Imaging lens and imaging device

Abstract

To provide an imaging lens which has a small weight and size, has a small F-number and a suppressed chromatic aberration, thereby presenting an excellent optical performance, and an imaging device having the imaging lens.SOLUTION: The imaging lens sequentially includes a front group, an aperture diaphragm, and a back group in descending order of the proximity to an object. The back group includes at least one Lp lens made of resin having a positive bending force, the Lp lens being joined to a lens. When the Abbe number and the index of refraction of the Lp lens are denoted by νp and Np, respectively, the Lp lens satisfies the conditional expression of 120<νp+94.24×Np<180. The imaging lens satisfies a predetermined conditional expression.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

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

[0003] [Patent Document 1] Patent Publication No. 2021-060475 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a demand for imaging lenses that are small, lightweight, have a small F-number, suppress chromatic aberration, and have good optical performance. These requirements are becoming higher every year.

[0005] The present disclosure has been made in view of the above circumstances, and aims to provide an imaging lens that is small and lightweight, yet has a small F-number, suppressed chromatic aberration, and good optical performance, and an imaging device equipped with this imaging lens. [Means for solving the problem]

[0006] An imaging lens according to one aspect of the present disclosure includes, in order from the object side to the image side, a front group, an aperture stop, and a rear group, the rear group including at least one Lp lens made of resin and having positive refractive power cemented to the lens; 120<νp+94.24×Np<186 (1) 0 <d×(1 / Rf-1 / Rr)<0.05 (2) -20 <TL×(1 / De-1 / Rr)<20 (3) 1 <FNo×TL / (f×tanωm)<30 (4) The lens satisfies conditional expressions (1), (2), (3), and (4) shown below. The symbols in the above conditional expressions are defined as follows: νp is the Abbe number of the Lp lens based on the d-line. Np is the refractive index of the Lp lens for the d-line. d is the central thickness of the Lp lens. Rf is the radius of curvature of the object-side surface of the Lp lens. Rr is the radius of curvature of the image-side surface of the Lp lens. When an object at infinity is focused, TL is the sum of the optical axial distance from the lens surface of the front group closest to the object to the lens surface of the rear group closest to the image, and the optical axial air-equivalent distance from the lens surface of the rear group closest to the image to the image plane. When an object at infinity is focused, assuming that a point on the optical axis located at the position of the aperture stop is an object point, De is the optical axial distance from the image-side surface of the Lp lens to the image-side surface of the Lp lens. De is calculated assuming that the medium on the image side of the image-side surface of the Lp lens is air. The sign of De is negative if the image point is closer to the object than the image-side surface of the Lp lens on the optical axis, and positive if the image point is closer to the image than the image-side surface of the Lp lens. FNo is the maximum F-number of the entire system when focused on an object at infinity. f is the focal length of the entire system when focused on an object at infinity. ωm is the maximum half angle of view of the entire system when focused on an object at infinity.

[0007] The Lp lens may be configured so that either the object-side surface or the image-side surface is in contact with air, or the Lp lens may be configured so that both the object-side surface and the image-side surface are cemented with a lens.

[0008] The Lp lens is preferably included in a focus group that moves along the optical axis during focusing.

[0009] The Lp lens may be configured so that either the object-side surface or the image-side surface has an aspherical shape.

[0010] When the air-equivalent distance on the optical axis from the lens surface of the rear group closest to the image side to the image plane in a state where the lens is focused on an object at infinity is Bf, the imaging lens of the above aspect satisfies the following conditions: 0.4 <Bf / (f×tanωm)<1.7 (5) It is preferable to satisfy conditional expression (5) below.

[0011] When the distance on the optical axis from the lens surface of the front group closest to the object to the paraxial entrance pupil position in a state where the lens is focused on an object at infinity is Denp, the imaging lens of the above aspect satisfies the following conditions: 0.3 <Denp / f<2.5 (6) It is preferable to satisfy conditional expression (6) below.

[0012] When the air-equivalent distance on the optical axis from the lens surface of the rear group closest to the image side to the image plane in a state where the lens is focused on an object at infinity is Bf, and the sum of the air-equivalent distance on the optical axis from the paraxial exit pupil position to the lens surface of the rear group closest to the image side and the air-equivalent distance from the lens surface of the rear group closest to the image side to the image plane in a state where the lens is focused on an object at infinity is Dexp, the imaging lens of the above aspect satisfies the following conditions: 1.95 <Dexp / Bf<7.2 (7) It is preferable to satisfy conditional expression (7) below.

[0013] When the focal length of the Lp lens is fp, the imaging lens of the above embodiment has the following characteristics: 0.1 <TL / fp<1.2 (8) It is preferable to satisfy conditional expression (8) below.

[0014] When the height from the optical axis of the principal ray of the maximum half angle of view on the object-side surface of the Lp lens in a state where the lens is focused on an object at infinity is Hpp, and the height from the optical axis of the on-axis marginal ray on the object-side surface of the Lp lens in a state where the lens is focused on an object at infinity is Hpm, the imaging lens of the above aspect satisfies the following conditions: 0.2 <Hpp / Hpm<1.1 (9) It is preferable to satisfy conditional expression (9) below.

[0015] The imaging lens of the above aspect is -0.9<(De-Rr) / (De+Rr)<0.9 (10) It is preferable to satisfy conditional expression (10) below.

[0016] The imaging lens of the above aspect is 0.005<(Rf-Rr) / (Rf+Rr)<0.45 (11) It is preferable to satisfy conditional expression (11) below.

[0017] When the focal length of the focus group that moves along the optical axis during focusing is ffoc and the focal length of the Lp lens is fp, the imaging lens of the above embodiment has the following characteristics: 0.04 <ffoc / fp<0.36 (12) It is preferable to satisfy conditional expression (12) below.

[0018] Lp lenses are 14<νp<28 (13) It is preferable to satisfy conditional expression (13) below.

[0019] If the partial dispersion ratio between the g-line and F-line of an Lp lens is θgFp, then the Lp lens is 0.67<θgFp<1.1 (14) It is preferable to satisfy conditional expression (14) below.

[0020] Lp lenses are 1.51 <Np<1.72 (15) It is preferable to satisfy conditional expression (15) below.

[0021] When the sum of the distance on the optical axis from the paraxial exit pupil position to the lens surface of the rear group closest to the image side and the air-equivalent distance on the optical axis from the lens surface of the rear group closest to the image side to the image plane in a state where the lens is focused on an object at infinity is defined as Dexp, and the sum of the distance on the optical axis from the object-side surface of the Lp lens to the lens surface of the rear group closest to the image side and the air-equivalent distance on the optical axis from the lens surface of the rear group closest to the image side to the image plane in a state where the lens is focused on an object at infinity is defined as Dpi, the imaging lens of the above aspect has the following characteristics: 0.8 <Dexp / Dpi<2.4 (16) It is preferable to satisfy conditional expression (16) below.

[0022] When the imaging lens of the above aspect is in focus on an object at infinity, the sum of the distance on the optical axis from the object-side surface of the Lp lens to the lens surface in the rear group closest to the image side and the air-equivalent distance on the optical axis from the lens surface in the rear group closest to the image side to the image plane is defined as Dpi, and the height from the optical axis of the axial marginal ray on the object-side surface of the Lp lens when the imaging lens is in focus on an object at infinity is defined as Hpm. 1.9 <Dpi / Hpm<5.9 (17) It is preferable to satisfy conditional expression (17) below.

[0023] The imaging lens of the above aspect is -2.5<(f×tanωm)×(1 / De-1 / Rr)<1 (18) It is preferable to satisfy conditional expression (18) below.

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

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

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

[0027] In this specification, "total system" refers to the imaging lens. The sign of the radius of curvature is positive for a surface with a convex surface facing the object side, and negative for a surface with a convex surface facing the image side. Unless otherwise specified, the radius of curvature, sign of refractive power, and surface shape of a lens including an aspheric surface are those in the paraxial region.

[0028] The "focal length" used in the conditional expressions is the paraxial focal length. The "distance on the optical axis" used in the conditional expressions is the geometric distance unless otherwise specified. The values ​​used in the conditional expressions are values ​​based on the d-line unless otherwise specified. The "d-line," "C-line," "F-line," and "g-line" used in this specification are emission lines, and the wavelength of the d-line is treated as 587.56 nm (nanometers), the wavelength of the C-line is 656.27 nm (nanometers), the wavelength of the F-line is 486.13 nm (nanometers), and the wavelength of the g-line is 435.84 nm (nanometers). [Effects of the Invention]

[0029] According to the present disclosure, it is possible to provide an imaging lens that is small and lightweight, yet has a small F-number, suppressed chromatic aberration, and good optical performance, and an imaging device that includes this imaging lens. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a cross-sectional view showing the configuration of an imaging lens according to one embodiment, corresponding to the imaging lens of Example 1. FIG. [Figure 2] 2A to 2C are cross-sectional views showing the configuration and light beams of the imaging lens of FIG. 1 in each focus state. [Figure 3] FIG. 10 is a diagram for explaining symbols in a conditional expression. [Figure 4] FIG. 10 is a diagram for explaining symbols in a conditional expression. [Figure 5] 3A to 3C are diagrams showing various aberrations of the imaging lens of Example 1. [Figure 6] FIG. 10 is a cross-sectional view showing the configuration of an imaging lens according to a second embodiment. [Figure 7] 10A to 10C are diagrams showing various aberrations of the imaging lens of Example 2. [Figure 8] FIG. 10 is a cross-sectional view showing the configuration of an imaging lens according to a third embodiment. [Figure 9] 10A to 10C are diagrams showing various aberrations of the imaging lens of Example 3. [Figure 10] FIG. 10 is a cross-sectional view showing the configuration of an imaging lens according to a fourth embodiment. [Figure 11] 10A to 10C are diagrams showing various aberrations of the imaging lens of Example 4. [Figure 12] FIG. 10 is a cross-sectional view showing the configuration of an imaging lens according to a fifth embodiment. [Figure 13] 10A to 10C are diagrams showing various aberrations of the imaging lens of Example 5. [Figure 14] FIG. 10 is a cross-sectional view showing the configuration of an imaging lens according to a sixth embodiment. [Figure 15] 13A to 13C are diagrams showing various aberrations of the imaging lens of Example 6. [Figure 16] FIG. 10 is a cross-sectional view showing the configuration of an imaging lens according to a seventh embodiment. [Figure 17] 13A to 13C are diagrams showing various aberrations of the imaging lens of Example 7. [Figure 18] FIG. 13 is a cross-sectional view showing the configuration of an imaging lens according to an eighth embodiment. [Figure 19] 13A to 13C are diagrams showing various aberrations of the imaging lens of Example 8. [Figure 20] FIG. 13 is a cross-sectional view showing the configuration of an imaging lens according to a ninth embodiment. [Figure 21] 13A to 13C are diagrams showing various aberrations of the imaging lens of Example 9. [Figure 22] FIG. 20 is a cross-sectional view showing the configuration of an imaging lens according to a tenth embodiment. [Figure 23] 13A to 13C are diagrams showing various aberrations of the imaging lens of Example 10. [Figure 24] 1 is a perspective view of the front side of an imaging device according to an embodiment. [Figure 25] FIG. 2 is a perspective view of the rear side of the imaging device according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0031] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0032] FIG. 1 shows a cross-sectional view of the configuration of an imaging lens according to an embodiment of the present disclosure when focused on an object at infinity. FIG. 2 shows cross-sectional views of the configuration and light beams of the imaging lens in each focus state of FIG. 1. In FIG. 2, the upper row labeled "infinity" shows the state focused on an object at infinity, and the lower row labeled "close" shows the state focused on a close object at a distance of 98.4 mm (millimeters) from the lens surface closest to the object. Note that in this specification, an object at infinity is referred to as an infinite object, and an object at a close distance is referred to as a close object. The upper row of FIG. 2 shows an axial light beam 2 and a light beam 3 with a maximum half angle of view ωm when focused on an object at infinity. The lower row of FIG. 2 shows an axial light beam and a light beam with a maximum half angle of view ωm when focused on a close object. The example shown in FIGS. 1 and 2 corresponds to the imaging lens of Example 1, which will be described later. In FIGS. 1 and 2, the left side is the object side, and the right side is the image side. The following explanation will be given mainly with reference to FIG.

[0033] FIG. 1 shows an example in which a parallel-plate optical member PP is arranged between the imaging lens and the image plane Sim, assuming that the imaging lens is applied to an imaging device. The optical member PP is a member that is assumed to include various filters and / or cover glass. The various filters are low-pass filters, infrared cut filters, and / or filters that cut off specific wavelength ranges. The optical member PP is a member that does not have refractive power. It is also possible to configure an imaging device without the optical member PP.

[0034] The imaging lens of the present disclosure comprises, in order from the object side to the image side along the optical axis Z, a front group GF, an aperture stop St, and a rear group GR. This configuration is advantageous for suppressing various aberrations while maintaining a compact and lightweight design. Note that the aperture stop St in Figure 1 does not indicate its size or shape, but rather its position along the optical axis.

[0035] As an example, the front group GF and rear group GR of the imaging lens in FIG. 1 are configured as follows: The front group GF is made up of a first lens group G1. The first lens group G1 is made up of nine lenses, lenses L11 to L19, in order from the object side to the image side. The rear group GR is made up of a second lens group G2 and a third lens group G3, in order from the object side to the image side. The second lens group G2 is made up of eight lenses, lenses L21 to L28. The third lens group G3 is made up of a single lens, lens L31.

[0036] In the example of FIG. 1, during focusing, the first lens group G1 and the third lens group G3 are fixed with respect to the image plane Sim, and the entire second lens group moves integrally along the optical axis Z. Here, "moving integrally" means moving simultaneously in the same direction by the same amount. In this specification, the group that moves along the optical axis Z during focusing is referred to as the focus group. Focusing is achieved by the movement of the focus group. The left-pointing arrow below the second lens group G2 in FIG. 1 indicates that the second lens group G2 is the focus group that moves toward the object when focusing from an object at infinity to a close object.

[0037] In this specification, a "lens group" is a component of an imaging lens that includes at least one lens and is separated by an air gap that changes during focusing. During focusing, each lens group is moved or fixed, and the mutual spacing between lenses within each lens group does not change. In other words, in this specification, a group in which the spacing between adjacent groups changes during focusing, but the total spacing between adjacent lenses within itself does not change, is defined as one lens group.

[0038] The rear group GR of the imaging lens of the present disclosure includes at least one Lp lens Lp made of resin and having positive refractive power, cemented to a lens. By arranging the above-mentioned Lp lens Lp made of resin in the rear group GR, it becomes easy to correct axial chromatic aberration and lateral chromatic aberration in a well-balanced manner while achieving weight reduction. In the example of FIG. 1, the lens L24 corresponds to the Lp lens Lp. In the example of FIG. 1, the lens L24 is cemented to the lenses L23 and L25.

[0039] The Lp lens Lp is a lens that satisfies the following conditional formula (1). Here, the Abbe number of the Lp lens Lp based on the d-line is vp, and the refractive index of the Lp lens Lp for the d-line is Np. By ensuring that the corresponding value of conditional formula (1) is not below the lower limit, it is possible to prevent chromatic aberration from being overcorrected. By ensuring that the corresponding value of conditional formula (1) is not above the upper limit, it is advantageous for improving chromatic aberration. In order to obtain better characteristics, it is more preferable that the Lp lens Lp satisfy the following conditional formula (1-1), and even more preferable that it satisfy the following conditional formula (1-2). 120<νp+94.24×Np<186 (1) 140<νp+94.24×Np<183 (1-1) 160<νp+94.24×Np<175 (1-2)

[0040] Assuming that the central thickness of the Lp lens Lp is d, the radius of curvature of the object-side surface of the Lp lens Lp is Rf, and the radius of curvature of the image-side surface of the Lp lens Lp is Rr, it is preferable that the Lp lens Lp satisfy the following conditional expression (2). As an example, FIG. 3 shows an enlarged view of a portion of the imaging lens of FIG. 1 including the Lp lens Lp, showing the central thickness d. The Lp lens Lp that satisfies conditional expression (2) has a small value of d and a shape in which Rf and Rr are close to each other. By ensuring that the corresponding value of conditional expression (2) is not below the lower limit, the refractive power of the Lp lens Lp can be strengthened, thereby achieving a higher chromatic aberration correction effect. By ensuring that the corresponding value of conditional expression (2) is not above the upper limit, the refractive power and thickness of the Lp lens Lp can be appropriately set, making it easier to suppress aberration fluctuations when the refractive index of the Lp lens Lp fluctuates due to environmental changes such as temperature. In order to obtain better characteristics, it is more preferable that the Lp lens Lp satisfy the following conditional formula (2-1), it is even more preferable that the Lp lens Lp satisfy the following conditional formula (2-2), and it is even more preferable that the Lp lens Lp satisfy the following conditional formula (2-3). 0 <d×(1 / Rf-1 / Rr)<0.05 (2) 0.0001 <d×(1 / Rf-1 / Rr)<0.025 (2-1) 0.0005 <d×(1 / Rf-1 / Rr)<0.015 (2-2) 0.0013 <d×(1 / Rf-1 / Rr)<0.009 (2-3)

[0041] Below, we will describe preferred and possible configurations of the imaging lens of the present disclosure, including the above-mentioned Lp lens Lp. In the following explanation of the conditional expressions, to avoid redundancy, the same symbols are used for elements with the same definitions, and duplicate explanations of symbols are omitted. Also, in the following explanation, to avoid redundancy, "the imaging lens of the present disclosure" will also be referred to simply as "the imaging lens."

[0042] With respect to the Lp lens Lp, it is preferable that the imaging lens satisfy the following conditional expression (3). Here, TL is the sum of the optical axial distance from the lens surface of the front group GF closest to the object to the lens surface of the rear group GR closest to the image when focused on an object at infinity, and the air-equivalent distance on the optical axis from the lens surface of the rear group GR closest to the image to the image plane Sim. Also, when focused on an object at infinity, assuming that a point on the optical axis at the position of the aperture stop St is an object point, De is the optical axial distance from the image-side surface of the Lp lens Lp to an image point formed by the optical system from the lens surface adjacent to the image side of the aperture stop St to the image-side surface of the Lp lens Lp. As an example, FIG. 3 shows the distance De in the imaging lens of FIG. 1. By ensuring that the corresponding value of conditional expression (3) is not less than the lower limit, it is easy to make the off-axis chief ray passing through the Lp lens Lp approximately perpendicular to the object-side surface of the Lp lens Lp. This increases the difference in optical path length between the off-axial chief ray and the on-axial ray, thereby differentiating the chromatic aberration correction effects between the off-axial ray and the on-axial ray, thereby enabling effective correction of lateral chromatic aberration. By ensuring that the corresponding value of conditional expression (3) does not exceed the upper limit, it is possible to prevent the off-axial chief ray passing through the Lp lens Lp from being incident at an angle in the convergent direction on the object-side surface of the Lp lens Lp, which is advantageous for miniaturizing the optical system on the object side of the Lp lens Lp. Note that "incident at an angle in the convergent direction" here means that the incident ray is incident from the optical axis side, i.e., from the radially inner side, with respect to the normal to the lens surface at the point of incidence. To obtain better characteristics, it is more preferable for the imaging lens to satisfy the following conditional expression (3-1), even more preferable for it to satisfy the following conditional expression (3-2), and even more preferable for it to satisfy the following conditional expression (3-3). -20 <TL×(1 / De-1 / Rr)<20 (3) -10 <TL×(1 / De-1 / Rr)<10 (3-1) -9 <TL×(1 / De-1 / Rr)<5 (3-2) -7.4 <TL×(1 / De-1 / Rr)<0.7 (3-3)

[0043] The distance De will be described in detail with reference to FIG. 3. FIG. 3 shows an enlarged view of the imaging lens in FIG. 1, from the aperture stop St to the lens L24 corresponding to the Lp lens Lp. In FIG. 3, the lens surface adjacent to the image side of the aperture stop St is the object-side surface of the lens L21, and the point on the optical axis at the position of the aperture stop St is point Pob. If point Pob is an object point, the image point formed by the optical system from the object-side surface of the lens L21 to the image-side surface of the lens L24 is point Pim. In other words, points Pob and Pim are in a conjugate relationship with respect to the optical system from the object-side surface of the lens L21 to the image-side surface of the lens L24. In FIG. 3, a light ray emerging from the object point Pob and entering the optical system from the object-side surface of the lens L21 to the image-side surface of the lens L24 is indicated by a solid line, and a light ray emerging from this optical system and entering point Pim is indicated by a two-dot chain line. The distance De is the distance on the optical axis from the image-side surface of the Lp lens Lp to the point Pim, with the image-side surface of the Lp lens Lp being used as the reference. Note that, although light rays are depicted in FIG. 3 for ease of explanation, the distance De will be calculated by paraxial ray tracing rather than using actual light rays. Furthermore, the distance De is calculated assuming that the medium on the image side of the image-side surface of the Lp lens Lp is air. The sign of the distance De is negative if the image point is closer to the object than the image-side surface of the Lp lens Lp on the optical axis, and positive if the image point is closer to the image than the image-side surface of the Lp lens Lp.

[0044] If FNo is the maximum F-number when focused on an object at infinity, f is the focal length of the entire system when focused on an object at infinity, and ωm is the maximum half angle of view when focused on an object at infinity, it is preferable that the imaging lens satisfy the following conditional expression (4). tan in conditional expression (4) is the tangent. By ensuring that the corresponding value of conditional expression (4) is not equal to or less than the lower limit, the size of the light beam passing through the optical system and the overall length of the optical system can be appropriately set, which is advantageous for suppressing various aberrations. By ensuring that the corresponding value of conditional expression (4) is not equal to or greater than the upper limit, it becomes easier to realize a compact, lightweight optical system with a smaller F-number. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (4-1), even more preferable that it satisfy the following conditional expression (4-2), and even more preferable that it satisfy the following conditional expression (4-3). 1 <FNo×TL / (f×tanωm)<30 (4) 3 <FNo×TL / (f×tanωm)<21 (4-1) 5 <FNo×TL / (f×tanωm)<14 (4-2) 8 <FNo×TL / (f×tanωm)<10 (4-3)

[0045] If the air-equivalent distance on the optical axis from the lens surface of the rear group GR closest to the image to the image plane Sim when focused on an object at infinity is Bf, it is preferable that the imaging lens satisfy the following conditional expression (5). Ensuring that the corresponding value of conditional expression (5) is not equal to or less than the lower limit thereof is advantageous for suppressing curvature of field. Ensuring that the corresponding value of conditional expression (5) is not equal to or greater than the upper limit thereof is advantageous for shortening the overall length of the optical system. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (5-1), and it is even more preferable that it satisfy the following conditional expression (5-2). 0.4 <Bf / (f×tanωm)<1.7 (5) 0.6 <Bf / (f×tanωm)<1.47 (5-1) 0.77 <Bf / (f×tanωm)<1.1 (5-2)

[0046] If Denp is the distance on the optical axis from the lens surface of the front group GF closest to the object to the paraxial entrance pupil position Penp when focused on an object at infinity, it is preferable that the imaging lens satisfy the following conditional expression (6). As an example, FIG. 2 shows the paraxial entrance pupil position Penp when focused on an object at infinity and the distance Denp defined above. Ensuring that the corresponding value of conditional expression (6) does not become equal to or less than the lower limit is advantageous for suppressing distortion. Ensuring that the corresponding value of conditional expression (6) does not become equal to or greater than the upper limit is advantageous for reducing the size of the front group GF. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (6-1), and it is even more preferable that it satisfy the following conditional expression (6-2). 0.3 <Denp / f<2.5 (6) 0.7 <Denp / f<2 (6-1) 0.92 <Denp / f<1.25 (6-2)

[0047] When the sum of the on-optical distance from the paraxial exit pupil position Pexp to the lens surface of the rear group GR closest to the image in a state where the lens is focused on an object at infinity, and the on-optical distance in air equivalent from the lens surface of the rear group GR closest to the image to the image plane Sim, is denoted as Dexp, the imaging lens preferably satisfies the following conditional expression (7). As an example, FIG. 2 shows the paraxial exit pupil position Pexp when the lens is focused on an object at infinity. Ensuring that the corresponding value of conditional expression (7) is not equal to or less than the lower limit is advantageous for suppressing astigmatism. Ensuring that the corresponding value of conditional expression (7) is not equal to or greater than the upper limit is advantageous for reducing the size of the rear group GR. In order to obtain better characteristics, it is more preferable for the imaging lens to satisfy the following conditional expression (7-1), and it is even more preferable for the imaging lens to satisfy the following conditional expression (7-2). 1.95 <Dexp / Bf<7.2 (7) 2.47 <Dexp / Bf<6.1 (7-1) 3.5 <Dexp / Bf<4.96 (7-2)

[0048] When the focal length of the Lp lens Lp is fp, it is preferable that the imaging lens satisfy the following conditional expression (8). Note that fp is calculated assuming that the medium on the object side and image side of the Lp lens Lp is air. By ensuring that the corresponding value of conditional expression (8) is not below the lower limit, it is possible to improve the chromatic aberration correction effect of the Lp lens Lp. By ensuring that the corresponding value of conditional expression (8) is not above the upper limit, it is possible to suppress aberration fluctuations when the refractive index of the Lp lens Lp fluctuates due to environmental changes such as temperature. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (8-1), and it is even more preferable that it satisfy the following conditional expression (8-2). 0.1 <TL / fp<1.2 (8) 0.15 <TL / fp<0.95 (8-1) 0.25 <TL / fp<0.61 (8-2)

[0049] It is preferable that the imaging lens satisfy the following conditional expression (9). Here, Hpp is the height from the optical axis Z of the chief ray 3p at the maximum half angle of view ωm on the object-side surface of the Lp lens Lp when focused on an object at infinity. Also, Hpm is the height from the optical axis Z of the axial marginal ray 2m on the object-side surface of the Lp lens Lp when focused on an object at infinity. As an example, FIG. 4 shows the heights Hpp and Hpm of the imaging lens of FIG. 1. FIG. 4 also shows an enlarged view of the lens L24 corresponding to the Lp lens Lp, from the image plane Sim, along with each ray. Ensuring that the value corresponding to conditional expression (9) is not equal to or less than the lower limit is advantageous for correcting lateral chromatic aberration. Ensuring that the value corresponding to conditional expression (9) is not equal to or greater than the upper limit is advantageous for correcting axial chromatic aberration. To obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (9-1), and even more preferable that it satisfy the following conditional expression (9-2). 0.2 <Hpp / Hpm<1.1 (9) 0.31 <Hpp / Hpm<0.9 (9-1) 0.5 <Hpp / Hpm<0.72 (9-2)

[0050] It is preferable that the imaging lens satisfy the following conditional expression (10). Ensuring that the corresponding value of conditional expression (10) is not below the lower limit is advantageous for correction of lateral chromatic aberration. Ensuring that the corresponding value of conditional expression (10) is not above the upper limit is advantageous for miniaturization. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (10-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (10-2). -0.9<(De-Rr) / (De+Rr)<0.9 (10) -0.7<(De-Rr) / (De+Rr)<0.5 (10-1) -0.56<(De-Rr) / (De+Rr)<0.16 (10-2)

[0051] It is preferable that the imaging lens satisfy the following conditional expression (11). Ensuring that the corresponding value of conditional expression (11) is not equal to or smaller than the lower limit thereof is advantageous for correcting chromatic aberration of magnification. Ensuring that the corresponding value of conditional expression (11) is not equal to or larger than the upper limit thereof is advantageous for suppressing differences in spherical aberration for each color. In order to obtain even better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (11-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (11-2). 0.005<(Rf-Rr) / (Rf+Rr)<0.45 (11) 0.01<(Rf-Rr) / (Rf+Rr)<0.25 (11-1) 0.03<(Rf-Rr) / (Rf+Rr)<0.17 (11-2)

[0052] If the focal length of the focus group that moves along the optical axis Z during focusing is ffoc, it is preferable that the imaging lens satisfy the following conditional expression (12). Ensuring that the corresponding value of conditional expression (12) is not below the lower limit is advantageous for suppressing fluctuations in chromatic aberration during focusing. Ensuring that the corresponding value of conditional expression (12) is not above the upper limit can suppress fluctuations in aberrations that occur when the refractive index of the Lp lens Lp varies due to environmental changes such as temperature. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (12-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (12-2). 0.04 <ffoc / fp<0.36 (12) 0.065 <ffoc / fp<0.28 (12-1) 0.094 <ffoc / fp<0.22 (12-2)

[0053] It is preferable that the Lp lens Lp satisfy the following conditional expression (13). By ensuring that the corresponding value of conditional expression (13) is not below the lower limit, it is possible to prevent chromatic aberration from being overcorrected. By ensuring that the corresponding value of conditional expression (13) is not above the upper limit, it is advantageous for correcting chromatic aberration. In order to obtain better characteristics, it is more preferable that the Lp lens Lp satisfy the following conditional expression (13-1), and it is even more preferable that it satisfy the following conditional expression (13-2). 14<νp<28 (13) 17<νp<26 (13-1) 19.3<νp<22.3 (13-2)

[0054] When the partial dispersion ratio between the g-line and F-line of the Lp lens Lp is θgFp, it is preferable that the Lp lens Lp satisfy the following conditional expression (14). Ensuring that the corresponding value of conditional expression (14) is not below the lower limit is advantageous for correction of secondary chromatic aberration. Ensuring that the corresponding value of conditional expression (14) is not above the upper limit can prevent secondary chromatic aberration from being overcorrected. In order to obtain better characteristics, it is more preferable that the Lp lens Lp satisfy the following conditional expression (14-1), and it is even more preferable that it satisfy the following conditional expression (14-2). 0.67<θgFp<1.1 (14) 0.72<θgFp<0.95 (14-1) 0.76<θgFp<0.88 (14-2)

[0055] If the refractive indices of a lens for the g-line, F-line, and C-line are Ng, NF, and NC, respectively, and the partial dispersion ratio of the lens between the g-line and F-line is θgF, then θgF is defined by the following equation: θgF=(Ng-NF) / (NF-NC)

[0056] It is preferable that the Lp lens Lp satisfy the following conditional expression (15). Ensuring that the corresponding value of conditional expression (15) is not below the lower limit is advantageous for suppressing curvature of field. Ensuring that the corresponding value of conditional expression (15) is not above the upper limit increases the availability of materials, which is advantageous for reducing costs. In order to obtain better characteristics, it is more preferable that the Lp lens Lp satisfy the following conditional expression (15-1), and it is even more preferable that it satisfy the following conditional expression (15-2). 1.51 <Np<1.72 (15) 1.55 <Np<1.67 (15-1) 1.58 <Np<1.63 (15-2)

[0057] When the sum of the on-optical axis distance from the object-side surface of the Lp lens Lp to the lens surface closest to the image in the rear group GR and the on-optical axis air-equivalent distance from the lens surface closest to the image in the rear group GR to the image plane Sim in a state where the lens is focused on an object at infinity is defined as Dpi, it is preferable that the imaging lens satisfy the following conditional expression (16). Ensuring that the corresponding value of conditional expression (16) is not equal to or smaller than the lower limit is advantageous for correction of lateral chromatic aberration. Ensuring that the corresponding value of conditional expression (16) is not equal to or larger than the upper limit is advantageous for correction of axial chromatic aberration. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (16-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (16-2). 0.8 <Dexp / Dpi<2.4 (16) 1 <Dexp / Dpi<2 (16-1) 1.21 <Dexp / Dpi<1.79 (16-2)

[0058] It is preferable that the imaging lens satisfy the following conditional expression (17). Ensuring that the corresponding value of conditional expression (17) is not below the lower limit is advantageous for reducing the size of the Lp lens Lp. Ensuring that the corresponding value of conditional expression (17) is not above the upper limit is advantageous for correcting chromatic aberration of magnification. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (17-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (17-2). 1.9 <Dpi / Hpm<5.9 (17) 2.1 <Dpi / Hpm<5.1 (17-1) 2.33 <Dpi / Hpm<4.7 (17-2)

[0059] It is preferable that the imaging lens satisfy the following conditional expression (18). By satisfying conditional expression (18), the same effect as when conditional expression (3) is satisfied can be obtained. By ensuring that the corresponding value of conditional expression (18) is not below the lower limit, it is easy to make the off-axial chief ray passing through the Lp lens Lp approximately perpendicular to the object-side surface of the Lp lens Lp. This increases the difference in optical path length between the off-axial chief ray and the on-axial ray, thereby differentiating the chromatic aberration correction effects between the off-axial ray and the on-axial ray, and effectively correcting lateral chromatic aberration. By ensuring that the corresponding value of conditional expression (18) is not above the upper limit, it is possible to prevent the off-axial chief ray passing through the Lp lens Lp from being incident on the object-side surface of the Lp lens Lp at an angle in the convergence direction, which is advantageous for reducing the size of the optical system on the object side of the Lp lens Lp. To obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (18-1), and even more preferable that the imaging lens satisfy the following conditional expression (18-2). -2.5<(f×tanωm)×(1 / De-1 / Rr)<1 (18) -1.5<(f×tanωm)×(1 / De-1 / Rr)<0.5 (18-1) -1.07<(f×tanωm)×(1 / De-1 / Rr)<0.12 (18-2)

[0060] It is preferable that the imaging lens satisfy the following conditional expression (19): ωm is expressed in degrees. By ensuring that the corresponding value of conditional expression (19) is not equal to or smaller than the lower limit, it is possible to obtain a more significant effect of correcting lateral chromatic aberration of the Lp lens Lp. By ensuring that the corresponding value of conditional expression (19) is not equal to or larger than the upper limit, it is possible to obtain a more significant effect of correcting axial chromatic aberration of the Lp lens Lp. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (19-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (19-2). 15<ωm<60 (19) 25<ωm<50 (19-1) 35<ωm<41 (19-2)

[0061] It is preferable that the imaging lens satisfy the following conditional expression (20). By ensuring that the corresponding value of conditional expression (20) is not below the lower limit, it is advantageous for miniaturization in the outer diameter direction. By ensuring that the corresponding value of conditional expression (20) is not above the upper limit, it is possible to obtain a more significant effect of correcting the axial chromatic aberration of the Lp lens Lp. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (20-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (20-2). 0.9 <FNo<4 (20) 1.1 <FNo<2.8 (20-1) 1.3 <FNo<1.5 (20-2)

[0062] It is preferable that the Lp lens Lp is included in a focus group that moves along the optical axis Z during focusing, which is advantageous for making the focus group smaller and lighter.

[0063] The Lp lens Lp may be configured so that either the object-side surface or the image-side surface is in contact with air, and the other surface is cemented to a lens. In this case, the refractive power of the air-contacting surface of the Lp lens Lp is strong, which is advantageous for correcting spherical aberration.

[0064] Alternatively, the Lp lens Lp may be configured so that both the object-side surface and the image-side surface are cemented with a lens, which is advantageous in suppressing the occurrence of various aberrations due to shape errors of the Lp lens Lp.

[0065] The Lp lens Lp may be cemented to a positive lens or to a negative lens. The cemented lens including the Lp lens Lp may be a cemented lens made up of two lenses or a cemented lens made up of three lenses.

[0066] The Lp lens Lp may be configured so that either the object-side surface or the image-side surface is aspherical. This is advantageous for correcting astigmatism. The Lp lens Lp may be configured so that both the object-side surface and the image-side surface are aspherical. This is even more advantageous for correcting astigmatism.

[0067] The imaging lens may be configured to include only one Lp lens Lp. By limiting the number of resin lenses, whose optical properties are prone to change depending on the environment, to just one, it is possible to suppress changes in the performance of the optical system due to the environment.

[0068] In the example of Figure 1, the front group GF is made up of one lens group and the rear group GR is made up of two lens groups, but the number of lens groups making up the front group GF and the number of lens groups making up the rear group GR may be different from those in the example of Figure 1. The technology of the present disclosure can also be applied to variable magnification optical systems. When the technology of the present disclosure is applied to variable magnification optical systems, the values ​​at the wide-angle end correspond to the values ​​of each conditional expression.

[0069] The above-described preferred and possible configurations can be arbitrarily combined, and are preferably selectively adopted as appropriate according to the required specifications. Note that the conditional expressions that the imaging lens of the present disclosure preferably satisfies are not limited to those written in the form of an expression, but include all conditional expressions obtained by arbitrarily combining lower and upper limits from among the conditional expressions that are deemed preferable, more preferable, even more preferable, and even more preferable. Furthermore, the imaging lens of the present disclosure can be modified in various ways without departing from the spirit of the technology of the present disclosure.

[0070] As an example, one preferred embodiment of the imaging lens of the present disclosure comprises, in order from the object side to the image side, a front group GF, an aperture stop St, and a rear group GR, the rear group GR including at least one Lp lens Lp made of resin and having positive refractive power cemented to the lens, and satisfying the above conditional expressions (1), (2), (3), and (4).

[0071] Next, examples of the imaging lens of the present disclosure will be described with reference to the drawings. The reference symbols assigned to the lenses in the cross-sectional views of each example are used independently for each example to avoid cluttering the explanation and the drawings due to an increase in the number of digits in the reference symbols. Therefore, even if common reference symbols are assigned in drawings of different examples, this does not necessarily mean that the configuration is the same.

[0072] [Example 1] A cross-sectional view of the configuration of the imaging lens of Example 1 is shown in Figure 1, and since the illustration method and configuration are as described above, some redundant explanation will be omitted here. The imaging lens of Example 1 consists of, in order from the object side to the image side, a first lens group G1 having positive refractive power, an aperture stop St, a second lens group G2 having positive refractive power, and a third lens group G3 having positive refractive power. The front group GF consists of the first lens group G1. The rear group GR consists of the second lens group G2 and the third lens group G3. When focusing from an object at infinity to a close object, the first lens group G1 and the third lens group G3 are fixed with respect to the image plane Sim, and the second lens group G2 moves toward the object side.

[0073] The Lp lens Lp is included in the third lens component from the object side of the second lens group G2. This lens component is a cemented lens constructed by cementing together, in order from the object side, a positive lens, an Lp lens Lp, and a negative lens. In this specification, "one lens component" means one cemented lens or one single lens. A "single lens" is a single lens that is not cemented.

[0074] For the imaging lens of Example 1, basic lens data is shown in Table 1, specifications and variable surface spacing are shown in Table 2, and aspherical coefficients are shown in Table 3. The table of basic lens data is written as follows: The Sn column shows the surface number, with the surface closest to the object as surface 1 and the numbers increasing by one toward the image side. The R column shows the radius of curvature of each surface. The D column shows the surface spacing on the optical axis between each surface and its adjacent surface on the image side. The Nd column shows the refractive index of each component element with respect to the d-line. The νd column shows the Abbe number of each component element with respect to the d-line. In the θgF column, the column for the lens corresponding to the Lp lens Lp shows the partial dispersion ratio between the g-line and F-line of that lens. Surfaces 23 and 24 in Table 1 correspond to the Lp lens Lp.

[0075] In the basic lens data table, the sign of the radius of curvature of a surface with a convex surface facing the object side is positive, and the sign of the radius of curvature of a surface with a convex surface facing the image side is negative. The surface number and the phrase (St) are entered in the column for the surface number corresponding to the aperture stop St. The value in the bottom column of the surface spacing column in the table is the distance between the surface in the table closest to the image side and the image plane Sim. The symbol DD[ ] is used to indicate the variable surface spacing during focusing, and the surface number on the object side of this distance is entered in the [ ] in the surface spacing column.

[0076] Table 2 shows the focal length, maximum F-number, maximum full-field angle, and variable surface spacing based on the d-line. The [°] in the maximum full-field angle column indicates that the unit is degrees. In Table 2, the "Infinity" column shows the values ​​when focused on an object at infinity, and the "Closest" column shows the values ​​when focused on a close object. Also, directly below the word "Closest," the distance from the lens surface closest to the object to the close object is shown. In Example 1, the distance from the lens surface closest to the object to the close object is 98.4 mm (millimeters).

[0077] In the basic lens data, the surface numbers of aspherical surfaces are marked with an *, and the numerical value of the paraxial radius of curvature is entered in the column for the radius of curvature of the aspherical surface. In Table 3, the row Sn shows the surface numbers of aspherical surfaces, and the rows KA and Am show the numerical values ​​of the aspherical coefficients for each aspherical surface. Note that m in Am is an integer of 3 or more, and varies depending on the surface. For example, for the first surface of Example 1, m = 3, 4, 5, ..., 16. The numerical values ​​of the aspherical coefficients in Table 3, "E±n" (n: integer), are expressed as "×10 ±n KA and Am are aspherical coefficients in the aspherical formula given below. Zd=C×h 2 / {1+(1-KA×C 2 ×h 2 ) 1 / 2}+ΣAm×h m however, Zd: Aspheric depth (length of the perpendicular line drawn from a point on the aspheric surface at height h to a plane perpendicular to the optical axis Z where the vertex of the aspheric surface is in contact) h: Height (distance from optical axis Z to lens surface) C: Reciprocal of paraxial radius of curvature KA, Am: aspherical coefficients In the aspherical formula, Σ means the summation over m.

[0078] In the data in each table, the angle unit is degrees and the length unit is mm (millimeters), but since the optical system can be used with proportional enlargement or reduction, other appropriate units can also be used. Also, in each table below, the values ​​are rounded to a predetermined number of decimal places.

[0079] [Table 1]

[0080] [Table 2]

[0081] [Table 3]

[0082] FIG. 5 shows aberration diagrams for the imaging lens of Example 1. From left to right, FIG. 5 shows spherical aberration, astigmatism, distortion, and lateral chromatic aberration. In FIG. 5, the upper row labeled "Infinity" shows aberration diagrams for a state focused on an object at infinity, while the lower row labeled "Close" shows aberration diagrams for a state focused on a close object. The distance from the lens surface closest to the object to the close object in the data for each aberration diagram is the same as the value listed in the specifications table. In the spherical aberration diagram, aberrations at the d-line, C-line, F-line, and g-line are shown by solid lines, long-dashed lines, short-dashed lines, and dash-dot lines, respectively. In the astigmatism diagram, aberrations at the d-line in the sagittal direction are shown by solid lines, and aberrations at the d-line in the tangential direction are shown by short-dashed lines. In the distortion diagram, aberrations at the d-line are shown by solid lines. In the lateral chromatic aberration diagram, aberrations for the C-line, F-line, and g-line are shown with long-dashed lines, short-dashed lines, and dash-dot lines, respectively. In the spherical aberration diagram, the maximum F-number is shown after "FNo.=". In the other aberration diagrams, the maximum half angle of view is shown after "ω=".

[0083] The symbols, meanings, notation methods, and illustration methods of each data item related to the above-described first embodiment are basically the same in the following embodiments unless otherwise specified, and therefore, redundant explanations will be omitted below. Also, in the following explanations of the embodiments, as mentioned above, the components of the imaging lens separated by the air gap that changes during focusing are referred to as a "lens group."

[0084] [Example 2] A cross-sectional view of the configuration of the imaging lens of Example 2 is shown in Figure 6. The imaging lens of Example 2 consists, in order from the object side to the image side, of a first lens group having positive refractive power and a second lens group having positive refractive power. The second lens group includes an aperture stop St. The front group GF consists of the first lens group and a part of the second lens group facing the object side. The rear group GR consists of the other part of the second lens group. When focusing from an object at infinity to a close object, the first lens group is fixed with respect to the image plane Sim, and the second lens group moves toward the object side.

[0085] The Lp lens Lp is included in the third lens component from the object side of the second lens group, and is a cemented lens formed by cementing together, in order from the object side, a positive lens, an Lp lens Lp, and a negative lens.

[0086] For the imaging lens of Example 2, basic lens data is shown in Table 4, specifications and variable surface spacings are shown in Table 5, aspherical coefficients are shown in Table 6, and aberration diagrams are shown in Fig. 7. Surfaces 20 and 21 in Table 4 correspond to the Lp lens element Lp.

[0087] [Table 4]

[0088] [Table 5]

[0089] [Table 6]

[0090] [Example 3] A cross-sectional view of the configuration of the imaging lens of Example 3 is shown in Figure 8. The imaging lens of Example 3 consists of, in order from the object side to the image side, a first lens group having positive refractive power, an aperture stop St, a second lens group having positive refractive power, and a third lens group having positive refractive power. The front group GF consists of the first lens group. The rear group GR consists of the second lens group and the third lens group. When focusing from an object at infinity to a close object, the first lens group and the third lens group are fixed with respect to the image plane Sim, and the second lens group moves toward the object side.

[0091] The Lp lens Lp is included in the third lens component from the object side of the second lens group, and is a cemented lens formed by cementing together, in order from the object side, a positive lens, an Lp lens Lp, and a negative lens.

[0092] For the imaging lens of Example 3, basic lens data is shown in Table 7, specifications and variable surface spacings are shown in Table 8, aspherical coefficients are shown in Table 9, and aberration diagrams are shown in Fig. 9. Surfaces 23 and 24 in Table 7 correspond to the Lp lens element Lp.

[0093] [Table 7]

[0094] [Table 8]

[0095] [Table 9]

[0096] [Example 4] A cross-sectional view of the configuration of the imaging lens of Example 4 is shown in Figure 10. The imaging lens of Example 4 consists of, in order from the object side to the image side, a first lens group having positive refractive power, an aperture stop St, a second lens group having positive refractive power, and a third lens group having positive refractive power. The front group GF consists of the first lens group. The rear group GR consists of the second lens group and the third lens group. When focusing from an object at infinity to a close object, the first lens group and the third lens group are fixed with respect to the image plane Sim, and the second lens group moves toward the object side.

[0097] The Lp lens Lp is included in the third lens component from the object side of the second lens group, and is a cemented lens formed by cementing together, in order from the object side, a positive lens, an Lp lens Lp, and a negative lens.

[0098] For the imaging lens of Example 4, basic lens data is shown in Table 10, specifications and variable surface spacings are shown in Table 11, aspherical coefficients are shown in Table 12, and aberration diagrams are shown in Fig. 11. Surfaces 23 and 24 in Table 10 correspond to the Lp lens element Lp.

[0099] [Table 10]

[0100] [Table 11]

[0101] [Table 12]

[0102] [Example 5] A cross-sectional view of the configuration of the imaging lens of Example 5 is shown in Figure 12. The imaging lens of Example 5 consists of, in order from the object side to the image side, a first lens group having positive refractive power, an aperture stop St, a second lens group having positive refractive power, and a third lens group having negative refractive power. The front group GF consists of the first lens group. The rear group GR consists of the second lens group and the third lens group. When focusing from an object at infinity to a close object, the first lens group and the third lens group are fixed with respect to the image plane Sim, and the second lens group moves toward the object side.

[0103] The Lp lens Lp is included in the second lens component from the object side of the second lens group. This lens component is a cemented lens formed by cementing, in order from the object side, a positive lens and an Lp lens Lp.

[0104] For the imaging lens of Example 5, basic lens data is shown in Table 13, specifications and variable surface spacings are shown in Table 14, aspherical coefficients are shown in Table 15, and aberration diagrams are shown in Fig. 13. Surfaces 20 and 21 in Table 13 correspond to the Lp lens element Lp.

[0105] [Table 13]

[0106] [Table 14]

[0107] [Table 15]

[0108] [Example 6] A cross-sectional view of the configuration of the imaging lens of Example 6 is shown in Figure 14. The imaging lens of Example 6 consists of, in order from the object side to the image side, a first lens group having positive refractive power, an aperture stop St, a second lens group having positive refractive power, and a third lens group having negative refractive power. The front group GF consists of the first lens group. The rear group GR consists of the second lens group and the third lens group. When focusing from an object at infinity to a close object, the first lens group and the third lens group are fixed with respect to the image plane Sim, and the second lens group moves toward the object side.

[0109] The Lp lens Lp is included in the second lens component from the object side of the second lens group. This lens component is a cemented lens formed by cementing together, in order from the object side, a positive lens, a negative lens, and the Lp lens Lp.

[0110] For the imaging lens of Example 6, basic lens data is shown in Table 16, specifications and variable surface spacings are shown in Table 17, aspherical coefficients are shown in Table 18, and aberration diagrams are shown in Fig. 15. Surfaces 21 and 22 in Table 16 correspond to the Lp lens element Lp.

[0111] [Table 16]

[0112] [Table 17]

[0113] [Table 18]

[0114] [Example 7] A cross-sectional view of the configuration of the imaging lens of Example 7 is shown in Figure 16. The imaging lens of Example 7 consists of, in order from the object side to the image side, a first lens group having positive refractive power, an aperture stop St, a second lens group having positive refractive power, and a third lens group having positive refractive power. The front group GF consists of the first lens group. The rear group GR consists of the second lens group and the third lens group. When focusing from an object at infinity to a close object, the first lens group and the third lens group are fixed with respect to the image plane Sim, and the second lens group moves toward the object side.

[0115] The Lp lens Lp is included in the second lens component from the object side of the second lens group. This lens component is a cemented lens formed by cementing, in order from the object side, the Lp lens Lp and a negative lens.

[0116] For the imaging lens of Example 7, basic lens data is shown in Table 19, specifications and variable surface spacings are shown in Table 20, aspherical coefficients are shown in Table 21, and aberration diagrams are shown in Fig. 17. Surfaces 20 to 21 in Table 19 correspond to the Lp lens element Lp.

[0117] [Table 19]

[0118] [Table 20]

[0119] [Table 21]

[0120] [Example 8] A cross-sectional view of the configuration of the imaging lens of Example 8 is shown in Figure 18. The imaging lens of Example 8 consists of, in order from the object side to the image side, a first lens group having positive refractive power, an aperture stop St, a second lens group having positive refractive power, and a third lens group having positive refractive power. The front group GF consists of the first lens group. The rear group GR consists of the second lens group and the third lens group. When focusing from an object at infinity to a close object, the first lens group and the third lens group are fixed with respect to the image plane Sim, and the second lens group moves toward the object side.

[0121] The Lp lens Lp is included in the lens component closest to the object in the second lens group, and is a cemented lens formed by cementing together, in order from the object side, a positive lens and an Lp lens Lp.

[0122] For the imaging lens of Example 8, basic lens data is shown in Table 22, specifications and variable surface spacings are shown in Table 23, aspherical coefficients are shown in Table 24, and aberration diagrams are shown in Fig. 19. Surfaces 19 and 20 in Table 22 correspond to the Lp lens element Lp.

[0123] [Table 22]

[0124] [Table 23]

[0125] [Table 24]

[0126] [Example 9] A cross-sectional view of the configuration of the imaging lens of Example 9 is shown in Figure 20. The imaging lens of Example 9 consists of, in order from the object side to the image side, a first lens group having positive refractive power, an aperture stop St, a second lens group having positive refractive power, and a third lens group having negative refractive power. The front group GF consists of the first lens group. The rear group GR consists of the second lens group and the third lens group. When focusing from an object at infinity to a close object, the first lens group and the third lens group are fixed with respect to the image plane Sim, and the second lens group moves toward the object side.

[0127] The Lp lens Lp is included in the third lens component from the object side of the second lens group. This lens component is a cemented lens formed by cementing, in order from the object side, a positive lens and an Lp lens Lp.

[0128] For the imaging lens of Example 9, basic lens data is shown in Table 25, specifications and variable surface spacings are shown in Table 26, aspherical coefficients are shown in Table 27, and aberration diagrams are shown in Fig. 21. Surfaces 22 and 23 in Table 25 correspond to the Lp lens element Lp.

[0129] [Table 25]

[0130] [Table 26]

[0131] [Table 27]

[0132] [Example 10] A cross-sectional view of the configuration of the imaging lens of Example 10 is shown in Figure 22. The imaging lens of Example 10 consists of, in order from the object side to the image side, a first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having negative refractive power. The second lens group includes an aperture stop St. The front group GF consists of the first lens group and a part of the second lens group facing the object side. The rear group GR consists of the other part of the second lens group and the third lens group. When focusing from an object at infinity to a close object, the first lens group and the third lens group are fixed with respect to the image plane Sim, and the second lens group moves toward the object side.

[0133] The Lp lens Lp is included in the second lens component from the object side of the second lens group. This lens component is a cemented lens formed by cementing, in order from the object side, the Lp lens Lp and a negative lens.

[0134] For the imaging lens of Example 10, basic lens data is shown in Table 28, specifications and variable surface spacings are shown in Table 29, aspherical coefficients are shown in Table 30, and aberration diagrams are shown in Fig. 23. Surfaces 12 and 13 in Table 28 correspond to the Lp lens element Lp.

[0135] [Table 28]

[0136] [Table 29]

[0137] [Table 30]

[0138] Tables 31 and 32 show values ​​corresponding to conditional expressions (1) to (20) for the imaging lenses of Examples 1 to 10. The values ​​corresponding to the Examples shown in Tables 31 and 32 may be used as upper or lower limits for the conditional expressions to set preferred ranges for the conditional expressions.

[0139] [Table 31]

[0140] [Table 32]

[0141] The imaging lenses of Examples 1 to 10 have a maximum F-number of less than 1.8 when focused on an object at infinity, and in particular, the imaging lenses of Examples 1 to 9 have a maximum F-number of less than 1.5 when focused on an object at infinity. Furthermore, the imaging lenses of Examples 1 to 10 are small and lightweight, and maintain good optical performance by suppressing various aberrations including chromatic aberration.

[0142] Imaging devices such as digital cameras are in demand for small, lightweight lens systems with small F-numbers. Conventionally, when such lens systems are made smaller, chromatic aberrations occur, making it difficult to maintain resolution performance, and correcting chromatic aberrations increases the number of lenses, making it difficult to reduce the weight. In contrast, Examples 1 to 10 of the present disclosure effectively arrange high-dispersion resin Lp lenses Lp, thereby achieving small, lightweight lens systems with small F-numbers while correcting various aberrations, including chromatic aberration.

[0143] Next, an imaging device according to an embodiment of the present disclosure will be described. Fig. 24 and Fig. 25 show external views of a camera 30, which is an imaging device according to an embodiment of the present disclosure. Fig. 24 shows a perspective view of the camera 30 as seen from the front side, and Fig. 25 shows a perspective view of the camera 30 as seen from the rear side. The camera 30 is a so-called mirrorless digital camera, to which an interchangeable lens 20 can be removably attached. The interchangeable lens 20 is configured to include an imaging lens 1 according to an embodiment of the present disclosure housed in a lens barrel.

[0144] The camera 30 includes a camera body 31, and a shutter button 32 and a power button 33 are provided on the top surface of the camera body 31. An operation unit 34, an operation unit 35, and a display unit 36 ​​are provided on the back surface of the camera body 31. The display unit 36 ​​can display a captured image and an image within the angle of view before the image was captured.

[0145] A photographic opening through which light from the subject to be photographed enters is provided in the center of the front face of the camera body 31, and a mount 37 is provided at a position corresponding to the photographic opening, and an interchangeable lens 20 is attached to the camera body 31 via the mount 37.

[0146] Inside the camera body 31 are provided an imaging element such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) that outputs an imaging signal corresponding to the subject image formed by the interchangeable lens 20, a signal processing circuit that processes the imaging signal output from the imaging element to generate an image, and a recording medium for recording the generated image. With the camera 30, it is possible to take still images or videos by pressing the shutter button 32, and the image data obtained by this shooting is recorded on the recording medium.

[0147] Although the technology of the present disclosure has been described above using embodiments and examples, the technology of the present disclosure is not limited to the above embodiments and examples and can be modified in various ways. For example, the radius of curvature, surface spacing, refractive index, Abbe number, aspherical coefficient, etc. of each lens are not limited to the values ​​shown in the above examples and can take other values.

[0148] Furthermore, the imaging device according to the embodiment of the present disclosure is not limited to the above example, and can take various forms, such as a camera other than a mirrorless type, a film camera, and a video camera. [Explanation of symbols]

[0149] 1 Imaging lens 2 On-axis luminous flux 2m axial marginal beam 3. Maximum half-angle luminous flux 3p Chief ray at maximum half angle of view 20 Interchangeable Lenses 30 Camera 31 Camera Body 32 Shutter button 33 Power button 34 Control section 35 Control section 36 Display section 37 Mount d center thickness De Distance Denp distance G1 First lens group G2 Second lens group G3 Third lens group GF front group GR rear group Hpm Height Hpp height L11~L31 lenses Lp Lp Lens Penp Paraxial entrance pupil position Pexp paraxial exit pupil position Pim point Pob point PP optical components Sim image plane St aperture stop Z optical axis ωm Maximum half angle of view

Claims

1. From the object side to the image side, it consists of a front group, an aperture stop, and a rear group. the rear group includes at least one Lp lens made of resin and having positive refractive power cemented to a lens; The Abbe number of the Lp lens based on the d line is νp, The refractive index of the Lp lens with respect to the d line is Np, The central thickness of the Lp lens is d, The radius of curvature of the object side surface of the Lp lens is Rf, The radius of curvature of the image side surface of the Lp lens is Rr, TL is the sum of the distance on the optical axis from the lens surface of the front group closest to the object to the lens surface of the rear group closest to the image, and the air-equivalent distance on the optical axis from the lens surface of the rear group closest to the image to the image plane when the lens is focused on an object at infinity; When the object is focused on an object at infinity, a point on the optical axis at the position of the aperture stop is defined as an object point. The distance on the optical axis from the image-side surface of the Lp lens to the image-side surface of the Lp lens to the image point formed by the optical system from the lens surface adjacent to the image side of the aperture stop to the image-side surface of the Lp lens is defined as De. De is calculated assuming that the medium on the image side of the image side surface of the Lp lens is air, and the sign of De is negative if the image point is closer to the object side than the image side surface of the Lp lens on the optical axis, and positive if the image point is closer to the image side than the image side surface of the Lp lens. The open F-number when focused on an object at infinity is FNo. The focal length of the entire system when focused on an object at infinity is f. The maximum half angle of view when focused on an object at infinity is ωm. When the lens surface closest to the image side of the rear group is focused on an object at infinity, the air-equivalent distance on the optical axis from the lens surface to the image plane is Bf, 120<νp+94.24×Np<186 (1) 0<d×(1 / Rf-1 / Rr)<0.05 (2) -20<TL×(1 / De-1 / Rr)<20 (3) 1<FNo×TL / (f×tanωm)<30 (4) 0.4<Bf / (f×tanωm)<1.7 (5) An imaging lens that satisfies conditional expressions (1), (2), (3), (4), and (5) expressed as follows:

2. From the object side to the image side, it consists of a front group, an aperture stop, and a rear group. the rear group includes at least one Lp lens made of resin and having positive refractive power cemented to a lens; The Abbe number of the Lp lens based on the d line is νp, The refractive index of the Lp lens with respect to the d line is Np, The central thickness of the Lp lens is d, The radius of curvature of the object side surface of the Lp lens is Rf, The radius of curvature of the image side surface of the Lp lens is Rr, TL is the sum of the distance on the optical axis from the lens surface of the front group closest to the object to the lens surface of the rear group closest to the image, and the air-equivalent distance on the optical axis from the lens surface of the rear group closest to the image to the image plane when the lens is focused on an object at infinity; When the object is focused on an object at infinity, a point on the optical axis at the position of the aperture stop is defined as an object point. The distance on the optical axis from the image-side surface of the Lp lens to the image-side surface of the Lp lens to the image point formed by the optical system from the lens surface adjacent to the image side of the aperture stop to the image-side surface of the Lp lens is defined as De. De is calculated assuming that the medium on the image side of the image side surface of the Lp lens is air, and the sign of De is negative if the image point is closer to the object side than the image side surface of the Lp lens on the optical axis, and positive if the image point is closer to the image side than the image side surface of the Lp lens. The open F-number when focused on an object at infinity is FNo. The focal length of the entire system when focused on an object at infinity is f. The maximum half angle of view when focused on an object at infinity is ωm. Bf is the air-equivalent distance on the optical axis from the lens surface of the rear group closest to the image side to the image plane when focused on an object at infinity, When the focus is on an object at infinity, the sum of the distance on the optical axis from the paraxial exit pupil position to the lens surface of the rear group closest to the image side and the air-equivalent distance on the optical axis from the lens surface of the rear group closest to the image side to the image plane is defined as Dexp, 120<νp+94.24×Np<186 (1) 0<d×(1 / Rf-1 / Rr)<0.05 (2) -20<TL×(1 / De-1 / Rr)<20 (3) 1<FNo×TL / (f×tanωm)<30 (4) 1.95<Dexp / Bf<7.2 (7) An imaging lens that satisfies conditional expressions (1), (2), (3), (4), and (7) expressed as follows:

3. From the object side to the image side, it consists of a front group, an aperture stop, and a rear group. the rear group includes at least one Lp lens made of resin and having positive refractive power cemented to a lens; The Abbe number of the Lp lens based on the d line is νp, The refractive index of the Lp lens with respect to the d line is Np, The central thickness of the Lp lens is d, The radius of curvature of the object side surface of the Lp lens is Rf, The radius of curvature of the image side surface of the Lp lens is Rr, TL is the sum of the distance on the optical axis from the lens surface of the front group closest to the object to the lens surface of the rear group closest to the image, and the air-equivalent distance on the optical axis from the lens surface of the rear group closest to the image to the image plane when the lens is focused on an object at infinity; When the object is focused on an object at infinity, a point on the optical axis at the position of the aperture stop is defined as an object point. The distance on the optical axis from the image-side surface of the Lp lens to the image-side surface of the Lp lens to the image point formed by the optical system from the lens surface adjacent to the image side of the aperture stop to the image-side surface of the Lp lens is defined as De. De is calculated assuming that the medium on the image side of the image side surface of the Lp lens is air, and the sign of De is negative if the image point is closer to the object side than the image side surface of the Lp lens on the optical axis, and positive if the image point is closer to the image side than the image side surface of the Lp lens. The open F-number when focused on an object at infinity is FNo. The focal length of the entire system when focused on an object at infinity is f. When the maximum half angle of view when focused on an object at infinity is ωm, 120<νp+94.24×Np<186 (1) 0<d×(1 / Rf-1 / Rr)<0.05 (2) -20<TL×(1 / De-1 / Rr)<20 (3) 1<FNo×TL / (f×tanωm)<30 (4) -0.9<(De-Rr) / (De+Rr)<0.9 (10) An imaging lens that satisfies conditional expressions (1), (2), (3), (4), and (10) expressed as follows:

4. From the object side to the image side, it consists of a front group, an aperture stop, and a rear group. the rear group includes at least one Lp lens made of resin and having positive refractive power cemented to a lens; The Abbe number of the Lp lens based on the d line is νp, The refractive index of the Lp lens with respect to the d line is Np, The central thickness of the Lp lens is d, The radius of curvature of the object side surface of the Lp lens is Rf, The radius of curvature of the image side surface of the Lp lens is Rr, TL is the sum of the distance on the optical axis from the lens surface of the front group closest to the object to the lens surface of the rear group closest to the image, and the air-equivalent distance on the optical axis from the lens surface of the rear group closest to the image to the image plane when the lens is focused on an object at infinity; When the object is focused on an object at infinity, a point on the optical axis at the position of the aperture stop is defined as an object point. The distance on the optical axis from the image-side surface of the Lp lens to the image-side surface of the Lp lens to the image point formed by the optical system from the lens surface adjacent to the image side of the aperture stop to the image-side surface of the Lp lens is defined as De. De is calculated assuming that the medium on the image side of the image side surface of the Lp lens is air, and the sign of De is negative if the image point is closer to the object side than the image side surface of the Lp lens on the optical axis, and positive if the image point is closer to the image side than the image side surface of the Lp lens. The open F-number when focused on an object at infinity is FNo. The focal length of the entire system when focused on an object at infinity is f. When the maximum half angle of view when focused on an object at infinity is ωm, 120<νp+94.24×Np<186 (1) 0<d×(1 / Rf-1 / Rr)<0.05 (2) -20<TL×(1 / De-1 / Rr)<20 (3) 1<FNo×TL / (f×tanωm)<30 (4) 0.005<(Rf-Rr) / (Rf+Rr)<0.45 (11) An imaging lens that satisfies conditional expressions (1), (2), (3), (4), and (11) expressed as follows:

5. From the object side to the image side, it consists of a front group, an aperture stop, and a rear group. the rear group includes at least one Lp lens made of resin and having positive refractive power cemented to a lens; The Abbe number of the Lp lens based on the d line is νp, The refractive index of the Lp lens with respect to the d line is Np, The central thickness of the Lp lens is d, The radius of curvature of the object side surface of the Lp lens is Rf, The radius of curvature of the image side surface of the Lp lens is Rr, TL is the sum of the distance on the optical axis from the lens surface of the front group closest to the object to the lens surface of the rear group closest to the image, and the air-equivalent distance on the optical axis from the lens surface of the rear group closest to the image to the image plane when the lens is focused on an object at infinity; When the object is focused on an object at infinity, a point on the optical axis at the position of the aperture stop is defined as an object point. The distance on the optical axis from the image-side surface of the Lp lens to the image-side surface of the Lp lens to the image point formed by the optical system from the lens surface adjacent to the image side of the aperture stop to the image-side surface of the Lp lens is defined as De. De is calculated assuming that the medium on the image side of the image side surface of the Lp lens is air, and the sign of De is negative if the image point is closer to the object side than the image side surface of the Lp lens on the optical axis, and positive if the image point is closer to the image side than the image side surface of the Lp lens. The open F-number when focused on an object at infinity is FNo. The focal length of the entire system when focused on an object at infinity is f. When the maximum half angle of view when focused on an object at infinity is ωm, 120<νp+94.24×Np<186 (1) 0<d×(1 / Rf-1 / Rr)<0.05 (2) -20<TL×(1 / De-1 / Rr)<20 (3) 1<FNo×TL / (f×tanωm)<30 (4) -2.5<(f×tanωm)×(1 / De-1 / Rr)<1 (18) An imaging lens that satisfies conditional expressions (1), (2), (3), (4), and (18) expressed by the following formulas.

6. The imaging lens according to claim 1 , wherein either one of the object-side surface and the image-side surface of the Lp lens is in contact with air.

7. The imaging lens according to claim 1 , wherein the Lp lens has both an object-side surface and an image-side surface cemented with a lens.

8. The imaging lens according to claim 1 , wherein the Lp lens is included in a focus group that moves along the optical axis during focusing.

9. 9. The imaging lens according to claim 1, wherein either the object-side surface or the image-side surface of the Lp lens is aspherical.

10. When the lens surface closest to the object side of the front group is focused on an object at infinity, the distance on the optical axis from the lens surface to the paraxial entrance pupil position is represented by Denp. 0.3<Denp / f<2.5 (6) 10. The imaging lens according to claim 1, which satisfies conditional expression (6) expressed as follows:

11. When the focal length of the Lp lens is fp, 0.1<TL / fp<1.2 (8) 11. The imaging lens according to claim 1, which satisfies conditional expression (8) expressed as follows:

12. When focused on an object at infinity, the height from the optical axis of the chief ray of the maximum half angle of view on the object-side surface of the Lp lens is Hpp, When the height of the axial marginal ray from the optical axis on the object-side surface of the Lp lens in a state where the lens is focused on an object at infinity is Hpm, 0.2<Hpp / Hpm<1.1 (9) 12. The imaging lens according to claim 1, which satisfies conditional expression (9) expressed as follows:

13. The focal length of the focus group that moves along the optical axis during focusing is ffoc, When the focal length of the Lp lens is fp, 0.04<ffoc / fp<0.36 (12) 13. The imaging lens according to claim 1, which satisfies conditional expression (12) expressed as follows:

14. 14<νp<28 (13) 14. The imaging lens according to claim 1, which satisfies conditional expression (13) expressed as follows:

15. When the partial dispersion ratio between the g-line and the F-line of the Lp lens is θgFp, 0.67<θgFp<1.1 (14) 15. The imaging lens according to claim 1, which satisfies conditional expression (14) expressed as follows:

16. 1.51<Np<1.72 (15) 16. The imaging lens according to claim 1, which satisfies conditional expression (15) expressed as follows:

17. Dexp is the sum of the distance on the optical axis from the paraxial exit pupil position to the lens surface of the rear group closest to the image side when focused on an object at infinity, and the air-equivalent distance on the optical axis from the lens surface of the rear group closest to the image side to the image plane, When the focus is on an object at infinity, the sum of the distance on the optical axis from the object-side surface of the Lp lens to the lens surface of the rear group closest to the image side and the air-equivalent distance on the optical axis from the lens surface of the rear group closest to the image side to the image plane is defined as Dpi, 0.8<Dexp / Dpi<2.4 (16) 17. The imaging lens according to claim 1, which satisfies conditional expression (16) expressed as follows:

18. Dpi is the sum of the distance on the optical axis from the object-side surface of the Lp lens to the lens surface of the rear group closest to the image side when focused on an object at infinity, and the air-equivalent distance on the optical axis from the lens surface of the rear group closest to the image side to the image plane, When the height of the axial marginal ray from the optical axis on the object-side surface of the Lp lens in a state where the lens is focused on an object at infinity is Hpm, 1.9<Dpi / Hpm<5.9 (17) 18. The imaging lens according to claim 1, which satisfies conditional expression (17) expressed as follows:

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

Images