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, wherein spaces between adjacent lens groups change during focusing. At least one lens group arranged in the intermediate group moves during focusing, thereby satisfying 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] The longer the focal length of an optical system, the larger and heavier it tends to be.

[0004] JP 2013-161076 A

[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 refractive index of the material of the positive lens arranged in the first lens group is low, 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.

[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 disposed in the intermediate group moves, and the first lens group comprises a first subgroup and a second subgroup disposed adjacent to the first subgroup on the image side, and the distance between adjacent lens groups changes during focusing. the air space on the optical axis between the first subgroup and the second subgroup is the largest among the air spaces on the optical axis between adjacent lenses, the second 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 second subgroup closest to the object side to the lens surface of the positive lens Gp is ​​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 D1b, the following conditional expressions are satisfied: 2.160<nd1p+0.02174×vd1p<2.320, 1.600<nd1p<1.850, and 0.00≦Dp / D1b<0.72

[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.

[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.

[0010] 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.

[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, 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.

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

[0019] 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.

[0020] 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 (°).

[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 expressed by the following equations: vd=(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 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.

[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. Of 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 also 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 vd1p 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 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.

[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 sub-unit B1b closest to the object side to the lens surface of the positive lens Gp becomes large, the position of the positive lens Gp will be positioned on the image side, and the height of the axial marginal ray will become too low, resulting 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 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.

[0037] It is preferable that the conditional expressions (1), (2), and (3) are set to the following conditions: 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: 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 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.

[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 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.

[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 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.

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

[0046] The first subunit 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 the like that occurs 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 the like.

[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 a close distance, 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 side 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 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] f1a is the focal length of the first sub-unit B1a. D1a is the axial distance from the lens surface of the first sub-unit B1a closest to the object to the lens surface of the first sub-unit B1a closest to the image. TD1 is the axial distance from the lens surface of the first sub-unit B1a closest to the object to the lens surface of the first sub-unit 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 unit 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 of all the lens groups located in the intermediate group Bf that move during focusing. νdnmin is the smallest Abbe number of 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 becomes 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 become 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 exceeded 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 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.

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

[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 and the like, 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 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.

[0065] If the lower limit of conditional expression (9) is not reached 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 small, 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, field curvature, 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, etc., 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 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.

[0069] 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.

[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 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

[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, which will result in an increase in the overall lens length of 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.

[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 large on-axis chromatic aberration between the c-line and the f-line occurs 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 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.

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

[0078] If the air gap D1max becomes small, falling below the lower limit of conditional expression (15), the diameter of the lens 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 not preferable.

[0080] It is more preferable that the conditions (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 the conditions (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 example will be described in detail. From Example 2 onwards, differences from Example 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 arranged 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] 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.

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

[0087] 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.

[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] 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 the F-line is also suppressed in a balanced manner.

[0090] In the optical system L0 of Example 3, the intermediate group Bf is composed of a single lens group Bf1 having a positive refractive power, and moves during focusing, thereby making it possible to suppress coma even when focusing at close range.

[0091] 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 example 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] [Modification] In contrast to 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 lens unit Bf may be configured to move along different loci during focusing. By moving them along different loci, fluctuations in spherical aberration and the like that occur during focusing can be more easily suppressed.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] Numerical examples 1 to 5 corresponding to the first to fifth embodiments, 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, and vd and θgf are the Abbe number and partial dispersion ratio between the g-line and the F-line of the optical element, respectively. The Abbe number vd and partial dispersion ratio θgf between the g-line and the F-line of a certain material can be expressed as follows. That is, let the g-line (wavelength 435.8 nm) be the Fraunhofer line. 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 vd = (Nd - 1) / (NF - NC) and θgf = (Ng - NF) / (NF - NC).

[0103] BF is the back focus. The back focus is the air-equivalent distance from the lens surface located closest to the object in the 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 the optical system L0 to the lens surface located closest to the image plane.

[0104] 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.

[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 Pitch diameter 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 Surface 26 K = 0.00000e+00 A4= 4.94767e-08 A6= 1.01013e-10 A8= 2.70572e-14 Other data Focal length 290.94 F-number 2.90 Half angle of view 4.25 Image height 21.64 Total 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 Rear principal point position -249.46 Lens group data Group Initial surface 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 Initial 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 Pitch diameter 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 surface ∞ Aspheric data Surface 26 K = 0.00000e+00 A4= 3.35881e-07 A6= 2.57635e-10 A8= 2.12541e-13 Other 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 Rear principal point position -252.91 Zoom lens group data Group Initial surface Focal length Lens construction 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 Initial 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 Pitch diameter 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 surface ∞ Aspheric data Surface 26 K = 0.00000e+00 A4= 2.59994e-07 A6= 1.31526e-10 A8=-9.26275e-14 Other 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 Rear principal point position -252.98 Lens group data Group Initial surface 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 Initial 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 Effective diameter 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 Total 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 Rear principal point position -262.18 Lens group data Group Starting surface 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 20 330.15 101.92 79.72 0.56 Single Lens Data Lens Initial 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 Effective diameter 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 Rear principal point position -368.96 Lens group data Group Initial surface Focal length Lens construction 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 Singlet lens data Lens Initial 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]

[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, 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 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 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, to apprise the public of the scope of the present invention, the following claims are appended.

[0116] This application claims priority based on Japanese Patent Application No. 2024-102706, filed on June 26, 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, in which the spacing between adjacent lens groups changes during focusing, wherein at least one lens group arranged in the intermediate group moves during focusing, the first lens group comprises a first subgroup and a second subgroup arranged adjacent to the first subgroup on the image side, 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 second subgroup has a positive lens Gp, an optical system characterized by satisfying the following conditional expressions: 2.160<nd1p+0.02174×νd1p<2.320, 1.600<nd1p<1.850, and 0.00≦Dp / D1b<0.72, where vd1p and nd1p are the Abbe number and the refractive index at the d-line of the material of said positive lens Gp, respectively, Dp is the distance on the optical axis from the lens surface of said second sub-group closest to the object side to the lens surface of said positive lens Gp, and D1b is the distance on the optical axis from the lens surface of said second sub-group closest to the object side to the lens surface of said second sub-group closest to the image side.

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: 0.15<f1p / f<1.50, 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: 1.0<BF / IH<3.5, 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: 0.20<f1 / f<2.20, 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: 0.10<f1a / f<2.00, 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: 0.10<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, and TD1 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: 0.50<OTD / f<1.50, 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, when 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, is taken as νdpmax, the optical system satisfies the condition: 70.0<νdpmax<100.

0.

10. An optical system according to any one of claims 1 to 9, 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.

11. An optical system according to any one of claims 1 to 10, characterized in that the conditional expression 0.60<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.

12. An optical system according to any one of claims 1 to 11, characterized in that, when the smallest Abbe number of the materials of all negative lenses arranged in the first lens group is νdnmin, the following condition is satisfied: 15.0<νdnmin<50.

0.

13. An optical system according to any one of claims 1 to 12, characterized in that the following condition is satisfied: 0.20<D1max / TD1<0.80, where TD1 is the distance on the optical axis from the lens surface of the first lens group closest to the object to the lens surface of the first lens group closest to the image, and D1max is the air gap on the optical axis between the first subgroup and the second subgroup.

14. An optical system according to any one of claims 1 to 13, characterized in that the following condition is satisfied: 0.50<|f1b| / f<3.50, where f1b is the focal length of the second subgroup and f is the focal length of the entire system.

15. An optical system according to any one of claims 1 to 14, 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.

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

17. The optical system according to any one of claims 1 to 16, wherein the positive lens Gp is ​​arranged closest to the object in the second sub-group.

18. An optical system according to any one of claims 1 to 17, characterized in that the first subgroup consists of two positive lenses.

19. The optical system according to any one of claims 1 to 18, wherein the second sub-group has three positive lenses and two negative lenses.

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, wherein the lens group disposed in the intermediate group and moving during focusing has positive refractive power.

22. The optical system according to any one of claims 1 to 21, wherein the subsequent lens group comprises an aspherical lens.

23. An optical system according to any one of claims 1 to 22, characterized in that the subsequent lens group has a variable magnification subgroup that can be inserted or removed, and the focal length of the entire system changes when the variable magnification subgroup is inserted or removed.

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, wherein at least one lens group arranged in the intermediate group moves during focusing, and the total number of lens elements arranged in the subsequent lens group is four or more.

25. An imaging device comprising the optical system according to any one of claims 1 to 24 and an imaging element for receiving an image formed by said optical system.

Images