# Patent

## Title
Zoom lens, still image camera comprising the zoom lens, and video camera comprising the zoom lens

## Abstract

Provided from the object side are a first lens group (11) having a positive refracting power and fixed to the image plane, a second lens group (12) having a negative refracting power and a magnification varying action exhibited when moving along the optical axis, a third lens group (13) fixed to the image plane and having a positive refracting power, and a fourth lens group (14) movable along the optical axis so as to maintain the image plane moving with the movements of the second lens group (12) and of the object in a fixed position from a reference plane. Hence the movement of the image due to camera shake is corrected by moving the whole third lens group (13) vertically to the optical axis. The size is reduced and the aberrations are small because the whole groups whose optical performance is united are decentered.

## Background
This application is a Division of application Ser. No. 11/067,432, filed Feb. 22, 2005, which is a Continuation-in-Part of application Ser. No. 09/701,754 filed Dec. 1, 2000, which is a National Stage of PCT/JP99/02910 filed May 31, 1999 which applications are incorporated herein by reference.


TECHNICAL FIELD
The present invention relates to a zoom lens used for a video camera or the like, and the zoom lens has a function optically to correct image movement caused by camera shake, vibration or the like.
BACKGROUND ART
Motion picture cameras such as video cameras have been required to have a function to prevent vibration caused by camera shake, and various types of vibration-proof optical systems have been disclosed. For example, a zoom lens disclosed in JP-A-8-29737 includes an optical system consisting of two parts attached in front of the zoom lens in order to correct camera shake, where either of the parts is moved vertically to an optical axis in order to correct movement of images caused by camera shake.
A zoom lens disclosed in JP-A-7-128619 comprises four groups, where a part of the third lens group comprising plural lenses is moved vertically to the optical axis in order to correct the movement of images caused by camera shake.
However, the zoom lens disclosed in JP-A-8-29737 has an increased lens diameter for an optical system to correct camera shake for the purpose of attaching the optical system in front of the zoom lens. Accordingly, the entire component is upsized and a load on a driving system will be heavier. As a result, the zoom lens is unfavorable in view of downsizing, weight-reduction and power-saving.
The zoom lens disclosed in JP-A-7-128619 corrects image movement caused by camera shake by moving a part of the third lens group vertically to the optical axis while the same lens group is fixed with respect to the image plane. This type of zoom lens is more favorable than a zoom lens of front-attachment type in view of downsizing, but a load on the actuator will be heavier since the lens group for correcting camera shake is composed of three lenses.
Since an optical system for correcting camera shake is attached in front of the zoom lens disclosed in JP-A-8-29737, the lens diameter of the optical system will be increased, and the entire component will be upsized. So a load on the driving system will be heavier, and thus, this zoom lens is unfavorable in view of downsizing, weight reduction and power-saving.
The latter zoom lens in JP-A-7-128619 is advantageous in downsizing and weight reduction when compared to a type comprising an optical system for correcting camera shake in front of the zoom lens, since a third lens group is fixed with respect to the image plane and a part thereof is moved vertically with respect to the optical axis. However, the zoom lens has a problem of deterioration in aberration, especially for chromatic aberration, when shifting lenses, since a part of the third lens group is moved.
DISCLOSURE OF INVENTION
A purpose of the present invention is to resolve the above mentioned problems in conventional zoom lenses by providing a small and compact zoom lens with less deterioration in the aberration performance and also a video camera using the same.
For this purpose, a first zoom lens of the present invention comprises a first lens group having a positive refracting power and being fixed with respect to an image plane, a second lens group having a negative refracting power and varying power by moving along an optical axis, a third lens group having a positive refracting power and being fixed with respect to the image plane, and a fourth lens group having a positive refracting power and moving along an optical axis so as to keep the image plane varied by a shift of the second lens group and an object at a predetermined position from a reference surface, and the first to the fourth lens group are disposed from the object in this order. The present invention is characterized in that the entire third lens group is moved vertically with respect to the optical axis so as to correct movement of an image during camera shake.
Accordingly, the zoom lens can be downsized when compared to a type of zoom lens comprising an optical system for correcting camera shake attached in front of the lens. Furthermore, since the entire group having a united optical performance is decentered, deterioration in the aberration can be decreased when compared to a zoom lens in which only a part in the groups are moved.
In the first zoom lens mentioned above, preferably the third group is composed of one lens. Accordingly, a load on the driving system will be decreased when correcting camera shake, and power consumption can be saved.
Preferably the third lens group is composed of two lenses: a positive lens and a negative lens. Accordingly, the aberration when correcting camera shake can be corrected more efficiently, and deterioration of image quality can be decreased even when correcting camera shake.
Preferably the third lens group is composed of three lenses comprising at least one positive lens and at least one negative lens. The third lens group is required to have a strong positive power to decrease the full length in order to obtain a small zoom lens. In this preferable embodiment, aberration occurring at this time can be corrected with the three lenses.
It is also preferable that the third lens group includes a positive lens, and a cemented lens of a positive lens and a negative lens. Accordingly, tolerance when assembling a group of correcting lenses can be eased.
Preferably the third lens group is composed of at least one aspherical surface. Accordingly, aberration when correcting camera shake can be corrected with further efficiency, and thus, performance when moving the lenses can be improved.
Preferably the fourth lens group comprises at least one aspherical surface. Accordingly, aberration when correcting camera shake can be corrected as well as when a stationary state with further efficiency.
Preferably, the shifting amount Y of the third lens group at a focal length f of an entire system when correcting camera shake, the shifting amount Yt of the third lens group at a telephoto end, and the focal length ft of the telephoto end satisfy the following conditional expressions.

Yt>Y; and

(Y/Yt)/(f/ft)<1.5

Accordingly, deterioration in the optical performance can be prevented when camera shake occurs.

Preferably, a focal length f3 of the third lens group and a focal length fw of an entire system at a wide-angle end satisfy the following conditional expression.

2.0<f3/fw<4.0

Accordingly, the shifting amount when correcting camera shake can be decreased and the zoom lens can be shortened as a whole, and thus, a small zoom lens can be provided.

Preferably, a surface on the object side of a lens disposed closest to the object side in the third lens group is aspherical, and a local radius of curvature R10 in the vicinity of an optical axis and a local radius of curvature R11 in an outer peripheral portion satisfy the following conditional expression.

1.05<R11/R10<2.5

Accordingly, spherical aberration can be corrected satisfactorily.

Preferably, a surface on the object side of a lens disposed closest to the object side in the fourth lens group is aspherical, and a local radius of curvature R20 in the vicinity of an optical axis and a local radius of curvature R21 in an outer peripheral portion satisfy the following conditional expression.

1.05<R21/R20<2.0

Accordingly, coma-aberration on the upper flux of the off-axis ray can be corrected favorably.

Next, a first video camera of the present invention is characterized in that it includes the above-mentioned first zoom lens. Accordingly, the video camera has a function to correct camera shake and can be downsized and weight-reduced.
Next, a second zoom lens of the present invention comprises a first lens group having a positive refracting power and being fixed with respect to an image plane; a second lens group having a negative refracting power and varying power by moving along an optical axis; a third lens group fixed with respect to the image plane; a fourth lens group fixed with respect to the image plane; and a fifth lens group having a positive refracting power and moving along an optical axis so as to keep the image plane varied by a shift of the second lens group and an object at a predetermined position from a reference surface. In this zoom lens, the first to the fifth lens groups are disposed from the object side in this order. The third lens group and the fourth lens group compose a combination of a lens group having a positive refracting power and a lens group having a negative refracting power, and either the third or fourth lens group is moved vertically with respect to the optical axis so as to correct movement of the image during camera shake.
In such a zoom lens, camera shake is corrected by moving lenses with smaller diameter. Therefore, this type of zoom lens is favorable in downsizing when compared to a zoom lens comprising an optical system for correcting camera shake attached in front of the lens. Moreover, since the aberration performance for each lens group can be adjusted, the aberration performance will deteriorate less when correcting camera shake.
In the second zoom lens, preferably either the third or fourth lens group that is moved is vertically with respect to the optical axis so as to correct movement of the image during camera shake is composed of two lenses: one positive lens and one negative lens.
It is also preferable that the third lens group has a positive refracting power and the fourth lens group has a negative refracting power, and the third lens group is moved vertically with respect to the optical axis so as to correct movement of the image during camera shake. In such a zoom lens, long back focus can be secured easily since the fourth lens group includes lenses having a negative refracting power. This is suitable for an optical system of a video camera using three imaging devices, which requires a long back focus.
Preferably, the fourth lens group is composed of two lenses separated from each other: one positive lens and one negative lens.
Preferably, the fourth lens group is composed of two cemented lenses: one positive lens and one negative lens.
Preferably, the third lens group has a negative refracting power and the fourth lens group has a positive refracting power, and the fourth lens group is moved vertically with respect to the optical axis so as to correct movement of the image during camera shake. Since the fourth lens group includes lenses having a positive refracting power in such a zoom lens, light entering the fifth lens group can be lowered and the lens diameter also can be reduced. Therefore, a load on a focusing actuator can be lighter.
Preferably, the third lens group and the fourth lens group are composed two lenses respectively, and Abbe's number v31 of one lens of the third group, Abbe's number v32 of the remaining lens of the third group, Abbe's number v41 of one lens of the fourth group and Abbe's number v42 of the remaining lens of the fourth group satisfy the following conditional expressions.

|v31-v32|>25

|v41-v42|>25

Since such a zoom lens can provide a sufficient achromatic effect, deterioration in magnification chromatic aberration can be decreased even when shifting the lenses.

Preferably, either the third or fourth lens group that is moved vertically with respect to the optical axis in order to correct movement of an image during camera shake is composed of two lenses: one lens having a positive refracting power and one lens having a negative refracting power being disposed separately from the object side in this order, and the lenses have sag amounts equal on the object side and on the image side.
Preferably, either the third or fourth lens group that group is moved vertically with respect to the optical axis in order to correct movement of an image during camera shake is composed of three lenses comprising at least one positive lens and at least one negative lens. In a small zoom lens, the third lens group is required to have a strong positive power to decrease the whole length. Aberrations occurring at this time can be corrected by using three lenses in this embodiment.
Preferably, either the third or fourth lens group that is moved vertically with respect to the optical axis in order to correct movement of an image during camera shake is composed of one lens. Accordingly, a load on the driving system will be lighter when correcting camera shake and power consumption can be decreased.
Preferably, either the third or fourth lens group that is moved vertically with respect to the optical axis in order to correct movement of an image during camera shake comprises at least one aspherical surface. Such a zoom lens can have improved performance during lens shifting.
Preferably, either the third or fourth lens group that is moved vertically with respect to the optical axis in order to correct movement of an image during camera shake comprises a convex lens having an aspherical surface when viewed from the object side, and a local radius of curvature rS1 for a diameter occupying 10% of lens effective diameter and a local radius of curvature rS9 for a diameter occupying 90% of lens effective diameter satisfy the following conditional expression.

0.01<rS1/rS9<2.00

Such a zoom lens can provide sufficient aberration performance.

Preferably, a focal length f3 of the third lens group and a focal length f34 of a composite focal length of the third and fourth lens groups satisfy the following conditional expression.

0.40<|f3/f34|<0.85

Since such a zoom lens can control the power of the correcting lenses, deterioration in the aberration performance can be prevented and moreover, degree of lens movement when correcting camera shake can be controlled. Therefore, the lens can be made smaller, and this is favorable for downsizing.
Preferably, a focal length fw of an entire system at the wide-angle end and a distance BF between the final surface of the lens and the image plane in the air satisfy the following conditional expression.

2.0<BF<fw<5.0

Accordingly, a zoom lens with a long back focus can be provided. Preferably, a focal length fw of an entire system at the wide-angle end, focal length fi (i=1−5) of the i-th lens group, and a composite focal length f34 of the third and fourth lens groups satisfy the following expressions.

5.0<f1/fw<8.0

0.5<|f2|/fw<1.6

4.0<f34/fw<9.5

2.0<f5/fw<5.0

Accordingly, a small zoom lens can be provided.

It is also preferable that the shifting amount Y of the third lens group at a focal length f of an entire system when correcting camera shake, the shifting amount Yt of the third lens group at a telephoto end and a focal length ft of the telephoto end satisfy the following conditional expressions.

Yt>Y; and

(Y/Yt)/(f/ft)<1.5

Accordingly, overcorrection and also deterioration in the optical performance can be prevented.

Next, a second video camera of the present invention is characterized in that it comprises the second zoom lens. Accordingly, a small video camera with high-performance and a function to correct camera shake is obtainable.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a view showing the arrangement of a zoom lens in a first embodiment according to the present invention.
FIG. 2 illustrates various aberrations at a wide-angle end in the first embodiment according to the present invention.
FIG. 3 illustrates various aberrations at a standard position in the first embodiment according to the present invention.
FIG. 4 illustrates various aberrations at a telephoto end in the first embodiment according to the present invention.
FIG. 5 is a view showing the arrangement of a zoom lens in a second embodiment according to the present invention.
FIG. 6 illustrates various aberrations at a wide-angle end in the second embodiment according to the present invention.
FIG. 7 illustrates various aberrations at a standard position in the second embodiment according to the present invention.
FIG. 8 illustrates various aberrations at a telephoto end in the second embodiment according to the present invention.
FIG. 9 is a view showing the arrangement of a zoom lens in a third embodiment according to the present invention.
FIG. 10 illustrates various aberrations at a wide-angle end in the third embodiment according to the present invention.
FIG. 11 illustrates various aberrations at a standard position in the third embodiment according to the present invention.
FIG. 12 illustrates various aberrations at a telephoto end in the third embodiment according to the present invention.
FIG. 13 is a view showing the arrangement of a zoom lens in a fourth embodiment according to the present invention.
FIG. 14 illustrates various aberrations at a wide-angle end in the fourth embodiment according to the present invention.
FIG. 15 illustrates various aberrations at a standard position in the fourth embodiment according to the present invention.
FIG. 16 illustrates various aberrations at a telephoto end in the fourth embodiment according to the present invention.
FIG. 17 is a view showing the arrangement of a zoom lens in a fifth embodiment according to the present invention.
FIG. 18 illustrates various aberrations at a wide-angle end in the fifth embodiment according to the present invention.
FIG. 19 illustrates various aberrations at a standard position in the fifth embodiment according to the present invention.
FIG. 20 illustrates various aberrations at a telephoto end in the fifth embodiment according to the present invention.
FIG. 21 illustrates various aberrations at a wide-angle end of a second example in the fifth embodiment according to the present invention.
FIG. 22 illustrates various aberrations at a standard position of the second example in the fifth embodiment according to the present invention.
FIG. 23 illustrates various aberrations at a telephoto end of the second example in the fifth embodiment according to the present invention.
FIG. 24 is a view showing the arrangement of a zoom lens in a sixth embodiment according to the present invention.
FIG. 25 illustrates various aberrations at a wide-angle end in the sixth embodiment according to the present invention.
FIG. 26 illustrates various aberrations at a standard position in the sixth embodiment according to the present invention.
FIG. 27 illustrates various aberrations at a telephoto end in the sixth embodiment according to the present invention.
FIG. 28 illustrates various aberrations at a telephoto end in the sixth embodiment according to the present invention at a correction of 0.5 degrees.
FIG. 29 is a view showing the arrangement of a zoom lens in a seventh embodiment according to the present invention.
FIG. 30 illustrates various aberrations at a wide-angle end in the seventh embodiment according to the present invention.
FIG. 31 illustrates various aberrations at a standard position in the seventh embodiment according to the present invention.
FIG. 32 illustrates various aberrations at a telephoto end in the seventh embodiment according to the present invention.
FIG. 33 illustrates various aberrations at a telephoto end in the seventh embodiment according to the present invention at a correction of 0.5 degrees.
FIG. 34 is a view showing the arrangement of a zoom lens in a eighth embodiment according to the present invention.
FIG. 35 illustrates various aberrations at a wide-angle end in the eighth embodiment according to the present invention.
FIG. 36 illustrates various aberrations at a standard position in the eighth embodiment according to the present invention.
FIG. 37 illustrates various aberrations at a telephoto end in the eighth embodiment according to the present invention.
FIG. 38 illustrates various aberrations at a telephoto end in the eighth embodiment according to the present invention at a correction of 0.5 degrees.
FIG. 39 is a view showing the arrangement of a zoom lens in a ninth embodiment according to the present invention.
FIG. 40 illustrates various aberrations at a wide-angle end in the ninth embodiment according to the present invention.
FIG. 41 illustrates various aberrations at a standard position in the ninth embodiment according to the present invention.
FIG. 42 illustrates various aberrations at a telephoto end in the ninth embodiment according to the present invention.
FIG. 43 illustrates various aberrations at a telephoto end in the ninth embodiment according to the present invention at a correction of 0.5 degrees.
FIG. 44 is a view showing the arrangement of a video camera in a tenth embodiment according to the present invention.
FIG. 45 is a view showing the arrangement of a zoom lens in an eleventh embodiment according to the present invention.
FIG. 46 is a view specifically showing the arrangement of the zoom lens in the eleventh embodiment according to the present invention.
FIG. 47 illustrates various aberrations at a wide-angle end in the eleventh embodiment according to the present invention.
FIG. 48 illustrates various aberrations at a standard position in the eleventh embodiment according to the present invention.
FIG. 49 illustrates various aberrations at a telephoto end in the eleventh embodiment according to the present invention.
FIG. 50 illustrates various aberrations at a wide-angle end of a second example in the eleventh embodiment according to the present invention.
FIG. 51 illustrates various aberrations at a standard position of the second example in the eleventh embodiment according to the present invention.
FIG. 52 illustrates various aberrations at a telephoto end of the second example in the eleventh embodiment according to the present invention.
FIG. 53 illustrates various aberrations at a wide-angle end of a third example in the eleventh embodiment according to the present invention.
FIG. 54 illustrates various aberrations at a standard position of the third example in the eleventh embodiment according to the present invention.
FIG. 55 illustrates various aberrations at a telephoto end of the third example in the eleventh embodiment according to the present invention.
FIG. 56 is a view showing the arrangement of a zoom lens in a twelfth embodiment according to the present invention.
FIG. 57 is a view specifically showing the arrangement of the zoom lens in the twelfth embodiment.
FIG. 58 illustrates various aberrations at a wide-angle end in the twelfth embodiment according to the present invention.
FIG. 59 illustrates various aberrations at a standard position in the twelfth embodiment according to the present invention.
FIG. 60 illustrates various aberrations at a telephoto end in the twelfth embodiment according to the present invention.
FIG. 61 is a view showing the arrangement of a zoom lens in a thirteenth embodiment according to the present invention.
FIG. 62 illustrates various aberrations at a wide-angle end in the thirteenth embodiment according to the present invention.
FIG. 63 illustrates various aberrations at a standard position in the thirteenth embodiment according to the present invention.
FIG. 64 illustrates various aberrations at a telephoto end in the thirteenth embodiment according to the present invention.
FIG. 65 is a view showing the arrangement of a video camera in a fourteenth embodiment according to the present invention.
FIG. 66 is a view showing the arrangement of a zoom lens in a fifteenth embodiment according to the present invention.
FIG. 67 illustrates various aberrations at a wide-angle end in the fifteenth embodiment according to the present invention.
FIG. 68 is illustrates various aberrations at a standard position in the fifteenth embodiment according to the present invention.
FIG. 69 illustrates various aberrations at a telephoto end in the fifteenth embodiment according to the present invention.
FIG. 70 is a view showing the arrangement of a zoom lens in a sixteenth embodiment according to the present invention.
FIG. 71 illustrates various aberrations at a wide-angle end in the sixteenth embodiment according to the present invention.
FIG. 72 illustrates various aberrations at a standard position in the sixteenth embodiment according to the present invention.
FIG. 73 illustrates various aberrations at a telephoto end in the sixteenth embodiment according to the present invention.
FIG. 74 is a view showing the arrangement of a zoom lens in a seventeenth embodiment according to the present invention.
FIG. 75 illustrates various aberrations at a wide-angle end in the seventeenth embodiment according to the present invention.
FIG. 76 illustrates various aberrations at a standard position in the seventeenth embodiment according to the present invention.
FIG. 77 illustrates various aberrations at a telephoto end in the seventeenth embodiment according to the present invention.
FIG. 78 is a view showing the arrangement of a zoom lens in a eighteenth embodiment according to the present invention.
FIG. 79 illustrates various aberrations at a wide-angle end in the eighteenth embodiment according to the present invention.
FIG. 80 illustrates various aberrations at a standard position in the eighteenth embodiment according to the present invention.
FIG. 81 illustrates various aberrations at a telephoto end in the eighteenth embodiment according to the present invention.
FIG. 82 is a view showing the arrangement of a zoom lens in a nineteenth embodiment according to the present invention.
FIG. 83 illustrates various aberrations at a wide-angle end in the nineteenth embodiment according to the present invention.
FIG. 84 illustrates various aberrations at a standard position in the nineteenth embodiment according to the present invention.
FIG. 85 illustrates various aberrations at a telephoto end in the nineteenth embodiment according to the present invention.
FIG. 86 is a view showing the arrangement of a zoom lens in a twentieth embodiment according to the present invention.
FIG. 87 illustrates various aberrations at a wide-angle end in the twentieth embodiment according to the present invention.
FIG. 88 illustrates various aberrations at a standard position in the twentieth embodiment according to the present invention.
FIG. 89 illustrates various aberrations at a telephoto end in the twentieth embodiment according to the present invention.
FIG. 90 is a view showing the arrangement of a zoom lens in a twenty-first embodiment according to the present invention.
FIG. 91 illustrates various aberrations at a wide-angle end in the twenty-first embodiment according to the present invention.
FIG. 92 illustrates various aberrations at a standard position in the twenty-first embodiment according to the present invention.
FIG. 93 illustrates various aberrations at a telephoto end in the twenty-first embodiment according to the present invention.
FIG. 94 is a view showing the arrangement of a video camera in a twenty-second embodiment according to the present invention.



BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described by way of illustrative embodiments.
First Embodiment
FIG. 1 is a view showing the arrangement of a zoom lens in a first embodiment according to the present invention. As shown in FIG. 1, a zoom lens has a structure in which a first lens group 11, a second lens group 12, a third lens group 13, and a fourth lens group 14 are disposed from an object side left side in FIG. 1) to an image plane side (right side in FIG. 1) in this order.
The first lens group 11 has a positive refracting power, and is fixed with respect to the image plane in varying power and focusing. The second lens group 12 has a negative refracting power and varies power by moving along an optical axis. The third lens group 13 is composed of a single lens having a positive refracting power and is fixed with respect to the image plane in varying power and focusing.
When camera shake occurs, shake of an image is corrected by moving the third lens group 13 in a direction vertical to the optical axis. Since camera shake is corrected in this way by moving a lens with smaller diameter, a small and lightweight video camera can be provided. Furthermore, power consumption also can be reduced since a load on the driving system becomes lighter.
The fourth lens group 14 has a positive refracting power, moves along an optical axis so as to keep the image plane varied by the shift of the second lens group 12 and the object at a predetermined position from a reference surface, thereby moving an image and adjusting the focus thereof at the same time in accordance with variable power. Since aberration of camera shake can be corrected more efficiently by providing at least one aspherical surface to the lens of the third group 13, performance in shifting the lenses can be improved.
Specific examples of zoom lenses according to this embodiment are shown in the following Table 1. In Table 1, r is a radius of curvature of a lens (mm), d is a thickness of a lens or air distance (mm) between lenses, n is a refractive index of each lens with respect to a d-line, and v is an Abbe's number of each lens with respect to the d-line. These also apply to Tables 4, 7, 10, 13, 19, 25, 31, 37, 43, 46, 49, 52, 55, 58, 61, 64, 67, 70, 73, and 76.












TABLE 1





Group
Surface
r
d
n
ν




















1
1
59.253
1.20
1.80518
25.4



2
25.011
7.30
1.60311
60.7



3
−142.977
0.20



4
21.743
3.95
1.69680
55.6



5
60.993
Variable


2
6
58.338
0.70
1.78500
43.7



7
6.000
3.39



8
−8.642
0.80
1.66547
55.2



9
8.000
2.60
1.80518
25.5



10
−85.700
Variable


3
11
13.702
3.00
1.51450
63.1



12
−43.933
Variable


4
13
137.583
0.80
1.84666
23.9



14
10.422
2.80
1.60602
57.4



15
−46.478
0.16



16
13.885
2.60
1.56883
56.0



17
−24.865
Variable


6
18
∞
4.00
1.51633
64.1



19
∞
—









Table 2 shows aspherical coefficients in the examples of Table 1. In Table 2, K is a conic constant, and D, E, F, G are aspherical coefficients. These also apply to Tables 5, 8, 11, 14, 26, 32, 38, 44, 47, 50, 53, 56, 59, 62, 65, 68, 71, 74, and 77.









TABLE 2









Surface












8
11
12
17















K
 2.44209 × 10−1
−2.94965 × 10−2
−7.06772 × 10
5.00685


D
 9.09600 × 10−5
−8.84486 × 10−5
−8.47419 × 10−5
8.59675 × 10−5


E
 3.54726 × 10−6
−2.01845 × 10−7
 1.51914 × 10−6
3.78258 × 10−7


F
−6.27173 × 10−7
 1.11591 × 10−8
−3.20919 × 10−8
4.82992 × 10−10


G
 1.82732 × 10−8
−1.53242 × 10−10
−1.00434 × 10−9
1.52605 × 10−10









The following Table 3 shows an air distance (mm) that is varied by zooming in the case where an object is positioned 2 m away from the tip end of the lens. The standard position is where the third lens group 13 is placed most closely to the fourth lens group 14. In Table 3, f(mm), F/NO, and ω(°) represent a focal length, an F number, and an incident half-angle of view at a wide-angle end, a standard position, and a telephoto end of the zoom lens. These also apply to Tables 6, 9, 12, 15, 26, 45, 48, 51, 54, 57, 60, 63, 66, 69, 72, 75, and 78.











TABLE 3







Wide-angle end
Standard position
Telephoto end





















f
4.018
23.629
64.517



F/NO
1.462
1.750
2.145



2ω
65.578
11.544
4.354



d5
0.500
16.120
20.600



d10
22.043
5.523
1.943



d14
9.733
5.467
9.131



d19
1.009
5.275
1.611










FIGS. 2 to 4 show various aberrations at the wide-angle end (FIG. 2), the standard position (FIG. 3), and the telephoto end (FIG. 4) of the zoom lens shown in Table 1. In each figure, (a) shows a spherical aberration, where a solid line represents values with respect to the d-line and a broken line represents sine condition; (b) shows astigmatism, where a solid line represents a curvature of a sagittal image plane, and a broken line represents a curvature of a meridional image plane; (c) shows a distortion aberration; (d) shows a longitudinal chromatic aberration, where a solid line represents values with respect to the d-line, a short broken line represents values with respect to an F-line, and a long broken line represents values with respect to a C-line; and (e) shows a chromatic aberration of magnification, where a short broken line represents values with respect to the F-line, and a long broken line represents values with respect to the C-line. This also applies to FIGS. 6 to 8, FIGS. 10 to 12, FIGS. 14 to 16, FIGS. 18 to 20, FIGS. 21 to 23, FIGS. 25 to 27, FIGS. 30 to 32, FIGS. 35 to 37, FIGS. 40 to 42, FIGS. 47 to 49, FIGS. 53 to 55, FIGS. 58 to 60, FIGS. 62 to 64, FIGS. 67 to 69, FIGS. 71 to 73, FIGS. 75 to 77, FIGS. 79 to 81, FIGS. 84 to 86, FIGS. 87 to 89, and FIGS. 91 to 93.
As is understood from FIGS. 2 to 4, the zoom lens in the present example exhibits satisfactory aberration performance.
The following expressions (1) and (2) relate to the shifting amount of the correcting lens (the third lens group 13).

Yt>Y  (1)

(Y/Yt)/(f/ft)<1.5  (2)

In the expressions (1) and (2), Y represents the shifting amount of the correcting lens (the third lens group 13) at the focal length f of the entire system when correcting camera shake; Yt represents the shifting amount of the correcting lens (the third lens group 13) at the telephoto end; and ft represents a focal length at the telephoto end.
For a zoom lens, a correcting lens moves further as the zoom ratio is great when the correction angle is constant in the whole zooming region. On the other hand, the correcting lens moves less when the zooming ratio is small. That is, when the shift of the lens exceeds the upper limit defined in the expressions (1) and (2), overcorrection occurs and the optical performance will deteriorate greatly. In conclusion, by satisfying the expressions (1) and (2), a zoom lens having a function to correct camera shake, where the aberration performance deteriorate less even during camera shake, can be obtained. This applies also to the following embodiments.
The aspherical shape of the third lens group 13 is defined by the following equation (A), which applies also to the allowing embodiments 2-5.




  
    
      
        SAG
        =
        
          
            
              
                H
                2
              
              /
              R
            
            
              1
              +
              
                
                  1
                  -
                  
                    
                      (
                      
                        1
                        +
                        K
                      
                      )
                    
                    ⁢
                    
                      
                        (
                        
                          H
                          /
                          R
                        
                        )
                      
                      2
                    
                  
                
              
            
          
          +
          
            D
            ·
            
              H
              4
            
          
          +
          
            E
            ·
            
              H
              6
            
          
          +
          
            F
            ·
            
              H
              8
            
          
          +
          
            G
            ·
            
              H
              10
            
          
        
      
    
    
      
        (
        A
        )
      
    
  




    SAG: a distance from the apex on the aspherical surface to a point on the same aspherical surface having a height H from the optical axis
    H: a height from an optical axis
    R is a radius of curvature at the apex on the aspherical surface
    K: a conical constant
    D, E, F, G: aspherical coefficients


Second Embodiment
FIG. 5 is a view showing the arrangement of a zoom lens in a second embodiment according to the present invention. As shown in FIG. 5, a zoom lens has a structure in which a first lens group 51, a second lens group 52, a third lens group 53, and a fourth lens group 64 are disposed from an object side deft side in FIG. 5) to an image plane side (right side in FIG. 5) in this order. Basic structure and operations are the same as the first embodiment. Specific examples of zoom lenses according to this embodiment are shown in the following Table 4.












TABLE 4





Group
Surface
r
d
n
ν




















1
1
41.544
0.90
1.80518
25.4



2
21.097
5.00
1.58913
61.2



3
−95.428
0.20



4
17.473
2.70
1.60311
60.7



5
42.181
Variable


2
6
41.372
0.65
1.77250
49.6



7
5.857
2.89



8
−7.776
0.85
1.66547
55.2



9
8.195
2.05
1.84666
23.9



10
340.000
Variable


3
11
17.024
2.00
1.68619
34.2



12
−400.000
Variable


4
13
−27.898
0.65
1.84666
23.9



14
18.114
2.35
1.51450
63.1



15
−18.114
0.10



16
18.601
3.40
1.51450
63.1



17
−9.892
Variable


5
18
∞
14.00
1.58913
61.0


6
19
∞
3.90
1.51633
64.1



20
∞
—









Table 5 shows aspherical coefficients in the examples of Table 4.









TABLE 5









Surface












8
11
12
15















K
−1.10251 × 10−1
 8.93500 × 10−2
 0.00000
−3.79663 × 10−1


D
−7.40852 × 10−5
−8.17245 × 10−5
 1.30862 × 10−5
 2.87398 × 10−4


E
 2.84234 × 10−5
−4.29821 × 10−6
−4.69807 × 10−6
 2.61848 × 10−6


F
−4.64719 × 10−6
 3.44381 × 10−7
 2.94604 × 10−7
 1.24341 × 10−7


G
 2.04967 × 10−7
−1.18101 × 10−8
−9.69640 × 10−9
−1.73992 × 10−9









The following Table 6 shows an air distance (mm) that is varied by zooming in the case where an object is positioned 2 m away from the tip end of the lens.











TABLE 6







Wide-angle end
Standard position
Telephoto end





















f
4.165
24.690
49.101



F/NO
1.674
2.070
2.373



2ω
59.818
10.314
5.244



d5
0.700
13.501
16.690



d10
18.493
5.692
2.503



d14
5.806
1.925
4.680



d19
1.009
4.890
2.135










FIGS. 6 to 8 show various aberrations at the wide-angle end (FIG. 6), the standard position (FIG. 7), and the telephoto end (FIG. 8) of the zoom lens shown in Table 4. As is understood from FIGS. 6 to 8, the zoom lens in the present example exhibits satisfactory aberration performance.
By satisfying the expressions (1) and (2), a zoom lens having a function to correct camera shake can be obtained, and the aberration performance deteriorate less during camera shake.
Third Embodiment
FIG. 9 is a view showing the arrangement of a zoom lens in a third embodiment according to the present invention. As shown in FIG. 9, a zoom lens has a structure in which a first lens group 91, a second lens group 92, a third lens group 93, and a fourth lens group 94 are disposed from an object side Deft side in FIG. 9) to an image plane side (right side in FIG. 9) in this order. The first lens group 91 has a positive refracting power and is fixed with respect to the image plane in varying power and focusing.
The second lens group 92 has a negative refracting power and varies power by moving along the optical axis. The third lens group 93 is composed of two lenses: one lens having a positive refracting power and one lens having a negative refracting power, and it is fixed with respect to the image plane in varying power and focusing. When camera shake occurs, shake of an image is corrected by moving the whole third lens group 93 in a direction vertical to the optical axis.
As mentioned above, by increasing the number of movable lenses, high optical performance can be maintained when the lenses are moved. Since a whole lens group of a united optical performance is decentered, deterioration in aberration can be decreased when compared to a type of zoom lens where a part of lenses in a group is moved.
The fourth lens group 94 has a positive refracting power, and it moves along an optical axis so as to keep the image plane varied by a shift of the second lens group 92 and an object at a predetermined position from a reference surface, thereby moving an image and adjusting the fcus thereof at the same time in accordance with variable power.
Since the aberration can be corrected during camera shake with greater efficiency by applying at least one aspherical surface to the lenses of the third group 93, performance during the move of the lenses can be improved.
Specific examples of zoom lenses according to this embodiment are shown in the following Table 7.












TABLE 7





Group
Surf
r
d
n
ν




















1
1
48.617
0.90
1.80518
25.4



2
24.708
4.90
1.60311
60.7



3
−355.522
0.15



4
24.085
2.90
1.60311
60.7



5
74.515
Variable


2
6
73.357
0.70
1.78500
43.7



7
5.318
3.22



8
−10.237
0.80
1.60602
57.5



9
7.306
2.40
1.80518
25.4



10
−350.000
Variable


3
11
7.997
4.45
1.60602
57.5



12
−17.026
0.60



13
57.521
0.70
1.80518
25.4



14
8.270
Variable


4
15
11.387
0.70
1.68613
34.2



16
6.389
2.60
1.60602
57.5



17
−41.310
Variable


5
18
∞
3.25
1.51633
64.0



19
∞









Table 8 shows aspherical coefficients in the examples of Table 7.









TABLE 8









Surface












8
11
12
17















K
−8.18660
−3.87371 × 10−1
 7.80366 × 10−1
−7.55214 × 10+1


D
−9.06079 × 10−4
−1.20009 × 10−4
 2.87007 × 10−4
−9.87827 × 10−5


E
 2.88719 × 10−5
 3.93781 × 10−7
−5.40973 × 10−7
 3.54330 × 10−6


F
−7.10067 × 10−7
 0.00000
 0.00000
 0.00000









The following Table 9 shows an air distance (mm) that is varied by zooming in the case where an object is positioned 2 m away from the tip end of the lens.











TABLE 9







Wide-angle end
Standard position
Telephoto-end





















f
3.827
38.626
91.142



F/NO
1.677
2.509
3.407



2ω
64.762
6.542
2.912



d5
0.5000
21.9344
26.2500



d10
27.8000
6.3655
2.0500



d14
10.1301
2.6424
9.3301



d17
5.0072
12.4949
5.8072










FIGS. 10 to 12 show various aberrations at the wide-angle end (FIG. 10), the standard position (FIG. 11), and the telephoto end (FIG. 12) of the zoom lens shown in Table 7. As is understood from FIGS. 10 to 12, the zoom lens in the present example exhibits satisfactory aberration performance.
By satisfying the expressions (1) and (2), a zoom lens having a function to correct camera shake can be obtained, and the aberration performance deteriorates less during camera shake.
Fourth Embodiment
FIG. 13 is a view showing the arrangement of a zoom lens in a fourth embodiment according to the present invention. As shown in FIG. 13, a zoom lens has a structure in which a first lens group 131, a second lens group 182, a third lens group 133, and a fourth lens group 134 are disposed from an object side (left side in FIG. 13) to an image plane side (right side in FIG. 13) in this order.
The first lens group 131 has a positive refracting power and is fixed with respect to the image plane even in varying power and focusing. The second lens group 182 has a negative refracting power and varies power by moving along the optical axis. The third lens group 133 is composed of two lenses: one lens having a positive refracting power and one lens having a negative refracting power, and it is fixed with respect to the image plane in varying power and focusing.
When camera shake occurs, shake of the image is corrected by moving the whole third lens group 133 in a direction vertical to the optical axis. As mentioned above, by increasing the number of movable lenses; high optical performance can be maintained when the lenses are moved.
Since the third lens group 133 in this embodiment is composed of two lenses: one lens having a positive refracting power and one lens having a negative refracting power, aberration can be corrected more efficiently when correcting camera shake, and deterioration in the image quality can be decreased when correcting camera shake.
The fourth lens group 134 has a positive refracting power, moves along an optical axis so as to keep the image plane varied by a shift of the second lens group 132 and an object at a predetermined position from a reference surface, thereby moving an image and adjusting the focus thereof at the same time in accordance with variable power. Since the aberration can be corrected when correcting camera shake further efficiently by applying at least one aspherical surface to the lenses of the third group 133, performance can be improved when the lenses are moved.
Specific examples of zoom lenses according to this embodiment are shown in the following Table 10.












TABLE 10





Group
Surface
r
d
n
ν




















1
1
41.544
0.90
1.80518
25.4



2
21.097
5.00
1.58913
61.2



3
−95.428
0.20



4
17.473
2.70
1.60311
60.7



5
42.181
Variable


2
6
41.372
0.65
1.77250
49.6



7
5.857
2.89



8
−7.776
0.85
1.66547
55.2



9
8.195
2.05
1.84666
23.9



10
340.000
Variable


3
11
14.743
2.45
1.51450
63.1



12
−45.960
1.50



13
33.378
1.50
1.66547
55.2



14
19.936
Variable


4
15
−41.230
0.65
1.84666
23.9



16
22.061
2.20
1.51450
63.1



17
−38.993
0.10



18
14.246
3.40
1.51450
63.1



19
−9.338
Variable


5
20
∞
14.00
1.58913
61.0


6
22
∞
3.90
1.51633
64.1



23
∞









Table 11 shows aspherical coefficients in the Examples of Table 10.









TABLE 11









Surface












8
11
12
17















K
−1.10251 × 10−1
 0.00000
0.00000
−3.79663 × 10−1


D
−7.40852 × 10−5
−1.56773 × 10−5
9.91198 × 10−5
 4.04267 × 10−4


E
 2.84234 × 10−5
 2.64330 × 10−6
4.19737 × 10−6
 3.44573 × 10−6


F
−4.64719 × 10−6
−2.20686 × 10−7
2.48747 × 10−8
 1.86356 × 10−7


G
 2.04967 × 10−7
 5.27090 × 10−10
1.70900 × 10−9
−2.73441 × 10−9









The following Table 12 shows an air distance (mm) that is varied by zooming in the case where an object is positioned 2 m away from the tip end of the lens.











TABLE 12







Wide-angle end
Standard position
Telephoto end





















f
4.129
24.191
49.099



F/NO
1.681
2.070
2.334



2ω
60.356
10.536
5.287



d5
0.700
13.501
16.690



d10
16.993
4.192
1.003



d14
5.806
1.925
4.680



d19
1.009
4.890
2.135










FIGS. 14 to 16 show various aberrations at the wide-angle end (FIG. 14), the standard position (FIG. 15), and the telephoto end (FIG. 16) of the zoom lens shown in Table 10. As is shown in FIGS. 14 to 16, the zoom lens in the present embodiment exhibits satisfactory aberration performance.
By satisfying the expressions (1) and (2), a zoom lens having a function to correct camera shake can be obtained, in which the aberration performance deteriorates less during camera shake.
Fifth Embodiment
FIG. 17 is a view showing the arrangement of a zoom lens in a fifth embodiment according to the present invention. As shown in FIG. 17, a zoom lens has a structure in which a first lens group 171, a second lens group 172, a third lens group 173, and a fourth lens group 174 are disposed from an object side (left side in FIG. 17) to an image plane side (right side in FIG. 17) in this order.
The first lens group 171 has a positive refracting power and is fixed with respect to the image plane even in varying power and focusing. The second lens group 172 has a negative refracting power and varies power by moving along the optical axis.
The third lens group 173 is composed of three lenses including at least one lens having a positive refracting power and at least one lens having a negative refracting power, and the group is fixed with respect to the image plane in varying power and focusing.
When camera shake occurs, shake of the image is corrected by moving the whole third lens group 173 in a direction vertical to the optical axis. For a small zoom lens, the third lens group 173 is required to have a strong positive refracting power to shorten the whole length, and this will cause aberration.
However, since the zoom lens in this embodiment has a third lens group 173 composed of three lenses, aberration occurring at the third lens group 173 is suppressed and high optical performance is maintained when the lenses are moved.
The fourth lens group 174 has a positive refracting power, and moves along an optical axis so as to keep the image plane varied by a shift of the second lens group 172 and an object at a predetermined position from a reference surface, thereby moving an image and adjusting the focus thereof at the same time in accordance with variable power.
Since the aberration can be corrected during camera shae with more efficiency by applying at least one aspherical surface to the lenses of the third group 173, performance can be improved when the lenses are moved.
Specific examples of zoom lenses according to this embodiment are shown in the following Table 13.












TABLE 13





Group
Surface
r
d
n
ν




















1
1
48.280
0.90
1.80518
25.4



2
17.748
4.53
1.60311
60.7



3
−67.680
0.20



4
14.615
2.67
1.69680
55.6



5
42.483
Variable


2
6
42.483
0.60
1.77250
49.6



7
4.842
2.15



8
−6.478
0.80
1.66547
55.2



9
5.874
1.80
1.80518
25.5



10
−323.142
Variable


3
11
7.889
4.55
1.66547
55.2



12
−14.939
0.10



13
9.748
2.40
1.51633
64.1



14
−104.180
0.60
1.84666
23.9



15
5.767
Variable


4
16
7.481
2.87
1.51450
63.1



17
−31.976
Variable


5
18
∞
4.30
1.51633
64.1



19
∞
—









Table 14 shows aspherical coefficients in the Examples of Table 13.









TABLE 14









Surface












8
11
12
16















K
−1.30349
−7.99910
−6.269020
−1.99544 × 10−2


D
−6.01825 × 10−4
−1.39502 × 10−4
−4.75872 × 10−6
−2.07422 × 10−5


E
−2.10812 × 10−5
 2.02487 × 10−7
 1.65237 × 10−7
−6.99987 × 10−6


F
 0.00000
 0.00000
 0.00000
 0.00000


G
 0.00000
 0.00000
 0.00000
 0.00000









The following Table 15 shows an air distance (mm) that is varied by zooming in the case where an object is positioned 2 m away from the tip end of the lens.











TABLE 15







Wide-angle end
Standard position
Telephoto end





















f
4.827
21.634
46.275



F/NO
1.461
2.197
2.851



2ω
59.897
12.728
6.609



d5
0.700
9.569
12.450



d10
13.383
4.514
1.633



d14
6.113
1.859
6.193



d19
1.000
5.254
0.920










FIGS. 18 to 20 show various aberrations at the wide-angle end (FIG. 18), the standard position (FIG. 19), and the telephoto end (FIG. 20) of the zoom lens shown in Table 13. As is shown in FIGS. 18 to 20, the zoom lens in the present example exhibits satisfactory aberration performance.
By satisfying the expressions (1) and (2), a zoom lens having a function to correct camera shake can be obtained, and the aberration performance deteriorates less during camera shake.
Specific examples of zoom lenses according to this embodiment, in addition to the above-mentioned lenses, are shown in the allowing Table 16.












TABLE 16





Group
Surface
r
d
n
ν




















1
1
31.758
0.90
1.80518
25.5



2
15.951
4.50
1.58913
61.2



3
−135.286
0.15



4
14.102
3.00
1.58913
61.2



5
45.000
Variable


2
6
45.000
0.50
1.77250
49.6



7
4.188
2.36



8
−6.630
0.70
1.60602
57.8



9
5.382
1.75
1.80518
25.5



10
88.671
Variable


3
11
6.731
3.50
1.60602
57.8



12
−11.394
0.50



13
12.785
1.70
1.51633
64.1



14
−350.000
0.50
1.84666
23.9



15
5.875
Variable


4
16
7.945
1.95
1.51450
63.1



17
−28.581
Variable


5
18
∞
3.70
1.51633
64.1



19
∞
—









Table 17 shows aspherical coefficients in the Examples of Table 16.









TABLE 17









Surface












8
11
12
16















K
−3.79187
−1.49571
−5.54316
−2.04960


D
−1.52553 × 10−3
 6.24513 × 10−5
 9.21711 × 10−6
 3.68450 × 10−4


E
−4.26600 × 10−6
−3.45653 × 10−6
−4.27080 × 10−6
−8.68455 × 10−6


F
−1.29623 × 10−6
 1.02115 × 10−7
 1.47247 × 10−7
−2.70755 × 10−9









The following Table 18 shows an air distance (mm) that is varied by zooming in the case where an object is positioned 2 m away from the tip end of the lens.











TABLE 18







Wide-angle end
Standard position
Telephoto end





















f
4.355
23.581
48.637



F/NO
1.857
2.101
2.485



2ω
57.157
10.756
5.259



d5
0.500
10.347
12.880



d10
14.442
4.595
2.062



d14
7.262
2.386
5.951



d19
1.011
5.888
2.323










FIGS. 21 to 23 show various aberrations at the wide-angle end (FIG. 21), the standard position (FIG. 22), and the telephoto end (FIG. 23) of the zoom lens shown in Table 16. As is understood from FIGS. 21 to 23, the zoom lens in the present example exhibits satisfactory aberration performance.
By satisfying the expressions (1) and (2), a zoom lens having a function to correct camera shake can be obtained, and the aberration performance deteriorates less during camera shake.
The first to fifth embodiments relate to zoom lenses. By using these zoom lenses, video cameras having a function to correct camera shake can be provided, and such video cameras can be downsized and lightweight.
Sixth Embodiment
FIG. 24 is a view showing the arrangement of a zoom lens in a sixth embodiment according to the present invention. As shown in FIG. 24, a zoom lens has a structure in which a first lens group 241, a second lens group 242, a third lens group 243, a fourth lens group 244, and a plate 245 equivalent to an optical low-pass filter and a face plate of a CCD are disposed from an object side to an image plane side in this order.
The first lens group 241 has a positive refracting power, and is fixed with respect to the image plane 246 in varying power and focusing. The second lens group 242 has a negative refracting power as a whole and varies power by moving along an optical axis. The third lens group 243 is composed of three lenses: a positive lens, a positive lens, and a negative lens disposed from the object side in this order, and is fixed with respect to the image plane 246 in varying power and focusing. The fourth lens group 244 is composed of one positive lens. The fourth lens group 244 moves along an optical axis 80 as to move an image and adjust the focus thereof at the same time in accordance with variable power.
When camera shake occurs, shake of an image is corrected by moving the third lens group 243 vertically with respect to the optical axis direction. Since the third lens group 243 is smaller in lens diameter than the first lens group 241, correction by moving the third lens group 243 will cause less load for the driving system, and electric power also can be saved. By satisfying the expressions (1) and (2), a zoom lens having a function to correct camera shake, where the aberration performance deteriorates less during camera shake, can be obtained.
The following expression (3) relates to a shift of a third lens group.

2.0<f3/fw<4.0  (3)

In the above expression (3), f3 represents a focal length of the third lens group and fw represents a focal length of the entire system at a wide-angle end.
When the value falls below the lower limit, the aberration will be difficult to correct in a stationary state or when correcting camera shake even if the third lens group is composed of three lenses. When the value exceeds the upper limit, the shifting amount is increased when correcting camera shake and the zoom lens barrel becomes large in diameter. Moreover, the entire length is increased and the zoom lens cannot be downsized. By satisfying the expression (3), the shifting amount when correcting camera shake can be decreased and the whole length of the zoom lens can be shortened, and thus, a small zoom lens can be provided.
Furthermore, by applying at least one aspherical surface to the third lens group as a shift lens group and also to the fourth lens group having focusing action, aberration can be corrected when correcting camera shake as well as in the stationary state.
The following expression (4) relates to an aspherical shape of the object side of a lens of the third lens group, when the lens is disposed closest to the object.

1.05<R11/R10<2.5  (4)

In the expression (4), R10 represents a local radius of curvature in the vicinity of the optical axis, and R11 represents a local radius of curvature in an outer peripheral portion.
The expression (4) defines a range to correct the spherical aberration satisfactorily. A negative spherical aberration occurs when the value falls below the lower limit, while positive spherical aberration occurs as a result of overcorrection when the value exceeds the upper limit.
The following expression (5) relates to an aspherical shape of a lens of the fourth lens group when viewed from the object side.

1.05<R21<R20<2.0  (5)

R20 represents a local radius of curvature in the vicinity of the optical axis, and R21 represents a local radius of curvature in an outer peripheral portion.
The expression (5) defines a range to satisfactorily correct a coma aberration of an upper flux of an off-axis ray. An internal coma occurs when the value falls below the lower limit, while an external coma occurs when the value exceeds the upper limit.
Specific examples of zoom lenses according to this embodiment are shown in the following Table 19.












TABLE 19





Group
Surface
r
d
n
ν




















1
1
31.089
0.90
1.80518
25.4



2
15.820
4.50
1.58913
61.2



3
−171.154
0.15



4
14.460
3.00
1.60311
60.7



5
48.740
Variable


2
6
48.740
0.50
1.77250
49.6



7
4.206
2.34



8
−8.647
0.55
1.60602
57.4



9
5.292
1.75
1.80518
25.4



10
88.671
Variable


3
11
7.268
3.25
1.51450
63.1



12
−14.052
0.10



13
9.072
2.20
1.51895
57.3



14
−37.099
0.50



15
60.905
0.50
1.84666
25.4



16
5.422
Variable


4
17
7.232
2.00
1.51450
63.1



18
−42.485
Variable


5
19
∞
3.70
1.51633
64.1



20
∞
—









The aspherical shape is defined by the following equation CB). (This also applies to examples 7 to 9.)




  
    
      
        SAG
        =
        
          
            
              
                H
                2
              
              /
              R
            
            
              1
              +
              
                
                  1
                  -
                  
                    
                      (
                      
                        1
                        +
                        K
                      
                      )
                    
                    ⁢
                    
                      (
                      
                        H
                        /
                        
                          R
                          2
                        
                      
                      )
                    
                  
                
              
            
          
          +
          
            D
            ·
            
              H
              4
            
          
          +
          
            E
            ·
            
              H
              6
            
          
          +
          
            F
            ·
            
              H
              8
            
          
        
      
    
    
      
        (
        B
        )
      
    
  




    SAG: a distance from the apex on the aspherical surface to a point on the same aspherical surface having a height H from the optical axis
    H: a height from an optical axis
    R: a radius of curvature at the apex on the aspherical surface
    K: a conical constant
    D, E, F: aspherical coefficients


The following Table 20 shows aspherical shapes of the zoom lens in the the present example.









TABLE 20









Surface












8
11
12
17















K
−3.46709
−1.57334
−4.56016
−1.39803


D
−1.36790 × 10−3
−6.68922 × 10−5
 1.39115 × 10−5
 1.90786 × 10−4


E
−1.82278 × 10−5
−1.31623 × 10−6
−1.82005 × 10−6
 9.90799 × 10−6


F
−5.96614 × 10−7
 8.53637 × 10−8
 1.00886 × 10−7
−6.93646 × 10−7









The following Table 21 shows an air distance (mm) that is varied by zooming in the case where an object is positioned 2 m away from the tip end of the lens. A standard position represents a position where the third lens group 243 is disposed the closest to the fourth lens group 244. The Table 21 indicates also a shifting amount Y of the third lens group at a correction of 0.5 degrees.











TABLE 21







Wide-angle end
Standard position
Telephoto end



















f
4.350
23.464
48.623


F/NO
1.873
2.096
2.490


ω
28.770
5.415
2.638


d5
0.500
10.344
12.893


d10
14.442
4.597
2.049


d16
7.262
2.393
5.880


d18
1.012
5.880
2.393


Y
0.034
0.197
0.392


Expression (2)
0.972
1.041
1.000









As shown in FIG. 21, the a shift of the third lens group in this embodiment satisfies the expressions (1) and (2), and thus, it realizes optical performance with less deterioration when compared to a stationary state.
Furthermore, in the zoom lens of the present example, a focal length f3 of the third lens group satisfies the expression (3) and a small zoom lens is provided.









TABLE 22





Fw
f3
Expression (3) (f3/fw)







4.350
11.311
2.60









In this embodiment, the third lens group has a lens at the side closest to the object, and the both surfaces of the lens are aspherical Especially, the local radius of curvature R10 in the vicinity of the object-side surface and the local radius of curvature R11 in an outer peripheral portion have values shown in the following Table 23, and satisfy the expression (4). As a result, the embodiment realizes excellent aberration performance not only in the stationary state but when correcting camera shake, and especially, the embodiment realizes a spherical aberration that is satisfactorily corrected.









TABLE 23





R10
R11
Expression (4) (R11/R10)







7.268
13.516
1.86









Furthermore, the lens of the fourth lens group has an aspherical surface when viewed from the object side, a local radius of curvature R20 in the vicinity of an optical axis and a local radius of curvature R11 in an outer peripheral portion with the values shown in Table 24. Moreover, when the expression (5) is satisfied, excellent aberration performance is realized not only in its station state but when correcting camera shake. Especially a satisfactory coma aberration is realized.









TABLE 24





R20
R21
Expression (5) (R21/R20)







7.232
10.112
1.40









FIGS. 25 to 27 show various aberrations at the wide-angle end, the standard position, and the telephoto end of the zoom lens shown in Table 19.
FIG. 28 shows aberrations at a telephoto end at a correction of 0.5 degrees. FIGS. 28(a), 28(b) and 28(c) show lateral aberrations at a relative angle of view of 0.75, along the axis, and at a relative angle of view of −0.75. A solid line, the dotted line and the wave line represent values with respect to the d-line, F-line and C-line (this applies to the following FIGS. 33, 38, and 43). As indicated in FIGS. 25-28, a zoom lens according to this embodiment provides a satisfactory aberration performance.
Seventh Embodiment
FIG. 29 is a view showing the arrangement of a zoom lens in a seventh embodiment according to the present invention. As shown in FIG. 29, a zoom lens has a structure in which a first lens group 61, a second lens group 62, a third lens group 63, a fourth lens group 64, and a plate 65 equivalent to an optical low-pass filter and a face plate of a CCD are disposed from an object side to an image plane side in this order.
The first lens group 61 has a positive refracting power, and is fixed with respect to the image plane 66 in varying power and focusing. The second lens group 62 has a negative refracting power and varies power by moving along an optical axis. The third lens group 63 is composed of three lenses: a positive lens, a positive lens, and a negative lens disposed from the object side in this order, and two of the lenses at the image plane side compose a cemented lens of a positive lens and a negative lens. The third lens group 63 is fixed with respect to the image plane 66 in varying power and focusing. The fourth lens group 64 is composed of one positive lens. The fourth lens group 64 moves along an optical axis so as to move an image and adjust the focus thereof at the same time in accordance with variable power.
When camera shake occurs, shake of an image is corrected by moving the third lens group 63 vertically with respect to the optical axis direction. Since the third lens group 63 is smaller in lens diameter than the first lens group 61, correction by moving the third lens group 63 will cause less load for the driving system, and electric power also can be saved. It is preferable that the expressions (1) to (5) are satisfied as in the sixth embodiment.
Specific examples of zoom lenses according to this embodiment are shown in the following Table 25.












TABLE 25





Group
Surface
r
d
n
ν




















1
1
31.758
0.90
1.80518
25.4



2
15.951
4.50
1.58913
61.2



3
−135.286
0.15



4
14.102
3.00
1.58913
61.2



5
45.000
Variable


2
6
45.000
0.50
1.77250
49.6



7
4.188
2.36



8
−6.630
0.70
1.60602
57.4



9
5.382
1.75
1.80518
25.4



10
88.671
Variable


3
11
6.731
3.50
1.60602
57.4



12
−11.394
0.50



13
12.785
1.70
1.51633
54.1



14
−350.000
0.50
1.84666
25.4



15
5.875
Variable


4
16
7.945
1.95
1.51450
63.1



17
−28.581
Variable


5
18
∞
3.70
1.51633
64.1



19
∞
—









The following Table 26 shows aspherical shapes of the zoom lens in the present example.









TABLE 26









Surface












8
11
12
16















K
−3.79187
−1.49571
−5.54316
−2.04960


D
−1.52553 × 10−3
 6.24513 × 10−5
 9.21711 × 10−6
 3.68450 × 10−4


E
−4.26600 × 10−6
−3.45653 × 10−6
−4.27080 × 10−6
−8.68455 × 10−6


F
−1.29623 × 10−6
 1.02115 × 10−7
 1.47247 × 10−7
−2.70755 × 10−9









The following Table 27 shows zooming distance and shifting amount.











TABLE 27







Wide-angle end
Standard position
Telephoto end



















f
4.355
23.464
48.623


F/NO
1.857
2.096
2.490


ω
28.579
5.415
2.638


d5
0.500
10.344
12.893


d10
14.415
4.597
2.049


d15
7.262
2.393
5.880


d17
1.012
5.880
2.393


Y
0.034
0.195
0.392


Expression (2)
0.970
1.027
1.000









As shown in Table 27, a shift of the third lens group satisfies the expressions (1) and (2), and it achieves optical performance with less deterioration when compared to a stationary state.
As shown in the following Table 28, the focal length f3 of the third lens group satisfies the expression (3), and thus, a small zoom lens is realized.









TABLE 28





fw
f3
Expression (3) (f3/fw)







4.350
11.317
2.60









In this embodiment, a lens of the third group, which is positioned closest to the object, has aspherical surfaces on both sides. Especially, the local radius of curvature R10 in the vicinity of the object side and the local radius of curvature R11 in an outer peripheral portion have values shown in the following Table 29, and satisfy the expression (4). As a result, the embodiment achieves excellent aberration performance not only in a stationary state but when correcting camera shake, and especially, aspherical aberration is corrected satisfactorily.









TABLE 29





R10
R11
Expression (4) (R11/R10)







6.731
12.417
1.85









Furthermore, the object-side surface of a lens of the fourth group is aspherical, a local radius of curvature R20 in the vicinity of an optical axis and a local radius of curvature R11 in an outer peripheral portion have the values shown in Table 30. Moreover, the expression (5) satisfied, excellent aberration performance is realized not only in its stationary state but at correcting. Especially a satisfactory coma aberration is realized.









TABLE 30





R20
R21
Expression (5) (R21/R20)







7.945
11.021
1.39









FIGS. 30 to 32 show various aberrations at the wide-angle end, the standard position, and the telephoto end of the zoom lens shown in Table 25. FIG. 33 shows an aberration at a telephoto end at a correction of 0.5 degrees. As indicated in FIGS. 30-33, a zoom lens according to this embodiment provides a satisfactory aberration performance.
Eighth Embodiment
FIG. 34 is a view showing the arrangement of a zoom lens in an eighth embodiment according to the present invention. As shown in FIG. 34, a zoom lens has a structure in which a first lens group 111, a second lens group 112, a third lens group 113, a fourth lens group 114, and a plate 115 equivalent to an optical low-pass filter and a face plate of a CCD are disposed from an object side to an image plane side in this order.
The first lens group 111 has a positive refracting power, and is fixed with respect to the image plane 116 in varying power and focusing. The second lens group 112 has a negative refracting power and varies power by moving along an optical axis.
The third lens group 113 is composed of three lenses: a positive lens, a negative lens, and a positive lens disposed from the object side in this order, and is fixed with respect to the image plane 306 in varying power and focusing. The fourth lens group 114 is composed of one positive lens, and moves along an optical axis so as to move an image and adjust the focus thereof at the same time in accordance with variable power.
When camera shake occurs, shake of an image is corrected by moving the third lens group 113 vertically with respect to the optical axis direction. Since the third lens group 113 is smaller in lens diameter than the first lens group 111, correction by moving the third lens group 113 will cause less load for the driving system, and electric power also can be saved. It is preferable that the expressions (1) to (5) are satisfied as in the sixth embodiment.
Specific examples of zoom lenses according to this embodiment are shown in the following Table 31. The first and second lens groups in these embodiments are the same as shown in Table 19.












TABLE 31





Group
Surface
r
d
n
ν




















3
11
6.854
3.95
1.51450
63.1



12
−7.934
1.20



13
−10.797
0.50
1.78472
25.7



14
16.985
0.86



15
−21.096
2.00
1.51895
57.3



16
−6.963
Variable


4
17
9.141
1.90
1.51450
63.1



18
335.606
Variable


5
19
∞
3.70
1.51633
64.1



20
∞
—









The following Table 32 shows aspherical shapes of the zoom lens in the present example.









TABLE 32









Surface












8
11
12
17















K
−3.46709
−1.99011
−3.12036
−1.04888


D
−1.36790 × 10−3
 2.73697 × 10−4
 2.30462 × 10−5
 1.27223 × 10−4


E
−1.82278 × 10−5
−2.65163 × 10−6
 1.73552 × 10−6
−1.69913 × 10−7


F
−5.96614 × 10−7
 2.37367 × 10−7
 1.42772 × 10−7
−4.55207 × 10−8









The following Table 33 shows zooming distance and shifting amount.











TABLE 33







Wide-angle end
Standard position
Telephoto end



















f
4.246
21.577
47.769


F/NO
1.859
2.003
2.426


ω
29.455
5.923
2.694


d5
0.500
10.344
12.893


d10
14.442
4.597
2.049


d15
7.261
2.300
5.779


d17
1.013
5.973
2.495


Y
0.031
0.161
0.347


Expression (2)
1.012
1.027
1.000









As shown in Table 33, a shift of the third lens group satisfies the expressions (1) and (2), and it provides an optical performance with less deterioration when compared to a stationary state.
As shown in the following Table 34, the focal length f3 of the third lens group satisfies the expression (3), and achieves a small zoom lens.









TABLE 34





fw
F3
Expression (3) (f3/fw)







4.246
13.079
3.08









In this example, a lens of the third group, which is positioned closest to the object, has aspherical surfaces on both sides. Especially, the local radius of curvature R10 in the vicinity of the object-side and the local radius of curvature R11 in an outer peripheral portion have values shown in the following Table 35, and satisfy the expression (4). As a result; the embodiment realizes excellent aberration performance not only in a stationary state but when correcting camera shake, and especially, aspherical aberration is corrected satisfactorily.









TABLE 35





R10
R11
Expression (4) (R11/R10)







6.854
8.352
1.22









Furthermore, the object-side surface of a lens of the fourth group is aspherical, a local radius of curvature R20 in the vicinity of an optical axis and a local radius of curvature R11 in an outer peripheral portion have the values shown in Table 36. Moreover, the expression (5) is satisfied, excellent aberration performance is realized not only in its stationary state but when correcting camera shake. Especially a satisfactory coma aberration is achieved.









TABLE 36





R20
R21
Expression (5) (R21/R20)







9.141
10.416
1.14









FIGS. 85 to 87 show various aberrations at the wide-angle end, the standard position, and the telephoto end of the zoom lens shown in Table 31. FIG. 38 shows an aberration at a telephoto end at a correction of 0.5 degrees. As indicated in FIGS. 35-38, a zoom lens according to this embodiment provides a satisfactory aberration performance.
Ninth Embodiment
FIG. 39 is a view showing the arrangement of a zoom lens in a ninth embodiment according to the present invention. As shown in FIG. 39, a zoom lens has a structure in which a first lens group 161, a second lens group 162, a third lens group 163, a fourth lens group 164, and a plate 165 equivalent to an optical low-pass filter and a face plate of a CCD are disposed from an object side to an image plane side in this order.
The first lens group 161 has a positive refracting power, and is fixed with respect to the image plane 166 in varying power and focusing. The second lens group 162 has a negative refracting power and varies power by moving along an optical axis. The third lens group 163 is composed of three lenses: a positive lens, a negative lens, and a positive lens disposed from the object side in this order, and two of the lenses at the image plane side compose a cemented lens of a negative lens and a positive lens.
The third lens group 163 is fixed with respect to the image plane 166 in varying power and focusing. The fourth lens group 164 is composed of one positive lens. The fourth lens group 164 moves along an optical axis so as to move an image and adjust the focus thereof at the same time in accordance with variable power.
When camera shake occurs, shake of an image is corrected by moving the third lens group 163 vertically with respect to the optical axis direction. Since the third lens group 163 is smaller in lens diameter than the first lens group 161, correction by moving the third lens group 163 will cause less load for the driving system, and electric power also can be saved.
It is preferable that the expressions (1) to (5) are satisfied as in the sixth to eighth embodiments.
Specific examples of zoom lenses according to this embodiment are shown in the following Table 37. The first and second lens groups in this embodiment are the same as shown in Table 19.












TABLE 37





Group
Surface
r
d
n
ν




















3
11
9.762
3.00
1.51450
63.1



12
−11.531
1.20



13
13.057
0.50
1.75520
27.5



14
−8.967
3.10
1.53358
51.6



15
−6.963
Variable


4
16
15.087
1.80
1.51450
63.1



17
−51.013
Variable


5
18
∞
3.70
1.51633
64.1



19
∞
—









The following Table 38 shows aspherical coefficients of the zoom lens in the present example.









TABLE 38









Surface












8
11
12
17















K
−3.46709
−3.79890
−1.61290
−2.22934


D
−1.36790 × 10−3
 1.01179 × 10−4
 4.06410 × 10−5
−1.33735 × 10−5


E
−1.82278 × 10−5
−6.62306 × 10−7
 8.30510 × 10−7
 1.01922 × 10−6


F
−5.96614 × 10−7
 1.67378 × 10−7
 1.66830 × 10−7
 3.34079 × 10−8









The following Table 39 shows zooming distance and shifting amount.











TABLE 39







Wide-angle end
Standard position
Telephoto end



















f
4.224
22.092
47.644


F/NO
1.823
2.112
2.441


ω
29.569
5.749
2.672


d5
0.500
10.344
12.893


d10
14.442
4.597
2.049


d15
7.260
1.815
5.657


d17
1.014
6.459
2.617


Y
0.030
0.150
0.332


Expression (2)
1.016
0.974
1.000









As shown in Table 39, the shifting amount of the third lens group satisfies the expressions (1) and (2), and thus, the optical performance deteriorates less when compared to a stationary state.
As shown in the following Table 40, the focal length f3 of the third lens group satisfies the expression (3), and thus, a small zoom lens is achieved.









TABLE 40





Fw
f3
Expression (3) (f3/fw)







4.224
13.100
3.10









In this embodiment, a lens of the third group, which is disposed closest to the object, has aspherical surfaces at both sides. Especially, the local radius of curvature R10 in the vicinity of an optical axis at the object-side and the local radius of curvature R11 in an outer peripheral portion have values shown in the following Table 41, and satisfy the expression (4). As a result, the embodiment realizes excellent aberration performance not only in the stationary state but when correcting camera shake, and especially, aspherical aberration is corrected satisfactorily.









TABLE 41





R10
R11
Expression (4) (R11/R10)







9.762
10.339
1.06









Furthermore, the object-side surface of a lens included in the fourth lens group is aspherical, a local radius of curvature R20 in the vicinity of an optical axis and a local radius of curvature R21 in an outer peripheral portion have the values shown in Table 42. Moreover, the expression (5) is satisfied, and excellent aberration performance is realized not only in its stationary state but when correcting camera shake. Especially, a satisfactory coma aberration is achieved.









TABLE 42





R20
R21
Expression (5) (R21/R20)







15.087
16.164
1.07









FIGS. 40 to 42 show various aberrations at the wide-angle end, the standard position, and the telephoto end of the zoom lens shown in Table 37. FIG. 43 shows an aberration at a telephoto end at a correction of 0.5 degrees.
As indicated in FIGS. 40-43, a zoom lens according to this embodiment provides satisfactory aberration performance.
Tenth Embodiment
FIG. 44 shows a video camera in one embodiment of the present invention. The video camera is composed of a first lens group of a zoom lens shown in the sixth to ninth embodiments, a second lens group 211, a third lens group 212, a fourth lens group 213, an imager 214, a signal processing circuit 215, a camera-shake detecting system 216, and a driving system 217 for correcting camera shake. As a result, a small video camera having an excellent function for correcting camera shake can be provided.
Eleventh Embodiment
FIG. 45 is a view to show a basic structure of a zoom lens having a function for correcting camera shake in an eleventh embodiment. As shown in FIG. 46, a zoom lens in this embodiment comprises a first lens group having a positive refracting power and being fixed with respect to an image plane; a second lens group having a negative refracting power and varying power by moving along an optical axis; a third lens group having a positive refracting power and being fixed with respect to the image plane; a fourth lens group having a negative refracting power and being fixed with respect to the image plane; and a fifth lens group having a positive refracting power and moving along an optical axis so as to keep the image plane varied by the a shift of the second lens group and an object at a predetermined position from a reference surface, and the elements are disposed from an object side (left side in FIG. 45) to an image plane side (right side in FIG. 45) in this order. When camera shake occurs, shake of an image is corrected by shifting the third lens group having a positive refracting power in a direction vertical to the optical axis.
FIG. 46 shows a zoom lens having basic elements as shown in FIG. 45. The zoom lens has a structure in which a first lens group 461, a second lens group 462, a third lens group 468, a fourth lens group 464, and a fifth lens group 465 are disposed from an object side to an image plane side in this order.
The first lens group 461 has a positive refracting power, and is fixed with respect to the image plane in varying power and focusing. The second lens group 462 has a negative refracting power and varies power by moving along an optical axis. The third lens group 463 is composed of a positive lens and a negative lens, and has a positive refracting power as a whole.
The fourth lens group 464 is composed of a negative lens and a positive lens, and has a negative refracting power as a whole. It is fixed with respect to the image plane in varying power and focusing. The fifth lens group 465 has a positive refracting power and moves along an optical axis so as to move an image and adjust the focus thereof at the same time in accordance with variable power. When camera shake occur, shake of an image is corrected by moving the third lens group 463 vertically with respect to the optical axis.
As described in this embodiment, the third lens group 463 having a positive refracting power and the fourth lens group 464 having a negative refracting power are combined in order to decrease the shifting amount of the shift lens group when correcting camera shake, and to extend the back focus. Especially a long back focus is easy to obtain since a lens group having a negative refracting power is disposed at the image plane side.
Moreover, the performance when shifting the lenses can be improved, and downsizing and high performance are obtainable by applying at least one aspherical surface to any of the lenses of the third group.
It is preferable that the following expressions (6) and (7) are satisfied when v31 is Abbe's number of one lens of the third lens group, and v32 is Abbe's number of the remaining lens of the third group; v41 is Abbe's number of one lens of the fourth lens group, and v42 is Abbe's number of the remaining lens of the fourth group.

|v31-v32|>25  (6)

|v41-v42|>25  (7)

When the expressions (6) and (7) are satisfied, deterioration in chromatic aberration of magnification when correcting camera shake can be reduced. Chromatic aberration of magnification occurs when correcting camera shake due to lens-shifting, however, deterioration of the chromatic aberration of magnification can be reduced even when shifting a lens since a sufficient effect is obtainable for achromatism by setting differences in the Abbe's number as mentioned above for the respective lens groups.
It is preferable that the following expression (8) is satisfied when the lens for correcting camera shake has an aspherical surface at the object side, and rS1 is a local radius of curvature for a diameter occupying 10% of lens effective diameter, and rS9 is a local radius of curvature for a diameter occupying 90% of lens effective diameter.

0.01<rS1/rS9<2.00  (8)

The expression (8) is a conditional expression to determine the aspherical amount, and it indicates a condition to obtain sufficient aberration performance to realize high resolution for a zoom lens. When the value exceeds the upper limit in the Expression (8), the correcting amount for the spherical aberration is excessively decreased. Moreover, coma flares will occur easily when moving the lens. When the value falls below the lower limit, correction amount of the spherical aberration is excessively increased, and sufficient aberration performance cannot be obtained. Here, the local radius of curvature C is obtainable through an algebraic calculation based on aspherical coefficients figured out from the sag amount of the plane shape. It is obtainable by the following equations (C) and (D).




  
    
      
        SAG
        =
        
          
            
              
                H
                2
              
              /
              R
            
            
              1
              +
              
                
                  1
                  -
                  
                    
                      (
                      
                        1
                        +
                        K
                      
                      )
                    
                    ⁢
                    
                      
                        (
                        
                          H
                          /
                          R
                        
                        )
                      
                      2
                    
                  
                
              
            
          
          +
          
            D
            ·
            
              H
              4
            
          
          +
          
            E
            ·
            
              H
              6
            
          
          +
          
            F
            ·
            
              H
              8
            
          
          +
          
            G
            ·
            
              H
              10
            
          
        
      
    
    
      
        (
        C
        )
      
    
  
  
    
      
        
          
        
        ⁢
        
          C
          =
          
            
              
                (
                
                  1
                  +
                  
                    
                      (
                      
                        
                          d
                          SAG
                        
                        
                          d
                          H
                        
                      
                      )
                    
                    2
                  
                
                )
              
              ⁢
              
                
                  1
                  +
                  
                    
                      (
                      
                        
                          d
                          SAG
                        
                        
                          d
                          H
                        
                      
                      )
                    
                    2
                  
                
              
            
            
              
                
                  d
                  2
                
                ⁢
                SAG
              
              
                d
                
                  H
                  2
                
              
            
          
        
      
    
    
      
        (
        D
        )
      
    
  




    SAG: a distance from the apex on the aspherical surface to a point on the same aspherical surface having a height H from the optical axis
    H: a height from an optical axis
    R is a radius of curvature at the apex on the aspherical surface
    K: a conical constant
    D, E, F, G: aspherical coefficients.


It is also preferable that the correcting lens satisfies the following Expression (9), when f is a focal length of the correcting lens and f34 is a composite focal length of the third and fourth lens groups.

0.40<|f3/f34|<0.85  (9)

The expression (9) is a conditional expression to define the focal length of a lens used for correcting camera shake. When the value falls below the lower limit in the expression (9), the correcting lens will have excessive power, deterioration in the aberration performance is increased and assembling tolerance in manufacturing will be strict. When the value exceeds the upper limit, the shifting amount of the lens when correcting camera shake is increased, and the lens diameter also is increased. This is not favorable for downsizing.
Preferably, the zoom lens satisfies the following expression (10) when fw is a focal length of the entire system at the wide-angle end, and BF is a distance between the final surface of the lens and the image plane in the air.

2.0<BF/fw<5.0  (10)

The expression (10) is a conditional expression to provide a zoom lens having a long back focus, for example, a zoom lens using three imaging devices. When the value falls below the lower limit, a color separation optical system with sufficient length to conduct a sufficient color separation cannot be inserted. When it exceeds the upper limit, the back focus becomes longer than required, and it will be an obstacle for downsizing.
Preferably, the following expressions (11) to (14) are satisfied when fw is a focal length of the entire system at a wide-angle end, fi (i=1-5) is the focal length of the i-th lens group, and f34 is a composite focal length of the third and fourth focal length.

5.0<f1/fw<8.0  (11)

0.5<|f2|/fw<1.6  (12)

4.0<f34/fw<9.5  (13)

2.0<f5/fw<5.0  (14)

The expression (11) indicates a condition relating to the refracting power of the first lens group. Since the first lens group has excessive refracting power when the value falls below the lower limit, correction of spherical aberration at the long focal point side becomes difficult. When it exceeds the upper limit, the lens will be long and thus, a compact zoom lens cannot be obtained.
The expression (12) indicates a condition relating to the refracting power of the second lens group. The zoom lens can be made compact when the value falls below the lower limit, however, the Petzval's sum of the entire system will be increased negatively and distortion of the image plane cannot be corrected. The aberration can be corrected easily when the value exceeds the upper limit, however, the variable power system becomes long and the entire system cannot be downsized.
The expression (13) indicates a condition relating to the refracting power of the third lens group. When the value falls below the lower limit, the third lens group will have excessive refracting power, and thus, correction of the spherical aberration will be difficult. When the value exceeds the upper limit, the composite system of the first to third lens group becomes a divergent system. In such a zoom lens, the outer diameter of the lenses of the fourth group positioned behind the first to third groups cannot be decreased, and Petzval's sum of the entire system cannot be decreased.
The expression (14) indicates a condition relating to the refracting power of the fourth lens group. When the value fails below the lower limit, the coverage of an image will be decreased. For obtaining a desired coverage, the lens diameter of the first group should be increased, and thus, this will be an obstacle for downsizing and weight reduction. When the value exceeds the upper limit, the aberration can be corrected easily. However, the shifting amount of the fourth lens group is increased at a close-range shooting, and thus, the entire system cannot be downsized. Moreover, it is difficult to correct unbalanced off-axis aberrations between short-range and long-range shootings.
It is also preferable that the following expressions (15) and (16) are satisfied when Y is a shifting amount of a correcting lens at a focal length f of the entire system for correcting camera shake, Yt is a shifting amount of the correcting lens at a telephoto end, and ft is a focal length of the telephoto end.

Yt>Y  (15)

(Y/Yt)/(f/ft)<1.5  (16)

The expressions (15) and (16) relate to the shifting amount of a correcting lens. For a zoom lens, the shifting amount of the correcting lens is large as the zoom ratio is great, while the same amount is decreased when the zoom ratio is small when the correcting angle is constant within a whole zooming range. When the value exceeds the upper limits of the expressions (15) and (16), overcorrection occurs and the optical performance will deteriorate further.
Specific examples for this embodiment are shown in the following Table 43.












TABLE 43





Group
Surface
r
d
n
ν




















1
1
43.712
0.90
1.80518
25.4



2
22.377
6.00
1.60311
60.7



3
−147.260
0.20



4
20.439
3.50
1.60311
60.7



5
64.129
Variable


2
6
47.371
0.60
1.77250
49.6



7
6.608
3.10



8
−8.756
0.80
1.66547
55.2



9
7.541
1.80
1.84666
23.9



10
61.377
Variable


3
11
18.722
2.90
1.60602
57.5



12
−14.771
0.10



13
−61.576
0.70
1.80518
25.4



14
82.921
2.45


4
15
−15.486
0.70
1.51633
64.1



16
21.635
1.65
1.80518
25.4



17
246.689
Variable


5
18
−90.847
0.60
1.84666
23.9



19
12.912
4.10
1.51633
64.1



20
−18.441
0.10



21
15.386
4.50
1.60602
57.5



22
−15.967
Variable


6
23
∞
14.00
1.58913
61.2



24
∞
3.90
1.51633
64.1



25
∞
—









The following Table 44 shows aspherical coefficients.









TABLE 44









Surface













8
11
12
21
22
















K
 4.65875 × 10−1
 1.42780 × 10−1
 1.14334 × 10−1
−1.25651
−6.94184 × 10−1


D
 9.66131 × 10−5
−9.38804 × 10−5
 5.30815 × 10−5
−1.94414 × 10−5
 2.31291 × 10−5


E
−7.08756 × 10−6
 6.02667 × 10−6
 5.05125 × 10−6
 5.49746 × 10−7
 2.50059 × 10−7


F
 1.91335 × 10−7
−2.97812 × 10−7
−1.94202 × 10−7
−8.03971 × 10−9
−6.03441 × 10−9


G
 0.00000
 2.28611 × 10−9
 0.00000
 0.00000
 0.00000









The following Table 45 shows an air distance (mm) that is varied by zooming in the case where an object is positioned 2 m away from the tip end of the lens. At the standard position magnification of the second lens group becomes −1 times.











TABLE 45







Wide-angle end
Standard position
Telephoto end





















f
4.166
23.073
48.386



F/NO
1.680
1.680
1.886



2ω
60.226
11.023
4.354



d5
0.700
15.560
18.886



d10
19.216
4.356
1.030



d14
5.331
1.967
4.258



d19
1.099
4.463
2.172










FIGS. 47-49 illustrate various aberrations at a wide-angle end, at a standard position and at a telephoto end of the zoom lens. The values of the expressions (6) to (14) are as follows.

|v31-v32|=32.3

|v41-v42|=38.7

rS1/rS9=0.52

|f3/f34|=0.64

BF/fw=3.34

f1/fw=7.19

|f2|/fw=1.28

f34/fw=7.61

f5/fw=3.14

As clearly shown in the aberrations of FIGS. 47-49, this example provides sufficient performance to correct aberration for obtaining high resolution of a zoom lens.
Furthermore, this example is useful in preventing deterioration of the optical performance since the expressions (15) and (16) are satisfied.
Other specific examples according to this embodiment are shown in the following Table 46.












TABLE 46





Group
Surface
r
d
n
ν




















1
1
45.790
0.90
1.80518
25.4



2
22.855
5.80
1.60311
60.7



3
−137.451
0.15



4
20.654
3.15
1.60311
60.7



5
66.413
Variable


2
6
49.547
0.60
1.51633
64.1



7
5.943
3.65



8
−8.260
0.80
1.66547
55.2



9
7.608
2.01
1.84666
23.9



10
31.856
Variable


3
11
20.308
2.80
1.51450
63.1



12
−11.071
0.10



13
−32.200
0.70
1.80518
25.4



14
−179.621
2.45


4
15
−11.566
0.70
1.51450
63.1



16
18.674
1.50
1.80518
25.4



17
−382.316
Variable


5
18
139.563
0.60
1.84666
23.9



19
11.702
3.70
1.51633
64.1



20
−27.808
0.10



21
13.425
4.90
1.51450
63.1



22
−12.590
Variable


6
23
∞
14.00
1.58913
61.2



24
∞
3.90
1.51633
64.1



25
∞
—









The following Table 47 shows aspherical coefficients.









TABLE 47









Surface













8
11
12
21
22
















K
 2.65508 × 10−1
 3.81101 × 10−1
 0.00000
−9.36333 × 10−1
−8.93853 × 10−1


D
 2.27944 × 10−4
−2.03395 × 10−4
−2.15420 × 10−5
−4.92768 × 10−5
 4.67131 × 10−5


E
−4.63825 × 10−6
 3.74881 × 10−6
 2.89479 × 10−6
 7.98657 × 10−7
 1.88913 × 10−7


F
 1.53384 × 10−7
−2.17585 × 10−7
−1.16142 × 10−7
−1.25522 × 10−8
−9.70141 × 10−9


G
 0.00000
 2.28611 × 10−9
 0.00000
 0.00000
 0.00000









The following Table 48 shows an air distance (mm) that is varied by zooming in the case where an object is positioned 2 m away from the tip end of the lens.











TABLE 48







Wide-angle end
Standard position
Telephoto end





















f
4.196
23.529
49.156



F/NO
1.668
1.682
1.907



2ω
59.743
10.822
5.414



d5
0.700
14.055
17.374



d10
19.204
5.842
2.530



d14
5.831
2.402
4.737



d19
0.995
4.425
2.090










FIGS. 50-52 illustrate various aberrations at a wide-angle end, at a standard position and at a telephoto end of the zoom lens. The values of the expressions (6) to (14) are as follows.

|v31-v32|=37.7

|v41-v42|=37.7

rS1/rS9=0.07

|f3/f34|=0.57

BF/fw=3.29

f1/fw=7.22

|f2|/fw=1.28

f34/fw=8.40

f5/fw=3.15

As clearly shown in the aberrations of FIGS. 50-52, this example provides sufficient performance to correct aberration to obtain high resolution of a zoom lens. Furthermore, this example is useful in preventing deterioration of the optical performance since the expressions (15) and (16) are satisfied.
Other specific examples according to this embodiment are shown in the following Table 49.












TABLE 49





Group
Surface
r
d
n
ν




















1
1
−43.258
0.90
1.80518
25.4



2
22.067
5.80
1.60311
60.7



3
−141.493
0.15



4
20.338
3.15
1.60311
60.7



5
64.306
Variable


2
6
46.991
0.60
1.77250
49.6



7
6.645
3.10



8
−8.848
0.80
1.66547
55.2



9
7.368
1.60
1.84666
23.9



10
53.923
Variable


3
11
16.972
2.61
1.60602
57.5



12
−13.177
0.09



13
−55.938
0.70
1.80518
25.4



14
73.946
2.45


4
15
−17.219
0.77
1.51633
64.1



16
22.997
1.82
1.80518
25.4



17
288.894
Variable


5
18
−88.752
0.60
1.84666
23.9



19
12.766
4.50
1.51633
64.1



20
−18.677
0.10



21
15.561
5.00
1.60602
57.6



22
−16.083
Variable


6
23
∞
13.00
1.58913
61.2



24
∞
3.00
1.51633
64.1



25
∞
—









The following Table 50 shows aspherical coefficients.









TABLE 50









Surface













8
11
12
21
22
















K
 4.747248 × 10−1
 2.101119 × 10−1
 1.007413 × 10−1
−1.279930
−6.730536 × 10−1


D
 4.453156 × 10−5
−9.582481 × 10−5
 9.286602 × 10−5
 9.244688 × 10−6
 3.352961 × 10−5


E
−7.953517 × 10−7
 1.260729 × 10−6
 1.333902 × 10−7
−1.306964 × 10−7
−3.521187 × 10−7


F
−5.757966 × 10−8
−2.487044 × 10−7
−5.579667 × 10−8
 9.358746 × 10−10
 1.832323 × 10−9


G
 0.000000
 5.900849 × 10−9
 0.000000
 0.000000
 0.000000









The following Table 51 shows an air distance (mm) that is varied by zooming in the case where an object is positioned 2 m away from the tip end of the lens.











TABLE 51







Wide-angle end
Standard position
Telephoto end





















f
4.256
22.469
49.343



F/NO
1.697
1.695
1.902



2ω
59.068
11.284
5.401



d5
0.700
14.053
17.391



d10
19.212
5.867
2.530



d14
5.831
2.537
4.742



d19
0.855
4.149
1.944










FIGS. 53-55 illustrate various aberrations at a wide-angle end, at a standard position and at a telephoto end of the zoom lens. The values of the expressions (6) to (14) are as follows.

|v31-v32|=32.3

|v41-v42|=38.6

rS1/rS9=0.58

|f3/f34|=0.72

BF/fw=2.93

f1/fw=6.97

|f2|/fw=1.26

f34/fw=5.89

f5/fw=3.11

As clearly shown in the aberrations of FIGS. 53-55, this example provides sufficient performance to correct aberration to obtain high resolution of a zoom lens. Furthermore, this example is useful in preventing deterioration of the optical performance since the expressions (15) and (16) are satisfied.
Twelfth Embodiment
FIG. 56 is a view showing the arrangement of a zoom lens in a twelfth embodiment according to the present invention. As shown in FIG. 56, a zoom lens has a structure in which a first lens group 1a, a second lens group 2a, a third lens group 3a, a fourth lens group 4a and a fifth lens group 5a are disposed from an object side in this order. The first lens group 1a has a positive refracting power and is fixed with respect to the image plane. The second lens group 2a has a negative refracting power and varies power by moving along an optical axis. The third lens group 3a is fixed with respect to the image plane and has a negative refracting power. The fourth lens group 4a is fixed with respect to the image plane and has a positive refracting power. The fifth lens group 5a has a positive refracting power and moves along an optical axis to keep the image plane varied by the shift of the second lens group and the object at a predetermined position from a reference surface. Camera shake is corrected by shifting the fourth lens group having a positive refracting power in a direction vertical to the optical axis.
FIG. 57 shows a zoom lens of the basic structure shown in FIG. 56. The zoom lens has a structure in which a first lens group 121, a second lens group 122, a third lens group 123, and a fourth lens group 124 are disposed from the object side to the image plane side in this order. The first lens group 121 has a positive refracting power, and is fixed with respect to the image plane in varying power and focusing. The second lens group 122 has a negative refracting power and varies power by moving along an optical axis.
The third lens group 123 is composed of a negative lens and a positive lens, and has a negative refracting power as a whole. The fourth lens group 124 is composed of a positive lens and a negative lens, and has a positive refracting power as a whole. The group is fixed with respect to the image plane in varying power and focusing. A fifth lens group 125 has a positive refracting power, and moves along an optical axis so as to move an image and adjust the focus thereof at the same time in accordance with variable power. When camera shake occurs, shake of an image is corrected by moving the fourth lens group 124 vertically with respect to the optical axis.
As described above, light beams entering the fifth lens group 125 can be lowered by combining the third lens group 123 having a negative refracting power and a fourth lens group 124 having a positive refracting power. Namely, the lens diameter of the fourth group can be decreased and a load on an actuator will be decreased in focusing.
The performance when shifting the lenses can be improved by applying at least one aspherical surface to any of the lenses of the fourth group. Similar to the eleventh embodiment, it is preferable that the expressions (6)-(16) are satisfied.
Specific examples for this embodiment are shown in the following Table 52.












TABLE 52





Group
Surface
r
d
n
ν




















1
1
43.700
0.90
1.80518
25.4



2
22.310
6.00
1.60311
60.7



3
−147.017
0.20



4
20.415
3.50
1.60311
60.7



5
64.027
Variable


2
6
64.027
0.60
1.77250
49.6



7
6.600
3.10



8
−8.963
0.80
1.66547
55.2



9
6.685
1.80
1.80518
25.4



10
65.269
Variable


3
11
−19.604
0.70
1.51633
64.1



12
24.259
1.65
1.84666
23.9



13
100.263
1.00


4
14
12.130
3.51
1.60602
57.6



15
−14.418
0.10



16
−42.218
0.60
1.80518
25.4



17
56.648
Variable


5
18
−106.725
0.70
1.80518
25.4



19
16.919
3.60
1.51633
64.1



20
−23.864
0.10



21
18.527
3.60
1.60602
57.6



22
−22.813
Variable


6
23
∞
14.00
1.58913
61.2



24
∞
3.90
1.51633
64.1



25
∞
—









The following Table 53 shows aspherical coefficients.









TABLE 53









Surface













8
11
12
21
22
















K
 5.37219 × 10−1
 2.97152 × 10−1
−2.48406
−5.61162
−5.96501


D
 8.69130 × 10−5
−1.56550 × 10−4
 2.68507 × 10−5
 5.63851 × 10−5
−4.80942 × 10−5


E
−5.67323 × 10−6
 6.96463 × 10−8
 3.64998 × 10−7
−2.49399 × 10−7
 3.72704 × 10−7









The following Table 54 shows an air distance (mm) that is varied by zooming in the case where an object is positioned 2 m away from the tip end of the lens.











TABLE 54







Wide-angle end
Standard position
Telephoto end





















f
4.029
23.328
50.226



F/NO
1.650
1.776
1.966



2ω
62.566
10.893
5.239



d5
0.700
14.408
17.686



d10
20.216
6.509
3.230



d14
5.331
1.876
4.155



d19
1.200
4.636
2.184










FIGS. 58-60 illustrate various aberrations at a wide-angle end, at a standard position and at a telephoto end of the zoom lens. The values of the expressions (6) to (14) are as follows.

|v31-v32|=40.2

|v41-v42|=32.3

rS1/rS9=0.74

|f3/f34|=0.69

BF/fw=3.45

f1/fw=7.43

|f2|/fw=1.29

f34/fw=6.20

f5/fw=4.19

As clearly shown in the aberrations of FIGS. 58-60, this example provides sufficient performance to correct aberration to obtain high resolution of a zoom lens. Furthermore, this example is useful in preventing deterioration of the optical system since the expressions (15) and (16) are satisfied.
Thirteenth Embodiment
FIG. 61 is a view showing the arrangement of a zoom lens in a thirteenth embodiment according to the present invention. As shown in FIG. 61, a zoom lens has a structure in which a first lens group 161, a second lens group 162, a third lens group 163, and a fourth lens group 164 are disposed from an object side to an image plane side in this order. The first lens group 161 has a positive refracting power, and is fixed with respect to the image plane in varying power and focusing. The second lens group 162 has a negative refracting power and varies power by moving along an optical axis.
The third lens group 163 is a cemented lens composed of two lenses and it has a positive refracting power. The fourth lens group 164 has a negative refracting power and is fixed with respect to the image plane in varying power and focusing. A fifth lens group 165 has a positive refracting power and moves along an optical axis so as to move an image and adjust the focus thereof at the same time in accordance with variable power. When camera shake occurs, shake of an image is corrected by moving the third lens group 163 vertically with respect to the optical axis. The tolerance can be eased by making the shift lens group 163 a cemented lens.
Performance when shifting the lenses can be improved by applying at least one aspherical surface to any of the lenses of the third group. Similar to the eleventh embodiment, it is preferable that the expressions (6)-(16) are satisfied.
Specific examples for this embodiment are shown in the following Table 55.












TABLE 55





Group
Surface
r
d
n
ν




















1
1
43.712
0.90
1.80518
25.4



2
22.377
6.00
1.60311
60.7



3
−147.260
0.20



4
20.439
3.50
1.60311
60.7



5
64.129
Variable


2
6
47.371
0.60
1.77250
49.6



7
6.608
3.10



8
−8.756
0.80
1.66547
55.2



9
7.541
1.80
1.84666
23.9



10
61.377
Variable


3
11
11.304
2.00
1.60602
57.5



12
29.656
1.00
1.80518
25.4



13
71.482
2.45


4
14
−45.255
0.70
1.51633
64.1



15
13.342
1.65
1.80518
25.4



16
23.203
Variable


5
17
−88.752
0.60
1.84666
23.9



18
12.766
4.10
1.51633
64.1



19
−18.677
0.10



20
15.561
4.50
1.60602
57.6



21
−16.083
Variable


6
22
∞
14.00
1.58913
61.2



23
∞
3.90
1.51633
64.1



24
∞
—









The following Table 56 shows aspherical coefficients.









TABLE 56









Surface













8
11
12
21
22
















K
 4.65875 × 10−1
 1.42789 × 10−1
 1.14334 × 10−1
−1.256510
−6.94184 × 10−1


D
 9.66131 × 10−5
 2.50260 × 10−4
 3.81894 × 10−4
−2.86326 × 10−5
−1.87081 × 10−5


E
−7.08756 × 10−7
 9.98537 × 10−6
 1.14292 × 10−5
 4.11743 × 10−7
 1.01992 × 10−7


F
 1.91335 × 10−7
−2.16512 × 10−7
−1.11482 × 10−7
−9.63753 × 10−9
−5.68100 × 10−9


G
 0.00000
 2.28611 × 10−9
 0.00000
 0.00000
 0.00000









The following Table 57 shows an air distance (mm) that is varied by zooming in the case where an object is positioned 2 m away from the tip end of the lens.











TABLE 57







Wide-angle end
Standard position
Telephoto end





















f
4.153
23.052
48.765



F/NO
1.853
1.952
1.877



2ω
60.636
11.025
5.426



d5
0.700
14.060
17.386



d10
19.216
5.856
2.530



d14
5.331
1.967
4.261



d19
1.200
4.846
2.532










FIGS. 62-64 illustrate various aberrations at a wide-angle end, at a standard position and at a telephoto end of the zoom lens. The values of the expressions (6) to (14) are as follows.

|v31-v32|=32.3

|v41-v42|=38.6

rS1/rS9=1.49

|f3/f34|=0.66

BF/fw=3.36

f1/fw=7.21

|f2|/fw=1.29

f34/fw=7.35

f5/fw=2.96

As clearly shown in the aberrations of FIGS. 62-64, this example provides sufficient performance to correct aberration to obtain high resolution of a zoom lens. Furthermore, this example is useful in preventing deterioration of the optical performance since the expressions (15) and (16) are satisfied.
Fourteenth Embodiment
This embodiment relates to a video camera using three imaging devices where the video camera has a function to correct camera shake by using a zoom lens in any of the eleventh to thirteenth embodiments, and the structure is shown in FIG. 65.
A video camera according to this embodiment comprises a zoom lens 201 of the eleventh embodiment, a low-pass filter 202, prisms 203a-203c for color separation, imagers 204a-204c, a signal processing circuit 205, a view finder 206, a sensor 207 for detecting camera shake, and an actuator 208 for driving the lens.
The zoom lens is not limited to what is shown in the eleventh embodiment, but zoom lenses described in the twelfth and thirteenth embodiments also can be used, though they are not shown specifically in any figures.
Although the shift lens group is composed of two single lenses in the eleventh to thirteenth embodiments, the lenses can be a cemented lens to ease the tolerance.
Although camera shake is corrected by shifting a lens group having a positive refracting power in the eleventh to thirteenth embodiments, similar effects can be obtained by shifting a lens group having a negative refracting power.
Fifteenth Embodiment
FIG. 66 is a view showing the arrangement of a zoom lens in a fifteenth embodiment according to the present invention. As shown in FIG. 66, a zoom lens has a structure in which a first lens group 21, a second lens group 22, a third lens group 23, a fourth lens group 24, and a fifth lens group 25 are disposed from an object side deft side in FIG. 66) to an image plane side (right side in FIG. 66) in this order.
The first lens group 21 has a positive refracting power and is fixed with respect to the image plane in varying power and focusing. The second lens group 22 has a negative refracting power and varies power by moving along an optical axis. The third lens group 23 is composed of three lenses: a negative lens, a positive lens and a positive lens disposed from the object side in this order. This group includes at least one aspherical surface and has a positive refracting power as a whole.
The fourth lens group 24 is composed of two lenses as a cemented lens of a negative lens and a positive lens disposed from the object side in this order and it has a negative refracting power as a whole, and is fixed with respect to the image plane in varying power and focusing. The fifth lens group 25 has a positive refracting power and moves along an optical axis so as to move an image and adjust the focus thereof at the same time in accordance with the variable power. When camera shake occurs, shake of an image is corrected by moving the third lens group 23 vertically with respect to the optical axis.
The performance when shifting the lenses can be improved by applying at least one aspherical surface to any of the lenses of the third group 23.
It is preferable that the above-described expression (8) about aspherical surface amount is satisfied for the third lens group 23 when rS1 represents a local radius of curvature for a diameter occupying 10% of the lens effective diameter, and rS9 is a local radius of curvature for a diameter occupying 90% of lens effective diameter.
Here, the local radius of curvature C is obtainable through an algebraic calculation based on aspherical coefficients figured out from the sag amount of the plane shape. It is obtainable by the following equations (E) and (F).




  
    
      
        SAG
        =
        
          
            
              
                H
                2
              
              /
              R
            
            
              1
              +
              
                
                  1
                  -
                  
                    
                      (
                      
                        1
                        +
                        K
                      
                      )
                    
                    ⁢
                    
                      
                        (
                        
                          H
                          /
                          R
                        
                        )
                      
                      2
                    
                  
                
              
            
          
          +
          
            D
            ·
            
              H
              4
            
          
          +
          
            E
            ·
            
              H
              6
            
          
        
      
    
    
      
        (
        E
        )
      
    
  
  
    
      
        C
        =
        
          
            
              (
              
                1
                +
                
                  
                    (
                    
                      
                        d
                        SAG
                      
                      
                        d
                        H
                      
                    
                    )
                  
                  2
                
              
              )
            
            ⁢
            
              
                1
                +
                
                  
                    (
                    
                      
                        d
                        SAG
                      
                      
                        d
                        H
                      
                    
                    )
                  
                  2
                
              
            
          
          
            
              
                d
                2
              
              ⁢
              SAG
            
            
              d
              
                H
                2
              
            
          
        
      
    
    
      
        (
        F
        )
      
    
  




    SAG: a distance from the apex on the aspherical surface to a point on the same aspherical surface having a height H from the optical axis
    H: a height from an optical axis
    R is a radius of curvature at the apex on the aspherical surface
    K: a conical constant
    D, E: aspherical coefficients
    C: local radius of curvature


It is also preferable that the correcting lens satisfies the expression (9), when f3 is the focal length of the third lens group 23 (a correcting lens group) and f34 is a composite focal length of the third and fourth lens groups.
Preferably, the expression (10) is satisfied when fv is a focal length of the entire system at the wide-angle end, and BF is a distance between the final surface of the lens and the image plane in the air.
Preferably, the expressions (11) to (14) are satisfied when fw is a focal length of the entire system at a wide-angle end, fi (i=1−5) is the focal length of the i-th lens group, and f34 is a composite focal length of the third and fourth lens group 23, 24.
It is also preferable that the expressions (15) and (16) are satisfied when Y is a shifting amount of the third lens group 23 at a focal length f of the entire system when correcting camera shake, Yt is a shifting amount of the third lens group 23 at the telephoto end, and ft is a focal length of the telephoto end.
Specific examples of zoom lenses according to this embodiment are shown in the following Table 58.












TABLE 58





Group
Surface
r
d
n
ν




















1
1
35.243
0.90
1.80518
25.4



2
18.353
5.25
1.60311
60.7



3
−154.339
0.15



4
17.449
3.00
1.60311
60.7



5
53.989
Variable


2
6
53.989
0.70
1.78500
43.7



7
5.142
2.97



8
−7.948
0.80
1.66547
55.2



9
5.519
2.70
1.80518
25.4



10
1291.253
Variable


3
11
136.351
1.00
1.84666
23.9



12
24.057
0.50



13
16.099
1.70
1.51450
63.1



14
−199.059
0.50



15
48.853
1.90
1.58913
61.2



16
−18.181
2.70


4
17
−22.167
0.80
1.58913
61.2



18
12.517
1.60
1.80518
25.4



19
52.330
Variable


5
20
−42.760
0.60
1.84666
23.9



21
15.607
2.80
1.51633
64.1



22
−14.704
0.10



23
12.767
3.00
1.51450
63.1



24
−16.499
Variable


6
25
∞
14.00
1.58913
61.2



26
∞
2.80
1.51633
64.1



27
∞
—









The following Table 59 shows aspherical coefficients of the zoom lens in the present example.










TABLE 59









Surface












8
13
22














K
−4.89985
−8.46317
−1.14637


D
−1.08175 × 10−3
 1.00945 × 10−4
−6.03706 × 10−5


E
−1.06040 × 10−5
−1.63114 × 10−6
−8.33884 × 10−6









The following Table 60 shows an air distance (mm) that is varied by zooming in the case where an object is positioned 2 m away from the tip end of the lens. At the standard position, magnification of the second lens group 22 becomes −1 times in Table 60.











TABLE 60







Wide-angle end
Standard position
Telephoto end





















f
3.680
17.737
42.686



F/NO
1.658
1.914
2.072



2ω
58.508
12.362
5.106



d5
0.600
11.675
14.927



d10
17.903
6.827
3.575



d14
5.200
2.519
5.200



d19
1.000
3.682
1.000










The values of the expressions (8) to (14) are as follows.

rS1/rS9=0.64

|f3/f34|=0.59

BF/fw=4.09

f1/fw=7.00

|f2|/fw=1.25

f34/fw=9.14

f5/fw=3.79

In this example, the above-described expression (8) is satisfied, and a sufficient aberration performance is provided to realize high resolution. Since the expression (9) is satisfied, deterioration in the aberration performance can be decreased and assembly tolerance in manufacturing can be eased. Moreover, since the shifting amount of the lenses is decreased when correcting camera shake, the lens diameter can be reduced for downsizing. Furthermore, since the expression (10) is satisfied, a color separation optical system having a length for a sufficient color separation can be inserted.
Furthermore, the back focus does not need to have extra length, and a small zoom lens can be provided. Since the expressions (11) to (14) are satisfied, the aberration can be corrected easily and the zoom lens can be downsized.
FIGS. 67-69 illustrate various aberrations at a wide-angle end, at a standard position and at a telephoto end of the zoom lens. As clearly shown in the aberrations of FIGS. 67-69, this example provides sufficient performance to correct aberration to obtain high resolution of a zoom lens.
Sixteenth Embodiment
FIG. 70 is a view showing the arrangement of a zoom lens in a sixteenth embodiment according to the present invention. As shown in FIG. 70, a zoom lens has a structure in which a first lens group 701, a second lens group 702, a third lens group 703, a fourth lens group 704, and a fifth lens group 705 are disposed from an object side deft side in FIG. 70) to an image plane side (right side in FIG. 70) in this order.
The first lens group 701 has a positive refracting power and is fixed with respect to the image plane in varying power and focusing. The second lens group 702 has a negative refracting power and varies power by moving along an optical axis.
The third lens group 703 is composed of three lenses: a negative lens, a positive lens and a positive lens disposed from the object side in this order. This group includes at least one aspherical surface and has a positive refracting power as a whole.
The fourth lens group 704 is composed of two lenses as a cemented lens of a negative lens and a positive lens disposed from the object side in this order and this group has a negative refracting power as a whole, and is fixed with respect to the image plane in varying power and focusing. The fifth lens group 705 has a positive refracting power and moves along an optical axis so as to move an image and adjust the focus thereof at the same time in accordance with variable power. When camera shake occurs, shake of an image is corrected by moving the third lens group 703 vertically with respect to the optical axis.
The performance at shifting the lenses can be improved by applying at least one aspherical surface to any of the lenses of the third group 703.
Similar to the fifteenth embodiment, it is preferable for the zoom lens of his embodiment that the conditional expressions (8)-(16) are satisfied.
Specific examples of zoom lenses according to this embodiment are shown in the following Table 61.












TABLE 61





Group
Surface
r
d
n
ν




















1
1
35.243
0.90
1.80518
25.4



2
18.353
5.25
1.60311
60.7



3
−154.339
0.15



4
17.449
3.00
1.60311
60.7



5
53.989
Variable


2
6
53.989
0.70
1.78500
43.7



7
5.142
2.97



8
−7.948
0.80
1.66547
55.2



9
5.519
2.70
1.80518
25.4



10
1291.253
Variable


3
11
58.041
1.00
1.51450
63.1



12
−19.193
0.50



13
−18.810
1.70
1.84666
23.9



14
−59.301
0.50



15
43.566
1.90
1.58913
61.2



16
−17.985
2.70


4
17
−20.041
0.80
1.58913
61.2



18
12.918
1.60
1.80518
25.4



19
63.402
Variable


5
20
−51.268
0.60
1.84666
23.9



21
15.447
2.80
1.51633
64.1



22
−14.704
0.10



23
12.767
3.00
1.51450
63.1



24
−16.499
Variable


6
25
∞
14.00
1.58913
61.2



26
∞
2.80
1.51633
64.1



27
∞
—









The following Table 62 shows aspherical coefficients of the zoom lens in the present example.










TABLE 62









Surface












8
13
22














K
−4.89985
−8.44752
−9.50310 × 10−1


D
−1.08175 × 10−3
−4.24504 × 10−5
−4.89670 × 10−5


E
−1.06040 × 10−5
 7.84853 × 10−7
−6.72180 × 10−8









The following Table 63 shows an air distance (mm) that is varied by zooming in the case where an object is positioned 2 m away from the tip end of the lens. At the standard position, magnification of the second lens group 702 becomes −1 times in Table 63.











TABLE 63







Wide-angle end
Standard position
Telephoto end





















f
3.691
17.802
42.813



F/NO
1.657
1.925
2.078



2ω
58.349
12.321
42.813



d5
0.600
11.675
14.927



d10
17.903
6.827
13.575



d14
5.200
2.485
5.200



d19
1.000
3.715
1.000










The values of the expressions (8) to (14) are as follows.

rS1/rS9=0.63

|f3/f34|=0.59

BF/fw=4.01

f1/fw=6.98

|f2|/fw=1.25

f34/fw=9.17

f5/fw=3.70

FIGS. 71-73 illustrate various aberrations at a wide-angle end, at a standard position and at a telephoto end of the zoom lens. As clearly shown in the aberrations of FIGS. 71-73, a zoom lens according to this embodiment has sufficient performance to correct aberration to realize high resolution.
Seventeenth Embodiment
FIG. 74 is a view showing the arrangement of a zoom lens in a seventeenth embodiment according to the present invention. As shown in FIG. 74, a zoom lens has a structure in which a first lens group 101, a second lens group 102, a third lens group 103, a fourth lens group 104, and a fifth lens group 105 are disposed from an object side (left side in FIG. 74) to an image plane side (right side in FIG. 74) in this order.
The first lens group 101 has a positive refracting power and is fixed with respect to the image plane in varying power and focusing. The second lens group 102 has a negative refracting power and varies power by moving along an optical axis. The third lens group 103 is composed of three lenses: a positive lens, a positive lens and a negative lens disposed from the object side in this order. The third lens group includes at least one aspherical surface and has a positive refracting power as a whole. The fourth lens group 104 is composed of two lenses as a cemented lens of a negative lens and a positive lens disposed from the object side in this order, and this group has a negative refracting power as a whole, and is fixed with respect to the image plane in varying power and focusing. The fifth lens group 105 has a positive refracting power and moves along an optical axis so as to move an image and adjust the focus thereof at the same time in accordance with variable power. When camera shake occurs, shake of an image is corrected by moving the third lens group 103 vertically with respect to the optical axis.
As mentioned above, the performance when shifting the lenses can be improved by applying at least one aspherical surface to any of the lenses of the third lens group 103.
Similar to the first embodiment, it is preferable for the zoom lens of this embodiment that the conditional expressions (8)-(16) are satisfied.
Specific examples of zoom lenses according to this embodiment are shown in the following Table 64.












TABLE 64





Group
Surface
r
d
n
ν




















1
1
35.243
0.90
1.80518
25.4



2
18.353
5.25
1.60311
60.7



3
−154.339
0.15



4
17.449
3.00
1.60311
60.7



5
53.989
Variable


2
6
53.989
0.70
1.78500
43.7



7
5.142
2.97



8
−7.948
0.80
1.66547
55.2



9
5.519
2.70
1.80518
25.4



10
1291.253
Variable


3
11
1044.254
1.70
1.51450
63.1



12
−16.361
0.10



13
15.774
1.90
1.58913
61.2



14
−45.969
0.50



15
−46.430
1.90
1.80518
25.4



16
42.087
2.70


4
17
−20.461
0.80
1.58913
61.2



18
16.458
1.60
1.80518
25.4



19
63.911
Variable


5
20
−54.786
0.60
1.84666
23.9



21
18.645
2.80
1.51633
64.1



22
−12.273
0.10



23
11.361
3.00
1.51450
63.1



24
−19.962
Variable


6
25
∞
14.00
1.58913
61.2



26
∞
2.80
1.51633
64.1



27
∞
—









The following Table 65 shows aspherical coefficients of the zoom lens in the present example.










TABLE 65









Surface












8
13
22














K
−4.89985
−4.53315
−8.12542 × 10−1


D
−1.08175 × 10−3
−6.30517 × 10−5
−5.78738 × 10−5


E
−1.06040 × 10−5
 2.50225 × 10−7
−1.83558 × 10−7









The following Table 66 shows an air distance (mm) that is varied by zooming in the case where an object is positioned 2 m away from the tip end of the lens. At the standard position magnification of the second lens group 102 becomes −1 times in Table 66.











TABLE 66







Wide-angle end
Standard position
Telephoto end





















f
3.685
18.123
42.738



F/NO
1.657
1.879
2.074



2ω
58.363
12.121
5.093



d5
0.600
11.675
14.927



d10
17.902
6.827
3.575



d14
5.200
2.329
5.200



d19
1.000
3.871
1.000










FIGS. 75-77 illustrate various aberrations at a wide-angle end, at a standard position and at a telephoto end of the zoom lens. As clearly shown in the aberrations of FIGS. 75-77, a zoom lens according to this embodiment has sufficient performance to correct aberration to realize high resolution.
Eighteenth Embodiment
FIG. 78 is a view showing the arrangement of a zoom lens in an eighteenth embodiment according to the present invention. As shown in FIG. 78, a zoom lens has a structure in which a first lens group 141, a second lens group 142, a third lens group 143, a fourth lens group 144, and a fifth lens group 145 are disposed from an object side (left side in FIG. 78) to an image plane side (right side in FIG. 78) in this order.
The first lens group 141 has a positive refracting power and is fixed with respect to the image plane in varying power and focusing. The second lens group 142 has a negative refracting power and varies power by moving along an optical axis. The third lens group 143 is composed of two lenses: a positive lens and a negative lens disposed from the object side in this order. The lenses of the third group have surfaces equal to each other in the sag amount, and this group has a positive refracting power as a whole.
The fourth lens group 144 is composed of two lenses as a cemented lens of a negative lens and a positive lens disposed from the object side in this order, and this group has a negative refracting power as a whole, and is fixed with respect to the image plane in varying power and focusing. The fifth lens group 145 has a positive refracting power and moves along an optical axis so as to move an image and adjust the focus thereof at the same time in accordance with variable power. When camera shake occurs, shake of an image is corrected by moving the third lens group 143 vertically with respect to the optical axis.
As described above, light beams entering the fifth lens group 145 can be lowered by combining the third lens group 143 having a positive refracting power as a whole and the fourth lens group 144 having a negative refracting power as a whole. Namely, since the lens diameter of the fourth group 144 can be decreased, a load on an actuator will be lighter in focusing.
The performance at shifting the lenses can be improved by applying at least one aspherical surface to any of the lenses of the third group 143.
Similar to the fourteenth embodiment, it is preferable for the zoom lens of this embodiment that the conditional expressions (8)-(16) are satisfied.
Specific examples of zoom lenses according to this embodiment are shown in the following Table 67.












TABLE 67





Group
Surface
r
d
n
ν




















1
1
35.171
0.90
1.80518
25.4



2
18.474
5.25
1.60311
60.7



3
−153.872
0.15



4
17.397
3.00
1.60311
60.7



5
52.501
Variable


2
6
52.501
0.60
1.78500
43.7



7
5.178
2.97



8
−7.914
1.00
1.66547
55.2



9
5.841
2.70
1.80518
25.4



10
∞
Variable


3
11
13.430
3.00
1.51450
63.1



12
−13.430
0.60



13
−45.224
1.20
1.80518
25.4



14
84.188
2.60


4
15
−23.195
0.60
1.58913
61.2



16
23.195
1.50
1.80518
25.4



17
70.085
Variable


5
18
−56.351
0.60
1.84666
23.9



19
18.833
2.80
1.51633
64.1



20
−13.089
0.10



21
11.081
2.85
1.51450
63.1



22
−19.280
Variable


6
23
∞
14.00
1.58913
61.2



24
∞
2.80
1.51633
64.1



25
∞
—









The following Table 68 shows aspherical coefficients of the zoom lens in the present example.









TABLE 68









Surface












8
11
12
20















K
−8.93826 × 10−1
−1.54989
−1.54989
−5.29341 × 10−1


D
−1.30720 × 10−4
−3.86132 × 10−5
 3.86132 × 10−5
−8.85522 × 10−5


E
−2.38410 × 10−5
 2.40598 × 10−7
−2.40598 × 10−7
−2.60439 × 10−7









The following Table 69 shows an air distance (mm) that is varied by zooming in the case where an object is positioned 2 m away from the tip end of the lens. At the standard position, magnification of the second lens group 142 becomes −1 times in Table 69.











TABLE 69







Wide-angle end
Standard position
Telephoto end





















f
3.681
18.240
42.656



F/NO
1.655
1.874
2.067



2ω
58.529
12.076
5.120



d5
0.600
11.710
14.974



d10
17.503
6.393
3.129



d14
5.200
2.321
5.200



d19
1.000
3.879
1.000










The values of the expressions (8) to (14) are as follows.

rS1/rS9=0.79

|f3/f34|=0.62

BF/fw=3.58

f1/fw=7.00

|f2|/fw=1.26

f34/fw=8.83

f5/fw=3.23

FIGS. 79-81 illustrate various aberrations at a wide-angle end, at a standard position and at a telephoto end of the zoom lens. As clearly shown in the aberrations of FIGS. 79-81, a zoom lens according to this embodiment has sufficient performance to correct aberration to realize high resolution.
Nineteenth Embodiment
FIG. 82 is a view showing the arrangement of a zoom lens in a nineteenth embodiment according to the present invention. As shown in FIG. 82, a zoom lens has a structure in which a first lens group 181, a second lens group 182, a third lens group 183, a fourth lens group 184, and a fifth lens group 185 are disposed from an object side (left side in FIG. 82) to an image plane side (right side in FIG. 82) in this order.
The first lens group 181 has a positive refracting power and is fixed with respect to the image plane in varying power and focusing. The second lens group 182 has a negative refracting power and varies power by moving along an optical axis. The third lens group 183 is composed of one lens having a positive refracting power.
The fourth lens group 184 is composed of two lenses as a cemented lens of a negative lens and a positive lens disposed from the object side in this order and this group has a negative refracting power as a whole, and is fixed with respect to the image plane varying power and focusing. The fifth lens group 185 has a positive refracting power and moves along an optical axis so as to move an image and adjust the focus thereof at the same time in accordance with variable power. When camera shake occurs, shake of an image is corrected by moving the third lens group 183 vertically with respect to the optical axis.
As a result, the tolerance can be eased by forming a shift lens group (the third lens group 183) with one lens.
The performance when shifting the lens can be improved by applying at least one aspherical surface to the lens of the third group 183.
Similar to the fourteenth embodiment, it is preferable for the zoom lens of this embodiment that the conditional expressions (8)-(16) are satisfied.
Specific examples of zoom lenses according to this embodiment are shown in the following Table 70.












TABLE 70





Group
Surface
r
d
n
ν




















1
1
35.243
0.90
1.80518
25.4



2
18.353
5.25
1.60311
60.7



3
−154.339
0.15



4
17.449
3.00
1.60311
60.7



5
53.989
Variable


2
6
53.989
0.70
1.78500
43.7



7
5.142
2.97



8
−7.948
0.80
1.66547
55.2



9
5.519
2.70
1.80518
25.4



10
1291.253
Variable


3
11
13.124
2.40
1.43425
95.0



12
−23.353
2.70


4
13
−45.406
0.60
1.58913
61.2



14
24.428
1.50
1.80528
25.4



15
36.015
Variable


5
16
−69.769
0.60
1.84666
23.9



17
18.397
2.70
1.51633
64.1



18
−13.178
0.10



19
11.587
2.95
1.51450
63.1



20
−21.551
Variable


6
21
∞
14.00
1.58913
61.2



22
∞
2.80
1.51633
64.1



23
∞
—









The following Table 71 shows aspherical coefficients of the zoom lens in the present example.









TABLE 71









Surface












8
11
12
19















K
−4.89985
−6.72168
−1.37149 × 10+1
−6.00589 × 10−1


D
−1.08175 × 10−3
 3.03174 × 10−4
 8.68352 × 10−6
−5.27645 × 10−5


E
−1.06040 × 10−5
−9.85138 × 10−7
 2.15192 × 10−6
−3.20955 × 10−7









The following Table 72 shows an air distance (mm) that is varied by zooming in the case where an object is positioned 2 m away from the tip end of the lens. At the standard position, magnification of the second lens group 182 becomes −1 times in Table 72.











TABLE 72







Wide-angle end
Standard position
Telephoto end





















f
3.690
18.643
42.802



F/NO
1.661
1.872
2.077



2ω
58.504
11.814
5.116



d5
0.600
11.675
14.927



d10
17.903
6.827
3.575



d14
5.200
2.299
5.200



d19
1.000
3.901
1.000










The values of the expressions (8) to (14) are as follows.

rS1/rS9=1.02  (eleventh plane)

rS1/rS9=0.26  (twelfth plane)

|f3/f34|=0.60

BF/fw=3.60

f1/fw=6.98

|f2|/fw=1.25

f34/fw=8.93

f5/fw=3.36

FIGS. 83-85 illustrate various aberrations at a wide-angle end, at a standard position and at a telephoto end of the zoom lens. As clearly shown in the aberrations of FIGS. 83-85, a zoom lens according to this embodiment has sufficient performance to correct aberration to obtain high resolution of a zoom lens.
Twentieth Embodiment
FIG. 86 is a view showing the arrangement of a zoom lens in a twentieth embodiment according to the present invention. As shown in FIG. 86, a zoom lens has a structure in which a first lens group 221, a second lens group 222, a third lens group 223, a fourth lens group 224, and a fifth lens group 225 are disposed from an object side (left side in FIG. 86) to an image plane side (right side in FIG. 86) in this order.
The first lens group 221 has a positive refracting power and is fixed with respect to the image plane in varying power and at focusing. The second lens group 222 has a negative refracting power and varies power by moving along the optical axis. The third lens group 223 is composed of two lenses: a positive lens and a negative lens disposed from the object side in this order, and this group has a positive refracting power as a whole.
The fourth lens group 224 is composed of two lenses: a positive lens and a negative lens disposed from the object side in this order and this group has a negative refracting power as a whole, and is fixed with respect to the image plane in varying power and focusing.
The fifth lens group 225 has a positive refracting power and moves along an optical axis so as to move an image and adjust the focus thereof at the same time in accordance with variable power. When camera shake occurs, shake of an image is corrected by moving the third lens group 223 vertically with respect to the optical axis.
The performance when shifting the lenses can be improved by applying at least one aspherical surface to any of the lenses of the third group 223.
Similar to the fourteenth embodiment, it is preferable for the zoom lens of this embodiment that the conditional expressions (8)-(16) are satisfied. Specific examples of zoom lenses according to this embodiment are shown in the following Table 73.












TABLE 73





Group
Surface
r
d
n
ν




















1
1
35.243
0.90
1.80518
25.4



2
18.353
5.25
1.60311
60.7



3
−154.339
0.15



4
17.449
3.00
1.60311
60.7



5
53.989
Variable


2
6
53.989
0.70
1.78500
43.7



7
5.142
2.97



8
−7.948
0.80
1.66547
55.2



9
5.519
2.70
1.80518
25.4



10
1291.253
Variable


3
11
13.385
2.45
1.51450
63.1



12
−17.352
0.60



13
−120.265
1.00
1.84666
25.4



14
68.318
2.70


4
15
−18.144
1.50
1.58913
61.2



16
−15.906
1.00
1.80518
25.4



17
−22.792
1.00



19
39.750
Variable


5
20
−47.899
0.60
1.84666
23.9



21
23.192
2.70
1.51633
64.1



22
−12.941
0.10



23
10.762
2.95
1.51450
63.1



24
−21.804
Variable


6
25
∞
14.00
1.58913
61.2



26
∞
2.80
1.51633
64.1



27
∞
—









The following Table 74 shows aspherical coefficients of the zoom lens in the present example.









TABLE 74









Surface












8
11
12
23















K
−4.89985
−5.91060
−5.50770
−7.58012 × 10−1


D
−1.08175 × 10−3
 1.96402 × 10−4
−2.82483 × 10−5
−5.38373 × 10−5


E
−1.06040 × 10−5
−1.63114 × 10−6
 3.84825 × 10−6
−2.44675 × 10−7









The following Table 75 shows an air distance (mm) that is varied by zooming in the case where an object is positioned 2 m away from the tip end of the lens. At the standard position, magnification of the second lens group 222 becomes −1 times in Table 75.











TABLE 75







Wide-angle end
Standard position
Telephoto end





















f
3.685
17.981
42.743



F/NO
1.728
1.936
2.074



2ω
58.590
12.248
5.113



d5
0.600
11.675
14.927



d10
17.903
6.827
3.575



d14
5.200
2.360
5.200



d19
1.000
3.840
1.000










The values of the expressions (8) to (14) are as follows.

rS1/rS9=1.05

rS1/rS9=0.46

|f3/f34|=0.62

BF/fw=3.58

f1/fw=6.99

|f2|/fw=1.25

f34/fw=8.79

f5/fw=3.25

FIGS. 87-89 illustrate various aberrations at a wide-angle end, at a standard position and at a telephoto end of the zoom lens. As clearly shown in the aberrations of FIGS. 87-89, a zoom lens according to this embodiment has sufficient performance to correct aberration to realize high resolution.
Twenty-First Embodiment
FIG. 90 is a view showing the arrangement of a zoom lens in a twenty-first embodiment according to the present invention. As shown in FIG. 90, a zoom lens has a structure in which a first lens group 261, a second lens group 262, a third lens group 263, a fourth lens group 264, and a fifth lens group 265 are disposed from an object side deft side in FIG. 90) to an image plane side (right side in FIG. 90) in this order.
The first lens group 261 has a positive refracting power and is fixed with respect to the image plane in varying power and focusing. The second lens group 262 has a negative refracting power and varies power by moving along an optical axis. The third lens group 263 is composed of two lenses: a positive lens and a negative lens disposed from the object side in this order, and this group has a positive refracting power as a whole.
The fourth lens group 264 is composed of two lenses: a negative lens and a positive lens disposed from the object side in this order and this group has a negative refracting power as a whole, and is fixed with respect to the image plane in varying power and focusing. The fifth lens group 265 has a positive refracting power and moves along an optical axis so as to move an image and adjust the focus thereof at the same time in accordance with variable power. When camera shake occurs, shake of an image is corrected by moving the third lens group 263 vertically with respect to the optical axis.
The performance when shifting the lenses can be improved by applying at least one aspherical surface to any of the lenses of the third group 263.
Similar to the fourteenth embodiment, it is preferable for the zoom lens of this embodiment that the conditional expressions (8)-(16) are satisfied.
Specific examples of zoom lenses according to this embodiment are shown in the following Table 76.












TABLE 76





Group
Surface
r
d
n
ν




















1
1
35.243
0.90
1.80518
25.4



2
18.353
5.25
1.60311
60.7



3
−154.339
0.15



4
17.449
3.00
1.60311
60.7



5
53.989
Variable


2
6
53.989
0.70
1.78500
43.7



7
5.142
2.97



8
−7.948
0.80
1.66547
55.2



9
5.519
2.70
1.80518
25.4



10
1291.253
Variable


3
11
13.379
2.45
1.51450
63.1



12
−14.156
0.60



13
−61.508
1.00
1.80518
25.4



14
64.122
2.70


4
17
−28.305
1.00
1.51633
61.2



18
24.977
1.60



19
19.641
1.50
1.80518
25.4



20
25.463
Variable


5
21
−54.314
0.60
1.84666
23.9



22
24.366
2.70
1.51633
64.1



23
−13.009
0.10



24
11.183
2.95
1.51450
63.1



25
−21.825
Variable


6
26
∞
14.00
1.58913
61.2



27
∞
2.80
1.51633
64.1



28
∞
—









The following Table 77 shows aspherical coefficients of the zoom lens in the present embodiment.










TABLE 77









Surface












8
13
22














K
−4.89985
−8.46317
−1.14637


D
−1.08175 × 10−3
 1.00945 × 10−4
−6.03706 × 10−5


E
−1.06040 × 10−5
−1.63114 × 10−6
−8.33884 × 10−8









The following Table 78 shows an air distance (mm) that is varied by zooming in the case where an object is positioned 2 m away from the tip end of the lens. At the standard position, magnification of the second lens group 262 becomes −1 times in Table 78.











TABLE 78







Wide-angle end
Standard position
Telephoto end





















f
3.684
18.016
42.724



F/NO
1.676
1.898
2.073



2ω
58.536
12.215
5.106



d5
0.600
11.675
14.927



d10
17.903
6.827
3.575



d14
5.200
2.343
5.200



d19
1.000
3.857
1.000










The values of the Expressions (8) to (14) are as follows.

rS1/rS9=0.93

rS1/rS9=0.63

|f3/f34|=0.61

BF/fw=3.59

f1/fw=6.99

|f2|/fw1.25

f34/fw=8.94

f5/f=3.26

FIGS. 91-93 illustrate various aberrations at a wide-angle end, at a standard position and at a telephoto end of the zoom lens. As clearly shown in the aberrations of FIGS. 91-93, a zoom lens according to this embodiment has sufficient performance to correct aberration to realize high resolution.
Twenty-Second Embodiment
FIG. 94 is a view showing the arrangement of a video camera (three-plate-type video camera) in a twenty-second embodiment according to the present invention. As shown in FIG. 94, a video camera according to this embodiment comprises a zoom lens 301, a low-pass filter 302, prisms 303a-303c for color separation, imagers 304a-304c, a signal processing circuit 305, a view finder 306, a sensor 307 for detecting camera shake, and an actuator 308 for driving the lens. The zoom lens of the fifteenth embodiment (see FIG. 66) is used for the zoom lens 301, and thus, a small and highly-qualified video camera having a function for correcting camera shake is realized.
In this embodiment, the zoom lens of FIG. 66 in the fifteenth embodiment is used. This zoom lens can be replaced by any of the zoom lenses shown in the sixteenth to twenty-first embodiments.
Although camera shake is corrected by shifting a lens group having a positive refracting power, similar effects can be obtained by shifting a lens group having a negative refracting power.
INDUSTRIAL APPLICABILITY
As mentioned above, the present invention provides a zoom lens having a function to correct camera shake, i.e., a function to optically correct shake of an image caused by camera shake, vibration etc. The zoom lens can be made small and compact with less deterioration in the aberration performance. Such a zoom lens can be used as a zoom lens for a video camera or for an electronic still camera.

## Claims

1. A zoom lens comprising:
a first lens group having a positive refracting power and being fixed with respect to an image plane:
a second lens group having a negative refracting power and being movable along an optical axis to vary a power;
a third lens aroup being fixed with respect to the image plane;
a fourth lens group being fixed with respect to the image plane; and
a fifth lens group having a positive refracting power and being movable along an optical axis;
wherein said first, second, third, fourth and fifth lens groups are disposed in this order from an object side;
wherein said third lens group and said fourth lens group compose a combination of a lens group havinn a positive refracting power and a lens group having a negative refracting power;
wherein one of said third and fourth lens group is vertically movable with respect to the optical axis; and
wherein the one of said third and fourth lens groups that is vertically movable with respect to the optical axis is composed of two lenses comprising one lens having a positive refracting power and one lens having a negative refracting power each being disposed separately from the object side in this order and each having sag amounts which are equal in the object side and in the image side.

2. A zoom lens according to claim 1, wherein the one of said third and fourth lens groups that is vertically movable with respect to the optical axis is composed of two lenses comprising one positive lens and one negative lens.

3. A zoom lens according to claim 1, wherein said third lens group has a positive refracting power and said fourth lens group has a negative refracting power, and said third lens group is vertically movable with respect to the optical axis.

4. A zoom lens according to claim 1, wherein said fourth tens group is composed of two lenses separated from each other and comprising one positive lens and one negative lens.

5. A zoom lens according to claim 1, wherein said fourth lens group is composed of two cemented lenses comprising one positive lens and one negative lens.

6. A zoom lens according to claim 1, wherein said third lens group has a negative refracting power and said fourth lens group has a positive refracting power, and said fourth lens group is vertically movable with respect to the optical axis.

7. A zoom lens according to claim 1, wherein said third lens group and said fourth lens group are composed of two lenses respectively, and Abbe's number v31 of one lens of the third group, Abbe's number v32 of the remaining lens of the third group, Abbe's number v41 of one lens of the fourth group and Abbe's number v 42 of the remaining lens of the fourth group satisfy the following conditional expressions


|v31−v32|>25



|v41−v42|>25.

8. A zoom lens according to claim 1, wherein the one of said third and fourth lens groups that is vertically movable with respect to the optical axis is composed of three Lenses comprising at least one positive lens and at least one negative lens.

9. A zoom lens according to claim 1, wherein the one of said third and fourth lens groups vertically movable with respect to the optical axis is composed of one lens.

10. A zoom lens according to claim 1, wherein the one of said third and fourth lens groups vertically movable with respect to the optical axis comprises at least one aspherical surface.

11. A zoom lens according to claim 1, wherein the one of said third and fourth lens groups vertically movable with respect to the optical axis comprises a convex lens having an aspherical surface when viewed from the object side and a local radius of curvature rS1 for a diameter occupying 10% of a lens effective diameter and a local radius of curvature rS9 for a diameter occupying 90% of a lens effective diameter satisfying the following conditional expression


0.0 1<rS1/rS9<2.00.

12. A zoom lens according to claim 1, wherein a focal length f3 of said third lens group and a focal length f34 of a composite focal length of said third and fourth lens groups satisfy the following conditional expression


0.40<|f3/f34|<0.85.

13. A zoom lens according to claim 1, wherein a focal length fw of an entire system at a wide-angle end and a distance BF between a final surface of a lens and the image plane in air satisfy the following conditional expression


0<BF<fw<5.0.

14. A zoom lens according to claim 1, wherein a focal length fW of an entire system at a wide-angle end, focal length fi (i=1−5) of an i-th lens group, and a composite focal length f34 of said third and fourth lens groups satisfy the following expressions


5.0<f1/fw<8.00



521 |f2|/fw1.6



4.0<f34/fw<9.5



2.0<f5/fw<5.0.

15. A zoom lens according to claim 1, wherein a shifting amount Y of said third lens group at a focal length f of an entire system when correcting a movement of an image during a shaking of said zoom lens, a shifting amount Yt of said third lens group at a telephoto end, and a focal length ft of the telephoto end satisfy the following conditional expressions


Yt>Y;



(Y/Yt)/(f/ft)<1.5.

16. A video camera provided with a zoom lens according to claim 1.

17. A zoom lens according to claim 1, wherein the one of said third and fourth lens group is vertically movable with respect to the optical axis in order to correct a movement of an image during a shaking of said zoom lens.

18. A still image camera provided with a zoom lens according to claim 1.

19. A video camera provided with a zoom lens according to claim 1.

20. A zoom lens comprising:
a first lens group having a positive refracting power and being fixed with respect to an image plane;
a second lens group having a negative refracting power and being movable along an optical axis to vary a power;
a third lens group being fixed with respect to the image plane;
a fourth lens group being fixed with respect to the image plane; and
a fifth lens group having a positive refracting power and being movable along an optical axis;
wherein said first, second, third, fourth and fifth lens groups are disposed in this order from an object side;
wherein said third lens group and said fourth lens group compose a combination of a lens group having a positive refracting power and a lens group having a negative refracting power,
wherein one of said third and fourth lens group is vertically movable with respect to the optical axis; and
wherein the one of said third and fourth lens groups vertically movable with respect to the optical axis comprises a convex lens having an aspherical surface when viewed from the object side and a local radius of curvature rS1 for a diameter occupying 10% of a lens effective diameter and a local radius of curvature rS9 for a diameter occupying 90% of a lens effective diameter satisfing the following conditional expression


0.0<rS1 /rs9<2.00.

21. A zoom lens according to claim 20, wherein the one of said third and fourth lens groups that is vertically movable with respect to the optical axis is composed of two lenses comprising one positive lens and one negative lens.

22. A zoom lens according to claim 20, wherein said third lens group has a positive refracting power and said fourth lens group has a negative refracting power, and said third lens group is vertically movable with respect to the optical axis.

23. A zoom lens according to claim 20, wherein said fourth lens group is composed of two lenses separated from each other and comprising one positive lens and one negative lens.

24. A zoom lens according to claim 20, wherein said fourth lens group is composed of two cemented lenses comprising one positive lens and one negative lens.

25. A zoom lens according to claim 20, wherein said third lens group has a negative refracting power and said fourth lens group has a positive refracting power, and said fourth lens group is vertically movable with respect to the optical axis.

26. A zoom lens according to claim 20, wherein said third lens group and said fourth lens group are composed of two lenses respectively, and Abbe's number v31 of one lens of the third group, Abbe's number v32 of the remaining lens of the third group, Abbe's number v41 of one lens of the fourth group and Abbe's number v 42 of the remaining lens of the fourth group satisfy the following conditional expressions


|v31-v32 |>25



|v41-v42 |>25.

27. A zoom lens according to claim 20, wherein the one of said third and fourth lens groups that is vertically movable with respect to the optical axis is composed of two lenses comprising one lens having a positive refracting power and one lens having a negative refracting power each being disposed separately from the object side in this order and each having sag amounts which are equal in the object side and in the image side.

28. A zoom lens according to claim 20, wherein the one of said third and fourth lens groups that is vertically movable with respect to the optical axis is composed of three lenses comprising at least one positive lens and at least one negative lens.

29. A zoom lens according to claim 20, wherein the one of said third and fourth lens groups vertically movable with respect to the optical axis is composed of one lens.

30. A zoom lens according to claim 20, wherein the one of said third and fourth lens groups vertically movable with respect to the optical axis comprises at least one aspherical surface.

31. A zoom lens according to claim 20, wherein a focal length f3 of said third lens group and a focal length f4 of a composite focal length of said third and fourth lens groups satisfy the following conditional expression


0.40<|f3/f34|<0.85.

32. A zoom lens according to claim 20, wherein a focal length fw of an entire system at a wide-angle end and a distance BF between a final surface of a lens and the image plane in air satisfy the following conditional expression


0<BF<fw<5.0.

33. A zoom lens according to claim 20. wherein a focal length fw of an entire system at a wide-angle end, focal length fi (1=1-5) of an i-th lens group, and a composite focal length f34 of said third and fourth lens groups satisty the following expressions


5.0<f1/fw<8.00



5<|f2|/fw1.6



4.0<f34/fw<9.5



2.0<f5/fw<5.0.

34. A zoom lens according to claim 20, wherein a shifting amount Y of said third lens group at a focal length f of an entire system when correcting a movement of an image during a shaking of said zoom lens, a shifting amount Yt of said third lens group at a telephoto end, and a focal length ft of the telephoto end satisfy the following conditional expressions


Yt>Y;



(Y/Yt)/(f/ft)<1.5.

35. A video camera provided with a zoom lens according to claim 20.

36. A zoom lens according to claim 20, wherein the one of said third and fourth lens group is vertically movable with respect to the optical axis in order to correct a movement of an image during a shaking of said zoom lens.

37. A still image camera provided with a zoom lens according to claim 20.

38. A video camera provided with a zoom lens according to claim 20.

39. A zoom lens comprising:
a first lens group having a positive refracting power and being fixed with respect to an image plane;
a second lens group having a negative refracting power and being movable along an optical axis to vary a power;
a third lens group being fixed with respect to the image plane;
a fourth lens group being fixed with respect to the image plane; and
a fifth lens group having a positive refracting power and being movable along an optical axis;
wherein said first, second, third, fourth and fifth lens groups are disposed in this order from an object side;
wherein said third lens group and said fourth lens group compose a combination of a lens group having a positive reftacting power and a lens group having a negative refracting power;
wherein one of said third and fourth lens group is vertically movable with respect to the optical axis; and
wherein a shifting amount Y of said third lens group at a focal length f of an entire system when correcting a movement of an image during a shaking of said zoom lens, a shifting amount Yt of said third lens group at a telephoto end, and a focal length ft of the telephoto end satisty the following conditional expressions


Yt>Y;



(Y/Yt)/(f/ft)<1.5.

40. A zoom lens according to claim 39, wherein the one of said third and fourth lens groups that is vertically movable with respect to the optical axis is composed of two lenses comprising one positive lens and one negative lens.

41. A zoom lens according to claim 39, wherein said third lens group has a positive refracting power and said fourth lens group has a negative refracting power, and said third lens group is vertically movable with respect to the optical axis.

42. A zoom lens according to claim 39, wherein said fourth lens group is composed of two lenses separated from each other and comprising one positive lens and one negative lens.

43. A zoom lens according to claim 39, wherein said fourth lens group is composed of two cemented lenses comprising one positive lens and one negative lens.

44. A zoom lens according to claim 39, wherein said third lens group has a negative refracting power and said fourth lens group has a positive refracting power, and said fourth lens group is vertically movable with respect to the optical axis.

45. A zoom lens according to claim 39, wherein said third lens group and said fourth lens group are composed of two lenses respectively, and Abbe's number v31 of one lens of the third group, Abbe's number v32 of the remaining lens of the third group, Abbe's number v41 of one lens of the fourth group and Abbe's number v 42 of the remaining lens of the fourth group satisfy the following conditional expressions


|v31-v32 |>25



|v41-v42 |>25.

46. A zoom lens according to claim 39, wherein the one of said third and fourth lens groups that is vertically movable with respect to the optical axis is composed of two lenses comprising one lens having a positive refracting power and one lens having a negative refracting power each being disposed separately from the object side in this order and each having sag amounts which are equal in the object side and in the image side.

47. A zoom lens according to claim 39, wherein the one of said third and fourth lens groups that is vertically movable with respect to the optical axis is composed of three lenses comprising at least one positive lens and at least one negative lens.

48. A zoom lens according to claim 39, wherein the one of said third and fourth lens groups vertically movable with respect to the optical axis is composed of one lens.

49. A zoom lens according to claim 39, wherein the one of said third and fourth lens groups vertically movable with respect to the optical axis comprises at least one aspherical surface.

50. A zoom lens according to claim 39, wherein the one of said third and fourth lens groups vertically movable with respect to the optical axis comprises a convex lens having an aspherical surface when viewed from the object side and a local radius of curvature rS1 for a diameter occupying 10% of a lens effective diameter and a local radius of curvature rS9 for a diameter occupying 90% of a lens effective diameter satisfying the following conditional expression


0.10<rS 1 /rs9<2.00.

51. A zoom lens according to claim 39, wherein a focal length f3 of said third lens group and a focal length f34 of a composite focal length of said third and fourth lens groups satisfy the following conditional expression


0.40<|f3/f34|<0.85.

52. A zoom lens according to claim 39, wherein a focal length fw of an entire system at a wide-angle end and a distance BF between a final surface of a lens and the image plane in air satisfy the following conditional expression


0<Bf<fw<5.0.

53. A zoom lens according to claim 39, wherein a focal length fw of an entire system at a wide-angle end, focal length fi (i=1-5) of an i-th lens group, and a composite focal length f34 of said third and fourth lens groups satisfy the following expressions


5.0<f1/fw<8.00



5=|f2|/fw1.6



4.0<f34/fw<9.5



2.0<f5/fw<5.0.

54. A video camera provided with a zoom lens according to claim 39.

55. A zoom lens according to claim 39, wherein the one of said third and fourth lens group is vertically movable with respect to the optical axis in order to correct a movement of an image during a shaking of said zoom lens.

56. A still image camera provided with a zoom lens according to claim 39.

57. A video camera provided with a zoom lens according to claim 39.