Zoom lens and image capturing device

Abstract

To provide a zoom lens which is advantageous in reducing the weight of a movable lens group and obtaining good optical performance over an entire zoom range.SOLUTION: A zoom lens L0 provided herein comprises a first lens group Lm1 having negative refractive power and a plurality of succeeding lens groups Lm2-Lm4 as lens groups arranged in order from the object side to the image side, and also includes an aperture stop SP. For zooming, the first lens group is stationary while the plurality of succeeding lens groups move, causing distances between adjacent lens groups to change. The zoom lens satisfies a condition expressed as: 5.5≤Tsw / fw≤9.5, where Tsw represents an optical axial distance from a lens surface of the zoom lens on the most object side to the aperture stop at the wide-angle end, and fw represents a focal length of the zoom lens at the wide-angle end.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a zoom lens used for imaging and the like. [Background technology]

[0002] As an example of an ultra-wide-angle zoom lens such as a fisheye lens, Patent Document 1 discloses a fisheye zoom lens in which various aberrations are corrected. Patent Document 2 discloses a fisheye lens capable of switching between two focal points. Patent Document 3 discloses a wide-angle zoom lens in which various aberrations are corrected.

[0003] In order to obtain a full-circle fisheye image when shooting video using an ultra-wide-angle lens, it is necessary to set the focal length short. In this case, the refractive power arrangement becomes a retrofocus type in which extremely negative refractive power takes the lead, and the fluctuation of various aberrations associated with magnification change (zooming) becomes large. Also, it is desirable to reduce the weight of the movable lens group so that it can be driven electrically. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-068115 A [Patent Document 2] JP 2004-240023 A [Patent Document 3] JP 2013-015621 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, with the lenses disclosed in Patent Documents 1 to 3, it is difficult to sufficiently suppress the fluctuation in aberration caused by zooming and to reduce the weight of the movable lens group.

[0006] The present invention provides a wide-angle zoom lens that is advantageous in reducing the weight of the movable lens group and achieving good optical performance over the entire zoom range. [Means for solving the problem]

[0007] A zoom lens according to one aspect of the present invention includes a first lens group having negative refractive power and multiple subsequent lens groups arranged in order from the object side to the image side, and also includes an aperture stop. During zooming, the first lens group is stationary, and the multiple subsequent lens groups move to change the distance between adjacent lens groups. If the distance on the optical axis from the lens surface closest to the object side of the zoom lens to the aperture stop at the wide-angle end is Tsw, and the focal length of the zoom lens at the wide-angle end is fw, then 5.5≦Tsw / fw≦9.5 The present invention is characterized in that the above conditions are satisfied. An image pickup apparatus including the above zoom lens also constitutes another aspect of the present invention. Effect of the Invention

[0008] According to the present invention, it is possible to provide a wide-angle zoom lens that is advantageous in terms of reducing the weight of the movable lens group and achieving good optical performance over the entire zoom range. [Brief description of the drawings]

[0009] [Figure 1] 1A is a cross-sectional view showing the configuration of a zoom lens of a first embodiment at a wide-angle end, at a middle zoom position, and at a telephoto end. [Diagram 2] 3A to 3C are diagrams showing aberrations of the zoom lens of Example 1 at (A) the wide-angle end, (B) a middle zoom position, and (C) a telephoto end. [Diagram 3] 10A to 10C are cross-sectional views showing the configuration of a zoom lens of a second embodiment at (A) the wide-angle end, (B) an intermediate zoom position, and (C) a telephoto end. [Figure 4] 10A to 10C are diagrams showing aberrations of the zoom lens of Example 2 at (A) the wide-angle end, (B) a middle zoom position, and (C) a telephoto end. [Diagram 5] 11A to 11C are cross-sectional views showing the configuration of a zoom lens of a third embodiment at (A) the wide-angle end, (B) an intermediate zoom position, and (C) a telephoto end. [Figure 6] 11A to 11C are diagrams showing aberrations of the zoom lens of Example 3 at (A) the wide-angle end, (B) a middle zoom position, and (C) a telephoto end. [Figure 7] FIG. 1 is a diagram showing an imaging device equipped with the zoom lenses according to first to third embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, prior to describing specific embodiments 1 to 3, matters common to the embodiments will be described.

[0011] When an extreme retrofocus type refractive power arrangement in which negative refractive power takes precedence is adopted to make a zoom lens ultra-wide-angle, the optical performance is affected throughout the entire zoom range. Also, as the angle of view becomes ultra-wide, the diameter and weight of the lens group on the object side tend to become larger than that of the aperture. Furthermore, when a so-called short zoom arrangement is adopted in an ultra-wide-angle zoom lens in which the negative lens group on the object side moves with zooming, it is difficult to electrically drive a large and heavy lens group.

[0012] As described above, in each embodiment, the fluctuation in aberration that occurs with zooming due to the ultra-wide angle is corrected in a well-balanced manner, thereby achieving good optical performance over the entire zoom range while reducing the weight of the movable lens unit.

[0013] Fig. 1(A), Fig. 3(A) and Fig. 5(A) respectively show the configuration of the zoom lens L0 in the first, second and third embodiments at the wide-angle end in a state focused on infinity (hereinafter referred to as the infinity focused state). Fig. 1(B), Fig. 3(B) and Fig. 5(B) respectively show the configuration of the zoom lens L0 in the first, second and third embodiments at the intermediate zoom position in the infinity focused state. Fig. 1(C), Fig. 3(C) and Fig. 5(C) respectively show the configuration of the zoom lens L0 in the first, second and third embodiments at the telephoto end in the infinity focused state. The zoom lens L0 in each embodiment is used as an imaging optical system of various imaging devices such as a digital video camera, a digital still camera, a broadcast camera, a silver halide film camera, and a surveillance camera.

[0014] In each of the above figures, the left side is the object side and the right side is the image side. The zoom lens L0 of each embodiment has multiple lens groups. A lens group is a group of one or more lenses that move or remain stationary as a whole during zooming or focusing. In other words, the spacing between adjacent lens groups changes during zooming or focusing. The lens groups may include an aperture stop.

[0015] The wide-angle end and telephoto end respectively indicate the maximum angle of view (shortest focal length) and minimum angle of view (maximum focal length) zoom states when the lens group that moves during zooming is positioned at either end of the range that it can move mechanically or controllably along the optical axis.

[0016] In each figure, Lmi represents the i-th lens group (i is a natural number) counting from the object side among the lens groups. The zoom lens L0 of each embodiment includes a first lens group Lm1 with negative refractive power and a plurality of subsequent lens groups arranged in order from the object side to the image side. The first lens group Lm1 is fixed (unmovable) for zooming. In addition, a lens group (including a sub lens group that is a part of one lens group) composed of at least one lens is moved for focusing. In the following description, the lens group that moves during focusing is referred to as the focus lens group Lmf. In each figure, the arrows shown under the lens groups (Lm2 to Lm4) that move during zooming indicate the movement locus of the lens group during zooming from the wide-angle end to the telephoto end. In addition, the focus lens group Lmf moves toward the object side as shown by the arrow under the focus lens group Lmf in each figure when focusing from an infinitely distant object to a close object.

[0017] The multiple subsequent lens groups move along different trajectories for zooming. In each figure, SP is an aperture stop. The aperture stop SP is provided in one of the multiple subsequent lens groups so as to move integrally with that lens group. FP1 is an auxiliary stop for cutting out unnecessary light that does not contribute to imaging.

[0018] IP is the image plane. The imaging surface of a solid-state imaging element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor, or the film surface (photosensitive surface) of a silver halide film is placed on the image plane IP.

[0019] The zoom lens L0 in each embodiment satisfies the condition of the following equation (1), where Tsw is the distance on the optical axis from the front surface, which is the lens surface closest to the object, to the aperture stop SP at the wide-angle end, and fw is the focal length of the zoom lens L0 at the wide-angle end.

[0020] 5.5≦Tsw / fw≦9.5 (1) The condition of formula (1) shows an appropriate relationship between the distance from the front surface of the zoom lens L0 to the aperture diaphragm SP at the wide-angle end and the focal length of the entire zoom lens L0 in order to make the zoom lens L0 wider-angle. If Tsw / fw exceeds the upper limit of formula (1), the aperture diaphragm SP is too far away from the front surface, making it difficult to ensure the necessary angle of view of the zoom lens L0, which is not preferable. If Tsw / fw falls below the lower limit of formula (1), the aperture diaphragm SP is too close to the front surface, making the refractive power of the lens group on the object side of the aperture diaphragm SP too strong, making it difficult to maintain good optical performance of the zoom lens L0, which is not preferable.

[0021] It is more preferable that the numerical range of formula (1) is as follows:

[0022] 7.0≦Tsw / fw≦9.0 (1a) Moreover, it is more preferable that the numerical range of the formula (1) is as follows:

[0023] 7.60≦Tsw / fw≦8.85 (1b) By satisfying the condition of formula (1) (or formulas (1a) or (1B)), it is possible to realize a wide-angle zoom lens having a lightweight movable lens unit and excellent optical performance over the entire zoom range.

[0024] It is preferable that the zoom lens L0 of each embodiment satisfies at least one of the conditions of the following expressions (2) to (5).

[0025] First, when the back focus of the zoom lens L0 at the wide-angle end is Skw, it is preferable that the condition of formula (2) be satisfied.

[0026] 2.5≦Skw / fw≦7.0 (2) The condition of formula (2) indicates an appropriate refractive power arrangement of the zoom lens L0. If Skw / fw exceeds the upper limit of formula (2), the asymmetry of the refractive power arrangement increases, making it difficult to ensure good optical performance over the entire zoom range, which is undesirable. If Skw / fw falls below the lower limit of formula (2), it becomes difficult to ensure the necessary angle of view at the wide-angle end, which is undesirable.

[0027] Furthermore, when the entrance pupil position at the wide-angle end of the zoom lens L0 is T1w, it is preferable that the condition of expression (3) be satisfied.

[0028] 0.60≦T1w / Skw≦1.00 (3) The condition of formula (3) indicates an appropriate entrance pupil position for the zoom lens L0. If the entrance pupil position is far from the front surface so that T1w / Skw exceeds the upper limit of formula (3), the zoom lens L0 becomes large, which is not preferable. If the entrance pupil position is close to the front surface so that T1w / Skw falls below the lower limit of formula (3), the refractive power of each lens group becomes too strong, making it difficult to ensure good optical performance over the entire zoom range, which is also not preferable.

[0029] In addition, when the radius of curvature of the object-side lens surface (front surface) of the front lens, which is the lens closest to the object side in the zoom lens L0, is R1 and the radius of curvature of the image-side lens surface is R2, it is preferable that formula (4) be satisfied.

[0030] -2.5≦(R2+R1) / (R2−R1)≦-1.8 (4) The condition of formula (4) indicates the appropriate shape (shape factor) of the front lens. If R1 and R2 are close to each other so that the shape factor exceeds the upper limit of formula (4), this leads to an increase in the size of the entire system, which is not preferable. If R1 and R2 are different enough that the shape factor falls below the lower limit of formula (4), it becomes difficult to correct various aberrations throughout the entire zoom range, which is also not preferable.

[0031] Furthermore, when the half angle of view of the zoom lens L0 at the wide-angle end is ω (°), it is preferable to satisfy the condition of expression (5).

[0032] 170°≦2ω≦190° (5) The condition of formula (5) relates to the appropriate angle of view of the zoom lens L0. If 2ω falls below the lower limit of formula (5), the necessary angle of view cannot be secured, which is undesirable. If 2ω exceeds the upper limit of formula (5), it is undesirable because a standalone optical system does not currently exist.

[0033] It is more preferable that the numerical ranges of the formulas (2) to (5) are as follows:

[0034] 2.7≦Skw / fw≦5.0 (2a) 0.64≦T1w / Skw≦0.90 (3a) -2.3≦(R2+R1) / (R2-R1)≦-1.9 (4a) 175°≦2ω≦190° (5a) It is more preferable that the numerical ranges of the formulas (2) to (5) are as follows:

[0035] 3.0≦Skw / fw≦4.0 (2b) 0.68≦T1w / Skw≦0.80 (3b) -2.2≦(R2+R1) / (R2-R1)≦-2.0 (4b) 178°≦2ω≦188° (5b) Below, a specific description will be given of Examples 1 to 3. After Example 3, Numerical Examples 1 and 2 corresponding to Examples 1 to 3, respectively, are shown.

[0036] In the first and third embodiments, Lm1 denotes a first lens group having a negative refractive power, Lm2 denotes a second lens group having a positive refractive power, Lm3 denotes a third lens group having a positive refractive power, and Lm4 denotes a fourth lens group having a positive refractive power.

[0037] The first lens group Lm1 does not move during zooming or focusing. For focusing from an object at infinity to a close object, the focus lens group Lmf, which serves as a sub-lens group within the second lens group Lm2, moves toward the object side as indicated by the arrow.

[0038] During zooming from the wide-angle end to the telephoto end, the second lens group Lm2, the third lens group Lm3, and the fourth lens group Lm4 move along different trajectories. Specifically, the second lens group Lm2 moves along a convex trajectory toward the object side, while the third lens group Lm3 and the fourth lens group Lm4 move monotonically toward the object side.

[0039] The aperture diaphragm SP is disposed within the second lens group Lm2, and the auxiliary diaphragm FP1 is provided at the most object side of the second lens group Lm2.

[0040] In the second embodiment, Lm1 is a first lens unit having a negative refractive power, Lm2 is a second lens unit having a negative refractive power, and Lm3 is a third lens unit having a positive refractive power.

[0041] The first lens group Lm1 does not move during zooming and focusing, and the second lens group Lm2 moves toward the object side as the focus lens group Lmf during focusing from an object at infinity to a close object.

[0042] During zooming from the wide-angle end to the telephoto end, the second lens group Lm2 and the third lens group Lm3 move along different trajectories. Specifically, the second lens group Lm2 moves along a convex trajectory toward the image side, and the third lens group Lm3 moves monotonically toward the object side.

[0043] The aperture stop SP is disposed within the third lens group Lm3, and the auxiliary stop FP1 is provided at the most object side of the third lens group Lm3.

[0044] In the surface data of Numerical Examples 1 to 3, r (mm) represents the radius of curvature of the m-th optical surface counted from the object side, and d (mm) represents the lens thickness or air space on the optical axis between the m-th surface and the (m+1)-th surface. nd represents the refractive index at the d-line of the m-th optical member, and νd represents the Abbe number based on the d-line of the m-th optical member. The Abbe number νd is expressed as νd=(Nd-1) / (NF-NC), where Nd, NF, and NC are the refractive indices at the d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) of the Fraunhofer line. The effective diameter (mm) is the maximum diameter of the area through which light rays that contribute to image formation on the m-th surface pass.

[0045] In each numerical example, d, focal length (mm), F-number, and half angle of view (°) are all values ​​when focused at infinity. BF stands for back focus (mm). Back focus is the distance on the optical axis from the final lens surface, which is the lens surface closest to the image side of the zoom lens, to the paraxial image plane, expressed as an air-equivalent length. The total lens length is the distance on the optical axis from the frontmost surface of the zoom lens to the final lens surface plus the back focus.

[0046] An asterisk (*) next to a surface number indicates that the surface has an aspheric shape. The aspheric shape is expressed by the following formula, where X is the displacement from the apex of the surface in the optical axis direction, H is the height from the optical axis in a direction perpendicular to the optical axis, the light traveling direction is positive, R is the paraxial radius of curvature, K is the conic constant, and A4, A6, A8, A10, and A12 are aspheric coefficients.

[0047] X=(H 2 / R) / [1+{1-(1+k)(h / R) 2}] 1 / 2 +A4×h 4 +A6×h 6 +A8×h 8 +A10×h 10 +A12×h 12 The conic constant and aspheric coefficient "E±x" are x10 -x means...

[0048] Moreover, the values ​​of the above-mentioned formulas (1) to (5) in Numerical Examples 1 to 3 are summarized in Table 1.

[0049] Furthermore, Figures 2(A), 4(A) and 6(A) respectively show longitudinal aberrations (spherical aberration, astigmatism, distortion and chromatic aberration) at the wide-angle end in the infinity focused state of Numerical Example 1, Numerical Example 2 and Numerical Example 3. Figures 2(B), 4(B) and 6(B) respectively show longitudinal aberrations at the intermediate zoom position in the infinity focused state of Numerical Example 1, Numerical Example 2 and Numerical Example 3. Figures 2(C), 4(C) and 6(C) respectively show longitudinal aberrations at the telephoto end in the infinity focused state of Numerical Example 1, Numerical Example 2 and Numerical Example 3.

[0050] The spherical aberration diagram shows the amount of spherical aberration for the d-line (wavelength 587.6 nm) and g-line (wavelength 435.8 nm), with Fno being the F-number. In the astigmatism diagram, dS shows the amount of astigmatism on the sagittal image plane, and dM shows the amount of astigmatism on the meridional image plane. The distortion diagram shows the amount of distortion for the d-line. The chromatic aberration diagram shows the amount of lateral chromatic aberration for the g-line. H is the image height at each focal length. Image height H is defined by the following equation:

[0051] H = 2fsin(θ / 2) This formula is the image height in equi-stereoscopic projection, which is commonly used for fisheye lenses. In the formula, f indicates the focal length of the zoom lens, and θ indicates the half angle of view (°) of the zoom lens. [Numerical example 1] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 45.772 2.09 1.804 46.6 60.36 2 15.927 14.1 1 0 31.8 3 55.756 1.35 1.59282 68.6 29.11 4 17.972 7.19 1 0 23.42 5 -36.505 1.14 1.59282 68.6 21.74 6 30.466 0.13 1 0 20.03 7 19.457 5.07 1.80518 25.4 19.8 8 -134.452 (variable) 1 0 18.54 9* -29.541 1 1.85135 40.1 16.74 10 -3236.084 (variable) 1 0 16.11 11 (auxiliary aperture) 1.39 1 0 8.63 12 30.238 1.36 1.883 40.8 9.27 13 -82.078 1.19 1 0 9.31 14 (Aperture) 1.78 1 0 9.28 15 -17.751 0.63 1.883 40.8 9.26 16 59.181 0.58 1 0 9.61 17 163.861 2.43 1.51633 64.1 9.89 18 -14.543 0.17 1 0 10.42 19 -312.647 3.34 1.48749 70.2 11.43 20 -10.87 0.67 1.883 40.8 12.62 21 -16.234 (variable) 1 0 13.75 22 45.972 2.53 1.5927 35.3 17.08 23 285.127 (variable) 1 0 17.86 24 -58.293 0.78 1.834 37.2 18.89 25 32.942 5 1.497 81.5 20.62 26 -38.111 0.17 1 0 22.15 27 96.649 6.37 1.49 81.5 24.91 28 -30.659 (variable) 1 0 26.32 Image plane ∞ Aspheric Data Page 11 K= 0.00E+00 A4= -1.66428E-05 A6= -7.40168E-08 A8= 2.97358E-09 A10= -3.61941E-11 A12= 1.59528E-13 Various data Zoom ratio 2.14 Wide Angle Mid-Telephoto Focal length 6.85 8.15 14.67 F-number 4.12 4.12 4.12 Half angle of view (°) 54.56 54.68 55.85 Image height 9.62 11.5 21.64 Lens length 111.91 111.91 111.91 BF 25.9 28.27 44.76 d8 2.18 2.18 2.18 d10 19.44 14.56 1.21 d21 2.01 4.38 0.99 d23 1.92 2.06 2.32 d28 25.9 28.27 44.76 Entrance pupil position 17.92 17.66 16.47 Exit pupil position -43.03 -52.95 -40.56 Front principal point position 24.08 24.99 28.62 Back principal point position 19.05 20.12 30.08 Lens Group Data Group starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 -25.98 31.07 1.35 -29.48 2 9 -35.02 1 0 -0.55 3 11 30.61 13.53 7.44 -4.42 4 22 92.11 2.53 -0.3 -1.89 5 24 75.77 12.31 14.66 8.37 Single lens data Lens starting surface focal length 1 1 -31.36 2 3 -45.34 3 5 -27.84 4 7 21.42 5 9 -35.02 6 12 25.17 7 15 -15.41 8 17 25.99 9 19 23.02 10 20 -39.58 11 22 92.11 12 24 -25.14 13 25 36.4 14 27 47.62 [Numerical example 2] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 50.558 2.09 1.804 46.6 64.68 2 17.028 14.3 1 0 34.03 3 41.223 1.35 1.59282 68.6 31.78 4 20.671 7.93 1 0 27.22 5 -49.863 1.14 1.59282 68.6 25.88 6 24.397 0.13 1 0 23.42 7 21.294 5.89 1.80518 25.4 23.39 8 -308.973 (variable) 1 0 22.11 9* -27.667 1 1.85135 40.1 16.02 10 -199.045 (variable) 1 0 15.46 11 (auxiliary aperture) 1.39 1 0 8.97 12 38.138 1.36 1.883 40.8 9.6 13 -105.103 1.19 1 0 9.67 14 (Aperture) 1.78 1 0 9.74 15 -12.602 0.63 1.883 40.8 9.79 16 -21.08 0.89 1 0 10.2 17 -61.039 3.62 1.51633 64.1 10.64 18 -12.617 0.17 1 0 11.36 19 -55.908 3.65 1.48749 70.2 11.26 20 -10.688 0.67 1.883 40.8 12.42 21 -21.337 (variable) 1 0 13.71 22 77.117 2.11 1.5927 35.3 16.18 23 -177.512 (variable) 1 0 16.89 24 -218.191 0.78 1.834 37.2 17.58 25 30.474 5 1.497 81.5 18.6 26 -38.392 0.17 1 0 20.17 27 45.699 2.49 1.497 81.5 22.5 28 -497.267 (variable) 1 0 22.8 Image plane ∞ Aspheric Data Side 9 k= 0.00000E+00 A4= -6.84076E-06 A6= 1.67973E-07 A8= -2.69229E-09 A10= 2.74481E-12 A12= 1.33918E-13 Various data Zoom ratio 2.18 Wide Angle Mid-Telephoto Focal length 6.94 8.14 15.14 F-number 4.12 4.12 4.12 Half angle of view (°) 54.22 54.71 55.02 Image height 9.62 11.5 21.64 Lens length 112.29 112.29 112.29 BF 27.17 30.44 45.36 d8 4.9 7.62 3.79 d10 18.63 12.64 1.55 d21 0.95 0.95 0.95 d23 0.91 0.91 0.91 d28 27.17 30.44 45.36 Entrance pupil position 19.28 19.29 17.75 Exit pupil position -28.15 -28.15 -28.15 Front principal point position 25.34 26.3 29.77 Back principal point position 20.24 22.3 30.22 Lens Group Data Group starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 -24.17 32.82 3.63 -25.35 2 9 -37.85 1 -0.09 -0.63 3 11 31.5 15.35 7.29 -5.61 4 22 90.99 2.11 0.4 -0.93 5 24 89.43 8.44 8.28 3.1 Single lens data Lens starting surface focal length 1 1 -32.85 2 3 -71.69 3 5 -27.48 4 7 24.94 5 9 -37.85 6 12 31.83 7 15 -36.76 8 17 30.04 9 19 26.41 10 20 -24.99 11 22 90.99 12 24 -32.02 13 25 35.03 14 27 84.34 [Numerical example 3] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 41.681 2.09 1.804 46.6 54.6 2 14.017 12.69 1 0 28 3 51.92 1.35 1.59282 68.6 25.47 4 16.676 5.57 1 0 20.51 5 -33.537 1.14 1.59282 68.6 19.68 6 32.09 0.13 1 0 18.07 7 19.749 4.42 1.80518 25.4 17.8 8 -131.09 (variable) 1 0 16.58 9* -29.553 1 1.85135 40.1 16.26 10 -334.817 (variable) 1 0 15.69 11 (Auxiliary aperture) 1.39 1 0 8.43 12 25.186 1.36 1.883 40.8 9.11 13 -67.721 1.19 1 0 9.13 14 (Aperture) 1.78 1 0 9.03 15 -15.269 0.63 1.883 40.8 8.94 16 51.964 0.62 1 0 9.31 17 154.66 2.76 1.51633 64.1 9.63 18 -10.762 0.17 1 0 10.18 19 97.222 3.67 1.48749 70.2 12 20 -11.296 0.67 1.883 40.8 13.03 21 -23.158 (variable) 1 0 14.4 22 44.333 2.87 1.5927 35.3 17.57 23 373.153 (variable) 1 0 18.46 24 -114.494 0.78 1.834 37.2 19.5 25 29.318 5 1.497 81.5 20.96 26 -47.487 0.17 1 0 22.39 27 183.166 6.53 1.497 81.5 24.32 28 -30.057 (variable) 1 0 26.13 Image plane ∞ Aspheric Data Side 9 k= 0.00000E+00 A4= -1.90220E-05 A6= -1.38843E-07 A8= 6.57260E-09 A10= -9.82800E-11 A12= 4.93245E-13 Various data Zoom ratio 2.15 Wide Angle Mid-Telephoto Focal length 6.81 8.16 14.65 F-number 4.12 4.12 4.12 Half angle of view (°) 54.72 54.63 55.9 Image height 9.62 11.5 21.64 Lens total length 103.36 103.36 103.36 BF 20.84 23.28 40.16 d8 1.19 1.19 1.19 d10 18.54 13.75 1.1 d21 2.63 4.92 0.99 d23 2.18 2.24 1.94 d28 20.84 23.28 40.16 Entrance pupil position 16 15.73 14.57 Exit pupil position -46.4 -56.48 -39.82 Front principal point position 22.12 23.06 26.54 Back principal point position 14.02 15.12 25.51 Lens Group Data Group starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 -20.7 27.38 2.57 -22.91 2 9 -38.13 1 -0.05 -0.6 3 11 27.54 14.24 6.07 -6.28 4 22 84.61 2.87 -0.24 -2.04 5 24 75.6 12.48 13.57 6.65 Single lens data Lens starting surface focal length 1 1 -27.18 2 3 -42.04 3 5 -27.48 4 7 21.6 5 9 -38.13 6 12 20.93 7 15 -13.31 8 17 19.6 9 19 20.99 10 20 -25.65 11 22 84.61 12 24 -27.92 13 25 37.28 14 27 52.49 [Table 1] Conditional expression Numerical value example 1 Numerical value example 2 Numerical value example 3 (1) 8.42 8.84 7.64 (2) 3.78 3.92 3.06 (3) 0.69 0.71 0.77 (4) -2.07 -2.02 -2.01 (5) 182 179 187 [Imaging device] Fig. 7 shows a digital still camera (imaging device) using, as an imaging optical system, the zoom lens L0 of any one of Examples 1 to 3. In Fig. 7, 10 denotes a camera body, and 11 denotes an imaging optical system constituted by any one of the zoom lenses of Examples 1 to 3. 12 denotes a solid-state imaging element (photoelectric conversion element) such as a CCD sensor or CMOS sensor that is built into the camera body 10 and receives and photoelectrically converts an optical image formed by the imaging optical system 11, i.e., captures an image of a subject.

[0052] The camera body 10 may be a single-lens reflex camera having a quick-turn mirror, or a mirrorless camera having no quick-turn mirror. The imaging optical system 11 may be configured as an interchangeable lens that is detachable from the camera body 10, or may constitute a lens portion of a lens-integrated camera.

[0053] In this way, by using the zoom lens L0 according to any one of Examples 1 to 3 as an imaging optical system, imaging can be performed with a wide angle of view and little fluctuation in optical performance associated with zooming.

[0054] The above embodiment includes the following configurations.

[0055] (Configuration 1) A zoom lens including a first lens group having a negative refractive power and a plurality of subsequent lens groups arranged in order from an object side to an image side, and including an aperture stop, For zooming, the first lens group is stationary, and the plurality of subsequent lens groups are moved to change the intervals between adjacent lens groups; Let Tsw be the distance on the optical axis from the lens surface closest to the object side of the zoom lens to the aperture stop at the wide-angle end, and fw be the focal length of the zoom lens at the wide-angle end. 5.5≦Tsw / fw≦9.5 A zoom lens characterized by satisfying the following conditions. (Configuration 2) When the back focus of the zoom lens at the wide-angle end is Skw, 2.5≦Skw / fw≦7.0 2. The zoom lens according to claim 1, wherein the following condition is satisfied: (Configuration 3) When the back focus of the zoom lens at the wide-angle end is Skw and the entrance pupil position of the zoom lens at the wide-angle end is T1w, 0.60≦T1w / Skw≦1.00 3. The zoom lens according to configuration 1 or 2, which satisfies the following conditions: (Configuration 4) The zoom lens described in any one of configurations 1 to 3, characterized in that for focusing, the first lens group is stationary, and any one of the multiple subsequent lens groups or a sub-lens group of the one lens group is moved. (Configuration 5) 5. The zoom lens according to configuration 4, wherein the lens group or the sub-lens group that moves for focusing has negative refractive power. (Configuration 6) 6. The zoom lens according to configuration 4 or 5, wherein the lens group or the sub lens group that moves for focusing moves toward the object side during focusing from infinity to a close distance. (Configuration 7) Let R1 be the radius of curvature of the lens surface on the object side of the lens closest to the object side of the zoom lens, and R2 be the radius of curvature of the surface on the image side of the lens. -2.5≦(R2+R1) / (R2-R1)≦-1.8 7. The zoom lens according to any one of configurations 1 to 6, which satisfies the following condition: (Configuration 8) When the half angle of view of the zoom lens at the wide-angle end is ω, 170°≦2ω≦190° 8. The zoom lens according to any one of configurations 1 to 7, which satisfies the following condition: (Configuration 9) The zoom lens according to any one of configurations 1 to 8, wherein the multiple subsequent lens groups are a second lens group with positive refractive power, a third lens group with positive refractive power, and a fourth lens group with positive refractive power, arranged in that order from the object side to the image side. (Configuration 10) 10. The zoom lens according to configuration 9, wherein a sub-lens group that is a part of the second lens group moves for focusing. (Configuration 11) The zoom lens according to any one of configurations 1 to 9, wherein the plurality of subsequent lens groups are a second lens group having negative refractive power and a third lens group having positive refractive power, arranged in that order from the object side to the image side. (Configuration 12) 12. The zoom lens according to configuration 11, wherein the second lens group moves for focusing. (Configuration 13) The zoom lens according to any one of configurations 1 to 12, and an image sensor for capturing an image of a subject through the zoom lens. (Other Examples) The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions.

[0056] The embodiments described above are merely representative examples, and various modifications and alterations are possible for each embodiment when implementing the present invention. [Explanation of symbols]

[0057] L0 Zoom Lens Lm1 First lens group Lm2 2nd lens group Lm3 3rd lens group Lm4 4th lens group SP aperture stop

Claims

1. A zoom lens that includes a first lens group with negative refractive power and a plurality of subsequent lens groups arranged sequentially from the object side to the image side, and also includes an aperture diaphragm, For zooming, the first lens group remains stationary, while the plurality of subsequent lens groups move, changing the spacing between adjacent lens groups. For focusing, the first lens group remains stationary, and one of the subsequent lens groups or a portion of the sub-lens groups within that single lens group is moved. When Tsw is the distance along the optical axis from the lens surface closest to the object to the aperture diaphragm at the wide-angle end of the zoom lens, and fw is the focal length at the wide-angle end of the zoom lens, 5.5 ≤ Tsw / fw ≤ 9.5 A zoom lens characterized by satisfying the following conditions.

2. When the back focus at the wide-angle end of the zoom lens is Skw, 2.5 ≤ Skw / fw ≤ 7.0 The zoom lens according to claim 1, characterized by satisfying the following conditions.

3. When the back focus at the wide-angle end of the zoom lens is Skw and the entrance pupil position at the wide-angle end of the zoom lens is T1w, 0.60 ≤ T1w / Skw ≤ 1.00 The zoom lens according to claim 1, characterized by satisfying the following conditions.

4. The zoom lens according to claim 1, characterized in that the lens group or sub-lens group that moves for focusing has a negative refractive power.

5. The zoom lens according to claim 1, characterized in that the lens group or sub-lens group that moves for focusing moves toward the object when focusing from infinity to close.

6. When the radius of curvature of the lens surface on the object side of the zoom lens closest to the object is R1, and the radius of curvature of the image-side surface of the same lens is R2, -2.5≦(R2+R1) / (R2-R1)≦-1.8 The zoom lens according to claim 1, characterized by satisfying the following conditions.

7. When the half-angle of view at the wide-angle end of the zoom lens is denoted as ω, 170° ≤ 2ω ≤ 190° The zoom lens according to claim 1, characterized by satisfying the following conditions.

8. The zoom lens according to claim 1, characterized in that the plurality of subsequent lens groups are a second lens group with positive refractive power, a third lens group with positive refractive power, and a fourth lens group with positive refractive power, arranged in order from the object side to the image side.

9. The zoom lens according to claim 8, characterized in that a sub-lens group of a part of the second lens group moves for focusing.

10. The zoom lens according to claim 1, characterized in that the plurality of subsequent lens groups are a second lens group with negative refractive power and a third lens group with positive refractive power, arranged in order from the object side to the image side.

11. The zoom lens according to claim 10, characterized in that the second lens group moves for focusing.

12. A zoom lens according to any one of claims 1 to 11, An imaging device characterized by having an image sensor that captures an image of a subject through the aforementioned zoom lens.

Images