# Patent

## Title
Zoom lens system

## Abstract

Object is to provide an inner-focusing type zoom lens system carrying out focusing by moving a portion of a first lens group suitable for an auto-focus SLR camera. A zoom lens system includes, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power. Upon zooming from a wide-angle end state to a telephoto end state, a distance between the first and the second lens groups increases, and a distance between the second and the third lens groups decreases. The first lens group is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. Focusing from infinity to a close-range object is carried out by moving only the 1B lens group G1B to the object.

## Background
CROSS-REFERENCE TO RELATED APPLICATION
This application is a division of application Ser. No. 11/446,319 filed Jun. 5, 2006, now U.S. Pat. No. 7,242,532 which is a division of application Ser. No. 11/091,652 filed Mar. 29, 2005 (now U.S. Pat. No. 7,158,315 filed Jan. 2, 2007).


The disclosure of the following priority applications are herein incorporated by reference:
Japanese Patent Application No. 2004-099773 filed on Mar. 30, 2004,
Japanese Patent Application No. 2004-105319 filed on Mar. 31, 2004,
Japanese Patent Application No. 2005-036624 filed on Feb. 14, 2005 and
Japanese Patent Application No. 2005-036633 filed on Feb. 14, 2005.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a zoom lens system suitable for a single-lens-reflex (SLR) camera using a silver-halide film or a solid-state imaging device and in particular to an internal-focusing zoom lens system capable of focusing by moving a portion of the optical system in a first lens group and also in particular to a compact zoom lens system having a vibration reduction function with a zoom ratio of about four and an angle of view of about 22° or more in a wide-angle end state.
2. Related Background Art
As a conventional focusing method for a zoom lens, a front-lens-group focusing carrying out by moving the most object side lens group to the object has been generally known. This method has a merit that the moving amount for focusing is determined in accordance with the object distance regardless of the zooming position, so that it is effective for simplifying the focusing mechanism. This method makes it possible to construct a first lens group with about three lens elements, so that it is effective for simplifying the construction of the lens system and lowering the manufacturing cost. However, since the moving lens group for focusing is exposed outside, when unexpected force is applied to the lens system, the focusing mechanism, in particular an auto-focusing mechanism, may be damaged. On the other hand, zoom lens systems with an internal focusing method, in which focusing is carried out by a lens group other than the first lens group, have been proposed in large numbers. However, it also has a problem that the moving amount for focusing largely varies in accordance with the zoom position.
In order to solve the problems, a focusing method, in which the first lens group is composed of a front lens group having positive refractive power and a rear lens group having positive refractive power and focusing is carried out by moving the rear lens group to the object, has been proposed in Japanese Patent Application Laid-Open Nos. 6-51202, 2000-19398, and 2000-284174.
However, although each example disclosed by Japanese Patent Application Laid-Open No. 6-51202 constructing the first lens group by three lens elements as a whole, two lens elements in the front lens group and one lens element in the rear lens group, is suitable for simplifying the construction and lowering the manufacturing cost, since focusing is carried out by moving only a single lens element with positive refractive power, spherical aberration, on-axis chromatic aberration and lateral chromatic aberration becomes large upon focusing a close-range object, so that it is undesirable for obtaining high optical performance.
Moreover, each example disclosed by Japanese Patent Application Laid-Open No. 2000-19398 requires five lens elements in the first lens group, three lens elements in the front lens group and two lens elements in the rear lens group, so that it is not suitable for simplifying the construction or lowering the manufacturing cost.
Furthermore, each example disclosed by Japanese Patent Application Laid-Open No. 2000-284174 requires four lens elements in the first lens group, one lens element in the front lens group and three lens elements in the rear lens group, so that it is not suitable for simplifying the construction or lowering the manufacturing cost.
Moreover, telephoto zoom lenses with a vibration reduction mechanism having a zoom ratio of about four have been proposed in Japanese Patent Application Laid-Open Nos. 8-62541 and 10-133114.
Examples disclosed in Japanese Patent Application Laid-Open No. 8-62541 are a five-group zoom lens with positive-negative-positeve-positeve-negative power arrangement or a six-group zoom lens with positive-negative-positive-negative-positive-negative power arrangement moving the second lens group having negative refractive power for vibration reduction. However, in these disclosures, since the effective diameter of the second lens group is 25 mm or more, the vibration reduction mechanism becomes large, so that it becomes difficult to make the zoom lens system be compact.
Examples disclosed in Japanese Patent Application Laid-Open No. 10-133114 are a five-group zoom lens with positive-negative-negateve-positeve-negative power arrangement moving a portion of lens group in the fourth lens group having positive refractive power for vibration reduction. However, in these disclosures, since the effective diameter of the vibration reduction lens group in the fourth lens group is 25 mm or more, the vibration reduction mechanism becomes large, so that it becomes difficult to make the zoom lens system be compact.
SUMMARY OF THE INVENTION
The present invention is made in view of the aforementioned problems and has an object to provide an internal focusing zoom lens system suitable for an auto focus SLR camera using a silver-halide film or a solid-state imaging device, carrying out focusing by moving a portion of a first lens group, having a zoom ratio of about four and an angle of view of 22° or more in the wide-angle end state, and suitable for simplifying the lens construction of the first lens group and lowering manufacturing cost without compromising compactness or high optical performance.
According to one aspect of the present invention, a zoom lens system includes, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power. When a state of lens group positions varies from a wide-angle end state to a telephoto end state, a distance between the first lens group and the second lens group increases, and a distance between the second lens group and the third lens group decreases. The first lens group is composed of, in order from the object, a 1A lens group having positive refractive power, and a 1B lens group having positive refractive power. Focusing from infinity to a close-range object is carried out by moving only the 1B lens group to the object, and the following conditional expressions (1) through (4) are satisfied:

1.55<f1/fw<2.20  (1)

−0.55<f2/fw<−0.30  (2)

2.0<f1A/f1B<4.0  (3)

0.16<DAB/fw<0.30  (4)

where fw denotes the focal length of the zoom lens system in the wide-angle end state, f1 denotes the focal length of the first lens group, f2 denotes the focal length of the second lens group, f1A denotes the focal length of the 1A lens group, f1B denotes the focal length of the 1B lens group, and DAB denotes the distance between the 1A lens group and the 1B lens group when the zoom lens system is focused on infinity.

In one preferred embodiment of the present invention, when the state of lens group positions varies from the wide-angle end state to the telephoto end state, the first lens group and the third lens group preferably move to the object.
In one preferred embodiment of the present invention, the zoom lens system further includes a fourth lens group having negative refractive power to an image side of the third lens group. When the state of lens group positions varies from the wide-angle end state to the telephoto end state, a distance between the third lens group and the fourth lens group varies, and the following conditional expressions (5) through (7) are preferably satisfied:

0.35<f3/fw<0.70  (5)

−1.50<f4/fw<−0.70  (6)

−0.10<(D34w−D34t)/fw<0.10  (7)

where f3 denotes the focal length of the third lens group, f4 denotes the focal length of the fourth lens group, D34w denotes the distance between the third lens group and the fourth lens group in the wide-angle end state, and D34t denotes the distance between the third lens group and the fourth lens group in the telephoto end state.

In one preferred embodiment of the present invention, the 1A lens group is composed of only one positive lens, the 1B lens group is composed of, in order from the object, a negative meniscus lens having a convex surface facing to the object, and a positive lens having a convex surface facing to the object, and the following conditional expressions (8) and (9) are preferably satisfied:

50<ν1A  (8)

35<ν1BP−ν1BN  (9)

where ν1A denotes Abbe number of the positive lens in the 1A lens group at d-line (λ=587.6 nm), ν1BP denotes Abbe number of the positive lens in the 1B lens group G1B at d-line, and ν1BN denotes Abbe number of the negative meniscus lens in the 1B lens group G1B at d-line.

In one preferred embodiment of the present invention, the negative meniscus lens and the positive lens in the 1B lens group are preferably cemented with each other.
According to another aspect of the present invention, a zoom lens system with a vibration reduction mechanism includes, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having negative refractive power. When a state of lens group positions varies from a wide-angle end state to a telephoto end state, a distance between the first lens group and the second lens group increases, a distance between the second lens group and the third lens group decreases, and a distance between the third lens group and the fourth lens group varies. The fourth lens group is composed of, in order from the object, a 41 lens group, a 42 lens group having negative refractive power, and a 43 lens group. At least one of the 41 lens group and the 43 lens group has positive refractive power. Image blur on an image plane caused by a camera shake is reduced by moving only the 42 lens group perpendicular to the optical axis.
In one preferred embodiment of the present invention, the following conditional expression (10) is preferably satisfied:

0.10<f42/f4<0.90  (10)

where f4 denotes the focal length of the fourth lens group, and f42 denotes the focal length of the 42 lens group.

In one preferred embodiment of the present invention, the following conditional expressions (11) and (12) are preferably satisfied:

−2.10<f4/fw<−0.70  (11)

−2.10<(1/f41+1/f43)·f4<−0.40  (12)

where fw denotes the focal length of the zoom lens system in the wide-angle end state, f41 denotes the focal length of the 41 lens group and f43 denotes the focal length of the 43 lens group.

In one preferred embodiment of the present invention, when the state of lens group positions varies from the wide-angle end state to the telephoto end state, the first lens group, the third lens group, and the fourth lens group preferably move to the object.
In one preferred embodiment of the present invention, the 41 lens group preferably includes at least one positive lens, the 42 lens group preferably includes at least one positive lens and at least one negative lens, and the 43 lens group preferably includes at least one positive lens.
In one preferred embodiment of the present invention, the 41 lens group includes, in order from the object, a negative lens having a concave surface facing to the image, and a positive lens having a convex surface facing to the object, and the following conditional expression (13) is preferably satisfied:

0.20<n41N−n41P  (13)

where n41N denotes refractive index of the negative lens in the 41 lens group at d-line (λ=587.6 nm), and n41P denotes refractive index of the positive lens in the 41 lens group at d-line.

In one preferred embodiment of the present invention, the 42 lens group includes, in order from the object, a positive lens having a convex surface facing to the image, and a double concave negative lens, and the following conditional expression (14) is preferably satisfied:

10.0<ν42N−ν42P  (14)

where ν42N denotes Abbe number of the double concave negative lens in the 42 lens group at d-line (λ=587.6 nm), and ν42P denotes Abbe dumber of the positive lens in the 42 lens group at d-line.

In one preferred embodiment of the present invention, the zoom lens system preferably consists only of, in order from the object, the first lens group, the second lens group, the third lens group, and the fourth lens group.
In one preferred embodiment of the present invention, a fifth lens group having positive refractive power is preferably arranged to the image side of the fourth lens group.
In one preferred embodiment of the present invention, focusing from infinity to a close-range object is preferably carried out by moving the first lens group as a whole to the object.
In one preferred embodiment of the present invention, focusing from infinity to a close-range object is carried out by moving the second lens group as a whole to the object, and the following conditional expression (15) is preferably satisfied:

−0.98<M2t<−0.80  (15)

where M2t denotes the magnification of the second lens group in the telephoto end state.

In one preferred embodiment of the present invention, the first lens group is composed of, in order from the object, a 1A lens group having positive refractive power, and a 1B lens group having positive refractive power, and focusing from infinity to a close-range object is preferably carried out by moving only the 1B lens group to the object.
According to another aspect of the present invention, a zoom lens system with a vibration reduction mechanism includes, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power. When a state of lens group positions varies from a wide-angle end state to a telephoto end state, a distance between the first lens group and the second lens group increases, and a distance between the second lens group and the third lens group decreases. The third lens group is composed of, in order from the object, a 31 lens group having positive refractive power, a 32 lens group having negative refractive power, and a 33 lens group. Image blur on an image plane caused by a camera shake is reduced by moving only the 32 lens group perpendicular to the optical axis.
In one preferred embodiment of the present invention, the following conditional expressions (16) through (20) are preferably satisfied:

1.40<f1/fw<2.00  (16)

−0.53<f2/fw<−0.32  (17)

0.35<f3/fw<0.65  (18)

−2.00<f32/f3<−0.80  (19)

−0.20<f3/f33<0.50  (20)

where fw denotes the focal length of the zoom lens system in the wide-angle end state, f1 denotes the focal length of the first lens group, f2 denotes the focal length of the second lens group, f3 notes the focal length of the third lens group, f32 denotes the focal length of the 32 lens group, and f33 notes the focal length of the 33 lens group.

In one preferred embodiment of the present invention, when the state of lens group positions varies from the wide-angle end state to the telephoto end state, the first lens group and the third lens group preferably move to the object.
In one preferred embodiment of the present invention, the 31 lens group preferably includes at least three positive lenses and at least one negative lens, the 32 lens group preferably includes at least one positive lens and at least one negative lens, and the 33 lens group preferably includes at least one positive lens and at least one negative lens.
In one preferred embodiment of the present invention, the 31 lens group includes, in order from the object, a double convex positive lens, a first cemented lens constructed by a double convex positive lens cemented with a negative lens having a concave surface facing to the object, a positive meniscus lens having a convex surface facing to the object, and a second cemented lens, and the following conditional expressions (21) and (22) are preferably satisfied:

0.20<n31N−n31P  (21)

30.0<ν31P−ν31N  (22)

where n31N denotes refractive index of the negative lens in the first cemented lens at d-line (λ=587.6 nm), n31P denotes refractive index of the positive lens in the first cemented lens at d-line, ν31N denotes Abbe number of the negative lens in the first cemented lens at d-line, and ν31P denotes Abbe number of the positive lens in the first cemented lens at d-line.

In one preferred embodiment of the present invention, the 32 lens group includes, in order from the object, a positive lens having a convex surface facing to the image, and a double concave negative lens, and the following conditional expression (23) is preferably satisfied:

10.0<ν32N−ν32P  (23)

where ν32N denotes Abbe number of the double concave negative lens in the 32 lens group at d-line (λ=587.6 nm), and ν32P denotes Abbe number of the positive lens in the 32 lens group at d-line.

In one preferred embodiment of the present invention, the 32 lens group is composed of, in order from the object, a cemented lens constructed by a positive lens having a convex surface facing to the image cemented with a double concave negative lens, and the following conditional expression (24) is preferably satisfied:

−2.00<(r32R+r32F)/(r32R−r32F)<−0.70  (24)

where r32F denotes the radius of curvature of the object side surface of the positive lens in the 32 lens group, r32R denotes the radius of curvature of the image side surface of the double concave negative lens in the 32 lens group.

In one preferred embodiment of the present invention, the following conditional expression (25) is preferably satisfied:

0.40<r32S/f32<0.90  (25)

where r32S denotes the radius of curvature of the cemented lens in the 32 lens group, and f32 denotes the focal length of the 32 lens group.

In one preferred embodiment of the present invention, the zoom lens system preferably consists only of, in order from the object, the first lens group, the second lens group, and the third lens group.
In one preferred embodiment of the present invention, the first lens group is composed of, in order from the object, a 1A lens group having positive refractive power, and a 1B lens group having positive refractive power, focusing from infinity to a close-range object is carried out by moving only the 1B lens group to the object, and the following conditional expression (26) is preferably satisfied:

1.70<f1A/f1B<4.00  (26)

where f1A denotes the focal length of the 1A lens group and f1B denotes the focal length of the 1B lens group.

Other features and advantages according to the present invention will be readily understood from the detailed description of the preferred embodiments in conjunction with the accompanying drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram showing a sectional view of a zoom lens system according to Example 1 of a first embodiment of the present invention together with a trajectory of each lens group upon zooming.
FIGS. 2A and 2B show various aberrations of the zoom lens system according to Example 1 of the first embodiment in a wide-angle end state upon focusing at infinity, and at a closest shooting distance (1500 mm), respectively.
FIGS. 3A and 3B show various aberrations of the zoom lens system according to Example 1 of the first embodiment in an intermediate focal length state upon focusing at infinity, and at a closest shooting distance, respectively.
FIGS. 4A and 4B show various aberrations of the zoom lens system according to Example 1 of the first embodiment in a telephoto end state upon focusing at infinity, and at a closest shooting distance, respectively.
FIG. 5 is a diagram showing a sectional view of a zoom lens system according to Example 2 of the first embodiment of the present invention together with a trajectory of each lens group upon zooming.
FIGS. 6A and 6B show various aberrations of the zoom lens system according to Example 2 of the first embodiment in a wide-angle end state upon focusing at infinity, and at a closest shooting distance (1500 mm), respectively.
FIGS. 7A and 7B show various aberrations of the zoom lens system according to Example 2 of the first embodiment in an intermediate focal length state upon focusing at infinity, and at a closest shooting distance, respectively.
FIGS. 8A and 8B show various aberrations of the zoom lens system according to Example 2 of the first embodiment in a telephoto end state upon focusing at infinity, and at a closest shooting distance, respectively.
FIG. 9 is a diagram showing a sectional view of a zoom lens system according to Example 3 of the first embodiment of the present invention together with a trajectory of each lens group upon zooming.
FIGS. 10A and 10B show various aberrations of the zoom lens system according to Example 3 of the first embodiment in a wide-angle end state upon focusing at infinity, and at a closest shooting distance (1500 mm), respectively.
FIGS. 11A and 11B show various aberrations of the zoom lens system according to Example 3 of the first embodiment in an intermediate focal length state upon focusing at infinity, and at a closest shooting distance, respectively.
FIGS. 12A and 12B show various aberrations of the zoom lens system according to Example 3 of the first embodiment in a telephoto end state upon focusing at infinity, and at a closest shooting distance, respectively.
FIG. 13 is a diagram showing a sectional view of a zoom lens system according to Example 4 of the first embodiment of the present invention together with a trajectory of each lens group upon zooming.
FIGS. 14A and 14B show various aberrations of the zoom lens system according to Example 4 of the first embodiment in a wide-angle end state upon focusing at infinity, and at a closest shooting distance (1500 mm), respectively.
FIGS. 15A and 15B show various aberrations of the zoom lens system according to Example 4 of the first embodiment in an intermediate focal length state upon focusing at infinity, and at a closest shooting distance, respectively.
FIGS. 16A and 16B show various aberrations of the zoom lens system according to Example 4 of the first embodiment in a telephoto end state upon focusing at infinity, and at a closest shooting distance, respectively.
FIG. 17 is a diagram showing a sectional view of a zoom lens system according to Example 5 of a second embodiment of the present invention together with a trajectory of each lens group upon zooming.
FIGS. 18A and 18B show various aberrations of the zoom lens system according to Example 5 of the second embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively.
FIG. 19 shows various aberrations of the zoom lens system according to Example 5 of the second embodiment in an intermediate focal length state upon focusing at infinity.
FIGS. 20A and 20B show various aberrations of the zoom lens system according to Example 5 of the second embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.
FIG. 21 is a diagram showing a sectional view of a zoom lens system according to Example 6 of the second embodiment of the present invention together with a trajectory of each lens group upon zooming.
FIGS. 22A and 22B show various aberrations of the zoom lens system according to Example 6 of the second embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively.
FIG. 23 shows various aberrations of the zoom lens system according to Example 6 of the second embodiment in an intermediate focal length state upon focusing at infinity.
FIGS. 24A and 24B show various aberrations of the zoom lens system according to Example 6 of the second embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.
FIG. 25 is a diagram showing a sectional view of a zoom lens system according to Example 7 of the second embodiment of the present invention together with a trajectory of each lens group upon zooming.
FIGS. 26A and 26B show various aberrations of the zoom lens system according to Example 7 of the second embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively.
FIG. 27 shows various aberrations of the zoom lens system according to Example 7 of the second embodiment in an intermediate focal length state upon focusing at infinity.
FIGS. 28A and 28B show various aberrations of the zoom lens system according to Example 7 of the second embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.
FIG. 29 is a diagram showing a sectional view of a zoom lens system according to Example 8 of the second embodiment of the present invention together with a trajectory of each lens group upon zooming.
FIGS. 30A and 30B show various aberrations of the zoom lens system according to Example 8 of the second embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively.
FIG. 31 shows various aberrations of the zoom lens system according to Example 8 of the second embodiment in an intermediate focal length state upon focusing at infinity.
FIGS. 32A and 32B show various aberrations of the zoom lens system according to Example 8 of the second embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.
FIG. 33 is a diagram showing a sectional view of a zoom lens system according to Example 9 of the second embodiment of the present invention together with a trajectory of each lens group upon zooming.
FIGS. 34A and 34B show various aberrations of the zoom lens system according to Example 9 of the second embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively.
FIG. 35 shows various aberrations of the zoom lens system according to Example 9 of the second embodiment in an intermediate focal length state upon focusing at infinity.
FIGS. 36A and 36B show various aberrations of the zoom lens system according to Example 9 of the second embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.
FIG. 37 is a diagram showing a sectional view of a zoom lens system according to Example 10 of a third embodiment of the present invention together with a trajectory of each lens group upon zooming.
FIGS. 38A and 38B show various aberrations of the zoom lens system according to Example 10 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively.
FIG. 39 shows various aberrations of the zoom lens system according to Example 10 of the third embodiment in an intermediate focal length state upon focusing at infinity.
FIGS. 40A and 40B show various aberrations of the zoom lens system according to Example 10 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.
FIG. 41 is a diagram showing a sectional view of a zoom lens system according to Example 11 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.
FIGS. 42A and 42B show various aberrations of the zoom lens system according to Example 11 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively.
FIG. 43 shows various aberrations of the zoom lens system according to Example 11 of the third embodiment in an intermediate focal length state upon focusing at infinity.
FIGS. 44A and 44B show various aberrations of the zoom lens system according to Example 11 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.
FIG. 45 is a diagram showing a sectional view of a zoom lens system according to Example 12 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.
FIGS. 46A and 46B show various aberrations of the zoom lens system according to Example 12 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively.
FIG. 47 shows various aberrations of the zoom lens system according to Example 12 of the third embodiment in an intermediate focal length state upon focusing at infinity.
FIGS. 48A and 48B show various aberrations of the zoom lens system according to Example 12 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.
FIG. 49 is a diagram showing a sectional view of a zoom lens system according to Example 13 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.
FIGS. 50A and 50B show various aberrations of the zoom lens system according to Example 13 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively.
FIG. 51 shows various aberrations of the zoom lens system according to Example 13 of the third embodiment in an intermediate focal length state upon focusing at infinity.
FIGS. 52A and 52B show various aberrations of the zoom lens system according to Example 13 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.
FIG. 53 is a diagram showing a sectional view of a zoom lens system according to Example 14 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.
FIGS. 54A and 54B show various aberrations of the zoom lens system according to Example 14 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively.
FIG. 55 shows various aberrations of the zoom lens system according to Example 14 of the third embodiment in an intermediate focal length state upon focusing at infinity.
FIGS. 56A and 56B show various aberrations of the zoom lens system according to Example 14 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.
FIG. 57 is a diagram showing a sectional view of a zoom lens system according to Example 15 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.
FIGS. 58A and 58B show various aberrations of the zoom lens system according to Example 15 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively.
FIG. 59 shows various aberrations of the zoom lens system according to Example 15 of the third embodiment in an intermediate focal length state upon focusing at infinity.
FIGS. 60A and 60B show various aberrations of the zoom lens system according to Example 15 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.
FIG. 61 is a diagram showing a sectional view of a zoom lens system according to Example 16 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.
FIGS. 62A and 62B show various aberrations of the zoom lens system according to Example 16 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively.
FIG. 63 shows various aberrations of the zoom lens system according to Example 16 of the third embodiment in an intermediate focal length state upon focusing at infinity.
FIGS. 64A and 64B show various aberrations of the zoom lens system according to Example 16 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.



DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment
The zoom lens system according to the first embodiment of the present invention is composed of, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power. When a state of lens group positions varies from a wide-angle end state to a telephoto end state, a distance between the first lens group and the second lens group increases, and a distance between the second lens group and the third lens group decreases.
The first lens group is composed of, in order from the object, a 1A lens group G1A having positive refractive power and a 1B lens group G1B having positive refractive power. Focusing from infinity to a close-rang object is carried out by moving only the 1B lens group G1B to the object.
With this construction, it can be prevented to expose movable lens group for focusing, so that it is advantageous for auto focus. Moreover, by composing the first lens group of the 1A lens group G1A having positive refractive power and the 1B lens group G1B having positive refractive power, increase in the number of lens elements can be prevented and variation in aberration upon focusing can be suppressed.
The zoom lens system according to the first embodiment of the present invention satisfies the following conditional expressions (1) through (4):

1.55<f1/fw<2.20  (1)

−0.55<f2/fw<−0.30  (2)

2.0<f1A/f1B<4.0  (3)

0.16<DAB/fw<0.30  (4)

where fw denotes the focal length of the zoom lens system in the wide-angle end state, f1 denotes the focal length of the first lens group, f2 denotes the focal length of the second lens group, f1A denotes the focal length of the 1A lens group, f1B denotes the focal length of the 1B lens group, and DAB denotes the distance between the 1A lens group and the 1B lens group when the zoom lens system is focused on infinity.

Conditional expression (1) defines an appropriate range of the focal length of the first lens group. When the ratio f1/fw is equal to or falls below the lower limit of conditional expression (1), positive refractive power of the first lens group becomes large, so that it becomes difficult to satisfactorily correct aberrations with fewer number of lens elements. On the other hand, when the ratio f1/fw is equal to or exceeds the upper limit of conditional expression (1), the total length of the zoom lens system becomes large, so that it is undesirable.
In order to secure the effect of the present invention, it is preferable that the lower limit of conditional expression (1) is set to 1.60 and the upper limit to 2.00.
Conditional expression (2) defines an appropriate range of the focal length of the second lens group. When the ratio f2/fw is equal to or exceeds the upper limit of conditional expression (2), negative refractive power of the second lens group becomes large, so that it becomes difficult to correct various aberrations. On the other hand, when the ratio f2/fw is equal to or falls below the lower limit of conditional expression (2), the total length of the zoom lens system becomes large, so that it is undesirable.
In order to fully secure the effect of the present invention, it is preferable that the lower limit of conditional expression (2) is set to −0.50 and the upper limit to −0.35.
Conditional expression (3) defines an appropriate range of the ratio of the focal length of the 1A lens group to that of the 1B lens group. When the ratio f1A/f1B is equal to or exceeds the upper limit of conditional expression (3), positive refractive power of the 1B lens group becomes strong, so that it takes larger number of lens elements in the 1B lens group to correct aberrations. On the other hand, when the ratio f1A/f1B is equal to or falls below the lower limit of conditional expression (3), positive refractive power of the 1A lens group becomes strong, so that it takes larger number of lens elements in the 1A lens group to correct aberrations.
In order to further secure the effect of the present invention, it is preferable that the lower limit of conditional expression (3) is set to 2.20 and the upper limit to 3.85.
Conditional expression (4) defines an appropriate range of the distance between the 1A lens group G1A and the 1B lens group G1B. When the ratio DAB/fw is equal to or exceeds the upper limit of conditional expression (4), the diameter of the 1A lens group becomes large, so that it is undesirable. On the other hand, when the ratio DAB/fw is equal to or falls below the lower limit of conditional expression (4), the air space for moving the 1B lens group upon focusing becomes narrow, so that it becomes difficult to secure the closest shooting distance to be sufficiently near.
In order to further secure the effect of the present invention, it is preferable that the lower limit of conditional expression (4) is set to 0.18 and the upper limit to 0.25.
It is preferable that when the state of lens group positions varies from the wide-angle end state to the telephoto end state, the first lens group and the third lens group move to the object. In this construction, the total lens length of the zoom lens system in the wide-angle end state can be compact.
Moreover, it may be possible to construct the zoom lens system by including a fourth lens group having negative refractive power to the image side of the third lens group and varying the distance between the third lens group and the fourth lens group upon zooming from the wide-angle end state to the telephoto end state. By arranging the fourth lens group having negative refractive power to the image side of the third lens group, the zoom lens system becomes a telephoto type power arrangement, so that it is effective to shorten the total lens length of the zoom lens system. Moreover, by varying the distance between the third lens group and the fourth lens group, variation in astigmatism and curvature of field can be suppressed.
In the zoom lens system according to the first embodiment of the present invention, it is preferable to satisfy the following conditional expressions (5) through (7):

0.35<f3/fw<0.70  (5)

−1.50<f4/fw<−0.70  (6)

−0.10<(D34w−D34t)/fw<0.10  (7)

where f3 notes the focal length of the third lens group, f4 denotes the focal length of the fourth lens group, D34w denotes the distance between the third lens group and the fourth lens group in the wide-angle end state, and D34t denotes the distance between the third lens group and the fourth lens group in the telephoto end state.

Conditional expression (5) defines an appropriate range of the focal length of the third lens group. When the ratio f3/fw is equal to or falls below the lower limit of conditional expression (5), positive refractive power of the third lens group becomes strong, so that it becomes difficult to correct various aberrations as well as spherical aberration. On the other hand, when the ratio f2/fw is equal to or exceeds the upper limit of conditional expression (5), the total length of the zoom lens system becomes large, so that it is undesirable.
In order to further secure the effect of the present invention, it is preferable that the lower limit of conditional expression (5) is set to 0.40 and the upper limit to 0.60.
Conditional expression (6) defines an appropriate range of the focal length of the fourth lens group. When the ratio f4/fw is equal to or exceeds the upper limit of conditional expression (6), negative refractive power of the fourth lens group becomes strong, so that it becomes difficult to correct coma and distortion. On the other hand, when the ratio f4/fw is equal to or falls below the lower limit of conditional expression (6), negative refractive power of the fourth lens group becomes weak decreasing the effect of the telephoto type power arrangement, so that it becomes difficult to make the total lens length be compact.
In order to further secure the effect of the present invention, it is preferable that the lower limit of conditional expression (6) is set to −1.20 and the upper limit to −0.85.
Conditional expression (7) defines an appropriate range of difference between the distance from the third lens group to the fourth lens group in the wide-angle end state and that in the telephoto end state. When the ratio (D34w−D34t)/fw is equal to or falls below the lower limit of conditional expression (7), or is equal to or exceeds the upper limit of conditional expression (7), it becomes difficult to satisfactorily correct variation in astigmatism and curvature of field upon zooming.
In order to further secure the effect of the present invention, it is preferable that the lower limit of conditional expression (7) is set to −0.05 and the upper limit to 0.05.
In order to suppress the number of lens elements in the first lens group to be three it is preferable that the 1A lens group G1A is composed of only one positive lens element and the 1B lens group G1B is composed of, in order from the object, a negative meniscus lens having a convex surface facing to the object and a positive lens having a convex surface facing to the object. The construction is effective to make the zoom lens system simple, compact, and cheep.
Since the focusing lens group, which is the 1B lens group G1B, is composed of a negative lens and a positive lens, it becomes possible to correct spherical aberration and chromatic aberration, so that variation in spherical aberration and chromatic aberration upon focusing can be suppressed.
In the zoom lens system according to the first embodiment of the present invention, it is preferable to satisfy the following conditional expressions (8) and (9):

50<ν1A  (8)

35<ν1BP−ν1BN  (9)

where ν1A denotes Abbe number of the positive lens in the 1A lens group G1A at d-line (λ=587.6 nm), ν1BP denotes Abbe number of the positive lens in the 1B lens group G1B at d-line, and ν1BN denotes Abbe number of the negative meniscus lens in the 1B lens group G1B at d-line.

Conditional expression (8) defines an appropriate range of Abbe number of the positive lens consisting of the 1A lens group G1A. When the value ν1A is equal to or falls below the lower limit of conditional expression (8), variation in chromatic aberration upon focusing becomes large, s that it is undesirable. In order to further secure the effect of the present invention, it is preferable that the lower limit of conditional expression (8) is set to 60.
Conditional expression (9) defines an appropriate range of difference between Abbe number of the positive lens and that of the negative meniscus lens consisting of the 1B lens group G1B. When the value ν1BP−ν1BN is equal to or falls below the lower limit of conditional expression (9), variation in chromatic aberration upon focusing and zooming becomes large, so that it is undesirable. In order to further secure the effect of the present invention, it is preferable that the lower limit of conditional expression (9) is set to 40.
Furthermore, it is preferable that the negative meniscus lens and the positive lens in the 1B lens group are cemented. With this construction, degradation of optical performance or production of ghost images caused by assembling can be reduced.
Each example according to the first embodiment of the present invention is explained with reference to accompanying drawings.
EXAMPLE 1
FIG. 1 is a diagram showing a sectional view of a zoom lens system according to Example 1 of a first embodiment of the present invention together with a trajectory of each lens group upon zooming. In FIG. 1, the zoom lens system is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, an aperture stop S, a third lens group G3 having positive refractive power, and a fourth lens group G4 having negative refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1, the third lens group G3, and the fourth lens group G4 move to the object and the second lens group G2 moves once to the image and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, a distance between the second lens group G2 and the third lens group G3 decreases, and a distance between the third lens group G3 and the fourth lens group G4 varies. The aperture stop S moves together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).
The first lens group G1 is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. Focusing from infinity to a close-range object is carried out by moving only the 1B lens group G1B to the object.
The 1A lens group G1A is composed of a double convex positive lens L11. The 1B lens group G1B is composed of a cemented lens constructed by a negative meniscus lens L12 having a convex surface facing to the object cemented with a double convex positive lens L13.
The second lens group G2 is composed of a double concave negative lens, a cemented lens constructed by a double concave negative lens cemented with a double convex positive lens and a double concave negative lens.
The third lens group G3 is composed of a double convex positive lens, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens, and a positive meniscus lens having a convex surface facing to the object.
The fourth lens group G4 is composed of a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens, a double convex positive lens, and a negative meniscus lens having a concave surface facing to the object.
Various values associated with Example 1 are listed in Table 1. In [Specifications], f denotes the focal length, FNO denotes the f-number, and 2ω denotes the angle of view. In [Lens Data], the first column is the surface number counted in order from the object side, the second column r denotes the radius of curvature, the third column d denotes the distance along the optical axis between the lens surfaces, and the fourth column ν denotes Abbe number at d-line (λ=587.6 nm) and the fifth column n denotes refractive index at d-line (λ=587.6 nm). In the second column r, reference symbol “∞” denotes a plane. In the fifth column, refractive index of the air 1.00000 is omitted. In [Variable Distances], f denotes the focal length, M denotes the shooting magnification, D0 denotes the distance between the object and the first lens surface, R denotes a distance between the object and the image plane, and Bf denotes the back focal length. In [Values for Conditional Expressions], values for respective conditional expressions are shown.
In the tables for various values, “mm” is generally used for the unit of length such as the focal length, the radius of curvature, and the distance between optical surfaces. However, since an optical system proportionally enlarged or reduced its dimension can be obtained similar optical performance, the unit is not necessary to be limited to “mm” and any other suitable unit can be used. The explanation of reference symbols is the same in the other examples and duplicated explanations are omitted.







TABLE 1







[Specifications]















f =
71.40
135.20
294.00



FNO =
3.98
4.42
5.83



2ω =
34.26°
17.57°
8.19°











[Lens Data]












r
d
ν
n





 1
401.1292
3.4320
64.14
1.516330


 2
−401.1292
(d2)


 3
73.7120
1.8000
28.46
1.728250


 4
49.4588
9.2239
81.54
1.496999


 5
−634.7712
(d5)


 6
−569.6277
1.4000
46.57
1.804000


 7
65.8130
2.9470


 8
−66.3802
1.4000
49.34
1.743198


 9
37.4535
4.4348
23.78
1.846660


10
−157.1502
1.2424


11
−56.4033
1.4000
46.57
1.804000


12
457.6562
(d12)











13
∞
1.0000
Aperture Stop S












14
174.8883
4.0762
60.08
1.639999


15
−54.3627
0.2000


16
52.6528
6.0766
81.54
1.496999


17
−40.7675
1.4000
34.97
1.800999


18
1440.7843
0.2000


19
33.5705
3.5534
61.13
1.589130


20
93.9894
(d20)


21
479.6438
1.4000
23.78
1.846660


22
43.7293
4.5629
59.84
1.522494


23
−51.1261
3.0000


24
1129.8061
3.6174
29.23
1.721507


25
−22.8122
1.4000
47.93
1.717004


26
29.6916
4.4859


27
35.9110
3.4607
33.79
1.647689


28
−167.9338
4.3753


29
−22.4279
1.4000
46.57
1.804000


30
−45.1019
(B.f.)














Wide-angle end
Intermediate
Telephoto end











[Variable Distances]


(Infinity)












f
71.40001
135.19966
294.00012



D0
∞
∞
∞



d2
13.96876
13.96876
13.96876



d5
1.50000
30.16863
45.04078



d12
26.95417
16.63929
1.00000



d20
15.26706
15.23225
16.01169



B.f.
45.82163
54.27048
80.82164



R
∞
∞
∞







(Closest Shooting Distance)












M
−0.05763
−0.11156
−0.24806



D0
1325.0000
1298.2322
1271.6687



d2
1.45642
1.18529
0.90427



d5
14.01234
42.95210
58.10527



d12
26.95417
16.63929
1.00000



d20
15.26706
15.23225
16.01169



B.f.
45.82163
54.27048
80.82164



R
1500.0000
1500.0000
1500.0000











[Values for Conditional Expressions]












(1) f1/fw = 1.680



(2) f2/fw = −0.405



(3) f1A/f1B = 2.335



(4) DAB/fw = 0.196



(5) f3/fw = 0.503



(6) f4/fw = −1.060



(7) (D34w − D34t) = −0.010



(8) ν1A = 64.14



(9) ν1BP − ν1BN = 53.08










FIGS. 2A and 2B show various aberrations of the zoom lens system according to Example 1 of the first embodiment in a wide-angle end state upon focusing at infinity, and at a closest shooting distance (1500 mm), respectively. FIGS. 3A and 3B show various aberrations of the zoom lens system according to Example 1 of the first embodiment in an intermediate focal length state upon focusing at infinity, and at a closest shooting distance, respectively. FIGS. 4A and 4B show various aberrations of the zoom lens system according to Example 1 of the first embodiment in a telephoto end state upon focusing at infinity, and at a closest shooting distance, respectively.
In respective graphs, FNO denotes the f-number, Y denotes an image height, and D, G denote aberration curves for d-line (λ=587.6 nm) and g-line (λ=435.8 nm), respectively. In graphs showing astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. In the following Examples, the same reference symbols as Example 1 are used.
As is apparent from respective graphs, the zoom lens system according to Example 1 of the first embodiment shows superb optical performance correcting various aberrations.
EXAMPLE 2
FIG. 5 is a diagram showing a sectional view of a zoom lens system according to Example 2 of the first embodiment of the present invention together with a trajectory of each lens group upon zooming. In FIG. 5, the zoom lens system is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, an aperture stop S, a third lens group G3 having positive refractive power, and a fourth lens group G4 having negative refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1, the third lens group G3, and the fourth lens group G4 move to the object and the second lens group G2 moves once to the image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, a distance between the second lens group G2 and the third lens group G3 decreases, and a distance between the third lens group G3 and the fourth lens group G4 varies. The aperture stop S moves together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).
The first lens group G1 is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. Focusing from infinity to a close-range object is carried out by moving only the 1B lens group G1B to the object.
The 1A lens group G1A is composed of a double convex positive lens L11. The 1B lens group G1B is composed of a cemented lens constructed by a negative meniscus lens L12 having a convex surface facing to the object cemented with a double convex positive lens L13.
The second lens group G2 is composed of a double concave negative lens, a cemented lens constructed by a double concave negative lens cemented with a double convex positive lens and a negative meniscus lens having a concave surface facing to the object.
The third lens group G3 is composed of a double convex positive lens, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens, and a positive meniscus lens having a convex surface facing to the object.
The fourth lens group G4 is composed of a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens, a double convex positive lens, a double concave negative lens, a double convex positive lens, and a negative meniscus lens having a concave surface facing to the object.
Various values associated with Example 2 are listed in Table 2.







TABLE 2







[Specifications]















f =
71.40
135.20
294.00



FNO =
3.92
4.34
5.79



2ω =
34.01°
17.48°
8.17°











[Lens Data]












r
d
ν
n





 1
393.7797
3.4666
64.14
1.516330


 2
−393.7797
(d2)


 3
72.1379
1.8000
28.46
1.728250


 4
48.5919
9.3212
81.54
1.496999


 5
−673.5520
(d5)


 6
−371.5827
1.4000
46.57
1.804000


 7
57.6115
3.0775


 8
−66.8503
1.4000
49.34
1.743198


 9
39.7971
4.4329
23.78
1.846660


10
−120.0368
1.3565


11
−48.2268
1.4000
46.57
1.804000


12
−623.8156
(d12)











13
∞
1.0000
Aperture Stop S












14
171.0600
4.2202
60.08
1.639999


15
−51.8912
0.2000


16
53.6971
5.9454
81.54
1.496999


17
−42.4415
1.4000
34.97
1.800999


18
798.2716
0.2000


19
34.9966
3.3788
61.13
1.589130


20
91.1723
(d20)


21
224.4236
1.4000
23.78
1.846660


22
39.7038
3.2867
59.84
1.522494


23
−225.6684
6.3172


24
337.2025
3.1647
27.79
1.740769


25
−33.6532
0.2000


26
−34.9705
1.4000
46.57
1.804000


27
41.8882
3.6016


28
48.8184
3.6441
33.79
1.647689


29
−72.7425
10.5386 


30
−22.2604
1.4000
46.57
1.804000


31
−42.1654
(B.f.)
















Wide-angle end
Intermediate
Telephoto end











[Variable Distances]


(Infinity)












f
71.40227
135.19993
294.00037



D0
∞
∞
∞



d2
13.53509
13.53509
13.53509



d5
1.60134
30.08411
44.43064



d12
26.58593
16.43870
1.00000



d20
14.32441
14.04027
14.43188



B.f.
40.00116
48.12784
75.00135



R
∞
∞
∞







(Closest Shooting Distance)












M
−0.05757
−0.11137
−0.24756



D0
1325.0001
1298.8220
1272.6491



d2
1.42931
1.17314
0.90588



d5
13.70712
42.44606
57.05985



d12
26.58593
16.43870
1.00000



d20
14.32441
14.04027
14.43188



B.f.
40.00116
48.12784
75.00135



R
1500.0000
1500.0000
1500.0000











[Values for Conditional Expressions]












(1) f1/fw = 1.653



(2) f2/fw = −0.402



(3) f1A/f1B = 2.326



(4) DAB/fw = 0.190



(5) f3/fw = 0.513



(6) f4/fw = −1.039



(7) (D34w − D34t) = −0.002



(8) ν1A = 64.14



(9) ν1BP − ν1BN = 53.08










FIGS. 6A and 6B show various aberrations of the zoom lens system according to Example 2 of the first embodiment in a wide-angle end state upon focusing at infinity, and at a closest shooting distance (1500 mm), respectively. FIGS. 7A and 7B show various aberrations of the zoom lens system according to Example 2 of the first embodiment in an intermediate focal length state upon focusing at infinity, and at a closest shooting distance, respectively. FIGS. 8A and 8B show various aberrations of the zoom lens system according to Example 2 of the first embodiment in a telephoto end state upon focusing at infinity, and at a closest shooting distance, respectively.
As is apparent from respective graphs, the zoom lens system according to Example 2 of the first embodiment shows superb optical performance correcting various aberrations.
EXAMPLE 3
FIG. 9 is a diagram showing a sectional view of a zoom lens system according to Example 3 of the first embodiment of the present invention together with a trajectory of each lens group upon zooming. In FIG. 9, the zoom lens system is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, an aperture stop S, a third lens group G3 having positive refractive power, and a fourth lens group G4 having negative refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1, the third lens group G3, and the fourth lens group G4 move to the object and the second lens group G2 moves once to the image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, a distance between the second lens group G2 and the third lens group G3 decreases, and a distance between the third lens group G3 and the fourth lens group G4 varies. The aperture stop S moves together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).
The first lens group G1 is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. Focusing from infinity to a close-range object is carried out by moving only the 1B lens group G1B to the object.
The 1A lens group G1A is composed of a double convex positive lens L11. The 1B lens group G1B is composed of a cemented lens constructed by a negative meniscus lens L12 having a convex surface facing to the object cemented with a double convex positive lens L13.
The second lens group G2 is composed of a double concave negative lens, a cemented lens constructed by a double concave negative lens cemented with a double convex positive lens and a negative meniscus lens having a concave surface facing to the object.
The third lens group G3 is composed of a double convex positive lens, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens, and a positive meniscus lens having a convex surface facing to the object.
The fourth lens group G4 is composed of a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens, a double convex positive lens a double concave negative lens, a double convex positive lens, and a negative meniscus lens having a concave surface facing to the object.
Various values associated with Example 3 are listed in Table 3.







TABLE 3







[Specifications]















f =
71.40
134.90
294.00



FNO =
4.00
4.40
5.87



2ω =
34.03°
17.50°
8.17°











[Lens Data]












r
d
ν
n





 1
14220.5510
2.7079
64.14
1.516330


 2
−321.5792
(d2)


 3
69.9601
1.8000
34.97
1.800999


 4
46.3766
0.2000


 5
45.9671
11.3706  
81.54
1.496999


 6
−419.6274
(d6)


 7
−579.1168
1.4000
46.57
1.804000


 8
63.8363
3.4452


 9
−52.7313
1.4000
49.34
1.743198


10
48.3987
4.2542
23.78
1.846660


11
−107.9428
0.8861


12
−61.0721
1.4000
46.57
1.804000


13
−623.8156
(d13)











14
∞
1.0000
Aperture Stop S












15
166.9626
3.9296
60.08
1.639999


16
−58.2127
0.2000


17
57.0867
5.4967
81.54
1.496999


18
−46.6872
1.4000
34.97
1.800999


19
1396.9076
0.2000


20
34.3256
3.4395
61.13
1.589130


21
91.8543
(d21)


22
203.1166
1.4000
23.78
1.846660


23
40.7958
3.2583
59.84
1.522494


24
−258.7153
7.3113


25
302.9723
3.0588
27.79
1.740769


26
−35.3253
0.2000


27
−36.4959
1.4000
46.57
1.804000


28
40.5142
4.9030


29
51.7471
3.3861
33.79
1.647689


30
−82.2838
9.1961


31
−22.3825
1.4000
46.57
1.804000


32
−41.2791
(B.f.)
















Wide-angle end
Intermediate
Telephoto end











[Variable Distances]


(Infinity)












f
71.39992
134.89970
293.99916



D0
∞
∞
∞



d2
15.80731
15.80731
15.80731



d3
1.5000
34.04735
50.19310



d13
29.37034
18.20055
1.00000



d21
13.27877
12.96969
12.95602



B.f.
40.00001
47.68741
74.99998



R
∞
∞
∞







(Closest Shooting Distance)












M
−0.05859
−0.11340
−0.25277



D0
1320.0000
1291.2441
1265.0000



d2
1.48390
1.14166
0.81459



d6
15.82341
48.71300
65.18582



d13
29.37034
18.20055
1.00000



d21
13.27877
12.96969
12.95602



B.f.
40.00001
47.68741
74.99998



R
1500.0000
1500.0000
1500.0000











[Values for Conditional Expressions]












(1) f1/fw = 1.823



(2) f2/fw = −0.449



(3) f1A/f1B = 3.778



(4) DAB/fw = 0.221



(5) f3/fw = 0.521



(6) f4/fw = −0.928



(7) (D34w − D34t) = −0.005



(8) ν1A = 64.14



(9) ν1BP − ν1BN = 46.57










FIGS. 10A and 10B show various aberrations of the zoom lens system according to Example 3 of the first embodiment in a wide-angle end state upon focusing at infinity, and at a closest shooting distance (1500 mm), respectively. FIGS. 11A and 11B show various aberrations of the zoom lens system according to Example 3 of the first embodiment in an intermediate focal length state upon focusing at infinity, and at a closest shooting distance, respectively. FIGS. 12A and 12B show various aberrations of the zoom lens system according to Example 3 of the first embodiment in a telephoto end state upon focusing at infinity, and at a closest shooting distance, respectively.
As is apparent from respective graphs, the zoom lens system according to Example 3 of the first embodiment shows superb optical performance correcting various aberrations.
EXAMPLE 4
FIG. 13 is a diagram showing a sectional view of a zoom lens system according to Example 4 of the first embodiment of the present invention together with a trajectory of each lens group upon zooming. In FIG. 13, the zoom lens system is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1 and the third lens group G3 move to the object and the second lens group G2 moves once to the image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, and a distance between the second lens group G2 and the third lens group G3 decreases.
The first lens group G1 is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. The 1A lens group G1A is composed of a double convex positive lens L11. The 1B lens group G1B is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens L12 having a convex surface facing to the object cemented with a double convex positive lens L13.
Focusing from infinity to a close-range object is carried out by moving only the 1B lens group G1B to the object.
The second lens group G2 is composed of, in order from the object, a double concave negative lens, a cemented lens constructed by a double concave negative lens cemented with a positive meniscus lens having a convex surface facing to the object, and a negative meniscus lens.
The third lens group G3 is composed of, in order from the object, a 31 lens group G31 having positive refractive power, a 32 lens group G32 having negative refractive power, and a 33 lens group G33 having positive refractive power. The 31 lens group G31 is composed of, in order from the object, a double convex positive lens, a first cemented lens constructed by a double convex positive lens cemented with a negative meniscus lens, a positive meniscus lens having a convex surface facing to the object, and a second cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens. The 32 lens group G32 is composed of, in order from the object, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens. The 33 lens group G33 is composed of, in order from the object, a fixed stop S2, a double convex positive lens, and a negative meniscus lens having a concave surface facing to the object.
An aperture stop S is arranged to the object side of the 31 lens group G31 and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).
Various values associated with Example 4 is listed in Table 4.







TABLE 4







[Specifications]















f =
71.40
135.00
294.00



FNO =
4.64
4.85
5.88



2ω =
34.46°
17.55°
8.20°











[Lens Data]












r
d
ν
n





 1
340.6588
4.2
64.14
1.51633


 2
−340.659
(d2)


 3
65.1639
1.8
26.3
1.784696


 4
45.8381
8.8
81.61
1.496999


 5
−1308.92
(d5)


 6
−271.25
1.4
49.61
1.772499


 7
71.7854
1.3


 8
−566.934
1.4
49.61
1.772499


 9
24.4437
4.7
23.78
1.84666


10
133.0962
 3.75


11
−46.0918
1.4
49.61
1.772499


12
1927.614
(d12)











13
∞
2  
Aperture Stop S












14
188.6747
3.4
60.09
1.639999


15
−72.245
0.2


16
73.7218
6  
81.61
1.496999


17
−38.1983
1.4
34.96
1.800999


18
−154.661
0.2


19
32.255
4.2
52.42
1.517417


20
143.854
7.9


21
333.5741
1.3
23.78
1.84666


22
54.3293
4.1
70.24
1.48749


23
−89.5707
10.2 


24
256.9205
3.6
25.43
1.805181


25
−35.5686
1.2
39.59
1.804398


26
35.5686
3.4











27
∞
3.1
Fixed Stop S2












28
47.0802
4  
34.47
1.639799


29
−96.8946
2.4


30
−23.3234
1.2
49.61
1.772499


31
−42.5579
(B.f.)














Wide-angle end
Intermediate
Telephoto end











[Variable Distances]


(Infinity)












f
71.39993
134.99982
294.00047



D0
∞
∞
∞



d2
13.43865
13.43865
13.43865



d5
2.49989
31.01849
43.01129



d12
28.21141
18.59271
2.50011



B.f.
53.40008
57.30852
87.10064



R
∞
∞
∞







(Closest Shooting Distance)












M
−0.05775
−0.11125
−0.24755



D0
1313.9000
1291.0916
1265.3993



d2
2.36289
2.15893
1.91994



d5
13.57565
42.29821
54.53000



d12
28.21141
18.59271
2.50011



B.f.
53.40008
57.30852
87.10064



R
1500.0000
1500.0000
1500.0000











[Values for Conditional Expressions]












(1) f1/fw = 1.563



(2) f2/fw = −0.368



(3) f1A/f1B = 2.051



(4) DAB/fw = 0.188



(5) f3/fw = 0.525



(8) ν1A = 64.14



(9) ν1BP − ν1BN = 55.31










FIGS. 14A and 14B show various aberrations of the zoom lens system according to Example 4 of the first embodiment in a wide-angle end state upon focusing at infinity, and at a closest shooting distance (1500 mm), respectively. FIGS. 15A and 15B show various aberrations of the zoom lens system according to Example 4 of the first embodiment in an intermediate focal length state upon focusing at infinity, and at a closest shooting distance, respectively. FIGS. 16A and 16B show various aberrations of the zoom lens system according to Example 4 of the first embodiment in a telephoto end state upon focusing at infinity, and at a closest shooting distance, respectively.
As is apparent from respective graphs, the zoom lens system according to Example 4 of the first embodiment shows superb optical performance correcting various aberrations.
Second Embodiment
A zoom lens system according to a second embodiment of the present invention is explained below.
The zoom lens system with a vibration reduction mechanism according to the second embodiment of the present invention is composed of, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having negative refractive power. When the state of lens group positions varies from a wide-angle end state to a telephoto end state, a distance between the first lens group and the second lens group increases, a distance between the second lens group and the third lens group decreases, and a distance between the third lens group and fourth lens group varies. The construction is effective for shortening the total lens length.
The fourth lens group is composed of, in order from the object, a 41 lens group, a 42 lens group having negative refractive power, and a 43 lens group. At least one of the 41 lens group and the 43 lens group has positive refractive power. By moving only the 42 lens group perpendicular to the optical axis, image blur on an image plane caused by a camera shake can be reduced.
With constructing the fourth lens group having negative refractive power, the effective diameter of the fourth lens group can be small relative to those of the first lens group through the third lens group. Moreover, by constructing power arrangement of the fourth lens group with positive-negative-positive, positive-negative-negative, or negative-negative-positive, the effective diameter of the 42 lens group, which is the vibration reduction lens group, can be small. Accordingly, the vibration reduction mechanism can be compact, so that it is effective for the zoom lens system as a whole to be compact. By constructing in this manner, degradation of optical performance caused by moving the 42 lens group perpendicular to the optical axis can be reduced.
In the zoom lens system according to the second embodiment of the present invention, the following conditional expression (10) is preferably satisfied:

0.10<f42/f4<0.90  (10)

where f4 denotes the focal length of the fourth lens group, and f42 denotes the focal length of the 42 lens group.

Conditional expression (10) defines an appropriate range of the focal length of the 42 lens group suitable for vibration reduction. When the ratio f42/f4 is equal to or exceeds the upper limit of conditional expression (10), negative refractive power of the 42 lens group becomes weak, so that an amount of decentering of the 42 lens required for vibration reduction becomes large. Accordingly, the vibration reduction mechanism becomes large, so that it becomes difficult to suppress the whole dimension of the zoom lens system to be compact. On the other hand, when the ratio f42/f4 is equal to or falls below the lower limit of conditional expression (10), negative refractive power of the 42 lens group becomes large. Accordingly, production of various aberrations in the 42 lens group becomes large, so that production of decentering aberration upon moving the 42 lens group for vibration reduction becomes large.
In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (10) to 0.25 and the upper limit to 0.70.
In the zoom lens system according to the second embodiment of the present invention, the following conditional expressions (11) and (12) are preferably satisfied:

−2.10<f4/fw<−0.70  (11)

−2.10<(1/f41+1/f43)·f4<−0.40  (12)

where fw denotes the focal length of the zoom lens system in the wide-angle end state, f41 denotes the focal length of the 41 lens group, and f43 notes the focal length of the 43 lens group.

Conditional expression (11) defines an appropriate range of the focal length of the fourth lens group suitable for miniaturizing the total length of the zoom lens system and the effective diameter of the fourth lens group. When the ratio f4/fw is equal to or exceeds the upper limit of conditional expression (11), negative refractive power of the fourth lens group becomes excessively large, so that it becomes difficult to satisfactorily correct aberrations. On the other hand, when the ratio f4/fw is equal to or falls below the lower limit of conditional expression (11), negative refractive power of the fourth lens group becomes small, so that it becomes difficult to miniaturize the total length of the zoom lens system and the effective diameter of the fourth lens group.
In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (11) to −2.00 and the upper limit to −0.90.
Conditional expression (12) defines an appropriate range of the summation of refractive power of the 41 lens group and that of the 43 lens group suitable for miniaturizing the effective diameter of the 42 lens group. When the value (1/f41+1/f43)·f4 is equal to or falls below the lower limit of conditional expression (12), the summation of refractive power of the 41 lens group and that of the 43 lens group becomes large, so that negative refractive power of the 42 lens group has to be large in order to obtain negative refractive power of the fourth lens group as a whole. As a result, production of various aberrations in the 42 lens group becomes large, so that production of decentering aberration caused by moving the 42 lens group for vibration reduction becomes large. On the other hand, when the value (1/f41+1/f43)·f4 is equal to or exceeds the upper limit of conditional expression (12), the summation of refractive power of the 41 lens group and that of the 43 lens group becomes small, so that the effect of converging the light flux becomes weak. As a result, miniaturizing the effective diameter of the 42 lens group becomes insufficient.
In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (12) to −2.00 and the upper limit to −0.50.
Moreover, the zoom lens system is preferably constructed such that when the state of lens group positions varies from the wide-angle end state to the telephoto end state, the first lens group, the third lens group, and the fourth lens group are moved to the object side. With this construction, the total lens length of the zoom lens system in the wide-angle end state can be compact.
Furthermore, it is preferable that the 41 lens group includes at least one positive lens element, the 42 lens group includes at least one positive lens element and at least one negative lens element, and the 43 lens group includes at least one positive lens element. With this construction, decentering aberration upon vibration reduction can be corrected well.
Furthermore, in the zoom lens system according to the second embodiment of the present invention, the 41 lens group includes, in order from the object, a negative lens having a concave surface facing to the object, a positive lens having a convex surface facing to the object, and the following conditional expression (13) is preferably satisfied:

0.20<n41N−n41P  (13)

where n41N denotes refractive index of the negative lens in the 41 lens group at d-line (λ=578.6 nm), and n41P denotes refractive index of the positive lens in the 41 lens group at d-line.

Conditional expression (13) is for satisfactorily correcting decentering aberration upon vibration reduction. When the value n41N−n41P is equal to or falls below the lower limit of conditional expression (13), it becomes difficult to correct decentering aberration upon vibration reduction. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (13) to 0.25.
In the zoom lens system according to the second embodiment of the present invention, the 42 lens group includes, in order from the object, a positive lens having a convex surface facing to the image, and a double concave negative lens, and the following conditional expression (14) is preferably satisfied:

10.0<ν42N−ν42P  (14)

where ν42N denotes Abbe number of the double concave negative lens in the 42 lens group at d-line (λ=578.6 nm), and ν42P denotes Abbe number of the positive lens in the 42 lens group at d-line.

Conditional expression (14) is for satisfactorily correcting decentering aberrations upon vibration reduction. When the value ν42N−ν42P is equal to or falls below the lower limit of conditional expression (14), it becomes difficult to correct lateral chromatic aberration produced by decentering upon vibration reduction. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (14) to 12.0.
In the zoom lens system according to the second embodiment of the present invention, it is preferable that the zoom lens system consists only of the first lens group, the second lens group, the third lens group, and the fourth lens group. By arranging no lens group with refractive power to the image side of the fourth lens group, the zoom lens system can be simple.
In the zoom lens system according to the second embodiment of the present invention, it is preferable that a fifth lens group having positive refractive power is arranged to the image side of the fourth lens group. With this construction, the degree of freedom for correcting aberration increases, so that various aberrations can be corrected easily.
Moreover, it is preferable that the first lens group as a whole is moved to the object upon focusing from infinity to a close-range object.
Furthermore, it is preferable that the second lens group as a whole is moved to the object upon focusing from infinity to a close-range object, and the following conditional expression (15) is preferably satisfied:

−0.98<M2t<−0.8  (15)

where M2t denotes magnification of the second lens group in the telephoto end state.

When the value M2t is equal to or falls below the lower limit of conditional expression (15), the magnification becomes nearly to −1, so that focusing cannot be carried out. On the other hand, when the value M2t is equal to or exceeds the upper limit of conditional expression (15), it becomes difficult to obtain zoom ratio of about four. In order to further secure the effect of the present invention, it is desirable to set the upper limit of conditional expression (15) to −0.90.
In the zoom lens system according to the second embodiment of the present invention, it is preferable that the first lens group is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power, and focusing from infinity to a close-range object is carried out by moving only the 1B lens group to the object.
Each example of the second embodiment is explained below with reference to accompanying drawings.
EXAMPLE 5
FIG. 17 is a diagram showing a sectional view of a zoom lens system according to Example 5 of the second embodiment of the present invention together with a trajectory of each lens group upon zooming.
In FIG. 17, a zoom lens system with a vibration reduction mechanism according to Example 5 is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, and a fourth lens group G4 having negative refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1, the third lens group G3, and the fourth lens group G4 move to the object and the second lens group G2 moves once to an image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, a distance between the second lens group G2 and the third lens group G3 decreases, and a distance between the third lens group G3 and the fourth lens group G4 increases.
The first lens group G1 is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens, and a positive meniscus lens having a convex surface facing to the object.
The second lens group G2 is composed of, in order from the object, a cemented lens constructed by a positive meniscus lens having a concave surface facing to the object cemented with a double concave negative lens, and a double concave negative lens.
The third lens group G3 is composed of, in order from the object, a double convex positive lens, a cemented lens constructed by a double convex positive lens cemented with a negative meniscus lens having a concave surface facing to the object, and a positive meniscus lens having a convex surface facing to the object.
An aperture stop S is arranged between a double convex positive lens and a cemented lens in the third lens group G3 and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).
The fourth lens group G4 is composed of, in order from the object, a 41 lens group G41 having negative refractive power, a 42 lens group G42 having negative refractive power, and a 43 lens group G43 having positive refractive power. The 41 lens group G41 is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens L41 having a convex surface facing to the object cemented with a positive meniscus lens L42 having a convex surface facing to the object. The 42 lens group G42 is composed of, in order from the object, a positive meniscus lens L43 having a concave surface facing to the object, and a double concave negative lens L44. The 43 lens group G43 is composed of, in order from the object, a double convex positive lens L45, and a positive meniscus lens L46 having convex surface facing to the object.
Upon detecting a camera shake, vibration reduction on the image plane I is carried out by moving only the 42 lens group G42 perpendicular to the optical axis.
Focusing from infinity to a close-range object is carried out by moving the first lens group G1 to the object.
In order to correct an image movement corresponding to a rotational angle of θ by a lens system having the focal length of f, and vibration reduction coefficient (the ratio of the moving amount of the image to the moving amount of the vibration reduction lens group upon carrying out vibration reduction) of K, the vibration reduction lens group may be moved by the amount of (f·tan θ)/K perpendicular to the optical axis. This relation is the same in the following examples and duplicated explanation is omitted.
In the wide-angle end state (W) of Example 5 of the second embodiment, vibration reduction coefficient K is 1.206, and the focal length f is 71.50 (mm), so that the image rotation of 0.30° can be corrected by moving the 42 lens group G42 by the amount of 0.311 (mm). In the telephoto end state (T), vibration reduction coefficient K is 1.800, and the focal length f is 294.00 (mm), so that the image rotation of 0.15° can be corrected by moving the 42 lens group G42 by the amount of 0.428 (mm).
Various values associated with Example 5 of the second embodiment of the present invention is listed in Table 5.
In [Moving Amount upon Focusing], δ1 denotes a moving amount of the first lens group G1 to the object side focusing at the shooting distance of 1500 (mm).







TABLE 5







[Specifications]















f =
71.50
134.90
294.00



FNO =
4.43
4.78
5.83



2ω =
34.69°
17.82°
8.25°











[Lens Data]












r
d
ν
n





 1
106.9922
1.4000
30.13
1.698947


 2
63.9533
8.5690
81.54
1.496999


 3
−244.9710
0.2000


 4
126.9321
2.8438
53.20
1.693501


 5
216.9031
(d5)


 6
−811.4085
3.2995
23.78
1.846660


 7
−45.9839
1.0000
60.08
1.639999


 8
53.9629
3.6848


 9
−41.3222
1.0000
46.57
1.804000


10
403.6997
(d10)


11
117.0360
3.4927
46.57
1.804000


12
−100.5857
1.5000











13
∞
1.0480
Aperture Stop S












14
52.7514
5.2513
81.54
1.496999


15
−62.0004
1.0000
34.97
1.800999


16
−445.4607
0.2000


17
37.5205
2.9883
81.54
1.496999


18
74.7018
(d18)


19
52.6572
1.4000
23.78
1.846660


20
16.3065
4.5499
45.78
1.548141


21
76.4617
12.6826 


22
−126.2398
3.9806
28.46
1.728250


23
−20.5284
0.2000


24
−20.6563
1.4000
46.57
1.804000


25
46.6744
4.6040


26
2036.2018
2.3561
29.23
1.721507


27
−113.7498
0.2000


28
47.0423
3.6545
34.97
1.800999


29
343.9390
(B.f.)














Wide-angle end
Intermediate
Telephoto end











[Variable Distances]












f
71.50000
134.90000
294.00000



d5
1.55195
36.01475
55.38418



d10
34.15302
21.90257
1.00000



d18
18.78991
19.40071
22.11070



B.f.
42.99999
49.92314
69.00000







[Moving Amount upon Focusing]












f
71.500
134.900
294.000



δ1
14.446
14.822
15.090











[Values for Conditional Expressions]












(10) f42/f4 = 0.356



(11) f4/fw = −1.483



(12) (1/f41 + 1/f43) · f4 = −1.309



(13) n41N − n41P = 0.298



(14) ν42N − ν42P = 28.11



(15) M2t = —










FIGS. 18A and 18B show various aberrations of the zoom lens system according to Example 5 of the second embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively. FIG. 19 shows various aberrations of the zoom lens system according to Example 5 of the second embodiment in an intermediate focal length state upon focusing at infinity. FIGS. 20A and 20B show various aberrations of the zoom lens system according to Example 5 of the first embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.
As is apparent from respective graphs, the zoom lens system according to Example 5 of the second embodiment shows superb optical performance correcting various aberrations.
EXAMPLE 6
FIG. 21 is a diagram showing a sectional view of a zoom lens system according to Example 6 of the second embodiment of the present invention together with a trajectory of each lens group upon zooming.
In FIG. 21, a zoom lens system with a vibration reduction mechanism according to Example 6 is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, and a fourth lens group G4 having negative refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1, the third lens group G3, and the fourth lens group G4 move to the object and the second lens group G2 moves once to an image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, a distance between the second lens group G2 and the third lens group G3 decreases, and a distance between the third lens group G3 and the fourth lens group G4 varies.
The first lens group G1 is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens, and a positive meniscus lens having a convex surface facing to the object.
The second lens group G2 is composed of, in order from the object, a double concave negative lens, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens, and a negative meniscus lens having a concave surface facing to the object.
The third lens group G3 is composed of, in order from the object, a double convex positive lens, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens, and a positive meniscus lens having a convex surface facing to the object.
An aperture stop S is arranged to the object side of the third lens group G3 and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).
The fourth lens group G4 is composed of, in order from the object, a 41 lens group G41 having positive refractive power, a 42 lens group G42 having negative refractive power, and a 43 lens group G43 having positive refractive power. The 41 lens group G41 is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens L41 having a convex surface facing to the object cemented with a double convex positive lens L42. The 42 lens group G42 is composed of, in order from the object, a double convex positive lens L43, and a double concave negative lens L44. The 43 lens group G43 is composed of, in order from the object, a double convex positive lens L45, and a negative meniscus lens L46 having concave surface facing to the object.
Upon detecting a camera shake, vibration reduction on the image plane I is carried out by moving only the 42 lens group G42 perpendicular to the optical axis.
Focusing from infinity to a close-range object is carried out by moving the second lens group G2 to the object.
In the wide-angle end state (W) of Example 6 of the second embodiment, vibration reduction coefficient K is 1.054, and the focal length f is 71.40 (mm), so that the image rotation of 0.30° can be corrected by moving the 42 lens group G42 by the amount of 0.355 (mm). In the telephoto end state (T), vibration reduction coefficient K is 1.800, and the focal length f is 294.00 (mm), so that the image rotation of 0.15° can be corrected by moving the 42 lens group G42 by the amount of 0.428 (mm).
Various values associated with Example 6 of the second embodiment of the present invention is listed in Table 6.
In [Moving Amount upon Focusing], δ2 denotes a moving amount of the second lens group G2 to the object side focusing at the shooting distance of 1500 (mm).







TABLE 6







[Specifications]















f =
71.40
134.90
294.00



FNO =
4.03
4.61
5.83



2ω =
34.73°
17.96°
8.29°











[Lens Data]












r
d
ν
n





 1
110.3430
1.8000
29.23
1.721507


 2
69.3904
7.9665
81.54
1.496999


 3
−294.8326
0.2000


 4
122.8189
2.6850
58.55
1.651597


 5
181.6203
(d5)


 6
−3611.5709
1.4000
47.82
1.756998


 7
49.7266
0.4871


 8
57.7644
5.3831
23.78
1.846660


 9
−42.0999
1.4000
36.26
1.620041


10
53.1079
4.0773


11
−38.0886
1.4000
34.97
1.800999


12
−502.7476
(d12)











13
∞
1.0000
Aperture Stop S












14
97.5978
3.6622
58.55
1.651597


15
−81.8300
0.2000


16
48.0953
4.9666
81.54
1.496999


17
−62.0949
1.4000
34.97
1.800999


18
268.7785
0.2000


19
38.8902
3.2836
55.53
1.696797


20
54.2852
(d20)


21
78.0173
2.0000
23.78
1.846660


22
24.6186
3.7355
64.14
1.516330


23
−185.3460
3.0000


24
176.2975
4.6442
27.79
1.740769


25
−25.6263
0.2072


26
−25.4689
1.4000
40.92
1.806098


27
35.9916
3.3747


28
32.3977
4.1609
30.13
1.698947


29
−160.3892
4.5174


30
−28.3572
1.4000
61.13
1.589130


31
−96.5409
(B.f.)














Wide-angle end
Intermediate
Telephoto end











[Variable Distances]












f
71.40045
134.89998
293.99991



d5
4.92513
37.53918
59.35524



d12
35.77592
21.59232
1.00000



d20
24.34764
24.24866
24.69346



B.f.
40.00576
51.49527
75.00890







[Moving Amount upon Focusing]












f
71.400
134.900
294.000



δ2
2.762
6.788
17.131











[Values for Conditional Expressions]












(10) f42/f4 = 0.366



(11) f4/fw = −1.891



(12) (1/f41 + 1/f43) · f4 = −1.866



(13) n41N − n41P = 0.330



(14) ν42N − ν42P = 13.13



(15) M2t = −0.950










FIGS. 22A and 22B show various aberrations of the zoom lens system according to Example 6 of the second embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively. FIG. 23 shows various aberrations of the zoom lens system according to Example 6 of the second embodiment in an intermediate focal length state upon focusing at infinity. FIGS. 24A and 24B show various aberrations of the zoom lens system according to Example 6 of the second embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.
As is apparent from respective graphs, the zoom lens system according to Example 6 of the second embodiment shows superb optical performance correcting various aberrations.
EXAMPLE 7
FIG. 25 is a diagram showing a sectional view of a zoom lens system according to Example 7 of the second embodiment of the present invention together with a trajectory of each lens group upon zooming.
In FIG. 25, a zoom lens system with a vibration reduction mechanism according to Example 7 is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, and a fourth lens group G4 having negative refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1, the third lens group G3, and the fourth lens group G4 move to the object and the second lens group G2 moves once to an image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, a distance between the second lens group G2 and the third lens group G3 decreases, and a distance between the third lens group G3 and the fourth lens group G4 increases.
The first lens group G1 is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens, and a positive meniscus lens having a convex surface facing to the object.
The second lens group G2 is composed of, in order from the object, a negative meniscus lens having a convex surface facing to the object, a cemented lens constructed by a double concave negative lens cemented with a double convex positive lens, and a negative meniscus lens having a concave surface facing to the object.
The third lens group G3 is composed of, in order from the object, a double convex positive lens, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens, and a positive meniscus lens having a convex surface facing to the object.
An aperture stop S is arranged to the object side of the third lens group G3 and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).
The fourth lens group G4 is composed of, in order from the object, a 41 lens group G41 having negative refractive power, a 42 lens group G42 having negative refractive power, and a 43 lens group G43 having positive refractive power. The 41 lens group G41 is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens L41 having a convex surface facing to the object cemented with a double convex positive lens L42. The 42 lens group G42 is composed of, in order from the object, a double convex positive lens L43, and a double concave negative lens L44. The 43 lens group G43 is composed of, in order from the object, a double convex positive lens L45, and a negative meniscus lens L46 having concave surface facing to the object.
Upon detecting a camera shake, vibration reduction on the image plane I is carried out by moving only the 42 lens group G42 perpendicular to the optical axis.
Focusing from infinity to a close-range object is carried out by moving the second lens group G2 to the object.
In the wide-angle end state (W) of Example 7 of the second embodiment, vibration reduction coefficient K is 1.059, and the focal length f is 71.40 (mm), so that the image rotation of 0.30° can be corrected by moving the 42 lens group G42 by the amount of 0.353 (mm). In the telephoto end state (T), vibration reduction coefficient K is 1.800, and the focal length f is 294.00 (mm), so that the image rotation of 0.15° can be corrected by moving the 42 lens group G42 by the amount of 0.428 (mm).
Various values associated with Example 7 of the second embodiment of the present invention is listed in Table 7.
In [Moving Amount upon Focusing], δ2 denotes a moving amount of the second lens group G2 to the object side focusing at the shooting distance of 1500 (mm).







TABLE 7







[Specifications]















f =
71.40
134.90
294.00



FNO =
3.99
4.52
5.75



2ω =
34.74°
17.97°
8.30°











[Lens Data]












r
d
ν
n





 1
92.3146
1.8000
34.97
1.800999


 2
60.1527
9.0323
81.54
1.496999


 3
−249.0431
0.2000


 4
80.8726
2.7760
70.23
1.487490


 5
103.7057
(d5)


 6
67.7254
1.4000
28.46
1.728250


 7
34.1420
4.4733


 8
−56.4538
1.4000
60.29
1.620411


 9
40.9332
3.9004
23.78
1.846660


10
−339.3969
1.7837


11
−50.6122
1.4000
51.47
1.733997


12
−623.8156
(d12)











13
∞
1.0000
Aperture Stop S












14
102.7196
3.8033
60.08
1.639999


15
−83.7403
0.2000


16
51.7820
5.2043
81.54
1.496999


17
−63.2478
1.4000
34.97
1.800999


18
327.7985
0.2000


19
41.6150
3.5656
46.57
1.804000


20
67.4980
(d20)


21
65.4401
1.4000
23.78
1.846660


22
20.9137
3.9266
70.23
1.487490


23
−450.5603
4.1017


24
167.1060
3.8379
28.46
1.728250


25
−25.2899
0.2000


26
−25.2945
1.4000
40.92
1.806098


27
36.0693
4.0874


28
32.4764
4.5076
30.13
1.698947


29
−134.5935
4.2066


30
−31.0368
1.4000
60.08
1.639999


31
−108.8255
(B.f.)














Wide-angle end
Intermediate
Telephoto end











[Variable Distances]












f
71.40000
134.90000
294.00000



d5
4.03725
36.57205
57.18679



d12
34.46408
20.96534
1.00000



d20
23.89184
23.91724
24.20639



B.f.
40.00000
50.65460
74.99996







[Moving Amount upon Focusing]












f
71.400
134.900
294.000



δ2
2.539
6.520
16.557











[Values for Conditional Expressions]












(10) f42/f4 = 0.505



(11) f4/fw = −1.358



(12) (1/f41 + 1/f43) · f4 = −1.079



(13) n41N − n41P = 0.359



(14) ν42N − ν42P = 12.46



(15) M2t = −0.961










FIGS. 26A and 26B show various aberrations of the zoom lens system according to Example 7 of the second embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively. FIG. 27 shows various aberrations of the zoom lens system according to Example 7 of the second embodiment in an intermediate focal length state upon focusing at infinity. FIGS. 28A and 28B show various aberrations of the zoom lens system according to Example 7 of the second embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.
As is apparent from respective graphs, the zoom lens system according to Example 7 of the second embodiment shows superb optical performance correcting various aberrations.
EXAMPLE 8
FIG. 29 is a diagram showing a sectional view of a zoom lens system according to Example 8 of the second embodiment of the present invention together with a trajectory of each lens group upon zooming.
In FIG. 29, a zoom lens system with a vibration reduction mechanism according to Example 8 is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, and a fourth lens group G4 having negative refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1, the third lens group G3, and the fourth lens group G4 move to the object and the second lens group G2 moves once to an image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, a distance between the second lens group G2 and the third lens group G3 decreases, and a distance between the third lens group G3 and the fourth lens group G4 varies.
The first lens group G1 is composed of, in order from the object, a 1A lens group G1A having positive refractive power and a 1B lens group G1B having positive refractive power. The 1A lens group G1A is composed of a double convex positive lens. The 1B lens group G1B is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens.
The second lens group G2 is composed of, in order from the object, a double concave negative lens, a cemented lens constructed by a double concave negative lens cemented with a double convex positive lens, and a double concave negative lens.
The third lens group G3 is composed of, in order from the object, a double convex positive lens, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens, and a positive meniscus lens having a convex surface facing to the object.
An aperture stop S is arranged to the object side of the third lens group G3 and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).
The fourth lens group G4 is composed of, in order from the object, a 41 lens group G41 having positive refractive power, a 42 lens group G42 having negative refractive power, and a 43 lens group G43 having positive refractive power. The 41 lens group G41 is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens L41 having a convex surface facing to the object cemented with a double convex positive lens L42. The 42 lens group G42 is composed of, in order from the object, a cemented lens constructed by a double convex positive lens L43 cemented with a double concave negative lens L44. The 43 lens group G43 is composed of, in order from the object, a double convex positive lens L45, and a negative meniscus lens L46 having concave surface facing to the object.
Upon detecting a camera shake, vibration reduction on the image plane I is carried out by moving only the 42 lens group G42 perpendicular to the optical axis.
Focusing from infinity to a close-range object is carried out by moving the 1B lens group G1B to the object.
In the wide-angle end state (W) of Example 8 of the second embodiment, vibration reduction coefficient K is 1.395, and the focal length f is 71.40 (mm), so that the image rotation of 0.30° can be corrected by moving the 42 lens group G42 by the amount of 0.268 (mm). In the telephoto end state (T), vibration reduction coefficient K is 2.261, and the focal length f is 294.00 (mm), so that the image rotation of 0.15° can be corrected by moving the 42 lens group G42 by the amount of 0.340 (mm).
Various values associated with Example 8 of the second embodiment of the present invention is listed in Table 8.
In [Moving Amount upon Focusing], δ1B denotes a moving amount of the 1B lens group G1B to the object side focusing at the shooting distance of 1500 (mm).







TABLE 8







[Specifications]















f =
71.40
135.20
294.00



FNO =
3.98
4.42
5.83



2ω =
34.26°
17.57°
8.19°











[Lens Data]












r
d
ν
n





 1
401.1292
3.4320
64.14
1.516330


 2
−401.1292
(d2)


 3
73.7120
1.8000
28.46
1.728250


 4
49.4588
9.2239
81.54
1.496999


 5
−634.7712
(d5)


 6
−569.6277
1.4000
46.57
1.804000


 7
65.8130
2.9470


 8
−66.3802
1.4000
49.34
1.743198


 9
37.4535
4.4348
23.78
1.846660


10
−157.1502
1.2424


11
−56.4033
1.4000
46.57
1.804000


12
457.6562
(d12)











13
∞
1.0000
Aperture Stop S












14
174.8883
4.0762
60.08
1.639999


15
−54.3627
0.2000

1.000000


16
52.6528
6.0766
81.54
1.496999


17
−40.7675
1.4000
34.97
1.800999


18
1440.7843
0.2000


19
33.5705
3.5534
61.13
1.589130


20
93.9894
(d20)


21
479.6438
1.4000
23.78
1.846660


22
43.7293
4.5629
59.84
1.522494


23
−51.1261
3.0000


24
1129.8061
3.6174
29.23
1.721507


25
−22.8122
1.4000
47.93
1.717004


26
29.6916
4.4859


27
35.9110
3.4607
33.79
1.647689


28
−167.9338
4.3753


29
−22.4279
1.4000
46.57
1.804000


30
−45.1019
(B.f.)














Wide-angle end
Intermediate
Telephoto end











[Variable Distances]












f
71.39999
135.19963
294.00017



d2
13.96876
13.96876
13.96876



d5
1.50000
30.16863
45.04078



d12
26.95417
16.63929
1.00000



d20
15.26706
15.23225
16.01169



B.f.
45.82163
54.27048
80.82164







[Moving Amount upon Focusing]












f
71.400
135.200
294.000



δ1B
12.512
12.783
13.064











[Values for Conditional Expressions]












(10) f42/f4 = 0.579



(11) f4/fw = −1.039



(12) (1/f41 + 1/f43) · f4 = −0.816



(13) n41N − n41P = 0.324



(14) ν42N − ν42P = 18.70



(15) M2t = —










FIGS. 30A and 30B show various aberrations of the zoom lens system according to Example 8 of the second embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively. FIG. 31 shows various aberrations of the zoom lens system according to Example 8 of the second embodiment in an intermediate focal length state upon focusing at infinity. FIGS. 32A and 32B show various aberrations of the zoom lens system according to Example 8 of the second embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.
As is apparent from respective graphs, the zoom lens system according to Example 8 of the second embodiment shows superb optical performance correcting various aberrations.
EXAMPLE 9
FIG. 33 is a diagram showing a sectional view of a zoom lens system according to Example 9 of the second embodiment of the present invention together with a trajectory of each lens group upon zooming.
In FIG. 33, a zoom lens system with a vibration reduction mechanism according to Example 9 is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having positive refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 move to the object and the second lens group G2 moves once to the object and, then, moves to an image I such that a distance between the first lens group G1 and the second lens group G2 increases, a distance between the second lens group G2 and the third lens group G3 decreases, a distance between the third lens group G3 and the fourth lens group G4 increases, and a distance between the fourth lens group G4 and the fifth lens group decreases.
The first lens group G1 is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens, and a positive meniscus lens having a convex surface facing to the object.
The second lens group G2 is composed of, in order from the object, a double concave negative lens, and a cemented lens constructed by a double concave negative lens cemented with a double convex positive lens.
The third lens group G3 is composed of, in order from the object, a plano-convex positive lens having a convex surface facing to the image, a double convex positive lens, a negative meniscus lens having a concave surface facing to the object, and a double convex positive lens.
An aperture stop S is arranged to the object side of the third lens group G3 and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).
The fourth lens group G4 is composed of, in order from the object, a 41 lens group G41 having positive refractive power, a 42 lens group G42 having negative refractive power, and a 43 lens group G43 having negative refractive power. The 41 lens group G41 is composed of a double convex positive lens L41. The 42 lens group G42 is composed of, in order from the object, a double concave negative lens L42, and a positive meniscus lens L43 having a convex surface facing to the object. The 43 lens group G43 is composed of a negative meniscus lens L44 having a concave surface facing to the object.
The fifth lens group G5 is composed of, in order from the object, a negative meniscus lens having a convex surface facing to the object, a double convex positive lens, and a negative meniscus lens having a concave surface facing to the object.
Upon detecting a camera shake, vibration reduction on the image plane I is carried out by moving only the 42 lens group G42 perpendicular to the optical axis.
Focusing from infinity to a close-range object is carried out by moving the second lens group G2 to the object.
In the wide-angle end state (W) of Example 9 of the second embodiment, vibration reduction coefficient K is 1.719, and the focal length f is 69.99 (mm), so that the image rotation of 0.30° can be corrected by moving the 42 lens group G42 by the amount of 0.213 (mm). In the telephoto end state (T), vibration reduction coefficient K is 2.284, and the focal length f is 299.93 (mm), so that the image rotation of 0.15° can be corrected by moving the 42 lens group G42 by the amount of 0.344 (mm).
Various values associated with Example 9 of the second embodiment of the present invention is listed in Table 9.
In [Moving Amount upon Focusing], δ2 denotes a moving amount of the second lens group G2 to the object side focusing at the shooting distance of 1500 (mm).







TABLE 9







[Specifications]















f =
69.99
134.96
299.93



FNO =
4.31
5.28
5.77



2ω =
34.39°
17.94°
8.06°











[Lens Data]












r
d
ν
n





 1
105.7828
1.5000
25.43
1.805180


 2
74.2801
7.7806
81.61
1.497000


 3
−314.2885
0.5000


 4
84.1721
4.0034
81.61
1.497000


 5
192.0413
(d5)


 6
−289.0462
1.5000
49.61
1.772500


 7
37.2942
5.1639


 8
−36.2718
1.5000
53.85
1.713000


 9
42.3070
3.9288
23.78
1.846660


10
−275.6800
(d10)











11
∞
0.5000
Aperture Stop S












12
∞
2.5521
49.61
1.772500


13
−91.7378
0.5000


14
44.2611
6.7347
81.61
1.497000


15
−34.2879
0.6605


16
−32.1236
1.5000
37.17
1.834000


17
−239.8905
0.5000


18
48.9662
4.7058
81.61
1.497000


19
−95.8226
(d19)


20
38.7220
5.1115
81.61
1.497000


21
−81.1156
3.8000


22
−1244.0407
1.5000
46.63
1.816000


23
18.1395
0.5544


24
18.4154
3.9902
34.47
1.639800


25
57.0111
3.8499


26
−24.5068
1.5000
49.32
1.743200


27
−42.2340
(d27)


28
106.2163
1.5000
23.78
1.846660


29
36.1752
3.2036


30
51.9898
4.5496
33.04
1.666800


31
−45.3816
3.9985


32
−24.1064
1.5000
46.63
1.816000


33
−36.1573
(B.f.)














Wide-angle end
Intermediate
Telephoto end











[Variable Distances]












f
69.98593
134.95979
299.92772



d5
7.77097
31.32565
57.66235



d10
25.75941
15.14446
0.50000



d19
3.94280
7.03157
7.76808



d27
10.15139
2.54225
0.50000



B.f.
50.26987
74.11967
85.25814







[Moving Amount upon Focusing]












f
69.986
134.960
299.928



δ2
1.324
2.865
12.223











[Values for Conditional Expressions]












(10) f42/f4 = 0.484



(11) f4/fw = −1.353



(12) (1/f41 + 1/f43) · f4 = −0.608



(13) n41N − n41P = —



(14) ν42N − ν42P = —



(15) M2t = −0.973










FIGS. 34A and 34B show various aberrations of the zoom lens system according to Example 9 of the second embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively. FIG. 35 shows various aberrations of the zoom lens system according to Example 9 of the second embodiment in an intermediate focal length state upon focusing at infinity. FIGS. 36A and 36B show various aberrations of the zoom lens system according to Example 9 of the second embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.
As is apparent from respective graphs, the zoom lens system according to Example 9 of the second embodiment shows superb optical performance correcting various aberrations.
Third Embodiment
A zoom lens system according to a third embodiment of the present invention is explained below.
The zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention is composed of, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power. When the state of lens group positions varies from a wide-angle end state to a telephoto end state, a distance between the first lens group and the second lens group increases, and a distance between the second lens group and the third lens group decreases. The construction is effective for simplifying the construction and shortening the total lens length.
The third lens group G3 is composed of, in order from the object, a 31 lens group having positive refractive power, a 32 lens group having negative refractive power, and a 33 lens group having positive refractive power. Upon detecting a camera shake, vibration reduction is carried out by moving only the 32 lens group perpendicular to the optical axis. By arranging positive refractive power to the 31 lens group and negative refractive power to the 32 lens group, the effective diameter of the 32 lens group can be small relative to those of the first lens group through the 31 lens group. Accordingly, the vibration reduction mechanism can be compact, so that it is effective for the zoom lens system as a whole to be compact. By constructing in this manner, degradation of optical performance caused by moving the 32 lens group perpendicular to the optical axis can be reduced.
In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, the following conditional expressions (16) through (20) are preferably satisfied:

1.40<f1/fw<2.00  (16)

−0.53<f2/fw<−0.32  (17)

0.35<f3/fw<0.65  (18)

−2.00<f32/f3<−0.80  (19)

−0.20<f3/f33<0.50  (20)

where fw denotes the focal length of the zoom lens system in the wide-angle end state, f1 denotes the focal length of the first lens group, f2 denotes the focal length of the second lens group, f3 denotes the focal length of the third lens group, f32 denotes the focal length of the 32 lens group, and f33 denotes the focal length of the 33 lens group.

Conditional expression (16) defines an appropriate range of the focal length of the first lens group. When the ratio f1/fw is equal to or exceeds the upper limit of conditional expression (16), refractive power of the first lens group becomes weak, so that the total lens length of the zoom lens system becomes large. On the other hand, when the ratio f1/fw is equal to or falls below the lower limit of conditional expression (16), refractive power of the first lens group becomes large, so that it becomes difficult to correct spherical aberration and on-axis chromatic aberration. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (16) to 1.50 and the upper limit to 1.90.
Conditional expression (17) defines an appropriate range of the focal length of the second lens group. When the ratio f2/fw is equal to or exceeds the upper limit of conditional expression (17), negative refractive power of the second lens group becomes large, so that it becomes difficult to correct spherical aberration and coma. On the other hand, when the ratio f2/fw is equal to or falls below the lower limit of conditional expression (17), negative refractive power of the second lens group becomes weak, so that it becomes difficult to obtain the zoom ratio of about four. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (17) to −0.50 and the upper limit to −0.35.
Conditional expression (18) defines an appropriate range of the focal length of the third lens group. When the ratio f3/fw is equal to or exceeds the upper limit of conditional expression (18), refractive power of the third lens group becomes weak, so that the total lens length of the zoom lens system becomes large. On the other hand, when the ratio f3/fw is equal to or falls below the lower limit of conditional expression (18), refractive power of the third lens group becomes large, so that it becomes difficult to correct various aberrations as well as spherical aberration. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (18) to 0.40 and the upper limit to 0.60.
Conditional expression (19) defines an appropriate range of the focal length of the 32 lens group. When the ratio f32/f3 is equal to or exceeds the upper limit of conditional expression (19), negative refractive power of the 32 lens group becomes large, so that the ratio of the moving amount of image relative to the moving amount of the 32 lens group upon vibration reduction becomes large. Accordingly, permissible driving error of the 32 lens group upon vibration reduction becomes small, so that it becomes difficult to control the 32 lens group. On the other hand, when the ratio f32/f3 is equal to or falls below the lower limit of conditional expression (19), negative refractive power of the 32 lens group becomes small, so that the ratio of the moving amount of image relative to the moving amount of the 32 lens group upon vibration reduction becomes small. Accordingly, moving amount of the 32 lens group upon vibration reduction becomes large, so that the vibration reduction mechanism becomes large. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (19) to −1.85 and the upper limit to −0.90.
Conditional expression (20) defines an appropriate range of the focal length of the 33 lens group. When the ratio f3/f33 is equal to or exceeds the upper limit of conditional expression (20), positive refractive power of the 33 lens group becomes large, so that the total lens length of the zoom lens system becomes large. On the other hand, when the ratio f3/f33 is equal to or falls below the lower limit of conditional expression (20), negative refractive power of the 33 lens group becomes large, so that it becomes difficult to correct coma and distortion. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (20) to −0.15 and the upper limit to 0.40.
In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, it is preferable that the first lens group and the third lens group move to the object when the state of lens group positions varies from the wide-angle end state to the telephoto end state. By construction like this, the total lens length of the zoom lens system in the wide-angle end state can be short, so that the zoom lens system can be compact.
In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, it is preferable that the 31 lens group includes at least three positive lens elements and at least one negative lens element, the 32 lens group includes at least one positive lens element and at least one negative lens element, and the 33 lens group includes at least one positive lens element and at least one negative lens element. By constructing like this, decentering aberration caused upon vibration reduction can be satisfactorily corrected.
In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, it is preferable that the 31 lens group is composed of, in order from the object, a double convex positive lens, a first cemented lens constructed by a double convex positive lens cemented with a negative lens having a concave surface facing to the object, a positive meniscus lens having a convex surface facing to the object, and a second cemented lens. With this construction, decentering aberration caused upon vibration reduction can be satisfactorily corrected.
In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, the following conditional expressions (21) and (22) are preferably satisfied:

0.20<n31N−n31P  (21)

30.0<ν31P−ν31N  (22)

where n31N denotes refractive index of the negative lens in the first cemented lens at d-line (λ=587.6 nm), n31P denotes refractive index of the double convex positive lens in the first cemented lens at d-line, ν31N denotes Abbe number of the negative lens in the first cemented lens at d-line, and ν31P denotes Abbe number of the double convex positive lens in the first cemented lens at d-line.

Conditional expression (21) defines an appropriate range of the difference in refractive indices between the double convex positive lens and the negative lens in the first cemented lens. When the difference n31N−n31P is equal to or falls below the lower limit of conditional expression (21), it becomes difficult to satisfactorily correct spherical aberration. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (21) to 0.25.
Conditional expression (22) defines an appropriate range of the difference in Abbe numbers between the double convex positive lens and the negative lens in the first cemented lens. When the difference ν31P−ν31N I equal to or falls below the lower limit of conditional expression (22), it becomes difficult to satisfactorily correct lateral chromatic aberration. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (22) to 35.0.
In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, it is preferable that the 32 lens group is composed of, in order from the object, a positive lens having a convex surface facing to the object, and a double concave negative lens. With this construction, decentering aberration caused upon vibration reduction can be satisfactorily corrected.
In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, the following conditional expression (23) is preferably satisfied:

10.0<ν32N−ν32P  (23)

where ν32N denotes Abbe number of the double concave negative lens in the 32 lens group at d-line (λ=587.6 nm), and ν32P denotes Abbe number of the positive lens in the 32 lens group at d-line.

Conditional expression (23) defines an appropriate range of the difference in Abbe numbers between the double concave negative lens and the positive lens in the 32 lens group. When the difference ν32N−ν32P is equal to or falls below the lower limit of conditional expression (23), it becomes difficult to correct lateral chromatic aberration caused by decentering upon vibration reduction. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (23) to 12.0.
In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, it is preferable that the 32 lens group is composed of, in order from the object, a cemented lens constructed by a positive lens having a convex surface facing to the image cemented with a double concave negative lens. With this construction, decentering aberration caused upon vibration reduction can be satisfactorily corrected.
In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, the following conditional expression (24) is preferably satisfied:

−2.00<(r32R+r32F)/(r32R−r32F)<−0.70  (24)

where r32F denotes the radius of curvature of the object side surface of the positive lens in the 32 lens group, r32R denotes the radius of curvature of the image side surface of the double concave negative lens in the 32 lens group.

Conditional expression (24) defines an appropriate range of the shape of the cemented lens in the 32 lens group. When the value (r32R+r32F)/(r32R−r32F) exceeds the upper limit of conditional expression (24) or falls below the lower limit of conditional expression (24), production of decentering aberration caused upon vibration reduction becomes large. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (24) to −1.90 and the upper limit to −0.80.
In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, the following conditional expression (25) is preferably satisfied:

0.40<r32S/f32<0.90  (25)

where r32S denotes the radius of curvature of the cemented surface of the cemented lens in the 32 lens group, and f32 denotes the focal length of the 32 lens group.

Conditional expression (25) defines an appropriate range of the radius of curvature of the cemented surface of the cemented lens in the 32 lens group. When the ratio r32S/f32 exceeds the upper limit of conditional expression (25) or falls below the lower limit of conditional expression (25), production of decentering aberration caused upon vibration reduction becomes large. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (25) to 0.45 and the upper limit to 0.85.
In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, it is preferable that the zoom lens system consists only of a first lens group, a second lens group, and a third lens group. By arranging no lens group with refractive power to the image side of the third lens group, the zoom lens system can be simple.
In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, the first lens group is composed of, in order from the object, it is preferable that a 1A lens group having positive refractive power and a 1B lens group having positive refractive power, and focusing from infinity to a close-range object is carried out by moving only the 1B lens group to the object.
In the zoom lens system with a vibration reduction mechanism according to the third embodiment of the present invention, the following conditional expression (26) is preferably satisfied:

1.70<f1A/f1B<4.00  (26)

where f1A denotes the focal length of the 1A lens group, and f1B denotes the focal length of the 1B lens group.

Conditional expression (26) defines an appropriate range of the ratio of the focal length of the 1A lens group to that of the 1B lens group. When the ratio f1A/f1B is equal to or exceeds the upper limit of conditional expression (26), refractive power of the 1B lens group becomes small, so that variation in various aberrations upon focusing becomes large. On the other hand, when the ratio f1A/f1B is equal to or falls below the lower limit of conditional expression (26), refractive power of the 1A lens group becomes small, so that moving amount of the 1A lens group upon focusing becomes large. Accordingly, the zoom lens system becomes large. In order to further secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (26) to 1.90 and the upper limit to 3.50.
Each example according to the third embodiment of the present invention is explained below with reference to accompanying drawings.
EXAMPLE 10
FIG. 37 is a diagram showing a sectional view of a zoom lens system according to Example 10 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.
In FIG. 37, the zoom lens system with a vibration reduction mechanism is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1 and the third lens group G3 move to the object and the second lens group G2 moves once to the image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, and a distance between the second lens group G2 and the third lens group G3 decreases.
The first lens group G1 is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. The 1A lens group G1A is composed of a double convex positive lens. The 1B lens group G1B is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens.
The second lens group G2 is composed of, in order from the object, a double concave negative lens, a cemented lens constructed by a double concave negative lens cemented with a positive meniscus lens having a convex surface facing to the object, and a double concave negative lens.
The third lens group G3 is composed of, in order from the object, a 31 lens group G31 having positive refractive power, a 32 lens group G32 having negative refractive power, and a 33 lens group G33 having positive refractive power. The 31 lens group G31 is composed of, in order from the object, a double convex positive lens, a first cemented lens constructed by a double convex positive lens cemented with a double concave negative lens, a positive meniscus lens having a convex surface facing to the object, and a second cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens. The 32 lens group G32 is composed of, in order from the object, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens. The 33 lens group G33 is composed of, in order from the object, a double convex positive lens and a negative meniscus lens having a concave surface facing to the object.
An aperture stop S is arranged between the positive meniscus lens and the second cemented lens in the 31 lens group G31, and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).
Upon detecting a camera shake, vibration reduction on the image plane I is carried out by moving only the 32 lens group G32 perpendicular to the optical axis.
Focusing from infinity to a close-range object is carried out by moving the 1B lens group G1B to the object.
In the wide-angle end state (W) of Example 10 of the third embodiment, vibration reduction coefficient K is 1.47, and the focal length f is 71.40 (mm), so that the image rotation of 0.30° can be corrected by moving the 32 lens group G32 by the amount of 0.254 (mm). In the telephoto end state (T), vibration reduction coefficient K is 2.68, and the focal length f is 294.00 (mm), so that the image rotation of 0.15° can be corrected by moving the 32 lens group G32 by the amount of 0.287 (mm).
Various values associated with Example 10 of the third embodiment of the present invention is listed in Table 10.
In [Moving Amount upon Focusing], δ1B denotes a moving amount of the 1B lens group G1B to the object side focusing at the shooting distance of 1500 (mm).







TABLE 10







[Specifications]















f =
71.40
134.90
294.00



FNO =
4.10
4.28
5.79



2ω =
22.50°
11.75°
5.44°











[Lens Data]












r
d
ν
n





1
485.2517
3.3856
64.14
1.516330


2
−485.2517
(d2)


3
74.6948
2.5000
26.52
1.761821


4
50.2473
8.5338
70.23
1.487490


5
−397.6433
(d5)


6
−445.5319
1.4000
49.60
1.772499


7
121.5057
1.7612


8
−139.8007
1.4000
49.60
1.772499


9
31.4033
4.4544
23.78
1.846660


10
195.1690
2.3037


11
−63.0020
1.4000
49.60
1.772499


12
863.7974
(d12)


13
209.2396
3.4957
51.47
1.733997


14
−78.5539
0.2000


15
53.3010
6.1013
81.54
1.496999


16
−47.6905
1.4000
34.97
1.800999


17
743.9564
0.2000


18
31.2964
4.0974
60.64
1.603112


19
86.8951
12.4001 











20
∞
1.0000
Aperture Stop S












21
67.3937
1.3000
23.78
1.846660


22
26.7354
5.4922
70.23
1.487490


23
−88.9999
5.5185


24
1974.4906
3.7052
26.52
1.761821


25
−26.6771
1.2000
49.60
1.772499


26
26.6771
3.2607


27
29.4872
3.9533
34.47
1.639799


28
−93.8522
2.2384


29
−21.9460
1.2000
49.60
1.772499


30
−59.2566
(B.f.)














Wide-angle end
Intermediate
Telephoto end











[Variable Distances]


(Infinity)












f
71.40000
134.90024
294.00000



d2
16.01875
16.01875
16.01875



d5
2.00000
31.41839
42.84564



d12
32.45495
19.43707
2.00000



B.f.
40.62478
47.41150
80.62502







[Moving Amount upon Focusing]












f
71.40000
134.90024
294.00000



δ1B
13.70747
13.96627
14.28274











[Values for Conditional Expressions]












(16) f1/fw = 1.773



(17) f2/fw = −0.463



(18) f3/fw = 0.500



(19) f32/f3 = −0.968



(20) f3/f33 = 0.306



(21) n31N − n31P = 0.304



(22) ν31P − ν31N = 46.57



(23) ν32N − ν32P = 23.08



(24) (r32R + r32F)/(r32R − r32F) = −1.027



(25) r32S/f32 = 0.772



(26) f1A/f1B = 2.819










FIGS. 38A and 38B show various aberrations of the zoom lens system according to Example 10 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively. FIG. 39 shows various aberrations of the zoom lens system according to Example 10 of the third embodiment in an intermediate focal length state upon focusing at infinity. FIGS. 40A and 40B show various aberrations of the zoom lens system according to Example 10 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.
As is apparent from respective graphs, the zoom lens system according to Example 10 of the third embodiment shows superb optical performance correcting various aberrations.
EXAMPLE 11
FIG. 41 is a diagram showing a sectional view of a zoom lens system according to Example 11 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.
In FIG. 41, the zoom lens system with a vibration reduction mechanism is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1 and the third lens group G3 move to the object and the second lens group G2 moves once to the image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, and a distance between the second lens group G2 and the third lens group G3 decreases.
The first lens group G1 is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. The 1A lens group G1A is composed of a double convex positive lens. The 1B lens group G1B is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens.
The second lens group G2 is composed of, in order from the object, a double concave negative lens, a cemented lens constructed by a double concave negative lens cemented with a positive meniscus lens having a convex surface facing to the object, and a double concave negative lens.
The third lens group G3 is composed of, in order from the object, a 31 lens group G31 having positive refractive power, a 32 lens group G32 having negative refractive power, and a 33 lens group G33 having positive refractive power. The 31 lens group G31 is composed of, in order from the object, a double convex positive lens, a first cemented lens constructed by a double convex positive lens cemented with a double concave negative lens, a positive meniscus lens having a convex surface facing to the object, and a second cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens. The 32 lens group G32 is composed of, in order from the object, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens. The 33 lens group G33 is composed of, in order from the object, a double convex positive lens and a negative meniscus lens having a concave surface facing to the object.
An aperture stop S is arranged between the positive meniscus lens and the second cemented lens in the 31 lens group G31, and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).
Upon detecting a camera shake, vibration reduction on the image plane I is carried out by moving only the 32 lens group G32 perpendicular to the optical axis.
Focusing from infinity to a close-range object is carried out by moving the 1B lens group G1B to the object.
In the wide-angle end state (W) of Example 11 of the third embodiment, vibration reduction coefficient K is 1.02, and the focal length f is 71.40 (mm), so that the image rotation of 0.30° can be corrected by moving the 32 lens group G32 by the amount of 0.367 (mm). In the telephoto end state (T), vibration reduction coefficient K is 1.70, and the focal length f is 294.00 (mm), so that the image rotation of 0.15° can be corrected by moving the 32 lens group G32 by the amount of 0.453 (mm).
Various values associated with Example 11 of the third embodiment of the present invention is listed in Table 11.







TABLE 11







[Specifications]















f =
71.40
134.90
294.00



FNO =
4.10
4.28
5.79



2ω =
22.51°
11.74°
5.43°











[Lens Data]












r
d
ν
n





 1
494.1160
3.3593
64.14
1.516330


 2
−494.1160
(d2)


 3
74.6142
2.5000
26.52
1.761821


 4
50.2492
8.5170
70.23
1.487490


 5
−409.6962
(d5)


 6
−572.2854
1.4000
49.60
1.772499


 7
118.2999
1.5934


 8
−150.1597
1.4000
49.60
1.772499


 9
28.9590
4.2332
23.78
1.846660


10
159.4762
2.3641


11
−56.2166
1.4000
49.60
1.772499


12
737.8222
(d12)


13
255.4424
3.4925
51.47
1.733997


14
−65.2491
0.2000


15
55.4617
5.8677
81.54
1.496999


16
−42.2335
1.4000
34.97
1.800999


17
391.1593
0.2000


18
29.8308
4.2307
60.64
1.603112


19
109.3078
9.9568











20
∞
1.0000
Aperture Stop S












21
111.2314
1.3000
23.78
1.846660


22
34.2913
3.8688
70.23
1.487490


23
−116.1639
3.0066


24
131.0022
2.6204
25.42
1.805181


25
−42.8081
1.2000
39.58
1.804398


26
35.6448
6.4837


27
44.2831
3.9886
31.07
1.688931


28
−53.8284
2.7522


29
−23.7792
1.2000
49.60
1.772499


30
−254.9277
(B.f.)














Wide-angle end
Intermediate
Telephoto end











[Variable Distances]


(Infinity)












f
71.40000
134.90024
294.00000



d2
16.22141
16.22141
16.22141



d5
2.00000
33.62022
46.49954



d12
29.66797
18.37991
2.00000



B.f.
47.57563
53.66382
85.74428







[Moving Amount upon Focusing]












f
71.40000
134.90024
294.00000



δ1B
13.90148
14.20164
13.03481











[Values for Conditional Expressions]












(16) f1/fw = 1.787



(17) f2/fw = −0.436



(18) f3/fw = 0.500



(19) f32/f3 = −1.738



(20) f3/f33 = 0.063



(21) n31N − n31P = 0.304



(22) ν31P − ν31N = 46.57



(23) ν32N − ν32P = 14.16



(24) (r32R + r32F)/(r32R − r32F) = −1.748



(25) r32S/f32 = 0.690



(26) f1A/f1B = 2.860










FIGS. 42A and 42B show various aberrations of the zoom lens system according to Example 11 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively. FIG. 43 shows various aberrations of the zoom lens system according to Example 11 of the third embodiment in an intermediate focal length state upon focusing at infinity. FIGS. 44A and 44B show various aberrations of the zoom lens system according to Example 11 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.
As is apparent from respective graphs, the zoom lens system according to Example 11 of the third embodiment shows superb optical performance correcting various aberrations.
EXAMPLE 12
FIG. 45 is a diagram showing a sectional view of a zoom lens system according to Example 12 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.
In FIG. 45, the zoom lens system with a vibration reduction mechanism is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1 and the third lens group G3 move to the object and the second lens group G2 moves once to the image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, and a distance between the second lens group G2 and the third lens group G3 decreases.
The first lens group G1 is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. The 1A lens group G1A is composed of a double convex positive lens. The 1B lens group G1B is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens.
The second lens group G2 is composed of, in order from the object, a double concave negative lens, a cemented lens constructed by a double concave negative lens cemented with a positive meniscus lens having a convex surface facing to the object, and a double concave negative lens.
The third lens group G3 is composed of, in order from the object, a 31 lens group G31 having positive refractive power, a 32 lens group G32 having negative refractive power, and a 33 lens group G33 having negative refractive power. The 31 lens group G31 is composed of, in order from the object, a double convex positive lens, a first cemented lens constructed by a double convex positive lens cemented with a double concave negative lens, a positive meniscus lens having a convex surface facing to the object, and a second cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens. The 32 lens group G32 is composed of, in order from the object, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens. The 33 lens group G33 is composed of, in order from the object, a double convex positive lens and a negative meniscus lens having a concave surface facing to the object.
An aperture stop S is arranged to the object side of the 31 lens group G31, and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).
Upon detecting a camera shake, vibration reduction on the image plane I is carried out by moving only the 32 lens group G32 perpendicular to the optical axis.
Focusing from infinity to a close-range object is carried out by moving the 1B lens group G1B to the object.
In the wide-angle end state (W) of Example 12 of the third embodiment, vibration reduction coefficient K is 1.20, and the focal length f is 71.40 (mm), so that the image rotation of 0.30° can be corrected by moving the 32 lens group G32 by the amount of 0.312 (mm). In the telephoto end state (T), vibration reduction coefficient K is 1.80, and the focal length f is 294.00 (mm), so that the image rotation of 0.15° can be corrected by moving the 32 lens group G32 by the amount of 0.428 (mm).
Various values associated with Example 12 of the third embodiment of the present invention is listed in Table 12.







TABLE 12







[Specifications]















f =
71.40
134.90
294.00



FNO =
4.11
4.34
5.80



2ω =
22.59°
11.77°
5.43°











[Lens Data]












r
d
ν
n





 1
470.2040
3.4304
64.14
1.516330


 2
−470.2040
(d2)


 3
66.8958
2.5000
26.52
1.761821


 4
45.5528
9.0276
70.23
1.487490


 5
−449.7939
(d5)


 6
−402.2639
1.4000
49.60
1.772499


 7
87.3056
1.8292


 8
−109.2528
1.4000
49.60
1.772499


 9
27.2177
4.2493
23.78
1.846660


10
238.8473
2.0018


11
−54.2941
1.4000
49.60
1.772499


12
405.9871
(d12)











13
∞
1.0000
Aperture Stop S












14
202.2803
3.3407
51.47
1.733997


15
−69.7514
0.2000


16
49.4756
6.2066
81.54
1.496999


17
−36.3641
1.4000
34.97
1.800999


18
417.1479
0.2000


19
30.2273
4.0221
60.64
1.603112


20
106.7084
4.7396


21
66.4249
1.3000
23.78
1.846660


22
38.1999
4.3369
70.23
1.487490


23
−91.4989
3.0000


24
195.2029
2.8722
25.42
1.805181


25
−40.8879
1.2000
39.58
1.804398


26
39.1832
12.6471 


27
71.7192
2.3982
31.07
1.688931


28
−76.4137
1.3004


29
−21.7636
1.2000
49.60
1.772499


30
−61.3686
(B.f.)














Wide-angle end
Intermediate
Telephoto end











[Variable Distances]


(Infinity)












f
71.40008
134.89998
294.00000



d2
14.05307
14.05307
14.05307



d5
2.00000
33.03379
46.59044



d12
25.89044
16.74440
2.00000



B.f.
54.45490
59.34588
88.75509







[Moving Amount upon Focusing]












f
71.40008
134.89998
294.00000



δ1B
11.82193
12.07969
12.36388











[Values for Conditional Expressions]












(16) f1/fw = 1.653



(17) f2/fw = −0.379



(18) f3/fw = 0.491



(19) f32/f3 = −1.762



(20) f3/f33 = −0.120



(21) n31N − n31P = 0.304



(22) ν31P − ν31N = 46.57



(23) ν32N − ν32P = 13.93



(24) (r32R + r32F)/(r32R − r32F) = −1.502



(25) r32S/f32 = 0.662



(26) f1A/f1B = 2.960










FIGS. 46A and 46B show various aberrations of the zoom lens system according to Example 12 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively. FIG. 47 shows various aberrations of the zoom lens system according to Example 12 of the third embodiment in an intermediate focal length state upon focusing at infinity. FIGS. 48A and 48B show various aberrations of the zoom lens system according to Example 12 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.
As is apparent from respective graphs, the zoom lens system according to Example 12 of the third embodiment shows superb optical performance correcting various aberrations.
EXAMPLE 13
FIG. 49 is a diagram showing a sectional view of a zoom lens system according to Example 13 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.
In FIG. 49, the zoom lens system with a vibration reduction mechanism is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1 and the third lens group G3 move to the object and the second lens group G2 moves once to the image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, and a distance between the second lens group G2 and the third lens group G3 decreases.
The first lens group G1 is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. The 1A lens group G1A is composed of a double convex positive lens. The 1B lens group G1B is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens.
The second lens group G2 is composed of, in order from the object, a double concave negative lens, a cemented lens constructed by a double concave negative lens cemented with a positive meniscus lens having a convex surface facing to the object, and a double concave negative lens.
The third lens group G3 is composed of, in order from the object, a 31 lens group G31 having positive refractive power, a 32 lens group G32 having negative refractive power, and a 33 lens group G33 having negative refractive power. The 31 lens group G31 is composed of, in order from the object, a double convex positive lens, a first cemented lens constructed by a double convex positive lens cemented with a double concave negative lens, a positive meniscus lens having a convex surface facing to the object, and a second cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens. The 32 lens group G32 is composed of, in order from the object, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens. The 33 lens group G33 is composed of, in order from the object, a double convex positive lens and a negative meniscus lens having a concave surface facing to the object.
An aperture stop S is arranged between the 32 lens group G32 and the 33 lens group G33, and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).
Upon detecting a camera shake, vibration reduction on the image plane I is carried out by moving only the 32 lens group G32 perpendicular to the optical axis.
Focusing from infinity to a close-range object is carried out by moving the 1B lens group G1B to the object.
In the wide-angle end state (W) of Example 13 of the third embodiment, vibration reduction coefficient K is 1.22, and the focal length f is 71.40 (mm), so that the image rotation of 0.30° can be corrected by moving the 32 lens group G32 by the amount of 0.306 (mm). In the telephoto end state (T), vibration reduction coefficient K is 1.77, and the focal length f is 294.00 (mm), so that the image rotation of 0.15° can be corrected by moving the 32 lens group G32 by the amount of 0.435 (mm).
Various values associated with Example 13 of the third embodiment of the present invention is listed in Table 13.







TABLE 13







[Specifications]















f =
71.40
134.90
294.00



FNO =
3.99
4.07
5.80



2ω =
22.60°
11.74°
5.43°











[Lens Data]















r
d
ν
n





1
435.2356
3.5738
64.14
1.516330


2
−435.2356
(d2)


3
65.0718
2.5000
26.52
1.761821


4
44.2697
9.2741
70.23
1.487490


5
−463.1280
(d5)


6
−312.4330
1.4000
49.60
1.772499


7
89.0862
1.9706


8
−89.6775
1.4000
49.60
1.772499


9
27.3391
4.2567
23.78
1.846660


10
234.4984
1.8028


11
−63.7183
1.4000
49.60
1.772499


12
421.2241
(d12)


13
128.9757
3.6394
49.34
1.743198


14
−65.2871
0.2000


15
45.1211
6.2141
81.54
1.496999


16
−34.9173
1.4000
33.89
1.803840


17
179.4381
0.2000


18
28.1967
3.1441
61.13
1.589130


19
51.4191
3.2906


20
61.2265
1.3000
23.78
1.846660


21
41.2033
4.3881
70.23
1.487490


22
−71.4444
3.0000


23
2400.8873
2.8952
25.42
1.805181


24
−34.5253
1.2000
40.10
1.762001


25
43.6975
3.0000











26
∞
10.7331 
Aperture Stop S












27
109.9589
2.6855
33.79
1.647689


28
−56.7968
1.6430


29
−21.1003
1.2000
50.23
1.719995


30
−54.1165
(B.f.)














Wide-angle end
Intermediate
Telephoto end











[Variable Distances]


(Infinity)












f
71.40000
134.90000
294.00000



d2
13.51363
13.51363
13.51363



d5
2.06047
33.56902
45.03690



d12
27.97643
18.33799
2.00000



B.f.
55.73858
57.28561
87.73867







[Moving Amount upon Focusing]












f
71.40000
134.90000
294.00000



δ1B
11.13016
11.34131
11.58141











[Values for Conditional Expressions]












(16) f1/fw = 1.600



(17) f2/fw = −0.382



(18) f3/fw = 0.512



(19) f32/f3 = −1.730



(20) f3/f33 = −0.099



(21) n31N − n31P = 0.307



(22) ν31P − ν31N = 47.65



(23) ν32N − ν32P = 14.68



(24) (r32R + r32F)/(r32R − r32F) = −1.037



(25) r32S/f32 = 0.546



(26) f1A/f1B = 2.791










FIGS. 50A and 50B show various aberrations of the zoom lens system according to Example 13 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively. FIG. 51 shows various aberrations of the zoom lens system according to Example 13 of the third embodiment in an intermediate focal length state upon focusing at infinity. FIGS. 52A and 52B show various aberrations of the zoom lens system according to Example 13 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.
As is apparent from respective graphs, the zoom lens system according to Example 13 of the third embodiment shows superb optical performance correcting various aberrations.
EXAMPLE 14
FIG. 53 is a diagram showing a sectional view of a zoom lens system according to Example 14 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.
In FIG. 53, the zoom lens system with a vibration reduction mechanism is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1 and the third lens group G3 move to the object and the second lens group G2 moves once to the image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, and a distance between the second lens group G2 and the third lens group G3 decreases.
The first lens group G1 is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. The 1A lens group G1A is composed of a double convex positive lens. The 1B lens group G1B is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens.
The second lens group G2 is composed of, in order from the object, a double concave negative lens, a cemented lens constructed by a double concave negative lens cemented with a positive meniscus lens having a convex surface facing to the object, and a double concave negative lens.
The third lens group G3 is composed of, in order from the object, a 31 lens group G31 having positive refractive power, a 32 lens group G32 having negative refractive power, and a 33 lens group G33 having negative refractive power. The 31 lens group G31 is composed of, in order from the object, a double convex positive lens, a first cemented lens constructed by a double convex positive lens cemented with a negative meniscus lens, a positive meniscus lens having a convex surface facing to the object, and a second cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens. The 32 lens group G32 is composed of, in order from the object, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens. The 33 lens group G33 is composed of, in order from the object, a double convex positive lens and a negative meniscus lens having a concave surface facing to the object.
An aperture stop S is arranged between the 31 lens group G31 and the 32 lens group G32, and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).
Upon detecting a camera shake, vibration reduction on the image plane I is carried out by moving only the 32 lens group G32 perpendicular to the optical axis.
Focusing from infinity to a close-range object is carried out by moving the 1B lens group G1B to the object.
In the wide-angle end state (W) of Example 14 of the third embodiment, vibration reduction coefficient K is 1.20, and the focal length f is 71.40 (mm), so that the image rotation of 0.30° can be corrected by moving the 32 lens group G32 by the amount of 0.312 (mm). In the telephoto end state (T), vibration reduction coefficient K is 1.75, and the focal length f is 294.00 (mm), so that the image rotation of 0.15° can be corrected by moving the 32 lens group G32 by the amount of 0.440 (mm).
Various values associated with Example 14 of the third embodiment of the present invention is listed in Table 14.







TABLE 14







[Specifications]















f =
71.40
134.91
294.00



FNO =
4.07
4.21
5.80



2ω =
22.52°
11.72°
5.42°











[Lens Data]












r
d
ν
n





1
469.3093
3.4317
64.14
1.516330


2
−469.3093
(d2)


3
70.6717
2.5000
26.52
1.761821


4
47.9817
8.6474
70.23
1.487490


5
−513.7728
(d5)


6
−449.1622
1.4000
49.60
1.772499


7
121.4673
1.3256


8
−170.8246
1.4000
49.60
1.772499


9
25.7253
4.1467
23.78
1.846660


10
114.2679
2.1893


11
−58.0505
1.4000
49.60
1.772499


12
427.6062
 (d12)


13
184.6338
3.0978
52.64
1.740999


14
−77.4294
0.2000


15
60.5320
6.2886
81.54
1.496999


16
−38.0057
1.4000
34.97
1.800999


17
−2769.6388
0.2000


18
29.4015
3.3326
60.64
1.603112


19
65.7395
7.2941


20
48.4532
1.3000
23.78
1.846660


21
28.7258
4.3311
70.23
1.487490


22
−116.3213
1.4000











23
∞
3.6000
Aperture Stop S












24
192.1240
2.6534
25.42
1.805181


25
−39.8609
1.2000
39.58
1.804398


26
36.5000
8.1971


27
74.0134
3.9109
31.07
1.688931


28
−49.3643
1.8413


29
−22.3167
1.2000
49.60
1.772499


30
−89.5841
(B.f.)














Wide-angle end
Intermediate
Telephoto end











[Variable Distances]


(Infinity)












f
71.40015
134.90898
294.00094



d2
15.55650
15.55650
15.55650



d5
2.00494
36.17786
49.70524



d12
29.70030
19.40726
2.00000



B.f.
51.85087
54.13440
80.85104







[Moving Amount upon Focusing]












f
71.40015
134.90898
294.00094



δ1B
13.28566
13.56940
13.82723











[Values for Conditional Expressions]












(16) f1/fw = 1.743



(17) f2/fw = −0.414



(18) f3/fw = 0.506



(19) f32/f3 = −1.569



(20) f3/f33 = −0.048



(21) n31N − n31P = 0.304



(22) ν31P − ν31N = 46.57



(23) ν32N − ν32P = 14.16



(24) (r32R + r32F)/(r32R − r32F) = −1.469



(25) r32S/f32 = 0.703



(26) f1A/f1B = 2.756










FIGS. 54A and 54B show various aberrations of the zoom lens system according to Example 14 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively. FIG. 55 shows various aberrations of the zoom lens system according to Example 14 of the third embodiment in an intermediate focal length state upon focusing at infinity. FIGS. 56A and 56B show various aberrations of the zoom lens system according to Example 14 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.
As is apparent from respective graphs, the zoom lens system according to Example 14 of the third embodiment shows superb optical performance correcting various aberrations.
EXAMPLE 15
FIG. 57 is a diagram showing a sectional view of a zoom lens system according to Example 15 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.
In FIG. 57, the zoom lens system with a vibration reduction mechanism is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1 and the third lens group G3 move to the object and the second lens group G2 moves once to the image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, and a distance between the second lens group G2 and the third lens group G3 decreases.
The first lens group G1 is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. The 1A lens group G1A is composed of a double convex positive lens. The 1B lens group G1B is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens.
The second lens group G2 is composed of, in order from the object, a double concave negative lens, a cemented lens constructed by a double concave negative lens cemented with a positive meniscus lens having a convex surface facing to the object, and a double concave negative lens.
The third lens group G3 is composed of, in order from the object, a 31 lens group G31 having positive refractive power, a 32 lens group G32 having negative refractive power, and a 33 lens group G33 having positive refractive power. The 31 lens group G31 is composed of, in order from the object, a double convex positive lens, a first cemented lens constructed by a double convex positive lens cemented with a negative meniscus lens, a positive meniscus lens having a convex surface facing to the object, and a second cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens. The 32 lens group G32 is composed of, in order from the object, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens. The 33 lens group G33 is composed of, in order from the object, a double convex positive lens and a negative meniscus lens having a concave surface facing to the object.
An aperture stop S is arranged to the object side of the 31 lens group G31, and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).
Upon detecting a camera shake, vibration reduction on the image plane I is carried out by moving only the 32 lens group G32 perpendicular to the optical axis.
Focusing from infinity to a close-range object is carried out by moving the 1B lens group G1B to the object.
In the wide-angle end state (W) of Example 14 of the third embodiment, vibration reduction coefficient K is 1.16, and the focal length f is 71.40 (mm), so that the image rotation of 0.30° can be corrected by moving the 32 lens group G32 by the amount of 0.322 (mm). In the telephoto end state (T), vibration reduction coefficient K is 1.75, and the focal length f is 294.00 (mm), so that the image rotation of 0.15° can be corrected by moving the 32 lens group G32 by the amount of 0.440 (mm).
Various values associated with Example 15 of the third embodiment of the present invention is listed in Table 15.







TABLE 15







[Specifications]















f =
71.40
134.90
294.00



FNO =
4.05
4.29
5.70



2ω =
22.57°
11.76°
5.44°











[Lens Data]















r
d
ν
n





1
381.8649
3.2698
64.14
1.516330


2
−381.8649
(d2)


3
71.5714
2.5000
26.52
1.761821


4
49.9993
8.2004
81.54
1.496999


5
−1251.0960
(d5)


6
−459.6483
1.4000
49.60
1.772499


7
73.4579
2.3256


8
−148.2025
1.4000
49.60
1.772499


9
30.9506
4.0346
23.78
1.846660


10
507.9596
2.1322


11
−53.4502
1.4000
49.60
1.772499


12
745.1895
(d12)











13
∞
1.0000
Aperture Stop S












14
299.4180
2.5704
52.64
1.740999


15
−74.3861
0.2000


16
58.6516
5.0344
81.54
1.496999


17
−40.9400
1.4000
34.97
1.800999


18
−586.8839
0.2000


19
32.9311
3.0580
60.64
1.603112


20
86.6358
8.7020


21
66.7204
1.3000
23.78
1.846660


22
34.9761
4.3431
70.23
1.487490


23
−113.9382
5.0000


24
249.3959
3.6484
25.42
1.805181


25
−36.8058
1.2000
39.58
1.804398


26
39.1458
10.9499 


27
57.2414
2.6768
31.07
1.688931


28
−326.2393
3.9442


29
−22.0804
1.2000
49.60
1.772499


30
−37.9653
(B.f.)














Wide-angle end
Intermediate
Telephoto end











[Variable Distances]


(Infinity)












f
71.40016
134.90320
294.00205



d2
14.63133
14.63133
14.63133



d5
2.00000
33.48260
46.17223



d12
28.49089
17.74860
0.31866



B.f.
48.78816
52.49212
81.78883







[Moving Amount upon Focusing]












f
71.40016
134.90320
294.00205



δ1B
12.86620
13.12031
13.38598











[Values for Conditional Expressions]












(16) f1/fw = 1.693



(17) f2/fw = −0.410



(18) f3/fw = 0.522



(19) f32/f3 = −1.566



(20) f3/f33 = 0.030



(21) n31N − n31P = 0.304



(22) ν31P − ν31N = 46.57



(23) ν32N − ν32P = 14.16



(24) (r32R + r32F)/(r32R − r32F) = −1.372



(25) r32S/f32 = 0.619



(26) f1A/f1B = 2.151










FIGS. 58A and 58B show various aberrations of the zoom lens system according to Example 15 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively. FIG. 59 shows various aberrations of the zoom lens system according to Example 15 of the third embodiment in an intermediate focal length state upon focusing at infinity. FIGS. 60A and 60B show various aberrations of the zoom lens system according to Example 15 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.
As is apparent from respective graphs, the zoom lens system according to Example 15 of the third embodiment shows superb optical performance correcting various aberrations.
EXAMPLE 16
FIG. 61 is a diagram showing a sectional view of a zoom lens system according to Example 16 of the third embodiment of the present invention together with a trajectory of each lens group upon zooming.
In FIG. 61, the zoom lens system with a vibration reduction mechanism is composed of, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power. When the state of lens group positions varies from a wide-angle end state (W) to a telephoto end state (T), the first lens group G1 and the third lens group G3 move to the object and the second lens group G2 moves once to the image I and, then, moves to the object such that a distance between the first lens group G1 and the second lens group G2 increases, and a distance between the second lens group G2 and the third lens group G3 decreases.
The first lens group G1 is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. The 1A lens group G1A is composed of a double convex positive lens. The 1B lens group G1B is composed of, in order from the object, a cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens.
The second lens group G2 is composed of, in order from the object, a double concave negative lens, a cemented lens constructed by a double concave negative lens cemented with a positive meniscus lens having a convex surface facing to the object, and a double concave negative lens.
The third lens group G3 is composed of, in order from the object, a 31 lens group G31 having positive refractive power, a 32 lens group G32 having negative refractive power, and a 33 lens group G33 having positive refractive power. The 31 lens group G31 is composed of, in order from the object, a double convex positive lens, a first cemented lens constructed by a double convex positive lens cemented with a negative meniscus lens, a positive meniscus lens having a convex surface facing to the object, and a second cemented lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a double convex positive lens. The 32 lens group G32 is composed of, in order from the object, a cemented lens constructed by a double convex positive lens cemented with a double concave negative lens. The 33 lens group G33 is composed of, in order from the object, a fixed stop S2, a double convex positive lens and a negative meniscus lens having a concave surface facing to the object.
An aperture stop S is arranged to the object side of the 31 lens group G31, and is moved together with the third lens group G3 upon zooming from the wide-angle end state (W) to the telephoto end state (T).
Upon detecting a camera shake, vibration reduction on the image plane I is carried out by moving only the 32 lens group G32 perpendicular to the optical axis.
Focusing from infinity to a close-range object is carried out by moving the 1B lens group G1B to the object.
In the wide-angle end state (W) of Example 14 of the third embodiment, vibration reduction coefficient K is 1.25, and the focal length f is 71.40 (mm), so that the image rotation of 0.30° can be corrected by moving the 32 lens group G32 by the amount of 0.299 (mm). In the telephoto end state (T), vibration reduction coefficient K is 1.90, and the focal length f is 294.00 (mm), so that the image rotation of 0.15° can be corrected by moving the 32 lens group G32 by the amount of 0.405 (mm).
Various values associated with Example 16 of the third embodiment of the present invention is listed in Table 16.







TABLE 16







[Specifications]















f =
71.40
135.00
294.00



FNO =
4.05
4.29
5.70



2ω =
22.57°
11.76°
5.44°











[Lens Data]















r
d
ν
n





1
340.6588
4.2
64.14
1.51633


2
−340.659
(d2)


3
65.1639
1.8
26.3
1.784696


4
45.8381
8.8
81.61
1.496999


5
−1308.92
(d5)


6
−271.25
1.4
49.61
1.772499


7
71.7854
1.3


8
−566.934
1.4
49.61
1.772499


9
24.4437
4.7
23.78
1.84666


10
133.0962
3.75


11
−46.0918
1.4
49.61
1.772499


12
1927.614
(d12)











13
∞
2
Aperture Stop S












14
188.6747
3.4
60.09
1.639999


15
−72.245
0.2


16
73.7218
6
81.61
1.496999


17
−38.1983
1.4
34.96
1.800999


18
−154.661
0.2


19
32.255
4.2
52.42
1.517417


20
143.854
7.9


21
333.5741
1.3
23.78
1.84666


22
54.3293
4.1
70.24
1.48749


23
−89.5707
10.2


24
256.9205
3.6
25.43
1.805181


25
−35.5686
1.2
39.59
1.804398


26
35.5686
3.4











27
∞
3.1
Fixed Stop S2












28
47.0802
4
34.47
1.639799


29
−96.8946
2.4


30
−23.3234
1.2
49.61
1.772499


31
−42.5579
(B.f.)














Wide-angle end
Intermediate
Telephoto end











[Variable Distances]


(Infinity)












f
71.39993
134.99982
294.00047



d2
13.43865
13.43865
13.43865



d5
2.49989
31.01849
43.01129



d12
28.21141
18.59271
2.50011



B.f.
53.40008
57.30852
87.10064







[Moving Amount upon Focusing]












f
71.39991
134.99979
294.00046



δ1B
11.08175
11.28593
11.5251











[Values for Conditional Expressions]












(16) f1/fw = 1.563



(17) f2/fw = −0.368



(18) f3/fw = 0.525



(19) f32/f3 = −1.384



(20) f3/f33 = 0.238



(21) n31N − n31P = 0.304



(22) ν31P − ν31N = 46.57



(23) ν32N − ν32P = 14.16



(24) (r32R + r32F)/(r32R − r32F) = −1.321



(25) r32S/f32 = 0.685



(26) f1A/f1B = 2.051










FIGS. 62A and 62B show various aberrations of the zoom lens system according to Example 16 of the third embodiment in a wide-angle end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.30°, respectively. FIG. 63 shows various aberrations of the zoom lens system according to Example 16 of the third embodiment in an intermediate focal length state upon focusing at infinity. FIGS. 64A and 64B show various aberrations of the zoom lens system according to Example 16 of the third embodiment in a telephoto end state upon focusing at infinity, and meridional lateral aberration at infinity when vibration reduction is carried out against rotation of 0.15°, respectively.
As is apparent from respective graphs, the zoom lens system according to Example 16 of the third embodiment shows superb optical performance correcting various aberrations.
In examples of the third embodiment, although three-group-type zoom lens systems have been proposed, it is needless to say that a zoom lens system merely adding a lens group to the three-group type zoom system is within the scope of the present invention. Moreover, in the construction of each lens group, it is needless to say that a zoom lens system merely adding a lens element to any one of lens groups of the zoom lens system according to the third embodiment is within the scope of the present invention.
Additional advantages and modification will readily occur to those skilled in the art. Therefore, the invention in its broader aspect is not limited to the specific details, and representative devices shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

## Claims

1. A zoom lens system with a vibration reduction mechanism comprising, in order from an object:
a first lens group having positive refractive power;
a second lens group having negative refractive power;
a third lens group having positive refractive power; and
a fourth lens group having negative refractive power,
when a state of lens group positions varies from a wide-angle end state to a telephoto end state, a distance between the first lens group and the second lens group increasing, a distance between the second lens group and the third lens group decreasing, and a distance between the third lens group and the fourth lens group varying,
the fourth lens group being composed of, in order from the object, a 41 lens group, a 42 lens group having negative refractive power, and a 43 lens group,
at least one of the 41 lens group and the 43 lens group having positive refractive power, and
image blur on an image plane caused by a camera shake being reduced by moving only the 42 lens group perpendicular to the optical axis.

2. The zoom lens system with a vibration reduction mechanism according to claim 1, wherein the following conditional expression is satisfied:


0.10<f42/f4<0.90

where f4 denotes the focal length of the fourth lens group, and f42 denotes the focal length of the 42 lens group.

3. The zoom lens system with a vibration reduction mechanism according to claim 2, wherein the following conditional expressions are satisfied:


−2.10<f4/fw<−0.70



−2.10<(1/f41+1/f43)·f4<−0.40

where fw denotes the focal length of the zoom lens system in the wide-angle end state, f41 denotes the focal length of the 41 lens group and f43 denotes the focal length of the 43 lens group.

4. The zoom lens system with a vibration reduction mechanism according to claim 1, wherein when the state of lens group positions varies from the wide-angle end state to the telephoto end state, the first lens group, the third lens group, and the fourth lens group move to the object.

5. The zoom lens system with a vibration reduction mechanism according to claim 1, wherein the 41 lens group includes at least one positive lens, the 42 lens group includes at least one positive lens and at least one negative lens, and the 43 lens group includes at least one positive lens.

6. The zoom lens system with a vibration reduction mechanism according to claim 5, wherein the 41 lens group includes, in order from the object, a negative lens having a concave surface facing to the image, and a positive lens having a convex surface facing to the object, and the following conditional expression is satisfied:


0.20<n41N−n41P

where n41N denotes refractive index of the negative lens in the 41 lens group at d-line (λ=587.6 nm), and n41P denotes refractive index of the positive lens in the 41 lens group at d-line.

7. The zoom lens system with a vibration reduction mechanism according to claim 5, wherein the 42 lens group includes, in order from the object, a positive lens having a convex surface facing to the image, and a double concave negative lens, and the following conditional expression is satisfied:


10.0<ν42N−ν42P

where ν42N denotes Abbe number of the double concave negative lens in the 42 lens group at d-line (λ=587.6 nm), and ν42P denotes Abbe dumber of the positive lens in the 42 lens group at d-line.