Imaging lens and imaging device

Abstract

This imaging lens includes, successively in order from a position closest to the object side, a first lens group which is fixed during focusing, and a focus lens group which moves during focusing. When a maximum image height is denoted by Ymax, the focal length of an entire system is denoted by f, and the sum of a distance on an optical axis from a lens surface closest to the object side to a lens surface closest to the image side and a back focus at an air-equivalent distance is denoted by TL, the imaging lens satisfies conditional expressions (1) and (2). (1): 0.1 < Ymax / f < 0.26 (2): 0.4 < TL / f < 1.1

Description

[Technical Field]

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

[0002] BACKGROUND ART Conventionally, lens systems described in, for example, Japanese Patent Application Laid-Open Nos. 2020-160100 and 2018-060079 have been known as imaging lenses used in imaging devices such as digital cameras and video cameras. Summary of the Invention

[0003] In recent years, there has been a demand for imaging lenses that are small and lightweight and have good optical performance.

[0004] The present disclosure has been made in consideration of the above circumstances, and aims to provide an imaging lens that is small and lightweight and has good optical performance, and an imaging device that includes this imaging lens. [Means for solving the problem]

[0005] An imaging lens according to one aspect of the present disclosure includes, in order from the object side to the image side, a first lens group that is fixed with respect to an image plane during focusing, and a focus lens group that moves along an optical axis during focusing, The maximum image height is Ymax, The focal length of the entire system when focused on an object at infinity is f. When the lens is focused on an object at infinity, the sum of the distance on the optical axis from the lens surface of the first lens group closest to the object to the lens surface of the entire system closest to the image and the back focus in air equivalent distance is defined as TL. 0.1 <Ymax / f<0.26 (1) 0.4 <TL / f<1.1 (2) The conditional expressions (1) and (2) are satisfied.

[0006] When the amount of distortion at an image height that is 50% of the maximum image height when focused on an object at infinity is Dst5, and the amount of distortion at the maximum image height when focused on an object at infinity is Dst10, the imaging lens of the above aspect has the following characteristics: 0.2<|Dst5 / Dst10|<0.6 (3) It is preferable to satisfy conditional expression (3) below.

[0007] When the distance on the optical axis from the image plane to the exit pupil position in a state where the focus is on an object at infinity is defined as Pe, and the sign of Pe is positive if the exit pupil position is closer to the object than the image plane, and negative if the exit pupil position is closer to the image than the image plane, the imaging lens of the above aspect has the following formula: 1.5 <Pe / Ymax<3 (4) It is preferable to satisfy conditional expression (4) below.

[0008] The imaging lens of the above aspect includes a negative lens closest to the image side, and when the radius of curvature of the object-side surface of the negative lens is Rf and the radius of curvature of the image-side surface of the negative lens is Rr, -0.6<(Rf-Rr) / (Rf+Rr)<-0.1 (5) It is preferable to satisfy conditional expression (5) below.

[0009] The imaging lens of the above aspect preferably includes a positive lens contiguous to the negative lens on the object side of the negative lens, and when the radius of curvature of the object side surface of the negative lens is Rf and the radius of curvature of the image side surface of the positive lens is Rpr, 0.03<(Rpr-Rf) / (Rpr+Rf)<0.4 (6) It is preferable to satisfy conditional expression (6) below.

[0010] In the imaging lens of the above aspect, when the Abbe number of the negative lens based on the d-line is vn, 12<νn<30 (7) It is preferable to satisfy conditional expression (7) below.

[0011] When the distance on the optical axis from the lens surface of the first lens group closest to the object side to the lens surface of the first lens group closest to the image side is defined as DG1, the imaging lens of the above aspect has the following characteristics: 0.02 <DG1 / f<0.2 (8) It is preferable to satisfy conditional expression (8) below.

[0012] When the maximum half angle of view when focused on an object at infinity is ω, and the angle between the chief ray of the maximum image height directed from the lens closest to the image side to the image plane when focused on an object at infinity and an axis parallel to the optical axis is ωi, the imaging lens of the above aspect satisfies the following equation: 1.4 <tanωi / tanω<3.6 (9) It is preferable to satisfy conditional expression (9) below.

[0013] When the maximum effective diameter of the lens surface of the first lens group closest to the object side is φf and the maximum effective diameter of the lens surface of the entire system closest to the image side is φr, the imaging lens of the above aspect is as follows: 0.2<φf / φr<1.5 (10) It is preferable to satisfy conditional expression (10) below.

[0014] When the back focus in air equivalent distance in a state where an object at infinity is focused is Bf, the imaging lens of the above embodiment has the following characteristics: 0.4 <Bf / Ymax<1.8 (11) It is preferable to satisfy conditional expression (11) below.

[0015] It is preferable that the focus lens group has negative refractive power as a whole, and that the number of lenses included in the focus lens group is two or less.

[0016] When the focal length of the first lens group is f1, the imaging lens of the above aspect has the following characteristics: 0.25 <f1 / f<0.5 (12) It is preferable to satisfy conditional expression (12) below.

[0017] The imaging lens of the above aspect comprises, in order from the object side to the image side, a first lens group, a focus lens group having negative refractive power as a whole, and a rear lens group that is fixed with respect to the image plane during focusing, and when the focal length of the rear lens group is fR, -0.9 <fR / f<-0.1 (13) It is preferable to satisfy conditional expression (13) below.

[0018] The imaging lens of the above aspect may be an imaging lens provided in an imaging device, and the imaging device may be configured to include an imaging element that captures an optical image formed by the imaging lens and to be capable of outputting an image with a narrower angle of view than the maximum imaging angle of view of the imaging element. Also, the imaging device may be configured to be capable of outputting an image with a narrower angle of view than the maximum imaging angle of view of the imaging element by using a composite image obtained by combining multiple images captured by the imaging element.

[0019] An imaging device according to another aspect of the present disclosure includes the imaging lens of the above aspect.

[0020] 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.

[0021] In this specification, a "single lens" refers to a single lens that is not cemented. However, a compound aspherical lens (a lens in which a spherical lens and an aspherical film formed on the spherical lens are integrally configured and function as a single aspherical lens as a whole) is not considered a cemented lens, but is treated as a single lens. Unless otherwise specified, the sign of the refractive power, radius of curvature, and surface shape of a lens including an aspherical surface are those in the paraxial region. The sign of the radius of curvature of a surface with a convex surface facing the object side is positive, and the sign of the radius of curvature of a surface with a convex surface facing the image side is negative.

[0022] In this specification, "total system" refers to the imaging lens. "Back focus in air equivalent distance" is the air equivalent distance on the optical axis from the lens surface closest to the image side of the total system to the image plane when focused on an object at infinity. The "focal length" used in the conditional expressions is the paraxial focal length. The values ​​used in the conditional expressions are values ​​based on the d-line.

[0023] The terms "d-line," "C-line," and "F-line" used in this specification are emission lines. In this specification, the wavelength of the d-line is treated as 587.56 nm (nanometers), the wavelength of the C-line is treated as 656.27 nm (nanometers), and the wavelength of the F-line is treated as 486.13 nm (nanometers). [Effects of the Invention]

[0024] According to the present disclosure, it is possible to provide an imaging lens that is small and lightweight and has good optical performance, and an imaging device that includes this imaging lens. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a cross-sectional view showing the configuration of an imaging lens according to an embodiment and a light beam, which corresponds to the imaging lens of Example 1. FIG. [Figure 2] 1 is a cross-sectional view showing the configuration of an imaging lens according to a first embodiment. [Figure 3] 3A to 3C are diagrams showing various aberrations of the imaging lens of Example 1. [Figure 4] FIG. 10 is a cross-sectional view showing the configuration of an imaging lens according to a second embodiment. [Figure 5] 10A to 10C are diagrams showing various aberrations of the imaging lens of Example 2. [Figure 6] FIG. 10 is a cross-sectional view showing the configuration of an imaging lens according to a third embodiment. [Figure 7] 10A to 10C are diagrams showing various aberrations of the imaging lens of Example 3. [Figure 8] FIG. 10 is a cross-sectional view showing the configuration of an imaging lens according to a fourth embodiment. [Figure 9] 10A to 10C are diagrams showing various aberrations of the imaging lens of Example 4. [Figure 10]FIG. 10 is a cross-sectional view showing the configuration of an imaging lens according to a fifth embodiment. [Figure 11] 10A to 10C are diagrams showing various aberrations of the imaging lens of Example 5. [Figure 12] FIG. 10 is a cross-sectional view showing the configuration of an imaging lens according to a sixth embodiment. [Figure 13] 10A to 10C are diagrams showing various aberrations of the imaging lens of Example 6. [Figure 14] FIG. 10 is a cross-sectional view showing the configuration of an imaging lens according to a seventh embodiment. [Figure 15] 10A to 10C are diagrams showing various aberrations of the imaging lens of Example 7. [Figure 16] FIG. 13 is a cross-sectional view showing the configuration of an imaging lens according to an eighth embodiment. [Figure 17] 13A to 13C are diagrams showing various aberrations of the imaging lens of Example 8. [Figure 18] 1 is a perspective view of the front side of an imaging device according to an embodiment. [Figure 19] FIG. 2 is a perspective view of the rear side of the imaging device according to the embodiment. [Figure 20] FIG. 10 is a diagram for explaining pixel shifting technology. [Figure 21] FIG. 10 is a diagram for explaining pixel shifting technology. [Figure 22] FIG. 10 is a conceptual diagram for explaining an example of a combination of a composite image and digital zoom. [Figure 23] FIG. 10 is a conceptual diagram for explaining another example of a combination of a composite image and digital zoom. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0027] FIG. 1 shows a cross-sectional view of the configuration and light beams of an imaging lens according to an embodiment of the present disclosure when focused on an object at infinity. In this specification, an "infinite object" refers to an object whose distance on the optical axis Z from the object to the lens surface of the imaging lens closest to the object is infinite. In FIG. 1, the light beams shown are an axial light beam, a light beam at an intermediate image height, and a light beam at the maximum image height. The example shown in FIG. 1 corresponds to the imaging lens of Example 1, which will be described later. In FIG. 1, the left side is the object side and the right side is the image side.

[0028] 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.

[0029] The imaging lens in Figure 1 includes, in order from the object side to the image side along the optical axis Z, a first lens group G1 that is fixed with respect to the image plane Sim during focusing, and a focus lens group Gf that moves along the optical axis Z during focusing. Because the lens group closest to the object can easily be made large in diameter, adopting the above configuration for this imaging lens is advantageous for reducing the size and weight of the focus drive mechanism. The right-pointing arrow below the focus lens group Gf in Figure 1 indicates that the focus lens group Gf moves toward the image side when focusing from an object at infinity to an object at a close distance.

[0030] As an example, the imaging lens of FIG. 1 is configured as follows. The imaging lens of FIG. 1 is composed of, in order from the object side to the image side, a first lens group G1 that is fixed with respect to the image plane Sim during focusing, a focus lens group Gf that moves along the optical axis Z during focusing, and a rear lens group GR that is fixed with respect to the image plane Sim during focusing. The first lens group G1 is composed of, in order from the object side to the image side, six lenses, L11 to L16, and an aperture stop St. The focus lens group Gf is composed of, in order from the object side to the image side, two lenses, L21 to L22. The rear lens group GR is composed of, in order from the object side to the image side, six lenses, L31 to L36. Note that the aperture stop St in FIG. 1 does not indicate its size or shape, but rather its position along the optical axis Z.

[0031] In the example of Fig. 1, only one lens group, the focus lens group Gf, moves during focusing. In the example of Fig. 1, during focusing, lenses L21 and L22 that make up the focus lens group Gf move integrally along the optical axis Z. In this specification, "moving integrally" means moving simultaneously in the same direction by the same amount.

[0032] Preferred and possible configurations of the imaging lens of this embodiment will be described below. In the following description of the preferred and possible configurations, to avoid redundancy, "the imaging lens of this embodiment" will also be referred to simply as "the imaging lens."

[0033] It is preferable that the focus lens group Gf has a negative refractive power as a whole, which is advantageous in suppressing fluctuations in chromatic aberration during focusing.

[0034] It is preferable that the number of lenses included in the focus lens group Gf is two or less, which is advantageous for reducing the weight of the focus lens group Gf.

[0035] When one lens component is a pair of cemented lenses or a single lens, the focus lens group Gf may be configured to consist of a single lens component arranged adjacent to the aperture stop St. This is advantageous for reducing the size and weight of the focus lens group Gf. When the focus lens group Gf consists of a cemented lens in which a positive lens and a negative lens are cemented together, this is advantageous for suppressing fluctuations in chromatic aberration during focusing. When the focus lens group Gf consists of a single lens, this is advantageous for reducing the size and weight.

[0036] It is preferable that the first lens group G1 has a positive refractive power as a whole, which is advantageous for reducing the size of the imaging lens in the optical axis Z direction and in the radial direction.

[0037] Assuming that the maximum image height is Ymax and the focal length of the entire system is f, it is preferable that the imaging lens satisfy the following conditional expression (1). f is the value when the lens is focused on an object at infinity. By ensuring that the corresponding value of conditional expression (1) is not equal to or less than the lower limit, a wide angle of view can be ensured, making it easier to prevent the subject from departing from the imaging range. By ensuring that the corresponding value of conditional expression (1) is not equal to or greater than the upper limit, it is easier to capture a magnified image of the subject. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (1-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (1-2). 0.1 <Ymax / f<0.26 (1) 0.12 <Ymax / f<0.23 (1-1) 0.15 <Ymax / f<0.21 (1-2)

[0038] If the focal length of the entire system is f and TL is the sum of the distance on the optical axis Z from the lens surface in the first lens group G1 closest to the object to the lens surface in the entire system closest to the image and the back focus in air equivalent distance, it is preferable that the imaging lens satisfy the following conditional expression (2). f and TL are values ​​when the lens is focused on an object at infinity. By ensuring that the corresponding value of conditional expression (2) is not equal to or less than the lower limit, the convergence of the light beam from the lens surface in the first lens group G1 closest to the object toward the image plane Sim can be made gentler, which is advantageous for suppressing spherical aberration. By ensuring that the corresponding value of conditional expression (2) is not equal to or greater than the upper limit, it is advantageous for reducing the size of the optical system. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (2-1), and even more preferable that it satisfy the following conditional expression (2-2). 0.4 <TL / f<1.1 (2) 0.43 <TL / f<0.92 (2-1) 0.5 <TL / f<0.85 (2-2)

[0039] Assuming that the amount of distortion at an image height that is 50% of the maximum image height is Dst5 and the amount of distortion at the maximum image height is Dst10, it is preferable that the imaging lens satisfy the following conditional expression (3). Dst5 and Dst10 are values ​​based on the d-line when focused on an object at infinity. By ensuring that the corresponding value of conditional expression (3) is not below the lower limit, the height of the off-axial light beam passing through the lens surface of the first lens group G1 closest to the object can be reduced, which is advantageous for compactness. By ensuring that the corresponding value of conditional expression (3) is not above the upper limit, distortion in the region of the imaging area from near the optical axis Z to a medium angle of view can be reduced, which is advantageous for increasing the resolution in this region. For example, this is effective when creating an image that excludes the peripheral portion of the imaging area and consists only of a region with an angle of view narrower than the maximum angle of view of the imaging lens, i.e., a cropped image as described below. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (3-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (3-2). 0.2<|Dst5 / Dst10|<0.6 (3) 0.22<|Dst5 / Dst10|<0.5 (3-1) 0.25<|Dst5 / Dst10|<0.4 (3-2)

[0040] If the distance on the optical axis Z from the image plane Sim to the exit pupil position is Pe and the maximum image height is Ymax, it is preferable that the imaging lens satisfy the following conditional expression (4). Pe is a value when the imaging lens is focused on an object at infinity. The sign of Pe is positive if the exit pupil position is closer to the object than the image plane Sim, and negative if the exit pupil position is closer to the image than the image plane Sim. By ensuring that the corresponding value of conditional expression (4) is not equal to or less than the lower limit, it is possible to prevent the angle of incidence of the chief ray of the off-axial light beam onto the image plane Sim from becoming too large, thereby reducing the influence of the angle of incidence characteristics of the imaging element disposed on the image plane Sim in the imaging device. By ensuring that the corresponding value of conditional expression (4) is not equal to or greater than the upper limit, it is easy to reduce the maximum diameter within the imaging lens, which is advantageous for miniaturization. To obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (4-1), and even more preferable that it satisfy the following conditional expression (4-2). 1.5 <Pe / Ymax<3 (4) 1.6 <Pe / Ymax<2.9 (4-1) 1.8 <Pe / Ymax<2.7 (4-2)

[0041] It is preferable that the imaging lens includes a negative lens closest to the image side of the entire system. Furthermore, if the radius of curvature of the object-side surface of this negative lens is Rf and the radius of curvature of the image-side surface of this negative lens is Rr, it is preferable that the imaging lens satisfies the following conditional expression (5): By ensuring that the corresponding value of conditional expression (5) is not equal to or less than the lower limit, the refraction of on-axis light beams at the negative lens closest to the image side can be strengthened, which is advantageous for correcting spherical aberration. By ensuring that the corresponding value of conditional expression (5) is not equal to or greater than the upper limit, the refraction effect of the negative lens closest to the image side on off-axis light beams can be strengthened, which is advantageous for correcting field curvature. To obtain better characteristics, it is more preferable that the imaging lens satisfies the following conditional expression (5-1), and even more preferable that the imaging lens satisfies the following conditional expression (5-2). -0.6<(Rf-Rr) / (Rf+Rr)<-0.1 (5) -0.58<(Rf-Rr) / (Rf+Rr)<-0.17 (5-1) -0.55<(Rf-Rr) / (Rf+Rr)<-0.25 (5-2)

[0042] When an imaging lens includes a negative lens closest to the image side of the entire system, it is preferable that the imaging lens also includes a positive lens contiguous to the negative lens on the object side. If the radius of curvature of the object-side surface of the negative lens is Rf and the radius of curvature of the image-side surface of the positive lens is Rpr, it is preferable that the imaging lens satisfies the following conditional expression (6): By ensuring that the corresponding value of conditional expression (6) is not equal to or less than the lower limit, the refraction of on-axis light beams between the negative lens and the positive lens is strengthened, which is advantageous for correcting on-axis chromatic aberration. By ensuring that the corresponding value of conditional expression (6) is not equal to or greater than the upper limit, the refraction of off-axis light beams between the negative lens and the positive lens is strengthened, which is advantageous for correcting chromatic aberration of magnification. To obtain better characteristics, it is more preferable that the imaging lens satisfies the following conditional expression (6-1), and it is even more preferable that the imaging lens satisfies the following conditional expression (6-2): 0.03<(Rpr-Rf) / (Rpr+Rf)<0.4 (6) 0.04<(Rpr-Rf) / (Rpr+Rf)<0.32 (6-1) 0.07<(Rpr-Rf) / (Rpr+Rf)<0.27 (6-2)

[0043] When an imaging lens includes a negative lens closest to the image side of the entire system, and the Abbe number of this negative lens based on the d-line is vn, it is preferable that the imaging lens satisfy the following conditional expression (7). By ensuring that the corresponding value of conditional expression (7) is not equal to or smaller than the lower limit, it is possible to prevent lateral chromatic aberration from being overcorrected. By ensuring that the corresponding value of conditional expression (7) is not equal to or larger than the upper limit, it is advantageous for good correction of lateral chromatic aberration. In order to obtain even better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (7-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (7-2). 12<νn<30 (7) 14<νn<25 (7-1) 17<νn<20 (7-2)

[0044] If the distance on the optical axis Z from the lens surface of the first lens group G1 closest to the object to the lens surface of the first lens group G1 closest to the image is DG1 and the focal length of the entire system is f, it is preferable that the imaging lens satisfy the following conditional expression (8). FIG. 1 shows an example of DG1. f is the value when the lens is focused on an object at infinity. By ensuring that the corresponding value of conditional expression (8) is not below the lower limit, it becomes easy to effectively correct the longitudinal chromatic aberration occurring in the first lens group G1. By ensuring that the corresponding value of conditional expression (8) is not above the upper limit, it becomes easy to reduce the size of the first lens group G1, which is advantageous for weight reduction. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (8-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (8-2). 0.02 <DG1 / f<0.2 (8) 0.04 <DG1 / f<0.18 (8-1) 0.07 <DG1 / f<0.15 (8-2)

[0045] If the maximum half angle of view of the imaging lens is ω and the angle between the chief ray at the maximum image height traveling from the lens closest to the image plane Sim and an axis Zp parallel to the optical axis Z is ωi, the imaging lens preferably satisfies the following conditional expression (9). tan is the tangent. ω and ωi are values ​​when focused on an object at infinity. ωi is a value in air. As an example, FIG. 1 shows ω, ωi, and Zp. ω is the angle between the chief ray at the maximum image height and the optical axis Z, and is half the maximum angle of view 2ω. Making sure that the value corresponding to conditional expression (9) is not equal to or less than the lower limit is advantageous for constructing a lens system with an angle of view more suitable for a telephoto system. Making sure that the value corresponding to conditional expression (9) is not equal to or greater than the upper limit facilitates reducing the maximum diameter within the imaging lens, which is advantageous for miniaturization. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (9-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (9-2). 1.4 <tanωi / tanω<3.6 (9) 1.5 <tanωi / tanω<3.3 (9-1) 1.8 <tanωi / tanω<2.9 (9-2)

[0046] If the maximum effective diameter of the lens surface closest to the object in the first lens group G1 is φf and the maximum effective diameter of the lens surface closest to the image in the entire system is φr, it is preferable that the imaging lens satisfy the following conditional expression (10). By ensuring that the corresponding value of conditional expression (10) is not below the lower limit, it is possible to widen the range of incidence of light rays incident on the imaging lens, which is advantageous for reducing the F-number and increasing the amount of peripheral light. By ensuring that the corresponding value of conditional expression (10) is not above the upper limit, it is possible to reduce the weight of the first lens group G1, which makes it possible to move the center of gravity of the imaging lens closer to the image side. 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 it satisfy the following conditional expression (10-2). 0.2<φf / φr<1.5 (10) 0.3<φf / φr<1.4 (10-1) 0.6<φf / φr<1.13 (10-2)

[0047] In the technology disclosed herein, the "maximum effective diameter" of a lens surface is defined as twice the distance from the point of intersection of the outermost ray and the lens surface, among the rays that enter the lens surface from the object side and exit to the image side, to the optical axis Z. Here, "outside" refers to the radially outward direction centered on the optical axis Z, i.e., the side away from the optical axis Z. The "outside ray" is determined taking into consideration all focusable object distances.

[0048] If the back focus in the air-equivalent distance of the entire system is Bf and the maximum image height is Ymax, it is preferable that the imaging lens satisfy the following conditional expression (11). Bf is the value when the lens is focused on an object at infinity. By ensuring that the corresponding value of conditional expression (11) is not below the lower limit, the height of off-axial rays passing through the lens closest to the image side of the entire system can be reduced, allowing the diameter of this lens to be reduced. This is advantageous for reducing weight. By ensuring that the corresponding value of conditional expression (11) is not above the upper limit, it is advantageous for shortening the overall length. In order to obtain 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). 0.4 <Bf / Ymax<1.8 (11) 0.5 <Bf / Ymax<1.7 (11-1) 0.8 <Bf / Ymax<1.4 (11-2)

[0049] If the focal length of the first lens group G1 is f1 and the focal length of the entire system is f, it is preferable that the imaging lens satisfy the following conditional expression (12). f is the value when focused on an object at infinity. Ensuring that the corresponding value of conditional expression (12) is not below the lower limit is advantageous for correcting spherical aberration occurring in the first lens group G1. Ensuring that the corresponding value of conditional expression (12) is not above the upper limit is advantageous for shortening the overall length. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (12-1), and it is even more preferable that it satisfy the following conditional expression (12-2). 0.25 <f1 / f<0.5 (12) 0.27 <f1 / f<0.48 (12-1) 0.3 <f1 / f<0.45 (12-2)

[0050] When an imaging lens includes, in order from the object side to the image side, a first lens group G1, a focus lens group Gf having negative refractive power overall, and a rear lens group GR that is fixed relative to the image plane Sim during focusing, it is preferable that the imaging lens satisfy the following conditional expression (13). Here, the focal length of the rear lens group GR is denoted by fR, and the focal length of the entire system when focused on an object at infinity is denoted by f. By ensuring that the corresponding value of conditional expression (13) is not below the lower limit, the negative refractive power of the rear lens group GR can be ensured, and the negative refractive power of the focus lens group Gf does not become too strong. This is advantageous for suppressing aberration fluctuations during focusing. By ensuring that the corresponding value of conditional expression (13) is not above the upper limit, the negative refractive power of the rear lens group GR can be suppressed, and the negative refractive power of the focus lens group Gf can be strengthened. This is advantageous for suppressing the amount of movement of the focus lens group Gf during focusing. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (13-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (13-2). -0.9 <fR / f<-0.1 (13) -0.8 <fR / f<-0.15 (13-1) -0.4 <fR / f<-0.18 (13-2)

[0051] The imaging lens preferably includes an image stabilization group that performs image blur correction by moving in a direction intersecting the optical axis Z. In this case, image blur caused by camera shake, vibration, etc. can be corrected, and a good image can be obtained. As will be described later, in an imaging device, the image sensor may be moved to obtain multiple images when creating a high-resolution image, so it is more convenient to move the lens rather than the image sensor for image blur correction.

[0052] As an example, the image stabilization group in Fig. 1 is made up of a cemented lens formed by cementing together lenses L31 and L32. The vertical double arrows below lenses L31 and L32 in Fig. 1 indicate that these lenses are part of the image stabilization group.

[0053] It is preferable that the image stabilization group as a whole have negative refractive power, which is advantageous in suppressing fluctuations in chromatic aberration during image blur correction.

[0054] It is preferable that the number of lenses included in the vibration isolation group be two or less, which is advantageous for reducing the weight of the vibration isolation group.

[0055] The vibration reduction group is preferably located closer to the image side than the focus lens group Gf. This is advantageous for suppressing aberration fluctuations associated with axial rays during image blur correction. The vibration reduction group may also be located closest to the object side of the rear lens group GR. This is advantageous for reducing the size and weight of the vibration reduction group.

[0056] When one lens component is a pair of cemented lenses or a single lens, the image stabilization group may be configured to consist of one lens component. This is advantageous for reducing the size and weight of the image stabilization group. When the image stabilization group consists of a cemented lens in which a positive lens and a negative lens are cemented together, this is advantageous for suppressing fluctuations in chromatic aberration during image blur correction. When the image stabilization group consists of a single lens, this is advantageous for reducing the size and weight.

[0057] If the focal length of the vibration reduction group is fv and the focal length of the entire system is f, it is preferable that the imaging lens satisfy the following conditional expression (14). f is the value when focused on an object at infinity. By ensuring that the corresponding value of conditional expression (14) is not below the lower limit, the refractive power of the vibration reduction group can be strengthened, and a high vibration reduction effect can be obtained with a small amount of movement. By ensuring that the corresponding value of conditional expression (14) is not above the upper limit, the refractive power of the vibration reduction group does not become too strong, which is advantageous for suppressing aberration fluctuations during image blur correction. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (14-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (14-2). -0.35 <fv / f<-0.1 (14) -0.33 <fv / f<-0.12 (14-1) -0.3 <fv / f<-0.15 (14-2)

[0058] The example shown in Fig. 1 is an example of an imaging lens according to the present disclosure. The number of lenses constituting each group of an imaging lens according to the present disclosure may be different from that shown in the example of Fig. 1. The "first lens group," "focus lens group," "rear lens group," and "image stabilization group" are not limited to being configured with multiple lenses, and may be configured with only one lens.

[0059] The above-described preferred and possible configurations, including those related to the conditional expressions, can be combined in any desired manner, and are preferably selectively adopted as appropriate according to the required specifications. Note that the conditional expressions that the imaging lens of the present disclosure preferably satisfies are not limited to conditional expressions written in the form of an expression, but include all conditional expressions obtained by arbitrarily combining lower limits and upper limits from among the preferred, more preferred, and even more preferred conditional expressions.

[0060] As an example, a preferred embodiment of the imaging lens of the present disclosure is an imaging lens that includes, in succession from the object side to the image side, a first lens group G1 that is fixed with respect to the image plane Sim during focusing, and a focus lens group Gf that moves along the optical axis Z during focusing, and satisfies the above conditional expressions (1) and (2).

[0061] 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.

[0062] [Example 1] 2 shows a cross-sectional view of the configuration of the imaging lens of Example 1. The imaging lens of Example 1 is composed of, in order from the object side to the image side, a first lens group G1, a focus lens group Gf, and a rear lens group GR. When focusing from an object at infinity to an object at a close distance, the entire focus lens group Gf moves integrally toward the image side, and the first lens group G1 and the rear lens group GR are fixed with respect to the image plane Sim.

[0063] The first lens group G1 consists, in order from the object side to the image side, of six lenses, lenses L11 to L16, and an aperture stop St. The focus lens group Gf consists, in order from the object side to the image side, of two lenses, lenses L21 to L22. The rear lens group GR consists, in order from the object side to the image side, of six lenses, lenses L31 to L36. The image stabilization group consists of lenses L31 and L32. Note that the aperture stop St in FIG. 2 does not indicate its size or shape, but rather its position along the optical axis Z.

[0064] For the imaging lens of Example 1, basic lens data is shown in Table 1, specifications are shown in Table 2, and variable surface spacing is shown in Table 3. In Example 1, a light blocking member (not shown) having a circular opening centered on a point on the optical axis Z is placed at a predetermined position to limit the height of light rays that can pass through.

[0065] Table 1 is written as follows. The Sn column indicates the surface number, with the surface closest to the object being surface 1 and the numbers increasing by one as you move toward the image side. The R column indicates the radius of curvature of each surface. The D column indicates the surface distance along the optical axis Z between each surface and its adjacent surface on the image side. The Nd column indicates the refractive index for the d-line of each component element. The νd column indicates the Abbe number of each component element based on the d-line. The VigD column indicates the diameter of the opening in the row of the surface where the light-blocking member is located.

[0066] In Table 1, the sign of the radius of curvature of a surface with a convex surface facing the object side is positive, and the sign of the radius of curvature of a surface with a convex surface facing the image side is negative. Table 1 also shows the aperture stop St and optical element PP. The column for the surface number of the surface corresponding to the aperture stop St contains the surface number and the phrase (St). The value in the bottom column of D in Table 1 is the distance between the surface closest to the image side in the table and the image plane Sim. In Table 1, the variable surface distance during focusing is represented by the symbol DD[ ], and the object-side surface number of this distance is entered in the [ ] in the D column.

[0067] Table 2 shows the focal length f of the entire system, the F-number FNo., the maximum angle of view 2ω, and the maximum image height Ymax. The (°) in the 2ω column indicates that the unit is degrees. Table 2 shows the values ​​when the lens is focused on an object at infinity.

[0068] In Table 3, the "Infinity" column shows the variable surface spacing value when focused on an object at infinity, and the "1.5m" column shows the variable surface spacing value when focused on an object at an object distance of 1.5m (meters). Tables 1, 2, and 3 show values ​​based on the d-line.

[0069] 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.

[0070] [Table 1]

[0071] [Table 2]

[0072] [Table 3]

[0073] FIG. 3 shows aberration diagrams of the imaging lens of Example 1 when focused on an object at infinity. From left to right, FIG. 3 shows spherical aberration, astigmatism, distortion, and lateral chromatic aberration. In the spherical aberration diagram, aberrations at 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, 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 at the C-line and F-line are shown by long-dashed lines and short-dashed lines, respectively. In the spherical aberration diagram, the F-number value is shown after "FNo.=". In the other aberration diagrams, the maximum half angle of view is shown after "ω=".

[0074] The symbols, meanings, notation methods, and illustration methods of each data item related to the above-mentioned Example 1 are the same in the following Examples unless otherwise specified, and therefore, redundant explanations will be omitted below.

[0075] [Example 2] 4 shows a cross-sectional view of the configuration of the imaging lens of Example 2. The imaging lens of Example 2 is composed of, in order from the object side to the image side, a first lens group G1, a focus lens group Gf, and a rear lens group GR. When focusing from an object at infinity to an object at a close distance, the entire focus lens group Gf moves integrally toward the image side, and the first lens group G1 and the rear lens group GR are fixed with respect to the image plane Sim.

[0076] The first lens group G1 consists, in order from the object side to the image side, of six lenses, lenses L11 to L16, and an aperture stop St. The focus lens group Gf consists, in order from the object side to the image side, of two lenses, lenses L21 to L22. The rear lens group GR consists, in order from the object side to the image side, of six lenses, lenses L31 to L36. The image stabilization group consists of lenses L31 and L32.

[0077] For the imaging lens of Example 2, basic lens data is shown in Table 4, specifications are shown in Table 5, variable surface spacing is shown in Table 6, and aberration diagrams when focused on an object at infinity are shown in FIG.

[0078] [Table 4]

[0079] [Table 5]

[0080] [Table 6]

[0081] [Example 3] 6 shows a cross-sectional view of the configuration of the imaging lens of Example 3. The imaging lens of Example 3 is composed of, in order from the object side to the image side, a first lens group G1, a focus lens group Gf, and a rear lens group GR. When focusing from an object at infinity to an object at a close distance, the entire focus lens group Gf moves integrally toward the image side, and the first lens group G1 and the rear lens group GR are fixed with respect to the image plane Sim.

[0082] The first lens group G1 consists, in order from the object side to the image side, of six lenses, lenses L11 to L16, and an aperture stop St. The focus lens group Gf consists, in order from the object side to the image side, of two lenses, lenses L21 to L22. The rear lens group GR consists, in order from the object side to the image side, of six lenses, lenses L31 to L36. The image stabilization group consists of lenses L31 and L32.

[0083] For the imaging lens of Example 3, basic lens data is shown in Table 7, specifications are shown in Table 8, variable surface spacing is shown in Table 9, and aberration diagrams when focused on an object at infinity are shown in FIG.

[0084] [Table 7]

[0085] [Table 8]

[0086] [Table 9]

[0087] [Example 4] 8 shows a cross-sectional view of the configuration of the imaging lens of Example 4. The imaging lens of Example 4 is composed of, in order from the object side to the image side, a first lens group G1, a focus lens group Gf, and a rear lens group GR. When focusing from an object at infinity to an object at a close distance, the entire focus lens group Gf moves integrally toward the image side, and the first lens group G1 and the rear lens group GR are fixed with respect to the image plane Sim.

[0088] The first lens group G1 consists, in order from the object side to the image side, of six lenses, lenses L11 to L16, and an aperture stop St. The focus lens group Gf consists, in order from the object side to the image side, of two lenses, lenses L21 to L22. The rear lens group GR consists, in order from the object side to the image side, of six lenses, lenses L31 to L36. The image stabilization group consists of lenses L31 and L32.

[0089] For the imaging lens of Example 4, basic lens data is shown in Table 10, specifications are shown in Table 11, variable surface spacing is shown in Table 12, and aspherical coefficients are shown in Table 13. FIG. 9 shows aberration diagrams when the lens is focused on an object at infinity.

[0090] 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 13, the Sn row shows the surface numbers of aspherical surfaces, and the KA and Am rows show the numerical values ​​of the aspherical coefficients for each aspherical surface. m is an integer of 3 or more, and for example, m = 4, 6, 8, 10 for the 21st surface of Example 4. The numerical values ​​of the aspherical coefficients in Table 13, "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×hm 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 and Σ in the aspherical formula means the summation with respect to m. The symbols, meanings, and notation methods for the aspherical coefficients are the same in the following examples unless otherwise specified.

[0091] [Table 10]

[0092] [Table 11]

[0093] [Table 12]

[0094] [Table 13]

[0095] [Example 5] 10 shows a cross-sectional view of the configuration of the imaging lens of Example 5. The imaging lens of Example 5 comprises, in order from the object side to the image side, a first lens group G1, a focus lens group Gf, and a rear lens group GR. When focusing from an object at infinity to an object at a close distance, the entire focus lens group Gf moves integrally toward the image side, and the first lens group G1 and the rear lens group GR are fixed with respect to the image plane Sim.

[0096] The first lens group G1 consists, in order from the object side to the image side, of six lenses, lenses L11 to L16, and an aperture stop St. The focus lens group Gf consists of one lens, lens L21. The rear lens group GR consists, in order from the object side to the image side, of five lenses, lenses L31 to L35. The image stabilization group consists of lens L31.

[0097] For the imaging lens of Example 5, basic lens data is shown in Table 14, specifications are shown in Table 15, variable surface spacing is shown in Table 16, and aberration diagrams when focused on an object at infinity are shown in FIG.

[0098] [Table 14]

[0099] [Table 15]

[0100] [Table 16]

[0101] [Example 6] 12 shows a cross-sectional view of the configuration of the imaging lens of Example 6. The imaging lens of Example 6 is composed of, in order from the object side to the image side, a first lens group G1, a focus lens group Gf, and a rear lens group GR. When focusing from an object at infinity to an object at a close distance, the entire focus lens group Gf moves integrally toward the image side, and the first lens group G1 and the rear lens group GR are fixed with respect to the image plane Sim.

[0102] The first lens group G1 consists, in order from the object side to the image side, of six lenses, lenses L11 to L16, and an aperture stop St. The focus lens group Gf consists of one lens, lens L21. The rear lens group GR consists, in order from the object side to the image side, of six lenses, lenses L31 to L36. The image stabilization group consists of lenses L31 and L32.

[0103] For the imaging lens of Example 6, basic lens data is shown in Table 17, specifications are shown in Table 18, variable surface spacing is shown in Table 19, and aberration diagrams when focused on an object at infinity are shown in FIG.

[0104] [Table 17]

[0105] [Table 18]

[0106] [Table 19]

[0107] [Example 7] 14 shows a cross-sectional view of the configuration of the imaging lens of Example 7. The imaging lens of Example 7 is composed of, in order from the object side to the image side, a first lens group G1, a focus lens group Gf, and a rear lens group GR. When focusing from an object at infinity to an object at a close distance, the entire focus lens group Gf moves integrally toward the image side, and the first lens group G1 and the rear lens group GR are fixed with respect to the image plane Sim.

[0108] The first lens group G1 consists, in order from the object side to the image side, of six lenses, lenses L11 to L16, and an aperture stop St. The focus lens group Gf consists, in order from the object side to the image side, of two lenses, lenses L21 to L22. The rear lens group GR consists, in order from the object side to the image side, of six lenses, lenses L31 to L36. The image stabilization group consists of lenses L31 and L32.

[0109] For the imaging lens of Example 7, basic lens data is shown in Table 20, specifications are shown in Table 21, variable surface spacing is shown in Table 22, and aspherical coefficients are shown in Table 23. FIG. 15 shows aberration diagrams when the lens is focused on an object at infinity.

[0110] [Table 20]

[0111] [Table 21]

[0112] [Table 22]

[0113] [Table 23]

[0114] [Example 8] 16 is a cross-sectional view of the configuration of the imaging lens of Example 8. The imaging lens of Example 8 comprises, in order from the object side to the image side, a first lens group G1, a focus lens group Gf, and a rear lens group GR. When focusing from an object at infinity to an object at a close distance, the entire focus lens group Gf moves integrally toward the image side, and the first lens group G1 and the rear lens group GR are fixed with respect to the image plane Sim.

[0115] The first lens group G1 consists, in order from the object side to the image side, of five lenses, L11 to L15, and an aperture stop St. The focus lens group Gf consists of one lens, lens L21. The rear lens group GR consists, in order from the object side to the image side, of six lenses, lens L31 to L36. The image stabilization group consists of lenses L31 and L32.

[0116] For the imaging lens of Example 8, basic lens data is shown in Table 24, specifications are shown in Table 25, variable surface spacing is shown in Table 26, and aspherical coefficients are shown in Table 27, and each aberration diagram when focused on an object at infinity is shown in FIG.

[0117] [Table 24]

[0118] [Table 25]

[0119] [Table 26]

[0120] [Table 27]

[0121] Table 28 shows the corresponding values ​​of conditional expressions (1) to (14) for the imaging lens of the above example. Table 28 shows the values ​​when the d line is used as the reference.

[0122] [Table 28]

[0123] Next, an imaging device according to an embodiment of the present disclosure will be described. Fig. 18 and Fig. 19 show external views of a camera 30, which is an imaging device according to an embodiment of the present disclosure. Fig. 18 shows a perspective view of the camera 30 as seen from the front side, and Fig. 19 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. The imaging lens 1 forms an optical image of a subject.

[0124] The camera 30 includes a camera body 31, the top of which is provided with a shutter button 32 and a power button 33. The back of the camera body 31 is provided with an operation unit 34, an operation unit 35, and a display unit 36. In response to user operations, the display unit 36 ​​can display a live view image of a subject within the angle of view before shooting, an image captured by pressing the shutter button 32, a recorded image, various types of information, and the like.

[0125] A photographic opening through which light from a subject 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.

[0126] The camera 30 includes an imaging element 38 in the camera body 31. The imaging element 38 captures an optical image formed by the imaging lens 1 and outputs a signal representing the captured image. The imaging element 38 may be, for example, a charge-coupled device (CCD) image sensor or a complementary metal oxide semiconductor (CMOS) image sensor. The imaging element 38 has an imaging area 38A (see FIGS. 20 and 22) in which a plurality of pixels are two-dimensionally arranged and photoelectrically converts received light into electrical signals. The imaging area 38A has a size capable of capturing an optical image corresponding to the maximum angle of view of the imaging lens 1. The imaging element 38 is positioned so that its imaging surface coincides with the position of the image plane Sim of the imaging lens 1. Note that "coincidence" here includes a practically acceptable error. In this positioning state, the maximum value of the angle of view that can be captured in the entire imaging area 38A is referred to as the maximum imaging angle of view of the imaging element 38.

[0127] The camera 30 includes a processor (not shown) in the camera body 31 that executes various processes such as image processing and output processing. The processor processes the captured image signal output from the image sensor 38. For example, the processor executes image correction processing and synthesis processing to synthesize multiple captured images to create a composite image as image processing. The processor also executes output processing to create an image for storage based on the captured images and the composite image, and record the created image for storage on a recording medium such as a memory card. The processor also executes output processing to create an image for display based on the captured images and the composite image, and display the created image for display on the display unit 36.

[0128] The processor can also create an image with a narrower angle of view than the maximum imaging angle of view of the image sensor 38 and output this image as a display image and an image for storage. This is a so-called digital zoom function, and an image corresponding to an enlarged image of a portion of the optical image can be output using digital zoom. When creating an image with a narrower angle of view, it is preferable to exclude areas of the optical image with a relatively large amount of aberration, such as a high-angle area, and use an area of ​​the optical image with a relatively small amount of aberration, such as an area including the optical axis Z. However, even if areas are selected in this way, an enlarged image obtained by digital zooming alone using a single captured image will have lower resolution than the captured image. Therefore, to obtain a high-resolution image, it is preferable to use, for example, a combination of a composite image and digital zoom, as described below.

[0129] First, as an example of a compositing process for creating a composite image, a compositing process using a so-called pixel shifting technique will be described. Pixel shifting is generally a technique aimed at increasing the resolution of an image. Pixel shifting is a technique for acquiring multiple captured images by shifting the image sensor 38 in a direction perpendicular to the optical axis Z of the imaging lens 1, i.e., in a direction parallel to the imaging surface, and capturing images at multiple shifted positions. The compositing process using the pixel shifting technique is a process for acquiring a composite image with a higher resolution than the captured images by combining the multiple captured images acquired by pixel shifting. When a color sensor having an imaging area 38A in which pixels corresponding to red (R), green (G), and blue (B) are arranged is used as the image sensor 38, the compositing process using the pixel shifting technique is, for example, as shown in FIGS. 20 and 21 .

[0130] As shown in Fig. 20, a plurality of RGB pixels are arranged two-dimensionally in an imaging region 38A of the image sensor 38. The example in Fig. 20 is a Bayer array, in which, in an area where four adjacent pixels are arranged in a square, two G pixels are arranged at one diagonal position, and one B pixel and one R pixel are arranged at the other diagonal position. Fig. 20 shows a portion of the imaging region 38A.

[0131] Because the R, G, and B pixels are arranged two-dimensionally in the imaging area 38A, only one of the three R, G, and B color signals can be acquired at each pixel position. The process shown in FIG. 20 uses pixel shifting technology to acquire the R, G, and B color signals at each pixel position. More precisely, as shown in FIG. 20, the image sensor 38 is shifted by one pixel at a time in accordance with a square array of four pixels: one R pixel, two G pixels, and one B pixel, thereby acquiring captured images at each of the four shift positions. In FIG. 20, the shift amount of the image sensor 38 is indicated as "1 pixel," and the shift direction is indicated by an arrow.

[0132] In FIG. 20, the leftmost position is the reference position of the imaging region 38A. The second shift position from the left is a position shifted one pixel to the left from the reference position. The third shift position is a position shifted one pixel downward from the second shift position. The fourth shift position is a position shifted one pixel to the right from the third shift position. Captured images 40-1 to 40-4 in FIG. 20 are captured at four positions, including the reference position and each shift position. Focusing on four pixels at the same position in the four captured images 40-1 to 40-4, each pixel is a combination of one R pixel, two G pixels, and one B pixel. This allows accurate color signals containing the three colors of RGB to be acquired at each pixel position, rather than a single color signal. The four captured images 40-1 to 40-4 shown in FIG. 20 are referred to as an image set ST40.

[0133] FIG. 21 is an explanatory diagram of pixel shifting for the purpose of increasing resolution. The resolution of a captured image is determined by the number of pixels in the imaging region 38A. The process shown in FIG. 21 is a process of acquiring image sets ST40 at four shift positions by shifting the imaging element 38 by 0.5 pixels, which is half the pitch of adjacent pixels, in a direction perpendicular to the optical axis Z. In FIG. 21, the shift amount of the imaging element 38 is indicated as "0.5 pixels," and the shift direction is indicated by an arrow. Note that in FIG. 21, to avoid cluttering the drawing, the imaging region 38A is omitted, and the position of the imaging region 38A is represented by the position of the image set ST40.

[0134] In FIG. 21, assuming that the leftmost position is the reference position of the imaging region 38A (shown as image set ST40), the second shift position from the left is a position shifted 0.5 pixels to the right from the reference position in the figure. The third shift position is a position shifted 0.5 pixels upward from the second shift position in the figure. The fourth shift position is a position shifted 0.5 pixels to the left from the third shift position in the figure. At each shift position shown in FIG. 21, the pixel shift shown in FIG. 20 is also performed, thereby acquiring an image set ST40 including four captured images 40-1 to 40-4. The four image sets ST40 acquired at each shift position shown in FIG. 21 are sets of images acquired at positions shifted 0.5 pixels each. In the camera 30, a processor performs a synthesis process using a total of 16 captured images included in the four image sets ST40 to generate a synthetic image 42. The composite image 42 is a high-definition image having a resolution four times that of the captured images included in each image set ST40.

[0135] As an example, FIG. 22 shows a conceptual diagram of a combination of the above-described composite image 42 and digital zoom. FIG. 22 mainly shows the approximate size of each image. The leftmost column of FIG. 22 shows an imaging area 38A corresponding to the maximum imaging angle of view of the image sensor 38. The second column from the left of FIG. 22 shows multiple captured images 40 captured by the image sensor 38. The multiple captured images 40 are 16 captured images 40 obtained using the pixel shifting technique described above. The camera 30 creates a composite image 42 by combining the 16 captured images 40. The camera 30 crops a portion of the composite image 42 to output a composite image 42A with a field of view narrower than the maximum imaging angle of view as an image for storage 44.

[0136] 22 obtained by the pixel shifting technique described above is an image with a higher resolution than the captured image 40. An enlarged image obtained by digital zoom using only one captured image, without performing such a synthesis process, will have a lower resolution than the captured image 40. However, by combining the above-described composite image 42 with digital zoom, it is possible to present the user with an enlarged image whose resolution is not lower than that of the captured image 40.

[0137] FIG. 23 shows an example of outputting a storage image 44 having a narrower angle of view than the maximum angle of view of the image capture using a method different from that shown in FIG. 22 . In comparison with the example shown in FIG. 22 , in the example shown in FIG. 23 , the camera 30 acquires multiple captured images 40S instead of the multiple captured images 40 shown in FIG. 22 . The captured images 40S are 16 captured images obtained using the pixel shifting technique described above, but are captured in a partial area 38B of the imaging area 38A of the image capture element 38. Therefore, the captured images 40S have a narrower angle of view than the maximum angle of view of the image capture element 38. The camera 30 combines the multiple captured images 40S to create a composite image 42A having a narrower angle of view than the maximum angle of view of the image capture and outputs the created composite image 42A as a storage image 44. The method shown in FIG. 23 also allows the user to view an enlarged image whose resolution is not reduced compared to the captured image 40S by combining the composite image 42A described above with digital zoom.

[0138] The above example is merely an example, and the number of captured images used to create a composite image and the shift amount of the image sensor in the pixel shifting technique may be values ​​different from those in the above example.

[0139] 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.

[0140] 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.

[0141] All publications, patent applications, and technical standards mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent application, or technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. The optical system comprises, in order from the object side to the image side, a first lens group that is fixed relative to the image plane when focusing, a focus lens group that has a negative refractive power as a whole and moves along the optical axis when focusing, and a rear lens group that is fixed relative to the image plane when focusing; The maximum image height is Ymax, The focal length of the entire system when focused on an object at infinity is f. TL is the sum of the distance on the optical axis from the lens surface of the first lens group closest to the object to the lens surface of the entire system closest to the image when focused on an object at infinity, and the back focus in air equivalent distance; When the focal length of the rear lens group is fR, 0.1<Ymax / f<0.26 (1) 0.4<TL / f<1.1 (2) -0.9<fR / f<-0.1 (13) An imaging lens that satisfies conditional expressions (1), (2), and (13) expressed by the following formulas.

2. Dst5 is the amount of distortion at an image height that is 50% of the maximum image height when focused on an object at infinity. When the amount of distortion at the maximum image height in a state where an object at infinity is focused is Dst10, 0.2<|Dst5 / Dst10|<0.6 (3) 2. The imaging lens according to claim 1, which satisfies conditional expression (3) expressed as follows:

3. Pe is the distance on the optical axis from the image plane to the exit pupil position when focused on an object at infinity, The sign of Pe is positive if the exit pupil position is closer to the object side than the image plane, and negative if the exit pupil position is closer to the image side than the image plane. 1.5<Pe / Ymax<3 (4) 3. The imaging lens according to claim 1, which satisfies conditional expression (4) expressed as follows:

4. It includes a negative lens closest to the image side, The radius of curvature of the object side surface of the negative lens is Rf, When the radius of curvature of the image-side surface of the negative lens is Rr, -0.6<(Rf-Rr) / (Rf+Rr)<-0.1 (5) 4. The imaging lens according to claim 1, which satisfies conditional expression (5) expressed as follows:

5. a positive lens disposed adjacent to the negative lens on the object side of the negative lens; When the radius of curvature of the image-side surface of the positive lens is Rpr, 0.03<(Rpr-Rf) / (Rpr+Rf)<0.4 (6) 5. The imaging lens according to claim 4, which satisfies conditional expression (6) expressed as follows:

6. When the Abbe number of the negative lens based on the d line is vn, 12<νn<30 (7) 6. The imaging lens according to claim 4, which satisfies conditional expression (7) expressed as follows:

7. When the distance on the optical axis from the lens surface of the first lens group closest to the object side to the lens surface of the first lens group closest to the image side is DG1, 0.02<DG1 / f<0.2 (8) 7. The imaging lens according to claim 1, which satisfies conditional expression (8) expressed as follows:

8. The maximum half angle of view when focused on an object at infinity is ω. When the angle between the principal ray of the maximum image height directed from the lens closest to the image plane to the image plane in a state where an object at infinity is focused on is ωi, and an axis parallel to the optical axis, 1.4<tanωi / tanω<3.6 (9) 8. The imaging lens according to claim 1, which satisfies conditional expression (9) expressed as follows:

9. The maximum effective diameter of the lens surface of the first lens group closest to the object is φf, When the maximum effective diameter of the lens surface closest to the image side of the entire system is φr, 0.2<φf / φr<1.5 (10) 9. The imaging lens according to claim 1, which satisfies conditional expression (10) expressed as follows:

10. When the back focus in air equivalent distance in a state where the lens is focused on an object at infinity is Bf, 0.4<Bf / Ymax<1.8 (11) 10. The imaging lens according to claim 1, which satisfies conditional expression (11) expressed as follows:

11. The imaging lens according to claim 1 , wherein the focus lens group has a negative refractive power as a whole.

12. The imaging lens according to claim 11, wherein the focus lens group includes two or less lenses.

13. When the focal length of the first lens group is f1, 0.25<f1 / f<0.5 (12) 13. The imaging lens according to claim 1, which satisfies conditional expression (12) expressed as follows:

14. The imaging lens provided in the imaging device, The imaging lens according to any one of claims 1 and 3 to 13, wherein the imaging device includes an imaging element that captures an optical image formed by the imaging lens, and is capable of outputting an image having a field of view narrower than the maximum imaging field of view of the imaging element.

15. The imaging lens provided in the imaging device, The imaging lens according to claim 2 , wherein the imaging device includes an imaging element that captures an optical image formed by the imaging lens, and is capable of outputting an image having a field angle narrower than the maximum imaging field angle of the imaging element.

16. The imaging lens according to claim 15 , wherein the imaging device is capable of outputting an image having a narrower angle of view than the maximum imaging angle of view of the imaging element, using a composite image obtained by combining a plurality of images captured by the imaging element.

17. The imaging lens provided in the imaging device, 15. The imaging lens according to claim 1, wherein the imaging device includes an imaging element that captures an optical image formed by the imaging lens, and is capable of outputting an image having a narrower angle of view than the maximum imaging angle of view of the imaging element by using a composite image obtained by combining a plurality of images captured by the imaging element.

18. An imaging device comprising the imaging lens according to any one of claims 1 to 17.

Images