JP2011039260A - High variable power ratio zoom lens having vibration-proof function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high variable power ratio zoom lens having a vibration-proof function, which has a field angle of 6.5&deg; or less at a telephoto end and is compact and has excellent optical performance. <P>SOLUTION: The high variable power ratio zoom lens having the vibration-proof function comprises, in order from an object side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having negative refractive power, a fourth lens group having positive refractive power, a fifth lens group having negative refractive power, a sixth lens group having positive refractive power, and a seventh lens group having negative refractive power. The intervals between the respective lens groups are changed and the second lens group is moved to an image surface side to thereby vary power. The third lens group includes a 3a-th lens group of a lens unit having positive refractive power and a 3b-th lens group having negative refractive power, in order from the object side. The 3b-th lens group is moved in a direction nearly perpendicular to an optical axis to thereby move an image in the direction nearly perpendicular to the optical axis. The high variable power ratio zoom lens having the vibration-proof function satisfies a predetermined condition. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

The present invention relates to a zoom lens used for a digital camera, a silver salt camera, and the like, and more particularly, to a high zoom ratio zoom lens having an anti-vibration function when the angle of view at the telephoto end is 6.5 degrees or less.

The following patent documents are disclosed as zoom lenses having a narrow angle of view on the telephoto side and a zoom ratio of 5 times or more.

Patent Documents 1 and 2 disclose a zoom lens having an image stabilization function with an angle of view on the telephoto side of about 6.2 degrees and a zoom ratio of about 5 times.

Patent Document 3 discloses a zoom lens having an anti-vibration function with a zoom ratio of about 10 times and an angle of view on the wide-angle side exceeding 75 degrees.

Patent Document 4 discloses a zoom lens having a zoom ratio of about 10 times and a telescopic angle of view of about 5 degrees.

JP-A-11-258504

JP 2004-61605 A

JP 2008-216481 A

JP 2001-108902 A

The lens optical systems according to the examples of Patent Document 1 and Patent Document 2 have a telescopic angle of view of about 6.2 degrees, which is sufficient for magnified shooting of long-distance objects, but the zoom ratio is about 5 times. The enlargement of the zoom ratio to the wide-angle side has been an issue.

Patent Document 3 discloses a zoom lens that has an anti-vibration function, a zoom ratio of about 10 times, a wide shooting field, and an easy-to-use zoom lens. Therefore, the angle of view on the telephoto side was 8.3 degrees, and there was a limit to the magnified shooting of long-distance objects.

In Patent Document 4, the zoom ratio is about 10 times, and the telescopic side angle of view is about 5 degrees, which is sufficient to magnify long-distance objects, but it does not have an anti-vibration function and is equipped with an anti-vibration function. It was an issue to do.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a high zoom ratio zoom lens having an anti-vibration function with a compact telephoto field angle of 6.5 degrees or less and good optical performance.

In order to solve the above-described problem, the first invention according to the present invention has a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a negative refractive power in order from the object side. A third lens group, a fourth lens group having a positive refractive power, a fifth lens group having a negative refractive power, a sixth lens group having a positive refractive power, and a seventh lens group having a negative refractive power The second lens group is moved to the image plane side by changing the interval between the lens groups, and zooming is performed. The third lens group is a lens unit having a positive refractive power in order from the object side. It has a 3a lens group and a 3b lens group having negative refractive power, and moves the 3b lens group in a direction substantially perpendicular to the optical axis, thereby moving the image in a direction substantially perpendicular to the optical axis. High zoom ratio zoom with anti-vibration function characterized by satisfying the following conditions To provide a lens.
(1) 0.35 <f1 / fT <0.45
(2) 0.15 <| L1T / fT | <0.23
f1: Focal length of the first lens group fT: Focal length of the entire lens system at the telephoto end L1T: Amount of movement of the first lens group from the wide-angle end to the telephoto end

According to a second aspect of the present invention, the anti-vibration function of the first aspect is characterized in that focusing is performed by moving the seventh lens group in the optical axis direction, and the following conditions are satisfied. A high zoom ratio zoom lens is provided.
(3) 0.07 <| f7 / fT | <0.12
f7: Focal length of the seventh lens group

According to a third aspect of the present invention, there is provided the image stabilization function of the first or second aspect, wherein the third lens group is substantially fixed with respect to the image plane at the time of zooming. A high zoom ratio zoom lens is provided.

According to a fourth aspect of the present invention, there is provided a high zoom ratio zoom lens having an anti-vibration function according to any one of the first to third aspects, wherein the following conditional expression is satisfied: To do.
(4) | f3a / f3 | <0.6
(5) 0.003 <| m2T × m3T / fT | <0.004
f3a: focal length of the third lens group f3: focal length of the third lens group m2T: lateral magnification at the telephoto end of the second lens group
m3T: lateral magnification of the third lens group at the telephoto end

According to the present invention, it is possible to provide a high zoom ratio zoom lens having an anti-vibration function that is compact and has good optical performance with a telescopic angle of view of 6.5 degrees or less.

Sectional view of the zoom lens of Example 1 at infinity at the wide-angle end Longitudinal aberration diagram of the zoom lens of Example 1 at infinity at the wide-angle end Longitudinal aberration diagram of the zoom lens of Example 1 at infinity at the telephoto end Lateral aberration diagram in the standard state at infinity at the wide-angle end of the zoom lens of Example 1 Transverse aberration diagram in the standard state at infinity at the telephoto end of the zoom lens of Example 1 Transverse aberration diagram during vibration isolation at infinity at the wide-angle end of the zoom lens of Example 1 Transverse aberration diagram during vibration isolation at infinity at the telephoto end of the zoom lens of Example 1 Sectional view of the zoom lens of Embodiment 2 at infinity at the wide-angle end Longitudinal aberration diagram at infinity at the wide-angle end of the zoom lens in Example 2 Longitudinal aberration diagram of the zoom lens of Example 2 at infinity at the telephoto end Transverse aberration diagram in the standard state at infinity at the wide-angle end of the zoom lens of Example 2 Transverse aberration diagram in the standard state at infinity at the telephoto end of the zoom lens of Example 2 Lateral aberration diagram during image stabilization at infinity at the wide-angle end of the zoom lens of Example 2 Lateral aberration diagram during vibration isolation at infinity at the telephoto end of the zoom lens of Example 2 Sectional view of the zoom lens of Embodiment 3 at infinity at the wide-angle end Longitudinal aberration diagram of the zoom lens of Example 3 at infinity at the wide-angle end Longitudinal aberration diagram at infinity of the telephoto end of the zoom lens of Example 3 Transverse aberration diagram in the standard state at infinity at the wide-angle end of the zoom lens of Example 3 Transverse aberration diagram in the standard state at infinity at the telephoto end of the zoom lens of Example 3 Lateral aberration diagram during vibration isolation at infinity at the wide-angle end of the zoom lens of Example 3 Lateral aberration diagram during vibration isolation at infinity at the telephoto end of the zoom lens of Example 3

The high zoom ratio zoom lens having an image stabilization function according to the present invention includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens having a negative refractive power. The lens group includes a fourth lens group having a positive refractive power, a fifth lens group having a negative refractive power, a sixth lens group having a positive refractive power, and a seventh lens group having a negative refractive power. . The second lens group is moved to the image plane side by changing the interval between the lens groups to perform zooming. Furthermore, the third lens group includes a 3a lens group of a lens unit having a positive refractive power and a 3b lens group having a negative refractive power in order from the object side, and the 3b lens group with respect to the optical axis. Thus, the image is moved in a substantially vertical direction with respect to the optical axis.

In the lens optical system of the high zoom ratio zoom lens having the image stabilization function according to the present invention, by designing the focal length of the first lens group to be short, the movement amount of the first lens group becomes small at the time of zooming, and the entire length of the zoom lens is reduced. Can be shortened.

However, if the focal length of the first lens group is designed too short, the magnification burden of the optical system after the first lens group becomes large, so that the longitudinal aberration generated in the first lens group is after the first lens group. It deteriorates with the square of the lateral magnification of the optical system. In particular, the spherical aberration becomes under or the longitudinal chromatic aberration becomes large. Therefore, it is desirable to satisfy the following conditional expressions (1) and (2).
(1) 0.35 <f1 / fT <0.45
(2) 0.15 <| L1T / fT | <0.23
f1: Focal length of the first lens group fT: Focal length of the entire lens system at the telephoto end L1T: Amount of movement of the first lens group from the wide-angle end to the telephoto end

Conditional expression (1) defines the ratio of the focal length between the first lens group and the entire zoom lens system at the telephoto end. If the upper limit of conditional expression (1) is exceeded, the focal length of the first lens group becomes relatively long, which is advantageous for correcting spherical aberration and axial chromatic aberration, but the movement of the first lens group at the time of zooming Since the amount becomes too large, the entire length of the zoom lens has to be increased in order to secure this amount of movement, leading to an increase in size of the zoom lens. When the lower limit of conditional expression (1) is exceeded, the focal length of the first lens group becomes relatively short, and the amount of movement of the first lens group at the time of zooming becomes small, so the zoom lens can be made compact. However, the spherical aberration becomes under or large on-axis chromatic aberration occurs, and the optical performance of the zoom lens cannot be corrected well.

Conditional expression (2) defines the ratio between the amount of movement of the first lens unit from the wide-angle end to the telephoto end and the focal length of the entire zoom lens system at the telephoto end. When the upper limit of conditional expression (2) is exceeded, the amount of movement of the first lens unit from the wide-angle end to the telephoto end becomes relatively large with respect to the focal length of the entire zoom lens system at the telephoto end, and changes to the telephoto side. Although it is easy to enlarge the magnification ratio, the movement amount of the first lens unit at the time of zooming becomes too large, and in order to secure this movement amount, the entire length of the zoom lens has to be increased. Leads to an increase in size. In addition, since a structure for maintaining the amount of movement must be provided in terms of the mechanical structure, the product outer diameter increases and the product weight increases, making it difficult to achieve compactness. When the lower limit of conditional expression (2) is exceeded, the amount of movement of the first lens unit from the wide-angle end to the telephoto end is relatively small with respect to the focal length of the entire zoom lens system at the telephoto end, and changes to the telephoto side. Since it becomes difficult to enlarge the magnification ratio, it becomes impossible to secure a magnification ratio of about 10 times, and the focal length at the telephoto end is shortened, so that it is not possible to take a magnified image of a long-distance object.

In the high zoom ratio zoom lens having an image stabilization function according to the present invention, it is desirable to perform focusing by moving the seventh lens unit in the optical axis direction, and to satisfy the following conditional expression (3).
(3) 0.07 <| f7 / fT | <0.12
f7: Focal length of the seventh lens group

Conditional expression (3) defines the ratio of the focal length between the seventh lens group and the entire zoom lens system at the telephoto end. If the upper limit of conditional expression (3) is exceeded, the focal length of the seventh lens group becomes relatively long, which is advantageous for correction of coma and aberration during focusing, but the first lens group during zooming and focusing is advantageous. The amount of movement of the seven lens groups becomes too large, making it difficult to establish a mechanism structure. If the lower limit of conditional expression (3) is exceeded, the focal length of the seventh lens group becomes relatively short, and the amount of movement of the seventh lens group at the time of zooming or focusing becomes small, which is advantageous for the mechanism structure. However, since the focal length of the seventh lens group becomes relatively short, it becomes difficult to correct coma aberration, and fluctuations in spherical aberration and astigmatism during focusing increase, so that good optical performance is maintained during focusing. It becomes difficult.

Further, in the high zoom ratio zoom lens having an image stabilization function according to the present invention, the third lens group is substantially fixed with respect to the image plane at the time of zooming, so that the third lens group is moved substantially perpendicular to the optical axis. Structures such as actuators and electrical parts of the 3b lens group can be easily formed, which can contribute to the compactness of the zoom lens.

Further, in the high zoom ratio zoom lens having the image stabilization function of the present invention, in order to perform the image stabilization with the 3b lens group, it is desired to make the 3b lens group compact and lightweight, and to reproduce this. In addition, it is desirable that the following conditional expressions (4) and (5) are satisfied.
(4) | f3a / f3 | <0.6
(5) 0.003 <| m2T × m3T / fT | <0.004
f3a: focal length of the third lens group f3: focal length of the third lens group m2T: lateral magnification at the telephoto end of the second lens group
m3T: lateral magnification of the third lens group at the telephoto end

Conditional expression (4) defines the ratio of the focal lengths of the 3a lens group and the third lens group. When the upper limit value of conditional expression (4) is exceeded, the focal length of the 3a lens group becomes relatively long, the off-axis rays incident on the 3b lens group remain high, and the outside diameter of the 3b lens group becomes large. Therefore, it is difficult to realize the compactness and weight reduction of the third lens group.

Conditional expression (5) defines the ratio of the focal length of the entire zoom lens system at the telephoto end to the product of the lateral magnifications of the second and third lens groups at the telephoto end. If the upper limit value of conditional expression (5) is exceeded, the combined lateral magnification of the second lens group and the third lens group at the telephoto end becomes relatively large, so that the second lens group is secured in order to ensure a large lateral magnification. And the distance between the second lens group and the third lens group is farthest away, so that the height of off-axis rays incident on the third lens group is reduced, and the compactness and weight of the 3b lens group are reduced. However, in order to secure the amount of movement of the second lens group, the total length of the lens must be increased, making it difficult to reduce the size. If the lower limit of conditional expression (5) is exceeded, the combined lateral magnification of the second lens group and the third lens group at the telephoto end becomes relatively small, and the magnification burden is reduced. The amount of movement can be reduced and the overall length of the lens can be made compact. However, if the amount of movement of the second lens group is small, the farthest positions of the second lens group and the third lens group are closer, so the third lens group. The height of the off-axis ray incident on the lens 3 becomes high, and it becomes difficult to realize the compactness and weight reduction of the third lens group.

Numerical Examples 1 to 3 according to the zoom lens of the present invention are shown below.

In each numerical example, f in the overall specifications indicates a focal length, Fno indicates an F number, and 2ω indicates an angle of view. The numbers in the lens specifications are the surface number of the lens from the object side, R is the radius of curvature of the lens surface, D is the distance between the lens surfaces, nd is the refractive index of the d-line, and νd is the Abbe number of the d-line. Bf represents the back focus, and Obj represents the distance from the subject to the first lens surface. In the drawing, d-line, g-line, and C-line are aberrations with respect to respective wavelengths, ΔS indicates a sagittal image plane, and ΔM indicates a meridional image plane.

(Numerical example 1)

(Numerical example 2)

(Numerical Example 3)

L1 1st lens group L2 2nd lens group L3 3rd lens group L4 4th lens group L5 5th lens group L6 6th lens group L7 7th lens group SP Aperture stop d d line g g line C C line ΔS sagittal image Surface ΔM Meridional image plane

Claims (4)

In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a negative refractive power, a fourth lens group having a positive refractive power, and a negative The second lens group is composed of a fifth lens group having a refractive power, a sixth lens group having a positive refractive power, and a seventh lens group having a negative refractive power. The third lens group includes a third lens group having a positive refractive power and a third lens group having negative refractive power in order from the object side. By moving the third lens group in a direction substantially perpendicular to the optical axis, the image is moved in a direction substantially perpendicular to the optical axis, and the following conditions are satisfied. Zoom ratio zoom lens.
(1) 0.35 <f1 / fT <0.45
(2) 0.15 <| L1T / fT | <0.23
f1: Focal length of the first lens group fT: Focal length of the entire lens system at the telephoto end L1T: Amount of movement of the first lens group from the wide-angle end to the telephoto end
2. The zoom lens having a high zoom ratio according to claim 1, wherein focusing is performed by moving the seventh lens group in the optical axis direction, and the following conditions are satisfied.
(3) 0.07 <| f7 / fT | <0.12
f7: Focal length of the seventh lens group
3. The zoom lens having a high zoom ratio according to claim 1, wherein the third lens group is substantially fixed with respect to the image plane during zooming.
The high zoom ratio zoom lens having the image stabilization function according to claim 1, wherein the following conditional expression is satisfied.
(4) | f3a / f3 | <0.6
(5) 0.003 <| m2T × m3T / fT | <0.004
f3a: focal length of the third lens group f3: focal length of the third lens group m2T: lateral magnification at the telephoto end of the second lens group
m3T: lateral magnification of the third lens group at the telephoto end

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