         [0009]    a third lens unit, 
         [0010]    wherein 
         [0011]    the telephoto lens includes no other lens units, 
         [0012]    the first lens unit comprises, in order from the object side, a front-side lens unit having a positive refractive power and a rear-side lens unit, and includes no other lens units, 
         [0013]    at a time of focusing, second lens unit moves, 
         [0014]    the third lens unit has a positive lens and a negative lens, 
         [0015]    the front-side lens unit comprises lens elements positioned closer to the object side than a predetermined negative lens element that satisfies following Conditional Expression (a), 
         [0016]    the lens elements positioned closer to the object side than the predetermined negative lens element include a plurality of positive lens elements, 
         [0017]    the rear-side lens unit has the predetermined negative lens element and a positive lens element, and 
         [0018]    following Conditional Expressions (1A) and (14) are satisfied, 
         [0000]      0.5 ≦|f/fLn|   (a),
 
         [0000]      0.015 ≦DGFGR/f≦ 0.25   (1A), and
 
         [0000]      0.19 ≦DGF airmax/ DGF≦ 1.0   (14),
 
         [0019]    where, 
         [0020]    f is a focal length of the entire telephoto lens; 
         [0021]    fLn is a focal length of the predetermined negative lens element; 
         [0022]    DGFGR is an axial air space between the front-side lens unit and the rear-side lens unit; 
         [0023]    DGFairmax is a largest axial air space, of axial air spaces in the front-side lens unit; and 
         [0024]    DGF is an axial thickness of the front-side lens unit. 
         [0025]    Another telephoto lens of the present invention comprises: 
         [0026]    in order from an object side, 
         [0027]    a first lens unit having a positive refractive power; 
         [0028]    a second lens unit having a negative refractive power; and 
         [0029]    a third lens unit, 
         [0030]    wherein 
         [0031]    the telephoto lens includes no other lens units, 
         [0032]    the first lens unit comprises, in order from the object side, a front-side lens unit having a positive refractive power, a first rear-side lens unit, and a second rear-side lens unit, and includes no other lens units, 
         [0033]    at a time of focusing, the second lens unit moves, 
         [0034]    the third lens unit has a positive lens element and a negative lens element, 
         [0035]    the front-side lens unit comprises lens elements positioned closer to the object side than a predetermined negative lens element that satisfies following Conditional Expression (a), 
         [0036]    the lens elements positioned closer to the object side than the predetermined negative lens element include a plurality of positive lens elements, 
         [0037]    the first rear-side lens unit has the predetermined negative lens element and a positive lens element, 
         [0038]    the second rear-side lens unit has a positive lens element, and 
         [0039]    following Conditional Expressions (2B) and (16) are satisfied: 
         [0000]      0.5 ≦|f/fLn|   (a),
 
         [0000]      0.10 ≦ΔGFGR 1 /f≦ 0.5   (2B), and
 
         [0000]      50 ≦νdLp 1   (16),
 
         [0040]    where, 
         [0041]    f is a focal length of the entire telephoto lens; 
         [0042]    fLn is a focal length of the predetermined negative lens element; 
         [0043]    ΔGFGR 1  is an axial air space from an object-side surface in the front-side lens unit to an object-side surface in the first rear-side lens unit; and 
         [0044]    νdLp 1  is an Abbe number of a positive lens positioned closest to the object. 
         [0045]    Another telephoto lens of the present invention comprises: 
         [0046]    in order from an object side, 
         [0047]    a first lens unit having a positive refractive power; 
         [0048]    a second lens unit having a negative refractive power; and 
         [0049]    a third lens unit, 
         [0050]    wherein 
         [0051]    the telephoto lens includes no other lens units, 
         [0052]    the first lens unit comprises, in order from the object side, a front-side lens unit having a positive refractive power, a first rear-side lens unit, and a second rear-side lens unit, and includes no other lens units, 
         [0053]    at a time of focusing, the second lens unit moves, 
         [0054]    the third lens unit has a positive lens element and a negative lens element, 
         [0055]    the front-side lens unit comprises a lens element positioned closer to the object side than a predetermined negative lens element that satisfies following Conditional Expression (a), 
         [0056]    the lens element positioned closer to the object side than the predetermined negative lens element includes a positive lens element, 
         [0057]    the first rear-side lens unit has the predetermined negative lens element and a positive lens element, 
         [0058]    the second rear-side lens unit has a positive lens element, and 
         [0059]    following Conditional Expressions (2B) and (3) are satisfied: 
         [0000]      0.5 ≦|f/fLn|   (a),
 
         [0000]      0.10 ≦ΔGFGR 1 /f≦ 0.5   (2B), and
 
         [0000]      72≦νdGFave   (3),
 
         [0060]    where, 
         [0061]    f is a focal length of the entire telephoto lens; 
         [0062]    fLn is a focal length of the predetermined negative lens element; 
         [0063]    ΔGFGR 1  is an axial air space from an object-side surface in the front-side lens unit to an object-side surface in the first rear-side lens unit; and 
         [0064]    νdGFave is an average Abbe number of the positive lens element in the front-side lens unit. 
         [0065]    Furthermore, an image pickup apparatus of the present invention comprises: 
         [0066]    an optical system; and 
         [0067]    an image pickup element having an image plane and converting an image formed on the image plane by the optical system to an electrical signal, 
         [0068]    wherein 
         [0069]    the optical system is any one of the telephoto lenses described above. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0070]      FIG. 1A  and  FIG. 1B  are lens cross-sectional views of a telephoto lens of Example 1; 
           [0071]      FIG. 2A  and  FIG. 2B  are lens cross-sectional views of a telephoto lens of Example 2; 
           [0072]      FIG. 3A  and  FIG. 3B  are lens cross-sectional views of a telephoto lens of Example 3; 
           [0073]      FIG. 4A  and  FIG. 4B  are lens cross-sectional views of a telephoto lens of Example 4; 
           [0074]      FIG. 5A  and  FIG. 5B  are lens cross-sectional views of a telephoto lens of Example 5; 
           [0075]      FIG. 6A  and  FIG. 6B  are lens cross-sectional views of a telephoto lens of Example 6; 
           [0076]      FIG. 7A  and  FIG. 7B  are lens cross-sectional views of a telephoto lens of Example 7; 
           [0077]      FIG. 8A  and  FIG. 8B  are lens cross-sectional views of a telephoto lens of Example 8; 
           [0078]      FIG. 9A  and  FIG. 9B  are lens cross-sectional views of a telephoto lens of Example 9; 
           [0079]      FIG. 10A ,  FIG. 10B ,  FIG. 10C ,  FIG. 10D ,  FIG. 10E , FIG.  10 F,  FIG. 10G , and  FIG. 10H  are aberration diagrams of the telephoto lens of Example 1; 
           [0080]      FIG. 11A ,  FIG. 11B ,  FIG. 11C ,  FIG. 11D ,  FIG. 11E ,  FIG. 11F ,  FIG. 11G , and  FIG. 11H  are aberration diagrams of the telephoto lens of Example 2; 
           [0081]      FIG. 12A ,  FIG. 12B ,  FIG. 12C ,  FIG. 12D ,  FIG. 12E ,  FIG. 12F ,  FIG. 12G , and  FIG. 12H  are aberration diagrams of the telephoto lens of Example 3; 
           [0082]      FIG. 13A ,  FIG. 13B ,  FIG. 13C ,  FIG. 13D ,  FIG. 13E ,  FIG. 13F ,  FIG. 13G , and  FIG. 13H  are aberration diagrams of the telephoto lens of Example 4; 
           [0083]      FIG. 14A ,  FIG. 14B ,  FIG. 14C ,  FIG. 14D ,  FIG. 14E ,  FIG. 14F ,  FIG. 14G , and  FIG. 14H  are aberration diagrams of the telephoto lens of Example 5; 
           [0084]      FIG. 15A ,  FIG. 15B ,  FIG. 15C ,  FIG. 15D ,  FIG. 15E ,  FIG. 15F ,  FIG. 15G , and  FIG. 15H  are aberration diagrams of the telephoto lens of Example 6; 
           [0085]      FIG. 16A ,  FIG. 16B ,  FIG. 16C ,  FIG. 16D ,  FIG. 16E ,  FIG. 16F ,  FIG. 16G , and  FIG. 16H  are is an aberration diagram of the telephoto lens of Example 7; 
           [0086]      FIG. 17A ,  FIG. 17B ,  FIG. 17C ,  FIG. 17D ,  FIG. 17E ,  FIG. 17F ,  FIG. 17G , and  FIG. 17H  are aberration diagrams of the telephoto lens of Example 8; 
           [0087]      FIG. 18A ,  FIG. 18B ,  FIG. 18C ,  FIG. 18D ,  FIG. 18E ,  FIG. 18F ,  FIG. 18G , and  FIG. 18H  are aberration diagrams of the telephoto lens of Example 9; 
           [0088]      FIG. 19  is a cross-sectional view of an image pickup apparatus; 
           [0089]      FIG. 20  is a front perspective view of the image pickup apparatus; 
           [0090]      FIG. 21  is a rear perspective view of the image pickup apparatus; and 
           [0091]      FIG. 22  is a structural block diagram showing an internal circuit of main components of the image pickup apparatus. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0092]    Prior to a description of examples, the operation effects of embodiments according to an aspect of the present invention will be described. When the operation effects of the present embodiment are described, specific examples will be illustrated. However, as is the case with the examples described later, the illustrated aspects are only a few of the aspects included in the present invention, and the aspects include a number of variations. Therefore, the present invention is not limited to the illustrated aspects. 
         [0093]    A telephoto lens of a first embodiment includes, in order from an object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit, and the first lens unit includes, in order from the object side, a front-side lens unit having a positive refractive power and a rear-side lens unit, and at a time of focusing, the second lens unit moves, and the third lens unit has a positive lens and a negative lens, and the front-side lens unit includes lenses positioned closer to the object side than a predetermined negative lens that satisfies following Conditional Expression (a), and the lenses positioned closer to the object side than the predetermined negative lens include a plurality of positive lenses, and the rear-side lens unit has the predetermined negative lens and a positive lens, and following Conditional Expressions (1A) and (14) are satisfied: 
         [0000]      0.5 ≦|f/fLn|   (a),
 
         [0000]      0.015 ≦DGFGR/f≦ 0.25   (1A), and
 
         [0000]      0.19 ≦DGF airmax/ DGF≦ 1.0   (14),
 
         [0094]    where, 
         [0095]    f is a focal length of the entire telephoto lens; 
         [0096]    fLn is a focal length of the predetermined negative lens; 
         [0097]    DGFGR is an axial air space between the front-side lens unit and the rear-side lens unit; 
         [0098]    DGFairmax is a maximum axial air space, of axial air spaces in the front-side lens unit; and 
         [0099]    DGF is an axial thickness of the front-side lens unit. 
         [0100]    In order to reduce the overall length of the optical system and to ensure favorable imaging performance from the center to the periphery of an image, it is important to ensure optical symmetry in the entire optical system. In the telephoto lens of the first embodiment, the optical system is constructed with a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit having a positive lens and a negative lens. In this case, with the first lens unit, the second lens unit, and the positive lens in the third lens unit, the refractive powers are disposed in the order of: positive refractive power, negative refractive power, and positive refractive power. That is, refractive powers are in symmetric arrangement. In this way, by adopting the arrangement as described above, in the telephoto lens of the present embodiment, since the optical symmetry can be ensured, it becomes easy to correct coma, distortion, and chromatic aberration of magnification favorably. 
         [0101]    In the first lens unit, the front-side lens unit is disposed closest to the object, and the rear-side lens unit is disposed on an image side of the front-side lens unit with an airspace with some degree of width. Then, the front-side lens unit includes lenses positioned closer to the object side than the predetermined negative lens that satisfies Conditional Expression (a), and the lenses positioned closer to the object side than the predetermined negative lens include a plurality of positive lenses. The rear-side lens unit has the predetermined negative lens and a positive lens. 
         [0102]    In this way, in the first lens unit, the front-side lens unit includes a plurality of positive lenses, and the rear-side lens unit includes a negative lens and a positive lens. Therefore, it is possible to increase the positive refractive power in the first lens unit while performing correction of spherical aberration and correction of chromatic aberration. Thus, it is possible to enhance telephoto action with a combination of the negative refractive power of the second lens unit. As a result, shortening overall length of the optical system can be achieved. 
         [0103]    In the telephoto lens of the first embodiment, the front-side lens unit and the rear-side lens unit are separated from each other by the predetermined negative lens as a boundary. The predetermined negative lens is a negative lens that satisfies Conditional Expression (a) and in which a refractive power is large to some degree. Thus, a negative lens in which a refractive power is large to some degree is not included in the front-side lens unit. 
         [0104]    By arranging a negative lens having a large refractive power in the front-side lens unit, it is possible to correct chromatic aberration favorably. However, the volume of the front-side lens unit is largest in the telephoto lens. Therefore, if a negative lens having a large refractive power is disposed in the front-side lens unit, the volume of the negative lens increases. As a result, the optical system increases in size. 
         [0105]    Then, the predetermined negative lens is disposed in the rear-side lens unit. By doing so, it is possible to prevent the negative lens having a larger volume from being disposed in the front-side lens unit In addition, by arranging the predetermined negative lens in the rear-side lens unit, it is possible to correct chromatic aberration favorably. Thus, it is possible to achieve both significant reduction in weight of the optical system and favorable correction of chromatic aberration at the same time. 
         [0106]    A lens that falls below a lower limit value of Conditional Expression (a) is a lens having a small refractive power. Therefore, even when a negative lens is disposed in the front-side lens unit, the volume of the lens is not increased as long as the negative lens is a lens that falls below the lower limit value of Conditional Expression (a). Moreover, since the refractive power is small, the positive refractive power required for the front-side lens unit can be ensured safely even when such a lens is disposed in the front-side lens unit. Thus, the lens that falls below the lower limit value of Conditional Expression (a) may be disposed in the front-side lens unit. 
         [0107]    Examples of the lens that falls below the lower limit value of Conditional Expression (a) include cover glass having a small refractive power, a lens with a thin resin layer having aspheric effects on the lens surface (HBL: hybrid lens), and an optical element having a diffraction-effect surface (DOE: diffractive optical element). 
         [0108]    The second lens unit has a negative refractive power. Therefore, it is possible to obtain telephoto action with a combination of the positive refractive power of the first lens unit and the negative refractive power of the second lens unit. As a result, the overall length of the optical system can be reduced. 
         [0109]    Since the first lens unit has a positive refractive power, light rays is converged on the side closer to the image side than the first lens unit. That is, the height of light rays is reduced at the position of the second lens unit. Therefore, an outer diameter of the second lens unit becomes small. 
         [0110]    In the telephoto lens of the first embodiment, the first lens unit includes the front-side lens unit and the rear-side lens unit, whereby it is possible to correct both spherical aberration and chromatic aberration in the first lens unit favorably. In this case, since the load of aberration correction in the second lens unit is reduced, it is possible to increase the refractive power of the second lens unit. Thus, a reduction in diameter and weight of the second lens unit can be achieved. 
         [0111]    Then, in the telephoto lens of the first embodiment, the second lens unit is set as a focus lens unit and focusing is performed in the second lens unit. By doing so, since it is possible to reduce the outer diameter of the focus lens unit, it becomes easy to make the focus lens unit light weight. 
         [0112]    Furthermore, when the second lens unit is moved, it follows that the lens unit is moved in the place where the height of light rays is low. Therefore, it becomes easy to ensure high imaging performance on the periphery of the image even at the time of focusing. 
         [0113]    By satisfying Conditional Expression (1A), it is possible to ensure a sufficient space between the front-side lens unit and the rear-side lens unit. In this case, since the front-side lens unit and the rear-side lens unit can be separated from each other, it is possible to enhance telephoto action in the first lens unit. As a result, it is possible to reduce the overall length of the optical system. It is further possible to reduce the weight of the lenses positioned closer to the image side than the front-side lens unit. 
         [0114]    When falling below a lower limit value of Conditional Expression (1A), since the telephoto action in the first lens unit is weakened, it becomes difficult to reduce the overall length of the optical system. To reduce the overall length of the optical system, the telephoto action may be enhanced with the first lens unit and the second lens unit. However, if doing so, since the optical symmetry is deteriorated, it difficult to ensure favorable imaging performance. In addition, since the weight of the negative lens in the rear-side lens unit is increased, it becomes difficult to make the optical system light weight. 
         [0115]    When exceeding an upper limit value of Conditional Expression (1A), since the overall length of the first lens unit is increased, it becomes difficult to reduce the overall length of the optical system. 
         [0116]    When falling below a lower limit value of Conditional Expression (14), since the weight of the positive lenses in the front-side lens unit is increased, it becomes difficult to make the optical system light weight. When exceeding an upper limit value of Conditional Expression (14), it becomes difficult to reduce the overall length of the optical system. 
         [0117]    It is preferable that following Conditional Expressions (a-1), (a-2), (a-3), or (a-4) is satisfied instead of Conditional Expression (a): 
         [0000]      0.35 ≦|f/fLn|   (a-1),
 
         [0000]      0.25 ≦|f/fLn|   (a-2),
 
         [0000]      0.15 ≦|f/fLn|   (a-3), and
 
         [0000]      0.1 ≦|f/fLn|   (a-4).
 
         [0118]    It is preferable that following Conditional Expressions (1A-1), (1A-2), or (1A-3) is satisfied instead of Conditional Expression (1A) 
         [0000]      0.02 ≦DGFGR/f≦ 0.2   (1A-1),
 
         [0000]      0.03 ≦DGFGR/f≦ 0.17   (1A-2), and
 
         [0000]      0.04 ≦DGFGR/f≦ 0.15   (1A-3).
 
         [0119]    It is preferable that following Conditional Expression (14-1) or (14-2) is satisfied instead of Conditional Expression (14): 
         [0000]      0.2 ≦DGF airmax/ DGF≦ 0.9   (14-1), and
 
         [0000]      0.25 ≦DGF airmax/ DGF≦ 0.8   (14-2).
 
         [0120]    A telephoto lens of a second embodiment includes, in order from the object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit, and the first lens unit includes, in order from the object side, a front-side lens unit having a positive refractive power, a first rear-side lens unit, and a second rear-side lens unit, and at a time of focusing, the second lens unit moves, and the third lens unit has a positive lens and a negative lens, and the front-side lens unit includes lenses positioned closer to the object side than a predetermined negative lens that satisfies following Conditional Expression (a), and the lenses positioned closer to the object side than the predetermined negative lens include a plurality of positive lenses, and the first rear-side lens unit has the predetermined negative lens and a positive lens, and the second rear-side lens unit has a positive lens, and following Conditional Expressions (2B) and (16) are satisfied: 
         [0000]      0.5 ≦|f/fLn|   (a),
 
         [0000]      0.10 ≦ΔGFGR 1 /f≦ 0.5   (2B), and
 
         [0000]      50≦νdLp1   (16),
 
         [0121]    where, 
         [0122]    f is the focal length of the entire telephoto lens; 
         [0123]    fLn is the focal length of the predetermined negative lens; 
         [0124]    ΔGFGR 1  is an axial air space from an object-side surface in the front-side lens unit to an object-side surface in the first rear-side lens unit; and 
         [0125]    νdLp 1  is an Abbe number of a positive lens positioned closest to the object. 
         [0126]    In order to reduce the overall length of the optical system and to ensure favorable imaging performance from the center to the periphery of the image, it is important to ensure optical symmetry in the entire optical system. In the telephoto lens of the second embodiment, the optical system is constructed with a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit having a positive lens and a negative lens. By adopting such arrangement, as described above, in the telephoto lens of the present embodiment, since the optical symmetry can be ensured, it becomes easy to correct coma, distortion, and chromatic aberration of magnification favorably. 
         [0127]    In the first lens unit, the front-side lens unit is disposed closest to the object, and the rear-side first lens unit is disposed on the image side of the front-side lens unit with an air space with some degree of width. Then, the front-side lens unit includes lenses positioned closer to the object side than the predetermined negative lens that satisfies Conditional Expression (a), and the lenses positioned closer to the object side than the predetermined negative lens include a plurality of positive lenses. The first rear-side lens unit has the predetermined negative lens and a positive lens. 
         [0128]    In this way, in the first lens unit, the front-side lens unit includes a plurality of positive lenses, and the first rear-side lens unit includes a negative lens and a positive lens. Therefore, it is possible to enhance telephoto action in the first lens unit while performing correction of spherical aberration and correction of chromatic aberration. As a result, shortening the overall length of the optical system can be achieved. 
         [0129]    In the telephoto lens of the second embodiment, the front-side lens unit and the first rear-side lens unit are separated from each other by the predetermined negative lens as a boundary. The predetermined negative lens is a negative lens that satisfies Conditional Expression (a) and in which a refractive power is large to some extent. Thus, a negative lens in which a refractive power is large to some degree is not included in the front-side lens unit. 
         [0130]    By arranging a negative lens having a large refractive power in the front-side lens unit, it is possible to correct chromatic aberration favorably. However, the volume of the front-side lens unit is largest in the telephoto lens. Therefore, if a negative lens having a large refractive power is disposed in the front-side lens unit, the volume of the negative lens increases. As a result, the optical system increases in size. 
         [0131]    Then, the predetermined negative lens is disposed in the first rear-side lens unit. By doing so, it is possible to prevent the negative lens having a larger volume from being disposed in the front-side lens unit. In addition, by arranging the predetermined negative lens in the first rear-side lens unit, it is possible to correct chromatic aberration favorably. Thus, it is possible to achieve both significant reduction in weight of the optical system and favorable correction of chromatic aberration at the same time. 
         [0132]    A lens that falls below the lower limit value of Conditional Expression (a) is a lens having a small refractive power. Therefore, even when a negative lens is disposed in the front-side lens unit, the volume of the lens is not increased as long as the negative lens is a lens that falls below the lower limit value of Conditional Expression (a). Moreover, since the refractive power is small, the positive refractive power required for the front-side lens unit can be ensured safely even when such a lens is disposed in the front-side lens unit. Thus, the lens that falls below the lower limit value of Conditional Expression (a) may be disposed in the front-side lens unit. 
         [0133]    Examples of the lens that falls below the lower limit value of Conditional Expression (a) include cover glass having a small refractive power, a lens with a thin resin layer having aspheric effects on the lens surface (HBL: hybrid lens), and an optical element having a diffraction-effect surface (DOE: diffractive optical element). 
         [0134]    On the image side of the first rear-side lens unit, the second rear-side lens unit is disposed with an air space interposed. The second rear-side lens unit has a positive lens. By the positive lenses in the front-side lens unit, the negative lens and the positive lens in the first rear-side lens unit, and the positive lens in the second rear-side lens unit, it is possible to enhance the correction effect for aberrations such as spherical aberration, astigmatism, longitudinal chromatic aberration, and chromatic aberration of magnification in the first lens unit. Therefore, it becomes possible to reduce the amount of aberration in the lens units positioned closer to the image side than the first lens unit. As a result, even when the overall length of the optical system is reduced, it is easier to reduce the weight of the lens units positioned closer to the image side than the first lens unit and to ensure high imaging performance at the time of focusing. 
         [0135]    The second lens unit has a negative refractive power. Therefore, it is possible to obtain telephoto action with a combination of the positive refractive power of the first lens unit and the negative refractive power of the second lens unit. As a result, the overall length of the optical system can be reduced. 
         [0136]    Since the first lens unit has a positive refractive power, light rays is converged on the side closer to the image side than the first lens unit. That is, the height of light rays is reduced at the position of the second lens unit. Therefore, the outer diameter of the second lens unit becomes small. 
         [0137]    In the telephoto lens of the second embodiment, the first lens unit includes the front-side lens unit, the first rear-side lens unit, and the second rear-side lens unit, whereby it is possible to correct both spherical aberration and chromatic aberration in the first lens unit favorably. In this case, since the load of aberration correction in the second lens unit is reduced, it is possible to increase the refractive power of the second lens unit. Thus, a reduction in diameter and weight of the second lens unit can be achieved. 
         [0138]    Then, in the telephoto lens of the second embodiment, the second lens unit is set as a focus lens unit and focusing is performed in the second lens unit. By doing so, since it is possible to reduce the outer diameter of the focus lens unit, it becomes easy to make the focus lens unit light weight. 
         [0139]    Furthermore, when the second lens unit is moved, it follows that the lens unit is moved in the place where the height of light rays is low. Therefore, it becomes easy to ensure high imaging performance on the periphery of the image even at the time of focusing. 
         [0140]    By satisfying Conditional Expression (2B), it is possible to ensure a sufficient space between the front-side lens unit and the first rear-side lens unit. In this case, since the front-side lens unit and the first rear-side lens unit can be separated from each other, it is possible to enhance telephoto action in the first lens unit. As a result, it is possible to reduce the overall length of the optical system. It is further possible to reduce the weight of the lenses positioned closer to the image side than the front-side lens unit. 
         [0141]    When falling below a lower limit value of Conditional Expression (2B), since the telephoto action in the first lens unit is weakened, it becomes difficult to reduce the overall length of the optical system. To reduce the overall length of the optical system, the telephoto action may be enhanced with the first lens unit and the second lens unit. However, if doing so, since the optical symmetry is deteriorated, it difficult to ensure favorable imaging performance. In addition, since the weight of the negative lens in the first rear-side lens unit is increased, it becomes difficult to make the optical system light weight. 
         [0142]    When exceeding an upper limit value of Conditional Expression (2B), since the overall length of the first lens unit is increased, it becomes difficult to reduce the overall length of the optical system. 
         [0143]    When falling below a lower limit value of Conditional Expression (16), since longitudinal chromatic aberration in the first sub-lens unit is increased, favorable imaging performance is not achieved. Alternatively, when favorable imaging performance is to be achieved, it is difficult to reduce the overall length of the optical system. 
         [0144]    It is preferable that following Conditional Expression (2B-1) or (2B-2) is satisfied instead of Conditional Expression (2B): 
         [0000]      0.12 ≦ΔGFGR 1 /f≦ 0.45   (2B-1), and
 
         [0000]      0.13 ≦ΔGFGR 1 /f≦ 0.4   (2B-2).
 
         [0145]    It is preferable that any one of following Conditional Expressions (16-1), (16-2), and (16-3) is satisfied instead of Conditional Expression (16): 
         [0000]      55≦νdLp1   (16-1),
 
         [0000]      62≦νdLp1   (16-2), and
 
         [0000]      65≦νdLp1   (16-3).
 
         [0146]    A telephoto lens of a third embodiment includes, in order from the object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit, and the first lens unit includes, in order from the object side, a front-side lens unit having a positive refractive power, a first rear-side lens unit, and a second rear-side lens unit, and at a time of focusing, the second lens unit moves, and the third lens unit has a positive lens and a negative lens, and the front-side lens unit includes a lens positioned closer to the object side than a predetermined negative lens that satisfies following Conditional Expression (a), and the lens positioned closer to the object side than the predetermined negative lens includes a positive lens, and the first rear-side lens unit has the predetermined negative lens and a positive lens, and the second rear-side lens unit has a positive lens, and following Conditional Expressions (2B) and (3) below are satisfied: 
         [0000]      0.5 ≦|f/fLn|   (a),
 
         [0000]      0.10 ≦ΔGFGR 1 /f≦ 0.5   (2B), and
 
         [0000]      72≦νdGFave   (3),
 
         [0147]    where, 
         [0148]    f is the focal length of the entire telephoto lens; 
         [0149]    fLn is the focal length of the predetermined negative lens; 
         [0150]    ΔGFGR 1  is an axial air space from an object-side surface in the front-side lens unit to an object-side surface in the first rear-side lens unit; and 
         [0151]    νdGFave is an average Abbe number of the positive lens in the front-side lens unit. 
         [0152]    In order to reduce the overall length of the optical system and to ensure favorable imaging performance from the center to the periphery of the image, it is important to ensure optical symmetry in the entire optical system. In the telephoto lens of the third embodiment, the optical system is constructed with a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit having a positive lens and a negative lens. By adopting such arrangement, as described above, in the telephoto lens of the present embodiment, since the optical symmetry can be ensured, it becomes easy to correct coma, distortion, and chromatic aberration of magnification favorably. 
         [0153]    In the first lens unit, the front-side lens unit is disposed closest to the object, and the rear-side first lens unit is disposed on the image side of the front-side lens unit with an air space with some degree of width. Then, the front-side lens unit includes a lens positioned closer to the object side than a predetermined negative lens that satisfies Conditional Expression (a), and the lens positioned closer to the object side than the predetermined negative lens includes a positive lens. The first rear-side lens unit has the predetermined negative lens and a positive lens. 
         [0154]    In this way, in the first lens unit, the front-side lens unit includes a positive lens, and the first rear-side lens unit includes a negative lens and a positive lens. Therefore, it is possible to enhance telephoto action in the first lens unit while performing correction of spherical aberration and correction of chromatic aberration. As a result, shortening the overall length of the optical system can be achieved. 
         [0155]    In the telephoto lens of the third embodiment, the front-side lens unit and the first rear-side lens unit are separated from each other by the predetermined negative lens as a boundary. The predetermined negative lens is a negative lens that satisfies Conditional Expression (a) and in which a refractive power is large to some extent. Thus, a negative lens in which a refractive power is large to some extent is not included in the front-side lens unit. 
         [0156]    By arranging a negative lens having a large refractive power in the front-side lens unit, it is possible to correct chromatic aberration favorably. However, the volume of the front-side lens unit is largest in the telephoto lens. Therefore, if a negative lens having a large refractive power is disposed in the front-side lens unit, the volume of the negative lens increases. As a result, the optical system increases in size. 
         [0157]    Then, the predetermined negative lens is disposed in the first rear-side lens unit. By doing so, it is possible to prevent a negative lens having a larger volume from being disposed in the front-side lens unit. In addition, by arranging the predetermined negative lens in the first rear-side lens unit, it is possible to correct chromatic aberration favorably. Thus, it is possible to achieve both significant reduction in weight of the optical system and favorable correction of chromatic aberration at the same time. 
         [0158]    A lens that falls below the lower limit value of Conditional Expression (a) is a lens having a small refractive power. Therefore, even when a negative lens is disposed in the front-side lens unit, the volume of the lens is not increased as long as the negative lens is a lens that falls below the lower limit value of Conditional Expression (a). Furthermore, since the refractive power is small, the positive refractive power required for the front-side lens unit can be ensured safely even when such a lens is disposed in the front-side lens unit. Thus, the lens that falls below the lower limit value of Conditional Expression (a) may be disposed in the front-side lens unit. 
         [0159]    Examples of the lens that falls below the lower limit value of Conditional Expression (a) include cover glass having a small refractive power, a lens with a thin resin layer having aspheric effects on the lens surface (HBL: hybrid lens), and an optical element having a diffraction-effect surface (DOE: diffractive optical element). 
         [0160]    On the image side of the first rear-side lens unit, the second rear-side lens unit is disposed with an air space interposed. The second rear-side lens unit has a positive lens. By the positive lens in the front-side lens unit, the negative lens and the positive lens in the first rear-side lens unit, and the positive lens in the second rear-side lens unit, it is possible to enhance the correction effect for aberrations such as spherical aberration, astigmatism, longitudinal chromatic aberration, and chromatic aberration of magnification in the first lens unit. Therefore, it becomes possible to reduce the amount of aberration in the lens units positioned closer to the image side than the first lens unit. As a result, even when the overall length of the optical system is reduced, it is easier to reduce the weight of the lens units positioned closer to the image side than the first lens unit and to ensure high imaging performance at the time of focusing. 
         [0161]    The second lens unit has a negative refractive power. Therefore, it is possible to obtain telephoto action with a combination of the positive refractive power of the first lens unit and the negative refractive power of the second lens unit. As a result, the overall length of the optical system can be reduced. 
         [0162]    Since the first lens unit has a positive refractive power, light rays is converged on the side closer to the image side than the first lens unit. That is, the height of light rays is reduced at the position of the second lens unit. Therefore, the outer diameter of the second lens unit becomes small. 
         [0163]    In the telephoto lens of the third embodiment, the first lens unit includes the front-side lens unit, the first rear-side lens unit, and the second rear-side lens unit, whereby it is possible to correct both spherical aberration and chromatic aberration in the first lens unit favorably. In this case, since the load of aberration correction in the second lens unit is reduced, it is possible to increase the refractive power of the second lens unit. Thus, a reduction in diameter and weight of the second lens unit can be achieved. 
         [0164]    Then, in the telephoto lens of the third embodiment, the second lens unit is set as a focus lens unit and focusing is performed in the second lens unit. By doing so, since it is possible to reduce the outer diameter of the focus lens unit, it becomes easy to make the focus lens unit light weight. 
         [0165]    Furthermore, when the second lens unit is moved, it follows that the lens unit is moved in the place where the height of light rays is low. Therefore, it becomes easy to ensure high imaging performance on the periphery of the image even at the time of focusing. 
         [0166]    The technical meaning of Conditional Expression (2B) has already been described and the description is omitted here. 
         [0167]    In a telephoto lens, size reduction of the optical system is required in addition to ensuring favorable imaging performance. In order to obtain favorable imaging performance in a telephoto lens, it is mainly necessary to suppress occurrence of longitudinal chromatic aberration. On the other hand, in order to achieve size reduction of the optical system, it is necessary to increase the positive refractive power of a lens unit positioned closer to the object side. However, in doing so, longitudinal chromatic aberration is more likely to occur. 
         [0168]    When falling below a lower limit value of Conditional Expression (3), since the amount of longitudinal chromatic aberration is increased, it becomes difficult to reduce the overall length of the optical system. 
         [0169]    It is preferable that following Conditional Expressions (3-1), (3-2), (3-3), or (3-4) is satisfied instead of Conditional Expression (3): 
         [0000]      75≦νdGFave   (3-1),
 
         [0000]      77≦νdGFave   (3-2),
 
         [0000]      80≦νdGFave   (3-3), and
 
         [0000]      82≦νdGFave   (3-4).
 
         [0170]    In the telephoto lens of the first embodiment, it is preferable that the rear-side lens unit have a first rear-side lens unit and a second rear-side lens unit. 
         [0171]    The front-side lens unit, the first rear-side lens unit, and the second rear-side lens unit are sub-lens units that constitute the first lens unit. The technical meaning of constituting the first lens unit with three sub-lens units has already described and the description is omitted here. 
         [0172]    In the telephoto lens of the first embodiment, the telephoto lens of the second embodiment, and the telephoto lens of the third embodiment (hereinafter referred to as “the telephoto lens of the present embodiment”), it is preferable that the first rear-side lens unit have a negative refractive power. 
         [0173]    By doing so, enhancing telephoto action in the first lens unit is further facilitated. As a result, it becomes easy to reduce the overall length of the optical system. Furthermore, the refractive powers in the first lens unit are disposed in the order of: positive refractive power (front-side lens unit) and negative refractive power (first rear-side lens unit). Here, when the second rear-side lens unit has a positive refractive power, the refractive powers in the first lens unit are disposed in the order of: positive refractive power, negative refractive power, and positive refractive power. Such refractive power arrangement can further enhance the correction effect for aberrations such as spherical aberration, astigmatism, longitudinal chromatic aberration, and chromatic aberration of magnification in the first lens unit. 
         [0174]    In the telephoto lens of the present embodiment, it is preferable that the second rear-side lens unit have a positive refractive power. 
         [0175]    By doing so, the refractive powers in the first lens unit are disposed in the order of: positive refractive power, negative refractive power, and positive refractive power. Such refractive power arrangement can further enhance the correction effect for aberrations such as spherical aberration, astigmatism, longitudinal chromatic aberration, and chromatic aberration of magnification in the first lens unit. 
         [0176]    In the telephoto lens of the second embodiment and the telephoto lens of the third embodiment, it is preferable that following Conditional Expression (1B) is satisfied: 
         [0000]      0.015 ≦DGFGR 1 /f≦ 0.25   (1B),
 
         [0177]    where, 
         [0178]    DGFGR 1  is an axial air space between the front-side lens unit and the first rear-side lens unit; and 
         [0179]    f is the focal length of the entire telephoto lens. 
         [0180]    The technical meaning of Conditional Expression (1B) is the same as the technical meaning of Conditional Expression (1A). 
         [0181]    It is preferable that following Conditional Expressions (1B-1), (1B-2), or (1B-3) is satisfied instead of Conditional Expression (1B): 
         [0000]      0.02 ≦DGFGR 1 /f≦ 0.2   (1B-1),
 
         [0000]      0.03 ≦DGFGR 1 /f≦ 0.17   (1B-2), and
 
         [0000]      0.04 ≦DGFGR 1 /f≦ 0.15   (1B-3).
 
         [0182]    In the telephoto lens of the first embodiment, it is preferable that following Conditional Expression (2A) is satisfied: 
         [0000]      0.10 ≦ΔGFGR/f≦ 0.5   (2A),
 
         [0183]    where, 
         [0184]    ΔGFGR is an axial air space from an object-side surface in the front-side lens unit to an object-side surface in the rear-side lens unit; and 
         [0185]    f is the focal length of the entire telephoto lens. 
         [0186]    The technical meaning of Conditional Expression (2A) is the same as the technical meaning of Conditional Expression (2B). 
         [0187]    It is preferable that following Conditional Expression (2A-1) or (2A-2) is satisfied instead of Conditional Expression (2A): 
         [0000]      0.12 ≦ΔGFGR/f≦ 0.45   (2A-1), and
 
         [0000]      0.13 ≦ΔGFGR/f≦ 0.4   (2A-2).
 
         [0188]    In the telephoto lens of the first embodiment, when the rear-side lens unit has the first rear-side lens unit and the second rear-side lens unit, it is preferable that above-mentioned Conditional Expression (2A) is satisfied. 
         [0189]    In the telephoto lens of the first embodiment and the telephoto lens of the second embodiment, it is preferable that following Conditional Expression (3) is satisfied: 
         [0000]      72≦νdGFave   (3),
 
         [0190]    where, 
         [0191]    νdGFave is the average Abbe number of the positive lens in the front-side lens unit. 
         [0192]    The technical meaning of Conditional Expression (3) has already been described and the description is omitted here. 
         [0193]    In the telephoto lens of the present embodiment, it is preferable that following Conditional Expression (3-2) is satisfied: 
         [0000]      77≦νdGFave   (3-2),
 
         [0194]    where, 
         [0195]    νdGFave is the average Abbe number of the positive lens in the front-side lens unit. 
         [0196]    The technical meaning of Conditional Expression (3-2) is the same as the technical meaning of Conditional Expression (3). 
         [0197]    In the telephoto lens of the present embodiment, it is preferable that following Conditional Expression (4) is satisfied: 
         [0000]      84≦νdGFmax   (4),
 
         [0198]    where, 
         [0199]    νdGFmax is a largest Abbe number, of Abbe numbers of the positive lens in the front-side lens unit. 
         [0200]    The technical meaning of Conditional Expression (4) is the same as the technical meaning of Conditional Expression (3). 
         [0201]    It is preferable that following Conditional Expression (4-1) or (4-2) is satisfied instead of Conditional Expression (4): 
         [0000]      90≦νdGFmax   (4-1), and
 
         [0000]      94≦νdGFmax   (4-2).
 
         [0202]    In the telephoto lens of the present embodiment, it is preferable that following Conditional Expression (5) is satisfied: 
         [0000]      0.02 ≦DGR 1 GR 2 /f≦ 0.3   (5),
 
         [0203]    where, 
         [0204]    DGR 1 GR 2  is an axial air space between the first rear-side lens unit and the second rear-side lens unit; and 
         [0205]    f is the focal length of the entire telephoto lens. 
         [0206]    When falling below a lower limit value of Conditional Expression (5), the difference is reduced between the light ray height in the first rear-side lens unit and the light ray height in the second rear-side lens unite Therefore, it becomes impossible to enhance the correction effect for aberrations such as spherical aberration, astigmatism, longitudinal chromatic aberration, and chromatic of magnification aberration. When exceeding an upper limit value of Conditional Expression (5), it becomes difficult to reduce the overall length of the optical system. 
         [0207]    It is preferable that following Conditional Expression (5-1), (5-2), or (5-3) is satisfied instead of Conditional Expression (5): 
         [0000]      0.03 ≦DGR 1 GR 2 /f≦ 0.25   (5-1),
 
         [0000]      0.04 ≦DGR 1GR2 /f≦ 0.23   (5-2), and
 
         [0000]      0.05 ≦DGR 1GR2 /f≦ 0.2   (5-3).
 
         [0208]    In the telephoto lens of the third embodiment, it is preferable that the front-side lens unit have a plurality of positive lenses. 
         [0209]    By doing so, it is possible to distribute positive refractive power among a plurality of lenses even when the refractive power of the front-side lens unit is increased. Therefore, it is possible to suppress occurrence of spherical aberration. Moreover, it is possible to enhance telephoto action in the first lens unit, it is easy to reduce the overall length of the optical system. 
         [0210]    In the telephoto lens of the present embodiment, it is preferable that following Conditional Expression (6) is satisfied: 
         [0000]      0.2 ≦fGF/f≦ 0.8   (6),
 
         [0211]    where, 
         [0212]    fGF is a focal length of the front-side lens unit; and 
         [0213]    f is the focal length of the entire telephoto lens. 
         [0214]    When falling below a lower limit value of Conditional Expression (6), the amount of axial chromatic aberration and the amount of spherical aberration in the front-side lens unit is increased. Therefore, favorable imaging performance cannot be obtained. When exceeding an upper limit value of Conditional Expression (6), it becomes difficult to reduce the size of the optical system. 
         [0215]    It is preferable that following Conditional Expression (6-1) or (6-2) is satisfied instead of Conditional Expression (6): 
         [0000]      0.25 ≦fGF/f≦ 0.6   (6-1), and
 
         [0000]      0.28 ≦fGF/f≦ 0.47   (6-2).
 
         [0216]    In the telephoto lens of the present embodiment, it is preferable that a first lens is disposed closest to the object and following Conditional Expression (7) is satisfied: 
         [0000]      1.6 ≦fL 1 /fGF≦ 5.0   (7),
 
         [0217]    where, 
         [0218]    fL 1  is a focal length of the first lens; and 
         [0219]    fGF is the focal length of the front-side lens unit. 
         [0220]    When falling below a lower limit value of Conditional Expression (7), the positive refractive power of the first lens becomes too large. In this case, the amount of spherical aberration in the front-side lens unit is increased. Therefore, it becomes difficult to reduce the size of the optical system. 
         [0221]    When exceeding an upper limit value of Conditional Expression (7), the positive refractive power of the first lens becomes too small. In this case, the positive refractive power of the front-side lens unit becomes also small. If an adequate positive refractive power is to be ensured in the front-side lens unit, the load of refractive power in the lenses positioned closer to the image side than the first lens is increased. As a result, the amount of spherical aberration in the front-side lens unit is increased. Therefore, it becomes difficult to reduce the size of the optical system. 
         [0222]    It is preferable that following Conditional Expression (7-1), (7-2), or (7-3) is satisfied instead of Conditional Expression (7): 
         [0000]      1.8 ≦fL 1 /fGF≦ 4.5   (7-1),
 
         [0000]      1.9 ≦fL 1 /fGF≦ 4.0   (7-2), and
 
         [0000]      2.0 ≦fL 1 /fGF≦ 3.5   (7-3).
 
         [0223]    In the telephoto lens of the present embodiment, it is preferable that following Conditional Expression (8) is satisfied: 
         [0000]      −3.0 ≦fGF/fGR 1≦0.1   (8),
 
         [0224]    where, 
         [0225]    fGF is the focal length of the front-side lens unit; and 
         [0226]    fGR 1  is a focal length of the first rear-side lens unit. 
         [0227]    When falling below a lower limit value of Conditional Expression (8), spherical aberration is overcorrected. Therefore, favorable imaging performance cannot be obtained. When exceeding an upper limit value of Conditional Expression (8), the negative refractive power of the first rear-side lens unit becomes too small. Therefore, it becomes difficult to reduce the overall length of the optical system. 
         [0228]    It is preferable that following Conditional Expression (8-1), (8-2), or (8-3) is satisfied instead of Conditional Expression (8): 
         [0000]      −2.5 ≦fGF/fGR 1≦0.0   (8-1),
 
         [0000]      −2.0 ≦fGF/fGR 1≦−0.2   (8-2), and
 
         [0000]      −1.8 ≦fGF/fGR 1≦−0.3   (8-3).
 
         [0229]    In the telephoto lens of the present embodiment, it is preferable that following Conditional Expression (9) is satisfied: 
         [0000]      0.06 ≦|fG 2 /f|≦ 0.25   (9),
 
         [0230]    where, 
         [0231]    fG 2  is a focal length of the second lens unit; and 
         [0232]    f is the focal length of the entire telephoto lens. 
         [0233]    In the second lens unit, light rays are refracted in a direction away from the optical axis. When falling below a lower limit value of Conditional Expression (9), light rays are refracted in a direction further away from the optical axis. As a result, the lens diameter of the third lens unit is increased. Therefore, it becomes difficult to reduce the size of the optical system. 
         [0234]    The second lens unit functions as a focus lens unit. When exceeding an upper limit value of Conditional Expression (9), the refractive power of the second lens unit becomes too small. In this case, since the amount of movement of the imaging position relative to the amount of movement of the second lens unit (focus lens unit) (hereinafter referred to as “focus sensitivity”) is too small, the amount of movement of the second lens unit at the time of focusing is increased. Therefore, it becomes difficult to reduce the overall length of the optical system. Moreover, telephoto action obtained with the first lens unit and the second lens unit is reduced. Therefore, it becomes difficult to reduce the overall length of the optical system. 
         [0235]    It is preferable that following Conditional Expression (9-1) or (9-2) is satisfied instead of Conditional Expression (9): 
         [0000]      0.07 ≦|fG 2 /f|≦ 0.2   (9-1), and
 
         [0000]      0.08 ≦|fG 2 /f|≦ 0.15   (9-2).
 
         [0236]    In the telephoto lens of the present embodiment, it is preferable that following Conditional Expression (10) is satisfied: 
         [0000]      3.5 ≦|MGG 2 B   2 ×( MGG 2 2 −1)|≦6.5   (10),
 
         [0237]    where, 
         [0238]    MGG 2 B is a lateral magnification of a first rear-side lens system; 
         [0239]    MGG 2  is a lateral magnification of the second lens unit; 
         [0240]    the lateral magnification is a lateral magnification at the time of focusing on an infinite object; and 
         [0241]    the first rear-side lens system is a lens system constituted with all of the lenses positioned closer to the image side than the second lens unit. 
         [0242]    When falling below a lower limit value of Conditional Expression (10), the amount of movement of the second lens unit at the time of focusing is too large. Therefore, it becomes difficult to reduce the overall length of the optical system. When exceeding an upper limit value of Conditional Expression (10), it becomes difficult to control the position of the second lens unit at the time of focusing. Therefore, accurate focusing cannot be achieved. 
         [0243]    It is preferable that following Conditional Expression (10-1) or (10-2) is satisfied instead of Conditional Expression (10): 
         [0000]      3.8 ≦|MGG 2 B   2 ×( MGG 2 2 −1)|≦6.0   (10-1), and
 
         [0000]      4.0 ≦|MGG 2 B   2 ×( MGG 2 2 −1)|≦5.6   (10-2).
 
         [0244]    In the telephoto lens of the present embodiment, it is preferable that the second lens unit include two or less lenses. 
         [0245]    As described above, in the telephoto lens of the present embodiment, the optical symmetry is ensured. Thus, coma, distortion, and chromatic aberration of magnification are corrected favorably. Therefore, even when the arrangement of the second lens unit is simplified, it is possible to ensure high imaging performance at the time of focusing. 
         [0246]    Then, the second lens unit is constituted with two or less lenses. By doing so, it is possible to reduce the weight of the second lens unit, that is, the focus lens unit, while keeping high imaging performance even at the time of focusing. 
         [0247]    In the telephoto lens of the present embodiment, it is preferable that the second lens unit includes a lens having a positive refractive power and a lens having a negative refractive power. 
         [0248]    By doing so, it is possible to reduce the amount of longitudinal chromatic aberration and the amount of chromatic aberration of magnification in the second lens unit. As a result, it is possible to ensure stable imaging performance at the time of focusing. Furthermore, the second lens unit includes two lenses whereby it is possible to reduce the weight of the second lens unit while keeping high imaging performance. 
         [0249]    In the telephoto lens of the present embodiment, it is preferable that the second lens unit have a plastic lens having a positive refractive power and a plastic lens having a negative refractive power, and following Conditional Expression (11) is satisfied: 
         [0000]      −0.6 ≦fPLn/fPLp≦− 0.15   (11),
 
         [0250]    where, 
         [0251]    fPLn is a focal length of the plastic lens having a negative refractive power; and 
         [0252]    fPLp is a focal length of the plastic lens having a positive refractive power. 
         [0253]    The second lens unit functions as a focus lens unit. Then, by using a plastic lens for the second lens unit, it is possible to reduce the weight of the second lens unit. Thus, it is possible to move the second lens unit at high speed at the time of focusing. As a result, it is possible to achieve fast focusing. 
         [0254]    Furthermore, the refractive power of one of the plastic lenses is a positive refractive power and the refractive power of the other plastic lens is a negative refractive power, whereby it is possible to keep stable imaging performance even when a temperature change occurs. 
         [0255]    When falling below a lower limit value of Conditional Expression (11), aberration variation due to temperature change becomes too large in the other plastic lens compared with the one plastic lens. In particular, variation of spherical aberration and variation of curvature of field become too large. Therefore, it becomes impossible to cancel variation of spherical aberration and variation of field curvature of field occurring in one plastic lens, with the other plastic lens. Therefore, favorable imaging performance cannot be obtained. 
         [0256]    Also when exceeding an upper limit value of Conditional Expression (11), the result is similar to when falling below the lower limit value of Conditional Expression (11). 
         [0257]    It is preferable that following Conditional Expression (11-1) or (11-2) is satisfied instead of Conditional Expression (11): 
         [0000]      −0.5 ≦fPLn/fPLp≦− 0.17   (11-1), and
 
         [0000]      −0.43 ≦fPLn/fPLp≦− 0.2   (11-2).
 
         [0258]    In the telephoto lens of the present embodiment, it is preferable that the second lens unit have a plastic lens having a positive refractive power and a glass lens having a negative refractive power, the plastic lens and the glass lens are integrally molded, and following Conditional Expression (12) is satisfied: 
         [0000]      0.2 ≦|fG 2 /fPLp|≦ 0.7   (12),
 
         [0259]    where, 
         [0260]    fG 2  is the focal length of the second lens unit; and 
         [0261]    fPLp is the focal length of the plastic lens having a positive refractive power. 
         [0262]    The second lens unit functions as a focus lens unit. Then, by using a plastic lens for the second lens unit, it is possible to reduce the weight of the second lens unit. Thus, it is possible to move the second lens unit at high speed at the time of focusing. As a result, it is possible to achieve fast focusing. 
         [0263]    Moreover, by combining a glass lens with a plastic lens, it is possible to correct chromatic aberration favorably. Furthermore, by integrally molding the glass lens and the plastic lens, it is possible to alleviate an assembly error at a time of assembling into a frame member. 
         [0264]    As described above, the second lens unit functions as a focus lens unit. In order to stabilize imaging performance at the time of focusing, for example, it is necessary to suppress variation of refractive power due to temperature change. The rigidity of plastic lenses is lower than the rigidity of glass. Therefore, the amount of change in shape of plastic lenses in temperature change is almost seven times larger than that of glass. 
         [0265]    When the shape of a lens changes, the refractive power also changes. Then, a glass lens is used for the negative lens and a plastic lens is used for the positive lens. In this case, since the rigidity of the negative lens is high, a change in shape of the negative lens can be minimized even when the positive lens is deformed due to temperature change. As a result, it is possible to suppress variation of refractive power of the negative lens. 
         [0266]    The negative refractive power of the second lens unit is provided by the refractive power of the negative lens. Thus, by suppressing the variation of refractive power of the negative lens, it is possible to suppress variation of negative refractive power of the second lens unit. As a result, it is possible to stabilize imaging performance at the time of focusing. 
         [0267]    When falling below a lower limit value of Conditional Expression (12), deformation at a time of temperature change increases. In this case, variation of spherical aberration and variation of curvature of field are increased. Therefore, favorable imaging performance cannot be obtained. 
         [0268]    Also when exceeding an upper limit value of Conditional Expression (12), the result is similar to when falling below the lower limit value of Conditional Expression (12). 
         [0269]    It is preferable that following Conditional Expression (12-1) or (12-2) is satisfied instead of Conditional Expression (12): 
         [0000]      0.25 ≦|fG 2 /fPLp|≦ 0.6   (12-1), and
 
         [0000]      0.3 ≦|fG 2 /fPLp|≦ 0.5   (12-2).
 
         [0270]    In the telephoto lens of the present embodiment, it is preferable that the third lens unit have a camera shake-correction lens unit and the camera shake-correction lens unit move in a direction vertical to the optical axis. 
         [0271]    By moving one or more lenses in a direction vertical to the optical axis, it is possible to correct a shift of the imaging position due to camera shake. Here, if the lens to be moved (hereinafter referred to as “camera shake-correction lens”) is compact and lightweight, it is possible to quickly correct a shift of the imaging position. 
         [0272]    In a telephoto-type optical system, the second lens unit and the third lens unit are units having a small diameter. Then, by constituting the camera shake-correction lens unit with the lenses in the third lens unit, it is possible to reduce the diameter and weight of the camera shake-correction lens. Thus, it is possible to enhance the responsivity of the camera shake-correction lens unit. As a result, it is possible to correct a shift of the imaging position due to camera shake at high speed. 
         [0273]    In the telephoto lens of the present embodiment, it is preferable that the third lens unit has a sub-lens unit on the object side and the sub-lens unit have a refractive power with a sign different from that of the camera shake-correction lens unit. 
         [0274]    By doing so, it is possible to increase the amount of shift of the imaging position relative to the amount of shift of the camera shake-correction lens unit (hereinafter referred to as “camera shake-correction sensitivity”). That is, it is possible to reduce the amount of shift of the camera shake-correction lens unit. As a result, it is possible to correct a shift of the imaging position due to camera shake at high speed. 
         [0275]    In the telephoto lens of the present embodiment, it is preferable that the third lens unit has a sub-lens unit on the image side and the sub-lens unit have a refractive power with a sign different from that of the camera shake-correction lens unit. 
         [0276]    By doing so, it is possible to increase the camera shake-correction sensitivity. That is, it is possible to reduce the amount of shift of the camera shake-correction lens unit. As a result, it is possible to correct a shift of the imaging position due to camera shake at high speed. 
         [0277]    In the telephoto lens of the present embodiment, it is preferable that the third lens unit has an object-side sub-lens unit and an image-side sub-lens unit on the object side and the image side, respectively, and the object-side sub-lens unit and the image-side sub-lens unit both have a refractive power with a sign different from that of the camera shake-correction lens unit. 
         [0278]    By doing so, it is possible to increase the camera shake-correction sensitivity. That is, it is possible to reduce the amount of shift of the camera shake-correction lens unit. As a result, it is possible to correct a shift of the imaging position due to camera shake at high speed. 
         [0279]    In the telephoto lens of the present embodiment, it is preferable that the camera shake-correction lens unit at least has a first correction lens, a second correction lens, and a third correction lens, and the first correction lens and the second correction lens have a refractive power with the same sign as the camera shake-correction lens unit, and the third correction lens has a refractive power with a sign different from that of the camera shake-correction lens unit. 
         [0280]    The camera shake-correction lens unit moves in a direction vertical to the optical axis. This movement mainly causes variation of spherical aberration, astigmatism, and chromatic aberration of magnification. If the amount of this variation is large, the imaging performance is reduced. 
         [0281]    Then, in the telephoto lens of the present embodiment, a refractive power with the same sign as the camera shake-correction lens unit is imparted to the first correction lens and the second correction lens. By doing so, the refractive power of the camera shake-correction lens unit is distributed between the first correction lens and the second correction lens. As a result, the refractive power of the first correction lens and the refractive power of the second correction lens are both reduced. Therefore, it is possible to reduce the amount of variation of spherical aberration and the amount of variation of astigmatism. 
         [0282]    Furthermore, a refractive power with a sign different from that of the camera shake-correction lens unit is imparted to the third correction lens. By doing so, it is possible to reduce the amount of variation of chromatic aberration of magnification. 
         [0283]    In the telephoto lens of the present embodiment, it is preferable that the camera shake-correction lens unit has a negative refractive power. 
         [0284]    The camera shake-correction lens unit moves in a direction vertical to the optical axis. Therefore, the camera shake-correction lens unit preferably has a small diameter. By setting the lens unit positioned where light rays converge more, as the camera shake-correction lens unit, it is possible to reduce the size of the camera shake-correction lens unit. Then, by setting the refractive power of the camera shake-correction lens unit to a negative refractive power, it is possible to further reduce the size of the camera shake-correction lens unit. 
         [0285]    In the telephoto lens of the present embodiment, it is preferable that the third lens unit has an object-side sub-lens unit having a positive refractive power, a camera shake-correction lens unit having a negative refractive power, and an image-side sub-lens unit having a positive refractive power. 
         [0286]    As described above, in the telephoto lens of the present embodiment, the first lens unit has a positive refractive power and the second lens unit has a negative refractive power. Therefore, since telephoto action can be obtained, it is possible to reduce the overall length of the optical system. 
         [0287]    Since the first lens unit has a positive refractive power, light rays converge on the side closer to the image side than the first lens unit. That is, the height of light rays is low at the position of the second lens unit. Therefore, the outer diameter of the second lens unit is reduced. Then, the second lens unit is set as the focus lens unit and focusing is performed in the second lens unit. By doing so, it is possible to reduce the outer diameter of the focus lens unit. 
         [0288]    In the focus lens unit, when the refractive power is increased, the focus sensitivity becomes high. When the focus sensitivity is high, the amount of movement of the focus lens unit at the time of focusing is reduced. As described above, the second lens unit functions as the focus lens unit. Then, the refractive power of the second lens unit is increased. By doing so, it is possible to enhance the focus sensitivity. As a result, it is possible to reduce the amount of movement of the focus lens unit at the time of focusing. 
         [0289]    A focus unit has a focus lens unit and a focus mechanism. Achieving a smaller diameter of the focus lens unit and reducing the amount of movement at the time of focusing can also reduce the size and weight of the entire focus unit. 
         [0290]    Furthermore, light incident on the focus lens unit is converging light. Therefore, even when the refractive power of the focus lens unit is increased, it is possible to reduce divergence of light rays passing through the focus lens unit. As a result, it is possible to reduce the diameter of the entire lens system positioned closer to the image side than the second lens unit while enhancing focus sensitivity. 
         [0291]    By arranging a positive lens unit on the image side of the second lens unit, it is possible to easily enhance the focus sensitivity. 
         [0292]    The camera shake-correction lens unit moves in a direction vertical to the optical axis. It is preferable to minimize the range of movement of the camera shake-correction lens unit. Based on this, it is desirable that a lens unit positioned where the height of light rays is low be set as the camera shake-correction lens unit. 
         [0293]    As described above, on the side closer to the image side than the first lens unit, the height of light rays is low. Thus, it is preferable that the camera shake-correction lens unit be provided in the second lens unit or the third lens unit. However, the second lens unit functions as a focus lens unit. Based on this, it is preferable that the camera shake-correction lens unit be disposed in the third lens unit. 
         [0294]    Here, the third lens unit is constituted with an object-side sub-lens unit having a positive refractive power, a camera shake-correction lens unit having a negative refractive power, and an image-side sub-lens unit having a positive refractive power. 
         [0295]    In such an arrangement, the lens units having a positive refractive power are disposed on both sides of the camera shake-correction lens unit. Therefore, it is possible to increase the camera shake-correction sensitivity. That is, it is possible to reduce the amount of shift of the camera shake-correction lens unit. As a result, it is possible to correct a shift of the imaging position due to camera shake at high speed. 
         [0296]    As described above, on the side closer to the image side than the first lens unit, the height of light rays is low. Then, an arrangement may be such that the second lens unit has a camera shake-correcting function and the third lens unit has the focusing function. However, in such an arrangement, variation of comatic aberration due to camera shake correction is increased by movement of the lens unit at the time of focusing. Thus, such an arrangement is not preferable. 
         [0297]    When the focus lens unit has a negative refractive power, it is possible to enhance focus sensitivity by disposing a positive lens unit on the image side of the focus lens unit. Furthermore, when the camera shake-correction lens unit has a negative refractive power, it is possible to enhance camera shake-correction sensitivity by disposing a positive lens unit on the object side of the camera shake-correction lens unit. 
         [0298]    The object-side sub-lens unit is positioned between the second lens unit and the camera shake-correction lens unit. The second lens unit has a negative refractive power and functions as a focus lens unit. Then, when the refractive power of the object-side sub-lens unit is set as a positive refractive power, it follows that a positive lens unit is positioned on the image side of the focus lens unit, and therefore it is possible to enhance the focus sensitivity. 
         [0299]    Furthermore, the object-side sub-lens unit is positioned on the object side of the camera shake-correction lens unit. It follows that a positive lens unit is positioned on the object side of the camera shake-correction lens unit, and therefore it is possible to enhance the camera shake-correction sensitivity. In this way, by setting the refractive power of the object-side sub-lens unit as a positive refractive power, it is possible to enhance focus sensitivity and camera shake-correction sensitivity at the same time. 
         [0300]    It is preferable that the second lens unit and the third lens unit is disposed closer to the image side than the aperture stop. By doing so, it is possible to further reduce the diameters of the focus lens unit and the camera shake-correction lens unit. 
         [0301]    At the time of focusing, a lens unit moves along the optical axis. When the lens unit moves, imaging performance tends to be degraded mainly due to variation of spherical aberration and variation of longitudinal chromatic aberration. In order to alleviate degradation of imaging performance, it is necessary to alleviate variation of spherical aberration and variation of longitudinal chromatic aberration. It is then desirable that the second lens unit at least have a positive lens and a negative lens. By doing so, it is possible to prevent degradation of imaging performance at the time of focusing. 
         [0302]    Variation of spherical aberration and variation of longitudinal chromatic aberration in the second lens unit change through the object-side sub-lens unit. Therefore, it is desirable that the object-side sub-lens unit have a positive lens and a negative lens. By doing so, it is possible to reduce variation of spherical aberration and variation of longitudinal chromatic aberration. 
         [0303]    At the time of camera shake correction, the lens unit moves in a direction vertical to the optical axis. When the lens unit moves, imaging performance tends to be degraded mainly due to variation of spherical aberration, variation of curvature of field, and variation of chromatic aberration of magnification. In order to alleviate degradation of imaging performance, it is necessary to alleviate variation of spherical aberration, variation of curvature of field, and variation of chromatic aberration of magnification. It is then desirable that the camera shake-correction lens unit at least have one positive lens and two negative lenses. By providing two negative lenses, it is possible to distribute the refractive power of the camera shake-correction lens unit between the two negative lenses. As a result, it is possible to prevent degradation of imaging performance at the time of camera shake correction. 
         [0304]    It is desirable that the second lens unit include two lenses, that the object-side sub-lens unit include two or less lenses, and that the camera shake-correction lens unit include three lenses. By doing so, it is possible to construct an optical system having high focusing performance and high camera shake-correcting function with a smaller number of lenses. 
         [0305]    In the telephoto lens of the present embodiment, it is preferable that following Conditional Expression (13) is satisfied: 
         [0000]      1.0 &lt;|MGISB ×( MGIS− 1)|&lt;4.0   (13),
 
         [0306]    where, 
         [0307]    MGISB is a lateral magnification of a second rear-side lens system; 
         [0308]    MGIS is a lateral magnification of the camera shake-correction lens unit; 
         [0309]    the lateral magnification is the lateral magnification at the time of focusing on an infinite object; and 
         [0310]    the second rear-side lens system is a lens system constituted with all of the lenses positioned closer to the image side than the camera shake-correction lens unit. 
         [0311]    When falling below a lower limit value of Conditional Expression (13), a sufficient camera shake-correction effect cannot be obtained. When exceeding an upper limit value of Conditional Expression (13), the refractive power of the camera shake-correction lens unit is increased. In this case, variation of spherical aberration, variation of curvature of field, and variation of chromatic aberration of magnification are increased. Therefore, it becomes difficult to correct spherical aberration, astigmatism, and chromatic aberration of magnification. 
         [0312]    It is preferable that following Conditional Expression (13-1) or (13-2) is satisfied instead of Conditional Expression (13): 
         [0000]      1.3 &lt;|MGISB ×( MGIS− 1)|&lt;3.0   (13-1), and
 
         [0000]      1.5 &lt;|MGISB ×( MGIS− 1)|&lt;2.7   (13-2).
 
         [0313]    In the telephoto lens of the present embodiment, it is preferable that the aperture stop is disposed between the first lens unit and the second lens unit. 
         [0314]    Since the first lens unit has a positive refractive power, a strong convergence action occurs in the first lens unit. Then, the aperture stop is disposed on the object side of the first lens unit, and the second lens unit is disposed on the image side of the aperture stop. By doing so, it is possible to reduce the diameter of the second lens unit. Furthermore, since the second lens unit is a focus lens unit, it is possible to form a very compact focus lens unit. 
         [0315]    In the telephoto lens of the present embodiment, it is preferable that the third lens unit has a space in which an optical filter can be disposed. 
         [0316]    In optical systems for photography, various optical filters Such as UV cut filters and polarizing filters are used with the optical systems. An optical filter is generally attached closest to the object of the optical system. However, in a telephoto lens having a long focal length, the aperture is largest on the side closest to the object of the optical system. In this case, an optical filter having a large aperture is to be attached, resulting in inconvenience in handling of the optical filter. In such a case, in general, a space for inserting an optical filter is allocated closest to the image of the optical system. 
         [0317]    However, in addition to the optical filter, for example, a teleconverter may be attached on the side closest to the image of the optical system. Considering the attachment of an optical filter and the attachment of a teleconverter, it is necessary to make the back focus of the optical system long to some degree. A change in back focus of the optical system has a significant effect on imaging performance and the overall length of the optical system. Therefore, it becomes difficult to reduce the size of the optical system. 
         [0318]    Based on this, it is preferable that the telephoto lens be configured such that an optical filter can be disposed in the optical system. Then, in the telephoto lens of the present embodiment, a space where an optical filter can be disposed is allocated in the third lens unit. By doing so, it is possible to reduce the size of the optical filter while preventing degradation of imaging performance. Furthermore, because of the size reduction of the optical filter, it becomes easy to handle the optical filter. 
         [0319]    When the third lens unit is constituted with a plurality of sub-lens units, the optical filter is preferably disposed, in particular, between two sub-lens units having a positive refractive power. By doing so, it is possible to reduce variation of the angle of light ray incident on the optical filter. As a result, it is possible to reduce the effects on degradation of imaging performance. 
         [0320]    In the first lens unit, basic aberrations, for example, spherical aberration and chromatic aberration are mainly corrected. Therefore, disposing an optical filter in the first lens unit has a significant effect on imaging performance. Meanwhile, the first lens unit is positioned on the object side. Therefore, when compared with the light flux diameter in the other lens units, the light flux diameter in the first lens unit is large. Thus, when an optical filter is disposed in the first lens unit, it is yet difficult to reduce the diameter of the optical filter. In this way, there are few merits in arranging an optical filter in the first lens unit. 
         [0321]    Furthermore, the second lens unit moves at the time of focusing in a range from the image-side surface of the first lens unit to the object-side surface of the third lens unit. Therefore, if an optical filter is disposed in this range, the range of movement of the second lens unit may be limited. Thus, it is not preferable to dispose an optical filter in the place where the second lens unit moves. 
         [0322]    In the telephoto lens of the present embodiment, it is preferable that following Conditional Expression (14) is satisfied: 
         [0000]      0.19 ≦DGF airmax/ DGF≦ 1.0   (14),
 
         [0323]    where, 
         [0324]    DGFairmax is the largest axial air space, of axial air spaces in the front-side lens unit; and 
         [0325]    DGF is the axial thickness of the front-side lens unit. 
         [0326]    The technical meaning of Conditional Expression (14) has already been described and the description thereof is omitted here. 
         [0327]    In the telephoto lens of the present embodiment, it is preferable that following Conditional Expression (15A) is satisfied: 
         [0000]      0.05 ≦DGFGR/fGF≦ 0.4   (15A),
 
         [0328]    where, 
         [0329]    DGFGR is the axial air space between the front-side lens unit and the rear-side lens unit; and 
         [0330]    fGF is the focal length of the front-side lens unit. 
         [0331]    When falling below a lower limit value of Conditional Expression (15A), the light flux-converging action in the front-side lens unit becomes weak. In this case, the outer diameter in the rear-side lens unit is increased. Therefore, it becomes difficult to reduce the size and weight of the first lens unit. 
         [0332]    When exceeding an upper limit value of Conditional Expression (15A), the amount of spherical aberration in the front-side lens unit is increased. Therefore, it becomes difficult to correct spherical aberration favorably with the lenses positioned closer to the image side than the front-side lens unit. 
         [0333]    It is preferable that following Conditional Expression (15A-1) or (15A-2) is satisfied instead of Conditional Expression (15A): 
         [0000]      0.06 ≦DGFGR/fGF≦ 0.35   (15A-1), and
 
         [0000]      0.08 ≦DGFGR/fGF≦ 0.33   (15A-2).
 
         [0334]    In the telephoto lens of the present embodiment, it is preferable that following Conditional Expression (15B) is satisfied: 
         [0000]      0.05 ≦DGFGR 1 /fGF≦ 0.4   (15B),
 
         [0335]    where, 
         [0336]    DGFGR 1  is an axial air space between the front-side lens unit and the first rear-side lens unit; and 
         [0337]    fGF is the focal length of the front-side lens unit. 
         [0338]    The technical meaning of Conditional Expression (15B) is the same as the technical meaning of Conditional Expression (15A). 
         [0339]    It is preferable that following Conditional Expression (15B-1) or (15B-2) is satisfied instead of Conditional Expression (15B): 
         [0000]      0.06 ≦DGFGR 1 /fGF≦ 0.35   (15B-1), and
 
         [0000]      0.08 ≦DGFGR 1 /fGF≦ 0.33   (158-2).
 
         [0340]    In the telephoto lens of the present embodiment, it is preferable that following Conditional Expression (16) is satisfied: 
         [0000]      50≦νdLp1   (16),
 
         [0341]    where, 
         [0342]    νdLp 1  is the Abbe number of a positive lens positioned closest to the object. 
         [0343]    The technical meaning of Conditional Expression (16) has already been described and the description is omitted here. 
         [0344]    In the telephoto lens of the present embodiment, it is preferable that the front-side lens unit includes two positive lenses. 
         [0345]    By doing so, it is becomes easy to reduce the amount of spherical aberration in the front-side lens unit, to reduce the weight of the optical system, and to reduce the overall length of the optical system. 
         [0346]    In the telephoto lens of the present embodiment, it is preferable that the first rear-side lens unit have at least two negative lenses. 
         [0347]    In the front-side lens unit, a negative lens having a large refractive power is not disposed. Therefore, it is difficult to correct chromatic aberration favorably in the front-side lens unit. Accordingly, in the first rear-side lens unit, it is necessary to enhance the function of correcting spherical aberration and longitudinal chromatic aberration remaining in the front-side lens unit. Then, by using at least two negative lenses in the first rear-side lens unit, it is possible to correct both spherical aberration and longitudinal chromatic aberration favorably while reducing the overall length of the optical system. 
         [0348]    In the telephoto lens of the present embodiment, it is preferable that following Conditional Expression (17) is satisfied: 
         [0000]      1.5 ≦|fG 1 /fG 2|≦6.5   (17),
 
         [0349]    where, 
         [0350]    fG 1  is a focal length of the first lens unit; and 
         [0351]    fG 2  is the focal length of the second lens unit. 
         [0352]    When falling below a lower limit value of Conditional Expression (17), the amount of spherical aberration in the first lens unit is increased. Therefore, favorable imaging performance cannot be obtained. When exceeding an upper limit value of Conditional Expression (17), focus sensitivity is reduced. In this case, the amount of movement of the second lens unit at the time of focusing is increased. Therefore, the overall length of the optical system is increased. 
         [0353]    It is preferable that following Conditional Expression (17-1) or (17-2) is satisfied instead of Conditional Expression (17): 
         [0000]      2.0 ≦|fG 1 /fG 2|≦6.0   (17-1), and
 
         [0000]      2.2 ≦|fG 1 /fG 2|≦5.0   (17-2).
 
         [0354]    In the telephoto lens of the present embodiment, it is preferable that only the second lens unit moves in the optical axis direction. 
         [0355]    An image pickup apparatus of the present embodiment includes an optical system and an image pickup element having an image plane and converting an image formed on the image plane by the optical system to an electrical signal, and the optical system is the telephoto lens of the present embodiment. 
         [0356]    It is possible to provide an image pickup apparatus having excellent portability and producing a high-quality image. 
         [0357]    Examples of the telephoto lens will be described in details below based on the drawings. It is noted that the present invention is not limited by those Examples. Although a thin resin layer formed on the surface of a lens may not be a lens, the thin resin layer is illustrated as a lens in the description of Example 6, for the sake of convenience. 
         [0358]    Lens cross-sectional views of Examples will be described. 
         [0359]      FIG. 1A ,  FIG. 2A ,  FIG. 3A ,  FIG. 4A ,  FIG. 5A ,  FIG. 6A ,  FIG. 7A ,  FIG. 8A , and  FIG. 9A  illustrate lens cross-sectional views at the time of focusing on an infinite object. 
         [0360]      FIG. 1B ,  FIG. 2B ,  FIG. 3B ,  FIG. 4B ,  FIG. 5B ,  FIG. 6B ,  FIG. 7B ,  FIG. 8B , and  FIG. 9B  illustrate lens cross-sectional views at the time of focusing on a close object. 
         [0361]    Aberration diagrams of Examples will be described. 
         [0362]      FIG. 10A ,  FIG. 11A ,  FIG. 12A ,  FIG. 13A ,  FIG. 14A ,  FIG. 15A ,  FIG. 16A ,  FIG. 17A , and  FIG. 18A  illustrate spherical aberration (SA) at the time of focusing on an infinite object. 
         [0363]      FIG. 10B ,  FIG. 11B ,  FIG. 12B ,  FIG. 13B ,  FIG. 14B ,  FIG. 15B ,  FIG. 16B ,  FIG. 17B , and  FIG. 18B  illustrate astigmatism (AS) at the time of focusing on an infinite object. 
         [0364]      FIG. 10C ,  FIG. 11C ,  FIG. 12C ,  FIG. 13C ,  FIG. 14C ,  FIG. 15C ,  FIG. 16C ,  FIG. 17C , and  FIG. 18C  illustrate distortion (DT) at the time of focusing on an infinite object. 
         [0365]      FIG. 10D ,  FIG. 11D ,  FIG. 12D ,  FIG. 13D ,  FIG. 14D ,  FIG. 15D ,  FIG. 16D ,  FIG. 17D , and  FIG. 18D  illustrate chromatic aberration of magnification (CC) at the time of focusing on an infinite object. 
         [0366]      FIG. 10E ,  FIG. 11E ,  FIG. 12E ,  FIG. 13E ,  FIG. 14E ,  FIG. 15E ,  FIG. 16E ,  FIG. 17E , and  FIG. 18E  illustrate spherical aberration (SA) at the time of focusing on a close object. 
         [0367]      FIG. 10F ,  FIG. 11F ,  FIG. 12F ,  FIG. 13F ,  FIG. 14F ,  FIG. 15F ,  FIG. 16F ,  FIG. 173 , and  FIG. 18F  illustrate astigmatism (AS) at the time of focusing on a close object focusing. 
         [0368]      FIG. 10G ,  FIG. 11G ,  FIG. 12G ,  FIG. 13G ,  FIG. 14G ,  FIG. 15G ,  FIG. 16G ,  FIG. 17G , and  FIG. 18G  illustrate distortion (DT) at the time of focusing on a close object focusing. 
         [0369]      FIG. 10H ,  FIG. 11H ,  FIG. 12H ,  FIG. 13H ,  FIG. 14H ,  FIG. 15H ,  FIG. 16H ,  FIG. 17H , and  FIG. 18H  illustrate chromatic aberration of magnification (CC) at the time of focusing on a close object focusing. 
         [0370]    A telephoto lens of Example 1 includes, in order from the object side, a first lens unit G 1  having a positive refractive power, a second lens unit G 2  having a negative refractive power, and a third lens unit G 3  having a positive refractive power. An aperture stop S is disposed between the first lens unit G 1  and the second lens unit G 2 . 
         [0371]    The first lens unit G 1  includes a positive meniscus lens L 1  having a convex surface facing the object side, a positive meniscus lens L 2  having a convex surface facing the object side, a negative meniscus lens L 3  having a convex surface facing the object side, a positive meniscus lens L 4  having a convex surface facing the object side, a biconvex positive lens L 5 , a biconcave negative lens L 6 , a biconvex positive lens L 7 , and a negative meniscus lens L 8  having a convex surface facing the image side. 
         [0372]    Here, the negative meniscus lens L 3  and the positive meniscus lens L 4  are cemented together. The biconvex positive lens L 5  and the biconcave negative lens L 6  are cemented together. The biconvex positive lens L 7  and the negative meniscus lens L 8  are cemented together. 
         [0373]    A front-side lens unit includes the positive meniscus lens L 1  and the positive meniscus lens L 2 . A rear-side lens unit includes a first rear-side lens unit and a second rear-side lens unit. The first rear-side lens unit includes the negative meniscus lens L 3 , the positive meniscus lens L 4 , the biconvex positive lens L 5 , and the biconcave negative lens L 6 . The second rear-side lens unit includes the biconvex positive lens L 7  and the negative meniscus lens L 8 . 
         [0374]    The second lens unit G 2  includes a biconvex positive lens L 9  and a biconcave negative lens L 10 . Here, the biconvex positive lens L 9  and the biconcave negative lens L 10  are cemented together. 
         [0375]    The third lens unit G 3  includes a negative meniscus lens L 11  having a convex surface facing the object side, a biconvex positive lens L 12 , a biconvex positive lens L 13 , a biconcave negative lens L 14 , a biconcave negative lens L 15 , a biconvex positive lens L 16 , a negative meniscus lens L 17  having a convex surface facing the image side, a biconvex positive lens L 18 , and a negative meniscus lens L 19  having a convex surface facing the image side. 
         [0376]    Here, the negative meniscus lens L 11  and the biconvex positive lens L 12  are cemented together. The biconvex positive lens L 13  and the biconcave negative lens L 14  are cemented together. The biconvex positive lens L 16  and the negative meniscus lens L 17  are cemented together. The biconvex positive lens L 18  and the negative meniscus lens L 19  are cemented together. 
         [0377]    An object-side sub-lens unit includes the negative meniscus lens L 11  and the biconvex positive lens L 12 . A camera shake-correction lens unit includes the biconvex positive lens L 13 , the biconcave negative lens L 14 , and the biconcave negative lens L 15 . An image-side sub-lens unit includes the biconvex positive lens L 16 , the negative meniscus lens L 17 , the biconvex positive lens L 18 , and the negative meniscus lens L 19 . 
         [0378]    At a time of focusing from an infinite object to a close object, the second lens unit G 2  moves toward the image side. At a time of camera shake correction, the camera shake-correction lens unit moves in a direction vertical to the optical axis. 
         [0379]    A telephoto lens of Example 2 includes, in order from the object side, a first lens unit G 1  having a positive refractive power, a second lens unit G 2  having a negative refractive power, and a third lens unit G 3  having a positive refractive power. An aperture stop S is disposed between the first lens unit G 1  and the second lens unit G 2 . 
         [0380]    The first lens unit G 1  includes a positive meniscus lens L 1  having a convex surface facing the object side, a positive meniscus lens L 2  having a convex surface facing the object side, a negative meniscus lens L 3  having a convex surface facing the object side, a positive meniscus lens L 4  having a convex surface facing the object side, a biconvex positive lens L 5 , a biconcave negative lens L 6 , and a biconvex positive lens L 7 . 
         [0381]    Here, the negative meniscus lens L 3  and the positive meniscus lens L 4  are cemented together. The biconvex positive lens L 5  and the biconcave negative lens L 6  are cemented together. 
         [0382]    A front-side lens unit includes the positive meniscus lens L 1  and the positive meniscus lens L 2 . A rear-side lens unit includes a first rear-side lens unit and a second rear-side lens unit. The first rear-side lens unit includes the negative meniscus lens L 3 , the positive meniscus lens L 4 , the biconvex positive lens L 5 , and the biconcave negative lens L 6 . The second rear-side lens unit includes the biconvex positive lens L 7 . 
         [0383]    The second lens unit G 2  includes a biconvex positive lens L 8  and a biconcave negative lens L 9 . Here, the biconvex positive lens L 8  and the biconcave negative lens L 9  are cemented together. 
         [0384]    The third lens unit G 3  includes a negative meniscus lens L 10  having a convex surface facing the object side, a biconvex positive lens L 11 , a biconvex positive lens L 12 , a biconcave negative lens L 13 , a biconcave negative lens L 14 , a biconvex positive lens L 15 , a negative meniscus lens L 16  having a convex surface facing the image side, a biconvex positive lens L 17 , and a negative meniscus lens L 18  having a convex surface facing the image side. 
         [0385]    Here, the negative meniscus lens L 10  and the biconvex positive lens L 11  are cemented together. The biconvex positive lens L 12  and the biconcave negative lens L 13  are cemented together. The biconvex positive lens L 15  and the negative meniscus lens L 16  are cemented together. The biconvex positive lens L 17  and the negative meniscus lens L 18  are cemented together. 
         [0386]    An object-side sub-lens unit includes the negative meniscus lens L 10  and the biconvex positive lens L 11 . A camera shake-correction lens unit includes the biconvex positive lens L 12 , the biconcave negative lens L 13 , and the biconcave negative lens L 14 . An image-side sub-lens unit includes the biconvex positive lens L 15 , the negative meniscus lens L 16 , the biconvex positive lens L 17 , and the negative meniscus lens L 18 . 
         [0387]    At a time of focusing from an infinite object to a close object, the second lens unit G 2  moves toward the image side. At a time of camera shake correction, the camera shake-correction lens unit moves in a direction vertical to the optical axis. 
         [0388]    A telephoto lens of Example 3 includes, in order from the object side, a first lens unit G 1  having a positive refractive power, a second lens unit G 2  having a negative refractive power, and a third lens unit G 3  having a positive refractive power. An aperture stop S is disposed between the first lens unit G 1  and the second lens unit G 2 . 
         [0389]    The first lens unit G 1  includes a positive meniscus lens L 1  having a convex surface facing the object side, a positive meniscus lens L 2  having a convex surface facing the object side, a negative meniscus lens L 3  having a convex surface facing the object side, a positive meniscus lens L 4  having a convex surface facing the object side, a biconvex positive lens L 5 , a biconcave negative lens L 6 , a biconvex positive lens L 7 , and a negative meniscus lens L 8  having a convex surface facing the image side. 
         [0390]    Here, the negative meniscus lens L 3  and the positive meniscus lens L 4  are cemented together. The biconvex positive lens L 5  and the biconcave negative lens L 6  are cemented together. The biconvex positive lens L 7  and the negative meniscus lens L 8  are cemented together. 
         [0391]    A front-side lens unit includes the positive meniscus lens L 1  and the positive meniscus lens L 2 . A rear-side lens unit includes a first rear-side lens unit and a second rear-side lens unit. The first rear-side lens unit includes the negative meniscus lens L 3 , the positive meniscus lens L 4 , the biconvex positive lens L 5 , and the biconcave negative lens L 6 . The second rear-side lens unit includes the biconvex positive lens L 7  and the negative meniscus lens L 8 . 
         [0392]    The second lens unit G 2  includes a biconvex positive lens L 9  and a biconcave negative lens L 10 . Here, the biconvex positive lens L 9  and the biconcave negative lens L 10  are cemented together. 
         [0393]    The third lens unit G 3  includes a biconvex positive lens L 11 , a biconvex positive lens L 12 , a biconcave negative lens L 13 , a biconcave negative lens L 14 , a biconvex positive lens L 15 , a negative meniscus lens L 16  having a convex surface facing the image side, a biconvex positive lens L 17 , and a negative meniscus lens L 18  having a convex surface facing the image side. 
         [0394]    Here, the biconvex positive lens L 12  and the biconcave negative lens L 13  are cemented together. The biconvex positive lens L 15  and the negative meniscus lens L 16  are cemented together. The biconvex positive lens L 17  and the negative meniscus lens L 18  are cemented together. 
         [0395]    An object-side sub-lens unit includes the biconvex positive lens L 11 . A camera shake-correction lens unit includes the biconvex positive lens L 12 , the biconcave negative lens L 13 , and the biconcave negative lens L 14 . An image-side sub-lens unit includes the biconvex positive lens L 15 , the negative meniscus lens L 16 , the biconvex positive lens L 17 , and the negative meniscus lens L 18 . 
         [0396]    At a time of focusing from an infinite object to a close object, the second lens unit G 2  moves toward the image side. At a time of camera shake correction, the camera shake-correction lens unit moves in a direction vertical to the optical axis. 
         [0397]    A telephoto lens of Example 4 includes, in order from the object side, a first lens unit G 1  having a positive refractive power, a second lens unit G 2  having a negative refractive power, and a third lens unit G 3  having a positive refractive power. An aperture stop S is disposed between the first lens unit G 1  and the second lens unit G 2 . 
         [0398]    The first lens unit G 1  includes a positive meniscus lens L 1  having a convex surface facing the object side, a positive meniscus lens L 2  having a convex surface facing the object side, a negative meniscus lens L 3  having a convex surface facing the object side, a positive meniscus lens L 4  having a convex surface facing the object side, a biconvex positive lens L 5 , a biconcave negative lens L 6 , a biconvex positive lens L 7 , and a negative meniscus lens L 8  having a convex surface facing the image side. 
         [0399]    Here, the negative meniscus lens L 3  and the positive meniscus lens L 4  are cemented together. The biconvex positive lens L 5  and the biconcave negative lens L 6  are cemented together. The biconvex positive lens L 7  and the negative meniscus lens L 8  are cemented together. 
         [0400]    A front-side lens unit includes the positive meniscus lens L 1  and the positive meniscus lens L 2 . A rear-side lens unit includes a first rear-side lens unit and a second rear-side lens unit. The first rear-side lens unit includes the negative meniscus lens L 3 , the positive meniscus lens L 4 , the biconvex positive lens L 5 , and the biconcave negative lens L 6 . The second rear-side lens unit includes the biconvex positive lens L 7  and the negative meniscus lens L 8 . 
         [0401]    The second lens unit G 2  includes a biconvex positive lens L 9  and a biconcave negative lens L 10 . Here, the biconvex positive lens L 9  and the biconcave negative lens L 10  are cemented together. 
         [0402]    The third lens unit G 3  includes a negative meniscus lens L 11  having a convex surface facing the object side, a biconvex positive lens L 12 , a biconvex positive lens L 13 , a biconcave negative lens L 14 , a biconcave negative lens L 15 , a biconvex positive lens L 16 , a negative meniscus lens L 17  having a convex surface facing the image side, a biconvex positive lens L 18 , and a biconcave negative lens L 19 . 
         [0403]    Here, the negative meniscus lens L 11  and the biconvex positive lens L 12  are cemented together. The biconvex positive lens L 13  and the biconcave negative lens L 14  are cemented together. The biconvex positive lens L 16  and the negative meniscus lens L 17  are cemented together. The biconvex positive lens L 18  and the biconcave negative lens L 19  are cemented together. 
         [0404]    An object-side sub-lens unit includes the negative meniscus lens L 11  and the biconvex positive lens L 12 . A camera shake-correction lens unit includes the biconvex positive lens L 13 , the biconcave negative lens L 14 , and the biconcave negative lens L 15 . An image-side sub-lens unit includes the biconvex positive lens L 16 , the negative meniscus lens L 17 , the biconvex positive lens L 18 , and the biconcave negative lens L 19 . 
         [0405]    At a time of focusing from an infinite object to a close object, the second lens unit G 2  moves toward the image side. At a time of camera shake correction, the camera shake-correction lens unit moves in a direction vertical to the optical axis. 
         [0406]    A telephoto lens of Example 5 includes, in order from the object side, a first lens unit G 1  having a positive refractive power, a second lens unit G 2  having a negative refractive power, and a third lens unit G 3  having a positive refractive power. An aperture stop S is disposed between the first lens unit G 1  and the second lens unit G 2 . 
         [0407]    The first lens unit G 1  includes a positive meniscus lens L 1  having a convex surface facing the object side, a positive meniscus lens L 2  having a convex surface facing the object side, a negative meniscus lens L 3  having a convex surface facing the object side, a positive meniscus lens L 4  having a convex surface facing the object side, a biconvex positive lens L 5 , a biconcave negative lens L 6 , a biconvex positive lens L 7 , and a negative meniscus lens L 8  having a convex surface facing the image side. 
         [0408]    Here, the negative meniscus lens L 3  and the positive meniscus lens L 4  are cemented together. The biconvex positive lens L 5  and the biconcave negative lens L 6  are cemented together. The biconvex positive lens L 7  and the negative meniscus lens L 8  are cemented together. 
         [0409]    A front-side lens unit includes the positive meniscus lens L 1  and the positive meniscus lens L 2 . A rear-side lens unit includes a first rear-side lens unit and a second rear-side lens unit. The first rear-side lens unit includes a negative meniscus lens L 3 , a positive meniscus lens L 4 , a biconvex positive lens L 5 , and a biconcave negative lens L 6 . The second rear-side lens unit includes the biconvex positive lens L 7  and the negative meniscus lens L 8 . 
         [0410]    The second lens unit G 2  includes a biconvex positive lens L 9  and a biconcave negative lens L 10 . Here, the biconvex positive lens L 9  and the biconcave negative lens L 10  are cemented together. 
         [0411]    The third lens unit G 3  includes a biconvex positive lens L 11 , a biconvex positive lens L 12 , a biconcave negative lens L 13 , a biconcave negative lens L 14 , a biconvex positive lens L 15 , a negative meniscus lens L 16  having a convex surface facing the image side, a biconvex positive lens L 17 , and a negative meniscus lens L 18  having a convex surface facing the image side. 
         [0412]    Here, the biconvex positive lens L 12  and the biconcave negative lens L 13  are cemented together. The biconvex positive lens L 15  and the negative meniscus lens L 16  are cemented together. The biconvex positive lens L 17  and the negative meniscus lens L 18  are cemented together. 
         [0413]    An object-side sub-lens unit includes the biconvex positive lens L 11 . A camera shake-correction lens unit includes the biconvex positive lens L 12 , the biconcave negative lens L 13 , and the biconcave negative lens L 14 . An image-side sub-lens unit includes the biconvex positive lens L 15 , the negative meniscus lens L 16 , the biconvex positive lens L 17 , and the negative meniscus lens L 18 . 
         [0414]    At a time of focusing from an infinite object to a close object, the second lens unit G 2  moves toward the image side. At a time of camera shake correction, the camera shake-correction lens unit moves in a direction vertical to the optical axis. 
         [0415]    A telephoto lens of Example 6 includes, in order from the object side, a first lens unit G 1  having a positive refractive power, a second lens unit G 2  having a negative refractive power, and a third lens unit G 3  having a positive refractive power. An aperture stop S is disposed between the first lens unit G 1  and the second lens unit G 2 . 
         [0416]    The first lens unit G 1  includes a positive meniscus lens L 1  having a convex surface facing the object side, a positive meniscus lens L 2  having a convex surface facing the object side, a negative meniscus lens L 3  having a convex surface facing the object side, a negative meniscus lens L 4  having a convex surface facing the object side, a positive meniscus lens L 5  having a convex surface facing the object side, a biconvex positive lens L 6 , a biconcave negative lens L 7 , and a positive meniscus lens L 8  having a convex surface facing the object side. The negative meniscus lens L 3  is a resin layer with a small thickness. 
         [0417]    Here, the positive meniscus lens L 2  and the negative meniscus lens L 3  are cemented together. The negative meniscus lens L 4  and the positive meniscus lens L 5  are cemented together. The biconvex positive lens L 6  and the biconcave negative lens L 7  are cemented together. 
         [0418]    A front-side lens unit includes the positive meniscus lens L 1 , the positive meniscus lens L 2 , and the negative meniscus lens L 3 . A rear-side lens unit includes a first rear-side lens unit and a second rear-side lens unit. The first rear-side lens unit includes the negative meniscus lens L 4 , the positive meniscus lens L 5 , the biconvex positive lens L 6 , and the biconcave negative lens L 7 . The second rear-side lens unit includes the positive meniscus lens L 8 . 
         [0419]    The second lens unit G 2  includes a biconvex positive lens L 9  and a biconcave negative lens L 10 . Here, the biconvex positive lens L 9  and the biconcave negative lens L 10  are cemented together. 
         [0420]    The third lens unit G 3  includes a negative meniscus lens L 11  having a convex surface facing the object side, a biconvex positive lens L 12 , a biconvex positive lens L 13 , a biconcave negative lens L 14 , a biconcave negative lens L 15 , a biconvex positive lens L 16 , a negative meniscus lens L 17  having a convex surface facing the image side, a biconvex positive lens L 18 , and a biconcave negative lens L 19 . 
         [0421]    Here, the negative meniscus lens L 11  and the biconvex positive lens L 12  are cemented together. The biconvex positive lens L 13  and the biconcave negative lens L 14  are cemented together. The biconvex positive lens L 16  and the negative meniscus lens L 17  are cemented together. The biconvex positive lens L 18  and the biconcave negative lens L 19  are cemented together. 
         [0422]    An object-side sub-lens unit includes the negative meniscus lens L 11  and the biconvex positive lens L 12 . A camera shake-correction lens unit includes the biconvex positive lens L 13 , the biconcave negative lens L 14 , and the biconcave negative lens L 15 . An image-side sub-lens unit includes the biconvex positive lens L 16 , the negative meniscus lens L 17 , the biconvex positive lens L 18 , and the biconcave negative lens L 19 . 
         [0423]    At a time of focusing from an infinite object to a close object, the second lens unit G 2  moves toward the image side. At a time of camera shake correction, the camera shake-correction lens unit moves in a direction vertical to the optical axis. 
         [0424]    An aspheric surface is provided on the image-side surface of the negative meniscus lens L 3 . 
         [0425]    A telephoto lens of Example 7 includes, in order from the object side, a first lens unit G 1  having a positive refractive power, a second lens unit G 2  having a negative refractive power, and a third lens unit G 3  having a positive refractive power. An aperture stop S is disposed between the first lens unit G 1  and the second lens unit G 2 . 
         [0426]    The first lens unit G 1  includes a positive meniscus lens L 1  having a convex surface facing the object side, a positive meniscus lens L 2  having a convex surface facing the object side, a negative meniscus lens L 3  having a convex surface facing the object side, a positive meniscus lens L 4  having a convex surface facing the object side, a biconvex positive lens L 5 , a biconcave negative lens L 6 , and a biconvex positive lens L 7 . 
         [0427]    Here, the negative meniscus lens L 3  and the positive meniscus lens L 4  are cemented together. The biconvex positive lens L 5  and the biconcave negative lens L 6  are cemented together. 
         [0428]    A front-side lens unit includes the positive meniscus lens L 1  and the positive meniscus lens L 2 . A rear-side lens unit includes a first rear-side lens unit and a second rear-side lens unit. The first rear-side lens unit includes the negative meniscus lens L 3 , the positive meniscus lens L 4 , the biconvex positive lens L 5 , and the biconcave negative lens L 6 . The second rear-side lens unit includes the biconvex positive lens L 7 . 
         [0429]    The second lens unit G 2  includes a positive meniscus lens L 8  having a convex surface facing the image side and a biconcave negative lens L 9 . 
         [0430]    The third lens unit G 3  includes a negative meniscus lens L 10  having a convex surface facing the object side, a biconvex positive lens L 11 , a biconvex positive lens L 12 , a biconcave negative lens L 13 , a biconcave negative lens L 14 , a biconvex positive lens L 15 , a negative meniscus lens L 16  having a convex surface facing the image side, a biconvex positive lens L 17 , and a negative meniscus lens L 18  having a convex surface facing the image side. 
         [0431]    Here, the negative meniscus lens L 10  and the biconvex positive lens L 11  are cemented together. The biconvex positive lens L 12  and the biconcave negative lens L 13  are cemented together. The biconvex positive lens L 15  and the negative meniscus lens L 16  are cemented together. The biconvex positive lens L 17  and the negative meniscus lens L 18  are cemented together. 
         [0432]    An object-side sub-lens unit includes the negative meniscus lens L 10  and the biconvex positive lens L 11 . A camera shake-correction lens unit includes the biconvex positive lens L 12 , the biconcave negative lens L 13 , and the biconcave negative lens L 14 . An image-side sub-lens unit includes the biconvex positive lens L 15 , the negative meniscus lens L 16 , the biconvex positive lens L 17 , and the negative meniscus lens L 18 . 
         [0433]    At a time of focusing from an infinite object to a close object, the second lens unit G 2  moves toward the image side. At a time of camera shake correction, the camera shake-correction lens unit moves in a direction vertical to the optical axis. 
         [0434]    An aspheric surface is provided on the image-side surface of the biconcave negative lens L 9 . 
         [0435]    A telephoto lens of Example 8 includes, in order from the object side, a first lens unit G 1  having a positive refractive power, a second lens unit G 2  having a negative refractive power, and a third lens unit G 3  having a positive refractive power. An aperture stop S is disposed between the first lens unit G 1  and the second lens unit G 2 . 
         [0436]    The first lens unit G 1  includes a positive meniscus lens L 1  having a convex surface facing the object side, a positive meniscus lens L 2  having a convex surface facing the object side, a negative meniscus lens L 3  having a convex surface facing the object side, a positive meniscus lens L 4  having a convex surface facing the object side, a biconvex positive lens L 5 , a biconcave negative lens L 6 , and a biconvex positive lens L 7 . 
         [0437]    Here, the negative meniscus lens L 3  and the positive meniscus lens L 4  are cemented together. The biconvex positive lens L 5  and the biconcave negative lens L 6  are cemented together. 
         [0438]    A front-side lens unit includes the positive meniscus lens L 1  and the positive meniscus lens L 2 . A rear-side lens unit includes a first rear-side lens unit and a second rear-side lens unit. The first rear-side lens unit includes the negative meniscus lens L 3 , the positive meniscus lens L 4 , the biconvex positive lens L 5 , and the biconcave negative lens L 6 . The second rear-side lens unit includes the biconvex positive lens L 7 . 
         [0439]    The second lens unit G 2  includes a positive meniscus lens L 8  having a convex surface facing the image side and a biconcave negative lens L 9 , 
         [0440]    The third lens unit G 3  includes a negative meniscus lens L 10  having a convex surface facing the object side, a biconvex positive lens L 11 , a biconvex positive lens L 12 , a biconcave negative lens L 13 , a biconcave negative lens L 14 , a biconvex positive lens L 15 , a negative meniscus lens L 16  having a convex surface facing the image side, a biconvex positive lens L 17 , and a negative meniscus lens L 18  having a convex surface facing the image side. 
         [0441]    Here, the negative meniscus lens L 10  and the biconvex positive lens L 11  are cemented together. The biconvex positive lens L 12  and the biconcave negative lens L 13  are cemented together. The biconvex positive lens L 15  and the negative meniscus lens L 16  are cemented together. The biconvex positive lens L 17  and the negative meniscus lens L 18  are cemented together. 
         [0442]    An object-side sub-lens unit includes the negative meniscus lens L 10  and the biconvex positive lens L 11 . A camera shake-correction lens unit includes the biconvex positive lens L 12 , the biconcave negative lens L 13 , and the biconcave negative lens L 14 . An image-side sub-lens unit includes the biconvex positive lens L 15 , the negative meniscus lens L 16 , the biconvex positive lens L 17 , and the negative meniscus lens L 18 . 
         [0443]    At a time of focusing from an infinite object to a close object, the second lens unit G 2  moves toward the image side. At a time of camera shake correction, the camera shake-correction lens unit moves in a direction vertical to the optical axis. 
         [0444]    An aspheric surface is provided on the image-side surface of the biconcave negative lens L 9 . 
         [0445]    A telephoto lens of Example 9 includes, in order from the object side, a first lens unit G 1  having a positive refractive power, a second lens unit G 2  having a negative refractive power, and a third lens unit G 3  having a positive refractive power. An aperture stop S is disposed between the first lens unit G 1  and the second lens unit G 2 . 
         [0446]    The first lens unit G 1  includes a positive meniscus lens L 1  having a convex surface facing the object side, a positive meniscus lens L 2  having a convex surface facing the object side, a negative meniscus lens L 3  having a convex surface facing the object side, a positive meniscus lens L 4  having a convex surface facing the object side, a biconvex positive lens L 5 , a biconcave negative lens L 6 , and a biconvex positive lens L 7 . 
         [0447]    Here, the negative meniscus lens L 3  and the positive meniscus lens L 4  are cemented together. The biconvex positive lens L 5  and the biconcave negative lens L 6  are cemented together. 
         [0448]    A front-side lens unit includes the positive meniscus lens L 1  and the positive meniscus lens L 2 . A rear-side lens unit includes a first rear-side lens unit and a second rear-side lens unit. The first rear-side lens unit includes the negative meniscus lens L 3 , the positive meniscus lens L 4 , the biconvex positive lens L 5 , and the biconcave negative lens L 6 . The second rear-side lens unit includes the biconvex positive lens L 7 . 
         [0449]    The second lens unit G 2  includes a positive meniscus lens L 8  having a convex surface facing the image side and a biconcave negative lens L 9 . Here, the positive meniscus lens L 8  and the biconcave negative lens L 9  are cemented together. 
         [0450]    The third lens unit G 3  includes a negative meniscus lens L 10  having a convex surface facing the object side, a biconvex positive lens L 11 , a biconvex positive lens L 12 , a biconcave negative lens L 13 , a biconcave negative lens L 14 , a biconvex positive lens L 15 , a negative meniscus lens L 16  having a convex surface facing the image side, a biconvex positive lens L 17 , and a negative meniscus lens L 18  having a convex surface facing the image side. 
         [0451]    Here, the negative meniscus lens L 10  and the biconvex positive lens L 11  are cemented together. The biconvex positive lens L 12  and the biconcave negative lens L 13  are cemented together. The biconvex positive lens L 15  and the negative meniscus lens L 16  are cemented together. The biconvex positive lens L 17  and the negative meniscus lens L 18  are cemented together. 
         [0452]    An object-side sub-lens unit includes the negative meniscus lens L 10  and the biconvex positive lens L 11 . A camera shake-correction lens unit includes the biconvex positive lens L 12 , the biconcave negative lens L 13 , and the biconcave negative lens L 14 . An image-side sub-lens unit includes the biconvex positive lens L 15 , the negative meniscus lens L 16 , the biconvex positive lens L 17 , and the negative meniscus lens L 18 . 
         [0453]    At a time of focusing from an infinite object to a close object, the second lens unit G 2  moves toward the image side. At a time of camera shake correction, the camera shake-correction lens unit moves in a direction vertical to the optical axis. 
         [0454]    An aspheric surface is provided on the object-side surface of the positive meniscus lens L 8 . 
         [0455]    Numerical data of each example described above is shown below. In Surface data, r denotes radius of curvature of each lens surface, d denotes a distance between respective lens surfaces, nd denotes a refractive index of each lens for a d-line, νd denotes an Abbe number for each lens and *denotes an aspheric surface. 
         [0456]    Further, in Various data, OB denotes a object distance, f denotes a focal length of the entire system, FNO. denotes an F number, ω a half angle of view, LTL denotes a lens total length of the optical system, BF denotes a back focus. Back focus is a unit which is expressed upon air conversion of a distance from a rearmost lens surface to a paraxial image surface. The lens total length is a distance from a frontmost lens surface to the rearmost lens surface plus back focus. Infinite denotes at the time of focusing on an infinite object, Close denotes at the time of focusing on a close object. Unit of OB is mm. 
         [0457]    A shape of an aspheric surface is defined by the following expression where the direction of the optical axis is represented by z, the direction orthogonal to the optical axis is represented by y, a conical coefficient is represented by K, aspheric surface coefficients are represented by A4, A6, A8, A10, A12 . . . 
         [0000]    
       
         
           
             Z 
             = 
             
               
                 
                   ( 
                   
                     
                       y 
                       2 
                     
                     / 
                     r 
                   
                   ) 
                 
                 / 
                 
                   [ 
                   
                     1 
                     + 
                     
                       
                         { 
                         
                           1 
                           - 
                           
                             
                               ( 
                               
                                 1 
                                 + 
                                 k 
                               
                               ) 
                             
                              
                             
                               
                                 ( 
                                 
                                   y 
                                   / 
                                   r 
                                 
                                 ) 
                               
                               2 
                             
                           
                         
                         } 
                       
                       
                         1 
                         / 
                         2 
                       
                     
                   
                   ] 
                 
               
               + 
               
                 A 
                  
                 
                     
                 
                  
                 4 
                  
                 
                   y 
                   4 
                 
               
               + 
               
                 A 
                  
                 
                     
                 
                  
                 6 
                  
                 
                   y 
                   6 
                 
               
               + 
               
                 A 
                  
                 
                     
                 
                  
                 8 
                  
                 
                   y 
                   8 
                 
               
               + 
               
                 A 
                  
                 
                     
                 
                  
                 10 
                  
                 
                   y 
                   10 
                 
               
               + 
               
                 A 
                  
                 
                     
                 
                  
                 12 
                  
                 
                   y 
                   12 
                 
               
               + 
               … 
             
           
         
       
     
         [0458]    Further, in the aspherical surface coefficients, ‘e-n’ (where, n is an integral number) indicates ‘10 −n ’. Moreover, these symbols are commonly used in the following numerical data for each example. 
       EXAMPLE 1 
       [0459]      
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
               
             
               
               
               
             
               
               
               
               
             
           
               
                   
               
               
                 Unit mm 
               
               
                   
               
             
             
               
                 Surface data 
               
             
          
           
               
                   
                 Surface no. 
                 r 
                 d 
                 nd 
                 νd 
               
               
                   
                   
               
               
                   
                 Object plane 
                 ∞ 
                 ∞ 
               
               
                   
                  1 
                 156.832 
                 12.000 
                 1.48749 
                 70.23 
               
               
                   
                  2 
                 975.891 
                 14.000 
               
               
                   
                  3 
                 76.441 
                 14.000 
                 1.43875 
                 94.66 
               
               
                   
                  4 
                 225.601 
                 30.254 
               
               
                   
                  5 
                 137.293 
                 3.200 
                 1.80400 
                 46.58 
               
               
                   
                  6 
                 46.986 
                 14.500 
                 1.43875 
                 94.66 
               
               
                   
                  7 
                 584.139 
                 0.819 
               
               
                   
                  8 
                 73.885 
                 11.500 
                 1.43875 
                 94.66 
               
               
                   
                  9 
                 −193.290 
                 2.800 
                 1.69680 
                 55.53 
               
               
                   
                 10 
                 131.732 
                 30.161 
               
               
                   
                 11 
                 170.200 
                 6.342 
                 1.69895 
                 30.13 
               
               
                   
                 12 
                 −126.703 
                 1.772 
                 1.91082 
                 35.25 
               
               
                   
                 13 
                 −2889.433 
                 3.000 
               
               
                   
                 14(Stop) 
                 ∞ 
                 Variable 
               
               
                   
                 15 
                 359.250 
                 2.100 
                 1.80810 
                 22.76 
               
               
                   
                 16 
                 −120.790 
                 0.850 
                 1.74320 
                 49.34 
               
               
                   
                 17 
                 33.468 
                 Variable 
               
               
                   
                 18 
                 32.651 
                 1.000 
                 1.92286 
                 20.88 
               
               
                   
                 19 
                 25.167 
                 5.000 
                 1.48749 
                 70.23 
               
               
                   
                 20 
                 −105.351 
                 3.600 
               
               
                   
                 21 
                 100.678 
                 3.000 
                 1.80810 
                 22.76 
               
               
                   
                 22 
                 −47.455 
                 0.900 
                 1.73400 
                 51.47 
               
               
                   
                 23 
                 20.878 
                 4.279 
               
               
                   
                 24 
                 −33.846 
                 0.900 
                 1.71300 
                 53.87 
               
               
                   
                 25 
                 107.524 
                 3.267 
               
               
                   
                 26 
                 45.267 
                 6.700 
                 1.60342 
                 38.03 
               
               
                   
                 27 
                 −32.937 
                 2.200 
                 1.92286 
                 20.88 
               
               
                   
                 28 
                 −56.485 
                 0.200 
               
               
                   
                 29 
                 62.735 
                 7.500 
                 1.73800 
                 32.26 
               
               
                   
                 30 
                 −28.328 
                 2.300 
                 1.92286 
                 20.88 
               
               
                   
                 31 
                 −84.120 
               
               
                   
                 Image plane 
                 ∞ 
               
               
                   
                   
               
             
          
           
               
                 Various data 
               
               
                   
               
             
          
           
               
                   
                 Telephoto ratio 
                 0.685 
               
               
                   
                 2ω 
                 3.2 
               
               
                   
                 LTL 
                 268.519 
               
               
                   
                 BF 
                 32.975 
               
               
                   
                   
               
             
          
           
               
                   
                   
                 Infinite 
                 Close 
               
               
                   
                   
               
               
                   
                 OB 
                 ∞ 
                 2.0 
               
               
                   
                 f 
                 391.988 
                 297.631 
               
               
                   
                 FNO. 
                 4.080 
                 3.077 
               
               
                   
                 d14 
                 19.000 
                 40.150 
               
               
                   
                 d17 
                 28.400 
                 7.250 
               
               
                   
                   
               
             
          
         
       
     
       EXAMPLE 2 
       [0460]      
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
               
             
               
               
               
             
               
               
               
               
             
           
               
                   
               
               
                 Unit mm 
               
               
                   
               
             
             
               
                 Surface data 
               
             
          
           
               
                   
                 Surface no. 
                 r 
                 d 
                 nd 
                 νd 
               
               
                   
                   
               
               
                   
                 Object plane 
                 ∞ 
                 ∞ 
               
               
                   
                  1 
                 150.727 
                 10.500 
                 1.48749 
                 70.23 
               
               
                   
                  2 
                 651.737 
                 15.541 
               
               
                   
                  3 
                 71.134 
                 16.724 
                 1.43875 
                 94.66 
               
               
                   
                  4 
                 362.718 
                 26.420 
               
               
                   
                  5 
                 158.408 
                 3.200 
                 1.69680 
                 55.53 
               
               
                   
                  6 
                 41.400 
                 14.500 
                 1.43875 
                 94.66 
               
               
                   
                  7 
                 414.878 
                 1.116 
               
               
                   
                  8 
                 61.312 
                 11.500 
                 1.43875 
                 94.66 
               
               
                   
                  9 
                 −114.766 
                 3.000 
                 1.77250 
                 49.60 
               
               
                   
                 10 
                 72.164 
                 30.845 
               
               
                   
                 11 
                 89.837 
                 7.000 
                 1.60342 
                 38.03 
               
               
                   
                 12 
                 −1077.583 
                 3.500 
               
               
                   
                 13(Stop) 
                 ∞ 
                 Variable 
               
               
                   
                 14 
                 379.994 
                 2.100 
                 1.80810 
                 22.76 
               
               
                   
                 15 
                 −187.856 
                 0.800 
                 1.71300 
                 53.87 
               
               
                   
                 16 
                 31.756 
                 Variable 
               
               
                   
                 17 
                 29.444 
                 1.000 
                 1.92119 
                 23.96 
               
               
                   
                 18 
                 23.133 
                 5.053 
                 1.48749 
                 70.23 
               
               
                   
                 19 
                 −127.088 
                 3.600 
               
               
                   
                 20 
                 188.909 
                 3.000 
                 1.85478 
                 24.80 
               
               
                   
                 21 
                 −42.257 
                 0.900 
                 1.69680 
                 55.53 
               
               
                   
                 22 
                 20.229 
                 4.624 
               
               
                   
                 23 
                 −30.088 
                 0.900 
                 1.69680 
                 55.53 
               
               
                   
                 24 
                 172.684 
                 3.300 
               
               
                   
                 25 
                 45.787 
                 6.751 
                 1.62004 
                 36.26 
               
               
                   
                 26 
                 −30.959 
                 2.500 
                 1.92286 
                 20.88 
               
               
                   
                 27 
                 −45.012 
                 0.100 
               
               
                   
                 28 
                 64.530 
                 7.523 
                 1.61293 
                 37.00 
               
               
                   
                 29 
                 −27.877 
                 2.500 
                 1.92286 
                 20.88 
               
               
                   
                 30 
                 −70.103 
               
               
                   
                 Image plane 
                 ∞ 
               
               
                   
                   
               
             
          
           
               
                 Various data 
               
               
                   
               
             
          
           
               
                   
                 Telephoto Ratio 
                 0.685 
               
               
                   
                 2ω 
                 3.2 
               
               
                   
                 LTL 
                 268.485 
               
               
                   
                 BF 
                 31.630 
               
               
                   
                   
               
             
          
           
               
                   
                   
                 Infinite 
                 Close 
               
               
                   
                   
               
               
                   
                 OB 
                 ∞ 
                 2.0 
               
               
                   
                 f 
                 392.007 
                 300.467 
               
               
                   
                 FNO. 
                 4.070 
                 3.097 
               
               
                   
                 d13 
                 20.400 
                 41.098 
               
               
                   
                 d16 
                 27.948 
                 7.250 
               
               
                   
                   
               
             
          
         
       
     
       EXAMPLE 3 
       [0461]      
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
               
             
               
               
               
             
               
               
               
               
             
           
               
                   
               
               
                 Unit mm 
               
               
                   
               
             
             
               
                 Surface data 
               
             
          
           
               
                   
                 Surface no. 
                 r 
                 d 
                 nd 
                 νd 
               
               
                   
                   
               
               
                   
                 Object plane 
                 ∞ 
                 ∞ 
               
               
                   
                  1 
                 264.623 
                 11.100 
                 1.48749 
                 70.23 
               
               
                   
                  2 
                 20014.598 
                 47.691 
               
               
                   
                  3 
                 81.993 
                 13.000 
                 1.43875 
                 94.66 
               
               
                   
                  4 
                 311.789 
                 44.610 
               
               
                   
                  5 
                 184.543 
                 3.200 
                 1.78800 
                 47.37 
               
               
                   
                  6 
                 50.778 
                 10.600 
                 1.43875 
                 94.66 
               
               
                   
                  7 
                 294.443 
                 1.286 
               
               
                   
                  8 
                 93.447 
                 9.800 
                 1.43875 
                 94.66 
               
               
                   
                  9 
                 −128.595 
                 2.900 
                 1.75500 
                 52.32 
               
               
                   
                 10 
                 232.754 
                 49.393 
               
               
                   
                 11 
                 72.189 
                 5.800 
                 1.56732 
                 42.82 
               
               
                   
                 12 
                 −80.817 
                 2.000 
                 1.91082 
                 35.25 
               
               
                   
                 13 
                 −194.303 
                 3.000 
               
               
                   
                 14(Stop) 
                 ∞ 
                 Variable 
               
               
                   
                 15 
                 657.445 
                 2.079 
                 1.80810 
                 22.76 
               
               
                   
                 16 
                 −100.323 
                 0.792 
                 1.71300 
                 53.87 
               
               
                   
                 17 
                 30.352 
                 Variable 
               
               
                   
                 18 
                 33.984 
                 5.346 
                 1.43875 
                 94.66 
               
               
                   
                 19 
                 −92.054 
                 3.871 
               
               
                   
                 20 
                 369.045 
                 2.426 
                 1.92286 
                 20.88 
               
               
                   
                 21 
                 −53.903 
                 0.891 
                 1.61800 
                 63.40 
               
               
                   
                 22 
                 23.158 
                 3.881 
               
               
                   
                 23 
                 −36.330 
                 0.891 
                 1.69680 
                 55.53 
               
               
                   
                 24 
                 46.784 
                 3.277 
               
               
                   
                 25 
                 56.274 
                 7.960 
                 1.74951 
                 35.33 
               
               
                   
                 26 
                 −23.449 
                 1.782 
                 1.92286 
                 20.88 
               
               
                   
                 27 
                 −79.583 
                 0.297 
               
               
                   
                 28 
                 59.359 
                 8.544 
                 1.61293 
                 37.00 
               
               
                   
                 29 
                 −27.503 
                 2.277 
                 1.92286 
                 20.88 
               
               
                   
                 30 
                 −47.248 
               
               
                   
                 Image plane 
                 ∞ 
               
               
                   
                   
               
             
          
           
               
                 Various data 
               
               
                   
               
             
          
           
               
                   
                 Telephoto Ratio 
                 0.836 
               
               
                   
                 2ω 
                 3.2 
               
               
                   
                 LTL 
                 327.555 
               
               
                   
                 BF 
                 34.678 
               
               
                   
                   
               
             
          
           
               
                   
                   
                 Infinite 
                 Close 
               
               
                   
                   
               
               
                   
                 OB 
                 ∞ 
                 2.5 
               
               
                   
                 f 
                 392.037 
                 327.311 
               
               
                   
                 FNO. 
                 4.079 
                 3.388 
               
               
                   
                 d14 
                 20.323 
                 35.325 
               
               
                   
                 d17 
                 23.862 
                 8.861 
               
               
                   
                   
               
             
          
         
       
     
       EXAMPLE 4 
       [0462]      
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
               
             
               
               
               
             
               
               
               
               
             
           
               
                   
               
               
                 Unit mm 
               
               
                   
               
             
             
               
                 Surface data 
               
             
          
           
               
                   
                 Surface no. 
                 r 
                 d 
                 nd 
                 νd 
               
               
                   
                   
               
               
                   
                 Object plane 
                 ∞ 
                 ∞ 
               
               
                   
                  1 
                 199.588 
                 13.500 
                 1.48749 
                 70.23 
               
               
                   
                  2 
                 1212.097 
                 35.000 
               
               
                   
                  3 
                 95.779 
                 16.600 
                 1.43875 
                 94.66 
               
               
                   
                  4 
                 343.469 
                 21.004 
               
               
                   
                  5 
                 168.922 
                 3.500 
                 1.77250 
                 49.60 
               
               
                   
                  6 
                 63.825 
                 16.500 
                 1.43875 
                 94.66 
               
               
                   
                  7 
                 388.340 
                 2.155 
               
               
                   
                  8 
                 116.181 
                 13.000 
                 1.43875 
                 94.66 
               
               
                   
                  9 
                 −305.996 
                 3.000 
                 1.69350 
                 53.21 
               
               
                   
                 10 
                 199.464 
                 66.671 
               
               
                   
                 11 
                 165.749 
                 8.000 
                 1.67270 
                 32.10 
               
               
                   
                 12 
                 −104.011 
                 4.000 
                 1.91082 
                 35.25 
               
               
                   
                 13 
                 −6747.942 
                 5.650 
               
               
                   
                 14 (Stop) 
                 ∞ 
                 Variable 
               
               
                   
                 15 
                 391.800 
                 2.200 
                 1.80810 
                 22.76 
               
               
                   
                 16 
                 −88.303 
                 0.900 
                 1.77250 
                 49.60 
               
               
                   
                 17 
                 37.564 
                 Variable 
               
               
                   
                 18 
                 34.190 
                 1.000 
                 1.92286 
                 20.88 
               
               
                   
                 19 
                 26.923 
                 5.000 
                 1.48749 
                 70.23 
               
               
                   
                 20 
                 −161.657 
                 3.600 
               
               
                   
                 21 
                 122.039 
                 3.100 
                 1.80810 
                 22.76 
               
               
                   
                 22 
                 −52.683 
                 0.900 
                 1.69680 
                 55.53 
               
               
                   
                 23 
                 22.975 
                 4.632 
               
               
                   
                 24 
                 −38.276 
                 0.900 
                 1.74100 
                 52.64 
               
               
                   
                 25 
                 196.791 
                 3.892 
               
               
                   
                 26 
                 48.160 
                 7.801 
                 1.56732 
                 42.82 
               
               
                   
                 27 
                 −22.764 
                 2.500 
                 1.92286 
                 20.88 
               
               
                   
                 28 
                 −35.997 
                 10.300 
               
               
                   
                 29 
                 46.777 
                 5.900 
                 1.73800 
                 32.26 
               
               
                   
                 30 
                 −91.048 
                 2.300 
                 1.92286 
                 20.88 
               
               
                   
                 31 
                 167.052 
               
               
                   
                 Image plane 
                 ∞ 
               
               
                   
                   
               
             
          
           
               
                 Various data 
               
               
                   
               
             
          
           
               
                   
                 Telephoto Ratio 
                 0.691 
               
               
                   
                 2ω 
                 2.5 
               
               
                   
                 LTL 
                 338.484 
               
               
                   
                 BF 
                 32.939 
               
               
                   
                   
               
             
          
           
               
                   
                   
                 Infinite 
                 Close 
               
               
                   
                   
               
               
                   
                 OB 
                 ∞ 
                 3.5 
               
               
                   
                 f 
                 489.999 
                 403.980 
               
               
                   
                 FNO. 
                 4.080 
                 3.346 
               
               
                   
                 d14 
                 16.650 
                 34.774 
               
               
                   
                 d17 
                 25.390 
                 7.266 
               
               
                   
                   
               
             
          
         
       
     
       EXAMPLE 5 
       [0463]      
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
               
             
               
               
               
             
               
               
               
               
             
           
               
                   
               
               
                 Unit mm 
               
               
                   
               
             
             
               
                 Surface data 
               
             
          
           
               
                   
                 Surface no. 
                 r 
                 d 
                 nd 
                 νd 
               
               
                   
                   
               
               
                   
                 Object plane 
                 ∞ 
                 ∞ 
               
               
                   
                  1 
                 215.266 
                 11.500 
                 1.48749 
                 70.23 
               
               
                   
                  2 
                 1535.372 
                 37.578 
               
               
                   
                  3 
                 88.716 
                 14.158 
                 1.43875 
                 94.66 
               
               
                   
                  4 
                 424.474 
                 37.426 
               
               
                   
                  5 
                 203.983 
                 3.546 
                 1.75500 
                 52.32 
               
               
                   
                  6 
                 54.116 
                 12.142 
                 1.43875 
                 94.66 
               
               
                   
                  7 
                 324.512 
                 4.778 
               
               
                   
                  8 
                 97.727 
                 9.879 
                 1.43875 
                 94.66 
               
               
                   
                  9 
                 −150.126 
                 2.800 
                 1.69680 
                 55.53 
               
               
                   
                 10 
                 150.668 
                 70.467 
               
               
                   
                 11 
                 78.749 
                 6.236 
                 1.57099 
                 50.80 
               
               
                   
                 12 
                 −91.000 
                 2.000 
                 1.88300 
                 40.76 
               
               
                   
                 13 
                 −259.795 
                 3.901 
               
               
                   
                 14 (Stop) 
                 ∞ 
                 Variable 
               
               
                   
                 15 
                 657.445 
                 2.079 
                 1.80810 
                 22.76 
               
               
                   
                 16 
                 −100.323 
                 0.792 
                 1.71300 
                 53.87 
               
               
                   
                 17 
                 30.352 
                 Variable 
               
               
                   
                 18 
                 33.984 
                 5.346 
                 1.43875 
                 94.66 
               
               
                   
                 19 
                 −92.054 
                 3.871 
               
               
                   
                 20 
                 369.045 
                 2.426 
                 1.92286 
                 20.88 
               
               
                   
                 21 
                 −53.903 
                 0.891 
                 1.61800 
                 63.40 
               
               
                   
                 22 
                 23.158 
                 3.881 
               
               
                   
                 23 
                 −36.330 
                 0.891 
                 1.69680 
                 55.53 
               
               
                   
                 24 
                 46.784 
                 3.277 
               
               
                   
                 25 
                 44.502 
                 7.960 
                 1.65412 
                 39.68 
               
               
                   
                 26 
                 −27.295 
                 1.782 
                 1.92286 
                 20.88 
               
               
                   
                 27 
                 −57.477 
                 0.297 
               
               
                   
                 28 
                 52.024 
                 8.544 
                 1.56732 
                 42.82 
               
               
                   
                 29 
                 −26.618 
                 2.277 
                 1.92286 
                 20.88 
               
               
                   
                 30 
                 −51.051 
               
               
                   
                 Image plane 
                 ∞ 
               
               
                   
                   
               
             
          
           
               
                 Various data 
               
               
                   
               
             
          
           
               
                   
                 Telephoto Ratio 
                 0.770 
               
               
                   
                 2ω 
                 2.8 
               
               
                   
                 LTL 
                 339.313 
               
               
                   
                 BF 
                 34.255 
               
               
                   
                   
               
             
          
           
               
                   
                   
                 Infinite 
                 Close 
               
               
                   
                   
               
               
                   
                 OB 
                 ∞ 
                 3.2 
               
               
                   
                 f 
                 440.935 
                 368.565 
               
               
                   
                 FNO. 
                 4.279 
                 3.559 
               
               
                   
                 d14 
                 20.308 
                 35.278 
               
               
                   
                 d17 
                 23.879 
                 8.908 
               
               
                   
                   
               
             
          
         
       
     
       EXAMPLE 6 
       [0464]      
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
               
             
               
               
             
               
             
               
               
               
             
               
               
               
               
             
           
               
                   
               
               
                 Unit mm 
               
               
                   
               
             
             
               
                 Surface data 
               
             
          
           
               
                   
                 Surface no. 
                 r 
                 d 
                 nd 
                 νd 
               
               
                   
                   
               
               
                   
                 Object plane 
                 ∞ 
                 ∞ 
               
               
                   
                  1 
                 185.654 
                 13.000 
                 1.48749 
                 70.23 
               
               
                   
                  2 
                 725.665 
                 47.516 
               
               
                   
                  3 
                 88.300 
                 19.000 
                 1.45860 
                 90.20 
               
               
                   
                  4 
                 460.000 
                 0.200 
                 1.63493 
                 23.90 
               
               
                   
                  5* 
                 425.730 
                 25.711 
               
               
                   
                  6 
                 159.278 
                 3.500 
                 1.69680 
                 55.53 
               
               
                   
                  7 
                 52.456 
                 16.678 
                 1.43875 
                 94.66 
               
               
                   
                  8 
                 642.788 
                 1.115 
               
               
                   
                  9 
                 75.639 
                 14.502 
                 1.43875 
                 94.66 
               
               
                   
                 10 
                 −169.631 
                 3.000 
                 1.77250 
                 49.60 
               
               
                   
                 11 
                 88.384 
                 49.365 
               
               
                   
                 12 
                 126.793 
                 7.012 
                 1.66680 
                 33.05 
               
               
                   
                 13 
                 1509.702 
                 7.032 
               
               
                   
                 14 (Stop) 
                 ∞ 
                 Variable 
               
               
                   
                 15 
                 272.463 
                 2.200 
                 1.80810 
                 22.76 
               
               
                   
                 16 
                 −188.242 
                 0.900 
                 1.77250 
                 49.60 
               
               
                   
                 17 
                 35.183 
                 Variable 
               
               
                   
                 18 
                 31.520 
                 1.000 
                 1.90366 
                 31.32 
               
               
                   
                 19 
                 21.805 
                 5.171 
                 1.51633 
                 64.14 
               
               
                   
                 20 
                 −215.706 
                 3.600 
               
               
                   
                 21 
                 208.803 
                 3.155 
                 1.85478 
                 24.80 
               
               
                   
                 22 
                 −41.327 
                 0.900 
                 1.69680 
                 55.53 
               
               
                   
                 23 
                 23.298 
                 4.989 
               
               
                   
                 24 
                 −30.877 
                 0.900 
                 1.69680 
                 55.53 
               
               
                   
                 25 
                 862.133 
                 3.300 
               
               
                   
                 26 
                 54.469 
                 7.881 
                 1.60342 
                 38.03 
               
               
                   
                 27 
                 −21.833 
                 2.480 
                 1.92286 
                 20.88 
               
               
                   
                 28 
                 −32.743 
                 10.300 
               
               
                   
                 29 
                 53.974 
                 5.900 
                 1.66680 
                 33.05 
               
               
                   
                 30 
                 −60.924 
                 2.500 
                 1.92286 
                 20.88 
               
               
                   
                 31 
                 691.964 
               
               
                   
                 Image plane 
                 ∞ 
               
               
                   
                   
               
             
          
           
               
                 Aspherical surface data 
               
               
                 5th surface 
               
               
                   
               
             
          
           
               
                   
                 k = 0.0000 
               
               
                   
                 A4 = 1.0000e−010, A6 = −5.0000e−014, A8 = 0.0000e+000, 
               
               
                   
                 A10 = 0.0000e+000 
               
               
                   
                   
               
             
          
           
               
                 Various data 
               
               
                   
               
             
          
           
               
                   
                 Telephoto Ratio 
                 0.669 
               
               
                   
                 2ω 
                 2.5 
               
               
                   
                 LTL 
                 324.169 
               
               
                   
                 BF 
                 17.323 
               
               
                   
                   
               
             
          
           
               
                   
                   
                 Infinite 
                 Close 
               
               
                   
                   
               
               
                   
                 OB 
                 ∞ 
                 3.5 
               
               
                   
                 f 
                 484.265 
                 392.425 
               
               
                   
                 FNO. 
                 4.066 
                 3.275 
               
               
                   
                 d14 
                 19.000 
                 36.586 
               
               
                   
                 d17 
                 25.039 
                 7.453 
               
               
                   
                   
               
             
          
         
       
     
       EXAMPLE 7 
       [0465]      
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
               
             
               
               
             
               
             
               
               
               
             
               
               
               
               
             
           
               
                   
               
               
                 Unit mm 
               
               
                   
               
             
             
               
                 Surface data 
               
             
          
           
               
                   
                 Surface no. 
                 r 
                 d 
                 nd 
                 νd 
               
               
                   
                   
               
               
                   
                 Object plane 
                 ∞ 
                 ∞ 
               
               
                   
                  1 
                 220.040 
                 11.000 
                 1.48749 
                 70.23 
               
               
                   
                  2 
                 999.794 
                 47.274 
               
               
                   
                  3 
                 73.569 
                 14.711 
                 1.49700 
                 81.61 
               
               
                   
                  4 
                 335.054 
                 23.909 
               
               
                   
                  5 
                 156.055 
                 3.200 
                 1.69680 
                 55.53 
               
               
                   
                  6 
                 43.325 
                 14.083 
                 1.43700 
                 95.10 
               
               
                   
                  7 
                 289.382 
                 1.115 
               
               
                   
                  8 
                 74.512 
                 12.006 
                 1.49700 
                 81.61 
               
               
                   
                  9 
                 −120.520 
                 2.800 
                 1.77250 
                 49.60 
               
               
                   
                 10 
                 74.646 
                 36.356 
               
               
                   
                 11 
                 84.036 
                 6.051 
                 1.58267 
                 46.42 
               
               
                   
                 12 
                 −640.863 
                 13.500 
               
               
                   
                 13 (Stop) 
                 ∞ 
                 Variable 
               
               
                   
                 14 
                 −216.858 
                 2.200 
                 1.63493 
                 23.90 
               
               
                   
                 15 
                 −61.068 
                 0.395 
               
               
                   
                 16 
                 −54.861 
                 1.000 
                 1.53071 
                 55.69 
               
               
                   
                 17* 
                 29.841 
                 Variable 
               
               
                   
                 18 
                 28.827 
                 1.000 
                 1.80810 
                 22.76 
               
               
                   
                 19 
                 21.247 
                 5.809 
                 1.48749 
                 70.23 
               
               
                   
                 20 
                 −159.140 
                 3.600 
               
               
                   
                 21 
                 533.374 
                 3.600 
                 1.80810 
                 22.76 
               
               
                   
                 22 
                 −38.800 
                 0.900 
                 1.69680 
                 55.53 
               
               
                   
                 23 
                 29.423 
                 3.490 
               
               
                   
                 24 
                 −59.334 
                 0.900 
                 1.77250 
                 49.60 
               
               
                   
                 25 
                 73.393 
                 3.300 
               
               
                   
                 26 
                 64.162 
                 6.500 
                 1.61293 
                 37.00 
               
               
                   
                 27 
                 −36.886 
                 2.500 
                 1.80810 
                 22.76 
               
               
                   
                 28 
                 −62.001 
                 3.663 
               
               
                   
                 29 
                 52.800 
                 9.000 
                 1.65412 
                 39.68 
               
               
                   
                 30 
                 −38.248 
                 2.500 
                 1.80810 
                 22.76 
               
               
                   
                 31 
                 −178.240 
               
               
                   
                 Image plane 
                 ∞ 
               
               
                   
                   
               
             
          
           
               
                 Aspherical surface data 
               
               
                 17th surface 
               
               
                   
               
             
          
           
               
                   
                 k = 0.0000 
               
               
                   
                 A4 = −2.3853e−006, A6 = −3.7627e−009, A8 = 1.6575e−012, 
               
               
                   
                 A10 = 0.0000e+000 
               
               
                   
                   
               
             
          
           
               
                 Various data 
               
               
                   
               
             
          
           
               
                   
                 Telephoto Ratio 
                 0.825 
               
               
                   
                 2ω 
                 3.2 
               
               
                   
                 LTL 
                 323.529 
               
               
                   
                 BF 
                 39.122 
               
               
                   
                   
               
             
          
           
               
                   
                   
                 Infinite 
                 Close 
               
               
                   
                   
               
               
                   
                 OB 
                 ∞ 
                 2.0 
               
               
                   
                 f 
                 391.993 
                 307.247 
               
               
                   
                 FNO. 
                 4.070 
                 3.174 
               
               
                   
                 d13 
                 19.00 
                 40.485 
               
               
                   
                 d17 
                 29.045 
                 7.559 
               
               
                   
                   
               
             
          
         
       
     
       EXAMPLE 8 
       [0466]      
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
               
             
               
               
             
               
             
               
               
               
             
               
               
               
               
             
           
               
                   
               
               
                 Unit mm 
               
               
                   
               
             
             
               
                 Surface data 
               
             
          
           
               
                   
                 Surface no. 
                 r 
                 d 
                 nd 
                 νd 
               
               
                   
                   
               
               
                   
                 Object plane 
                 ∞ 
                 ∞ 
               
               
                   
                  1 
                 207.585 
                 13.000 
                 1.48749 
                 70.23 
               
               
                   
                  2 
                 1550.011 
                 47.000 
               
               
                   
                  3 
                 83.672 
                 19.700 
                 1.43875 
                 94.66 
               
               
                   
                  4 
                 561.585 
                 24.340 
               
               
                   
                  5 
                 215.802 
                 3.588 
                 1.69680 
                 55.53 
               
               
                   
                  6 
                 52.249 
                 17.000 
                 1.43875 
                 94.66 
               
               
                   
                  7 
                 1149.881 
                 1.115 
               
               
                   
                  8 
                 83.478 
                 14.500 
                 1.43875 
                 94.66 
               
               
                   
                  9 
                 −135.670 
                 2.800 
                 1.77250 
                 49.60 
               
               
                   
                 10 
                 108.163 
                 45.091 
               
               
                   
                 11 
                 201.384 
                 7.000 
                 1.71736 
                 29.52 
               
               
                   
                 12 
                 −874.411 
                 9.753 
               
               
                   
                 13 (Stop) 
                 ∞ 
                 Variable 
               
               
                   
                 14 
                 −230.408 
                 2.200 
                 1.63493 
                 23.90 
               
               
                   
                 15 
                 −73.008 
                 0.349 
               
               
                   
                 16 
                 −68.280 
                 1.000 
                 1.53071 
                 55.69 
               
               
                   
                 17* 
                 30.624 
                 Variable 
               
               
                   
                 18 
                 31.232 
                 1.000 
                 1.92286 
                 20.88 
               
               
                   
                 19 
                 25.271 
                 5.000 
                 1.48749 
                 70.23 
               
               
                   
                 20 
                 −195.708 
                 3.600 
               
               
                   
                 21 
                 86.152 
                 3.669 
                 1.80810 
                 22.76 
               
               
                   
                 22 
                 −43.751 
                 0.900 
                 1.74100 
                 52.64 
               
               
                   
                 23 
                 26.477 
                 3.883 
               
               
                   
                 24 
                 −50.133 
                 0.900 
                 1.83481 
                 42.73 
               
               
                   
                 25 
                 60.796 
                 3.300 
               
               
                   
                 26 
                 53.028 
                 6.700 
                 1.68893 
                 31.07 
               
               
                   
                 27 
                 −28.074 
                 2.500 
                 1.92286 
                 20.88 
               
               
                   
                 28 
                 −64.741 
                 3.486 
               
               
                   
                 29 
                 61.094 
                 11.000 
                 1.62004 
                 36.26 
               
               
                   
                 30 
                 −30.502 
                 2.500 
                 1.92286 
                 20.88 
               
               
                   
                 31 
                 −64.979 
               
               
                   
                 Image plane 
                 ∞ 
               
               
                   
                   
               
             
          
           
               
                 Aspherical surface data 
               
               
                 17th surface 
               
               
                   
               
             
          
           
               
                   
                 k = 0.0000 
               
               
                   
                 A4 = −1.9239e−006, A6 = −2.5932e−009, A8 = 1.2780e−012, 
               
               
                   
                 A10 = 0.0000e+000 
               
               
                   
                   
               
             
          
           
               
                 Various data 
               
               
                   
               
             
          
           
               
                   
                 Telephoto Ratio 
                 0.691 
               
               
                   
                 2ω 
                 2.5 
               
               
                   
                 LTL 
                 338.667 
               
               
                   
                 BF 
                 34.582 
               
               
                   
                   
               
             
          
           
               
                   
                   
                 Infinite 
                 Close 
               
               
                   
                   
               
               
                   
                 OB 
                 ∞ 
                 3.0 
               
               
                   
                 f 
                 489.990 
                 385.385 
               
               
                   
                 FNO. 
                 4.080 
                 3.190 
               
               
                   
                 d13 
                 19.000 
                 39.698 
               
               
                   
                 d17 
                 28.210 
                 7.512 
               
               
                   
                   
               
             
          
         
       
     
       EXAMPLE 9 
       [0467]      
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
               
             
               
               
             
               
             
               
               
               
             
               
               
               
               
             
           
               
                   
               
               
                 Unit mm 
               
               
                   
               
             
             
               
                 Surface data 
               
             
          
           
               
                   
                 Surface no. 
                 r 
                 d 
                 nd 
                 νd 
               
               
                   
                   
               
               
                   
                 Object plane 
                 ∞ 
                 ∞ 
               
               
                   
                  1 
                 207.585 
                 13.000 
                 1.48749 
                 70.23 
               
               
                   
                  2 
                 1550.011 
                 47.000 
               
               
                   
                  3 
                 83.672 
                 19.700 
                 1.43875 
                 94.66 
               
               
                   
                  4 
                 561.585 
                 24.340 
               
               
                   
                  5 
                 215.802 
                 3.588 
                 1.69680 
                 55.53 
               
               
                   
                  6 
                 52.249 
                 17.000 
                 1.43875 
                 94.66 
               
               
                   
                  7 
                 1149.881 
                 1.116 
               
               
                   
                  8 
                 83.478 
                 14.500 
                 1.43875 
                 94.66 
               
               
                   
                  9 
                 −135.670 
                 2.800 
                 1.77250 
                 49.60 
               
               
                   
                 10 
                 108.163 
                 45.091 
               
               
                   
                 11 
                 201.384 
                 7.000 
                 1.71736 
                 29.52 
               
               
                   
                 12 
                 −874.411 
                 9.753 
               
               
                   
                 13 (Stop) 
                 ∞ 
                 Variable 
               
               
                   
                 14* 
                 −230.408 
                 1.000 
                 1.63400 
                 23.10 
               
               
                   
                 15 
                 −68.280 
                 0.600 
                 1.51742 
                 52.43 
               
               
                   
                 16 
                 30.624 
                 Variable 
               
               
                   
                 17 
                 31.232 
                 1.000 
                 1.92286 
                 20.88 
               
               
                   
                 18 
                 25.271 
                 5.000 
                 1.49700 
                 81.54 
               
               
                   
                 19 
                 −195.708 
                 3.600 
               
               
                   
                 20 
                 86.152 
                 3.669 
                 1.80810 
                 22.76 
               
               
                   
                 21 
                 −43.751 
                 0.900 
                 1.74100 
                 52.64 
               
               
                   
                 22 
                 26.477 
                 3.883 
               
               
                   
                 23 
                 −50.133 
                 0.900 
                 1.83481 
                 42.73 
               
               
                   
                 24 
                 60.796 
                 3.300 
               
               
                   
                 25 
                 53.028 
                 6.700 
                 1.68893 
                 31.07 
               
               
                   
                 26 
                 −28.074 
                 2.500 
                 1.92286 
                 20.88 
               
               
                   
                 27 
                 −64.741 
                 3.486 
               
               
                   
                 28 
                 59.175 
                 11.000 
                 1.61293 
                 37.00 
               
               
                   
                 29 
                 −30.502 
                 2.500 
                 1.92286 
                 20.88 
               
               
                   
                 30 
                 −64.979 
               
               
                   
                 Image plane 
                 ∞ 
               
               
                   
                   
               
             
          
           
               
                 Aspherical surface data 
               
               
                 14th surface 
               
               
                   
               
             
          
           
               
                   
                 k = 0.0000 
               
               
                   
                 A4 = 7.5150e−007, A6 = −5.1160e−010, A8 = −1.0000e−012, 
               
               
                   
                 A10 = 0.0000e+000 
               
               
                   
                   
               
             
          
           
               
                 Various data 
               
               
                   
               
             
          
           
               
                   
                 Telephoto Ratio 
                 0.724 
               
               
                   
                 2ω 
                 2.7 
               
               
                   
                 LTL 
                 333.396 
               
               
                   
                 BF 
                 31.260 
               
               
                   
                   
               
             
          
           
               
                   
                   
                 Infinite 
                 Close 
               
               
                   
                   
               
               
                   
                 OB 
                 ∞ 
                 3.0 
               
               
                   
                 f 
                 460.561 
                 374.991 
               
               
                   
                 FNO. 
                 3.812 
                 3.086 
               
               
                   
                 d13 
                 19.000 
                 40.007 
               
               
                   
                 d16 
                 28.210 
                 7.202 
               
               
                   
                   
               
             
          
         
       
     
         [0468]    The values of the conditional expressions in Examples are listed below. In Examples 1 to 6, no plastic lens is used. However, in the following, the value of Conditional Expression (11) and the value of Conditional Expression (12) are described assuming that a plastic lens is used. The value of Conditional Expression (1B) is the same as the value of Conditional Expression (1A). The value of Conditional Expression (2B) is the same as the value of Conditional Expression (2A). The value of Conditional Expression (15B) is the same as the value of Conditional Expression (15A). 
       Conditional 
       [0469]    Expression 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Example 1 
                 Example 2 
                 Example 3 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 (1A) DGFGR/f 
                 0.077 
                 0.067 
                 0.114 
               
               
                   
                 (1B) DGFGR1/f 
               
               
                   
                 (2A) ΔGFGR/f 
                 0.179 
                 0.176 
                 0.297 
               
               
                   
                 (2B) ΔGFGR1/f 
               
               
                   
                 (3) νdGFave 
                 82.445 
                 82.445 
                 82.445 
               
               
                   
                 (4) νdGFmax 
                 94.660 
                 94.660 
                 94.660 
               
               
                   
                 (5) DGR1GR2/f 
                 0.077 
                 0.079 
                 0.126 
               
               
                   
                 (6) fGF/f 
                 0.403 
                 0.351 
                 0.468 
               
               
                   
                 (7) fL1/fGF 
                 2.416 
                 2.905 
                 2.998 
               
               
                   
                 (8) fGF/fGR1 
                 −0.488 
                 −1.222 
                 −0.930 
               
               
                   
                 (9) |fG2/f| 
                 0.132 
                 0.129 
                 0.120 
               
               
                   
                 (10) |MGG2B 2  × 
                 4.700 
                 4.701 
                 4.716 
               
               
                   
                 (MGG22 − 1)| 
               
               
                   
                 (11) fPLn/fPLp 
                 −0.314 
                 −0.244 
                 −0.300 
               
               
                   
                 (12) |fG2/fPLp| 
                 0.461 
                 0.325 
                 0.436 
               
               
                   
                 (13) |MGISB × 
                 2.000 
                 2.000 
                 2.070 
               
               
                   
                 (MGIS − 1)| 
               
               
                   
                 (14) DGFairmax/DGF 
                 0.350 
                 0.363 
                 0.664 
               
               
                   
                 (15A) DGFGR/fGF 
                 0.192 
                 0.192 
                 0.243 
               
               
                   
                 (15B) DGFGR1/fGF 
               
               
                   
                 (16) νdLp1 
                 70.23 
                 70.23 
                 70.23 
               
               
                   
                 (17) |fG1/fG2| 
                 3.284 
                 3.363 
                 3.649 
               
               
                   
                 (a) |f/fLn| 
                 4.342 
                 4.819 
                 4.363 
               
               
                   
                   
               
             
          
         
       
     
       Conditional 
       [0470]    Expression 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Example 4 
                 Example 5 
                 Example 6 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 (1A) DGFGR/f 
                 0.043 
                 0.085 
                 0.053 
               
               
                   
                 (1B) DGFGR1/f 
               
               
                   
                 (2A) ΔGFGR/f 
                 0.176 
                 0.228 
                 0.218 
               
               
                   
                 (2B) ΔGFGR1/f 
               
               
                   
                 (3) νdGFave 
                 82.445 
                 82.445 
                 80.215 
               
               
                   
                 (4) νdGFmax 
                 94.660 
                 94.660 
                 90.200 
               
               
                   
                 (5) DGR1GR2/f 
                 0.136 
                 0.160 
                 0.102 
               
               
                   
                 (6) fGF/f 
                 0.398 
                 0.407 
                 0.364 
               
               
                   
                 (7) fL1/fGF 
                 2.505 
                 2.855 
                 2.881 
               
               
                   
                 (8) fGF/fGR1 
                 −0.955 
                 −0.425 
                 −0.976 
               
               
                   
                 (9) |fG2/f| 
                 0.113 
                 0.107 
                 0.110 
               
               
                   
                 (10) |MGG2B 2  × 
                 4.500 
                 4.560 
                 4.487 
               
               
                   
                 (MGG22 − 1)| 
               
               
                   
                 (11) fPLn/fPLp 
                 −0.381 
                 −0.302 
                 −0.277 
               
               
                   
                 (12) |fG2/fPLp| 
                 0.621 
                 0.436 
                 0.388 
               
               
                   
                 (13) |MGISB × 
                 2.000 
                 2.087 
                 1.570 
               
               
                   
                 (MGIS − 1)| 
               
               
                   
                 (14) DGFairmax/DGF 
                 0.538 
                 0.594 
                 0.596 
               
               
                   
                 (15A) DGFGR/fGF 
                 0.108 
                 0.209 
                 0.146 
               
               
                   
                 (15B) DGFGR1/fGF 
               
               
                   
                 (16) νdLp1 
                 70.23 
                 70.23 
                 70.230 
               
               
                   
                 (17) |fG1/fG2| 
                 3.919 
                 4.183 
                 3.987 
               
               
                   
                 (a) |f/fLn| 
                 3.636 
                 4.474 
                 4.256 
               
               
                   
                   
               
             
          
         
       
     
       Conditional 
       [0471]    Expression 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Example 7 
                 Example 8 
                 Example 9 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 (1A) DGFGR/f 
                 0.061 
                 0.050 
                   
               
               
                   
                 (1B) DGFGR1/f 
                   
                   
                 0.053 
               
               
                   
                 (2A) ΔGFGR/f 
                 0.247 
                 0.212 
               
               
                   
                 (2B) ΔGFGR1/f 
                   
                   
                 0.226 
               
               
                   
                 (3) νdGFave 
                 75.920 
                 82.445 
                 82.445 
               
               
                   
                 (4) νdGFmax 
                 81.610 
                 94.660 
                 94.660 
               
               
                   
                 (5) DGR1GR2/f 
                 0.093 
                 0.092 
                 0.098 
               
               
                   
                 (6) fGF/f 
                 0.386 
                 0.337 
                 0.359 
               
               
                   
                 (7) fL1/fGF 
                 3.804 
                 2.967 
                 2.967 
               
               
                   
                 (8) fGF/fGR1 
                 −1.305 
                 −1.016 
                 −1.016 
               
               
                   
                 (9) |fG2/f| 
                 0.128 
                 0.106 
                 0.121 
               
               
                   
                 (10) |MGG2B 2  × 
                 4.488 
                 4.680 
                 4.075 
               
               
                   
                 (MGG22 − 1)| 
               
               
                   
                 (11) fPLn/fPLp 
                 −0.272 
                 −0.237 
                 −0.267 
               
               
                   
                 (12) |fG2/fPLp| 
                 0.376 
                 0.311 
                 0.364 
               
               
                   
                 (13) |MGISB × 
                 2.000 
                 2.000 
                 1.898 
               
               
                   
                 (MGIS − 1)| 
               
               
                   
                 (14) DGFairmax/DGF 
                 0.648 
                 0.590 
                 0.590 
               
               
                   
                 (15A) DGFGR/fGF 
                 0.158 
                 0.147 
               
               
                   
                 (15B) DGFGR1/fGF 
                   
                   
                 0.147 
               
               
                   
                 (16) νdLp1 
                 70.23 
                 70.23 
                 70.23 
               
               
                   
                 (17) |fG1/fG2| 
                 3.578 
                 4.144 
                 3.881 
               
               
                   
                 (a) |f/fLn| 
                 4.501 
                 4.908 
                 4.613 
               
               
                   
                   
               
             
          
         
       
     
         [0472]      FIG. 19  is a cross-sectional view of a single-lens mirrorless camera as an electronic image pickup apparatus. In  FIG. 19 , a photographic optical system  2  is disposed inside a lens barrel of a single-lens mirrorless camera  1 . A mount portion  3  enables the photographic optical system  2  to be detachable from a body of the single-lens mirrorless camera  1 . As the mount portion  3 , a mount such as a screw-type mount and a bayonet-type mount is to be used. In this example, a bayonet-type mount is used. Moreover, an image pickup element surface  4  and a back monitor  5  are disposed in the body of the single-lens mirrorless camera  1 . As an image pickup element, an element such as a small-size CCD (charge coupled device) or a CMOS (complementary metal-oxide semiconductor) is to be used. 
         [0473]    Moreover, as the photographic optical system  2  of the single-lens mirrorless camera  1 , the telephoto lens described in any one of the examples from the first example to the nine example is to be used. 
         [0474]      FIG. 20  and  FIG. 21  are conceptual diagrams of an arrangement of the image pickup apparatus.  FIG. 20  is a front perspective view of a digital camera  40  as the image pickup apparatus, and  FIG. 21  is a rear perspective view of the digital camera  40 . The telephoto lens according to the present example is used in a photographic optical system  41  of the digital camera  40 . 
         [0475]    The digital camera  40  according to the present embodiment includes the photographic optical system  41  which is positioned in a photographic optical path  42 , a shutter button  45 , and a liquid-crystal display monitor  47 . As the shutter button  45  disposed on an upper portion of the digital camera  40  is pressed, in conjunction with the pressing of the shutter button  45 , photography is carried out by the photographic optical system  41  such as the telephoto lens according to the first example. An object image which is formed by the photographic optical system  41  is formed on an image pickup element (photoelectric conversion surface) which is provided near an image forming surface. The object image which has been received optically by the image pickup element is displayed on the liquid-crystal display monitor  47  which is provided to a rear surface of the camera, as an electronic image by a processing means. Moreover, it is possible to record the electronic image which has been photographed, in a storage means. 
         [0476]      FIG. 22  is a structural block diagram of an internal circuit of main components of the digital camera  40 . In the following description, the processing means described above includes for instance, a CDS/ADC section  24 , a temporary storage memory  117 , and an image processing section  18 , and a storage means consists of a storage medium section  19  for example. 
         [0477]    As shown in  FIG. 22 , the digital camera  40  includes an operating section  12 , a control section  13  which is connected to the operating section  12 , the temporary storage memory  17  and an imaging drive circuit  16  which are connected to a control-signal output port of the control section  13 , via a bus  14  and a bus  15 , the image processing section  18 , the storage medium section  19 , a display section  20 , and a set-information storage memory section  21 . 
         [0478]    The temporary storage memory  17 , the image processing section  18 , the storage medium section  19 , the display section  20 , and the set-information storage memory section  21  are structured to be capable of mutually inputting and outputting data via a bus  22 . Moreover, the CCD  49  and the CDS/ADC section  24  are connected to the imaging drive circuit  16 . 
         [0479]    The operating section  12  includes various input buttons and switches, and informs the control section  13  of event information which is input from outside (by a user of the digital camera) via these input buttons and switches. The control section  13  is a central processing unit (CPU), and has a built-in computer program memory which is not shown in the diagram. The control section  13  controls the entire digital camera  40  according to a computer program stored in this computer program memory. 
         [0480]    The CCD  49  is driven and controlled by the imaging drive circuit  16 , and which converts an amount of light for each pixel of the object image formed by the photographic optical system  41  to an electric signal, and outputs to the CDS/ADC section  24 . 
         [0481]    The CDS/ADC section  24  is a circuit which amplifies the electric signal which is input from the CCD  49 , and carries out analog/digital conversion, and outputs to the temporary storage memory  17  image raw data (Bayer data, hereinafter called as ‘RAW data’) which is only amplified and converted to digital data. 
         [0482]    The temporary storage memory  17  is a buffer which includes an SDRAM (Synchronous Dynamic Random Access Memory) for example, and is a memory device which stores temporarily the RAW data which is output from the CDS/ADC section  24 . The image processing section  18  is a circuit which reads the RAW data stored in the temporary storage memory  17 , or the RAW data stored in the storage medium section  19 , and carries out electrically various image-processing including the distortion correction, based on image-quality parameters specified by the control section  13 . 
         [0483]    The storage medium section  19  is a recording medium in the form of a card or a stick including a flash memory for instance, detachably mounted. The storage medium section  19  records and maintains the RAW data transferred from the temporary storage memory  17  and image data subjected to image processing in the image processing section  18  in the card flash memory and the stick flash memory. 
         [0484]    The display section  20  includes the liquid-crystal display monitor, and displays photographed RAW data, image data and operation menu on the liquid-crystal display monitor. The set-information storage memory section  21  includes a ROM section in which various image quality parameters are stored in advance, and a RAM section which stores image quality parameters which are selected by an input operation on the operating section  12 , from among the image quality parameters which are read from the ROM section. 
         [0485]    The present invention can have various modified examples without departing from the scope of the invention. Moreover, shapes of lenses and the number of lenses are not necessarily restricted to the shapes and the number of lenses indicated in the examples. In the examples described heretofore, the cover glass may not be disposed necessarily. A lens that is not shown in the diagrams of the examples described above, and that does not have a refractive power practically may be disposed in a lens unit or outside the lens unit. 
         [0486]    A lens may be formed of a single material or may be formed of a plurality of materials. Examples of the lens formed of a plurality of glass materials include cemented lenses as well as hybrid lenses and diffractive optical elements as described above. Diffractive optical elements exist, for example, in two forms. In the first form, a diffraction-effect surface is formed on the surface of a lens formed of a single material. In the second form, another material is formed on the surface of a lens formed of a single material and a diffraction-effect surface is formed on the surface of the other material. 
         [0487]    The present invention can provide a telephoto lens having excellent portability and in which aberration is corrected favorably, and an image pickup apparatus including the same. 
         [0488]    As described above, the present invention is suitable for a telephoto lens having excellent portability and in which aberration is corrected favorably, and for an image pickup apparatus having excellent portability and capable of producing a high-quality image.