Single-focus lens, interchangeable lens, and imaging device

Abstract

To provide a single focus lens which is compact, wide-angle, and well corrected for aberrations, and to provide an interchangeable lens and image capturing device.SOLUTION: A single focus lens provided herein consists of a front group, an aperture stop, and a rear group having positive refractive power arranged in order from the object side, and is configured such that a diameter of an axial ray incident on the side closest to the object in the front group is less than that of an axial ray passing through the aperture stop, the front group having a negative meniscus lens with a convex surface on the object side located on the side closest to the side of the object. The single focus lens satisfies the following conditional expression (1): 1.85<NdL1 ...(1), where NdL1 represents a refractive index of the negative meniscus lens located on the side closest to the object in the front group.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a single-focus lens, an interchangeable lens, and an imaging device.

Background Art

[0002] In recent years, a lens with a wide angle of view, high brightness, and small size has been desired. For example, a retrofocus lens configuration in which a negative lens group precedes has been conventionally known (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in general, a retrofocus lens has an asymmetric configuration with respect to the aperture, and as the angle of view becomes wider, various aberrations, particularly off-axis aberrations, tend to deteriorate. Further, there has been a problem that the lens on the object side becomes large and miniaturization becomes difficult. For example, the optical system of Patent Document 1 has room for improvement from the viewpoints of a wide angle of view and correction of various aberrations.

[0005] The present invention has been made in view of the above points, and an object thereof is to provide a small and wide-angle single-focus lens, an interchangeable lens, and an imaging device in which various aberrations are corrected.

Means for Solving the Problems

[0006] The single-focus lens of the present embodiment is composed of, in order from the object side, a front group, an aperture, and a rear group having a positive refractive power. The on-axis light beam diameter incident on the most object-side surface of the front group is smaller than the on-axis light beam diameter passing through the aperture. The front group has, on the most object side, a negative meniscus lens with a convex surface facing the object side. Adjacent to the image side of the negative meniscus lens located closest to the object side, there is a negative meniscus lens with a convex surface facing the object side. The front group has, in order from the object side, three or more negative lenses, a positive lens, and a cemented lens of a positive lens and a negative lens. The front group has, on the most image side, a lens component with a positive refractive power and a concave surface facing the object side. The front group has two or more positive lenses and satisfies the following conditional expressions (1) and (15). (1) 1.85 < NdL1 (15) 4.5 < TL / D < 12.5 However, NdL1: Refractive index of the negative meniscus lens located on the object side of the front group TL: Distance from the surface on the object side of the front group to the image plane D: Distance from the surface on the image side of the front group at infinity to the surface on the object side of the rear group That is. The single-focus lens of the present embodiment is composed of, in order from the object side, a front group, a diaphragm, and a rear group with a positive refractive power. The axial light beam diameter incident on the most object side of the front group is smaller than the axial light beam diameter passing through the diaphragm. The front group has, on the most object side, a negative meniscus lens with a convex surface facing the object side, and adjacent to the image side of the negative meniscus lens located closest to the object side, there is a negative meniscus lens with a convex surface facing the object side. The front group has, in order from the most object side, three or more negative lenses, a positive lens, and a cemented lens of a negative lens. The front group has, on the most image side, a lens component with a positive refractive power and a concave surface facing the object side. The front group has two or more positive lenses and satisfies the following conditional expressions (1), (2), and (15). (1) 1.85 < NdL1 (2) 1.0 < G1bf / f < 100 (15) 4.5 < TL / D < 12.5 However, NdL1: Refractive index of the negative meniscus lens located closest to the object side of the front group G1bf: Focal length on the object side of the lens component located closest to the image side of the front group f: Focal length of the entire single-focus lens TL: Distance from the most object-side surface of the front group to the image plane D: Distance from the most image-side surface of the front group at infinity to the most object-side surface of the rear group is. The single-focus lens of the present embodiment is composed of, in order from the object side, a front group, a diaphragm, and a rear group with a positive refractive power. The axial light beam diameter incident on the most object side of the front group is smaller than the axial light beam diameter passing through the diaphragm. The front group has, on the most object side, a negative meniscus lens with a convex surface facing the object side, and adjacent to the image side of the negative meniscus lens located closest to the object side, there is a negative meniscus lens with a convex surface facing the object side. The front group has, in order from the most object side, three or more negative lenses, a positive lens, and a cemented lens of a negative lens. The front group has, on the most image side, a lens component with a positive refractive power and a concave surface facing the object side. The front group has two or more positive lenses and satisfies the following conditional expressions (1), (7), and (15). (1) 1.85 < NdL1 (7) 1.0 < TL / f < 10 (15) 4.5 < TL / D < 12.5 However, NdL1: Refractive index of the negative meniscus lens located closest to the object side of the front group TL: Distance from the most object-side surface of the front group to the image plane f: Focal length of the entire single-focus lens D: The distance from the most image-side surface of the front group to the most object-side surface of the rear group when at infinity, is as follows.

[0007] The interchangeable lens and imaging device of this embodiment have the above-described single-focus lens.

Advantages of the Invention

[0008] According to the present invention, it is possible to provide a small and wide-angle single-focus lens, an interchangeable lens, and an imaging device in which various aberrations are corrected.

Brief Description of the Drawings

[0009]

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Mode for Carrying Out the Invention

[0010] The single-focus lens of this embodiment is suitable, for example, as a photographing optical system in an imaging device such as a digital single-lens reflex / digital single-lens camera, or an interchangeable lens used in the imaging device.

[0011] As shown in the lens configuration diagrams of FIGS. 1, 4, 7, 10, 13, 16, 19, 22, and 25, the single-focus lens of the present embodiment is composed of, in order from the object side, a front group G1, a diaphragm SP for light quantity adjustment, and a rear group G2 having a positive refractive power. The front group G1 can have either a positive refractive power or a negative refractive power. For example, in Numerical Examples 2, 8, and 9 described later, the front group G1 has a positive refractive power, and in Numerical Examples 1, 3, 4, 5, 6, and 7 described later, the front group G1 has a negative refractive power. Also, for example, when the single-focus lens of the present embodiment is mounted on a digital camera, a low-pass filter, an infrared cut filter, a cover glass of an imaging element, etc. (which may be collectively referred to as a parallel plane plate and are not shown) can be arranged between the rear group G2 and the image plane (the image plane in design).

[0012] In the present embodiment, on the premise of the above-described basic configuration, in order to realize a small and wide-angle single-focus lens with various aberrations corrected, the detailed structures of the lens groups and lens elements and the selection of lens materials are optimized. In this specification, "having a wide angle of view (wide-angle)" means, for example, that the semi-angle of view is 40° or more.

[0013] In the single-focus lens of the present embodiment, the on-axis light beam diameter incident on the object side of the front group G1 is smaller than the on-axis light beam diameter passing through the diaphragm SP. Thereby, while achieving a wider angle of view of the single-focus lens, a necessary back focus can be ensured, and the peripheral light quantity can also be ensured.

[0014] In the single-focus lens of the present embodiment, the front group G1 has, on the object side, a negative meniscus lens with a convex surface facing the object side (for example, L1A, L1B, L1C, L1D, L1E, L1F, L1G, L1H, L1I described later). Thereby, while reducing the size of the single-focus lens, various aberrations, particularly distortion aberration and astigmatism, can be corrected well.

[0015] The single-focus lens of the present embodiment preferably satisfies the following conditional expressions (1), (1A), (1B), and (1C). (1) 1.85 < NdL1 (1A) 1.90 < NdL1 (1B) 1.95 < NdL1 (1C) 2.00 < NdL1 However, NdL1: The refractive index of the negative meniscus lens located closest to the object side in the front group. is.

[0016] By satisfying the conditional expression (1), the size of the single-focus lens can be reduced, and various aberrations, particularly distortion aberration and field curvature, can be corrected well. This effect is more significantly manifested by satisfying the conditional expressions (1A), (1B), and (1C). When exceeding the lower limit of the conditional expression (1), the radius of curvature of the image-side surface of the negative meniscus lens located closest to the object side in the front group becomes small, and particularly the lens interval on the image side expands, making it difficult to reduce the size, and at the same time, it becomes difficult to correct the distortion aberration and field curvature.

[0017] The front group G1 can have two or more negative lenses (for example, L1A and L2A, L1B and L2B, L1C and L2C, L1D and L2D, L1E and L2E, L1F and L2F, L1G and L2G, L1H and L2H, L1I and L2I) in order from the object side. Thereby, the negative refractive power in the front group G1 can be ensured, and the distortion aberration can be corrected well. If this lens configuration is not satisfied, the negative refractive power in the front group G1 is too weak, making it difficult to correct the distortion aberration.

[0018] The front group G1 can have, in order from the object side, two or more negative lenses, a positive lens, and a cemented lens G1a composed of a positive lens and a negative lens. The arrangement order of the positive lens and the negative lens constituting the cemented lens G1a is not limited, and they may be arranged in the order of positive and negative from the object side, or in the order of negative and positive from the object side. Thus, in the front group G1, by dividing the negative refractive power among two or more lenses in order from the object side, the occurrence of various aberrations can be minimized, and particularly, coma aberration can be corrected well. Furthermore, by having a cemented lens G1a composed of a positive lens and a negative lens on the image side of two or more negative lenses, chromatic aberration can be corrected well.

[0019] The front group G1 can have, in order from the object side, three or more negative lenses (for example, L1A, L2A, and L3A, L1B, L2B, and L3B, L1C, L2C, and L3C, L1D, L2D, L3D, and L4D, L1E, L2E, and L3E, L1F, L2F, and L3F, L1G, L2G, and L3G, L1H, L2H, and L3H, L1I, L2I, and L3I described later). Thereby, by gradually refracting the light rays incident on the front group G1 with three or more negative lenses, the occurrence of various aberrations can be minimized, and particularly, field curvature aberration and astigmatism can be corrected well. In the numerical example 4 described later, four negative lenses (L1D, L2D, L3D, and L4D) are arranged in order from the object side of the front group G1, but five or more negative lenses may be continuously arranged in order from the object side of the front group G1. Considering miniaturization, four or less is preferable.

[0020] The front group G1 can have, adjacent to the image side of the negative meniscus lens located on the object side, a negative meniscus lens with its convex surface facing the object side (for example, L2A, L2B, L2C, L2D, L2E, L2F, L2G, L2H, L2I described later). Thereby, distortion aberration can be corrected well.

[0021] The front group G1 may have a lens component G1b, which is closest to the image side and has a concave surface facing the object side. This allows for good correction of field curvature. In this specification, the term "lens component" refers to, for example, a single lens or a cemented lens having only two air contact surfaces, one on the object side and the other on the image side. In Numerical Examples 1-4 and 6-9 described later, the lens component G1b is composed of a cemented lens, and in Numerical Example 5 described later, the lens component G1b is composed of a single lens.

[0022] The front group G1 can have a lens component G1b with positive refractive power closest to the image side, which can effectively correct spherical aberration and coma.

[0023] It is preferable that the single focal length lens of this embodiment satisfies the following conditional expressions (2), (2A), and (2B). (2) 1.0 <G1bf / f<100 (2A)1.0 <G1bf / f<50 (2B)3.0 <G1bf / f<10 however, G1bf: The focal length of the lens element located closest to the image side in the front group. f: focal length of the entire system of a single focal length lens, It is.

[0024] By satisfying conditional expression (2), it is possible to effectively correct curvature of field, spherical aberration, and coma. This effect is more pronounced when conditional expressions (2A) and (2B) are satisfied. If the upper limit of condition (2) is exceeded, the refractive power of the lens component in the front group located closest to the image side becomes too weak, making it difficult to correct (undercorrect) curvature of field, spherical aberration, and coma. If the lower limit of condition (2) is exceeded, the refractive power of the lens component in the front group located closest to the image side becomes too strong, resulting in overcorrection of field curvature, spherical aberration, and coma.

[0025] The front group G1 has at least one cemented lens (for example, G1a and G1b described later), and the cemented lens (for example, G1a described later) located closest to the object among the cemented lenses in the front group G1 can have positive refractive power, which allows for good correction of spherical aberration and coma in addition to chromatic aberration.

[0026] It is preferable that the single focal length lens of this embodiment satisfies the following conditional expressions (3), (3A), (3B) and (3C). (3)-1.0 <G1af / G1f<1.0 (3A)-0.5 <G1af / G1f<1.0 (3B)-0.5 <G1af / G1f<0.5 (3C)-0.5 <G1af / G1f<0.15 however, G1af: The focal length of the cemented lens in the front group that is located closest to the object. G1f: Focal length of the front group, It is.

[0027] By satisfying conditional formula (3), chromatic aberration and off-axis aberrations can be effectively corrected. This effect is more pronounced when conditional formulas (3A), (3B), and (3C) are also satisfied. If the upper limit of condition (3) is exceeded, chromatic aberration and off-axis aberrations become difficult to correct (are under-corrected). If the lower limit of condition (3) is exceeded, chromatic aberration and off-axis aberrations will be over-corrected.

[0028] The front group G1 can have two or more positive lenses. This allows for good correction of spherical aberration. If the front group G1 had only one positive lens, the correction of spherical aberration would be insufficient.

[0029] It is preferable that the single focal length lens of this embodiment satisfies the following conditional expressions (4), (4A), (4B), (4C), (4D), (4E), (4F), and (4G). (4) 0.1 <L1SF<1.0 (4A) 0.1 <L1SF<0.8 (4B) 0.2 < L1SF < 0.6 (4C) 0.25 < L1SF < 0.5 (4D) 0.1 < L1SF < 0.3 (4E) 0.2 < L1SF < 0.3 (4F) 0.25 < L1SF < 0.3 (4G) 0.22 < L1SF < 0.29 However, L1SF = (L1R1 - L1R2) / (L1R1 + L1R2) L1R1: The radius of curvature of the object side surface of the negative meniscus lens located closest to the object side in the front group, L1R2: The radius of curvature of the image side surface of the negative meniscus lens located closest to the object side in the front group, is as follows.

[0030] Conditional expression (4) defines the shape (shaping factor) of the negative meniscus lens located closest to the object side in the front group. By satisfying conditional expression (4), various aberrations such as coma aberration can be corrected well, and the overall length of the lens can be shortened. This effect is more significantly manifested by satisfying conditional expressions (4A), (4B), (4C), (4D), (4E), (4F), and (4G). If it exceeds the upper limit of conditional expression (4), the fluctuations of various aberrations such as coma aberration generated on the image side surface of the negative meniscus lens located closest to the object side in the front group will become large. If it exceeds the lower limit of conditional expression (4), since the principal point position of the negative meniscus lens located closest to the object side in the front group will be on the image side, the distance between the principal points of the lenses will become long, and the overall length of the lens will increase.

[0031] It is preferable that the single-focus lens of the present embodiment satisfies the following conditional expressions (5), (5A), (5B), and (5C). (5) 0.1 < L2SF < 0.5 (5A) 0.2 < L2SF < 0.5 (5B) 0.1 < L2SF < 0.45 (5C) 0.19 < L2SF < 0.3 However, L2SF = (L2R1 - L2R2) / (L2R1 + L2R2) L2R1: The radius of curvature of the object side surface of the second negative meniscus lens located second from the object side in the front group, L2R2: The radius of curvature of the image side surface of the second negative meniscus lens located second from the object side in the front group, is as follows.

[0032] Conditional expression (5) defines the shape (shaping factor) of the second negative meniscus lens located second from the object side in the front group. By satisfying conditional expression (5), various aberrations such as coma aberration can be corrected well, and the overall length of the lens can be shortened. This effect is more significantly manifested by satisfying conditional expressions (5A), (5B), and (5C). When exceeding the upper limit of conditional expression (5), the variations of various aberrations such as coma aberration generated on the image side surface of the second negative meniscus lens located second from the object side in the front group become large. When exceeding the lower limit of conditional expression (5), since the principal point position of the second negative meniscus lens located second from the object side in the front group is on the image side, the distance between the principal points of the lenses becomes long, and the overall length of the lens increases.

[0033] The single-focus lens of this embodiment preferably satisfies the following conditional expressions (6), (6A), (6B), and (6C). (6) -8.0 < L1f / f < 0 (6A) -5.0 < L1f / f < -1.0 (6B) -3.0 < L1f / f < -1.5 (6C) -2.5 < L1f / f < -2.0 However, L1f: The focal length of the negative meniscus lens located closest to the object side in the front group, f: The focal length of the entire single-focus lens system, is as follows.

[0034] By satisfying conditional expression (6), high image quality of the single-focus lens can be achieved, and coma aberration can be corrected well. This effect is more significantly manifested by satisfying conditional expressions (6A), (6B), and (6C). When exceeding the upper limit of conditional expression (6), the refractive power of the negative meniscus lens located closest to the object side of the front group becomes too weak, making it difficult to achieve high image quality of the single-focus lens. When exceeding the lower limit of conditional expression (6), the refractive power of the negative meniscus lens located closest to the object side of the front group becomes too strong, making it difficult to control coma aberration.

[0035] The single-focus lens of this embodiment preferably satisfies the following conditional expressions (7), (7A), and (7B). (7) 1.0 < TL / f < 10 (7A) 1.0 < TL / f < 6.0 (7B) 4.5 < TL / f < 6.0 However,[[]] TL: The distance from the surface closest to the object side of the front group to the image plane, f: The focal length of the entire system of the single-focus lens, is.[[]]

[0036] By satisfying conditional expression (7), miniaturization and wide-angle imaging of the optical system can be achieved, and spherical aberration, coma aberration, and distortion aberration can be corrected well. This effect is more significantly manifested by satisfying conditional expressions (7A) and (7B). When exceeding the upper limit of conditional expression (7), large distortion aberration and coma aberration occur, and the optical system becomes large-sized. When exceeding the lower limit of conditional expression (7), the focal length becomes long and the angle of view becomes narrow. Also, correction of spherical aberration and coma aberration becomes difficult.

[0037] The single-focus lens of this embodiment preferably satisfies the following conditional expressions (8), (8A), (8B), (8C), and (8D). (8) 1.0 < ZTL / f < 12.0 (8A) 1.0 < ZTL / f < 6.0 (8B) 1.0 < ZTL / f < 4.0 (8C) 1.0 < ZTL / f < 2.8 (8D) 1.3 < ZTL / f < 1.8 However, ZTL: Distance from the most object-side surface to the most image-side surface of the front group, f: Focal length of the entire single-focus lens system, is.

[0038] By satisfying conditional expression (8), the front group and thus the entire lens system can be thinned to shorten the overall lens length, and spherical aberration can be corrected well. This effect is more significantly manifested by satisfying conditional expressions (8A), (8B), (8C), and (8D). If the upper limit of conditional expression (8) is exceeded, as a result, the front group and thus the entire lens system become thick, and the overall lens length increases. If the lower limit of conditional expression (8) is exceeded, it becomes difficult to correct spherical aberration.

[0039] The single-focus lens of this embodiment preferably satisfies the following conditional expressions (9) and (9A). (9) 1.80 < LSPNd (9A) 1.85 < LSPNd However, LSPNd: Refractive index of the lens located most on the image side of the front group, is.

[0040] By satisfying conditional expression (9), distortion aberration, field curvature, coma aberration, and spherical aberration can be corrected well. This effect is more significantly manifested by satisfying conditional expression (9A). If the lower limit of conditional expression (9) is exceeded, distortion aberration, field curvature, coma aberration, and spherical aberration will be under-corrected.

[0041] The single-focus lens of this embodiment preferably has at least one positive lens in the rear group G2 and satisfies the following conditional expressions (10), (10A), and (10B). (10) 70 < G2νd (10A) 80 < G2νd (10B) 85 < G2νd However, G2νd: The average value of the Abbe number of the positive lenses in the rear group, is as follows.

[0042] By satisfying the conditional expression (10), axial chromatic aberration can be corrected well. This effect is more significantly manifested by satisfying the conditional expressions (10A) and (10B). When exceeding the lower limit of the conditional expression (10), it becomes difficult to correct axial chromatic aberration.

[0043] The single-focus lens of this embodiment preferably satisfies the following conditional expressions (11), (11A), (11B), and (11C). (11) 0.1 < L2SF / L1SF < 5.0 (11A) 0.5 < L2SF / L1SF < 3.0 (11B) 0.3 < L2SF / L1SF < 2.0 (11C) 0.9 < L2SF / L1SF < 1.5 However, L1SF = (L1R1 - L1R2) / (L1R1 + L1R2) L2SF = (L2R1 - L2R2) / (L2R1 + L2R2) L1R1: The radius of curvature of the object-side surface of the negative meniscus lens located closest to the object side in the front group, L1R2: The radius of curvature of the image-side surface of the negative meniscus lens located closest to the object side in the front group, L2R1: The radius of curvature of the object-side surface of the negative meniscus lens located second closest to the object side in the front group, L2R2: The radius of curvature of the image-side surface of the negative meniscus lens located second closest to the object side in the front group, is as follows.

[0044] By satisfying the conditional expression (11), various aberrations such as coma aberration can be corrected well, and the overall length of the lens can be shortened. This effect is more significantly manifested by satisfying the conditional expressions (11A), (11B), and (11C). If the upper limit of condition (11) is exceeded, the principal point position of the negative meniscus lens that is the second most negative lens element from the object side in the front group will be on the image side, so the distance between the principal points of the lenses will become long and the overall lens length will increase. If the lower limit of condition (11) is exceeded, the fluctuations of various aberrations such as coma will become large.

[0045] It is preferable that the single focal length lens of this embodiment satisfies the following conditional expressions (12), (12A), and (12B). (12)1.0 <G2f / f<5.0 (12A) 1.0 <G2f / f<3.0 (12B)1.5 <G2f / f<2.5 however, G2f: focal length of rear group, f: focal length of the entire system of a single focal length lens, It is.

[0046] By satisfying conditional expression (12), the size of the fixed focal length lens can be reduced and curvature of field can be effectively corrected. This effect is more pronounced when conditional expressions (12A) and (12B) are satisfied. If the upper limit of condition (12) is exceeded, the refractive power of the rear group becomes too weak, the amount of movement required for focusing becomes large, and the single focal length lens becomes large. If the lower limit of condition (12) is exceeded, the refractive power of the rear group becomes too strong, causing large fluctuations in the curvature of field that accompany focusing.

[0047] It is preferable that the single focal length lens of this embodiment satisfies the following conditional expression (13). (13)25 <L1νd however, L1νd: Abbe number of the negative meniscus lens located closest to the object in the front group, It is.

[0048] By satisfying conditional expression (13), lateral chromatic aberration can be effectively corrected. If the lower limit of condition (13) is exceeded, it becomes difficult to correct lateral chromatic aberration.

[0049] The single-focus lens of this embodiment preferably satisfies the following conditional expression (14). (14) 1.6 < (Y × Fno) / f < 4.1 However, Y: Image height of the entire single-focus lens Fno: F-number of the entire single-focus lens f: Focal length of the entire single-focus lens That is.

[0050] By satisfying the conditional expression (14), coma aberration, astigmatism, and spherical aberration can be corrected well, and a bright lens with a small F-number can be realized, and a wide-angle effect can be achieved. If it exceeds the upper limit of the conditional expression (14), it becomes difficult to correct off-axis, especially coma aberration and astigmatism, and the lens becomes a dark lens with a large F-number. If it exceeds the lower limit of the conditional expression (14), the beam diameter passing through the single-focus lens becomes large, making it difficult to correct spherical aberration and coma aberration. Also, the angle of view becomes narrow.

[0051] The single-focus lens of this embodiment preferably satisfies the following conditional expression (15). (15) 4.5 < TL / D < 12.5 However, TL: Distance from the most object-side surface of the front group to the image plane D: Distance from the most image-side surface of the front group to the most object-side surface of the rear group at infinity That is.

[0052] By satisfying the conditional expression (15), miniaturization of the single-focus lens can be achieved, and field curvature can be corrected well. If it exceeds the upper limit of the conditional expression (15), the overall length of the lens increases, or the air gap between the front group and the rear group becomes too narrow, making it difficult to correct field curvature. When the lower limit of conditional expression (15) is exceeded, the overall lens length becomes too short, resulting in difficulty in correcting spherical aberration and coma aberration, or the air space between the front group and the rear group becomes too wide, resulting in an increase in the overall length.

[0053] The single-focus lens of the present embodiment preferably satisfies the following conditional expression (16). (16) 1.5 < ZTL / D < 4.5 However, ZTL: The distance from the most object-side surface to the most image-side surface of the front group, D: The distance from the most image-side surface of the front group to the most object-side surface of the rear group at infinity, is.

[0054] By satisfying conditional expression (16), miniaturization of the single-focus lens can be achieved, and field curvature can be corrected well. When the upper limit of conditional expression (16) is exceeded, as a result of the increase in the thickness of the front group, the overall lens length and the outer diameter increase, or the air space between the front group and the rear group becomes too narrow, making it difficult to correct field curvature. When the lower limit of conditional expression (16) is exceeded, as a result of the thickness of the front group becoming too short, it becomes difficult to correct distortion aberration, or as a result of the air space between the front group and the rear group becoming too wide, the overall length increases.

[0055] The single-focus lens of the present embodiment preferably satisfies the following conditional expression (17). (17) 1.0 < CTL / D < 3.0 However, CTL: The distance from the most object-side surface to the most image-side surface of the rear group, D: The distance from the most image-side surface of the front group to the most object-side surface of the rear group at infinity, is.

[0056] By satisfying conditional expression (17), miniaturization of the single-focus lens can be achieved, and field curvature can be corrected well. When exceeding the upper limit of conditional expression (17), as a result of the increase in the thickness of the rear group, the overall length and outer diameter of the lens increase, or the air gap between the front group and the rear group becomes too narrow, making it difficult to correct the field curvature. When exceeding the lower limit of conditional expression (17), as a result of the thickness of the rear group becoming too short, it becomes difficult to correct the spherical aberration, or as a result of the air gap between the front group and the rear group becoming too wide, the overall length increases.

[0057] In the case of the single-focus lens of the present embodiment, during focusing, the rear focus method is more preferable than the overall extension method, which is advantageous for miniaturization, weight reduction, and high-speed autofocus. For example, a rear focus method of moving at least the rear group G2 toward the object side can be adopted. Alternatively, in the front group G1, a floating focus method can be adopted in which the cemented lens G1a and the lens component G1b move integrally toward the object side or the image side with a movement amount different from that of the rear group G2. The floating focus method is advantageous for correcting spherical aberration and field curvature in finite photography from infinity.

[0058] For the single-focus lens of the present embodiment, an aspherical surface or a diffractive surface may be used on any lens surface. The aspherical surface may be a glass-molded aspherical surface or a ground aspherical surface directly formed on the lens surface, a composite aspherical lens in which a resin layer is applied on the lens surface and an aspherical surface is formed thereon, or a plastic aspherical surface in which the lens itself is made of a resin material.

[0059] The single-focus lens of the present embodiment can be provided with a function of correcting image blur by moving any lens group or a part of the lens group in a direction perpendicular to the optical axis.

[0060] Specific numerical examples 1-9 are shown. In the various aberration diagrams and tables, d-line, g-line, and c-line represent aberrations for their respective wavelengths, S represents sagittal, M represents meridional, f represents the focal length of the entire system, Fno represents the F-number, w represents the semi-field angle, Y represents the image height, R represents the radius of curvature, D represents the lens thickness or lens interval, Nd represents the refractive index at the d-line, νd represents the Abbe number at the d-line, BF represents the back focus, L represents the overall lens length, K represents the conic constant of the aspheric surface, A4 represents the 4th-order aspheric coefficient, A6 represents the 6th-order aspheric coefficient, A8 represents the 8th-order aspheric coefficient, and A10 represents the 10th-order aspheric coefficient. The unit of length is [mm]. Here, the aspheric surface is defined by the following formula when the reciprocal of the paraxial radius of curvature (paraxial curvature) is C and the height from the optical axis is H. x = CH 2 / [1 + [1 - (1 + K)C 2 H 2 1 / 2 + A4H 4 + A6H 6 + A8H 8 + A 10 H 10

[0061] [Numerical Example 1] Figures 1-3 and Tables 1-3 show the single-focus lens of Numerical Example 1. Figure 1 is a lens configuration diagram at infinity focus, Figure 2 is a longitudinal aberration diagram at infinity focus, and Figure 3 is a lateral aberration diagram at infinity focus. Table 1 is surface data, Table 2 is aspheric surface data, and Table 3 is various data.

[0062] The single-focus lens of Numerical Example 1 is composed of, in order from the object side, a front group G1, an aperture SP for light quantity adjustment, and a rear group G2 with positive refractive power.

[0063] ​The front group G1 is composed of, in order from the object side, a negative meniscus lens L1A convex on the object side, a negative meniscus lens L2A convex on the object side, a negative meniscus lens L3A convex on the object side, a biconvex positive lens L4A, a negative meniscus lens L5A convex on the image side, and a positive meniscus lens L6A convex on the image side. The negative meniscus lens L2A has aspherical surfaces on both sides. The negative meniscus lens L3A and the biconvex positive lens L4A are joined together to form a joined lens G1a. The negative meniscus lens L5A and the positive meniscus lens L6A are joined together to form a lens component G1b.

[0064] The rear group G2 is composed of, in order from the object side, a positive meniscus lens L7A convex on the image side, a negative meniscus lens L8A convex on the image side, a biconvex positive lens L9A, a negative meniscus lens L10A convex on the image side, and a biconvex positive lens L11A. The positive meniscus lens L7A and the negative meniscus lens L8A are joined together. The biconvex positive lens L11A has aspherical surfaces on both sides.

[0065] (Table 1) Surface number R D Nd νd 1 32.748 2.200 2.00100 29.1 2 18.748 4.911 3* 19.816 2.700 1.58313 59.4 4* 11.002 12.650 5 1005.122 1.650 1.49700 81.6 6 29.310 5.411 1.91082 35.2 7 -287.518 3.256 8 -58.070 1.450 1.49700 81.6 9 -234.092 2.601 1.90043 37.4 10 -55.592 8.666 11 Stop INFINITY 4.661 12 -24.432 4.847 1.49700 81.6 13 -12.708 1.300 1.81600 46.6 14 -20.846 0.150 15 43.781 6.840 1.43875 95.0 16 -24.842 2.407 17 -39.399 1.200 2.00100 29.1 18 -677.910 1.353 19* 178.063 4.721 1.49700 81.6 20* -22.859 - * indicates an axially symmetric aspherical surface. (Table 2) Surface number K A4 A6 A8 A10 3 -1.000 0.7838E-05 -0.8816E-07 0.1687E-09 -0.1783E-12 4 -1.000 0.2576E-04 -0.1791E-06 -0.1143E-09 0.4059E-12 19 0.000 -0.8030E-05 -0.2489E-08 0.5595E-10 0.0000E+00 20 0.000 0.1778E-04 -0.2700E-08 0.1541E-09 0.0000E+00 (Table 3) f 21.08 Fno 2.4 w 46.3 Y 21.64 BF 40.88 L 113.86

[0066] [Numerical Example 2] Figures 4 to 6 and Tables 4 to 6 show the single-focus lens of Numerical Example 2. Figure 4 is the lens configuration diagram at infinity focus, Figure 5 is the longitudinal aberration diagram at infinity focus, and Figure 6 is the lateral aberration diagram at infinity focus. Table 4 is the surface data, Table 5 is the aspherical surface data, and Table 6 is the various data.

[0067] The front group G1 is composed of, in order from the object side, a negative meniscus lens L1B convex on the object side, a negative meniscus lens L2B convex on the object side, a biconvex positive lens L3B, a negative meniscus lens L4B convex on the image side, a negative meniscus lens L5B convex on the image side, and a positive meniscus lens L6B convex on the image side. The negative meniscus lens L1B has aspherical surfaces on both sides. The negative meniscus lens L2B has aspherical surfaces on both sides. The biconvex positive lens L3B and the negative meniscus lens L4B are joined together to form a joined lens G1a. The negative meniscus lens L5B and the positive meniscus lens L6B are joined together to form a lens component G1b.

[0068] The rear group G2 is composed of, in order from the object side, a positive meniscus lens L7B convex on the image side, a negative meniscus lens L8B convex on the image side, a biconvex positive lens L9B, a biconcave negative lens L10B, and a biconvex positive lens L11B. The positive meniscus lens L7B and the negative meniscus lens L8B are joined together. The biconvex positive lens L11B has aspherical surfaces on both sides.

[0069] (Table 4) Surface number R D Nd νd 1* 34.054 2.200 2.00100 29.1 2* 19.030 4.910 3* 19.607 2.700 1.58080 59.2 4* 10.815 12.650 5 373.720 5.410 1.91082 35.2 6 -33.388 1.650 1.49700 81.6 7 -128.250 3.260 8 -45.002 1.450 1.49700 81.6 9 -250.000 2.600 1.90043 37.4 10 -46.001 8.886 11 Aperture INFINITY 4.660 12 -23.663 4.850 1.49700 81.6 13 -12.108 1.300 1.81600 46.6 14 -19.911 0.150 15 67.506 6.840 1.43875 95.0 16 -21.670 2.410 17 -40.395 1.200 2.00100 29.1 18 9241.387 1.350 19* 126.733 6.350 1.49700 81.6 20* -24.151 - * indicates a rotationally symmetric aspherical surface. (Table 5) Surface number K A4 A6 A8 A10 1 0.000 0.6602E-05 -0.3640E-08 -0.1822E-10 -0.4486E-14 2 0.000 0.1348E-04 0.3867E-07 -0.1447E-10 0.4218E-12 3 -1.000 -0.2328E-05 -0.7287E-07 0.2559E-09 -0.5481E-12 4 -1.000 0.8666E-06 -0.2855E-06 0.1343E-09 0.2490E-12 19 0.000 -0.2411E-05 0.2624E-07 0.1630E-12 0.0000E+00 20 0.000 0.1986E-04 0.3576E-07 0.9209E-10 0.0000E+00 (Table 6) f 21.20 Fno 2.5 w 46.2 Y 21.64 BF 40.68 L 115.51

[0070] [Numerical Example 3] Figures 7 to 9 and Tables 7 to 9 show the single-focus lens of Numerical Example 3. Figure 7 is a lens configuration diagram at infinity focus, Figure 8 is a longitudinal aberration diagram at infinity focus, and Figure 9 is a lateral aberration diagram at infinity focus. Table 7 is surface data, Table 8 is aspherical data, and Table 9 is various data.

[0071] The front group G1 is composed of, in order from the object side, a negative meniscus lens L1C convex on the object side, a negative meniscus lens L2C convex on the object side, a negative meniscus lens L3C convex on the object side, a biconvex positive lens L4C, a negative meniscus lens L5C convex on the image side, a negative meniscus lens L6C convex on the image side, and a positive meniscus lens L7C convex on the image side. The negative meniscus lens L1C has aspherical surfaces on both sides. The negative meniscus lens L2C has aspherical surfaces on both sides. The negative meniscus lens L3C has aspherical surfaces on both sides. The biconvex positive lens L4C and the negative meniscus lens L5C are joined to form a cemented lens G1a. The negative meniscus lens L6C and the positive meniscus lens L7C are joined to form a lens component G1b.

[0072] The rear group G2 is composed of, in order from the object side, a positive meniscus lens L8C convex on the image side, a negative meniscus lens L9C convex on the image side, a biconvex positive lens L10C, a biconcave negative lens L11C, and a biconvex positive lens L12C. The positive meniscus lens L8C and the negative meniscus lens L9C are joined. The biconvex positive lens L12C has aspherical surfaces on both sides.

[0073] (Table 7) Surface number R D Nd νd 1* 34.054 2.200 2.00100 29.1 2* 19.030 4.910 3* 19.607 2.700 1.58080 59.2 4* 10.815 2.650 5* 17.009 3.000 1.58080 59.2 6* 15.413 7.000 7 373.720 5.410 1.91082 35.2 8 -33.388 1.650 1.49700 81.6 9 -128.250 3.260 10 -45.002 1.450 1.49700 81.6 11 -250.000 2.600 1.90043 37.4 12 -46.001 0.100 13 Twist INFINITY 13.446 14 -28.072 4.850 1.49700 81.6 15 -14.134 1.300 1.81600 46.6 16 -24.753 0.150 17 30.340 6.840 1.43875 95.0 18 -28.341 2.410 19 -85.623 1.200 2.00100 29.1 20 90.631 1.350 21* 96.109 6.350 1.49700 81.6 22* -27.321 - * indicates a rotationally symmetric aspherical surface. (Table 8) Surface number K A4 A6 A8 A10 1 0.000 0.1457E-05 0.9938E-10 0.1226E-10 -0.4887E-13 2 0.000 -0.1340E-05 0.3256E-07 0.9660E-11 0.3799E-12 3 -1.000 -0.1534E-04 -0.8417E-07 0.2146E-09 0.1891E-12 4 -1.000 0.1821E-04 -0.4206E-06 -0.6877E-09 -0.7451E-11 5 0.000 -0.5384E-04 -0.1927E-06 -0.1480E-08 -0.2415E-11 6 0.000 -0.8035E-04 -0.3021E-06 0.3476E-09 0.4630E-11 21 0.000 0.1052E-04 0.1383E-06 0.4348E-10 0.0000E+00 22 0.000 0.3492E-04 0.1468E-06 0.4775E-09 0.0000E+00 (Table 9) f 21.45 Fno 2.5 w 45.9 Y 21.64 BF 40.60 L 115.42

[0074] [Numerical Example 4] Figures 10 to 12 and Tables 10 to 12 show the single-focus lens of Numerical Example 4. Figure 10 is a lens configuration diagram at infinity focus, Figure 11 is a longitudinal aberration diagram at infinity focus, and Figure 12 is a lateral aberration diagram at infinity focus. Table 10 is surface data, Table 11 is aspherical surface data, and Table 12 is various data.

[0075] The front group G1 is composed of, in order from the object side, a negative meniscus lens L1D convex on the object side, a negative meniscus lens L2D convex on the object side, a negative meniscus lens L3D convex on the object side, a negative meniscus lens L4D convex on the object side, a biconvex positive lens L5D, a negative meniscus lens L6D convex on the image side, and a positive meniscus lens L7D convex on the image side. The negative meniscus lens L1D has aspherical surfaces on both sides. The negative meniscus lens L2D has aspherical surfaces on both sides. The negative meniscus lens L3D has aspherical surfaces on both sides. The negative meniscus lens L4D and the biconvex positive lens L5D are joined to form a cemented lens G1a. The negative meniscus lens L6D and the positive meniscus lens L7D are joined to form a lens component G1b.

[0076] The rear group G2 is composed of, in order from the object side, a positive meniscus lens L8D convex toward the image side, a negative meniscus lens L9D convex toward the image side, a biconvex positive lens L10D, a biconcave negative lens L11D, and a biconvex positive lens L12D. The positive meniscus lens L8D and the negative meniscus lens L9D are joined together. The biconvex positive lens L12D has aspherical surfaces on both sides.

[0077] (Table 10) Surface number R D Nd νd 1* 34.054 2.200 2.00100 29.1 2* 19.030 4.910 3* 19.607 2.700 1.58080 59.2 4* 10.815 2.650 5* 15.767 3.000 1.58080 59.2 6* 14.832 7.000 7 128.250 1.650 1.49700 81.6 8 33.388 5.410 1.91082 35.2 9 -373.720 3.260 10 -45.002 1.450 1.49700 81.6 11 -250.000 2.600 1.90043 37.4 12 -46.001 0.100 13 Stop INFINITY 13.446 14 -20.104 4.850 1.49700 81.6 15 -17.129 1.300 1.81600 46.6 16 -26.120 0.150 17 23.554 6.840 1.43875 95.0 18 -36.311 2.410 19 -155.791 1.200 2.00100 29.1 20 53.829 1.350 21* 41.369 6.350 1.49700 81.6 22* -29.151 - * is an axially symmetric aspherical surface. (Table 11) Surface number K A4 A6 A8 A10 1 0.000 0.2450E-05 -0.7174E-08 0.1574E-10 -0.2170E-13 2 0.000 -0.2538E-05 0.2938E-07 -0.1222E-09 0.3620E-12 3 -1.000 -0.1071E-04 -0.8756E-07 0.1696E-10 0.7235E-12 4 -1.000 0.4062E-04 -0.4848E-06 0.1877E-09 -0.5732E-11 5 0.000 -0.4292E-04 -0.2190E-06 -0.1378E-08 -0.7973E-12 6 0.000 -0.8154E-04 -0.2085E-06 -0.1370E-08 0.8714E-11 21 0.000 -0.6926E-05 0.8489E-07 0.2076E-10 0.0000E+00 22 0.000 0.2759E-04 0.1048E-06 0.3796E-09 0.0000E+00 (Table 12) f 21.39 Fno 2.4 w 45.9 Y 21.64 BF 40.64 L 115.47

[0078] [Numerical Example 5] Figures 13 to 15 and Tables 13 to 15 show the single-focus lens of Numerical Example 5. Figure 13 is a lens configuration diagram at infinite focus, Figure 14 is a longitudinal aberration diagram at infinite focus, and Figure 15 is a lateral aberration diagram at infinite focus. Table 13 is surface data, Table 14 is aspherical surface data, and Table 15 is various data.

[0079] The front group G1 is composed of, in order from the object side, a negative meniscus lens L1E convex on the object side, a negative meniscus lens L2E convex on the object side, a negative meniscus lens L3E convex on the object side, a biconvex positive lens L4E, and a positive meniscus lens L5E convex on the image side. The negative meniscus lens L2E has aspherical surfaces on both sides. The negative meniscus lens L3E and the biconvex positive lens L4E are joined together to form a joined lens G1a. The positive meniscus lens L5E forms a lens component G1b.

[0080] The rear group G2 is composed of, in order from the object side, a positive meniscus lens L6E convex on the image side, a negative meniscus lens L7E convex on the image side, a biconvex positive lens L8E, a biconcave negative lens L9E, and a biconvex positive lens L10E. The positive meniscus lens L6E and the negative meniscus lens L7E are joined together. The biconvex positive lens L10E has aspherical surfaces on both sides.

[0081] (Table 13) Surface number R D Nd νd 1 34.054 2.200 2.00100 29.1 2 19.030 4.910 3* 19.607 2.700 1.58080 59.2 4* 10.815 12.650 5 128.250 1.650 1.49700 81.6 6 33.388 5.410 1.91082 35.2 7 -373.720 3.260 8 -57.410 3.050 1.95906 17.5 9 -44.186 8.886 10 Stop INFINITY 4.660 11 -20.811 4.850 1.49700 81.6 12 -12.688 1.300 1.81600 46.6 13 -18.804 0.150 14 38.869 6.840 1.43875 95.0 15 -25.761 2.410 16 -40.470 1.200 2.00100 29.1 17 289.417 1.350 18* 73.078 6.350 1.49700 81.6 19* -24.858 - * indicates a rotationally symmetric aspherical surface. (Table 14) Surface number K A4 A6 A8 A10 3 -1.000 0.7570E-05 -0.1061E-06 0.2252E-09 -0.2661E-12 4 -1.000 0.2697E-04 -0.2334E-06 0.8845E-10 0.1194E-12 18 0.000 -0.6810E-05 0.1394E-07 -0.1213E-11 0.0000E+00 19 0.000 0.1828E-04 0.2146E-07 0.5656E-10 0.0000E+00 (Table 15) f 21.09 Fno 2.5 w 46.3 Y 21.64 BF 40.69 L 114.51

[0082] [Numerical Example 6] Figures 16 to 18 and Tables 16 to 18 show the single-focus lens of Numerical Example 6. Figure 16 is a lens configuration diagram at infinity focus, Figure 17 is a longitudinal aberration diagram at infinity focus, and Figure 18 is a lateral aberration diagram at infinity focus. Table 16 is surface data, Table 17 is aspherical surface data, and Table 18 is various data.

[0083] The front group G1 is composed of, in order from the object side, a negative meniscus lens L1F convex on the object side, a negative meniscus lens L2F convex on the object side, a negative meniscus lens L3F convex on the object side, a positive meniscus lens L4F convex on the object side, a biconcave negative lens L5F, and a biconvex positive lens L6F. The negative meniscus lens L2F has aspherical surfaces on both sides. The negative meniscus lens L3F and the positive meniscus lens L4F are joined together to form a cemented lens G1a. The biconcave negative lens L5F and the biconvex positive lens L6F are joined together to form a lens component G1b.

[0084] The rear group G2 is composed of, in order from the object side, a positive meniscus lens L7F convex on the image side, a biconcave negative lens L8F, a biconvex positive lens L9F, a negative meniscus lens L10F convex on the image side, and a biconvex positive lens L11F. The positive meniscus lens L7F and the biconcave negative lens L8F are joined together. The biconvex positive lens L11F has aspherical surfaces on both sides.

[0085] (Table 16) Surface number R D Nd νd 1 29.681 1.800 2.00069 25.5 2 16.294 5.907 3* 25.005 2.200 1.58913 60.9 4* 9.930 5.463 5 42.315 1.500 1.49700 81.6 6 19.234 5.129 1.90043 37.4 7 190.660 4.338 8 -32.433 1.400 1.49700 81.6 9 71.521 3.122 1.85150 40.8 10 -40.263 8.004 11 Stop INFINITY 5.559 12 -262.056 4.814 1.49700 81.6 13 -11.747 1.250 1.77250 49.6 14 1870.094 0.100 15 43.154 6.540 1.53775 74.7 16 -19.001 2.274 17 -29.504 1.200 2.00069 25.5 18 -88.434 0.100 19* 108.178 6.315 1.58913 60.9 20* -21.291 - * indicates a rotationally symmetric aspherical surface. (Table 17) Surface number K A4 A6 A8 A10 3 -1.000 -0.3357E-04 0.9053E-07 -0.2124E-09 0.2304E-12 4 -1.000 -0.3497E-04 -0.1830E-07 -0.1178E-09 -0.1059E-12 19 0.000 -0.1054E-04 0.3162E-07 -0.4110E-10 0.0000E+00 20 0.000 0.2101E-04 0.2702E-07 0.1680E-09 0.0000E+00 (Table 18) f 19.40 Fno 3.6 w 48.6 Y 21.64 BF 38.45 L 105.47

[0086] [Numerical Example 7] Figures 19 to 21 and Tables 19 to 21 show the single-focus lens of Numerical Example 7. Figure 19 is a lens configuration diagram at infinity focus, Figure 20 is a longitudinal aberration diagram at infinity focus, and Figure 21 is a lateral aberration diagram at infinity focus. Table 19 is surface data, Table 20 is aspherical surface data, and Table 21 is various data.

[0087] The front group G1 is composed of, in order from the object side, a negative meniscus lens L1G convex on the object side, a negative meniscus lens L2G convex on the object side, a negative meniscus lens L3G convex on the object side, a biconvex positive lens L4G, a negative meniscus lens L5G convex on the image side, and a positive meniscus lens L6G convex on the image side. The negative meniscus lens L1G has aspherical surfaces on both sides. The negative meniscus lens L2G has aspherical surfaces on both sides. The negative meniscus lens L3G and the biconvex positive lens L4G are joined together to form a cemented lens G1a. The negative meniscus lens L5G and the positive meniscus lens L6G are joined together to form a lens component G1b.

[0088] The rear group G2 is composed of, in order from the object side, a positive meniscus lens L7G convex on the image side, a negative meniscus lens L8G convex on the image side, a biconvex positive lens L9G, a biconcave negative lens L10G, and a biconvex positive lens L11G. The positive meniscus lens L7G and the negative meniscus lens L8G are joined together. The biconvex positive lens L11G has aspherical surfaces on both sides.

[0089] (Table 19) Surface number R D Nd νd 1* 32.214 2.200 1.95906 17.5 2* 18.226 4.910 3* 19.607 2.700 1.58080 59.2 4* 10.581 13.600 5 112.780 1.650 1.49700 81.6 6 33.451 5.410 1.91082 35.2 7 -450.820 3.260 8 -45.002 1.450 1.49700 81.6 9 -250.000 2.600 1.90043 37.4 10 -46.001 18.779 11 Stop INFINITY 5.125 12 -46.128 4.850 1.49700 81.6 13 -13.501 1.300 1.81600 46.6 14 -19.594 0.150 15 25.891 6.650 1.43875 95.0 16 -32.443 2.410 17 -39.001 1.200 2.00100 29.1 18 97.988 1.350 19* 29.953 6.350 1.49700 81.6 20* -263.658 - * is a rotationally symmetric aspherical surface. (Table 20) Surface number K A4 A6 A8 A10 1 0.000 0.1435E-04 -0.2070E-07 -0.6273E-10 0.1176E-12 2 0.000 0.2488E-05 0.4598E-07 -0.4491E-09 0.2116E-12 3 -1.000 -0.1068E-03 0.4939E-06 -0.1202E-08 0.1188E-11 4 -1.000 -0.8123E-04 0.3544E-06 0.4263E-09 -0.3878E-11 19 0.000 0.7102E-05 0.4652E-07 0.5553E-10 0.0000E+00 20 0.000 0.3215E-04 0.6473E-07 0.1328E-09 0.0000E+00 (Table 21) f 21.38 Fno 2.5 w 46.1 Y 21.64 BF 29.68 L 115.62

[0090] [Numerical Example 8] Figures 22 to 24 and Tables 22 to 24 show the single-focus lens of Numerical Example 8. Figure 22 is a lens configuration diagram at infinity focus, Figure 23 is a longitudinal aberration diagram at infinity focus, and Figure 24 is a lateral aberration diagram at infinity focus. Table 22 is surface data, Table 23 is aspherical surface data, and Table 24 is various data.

[0091] The front group G1 is composed of, in order from the object side, a negative meniscus lens L1H convex on the object side, a negative meniscus lens L2H convex on the object side, a negative meniscus lens L3H convex on the object side, a biconvex positive lens L4H, a negative meniscus lens L5H convex on the image side, and a positive meniscus lens L6H convex on the image side. The negative meniscus lens L2H has aspherical surfaces on both sides. The negative meniscus lens L3H and the biconvex positive lens L4H are joined to form a cemented lens G1a. The negative meniscus lens L5H and the positive meniscus lens L6H are joined to form a lens component G1b.

[0092] The rear group G2 is composed of, in order from the object side, a positive meniscus lens L7H convex on the image side, a negative meniscus lens L8H convex on the image side, a biconvex positive lens L9H, a negative meniscus lens L10H convex on the image side, and a biconvex positive lens L11H. The positive meniscus lens L7H and the negative meniscus lens L8H are joined. The biconvex positive lens L11H has aspherical surfaces on both sides.

[0093] (Table 22) Surface number R D Nd νd 1 30.616 2.200 1.91082 35.2 2 17.302 4.910 3* 19.816 2.700 1.58313 59.4 4* 10.581 15.883 5 112.780 1.650 1.49700 81.6 6 33.451 5.410 1.91082 35.2 7 -450.820 3.260 8 -45.002 1.450 1.49700 81.6 9 -250.000 2.600 1.90043 37.4 10 -46.001 4.154 11 aperture INFINITY 5.125 12 -23.664 4.850 1.49700 81.6 13 -11.418 1.300 1.81600 46.6 14 -20.100 0.150 15 88.031 6.650 1.43875 95.0 16 -19.444 2.410 17 -27.659 1.200 2.00100 29.1 18 -98.090 1.350 19* 187.995 6.350 1.49700 81.6 20* -21.999 - * is a rotationally symmetric aspheric surface. (Table 23) Surface number K A4 A6 A8 A10 3 -1.000 -0.1509E-04 -0.3182E-07 0.1519E-09 -0.3193E-12 4 -1.000 -0.7861E-05 -0.1811E-06 0.3404E-09 -0.9676E-12 19 0.000 -0.3113E-05 0.3833E-07 -0.1438E-10 0.0000E+00 20 0.000 0.2035E-04 0.4251E-07 0.1139E-09 0.0000E+00 (Table 24) f 20.20 Fno 2.5 w 47.7 Y 21.64 BF 42.22 L 115.82

[0094] [Numerical Example 9] Figures 25 to 27 and Tables 25 to 27 show the single-focus lens of Numerical Example 9. Figure 25 is a lens configuration diagram at infinity focus, Figure 26 is a longitudinal aberration diagram at infinity focus, and Figure 27 is a lateral aberration diagram at infinity focus. Table 25 is surface data, Table 26 is aspherical surface data, and Table 27 is various data.

[0095] The front group G1 is composed of, in order from the object side, a negative meniscus lens L1I convex on the object side, a negative meniscus lens L2I convex on the object side, a negative meniscus lens L3I convex on the object side, a biconvex positive lens L4I, a negative meniscus lens L5I convex on the image side, and a positive meniscus lens L6I convex on the image side. The negative meniscus lens L2I has aspherical surfaces on both sides. The negative meniscus lens L3I and the biconvex positive lens L4I are joined to form a cemented lens G1a. The negative meniscus lens L5I and the positive meniscus lens L6I are joined to form a lens component G1b.

[0096] The rear group G2 is composed of, in order from the object side, a positive meniscus lens L7I convex on the image side, a negative meniscus lens L8I convex on the image side, a biconvex positive lens L9I, a negative meniscus lens L10I convex on the image side, and a biconvex positive lens L11I. The positive meniscus lens L7I and the negative meniscus lens L8I are joined. The biconvex positive lens L11I has aspherical surfaces on both sides.

[0097] (Table 25) Surface number R D Nd νd 1 30.379 2.200 1.90366 31.3 2 17.165 4.910 3* 19.816 2.700 1.58313 59.4 4* 10.581 14.308 5 112.780 1.650 1.49700 81.6 6 33.451 5.410 1.91082 35.2 7 -450.820 3.260 8 -45.002 1.450 1.49700 81.6 9 -250.000 2.600 1.90043 37.4 10 -46.001 6.280 11 INFINITY 5.125 12 -24.208 4.850 1.49700 81.6 13 -12.152 1.300 1.81600 46.6 14 -20.596 0.150 15 66.663 6.650 1.43875 95.0 16 -20.991 2.410 17 -29.672 1.200 2.00100 29.1 18 -129.296 1.350 19* 131.919 6.350 1.49700 81.6 20* -23.046 - *は転対 is called an aspherical surface. (Table 26) Surface number K A4 A6 A8 A10 3 -1.000 -0.1683E-04 -0.3963E-07 0.1687E-09 -0.3188E-12 4 -1.000 -0.8717E-05 -0.2080E-06 0.4009E-09 -0.8585E-12 19 0.000 -0.2695E-05 0.2379E-07 -0.1161E-10 0.0000E+00 20 0.000 0.1968E-04 0.3488E-07 0.5897E-10 0.0000E+00 (Table 27) f / 20.78 Fno 2.5 w 46.8 Y 21.64 BF 41.69 L 115.84

[0098] The values for each conditional expression of each numerical example are shown in Table 28. As shown in Table 28, Numerical Examples 1 to 9 satisfy Conditional Expressions (1) to (17). (Table 28) Example 1 Example 2 Example 3 Conditional Expression (1) 2.00100 2.00100 2.00100 Conditional Expression (2) 7.57 6.33 6.26 Conditional Expression (3) -0.21 0.03 -0.31 Conditional Expression (4) 0.27 0.28 0.28 Conditional Expression (5) 0.29 0.29 0.29 Conditional Expression (6) -2.26 -2.19 -2.17 Conditional Expression (7) 5.39 5.45 5.38 Conditional Expression (8) 1.75 1.74 1.72 Conditional Expression (9) 1.9004 1.9004 1.9004 Conditional Expression (10) 86.01 86.01 86.01 Conditional Expression (11) 1.05 1.02 1.02 Conditional Expression (12) 1.82 1.92 1.81 Conditional Expression (13) 29.10 29.10 29.10 Conditional Expression (14) 2.46 2.55 2.52 Conditional Expression (15) 8.54 8.53 8.23 Conditional Expression (16) 2.76 2.72 2.72 Conditional Expression (17) 1.71 1.80 1.80 Example 4 Example 5 Example 6 Conditional Expression (1) 2.00100 2.00100 2.00069 Conditional Expression (2) 6.28 8.52 4.47 Conditional Expression (3) -0.34 -0.24 -0.11 Conditional Expression (4) 0.28 0.28 0.29 Conditional Expression (5) 0.29 0.29 0.43 Conditional Expression (6) -2.17 -2.20 -2.00 Conditional Expression (7) 5.40 5.43 5.44 Conditional formula (8) 1.72 1.70 1.59 Conditional formula (9) 1.9004 1.9591 1.8515 Conditional formula (10) 86.01 86.01 72.47 Conditional formula (11) 1.02 1.02 1.48 Conditional formula (12) 1.79 1.64 2.11 Conditional formula (13) 29.10 29.10 25.50 Conditional formula (14) 2.43 2.57 4.02 Conditional formula (15) 8.52 8.45 7.78 Conditional formula (16) 2.72 2.65 2.28 Conditional formula (17) 1.80 1.80 1.67 Example 7 Example 8 Example 9 Conditional formula (1) 1.95906 1.91082 1.90366 Conditional formula (2) 6.28 6.65 6.46 Conditional formula (3) -0.01 0.11 0.02 Conditional formula (4) 0.28 0.28 0.28 Conditional formula (5) 0.30 0.30 0.30 Conditional formula (6) -2.22 -2.35 -2.28 Conditional formula (7) 5.41 5.73 5.58 Conditional formula (8) 1.77 1.98 1.85 Conditional formula (9) 1.9004 1.9004 1.9004 Conditional formula (10) 86.01 86.01 86.01 Conditional formula (11) 1.08 1.09 1.09 Conditional formula (12) 1.92 2.06 1.96 Conditional formula (13) 17.50 35.20 31.30 Conditional formula (14) 2.53 2.68 2.60 Conditional formula (15) 4.84 12.48 10.16 Conditional formula (16) 1.58 4.32 3.37 Conditional formula (17) 1.01 2.61 2.13

[0099] Referring to FIGS. 28 and 29, a digital camera (imaging device) 100 equipped with the single-focus lens of the present embodiment will be described.

[0100] The digital camera 100 includes a camera body (housing) 101, a photographing lens 102, a viewfinder 103, a flash 104, a shutter button 105, a power button 106, a liquid crystal monitor 107, operation buttons 108, and a memory card slot 109.

[0101] The camera body 101 houses each component of the digital camera 100. The photographing lens 102 is, for example, a unit in which the single-focus lens of the present embodiment is incorporated into a lens barrel and / or an interchangeable lens. The viewfinder 103 is a viewing window for determining a subject and composition. The flash 104 emits a flash during night photography or low-light photography. The shutter button 105 is a physical switch for executing photography by the digital camera 100. The power button 106 is a physical switch for switching the power of the digital camera 100 on and off. The liquid crystal monitor 107 displays a photographed image or the like by the digital camera 100. The operation buttons 108 are physical switches for setting a photographing mode or the like of the digital camera 100. The memory card slot 109 is a slot for inserting a memory card (not shown) for storing a photographed image or the like by the digital camera 100.

[0102] As functional components inside the camera body 101, the digital camera 100 includes a central processing unit 111, an image processing unit 112, a light receiving element 113, a signal processing unit 114, a semiconductor memory 115, and a communication card 116.

[0103] The central processing unit 111 performs various arithmetic operations inside the digital camera 100. The image processing unit 112 performs various image processes on the captured image by the digital camera 100. The light receiving element 113 takes in and receives external light used for photometry processing. The signal processing unit 114 performs various signal processes such as a shooting instruction signal and an image processing signal. The semiconductor memory 115 constitutes a temporary storage area for the captured image by the digital camera 100. The communication card 116 is for enabling wireless communication with an external device (not shown).

[0104] FIG. 30 is an external perspective view showing an example of the interchangeable lens (lens barrel) 102 of the present embodiment. As shown in FIG. 30, the interchangeable lens 102 has a lens holding cylinder 102X and a single-focus lens held by this lens holding cylinder 102X. In FIG. 30, among the single-focus lenses, the lenses L1A to L1I arranged on the most object side of the front group G1 are drawn.

[0105] According to the present embodiment, it is possible to provide a small and wide-angle single-focus lens, an interchangeable lens, and an imaging device in which various aberrations are corrected.

[0106] The configuration of the digital camera 100 described here is merely an example, and various design changes are possible (there is freedom in the specific aspect of the digital camera 100).

[0107] The single-focus lens of the present embodiment can be applied to, for example, an interchangeable lens, a portable information terminal device, a video camera, a silver halide camera, an optical sensor, a projection optical system (projector), etc., even outside the digital camera 100 described above.

Description of Reference Numerals

[0108] G1 Front group G1a Cemented lens G1b Lens component L1A~L1I Negative meniscus lens with a convex surface facing the object side L2A~L2I Negative meniscus lens with a convex surface facing the object side G2 Rear group SP diaphragm 100 Digital camera (imaging device) 102 Photographing lens (lens barrel, interchangeable lens)

Claims

1. Composed of, in order from the object side, a front group, a diaphragm, and a rear group with positive refractive power, The on-axis light beam diameter incident on the most object-side surface of the front group is smaller than the on-axis light beam diameter passing through the diaphragm, The front group has, on the most object side, a negative meniscus lens with its convex surface facing the object side, and adjacent to the image side of the negative meniscus lens located on the most object side, has a negative meniscus lens with its convex surface facing the object side, The front group has, in order from the most object side, three or more negative lenses, a positive lens, and a cemented lens of a positive lens and a negative lens, The front group has, on the most image side, a lens component with positive refractive power and its concave surface facing the object side, The front group has two or more positive lenses, Satisfies the following conditional expressions (1) and (15), A single-focus lens characterized by this. (1) 1.85 < NdL1 (15) 4.5 < TL / D < 12.5 Provided that, NdL1: The refractive index of the negative meniscus lens located on the most object side of the front group, TL: The distance from the most object-side surface of the front group to the image plane, D: The distance from the most image-side surface of the front group to the most object-side surface of the rear group at infinity.

2. Composed of, in order from the object side, a front group, a diaphragm, and a rear group with positive refractive power, The on-axis light beam diameter incident on the most object-side surface of the front group is smaller than the on-axis light beam diameter passing through the diaphragm, The front group has, on the most object side, a negative meniscus lens with its convex surface facing the object side, and adjacent to the image side of the negative meniscus lens located on the most object side, has a negative meniscus lens with its convex surface facing the object side, The front group has, in order from the most object side, three or more negative lenses, a positive lens, and a cemented lens of a positive lens and a negative lens, The front group has, on the most image side, a lens component with positive refractive power and its concave surface facing the object side, The front group has two or more positive lenses, Satisfies the following conditional expressions (1), (2), and (15), A single-focus lens characterized by this. (1) 1.85 < NdL1 (2) 1.0 < G1bf / f < 100 (15) 4.5 < TL / D < 12.5 Provided that, NdL1: The refractive index of the negative meniscus lens located on the most object side of the front group, G1bf: The focal length on the object side of the lens component located on the most image side of the front group, f: The focal length of the entire single-focus lens system, TL: The distance from the most object-side surface of the front group to the image plane, D: The distance from the most image-side surface of the front group to the most object-side surface of the rear group at infinity.

3. Composed of, in order from the object side, a front group, a diaphragm, and a rear group with positive refractive power, The on-axis light beam diameter incident on the most object-side surface of the front group is smaller than the on-axis light beam diameter passing through the diaphragm, The front group has a negative meniscus lens with a convex surface facing the object side on the most object side, and has a negative meniscus lens with a convex surface facing the object side adjacent to the image side of the negative meniscus lens located on the most object side. The front group has, in order from the most object side, three or more negative lenses, and a cemented lens of a positive lens and a negative lens. The front group has, on the most image side, a lens component with a positive refractive power having a concave surface facing the object side. The front group has two or more positive lenses. Satisfies the following conditional expressions (1), (7), and (15). A single-focus lens characterized by this. (1) 1.85 < NdL1 (7) 1.0 < TL / f < 10 (15) 4.5 < TL / D < 12.5 However, NdL1: The refractive index of the negative meniscus lens located on the most object side of the front group. TL: The distance from the most object-side surface of the front group to the image plane. f: The focal length of the entire single-focus lens system. D: The distance from the most image-side surface of the front group at infinity to the most object-side surface of the rear group.

4. The front group has at least one cemented lens. Among the cemented lenses of the front group, the cemented lens located on the most object side has a positive refractive power. The single-focus lens according to any one of Claims 1 to 3, characterized by this.

5. The front group has at least one cemented lens. Satisfies the following conditional expression (3). The single-focus lens according to any one of Claims 1 to 3, characterized by this. (3) -1.0 < G1af / G1f < 1.0 However, G1af: The focal length of the cemented lens located on the most object side among the cemented lenses of the front group. G1f: The focal length of the front group.

6. Satisfies the following conditional expression (4). The single-focus lens according to any one of Claims 1 to 3, characterized by this. (4) 0.1 < L1SF < 1.0 However, L1SF = (L1R1 - L1R2) / (L1R1 + L1R2) L1R1: The radius of curvature of the object-side surface of the negative meniscus lens located on the most object side of the front group. L1R2: The radius of curvature of the image-side surface of the negative meniscus lens located on the most object side of the front group.

7. The front group has a negative meniscus lens with a convex surface facing the object side adjacent to the image side of the negative meniscus lens located on the most object side. Satisfies the following conditional expression (5). The single-focus lens according to any one of Claims 1 to 3, characterized by this. (5) 0.1 < L2SF < 0.5 However, L2SF = (L2R1 - L2R2) / (L2R1 + L2R2) L2R1: The radius of curvature of the object-side surface of the second negative meniscus lens from the most object side of the front group. L2R2: The radius of curvature of the image-side surface of the second negative meniscus lens located second from the object side in the front group.

8. Satisfying the following conditional expression (6), The single-focus lens according to any one of Claims 1 to 3, characterized in that. (6) -8.0 <L1f / f <0 However, L1f: The focal length of the negative meniscus lens located most on the object side of the front group, f: The focal length of the entire system of the single-focus lens.

9. Satisfying the following conditional expression (8), The single-focus lens according to any one of Claims 1 to 3, characterized in that. (8) 1.0 <ZTL / f <12.0 However, ZTL: The distance from the most object-side surface to the most image-side surface of the front group, f: The focal length of the entire system of the single-focus lens.

10. Satisfying the following conditional expression (9), The single-focus lens according to any one of Claims 1 to 3, characterized in that. (9) 1.80 <LSPNd However, LSPNd: The refractive index of the lens located most on the image side of the front group.

11. The rear group has at least one positive lens, Satisfying the following conditional expression (10), The single-focus lens according to any one of Claims 1 to 3, characterized in that. (10) 70 <G2νd However, G2νd: The average value of the Abbe numbers of the positive lenses in the rear group.

12. An interchangeable lens having the single-focus lens according to any one of Claims 1 to 3.

13. An imaging device having the single-focus lens according to any one of Claims 1 to 3.

Images