Zoom optical system and image capturing device

Abstract

To provide a zoom optical system which offers a high zoom ratio, good optical performance, and a reduced product size.SOLUTION: A zoom optical system provided herein comprises a first lens group, second lens group, third lens group, and a rear group comprising at least three lens groups consisting of fourth through N-th lenses, arranged in order from the object side to the image side, the first, third, and N-th lens groups being stationary relative to the image plane while zooming, and has specific optical characteristics represented by specific expressions.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In addition to imaging devices that can be carried by users such as single-lens reflex cameras, mirrorless single-lens cameras, and digital still cameras, optical systems used in various imaging devices such as surveillance imaging devices and in-vehicle imaging devices are required to have high performance and miniaturization. Therefore, an optical system is known in which the overall optical length is constant, a high magnification zoom is achieved, and only some lens groups are operated during zooming. Such an optical system is known in which a first lens group, a third lens group, and a final lens group are fixed with respect to an image plane, and a zoom optical system in which a diaphragm is disposed in the fixed lens group (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the conventional zoom optical system as described above, further improvement is required from the viewpoints of high performance and miniaturization.

[0005] One aspect of the present invention aims to provide a zoom optical system and an imaging device that achieve a high zoom ratio, good optical performance, and miniaturization of the product.

Means for Solving the Problems

[0006] In order to solve the above problems, a zoom optical system according to an aspect of the present invention includes N lens groups and performs zooming by changing the distance between adjacent lens groups. The zoom optical system includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a rear group having at least three lens groups, which are arranged in order from the object side to the image plane side. The rear group has a fourth lens group on the object side and an Nth lens group on the image plane side, and has an (N - 1)th lens group adjacent to the object side of the Nth lens group. The lens on the image plane side of the second lens group has a negative refractive power. The first lens group, the third lens group, and the Nth lens group do not move with respect to the image plane during zooming and satisfy the following formula. 0.50 < βwr / βtr < 0.85 ··· (1) -4.0 < βw4 / βt4 < -0.4 ··· (2) However, βwr: The product of the lateral magnifications of each lens group from the fourth lens group to the (N - 1)th lens group when focused at infinity at the wide-angle end βtr: The product of the lateral magnifications of each lens group from the fourth lens group to the (N - 1)th lens group when focused at infinity at the telephoto end βw4: The lateral magnification of the fourth lens group when focused at infinity at the wide-angle end βt4: The lateral magnification of the fourth lens group when focused at infinity at the telephoto end

[0007] In addition, in order to solve the above problems, an imaging device according to an aspect of the present invention includes the zoom optical system and an imaging element that converts an optical image formed by the zoom optical system into an electrical signal on the image plane side of the zoom optical system.

Effect of the Invention

[0008] According to an aspect of the present invention, it is possible to provide a zoom optical system and an imaging device that achieve a high zoom ratio, good optical performance, and miniaturization of the product.

Brief Description of the Drawings

[0009]

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Mode for Carrying Out the Invention

[0010] 〔Embodiment 1〕 Hereinafter, an embodiment of the present invention will be described in detail.

[0011] Hereinafter, embodiments of the zoom optical system and the imaging device according to the present invention will be described. More specifically, this embodiment relates to a zoom optical system and an imaging device suitable for an imaging device using a solid-state imaging device (such as a CCD or CMOS) such as a digital still camera or a digital video camera. However, the zoom optical system and the imaging device described below are one aspect of the zoom optical system and the imaging device according to the present invention, and the zoom optical system and the imaging device according to the present invention are not limited to the following aspects.

[0012] 1. Zoom optical system 1-1. Optical configuration An optical configuration of a zoom optical system according to an embodiment of the present invention will be described. The zoom optical system of this embodiment is a zoom optical system that includes N lens groups and performs zooming by changing the distance between adjacent lens groups. The zoom optical system of this embodiment is composed of a first lens group, a second lens group, a third lens group, and a rear group, which are arranged in order from the object side to the image plane side. Note that the set of the first lens group, the second lens group, and the third lens group may be referred to as the front group. The zoom optical system of this embodiment may be composed of only the front group and the rear group.

[0013] In this specification, the "lens group" means a set of one or more lenses that interlock in the zoom operation. The lenses in the lens group move while maintaining their relative positional relationship in the zoom operation. The zoom operation is performed by changing the distance between the lens groups, and the distance between the lenses belonging to the same lens group does not change in the zoom operation.

[0014] (1) Front group The first lens group has a positive refractive power, the second lens group has a negative refractive power, and the third lens group has a positive refractive power. This configuration is preferable from the viewpoint of easily adopting a refractive power arrangement of a telephoto type and realizing aberration correction and a high zoom ratio. Also, having the first lens group having a positive refractive power as the lens group closest to the object side is preferable from the viewpoint of obtaining a large-aperture zoom optical system. This configuration is particularly preferable when the second lens group is used as a variator during zooming.

[0015] The lens closest to the image plane side of the second lens group has a negative refractive power. This configuration is preferable from the viewpoint of realizing desired optical performance. The second lens group preferably consists of, in order from the object side, a lens having a negative refractive power, a lens having a negative refractive power, a lens having a positive refractive power, and a lens having a negative refractive power. This configuration is preferable from the viewpoint of realizing good optical performance.

[0016] That the first lens group and the third lens group have positive refractive powers facilitates the arrangement of a front group having a strong positive refractive power in the zoom optical system. Therefore, this is preferable from the viewpoint of being able to form a zoom optical system with a strong telephoto tendency and a short overall optical length compared to the focal length. Further, this configuration is preferable from the viewpoint of suppressing fluctuations in various aberrations such as spherical aberration, astigmatism, and axial chromatic aberration during zooming, and realizing a zoom optical system with higher resolution over the entire zoom range.

[0017] (2) Rear group The rear group is a set of lens groups from the fourth lens group to the Nth lens group, which is the lens group closest to the image plane, arranged in order from the object side to the image plane side. The rear group has at least three lens groups. That is, N is an integer of 6 or more, and the rear group includes at least the fourth lens group, the Nth lens group, and the (N - 1)th lens group. The (N - 1)th lens group is arranged adjacent to the object side of the Nth lens group. This configuration is preferable from the viewpoint of realizing a high zoom ratio of the zoom optical system. On the other hand, from the viewpoint of miniaturizing the zoom optical system, N is preferably 8 or less, and more preferably 7 or less.

[0018] The fourth lens group preferably has a negative refractive power, the (N - 1)th lens group preferably has a positive refractive power, and the Nth lens group preferably has a negative refractive power. In such a power arrangement of the lens groups, that the fourth lens group has a negative refractive power is preferable from the viewpoint of suitably distributing the zooming action and expanding the zoom ratio. Also, in such a power arrangement of the lens groups, that the Nth lens group is negative is preferable from the viewpoint of reducing the telephoto ratio. In this specification, the telephoto ratio refers to the ratio of the overall optical length of the optical system to the focal length when the optical system is focused at infinity.

[0019] The configuration of the lens groups arranged on the image plane side of the fourth lens group and on the object side of the Nth lens group, other than the (N - 1)th lens group, is not particularly limited. For example, there may be one or more lens groups other than the (N - 1)th lens group on the image plane side of the fourth lens group and on the object side of the Nth lens group.

[0020] The lenses constituting the rear lens group preferably have an outer diameter smaller than those of the first lens group and the third lens group. In particular, since the fourth lens group and the N-1 lens group are lens groups that move, it is preferable for the outer diameter to be small from the viewpoint of miniaturizing the moving mechanism.

[0021] (3) Aperture The zoom optical system may include a diaphragm. The diaphragm may be disposed inside the third lens group or may be disposed adjacent to the image plane side of the third lens group. This configuration is preferable from the viewpoint of performing aberration correction. In particular, it is preferable for the diaphragm to be disposed within the third lens group from the viewpoint of miniaturizing the entire zoom optical system.

[0022] (4) Others From the viewpoint of miniaturization, the telephoto ratio of the zoom optical system is preferably 0.85 or less, and more preferably 0.80 or less. On the other hand, from the viewpoints of appropriately performing aberration correction and suppressing the influence on manufacturing tolerances, for example, the telephoto ratio of the zoom optical system is preferably 0.50 or more, and preferably 0.60 or more.

[0023] 1-2. Operations (1) Operations during zooming During zooming, the first lens group does not move with respect to the image plane. This configuration is preferable from the viewpoints of not changing the lens barrel length during zooming and improving dustproof performance and drip-proof performance. Further, this configuration is preferable from the viewpoint of realizing a zoom optical system excellent in manufacturability and robustness.

[0024] When zooming from the wide-angle end to the telephoto end, the second lens group preferably moves from the object side to the image plane side. That is, the second lens group preferably functions as a first variator. A configuration in which the second lens group having a negative refractive power sandwiched between the first lens group and the third lens group having positive refractive powers is used as a variator during zooming is preferable from the viewpoint of realizing a high zoom ratio while correcting aberrations.

[0025] When zooming from the wide-angle end to the telephoto end, the movement pattern of the second lens group is not particularly limited. For example, from the perspective of simplifying the driving mechanism of the second lens group and improving the manufacturability of the lens system, it may move gradually. Here, "moving gradually" means that the lens group moves in a straight orbit in one direction.

[0026] During zooming, the third lens group does not move with respect to the image plane. This configuration is preferable from the perspective of stabilizing the decentration relationship from the first lens group to the third lens group because it enables the first lens group and the third lens group to be fixed in the same lens barrel.

[0027] The aperture stop is arranged within the third lens group and preferably does not move with respect to the image plane during zooming. This configuration is preferable from the perspective of miniaturizing the entire zoom optical system because it eliminates the need to move the driving mechanism for opening and closing the aperture stop during zooming.

[0028] When zooming from the wide-angle end to the telephoto end, the fourth lens group preferably moves from the object side to the image side. The fourth lens group preferably functions as a second variator. This configuration is preferable from the perspective of distributing the zooming action to the fourth lens group and achieving both miniaturization of the zoom optical system and an improvement in the zoom ratio.

[0029] When zooming from the wide-angle end to the telephoto end, the movement pattern of the fourth lens group is not particularly limited. For example, from the perspective of simplifying the driving mechanism of the fourth lens group and improving the manufacturability of the lens system, it may move gradually.

[0030] The (N-1)th lens group preferably moves along a trajectory different from that of the fourth lens group. This movement pattern is preferable from the viewpoint of further distributing the zooming effect in the rear lens groups. The (N-1)th lens group preferably functions as a so-called compensator. For example, when zooming from the wide-angle end to the telephoto end, it is preferable to move along a trajectory that is convex on the object side with respect to the image plane and in which the position of the (N-1)th lens group at the telephoto end is closer to the image plane than the position of the (N-1)th lens group at the wide-angle end. This movement pattern is preferable from the viewpoint of more suitably correcting the image plane movement associated with zooming in the lens configuration according to the present embodiment.

[0031] The Nth lens group does not move with respect to the image plane during zooming. This configuration is preferable from the viewpoint of improving the dust-proof and drip-proof performance on the image plane side. Also, the fact that the first lens group and the Nth lens group do not move with respect to the image plane is preferable from the viewpoint of stably holding the lens group on the most object side and the lens group on the most image plane side in the lens barrel or the like, thereby improving the robustness of the zoom optical system.

[0032] As described above, the zoom optical system according to the present embodiment has a plurality of lens groups that move during zooming. This configuration is preferable for shortening the movement distance of each lens group during zooming. On the other hand, it is preferable that the number of lenses that move during zooming is 4 or less. This configuration is preferable from the viewpoint of simplifying the zoom optical system.

[0033] (2) Operation at focusing When focusing the zoom optical system, it is preferable that the lens group that moves is the fourth lens group or the fifth lens group. Since these lens groups are lenses within the rear lens groups, they have a smaller outer diameter than the other lens groups. Also, since they are lens groups that move during zooming, a common movement mechanism can be used. Therefore, this configuration is preferable from the viewpoint of miniaturizing and lightening the movement mechanism for focusing. In particular, it is preferable that the fourth lens group moves along the optical axis of the zoom optical system. The fourth lens group is easier to lighten than the (N-1)th lens group, and thus is preferable from the viewpoint of further miniaturizing and lightening the movement mechanism.

[0034] 1-3. Equation The zoom optical system adopts the above-described configuration and preferably satisfies at least one of the following equations to be described next.

[0035] 1-3-1. Equation (1) 0.50 < βwr / βtr < 0.85 ··· (1) However, βwr: The product of the transverse magnifications of each lens group from the fourth lens group to the (N-1)th lens group when focused at infinity at the wide-angle end βtr: The product of the transverse magnifications of each lens group from the fourth lens group to the (N-1)th lens group when focused at infinity at the telephoto end

[0036] Equation (1) represents the influence degree of the refractive power of the rear group on the entire zoom optical system.

[0037] When βwr / βtr is less than 0.50, the influence degree of the rear group on the entire zoom optical system increases, and the influence on aberration may increase. Among them, in particular, the influence on spherical aberration may increase. As a result, it may be necessary to increase the configuration of the rear group lenses for aberration correction.

[0038] When βwr / βtr exceeds 0.85, while the influence of the rear group on aberration is reduced, the moving distance of the lens groups within the rear group during zooming increases, so the telephoto ratio may increase. Also, it may be necessary to increase the refractive power of the second lens group that moves during zooming.

[0039] From the viewpoint of avoiding the enlargement and complexity of the lens configuration for aberration correction and miniaturizing the zoom optical system, βwr / βtr is preferably 0.55 or more, and more preferably 0.60 or more. From the viewpoint of miniaturizing the zoom optical system and suppressing distortion aberration on the wide-angle end side, βwr / βtr is preferably 0.80 or less, and more preferably 0.75 or less.

[0040] 1-3-2. Equation (2) -4.0 < βw4 / βt4 < -0.4 ··· (2) However βw4: Lateral magnification of the fourth lens group at infinity focus at the wide-angle end βt4: Lateral magnification of the fourth lens group at infinity focus at the telephoto end

[0041] Equation (2) represents the magnification ratio of the fourth lens group. In the zoom optical system according to the present invention, when zooming from the wide-angle end to the telephoto end, since infinity is sandwiched, the value of βw4 / βt4 becomes negative. The value of βw4 / βt4 becoming negative reduces the telephoto ratio.

[0042] When βw4 / βt4 exceeds -0.4, the refractive power of the fourth lens group may become weak. As a result, the moving distance of the lens groups within the rear group that moves during zooming increases, and it may be necessary to perform aberration correction with the lens groups on the image plane side rather than the fourth lens group.

[0043] When βw4 / βt4 is less than -4, the refractive power of the fourth lens group becomes strong, and it may not be possible to suppress image plane distortion.

[0044] From the viewpoint of achieving both miniaturization of the zoom optical system and suppression of the variation in coma aberration by suppressing the moving distance of the lens groups within the rear group that moves during zooming and appropriately performing aberration correction, βw4 / βt4 is preferably -3.0 or more, and more preferably -2.5 or more. From the viewpoint of realizing good optical performance by setting the refractive power of the fourth lens group within an appropriate range and suppressing image plane distortion, βw4 / βt4 is preferably -1.0 or less, and more preferably -1.2 or less.

[0045] 1-3-3. Equation (3) Z > 20 ··· (3) However, Z: Zoom ratio of the zoom optical system

[0046] Equation (3) shows the preferred zoom ratio of the zoom optical system.

[0047] When Z is less than 20, for a zoom optical system having six or more lens groups, the zoom ratio is small, which is not preferable from the viewpoint of optical performance.

[0048] From the perspective of good optical performance, the zoom ratio Z of the zoom optical system according to this embodiment is preferably greater than 25, and more preferably greater than 27. Since the larger the zoom ratio Z is, the more preferable it is, the upper limit value of the formula (3) is not particularly limited. However, from the perspective of feasibility, for example, it may be less than 50.

[0049] 1-3-4. Formula (4) When N is 6, the zoom optical system according to this embodiment satisfies the following.

[0050] 0.50 < (βw4 × βw5) / (βt4 × βt5) < 0.85 ··· (4) However, βw5: Lateral magnification of the fifth lens group when focused at infinity at the wide-angle end βt5: Lateral magnification of the fifth lens group when focused at infinity at the telephoto end Formula (4) represents the influence degree of the refractive power of the rear group on the entire zoom optical system.

[0051] When (βw4 × βw5) / (βt4 × βt5) is less than 0.50, the influence degree of the rear group on the entire zoom optical system increases, and the influence on aberration increases. Among the influences on aberration, in particular, the influence on spherical aberration increases. As a result, it may be necessary to increase the configuration of the rear group lenses for aberration correction.

[0052] When (βw4 × βw5) / (βt4 × βt5) exceeds 0.85, while the influence of the rear group on aberration is reduced, the moving distance of the lens groups within the rear group during zooming becomes large, so there is a risk that the telephoto ratio will increase. In addition, it may be necessary to increase the refractive power of the second lens group that moves during zooming.

[0053] From the perspective of avoiding the enlargement and complication of the lens configuration for aberration correction and miniaturizing the zoom optical system, (βw4×βw5) / (βt4×βt5) is preferably 0.55 or more, and more preferably 0.60 or more. From the perspective of miniaturizing the zoom optical system and suppressing distortion aberration on the wide-angle end side, (βw4×βw5) / (βt4×βt5) is preferably 0.80 or less, and more preferably 0.75 or less.

[0054] 2. Imaging device Next, an imaging device according to an embodiment of the present invention will be described. The imaging device includes the zoom optical system according to the above-described embodiment, and an image sensor provided on the image plane side of the zoom optical system for converting an optical image formed by the zoom optical system into an electrical signal.

[0055] Here, there is no limitation on the image sensor, and solid-state image sensors such as CCD (Charge Coupled Device) sensors and CMOS (Complementary Metal Oxide Semiconductor) sensors can be used for the image sensor, and silver halide films, infrared cut filters (IRCF), etc. can also be used. The imaging device according to the present embodiment is suitable for imaging devices using the above solid-state image sensors such as digital cameras and video cameras. Further, the imaging device may be a lens-fixed imaging device in which the lens is fixed to the housing, or a lens-exchangeable imaging device such as a single-lens reflex camera and a mirrorless single-lens camera. In particular, the zoom optical system according to the present embodiment can ensure a back focus suitable for an interchangeable lens system. Therefore, it is suitable for imaging devices such as single-lens reflex cameras equipped with an optical viewfinder, a phase difference sensor, and a reflex mirror for branching light to these.

[0056] Figure 21 is a diagram schematically showing an example of the configuration of the imaging device according to the present embodiment. As shown in Figure 21, the mirrorless single-lens camera 1 has a main body 2 and a lens barrel 3 detachably attached to the main body 2. The lens barrel 3 is provided with a zoom optical system inside thereof, and a zoom lens is constituted by the lens barrel 3 and the zoom optical system. The mirrorless single-lens camera 1 is an aspect of the imaging device.

[0057] The zoom optical system includes a first lens group G1 to a sixth lens group G6. The zoom optical system is configured to satisfy, for example, the above-described formulas (1) and (2). Note that a diaphragm S is disposed on the object side of the lens L10 included in the lens group 3.

[0058] The first lens group G1 has a positive refractive power as a whole and is constituted by lenses L1 to L4. The second lens group G2 has a negative refractive power as a whole and is constituted by lenses L4 to L8. The third lens group G3 has a positive refractive power as a whole and is constituted by lenses L9 and L10. The fourth lens group G4 has a negative refractive power as a whole and is constituted by lenses L11 and L12. The fifth lens group G5 has a positive refractive power as a whole and is constituted by lenses L13 to L16. The sixth lens group G6 has a negative refractive power as a whole and is constituted by lenses L17 and L18.

[0059] The main body 2 has a CCD sensor I as an imaging element and a cover glass CG. The CCD sensor I is disposed at a position in the main body 2 where the optical axis OA of the zoom optical system in the lens barrel 3 attached to the main body 2 is the central axis. The main body 2 may have a parallel plate having substantially no refractive power, such as an infrared cut filter (IRCF), instead of the cover glass CG.

[0060] Since the mirrorless single-lens camera 1 includes a zoom optical system, high optical performance and miniaturization of the product can be achieved simultaneously.

[0061] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in 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.

[0062] (Summary) The zoom optical system according to Aspect 1 of the present invention is a zoom optical system that includes N lens groups and performs zooming by changing the distance between adjacent lens groups. The zoom optical system includes, in order from the object side to the image plane side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a rear group having at least three lens groups. The rear group has a fourth lens group on the most object side and an Nth lens group on the most image plane side, and has an (N - 1)th lens group adjacent to the object side of the Nth lens group. The lens on the most image plane side of the second lens group has a negative refractive power. The first lens group, the third lens group, and the Nth lens group do not move with respect to the image plane during zooming, and satisfy the following formula. 0.50 < βwr / βtr < 0.85 ··· (1) -4.0 < βw4 / βt4 < -0.4 ··· (2) However, βwr: The product of the lateral magnifications of each lens group from the fourth lens group to the (N - 1)th lens group at infinity focus at the wide-angle end βtr: The product of the lateral magnifications of each lens group from the fourth lens group to the (N - 1)th lens group at infinity focus at the telephoto end βw4: The lateral magnification of the fourth lens group at infinity focus at the wide-angle end βt4: The lateral magnification of the fourth lens group at infinity focus at the telephoto end

[0063] The zoom optical system according to Aspect 2 of the present invention is, in Aspect 1 or 2, the second lens group is composed of, in order from the object side, a lens having a negative refractive power, a lens having a negative refractive power, a lens having a positive refractive power, and a lens having a negative refractive power.

[0064] The zoom optical system according to Aspect 3 of the present invention satisfies the following formula (3). Z > 20 ··· (3) However, Z: Zoom ratio of the zoom optical system

[0065] The zoom optical system according to Embodiment 4 of the present invention is, in any one of Embodiments 1 to 3, when zooming from the wide-angle end to the telephoto end, convex toward the object side with respect to the image plane, and the position of the (N-1)th lens group at the telephoto end is configured to move on an orbit that is closer to the image plane than the position of the (N-1)th lens group at the wide-angle end.

[0066] The zoom optical system according to Embodiment 5 of the present invention is, in any one of Embodiments 1 to 4, N is 6, and satisfies the following formula (4). 0.50 < (βw4 × βw5) / (βt4 × βt5) < 0.85 ··· (4) However, βw5: Lateral magnification of the 5th lens group at infinity focus at the wide-angle end βt5: Lateral magnification of the 5th lens group at infinity focus at the telephoto end

[0067] The imaging device according to Embodiment 6 of the present invention includes any one of the zoom optical systems according to Embodiments 1 to 5, and an imaging element that converts the optical image formed by the zoom optical system into an electrical signal on the image plane side of the zoom optical system.

Example

[0068] One embodiment of the present invention will be described below. In the following tables, unless otherwise specified, the unit of length is all "mm", the unit of the angle of view is all "°", and "E+a" means "×10 a ".

[0069] [Example 1] (1) Configuration of the optical system FIG. 1 is a diagram schematically showing an optical configuration at the wide-angle end when the zoom optical system of Example 1 is focused at infinity. The zoom optical system of Example 1 includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a negative refractive power, a fifth lens group G5 having a positive refractive power, and a sixth lens group G6 having a negative refractive power. The fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 correspond to the aforementioned rear group.

[0070] The zoom optical system focuses from an infinite object to a near-distance object by moving the fifth lens group G5 toward the object side. The fourth lens group G4 is configured to be movable in a direction intersecting the optical axis and functions as an anti-shake lens group that corrects image blur during imaging.

[0071] In Example 1, the zoom optical system performs zooming by changing the air gap on the optical axis between adjacent lens groups. Since the same applies to the following examples, the description will be omitted below.

[0072] The arrows in FIG. 1 indicate the moving directions and moving patterns of the respective lens groups during zooming from the wide-angle end to the telephoto end. As shown in FIG. 1, when zooming from the wide-angle end to the telephoto end, the first lens group G1, the third lens group G3, and the sixth lens group G6 do not move. When zooming from the wide-angle end to the telephoto end, the second lens group G2 gradually moves toward the image plane side, and the fourth lens group gradually moves toward the image plane side. When zooming from the wide-angle end to the telephoto end, the fifth lens group G5 first moves toward the object side and then moves toward the image plane side. The position of the fifth lens group G5 at the telephoto end is closer to the image plane than its position at the wide-angle end. The moving speed of the fifth lens group G5 toward the object side is slower than that toward the image plane side.

[0073] The aperture stop S is disposed closest to the image plane within the third lens group G3. Also, "I" shown in FIG. 1 is the image plane, which is, for example, the imaging plane of a solid-state imaging device such as a CCD sensor and a CMOS sensor, or the film plane of a silver halide film. Further, a cover glass CG is disposed between the sixth lens group G6 and the CCD sensor I. Since these points are the same in the diagrams schematically showing the optical configurations shown in other embodiments, the description thereof will be omitted below.

[0074] The configurations of the respective lens groups will be described below. The first lens group G1 is composed of, in order from the object side, a cemented lens of a first lens having a negative meniscus shape with the convex surface facing the object side and a second lens which is a biconvex lens, a third lens having a positive meniscus shape with the convex surface facing the object side, and a fourth lens having a positive meniscus shape with the convex surface facing the object side. Note that a lens having a negative meniscus shape is a lens having a negative refractive power, and a lens having a positive meniscus shape is a lens having a positive refractive power.

[0075] The second lens group G2 is composed of, in order from the object side, a fifth lens having a negative meniscus shape with the convex surface facing the object side, a sixth lens having a negative meniscus shape with the convex surface facing the image plane side, a seventh lens which is a biconvex lens, and an eighth lens having a negative meniscus shape with the convex surface facing the image plane side.

[0076] The third lens group G3 is composed of, in order from the object side, an eighth lens which is a biconvex lens and a ninth lens having a positive meniscus shape with the convex surface facing the object side.

[0077] The fourth lens group G4 is composed of, in order from the object side, a tenth lens which is a biconcave lens and an eleventh lens having a positive meniscus shape with the convex surface facing the object side.

[0078] The fifth lens group G5 is composed of, in order from the object side, a twelfth lens which is a biconvex lens, a thirteenth lens which is a biconcave lens, a fourteenth lens which is a biconvex lens, and a fifteenth lens which is a biconvex lens.

[0079] The sixth lens group G6 is composed of, in order from the object side, a 16th lens which is a biconcave lens and a 17th lens which is a biconvex lens.

[0080] (2) Numerical examples Next, numerical examples applying specific numerical values of the zoom optical system will be described. Table 1 shows the specifications table of the zoom optical system of Example 1. In the specifications table, "BF" is the back focus.

[0081] [Table 1] Wide-angle end Intermediate Telephoto end Focal length 10.150 100.005 299.017 F number 2.8 3.5 5.0 Image height 6.8 6.8 6.8 Half field angle 38.058 3.889 1.279 BF 12.495 12.495 12.495

[0082] Table 2 shows the surface data of the zoom optical system. In the surface data in the examples of the present invention, "NS" is the order of the lens surface counted from the object side, "R" is the radius of curvature of the lens surface, "D" is the interval on the optical axis of the lens surface, "Nd" is the refractive index with respect to the d-line (wavelength λ = 587.56 nm), and "ABV" is the Abbe number with respect to the d-line (wavelength λ = 587.56 nm). Also, "STOP" displayed in the column next to the surface number indicates that it is the aperture stop S. Further, the display such as "D(8)" in the column of "D" means that it is a variable interval in which the interval on the optical axis of the lens surface changes during zooming or focusing. In the examples, "the lens group moves" means a movement that exhibits a desired optical effect, and does not include a movement in which even a slight movement does not exhibit a substantial optical effect. For example, D(39) varies slightly, but this does not mean that the sixth lens group moves, and substantially the sixth lens group is fixed.

[0083] In Table 2, Nos. 1 to 8 are the surface numbers of the first lens group G1. Nos. 9 to 16 are the surface numbers of the second lens group G2. Nos. 17 to 20 are the surface numbers of the third lens group G3. No. 21 is the surface number of the aperture stop S. Nos. 22 to 25 are the surface numbers of the fourth lens group G4. Nos. 26 to 33 are the surface numbers of the fifth lens group G5. Nos. 34 to 37 are the surface numbers of the sixth lens group G6. Nos. 38 and 39 are the surface numbers of the cover glass.

[0084] [Table 2] NS R D Nd ABV 1 383.3416 1.2000 1.83400 37.16 2 75.1842 0.0100 1.54814 45.78 3 75.1674 13.0350 1.49700 81.61 4 -548.9689 0.2000 5 81.3838 9.4046 1.49700 81.61 6 1444.0071 0.2000 7 79.3495 7.4983 1.49700 81.61 8 521.0670 D(8) 9 421.3225 1.2000 1.83481 42.72 10 21.8504 5.9833 11 -64.2437 1.0000 1.83481 42.72 12 -868.5381 0.5000 13 106.2687 2.7132 1.84666 23.78 14 -427.5411 2.3111 15 -34.4407 1.0000 1.83400 37.34 16 -112.9449 D(16) 17 2054.5920 2.9915 1.84666 23.78 18 -45.8948 0.2000 19 34.8892 3.2003 1.74330 49.22 20 303.4202 1.1693 21 STOP 0.0000 D(21) 22 -52.9893 1.0000 1.83481 42.72 23 25.0568 0.4619 24 24.5232 2.2908 1.51742 52.43 25 54.1400 D(25) 26 64.5914 4.0926 1.69100 54.82 27 -41.2993 2.0000 28 -31.9434 1.0000 1.85451 25.15 29 51.7352 0.5701 30 76.0403 4.3127 1.67790 55.34 31 -39.1597 0.2000 32 42.5686 5.4831 1.49700 81.61 33 -45.5476 D(33) 34 -26.5115 1.0000 1.83481 42.72 35 54.0115 0.2000 36 30.4859 3.6309 1.67270 32.10 37 -47.5272 1.0000 38 0.0000 0.7500 1.51680 64.20 39 0.0000 D(39)

[0085] Table 3 shows the distances of the respective variable intervals when the zoom optical system is focused at infinity.

[0086] [Table 3] Zoom interval Wide-angle end Middle Telephoto end D(8) 1.0000 52.7517 63.6395 D(16) 63.6395 11.8878 1.0000 D(21) 1.9090 15.1014 35.4578 D(25) 29.2016 7.1244 14.0940 D(33) 19.9412 28.8260 1.5000 D(39) 11.0022 11.0050 11.0023

[0087] Table 4 shows the focal lengths of the respective lens groups of the zoom optical system.

[0088] [Table 4] Group Starting Surface Focal Length 1 1 102.059 2 9 -16.239 3 17 26.456 4 21 -26.420 5 26 31.327 6 34 -107.853

[0089] Also, FIGS. 2, 3, and 4 are diagrams showing the longitudinal aberration diagrams at infinity focus at the wide-angle end, intermediate position, and telephoto end of the zoom optical system of Example 1, respectively. The longitudinal aberration diagrams shown in each figure are, in order from the left side toward the drawing surface, spherical aberration (mm), astigmatism (mm), and distortion (%) respectively. The same applies to other embodiments.

[0090] In the diagram representing spherical aberration, the vertical axis is the F number and the horizontal axis is defocus. In the diagram representing spherical aberration, the solid line indicates the spherical aberration at the d line (wavelength λ = 587.56 nm), and the broken line indicates the spherical aberration at the g line (wavelength λ = 435.84 nm).

[0091] In the diagram representing astigmatism, the vertical axis is the semi-field angle and the horizontal axis is defocus. In the diagram representing astigmatism, the solid line indicates the sagittal image plane (ΔS) with respect to the d line, and the broken line indicates the meridional image plane (ΔM) with respect to the d line.

[0092] In the diagram representing distortion, the vertical axis is the semi-field angle and the horizontal axis is %.

[0093] [Example 2] (1) Configuration of the optical system FIG. 5 is a diagram schematically showing the optical configuration at the wide-angle end when the zoom optical system of Example 2 is focused at infinity. The zoom optical system of Example 2 is composed of, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a negative refractive power, a fifth lens group G5 having a positive refractive power, and a sixth lens group G6 having a negative refractive power. The fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 correspond to the aforementioned rear group.

[0094] The zoom optical system focuses from an infinite object to a near-distance object by moving the fifth lens group G5 toward the object side. Further, the cemented lens of the 14th lens and the 15th lens included in the fourth lens group G4 is configured to be movable in a direction intersecting the optical axis, and functions as an anti-shake lens group that corrects image blur during imaging.

[0095] The arrows in FIG. 5 indicate the moving directions and moving patterns of the respective lens groups during zooming from the wide-angle end to the telephoto end. As shown in FIG. 5, during zooming from the wide-angle end to the telephoto end, the first lens group G1, the third lens group G3, and the sixth lens group G6 do not move. During zooming from the wide-angle end to the telephoto end, the second lens group G2 gradually moves toward the image plane side, and the fourth lens group gradually moves toward the image plane side. During zooming from the wide-angle end to the telephoto end, the fifth lens group G5 first moves toward the object side and then moves toward the image plane side. The position of the fifth lens group G5 at the telephoto end is closer to the image plane than its position at the wide-angle end. The moving speed of the fifth lens group G5 toward the object side is slower than that toward the image plane side.

[0096] Hereinafter, the configuration of each lens group will be described. The first lens group G1 is composed of, in order from the object side, a cemented lens of a first lens having a negative meniscus shape with a convex surface facing the object side and a second lens that is a biconvex lens, a third lens having a positive meniscus shape with a convex surface facing the object side, and a fourth lens having a positive meniscus shape with a convex surface facing the object side.

[0097] The second lens group G2 is composed of, in order from the object side, a fifth lens having a negative meniscus shape with a convex surface facing the object side, a sixth lens which is a biconcave lens, a seventh lens which is a biconvex lens, and a cemented lens of an eighth lens having a negative meniscus shape with a convex surface facing the image side.

[0098] The third lens group G3 is composed of, in order from the object side, a cemented lens of a ninth lens having a negative meniscus shape with a convex surface facing the object side and a tenth lens which is a biconvex lens, and an eleventh lens which is a biconvex lens.

[0099] The fourth lens group G4 is composed of, in order from the object side, a twelfth lens which is a biconcave lens, a thirteenth lens which is a biconvex lens, and a cemented lens of a fourteenth lens which is a biconcave lens and a fifteenth lens having a positive meniscus shape with a convex surface facing the object side.

[0100] The fifth lens group G5 is composed of, in order from the object side, a sixteenth lens which is a biconvex lens, a seventeenth lens which is a biconvex lens, and an eighteenth lens having a positive meniscus shape with a convex surface facing the object side.

[0101] The sixth lens group G6 is composed of, in order from the object side, a nineteenth lens which is a biconcave lens, a twentieth lens having a positive meniscus shape with a convex surface facing the object side, and a twenty-first lens which is a biconvex lens.

[0102] (2) Numerical Examples Next, numerical examples applying specific numerical values of the zoom optical system will be described. Table 5 shows the specifications table of the zoom optical system of Example 2.

[0103] [Table 5] Wide-angle end Intermediate Telephoto end Focal length 10.150 55.000 298.992 F-number 2.9 3.4 5.0 Image height 6.8 6.8 6.8 Half field angle 37.130 7.063 1.275 BF 12.495 12.495 12.495

[0104] Table 6 shows the surface data of the zoom optical system.

[0105] [Table 6] NS R D Nd ABV 1 250.1162 1.2000 1.83400 37.21 2 68.5167 0.0200 1.54814 45.78 3 68.5854 12.2082 1.49700 81.61 4 -656.6898 0.2000 5 100.4494 6.4593 1.45860 90.19 6 607.2089 0.2000 7 56.9864 9.2414 1.45860 90.19 8 522.6825 D(8) 9 10683.4437 1.2000 1.83400 37.34 10 16.1893 6.3605 11 -37.4114 1.0000 1.83481 42.72 12 76.3089 0.2000 13 61.1890 4.9547 1.84666 23.78 14 -31.1207 0.2000 15 -31.1436 1.0000 1.83481 42.72 16 -1128.0563 D(16) 17 55.9939 1.1000 1.84666 23.78 18 27.5129 0.0200 1.54814 45.78 19 27.5129 4.4910 1.81554 44.36 20 -60.1906 0.2000 21 40.5875 3.1696 1.75520 27.51 22 -124.9341 1.0000 23 STOP 0.0000 D(23) 24 -23.7501 1.0000 1.77250 49.60 25 21.1050 0.5571 26 21.7065 4.6941 1.51742 52.43 27 -17.5778 0.2000 28 -41.8619 1.0000 1.85883 30.00 29 28.8027 0.0200 1.54814 45.78 30 29.1367 2.3943 1.48749 70.44 31 99.7131 D(31) 32 145.5001 3.0721 1.43700 95.10 33 -38.5152 0.2000 34 55.2411 2.9393 1.43700 95.10 35 -94.8663 0.2000 36 32.6452 2.8949 1.43700 95.10 37 337.5941 D(37) 38 -68.7114 1.0000 1.83400 37.16 39 12.5891 0.0934 40 13.1106 2.1859 1.48749 70.44 41 21.1555 2.2529 42 17.6904 4.8286 1.43700 95.10 43 -24.5397 1.0000 44 0.0000 0.7500 1.51680 64.20 45 0.0000 D(45)

[0106] Table 7 shows the distances of each variable interval when the zoom optical system is focused at infinity.

[0107] [Table 7] Zoom Interval, Wide Angle End, Middle, Telephoto End D(8) 1.2281 46.1539 65.7041 D(16) 65.4760 20.5502 1.0000 D(23) 2.1849 3.9681 16.7514 D(31) 20.2433 8.3340 15.8372 D(37) 12.6605 22.7865 2.5000 D(45) 11.0000 11.0000 11.0000

[0108] Table 8 shows the focal lengths of the respective lens groups of the zoom optical system.

[0109] [Table 8] Group, Starting Surface, Focal Length 1 1 97.654 2 9 -13.310 3 17 20.036 4 21 -17.872 5 32 26.357 6 38 -85.024

[0110] Also, FIGS. 6, 7, and 8 are diagrams showing the longitudinal aberration diagrams at infinity focus at the wide angle end, middle position, and telephoto end of the zoom optical system of Example 2, respectively.

[0111] [Example 3] (1) Configuration of the Optical System FIG. 9 is a diagram schematically showing the optical configuration at the wide angle end at infinity focus of the zoom optical system of Example 3. The zoom optical system of Example 3 is composed of, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a negative refractive power, a fifth lens group G5 having a positive refractive power, and a sixth lens group G6 having a negative refractive power. The fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 correspond to the aforementioned rear group.

[0112] The zoom optical system focuses from an infinite object to a close object by moving the fifth lens group G5 toward the object side. The fourth lens group G4 is configured to be movable in a direction intersecting the optical axis and functions as an anti-shake lens group that corrects image blur during imaging.

[0113] The arrows in FIG. 9 indicate the moving directions and moving patterns of the respective lens groups during zooming from the wide-angle end to the telephoto end. As shown in FIG. 9, during zooming from the wide-angle end to the telephoto end, the first lens group G1, the third lens group G3, and the sixth lens group G6 do not move. During zooming from the wide-angle end to the telephoto end, the second lens group G2 gradually moves toward the image plane side, and the fourth lens group gradually moves toward the image plane side. During zooming from the wide-angle end to the telephoto end, the fifth lens group G5 first moves toward the object side and then moves toward the image plane side. The position of the fifth lens group G5 at the telephoto end is closer to the image plane than its position at the wide-angle end. The moving speed of the fifth lens group G5 toward the object side is slower than that toward the image plane side.

[0114] The configurations of the respective lens groups will be described below. The first lens group G1 is composed of, in order from the object side, a cemented lens of a first lens having a negative meniscus shape with a convex surface facing the object side and a second lens that is a biconvex lens, and a third lens that is a biconvex lens.

[0115] The second lens group G2 is composed of, in order from the object side, a fourth lens that is a biconcave lens, a fifth lens that is a biconcave lens, a sixth lens that is a biconvex lens, and a seventh lens that is a biconcave lens.

[0116] The third lens group G3 is composed of, in order from the object side, an eighth lens that is a biconvex lens, and a ninth lens having a positive meniscus shape with a convex surface facing the object side.

[0117] The fourth lens group G4 is composed of, in order from the object side, a tenth lens that is a biconcave lens, an eleventh lens that is a biconvex lens, and a twelfth lens having a negative meniscus shape with a convex surface facing the image plane side.

[0118] The fifth lens group G5 is composed of, in order from the object side, a 13th lens having a negative meniscus shape with a convex surface facing the object side, a 14th lens which is a biconvex lens, and a 15th lens which is a biconvex lens.

[0119] The sixth lens group G6 is composed of, in order from the object side, a cemented lens of a 16th lens which is a biconcave lens and a 17th lens which is a biconvex lens.

[0120] (2) Numerical Examples Next, numerical examples applying the specific numerical values of the zoom optical system will be described. Table 9 shows the specifications table of the zoom optical system of Example 3.

[0121] [Table 9] Wide-angle end Intermediate Telephoto end Focal length 10.150 100.000 298.958 F-number 2.8 3.2 5.0 Image height 6.8 6.8 6.8 Half field angle 38.928 3.853 1.265 BF 12.495 12.495 12.495

[0122] Table 10 shows the surface data of the zoom optical system. Note that "ASPH" displayed in the column next to the surface number indicates that the lens surface is an aspherical surface, and at this time, the paraxial radius of curvature is shown in the column of the radius of curvature R.

[0123] [Table 10] NS R D Nd ABV 1 277.8607 1.2000 1.83400 37.16 2 68.6151 0.0100 1.54814 45.78 3 68.5981 15.3811 1.49700 81.61 4 -329.0866 0.2000 5 71.4720 11.5271 1.55397 71.76 6 -900.2174 D(8) 7 ASPH -1849.0669 1.2000 1.83400 37.16 8 ASPH 28.7504 1.0000 9 -35.3499 1.0000 1.76200 40.10 10 641.3585 0.2000 11 114.0436 3.5145 1.80809 22.76 12 -123.3256 0.6425 13 -103.5045 1.0000 1.77250 49.60 14 9234.7052 D(14) 15 9588.5950 2.7854 1.84666 23.78 16 -53.9224 0.5659 17 34.3671 3.2461 1.72000 50.23 18 391.0530 1.3636 19 STOP 0.0000 D(18) 20 ASPH -51.9901 1.0000 1.80139 45.45 21 ASPH 18.7779 1.0000 22 20.6370 2.9960 1.45650 90.27 23 -107.0088 0.2146 24 -99.5537 1.0000 1.76182 26.61 25 1863.0727 D(25) 26 114.2694 1.0000 1.84666 23.78 27 29.9040 0.7712 28 43.6408 4.3330 1.59349 67.00 29 -46.3988 0.2000 30 27.2326 7.7550 1.45860 90.19 31 -36.4061 D(31) 32 -24.3948 1.0000 1.83481 42.72 33 374.4233 0.0100 1.54814 45.78 34 374.4001 2.9485 1.54072 47.23 35 -28.2729 1.0000 36 0.0000 0.7500 1.51680 64.20 37 0.0000 D(37)

[0124] Table 11 shows the distances of the respective variable intervals when the zoom optical system is focused at infinity.

[0125] [Table 11] Zoom interval Wide-angle end Middle Telephoto end D(6) 1.0000 67.2214 80.6252 D(14) 80.6252 14.4038 1.0000 D(19) 4.3540 16.5110 34.4809 D(25) 25.0161 6.6451 12.0774 D(31) 19.6881 25.9023 2.5000 D(37) 11.0018 11.0175 11.0014

[0126] Table 12 shows the focal lengths of the respective lens groups of the zoom optical system.

[0127] [Table 12] Group Start surface Focal length 1 1 123.218 2 7 -20.000 3 15 28.694 4 19 -24.958 5 26 28.649 6 32 -70.161

[0128] Table 13 shows the aspherical coefficients of the aspherical surfaces in the zoom optical system of Example 3. The aspherical coefficients in this table are the values when each aspherical shape is defined by the following formula (1).

[0129]

Number

[0130] In the above formula, "X" is the displacement amount of the aspherical surface in the optical axis direction from the reference plane perpendicular to the optical axis, and "H" is the height (distance) from the optical axis to the aspherical surface in the direction perpendicular to the optical axis. "r" is the paraxial curvature radius of the lens surface, "k" is the conic constant (conic coefficient), and "An" (n is an integer) is the aspherical coefficient of the nth order.

[0131] [Table 13] Surface number K A4 A6 7 0.00 -4.28570E-07 1.90704E-08 8 0.00 2.53744E-06 2.31506E-08 20 0.00 -5.75961E-05 1.08972E-06 21 0.00 -6.53937E-05 1.09345E-06 Surface number A8 A10 7 6.67592E-12 -5.36275E-14 8 -6.15151E-12 6.93631E-13 20 -1.10080E-08 5.09959E-11 21 -1.13926E-08 5.25467E-11

[0132] Also, FIGS. 10, 11, and 12 are diagrams showing the longitudinal aberration diagrams at infinity focus at the wide-angle end, intermediate position, and telephoto end of the zoom optical system of Example 3, respectively.

[0133] [Example 4] (1) Configuration of the optical system FIG. 13 is a diagram schematically showing the optical configuration at the wide-angle end when the varifocal optical system of Example 4 is focused at infinity. The varifocal optical system of Example 4 is composed of, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a negative refractive power, a fifth lens group G5 having a positive refractive power, a sixth lens group G6 having a positive refractive power, and a seventh lens group G7 having a negative refractive power. The fourth lens group G4, the fifth lens group G5, the sixth lens group G6, and the seventh lens group G7 correspond to the aforementioned rear group.

[0134] The varifocal optical system focuses from an infinite object to a near object by moving the sixth lens group G6 toward the object side. The fifth lens group G5 is configured to be movable in a direction intersecting the optical axis and functions as an anti-shake lens group that corrects image blur during imaging.

[0135] The arrows in FIG. 13 indicate the moving directions and moving modes of the respective lens groups during zooming from the wide-angle end to the telephoto end. As shown in FIG. 13, during zooming from the wide-angle end to the telephoto end, the first lens group G1, the third lens group G3, and the seventh lens group G7 do not move. During zooming from the wide-angle end to the telephoto end, the second lens group G2 gradually moves toward the image plane side, and the fourth lens group gradually moves toward the image plane side. During zooming from the wide-angle end to the telephoto end, the fifth lens group G5 and the sixth lens group G6 first move toward the object side and then move toward the image plane side. The positions of the fifth lens group G5 and the sixth lens group G6 at the telephoto end are closer to the image plane than their positions at the wide-angle end. The moving speed of the fifth lens group G5 and the sixth lens group G6 toward the object side is slower than that toward the image plane side.

[0136] Hereinafter, the configurations of the respective lens groups will be described. The first lens group G1 is composed of, in order from the object side, a cemented lens of a first lens having a negative meniscus shape with a convex surface facing the object side and a second lens that is a biconvex lens, and a third lens that is a biconvex lens.

[0137] The second lens group G2 is composed of, in order from the object side, a fourth lens having a negative meniscus shape with a convex surface facing the object side, a fifth lens which is a biconcave lens, a sixth lens which is a biconvex lens, and a seventh lens having a negative meniscus shape with a convex surface facing the image side.

[0138] The third lens group G3 is composed of, in order from the object side, an eighth lens having a positive meniscus shape with a convex surface facing the image side, and a ninth lens which is a biconvex lens.

[0139] The fourth lens group G4 is composed of, in order from the object side, a tenth lens which is a biconcave lens, an eleventh lens having a positive meniscus shape with a convex surface facing the object side, and a twelfth lens having a positive meniscus shape with a convex surface facing the object side.

[0140] The fifth lens group G5 is composed of, in order from the object side, a cemented lens of a thirteenth lens having a negative meniscus shape with a convex surface facing the object side and a fourteenth lens having a positive meniscus shape with a convex surface facing the object side.

[0141] The sixth lens group G6 is composed of, in order from the object side, a fifteenth lens having a negative meniscus shape with a convex surface facing the object side, a sixteenth lens which is a biconvex lens, and a seventeenth lens which is a biconvex lens.

[0142] The seventh lens group G7 is composed of a cemented lens of an eighteenth lens having a negative meniscus shape with a concave surface facing the object side and a nineteenth lens having a positive meniscus shape with a convex surface facing the image side.

[0143] (2) Numerical Examples Next, a numerical example applying specific numerical values of the zoom optical system will be described. Table 14 shows the specifications table of the zoom optical system of Example 4.

[0144] [Table 14] Wide-angle end Intermediate Telephoto end Focal length 10.150 99.998 298.997 F number 2.8 3.2 5.0 Image height 6.8 6.8 6.8 Half field angle 38.130 3.862 1.278 BF 12.495 12.495 12.495 Table 15 shows the surface data of the zoom optical system.

[0145] [Table 15] NS R D Nd ABV 1 278.4505 1.2000 1.83400 37.16 2 69.7382 0.0100 1.54814 45.78 3 69.7219 15.3237 1.49700 81.61 4 -269.1078 0.2000 5 69.5526 11.6288 1.55397 71.76 6 -2106.4912 D(6) 7 ASPH 422.3148 1.2000 1.83400 37.16 8 ASPH 28.4595 7.5665 9 -41.5521 1.0000 1.76200 40.10 10 167.4547 0.2000 11 71.1456 3.5021 1.80809 22.76 12 -377.2201 1.6869 13 -67.3025 1.0000 1.77250 49.60 14 -276.2948 D(14) 15 -285.1307 2.7718 1.84666 23.78 16 -51.8852 0.2000 17 44.2316 3.4220 1.72000 50.23 18 -263.1045 1.0000 19 STOP 0.0000 D(19) 20 ASPH -68.3158 1.0000 1.80139 45.45 21 ASPH 28.0504 0.2000 22 30.6930 1.9415 1.45650 90.27 23 37.8928 0.2000 24 21.8130 1.0991 1.76182 26.61 25 23.3082 D(25) 26 47.5448 1.0000 1.80100 34.97 27 23.4492 3.5453 1.60342 38.03 28 386.9577 D(28) 29 204.5623 1.0000 1.84666 23.78 30 30.9427 0.3985 31 33.3827 5.1167 1.59349 67.00 32 -54.8262 0.2000 33 34.6209 12.7183 1.45860 90.19 34 -47.7454 D(34) 35 -34.3546 1.0000 1.83481 42.72 36 0.0000 0.0100 1.54814 45.78 37 0.0000 2.3544 1.54072 47.23 38 -54.6437 1.0000 39 0.0000 0.7500 1.51680 64.20 40 0.0000 D(40)

[0146] Table 16 shows the distances of the respective variable intervals when the zoom optical system is focused at infinity.

[0147] [Table 16] Zoom Interval Wide Angle End Middle Telephoto End D(6) 1.0000 62.4138 74.7791 D(14) 74.7791 13.3653 1.0000 D(19) 1.4012 15.6051 40.0960 D(25) 24.9427 3.0000 6.3807 D(28) 10.0399 8.8179 7.2985 D(34) 19.8914 28.8522 2.5000 D(40) 11.0000 11.0000 11.0000

[0148] Table 17 shows the focal lengths of the respective lens groups of the zoom optical system.

[0149] [Table 17] Group Starting Surface Focal Length 1 1 119.058 2 7 -20.000 3 15 30.952 4 20 -28.024 5 26 143.170 6 29 36.269 7 35 -71.920

[0150] Table 18 shows the aspherical coefficients of the aspherical surfaces in the zoom optical system of Example 3.

[0151] [Table 18] Surface Number K A4 A6 7 0.00 2.04214E-06 5.74983E-09 8 0.00 5.59152E-06 1.08578E-08 20 0.00 -6.51632E-05 1.08894E-06 21 0.00 -6.62461E-05 1.09667E-06 Surface Number A8 A10 7 8.41930E-12 -3.04593E-14 8 2.43156E-11 3.13136E-13 20 -9.56543E-09 3.47678E-11 21 -9.62427E-09 3.51518E-11

[0152] Further, FIGS. 14, 15, and 16 are diagrams showing the longitudinal aberration diagrams at infinity focus at the wide-angle end, the intermediate position, and the telephoto end of the zoom optical system of Example 4, respectively.

[0153] [Example 5] (1) Configuration of the optical system FIG. 17 is a diagram schematically showing the optical configuration at the wide-angle end at infinity focus of the zoom optical system of Example 5. The zoom optical system of the example includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a negative refractive power, a fifth lens group G5 having a positive refractive power, a sixth lens group G6 having a negative refractive power, and a seventh lens group G7 having a negative refractive power. The fourth lens group G4, the fifth lens group G5, the sixth lens group G6, and the seventh lens group G7 correspond to the aforementioned rear group.

[0154] The zoom optical system focuses from an infinite object to a close object by moving the sixth lens group G6 toward the object side. Further, the fifth lens group G5 is configured to be movable in a direction intersecting the optical axis and functions as an anti-shake lens group that corrects image blur during imaging.

[0155] The arrows in FIG. 17 indicate the moving directions and moving patterns of the respective lens groups during zooming from the wide-angle end to the telephoto end. As shown in FIG. 17, during zooming from the wide-angle end to the telephoto end, the first lens group G1, the third lens group G3, and the seventh lens group G7 do not move. During zooming from the wide-angle end to the telephoto end, the second lens group G2 gradually moves toward the image plane side, the fourth lens group G4 gradually moves toward the image plane side, and the fifth lens group G5 gradually moves toward the image plane side. During zooming from the wide-angle end to the telephoto end, the sixth lens group G6 first moves toward the object side and then moves toward the image plane side. The position of the sixth lens group G6 at the telephoto end is closer to the image plane than its position at the wide-angle end. The moving speed of the sixth lens group G6 toward the object side is slower than that toward the image plane side.

[0156] The configurations of the respective lens groups will be described below. The first lens group G1 is composed of, in order from the object side, a cemented lens of a first lens having a negative meniscus shape with a convex surface facing the object side and a second lens that is a biconvex lens, and a third lens that is a biconvex lens.

[0157] The second lens group G2 is composed of, in order from the object side, a fourth lens having a negative meniscus shape with a convex surface facing the object side, a fifth lens that is a biconcave lens, a sixth lens that is a biconvex lens, and a seventh lens having a negative meniscus shape with a convex surface facing the image side.

[0158] The third lens group G3 is composed of, in order from the object side, an eighth lens having a positive meniscus shape with a convex surface facing the image side, and a ninth lens that is a biconvex lens.

[0159] The fourth lens group G4 is composed of, in order from the object side, a tenth lens that is a biconcave lens, an eleventh lens having a positive meniscus shape with a convex surface facing the object side, and a twelfth lens having a positive meniscus shape with a convex surface facing the object side.

[0160] The fifth lens group G5 is composed of, in order from the object side, a cemented lens of a thirteenth lens having a negative meniscus shape with a convex surface facing the object side and a fourteenth lens having a negative meniscus shape with a convex surface facing the object side.

[0161] The sixth lens group G6 is composed of, in order from the object side, a fifteenth lens having a negative meniscus shape with a convex surface facing the object side, a sixteenth lens that is a biconvex lens, and a seventeenth lens that is a biconvex lens.

[0162] The seventh lens group G7 is composed of, in order from the object side, a cemented lens of an eighteenth lens that is a biconcave lens and a nineteenth lens that is a biconvex lens.

[0163] (2) Numerical Examples Next, a numerical example applying specific numerical values of the zoom optical system will be described. Table 19 shows the specifications table of the zoom optical system of Example 5.

[0164] [Table 19] Wide-angle end Middle Telephoto end Focal length 10.150 100.000 299.000 F-number 2.8 3.2 5.0 Image height 6.8 6.8 6.8 Half field angle 38.469 3.862 1.273 BF 12.495 12.495 12.495

[0165] Table 20 shows the surface data of the zoom optical system.

[0166] [Table 20] NS R D Nd ABV 1 258.8434 1.2000 1.83400 37.16 2 71.0238 0.0100 1.54814 45.78 3 71.0066 15.7258 1.49700 81.61 4 -286.6651 0.2000 5 70.2596 11.2407 1.55397 71.76 6 -4343.193 D(6) 7 ASPH 1738.5267 1.2000 1.83400 37.16 8 ASPH 26.8198 8.2565 9 -34.672 1.0000 1.76200 40.10 10 183.2023 0.2000 11 85.7319 3.7770 1.80809 22.76 12 -128.1515 0.8597 13 -86.908 1.0000 1.77250 49.60 14 -218.7272 D(14) 15 -166.1139 2.5072 1.84666 23.78 16 -53.4187 0.2000 17 42.6068 3.4031 1.72000 50.23 18 -196.3502 1.0000 19 STOP 0 D(19) 20 ASPH -101.8512 1.0000 1.80139 45.45 21 ASPH 23.6533 0.5926 22 43.0382 2.1824 1.45650 90.27 23 130.3902 0.2000 24 28.0864 1.6526 1.76182 26.61 25 92.5569 D(25) 26 138.1888 1.0000 1.84666 23.78 27 39.1634 1.6000 1.58144 40.75 28 36.5326 D(28) 29 98.4784 1.0000 1.84666 23.78 30 30.7328 0.3586 31 33.5686 5.1574 1.59349 67.00 32 -55.8489 0.2000 33 29.9395 11.6288 1.45860 90.19 34 -54.8947 D(34) 35 -27.7146 1.0000 1.83481 42.72 36 561.9942 0.0100 1.54814 45.78 37 561.9222 2.8662 1.54072 47.23 38 -31.9118 1.0000 39 0 0.7500 1.51680 64.20 40 0 D(40)

[0167] Table 21 shows the distances of each variable interval when the zoom optical system is focused at infinity.

[0168] [Table 21] Zoom interval Wide-angle end Middle Telephoto end D(6) 1 64.4902 77.4101 D(14) 77.4923 14.0021 1.0822 D(19) 1.329 14.3721 38.3799 D(25) 3.0000 5.2948 3.0000 D(28) 30.8477 7.0222 11.1493 D(34) 19.8525 28.34 2.5 D(40) 11 11 10.9997

[0169] Table 22 shows the focal lengths of each lens group of the zoom optical system.

[0170] [Table 22] Group Starting surface Focal length 1 1 119.6288 2 7 -20.0024 3 15 31.9249 4 20 -69.7625 5 26 -60.6219 6 29 31.5666 7 35 -80.2475

[0171] Table 23 shows the aspherical coefficients of the aspherical surfaces in the zoom optical system.

[0172] [Table 23] Surface number K A4 A6 7 0 4.27590E-06 3.76307E-09 8 0 8.02871E-06 1.41609E-08 20 0 -6.60706E-05 1.05043E-06 21 0 -7.04682E-05 1.07415E-06 Surface numbers A8 A10 7 1.68375E-11 -4.80128E-14 8 1.80704E-11 6.56955E-13 20 -9.08405E-09 3.28107E-11 21 -9.43158E-09 3.42479E-11

[0173] Also, FIGS. 18, 19, and 20 are diagrams showing the longitudinal aberration diagrams at infinity focus at the wide-angle end, intermediate position, and telephoto end of the zoom optical system of Example 5, respectively.

[0174] The calculated values according to the above-mentioned various formulas in Examples 1 to 5 are shown in Table 24.

[0175] [Table 24] Formula Example 1 Example 2 Example 3 Example 4 Example 5 (1) 0.6394 0.7964 0.6340 0.5855 0.6103 (2) -1.4680 -3.3670 -1.4870 -0.5676 -0.7040 (3) 29.46 29.46 29.45 29.46 29.46

Explanation of symbols

[0176] 1 Mirrorless single-lens camera 2 Body 3 Lens barrel

Claims

1. A zoom optical system comprising N lens groups and performing zooming by changing the distance between adjacent lens groups, comprising, in order from the object side to the image plane side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a rear group having at least three lens groups, wherein the rear group has a fourth lens group on the object side and an Nth lens group on the image plane side, and has an (N - 1)th lens group adjacent to the object side of the Nth lens group, the lens on the image plane side of the second lens group has a negative refractive power, the first lens group, the third lens group, and the Nth lens group do not move with respect to the image plane during zooming, and a zoom optical system that satisfies the following formula. 0.50 < βwr / βtr < 0.85... (1) -4.0 < βw4 / βt4 < -0.4... (2) However, βwr: the product of the lateral magnifications of each lens group from the fourth lens group to the (N - 1)th lens group at infinity focus at the wide-angle end βtr: the product of the lateral magnifications of each lens group from the fourth lens group to the (N - 1)th lens group at infinity focus at the telephoto end βw4: the lateral magnification of the fourth lens group at infinity focus at the wide-angle end βt4: the lateral magnification of the fourth lens group at infinity focus at the telephoto end

2. The second lens group consists of, in order from the object side, a lens having a negative refractive power, a lens having a negative refractive power, a lens having a positive refractive power, and a lens having a negative refractive power. The zoom optical system according to claim 1.

3. The zoom optical system according to claim 1, which satisfies the following formula (3). Z > 20... (3) However, Z: the zoom ratio of the zoom optical system

4. The (N - 1)th lens group is configured to move on an orbit that is convex toward the object side with respect to the image plane during zooming from the wide-angle end to the telephoto end, and the position of the (N - 1)th lens group at the telephoto end is on the image plane side of the position of the (N - 1)th lens group at the wide-angle end. The zoom optical system according to claim 1.

5. N is 6, The zoom optical system according to claim 1, which satisfies the following formula (4). 0.50 < (βw4 × βw5) / (βt4 × βt5) < 0.85... (4) However, βw5: the lateral magnification of the fifth lens group at infinity focus at the wide-angle end βt5: the lateral magnification of the fifth lens group at infinity focus at the telephoto end

6. An imaging device comprising: a zoom optical system according to any one of claims 1 to 5; and an imaging element that converts an optical image formed by the zoom optical system into an electrical signal, disposed on the image plane side of the zoom optical system.

Images