Zoom lens and imaging apparatus

Abstract

To provide a zoom lens which is capable of miniaturizing the whole zoom lens regardless of a large aperture ratio and in which various aberrations are satisfactorily corrected in the whole zoom area, and an imaging apparatus including the zoom lens.SOLUTION: A zoom lens comprises, in order from an object side, a first lens group having positive refractive power, a second lens group having negative refractive power, an intermediate group including one or more lens groups and having positive refractive power as a whole, an n-1-th lens group having negative refractive power, and an n-th lens group. When varying power from a wide angle end to a telephoto end, an interval between adjacent lens groups is changed. When varying the power from the wide angle end to the telephoto end, at least the first lens group is moved in an optical axis direction. The zoom lens satisfies a predetermined conditional expression.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a zoom lens and an imaging device, and more particularly to a zoom lens suitable for imaging devices using solid-state imaging elements (CCD, CMOS, etc.) such as digital still cameras and digital video cameras, and an imaging device equipped with the zoom lens. [Background technology]

[0002] Imaging devices using solid-state imaging elements, such as digital still cameras and digital video cameras, are widely used. Interchangeable-lens imaging devices, such as single-lens reflex cameras and mirrorless cameras, allow users to capture images with various angles of view, brightness, depth of field, and other characteristics by simply changing lenses. In recent years, there has been a demand for interchangeable lenses with larger aperture ratios to enable capturing images with greater brightness and blur. Conventional zoom lenses often have an F-number of around 2.8, even at their fastest. Those seeking a lens faster than this often have no choice but to choose a prime lens. However, because prime lenses have a fixed focal length, they have drawbacks, such as a limited capture range, the hassle of changing lenses to change to a different focal length, and the need to carry multiple lenses with different focal lengths. To address these issues and improve convenience, a large-aperture zoom lens is desirable.

[0003] Furthermore, with the increasing popularity of compact mirrorless single-lens cameras that do not have mirrors or optical viewfinders, there is a demand for compact cameras as well as compact lenses. However, when attempting to realize a zoom lens with a large aperture ratio, the lens diameter and aperture diameter become large, and the overall length of the zoom lens also becomes long. Furthermore, the drive mechanism and other components also become large, which results in a problem of the overall size of the lens unit, including the lens barrel.

[0004] To achieve a compact zoom lens, it is necessary to reduce the aperture diameter, the diameter of the lens closest to the object, and the diameter of the lens closest to the image, as well as the overall length of the zoom lens. In addition, to achieve a compact overall lens unit, including the lens barrel, it is desirable to embed the focus drive mechanism, aperture unit, and various mechanical components in a location within the overall lens unit, including the lens barrel, where the optical system diameter is small. Therefore, it is necessary to provide an area in which lenses with small outer diameters are located. Furthermore, if the focus group is heavy, a drive mechanism with a large drive force is required, making it difficult to achieve a compact overall lens unit, including the lens barrel. Therefore, it is also necessary to reduce the size of the focus group.

[0005] In a positive-lead zoom lens in which a lens group with positive refractive power is positioned closest to the object, a lens group with strong negative refractive power (second lens group) is often positioned on the image side thereof to provide a large zooming effect. In this case, the lens group positioned on the image side of the second lens group receives axial light beams diverged by the negative refractive power of the second lens group, resulting in a high axial ray height. Furthermore, when a large aperture ratio is used, this axial ray height becomes particularly high, which poses a problem of increasing the size of lenses, etc. Thus, when a large aperture ratio is used, the lens group positioned on the image side of the second lens group experiences particularly high axial ray heights, resulting in increased amounts of spherical aberration, coma, etc., and making it difficult to effectively correct aberrations across the entire zoom range.

[0006] When a large aperture ratio is used, the need for a larger aperture diaphragm also becomes a problem. Regarding the location of the aperture diaphragm, it is preferable to locate it near the center of the optical system to facilitate aberration correction and prevent the lens from becoming too large, unless there are special circumstances that require the placement of the aperture diaphragm on the object side or image side of the optical system. Therefore, when the lens group located adjacent to the image side of the second lens group is designated as the third lens group, the aperture diaphragm is often located near or within the third lens group, and when a large aperture ratio is used, the need for a larger aperture diaphragm also becomes a problem. In addition, when a large aperture ratio is used, the diameters of the lenses closest to the object and the image side also become larger, resulting in an increase in the overall length of the zoom lens. Therefore, to achieve a compact zoom lens despite a large aperture ratio, it is important to appropriately set the refractive power, lateral magnification, and magnification load of each lens group.

[0007] Here, Patent Documents 1 and 2 are known as examples of positive-lead zoom lenses with a large aperture ratio and an F-number of about 2.0. Patent Document 1 proposes, for example, in Example 1, a zoom lens with a large aperture ratio and an F-number of 2.06, which is composed of, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having positive refractive power. Patent Document 2 also proposes, for example, in Example 1, a zoom lens with a large aperture ratio and an F-number of 2.06, which is composed of, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power, and a fifth lens group having negative refractive power. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent Publication No. 2019-015956 [Patent Document 2] Patent Publication No. 2016-014841 Summary of the Invention [Problem to be solved by the invention]

[0009] However, in the zoom lens of Patent Document 1, while the image-side lens in the second lens group has a relatively small outer diameter, lenses with high axial ray heights and large outer diameters are arranged consecutively from the third lens group to the fourth lens group toward the object side. As a result, it becomes difficult to secure space for arranging a focus drive mechanism, an aperture unit, and various mechanical components in a small-diameter position within the entire lens unit, including the lens barrel, resulting in a problem of the entire lens unit, including the lens barrel, becoming large. Furthermore, the second lens group, which is the focus group, has a large number of lenses (five), which makes the focus group heavy, requiring a drive mechanism with a large drive force, resulting in a problem of the entire lens unit, including the lens barrel, becoming large.

[0010] In addition, in the zoom lens of Patent Document 2, the fifth lens group, which is the final lens group, is fixed, resulting in a large final lens group. Furthermore, because the back focus is long, the overall length is long, resulting in insufficient miniaturization. Furthermore, the fourth lens group, which is the focus group, has a large axial ray diameter and a large lens outer diameter. This results in a heavy weight for the focus group, requiring a drive mechanism with a large driving force, which results in a problem of the overall size of the lens unit, including the lens barrel.

[0011] The present invention has been made in light of these circumstances, and aims to solve the above-mentioned problems and provide a zoom lens that allows the entire zoom lens to be miniaturized despite having a large aperture ratio and in which various aberrations are well corrected across the entire zoom range, as well as an imaging device equipped with the zoom lens. [Means for solving the problem]

[0012] In order to solve the above-mentioned problems, the inventors have conducted extensive research and have come up with the following zoom lens and imaging device.

[0013] The zoom lens of the present invention is composed of, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, an intermediate group including one or more lens groups and having positive refractive power as a whole, an (n-1)th lens group having negative refractive power, and an nth lens group, wherein the spacing between adjacent lens groups changes when changing magnification from the wide-angle end to the telephoto end, and the first lens group and the nth lens group move in the optical axis direction when changing magnification from the wide-angle end to the telephoto end, and the zoom lens is characterized by satisfying the following conditional expression: -1.00 ≦ βmt ≦ -0.30 ···(1) 1.20 ≦ β2t / β2w ≦ 1.90 (2) -0.31 ≦ xn / (fw×ft) 1 / 2 < 0.00 (3) however, βmt: lateral magnification of the intermediate group when focusing at infinity at the telephoto end β2t: lateral magnification of the second lens group when focused on infinity at the telephoto end β2w: lateral magnification of the second lens group when focusing on infinity at the wide-angle end xn: the difference in movement amount between the wide-angle end position of the nth lens group and the telephoto end position of the nth lens group when changing magnification from the wide-angle end to the telephoto end, where the sign of movement toward the object side is negative and the sign of movement toward the image side is positive fw: focal length of the entire zoom lens system at the wide-angle end ft: focal length of the entire zoom lens system at the telephoto end

[0014] The zoom lens of the present invention is composed of, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, an intermediate group including one or more lens groups and having positive refractive power as a whole, an (n-1)th lens group having negative refractive power, and an nth lens group, wherein the spacing between adjacent lens groups changes when changing magnification from the wide-angle end to the telephoto end, and the first lens group moves in the optical axis direction when changing magnification from the wide-angle end to the telephoto end, and wherein the zoom lens is characterized by satisfying the following conditional expression: -0.74 ≦ βmt ≦ -0.30 ···(1)' 1.20 ≦ β2t / β2w ≦ 2.10 ···(2)' 0.55 ≦ bfw / Y' ≦ 0.97 ···(4) however, βmt: lateral magnification of the intermediate group when focusing at infinity at the telephoto end β2t: lateral magnification of the second lens group when focused on infinity at the telephoto end β2w: lateral magnification of the second lens group when focusing on infinity at the wide-angle end bfw: Back focus at the wide-angle end, which is the distance on the optical axis from the image side of the lens closest to the image plane, and is the value when the cover glass thickness is converted into air Y': Maximum image height of the zoom lens

[0015] The zoom lens of the present invention is composed of, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, an intermediate group including one or more lens groups and having positive refractive power as a whole, an (n-1)th lens group having negative refractive power, and an nth lens group, wherein the spacing between adjacent lens groups changes when changing magnification from the wide-angle end to the telephoto end, and the first lens group moves in the optical axis direction when changing magnification from the wide-angle end to the telephoto end, and wherein the zoom lens is characterized by satisfying the following conditional expression: -0.74 ≦ βmt ≦ -0.30 ···(1)' 1.20 ≦ β2t / β2w ≦ 2.10 ···(2)' 0.80 ≦ fmt / frt ≦ 1.30 (5) however, βmt: lateral magnification of the intermediate group when focusing at infinity at the telephoto end β2t: lateral magnification of the second lens group when focused on infinity at the telephoto end β2w: lateral magnification of the second lens group when focusing on infinity at the wide-angle end fmt: focal length of the intermediate group at the telephoto end frt: composite focal length of all lenses arranged closer to the image than the second lens group at the telephoto end when focused at infinity

[0016] The imaging device according to the present invention employs an imaging device characterized by including the zoom lens described above and a solid-state imaging element that converts an optical image formed by the zoom lens into an electrical signal. [Effects of the Invention]

[0017] The zoom lens of the present invention has a large aperture ratio, yet can achieve a compact size for the entire zoom lens, and can effectively correct various aberrations such as spherical aberration and coma over the entire zoom range. The imaging device of the present invention equipped with the zoom lens is compact, yet is capable of shooting at different focal lengths, and can take advantage of brightness and bokeh. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a cross-sectional view of a zoom lens according to a first embodiment. [Figure 2] 1A to 1C are longitudinal aberration diagrams of Example 1 at the wide-angle end, at an intermediate focal position, and at the telephoto end when focusing on an object at infinity. [Figure 3] 1A to 1C are longitudinal aberration diagrams of Example 1 at the wide-angle end, at an intermediate focal position, and at the telephoto end when focusing on an object at a finite distance (magnification factor 1 / 40 (1:40)). [Figure 4] FIG. 10 is a cross-sectional view of a zoom lens according to a second embodiment. [Figure 5] 10A to 10C are longitudinal aberration diagrams of Example 2 at the wide-angle end, at an intermediate focal position, and at the telephoto end when focusing on an object at infinity. [Figure 6] 10A to 10C are longitudinal aberration diagrams of Example 2 at the wide-angle end, at an intermediate focal position, and at the telephoto end when focusing on an object at a finite distance (magnification factor 1 / 40 (1:40)). [Figure 7] FIG. 10 is a cross-sectional view of a zoom lens according to a third embodiment. [Figure 8] 10A to 10C are longitudinal aberration diagrams of Example 3 at the wide-angle end, at an intermediate focal position, and at the telephoto end when focusing on an object at infinity. [Figure 9] 10A to 10C are longitudinal aberration diagrams of Example 3 at the wide-angle end, at an intermediate focal position, and at the telephoto end when focusing on an object at a finite distance (magnification factor 1 / 40 (1:40)). [Figure 10]FIG. 10 is a cross-sectional view of a zoom lens according to a fourth embodiment. [Figure 11] 10A to 10C are longitudinal aberration diagrams of Example 4 at the wide-angle end, at an intermediate focal position, and at the telephoto end when focusing on an object at infinity. [Figure 12] 10A to 10C are longitudinal aberration diagrams of Example 4 at the wide-angle end, at an intermediate focal position, and at the telephoto end when focusing on an object at a finite distance (magnification 1 / 40 (1:40)). DETAILED DESCRIPTION OF THE INVENTION

[0019] The following describes embodiments of the zoom lens and the imaging device according to the present invention. Note that the following description merely shows one aspect, and should not be construed as being limited to the following description.

[0020] 1. Zoom Lens Embodiment 1-1.Optical configuration The zoom lens according to the present invention comprises, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, an intermediate group including one or more lens groups and having positive refractive power overall, an (n-1)th lens group having negative refractive power, and an nth lens group. In this configuration, the spacing between adjacent lens groups changes when zooming from the wide-angle end to the telephoto end, and at least the first lens group moves along the optical axis when zooming from the wide-angle end to the telephoto end. The first lens group and the nth lens group may also move along the optical axis when zooming from the wide-angle end to the telephoto end. In this zoom lens, a lens group is comprised of one or more lenses that move together or remain stationary when zooming between the wide-angle end and the telephoto end. The configuration of each lens group is described below.

[0021] (1) First lens group The first lens group is the lens group located closest to the object, and has positive refractive power as a whole, including at least one lens with positive refractive power. It is also preferable for the first lens group to include a lens with negative refractive power from the perspective of aberration correction. Furthermore, it is preferable for the first lens group to include at least two lenses with positive refractive power and at least one lens with negative refractive power. By including two or more lenses with positive refractive power, the positive refractive power of the first lens group can be shared by multiple lenses, thereby suppressing the occurrence of various aberrations. Furthermore, by including a lens with negative refractive power, chromatic aberrations can be effectively corrected within the first lens group. Therefore, fluctuations in chromatic aberrations can be suppressed even when the first lens group is moved during zooming, and chromatic aberrations can be effectively corrected throughout the entire zoom range.

[0022] (2) Second lens group The second lens group has negative refractive power as a whole and is composed of one or more lenses having negative refractive power. It is also preferable to include a lens having positive refractive power from the viewpoint of aberration correction. Furthermore, it is preferable that the second lens group be composed of at least two lenses having negative refractive power and at least one lens having positive refractive power. Because the second lens group has a relatively strong negative refractive power, by arranging two or more lenses having negative refractive power, the negative refractive power of the second lens group can be shared by multiple lenses, thereby suppressing the occurrence of various aberrations. Furthermore, by arranging a lens having positive refractive power, chromatic aberration can be effectively corrected within the second lens group, thereby suppressing fluctuations in chromatic aberration during magnification change and enabling effective correction of chromatic aberration throughout the entire zoom range.

[0023] (3) Intermediate group The intermediate group includes one or more lens groups and has positive refractive power overall. It is preferable that the surface of the intermediate group closest to the object has a convex shape facing the object side. The axial light beam diverged by the negative refractive power of the second lens group is incident on the surface of the intermediate group closest to the object. Since the axial ray height becomes particularly high at large aperture ratios, the size of the intermediate group is likely to increase. Therefore, it is preferable that the surface of the intermediate group closest to the object has a convex shape facing the object side, thereby quickly converging the axial light beam and reducing the beam diameter of the intermediate group. This allows the diameter of the optical system of the intermediate group to be reduced.

[0024] Furthermore, because the intermediate group is disposed between the second lens group and the (n-1)th lens group, its converging action reduces the diameter of the axial light beam incident on the (n-1)th lens group, making it possible to reduce the outer diameter of the lenses in the (n-1)th lens group. As a result, it is possible to provide a portion of the entire lens unit, including the barrel portion, where the optical system has a small diameter, and it is possible to arrange a focus drive mechanism and the like in the space inside the barrel of that optical system portion, thereby realizing a compact lens unit, including the barrel portion.

[0025] It is preferable that all of the lens groups constituting the intermediate group have positive refractive power, because this allows the axial light beam to converge quickly and the light beam diameter to be reduced.

[0026] It is preferable that the intermediate group be composed of three or fewer lens groups, and for even greater compactness, it is even more preferable that the intermediate group be composed of two or fewer lens groups. This is because, as the number of lens groups constituting a zoom lens increases, the overall optical length tends to increase, making compactness difficult. In the possible configurations of the intermediate group, the lens group located closest to the object is referred to as the third lens group.

[0027] When the intermediate group is composed of two lens groups with positive refractive power (the third lens group and the lens group with positive refractive power), it is possible to easily suppress aberration fluctuations by changing the axial spacing between adjacent lens groups during magnification, resulting in a zoom lens with higher optical performance. When the intermediate group is composed of one lens group with positive refractive power (the third lens group), it is possible to achieve even greater compactness.

[0028] The intermediate group preferably includes four or more lenses having positive refractive power. By including four or more lenses having positive refractive power, the relatively strong positive refractive power of the intermediate group can be shared by multiple lenses, thereby suppressing the occurrence of aberrations such as spherical aberration, coma, and axial chromatic aberration, even with a large aperture ratio. The intermediate group preferably includes two or more lenses having negative refractive power. By including two or more lenses having negative refractive power in the intermediate group, chromatic aberration, spherical aberration, and other aberrations can be effectively corrected within the intermediate group. This suppresses fluctuations in chromatic aberration, spherical aberration, and other aberrations during zooming, enabling effective correction of chromatic aberration, spherical aberration, and other aberrations throughout the entire zoom range. To achieve compactness, the intermediate group preferably includes 10 or fewer lenses. For even greater compactness, 9 or fewer lenses are more preferable, and 8 or fewer lenses are even more preferable.

[0029] The third lens group is composed of one or more lenses with positive refractive power. The intermediate group receives the axial light beam diverged by the negative refractive power of the second lens group, and the axial ray height becomes particularly high when the aperture ratio is large. Therefore, a lens with positive refractive power is located closest to the object in the intermediate group to quickly converge the axial light beam, thereby reducing the beam diameter of the intermediate group and the lens groups located closer to the image than the intermediate group. As a result, the diameters of the intermediate group and the lens groups located closer to the image than the intermediate group can be reduced, allowing the focus drive mechanism and other components to be located in a position with a small diameter within the entire lens unit, including the lens barrel, and thereby enabling the entire lens unit, including the lens barrel, to be made more compact.

[0030] From the viewpoint of aberration correction, it is also preferable that the third lens group includes a lens having negative refractive power. Furthermore, it is preferable that the third lens group be composed of at least two lenses having positive refractive power and at least one lens having negative refractive power. By arranging two or more lenses having positive refractive power, the positive refractive power of the third lens group can be shared by multiple lenses, thereby suppressing the occurrence of various aberrations. Furthermore, by arranging a lens having negative refractive power, chromatic aberration, spherical aberration, and the like can be effectively corrected within the third lens group. Therefore, fluctuations in chromatic aberration, spherical aberration, and the like during magnification change can be suppressed, and chromatic aberration, spherical aberration, and the like can be effectively corrected throughout the entire zoom range.

[0031] In order to suppress chromatic aberration occurring in the third lens group and suppress fluctuations in chromatic aberration due to magnification, it is preferable that the lens having positive refractive power in the third lens group be made of a glass material that satisfies the following conditional expression (17): 50.0 ≦ νd_3p (17) Here, νd_3p is the largest Abbe number at the d-line of all the lenses in the third lens group that have positive refractive power. The lower limit of conditional expression (17) is more preferably 56.0, even more preferably 60.0, and even more preferably 68.0.

[0032] Furthermore, in order to suppress chromatic aberration occurring in the third lens group and suppress fluctuations in chromatic aberration due to magnification change, it is preferable that the lens having negative refractive power in the third lens group be made of a glass material that satisfies the following conditional expression (18): 18.1 ≦ νd_3n ≦ 43.0 ···(18) Here, νd_3n is the smallest Abbe number among the Abbe numbers at the d-line of all lenses having negative refractive power in the third lens group. If the value is below the lower limit, chromatic aberration tends to be overcorrected, and if the value is above the upper limit, chromatic aberration tends to be undercorrected, which is undesirable.

[0033] The lower limit of conditional formula (18) is more preferably 19.0, even more preferably 19.5, even more preferably 20.1, even more preferably 20.5, even more preferably 21.0, and still more preferably 23.0. On the other hand, the upper limit of conditional formula (18) is more preferably 41.0, even more preferably 38.0, and still more preferably 36.0.

[0034] (4) n-1th lens group The n-1st lens group has negative refractive power as a whole and includes at least one lens with negative refractive power. Furthermore, from the viewpoint of chromatic aberration correction, it is also preferable to include a lens with positive refractive power. The n-1st lens group has a lower off-axial ray height than the first lens group, which is located closest to the object, and the nth lens group, which is located closest to the image. Furthermore, since the n-1st lens group has negative refractive power, the positive refractive power of the intermediate group is not excessively weakened, which allows the convergence action of the intermediate group to be fully effective and reduces the axial light beam diameter, thereby allowing the outer diameter of the n-1st lens group to be reduced. As a result, it is possible to position the focus drive mechanism, etc., at a position with a small diameter within the entire lens unit, including the barrel portion, thereby achieving a compact lens unit, including the barrel portion. Furthermore, by moving the n-1st lens group along the optical axis to focus from an object at infinity to an object at a finite distance, the focus group can be made smaller and lighter.

[0035] In particular, when the (n-1)th lens group is composed of one lens with negative refractive power, or when it is composed of one lens with negative refractive power and one lens with positive refractive power, the focus group can be made smaller and lighter, which is preferable. If the focus group can be made smaller and lighter, the focus drive mechanism can also be made smaller, and the entire lens unit, including the lens barrel, can be made smaller.

[0036] When the (n-1)th lens group is composed of one lens with negative refractive power and one lens with positive refractive power, it is preferable to use a cemented lens without an air gap, which allows for further miniaturization and weight reduction compared to a configuration in which two single lenses are arranged with an air gap between them.

[0037] (5) nth lens group The nth lens group is the lens group arranged closest to the image and includes one lens with positive refractive power or one lens with negative refractive power. Furthermore, from the viewpoint of aberration correction, it is preferable that the nth lens group includes one lens with positive refractive power and one lens with negative refractive power. By arranging a lens with positive refractive power and a lens with negative refractive power in the nth lens group, various aberrations can be effectively corrected within the nth lens group. Therefore, fluctuations in various aberrations during zooming can be suppressed, and various aberrations can be effectively corrected throughout the entire zoom range.

[0038] Furthermore, by arranging the nth lens group on the image side of the n-1th lens group, the n-1th lens group is no longer the lens group arranged closest to the image in the optical system, so that the height of off-axial rays does not become high and the outer diameter of the n-1th lens group can be reduced, making it possible to reduce the size of the entire lens unit, including the lens barrel portion.

[0039] (6) Focus group In this zoom lens, it is preferable to use the (n-1)th lens group as the focus group. As described above, the (n-1)th lens group can have a small lens outer diameter, and therefore, by moving the (n-1)th lens group in the optical axis direction to focus from an object at infinity to an object at a finite distance, the focus group can be made small and lightweight. Furthermore, if the focus group can be made small and lightweight, the focus drive mechanism can also be made small, allowing the entire lens unit, including the lens barrel, to be made smaller.

[0040] In order to reduce the size of the entire lens unit including the lens barrel without increasing the number of focus drive mechanisms, it is more preferable to use only the (n-1)th lens group as the focus group.

[0041] (7) Aperture diaphragm In this zoom lens, the location of the aperture stop is not particularly limited. However, the aperture stop referred to here refers to an aperture stop that determines the light beam diameter of the optical system, i.e., the F-number of the optical system. Generally, if the height of off-axial rays passing through the lenses constituting the optical system is high, i.e., if the distance from the optical axis at which the off-axial rays pass through the lenses is long, the amount of off-axial aberration that is generated tends to increase, making aberration correction difficult. Therefore, unless there are special circumstances that require the aperture stop to be located on the object side or image side of the optical system, it is preferable to locate the aperture stop near the center of the optical system.

[0042] It is preferable to locate the aperture stop on the object side of the third lens group or within the third lens group, as this makes it easier to reduce the effective light beam diameter of the first lens group. In particular, it is even more preferable to locate the aperture stop adjacent to the object side of the third lens group, as this makes it easier to reduce the effective light beam diameter of the first lens group.

[0043] By adopting the above configuration, it is possible to realize a compact zoom lens despite having a large aperture ratio, and various aberrations such as spherical aberration and coma can be corrected well over the entire zoom range.

[0044] 1-2.Operation 1-2-1. Operation when changing magnification In this zoom lens, the spacing between adjacent lens groups changes when zooming from the wide-angle end to the telephoto end. As long as the spacing between the lens groups changes, some lens groups may be fixed as fixed groups in the optical axis direction, while other lens groups may be movable groups that move in the optical axis direction. However, it is preferable that all lens groups (the first lens group to the nth lens group) constituting the zoom lens be movable groups when zooming. Making all lens groups movable groups makes it easier to achieve a desired zoom ratio, and also allows each lens group to be positioned in a way that is advantageous for aberration correction at each focal length, enabling excellent aberration correction throughout the entire zoom range.

[0045] It is preferable that the first lens group be moved toward the object side when changing magnification from the wide-angle end to the telephoto end. By moving the first lens group toward the object side when changing magnification from the wide-angle end to the telephoto end, it is possible to achieve a desired magnification ratio while preventing the lens from becoming too large. Alternatively, when changing magnification from the wide-angle end to the telephoto end, the first lens group may be moved toward the object side by extending the inner barrel portion of the lens barrel. In this case, since the inner barrel portion is retracted in the wide-angle end state, it is possible to shorten the overall length at the wide-angle end.

[0046] It is preferable that the second lens group moves toward the image side when changing magnification from the wide-angle end to the telephoto end. By moving the second lens group toward the image side when changing magnification from the wide-angle end to the telephoto end, the burden of changing magnification on the lens groups located closer to the image than the second lens group (the third lens group and subsequent lens groups) becomes relatively light, making it possible to achieve a desired magnification ratio, while also allowing for good aberration correction and preventing the zoom lens from becoming too large.

[0047] It is preferable that the third lens group moves toward the object when zooming from the wide-angle end to the telephoto end. By moving the third lens group toward the object when zooming from the wide-angle end to the telephoto end, the burden of zooming on the second lens group becomes relatively light, allowing a desired zoom ratio to be achieved, while also allowing for good aberration correction and preventing the zoom lens from becoming too large.

[0048] It is preferable that the (n-1)th lens group moves toward the object side when changing magnification from the wide-angle end to the telephoto end. By moving the (n-1)th lens group toward the object side when changing magnification from the wide-angle end to the telephoto end, it is possible to prevent the zoom lens from becoming too large.

[0049] It is preferable that the nth lens group move toward the object side when changing magnification from the wide-angle end to the telephoto end. By moving toward the object side when changing magnification from the wide-angle end to the telephoto end, it is possible to prevent the effective light beam diameter of the nth lens group from increasing at the telephoto end, and it is also possible to prevent the lens outer diameter from increasing, which is preferable in terms of realizing a compact zoom lens.

[0050] 1-2-2.Focus operation In this zoom lens, focusing from an object at infinity to an object at a finite distance is preferably performed by moving the (n-1)th lens group along the optical axis. The (n-1)th lens group has a lower off-axial ray height than the first lens group, which is located closest to the object, and the nth lens group, which is located closest to the image. Furthermore, the on-axis ray diameter can be reduced due to the converging action of the positive refractive power of the intermediate group. This allows the (n-1)th lens group to have a smaller outer diameter and be lighter. This in turn allows for a smaller focus drive mechanism, enabling the entire lens unit, including the lens barrel, to be more compact. Furthermore, a smaller and lighter (n-1)th lens group can achieve faster focusing.

[0051] In order to reduce the size of the entire lens unit including the lens barrel without increasing the focus drive mechanism, it is more preferable to perform focusing by moving only the (n-1)th lens group in the optical axis direction.

[0052] 1-3.Conditional Expressions The zoom lens preferably employs the above-described configuration and satisfies one or more of the following conditional expressions.

[0053] 1-3-1.Conditional Expression (1) -1.00 ≦ βmt ≦ -0.30 ···(1) however, βmt: Lateral magnification of the middle group when focusing at infinity at the telephoto end

[0054] Conditional formula (1) defines the lateral magnification of the intermediate group at the telephoto end, and is a condition for achieving compactness while maintaining a large aperture ratio. If the value of βmt in conditional formula (1) falls below the lower limit, the lateral magnification of the intermediate group at the telephoto end becomes too large, and the axial beam diameter of the (n-1)th lens group becomes large. As a result, it becomes difficult to position a focus drive mechanism, etc., at a position with a small diameter within the entire lens unit, including the lens barrel, which is undesirable from the perspective of achieving compactness of the entire lens unit, including the lens barrel.

[0055] On the other hand, if the value of βmt in conditional formula (1) exceeds the upper limit, the lateral magnification of the intermediate group at the telephoto end becomes too small, and therefore, if one tries to maintain the focal length at the telephoto end and the magnification ratio of the entire system, the negative composite refractive power of the first and second lens groups at the telephoto end weakens. As a result, the effective light beam diameter of the first lens group increases, which is undesirable from the perspective of compactness.

[0056] The lower limit of conditional expression (1) is preferably set to −0.95, more preferably −0.90, more preferably −0.85, more preferably −0.80, more preferably −0.75, more preferably −0.70, more preferably −0.65, and more preferably −0.60.

[0057] The upper limit of conditional expression (1) is preferably set to −0.35, more preferably −0.38, even more preferably −0.40, and even more preferably −0.43.

[0058] When these preferable lower limit values ​​or upper limit values ​​are adopted, the inequality sign with equality (≦) in conditional expression (1) may be replaced with an inequality sign (<). The same applies to other conditional expressions described below.

[0059] 1-3-2. Conditional Expression (1) -0.74 ≦ βmt ≦ -0.30 ···(1)' however, βmt: Lateral magnification of the middle group when focusing at infinity at the telephoto end

[0060] Conditional formula (1)' defines the lateral magnification of the intermediate group at the telephoto end, and is a condition for achieving compactness while maintaining a large aperture ratio. Note that conditional formula (1)' defines a different range of values ​​from conditional formula (1). If the value of βmt in conditional formula (1)' falls below the lower limit, the lateral magnification of the intermediate group at the telephoto end becomes too large, and the axial beam diameter of the (n-1)th lens group becomes large. As a result, it becomes difficult to locate a focus drive mechanism, etc., at a position with a small diameter within the entire lens unit, including the lens barrel, which is undesirable from the perspective of achieving compactness of the entire lens unit, including the lens barrel.

[0061] On the other hand, if the value of βmt in conditional formula (1)' exceeds the upper limit, the lateral magnification of the intermediate group at the telephoto end becomes too small, and therefore, if one tries to maintain the focal length at the telephoto end and the magnification ratio of the entire system, the negative composite refractive power of the first and second lens groups at the telephoto end weakens. As a result, the effective light beam diameter of the first lens group increases, which is undesirable from the perspective of compactness.

[0062] The lower limit of conditional formula (1)' is preferably set to -0.72, more preferably -0.69, more preferably -0.67, more preferably -0.64, more preferably -0.62, and more preferably -0.60.

[0063] On the other hand, the upper limit of conditional formula (1)' is preferably set to -0.35, more preferably -0.38, more preferably -0.40, and even more preferably -0.43.

[0064] 1-3-3.Conditional Expression (2) 1.20 ≦ β2t / β2w ≦ 1.90 (2) however, β2t: Lateral magnification of the second lens group when focusing at infinity at the telephoto end β2w: Lateral magnification of the second lens group when focusing on infinity at the wide-angle end

[0065] Conditional expression (2) defines the zoom ratio of the second lens group, and is a condition for achieving compactness while maintaining a large aperture ratio and excellent correction of aberrations throughout the entire zoom range. If the value of β2t / β2w in conditional expression (2) falls below its lower limit, the zoom contribution of the second lens group becomes too small. Therefore, to maintain the zoom ratio of the entire system, it is necessary to increase the zoom contribution of the lens group (third lens group) and subsequent groups located on the image side of the second lens group. In this case, it may be necessary to strengthen the refractive power of the lens groups from the third lens group onward or to increase their movement distance. Here, because the light beam diverged by the second lens group enters the lens groups from the third lens group onward, the height of the axial ray becomes particularly high when the aperture ratio is large, which tends to increase the amount of spherical aberration, coma, and other aberrations. Therefore, when the refractive power of the lens groups from the third lens group onwards is increased or when the amount of movement is increased, the aberration fluctuations that accompany magnification change also become larger, making it difficult to satisfactorily correct aberrations such as spherical aberration and coma over the entire zoom range, which is undesirable. Furthermore, in order to satisfactorily correct these aberrations, a large number of lenses are required, which tends to increase the overall optical length, which is undesirable in terms of achieving compactness.

[0066] On the other hand, if the value of β2t / β2w in conditional formula (2) exceeds the upper limit, the contribution of the second lens group to magnification becomes too large, which makes it necessary to increase the amount of movement of the second lens group or to strengthen the refractive power of the second lens group. Increasing the amount of movement of the second lens group increases the overall optical length, which is undesirable from the perspective of achieving compactness. Furthermore, increasing the refractive power of the second lens group also requires a large number of lenses for aberration correction, which also increases the overall optical length, which is undesirable from the perspective of achieving compactness.

[0067] The lower limit of conditional expression (2) is preferably set to 1.25, more preferably 1.30, more preferably 1.35, more preferably 1.40, more preferably 1.45, more preferably 1.50, and more preferably 1.55.

[0068] On the other hand, the upper limit of conditional expression (2) should preferably be set to 1.88, more preferably 1.85, and even more preferably 1.83.

[0069] 1-3-4. Conditional Expression (2) 1.20 ≦ β2t / β2w ≦ 2.10 ···(2)' however, β2t: Lateral magnification of the second lens group when focusing at infinity at the telephoto end β2w: Lateral magnification of the second lens group when focusing on infinity at the wide-angle end

[0070] Conditional formula (2)' is a conditional formula for defining the zoom ratio of the second lens group, and is a condition for achieving compactness while maintaining a large aperture ratio and excellent correction of aberrations throughout the entire zoom range. Conditional formula (2)' defines a different numerical range from conditional formula (2). If the value of β2t / β2w in conditional formula (2)' falls below the lower limit, the zoom contribution of the second lens group becomes too small. Therefore, to maintain the zoom ratio of the entire system, it is necessary to increase the zoom contribution of the lens group (third lens group) and subsequent groups located on the image side of the second lens group. In this case, it becomes necessary to strengthen the refractive power of the lens groups from the third lens group onward or to increase their movement distance. Here, because the light beam diverged by the second lens group enters the lens groups from the third lens group onward, the height of the axial ray becomes particularly high when the aperture ratio is large, which tends to increase the amount of spherical aberration, coma, and other aberrations. Therefore, when the refractive power of the lens groups from the third lens group onwards is increased or when the amount of movement is increased, the aberration fluctuations that accompany magnification change also become larger, making it difficult to satisfactorily correct aberrations such as spherical aberration and coma over the entire zoom range, which is undesirable. Furthermore, in order to satisfactorily correct these aberrations, a large number of lenses are required, which tends to increase the overall optical length, which is undesirable in terms of achieving compactness.

[0071] On the other hand, if the value of β2t / β2w in conditional formula (2)' exceeds the upper limit, the contribution of the second lens group to magnification becomes too large, which makes it necessary to increase the amount of movement of the second lens group or to strengthen the refractive power of the second lens group. Increasing the amount of movement of the second lens group increases the overall optical length, which is undesirable from the perspective of achieving compactness. Furthermore, increasing the refractive power of the second lens group also requires a large number of lenses for aberration correction, which also increases the overall optical length, which is undesirable from the perspective of achieving compactness.

[0072] The lower limit of conditional formula (2)' is preferably set to 1.25, more preferably 1.30, more preferably 1.35, more preferably 1.40, more preferably 1.45, more preferably 1.50, and more preferably 1.55.

[0073] On the other hand, the upper limit of conditional formula (2)' is preferably set to 2.05, more preferably 2.00, more preferably 1.95, more preferably 1.90, more preferably 1.88, more preferably 1.85, and more preferably 1.83.

[0074] 1-3-5.Conditional Expression (3) -0.31 ≦ xn / (fw×ft) 1 / 2 < 0.00 (3) however, xn: the difference in movement amount between the wide-angle end position of the nth lens group and the telephoto end position of the nth lens group when changing magnification from the wide-angle end to the telephoto end, where the sign of movement toward the object side is negative and the sign of movement toward the image side is positive fw: focal length of the entire zoom lens system at the wide-angle end ft: focal length of the entire zoom lens system at the telephoto end

[0075] Conditional expression (3) is a conditional expression that defines the amount of movement of the nth lens group when changing magnification from the wide-angle end to the telephoto end, and is a condition for realizing compactness. Note that when changing magnification from the wide-angle end to the telephoto end, the sign of the movement of the nth lens group toward the object side is negative, and the sign of the movement toward the image side is positive. xn / (fw×ft) in conditional expression (3) 1 / 2 If the value of (a) is below the lower limit, the amount of movement of the nth lens unit toward the object side during zooming from the wide-angle end to the telephoto end increases too much, which is likely to increase the overall optical length, and is therefore undesirable from the standpoint of compactness.

[0076] On the other hand, xn / (fw×ft) in conditional expression (3) 1 / 2 If the value of (a) is equal to or exceeds the upper limit, the n-th lens group will be fixed or will move toward the image side when zooming from the wide-angle end to the telephoto end. In this case, the effective light beam diameter of the n-th lens group will be large at the telephoto end, and the lens outer diameter will be large, which is undesirable from the viewpoint of compactness.

[0077] The lower limit of conditional expression (3) is preferably set to -0.29, more preferably -0.27, more preferably -0.25, more preferably -0.23, and even more preferably -0.21.

[0078] 1-3-6.Conditional Expression (4) 0.55 ≦ bfw / Y' ≦ 0.97 ···(4) however, bfw: Back focus at the wide-angle end, which is the distance on the optical axis from the image side of the lens closest to the image plane, and is the value when the cover glass thickness is converted into air Y': Maximum image height of the zoom lens

[0079] Conditional expression (4) defines the back focal length at the wide-angle end relative to the image height of the zoom lens, and is a condition for achieving compactness of the zoom lens. The back focal length is the distance on the optical axis from the image-side surface (final lens surface) of the lens closest to the image to the image plane, and is the value calculated by converting the cover glass thickness into air. If the value of bfw / Y' in conditional expression (4) falls below the lower limit, the back focal length at the wide-angle end becomes too short, increasing the effective light beam diameter of the nth lens group (the final lens group) and the outer diameter of the lens, which is undesirable from the perspective of achieving compactness.

[0080] On the other hand, if the value of bfw / Y' in conditional expression (4) exceeds the upper limit, the back focus at the wide-angle end becomes longer than necessary, increasing the overall optical length, which makes it difficult to achieve compact size, which is undesirable.

[0081] The lower limit of conditional expression (4) is preferably set to 0.58, more preferably 0.60, more preferably 0.63, and even more preferably 0.65.

[0082] On the other hand, the upper limit of conditional expression (4) should preferably be set to 0.95, more preferably 0.93, more preferably 0.91, and even more preferably 0.89.

[0083] 1-3-7.Conditional Expression (5) 0.80 ≦ fmt / frt ≦ 1.30 (5) however, fmt: focal length of the middle group at the telephoto end frt: The composite focal length of all lenses located closer to the image than the second lens group at the telephoto end when focused at infinity

[0084] Conditional expression (5) defines the focal length of the middle group at the telephoto end relative to the composite focal length of all lenses positioned closer to the image than the second lens group at the telephoto end when focusing at infinity. It is a condition for achieving compactness while maintaining a large aperture ratio and for effectively correcting aberrations. If the value of fmt / frt in conditional expression (5) falls below the lower limit, the positive refractive power of the middle group at the telephoto end becomes too strong, which increases the amount of spherical aberration, coma, and other aberrations generated at each surface of the middle group, making correction difficult, which is undesirable. Furthermore, attempting to effectively correct these aberrations would require a large number of lens elements, which would increase the overall optical length, which is undesirable from the perspective of achieving compactness.

[0085] On the other hand, if the value of fmt / frt in conditional formula (5) exceeds the upper limit, the positive refractive power of the intermediate group at the telephoto end becomes too weak, making it difficult for the intermediate group to sufficiently converge the axial light beam diverged by the second lens group, and therefore the diameter of the axial light beam incident on the (n-1)th lens group increases, making it difficult to make the (n-1)th lens group compact. As a result, it becomes difficult to arrange a focus drive mechanism, etc., at a position with a small diameter within the entire lens unit including the lens barrel, which is undesirable in terms of achieving compactness of the entire lens unit including the lens barrel.

[0086] The lower limit of conditional expression (5) is preferably set to 0.81, and more preferably to 0.82.

[0087] On the other hand, the upper limit of conditional expression (5) should preferably be set to 1.25, more preferably 1.20, more preferably 1.15, more preferably 1.10, and even more preferably 1.05.

[0088] 1-3-8.Conditional Expression (6) -1.20 ≦ β2t ≦ -0.30 ···(6) however, β2t: Lateral magnification of the second lens group when focusing at infinity at the telephoto end

[0089] Conditional expression (6) defines the lateral magnification of the second lens group at the telephoto end, and is a condition for achieving compactness while maintaining a large aperture ratio and simultaneously providing good correction for aberrations. If the value of β2t in conditional expression (6) falls below the lower limit, the lateral magnification of the second lens group at the telephoto end becomes too large, weakening the combined negative refractive power of the first and second lens groups at the telephoto end. As a result, the effective light beam diameter of the first lens group becomes large, which is undesirable from the perspective of compactness.

[0090] On the other hand, if the value of β2t in conditional formula (6) exceeds its upper limit, the lateral magnification of the second lens group at the telephoto end becomes too small, thereby increasing the negative composite refractive power of the first and second lens groups at the telephoto end. This increases the diameter of the axial light beam incident on the lens group (third lens group) located on the image side of the second lens group at the telephoto end. As a result, the outer diameter of the third lens group increases, and the diameter of the aperture stop, which is often located near or within the third lens group, also increases, which is undesirable in that it increases the size of the entire lens unit, including the lens barrel. Furthermore, if the height of the axial light beam increases in the third and subsequent lens groups, the amount of spherical aberration, coma, and other aberrations increases, making it difficult to effectively correct these aberrations, which is undesirable in terms of achieving a large aperture.

[0091] The lower limit of conditional expression (6) is preferably set to -1.15, more preferably -1.10, more preferably -1.05, more preferably -1.00, more preferably -0.95, and more preferably -0.90.

[0092] On the other hand, the upper limit of conditional expression (6) should preferably be set to -0.33, more preferably -0.36, more preferably -0.39, more preferably -0.42, and even more preferably -0.45.

[0093] 1-3-9.Conditional Expression (7) 1.05 ≦ βmt / βmw ≦ 1.80 (7) however, βmt: Lateral magnification of the middle group when focusing at infinity at the telephoto end βmw: Lateral magnification of the middle group when focusing at infinity at the wide-angle end

[0094] Conditional expression (7) defines the zoom ratio of the middle group, and is a condition for achieving compactness while maintaining a large aperture ratio and excellent correction of aberrations throughout the entire zoom range. If the value of βmt / βmw in conditional expression (7) falls below the lower limit, the contribution of the middle group to zooming becomes too small, and therefore, to maintain the zoom ratio of the entire system, the contribution of the second lens group to zooming becomes large. In this case, the movement amount of the second lens group increases, and the refractive power of the second lens group increases. If the movement amount of the second lens group increases, the overall optical length increases. Furthermore, if the refractive power of the second lens group increases, more lenses are required to correct aberrations, which increases the overall optical length, which is undesirable from the perspective of compactness.

[0095] On the other hand, if the value of βmt / βmw in conditional formula (7) exceeds the upper limit, the middle group's contribution to magnification becomes too large, resulting in an increase in the refractive power of the middle group and an increase in the amount of movement of the middle group. Because the light beam diverged by the second lens group is incident on the middle group, the height of axial rays becomes particularly high at large aperture ratios, resulting in increased amounts of spherical aberration, coma, and other aberrations. Therefore, if the refractive power of the middle group increases or the amount of movement increases, aberration fluctuations associated with magnification also increase, making it difficult to effectively correct aberrations such as spherical aberration and coma across the entire zoom range, which is undesirable. Furthermore, attempting to effectively correct these aberrations requires a large number of lens elements, which increases the overall optical length and is undesirable from the perspective of achieving compactness.

[0096] The lower limit of conditional expression (7) should preferably be set to 1.08, more preferably 1.10, more preferably 1.13, more preferably 1.15, and even more preferably 1.18.

[0097] On the other hand, the upper limit of conditional expression (7) should preferably be set to 1.75, more preferably 1.70, more preferably 1.65, more preferably 1.60, more preferably 1.55, more preferably 1.50, and more preferably 1.45.

[0098] 1-3-10.Conditional Expression (8) 0.15 ≦ fmt / ft ≦ 0.80 (8) however, fmt: focal length of the middle group at the telephoto end ft: focal length of the entire zoom lens system at the telephoto end

[0099] Conditional expression (8) regulates the focal length of the middle group at the telephoto end relative to the focal length of the entire lens system at the telephoto end, and is a condition for achieving compactness while maintaining a large aperture ratio and simultaneously providing good aberration correction. If the value of fmt / ft in conditional expression (8) falls below the lower limit, the positive refractive power of the middle group at the telephoto end becomes too strong, increasing the amount of spherical aberration, coma, and other aberrations generated at each surface of the middle group, making it difficult to provide good correction for spherical aberration, coma, and other aberrations, which is undesirable. Furthermore, attempting to provide good correction for these aberrations requires a large number of lens elements, which increases the overall optical length, which is undesirable from the perspective of achieving compactness.

[0100] On the other hand, if the value of fmt / ft in conditional formula (8) exceeds the upper limit, the positive refractive power of the intermediate group at the telephoto end weakens, making it difficult for the intermediate group to sufficiently converge the axial light beam diverged by the second lens group, resulting in an increase in the diameter of the axial light beam incident on the (n-1)th lens group and an increase in the size of the (n-1)th lens group.As a result, it becomes difficult to arrange a focus drive mechanism, etc., at a position with a small diameter within the entire lens unit including the barrel portion, making it difficult to achieve a compact overall lens unit including the barrel portion, which is undesirable.

[0101] The lower limit of conditional expression (8) should be set to preferably 0.18, more preferably 0.20, more preferably 0.23, more preferably 0.25, more preferably 0.28, more preferably 0.30, more preferably 0.33, more preferably 0.35, more preferably 0.38, and more preferably 0.40.

[0102] On the other hand, the upper limit of conditional expression (8) should preferably be set to 0.78, more preferably 0.75, more preferably 0.73, more preferably 0.70, more preferably 0.68, more preferably 0.65, more preferably 0.63, and more preferably 0.60.

[0103] 1-3-11.Conditional Expression (9) -1.50 ≦ f2 / fw ≦ -0.50 (9) however, f2: focal length of the second lens group fw: focal length of the entire zoom lens system at the wide-angle end

[0104] Conditional expression (9) defines the focal length of the second lens group relative to the focal length of the entire lens system at the wide-angle end, and is a condition for achieving compactness while maintaining a large aperture ratio and at the same time effectively correcting aberrations. If the value of f2 / fw in conditional expression (9) falls below the lower limit, the negative refractive power of the second lens group weakens, and the effective light beam diameter of the first lens group increases at the wide-angle end, which is undesirable from the perspective of compactness.

[0105] On the other hand, if the value of f2 / fw in conditional expression (9) exceeds the upper limit, the negative refractive power of the second lens group becomes stronger, and the diameter of the axial light beam incident on the lens group (third lens group) located on the image side of the second lens group at the wide-angle end becomes larger. As a result, the amount of spherical aberration, coma, etc. generated in the third lens group and subsequent groups increases, making it difficult to satisfactorily correct spherical aberration, coma, etc., which is undesirable from the perspective of achieving a large aperture. Furthermore, to satisfactorily correct these aberrations, a large number of lenses is required, which increases the overall optical length, and is undesirable from the perspective of achieving compactness.

[0106] The lower limit of conditional expression (9) is preferably set to -1.45, more preferably -1.40, more preferably -1.35, and even more preferably -1.30.

[0107] On the other hand, the upper limit of conditional expression (9) should preferably be set to −0.55, more preferably −0.60, even more preferably −0.65, even more preferably −0.70, and even more preferably −0.75.

[0108] 1-3-12.Conditional Expression (10) -8.0 ≦ f1 / f2 ≦ -2.0 (10) however, f1: focal length of the first lens group f2: focal length of the second lens group

[0109] Conditional expression (10) regulates the focal length of the first lens group relative to the focal length of the second lens group, and is a condition for achieving compactness while maintaining a large aperture ratio and excellent correction of aberrations. If the value of f1 / f2 in conditional expression (10) falls below the lower limit, the negative refractive power of the second lens group becomes stronger relative to the first lens group, increasing the diameter of the axial light beam incident on the lens group (third lens group) located on the image side of the second lens group. As a result, the outer diameter of the third lens group increases, and the diameter of the aperture stop, which is often located near or within the third lens group, also increases, which is undesirable in that it increases the size of the entire lens unit, including the lens barrel. Furthermore, if the height of the axial light beam increases in the third and subsequent lens groups, the amount of spherical aberration, coma, and other aberrations increases, making it difficult to effectively correct these aberrations, which is undesirable in achieving a large aperture.

[0110] On the other hand, if the value of f1 / f2 in conditional expression (10) exceeds the upper limit, the negative refractive power of the second lens group will be weakened relative to the first lens group, and the effective light beam diameter of the first lens group will increase, which is undesirable from the perspective of achieving compactness.

[0111] The lower limit of conditional expression (10) is preferably set to -7.5, more preferably -7.0, more preferably -6.5, more preferably -6.0, more preferably -5.5, and more preferably -5.0.

[0112] On the other hand, the upper limit of conditional expression (10) should preferably be set to -2.3, more preferably -2.5, more preferably -2.8, and even more preferably -3.0.

[0113] 1-3-13.Conditional Expression (11) 1.10 ≦ βrt / βrw ≦ 2.00 (11) however, βrt: The combined lateral magnification of all lenses located on the image side of the second lens group at the telephoto end when focused at infinity βrw: The combined lateral magnification of all lenses located closer to the image than the second lens group at the wide-angle end when focused at infinity

[0114] Conditional expression (11) defines the zoom ratio of the lens group located closer to the image side than the second lens group, and is a condition for achieving compactness while maintaining a large aperture ratio and excellent correction of aberrations throughout the entire zoom range. When the value of βrt / βrw in conditional expression (11) falls below the lower limit, the zoom contribution of the lens group located closer to the image side than the second lens group decreases. Therefore, to maintain the zoom ratio of the entire system, the zoom contribution of the second lens group increases. In this case, the movement amount of the second lens group increases, and the refractive power of the second lens group increases. Increasing the movement amount of the second lens group increases the overall optical length. Furthermore, increasing the refractive power of the second lens group requires a larger number of lenses for aberration correction, which increases the overall optical length, which is undesirable from the perspective of compactness.

[0115] On the other hand, if the value of βrt / βrw in conditional expression (11) exceeds its upper limit, the lens group located closer to the image side than the second lens group will have a larger contribution to zooming, which will increase the refractive power of the lens group located closer to the image side than the second lens group (the third lens group and subsequent groups) and increase the amount of movement. Because the light beam diverged by the second lens group is incident on the third lens group and subsequent groups, the height of the incident light beam becomes particularly high in the case of a large aperture ratio, resulting in increased amounts of spherical aberration, coma, and other aberrations. Therefore, if the refractive power of the lens groups from the third lens group and subsequent groups is increased or the amount of movement is increased, the aberration fluctuations associated with zooming will also increase, making it difficult to effectively correct aberrations such as spherical aberration and coma across the entire zoom range, which is undesirable. Furthermore, effectively correcting these aberrations would require a large number of lenses, which would increase the overall optical length and is undesirable in terms of achieving compactness.

[0116] The lower limit of conditional expression (11) should preferably be set to 1.13, more preferably 1.15, more preferably 1.18, more preferably 1.20, more preferably 1.23, and more preferably 1.25.

[0117] On the other hand, the upper limit of conditional expression (11) should preferably be set to 1.95, more preferably 1.90, more preferably 1.85, more preferably 1.80, more preferably 1.75, more preferably 1.70, more preferably 1.65, and more preferably 1.60.

[0118] 1-3-14.Conditional Expression (12) 0.00 < x2 / ft ≦ 0.55 (12) however, x2: The difference in the amount of movement between the wide-angle end position of the second lens group and the telephoto end position of the second lens group when changing magnification from the wide-angle end to the telephoto end, where the sign of the movement toward the object side is negative and the sign of the movement toward the image side is positive. ft: focal length of the entire zoom lens system at the telephoto end

[0119] Conditional expression (12) regulates the amount of movement of the second lens group when zooming from the wide-angle end to the telephoto end, and is a condition for achieving compactness while also providing excellent correction of aberrations throughout the entire zoom range. Note that, when zooming from the wide-angle end to the telephoto end, the movement of the second lens group toward the object side has a negative sign, and the movement toward the image side has a positive sign. If the value of x2 / ft in conditional expression (12) falls below the lower limit, the amount of movement of the second lens group toward the image side when zooming from the wide-angle end to the telephoto end decreases, which tends to reduce the second lens group's contribution to zooming. Therefore, to maintain the zoom ratio, it is necessary to increase the contribution of the lens groups located closer to the image side than the second lens group (the third and subsequent lens groups). In this case, the refractive power of the third and subsequent lens groups increases, and the amount of movement increases. Since the light beam diverged by the second lens group is incident on the lens groups from the third lens group onwards, the height of the incident light beam becomes particularly high in the case of a large aperture ratio, resulting in a large amount of spherical aberration, coma, etc. Therefore, if the refractive power of the groups from the third lens group onwards is strengthened or the amount of movement is increased, the aberration fluctuation associated with magnification change also becomes large, making it difficult to satisfactorily correct aberrations such as spherical aberration and coma over the entire zoom range, which is undesirable. Furthermore, to satisfactorily correct these aberrations, a large number of lenses would be required, which would increase the overall optical length, which is undesirable from the perspective of achieving compactness.

[0120] On the other hand, if the value of x2 / ft in conditional expression (12) exceeds the upper limit, the amount of movement that the second lens group moves toward the image side when changing magnification from the wide-angle end to the telephoto end increases, which tends to increase the overall optical length, and is therefore undesirable from the perspective of achieving compactness.

[0121] The lower limit of conditional expression (12) is preferably set to 0.03, more preferably 0.05, more preferably 0.08, more preferably 0.11, more preferably 0.13, more preferably 0.15, and more preferably 0.18.

[0122] On the other hand, the upper limit of conditional expression (12) should preferably be set to 0.53, more preferably 0.50, more preferably 0.48, more preferably 0.45, more preferably 0.43, more preferably 0.40, more preferably 0.38, and more preferably 0.35.

[0123] 1-3-15.Conditional Expression (13) 1.00 ≦ |(1-β(n-1)t 2 )×βnt 2 | ≦ 6.00 ···(13) however, β(n-1)t: Lateral magnification of the n-1th lens group when focusing on infinity at the telephoto end βnt: Lateral magnification of the nth lens group when focusing on infinity at the telephoto end

[0124] Conditional expression (13) is a conditional expression that defines the focus sensitivity of the (n-1)th lens group, which is the focus group. The focus sensitivity represents the amount of movement of the image plane when the focus group moves a unit amount, and by satisfying conditional expression (13), the focus sensitivity of the (n-1)th lens group falls within an appropriate range. 2 )×βnt 2 If the value of | falls below the lower limit, the focus sensitivity of the (n-1)th lens group will decrease, which will increase the amount of movement of the nth lens group when focusing from an object at infinity to an object at a finite distance. This will likely increase the overall optical length, making it difficult to achieve compact size, which is undesirable.

[0125] On the other hand, |(1-β(n-1)t 2 )×βnt 2 If the value of | exceeds its upper limit, the focus sensitivity of the (n-1)th lens group becomes high, and even a small movement of the (n-1)th lens group will cause a large change in image position. This requires highly accurate position control of the (n-1)th lens group during focusing, which is undesirable.

[0126] The lower limit of conditional expression (13) should preferably be set to 1.10, more preferably 1.20, more preferably 1.30, more preferably 1.40, more preferably 1.50, and more preferably 1.60.

[0127] On the other hand, the upper limit of conditional expression (13) should preferably be set to 5.50, more preferably 5.00, more preferably 4.50, more preferably 4.00, more preferably 3.50, and more preferably 3.00.

[0128] 1-3-16.Conditional Expression (14) 1.00 ≦ (β2t / β2w) / (βmt / βmw) ≦ 1.80 ···(14) however, β2t: Lateral magnification of the second lens group when focusing at infinity at the telephoto end β2w: Lateral magnification of the second lens group when focusing on infinity at the wide-angle end βmt: Lateral magnification of the middle group when focusing at infinity at the telephoto end βmw: Lateral magnification of the middle group when focusing at infinity at the wide-angle end

[0129] Conditional expression (14) defines the ratio between the zoom ratio of the second lens group and that of the middle lens group, and is a condition for achieving compactness while maintaining a large aperture ratio and providing excellent correction of aberrations throughout the entire zoom range. If the value of (β2t / β2w) / (βmt / βmw) in conditional expression (14) falls below its lower limit, the middle lens group's contribution to zooming becomes too large. In this case, the refractive power of the middle lens group becomes stronger or the amount of movement increases. Because the middle lens group receives a light beam diverged by the second lens group, the height of the incident ray becomes particularly high at large aperture ratios, resulting in increased amounts of spherical aberration, coma, and other aberrations. Therefore, if the refractive power of the middle lens group becomes stronger or the amount of movement increases, aberration fluctuations associated with magnification change also increase, making it difficult to effectively correct aberrations such as spherical aberration and coma throughout the entire zoom range, which is undesirable. Furthermore, in order to effectively correct these aberrations, a large number of lenses are required, which increases the overall optical length, which is not desirable in terms of achieving compactness.

[0130] On the other hand, if the value of (β2t / β2w) / (βmt / βmw) in conditional expression (14) exceeds the upper limit, the contribution of the second lens group to magnification becomes too large. In this case, the movement amount of the second lens group increases, or the refractive power of the second lens group increases. If the movement amount of the second lens group increases, the overall optical length increases. Furthermore, if the refractive power of the second lens group increases, a larger number of lenses is required to correct aberrations, which increases the overall optical length, which is undesirable in terms of achieving compactness.

[0131] The lower limit of conditional expression (14) should preferably be set to 1.02, more preferably 1.05, more preferably 1.07, more preferably 1.10, more preferably 1.12, and more preferably 1.15.

[0132] On the other hand, the upper limit of conditional expression (14) should preferably be set to 1.75, more preferably 1.70, more preferably 1.65, more preferably 1.60, more preferably 1.55, and more preferably 1.50.

[0133] 1-3-17.Conditional Expression (15) -1.20 ≦ f2 / fmt ≦ -0.70 ···(15) however, f2: focal length of the second lens group fmt: focal length of the middle group at the telephoto end

[0134] Conditional expression (15) regulates the focal length of the second lens group relative to the focal length of the intermediate lens group at the telephoto end, and is a condition for achieving compactness while maintaining a large aperture ratio. If the value of f2 / fmt in conditional expression (15) falls below the lower limit, the positive refractive power of the intermediate lens group becomes too strong relative to the negative refractive power of the second lens group. As a result, the amount of spherical aberration, coma, and other aberrations generated at each surface of the intermediate lens group increases. In order to effectively correct these aberrations, the intermediate lens group must contain a large number of lenses, which increases the overall optical length and is therefore undesirable from the perspective of compactness.

[0135] On the other hand, if the value of f2 / fmt in conditional expression (15) exceeds the upper limit, the negative refractive power of the second lens group becomes too strong relative to the positive refractive power of the intermediate group, which tends to result in insufficient convergence of the axial light beam incident on the (n-1)th lens group. As a result, the lenses in the (n-1)th lens group tend to become large, which makes it difficult to position a focus drive mechanism or the like at a position with a small diameter within the entire lens unit including the lens barrel, which is undesirable in terms of achieving a compact overall lens unit including the lens barrel.

[0136] The lower limit of conditional expression (15) should preferably be set to -1.18, more preferably -1.15, more preferably -1.13, more preferably -1.10, more preferably -1.08, and more preferably -1.05.

[0137] On the other hand, the upper limit of conditional expression (15) should preferably be set to -0.73, more preferably -0.75, more preferably -0.78, more preferably -0.80, more preferably -0.83, and more preferably -0.85.

[0138] 1-3-18.Conditional Expression (16) 2.00 ≦ Lsw / Y' ≦ 5.00 (16) however, Lsw: The distance on the optical axis from the object-side surface of the lens closest to the object to the aperture at the wide-angle end Y': Maximum image height of the zoom lens

[0139] Conditional expression (16) regulates the position of the aperture stop and is a condition for achieving compactness while maintaining a large aperture ratio. If the value of Lsw / Y' in conditional expression (16) falls below the lower limit, the distance on the optical axis from the object-side surface of the lens closest to the object to the aperture stop at the wide-angle end becomes short, which tends to lengthen the distance on the optical axis from the aperture stop to the lens group closest to the image. As a result, the luminous flux diameter of the lens group closest to the image tends to increase, and the lens outer diameter also tends to increase, which is undesirable from the perspective of achieving compactness.

[0140] On the other hand, if the value of Lsw / Y' in conditional expression (16) exceeds the upper limit, the distance on the optical axis from the object-side surface of the lens located closest to the object to the aperture stop at the wide-angle end becomes too long, and the light beam diameter of the lens closest to the object at the wide-angle end becomes large, which increases the lens outer diameter, which is undesirable from the perspective of achieving compactness.

[0141] The lower limit of conditional expression (16) should preferably be set to 2.20, more preferably 2.40, more preferably 2.60, more preferably 2.80, and even more preferably 3.00.

[0142] On the other hand, the upper limit of the above conditional expression (16) should preferably be set to 4.80, more preferably 4.60, more preferably 4.40, and even more preferably 4.20.

[0143] 2. Embodiment of the imaging device The imaging device according to the present invention includes the zoom lens according to the present invention described above and a solid-state imaging element that converts an optical image formed by the zoom lens into an electrical signal. The solid-state imaging element is not particularly limited as long as it can convert an optical image into an electrical signal, and a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor can be used. Suitable imaging devices include digital still cameras and digital video cameras, but particularly suitable imaging devices include interchangeable lens imaging devices such as single-lens reflex cameras and mirrorless cameras.

[0144] The zoom lens of the present invention has a large aperture ratio, yet can be made compact, and can effectively correct various aberrations such as spherical aberration and coma across the entire zoom range. Therefore, the imaging device of the present invention equipped with the zoom lens is compact, yet capable of shooting at different focal lengths, and can take advantage of brightness and bokeh.

[0145] The embodiment of the present invention described above is one aspect of the present invention, and can be modified as appropriate without departing from the spirit of the present invention. In addition, the present invention will be described in more detail below using examples, but the present invention is not limited to the following examples. [Example]

[0146] (1) Optical structure of the zoom lens FIG. 1 shows a lens cross-sectional view of a zoom lens according to Example 1 of the present invention. Note that "IMG" in the figure denotes an image plane, specifically the imaging surface of a solid-state imaging device such as a CCD sensor or CMOS sensor, or the film surface of a silver halide film. Furthermore, a parallel plate with no substantial refractive power, such as a cover glass "CG," is provided on the object side of the image plane IMG. These points are similar to those in the lens cross-sectional views shown in the other examples, and therefore will not be described below.

[0147] The zoom lens of Example 1 is composed of, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, and a sixth lens group G6 having positive refractive power. The third lens group G3 and the fourth lens group G4 correspond to the intermediate group Gm, the fifth lens group G5 corresponds to the (n-1)th lens group (Gn-1), and the sixth lens group G6 corresponds to the nth lens group (Gn). An aperture stop STOP is disposed between the second lens group G2 and the third lens group G3.

[0148] When changing magnification from the wide-angle end to the telephoto end, the first lens group G1 moves toward the object along the optical axis, the second lens group G2 moves toward the image along the optical axis, and the third lens group G3, the fourth lens group G4, and the fifth lens group G5 move toward the object along the optical axis. The sixth lens group G6 moves along the optical axis in a convex trajectory toward the object, and the movement of the sixth lens group G6 toward the object by the difference between its position at the wide-angle end and its position at the telephoto end. Furthermore, when focusing from an object at infinity to an object at a finite distance, the fifth lens group G5 moves toward the image along the optical axis.

[0149] The configuration of each lens group will be explained below. The first lens group G1 is composed of, in order from the object side, a lens with negative refractive power, a lens with positive refractive power, and a lens with positive refractive power, and has positive refractive power as a whole.

[0150] The second lens group G2 is composed of, in order from the object side, a lens with negative refractive power, a lens with negative refractive power, a lens with negative refractive power, a lens with positive refractive power, and a lens with negative refractive power, and has negative refractive power as a whole.

[0151] The third lens group G3 is composed of, in order from the object side, a lens with positive refractive power, a lens with negative refractive power, a lens with positive refractive power, and a lens with positive refractive power, and has positive refractive power as a whole.

[0152] The fourth lens group G4 is composed of, in order from the object side, a lens having negative refractive power and a lens having positive refractive power, and has positive refractive power as a whole.

[0153] The fifth lens group G5 is composed of, in order from the object side, a lens having positive refractive power and a lens having negative refractive power, the lens having positive refractive power and the lens having negative refractive power being cemented together, and the cemented lens has negative refractive power.

[0154] The sixth lens group G6 is composed of, in order from the object side, a lens having positive refractive power, a lens having negative refractive power, and a lens having negative refractive power, and has positive refractive power as a whole.

[0155] (2) Numerical examples Next, we will explain numerical examples that apply specific numerical values ​​of the zoom lens. Table 1 shows surface data for the zoom lens of Example 1 according to the present invention. Note that surfaces 36 and 37 in Table 1 represent surface data for the cover glass CG. In Table 1, "S" represents the surface number and the order of the lens surface counted from the object side to the image side, "R" represents the radius of curvature of each lens surface (mm), "D" represents the lens thickness or air gap (mm) on the optical axis, "Nd" represents the refractive index at the d-line (wavelength λ=587.56 nm), and "νd" represents the Abbe number at the d-line. In Table 1, "Variable D (surface number)" in the "D" column indicates that the spacing on the optical axis of the lens surface is a variable spacing that changes during magnification or focusing. Note that INF represents infinity, and the sign of the radius of curvature is positive when the surface is convex toward the object side. Surfaces with an "*" before the surface number are aspherical surfaces.

[0156] Table 2 shows the aspherical coefficients of each aspherical surface. The aspherical coefficients are values ​​when each aspherical shape is defined by the following formula (19). In Table 2, "en" means "×10 -n " means.

[0157] X(H)=(H 2 / R) / [1+{1-ε·H 2 / R 2} 1 / 2 ]+AH 4 +BH 6 +CH 8 +DH 10 +EH 12 ···(19) however, H: Coordinate perpendicular to the optical axis, with the surface vertex as the origin X(H): Displacement in the optical axis direction at H R: paraxial radius of curvature ε: conic coefficient A: 4th order aspheric coefficient B: Sixth-order aspheric coefficient C: 8th order aspheric coefficient D: 10th order aspheric coefficient E: 12th order aspheric coefficient

[0158] Table 3 shows the variable spacing on the optical axis of the zoom lens when focusing on an object at infinity. Starting from the left, Table 3 shows the values ​​at the wide-angle end, mid-focal length position, and telephoto end. In Table 3, "D (surface number)" in the spacing column indicates the spacing between the lens surfaces indicated by the surface number. All lengths in Table 3 are in millimeters.

[0159] Table 4 shows the variable spacing on the optical axis of the zoom lens when focusing on an object at a finite distance at a shooting magnification of 1 / 40x (1:40). Starting from the left, Table 4 shows the values ​​at the wide-angle end, mid-focal length position, and telephoto end. In Table 4, "D (surface number)" in the spacing column indicates the spacing between the lens surfaces indicated by the surface number. All lengths in Table 4 are in millimeters.

[0160] The specifications of this zoom lens are shown in Table 5. Starting from the left, Table 5 shows the values ​​at the wide-angle end, the mid-focal length position, and the telephoto end. Note that "FNo" indicates the F-number.

[0161] The group focal length of each lens group is shown in Table 6. Note that all lengths in Table 6 are in millimeters.

[0162] Table 25 shows the values ​​of conditional expressions (1) to (16).

[0163] The matters relating to the above-mentioned tables are the same as those for the tables shown in the other embodiments, and therefore, the explanation will be omitted below.

[0164] [Table 1] SRD Nd νd 1 228.1173 1.700 1.80518 25.46 2 93.2711 10.218 1.49700 81.61 3 -657.1718 0.200 4 68.6775 7.174 1.83481 42.72 5 166.4812 Variable D(5) 6 154.1064 1.400 1.83481 42.72 7 24.1848 8.925 8 -103.3029 1.200 1.51680 64.20 9 111.5476 2.702 10 -110.7755 1.200 1.59282 68.62 11 34.4258 11.563 1.83400 37.34 12 -52.9245 5.208 *13 -29.4114 1.500 1.59201 67.02 *14 -61.5331 Variable D(14) (Aperture) 15 INF 1.000 *16 78.4957 4.341 1.77377 47.17 *17 -117.1964 1.162 18 -84.6002 1.100 1.85451 25.15 19 237.6136 0.400 20 55.9835 10.073 1.43700 95.10 21 -41.6294 0.150 22 108.4971 3.427 1.94594 17.98 23 -1229.3449 Variable D(23) 24 96.5786 1.200 1.85451 25.15 25 26.2376 9.900 1.49700 81.61 26 -56.6344 Variable D(26) 27 134.8086 2.214 1.92286 20.88 28 -238.0793 0.800 1.80420 46.50 29 28.6272 Variable D(29) *30 31.9215 9.482 1.69350 53.18 *31 -126.9059 0.150 32 9031.6795 1.000 1.75211 25.05 33 65.2851 7.698 *34 -47.9751 1.800 1.85108 40.12 *35 -114.6421 Can be changed(35) 36 INF 2.500 1.51680 64.20 37 INF 1.000 (Image) 38 INF

[0165] [Table 2] ε ABCDE Side 13 1.0000 3.15695e-06 4.48987e-09 -1.96154e-12 5.40304e-16 0.00000e+00 Page 14 1.0000 4.82176e-07 2.77322e-09 -9.84282e-12 9.47662e-15 0.00000e+00 Page 16 0.6152 -7.84836e-07 -5.63055e-10 -1.05178e-11 1.02479e-14 0.00000e+00 Page 17 1.0000 5.83127e-06 1.11017e-09 -9.65591e-12 1.37587e-14 0.00000e+00 Page 30 1.0000 1.63932e-06 8.95605e-09 7.30386e-12 -2.11913e-14 0.00000e+00 Page 31 1.0000 -1.17994e-05 1.25277e-08 -3.62568e-11 8.28915e-14 0.00000e+00 Page 34 1.0000 -1.19714e-04 3.19957e-07 2.05792e-11 -4.78397e-13 0.00000e+00 Page 35 1.0000 -9.59467e-05 3.91917e-07 -4.73389e-10 3.28954e-13 0.00000e+00

[0166] [Table 3] Interval Wide-angle end Mid-range Telephoto end D(5) 1.097 12.863 33.340 D(14) 28.661 11.195 1.100 D(23) 3.175 2.176 0.900 D(26) 2.200 2.974 3.895 D(29) 7.022 7.765 9.423 D(35) 13.459 19.452 20.671

[0167] [Table 4] Interval Wide-angle end Mid-range Telephoto end D(26) 2.664 3.568 4.757 D(29) 6.558 7.171 8.561

[0168] [Table 5] Zoom ratio 2.35 Wide-angle end Mid-range Telephoto end Focal length (mm) 28.85 44.26 67.90 FNo 2.06 2.06 2.06 Angle of view (°) 74.9 50.5 33.8

[0169] [Table 6] Group number Group focal length G1 119.76 G2 -33.26 G3 35.59 G4 232.66 G5 -48.93 G6 109.47

[0170] Figure 2 shows longitudinal aberration diagrams of Example 1 when focused on an object at infinity at (A) the wide-angle end, (B) the intermediate focal position, and (C) the telephoto end. Also, Figure 3 shows longitudinal aberration diagrams of Example 1 when focused on an object at a finite distance at (A) the wide-angle end, (B) the intermediate focal position, and (C) the telephoto end (magnification is 1 / 40x (1:40)). From the left, the diagrams show spherical aberration (mm), astigmatism (mm), and distortion (%).

[0171] In the spherical aberration diagram, the vertical axis indicates the ratio to the maximum F-number, and the horizontal axis indicates defocus. "FNo" indicates the maximum F-number. The solid line d indicates spherical aberration at the d-line (wavelength 587.56 nm), the dashed line C indicates spherical aberration at the C-line (wavelength 656.28 nm), and the dashed line g indicates spherical aberration at the g-line (wavelength 435.84 nm).

[0172] In the astigmatism diagram, the vertical axis represents image height and the horizontal axis represents defocus. "ω" represents the half angle of view (°). Astigmatism is shown as a value at the d-line, with the solid line S representing astigmatism in the sagittal direction and the dashed line T representing astigmatism in the tangential direction.

[0173] In the distortion diagram, the vertical axis represents image height, and the horizontal axis represents distortion (%). "ω" represents the half angle of view (°). The distortion value shown is for the d-line.

[0174] The matters relating to these longitudinal aberration diagrams are the same as those in the longitudinal aberration diagrams shown in other embodiments, and therefore, the explanation thereof will be omitted below. [Example]

[0175] (1) Optical structure of the zoom lens FIG. 4 shows a cross-sectional view of a zoom lens according to a second embodiment of the present invention. The zoom lens according to the second embodiment is composed of, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, and a sixth lens group G6 having negative refractive power. The third lens group G3 and the fourth lens group G4 correspond to the intermediate group Gm, the fifth lens group G5 corresponds to the (n-1)th lens group (Gn-1), and the sixth lens group G6 corresponds to the nth lens group (Gn). An aperture stop STOP is disposed between the second lens group G2 and the third lens group G3.

[0176] When changing magnification from the wide-angle end to the telephoto end, the first lens group G1 moves toward the object along the optical axis, the second lens group G2 moves toward the image along the optical axis, and the third lens group G3, the fourth lens group G4, and the fifth lens group G5 move toward the object along the optical axis. The sixth lens group G6 moves along the optical axis in a convex trajectory toward the object, and the movement of the sixth lens group G6 toward the object by the difference between its position at the wide-angle end and its position at the telephoto end. Furthermore, when focusing from an object at infinity to an object at a finite distance, the fifth lens group G5 moves toward the image along the optical axis.

[0177] The configuration of each lens group will be explained below. The first lens group G1 is composed of, in order from the object side, a lens with negative refractive power, a lens with positive refractive power, and a lens with positive refractive power, and has positive refractive power as a whole.

[0178] The second lens group G2 is composed of, in order from the object side, a lens with negative refractive power, a lens with negative refractive power, a lens with negative refractive power, a lens with positive refractive power, and a lens with negative refractive power, and has negative refractive power as a whole.

[0179] The third lens group G3 is composed of, in order from the object side, a lens with positive refractive power, a lens with negative refractive power, a lens with positive refractive power, and a lens with negative refractive power, and has positive refractive power as a whole.

[0180] The fourth lens group G4 is composed of, in order from the object side, a lens having negative refractive power, a lens having positive refractive power, and a lens having positive refractive power, and has positive refractive power as a whole.

[0181] The fifth lens group G5 is composed of a lens having negative refractive power.

[0182] The sixth lens group G6 is composed of, in order from the object side, a lens having positive refractive power, a lens having negative refractive power, and a lens having negative refractive power, and has negative refractive power as a whole.

[0183] (2) Numerical examples Next, numerical examples using specific numerical values ​​of the zoom lens will be described. Table 7 shows surface data of the zoom lens of Example 2 according to the present invention. Note that surfaces 36 and 37 in Table 7 are surface data of the cover glass CG. Table 8 shows the aspherical coefficients of each aspherical surface. Table 9 shows the variable spacing on the optical axis of the zoom lens when focusing on an object at infinity. Table 10 shows the variable spacing on the optical axis of the zoom lens when focusing on an object at a finite distance at a shooting magnification of 1 / 40 (1:40). Table 11 shows the specifications of the zoom lens. Table 12 shows the group focal length of each lens group. Table 25 also shows the numerical values ​​of conditional expressions (1) to (16).

[0184] 5A, 5B, and 5C are longitudinal aberration diagrams of Example 2 when focused on an object at infinity at the wide-angle end, at the intermediate focal position, and at the telephoto end, respectively. 6A, 6B, and 6C are longitudinal aberration diagrams of Example 2 when focused on an object at a finite distance at the wide-angle end, at the intermediate focal position, and at the telephoto end, respectively (magnification is 1 / 40x (1:40)).

[0185] [Table 7] SRD Nd νd 1 839.2629 1.700 1.84666 23.78 2 203.8883 6.980 1.49700 81.61 3 -309.4436 0.200 4 67.0413 7.371 1.72916 54.67 5 210.8264 Variable D(5) 6 77.1890 1.500 1.72916 54.67 7 20.7727 9.393 *8 -81.3733 1.500 1.51633 64.06 *9 315.6178 3.492 10 -49.1460 1.200 1.49700 81.61 11 54.5749 7.921 1.60342 38.01 12 -35.4091 2.495 *13 -20.6577 1.500 1.59201 67.02 *14 -31.5132 Variable D(14) (Aperture) 15 INF 1.0000 16 38.1160 6.013 1.92286 20.88 17 185.7635 0.500 18 45.9653 1.200 1.90366 31.32 19 20.8000 10.300 1.59282 68.62 20 555.1785 3.053 21 -48.1035 1.000 1.92286 20.88 22 96.2683 Variable D(22) 23 31.6534 0.800 1.87070 40.73 24 20.1500 11.660 1.59282 68.62 25 -95.1488 0.150 *26 37.2848 7.314 1.59201 67.02 *27 -55.9539 Variable D(27) 28 63.0596 0.900 1.83481 42.72 29 25.4372 Variable D(29) 30 65.2797 9.000 1.80518 25.46 31 -45.7440 0.150 *32 -41.9300 1.500 1.77377 47.17 *33 -852.3888 7.193 34 -20.3495 1.200 1.83481 42.72 35 -33.5000 Can be changed(35) 36 INF 2.500 1.51680 64.20 37 INF 1.000 (Image) 38 INF

[0186] [Table 8] ε ABCDE Page 8 1.0000 1.12279e-05 -1.19074e-08 4.92650e-13 4.55475e-14 0.00000e+00 Page 9 1.0000 1.18400e-05 2.47416e-09 -8.77722e-12 1.48655e-13 0.00000e+00 Page 13 1.0000 2.81363e-05 -4.70514e-08 1.36988e-10 -1.42109e-13 0.00000e+00 Page 14 1.0000 1.84874e-05 -6.49455e-08 1.19111e-10 -2.00378e-13 0.00000e+00 Page 26 1.0000 -1.12975e-05 -7.10382e-09 1.07787e-12 -6.91352e-14 1.24016e-16 Page 27 7.0521 7.73197e-06 -5.87365e-09 5.00411e-12 -8.51985e-15 7.96204e-18 Page 32 1.0000 4.09604e-05 -2.56319e-07 1.44142e-09 -4.25829e-12 5.70374e-15 Page 33 1.0000 3.38937e-05 -2.80408e-07 1.58134e-09 -4.94709e-12 6.74874e-15

[0187] [Table 9] Interval Wide-angle end Mid-range Telephoto end D( 5) 1.000 12.515 30.962 D(14) 30.346 15.045 1.356 D(22) 0.915 0.700 2.085 D(27) 2.195 2.663 4.362 D(29) 8.300 8.744 11.950 D(35) 13.300 19.383 17.600

[0188] [Table 10] Interval Wide-angle end Mid-range Telephoto end D(27) 2.565 3.108 5.037 D(29) 7.930 8.299 11.275

[0189] [Table 11] Zoom ratio 2.35 Wide-angle end Mid-range Telephoto end Focal length (mm) 28.85 44.25 67.90 FNo 2.06 2.06 2.06 Angle of view (°) 74.5 50.7 33.4

[0190] [Table 12] Group number Group focal length G1 117.46 G2 -29.52 G3 221.69 G4 24.30 G5 -51.63 G6 -1577.20 [Example]

[0191] (1) Optical structure of the zoom lens 7 shows a cross-sectional view of a zoom lens according to a third embodiment of the present invention. The zoom lens according to the third embodiment is composed of, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative 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 third lens group G3 corresponds to the intermediate group Gm, the fourth lens group G4 corresponds to the (n-1)th lens group (Gn-1), and the fifth lens group G5 corresponds to the nth lens group (Gn). An aperture stop STOP is disposed between the second lens group G2 and the third lens group G3.

[0192] When changing magnification from the wide-angle end to the telephoto end, the first lens group G1 moves toward the object along the optical axis, the second lens group G2 moves toward the image along the optical axis, and the third lens group G3, the fourth lens group G4, and the fifth lens group G5 move toward the object along the optical axis. Furthermore, when focusing from an object at infinity to an object at a finite distance, the fourth lens group G4 moves toward the image along the optical axis.

[0193] The configuration of each lens group will be explained below. The first lens group G1 is composed of, in order from the object side, a lens with negative refractive power, a lens with positive refractive power, and a lens with positive refractive power, and has positive refractive power as a whole.

[0194] The second lens group G2 is composed of, in order from the object side, a lens with negative refractive power, a lens with negative refractive power, a lens with negative refractive power, a lens with positive refractive power, and a lens with negative refractive power, and has negative refractive power as a whole.

[0195] The third lens group G3 is composed of, in order from the object side, a lens having positive refractive power, a lens having negative refractive power, a lens having positive refractive power, a lens having positive refractive power, a lens having negative refractive power, and a lens having positive refractive power, and has positive refractive power as a whole.

[0196] The fourth lens group G4 is composed of, in order from the object side, a lens having positive refractive power and a lens having negative refractive power, the lens having positive refractive power and the lens having negative refractive power being cemented together, and the cemented lens has negative refractive power.

[0197] The fifth lens group G5 is composed of, in order from the object side, a lens having positive refractive power, a lens having negative refractive power, and a lens having negative refractive power, and has positive refractive power as a whole.

[0198] (2) Numerical examples Next, numerical examples using specific numerical values ​​of the zoom lens will be described. Table 13 shows surface data of the zoom lens of Example 3 according to the present invention. Note that surfaces 36 and 37 in Table 13 are surface data of the cover glass CG. Table 14 shows the aspherical coefficients of each aspherical surface. Table 15 shows the variable spacing on the optical axis of the zoom lens when focusing on an object at infinity. Table 16 shows the variable spacing on the optical axis of the zoom lens when focusing on an object at a finite distance at a shooting magnification of 1 / 40 (1:40). Table 17 shows the specifications of the zoom lens. Table 18 shows the group focal length of each lens group. Furthermore, Table 25 shows the numerical values ​​of conditional expressions (1) to (16).

[0199] 8A, 8B, and 8C are longitudinal aberration diagrams of Example 3 at the wide-angle end, the intermediate focal position, and the telephoto end, respectively, when focused on an object at infinity. 9A, 9B, and 9C are longitudinal aberration diagrams of Example 3 at the wide-angle end, the intermediate focal position, and the telephoto end, respectively, when focused on an object at a finite distance (magnification is 1 / 40 (1:40)).

[0200] [Table 13] SRD Nd νd 1 933.7859 1.700 1.85478 24.80 2 129.0265 10.100 1.49700 81.61 3 -228.1904 0.150 4 67.0179 6.000 1.83481 42.72 5 173.8419 Variable D(5) 6 102.4732 1.400 1.90043 37.37 7 26.0373 9.471 8 -67.8482 1.200 1.51680 64.20 9 121.8876 2.839 10 -89.6810 1.200 1.59282 68.62 11 35.5328 11.184 1.83400 37.34 12 -51.9237 4.715 *13 -29.1016 1.500 1.59201 67.02 *14 -57.5874 Variable D(14) (Aperture) 15 INF 1.000 *16 76.8302 4.000 1.77377 47.17 *17 -116.7889 2.830 18 -76.3231 1.100 1.85883 30.00 19 329.7037 2.378 20 61.7964 10.204 1.43700 95.10 21 -39.0335 0.193 22 137.8598 2.977 1.94594 17.98 23 -366.8440 1.285 24 127.6043 1.200 1.85451 25.15 25 27.2197 8.911 1.49700 81.61 26 -50.0259 Variable D(26) 27 133.1403 2.393 1.92286 20.88 28 -121.8723 0.800 1.80420 46.50 29 28.9588 Variable D(29) *30 28.8381 10.182 1.69350 53.18 *31 -57.1293 0.169 32 -77.3798 1.143 1.75211 25.05 33 51.7733 8.890 *34 -139.8828 1.800 1.85108 40.12 *35 898.7320 Can be changed(35) 36 INF 2.500 1.51680 64.20 37 INF 1.000 (Image) 38 INF

[0201] [Table 14] ε ABCDE Page 13 1.0000 3.37005e-06 -1.54491e-11 3.16462e-12 6.67477e-15 0.00000e+00 Page 14 1.0000 1.42484e-06 -4.11337e-10 -8.49808e-12 2.36660e-14 0.00000e+00 Page 16 1.0715 -7.08333e-07 2.66084e-09 -1.48319e-11 -9.96308e-15 0.00000e+00 Page 17 1.0000 7.00479e-06 5.96166e-09 -1.14758e-11 -8.62247e-15 0.00000e+00 Page 30 1.0000 -1.38572e-06 3.80478e-09 9.95398e-12 -1.73092e-14 0.00000e+00 Page 31 1.0000 -9.45907e-06 3.05891e-08 -3.98123e-11 3.25506e-14 0.00000e+00 Page 34 1.0000 -1.28179e-04 3.10857e-07 -5.08029e-11 -1.78608e-13 0.00000e+00 Page 35 1.0000 -1.11390e-04 3.77936e-07 -4.95938e-10 4.84106e-13 0.00000e+00

[0202] [Table 15] Interval Wide-angle end Mid-range Telephoto end D( 5) 1.000 12.667 30.772 D(14) 27.903 10.934 1.000 D(26) 2.061 3.362 3.675 D(29) 7.506 7.813 8.908 D(35) 15.717 19.491 21.232

[0203] [Table 16] Interval Wide-angle end Mid-range Telephoto end D(26) 2.498 3.941 4.480 D(29) 7.069 7.234 8.102

[0204] [Table 17] Zoom ratio 2.19 Wide-angle end Mid-range Telephoto end Focal length (mm) 28.85 42.65 63.05 FNo 2.06 2.06 2.06 Angle of view (°) 76.0 52.6 36.2

[0205] [Table 18] Group number Group focal length G1 120.56 G2 -33.27 G3 34.62 G4 -51.19 G5 109.71 [Example]

[0206] (1) Optical structure of the zoom lens FIG. 10 shows a cross-sectional view of a zoom lens according to a fourth embodiment of the present invention. The zoom lens according to the fourth embodiment is composed of, from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, and a sixth lens group G6 having positive refractive power. The third lens group G3 and the fourth lens group G4 correspond to the intermediate group Gm, the fifth lens group G5 corresponds to the (n-1)th lens group (Gn-1), and the sixth lens group G6 corresponds to the nth lens group (Gn). An aperture stop STOP is disposed between the second lens group G2 and the third lens group G3.

[0207] When changing magnification from the wide-angle end to the telephoto end, the first lens group G1 moves toward the object along the optical axis, the second lens group G2 moves toward the image along the optical axis, and the third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 move toward the object along the optical axis. Furthermore, when focusing from an object at infinity to an object at a finite distance, the fifth lens group G5 moves toward the image along the optical axis.

[0208] The configuration of each lens group will be explained below. The first lens group G1 is composed of, in order from the object side, a lens with negative refractive power, a lens with positive refractive power, and a lens with positive refractive power, and has positive refractive power as a whole.

[0209] The second lens group G2 is composed of, in order from the object side, a lens with negative refractive power, a lens with negative refractive power, a lens with negative refractive power, a lens with positive refractive power, and a lens with negative refractive power, and has negative refractive power as a whole.

[0210] The third lens group G3 is composed of, in order from the object side, a lens with positive refractive power, a lens with negative refractive power, a lens with positive refractive power, and a lens with positive refractive power, and has positive refractive power as a whole.

[0211] The fourth lens group G4 is composed of, in order from the object side, a lens having negative refractive power and a lens having positive refractive power, and has positive refractive power as a whole.

[0212] The fifth lens group G5 is composed of, in order from the object side, a lens having positive refractive power and a lens having negative refractive power, the lens having positive refractive power and the lens having negative refractive power being cemented together, and the cemented lens has negative refractive power.

[0213] The sixth lens group G6 is composed of, in order from the object side, a lens having positive refractive power, a lens having negative refractive power, and a lens having negative refractive power, and has positive refractive power as a whole.

[0214] (2) Numerical examples Next, numerical examples using specific numerical values ​​of the zoom lens will be described. Table 19 shows surface data for the zoom lens of Example 4 according to the present invention. Note that surfaces 36 and 37 in Table 19 are surface data for the cover glass CG. Table 20 shows the aspherical coefficients of each aspherical surface. Table 21 shows the variable spacing on the optical axis of the zoom lens when focusing on an object at infinity. Table 22 shows the variable spacing on the optical axis of the zoom lens when focusing on an object at a finite distance at a shooting magnification of 1 / 40 (1:40). Table 23 shows the specifications of the zoom lens. Table 24 shows the group focal length of each lens group. Table 25 shows the numerical values ​​for conditional expressions (1) to (16).

[0215] 11 shows longitudinal aberration diagrams of Example 4 when focused on an object at infinity at (A) the wide-angle end, (B) at the intermediate focal position, and (C) at the telephoto end. Also, FIG. 12 shows longitudinal aberration diagrams of Example 4 when focused on an object at a finite distance at (A) the wide-angle end, (B) at the intermediate focal position, and (C) at the telephoto end (magnification is 1 / 40x (1:40)).

[0216] [Table 19] SRD Nd νd 1 117.4777 1.700 1.80518 25.46 2 68.0172 10.467 1.49700 81.61 3 477.4086 0.150 4 80.4194 6.900 1.83481 42.72 5 290.7585 Variable D(5) 6 249.7114 1.400 1.83481 42.72 7 23.5390 10.333 8 -141.2175 1.200 1.51680 64.20 9 119.1274 3.075 10 -72.4458 1.200 1.59282 68.62 11 41.4501 9.161 1.83400 37.34 12 -45.4847 3.623 *13 -23.7043 1.500 1.59201 67.02 *14 -36.3645 Variable D(14) (Aperture) 15 INF 1.000 *16 67.6739 4.000 1.77377 47.17 *17 -124.4055 1.200 18 -118.6274 1.100 1.85451 25.15 19 93.1836 1.213 20 49.6625 10.000 1.43700 95.10 21 -42.2418 0.150 22 78.5067 3.166 1.94594 17.98 23 4977.1644 Variable D(23) 24 122.4403 1.200 1.85451 25.15 25 25.0098 8.569 1.49700 81.61 26 -59.3875 Variable D(26) 27 255.0634 2.388 1.92286 20.88 28 -79.5409 0.800 1.80420 46.50 29 30.0066 Variable D(29) *30 37.5828 9.746 1.69350 53.18 *31 -49.5799 0.150 32 -82.9886 2.000 1.75211 25.05 33 77.8354 9.296 *34 -66.8447 1.800 1.85108 40.12 *35 -130.8237 Variable D(35) 36 INF 2.500 1.51680 64.20 37 INF 1.000 (Image surface) 38 INF

[0217] [Table 20] ε ABCDE Page 13 1.0000 2.78321e-05 -6.19132e-08 1.46434e-10 -9.50668e-14 0.00000e+00 Page 14 1.0000 2.09823e-05 -6.53326e-08 1.27671e-10 -1.09057e-13 0.00000e+00 Side 16 -0.1957 -1.11552e-06 -2.37843e-09 -6.49932e-12 -4.69321e-14 0.00000e+00 Page 17 1.0000 5.16690e-06 -1.88785e-09 -5.11113e-12 -4.25102e-14 0.00000e+00 30th face 1.0000 3.84074e-06 7.59814e-09 1.04515e-11 2.63724e-14 0.00000e+00 Page 31 1.0000 3.82909e-06 -3.69725e-09 3.16657e-11 -4.69555e-14 0.00000e+00 Page 34 1.0000 -6.90361e-05 4.04496e-08 -3.64666e-10 1.35958e-12 0.00000e+00 Page 35 1.0000 -5.92083e-05 5.65658e-08 -1.23349e-10 5.92446e-13 0.00000e+00

[0218] [Table 21] Interval Wide-angle end Mid-range Telephoto end D( 5) 1.000 12.864 32.479 D(14) 32.614 13.448 2.133 D(23) 3.009 2.018 0.900 D(26) 1.994 2.769 3.533 D(29) 8.756 10.960 11.759 D(35) 12.459 17.854 19.208

[0219] [Table 22] Interval Wide-angle end Mid-range Telephoto end D(26) 2.413 3.307 4.323 D(29) 8.337 10.422 10.968

[0220] [Table 23] Zoom ratio 2.35 Wide-angle end Mid-range Telephoto end Focal length (mm) 28.85 44.26 67.89 FNo 2.06 2.06 2.06 Angle of view (°) 75.3 50.4 33.4

[0221] [Table 24] Group number Group focal length G1 113.70 G2 -34.94 G3 33.76 G4 700.64 G5 -46.48 G6 100.07

[0222] [Table 25] Example 1 Example 2 Example 3 Example 4 Conditional expression (1) βmt -0.53 -0.54 -0.56 -0.45 Conditional expression (1)' βmt -0.53 -0.54 -0.56 -0.45 Conditional expression (2) β2t / β2w 1.70 1.61 1.58 1.77 Conditional expression (2)' β2t / β2w 1.70 1.61 1.58 1.77 Conditional expression (3) xn / (fw×ft) 1 / 2 -0.16 -0.10 -0.13 -0.15 Conditional expression (4) bfw / Y' 0.74 0.74 0.85 0.70 Conditional expression (5) fmt / frt 0.91 0.98 0.93 0.83 Conditional expression (6) β2t -0.72 -0.60 -0.64 -0.86 Conditional expression (7) βmt / βmw 1.27 1.33 1.31 1.23 Condition (8) fmt / ft 0.49 0.49 0.55 0.50 Conditional expression (9) f2 / fw -1.15 -1.02 -1.15 -1.21 Conditional expression (10) f1 / f2 -3.60 -3.98 -3.62 -3.25 Conditional expression (11) βrt / βrw 1.38 1.46 1.39 1.33 Conditional expression (12) x2 / ft 0.27 0.26 0.29 0.31 Condition (13) | (1-β(n-1)t 2 )×βnt 2 | 1.95 2.48 1.91 2.14 Conditional expression (14) (β2t / β2w) / (βmt / βmw) 1.34 1.21 1.21 1.44 Conditional formula (15) f2 / fmt -1.00 -0.88 -0.96 -1.03 Conditional formula (16) Lsw / Y' 3.83 3.54 3.71 3.90

[0223] (summary) A zoom lens according to a first aspect of the present invention comprises: the lens comprises, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, an intermediate group including one or more lens groups and having positive refractive power as a whole, an (n-1)th lens group having negative refractive power, and an nth lens group; When zooming from the wide-angle end to the telephoto end, the spacing between adjacent lens groups changes. When changing magnification from the wide-angle end to the telephoto end, the first lens group and the nth lens group move along the optical axis, The zoom lens is characterized by satisfying the following conditional expressions: -1.00 ≦ βmt ≦ -0.30 ···(1) 1.20 ≦ β2t / β2w ≦ 1.90 (2) -0.31 ≦ xn / (fw×ft) 1 / 2 < 0.00 (3) however, βmt: lateral magnification of the intermediate group when focusing at infinity at the telephoto end β2t: lateral magnification of the second lens group when focused on infinity at the telephoto end β2w: lateral magnification of the second lens group when focusing on infinity at the wide-angle end xn: the difference in movement amount between the wide-angle end position of the nth lens group and the telephoto end position of the nth lens group when changing magnification from the wide-angle end to the telephoto end, where the sign of movement toward the object side is negative and the sign of movement toward the image side is positive fw: focal length of the entire zoom lens system at the wide-angle end ft: focal length of the entire zoom lens system at the telephoto end

[0224] A zoom lens according to a second aspect of the present invention comprises: the lens comprises, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, an intermediate group including one or more lens groups and having positive refractive power as a whole, an (n-1)th lens group having negative refractive power, and an nth lens group; When zooming from the wide-angle end to the telephoto end, the spacing between adjacent lens groups changes. When changing magnification from the wide-angle end to the telephoto end, the first lens group moves along the optical axis, The zoom lens is characterized by satisfying the following conditional expressions: -0.74 ≦ βmt ≦ -0.30 ···(1)' 1.20 ≦ β2t / β2w ≦ 2.10 ···(2)' 0.55 ≦ bfw / Y' ≦ 0.97 ···(4) however, βmt: lateral magnification of the intermediate group when focusing at infinity at the telephoto end β2t: lateral magnification of the second lens group when focused on infinity at the telephoto end β2w: lateral magnification of the second lens group when focusing on infinity at the wide-angle end bfw: Back focus at the wide-angle end, which is the distance on the optical axis from the image side of the lens closest to the image plane, and is the value when the cover glass thickness is converted into air Y': Maximum image height of the zoom lens

[0225] A zoom lens according to a third aspect of the present invention comprises: the lens comprises, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, an intermediate group including one or more lens groups and having positive refractive power as a whole, an (n-1)th lens group having negative refractive power, and an nth lens group; When zooming from the wide-angle end to the telephoto end, the spacing between adjacent lens groups changes. When changing magnification from the wide-angle end to the telephoto end, the first lens group moves along the optical axis, The zoom lens is characterized by satisfying the following conditional expressions: -0.74 ≦ βmt ≦ -0.30 ···(1)' 1.20 ≦ β2t / β2w ≦ 2.10 ···(2)' 0.80 ≦ fmt / frt ≦ 1.30 (5) however, βmt: lateral magnification of the intermediate group when focusing at infinity at the telephoto end β2t: lateral magnification of the second lens group when focused on infinity at the telephoto end β2w: lateral magnification of the second lens group when focusing on infinity at the wide-angle end fmt: focal length of the intermediate group at the telephoto end frt: composite focal length of all lenses arranged closer to the image than the second lens group at the telephoto end when focused at infinity

[0226] In the zoom lens according to a fourth aspect of the present invention, in any of the first to third aspects, focusing from an object at infinity to an object at a finite distance may be performed by moving the (n-1)th lens group in the optical axis direction.

[0227] The zoom lens according to the fifth aspect of the present invention may satisfy the following conditional expression in the first to fourth aspects. -1.20 ≦ β2t ≦ -0.30 ···(6)

[0228] A zoom lens according to a sixth aspect of the present invention is any of the first to fifth aspects, The intermediate group is Consists of a lens group having positive refractive power, Alternatively, it may be composed of two lens groups each having a positive refractive power.

[0229] The zoom lens according to the seventh aspect of the present invention may satisfy the following conditional expression in the first to sixth aspects. 1.05 ≦ βmt / βmw ≦ 1.80 (7) however, βmw: lateral magnification of the intermediate group when focusing at infinity at the wide-angle end

[0230] The zoom lens according to the eighth aspect of the present invention may satisfy the following conditional expression in the first to seventh aspects. 0.15 ≦ fmt / ft ≦ 0.80 (8) however, fmt: focal length of the intermediate group at the telephoto end ft: focal length of the entire zoom lens system at the telephoto end

[0231] The zoom lens according to the ninth aspect of the present invention may satisfy the following conditional expression in the first to eighth aspects. -1.50 ≦ f2 / fw ≦ -0.50 (9) however, f2: focal length of the second lens group fw: focal length of the entire zoom lens system at the wide-angle end

[0232] The zoom lens according to the tenth aspect of the present invention may satisfy the following conditional expression in the first to ninth aspects. -8.0 ≦ f1 / f2 ≦ -2.0 (10) however, f1: focal length of the first lens group f2: focal length of the second lens group

[0233] The zoom lens according to an eleventh aspect of the present invention may satisfy the following conditional expression in the first to tenth aspects. 1.10 ≦ βrt / βrw ≦ 2.00 (11) however, βrt: the combined lateral magnification of all lenses arranged on the image side of the second lens group at the telephoto end when focused at infinity βrw: the combined lateral magnification of all lenses arranged on the image side of the second lens group at the wide-angle end when focused at infinity

[0234] The zoom lens according to the twelfth aspect of the present invention may satisfy the following conditional expression in the first to eleventh aspects. 0.00 < x2 / ft ≦ 0.55 (12) however, x2: the difference in movement amount between the wide-angle end position of the second lens group and the telephoto end position of the second lens group when changing magnification from the wide-angle end to the telephoto end, where the sign of movement toward the object side is negative and the sign of movement toward the image side is positive ft: focal length of the entire zoom lens system at the telephoto end

[0235] The zoom lens according to the thirteenth aspect of the present invention may satisfy the following conditional expression in the first to twelfth aspects. 1.00 ≦ |(1-β(n-1)t 2 )×βnt 2 | ≦ 6.00 ···(13) however, β(n-1)t: lateral magnification of the n-1 lens group when focused on infinity at the telephoto end βnt: lateral magnification of the nth lens group when focused on infinity at the telephoto end

[0236] An imaging device according to the first aspect of the present invention may include a zoom lens according to any one of the first to thirteenth aspects, and a solid-state imaging element that converts an optical image formed by the zoom lens into an electrical signal. [Industrial Applicability]

[0237] The zoom lens according to the present invention has a large aperture ratio, yet allows for the realization of a compact zoom lens as a whole, and can effectively correct various aberrations such as spherical aberration and coma over the entire zoom range. In other words, it is suitable for imaging devices using solid-state imaging elements (CCD, CMOS, etc.), such as digital still cameras and digital video cameras, which require compact size. [Explanation of symbols]

[0238] G1 First lens group G2 Second lens group G3 3rd lens group G4 4th lens group G5 5th lens group G6 6th lens group Gm intermediate group Gn-1 n-1th lens group Gn nth lens group STOP Aperture CG cover glass IMG Image plane Focus: The direction of movement when focusing from an object at infinity to an object at a finite distance

Claims

1. The lens comprises, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, an intermediate group including one or more lens groups and having positive refractive power as a whole, an (n-1)th lens group having negative refractive power, and an nth lens group, When zooming from the wide-angle end to the telephoto end, the spacing between adjacent lens groups changes. When changing magnification from the wide-angle end to the telephoto end, the first lens group and the nth lens group move along the optical axis, A zoom lens characterized by satisfying the following conditional expression: -1.00 ≦ βmt ≦ -0.30 ... (1) 1.20 ≦ β2t / β2w ≦ 1.90 (2) -0.31 ≦ xn / (fw×ft) １／２ < 0.00 ・・・(3) however, βmt: lateral magnification of the intermediate group when focusing on infinity at the telephoto end β2t: lateral magnification of the second lens group when focused on infinity at the telephoto end β2w: lateral magnification of the second lens group when focusing on infinity at the wide-angle end xn: the difference in movement amount between the wide-angle end position of the nth lens group and the telephoto end position of the nth lens group when changing magnification from the wide-angle end to the telephoto end, where the sign of movement toward the object side is negative and the sign of movement toward the image side is positive fw: focal length of the entire zoom lens system at the wide-angle end ft: focal length of the entire zoom lens system at the telephoto end

2. The lens comprises, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, an intermediate group including one or more lens groups and having positive refractive power as a whole, an (n-1)th lens group having negative refractive power, and an nth lens group, When zooming from the wide-angle end to the telephoto end, the spacing between adjacent lens groups changes. When zooming from the wide-angle end to the telephoto end, the first lens group moves along the optical axis, A zoom lens characterized by satisfying the following conditional expression: -0.74 ≦ βmt ≦ -0.30 ... (1)' 1.20 ≦ β2t / β2w ≦ 2.10 ... (2)' 0.55 ≦ bfw / Y' ≦ 0.97 (4) however, βmt: lateral magnification of the intermediate group when focusing on infinity at the telephoto end β2t: lateral magnification of the second lens group when focused on infinity at the telephoto end β2w: lateral magnification of the second lens group when focusing on infinity at the wide-angle end bfw: back focus at the wide-angle end, which is the distance on the optical axis from the image side of the lens closest to the image to the image plane, and is the value when the cover glass thickness is converted into air Y': maximum image height of the zoom lens

3. The lens comprises, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, an intermediate group including one or more lens groups and having positive refractive power as a whole, an (n-1)th lens group having negative refractive power, and an nth lens group, When zooming from the wide-angle end to the telephoto end, the spacing between adjacent lens groups changes. When zooming from the wide-angle end to the telephoto end, the first lens group moves along the optical axis, A zoom lens characterized by satisfying the following conditional expression: -0.74 ≦ βmt ≦ -0.30 ... (1)' 1.20 ≦ β2t / β2w ≦ 2.10 ... (2)' 0.80 ≦ fmt / frt ≦ 1.30 (5) however, βmt: lateral magnification of the intermediate group when focusing on infinity at the telephoto end β2t: lateral magnification of the second lens group when focused on infinity at the telephoto end β2w: lateral magnification of the second lens group when focusing on infinity at the wide-angle end fmt: focal length of the intermediate group at the telephoto end frt: composite focal length of all lenses arranged on the image side of the second lens group at the telephoto end when focused at infinity

4. 4. The zoom lens according to claim 1, wherein focusing from an object at infinity to an object at a finite distance is performed by moving the (n-1)th lens group in the optical axis direction.

5. 4. The zoom lens according to claim 1, wherein the following condition is satisfied: -1.20 ≦ β2t ≦ -0.30 ... (6)

6. The intermediate group is Consists of a lens group having positive refractive power, Alternatively, the zoom lens according to any one of claims 1 to 3, which is composed of two lens groups each having a positive refractive power.

7. 4. The zoom lens according to claim 1, wherein the following condition is satisfied: 1.05 ≦ βmt / βmw ≦ 1.80 (7) however, βmw: lateral magnification of the intermediate group when focusing on infinity at the wide-angle end

8. 4. The zoom lens according to claim 1, wherein the following condition is satisfied: 0.15 ≦ fmt / ft ≦ 0.80 (8) however, fmt: focal length of the intermediate group at the telephoto end ft: focal length of the entire zoom lens system at the telephoto end

9. 4. The zoom lens according to claim 1, wherein the following condition is satisfied: -1.50 ≦ f2 / fw ≦ -0.50 (9) however, f2: focal length of the second lens group fw: focal length of the entire zoom lens system at the wide-angle end

10. 4. The zoom lens according to claim 1, wherein the following condition is satisfied: -8.0 ≦ f1 / f2 ≦ -2.0 (10) however, f1: focal length of the first lens group f2: focal length of the second lens group

11. 4. The zoom lens according to claim 1, wherein the following condition is satisfied: 1.10 ≦ βrt / βrw ≦ 2.00 (11) however, βrt: composite lateral magnification of all lenses arranged on the image side of the second lens group at the telephoto end when focused at infinity βrw: composite lateral magnification of all lenses arranged on the image side of the second lens group at the wide-angle end when focused at infinity

12. 4. The zoom lens according to claim 1, wherein the following condition is satisfied: 0.00 < x2 / ft ≦ 0.55 (12) however, x2: the difference in movement amount between the wide-angle end position of the second lens group and the telephoto end position of the second lens group when changing magnification from the wide-angle end to the telephoto end, where the sign of movement toward the object side is negative and the sign of movement toward the image side is positive ft: focal length of the entire zoom lens system at the telephoto end

13. 4. The zoom lens according to claim 1, wherein the following condition is satisfied: 1.000 ≦ |(1-β(n-1)t ２ )×βντ ２ | ≦ 6.00 ・・・ (13) however, β(n−1)t: lateral magnification of the n−1 lens group when focused on infinity at the telephoto end βnt: lateral magnification of the nth lens group when focused on infinity at the telephoto end

14. 4. An imaging device comprising: the zoom lens according to claim 1; and a solid-state imaging device that converts an optical image formed by the zoom lens into an electrical signal.

Images