Zoom lens and imaging apparatus

Abstract

To provide a compact zoom lens having high optical performance, capable of achieving both correction of axial chromatic aberration and chromatic aberration of magnification and correction of field curvature aberration, and to provide an imaging apparatus.SOLUTION: The zoom lens is equipped with positive, negative and positive lens groups and a rear group, and constituted so that a 1st lens group and the final lens group included in the rear group are fixed at the time of varying power, the final lens group includes a specified cemented lens and a meniscus lens, and a specified expression is satisfied as a whole.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Various imaging devices are known, such as mirrorless single-lens cameras, digital still cameras, and security cameras, and are used for a variety of purposes. These imaging devices are usually equipped with a zoom lens and a solid-state imaging element, and the zoom lens has been designed to exhibit the desired performance depending on the application of the imaging device.

[0003] Known zoom lenses include lens groups arranged, from the object side, with positive, negative, positive, negative, and positive refractive powers, thereby achieving a compact configuration and correction of axial chromatic aberration and chromatic aberration of magnification (see, for example, Patent Document 1). Also known are zoom lenses including lens groups arranged, from the object side, with positive, negative, positive, positive, and negative refractive powers, thereby achieving a compact configuration and correction of field curvature (see, for example, Patent Document 2). Still further known are zoom lenses including lens groups arranged, from the object side, with positive, negative, positive, negative, and positive refractive powers, thereby achieving improved optical performance (see, for example, Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-228500 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-102978 [Patent Document 3] Japanese Patent Publication No. 2023-176555 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in recent years, the pixel density of solid-state imaging devices mounted on imaging devices has been steadily increasing. Therefore, zoom lenses are required to achieve even higher performance to accommodate this trend. Zoom lenses, in particular, are required to achieve high performance that allows them to be used for multiple purposes. It is generally becoming increasingly difficult to simultaneously correct axial chromatic aberration and lateral chromatic aberration and correct curvature of field throughout the entire zoom range. For example, the zoom lens of Patent Document 1 may provide insufficient correction of curvature of field, the zoom lens of Patent Document 2 may provide insufficient correction of axial chromatic aberration and lateral chromatic aberration, and the zoom lens of Patent Document 3 may have a long overall length relative to the focal length due to the weak refractive power of the first lens group, resulting in a lack of compactness.

[0006] An object of one aspect of the present invention is to provide a zoom lens and an imaging device that are small in size and have high optical performance, and that can correct both axial chromatic aberration and chromatic aberration of magnification, and correct field curvature aberration. [Means for solving the problem]

[0007] In order to achieve the above object, a zoom lens according to one aspect of the present invention comprises, in order from the object side to the image plane side along the optical axis direction, 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 rear group, the rear group having two or three lens groups including a lens group having positive refractive power and a lens group having negative refractive power, the lens groups having positive refractive power and the lens groups having negative refractive power being arranged alternately, a distance between adjacent lens groups changes during zooming, the lens groups closest to the image plane in the first lens group and the rear group are each fixed in the optical axis direction, the lens group closest to the image plane in the rear group includes a cemented lens of a lens having negative refractive power and a lens having positive refractive power, and a meniscus lens arranged at a position closest to the image plane with its convex surface facing the image plane, and satisfies the following formula: 0.0<|fm / fr|≦1.3 (1) 0.1≦νdn / νdp≦0.9 (2) -8.0≦f1 / f2≦-3.5 (3) however, fm: focal length of the meniscus lens fr: focal length of the lens group closest to the image plane νdn: Abbe number of the lens having a negative refractive index that constitutes the cemented lens νdp: Abbe number of the lens having a positive refractive index that constitutes the cemented lens f1: focal length of the first lens group f2: focal length of the second lens group

[0008] In order to solve the above problem, an imaging device according to one aspect of the present invention includes the above zoom lens. [Effects of the Invention]

[0009] According to one aspect of the present invention, it is possible to realize a zoom lens and an imaging device that are small in size and have high optical performance, and that can correct both axial chromatic aberration and chromatic aberration of magnification and correct field curvature aberration. [Brief explanation of the drawings]

[0010] [Figure 1] 1A and 1B are diagrams illustrating the lens configurations at the wide-angle end and the telephoto end of a zoom lens according to a first embodiment. [Figure 2] 4A to 4C are diagrams showing longitudinal aberrations at the wide-angle end, at an intermediate focal position, and at the telephoto end in the zoom lens of Example 1. [Figure 3] 10A and 10B are diagrams illustrating the lens configurations at the wide-angle end and the telephoto end of a zoom lens according to a second embodiment. [Figure 4] 10A to 10C are diagrams showing longitudinal aberrations at the wide-angle end, at an intermediate focal position, and at the telephoto end in the zoom lens of Example 2. [Figure 5] 10A and 10B are diagrams illustrating the lens configurations at the wide-angle end and the telephoto end of a zoom lens according to a third embodiment. [Figure 6]10A to 10C are diagrams showing longitudinal aberrations at the wide-angle end, at the intermediate focal position, and at the telephoto end in the zoom lens of Example 3. [Figure 7] 10A and 10B are diagrams illustrating the lens configurations at the wide-angle end and the telephoto end of a zoom lens according to a fourth embodiment. [Figure 8] 10A and 10B are diagrams illustrating longitudinal aberrations at the wide-angle end, at the intermediate focal position, and at the telephoto end in the zoom lens of Example 4. [Figure 9] 1 is a diagram schematically illustrating a configuration of an imaging device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Zoom Lens] A zoom lens according to an embodiment of the present invention includes, in order from the object side to the image plane side along the optical axis, a first lens group, a second lens group, a third lens group, and a rear lens group.

[0012] The term "zoom lens" is a general term for an optical configuration that exhibits the optical characteristics described in this embodiment, and refers to either or both of an optical system that exhibits the optical characteristics and an article that includes the optical system. In this specification, the optical characteristics at the wide-angle end or telephoto end refer to the optical characteristics at the wide-angle end or telephoto end when focusing at infinity, unless otherwise specified.

[0013] Furthermore, the term "lens group" refers to a single lens or a collection of two or more lenses. In a lens group that moves during magnification change, the lenses that make up the lens group move while maintaining their relative positional relationships within the lens group. In other words, the spacing between the lenses that make up the lens group remains constant even when they move during magnification change.

[0014] The ordinal numbers of lens groups refer to their positions from the object side. Lens groups with consecutive ordinal numbers (e.g., first and second) are adjacent to each other in the optical axis direction, with no other lens groups interposed between them.

[0015] The "rear group" refers to a group of two or more lens groups that is located furthest back (closest to the image plane) when viewed from the object side. In this embodiment, the rear group is a group of the fourth lens group and the lens group closest to the fourth lens group.

[0016] The "lens" may be a single lens or a cemented lens. Examples of single lenses include a biconvex lens, a plano-convex lens, a convex meniscus lens, and a concave meniscus lens. A cemented lens has a structure in which two or more single lenses are integrated without an air gap. The lens may be a spherical lens or an aspherical lens. The aspherical lens may be a composite resin aspherical lens having a configuration in which a composite resin film molded into an aspherical shape is attached to the surface of a glass material.

[0017] [Optical configuration] The zoom lens of this embodiment includes a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power. Hereinafter, "having positive refractive power" will also be referred to simply as "positive" or "positive," and "having negative refractive power" will also be referred to simply as "negative" or "negative."

[0018] Generally, in a zoom lens with a relatively high magnification, a positive lens group is used as the first lens group, and magnification is changed by mainly moving the second lens group, which has a strong negative refractive power. In this case, it is effective to use a positive third lens group in order to effectively correct aberration fluctuations caused by magnification changes in the second lens group. Therefore, the arrangement of positive, negative, and positive lens groups from the first lens group to the third lens group in this embodiment is advantageous for achieving a relatively high zoom magnification.

[0019] Note that, when an additional negative lens group is disposed after the negative second lens group, aberrations occurring in the second lens group cannot be completely corrected, and therefore, it may be necessary to dispose a positive lens group on the image side of the additional negative lens group. As a result, the overall length (length along the optical axis) of the zoom lens is usually longer than when a positive lens group is disposed adjacent to the image side of the second lens group. Therefore, the arrangement of positive, negative, and positive lens groups from the first lens group to the third lens group in this embodiment is advantageous from the viewpoint of compactness.

[0020] In this embodiment, it is also preferable from the perspective of compactness that the third lens group and the rear lens group have a positive refractive power as a whole. If a negative lens group is present on the image side of the second lens group, as mentioned above, an additional positive lens group may be required on the image side to correct aberrations, which may result in an increase in the overall length of the zoom lens.

[0021] <First lens group> The first lens group has positive refractive power. The type and arrangement of lenses in the first lens group can be appropriately determined as long as the first lens group as a whole exhibits the desired positive refractive power. For example, a cemented lens can be used for the lens closest to the object (first lens) in the first lens group. A cemented lens for the first lens is preferable from the viewpoint of effectively correcting axial chromatic aberration and lateral chromatic aberration at the telephoto end.

[0022] <Second lens group> The second lens group has negative refractive power. The type and arrangement of lenses in the second lens group can be appropriately set within a range in which the second lens group as a whole exhibits the desired negative refractive power. For example, from the viewpoint of excellent correction of field curvature at the wide-angle end, a negative lens arranged closest to the object and having a concave surface facing the image plane can be suitably used as the lens in the second lens group. Furthermore, from the viewpoint of correcting field curvature at the wide-angle end, it is preferable that the second lens group includes a convex lens closest to the image plane.

[0023] <Third lens group> The third lens group has a positive refractive index. The type and arrangement of lenses in the third lens group can be appropriately determined as long as the third lens group as a whole exhibits the desired positive refractive power. For example, aspherical lenses can be used for the lenses in the third lens group. It is preferable for the third lens group to include aspherical lenses in order to effectively correct spherical aberration and astigmatism at the wide-angle end.

[0024] <Rear group> The rear group has two or three lens groups, including a positive lens group and a negative lens group. The rear group is configured with positive and negative lens groups arranged alternately. That is, the rear group can be configured with a positive or negative fourth lens group and a negative or positive fifth lens group, or a positive or negative fourth lens group, a negative or positive fifth lens group, and a positive or negative sixth lens group. Having the rear group alternate between positive and negative lens groups (the lens groups in the rear group are arranged in the order positive-negative, positive-negative-positive, negative-positive, or negative-positive-negative) is preferable from the perspective of effectively correcting aberrations in the zoom lens, since aberrations generated by each lens group cancel each other out.

[0025] The rear group may have either a positive refractive power as a whole or a negative refractive power as a whole. Having the rear group have a positive refractive power as a whole is preferable from the viewpoint of further compactifying the zoom lens. Having the rear group have a negative refractive power as a whole is preferable from the viewpoint of aberration correction by canceling out residual aberrations up to the third lens group.

[0026] Furthermore, the lens group in the rear group closest to the image surface (i.e., the fifth or sixth lens group, also referred to as the "final lens group") may include a cemented lens consisting of a lens with negative refractive power and a lens with positive refractive power, and a meniscus lens positioned closest to the image surface with its convex surface facing the image surface.

[0027] It is preferable that the final lens group includes a cemented lens of a negative lens and a positive lens, from the viewpoint of effectively correcting chromatic aberration of magnification from the wide-angle end to the telephoto end.

[0028] Furthermore, it is preferable that the final lens element of the final lens group be a meniscus lens element convex toward the image plane, in order to improve the optical characteristics of the zoom lens, which may require not only good correction of field curvature but also effective suppression of harmful ghosting.

[0029] Generally, light that passes through a lens and reflects off the image plane (sensor plane) may return to the object side, be reflected again by a lens surface, and reach the image plane again. This light can cause ghosts. Ghosts that occur in this way are generally bright and prone to becoming harmful ghosts. Because the final lens element is closest to the image plane, light reflected from the lens surface of the final lens element closest to the image plane acts most strongly on the image plane, easily generating high-brightness ghosts (harmful ghosts). Furthermore, the more easily light reflected from the lens surface of the final lens element is focused on the image plane, the more likely it is to become a harmful ghost. Therefore, the lens shape of the final lens element is important from the perspective of fully realizing the optical performance of a zoom lens.

[0030] If the lens surface of the final lens element facing the image plane is convex with respect to the image plane, light reflected from this convex surface will diffuse from the optical axis side to the outer periphery of the lens, making it difficult to form an image on the image plane. Therefore, as described above, it is preferable that the final lens element of the final lens group be a meniscus lens convex toward the image plane, from the perspective of suppressing the occurrence of harmful ghost images.

[0031] If the final lens element has a convex surface facing the image plane, a similar ghost suppression effect can be expected. Of the lenses with a convex surface facing the image plane, it is preferable to use a meniscus lens as the final lens element, from the viewpoint of suppressing the occurrence of the above-mentioned ghost on the object-side lens surface of the final lens element.

[0032] <Aperture diaphragm> The position of the aperture stop in a zoom lens may be determined as appropriate within the scope of the present invention. For example, the aperture stop may be located closest to the object in the third lens group. Locating the aperture stop closest to the object in the third lens group is preferable from the viewpoint of reducing flare.

[0033] <Other optical elements> In addition to the lens groups described above, the zoom lens may include additional optical elements as long as the effects of the present invention can be achieved. Examples of such additional optical elements include filters such as an IR cut filter that cuts light with wavelengths such as near-infrared light. For example, it is preferable for the zoom lens to include such filters between the final lens and the image plane from the perspective of reducing the diameter of the entire lens system.

[0034] [Operation] <Magnification> In a zoom lens, the magnification can be varied from the wide-angle end to the telephoto end by changing the air gap between adjacent lens groups on the optical axis. In a zoom lens, all of the lens groups may move along the optical axis to vary the magnification, or only some of the lens groups may move along the optical axis. For example, the first lens group may be fixed in the optical axis direction during magnification, and the final lens group in the rear group may be fixed in the optical axis direction during magnification. A zoom lens configuration in which the first lens group and the final lens group are fixed in the optical axis direction during magnification allows the overall length of the zoom lens to be constant, which is preferable from the perspective of compactness.

[0035] Furthermore, the third lens group may be fixed in the optical axis direction. A configuration in which the third lens group does not move along the optical axis during zooming is preferable from the viewpoint of reducing the diameter of the entire lens system and simplifying the mechanism of the zoom lens.

[0036] On the other hand, the second lens group may be a lens group that moves when the magnification is changed, and it is preferable from the viewpoint of achieving a high magnification ratio that the second lens group is a lens group that moves when the magnification is changed.

[0037] Furthermore, the fourth lens group may be a lens group that moves during zooming, and it is preferable that the fourth lens group be a lens group that moves during zooming, from the viewpoint of effectively correcting residual aberrations up to the third lens group from the wide-angle end to the telephoto end.

[0038] Furthermore, the fifth lens group may be a lens group that moves when the magnification is changed, and it is preferable that the fifth lens group be a lens group that moves when the magnification is changed, from the viewpoint of suppressing the curvature of field that occurs when the second lens group is changed in magnification, and from the viewpoint of reducing the amount of movement of the lens groups in the zoom lens.

[0039] Furthermore, in cases where the zoom lens includes a sixth lens group, the sixth lens group may be a lens group that moves during zooming, and it is preferable that the sixth lens group be a lens group that moves during zooming, from the viewpoint of further suppressing field curvature.

[0040] Furthermore, since the rear group includes two or three lens groups, two of the lens groups in the rear group (the fourth lens group and the fifth lens group) may both move during zooming. A configuration in which at least two lens groups in the rear group move during zooming makes it possible to further reduce the amount of movement of the second lens group during zooming, thereby further suppressing fluctuations in aberrations due to the movement of the second lens group during zooming. This is therefore suitable from the perspective of achieving good optical performance in a zoom lens and from the perspective of compactness.

[0041] Furthermore, the trajectory of movement of the lens group during magnification change may be linear or curved. Furthermore, the trajectory may be a trajectory toward either the object side or the image plane side, or a trajectory that moves toward either the object side or the image plane side and then moves toward the other side. For example, a linear trajectory of movement of the lens group during magnification change is preferable from the viewpoint of increasing the speed at which the lens group is moved, and a curved trajectory of movement of the lens group during magnification change is preferable from the viewpoint of reducing the overall lens length. Furthermore, a trajectory of movement of the lens group during magnification change that moves toward either the object side or the image plane side is preferable from the viewpoint of increasing the speed at which the lens group is moved, and a trajectory of movement of the lens group that moves toward either the object side or the image plane side and then moves toward the other side is preferable from the viewpoint of reducing the overall lens length.

[0042] <Focus> In a zoom lens, focusing can be achieved by moving any of the lens groups in the optical axis direction. Generally, a more convergent light beam is incident on a lens group closer to the image plane. Therefore, the lens group closer to the image plane can be composed of lenses with smaller lens diameters. Therefore, it is preferable that the lens group that moves during focusing (hereinafter also referred to as the "focus group") is the image plane lens group from the viewpoints of suppressing fluctuations in the angle of view that accompany the movement of the focus group and of moving the focus group quickly and with a low drive load during focusing. From these viewpoints, when the final lens group is the nth lens group, it is preferable that the (n-1)th lens group be the focus group.

[0043] Furthermore, having only one focus group makes it possible to simplify the drive mechanism for the focus group, which is preferable from the viewpoint of realizing a compact and lightweight zoom lens. From this viewpoint as well, it is preferable to use the (n-1)th lens group as the focus group.

[0044] [Optical properties] It is preferable that the zoom lens of this embodiment satisfy at least one of the following expressions, from the viewpoint of achieving simultaneous correction of axial chromatic aberration, lateral chromatic aberration, and field curvature aberration, and realizing a zoom lens and image pickup apparatus that are small in size and have high optical performance.

[0045] <Formula (1)> 0.0<|fm / fr|≦1.3 (1) however, fm: focal length of the final meniscus lens fr: focal length of the lens group closest to the image plane

[0046] Formula (1) defines the ratio between the refractive power of the lens group closest to the image surface (the final lens group) and the refractive power of the meniscus lens (the final lens) located closest to the image surface in the final lens group. It is preferable for a zoom lens to satisfy formula (1) in order to suppress aberrations due to curvature of field.

[0047] If |fm / fr| is 0.0 or less, the refractive power of the meniscus lens will be too strong, resulting in overcorrection of field curvature, making it difficult for the zoom lens to achieve the desired optical performance. If |fm / fr| is greater than 1.3, the refractive power of the meniscus lens will be insufficient, resulting in insufficient correction of field curvature, making it difficult for the zoom lens to achieve the desired optical performance. From the viewpoint of appropriately suppressing field curvature aberration, |fm / fr| is more preferably 0.01 or more, and even more preferably 0.02 or more. Furthermore, from the viewpoint of appropriately suppressing field curvature aberration, |fm / fr| is more preferably 1.2 or less, and even more preferably 1.1 or less.

[0048] <Formula (2)> 0.1≦νdn / νdp≦0.9 (2) however, νdn: Abbe number of the lens having a negative refractive index that constitutes the cemented lens in the final lens group νdp: Abbe number of the lens having a positive refractive index that constitutes the cemented lens in the final lens group

[0049] Equation (2) defines the ratio of the Abbe number of the negative lens that constitutes the cemented lens disposed in the final lens group to the Abbe number of the positive lens that constitutes the cemented lens. Unless otherwise specified, "Abbe number" refers to the Abbe number at the d-line (587.56 nm). It is preferable for a zoom lens to satisfy equation (2) in order to effectively suppress axial chromatic aberration and lateral chromatic aberration.

[0050] If νdn / νdp is less than 0.1, axial chromatic aberration and lateral chromatic aberration are overcorrected, which may make it difficult for the zoom lens to achieve the desired optical performance. If νdn / νdp is greater than 0.9, axial chromatic aberration and lateral chromatic aberration are not sufficiently suppressed, which may make it difficult for the zoom lens to achieve the desired optical performance. From the viewpoint of effectively suppressing axial chromatic aberration and lateral chromatic aberration, νdn / νdp is more preferably 0.3 or more, and even more preferably 0.5 or more. Furthermore, from the viewpoint of effectively suppressing axial chromatic aberration and lateral chromatic aberration, νdn / νdp is more preferably 0.84 or less, and even more preferably 0.80 or less.

[0051] <Formula (3)> -8.0≦f1 / f2≦-3.5 (3) however, f1: focal length of the first lens group f2: focal length of the second lens group

[0052] Equation (3) defines the ratio of the focal length of the first lens group to the focal length of the second lens group. It is preferable for a zoom lens to satisfy equation (3) from the viewpoints of effectively correcting aberrations at the telephoto end and achieving a compact zoom lens.

[0053] If f1 / f2 is less than -8.0, the fluctuation of aberrations due to the magnification change of the second lens group is small, but the curvature of field at the telephoto end is overcorrected, which may make it difficult to achieve the desired optical performance of the zoom lens. If f1 / f2 is less than -8.0, the refractive power of the first lens group is weak, which may make it difficult to achieve the desired overall length of the zoom lens. If f1 / f2 is greater than -3.5, the correction of aberrations at the telephoto end is easy, but the fluctuation of aberrations due to the magnification change of the second lens group is too large, which may make it difficult to correct aberrations at the wide-angle end. If f1 / f2 is greater than -3.5, the movement amount of the second lens group required for magnification change is large, which may make it difficult to achieve the desired overall length of the zoom lens. From the viewpoint of good correction of aberrations at the telephoto end and realizing a compact zoom lens, f1 / f2 is more preferably -7.0 or greater, and even more preferably -6.0 or greater. Furthermore, from the viewpoint of favorably correcting aberrations at the telephoto end and realizing a compact zoom lens, f1 / f2 is more preferably equal to or less than -3.8, and even more preferably equal to or less than -4.0.

[0054] <Formula (4)> 0.5≦βBw / βBt≦25.0 (4) however, βBw: Lateral magnification of the rear group at the wide-angle end when focusing on infinity βBt: Lateral magnification of the rear group at the telephoto end when focused on infinity

[0055] Equation (4) defines the ratio of the lateral magnification of the rear group at the wide-angle end to the lateral magnification of the rear group at the telephoto end. It is preferable for a zoom lens to satisfy equation (4) from the perspective of achieving a good balance between the curvature of field at the wide-angle end and the curvature of field at the telephoto end of the zoom lens.

[0056] If βBw / βBt is less than 0.5, the aberration of field curvature at the telephoto end will be excessively suppressed, making it difficult to achieve the desired optical performance of the zoom lens at the telephoto end. If βBw / βBt is greater than 25.0, the aberration of field curvature at the wide-angle end will be excessively suppressed, making it difficult to achieve the desired optical performance of the zoom lens at the wide-angle end. From the viewpoint of achieving a good balance between the field curvature at the wide-angle end and the field curvature at the telephoto end of the zoom lens, βBw / βBt is more preferably 0.7 or greater, and even more preferably 1.0 or greater. Furthermore, from the viewpoint of achieving a good balance between the field curvature at the wide-angle end and the field curvature at the telephoto end of the zoom lens, βBw / βBt is more preferably 23.0 or less, and even more preferably 22.0 or less.

[0057] <Formula (5)> 0.0<|f3 / fBw|≦1.0 (5) however, f3: focal length of the third lens group fBw: focal length at the wide-angle end of the rear group

[0058] Equation (5) defines the ratio of the focal length of the third lens group to the focal length of the rear group at the wide-angle end. It is preferable for a zoom lens to satisfy equation (5) from the perspective of effectively correcting aberrations at the wide-angle end.

[0059] If |f3 / fBw| is 0.0 or less, spherical aberration at the wide-angle end may be overcorrected, making it difficult for the zoom lens to achieve the desired optical performance at the wide-angle end. If |f3 / fBw| is greater than 1.0, spherical aberration at the wide-angle end may be insufficiently suppressed, making it difficult for the zoom lens to achieve the desired optical performance at the wide-angle end. From the viewpoint of effectively correcting aberration at the wide-angle end, |f3 / fBw| is more preferably 0.02 or more, and even more preferably 0.05 or more. Furthermore, from the viewpoint of effectively correcting aberration at the wide-angle end, |f3 / fBw| is more preferably 0.95 or less, and even more preferably 0.90 or less.

[0060] <Formula (6)> 0.5≦fBw / fBt≦5.0 (6) however, fBw: focal length at the wide-angle end of the rear group fBt: focal length at the telephoto end of the rear group

[0061] Equation (6) defines the ratio of the focal length of the rear group at the wide-angle end to the focal length of the rear group at the telephoto end. It is preferable for a zoom lens to satisfy equation (6) from the viewpoint of achieving a good balance between the curvature of field at the wide-angle end and the curvature of field at the telephoto end.

[0062] If fBw / fBt is less than 0.5, the curvature of field at the wide-angle end will be overcorrected, making it difficult to achieve the desired optical performance of the zoom lens at the wide-angle end. It will be difficult to maintain optical performance at the wide-angle end. If fBw / fBt is greater than 5.0, the curvature of field at the telephoto end will be overcorrected, making it difficult to achieve the desired optical performance of the zoom lens at the telephoto end. From the viewpoint of achieving a good balance between the curvature of field at the wide-angle end and the telephoto end, fBw / fBt is more preferably 0.7 or greater, and even more preferably 0.9 or greater. Furthermore, from the viewpoint of achieving a good balance between the curvature of field at the wide-angle end and the telephoto end, fBw / fBt is more preferably 4.6 or less, and even more preferably 4.2 or less.

[0063] <Formula (7)> 0.5≦D12t / f3≦4.5 (7) however, D12t: The distance on the optical axis from the surface of the lens in the first lens group closest to the object to the surface of the lens in the second lens group closest to the image plane at the telephoto end. f3: focal length of the third lens group

[0064] Equation (7) defines the ratio of the axial distance from the surface of the lens in the first lens group closest to the object to the surface of the lens in the second lens group closest to the image plane at the telephoto end to the focal length of the third lens group. It is preferable for a zoom lens to satisfy equation (7) from the perspective of effectively correcting aberrations at the telephoto end.

[0065] A D12t / f3 ratio of less than 0.5 is advantageous for miniaturizing the zoom lens (reducing the length of the zoom lens), but may result in insufficient correction of spherical aberration, making it difficult to achieve the desired optical performance at the telephoto end of the zoom lens. A D12t / f3 ratio of more than 4.5 may result in excessive correction of spherical aberration at the telephoto end of the zoom lens, making it difficult to achieve the desired optical performance at the telephoto end of the zoom lens and also making it difficult to miniaturize the zoom lens. From the perspective of effectively correcting aberration at the telephoto end of the zoom lens and achieving a compact zoom lens, D12t / f3 is preferably 0.7 or greater, and even more preferably 1.0 or greater. Furthermore, from the perspective of effectively correcting aberration at the telephoto end of the zoom lens and achieving a compact zoom lens, D12t / f3 is more preferably 4.3 or less, and even more preferably 4.0 or less.

[0066] <Formula (8)> 0.1≦f3 / ft≦1.0 (8) however, f3: focal length of the third lens group ft: focal length at the telephoto end of the zoom lens

[0067] Equation (8) defines the ratio of the focal length of the third lens group to the focal length of the zoom lens at the telephoto end. The focal length of the zoom lens refers to the focal length of all lenses (hereinafter referred to as the "entire lens system") from the lens in the first lens group closest to the object to the meniscus lens in the final lens group closest to the image plane. It is preferable for a zoom lens to satisfy equation (8) in order to effectively correct aberrations at the telephoto end.

[0068] If f3 / ft is less than 0.1, the focal length of the zoom lens at the telephoto end can be increased, but spherical aberration at the telephoto end may be overcorrected, making it difficult to achieve the desired optical performance of the zoom lens. If f3 / ft is greater than 1.0, spherical aberration at the telephoto end may be insufficiently corrected, making it difficult to achieve the desired optical performance of the zoom lens at the telephoto end and making it difficult to achieve a sufficiently long focal length at the telephoto end. From the perspective of effectively correcting aberration at the telephoto end of the zoom lens and achieving a sufficiently long focal length at the telephoto end of the zoom lens, f3 / ft is more preferably 0.15 or greater, and even more preferably 0.20 or greater. Furthermore, from the perspective of effectively correcting aberration at the telephoto end of the zoom lens and achieving a sufficiently long focal length at the telephoto end of the zoom lens, f3 / ft is more preferably 0.8 or less, and even more preferably 0.6 or less.

[0069] <Formula (9)> 0.1≦f3 / f1≦1.0 (9) however, f1: focal length of the first lens group f3: focal length of the third lens group

[0070] Equation (9) defines the ratio of the focal length of the third lens group to the focal length of the first lens group. It is preferable for a zoom lens to satisfy equation (9) from the viewpoint of effectively correcting aberrations at the wide-angle end and the telephoto end.

[0071] If f3 / f1 is less than 0.1, spherical aberration at the telephoto end is easily corrected, but spherical aberration at the wide-angle end is overcorrected, making it difficult to achieve the desired optical performance of the zoom lens at the wide-angle end. If f3 / f1 is greater than 1.0, spherical aberration at the wide-angle end is easily corrected, but spherical aberration at the telephoto end is overcorrected, making it difficult to achieve the desired optical performance of the zoom lens at the telephoto end. From the viewpoint of effectively correcting aberrations at the wide-angle end and the telephoto end of the zoom lens, f3 / f1 is more preferably 0.20 or more, and even more preferably 0.25 or more. Furthermore, from the viewpoint of effectively correcting aberrations at the wide-angle end and the telephoto end of the zoom lens, f3 / f1 is more preferably 0.9 or less, and even more preferably 0.8 or less.

[0072] <Formula (10)> 0.1≦|f2 / f3|≦1.2 (10) however, f2: focal length of the second lens group f3: focal length of the third lens group

[0073] Equation (10) defines the ratio of the focal length of the second lens group to the focal length of the third lens group. It is preferable for a zoom lens to satisfy equation (10) from the viewpoint of effectively correcting aberrations at the wide-angle end.

[0074] If |f2 / f3| is less than 0.1, spherical aberration at the wide-angle end is easily corrected, but astigmatism at the wide-angle end may be overcorrected, making it difficult to achieve the desired optical performance of the zoom lens at the wide-angle end. If |f2 / f3| is greater than 1.2, astigmatism at the wide-angle end is easily corrected, but spherical aberration at the wide-angle end may be overcorrected, making it difficult to achieve the desired optical performance of the zoom lens at the wide-angle end. From the viewpoint of effectively correcting aberrations at the wide-angle end of the zoom lens, |f2 / f3| is more preferably 0.20 or more, and even more preferably 0.25 or more. Furthermore, from the viewpoint of effectively correcting aberrations at the wide-angle end of the zoom lens, |f2 / f3| is more preferably 1.0 or less, and even more preferably 0.9 or less.

[0075] <Formula (11)> 0.5≦f1 / ft≦1.0 (11) however, f1: focal length of the first lens group ft: focal length at the telephoto end of the zoom lens

[0076] Equation (11) defines the ratio of the focal length of the first lens group to the focal length of the zoom lens at the telephoto end. It is preferable for the zoom lens to satisfy equation (11) from the perspective of effectively correcting aberrations at the telephoto end.

[0077] If f1 / ft is less than 0.5, the focal length at the telephoto end can be increased, but spherical aberration at the telephoto end may be overcorrected, making it difficult to achieve the desired optical performance of the zoom lens at the telephoto end. If f1 / ft is greater than 1.0, spherical aberration at the telephoto end may be insufficiently corrected, making it difficult to achieve the desired optical performance of the zoom lens at the telephoto end. From the viewpoint of effectively correcting aberration at the telephoto end of the zoom lens, f1 / ft is more preferably 0.55 or more, and even more preferably 0.60 or more. Furthermore, from the viewpoint of effectively correcting aberration at the telephoto end of the zoom lens, f1 / ft is more preferably 0.95 or less, and even more preferably 0.90 or less.

[0078] <Formula (12)> 1.0≦D23w / fw≦3.0 (12) however, fw: focal length at the wide-angle end of the zoom lens D23w: The distance on the optical axis from the surface of the lens in the second lens group closest to the image plane to the surface of the lens in the third lens group closest to the object at the wide-angle end.

[0079] Equation (12) defines the ratio of the distance from the surface of the lens in the second lens group closest to the image plane to the surface of the lens in the third lens group closest to the object (the distance between the second and third lens groups) at the wide-angle end to the focal length of the zoom lens at the wide-angle end. It is preferable for a zoom lens to satisfy equation (12) from the perspective of realizing a compact zoom lens (reducing the overall length of the zoom lens) and from the perspective of realizing a wider focal length at the wide-angle end.

[0080] If D23w / fw is less than 1.0, it is easy to reduce the size of the zoom lens, but it may be difficult to further increase the focal length at the wide-angle end. If D23w / fw is greater than 3.0, it is easy to further increase the focal length at the wide-angle end, but it may be difficult to reduce the size of the zoom lens. From the viewpoint of realizing a compact zoom lens and an even wider focal length at the wide-angle end, D23w / fw is more preferably 1.3 or more, and even more preferably 1.6 or more. Furthermore, from the viewpoint of realizing a compact zoom lens and an even wider focal length at the wide-angle end, D23w / fw is more preferably 2.0 or less, and even more preferably 1.9 or less.

[0081] [Imaging device] An imaging device according to one embodiment of the present invention includes the zoom lens according to the present embodiment described above. The configuration of the imaging device according to this embodiment is shown schematically in Fig. 9. As shown in Fig. 9, imaging device 1 includes a main body 2 and a lens barrel 3. Imaging device 1 is, for example, a mirrorless single-lens camera.

[0082] The main body 2 has an image sensor 21 and a cover glass CG. The image sensor 21 is an element that converts an optical image into an electrical signal, and is, for example, a solid-state image sensor. Examples of solid-state image sensors include a CCD (Charge Coupled Device) sensor and a CMOS (Complementary Metal Oxide Semiconductor) sensor.

[0083] The lens barrel 3 is detachably attached to the main body 2, and contains a first lens group G1, a second lens group G2, a third lens group G3, a fourth lens group G4, and a fifth lens group G5 in this order on an optical axis OA, which is an optical axis common to the lens groups of the lens barrel 3 and the image sensor 21 of the main body 2.

[0084] The first lens group G1 has a positive refractive power as a whole and is fixed in the direction along the optical axis OA (hereinafter also referred to as the "optical axis direction"). The first lens group G1 includes, for example, a lens L1 and a lens L2 from the object side. The lens L1 is a cemented lens.

[0085] The second lens group G2 has negative refractive power as a whole and is configured to be movable in the optical axis direction. The second lens group G2 includes, for example, from the object side, lenses L3 and L4. Lens L4 is a cemented lens.

[0086] The third lens group G3 has a positive refractive power as a whole and is fixed in the optical axis direction. The third lens group G3 includes, for example, an aperture stop S and a lens L5 from the object side.

[0087] The fourth lens group G4 has positive refractive power as a whole and is configured to be movable in the optical axis direction. The fourth lens group G4 includes, for example, from the object side, lenses L6 and L7. Lens L7 is a cemented lens. The fourth lens group G4 is also configured to be movable in the optical axis direction during focusing.

[0088] The fifth lens group G5 has negative refractive power as a whole and is fixed in the optical axis direction. The fifth lens group G5 includes, for example, lenses L8 and L9 from the object side. Lens L8 is a cemented lens consisting of a negative lens and a positive lens. Lens L9 is a meniscus lens convex toward the image side.

[0089] For example, when the fourth lens group G4 and the fifth lens group G5 are the rear group, the third lens group G3 and the rear group have a positive refractive power as a whole. The first lens group G1 to the fifth lens group G5 satisfy at least one of the above-mentioned formulas (1) to (12). That is, the first lens group G1 to the fifth lens group G5 correspond to the zoom lens of the above-mentioned embodiment.

[0090] Since the imaging device 1 has the zoom lens of this embodiment described above, it can correct axial chromatic aberration, lateral chromatic aberration, and field curvature aberration at the same time, and has high optical performance despite its small size.

[0091] The imaging device 1 may be a mirrorless single-lens camera, a security camera, a digital still camera, a medical camera, or any other type of device. The zoom lens of this embodiment can simultaneously correct axial chromatic aberration, lateral chromatic aberration, and field curvature aberration, and has high optical performance despite its compact size, and therefore can be applied to imaging devices for a variety of purposes.

[0092] Note that the imaging device according to the embodiment of the present invention may include another component capable of fixing an image focused by the zoom lens, instead of the imaging element 21. Examples of such another component include silver halide film.

[0093] Furthermore, the imaging device according to the embodiment of the present invention may include an additional optical element in the optical configuration described above, within the scope of obtaining the effects of the present invention and depending on the application of the imaging device. For example, the imaging device may include a plane-parallel plate having no substantial refractive power as the additional optical element, instead of the cover glass CG. Examples of the additional optical element include an infrared cut filter (IRCF).

[0094] 〔summary〕 A first aspect of the present invention is a zoom lens (1) comprising, in order from the object side to the image plane side along the optical axis direction, a positive first lens group (G1), a negative second lens group (G2), a positive third lens group (G3), and a rear group, the rear group having two or three lens groups (G4 to G6) including a positive lens group and a negative lens group, the positive lens groups and the negative lens groups being arranged alternately, the spacing between adjacent lens groups changes during zooming, the lens groups closest to the image plane in the first lens group and the rear group are each fixed in the optical axis direction, and the lens group closest to the image plane in the rear group includes a cemented lens of a lens having negative refractive power and a lens having positive refractive power, and a meniscus lens arranged closest to the image plane with its convex surface facing the image plane, and satisfying the following formula: 0.0<|fm / fr|≦1.3 (1) 0.1≦νdn / νdp≦0.9 (2) -8.0≦f1 / f2≦-3.5 (3) however, fm: focal length of meniscus lens fr: focal length of the lens group closest to the image plane νdn: Abbe number of the lens having a negative refractive index that constitutes the cemented lens νdp: Abbe number of the lens having a positive refractive index that constitutes the cemented lens f1: focal length of the first lens group f2: focal length of the second lens group

[0095] According to the first aspect, it is possible to realize a zoom lens that is compact and has high optical performance, capable of correcting both axial chromatic aberration and chromatic aberration of magnification, and of correcting aberration of field curvature.

[0096] The second aspect of the present invention satisfies the following formula in the first aspect: The second aspect is even more effective from the viewpoint of balancing the field curvature at the wide-angle end and the field curvature at the telephoto end of the zoom lens. 0.5≦βBw / βBt≦25.0 (4) however, βBw: Lateral magnification of the rear group at the wide-angle end when focusing on infinity βBt: Lateral magnification of the rear group at the telephoto end when focused on infinity

[0097] A third aspect of the present invention is the first or second aspect, and satisfies the following formula: The third aspect is even more effective from the viewpoint of favorable correction of aberrations at the wide-angle end. 0.0<|f3 / fBw|≦1.0 (5) however, f3: focal length of the third lens group fBw: focal length at the wide-angle end of the rear group

[0098] A fourth aspect of the present invention is any one of the first to third aspects, and satisfies the following formula: The fourth aspect is even more effective from the viewpoint of achieving a good balance between the curvature of field at the wide-angle end and the curvature of field at the telephoto end. 0.5≦fBw / fBt≦5.0 (6) however, fBw: focal length at the wide-angle end of the rear group fBt: focal length at the telephoto end of the rear group

[0099] A fifth aspect of the present invention, in any one of the first to fourth aspects, satisfies the following formula: The fifth aspect is even more effective from the viewpoint of favorable correction of aberrations at the telephoto end. 0.5≦D12t / f3≦4.5 (7) however, D12t: The distance on the optical axis from the surface of the lens in the first lens group closest to the object to the surface of the lens in the second lens group closest to the image plane at the telephoto end. f3: focal length of the third lens group

[0100] A sixth aspect of the present invention, in any one of the first to fifth aspects, satisfies the following formula: The sixth aspect is even more effective from the viewpoint of favorable correction of aberrations at the telephoto end. 0.1≦f3 / ft≦1.0 (8) however, f3: focal length of the third lens group ft: focal length at the telephoto end of the zoom lens

[0101] A seventh aspect of the present invention is any one of the first to sixth aspects, wherein the following formula is satisfied: The seventh aspect is even more effective from the viewpoint of excellent correction of aberrations at the wide-angle end and the telephoto end. 0.1≦f3 / f1≦1.0 (9) however, f3: focal length of the third lens group

[0102] An eighth aspect of the present invention is any one of the first to seventh aspects, wherein the following formula is satisfied: The eighth aspect is even more effective from the viewpoint of favorable correction of aberrations at the wide-angle end. 0.1≦|f2 / f3|≦1.2 (10) however, f3: focal length of the third lens group

[0103] A ninth aspect of the present invention is any one of the first to eighth aspects, wherein the following formula is satisfied: The ninth aspect is even more effective from the viewpoint of favorable correction of aberrations at the telephoto end. 0.5≦f1 / ft≦1.0 (11) however, ft: focal length at the telephoto end of the zoom lens

[0104] A tenth aspect of the present invention is any one of the first to ninth aspects, wherein the following formula is satisfied: The tenth aspect is even more effective from the viewpoint of realizing a compact zoom lens (reducing the overall length of the zoom lens) and from the viewpoint of realizing a wider focal length at the wide-angle end. 1.0≦D23w / fw≦3.0 (12) however, fw: focal length at the wide-angle end of the zoom lens D23w: The distance on the optical axis from the surface of the lens in the second lens group closest to the image plane to the surface of the lens in the third lens group closest to the object at the wide-angle end.

[0105] An eleventh aspect of the present invention is an image pickup apparatus including the zoom lens according to any one of the first to tenth aspects. According to the eleventh aspect, it is possible to realize an image pickup apparatus that is small in size and has high optical performance, capable of correcting both axial chromatic aberration and lateral chromatic aberration, and of correcting field curvature aberration.

[0106] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0107] According to the above-described embodiment, it is possible to provide a zoom lens and an image pickup apparatus that simultaneously corrects axial chromatic aberration, lateral chromatic aberration, and field curvature aberration, thereby providing a zoom lens and an image pickup apparatus that are small and have high optical performance. The present invention, which has such effects, is expected to contribute to the achievement of, for example, Goal 9 of the Sustainable Development Goals (SDGs) advocated by the United Nations, "Build resilient infrastructure, promote inclusive and sustainable industrialization, and promote innovation and foster resilience." [Example]

[0108] An embodiment of the present invention will now be described.

[0109] In the specifications table for each example, "No." indicates the surface number, "r" indicates the radius of curvature, "d" indicates the lens thickness or lens spacing, "Nd" indicates the refractive index for the d-line, "νd" indicates the Abbe number based on the d-line, and "H" indicates the effective radius of the lens. Additionally, an "*" next to a surface number indicates that the surface is aspherical.

[0110] In the aspherical data in each example, the aspherical surface is defined by the following formula: In the formula, "c" is the curvature (1 / r), "h" is the height from the optical axis, "k" is the conic coefficient, and "A4", "A6", "A8", and "A10" are the aspherical coefficients of each order. In the table, "E+a" is "×10 a In the following examples, all aspherical coefficients not shown in the aspherical data table are "0.00".

[0111]

number

[0112] In addition, the variable distance data in each example shows data at the wide-angle end, mid-focus position, and telephoto end, from left to right. In this data, "f" represents the focal length of the entire system (zoom lens), "FNO" represents the F-number of the entire system, and "W" represents the half angle of view (°) of the entire system. In each example, "D(n)" (n is an integer) represents the variable distance on the optical axis of the lens surfaces that changes when changing magnification or focusing. In addition, the units of "r," "d," "H," and "f" are all mm.

[0113] In addition, in the diagrams of the lens configurations of each embodiment (FIGS. 1, 3, 5, and 7), the upper diagrams show the lens configurations at the wide-angle end, and the lower diagrams show the lens configurations at the telephoto end. The arrows between the two diagrams show, from the left, the path of movement of the second lens group G2, the fourth lens group G4, or the fifth lens group G5 from the wide-angle end to the telephoto end. The arrow F indicates the direction of movement of the focus group during focusing. The symbols G1 to G6 in the diagrams represent the first to sixth lens groups, respectively, and the symbol CG represents the cover glass.

[0114] Furthermore, the three longitudinal aberration diagrams (FIGS. 2, 4, 6, and 8) for each example show, from the top of the diagram, longitudinal aberration diagrams at the wide-angle end, longitudinal aberration diagrams at the intermediate focal position, and longitudinal aberration diagrams at the telephoto end. Each longitudinal aberration diagram shows, from left to right, spherical aberration (SA (mm)), astigmatism (AST (mm)), and distortion (DIS (%)). In the spherical aberration diagrams, the vertical axis represents the F-number (indicated by FNO in the diagrams), with the solid line representing the d-line, the short-dashed line representing the F-line, and the long-dashed line representing the C-line characteristics. In the astigmatism diagrams, the vertical axis represents the angle of view (indicated by ω in the diagrams), with the solid line representing the sagittal plane (indicated by S in the diagrams) and the dashed line representing the meridional plane (indicated by T in the diagrams). In the diagram of distortion, the vertical axis represents the angle of view (indicated by ω in the diagram).

[0115] Example 1 As shown in Figure 1, the zoom lens of Example 1 has a first lens group G1 with positive refractive power, a second lens group G2 with negative refractive power, a third lens group G3 with positive refractive power, and a rear group. The rear group is composed of a fourth lens group G4 with positive refractive power and a fifth lens group G5 with negative refractive power. The third lens group G3 and the rear group have positive refractive power as a whole.

[0116] The first lens group G1 is composed of a cemented lens made up of a concave meniscus lens convex toward the object side and a biconvex lens, and a convex meniscus lens convex toward the object side.

[0117] The second lens group G2 is composed of a biconcave lens, and a biconcave lens and a convex meniscus lens whose convex surface faces the object side.

[0118] The third lens group G3 is composed of an aperture stop S and a biconvex aspherical lens.

[0119] The fourth lens group G4 is composed of a biconvex aspherical lens, and a cemented lens consisting of a concave meniscus lens convex on the object side and a biconvex lens.

[0120] The fifth lens group G5 is composed of a cemented lens consisting of a concave meniscus lens whose convex surface faces the object side and a biconvex lens, and a concave meniscus lens whose convex surface faces the image surface side.

[0121] The first lens group G1, the third lens group G3, and the fifth lens group G5 are all fixed in the optical axis direction. The second lens group G2 moves on an orbit that gradually approaches the image plane when zooming from the wide-angle end to the telephoto end. The fourth lens group G4 moves on an orbit that moves away from and then approaches the image plane when zooming from the wide-angle end to the telephoto end. The fourth lens group G4 is a focus group and moves toward the object side when focusing.

[0122] Table 1 shows the specifications for Example 1, Table 2 shows data on aspherical surfaces, Table 3 shows data on variable spacing, and Table 4 shows the focal lengths of each lens group. In Example 1, surface number 11 represents the aperture stop S, surface numbers 12 to 15 are all aspherical, surface number 24 represents the object-side surface of the cover glass CG, surface number 25 represents the image-side surface of the cover glass CG, and IMG represents the position of the image plane. Furthermore, the lens configurations at the wide-angle end and telephoto end of the zoom lens of Example 1 are shown in FIG. 1, and the longitudinal aberration at the wide-angle end, the longitudinal aberration at the intermediate focal position, and the longitudinal aberration at the telephoto end are shown in FIG. 2.

[0123] [Table 1] Specification table No. rd Nd νd H 1 42.3697 0.9000 1.92119 23.96 8.78 2 19.2534 3.5739 1.55032 75.50 8.35 3 -88.1148 0.1500 8.15 4 15.7915 2.6772 1.80420 46.50 7.52 5 59.4762 D(5) 7.14 6 -60.0503 0.6000 2.05090 26.94 3.68 7 5.7612 1.4519 3.08 8 -13.7861 0.6000 1.61800 63.39 3.05 9 6.0739 1.9776 1.92286 20.88 3.05 10 79.9199 D(10) 2.98 11 INF 0.4000 2.60 12* 9.4389 1.5259 1.55332 71.68 2.71 13* -75.8369 D(13) 2.69 14* 7.8035 1.7274 1.58313 59.46 2.61 15* -18.3357 0.5292 2.57 16 49.6667 0.6000 1.91082 35.25 2.48 17 5.5261 2.1126 1.49700 81.61 2.39 18 -15.0424 D(18) 2.43 19 40.2457 0.6000 1.95375 32.32 2.35 20 5.1779 2.8111 1.56732 42.84 2.28 21 -5.1779 0.5152 2.38 22 -4.5037 0.6000 1.77250 49.62 2.27 23 -26.0363 4.0000 2.42 24 INF 0.8000 1.51633 64.14 3.13 25 INF 1.1075 3.22 IMG

[0124] [Table 2] Aspheric data No. k A4 A6 A8 A10 12 0.00000E+00 -2.23006E-04 -1.70926E-05 3.72701E-06 -3.02673E-07 13 0.00000E+00 1.04916E-04 -1.11960E-05 4.44368E-06 -3.99425E-07 14 0.00000E+00 -2.38429E-04 2.65228E-05 5.47334E-07 -5.71780E-08 15 0.00000E+00 3.57140E-04 3.25152E-05 -1.18100E-06 6.77087E-08

[0125] [Table 3] Variable interval data Wide-angle end Mid-focus position Telephoto end f 6.1876 13.4772 29.2826 FNO 3.0622 3.3878 3.5128 W 29.8125 13.5360 6.2412 D(5) 1.1066 6.1969 10.1057 D(10) 11.0366 5.9463 2.0375 D(13) 2.9551 1.6231 1.1466 D(18) 0.6000 1.9319 2.4085

[0126] [Table 4] Focal length of each lens group Lens group Surface number Focal length G1 1-5 21.3936 G2 6-10 -4.8217 G3 12-13 15.2678 G4 14-18 12.1195 G5 19-23 -12.6180

[0127] Example 2 3, the zoom lens of Example 2 includes 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, and a rear group. The rear group is composed of a fourth lens group G4 having negative refractive power and a fifth lens group G5 having positive refractive power. The third lens group G3 and the rear group collectively have positive refractive power.

[0128] The first lens group G1 is composed of a cemented lens made up of a concave meniscus lens convex toward the object side and a biconvex lens, and a convex meniscus lens convex toward the object side.

[0129] The second lens group G2 is composed of a biconcave lens, a biconcave lens, and a biconvex lens.

[0130] The third lens group G3 is composed of an aperture stop S, a biconvex aspherical lens, and a cemented lens consisting of a concave meniscus lens convex on the object side and a biconvex lens.

[0131] The fourth lens group G4 is composed of an aspherical concave meniscus lens element whose convex surface faces the object side.

[0132] The fifth lens group G5 is composed of a cemented lens consisting of a concave meniscus lens whose convex surface faces the object side and a biconvex lens, and a concave meniscus lens whose convex surface faces the image surface side.

[0133] The first lens group G1, the third lens group G3, and the fifth lens group G5 are all fixed in the optical axis direction. The second lens group G2 moves on an orbit that gradually approaches the image plane when changing magnification from the wide-angle end to the telephoto end. The fourth lens group G4 moves on an orbit that approaches the image plane and then moves away from it when changing magnification from the wide-angle end to the telephoto end. The fourth lens group G4 is a focus group and moves toward the image plane when focusing.

[0134] Table 5 shows the specifications for Example 2, Table 6 shows data on aspherical surfaces, Table 7 shows data on variable spacing, and Table 8 shows the focal lengths of each lens group. In Example 2, surface number 12 represents aperture stop S, surface numbers 13, 14, and 18 and 19 are all aspherical, surface number 25 represents the object-side surface of cover glass CG, surface number 26 represents the image-side surface of cover glass CG, and IMG represents the position of the image plane. Furthermore, the lens configurations at the wide-angle end and telephoto end of the zoom lens of Example 2 are shown in FIG. 3, and the longitudinal aberration at the wide-angle end, the longitudinal aberration at the intermediate focal position, and the longitudinal aberration at the telephoto end are shown in FIG. 4.

[0135] [Table 5] Specifications table No. rd Nd νd H 1 58.2084 1.0000 1.92119 23.96 9.38 2 22.0146 4.1011 1.59282 68.62 8.95 3 -87.5297 0.1500 8.69 4 17.8923 2.7814 1.80420 46.50 7.92 5 67.0344 D(5) 7.52 6 -103.9671 0.6000 1.90043 37.37 4.36 7 6.9647 1.7708 3.64 8 -10.9213 0.6000 1.75500 52.32 3.61 9 15.7412 0.1500 3.63 10 13.6215 1.6851 1.92286 20.88 3.68 11 -78.8051 D(11) 3.64 12 INF 0.4000 2.49 13* 10.3114 1.9016 1.55332 71.68 2.76 14* -17.3359 0.1500 2.98 15 13.5581 0.6000 1.87070 40.73 3.09 16 7.2414 2.7282 1.55397 71.76 3.06 17 -8.0000 D(17) 3.14 18* 667.5107 0.6000 1.61881 63.85 2.79 19* 7.3600 D(19) 2.66 20 24.0067 0.6000 2.01725 20.42 2.76 21 5.6339 2.6991 1.71774 37.06 2.72 22 -8.0000 0.4182 2.79 23 -5.0919 0.6000 1.64038 35.59 2.77 24 -11.5986 4.0000 2.92 25 INF 0.7000 1.51633 64.14 3.21 26 INF 0.9995 3.24 IMG

[0136] [Table 6] Aspheric data No. k A4 A6 A8 A10 13 0.00000E+00 -7.47996E-04 -2.04389E-05 -2.48403E-06 -4.82808E-09 14 0.00000E+00 3.41776E-04 -1.80443E-05 -2.37888E-06 4.54308E-08 18 0.00000E+00 -1.02872E-04 -1.09824E-04 2.00165E-05 -7.21216E-07 19 0.00000E+00 -4.01938E-04 -1.67627E-04 2.93579E-05 -1.13014E-06

[0137] [Table 7] Variable interval data Wide-angle end Mid-focus position Telephoto end f 6.1784 13.4963 29.2640 FNO 2.9731 3.0279 3.0254 W 29.4892 13.1797 6.0556 D(5) 1.0000 7.1089 11.6923 D(11) 11.1037 4.9948 0.4111 D(17) 0.7000 1.8909 2.1600 D(19) 2.9218 1.7309 1.4619

[0138] [Table 8] Focal length of each lens group Lens group Surface number Focal length G1 1-5 24.2432 G2 6-11 -5.63711 G3 13-17 6.56446 G4 18-19 -12.0306 G5 20-24 81.2007

[0139] Example 3 5, the zoom lens of Example 3 has a first lens group G1 with positive refractive power, a second lens group G2 with negative refractive power, a third lens group G3 with positive refractive power, and a rear group. The rear group is composed of a fourth lens group G4 with positive refractive power, a fifth lens group G5 with negative refractive power, and a sixth lens group G6 with positive refractive power. The third lens group G3 and the rear group have positive refractive power as a whole.

[0140] The first lens group G1 is composed of a cemented lens made up of a concave meniscus lens convex toward the object side and a biconvex lens, and a convex meniscus lens convex toward the object side.

[0141] The second lens group G2 is composed of a biconcave lens and a cemented lens made of a biconcave lens and a convex meniscus lens whose convex surface faces the object side.

[0142] The third lens group G3 is composed of an aperture stop S and a biconvex aspherical lens.

[0143] The fourth lens group G4 is composed of a biconvex aspherical lens.

[0144] The fifth lens group G5 is composed of a cemented lens consisting of a biconcave lens and a convex meniscus lens whose convex surface faces the object side.

[0145] The sixth lens group G6 is composed of a cemented lens consisting of a concave meniscus lens whose convex surface faces the object side and a biconvex lens, and a concave meniscus lens whose convex surface faces the image surface side.

[0146] The first lens group G1, the third lens group G3, and the sixth lens group G6 are each fixed in the optical axis direction. The second lens group G2 moves on an orbit that gradually approaches the image plane when changing magnification from the wide-angle end to the telephoto end. The fourth lens group G4 moves on an orbit that gradually moves away from the image plane when changing magnification from the wide-angle end to the telephoto end. The fifth lens group G5 moves on an orbit that approaches the object and then stops when changing magnification from the wide-angle end to the telephoto end. The fifth lens group G5 is also a focus group and moves toward the object when focusing.

[0147] Table 9 shows the specifications for Example 3, Table 10 shows data on aspherical surfaces, Table 11 shows data on variable spacing, and Table 12 shows the focal lengths of each lens group. In Example 3, surface number 11 represents the aperture stop S, surface numbers 12 to 15 are all aspherical, surface number 24 represents the object-side surface of the cover glass CG, surface number 25 represents the image-side surface of the cover glass CG, and IMG represents the position of the image plane. Furthermore, the lens configurations at the wide-angle end and telephoto end of the zoom lens of Example 3 are shown in FIG. 5, and the longitudinal aberration at the wide-angle end, the longitudinal aberration at the intermediate focal position, and the longitudinal aberration at the telephoto end are shown in FIG. 6.

[0148] [Table 9] Specifications table No. rd Nd νd H 1 26.9583 0.9000 1.92119 23.96 8.35 2 15.5198 3.4753 1.55032 75.50 7.87 3 -605.3956 0.1500 8.15 4 16.3899 2.5251 1.80420 46.50 7.52 5 80.1423 D(5) 6.79 6 -47.0397 0.6000 2.05090 26.94 3.70 7 5.8214 1.3668 3.08 8 -14.0339 0.6000 1.61800 63.39 3.05 9 5.8249 1.9672 1.92286 20.88 3.03 10 50.3110 D(10) 2.98 11 INF 0.4000 2.60 12* 11.9637 1.4583 1.55332 71.68 2.70 13* -30.0000 D(13) 2.71 14* 6.3853 2.1048 1.58313 59.46 2.61 15* -10.1707 D(15) 2.78 16 -76.3346 0.6000 1.91082 35.25 2.60 17 5.0000 1.9577 1.49700 81.61 2.46 18 34.8156 D(18) 2.48 19 72.1688 0.6000 1.95375 32.32 2.35 20 7.5853 2.6333 1.56732 42.84 2.53 21 -7.5853 0.8916 2.71 22 -4.9363 0.6000 1.77250 49.62 2.68 23 -6.8806 4.0000 2.87 24 INF 0.8000 1.51633 64.14 3.26 25 INF 1.1009 3.31 IMG

[0149] [Table 10] Aspheric data No. k A4 A6 A8 A10 12 0.00000E+00 -1.39257E-04 -2.37908E-05 3.06866E-06 -2.40691E-07 13 0.00000E+00 1.33310E-04 -2.46713E-05 4.47520E-06 -3.16058E-07 14 0.00000E+00 -2.81132E-04 2.41184E-05 -8.83589E-07 1.85790E-07 15 0.00000E+00 8.32968E-04 2.94463E-05 -2.68655E-06 3.21648E-07

[0150] [Table 11] Variable interval data f 6.1829 13.4645 29.2487 FNO 3.0725 3.3727 3.4996 W 30.1802 13.5598 6.2336 D(5) 1.1012 5.4500 9.0062 D(10) 9.9644 5.6156 2.0593 D(13) 4.1357 1.8021 0.8503 D(15) 0.4185 0.4263 0.3977 D(18) 0.6000 2.9258 3.9062

[0151] [Table 12] Focal length of each lens group Lens group Surface number Focal length G1 1-5 20.0966 G2 6-10 -4.6041 G3 12-13 15.6512 G4 14-15 7.0573 G5 16-18 -9.0001 G6 19-23 1011.8900

[0152] Example 4 7, the zoom lens of Example 4 has a first lens group G1 with positive refractive power, a second lens group G2 with negative refractive power, a third lens group G3 with positive refractive power, and a rear group. The rear group is composed of a fourth lens group G4 with negative refractive power, a fifth lens group G5 with positive refractive power, and a sixth lens group G6 with negative refractive power. The third lens group G3 and the rear group have positive refractive power as a whole.

[0153] The first lens group G1 is composed of a cemented lens made up of a concave meniscus lens convex toward the object side and a convex meniscus lens convex toward the object side, and a convex meniscus lens convex toward the object side.

[0154] The second lens group G2 is composed of a concave meniscus lens whose convex surface faces the object side, and a cemented lens made of a biconcave lens and a convex meniscus lens whose convex surface faces the object side.

[0155] The third lens group G3 is composed of an aperture stop S and a biconvex aspherical lens.

[0156] The fourth lens group G4 is composed of a biconvex aspherical lens and a concave meniscus lens that is convex on the object side.

[0157] The fifth lens group G5 is composed of a biconvex lens.

[0158] The sixth lens group G6 is composed of a cemented lens of a biconcave lens and a biconvex lens, and a concave meniscus lens whose convex surface faces the image surface side.

[0159] The first lens group G1, the third lens group G3, and the sixth lens group G6 are each fixed in the optical axis direction. The second lens group G2 moves on an orbit that gradually approaches the image plane when changing magnification from the wide-angle end to the telephoto end. The fourth lens group G4 moves on an orbit that gradually approaches the object when changing magnification from the wide-angle end to the telephoto end. The fifth lens group G5 moves on an orbit that approaches the object and then stops when changing magnification from the wide-angle end to the telephoto end. The fifth lens group G5 is a focus group and moves toward the object when focusing.

[0160] Table 13 shows the specifications for Example 4, Table 14 shows data on aspherical surfaces, Table 15 shows data on variable spacing, and Table 16 shows the focal lengths of each lens group. In Example 4, surface number 11 represents the aperture stop S, surface numbers 12 to 15 are all aspherical, surface number 25 represents the object-side surface of the cover glass CG, surface number 26 represents the image-side surface of the cover glass CG, and IMG represents the position of the image plane. Furthermore, Fig. 7 shows the lens configurations at the wide-angle end and telephoto end of the zoom lens of Example 4, and Fig. 8 shows the longitudinal aberration at the wide-angle end, the longitudinal aberration at the intermediate focal position, and the longitudinal aberration at the telephoto end.

[0161] [Table 13] Specifications table No. rd Nd νd H 1 19.7080 0.9000 1.92119 23.96 8.94 2 12.5329 3.6226 1.55032 75.50 8.26 3 47.2346 0.1500 8.15 4 14.9784 2.6502 1.80420 46.50 7.52 5 58.0021 D(5) 7.05 6 74.7698 0.6000 2.05090 26.94 3.72 7 5.0301 1.5917 3.03 8 -15.1379 0.6000 1.61800 63.39 2.97 9 5.2058 1.8609 1.92286 20.88 2.90 10 17.1578 D(10) 2.98 11 INF 0.4000 2.60 12* 6.9869 1.8026 1.55332 71.68 2.92 13* -41.5091 D(13) 2.85 14* 11.3322 1.4116 1.58313 59.46 2.61 15* -52.3384 0.1000 2.71 16 18.9669 0.6000 1.91082 35.25 2.69 17 7.6661 D(17) 2.61 18 7.6719 1.9876 1.49700 81.61 2.65 19 -12.3139 D(19) 2.61 20 -35.4244 0.6000 2.00100 29.13 2.35 21 5.0000 2.7645 1.56732 42.84 2.23 22 -5.0000 0.5816 2.38 23 -4.1813 0.6000 1.77250 49.62 2.29 24 -11.3622 4.0000 2.48 25 INF 0.8000 1.51633 64.14 3.15 26 INF 1.0914 3.23 IMG

[0162] [Table 14] Aspheric data No. k A4 A6 A8 A10 12 0.00000E+00 -3.26880E-04 -2.26616E-07 1.32268E-06 -4.13017E-08 13 0.00000E+00 1.37301E-04 3.49980E-06 1.97559E-06 -8.26982E-08 14 0.00000E+00 -5.75516E-04 2.93998E-05 -3.30836E-06 1.05175E-07 15 0.00000E+00 8.32680E-05 4.53010E-05 -6.38160E-06 3.27371E-07

[0163] [Table 15] Variable interval data Wide-angle end Mid-focus position Telephoto end f 6.1833 13.4657 32.7571 FNO 3.0614 3.3354 4.6586 W 28.8925 13.7789 5.6650 D( 5) 1.0000 6.0024 10.0370 D(10) 10.9350 5.9327 1.8981 D(13) 3.3895 1.9842 0.8000 D(17) 0.2760 0.2988 0.4223 D(19) 0.6000 1.9823 3.0422

[0164] [Table 16] Focal length of each lens group Lens group Surface number Focal length G1 1-5 22.0719 G2 6-10 4.0125 G3 12-13 10.9530 G4 14-17 -1000.0200 G5 18-19 9.8357 G6 20-24 -8.7991

[0165] Table 17 shows the calculated values ​​from the above formulas in Examples 1 to 4. Table 18 also shows the numerical values ​​in the above formulas in Examples 1 to 4.

[0166] [Table 17] Formula Example 1 Example 2 Example 3 Example 4 (1) |fm / fr| 0.5656 0.1811 0.0258 1.0101 (2) νdn / νdp 0.7544 0.5510 0.7544 0.6800 (3) f1 / f2 -4.4370 -4.3006 -4.3650 -5.5007 (4) βBw / βBt 4.6853 1.0671 21.7051 2.7823 (5) |f3 / fBw| 0.5924 0.4352 0.8579 0.0925 (6) fBw / fBt 1.3048 1.0225 0.9910 4.0255 (7) D12t / f3 1.4433 3.7369 1.3156 2.0097 (8) f3 / ft 0.5214 0.2243 0.5351 0.3344 (9) f3 / f1 0.7137 0.2708 0.7788 0.4962 (10) |f2 / f3| 0.3158 0.8587 0.2942 0.3663 (11) f1 / ft 0.7306 0.8284 0.6871 0.6738 (12) D23w / fw 1.8483 1.8619 1.6763 1.8332

[0167] [Table 18] Example 1 Example 2 Example 3 Example 4 fw 6.1876 6.1784 6.1829 6.1833 ft 29.2826 29.2640 29.2487 32.7571 f1 21.3936 24.2432 20.0966 22.0719 f2 -4.8217 -5.6371 -4.6041 -4.0125 f3 15.2678 6.5645 15.6512 10.9530 fm -7.1361 -14.7030 -26.1274 -8.8879 fr -12.6180 81.2007 1011.8900 -8.7991 fBw 25.7740 -15.0835 18.2440 118.4320 fBt 19.7531 -14.7510 18.4092 29.4204 νdn 32.3200 20.4200 32.3200 29.1300 νdp 42.8400 37.0600 42.8400 42.8400 βBw 0.2910 1.8074 0.2008 0.6681 βBt 0.0621 1.6938 0.0093 0.2401 D12t 22.0361 24.5307 20.5907 22.0123 D23w 11.4366 11.5037 10.3644 11.3350 [Explanation of symbols]

[0168] 1. Imaging device 2 Main unit 3 Telescope 21 Image sensor CG cover glass F Arrow indicating the direction of focus group movement G1~G6 1st lens group to 6th lens group IMG image plane L1~L9 lenses OA optical axis S aperture stop

Claims

1. the lens comprises, in order from the object side to the image plane side along the optical axis direction, 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 rear lens group; the rear group has two or three lens groups including a lens group having positive refractive power and a lens group having negative refractive power, and the lens group having positive refractive power and the lens group having negative refractive power are arranged alternately, a distance between adjacent lens groups changes during zooming, and the first lens group and the lens group closest to the image plane in the rear group are fixed in the optical axis direction, the lens group closest to the image surface in the rear group includes a cemented lens of a lens having negative refractive power and a lens having positive refractive power, and a meniscus lens that is positioned closest to the image surface with its convex surface facing the image surface, A zoom lens that satisfies the following formula: 0.0<|fm / fr|≦1.3 (1) 0.1≦νdn / νdp≦0.9 (2) −8.0≦f1 / f2≦−3.5 (3) however, fm: focal length of the meniscus lens fr: focal length of the lens group closest to the image plane νdn: Abbe number of the lens having a negative refractive index that constitutes the cemented lens νdp: Abbe number of the lens having a positive refractive index that constitutes the cemented lens f1: focal length of the first lens group f2: focal length of the second lens group

2. 2. The zoom lens of claim 1, wherein the following formula is satisfied: 0.5≦βBw / βBt≦25.0 (4) however, βBw: lateral magnification of the rear group at the wide-angle end when focused on infinity βBt: lateral magnification of the rear group at the telephoto end when focused on infinity

3. 2. The zoom lens of claim 1, wherein the following formula is satisfied: 0.0<|f3 / fBw|≦1.0 (5) however, f3: focal length of the third lens group fBw: focal length of the rear group at the wide-angle end

4. 2. The zoom lens of claim 1, wherein the following formula is satisfied: 0.5≦fBw / fBt≦5.0 (6) however, fBw: focal length of the rear group at the wide-angle end fBt: focal length of the rear group at the telephoto end

5. 2. The zoom lens of claim 1, wherein the following formula is satisfied: 0.5≦D12t / f3≦4.5 (7) however, D12t: the distance on the optical axis from the surface of the lens in the first lens group closest to the object to the surface of the lens in the second lens group closest to the image plane at the telephoto end f3: focal length of the third lens group

6. 2. The zoom lens of claim 1, wherein the following formula is satisfied: 0.1≦f3 / ft≦1.0 (8) however, f3: focal length of the third lens group ft: focal length at the telephoto end of the zoom lens

7. 2. The zoom lens of claim 1, wherein the following formula is satisfied: 0.1≦f3 / f1≦1.0 (9) however, f3: focal length of the third lens group

8. 2. The zoom lens of claim 1, wherein the following formula is satisfied: 0.1≦|f2 / f3|≦1.2 (10) however, f3: focal length of the third lens group

9. 2. The zoom lens of claim 1, wherein the following formula is satisfied: 0.5≦f1 / ft≦1.0 (11) however, ft: focal length at the telephoto end of the zoom lens

10. 2. The zoom lens of claim 1, wherein the following formula is satisfied: 1.0≦D23w / fw≦3.0 (12) however, fw: focal length at the wide-angle end of the zoom lens D23w: the distance on the optical axis from the surface of the lens in the second lens group closest to the image plane to the surface of the lens in the third lens group closest to the object at the wide-angle end

11. An imaging device comprising the zoom lens according to any one of claims 1 to 10.

Images