JP7234034B2 - Zoom lens and optical equipment having same - Google Patents

Description

The present invention relates to a zoom lens and an optical instrument having the same.

In recent years, so-called mirrorless cameras, which do not have a quick-return mirror, are increasing. Since the body of this mirrorless camera is thin, compact and lightweight, there is a demand for the development of a compact and lightweight interchangeable lens that matches the mirrorless camera.

Since this mirrorless camera does not require a space for a quick return mirror, it is not necessary to secure the back focus as with conventional interchangeable lenses. Therefore, unlike conventional interchangeable lenses, the degree of freedom in designing the lens is increased, making it possible to design a compact and lightweight lens.

A wide-angle lens, in particular, tends to have a short back focus, so it can be made compact as an interchangeable lens for a mirrorless camera.

Furthermore, in recent years, advances in image processing technology have made it possible to electrically correct some aberrations. In particular, various aberrations such as chromatic aberration and distortion can be electrically corrected, and a configuration suitable for correction of other aberrations can be used to reduce size, improve image quality, and reduce costs.

JP 2014-235190 A JP 2015-79238 A

Conventionally, there is known a zoom lens comprising a first lens group having negative refractive power, a second lens group having positive refractive power, and a subsequent group having a plurality of lens groups. is disclosed. In this zoom lens, the second lens group is a main variable power group, and by moving a plurality of lens groups arranged on the image side, high magnification and high performance are achieved. This zoom lens is characterized by achieving both a compact overall optical length and good correction of various aberrations. However, the angle of view on the wide-angle side was not necessarily sufficient.

As an example of a zoom lens that widens the angle of view, for example, Patent Document 2 is proposed. This zoom lens has a four-group structure, and is characterized by excellent correction of image plane fluctuations and image blurring that accompany zooming. However, the change in curvature of field during focusing was large, and it was not necessarily sufficient in terms of good aberration correction.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, it is an object of the present invention to provide a zoom lens that suppresses variations in optical performance due to focusing at a wide angle of view, and an optical apparatus having the zoom lens.

A zoom lens as one aspect of the present invention includes a first lens group having negative refractive power, a second lens group having positive refractive power, and a plurality of lenses including an aperture, which are arranged in order from the object side to the image side. and a succeeding lens group consisting of a lens group of , and the distance between adjacent lens groups changes during zooming, wherein the first lens group is a first negative lens arranged in order from the object side. , a second negative lens, and a positive lens, wherein the first lens group has at least one negative lens, the subsequent group includes a focus lens group that moves during focusing, and the first Rf and Rr are the radii of curvature of the object-side lens surface and the image-side lens surface of the negative lens of the lens group, respectively, and the distance from the aperture to the focus lens group at the wide-angle end and at the time of focusing at infinity is on the optical axis. Let Df be the distance, Hf be the height of the off-axis principal ray incident on the focus lens group , and Rnr be the radius of curvature of the image-side lens surface of the second negative lens and the object-side lens surface of the positive lens. and Rpf ,
1.0<(Rf−Rr)/(Rf+Rr)<2.5
0.39<Hf/Df<0.55
0.05<(Rnr−Rpf)/(Rnr+Rpf)<0.25
It is characterized by satisfying the following conditions.
A zoom lens as another aspect of the present invention includes a first lens group having negative refractive power, a second lens group having positive refractive power, and an aperture, which are arranged in order from the object side to the image side. and a subsequent group consisting of a plurality of lens groups including , a first negative lens and a second negative lens, said trailing group including a focus lens group that moves during focusing, and an object-side lens surface and an image-side lens surface of said negative lens of said first lens group. Let Rf and Rr be the radii of curvature of the lens surface, Df be the distance on the optical axis from the stop to the focus lens group at the wide-angle end and in focus at infinity, and let off-axis principal rays incident on the focus lens group Let Hf be the height of and f1n and f2n be the focal lengths of the first and second negative lenses, respectively,
1.0<(Rf−Rr)/(Rf+Rr)<2.5
0.39<Hf/Df<0.55
0.6<f1n/f2n<1.2
It is characterized by satisfying the following conditions.

According to the present invention, it is possible to obtain a zoom lens that has a wide angle of view and suppresses fluctuations in optical performance due to focusing, and an optical apparatus having the zoom lens.

Cross-sectional view of the zoom lens of Reference Example 1 Aberration diagram at the wide-angle end of the zoom lens of Reference Example 1 Aberration diagram in the middle of the zoom lens of Reference Example 1 Aberration diagram at the telephoto end of the zoom lens of Reference Example 1 Cross-sectional view of the zoom lens of Reference Example 2 Aberration diagram at the wide-angle end of the zoom lens of Reference Example 2 Aberration diagram in the middle of the zoom lens of Reference Example 2 Aberration diagram at the telephoto end of the zoom lens of Reference Example 2 Cross-sectional view of the zoom lens of Reference Example 3 Aberration diagram at the wide-angle end of the zoom lens of Reference Example 3 Aberration diagram in the middle of the zoom lens of Reference Example 3 Aberration diagram at the telephoto end of the zoom lens of Reference Example 3 Cross-sectional view of the zoom lens of Reference Example 4 Aberration diagram at the wide-angle end of the zoom lens of Reference Example 4 Aberration diagram in the middle of the zoom lens of Reference Example 4 Aberration diagram at the telephoto end of the zoom lens of Reference Example 4 Cross-sectional view of the zoom lens of Reference Example 5 Aberration diagram at the wide-angle end of the zoom lens of Reference Example 5 Aberration diagram in the middle of the zoom lens of Reference Example 5 Aberration diagram at the telephoto end of the zoom lens of Reference Example 5 Cross-sectional view of the zoom lens of Reference Example 6 Aberration diagram at the wide-angle end of the zoom lens of Reference Example 6 Aberration diagram in the middle of the zoom lens of Reference Example 6 Aberration diagram at the telephoto end of the zoom lens of Reference Example 6 Cross-sectional view of the zoom lens of the example Aberration diagram at the wide-angle end of the zoom lens of the example Aberration diagram in the middle of the zoom lens of the example Aberration diagram at the telephoto end of the zoom lens of the example Device diagram of an optical device (digital camera) equipped with the zoom lens of the embodiment or each reference example

Hereinafter, embodiments and reference examples for carrying out the present invention will be described with reference to the accompanying drawings. In the drawings, the same reference numerals indicate the same members.

The zoom lenses of Examples and Reference Examples are characterized by being able to suppress variations in optical performance due to focusing at a wide angle of view. In particular, it is suitable for zoom lenses used in single-lens reflex cameras, digital still cameras, film cameras, video cameras, etc., and optical equipment having such zoom lenses.

2. Description of the Related Art In recent years, electronic distortion correction, which electrically corrects distortion in a wide-angle range, has been widely introduced in order to make imaging apparatuses compact. A photographing apparatus that incorporates electronic distortion correction is advantageous for compactness, such as a smaller lens diameter. However, zoom lenses using electronic distortion correction are known to have a problem of large aberration fluctuations during focusing.

According to aberration theory, the process of focusing from infinity to close distance consists of the process of moving the object distance from infinity to close distance (object distance movement) and the movement of the focus lens group to focus on that object distance. It can be separated into the process (moving the focus lens group). When the theory of aberrations is used, the variation in curvature of field increases in principle when moving the object distance, and the variation in curvature of field during focusing tends to increase as well. This is explained by the fact that the amount of variation (ΔIII) ₁ of the third-order aberration coefficient III relating to astigmatism when the object distance is moved is also large because the third-order aberration coefficient V relating to distortion is large. (where δ is the object distance transfer parameter, ^IIS is the 3rd order aberration coefficient for the coma aberration of the pupil, and ^IS is the 3rd order aberration coefficient for the spherical aberration of the pupil).
(ΔIII) ₁ = - δ (V + II ^S ) + δ^2 x I ^S
A zoom lens that employs inner focus facilitates miniaturization and weight reduction of the focus lens group and rapid focusing. However, in general, as image sensors used in imaging devices become larger, zoom lenses used in imaging devices are required to have high optical performance over the entire zoom range and the entire object distance. For example, there is a demand for small fluctuations in aberrations during focusing, and in particular, small fluctuations in curvature of field in order to maintain high optical performance over the entire screen.

On the other hand, a zoom lens used in an image pickup apparatus having a function of performing electronic distortion correction allows distortion, so that it is easy to reduce the size of the entire lens while widening the angle of view. However, such a zoom lens increases fluctuations in curvature of field, especially when focusing in a wide-angle range.

In a zoom lens, in order to obtain high optical performance over the entire frame while maintaining a predetermined shooting angle of view, it is necessary to appropriately set the zoom type and lens configuration. come. Furthermore, it is necessary to appropriately set the zoom type, lens configuration, etc. with respect to the off-axis chief ray incident on the focus lens group.

In the zoom lenses of the examples and reference examples , the incident angle α ^{1 ∼} and the height ^h ∼ of the off-axis chief ray in the focus lens group are increased at the wide-angle end. As a result, the amount of change in curvature of field (ΔIII) ₂ when the focus lens group moves
(ΔIII) ₂ ∝ (1/f)αα ^~ h ^~ (Δh)
is increasing. where α is the angle of incidence of the paraxial on-axis ray. As a result, at the wide-angle end, fluctuations in curvature of field when the object distance is moved are corrected when the focus lens group is moved. In this equation, f is the focal length of the focus lens group, and .DELTA.h is the variation in the incident height of the axial marginal ray on the focus lens group due to the movement of the focus lens group.

The zoom lenses of the working examples and each reference example have the above-mentioned lens configuration to suppress the deterioration of various aberrations, support short back focus, and suppress fluctuations in optical performance due to focusing in the wide-angle range with a wide angle of view. are doing.

Specifically, the zoom lenses of the examples and each reference example have, in order from the object side to the image side, a first lens group having negative refractive power, a second lens group having positive refractive power, an aperture stop and a plurality of lenses. The distance between adjacent lens groups changes during zooming.

Also, the first lens group has at least one negative lens, and the subsequent group includes a focus lens group that moves during focusing. Rf and Rr are the radii of curvature of the object-side and image-side lens surfaces of the negative lens in the first lens group, respectively, and the distance on the optical axis from the aperture to the focus lens group at the wide-angle end and when focusing on infinity is Df, and the height of the off-axis chief ray incident on the focus lens group is Hf,
1.0<(Rf−Rr)/(Rf+Rr)<2.5 (1)
0.39<Hf/Df<0.55 (2)
satisfy the following conditions.

Note that the off-axis principal ray is a pupil center ray incident on the maximum effective image circle on the image sensor when focusing on infinity at the wide-angle end.

As described above, in the embodiment and each reference example , it is important to appropriately set the shape of the lens included in the first lens group and the off-axis chief ray incident on the focus lens group.

Conditional expression (1) relates to the shape of the negative lens arranged in the first lens group, and particularly relates to correction of distortion and curvature of field. If the lower limit of conditional expression (1) is not reached, the object-side lens surface of the negative lens approaches a flat surface, which is advantageous for correction of distortion, but it becomes difficult to correct spherical aberration at the telephoto end. On the other hand, if the upper limit of conditional expression (1) is exceeded, the object-side lens surface of the negative lens becomes strongly concave, which is advantageous in terms of correcting curvature of field. It becomes difficult to correct coma aberration. Moreover, the lens thickness of the first lens group is increased, which is disadvantageous for miniaturization.

Conditional expression (2) is a conditional expression regarding light rays incident on the focus lens group arranged in the rear group, and in particular, a conditional expression regarding fluctuations in curvature of field accompanying focusing at the wide-angle end. If the lower limit of conditional expression (2) is not reached, the height of light rays incident on the focus lens group becomes low, making it difficult to suppress variations in curvature of field that accompany focusing. On the other hand, when the upper limit of conditional expression (2) is exceeded, the height of the light rays incident on the focus lens group becomes high, which is advantageous in suppressing fluctuations in curvature of field due to focusing. This is not preferable because it leads to deceleration of the focusing speed due to the increase in size.

It is more preferable to set the numerical ranges of conditional expressions (1) and (2) as follows for aberration correction.

1.2<(Rf−Rr)/(Rf+Rr)<2.5 (1a)
0.39<Hf/Df<0.53 (2a)
More preferably, the numerical ranges of conditional expressions (1) and (2) are set as follows.

1.5<(Rf−Rr)/(Rf+Rr)<2.5 (1b)
0.39<Hf/Df<0.50 (2b)
Furthermore, when the radii of curvature of the lens surfaces closest to the object side and the lens surface closest to the image side of the focus lens group are Rff and Rfr, respectively, the zoom lenses of Examples and Reference Examples are:
0.15<(Rff−Rfr)/(Rff+Rfr)<0.80 (3)
It is preferable to satisfy the following conditional expression.

Conditional expression (3) is a conditional expression regarding the shape of the focus lens group arranged in the rear group, and particularly regarding coma aberration correction on the wide-angle side and variations in curvature of field during focusing. If the lower limit of conditional expression (3) is not reached, the meniscus shape of the focus lens group becomes stronger, which is advantageous in suppressing fluctuations in curvature of field during focusing, but difficult in correcting spherical aberration. On the other hand, if the upper limit of conditional expression (3) is exceeded, the side surface of the object approaches a flat surface, making it difficult to correct coma.

The first lens group has a first negative lens and a second negative lens arranged in order from the object side to the image side. The zoom lens of each reference example is
0.6<f1n/f2n<1.2 (4)
It is preferable to satisfy the following conditional expression.

Conditional expression (4) relates to the power arrangement of the two negative lenses included in the first lens group, and particularly relates to coma and curvature of field on the wide-angle side. If the lower limit of conditional expression (4) is exceeded, the refracting power of the first negative lens increases, which is advantageous in achieving a wide angle of view. difficult to do. On the other hand, when the upper limit of conditional expression (4) is exceeded, the refracting power of the second negative lens increases, making it difficult to correct coma on the wide-angle side. Moreover, it is not preferable because it causes an increase in the diameter of the front lens.

Further, when the focal length of the i-th lens group is fi, the zoom lenses of the examples and reference examples are
-2.00<f1/f2<-0.25 (5)
It is preferable to satisfy the following conditional expression.

Conditional expression (5) is a conditional expression relating to the power arrangement of the first lens group and the second lens group, in particular, a conditional expression relating to the total optical length and coma aberration. If the lower limit of conditional expression (5) is not reached, the refracting power of the first lens group weakens and the refracting power of the second lens group strengthens, which is advantageous for shortening the back focus. It becomes difficult to correct coma aberration. On the other hand, when the upper limit of conditional expression (5) is exceeded, the refractive power of the first lens group is strengthened and the refractive power of the second lens group is weakened, making it difficult to correct spherical aberration on the wide-angle side. Also, in order to increase the zoom ratio, it is necessary to increase the amount of movement of the second lens group, which is a zoom group, which is not preferable because the overall length of the lens increases.

Further, when the average value of the refractive index for the d-line of each lens constituting the first lens group is Nd1ave, the zoom lenses of the examples and reference examples are:
Nd1ave > 1.75 (6)
It is preferable to satisfy the following conditional expression.

Conditional expression (6) is a conditional expression relating to the refractive index of the lenses forming the first lens group, and in particular is a conditional expression relating to the total optical length and spherical aberration on the telephoto side. If the lower limit of conditional expression (6) is not reached, the refractive index of the glass that makes up the first lens group becomes small, so the curvature of each lens increases, the thickness of the first lens group along the optical axis increases, and the overall length increases. It is not preferable because it increases the size. In addition, it becomes difficult to correct spherical aberration on the telephoto side.

The first lens group consists of a first negative lens, a second negative lens, and a positive lens in order from the object side. When the radii of curvature are Rnr and Rpf, respectively, the zoom lenses of Examples and Reference Examples are:
0.05<(Rnr−Rpf)/(Rnr+Rpf)<0.25 (7)
It is preferable to satisfy the following conditional expression.

Conditional expression (7) relates to the shape of the air layer between the negative lens and the positive lens included in the first lens group, and particularly relates to curvature of field and distortion on the wide-angle side. If the lower limit of conditional expression (7) is not reached, the meniscus shape becomes stronger, making it difficult to correct aberrations, particularly distortion, in the air layer. On the other hand, when the upper limit of conditional expression (7) is exceeded, it is advantageous in correcting distortion in the air layer, but it becomes difficult to correct curvature of field.

It is more preferable to set the numerical ranges of conditional expressions (3) to (7) as follows for aberration correction.

0.17<(Rff−Rfr)/(Rff+Rfr)<0.75 (3a)
0.65<f1n/f2n<1.15 (4a)
-2.00<f1/f2<-0.28 (5a)
1.75<Nd1ave<2.20 (6a)
0.05<(Rnr−Rpf)/(Rnr+Rpf)<0.22 (7a)
More preferably, the numerical ranges of conditional expressions (3)-(7) are set as follows.

0.20<(Rff−Rfr)/(Rff+Rfr)<0.70 (3b)
0.7<f1n/f2n<1.1 (4b)
-2.0<f1/f2<-0.3 (5b)
1.75<Nd1ave<2.00 (6b)
0.05<(Rnr−Rpf)/(Rnr+Rpf)<0.18 (7b)
Further, during photographing, the image is shifted in the direction perpendicular to the optical axis by moving the whole or part of the second lens unit L2 in the direction perpendicular to the optical axis. This corrects blurring of the captured image (movement of the image plane of the subject image) when the entire zoom lens vibrates. The term "perpendicular to the optical axis" as used herein does not have to be perpendicular to the optical axis in a strict sense, and means that a slight inclination from the direction perpendicular to the optical axis is permitted.

Note that the distortion aberration among various aberrations may be corrected by electrical image processing. In particular, by making the effective imaging range (effective image circle diameter) of the image sensor at the wide-angle side smaller than the effective imaging range (effective image circle diameter) at the telephoto end, and correcting the above-mentioned distortion aberration, the front lens diameter can be reduced. Contributes to miniaturization.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[ Reference example 1 ]
1 and 2-4 are a sectional view and an aberration diagram at the wide-angle end of the zoom lens of Reference Example 1, respectively. The left side of FIG. 1 is the object side, and the right side is the image side. In FIG. 1, L1 is the first lens group having negative refractive power, L2 is the second lens group having positive refractive power, and L3 is the third lens group having negative refractive power. It corresponds to the lens group LF. L4 is a fourth lens group having negative refractive power, and L5 is a fifth lens group having positive refractive power. An aperture stop SP is located inside the second lens unit L2 and moves integrally with the second lens unit L2 during zooming. IP is the image plane, which corresponds to the imaging plane of a solid-state imaging device such as a CCD sensor or CMOS sensor when used as a photographic optical system for a digital still camera or video camera, or to the film plane when used in a silver halide film camera. do. GB is a glass block and corresponds to a low-pass filter or an IR cut filter.

2-4, d and g represent the d-line and g-line, respectively, and ΔM and ΔS represent the meridional image plane and the sagittal image plane, respectively. Lateral chromatic aberration is represented by the g-line. Also, fno is the F-number, and ω is the half angle of view (°).

Next, the lens configuration of each lens group will be described.

The first lens unit L1 is composed of a negative meniscus lens with a convex lens surface on the object side, a negative lens with concave lens surfaces on both sides, and a positive meniscus lens with a convex lens surface on the object side. . In the zoom lens of Reference Example 1 , the refractive power of the first lens unit L1 is strengthened within an appropriate range in order to make the zoom lens compact. When the refracting power is increased, various aberrations occur in the first lens unit L1, especially distortion aberration and curvature of field at the wide-angle end. Therefore, the negative refractive power of the first lens unit L1 is divided between two negative lenses, and especially the distortion is satisfactorily corrected by applying electronic distortion correction.

The second lens unit L2 is a cemented lens obtained by cementing a positive lens having convex lens surfaces on both sides, a positive lens having a strongly convex lens surface on the object side, and a negative lens having a concave lens surface on the object side. , and a positive meniscus lens having a convex lens surface on the object side. In the zoom lens of Reference Example 1 , the refractive power of the second lens unit L2 is strengthened within an appropriate range in order to increase the zoom ratio. When the refractive power is increased, various aberrations, particularly spherical aberration and longitudinal chromatic aberration, occur in the second lens unit L2. In Reference Example 1 , three positive lenses share the positive refractive power of the second lens unit L2 to reduce the occurrence of spherical aberration. In addition, longitudinal chromatic aberration is suppressed by using low-dispersion glass for the positive lens. With such a lens configuration, the overall optical length is shortened while increasing the variable power ratio.

The third lens unit L3 is composed of one negative meniscus lens having a convex lens surface on the object side. In the zoom lens of Reference Example 1 , the size and weight are reduced by configuring the third lens unit L3 with a small number of lenses. In particular, the lens surface on the object side has a convex meniscus shape, thereby correcting spherical aberration generated in the second lens unit L2 and suppressing fluctuations in curvature of field during focusing.

The fourth lens unit L4 is composed of one negative lens having a convex lens surface on the object side. In the zoom lens of Reference Example 1 , the thickness is reduced by configuring the fourth lens unit L4 with a small number of lenses. In particular, field curvature is corrected by arranging an aspherical lens whose positive refractive power weakens toward the lens periphery.

The fifth lens unit L5 is composed of one positive meniscus lens having a convex lens surface on the image side. In the zoom lens of Reference Example 1 , the reduction in thickness and weight is achieved by constructing the fifth lens group with a small number of lenses. By forming a meniscus shape that is convex toward the image side, the field curvature is corrected and the angle of light rays incident on the image sensor is suppressed. In addition, lateral chromatic aberration is corrected over the entire zoom range.

In Reference Example 1 , the wide-angle end and the telephoto end refer to zoom positions when the zoom lens group is positioned at both ends of a range in which the zoom lens group is mechanically movable on the optical axis. The same applies to the following examples.

In Reference Example 1 , when zooming from the wide-angle end to the telephoto end, the first lens unit L1 moves along a convex locus toward the image side, and the second lens unit L2 and the fourth lens unit L4 move together toward the object side, as indicated by the arrows. Magnification is changed by moving. In addition, by moving the third lens unit L3 toward the object side, image plane fluctuations accompanying zooming are corrected.

In addition, an inner focus system is employed in which focusing is performed by moving the third lens group L3 along the optical axis. A solid-line curve 3a and a dotted-line curve 3b relating to the third lens unit L3 are movement trajectories for correcting image plane fluctuation accompanying zooming when focusing on an infinite distance object and a short distance object, respectively. By moving the third lens group L3 toward the object side in this manner, the space between the second lens group L2 and the fourth lens group L4 can be effectively utilized, and the overall optical length can be effectively shortened. there is

Further, when focusing from an infinity object to a short distance object at the telephoto end, the third lens unit L3 is retracted backward as indicated by an arrow 3c. Although the first lens unit L1 is fixed in the optical axis direction for focusing, it may be moved as necessary for correcting aberrations.

Further, during photographing, all or part of the second lens unit L2 may be moved in the direction perpendicular to the optical axis in order to correct blurring of the subject image.
[ Reference Example 2-5 ]
5 and 6-8 are a sectional view and an aberration diagram at the wide-angle end of the zoom lens of Reference Example 2, respectively.

9 and 10 to 12 are a sectional view and an aberration diagram at the wide-angle end of the zoom lens of Reference Example 3, respectively.

13, 14 to 16 are a cross-sectional view and an aberration diagram at the wide-angle end of the zoom lens of Reference Example 4, respectively.

17 and 18 to 20 are a sectional view and an aberration diagram at the wide-angle end of the zoom lens of Reference Example 5, respectively.

The letters and symbols used in the cross-sectional view and aberration diagram of Reference Example 2-5 are the same as those of Reference Example 1 . Also, the lens configuration of each lens group and others are the same as those of the first reference example .

In Reference Example 2-5 , the third lens group L3 corresponds to the focus lens group LF that moves during focusing.
[ Reference example 6 ]
21, 22 to 24 are a sectional view and an aberration diagram at the wide-angle end of the zoom lens of Reference Example 6, respectively. In FIG. 21, the left side is the object side, and the right side is the image side. L1 is a first lens group having negative refractive power, L2 is a second lens group having positive refractive power, and L3 is a third lens group having negative refractive power. Equivalent to. L4 is a fourth lens group having negative refractive power. An aperture stop SP is located inside the second lens unit L2 and moves integrally with the second lens unit L2 during zooming.

In Reference Example 6 , when zooming from the wide-angle end to the telephoto end, the first lens unit L1 is moved along a convex locus toward the image side, and the second lens unit L2 and the fourth lens unit L4 are integrally moved toward the object side, as indicated by the arrows. Magnification is changed by moving. In addition, by moving the third lens unit L3 toward the object side, image plane fluctuations accompanying zooming are corrected.

In addition, an inner focus system is employed in which focusing is performed by moving the third lens group L3 along the optical axis. A solid-line curve 3a and a dotted-line curve 3b relating to the third lens unit L3 are movement trajectories for correcting image plane fluctuation accompanying zooming when focusing on an infinite distance object and a short distance object, respectively. By moving the third lens group L3 toward the object side in this manner, the space between the second lens group L2 and the fourth lens group L4 can be effectively utilized, and the overall optical length can be effectively shortened. there is

Further, when focusing from an infinity object to a short distance object at the telephoto end, the third lens unit L3 is retracted backward as indicated by an arrow 3c. Although the first lens unit L1 is fixed in the optical axis direction for focusing, it may be moved as necessary for correcting aberrations. Others are the same as those of Reference Example 1 .

The characters and symbols used in the aberration diagrams of Reference Example 6 are the same as those of Reference Example 1. FIG .
[ Example]
25, 26 to 28 are a cross-sectional view and an aberration diagram at the wide-angle end of the zoom lens of the example , respectively. In FIG. 25, the left side is the object side, and the right side is the image side. L1 is a first lens group having negative refractive power, L2 is a second lens group having positive refractive power, and L3 is a third lens group having positive refractive power. L4 is a fourth lens group having a negative refractive power and corresponds to the focus lens group LF that moves during focusing. L5 is a fifth lens group having positive refractive power. An aperture stop SP is located inside the third lens unit L3 and moves integrally with the third lens unit L3 during zooming.

In this embodiment , when zooming from the wide-angle end to the telephoto end, the first lens unit L1 is moved toward the image side along a convex locus, the second lens unit L2 is moved toward the object side, and the third lens unit L3 and the third lens unit L3 are moved. Zooming is performed by moving the fifth lens unit L5 integrally to the object side. In addition, by moving the fourth lens unit L4 toward the object side, image plane fluctuations accompanying zooming are corrected.

In addition, an inner focus system is employed in which focusing is performed by moving the fourth lens unit L4 along the optical axis. A solid-line curve 4a and a dotted-line curve 4b relating to the fourth lens unit L4 are movement trajectories for correcting image plane fluctuations accompanying zooming when focusing on an infinite object and a close object, respectively. By moving the fourth lens group L4 toward the object side in this way, the space between the third lens group L3 and the fifth lens group L5 can be effectively utilized, and the overall optical length can be effectively shortened. there is

Further, when focusing from an infinity object to a short distance object at the telephoto end, the fourth lens unit L4 is retracted backward as indicated by an arrow 4c. Although the first lens unit L1 is fixed in the optical axis direction for focusing, it may be moved as necessary for correcting aberrations. Others are the same as those of Reference Example 1 .

Letters and symbols used in the aberration diagrams of the examples are the same as those of the first reference example .
(imaging device)
Next, an example of an imaging apparatus (digital camera) using the zoom lens of the example and each reference example as an imaging optical system will be described with reference to FIG.

In FIG. 29, reference numeral 30 denotes a camera body, and 31 denotes a photographing optical system constituted by one of the zoom lenses described in the examples and reference examples .

A solid-state imaging element (photoelectric conversion element) (not shown) such as a CCD sensor or a CMOS sensor that receives the subject image formed by the photographing optical system 31 is built in the camera body.
(Numerical data of examples and reference examples )
Numerical data of each reference example and examples are shown in Numerical Reference Examples 1 to 6 and Numerical Examples . In the numerical data of each reference example and embodiment , ri is the radius of curvature of the i-th surface from the object side, di is the surface distance between the i-th surface and the i+1-th surface from the object side, and ni is the i-th surface. Let vi be the Abbe number of the i-th lens at the d-line. Let K be a conic constant, and A4, A6, A8, A10, A12 be the 4th, 6th, 8th, 10th, and 12th aspheric coefficients, and the optical axis at the position of the height h from the optical axis When the directional displacement is x with respect to the vertex of the surface, the aspherical shape is
x=(h ² /R)/[1+[1−(1+K)(h/R) ² ] ^1/2 ]+A4h ⁴ +A6h ⁶ +A8h ⁸ +A10h ¹⁰ +A12h ¹²
is displayed. However, R is the radius of curvature, and “eX” means “×10 ^−X ”.

Aspherical surfaces are marked with an asterisk (*) on the right side of the surface number in each numerical example.

Table 1 shows the relationship between each conditional expression described above and various numerical values in each reference example and working example .
[Numeric reference example 1 ]
unit mm

Surface data surface number rd nd νd
1 67.756 1.75 1.80610 33.3
2 20.925 9.62
3 -174.702 1.75 1.77250 49.6
4 46.091 0.63
5 34.206 5.57 1.84666 23.9
6 206.576 (variable)
7 94.113 3.09 1.48749 70.2
8 -89.441 1.10
9 15.100 5.30 1.48749 70.2
10 -149.131 1.26 1.84666 23.9
11 142.042 3.98
12 ∞ 0.00
13 (Aperture) ∞ 2.55
14* 25.619 2.18 1.52996 55.8
15 48.107 (variable)
16 29.964 1.10 1.72825 28.5
17 14.558 (variable)
18* 907.991 2.85 1.52996 55.8
19* 83.616 (variable)
20 -65.569 4.84 1.79952 42.2
21 -37.352 12.40
22 ∞ 1.96 1.51633 64.1
23 ∞ 1.14
Image plane ∞

14th surface of aspheric data
K=0.00000e+000 A4=-5.81535e-005 A6=-2.91444e-007 A8=-1.67547e-009

18th side
K=0.00000e+000 A4=-1.62832e-004 A6= 4.52051e-007 A8=-1.66554e-009

19th side
K=0.00000e+000 A4=-1.47440e-004 A6= 5.22625e-007 A8=-2.46614e-009
A10= 6.59419e-012 A12=-1.39564e-014

Various data Zoom ratio 2.82
Wide Angle Medium Telephoto Focal Length 24.51 43.14 69.13
F number 4.10 5.10 6.44
Half angle of view (°) 38.46 26.63 17.38
Overall lens length 112.53 106.22 113.54
BF 14.83 14.83 14.83

d6 34.30 13.64 2.67
d15 1.64 3.01 4.86
d17 12.42 11.05 9.21
d19 1.75 16.10 34.38

Zoom lens group data group Starting surface Focal length Lens configuration length
1 1 -38.05 19.33
2 7 24.03 19.46
3 16 -40.09 1.10
4 18 -173.99 2.85
5 20 100.87 4.84

[Numeric reference example 2 ]
unit mm

Surface data surface number rd nd νd
1 65.245 1.75 1.80610 33.3
2 20.316 9.60
3 -165.143 1.75 1.77250 49.6
4 44.697 0.63
5 33.467 5.52 1.84666 23.9
6 235.117 (variable)
7 109.298 3.09 1.48749 70.2
8 -77.315 1.44
9 14.908 5.43 1.48749 70.2
10 -110.710 1.26 1.84666 23.9
11 171.321 3.75
12 ∞ 0.00
13 (Aperture) ∞ 2.50
14* 24.312 2.17 1.52996 55.8
15 43.530 (variable)
16 27.065 1.10 1.72151 29.2
17 13.448 (variable)
18* 57.166 2.85 1.52996 55.8
19* 35.677 (variable)
20 -74.021 5.26 1.79952 42.2
21 -37.911 12.40
22 ∞ 1.96 1.51633 64.1
23 ∞ 0.96
Image plane ∞

14th surface of aspheric data
K=0.00000e+000 A4=-5.82774e-005 A6=-3.84313e-007 A8=-1.23557e-009

18th side
K=0.00000e+000 A4=-1.65892e-004 A6= 5.21681e-007

19th side
K=0.00000e+000 A4=-1.65769e-004 A6=6.10061e-007 A8=-1.72131e-009
A10=3.07769e-012

Various data Zoom ratio 2.82
Wide Angle Medium Telephoto Focal Length 24.52 43.05 69.13
F number 4.10 5.10 6.44
Half angle of view (°) 38.46 26.68 17.38
Overall lens length 109.15 104.79 112.88
BF 14.65 14.65 14.65

d6 31.26 12.13 1.60
d15 1.64 2.70 4.40
d17 11.76 10.71 9.00
d19 1.75 16.52 35.13

Zoom lens group data group Starting surface Focal length Lens configuration length
1 1 -37.72 19.25
2 7 23.63 19.63
3 16 -38.34 1.10
4 18 -187.71 2.85
5 20 91.29 5.26

[Numerical reference example 3 ]
unit mm

Surface data surface number rd nd νd
1 65.810 1.75 1.80610 33.3
2 20.837 9.79
3 -151.747 1.75 1.77250 49.6
4 45.997 0.63
5 34.649 5.63 1.84666 23.9
6 251.898 (variable)
7 117.363 2.75 1.48749 70.2
8 -74.934 1.10
9 15.545 5.24 1.48749 70.2
10 -142.598 1.26 1.84666 23.9
11 139.520 4.40
12 ∞ 0.00
13 (Aperture) ∞ 2.44
14* 24.481 2.37 1.52996 55.8
15 43.955 (variable)
16 28.460 1.10 1.72825 28.5
17 14.652 (variable)
18* 179.009 2.85 1.52996 55.8
19* 63.955 (variable)
20 -61.418 4.64 1.79952 42.2
21 -36.969 12.40
22 ∞ 1.96 1.51633 64.1
23 ∞ 1.14
Image plane ∞

14th surface of aspheric data
K=0.00000e+000 A4=-5.05033e-005 A6=-2.07371e-007 A8=-1.92298e-009

18th side
K=0.00000e+000 A4=-1.73798e-004 A6= 5.28922e-007 A8=-2.46759e-009

19th side
K=0.00000e+000 A4=-1.60178e-004 A6=6.25353e-007 A8=-3.39220e-009
A10=1.03290e-011 A12=-2.17735e-014

Various data Zoom ratio 2.82
Wide Angle Medium Telephoto Focal Length 24.51 43.00 69.13
F number 4.10 5.10 6.44
Half angle of view (°) 38.46 26.71 17.38
Overall lens length 112.83 106.76 114.74
BF 14.83 14.83 14.83

d6 34.18 13.70 2.82
d15 1.65 2.99 4.76
d17 12.72 11.38 9.61
d19 1.74 16.16 35.01

Zoom lens group data group Starting surface Focal length Lens configuration length
1 1 -37.94 19.56
2 7 24.56 19.55
3 16 -42.91 1.10
4 18 -189.39 2.85
5 20 107.12 4.64

[Numerical reference example 4 ]
unit mm

Surface data surface number rd nd νd
1 64.587 1.75 1.95375 32.3
2 21.780 10.54
3 -116.648 1.75 1.69680 55.5
4 43.744 0.63
5 35.700 5.91 1.84666 23.9
6 299.992 (variable)
7 226.265 2.74 1.71700 47.9
8 -106.945 1.10
9 16.658 5.96 1.49700 81.5
10 -43.719 1.26 1.95375 32.3
11 -153.697 3.15
12 ∞ 0.00
13 (Aperture) ∞ 3.51
14* 26.292 2.26 1.52996 55.8
15 50.628 (variable)
16 26.967 1.10 1.84666 23.9
17 14.547 (variable)
18* 66.735 2.85 1.52996 55.8
19* 46.309 (variable)
20 -56.415 4.12 1.95375 32.3
21 -38.257 12.38
22 ∞ 1.96 1.51633 64.1
23 ∞ 1.12
Image plane ∞

14th surface of aspheric data
K=0.00000e+000 A4=-3.87678e-005 A6=-1.72023e-007 A8=-1.06453e-009

18th side
K=0.00000e+000 A4=-2.02049e-004 A6=7.04240e-007 A8=-4.61968e-009

19th side
K=0.00000e+000 A4=-1.91101e-004 A6=7.99103e-007 A8=-5.27751e-009
A10=1.68275e-011 A12=-3.90847e-014

Various data Zoom ratio 3.19
Wide Angle Medium Telephoto Focal Length 21.66 41.66 69.12
F number 4.10 5.10 6.44
Half angle of view (°) 41.95 27.45 17.38
Overall lens length 115.09 108.18 118.44
BF 14.79 14.79 14.79

d6 36.02 12.55 1.86
d15 1.62 3.16 5.03
d17 12.31 10.77 8.90
d19 1.72 18.29 39.23

Zoom lens group data group Starting surface Focal length Lens configuration length
1 1 -34.45 20.59
2 7 23.91 19.98
3 16 -38.89 1.10
4 18 -300.00 2.85
5 20 112.20 4.12

[Numerical reference example 5 ]
unit mm

Surface data surface number rd nd νd
1 56.534 1.75 1.80610 33.3
2 20.524 9.94
3 -128.069 1.75 1.71999 50.2
4 44.061 0.63
5 33.919 5.20 1.84666 23.9
6 154.428 (variable)
7 133.107 2.56 1.48749 70.2
8 -96.658 1.10
9 16.253 4.89 1.48749 70.2
10 -181.173 1.26 1.84666 23.9
11 109.669 3.59
12 ∞ 0.00
13 (Aperture) ∞ 3.26
14* 23.765 2.86 1.52996 55.8
15 220.845 (variable)
16 40.297 1.10 1.64769 33.8
17 14.802 (variable)
18* 169.469 2.85 1.52996 55.8
19* 56.500 (variable)
20 -54.777 5.39 1.49700 81.5
21 -30.701 13.62
22 ∞ 1.96 1.51633 64.1
23 ∞ 1.14
Image plane ∞

14th surface of aspheric data
K=0.00000e+000 A4=-4.23355e-005 A6=-1.37290e-007 A8=-1.17611e-009

18th side
K=0.00000e+000 A4=-1.49406e-004 A6= 4.22637e-007 A8=-1.43378e-009

19th side
K=0.00000e+000 A4=-1.32908e-004 A6=5.10350e-007 A8=-2.48426e-009
A10=8.70115e-012 A12=-1.93739e-014

Various data Zoom ratio 2.56
Wide Angle Medium Telephoto Focal Length 24.51 35.01 62.67
F number 4.10 5.10 6.44
Half angle of view (°) 38.47 31.71 19.05
Overall lens length 116.26 116.26 116.26
BF 16.06 16.06 16.06

d6 36.14 24.87 6.34
d15 2.08 1.64 4.24
d17 12.10 10.39 8.51
d19 1.75 15.16 32.97

Zoom lens group data group Starting surface Focal length Lens configuration length
1 1 -36.91 19.28
2 7 23.40 19.52
3 16 -36.74 1.10
4 18 -161.34 2.85
5 20 130.82 5.39

[Numeric reference example 6 ]
unit mm

Surface data surface number rd nd νd
1 55.073 1.75 1.85026 32.3
2 20.834 10.34
3 -111.551 1.75 1.78590 44.2
4 46.691 0.63
5 36.056 5.81 1.84666 23.9
6 523.052 (variable)
7 86.994 2.64 1.48749 70.2
8 -163.461 1.12
9 15.190 5.44 1.48749 70.2
10 -104.917 1.26 1.84666 23.9
11 176.057 3.60
12 ∞ 0.00
13 (Aperture) ∞ 3.05
14* 32.055 2.19 1.52996 55.8
15 79.204 (variable)
16 37.350 1.10 1.95375 32.3
17 20.644 (variable)
18* 96.087 2.85 1.52996 55.8
19* 55.123 (variable)
20 ∞ 1.96 1.51633 64.1
21 ∞ 1.15
Image plane ∞

14th surface of aspheric data
K=0.00000e+000 A4=-5.84496e-005 A6=-2.34463e-007 A8=-1.43401e-009

18th side
K=0.00000e+000 A4=-2.11463e-004 A6=7.58913e-007 A8=-5.10526e-009

19th side
K=0.00000e+000 A4=-1.99672e-004 A6=9.02437e-007 A8=-5.83576e-009
A10=1.72536e-011 A12=-3.06761e-014

Various data Zoom ratio 2.13
Wide Angle Medium Telephoto Focal Length 24.51 32.98 52.16
F number 4.10 5.10 6.44
Half angle of view (°) 38.46 33.26 22.53
Total lens length 114.74 114.74 114.74
BF 17.59 30.65 46.81

d6 37.22 27.85 12.76
d15 1.64 0.22 1.18
d17 14.76 12.51 10.48
d19 15.16 28.21 44.37


Zoom lens group data group Starting surface Focal length Lens configuration length
1 1 -37.77 20.28
2 7 25.33 19.29
3 16 -50.00 1.10
4 18 -250.00 2.85

[Numerical example]
unit mm

Surface data surface number rd nd νd
1 48.928 1.75 1.85478 24.8
2 20.322 10.64
3 -123.342 1.75 1.79952 42.2
4 43.298 0.63
5 34.703 5.19 1.92286 18.9
6 140.154 (variable)
7 74.890 2.65 1.49700 81.5
8 -195.539 (variable)
9 14.950 5.50 1.48749 70.2
10 -88.147 1.26 1.85478 24.8
11 1236.757 3.42
12 ∞ 0.00
13 (Aperture) ∞ 2.89
14* 25.461 2.08 1.52996 55.8
15 43.690 (variable)
16 76.498 1.10 1.85025 30.1
17 21.436 (variable)
18* 22.508 2.85 1.52996 55.8
19* 26.446 (variable)
20 ∞ 1.86 1.51633 64.1
21 ∞ 1.21
Image plane ∞

14th surface of aspheric data
K=0.00000e+000 A4=-6.91675e-005 A6=-3.25456e-007 A8=-3.01678e-009

18th side
K=0.00000e+000 A4=-8.91850e-005 A6=9.20762e-008

19th side
K=0.00000e+000 A4=-8.57958e-005 A6= 8.00367e-008

Various data Zoom ratio 2.82
Wide Angle Medium Telephoto Focal Length 24.52 47.50 69.13
F number 4.10 5.10 6.44
Half angle of view (°) 38.45 24.49 17.38
Overall lens length 117.65 105.88 109.89
BF 19.22 35.18 49.30

d6 30.63 7.64 1.59
d8 9.90 5.16 1.09
d15 1.73 4.27 5.69
d17 14.45 11.91 10.49
d19 16.79 32.74 46.86


Zoom lens group data group Starting surface Focal length Lens configuration length
1 1 -33.75 19.97
2 7 109.31 2.65
3 9 28.60 15.15
4 16 -35.35 1.10
5 18 228.05 2.85

Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist.

L1: first lens group L2: second lens group LF: focus lens group

Claims (10)

Consists of a first lens group with negative refractive power, a second lens group with positive refractive power, and a subsequent group consisting of a plurality of lens groups including an aperture, arranged in order from the object side to the image side. A zoom lens in which the distance between adjacent lens groups changes during zooming,
The first lens group is composed of a first negative lens, a second negative lens, and a positive lens arranged in order from the object side,
the trailing group includes a focus lens group that moves during focusing;
The radii of curvature of the object-side lens surface and the image-side lens surface of the negative lens of the first lens group are Rf and Rr, respectively, and light from the aperture to the focus lens group at the wide-angle end and infinity focus Let Df be the distance on the axis, Hf be the height of the off-axis chief ray incident on the focus lens group , and let Hf be the radius of curvature of the image-side lens surface of the second negative lens and the object-side lens surface of the positive lens. Let be Rnr and Rpf, respectively ,
1.0<(Rf−Rr)/(Rf+Rr)<2.5
0.39<Hf/Df<0.55
0.05<(Rnr−Rpf)/(Rnr+Rpf)<0.25
A zoom lens characterized by satisfying the following condition. The first lens group has a first negative lens and a second negative lens arranged in order from the object side to the image side,
When the focal lengths of the first and second negative lenses are f1n and f2n, respectively,
0.6<f1n/f2n<1.2
2. The zoom lens according to claim 1, which satisfies the following condition: Consists of a first lens group with negative refractive power, a second lens group with positive refractive power, and a subsequent group consisting of a plurality of lens groups including an aperture, arranged in order from the object side to the image side. A zoom lens in which the distance between adjacent lens groups changes during zooming,
The first lens group has a first negative lens and a second negative lens arranged in order from the object side to the image side,
the trailing group includes a focus lens group that moves during focusing;
The radii of curvature of the object-side lens surface and the image-side lens surface of the negative lens of the first lens group are Rf and Rr, respectively, and light from the aperture to the focus lens group at the wide-angle end and infinity focus Let Df be the distance on the axis, Hf be the height of the off-axis chief ray incident on the focus lens group, and f1n and f2n be the focal lengths of the first and second negative lenses, respectively.
1.0<(Rf−Rr)/(Rf+Rr)<2.5
0.39<Hf/Df<0.55
0.6<f1n/f2n<1.2
A zoom lens characterized by satisfying the following condition. The first lens group is composed of a first negative lens, a second negative lens, and a positive lens arranged in order from the object side,
When the radii of curvature of the image-side lens surface of the second negative lens and the object-side lens surface of the positive lens are Rnr and Rpf, respectively,
0.05<(Rnr−Rpf)/(Rnr+Rpf)<0.25
4. The zoom lens according to claim 3, which satisfies the following condition: When the radii of curvature of the lens surface closest to the object side and the lens surface closest to the image side of the focus lens group included in the subsequent group are Rff and Rfr, respectively,
0.15<(Rff−Rfr)/(Rff+Rfr)<0.80
5. The zoom lens according to any one of claims 1 to 4, wherein the following condition is satisfied. When the focal lengths of the first and second lens groups are f1 and f2, respectively,
-2.00<f1/f2<-0.25
6. The zoom lens according to any one of claims 1 to 5 , wherein the following condition is satisfied. When the average value of the refractive indices for the d-line of the lenses constituting the first lens group is Nd1ave,
Nd1ave > 1.75
7. The zoom lens according to any one of claims 1 to 6 , wherein the following condition is satisfied. 8. The zoom lens according to any one of Claims 1 to 7 , wherein the second lens group is wholly or partly moved perpendicularly to the optical axis direction to correct movement of the image plane of the subject image. . a zoom lens according to any one of claims 1 to 8 ;
and an imaging device for receiving an image formed by the zoom lens. 10. The optical apparatus according to claim 9 , wherein an effective image circle diameter on the wide-angle side of the imaging device is smaller than an effective image circle diameter on the telephoto end.

Images