阅读说明：本技术 变焦透镜、扩束透镜及摄像装置 (Zoom lens, beam expanding lens, and imaging device ) 是由 田中琢也 于 2019-06-26 设计创作，主要内容包括：本发明提供一种良好地校正伴随替换成扩束透镜时的温度变化的焦点位置偏移,并且降低色差的变焦透镜、扩束透镜及摄像装置。本发明的变焦透镜从物体侧起依次具有：对焦部,包括为了对焦而进行移动的对焦用透镜组；变倍部,包括为了变倍而改变相互间隔并进行移动的至少2个变倍用透镜组；孔径光圈；及成像部,包括成像用透镜组,成像部从物体侧起依次包括M1透镜组、M2N透镜组及M3透镜组,M2N透镜组能够与放大成像倍率的M2E透镜组进行替换,M2E透镜组满足规定的条件式(1)至(4)。(The invention provides a zoom lens, a beam expanding lens and an imaging device, which can well correct the focus position deviation along with the temperature change when replacing the beam expanding lens and reduce the chromatic aberration. The zoom lens of the present invention includes, in order from an object side: a focusing unit including a focusing lens group that moves for focusing; a variable magnification unit including at least 2 variable magnification lens groups which are moved while changing their intervals for variable magnification; an aperture stop; and an imaging section including an imaging lens group, the imaging section including, in order from the object side, an M1 lens group, an M2N lens group, and an M3 lens group, the M2N lens group being replaceable with the M2E lens group of magnification, and the M2E lens group satisfying predetermined conditional expressions (1) to (4).)

1. A zoom lens includes, in order from an object side: a focusing unit including a focusing lens group that moves for focusing; a variable magnification unit including at least 2 variable magnification lens groups which are moved while changing their intervals for variable magnification; an aperture stop; and an imaging section including a lens group for imaging,

the imaging part comprises an M1 lens group, an M2N lens group and an M3 lens group in sequence from the object side,

the M2N lens group can be replaced with an M2E lens group of magnified imaging power,

when the dispersion coefficient of the positive lens of the M2E lens group is v d1, the average value of the temperature change coefficients of refractive index at d-line in air from 0 ℃ to 40 ℃ is dn/dt, and dn/dt of the positive lens of the M2E lens group is dn/dt1, the M2E lens group includes at least one positive lens satisfying conditional expressions (1) and (2) as follows:

55＜v d1 (1)；

5.5＜dn/dtl＜10 (2)，

assuming that the average value of dn/dt of the positive lens of the M2E lens group is dn/dt _ ave _ P and the average value of dn/dt of the negative lens of the M2E lens group is dn/dt _ ave _ N, conditional expressions (3) and (4) shown below are satisfied:

3.5＜dn/dt_ave_P＜6 (3)；

1.5＜dn/dt_ave_N＜6 (4)。

2. the variable focus lens according to claim 1,

when the partial dispersion ratio between the g-line and the F-line of the positive lens of the M2E lens group is θ gF, at least 1 positive lens satisfying the conditional expressions (1) and (2) satisfies the conditional expression (5) shown below:

0.62＜θgF+0.001625×ν d1＜0.67 (5)。

3. zoom lens according to claim 1 or 2,

when the partial dispersion ratio between the g-line and the F-line of the positive lens of the M2E lens group is θ gF, and the average value of (θ gF +0.001625 × v d1) of the positive lens of the M2E lens group is (θ gF +0.001625 × v d1) _ ave _ P, conditional expression (6) shown below is satisfied:

0.62＜(θgF+0.001625×v d1)_ave_P＜0.67 (6)。

4. zoom lens according to claim 1 or 2,

when the average value of the refractive indexes of the negative lenses of the M2E lens group is nd _ ave _ N and the average value of the refractive indexes of the positive lenses of the M2E lens group is nd _ ave _ P, the following conditional expression (7) is satisfied:

0.01＜nd_ave_N-nd_ave_P＜0.2 (7)。

5. zoom lens according to claim 1 or 2,

the M2E lens group includes at least 3 cemented lenses including at least 1 positive lens and at least 1 negative lens.

6. Zoom lens according to claim 5,

when the d-line reference dispersion coefficient of the positive lens constituting the cemented lens of the M2E lens group is v d _ P1, the d-line reference dispersion coefficient of the positive lens constituting the cemented lens of the M2E lens group is vd _ P2, the d-line reference dispersion coefficient of the negative lens constituting the cemented lens of the M2E lens group is vd _ N1, and the d-line reference dispersion coefficient of the negative lens constituting the cemented lens of the M2E lens group is vd _ N2,

at least 2 of the cemented lenses included in the M2E lens group satisfy the conditional expression (8) shown below:

10＜ν d_P1-v d_N1＜30 (8)，

at least 1 of the cemented lenses included in the M2E lens group satisfies conditional expression (9) shown below:

10＜ν d_N2-v d_P2＜35 (9)。

7. zoom lens according to claim 5,

the M2E lens group includes, in order from the object side, 3 cemented lenses described above and a negative meniscus lens having a concave surface facing the object side.

8. Zoom lens according to claim 1 or 2,

the focusing lens group has positive refractive power,

the zoom portion includes, in order from the object side, a V1 lens group having negative refractive power, a V2 lens group having positive refractive power, and a V3 lens group having positive refractive power,

the imaging portion has a positive refractive power,

the V1 lens group and a combined group including the V2 lens group and the V3 lens group simultaneously pass through points at which respective lateral magnifications are-1 times when performing magnification variation from a wide-angle end to a telephoto end.

9. Zoom lens according to claim 1 or 2,

the M1 lens group has a negative refractive power, the M2E lens group and the M3 lens group have a positive refractive power.

10. The variable focus lens according to claim 1,

the positive lens satisfying the conditional expressions (1) and (2) satisfies the conditional expressions (1-1) and/or (2-1) represented as follows:

55＜v dl＜70 (1-1)；

5.75＜dn/dt1＜8.5 (2-1)。

11. the variable focus lens according to claim 1,

the positive lens satisfying the conditional expressions (1) and (2) satisfies the conditional expressions (1-2) and/or (2-2) represented as follows:

55＜v d1＜60 (1-2)；

6＜dn/dt1＜7.5 (2-2)。

12. the variable focus lens according to claim 1,

satisfying conditional formulae (3-1) and/or (4-1) represented as follows:

3.75＜dn/dt_ave_P＜5.5 (3-1)；

2＜dn/dt_ave_N＜5 (4-1)。

13. the variable focus lens according to claim 1,

satisfies the conditional formula (3-2) shown below:

4＜dn/dt_ave_P＜5 (3-2)。

14. the variable focus lens according to claim 2,

at least 1 positive lens satisfying the conditional expressions (1) and (2) satisfies the conditional expression (5-1) represented as follows:

0.63＜θgF+0.001625×v d1＜0.66 (5-1)。

15. zoom lens according to claim 3,

satisfies the conditional formula (6-1) shown below:

0.63＜(θgF+0.001625×ν d1)_ave_P＜0.66 (6-1)。

16. zoom lens according to claim 4,

satisfies the conditional formula (7-1) shown below:

0.01＜nd_ave_N-nd_ave_P＜0.15 (7-1)。

17. the variable focus lens according to claim 6,

at least 2 of the cemented lenses included in the M2E lens group satisfy the conditional expression (8-1) shown below:

17＜v d_P1-v d_N1＜30 (8-1)。

18. the variable focus lens according to claim 6,

at least 1 of the cemented lenses included in the M2E lens group satisfies the conditional expression (9-1) shown below:

17＜ν d_N2-ν d_P2＜35 (9-1)。

19. a beam expanding lens, comprising the M2E lens group of the zoom lens of any one of claims 1 to 18.

20. An imaging device comprising the zoom lens according to any one of claims 1 to 18.

Technical Field

The present disclosure relates to a zoom lens, a beam expanding lens, and an image pickup apparatus.

Background

In recent years, there has been a demand for a lens system having a resolution performance of 4K or more, which is capable of improving the image quality of a video image and being used in an imaging device such as a broadcasting camera. As a lens system for a broadcasting camera, a zoom lens is generally used because it is desired to have a zoom function so as to be able to cope with a variety of scenes. When further magnification change is required, a beam expanding lens capable of changing the focal length of the entire system is used. Patent documents 1 to 3 describe the following: a part of lens groups in the zoom lens can be plugged in and pulled out of an optical path, and the lens groups and the beam expanding lens are replaced.

Patent document 1: japanese patent laid-open publication No. 2011-075646

Patent document 2: japanese patent No. 3862117

Patent document 3: japanese patent No. 3513264

In the case where a lens group of a part of a zoom lens having a constant total length is replaced with a beam expansion lens, the temperature characteristics change with the magnification of the afocal magnification. When the temperature characteristics of the zoom lens change, a problem arises in that the focal position shifts due to the temperature change. In the zoom lenses of patent documents 1 to 3, there is a problem that chromatic aberration is particularly deteriorated when a part of the lens groups in the zoom lens is replaced with a beam expanding lens.

Disclosure of Invention

The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a zoom lens, a beam expander lens, and an imaging apparatus that satisfactorily correct a focus position shift associated with a temperature change when replacing a beam expander lens, and reduce chromatic aberration.

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

<1> a zoom lens comprising, in order from an object side: a focusing unit including a focusing lens group that moves for focusing; a variable magnification unit including at least 2 variable magnification lens groups which are moved while changing their intervals for variable magnification; an aperture stop; and an imaging unit including an imaging lens group, the imaging unit including, in order from the object side, an M1 lens group, an M2N lens group, and an M3 lens group, the M2N lens group being replaceable with the M2E lens group which enlarges an imaging magnification, the M2E lens group having a positive lens dispersion coefficient of vd1, an average value of temperature change coefficients of refractive index at d-line in air of 0 ℃ to 40 ℃ being dn/dt, the M2E lens group having a positive lens of dn/dt1, the M2E lens group including at least one positive lens satisfying conditional expressions (1) and (2), the M2E lens group having a positive lens of dn/dt average value being dn/dt _ ave _ P, and the M2E lens group having a negative lens of dn/dt average value being dn/dt _ ave _ N, the conditional expressions (3) and (4) being satisfied.

55＜vd1 (1)

5.5＜dn/dt1＜10 (2)

3.5＜dn/dt_ave_P＜6 (3)

1.5＜dn/dt_ave_N＜6 (4)

<2> according to the zoom lens of <1>, when the partial dispersion ratio between the g-line and the F-line of the positive lens of the M2E lens group is θ gF, at least 1 positive lens satisfying the conditional expressions (1) and (2) satisfies the conditional expression (5).

0.62＜θgF+0.001625×vd1＜0.67 (5)

<3> according to the zoom lens of <1> or <2>, the conditional expression (6) is satisfied where θ gF is a partial dispersion ratio between g-line and F-line of the positive lens of the M2E lens group, and (θ gF +0.001625 × vd1) _ ave _ P is an average value of (θ gF +0.001625 × vd1) of the positive lens of the M2E lens group.

0.62＜(θgF+0.001625×ν d1)_ave_P＜0.67 (6)

<4> according to any one of <1> to <3>, the conditional expression (7) is satisfied where nd _ ave _ N is an average value of refractive indices of the negative lenses of the M2E lens group, and nd _ ave _ P is an average value of refractive indices of the positive lenses of the M2E lens group.

0.01＜nd_ave_N-nd_ave_P＜0.2 (7)

<5> according to any one of <1> to <4>, the M2E lens group includes at least 3 cemented lenses including at least 1 positive lens and at least 1 negative lens.

<6> according to the zoom lens of <5>, when the d-line reference dispersion coefficient of the positive lens constituting the cemented lens of the M2E lens group is ν d _ P1, the d-line reference dispersion coefficient of the positive lens constituting the cemented lens of the M2E lens group is ν d _ P2, the d-line reference dispersion coefficient of the negative lens constituting the cemented lens of the M2E lens group is v d _ N1, and the d-line reference dispersion coefficient of the negative lens constituting the cemented lens of the M2E lens group is ν d _ N2, at least 2 cemented lenses included in the M2E lens group satisfy the conditional expression (8), and at least 1 cemented lens included in the M2E lens group satisfies the conditional expression (9).

10＜νd_P1-v d_N1＜30 (8)

10＜ν d_N2-ν d_P2＜35 (9)

In the case where the cemented lens includes a plurality of positive lenses, the positive lens having the highest absolute value of refractive power in the cemented lens is used for calculation of the conditional expressions (8) and (9). Similarly, in the case where the cemented lens includes a plurality of negative lenses, the negative lens having the highest absolute value of refractive power among the cemented lenses is used for the calculation of the conditional expression.

<7> the zoom lens according to <5> or <6>, the M2E lens group comprising, in order from the object side, 3 cemented lenses and a negative meniscus lens with a concave surface facing the object side.

<8> in accordance with any one of <1> to <7>, the focusing lens group has a positive refractive power, the magnification varying section includes, in order from the object side, a V1 lens group having a negative refractive power, a V2 lens group having a positive refractive power, and a V3 lens group having a positive refractive power, the image forming section has a positive refractive power, and when performing magnification varying from the wide angle end to the telephoto end, the V1 lens group and the combined group including the V2 lens group and the V3 lens group pass through a point where their lateral magnifications are-1.

<9> according to any one of <1> to <8>, the M1 lens group has negative refractive power, and the M2E lens group and the M3 lens group have positive refractive power.

<10> the zoom lens according to <1>, wherein the positive lens satisfying the conditional expressions (1) and (2) satisfies the conditional expressions (1-1) and/or (2-1).

55＜vd1＜70 (1-1)

5.75＜dn/dt1＜8.5 (2-1)

<11> the zoom lens according to <1>, wherein the positive lens satisfying the conditional expressions (1) and (2) satisfies the conditional expressions (1-2) and/or (2-2).

55＜vd1＜60 (1-2)

6＜dn/dt1＜7.5 (2-2)

< 12> the zoom lens according to <1>, which satisfies conditional expressions (3-1) and/or (4-1).

3.75＜dn/dt_ave_P＜5.5 (3-1)

2＜dn/dt_ave_N＜5 (4-1)

<13> the zoom lens according to <1>, which satisfies conditional expression (3-2).

4＜dn/dt_ave_P＜5 (3-2)

<14> the zoom lens according to <2>, wherein at least 1 positive lens satisfying the conditional expressions (1) and (2) satisfies the conditional expression (5-1).

0.63＜θgF+0.001625×vd1＜0.66 (5-1)

<15> the zoom lens according to <3>, which satisfies conditional expression (6-1).

0.63＜(θgF+0.001625×vd1)_ave_P＜0.66 (6-1)

<16> the zoom lens according to <4>, which satisfies conditional expression (7-1).

0.01＜nd_ave_N-nd_ave_P＜0.15 (7-1)

<17> in the zoom lens according to <6>, at least 2 cemented lenses included in the M2E lens group satisfy the conditional expression (8-1).

17＜v d_P1-ν d_N1＜30 (8-1)。

<18> according to the zoom lens of <6>, at least 1 of the cemented lenses included in the M2E lens group satisfies the conditional expression (9-1).

17＜v d_N2-ν d_P2＜35 (9-1)

<19> a beam expanding lens comprising the M2E lens group of any one of the zoom lenses <1> to <18 >.

<20> an image pickup apparatus, which comprises any one of the zoom lenses <1> to <18 >.

In addition, the terms "including" to "and" including "in the present specification mean that, in addition to the components listed above, the optical components other than a lens having substantially no refractive power, a lens such as a diaphragm, a filter, and a cover glass, and mechanism parts such as a lens flange, a lens barrel, an imaging element, and a hand-shake correction mechanism, and the like may be included.

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. The meaning of "lens having positive refractive power" and "positive lens" is the same. The meaning of "lens having negative refractive power" and "negative lens" is the same. The "lens group" is not limited to a structure including a plurality of lenses, and may be a structure including only 1 lens.

The value used in the conditional expression is a value other than the partial dispersion ratio, when d-line is set as a reference. The partial dispersion ratio θ gF between g-line and F-line of a certain lens is a value defined as (Ng-NF)/(NF-NC) when the refractive indices of the lens with respect to g-line, F-line and C-line are Ng, NF and NC, respectively. 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).

Effects of the invention

According to the present disclosure, it is possible to provide a zoom lens, a beam expander lens, and an imaging apparatus that can satisfactorily correct a focus position shift associated with a temperature change when a beam expander lens is replaced, and reduce chromatic aberration.

Drawings

Fig. 1 is a sectional view showing a configuration of a zoom lens in a reference state according to embodiment 1 of the present invention.

Fig. 2 is a sectional view showing a configuration of an imaging section and its vicinity in an alternative state of a zoom lens according to embodiment 1 of the present invention.

Fig. 3 is a sectional view showing a configuration of an imaging section and its vicinity in an alternative state of a zoom lens according to embodiment 2 of the present invention.

Fig. 4 is a sectional view showing a configuration of an imaging section and its vicinity in an alternative state of a zoom lens according to embodiment 3 of the present invention.

Fig. 5 is each aberration diagram of a zoom lens in a reference state according to embodiment 1 of the present invention.

Fig. 6 is each aberration diagram of an alternative state of the zoom lens of embodiment 1 of the present invention.

Fig. 7 is each aberration diagram of an alternative state of the zoom lens of embodiment 2 of the present invention.

Fig. 8 is each aberration diagram of an alternative state of the zoom lens according to embodiment 3 of the present invention.

Fig. 9 is a schematic configuration diagram of an imaging apparatus according to an embodiment of the present invention.

Detailed Description

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the zoom lens of the present embodiment, the M2N lens group M2N, which is a partial lens group, can be inserted into and removed from the optical path, and the M2N lens group M2N and the M2E lens group M2E, which is a beam expanding lens, are replaced with each other, so that the image formation magnification can be increased while the position of the image plane Sim is kept constant. In the following description, a state in which the M2N lens group M2N is disposed in the zoom lens is referred to as a reference state, and a state in which the M2N lens group M2N is replaced with the M2E lens group M2E which is a beam expanding lens is referred to as a replacement state.

Fig. 1 is a sectional view showing a configuration of a zoom lens according to an embodiment of the present invention in a reference state at a wide-angle end, and fig. 2 is a sectional view showing a configuration of an imaging section and its vicinity in an alternative state of the zoom lens shown in fig. 1. The configuration examples shown in fig. 1 and 2 correspond to a zoom lens according to example 1 of the present invention described later. In fig. 1 and 2, the left side is the object side and the right side is the image side.

The zoom lens shown in fig. 1 is configured to include, in order from an object side to an image side along an optical axis Z: a focusing unit F including a focusing lens group F2 that moves for focusing; a zoom unit V including at least 2 zoom lens groups which move while changing their intervals for zooming; an aperture stop St that limits the amount of light passing therethrough; and an imaging unit M including a lens group for imaging, the total length of which is constant at the time of magnification change.

The imaging section M includes, in order from the object side, an M1 lens group M1, an M2N lens group M2N, and an M3 lens group M3, and the M2N lens group M2N is replaceable with an M2E lens group M2E which is a beam expanding lens for enlarging the imaging magnification of the entire system after replacement more than the imaging magnification of the entire system before replacement.

In the example of fig. 1 and 2, an optical member PP having an incident surface and an exit surface perpendicular to the optical axis Z is disposed between the imaging unit M and the image plane Sim. The optical member PP assumes various filters, prisms, cover glasses, and the like. In the present invention, the optical member PP may be disposed at a position different from the example of fig. 1, and the configuration of the optical member PP may be omitted. The aperture stop St shown in fig. 1 and 2 does not necessarily indicate the size and shape, but indicates the position on the optical axis Z.

When the dispersion coefficient of the positive lens of the M2E lens group M2E is vd1, the average value of the temperature change coefficient of refractive index at d-line in air is dn/dt, and dn/dt of the positive lens of the M2E lens group M2E is dn/dt1, the M2E lens group M2E includes at least one positive lens satisfying the conditional expressions (1) and (2).

55＜vd1 (1)

5.5＜dn/dt1＜10 (2)

By satisfying the conditional expression (1), the first-order chromatic aberration can be corrected well. Further, if the conditional expressions (1-1) and/or (1-2) are satisfied, more favorable characteristics can be obtained.

55＜νd1＜70 (1-1)

55＜νd1＜60 (1-2)

By satisfying the conditional expression (2), it is possible to satisfactorily correct the focus position shift when replacing the expander lens (the lens group M2E M2E) associated with the temperature change. In particular, in the M2E lens group M2E, the positive lens made of a material satisfying both the conditional expressions (1) and (2) greatly contributes to satisfactory correction of the primary chromatic aberration and satisfactory correction of the shift in the focal position when the expander lens (M2E lens group M2E) accompanying the temperature change is replaced, and the other lenses can be made of a general material, so that the degree of freedom in design can be improved. Further, if the conditional expressions (2-1) and/or (2-2) are satisfied, more favorable characteristics can be obtained.

5.75＜dn/dt1＜8.5 (2-1)

6＜dn/dt1＜7.5 (2-2)

Further, conditional expressions (3) and (4) are satisfied when the average value of dn/dt of the positive lens of the M2E lens group M2E is dn/dt _ ave _ P and the average value of dn/dt of the negative lens of the M2E lens group M2E is dn/dt _ ave _ N.

3.5＜dn/dt_ave_P＜6 (3)

1.5＜dn/dt_ave_N＜6 (4)

By satisfying the conditional expression (3), it is possible to satisfactorily correct the focus position shift when replacing the expander lens (the lens group M2E M2E) associated with the temperature change. Further, if the conditional expressions (3-1) and/or (3-2) are satisfied, more favorable characteristics can be obtained.

3.75＜dn/dt_ave_P＜5.5 (3-1)

4＜dn/dt_ave_P＜5 (3-2)

By satisfying the conditional expression (4), it is possible to satisfactorily correct the focus position shift when replacing the expander lens (the lens group M2E M2E) associated with the temperature change. Further, if the conditional expression (4-1) is satisfied, more favorable characteristics can be obtained.

2＜dn/dt_ave_N＜5 (4-1)

In the zoom lens according to the present embodiment, when θ gF is a partial dispersion ratio between g-line and F-line of the positive lens in the M2E lens group M2E, it is preferable that at least 1 positive lens satisfying conditional expressions (1) and (2) of the M2E lens group M2E satisfies conditional expression (5). The positive lens satisfying conditional expressions (1) and (2) of the M2E lens group M2E further satisfies conditional expression (5), whereby the primary and secondary axial chromatic aberration can be corrected satisfactorily. Further, if the conditional expression (5-1) is satisfied, more favorable characteristics can be obtained.

0.62＜θgF+0.001625×ν d1＜0.67 (5)

0.63＜θgF+0.001625×vd1＜0.66 (5-1)

It is preferable that conditional expression (6) be satisfied when θ gF is a partial dispersion ratio between g-line and F-line of the positive lens in the M2E lens group M2E, and (θ gF +0.001625 × vd1) is an average value of (θ gF +0.001625 × ν d1) _ ave _ P of the positive lens in the M2E lens group M2E. By satisfying the conditional expression (6), the effects of the conditional expressions (1) and (5) can be further improved. Further, if conditional expression (6-1) is satisfied, more favorable characteristics can be obtained.

0.62＜(θgF+0.001625×vd1)_ave_P＜0.67 (6)

0.63＜(θgF+0.001625×ν d1)_ave_P＜0.66 (6-1)

It is preferable that conditional expression (7) is satisfied where nd _ ave _ N is an average value of the refractive index of the negative lens of the M2E lens group M2E, and nd _ ave _ P is an average value of the refractive index of the positive lens of the M2E lens group M2E. By setting the upper limit of conditional expression (7) or more, correction of spherical aberration becomes easy. By setting the value not to be lower than the lower limit of conditional expression (7), correction of field curvature becomes easy. Further, if the conditional expressions (7-1) and/or (7-2) are satisfied, more favorable characteristics can be obtained.

0.01＜nd_ave_N-nd_ave_P＜0.2 (7)

0.01＜nd_ave_N-nd_ave_P＜0.15 (7-1)

0.01＜nd_ave_N-nd_ave_P＜0.1 (7-2)

Preferably, the M2E lens group M2E includes at least 3 cemented lenses including at least 1 positive lens and at least 1 negative lens. With this configuration, chromatic aberration can be corrected satisfactorily. Further, the difference caused by the wavelength of the spherical aberration can be reduced. Moreover, the extension of the total length of the lens system can be suppressed.

When the d-line-based dispersion coefficient of the positive lens constituting the cemented lens in the M2E lens group M2E is vd _ P1, the d-line-based dispersion coefficient of the positive lens constituting the cemented lens in the M2E lens group M2E is vd _ P2, the d-line-based dispersion coefficient of the negative lens constituting the cemented lens in the M2E lens group M2E is vd _ N1, and the d-line-based dispersion coefficient of the negative lens constituting the cemented lens in the M2E lens group M2E is vd _ N2, at least 2 cemented lenses included in the M2E lens group M2E satisfy the conditional expression (8), and at least 1 cemented lens included in the M2E lens group M2E satisfies the conditional expression (9). With this configuration, chromatic aberration can be corrected satisfactorily. Further, the difference caused by the wavelength of the spherical aberration can be reduced. Further, if the conditional expressions (8-1) and/or (8-2) are satisfied, more favorable characteristics can be obtained. Similarly, if the conditional expressions (9-1) and/or (9-2) are satisfied, more favorable characteristics can be obtained.

10＜vd_P1-νd_N1＜30 (8)

17＜vd_P1-ν d_N1＜30 (8-1)

19＜vd_P1-vd_N1＜30 (8-2)

10＜vd_N2-νd_P2＜35 (9)

17＜νd_N2-νd_P2＜35 (9-1)

19＜ν d_N2-ν d_P2＜35 (9-2)

Preferably, the M2E lens group M2E includes, in order from the object side, 3 cemented lenses and a negative meniscus lens having a concave surface facing the object side. In this way, by disposing the negative lens on the most image side of the M2E in the M2E lens group, the magnification becomes easy. Further, by providing 3 cemented lenses, chromatic aberration can be corrected well, and by providing a negative meniscus lens with the concave surface facing the object side, occurrence of astigmatism can be suppressed.

Preferably, the focusing lens group F2 included in the focusing portion F has a positive refractive power, the variable power portion V includes, in order from the object side, a V1 lens group V1 having a negative refractive power, a V2 lens group V2 having a positive refractive power, and a V3 lens group V3 having a positive refractive power, the imaging portion M has a positive refractive power, and when performing magnification from the wide-angle end to the telephoto end, the combined group of the V1 lens group V1 and the V2 lens group V2 and the V3 lens group V3 passes through a point where the lateral magnification is-1 times. Fig. 1 shows the movement locus and the position of minus 1 × lateral magnification when the magnification is changed in the V1 lens group V1, the V2 lens group V2, and the V3 lens group V3.

In this way, with respect to the V1 lens group V1 having a negative refractive power of the variable power section V, by correcting the variation of the image plane accompanying the variable power in 2 groups of the V2 lens group V2 and the V3 lens group V3 having a positive refractive power, and by providing a floating system in which the V2 lens group V2 and the V3 lens group V3 are relatively moved, the variation of the image plane at the time of variable power can be corrected, and the variation of the spherical aberration at the time of variable power can be corrected well.

Preferably, M1 lens group M1 has negative refractive power, and M2E lens group M2E and M3 lens group M3 have positive refractive power. In this way, the M1 lens group M1 having negative refractive power is disposed on the most object side of the imaging section M, and the back focus can be easily secured. Further, by sharing the positive refractive power of the imaging section M among the M2E lens group M2E and the M3 lens group M3, it is possible to suppress occurrence of each aberration.

In the example shown in fig. 1, the 3 rd, 4 th, and 5 th lenses from the object side of the focusing unit F constitute a focusing lens group F2, but a lens group different from this example may be used as the focusing lens group. Similarly, in the zoom lens of the present invention, the number of the magnification-varying lens groups included in the magnification-varying unit V may be different from the example shown in fig. 1.

The preferred configurations and possible configurations described above can be arbitrarily combined, and are preferably selectively employed as appropriate in accordance with the required specifications.

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

Example 1 (reference state)

Fig. 1 shows a configuration of a zoom lens in a reference state of example 1. The method of fig. 1 is as described above, and therefore, a part of the description thereof will be omitted.