Zoom lens and imaging device
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,
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,
the zoom lens satisfies conditional expression (1) shown below,
0.001＜f3/f2＜0.14 (1)。
2. the variable focus lens according to claim 1,
the 2 nd lens group includes 1 negative lens.
3. Zoom lens according to claim 1 or 2,
when the lateral magnification of the 2 nd lens group at the telephoto end is set to β 2t,
satisfies the conditional expression (2) shown below,
0.1＜1/β2t＜1 (2)。
4. zoom lens according to claim 1 or 2,
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,
satisfies the conditional expression (3) shown below,
0.004＜Db12/f1＜0.8 (3)。
5. zoom lens according to claim 1 or 2,
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 claim 1 or 2,
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 claim 1 or 2,
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 claim 1 or 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 is f1,
satisfies the conditional expression (7) shown below,
1＜ft/f1＜5 (7)。
9. zoom lens according to claim 1 or 2,
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 claim 1 or 2,
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 claim 1 or 2,
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 claim 1 or 2,
the lens group disposed adjacent to the object side of the rear group has negative refractive power.
13. Zoom lens according to claim 1 or 2,
the rear group includes a vibration prevention group that performs image shake correction by moving in a direction intersecting the optical axis.
14. The variable focus lens according to claim 1,
satisfies the conditional expression (1-1) shown below,
0.005＜f3/f2＜0.13 (1-1)。
15. zoom lens according to claim 3,
satisfies the conditional expression (2-1) shown below,
0.62＜1/β2t＜0.99 (2-1)。
16. zoom lens according to claim 4,
satisfies the conditional expression (3-1) shown below,
0.005＜Db12/f1＜0.55 (3-1)。
17. zoom lens according to claim 5,
satisfies the conditional expression (4-1) shown below,
0.02＜Db13/D3wt＜0.085 (4-1)。
18. the variable focus lens according to claim 6,
satisfies the conditional expression (5-1) shown below,
-0.38＜f1/f2＜-0.03 (5-1)。
19. zoom lens according to claim 1 or 2,
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 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
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 fixed 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 to the image surface at the time of magnification change, intervals between lens groups adjacent to each other at the time of magnification change are changed, and when a focal length of the 2 nd lens group is f2 and a focal length of the 3 rd lens group is f3, a conditional expression (1) shown below is satisfied,
0.001＜f3/f2＜0.14 (1)。
according to the zoom lens according to aspect 1,
the zoom lens according to
According to the zoom lens according to
when the lateral magnification of the 2 nd lens group under the telephoto end is set to β 2t,
the zoom lens according to
0.1＜1/β2t＜1 (2)。
according to any one of the zoom lenses according to the 1 st to 3 rd aspects,
when 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 is Db1.2, and the focal length of the 1 st lens group is f1,
the zoom lens according to claim 4 satisfies conditional expression (3) shown below,
0.004＜Db12/f1＜0.8 (3)。
according to any one of the zoom lenses according to embodiments 1 to 4,
when Db13 is the distance on the optical axis between the lens surface closest to the image side of the 1 st lens group and the lens surface closest to the object side of the 3 rd lens group at the wide angle end, and D3wt is the difference in the optical axis direction between the position of the 3 rd lens group at the wide angle end and the position of the 3 rd lens group at the telephoto end,
the zoom lens according to
0.01＜Db13/D3wt＜0.12 (4)。
according to any one 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)。
according to any one of the zoom lenses according to embodiments 1 to 6,
when the average value of refractive indexes under d-lines of all lenses included in the 2 nd lens group is Nave and the average value of dispersion coefficients of d-line references of all lenses included in the 2 nd lens group is Nave,
the zoom lens according to
1.8＜Nave+0.006×νave＜2.1 (6)。
according to any one 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
1＜ft/f1＜5 (7)。
according to any one 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
-5＜βr＜-1 (8)。
according to any one 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 set to β 3rw and the combined lateral magnification from the 3 rd lens group to the rear group at the telephoto end is set to β 3rt,
the zoom lens according to
5＜β3rt/β3rw＜150 (9)。
according to any one 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.
According to any one of the zoom lenses according to embodiments 1 to 11,
in the zoom lens according to
According to any one of the zoom lenses according to embodiments 1 to 12,
the rear group in the zoom lens according to embodiment 13 includes a vibration-proof group that performs image shake correction by moving in a direction intersecting the optical axis.
According to the zoom lens according to aspect 1,
the zoom lens according to claim 14 satisfies conditional expression (1-1) shown below,
0.005＜f3/f2＜0.13 (1-1)。
according to the zoom lens according to
the zoom lens according to claim 15 satisfies conditional expression (2-1) shown below,
0.62＜1/β2t＜0.99 (2-1)。
according to the zoom lens according to claim 4,
the zoom lens according to claim 16 satisfies conditional expression (3-1) shown below,
0.005＜Db12/f1＜0.55 (3-1)。
according to the zoom lens according to the fifth aspect,
the zoom lens according to claim 17 satisfies conditional expression (4-1) shown below,
0.02＜Db13/D3wt＜0.085 (4-1)。
according to the zoom lens according to claim 6,
the zoom lens according to claim 18 satisfies conditional expression (5-1) shown below,
-0.38＜f1/f2＜-0.03 (5-1)。
according to any one of the zoom lenses according to embodiments 1 to 18,
a zoom lens according to embodiment 19 includes 5 or 6 lens groups in which intervals between lens groups adjacent to each other change during magnification change.
The imaging device according to embodiment 20 includes any one of the zoom lenses according to embodiments 1 to 19.
In the zoom lens according to embodiment 1, the "at least 1 lens group that moves along the optical axis during magnification variation" 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 configuration and a movement locus of the zoom lens according to embodiment 1 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
Fig. 4 is a sectional view showing a configuration and a movement locus of a zoom lens according to
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
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
Fig. 9 is a sectional view showing a configuration and a movement locus of a zoom lens according to
Fig. 10 is a sectional view showing a configuration and a movement locus of a zoom lens according to
Fig. 11 is a sectional view showing a configuration and a movement locus of a zoom lens according to
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
Fig. 14 is each aberration diagram of a zoom lens according to
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
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
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 includes, in order from the object side toward the image side along the optical axis Z, a 1 st lens group G1 having positive refractive power and fixed with respect to the image plane Sim at the time of magnification change, a 2 nd lens group G2 having negative refractive power and moving along the optical axis Z at the time of magnification change, a 3 rd lens group G3 having negative refractive power and moving along the optical axis Z at the time of magnification change, at least 1 lens group moving along the optical axis Z at the time of magnification change, and a rear group Gr fixed with respect to the image plane Sim 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 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.
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 zoom lens satisfies the following conditional expression (1). By not being equal to or less than the lower limit of conditional expression (1), 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 (1), it is possible to easily correct the field curvature on the wide angle side and the spherical aberration on the telephoto side with good balance while securing the refractive power of the 2 nd lens group G2. By not being equal to or more than the upper limit of conditional expression (1), the refractive power of
0.001＜f3/f2＜0.14 (1)
0.005＜f3/f2＜0.13 (1-1)
0.009＜f3/f2＜0.12 (1-2)
The 2 nd lens group G2 preferably 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.
Further, the zoom position at which the 2 nd lens group G2 is positioned most to the image side in variable magnification may be configured to be a zoom position between the wide angle end and the telephoto end, not the wide angle end nor the telephoto end. With such a configuration, by bringing the 2 nd lens group G2 close to the 1 st lens group G1, spherical aberration generated in the 1 st lens group G1 can be corrected at the time of magnification toward the telephoto end, and field curvature can be suppressed at the time of magnification 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 lateral power of the 2 nd lens group G2 at the telephoto end is β t, the zoom lens preferably satisfies the following conditional expression (2). by not being equal to or less than the lower limit of the conditional expression (2), it is possible to suppress an excessively large lateral power of the 2 nd lens group G2 at the telephoto end, and to suppress an excessively long combined focal length of the 1 st lens group G1 and the 2 nd lens group G2 at the telephoto end, whereby it is easy to secure the negative refractive power of the 3 rd lens group G3, and to suppress the zoom stroke of the 3 rd lens group G3, which is the main variable power group, at the time of high power, which is advantageous to achieve both high power and downsizing.
0.1＜1/β2t＜1 (2)
0.62＜1/β2t＜0.99 (2-1)
0.7＜1/β2t＜0.98 (2-2)
It is preferable that the following conditional expression (3) is satisfied, where Db12 is an axial distance between a most image-side lens surface of the 1 st lens group G1 and a most object-side lens surface of the 2 nd lens group G2 at the telephoto end, and f1 is a focal length of the 1 st lens group G1. By not being equal to or less than the lower limit of conditional expression (3), it is possible to easily suppress the fluctuation of the field curvature on the wide angle side and the fluctuation of the spherical aberration on the telephoto side with good balance without excessively decreasing the movement amount of the 2 nd lens group G2 from the wide angle end to the telephoto end. 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. It is further possible to make the 1 st lens group G1 not interfere with the 2 nd lens group G2. By not being equal to or more than the upper limit of conditional expression (3), 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, the effect of suppressing the variation of spherical aberration on the telephoto side can be ensured even when the magnification is increased. Further, the refractive power of the 1 st lens group G1 can be prevented from becoming excessively strong, and spherical aberration occurring in the 1 st lens group G1 can be suppressed. 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.
0.004＜Db12/f1＜0.8 (3)
0.005＜Db12/f1＜0.55 (3-1)
0.006＜Db12/f1＜0.32 (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 in the d-line and the d-line reference Abbe are Nave and vove, 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, the following conditional expression (8) is preferably satisfied, and when it is not below the lower limit of the conditional expression (8), it is possible to suppress the aberration from being greatly enlarged and suppress the variation of each aberration when the magnification is changed, 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 is smaller than the size of the object of the rear group Gr.
-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 1 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 1 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), the variation in the lateral magnification of the lens group after the 3 rd lens group G3 can be made small, which is advantageous for high magnification, and by not being equal to or more than the upper limit of the conditional expression (9), the variation in the lateral magnification of the lens group after the 3 rd lens group G3 can be made not excessively large, and the variation in the spherical aberration can be suppressed well.
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 1R. 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
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×hm
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 ]
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