JP7252002B2 - Zoom lens and imaging device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a zoom lens and an imaging device, and more particularly, a zoom lens and an imaging device suitable for imaging devices such as medical optical systems, digital still cameras, and digital video cameras, in which photoelectric conversion is performed by a solid-state imaging device such as a CCD or CMOS. Regarding.

In recent years, in medical applications, information from a rigid endoscope or the like is not only visually observed through an eyepiece, but also displayed on a large-screen monitor. Therefore, there is a demand for a compact imaging optical system with high optical performance.

As the first prior art of the compact imaging optical system described above, in order from the object side, there is a first lens unit L1 with negative refractive power, a second lens unit L2 with positive refractive power, and a third lens with positive refractive power. In a zoom lens having three lens groups, the group L3, when zooming from the wide-angle end to the telephoto end, the second lens group L2 is moved toward the object side, and the third lens group L3 is moved to a zoom position other than the wide-angle end. is positioned closest to the image side, the first lens unit L1 is moved so as to draw a convex locus or a part thereof on the image side, and the first lens unit L1 is not moved for zooming, and the first lens unit L1 is A negative lens having a concave surface on the image side and a positive lens having a convex surface on the object side are provided, and the second lens unit L2 is disposed on the image side of the negative lens having a concave surface on the image side. There has been proposed a zoom lens configured to have a positive lens with a positive angle (for example, see Patent Document 1).

Although the first prior art achieves a relatively small number of lenses and a small size, it is difficult to secure a light flux to the peripheral region of the wide-angle field of view and to perform good aberration correction in that region. That is, in the peripheral area imaging position of the first prior art, if all the light beams that have passed through the entrance pupil are allowed to contribute to image formation in the same manner as the light beams in the center of the field of view, the coma aberration will increase and the resolution will not be high. can't get In addition, in a 3CCD imaging device or the like capable of performing sharp and highly color reproducible imaging, the need to have a long back focus for arranging a 3-color separation filter or the like is not satisfied.

As the second prior art of the compact imaging optical system described above, in order from the object side, there is a negative first lens group G1, a positive second lens group G2, a positive third lens group G3, and a positive fourth lens group. G4, the first lens group G1 and the fourth lens group G4 are fixed during zooming, and the second lens group G2 and the third lens group G3 are changed depending on the operation from the wide-angle end to the telephoto end. proposed a zoom lens that moves along the optical axis O while changing the distance between the lenses to the enlargement side, and satisfies predetermined conditions regarding the focal length of the third lens group G3 and the focal length of the entire system at the wide-angle end. (See, for example, Patent Document 2).

The second prior art has a simple mechanical configuration and is a zoom lens suitable for a photographing optical system of a camera using a solid-state image sensor. They are provided to correspond to filters, faceplates, and the like.
However, in the second prior art, it is difficult to secure the luminous flux to the peripheral region of the wide-angle region and to satisfactorily correct aberrations in this region. In addition, since the total length of the lens relative to the focal length is long, it cannot be said that the miniaturization has been sufficiently achieved.

Japanese Patent Application Laid-Open No. 2004-046108 JP 2011-232653 A

(Purpose of Invention)
SUMMARY OF THE INVENTION It is an object of the present invention to provide a compact zoom lens and an imaging apparatus while maintaining high optical performance.

A zoom lens according to the present invention is
In order from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having positive refractive power,
When zooming from the wide-angle end to the telephoto end, the distance between adjacent lens groups on the optical axis changes,
This zoom lens is characterized by satisfying the following conditional expression.
-2.20 ≤ expt/f3 ≤ -1.20 (1)
0.70 ≤ f3/f2 ≤ 1.70 (2)
however
expt: Distance from the image formation position to the exit pupil at the telephoto end
f2: focal length of the second lens group
f3: focal length of the third lens group

An imaging device according to the present invention includes:
An imaging apparatus comprising: the zoom lens; and an imaging element that converts an optical image formed by the zoom lens into an electrical signal on an image plane side of the zoom lens.

According to the present invention, it is possible to configure a compact zoom lens and imaging device while maintaining high optical performance.

FIG. 2 is an optical diagram of the wide-angle end state, intermediate focal length state, and telephoto end state of the first embodiment of the zoom lens of the present invention; FIG. 4 is a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram when focusing on infinity in the wide-angle end state of the first embodiment of the zoom lens of the present invention; FIG. 4 is a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram when focusing on infinity in an intermediate focal length state of the zoom lens according to the first embodiment of the present invention; FIG. 2 is a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram when focusing on infinity in the telephoto end state of the zoom lens according to the first embodiment of the present invention; FIG. 10 is an optical diagram of the wide-angle end state, intermediate focal length state, and telephoto end state of the second embodiment of the zoom lens of the present invention; FIG. 10 is a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram when focusing on infinity in the wide-angle end state of the zoom lens according to the second embodiment of the present invention; FIG. 10 is a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram when focusing on infinity in an intermediate focal length state of the second embodiment of the zoom lens of the present invention; FIG. 10 is a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram when focusing on infinity in the telephoto end state of the zoom lens according to the second embodiment of the present invention; 8A and 8B are optical diagrams of the wide-angle end state, intermediate focal length state, and telephoto end state of the third embodiment of the zoom lens of the present invention; FIG. 10 is a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram when focusing on infinity in the wide-angle end state of the third embodiment of the zoom lens of the present invention; FIG. 10 is a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram when focusing on infinity in an intermediate focal length state of the zoom lens according to the third embodiment of the present invention; FIG. 10 is a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram when focusing on infinity in the telephoto end state of the zoom lens according to the third embodiment of the present invention; FIG. 10 is an optical diagram of the wide-angle end state, intermediate focal length state, and telephoto end state of the fourth embodiment of the zoom lens of the present invention; FIG. 10 is a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram when focusing on infinity in the wide-angle end state of the fourth embodiment of the zoom lens of the present invention; FIG. 10 is a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram when focusing on infinity in an intermediate focal length state of the zoom lens according to the fourth embodiment of the present invention; FIG. 10 is a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram when focusing on infinity in the telephoto end state of the zoom lens according to the fourth embodiment of the present invention; FIG. 10 is an optical diagram of the wide-angle end state, intermediate focal length state, and telephoto end state of the fifth embodiment of the zoom lens of the present invention; FIG. 10 is a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram when focusing on infinity in the wide-angle end state of the fifth embodiment of the zoom lens of the present invention; FIG. 11 is a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram when focusing on infinity in an intermediate focal length state of the fifth embodiment of the zoom lens of the present invention; FIG. 11 is a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram when focusing on infinity in the telephoto end state of the zoom lens according to the fifth embodiment of the present invention; FIG. 11 is an optical diagram of the wide-angle end state, intermediate focal length state, and telephoto end state of the sixth embodiment of the zoom lens of the present invention; FIG. 10 is a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram when focusing on infinity in the wide-angle end state of the sixth embodiment of the zoom lens of the present invention; FIG. 11 is a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram when focusing on infinity in an intermediate focal length state of the zoom lens according to the sixth embodiment of the present invention; FIG. 11 is a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram when focusing on infinity in the telephoto end state of the zoom lens according to the sixth embodiment of the present invention; 1 is a configuration diagram of an imaging device according to an embodiment of the present invention; FIG. FIG. 3 is an optical diagram of an example of three CCD members used in an imaging device of an example of the present invention;

The zoom lens according to the present invention preferably satisfies at least one of the following conditional expressions or conditions.
Preferred embodiments of the present invention are described below.

A zoom lens according to the present invention has, in order from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having positive refractive power. However, the interval on the optical axis between adjacent lens groups changes when zooming from the wide-angle end to the telephoto end.

By adopting a configuration having, in order from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having positive refractive power, It is possible to widen the angle of view. Furthermore, when an optical system with a long back focus is used, aberration correction becomes easy.

A fourth lens group having positive or negative refractive power may be provided on the image side of the third lens group. By having the fourth lens group, it is possible to satisfactorily correct aberrations that occur during zooming, and to achieve higher performance. At this time, since the fourth lens group is fixed in the optical axis direction during zooming, the structure for supporting the lens is simplified and the structure is more robust, which is preferable. More preferably, by arranging the fourth lens group having a negative refractive power, it is possible to secure good performance while securing the back focus.

The zoom lens according to the present invention preferably satisfies the following conditional expressions.
-2.20 ≤ expt/f3 ≤ -1.20 (1)
expt: Distance from the image formation position to the exit pupil at the telephoto end
f3: focal length of the third lens group

Conditional expression (1) is an expression for defining the ratio of the distance from the imaging position to the exit pupil at the telephoto end and the focal length of the third lens group. Regarding the distance from the imaging position to the exit pupil, the traveling direction of light rays, that is, the direction from the object side to the image plane is positive.

By satisfying the range of conditional expression (1), it is possible to keep the effective diameter of the lens within a predetermined range while keeping the aberration in the telephoto range within a predetermined range.
If the upper limit of conditional expression (1) is exceeded, coma will occur at the telephoto end. Therefore, in order to correct aberrations well, it is necessary to add an additional lens.
If the lower limit of conditional expression (1) is not reached, it becomes difficult to suppress the lens effective diameter.

The upper limit of conditional expression (1) is preferably -1.4, and more preferably -1.2.
The lower limit of conditional expression (1) is preferably -2.0, and more preferably -1.8.

The zoom lens according to the present invention preferably satisfies the following conditional expressions.
0.70 ≤ f3/f2 ≤ 1.70 (2)
f2: focal length of the second lens group
f3: focal length of the third lens group

Conditional expression (2) is an expression for defining the ratio of the focal lengths of the third lens group and the second lens group.

By satisfying the range of conditional expression (2), it is possible to effectively suppress axial aberration and coma aberration generated by each lens arranged after the second lens group.

If the upper limit of conditional expression (2) is exceeded, coma aberration will occur and the effective diameter of the lens arranged in the third lens group will increase.
If the lower limit of conditional expression (2) is not reached, correction of axial aberration becomes difficult. An attempt to correct the axial aberration increases the effective diameter of the lens arranged in the second lens group.

The upper limit of conditional expression (2) is more preferably 1.5, and even more preferably 1.4.
The lower limit of conditional expression (2) is more preferably 0.8, more preferably 1.0, and even more preferably 1.2.

In the zoom lens according to the present invention, it is preferable that the third lens group moves toward the object side during zooming from the wide-angle end to the telephoto end.

By moving the third lens group toward the object side, it is possible to satisfactorily correct aberrations that occur during zooming. More preferably, by monotonously moving the third lens group, it is possible to approximate the aberration at the wide-angle end and the aberration at the telephoto end, thereby improving the performance in the intermediate range of zooming. Here, "moving monotonously" means that the moving direction of the third lens group is only toward the object side and does not move toward the image side during zooming from the wide-angle end to the telephoto end.

In the zoom lens according to the present invention, it is preferable that the first lens group is fixed in the optical axis direction during zooming.

By fixing the first lens group in the optical axis direction during zooming, it becomes easy to maintain optical performance while reducing the amount of displacement of the entrance pupil position on the optical axis. Also, when the zoom lens according to the present invention is used as an adapter optical system, the amount of displacement of the adapter optical system on the optical axis during zooming can be reduced, and the structure of the lens barrel can be simplified. It becomes possible.

The zoom lens according to the present invention preferably satisfies the following conditional expressions.
-2.8 ≤ βw2 ≤ -1.0 (3)
where βw2: Lateral magnification of the second lens group when focusing on infinity at the wide-angle end

Conditional expression (3) defines the lateral magnification of the second lens group when focusing on infinity at the wide-angle end.

By satisfying conditional expression (3), axial aberration and coma at the wide-angle end can be effectively corrected.
If the upper limit of conditional expression (3) is exceeded, it becomes difficult to correct axial aberration and coma. Therefore, in order to correct this coma aberration, it is necessary to add a further lens, which unfavorably increases the cost.
If the lower limit of conditional expression (3) is not reached, the total length of the zoom lens (the distance from the first surface to the imaging position) will increase, and aberrations will need to be corrected unless the effective diameter of the second lens group is increased. becomes difficult. If the effective diameter of the second lens group is reduced, it becomes difficult to correct axial aberration and coma.

The upper limit of conditional expression (3) is more preferably -1.2, and even more preferably -1.4.
The lower limit of conditional expression (3) is preferably -2.5, and more preferably -2.3.

The zoom lens according to the present invention preferably satisfies the following conditional expressions.
1.5 ≤ f3/fw ≤ 3.0 (4)
however
f3: focal length of the third lens group
fw: Focal length at the wide-angle end of the zoom lens

Conditional expression (4) defines the ratio between the focal length of the third lens group and the focal length at the wide-angle end of the zoom lens.

By satisfying conditional expression (4), it is possible to suppress the effective diameter of the third lens group while suppressing coma, astigmatism and distortion.
If the upper limit of conditional expression (4) is exceeded, it becomes difficult to correct coma. In addition, the total length of the zoom lens becomes long, and it becomes difficult to suppress the effective diameter of the third lens group.
If the lower limit of conditional expression (4) is not reached, it becomes difficult to secure the back focus while correcting the aberration.

The upper limit of conditional expression (4) is more preferably 2.8, and even more preferably 2.5.
The lower limit of conditional expression (4) is more preferably 1.6, and even more preferably 1.8.

The zoom lens according to the present invention preferably satisfies the following conditional expressions.
-30.0 ≤ expt/Ymax ≤ -10.0 (5)
however
Ymax: Maximum image height

Conditional expression (5) is an expression for defining the ratio of the maximum image height to the distance from the imaging position to the exit pupil at the telephoto end.

By satisfying conditional expression (5), it is possible to effectively correct coma while suppressing the effective diameter of the lens arranged on the image side of the diaphragm.
If the upper limit of conditional expression (5) is exceeded, it becomes difficult to suppress the effective diameter of the lens arranged on the image side of the stop, and it becomes difficult to ensure a sufficient amount of peripheral light. In addition, it becomes difficult to correct coma and astigmatism while maintaining the amount of peripheral light.
If the lower limit of conditional expression (5) is not reached, it becomes difficult to secure the back focus while correcting the aberration.

The upper limit of conditional expression (5) is preferably -9.0, and more preferably -8.0.
The lower limit of conditional expression (5) is more preferably -27.0, and even more preferably -24.0.

The zoom lens according to the present invention preferably satisfies the following conditional expressions.
5.0 ≤ |βt2| ≤ 50.0 (6)
where βt2 is the lateral magnification of the second lens group when focusing on infinity at the telephoto end

Conditional expression (6) is an expression for defining the lateral magnification of the second lens group when focusing on infinity at the telephoto end.

By satisfying conditional expression (6), it becomes possible to effectively correct axial chromatic aberration and coma at the telephoto end.
If the upper limit of conditional expression (6) is exceeded, the aberration correcting effect of the second lens group cannot be sufficiently utilized, making it difficult to achieve miniaturization.
If the lower limit of conditional expression (6) is not reached, it becomes difficult to correct axial aberration and coma at the same time. In order to correct axial aberration and coma at the same time, it is necessary to add an additional lens, which is not preferable because the manufacturing cost increases.

The upper limit of conditional expression (6) is preferably 45.0, more preferably 40.0, even more preferably 30.0.
The lower limit of conditional expression (6) is preferably 6.0, preferably 7.0, preferably 8.0, more preferably 10.0, and even more preferably 15.0.

The zoom lens according to the present invention preferably satisfies the following conditional expressions.
0.5 ≤ G01R/f1 ≤ 1.5 (7)
however
G01R: Radius of curvature of the zoom lens closest to the object side
f1: focal length of the first lens group

Conditional expression (7) is an expression for defining the ratio between the radius of curvature of the zoom lens closest to the object side and the focal length of the first lens group.

By satisfying the conditional expression (7), it is possible to reduce the size of the zoom lens and make it possible to satisfactorily correct coma aberration and axial aberration.

If the upper limit of conditional expression (7) is exceeded, it becomes difficult to suppress the lens effective diameter while ensuring sufficient luminous flux in the peripheral portion.
If the lower limit of conditional expression (7) is not reached, it becomes difficult to simultaneously suppress coma and axial aberration, lateral chromatic aberration and distortion.

The upper limit of conditional expression (7) is preferably 1.2, more preferably 0.9, and even more preferably 0.8.
The lower limit of conditional expression (7) is more preferably 0.6, and even more preferably 0.7.

The zoom lens according to the present invention preferably satisfies the following conditional expressions.
0.5 ≤ hitomi/(enpw×tan(ωw)) ≤ 2.0 ・・・・ (8)
however
hitomi: Entrance pupil radius at the wide-angle end
enpw: Distance from the first surface to the entrance pupil at the wide-angle end ωw: Maximum angle of view of the principal ray at the wide-angle end (half angle of view)

Conditional expression (8) is an expression for defining the entrance pupil radius at the wide-angle end.

By satisfying the conditional expression (8), it is possible to correct coma aberration and axial chromatic aberration on the wide-angle side while making it possible to reduce the size of the lens.

Exceeding the upper limit of conditional expression (8) makes it difficult to correct axial aberration while maintaining the wide-angle F-number.
If the conditional expression (8) is exceeded, it becomes difficult to correct coma aberration in the peripheral region with a sufficient amount of light.

The upper limit of conditional expression (8) is more preferably 1.8, and even more preferably 1.6.
The lower limit of conditional expression (8) is more preferably 0.55, and even more preferably 0.60.

In the zoom lens according to the present invention, it is preferable that the surface of the first lens group closest to the object side has a concave shape. By having this configuration, it is possible to reduce the size and improve the performance.

In the zoom lens according to the present invention, it is preferable that the surface of the second lens group closest to the object side has a convex shape. By having this configuration, it is possible to satisfactorily correct spherical aberration, and it is possible to achieve high performance.

In the zoom lens according to the present invention, when zooming from the wide-angle end to the telephoto end, the distance between the second lens group and the third lens group widens so that the distance between the first lens group and the second lens group narrows. It is preferable that at least one or a plurality of lens groups move along the optical axis.

The zoom lens according to the present invention preferably has a lens with positive refractive power in the first lens group. With this configuration, it is possible to satisfactorily correct chromatic aberration and achieve high performance.

An imaging apparatus according to the present invention includes the zoom lens described above, and an imaging device that converts an optical image formed by the zoom lens into an electrical signal on the image plane side of the zoom lens.

In the imaging device of the imaging apparatus according to the present invention, excellent imaging performance and photoelectric conversion efficiency can be realized not only in the center of the field of view but also in the periphery of the field of view, and a preferable imaging signal can be formed.

(Example)
BEST MODE FOR CARRYING OUT THE INVENTION A zoom lens according to the present invention and an imaging apparatus having the zoom lens will be described below based on numerical examples and accompanying drawings.

Numerical examples to which specific numerical values of the optical system according to the present invention are applied will be described.
In the specification table, F is the focal length of the entire system, FNo is the F number, W is the half angle of view (°), WIDE is the wide angle state, MID is the intermediate focal length state, and TELE is the telephoto state.
In the surface data table, No. is the surface number, R is the radius of curvature, D is the lens thickness or lens spacing, Nd is the refractive index at the d-line, ABV is the Abbe number at the d-line, INF is infinity, and STOP is the stop. .

2 to 4, 6 to 8, 10 to 12, 14 to 16, 18 to 20, and 22 to 24), from left to right , spherical aberration (mm), astigmatism (mm), and distortion (%). In the spherical aberration chart, the vertical axis represents the ratio to the maximum F value, the solid line is the d-line (587.56 nm), the dashed line is the C-line (656.28 nm), and the dashed line is the g-line (435.84 nm). be. In the astigmatism diagram, the vertical axis represents the half angle of view (°) of the d-line, the solid line is the sagittal image plane (indicated by s in the figure), and the broken line is the meridional image plane (indicated by t in the figure). is. In the distortion diagrams, the vertical axis represents the half angle of view (°) of the d-line.

(First embodiment)
As shown in FIG. 1, the first embodiment of the zoom lens according to the present invention comprises, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, and a positive refractive power. It has a third lens group G3 and a color separation prism P, and a photoelectric conversion element PEC is arranged at an imaging position IMG. The photoelectric conversion element PEC may include a bandpass filter and cover glass.
The first lens group G1 is formed by cementing a negative first lens L11 and a positive second lens L12. The second lens group G2 consists of an aperture STOP, a positive third lens L21, a positive fourth lens L22 and a negative fifth lens L23 cemented together. The third lens group G3 is a positive sixth lens L31.

The first lens group G1 is stationary during zooming, and the second lens group G2 and the third lens group G3 move toward the object side along the optical axis during zooming from the wide-angle end to the telephoto end.

The specification table of the first embodiment is as follows.
(specification table)
WIDE MID TELE
F 13.317 22.321 28.710
Fno 4.557 5.833 6.425
W 13.268 7.755 6.000

The surface data table of the first embodiment is as follows.
(surface data table)
No. RD Nd ABV
1 -15.714 1.453 1.5345 68.38
2 11.006 2.819 1.8314 30.34
3 19.803D(3)
4STOP INF 0.101
5 22.101 1.798 1.7102 46.52
6 -26.707 0.100
7 13.192 3.229 1.5925 65.99
8 -8.100 1.753 1.6623 37.11
9 10.584D(9)
10 24.371 2.772 1.6124 63.93
11-55.756 D(11)
12 INF 4.232 1.5168 64.17
13INF 13.038 1.7015 41.24
14INF 0.700

The lens intervals in the first embodiment when focusing on infinity are as follows.
(Lens spacing chart)
WIDE MID TELE
D(3) 13.946 5.155 1.915
D(9) 4.602 7.134 5.172
D(11) 3.233 9.492 14.694

The focal length of each lens group in the first embodiment is as follows.
(focal length of each lens group)
f1 -20.04
f2 18.73
f3 28.06

(Second embodiment)
A second embodiment of a zoom lens according to the present invention, as shown in FIG. It has a third lens group G3 and a color separation prism P, and a photoelectric conversion element PEC is arranged at an imaging position IMG. The photoelectric conversion element PEC may include a bandpass filter and cover glass.
The first lens group G1 is formed by cementing a negative first lens L11 and a positive second lens L12. The second lens group G2 consists of an aperture STOP, a positive third lens L21, a positive fourth lens L22 and a negative fifth lens L23 cemented together. The third lens group G3 is a positive sixth lens L31.

The first lens group G1 is stationary during zooming, and the second lens group G2 and the third lens group G3 move along the optical axis toward the object side during zooming from the wide-angle end to the telephoto end.

The specification table of the second embodiment is as follows.
(specification table)
WIDE MID TELE
F 13.317 22.321 28.710
Fno 4.557 5.833 6.425
W 13.256 7.755 5.996

The surface data table of the second embodiment is as follows.
(surface data table)
No. RD Nd ABV
1 -16.440 1.487 1.5265 57.52
2 11.817 2.795 1.8171 24.91
3 20.707D(3)
4 STOP INF 0.100
5 18.101 1.800 1.6927 44.21
6 -32.674 0.831
7 17.911 3.186 1.5853 66.81
8 -7.647 1.726 1.6754 35.14
9 12.376 D(9)
10 27.155 2.765 1.7401 48.60
11-42.404 D(11)
12 INF 4.232 1.5168 64.17
13INF 13.038 1.7015 41.24
14INF 0.700

The lens intervals in the second embodiment when focusing on infinity are as follows.
(Lens spacing chart)
WIDE MID TELE
D(3) 14.235 4.707 1.500
D(9) 2.285 5.327 3.785
D(11) 5.095 11.581 16.330

The focal length of each lens group in the second embodiment is as follows.
(focal length of each lens group)
f1 -20.94
f2 22.63
f3 22.75

(Third embodiment)
As shown in FIG. 9, the third embodiment of the zoom lens according to the present invention comprises, from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, It has a third lens group G3 having a positive refractive power, a color separation prism P, and a photoelectric conversion element PEC arranged at an imaging position IMG. The photoelectric conversion element PEC may include a bandpass filter and cover glass.
The first lens group G1 is formed by cementing a negative first lens L11 and a positive second lens L12. The second lens group G2 consists of an aperture STOP, a positive third lens L21, a positive fourth lens L22 and a negative fifth lens L23 cemented together. The third lens group G3 is a positive sixth lens L31.

The first lens group G1 is fixed during zooming, and the second lens group G2 and the third lens group G3 move toward the object side along the optical axis during zooming from the wide-angle end to the telephoto end.

The specification table of the third embodiment is as follows.
(specification table)
WIDE MID TELE
F 13.317 22.321 28.710
Fno 4.557 5.833 6.425
W 13.259 7.741 5.989

The surface data table of the third embodiment is as follows.
(surface data table)
No. RD Nd ABV
1 -15.916 0.919 1.5338 57.03
2 13.771 2.719 1.9324 21.96
3 21.658D(3)
4 STOP INF 0.420
5 19.502 1.827 1.7940 44.07
6 -25.278 0.513
7 17.146 2.816 1.5655 69.26
8 -8.369 0.978 1.7085 33.81
9 14.103D(9)
10 53.870 2.711 1.7469 48.09
11-38.140 D(11)
12 INF 4.232 1.5168 64.17
13INF 13.038 1.7015 41.24
14INF 0.700

The lens intervals in the third embodiment when focusing on infinity are as follows.
(Lens spacing chart)
WIDE MID TELE
D(3) 13.974 4.996 1.500
D(9) 4.731 7.997 6.169
D(11) 3.568 9.281 14.605

The focal length of each lens group in the third embodiment is as follows.
(focal length of each lens group)
f1 -20.76
f2 18.53
f3 30.28

(Fourth embodiment)
As shown in FIG. 13, the fourth embodiment of the zoom lens according to the present invention comprises, from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, It has a third lens group G3 having a positive refractive power, a color separation prism P, and a photoelectric conversion element PEC arranged at an imaging position IMG. The photoelectric conversion element PEC may include a bandpass filter and cover glass.
The first lens group G1 is formed by cementing a negative first lens L11 and a positive second lens L12. The second lens group G2 consists of an aperture STOP, a positive third lens L21, a positive fourth lens L22 and a negative fifth lens L23 cemented together. The third lens group G3 is a positive sixth lens L31.

The first lens group G1 is fixed during zooming, and the second lens group G2 and the third lens group G3 move toward the object side along the optical axis during zooming from the wide-angle end to the telephoto end.

The specification table of the fourth embodiment is as follows.
(specification table)
WIDE MID TELE
F 13.317 22.321 28.710
Fno 4.557 5.833 6.425
W 13.259 7.743 5.989

The surface data table of the fourth embodiment is as follows.
(surface data table)
No. RD Nd ABV
1 -15.929 1.449 1.5313 60.19
2 13.771 2.719 1.9232 23.31
3 21.758D(3)
4 STOP INF 0.164
5 18.441 1.812 1.7937 45.01
6 -27.261 0.517
7 17.075 2.836 1.5649 69.35
8 -8.405 1.074 1.7092 34.16
9 13.278D(9)
10 42.678 2.708 1.7408 48.55
11-40.122D(11)
12 INF 4.232 1.5168 64.17
13INF 13.038 1.7015 41.24
14INF 0.700

The lens intervals at the time of focusing at infinity in the fourth embodiment are as follows.
(Lens spacing chart)
WIDE MID TELE
D(3) 13.715 4.847 1.500
D(9) 3.452 6.553 4.887
D(11) 4.071 9.837 14.850

The focal length of each lens group in the fourth embodiment is as follows.
(focal length of each lens group)
f1 -20.83
f2 19.10
f3 28.31

(Fifth embodiment)
As shown in FIG. 17, the fifth embodiment of the zoom lens according to the present invention comprises, from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, It has a third lens group G3 having a positive refractive power, a color separation prism P, and a photoelectric conversion element PEC arranged at an imaging position IMG. The photoelectric conversion element PEC may include a bandpass filter and cover glass.
The first lens group G1 is formed by cementing a negative first lens L11 and a positive second lens L12. The second lens group G2 consists of an aperture STOP, a positive third lens L21, a positive fourth lens L22 and a negative fifth lens L23 cemented together. The third lens group G3 consists of a negative sixth lens L31 and a positive seventh lens L32.

The first lens group G1 is fixed during zooming, and the second lens group G2 and the third lens group G3 move toward the object side along the optical axis during zooming from the wide-angle end to the telephoto end.

The specification table of the fifth embodiment is as follows.
(specification table)
WIDE MID TELE
F 13.317 22.321 28.710
Fno 4.557 5.833 6.425
W 13.217 7.763 6.016

The surface data table of the fifth embodiment is as follows.
(surface data table)
No. RD Nd ABV
1 -22.676 0.832 1.6793 54.34
2 11.317 1.420 1.8002 29.51
3 33.197 D(3)
4 STOP INF 0.100
5 5.023 1.393 1.8831 40.78
6 4.440 0.652
7 10.020 3.892 1.5484 71.44
8 -3.775 0.601 1.6110 50.67
9-137.883D(9)
10 22.564 2.236 1.6878 37.20
11 10.074 0.347
12 10.490 5.615 1.6179 62.06
13-36.767 D(13)
14 INF 4.232 1.5168 64.17
15INF 13.038 1.7015 41.24
16INF 0.700

The lens intervals in the fifth embodiment when focusing on infinity are as follows.
(Lens spacing chart)
WIDE MID TELE
D(3) 16.660 5.662 1.502
D(9) 2.025 6.851 5.883
D(13) 4.346 10.518 15.647

The focal length of each lens group in the fifth embodiment is as follows.
(focal length of each lens group)
f1 -22.76
f2 24.27
f3 26.85

(Sixth embodiment)
As shown in FIG. 21, the sixth embodiment of the zoom lens according to the present invention comprises, from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, It has a third lens group G3 with positive refractive power, a fourth lens group G4 with negative refractive power, and a color separation prism P, and a photoelectric conversion element PEC is arranged at an imaging position IMG. The photoelectric conversion element PEC may include a bandpass filter and cover glass.
The first lens group G1 is formed by cementing a negative first lens L11 and a positive second lens L12. The second lens group G2 consists of an aperture STOP, a positive third lens L21, a positive fourth lens L22 and a negative fifth lens L23 cemented together. The third lens group G3 consists of a positive sixth lens L31. The fourth lens group consists of a negative seventh lens L41.

The first lens group G1 and the fourth lens group G4 are fixed during zooming, and the second lens group G2 and the third lens group G3 move along the object side along the optical axis during zooming from the wide-angle end to the telephoto end. Move to

The specification table of the sixth embodiment is as follows.
(specification table)
WIDE MID TELE
F 13.317 22.321 28.710
Fno 4.557 5.833 6.425
W 13.279 7.759 6.007

The face data table of the sixth embodiment is as follows.
(surface data table)
No. RD Nd ABV
1 -16.306 1.424 1.5171 63.25
2 12.048 2.812 1.7658 30.38
3 21.459D(3)
4 STOP INF 0.726
5 20.350 1.860 1.6948 46.33
6 -28.313 0.445
7 12.743 3.299 1.5872 66.58
8 -8.900 1.282 1.6736 38.19
9 10.440 D(9)
10 27.396 2.592 1.7052 51.62
11-53.553D(11)
12 -41.001 0.824 1.9445 18.01
13 -74.633 1.855
14 INF 4.232 1.5168 64.17
15INF 13.038 1.7015 41.24
16INF 0.700

The lens intervals during infinity focusing in the sixth embodiment are as follows.
(Lens spacing chart)
WIDE MID TELE
D(4) 16.035 6.320 2.175
D(11) 3.665 8.971 8.447
D(14) 1.822 6.231 10.899

The focal length of each lens group in the sixth embodiment is as follows.
(focal length of each lens group)
f1 -20.92
f2 19.38
f3 26.05
f4 -97.49

(imaging device)
As shown in FIG. 25, an imaging apparatus 100 according to an embodiment of the present invention is configured by mounting a zoom lens 104 and a photoelectric conversion unit PEC arranged in an imaging area of the zoom lens 104 in an imaging apparatus housing 102. be done. An imaging element IS is arranged on each of the three image planes IP of the zoom lens 102 .

As shown in FIG. 26, the photoelectric conversion unit PEC includes a low-pass filter 200, an IR filter IR, and three cemented prisms, that is, a first prism 210, a second prism 212, and a third prism 214, on the imaging side of the lens system. have
The first prism 210 has a first reflecting film 216 that reflects red light rays, and has a cover glass 218 and a first light receiving element 220 on the light emitting side.
The second prism 212 has a second reflecting film 222 that reflects blue light rays, and has a cover glass 224 and a second light receiving element 226 on the light emitting side.
The third prism 214 has a cover glass 230 and a third light receiving element 232 on the light exit side.

The corresponding values of the conditional expressions in each embodiment are as follows.
(Conditional expression correspondence value table)
Example 1 Example 2 Example 3 Example 4 Example 5 Example 6
expt/f3 -1.45 -1.83 -1.41 -1.41 -2.00 -1.57
f3/f2 1.50 1.01 1.63 1.48 1.11 1.34
f3/fw 2.11 1.71 2.27 2.13 2.02 1.96
βw2 -1.50 -2.63 -1.30 -1.47 -1.85 -1.26
βt2 -40.43 5.47 -10.70 -24.76 12.07 -12.82
βw3 0.44 0.24 0.49 0.43 0.32 0.44
βt3 0.04 -0.25 0.13 0.06 -0.10 0.09
βw3/βt3 12.51 -0.96 3.80 7.81 -3.03 4.72
f1/ft -0.70 -0.73 -0.72 -0.73 -0.79 -0.73
G01r1/f1 0.78 0.79 0.77 0.76 1.00 0.78
hitomi/（enpw×tan(ωw）)
0.62 0.62 0.62 0.62 0.62 0.62
expt/ymax -13.51 -13.86 -14.23 -13.33 -17.85 -13.58

STOP Aperture IR IR filter CG Cover glass IS Light receiving element G1 First lens group G2 Second lens group G3 Third lens group 100 Imaging device 102 Imaging device housing 104 Zoom lens 200 Low-pass filter

Claims (8)

In order from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having positive refractive power,
When zooming from the wide-angle end to the telephoto end, the distance between adjacent lens groups on the optical axis changes,
A zoom lens that satisfies the following conditional expression.
-2.20 ≤ expt/f3 ≤ -1.20 (1)
1.0 ≤ f3/f2 ≤ 1.70 ・・・・ (2 -1 )
0.5 ≤ G01R1/f1 ≤ 0.9 ・・・・ (7-1)
however
expt: Distance from the image formation position to the exit pupil at the telephoto end
f1: focal length of the first lens group
f2: focal length of the second lens group
f3: focal length of the third lens group
G01R1: Radius of curvature of the zoom lens closest to the object side Consists of, in order from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having positive refractive power,
During zooming, the first lens group is fixed in the optical axis direction,
during zooming from the wide-angle end to the telephoto end, the third lens group moves toward the object side;
A zoom lens that satisfies the following conditional expression .
-2.20 ≤ expt/f3 ≤ -1.20 (1)
0.70 ≤ f3/f2 ≤ 1.70 (2)
-1.5 ≤ βw2 ≤ -1.0 (3-1)
however
expt: Distance from the image formation position to the exit pupil at the telephoto end
f2: focal length of the second lens group
f3: focal length of the third lens group
βw2: Lateral magnification of the second lens group when focusing on infinity at the wide-angle end 3. The zoom lens according to claim 1, wherein the third lens group moves toward the object side during zooming from the wide-angle end to the telephoto end . 4. The zoom lens according to any one of claims 1 to 3, which satisfies the following conditional expression.
1.5 ≤ f3/fw ≤ 3.0 (4)
however
fw: Focal length at the wide-angle end of the zoom lens 5. The zoom lens according to any one of claims 1 to 4, which satisfies the following conditional expression.
-30.0 ≤ expt/Ymax ≤ -10.0 (5)
however
Ymax: Maximum image height 6. The zoom lens according to any one of claims 1 to 5, which satisfies the following conditional expression.
5.0 ≤ |βt2| ≤ 50.0 (6)
however
βt2: Lateral magnification of the second lens group when focusing on infinity at the telephoto end 7. The zoom lens according to any one of claims 1 to 6, which satisfies the following conditional expression.
0.5 ≤ hitomi/（enpw×tan(ωw）) ≤ 2.0 ・・・ (8)
however
hitomi: Entrance pupil radius at the wide-angle end
enpw: Distance from the first surface to the entrance pupil at the wide-angle end
ωw: Maximum angle of view of chief ray at wide-angle end (half angle of view) A zoom lens comprising: the zoom lens according to any one of claims 1 to 7; and an image sensor for converting an optical image formed by the zoom lens into an electrical signal on the image side of the zoom lens. An imaging device characterized by:

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