Single focal length lens and imaging device

Abstract

To provide a single focus lens that is advantageous in terms of, for example, a wide angle, a small size, and high optical performance.SOLUTION: A single focus lens has a first lens group L1 that does not move for focusing and one or two second moving lens group(s) that move(s) for focusing, which are arranged in order from an object side to an image side. The first lens group has three negative lenses that are arranged continuously from the most object side. The focal distance of the single focus lens, the composite focal distance of the three negative lenses, and the average Abbe number of two negative lenses, of the three negative lenses, which are arranged continuously from the most object side, are appropriately set.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fixed focal length lens and an imaging device. [Background technology]

[0002] For imaging optical systems used in photo cameras and movie cameras, there is a demand for imaging optical systems with a wide angle, a small F-number, and a substantially uniform resolution across the entire object distance from the center of the screen to the periphery of the screen. In order to realize such an imaging optical system, a single-focus lens (single-focus optical system) has been proposed in which a first lens group that is fixed when focusing is disposed closest to the object, and multiple negative lenses are disposed in succession from the closest to the object in the first lens group. Patent Document 1 describes a single-focus optical system with a focal length of 24 mm and an F-number of 1.4, and Patent Document 2 describes a single-focus optical system with a focal length of 20 mm and an F-number of 1.4. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-038418 A [Patent Document 2] JP 2017-015941 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the optical system of Patent Document 1, the composite refractive power of the multiple negative lenses arranged in succession from the object side in the first lens group is insufficient, so when attempting to achieve a wider angle, the diameter of the front lens becomes excessively large, and the diameter of the lens barrel can become excessively large.

[0005] Furthermore, in the optical system of Patent Document 2, the composite refractive power of the multiple negative lenses arranged in succession from the most object side in the first lens group is insufficient, and the dispersion of the glass material of the two negative lenses arranged in succession from the most object side is also insufficient, so that when attempting to achieve a wider angle, this can be disadvantageous in terms of the lens barrel diameter and higher-order lateral chromatic aberration.

[0006] An object of the present invention is to provide a single focal length lens that is advantageous in terms of, for example, a wide angle, small size, and high optical performance. [Means for solving the problem]

[0007] In order to achieve the above object, a single focal length lens of the present invention has a first lens group that does not move for focusing, and one or two movable lens groups that move for focusing, which are arranged in order from the object side to the image side, and the first lens group has three negative lenses arranged consecutively from the most object side, the first lens group has a sub-lens group L1p arranged on the image side of the three negative lenses, the sub-lens group L1p having a negative lens and a plurality of positive lenses, The focal length of the single focal length lens is f, the composite focal length of the three negative lenses is f1n, and the average Abbe number of the two negative lenses that are arranged closest to the object side among the three negative lenses is ν1n, The partial dispersion ratio of the negative lens included in the sub-lens group L1p is θgFn, and the average partial dispersion ratio of the plurality of positive lenses included in the sub-lens group L1p is θgFp As, 0.3<|f1n / f|<0.98 64.2≦ ν1n<96 0.03<θgFn-θgFp≦0.0408 The present invention is characterized in that the following conditional expression is satisfied: Here, the Abbe number ν is expressed by the refractive indexes of the material for the F line (wavelength 486.1 nm), C line (wavelength 656.3 nm), and d line (wavelength 587.6 nm) as NF, NC, and Nd, respectively. ν=(Nd-1) / (NF-NC) It is expressed by the formula: The partial dispersion ratio θgF is expressed as follows, where Ng is the refractive index of the material for the g-line (wavelength 435.8 nm): θgF=(Ng-NF) / (NF-NC) It is expressed by the formula: Effect of the Invention

[0008] According to the present invention, for example, it is possible to provide a single focal length lens that is advantageous in terms of wide angle, small size, and high optical performance. [Brief description of the drawings]

[0009] [Figure 1] FIG. 4 is a cross-sectional view of a lens according to Numerical Example 1 when focused on an object at infinity. [Diagram 2] 11A to 11C are longitudinal aberration diagrams when the lens is focused on an object at infinity and at a distance of 0.9 m in Numerical Example 1. [Diagram 3] FIG. 11 is a cross-sectional view of a lens according to Numerical Example 2 when focused on an object at infinity. [Figure 4] 11A to 11C are longitudinal aberration diagrams when an object at infinity and an object at a distance of 0.7 m are focused in Numerical Example 2. [Diagram 5] FIG. 11 is a cross-sectional view of a lens according to Numerical Example 3 when focused on an object at infinity. [Figure 6] 13A to 13C are longitudinal aberration diagrams when an object at infinity and an object at a distance of 1.1 m are focused in Numerical Example 3. [Figure 7] FIG. 13 is a lens sectional view of Numerical Example 4 when focused on an object at infinity. [Figure 8] 13A to 13C are longitudinal aberration diagrams when the lens is focused on an object at infinity and at a distance of 1.1 m in Numerical Example 4. [Figure 9] FIG. 13 is a lens sectional view of Numerical Example 5 when focused on an object at infinity. [Figure 10] 13A to 13C are longitudinal aberration diagrams when the lens is focused on an object at infinity and at a distance of 0.7 m in Numerical Example 5. [Figure 11] FIG. 1 is a schematic diagram of a main part of an imaging device according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. First, the characteristics of the single focal length lens of the present invention will be described in accordance with each conditional expression. In order to achieve a wide angle of view, a small front lens diameter for a large aperture lens, and correction of high-order lateral chromatic aberration, the present invention is characterized by specifying the ratio between the composite focal length of three negative lenses arranged on the object side in the first lens group and the focal length of the entire system, and the average value of the Abbe numbers of two negative lenses arranged on the object side in the first lens group.

[0011] Specifically, the single focal length lens of the present invention has a first lens group that does not move for focusing, and one or two second lens groups (movable lens groups) that move for focusing, which are arranged in order from the object side to the image side, and the intervals between adjacent lens groups all change for focusing, and the first lens group has three negative lenses arranged consecutively from the most object side, the focal length of the single focal length lens is f, the composite focal length of the three negative lenses is f1n, and the average Abbe number of the two negative lenses that are arranged consecutively from the most object side among the three negative lenses is ν1n, 0.3<|f1n / f|<0.98 (1) 62<ν1n<96 (2) The present invention is characterized in that the following conditional expression is satisfied: Here, the Abbe number ν is expressed by the refractive indexes of the material for the F line (wavelength 486.1 nm), C line (wavelength 656.3 nm), and d line (wavelength 587.6 nm) as NF, NC, and Nd, respectively. ν=(Nd-1) / (NF-NC) It is expressed by the formula:

[0012] In the present invention, there is provided, in order from the object side, at least a first lens group that is fixed during focusing, and a second lens group that moves during focusing, and the first lens group is configured to have three negative lenses from the object side. The optical action of this configuration will be described below.

[0013] During focusing, the first lens group is fixed and the second lens group is moved. By fixing the first lens group, which tends to be the heaviest in a wide-angle lens, and driving the second lens group, it is possible to reduce the load on the drive system.

[0014] Furthermore, by configuring the first lens group L1 to have, in order from the object side, a negative 11 lens, a negative 12 lens, and a negative 13 lens, it is possible to achieve a wide angle of view of the lens while suppressing an increase in the diameter of the lens closest to the object side in the first lens group L1.

[0015] Furthermore, by satisfying the above-mentioned expressions (1) and (2), it is possible to achieve both a compact, large-diameter, fixed focal length lens with a wide angle of view and correction of high-order lateral chromatic aberration.

[0016] Formula (1) specifies the ratio of the composite focal length of the three negative lenses arranged on the object side in the first lens group to the focal length of the first lens group. By satisfying formula (1), it is possible to efficiently achieve a reduction in the lens diameter of the first lens group L1 closest to the object side and high optical performance. If the upper limit of formula (1) is not satisfied, the effect of refracting off-axis light beams by the three negative lenses arranged on the object side in the first lens group L1 becomes weak, and the lens diameter of the first lens group L1 closest to the object side becomes large. If the lower limit of formula (1) is not satisfied, the refractive power of the three negative lenses arranged on the object side in the first lens group L1 becomes too strong, making it difficult to satisfactorily correct high-order chromatic aberration of magnification. More preferably, formula (1) is set as follows: 0.5<|f1n / f|<0.975 (1a)

[0017] Formula (2) specifies the average Abbe number of the two negative lenses arranged on the object side in the first lens group. By satisfying formula (2), low dispersion glass is used for the two negative lenses on the object side through which the off-axis ray height passes at a position higher than the optical axis, suppressing the deterioration of lateral chromatic aberration when the refractive power is increased. If the upper limit of formula (1) is not satisfied, the lateral chromatic aberration occurring in the two negative lenses arranged on the object side becomes too large, and when the lateral chromatic aberration is corrected, high-order lateral chromatic aberration remains. If the lower limit of formula (1) is not satisfied, the refractive index of the two negative lenses becomes too small with the existing glasses, making it difficult to satisfactorily correct the curvature of field. More preferably, formula (2) should be set as follows: 64<ν1n<96 (2a)

[0018] As a further desirable aspect of the single focal length lens of the present invention, when the average focal length of the 11th lens which is located closest to the object among the three negative lenses and the 12th lens which is located second closest to the object among the three negative lenses is defined as f12n, and the focal length of the 13th lens which is located third closest to the object among the three negative lenses is defined as f13n, the single focal length lens of the present invention is characterized in that it satisfies the following conditional expression: 0.3 <f13n / f12n<0.9 (3)

[0019] Formula (3) specifies the ratio of the focal lengths of the negative 11 and 12 lenses, which are arranged on the object side in the first lens group, to the negative 13 lens. Compared to the negative 11 and 12 lenses, the refractive power of the negative 13 lens, which passes through a position where the height of off-axis rays passes close to the optical axis, is strengthened to reduce the diameter of the front lens and provide a configuration advantageous for correction of high-order lateral chromatic aberration.

[0020] If the upper limit of formula (3) is not satisfied, the effect of refracting off-axis light beams by the negative 13 lens will be weak, and in order to reduce the diameter of the front lens, it will be necessary to strengthen the refractive power of the negative 11 and 12 lenses, making it difficult to correct high-order lateral chromatic aberration. If the lower limit of formula (3) is not satisfied, the refractive power of the negative 13 lens will be too strong, making it difficult to satisfactorily correct field curvature over the entire object distance. More preferably, formula (3) should be set as follows: 0.3 <f13n / f12n<0.88 (3a) As a further desirable aspect of the single focal length lens of the present invention, when the refractive index of the 13th lens, which is the third lens from the object side among the three negative lenses, is defined as N13, the single focal length lens of the present invention is characterized in that it satisfies the following conditional formula: 1.7 <N13<2.0 (4)

[0021] If the upper limit of formula (4) is not satisfied, the dispersion of the negative 13 lens becomes too small for existing materials, making it difficult to satisfactorily correct high-order lateral chromatic aberration. If the lower limit of formula (4) is not satisfied, when the refractive power of the negative 13 lens is increased, the curvature becomes too sharp, making it difficult to satisfactorily correct the curvature of field generated by the negative 13 lens. More preferably, formula (4) is set as follows: 1.75 <N13<1.95 (4a)

[0022] As a further desirable aspect of the single focal length lens of the present invention, when the radius of curvature of the image side surface of the 12 lens that is the second most from the object side among the three negative lenses is R12i, and the radius of curvature of the object side surface of the 13 lens that is the third most from the object side among the three negative lenses is R13o, the following conditional expression is satisfied: -1.0<(R12i+R13o) / (R12i-R13o)<0 (5)

[0023] If the upper limit of formula (5) is not satisfied, the effect of refracting off-axis light beams in the air space formed between the negative 12 lens and the negative 13 lens becomes weak, and the lens diameter of the lens closest to the object in the first lens group L1 becomes large. If the lower limit of formula (4) is not satisfied, the effect of refracting off-axis light beams in the air space formed between the negative 11 lens and the negative 12 lens becomes too strong, making it difficult to satisfactorily correct high-order lateral chromatic aberration and field curvature. More preferably, formula (5) is set as follows: -0.7<(R11i+R12o) / (R11i-R12o)<-0.2 (5a)

[0024] As a further desirable aspect of the single focal length lens of the present invention, the first lens group has a sub-lens group L1p arranged on the image side of the three negative lenses, and when the focal length of the sub-lens group L1p is f1p, the following conditional expression is satisfied: 1.0 <f1p / |f1n|<3.0 (6)

[0025] Formula (6) defines the ratio between the composite focal length of the three negative lenses and the focal length of the sub-lens group L1p located on the image side of the three negative lenses. By giving the sub-lens group L1p positive refractive power, the lateral chromatic aberration generated by the three negative lenses located on the object side is corrected.

[0026] If the upper limit of formula (6) is not satisfied, the positive refractive power of the sub lens group L1p will be too weak, resulting in under-correction of the lateral chromatic aberration occurring in the three negative lenses arranged on the object side. If the lower limit of formula (6) is not satisfied, the positive refractive power of the sub lens group L1p will be too strong, resulting in over-correction of the lateral chromatic aberration occurring in the three negative lenses arranged on the object side. More preferably, formula (8) is set as follows: 1.5 <f1p / |f1n|<2.5 (6a)

[0027] As a further preferable aspect of the single focal length lens of the present invention, the sub-lens group L1p has at least one negative lens and two or more positive lenses, and is characterized in that when the partial dispersion ratio of the negative lens included in the sub-lens group L1p is θgFn and the average partial dispersion ratio of the multiple positive lenses included in the sub-lens group L1p is θgFp, the following conditional formula is satisfied. 0.03<θgFn-θgFp<0.06 (7)

[0028] Here, the partial dispersion ratio θgF is expressed by the following formula: where Ng, NF, and NC are the refractive indices of the materials for the g-line (wavelength 435.8 nm), F-line (wavelength 486.1 nm), and C-line (wavelength 656.3 nm), respectively. θgF=(Ng-NF) / (NF-NC) It is expressed by the formula:

[0029] Equation (7) specifies the difference in partial dispersion ratio between the negative lens and the two positive lenses included in the sub-lens group L1p. In order to correct the secondary spectrum of lateral chromatic aberration, the sub-lens group L1p is configured to have a negative lens and a positive lens, thereby adjusting the partial dispersion ratio within the sub-lens group L1p.

[0030] If the upper limit of formula (7) is not satisfied, the secondary spectrum of lateral chromatic aberration will be over-corrected. If the lower limit of formula (7) is not satisfied, the secondary spectrum of lateral chromatic aberration will be under-corrected. More preferably, formula (7) should be set as follows: 0.032<θgFn-θgFp<0.05 (7a)

[0031] As a further preferable aspect of the single focal length lens of the present invention, when the average dispersion of the positive lenses included in the sub-lens group L1p is taken as ν1p, the following conditional expression is satisfied: 30<ν1p<50 (8)

[0032] If the upper limit of formula (8) is not satisfied, the dispersion of the positive lens included in the sub-lens group L1p becomes too large, and the refractive power of the positive lens becomes too strong in order to correct the lateral chromatic aberration generated by the three negative lenses, resulting in deterioration of spherical aberration and astigmatism. If the lower limit of formula (1) is not satisfied, the dispersion of the positive lens included in the sub-lens group L1p becomes too small, making it difficult to correct the axial chromatic aberration. More preferably, formula (8) is set as follows: 35<ν1p<40 (8a)

[0033] As a further desirable aspect of the single focal length lens of the present invention, when the focal length of the first lens group is f1 and the focal length of the moving lens group closest to the object among the first or second moving lens group is f2, the following conditional expression is satisfied: 0.04 <f1 / f2<1.5 (9)

[0034] Equation (9) specifies the ratio of the focal length f1 of the first lens group L1 to the focal length f2 of the second lens group L2. If the upper limit of equation (9) is not satisfied, the refractive power of the first lens group L1 will be too weak. As a result, the height of the axial ray incident on the second lens group will increase, and the diameter of the second lens group, which is a movable group, will become large. If the lower limit of equation (9) is not satisfied, the refractive power of the first lens group L1 will be too strong. As a result, high-order chromatic aberration of magnification will occur in the first lens group L1. It is more preferable to set equation (9) as follows: 0.05 <f1 / f2<1.4 (9a)

[0035] As a further desirable aspect of the single focal length lens of the present invention, when the focal length of the moving lens group (second lens group) closest to the object among the first or second moving lens group is f2, and the focal length of the moving lens group (third lens group) closest to the image among the first or second moving lens group is f3, the following conditional expression is satisfied: 3.0 <f2 / f3<60 (10)

[0036] Moreover, formula (10) specifies the ratio of the focal length f3 of the third lens group L3 to the focal length f2 of the second lens group L2. If the upper limit of formula (10) is not satisfied, the refractive power of the second lens group L2 becomes too strong, and the height of the off-axis light beam of the third lens group becomes low. This reduces the ability of the third lens group to correct chromatic aberration of magnification, and the optical performance deteriorates. If the lower limit of formula (10) is not satisfied, the height of the on-axis light beam of the third lens group L3, which is disposed closer to the image side than the second lens group L2, becomes too high, and the third lens group becomes large. In particular, when the aperture diaphragm is disposed closer to the image side than the second lens group L2, the aperture diaphragm becomes large. More preferably, formula (10) is set as follows. 3.5 <f2 / f3<50 (10a)

[0037] Furthermore, the imaging device of the present invention is characterized by having the fixed focal length lens of each embodiment and a solid-state imaging element having a predetermined effective imaging range for receiving an image formed by the fixed focal length lens. The specific configuration of the fixed focal length lens of the present invention will be described below based on the characteristics of the lens configuration of Numerical Examples 1 to 4 corresponding to Examples 1 to 4. EXAMPLES

[0038] Fig. 1 is a cross-sectional view of a single focal length lens according to embodiment 1 (numerical embodiment 1) of the present invention, when the lens is focused at infinity. In Fig. 2, (a) shows longitudinal aberration diagrams when the lens is focused on an object at infinity, and (b) shows longitudinal aberration diagrams when the lens is focused at 0.9 m. The focal length values ​​are the values ​​in the numerical embodiments described later, expressed in mm. This is the same for all of the numerical embodiments described below.

[0039] In FIG. 1, from the object side, there is a first lens group L1 with positive refractive power that does not move when focusing. Furthermore, there is a second lens group L2 with positive refractive power that moves toward the object side when focusing from infinity to a close-distance object, and a third lens group L3 with positive refractive power that moves toward the object side by a different amount of movement than the second lens group L2. SP is an aperture stop. I is an image plane, and when used as an imaging optical system for a broadcast television camera, video camera, or digital still camera, it corresponds to the imaging plane of a solid-state imaging element (photoelectric conversion element) that receives an image formed by a fixed focal length lens and photoelectrically converts it. When used as an imaging optical system for a film camera, it corresponds to the film surface to which the image formed by the fixed focal length lens is exposed.

[0040] In the longitudinal aberration diagram, the solid and dashed lines in the spherical aberration are the d-line and g-line, respectively. The dashed and solid lines in the astigmatism are the meridional image plane and the sagittal image plane, respectively, and the dashed and dotted line in the lateral chromatic aberration is the g-line. ω is the half angle of view, and Fno is the F-number. In the longitudinal aberration diagram, the spherical aberration is drawn on a scale of 0.4 mm, the astigmatism is 0.4 mm, the distortion is 5%, and the lateral chromatic aberration is 0.05 mm.

[0041] Next, the first lens group L1 in this embodiment will be described. The first lens group L1 corresponds to the first to eleventh surfaces. The first lens group L1 is composed of, in order from the object side, a meniscus concave lens convex to the object side, a meniscus concave lens convex to the object side, a biconcave lens, a cemented lens of a meniscus concave lens convex to the object side and a meniscus convex lens convex to the object side, and a biconvex lens. The first surface is aspheric and mainly corrects distortion aberration and astigmatism. The tenth surface is aspheric and mainly corrects spherical aberration. The second lens group L2 corresponds to the twelfth to eighteenth surfaces. The second lens group L2 is composed of, in order from the object side, a cemented lens of a biconvex lens and a biconcave lens, a biconcave lens, and a biconvex lens. The third lens group L3 corresponds to the 19th to 26th surfaces. The third lens group L3 is composed of, in order from the object side, an aperture stop SP, a cemented lens consisting of a meniscus convex lens with a concave surface on the object side and a meniscus concave lens with a concave surface on the object side, a biconvex lens, and a meniscus convex lens with a concave surface on the object side. The 25th surface is aspheric and mainly corrects spherical aberration and astigmatism.

[0042] Numerical Example 1 corresponding to the above-mentioned Example 1 will be described. In all the numerical examples, not just Numerical Example 1, i indicates the order of the surface (optical surface) from the object side, ri indicates the radius of curvature of the i-th surface from the object side, and di indicates the distance (on the optical axis) between the i-th surface and the (i+1)th surface from the object side. Also, ndi and νdi indicate the refractive index, Abbe number, and partial dispersion ratio of the medium (optical member) between the i-th surface and the (i+1)th surface, and BF indicates the back focus in air equivalent. The aspheric shape is expressed by the following formula, with the X-axis in the optical axis direction, the H-axis perpendicular to the optical axis, and the light traveling direction being positive, R being the paraxial radius of curvature, k being the cone constant, and A4, A6, A8, A10, A12, A14, and A16 being aspheric coefficients, respectively. Also, "eZ" is "×10 -Z " means.

number

[0043] Table 1 shows the corresponding values ​​of each conditional expression in this embodiment. This embodiment satisfies expressions (1) to (10), and achieves a compact large-aperture wide-angle lens with a shooting angle of view (angle of view) of 99.1° and F1.73. It also achieves a single focal length lens with high optical performance in which various aberrations are well corrected over the entire focus range. It is essential for the single focal length lens of the present invention to satisfy expressions (1) to (2), but it is not necessary for expressions (3) to (10) to be satisfied. However, even better effects can be achieved if at least one of expressions (3) to (10) is satisfied. This is similar to the other embodiments.

[0044] FIG. 11 is a schematic diagram of the main parts of a digital still camera. In FIG. 11, an optical system 1 is the photographic optical system of this numerical embodiment. The photographic optical system 1 is held by a lens barrel 2, which is a holding member. Reference numeral 20 denotes a camera body. The camera body 20 is composed of a quick-return mirror 3, a focusing screen 4, a penta roof prism 5, an eyepiece 6, and the like. The quick-return mirror 3 reflects the light beam from the photographic optical system 10 upward. The focusing screen 4 is disposed at an image forming position of the photographic optical system 10. The penta roof prism 5 converts an inverse image formed on the focusing screen 4 into an erect image. An observer observes the erect image through the eyepiece 6. Reference numeral 7 denotes a photosensitive surface, on which a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or a CMOS sensor that receives an image, or a silver halide film is disposed. During photographing, the quick-return mirror 3 is withdrawn from the optical path, and an image is formed on the photosensitive surface 7 by the photographic optical system 10. The optical system of the present invention can be applied to broadcast television cameras, movie cameras, video cameras, digital still cameras, silver halide photography cameras, and the like.

[0045] In this way, by applying the fixed focal length lens of the present invention to a single-lens reflex camera, a television camera, or a cinema camera, an imaging device having high optical performance is realized. EXAMPLES

[0046] Fig. 3 is a cross-sectional view of a single focal length lens according to the second embodiment (Numerical Example 2) of the present invention, when the lens is focused on infinity. In Fig. 4, (a) shows longitudinal aberration diagrams when an object is focused on at infinity, and (b) shows longitudinal aberration diagrams when an object is focused on at 0.7 m.

[0047] 3, from the object side, there is a first lens group L1 with positive refractive power that does not move during focusing. In addition, there are a second lens group L2 with positive refractive power that moves toward the object side when focusing from infinity to a close-distance object, and a third lens group L3 with positive refractive power that moves toward the object side by a different amount of movement than the second lens group L2.

[0048] Next, the first lens group L1 in this embodiment will be described. The first lens group L1 corresponds to the first surface to the eleventh surface. The first lens group L1 is composed of, in order from the object side, a meniscus concave lens convex to the object side, a meniscus concave lens convex to the object side, a biconcave lens, a cemented lens of a meniscus concave lens convex to the object side and a meniscus convex lens convex to the object side, and a biconvex lens. The first surface is aspheric and mainly corrects distortion aberration and astigmatism. The tenth surface is aspheric and mainly corrects spherical aberration. The second lens group L2 corresponds to the twelfth surface to the eighteenth surface. The second lens group L2 is composed of, in order from the object side, a cemented lens of a biconvex lens and a biconcave lens, a meniscus concave lens concave to the object side, and a biconvex lens. The third lens group L3 corresponds to the nineteenth surface to the twenty-sixth surface. The third lens group L3 is composed of, in order from the object side, an aperture stop SP, a cemented lens consisting of a meniscus convex lens with a concave surface on the object side and a meniscus concave lens with a concave surface on the object side, a biconvex lens, and a meniscus convex lens with a concave surface on the object side. The 25th surface is aspheric and mainly corrects spherical aberration and astigmatism.

[0049] The corresponding values ​​of each conditional expression in this embodiment are shown in Table 1. This embodiment satisfies expressions (1) to (10), and achieves a compact large-aperture wide-angle lens with a shooting angle of view (angle of view) of 112.6° and F1.74. It also achieves a single focal length lens with high optical performance in which various aberrations are well corrected across the entire focus range. EXAMPLES

[0050] Fig. 5 is a cross-sectional view of a single focal length lens according to a third embodiment (Numerical Example 3) of the present invention, when the lens is focused on infinity. In Fig. 6, (a) shows longitudinal aberration diagrams when an object is focused on at infinity, and (b) shows longitudinal aberration diagrams when an object is focused on at 1.1 m.

[0051] 5, from the object side, there is a first lens group L1 with positive refractive power that does not move during focusing. In addition, there are a second lens group L2 with positive refractive power that moves toward the object side when focusing from infinity to a close-distance object, and a third lens group L3 with positive refractive power that moves toward the object side by a different amount of movement than the second lens group L2.

[0052] Next, the first lens group L1 in this embodiment will be described. The first lens group L1 corresponds to the first to eleventh surfaces. The first lens group L1 is composed of, in order from the object side, a meniscus concave lens convex to the object side, a meniscus concave lens convex to the object side, a biconcave lens, a cemented lens of a meniscus concave lens convex to the object side and a meniscus convex lens convex to the object side, and a biconvex lens. The first surface is aspheric and mainly corrects distortion aberration and astigmatism. The tenth surface is aspheric and mainly corrects spherical aberration. The second lens group L2 corresponds to the twelfth to eighteenth surfaces. The second lens group L2 is composed of, in order from the object side, a cemented lens of a biconvex lens and a biconcave lens, a biconcave lens, and a biconvex lens. The third lens group L3 corresponds to the 19th to 26th surfaces. The third lens group L3 is composed of, in order from the object side, an aperture stop SP, a cemented lens consisting of a meniscus convex lens with a concave surface on the object side and a meniscus concave lens with a concave surface on the object side, a biconvex lens, and a meniscus convex lens with a concave surface on the object side. The 25th surface is aspheric and mainly corrects spherical aberration and astigmatism.

[0053] The corresponding values ​​of each conditional expression in this embodiment are shown in Table 1. This embodiment satisfies expressions (1) to (10), and achieves a compact large-aperture wide-angle lens with a shooting angle of view (angle of view) of 89.0° and F1.46. It also achieves a single focal length lens with high optical performance in which various aberrations are well corrected across the entire focus range. EXAMPLES

[0054] Fig. 7 is a cross-sectional view of a single focal length lens according to the fourth embodiment (numerical embodiment) of the present invention, when the lens is focused at infinity. In Fig. 8, (a) shows longitudinal aberration diagrams when an object is focused at infinity, and (b) shows longitudinal aberration diagrams when an object is focused at 1.0 mm.

[0055] 7, from the object side, there is a first lens group L1 with positive refractive power that does not move during focusing. In addition, there are a second lens group L2 with negative refractive power that moves toward the object side when focusing from infinity to a close object, and a third lens group L3 with positive refractive power that moves toward the object side by a different amount of movement than the second lens group L2.

[0056] Next, the first lens group L1 in this embodiment will be described. The first lens group L1 corresponds to the first to eleventh surfaces. The first lens group L1 is composed of, in order from the object side, a meniscus concave lens convex to the object side, a meniscus concave lens convex to the object side, a biconcave lens, a cemented lens of a meniscus concave lens convex to the object side and a meniscus convex lens convex to the object side, and a biconvex lens. The first surface is aspheric and mainly corrects distortion aberration and astigmatism. The tenth surface is aspheric and mainly corrects spherical aberration. The second lens group L2 corresponds to the twelfth to eighteenth surfaces. The second lens group L2 is composed of, in order from the object side, a cemented lens of a biconvex lens and a biconcave lens, a biconcave lens, and a biconvex lens. The third lens group L3 corresponds to the 19th to 26th surfaces. The third lens group L3 is composed of, in order from the object side, an aperture stop SP, a cemented lens consisting of a meniscus convex lens with a concave surface on the object side and a meniscus concave lens with a concave surface on the object side, a biconvex lens, and a meniscus convex lens with a concave surface on the object side. The 25th surface is aspheric and mainly corrects spherical aberration and astigmatism.

[0057] The corresponding values ​​of each conditional expression in this embodiment are shown in Table 1. This embodiment satisfies expressions (1) to (10), and achieves a compact large-aperture wide-angle lens with a shooting angle of view (angle of view) of 94.5° and F1.46. It also achieves a single focal length lens with high optical performance in which various aberrations are well corrected across the entire focus range. EXAMPLES

[0058] Fig. 9 is a cross-sectional view of a single focal length lens according to the fifth embodiment (Numerical Example 5) of the present invention, when the lens is focused at infinity. In Fig. 10, (a) shows longitudinal aberration diagrams when an object is focused at infinity, and (b) shows longitudinal aberration diagrams when an object is focused at 0.7 mm.

[0059] 9, from the object side, there is a first lens unit L1 with positive refractive power that does not move during focusing, and a second lens unit L2 with positive refractive power that moves toward the object side when focusing from infinity to a close object.

[0060] Next, the first lens group L1 in this embodiment will be described. The first lens group L1 corresponds to surfaces 1 to 11. The first lens group L1 is composed of, in order from the object side, a meniscus concave lens convex to the object side, a meniscus concave lens convex to the object side, a biconcave lens, a cemented lens of a meniscus concave lens convex to the object side and a meniscus convex lens convex to the object side, and a biconvex lens. The first surface is aspheric and mainly corrects distortion aberration and astigmatism. The tenth surface is aspheric and mainly corrects spherical aberration. The second lens group L2 corresponds to surfaces 12 to 26. The second lens group L2 is composed of, in order from the object side, a cemented lens of a biconvex lens and a biconcave lens, a meniscus lens concave to the object side, a biconvex lens, an aperture stop SP, a cemented lens of a meniscus convex lens concave to the object side and a meniscus concave lens concave to the object side, a biconvex lens, and a meniscus convex lens concave to the object side. Furthermore, surface No. 26 is aspheric, and is used primarily to correct spherical aberration and astigmatism.

[0061] The corresponding values ​​of each conditional expression in this embodiment are shown in Table 1. This embodiment satisfies expressions (1) to (10), and achieves a compact large-aperture wide-angle lens with a shooting angle of view (angle of view) of 107° and F1.7. It also achieves a single focal length lens with high optical performance in which various aberrations are well corrected across the entire focus range.

[0062] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention.

[0063] (Numerical Example 1) Unit: mm Surface Data Surface number rd nd vd θgF 1* 130.422 2.32 1.60311 60.6 0.5415 2 28.297 12.90 3 105.311 1.88 1.59522 67.7 0.5442 4 31.187 10.28 5 -113.835 1.88 1.83481 42.7 0.5648 6 51.770 0.40 7 31.788 1.55 1.96300 24.1 0.6211 8 22.540 9.57 1.60562 43.7 0.5721 9 65.412 0.38 10* 32.219 9.62 1.91650 31.6 0.5911 11 -98.423 (variable) 12 57.960 5.78 1.85026 32.3 0.5929 13 -46.620 1.50 1.60342 38.0 0.5835 14 19.625 5.08 15 -76.613 1.30 1.65412 39.7 0.5737 16 76.613 0.20 17 26.753 6.55 1.49700 81.5 0.5375 18 -64.454 (variable) 19(Aperture) ∞ 6.41 20 -21.192 5.28 1.48749 70.2 0.5300 21 -14.938 1.28 1.96300 24.1 0.6212 22 -38.271 0.24 23 103.462 8.20 1.61800 63.4 0.5401 24 -28.163 0.19 25* -116.747 6.00 1.85100 40.4 0.5573 26 -33.776 (variable) Image plane ∞ Aspheric Data Front page K = 0.00000e+000 A 4= 6.14171e-006 A 6=-3.97885e-009 A 8= 3.38424e-012 A10=-1.90087e-015 A12= 1.60351e-018 A14=-1.18002e-021 A16= 4.07695e-025 Side 10 K =-5.01704e+000 A 4= 8.41689e-006 A 6=-2.53199e-008 A 8= 8.06368e-011 A10=-3.60389e-013 A12= 1.23510e-015 A14=-2.29723e-018 A16= 1.74624e-021 Page 25 K = 0.00000e+000 A 4=-1.19705e-005 A 6=-2.93407e-009 A 8=-6.98369e-012 A10=-1.35994e-014 Various data Focal length 18.46 F-number 1.73 Angle of view: 49.53 Image height 21.64 Lens length 144.17 BF 39.17 Focusing distance Infinity 0.9m d11 5.49 4.91 d18 0.72 0.85 d26 39.17 39.17 Lens Group Data Group starting plane focal length 1 1 107.18 2 12 1610.01 3 19 36.74

[0064] (Numerical Example 2) Unit: mm Surface Data Surface number rd nd vd θgF 1* 191.858 2.32 1.59282 68.6 0.5441 2 31.297 14.00 3 100.561 1.88 1.59522 67.7 0.5442 4 25.112 13.45 5 -89.884 1.88 1.77250 49.6 0.5520 6 74.496 1.59 7 119.957 1.55 1.84666 23.8 0.6205 8 22.995 11.06 1.72047 34.7 0.5834 9 115.824 0.38 10* 30.517 12.21 1.85026 32.3 0.5929 11 -67.704 (variable) 12 44.448 3.70 1.69350 53.2 0.5473 13 -107.775 1.50 1.53775 74.7 0.5392 14 17.350 5.08 15 -51.842 1.30 1.72000 43.7 0.5699 16 -589.091 0.20 17 34.817 5.07 1.43875 94.7 0.5340 18 -36.325 (variable) 19(Aperture) ∞ 6.85 20 -32.173 6.69 1.49700 81.5 0.5375 21 -12.673 1.28 1.90525 35.0 0.5848 22 -62.260 0.24 23 104.543 8.20 1.53775 74.7 0.5392 24 -21.307 0.19 25* -188.591 6.00 1.61800 63.3 0.5441 26 -28.540 (variable) Image plane ∞ Aspheric Data Front page K = 0.00000e+000 A 4= 7.03634e-006 A 6=-4.51273e-009 A 8= 2.81971e-012 A10= 3.18507e-016 A12=-1.28428e-018 A14= 6.24156e-022 A16=-5.21067e-026 Side 10 K =-2.01451e+000 A 4=-1.37386e-006 A 6= 1.63482e-009 A 8= 4.06386e-012 A10=-1.15890e-013 A12= 7.24302e-016 A14=-1.78359e-018 A16= 1.60459e-021 Page 25 K = 1.02126e+002 A 4=-1.46485e-005 A 6= 1.25188e-009 A 8=-3.41762e-011 A10=-6.92519e-015 Various data Focal length 14.42 F-number 1.74 Angle of view: 56.31 Image height 21.64 Lens length 151.49 BF 37.99 Focusing distance infinity 0.7m d11 8.56 7.23 d18 -1.68 -0.73 d26 37.99 37.99 Lens Group Data Group starting plane focal length 1 1 62.72 2 12 1112.16 3 19 37.23

[0065] (Numerical Example 3) Unit: mm Surface Data Surface number rd nd vd θgF 1* 90.398 2.32 1.60311 60.6 0.5415 2 26.831 12.96 3 200.730 1.88 1.43875 94.9 0.5340 4 31.472 10.14 5 -66.900 1.88 1.91650 31.6 0.5911 6 49.528 0.39 7 47.233 1.55 1.84666 23.8 0.6205 8 29.140 8.73 1.89190 37.1 0.5780 9 147.881 0.38 10* 37.721 10.76 1.90525 35.0 0.5848 11 -92.002 (variable) 12 50.534 5.92 1.83481 42.7 0.5648 13 -82.035 1.50 1.48749 70.2 0.5300 14 21.985 5.08 15 -717.639 1.30 1.59270 35.3 0.5933 16 77.617 0.20 17 36.656 5.30 1.43875 94.9 0.5340 18 -144.381 (variable) 19(Aperture) ∞ 3.76 20 -31.418 6.75 1.43875 94.9 0.5340 21 -15.693 1.28 1.85025 30.1 0.5979 22 -64.147 0.24 23 222.793 8.20 1.53775 74.7 0.5392 24 -25.586 0.19 25* -184.540 6.00 1.72916 54.7 0.5444 26 -34.480 (variable) Image plane ∞ Aspheric Data Front page K = 0.00000e+000 A 4= 5.92280e-006 A 6=-2.98393e-009 A 8= 2.44763e-012 A10=-8.41223e-016 A12= 1.91996e-018 A14=-2.67484e-021 A16= 1.29985e-024 Side 10 K =-7.08223e+000 A 4= 7.69659e-006 A 6=-2.66706e-008 A 8= 9.16354e-011 A10=-3.57486e-013 A12= 1.01920e-015 A14=-1.62923e-018 A16= 1.07255e-021 Page 25 K =-3.76787e+001 A 4=-9.85158e-006 A 6=-2.69403e-009 A 8= 9.19967e-012 A10=-3.39311e-014 A12= 1.50706e-017 Various data Focal length 22.01 F-number 1.46 Angle of view: 44.51 Image height 21.64 Lens length 144.80 BF 38.97 Focusing distance: Infinity 1.1m d11 8.08 7.30 d18 1.03 1.34 d26 38.97 38.97 Lens Group Data Group starting plane focal length 1 1 204.26 2 12 165.32 3 19 44.17

[0066] (Numerical Example 4) Unit: mm Surface Data Surface number rd nd vd θgF 1* 277.434 2.32 1.43875 94.9 0.5340 2 28.989 12.50 3 105.241 1.88 1.43875 94.9 0.5340 4 24.660 12.82 5 -70.435 1.88 1.91650 31.6 0.5911 6 52.652 0.39 7 40.379 1.55 1.96300 24.1 0.6212 8 25.514 9.15 1.89190 37.1 0.5780 9 77.725 0.38 10* 35.820 10.15 1.90525 35.0 0.5848 11 -84.133 (variable) 12 48.252 5.04 1.89190 37.1 0.5780 13 -112.789 1.50 1.48749 70.2 0.5300 14 20.129 5.08 15 -151.386 1.30 1.62004 36.3 0.5879 16 68.259 0.20 17 33.100 5.60 1.43875 94.9 0.5340 18 -82.388 (variable) 19(Aperture) ∞ 4.16 20 -28.166 7.91 1.53775 74.7 0.5392 21 -14.531 1.28 1.90366 31.3 0.5963 22 -46.066 0.24 23 202.233 8.20 1.53775 74.7 0.5392 24 -25.630 0.19 25* -291.017 6.00 1.65160 58.5 0.5425 26 -34.982 (variable) Image plane ∞ Aspheric Data Front page K = 0.00000e+000 A 4= 7.03420e-006 A 6=-4.13265e-009 A 8= 2.21096e-012 A10= 1.10467e-017 A12= 2.14510e-019 A14=-7.21221e-022 A16= 3.45393e-025 Side 10 K =-5.70964e+000 A 4= 5.94964e-006 A 6=-2.16871e-008 A 8= 7.92806e-011 A10=-3.57414e-013 A12= 1.15433e-015 A14=-2.08105e-018 A16= 1.55071e-021 Page 25 K =-5.01387e+001 A 4=-1.02280e-005 A 6=-1.54599e-009 A 8=-8.36411e-014 A10=-2.42132e-014 A12= 1.63653e-017 Various data Focal length 20.00 F-number 1.46 Angle of view: 47.25 Image height 21.64 Lens length 146.11 BF 38.99 Focusing distance Infinity 1.0m d11 7.84 6.86 d18 -0.44 0.11 d26 38.99 38.99 Lens Group Data Group starting plane focal length 1 1 220.87 2 12 220.96 3 19 39.97

[0067] (Numerical Example 5) Unit: mm Surface Data Surface number rd nd vd θgF 1* 151.331 2.32 1.59282 68.6 0.5440 2 28.534 8.94 3 55.434 1.88 1.59522 67.7 0.5442 4 23.089 11.77 5 -148.522 1.88 1.77250 49.6 0.5520 6 42.593 1.59 7 38.523 1.55 1.85478 24.8 0.6122 8 19.575 10.21 1.83481 42.7 0.5648 9 147.945 0.38 10* 24.526 7.92 1.89190 37.1 0.5780 11 -187.156 (variable) 12 85.468 2.57 1.84666 23.8 0.6205 13 -295.258 1.50 1.59522 67.7 0.5442 14 11.797 5.08 15 -61.888 1.30 1.88300 40.8 0.5667 16 -1124.407 0.20 17 29.283 4.34 1.53775 74.7 0.5392 18 -54.605 0.00 19(Aperture) ∞ 3.51 20 -37.801 5.79 1.43875 94.9 0.5340 21 -14.888 1.28 2.00100 29.1 0.5997 22 -47.475 0.24 23 84.145 8.20 1.53775 74.7 0.5392 24 -20.225 0.19 25* -143.648 6.00 1.60300 65.4 0.5401 26 -25.268 (variable) Image plane ∞ Aspheric Data Front page K = 0.00000e+000 A 4= 7.17772e-006 A 6=-4.87004e-009 A 8= 3.35022e-012 A10=-7.03257e-016 A12=-2.36736e-019 A14= 1.27546e-022 A16=-2.33649e-026 Side 10 K =-1.02314e+000 A 4=-1.71879e-006 A 6=-2.24861e-009 A 8=-6.84601e-012 A10=-1.25306e-014 A12= 6.24569e-016 A14=-2.28633e-018 A16= 2.42705e-021 Page 25 K = 7.18657e+001 A 4=-2.22861e-005 A 6=-2.59983e-009 A 8=-6.26774e-011 A10=-8.74449e-014 Focal length 16.00 F-number 1.74 Angle of view: 53.52 Image height 21.64 Lens length 127.35 BF 35.73 Focusing distance Infinity 1.0m d11 2.98 2.38 d26 35.73 36.32 Lens Group Data Group starting plane focal length 1 1 29.32 2 12 26.72

[0068] [Table 1] [Explanation of symbols]

[0069] L1 First lens group L2 Second lens group

Claims

1. A single focal length lens having a first lens group that does not move for focusing and one or two movable lens groups that move for focusing, which are arranged in order from an object side to an image side, the first lens group includes three negative lenses arranged consecutively from the most object side; the first lens group has a sub-lens group L1p arranged on the image side of the three negative lenses, The sub-lens group L1p has a negative lens and a plurality of positive lenses, The focal length of the single focal length lens is f, the composite focal length of the three negative lenses is f1n, the average Abbe number of the two negative lenses arranged consecutively from the object side among the three negative lenses is ν1n, the partial dispersion ratio of the negative lens included in the sub-lens group L1p is θgFn, and the average partial dispersion ratio of the plurality of positive lenses included in the sub-lens group L1p is θgFp, 0.3<|f1n / f|<0.98 64.2≦ν1n<96 0.03<θgFn-θgFp≦0.0408 A single focal length lens characterized by satisfying the following conditional expressions: Here, the Abbe number ν is expressed by the following formula: NF, NC, and Nd are the refractive indices of the material for the F line (wavelength 486.1 nm), C line (wavelength 656.3 nm), and d line (wavelength 587.6 nm), respectively. ν=(Nd-1) / (NF-NC) The partial dispersion ratio θgF is expressed by the following formula: where Ng is the refractive index of the material for the g-line (wavelength 435.8 nm), θgF=(Ng-NF) / (NF-NC) It is expressed by the formula:

2. Among the three negative lenses, an eleventh lens arranged closest to the object side and the three negative lenses The average focal length between the 12th lens and the 13th lens, which is the third lens from the object side among the three negative lenses, is f12n, and the average focal length between the 12th lens and the 12th lens, which is the second lens from the object side among the three negative lenses, is f13n. 0.3<f13n / f12n<0.9 2. The single focal length lens according to claim 1, which satisfies the following condition:

3. The refractive index of the 13th lens, which is the third lens from the object side among the three negative lenses, is defined as N13, 1.7<N13<2.0 3. The single focal length lens according to claim 1, wherein the following condition is satisfied:

4. The radius of curvature of the image side surface of the 12th lens, which is the second lens from the object side among the three negative lenses, is R12i, and the radius of curvature of the object side surface of the 13th lens, which is the third lens from the object side among the three negative lenses, is R13o.

4. The single focal length lens according to claim 1, which satisfies the condition: −1.0<(R12i+R13o) / (R12i−R13o)<0.

5. the first lens group has a sub-lens group L1p arranged on the image side of the three negative lenses, The focal length of the sub-lens group L1p is f1p, 1.0<f1p / |f1n|<3.0 5. The single focal length lens according to claim 1, which satisfies the following condition: 1.0 <0.015> ... 1.0 <0.015>

6. the first lens group has a sub-lens group L1p arranged on the image side of the three negative lenses, The sub-lens group L1p has a negative lens and a plurality of positive lenses, The partial dispersion ratio of the negative lens included in the sub-lens group L1p is θgFn, and the average partial dispersion ratio of the plurality of positive lenses included in the sub-lens group L1p is θgFp, 0.03<θgFn−θgFp<0.06 6. The single focal length lens according to claim 1, which satisfies the following condition: 1.0 <0.015> ... 1.0 <0.015>

7. the first lens group has a sub-lens group L1p arranged on the image side of the three negative lenses, The sub-lens group L1p has a plurality of positive lenses, The average dispersion of the plurality of positive lenses included in the sub-lens group L1p is defined as ν1p, 30<ν1p<50 7. The single focal length lens according to claim 1, which satisfies the following condition: 1.0 <0.015> ... 1.0 <0.015>

8. The focal length of the moving lens group closest to the image side among the first or second moving lens group is f3, 3.0<f2 / f3<60 8. The single focal length lens according to claim 1, which satisfies the following condition: 1.0 <0.015> ... 1.0 <0.015>

9. A single focal length lens having a first lens group that does not move for focusing and one or two movable lens groups that move for focusing, the first lens group and the second lens group being arranged in order from the object side to the image side, the first lens group includes three negative lenses arranged consecutively from the most object side, and a sub-lens group L1p arranged on the image side of the three negative lenses, The sub-lens group L1p has a negative lens and a plurality of positive lenses, The focal length of the single focal length lens is f, the composite focal length of the three negative lenses is f1n, the average Abbe number of the two negative lenses arranged consecutively from the most object side among the three negative lenses is ν1n, the focal length of the first lens group is f1, the focal length of the moving lens group closest to the object side among the one or two moving lens groups is f2, the partial dispersion ratio of the negative lens included in the sub-lens group L1p is θgFn, and the average partial dispersion ratio of the plurality of positive lenses included in the sub-lens group L1p is θgFp, 0.3<|f1n / f|<0.98 62<v1n<96 0.04<f1 / f2<1.5 0.03<θgFn−θgFp<0.06 A single focal length lens characterized by satisfying the following conditional expressions: Here, the Abbe number ν is expressed by the following formula: NF, NC, and Nd are the refractive indices of the material for the F line (wavelength 486.1 nm), C line (wavelength 656.3 nm), and d line (wavelength 587.6 nm), respectively. ν=(Nd-1) / (NF-NC) The partial dispersion ratio θgF is expressed by the following formula: where Ng is the refractive index of the material for the g-line (wavelength 435.8 nm), θgF=(Ng-NF) / (NF-NC) It is expressed by the formula:

10. A single focal length lens having a first lens group which does not move for focusing, and one or two movable lens groups which move for focusing, which are arranged in order from the object side to the image side, the first lens group includes three negative lenses arranged consecutively from the most object side, and a sub-lens group L1p arranged on the image side of the three negative lenses, The sub-lens group L1p has a plurality of positive lenses, The focal length of the single focal length lens is f, the composite focal length of the three negative lenses is f1n, the average Abbe number of the two negative lenses arranged consecutively from the most object side among the three negative lenses is ν1n, the focal length of the first lens group is f1, the focal length of the moving lens group closest to the object side among the one or two moving lens groups is f2, and the average dispersion of the multiple positive lenses included in the sub-lens group L1p is ν1p, 0.3<|f1n / f|<0.98 62<v1n<96 0.04<f1 / f2<1.5 30<ν1p<50 A single focal length lens characterized by satisfying the following conditional expressions: Here, the Abbe number ν is expressed by the following formula: NF, NC, and Nd are the refractive indices of the material for the F line (wavelength 486.1 nm), C line (wavelength 656.3 nm), and d line (wavelength 587.6 nm), respectively. ν=(Nd-1) / (NF-NC) It is expressed by the formula:

11. A single focal length lens having a first lens group which does not move for focusing, and one or two movable lens groups which move for focusing, which are arranged in order from the object side to the image side, the first lens group includes three negative lenses arranged consecutively from the most object side; The focal length of the single focal length lens is f, the composite focal length of the three negative lenses is f1n, the average Abbe number of the two negative lenses arranged consecutively from the most object side among the three negative lenses is ν1n, the focal length of the first lens group is f1, the focal length of the moving lens group closest to the object side among the first or second moving lens group is f2, and the focal length of the moving lens group closest to the image side among the first or second moving lens group is f3, 0.3<|f1n / f|<0.98 62<v1n<96 0.04<f1 / f2<1.5 3.0<f2 / f3<60 A single focal length lens characterized by satisfying the following conditional expressions: Here, the Abbe number ν is expressed by the following formula: NF, NC, and Nd are the refractive indices of the material for the F line (wavelength 486.1 nm), C line (wavelength 656.3 nm), and d line (wavelength 587.6 nm), respectively. ν=(Nd-1) / (NF-NC) It is expressed by the formula:

12. A single focal length lens according to any one of claims 1 to 11, an image sensor for capturing an image formed by the fixed focal length lens; An imaging device comprising:

Images