JP2007286601A - Zoom lens, imaging apparatus and method for varying focal length - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens capable of obtaining higher image quality, an imaging apparatus, and a method for varying a focal length of the zoom lens. <P>SOLUTION: The zoom lens includes, in order from an object: a first lens group G1 having negative refractive power; a second lens group G1 having positive refractive power; a third lens group G3 having negative refractive power; and a fourth lens group G4 having positive refractive power. Upon zooming from a wide-angle end state to a telephoto end state, each lens group moves along an optical axis such that a distance between the first and the second lens groups G1 and G2 decreases, a distance between the second and the third lens groups G2 and G3 increases, and the distance between the third and the fourth lens groups G3 and G4 decreases; and the first lens group G1 includes a negative lens, at least one lens in the negative lens includes an aspherical surface, and the negative lens of the first lens group G1 satisfies prescribed conditionals. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  Conventionally, so-called minus lead type zoom lenses equipped with a lens unit having negative refractive power on the most object side are many as zoom lenses for wide-angle shooting because of their advantages such as short close-up shooting distance and ease of wide-angle shooting. It is used. This negative lead type zoom lens is a negative and positive retrofocus type from the object side when the refractive power arrangement is at the wide-angle end state, and is a positive and negative telephoto type from the object side at the telephoto end state. Long focus can be achieved even in the end state.

As such a negative lead type zoom lens, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a negative refractive power; And a fourth lens group having positive refracting power, and a configuration in which zooming is performed by changing the interval between the lens groups has been proposed (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 5-19170

  However, the conventional zoom lens disclosed in Patent Document 1 has a wide angle of view and a predetermined zoom ratio as a standard zoom lens, and is small, light, and inexpensive, but has good optical performance over the entire zoom range. Since it is difficult to obtain performance, higher image quality is demanded.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a zoom lens, an imaging device, and a zooming method that achieve high image quality.

In order to solve the above problems, the present invention
In order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a fourth lens having a positive refractive power And having a group
Upon zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group decreases, the distance between the second lens group and the third lens group increases, The lens groups move along the optical axis so that the distance between the third lens group and the fourth lens group decreases,
The first lens group has a negative lens;
At least one of the negative lenses has an aspheric surface;
The negative lens in the first lens group satisfies the following conditional expressions (1) and (2), and provides a zoom lens.
(1) 30 ≦ νd1 ≦ 71
(2) When 30 ≦ νd1 <36
-0.013 × νd1 + 2.083 ≦ nd1 ≦ 1.7
When 36 ≦ νd1 <41
-0.013 × νd1 + 2.083 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 41 ≦ νd1 <51
-0.004 × νd1 + 1.714 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 51 ≦ νd1 <61
-0.0015 × νd1 + 1.5865 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 61 ≦ νd1 ≦ 71
-0.0015 × νd1 + 1.5865 ≦ nd1 ≦ −0.009 × νd1 + 2.149
However,
nd1: refractive index νd1: d-line (wavelength λ = 587.6 nm) of the negative lens material in the first lens group with respect to d-line (wavelength λ = 587.6 nm) of the negative lens material in the first lens group The Abbe number for
In order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a fourth lens having a positive refractive power And having a group
Upon zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group decreases, the distance between the second lens group and the third lens group increases, The lens groups move along the optical axis so that the distance between the third lens group and the fourth lens group decreases,
The first lens group has a negative lens;
The second lens group includes a positive lens,
The zoom in which the negative lens in the first lens group and the positive lens in the second lens group satisfy the following conditional expressions (1), (2), (3), and (4): Provide a lens.
(1) 30 ≦ νd1 ≦ 71
(2) When 30 ≦ νd1 <36
-0.013 × νd1 + 2.083 ≦ nd1 ≦ 1.7
When 36 ≦ νd1 <41
-0.013 × νd1 + 2.083 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 41 ≦ νd1 <51
-0.004 × νd1 + 1.714 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 51 ≦ νd1 <61
-0.0015 × νd1 + 1.5865 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 61 ≦ νd1 ≦ 71
-0.0015 × νd1 + 1.5865 ≦ nd1 ≦ −0.009 × νd1 + 2.149
(3) 30 ≦ νd2 ≦ 71
(4) When 30 ≦ νd2 <36
-0.013 × νd2 + 2.083 ≦ nd2 ≦ 1.7
When 36 ≦ νd2 <41
-0.013 × νd2 + 2.083 ≦ nd2 ≦ −0.004 × νd2 + 1.844
When 41 ≦ νd2 <51
-0.004 × νd2 + 1.714 ≦ nd2 ≦ −0.004 × νd2 + 1.844
When 51 ≦ νd2 <61
-0.0015 × νd2 + 1.5865 ≦ nd2 ≦ −0.004 × νd2 + 1.844
When 61 ≦ νd2 ≦ 71
-0.0015 × νd2 + 1.5865 ≦ nd2 ≦ −0.009 × νd2 + 2.149
However,
nd1: refractive index νd1: d-line (wavelength λ = 587.6 nm) of the negative lens material in the first lens group with respect to d-line (wavelength λ = 587.6 nm) of the negative lens material in the first lens group ) Abbe number nd2: refractive index νd2 for the positive lens material d-line (wavelength λ = 587.6 nm) in the second lens group: d-line (wavelength λ) of the positive lens material in the second lens group = Abbe number for (587.6 nm)
In order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a fourth lens having a positive refractive power And having a group
Upon zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group decreases, the distance between the second lens group and the third lens group increases, The lens groups move along the optical axis so that the distance between the third lens group and the fourth lens group decreases,
The first lens group has a negative lens;
The fourth lens group includes a positive lens;
The zoom lens characterized in that the negative lens in the first lens group and the positive lens in the fourth lens group satisfy the following conditional expressions (1), (2), (5), and (6): Provide a lens.
(1) 30 ≦ νd1 ≦ 71
(2) When 30 ≦ νd1 <36
-0.013 × νd1 + 2.083 ≦ nd1 ≦ 1.7
When 36 ≦ νd1 <41
-0.013 × νd1 + 2.083 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 41 ≦ νd1 <51
-0.004 × νd1 + 1.714 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 51 ≦ νd1 <61
-0.0015 × νd1 + 1.5865 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 61 ≦ νd1 ≦ 71
-0.0015 × νd1 + 1.5865 ≦ nd1 ≦ −0.009 × νd1 + 2.149
(5) 30 ≦ νd4 ≦ 71
(6) When 30 ≦ νd4 <36
-0.013 × νd4 + 2.083 ≦ nd4 ≦ 1.7
When 36 ≦ νd4 <41
-0.013 × νd4 + 2.083 ≦ nd4 ≦ −0.004 × νd4 + 1.844
When 41 ≦ νd4 <51
-0.004 × νd4 + 1.714 ≦ nd4 ≦ −0.004 × νd4 + 1.844
When 51 ≦ νd4 <61
-0.0015 × νd4 + 1.5865 ≦ nd4 ≦ −0.004 × νd4 + 1.844
When 61 ≦ νd4 ≦ 71
-0.0015 × νd4 + 1.5865 ≦ nd4 ≦ −0.009 × νd4 + 2.149
However,
nd1: refractive index νd1: d-line (wavelength λ = 587.6 nm) of the negative lens material in the first lens group with respect to d-line (wavelength λ = 587.6 nm) of the negative lens material in the first lens group ) Abbe number nd4: refractive index νd4 for the positive lens material d-line (wavelength λ = 587.6 nm) in the fourth lens group: d-line (wavelength λ) of the positive lens material in the fourth lens group = Abbe number for 587.6 nm)

Also provided is an imaging apparatus comprising the zoom lens of the present invention.
The present invention also provides
In order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a fourth lens having a positive refractive power A zooming method for a zoom lens having a group,
Upon zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group decreases, the distance between the second lens group and the third lens group increases, The lens groups move along the optical axis so that the distance between the third lens group and the fourth lens group decreases,
The first lens group has a negative lens;
At least one of the negative lenses has an aspheric surface;
The zoom lens zooming method according to claim 1, wherein the negative lens in the first lens group satisfies the following conditional expressions (1) and (2).
(1) 30 ≦ νd1 ≦ 71
(2) When 30 ≦ νd1 <36
-0.013 × νd1 + 2.083 ≦ nd1 ≦ 1.7
When 36 ≦ νd1 <41
-0.013 × νd1 + 2.083 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 41 ≦ νd1 <51
-0.004 × νd1 + 1.714 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 51 ≦ νd1 <61
-0.0015 × νd1 + 1.5865 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 61 ≦ νd1 ≦ 71
-0.0015 × νd1 + 1.5865 ≦ nd1 ≦ −0.009 × νd1 + 2.149
However,
nd1: refractive index νd1: d-line (wavelength λ = 587.6 nm) of the negative lens material in the first lens group with respect to d-line (wavelength λ = 587.6 nm) of the negative lens material in the first lens group Abbe number for

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a zoom lens, an imaging device, and a zooming method that achieve high image quality.

Hereinafter, the zoom lens, the imaging device, and the zooming method of the present application will be described.
In general, each lens group constituting the zoom lens corrects aberrations as follows.
Correction of chromatic aberration is performed by combining a positive lens made of low refractive index and low dispersion glass and a negative lens made of high refractive index and high dispersion glass in the positive lens group, and low refractive index and low dispersion in the negative lens group. This is performed by combining a negative lens made of glass and a positive lens made of high refractive index and high dispersion glass. For this reason, it is necessary to set the refractive power of the positive lens large in the positive lens group, and to set the refractive power of the negative lens large in the negative lens group.

Further, various aberrations such as spherical aberration and coma need to be corrected to some extent inside each lens group. In general, various aberrations occur as the declination increases, and become more pronounced as the refractive index decreases.
Therefore, in order to correct various aberrations while correcting chromatic aberration in a zoom lens, it is effective to arrange a plurality of positive lenses in the positive lens group and a plurality of negative lenses in the negative lens group. Become.

  Based on the above assumptions, the zoom lens of the present application is a lightweight and inexpensive glass as a glass material for the positive lens in the positive lens group and the negative lens in the negative lens group in order to realize high performance with a small size and light weight. Is used.

The zoom lens of the present application includes, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a positive refraction. A fourth lens group having power, and when changing the magnification from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group decreases, and the second lens group and the second lens group The lens groups move along the optical axis such that the distance between the third lens group increases and the distance between the third lens group and the fourth lens group decreases, and the first lens group The negative lens in the first lens group satisfies the following conditional expressions (1) and (2).
(1) 30 ≦ νd1 ≦ 71
(2) When 30 ≦ νd1 <36
-0.013 × νd1 + 2.083 ≦ nd1 ≦ 1.7
When 36 ≦ νd1 <41
-0.013 × νd1 + 2.083 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 41 ≦ νd1 <51
-0.004 × νd1 + 1.714 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 51 ≦ νd1 <61
-0.0015 × νd1 + 1.5865 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 61 ≦ νd1 ≦ 71
-0.0015 × νd1 + 1.5865 ≦ nd1 ≦ −0.009 × νd1 + 2.149
However,
nd1: refractive index νd1: d-line of the negative lens material in the first lens group (wavelength λ = 587.6 nm) with respect to the d-line (wavelength λ = 587.6 nm) of the negative lens material in the first lens group Abbe number for

  Here, in the minus lead type four-group zoom lens having a wide angle of view, the diameter of the first lens group is large in order to secure the angle of view in the wide-angle end state, and the ratio of the total cost and weight is large. On the other hand, the third lens group, which does not contribute much to zooming and mainly handles adjustment of the principal point position and correction of aberrations, has a small diameter and a small proportion of the total cost and weight. In addition, the second lens group and the fourth lens group having positive refractive power have a large role of zooming, and in particular, the diameter of the fourth lens group is large in order to ensure a field angle in the wide-angle end state.

The conditional expression (1) is a conditional expression for appropriately setting the Abbe number of the negative lens in the first lens group having negative refractive power.
If the lower limit of conditional expression (1) is not reached, it will be difficult to correct lateral chromatic aberration in the wide-angle end state.

  On the other hand, if the upper limit value of conditional expression (1) is exceeded, the refractive index generally decreases, and it becomes difficult to correct spherical aberration, distortion, and the like.

The conditional expression (2) is a conditional expression for appropriately setting the refractive index of the negative lens in the first lens group having negative refractive power.
If the lower limit of conditional expression (2) is not reached, it will be difficult to simultaneously correct lateral chromatic aberration and negative distortion in the wide-angle end state.

  On the other hand, if the upper limit value of conditional expression (2) is exceeded, expensive glass such as heavy crown or lanthanum crown will be used as the glass material for the negative lens in the first lens group. Therefore, in order to avoid such an increase in weight and price, the number of lenses in the first lens group must be reduced. As a result, the same problem as that in the case where the value falls below the lower limit value described above is caused. It will occur remarkably.

In the zoom lens of the present application, it is preferable that the second lens group has a positive lens, and the positive lens in the second lens group satisfies the following conditional expressions (3) and (4).
(3) 30 ≦ νd2 ≦ 71
(4) When 30 ≦ νd2 <36
-0.013 × νd2 + 2.083 ≦ nd2 ≦ 1.7
When 36 ≦ νd2 <41
-0.013 × νd2 + 2.083 ≦ nd2 ≦ −0.004 × νd2 + 1.844
When 41 ≦ νd2 <51
-0.004 × νd2 + 1.714 ≦ nd2 ≦ −0.004 × νd2 + 1.844
When 51 ≦ νd2 <61
-0.0015 × νd2 + 1.5865 ≦ nd2 ≦ −0.004 × νd2 + 1.844
When 61 ≦ νd2 ≦ 71
-0.0015 × νd2 + 1.5865 ≦ nd2 ≦ −0.009 × νd2 + 2.149
However,
nd2: Refractive index νd2 for the positive lens material d-line (wavelength λ = 587.6 nm) in the second lens group: d-line (wavelength λ = 587.6 nm) for the positive lens material in the second lens group Abbe number for

The conditional expression (3) is a conditional expression for appropriately setting the Abbe number of the positive lens in the second lens group having a positive refractive power.
If the lower limit of conditional expression (3) is not reached, it will be difficult to correct lateral chromatic aberration in the wide-angle end state.

  On the other hand, if the upper limit value of conditional expression (3) is exceeded, the refractive index generally decreases, and it becomes difficult to correct spherical aberration, distortion, and the like.

The conditional expression (4) is a conditional expression for appropriately setting the refractive index of the positive lens in the second lens group having positive refractive power.
If the lower limit of conditional expression (4) is not reached, it will be difficult to simultaneously correct spherical aberration and axial chromatic aberration in the telephoto end state.

  On the other hand, if the upper limit value of conditional expression (4) is exceeded, expensive glass such as heavy crown or lanthanum crown will be used as the glass material for the positive lens in the second lens group. Therefore, in order to avoid such an increase in weight and price, the number of lenses in the second lens group must be reduced. As a result, the same problem as that in the case where the value falls below the above lower limit value is caused. It will occur remarkably.

In the zoom lens of the present application, it is preferable that the fourth lens group has a positive lens, and the positive lens in the fourth lens group satisfies the following conditional expressions (5) and (6).
(5) 30 ≦ νd4 ≦ 71
(6) When 30 ≦ νd4 <36
-0.013 × νd4 + 2.083 ≦ nd4 ≦ 1.7
When 36 ≦ νd4 <41
-0.013 × νd4 + 2.083 ≦ nd4 ≦ −0.004 × νd4 + 1.844
When 41 ≦ νd4 <51
-0.004 × νd4 + 1.714 ≦ nd4 ≦ −0.004 × νd4 + 1.844
When 51 ≦ νd4 <61
-0.0015 × νd4 + 1.5865 ≦ nd4 ≦ −0.004 × νd4 + 1.844
When 61 ≦ νd4 ≦ 71
-0.0015 × νd4 + 1.5865 ≦ nd4 ≦ −0.009 × νd4 + 2.149
However,
nd4: refractive index νd4 for the positive lens material d-line (wavelength λ = 587.6 nm) in the fourth lens group: d-line (wavelength λ = 587.6 nm) for the positive lens material in the fourth lens group Abbe number for

The conditional expression (5) is a conditional expression for appropriately setting the Abbe number of the positive lens in the fourth lens group having a positive refractive power.
If the lower limit of conditional expression (5) is not reached, it will be difficult to correct lateral chromatic aberration in the wide-angle end state.

  On the other hand, if the upper limit value of conditional expression (5) is exceeded, the refractive index generally decreases, making it difficult to correct spherical aberration, distortion, and the like.

The conditional expression (6) is a conditional expression for appropriately setting the refractive index of the positive lens in the fourth lens group having a positive refractive power.
If the lower limit of conditional expression (6) is not reached, it will be difficult to simultaneously correct lateral chromatic aberration and field curvature aberration in the wide-angle end state, coma aberration in the intermediate focal length state, and axial chromatic aberration in the telephoto end state. End up.

  On the other hand, if the upper limit value of conditional expression (6) is exceeded, expensive glass such as heavy crown or lanthanum crown will be used as the glass material of the positive lens in the fourth lens group. Therefore, in order to avoid such an increase in weight and price, the number of lenses in the fourth lens group must be reduced. As a result, the same problem as that in the case where the value falls below the lower limit value described above is caused. It will occur remarkably.

In the zoom lens according to the present application, the first lens group includes, in order from the object side, a negative meniscus lens having a convex object side lens surface, a negative lens having a concave image side lens surface, and a positive lens having a convex object side lens surface. It is desirable to satisfy the following conditional expression (7).
(7) 0.7 ≦ (−f1) /fw≦1.7
However,
f1: Focal length fw of the first lens group fw: Focal length of the zoom lens in the wide-angle end state

  In general, as a method for suppressing the enlargement of the front lens diameter, that is, the diameter of the lens closest to the object side, while securing a sufficient angle of view in the zoom lens, a negative lens is disposed on the object side in the first lens group. It is well known. In addition, by arranging a plurality of negative lenses in the first lens group, it becomes possible to satisfactorily correct various aberrations relating to the angle of view such as field curvature aberration and distortion. The occurrence of aberration can be prevented by making the surface aplanatic toward the aperture stop. Further, by arranging a positive lens in the first lens group, it is possible to achieve both correction of chromatic aberration and correction of spherical aberration.

  As described above, in this zoom lens, when focusing on the correction of the field angle aberration in the wide-angle end state and the image side lens surface of the second negative lens from the object side in the first lens group is concave, the telephoto end state In this case, a large amount of spherical aberration occurs. Therefore, in order to correct this spherical aberration, a lens having a convex lens surface on the object side is required immediately after the second negative lens from the object side (image side), and this lens has a need for correcting chromatic aberration. It becomes a positive lens in consideration.

The conditional expression (7) is a conditional expression for defining the focal length of the first lens group.
If the lower limit of conditional expression (7) is not reached, it will be difficult to correct various aberrations relating to the angle of view such as distortion, curvature of field and astigmatism in the wide-angle end state.
If the lower limit value of conditional expression (7) is set to 1.0, more preferably 1.4, the effect of the present application can be further exerted.

  On the other hand, if the upper limit value of conditional expression (7) is exceeded, it is possible to correct the above-mentioned various aberrations, but it becomes difficult to ensure the back focus. Therefore, in order to ensure the back focus, the focal length of the third lens group must be reduced. As a result, it becomes difficult to correct spherical aberration in the telephoto end state and coma aberration over the entire zoom range. End up.

The zoom lens of the present application preferably includes at least one aspheric surface in the first lens group.
With this configuration, it is possible to satisfactorily correct field curvature aberration and astigmatism.

In the zoom lens of the present application, at least one of the image side lens surface of the negative meniscus lens and the image side lens surface of the negative lens in the first lens group is the aspheric surface, and the following conditional expression (8) is satisfied. It is desirable to do.
(8) 0.32 ≦ Rasp / (− f1) ≦ 1.0
However,
Rasp: Paraxial radius of curvature of the aspheric surface f1: Focal length of the first lens group

The conditional expression (8) is a conditional expression that defines the shape in order to set the degree of aberration correction performed by the aspherical surface in the first lens group.
If the upper limit value of conditional expression (8) is exceeded, the paraxial radius of curvature of the aspheric surface in the first lens group will become smaller. For this reason, it becomes difficult to correct aberration related to the angle of view such as distortion in the wide-angle end state by the aspheric surface.
In addition, if the upper limit of conditional expression (8) is set to 0.8, the effect of the present application can be exhibited more.

On the other hand, if the lower limit value of conditional expression (8) is not reached, the paraxial radius of curvature of the aspheric surface in the first lens group becomes large. For this reason, correction of spherical aberration generated on the paraxial spherical surface itself in the telephoto end state must be performed by the aspheric surface, which is difficult.
In addition, if the lower limit of conditional expression (8) is set to 0.37, the effect of the present application can be exhibited more.

In the zoom lens of the present application, it is desirable that the second lens group is composed of two positive lenses and one negative lens.
As described above, by arranging a plurality of positive lenses in the second lens group having a positive refractive power, various aberrations including chromatic aberration can be favorably corrected. Further, a positive lens is disposed on the object side, and a negative lens is disposed on the image side, thereby providing a telephoto type, and a bright F number is ensured in the telephoto end state.

In the zoom lens of the present application, in the second lens group, it is preferable that one of the two positive lenses and the one negative lens are cemented.
With this configuration, various aberrations including chromatic aberration can be corrected more favorably.

In the zoom lens according to the present application, it is preferable that the third lens group includes one positive lens and one negative lens.
With this configuration, it is possible to satisfactorily correct various aberrations including chromatic aberration. Further, by arranging a positive lens on the object side and a negative lens on the image side, the principal point position is adjusted in accordance with the telephoto conversion of the second lens group and the fourth lens group. An air space between the three lens groups can be secured.

The zoom lens of the present application has an aperture stop in the vicinity of the third lens group,
It is desirable that the aperture stop moves integrally with the third lens group.
As described above, in this zoom lens optical system, the aperture stop is disposed in the vicinity of the third lens group in which the land light beam (the light beam that reaches the image height of 0 and which is farthest from the optical axis) is narrowed. This is preferable because the configuration of the lens barrel can be simplified.

In the zoom lens according to the present application, it is preferable that the fourth lens group includes two positive lenses and one negative lens.
In this way, a positive lens is arranged on the object side in the fourth lens group, and a negative lens is arranged on the image side, so that it is a telephoto type, and a bright F number is secured in the telephoto end state.

In the zoom lens according to the present application, it is desirable that the second lens group and the fourth lens group move integrally when zooming from the telephoto end state to the wide-angle end state.
This configuration is preferable because the configuration of the lens barrel can be simplified.

Moreover, it is desirable that the zoom lens of the present application satisfies the following conditional expression (9).
(9) 1.0 ≦ f2 / fw ≦ 2.3
However,
fw: focal length of the zoom lens in the wide-angle end state f2: focal length of the second lens group

The conditional expression (9) is a conditional expression for defining the focal length of the second lens group having a positive refractive power.
If the lower limit of conditional expression (9) is not reached, it will be difficult to correct spherical aberration in the telephoto end state.
If the lower limit value of conditional expression (9) is set to 1.3, the effect of the present application can be further exerted.

On the other hand, if the upper limit value of conditional expression (9) is exceeded, it will be difficult to ensure the zoom ratio. For this reason, the focal length of the fourth lens group must be reduced in order to ensure the zoom ratio, and as a result, it becomes difficult to correct distortion aberration in the wide-angle end state and coma aberration in the intermediate focal length state. turn into.
In addition, if the upper limit of conditional expression (9) is set to 2.0, the effect of this application can be exhibited more.

It is desirable that the zoom lens of the present application satisfies the following conditional expression (10).
(10) 0.8 ≦ (−f3) /fw≦3.0
However,
fw: focal length of the zoom lens in the wide-angle end state f3: focal length of the third lens group

The conditional expression (10) is a conditional expression for defining the focal length of the third lens group having negative refractive power.
If the lower limit of conditional expression (10) is not reached, it will be difficult to correct coma and spherical aberration over the entire zoom range.
In addition, if the lower limit of conditional expression (10) is set to 1.1, the effect of the present application can be further exhibited. If the lower limit value of conditional expression (10) is set to 1.2, the effect of the present application can be further exhibited.

On the other hand, if the upper limit of conditional expression (10) is exceeded, it will be difficult to ensure the back focus. For this reason, in order to ensure the back focus, the focal length of the first lens group must be reduced. As a result, various aberrations relating to the angle of view such as distortion and field curvature aberration in the wide-angle end state are corrected. It becomes difficult.
In addition, if the upper limit of conditional expression (10) is set to 2.5, the effect of this application can be exhibited more.

It is desirable that the zoom lens of the present application satisfies the following conditional expression (11).
(11) 0.8 ≦ f4 / fw ≦ 2.0
However,
fw: focal length of the zoom lens in the wide-angle end state f4: focal length of the fourth lens group

The conditional expression (11) is a conditional expression for defining the focal length of the fourth lens group having a positive refractive power.
If the lower limit of conditional expression (11) is not reached, it will be difficult to correct distortion in the wide-angle end state and coma aberration in the intermediate focal length state.
If the lower limit value of conditional expression (11) is set to 1.2, more preferably 1.5, the effect of the present application can be further exerted.
On the other hand, if the upper limit value of conditional expression (11) is exceeded, it will be difficult to correct spherical aberration particularly in the telephoto end state.

The imaging device of the present application includes the zoom lens having the above-described configuration.
As a result, it is possible to realize an imaging device that achieves high image quality.
The zoom lens zooming method according to the present application includes, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a negative refractive power. And a zoom lens zooming method comprising a fourth lens group having a positive refractive power, wherein the first lens group and the second lens group when zooming from the wide-angle end state to the telephoto end state, The respective lens groups are light so that the distance between the second lens group and the third lens group increases, and the distance between the third lens group and the fourth lens group decreases. Moving along the axis, the first lens group has a negative lens, and the negative lens in the first lens group satisfies the following conditional expressions (1) and (2).
(1) 30 ≦ νd1 ≦ 71
(2) When 30 ≦ νd1 <36
-0.013 × νd1 + 2.083 ≦ nd1 ≦ 1.7
When 36 ≦ νd1 <41
-0.013 × νd1 + 2.083 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 41 ≦ νd1 <51
-0.004 × νd1 + 1.714 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 51 ≦ νd1 <61
-0.0015 × νd1 + 1.5865 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 61 ≦ νd1 ≦ 71
-0.0015 × νd1 + 1.5865 ≦ nd1 ≦ −0.009 × νd1 + 2.149
However,
nd1: refractive index νd1: d-line (wavelength λ = 587.6 nm) of the negative lens material in the first lens group with respect to d-line (wavelength λ = 587.6 nm) of the negative lens material in the first lens group Abbe's number with respect to () With this configuration, it is possible to improve the image quality of the zoom lens.

Hereinafter, zoom lenses according to numerical examples of the present application will be described with reference to the accompanying drawings.
(First embodiment)
FIG. 1 is a diagram showing a configuration of a zoom lens according to the first embodiment of the present application and a movement locus of each lens group.
The zoom lens according to the present embodiment has, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, an aperture stop S, and a negative refractive power. The third lens group G3 includes a fourth lens group G4 having a positive refractive power, and a flare cut stop FS. Then, upon zooming from the wide-angle end state (W) to the telephoto end state (T), the distance between the first lens group G1 and the second lens group G2 decreases, and the second lens group G2 and the third lens group G3. The lens groups G1, G2, G3, and G4 move along the optical axis so that the distance between the third lens group G3 and the fourth lens group G4 decreases.

The first lens group G1, in order from the object side, includes a negative meniscus lens L1 having a convex surface facing the object side, a negative meniscus lens L2 having a convex surface facing the object side, and a positive meniscus lens L3 having a convex surface facing the object side. Consists of.
The second lens group G2 includes, in order from the object side, a biconvex positive lens L4, and a cemented lens of a biconvex positive lens L5 and a biconcave negative lens L6.

The third lens group G3 includes, in order from the object side, a cemented lens of a positive meniscus lens L7 having a convex surface directed toward the image side and a biconcave negative lens L8.
The fourth lens group G4 includes, in order from the object side, a positive meniscus lens L9 having a convex surface directed to the image side, a cemented lens of a biconvex positive lens L10 and a negative meniscus lens L11 having a convex surface directed to the image side. Become.

The aperture stop S is disposed in the vicinity of the third lens group G3 on the object side, and moves integrally with the third lens group G3 upon zooming from the wide-angle end state to the telephoto end state.
In addition, the flare cut stop FS is disposed on the image side of the fourth lens group G4, so that coma flare with an intermediate image height can be effectively removed.

Table 1 below lists values of specifications of the zoom lens according to the first example of the present application.
In [Overall specifications], f represents a focal length, FNO represents an F number, and 2ω represents an angle of view.
In [Lens data], the surface represents the order of the lens surfaces from the object side, r represents the radius of curvature of the lens surfaces, and d represents the distance between the lens surfaces. Further, nd represents the refractive index with respect to the d line (λ = 587.6 nm), and νd represents the Abbe number with respect to the d line (λ = 587.6 nm). Furthermore, an aspherical surface in the lens data is marked with an asterisk (*) and the paraxial radius of curvature is indicated in the column of curvature radius r, and κ and each aspherical coefficient are described in the column of [Aspherical data]. To do. Further, the radius of curvature r = 0.000 indicates a plane, and the refractive index nd = 1.00000 of air is omitted from the description.

In [Aspherical data], “En” indicates “× 10 ⁻ⁿ ”. The rotationally symmetric aspherical surface shown in the specification table has a distance (sag amount) along the optical axis direction from the tangential plane of the apex of each aspherical surface at a height y in the vertical direction from the optical axis, X (y), and a reference spherical surface Where the radius of curvature is r, the cone coefficient is κ, and the n-th order aspheric coefficient is C n, the following aspheric expression is used. Note that the description of the aspherical coefficient that is 0 (zero) is omitted.
X (y) = (y ² / r) / [1+ (1−κ · y ² / r ² ) ^1/2 ]
+ C4 · y ⁴ + C6 · y ⁶ + C8 · y ⁸ + C10 · y ¹⁰ + C12 · y ¹²

In [lens data] and “variable interval data”, BF indicates back focus.
In [Conditional Expression Corresponding Value], when there are a plurality of corresponding lenses, a plurality of conditional expression corresponding values are also shown. The lens L2 is formed with a thin resin layer on the surface of the base lens. In this case, the base lens is the corresponding lens.
Here, the unit of the focal length f, the radius of curvature r, and other lengths listed in all the following specification values is generally “mm”. However, the optical system is not limited to this because an equivalent optical performance can be obtained even when proportional expansion or proportional reduction is performed.
In addition, also in the specification values of all the following examples, the same symbols as in this example are used.

(Table 1)
[Overall specifications]
f = 18.54 to 53.4
FNO = 3.6 to 5.9
2ω = 29.86 to 78.18 °

[Lens data]
Surface r d nd νd
1 87.9379 1.0000 1.516330 64.14
2 16.8369 9.6060
3 126.9038 1.0000 1.516330 64.14
4 21.4987 0.1500 1.553890 38.09
* 5 17.6389 3.9380
6 32.8432 3.5080 1.761821 26.52
7 81.9946 D07

8 53.2062 2.5000 1.516330 64.14
9 -51.8953 0.6926
10 22.9065 3.5000 1.516330 64.14
11 -33.8880 1.0000 1.761820 26.52
12 1827.6963 D12

13 0.0000 1.0027 Aperture stop S
14 -55.3061 2.0000 1.805180 25.43
15 -19.0973 1.0000 1.772500 49.61
16 46.4291 D16

17 -158.1401 2.5505 1.516330 64.14
18 -20.5717 0.4757
19 66.3104 4.6196 1.516330 64.14
20 -15.9854 1.0000 1.806100 33.25
21 -49.1416 D21

22 0.0000 BF Flare cut aperture FS

[Aspherical data]
<Fifth lens surface>
κ = -1.00000
C4 = -1.12900E-05
C6 = -2.73590E-08
C8 = -7.88710E-11
C10 = 8.89590E-14
C12 = 0.00000

[Variable interval data]
Wide-angle end state Intermediate focal length state Telephoto end state f 18.50000 35.00000 53.40000
D07 28.64500 7.97760 1.21180
D12 2.84980 9.20440 13.66200
D16 12.31840 5.97110 1.50000
D21 0.00000 12.58520 27.58320
BF 38.50001 38.49995 38.49998

[Conditional expression values]
Conditional expression (1) νd1 = 64.14 (L1), 64.14 (L2)
Conditional expression (2) nd1 = 1.516330 (L1), 1.516330 (L2)
Conditional expression (3) νd2 = 64.14 (L4), 64.14 (L5)
Conditional expression (4) nd2 = 1.516330 (L4), 1.516330 (L5)
Conditional expression (5) νd4 = 64.14 (L9), 64.14 (L10)
Conditional expression (6) nd4 = 1.516330 (L9), 1.516330 (L10)
Conditional expression (7) (−f1) /fw=1.473
Conditional expression (8) Rasp / (− f1) = 0.646
Conditional expression (9) f2 / fw = 1.556
Conditional expression (10) (−f3) /fw=1.807
Conditional expression (11) f4 / fw = 1.923

  2A, 2B, and 2C are graphs showing various aberrations of the zoom lens according to Example 1 of the present application in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively.

In each aberration diagram, FNO represents an F number, Y represents an image height, and A represents a half angle of view (unit: “°”). In the astigmatism diagram and the distortion diagram, the maximum value of the image height Y is shown. D and g indicate aberration curves of the d-line (λ = 587.6 nm) and the g-line (λ = 435.8 nm), respectively. In the spherical aberration diagram, FNO represents the F-number value corresponding to the maximum aperture. In the astigmatism diagram, the solid line indicates the sagittal image plane, and the dotted line indicates the meridional image plane. The coma aberration diagram represents the coma aberration at each half angle of view.
In addition, in the various aberration diagrams of each example shown below, the same reference numerals as those in this example are used.

  From the various aberration diagrams, the zoom lens according to the present embodiment corrects various aberrations well in each of the wide-angle end state, the intermediate focal length state, and the telephoto end state, and has excellent imaging performance. I understand that.

(Second embodiment)
FIG. 3 is a diagram showing the configuration of the zoom lens according to the second embodiment of the present application and the movement locus of each lens group.
The zoom lens according to the present embodiment has, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, an aperture stop S, and a negative refractive power. The third lens group G3 includes a fourth lens group G4 having a positive refractive power, and a flare cut stop FS. When zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group G1 and the second lens group G2 decreases, and the distance between the second lens group G2 and the third lens group G3 increases. The lens groups G1, G2, G3, and G4 move along the optical axis so that the distance between the third lens group G3 and the fourth lens group G4 decreases.

The first lens group G1 includes, in order from the object side, a negative meniscus lens L1 having a convex surface facing the object side, a biconcave negative lens L2, and a positive meniscus lens L3 having a convex surface facing the object side.
The second lens group G2 includes, in order from the object side, a biconvex positive lens L4, and a cemented lens of a biconvex positive lens L5 and a biconcave negative lens L6.

The third lens group G3 includes, in order from the object side, a cemented lens of a positive meniscus lens L7 having a convex surface directed toward the image side and a biconcave negative lens L8.
The fourth lens group G4 includes, in order from the object side, a positive meniscus lens L9 having a convex surface directed to the image side, a cemented lens of a biconvex positive lens L10 and a negative meniscus lens L11 having a convex surface directed to the image side. Become.

The aperture stop S is disposed in the vicinity of the third lens group G3 on the object side, and moves integrally with the third lens group G3 upon zooming from the wide-angle end state to the telephoto end state.
In addition, the flare cut stop FS is disposed on the image side of the fourth lens group G4, so that coma flare with an intermediate image height can be effectively removed.
Table 2 below lists values of specifications of the zoom lens according to the second example of the present application.

(Table 2)
[Overall specifications]
f = 18.54 to 53.4
FNO = 3.6 to 5.9
2ω = 29.86 to 78.18 °

[Lens data]
Surface r d nd νd
1 74.9810 1.0000 1.518230 58.96
2 18.9515 0.1500 1.553890 38.09
* 3 17.0398 8.0792
4 -93.0897 1.0000 1.516330 64.14
5 30.6538 5.3426
6 43.2507 2.5593 1.717362 29.51
7 133.4367 D07

8 92.6644 2.5000 1.518230 58.96
9 -36.6670 0.1000
10 19.6861 3.5000 1.518230 58.96
11 -37.9326 1.0000 1.740770 27.79
12 129.7648 D12

13 0.0000 1.9230 Aperture stop S
14 -42.8152 3.0000 1.805180 25.43
15 -13.8958 1.0000 1.772500 49.61
16 40.6606 D16

17 -101.5211 2.4781 1.516330 64.14
18 -19.8792 0.1000
19 74.2885 4.4863 1.516330 64.14
20 -15.6848 1.0000 1.805180 25.43
21 -37.5298 D21

22 0.0000 BF Flare cut aperture FS


[Aspherical data]
<Third lens surface>
κ = -1.00000
C4 = 1.00718E-05
C6 = 1.56467E-08
C8 = -4.55652E-11
C10 = 9.30745E-14
C12 = 0.00000

[Variable interval data]
Wide-angle end state Intermediate focal length state Telephoto end state f 18.50000 35.00000 53.40000
D07 31.74720 8.60140 1.10000
D12 3.09030 7.78510 11.38190
D16 9.79790 5.11060 1.50000
D21 0.00000 12.78450 27.24450
BF 38.49979 38.49921 38.49668

[Conditional expression values]
Conditional expression (1) νd1 = 58.96 (L1), 64.14 (L2)
Conditional expression (2) nd1 = 1.518230 (L1), 1.516330 (L2)
Conditional expression (3) νd2 = 58.96 (L4), 58.96 (L5)
Conditional expression (4) nd2 = 1.518230 (L4), 1.518230 (L5)
Conditional expression (5) νd4 = 64.14 (L9), 64.14 (L10)
Conditional expression (6) nd4 = 1.516330 (L9), 1.516330 (L10)
Conditional expression (7) (−f1) /fw=1.582
Conditional expression (8) Rasp / (− f1) = 0.581
Conditional expression (9) f2 / fw = 1.518
Conditional expression (10) (−f3) /fw=1.492
Conditional expression (11) f4 / fw = 1.754

FIGS. 4A, 4B, and 4C show various aberration diagrams of the zoom lens according to Example 2 of the present application in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively.
From the various aberration diagrams, the zoom lens according to the present embodiment corrects various aberrations well in each of the wide-angle end state, the intermediate focal length state, and the telephoto end state, and has excellent imaging performance. I understand that.

(Third embodiment)
FIG. 5 is a diagram showing the configuration of the zoom lens according to the third embodiment of the present application and the movement locus of each lens group.
The zoom lens according to the present embodiment has, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, an aperture stop S, and a negative refractive power. The third lens group G3 includes a fourth lens group G4 having a positive refractive power, and a flare cut stop FS. When zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group G1 and the second lens group G2 decreases, and the distance between the second lens group G2 and the third lens group G3 increases. The lens groups G1, G2, G3, and G4 move along the optical axis so that the distance between the third lens group G3 and the fourth lens group G4 decreases.

The first lens group G1 includes, in order from the object side, a negative meniscus lens L1 having a convex surface facing the object side, a biconcave negative lens L2, and a positive meniscus lens L3 having a convex surface facing the object side.
The second lens group G2 includes, in order from the object side, a biconvex positive lens L4, and a cemented lens of a biconvex positive lens L5 and a biconcave negative lens L6.

The third lens group G3 includes, in order from the object side, a cemented lens of a positive meniscus lens L7 having a convex surface directed toward the image side and a biconcave negative lens L8.
The fourth lens group G4 includes, in order from the object side, a positive meniscus lens L9 having a convex surface directed to the image side, a cemented lens of a biconvex positive lens L10 and a negative meniscus lens L11 having a convex surface directed to the image side. Become.

The aperture stop S is disposed in the vicinity of the third lens group G3 on the object side, and moves integrally with the third lens group G3 upon zooming from the wide-angle end state to the telephoto end state.
In addition, the flare cut stop FS is disposed on the image side of the fourth lens group G4, so that coma flare with an intermediate image height can be effectively removed.
Table 3 below lists values of specifications of the zoom lens according to the third example of the present application.

(Table 3)
[Overall specifications]
f = 18.54 to 53.4
FNO = 3.6 to 5.9
2ω = 29.86 to 78.18 °

[Lens data]
Surface r d nd νd
1 60.7025 1.0000 1.672700 32.11
2 20.1309 0.1500 1.553890 38.09
* 3 18.0307 7.8820
4 -67.9454 1.0000 1.516330 64.14
5 33.0065 5.1397
6 49.5584 3.2468 1.846660 23.78
7 256.7070 D07

8 111.0735 2.5188 1.581440 40.75
9 -40.8980 0.1000
10 19.5663 3.6188 1.516330 64.14
11 -42.8673 1.0000 1.805180 25.43
12 144.3448 D12

13 0.0000 3.0610 Aperture stop S
14 -43.9310 3.0000 1.805180 25.43
15 -13.9063 1.0000 1.772500 49.61
16 41.4061 D16

17 -124.9960 2.6553 1.516330 64.14
18 -18.7086 0.1000
19 67.1213 4.5017 1.516330 64.14
20 -15.4403 1.0000 1.805180 25.43
21 -46.9391 D21

22 0.0000 BF Flare cut aperture FS

[Aspherical data]
<Third lens surface>
κ = -1.00000
C4 = 6.47860E-06
C6 = 7.00070E-09
C8 = -5.09980E-11
C10 = 8.35270E-14
C12 = 0.00000

[Variable interval data]
Wide-angle end state Intermediate focal length state Telephoto end state f 18.50000 35.00000 53.40000
D07 34.42460 9.46090 1.10000
D12 1.82350 6.06090 9.24630
D16 9.22650 4.99530 1.79820
D21 0.00000 13.00890 28.00000
BF 38.49996 38.49984 38.49996

[Conditional expression values]
Conditional expression (1) νd1 = 32.11 (L1), 64.14 (L2)
Conditional expression (2) nd1 = 1.67270 (L1), 1.516330 (L2)
Conditional expression (3) νd2 = 40.75 (L4), 64.14 (L5)
Conditional expression (4) nd2 = 1.581440 (L4), 1.516330 (L5)
Conditional expression (5) νd4 = 64.14 (L9), 64.14 (L10)
Conditional expression (6) nd4 = 1.516330 (L9), 1.516330 (L10)
Conditional expression (7) (−f1) /fw=1.635
Conditional expression (8) Rasp / (− f1) = 0.595
Conditional expression (9) f2 / fw = 1.553
Conditional expression (10) (−f3) /fw=1.528
Conditional expression (11) f4 / fw = 1.807

FIGS. 6A, 6B, and 6C are graphs showing various aberrations of the zoom lens according to the third example of the present application in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively.
From the various aberration diagrams, the zoom lens according to the present embodiment corrects various aberrations well in each of the wide-angle end state, the intermediate focal length state, and the telephoto end state, and has excellent imaging performance. I understand that.

(Fourth embodiment)
FIG. 7 is a diagram showing the configuration of a zoom lens according to the fourth example of the present application and the movement locus of each lens group.
The zoom lens according to the present embodiment has, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, an aperture stop S, and a negative refractive power. The third lens group G3 includes a fourth lens group G4 having a positive refractive power, and a flare cut stop FS. When zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group G1 and the second lens group G2 decreases, and the distance between the second lens group G2 and the third lens group G3 increases. The lens groups G1, G2, G3, and G4 move along the optical axis so that the distance between the third lens group G3 and the fourth lens group G4 decreases.

The first lens group G1 includes, in order from the object side, a negative meniscus lens L1 having a convex surface facing the object side, a biconcave negative lens L2, and a positive meniscus lens L3 having a convex surface facing the object side.
The second lens group G2 includes, in order from the object side, a biconvex positive lens L4, and a cemented lens of a biconvex positive lens L5 and a biconcave negative lens L6.

The third lens group G3 includes, in order from the object side, a cemented lens of a positive meniscus lens L7 having a convex surface directed toward the image side and a biconcave negative lens L8.
The fourth lens group G4 includes, in order from the object side, a positive meniscus lens L9 having a convex surface directed to the image side, a cemented lens of a biconvex positive lens L10 and a negative meniscus lens L11 having a convex surface directed to the image side. Become.

The aperture stop S is disposed in the vicinity of the third lens group G3 on the object side, and moves integrally with the third lens group G3 upon zooming from the wide-angle end state to the telephoto end state.
In addition, the flare cut stop FS is disposed on the image side of the fourth lens group G4, so that coma flare with an intermediate image height can be effectively removed.
Table 4 below provides values of specifications of the zoom lens according to the fourth example of the present application.

(Table 4)
[Overall specifications]
f = 18.54 to 53.4
FNO = 3.6 to 5.9
2ω = 29.86 to 78.18 °

[Lens data]
Surface r d nd νd
1 95.7286 1.0000 1.517420 52.42
2 19.5918 0.1500 1.553890 38.09
* 3 17.4913 7.4525
4 -132.5935 1.0000 1.518230 58.96
5 29.4829 5.7549
6 41.3914 2.5000 1.761820 26.52
7 106.6932 D07

8 75.4871 2.5000 1.517420 52.42
9 -40.2097 0.1000
10 19.4944 3.5000 1.518230 58.96
11 -35.2115 1.0000 1.740770 27.79
12 110.7457 D12

13 0.0000 2.4103 Aperture stop S
14 -44.0740 3.0000 1.805180 25.43
15 -14.3817 1.0000 1.772500 49.61
16 42.8437 D16

17 -142.5530 2.7062 1.517420 52.42
18 -18.5433 0.1000
19 58.6387 4.5744 1.518230 58.96
20 -15.5034 1.0000 1.805180 25.43
21 -51.5403 D21

22 0.0000 BF Flare cut aperture FS

[Aspherical data]
<Third lens surface>
κ = -1.00000
C4 = 8.22140E-06
C6 = 3.35360E-09
C8 = -2.56140E-11
C10 = 4.91920E-14
C12 = 0.00000

[Variable interval data]
Wide-angle end state Intermediate focal length state Telephoto end state f 18.50000 35.00000 53.40000
D07 32.30390 8.92870 1.10000
D12 1.91770 6.52440 9.75010
D16 9.46300 4.86680 1.62190
D21 0.00000 12.82500 28.00000
BF 38.49944 38.49907 38.49945

[Conditional expression values]
Conditional expression (1) νd1 = 52.42 (L1), 58.96 (L2)
Conditional expression (2) nd1 = 1.517420 (L1), 1.518230 (L2)
Conditional expression (3) νd2 = 52.42 (L4), 58.96 (L5)
Conditional expression (4) nd2 = 1.517420 (L4), 1.518230 (L5)
Conditional expression (5) νd4 = 52.42 (L9), 58.96 (L10)
Conditional expression (6) nd4 = 1.517420 (L9), 1.518230 (L10)
Conditional expression (7) (−f1) /fw=1.614
Conditional expression (8) Rasp / (− f1) = 0.484
Conditional expression (9) f2 / fw = 1.564
Conditional expression (10) (−f3) /fw=1.556
Conditional expression (11) f4 / fw = 1.864

FIGS. 8A, 8B, and 8C show various aberration diagrams of the zoom lens according to Example 4 of the present application in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively.
From the various aberration diagrams, the zoom lens according to the present embodiment corrects various aberrations well in each of the wide-angle end state, the intermediate focal length state, and the telephoto end state, and has excellent imaging performance. I understand that.

According to each of the embodiments described above, it is possible to realize a zoom lens with high image quality that is particularly suitable for a single-lens reflex digital camera.
The numerical examples of the zoom lens of the present application are shown as having a four-group configuration. However, the group configuration of the zoom lens of the present application is not limited to this, and a zoom lens having another group configuration such as a third group or a fifth group is configured. You can also

  In the zoom lens of the present application, in order to focus from an object at infinity to an object at a short distance, a part of the lens group, one lens group, or a plurality of lens groups is used as the focusing lens group in the optical axis direction. It is good also as a structure to which it moves. This focusing lens group can be applied to autofocus, and is also suitable for driving an autofocus motor, such as an ultrasonic motor. In the zoom lens of the present application, it is particularly preferable that the first lens group is a focusing lens group.

In the zoom lens of the present application, in order to correct image blur caused by camera shake, a part of the lens group or one lens group may be moved as a vibration-proof lens group in a direction perpendicular to the optical axis. Good. In the zoom lens of the present application, it is particularly preferable that the third lens group is an anti-vibration lens group.
Each lens group constituting the zoom lens of the present application has an aspheric surface not only in the first lens group but also in other lens groups such as the second lens group, the third lens group, or the fourth lens group. You may do it. This aspherical surface may be any of an aspherical surface by grinding, a glass mold aspherical surface obtained by molding glass into an aspherical shape, or a composite aspherical surface in which a resin provided on the glass surface is formed into an aspherical shape.

Further, an antireflection film having a high transmittance in a wide wavelength range may be provided on the lens surface of the lens constituting the zoom lens of the present application. Thereby, flare and ghost can be reduced, and high optical performance can be achieved with high contrast.
Also in the negative lens of the third lens group, conditional expressions (1) and (2) equivalent to the negative lens of the first lens group may be satisfied.
In addition, each said Example has shown one specific example of this application, and this application is not limited to these.

Next, a camera equipped with the zoom lens of the present application will be described with reference to FIG.
FIG. 9 is a diagram illustrating a configuration of a camera including the zoom lens of the present application.
The camera 1 is a digital single-lens reflex camera provided with the zoom lens according to the first embodiment as a photographing lens 2 as shown in FIG.

  In the camera 1, light from an object (subject) (not shown) is collected by the taking lens 2 and imaged on the focusing screen 4 through the quick return mirror 3. The light imaged on the focusing screen 4 is reflected a plurality of times in the pentaprism 5 and guided to the eyepiece lens 6. Thus, the photographer can observe the subject image as an erect image through the eyepiece 6.

  When the release button (not shown) is pressed by the photographer, the quick return mirror 3 is retracted out of the optical path, and light from the subject (not shown) reaches the image sensor 7. Thereby, the light from the subject is picked up by the image pickup device 7 and recorded as a subject image in a memory (not shown). In this way, the photographer can shoot the subject with the camera 1.

Here, as described in the first embodiment, the zoom lens according to the first embodiment mounted on the camera 1 as the photographing lens 2 achieves high image quality by its characteristic lens configuration and zooming method. Has been. As a result, the camera 1 can achieve high image quality.
The present application is not limited to the above, and the same effect as that of the camera 1 can be obtained even if a camera in which the zoom lens according to the second embodiment, the third embodiment, or the fourth embodiment is mounted as the photographing lens 2 is configured. Of course you can play.

  As described above, it is possible to realize a zoom lens, an imaging device, and a zooming method that achieve high image quality particularly suitable for a single-lens reflex digital camera.

It is a figure which shows the structure of the zoom lens which concerns on 1st Example of this application, and the movement locus | trajectory of each lens group. (A), (b), and (c) show various aberration diagrams in the wide-angle end state, intermediate focal length state, and telephoto end state of the zoom lens according to Example 1 of the present application, respectively. It is a figure which shows the structure of the zoom lens which concerns on 2nd Example of this application, and the movement locus | trajectory of each lens group. (A), (b), and (c) show various aberration diagrams in the wide-angle end state, intermediate focal length state, and telephoto end state of the zoom lens according to Example 2 of the present application, respectively. It is a figure which shows the structure of the zoom lens which concerns on 3rd Example of this application, and the movement locus | trajectory of each lens group. (A), (b), and (c) show various aberration diagrams of the zoom lens according to the third example of the present application in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. It is a figure which shows the structure of the zoom lens which concerns on 4th Example of this application, and the movement locus | trajectory of each lens group. (A), (b), and (c) show various aberration diagrams in the wide-angle end state, intermediate focal length state, and telephoto end state of the zoom lens according to Example 4 of the present application, respectively. It is a figure which shows the structure of the camera provided with the zoom lens of this application.

Explanation of symbols

G1 First lens group G2 Second lens group G3 Third lens group G4 Fourth lens group S Aperture stop FS Flare cut stop I Image plane W Wide-angle end state M Intermediate focal length state T Telephoto end state

Claims (18)

In order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a fourth lens having a positive refractive power And having a group
Upon zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group decreases, the distance between the second lens group and the third lens group increases, The lens groups move along the optical axis so that the distance between the third lens group and the fourth lens group decreases,
The first lens group has a negative lens;
At least one of the negative lenses has an aspheric surface;
The zoom lens according to claim 1, wherein the negative lens in the first lens group satisfies the following conditional expression.
30 ≦ νd1 ≦ 71
When 30 ≦ νd1 <36
-0.013 × νd1 + 2.083 ≦ nd1 ≦ 1.7
When 36 ≦ νd1 <41
-0.013 × νd1 + 2.083 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 41 ≦ νd1 <51
-0.004 × νd1 + 1.714 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 51 ≦ νd1 <61
-0.0015 × νd1 + 1.5865 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 61 ≦ νd1 ≦ 71
-0.0015 × νd1 + 1.5865 ≦ nd1 ≦ −0.009 × νd1 + 2.149
However,
nd1: refractive index νd1: d-line (wavelength λ = 587.6 nm) of the negative lens material in the first lens group with respect to d-line (wavelength λ = 587.6 nm) of the negative lens material in the first lens group Abbe number for In order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a fourth lens having a positive refractive power And having a group
Upon zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group decreases, the distance between the second lens group and the third lens group increases, The lens groups move along the optical axis so that the distance between the third lens group and the fourth lens group decreases,
The first lens group has a negative lens;
The second lens group includes a positive lens,
The zoom lens according to claim 1, wherein the negative lens in the first lens group and the positive lens in the second lens group satisfy the following conditional expression.
30 ≦ νd1 ≦ 71
When 30 ≦ νd1 <36
-0.013 × νd1 + 2.083 ≦ nd1 ≦ 1.7
When 36 ≦ νd1 <41
-0.013 × νd1 + 2.083 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 41 ≦ νd1 <51
-0.004 × νd1 + 1.714 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 51 ≦ νd1 <61
-0.0015 × νd1 + 1.5865 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 61 ≦ νd1 ≦ 71
-0.0015 × νd1 + 1.5865 ≦ nd1 ≦ −0.009 × νd1 + 2.149
30 ≦ νd2 ≦ 71
When 30 ≦ νd2 <36
-0.013 × νd2 + 2.083 ≦ nd2 ≦ 1.7
When 36 ≦ νd2 <41
-0.013 × νd2 + 2.083 ≦ nd2 ≦ −0.004 × νd2 + 1.844
When 41 ≦ νd2 <51
-0.004 × νd2 + 1.714 ≦ nd2 ≦ −0.004 × νd2 + 1.844
When 51 ≦ νd2 <61
-0.0015 × νd2 + 1.5865 ≦ nd2 ≦ −0.004 × νd2 + 1.844
When 61 ≦ νd2 ≦ 71
-0.0015 × νd2 + 1.5865 ≦ nd2 ≦ −0.009 × νd2 + 2.149
However,
nd1: refractive index νd1: d-line (wavelength λ = 587.6 nm) of the negative lens material in the first lens group with respect to d-line (wavelength λ = 587.6 nm) of the negative lens material in the first lens group ) Abbe number nd2: refractive index νd2 for the positive lens material d-line (wavelength λ = 587.6 nm) in the second lens group: d-line (wavelength λ) of the positive lens material in the second lens group = Abbe number for 587.6 nm) In order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a fourth lens having a positive refractive power A group,
Upon zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group decreases, the distance between the second lens group and the third lens group increases, The lens groups move along the optical axis so that the distance between the third lens group and the fourth lens group decreases,
The first lens group has a negative lens;
The fourth lens group includes a positive lens;
The zoom lens according to claim 1, wherein the negative lens in the first lens group and the positive lens in the fourth lens group satisfy the following conditional expression.
30 ≦ νd1 ≦ 71
When 30 ≦ νd1 <36
-0.013 × νd1 + 2.083 ≦ nd1 ≦ 1.7
When 36 ≦ νd1 <41
-0.013 × νd1 + 2.083 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 41 ≦ νd1 <51
-0.004 × νd1 + 1.714 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 51 ≦ νd1 <61
-0.0015 × νd1 + 1.5865 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 61 ≦ νd1 ≦ 71
-0.0015 × νd1 + 1.5865 ≦ nd1 ≦ −0.009 × νd1 + 2.149
30 ≦ νd4 ≦ 71
When 30 ≦ νd4 <36
-0.013 × νd4 + 2.083 ≦ nd4 ≦ 1.7
When 36 ≦ νd4 <41
-0.013 × νd4 + 2.083 ≦ nd4 ≦ −0.004 × νd4 + 1.844
When 41 ≦ νd4 <51
-0.004 × νd4 + 1.714 ≦ nd4 ≦ −0.004 × νd4 + 1.844
When 51 ≦ νd4 <61
-0.0015 × νd4 + 1.5865 ≦ nd4 ≦ −0.004 × νd4 + 1.844
When 61 ≦ νd4 ≦ 71
-0.0015 × νd4 + 1.5865 ≦ nd4 ≦ −0.009 × νd4 + 2.149
However,
nd1: refractive index νd1: d-line (wavelength λ = 587.6 nm) of the negative lens material in the first lens group with respect to d-line (wavelength λ = 587.6 nm) of the negative lens material in the first lens group ) Abbe number nd4: refractive index νd4 for the positive lens material d-line (wavelength λ = 587.6 nm) in the fourth lens group: d-line (wavelength λ) of the positive lens material in the fourth lens group = Abbe number for 587.6 nm) The second lens group includes a positive lens,
The zoom lens according to claim 1, wherein the positive lens in the second lens group satisfies the following conditional expression.
30 ≦ νd2 ≦ 71
When 30 ≦ νd2 <36
-0.013 × νd2 + 2.083 ≦ nd2 ≦ 1.7
When 36 ≦ νd2 <41
-0.013 × νd2 + 2.083 ≦ nd2 ≦ −0.004 × νd2 + 1.844
When 41 ≦ νd2 <51
-0.004 × νd2 + 1.714 ≦ nd2 ≦ −0.004 × νd2 + 1.844
When 51 ≦ νd2 <61
-0.0015 × νd2 + 1.5865 ≦ nd2 ≦ −0.004 × νd2 + 1.844
When 61 ≦ νd2 ≦ 71
-0.0015 × νd2 + 1.5865 ≦ nd2 ≦ −0.009 × νd2 + 2.149
However,
nd2: Refractive index νd2 for the positive lens material d-line (wavelength λ = 587.6 nm) in the second lens group: d-line (wavelength λ = 587.6 nm) for the positive lens material in the second lens group Abbe number for The fourth lens group includes a positive lens;
5. The zoom lens according to claim 1, wherein the positive lens in the fourth lens group satisfies the following conditional expression.
30 ≦ νd4 ≦ 71
When 30 ≦ νd4 <36
-0.013 × νd4 + 2.083 ≦ nd4 ≦ 1.7
When 36 ≦ νd4 <41
-0.013 × νd4 + 2.083 ≦ nd4 ≦ −0.004 × νd4 + 1.844
When 41 ≦ νd4 <51
-0.004 × νd4 + 1.714 ≦ nd4 ≦ −0.004 × νd4 + 1.844
When 51 ≦ νd4 <61
-0.0015 × νd4 + 1.5865 ≦ nd4 ≦ −0.004 × νd4 + 1.844
When 61 ≦ νd4 ≦ 71
-0.0015 × νd4 + 1.5865 ≦ nd4 ≦ −0.009 × νd4 + 2.149
However,
nd4: refractive index νd4 for the positive lens material d-line (wavelength λ = 587.6 nm) in the fourth lens group: d-line (wavelength λ = 587.6 nm) for the positive lens material in the fourth lens group Abbe number for The first lens group includes, in order from the object side, a negative meniscus lens having a convex object side lens surface, a negative lens having a concave image side lens surface, and a positive lens having a convex object side lens surface.
The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
0.7 ≦ (−f1) /fw≦1.7
However,
f1: Focal length fw of the first lens group fw: Focal length of the zoom lens in the wide-angle end state At least one of the image side lens surface of the negative meniscus lens or the image side lens surface of the negative lens in the first lens group is the aspheric surface,
The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
0.32 ≦ Rasp / (− f1) ≦ 1.0
However,
Rasp: Paraxial radius of curvature of the aspheric surface f1: Focal length of the first lens group   The zoom lens according to any one of claims 1 to 7, wherein the second lens group includes two positive lenses and one negative lens.   9. The zoom lens according to claim 8, wherein in the second lens group, one of the two positive lenses and the one negative lens are cemented.   The zoom lens according to any one of claims 1 to 9, wherein the third lens group includes one positive lens and one negative lens. An aperture stop in the vicinity of the third lens group;
The zoom lens according to any one of claims 1 to 10, wherein the aperture stop moves integrally with the third lens group.   The zoom lens according to any one of claims 1 to 11, wherein the fourth lens group includes two positive lenses and one negative lens.   The said 2nd lens group and the said 4th lens group move integrally in the case of zooming from a telephoto end state to a wide-angle end state. The described zoom lens. The zoom lens according to any one of claims 1 to 13, wherein the following conditional expression is satisfied.
1.0 ≦ f2 / fw ≦ 2.3
However,
fw: focal length of the zoom lens in the wide-angle end state f2: focal length of the second lens group The zoom lens according to any one of claims 1 to 14, wherein the following conditional expression is satisfied.
0.8 ≦ (−f3) /fw≦3.0
However,
fw: focal length of the zoom lens in the wide-angle end state f3: focal length of the third lens group The zoom lens according to any one of claims 1 to 15, wherein the following conditional expression is satisfied.
0.8 ≦ f4 / fw ≦ 2.0
However,
fw: focal length of the zoom lens in the wide-angle end state f4: focal length of the fourth lens group   An image pickup apparatus comprising the zoom lens according to any one of claims 1 to 16. In order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a fourth lens having a positive refractive power A zooming method for a zoom lens having a group,
Upon zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group decreases, the distance between the second lens group and the third lens group increases, The lens groups move along the optical axis so that the distance between the third lens group and the fourth lens group decreases,
The first lens group has a negative lens;
At least one of the negative lenses has an aspheric surface;
The zoom lens zooming method, wherein the negative lens in the first lens group satisfies the following conditional expression:
30 ≦ νd1 ≦ 71
When 30 ≦ νd1 <36
-0.013 × νd1 + 2.083 ≦ nd1 ≦ 1.7
When 36 ≦ νd1 <41
-0.013 × νd1 + 2.083 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 41 ≦ νd1 <51
-0.004 × νd1 + 1.714 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 51 ≦ νd1 <61
-0.0015 × νd1 + 1.5865 ≦ nd1 ≦ −0.004 × νd1 + 1.844
When 61 ≦ νd1 ≦ 71
-0.0015 × νd1 + 1.5865 ≦ nd1 ≦ −0.009 × νd1 + 2.149
However,
nd1: refractive index νd1: d-line (wavelength λ = 587.6 nm) of the negative lens material in the first lens group with respect to d-line (wavelength λ = 587.6 nm) of the negative lens material in the first lens group Abbe number for

Images