Imaging lens and imaging apparatus

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 of the present disclosure relates to an imaging lens and an imaging device.

Background Art

[0002] Conventionally, as an imaging lens used in imaging devices such as digital cameras and video cameras, for example, lens systems described in Patent Document 1, Patent Document 2, and Patent Document 3 below are known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, there has been a demand for an imaging lens that is small in size and has good optical performance.

[0005] The present disclosure has been made in view of the above circumstances, and an object thereof is to provide an imaging lens that is small in size and has good optical performance, and an imaging device including this imaging lens.

Means for Solving the Problems

[0006] The imaging lens according to one aspect of the present disclosure includes, in order from the object side to the image side, a first lens group having a positive refractive power, a diaphragm, a second lens group having a positive refractive power, and a third lens group. The third lens group includes one or more positive lenses and one or more negative lenses. When focusing, the entire first lens group, diaphragm, and second lens group, or the entire second lens group moves integrally as a focus group, and the third lens group is fixed with respect to the image plane. When focusing on an infinite object, let the back focus at the air equivalent distance of the entire system be Bf, the focal length of the entire system in the state of focusing on an infinite object be f, the distance on the optical axis from the most object-side lens surface of the first lens group to the most image-side lens surface of the third lens group in the state of focusing on an infinite object, and the sum of Bf be TTL. When the open F-number in the state of focusing on an infinite object is FNo and the maximum image height is Ymax, the following conditional expressions (1) and (2) are satisfied. 0.1 < Bf / f < 1.2 (1) 5 < TTL×FNo / Ymax < 9.2 (2)

[0007] The imaging lens of the above aspect preferably satisfies the following conditional expression (1-3). 0.4 < Bf / f < 1 (1-3)

[0008] The imaging lens of the above aspect preferably satisfies the following conditional expression (2-1). 5.5 < TTL×FNo / Ymax < 9.2 (2-1)

[0009] When the focal length of the entire system in the state of focusing on an infinite object is f and the focal length of the second lens group is f2, the imaging lens of the above aspect preferably satisfies the following conditional expression (3), and more preferably satisfies the following conditional expression (3-1). 0.2 < f / f2 < 2 (3) 0.4 < f / f2 < 1.8 (3-1)

[0010] When the focal length of the entire system in the state of focusing on an infinite object is f and the focal length of the third lens group is f3, the imaging lens of the above aspect preferably satisfies the following conditional expression (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 of the above aspect preferably satisfies the following conditional expression (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 faces the convex surface toward the image side. When the focal length of the second lens group is f2 and the focal length of the Lp lens is f2p, the imaging lens of the above aspect preferably satisfies the following conditional expression (6). 0.9 < f2 / f2p < 3.5 (6)

[0013] The sum of the distance on the optical axis from the diaphragm in the state of focusing on an infinite object to the most image-side lens surface of the third lens group and Bf is StI, and the sum of the distance on the optical axis from the image-side surface of the Lp lens in the state of focusing on an infinite object to the most image-side lens surface of the third lens group and Bf is LpTI. When this is the case, the imaging lens of the above aspect preferably satisfies the following conditional expression (7). 1 < StI / LpTI < 4.5 (7)

[0014] In a configuration where 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 preferably located closer to the object side than the Lp lens. At this time, when the focal length of the Lp lens is f2p and the focal length of the Ln lens is f2n, the imaging lens of the above aspect preferably satisfies the following conditional expression (8). -2 < f2p / f2n < -0.4 (8)

[0015] The sum of the distance on the optical axis from the diaphragm in the state of focusing on an infinite object to the most image-side lens surface of the third lens group and Bf is StI, and the sum of the distance on the optical axis from the most object-side lens surface of the first lens group to the most image-side lens surface of the third lens group in the state of focusing on an infinite object and Bf is TTL. When this is the case, the imaging lens of the above aspect preferably satisfies the following conditional expression (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 from the image plane, and negative if the exit pupil position is on the image side from the image plane. γ = (1 - βf 2 ) × β3 2 When this is the case, it is preferable that the imaging lens of the above aspect 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 including 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 of the second lens group is Raf and the radius of curvature of the image-side surface is Rar, it is preferable that the imaging lens of the above aspect 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 the convex surface toward the object side, and the lens on the most image side of the focus group preferably faces the 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 including one or more positive lenses and one or more negative lenses.

[0023] The lens on the object side of the first lens group may be configured to be a negative lens with a concave surface facing the image side.

[0024] An imaging device according to another aspect of the present disclosure includes the imaging lens of the above aspect.

[0025] In this specification, “comprising ~” and “consisting of ~” are intended to mean that in addition to the recited components, lenses having substantially no refractive power, optical elements other than lenses such as diaphragms, filters, and cover glasses, and mechanical parts such as lens flanges, lens barrels, imaging elements, and shake correction mechanisms may be included.

[0026] In this specification, “a group having a positive refractive power” means having a positive refractive power as a whole group. Similarly, “a group having a negative refractive power” means having a negative refractive power as a whole group. “A lens having a positive refractive power” and “a positive lens” are synonymous. “A lens having a negative refractive power” and “a negative lens” are synonymous. “The first lens group”, “the second lens group”, and “the third lens group” are not limited to configurations including a plurality of lenses, and may be configured with only one lens.

[0027] A compound aspherical lens (a lens in which a spherical lens and an aspherical film formed on the spherical lens are integrally formed and function as one aspherical lens as a whole) is not regarded as a cemented lens and is treated as one lens. For the sign of the refractive power, the radius of curvature, and the surface shape of a lens including an aspherical surface, those in the paraxial region are used unless otherwise specified. The sign of the radius of curvature is positive for the radius of curvature of a surface having a convex surface facing the object side, and negative for the radius of curvature of a surface having a convex surface facing the image side.

[0028] In this specification, "entire system" means the imaging lens. "Back focus at air equivalent distance" is the air equivalent distance on the optical axis from the most image-side lens surface of the entire system to the image plane. The "focal length" used in the conditional expression is the paraxial focal length. The values used in the conditional expression are the values when the d-line is used as a reference in the state of focusing on an infinitely distant object.

[0029] The "d-line", "C-line", "F-line", and "g-line" described in this specification are spectral lines. In this specification, 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).

Effect of the Invention

[0030] According to the present disclosure, it is possible to provide an imaging lens that is configured to be small and has good optical performance, and an imaging device including this imaging lens.

Brief Description of the Drawings

[0031]

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Modes for Carrying Out the Invention

[0032] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0033] FIG. 1 shows a cross-sectional view of the configuration of an imaging lens according to an embodiment of the present disclosure in a state focused on an infinite object. In this specification, an object with an object distance (the distance on the optical axis from the object to the lens surface closest to the object side) being infinite is referred to as an infinite object. FIG. 2 shows a cross-sectional view of the configuration and light beam of the imaging lens of FIG. 1 in a state focused on an infinite object. In FIG. 2, as the light beams, an on-axis light beam 2 and a light beam 3 with the maximum image height Ymax are shown. The examples shown in FIGS. 1 and 2 correspond to the imaging lens of Example 1 described later. In FIGS. 1 and 2, the left side is the object side and the right side is the image side. Hereinafter, the imaging lens according to an embodiment of the present disclosure will be mainly described with reference to FIG. 1.

[0034] In FIG. 1, assuming that the imaging lens is applied to an imaging device, an example is shown in which an optical member PP in the shape of a parallel plate is disposed between the imaging lens and the image plane Sim. The optical member PP is a member assuming various filters and / or cover glass, etc. The various filters are a low-pass filter, an infrared cut filter, and / or a filter that cuts a specific wavelength range, etc. The optical member PP is a member having no refractive power. It is also possible to configure the imaging device by omitting the optical member PP.

[0035] The imaging lens of FIG. 1 is composed of a first lens group G1 having a positive refractive power, an aperture stop St, a second lens group G2 having a positive refractive power, and a third lens group G3 in order from the object side to the image side along the optical axis Z. By setting the first lens group G1 on the object side of the aperture stop St as a group having a positive refractive power, it is possible to suppress an increase in the diameter of the aperture stop St. By setting the second lens group G2, which is continuous with the first lens group G1, also as a group having a positive refractive power, it becomes easy to suppress the overall length of the optical system.

[0036] As an example, the imaging lens of FIG. 1 is configured as follows. The first lens group G1 consists of six lenses L11 to L16 in order from the object side to the image side. The second lens group G2 consists of six lenses L21 to L26 in order from the object side to the image side. The third lens group G3 consists of three lenses L31 to L33 in order from the object side to the image side. Note that the aperture stop St in FIG. 1 indicates the position in the optical axis direction rather than the size and shape. This method of illustrating the aperture stop St is the same in FIG. 2.

[0037] In the imaging lens of the present disclosure, during focusing, the entire first lens group G1, the aperture stop St, and the second lens group G2, or the entire second lens group G2 move integrally as a focus group, and the third lens group G3 is fixed with respect to the image plane Sim. In this specification, the group that moves during focusing is referred to as the "focus group". Focusing is performed by the movement of the focus group. "Moving integrally" means moving simultaneously in the same direction by the same amount. The imaging lens of the present disclosure is configured such that, during focusing, not the entire optical system moves but only a part of the optical system moves, so that the weight of the focus group can be suppressed, which is advantageous for realizing high-speed focusing. In addition, since the entire focus group moves integrally, the focusing mechanism can be simplified compared to an imaging lens using a floating focus method.

[0038] As an example, FIG. 1 shows an example in which, during focusing, the entire second lens group G2 moves integrally, and the first lens group G1, the aperture stop St, and the third lens group G3 are fixed with respect to the image plane Sim. That is, in the example of FIG. 1, the focus group consists of only the second lens group G2. The leftward arrow below the second lens group G2 in FIG. 1 indicates that the second lens group G2 is a focus group that moves toward the object side during focusing from an infinite object to a closest object. By adopting a configuration in which the first lens group G1 is fixed during focusing, a lens configuration suitable for a dustproof and drip-proof structure is obtained.

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

[0040] It is preferable that the lens on the object side of the focus group faces the convex surface toward the object side, and the lens on the image side of the focus group faces the convex surface toward the image side. In this case, it becomes easy to suppress fluctuations in various aberrations associated with focusing.

[0041] The focus group preferably includes one or more positive lenses and one or more negative lenses. In this case, it is advantageous for suppressing fluctuations in chromatic aberration associated with focusing.

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

[0043] The first lens group G1 preferably includes one or more cemented lenses each including one or more positive lenses and one or more negative lenses. In this case, it becomes easy to suitably correct axial chromatic aberration.

[0044] The lens on the object side of the first lens group G1 may be configured as a negative lens with a concave surface facing the image side. In this case, it is advantageous for securing a required angle of view.

[0045] The third lens group G3 preferably includes one or more positive lenses and one or more negative lenses. In this case, it is advantageous for suitably correcting axial chromatic aberration.

[0046] When the back focus at the entire system's air equivalent distance is Bf and the focal length of the entire system is f, the imaging lens preferably satisfies the following conditional expression (1). Bf and f are values in a state where the lens is focused on an infinitely distant object. By ensuring that the corresponding value of conditional expression (1) does not fall below the lower limit, it is possible to suppress the increase in the diameter of the lens located on the image side of the aperture stop St, and it also becomes easier to secure the angle of view. By ensuring that the corresponding value of conditional expression (1) does not exceed the upper limit, it is possible to suppress the increase in the overall length of the optical system. To obtain better characteristics, it is more preferable for the imaging lens to satisfy at least one of the following conditional expressions (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 on the optical axis from the most object-side lens surface of the first lens group G1 to the most image-side lens surface of the third lens group G3 and Bf is TTL, the open F-number is FNo, and the maximum image height is Ymax, the imaging lens preferably satisfies the following conditional expression (2). Bf is the back focus at the entire system's air equivalent distance. Bf, TTL, and FNo are values in a state where the lens is focused on an infinitely distant object. By ensuring that the corresponding value of conditional expression (2) does not fall below the lower limit, it is possible to prevent excessive miniaturization, which is advantageous for correcting various aberrations. By ensuring that the corresponding value of conditional expression (2) does not exceed the upper limit, it is possible to suppress the increase in the size of the entire optical system. To obtain better characteristics, it is more preferable for the imaging lens to satisfy the following conditional expression (2-1), and even more preferably to satisfy the following conditional expression (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 in the state of focusing on an infinite object is f and the focal length of the second lens group G2 is f2, it is preferable that the imaging lens satisfies the following conditional expression (3). By preventing the corresponding value of the conditional expression (3) from falling below the lower limit, the positive refractive power of the second lens group G2 does not become too weak, so that an increase in the overall length of the optical system can be suppressed. By preventing the corresponding value of the conditional expression (3) from exceeding 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. In order to obtain better characteristics, it is more preferable that the imaging lens satisfies the following conditional expression (3-1), and it is even more preferable that the imaging lens satisfies the following conditional expression (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 in the state of focusing on an infinite object is f and the focal length of the third lens group G3 is f3, it is preferable that the imaging lens satisfies the following conditional expression (4). By preventing the corresponding value of the conditional expression (4) from falling 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 for suppressing spherical aberration. By preventing the corresponding value of the conditional expression (4) from exceeding the upper limit, the Petzval sum does not become too large, which is advantageous for suppressing field curvature. In order to obtain better characteristics, it is more preferable that the imaging lens satisfies the following conditional expression (4-1), and it is even more preferable that the imaging lens satisfies the following conditional expression (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 conditional expression (5). By preventing the corresponding value of the conditional expression (5) from falling below the lower limit, the refractive power of the second lens group G2 with respect to the first lens group G1 does not become too weak, making it easier to suppress field curvature. By preventing the corresponding value of the conditional expression (5) from exceeding the upper limit, the refractive power of the second lens group G2 with respect to the first lens group G1 does not become too strong, which is advantageous for suppressing the aberration generated within the second lens group G2. To obtain better characteristics, it is more preferable that the imaging lens satisfies the following conditional expression (5-1), and it is even more preferable that the imaging lens satisfies the following conditional expression (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 within the second lens group G2, the positive lens with the strongest refractive power will be referred to as the Lp lens Lp. The Lp lens Lp preferably has a shape with a convex surface facing the image side. In this case, it is advantageous for correcting various aberrations with respect to the off-axis light beam, and it is also advantageous for suppressing the reduction of the peripheral light quantity. In the example of FIG. 1, the 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 conditional expression (6). By preventing the corresponding value of the conditional expression (6) from falling below the lower limit, it is advantageous for correcting various aberrations, particularly spherical aberration, with respect to the off-axis light beam, and it is also advantageous for suppressing the reduction of the peripheral light quantity. By preventing the corresponding value of the conditional expression (6) from exceeding the upper limit, the refractive power of the Lp lens Lp does not become overly prominent and too strong within the second lens group G2, making it easier to correct various aberrations within the second lens group G2. To obtain better characteristics, it is more preferable that the imaging lens satisfies the following conditional expression (6-1), and it is even more preferable that the imaging lens satisfies the following conditional expression (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 the sum of the distance on the optical axis from the aperture stop St to the most image-side lens surface of the third lens group G3 and Bf is StI, and the sum of the distance on the optical axis from the image-side surface of the Lp lens Lp to the most image-side lens surface of the third lens group G3 and Bf is LpTI, it is preferable that the imaging lens satisfies the following conditional expression (7). Bf is the back focus at the air-equivalent distance of the entire system. Bf, StI, and LpTI are the values in the state of being focused on an infinitely distant object. By preventing the corresponding value of the conditional expression (7) from falling below the lower limit, it is possible to prevent the Lp lens Lp from being disposed relatively close to the object side, so that the refractive power of the Lp lens Lp acting on the off-axis light beam does not become too weak. As a result, it is possible to suppress an increase in the incident angle of the chief ray of the off-axis light beam to the image plane Sim, which is advantageous for suppressing a reduction in the peripheral light quantity. By preventing the corresponding value of the conditional expression (7) from exceeding the upper limit, the refractive power of the Lp lens Lp acting on the off-axis light beam does not become too strong, so that it becomes easy to correct various aberrations in the second lens group G2. In order to obtain better characteristics, it is more preferable that the imaging lens satisfies the following conditional expression (7-1), and it is even more preferable that the imaging lens satisfies the following conditional expression (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. In this case, it is advantageous for suppressing fluctuations in chromatic aberration associated with focusing. Among the negative lenses within the second lens group G2, the negative lens with the strongest refractive power is referred to as the Ln lens Ln. The Ln lens Ln is preferably located closer to the object side than 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 disposing the Lp lens Lp on the image side of the Ln lens Ln, 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, which is advantageous for suppressing a reduction in peripheral light quantity. In the example of FIG. 1, the 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 conditional expression (8). By preventing the corresponding value of the conditional expression (8) from falling below the lower limit, the refractive power of the Ln lens Ln with respect to the Lp lens Lp does not become too weak, so that the action of separating the on-axis light beam 2 and the off-axis light beam can be effectively obtained, and thereby, it becomes easy to shorten the overall length of the optical system. By preventing the corresponding value of the conditional expression (8) from exceeding the upper limit, the refractive power of the Ln lens Ln with respect to the Lp lens Lp does not become too strong, which is advantageous for suppressing various aberrations of the off-axis light beam generated when the on-axis light beam 2 and the off-axis light beam are separated. In order to obtain better characteristics, it is more preferable that the imaging lens satisfies the following conditional expression (8-1), and it is even more preferable that the imaging lens satisfies the following conditional expression (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 the sum of the distance on the optical axis from the aperture stop St to the most image-side lens surface of the third lens group G3 and Bf is defined as StI, and the sum of the distance on the optical axis from the most object-side lens surface of the first lens group G1 to the most image-side lens surface of the third lens group G3 and Bf is defined as TTL, it is preferable that the imaging lens satisfies the following conditional expression (9). Bf is the back focus at the air-equivalent distance of the entire system. Bf, StI, and TTL are the values in the state of being focused on an infinite object. By preventing the corresponding value of the conditional expression (9) from falling below the lower limit, the position of the aperture stop St does not approach the image plane Sim too much, so it is possible to prevent the incident angle of the chief ray of the off-axis light beam incident on the imaging element arranged on the image plane Sim from becoming too large. By preventing the corresponding value of the conditional expression (9) from exceeding the upper limit, a sufficient space on the object side of the aperture stop St can be secured, so an appropriate number of lenses can be arranged. As a result, the configuration can be achieved without unreasonably reducing the absolute value of the radius of curvature of the lens, so various aberrations can be preferably corrected. To obtain better characteristics, it is more preferable that the imaging lens satisfies the following conditional expression (9-1), and it is even more preferable that the imaging lens satisfies the following conditional expression (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 the lateral magnification of the focus group be βf, the lateral magnification of the third lens group G3 be β3, the focal length of the focus group be ff, and the distance from the image plane Sim to the exit pupil position be De, and γ = (1 - βf 2 ) × β3 2When it is [a certain situation], it is preferable that the imaging lens satisfies the following conditional expression (10). βf, β3, and De are values in a state of being focused on an infinite object. The sign of De is positive if the exit pupil position is on the object side with respect to the image plane Sim, and negative if the exit pupil position is on the image side with respect to the image plane Sim. Regarding the lower limit of the conditional expression (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| holds. The conditional expression (10) is an expression representing the change rate of the image size accompanying focusing. By preventing the corresponding value of the conditional expression (10) from exceeding the upper limit, it is possible to suppress the increase in bleeding (the change in the angle of view during the focusing operation). In order to obtain better characteristics, it is more preferable that the imaging lens satisfies the following conditional expression (10-1), and it is even more preferable that the imaging lens satisfies the following conditional expression (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 interval sandwiched between two opposing lens surfaces is regarded as a lens with a refractive index of 1, and this air interval is referred to as an air lens. By the action of two lens surfaces of the second lens group G2 facing each other with concave surfaces, it becomes easy to preferably correct spherical aberration, and it also becomes easy to suppress the Petzval sum of the entire optical system. In the example of FIG. 1, a biconvex air lens is formed by the image-side surface of the lens L23 and the object-side surface of the lens L24.

[0059] When the radius of curvature of the object side surface of at least one air lens of 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 conditional expression (11). By satisfying the conditional expression (11), it is possible to prevent the refractive power of one surface forming the air lens from being too strong or too weak with respect to the refractive power of the other surface, and it becomes easy to suitably correct spherical aberration. In order to obtain better characteristics, it is more preferable that the imaging lens satisfies the following conditional expression (11-1), and it is even more preferable that the imaging lens satisfies the following conditional expression (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 FIG. 1 is an example of the 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 FIG. 1. Each group of the imaging lens can be configured, for example, as follows.

[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 include two positive lenses and two negative lenses. The first lens group G1 may be configured to include three positive lenses and three negative lenses. The first lens group G1 may be configured to include four positive lenses and three negative lenses. The first lens group G1 may be configured to include four positive lenses and four 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 include two positive lenses and two negative lenses. The second lens group G2 may be configured to include three positive lenses and one negative lens. The second lens group G2 may be configured to include three positive lenses and two negative lenses. The second lens group G2 may be configured to include three positive lenses and three negative lenses. The second lens group G2 may be configured to include four positive lenses and two negative lenses.

[0063] The third lens group G3 may be configured to be a lens group having a negative refractive power, or may be configured to be a lens group having a positive refractive power. The number of lenses included in the third lens group G3 can be 2 or more and 3 or less. More specifically, the third lens group G3 may be configured to include one positive lens and one negative lens. The third lens group G3 may be configured to include one positive lens and two negative lenses.

[0064] The focus group may be configured to include the first lens group G1, the aperture stop St, and the second lens group G2.

[0065] The preferred configurations and possible configurations described above, including the configuration regarding the conditional expressions, can be combined arbitrarily, and it is preferable to selectively adopt them as appropriate according to the required specifications. Note that the conditional expressions preferably satisfied by the imaging lens of the present disclosure are not limited to the conditional expressions described in the form of equations, and include all conditional expressions obtained by arbitrarily combining the lower limit and the upper limit from among the conditional expressions described as preferable, more preferable, and even more preferable.

[0066] As an example, a preferred embodiment of the imaging lens of the present disclosure includes, in order from the object side to the image side, a first lens group G1 having a positive refractive power, an aperture stop St, a second lens group G2 having a positive refractive power, and a third lens group G3. The third lens group G3 includes one or more positive lenses and one or more negative lenses. During focusing, the entire first lens group G1, the aperture stop St, and the second lens group G2, or the entire second lens group G2 moves integrally as a focus group, and the third lens group G3 is fixed with respect to the image plane Sim. The imaging lens satisfies the above conditional expressions (1) and (2).

[0067] Next, examples of the imaging lens of the present disclosure will be described with reference to the drawings. Note that the reference numerals attached to the lenses in the cross-sectional views of each example are used independently for each example in order to avoid the complexity of description due to the increase in the number of digits of the reference numerals and the complexity of the drawings. Therefore, even if common reference numerals are attached in the drawings of different examples, they are not necessarily of the same configuration. Further, the following Examples 7 to 9 are examples of the present disclosure, and Examples 1 to 6 and 10 to 12 are reference examples of the present disclosure.

[0068] [Example 1] The cross-sectional view of the configuration of the imaging lens of Example 1 is shown in FIG. 1, and since the illustration method and configuration are as described above, the duplicate description is partially omitted here. The imaging lens of Example 1 includes, in order from the object side to the image side, a first lens group G1 having a positive refractive power, an aperture stop St, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power. During focusing from an infinite object to a close-distance object, the entire second lens group G2 moves integrally toward the object side, and the first lens group G1, the aperture stop 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 are shown in Table 2, the variable surface intervals are shown in Table 3, and the aspherical coefficients are shown in Table 4.

[0070] Table 1 is described as follows. In the column of Sn, the surface numbers are shown when the numbers are incremented one by one with the surface closest to the object side being the first surface and moving towards the image side. In the column of R, the radius of curvature of each surface is shown. In the column of D, the axial surface interval between each surface and the surface adjacent to it on the image side is shown. In the column of Nd, the refractive index of each component with respect to the d-line is shown. In the column of νd, the Abbe number of each component based on the d-line is shown.

[0071] In Table 1, 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 the optical member PP. In the column of the surface number corresponding to the aperture stop St, the surface number and the phrase "(St)" are described. The value in the bottom row of D in Table 1 is the interval between the surface furthest on the image side in the table and the image plane Sim. In Table 1, for the variable surface interval during focusing, the symbol DD[ ] is used, and the surface number on the object side of this interval is appended in [ ] and entered in the column of D.

[0072] Table 2 shows the focal length f of the entire system, the back focus Bf at the air-equivalent distance of the entire system, the open F-number FNo., the maximum full field angle 2ω, and the maximum image height Ymax. The FNo in the conditional formula, the FNo. in the specification table, and the FNo. in the aberration diagram described later are the same. The (°) in the column of 2ω means that the unit is degrees. Table 2 shows the values in the state of focusing on an object at infinity.

[0073] In Table 3, the row of "infinity" shows the variable surface interval in the state of focusing on an object at infinity, and the row below it shows the object distance of the closest object distance and the variable surface interval in the state of focusing on that closest object distance. For example, in Table 3, the object distance of the closest object distance is 0.215 m (meter). Tables 1, 2, and 3 show the values based on the d-line.

[0074] In the basic lens data, an asterisk is attached to the surface number of the aspheric surface, and the value of the paraxial radius of curvature is described in the column of the radius of curvature of the aspheric surface. In Table 4, the row of Sn shows the surface number of the aspheric surface, and the rows of KA and Am show the numerical values of the aspheric coefficients for each aspheric surface. Note that m in Am is an integer of 3 or more and 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 aspheric coefficient in Table 4 means "×10 ±n ". KA and Am are the aspheric coefficients in the aspheric formula represented by the following formula. Zd = C × h 2 / {1+(1 - KA × C 2 × h 2 ) 1 / 2}+ ΣAm × h m However, Zd: Aspheric depth (the length of the perpendicular dropped from a point on the aspheric surface at height h to the plane perpendicular to the optical axis Z where the aspheric 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: Aspheric coefficients where Σ in the aspheric 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] FIG. 3 shows aberration diagrams of the imaging lens of Example 1. In FIG. 3, from the left in order, spherical aberration, astigmatism, distortion, and longitudinal chromatic aberration are shown. In the upper part of FIG. 3 labeled "Distance: Infinity", aberration diagrams in the state of focusing on an infinite object are shown, and in the lower part labeled "Distance: 0.215 m", aberration diagrams in the state of focusing on an object with an object distance of 0.215 m (meter) are shown. In the spherical aberration diagram, the aberrations in the d-line, C-line, F-line, and g-line are shown by a solid line, a long dashed line, a short dashed line, and a double-dashed line, respectively. In the astigmatism diagram, the aberration in the d-line in the sagittal direction is shown by a solid line, and the aberration in the d-line in the tangential direction is shown by a short dashed line. In the distortion diagram, the aberration in the d-line is shown by a solid line. In the longitudinal chromatic aberration diagram, the aberrations in the C-line, F-line, and g-line are shown by a long dashed line, a short dashed line, and a double-dashed line, respectively. In the spherical aberration diagram, the value of the open F-number is shown after "FNo.=". In the other aberration diagrams, the value of the maximum semi-aperture angle is shown after "ω=".

[0081] The symbols, meanings, description methods, and illustration methods of the respective data regarding the above Example 1 are the same in the following examples as well, unless otherwise specified, so redundant explanations are omitted below.

[0082] [Example 2] A cross-sectional view of the configuration of the imaging lens according to Embodiment 2 is shown in FIG. 4. The imaging lens according to Embodiment 2 includes, in order from the object side to the image side along the optical axis Z, a first lens group G1 having a positive refractive power, an aperture stop St, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power. The first lens group G1 includes four lenses L11 to L14 in order from the object side to the image side. The second lens group G2 includes five lenses L21 to L25 in order from the object side to the image side. The third lens group G3 includes three lenses L31 to L33 in order from the object side to the image side. When focusing from an infinite object to a close object, the entire second lens group G2 moves integrally toward the object side, and the first lens group G1, the aperture stop St, and the third lens group G3 are fixed with respect to the image plane Sim.

[0083] Regarding the imaging lens according to Embodiment 2, the basic lens data is shown in Table 5, the specifications are shown in Table 6, the variable surface intervals are shown in Table 7, the aspherical coefficients are shown in Table 8, and each aberration diagram is shown in FIG. 5.

[0084] [Table 5]

[0085] [Table 6]

[0086] [Table 7]

[0087] [Table 8]

[0088] [Embodiment 3] A cross-sectional view of the configuration of the imaging lens according to Embodiment 3 is shown in FIG. 6. The imaging lens according to Embodiment 3 includes, in order from the object side to the image side along the optical axis Z, a first lens group G1 having a positive refractive power, an aperture stop St, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power. The first lens group G1 includes six lenses L11 to L16 in order from the object side to the image side. The second lens group G2 includes six lenses L21 to L26 in order from the object side to the image side. The third lens group G3 includes three lenses L31 to L33 in order from the object side to the image side. When focusing from an infinite object to a close object, the entire second lens group G2 moves integrally toward the object side, and the first lens group G1, the aperture stop St, and the third lens group G3 are fixed with respect to the image plane Sim.

[0089] Regarding the imaging lens according to Embodiment 3, the basic lens data is shown in Table 9, the specifications are shown in Table 10, the variable surface intervals are shown in Table 11, the aspherical coefficients are shown in Table 12, and each aberration diagram is shown in FIG. 7.

[0090] [Table 9]

[0091] [Table 10]

[0092] [Table 11]

[0093] [Table 12]

[0094] [Embodiment 4] A cross-sectional view of the configuration of the imaging lens according to Example 4 is shown in FIG. 8. The imaging lens according to Example 4 includes, in order from the object side to the image side along the optical axis Z, a first lens group G1 having a positive refractive power, an aperture stop St, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. The first lens group G1 consists of six lenses L11 to L16 in order from the object side to the image side. The second lens group G2 consists of four lenses L21 to L24 in order from the object side to the image side. The third lens group G3 consists of three lenses L31 to L33 in order from the object side to the image side. When focusing from an infinite object to a close-distance object, the entire first lens group G1, the aperture stop St, and the second lens group G2 move integrally toward the object side, and the third lens group G3 is fixed with respect to the image plane Sim.

[0095] Regarding the imaging lens of Example 4, the basic lens data is shown in Table 13, the specifications are shown in Table 14, the variable surface intervals are shown in Table 15, the aspherical coefficients are shown in Table 16, and each aberration diagram is shown in FIG. 9.

[0096] [Table 13]

[0097] [Table 14]

[0098] [Table 15]

[0099] [Table 16]

[0100] [Example 5] A cross-sectional view of the configuration of the imaging lens according to Example 5 is shown in FIG. 10. The imaging lens according to Example 5 includes, in order from the object side to the image side along the optical axis Z, a first lens group G1 having a positive refractive power, an aperture stop St, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. The first lens group G1 consists of six lenses L11 to L16 in order from the object side to the image side. The second lens group G2 consists of four lenses L21 to L24 in order from the object side to the image side. The third lens group G3 consists of three lenses L31 to L33 in order from the object side to the image side. When focusing from an infinite object to a close object, the entire first lens group G1, the aperture stop St, and the second lens group G2 move integrally toward the object side, and the third lens group G3 is fixed with respect to the image plane Sim.

[0101] Regarding the imaging lens according to Example 5, the basic lens data is shown in Table 17, the specifications are shown in Table 18, the variable surface intervals are shown in Table 19, the aspherical coefficients are shown in Table 20, and each aberration diagram is shown in FIG. 11.

[0102] [Table 17]

[0103] [Table 18]

[0104] [Table 19]

[0105] [Table 20]

[0106] [Example 6] A cross-sectional view of the configuration of the imaging lens according to Example 6 is shown in FIG. 12. The imaging lens according to Example 6 includes, in order from the object side to the image side along the optical axis Z, a first lens group G1 having a positive refractive power, an aperture stop St, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. The first lens group G1 consists of six lenses L11 to L16 in order from the object side to the image side. The second lens group G2 consists of four lenses L21 to L24 in order from the object side to the image side. The third lens group G3 consists of three lenses L31 to L33 in order from the object side to the image side. When focusing from an infinite object to a close object, the entire first lens group G1, the aperture stop St, and the second lens group G2 move integrally toward the object side, and the third lens group G3 is fixed with respect to the image plane Sim.

[0107] Regarding the imaging lens according to Example 6, the basic lens data is shown in Table 21, the specifications are shown in Table 22, the variable surface intervals are shown in Table 23, the aspherical coefficients are shown in Table 24, and each aberration diagram is shown in FIG. 13.

[0108] [Table 21]

[0109] [Table 22]

[0110] [Table 23]

[0111] [Table 24]

[0112] [Example 7] A cross-sectional view of the configuration of the imaging lens of Example 7 is shown in FIG. 14. The imaging lens of Example 7 includes, in order from the object side to the image side along the optical axis Z, a first lens group G1 having a positive refractive power, an aperture stop St, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power. The first lens group G1 consists of seven lenses L11 to L17 in order from the object side to the image side. The second lens group G2 consists of six lenses L21 to L26 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. When focusing from an infinite object to a close object, the entire second lens group G2 moves integrally toward the object side, and the first lens group G1, the aperture stop St, and the third lens group G3 are fixed with respect to the image plane Sim.

[0113] For the imaging lens of Example 7, the basic lens data is shown in Table 25, the specifications are shown in Table 26, the variable surface intervals are shown in Table 27, the aspherical coefficients are shown in Table 28, and each aberration diagram is shown in FIG. 15.

[0114] [Table 25]

[0115] [Table 26]

[0116] [Table 27]

[0117] [Table 28]

[0118] [Example 8] A cross-sectional view of the configuration of the imaging lens according to Example 8 is shown in FIG. 16. The imaging lens according to Example 8 includes, in order from the object side to the image side along the optical axis Z, a first lens group G1 having a positive refractive power, an aperture stop St, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power. The first lens group G1 consists of seven lenses L11 to L17 in order from the object side to the image side. The second lens group G2 consists of six lenses L21 to L26 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. When focusing from an infinite object to a close-distance object, the entire second lens group G2 moves integrally toward the object side, and the first lens group G1, the aperture stop St, and the third lens group G3 are fixed with respect to the image plane Sim.

[0119] Regarding the imaging lens according to Example 8, the basic lens data is shown in Table 29, the specifications are shown in Table 30, the variable surface intervals are shown in Table 31, the aspherical coefficients are shown in Table 32, and each aberration diagram is shown in FIG. 17.

[0120] [Table 29]

[0121] [Table 30]

[0122] [Table 31]

[0123] [Table 32]

[0124] [Example 9] A cross-sectional view of the configuration of the imaging lens of Example 9 is shown in FIG. 18. The imaging lens of Example 9 includes, in order from the object side to the image side along the optical axis Z, a first lens group G1 having a positive refractive power, an aperture stop St, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power. The first lens group G1 consists of seven lenses L11 to L17 in order from the object side to the image side. The second lens group G2 consists of six lenses L21 to L26 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. When focusing from an infinite object to a close object, the entire second lens group G2 moves integrally toward the object side, and the first lens group G1, the aperture stop St, and the third lens group G3 are fixed with respect to the image plane Sim.

[0125] Regarding the imaging lens of Example 9, the basic lens data is shown in Table 33, the specifications are shown in Table 34, the variable surface intervals are shown in Table 35, the aspherical coefficients are shown in Table 36, and each aberration diagram is shown in FIG. 19.

[0126]

Table 33

[0127]

Table 34

[0128]

Table 35

[0129]

Table 36

[0130] [Example 10] A cross-sectional view of the configuration of the imaging lens according to Example 10 is shown in FIG. 20. The imaging lens according to Example 10 includes, in order from the object side to the image side along the optical axis Z, a first lens group G1 having a positive refractive power, an aperture stop St, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power. The first lens group G1 includes eight lenses L11 to L18 in order from the object side to the image side. The second lens group G2 includes four lenses L21 to L24 in order from the object side to the image side. The third lens group G3 includes three lenses L31 to L33 in order from the object side to the image side. When focusing from an infinite object to a close object, the entire second lens group G2 moves integrally toward the object side, and the first lens group G1, the aperture stop St, and the third lens group G3 are fixed with respect to the image plane Sim.

[0131] For the imaging lens according to Example 10, the basic lens data is shown in Table 37, the specifications are shown in Table 38, the variable surface intervals are shown in Table 39, the aspherical coefficients are shown in Table 40, and each aberration diagram is shown in FIG. 21.

[0132] [Table 37]

[0133] [Table 38]

[0134] [Table 39]

[0135] [Table 40]

[0136] [Example 11] A cross-sectional view of the configuration of the imaging lens of Example 11 is shown in FIG. 22. The imaging lens of Example 11 includes, in order from the object side to the image side along the optical axis Z, a first lens group G1 having a positive refractive power, an aperture stop St, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power. The first lens group G1 consists of six lenses L11 to L16 in order from the object side to the image side. The second lens group G2 consists of six lenses L21 to L26 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. When focusing from an infinite object to a close object, the entire second lens group G2 moves integrally toward the object side, and the first lens group G1, the aperture stop St, and the third lens group G3 are fixed with respect to the image plane Sim.

[0137] For the imaging lens of Example 11, the basic lens data is shown in Table 41, the specifications are shown in Table 42, the variable surface intervals are shown in Table 43, the aspherical coefficients are shown in Table 44, and each aberration diagram is shown in FIG. 23.

[0138] [Table 41]

[0139] [Table 42]

[0140] [Table 43]

[0141] [Table 44]

[0142] [Example 12] A cross-sectional view of the configuration of the imaging lens according to Example 12 is shown in FIG. 24. The imaging lens according to Example 12 includes, in order from the object side to the image side along the optical axis Z, a first lens group G1 having a positive refractive power, an aperture stop St, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power. The first lens group G1 consists of six lenses L11 to L16 in order from the object side to the image side. The second lens group G2 consists of six lenses L21 to L26 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. When focusing from an infinite object to a close object, the entire second lens group G2 moves integrally toward the object side, and the first lens group G1, the aperture stop St, and the third lens group G3 are fixed with respect to the image plane Sim.

[0143] For the imaging lens of Example 11, the basic lens data is shown in Table 45, the specifications are shown in Table 46, the variable surface intervals are shown in Table 47, the aspherical coefficients are shown in Table 48, and each aberration diagram is shown in FIG. 25.

[0144] [Table 45]

[0145] [Table 46]

[0146] [Table 47]

[0147] [Table 48]

[0148] Table 49 shows the corresponding values of the conditional expressions (1) to (11) of the imaging lens of the above example. Table 49 shows the values based on the d-line.

[0149]

Table 49

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

[0151] The camera 30 includes a camera body 31, and a shutter button 32 and a power button 33 are provided on the upper surface of the camera body 31. Further, 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 the captured image and the image within the angle of view before being captured.

[0152] A photographing aperture through which light from a photographing object enters is provided at the center of the front surface of the camera body 31, and a mount 37 is provided at a position corresponding to the photographing aperture. The interchangeable lens 20 is attached to the camera body 31 via the mount 37.

[0153] Inside the camera body 31, an imaging element such as a CCD (Charge Coupled Device) or a 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 are provided. In the camera 30, it is possible to photograph a still image or a moving image by pressing the shutter button 32, and the image data obtained by this photographing is recorded on the above recording medium.

[0154] The above has described the technology of the present disclosure by way of embodiments and examples. However, the technology of the present disclosure is not limited to the above embodiments and examples, and various modifications are possible. For example, the radius of curvature, surface interval, 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.

[0155] Also, the imaging device according to the embodiment of the present disclosure is not limited to the above example. For example, it can be in various forms such as cameras other than the mirrorless type, film cameras, and video cameras.

Explanation of Reference Numerals

[0156] 1 Imaging lens 2 On-axis light beam 3 Light beam at the maximum image height 20 Interchangeable lens 30 Camera 31 Camera body 32 Shutter button 33 Power button 34, 35 Operation unit 36 Display unit 37 Mount G1 First lens group G2 Second lens group G3 Third lens group L11~L33 Lenses Ln Ln lens Lp Lp lens PP Optical member Sim Image plane St Aperture stop Ymax Maximum image height Z Optical axis

Claims

1. It consists of a first lens group having a positive refractive power, a diaphragm, a second lens group having a positive refractive power, and a third lens group, in order from the object side to the image side. The first lens group includes, in order from the object side to the image side, a non-joined lens with a concave surface facing the image side and a positive lens, which are continuously arranged. The second lens group includes only one first joined lens formed by joining a biconvex lens and a biconcave lens in order from the object side. The second lens group includes only one second joined lens formed by joining a biconcave lens and a positive lens in order from the object side. The second lens group includes a non-joined biconvex lens arranged adjacent to the image side of the second joined lens. The third lens group includes one or more positive lenses and one or more negative lenses. A non-joined negative lens with a concave surface facing the object side is arranged on the most image side of the third lens group. The number of positive lenses included in the entire system is 9. During focusing, only the entire second lens group moves integrally as a focus group, and the first lens group and the third lens group are fixed with respect to the image plane. Let Bf be the back focus at the air equivalent distance of the entire system in the state of focusing on an infinite object. Let f be the focal length of the entire system in the state of focusing on an infinite object. Let TTL be the sum of the distance on the optical axis from the most object-side lens surface of the first lens group to the most image-side lens surface of the third lens group and Bf in the state of focusing on an infinite object. Let FNo be the open F-number in the state of focusing on an infinite object. When the maximum image height is Ymax. 0.1 < Bf / f < 1.2 (1) 5.5 < TTL × FNo / Ymax < 9.2 (2-1) An imaging lens that satisfies the conditional expressions (1) and (2-1) represented by the above.

2. When the focal length of the second lens group is f2. 0.2 < f / f2 < 2 (3) The imaging lens according to Claim 1, which satisfies the conditional expression (3) represented by the above.

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

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

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

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

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

8. When the focal length of the first lens group is f1, and the focal length of the second lens group is f2, 1 < f1 / f2 < 3.5 (5) The imaging lens according to any one of claims 1 to 7, which satisfies the conditional expression (5) represented by.

9. 1.2 < f1 / f2 < 3 (5-1) The imaging lens according to claim 8, which satisfies the conditional expression (5-1) represented by.

10. 1.4 < f1 / f2 < 2.5 (5-2) The imaging lens according to claim 9, which satisfies the conditional expression (5-2) represented by.

11. Among the positive lenses in the second lens group, the Lp lens with the strongest refractive power faces the convex surface toward the image side, when the focal length of the second lens group is f2, and the focal length of the Lp lens is f2p, 0.9 < f2 / f2p < 3.5 (6) The imaging lens according to any one of claims 1 to 10, which satisfies the conditional expression (6) represented by.

12. 1.1 < f2 / f2p < 3 (6-1) The imaging lens according to claim 11, which satisfies the conditional expression (6-1) represented by.

13. 1.3 < f2 / f2p < 2.5 (6-2) The imaging lens according to claim 12, which satisfies the conditional expression (6-2) represented by.

14. 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 side than the Lp lens, when the focal length of the Ln lens is f2n, -2 < f2p / f2n < -0.4 (8) The imaging lens according to any one of claims 11 to 13, which satisfies the conditional expression (8) represented by.

15. -1.75 < f2p / f2n < -0.45 (8-1) The imaging lens according to claim 14, which satisfies the conditional expression (8-1) represented by.

16. -1.5 < f2p / f2n < -0.5 (8-2) The imaging lens according to claim 15, which satisfies the conditional expression (8-2) represented by.

17. The second lens group includes one or more air lenses formed by two opposing lens surfaces, when 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) The imaging lens according to any one of claims 1 to 16, which satisfies the conditional expression (11) represented by the above.

18.

19. The first lens group includes, in order from the object side to the image side, a non-bonded lens with a concave surface facing the image side, the positive lens, a lens with a concave surface facing the image side, and a lens with a convex surface facing the object side. The imaging lens according to any one of claims 1 to 17.

19.

20. A double convex lens that is not bonded is disposed on the most object side of the third lens group. The imaging lens according to any one of claims 1 to 18.

20. An imaging device including the imaging lens according to any one of claims 1 to 19.

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