Imaging lens and camera device

Abstract

The present application provides a kind of imaging lens of internal focusing mode with small structure and good optical performance and camera device with the imaging lens. The imaging lens includes a first lens group with positive refractive power, a second lens group with positive refractive power and a third lens group in sequence from object side to image side. During focusing, only the second lens group moves. The second lens group includes at least four lenses. The imaging lens satisfies a predetermined condition.

Description

Technical Field

[0001] This invention relates to an imaging lens and a camera device. Background Technology

[0002] Previously, the lens systems described in Patent Document 1, Patent Document 2 and Patent Document 3 below were known as imaging lenses for digital cameras and the like.

[0003] Patent Document 1: Specification of Japanese Patent No. 06546752

[0004] Patent Document 2: Japanese Patent Application Publication No. 2019-090919

[0005] Patent Document 3: Japanese Patent Application Publication No. 2019-152773

[0006] In recent years, there has been a demand for imaging lenses with a compact structure and good optical performance using an internal focusing method. Summary of the Invention

[0007] The present invention was made in view of the above circumstances, and its object is to provide an imaging lens with an internal focusing method that has a small structure and good optical performance, and a camera device having the imaging lens.

[0008] The first imaging lens of the present invention includes, from the object side to the image side, a first lens group with positive refractive power, a second lens group with positive refractive power, and a third lens group. When focusing from an object at infinity to the nearest object, only the second lens group moves. The second lens group includes at least four lenses and an aperture. The system is defined as follows: TL is the sum of the distance along the optical axis from the lens surface of the first lens group closest to the object side to the lens surface of the third lens group closest to the image side, and the back focal length of the entire system (measured in air distance); Y is the maximum image height; and f is the focal length of the entire system when focusing on an object at infinity.

[0009] The imaging lens satisfies the following condition (1),

[0010] 4 < TL 2 / (Y×f)<7.5 (1).

[0011] The second imaging lens of the present invention includes, from the object side to the image side, a first lens group with positive refractive power, a second lens group with positive refractive power, and a third lens group. When focusing from an object at infinity to the nearest object, only the second lens group moves. The second lens group includes at least four lenses. When the distance on the optical axis from the lens surface of the first lens group closest to the object side to the lens surface of the first lens group closest to the image side is defined as G1TL, and the distance on the optical axis from the lens surface of the first lens group closest to the object side to the lens surface of the third lens group closest to the image side is defined as Gsum,

[0012] The imaging lens satisfies the following condition (2),

[0013] 0.04<G1TL / Gsum<0.14 (2).

[0014] Hereinafter, the first and second imaging lenses of the present invention will be collectively referred to as the imaging lenses of the present invention.

[0015] Preferably, the first lens group includes at least one positive lens and at least one negative lens.

[0016] Preferably, the third lens group includes at least three lenses.

[0017] Preferably, the object-side surface of the lens closest to the image side in the third lens group is concave. Furthermore, preferably, the lens closest to the image side in the third lens group is a negative lens with a concave object-side surface.

[0018] Preferably, the lens closest to the object in the second lens group is a positive lens. Preferably, when the lens closest to the object in the second lens group is a positive lens, and the refractive index of the positive lens closest to the object in the second lens group relative to the d-line is set to N2, the imaging lens of the present invention satisfies the following conditional expression (3).

[0019] 1.6 < N2 < 2.2 (3).

[0020] Preferably, the second lens group includes an aperture and at least one lens disposed on the object side of the aperture, wherein the image side surface of the lens adjacent to the object side of the aperture is concave.

[0021] Preferably, the second lens group includes an aperture and at least one lens disposed on the image side of the aperture. When the radius of curvature of the object-side surface of the lens adjacent to the image side of the aperture is set to Rc, and the combined focal length of all lenses in the second lens group that are closer to the image side than the aperture is set to f22, the imaging lens of the present invention satisfies the following conditional expression (4).

[0022] -0.7 < Rc / f22 < -0.1 (4).

[0023] Preferably, when the focal length of the entire system is set to f and the focal length of the first lens group is set to f1, the imaging lens of the present invention satisfies the following conditional expression (5).

[0024] 0.02 < f / f1 < 0.3 (5).

[0025] Preferably, the second lens group includes an aperture and at least one lens disposed on the object side of the aperture. When the focal length of the entire system is set to f when focusing on an object at infinity, and the combined focal length of all lenses in the second lens group that is closer to the object than the aperture is set to f21, the imaging lens of the present invention satisfies the following conditional expression (6).

[0026] 0.2 < f / f21 < 1 (6).

[0027] Preferably, the second lens group includes an aperture and at least one lens disposed on the image side of the aperture. When the focal length of the entire system is set to f when focusing on an object at infinity, and the combined focal length of all lenses in the second lens group, which is closer to the image side than the aperture, is set to f22, the imaging lens of the present invention satisfies the following conditional expression (7).

[0028] 0.4 < f / f22 < 1.5 (7).

[0029] Preferably, when the focal length of the entire system is set to f and the focal length of the third lens group is set to f3, the imaging lens of the present invention satisfies the following conditional expression (8).

[0030] 0 < |f / f3| < 0.3 (8).

[0031] Preferably, the second lens group includes at least one positive lens. When the dispersion coefficient of the d-line reference of the positive lens of the second lens group is set to ν2p, the imaging lens of the present invention includes at least one positive lens that satisfies the following condition (9).

[0032] 70<ν2p (9).

[0033] Preferably, the second lens group includes at least two sets of joint lenses, each joint lens including a positive lens and a negative lens, and the positive lenses of the at least two sets of joint lenses in the second lens group satisfy condition (9).

[0034] Preferably, when the d-line reference dispersion coefficients of the positive and negative lenses of the second lens group are set as νp and νn respectively, and the maximum value of the difference obtained by subtracting νn from νp is set as max(νp-νn), the imaging lens of the present invention satisfies the following conditional expression (10).

[0035] 30<max(νp-νn)<75 (10).

[0036] Preferably, the object-side surface of the lens closest to the object in the second lens group is a convex surface.

[0037] Preferably, when the back focal length of the entire system, measured in air distance, is set to Bf, and the focal length of the entire system when focused on an object at infinity is set to f, the imaging lens of the present invention satisfies the following conditional expression (11).

[0038] 0.1 < Bf / f < 0.5 (11).

[0039] The camera device of the present invention includes the imaging lens of the present invention.

[0040] In addition, the terms "including" and "including" in this specification mean that, in addition to the constituent elements listed, it may also include lenses that do not substantially have refractive power, as well as optical elements other than lenses such as apertures, filters and cover glass, and mechanism parts such as lens flanges, lens barrels, imaging elements and hand shaking correction mechanisms.

[0041] In addition, in this specification, "a group with positive refractive power" means that the group as a whole has positive refractive power. Similarly, "a group with negative refractive power" means that the group as a whole has negative refractive power. "Lens with positive refractive power," "positive lens," and "positive lens" have the same meaning. "Lens with negative refractive power," "negative lens," and "negative lens" have the same meaning. "A group of lenses" is not limited to a structure including multiple lenses; it can also be a structure including only one lens. "The entire system" refers to the imaging lens. "Back focal length" is the distance on the optical axis from the image-side lens surface of the entire system to the image-side focal point of the entire system.

[0042] "Single lens" refers to an unjoined single lens. However, a compound aspherical lens (a lens in which a spherical lens and an aspherical film formed on the spherical lens are integrated to function as a single aspherical lens) is used as a single lens and not considered a joined lens. Unless otherwise specified, the sign of the refractive power, surface shape, and radius of curvature associated with lenses including aspherical surfaces are assumed to be considered in the paraxial region. Regarding the sign of the radius of curvature, the radius of curvature of a surface with a convex shape facing the object side is signified as positive, and the radius of curvature of a surface with a convex shape facing the image side is signified as negative.

[0043] The "focal length" used in the conditional formula is the paraxial focal length. The values ​​used in the conditional formula are based on the d-line when focusing on an object at infinity. The "d-line," "C-line," and "g-line" described in this specification are bright lines. In this specification, the wavelength of the d-line is considered to be 587.56 nm, the wavelength of the C-line is considered to be 656.27 nm, and the wavelength of the g-line is considered to be 435.84 nm.

[0044] Invention Effects

[0045] According to the present invention, it is possible to provide an imaging lens with an internal focusing method that has a small structure and good optical performance, and a camera device having the imaging lens. Attached Figure Description

[0046] Figure 1 This is a cross-sectional view showing the structure and beam of an imaging lens according to one embodiment.

[0047] Figure 2 This is a cross-sectional view showing the structure of the imaging lens in Embodiment 1.

[0048] Figure 3 This is a diagram of the aberrations of the imaging lens in Example 1.

[0049] Figure 4 This is a cross-sectional view showing the structure of the imaging lens in Embodiment 2.

[0050] Figure 5 This is a diagram of the aberrations of the imaging lens in Example 2.

[0051] Figure 6 This is a cross-sectional view showing the structure of the imaging lens in Embodiment 3.

[0052] Figure 7 These are aberration diagrams of the imaging lens in Example 3.

[0053] Figure 8 This is a cross-sectional view showing the structure of the imaging lens in Embodiment 4.

[0054] Figure 9 This is a diagram of the aberrations of the imaging lens in Example 4.

[0055] Figure 10 This is a perspective view of the front side of a camera device according to an embodiment of the present invention.

[0056] Figure 11 This is a perspective view of the rear side of a camera device according to an embodiment of the present invention. Detailed Implementation

[0057] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Figure 1 The diagram illustrates the structure of an imaging lens, including a cross-section of the optical axis Z, and the beam according to an embodiment of the present invention. Figure 1 The example shown corresponds to the imaging lens of Embodiment 1, which will be described later. Figure 1 In the image, the left side is the object side, and the right side is the image side, illustrating the state of focusing on an object at infinity. As a light beam, Figure 1 The image also shows the on-axis beam 2 and the beam 3 with the maximum image height.

[0058] exist Figure 1The illustration shows an example assuming an imaging lens is used in a camera device, with a parallel flat optical component PP positioned between the imaging lens and the image plane (Sim). The optical component PP is assumed to be a component such as various filters and / or cover glass. These filters include, for example, low-pass filters, infrared cutoff filters, and filters that cut off specific wavelength regions. The optical component PP may be a component without refractive power, or it may be a structure in which the optical component PP is omitted.

[0059] The imaging lens, along the optical axis Z from the object side to the image side, comprises a first lens group G1 with positive refractive power, a second lens group G2 with positive refractive power, and a third lens group G3. This imaging lens is an internal focusing system in which only the second lens group G2 moves when focusing from an object at infinity to the nearest object, while the first lens group G1 and the third lens group G3 remain fixed relative to the image plane Sim. Hereinafter, the lens group that moves during focusing will be referred to as the focusing group. Figure 1 The arrow pointing to the left on the lower side of the second lens group G2 indicates that the second lens group G2 is the focusing group, which moves towards the object side when focusing from an object at infinity to the nearest object. By setting it so that only the second lens group G2 moves when focusing, while the first lens group G1 and the third lens group G3 do not move, not only can the focusing group be miniaturized and made lighter, but a lens structure suitable for dustproof and waterproof construction can also be achieved.

[0060] The first lens group G1 has positive refractive power as a whole. By making the lens group closest to the object a lens group with positive refractive power, it is beneficial to shorten the total optical length.

[0061] Preferably, the first lens group G1 includes at least one positive lens and at least one negative lens. This configuration is advantageous for correcting chromatic aberration.

[0062] As an example, Figure 1 The first lens group G1 consists of two lenses, a positive lens L11 and a negative lens L12, arranged sequentially from the object side to the image side. Figure 1 Lens L11 and lens L12 are single lenses.

[0063] The second lens group G2 has positive refractive power as a whole. Furthermore, the second lens group G2 comprises at least four lenses. By including more than four lenses in the second lens group G2, it is beneficial to suppress variations in aberrations when focusing from an object at infinity to the nearest object.

[0064] Preferably, the lens closest to the object side in the second lens group G2 is a positive lens. With this configuration, it is easy to reduce the beam diameter that is closer to the image side than the positive lens, thereby miniaturizing the lens diameter, which is beneficial for miniaturizing and lightening the focusing group.

[0065] Preferably, the object-side surface of the lens closest to the object in the second lens group G2 is convex. This configuration helps to appropriately suppress spherical aberration and to properly correct astigmatism and image plane curvature.

[0066] Preferably, the second lens group G2 includes an aperture St. By arranging the aperture St in the second lens group G2, the symmetry of the optical system with respect to the aperture St becomes better, making it easier to properly correct various aberrations. Furthermore, when focusing from an object at infinity to the nearest object, moving the aperture St along with the object helps to suppress variations in various aberrations. More preferably, the second lens group G2 includes at least one lens, an aperture St, and at least one lens sequentially from the object side to the image side. With this configuration, the symmetry of the optical system with respect to the aperture St becomes even better, making it easier to properly correct various aberrations.

[0067] Preferably, when the second lens group G2 includes an aperture St, the second lens group G2 includes at least one lens disposed on the object side of the aperture St, and the image-side surface of the lens adjacent to the object side of the aperture St is concave. With this configuration, it is advantageous to appropriately suppress the generation of spherical aberration and to appropriately correct astigmatism and image plane curvature.

[0068] Preferably, the second lens group G2 includes at least two sets of combined lenses, each consisting of a positive lens and a negative lens. This configuration is advantageous for correcting chromatic aberration.

[0069] As an example, Figure 1 The second lens group G2, from the object side to the image side, includes, in sequence, a positive lens L21, a positive lens L22, a negative lens L23, an aperture St, a positive lens L24, a negative lens L25, and a positive lens L26. Figure 1 The second lens group G2 comprises three lenses on both the object side and image side of the aperture St. Lenses L22 and L23 are joined together, and lenses L24 and L25 are joined together. Additionally, Figure 1 The aperture St indicates the position along the optical axis, not its size or shape.

[0070] The third lens group G3 can have positive or negative refractive power as a whole. Preferably, the third lens group G3 includes at least three lenses. With this configuration, it is beneficial to suppress variations in aberrations when focusing from an object at infinity to the nearest object.

[0071] Preferably, the object-side surface of the lens closest to the image side in the third lens group G3 is concave. This configuration is advantageous for correcting astigmatism.

[0072] Preferably, the lens closest to the image side in the third lens group G3 is a negative lens with its concave surface facing the object side. This configuration is advantageous for improving Pezvalence, shortening the overall optical length, and correcting distortion aberrations.

[0073] As an example, Figure 1 The third lens group G3 consists of four lenses from the object side to the image side: negative lens L31, negative lens L32, negative lens L33, and negative lens L34. Lenses L31 and L32 are joined together.

[0074] Next, the preferred structure related to the conditional expression will be described. However, the conditional expression preferably satisfied by the imaging lens is not limited to the conditional expression written in the form of the expression, but also includes all conditional expressions obtained by arbitrarily combining the lower limit and the upper limit from the preferred and more preferred conditional expressions.

[0075] Preferably, when the sum of the distance along the optical axis from the object-side lens surface of the first lens group G1 to the image-side lens surface of the third lens group G3 and the back focal length of the entire system (measured in air distance) is TL, the maximum image height is Y, and the focal length of the entire system when focusing on an object at infinity is f, the imaging lens satisfies the following conditional expression (1). TL is the total optical length. By ensuring that the corresponding value of conditional expression (1) is not below the lower limit, it is beneficial to ensure good optical performance and to easily ensure the movable area of ​​the focusing group, thus helping to suppress aberration variations during focusing. By ensuring that the corresponding value of conditional expression (1) is not above the upper limit, it is beneficial to miniaturize the lens system. In particular, it is beneficial to construct a lens system with a total optical length shorter than the image size. To obtain even better characteristics, the imaging lens more preferably satisfies at least one of the following conditional expressions (1-1) and (1-2).

[0076] 4 < TL 2 / (Y×f)<7.5 (1)

[0077] 4.5 < TL 2 / (Y×f)<7.2 (1-1)

[0078] 4.5 < TL 2 / (Y×f)<6 (1-2)

[0079] Preferably, when the distance on the optical axis from the object-side lens surface of the first lens group G1 to the image-side lens surface of the first lens group G1 is set to G1TL, and the distance on the optical axis from the object-side lens surface of the first lens group G1 to the image-side lens surface of the third lens group G3 is set to Gsum, the imaging lens satisfies the following conditional expression (2). By ensuring that the corresponding value of conditional expression (2) is not below the lower limit, it is easy to configure the number of lenses required for good aberration correction. By ensuring that the corresponding value of conditional expression (2) is not above the upper limit, it is possible to suppress the large diameter of the lenses in the first lens group G1, and it is easy to ensure the movable area of ​​the focusing group, thus which is beneficial to suppressing aberration variations during focusing. To obtain even better characteristics, the imaging lens more preferably satisfies the following conditional expression (2-1).

[0080] 0.04 < G1TL / Gsum < 0.14 (2)

[0081] 0.05 < G1TL / Gsum < 0.12 (2-1)

[0082] Preferably, in a structure where the object-side lens of the second lens group G2 is a positive lens, when the refractive index of the object-side positive lens of the second lens group G2 relative to the d-line is set to N2, the imaging lens satisfies the following conditional expression (3). By ensuring that the corresponding value of conditional expression (3) is not below the lower limit, it is easy to reduce the beam diameter on the image side, which is closer to the object side than the object-side positive lens of the second lens group G2, thereby minimizing the lens diameter. This is beneficial for miniaturization and weight reduction of the focusing group. By ensuring that the corresponding value of conditional expression (3) is not above the upper limit, it is beneficial to suppress variations in aberrations during focusing. To obtain even better characteristics, the imaging lens more preferably satisfies the following conditional expression (3-1).

[0083] 1.6 < N2 < 2.2 (3)

[0084] 1.7 < N2 < 2.1 (3-1)

[0085] Preferably, in the structure where the second lens group G2 includes an aperture St and at least one lens disposed on the image side of the aperture St, the imaging lens satisfies the following conditional expression (4) when the radius of curvature of the object-side surface of the lens adjacent to the image side of the aperture St is set to Rc, and the combined focal length of all lenses in the second lens group G2, which is closer to the image side than the aperture St, is set to f22. By ensuring that the corresponding value of conditional expression (4) is not below the lower limit, it is beneficial to suppress overcorrection of spherical aberration. By ensuring that the corresponding value of conditional expression (4) is not above the upper limit, it is beneficial to suppress undercorrection of spherical aberration. To obtain even better characteristics, the imaging lens more preferably satisfies the following conditional expression (4-1).

[0086] -0.7 < Rc / f22 < -0.1 (4)

[0087] -0.6 < Rc / f22 < -0.2 (4-1)

[0088] When the focal length of the entire system is set to f when focusing on an object at infinity, and the focal length of the first lens group G1 is set to f1, the imaging lens preferably satisfies the following condition (5). By ensuring that the corresponding value of condition (5) is not below the lower limit, the positive refractive power of the first lens group G1 can be ensured, thus facilitating a shorter overall optical length. By ensuring that the corresponding value of condition (5) is not above the upper limit, it is beneficial to suppress chromatic aberration in the first lens group G1 and to suppress variations in spherical aberration during focusing. To obtain even better characteristics, the imaging lens more preferably satisfies the following condition (5-1).

[0089] 0.02 < f / f1 < 0.3 (5)

[0090] 0.03 < f / f1 < 0.25 (5-1)

[0091] Preferably, in the structure where the second lens group G2 includes an aperture St and at least one lens disposed on the object side of the aperture St, when the focal length of the entire system is set to f when focusing on an object at infinity, and the combined focal length of all lenses in the second lens group G2, which is closer to the object side than the aperture St, is set to f21, the imaging lens satisfies the following conditional expression (6). By ensuring that the corresponding value of conditional expression (6) is not below the lower limit, the positive refractive power of the object-side sub-lens group, including all lenses in the second lens group G2, which is closer to the object side than the aperture St, can be ensured, thus facilitating a shorter overall optical length. By ensuring that the corresponding value of conditional expression (6) is not above the upper limit, the positive refractive power of the aforementioned object-side sub-lens group will not become excessive, thus facilitating the suppression of spherical aberration and astigmatism. To obtain even better characteristics, the imaging lens more preferably satisfies the following conditional expression (6-1).

[0092] 0.2 < f / f21 < 1 (6)

[0093] 0.3 < f / f21 < 0.7 (6-1)

[0094] Preferably, in the structure where the second lens group G2 includes an aperture St and at least one lens disposed on the image side of the aperture St, when the focal length of the entire system is set to f when focusing on an object at infinity, and the combined focal length of all lenses in the second lens group G2, which is closer to the image side than the aperture St, is set to f22, the imaging lens satisfies the following conditional expression (7). By ensuring that the corresponding value of conditional expression (7) is not below the lower limit, the positive refractive power of the image-side sub-lens group, including all lenses in the second lens group G2, which is closer to the image side than the aperture St, can be ensured, thus facilitating a shorter overall optical length. By ensuring that the corresponding value of conditional expression (7) is not above the upper limit, the positive refractive power of the aforementioned image-side sub-lens group will not become excessive, thus facilitating the suppression of spherical aberration and astigmatism. To obtain even better characteristics, the imaging lens more preferably satisfies the following conditional expression (7-1).

[0095] 0.4 < f / f²² < 1.5 (7)

[0096] 0.5 < f / f²² < 1.2 (7-1)

[0097] Preferably, when the focal length of the entire system is set to f when focusing on an object at infinity, and the focal length of the third lens group is set to f3, the imaging lens satisfies the following condition (8). |f / f3| is an absolute value, therefore its lower limit is 0. By making the imaging lens satisfy condition (8), it is beneficial to suppress Pezvar summation, and therefore beneficial to suppress the increase in image plane curvature. Furthermore, it is beneficial to suppress variations in various aberrations when focusing from an object at infinity to the nearest object. To obtain even better characteristics, the imaging lens more preferably satisfies the following condition (8-1).

[0098] 0 < |f / f3| < 0.3 (8)

[0099] 0 < |f / f3| < 0.2 (8-1)

[0100] Preferably, in the structure where the second lens group G2 includes at least one positive lens, when the dispersion coefficient of the d-line reference of the positive lens of the second lens group G2 is set to ν2p, the second lens group G2 includes at least one positive lens that satisfies the following conditional expression (9). This configuration is advantageous for correcting chromatic aberration. To obtain even better characteristics, the second lens group G2 more preferably includes at least one positive lens that satisfies the following conditional expression (9-1). By ensuring that the corresponding value of conditional expression (9-1) does not exceed the upper limit, overcorrection of chromatic aberration is easily suppressed.

[0101] 70<ν2p (9)

[0102] 80 < ν²p < 100 (9-1)

[0103] Preferably, in a structure where the second lens group G2 includes at least two sets of combined lenses, each set comprising a positive lens and a negative lens, the positive lenses of the at least two sets of combined lenses in the second lens group G2 satisfy condition (9). That is, preferably, at least two of the positive lenses among the plurality of such combined lenses included in the second lens group G2 satisfy condition (9). By ensuring that the at least two positive lenses combined with the negative lens satisfy condition (9), it is more advantageous to correct chromatic aberration. More preferably, the second lens group G2 includes positive lenses of the aforementioned combined lenses satisfying condition (9) on both the object side and the image side of the aperture St. To obtain even better characteristics, the positive lenses of the at least two sets of combined lenses in the second lens group G2 more preferably satisfy condition (9-1).

[0104] Preferably, in a structure where the second lens group G2 includes at least two sets of joint lenses, each including a positive lens and a negative lens, the imaging lens satisfies the following conditional expression (10) when the chromatic dispersion coefficients of the respective d-line references of the positive and negative lenses of the second lens group G2 are set as νp and νn, respectively, and the maximum value of the difference obtained by subtracting νn from νp is set as max(νp-νn). By ensuring that the corresponding value of conditional expression (10) is not below the lower limit, it is beneficial to properly correct chromatic aberration. By ensuring that the corresponding value of conditional expression (10) is not above the upper limit, it is easy to suppress overcorrection of chromatic aberration. To obtain even better characteristics, the imaging lens more preferably satisfies the following conditional expression (10-1).

[0105] 30<max(νp-νn)<75 (10)

[0106] 35 < max(νp - νn) < 65 (10-1)

[0107] Preferably, when the back focal length of the entire system, measured in air distance, is set to Bf, and the focal length of the entire system when focused on an object at infinity is set to f, the imaging lens satisfies the following conditional expression (11). By ensuring that the corresponding value of conditional expression (11) is not below the lower limit, it is advantageous to ensure an appropriate back focal length. In particular, it is advantageous to ensure the back focal length when the imaging lens is used as an interchangeable lens. By ensuring that the corresponding value of conditional expression (11) is not above the upper limit, it is advantageous to shorten the total optical length. To obtain even better characteristics, the imaging lens more preferably satisfies the following conditional expression (11-1).

[0108] 0.1 < Bf / f < 0.5 (11)

[0109] 0.15 < Bf / f < 0.45 (11-1)

[0110] The following describes two preferred embodiments considering the above structure and conditional equation. The first embodiment comprises, from the object side to the image side, a first lens group G1 with positive refractive power, a second lens group G2 with positive refractive power, and a third lens group. When focusing from an object at infinity to the nearest object, only the second lens group G2 moves. The second lens group G2 includes at least four lenses and an aperture St, satisfying conditional equation (1). According to the first embodiment, it is easy to realize an imaging lens with good optical performance, small structure, and suppression of aberrations during focusing.

[0111] The second method comprises, from the object side to the image side, a first lens group G1 with positive refractive power, a second lens group G2 with positive refractive power, and a third lens group. When focusing from an object at infinity to the nearest object, only the second lens group G2 moves. The second lens group G2 includes at least four lenses, satisfying condition (2) for the imaging lens. According to the second method, it is easy to realize an imaging lens with good optical performance, small structure, and suppression of aberrations during focusing.

[0112] in addition, Figure 1 The example shown is one instance, and various modifications can be made without departing from the spirit of the invention. For example, the number of lenses constituting each lens group can be [number missing]. Figure 1 The number of examples varies.

[0113] Each lens group can, for example, adopt the following structure. The first lens group G1 can be configured to include, from the object side to the image side, a positive meniscus lens with its convex surface facing the object side and a biconcave lens. Alternatively, the first lens group G1 can be configured to include, from the object side to the image side, a biconcave lens and a positive meniscus lens with its convex surface facing the object side.

[0114] The second lens group G2 can be configured as follows, from the object side to the image side, sequentially including a positive meniscus lens with its convex surface facing the object side, a conjoined lens formed by sequentially joining a positive meniscus lens with its convex surface facing the object side and a negative meniscus lens with its convex surface facing the object side, an aperture St, a conjoined lens formed by sequentially joining a positive meniscus lens with its concave surface facing the object side and a negative meniscus lens with its concave surface facing the object side, and a positive lens with its convex surface facing the image side. Alternatively, the second lens group G2 can be configured as follows, from the object side to the image side, sequentially including a biconvex lens, a conjoined lens formed by sequentially joining a positive meniscus lens with its convex surface facing the object side and a negative meniscus lens with its convex surface facing the object side, an aperture St, a conjoined lens formed by sequentially joining a positive meniscus lens with its concave surface facing the object side and a biconcave lens, and two biconvex lenses.

[0115] The third lens group G3 can be configured as follows, from the object side to the image side, a combined lens consisting of a biconvex lens and a negative lens with its concave surface facing the object side joined together, and two negative lenses with their concave surfaces facing the object side. Alternatively, the third lens group G3 can be configured as follows, from the object side to the image side, a combined lens consisting of a biconvex lens and a negative lens with its concave surface facing the object side joined together, and a negative meniscus lens with its concave surface facing the object side joined together.

[0116] Including structures related to conditional expressions, the above-mentioned preferred structures and implementable structures can be combined arbitrarily, and preferably selected appropriately according to the required specifications.

[0117] Next, an embodiment of the imaging lens of the present invention will be described.

[0118] [Example 1]

[0119] A cross-sectional view showing the structure of the imaging lens of Embodiment 1 is shown in Figure 2 . Figure 2 The image shows the state of focusing on an object at infinity. Figure 2 The light beam is not shown in the image, which is related to... Figure 1 The methods of illustration are different, but the other aspects are basically the same. Figure 1 same.

[0120] The imaging lens of Embodiment 1 comprises, from the object side to the image side, 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 positive refractive power. The first lens group G1 comprises two lenses, L11 to L12, from the object side to the image side. The second lens group G2 comprises three lenses, L21 to L23, an aperture St, and three lenses, L24 to L26, from the object side to the image side. The third lens group G3 comprises four lenses, L31 to L34, from the object side to the image side. When focusing from an object at infinity to the nearest object, only the second lens group G2 moves towards the object side, while the first lens group G1 and the third lens group G3 remain fixed relative to the image plane Sim. This is a summary of the imaging lens of Embodiment 1.

[0121] Regarding the imaging lens of Example 1, basic lens data is shown in Table 1, specifications in Table 2, variable surface spacing in Table 3, and aspherical coefficients in Table 4. In Table 1, the Sn column shows the surface numbering when the surface closest to the object side is designated as surface 1 and the numbering increases sequentially towards the image side; the R column shows the radius of curvature of each surface; and the D column shows the surface spacing along the optical axis between each surface and its image-side adjacent surface. The Nd column shows the refractive index of each component relative to the d-line, and the νd column shows the dispersion coefficient of each component based on the d-line reference.

[0122] In Table 1, the radius of curvature of the convex surface facing the object side is marked positive, and the radius of curvature of the convex surface facing the image side is marked negative. Table 1 also shows the aperture St and optical components PP. The term (St) is recorded along with the surface number in the surface number column corresponding to the aperture St. The value in the bottom column of D in Table 1 is the interval between the surface closest to the image side and the image plane Sim. In Table 1, the variable surface interval that changes during focusing is indicated by the notation DD[], with the object-side surface number of the interval marked in [] and recorded in column D.

[0123] Table 2 shows the values ​​for focal length f, back focal length Bf (air-converted distance), F-number FNo., maximum full angle of view 2ω, maximum image height Y, and total optical length TL. The total optical length is the sum of the distance along the optical axis from the object-side lens surface of the first lens group G1 to the image-side lens surface of the third lens group, and the back focal length (air-converted distance). The (°) in the 2ω column indicates the unit as degrees. The values ​​shown in Table 2 are based on the d-line when focusing on an object at infinity.

[0124] Table 3 shows the values ​​for the variable surface spacing. In Table 3, the values ​​for an object distance of infinity and 700 mm are shown in the columns described as "infinity" and "700 mm," respectively. The object distance referred to here is the distance along the optical axis from the object to the image plane (Sim).

[0125] In Table 1, the surface numbers of aspherical surfaces are marked with an asterisk (*), and the paraxial radius of curvature is recorded in the radius of curvature column. In Table 4, the surface number of the aspherical surface is shown in the Sn column, and the aspherical coefficient values ​​for each aspherical surface are shown in the KA and Am columns. Furthermore, m is an integer greater than or equal to 3, varying from surface to surface; for example, in the aspherical surfaces of Example 1, m = 3, 4, 5, ..., 20. The aspherical coefficient values ​​in Table 4, "E±n" (n: integer), represent "×10⁻¹⁰". ±n KA and Am are the aspheric coefficients in the aspheric formula expressed by the following equation.

[0126] Zd=C×h 2 / {1+(1-KA×C 2 ×h 2 ) 1 / 2}+∑Am×h m

[0127] in,

[0128] Zd: Aspherical depth (the length of the perpendicular line from a point on the aspherical surface at height h to a plane tangent to the vertex of the aspherical surface and perpendicular to the optical axis Z);

[0129] h: Height (distance from the optical axis Z to the lens surface);

[0130] C: The reciprocal of the paraxial radius of curvature;

[0131] KA, Am: Aspheric coefficients

[0132] In aspherical form, ∑ represents the summation related to m.

[0133] In the data in each table, degrees are used as the unit for angles and millimeters as the unit for lengths. Optical systems can be used at both magnified and reduced scales, so other appropriate units may also be used. Furthermore, the values ​​are rounded to a specified number of decimal places in the tables shown below.

[0134] [Table 1]

[0135] Example 1

[0136]

[0137]

[0138] [Table 2]

[0139] Example 1

[0140] f 78.68 Bf 23.28 FNo. 1.75 2ω(°) 38.0 Y 27.35 TL 103.58

[0141] [Table 3]

[0142] Example 1

[0143] DD[4] DD

[15] Infinity 16.3400 2.3200 700mm 1.9320 16.7280

[0144] [Table 4]

[0145] Example 1

[0146] Sn 14 15 KA 1.0000000E+00 1.0000000E+00 A3 0.0000000E+00 0.0000000E+00 A4 -1.0088242E-06 1.3965451E-07 A5 -2.6513493E-07 -2.3150181E-07 A6 1.7071672E-08 1.5432308E-08 A7 8.2564362E-10 4.7477332E-10 A8 -1.0054449E-12 -8.1934546E-11 A9 -1.7643417E-11 -8.2435003E-13 A10 6.0868319E-13 1.5740720E-13 A11 4.7629976E-14 1.2547704E-14 A12 1.3561314E-17 -9.8161787E-16 A13 -1.9007385E-16 -1.6440179E-17 A14 5.4134773E-18 3.9921882E-18 A15 -6.3292092E-19 -7.9972791E-20 A16 6.8084206E-21 -7.0611745E-21 A17 4.8308631E-21 1.5944044E-22 A18 -1.8685654E-22 3.8876927E-24 A19 -3.6580337E-24 5.0171611E-25 A20 1.8806460E-25 -2.1180317E-26

[0147] Figure 3 The diagram shows the aberrations of the imaging lens in Example 1. Figure 3 In the image, from left to right, spherical aberration, astigmatism, distortion aberration, and magnification chromatic aberration are shown. Figure 3In the diagram, the upper section marked "Infinity" shows the aberration diagrams for focusing on an object at infinity, and the lower section marked "700mm" shows the aberration diagrams for focusing on an object at a distance of 700mm. In the spherical aberration diagram, aberrations below the d-line, C-line, and g-line are shown with solid lines, long dashed lines, and short dashed lines, respectively. In the astigmatism diagram, aberrations below the d-line in the sagittal direction are shown with solid lines, and aberrations below the d-line in the meridional direction are shown with short dashed lines. In the distortion aberration diagram, aberrations below the d-line are shown with solid lines. In the magnification chromatic aberration diagram, aberrations below the C-line and g-line are shown with long dashed lines and short dashed lines, respectively. FNo. in the spherical aberration diagram represents the F-value, and ω in other aberration diagrams represents the half-angle of view. Figure 3 The values ​​of FNo. and ω corresponding to the upper end of the vertical axis of each graph are also shown.

[0148] Unless otherwise specified, the notation, meaning, recording method and illustration method of the data related to Embodiment 1 above are the same in the following embodiments, so repeated descriptions are omitted below.

[0149] [Example 2]

[0150] A cross-sectional view showing the structure of the imaging lens of Embodiment 2 is shown in Figure 4 The third lens group G3 comprises three lenses, L31 to L33, arranged sequentially from the object side to the image side. Apart from this, the imaging lens of Embodiment 2 has the same general structure as the imaging lens of Embodiment 1. Regarding the imaging lens of Embodiment 2, basic lens data is shown in Table 5, specifications in Table 6, variable surface spacing in Table 7, aspherical coefficients in Table 8, and various aberrations are illustrated in Table 1. Figure 5 .exist Figure 5 In the middle section, the upper section shows the aberration diagrams for the state of focusing on an object at infinity, and the lower section shows the aberration diagrams for the state of focusing on an object at a distance of 700 mm.

[0151] [Table 5]

[0152] Example 2

[0153] Sn R D Nd νd 1 -218.1174 1.6800 1.83819 20.98 2 862.8611 1.4217 3 100.6136 4.9999 1.81298 46.70 4 914.3003 DD[4] 5 44.8833 5.7211 2.05090 26.94 6 123.1683 0.2000 7 28.4030 9.1602 1.43875 94.66 8 227.5893 1.0000 1.72440 28.27 9 19.9563 10.7500 10 (St) ∞ 6.6910 11 -40.4112 5.6250 1.43875 94.66 12 -16.3406 1.0098 1.47999 58.05 13 -175.0160 2.1731 *14 348.9452 8.3250 1.68532 57.23 *15 -37.6856 DD

[15] 16 343.1297 7.7500 1.88300 39.22 17 -54.9467 1.9300 1.59270 35.31 18 114.5880 8.8751 *19 -88.6792 1.3000 1.51680 64.20 *20 -250.0222 20.0971 21 ∞ 3.2000 1.51680 64.20 22 ∞ 1.0708

[0154] [Table 6]

[0155] Example 2

[0156] f 80.09 Bf 23.28 FNo. 1.75 2ω(°) 37.8 Y 27.35 TL 101.89

[0157] [Table 7]

[0158] Example 2

[0159] DD[4] DD

[15] Infinity 16.3700 1.5000 700mm 4.0688 13.8012

[0160] [Table 8]

[0161] Example 2

[0162] Sn 14 15 KA 1.0000000E+00 1.0000000E+00 A3 0.0000000E+00 0.0000000E+00 A4 -3.3341899E-06 -5.4670280E-07 A5 -3.5284692E-07 -4.3175175E-07 A6 2.4789455E-08 2.5720606E-08 A7 2.1033099E-10 -2.5715428E-11 A8 -1.8944595E-11 -4.0127217E-11 A9 -1.5705848E-11 -5.4415585E-12 A10 5.4537854E-13 2.3112777E-13 A11 5.2372366E-14 1.1952014E-14 A12 4.1000990E-16 -5.3976159E-16 A13 -2.2801458E-16 3.6744505E-19 A14 3.3648748E-18 2.9682650E-18 A15 -5.4359920E-19 -1.5996152E-19 A16 7.8226914E-21 -1.0065782E-20 A17 4.6683964E-21 1.4335940E-22 A18 -1.8579452E-22 2.0085964E-23 A19 -1.8661223E-24 1.4351292E-24 A20 1.0896918E-25 -7.8554648E-26

[0163] Sn 19 20 KA 1.0000000E+00 1.0000000E+00 A4 -2.5070177E-05 -2.4232978E-05 A6 4.2675044E-08 4.3430575E-08 A8 -5.1611035E-11 -5.6962022E-11 A10 2.0533147E-15 1.6367093E-14

[0164] [Example 3]

[0165] A cross-sectional view showing the structure of the imaging lens of Embodiment 3 is shown in Figure 6 The imaging lens of Embodiment 3 has the same general structure as the imaging lens of Embodiment 1. Regarding the imaging lens of Embodiment 3, basic lens data are shown in Table 9, specifications are shown in Table 10, variable surface spacing is shown in Table 11, aspherical coefficients are shown in Tables 12A and 12B, and various aberrations are illustrated in... Figure 7 .exist Figure 7 In the middle section, the upper section shows the aberration diagrams for the state of focusing on an object at infinity, and the lower section shows the aberration diagrams for the state of focusing on an object at a distance of 700 mm.

[0166] [Table 9]

[0167] Example 3

[0168] Sn R D Nd νd *1 73.4849 5.6356 1.79952 42.25 2 229.4959 2.5217 3 -438.5951 1.6800 1.74077 27.76 4 176.1213 DD[4] *5 40.2987 7.1498 1.75500 52.34 *6 246.8313 0.2000 7 29.4118 7.5957 1.43875 94.66 8 483.4326 1.6300 1.57099 50.80 9 18.2710 8.5255 10 (St) ∞ 6.8606 11 -37.6461 5.1552 1.43875 94.66 12 -17.5652 1.2200 1.67270 32.18 13 -49.9998 5.6627 *14 -129.5016 6.6782 1.81000 41.00 *15 -33.8703 DD

[15] 16 171.0236 8.7121 1.88300 39.22 17 -46.9271 1.9350 1.59270 35.31 18 ∞ 1.9730 19 -125.1330 1.3000 1.51680 64.20 20 735.3274 4.9507 *21 -83.3308 1.3000 1.64769 33.84 *22 5447.9941 16.4421 23 ∞ 3.2000 1.51680 64.20 24 ∞ 1.0500

[0169] [Table 10]

[0170] Example 3

[0171] f 78.68 Bf 19.60 FNo. 1.75 2ω(°) 38.8 Y 27.35 TL 100.29

[0172] [Table 11]

[0173] Example 3

[0174] DD[4] DD

[15] Infinity 15.5748 2.3000 700mm 1.9413 15.9335

[0175] [Table 12A]

[0176] Example 3

[0177] Sn 1 5 6 KA 1.0000000E+00 1.0000000E+00 1.0000000E+00 A3 0.0000000E+00 0.0000000E+00 0.0000000E+00 A4 5.8147392E-08 6.6938462E-07 8.0538442E-07 A5 -1.4825586E-08 -5.6043044E-08 -9.5489701E-08 A6 1.0908357E-09 7.4883121E-10 2.7580974E-09 A7 -1.8829404E-11 3.3111264E-12 6.5655872E-11 A8 -6.4883790E-13 6.3887262E-12 3.1276358E-12 A9 2.8958803E-14 -3.3222385E-13 -4.9487224E-13 A10 -2.9525379E-16 4.0516547E-15 1.0242324E-14

[0178] Sn 14 15 KA 1.0000000E+00 1.0000000E+00 A3 0.0000000E+00 0.0000000E+00 A4 -1.0644494E-06 1.3717110E-06 A5 -3.6017804E-07 -5.3112154E-07 A6 3.2032549E-08 3.5119920E-08 A7 6.8928613E-10 2.8461265E-10 A8 -7.8457827E-11 -6.9980263E-11 A9 -1.7682627E-11 -3.9507175E-12 A10 8.5844447E-13 1.7906133E-13 A11 5.8591172E-14 1.3535812E-14 A12 -3.0095799E-16 -3.7931968E-16 A13 -2.1621120E-16 -1.9856162E-17 A14 4.3913697E-18 2.8581812E-18 A15 -6.9079727E-19 -6.4812430E-20 A16 7.3825370E-21 -7.9068628E-21 A17 5.0044650E-21 9.2658788E-23 A18 -1.7088563E-22 4.4664970E-24 A19 -3.4569432E-24 7.5449195E-25 A20 1.4963998E-25 -2.2407097E-26

[0179] [Table 12B]

[0180] Example 3

[0181] Sn 21 22 KA 1.0000000E+00 1.0000000E+00 A3 0.0000000E+00 0.0000000E+00 A4 -6.6321548E-05 -6.8790465E-05 A5 4.9514285E-06 5.2801984E-06 A6 -7.0543852E-08 -1.1443187E-07 A7 -2.9942679E-09 -5.5371144E-10 A8 5.5956776E-11 -5.0366166E-12 A9 1.1091435E-12 1.2598300E-12 A10 -1.9074734E-14 2.8934956E-15 A11 8.1566810E-16 1.3556599E-15 A12 -3.2897952E-17 -1.7693891E-17 A13 -7.5334927E-19 -4.4463708E-18 A14 3.1795836E-20 1.1057058E-19

[0182] [Example 4]

[0183] A cross-sectional view showing the structure of the imaging lens of Embodiment 4 is shown in Figure 8 In the imaging lens of Embodiment 4, the second lens group G2, from the object side to the image side, includes three lenses L21 to L23, an aperture St, and four lenses L24 to L27. The third lens group G3, from the object side to the image side, includes three lenses L31 to L33. Except as described above, the imaging lens of Embodiment 4 has the same general structure as the imaging lens of Embodiment 1. Regarding the imaging lens of Embodiment 4, basic lens data is shown in Table 13, specifications in Table 14, variable surface spacing in Table 15, aspherical coefficients in Table 16, and various aberrations are illustrated in Table 17. Figure 9 .exist Figure 9 In the middle section, the upper section shows the aberration diagrams for the state of focusing on an object at infinity, and the lower section shows the aberration diagrams for the state of focusing on an object at a distance of 700 mm.

[0184] [Table 13]

[0185] Example 4

[0186] Sn R D Nd νd 1 87.3685 3.5000 2.05090 26.94 2 146.8535 3.0889 3 -660.0639 1.5300 1.71198 26.75 4 193.2913 DD[4] *5 64.2762 7.0498 1.74320 49.29 *6 -748.1892 0.9999 7 28.0125 9.6248 1.43875 94.66 8 170.3378 1.1300 1.59928 31.14 9 23.1318 11.3827 10 (St) ∞ 6.7088 11 -55.3327 4.5189 1.43875 94.66 12 -22.0744 1.0100 1.51823 58.90 13 388.1858 0.4998 14 266.8384 2.8540 1.49700 81.54 15 -302.3940 0.5242 *16 625.1529 7.3422 1.81000 41.00 *17 -49.2247 DD

[17] 18 1078.3462 9.5000 1.88300 39.22 19 -36.0767 1.6900 1.59270 35.31 20 -442.7606 5.2185 21 -41.5086 1.2500 1.59186 38.81 22 -678.7198 18.6642 23 ∞ 3.2000 1.51680 64.20 24 ∞ 1.0500

[0187] [Table 14]

[0188] Example 4

[0189] f 77.80 Bf 21.82 FNo. 1.54 2ω(°) 38.4 Y 27.35 TL 101.25

[0190] [Table 15]

[0191] Example 4

[0192] DD[4] DD

[17] Infinity 17.4999 2.4999 700mm 6.0508 13.9490

[0193] [Table 16]

[0194] Example 4

[0195] Sn 5 6 KA 1.0000000E+00 1.0000000E+00 A4 -2.0815738E-07 3.1612101E-07 A6 -2.5618170E-11 -1.2886119E-10 A8 -5.3277726E-14 2.1204755E-13 A10 2.8059174E-16 2.0378850E-17

[0196] Sn 16 17 KA 1.0000000E+00 1.0000000E+00 A4 -2.9218701E-06 -2.2026040E-06 A6 -9.7250329E-09 -2.5755732E-09 A8 4.9003957E-11 -3.7951241E-11 A10 -4.3666590E-13 1.2937170E-13 A12 1.3227604E-15 4.1592996E-17 A14 1.5300552E-18 -3.6707730E-18 A16 -2.8974079E-20 1.4820054E-20 A18 8.9812385E-23 -2.4765310E-23 A20 -9.8857875E-26 1.3042237E-26

[0197] Table 17 shows the corresponding values ​​of conditional equations (1) to (11) for the imaging lenses of Examples 1 to 4. Examples 1 to 4 use the d-line as the reference wavelength. Table 17 shows the values ​​under the d-line reference.

[0198] [Table 17]

[0199] Formula number Conditional expression Example 1 Example 2 Example 3 Example 4 (1) <![CDATA[TL 2 / (Y×f)]]> 4.985 4.739 4.674 4.818 (2) G1TL / Gsum 0.092 0.084 0.100 0.069 (3) N2 1.755 2.051 1.755 1.743 (4) Rc / f22 -0.415 -0.477 -0.384 -0.560 (5) f / f1 0.097 0.197 0.154 0.034 (6) f / f21 0.587 0.359 0.546 0.686 (7) f / f22 0.797 0.946 0.803 0.787 (8) |f / f3| 0.047 0.069 0.035 0.182 (9) ν2p 94.66 94.66 94.66 94.66 (10) max(νp-νn) 62.48 66.39 62.48 63.52 (11) Bf / f 0.296 0.291 0.249 0.281

[0200] The imaging lenses in Examples 1-4 are internal focusing lenses, with a total optical length shorter than the image size and a compact structure. Furthermore, the imaging lenses in Examples 1-4 exhibit well-corrected aberrations, achieving high resolution and high optical performance.

[0201] Next, the imaging device according to the embodiments of the present invention will be described. Figure 10 and Figure 11 The diagram shows an external view of a camera 30, an imaging device according to an embodiment of the present invention. Figure 10 This is a stereoscopic view of camera 30 viewed from the front side. Figure 11 This is a perspective view of the camera 30 as seen from the rear side. The camera 30 is a so-called mirrorless digital camera, which can be detachably fitted with an interchangeable lens 20. The interchangeable lens 20 is configured to include an imaging lens 1 according to an embodiment of the present invention housed within a lens barrel.

[0202] The camera 30 includes a camera body 31, and a shutter button 32 and a power button 33 are provided on the upper surface of the camera body 31. 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 ​​can display the captured image and the image existing within the field of view before shooting.

[0203] A camera body 31 has a camera aperture for light from the subject to enter at the center of the front. A bayonet 37 is provided at the position corresponding to the camera aperture, and the interchangeable lens 20 is mounted on the camera body 31 via the bayonet 37.

[0204] The camera body 31 contains an imaging element such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) that outputs an image signal corresponding to the image of the subject formed by the interchangeable lens 20, a signal processing circuit that processes the image signal output from the imaging element to generate an image, and a recording medium for recording the generated image. In the camera 30, still images or moving images can be captured by pressing the shutter button 32, and the image data obtained through this capture is recorded in the aforementioned recording medium.

[0205] The above description, through examples and embodiments, illustrates the technology of the present invention. However, the technology of the present invention is not limited to the above examples and embodiments, and various modifications are possible. For example, the radius of curvature, interplanar spacing, refractive index, dispersion coefficient, and aspherical coefficient of each lens are not limited to the values ​​shown in the above embodiments, and other values ​​may be used.

[0206] Furthermore, the imaging device involved in the embodiments of the present invention is not limited to the examples described above. For example, it can also be configured as a camera other than a mirrorless camera, a film camera, a video camera, or other similar devices.

[0207] Symbol Explanation

[0208] 1-Imaging lens, 2-On-axis beam, 3-Beam with maximum image height, 20-Interchangeable lens, 30-Camera, 31-Camera body, 32-Shutter button, 33-Power button, 34, 35-Operation unit, 36-Display unit, 37-Mount, G1-First lens group, G2-Second lens group, G3-Third lens group, L11~L12, L21~L27, L31~L34-Lens, PP-Optical components, Sim-Image plane, St-Aperture, Z-Optical axis.

Claims

1. An imaging lens, comprising, from the object side to the image side, a first lens group having positive refractive power, a second lens group having positive refractive power, and a third lens group, in sequence. When focusing from an object at infinity to the nearest object, only the second lens group moves. The second lens group includes an aperture and at least one lens disposed on the object side of the aperture. Let TL be the sum of the distance along the optical axis from the lens surface of the first lens group closest to the object to the lens surface of the third lens group closest to the image, and the back focal length of the entire system measured in air-converted distance. Set the maximum image height to Y. Let the focal length of the entire system be f when focusing on an object at infinity. When the combined focal length of all lenses in the second lens group, which is closer to the object than the aperture, is set to f21, The imaging lens satisfies the following conditions (1) and (6). 4 < TL 2 (Y x f) < 7.5 (1), 0.2 < f / f21 < 1 (6), The first lens group consists of two lenses. The second lens group is composed of lenses with positive, positive, negative, positive, negative, and positive refractive power, or lenses with positive, positive, negative, positive, negative, positive, and positive refractive power. The third lens group is composed of lenses with positive, negative, and negative refractive power, or lenses with positive, negative, negative, and negative refractive power.

2. An imaging lens, comprising, from the object side to the image side, a first lens group having positive refractive power, a second lens group having positive refractive power, and a third lens group, in sequence. When focusing from an object at infinity to the nearest object, only the second lens group moves. The second lens group includes at least four lenses and an aperture. One of the at least four lenses in the second lens group is arranged adjacent to the object side of the aperture and has a concave image side. One of the at least four lenses in the second lens group is arranged adjacent to the image side of the aperture. Let TL be the sum of the distance along the optical axis from the lens surface of the first lens group closest to the object to the lens surface of the third lens group closest to the image, and the back focal length of the entire system measured in air-converted distance. Set the maximum image height to Y. Let the focal length of the entire system be f when focusing on an object at infinity. Let Rc be the radius of curvature of the object-side surface of the lens adjacent to the image side of the aperture. When the combined focal length of all lenses in the second lens group, which is located on the image side closer than the aperture, is set to f22... The imaging lens satisfies the following conditions (1) and (4a). 4 < TL 2 (Y x f) < 7.5 (1), -0.56≤Rc / f22<-0.1 (4a), The first lens group consists of two lenses. The second lens group is composed of lenses with positive, positive, negative, positive, negative, and positive refractive power, or lenses with positive, positive, negative, positive, negative, positive, and positive refractive power. The third lens group is composed of lenses with positive, negative, and negative refractive power, or lenses with positive, negative, negative, and negative refractive power.

3. An imaging lens, comprising, from the object side to the image side, a first lens group having positive refractive power, a second lens group having positive refractive power, and a third lens group, in sequence. When focusing from an object at infinity to the nearest object, only the second lens group moves. The second lens group includes an aperture and at least one lens disposed on the object side of the aperture. The distance along the optical axis from the lens surface closest to the object side of the first lens group to the lens surface closest to the image side of the first lens group is defined as G1TL. Let Gsum be the distance along the optical axis from the lens surface of the first lens group closest to the object side to the lens surface of the third lens group closest to the image side. Let the focal length of the entire system be f when focusing on an object at infinity. When the combined focal length of all lenses in the second lens group, which is closer to the object than the aperture, is set to f21, The imaging lens satisfies the following conditions (2) and (6). 0.04<G1TL / Gsum<0.14 (2), 0.2 < f / f21 < 1 (6), The first lens group consists of two lenses. The second lens group is composed of lenses with positive, positive, negative, positive, negative, and positive refractive power, or lenses with positive, positive, negative, positive, negative, positive, and positive refractive power. The third lens group is composed of lenses with positive, negative, and negative refractive power, or lenses with positive, negative, negative, and negative refractive power.

4. The imaging lens according to any one of claims 1 to 3, wherein, The first lens group includes a positive lens and a negative lens.

5. The imaging lens according to any one of claims 1 to 3, wherein, The object-side surface of the lens closest to the image side in the third lens group is concave.

6. The imaging lens according to claim 1, wherein, When the refractive index of the positive lens closest to the object in the second lens group is set to N2 relative to the d-line, The imaging lens satisfies the following condition (3). 1.6＜N2＜2.2 （3）。 7. The imaging lens according to any one of claims 1 to 3, wherein, When the focal length of the entire system is set to f, with the focus on an object at infinity. When the focal length of the first lens group is set to f1... The imaging lens satisfies the following condition (5). 0.02 < f / f1 < 0.3 (5).

8. The imaging lens according to claim 2, wherein, The second lens group includes at least one lens disposed on the object side of the aperture. When the focal length of the entire system is set to f, with the focus on an object at infinity. When the combined focal length of all lenses in the second lens group, which is closer to the object than the aperture, is set to f21, The imaging lens satisfies the following condition (6). 0.2 < f / f21 < 1 (6).

9. The imaging lens according to any one of claims 1 to 3, wherein, The second lens group includes at least one lens disposed on the image side of the aperture. When the focal length of the entire system is set to f, with the focus on an object at infinity. When the combined focal length of all lenses in the second lens group, which is located on the image side closer than the aperture, is set to f22... The imaging lens satisfies the following condition (7). 0.4 < f / f22 < 1.5 (7).

10. The imaging lens according to any one of claims 1 to 3, wherein, When the focal length of the entire system is set to f, with the focus on an object at infinity. When the focal length of the third lens group is set to f3... The imaging lens satisfies the following condition (8). 0 < |f / f3| < 0.3 (8).

11. The imaging lens according to any one of claims 1 to 3, wherein, When the dispersion coefficient of the d-line reference of the positive lens of the second lens group is set to ν2p, The imaging lens includes at least one positive lens that satisfies the following condition (9). 70<ν2p (9)。 12. The imaging lens according to claim 11, wherein, The second lens group includes at least two sets of combined lenses, each set comprising a positive lens and a negative lens. The positive lenses of at least two sets of the combined lenses in the second lens group satisfy the condition (9).

13. The imaging lens according to claim 12, wherein, The dispersion coefficients of the positive and negative lenses, which are the joint lenses of the second lens group, are set as νp and νn, respectively, for their d-line references. If the maximum value of the difference obtained by subtracting νn from νp is set as max(νp-νn), then... The imaging lens satisfies the following condition (10). 30<max(νp-νn)<75 (10).

14. The imaging lens according to any one of claims 1 to 3, wherein, The object-side surface of the lens closest to the object in the second lens group is convex.

15. The imaging lens according to any one of claims 1 to 3, wherein, With the back focal length of the entire system, converted to air distance, set to Bf, When the focal length of the entire system is set to f, and the object is focused at infinity, The imaging lens satisfies the following condition (11). 0.1 < Bf / f < 0.5 (11).

16. A camera device comprising an imaging lens according to any one of claims 1 to 15.

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