Imaging lens and imaging device

Abstract

The invention provides an imaging lens which is small in size and maintains good optical performance, and an imaging device provided with the imaging lens. The imaging lens sequentially comprises a front group, a diaphragm and a rear group from an object side to an image side. The rear group includes at least one aspherical lens having a concave surface facing the image side in a paraxial region and having an inflection point at which the concave-convex shape changes midway as the lens surface on the image side moves from the optical axis to the peripheral portion. The imaging lens meets the conditional expression related to the back focal length Bf of the whole system, the focal length f of the whole system and the maximum half visual angle omega m: 0.3 < Bf / (f * tan omega m) < 1.5. The imaging lens includes at least one lens satisfying a conditional expression related to a temperature coefficient (dN / dT) * 10 <-6 > of a refractive index of the lens: 0 < dN / dT < 15.

Description

Technical Field

[0001] The technology of the present invention relates to an imaging lens and a photographing device. Background Art

[0002] Conventionally, as an imaging lens that can be used in a photographing device such as a digital camera, there is known a photographing optical system described in Patent Document 1 below.

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2022-099402

[0004] There is a need for an imaging lens configured to be small and maintain good optical performance. The level of these requirements has been increasing year by year. Summary of the Invention

[0005] An object of the present invention is to provide an imaging lens configured to be small and maintain good optical performance, and a photographing device including the imaging lens.

[0006] A first aspect of the present invention is an imaging lens that sequentially includes, from the object side to the image side: a front group including one or more lenses, a diaphragm, and a rear group including a plurality of lenses. The rear group includes at least one first aspherical lens. The first aspherical lens has a concave surface facing the image side in the paraxial region, and an inflection point where the concavo-convex shape changes midway as it moves from the optical axis toward the peripheral portion on the lens surface on the image side. The imaging lens includes at least one lens that satisfies

[0007] 0.3 < Bf / (f × tan ωm) < 1.5 (1)

[0008] represented by the conditional expression (1), and satisfies

[0009] 0 < |dN / dT| < 15 (2)

[0010] represented by the conditional expression (2).

[0011] Here, Bf is the back focal length under the air-equivalent distance of the entire system in the state of focusing on an object at infinity. f is the focal length of the entire system in the state of focusing on an object at infinity. ωm is the maximum half-angle in the state of focusing on an object at infinity. (dN / dT)×10 -6 is the temperature coefficient of the refractive index of the lens included in the entire system with respect to the d-line under the condition of 25°C. The unit of dN / dT is °C.

[0012] In a second aspect of the present invention, in the imaging lens according to the first aspect, when the distance on the optical axis from the lens surface closest to the object side of the front group to the lens surface closest to the image side of the rear group in the state of focusing on an object at infinity and Bf are set as TL, it satisfies

[0013] 1.1 < TL / f < 3.5 (3)

[0014] The conditional expression (3) represented by

[0015] In the imaging lens of the third aspect of the present invention, the following is satisfied

[0016] 1.2 < TL / f < 3 (3-1)

[0017] The conditional expression (3-1) represented by

[0018] In the imaging lens of the fourth aspect of the present invention, the following is satisfied

[0019] 0.36 < Bf / (f × tan ωm) < 1.2 (1-1)

[0020] The conditional expression (1-1) represented by

[0021] In the imaging lens of the fifth aspect of the present invention, when the open F value in the state of focusing on an infinitely distant object is set as Fno, the following is satisfied

[0022] 1.6 < Fno / tan ωm < 5 (4)

[0023] The conditional expression (4) represented by

[0024] In the imaging lens of the sixth aspect of the present invention, the following is satisfied

[0025] 2 < Fno / tan ωm < 3.2 (4-1)

[0026] The conditional expression (4-1) represented by

[0027] In the imaging lens of the seventh aspect of the present invention, the following is satisfied

[0028] 0 < dFSt / TL < 0.8 (5)

[0029] 0 < dStR / TL < 0.8 (6)

[0030] The conditional expressions (5) and (6) represented by

[0031] Among them, the minimum value of the distance on the optical axis from the lens surface closest to the image side of the front group to the diaphragm is set as dFSt. Regarding the sign of dFSt, it is set as positive when the diaphragm is closer to the image side than the lens surface closest to the image side of the front group, and is set as negative when the diaphragm is closer to the object side than the lens surface closest to the image side of the front group. The minimum value of the distance on the optical axis from the diaphragm to the lens surface closest to the object side of the rear group is set as dStR. Regarding the sign of dStR, it is set as positive when the lens surface closest to the object side of the rear group is closer to the image side than the diaphragm, and is set as negative when the lens surface closest to the object side of the rear group is closer to the object side than the diaphragm. The sum of the distance on the optical axis from the lens surface closest to the object side of the front group to the lens surface closest to the image side of the rear group and Bf in the state of focusing on an infinite object is set as TL.

[0032] In the imaging lens according to the eighth aspect of the present invention, the following is satisfied

[0033] 0.67 < dSt / TL < 0.93 (7)

[0034] The conditional expression (7) represented.

[0035] Among them, the sum of the distance on the optical axis from the diaphragm to the lens surface closest to the image side of the rear group and Bf in the state of focusing on an infinite object is set as dSt. The sum of the distance on the optical axis from the lens surface closest to the object side of the front group to the lens surface closest to the image side of the rear group and Bf in the state of focusing on an infinite object is set as TL.

[0036] In the imaging lens according to the ninth aspect of the present invention, when the paraxial curvature radius of the object side surface of the lens closest to the object side of the front group is set as RL1f and the paraxial curvature radius of the image side surface of the lens closest to the object side of the front group is set as RL1r, the following is satisfied

[0037] -3 < (RL1r — RL1f) / (RL1r + RL1f) < 0 (8)

[0038] The conditional expression (8) represented.

[0039] In the imaging lens according to the tenth aspect of the present invention, the following is satisfied

[0040] 0.02 < dA1 / TL < 0.6 (9)

[0041] The conditional expression (9) represented.

[0042] Among them, the sum of the distance on the optical axis from the image-side surface of the first aspherical lens included in the rear group in the state of focusing on an infinitely distant object to the image-side lens surface of the rearmost lens of the rear group and Bf is defined as dA1. The sum of the distance on the optical axis from the object-side lens surface of the front group to the image-side lens surface of the rearmost lens of the rear group in the state of focusing on an infinitely distant object and Bf is defined as TL.

[0043] In the imaging lens according to the 11th aspect of the present invention, the following is satisfied

[0044] 0.08 < dA1 / TL < 0.35 (9 - 1)

[0045] represented by the conditional expression (9 - 1).

[0046] In the imaging lens according to the 12th aspect of the present invention, the front group includes at least one lens that satisfies the conditional expression (2).

[0047] In the imaging lens according to the 13th aspect of the present invention, the object-side lens of the front group closest to the object satisfies the conditional expression (2).

[0048] In the imaging lens according to the 14th aspect of the present invention, the rear group includes at least one lens that satisfies the conditional expression (2).

[0049] In the imaging lens according to the 15th aspect of the present invention, when the sum of the distance on the optical axis from the object-side lens surface of the front group to the image-side lens surface of the rearmost lens of the rear group in the state of focusing on an infinitely distant object and Bf is defined as TL, the following is satisfied

[0050] 1.2 < TL / (f × tanωm) < 3 (10)

[0051] represented by the conditional expression (10).

[0052] In the imaging lens according to the 16th aspect of the present invention, the following is satisfied

[0053] 1.7 < TL / (f × tanωm) < 2.5 (10 - 1)

[0054] represented by the conditional expression (10 - 1).

[0055] In the imaging lens according to the 17th aspect of the present invention, the following is satisfied

[0056] 1.2 < TL / f < 3 (3 - 1)

[0057] represented by the conditional expression (3 - 1).

[0058] In the 18th aspect of the present invention, in the imaging lens of the 17th aspect, when the open F-number in the state of focusing on an infinitely distant object is set to Fno, the following is satisfied:

[0059] 2 < Fno / tanωm < 3.2 (4 - 1)

[0060] The conditional expression (4 - 1) represented by the above.

[0061] In the 19th aspect of the present invention, in the imaging lens of the 18th aspect, the following is satisfied:

[0062] 0.36 < Bf / (f × tanωm) < 1.2 (1 - 1)

[0063] The conditional expression (1 - 1) represented by the above.

[0064] In the 20th aspect of the present invention, in the imaging lens of the 19th aspect, when the paraxial curvature radius of the object-side surface of the lens closest to the object in the front group is set to RL1f and the paraxial curvature radius of the image-side surface of the lens closest to the object in the front group is set to RL1r, the following is satisfied:

[0065] -1 < (RL1r - RL1f) / (RL1r + RL1f) < -0.07 (8 - 1)

[0066] The conditional expression (8 - 1) represented by the above.

[0067] In the 21st aspect of the present invention, in the imaging lens of the 18th aspect, when the sum of the distance on the optical axis from the aperture stop to the lens surface closest to the image in the rear group and Bf in the state of focusing on an infinitely distant object is set to dSt, the following is satisfied:

[0068] 0.67 < dSt / TL < 0.93 (7)

[0069] The conditional expression (7) represented by the above.

[0070] In the 22nd aspect of the present invention, in the imaging lens of the 21st aspect, when the sum of the distance on the optical axis from the image-side surface of the first aspherical lens closest to the image in the rear group, which is included in the rear group in the state of focusing on an infinitely distant object, to the lens surface closest to the image in the rear group and Bf is set to dA1, the following is satisfied:

[0071] 0.08 < dA1 / TL < 0.35 (9 - 1)

[0072] The conditional expression (9 - 1) represented by the above.

[0073] In the 23rd aspect of the present invention, in the imaging lens of the 22nd aspect, the front group includes at least one lens that satisfies the conditional expression (2).

[0074] In the 24th aspect of the present invention, in the imaging lens of the 23rd aspect, the lens closest to the object side in the front group satisfies the conditional expression (2).

[0075] In the 25th aspect of the present invention, in the imaging lens of the 1st aspect, the front group includes at least one lens that satisfies the following when the refractive index with respect to the d-line and the Abbe number based on the d-line of the lenses included in the entire system are set as Nd and vd, respectively:

[0076] 1.6 < Nd + 0.01 × vd < 2.6 (11)

[0077] represented by the conditional expression (11).

[0078] In the 26th aspect of the present invention, in the imaging lens of the 25th aspect, the lens closest to the object side in the front group satisfies the conditional expression (11).

[0079] In the 27th aspect of the present invention, in the imaging lens of the 1st aspect, when the focal length of the lens closest to the object side in the front group is set as fL1, it satisfies

[0080] -1.5 < f / fL1 < 0 (12)

[0081] represented by the conditional expression (12).

[0082] In the 28th aspect of the present invention, in the imaging lens of the 1st aspect, when the paraxial curvature radius of the image-side surface of the first aspherical lens closest to the image side among the first aspherical lenses included in the rear group is set as RA1c, and the curvature radius at the position of the maximum effective diameter of the image-side surface of the first aspherical lens closest to the image side among the first aspherical lenses included in the rear group is set as RA1y, it satisfies

[0083] -100 < RA1y / RA1c < 0 (13)

[0084] represented by the conditional expression (13).

[0085] In the 29th aspect of the present invention, in the imaging lens of the 1st aspect, when the refractive index with respect to the d-line and the Abbe number based on the d-line of the first aspherical lens closest to the image side among the first aspherical lenses included in the rear group are set as NdA1 and vdA1, respectively, it satisfies

[0086] 1.8 < NdA1 + 0.01 × vdA1 < 2.14 (14)

[0087] represented by the conditional expression (14).

[0088] In the 30th aspect of the present invention, in the imaging lens of the 1st aspect, the rear group includes at least one 2nd aspherical lens, and the 2nd aspherical lens has a convex surface facing the image side in the paraxial region, and has a lens surface on the image side where the refractive power at the position of the maximum effective diameter is shifted in the negative direction compared to the refractive power in the paraxial region.

[0089] In the 31st aspect of the present invention, in the imaging lens of the 30th aspect, when the paraxial curvature radius of the image-side surface of the 2nd aspherical lens is set as RA2c and the curvature radius at the position of the maximum effective diameter of the image-side surface of the 2nd aspherical lens is set as RA2y,

[0090] all the 2nd aspherical lenses included in the rear group satisfy

[0091] -1 < RA2c / RA2y < 1 (15)

[0092] the conditional expression (15) represented.

[0093] In the 32nd aspect of the present invention, in the imaging lens of the 30th aspect, it satisfies

[0094] 0.2 < dA2 / TL < 0.6 (16)

[0095] the conditional expression (16) represented.

[0096] Here, the sum of the distance on the optical axis from the image-side surface of the 2nd aspherical lens closest to the image side among the 2nd aspherical lenses included in the rear group to the image-side lens surface of the rear group and Bf in the state of focusing on an infinite object is set as dA2. The sum of the distance on the optical axis from the object-side lens surface of the front group closest to the object side to the image-side lens surface of the rear group and Bf in the state of focusing on an infinite object is set as TL.

[0097] In the 33rd aspect of the present invention, in the imaging lens of the 32nd aspect, the second lens from the image side of the rear group is the 2nd aspherical lens closest to the image side among the 2nd aspherical lenses included in the rear group.

[0098] In the 34th aspect of the present invention, in the imaging lens of the 33rd aspect, the second lens from the image side of the rear group has an inflection point where the concavo-convex shape changes midway as it moves from the optical axis to the peripheral part on the image-side lens surface.

[0099] In the 35th aspect of the present invention, in the imaging lens of the 1st aspect, the lens closest to the image side of the rear group is a 1st aspherical lens.

[0100] In the 36th aspect of the present invention, in the imaging lens of the 35th aspect, the lens closest to the image side of the rear group has a convex surface facing the object side in the paraxial region, and has an inflection point where the concavo-convex shape changes midway as it moves from the optical axis to the peripheral part on the object-side lens surface.

[0101] In the 37th aspect of the present invention, in the imaging lens of the 1st aspect, the rear group includes two 1st aspherical lenses.

[0102] In the 38th aspect of the present invention, in the imaging lens of the 30th aspect, the rear group includes two 2nd aspherical lenses.

[0103] In the 39th aspect of the present invention, in the imaging lens of the 1st aspect, at least one cemented lens is included.

[0104] In the 40th aspect of the present invention, in the imaging lens of the 1st aspect, the lens closest to the object side in the front group satisfies conditional expression (2) and satisfies

[0105] 1.2 < TL / f < 1.6 (3-2)

[0106] 2.5 < Fno / tanωm < 4 (4-2)

[0107] 0.67 < dSt / TL < 0.93 (7)

[0108] 0.08 < dA1 / TL < 0.35 (9-1)

[0109] The conditional expressions (3-2), (4-2), (7), and (9-1) represented.

[0110] Herein, the distance on the optical axis from the lens surface closest to the object side in the front group to the lens surface closest to the image side in the rear group in the state of focusing on an infinitely distant object plus Bf is defined as TL. The open F value in the state of focusing on an infinitely distant object is defined as Fno. The distance on the optical axis from the diaphragm to the lens surface closest to the image side in the rear group in the state of focusing on an infinitely distant object plus Bf is defined as dSt. The distance on the optical axis from the image side surface of the 1st aspherical lens closest to the image side in the rear group included in the rear group in the state of focusing on an infinitely distant object plus Bf is defined as dA1.

[0111] The 41st aspect of the present invention is an imaging device including the imaging lens of any one of the 1st aspect to the 40th aspect.

[0112] In addition, "including ~" and "composed of ~" in this specification mean that in addition to the components listed, lenses having substantially no refractive power, optical components 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 can also be included.

[0113] Regarding the radius of curvature, the sign of the refractive power, and the surface shape related to a lens including an aspherical surface, unless otherwise specified, the radius of curvature, the sign of the refractive power, and the surface shape in the paraxial region are used. Regarding the sign of the radius of curvature, the sign of the radius of curvature of the surface with the convex shape facing the object side is set to positive, and the sign of the radius of curvature of the surface with the convex shape facing the image side is set to negative.

[0114] The "entire system" in this specification refers to the imaging lens. The "focal length" used in the conditional expressions is the paraxial focal length. Regarding the "distance on the optical axis" used in the conditional expressions, unless otherwise specified, it is the geometric distance. Unless otherwise specifically stated, the values used in the conditional expressions are the values based on the d-line in the state of focusing on an infinitely distant object. The "~ group" in this specification is not limited to a structure including multiple lenses, and can also be a structure including only one lens. A "single lens" refers to one lens without being joined.

[0115] The "d-line", "C-line", and "F-line" described in this specification are bright lines. The wavelength of the d-line is regarded as 587.56 nm (nanometers), the wavelength of the C-line is regarded as 656.27 nm (nanometers), and the wavelength of the F-line is regarded as 486.13 nm (nanometers).

[0116] Advantages of the Invention

[0117] According to the present invention, it is possible to provide an imaging lens configured to be small-sized and maintain good optical performance, and an imaging device including the imaging lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0118] Figure 1 It is a cross-sectional view showing the structure of an imaging lens according to an embodiment corresponding to the imaging lens of Embodiment 1.

[0119] Figure 2 It shows Figure 1 the structure and light beam in each state of the imaging lens.

[0120] Figure 3 It is a diagram for explaining the notations of each conditional expression.

[0121] Figure 4 It is a diagram for explaining the position of the maximum effective diameter.

[0122] Figure 5 They are aberration diagrams of the imaging lens of Embodiment 1.

[0123] Figure 6 It is a cross-sectional view showing the structure of the imaging lens of Embodiment 2.

[0124] Figure 7 They are aberration diagrams of the imaging lens of Embodiment 2.

[0125] Figure 8 It is a cross-sectional view showing the structure of the imaging lens of Example 3.

[0126] Figure 9 They are aberration diagrams of the imaging lens of Example 3.

[0127] Figure 10 It is a cross-sectional view showing the structure of the imaging lens of Example 4.

[0128] Figure 11 They are aberration diagrams of the imaging lens of Example 4.

[0129] Figure 12 It is a cross-sectional view showing the structure of the imaging lens of Example 5.

[0130] Figure 13 They are aberration diagrams of the imaging lens of Example 5.

[0131] Figure 14 It is a cross-sectional view showing the structure of the imaging lens of Example 6.

[0132] Figure 15 They are aberration diagrams of the imaging lens of Example 6.

[0133] Figure 16 It is a cross-sectional view showing the structure of the imaging lens of Example 7.

[0134] Figure 17 They are aberration diagrams of the imaging lens of Example 7.

[0135] Figure 18 It is a cross-sectional view showing the structure of the imaging lens of Example 8.

[0136] Figure 19 They are aberration diagrams of the imaging lens of Example 8.

[0137] Figure 20 It is a cross-sectional view showing the structure of the imaging lens of Example 9.

[0138] Figure 21 They are aberration diagrams of the imaging lens of Example 9.

[0139] Figure 22 It is a cross-sectional view showing the structure of the imaging lens of Example 10.

[0140] Figure 23 They are aberration diagrams of the imaging lens of Example 10.

[0141] Figure 24 It is a cross-sectional view showing the structure of the imaging lens of Example 11.

[0142] Figure 25Are aberration diagrams of the imaging lens of Example 11.

[0143] Figure 26 Is a cross-sectional view showing the structure of the imaging lens of Example 12.

[0144] Figure 27 Are aberration diagrams of the imaging lens of Example 12.

[0145] Figure 28 Is a cross-sectional view showing the structure of the imaging lens of Example 13.

[0146] Figure 29 Are aberration diagrams of the imaging lens of Example 13.

[0147] Figure 30 Is a cross-sectional view showing the structure of the imaging lens of Example 14.

[0148] Figure 31 Are aberration diagrams of the imaging lens of Example 14.

[0149] Figure 32 Is a cross-sectional view showing the structure of the imaging lens of Example 15.

[0150] Figure 33 Are aberration diagrams of the imaging lens of Example 15.

[0151] Figure 34 Is a cross-sectional view showing the structure of the imaging lens of Example 16.

[0152] Figure 35 Are aberration diagrams of the imaging lens of Example 16.

[0153] Figure 36 Is a cross-sectional view showing the structure of the imaging lens of Example 17.

[0154] Figure 37 Are aberration diagrams of the imaging lens of Example 17.

[0155] Figure 38 Is a cross-sectional view showing the structure of the imaging lens of Example 18.

[0156] Figure 39 Are aberration diagrams of the imaging lens of Example 18.

[0157] Figure 40 Is a cross-sectional view showing the structure of the imaging lens of Example 19.

[0158] Figure 41 Are aberration diagrams of the imaging lens of Example 19.

[0159] Figure 42It is a cross-sectional view showing the structure of the imaging lens of Example 20.

[0160] Figure 43 They are aberration diagrams of the imaging lens of Example 20.

[0161] Figure 44 It is a cross-sectional view showing the structure of the imaging lens of Example 21.

[0162] Figure 45 They are aberration diagrams of the imaging lens of Example 21.

[0163] Figure 46 It is a perspective view of the front side of the imaging device according to an embodiment.

[0164] Figure 47 It is a perspective view of the back side of the imaging device according to an embodiment.

[0165] Symbol Explanation

[0166] 1 - Imaging lens, 20 - Interchangeable lens, 30 - Camera, 31 - Camera body, 32 - Shutter button, 33 - Power button, 34 - Operation unit, 35 - Operation unit, 36 - Display unit, 37 - Mount, 38 - Imaging element, Bf - Back focal length, dA1 - Distance, dA2 - Distance, dSt - Distance, dStR - Minimum interval, dFSt - Minimum interval, ED - Effective diameter, GF - Front group, GF1 - First front-side lens group, GF2 - Second front-side lens group, GF3 - Third front-side lens group, GR - Rear group, GR1 - First subsequent lens group, GR2 - Second subsequent lens group, GR3 - Third subsequent lens group, L11~L27 - Lenses, L22a - Lens, L22b - Resin, L24a - Lens, L24b - Resin, LA1 - First aspherical lens, LA2 - Second aspherical lens, Lx - Lens, Px - Position of the maximum effective diameter, Sim - Image plane, St - Aperture stop, TL - Total length, Xa - On-axis beam, Xb - Off-axis beam, Xb1 - Ray, Z - Optical axis, ωm - Maximum half viewing angle. Detailed Embodiment

[0167] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0168] Figure 1 A cross-sectional view showing the structure of the imaging lens according to an embodiment of the present invention is shown. Figure 2 Shown in Figure 1 is a cross-sectional view of the structure of the imaging lens and the light beam. In Figure 2 , the state of focusing on an object at infinity is shown in the upper part marked with "infinity", and the state of focusing on a nearby object is shown in the lower part marked with "close range". Figure 2The state of the lower part is a state where the absolute value of the photographic magnification is 0.11 times. In Figure 2 as the light beams, an on-axis light beam showing a state of focusing on an object at infinity and a light beam with a maximum half-angle ωm, and an on-axis light beam showing a state of focusing on a nearby object and a light beam with a maximum half-angle are shown. In Figure 1 and Figure 2 the left side is the object side and the right side is the image side. Figure 1 and Figure 2 The examples shown correspond to the imaging lens of Embodiment 1 described later. Hereinafter, mainly with reference to Figure 1 an explanation will be given.

[0169] The imaging lens of the present invention sequentially includes, from the object side to the image side along the optical axis Z: a front group GF including one or more lenses, an aperture stop St, and a rear group GR including a plurality of lenses. In this way, by not disposing the aperture stop St on either the object-side most or the image-side most of the lens system, it is advantageous for correcting various aberrations.

[0170] As an example, Figure 1 the respective groups of the imaging lens are configured as follows. The front group GF includes a single lens L11. The rear group GR sequentially includes five lenses L21 to L25 from the object side to the image side. Figure 1 The aperture stop St of

[0171] represents the position in the optical axis direction, rather than the size or shape. This method of showing the aperture stop St is the same in other cross-sectional views.

[0172] In Figure 1In the example, the lens L25 corresponds to the first aspherical lens LA1. In Figure 1 In the example, the first aspherical lens LA1 included in the rear group GR is only one piece, but in the imaging lens of the present invention, the rear group GR may also be configured to include two first aspherical lenses LA1. In such a configuration, it is more beneficial to correct the field curvature.

[0173] As Figure 1 shown in the example, when the lens closest to the image side in the rear group GR is configured as the first aspherical lens LA1, it is easy to correct the field curvature and prevent the incident angle of the chief ray on the image plane Sim from becoming too large.

[0174] The lens closest to the image side in the rear group GR may also be configured to have a shape with a convex surface facing the object side in the paraxial region, and the lens surface on the object side has an inflection point where the concavo-convex shape changes midway as it moves from the optical axis toward the peripheral portion. The phrase "having a shape with a convex surface facing the object side in the paraxial region" here means that the lens surface on the object side is convex in the paraxial region. When the lens closest to the image side in the rear group GR is set to the above structure, it is beneficial to shorten the overall optical length.

[0175] The rear group GR preferably includes at least one second aspherical lens LA2. The second aspherical lens LA2 has a shape with a convex surface facing the image side in the paraxial region. The phrase "having a shape with a convex surface facing the image side in the paraxial region" here means that the lens surface on the image side is convex in the paraxial region. The lens surface on the image side of the second aspherical lens LA2 also has a shape in which the refractive power at the position of the maximum effective diameter is shifted in the negative direction compared to the refractive power in the paraxial region. By having the second aspherical lens LA2 with the above shape, it is beneficial to suppress the increase in the overall optical length and correct various aberrations.

[0176] In addition, the phrase "the refractive power at the position of the maximum effective diameter is shifted in the negative direction compared to the refractive power in the paraxial region" in this specification means the meaning described below based on the sign of the refractive power. When this surface has a negative refractive power at both the paraxial region and the position of the maximum effective diameter, it means that the negative refractive power at the position of the maximum effective diameter is stronger than that in the paraxial region. When this surface has a positive refractive power at both the paraxial region and the position of the maximum effective diameter, it means that the positive refractive power at the position of the maximum effective diameter is weaker than that in the paraxial region. When this surface has refractive powers with different signs at the paraxial region and the position of the maximum effective diameter, it means that it has a positive refractive power in the paraxial region and a negative refractive power at the position of the maximum effective diameter.

[0177] In Figure 1 the example, the lens L24 corresponds to the second aspherical lens LA2. In Figure 1In the example, there is only one second aspherical lens LA2 included in the rear group GR. However, in the imaging lens of the present invention, the rear group GR may also be configured to include two second aspherical lenses LA2. In such a configuration, it is more beneficial to suppress the increase in the overall optical length and correct various aberrations.

[0178] The second lens from the image side of the rear group GR may also be configured as the second aspherical lens LA2 closest to the image side among the second aspherical lenses LA2 included in the rear group GR. In such a configuration, it is beneficial to suppress the increase in the overall optical length and correct various aberrations.

[0179] The second lens from the image side of the rear group GR may also be configured to have an inflection point where the concavo-convex shape of the lens surface on the image side changes midway as it moves from the optical axis toward the peripheral portion. In such a configuration, it is easy to miniaturize the lens system and correct spherical aberration and field curvature simultaneously.

[0180] At least one of the aspherical lenses included in the imaging lens may be a composite aspherical lens in which a resin having an aspherical shape as the air contact surface is formed on the spherical surface of a glass lens. In such a configuration, the manufacturing cost can be suppressed and an aspherical surface can be added to the lens surface. Therefore, it is possible to achieve both cost reduction and good correction of various aberrations. In addition, in this specification, the composite aspherical lens is treated as an unbonded single lens, rather than a bonded lens.

[0181] The imaging lens preferably includes at least one bonded lens. In this case, it is beneficial to correct chromatic aberration.

[0182] Hereinafter, a preferred structure of the imaging lens of the present invention related to the conditional expressions will be described. In the following description of the conditional expressions, in order to avoid redundancy, the same notations are used for the parts having the same definitions, and the repeated description of the notations is omitted. And hereinafter, in order to avoid redundancy, the "imaging lens of the present invention" is also simply referred to as the "imaging lens".

[0183] The imaging lens preferably satisfies the following conditional expression (1). Among them, the back focal length in the air equivalent distance of the entire system in the state of focusing on an object at infinity is set as Bf. The focal length of the entire system in the state of focusing on an object at infinity is set as f. Tan is the tangent. The maximum half angle of view in the state of focusing on an object at infinity is set as ωm. The back focal length Bf in the air equivalent distance of the entire system is the air equivalent distance on the optical axis from the lens surface closest to the image side of the imaging lens to the image plane Sim. As an example, Figure 3 shows the back focal length Bf. Figure 3 is in Figure 1 The cross-sectional view of the imaging lens shows a diagram of notations used in the conditional expressions, etc. In Figure 3In this case, the description of the symbols of a part of the lenses is omitted. By preventing the corresponding value of conditional expression (1) from falling below the lower limit value, the back focal length Bf defined above will not become too short, so it is easy to install the bayonet replacement mechanism. By preventing the corresponding value of conditional expression (1) from exceeding the upper limit value, the back focal length Bf defined above will not become too long, so miniaturization is facilitated.

[0184] 0.3 < Bf / (f × tanωm) < 1.5 (1)

[0185] To obtain better characteristics, the lower limit value of conditional expression (1) is more preferably set to 0.32, further preferably 0.34, further preferably 0.36, further preferably 0.38, and further preferably 0.4. To obtain better characteristics, the upper limit value of conditional expression (1) is more preferably set to 1.4, further preferably 1.3, further preferably 1.2, further preferably 1.1, and further preferably 0.9. For example, the imaging lens more preferably satisfies the following conditional expression (1-1).

[0186] 0.36 < Bf / (f × tanωm) < 1.2 (1—1)

[0187] The imaging lens preferably includes at least one lens that satisfies the following conditional expression (2). Here, the temperature coefficient of the refractive index of the lens included in the imaging lens with respect to the d-line at 25°C is set as (dN / dT) × 10. The unit of dN / dT is °C. Regarding the lower limit of conditional expression (2), since dN / dT is an absolute value, it becomes 0 < dN / dT. By preventing the corresponding value of conditional expression (2) from exceeding the upper limit value, it is easy to suppress the change in the focusing position of the imaging lens when the temperature changes.

[0188] 0 < |dN / dT| < 15 (2)

[0189] The front group GF preferably includes at least one lens that satisfies conditional expression (2). More specifically, it is preferable that the lens closest to the object side in the front group GF satisfies conditional expression (2). Also, the rear group GR preferably includes at least one lens that satisfies conditional expression (2).

[0190] To obtain better characteristics, the upper limit value of conditional expression (2) is more preferably set to 14, further preferably 13, further preferably 12, further preferably 11, and further preferably 10.

[0191] The imaging lens preferably satisfies the following conditional expression (3). Here, the sum of the distance on the optical axis from the lens surface closest to the object side of the front group GF to the lens surface closest to the image side of the rear group GR in the state of focusing on an infinite object and the above-mentioned back focal length Bf is set as TL. TL is the total length in the state of focusing on an infinite object. As an example, Figure 3The total length TL is shown. By preventing the corresponding value of conditional expression (3) from falling below the lower limit value, it is beneficial to suppressing various aberrations. By preventing the corresponding value of conditional expression (3) from exceeding the upper limit value, it is beneficial to miniaturizing the entire lens system.

[0192] 1.1 < TL / f < 3.5 (3)

[0193] In order to obtain better characteristics, the lower limit value of conditional expression (3) is more preferably set to 1.2, still more preferably 1.21, still more preferably 1.22, still more preferably 1.23, still more preferably 1.24, still more preferably 1.25, still more preferably 1.3, still more preferably 1.4, still more preferably 1.5, still more preferably 1.6, still more preferably 1.7, still more preferably 1.8, still more preferably 1.9. In order to obtain better characteristics, the upper limit value of conditional expression (3) is more preferably set to 3, still more preferably 2.9, still more preferably 2.85, still more preferably 2.8, still more preferably 2.75, still more preferably 2.7, still more preferably 2.65, still more preferably 2.6, still more preferably 1.6, still more preferably 1.55, still more preferably 1.5, still more preferably 1.48, still more preferably 1.46, still more preferably 1.45. For example, the imaging lens more preferably satisfies the following conditional expression (3-1), and still more preferably satisfies the following conditional expression (3-2).

[0194] 1.2 < TL / f < 3 (3-1)

[0195] 1.2 < TL / f < 1.6 (3-2)

[0196] The imaging lens preferably satisfies the following conditional expression (4). Here, the open F value in the state of focusing on an infinitely distant object is set to Fno. By preventing the corresponding value of conditional expression (4) from falling below the lower limit value, it is beneficial to obtaining good optical performance, suppressing an increase in the number of lens elements, and suppressing enlargement of the lens system. By preventing the corresponding value of conditional expression (4) from exceeding the upper limit value, it is easy to widen the viewing angle and reduce the open F value.

[0197] 1.6 < Fno / tanωm < 5 (4)

[0198] In order to obtain better characteristics, the lower limit value of conditional expression (4) is more preferably set to 1.7, further preferably 1.8, further preferably 1.9, further preferably 2, further preferably 2.1, further preferably 2.5, further preferably 2.8. In order to obtain better characteristics, the upper limit value of conditional expression (4) is more preferably set to 4, further preferably 3.5, further preferably 3.3, further preferably 3.2, further preferably 3.1. For example, the imaging lens more preferably satisfies the following conditional expression (4-1), and further preferably satisfies the following conditional expression (4-2).

[0199] 2 < Fno / tanωm < 3.2 (4-1)

[0200] 2.5 < Fno / tanωm < 4 (4-2)

[0201] The imaging lens preferably satisfies the following conditional expressions (5) and (6) simultaneously. Herein, the minimum value of the distance on the optical axis from the lens surface closest to the image side of the front group GF to the aperture stop St is defined as dFSt. The minimum value of the distance on the optical axis from the aperture stop St to the lens surface closest to the object side of the rear group GR is defined as dStR. That is, dFSt is the minimum interval between the front group GF and the aperture stop St, and dStR is the minimum interval between the aperture stop St and the rear group GR. In addition, the "minimum" mentioned here refers to the minimum in the focusing state from the state of focusing on an object at infinity to the state of focusing on the nearest object. Regarding the sign of dFSt, it is set to positive when the aperture stop St is on the image side of the lens surface closest to the image side of the front group GF, and negative when the aperture stop St is on the object side of the lens surface closest to the image side of the front group GF. Regarding the sign of dStR, it is set to positive when the lens surface closest to the object side of the rear group GR is on the image side of the aperture stop St, and negative when the lens surface closest to the object side of the rear group GR is on the object side of the aperture stop St. As an example, Figure 3 shows the above-mentioned minimum interval dFSt and minimum interval dStR. By ensuring that any corresponding value in conditional expressions (5) and (6) does not become less than the lower limit value, it is easy to set a mechanism for changing the opening diameter of the aperture stop St to any value. By ensuring that any corresponding value in conditional expressions (5) and (6) does not become greater than the upper limit value, it is beneficial to the miniaturization of the lens system.

[0202] 0 < dFSt / TL < 0.8 (5)

[0203] 0 < dStR / TL < 0.8 (6)

[0204] In order to obtain better characteristics, the lower limit value of conditional expression (5) is more preferably set to 0.001, further preferably 0.003, and still further preferably 0.005. In order to obtain better characteristics, the upper limit value of conditional expression (5) is more preferably set to 0.5, further preferably 0.35, and still further preferably 0.3.

[0205] In order to obtain better characteristics, the lower limit value of conditional expression (6) is more preferably set to 0.001, further preferably 0.003, and still further preferably 0.005. In order to obtain better characteristics, the upper limit value of conditional expression (6) is more preferably set to 0.5, further preferably 0.35, and still further preferably 0.3.

[0206] The imaging lens preferably satisfies the following conditional expression (7). Among them, the sum of the distance on the optical axis from the aperture stop St to the most image-side lens surface of the rear group GR in the state of focusing on an infinitely distant object and the above-mentioned back focal length Bf is set as dSt. As an example, Figure 3 the above-mentioned distance dSt is shown in. By making the corresponding value of conditional expression (7) not become below the lower limit value, it is easy to prevent the incident angle of the chief ray on the image plane Sim from becoming too large. By making the corresponding value of conditional expression (7) not become above the upper limit value, it is beneficial to well correct the distortion aberration.

[0207] 0.67 < dSt / TL < 0.93 (7)

[0208] In order to obtain better characteristics, the lower limit value of conditional expression (7) is more preferably set to 0.68, further preferably 0.69, still further preferably 0.7, and still further preferably 0.71. In order to obtain better characteristics, the upper limit value of conditional expression (7) is more preferably set to 0.89, further preferably 0.85, still further preferably 0.84, and still further preferably 0.83.

[0209] The imaging lens preferably satisfies the following conditional expression (8). Among them, the paraxial curvature radius of the object-side surface of the lens of the front group GF that is closest to the object is set as RL1f. The paraxial curvature radius of the image-side surface of the lens of the front group GF that is closest to the object is set as RL1r. Conditional expression (8) defines the shape factor of the lens. By making the corresponding value of conditional expression (8) not become below the lower limit, it is easy to well correct the astigmatism. By making the corresponding value of conditional expression (8) not become above the upper limit, it is easy to well correct the spherical aberration. And, by making the corresponding value of conditional expression (8) not become above the upper limit value, the refractive power of the lens of the front group GF that is closest to the object will not become too weak, so it is easy to achieve wide-angleization.

[0210] -3 < (RL1r - RL1f) / (RL1r + RL1f) < 0 (8)

[0211] In order to obtain better characteristics, the lower limit value of conditional expression (8) is more preferably set to -2, further preferably to -1.5, further preferably to -1, further preferably to -0.96, further preferably to -0.93, further preferably to -0.9. In order to obtain better characteristics, the upper limit value of conditional expression (8) is more preferably set to -0.04, further preferably to -0.06, further preferably to -0.07, further preferably to -0.08, further preferably to -0.09, further preferably to -0.1. For example, the imaging lens more preferably satisfies the following conditional expression (8-1).

[0212] -1 < (RL1r - RL1f) / (RL1r + RL1f) < -0.07 (8-1)

[0213] The imaging lens preferably satisfies the following conditional expression (9). Among them, the sum of the distance on the optical axis from the image-side surface of the first aspherical lens LA1 included in the rear group GR in the state of focusing on an infinitely distant object to the image-side lens surface of the rear group GR and the above-mentioned Bf is set as dA1. As an example, Figure 3 the above-mentioned distance dA1 is shown in. In addition, in Figure 3 the imaging lens of, since the first aspherical lens LA1 is arranged on the most image-side of the rear group GR, the above-mentioned Bf and the distance dA1 are equal. However, in the case where the first aspherical lens LA1 is not arranged on the most image-side of the rear group GR, the above-mentioned Bf and the distance dA1 are not equal. By making the corresponding value of conditional expression (9) not become below the lower limit value, it is easy to prevent the image-side surface of the first aspherical lens LA1 from interfering with various filters provided near the image surface. By making the corresponding value of conditional expression (9) not become above the upper limit value, it is easy to correct distortion aberration and field curvature.

[0214] 0.02 < dA1 / TL < 0.6 (9)

[0215] In order to obtain better characteristics, the lower limit value of conditional expression (9) is more preferably set to 0.03, further preferably to 0.04, further preferably to 0.06, further preferably to 0.07, further preferably to 0.08, further preferably to 0.09, further preferably to 0.1. In order to obtain better characteristics, the upper limit value of conditional expression (9) is more preferably set to 0.55, further preferably to 0.5, further preferably to 0.45, further preferably to 0.4, further preferably to 0.35, further preferably to 0.34, further preferably to 0.33. For example, the imaging lens more preferably satisfies the following conditional expression (9-1).

[0216] 0.08 < dA1 / TL < 0.35 (9-1)

[0217] The imaging lens preferably satisfies the following conditional expression (10). By preventing the corresponding value of the conditional expression (10) from falling below the lower limit value, it is beneficial to suppressing various aberrations. By preventing the corresponding value of the conditional expression (10) from exceeding the upper limit value, it is beneficial to miniaturizing the entire lens system.

[0218] 1.2 < TL / (f × tanωm) < 3 (10)

[0219] To obtain better characteristics, the lower limit value of the conditional expression (10) is more preferably set to 1.3, further preferably 1.4, further preferably 1.5, further preferably 1.6, further preferably 1.7, further preferably 1.8, and further preferably 1.85. To obtain better characteristics, the upper limit value of the conditional expression (10) is more preferably set to 2.9, further preferably 2.8, further preferably 2.7, further preferably 2.6, further preferably 2.5, further preferably 2.4, and further preferably 2.35. For example, the imaging lens more preferably satisfies the following conditional expression (10-1).

[0220] 1.7 < TL / (f × tanωm) < 2.5 (10-1)

[0221] The front group GF preferably includes at least one lens that satisfies the following conditional expression (11). Particularly preferably, the lens closest to the object side in the front group GF satisfies the conditional expression (11). Here, the refractive index with respect to the d-line and the Abbe number based on the d-line of the lens included in the imaging lens are respectively designated as Nd and vd. By preventing the corresponding value of the conditional expression (11) from falling below the lower limit value, it is possible to select materials other than those with a low refractive index and a low Abbe number, and thus it is easy to correct the magnification chromatic aberration. By preventing the corresponding value of the conditional expression (11) from exceeding the upper limit value, it is possible to select materials other than those with a high refractive index and a high Abbe number, and thus it is possible to select materials with a low specific gravity and it is easy to reduce the weight.

[0222] 1.6 < Nd + 0.01 × vd < 2.6 (11)

[0223] To obtain better characteristics, the lower limit value of the conditional expression (11) is more preferably set to 1.7, further preferably 1.8, and further preferably 1.85. To obtain better characteristics, the upper limit value of the conditional expression (11) is more preferably set to 2.5, further preferably 2.4, and further preferably 2.35.

[0224] When the focal length of the lens closest to the object side in the front group GF is designated as fL1, the imaging lens preferably satisfies the following conditional expression (12). By preventing the corresponding value of the conditional expression (12) from falling below the lower limit value, it is easy to correct the distortion aberration. By preventing the corresponding value of the conditional expression (12) from exceeding the upper limit value, it is easy to correct the field curvature.

[0225] -1.5 < f / fL1 < 0 (12)

[0226] In order to obtain better characteristics, the lower limit value of conditional expression (12) is more preferably set to -1.3, further preferably to -1.1, further preferably to -0.9, and further preferably to -0.8. In order to obtain better characteristics, the upper limit value of conditional expression (12) is more preferably set to -0.2, further preferably to -0.35, further preferably to -0.45, and further preferably to -0.55.

[0227] The imaging lens preferably satisfies the following conditional expression (13). Here, the paraxial curvature radius of the image side surface of the first aspherical lens LA1 closest to the image side among the first aspherical lenses LA1 included in the rear group GR is set as RA1c. The curvature radius at the position of the maximum effective diameter of the surface on the image side of the first aspherical lens LA1 closest to the image side among the first aspherical lenses LA1 included in the rear group GR is set as RA1y. By preventing the corresponding value of conditional expression (13) from becoming below the lower limit value, it is easy to prevent the incident angle of the chief ray on the image plane Sim from becoming too large. By preventing the corresponding value of conditional expression (13) from becoming above the upper limit value, it is easy to suppress the intensity of stray light caused by the light reflected from the surface on the image side of the first aspherical lens LA1 closest to the image side among the first aspherical lenses LA1 included in the rear group GR.

[0228] -100 < RA1y / RA1c < 0 (13)

[0229] In order to obtain better characteristics, the lower limit value of conditional expression (13) is more preferably set to -10, further preferably to -6, further preferably to -5, further preferably to -4, further preferably to -3, and further preferably to -2. In order to obtain better characteristics, the upper limit value of conditional expression (13) is more preferably set to -0.1, further preferably to -0.2, further preferably to -0.3, further preferably to -0.4, further preferably to -0.5, and further preferably to -0.6.

[0230] Here, refer to Figure 4 the description of "the position of the maximum effective diameter" in this specification. Figure 4 is an explanatory diagram. In Figure 4 the left side is the object side and the right side is the image side. Figure 4 the axial beam Xa and the off-axis beam Xb passing through the lens Lx are shown. In Figure 4In the example, the upper-side ray of the off-axis beam Xb, i.e., ray Xb1, is the ray passing through the outermost side. The "outer side" mentioned here refers to the radially outer side centered on the optical axis Z, i.e., the side away from the optical axis Z. In this specification, the position of the intersection of the ray passing through the outermost side and the lens surface is the position Px of the maximum effective diameter. And, twice the distance from the position Px of the maximum effective diameter to the optical axis Z becomes the effective diameter ED of the object-side surface of the lens Lx. In addition, in Figure 4 the example, the upper-side ray of the off-axis beam Xb is the ray passing through the outermost side, but which ray becomes the ray passing through the outermost side varies depending on the lens system.

[0231] The imaging lens preferably satisfies the following conditional expression (14). Among them, the refractive index with respect to the d-line and the Abbe number based on the d-line of the first aspherical lens LA1 closest to the image side among the first aspherical lenses LA1 included in the rear group GR are set as NdA1 and vdA1, respectively. By not making the corresponding value of the conditional expression (14) fall below the lower limit value, materials other than those with low refractive index and low Abbe number can be selected, so it is easy to correct the longitudinal chromatic aberration. By not making the corresponding value of the conditional expression (14) exceed the upper limit value, materials other than those with high refractive index and high Abbe number can be selected, so materials with low specific gravity can be selected and it is easy to reduce the weight.

[0232] 1.8 < NdA1 + 0.01 × vdA1 < 2.14 (14)

[0233] In order to obtain better characteristics, the lower limit value of the conditional expression (14) is more preferably set to 1.85, further preferably to 1.9, and further preferably to 1.95. In order to obtain better characteristics, the upper limit value of the conditional expression (14) is more preferably set to 2.13, further preferably to 2.12, and further preferably to 2.11.

[0234] In the structure where the rear group GR includes at least one second aspherical lens LA2, all the second aspherical lenses LA2 included in the rear group GR preferably satisfy the following conditional expression (15). Among them, the paraxial curvature radius of the image-side surface of the second aspherical lens LA2 is set as RA2c. The curvature radius at the position of the maximum effective diameter of the image-side surface of the second aspherical lens LA2 is set as RA2y. By not making the corresponding value of the conditional expression (15) fall below the lower limit value, it is beneficial to suppress astigmatism. By not making the corresponding value of the conditional expression (15) exceed the upper limit value, it is easy to suppress various aberrations and suppress the increase in the total optical length.

[0235] -1 < RA2c / RA2y < 1 (15)

[0236] In order to obtain better characteristics, the lower limit value of conditional expression (15) is more preferably set to -0.9, further preferably to -0.8, further preferably to -0.7, further preferably to -0.6, further preferably to -0.5, further preferably to -0.4, further preferably to -0.3. In order to obtain better characteristics, the upper limit value of conditional expression (15) is more preferably set to 0.9, further preferably to 0.8, further preferably to 0.7, further preferably to 0.6, further preferably to 0.5, further preferably to 0.4, further preferably to 0.3.

[0237] In a structure where the rear group GR includes at least one second aspherical lens LA2, the imaging lens preferably satisfies the following conditional expression (16). Here, the distance from the image-side surface of the second aspherical lens LA2 closest to the image side among the second aspherical lenses LA2 included in the rear group GR to the lens surface closest to the image side of the rear group GR on the optical axis is set to dA2 in sum with Bf. The distance from the lens surface closest to the object side of the front group GF to the lens surface closest to the image side of the rear group GR on the optical axis in a state of focusing on an infinitely distant object is set to TL in sum with Bf. As an example, Figure 3 the above distance dA2 is shown in. By preventing the corresponding value of conditional expression (16) from becoming below the lower limit value, it is easy to suppress various aberrations related to off-axis light beams and suppress the increase in the overall optical length. By preventing the corresponding value of conditional expression (16) from becoming above the upper limit value, it is easy to correct spherical aberration.

[0238] 0.2 < dA2 / TL < 0.6 (16)

[0239] In order to obtain better characteristics, the lower limit value of conditional expression (16) is more preferably set to 0.21, further preferably to 0.22, further preferably to 0.23, further preferably to 0.24, further preferably to 0.25. In order to obtain better characteristics, the upper limit value of conditional expression (16) is more preferably set to 0.58, further preferably to 0.56, further preferably to 0.54, further preferably to 0.52, further preferably to 0.5.

[0240] The front group GF preferably includes at least one single lens or cemented lens that satisfies the following conditional expression (17). Here, the focal length of one single lens or one cemented lens included in the front group GF is set to fLF. Hereinafter, for the sake of convenience of explanation, the single lens or cemented lens that satisfies conditional expression (17) included in the front group GF is referred to as the LFp lens. By preventing the corresponding value of conditional expression (17) from becoming below the lower limit value, the front group GF can include a single lens or a cemented lens having a positive refractive power, which is thus beneficial for shortening the overall optical length and easily ensuring the peripheral light quantity. By preventing the corresponding value of conditional expression (17) from becoming above the upper limit value, the positive refractive power of the LFp lens will not become too strong, which is thus beneficial for correcting distortion aberration and field curvature.

[0241] 0 < f / fLF < 2 (17)

[0242] In order to obtain better characteristics, the lower limit value of conditional expression (17) is more preferably set to 0.2. In this case, the positive refractive power of the LFp lens will not become too weak, so it is more beneficial to shorten the overall optical length and easier to ensure the peripheral light quantity. In order to obtain further better characteristics, the lower limit value of conditional expression (17) is further preferably set to 0.3, further preferably to 0.4, further preferably to 0.45, and further preferably to 0.5. In order to obtain better characteristics, the upper limit value of conditional expression (17) is more preferably set to 1.5, further preferably to 1.3, further preferably to 1.1, further preferably to 0.95, and further preferably to 0.9.

[0243] When the focal length of the front group GF is set to fF, the imaging lens preferably satisfies the following conditional expression (18). By preventing the corresponding value of conditional expression (18) from falling below the lower limit value, the negative refractive power of the front group GF will not become too strong, so it is beneficial to shorten the overall optical length and easy to ensure the peripheral light quantity. By preventing the corresponding value of conditional expression (18) from exceeding the upper limit value, the positive refractive power of the front group GF will not become too strong, so it is easy to correct spherical aberration and field curvature.

[0244] -1.5 < f / fF < 1.5(18)

[0245] In order to obtain better characteristics, the lower limit value of conditional expression (18) is more preferably set to -1.2, further preferably to -1, further preferably to -0.9, further preferably to -0.85, and further preferably to -0.8. In order to obtain better characteristics, the upper limit value of conditional expression (18) is more preferably set to 1.2, further preferably to 1, further preferably to 0.9, further preferably to 0.85, and further preferably to 0.8.

[0246] When the maximum shooting magnification is set to β, the imaging lens preferably satisfies the following conditional expression (19). The maximum shooting magnification is the shooting magnification when shooting the nearest object. By preventing the corresponding value of conditional expression (19) from falling below the lower limit value, the narrowness of the shootable area of the lens system can be suppressed, so the added value preferred for the imaging lens can be ensured. By preventing the corresponding value of conditional expression (19) from exceeding the upper limit value, the movement amount of the lens group during focusing can be suppressed, so it is helpful for the miniaturization of the lens system.

[0247] 0.07 < |β| < 1 (19)

[0248] In order to obtain better characteristics, the lower limit value of conditional expression (19) is more preferably set to 0.08, further preferably 0.09, and still further preferably 0.1. In order to obtain better characteristics, the upper limit value of conditional expression (19) is more preferably set to 0.6, further preferably 0.35, and still further preferably 0.25.

[0249] The rear group GR preferably includes at least two lenses satisfying the following conditional expression (20). Herein, the ratio of the lenses included in the rear group GR is set as ρr. By preventing the corresponding value of conditional expression (20) from falling below the lower limit value, materials with high availability can be used, and thus good correction of various aberrations can be easily achieved. By preventing the corresponding value of conditional expression (20) from exceeding the upper limit value, weight reduction of the rear group GR is facilitated. The rear group GR more preferably includes at least three lenses satisfying the following conditional expression (20).

[0250] 0.86 < ρr < 2.2 (20)

[0251] In order to obtain better characteristics, the lower limit value of conditional expression (20) is more preferably set to 0.88, further preferably 0.9, and still further preferably 0.92. In order to obtain better characteristics, the upper limit value of conditional expression (20) is more preferably set to 2, further preferably 1.8, and still further preferably 1.6.

[0252] The imaging lens preferably satisfies the following conditional expression (21). By preventing the corresponding value of conditional expression (21) from falling below the lower limit value, it is easy to correct various aberrations and shorten the overall optical length. By preventing the corresponding value of conditional expression (21) from exceeding the upper limit value, the brightness of the lens system can be ensured.

[0253] 1.2 < Fno < 3 (21)

[0254] In order to obtain better characteristics, the lower limit value of conditional expression (21) is more preferably set to 1.3, further preferably 1.4, and still further preferably 1.5. In order to obtain better characteristics, the upper limit value of conditional expression (21) is more preferably set to 2.5, further preferably 2.1, and still further preferably 1.9.

[0255] The imaging lens preferably satisfies the following conditional expression (22). By setting the surface shape of the lens closest to the object side of the front group GF in a manner that satisfies conditional expression (22), it is easy to suppress distortion aberration.

[0256] -0.8 < f / RL1r < 3 (22)

[0257] In order to obtain better characteristics, the lower limit value of conditional expression (22) is more preferably set to -0.5, further preferably 0, further preferably 0.2, further preferably 0.4, further preferably 0.6, further preferably 0.8, and further preferably 1. In order to obtain better characteristics, the upper limit value of conditional expression (22) is more preferably set to 2.7, further preferably 2.4, further preferably 2.1, further preferably 1.8, further preferably 1.7, further preferably 1.6, and further preferably 1.5.

[0258] In addition, Figure 1 The example shown is just one example, and various modifications can be made without departing from the gist of the technology of the present invention. For example, the positions where the first aspherical lens LA1 and the second aspherical lens LA2 are arranged can also be positions different from those in the Figure 1 example. The number of the first aspherical lens LA1 and the second aspherical lens LA2 included in the imaging lens can also be a number different from that in the Figure 1 example. The number of lenses included in the front group GF and the rear group GR can also be a number different from that in the Figure 1 example. The sign of the refractive power of the front group GF can be positive or negative. The sign of the refractive power of the rear group GR can be positive or negative.

[0259] In Figure 1 the example, focusing is performed by moving the entire imaging lens integrally, but in the imaging lens of the present invention, other focusing methods can also be adopted. In addition, in this specification, "moving integrally" means moving the same amount in the same direction simultaneously. Figure 1 The brackets described below the imaging lens in the

[0260] example indicate the lens groups that move during focusing, and the arrows attached to the brackets indicate the moving directions when focusing from an infinitely distant object to a nearby object.

[0261] Alternatively, in the imaging lens of the present invention, a front focusing method can also be adopted. For example, it can be configured such that the rear group GR includes a first subsequent lens group and a second subsequent lens group in order from the object side to the image side. During focusing, the front group GF, the aperture stop St, and the first subsequent lens group move integrally, and the second subsequent lens group is fixed relative to the image plane Sim. In this way, when only a part of the lenses move during focusing, it is beneficial for high-speed focusing compared to the case where all lenses move.

[0262] Alternatively, it may be configured such that the rear group GR includes a first subsequent lens group, a second subsequent lens group, and a third subsequent lens group in this order from the object side to the image side, and only the second subsequent lens group moves during focusing. In such a configuration, it is also more conducive to high-speed focusing.

[0263] In the case where the imaging lens includes only one lens group that moves during focusing, it is beneficial to simplify the drive mechanism. The imaging lens of the present invention may also be configured to include two lens groups that move while changing the interval between them during focusing. In such a configuration, it is beneficial to suppress aberration variation during focusing.

[0264] The above-mentioned preferred structures and possible structures can be arbitrarily combined within a non-contradictory range, and are preferably selectively adopted appropriately according to the required specifications.

[0265] As an example, a preferred embodiment of the imaging lens of the present invention is an imaging lens that includes, in order from the object side to the image side: a front group GF including one or more lenses, an aperture stop St, and a rear group GR including a plurality of lenses. At least one first aspherical lens LA1 is disposed in the rear group GR. The first aspherical lens LA1 has a concave surface facing the image side in the paraxial region, and an inflection point where the concavo-convex shape changes midway as it moves from the optical axis toward the peripheral portion on the lens surface on the image side. Further, it includes at least one lens that satisfies the above-mentioned conditional expression (2) and satisfies the above-mentioned conditional expression (1).

[0266] Moreover, in another preferred embodiment of the imaging lens of the present invention, in the structure of the above-mentioned preferred embodiment, the lens closest to the object side in the front group GF satisfies the conditional expression (2) and satisfies the above-mentioned conditional expressions (3-2), (4-2), (7), and (9-1).

[0267] Next, embodiments of the imaging lens of the present invention will be described with reference to the accompanying drawings. In addition, in order to avoid complication of the description and the drawings caused by an increase in the number of digits of the reference symbols, the reference symbols marked on the lenses in the cross-sectional views of the respective embodiments are used independently in each embodiment. Therefore, even if the same reference symbols are marked in the drawings of different embodiments, they do not necessarily represent the same structure.

[0268] [Embodiment 1]

[0269] A cross-sectional view of the structure of the imaging lens of Embodiment 1 is shown in Figure 1 As described above for the illustration method and structure, a part of the repeated description is omitted here. The imaging lens of Embodiment 1 includes a front group GF, an aperture stop St, and a rear group GR in order from the object side to the image side. When focusing from an infinitely distant object to a close object, the entire imaging lens moves integrally toward the object side.

[0270] Regarding the imaging lens of Example 1, the basic lens data is shown in Table 1, the specifications and variable surface intervals are shown in Table 2, and the aspherical coefficients are shown in Table 3.

[0271] The table of the basic lens data is described as follows. In the column of "Sn", the surface numbers are shown when the surface closest to the object side is set as the first surface and the numbers increase one by one toward the image side. In the column of "R", the curvature radii of the respective surfaces are shown. In the column of "D", the surface intervals on the optical axis between each surface and the surface adjacent to its image side are shown. In the column of "Nd", the refractive indices of the respective lenses with respect to the d-line are shown. In the column of "vd", the Abbe numbers of the respective lenses based on the d-line are shown.

[0272] Including the tables of the following-described embodiments, the column of "Material" in the table of the basic lens data is described as follows. In the column of "Material", for the lens whose material is resin, it is described as "Plastic", and for the lens whose material is other than resin, the material name is shown in the upper part of the column, and the manufacturing company name is shown in the lower part. In the table, the manufacturing company names are shown roughly as follows. "0HARA" represents 0HARAINC., "CDGM" represents Chengdu Guangming Optoelectronics Co., Ltd., "HIKARI" represents HIKARI GLASS Co., Ltd., and "HOYA" represents HOYA Corporation. And, in the column of "Material", for the lens corresponding to the first aspherical lens LA1, "(LA1)" is entered, and for the lens corresponding to the second aspherical lens LA2, "(LA2)" is entered.

[0273] In the column of "ED", the effective diameters of the respective surfaces are shown. In the column of "Nd + 0.01×vd", the corresponding values of the conditional expression (11) for the respective lenses are shown. In the column of "ρr", the specific gravity of the respective lenses, that is, the corresponding value of the conditional expression (20), is shown. "(dN / dT)×10 -6 " In the column, the temperature coefficients of the refractive indices of the respective lenses with respect to the d-line under the condition of 25°C, that is, the corresponding values of the conditional expression (2), are shown. Additionally, including the tables of the following-described embodiments, in the columns of "ED", "ρr", and "(dN / dT)×10 -6 ", for the surfaces and lenses not related to the conditional expressions, a part of the descriptions are omitted.

[0274] In the table of the basic lens data, the sign of the curvature radius of the surface with the convex shape facing the object side is set as positive, and the sign of the curvature radius of the surface with the convex shape facing the image side is set as negative. In the column of the surface number corresponding to the aperture stop St, the surface number and the statement (St) are entered. The value in the bottom row of the D column in the table is the interval between the surface closest to the image side in the table and the image plane Sim. Regarding the variable surface interval during focusing, the notation DD is used, and after DD, the surface number on the object side of the interval is marked and entered in the column of the surface interval.

[0275] In Table 2, the focal length, back focal length, open F value, maximum full view angle, and variable surface interval are represented based on the d line. The [°] in the maximum full view angle column indicates the unit is degrees. In Table 2, in the "Infinity" column, the values in the state of focusing on an object at infinity are shown, and in the "Close" column, the values in the state of focusing on the nearest object are shown. Among them, the focal length only shows the value in the state of focusing on an object at infinity. In the "Close" column, the absolute value of the maximum photographic magnification is indicated with "×".

[0276] In the basic lens data, an asterisk (*) is marked on the surface number of the aspherical surface, and the value of the paraxial curvature radius is recorded in the column of the curvature radius of the aspherical surface. In Table 3, the surface number of the aspherical surface is shown in the Sn row, and the values of the aspherical coefficients for each aspherical surface are shown in the KA and Am rows. In addition, m in Am is an integer of 3 or more and varies according to the surface. For example, in the first surface of Example 1, m = 4, 6, 8, 10. The "E±n" (n: integer) of the value of the aspherical coefficient in Table 3 means "×10 ±n ". KA and Am are the aspherical coefficients in the aspherical formula represented by the following formula.

[0277] Zd = C × h 2 / {1 + (1 - KA × C 2 × h 2 ) 1 / 2}+ ∑Am × h m

[0278] Among them,

[0279] Zd: Aspherical depth (the length of the perpendicular line dropped from a point on the aspherical surface at height h to the plane tangent to the vertex of the aspherical surface and perpendicular to the optical axis Z)

[0280] h: Height (the distance from the optical axis Z to the lens surface)

[0281] C: Reciprocal of the paraxial curvature radius

[0282] KA, Am: Aspherical coefficients

[0283] The ∑ in the aspherical formula represents the sum with respect to m.

[0284] In the data of each table, degrees are used as the angle unit and mm (millimeter) is used as the length unit. However, since the optical system can also be used with a magnification ratio or a reduction ratio, other appropriate units can also be used. And in each of the following tables, the values rounded to a preset number of digits are recorded.

[0285] [Table 1]

[0286] Example 1

[0287]

[0288] [Table 2] Example 1

[0289]

[0290] [Table 3]

[0291] Example 1

[0292]

[0293] Figure 5 The aberration diagrams of the imaging lens of Example 1 are shown. In Figure 5 , the spherical aberration, astigmatism, distortion aberration, and longitudinal chromatic aberration are shown in order from the left. In Figure 5 , the aberration diagrams of the state of focusing on an object at infinity are shown in the upper part marked with "infinity", and the aberration diagrams of the state of focusing on the nearest object are shown in the lower part marked with "near distance". In the spherical aberration diagram, the aberrations on the d-line, C-line, and F-line are shown by solid lines, long dashed lines, and short dashed lines, respectively. In the astigmatism diagram, the aberration on the d-line in the sagittal direction is shown by a solid line, and the aberration on the d-line in the meridional direction is shown by a short dashed line. In the distortion aberration diagram, the aberration on the d-line is shown by a solid line. In the longitudinal chromatic aberration diagram, the aberrations on the C-line and F-line are shown by long dashed lines and short dashed lines, 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 half field angle is shown after "ω =".

[0294] Regarding the notations, meanings, recording methods, and illustration methods of the various data related to the above Example 1, unless otherwise specified, they are basically the same in the following examples, so the repeated descriptions are omitted below.

[0295] [Example 2]

[0296] Figure 6 A cross-sectional view of the structure of the imaging lens of Example 2 is shown. The imaging lens of Example 2 includes a front group GF, an aperture stop St, and a rear group GR in order from the object side to the image side. The front group GF includes two lenses L11 to L12 in order from the object side to the image side. The lens L12 corresponds to the LFp lens. The rear group GR includes five lenses L21 to L25 in order from the object side to the image side. When focusing from an object at infinity to a near object, the entire imaging lens moves integrally toward the object side.

[0297] Regarding the imaging lens of Example 2, the basic lens data are shown in Table 4, the specifications and variable surface intervals are shown in Table 5, the aspherical coefficients are shown in Table 6, and the aberration diagrams are shown in Figure 7 .

[0298] [Table 4] Example 2

[0299]

[0300] [Table 5] Example 2

[0301]

[0302] [Table 6]

[0303] Example 2

[0304]

[0305] [Example 3]

[0306] Figure 8 A cross-sectional view showing the structure of the imaging lens of Example 3 is shown. The imaging lens of Example 3 includes a front group GF, an aperture stop St, and a rear group GR in order from the object side to the image side. The front group GF includes two lenses L11 to L12 in order from the object side to the image side. The lens L12 corresponds to the LFp lens. The rear group GR includes five lenses L21 to L25 in order from the object side to the image side. When focusing from an infinite object to a near object, the entire imaging lens moves integrally toward the object side.

[0307] Regarding the imaging lens of Example 3, the basic lens data is shown in Table 7, the specifications and variable surface intervals are shown in Table 8, the aspherical coefficients are shown in Table 9, and the aberration diagrams are shown in Figure 9 .

[0308] [Table 7] Example 3

[0309]

[0310] [Table 8] Example 3

[0311]

[0312] [Table 9]

[0313] Example 3

[0314]

[0315] [Example 4]

[0316] Figure 10A cross-sectional view showing the structure of the imaging lens of Example 4 is shown. The imaging lens of Example 4 includes a front group GF, an aperture stop St, and a rear group GR in order from the object side to the image side. The front group GF includes three lenses L11 to L13 in order from the object side to the image side. The cemented lens formed by cementing lens L12 and lens L13 corresponds to the LFp lens. The rear group GR includes four lenses L21 to L24 in order from the object side to the image side. When focusing from an infinitely distant object to a close object, the entire imaging lens moves integrally toward the object side.

[0317] Regarding the imaging lens of Example 4, the basic lens data is shown in Table 10, the specifications and variable surface intervals are shown in Table 11, the aspherical coefficients are shown in Table 12, and the aberration diagrams are shown in Figure 11 .

[0318] [Table 10]

[0319] Example 4

[0320]

[0321] [Table 11] Example 4

[0322]

[0323] [Table 12]

[0324] Example 4

[0325] Sn 10 11 12 13 KA 1.0000000E+00 1.0000000E+00 1.0000000E+00 1.0000000E+00 A4 7.5613282E-05 1.2930171E-04 2.0819015E-04 2.6771759E-04 A6 1.7251074E-06 1.1126147E-06 1.3131766E-06 1.3791550E-06 A8 7.2131810E-10 2.2617383E-08 4.6589232E-09 6.2334901E-09 A10 1.6922017E-10 2.6279418E-10 3.9640967E-12 1.8799778E-11 A12 6.4137446E-13 9.0360193E-13 1.7947030E-14 3.8349563E-14 A14 0.0000000E+00 0.0000000E+00 3.2594142E-17 3.5868486E-17

[0326] [Example 5]

[0327] Figure 12 A cross-sectional view showing the structure of the imaging lens of Example 5 is shown. The imaging lens of Example 5 includes a front group GF, an aperture stop St, and a rear group GR in order from the object side to the image side. The front group GF includes three lenses L11 to L13 in order from the object side to the image side. The cemented lens formed by cementing lens L12 and lens L13 corresponds to the LFp lens. The rear group GR includes five lenses L21 to L25 in order from the object side to the image side. When focusing from an infinitely distant object to a close object, the entire imaging lens moves integrally toward the object side.

[0328] Regarding the imaging lens of Example 5, the basic lens data is shown in Table 13, the specifications and variable surface intervals are shown in Table 14, the aspherical coefficients are shown in Table 15, and the aberration diagrams are shown in Figure 13 .

[0329] [Table 13] Example 5

[0330]

[0331] [Table 14] Example 5

[0332]

[0333] [Table 15]

[0334] Example 5

[0335]

[0336] [Example 6]

[0337] Figure 14 The cross-sectional view showing the structure of the imaging lens of Example 6 is shown. The imaging lens of Example 6 includes, in order from the object side to the image side, a front group GF, an aperture stop St, and a rear group GR. The front group GF includes, in order from the object side to the image side, two lenses L11 to L12. The lens L12 corresponds to the LFp lens. The rear group GR includes, in order from the object side to the image side, five lenses L21 to L25. When focusing from an infinitely distant object to a nearby object, the entire imaging lens moves integrally toward the object side.

[0338] Regarding the imaging lens of Example 6, the basic lens data is shown in Table 16, the specifications and variable surface intervals are shown in Table 17, the aspherical coefficients are shown in Table 18, and the aberration diagrams are shown in Figure 15 .

[0339] [Table 16] Example 6

[0340]

[0341] [Table 17] Example 6

[0342]

[0343] [Table 18]

[0344] Example 6

[0345]

[0346] [Example 7]

[0347] Figure 16A cross-sectional view showing the structure of the imaging lens of Example 7 is shown. The imaging lens of Example 7 includes a front group GF, an aperture stop St, and a rear group GR in order from the object side to the image side. The front group GF includes two lenses L11 to L12 in order from the object side to the image side. The lens L12 corresponds to the LFp lens. The rear group GR includes a first subsequent lens group GR1 and a second subsequent lens group GR2 in order from the object side to the image side. The first subsequent lens group GR1 includes three lenses L21 to L23 in order from the object side to the image side. The second subsequent lens group GR2 includes two lenses L24 to L25 in order from the object side to the image side. When focusing from an infinite object to a close object, the front group GF, the aperture stop St, and the first subsequent lens group GR1 move integrally toward the object side, and the second subsequent lens group GR2 is fixed with respect to the image plane Sim.

[0348] Regarding the imaging lens of Example 7, the basic lens data is shown in Table 19, the specifications and variable surface intervals are shown in Table 20, the aspherical coefficients are shown in Table 21, and the aberration diagrams are shown in Figure 17 .

[0349] [Table 19]

[0350] Example 7

[0351]

[0352] [Table 20] Example 7

[0353]

[0354] [Table 21]

[0355] Example 7

[0356]

[0357] [Example 8]

[0358] Figure 18A cross-sectional view showing the structure of the imaging lens of Example 8 is shown. The imaging lens of Example 8 includes, in order from the object side to the image side, a front group GF, an aperture stop St, and a rear group GR. The front group GF includes, in order from the object side to the image side, three lenses L11 to L13. The combined lens formed by joining lens L12 and lens L13 corresponds to the LFp lens. The rear group GR includes, in order from the object side to the image side, a first subsequent lens group GR1 and a second subsequent lens group GR2. The first subsequent lens group GR1 includes, in order from the object side to the image side, three lenses L21 to L23. The second subsequent lens group GR2 includes, in order from the object side to the image side, two lenses L24 to L25. When focusing from an infinite object to a close object, the front group GF, the aperture stop St, and the first subsequent lens group GR1 move integrally toward the object side, and the second subsequent lens group GR2 is fixed relative to the image plane Sim.

[0359] Regarding the imaging lens of Example 8, the basic lens data is shown in Table 22, the specifications and variable surface intervals are shown in Table 23, the aspherical coefficients are shown in Table 24, and the aberration diagrams are shown in Figure 19 .

[0360] [Table 22] Example 8

[0361]

[0362] [Table 23] Example 8

[0363]

[0364] [Table 24]

[0365] Example 8

[0366]

[0367] [Example 9]

[0368] Figure 20 A cross-sectional view showing the structure of the imaging lens of Example 9 is shown. The imaging lens of Example 9 includes, in order from the object side to the image side, a front group GF, an aperture stop St, and a rear group GR. The front group GF includes, in order from the object side to the image side, two lenses L11 to L12. Lens L12 corresponds to the LFp lens. The rear group GR includes, in order from the object side to the image side, a first subsequent lens group GR1 and a second subsequent lens group GR2. The first subsequent lens group GR1 includes, in order from the object side to the image side, four lenses L21 to L24. The second subsequent lens group GR2 includes, in order from the object side to the image side, two lenses L25 to L26. When focusing from an infinite object to a close object, the front group GF, the aperture stop St, and the first subsequent lens group GR1 move integrally toward the object side, and the second subsequent lens group GR2 is fixed relative to the image plane Sim.

[0369] Regarding the imaging lens of Example 9, the basic lens data is shown in Table 25, the specifications and variable surface intervals are shown in Table 26, the aspherical coefficients are shown in Table 27, and the aberration diagrams are shown in Figure 21 .

[0370] [Table 25] Example 9

[0371]

[0372] [Table 26] Example 9

[0373]

[0374] [Table 27]

[0375] Example 9

[0376]

[0377] [Example 10]

[0378] Figure 22 A cross-sectional view showing the structure of the imaging lens of Example 10 is shown in. The imaging lens of Example 10 includes, in order from the object side to the image side, a front group GF, an aperture stop St, and a rear group GR. The front group GF includes, in order from the object side to the image side, three lenses L11 to L13. The cemented lens formed by cementing lens L12 and lens L13 corresponds to the LFp lens. The rear group GR includes, in order from the object side to the image side, a first subsequent lens group GR1 and a second subsequent lens group GR2. The first subsequent lens group GR1 includes, in order from the object side to the image side, four lenses L21 to L24. The second subsequent lens group GR2 includes, in order from the object side to the image side, two lenses L25 to L26. When focusing from an infinite object to a close object, the front group GF, the aperture stop St, and the first subsequent lens group GR1 move integrally toward the object side, and the second subsequent lens group GR2 is fixed with respect to the image plane Sim.

[0379] Regarding the imaging lens of Example 10, the basic lens data is shown in Table 28, the specifications and variable surface intervals are shown in Table 29, the aspherical coefficients are shown in Table 30, and the aberration diagrams are shown in Figure 23 .

[0380] [Table 28] Example 10

[0381]

[0382] [Table 29] Example 10

[0383]

[0384] [Table 30]

[0385] Example 10

[0386]

[0387] [Example 11]

[0388] Figure 24 The cross-sectional view showing the structure of the imaging lens of Example 11 is shown. The imaging lens of Example 11 includes a front group GF, an aperture stop St, and a rear group GR in order from the object side to the image side. The front group GF includes three lenses L11 to L13 in order from the object side to the image side. The cemented lens formed by cementing lens L12 and lens L13 corresponds to the LFp lens. The rear group GR includes a first subsequent lens group GR1 and a second subsequent lens group GR2 in order from the object side to the image side. The first subsequent lens group GR1 includes four lenses L21 to L24 in order from the object side to the image side. The second subsequent lens group GR2 includes two lenses L25 to L26 in order from the object side to the image side. When focusing from an infinite object to a close object, the front group GF, the aperture stop St, and the first subsequent lens group GR1 move integrally toward the object side, and the second subsequent lens group GR2 is fixed with respect to the image plane Sim.

[0389] Regarding the imaging lens of Example 11, the basic lens data is shown in Table 31, the specifications and variable surface intervals are shown in Table 32, the aspherical coefficients are shown in Table 33, and the aberration diagrams are shown in Figure 25 .

[0390] [Table 31] Example 11

[0391]

[0392] [Table 32] Example 11

[0393]

[0394] [Table 33]

[0395] Example 11

[0396]

[0397] [Example 12]

[0398] Figure 26A cross-sectional view showing the structure of the imaging lens of Example 12 is shown. The imaging lens of Example 12 includes, in order from the object side to the image side, a front group GF, an aperture stop St, and a rear group GR. The front group GF includes, in order from the object side to the image side, three lenses L11 to L13. The cemented lens formed by cementing lens L12 and lens L13 corresponds to the LFp lens. The rear group GR includes, in order from the object side to the image side, a first subsequent lens group GR1 and a second subsequent lens group GR2. The first subsequent lens group GR1 includes, in order from the object side to the image side, four lenses L21 to L24. The second subsequent lens group GR2 includes, in order from the object side to the image side, two lenses L25 to L26. When focusing from an infinitely distant object to a close object, the front group GF, the aperture stop St, and the first subsequent lens group GR1 move integrally toward the object side, and the second subsequent lens group GR2 is fixed relative to the image plane Sim.

[0399] Regarding the imaging lens of Example 12, the basic lens data is shown in Table 34, the specifications and variable surface intervals are shown in Table 35, the aspherical coefficients are shown in Table 36, and the aberration diagrams are shown in Figure 27 .

[0400] [Table 34] Example 12

[0401]

[0402] [Table 35] Example 12

[0403]

[0404] [Table 36]

[0405] Example 12

[0406]

[0407] [Example 13]

[0408] Figure 28 A cross-sectional view showing the structure of the imaging lens of Example 13 is shown. The imaging lens of Example 13 includes, in order from the object side to the image side, a front group GF, an aperture stop St, and a rear group GR. The front group GF includes, in order from the object side to the image side, two lenses L11 to L12. The rear group GR includes, in order from the object side to the image side, five lenses L21 to L25. When focusing from an infinitely distant object to a close object, the entire imaging lens moves integrally toward the object side.

[0409] Regarding the imaging lens of Example 13, the basic lens data is shown in Table 37, the specifications and variable surface intervals are shown in Table 38, the aspherical coefficients are shown in Table 39, and the aberration diagrams are shown in Figure 29 .

[0410] [Table 37] Example 13

[0411]

[0412] [Table 38] Example 13

[0413]

[0414] [Table 39]

[0415] Example 13

[0416]

[0417] [Example 14]

[0418] Figure 30 The cross-sectional view showing the structure of the imaging lens of Example 14 is shown. The imaging lens of Example 14 includes a front group GF, an aperture stop St, and a rear group GR in order from the object side to the image side. The front group GF includes a single lens L11. The rear group GR includes five lenses L21 to L25 in order from the object side to the image side. When focusing from an infinitely distant object to a close object, the entire imaging lens moves integrally toward the object side.

[0419] Regarding the imaging lens of Example 14, the basic lens data is shown in Table 40, the specifications and variable surface intervals are shown in Table 41, the aspherical coefficients are shown in Table 42, and the aberration diagrams are shown in Figure 31 .

[0420] [Table 40] Example 14

[0421]

[0422] [Table 41] Example 14

[0423]

[0424] [Table 42]

[0425] Example 14

[0426]

[0427] [Example 15]

[0428] Figure 32A cross-sectional view showing the structure of the imaging lens of Embodiment 15 is shown. The imaging lens of Embodiment 15 includes a front group GF, an aperture stop St, and a rear group GR in order from the object side to the image side. The front group GF includes two lenses L11 to L12 in order from the object side to the image side. The cemented lens formed by cementing lens L11 and lens L12 corresponds to the LFp lens. The rear group GR includes a first subsequent lens group GR1 and a second subsequent lens group GR2 in order from the object side to the image side. The first subsequent lens group GR1 includes three lenses L21 to L23 in order from the object side to the image side. The second subsequent lens group GR2 includes two lenses L24 to L25 in order from the object side to the image side. Lens L22 is a compound aspherical lens in which a resin L22b having an aspherical air contact surface is formed on the spherical surface of a glass lens L22a. When focusing from an infinite object to a close object, only the first subsequent lens group GR1 moves toward the object side, and the other lenses are fixed with respect to the image plane Sim.

[0429] Regarding the imaging lens of Embodiment 15, the basic lens data is shown in Table 43, the specifications and variable surface intervals are shown in Table 44, the aspherical coefficients are shown in Table 45, and the aberration diagrams are shown in Figure 33 .

[0430] [Table 43]

[0431] Embodiment 15

[0432]

[0433] [Table 44] Embodiment 15

[0434]

[0435] [Table 45]

[0436] Embodiment 15

[0437]

[0438] [Embodiment 16]

[0439] Figure 34A cross-sectional view showing the structure of the imaging lens of Embodiment 16 is shown. The imaging lens of Embodiment 16 includes, in order from the object side to the image side, a front group GF, an aperture stop St, and a rear group GR. The front group GF includes, in order from the object side to the image side, two lenses L11 to L12. The cemented lens formed by cementing lens L11 and lens L12 corresponds to the LFp lens. The rear group GR includes, in order from the object side to the image side, a first subsequent lens group GR1 and a second subsequent lens group GR2. The first subsequent lens group GR1 includes, in order from the object side to the image side, three lenses L21 to L23. The second subsequent lens group GR2 includes, in order from the object side to the image side, two lenses L24 to L25. Lens L22 is a compound aspherical lens in which a resin L22b having an aspherical air contact surface is formed on the spherical surface of a glass lens L22a. When focusing from an infinitely distant object to a close object, only the first subsequent lens group GR1 moves toward the object side, and the other lenses are fixed with respect to the image plane Sim.

[0440] Regarding the imaging lens of Embodiment 16, the basic lens data is shown in Table 46, the specifications and variable surface intervals are shown in Table 47, the aspherical coefficients are shown in Table 48, and the aberration diagrams are shown in Figure 35 .

[0441] [Table 46] Embodiment 16

[0442]

[0443] [Table 47] Embodiment 16

[0444]

[0445] [Table 48]

[0446] Embodiment 16

[0447]

[0448] [Embodiment 17]

[0449] Figure 36A cross-sectional view showing the structure of the imaging lens of Example 17 is shown. The imaging lens of Example 17 includes a front group GF, an aperture stop St, and a rear group GR in order from the object side to the image side. The front group GF includes two lenses L11 to L12 in order from the object side to the image side. The lens L12 corresponds to the LFp lens. The rear group GR includes a first subsequent lens group GR1 and a second subsequent lens group GR2 in order from the object side to the image side. The first subsequent lens group GR1 includes six lenses L21 to L26 in order from the object side to the image side. The second subsequent lens group GR2 includes one lens L27. The lens L24 is a compound aspherical lens in which a resin L24b having an aspherical air contact surface is formed on the spherical surface of a glass lens L24a. When focusing from an infinite object to a close object, only the first subsequent lens group GRl moves toward the object side, and the other lenses are fixed with respect to the image plane Sim.

[0450] Regarding the imaging lens of Example 17, the basic lens data is shown in Table 49, the specifications and variable surface intervals are shown in Table 50, the aspherical coefficients are shown in Table 51, and the aberration diagrams are shown in Figure 37 .

[0451] [Table 49]

[0452] Example 17

[0453]

[0454] [Table 50]

[0455] Example 17

[0456]

[0457] [Table 51]

[0458] Example 17

[0459]

[0460] [Example 18]

[0461] Figure 38A cross-sectional view showing the structure of the imaging lens of Embodiment 18 is shown. The imaging lens of Embodiment 18 includes, in order from the object side to the image side, a front group GF, an aperture stop St, and a rear group GR. The front group GF includes, in order from the object side to the image side, three lenses L11 to L13. The lens L13 corresponds to the LFp lens. The rear group GR includes, in order from the object side to the image side, a first subsequent lens group GR1, a second subsequent lens group GR2, and a third subsequent lens group GR3. The first subsequent lens group GR1 includes one lens L21. The second subsequent lens group GR2 includes, in order from the object side to the image side, four lenses L22 to L25. The third subsequent lens group GR3 includes one lens L26. When focusing from an infinitely distant object to a close object, only the second subsequent lens group GR2 moves toward the object side, and the other lenses are fixed with respect to the image plane Sim.

[0462] Regarding the imaging lens of Embodiment 18, the basic lens data is shown in Table 52, the specifications and variable surface intervals are shown in Table 53, the aspherical coefficients are shown in Table 54, and the aberration diagrams are shown in Figure 39 .

[0463] [Table 52] Embodiment 18

[0464]

[0465] [Table 53]

[0466] Embodiment 18

[0467]

[0468] [Table 54]

[0469] Embodiment 18

[0470]

[0471] [Embodiment 19]

[0472] Figure 40A cross-sectional view showing the structure of the imaging lens of Embodiment 19 is shown. The imaging lens of Embodiment 19 includes, in order from the object side to the image side, a front group GF, an aperture stop St, and a rear group GR. The front group GF includes, in order from the object side to the image side, four lenses L11 to L14. Lenses L12 and L14 correspond to the LFp lenses. The rear group GR includes, in order from the object side to the image side, a first subsequent lens group GR1, a second subsequent lens group GR2, and a third subsequent lens group GR3. The first subsequent lens group GR1 includes one lens L21. The second subsequent lens group GR2 includes, in order from the object side to the image side, four lenses L22 to L25. The third subsequent lens group GR3 includes one lens L26. When focusing from an infinitely distant object to a close object, only the second subsequent lens group GR2 moves toward the object side, and the other lenses are fixed with respect to the image plane Sim.

[0473] Regarding the imaging lens of Embodiment 19, the basic lens data is shown in Table 55, the specifications and variable surface intervals are shown in Table 56, the aspherical coefficients are shown in Table 57, and the aberration diagrams are shown in Figure 41 .

[0474] [Table 55] Embodiment 19

[0475]

[0476] [Table 56]

[0477] Embodiment 19

[0478]

[0479] [Table 57]

[0480] Embodiment 19

[0481]

[0482] [Embodiment 20]

[0483] Figure 42A cross-sectional view showing the structure of the imaging lens according to Embodiment 20 is shown. The imaging lens according to Embodiment 20 includes, in order from the object side to the image side, a front group GF, an aperture stop St, and a rear group GR. The front group GF includes a single lens L11. The lens L11 corresponds to the LFp lens. The rear group GR includes, in order from the object side to the image side, a first subsequent lens group GR1 and a second subsequent lens group GR2. The first subsequent lens group GR1 includes four lenses L21 to L24 in order from the object side to the image side. The second subsequent lens group GR2 includes two lenses L25 to L26 in order from the object side to the image side. When focusing from an infinitely distant object to a close object, the front group GF, the aperture stop St, and the first subsequent lens group GR1 move integrally toward the object side, and the second subsequent lens group GR2 is fixed with respect to the image plane Sim.

[0484] Regarding the imaging lens according to Embodiment 20, the basic lens data is shown in Table 58, the specifications and variable surface intervals are shown in Table 59, the aspherical coefficients are shown in Table 60, and the aberration diagrams are shown in Figure 43 .

[0485] [Table 58]

[0486] Embodiment 20

[0487]

[0488] [Table 59]

[0489] Embodiment 20

[0490]

[0491] [Table 60]

[0492] Embodiment 20

[0493]

[0494] [Embodiment 21]

[0495] Figure 44A cross-sectional view showing the structure of the imaging lens of Example 21 is shown. The imaging lens of Example 21 includes a front group GF, an aperture stop St, and a rear group GR in order from the object side to the image side. The front group GF includes a first front-side lens group GF1, a second front-side lens group GF2, and a third front-side lens group GF3 in order from the object side to the image side. The first front-side lens group GF1 includes five lenses L11 to L15 in order from the object side to the image side. The second front-side lens group GF2 includes one lens L16. The third front-side lens group GF3 includes two lenses L17 to L18 in order from the object side to the image side. Lenses L12, L15, and L16 correspond to the LFp lens. The rear group GR includes a first subsequent lens group GR1 and a second subsequent lens group GR2 in order from the object side to the image side. The first subsequent lens group GR1 includes four lenses L21 to L24 in order from the object side to the image side. The second subsequent lens group GR2 includes two lenses L25 to L26 in order from the object side to the image side. When focusing from an infinitely distant object to a close object, the second front-side lens group GF2 and the first subsequent lens group GR1 change the interval between them and move toward the object side, and the other lenses are fixed with respect to the image plane Sim.

[0496] Regarding the imaging lens of Example 21, the basic lens data is shown in Tables 61A and 61B, the specifications and variable surface intervals are shown in Table 62, the aspherical coefficients are shown in Table 63, and the aberration diagrams are shown in Figure 45 . Among them, in order to avoid the length of one table from becoming too long, the basic lens data is shown in two tables.

[0497] [Table 61A]

[0498] Example 21

[0499]

[0500] [Table 61B] Example 21

[0501]

[0502] [Table 62] Example 21

[0503]

[0504] [Table 63]

[0505] Example 21

[0506]

[0507] Tables 64 to 67 show the corresponding values ​​of conditional expressions (1), (3) to (10), (12) to (19), (21), and (22) of the imaging lenses of Examples 1 to 21. In the corresponding value column of conditional expressions (15) and (17), the reference symbol of the corresponding lens is written in parentheses below each corresponding value of the conditional expression with multiple corresponding values. In addition, the corresponding values ​​of conditional expressions (2), (11), and (20) are shown in the table of basic lens data of each embodiment, so they are not recorded in Tables 64 to 67. The corresponding values ​​of the embodiments shown in Tables 64 to 67 can also be used as the upper limit or lower limit of the conditional expression to set the preferred range of the conditional expression.

[0508] [Table 64]

[0509]

[0510] [Table 65]

[0511]

[0512] [Table 66]

[0513]

[0514] [Table 67]

[0515]

[0516] Although the imaging lenses of Examples 1 to 21 are compact, various aberrations are well corrected and high optical performance is maintained.

[0517] Next, an imaging device according to an embodiment of the present invention will be described. Figure 46 and Figure 47 2 shows an external view of a camera 30 which is an imaging device according to an embodiment of the present invention. Figure 46 1 is a perspective view showing the camera 30 as viewed from the front side. Figure 47 The camera 30 is a perspective view viewed from the back. The camera 30 is a so-called mirrorless digital camera, and can detachably attach an interchangeable lens 20. The interchangeable lens 20 includes an imaging lens 1 according to an embodiment of the present invention housed in a lens barrel.

[0518] The camera 30 includes a camera body 31. A shutter button 32 and a power button 33 are provided on the upper surface of the camera body 31. In addition, 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 existing in the angle of view before the capture.

[0519] A photographic aperture through which light from a photographic subject enters is provided at the center of the front surface of the camera body 31. A bayonet mount 37 is provided at a position corresponding to the photographic aperture, and the interchangeable lens 20 is attached to the camera body 31 via the bayonet mount 37.

[0520] An imaging element 38 is provided within the camera body 31. The imaging element 38 outputs an imaging signal corresponding to the subject image formed by the interchangeable lens 20. As the imaging element 38, for example, a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) can be used. A signal processing circuit (not shown) and a recording medium (not shown) are provided within the camera body 31. The signal processing circuit processes the imaging signal output from the imaging element 38 to generate an image. The recording medium is used to record the generated image. In the camera 30, a still image or a moving image can be captured by pressing the shutter button 32, and the image data obtained by the capture is recorded in the above-described recording medium.

[0521] As described above, the technology of the present invention has been described by way of embodiments and examples, but the technology of the present invention is not limited to the above-described embodiments and examples, and various modifications can be made. 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-described examples, and other values can be adopted.

[0522] Moreover, the imaging device according to the embodiment of the present invention is not limited to the above example, and can be various types such as a camera other than a mirrorless type, a film camera, a video camera, and a security camera, for example.

[0523] Regarding the above-described embodiments and examples, the following additional notes are further disclosed.

[0524] [Additional Note 1]

[0525] An imaging lens that sequentially includes, from the object side to the image side: a front group including one or more lenses, a diaphragm, and a rear group including a plurality of lenses,

[0526] The rear group includes at least one first aspherical lens that has a concave surface facing the image side in the paraxial region and has an inflection point at which the concavo-convex shape changes midway as it moves from the optical axis toward the peripheral portion on the lens surface on the image side,

[0527] And includes at least one lens as follows:

[0528] Let the back focal length at the air equivalent distance of the entire system in the state of focusing on an infinitely distant object be Bf.

[0529] Let the focal length of the entire system in the state of focusing on an infinitely distant object be f.

[0530] When the maximum half angle of view in the state of focusing on an infinitely distant object is ωm, the conditional expression (1) represented by

[0531] 0.3 < Bf / (f × tan ωm) < 1.5 (1) is satisfied.

[0532] Let the temperature coefficient of the refractive index with respect to the d line at 25°C of the lenses included in the entire system be (dN / dT)×10 -6 ,

[0533] When the unit of dN / dT is °C -1 the conditional expression (2) represented by

[0534] 0 < |dN / dT| < 15 (2)

[0535] is satisfied.

[0536] [Supplementary Note 2]

[0537] For the imaging lens according to Supplementary Note 1, where

[0538] 0.36 < Bf / (f × tan ωm) < 1.2 (1 - 1)

[0539] the conditional expression (1 - 1) represented by is satisfied.

[0540] [Supplementary Note 3]

[0541] For the imaging lens according to Supplementary Note 1 or Supplementary Note 2, where

[0542] When the sum of the distance on the optical axis from the lens surface closest to the object side of the front group to the lens surface closest to the image side of the rear group and Bf in the state of focusing on an infinitely distant object is TL, the conditional expression (3) represented by

[0543] 1.1 < TL / f < 3.5 (3) is satisfied.

[0544] is satisfied.

[0545] [Supplementary Note 4]

[0546] For the imaging lens according to Supplementary Note 3, where

[0547] 1.2 < TL / f < 3 (3 - 1)

[0548] the conditional expression (3 - 1) represented by is satisfied.

[0549] [Supplementary Note 5]

[0550] The imaging lens according to any one of Supplementary Notes 1 to 4, wherein

[0551] when the open F-number in the state of focusing on an infinitely distant object is set to Fno, the following is satisfied

[0552] 1.6 < Fno / tanωm < 5 (4)

[0553] the conditional expression (4) represented by

[0554] [Supplementary Note 6]

[0555] The imaging lens according to Supplementary Note 5, wherein the following is satisfied

[0556] 2 < Fno / tanωm < 3.2 (4-1)

[0557] the conditional expression (4-1) represented by

[0558] [Supplementary Note 7]

[0559] The imaging lens according to any one of Supplementary Notes 1 to 6, wherein

[0560] the minimum value of the distance on the optical axis from the most image-side lens surface of the front group to the diaphragm is set to dFSt,

[0561] regarding the sign of dFSt, it is set to positive when the diaphragm is more image-side than the most image-side lens surface of the front group, and set to negative when the diaphragm is more object-side than the most image-side lens surface of the front group,

[0562] the minimum value of the distance on the optical axis from the diaphragm to the most object-side lens surface of the rear group is set to dStR,

[0563] regarding the sign of dStR, it is set to positive when the most object-side lens surface of the rear group is more image-side than the diaphragm, and set to negative when the most object-side lens surface of the rear group is more object-side than the diaphragm,

[0564] when the sum of the distance on the optical axis from the most object-side lens surface of the front group to the most image-side lens surface of the rear group and Bf in the state of focusing on an infinitely distant object is set to TL, the following is satisfied

[0565] 0 < dFSt / TL < 0.8 (5)

[0566] 0 < dStR / TL < 0.8 (6)

[0567] the conditional expressions (5) and (6) represented by

[0568] [Supplementary Note 8]

[0569] The imaging lens according to any one of Supplementary Notes 1 to 7, wherein

[0570] The sum of the distance on the optical axis from the aperture stop to the image-side lens surface closest to the rear group in the state of focusing on an infinitely distant object and Bf is defined as dSt,

[0571] When the sum of the distance on the optical axis from the object-side lens surface closest to the front group to the image-side lens surface closest to the rear group and Bf in the state of focusing on an infinitely distant object is defined as TL, the following is satisfied

[0572] 0.67 < dSt / TL < 0.93 (7)

[0573] The conditional expression (7) represented by

[0574] [Supplementary Note 9]

[0575] The imaging lens according to any one of Supplementary Notes 1 to 7, wherein

[0576] The paraxial curvature radius of the object-side surface of the lens closest to the object side of the front group is defined as RL1f,

[0577] When the paraxial curvature radius of the image-side surface of the lens closest to the object side of the front group is defined as RL1r, the following is satisfied

[0578] -3 < (RL1r - RL1f) / (RL1r + RL1f) < 0 (8)

[0579] The conditional expression (8) represented by

[0580] [Supplementary Note 10]

[0581] The imaging lens according to Supplementary Note 9, wherein the following is satisfied

[0582] -1 < (RL1r - RL1f) / (RL1r + RL1f) < -0.07 (8-1)

[0583] The conditional expression (8-1) represented by

[0584] [Supplementary Note 11]

[0585] The imaging lens according to any one of Supplementary Notes 1 to 10, wherein

[0586] In a state where the imaging lens is focused on an object at infinity, the distance from the image-side surface of the first aspherical lens included in the rear group, which is the closest to the image side, to the image-side lens surface of the rear group that is the closest to the image side on the optical axis is set as dA1, and the sum of dA1 and Bf is

[0587] When the distance from the object-side lens surface of the front group that is the closest to the object side to the image-side lens surface of the rear group that is the closest to the image side on the optical axis in a state where the imaging lens is focused on an object at infinity and the sum of this distance and Bf is set as TL, the following condition is satisfied:

[0588] 0.02 < dA1 / TL < 0.6 (9)

[0589] The conditional expression (9) represented by the above formula.

[0590] [Supplementary Note 12]

[0591] For the imaging lens according to Supplementary Note 11, the following condition is satisfied:

[0592] 0.08 < dA1 / TL < 0.35 (9-1)

[0593] The conditional expression (9-1) represented by the above formula.

[0594] [Supplementary Note 13]

[0595] For the imaging lens according to any one of Supplementary Notes 1 to 12,

[0596] The front group includes at least one lens that satisfies the conditional expression (2).

[0597] [Supplementary Note 14]

[0598] For the imaging lens according to Supplementary Note 13,

[0599] The lens on the object side of the front group that is the closest to the object side satisfies the conditional expression (2).

[0600] [Supplementary Note 15]

[0601] For the imaging lens according to any one of Supplementary Notes 1 to 14,

[0602] The rear group includes at least one lens that satisfies the conditional expression (2).

[0603] [Supplementary Note 16]

[0604] For the imaging lens according to any one of Supplementary Notes 1 to 15,

[0605] When the distance from the object-side lens surface of the front group that is the closest to the object side to the image-side lens surface of the rear group that is the closest to the image side on the optical axis in a state where the imaging lens is focused on an object at infinity and the sum of this distance and Bf is set as TL, the following condition is satisfied:

[0606] 1.2 < TL / (f × tan ωm) < 3 (10)

[0607] The conditional expression (10) represented by

[0608] [Supplementary Note 17]

[0609] The imaging lens according to Supplementary Note 16, wherein

[0610] 1.7 < TL / (f × tan ωm) < 2.5 (10-1)

[0611] The conditional expression (10-1) represented by

[0612] [Supplementary Note 18]

[0613] The imaging lens according to any one of Supplementary Notes 1 to 17, wherein

[0614] The front group includes at least one lens as follows:

[0615] When the refractive index with respect to the d-line and the Abbe number based on the d-line of the lenses included in the entire system are set as Nd and vd respectively,

[0616] 1.6 < Nd + 0.01 × vd < 2.6 (11)

[0617] The conditional expression (11) represented by

[0618] [Supplementary Note 19]

[0619] The imaging lens according to Supplementary Note 18, wherein

[0620] The lens closest to the object side of the front group satisfies the conditional expression (11).

[0621] [Supplementary Note 20]

[0622] The imaging lens according to any one of Supplementary Notes 1 to 19, wherein

[0623] When the focal length of the lens closest to the object side of the front group is set as fL1,

[0624] -1.5 < f / fL1 < 0 (12)

[0625] The conditional expression (12) represented by

[0626] [Supplementary Note 21]

[0627] The imaging lens according to any one of Supplementary Notes 1 to 20, wherein

[0628] Let the paraxial curvature radius of the image-side surface of the first aspherical lens closest to the image side among the first aspherical lenses included in the rear group be RA1c.

[0629] When the curvature radius at the position of the maximum effective diameter of the image-side surface of the first aspherical lens closest to the image side among the first aspherical lenses included in the rear group is set as RA1y, the following is satisfied:

[0630] -100 < RA1y / RA1c < 0 (13)

[0631] The conditional expression (13) represented by the above.

[0632] [Supplementary Note 22]

[0633] The imaging lens according to any one of Supplementary Notes 1 to 21, wherein

[0634] When the refractive index with respect to the d-line and the Abbe number based on the d-line of the first aspherical lens closest to the image side among the first aspherical lenses included in the rear group are set as NdA1 and vdA1 respectively, the following is satisfied:

[0635] 1.8 < NdA1 + 0.01×vdA1 < 2.14 (14)

[0636] The conditional expression (14) represented by the above.

[0637] [Supplementary Note 23]

[0638] The imaging lens according to any one of Supplementary Notes 1 to 22, wherein

[0639] The rear group includes at least one second aspherical lens, and this second aspherical lens has a convex surface facing the image side in the paraxial region and has a lens surface on the image side where the refractive power at the position of the maximum effective diameter is shifted in the negative direction compared to the refractive power in the paraxial region.

[0640] [Supplementary Note 24]

[0641] The imaging lens according to Supplementary Note 23, wherein

[0642] Let the paraxial curvature radius of the image-side surface of the second aspherical lens be RA2c.

[0643] When the curvature radius at the position of the maximum effective diameter of the image-side surface of the second aspherical lens is set as RA2y,

[0644] All the second aspherical lenses included in the rear group satisfy

[0645] -1 < RA2c / RA2y < 1 (15)

[0646] The conditional expression (15) represented by

[0647] [Supplementary Note 25]

[0648] The imaging lens according to Supplementary Note 23 or Supplementary Note 24, wherein

[0649] When the distance on the optical axis from the image-side surface of the second aspherical lens included in the rear group, which is the second aspherical lens closest to the image side among the second aspherical lenses included in the rear group, to the image-side lens surface of the rear group in a state where the object is focused at infinity is set as dA2 and added to Bf

[0650] When the distance on the optical axis from the object-side lens surface of the front group to the image-side lens surface of the rear group in a state where the object is focused at infinity is set as TL and added to Bf, it satisfies

[0651] 0.2 < dA2 / TL < 0.6 (16)

[0652] The conditional expression (16) represented by

[0653] [Supplementary Note 26]

[0654] The imaging lens according to any one of Supplementary Notes 23 to 25, wherein

[0655] The second lens from the image side of the rear group is the second aspherical lens closest to the image side among the second aspherical lenses included in the rear group.

[0656] [Supplementary Note 27]

[0657] The imaging lens according to any one of Supplementary Notes 1 to 26, wherein

[0658] The second lens from the image side of the rear group has an inflection point on the image-side lens surface where the concavo-convex shape changes midway as it moves from the optical axis toward the peripheral part.

[0659] [Supplementary Note 28]

[0660] The imaging lens according to any one of Supplementary Notes 1 to 27, wherein

[0661] The lens closest to the image side of the rear group is the first aspherical lens.

[0662] [Supplementary Note 29]

[0663] The imaging lens according to any one of Supplementary Notes 1 to 28, wherein

[0664] The lens closest to the image side in the rear group has a convex surface facing the object side in the paraxial region, and the lens surface on the object side has an inflection point where the concavo-convex shape changes midway as it moves from the optical axis toward the peripheral part.

[0665] [Supplementary Note 30]

[0666] The imaging lens according to any one of Supplementary Notes 1 to 29, wherein

[0667] the rear group includes two of the first aspherical lenses.

[0668] [Supplementary Note 31]

[0669] The imaging lens according to any one of Supplementary Notes 23 to 26, wherein

[0670] the rear group includes two of the second aspherical lenses.

[0671] [Supplementary Note 32]

[0672] The imaging lens according to any one of Supplementary Notes 1 to 31, which includes at least one cemented lens.

[0673] [Supplementary Note 33]

[0674] The imaging lens according to any one of Supplementary Notes 1 to 32, wherein

[0675] the lens closest to the object side in the front group satisfies the conditional expression (2),

[0676] the distance on the optical axis from the lens surface closest to the object side in the front group to the lens surface closest to the image side in the rear group in the state of focusing on an infinitely distant object, when added to Bf, is set as TL,

[0677] the open F value in the state of focusing on an infinitely distant object is set as Fno,

[0678] the distance on the optical axis from the diaphragm to the lens surface closest to the image side in the rear group in the state of focusing on an infinitely distant object, when added to Bf, is set as dSt,

[0679] when, in the state of focusing on an infinitely distant object, the distance on the optical axis from the image side surface of the first aspherical lens closest to the image side among the first aspherical lenses included in the rear group to the lens surface closest to the image side in the rear group, when added to Bf, is set as dA1, it satisfies

[0680] 1.2 < TL / f < 1.6 (3 - 2)

[0681] 2.5 < Fno / tanωm < 4 (4 - 2)

[0682] 0.67 < dSt / TL < 0.93 (7)

[0683] 0.08 < dA1 / TL < 0.35(9 - 1)

[0684] The conditional expressions (3 - 2), (4 - 2), (7), and (9 - 1) shown

[0685] [Supplementary Note 34]

[0686] An imaging device including the imaging lens according to any one of Supplementary Notes 1 to 33

Claims

1. An imaging lens, comprising, from the object side to the image side, the following components: A front group including one or more lenses, an aperture, and a rear group including multiple lenses. The rear group includes at least one first aspherical lens, the first aspherical lens having a concave surface facing the image side in a paraxial region, and having an inflection point on the lens surface on the image side whose concave-convex shape changes midway as it moves from the optical axis toward the peripheral portion, And contains at least one of the following lenses: The back focal length of the entire system at the air conversion distance when focusing on an object at infinity is set to Bf. Let the focal length of the entire system when focusing on an object at infinity be f, When the maximum half angle of view in the state of focusing on an object at infinity is set to ωm, 0.3<Bf / (f×tanωm)<1.5 (1) The conditional expression (1) is expressed as follows: The temperature coefficient of the refractive index of the lens included in the entire system with respect to the d-line at 25°C is set to (dN / dT)×10 -6 , Set the unit of dN / dT to °C -1 In the case of 0<|dN / dT|<15 (2) The conditional expression (2) is represented.

2. The imaging lens according to claim 1, wherein: When the sum of the distance on the optical axis from the lens surface closest to the object side of the front group to the lens surface closest to the image side of the rear group in a state of focusing on an infinitely distant object and Bf is TL, 1.1<TL / f<3.5 (3) The conditional expression (3) is represented.

3. The imaging lens according to claim 2, wherein: satisfy 1.2<TL / f<3 (3-1) The conditional expression (3-1) is represented.

4. The imaging lens according to any one of claims 1 to 3, wherein: satisfy 0.36<Bf / (f×tanωm)<1.2 (1-1) The conditional expression (1-1) is represented.

5. The imaging lens according to any one of claims 1 to 3, wherein: When the open F value in the state of focusing on an object at infinity is set to Fno, 1.6<Fno / tanωm<5 (4) The conditional expression (4) is represented.

6. The imaging lens according to claim 5, wherein: satisfy 2<Fno / tanωm<3.2 (4-1) The conditional expression (4-1) is represented.

7. The imaging lens according to any one of claims 1 to 3, wherein: The minimum value of the distance on the optical axis from the lens surface closest to the image side of the front group to the aperture stop is set to dFSt, The sign of dFSt is positive when the aperture is closer to the image side than the lens surface closest to the image side of the front group, and negative when the aperture is closer to the object side than the lens surface closest to the image side of the front group. The minimum value of the distance on the optical axis from the aperture to the lens surface of the rear group closest to the object side is set to dStR, The sign of dStR is positive when the lens surface closest to the object side of the rear group is closer to the image side than the aperture stop, and negative when the lens surface closest to the object side of the rear group is closer to the object side than the aperture stop. When the sum of the distance on the optical axis from the lens surface closest to the object side of the front group to the lens surface closest to the image side of the rear group in a state of focusing on an infinitely distant object and Bf is TL, 0<dFSt / TL<0.8 (5) 0<dStR / TL<0.8 (6) The conditional expressions (5) and (6) are represented.

8. The imaging lens according to any one of claims 1 to 3, wherein: The sum of the distance on the optical axis from the aperture to the lens surface closest to the image side of the rear group in a state of focusing on an infinitely distant object and Bf is dSt, When the sum of the distance on the optical axis from the lens surface closest to the object side of the front group to the lens surface closest to the image side of the rear group in a state of focusing on an infinitely distant object and Bf is TL, 0.67<dSt / TL<0.93 (7) The conditional expression (7) is represented.

9. The imaging lens according to any one of claims 1 to 3, wherein: The paraxial curvature radius of the object-side surface of the lens closest to the object side of the front group is RL1f, When the paraxial curvature radius of the image-side surface of the lens closest to the object side of the front group is RL1r, -3<(RL1r-RL1f) / (RL1r+RL1f)<0 (8) The conditional expression (8) is represented.

10. The imaging lens according to any one of claims 1 to 3, wherein: The sum of the distance on the optical axis from the image-side surface of the first aspherical lens most on the image side of the first aspherical lens included in the rear group to the lens surface most on the image side of the rear group in a state where the lens is focused on an object at infinity and Bf is set to dA1, When the sum of the distance on the optical axis from the lens surface closest to the object side of the front group to the lens surface closest to the image side of the rear group in a state of focusing on an infinitely distant object and Bf is TL, 0.02<dA1 / TL<0.6 (9) The conditional expression (9) is represented.

11. The imaging lens according to claim 10, wherein: satisfy 0.08<dA1 / TL<0.35 (9-1) The conditional expression (9-1) is represented.

12. The imaging lens according to any one of claims 1 to 3, wherein: The front group includes at least one lens satisfying the conditional expression (2).

13. The imaging lens according to claim 12, wherein: The lens closest to the object side of the front group satisfies the conditional expression (2).

14. The imaging lens according to claim 13, wherein: The rear group includes at least one lens satisfying the conditional expression (2).

15. The imaging lens according to claim 1 or 2, wherein: When the sum of the distance on the optical axis from the lens surface closest to the object side of the front group to the lens surface closest to the image side of the rear group in a state of focusing on an infinitely distant object and Bf is TL, 1.2<TL / (f×tanωm)<3 (10) The conditional expression (10) is represented.

16. The imaging lens according to claim 15, wherein: satisfy 1.7<TL / (f×tanωm)<2.5 (10-1) The conditional expression (10-1) is represented.

17. The imaging lens according to claim 16, wherein: satisfy 1.2<TL / f<3 (3-1) The conditional expression (3-1) is represented.

18. The imaging lens according to claim 17, wherein: When the open F value in the state of focusing on an object at infinity is set to Fno, 2<Fno / tanωm<3.2 (4-1) The conditional expression (4-1) is represented.

19. The imaging lens according to claim 18, wherein: satisfy 0.36<Bf / (f×tanωm)<1.2 (1-1) The conditional expression (1-1) is represented.

20. The imaging lens according to claim 19, wherein: The paraxial curvature radius of the object-side surface of the lens closest to the object side of the front group is RL1f, When the paraxial curvature radius of the image-side surface of the lens closest to the object side of the front group is RL1r, -1<(RL1r-RL1f) / (RL1r+RL1f)<-0.07 (8-1) The conditional expression (8-1) is represented.

21. The imaging lens according to claim 18, wherein: When the sum of the distance on the optical axis from the aperture to the lens surface closest to the image side of the rear group in a state of focusing on an infinitely distant object and Bf is dSt, 0.67<dSt / TL<0.93 (7) The conditional expression (7) is represented.

22. The imaging lens according to claim 21, wherein: When the sum of the distance on the optical axis from the image side surface of the first aspherical lens most on the image side of the first aspherical lens included in the rear group to the lens surface most on the image side of the rear group in the state of focusing on an infinitely distant object and Bf is set to dA1, 0.08<dA1 / TL<0.35 (9-1) The conditional expression (9-1) is represented.

23. The imaging lens according to claim 22, wherein: The front group includes at least one lens satisfying the conditional expression (2).

24. The imaging lens according to claim 23, wherein: The lens closest to the object side of the front group satisfies the conditional expression (2).

25. The imaging lens according to any one of claims 1 to 3, wherein: The front group includes at least one lens as follows: When the refractive index of the lens included in the entire system with respect to the d-line and the Abbe number based on the d-line are respectively Nd and vd, 1.6<Nd+O.01×vd<2.6 (11) The conditional expression (11) is represented.

26. The imaging lens according to claim 25, wherein: The lens closest to the object side of the front group satisfies the conditional expression (11).

27. The imaging lens according to any one of claims 1 to 3, wherein: When the focal length of the lens closest to the object in the front group is fL1, -1.5<f / fL1<0 (12) The conditional expression (12) is represented.

28. The imaging lens according to any one of claims 1 to 3, wherein: The paraxial curvature radius of the image-side surface of the first aspherical lens closest to the image side among the first aspherical lenses included in the rear group is RA1c, When the curvature radius at the position of the maximum effective diameter of the image-side surface of the first aspherical lens closest to the image side among the first aspherical lenses included in the rear group is RA1y, -100<RA1y / RA1c<0(13) is satisfied The conditional expression (13) is represented.

29. The imaging lens according to any one of claims 1 to 3, wherein: When the refractive index of the first aspherical lens closest to the image side in the first aspherical lens included in the rear group with respect to the d-line and the Abbe number based on the d-line are respectively NdA1 and vdA1, 1.8<NdA1+0.01×vdA1<2.14 (14) The conditional expression (14) is represented.

30. The imaging lens according to any one of claims 1 to 3, wherein: The rear group includes at least one second aspherical lens having a convex surface facing the image side in the paraxial region and having an image-side lens surface whose refractive power at the position of the maximum effective diameter is shifted in the negative direction compared with the refractive power in the paraxial region.

31. The imaging lens according to claim 30, wherein: The paraxial curvature radius of the image-side surface of the second aspheric lens is RA2c. When the curvature radius at the position of the maximum effective diameter of the image-side surface of the second aspherical lens is RA2y, All second aspherical lenses included in the rear group satisfy -1<RA2c / RA2y<1 (15) The conditional expression (15) is represented.

32. The imaging lens according to claim 30, wherein: The sum of the distance on the optical axis from the image-side surface of the second aspherical lens most on the image side of the second aspherical lens included in the rear group to the lens surface most on the image side of the rear group when focusing on an object at infinity and Bf is set to dA2, When the sum of the distance on the optical axis from the lens surface closest to the object side of the front group to the lens surface closest to the image side of the rear group in a state of focusing on an infinitely distant object and Bf is TL, 0.2<dA2 / TL<0.6 (16) The conditional expression (16) is represented.

33. The imaging lens according to claim 32, wherein: The second lens of the rear group from the image side is the second aspherical lens closest to the image side among the second aspherical lenses included in the rear group.

34. The imaging lens according to claim 33, wherein: The second lens from the image side of the rear group has an inflection point on the image side lens surface where the concavoconvex shape changes as it moves from the optical axis toward the periphery.

35. The imaging lens according to any one of claims 1 to 3, wherein: The lens closest to the image side of the rear group is the first aspherical lens.

36. The imaging lens according to claim 35, wherein: The lens closest to the image side of the rear group has a convex surface facing the object side in the paraxial region, and the lens surface on the object side has an inflection point where the concavo-convex shape changes as it moves from the optical axis toward the periphery.

37. The imaging lens according to any one of claims 1 to 3, wherein: The rear group includes two first aspherical lenses.

38. The imaging lens according to claim 30, wherein: The rear group includes two pieces of the second aspherical lenses.

39. The imaging lens of any one of claims 1 to 3, comprising at least one cemented lens.

40. The imaging lens according to claim 1, wherein: The lens closest to the object side of the front group satisfies the conditional expression (2), The sum of the distance on the optical axis from the lens surface closest to the object side of the front group to the lens surface closest to the image side of the rear group in a state of focusing on an infinitely distant object and Bf is TL, Set the open F value when focusing on an object at infinity to Fno. The sum of the distance on the optical axis from the aperture to the lens surface closest to the image side of the rear group in a state of focusing on an infinitely distant object and Bf is dSt, When the sum of the distance on the optical axis from the image side surface of the first aspherical lens most on the image side of the first aspherical lens included in the rear group to the lens surface most on the image side of the rear group in the state of focusing on an infinitely distant object and Bf is set to dA1, 1.2<TL / f<1.6 (3-2) 2.5<Fno / tanωm<4 (4-2) 0.67<dSt / TL<0.93 (7) 0.08<dA1 / TL<0.35 (9-1) The conditional expressions (3-2), (4-2), (7) and (9-1) are represented. An imaging device comprising the imaging lens according to any one of claims 1 to 40.

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