Optical system and image pickup apparatus including the same

Abstract

It is required to provide an optical system which is lightweight and in which various aberrations are corrected favorably while having a long focal length.SOLUTION: An optical system comprises a first lens group having positive refractive power, which is arranged in order from the object side to the image side, an intermediate group having one or more lens groups, and a subsequent lens group, wherein the distance between the adjacent lens groups changes during focusing, and at least one lens group arranged in the intermediate group moves during focusing to satisfy a predetermined condition.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical system suitable for use in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, and cameras for silver halide film. [Background technology]

[0002] 2. Description of the Related Art Optical systems with long focal lengths are known as optical systems used in imaging devices.

[0003] The longer the focal length of an optical system, the larger and heavier it tends to be. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-161076 Summary of the Invention [Problem to be solved by the invention]

[0005] The optical system in Patent Document 1 discloses a configuration consisting of, arranged in order from the object side to the image side, a first lens group with positive refractive power, a second lens group with negative refractive power that moves during focusing, and a third lens group with positive refractive power. However, the material of the positive lens in the first lens group has a low refractive index, and the absolute value of the curvature is large, making it difficult to reduce the weight. Also, the number of lens elements arranged in the third lens group is small, making it difficult to correct various aberrations.

[0006] Therefore, there is a demand for an optical system that has a long focal length, is lightweight, and has excellent correction of various aberrations. [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 intermediate group having one or more lens groups, and a subsequent lens group, and the distance between adjacent lens groups changes during focusing. During focusing, at least one lens group arranged in the intermediate group moves, and the first lens group comprises a first subgroup and a second subgroup arranged adjacent to the image side of the first subgroup, and the distance between adjacent lens groups changes during focusing. Among the air gaps on the optical axis between adjacent lenses, the air gap on the optical axis between the first subgroup and the second subgroup is the largest, the second subgroup has a positive lens Gp, the Abbe number and the refractive index at the d-line of the material of the positive lens Gp are respectively denoted as νd1p and nd1p, the distance on the optical axis from the lens surface of the second subgroup closest to the object side to the lens surface of the positive lens Gp is ​​denoted as Dp, and the distance on the optical axis from the lens surface of the second subgroup closest to the object side to the lens surface of the second subgroup closest to the image side is denoted as D1b. 2.160 <nd1p+0.02174×νd1p<2.320 1.600 <nd1p<1.850 0.00≦Dp / D1b<0.72 The present invention is characterized in that the following conditional expression is satisfied:

[0008] Another aspect of the present invention is an optical system that comprises, arranged in order from the object side to the image side, a first lens group having positive refractive power, an intermediate group having one or more lens groups, and a subsequent lens group, in which the spacing between adjacent lens groups changes during focusing, and is characterized in that, during focusing, at least one lens group arranged in the intermediate group moves, and the total number of lens elements arranged in the subsequent lens group is four or more. [Effects of the Invention]

[0009] According to the above-mentioned means, it is possible to provide an optical system that has a long focal length, is lightweight, and has various aberrations well corrected. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of the optical system of Example 1 when focusing to infinity. [Figure 2] In the optical system of Example 1, (A) is an aberration diagram when focusing at infinity, and (B) is an aberration diagram when focusing at close range. [Figure 3] 1 is a cross-sectional view of the optical system of Example 2 when focusing to infinity. [Figure 4] In the optical system of Example 2, (A) is an aberration diagram when focusing at infinity, and (B) is an aberration diagram when focusing at close range. [Figure 5] 10 is a cross-sectional view of the optical system of Example 3 when focusing to infinity. [Figure 6] In the optical system of Example 3, (A) is an aberration diagram when focusing at infinity, and (B) is an aberration diagram when focusing at close range. [Figure 7] 10 is a cross-sectional view of the optical system of Example 4 when focusing to infinity. [Figure 8] In the optical system of Example 4, (A) is an aberration diagram when focusing at infinity, and (B) is an aberration diagram when focusing at close range. [Figure 9] 10 is a cross-sectional view of the optical system of Example 5 when focusing to infinity. [Figure 10] In the optical system of Example 5, (A) is an aberration diagram when focusing at infinity, and (B) is an aberration diagram when focusing at close range. [Figure 11] Schematic diagram showing an imaging device DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, examples of an optical system according to an embodiment of the present invention and an imaging device having the same will be described with reference to the accompanying drawings.

[0012] 1, 3, 5, 7, and 9 are cross-sectional views of the optical system L0 of Examples 1 to 5, respectively, when focused at infinity. The optical system L0 of each Example is an optical system used in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, surveillance cameras, and vehicle-mounted cameras.

[0013] In each lens cross-sectional view, the left side is the object side and the right side is the image side. Note that the optical system L0 of each embodiment may be used as a projection lens for a projector, etc. In this case, the left side is the screen side and the right side is the projected image side.

[0014] In each lens cross-sectional view, SP denotes an aperture stop. IP denotes an image plane, and when the optical system L0 of each embodiment is used in 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 disposed thereon. When the optical system L0 of each embodiment is used as a photographic optical system for a silver halide film camera, a photosensitive surface corresponding to the film surface is disposed at the image plane IP.

[0015] The optical system L0 in each embodiment is composed of, arranged in order from the object side to the image side, a first lens unit B1 having positive refractive power, an intermediate lens unit Bf, and a subsequent lens unit Br. Each lens unit may be composed of a single lens or multiple lenses.

[0016] The solid arrows pointing downward in each lens cross-sectional view represent the movement locus of one or more lenses that move during focusing from infinity to close range.

[0017] The solid arrows pointing upward in each lens cross-sectional view represent the movement locus of one or more lenses that move so as to include a component in a direction perpendicular to the optical axis during image blur correction.

[0018] 2(A), 4(A), 6(A), 8(A), and 10(A) are aberration diagrams when focusing at infinity in the optical systems L0 of Examples 1 to 5, respectively.

[0019] 2(B), 4(B), 6(B), 8(B), and 10(B) are aberration diagrams when focusing at close range in the optical systems L0 of Examples 1 to 5, respectively.

[0020] In the spherical aberration diagram, Fno is the F-number, the solid line shows the amount of spherical aberration for the d-line (wavelength 587.6 nm), and the dashed line shows the amount of spherical aberration for the g-line (wavelength 435.8 nm). In the astigmatism diagram, the solid line shows the amount of aberration ΔS on the sagittal image plane, and the dashed line shows the amount of aberration ΔM 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. ω is the half angle of view (°).

[0021] Here, the Abbe number vd and the partial dispersion ratio θgf for the g-line and F-line are known as parameters related to the correction of chromatic aberration in an optical system. When the refractive indices of materials for the g-line (wavelength 435.8 nm), F-line (486.1 nm), C-line (656.3 nm), and d-line (587.6 nm) are Ng, NF, NC, and Nd, respectively, the Abbe number vd and the partial dispersion ratio θgf for the g-line and F-line are respectively expressed by the following equations. νd=(Nd-1) / (NF-NC) θgf=(Ng-NF) / (NF-NC)

[0022] Next, the optical system L0 according to the first embodiment will be described.

[0023] The optical system L0 according to the first embodiment comprises, arranged in order from the object side to the image side, a first lens group B1 having positive refractive power, an intermediate group Bf having one or more lens groups, and a subsequent lens group Br, with the spacing between adjacent lens groups changing during focusing. Because the first lens group B1 has positive refractive power, the first lens group B1 converges an axial light beam, making it easy to reduce the diameter of the lenses arranged in the intermediate group Bf. As a result, it is easy to reduce the weight of the lenses arranged in the intermediate group Bf despite the long focal length.

[0024] During focusing, at least one lens group arranged in the intermediate group Bf moves. At long focal lengths, the height from the optical axis of marginal rays of an axial light beam incident on the intermediate group Bf tends to be lower than that of the first lens group B1, and the height from the optical axis of off-axis chief rays tends to be lower than that of the subsequent lens group Br. Therefore, by moving at least one lens group arranged in the intermediate group Bf, it becomes easier to suppress fluctuations in spherical aberration, field curvature, and the like that occur during focusing.

[0025] The first lens group B1 is composed of a first subgroup B1a and a second subgroup B1b arranged adjacent to the first subgroup B1a on the image side. Among the air gaps between adjacent lenses in the first lens group B1, the air gap between the first subgroup B1a and the second subgroup B1b is the largest. The second subgroup B1b includes a positive lens Gp.

[0026] By including the positive lens Gp in the second sub-unit B1b, the diameter of the lens disposed closer to the image side than the positive lens Gp can be reduced, which makes it easier to reduce the weight of the optical system L0.

[0027] The optical system L0 according to the first embodiment is configured to satisfy the following conditional expressions. 2.160 <nd1p+0.02174×νd1p<2.320···(1) 1.600 <nd1p<1.850···(2) 0.00≦Dp / D1b<0.72 (3)

[0028] where νd1p and nd1p are the Abbe number and the refractive index at the d-line of the material of the positive lens Gp, respectively, Dp is the distance on the optical axis from the lens surface of the second sub-unit B1b closest to the object to the lens surface of the positive lens Gp closest to the object, and D1b is the distance on the optical axis from the lens surface of the second sub-unit B1b closest to the object to the lens surface of the second sub-unit B1b closest to the image.

[0029] If the Abbe number of the material of the positive lens element Gp becomes large, exceeding the upper limit of conditional expression (1), low-dispersion glass must be selected as the material of the positive lens element Gp. This reduces the partial dispersion ratio between the g-line and the F-line, and the refractive index for the g-line becomes too small. This results in excessively large axial chromatic aberration between the g-line and the F-line, which is undesirable.

[0030] If the Abbe number of the material of the positive lens Gp falls below the lower limit of conditional expression (1) and becomes small, the longitudinal chromatic aberration between the F-line and the C-line becomes too large, which is not preferable.

[0031] If the upper limit of conditional expression (2) is exceeded and the refractive index of the positive lens Gp for the d-line becomes large, the reflectance of the lens surface of the positive lens Gp becomes high, which tends to increase the intensity of ghost light, which is undesirable.

[0032] If the refractive index of the positive lens Gp for the d-line becomes small by falling below the lower limit of conditional expression (2), the absolute value of the curvature of at least one of the object-side lens surface and the image-side lens surface of the positive lens Gp becomes too large, resulting in an increase in the volume of the positive lens Gp and making it difficult to reduce its weight.

[0033] If the upper limit of conditional expression (3) is exceeded and the axial distance from the lens surface of the second subunit B1b closest to the object to the lens surface of the positive lens Gp closest to the object becomes large, the positive lens Gp will be positioned on the image side, and the height of the axial marginal ray will become too low, which will result in insufficient correction of axial chromatic aberration for the g-line, which is undesirable.

[0034] The lower limit of conditional expression (3) means that the positive lens Gp is ​​located closest to the object in the second sub-group. By locating the positive lens Gp closest to the object in the second sub-group, the positive lens Gp can be located at a position where the height from the optical axis of the axial marginal ray is relatively high. As a result, axial chromatic aberration for the g-line can be effectively corrected.

[0035] By satisfying the above-mentioned configuration, the optical system L0 according to the first embodiment can provide an optical system L0 that has a long focal length, is lightweight, and has various aberrations well corrected.

[0036] Here, the long focal length refers to the focal length of the optical system L0 where the maximum value of the imaging half angle of view is 16.0 degrees or less.

[0037] It is preferable that the conditional expressions (1), (2), and (3) are set to the following conditions, respectively. 2.200 <nd1p+0.02174×νd1p<2.310···(1a) 1.610 <nd1p<1.830···(2a) 0.00≦Dp / D1b<0.718 (3a)

[0038] Furthermore, it is preferable that the conditional expressions (1), (2), and (3) are set to the following conditions, respectively. 2.260 <nd1p+0.02174×νd1p<2.300···(1b) 1.620 <nd1p<1.810···(2b) 0.00≦Dp / D1b<0.45 (3b)

[0039] Next, the optical system L0 according to the second embodiment will be described.

[0040] The optical system L0 according to the second embodiment comprises, arranged in order from the object side to the image side, a first lens group B1 having positive refractive power, an intermediate group Bf having one or more lens groups, and a subsequent lens group Br, and the spacing between adjacent lens groups changes during focusing. Because the first lens group B1 has positive refractive power, the first lens group B1 converges an axial light beam, making it easy to reduce the diameter of the lenses arranged in the intermediate group Bf. As a result, it is easy to reduce the weight of the lenses arranged in the intermediate group Bf.

[0041] During focusing, at least one lens group arranged in the intermediate group Bf moves. At long focal lengths, the height of the optical axis of marginal rays of an on-axis light beam incident on the intermediate group Bf tends to be lower than that of the first lens group B1, and the height from the optical axis of off-axis chief rays tends to be lower than that of the subsequent lens group Br. Therefore, by moving at least one lens group arranged in the intermediate group Bf, it becomes easier to suppress fluctuations in spherical aberration, field curvature, and the like that occur during focusing.

[0042] The total number of lens elements arranged in the subsequent lens group Br is four or more. Here, a lens element is counted as one if it is a cemented lens or a single lens. Because the diameters of the lenses arranged in the subsequent lens group Br are relatively small, having four or more lens elements in the subsequent lens group Br makes it easy to reduce weight while correcting various aberrations.

[0043] Next, a preferred configuration of the optical system L0 according to each embodiment will be described.

[0044] It is preferable that the subsequent lens group Br include an image stabilization group IS that moves during image blur correction so as to include a component perpendicular to the optical axis. By arranging the image stabilization group IS in the subsequent lens group Br, which moves during image blur correction so as to include a component perpendicular to the optical axis, the diameter of the lenses arranged in the image stabilization group IS can be reduced, making it easier to reduce weight while still providing good image blur correction. Here, the image stabilization group IS includes one positive lens and two negative lenses, making it easier to correct decentering aberrations that occur during image blur.

[0045] It is preferable that the positive lens Gp is ​​located closest to the object in the second sub-unit B1b. This allows the positive lens Gp to be located at a relatively high position from the optical axis where the on-axis marginal ray is located. As a result, on-axis chromatic aberration for the g-line can be effectively corrected.

[0046] The first sub-unit B1a is preferably made up of two positive lenses, which makes it easier to correct spherical aberration and reduce the weight.

[0047] The second sub-unit B1b preferably has two or more negative lenses, which makes it easier to correct axial chromatic aberration and other aberrations that occur in the first sub-unit B1a. Furthermore, the second sub-unit B1b preferably has three positive lenses, which makes it easier to correct spherical aberration and other aberrations.

[0048] It is preferable that the lens group that moves during focusing, located in the intermediate group Bf, has negative refractive power and moves toward the image side during focusing from infinity to close distances, which makes it easier to prevent the diameter of the lens group that moves during focusing from increasing and to reduce its weight.

[0049] It is preferable that the lens group disposed in the intermediate group Bf that moves during focusing has positive refractive power and moves toward the object during focusing from infinity to close distances, which makes it easier to suppress fluctuations in coma and other aberrations that occur during focusing.

[0050] The subsequent lens group Br preferably has an aspherical lens, which makes it easier to correct for curvature of field and the like.

[0051] It is preferable that the optical system L0 according to each embodiment satisfies one or more of the following conditional expressions. 0.666<θgf1p+0.00182×νd1p<0.697 (4) 0.15 <f1p / f<1.50···(5) 1.0 <BF / IH<3.5···(6) 0.20 <f1 / f<2.20···(7) 0.10 <f1a / f<2.00···(8) 0.10 <D1a / TD1<0.70···(9) 0.50 <OTD / f<1.50···(10) 70.0<νdpmax<100.0 (11) 1.00≦Φfea×Fno / f<1.40 (12) 0.60 <Bab_max / Fno<2.00···(13) 15.0<νdnmin<50.0 (14) 0.20 <D1max / TD1<0.80···(15) 0.50<|f1b| / f<3.50 (16)

[0052] Here, θgf1p is the partial dispersion ratio between the g-line and the F-line of the material of the positive lens Gp. f1p is the focal length of the positive lens Gp, and f is the focal length of the entire system. BF is the back focus of the entire system, and IH is the maximum image height. Here, the maximum image height is the image height at which the peripheral light amount is 20% relative to an image height of 0.0 mm. f1 is the focal length of the first lens unit B1.

[0053] where f1a is the focal length of the first sub-group B1a, D1a is the axial distance from the lens surface of the first sub-group B1a closest to the object to the lens surface of the first sub-group B1a closest to the image, and TD1 is the axial distance from the lens surface of the first sub-group B1a closest to the object to the lens surface of the first sub-group B1a closest to the image.

[0054] OTD is the distance on the optical axis from the lens surface closest to the object in the optical system L0 to the image plane, and νdpmax is the Abbe number of the material of the positive lens Gr that has the largest Abbe number among the materials of all the positive lenses arranged in the first lens group B1.

[0055] Φfea is the effective diameter of the lens located closest to the object in the optical system L0, and Fno is the F-number of the entire system. Bab_max is the absolute value of the position sensitivity with the highest value among all the lens groups located in the intermediate group Bf that move during focusing. νdnmin is the minimum Abbe number among all the materials of the negative lenses located in the first lens group B1. D1max is the air gap on the optical axis between the first sub-group B1a and the second sub-group B1b. f1b is the focal length of the second sub-group B1b.

[0056] Next, the technical meaning of the above-mentioned conditional expressions (4) to (16) will be explained.

[0057] If the upper limit of conditional expression (4) is exceeded and the partial dispersion ratio of the material of the positive lens Gp becomes large, chromatic aberration of magnification for the g-line relative to the F-line will be overcorrected, which is not preferable.If the lower limit of conditional expression (4) is exceeded and the partial dispersion ratio of the material of the positive lens becomes small, axial chromatic aberration and chromatic aberration of magnification for the g-line relative to the F-line will be undercorrected, which is not preferable.

[0058] If the upper limit of conditional expression (5) is exceeded and the refractive power of the positive lens Gp becomes weak, it becomes difficult to correct axial chromatic aberration for the g-line relative to the F-line, etc. If the lower limit of conditional expression (5) is not reached and the refractive power of the positive lens Gp becomes strong, it is undesirable because the positive lens Gp will produce large spherical aberrations, etc.

[0059] If the upper limit of conditional expression (6) is exceeded, the back focal length becomes too long, which increases the weight of the mechanical components that support optical system L0, making it difficult to reduce the weight. If the lower limit of conditional expression (6) is exceeded, the back focal length becomes too short. As a result, the intensity of ghost light that is generated by reflection between the image sensor and the lens located closest to the image side in optical system L0 increases, which is undesirable.

[0060] If the upper limit of conditional expression (7) is exceeded and the refractive power of the first lens unit B1 becomes weak, the principal point of the optical system L0 is located on the image side, which increases the overall lens length, and as a result, the weight of the mechanical components that support the optical system L0 increases, making it difficult to reduce the weight.

[0061] Here, the total lens length is the sum of the distance on the optical axis from the surface of optical system L0 closest to the object to the surface closest to the image, and the back focus, which is the air-equivalent value of the distance on the optical axis between the surface of optical system L0 closest to the image and the image plane.

[0062] If the refractive power of the first lens unit B1 becomes too strong by going below the lower limit of conditional expression (7), the first lens unit B1 will produce large spherical aberrations and the like, which is not desirable.

[0063] If the upper limit of conditional expression (8) is exceeded and the refractive power of the first sub-unit B1a becomes weak, the diameter of each lens arranged closer to the image side than the first sub-unit B1a becomes large, making it difficult to reduce the weight.If the lower limit of conditional expression (8) is exceeded and the refractive power of the first sub-unit B1a becomes strong, the first sub-unit B1a will produce large spherical aberrations, etc., which is undesirable.

[0064] If the upper limit of conditional expression (9) is exceeded and the distance on the optical axis from the lens surface of the first subunit B1a closest to the object to the lens surface of the first subunit B1a closest to the image becomes large, the volume of the first subunit B1a, which tends to have a large lens diameter, becomes large in the first lens unit B1, making it difficult to reduce the weight.

[0065] If the lower limit of conditional expression (9) is not reached and the distance on the optical axis from the lens surface closest to the object in the first sub-unit B1a to the lens surface closest to the image becomes short, it becomes difficult to increase the refractive power of the first sub-unit B1a, and as a result, the diameter of the lens positioned closer to the image than the first sub-unit B1a becomes large, making it difficult to reduce the weight.

[0066] If the upper limit of conditional expression (10) is exceeded and the axial distance from the lens surface closest to the object in optical system L0 to the image plane becomes large, the weight of the mechanical components that support optical system L0 increases, making it difficult to reduce the weight. If the lower limit of conditional expression (10) is exceeded and the axial distance from the lens surface closest to the object in optical system L0 to the image plane becomes short, the refractive power of each lens becomes strong. As a result, it becomes difficult to correct various aberrations.

[0067] If the upper limit of conditional expression (11) is exceeded and the Abbe number of the material of the positive lens Gr becomes large, the refractive index of the glass material of the positive lens Gr becomes low, which is undesirable as it causes significant spherical aberration, curvature of field, etc. If the lower limit of conditional expression (11) is exceeded and the Abbe number of the material of the positive lens Gr becomes small, which is undesirable as it causes significant on-axis chromatic aberration between the c-line and the F-line due to the positive lens Gr.

[0068] Conditional expression (12) defines the relationship between the effective diameter of the lens closest to the object, the focal length of the entire system, and the F-number in order to ensure sufficient peripheral illumination. Generally, the F-number of an optical system L0 with a long focal length is determined by the effective diameter of the lens closest to the object, but in order to ensure sufficient peripheral illumination, it is better to increase the effective diameter of the lens closest to the object and ensure a large off-axis light beam.

[0069] If the effective diameter Φea increases beyond the upper limit of conditional expression (12), the diameter of the lens positioned closest to the object side also increases, making it difficult to reduce the weight.

[0070] If the effective diameter Φea falls below the lower limit of conditional expression (12) and becomes small, it is not possible to ensure a desired F-number.

[0071] Condition (13) defines the ratio between the F-number and the absolute value of the position sensitivity that is the highest among all the lens groups that are arranged in the intermediate group Bf and move during focusing.

[0072] Here, the position sensitivity refers to the amount of movement of the image plane when the lens group in question moves a unit amount in the optical axis direction, and is expressed by the following equation using the lateral magnification βf of the lens group in question and the combined lateral magnification βr of all lenses arranged on the image side of the lens group in question. B=(1-βf×βf)×βr×βr

[0073] If the upper limit of conditional expression (13) is exceeded, the absolute value of the position sensitivity increases, which is undesirable because it becomes difficult to appropriately control the focus position.

[0074] If the lower limit of conditional expression (13) is not reached, the absolute value of the position sensitivity will be small, so the amount of movement of the lens group that moves during focusing will be large, and the air gap required for movement in the optical axis direction will be large. As a result, the overall length of the lenses in optical system L0 will be long, and the weight of the mechanical components that support optical system L0 will be heavy, making it difficult to reduce the weight.

[0075] If the upper limit of conditional expression (14) is exceeded and the minimum Abbe number of the materials of all the negative lenses arranged in the first lens group B1 becomes large, it is not preferable because it causes significant on-axis chromatic aberration between the c-line and the f-line in the first lens group B1.

[0076] If the lower limit of conditional expression (14) is exceeded and the minimum Abbe number of the materials of all the negative lenses arranged in the first lens group B1 becomes small, the partial dispersion ratio between the g-line and the F-line becomes large, which is undesirable because it causes large on-axis chromatic aberration between the g-line and the f-line in the first lens group B1.

[0077] If the air gap D1max on the optical axis between the first subunit B1a and the second subunit B1b exceeds the upper limit of conditional expression (15) and becomes large, the total lens length of the optical system L0 becomes long, which is undesirable.

[0078] If the air gap D1max becomes small, falling below the lower limit of conditional expression (15), the diameter of the lenses arranged in the second subunit B1b becomes large, making it difficult to reduce the weight.

[0079] If the absolute value |f1b| of the focal length of the second sub-unit B1b becomes large, exceeding the upper limit of conditional expression (16), it becomes difficult to suppress spherical aberrations and the like that occur in the first sub-unit B1 or the subsequent lens unit Br. If the absolute value |f1b| of the focal length of the second sub-unit B1b becomes small, falling below the lower limit of conditional expression (16), coma aberrations and the like that occur in the second sub-unit B1b become too large, which is undesirable.

[0080] It is more preferable that conditional expressions (4) to (16) be set as follows: 0.668<θgf1p+0.00182×νd1p<0.690 (4a) 0.18 <f1p / f<1.00···(5a) 1.5 <BF / IH<3.0···(6a) 0.25 <f1 / f<1.50···(7a) 0.22 <f1a / f<1.50···(8a) 0.12 <D1a / TD1<0.50···(9a) 0.60 <OTD / f<1.20···(10a) 80.0<νdpmax<98.0 (11a) 1.00≦Φfea×Fno / f<1.30 (12a) 0.80 <Bab_max / Fno<1.80···(13a) 20.0<νdnmin<40.0 (14a) 0.30 <D1max / TD1<0.70···(15a) 0.60<|f1b| / f<3.20 (16a)

[0081] It is even more preferable that conditional expressions (4) to (16) be set as follows: 0.670<θgf1p+0.00182×νd1p<0.685 (4b) 0.20 <f1p / f<0.80···(5b) 2.0 <BF / IH<2.5···(6b) 0.30 <f1 / f<1.30···(7b) 0.23 <f1a / f<1.00···(8b) 0.13 <D1a / TD1<0.25···(9b) 0.70 <OTD / f<1.00···(10b) 90.0<νdpmax<96.0 (11b) 1.00≦Φfea×Fno / f<1.20 (12b) 0.90 <Bab_max / Fno<1.30···(13b) 22.0<νdnmin<35.0 (14b) 0.40 <D1max / TD1<0.60···(15b) 0.65<|f1b| / f<3.00 (16b)

[0082] Next, the configuration of the optical system L0 in each embodiment will be described in detail. From embodiment 2 onwards, differences from embodiment 1 will be mainly described.

[0083] [Example 1] The optical system L0 of Example 1 comprises, arranged in order from the object side to the image side, a first lens unit B1 having positive refractive power, an intermediate lens unit Bf consisting of one lens unit, and a subsequent lens unit Br, and the spacing between adjacent lens units changes during focusing. During focusing from infinity to a close distance, the lens unit Bf1 consisting of one negative lens located in the intermediate lens unit Bf moves toward the image side. This configuration makes it possible to easily suppress aberration fluctuations that occur during focusing while still being lightweight.

[0084] The first lens group B1 is composed of a first subgroup B1a and a second subgroup B1b arranged adjacent to the first subgroup B1a on the image side. Of the air gaps on the optical axis between adjacent lenses in the first lens group B1, the air gap on the optical axis between the first subgroup B1a and the second subgroup B1b is the largest, and the first subgroup B1a is composed of two positive lenses.

[0085] Constructing the first sub-group B1a with two positive lenses makes it easier to correct spherical aberration, etc. Furthermore, of the air gaps on the optical axis between adjacent lenses in the first lens group B1, the air gap on the optical axis between the first sub-group B1a and the second sub-group B1b is set to be the largest, thereby reducing the diameter of the lens arranged in the second sub-group B1b.

[0086] A positive lens Gp with a relatively high dispersion ratio is located closest to the object in the second sub-unit B1b, which makes it possible to suppress axial chromatic aberration for the g-line at a high position on the optical axis where marginal rays are at a high height.

[0087] Furthermore, when correcting image blur, the image stabilization group IS, which consists of one positive lens and two negative lenses, is moved so that it includes a component perpendicular to the optical axis, making it easier to suppress decentering aberrations that occur when image blur occurs.

[0088] The total number of lenses arranged in the first lens group B1 and the intermediate group Bf is eight. This reduces the total number of lenses arranged in the first lens group B1 and the intermediate group Bf, which tend to have large lens diameters, and makes it easier to reduce the weight.

[0089] [Example 2] In the optical system L0 of Example 2, a positive lens Gp is ​​disposed as the fourth lens element counting from the object side in the second sub-unit B1b. This specifies a larger value for conditional expression (3) than in Example 1. As a result, in addition to suppressing axial chromatic aberration for the g-line, correction of so-called first-order chromatic aberration between the c-line and F-line is also suppressed in a balanced manner.

[0090] [Example 3] In the optical system L0 of Example 3, the intermediate group Bf is made up of one lens group Bf1 with positive refractive power, and moves during focusing, which makes it possible to suppress coma even when focusing at close range.

[0091] [Example 4] In the optical system L0 of Example 4, the intermediate group Bf is made up of one lens group Bf1, which moves during focusing. The lens group Bf1 is made up of two negative lenses, which makes it possible to suppress spherical aberrations and the like when focusing at close distances.

[0092] [Example 5] The optical system L0 of Example 5 is an embodiment in which a variable magnification sub-group EXT is inserted into the subsequent group Br of the optical system of Example 4 to increase the focal length by approximately 1.4 times. The variable magnification sub-group EXT is removable and is inserted into the subsequent group Br of Example 4 between the lens closest to the image and the cemented lens that is second from the image side. By inserting the variable magnification sub-group EXT, a longer focal length can be obtained without changing the overall lens length.

[0093] [Variations] Unlike Example 1, the first sub-unit B1a may be configured with one positive lens. By configuring the first sub-unit B1a with one positive lens, the weight of the first sub-unit B1a can be easily reduced.

[0094] Furthermore, in Example 4, the two negative lenses disposed in the intermediate group Bf may be configured to move along different loci during focusing. By moving them along different loci, it becomes easier to suppress fluctuations in spherical aberration and the like that occur during focusing.

[0095] In the optical system L0 of each embodiment, it is preferable to deposit a fluorine coating on the object-side lens surface of the lens positioned closest to the object and the image-side lens surface of the lens positioned closest to the image. Because the object-side lens surface of the lens positioned closest to the object and the image-side lens surface of the lens positioned closest to the image are easily exposed to the outside world, depositing a fluorine coating on them can improve water and oil repellency, suppress flare, and achieve high optical performance. In particular, because the object-side lens surface of the lens positioned closest to the object has a large diameter, it is preferable to deposit a fluorine coating on them.

[0096] In the cemented lenses arranged in the optical system L0 of each embodiment, it is preferable that the positive lens and negative lens constituting at least one cemented lens are bonded with an adhesive having an axial thickness of 0.005 mm or more and 0.05 mm or less. If it is less than 0.005 mm, the adhesive is prone to peeling, and if it is more than 0.03 mm, the axial distance from the lens surface closest to the object to the lens surface closest to the image becomes long, resulting in a long overall lens length. It is more preferable that the adhesive thickness be 0.008 mm or more and 0.02 mm or less.

[0097] At least one lens in the optical system L0 in each embodiment is provided with an anti-reflection coating to prevent reflection, and the anti-reflection coating is composed of multiple films. Here, when the refractive index of the film closest to the air interface with respect to the d-line is Nd, the anti-reflection coating PC is preferably an Nd of 1.32 or less. By setting Nd to 1.32 or less, the difference in refractive index with air can be reduced, thereby further reducing light reflection and reducing ghosting.

[0098] Specific examples of the antireflection film PC include, but are not limited to, multilayer films formed using a wet method, as described in JP-A Nos. 2012-230211 and 2014-95877. More preferably, ghosts can be further reduced by setting Nd to 1.30 or less.

[0099] Here, it is preferable to apply an anti-reflection coating PC to the image-side lens surface of the negative lens arranged in the optical system L0, which has a concave surface facing the image side. Light reflected by a negative lens with a concave surface facing the image side is likely to be reflected at a large angle relative to the normal to the lens surface of the negative lens with a concave surface facing the image side, and therefore tends to have a high reflectance. Furthermore, light reflected by a negative lens with a concave surface facing the image side is likely to be focused on the image plane, making ghost images noticeable. Therefore, ghost images can be reduced by applying an anti-reflection coating PC to the image-side lens surface of a negative lens with a concave surface facing the image side.

[0100] Numerical Examples 1 to 5 corresponding to Examples 1 to 5, respectively, are shown below.

[0101] In the surface data of each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the axial distance (distance on the optical axis) between the mth surface and the (m+1)th surface, where m is the surface number counted from the light incident side.

[0102] Furthermore, nd is the refractive index of each optical element at the d-line, νd and θgf are the Abbe number of the optical element and the partial dispersion ratio of the g-line to the F-line, respectively. The Abbe number νd and the partial dispersion ratio θgf of a certain material at the g-line to the F-line are expressed as follows. That is, let us assume that the Fraunhofer line is the g-line (wavelength 435.8 nm). Furthermore, if the refractive indices at the d-line (wavelength 587.6 nm), F-line (wavelength 486.1 nm) and C-line (wavelength 656.3 nm) are Ng, Nd, NF and NC, respectively, then νd=(Nd-1) / (NF-NC) θgf=(Ng-NF) / (NF-NC) It is expressed as:

[0103] BF is the back focus. The back focus is the air-equivalent distance from the lens surface located closest to the object in optical system L0 to the image plane. The total lens length is the sum of the back focus and the distance on the optical axis from the lens surface located closest to the object in optical system L0 to the lens surface closest to the image.

[0104] 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.

[0105] The effective diameter is the diameter of a lens when a ray of light passing through each lens passes through the most peripheral portion and reaches the image plane.

[0106] [Numerical Example 1] Unit: mm Surface Data Surface number rd nd νd Clear aperture θgf 1 243.567 5.36 1.59349 67.0 100.32 0.536 2 1357.561 2.00 100.16 3 98.429 11.20 1.43387 95.1 97.30 0.537 4 345.553 64.00 96.49 5 92.960 4.44 1.79631 22.6 59.89 0.641 6 220.413 1.50 1.83400 37.2 58.99 0.578 7 46.205 0.15 54.01 8 46.460 8.67 1.43387 95.1 54.01 0.537 9 182.958 0.14 53.24 10 57.709 10.07 1.49700 81.5 51.39 0.537 11 -186.454 1.50 1.77047 29.7 49.94 0.595 12 773.797 (variable) 48.29 13 3689.640 1.00 1.64000 60.1 43.87 0.537 14 53.161 (variable) 41.43 15 (Aperture) ∞ 7.13 37.69 16 -452.500 1.00 1.84666 23.8 36.00 0.620 17 49.383 5.91 1.80610 33.3 35.54 0.589 18 -181.960 10.27 35.40 19 158.058 3.85 1.91650 31.6 31.67 0.591 20 -75.109 0.80 1.65412 39.7 31.31 0.574 21 48.197 4.60 29.52 22 -55.988 1.00 1.72916 54.7 29.46 0.544 23 -114.244 17.39 29.69 24 207.632 4.22 1.80610 33.3 38.16 0.589 25 -99.253 38.87 38.45 26* -500.000 2.50 1.58313 59.4 40.11 0.542 27 -2225.403 (variable) 40.25 Image plane ∞ Aspheric data Page 26 K = 0.00000e+00 A 4= 4.94767e-08 A 6= 1.01013e-10 A 8= 2.70572e-14 Various data Focal length 290.94 F-number 2.90 Half angle of view: 4.25 Image height 21.64 Lens length 274.02 BF 41.47 d12 5.78 d14 19.19 d27 41.47 Entrance pupil position 340.06 Exit pupil position -112.48 Front principal point position 81.19 Back principal point position -249.46 Lens group data Group starting plane Focal length Lens length Front principal point position Rear principal point position B1 1 130.28 109.04 40.53 -68.76 Bf 13 -84.29 1.00 0.62 0.01 Br 15 237.11 97.53 70.37 -12.41 Single lens data Lens starting surface focal length 1 1 499.23 2 3 312.93 3 5 198.81 4 6 -70.37 5 8 140.82 6 10 89.90 7 11 -194.88 8 13 -84.29 9 16 -52.54 10 17 48.74 11 19 55.99 12 20 -44.77 13 22 -151.68 14 24 83.82 15 26 -1106.52

[0107] [Numerical Example 2] Unit: mm Surface Data Surface number rd nd νd Clear aperture θgf 1 200.609 7.89 1.59349 67.0 106.52 0.536 2 6604.466 10.00 106.25 3 111.148 8.32 1.43387 95.1 96.50 0.537 4 288.663 55.55 95.71 5 78.590 7.57 1.49700 81.5 61.24 0.537 6 2474.870 1.50 1.65253 39.5 60.24 0.573 7 44.836 0.10 54.17 8 44.528 9.92 1.43387 95.1 54.16 0.537 9 326.456 4.67 53.32 10 125.436 4.98 1.79631 22.6 49.70 0.641 11 -332.659 4.66 1.85478 24.8 48.89 0.612 12 152.686 (variable) 45.35 13 1700.064 1.00 1.64000 60.1 43.84 0.537 14 66.654 (variable) 42.13 15 (Aperture) ∞ 24.75 37.14 16 377.309 1.00 1.84666 23.8 31.32 0.620 17 46.605 4.21 1.80610 33.3 30.78 0.589 18 -1239.772 1.00 30.56 19 75.750 3.80 1.91650 31.6 29.79 0.591 20 -112.259 0.80 1.65412 39.7 29.32 0.574 21 38.134 4.45 28.62 22 -77.142 1.00 1.72916 54.7 28.72 0.544 23 -611.018 5.12 29.46 24 138.273 3.30 1.80610 33.3 33.03 0.589 25 -146.374 39.13 33.29 26* -500.000 2.50 1.58313 59.4 39.74 0.542 27 -227.113 (variable) 39.97 Image plane ∞ Aspheric data Page 26 K = 0.00000e+00 A 4= 3.35881e-07 A 6= 2.57635e-10 A 8= 2.12541e-13 Various data Zoom ratio 1.00 Focal length 290.90 F-number 2.90 Half angle of view: 4.25 Image height 21.64 Lens length 274.04 BF 37.99 d12 3.86 d14 24.96 d27 37.99 Entrance pupil position 382.38 Exit pupil position -107.57 Front principal point position 91.92 Back principal point position -252.91 Zoom lens group data Group starting plane Focal length Lens length Front principal point position Rear principal point position B1 1 158.01 115.17 9.27 -86.24 Bf 13 -108.42 1.00 0.63 0.02 Br 15 217.62 91.07 58.47 -27.62 Single lens data Lens starting surface focal length 1 1 348.44 2 3 410.75 3 5 163.14 4 6 -70.00 5 8 117.59 6 10 114.94 7 11 -121.89 8 13 -108.42 9 16 -62.89 10 17 55.80 11 19 49.83 12 20 -43.43 13 22 -121.18 14 24 88.67 15 26 711.22

[0108] [Numerical Example 3] Unit: mm Surface Data Surface number rd nd νd Clear aperture θgf 1 240.659 6.84 1.48749 70.2 102.63 0.530 2 -14666.331 4.47 102.34 3 126.728 9.81 1.43387 95.1 97.13 0.537 4 756.766 57.28 96.48 5 59.687 8.49 1.75575 24.7 63.29 0.629 6 196.569 1.50 1.65253 39.5 61.79 0.573 7 37.143 0.17 53.14 8 36.703 15.04 1.43387 95.1 53.07 0.537 9 -449.144 0.07 50.97 10 -433.935 1.50 1.73037 32.2 50.91 0.590 11 54.689 (variable) 46.80 12 65.715 4.90 1.49700 81.5 41.32 0.537 13 -2220.667 (variable) 40.72 14 -2412.396 1.20 1.92286 18.9 38.86 0.650 15 79.993 5.24 37.77 16 (Aperture) ∞ 20.01 37.34 17 238.648 2.22 1.85478 24.8 34.36 0.612 18 -357.488 1.01 34.19 19 129.390 4.78 1.60342 38.0 33.30 0.584 20 -63.946 0.80 1.49700 81.5 32.80 0.537 21 56.144 3.12 30.83 22 -153.775 1.00 1.61340 44.3 30.78 0.563 23 87.792 6.11 30.46 24 129.740 3.17 1.90043 37.4 32.54 0.577 25 -171.817 49.99 32.77 26* -500.000 2.50 1.73037 32.2 40.01 0.590 27 -270.062 (variable) 40.24 Image plane ∞ Aspheric data Page 26 K = 0.00000e+00 A 4= 2.59994e-07 A 6= 1.31526e-10 A 8=-9.26275e-14 Various data Focal length 290.97 F-number 2.90 Half angle of view: 4.25 Image height 21.64 Lens length 274.01 BF 38.00 d11 21.83 d13 2.96 d27 38.00 Entrance pupil position 354.51 Exit pupil position -111.92 Front principal point position 80.75 Back principal point position -252.98 Lens group data Group starting plane Focal length Lens length Front principal point position Rear principal point position B1 1 351.53 105.16 -218.58 -183.08 Bf 12 128.51 4.90 0.09 -3.18 Br 14 -534.52 101.15 -170.45 -374.34 Single lens data Lens starting surface focal length 1 1 485.77 2 3 349.19 3 5 110.47 4 6 -70.45 5 8 78.94 6 10 -66.41 7 12 128.51 8 14 -83.88 9 17 167.71 10 19 71.59 11 20 -60.02 12 22 -90.97 13 24 82.51 14 26 800.37

[0109] [Numerical Example 4] Unit: mm Surface Data Surface number rd nd νd Clear aperture θgf 1 291.359 6.79 1.48749 70.2 103.30 0.530 2 2358.483 0.30 102.98 3 116.471 11.69 1.43387 95.1 101.24 0.537 4 436.756 61.81 100.07 5 127.447 7.80 1.43387 95.1 70.58 0.537 6 -3739.815 2.50 1.73037 32.2 69.27 0.590 7 60.012 1.31 64.41 8 60.199 12.51 1.62200 30.7 64.70 0.625 9 -953.808 0.20 63.80 10 73.319 6.57 1.43387 95.1 59.36 0.537 11 186.169 2.81 57.57 12 -1093.044 2.00 1.61340 44.3 57.40 0.563 13 45.993 10.22 1.49700 81.5 52.15 0.537 14 2488.766 4.41 51.16 15 (Aperture) ∞ (Variable) 48.30 16 -12214.540 1.70 1.59522 67.7 45.98 0.544 17 195.837 3.00 44.77 18 130.462 1.70 1.49700 81.5 42.99 0.537 19 56.489 (variable) 41.27 20 -128.822 1.50 1.98612 16.5 38.31 0.666 21 -410.742 3.05 1.73800 32.3 38.32 0.590 22 -95.103 1.02 38.31 23 -506.567 3.25 1.80000 29.8 37.46 0.602 24 -100.439 1.50 1.57144 71.6 37.19 0.543 25 112.466 1.49 36.14 26 3009.630 1.50 1.80400 46.5 36.13 0.558 27 138.649 8.30 35.88 28 -41.153 2.00 1.49700 81.5 35.98 0.537 29 -50.639 2.00 36.88 30 249.115 4.68 1.89190 37.1 37.66 0.578 31 -88.954 1.60 1.98612 16.5 37.64 0.666 32 -104.346 68.03 37.67 33 1618.856 2.00 1.72825 28.5 41.03 0.608 34 ∞ (variable) 41.09 Image plane ∞ Various data Focal length 300.61 F-number 2.91 Half angle of view: 4.12 Image height 21.64 Lens length 296.71 BF 38.43 d15 3.51 d19 15.52 d34 38.43 Entrance pupil position 220.77 Exit pupil position -150.14 Front principal point position 42.15 Back principal point position -262.18 Lens group data Group starting plane Focal length Lens length Front principal point position Rear principal point position B1 1 159.52 130.93 31.49 -86.57 Bf 16 -123.22 6.40 4.12 -1.04 Br20 330.15 101.92 79.72 0.56 Single lens data Lens starting surface focal length 1 1 681.18 2 3 362.07 3 5 284.24 4 6 -80.85 5 8 91.47 6 10 273.95 7 12 -71.90 8 13 94.15 9 16 -323.81 10 18 -202.00 11 20 -190.83 12 21 167.01 13 23 156.04 14 24 -92.61 15 26 -180.82 16 28 -475.29 17 30 73.98 18 31 -644.82 19 33 2222.94

[0110] [Numerical Example 5] Unit: mm Surface Data Surface number rd nd νd Clear aperture θgf 1 291.359 6.79 1.48749 70.2 103.30 0.530 2 2358.483 0.30 102.98 3 116.471 11.69 1.43387 95.1 101.24 0.537 4 436.756 61.81 100.07 5 127.447 7.80 1.43387 95.1 70.58 0.537 6 -3739.815 2.50 1.73037 32.2 69.27 0.590 7 60.012 1.31 64.41 8 60.199 12.51 1.62200 30.7 64.70 0.625 9 -953.808 0.20 63.80 10 73.319 6.57 1.43387 95.1 59.36 0.537 11 186.169 2.81 57.57 12 -1093.044 2.00 1.61340 44.3 57.40 0.563 13 45.993 10.22 1.49700 81.5 52.15 0.537 14 2488.766 4.41 51.16 15 (Aperture) ∞ (Variable) 48.30 16 -12214.540 1.70 1.59522 67.7 45.98 0.544 17 195.837 3.00 44.77 18 130.462 1.70 1.49700 81.5 42.99 0.537 19 56.489 (variable) 41.27 20 -128.822 1.50 1.98612 16.5 38.31 0.666 21 -410.742 3.05 1.73800 32.3 38.32 0.590 22 -95.103 1.02 38.31 23 -506.567 3.25 1.80000 29.8 37.46 0.602 24 -100.439 1.50 1.57144 71.6 37.19 0.543 25 112.466 1.49 36.14 26 3009.630 1.50 1.80400 46.5 36.13 0.558 27 138.649 8.30 35.88 28 -41.153 2.00 1.49700 81.5 35.98 0.537 29 -50.639 2.00 36.88 30 249.115 4.68 1.89190 37.1 37.66 0.578 31 -88.954 1.60 1.98612 16.5 37.64 0.666 32 -104.346 2.50 37.67 33 29.623 6.45 1.48749 70.2 33.00 0.530 34 122.942 0.17 31.45 35 50.485 3.33 1.58144 40.8 30.21 0.577 36 141.760 1.00 1.83481 42.7 28.88 0.564 37 32.946 28.91 26.78 38 -85.303 0.95 1.72916 54.7 23.63 0.544 39 35.677 9.65 1.59270 35.3 23.83 0.593 40 -19.747 0.95 1.81600 46.6 24.24 0.557 41 88.193 1.38 25.97 42 51.043 9.70 1.58144 40.8 27.96 0.577 43 -25.140 1.05 2.00100 29.1 28.79 0.600 44 -48.586 2.00 30.31 45 1618.856 2.00 1.72825 28.5 41.03 0.608 46 ∞ (variable) 41.09 Image plane ∞ Various data Focal length 407.40 F-number 4.12 Half angle of view 3.04 Image height 21.64 Lens length 296.72 BF 38.43 d15 3.51 d19 15.52 d46 38.43 Entrance pupil position 220.77 Exit pupil position -61.87 Front principal point position -1026.47 Back principal point position -368.96 Lens group data Group starting plane Focal length Lens length Front principal point position Rear principal point position B1 1 159.52 130.93 31.49 -86.57 Bf 16 -123.22 6.40 4.12 -1.04 Br 20 -159.70 101.93 95.91 6.53 Single lens data Lens starting surface focal length 1 1 681.18 2 3 362.07 3 5 284.24 4 6 -80.85 5 8 91.47 6 10 273.95 7 12 -71.90 8 13 94.15 9 16 -323.81 10 18 -202.00 11 20 -190.83 12 21 167.01 13 23 156.04 14 24 -92.61 15 26 -180.82 16 28 -475.29 17 30 73.98 18 31 -644.82 19 33 78.28 20 35 133.07 21 36 -51.63 22 38 -34.39 23 39 22.93 24 40 -19.69 25 42 30.39 26 43 -53.23 27 45 2222.94

[0111] The various values ​​in each numerical example are summarized in Table 1 below.

[0112] [Table 1]

[0113] [Imaging device] Next, an example of a digital still camera (imaging device) that uses an optical system according to an embodiment of the present invention as an imaging optical system will be described with reference to Fig. 11. In Fig. 11, 11 denotes an imaging optical system configured using any of the optical systems described in Examples 1 to 5. 12 denotes an imaging element (photoelectric conversion element) such as a CCD sensor or CMOS sensor that is built into a camera body 10 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 that has a quick-return mirror, or a so-called mirrorless camera that does not have a quick-return mirror.

[0114] In this way, by applying the optical system according to the embodiment of the present invention to an imaging device such as a digital still camera, it is possible to obtain images with a long focal length, a lightweight lens, and excellent correction of various aberrations.

[0115] The disclosure of each embodiment includes the following configuration.

[0116] (Configuration 1) An optical system comprising, arranged in order from the object side to the image side, a first lens group having positive refractive power, an intermediate group having one or more lens groups, and a subsequent lens group, in which the spacing between adjacent lens groups changes during focusing, During focusing, at least one lens group disposed in the intermediate group moves, the first lens group includes a first subgroup and a second subgroup arranged adjacent to the first subgroup on the image side, Among the air gaps on the optical axis between adjacent lenses in the first lens group, the air gap on the optical axis between the first subgroup and the second subgroup is the largest, the second sub-group includes a positive lens Gp, Let νd1p and nd1p be the Abbe number and the refractive index at the d-line of the material of the positive lens Gp, respectively; let Dp be the distance on the optical axis from the lens surface of the second sub-group closest to the object side to the lens surface of the positive lens Gp on the object side; and let D1b be the distance on the optical axis from the lens surface of the second sub-group closest to the object side to the lens surface of the second sub-group closest to the image side, 2.160 <nd1p+0.02174×νd1p<2.320 1.600 <nd1p<1.850 0.00≦Dp / D1b<0.72 An optical system characterized by satisfying the following conditional expression:

[0117] (Configuration 2) An optical system comprising, arranged in order from the object side to the image side, a first lens group having positive refractive power, an intermediate group having one or more lens groups, and a subsequent lens group, in which the spacing between adjacent lens groups changes during focusing, During focusing, at least one lens group disposed in the intermediate group moves, An optical system characterized in that the total number of lens elements arranged in the subsequent lens group is four or more.

[0118] (Configuration 3) the first lens group includes a first subgroup and a second subgroup arranged adjacent to the first subgroup on the image side, Among the air gaps on the optical axis between adjacent lenses in the first lens group, the air gap on the optical axis between the first subgroup and the second subgroup is the largest, the second sub-group includes a positive lens Gp, When the Abbe number and the refractive index for the d-line of the material of the positive lens Gp are νd1p and nd1p, respectively, 2.160 <nd1p+0.02174×νd1p<2.320 1.600 <nd1p<1.850 3. The optical system according to configuration 2, wherein the following condition is satisfied:

[0119] (Configuration 4) When the partial dispersion ratio of the material of the positive lens Gp for the g-line and the F-line is θgf1p, 0.666<θgf1p+0.00182×νd1p<0.697 4. The optical system according to any one of configurations 1 to 3, wherein the following condition is satisfied:

[0120] (Configuration 5) When the focal length of the positive lens Gp is ​​f1p and the focal length of the entire system is f, 0.15 <f1p / f<1.50 5. The optical system according to any one of configurations 1 to 4, wherein the following condition is satisfied:

[0121] (Configuration 6) When the back focus of the entire system is BF and the maximum image height is IH, 1.0 <BF / IH<3.5 6. The optical system according to any one of configurations 1 to 5, wherein the following condition is satisfied:

[0122] (Configuration 7) When the focal length of the first lens group is f1 and the focal length of the entire system is f, 0.20 <f1 / f<2.20 7. The optical system according to any one of configurations 1 to 6, wherein the following condition is satisfied:

[0123] (Configuration 8) When the focal length of the first subgroup is f1a and the focal length of the entire system is f, 0.10 <f1a / f<2.00 8. The optical system according to any one of configurations 1 to 7, wherein the following condition is satisfied:

[0124] (Configuration 9) Let D1a 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, and TD1 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, 0.10 <D1a / TD1<0.70 9. The optical system according to any one of configurations 1 to 8, wherein the following condition is satisfied:

[0125] (Configuration 10) When the distance on the optical axis from the lens surface closest to the object side of the optical system to the image plane is OTD and the focal length of the entire system is f, 0.50 <OTD / f<1.50 10. The optical system according to any one of configurations 1 to 9, wherein the following condition is satisfied:

[0126] (Configuration 11) When the Abbe number of the material of the positive lens Gr having the maximum Abbe number among the materials of all the positive lenses arranged in the first lens group is νdpmax, 70.0<νdpmax<100.0 11. The optical system according to any one of configurations 1 to 10, wherein the following condition is satisfied:

[0127] (Configuration 12) In the optical system, when the effective diameter of the lens arranged closest to the object is Φea, the F-number of the entire system is Fno, and the focal length of the entire system is f, 1.00≦Φfea×Fno / f<1.40 12. The optical system according to any one of configurations 1 to 11, wherein the following condition is satisfied:

[0128] (Configuration 13) Among all the lens groups disposed in the intermediate group that move during focusing, When the absolute value of the highest position sensitivity is Bab_max and the F-number of the entire system is Fno, 0.60 <Bab_max / Fno<2.00 13. The optical system according to any one of configurations 1 to 12, wherein the following condition is satisfied:

[0129] (Configuration 14) When the minimum Abbe number of the material of all the negative lenses arranged in the first lens group is νdnmin, 15.0<νdnmin<50.0 14. The optical system according to any one of configurations 1 to 13, wherein the following condition is satisfied:

[0130] (Configuration 15) 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 TD1, and the air gap on the optical axis between the first sub group and the second sub group is D1max, 0.20 <D1max / TD1<0.80 15. The optical system according to any one of configurations 1 to 14, wherein the following condition is satisfied:

[0131] (Configuration 16) When the focal length of the second subgroup is f1b and the focal length of the entire system is f, 0.50<|f1b| / f<3.50 16. The optical system according to any one of configurations 1 to 15, wherein the following condition is satisfied:

[0132] (Configuration 17) 17. The optical system according to any one of configurations 1 to 16, wherein the subsequent lens group has an image stabilization group that moves during image blur correction so as to include a component in a direction perpendicular to the optical axis.

[0133] (Configuration 18) 18. The optical system according to configuration 17, wherein the image stabilization group has one positive lens and two negative lenses.

[0134] (Configuration 19) 19. The optical system according to any one of configurations 1 to 18, wherein the positive lens Gp is ​​disposed closest to the object side in the second sub-group.

[0135] (Configuration 20) 20. The optical system according to any one of configurations 1 to 19, wherein the first subgroup is made up of two positive lenses.

[0136] (Configuration 21) 21. The optical system according to any one of configurations 1 to 20, wherein the second sub-group has three positive lenses and two negative lenses.

[0137] (Configuration 22) 22. The optical system according to any one of configurations 1 to 21, wherein the lens group disposed in the intermediate group and moving during focusing has negative refractive power.

[0138] (Configuration 23) 22. The optical system according to any one of configurations 1 to 21, wherein the lens group disposed in the intermediate group and moving during focusing has positive refractive power.

[0139] (Configuration 24) 24. The optical system according to any one of configurations 1 to 23, wherein the subsequent lens group includes an aspherical lens.

[0140] (Configuration 25) the subsequent lens group has a detachable magnification varying subgroup, 25. The optical system according to any one of configurations 1 to 24, wherein the focal length of the entire system changes when the magnification varying subgroup is inserted or removed.

[0141] (Configuration 26) 26. An imaging device comprising the optical system according to any one of configurations 1 to 25 and an imaging element that receives an image formed by the optical system.

[0142] 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]

[0143] L0 optical system B1 First lens group Bf intermediate group Br Subsequent lens group

Claims

1. An optical system comprising, arranged in order from the object side to the image side, a first lens group having positive refractive power, an intermediate group having one or more lens groups, and a subsequent lens group, in which the spacing between adjacent lens groups changes during focusing, During focusing, at least one lens group disposed in the intermediate group moves, the first lens group includes a first subgroup and a second subgroup arranged adjacent to the first subgroup on the image side, Among the air gaps on the optical axis between adjacent lenses in the first lens group, the air gap on the optical axis between the first subgroup and the second subgroup is the largest, the second sub-group has a positive lens Gp, Let vd1p and nd1p be the Abbe number and the refractive index at the d-line of the material of the positive lens Gp, respectively; let Dp be the distance on the optical axis from the lens surface of the second sub-group closest to the object side to the lens surface of the positive lens Gp on the object side; and let D1b be the distance on the optical axis from the lens surface of the second sub-group closest to the object side to the lens surface of the second sub-group closest to the image side, 2.160<nd1p+0.02174×νd1p<2.320 1.600<nd1p<1.850 0.00≦Dp / D1b<0.72 An optical system characterized by satisfying the following conditional expression:

2. When the partial dispersion ratio of the material of the positive lens Gp for the g-line and the F-line is θgf1p, 0.666<θgf1p+0.00182×νd1p<0.697 2. The optical system according to claim 1, wherein the following condition is satisfied:

3. When the focal length of the positive lens Gp is ​​f1p and the focal length of the entire system is f, 0.15<f1p / f<1.50 2. The optical system according to claim 1, wherein the following condition is satisfied:

4. When the back focus of the entire system is BF and the maximum image height is IH, 1.0<BF / IH<3.5 2. The optical system according to claim 1, wherein the following condition is satisfied:

5. When the focal length of the first lens group is f1 and the focal length of the entire system is f, 0.20<f1 / f<2.20 2. The optical system according to claim 1, wherein the following condition is satisfied:

6. When the focal length of the first subgroup is f1a and the focal length of the entire system is f, 0.10<f1a / f<2.00 2. The optical system according to claim 1, wherein the following condition is satisfied:

7. 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 defined as D1a, and 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 defined as TD1, 0.10<D1a / TD1<0.70 2. The optical system according to claim 1, wherein the following condition is satisfied:

8. When the distance on the optical axis from the lens surface closest to the object side of the optical system to the image plane is OTD and the focal length of the entire system is f, 0.50<OTD / f<1.50 2. The optical system according to claim 1, wherein the following condition is satisfied:

9. When the Abbe number of the material of the positive lens Gr having the largest Abbe number among the materials of all the positive lenses arranged in the first lens group is denoted by νdpmax, 70.0<νdpmax<100.0 2. The optical system according to claim 1, wherein the following condition is satisfied:

10. In the optical system, when the effective diameter of the lens arranged closest to the object side is Φea, the F-number of the entire system is Fno, and the focal length of the entire system is f, 1.00≦Φfea×Fno / f<1.40 2. The optical system according to claim 1, wherein the following condition is satisfied:

11. Among all the lens groups disposed in the intermediate group that move during focusing, When the absolute value of the position sensitivity having the highest value is Bab_max and the F-number of the entire system is Fno, 0.60<Bab_max / Fno<2.00 2. The optical system according to claim 1, wherein the following condition is satisfied:

12. When the smallest Abbe number of the materials of all the negative lenses arranged in the first lens group is νdnmin, 15.0<νdnmin<50.0 2. The optical system according to claim 1, wherein the following condition is satisfied:

13. 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 TD1, and the air gap on the optical axis between the first sub-group and the second sub-group is D1max, 0.20<D1max / TD1<0.80 2. The optical system according to claim 1, wherein the following condition is satisfied:

14. When the focal length of the second subgroup is f1b and the focal length of the entire system is f, 0.50<|f1b| / f<3.50 2. The optical system according to claim 1, wherein the following condition is satisfied:

15. 2. The optical system according to claim 1, wherein the subsequent lens group includes an image stabilization group that moves during image blur correction so as to include a component in a direction perpendicular to the optical axis.

16. 16. The optical system according to claim 15, wherein the vibration reduction group has one positive lens and two negative lenses.

17. 2. The optical system according to claim 1, wherein the positive lens Gp is ​​disposed closest to the object side in the second sub-group.

18. 2. The optical system according to claim 1, wherein the first sub-group is made up of two positive lenses.

19. 2. The optical system according to claim 1, wherein the second sub-group includes three positive lenses and two negative lenses.

20. 2. The optical system according to claim 1, wherein the lens group disposed in the intermediate group and moving during focusing has negative refractive power.

21. 2. The optical system according to claim 1, wherein the lens group disposed in the intermediate group and moving during focusing has positive refractive power.

22. 2. The optical system of claim 1, wherein the subsequent lens group comprises an aspheric lens.

23. the subsequent lens group has a detachable magnification varying subgroup, 2. The optical system according to claim 1, wherein the focal length of the entire system is changed by inserting or removing the variable magnification subgroup.

24. An optical system comprising, arranged in order from the object side to the image side, a first lens group having positive refractive power, an intermediate group having one or more lens groups, and a subsequent lens group, in which the spacing between adjacent lens groups changes during focusing, During focusing, at least one lens group disposed in the intermediate group moves, An optical system characterized in that the total number of lens elements arranged in the subsequent lens group is four or more.

25. 25. 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