Imaging lens and camera device

Abstract

The present application provides an imaging lens and a camera device with the imaging lens, which realizes miniaturization and high-speed focusing, has less aberration variation during focusing, and has high optical performance. The imaging lens only has a positive first lens group, a positive second lens group, and a negative third lens group as lens groups in sequence from the object side. An aperture stop is arranged between the lens surface closest to the image side of the first lens group and the lens surface closest to the object side of the third lens group. During focusing, the first lens group and the third lens group do not move, and the second lens group moves. The first lens group is composed of a negative lens and a positive lens in sequence from the object side. The third lens group has a negative lens and a positive lens in sequence from the object side.

Description

[0001] This application is a divisional application of application No. "201911163077.X" with a filing date of November 22, 2019, and with the title of "Imaging Lens and Camera". TECHNICAL FIELD

[0002] The present application relates to an imaging lens and a camera. BACKGROUND

[0003] In the past, as an imaging lens that can be applied to a camera such as a digital camera, a lens system of a 3-group structure has been proposed. For example, in Patent Literature 1, Patent Literature 2, and Patent Literature 3, a lens system is described in which a first lens group having positive refractive power, an aperture, a second lens group having positive refractive power, and a third lens group having negative refractive power are arranged in this order from the object side to the image side.

[0004] Patent Literature 1: Japanese Patent Application Publication No. 2012-063676

[0005] Patent Literature 2: Japanese Patent Application Publication No. 2015-043104

[0006] Patent Literature 3: Japanese Patent Application Publication No. 2013-061570

[0007] The imaging lens used in the above-described camera is configured to correspond to a large imaging element, and at the same time, is required to be small in size in order to ensure good portability. Furthermore, in order to satisfy the speedup of the autofocus in the camera, an imaging lens that achieves the speedup of focusing is also required. Moreover, the imaging lens is also required to have less variation in aberration at the time of focusing and to perform good aberration correction to have high optical performance.

[0008] In order to achieve the speedup of focusing, the lightening of the lens group (hereinafter referred to as the focus group) that moves at the time of focusing is required. However, the lens system described in Patent Literature 1 adopts a front focus method in which the first lens group and the second lens group move at the time of focusing, and thus there is room for improvement in the lightening of the focus group in the case of achieving the speedup of focusing.

[0009] The lens systems described in Patent Literature 2 and Patent Literature 3 adopt a structure of an inner focus method in which the second lens group moves at the time of focusing. However, the first lens group described in Patent Literature 2 is a lens system of a 2-piece structure in which a positive lens and a negative lens are arranged in this order from the object side. Therefore, it cannot be said that the symmetry of the refractive power of the entire lens system including the third lens group having negative refractive power is good, which is not good for the correction of the lateral chromatic aberration and the like. In the other lens system described in Patent Literature 2, the number of lens pieces of the first lens group is 3 or more, which is not good for the miniaturization.

[0010] The lens system described in Patent Literature 3 also adopts an inner focusing system in which the second lens group moves at the time of focusing. However, in the lens system described in Patent Literature 3, the third lens group is composed of only a negative lens having a concave surface toward the object side, and thus correction of astigmatism and suppression of the angle of incidence of chief rays of off-axis light beams on the image plane are disadvantageous.

[0011] The present application has been achieved in view of the above-described circumstances, and aims to provide an imaging lens which can achieve miniaturization and high-speed focusing, has less variation in aberration at the time of focusing, and has high optical performance, and an image pickup apparatus equipped with the imaging lens.

[0012] The imaging lens according to the first aspect of the present application is provided with only three lens groups as lens groups, the three lens groups being composed of, in order from the object side toward the image side, a first lens group having positive refractive power, a second lens group having positive refractive power, and a third lens group having negative refractive power, an aperture stop being disposed between a lens surface closest to the image side of the first lens group and a lens surface closest to the object side of the third lens group, the first lens group and the third lens group being fixed with respect to the image plane, and the second lens group moving along the optical axis at the time of focusing from an infinite distance object to a closest object, the first lens group being composed of, in order from the object side toward the image side, a negative lens and a positive lens, and the third lens group including, in order from the object side toward the image side, a negative lens and a positive lens, the following conditional expression (1) being satisfied in a case where a focal length of the second lens group is f2 and a focal length of the first lens group is fl:

[0013] 0.25 < f2 / fl < 1 (1).

[0014] The imaging lens according to the second aspect of the present application is provided with only three lens groups as lens groups, the three lens groups being composed of, in order from the object side toward the image side, a first lens group having positive refractive power, a second lens group having positive refractive power, and a third lens group having negative refractive power, an aperture stop being disposed between a lens surface closest to the image side of the first lens group and a lens surface closest to the object side of the third lens group, the first lens group and the third lens group being fixed with respect to the image plane, and the second lens group moving along the optical axis at the time of focusing from an infinite distance object to a closest object, the first lens group being composed of, in order from the object side toward the image side, a negative lens and a positive lens, the second lens group including at least two cemented lenses which cement at least one positive lens and at least one negative lens, and the third lens group including, in order from the object side toward the image side, a negative lens and a positive lens.

[0015] Hereinafter, the imaging lens according to the first and second aspects of the present application will be collectively referred to as the imaging lens according to the above-described aspect of the present application. The imaging lens according to the above-described aspect of the present application preferably satisfies at least one of the following conditional expressions (2) to (7), (9), (1-1) to (5-1).

[0016] 0.25 < f / f1 < 1 (2)

[0017] 0.8 < f / f2 < 1.6 (3)

[0018] -0.8 < f / f3 < 0 (4)

[0019] 1.15 < (1 - β2 2 ) x β3 2 < 2.5 (5)

[0020] 0 < ν1p-ν1n < 30 (6)

[0021] 1.8 < N3p< 2.2 (7)

[0022] 20 < ν3ave< 30 (9)

[0023] 0.25 < f2 / f1 < 0.9 (1-1)

[0024] 0.25 < f / f1 < 0.9 (2-1)

[0025] 0.9 < f / f2 < 1.45 (3-1)

[0026] -0.75 < f / f3 < 0 (4-1)

[0027] 1.25 < (1 - β2 2 ) x β3 2 < 2.4 (5-1)

[0028] wherein,

[0029] f : focal length of the imaging lens in a state focused on an object at infinity

[0030] f1 : focal length of the first lens group

[0031] f2 : focal length of the second lens group

[0032] f3 : focal length of the third lens group

[0033] β2 : lateral magnification of the second lens group in a state focused on an object at infinity

[0034] β3 : lateral magnification of the third lens group in a state focused on an object at infinity

[0035] ν1p : Abbe's number of d-line reference of the positive lens of the first lens group

[0036] ν1n : Abbe's number of d-line reference of the negative lens of the first lens group

[0037] N3p: refractive index of d-line with respect to the positive lens closest to the image side of the 3rd lens group

[0038] ν3ave: average value of the dispersion coefficient of d-line reference of all lenses included in the 3rd lens group.

[0039] In the imaging lens of the above-described aspect of the present application, it is preferable that the negative lens and the positive lens of the 1st lens group are bonded to each other.

[0040] In the imaging lens of the above-described aspect of the present application, it is preferable that the negative lens closest to the object side of the 3rd lens group is a meniscus lens with the convex surface toward the image side. Also, in the imaging lens of the above-described aspect of the present application, it is preferable that the surface of the positive lens closest to the image side of the 3rd lens group is convex.

[0041] In the imaging lens of the above-described aspect of the present application, it is preferable that the number of lenses included in the 3rd lens group is 2. In the structure in which the number of lenses included in the 3rd lens group is 2, it is preferable that the following conditional expression (8) is satisfied.

[0042] -5 < ν3p - ν3n < 15 (8)

[0043] wherein,

[0044] ν3p: dispersion coefficient of d-line reference of the positive lens of the 3rd lens group

[0045] ν3n: dispersion coefficient of d-line reference of the negative lens of the 3rd lens group.

[0046] The imaging device according to the 3rd aspect of the present application has at least one of the imaging lens according to the 1st aspect of the present application and the imaging lens according to the 2nd aspect of the present application.

[0047] Further, "composed of" and "composed of" in the present specification mean that, in addition to the recited constituent elements, it can include: a lens having substantially no refractive power; an optical element other than a lens such as an aperture, a filter, and a cover glass; a mechanism portion such as a lens flange, a lens barrel, an imaging element, and a hand-shake correction mechanism; and the like.

[0048] Further, "a group having positive refractive power" in the present specification means that the group as a whole has positive refractive power. Similarly, "a group having negative refractive power" means that the group as a whole has negative refractive power. "A lens having positive refractive power" and "a positive lens" have the same meaning. "A lens having negative refractive power" and "a negative lens" have the same meaning.

[0049] Compound aspherical lenses (lenses in which a spherical lens and an aspherical film formed on the spherical lens are integrated, and the whole lens functions as a single aspherical lens) are not considered as combined lenses, but are treated as a single lens. Unless otherwise specified, the symbols for refractive power and the surface shapes of the lens surfaces related to lenses including aspherical surfaces are considered in the paraxial region.

[0050] In this specification, the "focal length" used in the conditional formulas is the paraxial focal length. The values ​​used in the conditional formulas are those taken with reference to the d-line, when focused on an object at infinity. The "d-line," "C-line," "F-line," and "g-line" described in this specification are bright lines. The wavelength of the d-line is 587.56 nm, the wavelength of the C-line is 656.27 nm, the wavelength of the F-line is 486.13 nm, and the wavelength of the g-line is 435.84 nm.

[0051] Invention Effects

[0052] According to the present invention, an imaging lens and a camera device having the imaging lens can be provided. The imaging lens is miniaturized, can achieve high-speed focusing, has minimal aberration variation during focusing, and has high optical performance. Attached Figure Description

[0053] Figure 1 This is an imaging lens corresponding to Embodiment 1 of the present invention, and shows a cross-sectional view of the structure and beam of the imaging lens according to an embodiment of the present invention.

[0054] Figure 2 This is a cross-sectional view showing the structure of the imaging lens and the beam of Embodiment 2 of the present invention.

[0055] Figure 3 This is a cross-sectional view showing the structure of the imaging lens and the light beam of Embodiment 3 of the present invention.

[0056] Figure 4 This is a cross-sectional view showing the structure of the imaging lens and the light beam of Embodiment 4 of the present invention.

[0057] Figure 5 This is a cross-sectional view showing the structure and beam of the imaging lens of Embodiment 5 of the present invention.

[0058] Figure 6 This is a diagram of the aberrations of the imaging lens in Embodiment 1 of the present invention.

[0059] Figure 7 This is a diagram of the aberrations of the imaging lens in Embodiment 2 of the present invention.

[0060] Figure 8 These are aberration diagrams of the imaging lens in Embodiment 3 of the present invention.

[0061] Figure 9 are aberration diagrams of the imaging lens of Embodiment 4 of the present application.

[0062] Figure 10 are aberration diagrams of the imaging lens of Embodiment 5 of the present application.

[0063] Figure 11 is a perspective view of the front side of the imaging device according to an embodiment of the present application.

[0064] Figure 12 is a perspective view of the back side of the imaging device according to an embodiment of the present application. DETAILED DESCRIPTION

[0065] Hereinafter, embodiments of the present application will be described in detail with reference to the drawings. Figure 1 is a sectional view showing the structure of the imaging lens according to an embodiment of the present application. Figure 1 The example shown corresponds to the imaging lens of Embodiment 1 described later. Figure 1 In the figure, the left side is the object side, and the right side is the image side, and shows a state in which the focus is on an object at infinity. Also, Figure 1 In the figure, as the light beams, an on-axis light beam 2 and a light beam 3 of the maximum angle of view are shown.

[0066] Further, in the figure, an optical member PP is disposed between the imaging lens and the image plane Sim. The optical member PP is a member such as various filters and / or a cover glass. The various filters are, for example, a low-pass filter, an infrared cut filter, and a filter that cuts a specific wavelength region, and the like. The optical member PP is a member that does not have a refractive power, and a structure in which the optical member PP is omitted can also be realized. Figure 1 In the figure, an example is shown in which the imaging lens is assumed to be applied to an imaging device, and a parallel flat optical member PP is disposed between the imaging lens and the image plane Sim. The optical member PP is a member such as various filters and / or a cover glass. The various filters are, for example, a low-pass filter, an infrared cut filter, and a filter that cuts a specific wavelength region, and the like. The optical member PP is a member that does not have a refractive power, and a structure in which the optical member PP is omitted can also be realized.

[0067] The imaging lens of the present application has only three lens groups as lens groups, and is composed of a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power, in this order from the object side to the image side along the optical axis Z. Also, a diaphragm St is disposed between the lens surface closest to the image side of the first lens group G1 and the lens surface closest to the object side of the third lens group G3. Further, Figure 1 The diaphragm St shown is not indicative of the shape, but the position on the optical axis.

[0068] In the imaging lens of the present application, when focusing from an infinite distance object to a nearest object, the 1st lens group G1 and the 3rd lens group G3 are fixed with respect to the image plane Sim, and the 2nd lens group G2 moves along the optical axis Z. That is, the imaging lens of the present application adopts an inner focusing method in which the 2nd lens group G2 is set as a focusing group. The inner focusing method is constant in the total length of the lens system during focusing, and has the advantage of less variation in the angle of view during focusing compared to a front focusing method. In Figure 1 In the example shown, when focusing from an infinite distance object to a nearest object, the 2nd lens group G2 moves toward the object side. Figure 1 The arrow toward the left direction below the 2nd lens group G2 shown indicates that the 2nd lens group G2 is a focusing group that moves toward the object side during focusing from an infinite distance object to a nearest object.

[0069] By setting the focusing group as only the 2nd lens group, the focusing group can be made light compared to a lens system in which the focusing group is composed of a plurality of lens groups. Therefore, the focusing unit that moves during focusing, including the focusing group and the mechanical parts attached to the focusing group, can be made small and light, which is advantageous for high speed focusing.

[0070] Further, the 1st lens group G1 has positive refractive power, whereby the light flux emitted from the 1st lens group G1 is convergent and incident on the 2nd lens group G2, and thus the 2nd lens group G2 as the focusing group can be made small in diameter. Thus, the focusing group can be made small and light, and thus high speed focusing is facilitated.

[0071] The 3rd lens group G3 has negative refractive power, whereby the positive refractive power of the 2nd lens group G2 can be enhanced, and thus the movement amount of the focusing group during focusing can be reduced. Thus, high speed focusing and reduction of the total length of the lens system are facilitated.

[0072] As an example, in the imaging lens shown in Figure 1 In the imaging lens shown, the 1st lens group G1 is composed of two lenses L11 to L12 in order from the object side to the image side, the 2nd lens group G2 is composed of five lenses L21 to L25 in order from the object side to the image side, and the 3rd lens group G3 is composed of two lenses L31 to L32 in order from the object side to the image side. However, the number of lenses constituting the 2nd lens group G2 and the 3rd lens group G3 can be set to a number different from that shown in the example. Figure 1

[0073] ​The first lens group G1 is composed of a negative lens and a positive lens in order from the object side. The first lens group G1 has a negative lens and a positive lens, whereby it is easy to correct spherical aberration and on-axis chromatic aberration. In a configuration in which the third lens group G3 has a negative refractive power and the stop St is disposed within the above range, the lens arrangement of the first lens group G1 is set to a negative-positive order from the object side, whereby the symmetry of the refractive power becomes good, and thus it is advantageous for correction of the magnification chromatic aberration. Generally, the larger the image height, the more likely the magnification chromatic aberration becomes large, and thus when a lens system is configured to correspond to a large imaging element, the above lens arrangement of the first lens group G1 becomes advantageous. Furthermore, the first lens group G1 is configured by two lenses, and thus it is advantageous for size reduction.

[0074] The negative lens and the positive lens of the first lens group G1 are preferably bonded to each other. In this case, the lenses can be combined and bonded in a manner that suppresses performance degradation caused by eccentricity errors of the respective lenses at the time of manufacture, and thus it is possible to suppress performance reduction caused by manufacturing errors, which is advantageous for ensuring performance. Furthermore, in the case of not being bonded, an air gap is generated between the negative lens and the positive lens of the first lens group G1, which causes spherical aberration to change due to errors of the air gap, but this problem can be avoided in the case of being bonded, and thus it is advantageous for ensuring performance.

[0075] The negative lens of the first lens group G1 can be a meniscus lens with a convex surface toward the object side. The positive lens of the first lens group G1 can be a meniscus lens with a convex surface toward the object side. In the case in which the negative lens and the positive lens of the first lens group G1 are bonded to each other, if the bonding surface is set to a shape with a convex surface toward the object side, it is advantageous for correcting the magnification chromatic aberration.

[0076] The 2nd lens group G2 preferably has at least two cemented lenses which cement at least one positive lens and at least one negative lens. In this case, the degree of freedom of design is increased, and it is advantageous to suppress the variation of the on-axis chromatic aberration and the variation of the magnification chromatic aberration when focusing is performed by changing the photographing distance. This is based on the following described situation. If it is a so-called overall swing-out type lens system which moves the entire imaging lens to perform focusing, it is possible to use any lens within the entire system to suppress the variation of the aberration when focusing is performed. However, in the imaging lens of the present application, the focusing group is composed of only the 2nd lens group G2, and therefore, compared with the overall swing-out type lens system, the lenses which can be used to suppress the variation of the aberration when focusing is performed are limited. In the case where the 2nd lens group G2 is configured to have two cemented lenses, the heights of the light rays which greatly affect the magnification chromatic aberration are different in these two cemented lenses which are located at different positions on the optical axis, and therefore, the variation of the magnification chromatic aberration with respect to the variation of the design parameters is also different. Similarly, the heights of the light rays which greatly affect the on-axis chromatic aberration are different in the above two cemented lenses, and therefore, the variation of the on-axis chromatic aberration with respect to the variation of the design parameters is also different. By using the two cemented lenses which act differently in this way, the balance between the magnification chromatic aberration and the on-axis chromatic aberration is favorably obtained while optimization is performed, and therefore, the correction of the chromatic aberration can be appropriately performed, and furthermore, the variation of the chromatic aberration when focusing is performed can be appropriately suppressed.

[0077] In the case where the 2nd lens group G2 has two cemented lenses, for example, the 2nd lens group G2 can be configured to be composed of five lenses in order from the object side to the image side, and the five lenses are composed of two cemented lenses and a negative lens. Alternatively, in the case where the chromatic aberration is more valued than the miniaturization, the weight reduction, and the high speed of focusing, the 2nd lens group G2 can be configured to be composed of four lenses in order from the object side to the image side, and the four lenses are composed of a positive lens, one cemented lens, and a negative lens. In the above configuration where the 2nd lens group G2 is composed of four or five lenses, the cemented lenses which the 2nd lens group G2 has can each be sequentially cemented with a negative lens and a positive lens from the object side. Furthermore, the cemented lenses which the 2nd lens group G2 has can be configured to be composed of a double-concave lens and a double-convex lens. In the above configuration where the 2nd lens group G2 is composed of four or five lenses, the negative lens of the 2nd lens group G2 which is closest to the image side can be provided as a meniscus lens whose convex surface faces the image side.

[0078] The 3rd lens group G3 includes a negative lens and a positive lens in order from the object side to the image side. According to this configuration, it is advantageous to correct the curvature of field. Furthermore, in the 3rd lens group G3, by arranging the lenses in the order of negative-positive, it is possible to locate the exit pupil more on the object side, and therefore, it is advantageous to suppress the incident angle of the chief ray of the off-axis light beam to the image surface Sim. The above configuration of the 3rd lens group G3 is advantageous when configuring a lens system which can correspond to a large-sized imaging element.

[0079] In the negative lens included in the 3rd lens group G3, the negative lens closest to the object side is preferably a meniscus lens convex toward the image side. In this case, it is advantageous to suppress the astigmatism and the distortion aberration.

[0080] In the positive lens included in the 3rd lens group G3, the surface of the positive lens closest to the image side is preferably convex. In this case, it is advantageous to suppress the incidence angle of the chief ray of the marginal ray on the image surface Sim, and it is advantageous to suppress the astigmatism.

[0081] The number of lenses included in the 3rd lens group G3 is preferably 2. In this case, it is advantageous to miniaturize.

[0082] The aperture stop St is preferably fixed with respect to the image surface Sim at the time of focusing. In this case, it is advantageous to reduce the weight of the components that move at the time of focusing, and it is advantageous to speed up the focusing.

[0083] As illustrated in Embodiment 1, Figure 1 The aperture stop St is preferably disposed between the 1st lens group G1 and the 2nd lens group G2. In this case, the arrangement of positive refractive power, the aperture stop St, and positive refractive power becomes easy to maintain the symmetry of the refractive power disposed adjacent to the aperture stop St, and thus it is advantageous to correct the distortion aberration and the image surface curvature. Further, since the aperture stop St is disposed between the 1st lens group G1 and the 2nd lens group G2, the aperture stop St is not located in the focusing group, and thus it is possible to configure such that the aperture stop St is fixed with respect to the image surface Sim at the time of focusing, which is advantageous to speed up the focusing. Moreover, in the case where the aperture stop St is disposed as described above in the imaging lens of the present application, compared to the case where the aperture stop St is disposed between the 2nd lens group G2 and the 3rd lens group G3, it is advantageous to suppress the incidence angle of the chief ray of the marginal ray on the image surface Sim and to secure the peripheral light amount.

[0084] Next, the structure of the conditional expression is described. In the case where the focal length of the second lens group G2 is set to f2 and the focal length of the first lens group G1 is set to f1, the following conditional expression (1) is satisfied. By being set to not become lower than the lower limit of the conditional expression (1), it is easy to suppress the variation in aberration at the time of focusing. Also, since the refractive power of the first lens group G1 can be ensured, the miniaturization of the second lens group G2 becomes easy. Thus, since the miniaturization and lightening of the focusing group become easy, it is advantageous for the high speed of focusing. By being set to not become higher than the upper limit of the conditional expression (1), it is advantageous for shortening the moving amount of the focusing group at the time of focusing, and thus it is advantageous for the high speed of focusing and the total length of the lens system. The balance between the positive refractive power of the first lens group G1 and the positive refractive power of the second lens group G2 is obtained in a manner satisfying the conditional expression (1), and thus it is easy to suppress the variation in aberration at the time of focusing, the high speed of focusing, and the realization of miniaturization. In addition, if the structure satisfying the following conditional expression (1-1) is set, it can be set to better characteristics.

[0085] 0.25 < f2 / f1 < 1 (1)

[0086] 0.25 < f2 / f1 < 0.9 (1-1)

[0087] In the case where the focal length of the imaging lens in a state of focusing on an infinite object is set to f, and the focal length of the first lens group G1 is set to f1, the following conditional expression (2) is preferably satisfied. By being set to not become lower than the lower limit of the conditional expression (2), the enlargement of the second lens group G2 can be suppressed, and thus the increase in weight of the focusing group can be suppressed, and it is advantageous for the high speed of focusing. Also, by allocating the refractive power in the first lens group G1 so as not to become lower than the lower limit of the conditional expression (2), the refractive power of the second lens group G2 does not become too strong, and thus it is easy to suppress the variation in aberration at the time of focusing. By allocating the refractive power in the first lens group G1 so as to become higher than the upper limit of the conditional expression (2), the refractive power of the second lens group G2 does not become too weak, and thus the moving amount of the focusing group at the time of focusing can be shortened. Thus, it is advantageous for the high speed of focusing and the shortening of the total length of the lens system. In addition, if the structure satisfying the following conditional expression (2-1) is set, it can be set to better characteristics.

[0088] 0.25 < f / f1 < 1 (2)

[0089] 0.25 < f / f1 < 0.9 (2-1)

[0090] In a case where the focal length of the imaging lens in a state focused on an infinite object is set to f, and the focal length of the second lens group G2 is set to f2, it is preferable to satisfy the following conditional expression (3). By being set to not become lower than the lower limit of the conditional expression (3), the refractive power of the second lens group G2 does not become too weak, and thus the moving amount of the focus group at the time of focusing can be shortened. Thus, the speeding of the focusing and the shortening of the total length of the lens system are facilitated. By being set to not become higher than the upper limit of the conditional expression (3), the refractive power of the second lens group G2 does not become too strong, and thus the variation in aberration at the time of focusing is easily suppressed. In addition, if the structure is set to satisfy the following conditional expression (3-1), it is possible to set a better characteristic.

[0091] 0.8 < f / f2 < 1.6 (3)

[0092] 0.9 < f / f2 < 1.45 (3-1)

[0093] In a case where the focal length of the imaging lens in a state focused on an infinite object is set to f, and the focal length of the third lens group G3 is set to f3, it is preferable to satisfy the following conditional expression (4). By being set to not become lower than the lower limit of the conditional expression (4), the refractive power of the second lens group G2 does not become too strong, and thus the variation in aberration at the time of focusing is easily suppressed. By being set to not become higher than the upper limit of the conditional expression (4), the curvature of field is easily corrected. In addition, if the structure is set to satisfy the following conditional expression (4-1), it is possible to set a better characteristic.

[0094] -0.8 < f / f3 < 0 (4)

[0095] -0.75 < f / f3 < 0 (4-1)

[0096] In a case where the lateral magnification of the second lens group G2 in a state focused on an infinite object is set to β2, and the lateral magnification of the third lens group G3 in a state focused on an infinite object is set to β3, it is preferable to satisfy the following conditional expression (5). By being set to not become lower than the lower limit of the conditional expression (5), the moving amount of the focus group at the time of focusing can be shortened. Thus, the speeding of the focusing and the shortening of the total length of the lens system are facilitated. By being set to not become higher than the upper limit of the conditional expression (5), the variation in aberration at the time of focusing is easily suppressed, and in particular, the variation in the curvature of field is easily suppressed. By being constituted in a manner that the lateral magnification of the second lens group G2 and the lateral magnification of the third lens group G3 satisfy the conditional expression (5), the speeding of the focusing, the miniaturization, and the correction of aberration are facilitated. In addition, if the structure is set to satisfy the following conditional expression (5-1), it is possible to set a better characteristic.

[0097] 1.15 < (1 - β2 2 ) x β3 2 < 2.5 (5)

[0098] 1.25 < (1 - β2 2 ) x β3 2 < 2.4 (5 - 1)

[0099] In a case where a dispersion coefficient of a d-line reference of the positive lens of the first lens group G1 is set as vlp, and a dispersion coefficient of a d-line reference of the negative lens of the first lens group G1 is set as vln, it is preferable to satisfy the following conditional expression (6). By satisfying the conditional expression (6), it is possible to correct the on-axis chromatic aberration and the magnification chromatic aberration with good balance. In addition, if the structure is set to satisfy the following conditional expression (6-1), it is possible to set a better characteristic.

[0100] 0 < vlp - vln < 30 (6)

[0101] 0 < vlp - vln < 15 (6-1)

[0102] In the positive lens of the third lens group G3, in a case where a refractive index with respect to a d-line of the positive lens closest to the image side is set as N3p, it is preferable to satisfy the following conditional expression (7). By being set to be not lower than the lower limit of the conditional expression (7), it is advantageous to suppress the incidence angle of the chief ray of the off-axis light beam to the image surface Sim. By being set to be not higher than the upper limit of the conditional expression (7), it is easy to correct the curvature of field. In addition, if the structure is set to satisfy the following conditional expression (7-1), it is possible to set a better characteristic.

[0103] 1.8 < N3p < 2.2 (7)

[0104] 1.85 < N3p < 2.1 (7-1)

[0105] In a case where a dispersion coefficient of a d-line reference of the positive lens of the third lens group G3 is set as v3p, and a dispersion coefficient of a d-line reference of the negative lens of the third lens group G3 is set as v3n, it is preferable to satisfy the following conditional expression (8) in a structure in which the third lens group G3 is sequentially composed of a negative lens and a positive lens from the object side to the image side. By satisfying the conditional expression (8), it is possible to correct the on-axis chromatic aberration and the magnification chromatic aberration with good balance. In addition, if the structure is set to satisfy the following conditional expression (8-1), it is possible to set a better characteristic.

[0106] -5 < v3p - v3n < 15 (8)

[0107] -5 < v3p - v3n < 10 (8-1)

[0108] In a case where an average value of the Abbe number of the d-line reference of all the lenses of the third lens group G3 is set as v3ave, it is preferable to satisfy the following conditional expression (9). By satisfying the conditional expression (9), it is possible to correct the on-axis chromatic aberration and the magnification chromatic aberration with good balance. In addition, if the structure is set so as to satisfy the following conditional expression (9-1), it is possible to set a better characteristic.

[0109] 20 < v3ave < 30 (9)

[0110] 23.5 < v3ave < 30 (9-1)

[0111] In a case where the lateral magnification of the second lens group G2 in a state focused on an infinite object is set as β2, it is preferable to satisfy the following conditional expression (10). By being set so as not to be below the lower limit of the conditional expression (10), it is easy to suppress the aberration variation at the time of focusing. By being set so as not to be above the upper limit of the conditional expression (10), the refractive power of the second lens group G2 does not become too weak, and it is possible to shorten the movement amount of the focusing group at the time of focusing. Thereby, it is advantageous for the speeding of focusing and the shortening of the total length of the lens system. In addition, if the structure is set so as to satisfy the following conditional expression (10-1), it is possible to set a better characteristic.

[0112] 0.1 < β2 < 0.7 (10)

[0113] 0.2 < β2 < 0.6 (10-1)

[0114] In a case where the lateral magnification of the third lens group G3 in a state focused on an infinite object is set as β3, it is preferable to satisfy the following conditional expression (11). By being set so as not to be below the lower limit of the conditional expression (11), it is possible to shorten the movement amount of the focusing group at the time of focusing. Thereby, it is advantageous for the speeding of focusing and the shortening of the total length of the lens system. By being set so as not to be above the upper limit of the conditional expression (11), it is easy to correct the curvature of field. In addition, if the structure is set so as to satisfy the following conditional expression (11-1), it is possible to set a better characteristic.

[0115] 1 < β3 < 2.2 (11)

[0116] 1.1 < β3 < 1.6 (11-1)

[0117] In a case where the lateral magnification of the second lens group G2 and the lateral magnification of the third lens group G3 are set in a manner that satisfies the conditional expression (10) and the conditional expression (11) at the same time, it is more advantageous for the speeding, the miniaturization, and the good aberration correction of focusing.

[0118] In a case where a sum of a distance on an optical axis from a lens surface closest to an object side of the first lens group G1 to a lens surface closest to an image side of the third lens group G3 and an air converted distance on the optical axis from the lens surface closest to the image side of the third lens group G3 to a position of an image side focal point of the imaging lens in a state focused on an infinite object is set to TL, a focal length of the imaging lens in the state focused on the infinite object is set to f, and a maximum half view angle is set to ω, it is preferable to satisfy the following conditional expression (12). By being set to be not lower than a lower limit of the conditional expression (12), it is easy to correct image surface curvature and distortion aberration. By being set to be not higher than an upper limit of the conditional expression (12), it is advantageous to miniaturization and weight reduction of the lens system. By satisfying the conditional expression (12), it is easy to simultaneously achieve miniaturization and good aberration correction. In addition, if a structure satisfying the following conditional expression (12-1) is set, it is possible to set a better characteristic.

[0119] 2 < TL / { f x tan ( ω )} < 2.7 (12)

[0120] 2.1 < TL / { f x tan ( ω )} < 2.6 (12-1)

[0121] The structure regarding the conditional expression is also included, and the above-described preferable structure and / or achievable structure can be any combination, and it is preferable to appropriately selectively adopt according to a required specification. Hereinafter, two modes of the imaging lens in which the above-described structures are combined are described. The imaging lenses of the first mode and the second mode described below can also have at least one of the above-described preferable structure and / or achievable structure.

[0122] The imaging lens of the first mode has only three lens groups as lens groups, and the three lens groups are sequentially composed of the first lens group G1 having positive refractive power, the second lens group G2 having positive refractive power, and the third lens group G3 having negative refractive power from the object side to the image side, an aperture stop St is disposed between the lens surface closest to the image side of the first lens group G1 and the lens surface closest to the object side of the third lens group G3, when focusing from an infinite object to a closest object, the first lens group G1 and the third lens group G3 are fixed with respect to the image surface Sim, the second lens group G2 moves along the optical axis Z, the first lens group G1 is sequentially composed of a negative lens and a positive lens from the object side to the image side, the third lens group G3 sequentially has a negative lens and a positive lens from the object side to the image side, and satisfies the above-described conditional expression (1). According to the imaging lens of the first mode, miniaturization and high speed focusing can be achieved, aberration variation at the time of focusing is small, and high optical performance can be achieved.

[0123] The imaging lens of the second method has only three lens groups. These three lens groups are composed of a first lens group G1 with positive refractive power, a second lens group G2 with positive refractive power, and a third lens group G3 with negative refractive power, arranged sequentially from the object side to the image side. An aperture diaphragm St is arranged between the lens surface of the first lens group G1 closest to the image side and the lens surface of the third lens group G3 closest to the object side. When focusing from an infinity object to the nearest object, the first lens group G1 and the third lens group G3 are fixed relative to the image plane Sim, and the second lens group G2 moves along the optical axis Z. The first lens group G1 is composed of a negative lens and a positive lens sequentially from the object side to the image side. The second lens group G2 has at least two joining lenses, which join at least one positive lens and at least one negative lens. The third lens group G3 has a negative lens and a positive lens sequentially from the object side to the image side. The imaging lens according to the second method can achieve miniaturization and high-speed focusing, with less aberration variation during focusing, especially less variation in chromatic aberration, and can achieve high optical performance.

[0124] Next, a numerical embodiment of the imaging lens of the present invention will be described.

[0125] [Example 1]

[0126] A cross-sectional view showing the structure of the imaging lens of Embodiment 1 is shown in Figure 1 As illustrated above, the method and structure of the imaging lens are as described, therefore some repetitive descriptions are omitted here. The imaging lens of Embodiment 1, from the object side to the image side, consists of a first lens group G1 with positive refractive power, an aperture St, a second lens group G2 with positive refractive power, and a third lens group G3 with negative refractive power. When focusing from an infinity object to the nearest object, the first lens group G1, the aperture St, and the third lens group G3 are fixed relative to the image plane Sim, while only the second lens group G2 moves along the optical axis Z towards the object side. The first lens group G1, from the object side to the image side, consists of two lenses, L11 and L12. The second lens group G2, from the object side to the image side, consists of five lenses, L21 to L25. The third lens group G3, from the object side to the image side, consists of two lenses, L31 and L32. This is a summary of the imaging lens of Embodiment 1.

[0127] With respect to the imaging lens of Example 1, the basic lens data is shown in Table 1, the various factors are shown in Table 2, the variable face interval is shown in Table 3, and the aspheric coefficients are shown in Table 4. In Table 1, the surface number is shown in the Sn column for the case where the surface closest to the object side is set as the 1st surface, and the surface numbers are sequentially increased toward the image side. The radius of curvature of each surface is shown in the R column. The surface interval on the optical axis between each surface and the surface adjacent to the image side is shown in the D column. Also, the refractive index with respect to the d-line of each component is shown in the Nd column, and the Abbe number with respect to the d-line reference of each component is shown in the v d column.

[0128] In Table 1, the sign of the radius of curvature of the surface of the shape with the convex surface toward the object side is set to positive, and the sign of the radius of curvature of the surface of the shape with the convex surface toward the image side is set to negative. The aperture stop St and the optical component PP are also shown in Table 1, and the surface number column shows the so-called surface number and (St) in the surface number column of the surface corresponding to the aperture stop St. In Table 1, the symbol DD[] is used with respect to the variable face interval that changes with the focus time interval, and the surface number on the object side of the interval is noted in the [] and recorded in the D column.

[0129] In Table 2, the focal length f, the back focus Bf in the air conversion distance, the F number FNo., and the maximum total angle of view 2ω of the imaging lens are shown with respect to the d-line reference. The (°) in the 2ω column indicates that the unit is degrees. The values shown in Table 2 are values in the case where the d-line is set as the reference in the state where the focus is on an object at infinity.

[0130] In Table 3, the values of the variable face interval in the state where the focus is on an object at infinity and the values of the variable face interval in the state where the focus is on an object with an object distance of 2000 mm (millimeters) are shown in the columns denoted as "infinity" and "2000 mm", respectively. In addition, the object distance refers to the distance on the optical axis from the object to the lens surface closest to the object side.

[0131] In Table 1, the surface number of the aspheric surface is marked with an asterisk, and the numerical value of the curvature radius of the aspheric surface is recorded in the column of the radius of curvature of the aspheric surface. In Table 4, the surface number of the aspheric surface is shown in the Sn column, and the numerical values of the aspheric coefficients with respect to each aspheric surface are shown in the KA and Am (m = 3, 4, 5,..., 20) columns. "E±n" (n: integer) of the numerical values of the aspheric coefficients of Table 4 indicates "x 10 ±n ". KA and Am are the aspheric coefficients in the aspheric expression represented by the following formula.

[0132] Zd = C x h 2 / {1 + (1 - KA x C 2 x h 2 ) 1 / 2} + ∑Am x h m

[0133] wherein,

[0134] Zd: aspherical depth (length of a perpendicular from a point on the aspherical surface at height h to a perpendicular to the optical axis at the point of contact of the aspherical surface with the optical axis)

[0135] h: height (distance from the optical axis to the lens surface)

[0136] C: reciprocal of paraxial radius of curvature

[0137] KA, Am: aspherical coefficients,

[0138] ∑ of the aspherical formula refers to the sum with respect to m.

[0139] In the data of each table, degrees are used as the unit of angle and mm (millimeters) are used as the unit of length, but the optical system can be used even if it is scaled up or scaled down, and thus other appropriate units can be used. Also, in each table shown below, the values rounded off with a prescribed number of digits are described.

[0140] [Table 1]

[0141] Example 1

[0142] Sn R D Nd νd 1 80.042 1.03 1.64769 33.84 2 16.036 3.44 1.87070 40.73 3 90.657 3.21 4(St) DD[4] 5 -29.212 1.01 1.61293 37.01 6 21.196 3.89 1.88300 39.22 7 -30.375 1.00 8 -16.556 1.05 1.54814 45.83 9 45.149 5.26 1.65160 58.55 10 -18.741 1.19 *11 -22.131 1.50 1.77250 49.50 *12 -25.008 DD

[12] 13 -24.341 3.63 1.84667 23.79 14 -117.508 4.62 15 ∞ 4.86 2.00100 29.13 16 -62.542 18.83 17 ∞ 2.85 1.51680 64.20 18 ∞

[0143] [Table 2]

[0144] Example 1

[0145] f 48.57 Bf 22.01 FNo. 3.56 2ω(°) 60.4

[0146] [Table 3]

[0147] Example 1

[0148] Infinity 2000 mm DD[4] 6.76 6.03 DD

[12] 5.46 6.19

[0149] [Table 4]

[0150] Example 1

[0151] Sn 11 12 KA 1.0000000E+00 1.0000000E+00 A3 0.0000000E+00 0.0000000E+00 A4 6.9329378E-05 9.3215004E-05 A5 -1.1194555E-05 -1.5152273E-05 A6 1.0209655E-06 1.6898484E-06 A7 4.7100190E-08 1.1019899E-08 A8 -4.7484147E-09 -5.9591306E-09 A9 -3.7046349E-10 -3.7120650E-10 A10 -1.6184739E-11 8.5503067E-12 A11 2.1199506E-12 2.0154094E-12 A12 1.9561961E-13 2.1470193E-13 A13 5.5631129E-15 5.7714951E-15 A14 -2.0998957E-16 -8.4918900E-16 A15 1.0517148E-16 -1.6311106E-16 A16 -1.6198261E-17 -5.2589862E-18 A17 -3.1633953E-18 -2.6370718E-20 A18 3.6331743E-19 -1.6585141E-20 A19 -8.3331366E-21 2.6087053E-20 A20 2.3412194E-23 -1.4985752E-21

[0152] Figure 6 The aberration diagrams of the imaging lens of Example 1 are shown in FIGS. 12A to 12D. Figure 6 In FIGS. 12A to 12D, the spherical aberration, the astigmatism, the distortion aberration, and the magnification chromatic aberration are shown in order from the left side. Figure 6The aberration diagrams in the upper section labeled "infinity" show the state where the imaging lens of Example 1 is focused on an object at infinity, and the aberration diagrams in the lower section labeled "2000 mm" show the state where the imaging lens of Example 1 is focused on an object at an object distance of 2000 mm (millimeters). In the spherical aberration diagram, the aberrations in the d-line, C-line, F-line, and g-line are represented by solid line, long dashed line, short dashed line, and single-dot chain line, respectively. In the astigmatism diagram, the aberration in the d-line in the sagittal direction is represented by solid line, and the aberration in the d-line in the tangential direction is represented by short dashed line. In the distortion aberration diagram, the aberration in the d-line is represented by solid line. In the lateral chromatic aberration diagram, the aberrations in the C-line, F-line, and g-line are represented by long dashed line, short dashed line, and single-dot chain line, respectively. The FNo. in the spherical aberration diagram refers to F-number, and ω in the other aberration diagrams refers to maximum half viewing angle.

[0153] Unless otherwise specified, the symbols, meanings, description methods, and illustration methods of the data of Example 1 described above are also the same in the following examples, and thus the repeated description is omitted below.

[0154] [Example 2]

[0155] A sectional view showing the structure of the imaging lens of Example 2 is shown in Figure 2 Example 2. The imaging lens of Example 2 has the same structure as the outline of the imaging lens of Example 1. With regard to the imaging lens of Example 2, the basic lens data is shown in Table 5, the various factors are shown in Table 6, the variable face intervals are shown in Table 7, the aspheric coefficients are shown in Table 8, and the aberration diagrams are shown in Figure 7 Figure 7 In the upper section, the aberration diagrams in the state where the imaging lens of Example 2 is focused on an object at infinity are shown, and in the lower section, the aberration diagrams in the state where the imaging lens of Example 2 is focused on an object at an object distance of 2000 mm (millimeters) are shown.

[0156] [Table 5]

[0157] Example 2

[0158] Sn R D Nd νd 1 62.547 1.01 1.67270 32.10 2 15.881 3.18 1.83481 42.74 3 73.497 4.16 4(St) ∞ DD[4] 5 -32.001 1.01 1.59551 39.24 6 21.113 3.64 1.89190 37.13 7 -30.540 1.15 8 -16.240 1.64 1.53172 48.84 9 45.122 5.94 1.65160 58.55 10 -18.240 0.51 *11 -22.499 1.57 1.80625 40.91 *12 -24.003 DD

[12] 13 -24.421 3.34 1.85896 22.73 14 -122.438 5.95 15 ∞ 3.94 1.90366 31.31 16 -80.306 19.63 17 ∞ 2.85 1.51680 64.20 18 ∞

[0159] [Table 6]

[0160] Example 2

[0161] f 48.54 Bf 22.57 FNo. 3.55 2ω(°) 60.4

[0162] [Table 7]

[0163] Example 2

[0164] Infinity 2000 mm DD[4] 5.69 5.17 DD

[12] 4.74 5.26

[0165] [Table 8]

[0166] Example 2 ​

[0167] Sn 11 12 KA 1.0000000E+00 1.0000000E+00 A3 0.0000000E+00 0.0000000E+00 A4 6.7903826E-05 9.1740432E-05 A5 -1.1185017E-05 -1.4976327E-05 A6 1.0368349E-06 1.6963876E-06 A7 4.8207757E-08 1.1403876E-08 A8 -4.7498433E-09 -5.9322374E-09 A9 -3.7734309E-10 -3.7059522E-10 A10 -1.7108671E-11 8.3667279E-12 A11 2.0379508E-12 1.9843756E-12 A12 1.8912018E-13 2.1013188E-13 A13 5.3491724E-15 5.2973379E-15 A14 -2.1765961E-16 -8.8427059E-16 A15 1.0947969E-16 -1.6450576E-16 A16 -1.5644632E-17 -5.0478708E-18 A17 -3.1117477E-18 1.1876382E-20 A18 3.7210495E-19 -1.0798695E-20 A19 -7.2827709E-21 2.7227530E-20 A20 -1.8204800E-22 -1.6345380E-21

[0168] [Example 3]

[0169] A sectional view showing the structure of the imaging lens of Example 3 is shown in Figure 3 . The imaging lens of Example 3 has the same structure as the outline of the imaging lens of Example 1. With regard to the imaging lens of Example 3, the basic lens data is shown in Table 9, the various factors are shown in Table 10, the variable face intervals are shown in Table 11, the aspherical coefficients are shown in Table 12, and the various aberration diagrams are shown in Figure 8 . Figure 8 In , the upper segment shows the various aberration diagrams in a state focused on an object at infinity, and the lower segment shows the various aberration diagrams in a state focused on an object at an object distance of 2000 mm (millimeters).

[0170] [Table 9]

[0171] Example 3

[0172] Sn R D Nd νd 1 53.722 1.02 1.64769 33.79 2 14.540 2.70 1.83481 42.74 3 87.028 2.16 4(St) ∞ DD[4] 5 -29.348 1.01 1.62588 35.70 6 22.628 3.64 1.88300 40.76 7 -32.956 1.32 8 -17.604 1.28 1.51742 52.43 9 52.479 5.06 1.60311 60.64 10 -19.273 2.15 *11 -22.071 1.61 1.77400 49.60 *12 -24.835 DD

[12] 13 -23.152 1.00 1.80518 25.42 14 -90.743 4.07 15 ∞ 4.29 2.05090 26.94 16 -71.873 18.77 17 ∞ 2.85 1.51680 64.20 18 ∞

[0173] [Table 10]

[0174] Example 3

[0175] f 48.57 Bf 21.72 FNo. 3.60 2ω(°) 58.8

[0176] [Table 11]

[0177] Example 3

[0178] Infinity 2000 mm DD[4] 6.50 5.59 DD

[12] 4.51 5.42

[0179] [Table 12]

[0180] Example 3

[0181] Sn 11 12 KA 1.0000000E+00 1.0000000E+00 A3 0.0000000E+00 0.0000000E+00 A4 6.4943249E-05 8.8316681E-05 A5 -1.1316437E-05 -1.4934527E-05 A6 1.0562362E-06 1.7065143E-06 A7 4.8187085E-08 1.2186420E-08 A8 -4.6652975E-09 -5.9791746E-09 A9 -3.6812189E-01 -3.7924329E-10 A10 -1.6814738E-11 8.3620621E-12 A11 2.0048613E-12 2.0028923E-12 A12 1.8249796E13 2.1356201E-13 A13 4.4272700E15 5.5988897E-15 A14 -2.8190079E-16 -8.7528580E-16 A15 1.0453267E-16 -1.6442870E-16 A16 -1.6007201E-17 -5.4791889E-18 A17 -3.0480296E-18 -2.7245624E-20 A18 3.8315701E-19 -1.6842696E-20 A19 -8.8242004E-21 2.6378867E-20 A20 -4.4275403E-23 -1.4787612E-21

[0182] [Example 4]

[0183] A sectional view showing the structure of the imaging lens of Example 4 is shown in Figure 4 . The imaging lens of Example 4 has the same structure as the outline of the imaging lens of Example 1. With regard to the imaging lens of Example 4, the basic lens data is shown in Table 13, the various factors are shown in Table 14, the variable face intervals are shown in Table 15, the aspherical coefficients are shown in Table 16, and the various aberration diagrams are shown in Figure 9 . Figure 9 In , the upper segment shows the various aberration diagrams in a state focused on an object at infinity, and the lower segment shows the various aberration diagrams in a state focused on an object at an object distance of 2000 mm (millimeters).

[0184] [Table 13]

[0185] Example 4

[0186] Sn R D Nd νd 1 32.161 0.76 1.67270 32.10 2 15.601 2.30 1.80400 46.58 3 48.720 5.37 4(St) ∞ DD[4] 5 -46.768 0.81 1.60342 38.03 6 17.896 3.55 1.85150 40.78 7 -37.620 1.30 8 -15.846 0.76 1.54814 45.78 9 24.793 5.68 1.65160 58.55 10 -19.444 4.34 *11 -25.527 1.25 1.77400 49.60 *12 -26.540 DD

[12] 13 -17.751 2.76 1.80518 25.42 14 -95.649 1.56 15 954.163 5.21 1.96300 24.11 16 -56.789 11.07 17 ∞ 2.85 1.51680 64.20 18 ∞

[0187] [Table 14]

[0188] Example 4

[0189] f 44.20 Bf 14.01 FNo. 3.54 2ω(°) 62.8

[0190] [Table 15]

[0191] Example 4

[0192] Infinity 2000 mm DD[4] 4.82 4.24 DD

[12] 4.47 5.05

[0193] [Table 16]

[0194] Example 4

[0195] Sn 11 12 KA 1.0000000E+00 1.0000000E+00 A3 0.0000000E+00 0.0000000E+00 A4 7.1817193E-05 1.1128434E-04 A5 -6.4461023E-06 -1.5144397E-05 A6 7.1033849E-07 1.9132423E-06 A7 3.1399725E-08 -3.5732597E-10 A8 -4.9142794E-09 -7.5444206E-09 A9 -3.5189268E-10 -4.4101884E-10 A10 -1.3719128E-11 9.1082269E-12 A11 2.3047110E-12 2.3076457E-12 A12 1.9463475E-13 2.3329482E-13 A13 2.3660184E-15 6.7500117E-15 A14 -7.9887108E-16 -7.9799225E-16 A15 6.1511353E-17 -1.5986170E-16 A16 -1.5291807E-17 -5.9709336E-18 A17 -2.4944063E-18 -1.4867271E-20 A18 4.2520378E-19 -2.5583406E-20 A19 -5.6960778E-21 2.6038303E-20 A20 -6.9631398E-22 -1.4406905E-21

[0196] [Example 5]

[0197] A sectional view showing the structure of the imaging lens of Example 5 is shown in Figure 5 . The imaging lens of Example 5 has the same structure as the outline of the imaging lens of Example 1 except that the 2nd lens group G2 is composed of four lenses L21 to L24 in order from the object side to the image side. With respect to the imaging lens of Example 5, the basic lens data is shown in Table 17, various factors are shown in Table 18, the variable face interval is shown in Table 19, the aspheric surface coefficients are shown in Table 20, and the various aberration diagrams are shown in Figure 10 . Figure 10 In

[0198] [Table 17]

[0199] Example 5

[0200] Sn R D Nd νd 1 54.380 1.41 1.63980 34.47 2 22.209 2.70 1.88300 39.22 3 50.00C 2.88 4(St) ∞ DD[4] *5 36.947 3.00 1.69350 53.18 *6 -129.708 2.26 7 -16.214 1.01 1.67270 32.17 8 23.000 5.29 1.87070 40.73 9 -21.05C 4.00 *10 -10.401 2.00 1.69350 53.18 *11 -13.669 DD

[11] 12 -32.148 2.00 1.75520 27.53 13 553.528 3.00 14 212.375 6.00 1.95375 32.32 15 -57.809 19.16 16 ∞ 2.85 1.51680 64.20 17 ∞

[0201] [Table 18]

[0202] Example 5

[0203] f 48.84 Bf 22.11 FNo. 3.60 2ω(°) 59.2

[0204] [Table 19]

[0205] Example 5

[0206] Infinity 2000 mm DD[4] 6.50 5.59 DD

[11] 5.82 6.73

[0207] [Table 20]

[0208] Example 5

[0209] Sn 5 6 10 11 KA 1.0000000E+00 1.0000000E+00 1.0000000E+00 1.0000000E+00 A3 0.0000000E+00 0.0000000E+00 0.0000000E+00 0.0000000E+00 A4 -4.3707505E-05 -9.6105123E-05 1.4797454E-04 1.6916886E-04 A5 -4.3306735E-07 1.9212569E-06 8.8452449E-06 -7.7675551E-06 A6 -5.5804768E-07 -8.5668678E-07 4.9701757E-09 2.3112837E-06 A7 -8.0027824E-09 -1.6013757E-08 9.1392512E-08 -1.6391478E-08 A8 3.5902068E-09 -8.3227814E-10 7.0553411E-09 -8.2732702E-09 A9 4.4711695E-10 4.7908619E-10 -1.1594046E-10 -2.9022246E-10 A10 -1.7573484E-10 -3.4660063E-11 -7.3299775E-11 2.5620674E-11 A11 -2.5563945E-11 -5.9538971E-12 -6.8559264E-12 3.5394890E-12 A12 -3.6936627E-12 -1.1696405E-12 -2.1649008E-13 1.6409340E-13 A13 -4.6614703E-14 -1.0452064E-13 3.6418769E-14 -1.4416768E-14 A14 9.0177140E-14 -1.0211850E-15 7.6341071E-15 -3.2603129E-15 A15 1.6499968E-14 1.1638832E-15 6.9040638E-16 -2.9423023E-16 A16 2.5419290E-16 1.5197303E-16 2.6917744E-17 -6.7143418E-18 A17 1.7267336E-16 -3.1712370E-17 -3.5561484E-18 2.1405181E-18 A18 2.7825040E-16 -1.3611014E-19 -8.5525038E-19 4.0751470E-19 A19 -1.0653375E-16 6.4080645E-18 -5.7118302E-20 2.7056396E-20 A20 8.2140895E-18 -7.8166583E-19 1.1737306E-20 -4.3530299E-21

[0210] Table 21 shows the corresponding values ​​of conditional equations (1) to (12) for the imaging lenses of Examples 1 to 5. In Examples 1 to 5, the d-line is set as the reference wavelength. Table 21 shows the values ​​under the d-line reference.

[0211] [Table 21]

[0212] Equation No. Example 1 Example 2 Example 3 Example 4 Example 5 (1) f2 / f1 0.548 0.337 0.817 0.508 0.269 (2) f / f1 0.620 0.487 0.761 0.598 0.278 (3) f / f2 1.132 1.442 0.931 1.176 1.035 (4) f / f3 -0.337 -0.643 -0.413 -0.643 -0.037 (5) (1 -β2 2 )xβ3 2 ]]> 1.610 2.270 1.280 1.670 1.310 (6) ν1p-ν1n 6.89 10.64 8.95 14.48 4.75 (7) N3p 2.001 1.904 2.051 1.963 1.954 (8) ν3p-ν3n 5.34 8.58 1.52 -1.31 4.79 (9) ν3ave 26.46 27.02 26.18 24.77 29.92 (10) <![CDATA[β2]]> 0.44 0.31 0.56 0.42 0.24 (11) [Alpha]3 1.41 1.58 1.36 1.42 1.18 (12) TL / {f x tan(ω)} 2.47 3.47 4.47 5.47 6.47

[0213] As can be seen from the above data, the imaging lenses of Examples 1 to 5 can achieve miniaturization and high-speed focusing, with minimal aberration changes during focusing, and achieve high optical performance with good correction of various aberrations.

[0214] Next, the camera device according to the embodiments of the present invention will be described. Figure 11 and Figure 12 The diagram shows an external view of a camera 30, an imaging device according to an embodiment of the present invention. Figure 11 This is a stereoscopic view of camera 30 as seen from the front side. Figure 12 This is a perspective view of the camera 30 as seen from the rear side. The camera 30 is a so-called mirrorless type digital camera, capable of having a replaceable lens 20 detachably mounted. The replaceable lens 20 is configured to include an imaging lens 1 according to an embodiment of the present invention housed within a lens barrel.

[0215] The camera 30 includes a camera body 31, on the upper surface of which a shutter button 32 and a power button 33 are provided. Furthermore, an operation unit 34, an operation unit 35, and a display unit 36 ​​are provided on the back of the camera body 31. The display unit 36 ​​displays the captured image and the image from the perspective before the image was captured.

[0216] A photographic opening for light from the photographed object is provided at the center of the front of the camera body 31. A bayonet 37 is provided at the position corresponding to the photographic opening, and the interchangeable lens 20 is mounted on the camera body 31 via the bayonet 37.

[0217] In the camera body 31, a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) or the like that outputs an imaging signal corresponding to an object image formed by the interchangeable lens 20, a signal processing circuit that processes the imaging signal output from the imaging element to generate an image, a recording medium or the like for recording the generated image, and the like are provided. In the camera 30, a still image or a moving image can be captured by pressing the shutter button 32, and image data obtained by the capturing is recorded in the recording medium.

[0218] The above describes the technology of the present application with reference to the embodiments and examples, but the technology of the present application is not limited to the above-described embodiments and examples, and various modifications can be made. For example, the radius of curvature, the surface interval, the refractive index, the dispersion coefficient, the asphericity coefficient, and the like of each lens are not limited to the values shown in the above-described numerical examples, and other values can be used.

[0219] Also, the imaging device related to the embodiments of the present application is not limited to the above-described examples, and can be configured as a camera other than a mirrorless type, a film camera, a video camera, or the like.

[0220] Symbol explanation

[0221] 1 - imaging lens, 2 - on-axis light beam, 3 - light beam of maximum angle of view, 20 - interchangeable lens, 30 - camera, 31 - camera body, 32 - shutter button, 33 - power button, 34, 35 - operation section, 36 - display section, 37 - bayonet, G1 - first lens group, G2 - second lens group, G3 - third lens group, L11 to L12, L21 to L25, L31 to L32 - lens, PP - optical part, Sim - image plane, St - aperture, Z - optical axis.

Claims

1. An imaging lens having only three lens groups as lens groups, the three lens groups being composed of a first lens group having positive refractive power, a second lens group having positive refractive power, and a third lens group having negative refractive power in order from the object side to the image side, an aperture stop being disposed between a lens surface nearest the image side of the first lens group and a lens surface nearest the object side of the third lens group, the first lens group and the third lens group being fixed with respect to the image plane when focusing from an infinite object to a closest object, the second lens group moving along the optical axis, the first lens group being composed of a cemented lens including one negative lens and one positive lens, a lens surface nearest the object side of the first lens group being a convex surface, a lens surface nearest the image side of the first lens group being a concave surface, a double-concave lens being disposed nearest the object side of the second lens group, a double-convex lens being disposed adjacent to the image side of the double-concave lens, the double-concave lens and the double-convex lens being cemented to each other, a lens surface nearest the image side of the second lens group being a convex surface, a negative lens having a surface nearest the object side being concave being disposed nearest the object side of the third lens group, in a case where a focal length of the second lens group is set as f2, a focal length of the first lens group is set as fl, a condition formula (1-2) expressed by the following formula is satisfied: 0.508 ≤ f2 / fl < 1 (1-2), in a case where a focal length of the imaging lens in a state of focusing on an infinite object is set as f, a focal length of the third lens group is set as f3, a condition formula (4) expressed by the following formula is satisfied: -0.8 < f / f3 < 0 (4), the first lens group is composed of a first lens and a second lens in order from the object side to the image side, the first lens is a negative lens, a lens surface of the first lens on the object side is a convex surface, and a lens surface of the first lens on the image side is a concave surface, the second lens is a positive lens, a lens surface of the second lens on the object side is a convex surface, and a lens surface of the second lens on the image side is a concave surface, the second lens group is composed of a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens in order from the object side to the image side, the third lens is a negative lens, a lens surface of the third lens on the object side is a concave surface, and a lens surface of the third lens on the image side is a concave surface, the fourth lens is a positive lens, a lens surface of the fourth lens on the object side is a convex surface, and a lens surface of the fourth lens on the image side is a convex surface, the fifth lens is a negative lens, a lens surface of the fifth lens on the object side is a concave surface, and a lens surface of the fifth lens on the image side is a concave surface, the sixth lens is a positive lens, a lens surface of the sixth lens on the object side is a convex surface, and a lens surface of the sixth lens on the image side is a convex surface, the seventh lens is a negative lens, a lens surface of the seventh lens on the object side is a concave surface, and a lens surface of the seventh lens on the image side is a convex surface, the third lens group is composed of an eighth lens and a ninth lens in order from the object side to the image side, the eighth lens is a negative lens, a lens surface of the eighth lens on the object side is a concave surface, and a lens surface of the eighth lens on the image side is a convex surface, The ninth lens is a positive lens, an object side lens surface of the ninth lens is a plane or a convex surface, and an image side lens surface of the ninth lens is a convex surface.

2. The imaging lens according to claim 1, wherein a condition formula (2) expressed by the following expression is satisfied: 0.25 < f / f1 < 1 (2).

3. The imaging lens according to claim 1 or 2, wherein a condition formula (3) expressed by the following expression is satisfied: 0.8 < f / f2 < 1.6 (3).

4. The imaging lens according to claim 2, wherein a condition formula (2-1) expressed by the following expression is satisfied: 0.25 < f / f1 < 0.9 (2-1).

5. The imaging lens according to claim 3, wherein a condition formula (3-1) expressed by the following expression is satisfied: 0.9 < f / f2 < 1.45 (3-1).

6. The imaging lens according to claim 2, wherein a condition formula (2-2) expressed by the following expression is satisfied: 0.598 < f / f1 < 0.9 (2-2).

7. The imaging lens according to claim 1 or 2, wherein a condition formula (6) expressed by the following expression is satisfied in a case where a d-line reference Abbe number of the positive lens of the first lens group is set as ν1p, a d-line reference Abbe number of the negative lens of the first lens group is set as ν1n, 0 < ν1p-ν1n < 30 (6).

8. The imaging lens according to claim 7, wherein a condition formula (6-1) expressed by the following expression is satisfied: 0 < ν1p-ν1n < 15 (6-1).

9. The imaging lens according to claim 1 or 2, wherein a condition formula (10) expressed by the following expression is satisfied in a case where a lateral magnification of the second lens group in a state where the second lens group is focused on an infinite object is set as β2:

10. The imaging lens according to claim 9, wherein 0.1＜β2＜0.7（10）。 a condition formula (10-1) expressed by the following expression is satisfied:

11. The imaging lens according to claim 1 or 2, wherein 0.2＜β2＜0.6（10-1）。 a condition formula (11) expressed by the following expression is satisfied in a case where a lateral magnification of the third lens group in a state where the third lens group is focused on an infinite object is set as β3:

12. The imaging lens according to claim 11, wherein 1＜β3＜2.2（11）。 a condition formula (11-1) expressed by the following expression is satisfied:

13. The imaging lens according to claim 1, wherein 1.1＜β3＜1.6（11-1）。 a condition formula (4-1) expressed by the following expression is satisfied: -0.75 < f / f3 < 0 (4-1).

14. The imaging lens according to claim 1 or 2, wherein a condition formula (5) expressed by the following expression is satisfied in a case where a lateral magnification of the second lens group in a state where the second lens group is focused on an infinite object is set as β2, a lateral magnification of the third lens group in a state where the third lens group is focused on an infinite object is set as β3:

15. The imaging lens according to claim 14, wherein 1.15＜（1-β2 2 ）×β3 2 ＜2.5 （5）。 a condition formula (5-1) expressed by the following expression is satisfied:

16. The imaging lens according to claim 1 or 2, wherein 1.25＜（1-β2 2 ）×β3 2 ＜2.4 （5-1）。 ​ In a case where an average value of a dispersion coefficient of a d-line reference of all lenses included in the third lens group is set as v3ave, a conditional expression (9) expressed by the following expression is satisfied: 20 < v3ave < 30 (9).

17. The imaging lens according to claim 16, wherein a conditional expression (9-1) expressed by the following expression is satisfied: 23.5 < v3ave < 30 (9-1).

18. The imaging lens according to claim 1 or 2, wherein a sum of a distance on an optical axis from a lens surface closest to an object side of the first lens group to a lens surface closest to an image side of the third lens group and an air conversion distance on the optical axis from the lens surface closest to the image side of the third lens group to a position of an image-side focal point of the imaging lens in a state where the imaging lens is focused on an infinite object is set as TL, a maximum half viewing angle is set as ω, a conditional expression (12) expressed by the following expression is satisfied: 2 < TL / {f x tan(ω)} < 2.7 (12).

19. An image pickup apparatus provided with the imaging lens according to any one of claims 1 to 18.

Images