# Patent

## Title
Zoom lens and imaging apparatus

## Abstract

A zoom lens substantially consists of, in order from the object side, a positive first lens group, a negative second lens group, a positive third lens group, a positive fourth lens group, and a negative fifth lens group. When varying magnification, the distances between adjacent lens groups are changed, while all of the lens groups are moved with respect to an image formation position. If fw represents the focal length of the entire lens system at the wide angle end, f4 represents the focal length of the fourth lens group, F5 represents the focal length of the fifth lens group, and β5T is an image formation magnification of the fifth lens group when focusing on infinity at the telephoto end, formula (J): 0.50<fw/f4<0.65, formula (K): −0.32<fw/f5<−0.15, and (C): −6.0<1−(β5T)2<−2.5 are simultaneously satisfied.

## Background
CROSS REFERENCE TO RELATED APPLICATION
This application is a continuation of PCT/JP2012/003918 filed on Jun. 15, 2012, which claims foreign priority to Japanese Application No. 2011-137065 filed on Jun. 21, 2011. The entire contents of each of the above applications are hereby incorporated by reference.


BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a zoom lens having a high variable magnification ratio used in electronic cameras such as digital cameras, video cameras, broadcasting cameras, surveillance cameras and the like, and to an imaging apparatus including the zoom lens.
2. Description of the Related Art
Conventionally, a zoom lens substantially consists of: a first lens group having positive refractive power; a second lens group having negative refractive power; a third lens group having positive refractive power; a fourth lens group having positive refractive power; and a fifth lens group having negative refractive power, which are arranged in this order from the object side, is known as a zoom lens having relatively a high variable magnification ratio. The zoom lens with such a lens construction is known to be appropriate for realizing both a high variable magnification ratio and a reduction in size (see Japanese Unexamined Patent Publication No. 4(1992)-070707, U.S. Pat. No. 5,872,659, and Japanese Unexamined Patent Publication No. 11(1999)-064728).
SUMMARY OF THE INVENTION
Recently, there is demand for a zoom lens, which is compact, and yet has a high variable magnification ratio, e.g., a zoom lens which has a high variable magnification ratio of over 12×, and yet which is compact and capable of high performance.
However, conventionally known compact and high performance zoom lenses, e.g., the zoom lenses disclosed in Japanese Unexamined Patent Publication No. 4(1992)-070707, U.S. Pat. No. 5,872,659, and Japanese Unexamined Patent Publication No. 11(1999)-064728), have variable magnification ratios of less than 10×, and cannot necessarily be said to have high variable magnification ratios.
The present invention has been developed in view of the foregoing circumstances. It is an object of the present invention to provide a zoom lens, which has a high variable magnification ratio, and yet which is compact and capable of high performance, and an imaging apparatus including the zoom lens.
A zoom lens of the present invention substantially consists of:
a first lens group having positive refractive power;
a second lens group having negative refractive power;
a third lens group having positive refractive power;
a fourth lens group having positive refractive power; and
a fifth lens group having negative refractive power, which are arranged in this order from an object side,
wherein when varying magnification from a wide angle end to a telephoto end, the distance between the first lens group and the second lens group is consistently increased, the distance between the second lens group and the third lens group is consistently decreased, the distance between the third lens group and the fourth lens group is consistently decreased, and the distance between the fourth lens group and the fifth lens group is changed, while all of the lens groups are moved with respect to an image formation position,
wherein the following formulas (J) and (K) are simultaneously satisfied:

0.50<fw/f4<0.65  (J)

−0.32<fw/f5<−0.15  (K), where

fw is a focal length of the entire lens system at the wide angle end; f4 is a focal length of the fourth lens group; and f5 is a focal length of the fifth lens group.
The zoom lens can be substantially composed of five lens groups. In this case, the expression “zoom lens which is substantially composed of n lens groups” refers to a zoom lens that includes lenses substantially without any refractive power; optical elements other than lenses such as apertures and glass covers; and mechanical components such as lens flanges, lens barrels, imaging elements, and camera shake correction mechanisms; in addition to the n lens groups.
It is more desirable for the zoom lens to satisfy formula (J′): 0.60<fw/f4<0.65 and/or formula (K′): −0.32<fw/f5<−0.20.
It is desirable that when the point of focus is shifted from an infinity side to a near side and focused, only the fifth lens group is shifted to the image side.
It is desirable for the zoom lens to satisfy formula (C): 6.0<1−(β5T)2<−2.5, and more desirable to satisfy formula (C′): −5.5<1−(β5T)2<−2.9, wherein β5T is an image formation magnification of the fifth lens group when focusing on infinity at the telephoto end.
An imaging apparatus of the present invention is equipped with the zoom lens of the present invention.
The zoom lens and the imaging apparatus including the zoom lens according to the present invention substantially consists of:
a first lens group having positive refractive power;
a second lens group having negative refractive power;
a third lens group having positive refractive power;
a fourth lens group having positive refractive power; and
a fifth lens group having negative refractive power, which are arranged in this order from the object side of the zoom lens,
wherein when varying magnification from the wide angle end to the telephoto end, a distance between the first lens group and the second lens group is consistently increased, a distance between the second lens group and the third lens group is consistently decreased, a distance between the third lens group and the fourth lens group is consistently decreased, and a distance between the fourth lens group and the fifth lens group is changed such that each of the lens groups is moved with respect to an image formation position,
wherein the following formulas (J): 0.50<fw/f4<0.65 and (K): −0.32<fw/f5<−0.15 are simultaneously satisfied. This enables the zoom lens to have a high variable magnification ratio, and yet to be compact and capable of high performance.
Thus, for example, a zoom lens which has a full angle of view at a wide angle end exceeding 75°, that is, a large angle of view, and which further has a high variable magnification ratio exceeding 12×, and yet is compact and capable of high performance can be obtained.
Formula (J) regulates the ratio of the focal length of the entire lens system at a wide angle end to the focal length of the fourth lens group. If the zoom lens is constructed in such a manner that the value of fw/f4 is less than the lower limit defined by formula (J), the positive refractive power of the fourth lens group will be excessively reduced, which will increase the amount of movement of the fourth lens group when magnification is varied. This will cause a problem that the total length of the optical system will become great at the telephoto end. If the zoom lens is constructed in such a manner that the value of fw/f4 exceeds the upper limit defined by formula (J), the positive refractive power of the fourth lens group will be forced to be too strong. This will causes a problem of difficulties in maintaining optical performance when magnification is varied.
Formula (K) regulates the ratio of the focal length of the entire lens system at a wide angle end to the focal length of the fifth lens group. If the zoom lens is constructed in such a manner that the value of fw/f5 is less than the lower limit defined by formula (K), the negative refractive power of the fifth lens group will be excessively increased, which will causes a problem that the back focus length will becomes longer and the entire length of the optical system will become great. If the zoom lens is constructed in such a manner that the value of fw/f5 exceeds the upper limit defined by formula (K), negative refractive power of the fifth lens group 5G will be excessively reduced, which will diminish the back focus length. This will cause a problem that spaces for a mirror of a single-lens reflex camera, a filter, and the like cannot be secured, when using this zoom lens equipped with the single-lens reflex camera, for example. In addition, the amount of shift of the fifth lens group 5G will be increased at the time of focus, and further the outer diameters of the lenses of the fifth lens group will become great. This increases the burden on the focusing mechanism so that it will become difficult to achieve high-speed focus, for example.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic cross sectional diagram illustrating the structure of a zoom lens and an imaging apparatus including the zoom lens according to an embodiment of the present invention;
FIG. 2A is a cross sectional diagram illustrating a zoom lens of Example 1;
FIG. 2B is a cross sectional diagram illustrating each of a case that a zoom setting of the zoom lens of Example 1 is set to a wide angle end and a case that a zoom setting thereof is set to a telephoto end;
FIG. 3A is a cross sectional diagram illustrating a zoom lens of Example 2;
FIG. 3B is a cross sectional diagram illustrating each of a case that a zoom setting of the zoom lens of Example 2 is set to the wide angle end and a case that a zoom setting thereof is set to the telephoto end;
FIG. 4A is a cross sectional diagram illustrating a zoom lens of Example 3;
FIG. 4B is a cross sectional diagram illustrating each of a case that a zoom setting of the zoom lens of Example 3 is set to the wide angle end and a case that a zoom setting thereof is set to the telephoto end;
FIG. 5A is a cross sectional diagram illustrating a zoom lens of Example 4;
FIG. 5B is a cross sectional diagram illustrating each of a case that a zoom setting of the zoom lens of Example 4 is set to the wide angle end and a case that a zoom setting thereof is set to the telephoto end;
FIG. 6A is a cross sectional diagram illustrating a zoom lens of Example 5;
FIG. 6B is a cross sectional diagram illustrating each of a case that a zoom setting of the zoom lens of Example 5 is set to the wide angle end and a case that a zoom setting thereof is set to the telephoto end;
FIG. 7 is an aberration diagram of Example 1;
FIG. 8 is an aberration diagram of Example 2;
FIG. 9 is an aberration diagram of Example 3;
FIG. 10 is an aberration diagram of Example 4; and
FIG. 11 is an aberration diagram of Example 5.



DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, the zoom lens and the imaging apparatus including the lens of the present invention will be described with reference to the attached drawings.
FIG. 1 is a schematic cross sectional diagram illustrating the structure of a zoom lens and an imaging apparatus including the zoom lens according to an embodiment of the present invention.
The zoom lens 100 as shown in the Figure has a high variable magnification ratio, and yet is compact and capable of high performance. The imaging apparatus 200 equipped with the zoom lens 100 is used as a digital still camera, a video camera, a surveillance camera or the like.
The zoom lens 100 is composed of a first lens group 1G having positive refractive power, a second lens group 2G having negative refractive power, a third lens group 3G having positive refractive power, a fourth lens group 4G having positive refractive power, and a fifth lens group 5G having negative refractive power, in this order from an object side (the side of −Z in the Figures).
The zoom lens 100 consistently increases a distance δ12 between the first lens group 1G and the second lens group 2G, consistently decreases a distance δ23 between the second lens group 2G and the third lens group 3G, consistently decreases a distance δ34 between the third lens group 3G and the fourth lens group 4G, and changes a distance δ45 between the fourth lens group 4G and the fifth lens group 5G, while all of the lens groups 1G through 5G are moved with respect to an image formation surface Mk which is an image formation position of the zoom lens 100, when zooming from the wide angle end to the telephoto end (continuously varying magnification). The zoom lens is constructed to satisfy formulas (J): 0.50<fw/f4<0.65 and (K): −0.32<fw/f5<−0.15 are simultaneously satisfied, where fw is a focal length of the entire lens system at the wide angle end; f4 is a focal length of the fourth lens group; and f5 is a focal length of the fifth lens group.
In such a manner, the basic configuration of the zoom lens 100 is described above.
It is desirable that when the point of focus of the zoom lens 100 is shifted from the infinity side to the near side and focused, only the fifth lens group is moved toward the image side. This enables a focusing group (the fifth lens group 5G) to achieve a reduction in a size and weight, thereby reducing the burden on the focusing mechanism and achieving high-speed focus.
It is more desirable for the zoom lens 100 to satisfy formula (J′): 0.60<fw/f4<0.65 and/or formula (K′): −0.32<fw/f5<−0.20.
Further, it is desirable for the zoom lens 100 to satisfy formula (C): 6.0<1−(β5T)2<−2.5, and more desirably, formula (C′): −5.5<1−(β5T)2<−2.9, where β5T is an image formation magnification of the fifth lens group 5G when focusing on infinity at the telephoto end.
Formula (C) regulates the sensitivity to image shift with respect to a focal shift at the time of focusing on infinity at the telephoto end in the fifth lens group 5G. If the zoom lens 100 is constructed in such a manner that the value of 1−(β5T)2 is lower than the lower limit defined by formula (C), the sensitivity to the image shift with respect to the focal shift of the fifth lens group 5G at the telephoto end will be excessively increased, which causes the amount of amplitude shift of the fifth lens group 5G for finding the best point of focus to be excessively reduced. As a result, problems such that it will become difficult to perform focus control, for example, the focal shift of the fifth lens group 5G becoming suspended, will arise. If the zoom lens 100 is constructed in such a manner that the value of 1−(β5T)2 exceeds the upper limit defined by formula (C), the sensitivity of the image shift with respect to the focal shift of the fifth lens group 5G will be acceptable at the telephoto end, but the sensitivity at the wide angle end will be excessively reduced. This will cause the amount of amplitude shift of the fifth lens group 5G for finding the best point of focus to be excessively increased. As a result, for example, problems, that abnormal noises are made by the focusing mechanism at the time of the focus shift, will arise.
The imaging apparatus 200 illustrated in FIG. 1 includes the zoom lens 100, and an imaging element 210 constituted of a CCD which images an optical image Hk (an optical image representing a subject H) formed through the zoom lens 100, a CMOS or the like. An imaging surface 211 of the imaging element 210 is an image formation position (an image formation surface Mk) of the imaging lens 100.
In this case, an optical member Dg is disposed between the most-image-side lens (as indicated by the item Se in the zoom lens 100 of FIG. 1) and the imaging surface 211.
Various optical members may be employed as the optical member Dg depending on the configuration of the imaging apparatus 200 with which the imaging lens 100 is equipped. For example, a single or a plurality of a member or members that correspond(s) to an imaging surface protection cover glass, an infrared cut filter, an ND filter and the like may be provided.
Hereinafter, Examples 1 through 5 of the zoom lens of the present invention will be specifically described with reference to FIGS. 2A, 2B . . . 6A, 6B, 7 . . . 11 and the like.
Each zoom lens of Examples 1 through 5 satisfies the configuration of the zoom lens 100 and includes the following constituent elements.
Each zoom lens of Examples 1 through 5 is constituted by a first lens group 1G consisting of three lenses, a second lens group 2G consisting of four lenses, a third lens group 3G consisting of five lenses, a fourth lens group 4G consisting of three lenses, and a fifth lens group 5G consisting of two lenses.
In the first lens group 1G, a first group-first lens L1, a first group-second lens L2, and a first group-third lens L3 are arranged in this order from the object side.
Further, in the second lens group 2G, a second lens group-first lens L4, a second lens group-second lens L5, a second lens group-third lens L6, and a second lens group-fourth lens L7 are arranged in this order from the object side.
Further, in the third lens group 3G, a third lens group-first lens L8, a third lens group-second lens L9, a third lens group-third lens L10, a third lens group-fourth lens L11, and a third lens group-fifth lens L12 are arranged in this order from the object side.
In the fourth lens group 4G, a fourth lens group-first lens L13, a fourth lens group-second lens L14, and a fourth lens group-third lens L15 are arranged in this order from the object side.
Further, in the fifth lens group 5G, a fifth group-first lens L16, and a fifth group-second lens L17 are arranged in this order from the object side.
The third lens group 3G consisting of five lenses as described above, is constructed to have three lenses (a third-a lens group 3aG having positive refractive power) arranged closest to the object side and two lenses arranged closest to the image side (a third-b lens group 3bG). The third-b lens group 3bG is constructed to be movable in a direction perpendicular to an optical axis (a direction in which an X-Y plane extends), which enables a camera shake correction function to work.
In this case, the third-a lens group 3aG consists of the third group-first lens L8, the third group-second lens L9, and the third group-third lens L10, and the third-b lens group 3bG consists of the third group-fourth lens L11 and the third group-fifth lens L12.
An aperture stop St is disposed between the second lens group 2G and the third lens group 3G and is designed to be moved in an optical axis direction Z1, integrally with the third lens group 3G at the time of varying magnification.
Example 1
FIGS. 2A and 2B illustrate a zoom lens of Example 1. FIG. 2A is a detailed diagram illustrating the configuration of the zoom lens of Example 1. FIG. 2B illustrates a state in which the zoom setting of the zoom lens of Example 1 is set to the wide angle end (as indicated by “WIDE” in the Figure) at the upper part and a state in which the zoom setting thereof is set to the telephoto end (as indicated by “TELE” in the Figure) at the bottom part. Further, arrows indicate the paths of movements of the lens groups, respectively when magnification is changed from the wide angle end to the telephoto end.
In the fifth lens group 5G of the zoom lens of Example 1, two lenses, i.e., a negative lens and a positive lens are arranged in this order from the object side.
Further, Table 1A to be described later shows various data related to the zoom lens of Example 1. The upper part of Table 1A shows lens data, the middle part shows schematic specifications of the zoom lens, and the bottom part shows the focal length of each lens group.
In the lens data at the upper part of Table 1A, a surface number i represents the i-th (i=1, 2, 3, . . . ) lens surface or the like, and the number sequentially increases from the most-object side toward the image side. The aperture stop St and the optical member Dg are also listed in these lens data.
Radius Ri of curvature represents the radius of curvature of the i-th surface (i=1, 2, 3, . . . ). Distance Di between surfaces (i=1, 2, 3, . . . ) represents a distance between the i-th surface and an (i+1)th surface on the optical axis Z1. The item Ri and the item Di in the lens data correspond to the item Si (i=1, 2, 3, . . . ) representing a lens surface or the like.
In the column of distance Di between surfaces (i=1, 2, 3, . . . ), there are a case in which numeral values representing a distance between surfaces are listed and a case in which the item Dm (m is an integral number). Numbers in the item Dm correspond to a distance between surfaces (spatial distance), between the lens groups, and the distance between surfaces (spatial distance) varies depending on variable magnification ratios (zoom magnification).
Further, the item Nj represents the refractive index of a j-th (j=1, 2, 3, . . . ) optical element with respect to wavelength of 587.6 nm (the d-line), and numbers sequentially increase from the object side toward the image side. The item νj represents the Abbe number of the j-th optical element based on the d-line.
In the lens data of Table 1A, the unit of the radius of curvature and the distances between surfaces is mm. The radius of curvature is positive when a convex surface faces the object side and is negative when a convex surface faces the image side.
The optical system as described above is generally capable of maintaining a predetermined performance level in any of cases where the size of optical elements such as a lens or the like is proportionately increased or decreased, and therefore zoom lens in which the numbers of the entire lens data are proportionately increased or decreased can be Examples related to the present invention as well.
The middle part of Table 1A represents each value of a wide angle end (WIDE), the middle of varying magnification (MID), and a telephoto end (TELE), i.e., distances between lens groups: D5, D13, D23, D28 and D32; f: the focal length of the entire lens system (unit mm of each value); Fno: F number; and 2ω: whole angles of view (in “°” units).
Further, the bottom part of Table 1A represents the focal length of each group. In this case, f1: the focal length of the first lens group 1G, f2: the focal length of the second lens group 2G, f3: the focal length of the third lens group 3G, f4: the focal length of the fourth lens group 4G, f5: the focal length of the fifth lens group 5G, f3a: the focal length of the third-a lens group 3aG, and f3b: the focal length of the third-b lens group 3bG.
The term “the third-b group (OIS)” (OIS: Optical Image Stabilization) described in Table 1A represents being capable of achieving the performance of the camera shake correction function by allowing the third-b lens group 3bG to move in a direction perpendicular to the optical axis (in a direction to which X-Y plane extends).







TABLE 1A





EXAMPLE 1




















SURFACE




GROUP


NUMBER
Ri
Di
Nj
νj
STRUCTURE





1
85.7554
1.950
1.84661
23.9
FIRST GROUP


2
62.5697
9.119
1.49700
81.5


3
−31126.9375
0.100


4
77.2118
4.299
1.61800
63.3


5
186.7731
D5


6
108.0235
1.350
1.88300
40.8
SECOND


7
18.6071
8.337


GROUP


8
−55.8960
1.000
1.88300
40.8


9
66.9403
0.700


10
37.4987
6.589
1.84661
23.9


11
−38.9747
0.362


12
−34.0881
1.000
1.75500
52.3


13
105.4506
D13


(APERTURE
∞
1.000


THIRD-a


STOP) 14




GROUP


15
33.7005
3.568
1.56732
42.8


16
−52.6106
0.363


17
28.4699
4.073
1.49700
81.5


18
−32.0211
0.900
1.90366
31.3


19
211.4451
2.505


*20
−67.2274
1.500
1.80348
40.4
THIRD-b


21
24.5327
1.041


GROUP (OIS)


22
27.2898
2.358
1.84661
23.9


23
69.3194
D23


*24
49.0350
4.377
1.51560
63.1
FOURTH


*25
−43.0727
0.169


GROUP


26
46.1728
1.000
1.84661
23.9


27
22.9572
6.496
1.51680
64.2


28
−48.8859
D28


*29
85.0541
1.500
1.80348
40.4
FIFTH


*30
20.5630
0.099


GROUP


31
19.5078
2.277
1.92286
20.9


32
25.9096
D32


33
∞
3.700
1.51680
64.2
Dg


34
∞
















WIDE
MID
TELE







D5
0.950
32.298
66.596



D13
42.834
15.932
3.617



D23
12.578
6.213
3.622



D28
2.153
3.937
1.901



D32
35.505
66.444
82.661



f
18.384
67.549
248.190



Fno
3.60
5.48
6.49



2ω [°]
76.61
22.49
6.22



f1
111.303



f2
−17.195



f3
89.768



f4
28.523



f5
−59.029



f3a
33.607



f3b (OIS)
−39.462










Table 1B shows aspheric coefficients of aspheric surfaces of the zoom lens of Example 1. In the lens data of Table 1A, the mark “*” attached to a surface number indicates that a surface represented by the surface number is an aspheric surface. Further, Table 1B shows the aspheric coefficients of aspheric surfaces corresponding to these surface numbers.
The aspheric coefficients represented in Table 1B are prepared to define aspheric shapes by being applied in the following aspheric equation.

Z=C·h2/{1+(1−K·C2·h2)1/2}+ΣAn·hn  [Aspheric Equation 1]

where

    Z: the depth of an aspheric surface (mm)
    h: the distance from the optical axis to a lens surface (height) (mm)
    K: aspheric coefficients representing quadric surface
    C: paraxial curvature=1/R (R: paraxial curvature radius)
    An: n-dimensional (n is an integer not less than three) aspheric coefficient









TABLE 1B







ASPHERIC COEFFICIENT









SURFACE NUMBER












SIGN
*20
*24
*25
*29
*30















K
1.000000E+00
1.000000E+00
1.000000E+00
1.000000E+00
1.000000E+00


A3
−6.660863E−06
2.113073E−05
1.195308E−05
6.668667E−07
1.051388E−05


A4
1.068409E−05
−1.787018E−05
9.213718E−07
−1.182857E−07
−3.423284E−06


A5
−6.114474E−07
−3.133994E−07
2.202715E−08
−9.254225E−09
7.184053E−07


A6
3.008719E−08
1.883512E−07
−6.561077E−10
−4.950193E−10
−1.065630E−08


A7
2.785752E−09
−2.494012E−08
−1.302087E−10
−1.901654E−11
−4.565539E−09


A8
−7.187710E−11
1.247161E−09
−1.087276E−11
−1.551834E−13
−1.629647E−11


A9
−1.749371E−11
9.724427E−14
−6.432469E−13
7.118640E−14
4.500121E−11


A10
5.214071E−13
−1.350450E−12
−2.148723E−14
1.063682E−14
−1.679259E−12


A11
−9.928876E−17
9.672666E−16
−1.039705E−15
1.136476E−15
1.043516E−15


A12
−1.891767E−16
1.223378E−17
−3.166091E−17
1.069028E−16
7.735059E−17


A13
−6.521684E−17
−4.164422E−18
1.294460E−18
9.376248E−18
6.733229E−18


A14
−1.390141E−17
−7.285136E−19
3.747765E−19
7.834346E−19
6.654046E−19


A15
−1.714540E−18
7.231878E−20
8.216610E−20
2.319643E−19
2.466336E−19


A16
−2.682522E−19
4.235680E−21
9.394894E−21
1.747560E−20
2.657868E−20









FIG. 7 is a diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration at each of a wide angle end (WIDE), the middle of varying magnification (MID), and a telephoto end (TELE) of the zoom lens of Example 1. Further, aberrations of each light beam of the d-line and the g-line are shown in the Figure. The diagram of astigmatism represents aberrations with respect to sagittal image surfaces and tangential image surfaces.
As shown in FIG. 7, diagrams indicated by the symbols Wa, Ma, and Ta represents spherical aberration, diagrams indicated by the symbols Wb, Mb, and Tb represents astigmatism, diagrams indicated by the symbols Wc, Mc, and Tc represents distortion, and diagrams indicated by the symbols Wd, Md, and Td represents lateral chromatic aberration.
Table 6 as shown at the end of the description of the Examples represents values (values evaluated from mathematical expressions of formulas (J), (K) and (C), individually) of formulas (J), (K) and (C) for Examples 1 through 5, individually. The mathematical expression of each formula can be evaluated from various data and the like with respect to the zoom lenses in Tables 1A through 5A.
As can be seen from the above lens data and the like, the zoom lens of Example 1 has a high variable ratio, and yet is compact and capable of high performance.
FIGS. 2A and 2B illustrating a configuration of the zoom lens of Example 1, FIG. 7 illustrating aberrations of the zoom lens, Tables 1A & 1B representing the lens data and the like of the zoom lens, and Table 6 representing the values of each mathematical expression of formulas (H), and (C) are read in the same manner as in Examples 2 through 5 to be described later, and therefore detailed descriptions thereof will be omitted.
Example 2
FIGS. 3A and 3B shows a zoom lens of Example 2. FIG. 3A is a diagram illustrating the specific configuration of the zoom lens of Example 2. FIG. 3B is related to the zoom lens of Example 2, and illustrates a state in which the zoom setting is set to a wide angle end (as indicated by “WIDE” in the Figure) at the upper part and a state in which the zoom setting thereof is set to a telephoto end (as indicated by “TELE” in the Figure) at the bottom part. Further, arrows indicate the paths of movements of the lens groups, respectively when magnification is changed from the wide angle end to the telephoto end.
In the fifth lens group 5G of the zoom lens of Example 2, two lenses, i.e., a positive lens and a negative lens are arranged in this order from the object side.
Further, Table 2A shows various data related to the zoom lens of Example 2. The upper part of Table 2A shows lens data, the middle part shows schematic specifications of the zoom lens, and the bottom part shows the focal length of each lens group.







TABLE 2A





EXAMPLE 2




















SURFACE




GROUP


NUMBER
Ri
Di
Nj
νj
STRUCTUER





1
85.2292
2.520
1.84661
23.9
FIRST


2
61.7335
9.054
1.49700
81.5
GROUP


3
−1963.5475
0.100


4
66.8404
4.168
1.60300
65.4


5
147.8987
D5


6
88.0438
1.400
1.88300
40.8
SECOND


7
18.3402
8.245


GROUP


8
−50.9539
1.050
1.83481
42.7


9
63.5833
1.045


10
37.5330
6.423
1.84661
23.9


11
−37.5330
0.405


12
−32.6020
1.050
1.77250
49.6


13
97.2521
D13


(APERTURE
∞
1.000


THIRD-a


STOP) 14




GROUP


15
33.0761
3.238
1.54814
45.8


16
−58.1129
0.218


17
29.9896
4.828
1.49700
81.5


18
−29.9896
0.900
1.85026
32.3


19
200.1256
4.148


*20
−64.3421
1.500
1.80168
40.7
THIRD-b


*21
24.7941
0.835


GROUP (OIS)


22
27.9314
2.293
1.84661
23.9


23
67.4658
D23


*24
52.0924
4.603
1.51530
62.8
FOURTH


*25
−41.7940
0.118


GROUP


26
48.9063
1.050
1.75520
27.5


27
23.5612
5.631
1.48749
70.2


28
−52.7318
D28


29
−77.6900
2.362
1.80518
25.4
FIFTH


30
−34.1433
1.323


GROUP


*31
−38.3946
1.500
1.80168
40.7


*32
175.1091
D32


33
∞
5.200
1.51680
64.2
Dg


34
∞
















WIDE
MID
TELE







D5
0.900
34.251
61.985



D13
43.622
17.798
3.965



D23
10.401
5.906
3.496



D28
3.770
5.315
1.700



D32
33.109
60.979
85.617



f
18.388
67.562
248.238



Fno
3.60
5.18
6.47



2ω [°]
76.59
22.60
6.27



f1
105.536



f2
−16.856



f3
97.458



f4
29.520



f5
−84.482



f3a
35.192



f3b (OIS)
−37.423










Table 2B shows aspheric coefficients of aspheric surfaces of the zoom lens of Example 2.







TABLE 2B







ASPHERIC COEFFICIENT









SURFACE NUMBER













SIGN
*20
*21
*24
*25
*31
*32





K
  1.000000E+00
  1.000000E+00 
  1.000000E+00 
  1.000000E+00 
  1.000000E+00 
  1.000000E+00


A3
−6.214685E−06
  1.210237E−06 
  2.670345E−05
  1.418960E−05
−6.078072E−06
  7.219238E−07


A4
  1.178008E−05
−2.059917E−07
−1.699876E−05
  3.117539E−07
−8.397924E−08
−1.310513E−07


A5
−5.734545E−07
−7.148778E−09
−2.869234E−07
  2.819776E−09
−3.195286E−07
−3.857289E−09


A6
  2.988894E−08
  1.380535E−10 
  1.883256E−07
−7.772038E−10
−4.462125E−09
−5.848393E−10


A7
  2.617898E−09
  2.608762E−11
−2.502808E−08
−9.142656E−11
  2.561994E−09
−7.783658E−11


A8
−9.134118E−11
  1.435216E−13
  1.237420E−09
−6.908198E−12
  7.007254E−11
−7.925124E−12


A9
−1.920589E−11
−3.192440E−13
−6.986446E−13
−4.003267E−13
−2.680817E−11
−7.016044E−13


A10
  3.923019E−13
−5.843137E−14
−1.406596E−12
−1.483360E−14
  9.907504E−13
−5.825802E−14


A11
−7.929852E−15
−7.084585E−15
−2.653633E−15
−1.835598E−15
−9.622458E−15
−4.777413E−15


A12 
−6.308512E−16
−6.646965E−16
−2.176749E−16
−2.125550E−16
−9.379487E−16
−4.039401E−16


A13 
−5.271484E−17
−4.473916E−17
−2.116950E−17
−2.258551E−17
−8.488742E−17
−3.628087E−17


A14 
−2.605892E−18
−6.306065E−19
−2.497013E−18
−2.231667E−18
−7.080190E−18
−3.496352E−18


A15
  1.622770E−18
  4.767090E−19
−2.199383E−19
−3.898770E−19
−6.276121E−19
−8.095367E−19


A16
  3.760341E−19
  1.155446E−19
−2.569275E−20
−4.124631E−20
−3.345415E−20
−9.331008E−20









FIG. 8 is a diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration at each of a wide angle end (WIDE), the middle of varying magnification (MID), and a telephoto end (TELE) of the zoom lens of Example 2.
Example 3
FIGS. 4A and 4B show a zoom lens of Example 3. FIG. 4A is a diagram illustrating the specific configuration of the zoom lens of Example 3. FIG. 4B is related to the zoom lens of Example 3, and illustrates a state in which the zoom setting is set to a wide angle end (as indicated by “WIDE” in the Figure) at the upper part and a state in which the zoom setting thereof is set to a telephoto end (as indicated by “TELE” in the Figure) at the bottom part. Further, arrows indicate the paths of movement of the lens groups, respectively when magnification is changed from the wide angle end to the telephoto end.
In the fifth lens group 5G of the zoom lens of Example 3, two lenses, i.e., a positive lens and a negative lens, are arranged in this order from the object side.
Further, Table 3A shows various data related to the zoom lens of Example 3. The upper part of Table 3A shows lens data, the middle part shows schematic specifications of the zoom lens, and the bottom part shows the focal length of each lens group.







TABLE 3A





EXAMPLE 3




















SURFACE




GROUP


NUMBER
Ri
Di
Nj
νj
STRUCTURE





1
86.1227
1.650
1.84661
23.9
FIRST GROUP


2
62.0701
9.553
1.49700
81.5


3
−4250.8858
0.200


4
69.0201
5.134
1.61800
63.3


5
173.7706
D5


6
143.9195
1.250
1.88300
40.8
SECOND


7
17.9097
8.359


GROUP


*8
−54.1875
0.200
1.52771
41.8


9
−52.5929
1.000
1.80400
46.6


10
61.2864
1.229


11
38.6886
5.875
1.84661
23.9


12
−38.4723
1.010
1.80400
46.6


13
99.9343
D13


(APERTURE
∞
1.000


THIRD-a


STOP) 14




GROUP


15
32.7747
3.500
1.54814
45.8


16
−52.1190
1.172


17
28.6007
4.608
1.49700
81.5


18
−31.7142
1.000
1.90366
31.3


19
247.9630
2.532


*20
−62.9067
1.500
1.80348
40.4
THIRD-b


21
24.4096
1.000


GROUP (OIS)


22
26.9299
2.518
1.84661
23.9


23
65.6490
D23


*24
49.2954
4.978
1.51560
63.1
FOURTH


*25
−44.8007
1.459


GROUP


26
47.4064
0.900
1.84661
23.9


27
23.0755
6.115
1.51680
64.2


28
−45.9160
D28


29
−225.5534
2.848
1.84661
23.9
FIFTH


30
−35.6067
0.500


GROUP


*31
−39.1114
1.500
1.80348
40.4


*32
54.4009
D32


33
∞
3.700
1.51680
64.2
Dg


34
∞
















WIDE
MID
TELE







D5
0.999
31.879
61.061



D13
42.746
17.373
4.203



D23
11.516
5.965
3.499



D28
1.951
3.394
1.885



D32
35.490
64.031
78.012



f
18.382
64.988
229.769



Fno
3.62
5.22
6.08



2ω [°]
76.61
23.33
6.73



f1
103.033



f2
−16.513



f3
87.566



f4
29.127



f5
−66.647



f3a
33.407



f3b (OIS)
−37.492










Table 3B shows aspheric coefficients of aspheric surfaces of the zoom lens of Example 3.







TABLE 3B







ASPHERIC COEFFICIENT









SURFACE NUMBER













SIGN
*8
*20
*24
*25
*31
*32





K
  1.464546E+00
  1.000000E+00
  1.000000E+00
  1.000000E+00
  1.000000E+00
  1.000000E+00


A3
  0.000000E+00
−6.784837E−06
  2.196427E−05
  1.195660E−05
−1.149323E−05
−1.143922E−06


A4
  2.212057E−06
  1.073941E−05
−1.784348E−05
  8.656127E−07
−3.692099E−07
  8.049956E−10


A5
  0.000000E+00
−6.120021E−07
−3.189917E−07
  2.476411E−08
−3.237427E−07
−3.487018E−10


A6
−8.509320E−09
  2.983909E−08
  1.875408E−07
−4.076491E−11
−4.237706E−09
−1.612101E−10


A7
  0.000000E+00
  2.765409E−09
−2.501350E−08
−6.934857E−11
  2.612386E−09
−2.141371E−11


A8
  1.827402E−11
−7.300686E−11
  1.241716E−09
−6.189639E−12
  7.725014E−11
−1.924803E−12


A9
  0.000000E+00
−1.754200E−11
−2.534825E−13
−3.333725E−13
−2.592973E−11
−1.269553E−13


A10
−1.356278E−13
  5.200665E−13
−1.369651E−12
−3.716054E−15
  1.087591E−12
−4.597426E−15


A11

  4.577131E−17
  2.121105E−16
−2.243534E−16
  2.093262E−16
  3.219858E−16


A12

−1.519797E−16
  1.643937E−17
−1.434839E−17
−8.269620E−18
  9.836844E−17


A13

−5.440776E−17
  1.428068E−18
−9.633478E−19
−2.966776E−18
  1.494300E−17


A14

−1.137249E−17
  1.494776E−19
−8.031938E−20
−4.355006E−19
  1.856954E−18









FIG. 9 is a diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration at each of a wide angle end (WIDE), the middle of varying magnification (MID), and a telephoto end (TELE) of the zoom lens of Example 3.
Example 4
FIGS. 5A and 5B show a zoom lens of Example 4. FIG. 5A illustrates the specific configuration of the zoom lens of Example 4. FIG. 5B is related to the zoom lens of Example 4, and illustrates a state in which the zoom setting is set to a wide angle end (as indicated by “WIDE” in the Figure) at the upper part and a state in which the zoom setting thereof is set to a telephoto end (as indicated by “TELE” in the Figure) at the bottom part. Further, arrows indicate the paths of movement of the lens groups, respectively when magnification is changed from the wide angle end to the telephoto end.
In the fifth lens group 5G of the zoom lens of Example 4, two lenses, i.e., a positive lens and a negative lens, are arranged in this order from the object side.
Further, Table 4A shows various data related to the zoom lens of Example 4. The upper part of Table 4A shows lens data, the middle part shows schematic specifications of the zoom lens, and the bottom part shows the focal length of each lens group.







TABLE 4A





EXAMPLE 4




















SURFACE




GROUP


NUMBER
Ri
Di
Nj
νj
STRUCTURE





1
84.9463
1.950
1.84661
23.9
FIRST GROUP


2
62.2446
8.693
1.49700
81.5


3
∞
0.100


4
68.3452
4.363
1.60300
65.4


5
153.8323
D5


6
89.2120
1.350
1.88300
40.8
SECOND


7
18.2963
8.233


GROUP


8
−58.1632
1.000
1.88300
40.8


9
67.7426
0.948


10
37.5173
6.506
1.84661
23.9


11
−38.5206
0.408


12
−33.7911
1.000
1.77250
49.6


13
99.4178
D13


(APERTURE
∞
1.000


THIRD-a


STOP) 14




GROUP


15
33.6716
3.293
1.51742
52.4


16
−58.3051
0.100


17
28.2935
4.126
1.49700
81.5


18
−31.9738
0.900
1.83400
37.2


19
127.3405
2.569


20
−68.3981
2.272
1.84661
23.9
THIRD-b


21
−26.8082
0.886


GROUP (OIS)


22
−24.8406
1.500
1.80348
40.4


*23
62.6811
D23


*24
49.8918
4.452
1.51560
63.1
FOURTH


*25
−42.8733
0.100


GROUP


26
53.2553
1.000
1.80518
25.4


27
23.3404
5.973
1.51823
58.9


28
−46.7603
D28


29
−81.9572
2.357
1.80518
25.4
FIFTH GROUP


30
−34.7267
1.493


*31
−38.2183
1.500
1.80348
40.4


*32
179.9979
D33


33
∞
4.900
1.51680
64.2
Dg


34
∞
















WIDE
MID
TELE







D5
0.900
33.799
63.266



D13
44.713
17.634
3.566



D23
11.185
6.816
4.357



D28
3.245
4.848
1.970



D32
34.996
63.954
86.941



f
18.366
67.481
247.941



Fno
3.60
5.26
6.55



2ω [°]
76.64
22.68
6.28



f1
107.872



f2
−17.446



f3
116.489



f4
29.082



f5
−85.750



f3a
37.832



f3b (OIS)
−39.192










Table 4B shows aspheric coefficients of aspheric surfaces of the zoom lens of Example 4.







TABLE 4B







ASPHERIC COEFFICIENT









SURFACE NUMBER












SIGN
*23
*24
*25
*31
*32















K
1.000000E+00
1.000000E+00
1.000000E+00
1.000000E+00
1.000000E+00


A3
1.288744E−05
2.647809E−05
1.085607E−05
−7.403052E−06
−1.039624E−07


A4
−1.078292E−05
−1.725827E−05
4.339778E−07
−1.719981E−07
−1.241135E−07


A5
6.382901E−07
−2.955264E−07
7.445503E−09
−3.195104E−07
−6.411543E−09


A6
−2.635804E−08
1.884390E−07
−7.830304E−10
−4.172605E−09
−7.019777E−10


A7
−2.463874E−09
−2.498717E−08
−1.006144E−10
2.599459E−09
−6.791905E−11


A8
9.303492E−11
1.241227E−09
−7.050127E−12
7.428064E−11
−5.579190E−12


A9
1.836592E−11
−4.496962E−13
−3.044782E−13
−2.634935E−11
−4.226272E−13


A10
−5.521081E−13
−1.394620E−12
3.515842E−15
1.038713E−12
−3.175412E−14


A11
−1.312550E−14
−2.307759E−15
5.035691E−16
−4.914561E−15
−2.523663E−15


A12
−1.649716E−15
−2.136162E−16
3.668331E−17
−5.118335E−16
−2.219919E−16


A13
−1.438455E−16
−1.859723E−17
1.097923E−18
−5.040249E−17
−2.163300E−17


A14
−6.585779E−18
−1.568050E−18
−1.859078E−19
−4.774574E−18
−2.263951E−18


A15
−4.147342E−19
−2.121945E−20
−2.309610E−19
−5.390733E−19
−6.968129E−19


A16
1.147946E−19
8.062655E−21
−3.078231E−20
−4.101269E−20
−8.198580E−20









FIG. 10 is a diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration at each of a wide angle end (WIDE), the middle of varying magnification (MID), and a telephoto end (TELE) of the zoom lens of Example 4.
Example 5
FIGS. 6A and 6B show a zoom lens of Example 5. FIG. 6A illustrates the specific configuration of the zoom lens of Example 5. FIG. 6B is related to the zoom lens of Example 5, and illustrates a state in which the zoom setting is set to a wide angle end (as indicated by “WIDE” in the Figure) at the upper part and a state in which the zoom setting thereof is set to a telephoto end (as indicated by “TELE” in the Figure) at the bottom part. Further, arrows indicate the paths of movement of the lens groups, respectively when magnification is changed from the wide angle end to the telephoto end.
In the fifth lens group 5G of the zoom lens of Example 5, two lenses, i.e., a positive lens and a negative lens are arranged in this order from the object side.
Further, Table 5A shows various data related to the zoom lens of Example 5. The upper part of Table 5A shows lens data, the middle part shows schematic specifications of the zoom lens, and the bottom part shows the focal length of each lens group.







TABLE 5A





EXAMPLE 5




















SURFACE




GROUP


NUMBER
Ri
Di
Nj
νj
STRUCTURE





1
85.2992
2.520
1.84661
23.9
FIRST GROUP


2
61.8500
9.114
1.49700
81.5


3
−2375.7864
0.100


4
66.8941
4.269
1.60300
65.4


5
146.5034
D5


6
87.8998
1.400
1.88300
40.8
SECOND


7
18.3570
8.315


GROUP


8
−51.0001
1.050
1.83481
42.7


9
63.6139
0.815


10
37.4113
6.407
1.84666
23.8


11
−37.4113
0.388


12
−32.5753
1.050
1.77250
49.6


13
98.4906
D13


(APERTURE
∞
1.100


THIRD-a


STOP) 14




GROUP


15
34.2381
3.329
1.54814
45.8


16
−60.1143
0.937


17
27.0475
4.232
1.49700
81.5


18
−33.1140
0.900
1.85026
32.3


19
163.6420
3.836


*20
−63.3026
1.500
1.80168
40.7
THIRD-b


*21
24.7365
0.864


GROUP (OIS)


22
28.0299
2.277
1.84666
23.8


23
66.7227
D23


*24
52.7776
4.675
1.51530
62.8
FOURTH


*25
−42.2885
0.105


GROUP


26
48.3349
1.050
1.75520
27.5


27
23.5950
5.625
1.48749
70.2


28
−52.9320
D28


29
−77.2285
2.360
1.80518
25.4
FIFTH


30
−34.0317
1.053


GROUP


*31
−38.4236
1.500
1.80168
40.7


*32
175.0302
D32


33
∞
5.200
1.51680
64.2
Dg


34
∞
















WIDE
MID
TELE







D5
0.900
36.423
62.766



D13
43.473
17.944
3.610



D23
10.708
6.338
3.715



D28
3.842
5.548
1.698



D32
33.106
58.073
84.416



f
18.389
67.564
248.247



Fno
3.62
5.02
6.39



2ω [°]
76.66
22.61
6.27



f1
106.443



f2
−16.902



f3
94.599



f4
29.607



f5
−84.036



f3a
34.301



f3b (OIS)
−36.710










Table 5B shows aspheric coefficients of aspheric surfaces of the zoom lens of Example 5.







TABLE 5B







ASPHERIC COEFFICIENT









SURFACE NUMBER













SIGN
*20
*21
*24
*25
*31
*32





K
  1.000000E+00
  1.000000E+00
  1.000000E+00
  1.000000E+00
  1.000000E+00
  1.000000E+00


A3
−6.165192E−06
  1.136414E−06
  2.646484E−05
  1.455922E−05
−5.608010E−06
  3.111280E−07


A4
  1.180918E−05
−2.391292E−07
−1.700884E−05
  3.247792E−07
−6.243737E−08
−1.509737E−07


A5
−5.712797E−07 
−9.755106E−09
−2.879359E−07
  3.790736E−09
−3.186333E−07
−4.800208E−09


A6
  3.004106E−08 
−5.784070E−11
  1.882504E−07
−7.189621E−10
−4.429101E−09
−6.392048E−10


A7
  2.628840E−09
  1.065292E−11
−2.503214E−08
−8.915027E−11
  2.562357E−09
−8.139704E−11


A8
−9.058174E−11 
−1.062813E−12
  1.237303E−09
−6.929168E−12
  6.993044E−11
−8.143708E−12


A9
−1.916284E−11
−4.032273E−13 
−6.914544E−13
−4.165896E−13
−2.683328E−11
−7.108067E−13


A10
  3.931210E−13
−6.248737E−14 
−1.404954E−12
−1.706208E−14
  9.877237E−13
−5.801155E−14


A11
−8.205763E−15
−6.993822E−15 
−2.471879E−15
−2.065580E−15
−9.923479E−15
−4.652135E−15


A12
−6.918798E−16
−6.032048E−16
−2.028307E−16
−2.332995E−16
−9.630020E−16
−3.833882E−16


A13
−6.145538E−17
−3.361798E−17
−2.032344E−17
−2.430529E−17
−8.645582E−17
−3.363706E−17


A14
−3.613976E−18
  8.786762E−19 
−2.491248E−18
−2.366453E−18
−7.105990E−18
−3.193681E−18


A15
  1.528779E−18
  6.479148E−19
−2.276198E−19 
−4.001489E−19
−6.139199E−19
−7.773001E−19


A16
  3.702179E−19
  1.315589E−19 
−2.724708E−20
−4.204166E−20
−3.018856E−20
−9.005424E−20









FIG. 11 is a diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration at each of a wide angle end (WIDE), the middle of varying magnification (MID), and a telephoto end (TELE) of the zoom lens of Example 5.
The zoom lens of Example 5, which is constructed in such a manner, can have a high variable magnification ratio, and yet be compact and capable of high performance.













TABLE 6







EXAM-
EXAM-
EXAM-
EXAM-




PLE 1
PLE 2
PLE 3
PLE 4
EXAMPLE 5





















FORMULA (J)
0.645
0.623
0.631
0.632
0.621


FORMULA (K)
−0.311
−0.218
−0.276
−0.214
−0.219


FORMULA (C)
−5.00
−3.32
−3.99
−3.30
−3.30









The present invention is not limited to the embodiments and the examples described above, and various modifications are possible. For example, values, such as the radius of curvature of each lens element, distances between surfaces, and refractive indices, are not limited to the values in the numerical examples shown in the Tables, but may be other values.

## Claims

1. A zoom lens, substantially consisting of:
a first lens group having positive refractive power;
a second lens group having negative refractive power;
a third lens group having positive refractive power;
a fourth lens group having positive refractive power; and
a fifth lens group having negative refractive power, which are arranged in this order from an object side,
wherein when varying magnification from a wide angle end to a telephoto end, a distance between the first lens group and the second lens group is consistently increased, a distance between the second lens group and the third lens group is consistently decreased, a distance between the third lens group and the fourth lens group is consistently decreased, and a distance between the fourth lens group and the fifth lens group is changed, while all of the lens groups are moved with respect to an image formation position,
wherein the following formulas (J), (K), and (C) are simultaneously satisfied:


0.50<fw/f4<0.65  (J);



−0.32<fw/f5<−0.15  (K); and



−6.0<1−(β5T)2<−2.5  (C), where


fw: a focal length of the entire lens system at the wide angle end;
f4: a focal length of the fourth lens group;
f5: a focal length of the fifth lens group; and
β5T: an image formation magnification of the fifth lens group when focusing on infinity at the telephoto end.

2. An imaging apparatus comprising:
the zoom lens as defined in claim 1.

3. The zoom lens as defined in claim 1, wherein the following formula (C′) is satisfied:


−5.5<1−(β5T)2<−2.9  (C′).

4. The zoom lens as defined in claim 1, wherein when the point of focus is shifted from an infinity side to a near side and focused, only the fifth lens group is shifted to the image side.

5. The zoom lens as defined in claim 4, wherein the following formula (C′) is satisfied:


−5.5<1−(β5T)2<−2.9  (C′).

6. The zoom lens as defined in claim 1, wherein the following formula (K′) is satisfied:


−0.32<fw/f5<−0.20  (K′).

7. The zoom lens as defined in claim 6, wherein the following formula (C′) is satisfied:


−5.5<1−(β5T)2<−2.9  (C′).

8. The zoom lens as defined in claim 6, wherein when the point of focus is shifted from an infinity side to a near side and focused, only the fifth lens group is shifted to the image side.

9. The zoom lens as defined in claim 1, wherein the following formula (J′) is satisfied:


0.60<fw/f4<0.65  (J′).

10. The zoom lens as defined in claim 9, wherein the following formula (C′) is satisfied:


−5.5<1−(β5T)2<−2.9  (C′).

11. The zoom lens as defined in claim 9, wherein when the point of focus is shifted from an infinity side to a near side and focused, only the fifth lens group is shifted to the image side.

12. The zoom lens as defined in claim 9, wherein the following formula (K′) is satisfied:


−0.32<fw/f5<−0.20  (K′).