Zoom lens and imaging device

Abstract

To provide a compact and lightweight zoom lens having a large image circle and high optical performance, and an imaging apparatus comprising the zoom lens.SOLUTION: The zoom lens consists of, in order from an object side to an image side, a first lens group having a negative refractive power, a middle group, and a final group arranged. During zooming, a spacing between the first lens group and the middle group changes and a spacing between the middle group and the final group changes. During focusing, at least a part of the middle group moves, and the first lens group and the final group remain stationary with respect to the image plane. The zoom lens satisfies predetermined conditional expressions regarding a back focus, a focal length, and a maximum half angle of view.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] 2. Description of the Related Art As a zoom lens applicable to imaging devices such as digital cameras and video cameras, for example, the lens system described in Patent Document 1 below is known. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-140142 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for compact, lightweight zoom lenses that have a large image circle and high optical performance.

[0005] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a small, lightweight zoom lens having a large image circle and high optical performance, and an imaging device equipped with this zoom lens. [Means for solving the problem]

[0006] A zoom lens according to one embodiment of the present disclosure includes, in order from the object side to the image side, a first lens group having negative refractive power, an intermediate group, and a final group, The middle group consists of two or three lens groups, and the final group consists of only one lens group. When changing magnification, the distance between the first lens group and the intermediate group changes, and the distance between the intermediate group and the final group changes. The spacing between adjacent lens groups in the intermediate group changes, During focusing, at least a part of the intermediate group moves along the optical axis as a focusing group, and the first lens group and the final lens group are fixed relative to the image plane; the first lens group includes a negative meniscus lens whose object-side surface is convex, located closest to the object side; the intermediate group includes, in order from the object side to the image side, a front subgroup having positive refractive power and a rear subgroup having negative refractive power, the front subgroup consisting of one or two lens groups having positive refractive power, and the rear subgroup consisting of one lens group having negative refractive power;The back focus in the air equivalent distance of the entire system at the wide-angle end when focused on an object at infinity is Bfw, the focal length of the entire system at the wide-angle end when focused on an object at infinity is fw, and the maximum half angle of view at the wide-angle end when focused on an object at infinity is ωw. , the paraxial radius of curvature of the lens surface of the front subgroup closest to the object is RMff, the paraxial radius of curvature of the lens surface of the front subgroup closest to the image is RMfr, the paraxial radius of curvature of the object side surface of the negative meniscus lens is R1f, and the paraxial radius of curvature of the image side surface of the negative meniscus lens is R1r. In this case, 0.35 <Bfw / (fw×tan|ωw|)<1.5 (1) -0.5<(RMff+RMfr) / (RMff-RMfr)<1 (8-3) 1.5<(R1f+R1r) / (R1f-R1r)<4.3 (10-1) Conditional expression (1) , (8-3), and (10-1) Satisfy.

[0007] The zoom lens of the above aspect preferably satisfies the following conditional expression (1-1), and more preferably satisfies the following conditional expression (1-2). 0.45 <Bfw / (fw×tan|ωw|)<1.1 (1-1) 0.5 <Bfw / (fw×tan|ωw|)<0.85 (1-2)

[0008] When the amount of movement of the focus group at the telephoto end when the magnification changes from a state in which the focus is focused on an object at infinity to a state in which the magnification is -0.1x is defined as Dfoct, and when the difference in the optical axis direction between the position of the lens surface of the middle group closest to the object at the telephoto end and the position of the lens surface of the middle group closest to the object at the wide-angle end when the focus is focused on an object at infinity is defined as DpM, the zoom lens of the above aspect has the following characteristics: 0.005<|Dfoct / DpM|<0.3 (2) It is preferable to satisfy conditional expression (2) below.

[0009] When the effective diameter of the lens surface of the intermediate group closest to the object is EDMf and the effective diameter of the lens surface of the intermediate group closest to the image is EDMr, the zoom lens of the above aspect is as follows: 0.3 <EDMf / EDMr<1.5 (3) It is preferable to satisfy conditional expression (3) below.

[0010] When TLw is the sum of the distance on the optical axis from the lens surface of the first lens group closest to the object at the wide-angle end to the lens surface of the final lens group closest to the image at the wide-angle end and Bfw, the zoom lens of the above aspect satisfies the following equation: 2.5 <TLw / (fw×tan|ωw|)<7 (4) It is preferable to satisfy conditional expression (4) below.

[0012] If the angle between the normal to the lens surface at the effective diameter edge and the optical axis is α, and α is expressed in degrees, then: 13<|α|<50 (5) It is preferable that the rear sub-group includes one or more convex lens surfaces facing the air that satisfy conditional expression (5) expressed as follows:

[0013] If a stop is located closest to the object side of the intermediate group or inside the intermediate group, and the distance on the optical axis from the stop to the above-mentioned convex lens surface at the wide-angle end when focused on an object at infinity is DStw, and the focal length of the rear subgroup at the wide-angle end when focused on an object at infinity is fMrw, then: 0.05 <DStw / |fMrw|<2.5 (6) It is preferable that the rear sub-group includes at least one convex lens surface that satisfies conditional expression (6) expressed as follows:

[0014] When the height from the optical axis of the chief ray of the maximum image height on the lens surface of the front subgroup closest to the image at the wide-angle end when focused on an object at infinity is HMfb, the height from the optical axis of the axial marginal ray on the lens surface of the front subgroup closest to the image at the wide-angle end when focused on an object at infinity is HMfa, the height from the optical axis of the chief ray of the maximum image height on the lens surface of the rear subgroup closest to the image at the wide-angle end when focused on an object at infinity is HMrb, and the height from the optical axis of the axial marginal ray on the lens surface of the rear subgroup closest to the image at the wide-angle end when focused on an object at infinity is HMra, the zoom lens of the above aspect is as follows: 0.08<(HMfb / HMfa) / (HMrb / HMra)<0.8 (7) It is preferable to satisfy conditional expression (7) below.

[0015] During focusing, at least a part of the rear subgroup may move along the optical axis, while the other subgroups may be fixed relative to the image plane.

[0016] During focusing, at least a part of the front subgroup may move along the optical axis, while the other subgroups may be fixed relative to the image plane.

[0017] The rear subgroup preferably includes an image-side negative lens having a convex surface on the image side, and in that case, the rear subgroup preferably includes an object-side negative lens having a convex surface on the object side, located closer to the object side than the image-side negative lens.

[0019] When the distance from the image plane to the exit pupil position at the wide-angle end in a state where the focus is on an object at infinity is Pexpw, the zoom lens of the above aspect satisfies the following equation: 0.5 <Pexpw / fw<5 (9) It is preferable to satisfy conditional expression (9) below.

[0021] It is preferable that the first lens group includes two or more negative meniscus lenses each having a convex surface facing the object side.

[0022] If the refractive index of the positive lens included in the first lens group for the d-line is N1p, then 1.6 <N1p<2.15 (11) It is preferable that the first lens group includes at least one positive lens that satisfies conditional expression (11) expressed as follows:

[0023] When the focal length of the first lens group is f1, the zoom lens of the above aspect has the following characteristics: 0.3 <fw / |f1|<1.5 (12) It is preferable to satisfy conditional expression (12) below.

[0024] When the focal length of the middle group at the wide-angle end in a state where the lens is focused on an object at infinity is fMw, the zoom lens of the above embodiment has the following characteristics: 0.4 <fw / fMw<1.5 (13) It is preferable to satisfy conditional expression (13) below.

[0025] When the focal length of the focus group is ffoc, the zoom lens of the above embodiment has the following characteristics: 0.05 <fw / |ffoc|<2.5 (14) It is preferable to satisfy conditional expression (14) below.

[0026] If the average value of the specific gravity of all the lenses included in the middle group is GMave, then the zoom lens of the above embodiment will have the following: 3 <GMave<4.2 (15) It is preferable to satisfy conditional expression (15) below.

[0027] The temperature coefficient of the relative refractive index for the d-line of the negative lens included in the first lens group in the temperature range from 20°C to 40°C is (dN1n / dT) × 10 -6 , dN1n / dT is expressed in K (Kelvin) -1 In this case, -15 <dN1n / dT<0 (16) It is preferable that the first lens group includes at least one negative lens that satisfies conditional expression (16) expressed as follows:

[0028] During magnification variation, it is preferable that the final lens unit be fixed relative to the image plane.

[0029] An imaging device according to another aspect of the present disclosure includes the zoom lens of the present disclosure.

[0030] In this specification, the terms "consisting of" and "consisting of" are intended to mean that, in addition to the listed components, other components may also be included, such as lenses that have substantially no refractive power, optical elements other than lenses, such as apertures, filters, and cover glasses, and mechanical parts, such as lens flanges, lens barrels, image sensors, and image stabilization mechanisms.

[0031] In this specification, "a group having positive refractive power" 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" are synonymous. "A lens having negative refractive power" and "a negative lens" are synonymous. The "first lens group," "intermediate group," "front subgroup," "rear subgroup," "final group," "focus group," and "image stabilization group" are not limited to being configured with multiple lenses, and may be configured with only one lens.

[0032] A "single lens" refers to a single lens that is not cemented. However, a compound aspherical lens (a lens in which a spherical lens and an aspherical film formed on that spherical lens are integrally constructed and function as a single aspherical lens as a whole) is not considered a cemented lens, but is treated as a single lens. Unless otherwise specified, the sign of the refractive power and surface shape of a lens that includes an aspherical surface are those in the paraxial region. The sign of the radius of curvature is positive for a surface with a convex surface facing the object side, and negative for a surface with a convex surface facing the image side.

[0033] In this specification, "total system" refers to a zoom lens. "Back focus in air equivalent distance" is the air equivalent distance on the optical axis from the lens surface closest to the image side of the total system to the image plane. "Focal length" used in conditional expressions is the paraxial focal length. The values ​​used in conditional expressions are values ​​based on the d-line when focused on an object at infinity. "tan" used in conditional expressions is the tangent.

[0034] The "d-line," "C-line," "F-line," and "g-line" referred to in this specification are emission lines. In this specification, the wavelength of the d-line is treated as 587.56 nm (nanometers), the wavelength of the C-line as 656.27 nm (nanometers), the wavelength of the F-line as 486.13 nm (nanometers), and the wavelength of the g-line as 435.84 nm (nanometers). The partial dispersion ratio θgF between the g-line and F-line of a lens is defined as θgF = (Ng - NF) / (NF - NC), where Ng, NF, and NC are the refractive indices of the lens for the g-line, F-line, and C-line, respectively. [Effects of the Invention]

[0035] According to the present disclosure, it is possible to provide a small and lightweight zoom lens having a large image circle and high optical performance, and an imaging device equipped with this zoom lens. [Brief explanation of the drawings]

[0036] [Figure 1] 1A and 1B are diagrams showing a cross-sectional view of the configuration of a zoom lens according to an embodiment and a movement locus thereof, which corresponds to the zoom lens of Example 1. [Figure 2] 2A to 2C are diagrams illustrating the configuration and light beams of the zoom lens in each magnification state of FIG. 1. [Figure 3] FIG. 10 is a diagram for explaining Dfoct. [Figure 4] FIG. 2 is a diagram for explaining an effective diameter. [Figure 5] FIG. 10 is a diagram for explaining α. [Figure 6] FIG. 10 is a diagram for explaining the symbols in conditional expression (7). [Figure 7] 3A to 3C are diagrams showing various aberrations of the zoom lens of Example 1. [Figure 8] 10A and 10B are diagrams illustrating a cross-sectional view of the configuration of a zoom lens according to a second embodiment and a movement locus thereof. [Figure 9] 10A to 10C are diagrams showing various aberrations of the zoom lens of Example 2. [Figure 10] 10A and 10B are diagrams showing a cross-sectional view of the configuration of a zoom lens according to a third embodiment and a movement locus thereof; [Figure 11]10A to 10C are diagrams illustrating various aberrations of the zoom lens according to the third embodiment. [Figure 12] 10A and 10B are diagrams showing a cross-sectional view of the configuration of a zoom lens according to a fourth embodiment and a movement locus thereof; [Figure 13] 10A to 10C are diagrams illustrating various aberrations of the zoom lens according to the fourth embodiment. [Figure 14] 10A and 10B are diagrams showing a cross-sectional view of the configuration of a zoom lens according to a fifth embodiment and a movement locus thereof. [Figure 15] 10A to 10C are diagrams showing various aberrations of the zoom lens of Example 5. [Figure 16] 13A and 13B are diagrams showing a cross-sectional view of the configuration of a zoom lens according to a sixth embodiment and a movement locus thereof. [Figure 17] 13A to 13C are diagrams illustrating various aberrations of the zoom lens of Example 6. [Figure 18] 13A and 13B are diagrams showing a cross-sectional view of the configuration of a zoom lens according to a seventh embodiment and a movement locus thereof. [Figure 19] 10A to 10C are diagrams showing various aberrations of the zoom lens of Example 7. [Figure 20] 13A and 13B are diagrams showing a cross-sectional view of the configuration of a zoom lens according to an eighth embodiment and a movement locus thereof. [Figure 21] 10A and 10B are diagrams showing a cross-sectional view of the configuration of a zoom lens of Example 8A and a movement locus thereof. [Figure 22] 13A to 13C are diagrams showing various aberrations of the zoom lens of Example 8. [Figure 23] 13A and 13B are diagrams showing a cross-sectional view of the configuration of a zoom lens according to a ninth embodiment and a movement locus thereof. [Figure 24] 13A to 13C are diagrams showing various aberrations of the zoom lens of Example 9. [Figure 25] 13A and 13B are diagrams showing a cross-sectional view of the configuration of a zoom lens according to a tenth embodiment and a movement locus thereof. [Figure 26] 13A to 13C are diagrams showing various aberrations of the zoom lens of Example 10. [Figure 27] 1 is a perspective view of the front side of an imaging device according to an embodiment. [Figure 28] FIG. 2 is a perspective view of the rear side of the imaging device according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0037] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0038] FIG. 1 shows a cross-sectional view of the configuration and movement trajectory of a zoom lens according to an embodiment of the present disclosure at the wide-angle end. FIG. 2 shows cross-sectional views of the configuration and light beams of this zoom lens in various magnification states. The example shown in FIGS. 1 and 2 corresponds to the zoom lens of Example 1, which will be described later. In FIGS. 1 and 2, the state in which the lens is focused on an object at infinity is shown, with the left side being the object side and the right side being the image side. In FIG. 2, the wide-angle end state is shown in the upper row labeled "WIDE," the intermediate focal length state is shown in the middle row labeled "MIDDLE," and the telephoto end state is shown in the lower row labeled "TELE." In FIG. 2, the axial light beams shown are wa and wb at the maximum image height in the wide-angle end state, ma and mb at the maximum image height in the intermediate focal length state, and ta and tb at the maximum image height in the telephoto end state. The zoom lens according to an embodiment of the present disclosure will be described below, primarily with reference to FIG. 1.

[0039] A zoom lens according to an embodiment of the present disclosure comprises, in order from the object side to the image side, a first lens group G1 having negative refractive power, an intermediate group GM, and a final group GE. When zooming, the distance between the first lens group G1 and the intermediate group GM changes, and the distance between the intermediate group GM and the final group GE also changes. By using a negative-first lens system, the entrance pupil can be positioned closer to the object, which is advantageous for ensuring sufficient peripheral illumination.

[0040] The middle group GM is a group that includes one or more lens groups. The number of lens groups included in the middle group GM can be set as desired, but for compactness and weight reduction, it is preferable to have one, two, or three. Furthermore, for compactness and weight reduction, it is preferable that the final group GE consists of one lens group. Note that in this specification, the term "lens group" refers to a component of a zoom lens that includes at least one lens and is separated by an air gap that changes during magnification. During magnification reduction, each lens group is moved or fixed, and the spacing between lenses within a lens group does not change.

[0041] During focusing, at least a portion of the middle group GM moves along the optical axis Z as a focus group, while the first lens group G1 and the final lens group GE are fixed relative to the image plane Sim. In this specification, the group that moves during focusing is referred to as the "focus group." Focusing is achieved by the movement of the focus group. Configuring the focus group with lenses in the middle group GM, which has a relatively small lens diameter, is advantageous for miniaturizing the focus unit and also contributes to overall miniaturization.

[0042] The intermediate group GM can be configured to include, in order from the object side to the image side, a front subgroup GMf having positive refractive power and a rear subgroup GMR having negative refractive power, which is advantageous for suppressing changes in performance during zooming.

[0043] As an example, the zoom lens of Figure 1 is composed of, in order from the object side to the image side along the optical axis Z, a first lens group G1, a second lens group G2, a third lens group G3, and a fourth lens group G4. The correspondence between each of the above-mentioned groups and the example of Figure 1 is as follows: The middle group GM is composed of the second lens group G2 and the third lens group G3. The front subgroup GMf corresponds to the second lens group G2. The rear subgroup GMr corresponds to the third lens group G3. The final group GE corresponds to the fourth lens group G4.

[0044] The lens groups in FIG. 1 are configured as follows: The first lens group G1 consists of four lenses, L11 to L14, in order from the object side to the image side. The second lens group G2 consists of an aperture stop St and four lenses, L21 to L24, in order from the object side to the image side. The third lens group G3 consists of two lenses, L31 and L32, in order from the object side to the image side. The fourth lens group G4 consists of one lens, L41. Note that the aperture stop St shown in FIG. 1 does not indicate the shape, but rather its position in the optical axis direction.

[0045] FIG. 1 shows an example in which a parallel-plate optical member PP is arranged between the zoom lens and the image plane Sim, assuming that the zoom lens is applied to an imaging device. The optical member PP is a member that is assumed to include various filters and / or cover glass. The various filters include a low-pass filter, an infrared cut filter, and / or a filter that cuts off specific wavelength ranges. The optical member PP is a member that does not have refractive power. It is also possible to configure an imaging device without the optical member PP.

[0046] In the example of Fig. 1, during magnification variation, the first lens group G1, the second lens group G2, and the third lens group G3 move along the optical axis Z while changing the distance between the adjacent lens groups in the optical axis direction, and the fourth lens group G4 is fixed with respect to the image plane Sim. In Fig. 1, curved or diagonal arrows are shown below the lens groups that move during magnification variation, indicating the approximate movement trajectory when changing magnification from the wide-angle end to the telephoto end, and a grounding symbol is shown below the lens groups that are fixed during magnification variation.

[0047] In the example of Fig. 1, during focusing, the third lens group G3 moves along the optical axis Z, while the other lens groups are fixed with respect to the image plane Sim. That is, in the example of Fig. 1, the focus group consists of the third lens group G3. The horizontal right-pointing arrow below the third lens group G3 in Fig. 1 indicates that the third lens group G3 is the focus group that moves toward the image side during focusing from an object at infinity to a close object.

[0048] Next, preferred and possible configurations of the zoom lens of the present disclosure will be described. In the following description of preferred and possible configurations, to avoid redundancy, "the zoom lens of the present disclosure" will also be referred to simply as "the zoom lens."

[0049] Let Bfw be the back focal length in air equivalent of the entire system at the wide-angle end when focused on an object at infinity, fw be the focal length of the entire system at the wide-angle end when focused on an object at infinity, and ωw be the maximum half angle of view at the wide-angle end when focused on an object at infinity. It is preferable that the zoom lens satisfy the following conditional formula (1). Figure 2 shows an example of ωw. By ensuring that the value corresponding to conditional formula (1) is not below the lower limit, the back focal length does not become too short relative to the image circle, which is advantageous for reducing the diameter of the final lens group GE. By ensuring that the value corresponding to conditional formula (1) is not above the upper limit, the back focal length does not become too long relative to the image circle, which is advantageous for shortening the overall length. To obtain better characteristics, it is more preferable that the zoom lens satisfy the following conditional formula (1-1), and it is even more preferable that the zoom lens satisfy the following conditional formula (1-2). 0.35 <Bfw / (fw×tan|ωw|)<1.5 (1) 0.45 <Bfw / (fw×tan|ωw|)<1.1 (1-1) 0.5 <Bfw / (fw×tan|ωw|)<0.85 (1-2)

[0050] If DfOct is the amount of movement of the focus group when the magnification changes from a state in which an object at infinity is focused to a state in which the magnification is -0.1x at the telephoto end, and DpM is the difference in the optical axis direction between the position of the lens surface of the middle group GM closest to the object at the telephoto end and the position of the lens surface of the middle group GM closest to the object at the wide-angle end when focused on an object at infinity, it is preferable that the zoom lens satisfy the following conditional formula (2). As an example, FIG. 2 shows DpM, and FIG. 3 shows DfOct. In FIG. 3, the upper part shows the state in which an object at infinity is focused at the telephoto end, and the lower part shows the state in which the magnification is -0.1x at the telephoto end. By ensuring that the value corresponding to conditional formula (2) is not equal to or less than the lower limit, the positional accuracy of the focus group during focusing can be prevented from becoming too strict, thereby facilitating control. By ensuring that the value corresponding to conditional formula (2) is not equal to or greater than the upper limit, the amount of movement of the focus group during focusing can be prevented from becoming too large. This makes it possible to prevent the focus unit from becoming too large, which is advantageous for reducing the overall size and weight. In order to obtain better characteristics, it is more preferable that the zoom lens satisfy the following conditional expression (2-1), and it is even more preferable that the zoom lens satisfy the following conditional expression (2-2): 0.005<|Dfoct / DpM|<0.3 (2) 0.015<|Dfoct / DpM|<0.15 (2-1) 0.03<|Dfoct / DpM|<0.115 (2-2)

[0051] Assuming that the effective diameter of the lens surface of the intermediate group GM closest to the object is EDMf and the effective diameter of the lens surface of the intermediate group GM closest to the image is EDMr, it is preferable that the zoom lens satisfy the following conditional expression (3): Typically, the focusing unit is located radially outward of the effective diameter of the intermediate group GM. Therefore, the greater the difference between the effective diameter of the lens surface of the intermediate group GM closest to the object and the effective diameter of the lens surface of the intermediate group GM closest to the image, the larger the size of the focusing unit. Therefore, satisfying conditional expression (3) can prevent the focusing unit from becoming larger, which is advantageous for reducing the overall size and weight. To achieve better characteristics, it is more preferable that the zoom lens satisfy the following conditional expression (3-1), and even more preferable that the zoom lens satisfy the following conditional expression (3-2). 0.3 <EDMf / EDMr<1.5 (3) 0.4 <EDMf / EDMr<1 (3-1) 0.5 <EDMf / EDMr<0.85 (3-2)

[0052] In the technology disclosed herein, the "effective diameter" of a lens surface is defined as twice the distance from the point of intersection of the outermost ray and the lens surface, among the rays that enter the lens surface from the object side and exit to the image side, to the optical axis Z. "Outside" here refers to the radially outward direction centered on the optical axis Z, i.e., the side away from the optical axis Z. The "outside ray" is determined taking into account the entire range of magnification.

[0053] For explanatory purposes, FIG. 4 shows an example of the effective diameter ED. In FIG. 4, the left side is the object side and the right side is the image side. FIG. 4 shows an on-axis ray Xa and an off-axis ray Xb passing through the lens Lx. In the example of FIG. 4, ray Xb1, which is the upper ray of the off-axis ray Xb, is the outermost ray. Therefore, in the example of FIG. 4, the effective diameter ED of the object-side surface of the lens Lx is twice the distance from the intersection of the object-side surface of the lens Lx and ray Xb1 to the optical axis Z. Note that in FIG. 4, the upper ray of the off-axis ray Xb is the outermost ray, but which ray is the outermost ray varies depending on the optical system.

[0054] Let Bfw be the back focus in the air-equivalent distance of the entire system at the wide-angle end when focused on an object at infinity, fw be the focal length of the entire system at the wide-angle end when focused on an object at infinity, ωw be the maximum half angle of view at the wide-angle end when focused on an object at infinity, and TLw be the sum of Bfw and the distance on the optical axis from the lens surface of the first lens group G1 closest to the object at the wide-angle end to the lens surface of the final lens group GE closest to the image at the wide-angle end. It is preferable that the zoom lens satisfy conditional formula (4) below. By ensuring that the corresponding value of conditional formula (4) is not equal to or less than the lower limit, it is easy to provide a zoom lens with high optical performance. By ensuring that the corresponding value of conditional formula (4) is not equal to or greater than the upper limit, it is easy to provide a compact and lightweight camera system. In order to obtain better characteristics, it is more preferable that the zoom lens satisfy conditional formula (4-1) below, and it is even more preferable that the zoom lens satisfy conditional formula (4-2) below. 2.5 <TLw / (fw×tan|ωw|)<7 (4) 2.75 <TLw / (fw×tan|ωw|)<5.75 (4-1) 3 <TLw / (fw×tan|ωw|)<5 (4-2)

[0055] If the angle between the normal NL of the lens surface at the clear diameter end P and the optical axis Z is α, it is preferable that the rear subgroup GMr include at least one air-facing convex lens surface that satisfies the following conditional expression (5): In conditional expression (5), α is expressed in degrees. As an example, FIG. 5 shows the normal NL of the image-side surface of lens L32 at the clear diameter end P with a dashed line, and the angle α between the normal NL and the optical axis Z. Some reference numerals are omitted in FIG. 5. The clear diameter end P is the intersection of the outermost ray and the lens surface in the definition of the clear diameter above. By ensuring that the value corresponding to conditional expression (5) is not below the lower limit, the refractive power acting on off-axial light beams does not become too weak, thereby preventing the angle of incidence of off-axial chief rays on the image plane Sim from becoming too large. This is advantageous for ensuring sufficient peripheral illumination. By ensuring that the corresponding value of conditional expression (5) does not exceed the upper limit, it is possible to prevent the difficulty of processing the convex surface from increasing, which is advantageous for ensuring surface precision. In order to obtain better characteristics, it is more preferable that the following conditional expression (5-1) be satisfied instead of conditional expression (5), and it is even more preferable that the following conditional expression (5-2) be satisfied. 13<|α|<50 (5) 15<|α|<40 (5-1) 17<|α|<30 (5-2)

[0056] It is preferable that an aperture diaphragm St be located closest to the object side of the intermediate group GM or within the intermediate group GM. Note that a configuration in which "an aperture diaphragm St is located within the intermediate group GM" refers to a configuration in which one or more lenses are located in the intermediate group GM on both the object side and the image side of the aperture diaphragm St. Locating the aperture diaphragm St closest to the object side of the intermediate group GM is advantageous for ensuring sufficient peripheral illumination, since it is possible to prevent the angle of incidence of off-axial chief rays onto the image plane Sim from becoming large. It is also advantageous for reducing the lens diameter of the first lens group G1. Locating the aperture diaphragm St within the intermediate group GM improves optical symmetry, which is advantageous for suppressing distortion and curvature of field.

[0057] In a configuration in which the aperture stop St is disposed closest to the object side of the intermediate group GM or within the intermediate group GM, it is preferable that the rear sub-group GMr include at least one air-facing convex lens surface that satisfies conditional expression (5) and the following conditional expression (6): In conditional expression (6), the axial distance from the aperture stop St to the convex lens surface at the wide-angle end when focused on an object at infinity is denoted by DStw, and the focal length of the rear sub-group GMr at the wide-angle end when focused on an object at infinity is denoted by fMrw. By ensuring that the value corresponding to conditional expression (6) is not equal to or less than the lower limit, the degree of separation between the axial light beam and the off-axial light beam at the convex lens surface does not become too small, which is advantageous for suppressing field curvature. By ensuring that the value corresponding to conditional expression (6) is not equal to or greater than the upper limit, which is advantageous for miniaturizing the optical system. In order to obtain better characteristics, it is more preferable that the following conditional expression (6-1) be satisfied instead of conditional expression (6), and it is even more preferable that the following conditional expression (6-2) be satisfied. 0.05 <DStw / |fMrw|<2.5 (6) 0.35 <DStw / |fMrw|<2 (6-1) 0.5 <DStw / |fMrw|<1.65 (6-2)

[0058] It is preferable that the zoom lens satisfy the following conditional expression (7) for the axial marginal ray wa1 and the chief ray wb1 at the maximum image height at the wide-angle end when focused on an object at infinity. The symbols used in conditional expression (7) are shown in FIG. 6 as an example. FIG. 6 also shows an enlarged view of a portion of the middle group GM at the wide-angle end of the zoom lens of FIG. 1, along with a ray bundle. HMfb is the height from the optical axis Z of the chief ray at the maximum image height at the lens surface closest to the image of the front subgroup GMf at the wide-angle end when focused on an object at infinity. HMfa is the height from the optical axis Z of the axial marginal ray at the lens surface closest to the image of the front subgroup GMf at the wide-angle end when focused on an object at infinity. HMrb is the height from the optical axis Z of the chief ray at the maximum image height at the lens surface closest to the image of the rear subgroup GMr at the wide-angle end when focused on an object at infinity. HMra is the height from the optical axis Z of the on-axis marginal ray on the lens surface closest to the image in the rear sub-group GMR at the wide-angle end when focused on an object at infinity. By ensuring that the corresponding value of conditional expression (7) is not below the lower limit, the height from the optical axis Z of the off-axial ray in the rear sub-group GMR does not become too high, thereby reducing the amount of refraction in the final group GE. This is advantageous for correcting distortion. By ensuring that the corresponding value of conditional expression (7) is not above the upper limit, the degree of separation between the on-axis ray and the off-axial ray in the rear sub-group GMR does not become too small, thereby being advantageous for correcting various aberrations of the off-axial ray. In order to obtain better characteristics, it is more preferable for the zoom lens to satisfy the following conditional expression (7-1), and even more preferable for it to satisfy the following conditional expression (7-2). 0.08<(HMfb / HMfa) / (HMrb / HMra)<0.8 (7) 0.1<(HMfb / HMfa) / (HMrb / HMra)<0.6 (7-1) 0.12<(HMfb / HMfa) / (HMrb / HMra)<0.52 (7-2)

[0059] If the paraxial radius of curvature of the lens surface of the front subgroup GMf closest to the object is RMff and the paraxial radius of curvature of the lens surface of the front subgroup GMf closest to the image is RMfr, it is preferable that the zoom lens satisfy the following conditional expression (8). Ensuring that the corresponding value of conditional expression (8) is not equal to or smaller than the lower limit is advantageous in preventing under-correction of field curvature. Ensuring that the corresponding value of conditional expression (8) is not equal to or larger than the upper limit is advantageous in preventing over-correction of field curvature. In order to obtain better characteristics, it is more preferable that the zoom lens satisfy the following conditional expression (8-1), and it is even more preferable that the zoom lens satisfy the following conditional expression (8-2). -1<(RMff+RMfr) / (RMff-RMfr)<1 (8) -0.5<(RMff+RMfr) / (RMff-RMfr)<0.3 (8-1) -0.3<(RMff+RMfr) / (RMff-RMfr)<0.15 (8-2)

[0060] If the focal length of the entire system at the wide-angle end when focused on an object at infinity is fw and the focal length of the middle group GM at the wide-angle end when focused on an object at infinity is fMw, it is preferable that the zoom lens satisfy the following conditional expression (13). By ensuring that the corresponding value of conditional expression (13) is not below the lower limit, the amount of movement of the middle group GM during magnification change does not become too large, which is advantageous for shortening the overall length. By ensuring that the corresponding value of conditional expression (13) is not above the upper limit, it is advantageous for suppressing aberration fluctuations during magnification change. In order to obtain better characteristics, it is more preferable that the zoom lens satisfy the following conditional expression (13-1), and it is even more preferable that the zoom lens satisfy the following conditional expression (13-2). 0.4 <fw / fMw<1.5 (13) 0.5 <fw / fMw<1.35 (13-1) 0.6 <fw / fMw<1.2 (13-2)

[0061] If the focal length of the entire system at the wide-angle end when focused on an object at infinity is fw and the focal length of the focus group is ffoc, it is preferable that the zoom lens satisfy the following conditional expression (14). By ensuring that the corresponding value of conditional expression (14) is not below the lower limit, the amount of movement of the focus group during focusing does not become too large, which is advantageous for making the focus unit more compact. By ensuring that the corresponding value of conditional expression (14) is not above the upper limit, it is possible to avoid making the positional accuracy of the focus group during focusing too strict, which makes control easier. In order to obtain better characteristics, it is more preferable that the zoom lens satisfy the following conditional expression (14-1), and it is even more preferable that the zoom lens satisfy the following conditional expression (14-2). 0.05 <fw / |ffoc|<2.5 (14) 0.08 <fw / |ffoc|<2 (14-1) 0.12 <fw / |ffoc|<1.5 (14-2)

[0062] If the average value of the specific gravity of all the lenses included in the middle group GM is GMave, it is preferable that the zoom lens satisfy the following conditional expression (15). By ensuring that the corresponding value of conditional expression (15) is not below the lower limit, the range of materials usable for the middle group GM can be widened, which is advantageous for correcting axial chromatic aberration. By ensuring that the corresponding value of conditional expression (15) is not above the upper limit, the middle group GM does not become too heavy, which makes it possible to prevent the mechanism that drives the lens during magnification variation and / or focusing from becoming too large. In order to obtain better characteristics, it is more preferable that the zoom lens satisfy the following conditional expression (15-1), and it is even more preferable that the zoom lens satisfy the following conditional expression (15-2). 3 <GMave<4.2 (15) 3.1 <GMave<4 (15-1) 3.2 <GMave<3.85 (15-2)

[0063] If the partial dispersion ratio between the g-line and the F-line of the positive lens in the middle group GM is θMp and the Abbe number based on the d-line is νMp, it is preferable that the zoom lens satisfy the following conditional expression (18). Ensuring that the corresponding value of conditional expression (18) is not below the lower limit is advantageous in suppressing under-correction of the secondary spectrum of axial chromatic aberration. Ensuring that the corresponding value of conditional expression (18) is not above the upper limit is advantageous in suppressing over-correction of the secondary spectrum of axial chromatic aberration. In order to obtain even better characteristics, it is more preferable that the zoom lens satisfy the following conditional expression (18-1), and it is even more preferable that the zoom lens satisfy the following conditional expression (18-2). 0.01<θMp+0.0018×νMp-0.64833<0.06 (18) 0.017<θMp+0.0018×νMp-0.64833<0.05 (18-1) 0.022<θMp+0.0018×νMp-0.64833<0.04 (18-2)

[0064] If the focal length of the front subgroup GMf at the wide-angle end when focused on an object at infinity is fMfw and the focal length of the rear subgroup GMr at the wide-angle end when focused on an object at infinity is fMrw, it is preferable that the zoom lens satisfy the following conditional expression (26). By ensuring that the corresponding value of conditional expression (26) is not below the lower limit, the refractive power of the rear subgroup GMr does not become too weak, which is advantageous for correcting field curvature. By ensuring that the corresponding value of conditional expression (26) is not above the upper limit, the refractive power of the front subgroup GMf does not become too weak, which is advantageous for correcting spherical aberration. In order to obtain better characteristics, it is more preferable that the zoom lens satisfy the following conditional expression (26-1), and it is even more preferable that the zoom lens satisfy the following conditional expression (26-2). 0.25 <fMfw / |fMrw|<2 (26) 0.3 <fMfw / |fMrw|<1.75 (26-1) 0.35 <fMfw / |fMrw|<1.5 (26-2)

[0065] Let DMra be the sum of the air gaps on the optical axis from the lens surface of the rear sub-group GMr closest to the object to the lens surface of the rear sub-group GMr closest to the image at the wide-angle end when focused on an object at infinity, and DMrt be the distance on the optical axis from the lens surface of the rear sub-group GMr closest to the object to the lens surface of the rear sub-group GMr closest to the image at the wide-angle end when focused on an object at infinity. It is preferable that the zoom lens satisfy the following conditional expression (21). By ensuring that the corresponding value of conditional expression (21) is not equal to or less than the lower limit, an increase in the weight of the rear sub-group GMr can be suppressed, which is advantageous for reducing the weight of the drive mechanism. By ensuring that the corresponding value of conditional expression (21) is not equal to or greater than the upper limit, the aberration correction effect of the rear sub-group GMr can be ensured, which is advantageous for suppressing aberration fluctuations during zooming. In order to obtain better characteristics, it is more preferable that the zoom lens satisfy the following conditional expression (21-1), and it is even more preferable that the zoom lens satisfy the following conditional expression (21-2). 0.2 <DMra / DMrt<0.95 (21) 0.35 <DMra / DMrt<0.92 (21-1) 0.6 <DMra / DMrt<0.9 (21-2)

[0066] It is preferable that the rear sub-group GMr includes an image-side negative lens whose image-side surface is convex. This is advantageous for suppressing field curvature. It is also preferable that the rear sub-group GMr includes an object-side negative lens whose object-side surface is convex, located closer to the object than the image-side negative lens. This is advantageous for suppressing spherical aberration. In the example of FIG. 1, the object-side negative lens corresponds to lens L31, and the image-side negative lens corresponds to lens L32.

[0067] When the paraxial radius of curvature of the image-side surface of the object-side negative lens is Rnor and the paraxial radius of curvature of the object-side surface of the image-side negative lens is Rnif, it is preferable that the rear sub-group GMr includes one or more pairs of an object-side negative lens and an image-side negative lens that satisfy the following conditional expression (22). Ensuring that the corresponding value of conditional expression (22) is not equal to or less than the lower limit is advantageous for suppressing spherical aberration. Ensuring that the corresponding value of conditional expression (22) is not equal to or greater than the upper limit is advantageous for suppressing field curvature. In order to obtain better characteristics, it is more preferable that the following conditional expression (22-1) be satisfied instead of conditional expression (22), and it is even more preferable that the following conditional expression (22-2) be satisfied. -1.5<(Rnor+Rnif) / (Rnor-Rnif)<1 (22) -1.2<(Rnor+Rnif) / (Rnor-Rnif)<0.5 (22-1) -0.8<(Rnor+Rnif) / (Rnor-Rnif)<0.25 (22-2)

[0068] If the focal length of the entire system at the wide-angle end when focused on an object at infinity is fw and the focal length of the rear sub-group GMR at the wide-angle end when focused on an object at infinity is fMrw, it is preferable that the zoom lens satisfy the following conditional expression (25). By ensuring that the corresponding value of conditional expression (25) is not below the lower limit, the refractive power of the rear sub-group GMR does not become too weak, which is advantageous for correcting field curvature. By ensuring that the corresponding value of conditional expression (25) is not above the upper limit, the refractive power of the rear sub-group GMR does not become too strong, which is advantageous for making the diameter of the final group GE smaller. In order to obtain better characteristics, it is more preferable that the zoom lens satisfy the following conditional expression (25-1), and it is even more preferable that the zoom lens satisfy the following conditional expression (25-2). 0.15 <fw / |fMrw|<2 (25) 0.22 <fw / |fMrw|<1.75 (25-1) 0.28 <fw / |fMrw|<1.5 (25-2)

[0069] The temperature coefficient of the relative refractive index for the d-line of the positive lens included in the intermediate group GM in the temperature range from 20°C to 40°C is (dNMp / dT) × 10 -6 The unit of dNMp / dT is K (Kelvin). -1 In this case, it is preferable that the intermediate group GM include one or more positive lenses that satisfy the following conditional expression (29): Since many materials generally have positive temperature coefficients, including a positive lens element that satisfies the range of conditional expression (29) in the intermediate group GM is advantageous in suppressing changes in performance when the temperature changes. In order to obtain better characteristics, it is more preferable that the following conditional expression (29-1) be satisfied instead of conditional expression (29), and it is even more preferable that the following conditional expression (29-2) be satisfied. -15 <dNMp / dT<0 (29) -10 <dNMp / dT<-3 (29-1) -7 <dNMp / dT<-5 (29-2)

[0070] It is preferable that the intermediate group GM has positive refractive power overall. In this case, the first lens group G1 having negative refractive power and the intermediate group GM having positive refractive power make it easy to increase the magnification ratio and also work well for correcting spherical aberration. Furthermore, the intermediate group GM having positive refractive power allows the diameter of the final group GE following the intermediate group GM to be reduced, which also works well for overall compactness.

[0071] The intermediate group GM may be configured to consist of a front sub-group GMf and a rear sub-group GMR. This is advantageous for achieving a smaller and lighter lens than a lens that includes other groups in addition to the front sub-group GMf and the rear sub-group GMR. However, the intermediate group GM may also be configured to consist of a front sub-group GMf, a rear sub-group GMR, and other groups. This is advantageous for ensuring higher optical performance.

[0072] It is preferable that the lens closest to the object in the front subgroup GMf be a positive lens. This is advantageous for reducing the diameter of the intermediate group GM. It is preferable that the lens closest to the image in the front subgroup GMf be a positive lens. This is advantageous for reducing the diameter of the rear subgroup GMR.

[0073] It is preferable that the rear subgroup GMR includes two or more lenses, which is advantageous in suppressing performance changes during zooming.

[0074] The lens closest to the image in the rear subgroup GMR may be configured to be a negative lens. In this case, the height of off-axial rays incident on the final group GE can be increased, thereby preventing the angle of incidence of off-axial chief rays on the image sensor located on the image plane Sim from becoming too large. This is advantageous for ensuring sufficient peripheral illumination.

[0075] For example, the rear sub-group GMR may be configured to include two negative lenses. More specifically, the rear sub-group GMR may be configured to include two negative meniscus lenses with concave surfaces facing each other. Note that a "negative meniscus lens" is a meniscus lens having negative refractive power. Alternatively, the rear sub-group GMR may be configured to include two negative lenses and one positive lens. The rear sub-group GMR may be configured to include a cemented lens formed by cementing together one negative lens and one positive lens, and one negative lens. The rear sub-group GMR may be configured to include a biconvex air lens.

[0076] A biconcave air lens may be formed between the front sub-group GMf and the rear sub-group GMR. This is advantageous for reducing the diameter of the rear sub-group GMR. In the example of Figure 1, a biconcave air lens is formed by the image-side surface of lens L24 and the object-side surface of lens L31.

[0077] The distance between the front sub-group GMf and the rear sub-group GMR may be configured to change during magnification variation. This is advantageous for suppressing changes in performance during magnification variation. When the intermediate group GM is composed of multiple lens groups that move while changing the distance between adjacent groups in the optical axis direction during magnification variation, the front sub-group GMf and the rear sub-group GMR may be configured to be separated by one of the distances that changes during magnification variation. For example, the front sub-group GMf and the rear sub-group GMR may be configured to be separated by the distance closest to the object among the distances that change during magnification variation of the intermediate group GM. Alternatively, the front sub-group GMf and the rear sub-group GMR may be configured to be separated by the distance closest to the image among the distances that change during magnification variation of the intermediate group GM.

[0078] If the intermediate group GM consists of a single lens group that moves while changing the distance between it and an adjacent group in the optical axis direction during magnification variation, and if the focus group consists of only a part of the intermediate group GM, then the part of the intermediate group GM closer to the object than the focus group may be designated as a front subgroup GMf, and the part of the intermediate group GM closer to the image than this front subgroup GMf may be designated as a rear subgroup GMR. In this case, the front subgroup GMf has positive refractive power, which is advantageous for making the diameter of the focus group small.

[0079] During focusing, at least a portion of the front subgroup GMf may move along the optical axis Z, while the other subgroups may be fixed relative to the image plane Sim. Constructing a focus group using lenses in the front subgroup GMf with a relatively small effective diameter like this is advantageous for reducing the size of the focus unit. The focus group may be constructed from only a portion of the front subgroup GMf, or may be constructed from the entire front subgroup GMf. For example, if the front subgroup GMf is composed of multiple lens groups that move while changing the distance between them in the optical axis direction during magnification, only the lens group closest to the object among these multiple lens groups may constitute the focus group. Furthermore, if an aperture diaphragm St is disposed within the front subgroup GMf, only the portion of the front subgroup GMf closest to the object side of the aperture diaphragm St may constitute the focus group. Note that "an aperture diaphragm St is disposed within the front subgroup GMf" refers to a configuration in which one or more lenses are disposed in the front subgroup GMf on both the object side and the image side of the aperture diaphragm St.

[0080] During focusing, at least a portion of the rear sub-group GMR may move along the optical axis Z, while the other groups are fixed relative to the image plane Sim. This configuration is advantageous for suppressing fluctuations in spherical aberration that occur with changes in shooting distance. The focus group may be configured to consist of only a portion of the rear sub-group GMR, or may be configured to consist of the entire rear sub-group GMR. Furthermore, if the focus group consists of only one lens element in the rear sub-group GMR that is closest to the object, this has the added advantage of being advantageous for making the focus unit more compact.

[0081] All lenses that move during focusing may move along the same movement locus. In other words, the focus group included in the zoom lens may be configured to move along a single movement locus. By unifying the focus group in this way, it is advantageous for making the focus unit smaller and lighter.

[0082] It is preferable that the first lens group G1 includes a negative meniscus lens whose object-side surface is convex. By positioning the negative lens closest to the object, the entrance pupil can be brought closer to the object, which contributes to ensuring a sufficient angle of view at the wide-angle end and reducing the diameter. Furthermore, by making the lens closest to the object a meniscus shape, it is advantageous for suppressing astigmatism and distortion.

[0083] In a configuration in which the first lens group G1 includes a negative meniscus lens whose object-side surface is convex, and where the paraxial radius of curvature of the object-side surface of this negative meniscus lens is R1f and the paraxial radius of curvature of the image-side surface is R1r, it is preferable that the zoom lens satisfy the following conditional expression (10): Ensuring that the corresponding value of conditional expression (10) is not below the lower limit is advantageous for suppressing astigmatism from the wide-angle end to the telephoto end. Ensuring that the corresponding value of conditional expression (10) is not above the upper limit is advantageous for suppressing distortion and field curvature at the wide-angle end. In order to obtain better characteristics, it is more preferable that the zoom lens satisfy the following conditional expression (10-1), and even more preferable that the zoom lens satisfy the following conditional expression (10-2). 1<(R1f+R1r) / (R1f-R1r)<6 (10) 1.5<(R1f+R1r) / (R1f-R1r)<4.3 (10-1) 2.2<(R1f+R1r) / (R1f-R1r)<3.2 (10-2)

[0084] It is preferable that the first lens group G1 includes two or more negative meniscus lenses whose object-side surface is convex. In this case, the negative refractive power can be shared among multiple lenses, making it easy to increase the absolute value of the radius of curvature of the image-side surface of each negative meniscus lens. This is advantageous for suppressing astigmatism at wide-angle settings.

[0085] When the refractive index of the positive lens included in the first lens group G1 with respect to the d-line is N1p, it is preferable that the first lens group G1 include one or more positive lenses that satisfy the following conditional expression (11): By ensuring that the corresponding value of conditional expression (11) is not below the lower limit, the absolute value of the radius of curvature of the positive lens in the first lens group G1 does not become too small, which is advantageous for suppressing astigmatism. By ensuring that the corresponding value of conditional expression (11) is not above the upper limit, the absolute value of the radius of curvature of the positive lens in the first lens group G1 does not become too large, which is advantageous for correcting field curvature. In order to obtain better characteristics, it is more preferable that the following conditional expression (11-1) be satisfied instead of conditional expression (11), and it is even more preferable that the following conditional expression (11-2) be satisfied. 1.6 <N1p<2.15 (11) 1.75 <N1p<2.07 (11-1) 1.83 <N1p<2.02 (11-2)

[0086] If the focal length of the entire system at the wide-angle end when focused on an object at infinity is fw and the focal length of the first lens group G1 is f1, it is preferable that the zoom lens satisfy the following conditional expression (12): By ensuring that the corresponding value of conditional expression (12) is not below the lower limit, the amount of change in the distance between the first lens group G1 and the group closest to the object in the middle group GM does not become too large, which is advantageous for shortening the overall length. By ensuring that the corresponding value of conditional expression (12) is not above the upper limit, the diameter of the light beam entering the middle group GM does not become too large, which is advantageous for making the entire lens system more compact. In order to obtain better characteristics, it is more preferable that the zoom lens satisfy the following conditional expression (12-1), and it is even more preferable that the zoom lens satisfy the following conditional expression (12-2). 0.3 <fw / |f1|<1.5 (12) 0.45 <fw / |f1|<1.25 (12-1) 0.6 <fw / |f1|<1.1 (12-2)

[0087] The temperature coefficient of the relative refractive index for the d-line of the negative lens included in the first lens group G1 in the temperature range from 20°C to 40°C is (dN1n / dT)×10-6 and the unit of dN1n / dT is K (Kelvin) -1 In this case, it is preferable that the first lens group G1 includes one or more negative lenses that satisfy the following conditional expression (16): Since many materials generally have a positive temperature coefficient, including a negative lens that satisfies the range of conditional expression (16) in the first lens group G1 is advantageous in suppressing changes in performance when the temperature changes: In order to obtain better characteristics, it is more preferable that the following conditional expression (16-1) be satisfied instead of conditional expression (16), and it is even more preferable that the following conditional expression (16-2) be satisfied: -15 <dN1n / dT<0 (16) -10 <dN1n / dT<-3 (16-1) -7 <dN1n / dT<-5 (16-2)

[0088] A portion of the first lens group G1 may be configured to function as an image stabilization group and move in a direction intersecting the optical axis Z during image blur correction. In this specification, a group that moves during image blur correction is referred to as the "image stabilization group." Image blur correction is achieved by the movement of the image stabilization group. By configuring the image stabilization group using only a portion of the first lens group G1, the entire first lens group G1 and the image stabilization group can be given different refractive powers, making it easier to control the refractive power of the image stabilization group, which is advantageous for achieving both good image stabilization performance and compactness. For example, the image stabilization group may be configured to consist of a single lens closest to the image in the first lens group G1. This is advantageous for compactness of the image stabilization group.

[0089] In a zoom lens having an image stabilization group, where fw is the focal length of the entire system at the wide-angle end when focused on an object at infinity and fis is the focal length of the image stabilization group, it is preferable that the zoom lens satisfy the following conditional expression (17). By ensuring that the corresponding value of conditional expression (17) is not below the lower limit, the amount of movement of the image stabilization group during image blur correction does not become too large, which is advantageous for reducing the size of the image stabilization unit. By ensuring that the corresponding value of conditional expression (17) is not above the upper limit, it is advantageous for suppressing aberration fluctuations during image blur correction. Satisfying conditional expression (17) is advantageous for achieving good image blur correction performance while also achieving a compact image stabilization unit. In order to obtain better characteristics, it is more preferable that the zoom lens satisfy the following conditional expression (17-1), and it is even more preferable that the zoom lens satisfy the following conditional expression (17-2). 0.05 <fw / |fis|<0.75 (17) 0.1 <fw / |fis|<0.5 (17-1) 0.15 <fw / |fis|<0.25 (17-2)

[0090] If the refractive index of the negative lens closest to the object in the first lens group G1 with respect to the d-line is N1n, it is preferable that the zoom lens satisfy the following conditional expression (20): By ensuring that the corresponding value of conditional expression (20) is not below the lower limit, the absolute value of the radius of curvature of this negative lens does not become too small, which is advantageous for suppressing off-axis aberrations from the wide-angle end to the telephoto end. By ensuring that the corresponding value of conditional expression (20) is not above the upper limit, it is easy to prevent this negative lens from becoming high-dispersion and high-specific gravity, which is advantageous for correcting lateral chromatic aberration at the wide-angle end and for reducing weight. In order to obtain better characteristics, it is more preferable that the zoom lens satisfy the following conditional expression (20-1), and it is even more preferable that the zoom lens satisfy the following conditional expression (20-2): 1.6 <N1n<2.15 (20) 1.65 <N1n<2.07 (20-1) 1.7 <N1n<2 (20-2)

[0091] If the average value of the specific gravity of all lenses included in the first lens group G1 is G1ave, it is preferable that the zoom lens satisfy the following conditional expression (23): By ensuring that the corresponding value of conditional expression (23) is not below the lower limit, the range of materials usable for the first lens group G1 can be widened, which is advantageous for correcting lateral chromatic aberration. By ensuring that the corresponding value of conditional expression (23) is not above the upper limit, the first lens group G1 does not become too heavy, which prevents the center of gravity of the entire optical system from shifting toward the object side. This contributes to reducing the burden on the user when holding the zoom lens. In order to obtain better characteristics, it is more preferable that the zoom lens satisfy the following conditional expression (23-1), and it is even more preferable that the following conditional expression (23-2) be satisfied. 3 <G1ave<4.5 (23) 3.15 <G1ave<4.3 (23-1) 3.2 <G1ave<4.2 (23-2)

[0092] As shown in the example of FIG. 1, the first lens group G1 may be configured to move along the optical axis Z while changing the distance between it and the intermediate group GM during zooming. This is advantageous for suppressing aberration fluctuations during zooming. Alternatively, the first lens group G1 may be configured to be fixed relative to the image plane Sim during zooming. This eliminates the need for a moving mechanism for the first lens group G1, simplifying the mechanical configuration and contributing to a reduction in size and weight.

[0093] The number of lenses included in the first lens group G1 is preferably 3 to 6. This is advantageous for reducing size and weight and suppressing fluctuations in aberrations during magnification. The number of lenses included in the first lens group G1 is more preferably 3 to 5, and even more preferably 4 to 5.

[0094] The first lens group G1 may be configured to include a cemented lens in which a negative lens and a positive lens are cemented together. This is advantageous for correcting chromatic aberration. One of the cemented lenses included in the first lens group G1 may be configured to include a negative lens and a positive lens cemented together in this order from the object side. Furthermore, the cemented surface of the cemented lens included in the first lens group G1 may be shaped so that the convex surface faces the object side.

[0095] The first lens group G1 may be configured to include three negative lenses and one positive lens. In this case, the first lens group G1 may be configured to include, in order from the object side to the image side, two negative lenses that are single lenses, and a cemented lens in which a negative lens and a positive lens are cemented together in that order from the object side. Alternatively, the first lens group G1 may be configured to include, in order from the object side to the image side, one negative lens, a cemented lens in which a negative lens and a positive lens are cemented together in that order from the object side, and one negative lens.

[0096] The first lens group G1 may be configured to include four negative lenses and one positive lens. In that case, for example, the first lens group G1 may be configured to include, in order from the object side to the image side, two negative single lenses, a cemented lens in which a negative lens and a positive lens are cemented together, in that order from the object side, and one negative single lens.

[0097] If the focal length of the entire system at the wide-angle end when focused on an object at infinity is fw and the focal length of the final group GE at the wide-angle end is fE, it is preferable that the zoom lens satisfy the following conditional expression (27). Ensuring that the corresponding value of conditional expression (27) is not below the lower limit is advantageous in preventing the angle of incidence of off-axial chief rays on the image plane Sim from becoming large, particularly at the wide-angle end. Ensuring that the corresponding value of conditional expression (27) is not above the upper limit facilitates suppression of field curvature. In order to obtain better characteristics, it is more preferable that the zoom lens satisfy the following conditional expression (27-1), and it is even more preferable that the zoom lens satisfy the following conditional expression (27-2). 0.01 <fw / fE<0.75 (27) 0.03 <fw / fE<0.6 (27-1) 0.15 <fw / fE<0.52 (27-2)

[0098] If the average value of the specific gravity of all the lenses included in the final lens group GE is GEave, it is preferable that the zoom lens satisfy the following conditional expression (24). By ensuring that the corresponding value of conditional expression (24) is not below the lower limit, the final lens group GE will not become too light, and it is possible to prevent the center of gravity of the entire optical system from shifting toward the object side. This contributes to reducing the burden on the user when holding the zoom lens. By ensuring that the corresponding value of conditional expression (24) is not above the upper limit, it is possible to prevent the final lens group GE from becoming too heavy, which is advantageous for reducing the weight of the entire lens system. In order to obtain better characteristics, it is more preferable that the zoom lens satisfy the following conditional expression (24-1), and it is even more preferable that it satisfy the following conditional expression (24-2). 2.5 <GEave<5 (24) 3 <GEave<4 (24-1) 3.2 <GEave<3.7 (24-2)

[0099] It is preferable that the final group GE have positive refractive power, which is advantageous for ensuring sufficient peripheral illumination because it can prevent the angle of incidence of off-axial chief rays onto the image plane Sim from becoming too large.

[0100] When varying magnification, it is preferable that the final lens unit GE be fixed relative to the image plane Sim. By locating the lens unit closest to the image side that is fixed when varying magnification, this is advantageous for suppressing fluctuations in lateral chromatic aberration when varying magnification.

[0101] The final group GE may be configured to consist of two or fewer lenses. This is advantageous for achieving compactness and weight reduction. If the final group GE consists of a cemented lens formed by cementing one positive lens and one negative lens, this is advantageous for correcting chromatic aberration of magnification. Alternatively, the final group GE may be configured to consist of a single lens. This is advantageous for achieving compactness and weight reduction.

[0102] If the distance from the image plane Sim at the wide-angle end when focused on an object at infinity to the exit pupil position is Pexpw and the focal length of the entire system at the wide-angle end when focused on an object at infinity is fw, it is preferable that the zoom lens satisfy the following conditional expression (9). By ensuring that the corresponding value of conditional expression (9) is not below the lower limit, the angle of incidence of off-axial chief rays on the image plane Sim will not become too large, which is advantageous for ensuring sufficient peripheral light intensity. By ensuring that the corresponding value of conditional expression (9) is not above the upper limit, it is advantageous for making the lens system more compact. In order to obtain better characteristics, it is more preferable that the zoom lens satisfy the following conditional expression (9-1), and it is even more preferable that it satisfy the following conditional expression (9-2). 0.5 <Pexpw / fw<5 (9) 1 <Pexpw / fw<4.2 (9-1) 1.4 <Pexpw / fw<3.7 (9-2)

[0103] Let TLt be the sum of the optical axial distance from the lens surface of the first lens group G1 closest to the object at the telephoto end to the lens surface of the final lens group GE closest to the image at the telephoto end and the back focal length in terms of the air equivalent distance of the entire system at the telephoto end when focused on an object at infinity, ft be the focal length of the entire system at the telephoto end when focused on an object at infinity, and ωt be the maximum half angle of view at the telephoto end when focused on an object at infinity. It is preferable that the zoom lens satisfy the following conditional expression (19). FIG. 2 shows an example of ωt. By ensuring that the corresponding value of conditional expression (19) is not equal to or less than the lower limit, it is easy to provide a zoom lens with high optical performance. By ensuring that the corresponding value of conditional expression (19) is not equal to or greater than the upper limit, it is easy to provide a small and lightweight camera system. In order to obtain better characteristics, it is more preferable that the zoom lens satisfy the following conditional expression (19-1), and it is even more preferable that the zoom lens satisfy the following conditional expression (19-2). 2.85 <TLt / (ft×tan|ωt|)<7 (19) 3.2 <TLt / (ft×tan|ωt|)<6 (19-1) 3.5 <TLt / (ft×tan|ωt|)<5.25 (19-2)

[0104] If the focal length of the entire system at the wide-angle end when focused on an object at infinity is fw and the focal length of the entire system at the telephoto end when focused on an object at infinity is ft, it is preferable that the zoom lens satisfy the following conditional expression (28). By ensuring that the corresponding value of conditional expression (28) is not below the lower limit, a significant zoom ratio for the zoom lens can be ensured. By ensuring that the corresponding value of conditional expression (28) is not above the upper limit, it is advantageous for compactness. In order to obtain better characteristics, it is more preferable that the zoom lens satisfy the following conditional expression (28-1), and it is even more preferable that the zoom lens satisfy the following conditional expression (28-2). 1.3 <ft / fw<5 (28) 1.4 <ft / fw<3 (28-1) 1.45 <ft / fw<2.5 (28-2)

[0105] If the maximum half angle of view at the wide-angle end when focused on an object at infinity is ωw, and ωw is in degrees, it is preferable that the zoom lens satisfy the following conditional expression (30): By ensuring that the corresponding value of conditional expression (30) is not below the lower limit, the angle of view does not become too narrow, which is advantageous for shortening the overall length of a lens system in which the first lens group G1 closest to the object has negative refractive power. By ensuring that the corresponding value of conditional expression (30) is not above the upper limit, the angle of view does not become too wide, which makes it easy to reduce the diameter of the first lens group G1 and also prevents the entire lens system from becoming large. In order to obtain better characteristics, it is more preferable that the zoom lens satisfy the following conditional expression (30-1), and it is even more preferable that the zoom lens satisfy the following conditional expression (30-2): 28<ωw<90 (30) 32<ωw<65 (30-1) 35<ωw<60 (30-2)

[0106] The above-described preferred and possible configurations, including those related to the conditional expressions, can be combined in any desired manner, and are preferably selectively adopted as appropriate according to the required specifications. Note that the conditional expressions that the zoom lens of the present disclosure preferably satisfies are not limited to those written in the form of an expression, but include all conditional expressions obtained by arbitrarily combining lower and upper limits from among the preferred, more preferred, and even more preferred conditional expressions.

[0107] As an example, a preferred embodiment of a zoom lens according to the present disclosure is a zoom lens that includes, in order from the object side to the image side, a first lens group G1 having negative refractive power, an intermediate group GM, and a final group GE, wherein the distance between the first lens group G1 and the intermediate group GM changes during magnification variation, the distance between the intermediate group GM and the final group GE changes, during focusing, at least a portion of the intermediate group GM moves along the optical axis Z as a focusing group, the first lens group G1 and the final group GE are fixed with respect to the image plane Sim, and satisfies the above-mentioned conditional formula (1). This preferred embodiment makes it possible to provide a compact, lightweight zoom lens that has a large image circle and high optical performance.

[0108] Next, examples of the zoom lens of the present disclosure will be described with reference to the drawings. Note that the reference symbols assigned to the lenses in the cross-sectional views of each example are used independently for each example to avoid cluttering the explanation and the drawings due to an increase in the number of digits in the reference symbols. Therefore, even if common reference symbols are assigned in drawings of different examples, this does not necessarily mean that the configuration is the same. Furthermore, the following Examples 1 to 7 and 10 are examples of the present disclosure, and Examples 8, 8A and 9 are reference examples.

[0109] [Example 1] A cross-sectional view of the zoom lens configuration of Example 1 is shown in Figure 1, and since the illustration method and configuration are as described above, some overlapping explanations will be omitted here. The zoom lens of Example 1 comprises, in order from the object side to the image side along the optical axis Z, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, and a fourth lens group G4 having positive refractive power. The middle group GM comprises the second lens group G2 and the third lens group G3. The front subgroup GMf comprises the second lens group G2. The rear subgroup GMr comprises the third lens group G3. The final group GE comprises the fourth lens group G4.

[0110] During magnification change, the first lens group G1, the second lens group G2, and the third lens group G3 move along the optical axis Z while changing the distance between adjacent groups in the optical axis direction, and the fourth lens group G4 is fixed with respect to the image plane Sim. The focus group consists of the entire third lens group G3.

[0111] For the zoom lens of Example 1, basic lens data is shown in Table 1, specifications and variable surface spacing in Table 2, and aspherical coefficients in Table 3. Table 1 is written as follows: The Sn column shows the surface numbers, with the surface closest to the object being surface 1 and the numbers increasing by one as you move toward the image side. The R column shows the radius of curvature of each surface. The D column shows the surface spacing on the optical axis between each surface and its adjacent surface on the image side. The Nd column shows the refractive index of each component with respect to the d-line. The νd column shows the Abbe number of each component with respect to the d-line. The θgF column shows the partial dispersion ratio between the g-line and F-line of each component. The SG column shows the specific gravity of each component. The dNd / dT column shows the temperature coefficient of the relative refractive index with respect to the d-line in the range of 20°C to 40°C of each component. 6 The unit of temperature coefficient is K (Kelvin). -1 The column labeled ED indicates the effective diameter in diameter. ED indicates only the lens surface of the intermediate group GM closest to the object and the lens surface of the intermediate group GM closest to the image.

[0112] In Table 1, the sign of the radius of curvature of a surface with a convex surface facing the object side is positive, and the sign of the radius of curvature of a surface with a convex surface facing the image side is negative. Table 1 also shows the aperture stop St and optical element PP. The column for the surface number corresponding to the aperture stop St contains the surface number and the phrase (St). The value in the bottom column of D in Table 1 is the distance between the surface closest to the image side in the table and the image plane Sim. In Table 1, the variable surface distance is indicated by the symbol DD[ ], and the object-side surface number of this distance is entered in the [ ] in the D column.

[0113] Table 2 shows the zoom magnification Zr, focal length f, back focus in air equivalent distance, maximum F-number (FNo.), maximum full-angle (2ω), and variable surface spacing for each zoom and focus state. The approximate size of the image circle can be calculated from f and ω. The (°) in the 2ω column indicates degrees. In Table 2, the values ​​for the wide-angle, mid-focal length, and telephoto states are listed in the columns labeled "Wide-angle," "Mid-range," and "Telephoto," respectively. In Table 2, the values ​​for a state focused on an object at infinity are listed in the column labeled "Infinity," and the values ​​for a magnification of -0.1x are listed in the column labeled "β=-0.1." Note that some values ​​are omitted in the column labeled "β=-0.1." The values ​​in Tables 1 and 2 are based on the d-line.

[0114] In the basic lens data, the aspherical surface numbers are marked with an *, and the numerical value of the paraxial radius of curvature is given in the column for the radius of curvature of the aspherical surface. In Table 3, the Sn row shows the aspherical surface numbers, and the KA and Am rows show the numerical values ​​of the aspherical coefficients for each aspherical surface. Note that m in Am is an integer of 3 or more, and varies depending on the surface. For example, for surface 11, m = 3, 4, 5, ... 10. The numerical values ​​of the aspherical coefficients in Table 3, "E±n" (n: integer), are expressed as "×10 ±n KA and Am are aspherical coefficients in the aspherical formula given below. Zd=C×h 2 / {1+(1-KA×C 2 ×h 2 ) 1 / 2}+ΣAm×hm however, Zd: Aspheric depth (length of the perpendicular line drawn from a point on the aspheric surface at height h to a plane perpendicular to the optical axis Z where the vertex of the aspheric surface is in contact) h: Height (distance from optical axis Z to lens surface) C: Reciprocal of paraxial radius of curvature KA, Am: aspherical coefficients In the aspherical formula, Σ means the summation over m.

[0115] In the data in each table, the angle unit is degrees and the length unit is mm (millimeters), but since the optical system can be used with proportional enlargement or reduction, other appropriate units can also be used. Also, in each table below, the values ​​are rounded to a predetermined number of decimal places.

[0116] [Table 1]

[0117] [Table 2]

[0118] [Table 3]

[0119] FIG. 7 shows aberration diagrams of the zoom lens of Example 1 when focused on an object at infinity. From left to right, FIG. 7 shows spherical aberration, astigmatism, distortion, and lateral chromatic aberration. In FIG. 7, the upper row labeled "WIDE" shows aberrations at the wide-angle end, the middle row labeled "MIDDLE" shows aberrations at the intermediate focal length, and the lower row labeled "TELE" shows aberrations at the telephoto end. In the spherical aberration diagram, aberrations at the d-line, C-line, F-line, and g-line are shown by solid lines, long-dashed lines, short-dashed lines, and two-dot chain lines, respectively. In the astigmatism diagram, aberrations at the d-line in the sagittal direction are shown by solid lines, and aberrations at the d-line in the tangential direction are shown by short-dashed lines. In the distortion diagram, aberrations at the d-line are shown by solid lines. In the lateral chromatic aberration diagram, aberrations for the C-line, F-line, and g-line are shown with long-dashed lines, short-dashed lines, and two-dot chain lines, respectively. In the spherical aberration diagram, the maximum F-number is shown after "FNo.=". In the other aberration diagrams, the maximum half angle of view is shown after "ω=".

[0120] The symbols, meanings, notation methods, and illustration methods of each data item related to the above-mentioned Example 1 are the same in the following Examples unless otherwise specified, and therefore, redundant explanations will be omitted below.

[0121] [Example 2] FIG. 8 shows a cross-sectional view of the configuration and movement locus of the zoom lens of Example 2 at the wide-angle end when focused on an object at infinity. The zoom lens of Example 2 is composed of, in order from the object side to the image side along the optical axis Z, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, and a fourth lens group G4 having positive refractive power. The middle group GM is composed of the second lens group G2 and the third lens group G3. The front subgroup GMf is composed of the second lens group G2. The rear subgroup GMr is composed of the third lens group G3. The final group GE is composed of the fourth lens group G4.

[0122] The first lens group G1 consists of five lenses, L11 to L15, in order from the object side to the image side. The second lens group G2 consists of an aperture stop St and four lenses, L21 to L24, in order from the object side to the image side. The third lens group G3 consists of two lenses, L31 and L32, in order from the object side to the image side. The fourth lens group G4 consists of one lens, L41.

[0123] During magnification variation, the first lens group G1, the second lens group G2, and the third lens group G3 move along the optical axis Z while changing the distance between adjacent groups in the optical axis direction, and the fourth lens group G4 is fixed relative to the image plane Sim. The focusing group consists of the entire third lens group G3. The vibration reduction group consists of lens L15. In Figure 8, a vertical double-headed arrow is written below the vibration reduction group. This method of illustrating the vibration reduction group is the same in the following embodiments.

[0124] For the zoom lens of Example 2, basic lens data is shown in Table 4, specifications and variable surface spacings are shown in Table 5, aspherical coefficients are shown in Table 6, and aberration diagrams are shown in FIG.

[0125] [Table 4]

[0126] [Table 5]

[0127] [Table 6]

[0128] [Example 3] FIG. 10 shows a cross-sectional view of the configuration and movement locus of the zoom lens of Example 3 at the wide-angle end when focused on an object at infinity. The zoom lens of Example 3 is composed of, in order from the object side to the image side along the optical axis Z, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, and a fourth lens group G4 having positive refractive power. The middle group GM is composed of the second lens group G2 and the third lens group G3. The front subgroup GMf is composed of the second lens group G2. The rear subgroup GMr is composed of the third lens group G3. The final group GE is composed of the fourth lens group G4.

[0129] The first lens group G1 consists of four lenses, lenses L11 to L14, in order from the object side to the image side. The second lens group G2 consists of, in order from the object side to the image side, lens L21, aperture stop St, lens L22, and lens L23. The third lens group G3 consists of two lenses, lenses L31 to L32, in order from the object side to the image side. The fourth lens group G4 consists of one lens, lens L41.

[0130] During magnification change, the second lens group G2 and the third lens group G3 move along the optical axis Z while changing the distance between adjacent groups in the optical axis direction, while the first lens group G1 and the fourth lens group G4 are fixed relative to the image plane Sim. The focus group consists of the entire third lens group G3. The vibration reduction group consists of lens L14.

[0131] For the zoom lens of Example 3, basic lens data is shown in Table 7, specifications and variable surface spacings are shown in Table 8, aspherical coefficients are shown in Table 9, and aberration diagrams are shown in FIG.

[0132] [Table 7]

[0133] [Table 8]

[0134] [Table 9]

[0135] [Example 4] FIG. 12 shows a cross-sectional view of the configuration and movement locus of the zoom lens of Example 4 at the wide-angle end when focused on an object at infinity. The zoom lens of Example 4 is composed of, in order from the object side to the image side along the optical axis Z, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, and a fourth lens group G4 having positive refractive power. The middle group GM is composed of the second lens group G2 and the third lens group G3. The front subgroup GMf is composed of the second lens group G2. The rear subgroup GMr is composed of the third lens group G3. The final group GE is composed of the fourth lens group G4.

[0136] The first lens group G1 consists of five lenses, L11 to L15, in order from the object side to the image side. The second lens group G2 consists of an aperture stop St and seven lenses, L21 to L27, in order from the object side to the image side. The third lens group G3 consists of two lenses, L31 and L32, in order from the object side to the image side. The fourth lens group G4 consists of one lens, L41.

[0137] During magnification change, the first lens group G1, the second lens group G2, and the third lens group G3 move along the optical axis Z while changing the spacing between adjacent groups in the optical axis direction, while the fourth lens group G4 is fixed relative to the image plane Sim. The focus group consists of the entire third lens group G3. The vibration reduction group consists of lens L15.

[0138] For the zoom lens of Example 4, basic lens data is shown in Table 10, specifications and variable surface spacing are shown in Table 11, aspherical coefficients are shown in Table 12, and aberration diagrams are shown in FIG.

[0139] [Table 10]

[0140] [Table 11]

[0141] [Table 12]

[0142] [Example 5] FIG. 14 shows a cross-sectional view of the zoom lens of Example 5 at the wide-angle end when focused on an object at infinity, and its movement trajectory. The zoom lens of Example 5 is composed of, in order from the object side to the image side along the optical axis Z, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, and a fourth lens group G4 having positive refractive power. The middle group GM is composed of the second lens group G2 and the third lens group G3. The front subgroup GMf is composed of the second lens group G2. The rear subgroup GMr is composed of the third lens group G3. The final group GE is composed of the fourth lens group G4.

[0143] The first lens group G1 consists of four lenses, L11 to L14, in order from the object side to the image side. The second lens group G2 consists of, in order from the object side to the image side, lens L21, lens L22, aperture stop St, lens L23, and lens L24. The third lens group G3 consists of two lenses, L31 to L32, in order from the object side to the image side. The fourth lens group G4 consists of one lens, lens L41.

[0144] During magnification change, the first lens group G1, the second lens group G2, and the third lens group G3 move along the optical axis Z while changing the distance between adjacent groups in the optical axis direction, and the fourth lens group G4 is fixed with respect to the image plane Sim. The focus group consists of the entire third lens group G3.

[0145] For the zoom lens of Example 5, basic lens data is shown in Table 13, specifications and variable surface spacing are shown in Table 14, aspherical coefficients are shown in Table 15, and various aberration diagrams are shown in FIG.

[0146] [Table 13]

[0147] [Table 14]

[0148] [Table 15]

[0149] [Example 6] FIG. 16 shows a cross-sectional view of the configuration and movement locus of the zoom lens of Example 6 at the wide-angle end when focused on an object at infinity. The zoom lens of Example 6 is composed of, in order from the object side to the image side along the optical axis Z, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, and a fourth lens group G4 having positive refractive power. The middle group GM is composed of the second lens group G2 and the third lens group G3. The front subgroup GMf is composed of the second lens group G2. The rear subgroup GMr is composed of the third lens group G3. The final group GE is composed of the fourth lens group G4.

[0150] The first lens group G1 consists of five lenses, L11 to L15, in order from the object side to the image side. The second lens group G2 consists of an aperture stop St and four lenses, L21 to L24, in order from the object side to the image side. The third lens group G3 consists of two lenses, L31 and L32, in order from the object side to the image side. The fourth lens group G4 consists of one lens, L41.

[0151] During magnification change, the first lens group G1, the second lens group G2, and the third lens group G3 move along the optical axis Z while changing the spacing between adjacent groups in the optical axis direction, while the fourth lens group G4 is fixed relative to the image plane Sim. The focus group consists of the entire third lens group G3. The vibration reduction group consists of lens L15.

[0152] For the zoom lens of Example 6, basic lens data is shown in Table 16, specifications and variable surface spacing are shown in Table 17, aspherical coefficients are shown in Table 18, and each aberration diagram is shown in FIG.

[0153] [Table 16]

[0154] [Table 17]

[0155] [Table 18]

[0156] [Example 7] FIG. 18 shows a cross-sectional view of the zoom lens of Example 7 at the wide-angle end when focused on an object at infinity, and its movement trajectory. The zoom lens of Example 7 is composed of, in order from the object side to the image side along the optical axis Z, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having positive refractive power. The middle group GM is composed of the second lens group G2, the third lens group G3, and the fourth lens group G4. The front subgroup GMf is composed of the second lens group G2 and the third lens group G3. The rear subgroup GMr is composed of the fourth lens group G4. The final group GE is composed of the fifth lens group G5.

[0157] The first lens group G1 consists of four lenses, L11 to L14, in order from the object side to the image side. The second lens group G2 consists of two lenses, L21 to L22, in order from the object side to the image side. The third lens group G3 consists of an aperture stop St and four lenses, L31 to L34, in order from the object side to the image side. The fourth lens group G4 consists of three lenses, L41 to L43, in order from the object side to the image side. The fifth lens group G5 consists of a single lens, L51.

[0158] During magnification change, the second lens group G2, the third lens group G3, and the fourth lens group G4 move along the optical axis Z while changing the distance between adjacent groups in the optical axis direction, while the first lens group G1 and the fifth lens group G5 are fixed with respect to the image plane Sim. The focus group consists of the entire second lens group G2.

[0159] For the zoom lens of Example 7, basic lens data is shown in Table 19, specifications and variable surface spacing are shown in Table 20, aspherical coefficients are shown in Table 21, and various aberration diagrams are shown in FIG.

[0160] [Table 19]

[0161] [Table 20]

[0162] [Table 21]

[0163] [Example 8] FIG. 20 shows a cross-sectional view of the zoom lens of Example 8 at the wide-angle end when focused on an object at infinity, along with its movement trajectory. The zoom lens of Example 8 is composed of, in order from the object side to the image side along the optical axis Z, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having positive refractive power, and a fifth lens group G5 having positive refractive power. The middle group GM is composed of the second lens group G2, the third lens group G3, and the fourth lens group G4. The front subgroup GMf is composed of the second lens group G2. The rear subgroup GMr is composed of the third lens group G3 and the fourth lens group G4. The final group GE is composed of the fifth lens group G5.

[0164] The first lens group G1 consists of four lenses, L11 to L14, in order from the object side to the image side. The second lens group G2 consists of two lenses, L21 and L22, an aperture stop St, and four lenses, L23 to L26, in order from the object side to the image side. The third lens group G3 consists of three lenses, L31 to L33, in order from the object side to the image side. The fourth lens group G4 consists of one lens, L41. The fifth lens group G5 consists of one lens, L51.

[0165] During magnification variation, the first lens group G1, the second lens group G2, the third lens group G3, and the fourth lens group G4 move along the optical axis Z while changing the spacing between adjacent groups in the optical axis direction, and the fifth lens group G5 is fixed with respect to the image plane Sim. The focus group consists of two lenses, lenses L21 and L22.

[0166] For the zoom lens of Example 8, basic lens data is shown in Table 22, specifications and variable surface spacing are shown in Table 23, aspherical coefficients are shown in Table 24, and various aberration diagrams are shown in FIG.

[0167] [Table 22]

[0168] [Table 23]

[0169] [Table 24]

[0170] Example 8A Example 8A is a modification of Example 8. FIG. 21 shows a cross-sectional view of the configuration and movement locus of the zoom lens of Example 8A at the wide-angle end when focused on an object at infinity. Example 8A differs from Example 8 in that the rear subgroup GMR is composed only of the third lens group G3, and the fourth lens group G4 is included in the middle group GM but is not included in either the front subgroup GMf or the rear subgroup GMR. Other than the above, Example 8A is the same as Example 8. The basic lens data, specifications and variable surface spacings, aspherical coefficients, and various aberration diagrams for Example 8A are also the same as those for Example 8.

[0171] [Example 9] 23 shows a cross-sectional view of the configuration of the zoom lens of Example 9 at the wide-angle end when focused on an object at infinity and the movement locus thereof. The zoom lens of Example 9 is composed of, in order from the object side to the image side along the optical axis Z, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, and a third lens group G3 having positive refractive power.

[0172] The first lens group G1 consists of four lenses, L11 to L14, in order from the object side to the image side. The second lens group G2 consists of two lenses, L21 and L22, an aperture stop St, and four lenses, L23 to L26, in order from the object side to the image side. The third lens group G3 consists of two lenses, L31 and L32, in order from the object side to the image side.

[0173] The middle group GM is made up of the second lens group G2. The front subgroup GMf is made up of two lenses, L21 and L22, an aperture stop St, and two lenses, L23 and L24. The rear subgroup GMr is made up of two lenses, L25 and L26. The final group GE is made up of the third lens group G3.

[0174] During magnification change, the first lens group G1 and the second lens group G2 move along the optical axis Z while changing the distance between the adjacent groups in the optical axis direction, and the third lens group G3 is fixed relative to the image plane Sim. The focus group consists of lens L25.

[0175] For the zoom lens of Example 9, basic lens data is shown in Table 25, specifications and variable surface spacing are shown in Table 26, aspherical coefficients are shown in Table 27, and various aberration diagrams are shown in FIG.

[0176] [Table 25]

[0177] [Table 26]

[0178] [Table 27]

[0179] [Example 10] Figure 25 shows a cross-sectional view of the zoom lens of Example 10 at the wide-angle end when focused on an object at infinity, along with its movement trajectory. The zoom lens of Example 10 comprises, in order from the object side to the image side along the optical axis Z, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having positive refractive power. The middle group GM comprises the second lens group G2, the third lens group G3, and the fourth lens group G4. The front subgroup GMf comprises the second lens group G2 and the third lens group G3. The rear subgroup GMr comprises the fourth lens group G4. The final group GE comprises the fifth lens group G5.

[0180] The first lens group G1 consists of four lenses, L11 to L14, in order from the object side to the image side. The second lens group G2 consists of two lenses, L21 to L22, in order from the object side to the image side. The third lens group G3 consists of an aperture stop St and four lenses, L31 to L34, in order from the object side to the image side. The fourth lens group G4 consists of three lenses, L41 to L43, in order from the object side to the image side. The fifth lens group G5 consists of a single lens, L51.

[0181] During magnification change, the second lens group G2, the third lens group G3, and the fourth lens group G4 move along the optical axis Z while changing the distance between adjacent groups in the optical axis direction, while the first lens group G1 and the fifth lens group G5 are fixed with respect to the image plane Sim. The focus group consists of the entire second lens group G2.

[0182] For the zoom lens of Example 10, basic lens data is shown in Table 28, specifications and variable surface spacings are shown in Table 29, aspherical coefficients are shown in Table 30, and various aberration diagrams are shown in FIG.

[0183] [Table 28]

[0184] [Table 29]

[0185] [Table 30]

[0186] Tables 31, 32, and 33 show the values ​​corresponding to conditional expressions (1) to (30) of the zoom lenses of the above examples. In Example 1, there are two convex surfaces that satisfy conditional expressions (5) and (6), so the values ​​corresponding to the convex surface on the object side are listed in the upper row, and the values ​​corresponding to the convex surface on the image side are listed in the lower row. This notation method for conditional expressions (5) and (6) is also used in Examples 3, 9, and 10.

[0187] [Table 31]

[0188] [Table 32]

[0189] [Table 33]

[0190] Next, an imaging device according to an embodiment of the present disclosure will be described. Fig. 27 and Fig. 28 show external views of a camera 30, which is an imaging device according to an embodiment of the present disclosure. Fig. 27 shows a perspective view of the camera 30 as seen from the front side, and Fig. 28 shows a perspective view of the camera 30 as seen from the rear side. The camera 30 is a so-called mirrorless digital camera, to which an interchangeable lens 20 can be removably attached. The interchangeable lens 20 is configured to include a zoom lens 1 according to an embodiment of the present disclosure housed in a lens barrel.

[0191] The camera 30 includes a camera body 31, and a shutter button 32 and a power button 33 are provided on the top surface of the camera body 31. An operation unit 34, an operation unit 35, and a display unit 36 ​​are provided on the back surface of the camera body 31. The display unit 36 ​​can display a captured image and an image within the angle of view before the image was captured.

[0192] A photographic opening through which light from the subject to be photographed enters is provided in the center of the front face of the camera body 31, and a mount 37 is provided at a position corresponding to the photographic opening, and an interchangeable lens 20 is attached to the camera body 31 via the mount 37.

[0193] Inside the camera body 31 are provided an imaging element such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) that outputs an imaging signal corresponding to the subject 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, and a recording medium for recording the generated image. With the camera 30, it is possible to take still images or videos by pressing the shutter button 32, and the image data obtained by this shooting is recorded on the recording medium.

[0194] Although the technology of the present disclosure has been described above using embodiments and examples, the technology of the present disclosure is not limited to the above embodiments and examples and can be modified in various ways. For example, the radius of curvature, surface spacing, refractive index, Abbe number, aspherical coefficient, etc. of each lens are not limited to the values ​​shown in the above examples and can take other values.

[0195] Furthermore, the imaging device according to the embodiment of the present disclosure is not limited to the above example, and can take various forms, such as a camera other than a mirrorless type, a film camera, and a video camera. [Explanation of symbols]

[0196] 1 zoom lens 20 Interchangeable Lenses 30 Camera 31 Camera Body 32 Shutter button 33 Power button 34, 35 Operation section 36 Display section 37 Mount Dfoct focus group movement DpM position difference DStw distance ED effective diameter G1 First lens group G2 Second lens group G3 Third lens group G4 4th lens group G5 5th lens group GE final group GM intermediate group GMf anterior subgroup GMr posterior subgroup HMfa, HMfb, HMra, HMrb height L11~L51, Lx lenses ma, ta, wa Axial luminous flux mb, tb, wb Light flux at maximum image height NL normal P Effective diameter edge PP optical components Sim image plane St aperture stop wa1 Axial Marching Ray wb1 main ray Xa-axis beam Xb off-axis beam Xb1 light Z-axis α angle ωt, ωw maximum half-picture angle

Claims

1. The lens comprises, in order from the object side to the image side, a first lens group having negative refractive power, an intermediate group, and a final lens group, the intermediate group is composed of two or three lens groups, the final group consists of only one lens group, During magnification change, the distance between the first lens group and the intermediate lens group changes, the distance between the intermediate lens group and the final lens group changes, and the distance between adjacent lens groups within the intermediate lens group changes. During focusing, at least a part of the intermediate group moves along the optical axis as a focus group, and the first lens group and the final lens group are fixed with respect to an image plane; the first lens group includes a negative meniscus lens element having a convex surface closest to the object, the intermediate group includes, in order from the object side to the image side, a front subgroup having positive refractive power and a rear subgroup having negative refractive power, the front subgroup is composed of one or two lens groups having positive refractive power, the rear subgroup is made up of one lens group having negative refractive power, The back focus in air equivalent distance of the entire system at the wide-angle end when focused on an object at infinity is Bfw, The focal length of the entire system at the wide-angle end when focused on an object at infinity is fw. The maximum half angle of view at the wide-angle end when focused on an object at infinity is ωw. The paraxial radius of curvature of the lens surface of the front subgroup closest to the object is RMff, The paraxial radius of curvature of the lens surface closest to the image side in the front subgroup is RMfr, The paraxial radius of curvature of the object side surface of the negative meniscus lens is R1f, When the paraxial radius of curvature of the image side surface of the negative meniscus lens is R1r, 0.35<Bfw / (fw×tan|ωw|)<1.5 (1) -0.5<(RMff+RMfr) / (RMff-RMfr)<1 (8-3) 1.5<(R1f+R1r) / (R1f-R1r)<4.3 (10-1) A zoom lens that satisfies the conditions (1), (8-3), and (10-1) expressed by the following formulas.

2. At the telephoto end, the amount of movement of the focus group when the magnification changes from a state focused on an object at infinity to a state of −0.1 times is represented by Dfoct, When the lens is focused on an object at infinity, the difference in the optical axis direction between the position of the lens surface of the intermediate lens group closest to the object at the telephoto end and the position of the lens surface of the intermediate lens group closest to the object at the wide-angle end is denoted by DpM. 0.005<|Dfoct / DpM|<0.3 (2) 2. The zoom lens according to claim 1, which satisfies conditional expression (2) expressed as follows:

3. The effective diameter of the lens surface of the intermediate group closest to the object is EDMf, When the effective diameter of the lens surface of the intermediate group closest to the image side is EDMr, 0.3<EDMf / EDMr<1.5 (3) 3. The zoom lens according to claim 1, wherein conditional expression (3) expressed by the following formula is satisfied:

4. When TLw is the sum of the distance on the optical axis from the lens surface of the first lens group closest to the object at the wide-angle end to the lens surface of the final lens group closest to the image at the wide-angle end and Bfw, 2.5<TLw / (fw×tan|ωw|)<7 (4) 4. The zoom lens according to claim 1, which satisfies conditional expression (4) expressed as follows:

5. When the angle between the normal to the lens surface at the effective diameter end and the optical axis is defined as α, and the unit of α is degrees, １３＜｜α｜＜５０ （５） 5. The zoom lens according to claim 1, wherein the rear sub-unit includes one or more convex lens surfaces facing the air that satisfy conditional expression (5) expressed as follows:

6. a stop is disposed closest to the object side of the intermediate group or within the intermediate group, The distance on the optical axis from the aperture stop to the convex lens surface at the wide-angle end when focused on an object at infinity is DStw, When the focal length of the rear sub-group at the wide-angle end in a state where the lens is focused on an object at infinity is fMrw, 0.05<DStw / |fMrw|<2.5 (6) The rear subgroup includes one or more convex lens surfaces that satisfy conditional expression (6) expressed as follows:

6. The zoom lens according to claim 1.

7. HMfb is the height from the optical axis of the chief ray of the maximum image height on the lens surface of the front subgroup closest to the image side at the wide-angle end in a state where the lens is focused on an object at infinity, HMfa is the height from the optical axis of the on-axis marginal ray on the lens surface closest to the image side of the front subgroup at the wide-angle end when focused on an object at infinity, HMrb is the height from the optical axis of the chief ray of the maximum image height on the lens surface of the rear subgroup closest to the image side at the wide-angle end when focused on an object at infinity, When the height from the optical axis of an axial marginal ray on the lens surface closest to the image side of the rear subgroup at the wide-angle end in a state where the lens is focused on an object at infinity is HMra, 0.08<(HMfb / HMfa) / (HMrb / HMra)<0.8 (7) 7. The zoom lens according to claim 1, which satisfies conditional expression (7) expressed as follows:

8. 8. The zoom lens according to claim 1, wherein, during focusing, at least a part of the rear subgroup moves along the optical axis, and other groups are fixed relative to the image plane.

9. 8. The zoom lens according to claim 1, wherein, during focusing, at least a part of the front subgroup moves along the optical axis, and other subgroups are fixed relative to the image plane.

10. 10. The zoom lens according to claim 1, wherein the rear sub-group includes an image-side negative lens element having a convex surface on the image side.

11. 11. The zoom lens according to claim 10, wherein the rear subgroup includes an object-side negative lens whose object-side surface is convex, located closer to the object side than the image-side negative lens.

12. When the distance from the image plane to the exit pupil position at the wide-angle end in a state where the lens is focused on an object at infinity is Pexpw, 0.5<Pexpw / fw<5 (9) 12. The zoom lens according to claim 1, which satisfies conditional expression (9) expressed as follows:

13. 13. The zoom lens according to claim 1, wherein the first lens group includes two or more negative meniscus lenses each having a convex surface facing the object side.

14. When the refractive index of the positive lens included in the first lens group with respect to the d-line is N1p, 1.6<N1p<2.15 (11) 14. The zoom lens according to claim 1, wherein the first lens group includes one or more positive lenses that satisfy conditional expression (11) expressed as follows:

15. When the focal length of the first lens group is f1, 0.3<fw / |f1|<1.5 (12) 15. The zoom lens according to claim 1, which satisfies conditional expression (12) expressed as follows:

16. When the focal length of the intermediate lens group at the wide-angle end in a state focused on an object at infinity is fMw, 0.4<fw / fMw<1.5 (13) 16. The zoom lens according to claim 1, which satisfies conditional expression (13) expressed as follows:

17. When the focal length of the focus group is ffoc, 0.05<fw / |ffoc|<2.5 (14) 17. The zoom lens according to claim 1, which satisfies conditional expression (14) expressed as follows:

18. If the average value of the specific gravity of all the lenses included in the intermediate group is GMave, then 3<GMave<4.2 (15) 18. The zoom lens according to claim 1, which satisfies conditional expression (15) expressed as follows:

19. The temperature coefficient of the relative refractive index of the negative lens included in the first lens group with respect to the d line in the temperature range from 20° C. to 40° C. is (dN1n / dT)×10 －６ , dN1n / dT is in units of K －１ In this case, -15<dN1n / dT<0 (16) 19. The zoom lens according to claim 1, wherein the first lens group includes at least one negative lens that satisfies conditional expression (16) expressed as follows:

20. 0.45<Bfw / (fw×tan|ωw|)<1.1 (1-1) 20. The zoom lens according to claim 1, which satisfies conditional expression (1-1) expressed as follows:

21. 0.5<Bfw / (fw×tan|ωw|)<0.85 (1-2) 20. The zoom lens according to claim 1, which satisfies conditional expression (1-2) expressed as follows:

22. 22. The zoom lens according to claim 1, wherein the final lens unit is fixed relative to an image plane during zooming.

23. An imaging device comprising the zoom lens according to any one of claims 1 to 22.

Images