Optical system and imaging device having the same

Abstract

To provide an optical system that can reduce the weight of a focusing group, and an imaging apparatus having the same.SOLUTION: An optical system consists of a first lens group having a positive refractive power, an aperture stop, a second lens group having a negative refractive power, and a third lens group having a positive refractive power, which are arranged in order from an object side to an image side, wherein the interval between the adjacent lens groups changes in focusing. In focusing from an infinity object to a closest object, the second lens group moves to the image side. The first lens group includes a positive lens arranged on the most object side, and two or more negative lenses. The second lens group comprises one negative lens. The distance on an optical axis from a lens surface on the most object side of the first lens group to a lens surface on the most image side of the first lens group, the distance on the optical axis from the lens surface on the most object side of the first lens group to an image surface, the focal length of the optical system, and the back focus of the optical system in focusing the infinity object, are each appropriately set.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical system suitable for digital video cameras, digital still cameras, broadcast cameras, cameras for silver halide film, surveillance cameras, vehicle-mounted cameras, and the like. [Background technology]

[0002] Conventionally, telephoto-type imaging optical systems (telephoto lenses) with long focal lengths have been known. A long focal length refers to a focal length that is longer than the dimensions of the effective imaging area, for example. Generally, telephoto lenses become larger and heavier as the focal length increases. Furthermore, among various aberrations, axial chromatic aberration and lateral chromatic aberration fluctuate significantly during focusing.

[0003] Patent Document 1 discloses a telephoto lens having first, second, and third lens groups with positive, negative, and positive refractive powers arranged in that order from the object side to the image side, in which the second lens group moves toward the image side when focusing from an object at infinity to a closest object. The telephoto lens of Patent Document 1 can achieve a lightweight design and good correction of various aberrations by appropriately setting the refractive power of a subgroup within the third lens group. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-151664 Summary of the Invention [Problem to be solved by the invention]

[0005] In the telephoto lens of Patent Document 1, the second lens group, which is the focusing group, is composed of one positive lens and one negative lens, or one positive lens and two negative lenses, but the large number of lenses in the focusing group makes the lens heavy. Also, the load on the drive system for the focusing group increases, making it difficult to achieve high-speed focusing.

[0006] SUMMARY OF THE INVENTION An object of the present invention is to provide an imaging optical system that can realize a reduction in the weight of the focusing group, and an imaging apparatus having the same. [Means for solving the problem]

[0007] An optical system according to one aspect of the present invention comprises, in order from the object side to the image side, a first lens group having positive refractive power, an aperture stop, a second lens group having negative refractive power, and a third lens group having positive refractive power, and the spacing between adjacent lens groups changes during focusing. When focusing from an object at infinity to a closest object, the second lens group moves toward the image side. The first lens group includes a positive lens arranged closest to the object and two or more negative lenses, and the positive lens arranged closest to the object is a meniscus lens with its convex surface facing the object side. The second lens group consists of one negative lens. LD1 is the distance on the optical axis from the lens surface of the first lens group closest to the object to the lens surface of the first lens group closest to the image side, LD is the distance on the optical axis from the lens surface of the first lens group closest to the object to the image plane, f is the focal length of the optical system, and BF is the back focus of the optical system when focusing on an object at infinity. , the Abbe number νdG1 of the material of the positive lens arranged closest to the object When 0.2 <LD1 / LD<0.4 BF / f<0.25 15<νdG1<30 The present invention is characterized in that the following conditional expression is satisfied: [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an optical system that can realize a reduction in the weight of the focusing group, and an image taking apparatus having the same. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of the imaging optical system of Example 1 when focusing on an object at infinity. [Figure 2] 10A and 10B are aberration diagrams of Example 1 when focusing on an object at infinity and when focusing on a closest object. [Figure 3] FIG. 10 is a cross-sectional view of the imaging optical system of Example 2 when focusing on an object at infinity. [Figure 4] 10A and 10B are aberration diagrams of Example 2 when focusing on an object at infinity and when focusing on a closest object. [Figure 5] FIG. 10 is a cross-sectional view of the imaging optical system of Example 3 when focused on an object at infinity. [Figure 6] 10A and 10B are aberration diagrams of Example 3 when focusing on an object at infinity and when focusing on a closest object. [Figure 7] FIG. 10 is a cross-sectional view of the imaging optical system of Example 4 when focusing on an object at infinity. [Figure 8] 10A and 10B are aberration diagrams of Example 4 when focusing on an object at infinity and when focusing on a closest object. [Figure 9] FIG. 1 is a schematic diagram of an imaging device. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to designate the same components, and redundant explanations will be omitted.

[0011] 1, 3, 5, and 7 are cross-sectional views of the imaging optical systems (optical systems) of Examples 1 to 4 when focusing on an object at infinity. The imaging optical systems of the respective Examples are optical systems used in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, surveillance cameras, and vehicle-mounted cameras.

[0012] In each cross-sectional view, the left side is the object side and the right side is the image side. The optical system in each embodiment is configured with multiple lens groups. In this specification, a lens group refers to a group of lenses that move or remain stationary as a unit during focusing. That is, in the imaging optical system in each embodiment, the spacing between adjacent lens groups changes during focusing. Note that a lens group may be composed of a single lens or multiple lenses.

[0013] The imaging optical system of each embodiment has, arranged in order from the object side to the image side, a first lens unit L1 with positive refractive power, an aperture stop SP, a second lens unit L2 with negative refractive power, and a third lens unit L3 with positive refractive power.

[0014] IP is an image plane, and when the imaging optical system of each embodiment is used as the photographing optical system of a digital still camera or digital video camera, the imaging surface of a solid-state imaging element (photoelectric conversion element) such as a CCD sensor or CMOS sensor is placed thereon. When the imaging optical system of each embodiment is used as the photographing optical system of a silver halide film camera, a photosensitive surface equivalent to the film surface is placed on the image plane IP. GB is an optical filter placed on the object side of the image plane IP.

[0015] The arrows in each cross-sectional view indicate the direction of movement of the lens group (focusing group) when focusing from an object at infinity to a close object. In the imaging optical system of each embodiment, the second lens group L2, which is the focusing group, moves toward the image side when focusing from an object at infinity to a closest object.

[0016] 2, 4, 6, and 8 are aberration diagrams of the imaging optical systems of Examples 1 to 4. In each aberration diagram, (a) is an aberration diagram when an object at infinity is focused, and (b) is an aberration diagram when an object at the closest distance is focused.

[0017] In the spherical aberration diagram, Fno is the F-number, and shows the amount of spherical aberration for the d-line (wavelength 587.6 nm) and g-line (wavelength 435.8 nm). In the astigmatism diagram, S shows the amount of astigmatism on the sagittal image plane, and M shows the amount of astigmatism on the meridional image plane. In the distortion diagram, the amount of distortion for the d-line is shown. In the chromatic aberration diagram, the amount of chromatic aberration for the g-line is shown. ω is the half angle of view (degrees).

[0018] Next, the characteristic configuration of the imaging optical system of each embodiment will be described.

[0019] The lens closest to the object in the imaging optical system is a positive lens. That is, the first lens group L1 includes a positive lens arranged closest to the object. This enhances the convergence effect of light rays at the lens closest to the object, and reduces the diameter of the light beam incident on a lens located closer to the image than the lens closest to the object, thereby enabling the optical system to be made smaller in diameter and lighter in weight.

[0020] The first lens unit L1 includes two or more negative lenses, which allows for excellent correction of chromatic aberration, particularly axial chromatic aberration.

[0021] The second lens unit L2 is made up of one negative lens, which makes it possible to reduce the weight of the second lens unit L2, which is the focusing unit.

[0022] The second lens unit L2 is disposed adjacent to the image side of the aperture stop SP, which makes it possible to reduce the weight of the second lens unit L2, which is the focusing unit, and to suppress fluctuations in chromatic aberration of magnification during focusing.

[0023] The imaging optical system of each embodiment satisfies the following conditional expressions (1) and (2).

[0024] 0.2 <LD1 / LD<0.4 (1) BF / f<0.25 (2) Here, LD1 is the distance on the optical axis from the lens surface of the first lens group L1 closest to the object to the lens surface of the first lens group L1 closest to the image. LD is the distance on the optical axis from the lens surface of the first lens group L1 closest to the object to the image plane (hereinafter referred to as the total lens length). f is the focal length of the imaging optical system. BF is the back focus of the imaging optical system when focusing on an object at infinity (the distance on the optical axis from the lens surface of the imaging optical system closest to the image to the image plane expressed in air equivalent length).

[0025] Conditional expression (1) defines the ratio of the total lens length LD to the distance LD1 on the optical axis from the lens surface of the first lens unit L1 closest to the object to the lens surface of the first lens unit L1 closest to the image. If the lower limit of conditional expression (1) is not met, it becomes easy to reduce the weight of the imaging optical system, but it becomes difficult to correct spherical aberration and axial chromatic aberration. If the upper limit of conditional expression (1) is exceeded, it is advantageous from the perspective of aberration correction, but it becomes difficult to reduce the weight of the imaging optical system.

[0026] Conditional expression (2) defines the ratio between the back focal length BF and the focal length f of the imaging optical system. If the upper limit of conditional expression (2) is exceeded, the overall lens length becomes long.

[0027] The imaging optical system of each embodiment has the above-described configuration, which makes it possible to reduce the weight of the focusing group. This reduces the load on the drive system of the focusing group, thereby enabling faster focusing. Furthermore, the imaging optical system of each embodiment makes it possible to reduce the weight and achieve good correction of various aberrations.

[0028] It should be noted that even with a configuration of four or more groups, the same effect can be obtained as long as the above-mentioned configuration is satisfied.

[0029] It is preferable that the numerical ranges of the conditional expressions (1) and (2) be set to the numerical ranges of the following conditional expressions (1a) and (2a).

[0030] 0.23 <LD1 / LD<0.35 (1a) BF / f<0.2 (2a) It is more preferable that the numerical ranges of the conditional expressions (1) and (2) be set to the numerical ranges of the following conditional expressions (1b) and (2b).

[0031] 0.26 <LD1 / LD<0.35 (1b) BF / f<0.17 (2b) Next, a description will be given of configurations that are preferably satisfied in the imaging optical system of each embodiment.

[0032] The third lens group L3 is composed of, arranged in order from the object side to the image side, a first subgroup L3a with positive refractive power, a second subgroup L3b with negative refractive power, and a third subgroup L3c with positive refractive power. The second subgroup L3b, which is an image stabilization group, preferably moves in a direction including a component perpendicular to the optical axis during image shake correction (correction of fluctuations in image position due to vibrations of the imaging optical system, etc.).

[0033] Next, conditions that the imaging optical system of each embodiment should preferably satisfy will be described. The imaging optical system of each embodiment should preferably satisfy one or more of the following conditional expressions (3) to (7).

[0034] LD / f<1.5 (3) 0.50 <f1 / f<0.85 (4) -0.65 <f2 / f<-0.35 (5) 0.65 <f3 / f<0.95 (6) 15<νdG1<30 (7) Here, f1 is the focal length of the first lens group L1, f2 is the focal length of the second lens group L2, f3 is the focal length of the third lens group L3, and νdG1 is the Abbe number of the lens (positive lens) closest to the object in the imaging optical system.

[0035] Conditional expression (3) defines the ratio between the total lens length LD and the focal length f of the imaging optical system. If conditional expression (3) is satisfied, the imaging optical system can be considered to have a long focal length. The imaging optical system in each embodiment is preferably a medium telephoto lens to a telephoto lens, and if the upper limit of conditional expression (3) is exceeded, the imaging optical system will be considered to have a short focal length, which is not preferable.

[0036] Conditional expression (4) defines the ratio between the focal length f1 of the first lens unit L1 and the focal length f of the imaging optical system. If the lower limit of conditional expression (4) is not met, the refractive power of the first lens unit L1 becomes large, which is advantageous for shortening the overall lens length, but it becomes difficult to correct spherical aberration and axial chromatic aberration. If the upper limit of conditional expression (4) is met, the refractive power of the first lens unit L1 becomes small, which increases the overall lens length.

[0037] Conditional expression (5) defines the ratio between the focal length f2 of the second lens group L2 and the focal length f of the imaging optical system. If the lower limit of conditional expression (5) is not met, the refractive power of the second lens group L2 will be reduced, thereby reducing the focus sensitivity of the second lens group L2 (the amount of focus movement relative to the amount of movement of the focusing group), and the overall lens length will be increased. If the upper limit of conditional expression (5) is exceeded, the refractive power of the second lens group L2 will be increased, thereby increasing the focus sensitivity of the second lens group L2, making it difficult to satisfy the optical performance during focusing.

[0038] Conditional expression (6) defines the ratio between the focal length f3 of the third lens unit L3 and the focal length f of the imaging optical system. If the lower limit of conditional expression (6) is not met, the refractive power of the third lens unit L3 becomes large, which is advantageous for shortening the overall lens length, but it becomes difficult to correct lateral chromatic aberration. If the upper limit of conditional expression (6) is exceeded, the refractive power of the third lens unit L3 becomes small, which increases the overall lens length.

[0039] Conditional expression (7) defines the Abbe number νdG1 of the lens closest to the object in the imaging optical system. If the lower limit of conditional expression (7) is not met, excessive chromatic aberration will occur in the lens closest to the object in the imaging optical system, which is undesirable. If the upper limit of conditional expression (7) is exceeded, insufficient chromatic aberration will occur in the lens closest to the object in the imaging optical system, which is undesirable.

[0040] It is preferable that the numerical ranges of the conditional expressions (3) to (7) be set to the numerical ranges of the following conditional expressions (3a) to (7a).

[0041] LD / f<1.4 (3a) 0.60 <f1 / f<0.81 (4a) -0.61 <f2 / f<-0.40 (5a) 0.7 <f3 / f<0.9 (6a) 16<νdG1<26 (7a) It is more preferable that the numerical ranges of the conditional expressions (3) to (12) be set to the numerical ranges of the following conditional expressions (3b) to (7b).

[0042] LD / f<1.3 (3b) 0.65 <f1 / f<0.76 (4b) -0.58 <f2 / f<-0.46 (5b) 0.74 <f3 / f<0.86 (6b) 20<νdG1<24 (7b) Numerical Examples 1 to 4 corresponding to Examples 1 to 4, respectively, are shown below.

[0043] In the surface data of each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the axial spacing (distance on the optical axis) between the mth surface and the (m+1)th surface. Here, m is the surface number counted from the light incident side. Also, nd represents the refractive index of the optical element at the d-line, and vd represents the Abbe number of the optical element. Note that the Abbe number vd of a certain material is given by the following equation, 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 lines: νd=(Nd-1) / (NF-NC) It is expressed as:

[0044] In each numerical example, d, focal length (mm), F-number, and half angle of view (degrees) are all values ​​when the imaging optical system of each example is focused on an object at infinity. "Back focus" is the distance on the optical axis from the final lens surface (the lens surface closest to the image) to the paraxial image plane, expressed as an air-equivalent length. "Total lens length" is the distance on the optical axis from the forefront lens surface (the lens surface closest to the object) of the imaging optical system to the final surface plus the back focus. "Lens group" is not limited to cases where it is composed of multiple lenses, but also includes cases where it is composed of a single lens.

[0045] [Numerical Example 1] Unit: mm Surface Data Surface number rd nd νd 1 54.092 5.36 1.92286 20.9 2 198.248 3.02 3 35.481 5.48 1.59522 67.7 4 82.774 0.60 5 107.370 1.80 1.84666 23.8 6 27.867 3.28 7 35.143 8.00 1.59522 67.7 8 -96.723 1.50 1.85478 24.8 9 5640.333 2.02 10 (Aperture) ∞ (Variable) 11 -698.314 1.00 1.60311 60.6 12 31.166 (variable) 13 83.514 1.10 1.84666 23.8 14 24.973 5.36 1.80400 46.5 15 -1796.766 2.00 16 -262.626 2.91 1.80810 22.8 17 -41.460 1.00 1.62588 35.7 18 58.693 1.10 19 157.200 1.25 1.84666 23.8 20 74.459 3.64 21 32.506 9.60 1.56384 60.7 22 -53.118 9.28 23 -46.134 1.35 1.83481 42.7 24 64.875 0.20 25 55.064 7.72 2.00069 25.5 26 -52.596 4.45 27 -25.396 1.60 1.58913 61.1 28 -105.676 12.0 29 ∞ 1.50 1.51633 64.1 30 ∞ 0.4 Image plane ∞ Focal length 85.40 F-number 1.85 Half angle of view (degrees) 14.22 Image height 21.64 Lens length 109.49 BF 13.39 Infinity -0.12x d10 2.00 8.33 d12 9.49 3.16 Lens group data Group starting plane focal length 1 1 63.27 2 11 -49.44 3 13 70.23 [Numerical Example 2] Unit: mm Surface Data Surface number rd nd νd 1 60.657 7.33 1.84666 23.8 2 409.336 0.20 3 40.298 9.91 1.49700 81.5 4 779.127 2.20 1.75520 27.5 5 31.274 3.03 6 40.780 8.97 1.49700 81.5 7 -103.500 1.60 1.85478 24.8 8 -806.192 2.00 9 (Aperture) ∞ (Variable) 10 -591.831 1.53 1.60311 60.6 11 37.539 (variable) 12 69.246 1.30 1.84666 23.9 13 30.666 5.47 1.80400 46.5 14 6151.241 2.00 15 186.758 4.22 1.80810 22.8 16 -45.460 1.20 1.68893 31.1 17 43.170 2.73 18 -148.577 1.30 1.56732 42.8 19 82.711 2.36 20 35.376 9.14 1.60311 60.6 21 -69.076 11.60 22 -42.878 1.55 1.62004 36.3 23 97.308 0.20 24 58.760 6.50 1.84666 23.8 25 -79.431 6.16 26 -27.942 2.00 1.66672 48.3 27 -58.434 12.0 28 ∞ 1.50 1.51633 64.1 29∞0.4 Image plane ∞ Focal length 101.78 F-number 1.85 Half angle of view (degrees) 12.00 Image height 21.64 Lens length 123.44 BF 13.39 Infinity -0.11x d 9 2.00 9.42 d11 13.55 6.13 Lens group data Group starting plane focal length 1 1 76.54 2 10 -58.48 3 12 82.26 [Numerical Example 3] Unit: mm Surface Data Surface number rd nd νd 1 94.549 5.77 1.92286 20.9 2 195.625 0.20 3 60.642 10.59 1.49700 81.5 4 341.785 0.20 5 49.687 10.32 1.49700 81.5 6 240.913 2.50 1.77047 29.7 7 34.682 3.19 8 47.542 10.50 1.49700 81.5 9 -109.842 2.00 1.95375 32.3 10 -479.909 3.50 11 (Aperture) ∞ (Variable) 12 -925.883 1.60 1.59349 67.0 13 38.997 (variable) 14 124.810 1.30 1.80810 22.8 15 27.897 6.15 1.88300 40.8 16 -553.811 2.00 17 195.915 3.98 1.80810 22.8 18 -46.407 1.20 1.72342 38.0 19 39.388 2.84 20 -800.989 1.25 1.84666 23.8 21 94.152 2.00 22 38.004 9.78 1.56384 60.7 23 -65.608 7.60 24 -50.619 1.65 1.48749 70.2 25 62.722 0.20 26 47.145 7.54 1.80810 22.8 27 -114.410 7.29 28 -35.060 2.98 1.90366 31.3 29 -70.011 12.25 30 ∞ 1.50 1.51633 64.1 31∞0.4 Image plane ∞ Focal length 131.00 F-number 1.85 Half angle of view (degrees) 9.38 Image height 21.64 Lens total length 146.99 BF 13.64 Infinity -0.25x d11 3.05 21.26 d13 22.18 3.97 Lens group data Group starting plane focal length 1 1 85.68 2 12 -63.01 3 14 111.55 [Numerical Example 4] Unit: mm Surface Data Surface number rd nd νd 1 91.618 6.52 1.84666 23.8 2 198.438 0.20 3 63.838 12.27 1.49700 81.5 4 353.293 0.20 5 53.417 12.00 1.49700 81.5 6 367.373 2.50 1.80100 35.0 7 37.173 9.29 8 51.330 10.70 1.49700 81.5 9 -108.230 2.00 1.90366 31.3 10 -1209.064 5.91 11 (Aperture) ∞ (Variable) 12 -884.729 1.30 1.56384 60.7 13 40.375 (variable) 14 79.594 1.30 1.78470 26.3 15 25.477 8.14 1.75500 52.3 16 -339.346 2.00 17 502.665 5.16 1.84666 23.8 18 -35.225 1.20 1.80100 35.0 19 45.472 3.34 20 -422.202 1.60 2.00330 28.3 21 193.743 4.36 22 43.822 7.17 1.59522 67.7 23 -71.918 17.75 24 -44.886 1.65 1.48749 70.2 25 47.885 10.04 1.85478 24.8 26 -47.052 1.69 27 -36.901 1.70 1.83481 42.7 28 -257.883 13.30 29 ∞ 1.50 1.51633 64.1 30 ∞ 0.4 Image plane ∞ Focal length 148.00 F-number 1.85 Half angle of view (degrees) 8.32 Image height 21.64 Lens length 159.49 BF 14.69 Infinity -0.11x d11 2.00 6.36 d13 12.81 8.45 Lens group data Group starting plane focal length 1 1 101.56 2 12 -68.45 3 14 110.87 The various values ​​in each numerical example are summarized in Table 1 below.

[0046] [Table 1]

[0047] [Imaging device] Next, an embodiment of a digital still camera (imaging device) using the imaging optical system of each embodiment will be described with reference to Fig. 9. In Fig. 9, 10 denotes a camera body, and 11 denotes any of the imaging optical systems described in Embodiments 1 to 4. 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 and receives and photoelectrically converts an optical image formed by the imaging optical system 11. The camera body 10 may be a so-called single-lens reflex camera having a quick-turn mirror, or a so-called mirrorless camera having no quick-turn mirror.

[0048] In this way, by applying the imaging optical system of each embodiment to an imaging device such as a digital still camera, an imaging device with a small lens can be obtained.

[0049] Although the preferred embodiments and examples of the present invention have been described above, the present invention is not limited to these embodiments and examples, and various combinations, modifications, and changes are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0050] L1 First lens group L2 Second lens group L3: Third lens group SP aperture stop

Claims

1. An optical system comprising, arranged in order from the object side to the image side, a first lens group having a positive refractive power, an aperture stop, a second lens group having a negative refractive power, and a third lens group having a positive refractive power, wherein the spacing between adjacent lens groups changes during focusing, When focusing from an object at infinity to the closest object, the second lens group moves toward the image side. the first lens group includes a positive lens disposed closest to the object side and two or more negative lenses, the positive lens arranged closest to the object side is a meniscus lens with a convex surface facing the object side, the second lens group is made up of one negative lens, Let LD1 be the distance on the optical axis from the lens surface of the first lens group closest to the object side to the lens surface of the first lens group closest to the image side, LD be the distance on the optical axis from the lens surface of the first lens group closest to the object side to the image plane, f be the focal length of the optical system, BF be the back focus of the optical system when focused on an object at infinity, and νdG1 be the Abbe number of the material of the positive lens arranged closest to the object side. 0.2<LD1 / LD<0.4 BF / f<0.25 15<νdG1<30 An optical system characterized by satisfying the following conditional expression:

2. LD / f<1.5 2. The optical system according to claim 1, wherein the following condition is satisfied:

3. When the focal length of the first lens group is f1, 0.50<f1 / f<0.85 3. The optical system according to claim 1, wherein the following condition is satisfied:

4. When the focal length of the second lens group is f2, -0.65<f2 / f<-0.35 4. The optical system according to claim 1, wherein the following condition is satisfied:

5. When the focal length of the third lens group is f3, 0.65<f3 / f<0.95 5. The optical system according to claim 1, wherein the following condition is satisfied:

6. the third lens group comprises, arranged in order from the object side to the image side, a first sub-group having positive refractive power, a second sub-group having negative refractive power, and a third sub-group having positive refractive power; 6. The optical system according to claim 1, wherein the second sub-group moves in a direction including a component perpendicular to the optical axis during image blur correction.

7. 0.099≦BF / f<0.25 2. The optical system according to claim 1, wherein the following condition is satisfied:

8. An optical system comprising a first lens group with positive refractive power, an aperture stop, a second lens group with negative refractive power, and a third lens group with positive refractive power, arranged in this order from the object side to the image side, wherein the spacing between adjacent lens groups changes during focusing, When focusing from an object at infinity to the closest object, the second lens group moves toward the image side. the first lens group includes a positive lens disposed closest to the object side and two or more negative lenses, the positive lens arranged closest to the object side is a meniscus lens with a convex surface facing the object side, the second lens group is made up of one negative lens, the third lens group comprises, arranged in order from the object side to the image side, a first sub-group having positive refractive power, a second sub-group having negative refractive power, and a third sub-group having positive refractive power; the second sub-group moves in a direction including a component perpendicular to the optical axis during image blur correction, Let LD1 be the distance on the optical axis from the lens surface of the first lens group closest to the object to the lens surface of the first lens group closest to the image, LD be the distance on the optical axis from the lens surface of the first lens group closest to the object to the image plane, f be the focal length of the optical system, and BF be the back focus of the optical system when focused on an object at infinity. 0.2<LD1 / LD<0.4 BF / f<0.25 An optical system characterized by satisfying the following conditional expression:

9. 9. An imaging device comprising: the optical system according to claim 1; and an imaging element that receives an image formed by the optical system.

Images