Patent Publication Number: US-10761304-B2

Title: Zoom optical system, optical apparatus and method for manufacturing the zoom optical system

Description:
TECHNICAL FIELD 
     The present invention relates to a zoom optical system, an optical apparatus using the same and a method for manufacturing the zoom optical system. 
     TECHNICAL BACKGROUND 
     A zoom optical system suitable for photographic cameras, electronic still cameras, video cameras, and the like has conventionally been proposed (see, for example, Patent Document 1). Optical performance of such a conventional zoom optical system has been insufficient. 
     PRIOR ARTS LIST 
     Patent Document 
     Patent Document 1: Japanese Laid-Open Patent Publication No. H4-293007 (A) 
     SUMMARY OF THE INVENTION 
     A zoom optical system according to the present invention comprises, in order from an object: a first lens group having positive refractive power; an intermediate group including at least one lens group and having negative refractive power as a whole; an intermediate side lens group having positive refractive power; a subsequent side lens group having positive refractive power; and a subsequent group including at least one lens group. Upon zooming, distances between the first lens group and the intermediate group, between the intermediate group and the intermediate side lens group, between the intermediate side lens group and the subsequent side lens group, and between the subsequent side lens group and the subsequent group change. The subsequent side lens group moves upon focusing. The intermediate group includes a partial group satisfying following conditional expressions:
 
1.4&lt; fvr/fMt&lt; 2.5; and
 
0.15&lt;(− fvr )/ ft&lt; 0.35
 
     where, 
     fvr denotes a focal length of the partial group, 
     fMt denotes a focal length of the intermediate group in a telephoto end state, and 
     ft denotes a focal length of the zoom optical system in the telephoto end state. 
     An optical apparatus according to the present invention comprises the zoom optical system described above. 
     A method for manufacturing a zoom optical system according to the present invention is a method for manufacturing a zoom optical system which comprises, in order from an object: a first lens group having positive refractive power; an intermediate group including at least one lens group and having negative refractive power as a whole; an intermediate side lens group having positive refractive power; a subsequent side lens group having positive refractive power; and a subsequent group including at least one lens group, the method comprising a step of arranging the lens groups in a lens barrel so that: upon zooming, distances between the first lens group and the intermediate group, between the intermediate group and the intermediate side lens group, between the intermediate side lens group and the subsequent side lens group, and between the subsequent side lens group and the subsequent group change; the subsequent side lens group moves upon focusing; and the intermediate group includes a partial group satisfying following conditional expressions:
 
1.4&lt; fvr/fMt&lt; 2.5; and
 
0.15&lt;(− fvr )/ ft&lt; 0.35
 
     where, 
     fvr denotes a focal length of the partial group, 
     fMt denotes a focal length of the intermediate group in a telephoto end state, and 
     ft denotes a focal length of the zoom optical system in the telephoto end state. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a lens configuration of a zoom optical system according to Example 1 of the present embodiment. 
         FIG. 2A  is a graph showing various aberrations of the zoom optical system according to Example 1 upon focusing on infinity in a wide angle end state, and  FIG. 2B  is a meridional lateral aberration graph in a case where blur correction is performed for the roll blur of 0.30°. 
         FIG. 3  is a graph showing various aberrations of the zoom optical system according to Example 1 upon focusing on infinity in an intermediate focal length state. 
         FIG. 4A  is a graph showing various aberrations of the zoom optical system according to Example 1 upon focusing on infinity in a telephoto end state, and  FIG. 4B  is a meridional lateral aberration graph in a case where blur correction is performed for the roll blur of 0.20°. 
         FIGS. 5A, 5B, and 5C  are graphs showing various aberrations of the zoom optical system according to Example 1 upon focusing on a short distant object, respectively in the wide angle end state, the intermediate focal length state, and the telephoto end state. 
         FIG. 6  is a diagram illustrating a lens configuration of a zoom optical system according to Example 2 of the present embodiment. 
         FIG. 7A  is a graph showing various aberrations of the zoom optical system according to Example 2 upon focusing on infinity in the wide angle end state, and  FIG. 7B  is a meridional lateral aberration graph in a case where blur correction is performed for the roll blur of 0.30°. 
         FIG. 8  is a graph showing various aberrations of the zoom optical system according to Example 2 upon focusing on infinity in the intermediate focal length state. 
         FIG. 9A  is a graph showing various aberrations of the zoom optical system according to Example 2 upon focusing on infinity in the telephoto end state, and  FIG. 9B  is a meridional lateral aberration graph in a case where blur correction is performed for the roll blur of 0.20°. 
         FIGS. 10A, 10B, and 10C  are graphs showing various aberrations of the zoom optical system according to Example 2 upon focusing on a short distant object, respectively in the wide angle end state, the intermediate focal length state, and the telephoto end state. 
         FIG. 11  is a diagram illustrating a lens configuration of a zoom optical system according to Example 3 of the present embodiment. 
         FIG. 12A  is a graph showing various aberrations of the zoom optical system according to Example 3 upon focusing on infinity in the wide angle end state, and  FIG. 12B  is a meridional lateral aberration graph in a case where blur correction is performed for the roll blur of 0.30°. 
         FIG. 13  is a graph showing various aberrations of the zoom optical system according to Example 3 upon focusing on infinity in the intermediate focal length state. 
         FIG. 14A  is a graph showing various aberrations of the zoom optical system according to Example 3 upon focusing on infinity in the telephoto end state, and  FIG. 14B  is a meridional lateral aberration graph in a case where blur correction is performed for the roll blur of 0.20°. 
         FIGS. 15A, 15B, and 15C  are graphs showing various aberrations of the zoom optical system according to Example 3 upon focusing on a short distant object, respectively in the wide angle end state, the intermediate focal length state, and the telephoto end state. 
         FIG. 16  is a diagram illustrating a lens configuration of a zoom optical system according to Example 4 of the present embodiment. 
         FIG. 17A  is a graph showing various aberrations of the zoom optical system according to Example 4 upon focusing on infinity in the wide angle end state, and  FIG. 17B  is a meridional lateral aberration graph in a case where blur correction is performed for the roll blur of 0.30°. 
         FIG. 18  is a graph showing various aberrations of the zoom optical system according to Example 4 upon focusing on infinity in the intermediate focal length state. 
         FIG. 19A  is a graph showing various aberrations of the zoom optical system according to Example 4 upon focusing on infinity in the telephoto end state, and  FIG. 19B  is a meridional lateral aberration graph in a case where blur correction is performed for the roll blur of 0.20°. 
         FIGS. 20A, 20B, and 20C  are graphs showing various aberrations of the zoom optical system according to Example 4 upon focusing on a short distant object, respectively in the wide angle end state, the intermediate focal length state, and the telephoto end state. 
         FIG. 21  is a diagram illustrating a lens configuration of a zoom optical system according to Example 5 of the present embodiment. 
         FIG. 22A  is a graph showing various aberrations of the zoom optical system according to Example 5 upon focusing on infinity in the wide angle end state, and  FIG. 22B  is a meridional lateral aberration graph in a case where blur correction is performed for the roll blur of 0.30°. 
         FIG. 23  is a graph showing various aberrations of the zoom optical system according to Example 5 upon focusing on infinity in the intermediate focal length state. 
         FIG. 24A  is a graph showing various aberrations of the zoom optical system according to Example 5 upon focusing on infinity in the telephoto end state, and  FIG. 24B  is a meridional lateral aberration graph in a case where blur correction is performed for the roll blur of 0.20°. 
         FIGS. 25A, 25B, and 25C  are graphs showing various aberrations of the zoom optical system according to Example 5 upon focusing on a short distant object, respectively in the wide angle end state, the intermediate focal length state, and the telephoto end state. 
         FIG. 26  is a diagram illustrating a lens configuration of a zoom optical system according to Example 6 of the present embodiment. 
         FIG. 27A  is a graph showing various aberrations of the zoom optical system according to Example 6 upon focusing on infinity in the wide angle end state, and  FIG. 27B  is a meridional lateral aberration graph in a case where blur correction is performed for the roll blur of 0.30°. 
         FIG. 28  is a graph showing various aberrations of the zoom optical system according to Example 6 upon focusing on infinity in the intermediate focal length state. 
         FIG. 29A  is a graph showing various aberrations of the zoom optical system according to Example 6 upon focusing on infinity in the telephoto end state, and  FIG. 29B  is a meridional lateral aberration graph in a case where blur correction is performed for the roll blur of 0.20°. 
         FIGS. 30A, 30B, and 30C  are graphs showing various aberrations of the zoom optical system according to Example 6 upon focusing on a short distant object, respectively in the wide angle end state, the intermediate focal length state, and the telephoto end state. 
         FIG. 31  is a diagram illustrating a configuration of a camera comprising the zoom optical system according to the present embodiment. 
         FIG. 32  is a flowchart illustrating a method for manufacturing the zoom optical system according to the present embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     A zoom optical system and an optical apparatus according to the present embodiment are described below with reference to the drawings. As illustrated in  FIG. 1 , a zoom optical system ZL( 1 ) as an example of a zoom optical system (zoom lens) ZL according to the present embodiment comprises, in order from an object: a first lens group G 1  having positive refractive power; an intermediate group GM (second lens group G 2 ) including at least one lens group and having negative refractive power as a whole; an intermediate side lens group GRP 1  (third lens group G 3 ) having positive refractive power; a subsequent side lens group GRP 2  (fourth lens group G 4 ) having positive refractive power; and a subsequent group GR (fifth lens group G 5 ) including at least one lens group. Upon zooming, distances between the first lens group G 1  and the intermediate group GM, between the intermediate group GM and the intermediate side lens group GRP 1 , between the intermediate side lens group GRP 1  and the subsequent side lens group GRP 2 , and between the subsequent side lens group GRP 2  and the subsequent group GR change. The subsequent side lens group GRP 2  moves as a focusing lens group upon focusing. 
     The zoom optical system ZL according to the present embodiment may also be a zoom optical system ZL( 2 ) illustrated in  FIG. 6 , a zoom optical system ZL( 3 ) illustrated in  FIG. 11 , a zoom optical system ZL( 4 ) illustrated in  FIG. 16 , a zoom optical system ZL( 5 ) illustrated in  FIG. 21 , or a zoom optical system ZL( 6 ) illustrated in  FIG. 26 . The zoom optical systems ZL( 2 ), ZL( 3 ), and ZL( 4 ) respectively illustrated in  FIGS. 6, 11, and 16  have the same configuration as the zoom optical system ZL( 1 ) illustrated in  FIG. 1 . In the zoom optical system ZL( 5 ) illustrated in  FIG. 21 , the intermediate group GM (second lens group G 2 ), the intermediate side lens group GRP 1  (third lens group G 3 ), and the subsequent side lens group GRP 2  (fourth lens group G 4 ) have the same configurations as those in the zoom optical system ZL( 1 ) illustrated in  FIG. 1 . The subsequent group GR consists of the fifth lens group G 5  and a sixth lens group G 6 . In the zoom optical system ZL( 6 ) illustrated in  FIG. 26 , the intermediate group GM consists of the second lens group G 2  and the third lens group G 3 , the intermediate side lens group GRP 1  consists of the fourth lens group G 4 , the subsequent side lens group GRP 2  consists of the fifth lens group G 5 , and the subsequent group GR consists of the sixth lens group G 6 . 
     The zoom optical system ZL according to the present embodiment comprises at least five lens groups, and the distances among the lens groups change upon zooming. Thus, successful aberration correction can be achieved upon zooming. Focusing is performed with the subsequent side lens group GRP 2  serving as the focusing lens group, and thus the focusing lens group can be small and light weight. The intermediate group GM includes a vibration-proof lens group movable to have a component in a direction orthogonal to the optical axis to correct image blur. This effectively prevents the performance from being compromised by camera shake correction. 
     An aperture stop is preferably disposed to an object side or an image side of the intermediate side lens group GRP 1 . The aperture stop may be disposed between lenses forming the intermediate side lens group GRP 1 . 
     The intermediate group GM preferably comprises negative refractive power as a whole from the wide angle end state to the telephoto end state. For example, the intermediate group GM may consist of one lens group having negative refractive power, or may consist of two lens groups each having negative refractive power. For example, the intermediate group GM may consist of two lens groups including, in order from the object, a lens group having positive refractive power and a lens group having negative refractive power, or may consist of two lens groups including, in order from the object, a lens group having negative refractive power and a lens group having positive refractive power. 
     The subsequent group GR preferably comprises negative or positive refractive power as a whole. For example, the subsequent group GR may consist of one lens group having negative refractive power, or may consist of two lens groups each having negative refractive power. 
     A plurality of lens groups may be configured to move along the same movement locus upon zooming. Preferably, at least one lens group in the intermediate side lens group GRP 1  and at least one lens group in the subsequent group GR are configured to move along the same movement locus. More preferably, at least one lens group in the first lens group G 1 , at least one lens group in the intermediate side lens group GRP 1 , and at least one lens group in the subsequent group GR are configured to move along the same movement locus. 
     The zoom optical system ZL according to the present embodiment having the configuration described above includes the intermediate group GM comprising a partial group satisfying the following conditional expressions.
 
1.4&lt; fvr/fMt&lt; 2.5  (1)
 
0.15&lt;(− fvr )/ ft&lt; 0.35  (2)
 
     where, 
     fvr denotes a focal length of the partial group, 
     fMt denotes a focal length of the intermediate group GM in the telephoto end state, and 
     ft denotes a focal length of the zoom optical system ZL in the telephoto end state. 
     The conditional expression (1) is for setting an appropriate range of a ratio between the focal lengths of the partial group (provided in the intermediate group GM) and the intermediate group GM in the telephoto end state. Variation of various aberrations including the spherical aberration can be prevented upon zooming and various aberrations including decentering coma aberration can be prevented upon blur correction, when the conditional expression (1) is satisfied. The partial group according to the present embodiment includes some of lenses in a lens group in the intermediate group GM or includes all of the lenses in a lens group in the intermediate group GM. 
     A value higher than the upper limit value of the conditional expression (1) leads to large refractive power of the intermediate group GM, rendering variation of various aberrations including the spherical aberration upon zooming difficult to prevent. The effects of the present embodiment can be more effectively guaranteed with the upper limit value of the conditional expression (1) set to be 2.3. To more effectively guarantee the effects of the present embodiment, the upper limit value of the conditional expression (1) is preferably set to be 2.1. 
     A value lower than the lower limit value of the conditional expression (1) leads to large refractive power of the partial group, rendering various aberrations including the decentering coma aberration upon blur correction difficult to prevent. The effects of the present embodiment can be more effectively guaranteed with the lower limit value of the conditional expression (1) set to be 1.5. To more effectively guarantee the effects of the present embodiment, the lower limit value of the conditional expression (1) is preferably set to be 1.6. 
     The conditional expression (2) is for setting an appropriate range of a ratio between the focal lengths of the partial group (provided in the intermediate group GM) and the zoom optical system ZL in the telephoto end state. Various aberrations including the decentering coma aberration can be prevented upon blur correction without using a large barrel, when the conditional expression (2) is satisfied. 
     A value higher than the upper limit value of the conditional expression (2) leads to small refractive power of the partial group, resulting in a large movement amount of the vibration-proof lens group in a direction orthogonal to the optical axis for blur correction. As a result, a large barrel is required, and various aberrations including the decentering coma aberration becomes difficult to prevent. The effects of the present embodiment can be more effectively guaranteed with the upper limit value of the conditional expression (2) set to be 0.33. To more effectively guarantee the effects of the present embodiment, the upper limit value of the conditional expression (2) is preferably set to be 0.31. 
     A value lower than the lower limit value of the conditional expression (2) leads to large refractive power of the partial group, rendering various aberrations including the decentering coma aberration upon blur correction difficult to prevent. The effects of the present embodiment can be more effectively guaranteed with the lower limit value of the conditional expression (2) set to be 0.17. To more effectively guarantee the effects of the present embodiment, the lower limit value of the conditional expression (2) is preferably set to be 0.19. 
     In the zoom optical system according to the present embodiment, the partial group (provided in the intermediate group GM) is preferably a vibration-proof lens group movable to comprise a component in a direction orthogonal to the optical axis to correct image blur. This effectively prevents the performance from being compromised by blur correction. 
     The zoom optical system according to the present embodiment preferably satisfies the following conditional expression (3).
 
2.9&lt; f 1/(− fMt )&lt;5.5  (3)
 
     where, 
     f1 denotes a focal length of the first lens group G 1 . 
     The conditional expression (3) is for setting an appropriate range of a ratio between the focal lengths of the first lens group G 1  and the intermediate group GM in the telephoto end state. Variation of various aberrations including the spherical aberration can be prevented upon zooming when the conditional expression (3) is satisfied. 
     A value higher than the upper limit value of the conditional expression (3) leads to large refractive power of the intermediate group GM, rendering variation of various aberrations including the spherical aberration upon zooming difficult to prevent. The effects of the present embodiment can be more effectively guaranteed with the upper limit value of the conditional expression (3) set to be 5.2. To more effectively guarantee the effects of the present embodiment, the upper limit value of the conditional expression (3) is preferably set to be 4.9. 
     A value lower than the lower limit value of the conditional expression (3) leads to large refractive power of the first lens group G 1 , rendering various aberrations including the spherical aberration upon zooming difficult to correct. The effects of the present embodiment can be more effectively guaranteed with the lower limit value of the conditional expression (3) set to be 3.1. To more effectively guarantee the effects of the present embodiment, the lower limit value of the conditional expression (3) is preferably set to be 3.3. 
     The zoom optical system according to the present embodiment preferably has a configuration in which the first lens group G 1  moves toward the object upon zooming from the wide angle end state to the telephoto end state. With this configuration, a short total length of the lenses in the wide angle end state can be achieved, whereby a small size of the zoom optical system can be achieved. 
     The zoom optical system according to the present embodiment preferably comprises the subsequent side lens group GRP 2  having at least one lens having positive refractive power and at least one lens having negative refractive power. With this configuration, variation of various aberrations including the spherical aberration can be prevented upon focusing. 
     The zoom optical system according to the present embodiment preferably satisfies the following conditional expression (4).
 
0.2&lt; fP /(− fN )&lt;0.8  (4)
 
     where, 
     fP denotes a focal length of a lens with largest positive refractive power in the subsequent side lens group GRP 2 , and 
     fN denotes a focal length of a lens with largest negative refractive power in the subsequent side lens group GRP 2 . 
     The conditional expression (4) is for defining an appropriate range of a ratio between the focal lengths of the lens with the largest positive refractive power in the subsequent side lens group GRP 2  and the lens with the largest negative refractive power in the subsequent side lens group GRP 2 . Variation of various aberrations including the spherical aberration can be prevented upon focusing when the conditional expression (4) is satisfied. 
     A value higher than the upper limit value of the conditional expression (4) leads to large refractive power of the lens with the largest negative refractive power in the subsequent side lens group GRP 2 , rendering variation of various aberrations including the spherical aberration upon focusing difficult to prevent. The effects of the present embodiment can be more effectively guaranteed with the upper limit value of the conditional expression (4) set to be 0.75. To more effectively guarantee the effects of the present embodiment, the upper limit value of the conditional expression (4) is preferably set to be 0.70. 
     A value lower than the lower limit value of the conditional expression (4) leads to large refractive power of the lens with the largest positive refractive power in the subsequent side lens group GRP 2 , rendering variation of various aberrations including the spherical aberration upon focusing difficult to prevent. The effects of the present embodiment can be more effectively guaranteed with the lower limit value of the conditional expression (4) set to be 0.25. To more effectively guarantee the effects of the present embodiment, the lower limit value of the conditional expression (4) is preferably set to be 0.30. 
     The zoom optical system according to the present embodiment preferably comprises the first lens group G 1  including, in order from an object: a 1-1st lens having positive refractive power; a 1-2nd lens having negative refractive power; and a 1-3rd lens having positive refractive power. With this configuration, the spherical aberration and the chromatic aberration can be successfully corrected. 
     The zoom optical system according to the present embodiment preferably satisfies the following conditional expression (5).
 
0.85&lt; nP/nN&lt; 1.00  (5)
 
     where, 
     nP denotes a refractive index of a lens with largest positive refractive power in the first lens group G 1 , and 
     nN denotes a refractive index of a lens with largest negative refractive power in the first lens group G 1 . 
     The conditional expression (5) is for defining an appropriate range of a ratio between the refractive indices of the lens with the largest positive refractive power in the first lens group G 1  and the lens with the largest negative refractive power in the first lens group G 1 . Various aberrations including the spherical aberration can be successfully corrected when the conditional expression (5) is satisfied. 
     A value higher than the upper limit value of the conditional expression (5) leads to a small refractive index of the lens with the largest negative refractive power in the first lens group G 1 , rendering various aberrations including the spherical aberration difficult to correct. The effects of the present embodiment can be more effectively guaranteed with the upper limit value of the conditional expression (5) set to be 0.98. To more effectively guarantee the effects of the present embodiment, the upper limit value of the conditional expression (5) is preferably set to be 0.96. 
     A value lower than the lower limit value of the conditional expression (5) leads to a small refractive index of the lens with the largest positive refractive power in the first lens group G 1 , leading to extremely large spherical aberration that is difficult to correct. The effects of the present embodiment can be more effectively guaranteed with the lower limit value of the conditional expression (5) set to be 0.86. To more effectively guarantee the effects of the present embodiment, the lower limit value of the conditional expression (5) is preferably set to be 0.87. 
     The zoom optical system according to the present embodiment preferably satisfies the following conditional expression (6).
 
2.25&lt; νP/νN&lt; 2.90  (6)
 
     where, 
     νP denotes an Abbe number of the lens with the largest positive refractive power in the first lens group G 1 , and 
     νN denotes an Abbe number of the lens with the largest negative refractive power in the first lens group G 1 . 
     The conditional expression (6) is for defining an appropriate range of a ratio between the Abbe numbers of the lens with the largest positive refractive power in the first lens group G 1  and the lens with the largest negative refractive power in the first lens group G 1 . The chromatic aberration can be successfully corrected when the conditional expression (6) is satisfied. 
     A value higher than the upper limit value of the conditional expression (6) leads to a small Abbe number of the lens with the largest negative refractive power in the first lens group G 1 , resulting in an extremely large chromatic aberration that is difficult to correct. The effects of the present embodiment can be more effectively guaranteed with the upper limit value of the conditional expression (6) set to be 2.85. To more effectively guarantee the effects of the present embodiment, the upper limit value of the conditional expression (6) is preferably set to be 2.80. 
     A value lower than the lower limit value of the conditional expression (6) leads to a small Abbe number of the lens with the largest positive refractive power in the first lens group G 1 , leading to extremely large chromatic aberration that is difficult to correct. The effects of the present embodiment can be more effectively guaranteed with the lower limit value of the conditional expression (6) set to be 2.30. To more effectively guarantee the effects of the present embodiment, the lower limit value of the conditional expression (6) is preferably set to be 2.35. 
     The optical apparatus according to the present embodiment comprises the zoom optical system with the configuration described above. A camera (optical apparatus) including the zoom optical system ZL is described, as a specific example, with reference to  FIG. 31 . This camera  1  is a digital camera including the zoom optical system according to the present embodiment serving as an imaging lens  2  as illustrated in  FIG. 31 . In the camera  1 , the imaging lens  2  collects light from an object (subject) (not illustrated), and then the light reaches an image sensor  3 . Thus, an image based on the light from the subject is formed with the image sensor  3  to be stored as a subject image in a memory (not illustrated). In this manner, the photographer can capture an image of the subject with the camera  1 . The camera may be a mirrorless camera, or may be a single lens reflex camera having a quick return mirror. 
     With the configuration described above, the camera  1  comprising the zoom optical system ZL serving as the imaging lens  2  can have the subsequent side lens group GRP 2  serving as the focusing lens group that is small and light weight, and thus quick and quiet AF (autofocus) can be achieved without using a large barrel. Furthermore, with this configuration, variation of aberrations upon zooming from the wide angle end state to the telephoto end state, as well as variation of aberrations upon focusing on a short distant object from an infinite distant object can be successfully prevented, whereby excellent optical performance can be achieved. 
     Next, a method for manufacturing the zoom optical system ZL described above is described with reference to  FIG. 32 . First of all, in order from the object, the first lens group G 1  having positive refractive power, the intermediate group GM including at least one lens group and having negative refractive power, the intermediate side lens group GRP 1  having positive refractive power, the subsequent side lens group GRP 2  having positive refractive power, and the subsequent group GR including at least one lens group are arranged in a barrel (step ST 1 ). The lens groups are arranged in the lens barrel so that, upon zooming, the distances between the first lens group G 1  and the intermediate group GM, between the intermediate group GM and the intermediate side lens group GRP 1 , between the intermediate side lens group GRP 1  and the subsequent side lens group GRP 2 , and between the subsequent side lens group GRP 2  and the subsequent group GR change (step ST 2 ). The lens groups are arranged in the lens barrel so that the subsequent side lens group GRP 2  moves upon focusing (step ST 3 ). The lens groups are arranged in the lens barrel so that the intermediate group GM comprises the partial group satisfying at least the conditional expressions (1) and (2) described above (step ST 4 ). 
     EXAMPLES 
     Zoom optical systems (zoom lenses) ZL according to Examples of the present embodiment are described below with reference to the drawings.  FIG. 1 ,  FIG. 6 ,  FIG. 11 ,  FIG. 16 ,  FIG. 21 , and  FIG. 26  are cross-sectional views illustrating configurations and refractive power distributions of the zoom optical systems ZL {ZL( 1 ) to ZL( 6 )} according to Examples 1 to 6. In the lower portion of each cross-sectional view of the zoom optical systems ZL( 1 ) to ZL( 6 ), the directions in which the lens groups are moved along the optical axis upon zooming from the wide angle end state (W) to the telephoto end state (T) are shown by arrows. A direction in which the subsequent side lens group GRP 2  serving as the focusing lens group moves upon focusing on a short distant object from infinity is shown by an arrow appended with “focusing”. 
     In  FIGS. 1, 6, 11, 16, 21, and 26 , a combination of a sign G and a number represents each lens group, and a combination of a sign L and a number represents each lens. In each Example, lens groups and the like are each denoted with a combination of the reference sign and numeral independently from other Examples to prevent cumbersomeness due to an excessively wide variety or a large number of signs and numerals. Thus, components in different Examples denoted with the same combination of reference sign and numeral does not necessarily have the same configuration. 
     Tables 1 to 6 include Table 1 that is a specification table of Example 1, Table 2 that is a specification table of Example 2, Table 3 that is a specification table of Example 3, Table 4 that is a specification table of Example 4, Table 5 that is a specification table of Example 5, and Table 6 that is a specification table of Example 6. In Examples, d-line (wavelength λ=587.6 nm) and g-line (wavelength λ=435.8 nm) are selected as calculation targets of the aberration characteristics. 
     In Table [Lens specifications], a surface number represents an order of an optical surface from the object side in a traveling direction of a light beam, R represents a radius of curvature of each optical surface (with a surface having the center of curvature position on the image side provided with a positive value), D represents a distance between each optical surface and the next optical surface (or the image surface) on the optical axis, nd represents a refractive index of a material of an optical member with respect to the d-line, and νd represents an Abbe number of the material of the optical member based on the d-line. In the table, object surface represents an object surface, “∞” of the radius of curvature represents a plane or an aperture, (stop S) represents the aperture stop S, and image surface represents an image surface I. The refractive index nd=1.00000 of air is omitted. 
     Specifically, in Table [Various data], f represents a focal length of the whole zoom lens, FNO represents F number, 2ω represents an angle of view (ω represents a half angle of view (unit: º)), and Ymax represents the maximum image height. TL represents a distance obtained by adding BF to a distance between the lens forefront surface and a lens last surface on the optical axis upon focusing on infinity, and BF (back focus) represents a distance between the lens last surface and the image surface I on the optical axis upon focusing on infinity. These values are provided for each of the zooming states including the wide angle end state (W), the intermediate focal length state (M), and the telephoto end state (T). 
     Table [Variable distance data] includes surface distances corresponding to surfaces corresponding to surface numbers appended with “variable” in Table [Lens specifications] and the next surface. The surface distances are provided for each of the zooming states including the wide angle end state (W), the intermediate focal length state (M), and the telephoto end state (T) upon focusing on infinity and upon focusing on a short distant object. 
     Table [Lens group data] includes the group starting surface (surface closest to the object) and the focal length of each of the first to the fifth (or sixth) lens groups. 
     Table [Conditional expression corresponding value] includes values corresponding to the conditional expressions (1) to (6). 
     The focal length f, the radius of curvature R, the surface distance D and the other units of length described below as all the specification values, which are generally described with “mm” unless otherwise noted should not be construed in a limiting sense because the optical system proportionally expanded or reduced can have a similar or the same optical performance. 
     The description on the tables de scribed above commonly applies to all Examples, and thus will not be redundantly given below. 
     Example 1 
     Example 1 is described with reference to  FIG. 1 ,  FIGS. 2A and 2B ,  FIG. 3 ,  FIGS. 4A and 4B , and  FIGS. 5A-5C  and Table 1.  FIG. 1  is a diagram illustrating a lens configuration of a zoom optical system according to Example 1 of the present embodiment. The zoom optical system ZL( 1 ) according to Example 1 consists of, in order from an object: a first lens group G 1  having positive refractive power; a second lens group G 2  having negative refractive power; a third lens group G 3  having positive refractive power; an aperture stop S; a fourth lens group G 4  having positive refractive power; and a fifth lens group G 5  having negative refractive power. The first to the fifth lens groups G 1  to G 5  each move in a direction indicated by an arrow in  FIG. 1  upon zooming from a wide angle end state (W) to a telephoto end state (T). In this Example, the intermediate group GM includes the second lens group G 2 , the intermediate side lens group GRP 1  includes the third lens group G 3  and the aperture stop S, the subsequent side lens group GRP 2  includes the fourth lens group G 4 , and the subsequent group GR includes the fifth lens group G 5 . A sign (+) or (−) provided to a sign of each lens group represents refractive power of the lens group. The same applies to all of Examples described below. 
     The first lens group G 1  consists of, in order from the object, a positive lens (1-1st lens) L 11  having a biconvex shape and a cemented positive lens consisting of a negative meniscus lens (1-2nd lens) L 12  having a convex surface facing the object and a positive meniscus lens (1-3rd lens) L 13  having a convex surface facing the object. 
     The second lens group G 2  consists of, in order from the object, a negative meniscus lens L 21  having a convex surface facing the object, a positive meniscus lens L 22  having a convex surface facing the object, and a cemented negative lens consisting of a negative lens L 23  having a biconcave shape and a positive meniscus lens L 24  having a convex surface facing the object. 
     The third lens group G 3  consists of, in order from the object, a positive lens L 31  having a biconvex shape and a cemented positive lens consisting of a positive lens L 32  having a biconvex shape and a negative lens L 33  having a biconcave shape. The aperture stop S is disposed in the neighborhood of and to the image side of the third lens group G 3 , and integrally moves with the third lens group G 3  upon zooming. 
     The fourth lens group G 4  consists of a cemented positive lens consisting of a positive lens L 41  having a biconvex shape and a negative meniscus lens L 42  having a concave surface facing the object. 
     The fifth lens group G 5  consists of, in order from the object, a negative lens L 51  having a biconcave shape, a positive meniscus lens L 52  having a concave surface facing the object, a negative meniscus lens L 53  having a concave surface facing the object, and a positive lens L 54  having a biconvex shape. An image surface I is disposed to the image side of the fifth lens group G 5 . 
     In the zoom optical system ZL( 1 ) according to Example 1, the fourth lens group G 4  (subsequent side lens group GRP 2 ) moves toward the object upon focusing from a long distant object to a short distant object. In the zoom optical system ZL( 1 ) according to Example 1, the cemented negative lens consisting of the negative lens L 23  and the positive meniscus lens L 24  in the second lens group G 2  serves as a vibration-proof lens group (partial group), movable in a direction orthogonal to the optical axis, to be in charge of correcting displacement of the imaging position due to camera shake or the like (image blur on the image surface I). 
     To correct roll blur of an angle θ with a focal length of the whole system being f and with a lens having a vibration proof coefficient K (the ratio of the image movement amount on the imaging surface to the movement amount of the moving lens group for camera shake correction), a moving lens group for camera shake correction is moved in the direction orthogonal to the optical axis by (f·tan θ)/K. In the wide angle end state in Example 1, the vibration proof coefficient is 0.97 and the focal length is 72.1 ram, and thus the movement amount of the vibration-proof lens group to correct a roll blur of 0.30° is 0.39 mm. In the telephoto end state in Example 1, the vibration proof coefficient is 2.01 and the focal length is 292.0 mm, and thus the movement amount of the vibration-proof lens group to correct a roll blur of 0.20° is 0.51 mm. 
     Table 1 below lists specification values of the optical system according to Example 1. 
     
       
         
           
               
             
               
                 TABLE 1 
               
               
                   
               
             
            
               
                 [Lens specifications] 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                   
                   
                   
                   
                   
               
               
                 number 
                 R 
                 D 
                 nd 
                 νd 
               
               
                   
               
               
                 Object 
                 ∞ 
                   
                   
                   
                   
               
               
                 surface 
                   
                   
                   
                   
                   
               
               
                 1 
                 443.9646 
                 3.817 
                 1.48749 
                 70.31 
                   
               
               
                 2 
                 −469.6963 
                 0.200 
                   
                   
                   
               
               
                 3 
                 100.9381 
                 1.700 
                 1.67270 
                 32.19 
                   
               
               
                 4 
                 64.8256 
                 8.767 
                 1.49700 
                 81.73 
                   
               
               
                 5 
                 2578.1121 
                 Variable 
                   
                   
                   
               
               
                 6 
                 189.1236 
                 1.000 
                 1.77250 
                 49.62 
                   
               
               
                 7 
                 35.4799 
                 7.123 
                   
                   
                   
               
               
                 8 
                 37.2041 
                 2.691 
                 1.80518 
                 25.45 
                   
               
               
                 9 
                 57.9432 
                 4.513 
                   
                   
                   
               
               
                 10 
                 −64.2854 
                 1.000 
                 1.67003 
                 47.14 
                   
               
               
                 11 
                 37.2626 
                 3.500 
                 1.75520 
                 27.57 
                   
               
               
                 12 
                 146.7584 
                 Variable 
                   
                   
                   
               
               
                 13 
                 107.2202 
                 3.817 
                 1.80610 
                 40.97 
                   
               
               
                 14 
                 −71.1994 
                 0.200 
                   
                   
                   
               
               
                 15 
                 41.9753 
                 5.272 
                 1.49700 
                 81.73 
                   
               
               
                 16 
                 −54.1569 
                 1.000 
                 1.85026 
                 32.35 
                   
               
               
                 17 
                 154.3187 
                 1.508 
                   
                   
                   
               
               
                 18 
                 ∞ 
                 Variable 
                   
                   
                 (Aperture  
               
               
                   
                   
                   
                   
                   
                 stop S)  
               
               
                 19 
                 104.1819 
                 4.528 
                 1.51680 
                 63.88 
                   
               
               
                 20 
                 −28.6539 
                 1.000 
                 1.80100 
                 34.92 
                   
               
               
                 21 
                 −53.7161 
                 Variable 
                   
                   
                   
               
               
                 22 
                 −120.9949 
                 1.000 
                 1.90366 
                 31.27 
                   
               
               
                 23 
                 61.5584 
                 10.276 
                   
                   
                   
               
               
                 24 
                 −319.9239 
                 4.049 
                 1.68893 
                 31.16 
                   
               
               
                 25 
                 −33.0322 
                 16.448 
                   
                   
                   
               
               
                 26 
                 −24.1471 
                 1.000 
                 1.77250 
                 49.62 
                   
               
               
                 27 
                 −213.3380 
                 0.200 
                   
                   
                   
               
               
                 28 
                 79.7473 
                 3.205 
                 1.71736 
                 29.57 
                   
               
               
                 29 
                 −323.3417 
                 BF 
                   
                   
                   
               
               
                 Image 
                 ∞ 
                   
                   
                   
                   
               
               
                 surface 
               
               
                   
               
            
           
           
               
            
               
                 [Various data] 
               
               
                 Zooming rate 4.05 
               
            
           
           
               
               
               
               
            
               
                   
                 W 
                 M 
                 T 
               
               
                   
               
               
                 f 
                 72.1 
                 99.9 
                 292.0 
               
               
                 FNO 
                 4.54 
                 4.73 
                 5.88 
               
               
                 2ω 
                 33.60 
                 23.92 
                 8.26 
               
               
                 Ymax 
                 21.60 
                 21.60 
                 21.60 
               
               
                 TL 
                 193.31 
                 211.69 
                 248.31 
               
               
                 BF 
                 38.31 
                 41.11 
                 61.31 
               
               
                   
               
            
           
           
               
            
               
                 [Various distance data] 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                 W 
                 M 
                 T 
               
               
                   
                 W 
                 M 
                 T 
                 Short 
                 Short 
                 Short 
               
               
                   
                 Infinity 
                 Infinity 
                 Infinity 
                 distant 
                 distant 
                 distant 
               
               
                   
               
               
                 d5  
                 2.000 
                 26.394 
                 73.625 
                 2.000 
                 26.394 
                 73.625 
               
               
                 d12 
                 41.625 
                 32.810 
                 2.000 
                 41.625 
                 32.810 
                 2.000 
               
               
                 d18 
                 21.563 
                 20.201 
                 21.407 
                 20.665 
                 19.062 
                 19.151 
               
               
                 d21 
                 2.000 
                 3.362 
                 2.156 
                 2.899 
                 4.501 
                 4.413 
               
               
                   
               
            
           
           
               
            
               
                 [Lens group data] 
               
            
           
           
               
               
               
            
               
                   
                 Starting 
                 Focal 
               
               
                 Group 
                 surface 
                 length 
               
               
                   
               
               
                 G1 
                 1 
                 169.064 
               
               
                 G2 
                 6 
                 −41.090 
               
               
                 G3 
                 13 
                 50.436 
               
               
                 G4 
                 19 
                 100.808 
               
               
                 G5 
                 22 
                 −52.611 
               
               
                   
               
            
           
           
               
            
               
                 [Conditional expression corresponding value] 
               
            
           
           
               
               
            
               
                 Conditional expression 
                 (1) fvr/fMt = 1.818 
               
               
                 Conditional expression 
                 (2) (−fvr)/ft = 0.256 
               
               
                 Conditional expression 
                 (3) f1/(−fMt) = 4.114 
               
               
                 Conditional expression 
                 (4) fP/(−fN) = 0.564 
               
               
                 Conditional expression 
                 (5) nP/nN = 0.895 
               
               
                 Conditional expression 
                 (6) νP/νN = 2.539 
               
               
                   
               
            
           
         
       
     
       FIG. 2A  is a graph showing various aberrations of the zoom optical system according to Example 1 having a vibration-proof function upon focusing on infinity in the wide angle end state, and  FIG. 2B  is a meridional lateral aberration graph in a case where blur correction is performed for the roll blur of 0.30°.  FIG. 3  is a graph showing various aberrations of the zoom optical system according to Example 1 having the vibration proof function upon focusing on infinity in the intermediate focal length state.  FIG. 4A  is a graph showing various aberrations of the zoom optical system according to Example 1 having a vibration-proof function upon focusing on infinity in the telephoto end state, and  FIG. 4B  is a meridional lateral aberration graph in a case where blur correction is performed for the roll blur of 0.20°.  FIGS. 5A, 5B, and 5C  are graphs showing various aberrations of the zoom optical system according to Example 1 upon focusing on a short distant object, respectively in the wide angle end state, the intermediate focal length state, and the telephoto end state. 
     In the aberration graphs in  FIGS. 2A and 2B ,  FIG. 3 ,  FIGS. 4A and 4B , and  FIGS. 5A-5C , FNO denotes an F number, NA denotes the number of apertures, and Y denotes an image height. The spherical aberration graphs illustrate an F number or the number of apertures corresponding to the maximum aperture, astigmatism graphs and distortion graphs illustrate the maximum image height, and coma aberration graphs illustrate values of image heights. d denotes a d line (wavelength λ=587.6 nm) and g denotes a g line (wavelength λ=435.8 nm). In the astigmatism graphs, a solid line represents a sagittal image surface, and a broken line represents a meridional image surface. In aberration graphs in Examples described below, the same reference signs as in this Example are used, and a redundant description is omitted. 
     It can be seen in these aberration graphs that the zoom optical system according to Example 1 can achieve excellent imaging performance with various aberrations successfully corrected from the wide angle end state to the telephoto end state, and can achieve excellent imaging performance upon focusing on a short distant object. 
     Example 2 
     Example 2 is described with reference to  FIG. 6 ,  FIGS. 7A and 7B ,  FIG. 8 ,  FIGS. 9A and 9B , and  FIGS. 10A-10C  and Table 2.  FIG. 6  is a diagram illustrating a lens configuration of a zoom optical system according to Example 2 of the present embodiment. The zoom optical system ZL( 2 ) according to Example 2 consists of, in order from an object: a first lens group G 1  having positive refractive power; a second lens group G 2  having negative refractive power; a third lens group G 3  having positive refractive power; an aperture stop S; a fourth lens group G 4  having positive refractive power; and a fifth lens group G 5  having negative refractive power. The first to the fifth lens groups G 1  to G 5  each move in a direction indicated by an arrow in  FIG. 6  upon zooming from a wide angle end state (W) to a telephoto end state (T). In this Example, the intermediate group GM includes the second lens group G 2 , the intermediate side lens group GRP 1  includes the third lens group G 3  and the aperture stop S, the subsequent side lens group GRP 2  includes the fourth lens group G 4 , and the subsequent group GR includes the fifth lens group G 5 . 
     The first lens group G 1  consists of, in order from the object, a positive lens (1-1st lens) L 11  having a biconvex shape and a cemented positive lens consisting of a negative meniscus lens (1-2nd lens) L 12  having a convex surface facing the object and a positive meniscus lens (1-3rd lens) L 13  having a convex surface facing the object. 
     The second lens group G 2  consists of, in order from the object, a negative meniscus lens L 21  having a convex surface facing the object, a negative meniscus lens L 22  having a concave surface facing the object, a positive meniscus lens L 23  having a convex surface facing the object, and a cemented negative lens consisting of a negative lens L 24  having a biconcave shape and a positive meniscus lens L 25  having a convex surface facing the object. 
     The third lens group G 3  consists of, in order from the object, a positive lens L 31  having a biconvex shape and a cemented positive lens consisting of a positive lens L 32  having a biconvex shape and a negative lens L 33  having a biconcave shape. The aperture stop S is disposed in the neighborhood of and to the image side of the third lens group G 3 , and integrally moves with the third lens group G 3  upon zooming. 
     The fourth lens group G 4  consists of a cemented positive lens consisting of a positive lens L 41  having a biconvex shape and a negative meniscus lens L 42  having a concave surface facing the object. 
     The fifth lens group G 5  consists of, in order from the object, a negative lens L 51  having a biconcave shape, a positive lens L 52  having a biconvex shape, a negative meniscus lens L 53  having a concave surface facing the object, and a positive lens L 54  having a biconvex shape. An image surface I is disposed to the image side of the fifth lens group G 5 . 
     In the zoom optical system ZL( 2 ) according to Example 2, the fourth lens group G 4  (subsequent side lens group GRP 2 ) moves toward the object upon focusing from a long distant object to a short distant object. In the zoom optical system ZL( 2 ) according to Example 2, the cemented negative lens consisting of the negative lens L 24  and the positive meniscus lens L 25  in the second lens group G 2  serves as a vibration-proof lens group (partial group), movable in a direction orthogonal to the optical axis, to be in charge of correcting displacement of the imaging position due to camera shake or the like (image blur on the image surface I). 
     To correct roll blur of an angle θ with a focal length of the whole system being f and with a lens having a vibration proof coefficient K (the ratio of the image movement amount on the imaging surface to the movement amount of the moving lens group for camera shake correction), a moving lens group for camera shake correction is moved in the direction orthogonal to the optical axis by (f·tan θ)/K. In the wide angle end state in Example 2, the vibration proof coefficient is 0.97 and the focal length is 72.1 ram, and thus the movement amount of the vibration-proof lens group to correct a roll blur of 0.30° is 0.39 mm. In the telephoto end state in Example 2, the vibration proof coefficient is 2.03 and the focal length is 292.0 mm, and thus the movement amount of the vibration-proof lens group to correct a roll blur of 0.20° is 0.50 mm. 
     Table 2 below lists specification values of the optical system according to Example 2. 
     
       
         
           
               
             
               
                 TABLE 2 
               
               
                   
               
             
            
               
                 [Lens specifications] 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                   
                   
                   
                   
                   
               
               
                 number 
                 R 
                 D 
                 nd 
                 νd 
               
               
                   
               
               
                 Object 
                 ∞ 
                   
                   
                   
                   
               
               
                 surface 
                   
                   
                   
                   
                   
               
               
                 1 
                 524.3080 
                 3.649 
                 1.48749 
                 70.31 
                   
               
               
                 2 
                 −473.1509 
                 0.200 
                   
                   
                   
               
               
                 3 
                 99.8647 
                 1.700 
                 1.67270 
                 32.19 
                   
               
               
                 4 
                 65.5021 
                 8.680 
                 1.49700 
                 81.73 
                   
               
               
                 5 
                 1712.5853 
                 Variable 
                   
                   
                   
               
               
                 6 
                 93.5170 
                 1.000 
                 1.83400 
                 37.18 
                   
               
               
                 7 
                 34.3474 
                 6.920 
                   
                   
                   
               
               
                 8 
                 −111.6255 
                 1.000 
                 1.60300 
                 65.44 
                   
               
               
                 9 
                 −404.2382 
                 0.200 
                   
                   
                   
               
               
                 10 
                 45.6203 
                 2.882 
                 1.84666 
                 23.80 
                   
               
               
                 11 
                 103.2990 
                 3.776 
                   
                   
                   
               
               
                 12 
                 −66.2945 
                 1.000 
                 1.70000 
                 48.11 
                   
               
               
                 13 
                 38.4320 
                 3.453 
                 1.79504 
                 28.69 
                   
               
               
                 14 
                 151.5709 
                 Variable 
                   
                   
                   
               
               
                 15 
                 101.1563 
                 3.699 
                 1.80400 
                 46.60 
                   
               
               
                 16 
                 −81.9293 
                 0.200 
                   
                   
                   
               
               
                 17 
                 39.5595 
                 5.119 
                 1.49700 
                 81.73 
                   
               
               
                 18 
                 −67.2517 
                 1.000 
                 1.85026 
                 32.35 
                   
               
               
                 19 
                 148.7139 
                 1.531 
                   
                   
                   
               
               
                 20 
                 ∞ 
                 Variable 
                   
                   
                 (Aperture  
               
               
                   
                   
                   
                   
                   
                 stop S)  
               
               
                 21 
                 99.6360 
                 4.438 
                 1.51680 
                 63.88 
                   
               
               
                 22 
                 −28.3755 
                 1.000 
                 1.80610 
                 40.97 
                   
               
               
                 23 
                 −55.9883 
                 Variable 
                   
                   
                   
               
               
                 24 
                 −69.2441 
                 1.000 
                 1.90366 
                 31.27 
                   
               
               
                 25 
                 64.7455 
                 7.965 
                   
                   
                   
               
               
                 26 
                 1599.2908 
                 4.469 
                 1.67270 
                 32.19 
                   
               
               
                 27 
                 −30.6814 
                 16.326 
                   
                   
                   
               
               
                 28 
                 −23.5416 
                 1.000 
                 1.80400 
                 46.60 
                   
               
               
                 29 
                 −175.4914 
                 0.343 
                   
                   
                   
               
               
                 30 
                 82.8193 
                 3.436 
                 1.67270 
                 32.19 
                   
               
               
                 31 
                 −167.6215 
                 BF 
                   
                   
                   
               
               
                 Image 
                 ∞ 
                   
                   
                   
                   
               
               
                 surface 
               
               
                   
               
            
           
           
               
            
               
                 [Various data] 
               
               
                 Zooming rate 4.05 
               
            
           
           
               
               
               
               
            
               
                   
                 W 
                 M 
                 T 
               
               
                   
               
               
                 f 
                 72.1 
                 100.0 
                 292.0 
               
               
                 FNO 
                 4.54 
                 4.76 
                 5.88 
               
               
                 2ω 
                 33.58 
                 23.98 
                 8.28 
               
               
                 Ymax 
                 21.60 
                 21.60 
                 21.60 
               
               
                 TL 
                 193.32 
                 210.95 
                 248.32 
               
               
                 BF 
                 38.32 
                 41.61 
                 61.32 
               
               
                   
               
            
           
           
               
            
               
                 [Various distance data] 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                 W 
                 M 
                 T 
               
               
                   
                 W 
                 M 
                 T 
                 Short 
                 Short 
                 Short 
               
               
                   
                 Infinity 
                 Infinity 
                 Infinity 
                 distant 
                 distant 
                 distant 
               
               
                   
               
               
                 d5  
                 2.000 
                 25.989 
                 75.552 
                 2.000 
                 25.989 
                 75.552 
               
               
                 d14 
                 43.552 
                 33.897 
                 2.000 
                 43.552 
                 33.897 
                 2.000 
               
               
                 d20 
                 21.465 
                 19.956 
                 21.465 
                 20.527 
                 18.788 
                 19.123 
               
               
                 d23 
                 2.000 
                 3.509 
                 2.000 
                 2.938 
                 4.677 
                 4.341 
               
               
                   
               
            
           
           
               
            
               
                 [Lens group data] 
               
            
           
           
               
               
               
            
               
                   
                 Starting 
                 Focal 
               
               
                 Group 
                 surface 
                 length 
               
               
                   
               
               
                 G1 
                 1 
                 173.986 
               
               
                 G2 
                 6 
                 −42.714 
               
               
                 G3 
                 15 
                 49.108 
               
               
                 G4 
                 21 
                 106.792 
               
               
                 G5 
                 24 
                 −51.186 
               
               
                   
               
            
           
           
               
            
               
                 [Conditional expression corresponding value] 
               
            
           
           
               
               
            
               
                 Conditional expression 
                 (1) fvr/fMt = 1.743 
               
               
                 Conditional expression 
                 (2) (−fvr)/ft = 0.255 
               
               
                 Conditional expression 
                 (3) f1/(−fMt) = 4.073 
               
               
                 Conditional expression 
                 (4) fP/(−fN) = 0.596 
               
               
                 Conditional expression 
                 (5) nP/nN = 0.895 
               
               
                 Conditional expression 
                 (6) νP/νN = 2.539 
               
               
                   
               
            
           
         
       
     
       FIG. 7A  is a graph showing various aberrations of the zoom optical system according to Example 2 having a vibration-proof function upon focusing on infinity in the wide angle end state, and  FIG. 7B  is a meridional lateral aberration graph in a case where blur correction is performed for the roll blur of 0.30°.  FIG. 8  is a graph showing various aberrations of the zoom optical system according to Example 2 having a vibration proof function upon focusing on infinity in the intermediate focal length state.  FIG. 9A  is a graph showing various aberrations of the zoom optical system according to Example 2 having a vibration-proof function upon focusing on infinity in the telephoto end state, and  FIG. 9B  is a meridional lateral aberration graph in a case where blur correction is performed for the roll blur of 0.20°.  FIGS. 10A, 10B, and 10C  are graphs showing various aberrations of the zoom optical system according to Example 2 upon focusing on a short distant object, respectively in the wide angle end state, the intermediate focal length state, and the telephoto end state. 
     It can be seen in these aberration graphs that the zoom optical system according to Example 2 can achieve excellent imaging performance with various aberrations successfully corrected from the wide angle end state to the telephoto end state, and can achieve excellent imaging performance upon focusing on a short distant object. 
     Example 3 
     Example 3 is described with reference to  FIG. 11 ,  FIGS. 12A and 12B ,  FIG. 13 ,  FIGS. 14A and 14B , and  FIGS. 15A-15C  and Table 3.  FIG. 11  is a diagram illustrating a lens configuration of a zoom optical system according to Example 3 of the present embodiment. The zoom optical system ZL( 3 ) according to Example 3 consists of, in order from an object: a first lens group G 1  having positive refractive power; a second lens group G 2  having negative refractive power; a third lens group G 3  having positive refractive power; an aperture stop S; a fourth lens group G 4  having positive refractive power; and a fifth lens group G 5  having negative refractive power. The first to the fifth lens groups G 1  to G 5  each move in a direction indicated by an arrow in  FIG. 11  upon zooming from a wide angle end state (W) to a telephoto end state (T). In this Example, the intermediate group GM includes the second lens group G 2 , the intermediate side lens group GRP 1  includes the third lens group G 3  and the aperture stop S, the subsequent side lens group GRP 2  includes the fourth lens group G 4 , and the subsequent group GR includes the fifth lens group G 5 . 
     The first lens group G 1  consists of, in order from the object, a positive lens (1-1st lens) L 11  having a biconvex shape and a cemented positive lens consisting of a negative meniscus lens (1-2nd lens) L 12  having a convex surface facing the object and a positive meniscus lens (1-3rd lens) L 13  having a convex surface facing the object. 
     The second lens group G 2  consists of, in order from the object, a negative meniscus lens L 21  having a convex surface facing the object, a positive meniscus lens L 22  having a convex surface facing the object, and a cemented negative lens consisting of a negative lens L 23  having a biconcave shape and a positive meniscus lens L 24  having a convex surface facing the object. 
     The third lens group G 3  consists of, in order from the object, a positive lens L 31  having a biconvex shape and a cemented positive lens consisting of a positive lens L 32  having a biconvex shape and a negative lens L 33  having a biconcave shape. The aperture stop S is disposed in the neighborhood of and to the image side of the third lens group G 3 , and integrally moves with the third lens group G 3  upon zooming. 
     The fourth lens group G 4  consists of a cemented positive lens consisting of a positive lens L 41  having a biconvex shape and a negative meniscus lens L 42  having a concave surface facing the object. 
     The fifth lens group G 5  consists of, in order from the object, a negative lens L 51  having a biconcave shape, a negative lens L 52  having a biconcave shape, a positive lens L 53  having a biconvex shape, a negative meniscus lens L 54  having a concave surface facing the object, and a positive meniscus lens L 55  having a convex surface facing the object. An image surface I is disposed to the image side of the fifth lens group G 5 . 
     In the zoom optical system ZL( 3 ) according to Example 3, the fourth lens group G 4  (subsequent side lens group GRP 2 ) moves toward the object upon focusing from a long distant object to a short distant object. In the zoom optical system ZL( 3 ) according to Example 3, the cemented negative lens consisting of the negative lens L 23  and the positive meniscus lens L 24  in the second lens group G 2  serves as a vibration-proof lens group (partial group), movable in a direction orthogonal to the optical axis, to be in charge of correcting displacement of the imaging position due to camera shake or the like (image blur on the image surface I). 
     To correct roll blur of an angle θ with a focal length of the whole system being f and with a lens having a vibration proof coefficient K (the ratio of the image movement amount on the imaging surface to the movement amount of the moving lens group for camera shake correction), a moving lens group for camera shake correction is moved in the direction orthogonal to the optical axis by (f·tan θ)/K. In the wide angle end state in Example 3, the vibration proof coefficient is 0.96 and the focal length is 72.1 mm, and thus the movement amount of the vibration-proof lens group to correct a roll blur of 0.30° is 0.39 mm. In the telephoto end state in Example 3, the vibration proof coefficient is 1.99 and the focal length is 292.0 mm, and thus the movement amount of the vibration-proof lens group to correct a roll blur of 0.20° is 0.51 mm. 
     Table 3 below lists specification values of the optical system according to Example 3. 
     
       
         
           
               
             
               
                 TABLE 3 
               
               
                   
               
             
            
               
                 [Lens specifications] 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                   
                   
                   
                   
                   
               
               
                 number 
                 R 
                 D 
                 nd 
                 νd 
               
               
                   
               
               
                 Object 
                 ∞ 
                   
                   
                   
                   
               
               
                 surface 
                   
                   
                   
                   
                   
               
               
                 1 
                 394.8396 
                 3.845 
                 1.48749 
                 70.31 
                   
               
               
                 2 
                 −543.4808 
                 0.200 
                   
                   
                   
               
               
                 3 
                 105.1984 
                 1.700 
                 1.67270 
                 32.19 
                   
               
               
                 4 
                 67.0764 
                 8.688 
                 1.49700 
                 81.73 
                   
               
               
                 5 
                 3999.3650 
                 Variable 
                   
                   
                   
               
               
                 6 
                 187.7927 
                 1.000 
                 1.83481 
                 42.73 
                   
               
               
                 7 
                 39.3002 
                 8.392 
                   
                   
                   
               
               
                 8 
                 40.6875 
                 2.537 
                 1.84666 
                 23.80 
                   
               
               
                 9 
                 61.9560 
                 4.302 
                   
                   
                   
               
               
                 10 
                 −65.9607 
                 1.000 
                 1.70000 
                 48.11 
                   
               
               
                 11 
                 47.5227 
                 2.966 
                 1.84666 
                 23.80 
                   
               
               
                 12 
                 155.3071 
                 Variable 
                   
                   
                   
               
               
                 13 
                 100.1220 
                 3.921 
                 1.80400 
                 46.60 
                   
               
               
                 14 
                 −71.7118 
                 0.200 
                   
                   
                   
               
               
                 15 
                 39.6874 
                 5.409 
                 1.49700 
                 81.73 
                   
               
               
                 16 
                 −55.1551 
                 1.000 
                 1.85026 
                 32.35 
                   
               
               
                 17 
                 138.4368 
                 1.566 
                   
                   
                   
               
               
                 18 
                 ∞ 
                 Variable 
                   
                   
                 (Aperture  
               
               
                   
                   
                   
                   
                   
                 stop S)  
               
               
                 19 
                 90.1287 
                 4.430 
                 1.51680 
                 63.88 
                   
               
               
                 20 
                 −29.8148 
                 1.000 
                 1.83400 
                 37.18 
                   
               
               
                 21 
                 −56.5509 
                 Variable 
                   
                   
                   
               
               
                 22 
                 −89.4853 
                 1.000 
                 1.90366 
                 31.27 
                   
               
               
                 23 
                 58.7258 
                 1.623 
                   
                   
                   
               
               
                 24 
                 −119.8149 
                 1.000 
                 1.77250 
                 49.62 
                   
               
               
                 25 
                 125.4243 
                 2.815 
                   
                   
                   
               
               
                 26 
                 86.3318 
                 5.240 
                 1.67270 
                 32.19 
                   
               
               
                 27 
                 −30.2745 
                 18.277 
                   
                   
                   
               
               
                 28 
                 −22.8447 
                 1.000 
                 1.80400 
                 46.60 
                   
               
               
                 29 
                 −60.6486 
                 0.200 
                   
                   
                   
               
               
                 30 
                 89.8891 
                 2.703 
                 1.66446 
                 35.87 
                   
               
               
                 31 
                 3303.4609 
                 BF 
                   
                   
                   
               
               
                 Image 
                 ∞ 
                   
                   
                   
                   
               
               
                 surface 
               
               
                   
               
            
           
           
               
            
               
                 [Various data] 
               
               
                 Zooming rate 4.05 
               
            
           
           
               
               
               
               
            
               
                   
                 W 
                 M 
                 T 
               
               
                   
               
               
                 f 
                 72.1 
                 99.9 
                 292.0 
               
               
                 FNO 
                 4.53 
                 4.71 
                 5.88 
               
               
                 2ω 
                 33.50 
                 23.86 
                 8.24 
               
               
                 Ymax 
                 21.60 
                 21.60 
                 21.60 
               
               
                 TL 
                 193.32 
                 211.55 
                 248.32 
               
               
                 BF 
                 38.32 
                 41.10 
                 61.32 
               
               
                   
               
            
           
           
               
            
               
                 [Various distance data] 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                 W 
                 M 
                 T 
               
               
                   
                 W 
                 M 
                 T 
                 Short 
                 Short 
                 Short 
               
               
                   
                 Infinity 
                 Infinity 
                 Infinity 
                 distant 
                 distant 
                 distant 
               
               
                   
               
               
                 d5  
                 2.000 
                 26.748 
                 74.901 
                 2.000 
                 26.748 
                 74.901 
               
               
                 d12 
                 42.901 
                 33.607 
                 2.000 
                 42.901 
                 33.607 
                 2.000 
               
               
                 d18 
                 22.086 
                 20.598 
                 21.608 
                 21.186 
                 19.465 
                 19.388 
               
               
                 d21 
                 2.000 
                 3.489 
                 2.479 
                 2.900 
                 4.621 
                 4.698 
               
               
                   
               
            
           
           
               
            
               
                 [Lens group data] 
               
            
           
           
               
               
               
            
               
                   
                 Starting 
                 Focal 
               
               
                 Group 
                 surface 
                 length 
               
               
                   
               
               
                 G1 
                 1 
                 172.579 
               
               
                 G2 
                 6 
                 −42.044 
               
               
                 G3 
                 13 
                 48.716 
               
               
                 G4 
                 19 
                 101.916 
               
               
                 G5 
                 22 
                 −49.748 
               
               
                   
               
            
           
           
               
            
               
                 [Conditional expression corresponding value] 
               
            
           
           
               
               
            
               
                 Conditional expression 
                 (1) fvr/fMt = 1.821 
               
               
                 Conditional expression 
                 (2) (−fvr)/ft = 0.262 
               
               
                 Conditional expression 
                 (3) f1/(−fMt) = 4.105 
               
               
                 Conditional expression 
                 (4) fP/(−fN) = 0.571 
               
               
                 Conditional expression 
                 (5) nP/nN = 0.895 
               
               
                 Conditional expression 
                 (6) νP/νN = 2.539 
               
               
                   
               
            
           
         
       
     
       FIG. 12A  is a graph showing various aberrations of the zoom optical system according to Example 3 having a vibration-proof function upon focusing on infinity in the wide angle end state, and  FIG. 12B  is a meridional lateral aberration graph in a case where blur correction is performed for the roll blur of 0.30°.  FIG. 13  is a graph showing various aberrations of the zoom optical system according to Example 3 having a vibration proof function upon focusing on infinity in the intermediate focal length state.  FIG. 14A  is a graph showing various aberrations of the zoom optical system according to Example 3 having a vibration-proof function upon focusing on infinity in the telephoto end state, and  FIG. 14B  is a meridional lateral aberration graph in a case where blur correction is performed for the roll blur of 0.20°.  FIGS. 15A, 15B, and 15C  are graphs showing various aberrations of the zoom optical system according to Example 3 upon focusing on a short distant object, respectively in the wide angle end state, the intermediate focal length state, and the telephoto end state. 
     It can be seen in these aberration graphs that the zoom optical system according to Example 3 can achieve excellent imaging performance with various aberrations successfully corrected from the wide angle end state to the telephoto end state, and can achieve excellent imaging performance upon focusing on a short distant object. 
     Example 4 
     Example 4 is described with reference to  FIG. 16 ,  FIGS. 17A and 17B ,  FIG. 18 ,  FIGS. 19A and 19B , and  FIGS. 20A-20C  and Table 4.  FIG. 16  is a diagram illustrating a lens configuration of a zoom optical system according to Example 4 of the present embodiment. The zoom optical system ZL( 4 ) according to Example 4 consists of, in order from an object: a first lens group G 1  having positive refractive power; a second lens group G 2  having negative refractive power; a third lens group G 3  having positive refractive power; an aperture stop S; a fourth lens group G 4  having positive refractive power; and a fifth lens group G 5  having negative refractive power. The first to the fifth lens groups G 1  to G 5  each move in a direction indicated by an arrow in  FIG. 16  upon zooming from a wide angle end state (W) to a telephoto end state (T). In this Example, the intermediate group GM includes the second lens group G 2 , the intermediate side lens group GRP 1  includes the third lens group G 3  and the aperture stop S, the subsequent side lens group GRP 2  includes the fourth lens group G 4 , and the subsequent group GR includes the fifth lens group G 5 . 
     The first lens group G 1  consists of, in order from the object, a positive lens (1-1st lens) L 11  having a biconvex shape and a cemented positive lens consisting of a negative meniscus lens (1-2nd lens) L 12  having a convex surface facing the object and a positive meniscus lens (1-3rd lens) L 13  having a convex surface facing the object. 
     The second lens group G 2  consists of, in order from the object, a negative meniscus lens L 21  having a convex surface facing the object, a positive meniscus lens L 22  having a convex surface facing the object, and a cemented negative lens consisting of a negative lens L 23  having a biconcave shape and a positive meniscus lens L 24  having a convex surface facing the object. 
     The third lens group G 3  consists of, in order from the object, a positive lens L 31  having a biconvex shape and a cemented positive lens consisting of a positive lens L 32  having a biconvex shape and a negative lens L 33  having a biconcave shape. The aperture stop S is disposed in the neighborhood of and to the image side of the third lens group G 3 , and integrally moves with the third lens group G 3  upon zooming. 
     The fourth lens group G 4  consists of, in order from the object, a positive lens L 41  having a biconvex shape and a negative meniscus lens L 42  having a concave surface facing the object. 
     The fifth lens group G 5  consists of, in order from the object, a negative meniscus lens L 51  having a convex surface facing the object, a positive meniscus lens L 52  having a concave surface facing the object, a negative meniscus lens L 53  having a concave surface facing the object, and a positive lens L 54  having a biconvex shape. An image surface I is disposed to the image side of the fifth lens group G 5 . 
     In the zoom optical system ZL( 4 ) according to Example 4, the fourth lens group G 4  (subsequent side lens group GRP 2 ) moves toward the object upon focusing from a long distant object to a short distant object. In the zoom optical system ZL( 4 ) according to Example 4, the cemented negative lens consisting of the negative lens L 23  and the positive meniscus lens L 24  in the second lens group G 2  serves as a vibration-proof lens group (partial group), movable in a direction orthogonal to the optical axis, to be in charge of correcting displacement of the imaging position due to camera shake or the like (image blur on the image surface I). 
     To correct roll blur of an angle θ with a focal length of the whole system being f and with a lens having a vibration proof coefficient K (the ratio of the image movement amount on the imaging surface to the movement amount of the moving lens group for camera shake correction), a moving lens group for camera shake correction is moved in the direction orthogonal to the optical axis by (f·tan θ)/K. In the wide angle end state in Example 4, the vibration proof coefficient is 0.99 and the focal length is 72.1 ram, and thus the movement amount of the vibration-proof lens group to correct a roll blur of 0.30° is 0.38 mm. In the telephoto end state in Example 4, the vibration proof coefficient is 2.04 and the focal length is 292.0 mm, and thus the movement amount of the vibration-proof lens group to correct a roll blur of 0.20° is 0.50 mm. 
     Table 4 below lists specification values of the optical system according to Example 4. 
     
       
         
           
               
             
               
                 TABLE 4 
               
               
                   
               
             
            
               
                 [Lens specifications] 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                   
                   
                   
                   
                   
               
               
                 number 
                 R 
                 D 
                 nd 
                 νd 
               
               
                   
               
               
                 Object 
                 ∞ 
                   
                   
                   
                   
               
               
                 surface 
                   
                   
                   
                   
                   
               
               
                 1 
                 397.7403 
                 3.807 
                 1.48749 
                 70.31 
                   
               
               
                 2 
                 −541.2704 
                 0.200 
                   
                   
                   
               
               
                 3 
                 98.5962 
                 1.700 
                 1.67270 
                 32.19 
                   
               
               
                 4 
                 64.4142 
                 7.530 
                 1.49700 
                 81.73 
                   
               
               
                 5 
                 2167.3548 
                 Variable 
                   
                   
                   
               
               
                 6 
                 153.3759 
                 1.000 
                 1.80610 
                 40.97 
                   
               
               
                 7 
                 35.8256 
                 8.557 
                   
                   
                   
               
               
                 8 
                 37.5306 
                 2.567 
                 1.84666 
                 23.80 
                   
               
               
                 9 
                 55.0899 
                 4.528 
                   
                   
                   
               
               
                 10 
                 −64.5906 
                 1.000 
                 1.70000 
                 48.11 
                   
               
               
                 11 
                 45.3004 
                 3.006 
                 1.84666 
                 23.80 
                   
               
               
                 12 
                 146.7719 
                 Variable 
                   
                   
                   
               
               
                 13 
                 120.3729 
                 3.847 
                 1.79952 
                 42.09 
                   
               
               
                 14 
                 −66.6553 
                 0.200 
                   
                   
                   
               
               
                 15 
                 40.5542 
                 5.444 
                 1.49700 
                 81.73 
                   
               
               
                 16 
                 −51.5427 
                 1.000 
                 1.85026 
                 32.35 
                   
               
               
                 17 
                 136.7432 
                 1.574 
                   
                   
                   
               
               
                 18 
                 ∞ 
                 Variable 
                   
                   
                 (Aperture  
               
               
                   
                   
                   
                   
                   
                 stop S)  
               
               
                 19 
                 73.0072 
                 4.267 
                 1.51680 
                 63.88 
                   
               
               
                 20 
                 −41.6199 
                 1.157 
                   
                   
                   
               
               
                 21 
                 −36.8096 
                 1.000 
                 1.80100 
                 34.92 
                   
               
               
                 22 
                 −63.5855 
                 Variable 
                   
                   
                   
               
               
                 23 
                 142.7978 
                 1.000 
                 1.90366 
                 31.27 
                   
               
               
                 24 
                 39.2858 
                 5.972 
                   
                   
                   
               
               
                 25 
                 −32.2173 
                 2.394 
                 1.80518 
                 25.45 
                   
               
               
                 26 
                 −25.4336 
                 17.643 
                   
                   
                   
               
               
                 27 
                 −22.2559 
                 1.000 
                 1.77250 
                 49.62 
                   
               
               
                 28 
                 −60.4849 
                 0.200 
                   
                   
                   
               
               
                 29 
                 133.6379 
                 3.767 
                 1.69895 
                 30.13 
                   
               
               
                 30 
                 −86.4148 
                 BF 
                   
                   
                   
               
               
                 Image 
                 ∞ 
                   
                   
                   
                   
               
               
                 surface 
               
               
                   
               
            
           
           
               
            
               
                 [Various data] 
               
               
                 Zooming rate 4.05 
               
            
           
           
               
               
               
               
            
               
                   
                 W 
                 M 
                 T 
               
               
                   
               
               
                 f 
                 72.1 
                 100.0 
                 292.0 
               
               
                 FNO 
                 4.58 
                 4.77 
                 5.88 
               
               
                 2ω 
                 33.52 
                 23.92 
                 8.28 
               
               
                 Ymax 
                 21.60 
                 21.60 
                 21.60 
               
               
                 TL 
                 193.32 
                 210.92 
                 248.32 
               
               
                 BF 
                 38.32 
                 41.32 
                 62.32 
               
               
                   
               
            
           
           
               
            
               
                 [Various distance data] 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                 W 
                 M 
                 T 
               
               
                   
                 W 
                 M 
                 T 
                 Short 
                 Short 
                 Short 
               
               
                   
                 Infinity 
                 Infinity 
                 Infinity 
                 distant 
                 distant 
                 distant 
               
               
                   
               
               
                 d5  
                 2.000 
                 25.714 
                 72.838 
                 2.000 
                 25.714 
                 72.838 
               
               
                 d12 
                 41.838 
                 32.720 
                 2.000 
                 41.838 
                 32.720 
                 2.000 
               
               
                 d18 
                 24.804 
                 23.298 
                 24.804 
                 23.943 
                 22.207 
                 22.596 
               
               
                 d22 
                 2.000 
                 3.505 
                 2.000 
                 2.861 
                 4.597 
                 4.208 
               
               
                   
               
            
           
           
               
            
               
                 [Lens group data] 
               
            
           
           
               
               
               
            
               
                   
                 Starting 
                 Focal 
               
               
                 Group 
                 surface 
                 length 
               
               
                   
               
               
                 G1 
                 1 
                 166.403 
               
               
                 G2 
                 6 
                 −40.599 
               
               
                 G3 
                 13 
                 52.091 
               
               
                 G4 
                 19 
                 95.393 
               
               
                 G5 
                 23 
                 −58.282 
               
               
                   
               
            
           
           
               
            
               
                 [Conditional expression corresponding value] 
               
            
           
           
               
               
            
               
                 Conditional expression 
                 (1) fvr/fMt = 1.831 
               
               
                 Conditional expression 
                 (2) (−fvr)/ft = 0.255 
               
               
                 Conditional expression 
                 (3) f1/(−fMt) = 4.099 
               
               
                 Conditional expression 
                 (4) fP/(−fN) = 0.468 
               
               
                 Conditional expression 
                 (5) nP/nN = 0.895 
               
               
                 Conditional expression 
                 (6) νP/νN = 2.539 
               
               
                   
               
            
           
         
       
     
       FIG. 17A  is a graph showing various aberrations of the zoom optical system according to Example 4 having a vibration-proof function upon focusing on infinity in the wide angle end state, and  FIG. 17B  is a meridional lateral aberration graph in a case where blur correction is performed for the roll blur of 0.30°.  FIG. 18  is a graph showing various aberrations of the zoom optical system according to Example 4 having a vibration proof function upon focusing on infinity in the intermediate focal length state.  FIG. 19A  is a graph showing various aberrations of the zoom optical system according to Example 4 having a vibration-proof function upon focusing on infinity in the telephoto end state, and  FIG. 19B  is a meridional lateral aberration graph in a case where blur correction is performed for the roll blur of 0.20°.  FIGS. 20A, 20B, and 20C  are graphs showing various aberrations of the zoom optical system according to Example 4 upon focusing on a short distant object, respectively in the wide angle end state, the intermediate focal length state, and the telephoto end state. 
     It can be seen in these aberration graphs that the zoom optical system according to Example 4 can achieve excellent imaging performance with various aberrations successfully corrected from the wide angle end state to the telephoto end state, and can achieve excellent imaging performance upon focusing on a short distant object. 
     Example 5 
     Example 5 is described with reference to  FIG. 21 ,  FIGS. 22A and 22B ,  FIG. 23 ,  FIGS. 24A and 24B , and  FIGS. 25A-25C  and Table 5.  FIG. 21  is a diagram illustrating a lens configuration of a zoom optical system according to Example 5 of the present embodiment. The zoom optical system ZL( 5 ) according to Example 5 consists of, in order from an object: a first lens group G 1  having positive refractive power; a second lens group G 2  having negative refractive power; a third lens group G 3  having positive refractive power; an aperture stop S; a fourth lens group G 4  having positive refractive power; a fifth lens group G 5  having negative refractive power; and a sixth lens group G 6  having negative refractive power. The first to the sixth lens groups G 1  to G 6  each move in a direction indicated by an arrow in  FIG. 21  upon zooming from a wide angle end state (W) to a telephoto end state (T). In this Example, the intermediate group GM includes the second lens group G 2 , the intermediate side lens group GRP 1  includes the third lens group G 3  and the aperture stop S, the subsequent side lens group GRP 2  includes the fourth lens group G 4 , and the subsequent group GR includes the fifth lens group G 5  and the sixth lens group G 6 . The subsequent group GR has negative refractive power as a whole. 
     The first lens group G 1  consists of, in order from the object, a positive lens (1-1st lens) L 11  having a biconvex shape and a cemented positive lens consisting of a negative meniscus lens (1-2nd lens) L 12  having a convex surface facing the object and a positive meniscus lens (1-3rd lens) L 13  having a convex surface facing the object. 
     The second lens group G 2  consists of, in order from the object, a negative meniscus lens L 21  having a convex surface facing the object, a positive meniscus lens L 22  having a convex surface facing the object, and a cemented negative lens consisting of a negative lens L 23  having a biconcave shape and a positive meniscus lens L 24  having a convex surface facing the object. 
     The third lens group G 3  consists of, in order from the object, a positive lens L 31  having a biconvex shape and a cemented positive lens consisting of a positive lens L 32  having a biconvex shape and a negative lens L 33  having a biconcave shape. The aperture stop S is disposed in the neighborhood of and to the image side of the third lens group G 3 , and integrally moves with the third lens group G 3  upon zooming. 
     The fourth lens group G 4  consists of, in order from the object, a positive lens L 41  having a biconvex shape and a negative meniscus lens L 42  having a concave surface facing the object. 
     The fifth lens group G 5  consists of, in order from the object, a negative meniscus lens L 51  having a convex surface facing the object and a positive meniscus lens L 52  having a concave surface facing the object. 
     The sixth lens group G 6  consists of, in order from the object, a negative meniscus lens L 61  having a concave surface facing the object and a positive lens L 62  having a biconvex shape. An image surface I is disposed to the image side of the sixth lens group G 6 . 
     In the zoom optical system ZL( 5 ) according to Example 5, the fourth lens group G 4  (subsequent side lens group GRP 2 ) moves toward the object upon focusing from a long distant object to a short distant object. In the zoom optical system ZL( 5 ) according to Example 5, the cemented negative lens consisting of the negative lens L 23  and the positive meniscus lens L 24  in the second lens group G 2  serves as a vibration-proof lens group (partial group), movable in a direction orthogonal to the optical axis, to be in charge of correcting displacement of the imaging position due to camera shake or the like (image blur on the image surface I). 
     To correct roll blur of an angle θ with a focal length of the whole system being f and with a lens having a vibration proof coefficient K (the ratio of the image movement amount on the imaging surface to the movement amount of the moving lens group for camera shake correction), a moving lens group for camera shake correction is moved in the direction orthogonal to the optical axis by (f·tan θ)/K. In the wide angle end state in Example 5, the vibration proof coefficient is 1.00 and the focal length is 72.1 mm, and thus the movement amount of the vibration-proof lens group to correct a roll blur of 0.30° is 0.38 mm. In the telephoto end state in Example 5, the vibration proof coefficient is 2.07 and the focal length is 292.0 mm, and thus the movement amount of the vibration-proof lens group to correct a roll blur of 0.20° is 0.49 mm. 
     Table 5 below lists specification values of the optical system according to Example 5. 
     
       
         
           
               
             
               
                 TABLE 5 
               
               
                   
               
             
            
               
                 [Lens specifications] 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                   
                   
                   
                   
                   
               
               
                 number 
                 R 
                 D 
                 nd 
                 νd 
               
               
                   
               
               
                 Object 
                 ∞ 
                   
                   
                   
                   
               
               
                 surface 
                   
                   
                   
                   
                   
               
               
                 1 
                 410.0484 
                 3.688 
                 1.48749 
                 70.31 
                   
               
               
                 2 
                 −563.1103 
                 0.200 
                   
                   
                   
               
               
                 3 
                 102.5753 
                 1.700 
                 1.67270 
                 32.19 
                   
               
               
                 4 
                 66.0707 
                 7.494 
                 1.49700 
                 81.73 
                   
               
               
                 5 
                 15350.0260 
                 Variable 
                   
                   
                   
               
               
                 6 
                 139.4435 
                 1.000 
                 1.80610 
                 40.97 
                   
               
               
                 7 
                 35.1229 
                 7.231 
                   
                   
                   
               
               
                 8 
                 37.6103 
                 2.601 
                 1.84666 
                 23.80 
                   
               
               
                 9 
                 56.2791 
                 4.573 
                   
                   
                   
               
               
                 10 
                 −62.1771 
                 1.000 
                 1.70000 
                 48.11 
                   
               
               
                 11 
                 45.7876 
                 3.019 
                 1.84666 
                 23.80 
                   
               
               
                 12 
                 152.3777 
                 Variable 
                   
                   
                   
               
               
                 13 
                 118.3464 
                 3.864 
                 1.79952 
                 42.09 
                   
               
               
                 14 
                 −66.5127 
                 0.200 
                   
                   
                   
               
               
                 15 
                 41.1734 
                 5.431 
                 1.49700 
                 81.73 
                   
               
               
                 16 
                 −51.3614 
                 1.000 
                 1.85026 
                 32.35 
                   
               
               
                 17 
                 129.2055 
                 1.610 
                   
                   
                   
               
               
                 18 
                 ∞ 
                 Variable 
                   
                   
                 (Aperture  
               
               
                   
                   
                   
                   
                   
                 stop S)  
               
               
                 19 
                 79.6726 
                 4.263 
                 1.51680 
                 63.88 
                   
               
               
                 20 
                 −41.5025 
                 1.192 
                   
                   
                   
               
               
                 21 
                 −36.1506 
                 1.000 
                 1.80100 
                 34.92 
                   
               
               
                 22 
                 −57.7482 
                 Variable 
                   
                   
                   
               
               
                 23 
                 360.1366 
                 1.000 
                 1.90366 
                 31.27 
                   
               
               
                 24 
                 48.3936 
                 6.817 
                   
                   
                   
               
               
                 25 
                 −37.2103 
                 2.515 
                 1.80518 
                 25.45 
                   
               
               
                 26 
                 −27.2408 
                 Variable 
                   
                   
                   
               
               
                 27 
                 −22.1710 
                 1.000 
                 1.80400 
                 46.60 
                   
               
               
                 28 
                 −62.3440 
                 0.200 
                   
                   
                   
               
               
                 29 
                 129.8338 
                 3.640 
                 1.71736 
                 29.57 
                   
               
               
                 30 
                 −94.8486 
                 BF 
                   
                   
                   
               
               
                 Image 
                 ∞ 
                   
                   
                   
                   
               
               
                 surface 
               
               
                   
               
            
           
           
               
            
               
                 [Various data] 
               
               
                 Zooming rate 4.05 
               
            
           
           
               
               
               
               
            
               
                   
                 W 
                 M 
                 T 
               
               
                   
               
               
                 f 
                 72.1 
                 100.0 
                 292.0 
               
               
                 FNO 
                 4.57 
                 4.79 
                 5.88 
               
               
                 2ω 
                 33.64 
                 23.96 
                 8.26 
               
               
                 Ymax 
                 21.60 
                 21.60 
                 21.60 
               
               
                 TL 
                 193.32 
                 211.43 
                 248.32 
               
               
                 BF 
                 38.32 
                 41.66 
                 60.02 
               
               
                   
               
            
           
           
               
            
               
                 [Various distance data] 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                 W 
                 M 
                 T 
               
               
                   
                 W 
                 M 
                 T 
                 Short 
                 Short 
                 Short 
               
               
                   
                 Infinity 
                 Infinity 
                 Infinity 
                 distant 
                 distant 
                 distant 
               
               
                   
               
               
                 d5  
                 2.000 
                 25.563 
                 73.573 
                 2.000 
                 25.563 
                 73.573 
               
               
                 d12 
                 42.573 
                 33.490 
                 2.000 
                 42.573 
                 33.490 
                 2.000 
               
               
                 d18 
                 24.947 
                 23.743 
                 24.947 
                 24.097 
                 22.674 
                 22.767 
               
               
                 d22 
                 2.000 
                 3.203 
                 2.000 
                 2.849 
                 4.273 
                 4.180 
               
               
                 d26 
                 17.243 
                 17.537 
                 19.544 
                 17.243 
                 17.537 
                 19.544 
               
               
                   
               
            
           
           
               
            
               
                 [Lens group data] 
               
            
           
           
               
               
               
            
               
                   
                 Starting 
                 Focal 
               
               
                 Group 
                 surface 
                 length 
               
               
                   
               
               
                 G1 
                 1 
                 168.635 
               
               
                 G2 
                 6 
                 −41.024 
               
               
                 G3 
                 13 
                 53.154 
               
               
                 G4 
                 19 
                 92.760 
               
               
                 G5 
                 23 
                 −175.236 
               
               
                 G6 
                 27 
                 −106.197 
               
               
                   
               
            
           
           
               
            
               
                 [Conditional expression corresponding value] 
               
            
           
           
               
               
            
               
                 Conditional expression 
                 (1) fvr/fMt = 1.779 
               
               
                 Conditional expression 
                 (2) (−fvr)/ft = 0.250 
               
               
                 Conditional expression 
                 (3) f1/(−fMt) = 4.111 
               
               
                 Conditional expression 
                 (4) fP/(−fN) = 0.434 
               
               
                 Conditional expression 
                 (5) nP/nN = 0.895 
               
               
                 Conditional expression 
                 (6) νP/νN = 2.539 
               
               
                   
               
            
           
         
       
     
       FIG. 22A  is a graph showing various aberrations of the zoom optical system according to Example 5 having a vibration-proof function upon focusing on infinity in the wide angle end state, and  FIG. 22B  is a meridional lateral aberration graph in a case where blur correction is performed for the roll blur of 0.30°.  FIG. 23  is a graph showing various aberrations of the zoom optical system according to Example 5 having a vibration proof function upon focusing on infinity in the intermediate focal length state.  FIG. 24A  is a graph showing various aberrations of the zoom optical system according to Example 5 having a vibration-proof function upon focusing on infinity in the telephoto end state, and  FIG. 24B  is a meridional lateral aberration graph in a case where blur correction is performed for the roll blur of 0.20°.  FIGS. 25A, 25B, and 25C  are graphs showing various aberrations of the zoom optical system according to Example 5 upon focusing on a short distant object, respectively in the wide angle end state, the intermediate focal length state, and the telephoto end state. 
     It can be seen in these aberration graphs that the zoom optical system according to Example 5 can achieve excellent imaging performance with various aberrations successfully corrected from the wide angle end state to the telephoto end state, and can achieve excellent imaging performance upon focusing on a short distant object. 
     Example 6 
     Example 6 is described with reference to  FIG. 26 ,  FIGS. 27A and 27B ,  FIG. 28 ,  FIGS. 29A and 29B , and  FIGS. 30A-30C  and Table 6.  FIG. 26  is a diagram illustrating a lens configuration of a zoom optical system according to Example 6 of the present embodiment. The zoom optical system ZL( 6 ) according to Example 6 consists of, in order from an object: a first lens group G 1  having positive refractive power; a second lens group G 2  having negative refractive power; a third lens group G 3  having negative refractive power; a fourth lens group G 4  having positive refractive power; an aperture stop S; a fifth lens group G 5  having positive refractive power; and a sixth lens group G 6  having negative refractive power. The first to the sixth lens groups G 1  to G 6  each move in a direction indicated by an arrow in  FIG. 26  upon zooming from a wide angle end state (W) to a telephoto end state (T). In this Example, the intermediate group GM includes the second lens group G 2  and the third lens group G 3 , the intermediate side lens group GRP 1  includes the fourth lens group G 4  and the aperture stop S, the subsequent side lens group GRP 2  includes the fifth lens group G 5 , and the subsequent group GR includes the sixth lens group G 6 . The intermediate group GM has negative refractive power as a whole. 
     The first lens group G 1  consists of, in order from the object, a positive lens (1-1st lens) L 11  having a biconvex shape and a cemented positive lens consisting of a negative meniscus lens (1-2nd lens) L 12  having a convex surface facing the object and a positive meniscus lens (1-3rd lens) L 13  having a convex surface facing the object. 
     The second lens group G 2  consists of, in order from the object, a negative meniscus lens L 21  having a convex surface facing the object and a positive meniscus lens L 22  having a convex surface facing the object. 
     The third lens group G 3  consists of a cemented negative lens consisting of a negative lens L 31  having a biconcave shape and a positive meniscus lens L 32  having a convex surface facing the object. 
     The fourth lens group G 4  consists of, in order from the object, a positive lens L 41  having a biconvex shape and a cemented positive lens consisting of a positive lens L 42  having a biconvex shape and a negative lens L 43  having a biconcave shape. The aperture stop S is disposed in the neighborhood of and to the image side of the fourth lens group G 4 , and integrally moves with the fourth lens group G 4  upon zooming. 
     The fifth lens group G 5  consists of a cemented positive lens consisting of a positive lens L 51  having a biconvex shape and a negative meniscus lens L 52  having a concave surface facing the object. 
     The sixth lens group G 6  consists of, in order from the object, a negative lens L 61  having a biconcave shape, a positive meniscus lens L 62  having a concave surface facing the object, a negative meniscus lens L 63  having a concave surface facing the object, and a positive lens L 64  having a biconvex shape. An image surface I is disposed to the image side of the sixth lens group G 6 . 
     In the zoom optical system ZL( 6 ) according to Example 6, the fifth lens group G 5  (subsequent side lens group GRP 2 ) moves toward the object upon focusing from a long distant object to a short distant object. In the zoom optical system ZL( 6 ) according to Example 6, all the lenses (cemented negative lens) in the third lens group G 3  serves as a vibration-proof lens group (partial group), movable in a direction orthogonal to the optical axis, to be in charge of correcting displacement of the imaging position due to camera shake or the like (image blur on the image surface I). 
     To correct roll blur of an angle θ with a focal length of the whole system being f and with a lens having a vibration proof coefficient K (the ratio of the image movement amount on the imaging surface to the movement amount of the moving lens group for camera shake correction), a moving lens group for camera shake correction is moved in the direction orthogonal to the optical axis by (f·tan θ)/K. In the wide angle end state in Example 6, the vibration proof coefficient is 0.97 and the focal length is 72.1 mm, and thus the movement amount of the vibration-proof lens group to correct a roll blur of 0.30° is 0.39 mm. In the telephoto end state in Example 6, the vibration proof coefficient is 2.01 and the focal length is 292.0 mm, and thus the movement amount of the vibration-proof lens group to correct a roll blur of 0.20° is 0.51 mm. 
     Table 6 below lists specification values of the optical system according to Example 6. 
     
       
         
           
               
             
               
                 TABLE 6 
               
               
                   
               
             
            
               
                 [Lens specifications] 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                   
                   
                   
                   
                   
               
               
                 number 
                 R 
                 D 
                 nd 
                 νd 
               
               
                   
               
               
                 Object 
                 ∞ 
                   
                   
                   
                   
               
               
                 surface 
                   
                   
                   
                   
                   
               
               
                 1 
                 508.9189 
                 3.766 
                 1.48749 
                 70.31 
                   
               
               
                 2 
                 −429.0392 
                 0.200 
                   
                   
                   
               
               
                 3 
                 100.5086 
                 1.700 
                 1.67270 
                 32.19 
                   
               
               
                 4 
                 64.9622 
                 8.695 
                 1.49700 
                 81.73 
                   
               
               
                 5 
                 2159.2215 
                 Variable 
                   
                   
                   
               
               
                 6 
                 177.6966 
                 1.000 
                 1.83481 
                 42.73 
                   
               
               
                 7 
                 35.6714 
                 6.299 
                   
                   
                   
               
               
                 8 
                 37.8917 
                 2.779 
                 1.84666 
                 23.80 
                   
               
               
                 9 
                 62.3935 
                 Variable 
                   
                   
                   
               
               
                 10 
                 −64.2559 
                 1.000 
                 1.67003 
                 47.14 
                   
               
               
                 11 
                 36.7145 
                 3.536 
                 1.75520 
                 27.57 
                   
               
               
                 12 
                 146.9123 
                 Variable 
                   
                   
                   
               
               
                 13 
                 109.3840 
                 3.810 
                 1.80610 
                 40.97 
                   
               
               
                 14 
                 −70.8019 
                 0.200 
                   
                   
                   
               
               
                 15 
                 42.2948 
                 5.265 
                 1.49700 
                 81.73 
                   
               
               
                 16 
                 −53.8261 
                 1.000 
                 1.85026 
                 32.35 
                   
               
               
                 17 
                 161.9717 
                 1.485 
                   
                   
                   
               
               
                 18 
                 ∞ 
                 Variable 
                   
                   
                 (Aperture  
               
               
                   
                   
                   
                   
                   
                 stop S)  
               
               
                 19 
                 106.0675 
                 4.532 
                 1.51680 
                 63.88 
                   
               
               
                 20 
                 −28.5067 
                 1.000 
                 1.80100 
                 34.92 
                   
               
               
                 21 
                 −53.2383 
                 Variable 
                   
                   
                   
               
               
                 22 
                 −126.6137 
                 1.000 
                 1.90366 
                 31.27 
                   
               
               
                 23 
                 60.3618 
                 10.455 
                   
                   
                   
               
               
                 24 
                 −323.4470 
                 4.054 
                 1.68893 
                 31.16 
                   
               
               
                 25 
                 −33.1410 
                 16.327 
                   
                   
                   
               
               
                 26 
                 −24.3740 
                 1.000 
                 1.77250 
                 49.62 
                   
               
               
                 27 
                 −200.9248 
                 0.200 
                   
                   
                   
               
               
                 28 
                 79.6785 
                 3.126 
                 1.71736 
                 29.57 
                   
               
               
                 29 
                 −428.7833 
                 BF 
                   
                   
                   
               
               
                 Image 
                 ∞ 
                   
                   
                   
                   
               
               
                 surface 
               
               
                   
               
            
           
           
               
            
               
                 [Various data] 
               
               
                 Zooming rate 4.05 
               
            
           
           
               
               
               
               
            
               
                   
                 W 
                 M 
                 T 
               
               
                   
               
               
                 f 
                 72.1 
                 100.0 
                 292.0 
               
               
                 FNO 
                 4.54 
                 4.72 
                 5.88 
               
               
                 2ω 
                 33.58 
                 23.90 
                 8.26 
               
               
                 Ymax 
                 21.60 
                 21.60 
                 21.60 
               
               
                 TL 
                 193.32 
                 211.83 
                 248.32 
               
               
                 BF 
                 38.32 
                 41.01 
                 61.32 
               
               
                   
               
            
           
           
               
            
               
                 [Various distance data] 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                 W 
                 M 
                 T 
               
               
                   
                 W 
                 M 
                 T 
                 Short 
                 Short 
                 Short 
               
               
                   
                 Infinity 
                 Infinity 
                 Infinity 
                 distant 
                 distant 
                 distant 
               
               
                   
               
               
                 d5  
                 2.000 
                 26.835 
                 74.493 
                 2.000 
                 26.835 
                 74.493 
               
               
                 d9  
                 5.400 
                 5.100 
                 4.500 
                 5.400 
                 5.100 
                 4.500 
               
               
                 d12 
                 41.592 
                 32.879 
                 2.000 
                 41.592 
                 32.879 
                 2.000 
               
               
                 d18 
                 21.578 
                 20.267 
                 21.578 
                 20.680 
                 19.126 
                 19.320 
               
               
                 d21 
                 2.000 
                 3.311 
                 2.001 
                 2.898 
                 4.453 
                 4.259 
               
               
                   
               
            
           
           
               
            
               
                 [Lens group data] 
               
            
           
           
               
               
               
            
               
                   
                 Starting 
                 Focal 
               
               
                 Group 
                 surface 
                 length 
               
               
                   
               
               
                 G1 
                 1 
                 170.267 
               
               
                 G2 
                 6 
                 −114.490 
               
               
                 G3 
                 10 
                 −74.908 
               
               
                 G4 
                 13 
                 50.411 
               
               
                 G5 
                 19 
                 100.849 
               
               
                 G6 
                 22 
                 −52.429 
               
               
                   
               
            
           
           
               
            
               
                 [Conditional expression corresponding value] 
               
            
           
           
               
               
            
               
                 Conditional expression 
                 (1) fvr/fMt = 1.807 
               
               
                 Conditional expression 
                 (2) (−fvr)/ft = 0.257 
               
               
                 Conditional expression 
                 (3) f1/(−fMt) = 4.107 
               
               
                 Conditional expression 
                 (4) fP/(−fN) = 0.564 
               
               
                 Conditional expression 
                 (5) nP/nN = 0.895 
               
               
                 Conditional expression 
                 (6 νP/νN = 2.539 
               
               
                   
               
            
           
         
       
     
       FIG. 27A  is a graph showing various aberrations of the zoom optical system according to Example 6 having a vibration-proof function upon focusing on infinity in the wide angle end state, and  FIG. 27B  is a meridional lateral aberration graph in a case where blur correction is performed for the roll blur of 0.30°.  FIG. 28  is a graph showing various aberrations of the zoom optical system according to Example 6 having a vibration proof function upon focusing on infinity in the intermediate focal length state.  FIG. 29A  is a graph showing various aberrations of the zoom optical system according to Example 6 having a vibration-proof function upon focusing on infinity in the telephoto end state, and  FIG. 29B  is a meridional lateral aberration graph in a case where blur correction is performed for the roll blur of 0.20°.  FIGS. 30A, 30B, and 30C  are graphs showing various aberrations of the zoom optical system according to Example 6 upon focusing on a short distant object, respectively in the wide angle end state, the intermediate focal length state, and the telephoto end state. 
     It can be seen in these aberration graphs that the zoom optical system according to Example 6 can achieve excellent imaging performance with various aberrations successfully corrected from the wide angle end state to the telephoto end state, and can achieve excellent imaging performance upon focusing on a short distant object. 
     According to Examples described above, the subsequent side lens group GRP 2  serves as the focusing lens group to achieve a small size and light weight so that quick and quiet AF (autofocus) can be implemented without using a large barrel. Furthermore, a zoom optical system successfully preventing variation of aberrations upon zooming from the wide angle end state to the telephoto end state, as well as variation of aberrations upon focusing on a short distant object from an infinite distant object can be implemented. 
     Examples described above are merely examples of the invention according to the present application. The invention according to the present application is not limited to these examples. 
     The following configurations can be appropriately employed as long as the optical performance of the zoom optical system according to the present embodiment is not compromised. 
     Examples of values of the zoom optical system according to the present embodiment having five or six lens groups are described above. However, this should not be construed in a limiting sense, and a zoom optical system with other lens group configurations (for example, a configuration with seven lens groups or the like) may be employed. More specifically, the zoom optical system according to the present embodiment may be further provided with a lens or a lens group closest to an object or further provided with a lens or a lens group closest to the image surface. The lens group is a portion comprising at least one lens separated from another lens with a distance varying upon zooming. 
     The focusing lens group is a portion comprising at least one lens separated from another lens with a distance varying upon focusing. Thus, the focusing lens group may be provided for focusing from an infinite distant object to a short distant object, with a single or a plurality of lens groups or a partial lens group moved in the optical axis direction. The focusing lens group can be applied to auto focus, and is suitable for motor driving for auto focus (using supersonic wave motors, etc.). 
     The lens surface may be formed to have a spherical surface or a planer surface, or may be formed to have an aspherical surface. The lens surface having a spherical surface or a planer surface features easy lens processing and assembly adjustment, which leads to the processing and assembly adjustment less likely to involve an error compromising the optical performance, and thus is preferable. Furthermore, there is an advantage that a rendering performance is not largely compromised even when the image surface is displaced. 
     The lens surface having an aspherical surface may be achieved with any one of an aspherical surface formed by grinding, a glass-molded aspherical surface obtained by molding a glass piece into an aspherical shape, and a composite type aspherical surface obtained by providing an aspherical shape resin piece on a glass surface. A lens surface may be a diffractive surface. The lens may be a gradient index lens (GRIN lens) or a plastic lens. 
     The aperture stop is preferably disposed in the neighborhood of the third or the fourth lens group. Alternatively, the aperture stop may be disposed in the third or the fourth lens group. A lens frame may serve as the aperture stop so that the member serving as the aperture stop needs not to be provided. 
     The lens surfaces may be provided with an antireflection film comprising high transmittance over a wide range of wavelengths to achieve an excellent optical performance with reduced flare and ghosting and increased contrast. Thus, an excellent optical performance with reduced flare and ghosting and increased contrast can be achieved. 
     EXPLANATION OF NUMERALS AND CHARACTERS 
     
         
         
           
             G 1  first lens group 
             G 2  second lens group 
             G 3  third lens group 
             G 4  fourth lens group 
             G 5  fifth lens group 
             G 6  sixth lens group 
             GM intermediate group 
             GR subsequent group 
             GRP 1  intermediate side lens group 
             GRP 2  subsequent side lens group 
             I image surface 
             S aperture stop