Abstract:
A zoom lens system comprising: a negative first lens unit; a positive second lens unit; a negative third lens unit; and a positive fourth lens unit, wherein in zooming, the first lens unit moves with locus of a convex to the image side and the second lens unit moves to the object side, and the conditions: 0&lt;(D aW −D aT )/TL W &lt;0.26 and 0&lt;TG 2G /TG a11 &lt;0.4 (D aW : optical axial interval between the first and second lens units at the wide-angle limit, D aT : optical axial interval between the first and second lens units at the telephoto limit, TL W : overall length of the lens system at the wide-angle limit, TG 2G : optical axial thickness of the second lens unit, TG all : sum of optical axial thicknesses of the respective lens units) are satisfied.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based on application No. 2013-210322 filed in Japan on Oct. 7, 2013, the contents of which are hereby incorporated by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    The present disclosure relates to zoom lens systems, interchangeable lens apparatuses, and camera systems. 
         [0004]    2. Description of the Related Art 
         [0005]    In recent years, interchangeable-lens type digital camera systems (also referred to simply as “camera systems”, hereinafter) have been spreading rapidly. Such interchangeable-lens type digital camera systems realize: taking of high-sensitive and high-quality images; high-speed focusing and high-speed image processing after image taking; and easy replacement of an interchangeable lens apparatus in accordance with a desired scene. Meanwhile, an interchangeable lens apparatus having a zoom lens system that forms an optical image with variable magnification is popular because it allows free change of focal length. 
         [0006]    Zoom lens systems having excellent optical performance from a wide-angle limit to a telephoto limit have been desired as zoom lens systems to be used in interchangeable lens apparatuses. For example, various kinds of zoom lens systems, having a multiple-unit construction in which a negative lens unit is located closest to an object side, have been proposed. 
         [0007]    Japanese Patent No. 5083219 discloses a variable magnification optical system having a four-unit construction of negative, positive, negative, and positive, in which the interval between a first lens unit and a second lens unit is decreased in zooming. 
         [0008]    Japanese Laid-Open Patent Publication No. 2012-133228 discloses a zoom lens system having a four-unit construction of negative, positive, negative, and positive, in which a first lens unit including at least one lens element having positive optical power is moved in zooming. 
       SUMMARY 
       [0009]    The present disclosure provides a zoom lens system having excellent optical performance over the entire zoom range while being compact in size. Further, the present disclosure provides an interchangeable lens apparatus and a camera system each employing the zoom lens system. 
         [0010]    The novel concepts disclosed herein were achieved in order to solve the foregoing problems in the related art, and herein is disclosed: 
         [0011]    a zoom lens system, in order from an object side to an image side, comprising: 
         [0012]    a first lens unit having negative optical power; 
         [0013]    a second lens unit having positive optical power; 
         [0014]    a third lens unit having negative optical power; and 
         [0015]    a fourth lens unit having positive optical power, wherein 
         [0016]    the first lens unit moves with locus of a convex to the image side in zooming from a wide-angle limit to a telephoto limit at a time of image taking 
         [0017]    the second lens unit moves to the object side in the zooming, and 
         [0018]    the following conditions (1) and (2) are satisfied: 
         [0000]      0&lt;( D   aW   −D   aT )/ TL   W &lt;0.26  (1)
 
         [0000]      0 &lt;TG   2G   /TG   a11 &lt;0.4  (2)
 
         [0019]    where 
         [0020]    D aW  is an optical axial interval between the first lens unit and the second lens unit at the wide-angle limit, 
         [0021]    D aT  is an optical axial interval between the first lens unit and the second lens unit at the telephoto limit, 
         [0022]    TL W  is an overall length of the lens system at the wide-angle limit being an optical axial distance from an object side surface of a lens element closest to the object side in the first lens unit to an image surface, 
         [0023]    TG 2G  is an optical axial thickness of the second lens unit, and 
         [0024]    TG all  is a sum of optical axial thicknesses of the respective lens units. 
         [0025]    The novel concepts disclosed herein were achieved in order to solve the foregoing problems in the related art, and herein is disclosed: 
         [0026]    an interchangeable lens apparatus comprising: 
         [0027]    a zoom lens system; and 
         [0028]    a lens mount section which is connectable to a camera body including an image sensor for receiving an optical image formed by the zoom lens system and converting the optical image into an electric image signal, 
         [0029]    the zoom lens system, in order from an object side to an image side, comprising: 
         [0030]    a first lens unit having negative optical power; 
         [0031]    a second lens unit having positive optical power; 
         [0032]    a third lens unit having negative optical power; and 
         [0033]    a fourth lens unit having positive optical power, wherein 
         [0034]    the first lens unit moves with locus of a convex to the image side in zooming from a wide-angle limit to a telephoto limit at a time of image taking 
         [0035]    the second lens unit moves to the object side in the zooming, and 
         [0036]    the following conditions (1) and (2) are satisfied: 
         [0000]      0&lt;( D   aW   −D   aT )/ TL   W &lt;0.26  (1)
 
         [0000]      0 &lt;TG   2G   /TG   a11 &lt;0.4  (2)
 
         [0037]    where 
         [0038]    D aW  is an optical axial interval between the first lens unit and the second lens unit at the wide-angle limit, 
         [0039]    D aT  is an optical axial interval between the first lens unit and the second lens unit at the telephoto limit, 
         [0040]    TL W  is an overall length of the lens system at the wide-angle limit being an optical axial distance from an object side surface of a lens element closest to the object side in the first lens unit to an image surface, 
         [0041]    TG 2G  is an optical axial thickness of the second lens unit, and 
         [0042]    TG all  is a sum of optical axial thicknesses of the respective lens units. 
         [0043]    The novel concepts disclosed herein were achieved in order to solve the foregoing problems in the related art, and herein is disclosed: 
         [0044]    a camera system comprising: 
         [0045]    an interchangeable lens apparatus including a zoom lens system; and 
         [0046]    a camera body which is detachably connected to the interchangeable lens apparatus via a camera mount section, and includes an image sensor for receiving an optical image formed by the zoom lens system and converting the optical image into an electric image signal, 
         [0047]    the zoom lens system, in order from an object side to an image side, comprising: 
         [0048]    a first lens unit having negative optical power; 
         [0049]    a second lens unit having positive optical power; 
         [0050]    a third lens unit having negative optical power; and 
         [0051]    a fourth lens unit having positive optical power, wherein 
         [0052]    the first lens unit moves with locus of a convex to the image side in zooming from a wide-angle limit to a telephoto limit at a time of image taking 
         [0053]    the second lens unit moves to the object side in the zooming, and 
         [0054]    the following conditions (1) and (2) are satisfied: 
         [0000]      0&lt;( D   aW   −D   aT )/ TL   W &lt;0.26  (1)
 
         [0000]      0 &lt;TG   2G   /TG   a11 &lt;0.4  (2)
 
         [0055]    where 
         [0056]    D aW  is an optical axial interval between the first lens unit and the second lens unit at the wide-angle limit, 
         [0057]    D aT  is an optical axial interval between the first lens unit and the second lens unit at the telephoto limit, 
         [0058]    TL W  is an overall length of the lens system at the wide-angle limit being an optical axial distance from an object side surface of a lens element closest to the object side in the first lens unit to an image surface, 
         [0059]    TG 2G  is an optical axial thickness of the second lens unit, and 
         [0060]    TG all  is a sum of optical axial thicknesses of the respective lens units. 
         [0061]    The zoom lens system according to the present disclosure has excellent optical performance over the entire zoom range while being compact in size. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0062]    This and other objects and features of the present disclosure will become clear from the following description, taken in conjunction with the exemplary embodiments with reference to the accompanied drawings in which: 
           [0063]      FIG. 1  is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment 1 (Numerical Example 1); 
           [0064]      FIG. 2  is a longitudinal aberration diagram of an infinity in-focus condition of the zoom lens system according to Numerical Example 1; 
           [0065]      FIG. 3  is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment 2 (Numerical Example 2); 
           [0066]      FIG. 4  is a longitudinal aberration diagram of an infinity in-focus condition of the zoom lens system according to Numerical Example 2; 
           [0067]      FIG. 5  is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment 3 (Numerical Example 3); 
           [0068]      FIG. 6  is a longitudinal aberration diagram of an infinity in-focus condition of the zoom lens system according to Numerical Example 3; and 
           [0069]      FIG. 7  is a schematic construction diagram of an interchangeable-lens type digital camera system according to Embodiment 4. 
       
    
    
     DETAILED DESCRIPTION 
       [0070]    Hereinafter, embodiments will be described with reference to the drawings as appropriate. However, descriptions more detailed than necessary may be omitted. For example, detailed description of already well known matters or description of substantially identical configurations may be omitted. This is intended to avoid redundancy in the description below, and to facilitate understanding of those skilled in the art. 
         [0071]    It should be noted that the applicants provide the attached drawings and the following description so that those skilled in the art can fully understand this disclosure. Therefore, the drawings and description are not intended to limit the subject defined by the claims. 
       Embodiments 1 to 3 
       [0072]      FIGS. 1 ,  3 , and  5  are lens arrangement diagrams of zoom lens systems according to Embodiments 1 to 3, respectively. Each zoom lens system is in an infinity in-focus condition. 
         [0073]    In each Fig., part (a) shows a lens configuration at a wide-angle limit (in the minimum focal length condition: focal length f w ), part (b) shows a lens configuration at a middle position (in an intermediate focal length condition: focal length f M =√{square root over ((f W *f T ))}), and part (c) shows a lens configuration at a telephoto limit (in the maximum focal length condition: focal length f T ). Further, in each Fig., each bent arrow located between part (a) and part (b) indicates a line obtained by connecting the positions of each lens unit respectively at a wide-angle limit, a middle position and a telephoto limit, in order from the top. In the part between the wide-angle limit and the middle position and the part between the middle position and the telephoto limit, the positions are connected simply with a straight line, and hence this line does not indicate actual motion of each lens unit. 
         [0074]    Further, in each Fig., an arrow imparted to a lens unit indicates focusing from an infinity in-focus condition to a close-object in-focus condition. That is, the arrow indicates a direction along which a third lens unit G 3  described later moves in focusing from an infinity in-focus condition to a close-object in-focus condition. In  FIGS. 1 ,  3 , and  5 , since the symbols of the respective lens units are imparted to part (a), the arrow indicating focusing is placed beneath each symbol of each lens unit for the convenience sake. However, the direction along which each lens unit moves in focusing in each zooming condition will be hereinafter described in detail for each embodiment. 
         [0075]    Each of the zoom lens systems according to Embodiments 1 to 3, in order from the object side to the image side, comprises a first lens unit G 1  having negative optical power, a second lens unit G 2  having positive optical power, a third lens unit G 3  having negative optical power, and a fourth lens unit G 4  having positive optical power. In the zoom lens system according to each embodiment, in zooming, the first lens unit G 1 , the second lens unit G 2 , and the third lens unit G 3  individually move in a direction along the optical axis such that the intervals between the respective lens units, that is, the interval between the first lens unit G 1  and the second lens unit G 2 , the interval between the second lens unit G 2  and the third lens unit G 3 , and the interval between the third lens unit G 3  and the fourth lens unit G 4 , vary. In the zoom lens system according to each embodiment, these lens units are arranged in a desired optical power allocation, whereby size reduction of the entire lens system is achieved while maintaining excellent optical performance. 
         [0076]    In  FIGS. 1 ,  3 , and  5 , an asterisk “*” imparted to a particular surface indicates that the surface is aspheric. In each Fig., symbol (+) or (−) imparted to the symbol of each lens unit corresponds to the sign of the optical power of the lens unit. In each Fig., a straight line located on the most right-hand side indicates the position of an image surface S. 
         [0077]    Further, as shown in  FIGS. 1 ,  3 , and  5 , an aperture diaphragm A is provided between the first lens unit G 1  and the second lens unit G 2 . The aperture diaphragm A moves along the optical axis together with the second lens unit G 2  in zooming from a wide-angle limit to a telephoto limit at the time of image taking 
       Embodiment 1 
       [0078]    As shown in  FIG. 1 , the first lens unit G 1 , in order from the object side to the image side, comprises: a negative meniscus first lens element L 1  with the convex surface facing the object side; a bi-concave second lens element L 2 ; and a positive meniscus third lens element L 3  with the convex surface facing the object side. The second lens element L 2  has two aspheric surfaces. 
         [0079]    The second lens unit G 2 , in order from the object side to the image side, comprises: a positive meniscus fourth lens element L 4  with the convex surface facing the object side; a negative meniscus fifth lens element L 5  with the convex surface facing the object side; and a bi-convex sixth lens element L 6 . Among these, the fifth lens element L 5  and the sixth lens element L 6  are cemented with each other. In the surface data of the corresponding Numerical Example described later, a surface number  11  is imparted to an adhesive layer between the fifth lens element L 5  and the sixth lens element L 6 . The fourth lens element L 4  has two aspheric surfaces. 
         [0080]    The entirety of the second lens unit G 2  corresponds to an image blur compensating lens unit described later, which moves in a direction perpendicular to the optical axis to optically compensate image blur. 
         [0081]    The third lens unit G 3  comprises solely a bi-concave seventh lens element L 7 . The seventh lens element L 7  has an aspheric image side surface. The seventh lens element L 7  is a lens element formed of a resin material. 
         [0082]    The fourth lens unit G 4  comprises solely a bi-convex eighth lens element L 8 . 
         [0083]    In zooming from a wide-angle limit to a telephoto limit at the time of image taking, the first lens unit G 1  moves with locus of a convex to the image side, the second lens unit G 2  moves to the object side, the third lens unit G 3  moves with locus of a slight convex to the object side, and the fourth lens unit G 4  is fixed with respect to the image surface S. That is, in zooming, the first lens unit G 1 , the second lens unit G 2 , and the third lens unit G 3  individually move along the optical axis so that the interval between the first lens unit G 1  and the second lens unit G 2  decreases, and the interval between the second lens unit G 2  and the third lens unit G 3  and the interval between the third lens unit G 3  and the fourth lens unit G 4  increase. 
         [0084]    In focusing from an infinity in-focus condition to a close-object in-focus condition, the third lens unit G 3  serving as a focusing lens unit moves to the image side along the optical axis in any zooming condition. 
       Embodiment 2 
       [0085]    As shown in  FIG. 3 , the first lens unit G 1 , in order from the object side to the image side, comprises: a negative meniscus first lens element L 1  with the convex surface facing the object side; a bi-concave second lens element L 2 ; and a positive meniscus third lens element L 3  with the convex surface facing the object side. The second lens element L 2  has two aspheric surfaces. 
         [0086]    The second lens unit G 2 , in order from the object side to the image side, comprises: a positive meniscus fourth lens element L 4  with the convex surface facing the object side; a negative meniscus fifth lens element L 5  with the convex surface facing the object side; and a bi-convex sixth lens element L 6 . Among these, the fifth lens element L 5  and the sixth lens element L 6  are cemented with each other. In the surface data of the corresponding Numerical Example described later, a surface number  11  is imparted to an adhesive layer between the fifth lens element L 5  and the sixth lens element L 6 . The fourth lens element L 4  has two aspheric surfaces. 
         [0087]    The entirety of the second lens unit G 2  corresponds to an image blur compensating lens unit described later, which moves in a direction perpendicular to the optical axis to optically compensate image blur. 
         [0088]    The third lens unit G 3  comprises solely a bi-concave seventh lens element L 7 . The seventh lens element L 7  has two aspheric surfaces. 
         [0089]    The fourth lens unit G 4  comprises solely a bi-convex eighth lens element L 8 . 
         [0090]    In zooming from a wide-angle limit to a telephoto limit at the time of image taking, the first lens unit G 1  moves with locus of a convex to the image side, the second lens unit G 2  moves to the object side, the third lens unit G 3  moves with locus of a convex to the object side, and the fourth lens unit G 4  is fixed with respect to the image surface S. That is, in zooming, the first lens unit G 1 , the second lens unit G 2 , and the third lens unit G 3  individually move along the optical axis so that the interval between the first lens unit G 1  and the second lens unit G 2  decreases, and the interval between the second lens unit G 2  and the third lens unit G 3  and the interval between the third lens unit G 3  and the fourth lens unit G 4  increase. 
         [0091]    In focusing from an infinity in-focus condition to a close-object in-focus condition, the third lens unit G 3  serving as a focusing lens unit moves to the image side along the optical axis in any zooming condition. 
       Embodiment 3 
       [0092]    As shown in  FIG. 5 , the first lens unit G 1 , in order from the object side to the image side, comprises: a negative meniscus first lens element L 1  with the convex surface facing the object side; a bi-concave second lens element L 2 ; and a positive meniscus third lens element L 3  with the convex surface facing the object side. The second lens element L 2  has two aspheric surfaces. 
         [0093]    The second lens unit G 2 , in order from the object side to the image side, comprises: a bi-convex fourth lens element L 4 ; a negative meniscus fifth lens element L 5  with the convex surface facing the object side; and a bi-convex sixth lens element L 6 . Among these, the fifth lens element L 5  and the sixth lens element L 6  are cemented with each other. In the surface data of the corresponding Numerical Example described later, a surface number  11  is imparted to an adhesive layer between the fifth lens element L 5  and the sixth lens element L 6 . The fourth lens element L 4  has two aspheric surfaces. 
         [0094]    The entirety of the second lens unit G 2  corresponds to an image blur compensating lens unit described later, which moves in a direction perpendicular to the optical axis to optically compensate image blur. 
         [0095]    The third lens unit G 3  comprises solely a bi-concave seventh lens element L 7 . The seventh lens element L 7  has an aspheric image side surface. The seventh lens element L 7  is a lens element formed of a resin material. 
         [0096]    The fourth lens unit G 4  comprises solely a bi-convex eighth lens element L 8 . 
         [0097]    In zooming from a wide-angle limit to a telephoto limit at the time of image taking, the first lens unit G 1  moves with locus of a convex to the image side, the second lens unit G 2  moves to the object side, the third lens unit G 3  moves with locus of a slight convex to the object side, and the fourth lens unit G 4  is fixed with respect to the image surface S. That is, in zooming, the first lens unit G 1 , the second lens unit G 2 , and the third lens unit G 3  individually move along the optical axis so that the interval between the first lens unit G 1  and the second lens unit G 2  decreases, and the interval between the second lens unit G 2  and the third lens unit G 3  and the interval between the third lens unit G 3  and the fourth lens unit G 4  increase. 
         [0098]    In focusing from an infinity in-focus condition to a close-object in-focus condition, the third lens unit G 3  serving as a focusing lens unit moves to the image side along the optical axis in any zooming condition. 
         [0099]    In the zoom lens systems according to Embodiments 1 to 3, in zooming from a wide-angle limit to a telephoto limit at the time of image taking, the first lens unit G 1  moves with locus of a convex to the image side, and the second lens unit G 2  moves to the object side, so that the interval between the first lens unit G 1  and the second lens unit G 2  is smaller at the telephoto limit than at the wide-angle limit. Thereby, the dimension, in the optical-axis direction, of a zoom cam ring of a lens barrel that moves with the locus of the first lens unit G 1  and the second lens unit G 2  is reduced, and the length of the lens barrel when retracted can be reduced. As a result, it is possible to provide compact interchangeable lens apparatuses and camera systems. 
         [0100]    In the zoom lens systems according to Embodiments 1 to 3, the first lens unit G 1 , in order from the object side to the image side, comprises: the negative meniscus first lens element L 1 ; the second lens element L 2  having negative optical power; and the positive meniscus third lens element L 3 . At least one of two surfaces of the second lens element L 2  having negative optical power is an aspherical surface. Therefore, off-axis aberration at the wide-angle limit can be successfully compensated, thereby realizing excellent optical performance even at a focal length of 24 mm (in still conversion) or smaller. 
         [0101]    In the zoom lens systems according to Embodiments 1 to 3, the second lens unit G 2 , in order from the object side to the image side, comprises: the fourth lens element L 4  having positive optical power; and a cemented lens element obtained by cementing the negative meniscus fifth lens element L 5  with the sixth lens element L 6  having positive optical power. Thereby, the second lens unit G 2  has a triplet configuration. The triplet configuration is well known as an optical system suitable for compensation of chromatic aberration and Seidel&#39;s five aberrations while having a small number of lenses, i.e., three lenses of positive, negative, and positive powers. Since the present disclosure adopts the triplet configuration, simplified configuration is achieved and the aberrations can be successfully compensated. As a result, it is possible to provide compact interchangeable lens apparatuses and camera systems. Further, as described above, the second lens unit G 2  is an image blur compensating lens unit. By using the second lens unit G 2  of the above-mentioned lens configuration as an image blur compensating lens unit, size reduction of an actuator can also be achieved. 
         [0102]    In the zoom lens systems according to Embodiments 1 and 3, the third lens unit G 3  is composed of one lens element formed of a resin material such as acrylic resin. As described above, the third lens unit G 3  is a focusing lens unit, and therefore, weight reduction of the focusing lens unit and size reduction of the actuator can be achieved. As a result, further size reduction of the zoom lens system can be achieved, thereby providing compact interchangeable lens apparatuses and camera systems. 
         [0103]    It is beneficial to have an image blur compensating lens unit like the zoom lens systems according to Embodiments 1 to 3. The image blur compensating lens unit can compensate image point movement caused by vibration of the entire system. 
         [0104]    When compensating image point movement caused by vibration of the entire system, the image blur compensating lens unit moves in the direction perpendicular to the optical axis, whereby image blur is compensated in a state that size increase in the entire zoom lens system is suppressed to realize a compact configuration and that excellent imaging characteristics such as small decentering coma aberration and small decentering astigmatism are satisfied. 
         [0105]    As described above, Embodiments 1 to 3 have been described as examples of art disclosed in the present application. However, the art in the present disclosure is not limited to these embodiments. It is understood that various modifications, replacements, additions, omissions, and the like have been performed in these embodiments to give optional embodiments, and the art in the present disclosure can be applied to the optional embodiments. 
         [0106]    The following description is given for conditions that a zoom lens system like the zoom lens systems according to Embodiments 1 to 3 can satisfy. Here, a plurality of beneficial conditions is set forth for the zoom lens system according to each embodiment. A construction that satisfies all the plurality of conditions is most effective for the zoom lens system. However, when an individual condition is satisfied, a zoom lens system having the corresponding effect is obtained. 
         [0107]    For example, in a zoom lens system like the zoom lens systems according to Embodiments 1 to 3, which comprises, in order from the object side to the image side, a first lens unit having negative optical power, a second lens unit having positive optical power, a third lens unit having negative optical power, and a fourth lens unit having positive optical power, and in which, in zooming from a wide-angle limit to a telephoto limit at the time of image taking, the first lens unit moves with locus of a convex to the image side, and the second lens unit moves to the object side (this lens configuration is referred to as a basic configuration of the embodiment, hereinafter), the following conditions (1) and (2) are satisfied: 
         [0000]      0&lt;( D   aW   −D   aT )/ TL   W &lt;0.26  (1)
 
         [0000]      0 &lt;TG   2G   /TG   a11 &lt;0.4  (2)
 
         [0108]    where 
         [0109]    D aW  is an optical axial interval between the first lens unit and the second lens unit at the wide-angle limit, 
         [0110]    D aT  is an optical axial interval between the first lens unit and the second lens unit at the telephoto limit, 
         [0111]    TL W  is an overall length of the lens system at the wide-angle limit being an optical axial distance from an object side surface of a lens element closest to the object side in the first lens unit to an image surface, 
         [0112]    TG 2G  is an optical axial thickness of the second lens unit, and 
         [0113]    TG all  is a sum of optical axial thicknesses of the respective lens units. 
         [0114]    The condition (1) sets forth a ratio of a difference between the interval between the first lens unit and the second lens unit at the wide-angle limit and that interval at the telephoto limit, to the overall length of the lens system at the wide-angle limit. When the condition (1) is satisfied, the dimension, in the optical-axis direction, of the zoom cam ring of the lens barrel that moves with the locus of the first lens unit and the second lens unit is reduced, and thereby the length of the lens barrel when retracted can be reduced. As a result, it is possible to provide compact interchangeable lens apparatuses and camera systems. 
         [0115]    When at least one of the following conditions (1)′ and (1)″ is satisfied, the above-mentioned effect is achieved more successfully. 
         [0000]      0.220&lt;( D   aW   −D   aT )/ TL   W   (1)′
 
         [0000]      ( D   aW   −D   aT )/ TL   W &lt;0.258  (1)″
 
         [0116]    The condition (2) sets forth a ratio of the thickness of the second lens unit to the sum of the thicknesses of the respective lens units. When the condition (2) is satisfied, the ratio of the thickness of the second lens unit to the sum of the thicknesses of the respective lens units is reduced, and thereby the length of the lens barrel when retracted can be reduced. As a result, it is possible to provide compact interchangeable lens apparatuses and camera systems. 
         [0117]    When at least one of the following conditions (2)′ and (2)″ is satisfied, the above-mentioned effect is achieved more successfully. 
         [0000]      0.350 &lt;TG   2G   /TG   all   (2)′
 
         [0000]        TG   2G   /TG   all &lt;0.398  (2)″
 
         [0118]    It is beneficial that a zoom lens system having the basic configuration like the zoom lens systems according to Embodiments 1 to 3 satisfies the following condition (3): 
         [0000]        TL   W   −TL   T &gt;0  (3)
 
         [0119]    where 
         [0120]    TL W  is the overall length of the lens system at the wide-angle limit being the optical axial distance from the object side surface of the lens element closest to the object side in the first lens unit to the image surface, and 
         [0121]    TL T  is an overall length of the lens system at the telephoto limit being an optical axial distance from the object side surface of the lens element closest to the object side in the first lens unit to the image surface. 
         [0122]    The condition (3) sets forth a difference between the overall length of the lens system at the wide-angle limit and the overall length of the lens system at the telephoto limit. When the condition (3) is satisfied, the overall length of the lens system at the wide-angle limit becomes larger than the overall length of the lens system at the telephoto limit, whereby the dimension, in the optical-axis direction, of the zoom cam ring of the lens barrel is further reduced, and the length of the lens barrel when retracted can be further reduced. As a result, it is possible to provide more compact interchangeable lens apparatuses and camera systems. 
         [0123]    When the following condition (3)′ is satisfied, the above-mentioned effect is achieved more successfully. 
         [0000]        TL   W   −TL   T &gt;0.20  (3)′
 
         [0124]    It is beneficial that a zoom lens system having the basic configuration like the zoom lens systems according to Embodiments 1 to 3 satisfies the following condition (4): 
         [0000]      0 &lt;TG   all   /TL   W &lt;0.35  (4)
 
         [0125]    where 
         [0126]    TG all  is the sum of the optical axial thicknesses of the respective lens units, and 
         [0127]    TL W  is the overall length of the lens system at the wide-angle limit being the optical axial distance from the object side surface of the lens element closest to the object side in the first lens unit to the image surface. 
         [0128]    The condition (4) sets forth a ratio of the sum of the thicknesses of the respective lens units to the overall length of the lens system at the wide-angle limit. When the condition (4) is satisfied, the ratio of the sum of the thicknesses of the respective lens units to the overall length of the lens system at the wide-angle limit is reduced, and thereby the length of the lens barrel when retracted can be further reduced. As a result, it is possible to provide more compact interchangeable lens apparatuses and camera systems. 
         [0129]    When at least one of the following conditions (4)′ and (4)″ is satisfied, the above-mentioned effect is achieved more successfully. 
         [0000]      0.320 &lt;TG   all   /TL   W   (4)′
 
         [0000]        TG   all   /TL   W &lt;0.348  (4)″
 
         [0130]    It is beneficial that a zoom lens system having the basic configuration like the zoom lens systems according to Embodiments 1 to 3 satisfies the following condition (5). 
         [0000]        nd   L1 &gt;1.9  (5)
 
         [0131]    where 
         [0132]    nd L1  is a refractive index to the d-line of the lens element closest to the object side in the first lens unit. 
         [0133]    The condition (5) sets forth the refractive index to the d-line of the lens element closest to the object side in the first lens unit, i.e., the first lens element. When the condition (5) is satisfied, it is possible to realize a zoom lens system having a small lens diameter in spite of its wide view angle. 
         [0134]    When the following condition (5)′ is satisfied, the above-mentioned effect is achieved more successfully. 
         [0000]        nd   L1 &gt;1.902  (5)′
 
         [0135]    It is beneficial that a zoom lens system having the basic configuration like the zoom lens systems according to Embodiments 1 to 3 satisfies the following condition (6). 
         [0000]      |Σ1/( f   i   ×νd   i )|&lt; 5 . 0   E -04  (6)
 
         [0136]    where 
         [0137]    f i  is a focal length of an i-th lens element from the object side in the second lens unit, 
         [0138]    νd i  is an Abbe number to the d-line of the i-th lens element from the object side in the second lens unit. 
         [0139]    The condition (6) sets forth a condition relating to reduction of chromatic aberration in the second lens unit. When the condition (6) is satisfied, it is possible to realize a zoom lens system in which axial chromatic aberration is successfully compensated, in spite of its wide view angle. 
         [0140]    When the following condition (6)′ is satisfied, the above-mentioned effect is achieved more successfully. 
         [0000]      |Σ1/( f   i   ×νd   i )|&lt; 4 . 5   E -04  (6)′
 
         [0141]    The individual lens units constituting the zoom lens systems according to Embodiments 1 to 3 are each composed exclusively of refractive type lens elements that deflect incident light by refraction (that is, lens elements of a type in which deflection is achieved at the interface between media having different refractive indices). However, the present disclosure is not limited to this construction. For example, the lens units may employ diffractive type lens elements that deflect incident light by diffraction; refractive-diffractive hybrid type lens elements that deflect incident light by a combination of diffraction and refraction; or gradient index type lens elements that deflect incident light by distribution of refractive index in the medium. In particular, in the refractive-diffractive hybrid type lens element, when a diffraction structure is formed in the interface between media having different refractive indices, wavelength dependence of the diffraction efficiency is improved. Thus, such a configuration is beneficial. 
       Embodiment 4 
       [0142]      FIG. 7  is a schematic construction diagram of an interchangeable-lens type digital camera system according to Embodiment 4. 
         [0143]    The interchangeable-lens type digital camera system  100  according to Embodiment 4 includes a camera body  101 , and an interchangeable lens apparatus  201  which is detachably connected to the camera body  101 . 
         [0144]    The camera body  101  includes: an image sensor  102  which receives an optical image formed by a zoom lens system  202  of the interchangeable lens apparatus  201 , and converts the optical image into an electric image signal; a liquid crystal monitor  103  which displays the image signal obtained by the image sensor  102 ; and a camera mount section  104 . On the other hand, the interchangeable lens apparatus  201  includes: a zoom lens system  202  according to any of Embodiments 1 to 3; a lens barrel  203  which holds the zoom lens system  202 ; and a lens mount section  204  connected to the camera mount section  104  of the camera body  101 . The camera mount section  104  and the lens mount section  204  are physically connected to each other. Moreover, the camera mount section  104  and the lens mount section  204  function as interfaces which allow the camera body  101  and the interchangeable lens apparatus  201  to exchange signals, by electrically connecting a controller (not shown) in the camera body  101  and a controller (not shown) in the interchangeable lens apparatus  201 . In  FIG. 7 , the zoom lens system according to Embodiment 1 is employed as the zoom lens system  202 . 
         [0145]    In Embodiment 4, since the zoom lens system  202  according to any of Embodiments 1 to 3 is employed, a compact interchangeable lens apparatus having excellent imaging performance can be realized at low cost. Moreover, size reduction and cost reduction of the entire camera system  100  according to Embodiment 4 can be achieved. In the zoom lens systems according to Embodiments 1 to 3, the entire zooming range need not be used. That is, in accordance with a desired zooming range, a range where satisfactory optical performance is obtained may exclusively be used. Then, the zoom lens system may be used as one having a lower magnification than the zoom lens systems described in Embodiments 1 to 3. 
         [0146]    As described above, Embodiment 4 has been described as an example of art disclosed in the present application. However, the art in the present disclosure is not limited to this embodiment. It is understood that various modifications, replacements, additions, omissions, and the like have been performed in this embodiment to give optional embodiments, and the art in the present disclosure can be applied to the optional embodiments. 
         [0147]    Numerical examples are described below in which the zoom lens systems according to Embodiments 1 to 3 are implemented. Here, in the numerical examples, the units of length are all “mm”, while the units of view angle are all “°”. Moreover, in the numerical examples, r is the radius of curvature, d is the axial distance, nd is the refractive index to the d-line, and vd is the Abbe number to the d-line. In the numerical examples, the surfaces marked with * are aspherical surfaces, and the aspherical surface configuration is defined by the following expression. 
         [0000]    
       
         
           
             Z 
             = 
             
               
                 
                   
                     h 
                     2 
                   
                   / 
                   r 
                 
                 
                   1 
                   + 
                   
                     
                       1 
                       - 
                       
                         
                           ( 
                           
                             1 
                             + 
                             κ 
                           
                           ) 
                         
                          
                         
                           
                             ( 
                             
                               h 
                               / 
                               r 
                             
                             ) 
                           
                           2 
                         
                       
                     
                   
                 
               
               + 
               
                 ∑ 
                 
                   
                     A 
                     n 
                   
                    
                   
                     h 
                     n 
                   
                 
               
             
           
         
       
     
         [0000]    Here, the symbols in the formula indicate the following quantities. 
         [0148]    Z is a distance from a point on an aspherical surface at a height h relative to the optical axis to a tangential plane at the vertex of the aspherical surface, 
         [0149]    h is a height relative to the optical axis, 
         [0150]    r is a radius of curvature at the top, 
         [0151]    κ is a conic constant, and 
         [0152]    A n  is a n-th order aspherical coefficient. 
         [0153]      FIGS. 2 ,  4 , and  6  are longitudinal aberration diagrams of an infinity in-focus condition of the zoom lens systems according to Numerical Examples 1 to 3, respectively. 
         [0154]    In each longitudinal aberration diagram, part (a) shows the aberration at a wide-angle limit, part (b) shows the aberration at a middle position, and part (c) shows the aberration at a telephoto limit. Each longitudinal aberration diagram, in order from the left-hand side, shows the spherical aberration (SA (mm)), the astigmatism (AST (mm)) and the distortion (DIS (%)). In each spherical aberration diagram, the vertical axis indicates the F-number (in each Fig., indicated as F), and the solid line, the short dash line and the long dash line indicate the characteristics to the d-line, the F-line and the C-line, respectively. In each astigmatism diagram, the vertical axis indicates the image height (in each Fig., indicated as H), and the solid line and the dash line indicate the characteristics to the sagittal plane (in each Fig., indicated as “s”) and the meridional plane (in each Fig., indicated as “m”), respectively. In each distortion diagram, the vertical axis indicates the image height (in each Fig., indicated as H). 
       Numerical Example 1 
       [0155]    The zoom lens system of Numerical Example 1 corresponds to Embodiment 1 shown in  FIG. 1 . Table 1 shows the surface data of the zoom lens system of Numerical Example 1. Table 2 shows the aspherical data. Table 3 shows the various data. 
         [0000]    
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 (Surface data) 
               
             
          
           
               
                 Surface number 
                 r 
                 d 
                 nd 
                 vd 
               
               
                   
               
               
                 Object surface 
                 ∞ 
                   
                   
                   
               
               
                  1 
                 30.49670 
                 0.80000 
                 1.91082 
                 35.2 
               
               
                  2 
                 9.57330 
                 4.67870 
               
               
                  3* 
                 −250.00000 
                 0.65000 
                 1.80755 
                 40.9 
               
               
                  4* 
                 23.82190 
                 0.70000 
               
               
                  5 
                 20.15200 
                 2.29900 
                 1.92286 
                 20.9 
               
               
                  6 
                 154.75950 
                 Variable 
               
               
                  7(Diaphragm) 
                 ∞ 
                 1.00000 
               
               
                  8* 
                 12.06370 
                 2.90000 
                 1.80755 
                 40.9 
               
               
                  9* 
                 72.81590 
                 2.50090 
               
               
                 10 
                 162.28230 
                 0.60000 
                 1.90366 
                 31.3 
               
               
                 11 
                 8.22930 
                 0.01000 
                 1.56732 
                 42.8 
               
               
                 12 
                 8.22930 
                 2.80000 
                 1.59282 
                 68.6 
               
               
                 13 
                 −15.07320 
                 Variable 
               
               
                 14 
                 −36.48910 
                 0.60000 
                 1.51633 
                 64.1 
               
               
                 15* 
                 19.51650 
                 Variable 
               
               
                 16 
                 38.04970 
                 3.76140 
                 1.59349 
                 67.0 
               
               
                 17 
                 −38.04970 
                 (BF) 
               
               
                 Image surface 
                 ∞ 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 (Aspherical data) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Surface No. 3 
               
               
                   
                 K = 0.00000E+00, A4 = 6.42456E−05, A6 = −1.48819E−06, 
               
               
                   
                 A8 = 1.91171E−08 A10 = −1.41959E−10, A12 = 0.00000E+00 
               
               
                   
                 Surface No. 4 
               
               
                   
                 K = −1.00000E+00, A4 = 4.34003E−05, A6 = −1.90102E−06, 
               
               
                   
                 A8 = 2.13128E−08 A10 = −1.83613E−10, A12 = 0.00000E+00 
               
               
                   
                 Surface No. 8 
               
               
                   
                 K = 0.00000E+00, A4 = 1.75599E−05, A6 = 1.10808E−06, 
               
               
                   
                 A8 = −7.85898E−08 A10 = 1.60668E−09, A12 = 0.00000E+00 
               
               
                   
                 Surface No. 9 
               
               
                   
                 K = 0.00000E+00, A4 = 1.17843E−04, A6 = 9.94808E−07, 
               
               
                   
                 A8 = −9.50843E−08 A10 = 2.13059E−09, A12 = 0.00000E+00 
               
               
                   
                 Surface No. 15 
               
               
                   
                 K = 0.00000E+00, A4 = 6.54271E−05, A6 = −2.79405E−06, 
               
               
                   
                 A8 = 1.21768E−07 A10 = −2.82845E−09, A12 = 2.56285E−11 
               
               
                   
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
             
               
               
               
             
               
             
               
               
               
               
               
               
             
               
             
               
               
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                 (Various data) 
               
               
                   
               
             
             
               
                 Zooming ratio 2.29667 
               
             
          
           
               
                   
                   
                 Wide-angle 
                 Middle 
                 Telephoto 
               
               
                   
                   
                 limit 
                 position 
                 limit 
               
               
                   
                   
               
               
                   
                 Focal length 
                 12.5400 
                 18.9540 
                 28.8002 
               
               
                   
                 F-number 
                 3.60581 
                 4.55961 
                 5.69578 
               
               
                   
                 Half view angle 
                 44.8139 
                 30.6293 
                 20.3145 
               
               
                   
                 Image height 
                 10.8150 
                 10.8150 
                 10.8150 
               
               
                   
                 Overall length 
                 66.1576 
                 63.1222 
                 64.2717 
               
               
                   
                 of lens system 
               
               
                   
                 BF 
                 14.19898 
                 14.19917 
                 14.19933 
               
               
                   
                 d6 
                 18.4000 
                 9.1818 
                 2.5475 
               
               
                   
                 d13 
                 5.9766 
                 9.9097 
                 16.4293 
               
               
                   
                 d15 
                 4.2820 
                 6.5315 
                 7.7956 
               
               
                   
                 Entrance pupil 
                 10.3509 
                 8.4954 
                 6.3952 
               
               
                   
                 position 
               
               
                   
                 Exit pupil 
                 −28.3422 
                 −43.7086 
                 −64.6559 
               
               
                   
                 position 
               
               
                   
                 Front principal 
                 19.1944 
                 21.2455 
                 24.6767 
               
               
                   
                 points position 
               
               
                   
                 Back principal 
                 53.6176 
                 44.1681 
                 35.4716 
               
               
                   
                 points position 
               
               
                   
                   
               
             
          
           
               
                 Single lens data 
               
             
          
           
               
                 Lens 
                 Initial surface 
                 Focal 
               
               
                 element 
                 number 
                 length 
               
               
                   
               
               
                 1 
                 1 
                 −15.6040 
               
               
                 2 
                 3 
                 −26.9041 
               
               
                 3 
                 5 
                 24.9015 
               
               
                 4 
                 8 
                 17.5312 
               
               
                 5 
                 10 
                 −9.6109 
               
               
                 6 
                 12 
                 9.3996 
               
               
                 7 
                 14 
                 −24.5372 
               
               
                 8 
                 16 
                 32.6569 
               
               
                   
               
             
          
           
               
                 Zoom lens unit data 
               
             
          
           
               
                   
                   
                   
                   
                 Front 
                 Back 
               
               
                   
                 Initial 
                   
                 Overall 
                 principal 
                 principal 
               
               
                 Lens 
                 surface 
                 Focal 
                 length of 
                 points 
                 points 
               
               
                 unit 
                 No. 
                 length 
                 lens unit 
                 position 
                 position 
               
               
                   
               
               
                 1 
                 1 
                 −17.34042 
                 9.12770 
                 −0.08239 
                 1.33503 
               
               
                 2 
                 7 
                 16.66030 
                 9.81090 
                 2.54959 
                 4.33557 
               
               
                 3 
                 14 
                 −24.53719 
                 0.60000 
                 0.25687 
                 0.46261 
               
               
                 4 
                 16 
                 32.65691 
                 3.76140 
                 1.20237 
                 2.55903 
               
               
                   
               
             
          
           
               
                 Magnification of zoom lens unit 
               
             
          
           
               
                   
                 Initial 
                   
                   
                   
               
               
                 Lens 
                 surface 
                 Wide-angle 
                 Middle 
                 Telephoto 
               
               
                 unit 
                 No. 
                 limit 
                 position 
                 limit 
               
               
                   
               
               
                 1 
                 1 
                 0.00000 
                 0.00000 
                 0.00000 
               
               
                 2 
                 7 
                 −0.56625 
                 −0.82460 
                 −1.22774 
               
               
                 3 
                 14 
                 2.41701 
                 2.50872 
                 2.56026 
               
               
                 4 
                 16 
                 0.52839 
                 0.52838 
                 0.52838 
               
               
                   
               
             
          
         
       
     
       Numerical Example 2 
       [0156]    The zoom lens system of Numerical Example 2 corresponds to Embodiment 2 shown in  FIG. 3 . Table 4 shows the surface data of the zoom lens system of Numerical Example 2. Table 5 shows the aspherical data. Table 6 shows the various data. 
         [0000]    
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 (Surface data) 
               
             
          
           
               
                 Surface number 
                 r 
                 d 
                 nd 
                 vd 
               
               
                   
               
               
                 Object surface 
                 ∞ 
                   
                   
                   
               
               
                  1 
                 25.11400 
                 0.80000 
                 1.90366 
                 31.3 
               
               
                  2 
                 9.32200 
                 5.15000 
               
               
                  3* 
                 −100.00000 
                 0.65000 
                 1.80755 
                 40.9 
               
               
                  4* 
                 29.48100 
                 0.70000 
               
               
                  5 
                 20.44000 
                 2.00000 
                 1.94595 
                 18.0 
               
               
                  6 
                 79.77000 
                 Variable 
               
               
                  7(Diaphragm) 
                 ∞ 
                 1.00000 
               
               
                  8* 
                 11.88800 
                 2.00000 
                 1.80755 
                 40.9 
               
               
                  9* 
                 130.07200 
                 2.92000 
               
               
                 10 
                 97.99300 
                 0.60000 
                 1.90366 
                 31.3 
               
               
                 11 
                 7.45200 
                 0.01000 
                 1.56732 
                 42.8 
               
               
                 12 
                 7.45200 
                 2.80000 
                 1.59282 
                 68.6 
               
               
                 13 
                 −16.34800 
                 Variable 
               
               
                 14* 
                 −35.24500 
                 0.80000 
                 1.54360 
                 56.0 
               
               
                 15* 
                 18.97400 
                 Variable 
               
               
                 16 
                 38.20700 
                 3.87000 
                 1.61800 
                 63.4 
               
               
                 17 
                 −38.20700 
                 (BF) 
               
               
                 Image surface 
                 ∞ 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
             
           
               
                 TABLE 5 
               
               
                   
               
               
                 (Aspherical data) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Surface No. 3 
               
               
                   
                 K = 0.00000E+00, A4 = 1.40550E−04, A6 = −1.58941E−06, 
               
               
                   
                 A8 = 6.43519E−09 A10 = −1.87697E−11, A12 = 0.00000E+00 
               
               
                   
                 Surface No. 4 
               
               
                   
                 K = 5.86836E−01, A4 = 1.15112E−04, A6 = −1.97769E−06, 
               
               
                   
                 A8 = 6.16703E−09 A10 = −4.93618E−11, A12 = 0.00000E+00 
               
               
                   
                 Surface No. 8 
               
               
                   
                 K = 0.00000E+00, A4 = 3.20964E−06, A6 = 2.93568E−06, 
               
               
                   
                 A8 = −1.57598E−07 A10 = 3.09974E−09, A12 = 0.00000E+00 
               
               
                   
                 Surface No. 9 
               
               
                   
                 K = 0.00000E+00, A4 = 8.54042E−05, A6 = 2.80481E−06, 
               
               
                   
                 A8 = −1.72924E−07 A10 = 3.57409E−09, A12 = 0.00000E+00 
               
               
                   
                 Surface No. 14 
               
               
                   
                 K = 0.00000E+00, A4 = −2.30192E−04, A6 = 9.60767E−06, 
               
               
                   
                 A8 = −1.56985E−07 A10 = 9.91907E−10, A12 = 0.00000E+00 
               
               
                   
                 Surface No. 15 
               
               
                   
                 K = 0.00000E+00, A4 = −1.70128E−04, A6 = 7.65291E−06, 
               
               
                   
                 A8 = −8.80044E−08 A10 = −1.19460E−09, A12 = 2.87826E−11 
               
               
                   
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
             
               
               
               
             
               
             
               
               
               
               
               
               
             
               
             
               
               
               
               
               
             
           
               
                 TABLE 6 
               
               
                   
               
               
                 (Various data) 
               
               
                   
               
             
             
               
                 Zooming ratio 2.46153 
               
             
          
           
               
                   
                   
                 Wide-angle 
                 Middle 
                 Telephoto 
               
               
                   
                   
                 limit 
                 position 
                 limit 
               
               
                   
                   
               
               
                   
                 Focal length 
                 12.4800 
                 19.5303 
                 30.7200 
               
               
                   
                 F-number 
                 3.62286 
                 4.70493 
                 5.83562 
               
               
                   
                 Half view angle 
                 44.9235 
                 29.9783 
                 19.1404 
               
               
                   
                 Image height 
                 10.8150 
                 10.8150 
                 10.8150 
               
               
                   
                 Overall length 
                 65.3658 
                 63.3359 
                 63.6079 
               
               
                   
                 of lens system 
               
               
                   
                 BF 
                 14.19915 
                 14.19920 
                 14.19922 
               
               
                   
                 d6 
                 18.2733 
                 8.9425 
                 1.7736 
               
               
                   
                 d13 
                 4.9675 
                 8.6184 
                 16.0093 
               
               
                   
                 d15 
                 4.6258 
                 8.2758 
                 8.3258 
               
               
                   
                 Entrance pupil 
                 10.6761 
                 8.7730 
                 6.3908 
               
               
                   
                 position 
               
               
                   
                 Exit pupil 
                 −27.9972 
                 −51.8418 
                 −68.7119 
               
               
                   
                 position 
               
               
                   
                 Front principal 
                 19.4651 
                 22.5276 
                 25.7285 
               
               
                   
                 points position 
               
               
                   
                 Back principal 
                 52.8857 
                 43.8056 
                 32.8879 
               
               
                   
                 points position 
               
               
                   
                   
               
             
          
           
               
                 Single lens data 
               
             
          
           
               
                 Lens 
                 Initial surface 
                 Focal 
               
               
                 element 
                 number 
                 length 
               
               
                   
               
               
                 1 
                 1 
                 −16.8095 
               
               
                 2 
                 3 
                 −28.1316 
               
               
                 3 
                 5 
                 28.5839 
               
               
                 4 
                 8 
                 16.0803 
               
               
                 5 
                 10 
                 −8.9534 
               
               
                 6 
                 12 
                 9.0298 
               
               
                 7 
                 14 
                 −22.5722 
               
               
                 8 
                 16 
                 31.5217 
               
               
                   
               
             
          
           
               
                 Zoom lens unit data 
               
             
          
           
               
                   
                   
                   
                   
                 Front 
                 Back 
               
               
                   
                 Initial 
                   
                 Overall 
                 principal 
                 principal 
               
               
                 Lens 
                 surface 
                 Focal 
                 length of 
                 points 
                 points 
               
               
                 unit 
                 No. 
                 length 
                 lens unit 
                 position 
                 position 
               
               
                   
               
               
                 1 
                 1 
                 −17.05925 
                 9.30000 
                 0.42826 
                 1.90725 
               
               
                 2 
                 7 
                 15.96962 
                 9.33000 
                 2.28401 
                 3.78521 
               
               
                 3 
                 14 
                 −22.57224 
                 0.80000 
                 0.33516 
                 0.61957 
               
               
                 4 
                 16 
                 31.52167 
                 3.87000 
                 1.21951 
                 2.65049 
               
               
                   
               
             
          
           
               
                 Magnification of zoom lens unit 
               
             
          
           
               
                   
                 Initial 
                   
                   
                   
               
               
                 Lens 
                 surface 
                 Wide-angle 
                 Middle 
                 Telephoto 
               
               
                 unit 
                 No. 
                 limit 
                 position 
                 limit 
               
               
                   
               
               
                 1 
                 1 
                 0.00000 
                 0.00000 
                 0.00000 
               
               
                 2 
                 7 
                 −0.54992 
                 −0.81027 
                 −1.27349 
               
               
                 3 
                 14 
                 2.60409 
                 2.76580 
                 2.76802 
               
               
                 4 
                 16 
                 0.51086 
                 0.51085 
                 0.51085 
               
               
                   
               
             
          
         
       
     
       Numerical Example 3 
       [0157]    The zoom lens system of Numerical Example 3 corresponds to Embodiment 3 shown in  FIG. 5 . Table 7 shows the surface data of the zoom lens system of Numerical Example 3. Table 8 shows the aspherical data. Table 9 shows the various data. 
         [0000]    
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE 7 
               
             
             
               
                   
               
               
                 (Surface data) 
               
             
          
           
               
                 Surface number 
                 r 
                 d 
                 nd 
                 vd 
               
               
                   
               
               
                 Object surface 
                 ∞ 
                   
                   
                   
               
               
                  1 
                 21.00190 
                 0.70000 
                 1.95375 
                 32.3 
               
               
                  2 
                 9.60990 
                 4.81600 
               
               
                  3* 
                 −71.95040 
                 0.80000 
                 1.80998 
                 40.9 
               
               
                  4* 
                 22.31910 
                 0.41100 
               
               
                  5 
                 15.17570 
                 1.99480 
                 2.00272 
                 19.3 
               
               
                  6 
                 36.47600 
                 Variable 
               
               
                  7(Diaphragm) 
                 ∞ 
                 1.00000 
               
               
                  8* 
                 11.84810 
                 2.50000 
                 1.80998 
                 40.9 
               
               
                  9* 
                 −220.70170 
                 2.38600 
               
               
                 10 
                 89.66070 
                 0.80000 
                 1.90366 
                 31.3 
               
               
                 11 
                 6.83550 
                 0.01000 
                 1.56732 
                 42.8 
               
               
                 12 
                 6.83550 
                 2.74830 
                 1.59282 
                 68.6 
               
               
                 13 
                 −18.13250 
                 Variable 
               
               
                 14 
                 −60.36680 
                 0.60000 
                 1.51760 
                 63.5 
               
               
                 15* 
                 12.95890 
                 Variable 
               
               
                 16* 
                 60.77360 
                 4.45510 
                 1.58913 
                 61.3 
               
               
                 17* 
                 −24.74990 
                 (BF) 
               
               
                 Image surface 
                 ∞ 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
             
           
               
                 TABLE 8 
               
               
                   
               
               
                 (Aspherical data) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Surface No. 3 
               
               
                   
                 K = 0.00000E+00, A4 = 7.75922E−05, A6 = 1.09510E−06, 
               
               
                   
                 A8 = −4.41288E−08 A10 = 3.92774E−10 
               
               
                   
                 Surface No. 4 
               
               
                   
                 K = 0.00000E+00, A4 = 8.43604E−05, A6 = 1.49011E−06, 
               
               
                   
                 A8 = −6.21553E−08 A10 = 5.77970E−10 
               
               
                   
                 Surface No. 8 
               
               
                   
                 K = 0.00000E+00, A4 = −5.38137E−05, A6 = 6.17057E−07, 
               
               
                   
                 A8 = −9.65154E−08 A10 = −3.50025E−10 
               
               
                   
                 Surface No. 9 
               
               
                   
                 K = 0.00000E+00, A4 = 2.99230E−05, A6 = 2.22507E−07, 
               
               
                   
                 A8 = −1.34771E−07 A10 = 6.22151E−10 
               
               
                   
                 Surface No. 15 
               
               
                   
                 K = 0.00000E+00, A4 = 1.11804E−04, A6 = −2.09485E−06, 
               
               
                   
                 A8 = 0.00000E+00 A10 = 0.00000E+00 
               
               
                   
                 Surface No. 16 
               
               
                   
                 K = 0.00000E+00, A4 = 5.08926E−05, A6 = −1.10680E−07, 
               
               
                   
                 A8 = 0.00000E+00 A10 = 0.00000E+00 
               
               
                   
                 Surface No. 17 
               
               
                   
                 K = 0.00000E+00, A4 = 5.67430E−06, A6 = 5.75636E−08, 
               
               
                   
                 A8 = 0.00000E+00 A10 = 0.00000E+00 
               
               
                   
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
             
               
               
               
             
               
             
               
               
               
               
               
               
             
               
             
               
               
               
               
               
             
           
               
                 TABLE 9 
               
               
                   
               
               
                 (Various data) 
               
               
                   
               
             
             
               
                 Zooming ratio 2.74164 
               
             
          
           
               
                   
                   
                 Wide-angle 
                 Middle 
                 Telephoto 
               
               
                   
                   
                 limit 
                 position 
                 limit 
               
               
                   
                   
               
               
                   
                 Focal length 
                 12.5399 
                 20.7134 
                 34.3799 
               
               
                   
                 F-number 
                 3.58518 
                 5.25686 
                 5.83600 
               
               
                   
                 Half view angle 
                 44.7801 
                 28.1443 
                 17.3825 
               
               
                   
                 Image height 
                 10.8150 
                 10.8150 
                 10.8150 
               
               
                   
                 Overall length 
                 64.4404 
                 60.6907 
                 64.1196 
               
               
                   
                 of lens system 
               
               
                   
                 BF 
                 14.19787 
                 14.19842 
                 14.19834 
               
               
                   
                 d6 
                 18.3000 
                 8.1818 
                 1.8918 
               
               
                   
                 d13 
                 3.9057 
                 8.6887 
                 16.4544 
               
               
                   
                 d15 
                 4.8156 
                 6.4006 
                 8.3539 
               
               
                   
                 Entrance pupil 
                 10.9672 
                 8.7488 
                 6.4021 
               
               
                   
                 position 
               
               
                   
                 Exit pupil 
                 −28.3950 
                 −43.2335 
                 −75.5372 
               
               
                   
                 position 
               
               
                   
                 Front principal 
                 19.8152 
                 21.9917 
                 27.6102 
               
               
                   
                 points position 
               
               
                   
                 Back principal 
                 51.9004 
                 39.9773 
                 29.7397 
               
               
                   
                 points position 
               
               
                   
                   
               
             
          
           
               
                 Single lens data 
               
             
          
           
               
                 Lens 
                 Initial surface 
                 Focal 
               
               
                 element 
                 number 
                 length 
               
               
                   
               
               
                 1 
                 1 
                 −19.1501 
               
               
                 2 
                 3 
                 −20.9517 
               
               
                 3 
                 5 
                 24.7565 
               
               
                 4 
                 8 
                 13.9495 
               
               
                 5 
                 10 
                 −8.2262 
               
               
                 6 
                 12 
                 8.7314 
               
               
                 7 
                 14 
                 −20.5545 
               
               
                 8 
                 16 
                 30.4411 
               
               
                   
               
             
          
           
               
                 Zoom lens unit data 
               
             
          
           
               
                   
                   
                   
                   
                 Front 
                 Back 
               
               
                   
                 Initial 
                   
                 Overall 
                 principal 
                 principal 
               
               
                 Lens 
                 surface 
                 Focal 
                 length of 
                 points 
                 points 
               
               
                 unit 
                 No. 
                 length 
                 lens unit 
                 position 
                 position 
               
               
                   
               
               
                 1 
                 1 
                 −16.09156 
                 8.72180 
                 1.38242 
                 3.31821 
               
               
                 2 
                 7 
                 14.82467 
                 9.44430 
                 1.81106 
                 3.80453 
               
               
                 3 
                 14 
                 −20.55451 
                 0.60000 
                 0.32458 
                 0.53032 
               
               
                 4 
                 16 
                 30.44114 
                 4.45510 
                 2.03141 
                 3.62782 
               
               
                   
               
             
          
           
               
                 Magnification of zoom lens unit 
               
             
          
           
               
                   
                 Initial 
                   
                   
                   
               
               
                 Lens 
                 surface 
                 Wide-angle 
                 Middle 
                 Telephoto 
               
               
                 unit 
                 No. 
                 limit 
                 position 
                 limit 
               
               
                   
               
               
                 1 
                 1 
                 0.00000 
                 0.00000 
                 0.00000 
               
               
                 2 
                 7 
                 −0.55354 
                 −0.88966 
                 −1.42911 
               
               
                 3 
                 14 
                 2.77995 
                 2.85717 
                 2.95219 
               
               
                 4 
                 16 
                 0.50642 
                 0.50640 
                 0.50640 
               
               
                   
               
             
          
         
       
     
         [0158]    The following Table 10 shows the corresponding values to the individual conditions in the zoom lens systems of each of Numerical Examples. 
         [0000]    
       
         
               
             
               
               
             
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 10 
               
             
             
               
                   
               
               
                 (Values corresponding to conditions) 
               
             
          
           
               
                   
                 Numerical Example 
               
             
          
           
               
                 Condition 
                 1 
                 2 
                 3 
               
               
                   
               
             
          
           
               
                 (1) 
                 (D aW  − D aT )/TL W   
                 0.240 
                 0.252 
                 0.255 
               
               
                 (2) 
                 TG 2G /TG all   
                 0.395 
                 0.374 
                 0.380 
               
               
                 (3) 
                 TL W  − TL T   
                 1.89 
                 1.76 
                 0.32 
               
               
                 (4) 
                 TG all /TL W   
                 0.337 
                 0.341 
                 0.345 
               
               
                 (5) 
                 nd L1   
                 1.91082 
                 1.90366 
                 1.95375 
               
               
                 (6) 
                 |Σ1/(f i  × vd i )| 
                 3.785E−04 
                 4.334E−04 
                 2.743E−05 
               
               
                   
               
             
          
         
       
     
         [0159]    The present disclosure is applicable to a digital still camera, a digital video camera, a camera for a mobile terminal device such as a smart-phone, a camera for a PDA (Personal Digital Assistance), a surveillance camera in a surveillance system, a Web camera, a vehicle-mounted camera or the like. In particular, the present disclosure is applicable to a photographing optical system where high image quality is required like in a digital still camera system or a digital video camera system. 
         [0160]    Also, the present disclosure is applicable to, among the interchangeable lens apparatuses according to the present disclosure, an interchangeable lens apparatus having motorized zoom function, i.e., activating function for the zoom lens system by a motor, with which a digital video camera system is provided. 
         [0161]    As described above, embodiments have been described as examples of art in the present disclosure. Thus, the attached drawings and detailed description have been provided. 
         [0162]    Therefore, in order to illustrate the art, not only essential elements for solving the problems but also elements that are not necessary for solving the problems may be included in elements appearing in the attached drawings or in the detailed description. Therefore, such unnecessary elements should not be immediately determined as necessary elements because of their presence in the attached drawings or in the detailed description. 
         [0163]    Further, since the embodiments described above are merely examples of the art in the present disclosure, it is understood that various modifications, replacements, additions, omissions, and the like can be performed in the scope of the claims or in an equivalent scope thereof.