Imaging lens and imaging device

Abstract

To provide an image capturing lens which is compact and yet offers high optical performance even in close-up shooting, and to provide an image capturing device having the same.SOLUTION: An image capturing lens provided herein comprises a first lens group having positive refractive power and a second lens group having negative refractive power arranged successively in order from the most object side. Only the second lens group moves while focusing. The first lens group consists of a 1A lens group, aperture stop, and 1B lens group in order from the object side. The second lens group comprises at least one positive lens. The image capturing lens satisfies predefined conditional expressions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology of the present disclosure relates to an imaging lens and an imaging device. [Background technology]

[0002] 2. Description of the Related Art Conventionally, an imaging lens that can be used in imaging devices such as digital cameras is known from Patent Document 1 below. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-159613 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for imaging lenses that are compact yet maintain high optical performance even in close-up photography.

[0005] The present disclosure has been made in consideration of the above circumstances, and aims to provide an imaging lens that is compact yet maintains high optical performance even in close-up photography, and an imaging device equipped with this imaging lens. [Means for solving the problem]

[0006] An imaging lens according to one embodiment of the present disclosure includes, in succession from the object side to the image side, a first lens group having positive refractive power and a second lens group having negative refractive power, wherein during focusing, only the second lens group moves along the optical axis, and the first lens group is composed of, in order from the object side to the image side, a 1A group, an aperture stop, and a 1B group, and the second lens group includes at least one positive lens, and when the maximum imaging magnification is β, the focal length of the 1A group is f1A, and the focal length of the 1B group is f1B, 0.45<|β| (1) -15 <f1A / f1B<-1.7 (2) The conditional expressions (1) and (2) are satisfied.

[0007] The imaging lens of the above aspect is -10 <f1A / f1B<-2 (2-1) It is preferable to satisfy the conditional expression (2-1) expressed as follows:

[0008] When the 1Bth group includes a positive lens closest to the object side, and the Abbe number of the positive lens closest to the object side in the 1Bth group is ν1Bp1 based on the d-line, the imaging lens of the above aspect is 60<ν1Bp1<105 (3) It is preferable to satisfy conditional expression (3) below.

[0009] When the first subgroup B includes a positive lens closest to the image, and the larger of the diameter of the axial light beam when focused on an object at infinity and the diameter of the axial light beam when focused on the nearest object, at the object-side surface of the positive lens closest to the image in the first subgroup B, is denoted as DMp, and the larger of the diameter of the axial light beam when focused on an object at infinity and the diameter of the axial light beam when focused on the nearest object, at the image-side surface of the lens adjacent to the object-side of the positive lens closest to the image in the first subgroup B, is denoted as DMpa, the imaging lens of the above aspect is as follows: 0.5 <DMpa / DMp<1 (4) It is preferable to satisfy conditional expression (4) below.

[0010] When the 1Bth group includes a cemented lens consisting of one negative lens and one positive lens, and the refractive index of the positive lens in the cemented lens in the 1Bth group for the d-line is N1Bp, the refractive index of the negative lens in the cemented lens in the 1Bth group for the d-line is N1Bn, the Abbe number of the positive lens in the cemented lens in the 1Bth group based on the d-line is v1Bp, the Abbe number of the negative lens in the cemented lens in the 1Bth group based on the d-line is v1Bn, the partial dispersion ratio between the g-line and the F-line of the positive lens in the cemented lens in the 1Bth group is θ1Bp, and the partial dispersion ratio between the g-line and the F-line of the negative lens in the cemented lens in the 1Bth group is θ1Bn, the imaging lens of the above aspect is as follows: -0.5 <N1Bp-N1Bn<0 (5) 30<ν1Bp-ν1Bn<70 (6) -0.1<θ1Bp-θ1Bn<-0.03 (7) It is preferable to satisfy the following conditional expressions (5), (6), and (7):

[0011] When the focal length of the imaging lens when focused on an object at infinity is f, the imaging lens of the above embodiment has the following characteristics: 0 <f / f1B<4 (8) It is preferable to satisfy conditional expression (8) below.

[0012] It is preferable that the 1Ath group include at least one positive lens element.

[0013] When the minimum value of the Abbe numbers of all the positive lenses in the second lens group based on the d-line is taken as ν2min, the imaging lens of the above aspect satisfies the following conditions: 10<ν2min<22 (9) It is preferable to satisfy conditional expression (9) below.

[0014] When the lateral magnification of the second lens group when focused on an object at infinity is β2i, the combined lateral magnification of all lenses on the image side of the second lens group when focused on an object at infinity is βri, and when no lens is disposed on the image side of the second lens group, βri=1, the imaging lens of the above aspect has the following formula: -6<(1-β2i 2 )×βri 2 <-2 (10) It is preferable to satisfy conditional expression (10) below.

[0015] The imaging lens of the above aspect may be configured to include, in order from the object side to the image side, a first lens group, a second lens group, and a third lens group that is fixed relative to the image plane when focusing. In such a configuration, if the focal length of the imaging lens when focused on an object at infinity is f and the focal length of the third lens group is f3, the imaging lens of the above aspect will have the following: -0.3 <f / f3<0.8 (11) It is preferable to satisfy conditional expression (11) expressed as follows: Furthermore, when one lens component is one single lens or one cemented lens, it is preferable that the third lens group consists of one lens component.

[0016] When the sum of the distance on the optical axis from the paraxial exit pupil position to the lens surface of the imaging lens closest to the image side and the air-equivalent distance on the optical axis from the lens surface of the imaging lens closest to the image side to the image plane in a state where the lens is focused on a closest object is defined as Expm, and when the sum of the distance on the optical axis from the paraxial exit pupil position to the lens surface of the imaging lens closest to the image side and the air-equivalent distance on the optical axis from the lens surface of the imaging lens closest to the image side to the image plane in a state where the lens is focused on an object at infinity is defined as Expi, the imaging lens of the above aspect has the following characteristics: 0.35 <Expm / Expi<1 (12) It is preferable to satisfy conditional expression (12) below.

[0017] When the focal length of the imaging lens in a state where it is focused on an object at infinity is f, and the focal length of the first lens group is f1, the imaging lens of the above aspect has the following characteristics: 0.2 <f / f1<4 (13) It is preferable to satisfy conditional expression (13) below.

[0018] When one lens component is one single lens or one cemented lens, and when the paraxial radius of curvature of the surface closest to the object side of the lens component closest to the object side of the imaging lens is R1f and the paraxial radius of curvature of the surface closest to the image side of the lens component closest to the object side of the imaging lens is R1r, the imaging lens of the above aspect has the following properties: 0<(R1f+R1r) / (R1f-R1r)<3 (14) It is preferable to satisfy conditional expression (14) below.

[0019] When the air-equivalent distance on the optical axis from the lens surface closest to the image side of the imaging lens to the image plane in a state where the lens is focused on an object at infinity is Bf, the focal length of the imaging lens in a state where the lens is focused on an object at infinity is f, and the maximum half angle of view in a state where the lens is focused on an object at infinity is ωi, the imaging lens of the above aspect satisfies the following equation: 0.3 <Bf / (f×tanωi)<4 (15) It is preferable to satisfy conditional expression (15) below.

[0020] The second lens group preferably includes at least two positive lenses.

[0021] When the second lens group includes a cemented lens consisting of one positive lens and one negative lens, and the refractive index of the positive lens in the cemented lens of the second lens group for the d-line is N2p, the refractive index of the negative lens in the cemented lens of the second lens group for the d-line is N2n, the Abbe number of the positive lens in the cemented lens of the second lens group based on the d-line is v2p, the Abbe number of the negative lens in the cemented lens of the second lens group based on the d-line is v2n, the partial dispersion ratio between the g-line and the F-line of the positive lens in the cemented lens of the second lens group is θ2p, and the partial dispersion ratio between the g-line and the F-line of the negative lens in the cemented lens of the second lens group is θ2n, the imaging lens of the above aspect is as follows: -0.6 <N2p-N2n<-0.1 (16) -20<ν2p-ν2n<50 (17) -0.3<θ2p-θ2n<0.15 (18) It is preferable to satisfy the following conditions (16), (17), and (18):

[0022] When the second lens group includes a cemented lens made up of one positive lens and one negative lens, the refractive index of the negative lens in the cemented lens in the second lens group with respect to the d-line is N2n, and the Abbe number of the negative lens in the cemented lens in the second lens group with respect to the d-line is ν2n, the imaging lens of the above aspect has the following properties: 1.75 <N2n<2.2 (19) 20<ν2n<40 (20) It is preferable to satisfy the following conditions (19) and (20):

[0023] An imaging device according to another aspect of the present disclosure includes the imaging lens according to the above aspect of the present disclosure.

[0024] In this specification, the terms "consisting of" and "consisting of" are intended to mean that, in addition to the listed components, other components may also be included, such as lenses that have substantially no refractive power, optical elements other than lenses, such as apertures, filters, and cover glasses, and mechanical parts, such as lens flanges, lens barrels, image sensors, and image stabilization mechanisms.

[0025] In this specification, "a lens group having positive refractive power" and "the lens group has positive refractive power" mean that the lens group as a whole has positive refractive power. Similarly, "a lens group having negative refractive power" and "the lens group has negative refractive power" mean that the lens group as a whole has negative refractive power. Similarly, "a lens component having negative refractive power" means that the lens component as a whole has negative refractive power. "A lens having positive refractive power" and "a positive lens" are synonymous. In this specification, the "first lens group," "second lens group," "third lens group," "focus group," and "image stabilization group" are not limited to being configured with multiple lenses, and may be configured with only one lens.

[0026] A "single lens" refers to a single, uncemented lens. However, a compound aspherical lens (a lens in which a spherical lens and an aspherical film formed on that spherical lens are integrally constructed and function as a single aspherical lens as a whole) is not considered a cemented lens, but is treated as a single lens. Unless otherwise specified, the radius of curvature, sign of refractive power, and surface shape of lenses including aspherical surfaces are those in the paraxial region. The sign of the radius of curvature of a surface with a convex surface facing the object side is positive, and the sign of the radius of curvature of a surface with a convex surface facing the image side is negative.

[0027] The "focal length" used in the conditional expressions is the paraxial focal length. The "distance on the optical axis" used in the conditional expressions is the geometric distance unless otherwise specified. The values ​​used in the conditional expressions are values ​​based on the d-line unless otherwise specified. Furthermore, the "d-line," "C-line," "F-line," and "g-line" used in this specification are emission lines, and the wavelength of the d-line is treated as 587.56 nm (nanometers), the wavelength of the C-line is 656.27 nm (nanometers), the wavelength of the F-line is 486.13 nm (nanometers), and the wavelength of the g-line is 435.84 nm (nanometers). [Effects of the Invention]

[0028] According to the present disclosure, it is possible to provide an imaging lens that is compact yet maintains high optical performance even in close-up photography, and an imaging device that includes this imaging lens. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a cross-sectional view showing the configuration of an imaging lens according to one embodiment, corresponding to the imaging lens of Example 1. FIG. [Figure 2] 2A to 2C are cross-sectional views showing the configuration and light beams of the imaging lens of FIG. 1 in each focus state. [Figure 3] FIG. 10 is a diagram for explaining an effective diameter. [Figure 4] 3A to 3C are diagrams showing various aberrations of the imaging lens of Example 1. [Figure 5] FIG. 10 is a cross-sectional view showing the configuration of an imaging lens according to a second embodiment. [Figure 6] 10A to 10C are diagrams showing various aberrations of the imaging lens of Example 2. [Figure 7] FIG. 10 is a cross-sectional view showing the configuration of an imaging lens according to a third embodiment. [Figure 8] 10A to 10C are diagrams showing various aberrations of the imaging lens of Example 3. [Figure 9] FIG. 10 is a cross-sectional view showing the configuration of an imaging lens according to a fourth embodiment. [Figure 10] 10A to 10C are diagrams showing various aberrations of the imaging lens of Example 4. [Figure 11] FIG. 10 is a cross-sectional view showing the configuration of an imaging lens according to a fifth embodiment. [Figure 12] 10A to 10C are diagrams showing various aberrations of the imaging lens of Example 5. [Figure 13] FIG. 10 is a cross-sectional view showing the configuration of an imaging lens according to a sixth embodiment. [Figure 14] 10A to 10C are diagrams showing various aberrations of the imaging lens of Example 6. [Figure 15] FIG. 10 is a cross-sectional view showing the configuration of an imaging lens according to a seventh embodiment. [Figure 16] 10A to 10C are diagrams showing various aberrations of the imaging lens of Example 7. [Figure 17] FIG. 13 is a cross-sectional view showing the configuration of an imaging lens according to an eighth embodiment. [Figure 18] 13A to 13C are diagrams showing various aberrations of the imaging lens of Example 8. [Figure 19] 1 is a perspective view of the front side of an imaging device according to an embodiment. [Figure 20] FIG. 2 is a perspective view of the rear side of the imaging device according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0030] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0031] FIG. 1 shows a cross-sectional view of an imaging lens according to an embodiment of the present disclosure, when focused on an object at infinity. FIG. 2 shows cross-sectional views of the configuration and light beams of the imaging lens in FIG. 1 in various focusing states. In FIG. 2, the upper row labeled "infinity" shows a state focused on an object at infinity, and the lower row labeled "closest" shows a state focused on a closest object, which is 18.2 mm (millimeters) from the lens surface closest to the object. Note that in this specification, an object at infinity is referred to as an "infinite object," and an object at the closest distance is referred to as a "closest object." The upper row of FIG. 2 shows, as light beams, an axial light beam 2i and a light beam 3i with a maximum half angle of view ωi when focused on an object at infinity. The lower row of FIG. 2 shows, as light beams, an axial light beam 2m and a light beam 3m with a maximum half angle of view ωm when focused on a closest object. The example shown in FIGS. 1 and 2 corresponds to the imaging lens of Example 1, which will be described later. 1 and 2, the left side is the object side and the right side is the image side. The following description will be mainly made with reference to FIG.

[0032] FIG. 1 shows an example in which a parallel-plate optical member PP is arranged between the imaging lens and the image plane Sim, assuming that the imaging lens is applied to an imaging device. The optical member PP is a member that is assumed to include various filters and / or cover glass. The various filters are low-pass filters, infrared cut filters, and / or filters that cut off specific wavelength ranges. The optical member PP is a member that does not have refractive power. It is also possible to configure an imaging device without the optical member PP.

[0033] The imaging lens of the present disclosure includes, in succession along the optical axis Z from the object side to the image side, a first lens group G1 having positive refractive power and a second lens group G2 having negative refractive power. During focusing, the first lens group G1 is fixed with respect to the image plane Sim, and only the second lens group G2 moves along the optical axis Z. In this specification, the group that moves along the optical axis Z during focusing is referred to as the focus group. Focusing is performed by moving the focus group. In the imaging lens of the present disclosure, the second lens group G2 is the focus group.

[0034] In the imaging lens of the present disclosure, lens groups having positive and negative refractive powers are arranged in order from the object side to the image side, and the behavior of each lens group during focusing is set as described above, which is advantageous for achieving a high imaging magnification. By arranging groups with refractive powers of opposite signs, the refractive power of the focus group can be strengthened, which shortens the amount of movement of the focus group during focusing, which is advantageous for miniaturization. Note that in this specification, "high imaging magnification" means that the absolute value of the imaging magnification is large.

[0035] The first lens group G1 of the imaging lens of the present disclosure is configured to include an aperture stop St. The first lens group G1 is made up of, in order from the object side to the image side, a firstA group G1A, an aperture stop St, and a firstB group G1B.

[0036] As an example, the imaging lens of FIG. 1 is configured as follows. The imaging lens of FIG. 1 comprises, in order from the object side to the image side, a first lens group G1, a second lens group G2, and a third lens group G3. The first lens group G1 comprises, in order from the object side to the image side, a first-axis group G1A, an aperture stop St, and a first-axis group G1B. The first-axis group G1A comprises, in order from the object side to the image side, three lenses, L11 to L13, and the first-axis group G1B comprises, in order from the object side to the image side, four lenses, L14 to L17. The second lens group G2 comprises, in order from the object side to the image side, three lenses, L21 to L23. The third lens group G3 comprises a single lens, L31. The aperture stop St in FIG. 1 does not indicate its shape or size, but rather its position in the optical axis direction.

[0037] In the example shown in Figure 1, the entire second lens group moves as a unit during focusing, while the other lens groups are fixed relative to the image plane Sim. "Moving as a unit" here means moving simultaneously, in the same direction, and by the same amount. The right-pointing arrow below the second lens group G2 in Figure 1 indicates that the second lens group G2 is a focus group that moves toward the image when focusing from an object at infinity to the closest object.

[0038] In this specification, a "lens group" is a component of an imaging lens that includes at least one lens and is separated by an air gap that changes during focusing. During focusing, each lens group is moved or fixed, and the mutual spacing between lenses within each lens group does not change. In other words, in this specification, a group in which the spacing between adjacent groups changes during focusing, but the total spacing between adjacent lenses within itself does not change, is defined as one lens group.

[0039] Preferred and possible configurations of the imaging lens of the present disclosure will be described below. In the following description of the preferred and possible configurations, "the imaging lens of the present disclosure" will also be simply referred to as "the imaging lens" to avoid redundancy.

[0040] The first-A group G1A may be configured to have negative refractive power, and the first-B group G1B may be configured to have positive refractive power, which is advantageous for correcting aberrations.

[0041] It is preferable that the firstA group G1A includes at least one positive lens, which is advantageous for correcting distortion and lateral chromatic aberration.

[0042] The first-A group G1A may be configured to include a cemented lens consisting of one negative lens and one positive lens. This is advantageous for suppressing fluctuations in chromatic aberration that accompany changes in object distance. In this specification, the "object distance" refers to the distance on the optical axis from the object being photographed to the lens surface closest to the object in the imaging lens.

[0043] The first-A group G1A may be configured to consist of three lenses. For example, the first-A group G1A may be configured to consist, in order from the object side to the image side, of a negative lens, a negative lens, and a positive lens. This is advantageous for aberration correction.

[0044] The lens component closest to the object in the first A group G1A may be configured to have an aspherical surface. This is advantageous for correcting distortion. In this specification, "one lens component" means one cemented lens or one single lens.

[0045] It is preferable that the first-subgroup G1B includes a cemented lens consisting of one negative lens and one positive lens, which is advantageous for suppressing fluctuations in chromatic aberration that accompany changes in object distance.

[0046] The first-subgroup G1B may be configured to consist of four lenses. For example, the first-subgroup G1B may be configured to consist, in order from the object side to the image side, of a single lens having positive refractive power, a cemented lens, and another single lens having positive refractive power. This is advantageous for aberration correction.

[0047] It is preferable that the second lens group G2 includes at least one positive lens. This is advantageous for suppressing fluctuations in chromatic aberration that accompany changes in object distance. It is more preferable that the second lens group G2 includes at least two positive lenses. This is even more advantageous for suppressing fluctuations in chromatic aberration that accompany changes in object distance.

[0048] The second lens group G2 preferably includes a cemented lens consisting of one positive lens and one negative lens, which is advantageous for suppressing fluctuations in chromatic aberration that accompany changes in object distance.

[0049] The second lens group G2 may be configured with two or three lenses. If the second lens group G2 consists of two lenses, it may be configured with, in order from the object side to the image side, a positive lens and a negative lens. If the second lens group G2 consists of three lenses, it may be configured with, in order from the object side to the image side, a single lens with positive refractive power and a cemented lens. This configuration is advantageous for suppressing fluctuations in chromatic aberration caused by changes in object distance. If the second lens group G2 consists of, in order from the object side to the image side, a single lens with positive refractive power and a cemented lens, it is preferable that this cemented lens be a cemented lens in which, in order from the object side, a positive lens and a negative lens are cemented together. This configuration is advantageous for suppressing fluctuations in chromatic aberration caused by changes in object distance.

[0050] The second lens group G2 may be configured to include a lens component that has an aspherical surface and negative refractive power, which is advantageous for correcting curvature of field for each object distance.

[0051] The imaging lens may be configured to include, in order from the object side to the image side, a first lens group G1, a second lens group G2, and a third lens group G3 that is fixed relative to the image plane Sim during focusing, which is advantageous for correcting field curvature.

[0052] When the imaging lens is composed of, in order from the object side to the image side, the first lens group G1, the second lens group G2, and the third lens group G3, it is preferable that the third lens group G3 includes a cemented lens consisting of one positive lens and one negative lens, which is advantageous for suppressing fluctuations in chromatic aberration that accompany fluctuations in object distance.

[0053] When the imaging lens is composed of, in order from the object side to the image side, a first lens group G1, a second lens group G2, and the third lens group G3, it is preferable that the third lens group G3 be composed of a single lens component. This is advantageous for shortening the overall length of the lens system. More specifically, the third lens group G3 may be composed of a single lens having positive refractive power. Alternatively, the third lens group G3 may be composed of a cemented lens in which, in order from the object side, a negative lens and a positive lens are cemented together, or the third lens group G3 may be composed of a cemented lens in order from the object side, a positive lens and a negative lens.

[0054] When the imaging lens is composed of, in order from the object side to the image side, a first lens group G1, a second lens group G2, and the third lens group G3, the third lens group G3 may be configured to include an aspherical lens, which is advantageous for correcting field curvature for each object distance.

[0055] If the maximum imaging magnification is β, it is preferable that the imaging lens satisfy the following conditional expression (1). The maximum imaging magnification is the imaging magnification when photographing the closest object. By satisfying conditional expression (1), it becomes possible to photograph at a high imaging magnification. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (1-1), it is even more preferable that it satisfy the following conditional expression (1-2), and it is even more preferable that it satisfy the following conditional expression (1-3). 0.45<|β| (1) 0.5≦|β| (1-1) 0.75<|β| (1-2) 0.9<|β| (1-3)

[0056] If the focal length of the first-A group G1A is f1A and the focal length of the first-B group G1B is f1B, it is preferable that the imaging lens satisfy the following conditional expression (2). By ensuring that the corresponding value of conditional expression (2) is not below the lower limit, the refractive power of the first-A group G1A can be ensured, which is advantageous for correction of distortion and curvature of field. By ensuring that the corresponding value of conditional expression (2) is not above the upper limit, the refractive power of the first-B group G1B can be ensured, which is advantageous for reducing the diameter of the group closer to the image than the first-B group G1B. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (2-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (2-2). -15 <f1A / f1B<-1.7 (2) -10 <f1A / f1B<-2 (2-1) -6 <f1A / f1B<-2.4 (2-2)

[0057] It is preferable that the first-subgroup G1B includes a positive lens closest to the object. If the Abbe number based on the d-line of the positive lens closest to the object in the first-subgroup G1B is ν1Bp1, the imaging lens preferably satisfies the following conditional expression (3). Ensuring that the corresponding value of conditional expression (3) is not below the lower limit is advantageous for correcting axial chromatic aberration. Ensuring that the corresponding value of conditional expression (3) is not above the upper limit prevents the refractive index from becoming too low, and therefore prevents the absolute value of the radius of curvature from becoming too small, thereby suppressing sensitivity to errors. In order to obtain better characteristics, it is more preferable that the imaging lens satisfies the following conditional expression (3-1), and even more preferable that it satisfies the following conditional expression (3-2). 60<ν1Bp1<105 (3) 70<ν1Bp1<105 (3-1) 80<ν1Bp1<105 (3-2)

[0058] It is preferable that the first-subgroup G1B includes a positive lens closest to the image. In a configuration in which the first-subgroup G1B includes a positive lens closest to the image, the imaging lens preferably satisfies the following conditional expression (4). Here, DMp is defined as the larger of the diameter of the axial ray bundle 2i when focused on an object at infinity and the diameter of the axial ray bundle 2m when focused on the closest object, at the object-side surface of the positive lens closest to the image in the first-subgroup G1B. Also, DMpa is defined as the larger of the diameter of the axial ray bundle 2i when focused on an object at infinity and the diameter of the axial ray bundle 2m when focused on the closest object, at the image-side surface of the lens adjacent to the object-side of the positive lens closest to the image in the first-subgroup G1B. Ensuring that the value corresponding to conditional expression (4) is not equal to or less than the lower limit is advantageous for correcting field curvature. Ensuring that the value corresponding to conditional expression (4) is not equal to or greater than the upper limit is advantageous for correcting spherical aberration. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional formula (4-1), and it is even more preferable that the imaging lens satisfy the following conditional formula (4-2). 0.5 <DMpa / DMp<1 (4) 0.7 <DMpa / DMp<1 (4-1) 0.9 <DMpa / DMp<1 (4-2)

[0059] As an example, the diameters DMp and DMpa in the example shown in FIG. 1 are shown in FIG. 2. In the example shown in FIG. 1, the positive lens closest to the image in the first-subgroup G1B corresponds to lens L17, and the lens adjacent to the positive lens closest to the image in the first-subgroup G1B on the object side corresponds to lens L16. In this example, the diameter of the axial beam 2m at the object-side surface of lens L17 is larger than the diameter of the axial beam 2i at the object-side surface of lens L17, so the latter is shown as diameter DMp in FIG. 2. Also, in this example, the diameter of the axial beam 2i at the image-side surface of lens L16 is larger than the diameter of the axial beam 2m at the image-side surface of lens L16, so the latter is shown as diameter DMpa in FIG. 2.

[0060] In a configuration in which the first-subgroup G1B includes a cemented lens consisting of one negative lens and one positive lens, it is preferable that the imaging lens satisfy the following conditional expression (5). Here, the refractive index for the d-line of the positive lens in the cemented lens in the first-subgroup G1B is N1Bp, and the refractive index for the d-line of the negative lens in the cemented lens in the first-subgroup G1B is N1Bn. Satisfying conditional expression (5) is advantageous for correcting axial chromatic aberration. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (5-1), and it is even more preferable that it satisfy the following conditional expression (5-2). -0.5 <N1Bp-N1Bn<0 (5) -0.4 <N1Bp-N1Bn<0 (5-1) -0.3 <N1Bp-N1Bn<-0.1 (5-2)

[0061] In a configuration in which the first-subgroup G1B includes the cemented lens, it is preferable that the imaging lens satisfy the following conditional expression (6). Here, the Abbe number based on the d-line of the positive lens in the cemented lens in the first-subgroup G1B is v1Bp, and the Abbe number based on the d-line of the negative lens in the cemented lens in the first-subgroup G1B is v1Bn. Satisfying conditional expression (6) is advantageous for correcting axial chromatic aberration. In order to obtain even better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (6-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (6-2). 30<ν1Bp-ν1Bn<70 (6) 35<ν1Bp-ν1Bn<65 (6-1) 40<ν1Bp-ν1Bn<60 (6-2)

[0062] In a configuration in which the first-subgroup G1B includes the cemented lens, it is preferable that the imaging lens satisfy the following conditional expression (7). Here, the partial dispersion ratio between the g-line and the F-line of the positive lens in the cemented lens in the first-subgroup G1B is set to θ1Bp, and the partial dispersion ratio between the g-line and the F-line of the negative lens in the cemented lens in the first-subgroup G1B is set to θ1Bn. Satisfying conditional expression (7) is advantageous for correcting axial chromatic aberration. In order to obtain even better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (7-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (7-2). -0.1<θ1Bp-θ1Bn<-0.03 (7) -0.1<θ1Bp-θ1Bn<-0.04 (7-1) -0.095<θ1Bp-θ1Bn<-0.05 (7-2)

[0063] If the refractive indices of a lens for the g-line, F-line, and C-line are Ng, NF, and NC, respectively, and the partial dispersion ratio of the lens between the g-line and F-line is θgF, then θgF is defined by the following equation: θgF=(Ng-NF) / (NF-NC)

[0064] In a configuration in which the first-subgroup G1B includes the cemented lens, it is more preferable that the imaging lens simultaneously satisfy conditional expressions (5), (6), and (7). In order to obtain better characteristics, it is even more preferable that the imaging lens simultaneously satisfy conditional expressions (5), (6), and (7), and also satisfy at least one of conditional expressions (5-1), (5-2), (6-1), (6-2), (7-1), and (7-2).

[0065] If the focal length of the imaging lens when focused on an object at infinity is f and the focal length of the first-subgroup G1B is f1B, it is preferable that the imaging lens satisfy the following conditional expression (8). By ensuring that the corresponding value of conditional expression (8) is not below the lower limit, the height of light rays passing through lenses on the image side of the first-subgroup G1B can be made lower, which is advantageous for reducing the diameter of lenses on the image side of the first-subgroup G1B. By ensuring that the corresponding value of conditional expression (8) is not above the upper limit, the refractive power of the first-subgroup G1B does not become too strong, which is advantageous for correcting spherical aberration. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (8-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (8-2). 0 <f / f1B<4 (8) 0.3 <f / f1B<3 (8-1) 0.6 <f / f1B<2 (8-2)

[0066] When the minimum value of the Abbe numbers based on the d-line of all the positive lenses in the second lens group G2 is ν2min, it is preferable that the imaging lens satisfy the following conditional expression (9). Satisfying conditional expression (9) is advantageous for suppressing fluctuations in chromatic aberration that accompany fluctuations in object distance. In order to obtain even better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (9-1), and it is even more preferable that it satisfy the following conditional expression (9-2). 10<ν2min<22 (9) 10<ν2min<20 (9-1) 10<ν2min<17 (9-2)

[0067] If the lateral magnification of the second lens group G2 when focused on an object at infinity is β2i and the combined lateral magnification of all lenses located closer to the image side than the second lens group G2 when focused on an object at infinity is βri, it is preferable that the imaging lens satisfy the following conditional expression (10). However, if no lens is located closer to the image side than the second lens group G2, βri = 1. By ensuring that the corresponding value of conditional expression (10) is not equal to or less than the lower limit, it is possible to avoid stricter stopping accuracy of the focus group during focusing. By ensuring that the corresponding value of conditional expression (10) is not equal to or greater than the upper limit, it is possible to reduce the amount of movement of the focus group during focusing, which is advantageous for shortening the overall length of the lens system. To obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (10-1), and it is even more preferable that it satisfy the following conditional expression (10-2). -6<(1-β2i 2 )×βri 2 <-2 (10) -5.5<(1-β2i 2 )×βri 2 <-2.4 (10-1) -5<(1-β2i 2 )×βri 2 <-2.8 (10-2)

[0068] When an imaging lens is configured to include, in order from the object side to the image side, a first lens group G1, a second lens group G2, and a third lens group G3 that is fixed relative to the image plane Sim during focusing, it is preferable that the imaging lens satisfy the following conditional expression (11). Here, the focal length of the imaging lens when focused on an object at infinity is f, and the focal length of the third lens group G3 is f3. By ensuring that the corresponding value of conditional expression (11) is not below the lower limit, the negative refractive power of the third lens group G3 does not become too strong, thereby preventing the angle of incidence of the chief ray of the off-axis light beam onto the image plane Sim from becoming large. By ensuring that the corresponding value of conditional expression (11) is not above the upper limit, the positive refractive power of the third lens group G3 does not become too strong, thereby preventing the curvature of field from becoming large. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (11-1), and even more preferable that the imaging lens satisfy the following conditional expression (11-2). -0.3 <f / f3<0.8 (11) -0.2 <f / f3<0.7 (11-1) -0.1 <f / f3<0.65 (11-2)

[0069] With regard to the paraxial exit pupil position, it is preferable that the imaging lens satisfy the following conditional expression (12): Here, Expm is defined as the sum of the on-optical axial distance from the paraxial exit pupil position Pexpm to the lens surface of the imaging lens closest to the image side when focused on a closest object, and the on-optical axial air-equivalent distance from the lens surface of the imaging lens closest to the image side to the image plane Sim when focused on an object at infinity. Also, Expi is defined as the sum of the on-optical axial distance from the paraxial exit pupil position Pexpi to the lens surface of the imaging lens closest to the image side when focused on an object at infinity, and the on-optical axial air-equivalent distance from the lens surface of the imaging lens closest to the image side to the image plane Sim when focused on an object at infinity. As an example, FIG. 2 shows the paraxial exit pupil position Pexpi when focused on an object at infinity, and the paraxial exit pupil position Pexpm when focused on a closest object. By ensuring that the corresponding value of conditional expression (12) is not equal to or greater than the lower limit, it is possible to prevent the angle of incidence of the chief ray of the off-axial light beam on the image plane Sim when focused on the closest object from becoming too large. By ensuring that the corresponding value of conditional expression (12) is not equal to or greater than the upper limit, it is possible to change the height of the light ray on the lens surface closest to the image between when focused on an object at infinity and when focused on the closest object, which is advantageous for correcting field curvature for each object distance. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (12-1), and it is even more preferable that it satisfy the following conditional expression (12-2). 0.35 <Expm / Expi<1 (12) 0.4 <Expm / Expi<0.9 (12-1) 0.45 <Expm / Expi<0.8 (12-2)

[0070] If the focal length of the imaging lens when focused on an object at infinity is f and the focal length of the first lens group G1 is f1, it is preferable that the imaging lens satisfy the following conditional expression (13). By ensuring that the corresponding value of conditional expression (13) is not below the lower limit, the height of light rays passing through lenses on the image side of the first lens group G1 can be made lower, which is advantageous for reducing the diameter of lenses on the image side of the first lens group G1. By ensuring that the corresponding value of conditional expression (13) is not above the upper limit, the refractive power of the first lens group G1 does not become too strong, which is advantageous for correcting spherical aberration. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (13-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (13-2). 0.2 <f / f1<4 (13) 0.4 <f / f1<3 (13-1) 0.6 <f / f1<2.5 (13-2)

[0071] If the paraxial radius of curvature of the surface closest to the object in the lens component closest to the object in the imaging lens is R1f and the paraxial radius of curvature of the surface closest to the image in the lens component closest to the object in the imaging lens is R1r, it is preferable that the imaging lens satisfy the following conditional expression (14). Ensuring that the corresponding value of conditional expression (14) is not equal to or smaller than the lower limit is advantageous for correcting field curvature. Ensuring that the corresponding value of conditional expression (14) is not equal to or larger than the upper limit is advantageous for correcting distortion. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (14-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (14-2). 0<(R1f+R1r) / (R1f-R1r)<3 (14) 0.5<(R1f+R1r) / (R1f-R1r)<2.5 (14-1) 1<(R1f+R1r) / (R1f-R1r)<2.2 (14-2)

[0072] It is preferable that the imaging lens satisfy the following conditional expression (15). Here, Bf is the air-equivalent distance on the optical axis from the lens surface closest to the image side of the imaging lens to the image plane Sim when focused on an object at infinity. That is, Bf is the back focus in air-equivalent distance when focused on an object at infinity. f is the focal length of the imaging lens when focused on an object at infinity, and ωi is the maximum half angle of view when focused on an object at infinity. tan is the tangent. Ensuring that the corresponding value of conditional expression (15) is not equal to or less than the lower limit is advantageous for ensuring the back focus. Ensuring that the corresponding value of conditional expression (15) is not equal to or greater than the upper limit is advantageous for shortening the overall length of the lens system. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (15-1), and it is even more preferable for the imaging lens to satisfy the following conditional expression (15-2). 0.3 <Bf / (f×tanωi)<4 (15) 0.5 <Bf / (f×tanωi)<3.5 (15-1) 1 <Bf / (f×tanωi)<3 (15-2)

[0073] In a configuration in which the second lens group G2 includes a cemented lens consisting of one positive lens and one negative lens, it is preferable that the imaging lens satisfy the following conditional expression (16). Here, the refractive index for the d-line of the positive lens in the cemented lens of the second lens group G2 is N2p, and the refractive index for the d-line of the negative lens in the cemented lens of the second lens group G2 is N2n. Satisfying conditional expression (16) is advantageous for suppressing fluctuations in chromatic aberration that accompany fluctuations in object distance. In order to obtain even better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (16-1), and it is even more preferable that it satisfy the following conditional expression (16-2). -0.6 <N2p-N2n<-0.1 (16) -0.5 <N2p-N2n<-0.15 (16-1) -0.45 <N2p-N2n<-0.2 (16-2)

[0074] In a configuration in which the second lens group G2 includes the above-mentioned cemented lens, it is preferable that the imaging lens satisfy the following conditional expression (17). Here, the Abbe number based on the d-line of the positive lens in the cemented lens of the second lens group G2 is v2p, and the Abbe number based on the d-line of the negative lens in the cemented lens of the second lens group G2 is v2n. Satisfying conditional expression (17) is advantageous for suppressing fluctuations in chromatic aberration that accompany fluctuations in object distance. In order to obtain even better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (17-1), and it is even more preferable that it satisfy the following conditional expression (17-2). -20<ν2p-ν2n<50 (17) -15<ν2p-ν2n<40 (17-1) -10<ν2p-ν2n<30 (17-2)

[0075] In a configuration in which the second lens group G2 includes the above-mentioned cemented lens, it is preferable that the imaging lens satisfy the following conditional expression (18). Here, the partial dispersion ratio between the g-line and the F-line of the positive lens in the cemented lens of the second lens group G2 is θ2p, and the partial dispersion ratio between the g-line and the F-line of the negative lens in the cemented lens of the second lens group G2 is θ2n. Satisfying conditional expression (18) is advantageous for suppressing fluctuations in chromatic aberration that accompany fluctuations in object distance. In order to obtain even better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (18-1), and it is even more preferable that it satisfy the following conditional expression (18-2). -0.3<θ2p-θ2n<0.15 (18) -0.15<θ2p-θ2n<0.1 (18-1) -0.05<θ2p-θ2n<0.03 (18-2)

[0076] In a configuration in which the second lens group G2 includes the above cemented lens, it is more preferable that the imaging lens simultaneously satisfy conditional expressions (16), (17), and (18). In order to obtain better characteristics, it is even more preferable that the imaging lens simultaneously satisfy conditional expressions (16), (17), and (18), and also satisfy at least one of conditional expressions (16-1), (16-2), (17-1), (17-2), (18-1), and (18-2).

[0077] In a configuration in which the second lens group G2 includes the cemented lens, when the refractive index at the d-line of the negative lens in the cemented lens of the second lens group G2 is N2n, it is preferable that the imaging lens satisfy the following conditional expression (19): Ensuring that the corresponding value of conditional expression (19) does not become equal to or less than the lower limit thereof is advantageous for correcting curvature of field. In general, as the refractive index of optical materials for lenses increases, the Abbe number decreases. Therefore, ensuring that the corresponding value of conditional expression (19) does not become equal to or greater than the upper limit thereof is advantageous for suppressing fluctuations in chromatic aberration that accompany fluctuations in object distance. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (19-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (19-2): 1.75 <N2n<2.2 (19) 1.8 <N2n<2.2 (19-1) 1.85 <N2n<2.2 (19-2)

[0078] In a configuration in which the second lens group G2 includes the above-mentioned cemented lens, when the Abbe number based on the d-line of the negative lens in the above-mentioned cemented lens in the second lens group G2 is v2n, it is preferable that the imaging lens satisfy the following conditional expression (20). Satisfying conditional expression (20) is advantageous for suppressing fluctuations in chromatic aberration that accompany fluctuations in object distance. In order to obtain even better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (20-1), and it is even more preferable that it satisfy the following conditional expression (20-2). 20<ν2n<40 (20) 30<ν2n<40 (20-1) 35<ν2n<40 (20-2)

[0079] In a configuration in which the second lens group G2 includes the above cemented lens, it is more preferable that the imaging lens simultaneously satisfy conditional expressions (19) and (20). In order to obtain better characteristics, it is even more preferable that the imaging lens simultaneously satisfy conditional expressions (19) and (20), and also satisfy at least one of conditional expressions (19-1), (19-2), (20-1), and (20-2).

[0080] When the paraxial radius of curvature of the surface nearest to the object of the lens component nearest to the image in the third lens group G3 is R3f and the paraxial radius of curvature of the surface nearest to the image of the lens component nearest to the image in the third lens group G3 is R3r, it is preferable that the imaging lens satisfy the following conditional expression (21). Ensuring that the corresponding value of conditional expression (21) is not equal to or less than the lower limit thereof is advantageous for suppressing ghosting and the like and obtaining clear images under backlit shooting conditions. Ensuring that the corresponding value of conditional expression (21) is not equal to or greater than the upper limit thereof is advantageous for correcting field curvature. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (21-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (21-2). 0<(R3f+R3r) / (R3f-R3r)<2 (21) 0.3<(R3f+R3r) / (R3f-R3r)<1.5 (21-1) 0.6<(R3f+R3r) / (R3f-R3r)<1.4 (21-2)

[0081] If the amount of movement of the second lens group G2 when focusing from an object at infinity to the closest object is M2 and the focal length of the imaging lens when focused on an object at infinity is f, it is preferable that the imaging lens satisfy the following conditional expression (22). As an example, FIG. 2 shows the above-mentioned amount of movement M2. By ensuring that the corresponding value of conditional expression (22) is not equal to or less than the lower limit, it is possible to prevent the stopping accuracy of the focus group during focusing from becoming too strict. By ensuring that the corresponding value of conditional expression (22) is not equal to or greater than the upper limit, it is possible to reduce the amount of movement of the focus group during focusing, which is advantageous for shortening the overall length of the lens system. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (22-1), and it is even more preferable that it satisfy the following conditional expression (22-2). 0.05 <M2 / f<0.5 (22) 0.1 <M2 / f<0.4 (22-1) 0.15 <M2 / f<0.35 (22-2)

[0082] It is preferable that the imaging lens satisfy the following conditional expression (23). Here, D1St is the distance on the optical axis from the lens surface of the imaging lens closest to the object to the aperture stop St. Also, TL is the sum of the distance on the optical axis from the lens surface of the imaging lens closest to the object to the lens surface of the imaging lens closest to the image and the air-equivalent distance on the optical axis from the lens surface of the imaging lens closest to the image to the image plane Sim. Ensuring that the value corresponding to conditional expression (23) is not equal to or smaller than the lower limit is advantageous for aberration correction. Ensuring that the value corresponding to conditional expression (23) is not equal to or larger than the upper limit is advantageous for reducing the diameter of the first lens group G1. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (23-1), and it is even more preferable that it satisfy the following conditional expression (23-2). 0 <D1St / TL<0.4 (23) 0.05 <D1St / TL<0.3 (23-1) 0.1 <D1St / TL<0.25 (23-2)

[0083] If the focal length of the imaging lens when focused on an object at infinity is f and the focal length of the firstA group G1A is f1A, it is preferable that the imaging lens satisfy the following conditional expression (24). Ensuring that the corresponding value of conditional expression (24) is not below the lower limit is advantageous for making the diameter of the aperture stop St small. Ensuring that the corresponding value of conditional expression (24) is not above the upper limit is advantageous for correcting distortion and field curvature. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (24-1), and it is even more preferable that it satisfy the following conditional expression (24-2). -1 <f / f1A<0 (24) -0.9 <f / f1A<-0.1 (24-1) -0.8 <f / f1A<-0.2 (24-2)

[0084] It is preferable that the imaging lens satisfy the following conditional expression (25). Here, M2 is the amount of movement of the second lens group G2 when focusing from an object at infinity to the closest object. TL is the sum of the axial distance from the lens surface of the imaging lens closest to the object to the lens surface of the imaging lens closest to the image and the air-equivalent distance on the optical axis from the lens surface of the imaging lens closest to the image to the image plane Sim. By ensuring that the value corresponding to conditional expression (25) is not equal to or less than the lower limit, it is possible to prevent the stopping accuracy of the focus group during focusing from becoming too strict. By ensuring that the value corresponding to conditional expression (25) is not equal to or greater than the upper limit, it is possible to reduce the amount of movement of the focus group during focusing, which is advantageous for shortening the overall length of the lens system. To obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (25-1), and even more preferable that it satisfy the following conditional expression (25-2). 0.03 <M2 / TL<0.3 (25) 0.04 <M2 / TL<0.2 (25-1) 0.05 <M2 / TL<0.15 (25-2)

[0085] If the paraxial radius of curvature of the lens surface in the second lens group G2 closest to the object is R2f and the paraxial radius of curvature of the lens surface in the second lens group G2 closest to the image is R2r, it is preferable that the imaging lens satisfy the following conditional expression (26). Ensuring that the corresponding value of conditional expression (26) is not equal to or smaller than the lower limit is advantageous for correcting field curvature. Ensuring that the corresponding value of conditional expression (26) is not equal to or larger than the upper limit is advantageous for correcting spherical aberration. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (26-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (26-2). 0<(R2f-R2r) / (R2f+R2r)<3 (26) 0.3<(R2f-R2r) / (R2f+R2r)<2 (26-1) 0.6<(R2f-R2r) / (R2f+R2r)<1.5 (26-2)

[0086] If the focal length of the imaging lens when focused on an object at infinity is f and the focal length of the second lens group G2 is f2, it is preferable that the imaging lens satisfy the following conditional expression (27). By ensuring that the corresponding value of conditional expression (27) is not equal to or less than the lower limit, it is possible to prevent the stopping accuracy of the focus group during focusing from becoming too strict. By ensuring that the corresponding value of conditional expression (27) is not equal to or greater than the upper limit, it is possible to reduce the amount of movement of the focus group during focusing, which is advantageous for shortening the overall length of the lens system. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (27-1), and it is even more preferable that it satisfy the following conditional expression (27-2). -2.5 <f / f2<0 (27) -2 <f / f2<-0.5 (27-1) -1.8 <f / f2<-0.8 (27-2)

[0087] If the focal length of the first lens group G1 is f1 and the focal length of the second lens group G2 is f2, it is preferable that the imaging lens satisfy the following conditional expression (28). By ensuring that the corresponding value of conditional expression (28) is not below the lower limit, it is possible to prevent the stopping accuracy of the focus group during focusing from becoming too strict. By ensuring that the corresponding value of conditional expression (28) is not above the upper limit, it is possible to reduce the amount of movement of the focus group during focusing, which is advantageous for shortening the overall length of the lens system. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (28-1), and it is even more preferable that it satisfy the following conditional expression (28-2). -1.5 <f1 / f2<0 (28) -1.2 <f1 / f2<-0.2 (28-1) -1 <f1 / f2<-0.4 (28-2)

[0088] When an imaging lens is configured to include, in order from the object side to the image side, a first lens group G1, a second lens group G2, and a third lens group G3 that is fixed relative to the image plane Sim during focusing, it is preferable that the imaging lens satisfy the following conditional expression (29). Here, the focal length of the first lens group G1 is f1, and the focal length of the third lens group G3 is f3. By ensuring that the corresponding value of conditional expression (29) is not below the lower limit, the negative refractive power of the third lens group G3 does not become too strong, thereby preventing the angle of incidence of the chief ray of the off-axis light beam onto the image plane Sim from becoming large. By ensuring that the corresponding value of conditional expression (29) is not above the upper limit, the positive refractive power of the third lens group G3 does not become too strong, thereby preventing the curvature of field from becoming large. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (29-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (29-2). -1 <f1 / f3<2 (29) -0.5 <f1 / f3<1.5 (29-1) -0.1 <f1 / f3<1 (29-2)

[0089] When the imaging lens is configured to include, in order from the object side to the image side, a first lens group G1, a second lens group G2, and the third lens group G3, it is preferable that the imaging lens satisfy the following conditional expression (30). Here, the focal length of the second lens group G2 is f2, and the focal length of the third lens group G3 is f3. By ensuring that the corresponding value of conditional expression (30) is not below the lower limit, the negative refractive power of the third lens group G3 does not become too strong, thereby preventing the angle of incidence of the chief ray of the off-axis light beam onto the image plane Sim from becoming large. By ensuring that the corresponding value of conditional expression (30) is not above the upper limit, the positive refractive power of the third lens group G3 does not become too strong, thereby preventing the curvature of field from becoming large. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (30-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (30-2). -0.5 <f2 / f3<0.5 (30) -0.45 <f2 / f3<0.3 (30-1) -0.4 <f2 / f3<0.1 (30-2)

[0090] If the minimum value of the Z coefficient of all lenses in the second lens group G2 is Z2min, it is preferable that the imaging lens satisfy the following conditional expression (31). Ensuring that the corresponding value of conditional expression (31) is not equal to or smaller than the lower limit thereof is advantageous for improving the workability of the lens. Ensuring that the corresponding value of conditional expression (31) is not equal to or larger than the upper limit thereof is advantageous for correcting field curvature. In order to obtain even better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (31-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (31-2). 0.035 <Z2min<0.13 (31) 0.04 <Z2min<0.1 (31-1) 0.045 <Z2min<0.09 (31-2)

[0091] The Z coefficient of a lens is defined by the following equation, where EDf is the effective diameter of the object-side surface of the lens, EDr is the effective diameter of the image-side surface of the lens, Rf is the paraxial radius of curvature of the object-side surface of the lens, and Rr is the paraxial radius of curvature of the image-side surface of the lens. Z factor = (1 / 4) × |EDf / Rf - EDr / Rr|

[0092] In this specification, the "effective diameter" of a lens surface is defined as twice the distance from the point of intersection of the outermost ray and the lens surface, among the rays that enter the lens surface from the object side and exit to the image side, to the optical axis Z. Here, "outside" refers to the radially outward direction centered on the optical axis Z, i.e., the side away from the optical axis Z. The "outside ray" is determined taking into account the full focusing state.

[0093] For explanatory purposes, FIG. 3 shows an example of the effective diameter ED. In FIG. 3, the left side is the object side and the right side is the image side. FIG. 3 also shows an on-axis ray Xa and an off-axis ray Xb passing through the lens Lx. In the example of FIG. 3, ray Xb1, which is the upper ray of the off-axis ray Xb, is the outermost ray. Therefore, in the example of FIG. 3, the effective diameter ED of the object-side surface of the lens Lx is twice the distance from the intersection of the object-side surface of the lens Lx and ray Xb1 to the optical axis Z. Note that in FIG. 3, the upper ray of the off-axis ray Xb is the outermost ray, but which ray is the outermost ray varies depending on the optical system.

[0094] If the lateral magnification of the second lens group G2 when focused on the closest object is β2m and the combined lateral magnification of all lenses located closer to the image side than the second lens group G2 when focused on the closest object is βrm, it is preferable that the imaging lens satisfy the following conditional expression (32). However, if no lens is located closer to the image side than the second lens group G2, βrm = 1. By ensuring that the corresponding value of conditional expression (32) is not equal to or less than the lower limit, it is possible to avoid stricter stopping accuracy of the focus group during focusing. By ensuring that the corresponding value of conditional expression (32) is not equal to or greater than the upper limit, it is possible to reduce the amount of movement of the focus group during focusing, which is advantageous for reducing the overall length of the lens system. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (32-1), and it is even more preferable that it satisfy the following conditional expression (32-2). -5<(1-β2m 2 )×βrm 2 <-1 (32) -4.5<(1-β2m 2 )×βrm 2 <-1.5 (32-1) -4<(1-β2m 2 )×βrm 2 <-2 (32-2)

[0095] In a configuration where an imaging lens includes, in order from the object side to the image side, a first lens group G1, a second lens group G2, and a third lens group G3 that is fixed with respect to an image plane Sim during focusing, it is preferable that the imaging lens satisfies the following conditional expression (33). Here, the effective diameter on the most object-side lens surface of the third lens group G3 in a state of focusing on the closest object is defined as ED3m. Also, the effective diameter on the most object-side lens surface of the third lens group G3 in a state of focusing on an infinite object is defined as ED3i. By preventing the corresponding value of the conditional expression (33) from falling below the lower limit, it is possible to suppress an increase in the incident angle of the chief ray of the off-axis light beam onto the image plane Sim in a state of focusing on the closest object. By preventing the corresponding value of the conditional expression (33) from exceeding the upper limit, it is advantageous for correcting the curvature of the image plane for each object distance. In order to obtain better characteristics, it is more preferable that the imaging lens satisfies the following conditional expression (33-1), and it is even more preferable that the imaging lens satisfies the following conditional expression (33-2). 0.5 < ED3m / ED3i < 1 (33) 0.6 < ED3m / ED3i < 0.9 (33-1) 0.7 < ED3m / ED3i < 0.85 (33-2)

[0096] It is preferable that the imaging lens satisfies the following conditional expression (34). Here, the minimum air gap on the optical axis within the second lens group G2 is defined as D2min. Also, the sum of the distance on the optical axis from the most object-side lens surface of the imaging lens to the most image-side lens surface of the imaging lens and the air-equivalent distance on the optical axis from the most image-side lens surface of the imaging lens to the image plane Sim is defined as TL. Since D2min is an air gap and TL is a distance, for the lower limit of the conditional expression (34), 0 < D2min / TL holds. By preventing the corresponding value of the conditional expression (34) from exceeding the upper limit, it is advantageous for miniaturization. In order to obtain better characteristics, it is more preferable that the imaging lens satisfies the following conditional expression (34-1), and it is even more preferable that the imaging lens satisfies the following conditional expression (34-2). 0 < D2min / TL < 0.05 (34) 0 < D2min / TL < 0.03 (34-1) 0 <D2min / TL<0.015 (34-2)

[0097] When the imaging lens is configured to include, in order from the object side to the image side, a first lens group G1, a second lens group G2, and the third lens group G3, and the third lens group G3 includes a cemented lens consisting of one positive lens and one negative lens, it is preferable that the imaging lens satisfy the following conditional expression (35). Here, the refractive index for the d-line of the positive lens in the cemented lens of the third lens group G3 is N3p, and the refractive index for the d-line of the negative lens in the cemented lens of the third lens group G3 is N3n. Satisfying conditional expression (35) is advantageous for correcting lateral chromatic aberration. To obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (35-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (35-2). -0.7 <N3p-N3n<0 (35) -0.6 <N3p-N3n<-0.2 (35-1) -0.5 <N3p-N3n<-0.4 (35-2)

[0098] When the imaging lens is composed of, in order from the object side to the image side, a first lens group G1, a second lens group G2, and the third lens group G3, and the third lens group G3 includes the cemented lens, it is preferable that the imaging lens satisfy the following conditional expression (36). Here, the Abbe number based on the d-line of the positive lens in the cemented lens of the third lens group G3 is v3p, and the Abbe number based on the d-line of the negative lens in the cemented lens of the third lens group G3 is v3n. Satisfying conditional expression (36) is advantageous for correction of lateral chromatic aberration. To obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (36-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (36-2). 5<ν3p-ν3n<80 (36) 10<ν3p-ν3n<75 (36-1) 15<ν3p-ν3n<70 (36-2)

[0099] When the imaging lens is composed of, in order from the object side to the image side, a first lens group G1, a second lens group G2, and the third lens group G3, and the third lens group G3 includes the cemented lens, it is preferable that the imaging lens satisfy the following conditional expression (37). Here, the partial dispersion ratio between the g-line and the F-line of the positive lens in the cemented lens of the third lens group G3 is θ3p, and the partial dispersion ratio between the g-line and the F-line of the negative lens in the cemented lens of the third lens group G3 is θ3n. Satisfying conditional expression (37) is advantageous for correcting lateral chromatic aberration. To obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (37-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (37-2). -0.2<θ3p-θ3n<0 (37) -0.17<θ3p-θ3n<-0.01 (37-1) -0.15<θ3p-θ3n<-0.03 (37-2)

[0100] In a configuration in which the imaging lens is composed of, in order from the object side to the image side, a first lens group G1, a second lens group G2, and the third lens group G3, and the third lens group G3 includes the cemented lens, it is more preferable that the imaging lens simultaneously satisfy conditional expressions (35), (36), and (37). In order to obtain better characteristics, it is even more preferable that the imaging lens simultaneously satisfy conditional expressions (35), (36), and (37), and furthermore satisfy at least one of conditional expressions (35-1), (35-2), (36-1), (36-2), (37-1), and (37-2).

[0101] When the imaging lens is configured to include, in order from the object side to the image side, a first lens group G1, a second lens group G2, and the third lens group G3, and the third lens group G3 includes the cemented lens, it is preferable that the imaging lens satisfy the following conditional expression (38). Here, the refractive index of the positive lens of the cemented lens in the third lens group G3 at the d-line is set to N3p. By ensuring that the corresponding value of conditional expression (38) is not below the lower limit, the refractive index does not become too low, and the absolute value of the radius of curvature does not become too small, thereby suppressing sensitivity to errors. Generally, the Abbe number of optical materials for lenses decreases as the refractive index increases. Therefore, ensuring that the corresponding value of conditional expression (38) is not above the upper limit is advantageous for correcting lateral chromatic aberration. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (38-1), and even more preferable that the following conditional expression (38-2) is satisfied. 1.3 <N3p<1.7 (38) 1.3 <N3p<1.6 (38-1) 1.4 <N3p<1.55 (38-2)

[0102] In a configuration in which the first-subgroup G1B includes a cemented lens, when the paraxial radius of curvature of the surface of the cemented lens in the first-subgroup G1B closest to the object is R1Bf and the paraxial radius of curvature of the surface of the cemented lens in the first-subgroup G1B closest to the image is R1Br, it is preferable that the imaging lens satisfy the following conditional expression (39). Ensuring that the corresponding value of conditional expression (39) is not equal to or smaller than the lower limit is advantageous for correction of field curvature. Ensuring that the corresponding value of conditional expression (39) is not equal to or larger than the upper limit is advantageous for correction of spherical aberration. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (39-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (39-2). -20<(R1Bf+R1Br) / (R1Bf-R1Br)<0 (39) -15<(R1Bf+R1Br) / (R1Bf-R1Br)<-1 (39-1) -10<(R1Bf+R1Br) / (R1Bf-R1Br)<-2 (39-2)

[0103] In a configuration in which the first A group G1A includes a cemented lens consisting of one negative lens and one positive lens, it is preferable that the imaging lens satisfy the following conditional expression (40). Here, the refractive index for the d-line of the positive lens in the cemented lens in the first A group G1A is N1Ap, and the refractive index for the d-line of the negative lens in the cemented lens in the first A group G1A is N1An. Satisfying conditional expression (40) is advantageous for correcting axial chromatic aberration. In order to obtain even better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (40-1), and it is even more preferable that it satisfy the following conditional expression (40-2). 0 <N1Ap-N1An<0.5 (40) 0.1 <N1Ap-N1An<0.3 (40-1) 0.12 <N1Ap-N1An<0.17 (40-2)

[0104] In a configuration in which the first A group G1A includes a cemented lens consisting of one negative lens and one positive lens, it is preferable that the imaging lens satisfy the following conditional expression (41). Here, the Abbe number based on the d-line of the positive lens in the cemented lens in the first A group G1A is v1Ap, and the Abbe number based on the d-line of the negative lens in the cemented lens in the first A group G1A is v1An. Satisfying conditional expression (41) is advantageous for correcting axial chromatic aberration. In order to obtain even better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (41-1), and it is even more preferable that it satisfy the following conditional expression (41-2). -50<ν1Ap-ν1An<0 (41) -40<ν1Ap-ν1An<-10 (41-1) -35<ν1Ap-ν1An<-20 (41-2)

[0105] In a configuration in which the first A group G1A includes a cemented lens consisting of one negative lens and one positive lens, it is preferable that the imaging lens satisfy the following conditional expression (42). Here, the partial dispersion ratio between the g-line and the F-line of the positive lens in the cemented lens in the first A group G1A is θ1Ap, and the partial dispersion ratio between the g-line and the F-line of the negative lens in the cemented lens in the first A group G1A is θ1An. Satisfying conditional expression (42) is advantageous for correcting axial chromatic aberration. In order to obtain even better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (42-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (42-2). 0<θ1Ap-θ1An<0.1 (42) 0.02<θ1Ap-θ1An<0.08 (42-1) 0.04<θ1Ap-θ1An<0.07 (42-2)

[0106] In a configuration in which the firstA group G1A includes a cemented lens consisting of one negative lens and one positive lens, it is more preferable that the imaging lens simultaneously satisfy conditional expressions (40), (41), and (42). In order to obtain even better characteristics, it is even more preferable that the imaging lens simultaneously satisfy conditional expressions (40), (41), and (42), and also satisfy at least one of conditional expressions (40-1), (40-2), (41-1), (41-2), (42-1), and (42-2).

[0107] The first-subgroup G1B may be configured to include two or more lens components. In a configuration in which the first-subgroup G1B includes two or more lens components and a single lens having positive refractive power is disposed closest to the object in the first-subgroup G1B, it is preferable that the imaging lens satisfy the following conditional expression (43). Here, the paraxial radius of curvature of the image-side surface of the single lens having positive refractive power closest to the object in the first-subgroup G1B is defined as R1Baf. Also, the paraxial radius of curvature of the object-side surface of the lens component disposed adjacent to the image side of the single lens having positive refractive power closest to the object in the first-subgroup G1B is defined as R1Bar. In the example of FIG. 1, the single lens having positive refractive power closest to the object in the first-subgroup G1B corresponds to lens L14, and the lens component disposed adjacent to the image side of the single lens having positive refractive power closest to the object in the first-subgroup G1B corresponds to a cemented lens formed by cementing lenses L15 and L16. In the example of Figure 1, conditional expression (43) is an expression for the shape factor of the air lens formed by the air gap between the image-side surface of lens L14 and the object-side surface of lens L15. Satisfying conditional expression (43) is advantageous for correcting spherical aberration. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (43-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (43-2): -0.3<(R1Baf-R1Bar) / (R1Baf+R1Bar)<0.6 (43) -0.2<(R1Baf-R1Bar) / (R1Baf+R1Bar)<0.5 (43-1) -0.1<(R1Baf-R1Bar) / (R1Baf+R1Bar)<0.4 (43-2)

[0108] The second lens group G2 may be configured to include two or more lens components. In a configuration in which the second lens group G2 includes two or more lens components and a single lens having positive refractive power is disposed closest to the object in the second lens group G2, it is preferable that the imaging lens satisfy the following conditional expression (44). Here, the paraxial radius of curvature of the image-side surface of the single lens having positive refractive power closest to the object in the second lens group G2 is defined as R2af. Also, the paraxial radius of curvature of the object-side surface of the lens component disposed adjacent to the image side of the single lens having positive refractive power closest to the object in the second lens group G2 is defined as R2ar. In the example of FIG. 1, the single lens having positive refractive power closest to the object in the second lens group G2 corresponds to lens L21, and the lens component disposed adjacent to the image side of the single lens having positive refractive power closest to the object in the second lens group G2 corresponds to a cemented lens formed by cementing lenses L22 and L23. In the example of Figure 1, conditional expression (44) is an expression for the shape factor of the air lens formed by the air gap between the image-side surface of lens L21 and the object-side surface of lens L22. Satisfying conditional expression (44) is advantageous for correcting spherical aberration. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (44-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (44-2): -0.4<(R2af-R2ar) / (R2af+R2ar)<0.4 (44) -0.3<(R2af-R2ar) / (R2af+R2ar)<0.3 (44-1) -0.2<(R2af-R2ar) / (R2af+R2ar)<0.2 (44-2)

[0109] The imaging lens preferably satisfies the following conditional expression (45). Here, the minimum air interval on the optical axis within the first B group G1B is defined as D1Bmin. Also, the sum of the distance on the optical axis from the most object-side lens surface of the imaging lens to the most image-side lens surface of the imaging lens and the air-equivalent distance on the optical axis from the most image-side lens surface of the imaging lens to the image plane Sim is defined as TL. Since D1Bmin is an air interval and TL is a distance, for the lower limit of the conditional expression (45), 0 < D1Bmin / TL holds. By ensuring that the corresponding value of the conditional expression (45) does not exceed the upper limit, it is advantageous for miniaturization. To obtain better characteristics, it is more preferable for the imaging lens to satisfy the following conditional expression (45-1), and even more preferable to satisfy the following conditional expression (45-2). 0 < D1Bmin / TL < 0.05 (45) 0 < D1Bmin / TL < 0.03 (45-1) 0 < D1Bmin / TL < 0.015 (45-2)

[0110] When the maximum image height is Ymax and the focal length of the imaging lens in the state of focusing on an infinite object is f, the imaging lens preferably satisfies the following conditional expression (46). Arctan is the inverse tangent function. By ensuring that the corresponding value of the conditional expression (46) does not fall below the lower limit, the effects of the technology of the present disclosure can be obtained well within the range from a so-called wide-angle lens to a standard lens. By ensuring that the corresponding value of the conditional expression (46) does not exceed the upper limit, it is possible to prevent the angle of view from becoming too wide and making aberration correction difficult. To obtain better characteristics, it is more preferable for the imaging lens to satisfy the following conditional expression (46-1), and even more preferable to satisfy the following conditional expression (46-2). 20 < arctan(Ymax / f) < 60 (46) 22 < arctan(Ymax / f) < 50 (46-1) 25 < arctan(Ymax / f) < 40 (46-2)

[0111] The imaging lens may be configured to have a function for correcting image blur, i.e., an image stabilization function. For example, the imaging lens may be configured to perform image stabilization by moving a portion of the first-A group G1A in a direction intersecting the optical axis Z. Alternatively, the imaging lens may be configured to perform image stabilization by moving a portion of the first-B group G1B in a direction intersecting the optical axis Z. In this specification, a group that moves in a direction intersecting the optical axis Z during image stabilization is referred to as an image stabilization group. If a portion of the first lens group G1 is configured as an image stabilization group, the image stabilization group can be configured using a lens with a relatively small diameter near the aperture stop St, which is advantageous for reducing the size and weight of the image stabilization group. For example, the image stabilization group may be configured to consist of a single lens adjacent to the aperture stop St. This is advantageous for reducing the size and weight of the image stabilization group.

[0112] 1 is merely an example, and various modifications are possible without departing from the spirit of the technology of the present disclosure. For example, the number of lenses included in each lens group may be different from that in the example of FIG.

[0113] The above-described preferred configurations and possible configurations can be arbitrarily combined, and are preferably selectively adopted as appropriate according to the required specifications. Note that the conditional expressions that the imaging lens of the present disclosure preferably satisfies are not limited to conditional expressions written in the form of an equation, but include all conditional expressions obtained by arbitrarily combining lower limits and upper limits from among the conditional expressions that are deemed to be preferred, more preferred, even more preferred, and even more preferred.

[0114] As an example, a preferred embodiment of the imaging lens of the present disclosure includes, in succession from the object side to the image side, a first lens group G1 having positive refractive power and a second lens group G2 having negative refractive power, wherein during focusing, only the second lens group G2 moves along the optical axis Z, and the first lens group G1 includes, in that order from the object side to the image side, a firstA group G1A, an aperture stop St, and a firstB group G1B, and the second lens group G2 includes at least one positive lens, and satisfies the above conditional expressions (1) and (2).

[0115] Next, examples of the imaging lens of the present disclosure will be described with reference to the drawings. The reference symbols assigned to the lenses in the cross-sectional views of each example are used independently for each example to avoid cluttering the explanation and the drawings due to an increase in the number of digits in the reference symbols. Therefore, even if common reference symbols are assigned in drawings of different examples, this does not necessarily mean that the configuration is the same.

[0116] [Example 1] A cross-sectional view of the configuration of the imaging lens of Example 1 is shown in FIG. 1. The illustration method and configuration are as described above, so some overlapping explanations will be omitted here. The imaging lens of Example 1 comprises, in order from the object side to the image side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power. The first lens group G1 comprises, in order from the object side to the image side, a firstA lens group G1A having negative refractive power, an aperture stop St, and a firstB lens group G1B having positive refractive power. When focusing from an object at infinity to a closest object, the first lens group G1 and the third lens group G3 are fixed with respect to the image plane Sim, and the second lens group G2 moves toward the image side. This concludes the overview of the imaging lens of Example 1.

[0117] For the imaging lens of Example 1, basic lens data is shown in Table 1, specifications and variable surface spacing in Table 2, and aspherical coefficients in Table 3. The table of basic lens data is written as follows: The Sn column shows the surface number, with the surface closest to the object being surface 1 and the numbers increasing by one toward the image side. The R column shows the radius of curvature of each surface. The D column shows the surface spacing on the optical axis between each surface and its adjacent surface on the image side. The Nd column shows the refractive index for the d-line of each component element. The νd column shows the Abbe number of each component element based on the d-line. The θgF column shows the partial dispersion ratio between the g-line and F-line of each component element. The ED column shows the effective diameter of each lens surface.

[0118] In the table of basic lens data, the sign of the radius of curvature of a surface with a convex surface facing the object side is positive, and the sign of the radius of curvature of a surface with a convex surface facing the image side is negative. Table 1 also shows the aperture stop St and optical element PP. The surface number column for the surface corresponding to aperture stop St is entered with the surface number and the phrase (St). The value at the bottom of the surface spacing column in the table is the distance between the surface closest to the image side in the table and the image plane Sim. The symbol DD[ ] is used to indicate variable surface spacing during focusing, and the object-side surface number of this distance is entered in the [ ] in the surface spacing column.

[0119] Table 2 shows the focal length, F-number, maximum full angle of view, maximum image height, and variable surface spacing based on the d-line. The [°] in the maximum full angle of view column indicates that the unit is degrees. In Table 2, the "Infinity" column shows the values ​​when focused on an object at infinity, and the "Closest" column shows the values ​​when focused on the closest object. However, the F-number and maximum image height when focused on the closest object are omitted. In Example 1, the distance on the optical axis from the lens surface closest to the object to the closest object is 18.2 mm (millimeters).

[0120] In the basic lens data, the surface numbers of aspherical surfaces are marked with an *, and the numerical value of the paraxial radius of curvature is entered in the column for the radius of curvature of the aspherical surface. In Table 3, the row Sn shows the surface numbers of aspherical surfaces, and the rows KA and Am show the numerical values ​​of the aspherical coefficients for each aspherical surface. Note that m in Am is an integer of 3 or more, and varies depending on the surface. For example, for the first surface of Example 1, m = 4, 6, 8, ..., 16. The numerical values ​​of the aspherical coefficients in Table 3, "E±n" (n: integer), are expressed as "×10 ±n " KA and Am are aspherical coefficients in the aspherical formula given below. Zd=C×h 2 / {1+(1-KA×C 2 ×h 2 ) 1 / 2}+ΣAm×h m however, Zd: Aspheric depth (length of the perpendicular line drawn from a point on the aspheric surface at height h to a plane perpendicular to the optical axis Z where the vertex of the aspheric surface is in contact) h: Height (distance from optical axis Z to lens surface) C: Reciprocal of paraxial curvature radius KA, Am: aspherical coefficients In the aspherical formula, Σ means the summation over m.

[0121] In the data in each table, degrees are used as the unit of angle and mm (millimeters) as the unit of length, but since the optical system can be used with proportional enlargement or reduction, other appropriate units can also be used. Also, in each table below, values ​​are listed rounded to a certain number of decimal places.

[0122] [Table 1]

[0123] [Table 2]

[0124] [Table 3]

[0125] FIG. 4 shows aberration diagrams of the imaging lens of Example 1. From left to right, FIG. 4 shows spherical aberration, astigmatism, distortion, and lateral chromatic aberration. In FIG. 4, the upper row labeled "Infinity" shows aberration diagrams in a state focused on an object at infinity, while the lower row labeled "Closest" shows aberration diagrams in a state focused on an object at closest range. In the spherical aberration diagrams, aberrations at the d-line, C-line, F-line, and g-line are shown by solid lines, long-dashed lines, short-dashed lines, and dash-dot lines, respectively. In the astigmatism diagrams, aberrations at the d-line in the sagittal direction are shown by solid lines, and aberrations at the d-line in the tangential direction are shown by short-dashed lines. In the distortion diagrams, aberrations at the d-line are shown by solid lines. In the lateral chromatic aberration diagrams, aberrations at the C-line, F-line, and g-line are shown by long-dashed lines, short-dashed lines, and dash-dot lines, respectively. In spherical aberration diagrams, the F-number value is shown after "FNo.=". In other aberration diagrams, the maximum half angle of view is shown after "ω=". The maximum half angle of view shown in the upper row of Figure 4 corresponds to ωi, and the maximum half angle of view shown in the lower row corresponds to ωm.

[0126] The symbols, meanings, notation methods, and illustration methods of each data item related to the above-mentioned Example 1 are basically the same in the following Examples unless otherwise specified, and therefore, redundant explanations will be omitted below.

[0127] [Example 2] FIG. 5 shows a cross-sectional view of the configuration of the imaging lens of Example 2. The imaging lens of Example 2 has a configuration similar to that of the imaging lens of Example 1. The imaging lens of Example 2 has the following configurations: The first A group G1A consists of three lenses, L11 to L13, in order from the object side to the image side. The first B group G1B consists of four lenses, L14 to L17, in order from the object side to the image side. The second lens group G2 consists of three lenses, L21 to L23, in order from the object side to the image side. The third lens group G3 consists of one lens, L31. The imaging lens of Example 2 has an image stabilization group consisting of lens L14. The vertical arrows below lens L14 in FIG. 5 indicate that lens L14 is an image stabilization group. This method of illustrating image stabilization groups is the same in the following examples.

[0128] For the imaging lens of Example 2, basic lens data is shown in Table 4, specifications and variable surface spacing are shown in Table 5, aspherical coefficients are shown in Table 6, and various aberration diagrams are shown in Fig. 6. In Example 2, the distance on the optical axis from the lens surface closest to the object to the closest object is 18.7 mm (millimeters).

[0129] [Table 4]

[0130] [Table 5]

[0131] [Table 6]

[0132] [Example 3] FIG. 7 shows a cross-sectional view of the configuration of the imaging lens of Example 3. The imaging lens of Example 3 has a configuration similar to that of the imaging lens of Example 1, except that the third lens group G3 has negative refractive power. The groups of the imaging lens of Example 3 are configured as follows. The first A group G1A consists of three lenses, L11 to L13, in order from the object side to the image side. The first B group G1B consists of four lenses, L14 to L17, in order from the object side to the image side. The second lens group G2 consists of two lenses, L21 to L22, in order from the object side to the image side. The third lens group G3 consists of two lenses, L31 to L32, in order from the object side to the image side. The imaging lens of Example 3 has an image stabilization group consisting of lens L13.

[0133] For the imaging lens of Example 3, basic lens data is shown in Table 7, specifications and variable surface spacing are shown in Table 8, aspherical coefficients are shown in Table 9, and various aberration diagrams are shown in Fig. 8. In Example 3, the distance on the optical axis from the lens surface closest to the object to the closest object is 18.8 mm (millimeters).

[0134] [Table 7]

[0135] [Table 8]

[0136] [Table 9]

[0137] [Example 4] FIG. 9 shows a cross-sectional view of the configuration of the imaging lens of Example 4. The imaging lens of Example 4 has a configuration similar to that of the imaging lens of Example 1, except that it consists of, in order from the object side to the image side, a first lens group G1 having positive refractive power and a second lens group G2 having negative refractive power. The groups of the imaging lens of Example 4 are configured as follows. The first A group G1A consists of three lenses, lenses L11 to L13, in order from the object side to the image side. The first B group G1B consists of four lenses, lenses L14 to L17, in order from the object side to the image side. The second lens group G2 consists of two lenses, lenses L21 and L22, in order from the object side to the image side. The imaging lens of Example 4 has an image stabilization group consisting of lens L13.

[0138] For the imaging lens of Example 4, basic lens data is shown in Table 10, specifications and variable surface spacing are shown in Table 11, aspherical coefficients are shown in Table 12, and various aberration diagrams are shown in Fig. 10. In Example 4, the distance on the optical axis from the lens surface closest to the object to the closest object is 21.3 mm (millimeters).

[0139] [Table 10]

[0140] [Table 11]

[0141] [Table 12]

[0142] [Example 5] FIG. 11 shows a cross-sectional view of the configuration of the imaging lens of Example 5. The imaging lens of Example 5 has the same general configuration as the imaging lens of Example 1. The imaging lens of Example 5 has the following configurations: 1A group G1A consists of three lenses, L11 to L13, in order from the object side to the image side. 1B group G1B consists of four lenses, L14 to L17, in order from the object side to the image side. 2nd lens group G2 consists of two lenses, L21 to L22, in order from the object side to the image side. 3rd lens group G3 consists of two lenses, L31 to L32, in order from the object side to the image side.

[0143] For the imaging lens of Example 5, basic lens data is shown in Table 13, specifications and variable surface spacing are shown in Table 14, aspherical coefficients are shown in Table 15, and various aberration diagrams are shown in Fig. 12. In Example 5, the distance on the optical axis from the lens surface closest to the object to the closest object is 26.6 mm (millimeters).

[0144] [Table 13]

[0145] [Table 14]

[0146] [Table 15]

[0147] [Example 6] A cross-sectional view of the configuration of the imaging lens of Example 6 is shown in Figure 13. The imaging lens of Example 6 has a configuration similar to that of the imaging lens of Example 1. The groups of the imaging lens of Example 6 are configured as follows. The first A group G1A consists of three lenses, L11 to L13, in order from the object side to the image side. The first B group G1B consists of four lenses, L14 to L17, in order from the object side to the image side. The second lens group G2 consists of three lenses, L21 to L23, in order from the object side to the image side. The third lens group G3 consists of one lens, L31.

[0148] For the imaging lens of Example 6, basic lens data is shown in Table 16, specifications and variable surface spacing are shown in Table 17, aspherical coefficients are shown in Table 18, and various aberration diagrams are shown in Fig. 14. In Example 6, the distance on the optical axis from the lens surface closest to the object to the closest object is 20.9 mm (millimeters).

[0149] [Table 16]

[0150] [Table 17]

[0151] [Table 18]

[0152] [Example 7] FIG. 15 shows a cross-sectional view of the configuration of the imaging lens of Example 7. The imaging lens of Example 7 has the same general configuration as the imaging lens of Example 1. The groups of the imaging lens of Example 7 are configured as follows. The first A group G1A consists of three lenses, lenses L11 to L13, in order from the object side to the image side. The first B group G1B consists of four lenses, lenses L14 to L17, in order from the object side to the image side. The second lens group G2 consists of two lenses, lenses L21 and L22, in order from the object side to the image side. The third lens group G3 consists of one lens, lens L31.

[0153] For the imaging lens of Example 7, basic lens data is shown in Table 19, specifications and variable surface spacing are shown in Table 20, aspherical coefficients are shown in Table 21, and various aberration diagrams are shown in Fig. 16. In Example 7, the distance on the optical axis from the lens surface closest to the object to the closest object is 19.4 mm (millimeters).

[0154] [Table 19]

[0155] [Table 20]

[0156] [Table 21]

[0157] [Example 8] FIG. 17 shows a cross-sectional view of the configuration of the imaging lens of Example 8. The imaging lens of Example 8 has the same general configuration as the imaging lens of Example 1. The groups of the imaging lens of Example 8 are configured as follows. The first A group G1A consists of three lenses, L11 to L13, in order from the object side to the image side. The first B group G1B consists of four lenses, L14 to L17, in order from the object side to the image side. The second lens group G2 consists of three lenses, L21 to L23, in order from the object side to the image side. The third lens group G3 consists of one lens, L31.

[0158] For the imaging lens of Example 8, basic lens data is shown in Table 22, specifications and variable surface spacing are shown in Table 23, aspherical coefficients are shown in Table 24, and various aberration diagrams are shown in Fig. 18. In Example 8, the distance on the optical axis from the lens surface closest to the object to the closest object is 19.0 mm (millimeters).

[0159] [Table 22]

[0160] [Table 23]

[0161] [Table 24]

[0162] Tables 25 to 28 show the corresponding values ​​of conditional formulas (1) to (46) for the imaging lenses of Examples 1 to 8. In Tables 25 to 28, columns with no corresponding lenses are shaded. The corresponding values ​​of the Examples shown in Tables 25 to 28 may be used as the upper or lower limits of the conditional formulas to set preferred ranges for the conditional formulas.

[0163] [Table 25]

[0164] [Table 26]

[0165] [Table 27]

[0166] [Table 28]

[0167] The imaging lenses of Examples 1 to 8 have a maximum imaging magnification of 0.5 or more in absolute value, and the imaging lenses of Examples 1 to 4 and 6 to 8 have a particularly high maximum imaging magnification of 1 in absolute value. Furthermore, the imaging lenses of Examples 1 to 8 are compact, yet maintain high optical performance with various aberrations well corrected both when focused on an object at infinity and when focused on a closest object.

[0168] There is a demand for lens systems with high magnification ratios for use in imaging devices such as digital cameras. Front-focus types are often used in lens systems with high magnification ratios. However, front-focus types tend to have heavy focus groups, which can be disadvantageous when attempting to increase the focus speed. Compared to front-focus types, inner-focus types make it easier to reduce the weight of the focus group, but conventional inner-focus type lens systems have not easily improved optical performance in close-up photography. In contrast, the imaging lenses of Examples 1 to 8 of the present disclosure are inner-focus type lens systems with lightweight focus groups, which achieve a compact configuration, high magnification ratios, and high performance in close-up photography.

[0169] Next, an imaging device according to an embodiment of the present disclosure will be described. Fig. 19 and Fig. 20 show external views of a camera 30, which is an imaging device according to an embodiment of the present disclosure. Fig. 19 shows a perspective view of the camera 30 as seen from the front side, and Fig. 20 shows a perspective view of the camera 30 as seen from the rear side. The camera 30 is a so-called mirrorless digital camera, to which an interchangeable lens 20 can be removably attached. The interchangeable lens 20 is configured to include an imaging lens 1 according to an embodiment of the present disclosure housed in a lens barrel.

[0170] The camera 30 includes a camera body 31, and a shutter button 32 and a power button 33 are provided on the top surface of the camera body 31. An operation unit 34, an operation unit 35, and a display unit 36 ​​are provided on the back surface of the camera body 31. The display unit 36 ​​can display a captured image and an image within the angle of view before the image was captured.

[0171] A photographic opening through which light from the subject to be photographed enters is provided in the center of the front face of the camera body 31, and a mount 37 is provided at a position corresponding to the photographic opening, and an interchangeable lens 20 is attached to the camera body 31 via the mount 37.

[0172] Inside the camera body 31 are provided an imaging element such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) that outputs an imaging signal corresponding to the subject image formed by the interchangeable lens 20, a signal processing circuit that processes the imaging signal output from the imaging element to generate an image, and a recording medium for recording the generated image. With the camera 30, it is possible to take still images or videos by pressing the shutter button 32, and the image data obtained by this shooting is recorded on the recording medium.

[0173] Although the technology of the present disclosure has been described above using embodiments and examples, the technology of the present disclosure is not limited to the above embodiments and examples and can be modified in various ways. For example, the radius of curvature, surface spacing, refractive index, Abbe number, aspherical coefficient, etc. of each lens are not limited to the values ​​shown in the above examples and can take other values.

[0174] Furthermore, the imaging device according to the embodiment of the present disclosure is not limited to the above example, and can take various forms, such as a camera other than a mirrorless type, a film camera, and a video camera. [Explanation of symbols]

[0175] 1 Imaging lens 2i On-axis luminous flux 2m axial luminous flux 3i Maximum half-angle luminous flux 3m Maximum half angle of view 20 Interchangeable Lenses 30 Camera 31 Camera Body 32 Shutter button 33 Power button 34 Control section 35 Control section 36 Display section 37 Mount DMp diameter DMpa diameter ED Effective Diameter G1 First lens group G1A Group 1A G1B Group 1B G2 Second lens group G3 Third lens group L11~L32 lenses Lx Lens M2 Travel amount Pexpi paraxial exit pupil position Pexpm paraxial exit pupil position PP optical components Sim image plane St aperture stop Xa On-axis luminous flux Xb Off-axis luminous flux Xb1 ray Z optical axis ωi Maximum half angle of view ωm Maximum half angle of view

Claims

1. the first lens group having positive refractive power and the second lens group having negative refractive power, During focusing, only the second lens group moves along the optical axis, the first lens group comprises, in order from the object side to the image side, a first-A group, an aperture stop, and a first-B group; the first subgroup B includes a positive lens closest to the image side, the second lens group includes at least one positive lens, Maximum magnification is β, The focal length of the first A group is f1A, The focal length of the first B group is f1B, DMp is the larger of the diameter of the axial light beam when focused on an object at infinity and the diameter of the axial light beam when focused on a closest object, on the object-side surface of the positive lens closest to the image side in the first B group, When the larger of the diameter of an axial light beam when focused on an object at infinity and the diameter of an axial light beam when focused on a closest object is defined as DMpa, on the image-side surface of the lens in the first B group that is adjacent to the object side of the positive lens that is closest to the image, ０．４５＜｜β｜ （１） -15<f1A / f1B<-1.7 (2) 0.5<DMpa / DMp<1 (4) An imaging lens that satisfies conditional expressions (1), (2), and (4) expressed as follows:

2. the first lens group having positive refractive power and the second lens group having negative refractive power, During focusing, only the second lens group moves along the optical axis, the first lens group comprises, in order from the object side to the image side, a first-A group, an aperture stop, and a first-B group; the second lens group includes at least one positive lens, Maximum magnification is β, The focal length of the first A group is f1A, The focal length of the first B group is f1B, The lateral magnification of the second lens group when focused on an object at infinity is β2i, The composite lateral magnification of all lenses on the image side of the second lens group when focused on an object at infinity is βri, If no lens is disposed on the image side of the second lens group, then βri=1, ０．４５＜｜β｜ （１） -15<f1A / f1B<-1.7 (2) -6<(1-β2i 2 )×βri 2 <-2 (10) An imaging lens that satisfies conditional expressions (1), (2), and (10) expressed by the following formulas.

3. the first lens group having positive refractive power and the second lens group having negative refractive power, During focusing, only the second lens group moves along the optical axis, the first lens group comprises, in order from the object side to the image side, a first-A group, an aperture stop, and a first-B group; The second lens group includes a cemented lens consisting of one positive lens and one negative lens, and has a maximum imaging magnification of β, The focal length of the first A group is f1A, The focal length of the first B group is f1B, The refractive index of the positive lens of the cemented lens in the second lens group with respect to the d-line is N2p, The refractive index of the negative lens of the cemented lens in the second lens group with respect to the d-line is N2n, ν2p is the Abbe number of the positive lens of the cemented lens in the second lens group based on the d-line; ν2n is the Abbe number of the negative lens of the cemented lens in the second lens group based on the d-line; The partial dispersion ratio between the g-line and the F-line of the positive lens of the cemented lens in the second lens group is θ2p, When the partial dispersion ratio between the g-line and the F-line of the negative lens of the cemented lens in the second lens group is θ2n, ０．４５＜｜β｜ （１） -15<f1A / f1B<-1.7 (2) -0.6<N2p-N2n<-0.1 (16) -20<ν2p-ν2n<50 (17) -0.3<θ2p-θ2n<0.15 (18) An imaging lens that satisfies conditional expressions (1), (2), (16), (17), and (18) expressed by the following formulas:

4. the first subgroup B includes a positive lens closest to the object, When the Abbe number based on the d-line of the positive lens closest to the object side in the 1B group is ν1Bp1, 60<ν1Bp1<105 (3) 4. The imaging lens according to claim 1, which satisfies conditional expression (3) expressed as follows:

5. the first subgroup B includes a cemented lens composed of one negative lens and one positive lens, The refractive index of the positive lens of the cemented lens in the first B group with respect to the d-line is N1Bp, The refractive index of the negative lens of the cemented lens in the first B group with respect to the d-line is N1Bn, ν1Bp is the Abbe number of the positive lens of the cemented lens in the 1B group based on the d-line; ν1Bn is the Abbe number of the negative lens of the cemented lens in the 1B group based on the d-line; The partial dispersion ratio between the g-line and the F-line of the positive lens of the cemented lens in the first B group is θ1Bp, When the partial dispersion ratio between the g-line and the F-line of the negative lens of the cemented lens in the 1B group is θ1Bn, -0.5<N1Bp-N1Bn<0 (5) 30<ν1Bp−ν1Bn<70 (6) -0.1<θ1Bp-θ1Bn<-0.03 (7) 5. The imaging lens according to claim 1, which satisfies conditional expressions (5), (6), and (7) expressed by the following formulas:

6. When the focal length of the imaging lens is set to f when focused on an object at infinity, 0<f / f1B<4 (8) 6. The imaging lens according to claim 1, which satisfies conditional expression (8) expressed as follows:

7. The imaging lens according to claim 1 , wherein the first A group includes at least one positive lens.

8. When the minimum value of the Abbe numbers of all the positive lenses in the second lens group based on the d-line is ν2min, 10<ν2min<22 (9) 8. The imaging lens according to claim 1, which satisfies conditional expression (9) expressed as follows:

9. 9. The imaging lens according to claim 1, comprising, in order from the object side to the image side, the first lens group, the second lens group, and a third lens group that is fixed with respect to an image plane during focusing.

10. The focal length of the imaging lens when focused on an object at infinity is f, When the focal length of the third lens group is f3, -0.3<f / f3<0.8 (11) 10. The imaging lens according to claim 9, which satisfies conditional expression (11) expressed as follows:

11. When one lens component is a single lens or a cemented lens, 11. The imaging lens according to claim 9, wherein the third lens group is made up of one lens component.

12. Exp is the sum of the distance on the optical axis from the paraxial exit pupil position to the lens surface of the imaging lens closest to the image side when the lens is focused on the closest object, and the air-equivalent distance on the optical axis from the lens surface of the imaging lens closest to the image side to the image plane, When the focus is on an object at infinity, the sum of the distance on the optical axis from the paraxial exit pupil position to the lens surface of the imaging lens closest to the image side and the air-equivalent distance on the optical axis from the lens surface of the imaging lens closest to the image side to the image plane is defined as Expi. 0.35<Expm / Expi<1 (12) 12. The imaging lens according to claim 1, which satisfies conditional expression (12) expressed as follows:

13. The focal length of the imaging lens when focused on an object at infinity is f, When the focal length of the first lens group is f1, 0.2<f / f1<4 (13) 13. The imaging lens according to claim 1, which satisfies conditional expression (13) expressed as follows:

14. When one lens component is a single lens or a cemented lens, The paraxial curvature radius of the surface of the lens component closest to the object side of the imaging lens is R1f, When the paraxial radius of curvature of the surface closest to the image side of the lens component closest to the object side of the imaging lens is R1r, 0<(R1f+R1r) / (R1f-R1r)<3 (14) 14. The imaging lens according to claim 1, which satisfies conditional expression (14) expressed as follows:

15. Bf is the air-equivalent distance on the optical axis from the lens surface of the imaging lens closest to the image plane when the lens is focused on an object at infinity, The focal length of the imaging lens when focused on an object at infinity is f, When the maximum half angle of view in a state where the focus is on an object at infinity is ωi, 0.3<Bf / (f×tanωi)<4 (15) 15. The imaging lens according to claim 1, which satisfies conditional expression (15) expressed as follows:

16. The imaging lens according to claim 1 , wherein the second lens group includes at least two positive lenses.

17. the second lens group includes a cemented lens made up of one positive lens and one negative lens, The refractive index of the negative lens of the cemented lens in the second lens group with respect to the d-line is N2n, When the Abbe number of the negative lens of the cemented lens in the second lens group based on the d-line is ν2n, 1.75<N2n<2.2 (19) 20<ν2n<40 (20) 17. The imaging lens according to claim 1, which satisfies conditional expressions (19) and (20) expressed by the following formulas:

18. -10<f1A / f1B<-2 (2-1) 18. The imaging lens according to claim 1, which satisfies conditional expression (2-1) expressed as follows:

19. An imaging device comprising the imaging lens according to any one of claims 1 to 18.

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