Optical system and imaging apparatus having same

Abstract

Provided is an optical system comprising, in order from an object side to an image side, a first lens group having positive refractive power, an intermediate group having one or more lens groups, and a subsequent lens group, the interval between adjacent lens groups changing during focusing, wherein, during focusing, at least one lens group arranged in the intermediate group moves, and the optical system satisfies a predetermined condition.

Description

Optical system and imaging device having the same

[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.

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

[0003] Generally, the longer the focal length of an optical system, the larger and heavier it tends to be. Therefore, there is a demand for optical systems that are lightweight and have excellent correction for various aberrations.

[0004] There is a demand for an optical system that has a long focal length, is lightweight, and has excellent correction of various aberrations.

[0005] An optical system according to one aspect of the present invention 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, wherein the distance between adjacent lens groups changes during focusing, and 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 of the air spaces on the optical axis between adjacent lenses in the first lens group, the air space on the optical axis between the first subgroup and the second subgroup is the largest, and the first subgroup has a positive lens Gp, and when the Abbe number and the refractive index at the d-line of the material of the positive lens Gp are respectively vd1p and nd1p, the distance on the optical axis from the lens surface of the first lens group closest to the object to the lens surface of the first lens group closest to the image is TD1, and the air space on the optical axis between the first subgroup and the second subgroup is D1max, The present invention is characterized in that the following conditional expressions are satisfied: 2.160<nd1p+0.02174×νd1p<2.320, 1.600<nd1p<1.850, and 0.10<D1max / TD1<0.50.

[0006] 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 at least one lens group arranged in the intermediate group moves during focusing, and the total number of lenses arranged in the first lens group and the intermediate group is 16 or less.

[0007] Aberration diagram of the optical system of Example 1 when focused at infinity. Aberration diagram of the optical system of Example 1 when focused at infinity. Aberration diagram of the optical system of Example 1 when focused at a close distance. Aberration diagram of the optical system of Example 2 when focused at infinity. Aberration diagram of the optical system of Example 2 when focused at infinity. Aberration diagram of the optical system of Example 2 when focused at a close distance. Aberration diagram of the optical system of Example 2 when focused at infinity. Aberration diagram of the optical system of Example 3 when focused at infinity. Aberration diagram when focusing at close range in the optical system of Example 3. Aberration diagram when focusing at infinity in the optical system of Example 4. Lens cross-sectional view of the optical system of Example 4 when focusing at infinity. Aberration diagram when focusing at close range in the optical system of Example 4. Lens cross-sectional view of the optical system of Example 5 when focusing at infinity. Aberration diagram when focusing at infinity in the optical system of Example 5. Aberration diagram when focusing at close range in the optical system of Example 5. Schematic diagram showing an imaging device.

[0008] 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.

[0009] 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.

[0010] In each lens cross-sectional view, the left side is the object side and the right side is the image side.

[0011] In each lens cross-sectional view, SP denotes an aperture stop. IP 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 L0 of each embodiment is used in a digital still camera or digital video camera. When the optical system L0 of each embodiment is used as the photographic optical system of a silver halide film camera, a photosensitive surface corresponding to the film surface is placed on the image plane IP.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 2A, 4A, 6A, 8A, and 10A are aberration diagrams when focusing at infinity in the optical systems L0 of Examples 1 to 5, respectively.

[0016] 2B, 4B, 6B, 8B, and 10B are aberration diagrams when focusing at close range in the optical systems L0 of Examples 1 to 5, respectively.

[0017] In the spherical aberration diagram, Fno is the F-number, the solid line indicates the amount of spherical aberration for the d-line (wavelength 587.6 nm), and the dashed line indicates the amount of spherical aberration for the g-line (wavelength 435.8 nm). In the astigmatism diagram, the solid line indicates the amount of aberration ΔS on the sagittal image plane, and the dashed line indicates the amount of aberration ΔM 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 of magnification for the g-line is shown. ω is the half angle of view (°).

[0018] 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 expressed by the following equations: vd=(Nd-1) / (NF-NC) θgf=(Ng-NF) / (NF-NC)

[0019] Next, the optical system L0 according to the first embodiment will be described.

[0020] The optical system L0 according to the first embodiment 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 having one or more lens units, and a subsequent lens unit Br, and the spacing between adjacent lens units changes during focusing. Because the first lens unit B1 has positive refractive power, the first lens unit B1 converges an axial light beam, making it easy to reduce the diameter of the lenses arranged in the intermediate lens unit Bf. As a result, it is easy to reduce the weight of the lenses arranged in the intermediate lens unit Bf despite the long focal length.

[0021] 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 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.

[0022] 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 first subgroup B1a also includes a positive lens Gp.

[0023] Since the first sub-unit B1a includes the positive lens Gp, the axial light beam is converged by the first sub-unit B1a, and the air gap on the optical axis between the first sub-unit B1a and the second sub-unit B1b is widened, which makes it easy to lower the height of the axial marginal ray incident on the second sub-unit B1b. As a result, it becomes easy to reduce the diameter of the lenses arranged in the second sub-unit B1b and reduce its weight.

[0024] 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) 0.10<D1max / TD1<0.50 (3)

[0025] where vd1p and nd1p are the Abbe number and the refractive index at the d-line of the material of the positive lens Gp, respectively. TD1 is the distance on the optical axis from the lens surface of the first lens unit B1 closest to the object to the lens surface of the first lens unit B1 closest to the image. D1max is the air gap on the optical axis between the first sub-unit B1a and the second sub-unit B1b.

[0026] If the Abbe number of the material of the positive lens Gp becomes large, exceeding the upper limit of conditional expression (1), low-dispersion glass will be selected as the material of the positive lens Gp. This will reduce the partial dispersion ratio between the g-line and the F-line, and the refractive index for the g-line will become too small. As a result, axial chromatic aberration between the g-line and the F-line will become too large, which is undesirable.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] If D1max becomes large, exceeding the upper limit of conditional expression (3), the height from the optical axis of the on-axis marginal ray incident on the second sub-unit B1b becomes too small, which is undesirable because it becomes difficult for the second sub-unit B1b to suppress spherical aberrations and the like generated in the first sub-unit B1a.

[0031] If D1max becomes small, falling below the lower limit of conditional expression (3), the height from the optical axis of the on-axis marginal ray incident on the second sub-unit B1b becomes too large, and as a result, the diameter of the lenses arranged in the second sub-unit B1b becomes too large, making it difficult to reduce the weight.

[0032] 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.

[0033] Here, the long focal length refers to a focal length of the optical system L0 where the maximum value of the imaging half angle of view is 16.0 degrees or less.

[0034] It is more preferable that the lower limit of conditional expression (1) be set to 2.180, 2.200, 2.220, 2.240, or 2.260.

[0035] It is more preferable that the upper limit of conditional expression (1) be set to 2.315, 2.310, or 2.305.

[0036] It is more preferable that the lower limit of conditional expression (2) be set to 1.605, 1.610, 1.615, or 1.620.

[0037] It is more preferable that the upper limit of conditional expression (2) be set to 1.840, 1.830, 1.820, or 1.810.

[0038] It is more preferable that the lower limit of conditional expression (3) be set to 0.102, 0.104, 0.106, 0.108, or 0.110.

[0039] It is more preferable that the upper limit of conditional expression (3) be set to 0.49, 0.48, 0.47, or 0.46.

[0040] Next, the optical system L0 according to the second embodiment will be described.

[0041] The optical system L0 according to the second embodiment 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 having one or more lens units, and a subsequent lens unit Br, and the spacing between adjacent lens units changes during focusing. Because the first lens unit B1 has positive refractive power, the first lens unit B1 converges an axial light beam, making it easy to reduce the diameter of the lenses arranged in the intermediate lens unit Bf. As a result, it is easy to reduce the weight of the lenses arranged in the intermediate lens unit Bf.

[0042] 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 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.

[0043] The total number of lenses arranged in the first lens group B1 and the intermediate group Bf is 16 or less. Because the first lens group B1 has positive refractive power and is a telephoto type with its principal point located on the object side, the diameter of the lens located on the object side is relatively large. Therefore, by limiting the total number of lenses arranged in the first lens group B1 and the intermediate group Bf to 16 or less, it becomes easy to reduce the weight of the optical system L0.

[0044] Next, a preferred configuration of the optical system L0 according to each embodiment will be described.

[0045] It is preferable that the subsequent lens group Br has an image stabilization group IS that moves during image blur correction so as to include a component perpendicular to the optical axis. By disposing 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, it is possible to reduce the diameter of the lenses disposed in the image stabilization group IS, facilitating weight reduction while effectively correcting image blur. Here, the image stabilization group IS includes one positive lens and two negative lenses, which makes it easy to correct decentering aberrations that occur during image blur.

[0046] At least one lens group that moves during focusing and is disposed in the intermediate group Bf is preferably located behind the aperture stop, which makes it easier to reduce the diameter of the lenses disposed in the lens group that moves during focusing, thereby enabling weight reduction.

[0047] It is preferable that all of the lens groups in the intermediate group Bf that move during focusing have negative refractive power and move toward the image side during focusing from infinity to close distances, which makes it easier to suppress fluctuations in spherical aberration and the like that occur during focusing.

[0048] It is preferable that the intermediate group Bf has two lens groups that move during focusing, which weakens the refractive power of each lens group that moves during focusing and makes it easier to suppress fluctuations in aberrations that occur during focusing.

[0049] The first sub-unit B1a preferably comprises two positive lenses, which makes it easy to correct spherical aberration and the like and to reduce weight. The second sub-unit B1b preferably comprises two or more negative lenses, which makes it easy to correct axial chromatic aberration and the like that occurs in the first sub-unit B1a. The second sub-unit B1b preferably comprises three positive lenses, which makes it easy to correct spherical aberration and the like.

[0050] The positive lens Gp is ​​preferably disposed closest to the object in the optical system L0. Because the positive lens Gp has a relatively high dispersion, the lens material has high hardness and environmental resistance, and by disposing the positive lens Gp closest to the object in the optical system L0, it becomes easy to prevent deterioration of the optical performance due to the environment when the optical system L0 is used.

[0051] The subsequent lens group Br preferably has an aspherical lens, which makes it easier to correct curvature of field and the like.

[0052] 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) 0.60<f1p / f<4.00...(5) 0.40<BF / IH<3.50...(6) 0.30<f1 / f<0.90...(7) 0.40<f1a / f<3.00...(8) 0.02<D1a / TD1<0.70...(9) 0.45<OTD / f<1.60...(10) 70.0<νdpmax<100.0...(11) 1.00≦Φfea×Fno / f<1.40...(12) 0.40<Bab_max / Fno<2.00...(13) 15.0<νdnmin<50.0 (14)

[0053] 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.

[0054] where f1a is the focal length of the first sub-group B1a. D1a is the distance on the optical axis 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. OTD is the distance on the optical axis from the lens surface of the optical system L0 closest to the object to the image plane. 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] Φea is the effective diameter of the lens located closest to the object in the optical system L0, 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, and νdmin is the smallest Abbe number among all the materials of the negative lenses located in the first lens group B1.

[0056] Next, the technical meaning of the above-mentioned conditional expressions (4) to (14) 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 becomes overcorrected, which is undesirable.

[0058] If the lower limit of conditional expression (4) is exceeded and the partial dispersion ratio of the material of the positive lens becomes small, the axial chromatic aberration and lateral chromatic aberration for the g-line relative to the F-line will be undercorrected, which is undesirable.

[0059] 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.

[0060] If the refractive power of the positive lens Gp becomes too strong, falling below the lower limit of conditional expression (5), the positive lens Gp will produce large spherical aberrations and the like, which is not preferable.

[0061] If the upper limit of conditional expression (6) is exceeded, the back focus becomes too long, and the weight of the mechanical components that hold the optical system L0 increases, making it difficult to reduce the weight.

[0062] If the lower limit of conditional expression (6) is not reached, the back focus becomes too short, which is undesirable because it increases 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.

[0063] 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.

[0064] Here, the total lens length is the sum of the distance on the optical axis from the surface of the optical system L0 closest to the object to the surface of the optical system L0 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 the optical system L0 closest to the image and the image plane.

[0065] 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 generates large spherical aberrations and the like, which is not preferable.

[0066] If the upper limit of conditional expression (8) is exceeded and the refractive power of the first subunit B1a becomes weak, the diameter of each lens arranged on the image side of the first subunit B1a becomes large, making it difficult to reduce the weight.

[0067] If the refractive power of the first subunit B1a becomes too strong by going below the lower limit of conditional expression (8), the first subunit B1a will produce large spherical aberrations and the like, which is not preferable.

[0068] If the upper limit of conditional expression (9) is exceeded and the distance on the optical axis from the lens surface of the first sub-unit B1a closest to the object to the lens surface closest to the image becomes large, the volume of the first sub-unit B1a, which tends to have a large lens diameter, becomes large in the first lens unit B1, making it difficult to reduce the weight.

[0069] If the lower limit of conditional expression (9) is exceeded and the axial distance 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, which makes it difficult to correct spherical aberrations and the like that occur in the second sub-unit B1b and the like.

[0070] If the upper limit of conditional expression (10) is exceeded and the distance on the optical axis 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 hold optical system L0 becomes large, making it difficult to reduce the weight.

[0071] If the lower limit of conditional expression (10) is exceeded and the distance on the optical axis from the lens surface closest to the object side of the optical system L0 to the image plane becomes short, the refractive power of each lens becomes strong, making it difficult to correct various aberrations.

[0072] If the Abbe number of the material of the positive lens Gr becomes large beyond the upper limit of conditional expression (11), the refractive index of the glass material of the positive lens Gr becomes low, which is undesirable as it causes large spherical aberrations and curvature of field.

[0073] If the Abbe number of the material of the positive lens element Gr becomes small below the lower limit of conditional expression (11), it is not preferable because the positive lens element Gr generates large axial chromatic aberration between the c-line and the F-line.

[0074] Conditional expression (12) defines the relationship between the effective diameter of the lens located 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 located closest to the object, but in order to ensure sufficient peripheral illumination, it is better to increase the effective diameter of the lens located closest to the object and ensure a large off-axis light flux.

[0075] If the effective diameter Φea becomes large beyond the upper limit of conditional expression (12), the diameter of the lens positioned closest to the object side becomes large, making it difficult to reduce the weight.

[0076] 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.

[0077] 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.

[0078] Here, the position sensitivity is the amount of movement of the image plane when the lens group moves a unit amount in the optical axis direction, and is expressed by the following formula using the lateral magnification βf of the lens group and the combined lateral magnification βr of all lenses arranged on the image side of the lens group: B=(1-βf×βf)×βr×βr

[0079] If the upper limit of conditional expression (13) is exceeded, the position sensitivity increases, which is undesirable because it becomes difficult to appropriately control the focus position.

[0080] If the lower limit of conditional expression (13) is not reached, the position sensitivity decreases, the amount of movement of the lens group that moves during focusing increases, and the air gap required for movement along the optical axis increases, which results in an increase in the overall length of the lenses in optical system L0 and an increase in the weight of the mechanical components that support optical system L0, making it difficult to reduce the weight.

[0081] 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 large on-axis chromatic aberration between the c-line and the f-line occurs in the first lens group B1.

[0082] 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 unit B1 becomes small, the partial dispersion ratio between the g-line and the F-line becomes large, which is undesirable because it results in significant on-axis chromatic aberration between the g-line and the f-line occurring in the first lens unit B1.

[0083] It is more preferable to set it as follows:

[0084] It is more preferable that the lower limit of conditional expression (4) be set to 0.668, 0.670, or 0.671.

[0085] It is more preferable that the upper limit of conditional expression (4) be set to 0.694, 0.691, 0.688, or 0.685.

[0086] It is more preferable that the lower limit of conditional expression (5) be set to 0.70, 0.80, 0.90, 1.00, or 1.10.

[0087] It is more preferable that the upper limit of conditional expression (5) be set to 3.80, 3.60, 3.40, 3.20, 3.00, or 2.80.

[0088] It is more preferable that the lower limit of conditional expression (6) be set to 0.43, 0.47, 0.50, 0.53, or 0.56.

[0089] It is more preferable that the upper limit of conditional expression (6) be set to 3.30, 3.10, 2.90, 2.70, 2.50, or 2.30.

[0090] It is more preferable that the lower limit of conditional expression (7) be set to 0.35, 0.40, 0.45, or 0.50.

[0091] It is more preferable that the upper limit of conditional expression (7) be set to 0.85, 0.80, or 0.75.

[0092] It is more preferable that the lower limit of conditional expression (8) be set to 0.45, 0.50, 0.55, or 0.60.

[0093] It is more preferable that the upper limit of conditional expression (8) be set to 2.80, 2.60, 2.40, 2.20, or 2.00.

[0094] It is more preferable that the lower limit of conditional expression (9) be set to 0.025, 0.030, 0.035, 0.040, or 0.045.

[0095] It is more preferable that the upper limit of conditional expression (9) be set to 0.65, 0.60, 0.55, 0.50, 0.45, or 0.40.

[0096] It is more preferable that the lower limit of conditional expression (10) be set to 0.55, 0.65, 0.75, 0.85, 0.95, or 1.05.

[0097] It is more preferable that the upper limit of conditional expression (10) be set to 1.57, 1.54, 1.51, 1.48, 1.45, or 1.42.

[0098] It is more preferable that the lower limit of conditional expression (11) be set to 72.0, 74.0, 76.0, 78.0, or 80.0.

[0099] It is more preferable that the upper limit of conditional expression (11) be set to 99.0, 98.0, 97.0, or 96.0.

[0100] It is more preferable that the upper limit of conditional expression (12) be set to 1.35, 1.30, 1.25, 1.20, 1.15, or 1.10.

[0101] It is more preferable that the lower limit of conditional expression (13) be set to 0.42, 0.44, 0.46, 0.48, or 0.50.

[0102] It is more preferable that the upper limit of conditional expression (13) be set to 1.35, 1.30, 1.25, or 1.20.

[0103] It is more preferable that the lower limit of conditional expression (14) be set to 17.0, 19.0, 21.0, or 23.0.

[0104] It is more preferable that the upper limit of conditional expression (14) be set to 48.0, 46.0, 44.0, 42.0, or 40.0.

[0105] Next, the configuration of the optical system L0 in each example will be described in detail. From Example 2 onwards, differences from Example 1 will be mainly described.

[0106] [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 two lens units, and a subsequent lens unit Br, and the spacing between adjacent lens units changes during focusing. During focusing, the lens units Bf1 and Bf2 arranged in the intermediate lens unit Bf move along different trajectories, while the first lens unit B1 and the subsequent lens unit Br remain stationary. This results in a lightweight configuration that makes it easy to suppress aberration fluctuations that occur during focusing.

[0107] 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.

[0108] By configuring the first sub-unit B1a with two positive lenses, it becomes easier to correct spherical aberration, etc. Furthermore, among the air gaps on the optical axis between adjacent lenses in the first lens unit B1, the air gap on the optical axis between the first sub-unit B1a and the second sub-unit B1b is maximized, thereby reducing the diameter of the lens arranged in the second sub-unit B1b.

[0109] Furthermore, during image blur correction, the image stabilization group IS, which is made up of one positive lens and two negative lenses, is moved so as to include a component perpendicular to the optical axis, thereby making it easier to suppress decentering aberrations that occur during image blur.

[0110] The total number of lenses arranged in the first lens group B1 and the intermediate group Bf is nine. 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.

[0111] Second Embodiment In the optical system L0 of the second embodiment, the intermediate group Bf is made up of one lens group Bf1, which moves during focusing, which makes it easy to reduce the weight of the lens group that moves during focusing.

[0112] 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.

[0113] Example 3 In the optical system L0 of Example 3, a larger value is specified for conditional expression (1) than in Example 1. This increases the air gap on the optical axis between the first sub-unit B1a and the second sub-unit B1b, making it easier to reduce the diameter of the lens disposed closer to the image side than the first sub-unit B1a.

[0114] Fourth Embodiment In the optical system L0 of the fourth embodiment, the intermediate group Bf is made up of one lens group Bf1, which moves during focusing, thereby making it possible to reduce the weight of the lens group that moves during focusing.

[0115] The first sub-unit B1a is configured to be composed of one positive lens, which allows for only one lens to be placed in a position where the lens diameter is likely to be large, making it possible to achieve a lightweight configuration.

[0116] In the optical system L0 of Example 5, the intermediate group Bf is composed of three lens groups, and during focusing, the lens group Bf1 located closest to the object and the lens group Bf2 located closest to the image in the intermediate group Bf move, thereby reducing the weight of the lens groups that move during focusing and making it easy to suppress fluctuations in various aberrations that occur during focusing.

[0117] The total number of lenses arranged in the first lens group B1 and the intermediate group Bf is set to 14. This makes it possible to reduce 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 thus makes it easier to reduce the weight.

[0118] [Modification] Two more lenses may be added to the first lens unit B1 and the intermediate lens unit Bf in Example 5. This makes it easier to correct various aberrations.

[0119] In the optical system L0 of each embodiment, it is preferable to vapor-deposit a fluorine coating on the object-side lens surface of the lens located closest to the object and the image-side lens surface of the lens located closest to the image. Because the object-side lens surface of the lens located closest to the object and the image-side lens surface of the lens located closest to the image are easily exposed to the outside world, vapor-depositing a fluorine coating can improve water and oil repellency, suppress flare, and achieve high optical performance. In particular, because the object-side lens surface of the lens located closest to the object has a large diameter, it is preferable to vapor-deposit a fluorine coating.

[0120] In the cemented lenses arranged in the optical system L0 of each example, 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 cemented lens 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 it satisfies the requirement of 0.008 mm or more and 0.02 mm or less.

[0121] At least one lens arranged in the optical system L0 in each example is provided with an anti-reflection coating for preventing 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, it is preferable that the anti-reflection coating PC has Nd of 1.32 or less. By making Nd 1.32 or less, the difference in refractive index with air can be reduced, making it possible to further reduce light reflection and reduce ghosting.

[0122] Specific examples of the configuration of the antireflection film PC include, but are not limited to, multilayer films formed using a wet method, as described in JP-A-2012-230211, JP-A-2014-95877, etc. More preferably, by setting Nd to 1.30 or less, ghosts can be further reduced.

[0123] Here, it is preferable to provide an anti-reflection film PC on the image-side lens surface of the negative lens arranged in the optical system L0 that 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 direction of the lens surface of the negative lens with a concave surface facing the image side, and therefore the reflectance is likely to be high. 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, by providing an anti-reflection film PC on the image-side lens surface of a negative lens with a concave surface facing the image side, ghost images can be reduced.

[0124] Numerical examples 1 to 5 corresponding to the first to fifth embodiments, respectively, are shown below.

[0125] 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 νd and θgf represent the Abbe number and partial dispersion ratio of the optical element with respect to the g-line and F-line, respectively. The Abbe number νd and the partial dispersion ratio θgf of a certain material with respect to the g-line and F-line can be expressed as follows, where Ng, Nd, NF, and NC are the refractive indices of the Fraunhofer lines at the g-line (wavelength 435.8 nm), d-line (wavelength 587.6 nm), F-line (wavelength 486.1 nm), and C-line (wavelength 656.3 nm).

[0126] BF is the back focus, which is the air-equivalent distance from the lens surface located closest to the object in the optical system L0 to the image plane.

[0127] If the optical surface is aspherical, a * symbol is added to the right of the surface number. The aspherical shape is expressed as follows: x = (h ２ / R) / [1+{1-(1+k)(h / R) ２} １／２ ]+A4×h ４ + A6 x h ６ +A8 x h ８ + A10 x h １０ + A12 x h １２ In addition, "e±XX" in each aspherical coefficient is "×10± ＸＸ " means.

[0128] [Numerical Example 1] Unit: mm Surface data Surface number rd nd νd Pitch diameter θgf 1 176.949 5.77 1.79631 22.6 97.48 0.641 2 396.030 0.30 96.78 3 92.506 11.30 1.49700 81.7 92.18 0.538 4 304.387 28.08 90.89 5 81.268 6.51 1.49700 81.7 69.71 0.538 6 167.120 2.50 1.77047 29.7 68.10 0.595 7 55.637 1.90 62.20 8 65.939 8.59 1.49700 81.5 62.16 0.537 9 369.453 0.20 61.11 10 67.307 11.10 1.49700 81.5 57.42 0.537 11 -239.951 2.00 1.65253 39.5 55.04 0.573 12 267.958 (Variable) 51.85 13 435.685 1.70 1.64000 60.1 49.37 0.537 14 83.583 (Variable) 46.66 15 274.430 1.70 1.64000 60.1 44.36 0.537 16 49.181 (Variable) 41.87 17 (Aperture) ∞ 6.06 40.36 18 103.588 1.50 1.84666 23.8 39.07 0.620 19 35.481 7.73 1.75500 52.3 37.74 0.547 20 -11651.540 1.30 37.25 21 188.009 5.23 1.91650 31.6 36.40 0.591 22 -75.305 1.30 1.67300 38.1 35.76 0.575 23 48.843 5.51 33.12 24 -61.027 1.50 1.64000 60.1 33.05 0.537 25 -140.496 5.91 33.30 26 161.373 3.59 1.79952 42.2 35.28 0.568 27 -130.899 20.24 35.63 28 -773.443 5.62 1.77830 23.9 40.52 0.625 29 -56.087 1.60 1.88300 40.8 40.84 0.566 30 -62.167 4.94 41.20 31* -58.176 2.30 1.58313 59.4 39.83 0.542 32 -367.653 BF 40.29 Image plane ∞ Aspheric data Surface 31 K = 0.00000e+00 A4= 2.89137e-07 A6= 4.32596e-10 A8=-2.16232e-13 Other data Focal length 195.94 F-number 2.06 Half angle of view 6.30 Image height 21.64 Total lens length 217.02 BF 38.12 (Object distance at infinity) d12 3.01 d14 5.92 d16 13.97 d32 38.12 (Object distance at -2.0m) d12 9.37 d14 5.91 d16 7.62 d32 38.12 Entrance pupil position 228.22 Exit pupil position -78.25 Front principal point position 94.25 Rear principal point position -157.82 Lens group data Group Initial surface Focal length Lens length Front principal point position Rear principal point position B1 1 101.65 78.26 18.72 -47.19 Bf1 13 -161.91 1.70 1.29 0.25 Bf2 15 -93.90 1.70 1.27 0.23 Br 17 114.01 74.34 33.71 -30.39 Single lens data Lens Initial surface Focal length 1 1 397.05 2 3 262.74 3 5 310.49 4 6 -109.32 5 8 160.00 6 10 107.05 7 11 -193.70 8 13 -161.91 9 15 -93.90 10 18 -64.39 11 19 46.87 12 21 59.23 13 22 -43.84 14 24 -169.83 15 26 90.89 16 28 77.43 17 29 -740.99 18 31 -118.85 .

[0129] [Numerical Example 2] Unit: mm Surface data Surface number rd nd νd Pitch diameter θgf 1 155.102 10.76 1.49700 81.5 105.64 0.537 2 1737.439 0.30 104.66 3 149.304 6.74 1.71338 26.0 99.58 0.630 4 305.986 32.96 98.15 5 73.866 7.42 1.49700 81.7 74.46 0.538 6 138.114 2.50 1.65253 39.5 72.77 0.573 7 49.651 0.68 65.42 8 51.566 9.24 1.49700 81.5 65.41 0.537 9 135.223 0.20 64.51 10 77.762 10.82 1.49700 81.5 62.54 0.537 11 -221.788 2.00 1.65253 39.5 60.92 0.573 12 395.906 (Variable) 57.63 13 -6049.211 1.70 1.75500 52.3 55.71 0.547 14 57.330 (Variable) 51.54 15(Aperture) ∞ 11.06 49.59 16 82.455 1.50 1.84666 23.8 46.82 0.620 17 32.760 11.34 1.75500 52.3 44.31 0.547 18 -1312.711 3.42 43.54 19 357.204 6.26 1.91650 31.6 41.12 0.591 20 -59.297 1.30 1.67300 38.1 40.38 0.575 21 43.761 8.38 35.79 22 -44.348 1.50 1.56873 63.1 36.22 0.537 23 -65.767 0.98 38.08 24 66.540 7.63 1.69680 55.5 44.09 0.543 25 -136.449 8.46 44.33 26 -525.227 6.34 1.89286 20.4 44.08 0.639 27 -52.425 1.60 1.88300 40.8 44.13 0.566 28 -129.093 16.08 44.23 29* -55.447 2.30 1.58313 59.4 40.36 0.542 30 -99627.615 BF 41.06 Image plane ∞ Aspheric surface data: Surface 29 K = 0.00000e+00 A 4=-9.36786e-07 A 6= 2.81345e-09 A 8=-1.48749e-12 Various data Focal length 145.99 F-number 1.44 Half angle of view 8.43 Image height 21.64 Total lens length 205.08 BF 12.35 (Object distance at infinity) d12 3.02 d14 16.27 d30 12.35 (Object distance at -2.0m) d12 10.71 d14 8.57 d30 12.35 Entrance pupil 189.20 Exit pupil -57.72 Front principal point 31.02 Rear principal point -133.64 Lens group data Group Initial surface Focal length Lens length Front principal point Rear principal point B1 1 107.19 83.62 21.84 -47.99 Bf 13 -75.21 1.70 0.96 -0.01 Br 15 108.00 88.13 1.14 -56.57 Single Lens Data Lens Initial Surface Focal Length 1 1 341.89 2 3 401.53 3 5 307.70 4 6 -120.14 5 8 161.78 6 10 117.25 7 11 -217.57 8 13 -75.21 9 16 -65.10 10 17 42.49 11 19 55.89 12 20 -37.22 13 22 -245.68 14 24 65.20 15 26 64.82 16 27 -100.96 17 29 -95.14 .

[0130] [Numerical Example 3] Unit: mm Surface data Surface number rd nd νd Pitch diameter θgf 1 206.415 7.16 1.80810 22.8 108.13 0.631 2 686.131 0.30 107.39 3 112.218 9.74 1.43875 94.7 101.84 0.534 4 264.780 42.48 100.64 5 85.973 8.22 1.49700 81.7 74.61 0.538 6 250.014 2.50 1.77047 29.7 72.96 0.595 7 59.786 1.54 66.70 8 67.650 8.83 1.49700 81.5 66.68 0.537 9 347.802 0.20 65.96 10 69.868 9.53 1.49700 81.5 62.46 0.537 11 4807.382 2.00 1.65253 39.5 60.85 0.573 12 369.605 (Variable) 58.87 13 822.145 1.70 1.64000 60.1 56.62 0.537 14 132.860 (Variable) 54.20 15 210.579 1.70 1.64000 60.1 51.66 0.537 16 50.787 (variable) 48.34 17 (aperture) ∞ 2.01 46.01 18 93.603 1.50 1.84666 23.8 45.02 0.620 19 30.597 11.28 1.75500 52.3 42.53 0.547 20 6342.969 4.97 41.82 21 213.260 5.70 1.91650 31.6 39.10 0.591 22 -71.032 1.30 1.67300 38.1 38.38 0.575 23 44.919 6.40 34.85 24 -62.245 1.50 1.64000 60.1 34.76 0.537 25 -247.226 4.18 35.04 26 159.865 4.01 1.79952 42.2 36.77 0.568 27 -132.465 14.72 37.24 28 367.599 6.96 1.77830 23.9 42.11 0.625 29 -54.962 1.60 1.88300 40.8 42.34 0.566 30 -59.288 5.72 42.63 31* -52.580 2.30 1.58313 59.4 40.23 0.542 32 -99858.415 BF 40.52 Image plane ∞ Aspheric data Surface 31 K = 0.00000e+00 A4= 1.21667e-07 A6= 9.43449e-10 A8=-7.16083e-13 Other data Focal length 195.66 F-number 1.85 Half angle of view 6.31 Image height 21.64 Total lens length 233.03 BF 37.99 (Object distance at infinity) d12 2.92 d14 4.68 d16 17.39 d32 37.99 (Object distance at -1.9m) d12 11.58 d14 4.60 d16 8.81 d32 37.99 Entrance pupil position 254.29 Exit pupil position -71.29 Front principal point position 99.63 Rear principal point position -157.67 Lens group data Group Initial surface Focal length Lens length Front principal point position Rear principal point position B1 1 112.68 92.49 35.38 -51.27 Bf1 13 -247.85 1.70 1.24 0.20 Bf2 15 -105.01 1.70 1.37 0.33 Br 17 129.68 74.16 30.36 -31.65 Singlet lens data Lens Initial surface Focal length 1 1 362.92 2 3 435.42 3 5 259.33 4 6 -102.57 5 8 167.24 6 10 142.56 7 11 -613.70 8 13 -247.85 9 15 -105.01 10 18 -54.28 11 19 40.69 12 21 58.70 13 22 -40.70 14 24 -130.40 15 26 91.16 16 28 61.88 17 29 -1032.23 18 31 -90.22 .

[0131] [Numerical Example 4] Unit: mm Surface data Surface number rd nd νd Pitch diameter θgf 1 337.926 9.96 1.62200 30.7 143.18 0.625 2 6412.770 67.63 142.73 3 99.038 19.56 1.43387 95.1 120.36 0.537 4 435.261 56.32 118.39 5 69.823 13.92 1.49700 81.5 70.99 0.537 6 -568.986 2.50 1.85478 24.8 68.12 0.612 7 41.368 0.07 57.86 8 41.368 14.36 1.43387 95.1 57.89 0.537 9 685.498 13.95 56.79 10 -131.662 1.70 1.51742 52.4 51.64 0.556 11 55.842 9.16 1.85478 24.8 49.98 0.612 12 -264.832 4.41 49.33 13(Aperture) ∞ (Variable) 44.92 14 876.196 1.50 1.66565 35.6 42.33 0.582 15 49.708 (Variable) 39.77 16 135.408 4.24 1.48749 70.2 34.29 0.530 17 -104.746 1.23 33.95 18 -164.711 3.56 1.77047 29.7 34.13 0.595 19 -58.939 1.30 1.49700 81.5 34.41 0.537 20 53.670 2.03 34.87 21 163.083 1.20 1.80400 46.6 34.89 0.557 22 66.457 4.18 35.31 23 92.456 4.23 1.89190 37.1 38.46 0.578 24 -18414.502 0.93 38.88 25 56.870 5.36 1.73037 32.2 40.56 0.590 26 240.471 1.60 1.92286 20.9 40.26 0.639 27 108.746 3.61 39.92 28* -223.370 3.27 1.58313 59.4 40.02 0.542 29 -200.000 BF 40.36 Image surface ∞ Aspheric surface data Surface 28 K = 0.00000e+00 A 4= 5.84968e-07 A 6= 3.46437e-10 A 8=-3.56304e-13 Various data Focal length 294.95 F-number 2.06 Half angle of view 4.20 Image height 21.64 Lens total length 330.02 BF 47.82 (When object distance is infinite) d13 3.01 d15 27.41 d29 47.82 (When object distance is -2.3m) d13 24.36 d15 6.05 d29 47.82 Entrance pupil position 542.11 Exit pupil position -81.91 Front principal point position 166.47 Rear principal point position -247.13 Lens group data Group Start plane Focal length Lens length Front principal point position Rear principal point position B1 1 188.14 213.54 106.78 -131.37 Bf 14 -79.22 1.50 0.96 0.05 Br16 128.72 36.74 13.49 -13.62 Single Lens Data Lens Initial Surface Focal Length 1 1 573.15 2 3 290.39 3 5 126.05 4 6 -45.03 5 8 100.79 6 10 -75.55 7 11 54.67 8 14 -79.22 9 16 121.86 10 18 117.40 11 19 -56.30 12 21 -140.28 13 23 103.16 14 25 100.74 15 26 -216.38 16 28 3117.35

[0132] [Numerical Example 5] Unit: mm Surface data Surface number rd nd νd Pitch diameter θgf 1 110.158 12.76 1.68430 26.8 103.88 0.623 2 498.254 0.30 102.54 3 67.396 14.84 1.43387 95.1 90.16 0.537 4 161.920 8.08 86.44 5 94.511 7.06 1.49700 81.7 74.54 0.538 6 217.487 2.00 1.77047 29.7 72.25 0.595 7 50.036 5.96 63.53 8 85.955 6.98 1.49700 81.5 63.32 0.537 9 471.818 0.20 62.39 10 61.978 13.04 1.49700 81.5 58.19 0.537 11 -168.886 1.30 1.65253 39.5 55.45 0.573 12 114.245 (Variable) 51.17 13 -1380.595 1.00 1.64000 60.1 49.19 0.537 14 53.316 (Variable) 46.28 15 (Aperture) ∞ 4.65 43.65 16 184.567 1.00 1.80810 22.8 42.85 0.631 17 39.931 9.60 1.75500 52.3 41.83 0.547 18 -178.092 1.00 41.46 19 92.963 6.27 1.91650 31.6 39.50 0.591 20 -103.315 1.00 1.67300 38.1 38.45 0.575 21 38.932 6.49 34.49 22 -72.535 1.00 1.64000 60.1 34.36 0.537 23 -1112.842 (Variable) 34.36 24 69.760 3.46 1.83481 42.7 34.29 0.564 25 617.225 (Variable) 33.92 26 560.230 6.70 1.77830 23.9 37.77 0.625 27 -51.080 1.00 1.88300 40.8 38.13 0.566 28 -76.130 5.93 38.50 29* -82.968 2.30 1.58313 59.4 37.61 0.542 30 -100000.000 BF 38.00 Image plane ∞ Aspheric data Surface 29 K = 0.00000e+00 A 4=-5.00236e-07 A 6= 3.77550e-10 A 8=-1.82338e-13 Various data Focal length 180.00 F-number 1.85 Half angle of view 6.85 Image height 21.64 Total lens length 206.35 BF 38.00 (Object distance at infinity) d12 5.60 d14 24.61 d23 1.03 d25 13.20 d30 38.00 (Object distance at -1.5m) d12 21.24 d14 8.97 d23 3.34 d25 10.89 d30 38.00 Entrance pupil position 238.65 Exit pupil position -55.48 Front principal point position 72.05 Rear principal point position -142.00 Lens group data Group Initial surface Focal length Lens length Front principal point position Rear principal point position B1 1 126.96 72.51 -15.22 -59.60 Bf1 13 -80.19 1.00 0.59 -0.02 Bf3 15 -249.00 31.01 56.24 27.70 Bf2 24 93.94 3.46 -0.24 -2.12 Br 26 229.51 15.93 -6.40 -17.39 Single lens data Lens First surface Focal length 1 1 203.95 2 3 254.02 3 5 330.02 4 6 -84.79 5 8 210.21 6 10 92.97 7 11 -104.25 8 13 -80.19 9 16 -63.25 10 17 44.04 11 19 54.22 12 20 -41.90 13 22 -121.28 14 24 93.94 15 26 60.44 16 27 -179.16 17 29 -142.40.

[0133] The various values ​​in each numerical example are summarized in Table 1 below.

[0134]

[0135] [Imaging Device] Next, an embodiment of a digital still camera (imaging device) using the optical system of the present invention as an imaging optical system will be described with reference to Fig. 11. In Fig. 11, reference numeral 11 denotes an imaging optical system configured using any of the optical systems described in Examples 1 to 5. Reference numeral 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 having a quick-return mirror, or a so-called mirrorless camera having no quick-return mirror.

[0136] In this way, by applying the optical system 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.

[0137] 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.

[0138] The present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention.

[0139] This application claims priority based on Japanese Patent Application No. 2024-086419, filed May 28, 2024, the entire contents of which are incorporated herein by reference.

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, wherein the spacing between adjacent lens groups changes during focusing, wherein at least one lens group arranged in the intermediate group moves during focusing, wherein the first lens group comprises a first subgroup and a second subgroup arranged adjacent to the image side of the first subgroup, wherein of the air spaces on the optical axis between adjacent lenses in the first lens group, the air space on the optical axis between the first subgroup and the second subgroup is the largest, wherein the first subgroup has a positive lens Gp, wherein the Abbe number and the refractive index at the d-line of the material of the positive lens Gp are respectively vd1p and nd1p, the distance on the optical axis from the lens surface of the first lens group closest to the object to the lens surface of the first lens group closest to the image is TD1, and the air space on the optical axis between the first subgroup and the second subgroup is D1max, An optical system characterized by satisfying the following conditional expressions: 2.160<nd1p+0.02174×νd1p<2.320, 1.600<nd1p<1.850, and 0.10<D1max / TD1<0.

50.

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

3. The optical system according to claim 1 or 2, wherein the following condition is satisfied: 0.60<f1p / f<4.00, where f1p is the focal length of the positive lens Gp and f is the focal length of the entire system.

4. The optical system according to any one of claims 1 to 3, characterized in that the following condition is satisfied: 0.40<BF / IH<3.50, where BF is the back focus of the entire system and IH is the maximum image height.

5. An optical system according to any one of claims 1 to 4, characterized in that the following condition is satisfied: 0.30<f1 / f<0.90, where f1 is the focal length of the first lens group and f is the focal length of the entire system.

6. An optical system according to any one of claims 1 to 5, characterized in that the following condition is satisfied: 0.40<f1a / f<3.00, where f1a is the focal length of the first subgroup and f is the focal length of the entire system.

7. An optical system according to any one of claims 1 to 6, characterized in that the following condition is satisfied: 0.02<D1a / TD1<0.70, where D1a is the distance on the optical axis from the lens surface of the first subgroup closest to the object to the lens surface of the first subgroup closest to the image.

8. An optical system according to any one of claims 1 to 7, characterized in that the following condition is satisfied: 0.45<OTD / f<1.60, where OTD is the distance on the optical axis from the lens surface closest to the object side of the optical system to the image plane, and f is the focal length of the entire system.

9. An optical system according to any one of claims 1 to 8, characterized in that the following condition is satisfied: 70.0<νdpmax<100.0, where νdpmax is the Abbe number of the material of the positive lens Gr, which has the largest Abbe number among the materials of all the positive lenses arranged in the first lens group.

10. The optical system according to claim 9, wherein the positive lens Gr and the positive lens Gp are disposed adjacent to each other.

11. An optical system according to any one of claims 1 to 10, characterized in that the optical system satisfies the condition: 1.00≦Φfea×Fno / f<1.40, where Φea is the effective diameter of the lens located closest to the object, Fno is the F-number of the entire system, and f is the focal length of the entire system.

12. An optical system according to any one of claims 1 to 11, characterized in that the conditional expression 0.40<Bab_max / Fno<2.00 is satisfied, where Bab_max is the value with the highest absolute value of position sensitivity among all lens groups arranged in the intermediate group that move during focusing, and Fno is the F-number of the entire system.

13. An optical system according to any one of claims 1 to 12, characterized in that the following condition is satisfied: 15.0<νdnmin<50.0, where νdmin is the minimum Abbe number of the materials of all negative lenses arranged in the first lens group.

14. An optical system according to any one of claims 1 to 13, characterized in that 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.

15. The optical system according to claim 14, wherein said vibration control group has one positive lens and two negative lenses.

16. The optical system according to any one of claims 1 to 15, characterized in that the positive lens Gp is ​​disposed closest to the object side in the optical system.

17. An optical system according to any one of claims 1 to 16, characterized in that the first sub-group consists of two positive lenses.

18. An optical system according to any one of claims 1 to 17, characterized in that the second sub-group has three positive lenses and two negative lenses.

19. An optical system according to any one of claims 1 to 18, characterized in that the intermediate group has two lens groups that move during focusing.

20. An optical system according to any one of claims 1 to 19, characterized in that the lens group disposed in the intermediate group and moving during focusing has negative refractive power.

21. The optical system according to any one of claims 1 to 20, characterized in that the subsequent lens group comprises an aspherical lens.

22. 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, wherein the spacing between adjacent lens groups changes during focusing, wherein at least one lens group arranged in the intermediate group moves during focusing, and the total number of lenses arranged in the first lens group and the intermediate group is 16 or less.

23. An imaging device comprising the optical system according to any one of claims 1 to 22 and an imaging element for receiving an image formed by said optical system.

Images