JP2020030249A - Zoom lens and image capturing device having the same - Google Patents

Abstract

Provided is a zoom lens that can shoot from an ultra-wide angle of view to a standard angle of view, but does not distort a three-dimensional object at a wide angle end.
A zoom lens LA includes, in order from an object side to an image side, a negative first lens group B1 and a positive second lens group B2, the thickness of the first lens group being D1, the first lens group. Where f1 is the focal length, M2 is the amount of movement of the second lens unit from the wide-angle end to the telephoto end, and Lw is the total lens length at the wide-angle end, -5.0 <M2 / f1 <-2.4, 0.3 <D1 / Lw <1.0 is satisfied.
[Selection diagram] Fig. 1

Description

  The present invention relates to a zoom lens and an image pickup apparatus having the same, and for example, relates to an image pickup optical system used for an image pickup apparatus such as a silver halide film camera, a digital still camera, a digital video camera, a surveillance camera, a TV camera, and the like, and the image pickup apparatus. .

In recent years, an optical system used in an image pickup apparatus is firstly a high-magnification super-wide-angle zoom lens capable of photographing from an ultra-wide angle of view to a standard angle of view. In order to enhance the visibility in the periphery, it is required to adopt a stereoscopic projection method in which a three-dimensional object is not distorted.
In order to satisfy a super wide angle of view common to both, it is mainstream to adopt a lens configuration having a first negative lens unit and a second positive lens unit.

  Furthermore, regarding the first point, conventionally, in a super-wide-angle zoom lens in which a shooting angle of view at the wide-angle end is about 180 °, an equi-solid angle projection method is employed in order to obtain an ultra-wide angle of view at the wide-angle end. Is the mainstream (Patent Document 1). In this equal solid angle projection method, the focal length at the wide-angle end is not reduced, thereby allowing the solid object to be compressed in the sagittal direction and sacrificing the distortion of the solid object, thereby reducing the overall length of the entire lens system. Is a method of shortening

  Patent Literature 1 includes, in order from the object side to the image side, a first lens group having a negative refractive power and a second lens group having a positive refractive power. A 9x high magnification ultra wide angle zoom lens is disclosed. The wide-angle end of the high-magnification super-wide-angle zoom lens has a distortion of −5% in the equal solid angle projection system.

  Regarding the second point, conventionally, in a video camera, an in-vehicle camera, or the like, a stereoscopic projection method is adopted at a wide-angle end in order to reduce distortion of a three-dimensional object at an ultra-wide angle of view (Patent Document 2). This stereoscopic projection system is a system in which the three-dimensional object is prevented from being compressed or stretched in the sagittal direction by reducing the focal length at the wide-angle end so that the three-dimensional object is not distorted.

  Patent Literature 2 discloses a single focus having a first lens unit having a negative refractive power, an aperture stop, and a second lens unit having a positive refractive power and having a small distortion in a stereoscopic projection system, in order from the object side to the image side. A lens is disclosed.

JP 2014-178388 A JP 2013-25255 A

  However, the following two points are difficult in the related art disclosed in the above-mentioned patent documents.

  First, in order to adopt a stereoscopic projection method in a conventional high-magnification ultra-wide-angle zoom lens, if the focal length at the wide-angle end is reduced, the refractive power of the negative first lens unit and the positive second lens unit will increase. And it becomes difficult to keep distortion and astigmatism small. In Patent Document 1, distortion and astigmatism can be reduced by adopting an equal solid angle projection method at the wide-angle end and not strengthening the negative first lens unit and the positive second lens unit.

  Second, if the refractive power of the negative first lens unit and the positive second lens unit is increased in order to obtain a high-magnification super-wide-angle zoom lens using a lens that adopts the stereoscopic projection method at the wide-angle end, distortion will occur. And it becomes difficult to keep astigmatism small. In Patent Document 2, distortion and astigmatism can be reduced by not using a zoom lens.

  Therefore, an object of the present invention is to provide a zoom lens that can shoot from an ultra-wide angle of view to a standard angle of view, and does not distort a three-dimensional object at a wide angle end.

In order to achieve the above object, a zoom lens according to the present invention includes a zoom lens having a negative first lens unit B1 and a positive second lens unit B2 in order from the object side to the image side.
When the thickness of the first lens unit B1 is D1, the focal length of the first lens unit B1 is f1, the amount of movement of the second lens unit B2 from the wide-angle end to the telephoto end is M2, and the total lens length at the wide-angle end is Lw,
−5.0 <M2 / f1 <−2.4
0.3 <D1 / Lw <1.0
It is characterized by satisfying the following conditional expression.

  According to the present invention, it is possible to provide a zoom lens that can shoot from an ultra-wide angle of view to a standard angle of view, but does not distort a three-dimensional object at the wide angle end.

Sectional view of the zoom lens according to the first embodiment when focusing on an object at infinity (A), (B), (C) Longitudinal aberration diagrams at the wide-angle end, an intermediate zoom position, and the telephoto end when focusing on an object at infinity in the zoom lens according to the first embodiment. Sectional view of the zoom lens of Embodiment 2 when focusing on an object at infinity (A), (B), (C) Longitudinal aberration diagrams at the wide-angle end, at an intermediate zoom position, and at the telephoto end when focusing on an object at infinity in the zoom lens according to the second embodiment. Sectional view of the zoom lens of Embodiment 3 when focusing on an object at infinity (A), (B), (C) Longitudinal aberration diagrams at the wide-angle end, an intermediate zoom position, and the telephoto end when focusing on an object at infinity in the zoom lens according to the third embodiment. Schematic diagram of main parts of the imaging device of the present invention

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

[Description common to the embodiments]
FIG. 1 is a sectional view of a lens according to a first embodiment. FIG. 2 is a longitudinal aberration diagram when focusing on infinity according to the first embodiment. FIG. 3 is a sectional view of a lens according to the second embodiment. FIG. 4 is a longitudinal aberration diagram of Example 2 when focused on infinity. FIG. 5 is a lens sectional view of the third embodiment. FIG. 6 is a longitudinal aberration diagram of Example 3 when focused on infinity. FIG. 7 is a schematic diagram of a camera (imaging device) including the optical system of the present invention.

  The optical system of each embodiment is suitable as an imaging optical system used for an imaging device (optical device) such as a digital still camera, a digital video camera, and a camera for a silver halide film. In the lens cross-sectional view, the left is the object side (front) and the right is the image side (rear). The optical system of each embodiment may be used as a projection lens of a projector or the like. In this case, the left side is the screen side, and the right side is the projected image side.

  In the lens sectional view, LA is an optical system. Bi is an i-th lens group. SP is an aperture stop. IP is an image plane, and when used as a photographing optical system of a digital video camera or a digital still camera, an imaging surface of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor is used for a camera of a silver halide film camera. Time corresponds to the film surface.

  Each longitudinal aberration diagram represents, from the left, spherical aberration, astigmatism, distortion, and chromatic aberration of magnification. In the diagram showing the spherical aberration, the solid line d represents the d-line (587.6 nm), and the two-dot chain line g represents the g-line (435.8 nm). Further, in the figure showing astigmatism, ΔS of the solid line represents a sagittal image plane of the d-line, and ΔM of a broken line represents a meridional image plane of the d-line. Further, the diagram showing distortion shows distortion at d-line. The lateral chromatic aberration is shown for the g-line with respect to the d-line. Fno indicates an F number, and ω indicates a half angle of view (degree) of a shooting angle of view. The distortion diagram shows the amount of deviation from an ideal image height of Y = 2f × tan (ω / 2).

  Next, the lens configuration of the optical system LA of each embodiment will be described.

[Example 1]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

  The lens configuration is as follows in order from the object side to the image side. The first lens unit B1 has a negative refractive power, the second lens unit B2 has a positive refractive power, and the third lens unit B3 has a positive refractive power. The first lens unit B1 includes four negative lenses and one positive lens, thereby reducing astigmatism, distortion, and lateral chromatic aberration at the wide-angle end. The second lens group B2 reduces spherical aberration and coma by arranging a plurality of positive lenses near the aperture stop. The third lens group B3 is composed of one positive lens and is a focus group.

[Example 2]
Hereinafter, a second embodiment of the present invention will be described with reference to FIGS.

  The lens configuration is as follows in order from the object side to the image side. The first lens unit B1 has a negative refractive power, the second lens unit B2 has a positive refractive power, and the third lens unit B3 has a positive refractive power. The first lens unit B1 includes four negative lenses and one positive lens, thereby reducing astigmatism, distortion, and lateral chromatic aberration at the wide-angle end. The second lens group B2 reduces spherical aberration and coma by arranging a plurality of positive lenses near the aperture stop. The third lens group B3 is composed of one positive lens and is a focus group.

[Example 3]
Hereinafter, a third embodiment of the present invention will be described with reference to FIGS.

  The lens configuration is as follows in order from the object side to the image side. The first lens unit B1 has a negative refractive power, the second lens unit B2 has a positive refractive power, and the third lens unit B3 has a positive refractive power. The first lens unit B1 includes four negative lenses and one positive lens, thereby reducing astigmatism, distortion, and lateral chromatic aberration at the wide-angle end. The second lens group B2 reduces spherical aberration and coma by arranging a plurality of positive lenses near the aperture stop. The third lens group B3 is composed of one positive lens and is a focus group.

[Description of lens configuration]
The optical system LA of each embodiment includes a negative first lens unit B1 and a positive second lens unit B2 in order from the object side to the image side. The thickness of the first lens unit B1 is D1, the focal length of the first lens unit B1 is f1, the amount of movement of the second lens unit B2 from the wide-angle end to the telephoto end is M2, and the total length of the lens at the wide-angle end is Lw. Note that the sign of the movement amount M2 indicates that the movement amount toward the object is positive.
At this time,
−5.0 <M2 / f1 <−2.4 (1)
0.3 <D1 / Lw <1.0 (2)
The following conditional expression is satisfied.

[Explanation of conditional expression]
Next, the technical meaning of the above conditional expression will be described.

  Conditional expression (1) appropriately determines the ratio of the amount of movement of the second lens unit B2 from the wide-angle end to the telephoto end and the focal length of the first lens unit B1 in order to increase the zoom magnification and reduce the size. Things. When the amount of movement of the second lens group becomes larger than the upper limit of conditional expression (1), the group distance between the first lens group B1 and the second lens group B2 at the wide-angle end becomes longer, and the stop and the first lens group become larger. The distance to the group B1 becomes long, and it becomes difficult to reduce the diameter of the front lens. If the amount of movement of the second lens group becomes smaller than the lower limit of conditional expression (1), the refractive power of the first lens group B1 and the second lens group B2 must be increased in order to increase the zoom magnification. This makes it difficult to reduce the occurrence of spherical aberration and coma.

  Conditional expression (2) appropriately defines the ratio between the thickness of the first lens unit B1 and the distance of the entire lens system at the wide-angle end in order to reduce the occurrence of distortion and astigmatism in the first lens unit B1. Things. If the thickness of the first lens unit B1 becomes smaller than the lower limit value of the conditional expression (2), it becomes impossible to secure a large number of negative lenses of the first lens unit B1, and distortion and astigmatism occur. Is difficult to reduce.

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

-4.0 <M2 / f1 <-2.5 (1a)
0.35 <D1 / Lw <0.50 (2a)
In the present invention, it is more desirable to satisfy at least one of the following conditional expressions.
The lateral magnifications of the second lens unit B2 at the wide-angle end and the telephoto end are denoted by β2w and β2t, respectively. The focal length of the entire system at the wide-angle end is fw, and the maximum image height at the wide-angle end is Yw. The photographing half angle of view at the wide angle end is ωw.
2.2 <β2t / β2w <2.8 (3)
1.4 <Yw / fw <4.0 (4)
ωw> 60 ° (5)
Next, the technical meaning of each of the above conditional expressions will be described.

  Conditional expression (3) appropriately sets the ratio of the lateral magnification at the wide-angle end to the lateral magnification at the telephoto end of the second lens unit B2 in order to increase the zoom magnification and reduce the occurrence of spherical aberration and coma. It is. When the lateral magnification at the telephoto end of the second lens unit B2 is increased beyond the upper limit value of the conditional expression (3), the refractive power of the second lens unit B2 is increased, and the occurrence of spherical aberration and coma is reduced. Becomes difficult. If the lateral magnification at the telephoto end of the second lens unit B2 becomes smaller than the lower limit of conditional expression (3), it becomes difficult to increase the zoom magnification.

  Conditional expression (4) appropriately determines the ratio of the maximum image height of the imaging device at the wide-angle end to the focal length of the entire system at the wide-angle end in order to reduce distortion of a three-dimensional object at the wide-angle end. If the focal length of the entire system at the wide-angle end becomes smaller than the upper limit of conditional expression (4), the three-dimensional object is stretched in the sagittal direction around the screen, and it becomes difficult to reduce the distortion. If the focal length of the entire system at the wide-angle end becomes larger than the lower limit of conditional expression (4), the three-dimensional object is compressed in the sagittal direction around the screen, and it becomes difficult to reduce the distortion.

  Conditional expression (5) appropriately defines the photographing half angle of view at the wide-angle end in order to photograph a wide range. When the half angle of view becomes smaller than the lower limit of conditional expression (5), it becomes difficult to shoot a wide area.

In each embodiment, it is more preferable to set the numerical ranges of the conditional expressions (3) to (5) as follows.
2.4 <β2t / β2w <2.7 (3a)
1.6 <Yw / fw <3.0 (4a)
ωw> 70 ° (5a)
As described above, the preferred embodiments of the present invention have been described, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist.

  Next, a single-lens reflex camera as the imaging device in FIG. 7 will be described. In FIG. 7, reference numeral 10 denotes an imaging optical system including the optical system 1 according to the first to third embodiments. The imaging optical system 10 is held by a lens barrel 2 which is a holding member. Reference numeral 20 denotes a camera body. The camera body 20 includes a quick return mirror 3, a reticle 4, a penta roof prism 5, an eyepiece 6, and the like. The quick return mirror 3 reflects the light beam from the imaging optical system 10 upward. The focusing screen 4 is disposed at an image forming position of the imaging optical system 10. The penta roof prism 5 converts the reverse image formed on the focusing screen 4 into an erect image.

  The observer observes the erect image via the eyepiece 6. Reference numeral 7 denotes a photosensitive surface on which a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor for receiving an image and a silver halide film are arranged. During photographing, the quick return mirror 3 is retracted from the optical path, and an image is formed on the photosensitive surface 7 by the imaging optical system 10.

  By applying the optical system as an imaging optical system such as a single-lens reflex camera interchangeable lens, an imaging apparatus having high optical performance is realized. The optical system of the present invention can be applied to optical devices such as telescopes, binoculars, copying machines, and projectors in addition to digital cameras, video cameras, cameras for silver halide films, and the like. Also, the present invention can be applied to a mirrorless single-lens reflex camera without a quick return mirror.

  Hereinafter, numerical data 1 to 3 corresponding to the first to third embodiments are shown. In each numerical data, i indicates the order of the surface from the object side, ri is the radius of curvature of the i-th (i-th surface), di is the distance between the i-th surface and the (i + 1) -th surface, and ndi and νdi are Each shows the refractive index and Abbe number based on d-line. BF is a back focus in air conversion. The total lens length is a value obtained by adding a back focus value to the distance from the first lens surface to the final lens surface.

  The aspherical surface is represented by adding a symbol * to the surface number. For the aspherical shape, X is the displacement from the surface vertex in the optical axis direction, h is the height from the optical axis in a direction perpendicular to the optical axis, r is the paraxial radius of curvature, K is the conic constant, A4, A6, When A8 and A10 are aspherical coefficients of respective orders,

Expressed by

  Note that “e ± XX” in each aspheric coefficient means “× 10 ± XX”. Table 1 shows numerical values corresponding to the above-described conditional expressions.

(Numerical data 1)
Unit: mm

Surface data surface number rd nd vd
1 17.146 0.60 2.00 100 29.1
2 8.571 2.62
3 11.472 0.60 1.88202 37.2
4 * 6.266 2.24
5 12.959 0.50 1.88213 37.2
6 4.809 3.91
7 -7.934 0.50 1.49700 81.5
8 14.659 0.13
9 12.951 1.87 1.87996 21.5
10 -32.380 (variable)
11 8.118 0.40 1.90792 35.4
12 3.017 1.85 1.82760 41.2
13 * -24.863 0.61
14 (aperture) ∞ 0.89
15 18.146 1.61 1.49700 81.5
16 -12.114 0.20
17 7.718 0.40 2.00169 22.1
18 3.891 1.30 1.49700 81.5
19 5.940 0.66
20 14.844 0.40 1.96805 31.1
21 5.165 2.18 1.49700 81.5
22 -21.043 (variable)
23 22.521 2.85 1.49710 81.6
24 * -10.153 (variable)
25 ∞ 1.20 1.51633 64.1
26 ∞ (variable)
Image plane ∞

Aspheric surface 4th surface
K = 0.00000e + 000 A 4 = -4.10610e-004 A 6 = 1.53658e-005 A 8 = -1.88021e-006 A10 = 6.83178e-008 A12 = -1.07174e-009

Thirteenth
K = 0.00000e + 000 A 4 = 5.34267e-004 A 6 = -1.74085e-005 A 8 = -1.65239e-006

Side 24
K = 0.00000e + 000 A 4 = 6.30992e-004 A 6 = -2.28136e-005 A 8 = 3.23877e-007

Various data Zoom ratio 2.61
Wide-angle medium telephoto focal length 2.39 4.30 6.26
F-number 2.88 4.30 5.69
Angle of view 62.75 47.25 36.63
Image height 4.65 4.65 4.65
Total lens length 35.59 36.86 40.09
BF 2.93 2.17 2.09

d10 5.62 2.03 0.40
d22 0.71 6.33 11.28
d24 1.84 1.08 1.00
d26 0.30 0.30 0.30

Zoom lens group data group Start surface Focal length
1 1 -3.72
2 11 7.57
3 23 14.50
4 25 ∞


(Numerical data 2)
Unit: mm

Surface data surface number rd nd vd
1 25.852 1.60 2.00100 29.1
2 12.380 3.89
3 15.850 1.00 2.00100 29.1
4 8.926 5.09
5 39.212 0.70 2.00100 29.1
6 12.181 3.28
7 -22.381 0.50 1.49700 81.5
8 12.819 2.61 1.95906 17.5
9 145.489 (variable)
10 (aperture) ∞ 0.00
11 * 9.136 1.60 1.82465 43.8
12 * 76.074 0.10
13 9.304 3.11 1.49700 81.5
14 -13.878 0.10
15 12.335 0.50 1.99516 25.5
16 3.998 1.59 1.49700 81.5
17 6.348 (variable)
18 23.742 0.50 1.88300 40.8
19 7.980 2.42 1.49700 81.5
20 -51.368 (variable)
21 -1539.688 3.40 1.49700 81.5
22 -8.983 (variable)
23 * -12.113 0.50 1.83474 42.7
24 -18.892 (variable)
25 ∞ 2.04 1.51633 64.1
26 ∞ (variable)
Image plane ∞

Aspheric surface eleventh surface
K = 0.00000e + 000 A 4 = 8.17607e-005 A 6 = 1.50359e-005

Side 12
K = 0.00000e + 000 A 4 = 6.05564e-004 A 6 = 2.18531e-005

Side 23
K = 0.00000e + 000 A 4 = 2.94153e-007

Various data Zoom ratio 2.62
Wide-angle medium telephoto focal length 4.06 7.43 10.65
F-number 2.88 4.16 5.16
Angle of view 62.75 46.74 36.53
Image height 7.89 7.89 7.89
Total lens length 50.79 52.06 56.33
BF 3.35 5.50 9.78

d 9 10.90 4.69 1.48
d17 1.17 1.39 2.91
d20 0.56 5.17 5.21
d22 2.29 2.80 4.44
d24 1.72 3.87 8.15
d26 0.28 0.28 0.28

Zoom lens group data group Start surface Focal length
1 1 -5.99
2 10 10.37
3 18 -1045.04
4 21 18.17
5 23 -41.84
6 25 ∞


(Numerical data 3)
Unit: mm

Surface data surface number rd nd vd
1 23.588 1.60 2.00100 29.1
2 11.804 4.62
3 17.832 1.00 2.00100 29.1
4 7.946 4.63
5 38.662 0.70 2.00100 29.1
6 12.522 2.50
7 -40.220 0.50 1.49700 81.5
8 9.952 2.62 1.95906 17.5
9 69.091 (variable)
10 (aperture) ∞ 0.00
11 * 9.975 1.47 1.83666 38.4
12 * 53.069 0.10
13 7.188 2.36 1.49700 81.5
14 -16.896 0.10
15 23.090 0.50 1.84639 23.7
16 4.288 1.54 1.49700 81.5
17 6.527 (variable)
18 22.320 0.50 1.88300 40.8
19 9.764 2.50 1.49700 81.5
20 -18.929 (variable)
21 -76.739 3.30 1.49700 81.5
22 * -11.028 (variable)
23 ∞ 2.04 1.51633 64.1
24 ∞ (variable)
Image plane ∞

Aspheric surface eleventh surface
K = 0.00000e + 000 A 4 = 3.15924e-004 A 6 = 1.65569e-005

Side 12
K = 0.00000e + 000 A 4 = 8.00406e-004 A 6 = 2.54907e-005

Side 22
K = 0.00000e + 000 A 4 = 2.07519e-004

Various data Zoom ratio 2.72
Wide-angle Medium telephoto focal length 4.06 7.26 11.05
F-number 2.88 4.27 6.00
Angle of view 62.75 47.39 35.52
Image height 7.89 7.89 7.89
Total lens length 47.55 50.55 56.32
BF 7.10 5.45 2.69

d 9 8.15 3.66 1.94
d17 1.19 1.41 2.94
d20 0.56 9.47 18.20
d22 5.46 3.81 1.04
d24 0.30 0.30 0.30

Zoom lens group data group Start surface Focal length
1 1 -6.03
2 10 11.48
3 18 37.87
4 21 25.49
5 23 ∞

LA optical system, B1 first lens group, B2 second lens group,
B3 third lens group, B4 fourth lens group, SP aperture stop

Claims (7)

In order from the object side to the image side, it has a negative first lens unit B1 and a positive second lens unit B2,
When the thickness of the first lens unit B1 is D1, the focal length of the first lens unit B1 is f1, the amount of movement of the second lens unit B2 from the wide-angle end to the telephoto end is M2, and the total lens length at the wide-angle end is Lw,
−5.0 <M2 / f1 <−2.4
0.3 <D1 / Lw <1.0
A zoom lens characterized by satisfying the following conditional expression.   The zoom lens according to claim 1, wherein the first lens group B1 includes a first lens having a negative refractive power and a concave surface facing the image side.   The zoom lens according to claim 1, wherein the first lens group B <b> 1 includes three or more lenses having negative refractive power. When the lateral magnifications of the second lens unit B2 at the wide angle end and the telephoto end are respectively β2w and β2t,
2.2 <β2t / β2w <2.8
The zoom lens according to any one of claims 1 to 3, wherein the following conditional expression is satisfied.   An imaging apparatus comprising: the zoom lens according to claim 1; and a photoelectric conversion element that receives an image formed by the zoom lens. When the focal length of the entire system at the wide-angle end is fw and the maximum image height at the wide-angle end is Yw,
1.4 <Yw / fw <4.0
The imaging device according to claim 5, wherein the following conditional expression is satisfied: When the photographing half angle of view at the wide angle end is ωw,
ωw> 60 °
The imaging device according to claim 5, wherein the following conditional expression is satisfied.