Imaging lens and imaging device

Abstract

To provide an imaging lens which is compactly configured and has good optical performance, and an imaging apparatus comprising the imaging lens.SOLUTION: An imaging lens is comprised of a first lens group having positive refractive power, a diaphragm, a second lens group having positive refractive power, and a third lens group which are arranged in this order from the object side. The third lens group includes one or more positive lenses and one or more negative lenses. When focusing, all of the first lens group, diaphragm, and second lens group move, or the entire second lens group moves together as a focusing group, while the third lens group is stationary relative to the image plane. The imaging optical system satisfies predefined conditional expressions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology disclosed herein relates to imaging lenses and imaging devices. [Background technology]

[0002] Conventionally, as imaging lenses used in imaging devices such as digital cameras and video cameras, lens systems such as those described in Patent Document 1, Patent Document 2, and Patent Document 3 below are known. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-016787 [Patent Document 2] Japanese Patent Publication No. 2017-044887 [Patent Document 3] Patent No. 5315755 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In recent years, there has been a demand for imaging lenses that are compact in size and possess good optical performance.

[0005] This disclosure has been made in view of the above circumstances and aims to provide a compact imaging lens with good optical performance, and an imaging device equipped with this imaging lens. [Means for solving the problem]

[0006] An imaging lens according to one aspect of this disclosure comprises, in order from the object side to the image side, a first lens group having positive refractive power, an aperture, a second lens group having positive refractive power, and a third lens group, the third lens group including one or more positive lenses and one or more negative lenses, and when focusing, the entire first lens group, aperture, and second lens group, or the entire second lens group, moves together as a focus group, and the third lens group is fixed with respect to the image plane, and when the back focus of the entire system in air equivalent distance when focused on an object at infinity is Bf, the focal length of the entire system when focused on an object at infinity is f, the sum of the distance on the optical axis from the lens surface on the object side of the first lens group to the lens surface on the image side of the third lens group and Bf when focused on an object at infinity is TTL, the open aperture F number when focused on an object at infinity is FNo, and the maximum image height is Ymax, then the following conditions (1) and (2) are satisfied. 0.1 <Bf / f<1.2 (1) 5 <TTL×FNo / Ymax<9.2 (2)

[0007] The imaging lens in the above embodiment preferably satisfies the following conditional equation (1-3). 0.4 <Bf / f<1 (1-3)

[0008] The imaging lens in the above embodiment preferably satisfies the following condition (2-1). 5.5 <TTL×FNo / Ymax<9.2 (2-1)

[0009] When the entire system is in focus on an object at infinity, and the focal length of the second lens group is f2, the imaging lens of the above embodiment preferably satisfies the following condition (3), and more preferably satisfies the following condition (3-1). 0.2 <f / f2<2 (3) 0.4 <f / f2<1.8 (3-1)

[0010] When the entire system is in focus on an object at infinity, and the focal length of the third lens group is f3, it is preferable that the imaging lens of the above configuration satisfies the following condition (4). -0.5 <f / f3<-0.05 (4)

[0011] When the focal length of the first lens group is f1 and the focal length of the second lens group is f2, the imaging lens in the above configuration preferably satisfies the following condition (5). 1 <f1 / f2<3.5 (5)

[0012] Among the positive lenses in the second lens group, the Lp lens with the strongest refractive power has its convex surface facing the image side, and when the focal length of the second lens group is f2 and the focal length of the Lp lens is f2p, it is preferable that the imaging lens in the above configuration satisfies the following condition (6). 0.9 <f2 / f2p<3.5 (6)

[0013] When the aperture is in focus on an object at infinity, the sum of the distance along the optical axis from the lens surface closest to the image of the third lens group to StI and Bf is defined as the sum of the distance along the optical axis from the image-side surface of the Lp lens to the lens surface closest to the image of the third lens group to StI and Bf is defined as the sum of the distance along the optical axis from the image-side surface of the Lp lens to the lens surface closest to the image of the third lens group to StI and Bf. In this case, the imaging lens of the above embodiment preferably satisfies the following condition (7). 1 <StI / LpTI<4.5 (7)

[0014] In a configuration in which the second lens group includes one or more negative lenses, it is preferable that the Ln lens, which has the strongest refractive power among the negative lenses in the second lens group, is located closer to the object than the Lp lens. In this case, when the focal length of the Lp lens is f2p and the focal length of the Ln lens is f2n, it is preferable that the imaging lens in the above configuration satisfies the following condition (8). -2 <f2p / f2n<-0.4 (8)

[0015] When the aperture is in focus on an object at infinity, the sum of the distance along the optical axis from the lens surface closest to the image of the third lens group to StI and Bf is defined as the sum of the distance along the optical axis from the lens surface closest to the object of the first lens group to the lens surface closest to the image of the third lens group to TTL is defined as the sum of Bf. In this case, the imaging lens of the above configuration preferably satisfies the following condition (9). 0.3 < StI / TTL < 0.85 (9)

[0016] Let the lateral magnification of the focus group in the state of focusing on an infinite object be βf, the lateral magnification of the third lens group in the state of focusing on an infinite object be β3, the focal length of the focus group be ff, and the distance from the image plane to the exit pupil position in the state of focusing on an infinite object be De. The sign of De is positive if the exit pupil position is on the object side with respect to the image plane, and negative if the exit pupil position is on the image side with respect to the image plane. γ = (1 - βf 2 ) × β3 2 When defined as such, the imaging lens of the above aspect preferably satisfies the following conditional expression (10). 0 < |{βf / (ff × γ) - 1 / (β3 × f3) - (1 / De)} × Ymax| < 0.15 (10)

[0017] The focus group preferably includes one or more cemented lenses each containing one or more positive lenses and one or more negative lenses.

[0018] The second lens group includes one or more air lenses formed by two opposing concave lens surfaces. When the radius of curvature of the object-side surface of at least one air lens in the second lens group is Raf and the radius of curvature of the image-side surface is Rar, the imaging lens of the above aspect preferably satisfies the following conditional expression (11). -0.4 < (Raf + Rar) / (Raf - Rar) < 0.6 (11)

[0019] The lens on the most object side of the focus group preferably faces a convex surface toward the object side, and the lens on the most image side of the focus group preferably faces a convex surface toward the image side.

[0020] The focus group preferably includes one or more positive lenses and one or more negative lenses.

[0021] During focusing, the entire second lens group may be configured to move integrally, and the first lens group may be fixed with respect to the image plane.

[0022] The first lens group preferably includes one or more cemented lenses, each containing one or more positive lenses and one or more negative lenses.

[0023] The lens closest to the object in the first lens group may be configured as a negative lens with its concave surface facing the image side.

[0024] An imaging device according to another aspect of the present disclosure comprises an imaging lens as described above.

[0025] Furthermore, the terms "~consisting of" and "~consisting of" in this specification are intended to include, in addition to the listed components, lenses that substantially have no refractive power, optical elements other than lenses such as apertures, filters, and cover glass, and mechanical parts such as lens flanges, lens barrels, image sensors, and image stabilization mechanisms.

[0026] In this specification, "a group of lenses having positive refractive power" means that the group as a whole has positive refractive power. Similarly, "a group of lenses having negative refractive power" means that the group as a whole has negative refractive power. "A lens having positive refractive power" and "a positive lens" are synonymous. "A lens having negative refractive power" and "a negative lens" are synonymous. The "first lens group," "second lens group," and "third lens group" are not limited to configurations consisting of multiple lenses, but may also consist of only one lens.

[0027] A composite 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 and is treated as a single lens. Unless otherwise specified, the sign of the refractive force, radius of curvature, and surface shape for lenses including aspherical surfaces are those of the paraxial region. The sign of the radius of curvature is positive for a surface with a convex shape facing the object side and negative for a surface with a convex shape facing the image side.

[0028] In this specification, "entire system" refers to the imaging lens. "Back focus in air equivalent distance" is the air equivalent distance along the optical axis from the image-side lens surface to the image plane of the entire system. The "focal length" used in the conditional formula is the paraxial focal length. The values ​​used in the conditional formula are those with the d line as the reference when the system is in focus on an object at infinity.

[0029] The terms "d-line," "C-line," "F-line," and "g-line" as used herein are emission lines. In this specification, the wavelength of the d-line is treated as 587.56 nm (nanometers), the wavelength of the C-line as 656.27 nm (nanometers), the wavelength of the F-line as 486.13 nm (nanometers), and the wavelength of the g-line as 435.84 nm (nanometers). [Effects of the Invention]

[0030] According to this disclosure, it is possible to provide an imaging lens that is compact in size and has good optical performance, and an imaging device equipped with this imaging lens. [Brief explanation of the drawing]

[0031] [Figure 1] This is a cross-sectional view corresponding to the imaging lens of Example 1, showing the configuration of an imaging lens according to one embodiment. [Figure 2] Figure 1 is a cross-sectional view showing the configuration of the imaging lens and the light beam. [Figure 3] These are aberration diagrams of the imaging lens in Example 1. [Figure 4] This is a cross-sectional view showing the configuration of the imaging lens in Example 2. [Figure 5] These are aberration diagrams for the imaging lens of Example 2. [Figure 6] This is a cross-sectional view showing the configuration of the imaging lens in Example 3. [Figure 7] These are aberration diagrams for the imaging lens of Example 3. [Figure 8] This is a cross-sectional view showing the configuration of the imaging lens in Example 4. [Figure 9] These are aberration diagrams for the imaging lens of Example 4. [Figure 10]This is a cross-sectional view showing the configuration of the imaging lens in Example 5. [Figure 11] These are aberration diagrams for the imaging lens of Example 5. [Figure 12] This is a cross-sectional view showing the configuration of the imaging lens in Embodiment 6. [Figure 13] These are aberration diagrams for the imaging lens of Example 6. [Figure 14] This is a cross-sectional view showing the configuration of the imaging lens in Example 7. [Figure 15] These are aberration diagrams for the imaging lens of Example 7. [Figure 16] This is a cross-sectional view showing the configuration of the imaging lens in Example 8. [Figure 17] These are aberration diagrams for the imaging lens of Example 8. [Figure 18] This is a cross-sectional view showing the configuration of the imaging lens in Example 9. [Figure 19] These are aberration diagrams for the imaging lens of Example 9. [Figure 20] This is a cross-sectional view showing the configuration of the imaging lens in Example 10. [Figure 21] These are aberration diagrams of the imaging lens in Example 10. [Figure 22] This is a cross-sectional view showing the configuration of the imaging lens in Example 11. [Figure 23] These are aberration diagrams of the imaging lens in Example 11. [Figure 24] This is a cross-sectional view showing the configuration of the imaging lens in Example 12. [Figure 25] These are aberration diagrams for the imaging lens of Example 12. [Figure 26] This is a front perspective view of an imaging device according to one embodiment. [Figure 27] This is a perspective view of the rear side of an imaging device according to one embodiment. [Modes for carrying out the invention]

[0032] Embodiments of this disclosure will be described below with reference to the drawings.

[0033] Figure 1 shows a cross-sectional view of the configuration of an imaging lens according to one embodiment of this disclosure when focused on an object at infinity. In this specification, an object whose object distance (the distance along the optical axis from the object to the lens surface closest to the object) is infinity is referred to as an object at infinity. Figure 2 shows a cross-sectional view of the configuration and light beam of the imaging lens of Figure 1 when focused on an object at infinity. In Figure 2, the light beams shown are the on-axial light beam 2 and the light beam 3 at the maximum image height Ymax. The examples shown in Figures 1 and 2 correspond to the imaging lens of Embodiment 1 described later. In Figures 1 and 2, the left side is the object side and the right side is the image side. The imaging lens according to one embodiment of this disclosure will be described below, mainly with reference to Figure 1.

[0034] Figure 1 shows an example where a parallel plate-shaped optical element PP is placed between the imaging lens and the image plane Sim, assuming that the imaging lens is applied to an imaging device. The optical element PP is a component that is intended to be various filters and / or cover glass. The various filters include low-pass filters, infrared cut filters, and / or filters that cut out a specific wavelength range. The optical element PP is a component that does not have refractive power. It is also possible to configure the imaging device without the optical element PP.

[0035] The imaging lens in Figure 1 consists of a first lens group G1 with positive refractive power, an aperture diaphragm St, a second lens group G2 with positive refractive power, and a third lens group G3, arranged in order from the object side to the image side along the optical axis Z. By making the first lens group G1, which is on the object side of the aperture diaphragm St, a group with positive refractive power, it is possible to suppress the increase in diameter of the aperture diaphragm St. By making the second lens group G2, which is continuous with the first lens group G1, a group with positive refractive power, it becomes easier to reduce the overall length of the optical system.

[0036] As an example, the imaging lens in Figure 1 is configured as follows: The first lens group G1 consists of six lenses, L11 to L16, arranged in order from the object side to the image side. The second lens group G2 consists of six lenses, L21 to L26, arranged in order from the object side to the image side. The third lens group G3 consists of three lenses, L31 to L33, arranged in order from the object side to the image side. Note that the aperture diaphragm St in Figure 1 does not indicate size or shape, but rather its position in the optical axis direction. This method of illustrating the aperture diaphragm St is the same in Figure 2.

[0037] In the imaging lens of this disclosure, when focusing occurs, the entirety of the first lens group G1, the aperture diaphragm St, and the second lens group G2, or the entirety of the second lens group G2, moves together as a focus group, while the third lens group G3 is fixed to the image plane Sim. In this specification, the group that moves when focusing is referred to as the "focus group." Focusing is achieved by the movement of the focus group. "Moving together" means moving simultaneously in the same direction by the same amount. The imaging lens of this disclosure is configured so that only a part of the optical system moves, rather than the entire optical system moving, when focusing, thereby reducing the weight of the focus group, which is advantageous for achieving high-speed focusing. Furthermore, because the entire focus group moves together, the focusing mechanism can be simplified compared to imaging lenses with a floating focus system.

[0038] As an example, Figure 1 shows a case where, during focusing, the entire second lens group G2 moves as a single unit, while the first lens group G1, the aperture diaphragm St, and the third lens group G3 are fixed relative to the image plane Sim. In other words, in the example in Figure 1, the focusing group consists only of the second lens group G2. The leftward arrow below the second lens group G2 in Figure 1 indicates that the second lens group G2 is a focusing group that moves toward the object when focusing from an object at infinity to an object at close range. By configuring the first lens group G1 to be fixed during focusing, a lens configuration suitable for dustproof and splashproof structures is achieved.

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

[0040] Preferably, the lens closest to the object in the focusing group has its convex surface facing the object, and the lens closest to the image in the focusing group has its convex surface facing the image. In this case, it becomes easier to suppress variations in various aberrations associated with focusing.

[0041] The focusing group preferably includes one or more positive lenses and one or more negative lenses. This arrangement is advantageous in suppressing variations in chromatic aberration associated with focusing.

[0042] The focusing group preferably includes one or more cemented lenses, each containing one or more positive lenses and one or more negative lenses. In this case, it becomes easier to suppress variations in chromatic aberration associated with focusing.

[0043] The first lens group G1 preferably includes one or more cemented lenses, each containing one or more positive lenses and one or more negative lenses. In this case, axial chromatic aberration can be easily corrected.

[0044] The lens closest to the object in the first lens group G1 may be configured as a negative lens with its concave surface facing the image. This configuration is advantageous in securing the required field of view.

[0045] The third lens group G3 preferably includes one or more positive lenses and one or more negative lenses. This configuration is advantageous for effectively correcting axial chromatic aberration.

[0046] When the back focus of the entire system in air equivalent distance is Bf and the focal length of the entire system is f, it is preferable that the imaging lens satisfies the following condition (1). Bf and f are the values ​​when in focus on an object at infinity. By ensuring that the corresponding value in condition (1) does not fall below the lower limit, it is possible to suppress the enlargement of the lens located on the image side of the aperture diaphragm St, and it becomes easier to secure the angle of view. By ensuring that the corresponding value in condition (1) does not exceed the upper limit, it is possible to suppress the increase in the overall length of the optical system. To obtain even better characteristics, it is more preferable that the imaging lens satisfies at least one of the following conditions (1-1) to (1-5). 0.1 <Bf / f<1.2 (1) 0.15 <Bf / f<1.1 (1-1) 0.2 <Bf / f<1 (1-2) 0.4 <Bf / f<1 (1-3) 0.45 <Bf / f<0.95 (1-4) 0.5 <Bf / f<0.9 (1-5)

[0047] When the sum of the distance along the optical axis from the lens surface closest to the object in the first lens group G1 to the lens surface closest to the image in the third lens group G3 and Bf is defined as TTL, the maximum aperture F-number is FNo, and the maximum image height is Ymax, it is preferable that the imaging lens satisfies the following condition (2). Bf is the back focus of the entire system in terms of air-equivalent distance. Bf, TTL, and FNo are values ​​when the lens is in focus on an object at infinity. By ensuring that the corresponding value in condition (2) does not fall below the lower limit, excessive miniaturization can be prevented, which is advantageous for correcting various aberrations. By ensuring that the corresponding value in condition (2) does not exceed the upper limit, the overall size of the optical system can be suppressed. To obtain even better characteristics, it is more preferable that the imaging lens satisfies the following condition (2-1), and even more preferable that it satisfies the following condition (2-2). 5 <TTL×FNo / Ymax<9.2 (2) 5.5 <TTL×FNo / Ymax<9.2 (2-1) 6 <TTL×FNo / Ymax<9.2 (2-2)

[0048] When the focal length of the entire system is f and the focal length of the second lens group G2 is f2, it is preferable that the imaging lens satisfies the following condition (3). By ensuring that the corresponding value in condition (3) does not fall below the lower limit, the positive refractive power of the second lens group G2 does not become too weak, thus suppressing an increase in the overall length of the optical system. By ensuring that the corresponding value in condition (3) does not exceed the upper limit, the positive refractive power of the second lens group G2 does not become too strong, which is advantageous for suppressing spherical aberration and astigmatism. To obtain even better characteristics, it is more preferable that the imaging lens satisfies the following condition (3-1), and even more preferable that it satisfies the following condition (3-2). 0.2 <f / f2<2 (3) 0.4 <f / f2<1.8 (3-1) 0.5 <f / f2<1.5 (3-2)

[0049] When the focal length of the entire system is f and the focal length of the third lens group G3 is f3, it is preferable that the imaging lens satisfies the following condition (4). By ensuring that the corresponding value in condition (4) does not fall below the lower limit, the positive refractive power of the first lens group G1 or the second lens group G2 does not become too strong, which is advantageous in suppressing spherical aberration. By ensuring that the corresponding value in condition (4) does not exceed the upper limit, the Petzval sum does not become too large, which is advantageous in suppressing field curvature. To obtain even better characteristics, it is more preferable that the imaging lens satisfies the following condition (4-1), and even more preferable that it satisfies the following condition (4-2). -0.5 <f / f3<-0.05 (4) -0.45 <f / f3<-0.07 (4-1) -0.4 <f / f3<-0.1 (4-2)

[0050] When 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 satisfies the following condition (5). By ensuring that the corresponding value in condition (5) does not fall below the lower limit, the refractive power of the second lens group G2 relative to the first lens group G1 does not become too weak, making it easier to suppress field curvature. By ensuring that the corresponding value in condition (5) does not exceed the upper limit, the refractive power of the second lens group G2 relative to the first lens group G1 does not become too strong, which is advantageous in suppressing astigmatism occurring within the second lens group G2. To obtain even better characteristics, it is more preferable that the imaging lens satisfies the following condition (5-1), and even more preferable that it satisfies the following condition (5-2). 1 <f1 / f2<3.5 (5) 1.2 <f1 / f2<3 (5-1) 1.4 <f1 / f2<2.5 (5-2)

[0051] Among the positive lenses in the second lens group G2, the positive lens with the strongest refractive power will be called the Lp lens Lp. It is preferable that the Lp lens Lp has a shape with its convex surface facing the image side. This is advantageous for effectively correcting aberrations with respect to off-axis light beam and for suppressing the reduction of peripheral light intensity. In the example in Figure 1, lens L26 corresponds to the Lp lens Lp.

[0052] When the focal length of the second lens group G2 is f2 and the focal length of the Lp lens Lp is f2p, it is preferable that the imaging lens satisfies the following condition (6). By ensuring that the corresponding value of condition (6) does not fall below the lower limit, it is advantageous for correcting various aberrations with respect to off-axis light beam, especially astigmatism, and is also advantageous for suppressing the reduction of peripheral light intensity. By ensuring that the corresponding value of condition (6) does not exceed the upper limit, the refractive power of the Lp lens Lp does not become excessively strong within the second lens group G2, making it easier to correct various aberrations within the second lens group G2. To obtain even better characteristics, it is more preferable that the imaging lens satisfies the following condition (6-1), and even more preferable that it satisfies the following condition (6-2). 0.9 <f2 / f2p<3.5 (6) 1.1 <f2 / f2p<3 (6-1) 1.3 <f2 / f2p<2.5 (6-2)

[0053] When StI is the sum of the distance along the optical axis from the aperture diaphragm St to the image-side lens surface of the third lens group G3 and Bf, and LpTI is the sum of the distance along the optical axis from the image-side surface of the Lp lens Lp to the image-side lens surface of the third lens group G3 and Bf, it is preferable that the imaging lens satisfies the following condition (7). Bf is the back focus in terms of the air-equivalent distance of the entire system. Bf, StI, and LpTI are values ​​when the lens is in focus on an object at infinity. By ensuring that the corresponding value in condition (7) does not fall below the lower limit, it is possible to prevent the Lp lens Lp from being positioned relatively close to the object, thus preventing the refractive power of the Lp lens Lp acting on the off-axis light beam from becoming too weak. This makes it possible to suppress the angle of incidence of the principal rays of the off-axis light beam onto the image plane Sim, which is advantageous in suppressing the reduction of peripheral light intensity. By ensuring that the corresponding value in condition (7) does not exceed the upper limit, the refractive power of the Lp lens Lp acting on the off-axis light beam does not become too strong, making it easier to correct various aberrations within the second lens group G2. To obtain even better characteristics, it is more preferable that the imaging lens satisfies the following condition (7-1), and even more preferable that it satisfies the following condition (7-2). 1 <StI / LpTI<4.5 (7) 1.6 <StI / LpTI<4 (7-1) 1.8 <StI / LpTI<3.5 (7-2)

[0054] The second lens group G2 preferably includes one or more positive lenses and one or more negative lenses. This arrangement is advantageous in suppressing fluctuations in chromatic aberration associated with focusing. Among the negative lenses in the second lens group G2, the negative lens with the strongest refractive power will be called the Ln lens Ln. The Ln lens Ln is preferably located on the object side of the Lp lens Lp. The Ln lens Ln has the role of separating the on-axis light beam 2 and the off-axis light beam. By placing the Lp lens Lp on the image side of the Ln lens Ln, it is possible to suppress the increase in the angle of incidence of the principal rays of the off-axis light beam onto the image plane Sim, which is advantageous in suppressing the reduction of peripheral light intensity. In the example in Figure 1, lens L25 corresponds to the Ln lens Ln.

[0055] When the focal length of the Lp lens Lp is f2p and the focal length of the Ln lens Ln is f2n, it is preferable that the imaging lens satisfies the following condition (8). By ensuring that the corresponding value in condition (8) does not fall below the lower limit, the refractive power of the Ln lens Ln relative to the Lp lens Lp does not become too weak, thus effectively separating the on-axial light beam 2 from the off-axial light beam, which facilitates shortening the overall length of the optical system. By ensuring that the corresponding value in condition (8) does not exceed the upper limit, the refractive power of the Ln lens Ln relative to the Lp lens Lp does not become too strong, which is advantageous in suppressing various aberrations of the off-axial light beam that occur when the on-axial light beam 2 from the off-axial light beam is separated. To obtain even better characteristics, it is more preferable that the imaging lens satisfies the following condition (8-1), and even more preferable that it satisfies the following condition (8-2). -2 <f2p / f2n<-0.4 (8) -1.75 <f2p / f2n<-0.45 (8-1) -1.5 <f2p / f2n<-0.5 (8-2)

[0056] When StI is the sum of the distance along the optical axis from the aperture diaphragm St to the image-side lens surface of the third lens group G3 and Bf, and TTL is the sum of the distance along the optical axis from the object-side lens surface of the first lens group G1 to the image-side lens surface of the third lens group G3 and Bf, it is preferable that the imaging lens satisfies the following condition (9). Bf is the back focus in terms of the air-equivalent distance of the entire system. Bf, StI, and TTL are values ​​when the system is in focus on an object at infinity. By ensuring that the corresponding value in condition (9) does not fall below the lower limit, the position of the aperture diaphragm St does not get too close to the image plane Sim, thus preventing the incident angle of the principal rays of the off-axis light beam incident on the image sensor placed on the image plane Sim from becoming too large. By ensuring that the corresponding value in condition (9) does not exceed the upper limit, sufficient space on the object side of the aperture diaphragm St can be secured, allowing for the placement of an appropriate number of lenses. This allows the lens to be constructed without forcibly reducing the absolute value of the radius of curvature, thus enabling favorable correction of various aberrations. To obtain even better characteristics, it is more preferable for the imaging lens to satisfy the following condition (9-1), and even more preferable for it to satisfy the following condition (9-2). 0.3 <StI / TTL<0.85 (9) 0.35 <StI / TTL<0.8 (9-1) 0.4 <StI / TTL<0.75 (9-2)

[0057] Let βf be the lateral magnification of the focusing group, β3 be the lateral magnification of the third lens group G3, ff be the focal length of the focusing group, and De be the distance from the image plane Sim to the exit pupil position. Then γ = (1 - βf 2 )×β3 2In this case, it is preferable that the imaging lens satisfies the following condition (10). βf, β3, and De are the values ​​when in focus on an object at infinity. The sign of De is positive if the exit pupil position is on the object side of the image plane Sim, and negative if the exit pupil position is on the image side of the image plane Sim. For the lower limit of condition (10), since |{βf / (ff×γ)-1 / (β3×f3)-(1 / De)}×Ymax| is an absolute value, 0<|{βf / (ff×γ)-1 / (β3×f3)-(1 / De)}×Ymax|. Condition (10) is an equation that represents the rate of change of image size associated with focusing. By ensuring that the corresponding value of condition (10) does not exceed the upper limit, breathing (change in the angle of view during focusing) can be suppressed. To obtain better characteristics, it is more preferable that the imaging lens satisfies the following condition (10-1), and even more preferable that it satisfies the following condition (10-2). 0<|{βf / (ff×γ)-1 / (β3×f3)-(1 / De)}×Ymax|<0.15 (10) 0<|{βf / (ff×γ)-1 / (β3×f3)-(1 / De)}×Ymax|<0.13 (10-1) 0<|{βf / (ff×γ)-1 / (β3×f3)-(1 / De)}×Ymax|<0.1 (10-2)

[0058] The second lens group G2 preferably includes one or more biconvex air lenses formed by two opposing concave lens surfaces. In this specification, the air gap sandwiched between two opposing lens surfaces is considered a lens with a refractive index of 1, and this air gap is referred to as an air lens. The action of the two lens surfaces of the second lens group G2, with their concave surfaces facing each other, makes it easier to suitably correct spherical aberration and also makes it easier to suppress the Petzval sum of the entire optical system. In the example in Figure 1, a biconvex air lens is formed by the image-side surface of lens L23 and the object-side surface of lens L24.

[0059] When the radius of curvature of the object-side surface of at least one air lens in the second lens group G2 is Raf and the radius of curvature of the image-side surface is Rar, it is preferable that the imaging lens satisfies the following condition (11). By satisfying condition (11), it is possible to prevent the refractive power of one surface forming the air lens from being too strong or too weak compared to the refractive power of the other surface, and to facilitate appropriate correction of spherical aberration. To obtain even better characteristics, it is more preferable that the imaging lens satisfies the following condition (11-1), and even more preferable that it satisfies the following condition (11-2). -0.4<(Raf+Rar) / (Raf-Rar)<0.6 (11) -0.3<(Raf+Rar) / (Raf-Rar)<0.5 (11-1) -0.25<(Raf+Rar) / (Raf-Rar)<0.4 (11-2)

[0060] The example shown in Figure 1 is an example of an imaging lens of the present disclosure. The number of lenses constituting each group of the imaging lens of the present disclosure can be different from the example shown in Figure 1. Each group of the imaging lens can be configured as follows, for example.

[0061] The number of lenses included in the first lens group G1 can be 4 or more and 8 or less. More specifically, the first lens group G1 may be configured to consist of 2 positive lenses and 2 negative lenses. The first lens group G1 may be configured to consist of 3 positive lenses and 3 negative lenses. The first lens group G1 may be configured to consist of 4 positive lenses and 3 negative lenses. The first lens group G1 may be configured to consist of 4 positive lenses and 4 negative lenses.

[0062] The number of lenses included in the second lens group G2 can be 4 or more and 6 or less. More specifically, the second lens group G2 may be configured to consist of 2 positive lenses and 2 negative lenses. The second lens group G2 may be configured to consist of 3 positive lenses and 1 negative lens. The second lens group G2 may be configured to consist of 3 positive lenses and 2 negative lenses. The second lens group G2 may be configured to consist of 3 positive lenses and 3 negative lenses. The second lens group G2 may be configured to consist of 4 positive lenses and 2 negative lenses.

[0063] The third lens group G3 may be configured to have negative refractive power, or to have positive refractive power. The number of lenses included in the third lens group G3 may be two or more and three or less. More specifically, the third lens group G3 may be configured to consist of one positive lens and one negative lens. The third lens group G3 may be configured to consist of one positive lens and two negative lenses.

[0064] The focusing group may be configured to consist of a first lens group G1, an aperture diaphragm St, and a second lens group G2.

[0065] The preferred and possible configurations described above, including the configurations relating to the conditional expressions, can be combined in any way and are preferably selected as appropriate according to the required specifications. It should be noted that the preferred conditional expressions that the imaging lens of this disclosure satisfies are not limited to those described in formula form, but include all conditional expressions obtained by arbitrarily combining lower and upper limits from the preferred, more preferred, and even more preferred conditional expressions.

[0066] As an example, a preferred embodiment of the imaging lens of this disclosure comprises, in order from the object side to the image side, a first lens group G1 having positive refractive power, an aperture diaphragm St, a second lens group G2 having positive refractive power, and a third lens group G3, wherein the third lens group G3 includes one or more positive lenses and one or more negative lenses, and when focusing, the entirety of the first lens group G1, the aperture diaphragm St, and the second lens group G2, or the entirety of the second lens group G2, moves together as a focus group, and the third lens group G3 is fixed with respect to the image plane Sim, satisfying the above-mentioned conditions (1) and (2).

[0067] Next, embodiments of the imaging lens of this disclosure will be described with reference to the drawings. Note that the reference numerals assigned to the lenses in the cross-sectional views of each embodiment are used independently for each embodiment to avoid complexity in explanation and drawings due to an increase in the number of digits in the reference numerals. Therefore, even if the same reference numerals are assigned to different embodiments, the configuration is not necessarily the same. Furthermore, embodiments 7-9 below are embodiments of this disclosure, while embodiments 1-6 and 10-12 are reference examples of this disclosure.

[0068] [Example 1] A cross-sectional view of the imaging lens configuration of Example 1 is shown in Figure 1, and its illustration method and configuration are as described above, so some redundant explanations will be omitted here. The imaging lens of Example 1 consists of, in order from the object side to the image side, a first lens group G1 having positive refractive power, an aperture diaphragm St, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power. When focusing from an object at infinity to an object at close range, the entire second lens group G2 moves integrally towards the object side, and the first lens group G1, the aperture diaphragm St, and the third lens group G3 are fixed with respect to the image plane Sim.

[0069] For the imaging lens of Example 1, the basic lens data is shown in Table 1, the specifications in Table 2, the variable plane spacing in Table 3, and the aspheric coefficient in Table 4.

[0070] Table 1 is described as follows: The Sn column shows the face numbers, with the face closest to the object being designated as the first face and the numbers increasing by one as you move toward the image side. The R column shows the radius of curvature of each face. The D column shows the interplanar spacing on the optical axis between each face and the face adjacent to it on the image side. The Nd column shows the refractive index of each component with respect to the d line. The νd column shows the Abbe number of each component with respect to the d line.

[0071] In Table 1, the sign of the radius of curvature of a surface with a convex face towards the object is positive, and the sign of the radius of curvature of a surface with a convex face towards the image is negative. Table 1 also shows the aperture diaphragm St and the optical element PP. In the column for the surface number corresponding to the aperture diaphragm St, the surface number and the phrase (St) are written. The value in the bottom column of D in Table 1 is the distance between the surface closest to the image in the table and the image plane Sim. In Table 1, the variable surface spacing at focus is represented by the symbol DD[ ], and the surface number on the object side for this spacing is written in column D with the [ ] inside.

[0072] Table 2 shows the overall focal length f, the back focus Bf (air-equivalent distance) of the entire system, the maximum aperture F-number FNo., the maximum angle of view 2ω, and the maximum image height Ymax. The FNo. in the conditional equation, the FNo. in the specifications table, and the FNo. in the aberration diagram described later are the same. The (°) in the 2ω column indicates that the unit is degrees. Table 2 shows the values ​​when the lens is in focus on an object at infinity.

[0073] Table 3 shows the variable plane spacing when the object at infinity is in focus in the row labeled "Infinity," and the object distance of the nearest object and the variable plane spacing when the nearest object is in focus in the row below it. For example, in Table 3, the object distance of the nearest object is 0.215 m (meters). Tables 1, 2, and 3 show values ​​relative to the d line.

[0074] In the basic lens data, an asterisk (*) is attached to the surface number of the aspherical surface, and the numerical value of the paraxial radius of curvature is described in the column of the radius of curvature of the aspherical surface. In Table 4, the row of Sn shows the surface number of the aspherical surface, and the rows of 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 it varies depending on the surface. For example, at the 20th surface, m = 3, 4, 5, ··· 12. The "E±n" (n: integer) of the numerical value of the aspherical coefficient in Table 4 means "×10 ±n ". KA and Am are the aspherical coefficients in the aspherical formula represented by the following formula. Zd = C × h 2 / {1 + (1 - KA × C 2 × h 2 ) 1 / 2}+ ΣAm × h m However, Zd: Aspherical depth (the length of the perpendicular line dropped from the point on the aspherical surface at height h to the plane perpendicular to the optical axis Z where the aspherical vertex touches) h: Height (the distance from the optical axis Z to the lens surface) C: Reciprocal of the paraxial radius of curvature KA, Am: Aspherical coefficients where Σ in the aspherical formula means the sum with respect to m.

[0075] In the data of each table, degrees are used as the unit of angle, and mm (millimeter) is used as the unit of length. However, since the optical system can be used even if it is proportionally enlarged or reduced, other appropriate units can also be used. Also, in each of the following tables, the numerical values are rounded to a predetermined number of digits.

[0076]

Table 1

[0077]

Table 2

[0078]

Table 3

[0079] [Table 4]

[0080] Figure 3 shows the aberration diagrams for the imaging lens of Example 1. From left to right in Figure 3, the diagrams show spherical aberration, astigmatism, distortion, and chromatic aberration. In Figure 3, the upper section labeled "Distance: Infinity" shows the aberration diagrams when the lens is focused on an object at infinity, and the lower section labeled "Distance: 0.215m" shows the aberration diagrams when the lens is focused on an object at a distance of 0.215m. In the spherical aberration diagram, the aberrations along the d, C, F, and g lines are shown as solid lines, long dashed lines, short dashed lines, and dotted lines, respectively. In the astigmatism diagram, the aberration along the d line in the sagittal direction is shown as a solid line, and the aberration along the d line in the tangential direction is shown as a short dashed line. In the distortion diagram, the aberration along the d line is shown as a solid line. In the chromatic aberration diagram, the aberrations along the C, F, and g lines are shown by long dashed lines, short dashed lines, and dotted lines, respectively. In the spherical aberration diagram, the value of the wide-open F number is shown after "FNo.=". In other aberration diagrams, the value of the maximum half-angle of view is shown after "ω=".

[0081] The symbols, meanings, methods of description, and methods of illustration for each data point in Example 1 described above are the same in the following examples unless otherwise specified, so redundant explanations will be omitted below.

[0082] [Example 2] Figure 4 shows a cross-sectional view of the imaging lens configuration of Example 2. The imaging lens of Example 2 consists of a first lens group G1 with positive refractive power, an aperture diaphragm St, a second lens group G2 with positive refractive power, and a third lens group G3 with negative refractive power, arranged in order from the object side to the image side along the optical axis Z. The first lens group G1 consists of four lenses, L11 to L14, arranged in order from the object side to the image side. The second lens group G2 consists of five lenses, L21 to L25, arranged in order from the object side to the image side. The third lens group G3 consists of three lenses, L31 to L33, arranged in order from the object side to the image side. When focusing from an object at infinity to an object at close range, the entire second lens group G2 moves integrally towards the object side, and the first lens group G1, aperture diaphragm St, and third lens group G3 are fixed relative to the image plane Sim.

[0083] For the imaging lens of Example 2, the basic lens data is shown in Table 5, the specifications in Table 6, the variable plane spacing in Table 7, the aspherical coefficient in Table 8, and the aberration diagrams in Figure 5.

[0084] [Table 5]

[0085] [Table 6]

[0086] [Table 7]

[0087] [Table 8]

[0088] [Example 3] Figure 6 shows a cross-sectional view of the imaging lens configuration of Example 3. The imaging lens of Example 3 consists of a first lens group G1 with positive refractive power, an aperture diaphragm St, a second lens group G2 with positive refractive power, and a third lens group G3 with negative refractive power, arranged in order from the object side to the image side along the optical axis Z. The first lens group G1 consists of six lenses, L11 to L16, arranged in order from the object side to the image side. The second lens group G2 consists of six lenses, L21 to L26, arranged in order from the object side to the image side. The third lens group G3 consists of three lenses, L31 to L33, arranged in order from the object side to the image side. When focusing from an object at infinity to an object at close range, the entire second lens group G2 moves integrally towards the object side, and the first lens group G1, aperture diaphragm St, and third lens group G3 are fixed relative to the image plane Sim.

[0089] For the imaging lens of Example 3, the basic lens data is shown in Table 9, the specifications in Table 10, the variable plane spacing in Table 11, the aspherical coefficient in Table 12, and the aberration diagrams in Figure 7.

[0090] [Table 9]

[0091] [Table 10]

[0092] [Table 11]

[0093] [Table 12]

[0094] [Example 4] Figure 8 shows a cross-sectional view of the imaging lens configuration of Example 4. The imaging lens of Example 4 consists of a first lens group G1 with positive refractive power, an aperture diaphragm St, a second lens group G2 with positive refractive power, and a third lens group G3 with positive refractive power, arranged in order from the object side to the image side along the optical axis Z. The first lens group G1 consists of six lenses, L11 to L16, arranged in order from the object side to the image side. The second lens group G2 consists of four lenses, L21 to L24, arranged in order from the object side to the image side. The third lens group G3 consists of three lenses, L31 to L33, arranged in order from the object side to the image side. When focusing from an object at infinity to an object at close range, the entire structure of the first lens group G1, aperture diaphragm St, and second lens group G2 moves integrally toward the object side, while the third lens group G3 is fixed relative to the image plane Sim.

[0095] For the imaging lens of Example 4, the basic lens data is shown in Table 13, the specifications in Table 14, the variable plane spacing in Table 15, the aspherical coefficient in Table 16, and the aberration diagrams in Figure 9.

[0096] [Table 13]

[0097] [Table 14]

[0098] [Table 15]

[0099] [Table 16]

[0100] [Example 5] Figure 10 shows a cross-sectional view of the imaging lens configuration of Example 5. The imaging lens of Example 5 consists of a first lens group G1 with positive refractive power, an aperture diaphragm St, a second lens group G2 with positive refractive power, and a third lens group G3 with positive refractive power, arranged in order from the object side to the image side along the optical axis Z. The first lens group G1 consists of six lenses, L11 to L16, arranged in order from the object side to the image side. The second lens group G2 consists of four lenses, L21 to L24, arranged in order from the object side to the image side. The third lens group G3 consists of three lenses, L31 to L33, arranged in order from the object side to the image side. When focusing from an object at infinity to an object at close range, the entire first lens group G1, aperture diaphragm St, and second lens group G2 move together toward the object side, and the third lens group G3 is fixed relative to the image plane Sim.

[0101] For the imaging lens of Example 5, the basic lens data is shown in Table 17, the specifications in Table 18, the variable plane spacing in Table 19, the aspherical coefficient in Table 20, and the aberration diagrams in Figure 11.

[0102] [Table 17]

[0103] [Table 18]

[0104] [Table 19]

[0105] [Table 20]

[0106] [Example 6] Figure 12 shows a cross-sectional view of the imaging lens configuration of Example 6. The imaging lens of Example 6 consists of a first lens group G1 with positive refractive power, an aperture diaphragm St, a second lens group G2 with positive refractive power, and a third lens group G3 with positive refractive power, arranged in order from the object side to the image side along the optical axis Z. The first lens group G1 consists of six lenses, L11 to L16, arranged in order from the object side to the image side. The second lens group G2 consists of four lenses, L21 to L24, arranged in order from the object side to the image side. The third lens group G3 consists of three lenses, L31 to L33, arranged in order from the object side to the image side. When focusing from an object at infinity to an object at close range, the entire structure of the first lens group G1, aperture diaphragm St, and second lens group G2 moves integrally toward the object side, and the third lens group G3 is fixed relative to the image plane Sim.

[0107] For the imaging lens of Example 6, the basic lens data is shown in Table 21, the specifications in Table 22, the variable plane spacing in Table 23, the aspherical coefficient in Table 24, and the aberration diagrams in Figure 13.

[0108] [Table 21]

[0109] [Table 22]

[0110] [Table 23]

[0111] [Table 24]

[0112] [Example 7] Figure 14 shows a cross-sectional view of the imaging lens configuration of Example 7. The imaging lens of Example 7 consists of a first lens group G1 with positive refractive power, an aperture diaphragm St, a second lens group G2 with positive refractive power, and a third lens group G3 with negative refractive power, arranged in order from the object side to the image side along the optical axis Z. The first lens group G1 consists of seven lenses, L11 to L17, arranged in order from the object side to the image side. The second lens group G2 consists of six lenses, L21 to L26, arranged in order from the object side to the image side. The third lens group G3 consists of two lenses, L31 to L32, arranged in order from the object side to the image side. When focusing from an object at infinity to an object at close range, the entire second lens group G2 moves integrally towards the object side, and the first lens group G1, aperture diaphragm St, and third lens group G3 are fixed relative to the image plane Sim.

[0113] For the imaging lens of Example 7, the basic lens data is shown in Table 25, the specifications in Table 26, the variable plane spacing in Table 27, the aspheric coefficient in Table 28, and the aberration diagrams in Figure 15.

[0114] [Table 25]

[0115] [Table 26]

[0116] [Table 27]

[0117] [Table 28]

[0118] [Example 8] Figure 16 shows a cross-sectional view of the imaging lens configuration of Example 8. The imaging lens of Example 8 consists of a first lens group G1 with positive refractive power, an aperture diaphragm St, a second lens group G2 with positive refractive power, and a third lens group G3 with negative refractive power, arranged in order from the object side to the image side along the optical axis Z. The first lens group G1 consists of seven lenses, L11 to L17, arranged in order from the object side to the image side. The second lens group G2 consists of six lenses, L21 to L26, arranged in order from the object side to the image side. The third lens group G3 consists of two lenses, L31 to L32, arranged in order from the object side to the image side. When focusing from an object at infinity to an object at close range, the entire second lens group G2 moves integrally towards the object side, and the first lens group G1, aperture diaphragm St, and third lens group G3 are fixed relative to the image plane Sim.

[0119] For the imaging lens of Example 8, the basic lens data is shown in Table 29, the specifications in Table 30, the variable plane spacing in Table 31, the aspherical coefficient in Table 32, and the aberration diagrams in Figure 17.

[0120] [Table 29]

[0121] [Table 30]

[0122] [Table 31]

[0123] [Table 32]

[0124] [Example 9] Figure 18 shows a cross-sectional view of the imaging lens configuration of Example 9. The imaging lens of Example 9 consists of a first lens group G1 with positive refractive power, an aperture diaphragm St, a second lens group G2 with positive refractive power, and a third lens group G3 with negative refractive power, arranged in order from the object side to the image side along the optical axis Z. The first lens group G1 consists of seven lenses, L11 to L17, arranged in order from the object side to the image side. The second lens group G2 consists of six lenses, L21 to L26, arranged in order from the object side to the image side. The third lens group G3 consists of two lenses, L31 to L32, arranged in order from the object side to the image side. When focusing from an object at infinity to an object at close range, the entire second lens group G2 moves integrally towards the object side, and the first lens group G1, aperture diaphragm St, and third lens group G3 are fixed relative to the image plane Sim.

[0125] For the imaging lens of Example 9, the basic lens data is shown in Table 33, the specifications in Table 34, the variable plane spacing in Table 35, the aspherical coefficient in Table 36, and the aberration diagrams in Figure 19.

[0126] [Table 33]

[0127] [Table 34]

[0128] [Table 35]

[0129] [Table 36]

[0130] [Example 10] Figure 20 shows a cross-sectional view of the imaging lens configuration of Example 10. The imaging lens of Example 10 consists of a first lens group G1 with positive refractive power, an aperture diaphragm St, a second lens group G2 with positive refractive power, and a third lens group G3 with negative refractive power, arranged in order from the object side to the image side along the optical axis Z. The first lens group G1 consists of eight lenses, L11 to L18, arranged in order from the object side to the image side. The second lens group G2 consists of four lenses, L21 to L24, arranged in order from the object side to the image side. The third lens group G3 consists of three lenses, L31 to L33, arranged in order from the object side to the image side. When focusing from an object at infinity to an object at close range, the entire second lens group G2 moves integrally towards the object side, and the first lens group G1, aperture diaphragm St, and third lens group G3 are fixed relative to the image plane Sim.

[0131] For the imaging lens of Example 10, the basic lens data is shown in Table 37, the specifications in Table 38, the variable plane spacing in Table 39, the aspherical coefficient in Table 40, and the aberration diagrams in Figure 21.

[0132] [Table 37]

[0133] [Table 38]

[0134] [Table 39]

[0135] [Table 40]

[0136] [Example 11] Figure 22 shows a cross-sectional view of the imaging lens configuration of Example 11. The imaging lens of Example 11 consists of a first lens group G1 with positive refractive power, an aperture diaphragm St, a second lens group G2 with positive refractive power, and a third lens group G3 with negative refractive power, arranged in order from the object side to the image side along the optical axis Z. The first lens group G1 consists of six lenses, L11 to L16, arranged in order from the object side to the image side. The second lens group G2 consists of six lenses, L21 to L26, arranged in order from the object side to the image side. The third lens group G3 consists of two lenses, L31 to L32, arranged in order from the object side to the image side. When focusing from an object at infinity to an object at close range, the entire second lens group G2 moves integrally towards the object side, and the first lens group G1, aperture diaphragm St, and third lens group G3 are fixed relative to the image plane Sim.

[0137] For the imaging lens of Example 11, the basic lens data is shown in Table 41, the specifications in Table 42, the variable plane spacing in Table 43, the aspherical coefficient in Table 44, and the aberration diagrams in Figure 23.

[0138] [Table 41]

[0139] [Table 42]

[0140] [Table 43]

[0141] [Table 44]

[0142] [Example 12] Figure 24 shows a cross-sectional view of the imaging lens configuration of Example 12. The imaging lens of Example 12 consists of a first lens group G1 with positive refractive power, an aperture diaphragm St, a second lens group G2 with positive refractive power, and a third lens group G3 with negative refractive power, arranged in order from the object side to the image side along the optical axis Z. The first lens group G1 consists of six lenses, L11 to L16, arranged in order from the object side to the image side. The second lens group G2 consists of six lenses, L21 to L26, arranged in order from the object side to the image side. The third lens group G3 consists of two lenses, L31 to L32, arranged in order from the object side to the image side. When focusing from an object at infinity to an object at close range, the entire second lens group G2 moves integrally towards the object side, and the first lens group G1, aperture diaphragm St, and third lens group G3 are fixed relative to the image plane Sim.

[0143] For the imaging lens of Example 11, the basic lens data is shown in Table 45, the specifications in Table 46, the variable plane spacing in Table 47, the aspherical coefficient in Table 48, and the aberration diagrams in Figure 25.

[0144] [Table 45]

[0145] [Table 46]

[0146] [Table 47]

[0147] [Table 48]

[0148] Table 49 shows the corresponding values ​​for the imaging lens condition equations (1) to (11) in the above embodiment. Table 49 shows the values ​​when the d line is used as the reference.

[0149] [Table 49]

[0150] Next, an imaging device according to an embodiment of the present disclosure will be described. Figures 26 and 27 show external views of a camera 30, which is an imaging device according to one embodiment of the present disclosure. Figure 26 shows a perspective view of the camera 30 from the front, and Figure 27 shows a perspective view of the camera 30 from the rear. The camera 30 is a so-called mirrorless type digital camera, and an interchangeable lens 20 can be detachably attached. The interchangeable lens 20 is configured to include an imaging lens 1 according to one embodiment of the present disclosure, which is housed in the lens barrel.

[0151] The camera 30 comprises a camera body 31, the top of which is provided a shutter button 32 and a power button 33. The rear of the camera body 31 is provided with an operation unit 34, an operation unit 35, and a display unit 36. The display unit 36 ​​can display captured images and images within the field of view before capture.

[0152] A shooting aperture is provided in the center of the front of the camera body 31, into which light from the subject to be photographed enters. A mount 37 is provided at a position corresponding to the shooting aperture, and an interchangeable lens 20 is attached to the camera body 31 via the mount 37.

[0153] The camera body 31 contains an image sensor 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 image sensor to generate an image, and a recording medium for recording the generated image. The camera 30 can take still images or videos by pressing the shutter button 32, and the image data obtained from this shooting is recorded on the recording medium.

[0154] Although the technology of this disclosure has been described above with reference to embodiments and examples, the technology of this disclosure is not limited to the above embodiments and examples, and various modifications are possible. For example, the radius of curvature, interplanar spacing, refractive index, Abbe number, and aspheric coefficient of each lens are not limited to the values ​​shown in each of the above embodiments, but can take other values.

[0155] Furthermore, the imaging device according to the embodiments of this disclosure is not limited to the above example, and can take various forms, such as cameras other than mirrorless cameras, film cameras, and video cameras. [Explanation of Symbols]

[0156] 1 imaging lens 2 On-axis luminous flux 3. Light beam at maximum image height 20 interchangeable lenses 30 Cameras 31 Camera Body 32 Shutter button 33 Power button 34, 35 Operation section 36 Display section 37 Mount G1 First Lens Group G2 Second Lens Group G3 3rd lens group L11~L33 Lenses Ln Ln lens Lp Lp lens PP optical components Sim image plane St aperture diaphragm Ymax Maximum image height Z optical axis

Claims

1. It consists of, in order from the object side to the image side, a first lens group with positive refractive power, an aperture, a second lens group with positive refractive power, and a third lens group. The second lens group consists of four positive lenses and two negative lenses. The third lens group includes one or more positive lenses and one or more negative lenses. When focusing occurs, only the entire second lens group moves as a single unit as the focusing group, while the first lens group and the third lens group remain fixed relative to the image plane. Bf is the back focus of the entire system in terms of its air-reduced distance when focused on an object at infinity. f is the focal length of the entire system when it is in focus on an object at infinity. The sum of the distance along the optical axis from the lens surface closest to the object in the first lens group to the lens surface closest to the image in the third lens group, when in focus on an object at infinity, and Bf is TTL. The open aperture F-number when focused on an object at infinity is denoted as FNo. The maximum image height is Ymax. The focal length of the first lens group is f1, When the focal length of the second lens group is set to f2, 0.1<Bf / f<1.2 (1) 5.5<TTL×FNo / Ymax<9.2 (2-1) 1<f1 / f2<3.5 (5) An imaging lens that satisfies the conditions (1), (2-1), and (5) represented by .

2. 0.2<f / f2<2 (3) The imaging lens according to claim 1 that satisfies the conditional expression (3) represented by .

3. 0.4<f / f2<1.8 (3-1) The imaging lens according to claim 2 that satisfies the conditional expression (3-1) represented by .

4. 0.5<f / f2<1.5 (3-2) The imaging lens according to claim 3 that satisfies the conditional expression (3-2) represented by .

5. When the focal length of the third lens group is set to f3, -0.5<f / f3<-0.05 (4) An imaging lens according to any one of claims 1 to 4 that satisfies the conditional expression (4) represented by .

6. -0.45<f / f3<-0.07 (4-1) The imaging lens according to claim 5 that satisfies the conditional expression (4-1) represented by .

7. -0.4<f / f3<-0.1 (4-2) The imaging lens according to claim 6 that satisfies the conditional expression (4-2) represented by .

8. 1.2<f1 / f2<3 (5-1) An imaging lens according to any one of claims 1 to 7 that satisfies the conditional expression (5-1) represented by .

9. 1.4<f1 / f2<2.5 (5-2) The imaging lens according to claim 8, satisfying the conditional expression (5-2) represented by .

10. Among the positive lenses in the second lens group, the Lp lens with the strongest refractive power has its convex surface facing the image side. The focal length of the second lens group is f2, When the focal length of the Lp lens is set to f2p, 0.9<f2 / f2p<3.5 (6) An imaging lens according to any one of claims 1 to 9 that satisfies the conditional expression (6) represented by .

11. 1.1<f2 / f2p<3 (6-1) The imaging lens according to claim 10, satisfying the conditional expression (6-1) represented by .

12. 1.3<f2 / f2p<2.5 (6-2) The imaging lens according to claim 11, satisfying the conditional expression (6-2) represented by .

13. The second lens group includes one or more negative lenses. Among the negative lenses in the second lens group, the Ln lens with the strongest refractive power is located closer to the object than the Lp lens. When the focal length of the Ln lens is set to f2n, -2<f2p / f2n<-0.4 (8) An imaging lens according to any one of claims 10 to 12 that satisfies the conditional expression (8) represented by .

14. -1.75<f2p / f2n<-0.45 (8-1) The imaging lens according to claim 13, satisfying the conditional expression (8-1) represented by .

15. -1.5<f2p / f2n<-0.5 (8-2) The imaging lens according to claim 14, satisfying the conditional expression (8-2) represented by .

16. The second lens group includes one or more air lenses formed by two opposing lens surfaces, If the radius of curvature of the object-side surface of at least one of the air lenses in the second lens group is Raf, and the radius of curvature of the image-side surface is Rar, -0.4<(Raf+Rar) / (Raf-Rar)<0.6 (11) An imaging lens according to any one of claims 1 to 15 that satisfies the conditional expression (11) represented by .

17. An imaging device comprising an imaging lens according to any one of claims 1 to 16.

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