Optical system and imaging device having the same

Abstract

To provide an optical system which kas good optical performance exerted when the system is isolated from vibration, and an imaging apparatus having the optical system.SOLUTION: An optical system is provided, comprised of 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, which are arranged in order from an object side. For image blur correction, the second lens group moves in a direction having a component perpendicular to an optical axis of the optical system, while the first and third lens groups are stationary. A focal length of the optical system when focused at infinity, a focal length of the first lens group, and a focal length of the second lens group are each set appropriately.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, and the like. [Background technology]

[0002] Conventionally, optical systems have been proposed that have a wide angle of view, a large aperture ratio, a small size, high optical performance, and an image stabilization function for correcting blur in captured images (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2015-152812 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the optical system of Patent Document 1 with a wide angle of view and a large aperture ratio, it is difficult to correct coma aberration, chromatic aberration, and one-sided blur during image stabilization.

[0005] An object of the present invention is to provide an optical system that has good optical performance during image stabilization, and an imaging apparatus having the same. [Means for solving the problem]

[0006] An optical system according to one aspect of the present invention is an optical system including 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, which are arranged in this order from an object side to an image side, wherein, during image blur correction, the second lens group moves in a direction including a component in a direction perpendicular to an optical axis of the optical system, and the first lens group and the third lens group are stationary; the third lens group includes four positive lenses and four negative lenses;When the focal length of the optical system when focused at infinity is f, the focal length of the first lens group is f1, the focal length of the second lens group is f2, and the radius of curvature of the lens surface of the second lens group closest to the object is r21, 2.0<|f1 / f|<100.0 4.4 <f2 / f<100.0 -0.3 <f / r21<0.1 The present invention is characterized in that the following conditional expression is satisfied: [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an optical system that has good optical performance during vibration reduction, and an imaging apparatus having the same. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a cross-sectional view of the optical system of Example 1 when focused at infinity. [Figure 2] FIG. 2 is a longitudinal aberration diagram of the optical system of Example 1 when focused on infinity. [Figure 3] FIG. 10 is a diagram illustrating lateral aberration of the optical system of Example 1 when focused on infinity with 0.5-degree image stabilization. [Figure 4] FIG. 10 is a cross-sectional view of the optical system of Example 2 when focused at infinity. [Figure 5] FIG. 10 is a longitudinal aberration diagram of the optical system of Example 2 when focused on infinity. [Figure 6] FIG. 10 is a diagram illustrating lateral aberration of the optical system of Example 2 when focused on infinity with 0.5-degree image stabilization. [Figure 7] FIG. 10 is a cross-sectional view of the optical system of Example 3 when focused at infinity. [Figure 8] FIG. 10 is a longitudinal aberration diagram of the optical system of Example 3 when focused at infinity. [Figure 9] FIG. 10 is a diagram illustrating lateral aberration of the optical system of Example 3 when focused on infinity with 0.5-degree image stabilization. [Figure 10] FIG. 1 is a schematic diagram of an imaging device. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of an optical system and an imaging apparatus having the same according to the present invention will be described with reference to the accompanying drawings.

[0010] 1, 4, and 7 are cross-sectional views of the optical systems of Examples 1 to 3 when focused at infinity. The optical systems of the examples are optical systems used in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, and surveillance cameras.

[0011] 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 to have multiple lens groups. In this specification, a lens group refers to a group of lenses that move or remain stationary as a unit during image stabilization. Note that a lens group may be configured with a single lens, or may be configured with multiple lenses. Furthermore, a lens group may include an aperture stop.

[0012] The optical system L0 in each embodiment comprises, arranged in order from the object side to the image side, a first lens unit L1 with negative refractive power, a second lens unit L2 with positive refractive power, and a third lens unit L3 with positive refractive power.

[0013] Furthermore, SP denotes an aperture stop. IMG denotes an image plane, on which the imaging surface of a solid-state imaging element (photoelectric conversion element) such as a CCD sensor or CMOS sensor is placed when the optical system of each embodiment is used as the imaging optical system of a digital still camera or digital video camera. When the optical system of each embodiment is used as the imaging optical system of a silver halide film camera, a photosensitive surface corresponding to the film surface is placed on the image plane IMG.

[0014] 2, 5, and 8 are longitudinal aberration diagrams of the optical systems of Examples 1 to 3 when focused at infinity, respectively. Figures 3, 6, and 9 are lateral aberration diagrams of the optical systems of Examples 1 to 3 when focused at infinity with 0.5-degree image stabilization.

[0015] 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, ΔS shows the amount of astigmatism on the sagittal image plane, and ΔM 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).

[0016] Next, the characteristic configuration of the optical system L0 of each embodiment will be described.

[0017] The optical system L0 in each embodiment is a so-called retrofocus type lens configuration in which a negative lens group is arranged on the object side and a positive lens group is arranged on the image side, which makes it easy to achieve a wide angle of view.

[0018] During image blur correction, the second lens group L2 moves in a direction that includes a component perpendicular to the optical axis of the optical system L0, while the first lens group L1 and the third lens group L3 remain stationary. This moves the imaging position and performs image stabilization. By using the second lens group L2, located at the middle position of the optical system L0, as an image stabilization lens group, the ray height of off-axial light beams is relatively low, and the second lens group L2, which is an image stabilization lens group, can be made smaller.

[0019] The optical system of each embodiment satisfies the following conditional expressions (1) and (2).

[0020] 2.0<|f1 / f|<100.0 (1) 4.4 <f2 / f<100.0 (2) Here, f is the focal length of the optical system L0 when focused at infinity, f1 is the focal length of the first lens group L1, and f2 is the focal length of the second lens group L2.

[0021] Conditional formula (1) defines the ratio between the focal length of the first lens group L1 and the focal length of the optical system L0 when focused at infinity. If the upper limit of conditional formula (1) is exceeded and the absolute value of the focal length of the first lens group L1 becomes large, the retrofocus power arrangement weakens, making it difficult to achieve a wide angle of view, which is undesirable. If the lower limit of conditional formula (1) is exceeded and the absolute value of the focal length of the first lens group L1 becomes small, the divergence effect of the first lens group L1 becomes stronger. This increases the angle of the axial ray incident on the second lens group L2, making it difficult to correct aberrations, particularly coma, during image stabilization, which is undesirable.

[0022] Conditional expression (2) defines the ratio between the focal length of the second lens group L2 and the focal length of the optical system L0. If the upper limit of conditional expression (2) is exceeded and the focal length of the second lens group L2 becomes longer, the amount of movement required for vibration reduction becomes larger, the drive mechanism becomes larger, and it becomes difficult to miniaturize the imaging device, which is undesirable. If the lower limit of conditional expression (2) is exceeded and the focal length of the second lens group L2 becomes shorter, it becomes difficult to correct aberrations during vibration reduction, particularly correction of one-sided blur and chromatic aberration, which is undesirable.

[0023] The optical system L0 of each embodiment has the above-described configuration, which allows it to have good optical performance during image stabilization. Furthermore, the optical system L0 of each embodiment is small and has high optical performance while achieving both a wide angle of view and a large aperture ratio.

[0024] 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).

[0025] 2.5<|f1 / f|<30.0 (1a) 4.6 <f2 / f<20.0 (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).

[0026] 3.0<|f1 / f|<20.0 (1b) 4.8 <f2 / f<12.0 (2b) Next, the configurations that are preferably satisfied in the optical systems of the respective embodiments will be described.

[0027] It is preferable that a portion of the third lens group L3 moves along the optical axis of the optical system L0 during focusing. The arrows in each cross-sectional view indicate the direction of movement of the lens group during focusing from infinity to a close distance. By performing focusing using a portion of the third lens group L3 located on the image side, it is possible to reduce the weight and size of the third lens group L3, which is the focus lens group.

[0028] It is preferable that the second lens group L2 does not move during focusing. If the second lens group L2, which is an image stabilizing lens group, were to move during focusing, the drive mechanism would become complicated and the imaging device would become larger, which is not preferable.

[0029] It is preferable that a negative lens L11 is disposed closest to the object side of the first lens group L1, which makes it easier to achieve a wide angle of view.

[0030] The first lens group L1 preferably includes one positive lens and three negative lenses, which makes it easy to achieve good optical performance while maintaining a wide angle of view.

[0031] The second lens group L2 preferably has a three-element configuration consisting of a negative lens, a positive lens, and a positive lens, arranged in that order from the object side to the image side, a two-element configuration consisting of a negative lens and a positive lens, or a single positive lens. By configuring the second lens group L2 with a relatively small number of elements, it becomes possible to reduce the weight and size of the second lens group L2, which is an image stabilization lens group. Furthermore, when the second lens group L2 is configured with multiple lenses, arranging a negative lens on the object side and a positive lens on the image side is advantageous for achieving a wide angle of view.

[0032] The third lens group L3 preferably includes four positive lenses and four negative lenses, which facilitates favorable correction of spherical aberration, axial chromatic aberration, and field curvature, and facilitates achieving favorable optical performance despite a large aperture ratio.

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

[0034] 1.0 <f3 / f<10.0 (3) 0.3 <sk / f<3.0 (4) -0.3 <f / r21<0.2 (5) 0.5 <t1 / f<5.0 (6) 1.0<|f11 / f|<5.0 (7) Here, f3 is the focal length of the third lens group L3 when focusing at infinity. sk is the distance on the optical axis from the lens surface closest to the image to the image plane when focusing at infinity (hereinafter referred to as back focus). r21 is the radius of curvature of the lens surface closest to the object in the second lens group L2. t1 is the distance on the optical axis from the lens surface closest to the object in the first lens group L1 to the lens surface closest to the image in the first lens group (hereinafter referred to as the thickness of the first lens group L1). f11 is the focal length of the negative lens L11 arranged closest to the object in the first lens group L1.

[0035] Conditional expression (3) defines the ratio between the focal length of the third lens group L3 and the focal length of the optical system L0. If the upper limit of conditional expression (3) is exceeded and the focal length of the third lens group L3 becomes long, it becomes difficult to ensure the back focus, which is undesirable. If the lower limit of conditional expression (3) is exceeded and the focal length of the third lens group L3 becomes short, it becomes undesirable because the aberrations generated by the third lens group L3 become large, making it particularly difficult to correct distortion and chromatic aberration of magnification.

[0036] Conditional expression (4) defines the ratio between the back focal length and the focal length of optical system L0. If the upper limit of conditional expression (4) is exceeded and the back focal length becomes large, optical system L0 becomes large, which is undesirable. If the lower limit of conditional expression (4) is exceeded and the back focal length becomes small, it is undesirable because it becomes difficult to arrange a lens close to the image plane.

[0037] Conditional expression (5) defines the ratio between the focal length of the optical system L0 and the radius of curvature of the lens surface of the second lens group L2 closest to the object. If the upper limit of conditional expression (5) is exceeded and the radius of curvature of the lens surface of the second lens group L2 closest to the object increases in the positive direction, i.e., the lens surface becomes convex toward the object, the angle of incidence of on-axis light onto the second lens group L2 increases. This is undesirable because it makes it difficult to correct various aberrations caused by decentration, particularly decentration coma. If the lower limit of conditional expression (5) is exceeded and the radius of curvature of the lens surface of the second lens group L2 closest to the object increases in the negative direction, i.e., the lens surface becomes convex toward the image, the angle of incidence of off-axial light onto the second lens group L2 increases. This is undesirable because it makes it difficult to correct various aberrations caused by decentration, particularly one-sided blur.

[0038] Conditional expression (6) defines the ratio between the thickness of the first lens unit L1 and the focal length of the optical system L0. If the thickness of the first lens unit L1 exceeds the upper limit of conditional expression (6), the optical system L0 becomes large, which is undesirable. If the thickness of the first lens unit L1 falls below the lower limit of conditional expression (6), the correction of off-axis aberrations becomes insufficient, making it particularly difficult to correct distortion and chromatic aberration of magnification, which is undesirable.

[0039] Conditional expression (7) defines the ratio between the focal length of the negative lens L11 located closest to the object in the first lens group L1 and the focal length of the optical system L0. If the absolute value of the focal length of the negative lens L11 exceeds the upper limit of conditional expression (7), it becomes difficult to achieve a wide angle of view, which is undesirable. If the absolute value of the focal length of the negative lens L11 falls below the lower limit of conditional expression (7), it becomes difficult to correct the aberrations generated by the negative lens L11, which is undesirable, because distortion and chromatic aberration of magnification in particular become large.

[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] 1.4 <f3 / f<4.0 (3a) 0.4 <sk / f<2.0 (4a) -0.2 <f / r21<0.1 (5a) 0.8 <t1 / f<4.0 (6a) 1.5<|f11 / f|<4.0 (7a) It is more preferable that the numerical ranges of the conditional expressions (3) to (7) be the numerical ranges of the following conditional expressions (3b) to (7b).

[0042] 1.5 <f3 / f<3.5 (3b) 0.5 <sk / f<1.0 (4b) -0.18 <f / r21<0.06 (5b) 1.1 <t1 / f<3.2 (6b) 1.8<|f11 / f|<3.3 (7b) Next, the optical system L0 of each embodiment will be described in detail.

[0043] The optical system L0 of Examples 1 to 3 comprises, arranged in order from the object side to the image side, a first lens group L1 with negative refractive power, a second lens group L2 with positive refractive power, and a third lens group L3 with positive refractive power. A portion of the third lens group L3 moves along the optical axis of the optical system L0 during focusing. A negative lens L11 is disposed closest to the object side of the first lens group L1. An aperture stop SP is disposed within the third lens group L3. Image stabilization is performed by moving the second lens group L2 in a direction that includes a component perpendicular to the optical axis.

[0044] Numerical Examples 1 to 3 corresponding to Examples 1 to 3, respectively, are shown below.

[0045] 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. Furthermore, nd represents the refractive index of each optical element with respect to 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:

[0046] In each numerical example, d, focal length (mm), F-number, and half angle of view (degrees) are all values when the 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) to the final lens 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.

[0047] If the optical surface is aspherical, an asterisk (*) is added to the right of the surface number. The aspherical shape is expressed as follows: X is the displacement from the vertex of the surface in the optical axis direction, h is the height from the optical axis in the direction perpendicular to the optical axis, R is the paraxial radius of curvature, K is the conic constant, and A4, A6, A8, A10, and A12 are the aspherical coefficients of each order. 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 In addition, "e±XX" in each aspherical coefficient is "×10± XX " means.

[0048] [Numerical Example 1] Unit: mm Surface Data Surface number rd nd νd 1 45.999 2.00 1.77250 49.6 2 19.037 6.11 3* 20.524 2.00 1.49700 81.5 4* 11.924 14.53 5 -34.204 1.40 1.49700 81.5 6 66.841 6.18 1.84666 23.8 7 -43.198 1.54 8 -29.354 1.20 1.94594 18.0 9 -345.384 2.04 10 76.242 5.53 2.00100 29.1 11 -52.136 1.00 12 -87.065 1.00 1.80000 29.8 13 39.112 5.88 1.53775 74.7 14 -61.329 0.15 15 140.232 3.30 2.00100 29.1 16 -79.219 3.27 17 -35.786 1.00 1.59551 39.2 18 56.288 1.79 1.94594 18.0 19 90.764 2.39 20 161.169 3.05 1.59522 67.7 21 -88.110 1.00 22 (Aperture) ∞ 6.03 23 -267.436 0.80 1.65412 39.7 24 73.925 0.15 25 26.821 10.66 1.49700 81.5 26 -26.956 0.90 1.72047 34.7 27 -95.816 0.15 28 26.034 6.33 1.49700 81.5 29 -115.808 8.70 30* -11385.852 2.50 1.85400 40.4 31* 53.435 1.00 32 39.949 6.77 1.49700 81.5 33 -67.804 1.20 1.85478 24.8 34 -148.451 12.15 Image plane ∞ Aspheric data 3rd page K = 0.00000e+000 A 4=-2.41374e-005 A 6= 2.66951e-008 A 8=-7.74059e-011 A10= 1.77746e-014 Side 4 K =-1.04458e+000 A 4= 2.06945e-006 A 6= 2.46920e-008 A 8=-8.48027e-011 Page 30 K = 0.00000e+000 A 4=-8.19322e-005 A 6= 1.55857e-007 A 8= 8.01308e-011 A10=-9.41515e-013 Page 31 K = 0.00000e+000 A 4=-4.83741e-005 A 6= 2.39145e-007 A 8=-5.32181e-011 A10=-6.89055e-013 Focal length 14.30 F-number 1.44 Half angle of view (degrees) 56.5 Lens length 123.69 BF 12.15 [Numerical Example 2] Unit: mm Surface Data Surface number rd nd νd 1 41.167 2.00 1.77250 49.6 2 18.277 6.48 3* 20.216 2.00 1.49700 81.5 4* 11.196 12.72 5 -36.549 1.40 1.49700 81.5 6 96.566 4.36 1.85478 24.8 7 -51.541 2.45 8 -24.329 1.20 1.94594 18.0 9 -89.671 2.38 10 228.445 4.67 1.90043 37.4 11 -40.827 1.00 12 290.730 1.00 1.84666 23.8 13 37.037 5.59 1.70154 41.2 14 -89.055 1.00 15 50.578 3.46 1.94594 18.0 16 -1297.226 0.15 17 48.954 0.99 1.64769 33.8 18 26.161 6.06 19 -29.945 1.00 1.61293 37.0 20 -43.997 1.00 21 (Aperture) ∞ 6.00 22 -228.377 0.80 1.63980 34.5 23 70.060 0.15 24 29.850 9.75 1.49700 81.5 25 -23.499 0.90 1.76182 26.5 26 -53.730 0.15 27 27.052 8.04 1.49700 81.5 28 -77.884 6.86 29* -9993.255 2.50 1.85400 40.4 30* 57.332 1.00 31 36.236 5.98 1.49700 81.5 32 -224.962 1.20 1.85478 24.8 33 -839.098 13.26 Image plane ∞ Aspheric data 3rd page K = 0.00000e+000 A 4=-3.25963e-005 A 6= 3.69158e-008 A 8=-1.11928e-010 A10= 7.18986e-014 Side 4 K =-1.51002e+000 A 4= 4.08082e-005 A 6=-6.86300e-008 A 8= 5.70637e-011 Page 29 K = 0.00000e+000 A 4=-1.96185e-005 A 6=-7.39653e-008 A 8= 2.56837e-010 A10=-5.67631e-013 Page 30 K = 0.00000e+000 A 4= 1.28253e-005 A 6=-3.74763e-008 A 8= 3.47109e-010 A10=-7.18916e-013 Focal length 14.30 F-number 1.44 Half angle of view (degrees) 56.53 Lens length 117.50 BF 13.26 [Numerical Example 3] Unit: mm Surface Data Surface number rd nd νd 1 110.478 1.20 1.48749 70.2 2 21.266 11.48 3 -29.640 1.00 1.49700 81.5 4 49.198 3.48 5 94.394 10.37 1.91082 35.3 6 -22.678 1.20 1.85478 24.8 7 -65.536 1.00 8 -3505.263 2.73 1.59282 68.6 9 -110.997 4.90 10 41.287 4.41 1.59282 68.6 11 3116.861 1.29 12 140.240 6.13 1.80400 46.6 13 -34.574 1.00 1.56660 19.1 14 -27.319 0.99 1.59551 39.2 15 61.895 3.30 16 (Aperture) ∞ 6.65 17 -33.899 5.61 1.59522 67.7 18 -15.080 0.90 1.68893 31.1 19 -1688.609 0.15 20 35.766 9.47 1.59282 68.6 21 -33.311 0.15 22* 140.088 3.90 1.85400 40.4 23* -70.411 1.00 24 87.268 1.00 1.61340 44.3 25 26.907 6.40 26 -64.818 1.00 1.85478 24.8 27 746.640 0.22 28 61.048 4.14 1.92286 20.9 29 -4739.779 13.46 Image plane ∞ Aspheric data Page 22 K = 0.00000e+000 A 4=-2.75324e-005 A 6=-4.86143e-008 A 8=-1.73828e-010 A10= 9.21692e-013 Page 23 K = 0.00000e+000 A 4=-1.02537e-005 A 6=-4.09503e-008 A 8=-3.61973e-011 A10= 5.72179e-013 Various data Focal length 24.48 F-number 1.44 Half angle of view (degrees) 41.47 Lens length 108.53 BF 13.46 The various values in each numerical example are summarized in Table 1 below.

[0049] [Table 1]

[0050] [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. 10. In Fig. 10, 10 denotes a camera body, and 11 denotes any of the imaging optical systems described in Embodiments 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 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.

[0051] 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.

[0052] 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]

[0053] L0 optical system L1 First lens group L2 Second lens group L3: Third lens group

Claims

1. An optical system comprising a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, arranged in this order from the object side to the image side, During image blur correction, the second lens group moves in a direction including a component of a direction perpendicular to an optical axis of the optical system, and the first lens group and the third lens group are stationary, the third lens group includes four positive lenses and four negative lenses, When the focal length of the optical system when focused at infinity is f, the focal length of the first lens group is f1, the focal length of the second lens group is f2, and the radius of curvature of the lens surface of the second lens group closest to the object side is r21, 2.0<|f1 / f|<100.0 4.4<f2 / f<100.0 -0.3<f / r21<0.1 An optical system characterized by satisfying the following conditional expression:

2. 2. The optical system according to claim 1, wherein a part of the third lens group moves during focusing.

3. When the focal length of the third lens group when focused at infinity is f3, 1.0<f3 / f<10.0 3. The optical system according to claim 1, wherein the following condition is satisfied:

4. When focusing at infinity, the distance on the optical axis from the lens surface closest to the image side to the image plane is denoted by sk, 0.3<sk / f<3.0 4. The optical system according to claim 1, wherein the following condition is satisfied:

5. When 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 is t1, 0.5<t1 / f<5.0 5. The optical system according to claim 1, wherein the following condition is satisfied:

6. 6. The optical system according to claim 1, wherein a negative lens is disposed closest to the object side of the first lens group.

7. When the focal length of the lens arranged closest to the object in the first lens group is f11, 1.0<|f11 / f|<5.0 7. The optical system according to claim 1, wherein the following condition is satisfied:

8. 8. The optical system according to claim 1, wherein the first lens group includes one positive lens and three negative lenses.

9. 9. The optical system according to claim 1, wherein the second lens group comprises, in order from the object side to the image side, a negative lens, a positive lens, and a positive lens.

10. An optical system comprising a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, arranged in this order from the object side to the image side, During image blur correction, the second lens group moves in a direction including a component of a direction perpendicular to an optical axis of the optical system, and the first lens group and the third lens group are stationary, the second lens group comprises, in order from the object side to the image side, a negative lens, a positive lens, and a positive lens; When the focal length of the optical system when focused at infinity is f, the focal length of the first lens group is f1, the focal length of the second lens group is f2, the radius of curvature of the lens surface of the second lens group closest to the object side is r21, and the focal length of the lens arranged closest to the object side in the first lens group is f11, 2.0<|f1 / f|<100.0 4.4<f2 / f<100.0 -0.3<f / r21<0.1 1.0<|f11 / f|<5.0 An optical system characterized by satisfying the following conditional expression:

11. 9. The optical system according to claim 1, wherein the second lens group comprises a negative lens and a positive lens arranged in this order from the object side to the image side.

12. An optical system comprising a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, arranged in this order from the object side to the image side, During image blur correction, the second lens group moves in a direction including a component of a direction perpendicular to an optical axis of the optical system, and the first lens group and the third lens group are stationary, the second lens group comprises a negative lens and a positive lens, arranged in this order from the object side to the image side, When the focal length of the optical system when focused at infinity is f, the focal length of the first lens group is f1, the focal length of the second lens group is f2, the radius of curvature of the lens surface of the second lens group closest to the object side is r21, and the focal length of the lens arranged closest to the object side in the first lens group is f11, 2.0<|f1 / f|<100.0 4.4<f2 / f<100.0 -0.3<f / r21<0.1 1.0<|f11 / f|<5.0 An optical system characterized by satisfying the following conditional expression:

13. 9. The optical system according to claim 1, wherein the second lens group is made up of one positive lens.

14. 14. The optical system according to claim 1, wherein the second lens group is stationary during focusing.

15. 15. The optical system according to claim 1, wherein the first lens group is stationary during focusing.

16. An optical system according to any one of claims 1 to 15; and an image sensor that receives an image formed by the optical system.

Images