Patent Publication Number: US-2023152556-A1

Title: Optical system, optical apparatus, and method for manufacturing optical system

Description:
FIELD 
     The present invention relates to an optical system, an optical apparatus, and a method for manufacturing an optical system. 
     BACKGROUND 
     Optical systems used in cameras for photographs, electronic still cameras, video cameras and the like have been proposed (see, e.g., Patent Literature 1). 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: Japanese Unexamined Patent Publication No. 2016-200685 
       
    
     SUMMARY 
     An optical system of the present disclosure includes a first lens group having positive refractive power, a focusing group that moves along an optical axis at focusing, and a rear group, in order from an object side; the first lens group includes a first-A lens group disposed on the object side of the largest air space A in the first lens group; and all of the following conditional expressions are satisfied: 
       1.00&lt; FNo ×( TL/f ) 2 &lt;2.50
 
       0.30&lt; dA/dG 1&lt;0.85 
     where 
     FNo is the f-number of the optical system focusing on infinity, 
     TL is the total optical length of the optical system focusing on infinity, 
     f is the focal length of the optical system focusing on infinity, 
     dA is the length on the optical axis of the air space A, and 
     dG1 is the length on the optical axis of the first lens group. 
     An optical system of the present disclosure includes a first lens group having positive refractive power, a focusing group that moves along an optical axis at focusing, and a rear group, in order from an object side; the first lens group includes a first-A lens group disposed on the object side of the largest air space A in the first lens group; and all of the following conditional expressions are satisfied: 
       0.30&lt; TL/f&lt; 0.80 
       0.30&lt; dA/dG 1&lt;0.85 
     where 
     TL is the total optical length of the optical system focusing on infinity, 
     f is the focal length of the optical system focusing on infinity, 
     dA is the length on the optical axis of the air space A, and 
     dG1 is the length on the optical axis of the first lens group. 
     An optical system of the present disclosure is an optical system including a plurality of lenses including at least one positive lens component and a negative lens N, in order from an object side; and all of the following conditional expressions are satisfied: 
       1.00&lt; FNo ×( TL/f ) 2 &lt;2.50
 
       0.18&lt; dN/TL&lt; 0.45 
     where 
     FNo is the f-number of the optical system focusing on infinity, 
     TL is the total optical length of the optical system focusing on infinity, 
     f is the focal length of the optical system focusing on infinity, and 
     dN is the distance on an optical axis from a surface closest to the object side in the optical system to an object-side surface of the negative lens N. 
     An optical system of the present disclosure is an optical system including a plurality of lenses that includes a positive lens component closest to an object side and that includes a negative lens N disposed closest to the object side of negative lenses disposed closer to an image side than the positive lens component; and all of the following conditional expressions are satisfied: 
       1.00&lt; FNo ×( TL/f ) 2 &lt;2.50
 
       0.18&lt; dN/TL&lt; 0.45 
     where 
     FNo is the f-number of the optical system focusing on infinity, 
     TL is the total optical length of the optical system focusing on infinity, 
     f is the focal length of the optical system focusing on infinity, and 
     dN is the distance on an optical axis from a surface closest to the object side in the optical system to an object-side surface of the negative lens N. 
     A method for manufacturing an optical system of the present disclosure is a method for manufacturing an optical system including a plurality of lenses. The method includes disposing a first lens group having positive refractive power, a focusing group that moves along an optical axis at focusing, and a rear group, in order from an object side; disposing a first-A lens group on the object side of the largest air space A in the first lens group; and arranging so that all of the following conditional expressions are satisfied: 
       1.00&lt; FNo ×( TL/f ) 2 &lt;2.50
 
       0.30&lt; dA/dG 1&lt;0.85 
     where 
     FNo is the f-number of the optical system focusing on infinity, 
     TL is the total optical length of the optical system focusing on infinity, 
     f is the focal length of the optical system focusing on infinity, 
     dA is the length on the optical axis of the air space A, and 
     dG1 is the length on the optical axis of the first lens group. 
     A method for manufacturing an optical system of the present disclosure is a method for manufacturing an optical system including a plurality of lenses. The method includes disposing at least one positive lens component and a negative lens N, in order from an object side; and arranging so that all of the following conditional expressions are satisfied: 
       1.00&lt; FNo ×( TL/f ) 2 &lt;2.50
 
       0.18&lt; dN/TL&lt; 0.45 
     where 
     FNo is the f-number of the optical system focusing on infinity, 
     TL is the total optical length of the optical system focusing on infinity, 
     f is the focal length of the optical system focusing on infinity, and 
     dN is the distance on an optical axis from a surface closest to the object side in the optical system to an object-side surface of the negative lens N. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1 A  is a cross-sectional view of an optical system of a first example focusing on an object at infinity. 
         FIG.  1 B  is a cross-sectional view of the optical system of the first example focusing on a nearby object. 
         FIG.  2    shows aberrations of the optical system of the first example focusing on an object at infinity. 
         FIG.  3 A  is a cross-sectional view of an optical system of a second example focusing on an object at infinity. 
         FIG.  3 B  is a cross-sectional view of the optical system of the second example focusing on a nearby object. 
         FIG.  4    shows aberrations of the optical system of the second example focusing on an object at infinity. 
         FIG.  5 A  is a cross-sectional view of an optical system of a third example focusing on an object at infinity. 
         FIG.  5 B  is a cross-sectional view of the optical system of the third example focusing on a nearby object. 
         FIG.  6    shows aberrations of the optical system of the third example focusing on an object at infinity. 
         FIG.  7 A  is a cross-sectional view of an optical system of a fourth example focusing on an object at infinity. 
         FIG.  7 B  is a cross-sectional view of the optical system of the fourth example focusing on a nearby object. 
         FIG.  8    shows aberrations of the optical system of the fourth example focusing on an object at infinity. 
         FIG.  9 A  is a cross-sectional view of an optical system of a fifth example focusing on an object at infinity. 
         FIG.  9 B  is a cross-sectional view of the optical system of the fifth example focusing on a nearby object. 
         FIG.  10    shows aberrations of the optical system of the fifth example focusing on an object at infinity. 
         FIG.  11 A  is a cross-sectional view of an optical system of a sixth example focusing on an object at infinity. 
         FIG.  11 B  is a cross-sectional view of the optical system of the sixth example focusing on a nearby object. 
         FIG.  12    shows aberrations of the optical system of the sixth example focusing on an object at infinity. 
         FIG.  13 A  is a cross-sectional view of an optical system of a seventh example focusing on an object at infinity. 
         FIG.  13 B  is a cross-sectional view of the optical system of the seventh example focusing on a nearby object. 
         FIG.  14    shows aberrations of the optical system of the seventh example focusing on an object at infinity. 
         FIG.  15 A  is a cross-sectional view of an optical system of an eighth example focusing on an object at infinity. 
         FIG.  15 B  is a cross-sectional view of the optical system of the eighth example focusing on a nearby object. 
         FIG.  16    shows aberrations of the optical system of the eighth example focusing on an object at infinity. 
         FIG.  17 A  is a cross-sectional view of an optical system of a ninth example focusing on an object at infinity. 
         FIG.  17 B  is a cross-sectional view of the optical system of the ninth example focusing on a nearby object. 
         FIG.  18    shows aberrations of the optical system of the ninth example focusing on an object at infinity. 
         FIG.  19 A  is a cross-sectional view of an optical system of a tenth example focusing on an object at infinity. 
         FIG.  19 B  is a cross-sectional view of the optical system of the tenth example focusing on a nearby object. 
         FIG.  20    shows aberrations of the optical system of the tenth example focusing on an object at infinity. 
         FIG.  21 A  is a cross-sectional view of an optical system of an eleventh example focusing on an object at infinity. 
         FIG.  21 B  is a cross-sectional view of the optical system of the eleventh example focusing on a nearby object. 
         FIG.  22    shows aberrations of the optical system of the eleventh example focusing on an object at infinity. 
         FIG.  23    schematically shows a camera including an optical system of the embodiment. 
         FIG.  24    is a first flowchart outlining a method for manufacturing an optical system of the embodiment. 
         FIG.  25    is a second flowchart outlining a method for manufacturing an optical system of the embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The following describes an optical system, an optical apparatus, and a method for manufacturing an optical system of an embodiment of the present application. 
     An optical system of the present embodiment includes a first lens group having positive refractive power, a focusing group that moves along an optical axis at focusing, and a rear group, in order from an object side; the first lens group includes a first-A lens group disposed on the object side of the largest air space A in the first lens group; and all of the following conditional expressions are satisfied: 
       1.00&lt; FNo ×( TL/f ) 2 &lt;2.50  (1)
 
       0.30&lt; dA/dG 1&lt;0.85  (2)
 
     where 
     FNo is the f-number of the optical system focusing on infinity, 
     TL is the total optical length of the optical system focusing on infinity, 
     f is the focal length of the optical system focusing on infinity, 
     dA is the length on the optical axis of the air space A, and 
     dG1 is the length on the optical axis of the first lens group. 
     The optical system of the present embodiment makes a correction with lenses closer to the image side than the first-A lens group, which enables achieving both reduction in size and weight and favorable optical performance. The optical system of the present embodiment can be downsized by satisfying conditional expression (1). The optical system of the present embodiment can be lightened by satisfying conditional expression (2). The effect of the optical system of the present embodiment can be further ensured by setting the upper limit of conditional expression (1) at 2.50. To further ensure the effect of the present embodiment, the upper limit of conditional expression (1) is preferably set at 2.45, 2.40, 2.35, 2.30, 2.25, or 2.20, more preferably at 2.15. 
     The effect of the optical system of the present embodiment can be further ensured by setting the lower limit of conditional expression (1) at 1.00. To further ensure the effect of the present embodiment, the lower limit of conditional expression (1) is preferably set at 1.10, 1.20, 1.25, or 1.30, more preferably at 1.35. 
     The effect of the optical system of the present embodiment can be further ensured by setting the upper limit of conditional expression (2) at 0.85. To further ensure the effect of the present embodiment, the upper limit of conditional expression (2) is preferably set at 0.80, 0.76, 0.73, or 0.70, more preferably at 0.68. 
     The effect of the optical system of the present embodiment can be further ensured by setting the lower limit of conditional expression (2) at 0.30. To further ensure the effect of the present embodiment, the lower limit of conditional expression (2) is preferably set at 0.31 or 0.33, more preferably at 0.35. 
     A small and lightweight optical system of favorable imaging performance can be achieved by the above configuration. 
     An optical system of the present embodiment includes a first lens group having positive refractive power, a focusing group that moves along an optical axis at focusing, and a rear group, in order from an object side; the first lens group includes a first-A lens group disposed on the object side of the largest air space A in the first lens group; and all of the following conditional expressions are satisfied: 
       0.30&lt; TL/f&lt; 0.80  (3)
 
       0.30&lt; dA/dG 1&lt;0.85  (2)
 
     where 
     TL is the total optical length of the optical system focusing on infinity, 
     f is the focal length of the optical system focusing on infinity, 
     dA is the length on the optical axis of the air space A, and 
     dG1 is the length on the optical axis of the first lens group. 
     The optical system of the present embodiment makes a correction with lenses closer to the image side than the first-A lens group, which enables achieving both reduction in size and weight and favorable optical performance. The optical system of the present embodiment can be downsized by satisfying conditional expression (3). The optical system of the present embodiment can be lightened by satisfying conditional expression (2). 
     The whole optical system of the present embodiment can be prevented from being too long by setting the ratio of the total optical length of the optical system to the focal length of the optical system less than the upper limit. The effect of the present embodiment can be further ensured by setting the upper limit of conditional expression (3) at 0.80. To further ensure the effect of the present embodiment, the upper limit of conditional expression (3) is preferably set at 0.78, 0.76, 0.74, or 0.72, more preferably at 0.70. 
     The optical system of the present embodiment can correct curvature of field favorably by setting the ratio of the total optical length of the optical system to the focal length of the optical system greater than the lower limit. The effect of the present embodiment can be further ensured by setting the lower limit of conditional expression (3) at 0.30. To further ensure the effect of the present embodiment, the lower limit of conditional expression (3) is preferably set at 0.33, 0.36, 0.40, or 0.42, more preferably at 0.44. 
     The effect of the optical system of the present embodiment can be further ensured by setting the upper limit of conditional expression (2) at 0.85. To further ensure the effect of the present embodiment, the upper limit of conditional expression (2) is preferably set at 0.80, 0.76, 0.73, or 0.70, more preferably at 0.68. 
     The effect of the optical system of the present embodiment can be further ensured by setting the lower limit of conditional expression (2) at 0.30. To further ensure the effect of the present embodiment, the lower limit of conditional expression (2) is preferably set at 0.31 or 0.33, more preferably at 0.35. 
     A small and lightweight optical system of favorable imaging performance can be achieved by the above configuration. 
     An optical system of the present embodiment is an optical system including a plurality of lenses including at least one positive lens component and a negative lens N, in order from an object side; and all of the following conditional expressions are satisfied: 
       1.00&lt; FNo ×( TL/f ) 2 &lt;2.50  (1)
 
       0.18&lt; dN/TL&lt; 0.45  (4)
 
     where 
     FNo is the f-number of the optical system focusing on infinity, 
     TL is the total optical length of the optical system focusing on infinity, 
     f is the focal length of the optical system focusing on infinity, and 
     dN is the distance on an optical axis from a surface closest to the object side in the optical system to an object-side surface of the negative lens N. 
     The optical system of the present embodiment satisfying conditional expressions (1) and (4) can be configured to have a small and lightweight object side and can correct aberrations with the image side of the optical system to achieve favorable imaging performance. A “lens component” herein refers to a single lens or a cemented lens. The effect of the optical system of the present embodiment can be further ensured by setting the upper limit of conditional expression (1) at 2.50. To further ensure the effect of the present embodiment, the upper limit of conditional expression (1) is preferably set at 2.45, 2.40, 2.35, 2.30, 2.25, or 2.20, more preferably at 2.15. 
     The effect of the optical system of the present embodiment can be further ensured by setting the lower limit of conditional expression (1) at 1.00. To further ensure the effect of the present embodiment, the lower limit of conditional expression (1) is preferably set at 1.10, 1.20, 1.25, or 1.30, more preferably at 1.35. 
     The effect of the optical system of the present embodiment can be further ensured by setting the upper limit of conditional expression (4) at 0.45. To further ensure the effect of the present embodiment, the upper limit of conditional expression (4) is preferably set at 0.42, 0.40, or 0.38, more preferably at 0.36. 
     The effect of the optical system of the present embodiment can be further ensured by setting the lower limit of conditional expression (4) at 0.18. To further ensure the effect of the present embodiment, the lower limit of conditional expression (4) is preferably set at 0.19, 0.20, or 0.21, more preferably at 0.22. 
     A small and lightweight optical system of favorable imaging performance can be achieved by the above configuration. 
     An optical system of the present embodiment is an optical system including a plurality of lenses that includes a positive lens component closest to an object side and that includes a negative lens N disposed closest to the object side of negative lenses disposed closer to an image side than the positive lens component; and all of the following conditional expressions are satisfied: 
       1.00&lt; FNo ×( TL/f ) 2 &lt;2.50  (1)
 
       0.18&lt; dN/TL&lt; 0.45  (4)
 
     where 
     FNo is the f-number of the optical system focusing on infinity, 
     TL is the total optical length of the optical system focusing on infinity, 
     f is the focal length of the optical system focusing on infinity, and 
     dN is the distance on an optical axis from a surface closest to the object side in the optical system to an object-side surface of the negative lens N. 
     The optical system of the present embodiment satisfying conditional expressions (1) and (4) can be configured to have a small and lightweight object side and can correct aberrations with the image side of the optical system to achieve favorable imaging performance. The effect of the optical system of the present embodiment can be further ensured by setting the upper limit of conditional expression (1) at 2.50. To further ensure the effect of the present embodiment, the upper limit of conditional expression (1) is preferably set at 2.45, 2.40, 2.35, 2.30, 2.25, or 2.20, more preferably at 2.15. 
     The effect of the optical system of the present embodiment can be further ensured by setting the lower limit of conditional expression (1) at 1.00. To further ensure the effect of the present embodiment, the lower limit of conditional expression (1) is preferably set at 1.10, 1.20, 1.25, or 1.30, more preferably at 1.35. 
     The effect of the optical system of the present embodiment can be further ensured by setting the upper limit of conditional expression (4) at 0.45. To further ensure the effect of the present embodiment, the upper limit of conditional expression (4) is preferably set at 0.42, 0.40, or 0.38, more preferably at 0.36. 
     The effect of the optical system of the present embodiment can be further ensured by setting the lower limit of conditional expression (4) at 0.18. To further ensure the effect of the present embodiment, the lower limit of conditional expression (4) is preferably set at 0.19, 0.20, or 0.21, more preferably at 0.22. 
     A small and lightweight optical system of favorable imaging performance can be achieved by the above configuration. 
     Preferably, the optical system of the present embodiment includes a first lens group, a focusing group that moves along the optical axis at focusing, and a rear group, in order from the object side; the first lens group includes a first-A lens group disposed on the object side of the largest air space A in the first lens group; and the following conditional expression is satisfied: 
       0.30&lt; dA/dG 1&lt;0.85  (2)
 
     where 
     dA is the length on the optical axis of the air space A, and 
     dG1 is the length on the optical axis of the first lens group. 
     The whole optical system of the present embodiment can be further lightened by satisfying conditional expression (2). The effect of the optical system of the present embodiment can be further ensured by setting the upper limit of conditional expression (2) at 0.85. To further ensure the effect of the present embodiment, the upper limit of conditional expression (2) is preferably set at 0.80, 0.76, 0.73, or 0.70, more preferably at 0.68. 
     The effect of the optical system of the present embodiment can be further ensured by setting the lower limit of conditional expression (2) at 0.30. To further ensure the effect of the present embodiment, the lower limit of conditional expression (2) is preferably set at 0.31 or 0.33, more preferably at 0.35. 
     The optical system of the present embodiment preferably satisfies the following conditional expression: 
       0.30&lt; TL/f&lt; 0.80.  (3)
 
     The optical system of the present embodiment can achieve both downsizing and favorable correction of curvature of field by satisfying conditional expression (3). The whole optical system of the present embodiment can be prevented from being too long by setting the ratio of the total optical length of the optical system to the focal length of the optical system less than the upper limit. The effect of the present embodiment can be further ensured by setting the upper limit of conditional expression (3) at 0.80. To further ensure the effect of the present embodiment, the upper limit of conditional expression (3) is preferably set at 0.78, 0.76, 0.74, or 0.72, more preferably at 0.70. 
     The optical system of the present embodiment can correct curvature of field favorably by setting the ratio of the total optical length of the optical system to the focal length of the optical system greater than the lower limit. The effect of the present embodiment can be further ensured by setting the lower limit of conditional expression (3) at 0.30. To further ensure the effect of the present embodiment, the lower limit of conditional expression (3) is preferably set at 0.33, 0.36, 0.40, or 0.42, more preferably at 0.44. 
     In the optical system of the present embodiment, the first lens group preferably includes the positive lens component and the negative lens N. 
     Preferably, the optical system of the present embodiment includes a first lens group, a focusing group that moves along the optical axis at focusing, and a rear group, in order from the object side; the first lens group includes a first-A lens group on the object side of the largest air space A in the first lens group and a first-B lens group on an image side of the air space A; and the following conditional expression is satisfied: 
       −2.00&lt; f 1 A/f 1 B&lt; 0.30  (5)
 
     where 
     f1A is the focal length of the first-A lens group, and 
     f1B is the focal length of the first-B lens group. 
     The optical system of the present embodiment can correct aberrations favorably by satisfying conditional expression (5). Setting the ratio of the focal length of the first-A lens group to the focal length of the first-B lens group less than the upper limit prevents the first-B lens group from having excessive positive power and enables the optical system of the present embodiment to correct spherical aberration and the like favorably. The effect of the present embodiment can be further ensured by setting the upper limit of conditional expression (5) at 0.30. To further ensure the effect of the present embodiment, the upper limit of conditional expression (5) is preferably set at 0.25, 0.20, 0.15, or 0.10, more preferably at 0.07. 
     Setting the ratio of the focal length of the first-A lens group to the focal length of the first-B lens group greater than the lower limit prevents the first-B lens group from having excessive negative power and enables the optical system of the present embodiment to correct coma aberration and the like favorably. The effect of the present embodiment can be further ensured by setting the lower limit of conditional expression (5) at −2.00. To further ensure the effect of the present embodiment, the lower limit of conditional expression (5) is preferably set at −1.60, −1.30, −1.00, or −0.80, more preferably at −0.60. 
     Preferably, the optical system of the present embodiment includes a first lens group, a focusing group that moves along the optical axis at focusing, and a rear group, in order from the object side; the first lens group includes a first-A lens group disposed on the object side of the largest air space A in the first lens group; and the following conditional expression is satisfied: 
       0.10&lt; f 1 A/f&lt; 0.60  (6)
 
     where 
     f1A is the focal length of the first-A lens group. 
     The optical system of the present embodiment can achieve both weight reduction and favorable correction of coma aberration by satisfying conditional expression (6). Setting the ratio of the focal length of the first-A lens group to the focal length of the optical system less than the upper limit prevents the power of the first-A lens group from being low and enables reduction in the diameter of the first lens group except the first-A lens group, which enables weight reduction of the optical system of the present embodiment. The effect of the present embodiment can be further ensured by setting the upper limit of conditional expression (6) at 0.60. To further ensure the effect of the present embodiment, the upper limit of conditional expression (6) is preferably set at 0.57, 0.55, 0.52, or 0.48, more preferably at 0.45. 
     Setting the ratio of the focal length of the first-A lens group to the focal length of the optical system greater than the lower limit prevents the power of the first-A lens group from being high and thus enables the optical system of the present embodiment to correct coma aberration favorably. The effect of the present embodiment can be further ensured by setting the lower limit of conditional expression (6) at 0.10. To further ensure the effect of the present embodiment, the lower limit of conditional expression (6) is preferably set at 0.13, 0.16, 0.20, or 0.22, more preferably at 0.25. 
     Preferably, the optical system of the present embodiment includes a first lens group, a focusing group that moves along the optical axis at focusing, and a rear group, in order from the object side; the first lens group includes a first-B lens group disposed on an image side of the largest air space A in the first lens group; and the following conditional expression is satisfied: 
       0.40 &lt;dB/dG 1&lt;0.85  (7)
 
     where 
     dB is the distance on the optical axis from a surface closest to the object side in the optical system to a surface closest to the object side in the first-B lens group, and 
     dG1 is the length on the optical axis of the first lens group. 
     The optical system of the present embodiment can achieve both weight reduction and favorable correction of spherical aberration by satisfying conditional expression (7). The optical system of the present embodiment can correct spherical aberration favorably by setting the value of conditional expression (7) less than the upper limit. The effect of the present embodiment can be further ensured by setting the upper limit of conditional expression (7) at 0.85. To further ensure the effect of the present embodiment, the upper limit of conditional expression (7) is preferably set at 0.82, 0.80, 0.78, or 0.76, more preferably at 0.74. 
     Setting the value of conditional expression (7) greater than the lower limit enables reduction in the diameter of the first-B lens group and thus enables weight reduction of the optical system of the present embodiment. The effect of the present embodiment can be further ensured by setting the lower limit of conditional expression (7) at 0.40. To further ensure the effect of the present embodiment, the lower limit of conditional expression (7) is preferably set at 0.44, 0.47, 0.50, or 0.52, more preferably at 0.54. 
     Preferably, the optical system of the present embodiment includes a first lens group, a focusing group that moves along the optical axis at focusing, and a rear group, in order from the object side; the first lens group includes a first-A lens group disposed on the object side of the largest air space A in the first lens group; and the first-A lens group includes two or fewer positive lenses. 
     The optical system of the present embodiment having such a configuration can be lightened. 
     Preferably, the optical system of the present embodiment includes a first lens group, a focusing group that moves along the optical axis at focusing, and a rear group, in order from the object side; the first lens group includes a first-A lens group disposed on the object side of the largest air space A in the first lens group; and the following conditional expression is satisfied: 
       0.80&lt; fL 1/ fL 2&lt;3.30  (8)
 
     where 
     fL1 is the focal length of a first lens disposed closest to the object side in the first-A lens group, and 
     fL2 is the focal length of a second lens disposed second from the object side in the first-A lens group. 
     The optical system of the present embodiment can correct spherical aberration and coma aberration favorably by satisfying conditional expression (8). Setting the ratio of the focal length of the first lens to the focal length of the second lens less than the upper limit prevents the power of the first lens from being too low and enables the optical system of the present embodiment to correct coma aberration favorably. The effect of the present embodiment can be further ensured by setting the upper limit of conditional expression (8) at 3.30. To further ensure the effect of the present embodiment, the upper limit of conditional expression (8) is preferably set at 3.20, 3.10, 3.00, or 2.90, more preferably at 2.80. 
     Setting the ratio of the focal length of the first lens to the focal length of the second lens greater than the lower limit prevents the power of the first lens from being too high and enables the optical system of the present embodiment to correct spherical aberration favorably. The effect of the present embodiment can be further ensured by setting the lower limit of conditional expression (8) at 0.80. To further ensure the effect of the present embodiment, the lower limit of conditional expression (8) is preferably set at 0.85, 0.90, 0.95, or 1.00, more preferably at 1.05. 
     Preferably, the optical system of the present embodiment includes a first lens group, a focusing group that moves along the optical axis at focusing, and a rear group, in order from the object side; the first lens group includes a first-A lens group on the object side of the largest air space A in the first lens group and a first-B lens group on an image side of the air space A; and the first-B lens group includes at least one positive lens Z satisfying the following conditional expression: 
       60.00&lt;ν d 1 A max−ν dLZ   (9)
 
     where 
     νd1Amax is the highest of the Abbe numbers for d-line of lenses included in the first-A lens group, and 
     νdLZ is the Abbe number for d-line of the positive lens Z. 
     The optical system of the present embodiment can correct quadratic variance of axial chromatic aberration favorably by setting the value of conditional expression (9) greater than the lower limit. The effect of the present embodiment can be further ensured by setting the lower limit of conditional expression (9) at 60.00. To further ensure the effect of the present embodiment, the lower limit of conditional expression (9) is preferably set at 62.00, 63.00, 64.00, or 65.00, more preferably at 66.00. 
     Preferably, the optical system of the present embodiment includes a first lens group, a focusing group that moves along the optical axis at focusing, and a rear group, in order from the object side; the first lens group includes a first-A lens group disposed on the object side of the largest air space A in the first lens group; and the following conditional expression is satisfied: 
       55.00&lt;ν d 1 Aave   (10)
 
     where 
     νd1Aave is an average of the Abbe numbers for d-line of lenses included in the first-A lens group. 
     The optical system of the present embodiment can correct axial chromatic aberration and lateral chromatic aberration favorably by setting the value of conditional expression (10) greater than the lower limit. The effect of the present embodiment can be further ensured by setting the lower limit of conditional expression (10) at 55.00. To further ensure the effect of the present embodiment, the lower limit of conditional expression (10) is preferably set at 60.00, 65.00, 70.00, or 75.00, more preferably at 80.00. 
     Preferably, the optical system of the present embodiment includes a first lens group, a focusing group that moves along the optical axis at focusing, and a rear group, in order from the object side; the first lens group includes a first-B lens group disposed on an image side of the largest air space A in the first lens group; and the first-B lens group includes at least one positive lens Z satisfying all of the following conditional expressions: 
         ndLZ+ (0.01425×ν dLZ )&lt;2.12  (11)
 
       ν dLZ&lt; 35.00  (12)
 
       0.702 &lt;θgFLZ+ (0.00316×ν dLZ )  (13)
 
     where 
     ndLZ is the refractive index for d-line of the positive lens Z, 
     νdLZ is the Abbe number for d-line of the positive lens Z, and 
     θgFLZ is a partial dispersion ratio of the positive lens Z and is defined by the following equation: 
       θ gFLZ =( ngLZ−nFLZ )/( nFLZ−nCLZ )
 
     where the refractive indices for g-line, F-line, and C-line of the positive lens Z are denoted by ngLZ, nFLZ, and nCLZ, respectively. 
     The optical system of the present embodiment having such a configuration can correct aberrations favorably. Setting the value of conditional expression (11) less than the upper limit prevents the Petzval sum from being too small and enables the optical system of the present embodiment to correct curvature of field favorably. The effect of the present embodiment can be further ensured by setting the upper limit of conditional expression (11) at 2.12. To further ensure the effect of the present embodiment, the upper limit of conditional expression (11) is preferably set at 2.10, 2.09, 2.08, or 2.07, more preferably at 2.06. 
     The optical system of the present embodiment can correct quadratic variance of axial chromatic aberration favorably by setting the value of conditional expression (12) less than the upper limit. The effect of the present embodiment can be further ensured by setting the upper limit of conditional expression (12) at 35.00. To further ensure the effect of the present embodiment, the upper limit of conditional expression (12) is preferably set at 33.00, 31.00, 30.50, or 30.00, more preferably at 29.50. 
     The optical system of the present embodiment can correct quadratic variance of axial chromatic aberration favorably by setting the value of conditional expression (13) greater than the lower limit. The effect of the present embodiment can be further ensured by setting the upper limit of conditional expression (13) at 0.702. To further ensure the effect of the present embodiment, the upper limit of conditional expression (13) is preferably set at 0.704, 0.707, 0.710, or 0.712, more preferably at 0.715. 
     Preferably, the optical system of the present embodiment includes a first lens group, a focusing group that moves along the optical axis at focusing, and a rear group, in order from the object side; the first lens group includes a first-A lens group disposed on the object side of the largest air space A in the first lens group; and the following conditional expression is satisfied: 
       0.00&lt;( L 1 R 2+ L 1 R 1)/( L 1 R 2− L 1 R 1)&lt;3.00  (14)
 
     where 
     L1R1 is the radius of curvature of an object-side surface of a first lens disposed closest to the object side, and 
     L1R2 is the radius of curvature of an image-side surface of the first lens. 
     The optical system of the present embodiment can correct spherical aberration and coma aberration favorably by satisfying conditional expression (14). The optical system of the present embodiment can correct spherical aberration favorably by setting the value of conditional expression (14) less than the upper limit. The effect of the present embodiment can be further ensured by setting the upper limit of conditional expression (14) at 3.00. To further ensure the effect of the present embodiment, the upper limit of conditional expression (14) is preferably set at 2.70, 2.50, 2.20, or 2.00, more preferably at 1.80. 
     The optical system of the present embodiment can correct coma aberration favorably by setting the value of conditional expression (14) greater than the lower limit. The effect of the present embodiment can be further ensured by setting the lower limit of conditional expression (14) at 0.00. To further ensure the effect of the present embodiment, the lower limit of conditional expression (14) is preferably set at 0.20, 0.40, 0.50, or 0.60, more preferably at 0.70. 
     Preferably, the optical system of the present embodiment includes a first lens group, a focusing group that moves along the optical axis at focusing, and a rear group, in order from the object side; the first lens group includes a first-A lens group disposed on the object side of the largest air space A in the first lens group; and the following conditional expression is satisfied: 
       0.00&lt;( L 2 R 2+ L 2 R 1)/( L 2 R 2− L 2 R 1)&lt;3.50  (15)
 
     where 
     L2R1 is the radius of curvature of an object-side surface of a second lens disposed second from the object side in the first-A lens group, and 
     L2R2 is the radius of curvature of an image-side surface of the second lens. 
     The optical system of the present embodiment can correct spherical aberration and coma aberration favorably by satisfying conditional expression (15). The optical system of the present embodiment can correct spherical aberration favorably by setting the value of conditional expression (15) less than the upper limit. The effect of the present embodiment can be further ensured by setting the upper limit of conditional expression (14) at 3.50. To further ensure the effect of the present embodiment, the upper limit of conditional expression (15) is preferably set at 3.20, 3.00, 2.80, or 2.60, more preferably at 2.40. 
     The optical system of the present embodiment can correct coma aberration favorably by setting the value of conditional expression (15) greater than the lower limit. The effect of the present embodiment can be further ensured by setting the lower limit of conditional expression (15) at 0.00. To further ensure the effect of the present embodiment, the lower limit of conditional expression (15) is preferably set at 0.20, 0.50, 0.80, or 1.00, more preferably at 1.20. 
     Preferably, the optical system of the present embodiment includes a first lens group, a focusing group that moves along the optical axis at focusing, and a rear group, in order from the object side; and the following conditional expression is satisfied: 
       0.10&lt; f 1/ f&lt; 0.60  (16)
 
     where 
     f1 is the focal length of the first lens group. 
     The optical system of the present embodiment can achieve both downsizing and favorable correction of spherical aberration by satisfying conditional expression (16). Setting the ratio of the focal length of the first lens group to the focal length of the optical system less than the upper limit prevents the power of the first lens group from being too low and thus enables the optical system of the present embodiment to be downsized. The effect of the present embodiment can be further ensured by setting the upper limit of conditional expression (16) at 0.60. To further ensure the effect of the present embodiment, the upper limit of conditional expression (16) is preferably set at 0.56, 0.53, 0.50, or 0.48, more preferably at 0.45. 
     Setting the value of conditional expression (16) greater than the lower limit prevents the power of the first lens group from being too high and thus enables the optical system of the present embodiment to correct spherical aberration favorably. The effect of the present embodiment can be further ensured by setting the lower limit of conditional expression (16) at 0.10. To further ensure the effect of the present embodiment, the lower limit of conditional expression (16) is preferably set at 0.14, 0.18, 0.22, or 0.25, more preferably at 0.28. 
     Preferably, the optical system of the present embodiment includes a first lens group, a focusing group that moves along the optical axis at focusing, and a rear group, in order from the object side; and the following conditional expression is satisfied: 
       0.20&lt;(− fF )/ f 1&lt;0.85  (17)
 
     where 
     fF is the focal length of the focusing group, and 
     f1 is the focal length of the first lens group. 
     The optical system of the present embodiment can correct spherical aberrations favorably from infinity to close range by satisfying conditional expression (17). Setting the ratio of the focal length of the focusing group to the focal length of the first lens group less than the upper limit prevents the power of the focusing group from being too low and thus enables the optical system of the present embodiment to reduce variations in curvature of field. The effect of the present embodiment can be further ensured by setting the upper limit of conditional expression (17) at 0.85. To further ensure the effect of the present embodiment, the upper limit of conditional expression (17) is preferably set at 0.80, 0.77, 0.75, or 0.72, more preferably at 0.65. 
     Setting the ratio of the focal length of the focusing group to the focal length of the first lens group greater than the lower limit prevents the power of the focusing group from being too high and thus enables the optical system of the present embodiment to reduce variations in axial chromatic aberration. The effect of the present embodiment can be further ensured by setting the lower limit of conditional expression (17) at 0.20. To further ensure the effect of the present embodiment, the lower limit of conditional expression (17) is preferably set at 0.24, 0.28, 0.32, or 0.36, more preferably at 0.40. 
     Preferably, the optical system of the present embodiment includes a first lens group, a focusing group that moves along the optical axis at focusing, and a rear group, in order from the object side; and the following conditional expression is satisfied: 
       −1.50&lt;(− fF )/ fR&lt; 0.60  (18)
 
     where 
     fF is the focal length of the focusing group, and 
     fR is the focal length of the rear group. 
     The optical system of the present embodiment can correct aberrations favorably by satisfying conditional expression (18). Setting the value of conditional expression (18) less than the upper limit prevents the power of the focusing group from being too low and thus enables the optical system of the present embodiment to correct curvature of field favorably. The effect of the present embodiment can be further ensured by setting the upper limit of conditional expression (18) at 0.60. To further ensure the effect of the present embodiment, the upper limit of conditional expression (18) is preferably set at 0.50, 0.40, 0.30, or 0.20, more preferably at 0.10. 
     Setting the value of conditional expression (18) greater than the lower limit prevents the power of the focusing group from being too high and thus enables the optical system of the present embodiment to correct lateral chromatic aberration favorably. The effect of the present embodiment can be further ensured by setting the lower limit of conditional expression (18) at −1.50. To further ensure the effect of the present embodiment, the lower limit of conditional expression (18) is preferably set at −1.40, −1.30, −1.20, or −1.10, more preferably at −1.00. 
     Preferably, the optical system of the present embodiment includes a first lens group, a focusing group that moves along the optical axis at focusing, and a rear group, in order from the object side; and the following conditional expression is satisfied: 
       0.30&lt; dF/TL&lt; 0.70  (19)
 
     where 
     dF is the distance on the optical axis from a surface closest to the object side in the optical system to a surface closest to the object side in the focusing group. 
     The optical system of the present embodiment can achieve both speedup of focusing with the lightweight focusing group and reduction in variations in curvature of field by satisfying conditional expression (19). Setting the value of conditional expression (19) less than the upper limit prevents the focusing group from being placed too backward and enables the optical system of the present embodiment to reduce variations in curvature of field. The effect of the present embodiment can be further ensured by setting the upper limit of conditional expression (19) at 0.70. To further ensure the effect of the present embodiment, the upper limit of conditional expression (19) is preferably set at 0.67, 0.64, 0.61, or 0.58, more preferably at 0.56. 
     In the optical system of the present embodiment, setting the value of conditional expression (19) greater than the lower limit prevents the focusing group from being placed too forward and enables weight reduction of the focusing group. The effect of the present embodiment can be further ensured by setting the lower limit of conditional expression (19) at 0.30. To further ensure the effect of the present embodiment, the lower limit of conditional expression (19) is preferably set at 0.32, 0.34, 0.36, or 0.38, more preferably at 0.40. 
     Preferably, the optical system of the present embodiment includes a first lens group, a focusing group that moves along the optical axis at focusing, and a rear group, in order from the object side; and the following conditional expression is satisfied: 
       40.00 &lt;νdFave   (20)
 
     where 
     νdFave is an average of the Abbe numbers for d-line of lenses included in the focusing group. 
     The optical system of the present embodiment can correct axial chromatic aberration favorably from infinity to close range by setting the value of conditional expression (20) greater than the lower limit. The effect of the present embodiment can be further ensured by setting the lower limit of conditional expression (20) at 40.00. To further ensure the effect of the present embodiment, the lower limit of conditional expression (20) is preferably set at 50.00, 55.00, 60.00, or 65.00, more preferably at 70.00. 
     The optical system of the present embodiment preferably satisfies the following conditional expression: 
       1.00°&lt;2ω&lt;20.00°  (21)
 
     where 
     2ω is the total angle of view of the optical system. 
     Conditional expression (21) is to set an appropriate value of the total angle of view of the optical system of the present embodiment. Variations in aberrations, such as coma aberration, curvature of field, and distortion, associated with focusing can be reduced by satisfying conditional expression (21). The effect of the present embodiment can be further ensured by setting the upper limit of conditional expression (21) at 20.00°. To further ensure the effect of the present embodiment, the upper limit of conditional expression (21) is preferably set at 18.00°, 16.00°, 14.00°, or 12.00°, more preferably at 10.00°. 
     The effect of the present embodiment can be further ensured by setting the lower limit of conditional expression (21) at 1.00°. To further ensure the effect of the present embodiment, the lower limit of conditional expression (21) is preferably set at 1.50°, 2.00°, 2.20°, or 2.50°, more preferably at 2.80°. 
     The optical system of the present embodiment preferably satisfies the following conditional expression: 
       0.075&lt; Bf/f&lt; 0.185  (22)
 
     where 
     Bf is the back focus of the optical system. 
     The optical system of the present embodiment can achieve both downsizing and weight reduction by satisfying conditional expression (22). Setting the ratio of the back focus to the focal length of the optical system less than the upper limit prevents the back focus from being too long and enables the whole optical system of the present embodiment to be shortened. The effect of the present embodiment can be further ensured by setting the upper limit of conditional expression (22) at 0.185. To further ensure the effect of the present embodiment, the upper limit of conditional expression (22) is preferably set at 0.180, 0.175, 0.170, or 0.165, more preferably at 0.160. 
     Setting the ratio of the back focus to the focal length of the optical system greater than the lower limit ensures an appropriate back focus and enables weight reduction of the optical system of the present embodiment. The effect of the present embodiment can be further ensured by setting the lower limit of conditional expression (22) at 0.075. To further ensure the effect of the present embodiment, the lower limit of conditional expression (22) is preferably set at 0.080, 0.082, 0.085, or 0.088, more preferably at 0.090. 
     Preferably, the optical system of the present embodiment includes a first lens group, a focusing group that moves along the optical axis at focusing, and a rear group, in order from the object side; and the rear group includes a vibration reduction lens group movable so that movement has a component in a direction perpendicular to the optical axis to correct an image blur. 
     The optical system of the present embodiment having such a configuration can correct an image blur favorably. 
     A small and lightweight optical system of favorable imaging performance can be achieved by the above configuration. 
     An optical apparatus of the present embodiment includes the optical system having the above configuration. This enables achieving a small and lightweight optical apparatus of favorable imaging performance. 
     A method for manufacturing an optical system of the present embodiment is a method for manufacturing an optical system including a plurality of lenses. The method includes disposing a first lens group having positive refractive power, a focusing group that moves along an optical axis at focusing, and a rear group, in order from an object side; disposing a first-A lens group on the object side of the largest air space A in the first lens group; and arranging so that all of the following conditional expressions are satisfied: 
       1.00&lt; FNo ×( TL/f ) 2 &lt;2.50  (1)
 
       0.30&lt; dA/dG 1&lt;0.85  (2)
 
     where 
     FNo is the f-number of the optical system focusing on infinity, 
     TL is the total optical length of the optical system focusing on infinity, 
     f is the focal length of the optical system focusing on infinity, 
     dA is the length on the optical axis of the air space A, and 
     dG1 is the length on the optical axis of the first lens group. 
     A method for manufacturing an optical system of the present embodiment is a method for manufacturing an optical system including a plurality of lenses. The method includes disposing at least one positive lens component and a negative lens N, in order from an object side; and arranging so that all of the following conditional expressions are satisfied: 
       1.00&lt; FNo ×( TL/f ) 2 &lt;2.50  (1)
 
       0.18&lt; dN/TL&lt; 0.45  (4)
 
     where 
     FNo is the f-number of the optical system focusing on infinity, 
     TL is the total optical length of the optical system focusing on infinity, 
     f is the focal length of the optical system focusing on infinity, and 
     dN is the distance on an optical axis from a surface closest to the object side in the optical system to an object-side surface of the negative lens N. 
     A small and lightweight optical system of favorable imaging performance can be manufactured by such a method for manufacturing an optical system. 
     NUMERICAL EXAMPLES 
     Examples of the present application will be described below with reference to the drawings. 
     First Example 
       FIG.  1 A  is a cross-sectional view of an optical system of a first example focusing on an object at infinity.  FIG.  1 B  is a cross-sectional view of the optical system of the first example focusing on a nearby object. 
     The optical system of the present example includes a first lens group G 1  having positive refractive power, a focusing group GF having negative refractive power, and a rear group GR having negative refractive power, in order from the object side. An aperture stop S is disposed between the first lens group G 1  and the focusing group GF. The first lens group G 1  includes a first-A lens group G 1 A having positive refractive power and a first-B lens group G 1 B having negative refractive power, separated by the largest air space A in the first lens group; the first-A lens group G 1 A is disposed on the object side of the air space A, and the first-B lens group G 1 B is disposed on the image side of the air space A. 
     The first-A lens group G 1 A includes a positive meniscus lens L 1  convex on the object side, and a positive meniscus lens L 2  convex on the object side, in order from the object side. 
     The first-B lens group G 1 B includes a negative cemented lens composed of a positive meniscus lens L 3  convex on the object side and a negative meniscus lens L 4  convex on the object side; a positive meniscus lens L 5  convex on the object side; and a positive cemented lens composed of a biconvex positive lens L 6  and a biconcave negative lens L 7 , in order from the object side. 
     The focusing group GF includes a negative meniscus lens L 8  convex on the object side. 
     The rear group GR includes a positive meniscus lens L 9  convex on the image side; a negative cemented lens composed of a biconvex positive lens L 10  and a biconcave negative lens L 11 ; a biconcave negative lens L 12 ; a positive cemented lens composed of a biconvex positive lens L 13  and a biconcave negative lens L 14 ; a positive cemented lens composed of a negative meniscus lens L 15  convex on the object side and a biconvex positive lens L 16 ; a negative cemented lens composed of a biconcave negative lens L 17  and a positive meniscus lens L 18  convex on the object side; and a biconvex positive lens L 19 , in order from the object side. 
     An imaging device (not shown) constructed from CCD, CMOS or the like is disposed on an image plane I. 
     The optical system of the present example focuses by moving the focusing group GF along the optical axis. When the focus is shifted from infinity to a nearby object, the focusing group GF moves from the object side toward the image side. 
     In the optical system of the present example, the negative cemented lens composed of the positive lens L 10  and the negative lens L 11  and the negative lens L 12 , which are lenses included in the rear group GR, are configured as a vibration reduction lens group movable so that movement has a component in a direction perpendicular to the optical axis to correct an image blur. 
     In the optical system of the present example, the positive meniscus lens L 1  corresponds to the first lens, and the positive meniscus lens L 2  corresponds to the second lens. In the optical system of the present example, the negative meniscus lens L 4  corresponds to the negative lens N, and the positive lens L 6  corresponds to the positive lens Z. 
     In the optical system of the present example, dA is the distance on the optical axis between the image-side surface of the positive meniscus lens L 2  and the object-side surface of the positive meniscus lens L 3 . dG1 is the distance on the optical axis between the object-side surface of the positive meniscus lens L 1  and the image-side surface of the negative lens L 7 . dB is the distance on the optical axis between the object-side surface of the positive meniscus lens L 1  and the object-side surface of the positive meniscus lens L 3 . dN is the distance on the optical axis between the object-side surface of the positive meniscus lens L 1  and the object-side surface of the negative meniscus lens L 4 . In the cross-sectional views of the optical systems of the other examples described below, illustration of dA, dG1, dB, and dN will be omitted. 
     Table 1 below shows specifications of the optical system of the present example. In Table 1, f, Fno, and TL denote the focal length, the f-number, and the total optical length of the optical system focusing on infinity, respectively, and Bf denotes the back focus of the optical system. 
     In [Lens specifications], m denotes the positions of optical surfaces counted from the object side, r the radii of curvature, d the surface-to-surface distances, nd the refractive indices for d-line (wavelength 587.6 nm), and νd the Abbe numbers for d-line. In [Lens specifications], the radius of curvature r=∞. means a plane. 
     The unit of the focal lengths f, the radii of curvature r, and the other lengths listed in Table 1 is “mm.” However, the unit is not limited thereto because the optical performance of a proportionally enlarged or reduced optical system is the same as that of the original optical system. 
     The above reference symbols in Table 1 will also be used similarly in the tables of the other examples described below. 
     
       
         
           
               
             
               
                 TABLE 1 
               
               
                   
               
             
            
               
                 [General specifications] 
               
               
                   
               
            
           
           
               
               
               
            
               
                   
                 f 
                 292.50 
               
               
                   
                 Fno 
                 4.10 
               
               
                   
                 Bf 
                 35.641 
               
               
                   
                 image height 
                 21.700 
               
               
                   
                 TL 
                 190.638 
               
               
                   
                 2ω 
                 8.43 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens specifications] 
               
            
           
           
               
               
               
               
               
            
               
                 m 
                 r 
                 d 
                 nd 
                 νd 
               
               
                   
               
               
                  1) 
                 125.140 
                 6.663 
                 1.537750 
                 74.70 
               
               
                  2) 
                 1851.356 
                 0.150 
               
               
                  3) 
                 59.805 
                 10.676  
                 1.437001 
                 95.10 
               
               
                  4) 
                 262.678 
                 28.838  
               
               
                  5) 
                 46.054 
                 7.325 
                 1.437001 
                 95.10 
               
               
                  6) 
                 4710.018 
                 1.600 
                 1.902650 
                 35.72 
               
               
                  7) 
                 30.903 
                 1.232 
               
               
                  8) 
                 31.124 
                 7.235 
                 1.437001 
                 95.10 
               
               
                  9) 
                 211.923 
                 4.436 
               
               
                 10) 
                 64.379 
                 5.654 
                 1.663820 
                 27.35 
               
               
                 11) 
                 −76.867 
                 1.300 
                 1.654115 
                 39.68 
               
               
                 12) 
                 84.138 
                 4.271 
               
            
           
           
               
               
               
               
               
            
               
                  13&gt; 
                 ∞ 
                 D13 
                 (aperture stop) 
                   
               
            
           
           
               
               
               
               
               
            
               
                 14) 
                 898.004 
                 1.100 
                 1.496997 
                 81.61 
               
               
                 15) 
                 37.914 
                 D15 
               
               
                 16) 
                 −122.862 
                 2.483 
                 1.487490 
                 70.32 
               
               
                 17) 
                 −51.275 
                 1.500 
               
               
                 18) 
                 212.753 
                 3.300 
                 1.620040 
                 36.40 
               
               
                 19) 
                 −38.078 
                 1.100 
                 1.593190 
                 67.90 
               
               
                 20) 
                 42.404 
                 1.650 
               
               
                 21) 
                 −1123.057 
                 1.100 
                 1.593490 
                 67.00 
               
               
                 22) 
                 48.084 
                 1.500 
               
               
                 23) 
                 36.980 
                 7.966 
                 1.612660 
                 44.46 
               
               
                 24) 
                 −28.819 
                 1.300 
                 1.593190 
                 67.90 
               
               
                 25) 
                 237.490 
                 2.000 
               
               
                 26) 
                 60.518 
                 1.300 
                 1.922860 
                 20.88 
               
               
                 27) 
                 21.378 
                 7.261 
                 1.720467 
                 34.71 
               
               
                 28) 
                 −1990.403 
                 5.379 
               
               
                 29) 
                 −44.860 
                 1.300 
                 1.816000 
                 46.59 
               
               
                 30) 
                 36.494 
                 4.671 
                 1.737999 
                 32.33 
               
               
                 31) 
                 197.557 
                 0.500 
               
               
                 32) 
                 53.113 
                 5.700 
                 1.581440 
                 40.98 
               
               
                 33) 
                 −118.041 
                 Bf 
               
               
                   
               
            
           
           
               
            
               
                 [Focal length data of groups] 
               
            
           
           
               
               
               
               
            
               
                   
                 Groups 
                 Starting surfaces 
                 Focal lengths 
               
               
                   
                   
               
               
                   
                 G1 
                 1 
                 121.914 
               
               
                   
                 G1A 
                 1 
                 103.249 
               
               
                   
                 G1B 
                 5 
                 −276.316 
               
               
                   
                 GF 
                 14 
                 −79.683 
               
               
                   
                 GR 
                 16 
                 −342.518 
               
               
                   
                 f1 
                 1 
                 −48.395 
               
               
                   
                 f2 
                 6 
                 105.403 
               
               
                   
                 f3 
                 9 
                 64.392 
               
               
                   
                 f4 
                 13 
                 −112.410 
               
               
                   
                 f5 
                 19 
                 134.882 
               
               
                   
                 f6 
                 22 
                 81.543 
               
               
                   
                 f7 
                 24 
                 −60.633 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Variable distance data] 
               
            
           
           
               
               
               
            
               
                   
                 At focusing on infinity 
                 At focusing on a nearby object 
               
               
                   
               
               
                 D13 
                 4.000 
                 19.946 
               
               
                 D15 
                 20.506 
                 4.560 
               
               
                   
               
            
           
         
       
     
       FIG.  2    shows aberrations of the optical system of the first example focusing on an object at infinity. 
     In the graphs of aberrations, FNO and Y denote f-number and image height, respectively. More specifically, the graph of spherical aberration shows the f-number corresponding to the maximum aperture, the graphs of astigmatism and distortion show the maximum of image height, and the graph of coma aberration shows the values of image height. d and g denote d-line and g-line (wavelength 435.8 nm), respectively. In the graph of astigmatism, the solid lines and the broken lines show a sagittal plane and a meridional plane, respectively. The reference symbols in the graphs of aberrations of the present example will also be used in those of the other examples described below. 
     The graphs of aberrations suggest that the optical system of the present example effectively reduces variations in aberrations at focusing and has high optical performance. 
     Second Example 
       FIG.  3 A  is a cross-sectional view of an optical system of a second example focusing on an object at infinity.  FIG.  3 B  is a cross-sectional view of the optical system of the second example focusing on a nearby object. 
     The optical system of the present example includes a first lens group G 1  having positive refractive power, a focusing group GF having negative refractive power, and a rear group GR having positive refractive power, in order from the object side. An aperture stop S is disposed between the first lens group G 1  and the focusing group GF. The first lens group G 1  includes a first-A lens group G 1 A having positive refractive power and a first-B lens group G 1 B having negative refractive power, separated by the largest air space A in the first lens group; the first-A lens group G 1 A is disposed on the object side of the air space A, and the first-B lens group G 1 B is disposed on the image side of the air space A. 
     The first-A lens group G 1 A includes a positive meniscus lens L 1  convex on the object side, and a positive meniscus lens L 2  convex on the object side, in order from the object side. 
     The first-B lens group G 1 B includes a negative cemented lens composed of a biconvex positive lens L 3  and a biconcave negative lens L 4 ; a positive meniscus lens L 5  convex on the object side; and a positive cemented lens composed of a biconvex positive lens L 6  and a biconcave negative lens L 7 , in order from the object side. 
     The focusing group GF includes a biconcave negative lens L 8 . 
     The rear group GR includes a positive meniscus lens L 9  convex on the image side; a negative cemented lens composed of a biconvex positive lens L 10  and a biconcave negative lens L 11 ; a biconcave negative lens L 12 ; a positive cemented lens composed of a biconvex positive lens L 13  and a negative meniscus lens L 14  convex on the image side; a positive cemented lens composed of a negative meniscus lens L 15  convex on the object side and a positive meniscus lens L 16  convex on the object side; a negative cemented lens composed of a biconcave negative lens L 17  and a positive meniscus lens L 18  convex on the object side; and a biconvex positive lens L 19 , in order from the object side. 
     An imaging device (not shown) constructed from CCD, CMOS or the like is disposed on an image plane I. 
     The optical system of the present example focuses by moving the focusing group GF along the optical axis. When the focus is shifted from infinity to a nearby object, the focusing group GF moves from the object side toward the image side. 
     In the optical system of the present example, the negative cemented lens composed of the positive lens L 10  and the negative lens L 11  and the negative lens L 12 , which are lenses included in the rear group GR, are configured as a vibration reduction lens group movable so that movement has a component in a direction perpendicular to the optical axis to correct an image blur. 
     In the optical system of the present example, the positive meniscus lens L 1  corresponds to the first lens, and the positive meniscus lens L 2  corresponds to the second lens. In the optical system of the present example, the negative lens L 4  corresponds to the negative lens N, and the positive lens L 6  corresponds to the positive lens Z. 
     In the optical system of the present example, dA is the distance on the optical axis between the image-side surface of the positive meniscus lens L 2  and the object-side surface of the positive lens L 3 . dG1 is the distance on the optical axis between the object-side surface of the positive meniscus lens L 1  and the image-side surface of the negative lens L 7 . dB is the distance on the optical axis between the object-side surface of the positive meniscus lens L 1  and the object-side surface of the positive lens L 3 . dN is the distance on the optical axis between the object-side surface of the positive meniscus lens L 1  and the object-side surface of the negative lens L 4 . 
     Table 2 below shows specifications of the optical system of the present example. 
     
       
         
           
               
             
               
                 TABLE 2 
               
               
                   
               
             
            
               
                 [General specifications] 
               
               
                   
               
            
           
           
               
               
               
            
               
                   
                 f 
                 390.00 
               
               
                   
                 Fno 
                 4.10 
               
               
                   
                 Bf 
                 60.901 
               
               
                   
                 image height 
                 21.700 
               
               
                   
                 TL 
                 267.445 
               
               
                   
                 2ω 
                 6.30 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens specifications] 
               
            
           
           
               
               
               
               
               
            
               
                 m 
                 r 
                 d 
                 nd 
                 νd 
               
               
                   
               
               
                  1) 
                 187.004 
                 7.233 
                 1.537750 
                 74.70 
               
               
                  2) 
                 1083.302 
                 0.200 
               
               
                  3) 
                 90.597 
                 12.867  
                 1.433837 
                 95.16 
               
               
                  4) 
                 430.769 
                 53.926  
               
               
                  5) 
                 60.452 
                 9.061 
                 1.437001 
                 95.10 
               
               
                  6) 
                 −2517.992 
                 2.200 
                 1.902650 
                 35.72 
               
               
                  7) 
                 43.878 
                 1.547 
               
               
                  8) 
                 43.725 
                 8.825 
                 1.437001 
                 95.10 
               
               
                  9) 
                 492.119 
                 11.552  
               
               
                 10) 
                 89.096 
                 6.561 
                 1.663820 
                 27.35 
               
               
                 11) 
                 −94.634 
                 1.600 
                 1.654115 
                 39.68 
               
               
                 12) 
                 141.270 
                 6.541 
               
            
           
           
               
               
               
               
               
            
               
                  13&gt; 
                 ∞ 
                 D13 
                 (aperture stop) 
                   
               
            
           
           
               
               
               
               
               
            
               
                 14) 
                 −2070.936 
                 1.200 
                 1.496997 
                 81.61 
               
               
                 15) 
                 46.571 
                 D15 
               
               
                 16) 
                 −370.106 
                 2.907 
                 1.487490 
                 70.32 
               
               
                 17) 
                 −72.395 
                 1.500 
               
               
                 18) 
                 178.417 
                 3.000 
                 1.737999 
                 32.33 
               
               
                 19) 
                 −91.168 
                 1.100 
                 1.593190 
                 67.90 
               
               
                 20) 
                 49.487 
                 2.200 
               
               
                 21) 
                 −130.831 
                 1.100 
                 1.593490 
                 67.00 
               
               
                 22) 
                 65.238 
                 2.000 
               
               
                 23) 
                 47.376 
                 9.008 
                 1.579570 
                 53.74 
               
               
                 24) 
                 −30.682 
                 1.400 
                 1.593190 
                 67.90 
               
               
                 25) 
                 −219.958 
                 2.409 
               
               
                 26) 
                 72.361 
                 1.400 
                 1.922860 
                 20.88 
               
               
                 27) 
                 26.665 
                 6.906 
                 1.720467 
                 34.71 
               
               
                 28) 
                 352.438 
                 3.947 
               
               
                 29) 
                 −84.126 
                 1.400 
                 1.816000 
                 46.59 
               
               
                 30) 
                 35.011 
                 5.000 
                 1.737999 
                 32.33 
               
               
                 31) 
                 83.719 
                 2.000 
               
               
                 32) 
                 67.601 
                 5.368 
                 1.801000 
                 34.92 
               
               
                 33) 
                 −179.297 
                 Bf 
               
               
                   
               
            
           
           
               
            
               
                 [Focal length data of groups] 
               
            
           
           
               
               
               
               
            
               
                   
                 Groups 
                 Starting surfaces 
                 Focal lengths 
               
               
                   
                   
               
               
                   
                 G1 
                 1 
                 168.518 
               
               
                   
                 G1A 
                 1 
                 161.845 
               
               
                   
                 G1B 
                 5 
                 −1807.658 
               
               
                   
                 GF 
                 14 
                 −91.627 
               
               
                   
                 GR 
                 16 
                 1823.408 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Variable distance data] 
               
            
           
           
               
               
               
            
               
                   
                 At focusing on infinity 
                 At focusing on a nearby object 
               
               
                   
               
               
                 D13 
                 6.480 
                 23.792 
               
               
                 D15 
                 24.107 
                 6.795 
               
               
                   
               
            
           
         
       
     
       FIG.  4    shows aberrations of the optical system of the second example focusing on an object at infinity. 
     The graphs of aberrations suggest that the optical system of the present example effectively reduces variations in aberrations at focusing and has high optical performance. 
     Third Example 
       FIG.  5 A  is a cross-sectional view of an optical system of a third example focusing on an object at infinity.  FIG.  5 B  is a cross-sectional view of the optical system of the third example focusing on a nearby object. 
     The optical system of the present example includes a first lens group G 1  having positive refractive power, a focusing group GF having negative refractive power, and a rear group GR having negative refractive power, in order from the object side. An aperture stop S is disposed between the first lens group G 1  and the focusing group GF. The first lens group G 1  includes a first-A lens group G 1 A having positive refractive power and a first-B lens group G 1 B having negative refractive power, separated by the largest air space A in the first lens group; the first-A lens group G 1 A is disposed on the object side of the air space A and the first-B lens group G 1 B is disposed on the image side of the air space A. 
     The first-A lens group G 1 A includes a positive meniscus lens L 1  convex on the object side, and a positive meniscus lens L 2  convex on the object side, in order from the object side. 
     The first-B lens group G 1 B includes a negative cemented lens composed of a biconvex positive lens L 3  and a biconcave negative lens L 4 ; a positive meniscus lens L 5  convex on the object side; and a positive cemented lens composed of a biconvex positive lens L 6  and a biconcave negative lens L 7 , in order from the object side. 
     The focusing group GF includes a biconcave negative lens L 8 . 
     The rear group GR includes a positive meniscus lens L 9  convex on the image side; a negative cemented lens composed of a biconvex positive lens L 10  and a biconcave negative lens L 11 ; a biconcave negative lens L 12 ; a positive cemented lens composed of a biconvex positive lens L 13  and a negative meniscus lens L 14  convex on the image side; a negative cemented lens composed of a biconcave negative lens L 15  and a biconvex positive lens L 16 ; a negative cemented lens composed of a biconcave negative lens L 17  and a biconvex positive lens L 18 ; and a positive meniscus lens L 19  convex on the object side, in order from the object side. 
     An imaging device (not shown) constructed from CCD, CMOS or the like is disposed on an image plane I. 
     The optical system of the present example focuses by moving the focusing group GF along the optical axis. When the focus is shifted from infinity to a nearby object, the focusing group GF moves from the object side toward the image side. 
     In the optical system of the present example, the negative cemented lens composed of the positive lens L 10  and the negative lens L 11  and the negative lens L 12 , which are lenses included in the rear group GR, are configured as a vibration reduction lens group movable so that movement has a component in a direction perpendicular to the optical axis to correct an image blur. 
     In the optical system of the present example, the positive meniscus lens L 1  corresponds to the first lens, and the positive meniscus lens L 2  corresponds to the second lens. In the optical system of the present example, the negative lens L 4  corresponds to the negative lens N, and the positive lens L 6  corresponds to the positive lens Z. 
     In the optical system of the present example, dA is the distance on the optical axis between the image-side surface of the positive meniscus lens L 2  and the object-side surface of the positive lens L 3 . dG1 is the distance on the optical axis between the object-side surface of the positive meniscus lens L 1  and the image-side surface of the negative lens L 7 . dB is the distance on the optical axis between the object-side surface of the positive meniscus lens L 1  and the object-side surface of the positive lens L 3 . dN is the distance on the optical axis between the object-side surface of the positive meniscus lens L 1  and the object-side surface of the negative lens L 4 . 
     Table 3 below shows specifications of the optical system of the present example. 
     
       
         
           
               
             
               
                 TABLE 3 
               
               
                   
               
             
            
               
                 [General specifications] 
               
               
                   
               
            
           
           
               
               
               
            
               
                   
                 f 
                 390.00 
               
               
                   
                 Fno 
                 4.60 
               
               
                   
                 Bf 
                 55.218 
               
               
                   
                 image height 
                 21.700 
               
               
                   
                 TL 
                 243.435 
               
               
                   
                 2ω 
                 6.30 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens specifications] 
               
            
           
           
               
               
               
               
               
            
               
                 m 
                 r 
                 d 
                 nd 
                 νd 
               
               
                   
               
               
                  1) 
                 221.433 
                 5.870 
                 1.537750 
                 74.70 
               
               
                  2) 
                 4228.581 
                 0.300 
               
               
                  3) 
                 81.234 
                 11.748  
                 1.437001 
                 95.10 
               
               
                  4) 
                 472.777 
                 48.082  
               
               
                  5) 
                 53.231 
                 8.876 
                 1.437001 
                 95.10 
               
               
                  6) 
                 −626.318 
                 2.000 
                 1.900430 
                 37.37 
               
               
                  7) 
                 42.149 
                 1.500 
               
               
                  8) 
                 41.831 
                 7.935 
                 1.437001 
                 95.10 
               
               
                  9) 
                 1105.379 
                 11.821  
               
               
                 10) 
                 109.247 
                 5.876 
                 1.663820 
                 27.35 
               
               
                 11) 
                 −70.652 
                 1.500 
                 1.672999 
                 38.26 
               
               
                 12) 
                 195.927 
                 7.351 
               
            
           
           
               
               
               
               
               
            
               
                  13&gt; 
                 ∞ 
                 D13 
                 (aperture stop) 
                   
               
            
           
           
               
               
               
               
               
            
               
                 14) 
                 −1280.351 
                 1.200 
                 1.496997 
                 81.61 
               
               
                 15) 
                 43.128 
                 D15 
               
               
                 16) 
                 −115.551 
                 2.531 
                 1.487490 
                 70.32 
               
               
                 17) 
                 −51.834 
                 2.000 
               
               
                 18) 
                 184.433 
                 3.000 
                 1.647690 
                 33.72 
               
               
                 19) 
                 −50.330 
                 1.100 
                 1.593190 
                 67.90 
               
               
                 20) 
                 44.097 
                 2.000 
               
               
                 21) 
                 −159.759 
                 1.100 
                 1.593490 
                 67.00 
               
               
                 22) 
                 56.912 
                 2.000 
               
               
                 23) 
                 35.605 
                 6.762 
                 1.737999 
                 32.33 
               
               
                 24) 
                 −45.880 
                 1.400 
                 1.763850 
                 48.49 
               
               
                 25) 
                 −190.397 
                 2.000 
               
               
                 26) 
                 −742.135 
                 1.400 
                 1.922860 
                 20.88 
               
               
                 27) 
                 23.106 
                 7.608 
                 1.620040 
                 36.40 
               
               
                 28) 
                 −75.897 
                 3.414 
               
               
                 29) 
                 −37.788 
                 1.400 
                 1.763850 
                 48.49 
               
               
                 30) 
                 38.546 
                 6.695 
                 1.737999 
                 32.33 
               
               
                 31) 
                 −86.210 
                 0.200 
               
               
                 32) 
                 52.571 
                 3.600 
                 1.581440 
                 40.98 
               
               
                 33) 
                 147.363 
                 Bf 
               
               
                   
               
            
           
           
               
            
               
                 [Focal length data of groups] 
               
            
           
           
               
               
               
               
            
               
                   
                 Groups 
                 Starting surfaces 
                 Focal lengths 
               
               
                   
                   
               
               
                   
                 G1 
                 1 
                 150.216 
               
               
                   
                 G1A 
                 1 
                 147.690 
               
               
                   
                 G1B 
                 5 
                 −2684.159 
               
               
                   
                 GF 
                 14 
                 −89.923 
               
               
                   
                 GR 
                 16 
                 −443.717 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Variable distance data] 
               
            
           
           
               
               
               
            
               
                   
                 At focusing on infinity 
                 At focusing on a nearby object 
               
               
                   
               
               
                 D13 
                 5.381 
                 19.508 
               
               
                 D15 
                 20.568 
                 6.440 
               
               
                   
               
            
           
         
       
     
       FIG.  6    shows aberrations of the optical system of the third example focusing on an object at infinity. 
     The graphs of aberrations suggest that the optical system of the present example effectively reduces variations in aberrations at focusing and has high optical performance. 
     Fourth Example 
       FIG.  7 A  is a cross-sectional view of an optical system of a fourth example focusing on an object at infinity.  FIG.  7 B  is a cross-sectional view of the optical system of the fourth example focusing on a nearby object. 
     The optical system of the present example includes a first lens group G 1  having positive refractive power, a focusing group GF having negative refractive power, and a rear group GR having negative refractive power, in order from the object side. An aperture stop S is disposed between the first lens group G 1  and the focusing group GF. The first lens group G 1  includes a first-A lens group G 1 A having positive refractive power and a first-B lens group G 1 B having negative refractive power, separated by the largest air space A in the first lens group; the first-A lens group G 1 A is disposed on the object side of the air space A and the first-B lens group G 1 B is disposed on the image side of the air space A. 
     The first-A lens group G 1 A includes a positive meniscus lens L 1  convex on the object side, and a positive meniscus lens L 2  convex on the object side, in order from the object side. 
     The first-B lens group G 1 B includes a negative cemented lens composed of a positive meniscus lens L 3  convex on the object side and a negative meniscus lens L 4  convex on the object side; a positive meniscus lens L 5  convex on the object side; and a positive cemented lens composed of a biconvex positive lens L 6  and a biconcave negative lens L 7 , in order from the object side. 
     The focusing group GF includes a negative meniscus lens L 8  convex on the object side. 
     The rear group GR includes a positive meniscus lens L 9  convex on the image side; a negative cemented lens composed of a biconvex positive lens L 10  and a biconcave negative lens L 11 ; a biconcave negative lens L 12 ; a positive cemented lens composed of a biconvex positive lens L 13  and a biconcave negative lens L 14 ; a negative cemented lens composed of a negative meniscus lens L 15  convex on the object side and a biconvex positive lens L 16 ; a negative cemented lens composed of a biconcave negative lens L 17  and a biconvex positive lens L 18 ; and a positive meniscus lens L 19  convex on the object side, in order from the object side. 
     An imaging device (not shown) constructed from CCD, CMOS or the like is disposed on an image plane I. 
     The optical system of the present example focuses by moving the focusing group GF along the optical axis. When the focus is shifted from infinity to a nearby object, the focusing group GF moves from the object side toward the image side. 
     In the optical system of the present example, the negative cemented lens composed of the positive lens L 10  and the negative lens L 11  and the negative lens L 12 , which are lenses included in the rear group GR, are configured as a vibration reduction lens group movable so that movement has a component in a direction perpendicular to the optical axis to correct an image blur. 
     In the optical system of the present example, the positive meniscus lens L 1  corresponds to the first lens, and the positive meniscus lens L 2  corresponds to the second lens. In the optical system of the present example, the negative meniscus lens L 4  corresponds to the negative lens N, and the positive lens L 6  corresponds to the positive lens Z. 
     In the optical system of the present example, dA is the distance on the optical axis between the image-side surface of the positive meniscus lens L 2  and the object-side surface of the positive meniscus lens L 3 . dG1 is the distance on the optical axis between the object-side surface of the positive meniscus lens L 1  and the image-side surface of the negative lens L 7 . dB is the distance on the optical axis between the object-side surface of the positive meniscus lens L 1  and the object-side surface of the positive meniscus lens L 3 . dN is the distance on the optical axis between the object-side surface of the positive meniscus lens L 1  and the object-side surface of the negative meniscus lens L 4 . 
     Table 4 below shows specifications of the optical system of the present example. 
     
       
         
           
               
             
               
                 TABLE 4 
               
               
                   
               
             
            
               
                 [General specifications] 
               
               
                   
               
            
           
           
               
               
               
            
               
                   
                 f 
                 390.00 
               
               
                   
                 Fno 
                 5.77 
               
               
                   
                 Bf 
                 54.579 
               
               
                   
                 image height 
                 21.700 
               
               
                   
                 TL 
                 221.435 
               
               
                   
                 2ω 
                 6.35 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens specifications] 
               
            
           
           
               
               
               
               
               
            
               
                 m 
                 r 
                 d 
                 nd 
                 νd 
               
               
                   
               
               
                  1) 
                 129.411 
                 6.119 
                 1.497000 
                 81.61 
               
               
                  2) 
                 4105.548 
                 0.300 
               
               
                  3) 
                 61.730 
                 9.074 
                 1.437000 
                 95.00 
               
               
                  4) 
                 230.361 
                 35.312 
               
               
                  5) 
                 48.186 
                 5.994 
                 1.437000 
                 95.00 
               
               
                  6) 
                 581.000 
                 2.000 
                 1.902650 
                 35.73 
               
               
                  7) 
                 34.413 
                 2.138 
               
               
                  8) 
                 35.952 
                 5.925 
                 1.437000 
                 95.00 
               
               
                  9) 
                 353.395 
                 6.718 
               
               
                 10) 
                 70.865 
                 4.563 
                 1.663820 
                 27.35 
               
               
                 11) 
                 −93.974 
                 1.300 
                 1.785900 
                 44.17 
               
               
                 12) 
                 95.404 
                 12.499 
               
            
           
           
               
               
               
               
               
            
               
                  13&gt; 
                 ∞ 
                 D13 
                 (aperture stop) 
                   
               
            
           
           
               
               
               
               
               
            
               
                 14) 
                 9370.670 
                 1.200 
                 1.497000 
                 81.61 
               
               
                 15) 
                 37.965 
                 D15 
               
               
                 16) 
                 −85.435 
                 2.194 
                 1.487490 
                 70.31 
               
               
                 17) 
                 −44.298 
                 1.500 
               
               
                 18) 
                 442.035 
                 2.700 
                 1.595509 
                 39.24 
               
               
                 19) 
                 −37.068 
                 1.200 
                 1.593190 
                 67.90 
               
               
                 20) 
                 43.657 
                 2.000 
               
               
                 21) 
                 −387.508 
                 1.200 
                 1.593490 
                 67.00 
               
               
                 22) 
                 68.415 
                 2.000 
               
               
                 23) 
                 30.027 
                 6.830 
                 1.581440 
                 40.98 
               
               
                 24) 
                 −33.765 
                 1.400 
                 1.593190 
                 67.90 
               
               
                 25) 
                 639.490 
                 2.500 
               
               
                 26) 
                 97.030 
                 1.400 
                 1.922860 
                 20.88 
               
               
                 27) 
                 20.045 
                 6.147 
                 1.620040 
                 36.40 
               
               
                 28) 
                 −13075.855 
                 4.849 
               
               
                 29) 
                 −31.154 
                 1.400 
                 1.816000 
                 46.59 
               
               
                 30) 
                 42.152 
                 7.769 
                 1.738000 
                 32.26 
               
               
                 31) 
                 −42.051 
                 0.200 
               
               
                 32) 
                 45.857 
                 4.009 
                 1.603420 
                 38.03 
               
               
                 33) 
                 125.000 
                 Bf 
               
               
                   
               
            
           
           
               
            
               
                 [Focal length data of groups] 
               
            
           
           
               
               
               
               
            
               
                   
                 Groups 
                 Starting surfaces 
                 Focal lengths 
               
               
                   
                   
               
               
                   
                 G1 
                 1 
                 141.309 
               
               
                   
                 G1A 
                 1 
                 111.803 
               
               
                   
                 G1B 
                 5 
                 −226.733 
               
               
                   
                 GF 
                 14 
                 −76.703 
               
               
                   
                 GR 
                 16 
                 −741.023 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Variable distance data] 
               
            
           
           
               
               
               
            
               
                   
                 At focusing on infinity 
                 At focusing on a nearby object 
               
               
                   
               
               
                 D13 
                 3.000 
                 19.346 
               
               
                 D15 
                 21.414 
                 5.069 
               
               
                   
               
            
           
         
       
     
       FIG.  8    shows aberrations of the optical system of the fourth example focusing on an object at infinity. 
     The graphs of aberrations suggest that the optical system of the present example effectively reduces variations in aberrations at focusing and has high optical performance. 
     Fifth Example 
       FIG.  9 A  is a cross-sectional view of an optical system of a fifth example focusing on an object at infinity.  FIG.  9 B  is a cross-sectional view of the optical system of the fifth example focusing on a nearby object. 
     The optical system of the present example includes a first lens group G 1  having positive refractive power, a focusing group GF having negative refractive power, and a rear group GR having negative refractive power, in order from the object side. An aperture stop S is disposed between the first lens group G 1  and the focusing group GF. The first lens group G 1  includes a first-A lens group G 1 A having positive refractive power and a first-B lens group G 1 B having negative refractive power separated by the largest air space A in the first lens group; the first-A lens group G 1 A is disposed on the object side of the air space A and the first-B lens group G 1 B is disposed on the image side of the air space A. 
     The first-A lens group G 1 A includes a biconvex positive lens L 1  and a positive meniscus lens L 2  convex on the object side, in order from the object side. 
     The first-B lens group G 1 B includes a positive cemented lens composed of a biconvex positive lens L 3  and a biconcave negative lens L 4 ; a negative cemented lens composed of a negative meniscus lens L 5  convex on the object side and a biconvex positive lens L 6 ; and a positive cemented lens composed of a positive meniscus lens L 7  convex on the image side and a negative meniscus lens L 8  convex on the image side, in order from the object side. 
     The focusing group GF includes a negative meniscus lens L 9  convex on the object side. 
     The rear group GR includes a positive meniscus lens L 10  convex on the image side; a negative cemented lens composed of a biconvex positive lens L 11  and a biconcave negative lens L 12 ; a biconcave negative lens L 13 ; a positive cemented lens composed of a biconvex positive lens L 14  and a negative meniscus lens L 15  convex on the image side; a positive cemented lens composed of a negative meniscus lens L 16  convex on the object side and a biconvex positive lens L 17 ; a negative cemented lens composed of a biconcave negative lens L 18  and a positive meniscus lens L 19  convex on the object side; and a positive meniscus lens L 20  convex on the object side, in order from the object side. 
     An imaging device (not shown) constructed from CCD, CMOS or the like is disposed on an image plane I. 
     The optical system of the present example focuses by moving the focusing group GF along the optical axis. When the focus is shifted from infinity to a nearby object, the focusing group GF moves from the object side toward the image side. 
     In the optical system of the present example, the negative cemented lens composed of the positive lens L 11  and the negative lens L 12  and the negative lens L 13 , which are lenses included in the rear group GR, are configured as a vibration reduction lens group movable so that movement has a component in a direction perpendicular to the optical axis to correct an image blur. 
     In the optical system of the present example, the positive lens L 1  corresponds to the first lens, and the positive meniscus lens L 2  corresponds to the second lens. In the optical system of the present example, the negative lens L 4  corresponds to the negative lens N, and the positive meniscus lens L 7  corresponds to the positive lens Z. 
     In the optical system of the present example, dA is the distance on the optical axis between the image-side surface of the positive meniscus lens L 2  and the object-side surface of the positive lens L 3 . dG1 is the distance on the optical axis between the object-side surface of the positive lens L 1  and the image-side surface of the negative meniscus lens L 8 . dB is the distance on the optical axis between the object-side surface of the positive lens L 1  and the object-side surface of the positive lens L 3 . dN is the distance on the optical axis between the object-side surface of the positive lens L 1  and the object-side surface of the negative lens L 4 . 
     Table 5 below shows specifications of the optical system of the present example. 
     
       
         
           
               
             
               
                 TABLE 5 
               
               
                   
               
             
            
               
                 [General specifications] 
               
               
                   
               
            
           
           
               
               
               
            
               
                   
                 f 
                 489.98 
               
               
                   
                 Fno 
                 5.77 
               
               
                   
                 Bf 
                 53.163 
               
               
                   
                 image height 
                 21.700 
               
               
                   
                 TL 
                 270.475 
               
               
                   
                 2ω 
                 5.05 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens specifications] 
               
            
           
           
               
               
               
               
               
            
               
                 m 
                 r 
                 d 
                 nd 
                 νd 
               
               
                   
               
               
                  1) 
                 301.516 
                 7.653 
                 1.518600 
                 69.89 
               
               
                  2) 
                 −2994.078 
                 0.248 
               
               
                  3) 
                 74.588 
                 16.015 
                 1.433837 
                 95.16 
               
               
                  4) 
                 529.942 
                 42.196 
               
               
                  5) 
                 60.571 
                 11.051 
                 1.437001 
                 95.10 
               
               
                  6) 
                 −204.604 
                 2.000 
                 1.816000 
                 46.59 
               
               
                  7) 
                 358.323 
                 0.509 
               
               
                  8) 
                 1130.257 
                 2.000 
                 1.816000 
                 46.59 
               
               
                  9) 
                 40.518 
                 10.429 
                 1.437001 
                 95.10 
               
               
                 10) 
                 −366.911 
                 18.665 
               
               
                 11) 
                 −92.650 
                 5.315 
                 1.663820 
                 27.35 
               
               
                 12) 
                 −46.744 
                 1.750 
                 1.612660 
                 44.46 
               
               
                 13) 
                 −89.781 
                 0.100 
               
            
           
           
               
               
               
               
               
            
               
                  14&gt; 
                 ∞ 
                 D14 
                 (aperture stop) 
                   
               
            
           
           
               
               
               
               
               
            
               
                 15) 
                 546.830 
                 1.500 
                 1.496997 
                 81.61 
               
               
                 16) 
                 50.544 
                 D16 
               
               
                 17) 
                 −43.675 
                 3.106 
                 1.487490 
                 70.32 
               
               
                 18) 
                 −39.919 
                 17.617 
               
               
                 19) 
                 196.739 
                 4.641 
                 1.603420 
                 38.03 
               
               
                 20) 
                 −46.252 
                 1.375 
                 1.593190 
                 67.90 
               
               
                 21) 
                 44.844 
                 2.750 
               
               
                 22) 
                 −2713.065 
                 1.375 
                 1.593490 
                 67.00 
               
               
                 23) 
                 63.562 
                 2.500 
               
               
                 24) 
                 38.733 
                 6.368 
                 1.581440 
                 40.98 
               
               
                 25) 
                 −73.473 
                 1.750 
                 1.593190 
                 67.90 
               
               
                 26) 
                 −1339.601 
                 0.100 
               
               
                 27) 
                 112.830 
                 1.750 
                 1.922860 
                 20.88 
               
               
                 28) 
                 24.865 
                 7.420 
                 1.737999 
                 32.33 
               
               
                 29) 
                 −148.051 
                 0.889 
               
               
                 30) 
                 −62.799 
                 1.750 
                 1.816000 
                 46.59 
               
               
                 31) 
                 29.752 
                 6.237 
                 1.737999 
                 32.33 
               
               
                 32) 
                 306.380 
                 0.100 
               
               
                 33) 
                 56.901 
                 4.936 
                 1.603420 
                 38.03 
               
               
                 34) 
                 1041.086 
                 Bf 
               
               
                   
               
            
           
           
               
            
               
                 [Focal length data of groups] 
               
            
           
           
               
               
               
               
            
               
                   
                 Groups 
                 Starting surfaces 
                 Focal lengths 
               
               
                   
                   
               
               
                   
                 G1 
                 1 
                 178.023 
               
               
                   
                 G1A 
                 1 
                 144.638 
               
               
                   
                 G1B 
                 5 
                 −410.279 
               
               
                   
                 GF 
                 15 
                 −112.168 
               
               
                   
                 GR 
                 17 
                 −261.402 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Variable distance data] 
               
            
           
           
               
               
               
            
               
                   
                 At focusing on infinity 
                 At focusing on a nearby object 
               
               
                   
               
               
                 D14 
                 3.286 
                 20.151 
               
               
                 D16 
                 38.932 
                 22.067 
               
               
                   
               
            
           
         
       
     
       FIG.  10    shows aberrations of the optical system of the fifth example focusing on an object at infinity. 
     The graphs of aberrations suggest that the optical system of the present example effectively reduces variations in aberrations at focusing and has high optical performance. 
     Sixth Example 
       FIG.  11 A  is a cross-sectional view of an optical system of a sixth example focusing on an object at infinity.  FIG.  11 B  is a cross-sectional view of the optical system of the sixth example focusing on a nearby object. 
     The optical system of the present example includes a first lens group G 1  having positive refractive power, a focusing group GF having negative refractive power, and a rear group GR having negative refractive power, in order from the object side. An aperture stop S is disposed between the first lens group G 1  and the focusing group GF. The first lens group G 1  includes a first-A lens group G 1 A having positive refractive power and a first-B lens group G 1 B having negative refractive power separated by the largest air space A in the first lens group; the first-A lens group G 1 A is disposed on the object side of the air space A and the first-B lens group G 1 B is disposed on the image side of the air space A. 
     The first-A lens group G 1 A includes a positive meniscus lens L 1  convex on the object side, and a positive meniscus lens L 2  convex on the object side, in order from the object side. 
     The first-B lens group G 1 B includes a negative cemented lens composed of a positive meniscus lens L 3  convex on the object side and a negative meniscus lens L 4  convex on the object side; a positive meniscus lens L 5  convex on the object side; and a positive cemented lens composed of a biconvex positive lens L 6  and a biconcave negative lens L 7 , in order from the object side. 
     The focusing group GF includes a biconcave negative lens L 8 . 
     The rear group GR includes a positive meniscus lens L 9  convex on the image side; a negative cemented lens composed of a positive meniscus lens L 10  convex on the image side and a biconcave negative lens L 11 ; a biconcave negative lens L 12 ; a positive cemented lens composed of a biconvex positive lens L 13  and a biconcave negative lens L 14 ; a negative cemented lens composed of a biconcave negative lens L 15  and a biconvex positive lens L 16 ; a positive cemented lens composed of a biconvex positive lens L 17  and a negative meniscus lens L 18  convex on the image side; and a negative cemented lens composed of a biconcave negative lens L 19 , a biconvex positive lens L 20 , and a negative meniscus lens L 21  convex on the image side, in order from the object side. 
     An imaging device (not shown) constructed from CCD, CMOS or the like is disposed on an image plane I. 
     The optical system of the present example focuses by moving the focusing group GF along the optical axis. When the focus is shifted from infinity to a nearby object, the focusing group GF moves from the object side toward the image side. 
     In the optical system of the present example, the negative cemented lens composed of the positive meniscus lens L 10  and the negative lens L 11  and the negative lens L 12 , which are lenses included in the rear group GR, are configured as a vibration reduction lens group movable so that movement has a component in a direction perpendicular to the optical axis to correct an image blur. 
     In the optical system of the present example, the positive meniscus lens L 1  corresponds to the first lens, and the positive meniscus lens L 2  corresponds to the second lens. In the optical system of the present example, the negative meniscus lens L 4  corresponds to the negative lens N, and the positive lens L 6  corresponds to the positive lens Z. 
     In the optical system of the present example, dA is the distance on the optical axis between the image-side surface of the positive meniscus lens L 2  and the object-side surface of the positive meniscus lens L 3 . dG1 is the distance on the optical axis between the object-side surface of the positive meniscus lens L 1  and the image-side surface of the negative lens L 7 . dB is the distance on the optical axis between the object-side surface of the positive meniscus lens L 1  and the object-side surface of the positive meniscus lens L 3 . dN is the distance on the optical axis between the object-side surface of the positive meniscus lens L 1  and the object-side surface of the negative meniscus lens L 4 . 
     Table 6 below shows specifications of the optical system of the present example. 
     
       
         
           
               
             
               
                 TABLE 6 
               
               
                   
               
             
            
               
                 [General specifications] 
               
               
                   
               
            
           
           
               
               
               
            
               
                   
                 f 
                 582.00 
               
               
                   
                 Fno 
                 5.80 
               
               
                   
                 Bf 
                 57.650 
               
               
                   
                 image height 
                 21.700 
               
               
                   
                 TL 
                 305.483 
               
               
                   
                 2ω 
                 4.20 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens specifications] 
               
            
           
           
               
               
               
               
               
            
               
                 m 
                 r 
                 d 
                 nd 
                 νd 
               
               
                   
               
               
                  1) 
                 209.874 
                 7.062 
                 1.537750 
                 74.70 
               
               
                  2) 
                 952.422 
                 0.400 
               
               
                  3) 
                 91.788 
                 13.513 
                 1.433837 
                 95.16 
               
               
                  4) 
                 361.924 
                 60.210 
               
               
                  5) 
                 66.958 
                 8.900 
                 1.437001 
                 95.10 
               
               
                  6) 
                 1878.152 
                 2.300 
                 1.902650 
                 35.72 
               
               
                  7) 
                 52.955 
                 1.200 
               
               
                  8) 
                 54.318 
                 8.485 
                 1.437001 
                 95.10 
               
               
                  9) 
                 954.336 
                 15.349 
               
               
                 10) 
                 115.853 
                 6.613 
                 1.663820 
                 27.35 
               
               
                 11) 
                 −90.371 
                 1.600 
                 1.834810 
                 42.73 
               
               
                 12) 
                 221.211 
                 15.183 
               
            
           
           
               
               
               
               
               
            
               
                  13&gt; 
                 ∞ 
                 D13 
                 (aperture stop) 
                   
               
            
           
           
               
               
               
               
               
            
               
                 14) 
                 −19374.039 
                 1.200 
                 1.496997 
                 81.61 
               
               
                 15) 
                 46.568 
                 D15 
               
               
                 16) 
                 −106.679 
                 2.037 
                 1.487490 
                 70.32 
               
               
                 17) 
                 −61.741 
                 1.500 
               
               
                 18) 
                 −2608.847 
                 3.600 
                 1.612660 
                 44.46 
               
               
                 19) 
                 −47.129 
                 1.200 
                 1.593190 
                 67.90 
               
               
                 20) 
                 69.720 
                 2.300 
               
               
                 21) 
                 −1020.983 
                 1.200 
                 1.593490 
                 67.00 
               
               
                 22) 
                 91.287 
                 2.000 
               
               
                 23) 
                 33.441 
                 7.067 
                 1.581440 
                 40.98 
               
               
                 24) 
                 −48.899 
                 1.400 
                 1.593190 
                 67.90 
               
               
                 25) 
                 173.712 
                 3.445 
               
               
                 26) 
                 −751.444 
                 1.400 
                 1.922860 
                 20.88 
               
               
                 27) 
                 25.644 
                 6.052 
                 1.620040 
                 36.40 
               
               
                 28) 
                 −1371.263 
                 5.043 
               
               
                 29) 
                 65.099 
                 9.464 
                 1.737999 
                 32.33 
               
               
                 30) 
                 −26.310 
                 1.600 
                 1.638540 
                 55.34 
               
               
                 31) 
                 −90.430 
                 5.913 
               
               
                 32) 
                 −46.530 
                 1.600 
                 1.883000 
                 40.66 
               
               
                 33) 
                 59.262 
                 8.391 
                 1.737999 
                 32.33 
               
               
                 34) 
                 −30.461 
                 1.600 
                 1.883000 
                 40.66 
               
               
                 35) 
                 −104.675 
                 Bf 
               
               
                   
               
            
           
           
               
            
               
                 [Focal length data of groups] 
               
            
           
           
               
               
               
               
            
               
                   
                 Groups 
                 Starting surfaces 
                 Focal lengths 
               
               
                   
                   
               
               
                   
                 G1 
                 1 
                 206.631 
               
               
                   
                 G1A 
                 1 
                 179.755 
               
               
                   
                 G1B 
                 5 
                 −499.661 
               
               
                   
                 GF 
                 14 
                 −93.471 
               
               
                   
                 GR 
                 16 
                 −277.391 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Variable distance data] 
               
            
           
           
               
               
               
            
               
                   
                 At focusing on infinity 
                 At focusing on a nearby object 
               
               
                   
               
               
                 D13 
                 11.493 
                 28.469 
               
               
                 D15 
                 27.470 
                 10.494 
               
               
                   
               
            
           
         
       
     
       FIG.  12    shows aberrations of the optical system of the sixth example focusing on an object at infinity. 
     The graphs of aberrations suggest that the optical system of the present example effectively reduces variations in aberrations at focusing and has high optical performance. 
     Seventh Example 
       FIG.  13 A  is a cross-sectional view of an optical system of a seventh example focusing on an object at infinity.  FIG.  13 B  is a cross-sectional view of the optical system of the seventh example focusing on a nearby object. 
     The optical system of the present example includes a first lens group G 1  having positive refractive power, a focusing group GF having negative refractive power, and a rear group GR having negative refractive power, in order from the object side. An aperture stop S is disposed between the first lens group G 1  and the focusing group GF. The first lens group G 1  includes a first-A lens group G 1 A having positive refractive power and a first-B lens group G 1 B having negative refractive power, separated by the largest air space A in the first lens group; the first-A lens group G 1 A is disposed on the object side of the air space A, and the first-B lens group G 1 B is disposed on the image side of the air space A. 
     The first-A lens group G 1 A includes a biconvex positive lens L 1  and a positive meniscus lens L 2  convex on the object side, in order from the object side. 
     The first-B lens group G 1 B includes a negative cemented lens composed of a biconvex positive lens L 3  and a biconcave negative lens L 4 ; a positive meniscus lens L 5  convex on the object side; and a negative cemented lens composed of a biconvex positive lens L 6  and a biconcave negative lens L 7 , in order from the object side. 
     The focusing group GF includes a biconcave negative lens L 8 . 
     The rear group GR includes a positive meniscus lens L 9  convex on the image side; a negative cemented lens composed of a biconvex positive lens L 10  and a biconcave negative lens L 11 ; a biconcave negative lens L 12 ; a positive cemented lens composed of a biconvex positive lens L 13  and a biconcave negative lens L 14 ; a negative cemented lens composed of a biconcave negative lens L 15  and a biconvex positive lens L 16 ; a positive cemented lens composed of a biconvex positive lens L 17  and a negative meniscus lens L 18  convex on the image side; and a negative cemented lens composed of a biconcave negative lens L 19 , a biconvex positive lens L 20 , and a negative meniscus lens L 21  convex on the image side, in order from the object side. 
     An imaging device (not shown) constructed from CCD, CMOS or the like is disposed on an image plane I. 
     The optical system of the present example focuses by moving the focusing group GF along the optical axis. When the focus is shifted from infinity to a nearby object, the focusing group GF moves from the object side toward the image side. 
     In the optical system of the present example, the negative cemented lens composed of the positive lens L 10  and the negative lens L 11  and the negative lens L 12 , which are lenses included in the rear group GR, are configured as a vibration reduction lens group movable so that movement has a component in a direction perpendicular to the optical axis to correct an image blur. 
     In the optical system of the present example, the positive lens L 1  corresponds to the first lens, and the positive meniscus lens L 2  corresponds to the second lens. In the optical system of the present example, the negative lens L 4  corresponds to the negative lens N, and the positive lens L 6  corresponds to the positive lens Z. 
     In the optical system of the present example, dA is the distance on the optical axis between the image-side surface of the positive meniscus lens L 2  and the object-side surface of the positive lens L 3 . dG1 is the distance on the optical axis between the object-side surface of the positive lens L 1  and the image-side surface of the negative lens L 7 . dB is the distance on the optical axis between the object-side surface of the positive lens L 1  and the object-side surface of the positive lens L 3 . dN is the distance on the optical axis between the object-side surface of the positive lens L 1  and the object-side surface of the negative lens L 4 . 
     Table 7 below shows specifications of the optical system of the present example. 
     
       
         
           
               
             
               
                 TABLE 7 
               
               
                   
               
             
            
               
                 [General specifications] 
               
               
                   
               
            
           
           
               
               
               
            
               
                   
                 f 
                 780.00 
               
               
                   
                 Fno 
                 5.80 
               
               
                   
                 Bf 
                 72.401 
               
               
                   
                 image height 
                 21.700 
               
               
                   
                 TL 
                 395.435 
               
               
                   
                 2ω 
                 3.14 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens specifications] 
               
            
           
           
               
               
               
               
               
            
               
                 m 
                 r 
                 d 
                 nd 
                 νd 
               
               
                   
               
               
                  1) 
                 278.114 
                 11.437 
                 1.433837 
                 95.16 
               
               
                  2) 
                 −9931.397 
                 0.536 
               
               
                  3) 
                 118.790 
                 17.646 
                 1.433837 
                 95.16 
               
               
                  4) 
                 411.233 
                 88.454 
               
               
                  5) 
                 80.169 
                 11.750 
                 1.437001 
                 95.10 
               
               
                  6) 
                 −7177.582 
                 2.800 
                 1.902650 
                 35.72 
               
               
                  7) 
                 70.344 
                 1.582 
               
               
                  8) 
                 75.393 
                 9.074 
                 1.437001 
                 95.10 
               
               
                  9) 
                 609.803 
                 23.491 
               
               
                 10) 
                 149.143 
                 7.987 
                 1.663820 
                 27.35 
               
               
                 11) 
                 −111.061 
                 1.800 
                 1.834810 
                 42.73 
               
               
                 12) 
                 276.625 
                 15.689 
               
            
           
           
               
               
               
               
               
            
               
                  13&gt; 
                 ∞ 
                 D13 
                 (aperture stop) 
                   
               
            
           
           
               
               
               
               
               
            
               
                 14) 
                 −2132.794 
                 1.400 
                 1.487490 
                 70.32 
               
               
                 15) 
                 59.025 
                 D15 
               
               
                 16) 
                 −100.905 
                 3.000 
                 1.552981 
                 55.07 
               
               
                 17) 
                 −67.183 
                 1.500 
               
               
                 18) 
                 913.713 
                 3.800 
                 1.581440 
                 40.98 
               
               
                 19) 
                 −64.402 
                 1.200 
                 1.593190 
                 67.90 
               
               
                 20) 
                 77.939 
                 2.700 
               
               
                 21) 
                 −251.245 
                 1.200 
                 1.593490 
                 67.00 
               
               
                 22) 
                 144.773 
                 2.000 
               
               
                 23) 
                 48.967 
                 7.712 
                 1.581440 
                 40.98 
               
               
                 24) 
                 −36.112 
                 1.600 
                 1.593190 
                 67.90 
               
               
                 25) 
                 2585.012 
                 8.971 
               
               
                 26) 
                 −64.468 
                 1.600 
                 1.922860 
                 20.88 
               
               
                 27) 
                 41.597 
                 7.601 
                 1.620040 
                 36.40 
               
               
                 28) 
                 −60.377 
                 5.315 
               
               
                 29) 
                 118.399 
                 9.843 
                 1.737999 
                 32.33 
               
               
                 30) 
                 −31.787 
                 1.600 
                 1.593490 
                 67.00 
               
               
                 31) 
                 −65.797 
                 5.539 
               
               
                 32) 
                 −61.040 
                 1.600 
                 1.883000 
                 40.66 
               
               
                 33) 
                 62.377 
                 9.440 
                 1.737999 
                 32.33 
               
               
                 34) 
                 −36.957 
                 1.600 
                 1.883000 
                 40.66 
               
               
                 35) 
                 −146.016 
                 Bf 
               
               
                   
               
            
           
           
               
            
               
                 [Focal length data of groups] 
               
            
           
           
               
               
               
               
            
               
                   
                 Groups 
                 Starting surfaces 
                 Focal lengths 
               
               
                   
                   
               
               
                   
                 G1 
                 1 
                 279.705 
               
               
                   
                 G1A 
                 1 
                 236.223 
               
               
                   
                 G1B 
                 5 
                 −511.433 
               
               
                   
                 GF 
                 14 
                 −117.794 
               
               
                   
                 GR 
                 16 
                 −437.474 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Variable distance data] 
               
            
           
           
               
               
               
            
               
                   
                 At focusing on infinity 
                 At focusing on a nearby object 
               
               
                   
               
               
                 D13 
                 16.594 
                 41.036 
               
               
                 D15 
                 34.974 
                 10.531 
               
               
                   
               
            
           
         
       
     
       FIG.  14    shows aberrations of the optical system of the seventh example focusing on an object at infinity. 
     The graphs of aberrations suggest that the optical system of the present example effectively reduces variations in aberrations at focusing and has high optical performance. 
     Eighth Example 
       FIG.  15 A  is a cross-sectional view of an optical system of an eighth example focusing on an object at infinity.  FIG.  15 B  is a cross-sectional view of the optical system of the eighth example focusing on a nearby object. 
     The optical system of the present example includes a first lens group G 1  having positive refractive power, a focusing group GF having negative refractive power, and a rear group GR having negative refractive power, in order from the object side. An aperture stop S is disposed between the first lens group G 1  and the focusing group GF. The first lens group G 1  includes a first-A lens group G 1 A having positive refractive power and a first-B lens group G 1 B having negative refractive power, separated by the largest air space A in the first lens group; the first-A lens group G 1 A is disposed on the object side of the air space A and the first-B lens group G 1 B is disposed on the image side of the air space A. 
     The first-A lens group G 1 A includes a biconvex positive lens L 1  and a positive meniscus lens L 2  convex on the object side, in order from the object side. 
     The first-B lens group G 1 B includes a negative cemented lens composed of a negative meniscus lens L 3  convex on the object side and a positive meniscus lens L 4  convex on the object side; a positive cemented lens composed of a biconvex positive lens L 5  and a biconcave negative lens L 6 ; and a negative cemented lens composed of a positive meniscus lens L 7  convex on the object side and a negative meniscus lens L 8  convex on the object side, in order from the object side. 
     The focusing group GF includes a negative meniscus lens L 9  convex on the object side. 
     The rear group GR includes a positive meniscus lens L 10  convex on the image side; a negative cemented lens composed of a positive meniscus lens L 11  convex on the image side and a biconcave negative lens L 12 ; a biconcave negative lens L 13 ; a positive cemented lens composed of a biconvex positive lens L 14  and a biconcave negative lens L 15 ; a negative cemented lens composed of a biconcave negative lens L 16  and a biconvex positive lens L 17 ; a positive cemented lens composed of a biconvex positive lens L 18  and a negative meniscus lens L 19  convex on the image side; and a negative cemented lens composed of a biconcave negative lens L 20 , a biconvex positive lens L 21 , and a negative meniscus lens L 22  convex on the image side, in order from the object side. 
     An imaging device (not shown) constructed from CCD, CMOS or the like is disposed on an image plane I. 
     The optical system of the present example focuses by moving the focusing group GF along the optical axis. When the focus is shifted from infinity to a nearby object, the focusing group GF moves from the object side toward the image side. 
     In the optical system of the present example, the negative cemented lens composed of the positive meniscus lens L 11  and the negative lens L 12  and the negative lens L 13 , which are lenses included in the rear group GR, are configured as a vibration reduction lens group movable so that movement has a component in a direction perpendicular to the optical axis to correct an image blur. 
     In the optical system of the present example, the positive lens L 1  corresponds to the first lens, and the positive meniscus lens L 2  corresponds to the second lens. In the optical system of the present example, the negative meniscus lens L 3  corresponds to the negative lens N, and the positive meniscus lens L 7  corresponds to the positive lens Z. 
     In the optical system of the present example, dA is the distance on the optical axis between the image-side surface of the positive meniscus lens L 2  and the object-side surface of the negative meniscus lens L 3 . dG1 is the distance on the optical axis between the object-side surface of the positive lens L 1  and the image-side surface of the negative meniscus lens L 8 . dB is the distance on the optical axis between the object-side surface of the positive lens L 1  and the object-side surface of the negative meniscus lens L 3 . dN is the distance on the optical axis between the object-side surface of the positive lens L 1  and the object-side surface of the negative meniscus lens L 3 . 
     Table 8 below shows specifications of the optical system of the present example. 
     
       
         
           
               
             
               
                 TABLE 8 
               
               
                   
               
             
            
               
                 [General specifications] 
               
               
                   
               
            
           
           
               
               
               
            
               
                   
                 f 
                 779.95 
               
               
                   
                 Fno 
                 5.80 
               
               
                   
                 Bf 
                 76.376 
               
               
                   
                 image height 
                 21.700 
               
               
                   
                 TL 
                 383.444 
               
               
                   
                 2ω 
                 3.14 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens specifications] 
               
            
           
           
               
               
               
               
               
            
               
                 m 
                 r 
                 d 
                 nd 
                 νd 
               
               
                   
               
               
                  1) 
                 267.172 
                 12.157 
                 1.433837 
                 95.16 
               
               
                  2) 
                 −3942.417 
                 0.536 
               
               
                  3) 
                 129.878 
                 14.435 
                 1.433837 
                 95.16 
               
               
                  4) 
                 334.092 
                 69.154 
               
               
                  5) 
                 130.441 
                 3.000 
                 1.883000 
                 40.66 
               
               
                  6) 
                 71.048 
                 15.415 
                 1.437001 
                 95.10 
               
               
                  7) 
                 408.661 
                 1.000 
               
               
                  8) 
                 90.710 
                 16.409 
                 1.437001 
                 95.10 
               
               
                  9) 
                 −185.763 
                 2.800 
                 1.487490 
                 70.32 
               
               
                 10) 
                 138.066 
                 19.365 
               
               
                 11) 
                 88.996 
                 5.626 
                 1.663820 
                 27.35 
               
               
                 12) 
                 214.056 
                 2.100 
                 1.883000 
                 40.66 
               
               
                 13) 
                 78.689 
                 29.715 
               
            
           
           
               
               
               
               
               
            
               
                  14&gt; 
                 ∞ 
                 D14 
                 (aperture stop) 
                   
               
            
           
           
               
               
               
               
               
            
               
                 15) 
                 16674.224 
                 1.400 
                 1.487490 
                 70.32 
               
               
                 16) 
                 64.208 
                 D16 
               
               
                 17) 
                 −116.010 
                 3.000 
                 1.552981 
                 55.07 
               
               
                 18) 
                 −69.086 
                 1.500 
               
               
                 19) 
                 −644.448 
                 4.500 
                 1.612660 
                 44.46 
               
               
                 20) 
                 −48.050 
                 1.200 
                 1.593190 
                 67.90 
               
               
                 21) 
                 72.757 
                 2.700 
               
               
                 22) 
                 −880.699 
                 1.200 
                 1.593490 
                 67.00 
               
               
                 23) 
                 104.682 
                 2.000 
               
               
                 24) 
                 40.326 
                 7.576 
                 1.581440 
                 40.98 
               
               
                 25) 
                 −39.781 
                 1.600 
                 1.593190 
                 67.90 
               
               
                 26) 
                 960.480 
                 2.513 
               
               
                 27) 
                 −280.010 
                 1.600 
                 1.922860 
                 20.88 
               
               
                 28) 
                 34.990 
                 5.733 
                 1.620040 
                 36.40 
               
               
                 29) 
                 −146.116 
                 9.399 
               
               
                 30) 
                 73.204 
                 7.919 
                 1.620040 
                 36.40 
               
               
                 31) 
                 −32.773 
                 1.600 
                 1.593190 
                 67.90 
               
               
                 32) 
                 −531.178 
                 2.818 
               
               
                 33) 
                 −112.016 
                 1.600 
                 1.883000 
                 40.66 
               
               
                 34) 
                 37.168 
                 9.936 
                 1.737999 
                 32.33 
               
               
                 35) 
                 −32.206 
                 1.600 
                 1.883000 
                 40.66 
               
               
                 36) 
                 −153.819 
                 Bf 
               
               
                   
               
            
           
           
               
            
               
                 [Focal length data of groups] 
               
            
           
           
               
               
               
               
            
               
                   
                 Groups 
                 Starting surfaces 
                 Focal lengths 
               
               
                   
                   
               
               
                   
                 G1 
                 1 
                 271.114 
               
               
                   
                 G1A 
                 1 
                 262.482 
               
               
                   
                 G1B 
                 5 
                 −704.528 
               
               
                   
                 GF 
                 15 
                 −132.223 
               
               
                   
                 GR 
                 17 
                 −196.255 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Variable distance data] 
               
            
           
           
               
               
               
            
               
                   
                 At focusing on infinity 
                 At focusing on a nearby object 
               
               
                   
               
               
                 D14 
                 14.482 
                 39.187 
               
               
                 D16 
                 29.480 
                 4.775 
               
               
                   
               
            
           
         
       
     
       FIG.  16    shows aberrations of the optical system of the eighth example focusing on an object at infinity. 
     The graphs of aberrations suggest that the optical system of the present example effectively reduces variations in aberrations at focusing and has high optical performance. 
     Ninth Example 
       FIG.  17 A  is a cross-sectional view of an optical system of a ninth example focusing on an object at infinity.  FIG.  17 B  is a cross-sectional view of the optical system of the ninth example focusing on a nearby object. 
     The optical system of the present example includes a first lens group G 1  having positive refractive power, a focusing group GF having negative refractive power, and a rear group GR having negative refractive power, in order from the object side. An aperture stop S is disposed between the focusing group GF and the rear group GR. The first lens group G 1  includes a first-A lens group G 1 A having positive refractive power and a first-B lens group G 1 B having negative refractive power, separated by the largest air space A in the first lens group; the first-A lens group G 1 A is disposed on the object side of the air space A and the first-B lens group G 1 B is disposed on the image side of the air space A. 
     The first-A lens group G 1 A includes a positive meniscus lens L 1  convex on the object side, and a positive meniscus lens L 2  convex on the object side, in order from the object side. 
     The first-B lens group G 1 B includes a negative cemented lens composed of a negative meniscus lens L 3  convex on the object side and a positive meniscus lens L 4  convex on the object side; a positive cemented lens composed of a biconvex positive lens L 5  and a biconcave negative lens L 6 ; and a negative cemented lens composed of a positive meniscus lens L 7  convex on the object side and a negative meniscus lens L 8  convex on the object side, in order from the object side. 
     The focusing group GF includes a biconcave negative lens L 9 . 
     The rear group GR includes a positive meniscus lens L 10  convex on the image side; a negative cemented lens composed of a biconvex positive lens L 11  and a biconcave negative lens L 12 ; a biconcave negative lens L 13 ; a positive cemented lens composed of a biconvex positive lens L 14  and a biconcave negative lens L 15 ; a negative cemented lens composed of a negative meniscus lens L 16  convex on the object side and a biconvex positive lens L17; a positive cemented lens composed of a biconvex positive lens L 18  and a biconcave negative lens L 19 ; and a negative cemented lens composed of a biconcave negative lens L 20 , a biconvex positive lens L 21 , and a negative meniscus lens L 22  convex on the image side, in order from the object side. 
     An imaging device (not shown) constructed from CCD, CMOS or the like is disposed on an image plane I. 
     The optical system of the present example focuses by moving the focusing group GF along the optical axis. When the focus is shifted from infinity to a nearby object, the focusing group GF moves from the object side toward the image side. 
     In the optical system of the present example, the negative cemented lens composed of the positive lens L 11  and the negative lens L 12  and the negative lens L 13 , which are lenses included in the rear group GR, are configured as a vibration reduction lens group movable so that movement has a component in a direction perpendicular to the optical axis to correct an image blur. 
     In the optical system of the present example, the positive meniscus lens L 1  corresponds to the first lens, and the positive meniscus lens L 2  corresponds to the second lens. In the optical system of the present example, the negative meniscus lens L 3  corresponds to the negative lens N, and the positive meniscus lens L 7  corresponds to the positive lens Z. 
     In the optical system of the present example, dA is the distance on the optical axis between the image-side surface of the positive meniscus lens L 2  and the object-side surface of the negative meniscus lens L 3 . dG1 is the distance on the optical axis between the object-side surface of the positive meniscus lens L 1  and the image-side surface of the negative meniscus lens L 8 . dB is the distance on the optical axis between the object-side surface of the positive meniscus lens L 1  and the object-side surface of the negative meniscus lens L 3 . dN is the distance on the optical axis between the object-side surface of the positive meniscus lens L 1  and the object-side surface of the negative meniscus lens L 3 . 
     Table 9 below shows specifications of the optical system of the present example. 
     
       
         
           
               
             
               
                 TABLE 9 
               
               
                   
               
             
            
               
                 [General specifications] 
               
               
                   
               
            
           
           
               
               
               
            
               
                   
                 f 
                 779.97 
               
               
                   
                 Fno 
                 6.40 
               
               
                   
                 Bf 
                 79.800 
               
               
                   
                 image height 
                 21.700 
               
               
                   
                 TL 
                 399.450 
               
               
                   
                 2ω 
                 3.15 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens specifications] 
               
            
           
           
               
               
               
               
               
            
               
                 m 
                 r 
                 d 
                 nd 
                 νd 
               
               
                   
               
               
                  1) 
                 255.258 
                 9.091 
                 1.537750 
                 74.70 
               
               
                  2) 
                 1685.759 
                 0.500 
               
               
                  3) 
                 138.346 
                 12.666 
                 1.433837 
                 95.16 
               
               
                  4) 
                 418.938 
                 72.302 
               
               
                  5) 
                 177.080 
                 3.000 
                 1.883000 
                 40.66 
               
               
                  6) 
                 76.888 
                 13.971 
                 1.437001 
                 95.10 
               
               
                  7) 
                 2084.544 
                 1.000 
               
               
                  8) 
                 95.651 
                 14.302 
                 1.437001 
                 95.10 
               
               
                  9) 
                 −201.556 
                 2.800 
                 1.487490 
                 70.32 
               
               
                 10) 
                 121.665 
                 9.654 
               
               
                 11) 
                 151.928 
                 5.707 
                 1.663820 
                 27.35 
               
               
                 12) 
                 1406.765 
                 2.100 
                 1.902650 
                 35.72 
               
               
                 13) 
                 183.823 
                 D13 
               
               
                 14) 
                 −1678.708 
                 1.300 
                 1.487490 
                 70.32 
               
               
                 15) 
                 76.764 
                 D15 
               
            
           
           
               
               
               
               
               
            
               
                  16&gt; 
                 ∞ 
                 19.548 
                 (aperture stop) 
                   
               
            
           
           
               
               
               
               
               
            
               
                 17) 
                 −279.837 
                 3.000 
                 1.487490 
                 70.32 
               
               
                 18) 
                 −80.022 
                 1.500 
               
               
                 19) 
                 412.066 
                 3.500 
                 1.612660 
                 44.46 
               
               
                 20) 
                 −55.502 
                 1.200 
                 1.593190 
                 67.90 
               
               
                 21) 
                 63.474 
                 2.700 
               
               
                 22) 
                 −284.371 
                 1.200 
                 1.593490 
                 67.00 
               
               
                 23) 
                 84.284 
                 2.000 
               
               
                 24) 
                 38.563 
                 7.200 
                 1.581440 
                 40.98 
               
               
                 25) 
                 −69.150 
                 1.400 
                 1.593190 
                 67.90 
               
               
                 26) 
                 285.565 
                 2.553 
               
               
                 27) 
                 348.792 
                 1.400 
                 1.922860 
                 20.88 
               
               
                 28) 
                 31.874 
                 6.500 
                 1.620040 
                 36.40 
               
               
                 29) 
                 −610.498 
                 9.220 
               
               
                 30) 
                 59.656 
                 9.000 
                 1.620040 
                 36.40 
               
               
                 31) 
                 −34.040 
                 1.400 
                 1.593190 
                 67.90 
               
               
                 32) 
                 549.515 
                 4.295 
               
               
                 33) 
                 −54.352 
                 1.400 
                 1.883000 
                 40.66 
               
               
                 34) 
                 60.916 
                 9.500 
                 1.737999 
                 32.33 
               
               
                 35) 
                 −29.296 
                 1.400 
                 1.883000 
                 40.66 
               
               
                 36) 
                 −73.592 
                 Bf 
               
               
                   
               
            
           
           
               
            
               
                 [Focal length data of groups] 
               
            
           
           
               
               
               
               
            
               
                   
                 Groups 
                 Starting surfaces 
                 Focal lengths 
               
               
                   
                   
               
               
                   
                 G1 
                 1 
                 266.946 
               
               
                   
                 G1A 
                 1 
                 255.843 
               
               
                   
                 G1B 
                 5 
                 −1307.740 
               
               
                   
                 GF 
                 14 
                 −150.545 
               
               
                   
                 GR 
                 17 
                 −208.953 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Variable distance data] 
               
            
           
           
               
               
               
            
               
                   
                 At focusing on infinity 
                 At focusing on a nearby object 
               
               
                   
               
               
                 D13 
                 51.181 
                 73.947 
               
               
                 D15 
                 30.161 
                 7.394 
               
               
                   
               
            
           
         
       
     
       FIG.  18    shows aberrations of the optical system of the ninth example focusing on an object at infinity. 
     The graphs of aberrations suggest that the optical system of the present example effectively reduces variations in aberrations at focusing and has high optical performance. 
     Tenth Example 
       FIG.  19 A  is a cross-sectional view of an optical system of a tenth example focusing on an object at infinity.  FIG.  19 B  is a cross-sectional view of the optical system of the tenth example focusing on a nearby object. 
     The optical system of the present example includes a first lens group G 1  having positive refractive power, a focusing group GF having negative refractive power, and a rear group GR having negative refractive power, in order from the object side. An aperture stop S is disposed between the first lens group G 1  and the focusing group GF. The first lens group G 1  includes a first-A lens group G 1 A having positive refractive power and a first-B lens group G 1 B having negative refractive power, separated by the largest air space A in the first lens group; the first-A lens group G 1 A is disposed on the object side of the air space A and the first-B lens group G 1 B is disposed on the image side of the air space A. 
     The first-A lens group G 1 A includes a biconvex positive lens L 1  and a positive meniscus lens L 2  convex on the object side, in order from the object side. 
     The first-B lens group G 1 B includes a negative cemented lens composed of a negative meniscus lens L 3  convex on the object side and a positive meniscus lens L 4  convex on the object side; a positive cemented lens composed of a biconvex positive lens L 5  and a biconcave negative lens L 6 ; and a negative cemented lens composed of a negative meniscus lens L 7  convex on the object side and a positive meniscus lens L 8  convex on the object side, in order from the object side. 
     The focusing group GF includes a biconcave negative lens L 9 . 
     The rear group GR includes a positive meniscus lens L 10  convex on the image side; a negative cemented lens composed of a positive meniscus lens L 11  convex on the image side and a biconcave negative lens L 12 ; a biconcave negative lens L 13 ; a positive cemented lens composed of a biconvex positive lens L 14  and a biconcave negative lens L 15 ; a negative cemented lens composed of a biconcave negative lens L 16  and a biconvex positive lens L 17 ; a positive cemented lens composed of a biconvex positive lens L 18  and a negative meniscus lens L 19  convex on the image side; and a negative cemented lens composed of a biconcave negative lens L 20 , a biconvex positive lens L 21 , and a negative meniscus lens L 22  convex on the image side, in order from the object side. 
     An imaging device (not shown) constructed from CCD, CMOS or the like is disposed on an image plane I. 
     The optical system of the present example focuses by moving the focusing group GF along the optical axis. When the focus is shifted from infinity to a nearby object, the focusing group GF moves from the object side toward the image side. 
     In the optical system of the present example, the negative cemented lens composed of the positive meniscus lens L 11  and the negative lens L 12  and the negative lens L 13 , which are lenses included in the rear group GR, are configured as a vibration reduction lens group movable so that movement has a component in a direction perpendicular to the optical axis to correct an image blur. 
     In the optical system of the present example, the positive lens L 1  corresponds to the first lens, and the positive meniscus lens L 2  corresponds to the second lens. In the optical system of the present example, the negative meniscus lens L 3  corresponds to the negative lens N, and the positive meniscus lens L 8  corresponds to the positive lens Z. 
     In the optical system of the present example, dA is the distance on the optical axis between the image-side surface of the positive meniscus lens L 2  and the object-side surface of the negative meniscus lens L 3 . dG1 is the distance on the optical axis between the object-side surface of the positive lens L 1  and the image-side surface of the positive meniscus lens L 8 . dB is the distance on the optical axis between the object-side surface of the positive lens L 1  and the object-side surface of the negative meniscus lens L 3 . dN is the distance on the optical axis between the object-side surface of the positive lens L 1  and the object-side surface of the negative meniscus lens L 3 . 
     Table 10 below shows specifications of the optical system of the present example. 
     
       
         
           
               
             
               
                 TABLE 10 
               
               
                   
               
             
            
               
                 [General specifications] 
               
               
                   
               
            
           
           
               
               
               
            
               
                   
                 f 
                 780.00 
               
               
                   
                 Fno 
                 8.00 
               
               
                   
                 Bf 
                 92.159 
               
               
                   
                 image height 
                 21.700 
               
               
                   
                 TL 
                 351.452 
               
               
                   
                 2ω 
                 3.13 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens specifications] 
               
            
           
           
               
               
               
               
               
            
               
                 m 
                 r 
                 d 
                 nd 
                 νd 
               
               
                   
               
               
                  1) 
                 195.329 
                 8.988 
                 1.433837 
                 95.16 
               
               
                  2) 
                 −26364.519 
                 0.500 
               
               
                  3) 
                 109.812 
                 9.691 
                 1.433837 
                 95.16 
               
               
                  4) 
                 284.676 
                 60.820 
               
               
                  5) 
                 114.988 
                 2.700 
                 1.883000 
                 40.66 
               
               
                  6) 
                 58.226 
                 9.887 
                 1.437001 
                 95.10 
               
               
                  7) 
                 257.690 
                 1.000 
               
               
                  8) 
                 82.822 
                 10.837 
                 1.437001 
                 95.10 
               
               
                  9) 
                 −150.828 
                 2.500 
                 1.487490 
                 70.32 
               
               
                 10) 
                 114.026 
                 9.268 
               
               
                 11) 
                 69.040 
                 1.800 
                 1.883000 
                 40.66 
               
               
                 12) 
                 52.239 
                 4.278 
                 1.663820 
                 27.35 
               
               
                 13) 
                 68.880 
                 36.122 
               
            
           
           
               
               
               
               
               
            
               
                  14&gt; 
                 ∞ 
                 D14 
                 (aperture stop) 
                   
               
            
           
           
               
               
               
               
               
            
               
                 15) 
                 −6404.001 
                 1.400 
                 1.487490 
                 70.32 
               
               
                 16) 
                 60.905 
                 D16 
               
               
                 17) 
                 −62.158 
                 3.000 
                 1.487490 
                 70.32 
               
               
                 18) 
                 −50.943 
                 1.500 
               
               
                 19) 
                 −348.240 
                 3.500 
                 1.612660 
                 44.46 
               
               
                 20) 
                 −40.905 
                 1.200 
                 1.593190 
                 67.90 
               
               
                 21) 
                 107.146 
                 2.700 
               
               
                 22) 
                 −282.696 
                 1.200 
                 1.593490 
                 67.00 
               
               
                 23) 
                 118.438 
                 2.000 
               
               
                 24) 
                 34.139 
                 6.300 
                 1.581440 
                 40.98 
               
               
                 25) 
                 −31.938 
                 1.400 
                 1.593190 
                 67.90 
               
               
                 26) 
                 86.990 
                 3.741 
               
               
                 27) 
                 −81.495 
                 1.400 
                 1.922860 
                 20.88 
               
               
                 28) 
                 36.499 
                 6.000 
                 1.620040 
                 36.40 
               
               
                 29) 
                 −51.643 
                 4.422 
               
               
                 30) 
                 70.463 
                 7.000 
                 1.664460 
                 35.87 
               
               
                 31) 
                 −28.039 
                 1.400 
                 1.593190 
                 67.90 
               
               
                 32) 
                 −52.198 
                 2.000 
               
               
                 33) 
                 −52.381 
                 1.400 
                 1.883000 
                 40.66 
               
               
                 34) 
                 27.748 
                 9.000 
                 1.737999 
                 32.33 
               
               
                 35) 
                 −26.889 
                 1.400 
                 1.883000 
                 40.66 
               
               
                 36) 
                 −195.546 
                 Bf 
               
               
                   
               
            
           
           
               
            
               
                 [Focal length data of groups] 
               
            
           
           
               
               
               
               
            
               
                   
                 Groups 
                 Starting surfaces 
                 Focal lengths 
               
               
                   
                   
               
               
                   
                 G1 
                 1 
                 232.062 
               
               
                   
                 G1A 
                 1 
                 213.189 
               
               
                   
                 G1B 
                 5 
                 −700.761 
               
               
                   
                 GF 
                 15 
                 −123.749 
               
               
                   
                 GR 
                 17 
                 −139.187 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Variable distance data] 
               
            
           
           
               
               
               
            
               
                   
                 At focusing on infinity 
                 At focusing on a nearby object 
               
               
                   
               
               
                 D14 
                 14.926 
                 33.005 
               
               
                 D16 
                 24.011 
                 5.933 
               
               
                   
               
            
           
         
       
     
       FIG.  20    shows aberrations of the optical system of the tenth example focusing on an object at infinity. 
     The graphs of aberrations suggest that the optical system of the present example effectively reduces variations in aberrations at focusing and has high optical performance. 
     Eleventh Example 
       FIG.  21 A  is a cross-sectional view of an optical system of an eleventh example focusing on an object at infinity.  FIG.  21 B  is a cross-sectional view of the optical system of the eleventh example focusing on a nearby object. 
     The optical system of the present example includes a first lens group G 1  having positive refractive power, a focusing group GF having negative refractive power, and a rear group GR having negative refractive power, in order from the object side. 
     An aperture stop S is disposed between the first lens group G 1  and the focusing group GF. The first lens group G 1  includes a first-A lens group G 1 A having positive refractive power and a first-B lens group G 1 B having positive refractive power, separated by the largest air space A in the first lens group; the first-A lens group G 1 A is disposed on the object side of the air space A and the first-B lens group G 1 B is disposed on the image side of the air space A. 
     The first-A lens group G 1 A includes a positive meniscus lens L 1  convex on the object side. 
     The first-B lens group G 1 B includes a positive cemented lens composed of a negative meniscus lens L 2  convex on the object side and a positive meniscus lens L 3  convex on the object side; a negative cemented lens composed of a biconvex positive lens L 4  and a biconcave negative lens L 5 ; and a positive meniscus lens L 6  convex on the object side, in order from the object side. 
     The focusing group GF includes a biconcave negative lens L 7 . 
     The rear group GR includes a positive meniscus lens L 8  convex on the image side; a negative cemented lens composed of a positive meniscus lens L 9  convex on the image side and a biconcave negative lens L 10 ; a planoconcave negative lens L 11  concave on the image side; a positive cemented lens composed of a biconvex positive lens L 12  and a biconcave negative lens L 13 ; a negative cemented lens composed of a negative meniscus lens L 14  convex on the object side and a biconvex positive lens L 15 ; a positive cemented lens composed of a biconvex positive lens L 16  and a biconcave negative lens L 17 ; and a negative cemented lens composed of a biconcave negative lens L 18 , a biconvex positive lens L 19 , and a negative meniscus lens L 20  convex on the image side, in order from the object side. 
     An imaging device (not shown) constructed from CCD, CMOS or the like is disposed on an image plane I. 
     The optical system of the present example focuses by moving the focusing group GF along the optical axis. When the focus is shifted from infinity to a nearby object, the focusing group GF moves from the object side toward the image side. 
     In the optical system of the present example, the negative cemented lens composed of the positive meniscus lens L 9  and the negative lens L 10  and the negative lens L 11 , which are lenses included in the rear group GR, are configured as a vibration reduction lens group movable so that movement has a component in a direction perpendicular to the optical axis to correct an image blur. 
     In the optical system of the present example, the positive meniscus lens L 1  corresponds to the first lens. In the optical system of the present example, the negative meniscus lens L 2  corresponds to the negative lens N, and the positive meniscus lens L 6  corresponds to the positive lens Z. 
     In the optical system of the present example, dA is the distance on the optical axis between the image-side surface of the positive meniscus lens L 1  and the object-side surface of the negative meniscus lens L 2 . dG1 is the distance on the optical axis between the object-side surface of the positive meniscus lens L 1  and the image-side surface of the positive meniscus lens L 6 . dB is the distance on the optical axis between the object-side surface of the positive meniscus lens L 1  and the object-side surface of the negative meniscus lens L 2 . dN is the distance on the optical axis between the object-side surface of the positive meniscus lens L 1  and the object-side surface of the negative meniscus lens L 2 . 
     Table 11 below shows specifications of the optical system of the present example. 
     
       
         
           
               
             
               
                 TABLE 11 
               
               
                   
               
             
            
               
                 [General specifications] 
               
               
                   
               
            
           
           
               
               
               
            
               
                   
                 f 
                 779.95 
               
               
                   
                 Fno 
                 8.00 
               
               
                   
                 Bf 
                 87.483 
               
               
                   
                 image height 
                 21.700 
               
               
                   
                 TL 
                 399.482 
               
               
                   
                 2ω 
                 3.14 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens specifications] 
               
            
           
           
               
               
               
               
               
            
               
                 m 
                 r 
                 d 
                 nd 
                 νd 
               
               
                   
               
               
                  1) 
                 136.085 
                 11.698 
                 1.433837 
                 95.16 
               
               
                  2) 
                 2886.820 
                 93.585 
               
               
                  3) 
                 84.536 
                 3.000 
                 1.900430 
                 37.37 
               
               
                  4) 
                 57.130 
                 11.614 
                 1.437001 
                 95.10 
               
               
                  5) 
                 342.893 
                 1.000 
               
               
                  6) 
                 77.480 
                 12.561 
                 1.496997 
                 81.61 
               
               
                  7) 
                 −125.841 
                 2.800 
                 1.589130 
                 61.22 
               
               
                  8) 
                 56.630 
                 2.000 
               
               
                  9) 
                 49.759 
                 4.345 
                 1.663820 
                 27.35 
               
               
                 10) 
                 60.512 
                 51.451 
               
            
           
           
               
               
               
               
               
            
               
                  11&gt; 
                 ∞ 
                 D11 
                 (aperture stop) 
                   
               
            
           
           
               
               
               
               
               
            
               
                 12) 
                 −1013.842 
                 1.400 
                 1.487490 
                 70.32 
               
               
                 13) 
                 88.130 
                 D13 
               
               
                 14) 
                 −77.126 
                 3.000 
                 1.487490 
                 70.32 
               
               
                 15) 
                 −53.565 
                 2.000 
               
               
                 16) 
                 −3867.417 
                 4.000 
                 1.617720 
                 49.81 
               
               
                 17) 
                 −42.148 
                 1.200 
                 1.593190 
                 67.90 
               
               
                 18) 
                 116.314 
                 1.200 
               
               
                 19) 
                 ∞ 
                 1.200 
                 1.593490 
                 67.00 
               
               
                 20) 
                 81.561 
                 3.000 
               
               
                 21) 
                 40.019 
                 6.700 
                 1.531720 
                 48.78 
               
               
                 22) 
                 −37.697 
                 1.500 
                 1.593190 
                 67.90 
               
               
                 23) 
                 238.406 
                 3.118 
               
               
                 24) 
                 345.221 
                 1.500 
                 1.922860 
                 20.88 
               
               
                 25) 
                 38.137 
                 5.300 
                 1.603420 
                 38.03 
               
               
                 26) 
                 −123.170 
                 14.480 
               
               
                 27) 
                 62.684 
                 6.500 
                 1.620040 
                 36.40 
               
               
                 28) 
                 −35.175 
                 1.500 
                 1.593190 
                 67.90 
               
               
                 29) 
                 189.726 
                 4.455 
               
               
                 30) 
                 −79.833 
                 1.500 
                 1.883000 
                 40.66 
               
               
                 31) 
                 36.649 
                 8.000 
                 1.737999 
                 32.33 
               
               
                 32) 
                 −30.820 
                 1.500 
                 1.883000 
                 40.66 
               
               
                 33) 
                 −167.720 
                 Bf 
               
               
                   
               
            
           
           
               
            
               
                 [Focal length data of groups] 
               
            
           
           
               
               
               
               
            
               
                   
                 Groups 
                 Starting surfaces 
                 Focal lengths 
               
               
                   
                   
               
               
                   
                 G1 
                 1 
                 277.319 
               
               
                   
                 G1A 
                 1 
                 328.772 
               
               
                   
                 G1B 
                 3 
                 7228.305 
               
               
                   
                 GF 
                 12 
                 −166.256 
               
               
                   
                 GR 
                 14 
                 −168.016 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Variable distance data] 
               
            
           
           
               
               
               
            
               
                   
                 At focusing on infinity 
                 At focusing on a nearby object 
               
               
                   
               
               
                 D11 
                 13.975 
                 40.029 
               
               
                 D13 
                 30.918 
                 4.865 
               
               
                   
               
            
           
         
       
     
       FIG.  22    shows aberrations of the optical system of the eleventh example focusing on an object at infinity. 
     The graphs of aberrations suggest that the optical system of the present example effectively reduces variations in aberrations at focusing and has high optical performance. 
     According to the above examples, a small and lightweight optical system of favorable imaging performance can be achieved. 
     The following is a list of the conditional expressions and the values for the conditional expressions in the examples. 
     FNo, TL, and f are the f-number, the total optical length, and the focal length of the optical system focusing on infinity, respectively. dA is the length on the optical axis of the air space A, and dG1 is the length on the optical axis of the first lens group. dN is the distance on the optical axis from a surface closest to the object side in the optical system to an object-side surface of the negative lens N. f1A is the focal length of the first-A lens group, and f1B is the focal length of the first-B lens group. dB is the distance on the optical axis from a surface closest to the object side in the optical system to a surface closest to the object side in the first-B lens group. fL1 is the focal length of a first lens disposed closest to the object side, and fL2 is the focal length of a second lens disposed second from the object side. νd1Amax is the highest of the Abbe numbers for d-line of lenses included in the first-A lens group, and νdLZ is the Abbe number for d-line of the positive lens Z. νd1Aave is an average of the Abbe numbers for d-line of lenses included in the first-A lens group. 
     ndLZ is the refractive index for d-line of the positive lens Z, and θgFLZ is a partial dispersion ratio of the positive lens Z and is defined by the following equation: 
       θ gFLZ= ( ngLZ−nFLZ )/( nFLZ−nCLZ )
 
     where the refractive indices for g-line, F-line, and C-line of the positive lens Z are denoted by ngLZ, nFLZ, and nCLZ, respectively. 
     L1R1 is the radius of curvature of an object-side surface of a first lens disposed closest to the object side, and L1R2 is the radius of curvature of an image-side surface of the first lens. L2R1 is the radius of curvature of an object-side surface of a second lens disposed second from the object side, and L2R2 is the radius of curvature of an image-side surface of the second lens. f1 is the focal length of the first lens group. fF is the focal length of the focusing group. fR is the focal length of the rear group. dF is the distance on the optical axis from a surface closest to the object side in the optical system to a surface closest to the object side in the focusing group. νdFave is an average of the Abbe numbers for d-line of lenses included in the focusing group. 2ω is the total angle of view of the optical system. BF is the back focus of the optical system. 
     LIST OF CONDITIONAL EXPRESSIONS 
     
         
         (1) Fno*(TL/f) 2    
         (2) dA/dG1 
         (3) TL/f 
         (4) dN/TL 
         (5) f1A/f1B 
         (6) f1A/f 
         (7) dB/dG1 
         (8) fL1/fL2 
         (9) νd1Amax−νdLZ 
         (10) νd1Aave 
         (11) ndLZ+(0.01425*νdLZ) 
         (12) νdLZ 
         (13) egFLZ+(0.00316*νdLZ) 
         (14) (L1R2+L1R1)/(L1R2-L1R1) 
         (15) (L2R2+L2R1)/(L2R2-L2R1) 
         (16) f1/f 
         (17) (−fF)/f1 
         (18) (−fF)/fR 
         (19) dF/TL 
         (20) νdFave 
         (21) 2ω 
         (22) Bf/f 
       
    
     VALUES FOR CONDITIONAL EXPRESSIONS 
     Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 
       
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
               
             
            
               
                  (1) 
                 1.742 
                   
                 1.928 
                 1.792 
                   
                 1.860 
               
               
                   
                 1.877 
                   
                 1.597 
               
               
                  (2) 
                 0.384 
                   
                 0.467 
                 0.456 
                   
                 0.444 
               
               
                   
                 0.358 
                   
                 0.479 
               
               
                  (3) 
                 0.652 
                   
                 0.686 
                 0.624 
                   
                 0.568 
               
               
                   
                 0.570 
                   
                 0.525 
               
               
                  (4) 
                 0.281 
                   
                 0.311 
                 0.308 
                   
                 0.257 
               
               
                   
                 0.276 
                   
                 0.295 
               
               
                  (5) 
                 −0.374 
                   
                 −0.090 
                 −0.055 
                   
                 −0.493 
               
               
                   
                 −0.353 
                   
                 −0.360 
               
               
                  (6) 
                 0.353 
                   
                 0.415 
                 0.379 
                   
                 0.287 
               
               
                   
                 0.295 
                   
                 0.309 
               
               
                  (7) 
                 0.617 
                   
                 0.642 
                 0.626 
                   
                 0.640 
               
               
                   
                 0.561 
                   
                 0.646 
               
               
                  (8) 
                 1.429 
                   
                 1.603 
                 1.953 
                   
                 1.415 
               
               
                   
                 2.670 
                   
                 1.785 
               
               
                  (9) 
                 67.75 
                   
                 67.81 
                 67.75 
                   
                 67.75 
               
               
                   
                 67.81 
                   
                 67.81 
               
               
                 (10) 
                 84.90 
                   
                 84.93 
                 84.90 
                   
                 88.36 
               
               
                   
                 82.53 
                   
                 84.93 
               
               
                 (11) 
                 2.054 
                   
                 2.054 
                 2.054 
                   
                 2.054 
               
               
                   
                 2.054 
                   
                 2.054 
               
               
                 (12) 
                 27.35 
                   
                 27.35 
                 27.35 
                   
                 27.35 
               
               
                   
                 27.35 
                   
                 27.35 
               
               
                 (13) 
                 0.120 
                   
                 0.120 
                 0.120 
                   
                 0.120 
               
               
                   
                 0.120 
                   
                 0.120 
               
               
                 (14) 
                 1.145 
                   
                 1.417 
                 1.111 
                   
                 1.065 
               
               
                   
                 0.817 
                   
                 1.565 
               
               
                 (15) 
                 1.590 
                   
                 1.533 
                 1.415 
                   
                 1.732 
               
               
                   
                 1.328 
                   
                 1.680 
               
               
                 (16) 
                 0.417 
                   
                 0.432 
                 0.385 
                   
                 0.362 
               
               
                   
                 0.363 
                   
                 0.355 
               
               
                 (17) 
                 0.654 
                   
                 0.544 
                 0.599 
                   
                 0.543 
               
               
                   
                 0.630 
                   
                 0.452 
               
               
                 (18) 
                 −0.233 
                   
                 0.050 
                 −0.203 
                   
                 −0.104 
               
               
                   
                 −0.429 
                   
                 −0.337 
               
               
                 (19) 
                 0.437 
                   
                 0.481 
                 0.486 
                   
                 0.429 
               
               
                   
                 0.434 
                   
                 0.499 
               
               
                 (20) 
                 81.61 
                   
                 81.61 
                 81.61 
                   
                 81.61 
               
               
                   
                 81.61 
                   
                 81.61 
               
               
                 (21) 
                 8.43 
                 6.30 
                 6.30 
                 6.35 
                 5.05 
                 4.20 
               
               
                 (22) 
                 0.122 
                   
                 0.156 
                 0.142 
                   
                 0.140 
               
               
                   
                 0.108 
                   
                 0.099 
               
               
                   
               
            
           
         
       
     
     Example 7 Example 8 Example 9 Example 10 Example 11 
       
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
               
             
            
               
                  (1) 
                 1.490 
                   
                 1.402 
                 1.679 
                   
                 1.624 
               
               
                   
                 2.099 
               
               
                  (2) 
                 0.501 
                   
                 0.427 
                 0.492 
                   
                 0.497 
               
               
                   
                 0.656 
               
               
                  (3) 
                 0.507 
                   
                 0.492 
                 0.512 
                   
                 0.451 
               
               
                   
                 0.512 
               
               
                  (4) 
                 0.328 
                   
                 0.251 
                 0.237 
                   
                 0.228 
               
               
                   
                 0.264 
               
               
                  (5) 
                 −0.462 
                   
                 −0.373 
                 −0.196 
                   
                 −0.304 
               
               
                   
                 0.045 
               
               
                  (6) 
                 0.303 
                   
                 0.337 
                 0.328 
                   
                 0.273 
               
               
                   
                 0.422 
               
               
                  (7) 
                 0.669 
                   
                 0.594 
                 0.643 
                   
                 0.654 
               
               
                   
                 0.738 
               
               
                  (8) 
                 1.650 
                   
                 1.204 
                 1.188 
                   
                 1.103 
               
               
                   
                 (N/A) 
               
               
                  (9) 
                 67.81 
                   
                 67.81 
                 67.81 
                   
                 67.81 
               
               
                   
                 67.81 
               
               
                 (10) 
                 95.16 
                   
                 95.16 
                 84.93 
                   
                 95.16 
               
               
                   
                 95.16 
               
               
                 (11) 
                 2.054 
                   
                 2.054 
                 2.054 
                   
                 2.054 
               
               
                   
                 2.054 
               
               
                 (12) 
                 27.35 
                   
                 27.35 
                 27.35 
                   
                 27.35 
               
               
                   
                 27.35 
               
               
                 (13) 
                 0.120 
                   
                 0.120 
                 0.120 
                   
                 0.120 
               
               
                   
                 0.120 
               
               
                 (14) 
                 0.946 
                   
                 0.873 
                 1.357 
                   
                 0.985 
               
               
                   
                 1.099 
               
               
                 (15) 
                 1.812 
                   
                 2.272 
                 1.986 
                   
                 2.256 
               
               
                   
                 (N/A) 
               
               
                 (16) 
                 0.359 
                   
                 0.348 
                 0.342 
                   
                 0.298 
               
               
                   
                 0.356 
               
               
                 (17) 
                 0.421 
                   
                 0.488 
                 0.564 
                   
                 0.533 
               
               
                   
                 0.600 
               
               
                 (18) 
                 −0.269 
                   
                 −0.674 
                 −0.720 
                   
                 −0.889 
               
               
                   
                 −0.990 
               
               
                 (19) 
                 0.528 
                   
                 0.538 
                 0.496 
                   
                 0.493 
               
               
                   
                 0.521 
               
               
                 (20) 
                 70.32 
                   
                 70.32 
                 70.32 
                   
                 70.32 
               
               
                   
                 70.32 
               
               
                 (21) 
                 3.14 
                 3.14 
                 3.15 
                 3.13 
                 3.14 
               
               
                 (22) 
                 0.093 
                   
                 0.098 
                 0.102 
                   
                 0.118 
               
               
                   
                 0.112 
               
               
                   
               
            
           
         
       
     
     The above examples illustrate specific examples of the present invention, and the present invention is not limited thereto. The following details can be appropriately employed unless the optical performance of the optical system of the embodiment of the present application is lost. 
     The lens surfaces of the lenses constituting any of the optical systems of the above examples may be covered with antireflection coating having high transmittance in a wide wavelength range. This reduces flares and ghosts, and enables achieving optical performance with high contrast. 
     Next, a camera including the optical system of the present embodiment is described with reference to  FIG.  23   . 
       FIG.  23    schematically shows a camera including the optical system of the present embodiment. 
     The camera  1  is a camera of an interchangeable lens type including the optical system according to the first example as an imaging lens  2 . 
     In the camera  1 , light from an object (subject) (not shown) is condensed by the imaging lens  2 , and forms an image on a focusing glass  4  via a quick-return mirror  3 . The light forming an image on the focusing glass  4  is reflected multiple times in a pentaprism  5  and guided to an eyepiece  6 . This enables a photographer who positions his/her eye at an eye point EP to observe an image of the subject as an erect image. 
     When a release button (not shown) is pressed by the photographer, the quick-return mirror  3  moves outside the optical path, causing the light from the subject (not shown) to reach an imaging device  7 . Then the light from the subject is captured by the imaging device  7  and stored in a memory (not shown) as a subject image. In this way, the photographer can take a picture of the subject with the camera  1 . 
     The optical system of the first example included in the camera  1  as the imaging lens  2  is a small and lightweight optical system of favorable imaging performance. Thus the camera  1  can be small and achieve favorable optical performance. A camera configured by including any of the optical systems of the second to eleventh examples as the imaging lens  2  can have the same effect as the camera  1 . 
     Finally, methods for manufacturing an optical system of the present embodiment are described in outline with reference to  FIGS.  24  and  25   . 
       FIG.  24    is a first flowchart outlining a method for manufacturing an optical system of the present embodiment. 
     The method for manufacturing an optical system of the present embodiment shown in  FIG.  24    is a method for manufacturing an optical system including a plurality of lenses and includes the following steps S11, S12, and S13: 
     Step S11: disposing a first lens group having positive refractive power, a focusing group that moves along an optical axis at focusing, and a rear group, in order from an object side; 
     Step S12: disposing a first-A lens group on the object side of the largest air space A in the first lens group; and 
     Step S13: making the optical system satisfy all of predetermined conditional expressions: 
       1.00&lt; FNo ×( TL/f ) 2 &lt;2.50  (1)
 
       0.30&lt; dA/dG 1&lt;0.85  (2)
 
     where 
     FNo is the f-number of the optical system focusing on infinity, 
     TL is the total optical length of the optical system focusing on infinity, 
     f is the focal length of the optical system focusing on infinity, 
     dA is the length on the optical axis of the air space A, and 
     dG1 is the length on the optical axis of the first lens group. 
     A small and lightweight optical system of favorable imaging performance can be manufactured by the method for manufacturing an optical system of the present embodiment. 
       FIG.  25    is a second flowchart outlining a method for manufacturing an optical system of the present embodiment. 
     The method for manufacturing an optical system of the present embodiment shown in  FIG.  25    is a method for manufacturing an optical system including a plurality of lenses and includes the following steps S21, S22, and S23: 
     Step S21: preparing a plurality of lenses; 
     Step S22: disposing at least one positive lens component and a negative lens N, in order from an object side; and 
     Step S23: making the optical system satisfy all of predetermined conditional expressions: 
       1.00&lt; FNo ×( TL/f ) 2 &lt;2.50  (1)
 
       0.18&lt; dN/TL&lt; 0.45  (4)
 
     where 
     FNo is the f-number of the optical system focusing on infinity, 
     TL is the total optical length of the optical system focusing on infinity, 
     f is the focal length of the optical system focusing on infinity, and 
     dN is the distance on an optical axis from a surface closest to the object side in the optical system to an object-side surface of the negative lens N. 
     A small and lightweight optical system of favorable imaging performance can be manufactured by the method for manufacturing an optical system of the present embodiment. 
     Note that those skilled in the art can make various changes, substitutions, and modifications without departing from the spirit and scope of the present invention. 
     REFERENCE SIGNS LIST 
     
         
         
           
             S aperture stop 
             I image plane 
               1  camera 
               2  imaging lens 
               7  imaging device