Abstract:
A telescopic zoom lens system includes first through fourth lens groups, wherein upon zooming from the short to long focal length extremities, the first and fourth lens groups remain stationary, the second lens group moves toward the image sides, and the third lens group moves toward the image side and thereafter moves toward the object side. The first lens group includes positive first and second sub-lens groups, the second sub-lens group being a focusing lens group and including a negative meniscus lens, element having a convex surface on the object side and a positive lens element having a convex surface on the object side. The following condition (1) is satisfied: 
     2.7&lt;f1R/ft&lt;3.5 . . . (1); wherein f1R and ft designate the focal lengths of the -second sub-lens group and the entire zoom lens system at the long focal length extremity, respectively.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a telescopic zoom lens system suitable for a single-lens reflex (SLR) camera. 
         [0003]    2. Description of the Prior Art 
         [0004]    In conventional telescopic zoom lens systems, a four-lens-group zoom lens system including a lens group having a positive refractive power (hereinafter, a positive lens group), a lens group having a negative refractive power (hereinafter, a negative lens group), a positive lens group and a positive lens group, in this order from the object, has been widely used, as disclosed in, e.g., Japanese Unexamined Patent Publication (JUPP) No. 2000-019398, JUPP No. 2002-006215, JUPP No. 2003-090958, JUPP No. 2003-202497, JUPP No. 2003-344766 and JUPP No. 2004-109559. 
         [0005]    The above-discussed conventional telescopic zoom lens systems have been designed for a SLR camera with the 135 (35 mm) film format users already owning a lot of exchangeable photographing lenses- for the 135 (35 mm) film format strongly wish to use a conventional exchangeable photographing lens with a recent digital SLR camera. Here, it should be understood that such a compatibility can be attained only when a digital SLR camera is provided with the same flange back length as that of a conventional SLR camera. 
         [0006]    However, the size of an imaging device (CCD) of a digital SLR camera is considerably smaller than the frame size of the 135 (35 mm) film format. If an exchangeable photographing lens for the 135 (35 mm) film format is simply mounted on a digital SLR camera, the angle-of-view for photographing becomes smaller. 
         [0007]    If an attempt is made, in a digital SLR camera, to maintain the same angle-of-view that can be attained in a conventional SLR camera, there is a need to shorten the focal length of an exchangeable photographing lens by the dimensional-ratio of frame size of the 135 (35 mm) film format to the size of an imaging device (CCD). 
         [0008]    On the other hand, as discussed above, for the purpose of attaining the compatibility in which a conventional exchangeable photographing lens can be used with a digital SLR camera, the flange back length of a digital SLR camera has to be made the same as that of a conventional SLR camera. Accordingly, in the case when an exchangeable photographing lens for a digital SLR camera is newly designed, there exists a problem to be solved, i.e., both a shorter focal length and a longer back focal distance have to be attained at the same time. Here, note that just redesigning conventional photographing lenses for adjusting the same with the size of an imaging device (CCD) cannot solve the above problem, because according to such a simple re-scaling, when the focal length becomes shorter, the back focal distance also becomes shorter. 
         [0009]    The present invention is to provide a miniaturized telescopic zoom lens system having the following features:
       (i) an angle-of-view of approximately 10° to 30° (the zoom ratio: a little less than 3);   (ii) a long back focal distance;   (iii) a short focal length;   (iv) high optical quality; and   (v) high operability.       
 
       SUMMARY OF THE INVENTION 
       [0015]    According to an aspect of the present invention, there is provided a telescopic zoom lens system including a positive first lens group, a negative second lens group, a positive third lens group and a positive fourth lens group, in this order from the object. 
         [0016]    Upon zooming from the short focal length extremity to the long focal length extremity, the positive first and the positive fourth lens group remain stationary, the negative second lens group moves toward the image, and the positive third lens group first moves toward the image and thereafter moves toward the object. 
         [0017]    The positive first lens group is constituted by a positive front sub-lens group and a positive rear sub-lens group which are separated at a maximum air-distance therebetween. 
         [0018]    The positive rear sub-lens group functions as a focusing lens group, and is constituted by a negative meniscus lens element having the convex; surface facing toward the object, and a positive lens element having a convex surface facing toward the object, in this order from the object. 
         [0019]    The positive rear sub-lens group satisfies the following condition: 
         [0000]      2.7&lt; f 1 R/ft&lt; 3.5   (1) 
         [0020]    wherein 
         [0021]    f1R designates the focal length of the positive rear sub-lens group; and 
         [0022]    ft designates the focal length of the entire telescopic zoom lens system at the long focal length extremity 
         [0023]    It is preferable that the positive fourth lens group include a front sub-lens group and a rear sub-lens group separated at a maximum air-distance therebetween, and that the rear sub-lens group satisfy the following condition: 
         [0000]      1.8&lt; f 4 R/fw &lt;3.6   (2) 
         [0024]    wherein 
         [0025]    f4R designates the focal length of the rear sub-lens group of the positive fourth lens group; and 
         [0026]    fw designates the focal length of the entire telescopic zoom lens system at the short focal length extremity. 
         [0027]    A fixed-aperture diaphragm FS is preferably provided between the front sub-lens group and the rear sub-lens group of the positive fourth lens group. 
         [0028]    According to another aspect of the present invention, there is provided a telescopic zoom lens system including a positive first lens group, a negative second lens group, a positive third lens group and a positive fourth lens group, in this order from the object. 
         [0029]    Upon zooming from the short focal length extremity to the long focal length extremity, the positive first and the positive fourth lens group remain stationary, the negative second lens group moves toward the image, and the positive third lens group first moves toward the image and thereafter moves toward the object. 
         [0030]    The positive first lens group is constituted by a positive front sub-lens group and a positive rear sub-lens group which are separated at a maximum air-distance therebetween. The positive rear sub-lens group of the positive first lens group functions as a focusing lens group. 
         [0031]    The positive fourth lens group includes a front sub-lens group and a rear sub-lens group separated at a maximum air-distance therebetween. 
         [0032]    The telescopic zoom lens system satisfies the following conditions: 
         [0000]      2.7 &lt;f 1 R/ft&lt; 3.5   (1) 
         [0000]      1.8&lt; f 4 R/fw &lt;3.6   (2) 
         [0033]    wherein 
         [0034]    F1R designates the focal length of the positive rear sub-lens group; 
         [0035]    f4R designates the focal length of the rear sub-lens group of the positive fourth lens group; 
         [0036]    ft designates the focal length of the entire telescopic zoom lens system at the long focal length extremity; and 
         [0037]    fw designates the focal length of the entire telescopic zoom lens system at the short focal length extremity. 
         [0038]    In the above telescopic zoom lens system of another aspect of the present invention, a fixed-aperture diaphragm FS is preferably provided between the front sub-lens group and the rear sub-lens group of the positive fourth lens group 
         [0039]    In each aspect of the present invention, one positive lens element of the positive first lens group is preferably made of a glass material having an Abbe number of 80 or more. 
         [0040]    In each aspect of the present invention, the telescopic zoom lens system preferably satisfies the following condition: 
         [0000]      1.6&lt; f 1 /fw&lt; 2.5   (3) 
         [0041]    wherein 
         [0042]    f1 designates the focal length of the positive first lens group; and 
         [0043]    fw designates the focal length of the entire telescopic zoom lens system at the short focal length extremity. 
         [0044]    The present disclosure relates to subject matter contained in Japanese Patent Application No. 2006-033506 (filed on Feb. 10, 2006) which is expressly incorporated herein in its entirety. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0045]    The present invention will be discussed below in detail with reference to the accompanying drawings, in which: 
           [0046]      FIG. 1  is a lens arrangement of, the telescopic zoom lens system, at the short focal length extremity, according to a first embodiment of the present invention; 
           [0047]      FIGS. 2A ,  2 B,  2 C,  2 D and  2 E show aberrations occurred, at the short focal length extremity, in the lens arrangement shown in  FIG. 1 ; 
           [0048]      FIG. 3  is a lens arrangement of the telescopic zoom lens system, at the long focal length extremity, according to the first embodiment of the present invention; 
           [0049]      FIGS. 4A ,  4 B,  4 C,  4 D and  4 E show aberrations occurred, at the long focal length extremity, in the lens arrangement shown in  FIG. 3 ; 
           [0050]      FIG. 5  is a lens arrangement of the telescopic zoom lens system, at the short focal length extremity, according to a second embodiment of the present invention; 
           [0051]      FIGS. 6A ,  6 B,  6 C,  6 D and  6 E show aberrations occurred, at the short focal length extremity, in the lens arrangement shown in  FIG. 5 ; 
           [0052]      FIG. 7  is a lens arrangement of the telescopic zoom lens system, at the long focal length extremity, according to the second embodiment of the present invention; 
           [0053]      FIGS. 8A ,  8 B,  8 C,  8 D and  8 E show aberrations occurred, at the long focal length extremity, in the lens arrangement shown in  FIG. 7 ; 
           [0054]      FIG. 9  is a lens arrangement of the telescopic zoom lens system, at the short focal length extremity, according to a third embodiment of the present invention; 
           [0055]      FIGS. 10A ,  10 B,  10 c,  10 D and  10 E show aberrations occurred, at the short focal length extremity, in the lens arrangement shown in  FIG. 9 ; 
           [0056]      FIG. 11  is a lens arrangement of the telescopic zoom lens system, at the long focal length extremity, according to the third embodiment of the present invention; 
           [0057]      FIGS. 12A ,  12 B,  12 C,  12 D and  12 E show aberrations occurred, at the long focal length extremity, in the lens arrangement shown in  FIG. 11 ; 
           [0058]      FIG. 13  is a lens arrangement of the telescopic zoom lens system, at the short focal length extremity, according to a fourth embodiment of the present invention; 
           [0059]      FIGS. 14A ,  14 B,  14 C,  14 D and  14 E show aberrations occurred, at the short focal length extremity, in the lens arrangement shown in  FIG. 13 ; 
           [0060]      FIG. 15  is a lens arrangement of the telescopic zoom lens system, at the long focal length extremity, according to the fourth embodiment of the present invention; 
           [0061]      FIGS. 16A ,  16 B,  16 C,  16 D and  16 E show aberrations occurred, at the long focal length extremity, in the lens arrangement shown in  FIG. 15 ; 
           [0062]      FIG. 17  is a lens arrangement of the telescopic zoom lens system, at the short focal length extremity, according to a fifth embodiment of the present invention; 
           [0063]      FIGS. 18A ,  18 B,  18 C,  18 D and  18 E show aberrations occurred, at the short focal length extremity, in the lens arrangement shown in  FIG. 17 ; 
           [0064]      FIG. 19  is a lens arrangement of the telescopic zoom lens system, at the long focal length extremity, according to the fifth embodiment of the present invention; 
           [0065]      FIGS. 20A ,  20 B,  20 C,  20 D and  20 E show aberrations occurred, at the long focal length extremity, in the lens arrangement shown in  FIG. 19 ; and 
           [0066]      FIG. 21  is the schematic view of the lens-group moving paths for the telescopic zoom lens system according to the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0067]    The telescopic zoom lens system of the present invention, as shown in the lens-group moving paths of  FIG. 21 , includes a positive first lens group  10 , a negative second lens group  20 , a positive third lens group  30 , and a positive fourth lens group  40 , in this order from the object. 
         [0068]    Upon zooming from the short focal length extremity to the long focal length extremity, the positive first lens group  10  and the positive fourth lens group  40  remain stationary (i.e., the distance therefrom to the image plane I does not vary), the negative second lens group  20  moves toward to the image, and the positive third lens group  30  first moves toward the image, and thereafter moves toward the object. 
         [0069]    A variable-aperture diaphragm KS is provided between the positive third lens group  30  and the positive fourth lens group  40 . 
         [0070]    The positive first lens group  10  includes a front sub-lens group  10 F and a rear sub-lens group  10 R which are separated at a maximum air-distance therebetween. The front sub-lens group  10 F and the rear sub-lens group  10 R have a positive refractive power; and the rear sub-lens group  10 R functions as a focusing lens group. 
         [0071]    Furthermore, the positive fourth lens group  40  includes a front sub-lens group  40 F and a rear sub-lens group  40 R which are separated at a maximum air-distance therebetween. The front sub-lens group  40 F and the rear sub-lens group  40 R have a positive refractive power; and a fixed-aperture diaphragm FS is provided therebetween. 
         [0072]    In a telescopic zoom lens system having a large f-number, the diameter of the first lens group is relatively small, so that an optical system in which the first lens group is movable upon zooming is generally employed. This is because the, overall length of such a telescopic zoom lens system at the short focal length extremity becomes shorter, which is advantageous for miniaturization. 
         [0073]    On the other hand, in a fast telescopic zoom lens system having a smaller f-number, it is preferable not to move the first lens group upon zooming since the first lens group has a large diameter and is relatively heavy. 
         [0074]    In the telescopic zoom lens system of the present invention, for attaining a faster telescopic zoom lens system, the positive first lens group  10  and the positive fourth lens group  40  are arranged not to move upon zooming; and the negative second lens group  20  and the positive third lens group  30  which have smaller diameters and smaller number of lens elements are arranged to move upon zooming. 
         [0075]    In the above arrangement (zoom mechanism) of the telescopic zoom lens system of the present invention, the front sub-lens group  10 F and the rear sub-lens group  10 R of the positive first lens group  10  are separated at a maximum air-distance therebetween, and focusing is carried out by the rear sub-lens group  10 R. 
         [0076]    More Specifically, upon focusing from an infinite object to a close-up object, the rear sub-lens group  10 R moves from the image side toward the object side. 
         [0077]    In a zoom lens system having a positive first lens group, a negative second lens group, a positive third lens group and positive fourth lens group, in this order from the object, there are such zoom lens systems in which focusing is carried out by the positive second lens group thereof which functions as a variator lens group. However, control of such a variator lens group is complicated, unlike a vari-focal lens system in which a traveling distance of the focusing lens group varies according to the focal length. 
         [0078]    If an attempt is made to carry out focusing by the positive first lens group which remains stationary upon zooming, the control of a telescopic zoom lens system becomes easier. This is because the traveling distance of the focusing lens group is the same throughout all the focal-length ranges. 
         [0079]    Even if there is an advantage of carrying out focusing by the positive first lens group  10  which remains stationary upon zooming, the positive first lens group  10  has a large diameter and is heavy. Therefore using the entire positive first lens group  10  to carry out focusing would cause much burden on the driving system (driving motor) for the positive first lens group (the focusing lens group), so that a quick focusing operation would be difficult. 
         [0080]    Then, the positive first lens group  10  is divided into the front sub-lens group  10 F and the rear sub-lens group  10 R; and the rear sub-lens group  10 R is arranged to function as a focusing lens group. Due to this arrangement, a quick focusing operation is possible. Furthermore, since the front sub-lens group  10 F is arranged to remain stationary upon both zooming and focusing, the overall length of the telescopic zoom lens system does not vary, so that usability of the telescopic zoom lens system can be enhanced. 
         [0081]    The rear sub-lens group  10 R, which functions as a focusing lens group, is preferably constituted by a negative meniscus lens element having the convex surface toward the object and a positive lens element having a convex surface facing toward the object, in this order from the object. 
         [0082]    In the prior art, there is a case where a rear sub-lens group (corresponding to the rear sub-lens group  10 R of the illustrated embodiment) is constituted by a positive single lens element. However, a focusing lens group constituted by a positive single lens element cannot correct chromatic aberration by the focusing lens group itself. Therefore fluctuations in chromatic aberrations upon focusing become larger. 
         [0083]    In the embodiments of the present invention, for the purpose of eliminate the drawback discussed above, by constituting the focusing lens group (i.e., the rear sub-lens group  10 R) with two lens elements, i.e., a negative meniscus lens element and a positive lens element, chromatic aberrations can be corrected by the focusing lens group itself, and fluctuations in chromatic aberration can be made smaller over the entire telescopic zoom lens system upon focusing furthermore, by forming the most object-side lens surface of the rear sub-lens group  10 R as a convex surface, an incident angle of a bundle of light rays incident on each lens surface can be made smaller; thereby, the correcting of spherical aberration and coma can be made within the rear sub-lens group  10 R. Consequently, fluctuations in aberrations upon focusing over the entire telescopic zoom lens system can be reduced. 
         [0084]    Condition (1) specifies the ratio of the focal length of the rear sub-lens group  10 R (i.e., the focusing lens group) of the positive first lens group  10  to the focal length of the entire telescopic zoom lens system at the long focal length extremity. 
         [0085]    If the positive refractive power df the rear sub-lens group  10 R becomes weaker to the extent that f1R/ft exceeds the upper limit of condition (1), the travelling distance of the rear sub-lens group  10 R upon focusing becomes longer. Consequently, a position (from the optical axis) where a bundle of off-axis light rays passes through the rear sub-lens group  10 R largely varies according to a focusing position of the rear sub-lens group  10 R, so that fluctuations in field curvature and fluctuations in off-axis coma become larger. 
         [0086]    If the positive refractive power of the rear sub-lens group  10 R becomes stronger to the extent that f1R/ft exceeds the lower limit of condition (1), the correcting of spherical aberration and coma becomes difficult. 
         [0087]    In the telescopic zoom lens system of the present invention, the positive fourth lens group  40  is preferably divided into the front sub-lens group  40 F and the rear sub-lens group  40 R at a maximum air-distance therebetween; and the rear sub-lens group  40 R preferably satisfies condition (2). 
         [0088]    If the positive refractive power of the rear sub-lens group  4 OR becomes weaker to the extent that f4R/fw exceeds the upper limit of condition (2), the correcting of distortion becomes insufficient. 
         [0089]    If the positive refractive power of the rear sub-lens group  40 R becomes stronger to the extent that f4R/fw exceeds the lower limit of condition (2), the correcting of spherical aberration and coma becomes difficult, 
         [0090]    Furthermore, a fixed-aperture diaphragm PS is preferably provided between the front sub-lens group  40 F and the rear sub-lens group  40 R of the positive fourth lens group  40 . By providing the fixed-aperture diaphragm FS in the positive fourth lens group  40  which is the most image-side lens group in the telescopic zoom lens system, a bundle of off-axis light rays can be effectively shielded, regardless of the focal length, at the rear sub-lens group  40 R which is position on the image-side of the fixed-aperture diaphragm FS. 
         [0091]    In the telescopic zoom lens system of the present invention, one of the positive lens elements in the positive first lens group  10  is preferably made of a glass material having an Abbe number of 80 or more. 
         [0092]    If plural positive lens elements are made of a glass material having an Abbe number of 80 or more are provided in the first lens group  10 , it is advantageous to correct axial chromatic aberration; however, the correcting of lateral chromatic aberration becomes difficult. 
         [0093]    Furthermore, a glass material having an Abbe number of 80 or more generally has large shape-deforming properties due to changes in temperature. 
         [0094]    In the telescopic zoom lens system according to the present invention, the positive lens elements of the positive first lens group  10  have large diameters. Therefore if plural positive lens elements are made of a glass material having an Abbe number of 80 or more, the changes in the focal length and the back focal distance due to changes in temperature, and the changes in aberrations due to changes in temperature becomes undesirably noticeable. 
         [0095]    In order to adequately correct spherical aberration and axial chromatic aberration, it is preferable that condition (3) be satisfied. 
         [0096]    If the positive refractive power of the positive first lens group  10  becomes weaker to the extent that f1/fw exceeds the upper limit of condition (3), the correcting of lateral chromatic aberration becomes insufficient. 
         [0097]    If the positive refractive power of the positive first lens group  10  becomes stronger to the extent that f1/fw exceeds the lower limit of condition (3), the correcting of spherical aberration and axial chromatic aberration becomes difficult. 
         [0098]    Specific numerical data of the embodiments will be described hereinafter. 
         [0099]    In the diagrams of spherical aberration and the sine condition, SA designates spherical aberration, and SC designates the sine condition. 
         [0100]    In the diagrams of chromatic aberration (axial chromatic aberration) represented by spherical aberration, the solid line and the two types of dotted lines respectively indicate spherical aberrations with respect to the d, g and C lines. 
         [0101]    In the diagrams of lateral chromatic aberration, the two types of dotted lines respectively indicate magnification with respect to the g and C lines; however, the d line as the base line coincides with the ordinate. 
         [0102]    In the diagrams of astigmatism, S designates the sagittal image, and M designates the meridional image. 
         [0103]    The tables, FNO. designates the f-number, f designates the focal length of the entire fisheye zoom lens system, W designates the half angle-of-view (°), fB designates the back focal distance, r designates the radius of curvature, d designates the lens-element thickness or a distance between lens elements (lens groups) which is variable upon zooming, N d  designates the refractive index of the d-line, and v designates the Abbe number. 
         [0104]    The values for the distance “d” are indicated in the order of the short focal length extremity, an intermediate focal length and the long focal length extremity. 
       Embodiment 1 
       [0105]      FIG. 1  is the lens arrangement of the telescopic zoom lens system, at the short focal length extremity.  FIGS. 2A through 2E  show aberrations occurred, at the short focal length extremity, in the lens arrangement shown in  FIG. 1 . 
         [0106]      FIG. 3  is the lens arrangement of the telescopic zoom lens system, at the long focal length extremity.  FIGS. 4A through 4E  show aberrations occurred, at the long focal length extremity, in the to lens arrangement shown in  FIG. 3 . 
         [0107]    Table 1 shows the numerical values of the first embodiment. 
         [0108]    The telescopic zoom lens system of the present invention includes a positive first lens group  10 , a negative second lens group  20 , a positive third lens group  30 , and a positive fourth lens group  40 , in this order from the object. 
         [0109]    The positive first lens group  10  includes cemented lens elements having a negative meniscus lens element having the convex surface fading toward the object and a positive meniscus lens element having the convex surface facing toward the object, a positive meniscus lens element having the convex surface facing toward the object, a negative meniscus lens element having the convex surface facing toward the object, and a positive biconvex lens element, in this order from the object. The three lens elements from the object constitute the front sub-lens group  10 F and the remaining lens elements constitute the rear sub-lens group  10 R. 
         [0110]    The negative second lens group  20  includes a negative biconcave lens element, cemented lens elements having a negative biconcave lens element and a positive meniscus lens element having the convex surface facing toward the object, and a negative meniscus lens element having the convex surface facing toward the image, in this order from the object The positive third lens group  30  includes a positive meniscus lens element having the convex surface facing toward the image, and cemented lens elements having a positive biconvex lens element and a negative meniscus lens element having the convex surface facing toward the image, in this order from the object. 
         [0111]    The positive fourth lens group  40  includes a positive meniscus lens element having the convex surface facing toward the object, cemented lens elements having a positive biconvex lens element and a negative biconcave lens element, a positive biconvex lens element, a negative meniscus lens element having the convex surface facing toward the image, and a positive meniscus lens element having the convex surface facing toward the object, in this order from the object The three lens elements from the object constitute the front sub-lens group  40 F and the remaining lens elements constitute the rear sub-lens group  40 R. 
         [0112]    The variable-aperture diaphragm KS is provided 2.00 in front of surface No. 22 (the positive fourth lens group  40 ), and the fixed-aperture diaphragm FS is provided 4.00 behind surface No. 26. 
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 F = 1:2.9—2.9—2.9 
               
               
                 f = 51.50–100.00–146.00 (Zoom Ratio = 2.83) 
               
               
                 W = 15.8–8.0–5.5 
               
               
                 fB = 39.70—39.70—39.70 
               
             
          
           
               
                 Surf. No. 
                 r 
                 d 
                 N d   
                 ν 
               
               
                   
               
             
          
           
               
                 1 
                 117.259 
                 2.20 
                 1.77716 
                 46.0 
               
               
                 2 
                 56.610 
                 8.78 
                 1.48749 
                 70.2 
               
               
                 3 
                 514.871 
                 0.10 
                 — 
                 — 
               
               
                 4 
                 61.808 
                 6.59 
                 1.49700 
                 81.6 
               
               
                 5 
                 201.351 
                 13.04  
                 — 
                 — 
               
               
                 6 
                 53.555 
                 2.00 
                 1.84666 
                 23.8 
               
               
                 7 
                 42.355 
                 1.24 
                 — 
                 — 
               
               
                 8 
                 47.572 
                 8.69 
                 1.48749 
                 70.2 
               
               
                 9 
                 −1480.709 
                 1.50–21.11–27.55 
                 — 
                 — 
               
               
                 10 
                 −541.075 
                 1.20 
                 1.80400 
                 46.6 
               
               
                 11 
                 24.441 
                 5.51 
                 — 
                 — 
               
               
                 12 
                 −89.935 
                 1.20 
                 1.48749 
                 70.2 
               
               
                 13 
                 25.174 
                 4.60 
                 1.84666 
                 23.8 
               
               
                 14 
                 152.990 
                 2.87 
                 — 
                 — 
               
               
                 15 
                 −42.933 
                 1.20 
                 1.72916 
                 54.7 
               
               
                 16 
                 −345.673 
                 19.87–10.65–2.00 
                 — 
                 — 
               
               
                 17 
                 −25471.148 
                 2.94 
                 1.80610 
                 40.9 
               
               
                 18 
                 −94.400 
                 0.10 
                 — 
                 — 
               
               
                 19 
                 120.786 
                 5.60 
                 1.49700 
                 81.6 
               
               
                 20 
                 −28.577 
                 1.20 
                 1.80518 
                 25.4 
               
               
                 21 
                 −51.630 
                 13.60–3.21–5.42 
                 — 
                 — 
               
               
                 22 
                 100.269 
                 2.19 
                 1.65726 
                 34.4 
               
               
                 23 
                 280.987 
                 0.40 
                 — 
                 — 
               
               
                 24 
                 22.271 
                 8.26 
                 1.48749 
                 70.2 
               
               
                 25 
                 −1351.900 
                 1.40 
                 1.68965 
                 40.5 
               
               
                 26 
                 31.458 
                 14.93  
                 — 
                 — 
               
               
                 27 
                 135.502 
                 5.79 
                 1.58821 
                 39.4 
               
               
                 28 
                 −30.765 
                 3.61 
                 — 
                 — 
               
               
                 29 
                 −20.339 
                 1.20 
                 1.80100 
                 35.0 
               
               
                 30 
                 −63.586 
                 0.10 
                 — 
                 — 
               
               
                 31 
                 62.025 
                 3.40 
                 1.51633 
                 64.1 
               
               
                 32 
                 4807.794 
                 — 
                 — 
                 — 
               
               
                   
               
             
          
         
       
     
       Embodiment 2  
       [0113]      FIG. 5  is the lens arrangement of the telescopic zoom lens system, at the short focal length extremity.  FIGS. 6A through 6E  show aberrations occurred, at the short focal length extremity, in the lens arrangement shown in  FIG. 5 . 
         [0114]      FIG. 7  is the lens arrangement of the telescopic zoom lens system, at the long focal length extremity.  FIGS. 8A through 8E  show aberrations occurred, at the long focal length extremity, in the lens arrangement shown in  FIG. 7 . 
         [0115]    Table 2 shows the numerical values of the second embodiment 
         [0116]    The basic lens arrangement of the second embodiment is the same as that of the first embodiment. 
         [0117]    The variable diaphragm KS is provided 2.00 in front of surface No. 22 (the positive fourth lens group  40 ), and the fixed diaphragm FS is provided 3.00 behind surface No. 26. 
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 F = 1:2.9—2.9—2.9 
               
               
                 f = 51.50–100.00–145.50 (Zoom Ratio = 2.83) 
               
               
                 W = 15.9–8.0–5.5 
               
               
                 fB = 39.70—39.70—39.70 
               
             
          
           
               
                 Surf. No. 
                 r 
                 d 
                 N d   
                 ν 
               
               
                   
               
             
          
           
               
                 1 
                 120.112 
                 2.20 
                 1.74400 
                 44.8 
               
               
                 2 
                 57.176 
                 9.08 
                 1.48749 
                 70.2 
               
               
                 3 
                 342.241 
                 0.10 
                 — 
                 — 
               
               
                 4 
                 63.311 
                 6.72 
                 1.49700 
                 81.6 
               
               
                 5 
                 196.124 
                 14.96  
                 — 
                 — 
               
               
                 6 
                 56.412 
                 2.00 
                 1.80518 
                 25.4 
               
               
                 7 
                 44.128 
                 1.27 
                 — 
                 — 
               
               
                 8 
                 50.212 
                 8.57 
                 1.48749 
                 70.2 
               
               
                 9 
                 −1557.840 
                 1.50–22.56–29.75 
                 — 
                 — 
               
               
                 10 
                 −848.132 
                 1.20 
                 1.80400 
                 46.6 
               
               
                 11 
                 26.227 
                 4.37 
                 — 
                 — 
               
               
                 12 
                 −75.533 
                 1.20 
                 1.48749 
                 70.2 
               
               
                 13 
                 27.977 
                 4.60 
                 1.84666 
                 23.8 
               
               
                 14 
                 451.537 
                 2.50 
                 — 
                 — 
               
               
                 15 
                 −43.202 
                 1.20 
                 1.77250 
                 49.6 
               
               
                 16 
                 −269.577 
                 21.79–11.75–2.10 
                 — 
                 — 
               
               
                 17 
                 −716.034 
                 2.66 
                 1.78590 
                 44.2 
               
               
                 18 
                 −109.045 
                 0.10 
                 — 
                 — 
               
               
                 19 
                 142.314 
                 5.52 
                 1.49700 
                 81.6 
               
               
                 20 
                 −30.335 
                 1.20 
                 1.80518 
                 25.4 
               
               
                 21 
                 −53.835 
                 14.51–3.48–5.95 
                 — 
                 — 
               
               
                 22 
                 99.477 
                 2.44 
                 1.78590 
                 44.2 
               
               
                 23 
                 533.447 
                 0.40 
                 — 
                 — 
               
               
                 24 
                 22.108 
                 9.00 
                 1.49700 
                 81.6 
               
               
                 25 
                 −360.599 
                 1.90 
                 1.70000 
                 48.1 
               
               
                 26 
                 29.066 
                 13.22  
                 — 
                 — 
               
               
                 27 
                 82.537 
                 6.72 
                 1.56732 
                 42.8 
               
               
                 28 
                 −30.817 
                 3.24 
                 — 
                 — 
               
               
                 29 
                 −20.744 
                 1.20 
                 1.80100 
                 35.0 
               
               
                 30 
                 −63.956 
                 0.10 
                 — 
                 — 
               
               
                 31 
                 71.278 
                 2.25 
                 1.60562 
                 43.7 
               
               
                 32 
                 223.872 
                 — 
                 — 
                 — 
               
               
                   
               
             
          
         
       
     
       Embodiment 3 
       [0118]      FIG. 9  is the lens arrangement of the telescopic zoom lens system, at the short focal length extremity.  FIGS. 10A through 10E  show aberrations occurred, at the short focal length extremity, in the lens arrangement shown in  FIG. 9 . 
         [0119]      FIG. 11  is the lens arrangement of the telescopic zoom lens system, at the long focal length extremity.  FIGS. 12A through 12E  show aberrations occurred, at the long focal length extremity, in the lens arrangement shown in  FIG. 11 . 
         [0120]    Table 3 shows the numerical values of the third embodiment. 
         [0121]    The positive first lens group  10  includes cemented lens elements having a negative meniscus lens element having the convex surface facing toward the object and a positive meniscus lens element having the convex surface facing toward the object, a positive meniscus lens element having the convex surface facing toward the object, a negative meniscus lens element having the convex surface facing toward the object, and a positive meniscus lens element having the convex surface facing toward the object, in this order from the object. The three lens elements from the object constitute the front sub-lens group,  10 F and the remaining lens elements constitute the rear sub-lens group  10 R. 
         [0122]    The positive third lens group  30  includes a positive biconvex lens element, and cemented lens elements having a positive biconvex lens element and a negative meniscus lens element having the convex surface facing toward the image, in this order from the object. 
         [0123]    The remaining lens arrangement of the third embodiment is the same as that of the first embodiment. 
         [0124]    The variable-aperture diaphragm KS is provided 2.00 in front of surface No. 22 (the positive fourth lens group  40 ), and the fixed-aperture diaphragm FS is provided 3.50 behind surface No. 26. 
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 F = 1:2.9—2.9—2.9 
               
               
                 f = 51.50–85.00–131.00 (Zoom Ratio = 2.54) 
               
               
                 W = 16.8–10.2–6.6 
               
               
                 fB = 39.69—39.69—39.69 
               
             
          
           
               
                 Surf. No. 
                 r 
                 d 
                 N d   
                 ν 
               
               
                   
               
             
          
           
               
                 1 
                 96.690 
                 2.20 
                 1.74400 
                 44.8 
               
               
                 2 
                 53.418 
                 8.64 
                 1.48749 
                 70.2 
               
               
                 3 
                 187.506 
                 0.10 
                 — 
                 — 
               
               
                 4 
                 63.413 
                 6.84 
                 1.49700 
                 81.6 
               
               
                 5 
                 247.469 
                 14.39  
                 — 
                 — 
               
               
                 6 
                 55.107 
                 2.00 
                 1.80518 
                 25.4 
               
               
                 7 
                 42.296 
                 1.11 
                 — 
                 — 
               
               
                 8 
                 46.561 
                 8.94 
                 1.48749 
                 70.2 
               
               
                 9 
                 8488.074 
                 1.50–18.02–26.89 
                 — 
                 — 
               
               
                 10 
                 −240.375 
                 1.20 
                 1.80400 
                 46.6 
               
               
                 11 
                 25.128 
                 4.41 
                 — 
                 — 
               
               
                 12 
                 −61.757 
                 1.20 
                 1.48749 
                 70.2 
               
               
                 13 
                 27.287 
                 4.68 
                 1.84666 
                 23.8 
               
               
                 14 
                 337.845 
                 2.17 
                 — 
                 — 
               
               
                 15 
                 −45.767 
                 1.20 
                 1.77250 
                 49.6 
               
               
                 16 
                 −202.850 
                 18.04–11.60–2.80 
                 — 
                 — 
               
               
                 17 
                 336.148 
                 3.07 
                 1.80400 
                 46.6 
               
               
                 18 
                 −95.869 
                 0.10 
                 — 
                 — 
               
               
                 19 
                 229.790 
                 4.91 
                 1.49700 
                 81.6 
               
               
                 20 
                 −29.598 
                 1.20 
                 1.80518 
                 25.4 
               
               
                 21 
                 −53.537 
                 14.51–4.42–4.35 
                 — 
                 — 
               
               
                 22 
                 91.958 
                 2.29 
                 1.77250 
                 49.6 
               
               
                 23 
                 321.853 
                 0.20 
                 — 
                 — 
               
               
                 24 
                 21.190 
                 7.93 
                 1.49700 
                 81.6 
               
               
                 25 
                 −157.683 
                 1.20 
                 1.66672 
                 48.3 
               
               
                 26 
                 26.183 
                 12.95  
                 — 
                 — 
               
               
                 27 
                 79.584 
                 5.92 
                 1.58144 
                 40.7 
               
               
                 28 
                 −28.507 
                 2.79 
                 — 
                 — 
               
               
                 29 
                 −20.892 
                 1.20 
                 1.80100 
                 35.0 
               
               
                 30 
                 −59.213 
                 0.10 
                 — 
                 — 
               
               
                 31 
                 105.684 
                 2.07 
                 1.51633 
                 64.1 
               
               
                 32 
                 458.366 
                 — 
                 — 
                 — 
               
               
                   
               
             
          
         
       
     
       Embodiment 4  
       [0125]      FIG. 13  is the lens arrangement of the telescopic zoom lens system, at the short focal length extremity.  FIGS. 14A through 14E  show aberrations occurred, at the short focal length extremity, in the lens arrangement shown in  FIG. 13 . 
         [0126]      FIG. 15  is the lens arrangement of the telescopic zoom lens system, at the long focal length extremity.  FIGS. 16A through 16E  show aberrations occurred, at the long focal length extremity, in the lens arrangement shown in  FIG. 15 . 
         [0127]    Table  4  shows the numerical values of the fourth embodiment. 
         [0128]    The positive third lens group  30  includes a positive biconvex lens element, and cemented lens elements having a positive biconvex lens element and a negative meniscus lens element having the convex surface facing toward the image, in this order from the object. 
         [0129]    The positive fourth lens group  40  includes a positive meniscus lens element having the convex surface facing toward the object, cemented lens elements having a positive biconvex lens element and a negative biconcave lens element, a positive biconvex lens element, a negative meniscus lens element having the convex surface facing toward the image, and a positive biconvex lens element, in this order from the object. The three lens elements from the object constitute the front sub-lens group  40 F and the remaining lens elements constitute the rear sub-lens group  40 R. 
         [0130]    The remaining lens arrangement of the fourth embodiment is the same as that of the first embodiment. 
         [0131]    The variable-aperture diaphragm KS is provided 1.00 in front of surface No. 22 (the positive fourth lens group  40 ), and the fixed-aperture diaphragm FS is provided 3.00 behind surface No. 26. 
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 F = 1:2.9—2.9—2.9 
               
               
                 f = 51.50–85.00–131.00 (Zoom Ratio = 2.54) 
               
               
                 W = 16.8–10.1–6.6 
               
               
                 fB = 39.70—39.70—39.70 
               
             
          
           
               
                 Surf. No. 
                 r 
                 d 
                 N d   
                 ν 
               
               
                   
               
             
          
           
               
                 1 
                 95.120 
                 2.30 
                 1.74400 
                 44.8 
               
               
                 2 
                 52.415 
                 8.42 
                 1.48749 
                 70.2 
               
               
                 3 
                 178.821 
                 0.10 
                 — 
                 — 
               
               
                 4 
                 62.843 
                 6.72 
                 1.49700 
                 81.6 
               
               
                 5 
                 223.592 
                 15.13  
                 — 
                 — 
               
               
                 6 
                 55.545 
                 2.00 
                 1.80518 
                 25.4 
               
               
                 7 
                 42.737 
                 1.17 
                 — 
                 — 
               
               
                 8 
                 47.601 
                 8.75 
                 1.48749 
                 70.2 
               
               
                 9 
                 −3615.125 
                 1.70–18.38–27.46 
                 — 
                 — 
               
               
                 10 
                 −241.157 
                 1.20 
                 1.80400 
                 46.6 
               
               
                 11 
                 25.125 
                 4.70 
                 — 
                 — 
               
               
                 12 
                 −52.450 
                 1.20 
                 1.48749 
                 70.2 
               
               
                 13 
                 28.699 
                 5.66 
                 1.84666 
                 23.8 
               
               
                 14 
                 340.364 
                 1.94 
                 — 
                 — 
               
               
                 15 
                 −47.319 
                 1.20 
                 1.74320 
                 49.3 
               
               
                 16 
                 −123.977 
                 17.51–10.79–1.50 
                 — 
                 — 
               
               
                 17 
                 226.079 
                 2.73 
                 1.77250 
                 49.6 
               
               
                 18 
                 −102.714 
                 0.10 
                 — 
                 — 
               
               
                 19 
                 753.451 
                 4.48 
                 1.49700 
                 81.6 
               
               
                 20 
                 −30.585 
                 1.20 
                 1.80518 
                 25.4 
               
               
                 21 
                 −53.883 
                 13.15–3.19–3.39 
                 — 
                 — 
               
               
                 22 
                 81.191 
                 2.49 
                 1.77250 
                 49.6 
               
               
                 23 
                 494.973 
                 0.31 
                 — 
                 — 
               
               
                 24 
                 21.664 
                 7.44 
                 1.49700 
                 81.6 
               
               
                 25 
                 −91.189 
                 1.22 
                 1.65844 
                 50.9 
               
               
                 26 
                 25.338 
                 14.53  
                 — 
                 — 
               
               
                 27 
                 105.893 
                 5.88 
                 1.60562 
                 43.7 
               
               
                 28 
                 −27.998 
                 2.79 
                 — 
                 — 
               
               
                 29 
                 −21.830 
                 2.10 
                 1.80100 
                 35.0 
               
               
                 30 
                 −65.262 
                 0.11 
                 — 
                 — 
               
               
                 31 
                 109.134 
                 2.07 
                 1.48749 
                 70.2 
               
               
                 32 
                 −2798.868 
                 — 
                 — 
                 — 
               
               
                   
               
             
          
         
       
     
       Embodiment 5  
       [0132]      FIG. 17  is the lens arrangement of the telescopic zoom lens system, at the short focal length extremity.  FIGS. 18A through 18E  show aberrations occurred, at the short focal length extremity, in the lens arrangement shown in  FIG. 17 . 
         [0133]      FIG. 19  is the lens arrangement of the telescopic zoom lens system, at the long focal length extremity.  FIGS. 20A through 20E  show aberrations occurred, at the long focal length extremity, in the lens arrangement shown in  FIG. 19 . 
         [0134]    Table 5 shows the numerical values of the fifth embodiment. 
         [0135]    The positive third lens group  30  includes a positive biconvex lens element, and cemented lens elements having a positive meniscus lens element having the convex surface facing toward the image and a negative meniscus lens element having the convex surface facing toward the image, in this order from the object, 
         [0136]    The remaining lens arrangement of the fifth embodiment is the same as that of the first embodiment. 
         [0137]    The variable diaphragm KS is provided 1.00 in front of surface No. 22 (the positive fourth lens group  40 ), and the fixed diaphragm FS is provided 3.50 behind surface No. 26. 
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 F = 1:2.9—2.9—2.9 
               
               
                 f = 51.50–85.00–131.00 (Zoom Ratio = 2.54) 
               
               
                 W = 16.8–10.1–6.6 
               
               
                 fB = 39.70—39.70—39.70 
               
             
          
           
               
                 Surf. No. 
                 r 
                 d 
                 N d   
                 ν 
               
               
                   
               
             
          
           
               
                 1 
                 105.398 
                 2.30 
                 1.74400 
                 44.8 
               
               
                 2 
                 56.082 
                 7.84 
                 1.48749 
                 70.2 
               
               
                 3 
                 180.272 
                 0.10 
                 — 
                 — 
               
               
                 4 
                 66.104 
                 6.43 
                 1.49700 
                 81.6 
               
               
                 5 
                 230.241 
                 15.23  
                 — 
                 — 
               
               
                 6 
                 54.225 
                 2.00 
                 1.80518 
                 25.4 
               
               
                 7 
                 42.675 
                 1.05 
                 — 
                 — 
               
               
                 8 
                 48.313 
                 8.82 
                 1.48749 
                 70.2 
               
               
                 9 
                 −1617.704 
                 2.30–19.73–29.44 
                 — 
                 — 
               
               
                 10 
                 −181.711 
                 1.20 
                 1.80400 
                 46.6 
               
               
                 11 
                 26.585 
                 4.85 
                 — 
                 — 
               
               
                 12 
                 −50.615 
                 1.20 
                 1.48749 
                 70.2 
               
               
                 13 
                 30.138 
                 3.60 
                 1.84666 
                 23.8 
               
               
                 14 
                 311.871 
                 1.65 
                 — 
                 — 
               
               
                 15 
                 −52.317 
                 1.10 
                 1.72916 
                 54.7 
               
               
                 16 
                 −100.273 
                 19.04–11.78–1.50 
                 — 
                 — 
               
               
                 17 
                 174.749 
                 2.14 
                 1.77250 
                 49.6 
               
               
                 18 
                 −174.749 
                 1.06 
                 — 
                 — 
               
               
                 19 
                 −4485.526 
                 4.73 
                 1.49700 
                 81.6 
               
               
                 20 
                 −29.038 
                 1.10 
                 1.80518 
                 25.4 
               
               
                 21 
                 −49.755 
                 13.18–3.01–3.58 
                 — 
                 — 
               
               
                 22 
                 73.832 
                 2.65 
                 1.77250 
                 49.6 
               
               
                 23 
                 743.114 
                 0.50 
                 — 
                 — 
               
               
                 24 
                 22.109 
                 7.93 
                 1.49700 
                 81.6 
               
               
                 25 
                 −105.602 
                 1.58 
                 1.65844 
                 50.9 
               
               
                 26 
                 24.579 
                 14.57  
                 — 
                 — 
               
               
                 27 
                 120.433 
                 5.20 
                 1.60562 
                 43.7 
               
               
                 28 
                 −28.928 
                 3.00 
                 — 
                 — 
               
               
                 29 
                 −22.288 
                 1.24 
                 1.80100 
                 35.0 
               
               
                 30 
                 −67.039 
                 0.65 
                 — 
                 — 
               
               
                 31 
                 95.907 
                 2.07 
                 1.48749 
                 70.2 
               
               
                 32 
                 3646.801 
                 — 
                 — 
                 — 
               
               
                   
               
             
          
         
       
     
         [0138]    The numerical values of each condition for each embodiment are shown in Table 6. 
         [0000]    
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
                 TABLE 6 
               
               
                   
                   
               
               
                   
                 Embod. 1 
                 Embod. 2 
                 Embod. 3 
                 Embod. 4 
                 Embod. 5 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Cond. (1) 
                 2.94 
                 3.12 
                 3.14 
                 3.13 
                 2.97 
               
               
                 Cond. (2) 
                 2.94 
                 2.85 
                 2.32 
                 2.12 
                 2.30 
               
               
                 Cond. (3) 
                 1.64 
                 1.77 
                 1.71 
                 1.74 
                 1.79 
               
               
                   
               
             
          
         
       
     
         [0139]    As can be understood from Table 6, the first through fifth embodiments satisfy conditions (1) through (3). Furthermore, as can be understood from the aberration diagrams, the various aberrations are adequately corrected. 
         [0140]    According to the description, a miniaturized telescopic zoom lens system having the following features can be attained;
       (i) an angle-of-view of approximately 10° to 30° (the zoom ratio: a little less than 3);   (ii) a long back focal distance;   (iii) a short focal length;   (iv) high optical quality; and   (v) high operability.