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Zoom lens system, imaging apparatus, and method for zooming the zoom lens system

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20120275032 patent thumbnailZoom

Zoom lens system, imaging apparatus, and method for zooming the zoom lens system


Providing a zoom lens system having excellent optical performance with a high zoom ratio, an imaging apparatus, and a method for zooming the zoom lens system. The system including, in order from an object, a first group G1 having negative refractive power, a second group G2 having positive refractive power, a third group G3 having negative refractive power, and a fourth group G4 having positive refractive power. An aperture stop S is disposed between the second group G2 and the fourth group G4. Upon zooming from a wide-angle end state to a telephoto end state, each group is moved such that a distance between the second group G2 and the third group G3 increases, a distance between the third group G3 and the fourth group G4 decreases, and the aperture stop S is moved together with the third group G3. Given conditions are satisfied.

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Inventors: SATORU SHIBATA, Takeshi Suzuki, Hiroshi Yamamoto
USPTO Applicaton #: #20120275032 - Class: 359680 (USPTO) - 11/01/12 - Class 359 


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The Patent Description & Claims data below is from USPTO Patent Application 20120275032, Zoom lens system, imaging apparatus, and method for zooming the zoom lens system.

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TECHNICAL FIELD

The present invention relates to a zoom lens system, an imaging apparatus and a method for zooming the zoom lens system.

BACKGROUND ART

A zoom lens system suitable for a film camera, an electronic still camera, and a video camera has been proposed (for example, Japanese Patent Application Laid-Open Nos. 2004-61910, and 11-174329).

However, conventional zoom lens system has a zoom ratio of about two, so that a requirement for a high zoom ratio cannot be sufficiently satisfied. Moreover, since the position of an aperture stop is not optimized, excellent optical performance cannot be accomplished.

DISCLOSURE OF THE INVENTION

The present invention is made in view of the aforementioned problems and has an object to provide a zoom lens system having excellent optical performance with a high zoom ratio, an imaging apparatus, and a method for zooming the zoom lens system.

According to a first aspect of the present invention, there is provided a zoom lens system comprising, in order from an object: a first lens group having negative refractive power; a second lens group having positive refractive power; a third lens group having negative refractive power; and a fourth lens group having positive refractive power; an aperture stop being disposed between the second lens group and the fourth lens group, upon zooming from a wide-angle end state to a telephoto end state, each lens group being moved such that a distance between the second lens group and the third lens group varies, and a distance between the third lens group and the fourth lens group varies, and the aperture stop being moved together with the third lens group, and the following conditional expressions (1) and (2) being satisfied:

1.20<f2/fw<2.50  (1)

−2.10<f3/fw<−0.80  (2)

where f2 denotes a focal length of the second lens group, f3 denotes a focal length of the third lens group, and fw denotes a focal length of the zoom lens system in the wide-angle end state.

According to a second aspect of the present invention, there is provided an imaging apparatus equipped with the zoom lens system according the first aspect.

According to a third aspect of the present invention, there is provided a zoom lens system comprising, in order from an object: a first lens group having negative refractive power; a second lens group having positive refractive power; a third lens group having negative refractive power; and a fourth lens group having positive refractive power; an aperture stop being disposed between the second lens group and the fourth lens group, upon zooming from a wide-angle end state to a telephoto end state, each lens group being moved such that a distance between the second lens group and the third lens group varies and a distance between the third lens group and the fourth lens group varies, and the aperture stop being moved together with the third lens group, each of the second lens group, the third lens group, and the fourth lens group including at least one cemented lens, the cemented lens in the fourth lens group being composed of, in order from the object, a positive lens cemented with a negative lens, the most image plane side lens surface of the zoom lens system being a convex shape facing the image plane, and the following conditional expression (3) being satisfied:

−0.3<(d1w−d1t)/Ymax<0.17  (3)

where d1w denotes a distance along an optical axis between the most object side lens surface of the zoom lens system to the image plane in the wide-angle end state, d1t denotes a distance along the optical axis between the most object side lens surface of the zoom lens system to the image plane in the telephoto end state, and Ymax denotes the maximum image height.

According to a fourth aspect of the present invention, there is provided a zoom lens system comprising, in order from an object: a first lens group having negative refractive power; a second lens group having positive refractive power; a third lens group having negative refractive power; and a fourth lens group having positive refractive power; upon zooming from a wide-angle end state to a telephoto end state, a distance between the second lens group and the third lens group varying and a distance between the third lens group and the fourth lens group varying, the third lens group or a portion of the third lens group being moved as a vibration reduction lens group in a direction perpendicular to the optical axis, and the following conditional expression (5) being satisfied:

0.12<(r2+r1)/(r2−r1)<1.30  (5)

where r1 denotes a radius of curvature of the object side of the vibration reduction lens group, and r2 denotes a radius of curvature of the image side of the vibration reduction lens group.

According to a fifth aspect of the present invention, there is provided an imaging apparatus equipped with the zoom lens system according fourth aspect.

According to a sixth aspect of the present invention, there is provided a method for zooming a zoom lens system including, in order from an object, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, and a fourth lens group having positive refractive power, the method comprising steps of: providing an aperture stop between the second lens group and the fourth lens group; moving each lens group upon zooming from a wide-angle end state to a telephoto end state such that a distance between the second lens group and the third lens group varies, and a distance between the third lens group and the fourth lens group varies; moving aperture stop together with the third lens group upon zooming from the wide-angle end state to the telephoto end state; and satisfying the following conditional expressions (1) and (2):

1.20<f2/fw<2.50  (1)

−2.10<f3/fw<−0.80  (2)

where f2 denotes a focal length of the second lens group, f3 denotes a focal length of the third lens group, and fw denotes a focal length of the zoom lens system in the wide-angle end state.

According to a seventh aspect of the present invention, there is provided a method for zooming a zoom lens system including, in order from an object, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, and a fourth lens group having positive refractive power, the method comprising steps of: providing an aperture stop between the second lens group and the fourth lens group; moving each lens group upon zooming from a wide-angle end state to a telephoto end state such that a distance between the second lens group and the third lens group varies, a distance between the third lens group and the fourth lens group varies; moving the aperture stop together with the third lens group upon zooming from the wide-angle end state to the telephoto end state; providing each of the second lens group, the third lens group, and the fourth lens group including at least one cemented lens; providing the cemented lens in the fourth lens group composed of, in order from the object, a positive lens cemented with a negative lens; providing the most image plane side lens surface being convex shape facing the image plane; and satisfying the following conditional expression (3):

−0.3<(d1w−d1t)/Ymax<0.17  (3)

where d1w denotes a distance between the most object side lens surface of the zoom lens system to the image plane in the wide-angle end state, d1t denotes a distance between the most object side lens surface of the zoom lens system to the image plane in the telephoto end state, and Ymax denotes the maximum image height.

According to a eighth aspect of the present invention, there is provided a method for zooming a zoom lens system including, in order from an object, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, and a fourth lens group having positive refractive power, the method comprising steps of: varying a distance between the second lens group and the third lens group, and a distance between the third lens group and the fourth lens group upon zooming from a wide-angle end state to a telephoto end state; shifting the third lens group or a portion of the third lens group in a direction perpendicular to an optical axis as a vibration reduction lens group; and satisfying the following conditional expression (5):

0.12<(r2+r1)/(r2−r1)<1.30  (5)

where r1 denotes a radius of curvature of the object side of the vibration reduction lens group, and r2 denotes a radius of curvature of the image side of the vibration reduction lens group.

The present invention makes it possible to provide a zoom lens system having a vibration reduction function with excellent optical performance capable of correcting an image blur on the image plane caused by a camera shake with keeping a high zoom ratio.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a lens configuration of a zoom lens system according to Example 1 of a first embodiment in a wide-angle end state.

FIGS. 2A and 2B are graphs showing various aberrations of the zoom lens system according to Example 1 of the first embodiment in the wide-angle end state upon focusing on infinity, and coma upon correcting rotational camera shake of 0.734 degrees, respectively.

FIG. 3 is graphs showing various aberrations of the zoom lens system according to Example 1 of the first embodiment in an intermediate focal length state upon focusing on infinity.

FIGS. 4A and 4B are graphs showing various aberrations of the zoom lens system according to Example 1 of the first embodiment in a telephoto end state upon focusing on infinity, and coma upon correcting rotational camera shake of 0.432 degrees, respectively.

FIG. 5 is a sectional view showing a lens configuration of a zoom lens system according to Example 2 of the first embodiment in the wide-angle end state.

FIGS. 6A and 6B are graphs showing various aberrations of the zoom lens system according to Example 2 of the first embodiment in the wide-angle end state upon focusing on infinity, and coma upon correcting rotational camera shake of 0.734 degrees, respectively.

FIG. 7 is graphs showing various aberrations of the zoom lens system according to Example 2 of the first embodiment in the intermediate focal length state upon focusing on infinity.

FIGS. 8A and 8B are graphs showing various aberrations of the zoom lens system according to Example 2 of the first embodiment in the telephoto end state upon focusing on infinity, and coma upon correcting rotational camera shake of 0.432 degrees, respectively.

FIG. 9 is a sectional view showing a lens configuration of a zoom lens system according to Example 3 of the first embodiment in the wide-angle end state.

FIGS. 10A and 10B are graphs showing various aberrations of the zoom lens system according to Example 3 of the first embodiment in the wide-angle end state upon focusing on infinity, and coma upon correcting rotational camera shake of 0.734 degrees, respectively.

FIG. 11 is graphs showing various aberrations of the zoom lens system according to Example 3 of the first embodiment in the intermediate focal length state upon focusing on infinity.

FIGS. 12A and 12B are graphs showing various aberrations of the zoom lens system according to Example 3 of the first embodiment in the telephoto end state upon focusing on infinity, and coma upon correcting rotational camera shake of 0.432 degrees, respectively.

FIG. 13 is a sectional view showing a lens configuration of a zoom lens system according to Example 4 of the first embodiment in the wide-angle end state.

FIGS. 14A and 14B are graphs showing various aberrations of the zoom lens system according to Example 4 of the first embodiment in the wide-angle end state upon focusing on infinity, and coma upon correcting rotational camera shake of 0.734 degrees, respectively.

FIG. 15 is graphs showing various aberrations of the zoom lens system according to Example 4 of the first embodiment in the intermediate focal length state upon focusing on infinity.

FIGS. 16A and 165 are graphs showing various aberrations of the zoom lens system according to Example 4 of the first embodiment in the telephoto end state upon focusing on infinity, and coma upon correcting rotational camera shake of 0.432 degrees, respectively.

FIG. 17 is a sectional view showing a lens configuration of a zoom lens system according to Example 5 of the first embodiment in the wide-angle end state.

FIGS. 18A and 18B are graphs showing various aberrations of the zoom lens system according to Example 5 of the first embodiment in the wide-angle end state upon focusing on infinity, and coma upon correcting camera shake, respectively.

FIG. 19 is graphs showing various aberrations of the zoom lens system according to Example 5 of the first embodiment in the intermediate focal length state upon focusing on infinity.

FIGS. 20A and 20B are graphs showing various aberrations of the zoom lens system according to Example 5 of the first embodiment in the telephoto end state upon focusing on infinity, and coma upon correcting camera shake, respectively.

FIG. 21 is a sectional view showing a lens configuration of a zoom lens system according to Example 6 of the first embodiment in the wide-angle end state.

FIGS. 22A and 22B are graphs showing various aberrations of the zoom lens system according to Example 6 of the first embodiment in the wide-angle end state upon focusing on infinity, and coma upon correcting camera shake, respectively.

FIG. 23 is graphs showing various aberrations of the zoom lens system according to Example 6 of the first embodiment in the intermediate focal length state upon focusing on infinity.

FIGS. 24A and 24B are graphs showing various aberrations of the zoom lens system according to Example 6 of the first embodiment in the telephoto end state upon focusing on infinity, and coma upon correcting camera shake, respectively.

FIG. 25 is a sectional view showing a lens configuration of a zoom lens system according to Example 7 of a second embodiment in the wide-angle end state.

FIGS. 26A and 26B are graphs showing various aberrations of the zoom lens system according to Example 7 of the second embodiment in the wide-angle end state upon focusing on infinity, and coma upon correcting camera shake, respectively.

FIG. 27 is graphs showing various aberrations of the zoom lens system according to Example 7 of the first embodiment in the intermediate focal length state upon focusing on infinity.

FIGS. 28A and 28B are graphs showing various aberrations of the zoom lens system according to Example 7 of the second embodiment in the telephoto end state upon focusing on infinity, and coma upon correcting camera shake, respectively.

FIG. 29 is a sectional view showing a lens configuration of a zoom lens system according to Example 8 of the second embodiment in the wide-angle end state.

FIGS. 30A and 30B are graphs showing various aberrations of the zoom lens system according to Example 8 of the second embodiment in the wide-angle end state upon focusing on infinity, and coma upon correcting camera shake, respectively.

FIG. 31 is graphs showing various aberrations of the zoom lens system according to Example 8 of the second embodiment in the intermediate focal length state upon focusing on infinity.

FIGS. 32A and 32B are graphs showing various aberrations of the zoom lens system according to Example 8 of the second embodiment in the telephoto end state upon focusing on infinity, and coma upon correcting camera shake, respectively.

FIG. 33 is a sectional view showing a lens configuration of a zoom lens system according to Example 9 of the second embodiment in the wide-angle end state.

FIGS. 34A and 34B are graphs showing various aberrations of the zoom lens system according to Example 9 of the second embodiment in the wide-angle end state upon focusing on infinity, and coma upon correcting camera shake, respectively.

FIG. 35 is graphs showing various aberrations of the zoom lens system according to Example 9 of the second embodiment in the intermediate focal length state upon focusing on infinity.

FIGS. 36A and 36B are graphs showing various aberrations of the zoom lens system according to Example 9 of the second embodiment in the telephoto end state upon focusing on infinity, and coma upon correcting camera shake, respectively.

FIG. 37 is a sectional view showing a lens configuration of a zoom lens system according to Example 10 of a third embodiment in the wide-angle end state.

FIGS. 38A and 38B are graphs showing various aberrations of the zoom lens system according to Example 10 of the third embodiment in the wide-angle end state upon focusing on infinity, and coma upon correcting camera shake, respectively.

FIG. 39 is graphs showing various aberrations of the zoom lens system according to Example 10 of the third embodiment in the intermediate focal length state upon focusing on infinity.

FIGS. 40A and 40B are graphs showing various aberrations of the zoom lens system according to Example 10 of the third embodiment in the telephoto end state upon focusing on infinity, and coma upon correcting camera shake, respectively.



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stats Patent Info
Application #
US 20120275032 A1
Publish Date
11/01/2012
Document #
13545651
File Date
07/10/2012
USPTO Class
359680
Other USPTO Classes
International Class
02B15/177
Drawings
50


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