Patent Publication Number: US-2021191112-A1

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

Description:
TECHNICAL FIELD 
     The present invention relates to an optical system, an optical apparatus, and a method of manufacturing the optical system. 
     TECHNICAL BACKGROUND 
     In recent years, the numbers of pixels of imaging elements used for imaging devices, such as digital cameras and video cameras, have been increasing. Photographic lenses provided in imaging devices including such imaging elements are desired to be lenses which have a high resolving power and in which in addition to reference aberrations (aberrations for a single wavelength), such as the spherical aberration and coma aberration, chromatic aberrations are also favorably corrected so as to eliminate color shift in an image with a white light source. In particular, for correcting the chromatic aberration, it is desired that in addition to the primary achromatization, the secondary spectrum be favorably corrected. For example, a method of using a resin material having anomalous dispersion (for example, see Patent Literature 1) has been known as means for correcting the chromatic aberration. As described above, accompanied by improvement in numbers of pixels of imaging elements in recent years, a photographic lens with various aberrations being preferably corrected has been desired. 
     PRIOR ARTS LIST 
     Patent Document 
     Patent Literature 1: Japanese Laid-Open Patent Publication No. 2016-194609 
     SUMMARY OF THE INVENTION 
     An optical system according to a first aspect comprises a lens satisfying following conditional expressions, 
         ndLZ +(0.01425×ν dLZ )&lt;2.12, and
 
       0.702 &lt;θgFLZ +(0.00316×ν dLZ ),
 
     where ndLZ: a refractive index of the lens with reference to d-line, 
     νdLZ: Abbe number of the lens with reference to d-line, and 
     θgFLZ: a partial dispersion ratio of the lens, 
     wherein θgFLZ is defined by the following expression, 
       θ gFLZ =( ngLZ−nFLZ )/( nFLZ−nCLZ ).
 
     wherein a refractive index of the lens with reference to g-line is ngLZ, a refractive index of the lens with reference to F-line is nFLZ, and a refractive index of the lens with reference to C-line is nCLZ. 
     An optical apparatus according to a second aspect is configured to comprise the optical system described above. 
     A method of manufacturing an optical system according to a third aspect disposes lenses within a lens barrel so as to comprise a lens satisfying following conditional expressions, 
         ndLZ +(0.01425 ×νdLZ )&lt;2.12, and 
       0.702 &lt;θgFLZ +(0.00316 ×νdLZ ), 
     where ndLZ: a refractive index of the lens with reference to d-line, 
     νdLZ: Abbe number of the lens with reference to d-line, and 
     θgFLZ: a partial dispersion ratio of the lens, 
     wherein θgFLZ is defined by the following expression, 
       θ gFLZ =( ngLZ−nFLZ )/( nFLZ−nCLZ ).
 
     wherein a refractive index of the lens with reference to g-line is ngLZ, a refractive index of the lens with reference to F-line is nFLZ, and a refractive index of the lens with reference to C-line is nCLZ. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a lens configuration of an optical system according to a first example upon focusing on infinity; 
         FIG. 2  shows various aberration graphs of the optical system according to the first example upon focusing on infinity; 
         FIG. 3  shows a lens configuration of an optical system according to a second example upon focusing on infinity; 
         FIGS. 4A, 48 and 4C  show various aberration graphs of the optical system according to the second example upon focusing on infinity in a wide angle end state, an intermediate focal length state, and a telephoto and state, respectively; 
         FIG. 5  shows a lens configuration of an optical system according to a third example upon focusing on infinity; 
         FIG. 6  shows various aberration graphs of the optical system according to the third example upon focusing on infinity; 
         FIG. 7  shows a lens configuration of an optical system according to a fourth example upon focusing on infinity; 
         FIGS. 8A, 8B and 8C  show various aberration graphs of the optical system according to the fourth example upon focusing on infinity in a wide angle end state, an intermediate focal length state, and a telephoto end state, respectively; 
         FIG. 9  shows a les configuration of an optical system according to a fifth example upon focusing on infinity; 
         FIGS. 10A, 10B and 10C  show various aberration graphs of the optical system according to the fifth example upon focusing on infinity in a wide angle and state, an intermediate focal length state, and a telephoto end state, respectively; 
         FIG. 11  shows a lens configuration of an optical system according to a sixth example upon focusing on infinity; 
         FIG. 12  shows various aberration graphs of the optical system according to the sixth example upon focusing on infinity; 
         FIG. 13  shows a lens configuration of an optical system according to a seventh example upon focusing on infinity; 
         FIG. 14  shows various aberration graphs of the optical system according to the seventh example upon focusing on infinity; 
         FIG. 15  shows a configuration of a camera comprising the optical system according to this embodiment; and 
         FIG. 16  is a flowchart showing a method of manufacturing the optical system according to this embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, optical systems and optical apparatuses according to this embodiment are described with reference to the drawings. First, a camera (optical apparatus) including an optical system according to this embodiment is described with reference to  FIG. 15 . This camera  1  is a digital camera comprising an optical system according to this embodiment as a photographic lens  2  as shown in  FIG. 15 . In the camera  1 , light from an object (subject), not shown, is condensed by the photographic lens  2  and reaches an imaging element  3 . Accordingly, the light from the subject is imaged by the imaging element  3 , and is recorded as a subject image in a memory, not shown. As described above, a photographer can image the subject through the camera  1 . Note that the camera may be a mirrorless camera, or a camera of a single-lens reflex type including a quick-return mirror. 
     An optical system LS( 1 ) as an example of an optical system (photographic lens) LS according to this embodiment includes lenses (L22 and L33) satisfying the following conditional expressions (1) and (2), as shown in  FIG. 1 . In this embodiment, to discriminate from the other lenses, the lenses satisfying the conditional expressions (1) and (2) are sometimes called specified lenses. 
         ndL +(0.01425 ×νdLZ )&lt;2.12  (1)
 
       0.702 &lt;θgFLZ +(0.00316 ×νdLZ )  (2)
 
     where ndLZ: the refractive index of the specified lens with reference to d-line, 
     νdLZ: Abbe number of the specified lens with reference to d-line, and 
     θgFLZ: a partial dispersion ratio of the specified lens, 
     wherein θgFLZ is defined by the following expression, 
       θ gFLZ =( ngLZ−nFLZ )/( nFLZ−nCLZ ).
 
     wherein a refractive index of the lens with reference to g-line is ngLZ, a refractive index of the lens with reference to F-line is nFLZ, and a refractive index of the lens with reference to C-line is nCLZ. 
     Note that the Abbe number νdLZ of the specified lens with reference to d-line is defined by the following expression, 
       ν dLZ =( ndLZ −1)/( nFLZ−nCLZ ).
 
     According to this embodiment, as for correction of the chromatic aberrations, an optical system and an optical apparatus including the optical system can be obtained where in addition to the primary achromatization, the secondary spectrum is favorably corrected. The optical system LS according to this embodiment may be an optical system LS( 2 ) shown in  FIG. 3 , an optical system LS( 3 ) shown in  FIG. 5 , or an optical system LS( 4 ) shown in  FIG. 7 . The optical system LS according to this embodiment may be an optical system LS( 5 ) shown in  FIG. 9 , an optical system LS( 6 ) shown in  FIG. 11 , or an optical system LS( 7 ) shown in  FIG. 13 . 
     The conditional expression (1) defines an appropriate relationship between the refractive index of the specified lens with reference to d-line and the Abbe number with reference to d-line. By satisfying the conditional expression (1), correction of reference aberrations, such as the spherical aberration and coma aberration, and correction of primary chromatic aberration (achromatization) can be favorably performed. 
     When the corresponding value of the conditional expression (1) exceeds the upper limit value, the Petzval sum becomes small, for example, and correction of the curvature of field becomes difficult. Accordingly, this is not preferable. Setting the upper limit value of the conditional expression (1) to 2.11 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the upper limit value of the conditional expression (1) to 2.10, 2.09, 2.08, 2.07, or furthermore, 2.06. 
     The conditional expression (2) appropriately specifies the anomalous dispersion of the specified lens. By satisfying the conditional expression (2), as for correction of the chromatic aberrations, in addition to the primary achromatization, the secondary spectrum can be favorably corrected. 
     When the corresponding value of the conditional expression (2) falls below the lower limit value, the anomalous dispersion of the specified lens becomes small. Accordingly, it becomes difficult to correct the chromatic aberration. Setting the lower limit value of the conditional expression (2) to 0.704 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the lower limit value of the conditional expression (2) to 0.708, 0.710, 0.712, or furthermore, 0.715. 
     In the optical system of this embodiment, it is desired that the specified lens satisfy the following conditional expression (3). 
       ν dLZ &lt;35.0  (3)
 
     The conditional expression (3) defines an appropriate range of the Abbe number of the specified lens with reference to d-line. By satisfying the conditional expression (3), correction of reference aberrations, such as the spherical aberration and coma aberration, and correction of primary chromatic aberration (achromatization) can be favorably performed. 
     When the corresponding value of the conditional expression (3) exceeds the upper limit value, for example, it is difficult to correct the longitudinal chromatic aberration of a partial group nearer to an object or an image than an aperture stop S. Accordingly, this is not preferable. Setting the upper limit value of the conditional expression (3) to 32.5 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the upper limit value of the conditional expression (3) to 32.0, 31.5, 31.0, 30.5, 30.0, or furthermore, 29.5. 
     In the optical system of this embodiment, the specified lens may satisfy the following conditional expression (3-1). 
       18.0 &lt;νdLZ &lt;35.0  (3-1)
 
     The conditional expression (3-1) is an expression similar to the conditional expression (3). By satisfying the conditional expression (3-1), correction of reference aberrations, such as the spherical aberration and coma aberration, and correction of primary chromatic aberration (achromatization) can be favorably performed. Setting the upper limit value of the conditional expression (3-1) to 32.5 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the upper limit value of the conditional expression (3-1) to 32.0, 31.5, 31.0, 30.5, 30.0, or furthermore, 29.5. On the other hand, setting the lower limit value of the conditional expression (3-1) to 20.0 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the lower limit value of the conditional expression (3-1) to 23.0, 23.5, 24.0, 24.5, 25.0, 25.5, 26.0, 26.5, 27.0, 27.5, or furthermore, 27.7. 
     In the optical system of this embodiment, it is desired that the specified lens satisfy the following conditional expression (4). 
       1.83 &lt;ndLZ +(0.00787 ×νdLZ )  (4)
 
     The conditional expression (4) defines an appropriate relationship between the refractive index of the specified lens with reference to d-line and the Abbe number with reference to d-line. By satisfying the conditional expression (4), correction of reference aberrations, such as the spherical aberration and coma aberration, and correction of primary chromatic aberration (achromatization) can be favorably performed. 
     When the corresponding value of the conditional expression (4) falls below the lower limit value, correction of the reference aberrations, in particular, the spherical aberration becomes difficult due to, for example, reduction in the refractive index of the specified lens. Accordingly, this is not preferable. Setting the lower limit value of the conditional expression (4) to 1.84 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the lower limit value of the conditional expression (4) to 1.85, or furthermore, 1.86. 
     In the optical system of this embodiment, it is desired that the specified lens satisfy the following conditional expression (5). 
       1.55 &lt;ndLZ   (5)
 
     The conditional expression (5) defines an appropriate range of the refractive index of the specified lens with reference to d-line. By satisfying the conditional expression (5), the various aberrations, such as the coma aberration and the chromatic aberrations (the longitudinal chromatic aberration and the chromatic aberration of magnification), can be favorably corrected. 
     When the corresponding value of the conditional expression (5) falls below the lower limit value, correction of the various aberrations, such as the coma aberration and the chromatic aberrations (the longitudinal chromatic aberration and the chromatic aberration of magnification). Accordingly, this is not preferable. Setting the lower limit value of the conditional expression (5) to 1.58 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the lower limit value of the conditional expression (5) to 1.60, 1.62, 1.65, 1.68, 1.70, or furthermore, 1.72. 
     In the optical system of this embodiment, it is desired that the specified lens satisfy the following conditional expression (6). 
         DLZ &gt;0.80  (6)
 
     where DL: a thickness [mm] of the lens on an optical axis. 
     The conditional expression (6) defines an appropriate range of the thickness of the specified lens on the optical axis. By satisfying the conditional expression (6), the various aberrations, such as the coma aberration and the chromatic aberrations (the longitudinal chromatic aberration and the chromatic aberration of magnification), can be favorably corrected. 
     When the corresponding value of the conditional expression (6) falls below the lower limit value, correction of the various aberrations, such as the coma aberration, and chromatic aberrations (the longitudinal chromatic aberration and the chromatic aberration of magnification) becomes difficult. Accordingly, this is not preferable. Setting the lower limit value of the conditional expression (6) to 0.90 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the lower limit value of the conditional expression (6) to 1.00, 1.10, 1.20, or furthermore, 1.30. 
     In the optical system of this embodiment, it is desired that the specified lens satisfy the following conditional expressions (5-1) and (7). 
         ndLZ &lt;1.63  (5-1)
 
         ndLZ −(0.040 ×νdLZ −2.470)×ν dLZ &lt;39.809  (7)
 
     The conditional expression (5-1) is an expression similar to the conditional expression (5). By satisfying the conditional expression (5-1), the various aberrations, such as the coma aberration, and the chromatic aberrations (the longitudinal chromatic aberration and the chromatic aberration of magnification), can be favorably corrected. Setting the upper limit value of the conditional expression (5-1) to 1.62 can securely achieve the advantageous effects of this embodiment. 
     The conditional expression (7) defines an appropriate relationship between the refractive index of the specified lens with reference to d-line and the Abbe number with reference to d-line. By satisfying the conditional expression (7), correction of reference aberrations, such as the spherical aberration and coma aberration, and correction of primary chromatic aberration (achromatization) can be favorably performed. 
     When the corresponding value of the conditional expression (7) exceeds the upper limit value, the Petzval sum becomes small, for example, and correction of the curvature of field becomes difficult. Accordingly, this is not preferable. Setting the upper limit value of the conditional expression (7) to 39.800 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the upper limit value of the conditional expression (7) to 39.500, 39.000, 38.500, 38.000, 37.500, or furthermore, 36.800. 
     In the optical system of this embodiment, it is desired that the specified lens satisfy the following conditional expression (8). 
         ndLZ −(0.020 ×νdLZ −1.080)×ν dLZ &lt;16.260  (8)
 
     The conditional expression (8) defines an appropriate relationship between the refractive index of the specified lens with reference to d-line and the Abbe number with reference to d-line. By satisfying the conditional expression (8), correction of reference aberrations, such as the spherical aberration and coma aberration, and correction of primary chromatic aberration (achromatization) can be favorably performed. 
     When the corresponding value of the conditional expression (8) exceeds the upper limit value, the Petzval sum becomes small, for example, and correction of the curvature of field becomes difficult. Accordingly, this is not preferable. Setting the upper limit value of the conditional expression (8) to 16.240 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the upper limit value of the conditional expression (8) to 16.000, 15.800, 15.500, 15.300, 15.000, 14.800, 14.500, 14.000, or furthermore, 13.500. 
     In the optical system of this embodiment, the specified lens may satisfy the following conditional expression (3-2). 
       18.0 &lt;νdLZ &lt;27.0  (3-2)
 
     The conditional expression (3-2) is an expression similar to the conditional expression (3). By satisfying the conditional expression (3-2), correction of reference aberrations, such as the spherical aberration and coma aberration, and correction of primary chromatic aberration (achromatization) can be favorably performed. Setting the upper limit value of the conditional expression (3-2) to 26.6 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the upper limit value of the conditional expression (3-2) to 26.3, 26.0, 25.7, or furthermore, 25.4. On the other hand, setting the lower limit value of the conditional expression (3-2) to 21.0 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the lower limit value of the conditional expression (3-2) to 21.5, 22.0, 22.5, or furthermore, 23.0. 
     In the optical system of this embodiment, the specified lens may satisfy the following conditional expression (5-2). 
       1.700 &lt;ndLZ &lt;1.850  (5-2)
 
     The conditional expression (5-2) is an expression similar to the conditional expression (5). By satisfying the conditional expression (5-2), the various aberrations, such as the coma aberration and the chromatic aberrations (longitudinal chromatic aberration and the chromatic aberration of magnification), can be favorably corrected. Setting the upper limit value of the conditional expression (5-2) to 1.830 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the upper limit value of the conditional expression (5-2) to 1.810, 1.790, 1.770, or furthermore, 1.764. On the other hand, setting the lower limit value of the conditional expression (5-2) to 1.709 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the lower limit value of the conditional expression (5-2) to 1.718, 1.727, 1.736, or furthermore, 1.745. 
     In the optical system of this embodiment, the specified lens may satisfy the following conditional expression (2-1). 
       0.702 &lt;θgFLZ +(0.00316 ×νdLZ )&lt;0.900  (2-1)
 
     The conditional expression (2-1) is an expression similar to the conditional expression (2). By satisfying the conditional expression (2-1), as for correction of the chromatic aberrations, in addition to the primary achromatization, the secondary spectrum can be favorably corrected. Setting the upper limit value of the conditional expression (2-1) to 0.850 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the upper limit value of the conditional expression (2-1) to 0.800, or furthermore, 0.720. On the other hand, setting the lower limit value of the conditional expression (2-1) to 0.704 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the lower limit value of the conditional expression (2-1) to 0.706. 
     In the optical system of this embodiment, the specified lens may satisfy the following conditional expression (5-3). 
       1.550 &lt;ndL &lt;1.700  (5-3)
 
     The conditional expression (5-3) is an expression similar to the conditional expression (5). By satisfying the conditional expression (5-3), the various aberrations, such as the coma aberration and the chromatic aberrations (the longitudinal chromatic aberration and the chromatic aberration of magnification) can be favorably corrected. Setting the upper limit value of the conditional expression (5-3) to 1.699 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the upper limit value of the conditional expression (5-3) to 1.698, 1.697, 1.696, or furthermore, 1.695. On the other hand, setting the lower limit value of the conditional expression (5-3) to 1.560 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the lower limit value of the conditional expression (5-3) to 1.570, 1.560, 1.590, or furthermore, 1.600. 
     In the optical system of this embodiment, the specified lens may satisfy the following conditional expression (3-3). 
       27.0 &lt;νdLZ &lt;35.0  (3-3)
 
     The conditional expression (3-3) is an expression similar to the conditional expression (3). By satisfying the conditional expression (3-3), correction of reference aberrations, such as the spherical aberration and coma aberration, and correction of primary chromatic aberration (achromatization) can be favorably performed. Setting the upper limit value of the conditional expression (3-3) to 34.5 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the upper limit value of the conditional expression (3-3) to 34.0, 33.5, or furthermore, 32.9. On the other hand, setting the lower limit value of the conditional expression (3-3) to 28.0 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the lower limit value of the conditional expression (3-3) to 29.0, 30.0, or furthermore, 31.0. 
     In the optical system of this embodiment, the specified lens may satisfy the following conditional expression (5-4). 
       1.550 &lt;ndLZ &lt;1.700  (5-4)
 
     The conditional expression (5-4) is an expression similar to the conditional expression (5). By satisfying the conditional expression (5-4), the various aberrations, such as the coma aberration and the chromatic aberrations (the longitudinal chromatic aberration and the chromatic aberration of magnification), can be favorably corrected. Setting the upper limit value of the conditional expression (5-4) to 1.675 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the upper limit value of the conditional expression (5-4) to 1.660, 1.645, 1.630, or furthermore, 1.615. On the other hand, setting the lower limit value of the conditional expression (5-4) to 1.560 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the lower limit value of the conditional expression (5-4) to 1.570, 1.580, 1.590, or furthermore, 1.600. 
     In the optical system of this embodiment, the specified lens may satisfy the following conditional expression (3-4). 
       25.0 &lt;νdLZ &lt;31.0  (3-4)
 
     The conditional expression (3-4) is an expression similar to the conditional expression (3). By satisfying the conditional expression (3-4), correction of reference aberrations, such as the spherical aberration and coma aberration, and correction of primary chromatic aberration (achromatization) can be favorably performed. Setting the upper limit value of the conditional expression (3-4) to 30.9 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the upper limit value of the conditional expression (3-4) to 30.8. On the other hand, setting the lower limit value of the conditional expression (3-4) to 25.6 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the lower limit value of the conditional expression (3-4) to 26.0, 26.4, or furthermore, 26.8. 
     In the optical system of this embodiment, the specified lens may satisfy the following conditional expression (5-5). 
       1.550 &lt;ndLZ &lt;1.800  (5-5)
 
     The conditional expression (5-5) is an expression similar to the conditional expression (5). By satisfying the conditional expression (5-5), the various aberrations, such as the coma aberration and the chromatic aberrations (the longitudinal chromatic aberration and the chromatic aberration of magnification), can be favorably corrected. Setting the upper limit value of the conditional expression (5-5) to 1.770 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the upper limit value of the conditional expression (5-5) to 1.745, 1.720, or furthermore, 1.695. On the other hand, setting the lower limit value of the conditional expression (5-5) to 1.565 can securely achieve the advantageous effects of this embodiment. To achieve the advantageous effects of this embodiment further securely, it is preferable to set the lower limit value of the conditional expression (5-5) to 1.590, 1.605, or furthermore, 1.622. 
     It is desired that the optical system of this embodiment further comprise an object-side lens disposed nearest to an object, wherein the specified lens be disposed nearer to an image than the object-side lens. Accordingly, the various aberrations, such as the coma aberration and the chromatic aberrations (the longitudinal chromatic aberration and the chromatic aberration of magnification), can be favorably corrected. 
     It is desired that the optical system of this embodiment further comprise an image-side lens disposed nearest to an image, wherein the specified lens be disposed nearer to an object than the image-side lens. Accordingly, the various aberrations, such as the coma aberration and the chromatic aberrations (the longitudinal chromatic aberration and the chromatic aberration of magnification), can be favorably corrected. 
     In the optical system of this embodiment, it is desired that the specified lens be a glass lens. Accordingly, in comparison with a case where the material is a resin, the lens that is resistant to temporal change and is resistant to environmental change, such as change in temperature, can be obtained. 
     Subsequently, referring to  FIG. 16 , a method of manufacturing the aforementioned optical system LS is generally described. First, at least one lens is disposed (step ST 1 ). At this time, the lenses are arranged within a lens barrel such that at least one (specified lens) of the lenses can satisfy the conditional expressions (1) to (2) and the like (step ST 2 ). According to such a manufacturing method, as for correction of the chromatic aberrations, an optical system can be manufactured where in addition to the primary achromatization, the secondary spectrum is favorably corrected. 
     EXAMPLES 
     Hereinafter, the optical system LS according to examples of this embodiment are described with reference to the drawings.  FIGS. 1, 3, 5, 7, 9, 11 and 13  are sectional views showing the configurations and refractive power distributions of optical system LS (LS( 1 ) to LS( 7 )) according to first to seventh examples. For the optical system LS( 1 ) according to the first example, the optical system LS( 3 ) according to the third example, and the optical systems LS( 6 ) to LS( 7 ) according to the sixth to seventh examples, the movement direction during focusing of a focusing lens group from infinity to a short-distance object is indicated by an arrow accompanied by characters “FOCUSING”. In the sectional views of the optical system LS( 2 ) according to the second example and the optical systems LS( 4 ) to LS( 5 ) according to fourth to fifth examples, the movement direction of each lens group along the optical axis during zooming from the wide angle and state (W) to the telephoto end state (T) is indicated by an arrow. 
     In these  FIGS. 1, 3, 5, 7, 9, 11 and 13 , each lens group is represented by a combination of a symbol G and a numeral, and each lens is represented by a combination of a symbol L and a numeral. In this case, to prevent complication due to increase in the number of types of symbols and numerals, combinations of symbols and numerals are used independently among the individual examples to represent the lens groups and the like. Accordingly, even though the same combinations between symbols and numerals are used among the examples, such usage does not mean the same configuration. 
     Tables 1 to 7 are hereinafter shown. Among the tables, Table 1 is a table indicating data on the first example, Table 2 is that on the second example, Table 3 is that on the third example, Table 4 is that on the fourth example, Table 5 is that on the fifth example, Table 6 is that on the sixth example, and Table 7 is that on the seventh example. In each example, d-line (wavelength λ=587.6 nm), g-line (wavelength λ=435.8 nm), C-line (wavelength λ=656.3 nm) and T-line (wavelength λ=486.1 nm) are selected as aberration characteristics to be calculated. 
     In [General Data] table, f indicates the focal length of the entire zoom lens, FNO indicates the F-number, 2ω indicates the angle of view (the unit is ° (degrees), and ω indicates the half angle of view), and Y indicates the image height. TL indicates the distance obtained by adding BF to the distance from the lens forefront surface to the lens last surface on the optical axis upon focusing on infinity. BF indicates the distance (backfocus) from the lens last surface to an image surface I on the optical axis upon focusing on infinity. Note that in a case where the optical system is a zoom optical system, these values indicate data in each of zooming states at the wide-angle end (R), intermediate focal length (K) and telephoto end (T). 
     In [Lens Data] table, Surface Number indicates the order of optical surfaces from the object side along the ray traveling direction, R indicates the radius of curvature of each optical surface (a surface whose center of curvature is positioned on the image side is assumed to have a positive value), D indicates the surface distance that is the distance from each optical surface to the next optical surface (or the image surface), nd indicates the refractive index of the material of the optical member with reference to d-line, νd indicates the Abbe number of the material of the optical member with reference to d-line, and θgF indicates the partial dispersion ratio of the material of the optical member. The “∞” of the radius of curvature indicates a flat surface or an aperture, and (Aperture Stop S) indicates the aperture stop S. The description of the refractive index of air nd=1.00000 is emitted. In a case where the optical surface is an aspherical surface, the surface number is assigned *a symbol. In a case where the optical surface is a diffractive optical surface, the surface number is assigned *b symbol. The field of the radius of curvature R indicates the paraxial radius of curvature. 
     The refractive index of the material of the optical member with reference to g-line (wavelength λ=435.8 nm) is assumed as ng. The refractive index of the material of the optical member with reference to F-line (wavelength λ=486.1 nm) is assumed as r. The refractive index of the material of the optical member with reference to C-line (wavelength I=656.3 n a) is assumed as nC. At this time, the partial dispersion ratio θgF of the material of the optical member is defined by the following expression (A). 
       θ gF =( ng−nF )/( nF−nC )  (A)
 
     [Aspherical Surface Data] table indicates the shape of an aspherical surface indicated in [Lens Data] by the following expression (B). X(y) indicates the distance (sag amount) along the optical axis direction from the tangent plane on the vertex of an aspherical surface to the position on the aspherical surface at the height y. R indicates the radius of curvature of the reference spherical surface (paraxial radius of curvature). κ indicates the conical coefficient. Ai indicates the i-th order aspherical coefficient. “E-n” indicates “×10 ˜n ”. For example, 1.234E-05=1.234×10 −5 . Note that the second order aspherical coefficient A2 is 0. The description thereof is omitted. 
         X ( y )=( y   2   /R )/{1+(1−κ× y   2   /R   2 ) 1/2   }+A 4× y   4   +A 6× y   6   +A 8× y   8   +A 10× y   10   (B)
 
     In a case where the optical system includes a diffractive optical element, the phase shape Ψ of the diffractive optical surface indicated in [Diffractive Optical Surface Data] is represented by the following expression (C). 
       Ψ( h,m )={2π/( m×λ 0)}×( C 2× h   2   +C 4× h   4   +C 6× h   6  . . . )  (C)
 
     Where 
     h: the height in the direction perpendicular to the optical axis, 
     m: the diffractive order of diffracted light, 
     λ0: design wavelength, and 
     Ci: phase coefficient (i=2, 4, . . . ). 
     Note that the refractive power ϕD of the diffractive surface for any wavelength λ and at any diffractive order a can be represented as the following expression (D) using the lowest order phase coefficient C2. 
       ϕ D ( h,m )=−2× C 2× m×λ/λ 0  (D)
 
     In [Diffractive Optical Surface Data] table, for the diffractive optical surface indicated in [Lens Data], the design wavelength λ0, the diffractive order m, the second order phase coefficient C2, and the fourth order phase coefficient C4 in the expression (C) are indicated. Similar to [Aspherical Surface Data] table, “E-n” indicates “×10 ˜n ”. 
     In a case where the optical system is not a zoom optical system, f is the focal length of the entire zoom lens and β indicates the photographing magnification as [Variable Distance Data on Short-Distance Photographing]. [Variable Distance Data on Short-Distance Photographing] table indicates the surface distance at the surface number where the surface distance corresponds to each focal length and photographing magnification and the surface distance in [Lens Data] is “Variable”. 
     In a case where the optical system is a zoom optical system, the surface distance at the surface number where the surface distance corresponds to each of zooming states including the wide-angle end (W), intermediate focal length (M) and telephoto and (T) and the surface distance is “Variable” in [Lens Data] is indicated as [Variable Distance Data on Zoom Photographing]. [Lens Group Data] table indicates the first surface (surface nearest to the object) and the focal length of each lens group. 
     [Conditional Expression Corresponding Value] table indicates the value corresponding to each conditional expression. 
     Hereinafter, in all data values, for the listed focal length f, radius of curvature R, surface distance D, other lengths and the like, “mm” is generally used if not otherwise specified. However, no limitation is imposed thereon because the optical system can achieve an equivalent optical performance even with proportional scaling (enlargement or contraction). 
     The entire description of tables so far commonly applies to all the examples. Redundant description is hereinafter omitted. 
     First Example 
     A first example is described with reference to  FIGS. 1 and 2  and Table 1.  FIG. 1  shows a lens configuration of an optical system according to the first example of this embodiment upon focusing on infinity. The optical system LS( 1 ) according to the first example consists of, arranged sequentially from an object side: a first lens group G 1  having a positive refractive power; a second lens group G 2  having a negative refractive power; and a third lens group G 3  having a positive refractive power. Upon focusing from an infinite distant object to a short-distance (finite distant) object, the second lens group G 2  moves toward the image along the optical axis. The aperture stop S is disposed on an object-side neighborhood of the third lens group G 3 . Similar to the first lens group G 1  and the third lens group G 3 , the aperture stop S is fixed with respect to the image surface I upon focusing. The symbol (+) or (−) assigned to each lens group symbol indicates the refractive power of the corresponding lens group. This also applies to all the examples. 
     The first lens group G 1  consists of, arranged sequentially from an object side: a protective glass HG having a significantly low refractive power; a biconvex positive lens L11; a biconvex positive lens L12; a biconcave negative lens L13; and a cemented lens that consists of a negative meniscus lens L14 having a convex surface facing the object, and a positive meniscus lens L15 having a convex surface facing the object. In this example, the positive lens L11 of the first lens group G 1  corresponds to the object-side lens. 
     The second lens group G 2  consists of, arranged sequentially from the object side: a biconcave negative lens L21; and a cemented lens that consists of a positive meniscus lens L22 having a concave surface facing the object, and a biconcave negative lens L23. In this example, the positive meniscus lens L22 of the second lens group G 2  corresponds to the lens (specified lens) satisfying the conditional expressions (1) to (2) and the like. 
     The third lens group G 3  includes, arranged sequentially from an object side: a first partial group G 31  having a positive refractive power; a second partial group G 32  having a negative refractive power; and a third partial group G 33  having a positive refractive power. The first partial group G 31  consists of a cemented lens consisting of a biconvex positive lens L31 and a negative meniscus lens L32 having a concave surface facing the object, the lenses being arranged sequentially from the object side. The second partial group G 32  consists of, arranged sequentially from an object side: a cemented lens consisting of a biconvex positive lens L33 and a biconcave negative lens L34; and a biconcave negative lens L35. The third partial group G 33  consists of, arranged sequentially from an object side: a biconvex positive lens L36; and a cemented lens consisting of a biconvex positive lens L37 and a biconcave negative lens L38. In this example, the negative lens L38 of the third lens group G 3  corresponds to the image-side lens. The positive lens L33 of the third lens group G 3  corresponds to the lens satisfying the conditional expressions (1) to (2) and the like. The second partial group G 33  of the third lens group G 3  constitutes a vibration-proof lens group that is movable in a direction perpendicular to the optical axis, and corrects displacement in imaging position due to a camera shake or the like (an image blur on the image surface I). Note that a fixed aperture stop (flare cut diaphragm) Sa is disposed between the second partial group G 32  and the third partial group G 33  of the third lens group G 3 . 
     An image surface I is disposed on the image side of the third lens group G 3 . An insertable and replaceable optical filter FL is disposed between the third lens group G 3  and the image surface I. For example, an NC filter (neutral color filter), a color filter, a polarizing filter, an ND filter (neutral density filter), an IR filter (infrared-cut filter) or the like is adopted as the insertable and replaceable optical filter FL. 
     The following Table 1 lists the values of data on the optical system according to the first example. 
     
       
         
           
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 [General Data] 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 f 
                 392.000 
               
               
                   
                 FNO 
                 2.881 
               
               
                   
                 2ω 
                 6.245 
               
               
                   
                 Y 
                 21.63 
               
               
                   
                 TL 
                 396.319 
               
               
                   
                 BF 
                 74.502 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens Data] 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                   
                   
                   
                   
                   
               
               
                 Number 
                 R 
                 D 
                 nd 
                 νd 
                 θgF 
               
               
                   
               
               
                 1 
                 1200.37020 
                 5.000 
                 1.51680 
                 63.88 
                 0.536 
               
               
                 2 
                 1199.78950 
                 1.000 
               
               
                 3 
                 250.71590 
                 16.414  
                 1.43385 
                 95.25 
                 0.540 
               
               
                 4 
                 −66.97150 
                 45.000  
               
               
                 5 
                 158.99440 
                 18.720  
                 1.43385 
                 95.25 
                 0.540 
               
               
                 6 
                 −400.00000 
                 2.261 
               
               
                 7 
                 −377.29180 
                 6.000 
                 1.61266 
                 44.46 
                 0.564 
               
               
                 8 
                 461.79700 
                 95.451  
               
               
                 9 
                 70.05760 
                 4.000 
                 1.79500 
                 45.31 
                 0.560 
               
               
                 10 
                 47.57190 
                 11.944  
                 1.49782 
                 82.57 
                 0.539 
               
               
                 11 
                 1223.84820 
                 D11(Variable) 
               
               
                 12 
                 −546.41280 
                 2.500 
                 1.80610 
                 40.97 
                 0.569 
               
               
                 13 
                 76.73180 
                 6.996 
               
               
                 14 
                 −241.81680 
                 4.500 
                 1.65940 
                 26.87 
                 0.633 
               
               
                 15 
                 −56.62280 
                 2.500 
                 1.48749 
                 70.32 
                 0.529 
               
               
                 16 
                 234.80990 
                 D16(Variable) 
               
               
                 17 
                 ∞ 
                 5.100 
                   
                   
                 (Aperture Stop S) 
               
               
                 18 
                 95.57020 
                 6.000 
                 1.75500 
                 52.33 
                 0.548 
               
               
                 19 
                 −5.36620 
                 1.800 
                 1.80809 
                 22.74 
                 0.629 
               
               
                 20 
                 −757.80810 
                 4.500 
               
               
                 21 
                 279.80870 
                 4.700 
                 1.74971 
                 24.66 
                 0.627 
               
               
                 22 
                 −82.76070 
                 1.800 
                 1.59319 
                 67.90 
                 0.544 
               
               
                 23 
                 50.04470 
                 3.390 
               
               
                 24 
                 −226.07440 
                 1.800 
                 1.83481 
                 42.73 
                 0.565 
               
               
                 25 
                 105.63280 
                 4.250 
               
               
                 26 
                 ∞ 
                 0.250 
               
               
                 27 
                 105.07290 
                 3.700 
                 1.69680 
                 55.52 
                 0.543 
               
               
                 28 
                 −158.46840 
                 0.100 
               
               
                 29 
                 92.25180 
                 4.000 
                 1.72047 
                 34.71 
                 0.583 
               
               
                 30 
                 −129.17240 
                 1.800 
                 1.92119 
                 23.96 
                 0.620 
               
               
                 31 
                 404.52160 
                 7.500 
               
               
                 32 
                 ∞ 
                 1.500 
                 1.51680 
                 63.88 
                 0.536 
               
               
                 33 
                 ∞ 
                 BF 
               
               
                   
               
            
           
           
               
            
               
                 [Variable distance data on short-diatance photographing] 
               
            
           
           
               
               
               
               
            
               
                   
                   
                   
                 Upon focusing 
               
               
                   
                   
                 Upon focusing 
                 on a short-distance 
               
               
                   
                   
                 on infinity 
                 object 
               
               
                   
                   
                 f = 92.000 
                 β = −0.173 
               
               
                   
                   
               
               
                   
                 D11 
                 13.847 
                 29.047 
               
               
                   
                 D16 
                 33.495 
                 18.295 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Conditional Expression Corresponding Value] 
               
               
                 &lt;positive meniscus lens L22&gt; 
               
               
                   
               
            
           
           
               
               
            
               
                   
                 Conditional Expression(1) 
               
               
                   
                 ndLZ + (0.01425 × νdLZ) = 2.042 
               
               
                   
                 Conditional Expression(2), (2-1) 
               
               
                   
                 θgFLZ + (0.00316 × νdLZ) = 0.7179 
               
               
                   
                 Conditional Expression(3), (3-1), (3-2), (3-3), (3-4) 
               
               
                   
                 νdLZ = 26.87 
               
               
                   
                 Conditional Expression(4) 
               
               
                   
                 ndLZ + (0.00787 × νdLZ) = 1.871 
               
               
                   
                 Conditional Expression(5), (5-1), (5-2), (5-3), (5-4), (5-5) 
               
               
                   
                 ndLZ = 1.65940 
               
               
                   
                 Conditional Expression(6) 
               
               
                   
                 DLZ = 4.500 
               
               
                   
                 Conditional Expression(7) 
               
               
                   
                 ndLZ − (0.040 × νdLZ − 2.470) × νdLZ = 35.830 
               
               
                   
                 Conditional Expression(8) 
               
               
                   
                 ndLZ − (0.020 × νdLZ − 1.080) × νdLZ = 12.920 
               
               
                   
                   
               
            
           
           
               
            
               
                 &lt;positive lens L33&gt; 
               
               
                   
               
            
           
           
               
               
            
               
                   
                 Conditional Expression(1) 
               
               
                   
                 ndLZ + (0.01425 × νdLZ) = 2.101 
               
               
                   
                 Conditional Expression(2), (2-1) 
               
               
                   
                 θgFLZ + (0.00316 × νdLZ) = 0.7049 
               
               
                   
                 Conditional Expression(3), (3-1), (3-2), (3-3), (3-4) 
               
               
                   
                 νdLZ = 24.66 
               
               
                   
                 Conditional Expression(4) 
               
               
                   
                 ndLZ + (0.00787 × νdLZ) = 1.944 
               
               
                   
                 Conditional Expression(5), (5-1), (5-2), (5-3), (5-4), (5-5) 
               
               
                   
                 ndLZ = 1.74971 
               
               
                   
                 Conditional Expression(6) 
               
               
                   
                 DLZ = 4.700 
               
               
                   
                 Conditional Expression(7) 
               
               
                   
                 ndLZ − (0.040 × νdLZ − 2.470) × νdLZ = 34.836 
               
               
                   
                 Conditional Expression(8) 
               
               
                   
                 ndLZ − (0.020 × νdLZ − 1.080) × νdLZ = 12.721 
               
               
                   
                   
               
            
           
         
       
     
       FIG. 2  shows various aberration graphs of the optical system according to the first example upon focusing on infinity. In each aberration graph, MN indicates the r-number, and Y indicates the image height. Note that the spherical aberration graph indicates the value of the F-number or the numerical aperture corresponding to the maximum diameter. The astigmatism graph and the distortion graph each indicate the maximum value of the image height. The coma aberration graph indicates the value of each image height. d indicates d-line (wavelength λ=587.6 nm), g indicates g-line (wavelength λ=435.8 nm), C indicates C-line (wavelength λ=656.3 nm) and F indicates F-line (wavelength λ=486.1 nm). In the astigmatism graph, the solid line indicates a sagittal image surface, and the broken line indicates a meridional image surface. Note that also in aberration graphs of the following examples, symbols similar to those in this example are used, and redundant description is emitted. 
     Based on each of various aberration graphs, in the optical system according to the first example, the various aberrations are favorably corrected, and excellent image forming performances are achieved. 
     Second Example 
     A second example is described with reference to  FIGS. 3 and 4A to 4C  and Table 2.  FIG. 3  shows a lens configuration of an optical system according to the second example of this embodiment upon focusing on infinity. The optical system LS( 2 ) according to the second example consists of, arranged sequentially from an object side: a first lens group G 1  having a positive refractive power; a second lens group G 2  having a negative refractive power; a third lens group G 3  having a positive refractive power; a fourth lens group G 4  having a positive refractive power; a fifth lens group G 5  having a negative refractive power; and a sixth lens group G 6  having a negative refractive power. During zooming from the wide angle end state (W) to the telephoto and state (T), the first to fifth lens groups G 1  to G 5  respectively move in directions indicated by arrows in  FIG. 3 . The aperture stop S is disposed in the second lens group G 2 . 
     The first lens group G 1  consists of, arranged sequentially from an object side: a cemented lens consisting of a negative meniscus lens L11 having a convex surface facing the object, and a biconvex positive lens L12; and a positive meniscus lens L13 having a convex surface facing the object. In this example, the negative meniscus lens L11 of the first lens group G 1  corresponds to the object-side lens. A diffractive optical element DO is disposed on the image-side lens surface of the positive meniscus lens L13. The diffractive optical element DOE is, for example, a close-contact multi-layer type diffractive optical element where two types of diffractive optical element items different in material from each other are in contact on the same diffractive optical groove. A primary diffraction grating (a diffraction grating having a rotationally symmetric shape with respect to the optical axis) having a predetermined grating height is formed by two types of ultraviolet-curing resins. 
     The second lens group G 2  consists of, arranged sequentially from an object side: a cemented lens consisting of a biconcave negative lens L21, and a positive meniscus lens L22 having a convex surface facing the object; a positive meniscus lens L23 having a concave surface facing the object; and a positive meniscus lens L24 having a convex surface facing the object. An aperture stop S is disposed between the positive meniscus lens L23 and the positive meniscus lens L24 of the second lens group G 2 . In this example, the positive meniscus lens L22 of the second lens group G 2  corresponds to the lens satisfying the conditional expressions (1) to (2) and the like. The cemented lens consisting of the negative lens L21 and the positive meniscus lens L22 of the second lens group G 2 , and the positive meniscus lens L23 constitute a vibration-proof lens group (partial group) movable in a direction perpendicular to the optical axis, and corrects displacement in the imaging position due to a camera shake and the like (an image blur on the image surface I). 
     The third lens group G 3  consists of, arranged sequentially from an object side: a negative meniscus lens L31 having a convex surface facing the object; and a biconvex positive lens L32. 
     The fourth lens group G 4  consists of a cemented lens consisting of a biconvex positive lens L41 and a negative meniscus lens L42 having a concave surface facing the object, the lenses being arranged sequentially from the object side. 
     The fifth lens group G 5  consists of a cemented lens consisting of a biconvex positive lens L51 and a biconcave negative lens L52, the lenses being arranged sequentially from an object side. In this example, focusing is achieved by moving the entire fifth lens group G 5  along the optical axis. 
     The sixth lens group G 6  consists of, arranged sequentially from the object side: a cemented lens consisting of a negative meniscus lens L61 having a convex surface facing the object, and a biconvex positive lens L62; a biconcave negative lens L63; and a negative meniscus lens L64 having a concave surface facing the object. An image surface I is disposed on the image side of the sixth lens group G 6 . In this example, the negative meniscus lens L64 of the sixth lens group G corresponds to the image-side lens. The negative meniscus lens L61 of the sixth lens group G 6  corresponds to the lens satisfying the conditional expressions (1) to (2) and the like. 
     The following Table 2 lists the values of data on the optical system according to the second example. 
     
       
         
           
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 [General Data] 
               
               
                 Zooming ratio 2.00 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 W 
                 M 
                 T 
               
               
                   
                   
               
               
                   
                 f 
                 199.985 
                 300.128 
                 400.487 
               
               
                   
                 FNO 
                 5.770 
                 5.773 
                 7.777 
               
               
                   
                 2ω 
                 12.088 
                 8.032 
                 3.016 
               
               
                   
                 Y 
                 21.60 
                 21.60 
                 21.60 
               
               
                   
                 TL 
                 218.509 
                 276.018 
                 309.437 
               
               
                   
                 BF 
                 63.575 
                 63.605 
                 63.797 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens Data] 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                   
                   
                   
                   
                   
               
               
                 Number 
                 R 
                 D 
                 nd 
                 νd 
                 θgF 
               
               
                   
               
               
                  1 
                 338.9295 
                 3.0000 
                 1.806100 
                 33.34 
                 0.5904 
               
               
                  2 
                 157.1292 
                 7.1098 
                 1.487490 
                 70.32 
               
               
                  3 
                 −645.1901 
                 0.1000 
               
               
                  4 
                 127.7241 
                 6.3846 
                 1.516800 
                 64.13 
               
               
                   5*b 
                 1000.0000 
                  D5(Variable) 
               
               
                  6 
                 −122.6329 
                 1.7000 
                 1.743997 
                 44.79 
               
               
                  7 
                 65.7202 
                 3.5689 
                 1.659398 
                 26.87 
                 0.6323 
               
               
                  8 
                 249.7691 
                 15.0000  
               
               
                  9 
                 −47.9778 
                 3.5000 
                 1.756462 
                 24.89 
                 0.6196 
               
               
                 10 
                 −45.0509 
                 2.2932 
               
               
                 11 
                 ∞ 
                 0.5000 
                   
                   
                 (Aperture Stop S) 
               
               
                 12 
                 43.2479 
                 2.9936 
                 1.620041 
                 36.26 
               
               
                 13 
                 64.4050 
                 D13(Variable) 
               
               
                 14 
                 82.9323 
                 1.7000 
                 1.808099 
                 22.74 
               
               
                 15 
                 46.2622 
                 3.6463 
               
               
                 16 
                 71.4836 
                 4.1939 
                 1.612720 
                 58.54 
               
               
                 17 
                 −405.4059 
                 D17(Variable) 
               
               
                 18 
                 56.3851 
                 6.9255 
                 1.497820 
                 82.57 
               
               
                 19 
                 −60.8758 
                 1.7000 
                 1.755000 
                 52.33 
               
               
                 20 
                 −374.3030 
                 D20(Variable) 
               
               
                 21 
                 102.7274 
                 2.4918 
                 1.592701 
                 35.31 
               
               
                 22 
                 −125.8788 
                 1.0000 
                 1.755000 
                 52.33 
               
               
                 23 
                 40.8982 
                 D23(Variable) 
               
               
                 24 
                 121.6273 
                 1.7000 
                 1.659398 
                 26.87 
                 0.6323 
               
               
                 25 
                 52.1810 
                 5.7438 
                 1.595510 
                 39.21 
               
               
                 26 
                 −42.4345 
                 0.000 
               
               
                 27 
                 −97.3797 
                 1.5000 
                 1.456000 
                 91.37 
               
               
                 28 
                 59.1706 
                 12.2493  
               
               
                 29 
                 −26.6286 
                 1.5000 
                 1.755000 
                 52.33 
                 0.5476 
               
               
                 30 
                 −37.6940 
                 BF 
               
               
                   
               
            
           
           
               
            
               
                 [Diffractive optical surface data] 
               
               
                   
               
            
           
           
               
               
            
               
                   
                 5th Surface 
               
               
                   
                 λ0 = 587.6 
               
               
                   
                 m = 1 
               
               
                   
                 C2 = −2.57E−05 
               
               
                   
                 C4 = −2.04E−11 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Variable distance data on zoom photographing] 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 W 
                 M 
                 T 
               
               
                   
                   
               
               
                   
                 D5 
                 11.860 
                 93.192 
                 119.742 
               
               
                   
                 D13 
                 10.900 
                 0.500 
                 3.244 
               
               
                   
                 D17 
                 0.600 
                 5.172 
                 0.600 
               
               
                   
                 D20 
                 34.41.1 
                 13.877 
                 0.200 
               
               
                   
                 D23 
                 6.561 
                 9.070 
                 31.254 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens Group Data] 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 First 
                 Focal 
               
               
                   
                 Group 
                 surface 
                 length 
               
               
                   
                   
               
               
                   
                 G1 
                 1 
                 213.671 
               
               
                   
                 G2 
                 6 
                 −546.584 
               
               
                   
                 G3 
                 14 
                 370.319 
               
               
                   
                 G4 
                 18 
                 149.206 
               
               
                   
                 G5 
                 21 
                 −72.703 
               
               
                   
                 G6 
                 24 
                 −875.523 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Conditional Expression Corresponding Value] 
               
               
                 &lt;positive meniscus lens L22&gt; 
               
               
                   
               
            
           
           
               
               
            
               
                   
                 Conditional Expression(1) 
               
               
                   
                 ndLZ + (0.01425 × νdLZ) = 2.042 
               
               
                   
                 Conditional Expression(2), (2-1) 
               
               
                   
                 θgFLZ + (0.00316 × νdLZ) = 0.7172 
               
               
                   
                 Conditional Expression(3), (3-1), (3-2), (3-3), (3-4) 
               
               
                   
                 νdLZ = 26.87 
               
               
                   
                 Conditional Expression(4) 
               
               
                   
                 ndLZ + (0.00787 × νdLZ) = 1.871 
               
               
                   
                 Conditional Expression(5), (5-1), (5-2), (5-3), (5-4), (5-5) 
               
               
                   
                 ndLZ = 1.659398 
               
               
                   
                 Conditional Expression(6) 
               
               
                   
                 DLZ = 3.5689 
               
               
                   
                 Conditional Expression(7) 
               
               
                   
                 ndLZ − (0.040 × νdLZ − 2.470) × νdLZ = 35.830 
               
               
                   
                 Conditional Expression(8) 
               
               
                   
                 ndLZ − (0.020 × νdLZ − 1.080) × νdLZ = 12.920 
               
               
                   
                   
               
            
           
           
               
            
               
                 &lt;negative meniscus lens L61&gt; 
               
               
                   
               
            
           
           
               
               
            
               
                   
                 Conditional Expression(1) 
               
               
                   
                 ndLZ + (0.01425 × νdLZ) = 2.042 
               
               
                   
                 Conditional Expression(2), (2-1) 
               
               
                   
                 θgFLZ + (0.00316 × νdLZ) = 0.7172 
               
               
                   
                 Conditional Expression(3), (3-1), (3-2), (3-3), (3-4) 
               
               
                   
                 νdLZ = 26.87 
               
               
                   
                 Conditional Expression(4) 
               
               
                   
                 ndLZ + (0.00787 × νdLZ) = 1.871 
               
               
                   
                 Conditional Expression(5), (5-1), (5-2), (5-3), (5-4), (5-5) 
               
               
                   
                 ndLZ = 1.659398 
               
               
                   
                 Conditional Expression(6) 
               
               
                   
                 DLZ = 1.7000 
               
               
                   
                 Conditional Expression(7) 
               
               
                   
                 ndLZ − (0.040 × νdLZ − 2.470) × νdLZ = 35.830 
               
               
                   
                 Conditional Expression(8) 
               
               
                   
                 ndLZ − (0.020 × νdLZ − 1.080) × νdLZ = 12.920 
               
               
                   
                   
               
            
           
         
       
     
       FIGS. 4A, 48 and 4C  show various aberration graphs of the optical system according to the second example upon focusing on infinity in a wide angle end state, an intermediate focal length state, and a telephoto end state, respectively. Based on each of various aberration graphs, in the optical system according to the second example, the various aberrations are favorably corrected, and excellent image forming performances are achieved. 
     Third Example 
     A third example is described with reference to  FIGS. 5 and 6  and Table 3.  FIG. 5  shows a lens configuration of an optical system according to the third example of this embodiment upon focusing on infinity. The optical system LS( 3 ) according to the third example consists of, arranged sequentially from an object side: a first lens group G 1  having a negative refractive power; and a second lens group G 2  having a positive refractive power. Upon focusing from an infinite distant object to a short-distance (finite distant) object, the second lens group G 2  moves toward the object along the optical axis. The aperture stop S is disposed in the second lens group G 2 . 
     The first lens group G 1  consists of, arranged sequentially from an object side: a negative meniscus lens L11 having a convex surface facing the object; a biconvex positive lens L12; a biconcave negative lens L13; and a cemented lens consisting of a biconvex positive lens L14 and a biconcave negative lens L15. In this example, the negative meniscus lens Li of the first lens group G corresponds to the object-side lens. The negative lens L15 of the first lens group G 1  corresponds to the lens satisfying the conditional expressions (1) to (2) and the like. The image-side lens surface of the negative lens L13 is an aspherical surface. 
     The second lens group G 2  consists of, arranged sequentially from an object side: a biconvex positive lens L21; a cemented lens consisting of a positive meniscus lens L22 having a convex surface facing the object, and a negative meniscus lens L23 having a convex surface facing the object; a cemented lens consisting of a biconcave negative lens L24 and a biconvex positive lens L25; a plano-convex positive lens L26 having a convex surface facing the image; and a positive meniscus lens L27 having a concave surface facing the object. An image surface I is disposed on the image side of the second lens group G 2 . An aperture stop S is disposed between the positive lens L21 and the positive meniscus lens L22 of the second lens group G 2 . In this example, the positive meniscus lens  27  of the second lens group G 2  corresponds to the image-side lens. The positive meniscus lens L22 of the second lens group G 2  corresponds to the lens satisfying the conditional expressions (1) to (2) and the like. The image-side lens surface of the positive lens L26 is an aspherical surface. 
     The following Table 3 lists the values of data on the optical system according to the third example. 
     
       
         
           
               
             
               
                 TABLE 3 
               
               
                   
               
               
                 [General Data] 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 f 
                 28.773 
               
               
                   
                 FNO 
                 1.8796 
               
               
                   
                 2ω 
                 75.3311 
               
               
                   
                 Y 
                 21.60 
               
               
                   
                 TL 
                 131.9655 
               
               
                   
                 BF 
                 36.457 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens Data] 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                   
                   
                   
                   
                   
               
               
                 Number 
                 R 
                 D 
                 nd 
                 νd 
                 θgF 
               
               
                   
               
               
                  1 
                 57.6700 
                 1.7000 
                 1.713000 
                 53.94 
                 0.5441 
               
               
                  2 
                 23.6385 
                 10.630  
               
               
                  3 
                 360.0000 
                 3.4200 
                 1.846660 
                 23.78 
               
               
                  4 
                 −149.5844 
                 2.1000 
               
               
                  5 
                 −91.6110 
                 1.7000 
                 1.487490 
                 70.31 
               
               
                  6 
                 34.8169 
                 0.1000 
                 1.520500 
                 51.02 
               
               
                   7*a 
                 31.0734 
                 7.4700 
               
               
                  8 
                 54.5000 
                 8.5700 
                 1.834000 
                 37.18 
               
               
                  9 
                 −43.5000 
                 1.7000 
                 1.749714 
                 24.66 
                 0.6272 
               
               
                 10 
                 475.5646 
                 D10(Variable) 
               
               
                 11 
                 41.6500 
                 6.2000 
                 1.589130 
                 61.24 
               
               
                 12 
                 −79.7342 
                 8.8800 
               
               
                 13 
                 ∞ 
                 1.0000 
                   
                   
                 (Aperture Stop S) 
               
               
                 14 
                 71.7000 
                 1.3000 
                 1.659398 
                 26.87 
                 0.6323 
               
               
                 15 
                 165.1470 
                 1.0000 
                 1.672700 
                 32.19 
               
               
                 16 
                 41.0000 
                 6.0900 
               
               
                 17 
                 −19.3844 
                 1.5200 
                 1.805180 
                 25.46 
               
               
                 18 
                 400.0000 
                 2.4200 
                 1.772500 
                 49.65 
               
               
                 19 
                 −67.0000 
                 0.6000 
               
               
                 20 
                 ∞ 
                 3.0800 
                 1.729160 
                 54.66 
               
               
                 21 
                 −50.8920 
                 0.2000 
                 1.520500 
                 51.02 
               
               
                  22*a 
                 −37.6986 
                 1.1400 
               
               
                 23 
                 −98.0000 
                 5.2100 
                 1.834810 
                 42.72 
                 0.5651 
               
               
                 24 
                 −26.8452 
                 2.3629 
               
               
                 25 
                 ∞ 
                 BF 
               
               
                   
               
            
           
           
               
            
               
                 [Aspherical Surface Data] 
               
               
                   
               
            
           
           
               
               
            
               
                   
                 7th Surface 
               
               
                   
                 κ = 0.0000 
               
               
                   
                 A4 = −2.99E−06, A6 = −2.39E−08, A8 = 1.13E−10, A10 = −3.69E−13 
               
               
                   
                 22nd Surface 
               
               
                   
                 κ = 0.0000 
               
               
                   
                 A4 = 2.03E−05, A6 = 4.37E−09, A8 = 1.85E−10, A10 = −1.33E−12 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Variable distance data on short-distance photographing] 
               
            
           
           
               
               
               
               
            
               
                   
                   
                   
                 Upon focusing 
               
               
                   
                   
                 Upon focusing 
                 on a short-distance 
               
               
                   
                   
                 on infinity 
                 object 
               
               
                   
                   
                 f = 28.7734 
                 β = −0.2174 
               
               
                   
                   
               
               
                   
                 D10 
                 9.5660 
                 2.3031 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Conditional Expression Corresponding Value] 
               
               
                 &lt;negative lens L15&gt; 
               
               
                   
               
            
           
           
               
               
            
               
                   
                 Conditional Expression(1) 
               
               
                   
                 ndLZ + (0.01425 × νdLZ) = 2.101 
               
               
                   
                 Conditional Expression(2), (2-1) 
               
               
                   
                 θgFLZ + (0.00316 × νdLZ) = 0.7051 
               
               
                   
                 Conditional Expression(3), (3-1), (3-2), (3-3), (3-4) 
               
               
                   
                 νdLZ = 24.66 
               
               
                   
                 Conditional Expression(4) 
               
               
                   
                 ndLZ + (0.00787 × νdLZ) = 1.944 
               
               
                   
                 Conditional Expression(5), (5-1), (5-2), (5-3), (5-4), (5-5) 
               
               
                   
                 ndLZ = 1.749714 
               
               
                   
                 Conditional Expression(6) 
               
               
                   
                 DLZ = 1.7000 
               
               
                   
                 Conditional Expression(7) 
               
               
                   
                 ndLZ − (0.040 × νdLZ − 2.470) × νdLZ = 34.836 
               
               
                   
                 Conditional Expression(8) 
               
               
                   
                 ndLZ − (0.020 × νdLZ − 1.080) × νdLZ = 12.721 
               
               
                   
                   
               
            
           
           
               
            
               
                 &lt;positive meniscus lens L22&gt; 
               
               
                   
               
            
           
           
               
               
            
               
                   
                 Conditional Expression(1) 
               
               
                   
                 ndLZ + (0.01425× νdLZ) = 2.042 
               
               
                   
                 Conditional Expression(2), (2-1) 
               
               
                   
                 θgFLZ + (0.00316 × νdLZ) = 0.7172 
               
               
                   
                 Conditional Expression(3), (3-1), (3-2), (3-3), (3-4) 
               
               
                   
                 νdLZ = 26.87 
               
               
                   
                 Conditional Expression(4) 
               
               
                   
                 ndLZ + (0.00787 × νdLZ) = 1.871 
               
               
                   
                 Conditional Expression(5), (5-1), (5-2), (5-3), (5-4), (5-5) 
               
               
                   
                 ndLZ = 1.659398 
               
               
                   
                 Conditional Expression(6) 
               
               
                   
                 DLZ = 1.3000 
               
               
                   
                 Conditional Expression(7) 
               
               
                   
                 ndLZ − (0.040 × νdLZ − 2.470) × νdLZ = 35.830 
               
               
                   
                 Conditional Expression(8) 
               
               
                   
                 ndLZ − (0.020 × νdLZ − 1.080) × νdLZ = 12.920 
               
               
                   
                   
               
            
           
         
       
     
       FIG. 6  shows various aberration graphs of the optical system according to the third example upon focusing on infinity. Based on each of various aberration graphs, in the optical system according to the third example, the various aberrations are favorably corrected, and excellent image forming performances are achieved. 
     Fourth Example 
     A fourth example is described with reference to  FIGS. 7 and 8A to 8C  and Table 4.  FIG. 7  shows a lens configuration of an optical system according to the fourth example of this embodiment upon focusing on infinity. The optical system LS( 4 ) according to the fourth example consists of, arranged sequentially from an object side: a first lens group G 1  having a positive refractive power; a second lens group G 2  having a negative refractive power; a third lens group G 3  having a positive refractive power; and a fourth lens group G 4  having a positive refractive power. During zooming from the wide angle end state (W) to the telephoto and state (T), the first to fourth lens groups G 1  to G 4  respectively move in directions indicated by arrows in  FIG. 7 . The aperture stop S is disposed in the fourth lens group G 4 . 
     The first lens group G 1  consists of, arranged sequentially from an object side: a biconvex positive lens L11; and a cemented lens consisting of a negative meniscus lens L12 having a convex surface facing the object, and a positive meniscus lens L13 having a convex surface facing the object. In this example, the positive lens L11 of the first lens group G 1  corresponds to the object-side lens. The negative meniscus lens L12 of the first lens group G 1  corresponds to the lens satisfying the conditional expressions (1) to (2) and the like. 
     The second lens group G 2  consists of, arranged sequentially from the object side: a biconcave negative lens L21; a cemented lens that consists of a biconcave negative lens L21 and a positive meniscus lens L22 having a convex surface facing the object; and a biconcave negative lens L23. 
     The third lens group G 3  consists of a biconvex positive lens L31. In this example, upon focusing from an infinite distant object to a short-distance (finite distant) object, the entire third lens group G 3  moves toward the object along the optical axis. 
     The fourth lens group G 4  consists of, arranged sequentially from an object side: a cemented lens consisting of a biconvex positive lens L41, and a biconcave negative lens L42; a biconvex positive lens L43; a cemented lens consisting of a positive meniscus lens L44 having a concave surface facing the object, and a biconcave negative lens L45; a biconvex positive lens L46; and a negative meniscus lens L47 having a concave surface facing the object. An image surface I is disposed on the image side of the fourth lens group G 4 . An aperture stop S is disposed between the positive lens L43 and the positive meniscus lens L44 of the fourth lens group G 4 . In this example, the negative meniscus lens L47 of the fourth lens group G 4  corresponds to the image-side lens. 
     The following Table 4 lists the values of data on the optical system according to the fourth example. 
     
       
         
           
               
             
               
                 TABLE 4 
               
               
                   
               
               
                 [General Data] 
               
               
                 Zooming ratio 4.05 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 W 
                 M 
                 T 
               
               
                   
                   
               
               
                   
                 f 
                 72.1 
                 135.0 
                 292.1 
               
               
                   
                 FNO 
                 4.707 
                 4.863 
                 6.494 
               
               
                   
                 2ω 
                 23.341 
                 12.218 
                 5.684 
               
               
                   
                 Y 
                 14.75 
                 14.75 
                 14.75 
               
               
                   
                 TL 
                 168.674 
                 197.818 
                 220.732 
               
               
                   
                 BF 
                 43.294 
                 45.652 
                 70.374 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens Data] 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                   
                   
                   
                   
                   
               
               
                 Number 
                 R 
                 D 
                 nd 
                 νd 
                 θgF 
               
               
                   
               
               
                 1 
                 93.841 
                 5.6 
                 1.51680 
                 63.88 
                 0.536 
               
               
                 2 
                 −447.915 
                 0.2 
               
               
                 3 
                 112.303 
                 1.7 
                 1.61155 
                 31.26 
                 0.618 
               
               
                 4 
                 39.024 
                 8 
                 1.51742 
                 52.20 
                 0.558 
               
               
                 5 
                 262.500 
                  D5(Variable) 
               
               
                 6 
                 −239.035 
                 1.3 
                 1.69680 
                 55.52 
                 0.543 
               
               
                 7 
                 20.159 
                 4 
                 1.80809 
                 22.74 
                 0.629 
               
               
                 8 
                 61.046 
                 2.038 
               
               
                 9 
                 −54.537 
                 1.4 
                 1.85026 
                 32.35 
                 0.595 
               
               
                 10 
                 167.455 
                 D10(Variable) 
               
               
                 11 
                 102.636 
                 3.4 
                 1.58913 
                 61.22 
                 0.540 
               
               
                 12 
                 −68.899 
                 D12(Variable) 
               
               
                 13 
                 39.218 
                 5.5 
                 1.49700 
                 81.73 
                 0.537 
               
               
                 14 
                 −39.212 
                 1.3 
                 1.85026 
                 32.35 
                 0.595 
               
               
                 15 
                 267.543 
                 0.2 
               
               
                 16 
                 51.830 
                 3.7 
                 1.48749 
                 70.31 
                 0.529 
               
               
                 17 
                 −98.216 
                 0.9 
               
               
                 18 
                 ∞ 
                 23.297 
                   
                   
                 (Aperture Stop S) 
               
               
                 19 
                 −79.941 
                 3.3 
                 1.80100 
                 34.92 
                 0.585 
               
               
                 20 
                 −17.991 
                 1 
                 1.70000 
                 48.11 
                 0.560 
               
               
                 21 
                 29.977 
                 2 
               
               
                 22 
                 35.573 
                 3.5 
                 1.60342 
                 38.03 
                 0.583 
               
               
                 23 
                 −52.781 
                 6.6996 
               
               
                 24 
                 −20.538 
                 1.2 
                 1.77250 
                 49.62 
                 0.552 
               
               
                 25 
                 −34.657 
                 BF 
               
               
                   
               
            
           
           
               
            
               
                 [Variable distance data or zoom photographing] 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 W 
                 M 
                 T 
               
               
                   
                   
               
               
                   
                 D5 
                 2.306 
                 36.768 
                 51.599 
               
               
                   
                 D10 
                 32.727 
                 21.603 
                 2.157 
               
               
                   
                 D12 
                 10.112 
                 13.560 
                 16.367 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens Group Data] 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 First 
                 Focal 
               
               
                   
                 Group 
                 surface 
                 length 
               
               
                   
                   
               
               
                   
                 G1 
                 1 
                 127.677 
               
               
                   
                 G2 
                 6 
                 −31.532 
               
               
                   
                 G3 
                 11 
                 70.494 
               
               
                   
                 G4 
                 13 
                 147.512 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Conditional Expression Corresponding Value] 
               
               
                   
               
            
           
           
               
               
            
               
                   
                 Conditional Expression(1) 
               
               
                   
                 ndLZ + (0.01425 × νdLZ) = 2.057 
               
               
                   
                 Conditional Expression(2), (2-1) 
               
               
                   
                 θgFLZ + (0.00316 × νdLZ) = 0.7168 
               
               
                   
                 Conditional Expression(3), (3-1), (3-2), (3-3), (3-4) 
               
               
                   
                 νdLZ = 31.26 
               
               
                   
                 Conditional Expression(4) 
               
               
                   
                 ndLZ + (0.00787 × νdLZ) = 1.858 
               
               
                   
                 Conditional Expression(5), (5-1), (5-2), (5-3), (5-4), (5-5) 
               
               
                   
                 ndLZ = 1.61155 
               
               
                   
                 Conditional Expression(6) 
               
               
                   
                 DLZ = 1.7 
               
               
                   
                 Conditional Expression(7) 
               
               
                   
                 ndLZ − (0.040 × νdLZ − 2.470) × νdLZ = 36.513 
               
               
                   
                 Conditional Expression(8) 
               
               
                   
                 ndLZ − (0.020 × νdLZ − 1.080) × νdLZ = 12.605 
               
               
                   
                   
               
            
           
         
       
     
       FIGS. 8A, 8B and 8C  show various aberration graphs of the optical system according to the fourth example upon focusing on infinity in a wide angle end state, an intermediate focal length state, and a telephoto end state, respectively. Based on each of various aberration graphs, in the optical system according to the fourth example, the various aberrations are favorably corrected, and excellent image forming performances are achieved. 
     Fifth Example 
     A fifth example is described with reference to  FIGS. 9 and 10A to 10C  and Table 5.  FIG. 9  shows a lens configuration of an optical system according to the fifth example of this embodiment upon focusing on infinity. The optical system LS( 5 ) according to the fifth example consists of, arranged sequentially from an object side: a first lens group G 1  having a negative refractive power; a second lens group G 2  having a positive refractive power; a third lens group G 3  having a negative refractive power; and a fourth lens group G 4  having a positive refractive power. During zooming from the wide angle end state (N) to the telephoto end state (T), the first to fourth lens groups G 1  to G 4  respectively move in directions indicated by arrows in  FIG. 9 . An aperture stop S is disposed between the first lens group G 1  and the second lens group G 2 , and moves together with the second lens group G 2  along the optical axis during zooming. 
     The first lens group G 1  consists of, arranged sequentially from an object side: a negative meniscus lens L11 having a convex surface facing the object; a negative meniscus lens L12 having a convex surface facing the object; a biconcave negative lens L13; and a biconvex positive lens L14. In this example, the negative meniscus lens L11 of the first lens group G 1  corresponds to the object-side lens. The lens surfaces on both the sides of the negative meniscus lens L11 are aspherical surfaces. The image-side lens surface of the negative lens L13 is an aspherical surface. 
     The second lens group G 2  consists of, arranged sequentially from an object side: a cemented lens consisting of a negative meniscus lens L21 having a convex surface facing the object, and a positive meniscus lens L22 having a convex surface facing the object; and a biconvex positive lens L23. In this example, the negative meniscus lens L21 of the second lens group G 2  corresponds to the lens satisfying the conditional expressions (1) to (2) and the like. 
     The third lens group G 3  consists of, arranged sequentially from an object side: a cemented lens consisting of a biconvex positive lens L31, and a biconcave negative lens L32; a negative meniscus lens L33 having a concave surface facing the object; and a biconvex positive lens L34. In this example, upon focusing from an infinite distant object to a short-distance (finite distant) object, the negative meniscus lens L33 and the positive lens L34 of the third lens group G 3  move toward the image along the optical axis. 
     The fourth lens group G 4  consists of arranged sequentially from an object side: a cemented lens consisting of a biconvex positive lens L41 and a biconcave negative lens L42; a biconvex positive lens L43; and a cemented lens consisting of a biconvex positive lens L44 and a biconcave negative lens L45. An image surface  2  is disposed on the image side of the fourth lens group G 4 . In this example, the negative lens L45 of the fourth lens group G 4  corresponds to the image-side lens. The image-side lens surface of the negative lens L45 is an aspherical surface. 
     The following Table 5 lists the values of data on the optical system according to the fifth example. 
     
       
         
           
               
             
               
                 TABLE 5 
               
               
                   
               
               
                 [General Data] 
               
               
                 Zooming ratio 2.07 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 W 
                 M 
                 T 
               
               
                   
                   
               
               
                   
                 f 
                 16.65 
                 24.00 
                 34.44 
               
               
                   
                 FNO 
                 4.12 
                 4.12 
                 4.18 
               
               
                   
                 2ω 
                 53.80 
                 41.66 
                 31.60 
               
               
                   
                 Y 
                 21.60 
                 21.60 
                 21.60 
               
               
                   
                 TL 
                 168.91 
                 164.50 
                 169.42 
               
               
                   
                 BF 
                 39.00 
                 48.25 
                 65.00 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens Data] 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                   
                   
                   
                   
                   
               
               
                 Number 
                 R 
                 D 
                 nd 
                 νd 
                 θgF 
               
               
                   
               
               
                   1*a 
                 157.02850 
                 3.000 
                 1.76684 
                 46.78 
                 0.5576 
               
               
                   2*a 
                 19.73150 
                 8.955 
               
               
                  3 
                 397.62390 
                 1.550 
                 1.88300 
                 40.66 
                 0.5668 
               
               
                  4 
                 51.01700 
                 5.065 
               
               
                  5 
                 −57.91430 
                 1.500 
                 1.88300 
                 40.66 
                 0.5668 
               
               
                  6 
                 51.94950 
                 0.400 
                 1.55389 
                 38.09 
                 0.5928 
               
               
                   7*a 
                 70.15770 
                 1.237 
               
               
                  8 
                 44.62150 
                 6.911 
                 1.69895 
                 30.13 
                 0.6021 
               
               
                  9 
                 −47.20650 
                  D9(Variable) 
               
               
                 10 
                 ∞ 
                 0.000 
                   
                   
                 (Aperture Step S) 
               
               
                 11 
                 42.61580 
                 1.050 
                 1.74971 
                 24.66 
                 0.6272 
               
               
                 12 
                 17.74250 
                 4.132 
                 1.59154 
                 39.29 
                 0.5779 
               
               
                 13 
                 75.16900 
                 0.100 
               
               
                 14 
                 34.28950 
                 4.194 
                 1.53404 
                 48.26 
                 0.5617 
               
               
                 15 
                 −63.55520 
                 D15(Variable) 
               
               
                 16 
                 151.28780 
                 2.518 
                 1.62004 
                 36.40 
                 0.5833 
               
               
                 17 
                 −33.01780 
                 1.000 
                 1.88300 
                 40.66 
                 0.5668 
               
               
                 18 
                 44.83300 
                 2.756 
               
               
                 19 
                 −20.44030 
                 0.800 
                 1.88300 
                 40.66 
                 0.5668 
               
               
                 20 
                 −59.69050 
                 0.150 
               
               
                 21 
                 151.29690 
                 3.966 
                 1.84666 
                 23.80 
                 0.6215 
               
               
                 22 
                 −32.91290 
                 D22(Variable) 
               
               
                 23 
                 34.01270 
                 10.039  
                 1.49782 
                 82.57 
                 0.5386 
               
               
                 24 
                 −29.32300 
                 1.100 
                 1.83400 
                 37.18 
                 0.5778 
               
               
                 25 
                 71.52300 
                 0.100 
               
               
                 26 
                 34.90120 
                 10.548  
                 1.49782 
                 82.57 
                 0.5386 
               
               
                 27 
                 −38.97720 
                 0.100 
               
               
                 28 
                 40.26640 
                 11.985  
                 1.50377 
                 63.91 
                 0.536  
               
               
                 29 
                 −23.35670 
                 1.600 
                 1.80610 
                 40.97 
                 0.5688 
               
               
                  30*a 
                 −1764.39570 
                 BF 
               
               
                   
               
            
           
           
               
            
               
                 [Aspherical Surface Data] 
               
               
                   
               
            
           
           
               
               
            
               
                   
                 1st Surface 
               
               
                   
                 κ = 1.0000 
               
               
                   
                 A4 = 3.00E−06, A6 = 3.39E−09, A8 = 0.00E+00, A10 = 0.00E+00 
               
               
                   
                 2nd Surface 
               
               
                   
                 κ = 1.0000 
               
               
                   
                 A4 = −2.11E−05, A6 = 0.00E+00, A8 = 0.00E+00, A10 = 0.00E+00 
               
               
                   
                 7th Surface 
               
               
                   
                 κ = 1.0000 
               
               
                   
                 A4 = 1.75E−05, A6 = −2.74E−08, A8 = 1.77E−11, A10 = 0.00E+00 
               
               
                   
                 30th Surface 
               
               
                   
                 κ = 1.0000 
               
               
                   
                 A4 = 1.53E−05, A6 = 8.95E−09, A8 = 0.00E+00, A10 = 0.00E+00 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Variable distance data on zoom photographing] 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 W 
                 M 
                 T 
               
               
                   
                   
               
               
                   
                 D9 
                 29.355 
                 13.227 
                 2.000 
               
               
                   
                 D15 
                 6.263 
                 12.605 
                 16.459 
               
               
                   
                 D22 
                 9.534 
                 5.666 
                 1.200 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens Group Data] 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 First 
                 Focal 
               
               
                   
                 Group 
                 surface 
                 length 
               
               
                   
                   
               
               
                   
                 G1 
                 1 
                 −23.700 
               
               
                   
                 G2 
                 10 
                 41.700 
               
               
                   
                 G3 
                 16 
                 −62.000 
               
               
                   
                 G4 
                 23 
                 49.100 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Conditional Expression Corresponding Value] 
               
               
                   
               
            
           
           
               
               
            
               
                   
                 Conditional Expression(1) 
               
               
                   
                 ndLZ + (0.01425 × νdLZ) = 2.101 
               
               
                   
                 Conditional Expression(2), (2-1) 
               
               
                   
                 θgFLZ + (0.00316 × νdLZ) = 0.7051 
               
               
                   
                 Conditional Expression(3), (3-1), (3-2), (3-3), (3-4) 
               
               
                   
                 νdLZ = 24.66 
               
               
                   
                 Conditional Expression(4) 
               
               
                   
                 ndLZ + (0.00787 × νdLZ) = 1.944 
               
               
                   
                 Conditional Expression(5), (5-1), (5-2), (5-3), (5-4), (5-5) 
               
               
                   
                 ndLZ = 1.74971 
               
               
                   
                 Conditional Expression(6) 
               
               
                   
                 DLZ = 1.050 
               
               
                   
                 Conditional Expression(7) 
               
               
                   
                 ndLZ − (0.040 × νdLZ − 2.470) × νdLZ = 34.836 
               
               
                   
                 Conditional Expression(8) 
               
               
                   
                 ndLZ − (0.020 × νdLZ − 1.080) × νdLZ = 12.721 
               
               
                   
                   
               
            
           
         
       
     
       FIGS. 10A, 10B and 10C  show various aberration graphs of the optical system according to the fifth example upon focusing on infinity in a wide angle end state, an intermediate focal length state, and a telephoto and state, respectively. Based on each of various aberration graphs, in the optical system according to the fifth example, the various aberrations are favorably corrected, and excellent image forming performances are achieved. 
     Sixth Example 
     A sixth example is described with reference to  FIGS. 11 and 12  and Table 6.  FIG. 11  shows a lens configuration of an optical system according to the sixth example of this embodiment upon focusing on infinity. The optical system LS( 6 ) according to the sixth example consists of, arranged sequentially from an object side: a first lens group G 1  having a positive refractive power; a second lens group G 2  having a negative refractive power; and a third lens group G 3  having a positive refractive power. Upon focusing from an infinite distant object to a short-distance (finite distant) object, the second lens group G 2  moves toward the image along the optical axis. The aperture stop S is disposed on an object-side neighborhood of the third lens group G 3 . Similar to the first lens group G 1  and the third lens group G 3 , the aperture stop S is fixed with respect to the image surface I upon focusing. 
     The first lens group G 1  consists of, arranged sequentially from an object side: a protective glass G having a significantly low refractive power; a biconvex positive lens L11; a biconvex positive lens L12; a biconcave negative lens L13; and a cemented lens that consists of a negative meniscus lens L14 having a convex surface facing the object, and a positive meniscus lens L15 having a convex surface facing the object. In this example, the positive lens L11 of the first lens group G 1  corresponds to the object-side lens. 
     The second lens group G 2  consists of, arranged sequentially from the object side: a biconcave negative lens L21; and a cemented lens that consists of a positive meniscus lens L22 having a concave surface facing the object, and a biconcave negative lens L23. 
     The third lens group G 3  consists of, arranged sequentially from an object side: a biconvex positive lens L31; a negative meniscus lens L32 having a concave surface facing the object; a cemented lens consisting of a biconvex positive lens L33 and a biconcave negative lens L34; a biconcave negative lens L35; a biconvex positive lens L36; a cemented lens consisting of a biconvex positive lens L37 and a biconcave negative lens L38; a cemented lens consisting of a positive meniscus lens L39 having a concave surface facing the object, and a negative meniscus lens L40 having a concave surface facing the object; a cemented lens consisting of a negative meniscus lens L41 having a convex surface facing the object, and a positive meniscus lens L42 having a convex surface facing the object; a biconcave negative lens L43; and a cemented lens consisting of a biconvex positive lens L44, and a negative meniscus lens L45 having a concave surface facing the object. In this example, the negative meniscus lens L45 of the third lens group G 3  corresponds to the image-side lens. The positive meniscus lens L39 of the third lens group G 3  corresponds to the lens satisfying the conditional expressions (1) to (2) and the like. 
     An image surface I is disposed on the image side of the third lens group G 3 . An insertable and replaceable optical filter FL is disposed between the negative lens L38 and the positive meniscus lens L39 of the third lens group G 3 . For example, an NC filter (neutral color filter), a color filter, a polarizing filter, an RD filter (neutral density filter), an IR filter (infrared-cut filter) or the like is adopted as the insertable and replaceable optical filter FL. 
     The following Table 6 lists the values of data on the optical system according to the sixth example. 
     
       
         
           
               
             
               
                 TABLE 6 
               
               
                   
               
               
                 [General Data] 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 f 
                 548.897246 
               
               
                   
                 FNO 
                 4.028 
               
               
                   
                 2ω 
                 4.529 
               
               
                   
                 Y 
                 21.60 
               
               
                   
                 TL 
                 421.51451 
               
               
                   
                 BF 
                 41.79450 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens Data] 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                   
                   
                   
                   
                   
               
               
                 Number 
                 R 
                 D 
                 nd 
                 νd 
                 θgF 
               
               
                   
               
               
                 1 
                 1200.3704 
                 5.0000 
                 1.516800 
                 63.88 
                 0.536 
               
               
                 2 
                 1199.7897 
               
               
                 3 
                 207.5249 
                 17.5000 
                 1.433843 
                 95.26 
                 0.540 
               
               
                 4 
                 −1086.1158 
                 44.9000 
               
               
                 5 
                 176.7586 
                 18.0000 
                 1.433843 
                 95.26 
                 0.540 
               
               
                 6 
                 −399.9688 
                 3.0700 
               
               
                 7 
                 −360.7137 
                 6.0000 
                 1.612660 
                 44.46 
                 0.564 
               
               
                 8 
                 360.6858 
                 90.0000 
               
               
                 9 
                 66.6831 
                 4.0000 
                 1.794997 
                 45.32 
                 0.560 
               
               
                 10 
                 46.0960 
                 15.0000 
                 1.497820 
                 82.54 
                 0.539 
               
               
                 11 
                 1030.2823 
                 D11(Variable) 
               
               
                 12 
                 −1579.9519 
                 2.5000 
                 1.772499 
                 49.68 
                 0.552 
               
               
                 13 
                 115.8247 
                 3.3500 
               
               
                 14 
                 −274.6805 
                 3.5000 
                 1.846679 
                 23.83 
                 0.620 
               
               
                 15 
                 −87.1354 
                 2.4000 
                 1.518229 
                 58.84 
                 0.546 
               
               
                 16 
                 65.0724 
                 D16(Variable) 
               
               
                 17 
                 ∞ 
                 1.5000 
                   
                   
                 (Aperture Stop S) 
               
               
                 18 
                 89.0765 
                 7.6000 
                 1.487490 
                 70.43 
                 0.530 
               
               
                 19 
                 −64.1681 
                 1.2000 
               
               
                 20 
                 −66.2092 
                 1.9000 
                 1.846679 
                 23.83 
                 0.620 
               
               
                 21 
                 −113.6112 
                 5.0000 
               
               
                 22 
                 309.3141 
                 3.5000 
                 1.846679 
                 23.83 
                 0.620 
               
               
                 23 
                 −136.2550 
                 1.9000 
                 1.593190 
                 67.94 
                 0.544 
               
               
                 24 
                 53.6104 
                 3.1000 
               
               
                 25 
                 −343.3953 
                 1.9000 
                 1.754999 
                 52.33 
                 0.548 
               
               
                 26 
                 94.6723 
                 4.1900 
               
               
                 27 
                 117.8519 
                 3.5000 
                 1.772499 
                 49.68 
                 0.552 
               
               
                 28 
                 −385.7489 
                 0.1000 
               
               
                 29 
                 67.6179 
                 4.5000 
                 1.639999 
                 60.14 
                 0.537 
               
               
                 30 
                 −410.4180 
                 1.9000 
                 1.846679 
                 23.83 
                 0.620 
               
               
                 31 
                 247.6487 
                 6.5000 
               
               
                 32 
                 ∞ 
                 1.5000 
                 1.516800 
                 63.88 
                 0.536 
               
               
                 33 
                 ∞ 
                 25.3277 
               
               
                 34 
                 −212.6904 
                 6.2000 
                 1.659398 
                 26.84 
                 0.632 
               
               
                 35 
                 −34.5457 
                 1.6000 
                 1.850000 
                 27.03 
                 0.609 
               
               
                 36 
                 −57.9415 
                 0.1000 
               
               
                 37 
                 171.5239 
                 1.7000 
                 1.729160 
                 54.61 
                 0.544 
               
               
                 38 
                 20.3538 
                 7.1000 
                 1.581440 
                 40.98 
                 0.576 
               
               
                 39 
                 199.2504 
                 3.7000 
               
               
                 40 
                 −61.4914 
                 1.7000 
                 1.772500 
                 49.62 
                 0.552 
               
               
                 41 
                 80.1566 
                 0.1000 
               
               
                 42 
                 39.9229 
                 7.8000 
                 1.581440 
                 40.98 
                 0.576 
               
               
                 43 
                 −38.2861 
                 1.7000 
                 1.808090 
                 22.74 
                 0.629 
               
               
                 44 
                 −171.6744 
                 BF 
               
               
                   
               
            
           
           
               
            
               
                 [Variable distance data on short-distance photographing] 
               
            
           
           
               
               
               
               
            
               
                   
                   
                   
                 Upon focusing 
               
               
                   
                   
                 Upon focusing 
                 on a short-distance 
               
               
                   
                   
                 on infinity 
                 object 
               
               
                   
                   
                 f = 548.89725 
                 β = −0.24282 
               
               
                   
                   
               
               
                   
                 D11 
                 18.50291 
                 33.77284 
               
               
                   
                 D16 
                 38.17937 
                 22.90945 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Conditional Expression Corresponding Value] 
               
               
                   
               
            
           
           
               
               
            
               
                   
                 Conditional Expression(1) 
               
               
                   
                 ndLZ + (0.01425 × νdLZ) = 2.042 
               
               
                   
                 Conditional Expression(2), (2-1) 
               
               
                   
                 θgFLZ + (0.00316 × νdLZ) = 0.7168 
               
               
                   
                 Conditional Expression(3), (3-1), (3-2), (3-3), (3-4) 
               
               
                   
                 νdLZ = 26.84 
               
               
                   
                 Conditional Expression(4) 
               
               
                   
                 ndLZ + (0.00787 × νdLZ) = 1.871 
               
               
                   
                 Conditional Expression(5), (5-1), (5-2), (5-3), (5-4), (5-5) 
               
               
                   
                 ndLZ = 1.659398 
               
               
                   
                 Conditional Expression(6) 
               
               
                   
                 DLZ = 6.2000 
               
               
                   
                 Conditional Expression(7) 
               
               
                   
                 ndLZ − (0.040 × νdLZ − 2.470) × νdLZ = 35.820 
               
               
                   
                 Conditional Expression(8) 
               
               
                   
                 ndLZ − (0.020 × νdLZ − 1.080) × νdLZ = 12.920 
               
               
                   
                   
               
            
           
         
       
     
       FIG. 12  shows various aberration graphs of the optical system according to the sixth example upon focusing on infinity. Based on each of various aberration graphs, in the optical system according to the sixth example, the various aberrations are favorably corrected, and excellent image forming performances are achieved. 
     Seventh Example 
     A seventh example is described with reference to  FIGS. 13 and 14  and Table 7.  FIG. 13  shows a lens configuration of an optical system according to the seventh example of this embodiment upon focusing on infinity. The optical system L( 7 ) according to the seventh example consists of, arranged sequentially fro an object side: a first lens group G 1  having a positive refractive power; a second lens group G 2  having a negative refractive power; and a third lens group G 3  having a positive refractive power. Upon focusing from an infinite distant object to a short-distance (finite distant) object, the second lens group G 2  moves toward the image along the optical axis. The aperture stop S is disposed on an object-side neighborhood of the third lens group G 3 . Similar to the first lens group G 1  and the third lens group G 3 , the aperture stop S is fixed with respect to the image surface I upon focusing. 
     The first lens group G consists of, arranged sequentially from an object side: a positive meniscus lens L11 having a convex surface facing the object; a cemented lens consisting of a biconvex positive lens L12 and a biconcave negative lens L13; a biconvex positive lens L14; and a cemented lens consisting of a negative meniscus lens L15 having a convex surface facing the object, and a positive meniscus lens L16 having a convex surface facing the object. In this example, the positive meniscus lens L11. of the first lens group G 1  corresponds to the object-side lens. 
     The second lens group G 2  consists of, arranged sequentially from an object side: a cemented lens consisting of a positive meniscus lens L21 having a concave surface facing the object, and a biconcave negative lens L22; and a cemented lens consisting of a positive meniscus lens L23 having a concave surface facing the object and a biconcave negative lens L24. 
     The third lens group G 3  consists of, arranged sequentially from an object side: a biconvex positive lens L31; a negative meniscus lens L32 having a concave surface facing the object; a positive meniscus lens L33 having a concave surface facing the object; a biconvex positive lens L34; a negative meniscus lens L35 having a convex surface facing the object; a cemented lens consisting of a biconvex positive lens L36, a biconcave negative lens L37, and a biconvex positive lens L38; a positive meniscus lens L39 having a concave surface facing the object; and a negative meniscus lens L40 having a concave surface facing the object. In this example, the negative meniscus lens  40  of the third lens group G 3  corresponds to the image-side lens. The positive lens L34 of the third lens group G 3  corresponds to the lens satisfying the conditional expressions (1) to (2) and the like. The object-side lens surface of the positive meniscus lens L39 is an aspherical surface. 
     An image surface I is disposed on the image side of the third lens group G 3 . An insertable and replaceable optical filter FL is disposed between the positive meniscus lens L33 and the positive lens L34 of the third lens group G 3 . For example, an NC filter (neutral color filter), a color filter, a polarizing filter, an ND filter (neutral density filter), an IR filter (infrared-cut filter) or the like is adopted as the insertable and replaceable optical filter FL. 
     The following Table 7 lists the values of data on the optical system according to the seventh example. 
     
       
         
           
               
             
               
                 TABLE 7 
               
               
                   
               
               
                 [General Data] 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 f 
                 388.032537 
               
               
                   
                 FNO 
                 4.038 
               
               
                   
                 2ω 
                 6.416 
               
               
                   
                 Y 
                 21.60 
               
               
                   
                 TL 
                 283.53069 
               
               
                   
                 BF 
                 53.66784 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Lens Data] 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                   
                   
                   
                   
                   
               
               
                 Number 
                 R 
                 D 
                 nd 
                 νd 
                 θgF 
               
               
                   
               
               
                  1 
                 167.3500 
                 10.6000  
                 1.497820 
                 82.52 
                 0.539 
               
               
                  2 
                 2361.5509 
                 0.3000 
               
               
                  3 
                 98.4074 
                 20.8000  
                 1.497820 
                 82.52 
                 0.539 
               
               
                  4 
                 −306.6320 
                 5.0000 
                 1.772499 
                 49.61 
                 0.552 
               
               
                  5 
                 165.4047 
                 20.0000  
               
               
                  6 
                 135.6601 
                 9.6000 
                 1.446791 
                 91.03 
                 0.534 
               
               
                  7 
                 −731.2064 
                 0.3000 
               
               
                  8 
                 71.2883 
                 4.0000 
                 1.754999 
                 52.31 
                 0.547 
               
               
                  9 
                 42.3960 
                 16.5000  
                 1.497820 
                 82.52 
                 0.539 
               
               
                 10 
                 435.6465 
                 D10(Variable) 
               
               
                 11 
                 −1745.8851 
                 5.0000 
                 1.850260 
                 32.35 
                 0.594 
               
               
                 12 
                 −78.6510 
                 3.0808 
                 1.639999 
                 60.09 
                 0.538 
               
               
                 13 
                 55.9799 
                 6.0808 
               
               
                 14 
                 −79.8113 
                 4.2000 
                 1.766840 
                 46.80 
                 0.558 
               
               
                 15 
                 −45.8300 
                 2.8000 
                 1.516800 
                 64.10 
                 0.536 
               
               
                 16 
                 51.2954 
                 D16(Variable) 
               
               
                 17 
                 ∞ 
                 3.2000 
                   
                   
                 (Aperture Stop S) 
               
               
                 18 
                 126.0707 
                 5.0808 
                 1.729157 
                 54.66 
                 0.544 
               
               
                 19 
                 −81.3057 
                 2.1000 
               
               
                 20 
                 −43.1962 
                 3.4000 
                 1.795040 
                 28.54 
                 0.607 
               
               
                 21 
                 −104.9670 
                 7.0000 
               
               
                 22 
                 −827.9284 
                 5.3000 
                 1.603001 
                 65.47 
                 0.541 
               
               
                 23 
                 −52.9313 
                 5.3151 
               
               
                 24 
                 ∞ 
                 2.0000 
                 1.516800 
                 64.12 
                 0.536 
               
               
                 25 
                 ∞ 
                 9.4440 
               
               
                 26 
                 64.5713 
                 5.0000 
                 1.611553 
                 31.26 
                 0.618 
               
               
                 27 
                 −280.9473 
                 0.8000 
               
               
                 28 
                 350.7347 
                 1.5000 
                 1.804000 
                 46.58 
                 0.557 
               
               
                 29 
                 24.0250 
                 5.4000 
               
               
                 30 
                 33.9853 
                 9.0000 
                 1.620040 
                 36.30 
                 0.587 
               
               
                 31 
                 −23.4510 
                 2.0000 
                 1.882997 
                 40.76 
                 0.567 
               
               
                 32 
                 36.4535 
                 8.2000 
                 1.575010 
                 41.49 
                 0.576 
               
               
                 33 
                 −45.3865 
                 2.9000 
               
               
                  34*a 
                 −91.9573 
                 6.4000 
                 1.589130 
                 61.18 
                 0.539 
               
               
                 35 
                 −28.9225 
                 0.5000 
               
               
                 36 
                 −33.4300 
                 2.5000 
                 1.882997 
                 40.76 
                 0.567 
               
               
                 37 
                 −192.4648 
                 BF 
               
               
                   
               
            
           
           
               
            
               
                 [Aspherical Surface Data] 
               
               
                   
               
            
           
           
               
               
            
               
                   
                 34th Surface 
               
               
                   
                 κ = 1.0000 
               
               
                   
                 A4 = 8.36373E−06, A6 = 2.40160E−09, A8 = 0.00000E+00, A10 = 0.00000E+00 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Variable distance data on short-distance photographing] 
               
            
           
           
               
               
               
               
            
               
                   
                   
                   
                 Upon focusing 
               
               
                   
                   
                 Upon focusing 
                 on a short-distance 
               
               
                   
                   
                 on infinity 
                 object 
               
               
                   
                   
                 f = 388.03254 
                 β = −0.25415 
               
               
                   
                   
               
               
                   
                 D10 
                 19.01315 
                 27.19783 
               
               
                   
                 D16 
                 15.10916 
                 6.92448 
               
               
                   
                   
               
            
           
           
               
            
               
                 [Conditional Expression Corresponding Value] 
               
               
                   
               
            
           
           
               
               
            
               
                   
                 Conditional Expression(1) 
               
               
                   
                 ndLZ + (0.01425 × νdLZ) = 2.057 
               
               
                   
                 Conditional Expression(2), (2-1) 
               
               
                   
                 θgFLZ + (0.00316 × νdLZ) = 0.7168 
               
               
                   
                 Conditional Expression(3), (3-1), (3-2), (3-3), (3-4) 
               
               
                   
                 νdLZ = 31.26 
               
               
                   
                 Conditional Expression(4) 
               
               
                   
                 ndLZ + (0.00787 × νdLZ) = 1.858 
               
               
                   
                 Conditional Expression(5), (5-1), (5-2), (5-3), (5-4), (5-5) 
               
               
                   
                 ndLZ = 1.611553 
               
               
                   
                 Conditional Expression(6) 
               
               
                   
                 DLZ = 5.0000 
               
               
                   
                 Conditional Expression(7) 
               
               
                   
                 ndLZ − (0.040 × νdLZ − 2.470) × νdLZ = 36.513 
               
               
                   
                 Conditional Expression(8) 
               
               
                   
                 ndLZ − (0.020 × νdLZ − 1.080) × νdLZ = 12.605 
               
               
                   
                   
               
            
           
         
       
     
       FIG. 14  shows various aberration graphs of the optical system according to the seventh example upon focusing on infinity. Based on each of various aberration graphs, in the optical system according to the seventh example, the various aberrations are favorably corrected, and excellent image forming performances are achieved. 
     According to each example described above, as for correction of the chromatic aberrations, an optical system can be achieved where in addition to the primary achromatization, the secondary spectrum is favorably corrected. 
     Here, each example described above indicates a specific example of the invention of the present application. The invention of the present application is not limited thereto. 
     Note that the following details can be appropriately adopted in a range without degrading the optical performance of the optical system of this embodiment. 
     It is assumed that the focusing lens group indicates a portion that includes at least a single lens and is separated by air distances changing during focusing. That is, the group may be a focusing lens group that performs focusing from an infinite distant object to a short-distance object by moving a single or multiple lens groups, or a partial lens group in the optical axis direction. The focusing lens group may be applicable also to autofocusing, and is suitable also to motor driving for autofocusing (using an ultrasonic motor or the like). 
     The first and second examples of the optical system of this embodiment indicate what has the configuration having a vibration-proof function. The present application is not limited thereto, and may have a configuration having no vibration-proof function. The other examples having no vibration-proof function may have configurations having the vibration-proof function. 
     The lens surface may be formed by a spherical surface or a flat surface, or by an aspherical surface. In a case where the lens surface is a spherical surface or a flat surface, lens processing and assembly adjustment are facilitated, and degradation in the optical performance due to an error of processing and assembling adjustment can be prevented. Accordingly, the case is preferable. furthermore, it is preferable because degradation in drawing performance is small even if the image surface deviates. 
     In a case where the lens surface is an aspherical surface, the aspherical surface may be any of an aspherical surface made by a grinding process, a glass mold aspherical surface made by forming glass into an aspherical surface shape, and a composite type aspherical surface where resin is formed on a glass surface into an aspherical surface shape. The lens surface may be a diffractive surface. The lens may be a gradient index lens (GRIN lens) or a plastic lens. 
     To reduce flares and ghosts and achieve an optical performance with high contrast, an antireflection coating film having a high transmissivity over a wide wavelength region may be applied to each lens surface. Accordingly, the flares and ghosts can be reduced, and a high optical performance with a high contrast can be achieved. 
     EXPLANATION OF NUMERALS AND CHARACTERS 
       
     
       
         
           
               
               
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 G1 
                 First lens group 
                 G2 
                 Second lens group 
               
               
                   
                 G3 
                 Third lens group 
                 G4 
                 Fourth lens group 
               
               
                   
                 G5 
                 Fifth lens group 
                 G6 
                 Sixth lens group 
               
               
                   
                 I 
                 Image surface 
                 S 
                 Aperture stop