阅读说明：本技术 变焦透镜及摄像装置 (Zoom lens and imaging device ) 是由 大田基在 米泽贤 田中琢也 于 2019-08-19 设计创作，主要内容包括：本发明提供一种高分辨率且高倍率、实现小型化及轻型化、具有良好的性能的变焦透镜及具备该变焦透镜的摄像装置。本发明的变焦透镜从物体侧依次包括变倍时不动的正的第1透镜组、变倍时移动的负的第2透镜组、变倍时移动的负的第3透镜组、变倍时移动的至少1个透镜组及变倍时不动的后组。变倍时彼此相邻的透镜组之间的间隔均发生变化。变焦透镜满足预定的条件式。(The invention provides a zoom lens with high resolution, high magnification, small size, light weight and good performance and an imaging device with the zoom lens. The zoom lens of the present invention includes, in order from the object side, a positive 1 st lens group which is not moved at the time of magnification change, a negative 2 nd lens group which is moved at the time of magnification change, a negative 3 rd lens group which is moved at the time of magnification change, at least 1 lens group which is moved at the time of magnification change, and a rear group which is not moved at the time of magnification change. The intervals between lens groups adjacent to each other are varied at the time of magnification variation. The zoom lens satisfies a predetermined conditional expression.)

1. A zoom lens characterized in that a lens element is provided,

the image pickup device includes, in order from an object side to an image side: a 1 st lens group having positive refractive power fixed relative to an image surface at the time of magnification change, a 2 nd lens group having negative refractive power moving along an optical axis at the time of magnification change, a 3 rd lens group having negative refractive power moving along the optical axis at the time of magnification change, at least 1 lens group moving along the optical axis at the time of magnification change, and a rear group fixed relative to the image surface at the time of magnification change,

the intervals between lens groups adjacent to each other are varied at the time of magnification variation,

the 2 nd lens group includes 1 negative lens,

the zooming position of the 2 nd lens group which is positioned at the most image side in zooming is a zooming position between a wide-angle end and a telephoto end,

when Db12 is the distance on the optical axis between the most image side lens surface of the 1 st lens group and the most object side lens surface of the 2 nd lens group at the telephoto end, and f1 is the focal length of the 1 st lens group,

the zoom lens satisfies conditional expression (1) shown below,

0.004＜Db12/f1＜0.8 (1)。

2. the variable focus lens according to claim 1,

when the lateral magnification of the 2 nd lens group at the telephoto end is set to β 2t,

satisfies the conditional expression (2A) shown below,

0.1＜1/β2t＜1 (2A)。

3. a zoom lens characterized in that a lens element is provided,

the image pickup device includes, in order from an object side to an image side: a 1 st lens group having positive refractive power fixed relative to an image surface at the time of magnification change, a 2 nd lens group having negative refractive power moving along an optical axis at the time of magnification change, a 3 rd lens group having negative refractive power moving along the optical axis at the time of magnification change, at least 1 lens group moving along the optical axis at the time of magnification change, and a rear group fixed relative to the image surface at the time of magnification change,

the intervals between lens groups adjacent to each other are varied at the time of magnification variation,

when Db12 is the distance on the optical axis between the most image side lens surface of the 1 st lens group and the most object side lens surface of the 2 nd lens group at the telephoto end, f1 is the focal length of the 1 st lens group, and β 2t is the lateral magnification of the 2 nd lens group at the telephoto end,

the zoom lens satisfies conditional expressions (1) and (2B) shown below,

0.004＜Db12/f1＜0.8 (1)；

0.62＜1/β2t＜1 (2B)。

4. zoom lens according to any one of claims 1 to 3,

when the focal length of the 2 nd lens group is set to f2 and the focal length of the 3 rd lens group is set to f3,

satisfies the conditional expression (3) shown below,

0.001＜f3/f2＜0.375 (3)。

5. zoom lens according to any one of claims 1 to 3,

when Db13 is a distance on an optical axis between a lens surface closest to the image side of the 1 st lens group and a lens surface closest to the object side of the 3 rd lens group at a wide angle end, and D3wt is a difference in an optical axis direction between a position of the 3 rd lens group at the wide angle end and a position of the 3 rd lens group at a telephoto end,

satisfies the conditional expression (4) shown below,

0.01＜Db13/D3wt＜0.12 (4)。

6. zoom lens according to any one of claims 1 to 3,

when the focal length of the 1 st lens group is set to f1 and the focal length of the 2 nd lens group is set to f2,

satisfies the conditional expression (5) shown below,

-0.4＜f1/f2＜-0.01 (5)。

7. zoom lens according to any one of claims 1 to 3,

when the average of refractive indices under d-lines of all lenses included in the 2 nd lens group is Nave and the average of dispersion coefficients of d-line references of all lenses included in the 2 nd lens group is vave,

satisfies the conditional expression (6) shown below,

1.8＜Nave+0.006×νave＜2.1 (6)。

8. zoom lens according to any one of claims 1 to 3,

when the focal length of the zoom lens at the telephoto end is ft and the focal length of the 1 st lens group is f1,

satisfies the conditional expression (7) shown below,

1＜ft/f1＜5 (7)。

9. zoom lens according to any one of claims 1 to 3,

when the lateral magnification of the rear group is β r,

satisfies the conditional expression (8) shown below,

-5＜βr＜-1 (8)。

10. zoom lens according to any one of claims 1 to 3,

when a combined lateral magnification from the 3 rd lens group to the rear group at a wide angle end is set to β 3rw and a combined lateral magnification from the 3 rd lens group to the rear group at a telephoto end is set to β 3rt,

satisfies the conditional expression (9) shown below,

5＜β3rt/β3rw＜150 (9)。

11. zoom lens according to any one of claims 1 to 3,

the 3 rd lens group is always moved from the object side to the image side when zooming from the wide angle end to the telephoto end.

12. Zoom lens according to any one of claims 1 to 3,

the lens group disposed adjacent to the object side of the rear group has negative refractive power.

13. Zoom lens according to any one of claims 1 to 3,

the rear group includes a vibration prevention group that performs image shake correction by moving in a direction intersecting the optical axis.

14. Zoom lens according to any one of claims 1 to 3,

satisfies the conditional expression (1-1) shown below,

0.005＜Db12/f1＜0.55 (1-1)。

15. the variable focus lens according to claim 2,

satisfies the conditional expression (2A-1) shown below,

0.52＜1/β2t＜0.99 (2A-1)。

16. zoom lens according to claim 3,

satisfies the conditional expression (2B-1) shown below,

0.66＜1/β2t＜0.99 (2B-1)。

17. zoom lens according to claim 4,

satisfies the conditional expression (3-1) shown below,

0.005＜f3/f2＜0.24 (3-1)。

18. zoom lens according to claim 5,

satisfies the conditional expression (4-1) shown below,

0.02＜Db13/D3wt＜0.085 (4-1)。

19. zoom lens according to any one of claims 1 to 3,

including 5 or 6 lens groups in which an interval between lens groups adjacent to each other is changed when magnification is changed.

20. An imaging device comprising the zoom lens according to any one of claims 1 to 19.

Technical Field

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

Background

Conventionally, 5-group or 6-group zoom lenses have been used in broadcasting video cameras, movie cameras, digital cameras, and the like. For example, patent documents 1 and 2 listed below describe a zoom lens that can be used in the above-described video camera, in which a lens group having positive refractive power is disposed closest to the object side, and the total length of the lens system is kept constant during zooming.

Patent document 1: japanese laid-open patent publication No. 2003-241096

Patent document 2: international publication No. 2014/115230

The zoom lens used for the above-described video camera is required to have high resolution while achieving miniaturization and weight saving and also to have high magnification. These demand levels have increased year by year.

The lens system described in patent document 1 has a low magnification, and it is difficult to secure a moving amount of the 3 rd lens group, which is a main variable power group, and to increase the magnification. The lens system described in patent document 2 also needs to have a further high magnification to sufficiently meet the recent demand for a high magnification. In the lens system described in patent document 2, when the magnification is increased while maintaining high performance, it is difficult to suppress field curvature in the entire zoom region, and the 1 st lens group and the 2 nd lens group are too far apart on the telephoto side, so that it is difficult to appropriately suppress variation of spherical aberration on the telephoto side, and it is difficult to increase the magnification.

Disclosure of Invention

The present invention has been made in view of the above circumstances. An object of one embodiment of the present invention is to provide a zoom lens having high resolution and high magnification, which is reduced in size and weight, and which has excellent performance, and an imaging device including the zoom lens.

Specific methods for solving the above problems include the following ways.

The zoom lens according to embodiment 1 includes, in order from an object side to an image side: a 1 st lens group having positive refractive power which is fixed with respect to an image surface at the time of magnification change, a 2 nd lens group having negative refractive power which moves along an optical axis at the time of magnification change, a 3 rd lens group having negative refractive power which moves along the optical axis at the time of magnification change, at least 1 lens group which moves along the optical axis at the time of magnification change, and a rear group which is fixed with respect to the image surface at the time of magnification change, intervals between the lens groups adjacent to each other at the time of magnification change each vary, the 2 nd lens group including 1 negative lens, a zoom position at which the 2 nd lens group is positioned on the most image side at the time of magnification change being a zoom position between a wide-angle end and a telephoto end, a distance on the optical axis between a lens surface of the 1 st lens group on the most image side at the telephoto end and a lens surface of the 2 nd lens group on the most object side being Db 85,

satisfies the conditional expression (1) shown below,

0.004＜Db12/f1＜0.8 (1)。

according to the zoom lens of embodiment 1, when the lateral magnification of the 2 nd lens group at the telephoto end is β 2t,

the zoom lens according to embodiment 2 satisfies conditional expression (2A) shown below,

0.1＜1/β2t＜1 (2A)。

the zoom lens according to embodiment 3 includes, in order from the object side toward the image side, a 1 st lens group having positive refractive power which is fixed with respect to an image surface at the time of magnification change, a 2 nd lens group having negative refractive power which moves along an optical axis at the time of magnification change, a 3 rd lens group having negative refractive power which moves along an optical axis at the time of magnification change, at least 1 lens group which moves along an optical axis at the time of magnification change, and a rear group which is fixed with respect to an image surface at the time of magnification change, wherein intervals between adjacent lens groups at the time of magnification change are changed, and when an optical-axial distance between a lens surface closest to the image side of the 1 st lens group at a telephoto end and a lens surface closest to the object side of the 2 nd lens group is Db12, a focal length of the 1 st lens group is f1, and a lateral magnification of the 2 nd lens group at the telephoto,

satisfying conditional expressions (1) and (2B) shown below,

0.004＜Db12/f1＜0.8 (1)

0.62＜1/β2t＜1 (2B)。

in any of the zoom lenses according to embodiments 1 to 3, when the focal length of the 2 nd lens group is f2 and the focal length of the 3 rd lens group is f3,

the zoom lens according to embodiment 4 satisfies conditional expression (3) shown below,

0.001＜f3/f2＜0.375 (3)。

in any of the zoom lenses according to embodiments 1 to 4, when an optical-axis distance between a lens surface closest to the image side in the 1 st lens group and a lens surface closest to the object side in the 3 rd lens group at the wide-angle end is Db13, and a difference in an optical-axis direction between a position of the 3 rd lens group at the wide-angle end and a position of the 3 rd lens group at the telephoto end is D3wt,

the zoom lens according to embodiment 5 satisfies conditional expression (4) shown below,

0.01＜Db13/D3wt＜0.12 (4)。

in any of the zoom lenses according to embodiments 1 to 5, when the focal length of the 1 st lens group is f1 and the focal length of the 2 nd lens group is f2,

the zoom lens according to embodiment 6 satisfies conditional expression (5) shown below,

-0.4＜f1/f2＜-0.01 (5)。

in any of the zoom lenses according to embodiments 1 to 6, when Nave is an average value of refractive indexes at d-lines of all lenses included in the 2 nd lens group, and ve is an average value of d-line-based dispersion coefficients of all lenses included in the 2 nd lens group,

the zoom lens according to embodiment 7 satisfies conditional expression (6) shown below,

1.8＜Nave+0.006×νave＜2.1 (6)。

in any of the zoom lenses according to embodiments 1 to 7, when the focal length of the zoom lens at the telephoto end is ft and the focal length of the 1 st lens group is f1,

the zoom lens according to embodiment 8 satisfies conditional expression (7) shown below,

1＜ft/f1＜5 (7)。

in any of the zoom lenses according to embodiments 1 to 8, when the lateral magnification of the rear group is β r,

the zoom lens according to embodiment 9 satisfies conditional expression (8) shown below,

-5＜βr＜-1 (8)。

in any of the zoom lenses according to embodiments 1 to 9, when the combined lateral magnification from the 3 rd lens group to the rear group at the wide angle end is β 3rw and the combined lateral magnification from the 3 rd lens group to the rear group at the telephoto end is β 3rt,

the zoom lens according to embodiment 10 satisfies conditional expression (9) shown below,

5＜β3rt/β3rw＜150 (9)。

with any of the zoom lenses according to embodiments 1 to 10, in the zoom lens according to embodiment 11, the 3 rd lens group always moves from the object side to the image side when zooming from the wide angle end to the telephoto end.

In the zoom lens according to embodiment 12, the lens group disposed adjacent to the object side of the rear group has a negative refractive power.

According to any one of the zoom lenses according to embodiments 1 to 12, in the zoom lens according to embodiment 13, the rear group includes a vibration prevention group that performs image shake correction by moving in a direction intersecting the optical axis.

According to any one of the zoom lenses according to embodiments 1 to 13,

the zoom lens according to embodiment 14 satisfies conditional expression (1-1) shown below,

0.005＜Db12/f1＜0.55 (1-1)。

according to the zoom lens according to embodiment 2,

the zoom lens according to embodiment 15 satisfies conditional expression (2A-1) shown below,

0.52＜1/β2t＜0.99 (2A-1)。

according to the zoom lens according to embodiment 3,

the zoom lens according to embodiment 16 satisfies conditional expression (2B-1) shown below,

0.66＜1/β2t＜0.99 (2B-1)。

according to the zoom lens according to embodiment 4,

the zoom lens according to embodiment 17 satisfies conditional expression (3-1) shown below,

0.005＜f3/f2＜0.24 (3-1)。

according to the zoom lens according to embodiment 5,

the zoom lens according to embodiment 18 satisfies conditional expression (4-1) shown below,

0.02＜Db13/D3wt＜0.085 (4-1)。

according to any one of the zoom lenses according to embodiments 1 to 18, the zoom lens according to embodiment 19 includes 5 or 6 lens groups in which the interval between the lens groups adjacent to each other changes during magnification change.

The imaging device according to embodiment 20 includes any one of the zoom lenses according to embodiments 1 to 19.

In addition, the "at least 1 lens group that moves along the optical axis at the time of magnification change" of the zoom lens according to embodiments 1 and 3 described above is a lens group different from both the "2 nd lens group" and the "3 rd lens group".

In addition, the terms "include" and "include" in the present specification mean that, in addition to the components listed above, the components may include: a lens having substantially no optical power; optical elements other than lenses such as an aperture, a filter, and cover glass; and mechanism parts such as a lens flange, a lens barrel, an imaging element, and a handshake correction mechanism.

In the present specification, "group having positive refractive power" means that the group as a whole has positive refractive power. Similarly, "group having negative refractive power" means that the group as a whole has negative refractive power. "a lens having positive refractive power" means the same as "a positive lens". The "lens having negative refractive power" has the same meaning as the "negative lens". The "lens group" is not limited to a structure including a plurality of lenses, and may be a structure including only 1 lens. Further, regarding "1 lens group", a lens group that changes an interval in the optical axis direction between adjacent groups at the time of magnification change is taken as "1 lens group". That is, a lens group included in 1 division when dividing the lens group at intervals that vary at the time of magnification variation is taken as 1 lens group.

A compound aspherical lens (a lens in which a spherical lens and an aspherical film formed on the spherical lens are integrally configured to function as 1 aspherical lens as a whole) is handled as 1 lens, and is not regarded as a cemented lens. The refractive power symbol and the surface shape of the lens surface relating to the lens including the aspherical surface are considered in the paraxial region unless otherwise specified.

The "focal length" and "lateral magnification" of the conditional expression use values in the paraxial region. The values of the conditional expressions are values based on the d-line in a state of focusing on an object at infinity. The "d line", "C line", "F line" and "g line" described in the present specification are open lines, the wavelength of the d line is 587.56nm (nm), the wavelength of the C line is 656.27nm (nm), the wavelength of the F line is 486.13nm (nm), and the wavelength of the g line is 435.84nm (nm). When the refractive indices of a lens with respect to g, F and C lines are Ng, NF and NC, respectively, the partial dispersion ratio θ gF between the g and F lines of the lens is defined by (Ng-NF)/(NF-NC).

Effects of the invention

According to one embodiment of the present invention, a zoom lens having high resolution and high magnification, which is small and light, and which has excellent performance, and an imaging apparatus including the zoom lens can be provided.

Drawings

Fig. 1 corresponds to a zoom lens according to embodiment 1 of the present invention, and is a sectional view showing a structure and a movement locus of the zoom lens according to embodiment 1 and embodiment 2 of the present invention.

Fig. 2 is a sectional view showing the structure and light flux of the zoom lens shown in fig. 1.

Fig. 3 is a sectional view showing a configuration and a movement locus of a zoom lens according to embodiment 2 of the present invention.

Fig. 4 is a sectional view showing a configuration and a movement locus of a zoom lens according to embodiment 3 of the present invention.

Fig. 5 is a sectional view showing a configuration and a movement locus of a zoom lens according to embodiment 4 of the present invention.

Fig. 6 is a sectional view showing a configuration and a movement locus of a zoom lens according to embodiment 5 of the present invention.

Fig. 7 is a sectional view showing a configuration and a movement locus of a zoom lens according to embodiment 6 of the present invention.

Fig. 8 is a sectional view showing a configuration and a movement locus of a zoom lens according to embodiment 7 of the present invention.

Fig. 9 is a sectional view showing a configuration and a movement locus of a zoom lens according to embodiment 8 of the present invention.

Fig. 10 is a sectional view showing a configuration and a movement locus of a zoom lens according to embodiment 9 of the present invention.

Fig. 11 is a sectional view showing a configuration and a movement locus of a zoom lens according to embodiment 10 of the present invention.

Fig. 12 is each aberration diagram of a zoom lens according to embodiment 1 of the present invention.

Fig. 13 is each aberration diagram of a zoom lens according to embodiment 2 of the present invention.

Fig. 14 is each aberration diagram of a zoom lens according to embodiment 3 of the present invention.

Fig. 15 is each aberration diagram of a zoom lens according to embodiment 4 of the present invention.

Fig. 16 is each aberration diagram of a zoom lens according to embodiment 5 of the present invention.

Fig. 17 is each aberration diagram of a zoom lens according to embodiment 6 of the present invention.

Fig. 18 is each aberration diagram of a zoom lens according to embodiment 7 of the present invention.

Fig. 19 is each aberration diagram of a zoom lens according to example 8 of the present invention.

Fig. 20 is each aberration diagram of a zoom lens according to example 9 of the present invention.

Fig. 21 is each aberration diagram of a zoom lens according to example 10 of the present invention.

Fig. 22 is a schematic configuration diagram of an imaging apparatus according to an embodiment of the present invention.

Description of the symbols

1-zoom lens, 2-filter, 3-imaging element, 5-signal processing section, 6-display section, 7-zoom control section, 100-image pickup device, G1-1 St lens group, G2-2 nd lens group, G3-3 rd lens group, G4-4 th lens group, G5-5 th lens group, G6-6 th lens group, Gr-rear group, ma, ta, wa-on-axis beam, mb, tb, wb-maximum angle of view beam, PP-optical component, Sim-image plane, St-aperture diaphragm, Z-optical axis.

Detailed Description

Hereinafter, embodiments of the zoom lens of the present invention will be described in detail with reference to the drawings. Fig. 1 is a cross-sectional view showing the structure of a zoom lens according to embodiment 1 of the present invention. The example shown in fig. 1 corresponds to a zoom lens of embodiment 1 described later. In fig. 1, the WIDE-angle end state is shown in the upper row labeled "WIDE", and the TELE end state is shown in the lower row labeled "TELE". In fig. 1, the left side is the object side, and the right side is the image side, and a state of focusing on an object at infinity is shown.

Fig. 1 shows an example in which an optical member PP having an incident surface and an exit surface parallel to each other is disposed between the zoom lens and the image plane Sim, assuming that the zoom lens is applied to an imaging apparatus. The optical member PP is a member assumed to be various filters, prisms, cover glass, and the like. Examples of the various filters include a low-pass filter, an infrared cut filter, and a filter for cutting off a specific wavelength region. The optical member PP has no optical power, and may be omitted.

The zoom lens according to embodiment 1 of the present invention includes, in order from the object side to the image side along the optical axis Z, a 1 st lens group G1 having positive refractive power and fixed to the image plane Sim during magnification change, a 2 nd lens group G2 having negative refractive power and moving along the optical axis Z during magnification change, a 3 rd lens group G3 having negative refractive power and moving along the optical axis Z during magnification change, at least 1 lens group moving along the optical axis Z during magnification change, and a rear group Gr fixed to the image plane Sim during magnification change. The intervals between lens groups adjacent to each other are varied at the time of magnification variation.

The zoom lens of the example shown in fig. 1 includes, in order from the object side toward the image side, a 1 st lens group G1, a 2 nd lens group G2, a 3 rd lens group G3, a 4 th lens group G4, a 5 th lens group G5, and a 6 th lens group G6. An aperture stop St is disposed on the most object side of the 6 th lens group G6. In addition, the aperture stop St shown in fig. 1 indicates a position in the optical axis direction, and does not indicate a shape. In the example shown in fig. 1, the 6 th lens group G6 corresponds to the rear group Gr. At the time of magnification change, the 1 st lens group G1 and the 6 th lens group G6 are fixed with respect to the image plane Sim, and the 2 nd lens group G2, the 3 rd lens group G3, the 4 th lens group G4, and the 5 th lens group G5 move in the optical axis direction while changing the interval between the lens groups adjacent to each other. In fig. 1, the moving locus of each lens group at the time of varying magnification from the wide-angle end to the telephoto end is schematically shown by an arrow below each lens group moving at the time of varying magnification, and a ground mark is shown below each lens group fixed with respect to the image plane Sim at the time of varying magnification.

In the example shown in fig. 1, the 1 St lens group G1 includes 5 lenses, the 2 nd lens group G2 includes 1 lens, the 3 rd lens group G3 includes 4 lenses, the 4 th lens group G4 includes 2 lenses, the 5 th lens group G5 includes 2 lenses, and the 6 th lens group G6 includes an aperture stop St and 10 lenses. However, in the zoom lens of the present invention, the number of lens groups constituting the zoom lens, the number of lenses constituting each lens group, and the position of the aperture stop St may be different from those in the example shown in fig. 1.

By providing the 1 st lens group G1 closest to the object side as a lens group having positive refractive power, the total length of the lens system can be shortened, which is advantageous for downsizing.

By moving the 2 nd lens group G2 at the time of magnification change as a lens group having a negative refractive power, it is possible to correct curvature of field from the wide angle end to the intermediate zoom position and spherical aberration from the intermediate zoom position to the telephoto end, and thereby it is possible to suppress variation in curvature of field from the wide angle end to the intermediate zoom position and variation in spherical aberration from the intermediate zoom position to the telephoto end.

By providing the 3 rd lens group G3 with a lens group having negative refractive power, the 3 rd lens group G3 can be a main zoom group that is responsible for a main zoom function.

By disposing at least 1 lens group that moves along the optical axis Z at the time of magnification change on the image side of the 3 rd lens group G3, it is possible to suppress variation in image position at the time of magnification change and also suppress variation in field curvature at the time of magnification change.

The rear group Gr closest to the image side can be mainly responsible for the imaging effect. When the 1 st lens group G1 closest to the object side and the rear group Gr closest to the image side are made to be fixed with respect to the image plane Sim during magnification variation, the total length of the lens system can be kept constant during magnification variation.

In the zoom lens of embodiment 1, the 2 nd lens group G2 includes 1 negative lens. By setting the number of lenses constituting the 2 nd lens group G2 to 1, the space for movement of the 3 rd lens group G3, which is the main variable power group, can be secured wide, which is advantageous for higher power.

In the zoom lens according to embodiment 1, the zoom position at which the 2 nd lens group G2 is positioned most on the image side during magnification variation is set to a zoom position between the wide-angle end and the telephoto end, instead of the wide-angle end and the telephoto end. By the 2 nd lens group G2 being close to the 1 st lens group G1, spherical aberration generated in the 1 st lens group G1 can be corrected upon zooming toward the telephoto end, and field curvature can be suppressed upon zooming toward the wide-angle end, thus contributing to high magnification.

Fig. 2 is a cross-sectional view showing a configuration of the zoom lens shown in fig. 1 in each state. In fig. 2, the WIDE-angle end state is shown in the upper row labeled "WIDE", the state in which the 2 nd lens group G2 is located at the most image side zoom position is shown in the MIDDLE row labeled "MIDDLE", and the telephoto end state is shown in the lower row labeled "TELE". Fig. 2 also shows an on-axis light flux wa and a maximum angle of view light flux wb in the wide-angle end state, an on-axis light flux ma and a maximum angle of view light flux mb in a state where the 2 nd lens group G2 is located at the most image-side zoom position, and an on-axis light flux ta and a maximum angle of view light flux tb in the telephoto end state.

When the distance on the optical axis between the most image side lens surface of the 1 st lens group G1 and the most object side lens surface of the 2 nd lens group G2 at the telephoto end is Db12, and the focal length of the 1 st lens group G1 is f1, the zoom lens of embodiment 1 satisfies the following conditional expression (1). By not being equal to or less than the lower limit of the conditional expression (1), the amount of movement of the 2 nd lens group G2 from the wide angle end to the telephoto end can be prevented from being excessively small, and the fluctuation of the field curvature on the wide angle side and the fluctuation of the spherical aberration on the telephoto side can be easily suppressed with good balance. Further, the refractive power of the 1 st lens group G1 can be prevented from becoming too weak, which is advantageous for downsizing and weight saving of the lens system. Further, the 1 st lens group G1 and the 2 nd lens group G2 can be made not to interfere with each other. By not being equal to or more than the upper limit of conditional expression (1), the distance between the 1 st lens group G1 and the 2 nd lens group G2 can be prevented from becoming excessively large, and therefore, even when the magnification is increased, the effect of suppressing the variation of spherical aberration on the telephoto side can be ensured.

Further, the refractive power of the 1 st lens group G1 can be prevented from becoming excessively strong, and spherical aberration generated in the 1 st lens group G1 can be suppressed. Further, a configuration satisfying the following conditional expression (1-1) can provide more favorable characteristics, and a configuration satisfying the following conditional expression (1-2) can provide further more favorable characteristics.

0.004＜Db12/f1＜0.8 (1)

0.005＜Db12/f1＜0.55 (1-1)

0.006＜Db12/f1＜0.32 (1-2)

In the zoom lens according to embodiment 1, it is preferable that conditional expression (2A) is satisfied when the lateral magnification of the 2 nd lens group G2 at the telephoto end is β 2t, and that the lateral magnification of the 2 nd lens group G2 at the telephoto end is prevented from becoming excessively large and the combined focal length of the 1 st lens group G1 and the 2 nd lens group G2 at the telephoto end is prevented from becoming excessively long, so that it is easy to secure the negative refractive power of the 3 rd lens group G3, suppress the zoom stroke of the 3 rd lens group G3 as the main zoom group at the time of high magnification, and achieve both high magnification and downsizing, and that the negative refractive power of the 2 nd lens group G2 is not excessively weakened by not becoming equal to or more than the upper limit of conditional expression (2A), and that the aberration correction effect of the negative lens of the 2 nd lens group G2 can be secured, and that it is further preferable if the lateral magnification of the 2 nd lens group G2 at the telephoto end is satisfied with conditional expression (2A-1).

0.1＜1/β2t＜1 (2A)

0.52＜1/β2t＜0.99 (2A-1)

0.7＜1/β2t＜0.98 (2A-2)

Next, a zoom lens according to embodiment 2 of the present invention will be described. The zoom lens according to embodiment 2 of the present invention has a configuration partially similar to that of the zoom lens according to embodiment 1 of the present invention. A cross-sectional view showing the configuration of a zoom lens according to embodiment 2 of the present invention is the same as the cross-sectional view shown in fig. 1.

The zoom lens according to embodiment 2 of the present invention includes, in order from the object side to the image side along the optical axis Z, a 1 st lens group G1 having positive refractive power and fixed to the image plane Sim during magnification change, a 2 nd lens group G2 having negative refractive power and moving along the optical axis Z during magnification change, a 3 rd lens group G3 having negative refractive power and moving along the optical axis Z during magnification change, at least 1 lens group moving along the optical axis Z during magnification change, and a rear group Gr fixed to the image plane Sim during magnification change. The intervals between lens groups adjacent to each other are varied at the time of magnification variation.

When the distance on the optical axis between the most image side lens surface of the 1 st lens group G1 and the most object side lens surface of the 2 nd lens group G2 at the telephoto end is Db12, and the focal length of the 1 st lens group G1 is f1, the zoom lens according to embodiment 2 of the present invention satisfies the following conditional expression (1).

0.004＜Db12/f1＜0.8 (1)

The configuration of the zoom lens according to embodiment 2 described above is the same as that of the zoom lens according to embodiment 1, and the operational effects of the respective configurations are the same as those described in the description of the zoom lens according to embodiment 1, and therefore, redundant description is omitted. Similarly, in embodiment 2, if the configuration satisfies conditional expression (1-1), more favorable characteristics can be obtained, and if the configuration satisfies conditional expression (1-2), more favorable characteristics can be obtained.

When the lateral magnification of the 2 nd lens group G2 at the telephoto end is β 2t, the zoom lens according to embodiment 2 of the present invention has a structure satisfying the following conditional expression (2B). by not being equal to or less than the lower limit of the conditional expression (2B), the lateral magnification of the 2 nd lens group G2 at the telephoto end can be suppressed, and the combined focal length of the 1 st lens group G1 and the 2 nd lens group G2 at the telephoto end is easily not excessively increased.by not being equal to or less than the lower limit of the conditional expression (2B), the zoom stroke of the 3 rd lens group G3, which is the principal variable power group, can be further suppressed at the time of increasing the magnification than when not being equal to or less than the lower limit of the conditional expression (2A), which is more advantageous for increasing the magnification and downsizing, by not being equal to or more than the lower limit of the conditional expression (2B), the negative refractive power of the 2 nd lens group G2 can be made not excessively weak, and the aberration correction effect of the negative lens group of the 2G 2 can be ensured, and the characteristic can be further improved if the structure satisfying the conditional expression (2B-1) is made, which is made to satisfy the condition (2B).

0.62＜1/β2t＜1 (2B)

0.66＜1/β2t＜0.99 (2B-1)

0.7＜1/β2t＜0.98 (2B-2)

The zoom lens according to embodiment 1 has a configuration in which the 2 nd lens group G2 includes 1 negative lens, and a configuration in which the zoom position at which the 2 nd lens group G2 is located closest to the image side at the time of magnification variation is the zoom position between the wide angle end and the telephoto end, but the zoom lens according to embodiment 2 does not require these configurations, however, by having the same configuration as the zoom lens according to embodiment 1 and a configuration in which β 2t is within the range of the conditional expression (2B), the zoom lens according to embodiment 2 is advantageous in achieving both high magnification and downsizing and can have good performance, as the zoom lens according to embodiment 1.

The zoom lens according to embodiment 2 may have the above-described configuration of the zoom lens according to embodiment 1. That is, in the zoom lens according to embodiment 2, the 2 nd lens group G2 may include 1 negative lens. In the zoom lens according to embodiment 2, the zoom position at which the 2 nd lens group G2 is positioned closest to the image side during magnification variation may be a zoom position between the wide angle end and the telephoto end. The operational effects of these configurations are the same as those of the configurations described in the description of the zoom lens according to embodiment 1.

Hereinafter, a preferred structure and an achievable structure of the zoom lens according to embodiment 1 and embodiment 2 of the present invention will be described. When the focal length of the 2 nd lens group G2 is f2 and the focal length of the 3 rd lens group G3 is f3, the following conditional expression (3) is preferably satisfied. By not being equal to or less than the lower limit of conditional expression (3), the refractive power of the 3 rd lens group G3 can be suppressed, and variation in spherical aberration during magnification variation can be suppressed. Further, by not being equal to or less than the lower limit of conditional expression (3), the refractive power of the 2 nd lens group G2 can be secured, and the field curvature on the wide angle side and the spherical aberration on the telephoto side can be corrected easily with good balance. By not being equal to or more than the upper limit of conditional expression (3), the refractive power of lens group 3G 3 can be ensured, which is advantageous for higher magnification and smaller size. Further, a configuration satisfying the following conditional expression (3-1) can provide more favorable characteristics, and a configuration satisfying the following conditional expression (3-2) can provide further more favorable characteristics.

0.001＜f3/f2＜0.375 (3)

0.005＜f3/f2＜0.24 (3-1)

0.009＜f3/f2＜0.12 (3-2)

When the distance on the optical axis between the most image side lens surface of the 1 st lens group G1 at the wide angle end and the most object side lens surface of the 3 rd lens group G3 is Db13 and the difference in the optical axis direction between the position of the 3 rd lens group G3 at the wide angle end and the position of the 3 rd lens group G3 at the telephoto end is D3wt, the following conditional expression (4) is preferably satisfied. By not being equal to or less than the lower limit of conditional expression (4), the distance between the 1 st lens group G1 and the 3 rd lens group G3 at the wide-angle end can be prevented from being excessively short, and the thickness of the lens of the 2 nd lens group G2 can be suppressed from becoming thin. This can suppress deformation of the lens during temperature change, improve surface accuracy of the lens during processing, and/or suppress deformation of the lens during assembly, for example. By not being equal to or more than the upper limit of the conditional expression (4), the zoom stroke from the wide angle end to the telephoto end of the 3 rd lens group G3 can be ensured, which is advantageous for higher magnification. Further, a configuration satisfying the following conditional expression (4-1) can provide more favorable characteristics, and a configuration satisfying the following conditional expression (4-2) can provide further more favorable characteristics.

0.01＜Db13/D3wt＜0.12 (4)

0.02＜Db13/D3wt＜0.085 (4-1)

0.028＜Db13/D3wt＜0.05 (4-2)

When the focal length of the 1 st lens group G1 is f1 and the focal length of the 2 nd lens group G2 is f2, the following conditional expression (5) is preferably satisfied. By not being equal to or less than the lower limit of conditional expression (5), the refractive power of the 2 nd lens group G2 can be prevented from becoming excessively strong, and the field curvature in the periphery of the imaging region on the wide angle side can be corrected satisfactorily. By not being equal to or more than the upper limit of conditional expression (5), the refractive power of the 2 nd lens group G2 can be prevented from being excessively weakened, and spherical aberration on the telephoto side can be corrected favorably. Further, a configuration satisfying the following conditional expression (5-1) can provide more favorable characteristics, and a configuration satisfying the following conditional expression (5-2) can provide further more favorable characteristics.

-0.4＜f1/f2＜-0.01 (5)

-0.38＜f1/f2＜-0.03 (5-1)

-0.35＜f1/f2＜-0.05 (5-2)

When the average value of refractive indices in d-lines of all lenses included in the 2 nd lens group G2 is Nave and the average value of dispersion coefficients of d-line references of all lenses included in the 2 nd lens group G2 is Nave, the following conditional expression (6) is preferably satisfied. When the 2 nd lens group G2 includes 1 lens, the refractive index of the lens at the d-line and the d-line reference abbe are Nave and vave, respectively. By not being equal to or less than the lower limit of conditional expression (6), it is possible to achieve downsizing and higher magnification, and to favorably correct chromatic aberration on the telephoto side. By not being equal to or more than the upper limit of conditional expression (6), the lens of the 2 nd lens group G2 can be suppressed from becoming too low dispersion and high refractive index. In the zoom lens of the present invention, by moving the 2 nd lens group G2 at the time of magnification change, it is possible to correct aberrations that vary at the time of magnification change, such as field curvature and spherical aberration. At this time, it is effective to configure such that aberration remains in the single 2 nd lens group G2 and the aberration of the 2 nd lens group G2 and the aberration varying at the time of magnification change cancel each other out, instead of realizing aberration correction by the single 2 nd lens group G2. By not being equal to or more than the upper limit of the conditional expression (6), it is possible to appropriately leave aberrations in the single 2 nd lens group G2 and secure the aberration correction effect of the 2 nd lens group. Further, a configuration satisfying the following conditional expression (6-1) can provide more favorable characteristics, and a configuration satisfying the following conditional expression (6-2) can provide further more favorable characteristics.

1.8＜Nave+0.006×νave＜2.1 (6)

1.88＜Nave+0.006×νave＜2.05 (6-1)

1.96＜Nave+0.006×νave＜2.03 (6-2)

When the focal length of the zoom lens at the telephoto end is ft and the focal length of the 1 st lens group G1 is f1, the following conditional expression (7) is preferably satisfied. By not being equal to or less than the lower limit of conditional expression (7), the refractive power of the 1 st lens group G1 can be prevented from being excessively weakened, which is advantageous for downsizing and weight saving of the lens system. By not being equal to or more than the upper limit of conditional expression (7), the refractive power of the 1 st lens group G1 can be prevented from becoming excessively strong, and the incident angle of the on-axis light beam incident on the 3 rd lens group G3, which is the main magnification group, from the object side can be made small, so that the occurrence of spherical aberration can be suppressed. Further, a configuration satisfying the following conditional expression (7-1) can provide more favorable characteristics, and a configuration satisfying the following conditional expression (7-2) can provide further more favorable characteristics.

1＜ft/f1＜5 (7)

1.7＜ft/f1＜4.2 (7-1)

2.4＜ft/f1＜3.4 (7-2)

When the lateral magnification of the rear group Gr is β r, it is preferable to satisfy the following conditional expression (8). when β r is larger than the upper limit of the conditional expression (8) and β r is negative, β r becomes a reduction magnification, and the size of the image of the rear group Gr becomes smaller than the size of the object of the rear group gr.a configuration in which the upper limit of the conditional expression (8) is not larger is advantageous in suppressing the size of the entire lens system and in which a high magnification is achieved.a configuration in which the following conditional expression (8-1) is satisfied can provide more favorable characteristics, and a configuration in which the following conditional expression (8-2) is satisfied can provide more favorable characteristics.

-5＜βr＜-1 (8)

-3.6＜βr＜-1 (8-1)

-2.2＜βr＜-1 (8-2)

When the combined lateral magnification of the 3 rd lens group G3, the at least one lens group, and the rear group Gr at the wide angle end is β 3rw, and the combined lateral magnification of the 3 rd lens group G3, the at least one lens group, and the rear group Gr at the telephoto end is β 3rt, it is preferable to satisfy the following conditional expression (9). by not being equal to or less than the lower limit of the conditional expression (9), it is possible to suppress the variation in the lateral magnification of the lens group after the 3 rd lens group G3 to a small extent and to facilitate high magnification, and by not being equal to or more than the upper limit of the conditional expression (9), it is possible to prevent the variation in the lateral magnification of the lens group after the 3 rd lens group G3 from being excessively large and to favorably suppress the variation in the magnification of spherical aberration.

5＜β3rt/β3rw＜150 (9)

21＜β3rt/β3rw＜105 (9-1)

37＜β3rt/β3rw＜60 (9-2)

When zooming from the wide angle end to the telephoto end, the 3 rd lens group G3 is preferably moved from the object side to the image side all the time. With such a configuration, the magnification varying effect by the 3 rd lens group G3 can be ensured even on the telephoto side, and reduction in magnification on the telephoto side can be suppressed.

Preferably, the lens group disposed adjacent to the object side of the rear group Gr has negative refractive power. In the case of such a configuration, since the lens group disposed adjacent to the object side of the rear group Gr can move to the image side on the telephoto side when correcting the fluctuation of the image position at the time of magnification change, it is easy to secure the zoom stroke of the 3 rd lens group G3, and it is advantageous for downsizing and increasing the magnification.

In addition, the rear group Gr preferably includes a vibration-proof group that performs image shake correction by moving in a direction intersecting the optical axis Z. The rear group Gr is fixed with respect to the image plane Sim at the time of magnification change, and therefore the optical path of the principal rays in the rear group Gr is kept unchanged even at the time of magnification change. By including the anti-vibration group in the rear group Gr, performance at the time of image shake correction can be ensured well over the entire zoom region. In the example shown in fig. 1, the rear group Gr includes an aperture stop St and 10 lenses, and an anti-vibration group is constituted by the 4 th lens and the 5 th lens from the object side of the rear group Gr. In fig. 1, brackets and a double arrow in the up-down direction are shown below the lenses corresponding to the vibration prevention groups.

The zoom lens can be configured to include 5 or 6 lens groups in which intervals in the optical axis direction of lens groups adjacent to each other change at the time of magnification change. With such a configuration, the following lens system is easily realized: the miniaturization is realized, and the high resolution and the high multiplying power are realized.

The above-described preferred configurations and realizable configurations can be arbitrarily combined and preferably selectively employed as appropriate in accordance with the required specifications. According to the technology of the present invention, a zoom lens having high resolution and high magnification, which is small and light, and which has excellent performance can be realized. The "high magnification" referred to herein means 20 times or more.

Next, a numerical example of the zoom lens of the present invention will be described.

[ example 1]

Fig. 1 shows a cross-sectional view showing the structure of a zoom lens according to example 1, and the method and structure for the illustration are as described above, and therefore a part of the description thereof will not be repeated. The zoom lens of embodiment 1 includes, in order from the object side toward the image side, a 1 st lens group G1 having positive refractive power, a 2 nd lens group G2 having negative refractive power, a 3 rd lens group G3 having negative refractive power, a 4 th lens group G4 having negative refractive power, a 5 th lens group G5 having negative refractive power, and a 6 th lens group G6 having positive refractive power. The 6 th lens group G6 corresponds to the rear group Gr. At the time of magnification change, the 1 st lens group G1 and the 6 th lens group G6 are fixed with respect to the image plane Sim, and the 2 nd lens group G2, the 3 rd lens group G3, the 4 th lens group G4, and the 5 th lens group G5 move in the optical axis direction while changing the interval between the lens groups adjacent to each other. The vibration prevention group includes the 4 th lens and the 5 th lens from the object side of the 6 th lens group G6.

Table 1A and table 1B show the basic lens data of the zoom lens of example 1, table 2 shows the specifications and the variable surface distances, and table 3 shows the aspherical coefficients. In order to avoid lengthening 1 table, the basic lens data is divided into 2 tables of table 1A and table 1B. In tables 1A and 1B, the surface number is shown in the column Sn when the surface closest to the object side is the 1 st surface and the numbers are increased one by one toward the image side, the curvature radius of each surface is shown in the column R, and the surface interval on the optical axis between each surface and the surface adjacent to the image side is shown in the column D. The refractive index of each component element with respect to the d-line is shown in the Nd column, the d-line-based dispersion coefficient of each component element is shown in the vd column, and the partial dispersion ratio between the g-line and the F-line of each component element is shown in the θ gF column.

In table 1A and table 1B, the sign of the radius of curvature of the surface of the shape in which the convex surface faces the object side is positive, and the sign of the radius of curvature of the surface of the shape in which the convex surface faces the image side is negative. Table 1B also shows the aperture stop St and the optical member PP, and the column of the surface number corresponding to the surface of the aperture stop St describes the terms of the surface number (St) and (St). The value in the lowermost column of D in table 1B is the distance between the image plane Sim and the surface closest to the image side in the table. In tables 1A and 1B, the variable surface interval is marked with DD [ ], and the object-side surface number of the interval is marked with [ ], and is shown in the column D.

In table 2, values of zoom magnification Zr, focal length F, F value fno, maximum full view angle 2 ω, and variable surface interval are shown on the d-line basis. The (°) column 2 ω represents units of degrees. In table 2, respective values of the WIDE-angle end state, the state in which the 2 nd lens group G2 is located at the most image side zoom position, and the telephoto end state are shown in columns labeled WIDE, MIDDLE, and TELE, respectively.

In table 1B, the number of the aspheric surface is denoted by a symbol, and the column of the curvature radius of the aspheric surface shows the numerical value of the paraxial curvature radius. In table 3, the column of Sn shows the surface number of the aspherical surface, and the columns of KA and Am (m is an integer of 3 or more) show the numerical values of the aspherical surface coefficients of the respective aspherical surfaces. "E. + -. n" (n: integer) of numerical values of aspherical surface coefficients of Table 3 represents ". times.10^±n". KA and Am are aspheric coefficients in an aspheric expression represented by the following expression.

Zd＝C×h²/{1+(1-KA×C²×h²)^1/2}+∑Am×h^m

Wherein the content of the first and second substances,

and (d) is as follows: aspheric depth (length of a perpendicular line that depends from a point on the aspheric surface of height h to a plane tangent to the aspheric vertex and perpendicular to the optical axis);

h: height (distance from the optical axis to the lens surface);

c: the reciprocal of the paraxial radius of curvature;

KA. Am, and (2): the coefficient of the aspherical surface is,

the aspherical Σ represents a sum associated with m.

In the data of each table, degrees are used as a unit of angle and mm (millimeter) is used as a unit of length, but the optical system can be used in an enlarged scale or in a reduced scale, and therefore other appropriate units can be used. In each table shown below, numerical values rounded to a predetermined number of digits are shown.

[ Table 1A ]