Zoom lens and imaging device

Abstract

To realize a zoom lens and imaging device that can achieve both miniaturization and high performance. [Solution] The zoom lens consists of, in order from the object side, a positive first lens group, a negative second lens group, an nth group including one or more lens groups, a negative (n+1)th lens group, a positive (n+2)th lens group, and a negative (n+3)th lens group. During zooming, the first lens group is fixed in the direction of the optical axis, the final lens is a negative lens, and satisfies a specific equation relating to the (n+2)th and (n+3)th lens groups.

Description

Technical Field

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

Background Art

[0002] Various imaging devices such as mirrorless single-lens cameras, digital still cameras, and security cameras are known, and many imaging devices with sufficiently high performance are found in the market. A zoom lens that exhibits optical performance in such a conventional imaging device is known to include seven lens groups with refractive powers of positive, negative, positive, positive, negative, positive, and negative from the object side (see, for example, Patent Documents 1 to 3).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] On the other hand, there is still room for improvement in conventional zoom lenses from the viewpoints of high performance and convenience. For example, in the zoom lens of Patent Document 1, the first lens group is fixed, the overall length of the zoom lens is fixed, while the total thickness of the other lens groups is large, and it may be difficult to shorten the overall length of the zoom lens. Further, in the zoom lens of Patent Document 2, the first lens group is fixed, the overall length of the zoom lens is fixed, while sufficient aberration correction may be difficult due to the relationship of the refractive powers of the other lens groups. Further, in the zoom lens of Patent Document 3, since the first lens group moves in the optical axis direction, a sliding mechanism is required for this purpose, and miniaturization in the radial direction may be difficult.

[0005] One aspect of the present invention aims to realize a zoom lens and imaging device that can achieve both miniaturization and high performance. [Means for solving the problem]

[0006] To solve the above problems, a zoom lens according to one aspect of 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 nth group including one or more lens groups, an (n+1)th lens group having negative refractive power, an (n+2)th lens group having positive refractive power, and an (n+3)th lens group having negative refractive power, wherein the first lens group is fixed in the direction of the optical axis during zooming, the lens closest to the image plane has negative refractive power, and satisfies the following equation. 0.77 <f(n+2) / |f(n+3)| (1) however, f(n+2): Focal length of the aforementioned n+2 lens group f(n+3): Focal length of the aforementioned n+3 lens group

[0007] Furthermore, in order to solve the above problems, an imaging device according to one aspect of the present invention comprises the above-mentioned zoom lens and an image sensor on the image plane side of the zoom lens that converts the optical image formed by the zoom lens into an electrical signal. [Effects of the Invention]

[0008] According to one aspect of the present invention, it is possible to realize a zoom lens and an imaging device that can achieve both miniaturization and high performance. [Brief explanation of the drawing]

[0009] [Figure 1] This diagram schematically shows the lens configuration of the zoom lens of Example 1 when focusing at infinity at the wide-angle end, intermediate focal length, and telephoto end. [Figure 2] This figure shows the longitudinal aberrations at infinity focus at the wide-angle end, intermediate focal length, and telephoto end of the zoom lens of Example 1. [Figure 3] This diagram schematically shows the lens configuration of the zoom lens of Example 2 when focusing at infinity at the wide-angle end, intermediate focal length, and telephoto end. [Figure 4] This figure shows the longitudinal aberrations at infinity focus at the wide-angle end, intermediate focal length, and telephoto end of the zoom lens of Example 2. [Figure 5] This diagram schematically shows the lens configuration of the zoom lens of Example 3 when focusing at infinity at the wide-angle end, intermediate focal length, and telephoto end. [Figure 6] This figure shows the longitudinal aberrations at infinity focus at the wide-angle end, intermediate focal length, and telephoto end of the zoom lens of Example 3. [Figure 7] This diagram schematically shows the lens configuration of the zoom lens of Example 4 when focusing at infinity at the wide-angle end, intermediate focal length, and telephoto end. [Figure 8] This figure shows the longitudinal aberrations at infinity focus at the wide-angle end, intermediate focal length, and telephoto end of the zoom lens of Example 4. [Figure 9] This diagram schematically shows the lens configuration of the zoom lens of Example 5 when focusing at infinity at the wide-angle end, intermediate focal length, and telephoto end. [Figure 10] This figure shows the longitudinal aberrations at infinity focus at the wide-angle end, intermediate focal length, and telephoto end of the zoom lens of Example 5. [Figure 11] This diagram schematically shows the configuration of an imaging device according to one embodiment of the present invention. [Modes for carrying out the invention]

[0010] One embodiment of the present invention will be described in detail below. In the following description, the direction along the optical axis of the zoom lens will also be simply referred to as the "optical axis direction." Furthermore, the distance along the optical axis from the lens surface on the object side of the lens closest to the object in the zoom lens to the image plane will also be referred to as the "total optical length."

[0011] In addition, the "lens group" means a single lens that moves independently or a set of two or more lenses that move while maintaining their relative positional relationship. Also, the distance on the optical axis from the lens surface on the object side of the lens closest to the object in the lens group to the lens surface on the image side of the lens closest to the image plane in the lens group is also referred to as the "total thickness of the lens group".

[0012] A "lens" can be a single lens or a cemented lens. Examples of single lenses include biconvex lenses, plano-convex lenses, convex meniscus lenses, and concave meniscus lenses. A cemented lens has a structure in which two or more single lenses are integrated without an air gap. Also, the lens may be a spherical lens or an aspherical lens. An aspherical lens means a lens in which at least one lens surface is aspherical. Examples of aspherical lenses include composite lenses having an aspherical resin layer on at least one lens surface of the lens, and glass-molded aspherical lenses made of optical glass and having at least one lens surface with an aspherical shape. Also, a lens having a positive refractive power is also referred to as a "positive lens", and a lens having a negative refractive power is also referred to as a "negative lens".

[0013] 〔Zoom lens〕 [Optical configuration] The zoom lens according to an embodiment of the present invention is composed of, in order from the object side, a first lens group, a second lens group, an nth group including, an (n + 1)th lens group, an (n + 2)th lens group, and an (n + 3)th lens group. It is preferable from the viewpoint of achieving both miniaturization and high performance that the zoom lens consists only of the above lens groups and does not have other lens groups.

[0014] <First lens group> The first lens group has a positive refractive power. The types and arrangements of the lenses in the first lens group can be appropriately set within the range in which the first lens group as a whole exhibits the desired positive refractive power.

[0015] For example, the lens closest to the object in a zoom lens (the first lens) tends to have a large aperture. Therefore, it is preferable from the viewpoint of miniaturization by shortening the overall length for the first lens to be made of a high refractive index glass material, as shown in equation (6) described later. By making the first lens out of a high refractive index glass material, the shape factor of the first lens can be suppressed. In addition, by making the first lens out of a high refractive index glass material, the shape of the first lens that protrudes roundly towards the object side is reduced. Therefore, the risk of the first lens colliding with the ground when the zoom lens or imaging device having it is dropped is reduced, and advantages in handling are also created.

[0016] Furthermore, for example, a cemented lens can be used for the first lens of the first lens group. Having a cemented lens for the first lens is preferable from the viewpoint of achieving high performance through good aberration correction.

[0017] <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, the lens positioned closest to the object in the second lens group can be a negative lens with its concave surface facing the image plane. Using such a lens in the second lens group is preferable from the viewpoint of improving performance through good correction of aberrations.

[0018] <Group n> The nth group includes one or more lens groups. The number of lens groups included in the nth group can be appropriately set within a range in which the effects of the present invention can be obtained. Generally, a small number of lens groups in the nth group is advantageous from the viewpoint of miniaturization, while a large number is advantageous from the viewpoint of performance. From the viewpoint of achieving both miniaturization and performance, it is preferable that the number of lens groups included in the nth group be 1 to 3.

[0019] In this specification, "n" refers to the ordinal number of the lens group closest to the image plane in the nth group, within the entire zoom lens. For example, if the nth group has one lens group, that lens group is the third lens group, so n is 3. If the nth group has two lens groups, the nth group includes the third and fourth lens groups, so n is 4. If the nth group has three lens groups, the nth group includes the third, fourth, and fifth lens groups, so n is 5. Thus, in this invention, "n" is a value specific to the number of lens groups included in the nth group.

[0020] The overall refractive power of the nth group can be appropriately set within the range in which the effects of the present invention can be obtained. It is preferable for the nth group to have a positive refractive power as a whole from the viewpoint of improving performance through aberration correction and miniaturization by shortening the overall length. The nth group, which has a positive refractive power as a whole, may include a lens group having a negative refractive power, but when the number of lens groups in the nth group is two or less, it is preferable from the above viewpoint that the lens groups in the nth group are lens groups having a positive refractive power.

[0021] Furthermore, it is preferable that the nth group includes a cemented lens formed by joining three single lenses. Generally, in zoom lenses, intermediate lens groups with large optical beam diameters (lens groups relatively closer to the object; for example, the nth group in this invention) tend to have lenses with high eccentricity sensitivity. Including a cemented lens in the nth group as described above is preferable from the viewpoint of stably ensuring the optical performance as designed during the manufacture of the zoom lens. The position and number of the cemented lens in the nth group can be appropriately set within a range in which the effects of the cemented lens and the effects of the present invention can be obtained. That is, if the nth group has one lens group, the cemented lens may be in the third lens group; if the nth group has two lens groups, it may be in at least one of the third and fourth lens groups; and if the nth group has three lens groups, it may be in at least one of the third to fifth lens groups.

[0022] <Lens group n+1> The (n+1)th lens group has a negative refractive power. The type and arrangement of lenses in the (n+1)th lens group can be appropriately set within a range in which the (n+1)th lens group as a whole exhibits the desired negative refractive power. It is preferable for the (n+1)th lens group to include a cemented lens from the viewpoint of miniaturization by reducing the total thickness of the lens group, as well as from the viewpoint of achieving the desired optical performance and production stability.

[0023] <Lens group n+2> The (n+2)th lens group has a positive refractive power. The type and arrangement of lenses in the (n+2)th lens group can be appropriately set within a range in which the (n+2)th lens group as a whole exhibits the desired positive refractive power. It is preferable for the (n+2)th lens group to include a cemented lens from the viewpoint of miniaturization by reducing the total thickness of the lens group, as well as from the viewpoint of achieving the desired optical performance and production stability.

[0024] <Lens group n+3> The (n+3)th lens group has negative refractive power. The type and arrangement of lenses in the (n+3)th lens group can be appropriately set within a range in which the (n+3)th lens group as a whole exhibits the desired negative refractive power.

[0025] In the (n+3)th lens group, the lens closest to the image plane (the final lens) of the zoom lens is a lens with negative refractive power. Having a negative refractive power final lens is preferable from the viewpoint of reducing the diameter of the final lens and from the viewpoint of achieving high performance without increasing the total thickness of the (n+3)th group.

[0026] In the (n+3)th lens group, it is preferable that the lens closest to the image plane is an aspherical lens. The lens closest to the image plane has a small light beam diameter and tends to allow light rays to pass to the periphery of the lens. Therefore, it is preferable for this lens to be an aspherical lens from the viewpoint of effectively correcting field curvature.

[0027] Furthermore, having the (n+3)th lens group consist of only one aspherical lens is advantageous from the standpoint of reducing the total thickness of the final (n+3)th lens group. Therefore, having the lens closest to the image plane be an aspherical lens is a desirable configuration from the standpoint of miniaturization by shortening the overall length.

[0028] Furthermore, it is preferable that the lens closest to the image plane has a convex surface on the image plane side. In this case, the reflected light from the convex surface diffuses from the optical axis side of the lens to the outer edge, making it difficult to form an image on the image plane. Therefore, it is preferable for the lens closest to the image plane to have a convex surface on the image plane side, for example, for the lens to be a meniscus lens that is convex toward the image plane, from the viewpoint of improving performance by suppressing the generation of harmful ghosting.

[0029] <Opening diaphragm> A zoom lens may include an aperture diaphragm. The position of the aperture diaphragm can be appropriately set within a range in which the effects of the present invention can be obtained. In a zoom lens, it is preferable to position the aperture diaphragm closer to the object (for example, in the nth lens group). By positioning the aperture diaphragm closer to the object, the ray angle from the last lens group (the n+3rd lens group) to the image plane (image sensor) can be suppressed. The more the ray angle is suppressed, the more the oblique incidence characteristics of the peripheral image height are reduced, and the peripheral illumination ratio can be ensured. Also, the shorter the overall optical length, the shorter the distance between the aperture diaphragm and the image sensor becomes (the aperture diaphragm gets closer to the image plane). Therefore, positioning the aperture diaphragm closer to the object is effective from the viewpoint of achieving both high performance and a shorter overall length.

[0030] <Other components> From the viewpoint of achieving high performance by optimizing the shape factor of the lens, it is preferable for the zoom lens to include one or more lenses having a refractive index represented by equation (7) described later and an Abbe number represented by equation (8) described later. From the above viewpoint, the lens may be placed in any of the lens groups from the first lens group to the n+3 lens group, and multiple lenses may be included in the zoom lens.

[0031] The number of lens groups in a zoom lens can be appropriately determined within the range in which the effects of the present invention can be obtained. Generally, a smaller number of lens groups in a zoom lens is advantageous from the viewpoint of miniaturization, while a larger number is advantageous from the viewpoint of performance. From the viewpoint of achieving both miniaturization and performance, it is preferable that the number of lens groups in a zoom lens be 6 to 8.

[0032] In addition to the lens group described above, the zoom lens may include further optical elements to the extent that the effects of the present invention can be obtained. Examples of further optical elements include filters such as IR cut filters that cut out light of wavelengths such as near-infrared light. For example, it is preferable for the zoom lens to include the above filters between the final lens and the image plane in order to reduce the risk of ghosting due to inter-plane reflection by cutting out light in wavelength ranges that are not needed in imaging.

[0033] Furthermore, the zoom lens may further include an image-stabilizing lens group. The image-stabilizing lens group is a group of lenses that can move in a direction intersecting the optical axis. Including an additional image-stabilizing lens group is preferable from the viewpoint of preventing image defects caused by camera shake during imaging and achieving high-definition imaging.

[0034] [Operation] <Multiply> In zoom lenses, zooming from the wide-angle end to the telephoto end can be achieved by changing the air gap on the optical axis between adjacent lens groups. In the zoom lens of this embodiment, the first lens group is fixed in the direction of the optical axis during zooming. The first lens group generally tends to have the largest lens diameter. Fixing the first lens group in the direction of the optical axis during zooming is preferable from the viewpoint of improving the operability of the zoom lens and imaging device, as the first lens group is fixed to the image plane, stabilizing the center of gravity during shooting. Furthermore, fixing the first lens group in the direction of the optical axis during zooming simplifies the mechanical cam structure in the zoom lens and eliminates the need for additional parts such as sliding frames, thus being effective from the viewpoint of reducing the diameter.

[0035] Furthermore, during zooming, the (n+3)th lens group may be fixed in the direction of the optical axis. A configuration in which the first lens group and the final lens group, the (n+3)th lens group, are fixed in the direction of the optical axis during zooming is preferable from the viewpoint of improving user comfort, as dust and other debris are less likely to adhere inside the lens barrel. In addition, the above configuration is preferable from the viewpoint of miniaturization and the above-mentioned operational stability, as the overall length of the zoom lens remains constant.

[0036] The trajectory of the lens group during magnification can be linear or curved. Furthermore, the trajectory can be directed toward either the object side or the image plane side, or it can be directed toward either the object side or the image plane side before moving toward the other. For example, a linear trajectory of the lens group during magnification is preferable from the viewpoint of increasing the speed at which the lens group is moved, and a curved trajectory of the lens group during magnification is preferable from the viewpoint of miniaturizing the overall optical length. Also, a trajectory of the lens group during magnification that is directed 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 the lens group that is directed toward either the object side or the image plane side before moving toward the other is preferable from the viewpoint of miniaturizing the overall optical length.

[0037] <Focus> In a zoom lens, focusing can be achieved by moving one of the lens groups along the optical axis. Generally, a more converged beam of light is incident on the lens group closer to the image plane. Therefore, the lens group closer to the image plane can be composed of lenses with smaller diameters. Consequently, it is preferable that the lens group that moves during focusing (hereinafter also referred to as the "focus group") is the lens group closer to the image plane, from the viewpoint of suppressing changes in the angle of view associated with the movement of the focus group, and from the viewpoint of moving the focus group quickly and with low driving load during focusing. From this viewpoint, in this embodiment, it is preferable that the (n+1)th lens group be the focus group.

[0038] Furthermore, having only one lens group for the focus group allows for simplification of the drive mechanism for the focus group, which is preferable from the viewpoint of achieving miniaturization and weight reduction of the zoom lens. In this embodiment, since the lens group located relatively closer to the image plane, and closer to the image plane than the nth group, can be suitably configured with a single cemented lens, it is preferable from the above viewpoint as well to make the (n+1)th lens group the focus group.

[0039] [Optical properties] From the viewpoint of achieving both miniaturization and high performance, it is preferable that the zoom lens of this embodiment satisfies at least one of the following formulas.

[0040] <Formula (1)> 0.77 <f(n+2) / |f(n+3)| (1) however, f(n+2): Focal length of the (n+2)th lens group f(n+3): Focal length of the (n+3)th lens group

[0041] Equation (1) defines the ratio of the refractive power of the (n+2) lens group to that of the (n+3) lens group. It is preferable for a zoom lens to satisfy equation (1) from the viewpoint of effectively correcting field curvature. Furthermore, f(n+2) / |f(n+3)| can be appropriately determined within a range in which an effect of effectively correcting field curvature is obtained, and may be, for example, 1.45 or less.

[0042] <Formula (2)> 1.0 <b2t / b2w<6.0 (2) however, b2t: Horizontal magnification of the second lens group when focusing at infinity at the telephoto end. b2w: Horizontal magnification of the second lens group when focusing at infinity at the wide-angle end.

[0043] Equation (2) defines the lateral magnification ratio of the second lens group. It is preferable for a zoom lens to satisfy equation (2) from the viewpoint of achieving both a good zoom ratio and miniaturization. If b2t / b2w is 1.0 or less, the difference in lateral magnification between the wide-angle end and the telephoto end of the second lens group becomes excessively small, and it may become difficult to ensure a good zoom ratio because an appropriate zoom ratio cannot be maintained regardless of the amount of movement during zooming. On the other hand, if b2t / b2w is 6.0 or more, the difference in lateral magnification between the wide-angle end and the telephoto end of the second lens group becomes excessively large, and it may become difficult to miniaturize the lens because a large amount of movement during zooming is required to maintain an appropriate zoom ratio.

[0044] From the viewpoint of achieving a good zoom ratio, it is more preferable for b2t / b2w to be greater than 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, or 2.7, in that order. Also, from the viewpoint of achieving miniaturization, it is more preferable for b2t / b2w to be smaller than 5.8, 5.6, 5.4, 5.2, 5.0, 4.8, 4.6, 4.4, 4.2, 4.0, 3.8, 3.6, 3.4, 3.2, or 3.1, in that order.

[0045] <Formula (3)> 0.10 <oal2 / |f2|<1.20 (3) oal2: Total thickness of the second lens group f2: Focal length of the second lens group

[0046] Equation (3) defines the relationship between the power of the second lens group and the total thickness. It is desirable for a zoom lens to satisfy equation (3) from the viewpoint of achieving both high performance and a shorter overall length. If oal2 / |f2| is 0.1 or less, the power of the second lens group becomes weak, making it difficult to achieve both high performance at the wide-angle and telephoto ends. Also, if oal2 / |f2| is 1.2 or more, the second lens group becomes unnecessarily thick, making it difficult to achieve miniaturization.

[0047] From the perspective of achieving high performance at both the wide-angle and telephoto ends, it is preferable that oal2 / |f2| is greater than 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, or 0.62, in that order. Also, from the perspective of achieving miniaturization, it is preferable that oal2 / |f2| is less than 1.00, 0.95, 0.90, 0.85, 0.80, 0.75, 0.70, or 0.68, in that order.

[0048] <Formula (4)> 0.30 <oals / oalw (4) however, oals: Distance from the aperture diaphragm to the image plane when focusing at infinity at the wide-angle end. oalw; Optical length when focusing at infinity at the wide-angle end

[0049] Equation (4) defines the position of the aperture diaphragm in a zoom lens. It is preferable for a zoom lens to satisfy equation (4) from the viewpoint of achieving both high performance and a shorter overall length. From the viewpoint of obtaining such an effect, it is preferable that oals / oalw is greater than 0.32, 0.34, 0.36, 0.38, 0.40, or 0.42, in that order. Furthermore, oals / oalw can be appropriately determined within a range that achieves both high performance and a shorter overall length, and may be, for example, 0.65 or less.

[0050] <Formula (5)> 2.0 <ft / fw<6.0 (5) however, ft: Focal length of a zoom lens at infinity focus at the telephoto end. fw: Focal length of the zoom lens at infinity focus at the wide-angle end

[0051] Equation (5) defines the ratio of the focal length at the telephoto end to the focal length at the wide-angle end of a zoom lens. It is preferable for a zoom lens to satisfy equation (5) from the viewpoint of achieving both miniaturization and high performance, and is particularly preferable from the viewpoint of further enhancing the effect of equation (1). From this viewpoint, ft / fw is more preferably greater than 2.1, 2.2, 2.3, 2.4 or 2.5, in that order, and more preferably less than 5.5, 5.0, 4.5, 4.0, 3 or 5, 3, in that order.

[0052] <Formula (6)> 1.80 <nd1 (6) however, nd1: Refractive index of the lens closest to the object with respect to the d line.

[0053] Equation (6) specifies the glass material of the lens closest to the object (the first lens). It is preferable for a zoom lens to satisfy equation (6) from the viewpoint of shortening the overall length and from the viewpoint of suppressing damage to the first lens due to dropping or impact. From this viewpoint, it is preferable that nd1 is greater than 1.82, 1.84, 1.86, 1.88, or 1.90, in that order. Furthermore, nd1 can be appropriately determined within the range in which the above effects are obtained, and for example, since glass materials with higher refractive indices tend to be more yellowish, it may be 1.96 or less from the viewpoint of more easily controlling the CCI (Color Characteristic Index).

[0054] <Formula (7)> 1.70 <nd<1.85 (7) however, nd: Refractive index of the lens relative to the d line

[0055] Equation (7) specifies the refractive index of a particular lens included in the optical system. It is preferable for a zoom lens to satisfy equation (7) from the viewpoint of achieving high performance. If the nd is 1.7 or less or 1.85 or more, it may be difficult to optimize the shape factor of the lens. From the above viewpoint, it is more preferable for the nd to be greater than 1.70, 1.71, 1.72, 1.73, 1.74, 1.75 or 1.76, in that order, and more preferable for it to be less than 1.84, 1.83, 1.82 or 1.81, in that order.

[0056] <Formula (8)> 29 <vd<40 (8) however, vd: Abbe number for the d line of the lens

[0057] Equation (8) specifies the Abbe number of a particular lens included in the optical system. It is preferable for a zoom lens to satisfy equation (8) from the viewpoint of achieving high performance. If vd is 29 or less or 40 or more, it may become difficult to correct chromatic aberration. From the above viewpoint, it is more preferable for vd to be greater than 30 or 31, in that order, and more preferable for vd to be less than 39, 38, 37 or 36, in that order.

[0058] In the case of cemented lenses, it is sufficient that at least one of the two or more cemented lenses satisfies equations (7) and (8).

[0059] [Imaging device] An imaging device according to one embodiment of the present invention has the zoom lens described above. The configuration of the imaging device of this embodiment is schematically shown in Figure 11. As shown in Figure 11, the imaging device 1 has a main body 2 and a lens barrel 3. The imaging device 1 is, for example, a mirrorless single-lens reflex camera.

[0060] The main body 2 has an image sensor I and a cover glass CG. The image sensor I 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 CCD (Charge Coupled Device) sensors and CMOS (Complementary Metal Oxide Semiconductor) sensors.

[0061] The lens barrel 3 is detachably attached to the main body 2 and contains the first lens group G1, the second lens group G2, the third lens group G3, the fourth lens group G4, the fifth lens group G5, the sixth lens group G6, and the seventh lens group G7 in that order on the optical axis OA. The optical axis OA is the optical axis common to the lens groups of the lens barrel 3 and the image sensor I of the main body 2.

[0062] The first lens group G1 has a positive refractive power as a whole. The first lens group G1 is fixed in the direction of the optical axis during zooming. The first lens group G1 is composed of, for example, a cemented lens of a negative lens L1 and a positive lens L2, and a positive lens L3, starting from the object side.

[0063] The second lens group G2 has a negative refractive power as a whole. The second lens group G2 is configured to be movable in the optical axis direction. The second lens group G2 consists of, for example, a negative lens L4, a cemented lens of a biconcave lens L5 and a biconvex lens L6, and a negative lens L7, starting from the object side.

[0064] The third lens group G3 has a positive refractive power as a whole. The third lens group G3 is configured to be movable in the optical axis direction. The third lens group G3 is composed of, for example, a positive lens L8.

[0065] The fourth lens group G4 has a positive refractive power as a whole. The fourth lens group G4 is configured to be movable in the optical axis direction. The fourth lens group G4 is composed of, for example, a cemented lens made of three lenses: a negative lens L9, a biconvex lens L10, and a biconcave lens L11, and a biconvex lens L12, in that order from the object side. The third lens group G3 and the fourth lens group G4 have a positive refractive power as a whole.

[0066] The fifth lens group G5 has a negative refractive power as a whole. The fifth lens group G5 is configured to be movable in the optical axis direction. The fifth lens group G5 is composed of, for example, a cemented lens of a positive lens L13 and a biconcave lens L14. Furthermore, the fifth lens group G5 is configured to perform focusing by moving toward the image plane when focusing from an object at infinity to an object at a close distance.

[0067] The sixth lens group G6 has a positive refractive power as a whole. The sixth lens group G6 is configured to be movable in the optical axis direction. The sixth lens group G6 is composed of, for example, a cemented lens of a positive lens L15 and a negative lens L16.

[0068] The seventh lens group G7 has a negative refractive power as a whole. The seventh lens group G7 is fixed in the optical axis direction during zooming. The seventh lens group G7 is composed of, for example, a negative lens L17.

[0069] If we consider the third lens group G3 and the fourth lens group G4 together as the nth group, the fifth lens group G5 as the (n+1)th lens group, the sixth lens group G6 as the (n+2)th lens group, and the seventh lens group G7 as the (n+3)th lens group, then the above zoom lens satisfies at least one of the aforementioned equations (1) to (8). In other words, the first lens group G1 to the seventh lens group G7 correspond to a zoom lens of a specific embodiment of the present invention described above.

[0070] Thus, the imaging device 1 includes the zoom lens of this embodiment described above, and an image sensor I on the image plane side of the zoom lens that converts the optical image formed by the zoom lens into an electrical signal. Therefore, the imaging device 1 has high optical performance even when it is small and has high magnification.

[0071] The imaging device 1 can be various imaging devices, including mirrorless interchangeable-lens cameras, security cameras, digital still cameras, or medical cameras. The zoom lens of this embodiment can be miniaturized even at high magnification. Therefore, the imaging device 1 can be applied to imaging devices for various purposes.

[0072] In addition, the imaging device according to the embodiment of the present invention may include other components capable of fixing the image focused by the zoom lens, instead of the image sensor I. Examples of such other components include silver halide film.

[0073] Furthermore, the imaging apparatus according to the embodiment of the present invention may include additional optical elements in the optical configuration described above, to the extent that the effects of the present invention can be obtained, and depending on the application of the imaging apparatus. For example, the imaging apparatus may have a parallel flat plate with substantially no refractive power instead of the cover glass CG as the additional optical element. An example of such additional optical element is an infrared cut filter (IRCF).

[0074] 〔summary〕 In this day and age, where even elementary school students own smartphones, people can easily obtain reasonably high-resolution images. While the demand for compact digital cameras is declining, there is still a certain level of demand for interchangeable photographic lenses, likely because they can produce images with higher resolution than smartphones. However, in recent years, products from all manufacturers have achieved a high standard of resolution, and the range of lenses available has also expanded. Therefore, high performance in zoom lenses can be considered a prerequisite for products to be launched.

[0075] On the other hand, unless a user has an insatiable desire for higher resolution performance, they tend to choose a product based on their preferred brand, cost, and convenience, from among those offering satisfactory resolution performance at their desired field of view. Therefore, in a market already somewhat satisfied with the pursuit of high performance, differentiating products based on the reasons mentioned above is crucial in product development.

[0076] Examples of effective reasons for users to choose a product, such as cost and convenience, include miniaturization, including shortening the optical length and / or reducing the diameter of the zoom lens, and fixing the optical length. Miniaturization allows for lower product prices by reducing component costs and improves the ease of storage and carrying of zoom lenses and imaging devices equipped with them. Fixing the optical length stabilizes the center of gravity during shooting and can improve operability. Furthermore, fixing the optical length eliminates the need for cams in the fixed lens group. Therefore, as mentioned above, it can also contribute to reducing the diameter. In this respect, the zoom lens described in Patent Document 3 mentioned above has a movable first lens group, which results in a large change in the center of gravity balance due to zoom fluctuations. Therefore, operability is poor and it may be insufficient from a convenience standpoint.

[0077] A first aspect of the present invention is a zoom lens comprising, in order from the object side, a first lens group (G1) having positive refractive power, a second lens group (G2) having negative refractive power, an nth group (G3, G4) including one or more lens groups, an (n+1)th lens group (G5) having negative refractive power, an (n+2)th lens group (G6) having positive refractive power, and an (n+3)th lens group (G7) having negative refractive power, wherein the first lens group is fixed in the direction of the optical axis (OA) during zooming, the lens closest to the image plane has negative refractive power, and satisfies the aforementioned equation (1). According to the first aspect, a zoom lens that can achieve both miniaturization and high performance can be realized.

[0078] A second aspect of the present invention satisfies formula (2) above in the first aspect. The second aspect is even more effective in achieving both a good zoom ratio and miniaturization in a zoom lens.

[0079] A third aspect of the present invention satisfies formula (3) above in the first or second aspect. The third aspect is even more effective in achieving both high performance and a reduction in the overall optical length of a zoom lens.

[0080] A fourth aspect of the present invention includes an aperture diaphragm (S) in any of the first to third aspects and satisfies the aforementioned formula (4). The fourth aspect is even more effective in achieving both high performance and a reduction in the overall optical length of a zoom lens.

[0081] A fifth aspect of the present invention satisfies formula (5) above in any of the first to fourth aspects. The fifth aspect is even more effective in achieving both miniaturization and high performance of the zoom lens.

[0082] A sixth aspect of the present invention satisfies formula (6) above in any of the first to fifth aspects. The sixth aspect is even more effective in terms of shortening the overall optical length and suppressing damage to the first lens due to dropping or impact.

[0083] A seventh aspect of the present invention is that, in any of the first to sixth aspects, there is at least one lens that simultaneously satisfies the aforementioned formulas (7) and (8). The seventh aspect is even more effective from the viewpoint of achieving high performance of zoom lenses.

[0084] The eighth aspect of the present invention is more effective in terms of effectively correcting field curvature, in which the lens closest to the image plane is an aspherical lens, compared to any of the first to seventh aspects.

[0085] The ninth aspect of the present invention is a cemented lens in which the nth group is formed by joining three single lenses, in any of the first to eighth aspects. The ninth aspect is even more effective in terms of improving the stability of achieving the desired optical performance through manufacturing.

[0086] A tenth aspect of the present invention is an imaging device comprising a zoom lens according to any of the first to ninth aspects, and an image sensor on the image plane side of the zoom lens that converts the optical image formed by the zoom lens into an electrical signal. According to the tenth aspect, an imaging device that can achieve both miniaturization and high performance can be realized.

[0087] According to the embodiments described above, a zoom lens and an imaging device can be provided that are compact, have high magnification, and possess high optical performance. The present invention, which achieves such effects, is expected to contribute to achieving, for example, Goal 9 of the United Nations Sustainable Development Goals (SDGs), "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation."

[0088] The present invention is not limited to the embodiments described above, 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. [Examples]

[0089] One embodiment of the present invention is described below.

[0090] Each embodiment is shown in a specifications table (Tables 1, 4, 7, or 10). In these specifications tables, "No." is the surface number, "R" is the radius of curvature, "D" is the lens thickness or lens spacing, "Nd" is the refractive index of the d line, and "ABV" is the Abbe number based on the d line. In addition, "ASPH" written alongside the surface number indicates that it is an aspherical surface.

[0091] Furthermore, each embodiment shows a table of variable interval data (Tables 2, 5, 8, or 11). In this table of variable interval data, the data is shown from left to right at the wide-angle end, intermediate focal position, and telephoto end. 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 embodiment, "D(n)" (where n is an integer) represents a variable interval in which the spacing of the lens surfaces on the optical axis changes during zooming or focusing. The units for "R", "D", and "F" are all in mm.

[0092] Furthermore, a table of aspherical data (Tables 3, 6, 9, or 12) is shown for each embodiment. In the table of aspherical data, an aspherical surface is defined by the following equation. In the following equation, "r" represents the radius, "h" represents the height from the optical axis, "k" represents the conic constant, and "An" represents the nth-order aspherical coefficient. In the table, "E+a" represents "×10 a " represents " and "Ea" is "×10 -a This represents ".

[0093]

number

[0094] Furthermore, each embodiment includes a diagram of the lens configuration (Figures 1, 3, 5, or 7). These diagrams schematically show, from top to bottom, the lens configuration at the wide-angle end, the intermediate focal length, and the telephoto end. All diagrams show the lens configuration at infinity focus. The arrows between each lens configuration schematically indicate the trajectory of movement in each lens group from the wide-angle end to the intermediate focal length, and from the intermediate focal length to the telephoto end. The symbols G1 to G7 in the figures represent the first to seventh lens groups, respectively. The intermediate focal length is calculated using the formula "√(fw × ft)". In the formula, "fw" represents the focal length at infinity focus at the wide-angle end, and "ft" represents the focal length at infinity focus at the telephoto end.

[0095] Furthermore, each embodiment shows a longitudinal aberration diagram (Figures 2, 4, 6, or 8). In these longitudinal aberration diagrams, from top to bottom, they show the longitudinal aberration diagrams at the wide-angle end, the longitudinal aberration diagrams at the intermediate focal position, and the longitudinal aberration diagrams at the telephoto end, respectively. Each group of longitudinal aberration diagrams contains three aberration diagrams, from left to right, showing spherical aberration (SA (mm)), astigmatism (AST (mm)), and distortion (DIS (%)). In the spherical aberration diagram, the vertical axis represents the F-number, the solid line represents the d-line (587.56 nm), the long dashed line represents the F-line (486.13 nm), and the short dashed line represents the C-line (656.27 nm). In the astigmatism diagram, the vertical axis represents the field of view, the solid line shows the characteristics of the sagittal plane (indicated as S in the diagram), and the dotted line shows the characteristics of the meridional plane (indicated as T in the diagram). In the distortion diagram, the vertical axis represents the field of view.

[0096] [Example 1] As shown in Figure 1, the zoom lens in Example 1 is composed of, in order from the object side, 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, a fourth lens group G4 with positive refractive power, a fifth lens group G5 with negative refractive power, a sixth lens group G6 with positive refractive power, and a seventh lens group G7 with negative refractive power. The aperture diaphragm S is located adjacent to the fourth lens group G4 on the object side of the fourth lens group G4.

[0097] The first lens group G1 consists of, in order from the object side, a cemented lens formed by a negative meniscus lens L1 with its convex surface facing the object and a positive meniscus lens L2 with its convex surface facing the object, and a positive meniscus lens L3 with its convex surface facing the object.

[0098] The second lens group G2 consists of, in order from the object side, a negative meniscus lens L4 with its convex surface facing the object, a cemented lens of a biconcave lens L5 and a biconvex lens L6, and a negative meniscus lens L7 with its concave surface facing the object. The negative meniscus lens L4 is a composite lens having an aspherical resin layer on the surface facing the object.

[0099] The third lens group G3 consists of a positive meniscus lens L8 with its convex surface facing the object.

[0100] The fourth lens group G4 consists of, in order from the object side, a negative meniscus lens L9 with its convex surface facing the object, a cemented lens made of three lenses: a biconvex lens L10 and a biconcave lens L11, and a biconvex lens L12. The biconvex lens L12 is a glass-molded aspherical lens with aspherical shapes on both sides.

[0101] The fifth lens group G5 consists of a cemented lens made up of a positive meniscus lens L13 with its concave surface facing the object and a biconcave lens L14.

[0102] The sixth lens group G6 consists of a cemented lens made up of a positive meniscus lens L15 with its concave surface facing the object and a negative meniscus lens L16 with its concave surface facing the object.

[0103] The seventh lens group G7 consists of a negative meniscus lens L17 with its concave surface facing the object. The negative meniscus lens L17 is a glass-molded aspherical lens with aspherical shapes on both sides.

[0104] In the zoom lens of Example 1, the third lens group G3 and the fourth lens group G4 constitute the aforementioned nth group. The fifth lens group G5 corresponds to the aforementioned (n+1)th lens group, the sixth lens group G6 corresponds to the aforementioned (n+2)th lens group, and the seventh lens group G7 corresponds to the aforementioned (n+3)th lens group.

[0105] The zoom lens of Example 1 achieves magnification by changing the air gap on the optical axis between adjacent lens groups. When zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, and the second lens group G2 moves toward the image plane. The third lens group G3, the fourth lens group G4, and the fifth lens group G5 all move toward the image plane in a parabolic trajectory as shown in the figure, and when zooming toward the telephoto end, they ultimately move toward the image plane even further than their position at the wide-angle end. The sixth lens group G6 moves toward the image plane, and the seventh lens group G7 is fixed.

[0106] In the zoom lens of Example 1, focusing from an object at infinity to an object at close range is achieved by the fifth lens group G5 moving toward the image plane.

[0107] Tables 1 to 3 show the specifications, variable interval data, and aspherical data for the zoom lens of Example 1. Figure 2 shows the aberration diagram for the zoom lens of Example 1. The lens containing surface number 10 and the lens containing surface number 17 are both lenses that satisfy both equations (7) and (8) described above.

[0108] [Table 1] No. RD Nd ABV 1 84.0573 1.5000 1.91082 35.25 2 54.6346 9.4906 1.45860 90.19 3 4039.1630 0.1500 4 52.4632 7.5163 1.49700 81.61 5 662.7388 D(5) 6ASPH 207.7760 0.2000 1.53610 41.21 7 140.9083 1.0000 1.64769 33.84 8 25.2900 9.1650 9 -56.9869 1.0000 1.55032 75.50 10 30.0821 6.4335 1.80610 33.27 11 -63.2524 1.2865 12 -36.5649 1.0000 1.72916 54.67 13 -468.0116 D(13) 14 32.6085 3.6845 1.95375 32.32 15 97.3793 D(15) 16STOP 0.0000 1.0000 17 39.0523 1.0000 1.76634 35.83 18 15.8104 9.6440 1.52841 76.45 19 -23.8576 1.0000 1.95375 32.32 20 151.1695 D(20) 21ASPH 50.2138 6.1822 1.76802 49.24 22ASPH -35.9050 D(22) 23 -3235.4196 2.2566 1.94595 17.98 24 -73.3210 1.0000 1.69680 55.46 25 29.5471 D(25) 26 -4063.5090 6.2441 1.62299 58.12 27 -24.6064 1.0000 1.92286 20.88 28 -36.9717 D(28) 29ASPH -34.5044 2.8000 1.76802 49.24 30ASPH -213.6654 12.8000 31 0.0000 2.5000 1.51680 64.20 32 0.0000 1.0000

[0109] [Table 2] F 51.5100 79.5313 130.9425 Fno 2.8840 2.8840 2.8840 W 22.5646 14.5960 8.9407 D( 5) 1.5000 16.8270 31.0058 D(13) 30.2241 16.2200 1.5000 D(15) 2.3901 2.7543 1.9406 D(22) 2.5574 4.6821 2.5010 D(25) 10.6240 10.5395 18.0782 D(28) 20.4152 16.6880 12.6852

[0110] [Table 3] No. K *4 *6 *8 *10 6 0.00000E+00 3.31986E-06 1.54196E-12 2.19318E-12 7.16825E-16 21 -2.28880E+00 -5.19711E-06 4.94261E-09 -3.87206E-11 2.92135E-13 22 0.00000E+00 3.20986E-06 -8.14898E-09 2.25161E-11 -5.48290E-14 29 1.51088E+00 -3.36082E-05 2.01003E-07 -6.23881E-10 1.41899E-12 30 0.00000E+00 -4.12114E-05 1.72534E-07 -5.07182E-10 9.38959E-13 No. *12 6 8.49398E-18 21 -8.25597E-16 22 -2.62294E-17 29 -1.52005E-15 30 -8.22139E-16

[0111] [Example 2] As shown in Figure 3, the zoom lens in Example 2 is composed of, in order from the object side, 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, a fourth lens group G4 with positive refractive power, a fifth lens group G5 with negative refractive power, a sixth lens group G6 with positive refractive power, and a seventh lens group G7 with negative refractive power. The aperture diaphragm S is located adjacent to the fourth lens group G4 on the object side of the fourth lens group G4.

[0112] The first lens group G1 consists of, in order from the object side, a cemented lens formed by a negative meniscus lens L1 with its convex surface facing the object and a biconvex lens L2, and a positive meniscus lens L3 with its convex surface facing the object.

[0113] The second lens group G2 consists of, in order from the object side, a negative meniscus lens L4 with its convex surface facing the object, a cemented lens of a biconcave lens L5 and a biconvex lens L6, and a negative meniscus lens L7 with its concave surface facing the object. The negative meniscus lens L4 is a composite lens having an aspherical resin layer on the surface facing the object.

[0114] The third lens group G3 consists of a positive meniscus lens L8 with its convex surface facing the object.

[0115] The fourth lens group G4 consists of, in order from the object side, a negative meniscus lens L9 with its convex surface facing the object, a cemented lens made of three lenses: a biconvex lens L10 and a biconcave lens L11, and a biconvex lens L12. The biconvex lens L12 is a glass-molded aspherical lens with aspherical shapes on both sides.

[0116] The fifth lens group G5 consists of a cemented lens made up of a biconvex lens L13 and a biconcave lens L14.

[0117] The sixth lens group G6 consists of a cemented lens made up of a biconvex lens L15 and a negative meniscus lens L16 with its concave surface facing the object.

[0118] The seventh lens group G7 consists of a negative meniscus lens L17 with its concave surface facing the object. The negative meniscus lens L17 is a glass-molded aspherical lens with aspherical shapes on both sides.

[0119] In the zoom lens of Example 2, the third lens group G3 and the fourth lens group G4 constitute the aforementioned nth group. The fifth lens group G5 corresponds to the aforementioned (n+1)th lens group, the sixth lens group G6 corresponds to the aforementioned (n+2)th lens group, and the seventh lens group G7 corresponds to the aforementioned (n+3)th lens group.

[0120] The zoom lens of Example 2 achieves magnification by changing the air gap on the optical axis between adjacent lens groups. When zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, and the second lens group G2 moves toward the image plane. The third lens group G3, the fourth lens group G4, and the fifth lens group G5 all move toward the image plane in a parabolic trajectory as shown in the figure, and when zooming to the telephoto end, they ultimately move closer to the object than their position at the wide-angle end. The sixth lens group G6 moves toward the image plane, and the seventh lens group G7 is fixed.

[0121] In the zoom lens of Example 2, focusing from an object at infinity to an object at close range is achieved by the fifth lens group G5 moving toward the image plane.

[0122] Tables 4 to 6 show the specifications, variable interval data, and aspherical data for the zoom lens of Example 2. Figure 4 shows the aberration diagram for the zoom lens of Example 2. The lens containing surface number 10 and the lens containing surface number 17 are both lenses that satisfy both equations (7) and (8) described above.

[0123] [Table 4] No. RD Nd ABV 1 92.3853 1.5000 1.91082 35.25 2 59.2813 9.3063 1.45860 90.19 3 -1059.1647 0.1500 4 52.4943 7.3590 1.49700 81.61 5 478.6872 D(5) 6ASPH 181.1527 0.2000 1.53610 41.21 7 134.2810 1.0000 1.64769 33.84 8 26.1744 8.6792 9 -62.3330 1.0000 1.54835 73.92 10 30.1234 6.4959 1.83781 30.21 11 -74.5808 2.6113 12 -36.4902 1.0000 1.78848 44.73 13 -1040.2837 D(13) 14 35.9154 3.9479 1.95103 31.69 15 183.0644 D(15) 16 STOP 0.0000 1.0000 17 40.3368 1.0000 1.81186 31.97 18 16.7257 9.0099 1.56743 65.84 19 -27.6303 1.0000 1.94765 29.25 20 104.4105 6.1734 21 ASPH 43.8370 5.5396 1.76802 49.24 22 ASPH -44.0923 D(22) 23 393.5630 2.2726 1.94595 17.98 24 -90.3635 1.0000 1.75222 50.16 25 27.1880 D(25) 26 590.8229 6.7022 1.60467 47.47 27 -25.2918 1.0000 1.92286 20.88 28 -36.1287 D(28) 29 ASPH -39.5105 2.8000 1.76802 49.24 30 ASPH -446.1756 12.8000 31 0.0000 2.5000 1.51680 64.20 32 0.0000 1.0000

[0124] [Table 5] F 51.5041 79.6065 130.9279 Fno 2.8840 2.8840 2.8840 W 22.7257 14.6228 8.9848 D(5) 1.5000 16.9044 30.2378 D(13) 30.2873 16.4856 1.5000 D(15) 2.5231 2.5247 1.4986 D(22) 3.3527 4.8085 2.5029 D(25) 13.9343 12.3317 18.2748 D(28) 14.3553 12.8977 11.9386

[0125] [Table 6] No. K *4 *6 *8 *10 6 0.00000E+00 2.65697E-06 3.11557E-10 4.20976E-12 -9.77781E-15 21 -1.38469E+00 -4.26917E-06 2.43278E-09 -2.72446E-11 1.78172E-13 22 0.00000E+00 3.67477E-06 -7.03693E-09 4.71452E-12 2.09600E-14 29 2.21099E+00 -3.19711E-05 1.93237E-07 -6.52062E-10 1.44813E-12 30 0.00000E+00 -3.87392E-05 1.59694E-07 -5.02812E-10 9.45225E-13 No. *12 6 1.97788E-17 21 -7.43053E-16 22 -4.03528E-16 29 -1.36575E-15 30 -7.87979E-16

[0126] [Example 3] As shown in Figure 5, the zoom lens in Example 3 is composed of, in order from the object side, 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, a fourth lens group G4 with positive refractive power, a fifth lens group G5 with negative refractive power, a sixth lens group G6 with positive refractive power, and a seventh lens group G7 with negative refractive power. The aperture diaphragm S is located adjacent to the fourth lens group G4 on the object side of the fourth lens group G4.

[0127] The first lens group G1 consists of, in order from the object side, a cemented lens formed by a negative meniscus lens L1 with its convex surface facing the object and a positive meniscus lens L2 with its convex surface facing the object, and a positive meniscus lens L3 with its convex surface facing the object.

[0128] The second lens group G2 consists of, in order from the object side, a negative meniscus lens L4 with its convex surface facing the object, a cemented lens of a biconcave lens L5 and a biconvex lens L6, and a negative meniscus lens L7 with its concave surface facing the object. The negative meniscus lens L4 is a composite lens having an aspherical resin layer on the surface facing the object.

[0129] The third lens group G3 consists of a positive meniscus lens L8 with its convex surface facing the object.

[0130] The fourth lens group G4 consists of, in order from the object side, a negative meniscus lens L9 with its convex surface facing the object, a cemented lens made of three lenses: a biconvex lens L10 and a biconcave lens L11, and a biconvex lens L12. The biconvex lens L12 is a glass-molded aspherical lens with aspherical shapes on both sides.

[0131] The fifth lens group G5 consists of a cemented lens made up of a positive meniscus lens L13 with its concave surface facing the object and a biconcave lens L14.

[0132] The sixth lens group G6 consists of a cemented lens made up of a biconvex lens L15 and a negative meniscus lens L16 with its concave surface facing the object.

[0133] The seventh lens group G7 consists of a negative meniscus lens L17 with its concave surface facing the object. The negative meniscus lens L17 is a glass-molded aspherical lens with aspherical shapes on both sides.

[0134] In the zoom lens of Example 3, the third lens group G3 and the fourth lens group G4 constitute the aforementioned nth group. The fifth lens group G5 corresponds to the aforementioned (n+1)th lens group, the sixth lens group corresponds to the aforementioned (n+2)th lens group, and the seventh lens group G7 corresponds to the aforementioned (n+3)th lens group.

[0135] In the zoom lens of Example 3, magnification is achieved by changing the air gap on the optical axis between adjacent lens groups. When zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, and the second lens group G2 moves toward the image plane. The third lens group G3, the fourth lens group G4, and the fifth lens group G5 all move toward the image plane in a parabolic trajectory as shown in the figure, and when magnifying to the telephoto end, they ultimately move toward the image plane more than their position at the wide-angle end. The sixth lens group G6 moves toward the image plane, and the seventh lens group G7 is fixed.

[0136] In the zoom lens of Example 3, focusing from an object at infinity to an object at close range is achieved by the fifth lens group G5 moving toward the image plane.

[0137] Tables 7 to 9 show the specifications, variable interval data, and aspherical data for the zoom lens of Example 3. Figure 6 shows the aberration diagram for the zoom lens of Example 3. The lens containing surface number 10 and the lens containing surface number 17 are both lenses that satisfy both equations (7) and (8) described above.

[0138] [Table 7] No. RD Nd ABV 1 75.9666 1.5000 1.91082 35.25 2 51.8859 9.7358 1.45860 90.19 3 1257.2141 0.1500 4 50.2742 7.6320 1.49700 81.61 5 429.9217 D(5) 6ASPH 306.1931 0.2000 1.53610 41.21 7 171.0813 1.0000 1.64769 33.84 8 24.8602 9.9162 9 -46.1402 1.0000 1.55032 75.50 10 33.4900 6.4713 1.80610 33.27 11 -48.4367 1.0619 12 -33.5160 1.0000 1.72916 54.67 13 -292.4461 D(13) 14 33.9626 5.3123 1.95375 32.32 15 140.0234 D(15) 16STOP 0.0000 1.0000 17 34.8004 1.0000 1.76634 35.83 18 15.5285 9.2417 1.52841 76.45 19 -27.9335 1.0000 1.95375 32.32 20 50.7440 1.2033 21ASPH 37.5153 5.3278 1.76802 49.24 22ASPH -39.5215 D(22) 23 -143.3742 2.1393 1.94595 17.98 24 -59.2301 1.0000 1.69680 55.46 25 31.2696 D(25) 26 197.4731 7.1934 1.62299 58.12 27 -29.9167 1.0000 1.92286 20.88 28 -36.8593 D(28) 29ASPH -30.9168 1.0754 1.76802 49.24 30ASPH -76.2561 12.8000 31 0.0000 2.5000 1.51680 64.20 32 0.0000 1.0000

[0139] [Table 8] F 51.5252 79.5520 130.9484 Fno 2.8840 2.8840 2.8840 W 22.6782 14.6305 8.9737 D( 5) 1.5000 16.1294 29.9547 D(13) 29.2392 16.6682 1.5000 D(15) 1.6793 2.2366 1.6243 D(22) 3.2756 5.8675 3.2919 D(25) 10.6926 10.2859 17.5573 D(28) 24.1529 19.3521 16.6116

[0140] [Table 9] No. K *4 *6 *8 *10 6 0.00000E+00 3.98557E-06 -5.35702E-10 2.17186E-12 1.54615E-16 21 -9.68790E-01 -3.60405E-06 8.52148E-09 -4.30649E-11 4.90084E-13 22 0.00000E+00 4.03629E-06 -5.72343E-09 3.78685E-11 -1.71034E-13 29 9.56786E-01 -3.77805E-05 1.99830E-07 -6.16962E-10 1.34442E-12 30 0.00000E+00 -4.31898E-05 1.72174E-07 -5.19264E-10 9.56819E-13 No. *12 6 1.38658E-17 21 -6.79078E-16 22 1.29895E-15 29 -1.42994E-15 30 -8.62373E-16

[0141] [Example 4] As shown in Figure 7, the zoom lens in Example 4 is composed of, in order from the object side, 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, 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 aperture diaphragm S is located inside the third lens group G3.

[0142] The first lens group G1 consists of, in order from the object side, a cemented lens formed by a negative meniscus lens L1 with its convex surface facing the object and a positive meniscus lens L2 with its convex surface facing the object, and a positive meniscus lens L3 with its convex surface facing the object.

[0143] The second lens group G2 consists of, in order from the object side, a negative meniscus lens L4 with its convex surface facing the object, a cemented lens of a biconcave lens L5 and a biconvex lens L6, and a negative meniscus lens L7 with its concave surface facing the object. The negative meniscus lens L4 is a composite lens having an aspherical resin layer on the object-facing surface.

[0144] The third lens group G3 consists of, in order from the object side, a positive meniscus lens L8 with its convex surface facing the object, a negative meniscus lens L9 with its convex surface facing the object, a cemented lens formed from a biconvex lens L10 and a biconcave lens L11, and a biconvex lens L12. The biconvex lens L12 is a glass-molded aspherical lens with aspherical shapes on both sides.

[0145] The fourth lens group G4 consists of a cemented lens made up of a single convex lens L13 and a double concave lens L14, with the plane facing the object.

[0146] The fifth lens group G5 consists of a cemented lens made up of a biconvex lens L15 and a negative meniscus lens L16 with its concave surface facing the object.

[0147] The sixth lens group G6 consists of, in order from the object side, a cemented lens formed by a positive meniscus lens L17 with its concave surface facing the object and a biconcave lens L18, and a negative meniscus lens L19 with its concave surface facing the object. The negative meniscus lens L19 is a glass-molded aspherical lens with aspherical shapes on both sides.

[0148] In the zoom lens of Example 4, the third lens group G3 corresponds to the nth group mentioned above, the fourth lens group G4 corresponds to the (n+1)th lens group mentioned above, the fifth lens group G5 corresponds to the (n+2)th lens group mentioned above, and the sixth lens group G6 corresponds to the (n+3)th lens group mentioned above.

[0149] The zoom lens of Example 4 achieves magnification by changing the air gap on the optical axis between adjacent lens groups. When zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, and the second lens group G2 moves toward the image plane. The third lens group G3 and the fourth lens group G4 both move toward the image plane in a parabolic trajectory as shown in the figure, and when zooming toward the telephoto end, they ultimately move toward the image plane even further than their position at the wide-angle end. The fifth lens group G5 moves toward the image plane, and the sixth lens group G6 is fixed.

[0150] In the zoom lens of Example 4, focusing from an object at infinity to an object at close range is performed by the fourth lens group G4 moving toward the image plane.

[0151] Tables 10 to 12 show the specifications, variable interval data, and aspherical data for the zoom lens of Example 4. Figure 8 shows the aberration diagram for the zoom lens of Example 4. The lens containing surface number 10 and the lens containing surface number 17 are both lenses that satisfy both equations (7) and (8) described above.

[0152] [Table 10] No. RD Nd ABV 1 87.0174 1.5000 1.91082 35.25 2 57.3451 9.0337 1.45860 90.19 3 2507.2677 0.1500 4 55.5645 7.2263 1.49700 81.61 5 548.1482 D(5) 6ASPH 174.6769 0.2000 1.53610 41.21 7 126.9479 1.0000 1.64769 33.84 8 25.0977 10.5731 9 -54.7198 1.0353 1.55032 75.50 10 30.5053 6.3290 1.80610 33.27 11 -64.9367 1.4858 12 -35.3281 1.0000 1.72916 54.67 13 -194.7608 D(13) 14 34.5765 6.1390 ​​1.95375 32.32 15 109.1167 1.8864 16STOP 0.0000 1.0000 17 39.1985 1.0000 1.76634 35.83 18 15.6395 9.6750 1.52841 76.45 19 -25.0914 1.0000 1.95375 32.32 20 141.0370 2.0778 21ASPH 51.6727 6.5049 1.76802 49.24 22ASPH -37.3978 D(22) 23 -10889.2195 2.1410 1.94595 17.98 24 -87.5335 1.0000 1.69680 55.46 25 29.4414 D(25) 26 65.5351 7.3875 1.62299 58.12 27 -27.1625 1.0000 1.92286 20.88 28 -37.0650 D(28) 29 -366.6481 6.1469 1.58144 40.89 30 -29.5815 2.5000 1.74330 49.22 31 87.7656 6.5426 32ASPH -30.2397 3.0000 1.76802 49.24 33ASPH -71.7325 12.8000 34 0.0000 2.5000 1.51680 64.20 35 0.0000 1.0000

[0153] [Table 11] F 51.5006 84.4354 130.9317 Fno 2.8983 2.8840 2.9540 W 22.6362 13.7479 8.9529 D( 5) 1.5000 20.5067 33.1860 k D(13) 32.3759 15.7800 1.5000 D(22) 2.5656 4.0947 2.5023 D(25) 14.2391 10.9905 15.4777 D(28) 4.4853 3.7938 2.5000

[0154] [Table 12] No. K *4 *6 *8 *10 6 0.00000E+00 3.09911E-06 -1.54822E-10 2.20176E-12 1.46165E-15 21 -1.41024E+00 -4.38753E-06 7.40328E-09 -2.85624E-11 2.33697E-13 22 0.00000E+00 3.06050E-06 -5.55268E-09 2.45046E-11 -8.45304E-14 32 1.50537E+00 -4.53515E-05 1.97218E-07 -6.37397E-10 1.36188E-12 33 0.00000E+00 -4.86001E-05 1.67095E-07 -5.16251E-10 9.43564E-13 No. *12 6 3.85964E-18 21 -1.36452E-15 22 -6.04954E-16 32 -1.00172E-15 33 -7.93053E-16

[0155] [Example 5] As shown in Figure 9, the zoom lens in Example 5 is composed of, in order from the object side, 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, a fourth lens group G4 with negative refractive power, a fifth lens group G5 with positive refractive power, a sixth lens group G6 with negative refractive power, a seventh lens group G7 with positive refractive power, and an eighth lens group G8 with negative refractive power. The aperture diaphragm is located on the object side of the fourth lens group G4, adjacent to the third lens group G3.

[0156] The first lens group G1 consists of, in order from the object side, a cemented lens formed by a negative meniscus lens L1 with its convex surface facing the object and a positive meniscus lens L2 with its convex surface facing the object, and a positive meniscus lens L3 with its convex surface facing the object.

[0157] The second lens group G2 consists of, in order from the object side, a negative meniscus lens L4 with its convex surface facing the object, a cemented lens of a biconcave lens L5 and a biconvex lens L6, and a negative meniscus lens L7 with its concave surface facing the object. The negative meniscus lens L4 is a composite lens having an aspherical resin layer on the surface facing the object.

[0158] The third lens group G3 consists of a positive meniscus lens L8 with its convex surface facing the object.

[0159] The fourth lens group G4 is composed of a cemented lens made up of three lenses: a negative meniscus lens L9 with its convex surface facing the object, a biconvex lens L10, and a biconcave lens L11.

[0160] The fifth lens group G5 consists of a biconvex lens L12. The biconvex lens L12 is a glass-molded aspherical lens with aspherical shapes on both sides.

[0161] The sixth lens group G6 consists of a cemented lens made up of a positive meniscus lens L13 with its concave surface facing the object and a biconcave lens L14.

[0162] The seventh lens group G7 consists of a cemented lens made up of a positive meniscus lens L15 with its concave surface facing the object and a negative meniscus lens L16 with its concave surface facing the object.

[0163] The eighth lens group G8 consists of a negative meniscus lens L17 with its concave surface facing the object. The negative meniscus lens L17 is a glass-molded aspherical lens with aspherical shapes on both sides.

[0164] In the zoom lens of Example 5, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 constitute the aforementioned nth group. The sixth lens group G6 corresponds to the aforementioned n+1th group, the seventh lens group G7 corresponds to the aforementioned n+2nd group, and the eighth lens group G8 corresponds to the aforementioned n+3rd group.

[0165] In the zoom lens of Example 5, magnification is achieved by changing the air gap on the optical axis between adjacent lens groups. When zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, and the second lens group G2 moves toward the image plane. The third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 all move toward the image plane in a parabolic trajectory as shown in the figure, and when magnifying to the telephoto end, they ultimately move toward the image plane even further than their position at the wide-angle end. The seventh lens group G7 moves toward the image plane, and the eighth lens group G8 is fixed.

[0166] In the zoom lens of Example 5, focusing from an object at infinity to an object at close range is achieved by the sixth lens group G6 moving toward the image plane.

[0167] Tables 13 to 15 show the specifications, variable interval data, and aspherical data for the zoom lens of Example 5. Figure 10 shows the aberration diagram for the zoom lens of Example 5. The lens containing surface number 10 and the lens containing surface number 17 are both lenses that satisfy both equations (7) and (8) described above.

[0168] [Table 13] No. RD Nd ABV 1 83.7494 1.5000 1.91082 35.25 2 54.4717 9.4094 1.45860 90.19 3 3175.4281 0.1500 4 52.3981 7.5524 1.49700 81.61 5 672.3067 D(5) 6ASPH 206.3414 0.2000 1.53610 41.21 7 139.9785 1.0000 1.64769 33.84 8 25.2605 9.1810 9 -56.8421 1.0000 1.55032 75.50 10 30.1215 6.4510 1.80610 33.27 11 -63.1044 1.2865 12 -36.5690 1.0000 1.72916 54.67 13 -450.7994 D(13) 14 32.6454 3.6755 1.95375 32.32 15 95.8206 D(15) 16STOP 0.0000 1.0000 17 38.9152 1.0000 1.76634 35.83 18 15.8124 9.6716 1.52841 76.45 19 -23.6756 1.0000 1.95375 32.32 20 158.1355 D(20) 21ASPH 51.2092 6.2634 1.76802 49.24 22ASPH -35.5709 D(22) 23 -2244.3513 2.2767 1.94595 17.98 24 -70.8714 1.0000 1.69680 55.46 25 29.6502 D(25) 26 9427.2534 6.3096 1.62299 58.12 27 -24.5425 1.0000 1.92286 20.88 28 -37.0537 D(28) 29ASPH -34.3786 2.8000 1.76802 49.24 30ASPH -222.9637 12.8000 31 0.0000 2.5000 1.51680 64.20 32 0.0000 1.0000

[0169] [Table 14] F 51.5094 79.5312 130.9453 Fno 2.8840 2.8840 2.8840 W 22.5578 14.5934 8.9407 D( 5) 1.5000 16.8284 30.9411 D(13) 30.2809 16.2838 1.5000 D(15) 2.4313 2.8109 1.9560 D(20) 4.3114 4.2900 4.3278 D(22) 2.6071 4.6924 2.5009 D(25) 10.5991 10.4634 18.1888 D(28) 20.2431 16.6049 12.5580

[0170] [Table 15] No. K *4 *6 *8 *10 6 0.00000E+00 3.32649E-06 -2.35501E-11 2.21588E-12 8.17086E-16 21 -2.34516E+00 -5.23931E-06 5.15977E-09 -3.84457E-11 2.96394E-13 22 0.00000E+00 3.16091E-06 -8.15672E-09 2.40340E-11 -5.38801E-14 29 1.48913E+00 -3.35906E-05 2.01292E-07 -6.23243E-10 1.41678E-12 30 0.00000E+00 -4.12598E-05 1.72820E-07 -5.07426E-10 9.39063E-13 No. *12 6 8.11075E-18 21 -8.23666E-16 22 -2.81757E-17 29 -1.52343E-15 30 -8.23331E-16

[0171] The calculated values of the above-described formulae in Examples 1 to 5 are shown in Table 16.

[0172] [Table 16] Example 1 Example 2 Example 3 Example 4 Example 5 f(n+2) / |f(n+3)| 1.45 1.25 0.81 1.38 1.45 b2t / b2w 2.93 2.74 3.04 2.76 2.93 oal2 / |f2| 0.62 0.68 0.67 0.64 0.62 oals / oalw 0.43 0.42 0.43 0.43 0.43 ft / fw 2.54 2.54 2.54 2.54 2.54 nd1 1.91 1.91 1.91 1.91 1.91

Explanation of Symbols

[0173] 1 Imaging device 2 Main body 3 Lens barrel G1~G7 Lens groups L1~L17 Lenses OA Optical axis S Aperture stop

Claims

1. Starting from the object side, the lens system consists of, in order: a first lens group with positive refractive power, a second lens group with negative refractive power, an nth lens group containing one or more lens groups, an (n+1)th lens group with negative refractive power, an (n+2)th lens group with positive refractive power, and an (n+3)th lens group with negative refractive power. During zooming, the first lens group is fixed in the direction of the optical axis. The lens closest to the image plane has negative refractive power, and A zoom lens that satisfies the following equation. 0.77<f(n+2) / |f(n+3)| (1) however, f(n+2): Focal length of the n+2 lens group f(n+3): Focal length of the n+3 lens group

2. A zoom lens according to claim 1, satisfying the following formula. 1.0<b2t / b2w<6.0 (2) however, b2t: Lateral magnification of the second lens group when infinity focus is achieved at the telephoto end. b2w: Lateral magnification of the second lens group when focused at infinity at the wide-angle end.

3. A zoom lens according to claim 1, satisfying the following formula. 0.10<oal2 / |f2|<1.20 (3) however, oal2: Total thickness of the second lens group f2: Focal length of the second lens group

4. A zoom lens according to claim 1, which includes an aperture diaphragm and satisfies the following formula. 0.30< oals / oalw (4) however, oals: Distance from the aperture diaphragm to the image plane when in focus at the wide-angle end. oalw; Optical length at infinity focus at the wide-angle end

5. A zoom lens according to claim 1 that satisfies the following formula. 1.80<nd1 (6) however, nd1: Refractive index of the lens closest to the object with respect to the d line.

6. The zoom lens according to claim 1, having at least one lens that simultaneously satisfies the following equation. 1.70<nd<1.85 (7) 29<vd<40 (8) however, nd: Refractive index of the lens with respect to the d line. vd: Abbe number of the lens with respect to the d line

7. The zoom lens according to claim 1, wherein the nth group has a cemented lens formed by joining three single lenses.

8. An imaging device comprising a zoom lens according to any one of claims 1 to 7, and an image sensor on the image plane side of the zoom lens that converts an optical image formed by the zoom lens into an electrical signal.

Images