Zoom lens and imaging device

Abstract

The present invention addresses the problem of providing a compact and high-performance zoom lens and an imaging device. [Solution] The zoom lens comprises, in order from the object side: a first lens group having a positive refractive power; the zoom lens includes a rear group including a plurality of lens groups, an interval between adjacent lens groups changes during zooming, the rear group includes a lens A having a negative refractive power closest to the image side, and the zoom lens satisfies a predetermined conditional expression.

Description

Technical Field

[0001] The present invention relates to a zoom lens and an imaging device, and more particularly to a zoom lens and an imaging device suitable for a compact and high-performance imaging device using a solid-state imaging element or the like. Background Art

[0002] Image pickup devices such as digital still cameras and digital video cameras that use solid-state image pickup devices have become increasingly popular. As the number of pixels of solid-state image pickup devices used in these image pickup devices increases, the optical system is required to have high resolution performance while maintaining a small size and light weight.

[0003] In order to meet these requirements, for example, a small zoom lens has been proposed, which includes: a first lens group with positive optical power, a second lens group with negative optical power, a third lens group with positive optical power, a fourth lens group with positive optical power, and a fifth lens group to suppress various aberrations (refer to "Patent Document 1").

[0004] Prior Art Literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2014-126850 Summary of the invention

[0007] Problems to be solved by the invention

[0008] In order to achieve miniaturization of zoom lenses, it is effective to adopt a telephoto type focal power configuration that has positive focal power on the object side and negative focal power on the image side. However, the stronger the focal power configuration, the more difficult it is to achieve good correction of various aberrations with a small number of lenses. Therefore, in order to achieve both miniaturization and high performance of zoom lenses, it is necessary to optimize the focal power or lens composition of each lens group.

[0009] An object of the present invention is to provide a compact and high-performance zoom lens and an imaging device.

[0010] Means for solving problems

[0011] In order to solve the above-mentioned problems, the zoom lens according to the present invention comprises, in order from the object side, a first lens group having positive refractive power, a rear group having a plurality of lens groups, the intervals between adjacent lens groups changing when the magnification is changed, and the rear group having a lens A having negative refractive power closest to the image side, and the zoom lens satisfies the following conditional formula:

[0012] 1.83 <Nd2<2.50…(1)

[0013] 0.20 <TLt / ft<0.96…(2)

[0014] 1.16<βLt…(3)

[0015] in,

[0016] Nd2: The d-line refractive index of the lens closest to the object side in the rear group

[0017] TLt: The distance from the side closest to the object to the image plane at the telephoto end of the zoom lens

[0018] ft: focal length at the telephoto end of the zoom lens

[0019] βLt: lateral magnification of the lens group closest to the image side in the rear group at the telephoto end

[0020] In order to solve the above-mentioned problems, the zoom lens according to the present invention includes, in order from the object side, a first lens group having positive refractive power, and a rear group having a plurality of lens groups, wherein the intervals between adjacent lens groups change when the magnification is changed, the rear group closest to the image side includes a lens A having negative refractive power, and the rear group includes a focus adjustment group that moves along the optical axis direction when focusing, and the zoom lens satisfies the following conditional formula:

[0021] 1.83 <Nd2<2.50…(1)

[0022] 0.20 <TLt / ft<0.96…(2)

[0023] 7.1<|(1-βFt 2 )×βrt 2 |<20.0…(14)

[0024] in,

[0025] Nd2: The d-line refractive index of the lens closest to the object side in the rear group

[0026] TLt: The distance from the side closest to the object to the image plane at the telephoto end of the zoom lens

[0027] βFt: lateral magnification of the focusing group at the telephoto end

[0028] βrt: The combined lateral magnification at the telephoto end of all lens groups closer to the image side than the focusing group

[0029] In addition, in order to solve the above-mentioned problems, the zoom lens involved in the present invention includes, from the object side, in order: a first lens group with positive refractive power, and a rear group including a plurality of lens groups, wherein the intervals between adjacent lens groups change when the magnification is changed, and a group including a lens group N with negative refractive power closest to the object side in the rear group is referred to as an FR group, and a lens group from a lens group P with positive refractive power closer to the image side and closest to the object side than the lens group N to a lens group closest to the image side is referred to as an RR group, the rear group is composed of the FR group and the RR group, and a lens A with negative refractive power closest to the image side of the rear group satisfies the following conditional expression:

[0030] 1.83 <Nd2<2.70…(1)

[0031] 0.20 <TLt / ft<0.96…(2)

[0032] 2.70<βCt…(4)

[0033] in,

[0034] Nd2: The d-line refractive index of the lens closest to the object side in the rear group

[0035] TLt: The distance from the side closest to the object to the image plane at the telephoto end of the zoom lens

[0036] ft: focal length at the telephoto end of the zoom lens

[0037] βCt: The combined lateral magnification at the telephoto end of the RR group from the negative lens group closest to the object side to the lens group closest to the image side

[0038] In order to solve the above-mentioned problems, an imaging device according to the present invention includes the above-mentioned optical system and an imaging element that receives an optical image formed by the optical system and converts the image into an electrical image signal.

[0039] Effects of the Invention

[0040] According to the present invention, it is possible to provide a compact and high-performance zoom lens and an imaging device. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a cross-sectional view at the wide-angle end of the zoom lens according to Example 1 of the present invention.

[0042] Figure 2 These are diagrams showing spherical aberration, astigmatism, and distortion when the zoom lens according to Example 1 of the present invention is at the wide-angle end and photographing an object at infinity.

[0043] Figure 3The diagrams are spherical aberration diagrams, astigmatism diagrams, and distortion diagrams when photographing an infinitely distant subject at an intermediate focal length of the zoom lens according to Example 1 of the present invention.

[0044] Figure 4 The diagrams are spherical aberration diagrams, astigmatism diagrams, and distortion diagrams when the zoom lens according to Example 1 of the present invention is at the telephoto end and photographs an object at infinity.

[0045] Figure 5 It is a cross-sectional view at the wide-angle end of the zoom lens according to Example 2 of the present invention.

[0046] Figure 6 These are diagrams showing spherical aberration, astigmatism, and distortion when the zoom lens according to Example 2 of the present invention is at the wide-angle end and photographing an object at infinity.

[0047] Figure 7 The diagrams are spherical aberration diagrams, astigmatism diagrams, and distortion diagrams when photographing an object at infinity at an intermediate focal length of the zoom lens according to Example 2 of the present invention.

[0048] Figure 8 The diagrams are spherical aberration diagrams, astigmatism diagrams, and distortion diagrams when the zoom lens according to Example 2 of the present invention is at the telephoto end and photographs an object at infinity.

[0049] Fig. 9 It is a cross-sectional view at the wide-angle end of the zoom lens according to Example 3 of the present invention.

[0050] Fig.10 These are diagrams showing spherical aberration, astigmatism, and distortion when the zoom lens according to Example 3 of the present invention is at the wide-angle end and photographing an object at infinity.

[0051] Fig.11 The diagrams are spherical aberration diagrams, astigmatism diagrams, and distortion diagrams when photographing an infinitely distant subject at an intermediate focal length of the zoom lens according to Example 3 of the present invention.

[0052] Fig.12 The diagrams are spherical aberration diagrams, astigmatism diagrams, and distortion diagrams when the zoom lens according to Example 3 of the present invention is at the telephoto end and photographs an object at infinity.

[0053] Fig.13 It is a cross-sectional view at the wide-angle end of the zoom lens according to Example 4 of the present invention.

[0054] Fig.14 These are diagrams showing spherical aberration, astigmatism, and distortion when the zoom lens according to Example 4 of the present invention is at the wide-angle end and photographing an object at infinity.

[0055] Fig.15 The diagrams are spherical aberration diagrams, astigmatism diagrams, and distortion diagrams when photographing an infinitely distant subject at an intermediate focal length of the zoom lens according to Example 4 of the present invention.

[0056] Fig.16 The diagrams are spherical aberration diagrams, astigmatism diagrams, and distortion diagrams when the zoom lens according to Example 4 of the present invention is at the telephoto end and photographs an object at infinity.

[0057] Fig.17 It is a cross-sectional view at the wide-angle end of the zoom lens according to Example 5 of the present invention.

[0058] Fig.18 These are diagrams showing spherical aberration, astigmatism, and distortion when the zoom lens according to Example 5 of the present invention is at the wide-angle end and photographing an object at infinity.

[0059] Fig.19 The diagrams are spherical aberration diagrams, astigmatism diagrams, and distortion diagrams when photographing an object at infinity at an intermediate focal length of the zoom lens according to Example 5 of the present invention.

[0060] Fig. 20 These are diagrams of spherical aberration, astigmatism, and distortion when the zoom lens according to Example 5 of the present invention is at the telephoto end and photographs an object at infinity.

[0061] Fig.21 It is a diagram schematically showing an example of the configuration of an imaging device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0062] Hereinafter, embodiments of a zoom lens and an imaging device according to the present invention will be described.

[0063] 1. Zoom lens

[0064] 1-1. Optical structure of a zoom lens

[0065] First, the optical structure of the zoom lens involved in the present invention will be described. The zoom lens of this embodiment is composed of a first lens group having positive optical power and a rear group having multiple lens groups. In this zoom lens, the magnification is changed from the wide-angle end to the telephoto end by changing the interval between the lens groups. A "lens group" has one or more lenses. A "lens group" is a collection of one lens or two or more lenses, wherein the intervals between adjacent lens groups change when changing the magnification between the wide-angle end and the telephoto end. When the lens group has multiple lenses, the multiple lenses maintain a relative positional relationship when changing the magnification between the wide-angle end and the telephoto end. The lens group can be configured to be movable on the optical axis, or it can be configured to be fixed on the optical axis.

[0066] In this zoom lens, the lens group closest to the object side has a positive focal power. By arranging the lens group with a light-gathering function closest to the object side, it is easy to adopt a telephoto focal power configuration, so it is easy to achieve miniaturization of the total optical length at the telephoto end. In addition, since the lens group closest to the object side has a light-gathering function, it is easy to achieve miniaturization of the diameter of the rear group arranged on its image side.

[0067] In this zoom lens, the rear group has a lens A with negative optical power on the side closest to the image. By having negative optical power on the side closest to the image, it is easy to adopt a telephoto optical power configuration, so it is easy to achieve miniaturization of the total optical length at the telephoto end. In addition, since the side closest to the image has a divergent effect, it is easy to achieve miniaturization of the diameter of the lens closest to the image. Lens A is a single lens, which can be a spherical lens or an aspherical lens. In addition, the aspherical lens includes a so-called composite aspherical lens with an aspherical film attached to the surface.

[0068] Hereinafter, the optical configuration of the zoom lens will be described in more detail.

[0069] (1) Lens Group 1

[0070] The first lens group is a lens group having positive optical power that is arranged closest to the object side among the multiple lens groups constituting the zoom lens. Among them, an optical element having no optical power or extremely small optical power may be arranged closer to the object side than the first lens group. As such optical elements, for example, various filters such as a prism that bends the optical axis of the lens, a protective filter that protects the lens from dirt and scratches, an ND filter for reducing the amount of incident light, and a PL filter for adjusting color are cited.

[0071] As long as the first lens group has positive power, its specific lens composition is not particularly limited. Since the first lens group as a whole has positive power, the first lens group may have at least one lens with positive power. As long as the first lens group is composed of a plurality of lenses with positive power, it is possible to easily correct chromatic aberration or spherical aberration at the telephoto end, and therefore it is preferred.

[0072] The number of lenses constituting the first lens group is not particularly limited, but in order to realize compactness, lightness, and low cost of the zoom lens while achieving high optical performance, preferably, the number of lenses with positive refractive power in the first lens group is 2 or less.

[0073] (2) Rear group

[0074] The rear group is a general term for a plurality of lens groups arranged on the image side of the first lens group having positive refractive power. As long as there are a plurality of lens groups and the lens closest to the image side has negative refractive power, the configuration of the lens groups and the configuration of the lenses are not particularly limited.

[0075] When a composite group consisting of one or more lens groups including a lens group N having negative power closest to the object side in the rear group is used as the FR group, and a composite group consisting of one or more lens groups from a lens group P having positive power closest to the object side to a lens group closest to the image side is used as the RR group, it is preferred that the rear group is composed of two composite groups of the FR group and the RR group. Accordingly, a telephoto configuration is formed by the first lens group and the lens group N having negative power, and a telephoto configuration is further formed by the lens group P having positive power and the lens A having negative power closest to the image side of the rear group. As a result, miniaturization in the overall length direction and radial direction at the telephoto end becomes easy.

[0076] Preferably, the air gap between the FR group and the RR group is the widest among the air gaps in the rear group at the wide-angle end. Since the zooming effect of the lens group N with negative power included in the FR group is large, if the distance change between the first lens group and the lens group N and the distance change between the lens group N and the lens group P with positive power are large, a large zooming effect is achieved. Therefore, the air gap between the FR group and the RR group becomes wider at the wide-angle end, which is preferred for high magnification.

[0077] Preferably, the lens group closest to the image side in the rear group has negative focal power. By having negative focal power closest to the image side, it is easy to adopt a telephoto focal power configuration, so it is easy to achieve miniaturization of the total optical length at the telephoto end. In addition, since the lens group closest to the image side has a divergent effect, it is easy to achieve miniaturization of the diameter of the lens group closest to the image side. In addition, from the perspective of cost reduction, preferably, the lens group closest to the image side in the rear group is composed of lenses with a number of 4 or less.

[0078] The number of lens groups constituting the rear group is not particularly limited, but preferably, the number of lens groups constituting the rear group is large, so that aberration correction can be performed well in the entire zoom range. From this point of view, the number of lens groups constituting the rear group is preferably 2 or more, and more preferably 3 or more. When the number of lens groups constituting the rear group is 3 or more, the field curvature can be well corrected at the intermediate focal length, so a zoom lens with higher optical performance can be obtained in the entire zoom range, which is preferred. In addition, the number of lens groups constituting the RR group included in the rear group is preferably 2 or more, and more preferably 3 or more. For example, more preferably, the RR group is composed of one or more lens groups with positive optical power and two or more lens groups with negative optical power.

[0079] (3) FR group

[0080] The FR group is disposed between the first lens group and the RR group, and the overall refractive power of the FR group may be positive or negative. When the overall FR group has positive refractive power, it has a light-gathering effect, and thus it is easy to increase the aperture. When the overall FR group has negative refractive power, it is more preferable to form a telephoto type structure by the first lens group and the FR group, from the point of view that it is easy to reduce the total optical length.

[0081] The composition of the FR group is not particularly limited as long as it includes the lens group N having negative power closest to the object side in the rear group. When a lens group having positive power is included in the FR group closer to the object side than the lens group N, it is effective in correcting spherical aberration, which is preferred from the perspective of high performance. In addition, when a lens group having negative power is included in the FR group closer to the image side than the lens group N, it is effective in correcting field curvature, which is preferred from the perspective of high performance.

[0082] In addition, the FR group has at least one lens with positive power, which is preferred from the perspective of correcting chromatic aberration. At this time, if a lens with negative power is arranged on the image side of the lens with positive power, chromatic aberration can be well corrected at the telephoto end, so it is preferred. In addition, the lens group N with negative power has at least one lens with positive power, which is preferred from the perspective of correcting chromatic aberration. If the d-line Abbe number of the lens with positive power included in the lens group N is smaller than 45, chromatic aberration can be better corrected, which is more preferred. In addition, in order to correct chromatic aberration better, it is more preferred that the d-line Abbe number of at least one lens with positive power included in the lens group N is smaller than 40, and it is further more preferred that the d-line Abbe number of at least one lens with positive power included in the lens group N is smaller than 35.

[0083] In addition, the number of lens groups constituting the FR group is not particularly limited. When the number of lens groups constituting the FR group is 1, the mechanical components for holding the lens group can be reduced, which is preferred from the perspective of cost reduction. When the number of lens groups constituting the FR group is large, good aberration correction can be achieved in the entire zoom range, which is preferred from the perspective of high performance.

[0084] (4) RR group

[0085] The RR group is a general term for a composite group, which is arranged on the image side of the FR group and is composed of a lens group P having positive focal power that is closer to the image side and closest to the object side than the FR group, to a lens group closest to the image side. The focal power of the RR group as a whole can be positive or negative. When the RR group as a whole has negative focal power, it is preferred to form a telephoto structure with the first lens group and the RR group from the point of view that it becomes easy to reduce the total optical length. When the RR group as a whole has positive focal power, it has a light-gathering effect and has the effect of offsetting the divergence of the lens group N, so it is more preferred from the point of view that it becomes easy to achieve high performance.

[0086] There is no particular restriction on the composition within the RR group, as long as it includes a lens group P with positive focal power that is closer to the image side than the FR group and closest to the object side. Preferably, the lens group closest to the image side of the RR group has negative focal power. By having negative focal power closest to the image side, it is easy to adopt a telephoto focal power configuration, and thus it is easy to achieve miniaturization of the total optical length at the telephoto end. In addition, since there is a divergent effect closest to the image side, it is easy to achieve miniaturization of the diameter of the lens group closest to the image side. In addition, more preferably, the image side of the lens group P has two or more lens groups with negative focal power. In this case, it is easy to adopt a telephoto focal power configuration and it becomes easy to correct the curvature of field, so it is more preferred from the point of view of both miniaturization and high performance.

[0087] In addition, it is preferable that the RR group has at least one lens with negative power from the viewpoint of correcting curvature of field. If the d-line refractive index of at least one lens with negative power included in the RR group is greater than 1.86, it is more preferable because curvature of field can be better corrected. In addition, in order to correct curvature of field better, it is more preferable that the d-line refractive index of at least one lens with negative power included in the RR group is greater than 1.88, and it is even more preferable that the d-line refractive index of at least one lens with negative power included in the RR group is greater than 1.90.

[0088] The number of lens groups constituting the RR group is not particularly limited. If the number of lens groups constituting the RR group is large, good aberration correction can be performed in the entire zoom range, so it is preferred. From this point of view, preferably, the number of lens groups constituting the RR group is 2 or more, and more preferably, 3 or more. When the number of lens groups constituting the RR group is 3 or more, the field curvature can be well corrected at the intermediate focal length, so a zoom lens with higher optical performance can be obtained in the entire zoom range.

[0089] (5) Focusing group

[0090] In the zoom lens, the presence or absence of a focus group is not particularly limited. When a focus group is provided, at least one lens of the lenses constituting the zoom lens is used as a focus group, and when focusing, the focus group can be moved along the optical axis direction to focus on the subject. In the zoom lens, the position or optical power of the lens used as the focus group is not particularly limited.

[0091] When the zoom lens is provided with a focus group, the number of lenses constituting the focus group is not particularly limited, and the number of lenses constituting the focus group may be one or more. However, in order to suppress the variation of aberrations generated when focusing on a close-range subject, preferably, the focus group is composed of a plurality of lenses.

[0092] In addition, in order to realize the miniaturization and lightweight of the focusing group, preferably, the focusing group is composed of a single lens unit. Here, the single lens unit refers to a lens unit such as a single lens or a joined lens, and the joined lens is obtained by integrating multiple single lenses without air gaps. In other words, a single lens unit means that when it has multiple optical surfaces, only its most object side and most image side are in contact with the air, and the other surfaces are not in contact with the air. In addition, in the present specification, a single lens can be a spherical lens or an aspherical lens. In addition, the aspherical lens includes a so-called composite aspherical lens with an aspherical film attached to the surface. In particular, from the viewpoint of realizing the miniaturization and lightweight of the focusing group while suppressing the change of aberrations generated when focusing on the above-mentioned close-range subject, it is more preferred that the focusing group is composed of a joined lens obtained by integrating multiple single lenses without air gaps.

[0093] When the focus group is composed of the above-mentioned single lens unit, the focus group does not include an air gap. Therefore, if the focus group is compared with a structure in which a plurality of single lenses are arranged with air gaps, the focus group can be miniaturized and lightweight. As a result, the mechanical parts (hereinafter referred to as "focus drive mechanism") that move the focus group along the optical axis when focusing can be miniaturized and lightweight, and the zoom lens unit as a whole can be miniaturized and lightweight. In addition, the zoom lens unit includes the zoom lens, and also includes a drive mechanism or the above-mentioned focus drive mechanism that moves each lens group relative to each other when changing the magnification, and also includes a lens barrel that accommodates these.

[0094] When the zoom lens is provided with a focus group, the arrangement of the focus group is not particularly limited, and preferably, any one of the lens groups constituting the rear group, or a part thereof, is used as the focus group. The first lens group is composed of lenses with a relatively large diameter, so the focus group is arranged in the lens group of the rear group or a part thereof, making it easy to miniaturize and lighten the focus group.

[0095] In particular, it is preferred to use any one of the lens groups constituting the RR group or a part thereof as a focusing group. By adopting the above-mentioned optical focal length configuration of the zoom lens, the diameter of the incident light beam to the RR group can be made smaller than the diameter of the incident light beam to the first lens group or the FR group. Therefore, by using any one of the lens groups constituting the RR group or a part thereof as a focusing group, the miniaturization and lightweight of the focusing group can be achieved compared with the case where the focusing group is configured in the first lens group or the FR group. In addition, it is more preferred to use any one of the lens groups or a part thereof that is closer to the image side than the lens group P with positive optical focal length included in the RR group as a focusing group. By using the lens group P with a light-gathering effect, the diameter of the incident light beam can be further reduced. Therefore, it becomes easier to achieve miniaturization and lightweight of the focusing group.

[0096] The focal length of the focus group can be positive or negative. When the focal length of the focus group is positive, preferably, the lens group on the object side thereof has a negative focal length. In addition, when the focal length of the focus group is negative, preferably, the lens group on the object side thereof has a positive focal length. As a result, it becomes easy to increase the lateral magnification of the focus group, and it becomes easy to increase the focusing sensitivity of the focus group. As a result, it is possible to focus with a small amount of movement, so it is preferred from the perspective of miniaturization.

[0097] The lens structure of the focus group is not limited, but it is preferred to include a lens with positive power from the viewpoint of chromatic aberration correction. If the d-line Abbe number of the lens with positive power included in the focus group is smaller than 35, chromatic aberration can be corrected more effectively, which is more preferred. In addition, in order to correct chromatic aberration more effectively, it is more preferred that the d-line Abbe number of at least one lens with positive power included in the focus group is smaller than 32, and it is further more preferred that the d-line Abbe number of at least one lens with positive power included in the focus group is smaller than 29.

[0098] In addition, the zoom lens is not limited to one focusing group, and multiple lens groups or a part of multiple lens groups can be used as a focusing group. In other words, focusing can be performed by floating. By adopting a floating method, spherical aberration or image plane properties during close-range focusing can be further improved, so a zoom lens with higher optical performance can be achieved, which is preferred.

[0099] (6) Anti-vibration group

[0100] In the zoom lens, the presence or absence of an anti-vibration group is not particularly limited. In order to correct image blur caused by vibration transmitted to the camera device during shooting, it can be done by electrically correcting the image or moving the camera element. When the zoom lens is not provided with an anti-vibration group, image blur can be corrected by these methods.

[0101] When the zoom lens is provided with an anti-vibration group, the image may be shifted by decentering at least one lens among the lenses constituting the zoom lens, and the method is not particularly limited.

[0102] For example, if at least one of the lenses constituting the zoom lens is used as an anti-vibration group and the image is shifted by moving the anti-vibration group in a direction substantially orthogonal to the optical axis, the entire zoom lens unit including the lens barrel can be miniaturized, which is preferred from the perspective of achieving miniaturization.

[0103] When the zoom lens is provided with an anti-vibration group, the arrangement of the anti-vibration group is not particularly limited, but preferably, the anti-vibration group is provided in the rear lens group. By adopting the above-mentioned optical power arrangement in the zoom lens, the diameter of the incident light beam to the rear lens group can be made smaller than the diameter of the incident light beam to the first lens group. Therefore, by arranging the anti-vibration group in the rear lens group, it is possible to achieve a smaller and lighter anti-vibration group than in the case where the anti-vibration group is arranged in the first lens group.

[0104] When the zoom lens is provided with an anti-vibration group, the number of lenses constituting the anti-vibration group is not particularly limited. As long as the anti-vibration group is composed of a plurality of lenses, the change of aberration during anti-vibration can be suppressed, which is preferred. In this case, preferably, the anti-vibration group has at least one lens with negative power and at least one lens with positive power. When the anti-vibration group has at least one lens with negative power and one lens with positive power, chromatic aberration generated during anti-vibration can be suppressed, and a zoom lens with higher optical performance can be realized.

[0105] (6) Aperture diaphragm

[0106] In the zoom lens, the arrangement of the aperture stop is not particularly limited. The aperture stop here refers to an aperture stop that specifies the beam diameter of the zoom lens, that is, an aperture stop that specifies the Fno of the zoom lens.

[0107] In this zoom lens, the aperture stop is arranged in the rear group so that the aperture diameter can be reduced, which is preferred from the point of view of miniaturization of the aperture unit. The aperture stop is arranged in the rear group means that the aperture stop is arranged on the object side or image side of each lens group constituting the rear group or in each lens group constituting the rear group. In this zoom lens, the first lens group with a focusing effect is arranged closest to the object side, so the incident light beam to the rear group is reduced. Therefore, the aperture diameter of the aperture stop can be further reduced, which is preferred from the point of view of miniaturization. As described above, in this zoom lens, the magnification effect produced by the lens group N is relatively large, so the change in the diameter of the incident light beam to the RR group is small. Therefore, the aperture diameter of the aperture stop can be further reduced. In order to suppress the change in the aperture diameter, it is more preferred to arrange the aperture stop on the object side of the RR group or in the lens group closest to the object side among the lens groups constituting the RR group from the point of view of miniaturization.

[0108] 1-2. Action

[0109] (1) Actions during zooming

[0110] In this zoom lens, the magnification is changed from the wide-angle end to the telephoto end by changing the intervals between adjacent lens groups on the optical axis. As long as the intervals between mutually adjacent lens groups on the optical axis change, the increase or decrease of the intervals between the lens groups is not particularly limited. For example, as long as the first lens group and the second lens group are relatively moved in a manner that increases the interval on the optical axis between the first lens group and the rear group when changing the magnification from the wide-angle end to the telephoto end, a small zoom lens with a high magnification ratio can be obtained, so it is preferred. At this time, the lens group closest to the image side of the FR group and the lens group closest to the object side of the RR group are relatively moved in a manner that reduces the interval on the optical axis between the FR group and the RR group in the rear group, which is more preferred from the perspective of obtaining a small zoom lens with a high magnification ratio. In addition, the relative movement of the lens groups includes moving each of the two lens groups adjacent to each other with an air gap, and also includes moving the lens group of either of the two lens groups adjacent to each other with an air gap.

[0111] As long as the intervals between the lens groups on the optical axis change when the magnification is changed, the increase or decrease of the intervals between the lens groups is not particularly limited. In addition, when the magnification is changed, the lens groups can be relatively moved in a manner that the intervals between the lens groups on the optical axis change, and all lens groups can be moved along the optical axis, or any one or more lens groups can be fixed relative to the image plane, and the other lens groups can be moved along the optical axis.

[0112] (2) Focusing action

[0113] In the zoom lens, when the zoom lens is provided with a focus group, as described above, the position or optical focal length of the focus group is not particularly limited. In addition, when focusing from infinity to a close object, the direction of movement of the focus group is not particularly limited. The direction of movement of the focus group is preferably such that the focus group moves from the object side to the image side when focusing from infinity to a close object. For example, if the lateral magnification of the focus group is βN, and the combined lateral magnification of all lens groups closer to the image side of the focus group is βR, then the focus sensitivity of the focus group can be expressed as (1-βN). 2 )×βR 2 . If the horizontal magnification of the focusing group becomes larger than 1, it means that when focusing from an infinitely distant object to an object at a finite distance, the focusing group moves toward the image side. In addition, by having a horizontal magnification greater than 1, the focal length can be stretched to shorten the total length. In order to miniaturize the total optical length, it is preferred to configure a lens group with a horizontal magnification greater than 1 as a focusing group.

[0114] 1-3.Conditional expression

[0115] It is preferable that the optical system adopts the above-mentioned configuration and satisfies the conditional expressions described below.

[0116] 1-3-1.Conditional expression (1)

[0117] Preferably, the zoom lens satisfies the following conditional expression.

[0118] 1.83 <Nd2<2.50…(1)

[0119] in,

[0120] Nd2: The d-line refractive index of the lens closest to the object side in the rear group

[0121] The above-mentioned conditional expression (1) is a formula for specifying the d-line refractive index of the lens closest to the object side in the rear group of the zoom lens. It is important to suppress the radius of curvature of the side of the rear group closest to the object within an appropriate range for the light incident on the rear group from the first lens group having a focusing effect, from the perspective of performance and manufacturability. The optical focal length of the side of the rear group closest to the object is determined by the radius of curvature of the surface and the refractive index of the glass material. Therefore, if the refractive index is specified within a certain range, it is also easy to suppress the optical focal length of the surface within an appropriate range. Here, when conditional expression (1) is satisfied, a zoom lens with high off-axis performance can be achieved while suppressing costs. In addition, when an aspheric film is attached to the object side surface of the lens closest to the object side in the rear group, i.e., a so-called composite aspheric lens, Nd2 is not the refractive index of the aspheric film but the refractive index of the base lens.

[0122] On the other hand, if the value of the above conditional expression (1) reaches above the upper limit, the material cost becomes too high, which is not preferable from the perspective of cost reduction. If the value of the above conditional expression (1) reaches below the lower limit, it is difficult to correct the field curvature and to suppress the curvature radius within an appropriate range, thereby deteriorating the manufacturability. Therefore, it is not preferable from the perspective of off-axis performance and manufacturability.

[0123] In order to obtain the above-mentioned effect, the upper limit value of the above-mentioned conditional expression (1) is preferably 2.30, 2.15, and 2.12, respectively. In addition, the lower limit value of the above-mentioned conditional expression (1) is preferably 1.84 and 1.85, respectively.

[0124] 1-3-2.Conditional expression (2)

[0125] Preferably, the zoom lens satisfies the following conditional expression.

[0126] 20 <TLt / ft<0.96…(2)

[0127] in,

[0128] TLt: The distance from the side closest to the object to the image plane at the telephoto end of the zoom lens

[0129] ft: focal length at the telephoto end of the zoom lens

[0130] The above conditional expression (2) is a formula that specifies the ratio of the total optical length at the telephoto end of the zoom lens to the focal length at the telephoto end. In order to reduce the total optical length relative to the focal length, aberration correction becomes difficult and causes the error sensitivity to deteriorate. In addition, if the total optical length is increased too much relative to the focal length, the weight including the mechanical structure becomes heavier, so there is an appropriate range for the ratio of the total length to the focal length. Here, when conditional expression (2) is satisfied, an optical system that is both compact and lightweight and high-performance can be achieved.

[0131] On the other hand, if the value of the above conditional expression (2) reaches or exceeds the upper limit, the focal length becomes too large relative to the total optical length, and the weight including the mechanical structure becomes heavy, which is not preferable from the perspective of lightweighting. If the value of the above conditional expression (2) reaches or exceeds the lower limit, the focal length becomes too small relative to the total optical length, and from the perspective of aberration correction, multiple lenses are required, which is not preferable from the perspective of cost. Furthermore, it leads to deterioration of manufacturability, which is not preferable from the perspective of high performance.

[0132] In order to obtain the above effect, the upper limit value of the above conditional expression (2) is preferably 0.93, 0.91, 0.88, 0.85, 0.83, 0.80, 0.78, 0.75, 0.72, 0.69, respectively. In addition, the lower limit value of the above conditional expression (2) is preferably 0.25, 0.30, 0.35, respectively.

[0133] 1-3-3.Conditional expression (3)

[0134] Preferably, the zoom lens satisfies the following conditional expression.

[0135] 1.16<βLt…(3)

[0136] in,

[0137] βLt: lateral magnification of the lens group closest to the image side in the rear group at the telephoto end

[0138] The above conditional formula (3) is a formula that specifies the lateral magnification of the lens group closest to the image side at the telephoto end of the rear group. If the lateral magnification of the lens group closest to the image side is increased, it is easy to adopt a telephoto optical focal length configuration, so it is easy to achieve miniaturization of the total optical length at the telephoto end. In addition, since the lens group closest to the image side has an enlarging effect, it is effective to miniaturize the diameter of the lens closest to the image side. Therefore, if conditional formula (3) is satisfied, miniaturization can be achieved.

[0139] If the value of the above conditional expression (3) reaches below the lower limit, the telephoto optical power configuration becomes weak, resulting in an increase in the total optical length or the diameter of the lens, which is not preferred from the perspective of miniaturization. In addition, if the lateral magnification of the lens group closest to the image side becomes too large, the error sensitivity becomes large, so from the perspective of manufacturability, it is preferred to specify an upper limit value. More preferably, the upper limit value in the above conditional expression (3) is set to be less than 5.0.

[0140] In order to obtain the above effect, the lower limit of the above conditional expression (3) is preferably 1.18, 1.19, 1.20,

[0141] In addition, the upper limit value of the conditional expression (3) is preferably 4.80, 4.50, 4.20, 3.90, and 3.60, respectively.

[0142] 1-3-4.Conditional expression (4)

[0143] Preferably, the zoom lens satisfies the following conditional expression.

[0144] 2.70<βCt…(4)

[0145] in,

[0146] βCt: The combined lateral magnification at the telephoto end of the RR group from the negative lens group closest to the object side to the lens group closest to the image side

[0147] The above-mentioned conditional formula (4) is a formula that specifies the composite lateral magnification at the telephoto end of the lens group from the negative lens group closest to the object side to the lens group closest to the image side in the RR group. Here, the zoom lens is composed of the first lens group, the FR group, and the RR group in sequence from the object side as described above. By configuring an expansion system on the image side of the zoom lens, a telephoto optical focal length configuration is configured to achieve miniaturization. Therefore, it is important to set the lateral magnification on the image side within the RR group within an appropriate range for miniaturization. Miniaturization is achieved by satisfying conditional formula (4).

[0148] If the value of the above conditional expression (4) reaches below the lower limit, the telephoto optical power configuration becomes weak, resulting in an increase in the total optical length or the diameter of the lens, which is not preferred from the perspective of miniaturization. In addition, if the lateral magnification of the lens group closest to the image side becomes too large, the error sensitivity becomes large, so from the perspective of manufacturability, it is preferred to specify an upper limit value. More preferably, the upper limit value in the above conditional expression (4) is set to be less than 9.0.

[0149] In order to obtain the above effect, the lower limit of the above conditional expression (4) is preferably 2.80, 2.85, 2.90, 2.95, 3.00, 3.05, 3.10, 3.12, 3.14, and the upper limit of the above conditional expression (4) is preferably 8.50, 8.00, 7.50, 7.00, 6.50, 6.00, 5.50, 5.20, 4.90, 4.70, 4.50, 4.20.

[0150] 1-3-5.Conditional expression (5)

[0151] Preferably, the zoom lens satisfies the following conditional expression.

[0152] 1.73 <NdA<2.50…(5)

[0153] in,

[0154] NdA: d-line refractive index of the lens A

[0155] The above-mentioned conditional formula (5) is a formula that specifies the d-line refractive index of the lens A with negative optical power that is configured closest to the image side of the zoom lens. Since the zoom lens has positive optical power as a whole, in order to reduce the Petzval sum, it is necessary to increase the refractive index of the lens with negative optical power. However, glass materials with high refractive index are expensive. Therefore, in order to achieve both high performance and low cost, it is important to specify the refractive index within an appropriate range. Here, when conditional formula (5) is satisfied, it is possible to suppress costs while achieving a zoom lens with high off-axis performance. In addition, when an aspheric film, i.e., a so-called composite aspheric lens, is attached to the image side surface of the lens A with negative optical power that is configured closest to the image side, NdA is not the refractive index of the aspheric film but the refractive index of the base lens.

[0156] On the other hand, if the value of the above conditional expression (5) reaches above the upper limit, the cost of the glass material becomes too high, which is not preferable from the perspective of cost reduction. If the value of the above conditional expression (5) reaches below the lower limit, correction of field curvature becomes difficult, which is not preferable from the perspective of high performance.

[0157] In order to obtain the above effect, the upper limit value of the above conditional expression (5) is preferably 2.30, 2.15, 2.12, 2.06, 2.01, 2.00, 1.99, 1.97, 1.96, 1.95, 1.93, respectively. In addition, the lower limit value of the above conditional expression (5) is preferably 1.74, 1.75, respectively.

[0158] 1-3-6.Conditional expression (6)

[0159] Preferably, the zoom lens satisfies the following conditional expression.

[0160] (CrAf+CrAr) / (CrAf-CrAr)<0.30…(6)

[0161] in,

[0162] CrAf: The radius of curvature of the object side of the lens A

[0163] CrAr: The radius of curvature of the image side of the lens A

[0164] The above conditional expression (6) is a formula that specifies the shape of the lens A having negative power that is disposed closest to the image side of the zoom lens. By making the shape of the lens A closest to the image side the shape specified by the above conditional expression (6), coma correction can be performed well, and a zoom lens with high off-axis performance can be realized. In addition, when the lens A having negative power that is disposed closest to the image side is attached with an aspheric film, i.e., a so-called composite aspheric lens, CrAf and CrAr are not the curvature radii of the aspheric film but the curvature radii of the base lens.

[0165] On the other hand, if the value of the above conditional expression (6) reaches or exceeds the upper limit, the radius of curvature of the image side becomes too small relative to the radius of curvature of the object side, so that correction of coma becomes difficult, which is not preferable from the perspective of high performance. In addition, for the shape of the lens A closest to the image side, if the radius of curvature of the object side becomes too small relative to the radius of curvature of the image side, the error sensitivity becomes large, so from the perspective of manufacturability, it is preferable to specify a lower limit value. More preferably, the lower limit value of the above conditional expression (6) is greater than -30.0.

[0166] In order to obtain the above effect, the upper limit of the above conditional expression (6) is preferably 0.20, 0.18, 0.10, 0.00, -0.10, -0.15, -0.20, -0.20, -0.26, -0.30, -0.35, -0.40, -0.45, -0.50, -0.55, -0.60. In addition, the lower limit of the above conditional expression (6) is preferably -20.00, -10.00, -9.00, -7.90, -6.80.

[0167] 1-3-7.Conditional expression (7)

[0168] Preferably, the zoom lens satisfies the following conditional expression.

[0169] 0.02 <BFw / fw<0.98…(7)

[0170] in,

[0171] BFw: The distance from the side closest to the image to the image plane at the wide-angle end of the zoom lens

[0172] fw: focal length of the zoom lens at the wide-angle end

[0173] The above-mentioned conditional formula (7) is a formula that specifies the ratio of the value obtained by converting the distance from the side closest to the image to the image plane on the optical axis at the wide-angle end of the zoom lens into air to the focal length at the wide-angle end of the zoom lens. It is necessary to configure an optical element such as a low-pass filter between the side closest to the image and the image plane at the wide-angle end. Therefore, in order to achieve miniaturization while configuring the optical elements, it is important to set the back focus at the wide-angle end to the most optimal range. When the conditional formula (7) is satisfied, the back focus at the wide-angle end is set to the optimal range, so it becomes easy to realize a small zoom lens.

[0174] On the other hand, if the value of the conditional expression (7) is above the upper limit, the total optical length at wide angle becomes larger and the weight including the mechanical part becomes heavier. Therefore, it is not preferable from the point of view of compactness and lightness. On the other hand, if the value of the conditional expression (7) is below the lower limit, it is difficult to configure optical elements such as low-pass filters, so it is not preferable. In addition, it causes the diameter of the final lens to be enlarged, so it is not preferable.

[0175] In order to obtain the above effect, the upper limit value of the above conditional expression (7) is preferably 0.93, 0.91, 0.84, 0.78, 0.75, 0.70, 0.68, 0.66, 0.64, and the lower limit value of the above conditional expression (7) is preferably 0.04, 0.06, 0.07, 0.10, 0.13, 0.16, respectively.

[0176] 1-3-8.Conditional expression (8)

[0177] Preferably, the zoom lens satisfies the following conditional expression.

[0178] 0.15 <f1 / ft<0.70…(8)

[0179] in,

[0180] f1: focal length of the first lens group

[0181] ft: focal length at the telephoto end of the zoom lens

[0182] The above conditional expression (8) is a formula that specifies the ratio of the focal length of the first lens group to the focal length of the optical system. By satisfying conditional expression (8), the change of spherical aberration and field curvature during zooming can be reduced, thereby achieving high performance. In addition, when conditional expression (8) is satisfied, it is easy to adopt a telephoto optical focal length configuration, thereby achieving miniaturization of the optical system in the optical length direction.

[0183] On the other hand, if the value of the conditional expression (8) is greater than the upper limit, the power of the first lens group becomes weak. As a result, the telephoto power configuration becomes weak, so it becomes difficult to miniaturize the zoom lens, which is not preferred. On the other hand, if the value of the conditional expression (8) is less than the lower limit, the power of the first lens group becomes too strong, making it difficult to reduce the change of spherical aberration or field curvature during zooming, which is not preferred from the perspective of high performance.

[0184] In order to obtain the above effect, the upper limit value of the above conditional expression (8) is preferably 0.68, 0.66, 0.64, 0.63, 0.61, 0.60, and the lower limit value of the above conditional expression (8) is preferably 0.18, 0.21, 0.24, 0.26, 0.28, 0.30, 0.31, respectively.

[0185] 1-3-9.Conditional expression (9)

[0186] Preferably, the zoom lens satisfies the following conditional expression.

[0187] 0.10 <Lnsr / Lnall<0.74…(9)

[0188] in,

[0189] Lnsr: The total number of lenses on the image side of the aperture stop

[0190] Lnall: The total number of lenses in this zoom lens

[0191] The above-mentioned conditional formula (9) is a formula that specifies the ratio of the total number of lenses that are closer to the image side than the aperture stop to the total number of lenses of the zoom lens. If the number of lenses increases, aberration correction becomes easier. In addition, among off-axis light rays, if the main light ray on the object side of the aperture stop passes through the lower side of the optical axis, it passes through the upper side of the optical axis on the image side of the aperture stop. Therefore, the off-axis coma or chromatic aberration of magnification cancels each other out on the object side and image side of the aperture stop, and it becomes easier to improve the off-axis performance. It can be seen from this that on the image side of the aperture stop, there is an appropriate range for the ratio of the number of lenses to the total number of lenses. By satisfying conditional formula (9), the number of lenses is in the optimal range, and it is easy to strike a balance between high performance and low cost. The number of lenses represents the number of lenses, excluding components that do not have optical power, such as protective glass, IR cutoff filters, or prisms. In addition, regarding the number of lenses, a compound aspherical lens is counted as one lens, and a cemented lens in which two lenses are cemented is counted as two lenses.

[0192] On the other hand, if the value of the above conditional expression (9) reaches above the upper limit, the ratio of the number of lenses on the image side of the aperture stop becomes too large. Therefore, the aberration correction capability on the object side of the aperture stop becomes insufficient, which is not preferable from the perspective of high performance. On the other hand, if the value of the above conditional expression (9) reaches below the lower limit, the ratio of the number of lenses on the image side of the aperture stop becomes too small. Therefore, the aberration correction capability on the image side of the aperture stop becomes insufficient, which is not preferable from the perspective of high performance.

[0193] In order to obtain the above effect, the upper limit of the above conditional expression (9) is preferably 0.71, 0.69, 0.66, 0.65, 0.64, 0.63, 0.62, and the lower limit of the above conditional expression (9) is preferably 0.15, 0.20, 0.25, 0.29, 0.31, 0.33, 0.34, 0.36, 0.38, 0.40, 0.41, 0.42, respectively.

[0194] 1-3-10.Conditional expression (10)

[0195] Preferably, the zoom lens satisfies the following conditional expression.

[0196] 1.20 <TLsrw / BFw<6.95…(10)

[0197] in,

[0198] TLsrw: The distance from the aperture stop to the image side of lens A at the wide angle end

[0199] BFw: The distance from the side closest to the image to the image plane at the wide-angle end of the zoom lens

[0200] The above-mentioned conditional formula (10) is a formula that specifies the ratio of the distance from the aperture stop to the image side surface of lens A at the wide-angle end of the zoom lens to the value obtained by converting the distance from the image side surface closest to the image plane on the optical axis at the wide-angle end of the zoom lens into air. The lens A having a negative optical power is arranged on the image side closest to the zoom lens. By arranging the lens A in an appropriate range between the aperture stop and the image plane, the off-axis aberration correction capability of the lens A is optimized. By satisfying conditional formula (10), the distance from the lens A to the aperture stop and the distance from the lens A to the image plane are both in the optimal range, making it easy to achieve high performance of the zoom lens.

[0201] In contrast, when the value of the above conditional expression (10) reaches above the upper limit, that is, the lens A is close to the image plane between the aperture stop and the image plane. At this time, the height of the off-axis light passing through the lens A becomes too high, and the aberration correction ability of the lens A becomes weak. In addition, if the optical focal length of the lens A becomes too strong, it becomes difficult to correct field curvature and coma. Due to these, it is not preferred from the perspective of high performance. When the value of the above conditional expression (10) reaches below the lower limit, that is, the lens A is far from the image plane between the aperture stop and the image plane. At this time, the height of the off-axis light passing through the lens A becomes too low, and the aberration correction ability of the lens A becomes weak. Therefore, it becomes difficult to correct field curvature and coma, which is not preferred from the perspective of high performance.

[0202] In order to obtain the above effect, the upper limit of the conditional expression (10) is preferably 6.50, 6.20, 5.90, 5.60, 5.40, 5.10, 4.90, 4.60, 4.35, 4.10, 4.00, and the lower limit of the conditional expression (10) is preferably 1.30, 1.40, 1.50, 1.60, 1.70, respectively.

[0203] 1-3-11.Conditional expression (11)

[0204] Preferably, the zoom lens satisfies the following conditional expression.

[0205] 0.06 <BFt / TLt<0.32…(11)

[0206] in,

[0207] BFt: The distance from the side closest to the image to the image plane at the telephoto end of the zoom lens

[0208] TLt: The distance from the side closest to the object to the image plane at the telephoto end of the zoom lens

[0209] The above-mentioned conditional formula (11) is a formula that specifies the ratio of the value obtained by converting the distance from the closest image side to the image plane on the optical axis at the telephoto end of the zoom lens to air and the value of the distance from the closest image side to the image plane at the telephoto end of the zoom lens (converted to air from the closest image side to the image plane). In order to make the back focus longer at the telephoto end relative to the total optical length, it is necessary to strengthen the positive focal length on the object side. If the positive focal length on the object side is too strong, it becomes difficult to correct spherical aberration or field curvature. In addition, if the back focus is shortened at the telephoto end, the diameter of the lens on the image side will be enlarged. Therefore, it is important to set the back focus and the total length at the telephoto end to an appropriate range. By satisfying conditional formula (11), the back focus at the telephoto end becomes appropriate relative to the total optical length, making it easy to achieve both high performance and miniaturization.

[0210] On the other hand, if the value of the above conditional expression (11) reaches or exceeds the upper limit, the back focus becomes longer relative to the total optical length. Therefore, the focusing power of the object side of the zoom lens becomes stronger, and the correction of spherical aberration and field curvature becomes difficult. On the other hand, if the value of the above conditional expression (11) reaches or exceeds the lower limit, the back focus becomes shorter relative to the total optical length. As a result, the diameter of the lens on the image side is enlarged by bringing the lens on the image side closer to the image plane, which is not preferable from the perspective of miniaturization.

[0211] In order to obtain the above effect, the upper limit of the above conditional expression (11) is preferably 0.31, 0.30, 0.29, 0.28, 0.27, 0.26, 0.25, 0.24, and the lower limit of the above conditional expression (11) is preferably 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, respectively.

[0212] 1-3-12.Conditional expression (12)

[0213] Preferably, the zoom lens satisfies the following conditional expression.

[0214] 2.90 <f1 / |fFRt|<8.00…(12)

[0215] in,

[0216] f1: focal length of the first lens group

[0217] fFRt: focal length at the telephoto end of the FR group

[0218] The above conditional expression (12) is a formula that specifies the ratio of the focal length of the first lens group to the focal length of the FR group at the telephoto end. By satisfying conditional expression (12), the change of spherical aberration or field curvature during zooming can be reduced, thereby achieving high performance. In addition, when conditional expression (12) is satisfied, it is easy to adopt a telephoto optical focal length configuration, thereby achieving miniaturization of the optical system in the optical length direction.

[0219] On the other hand, if the value of the above conditional expression (12) reaches or exceeds the upper limit, the focal length of the first lens group becomes too large relative to the focal length at the telephoto end of the FR group. Therefore, the telephoto optical focal length configuration becomes weak, miniaturization becomes difficult, and is not preferred. On the other hand, if the value of the above conditional expression (12) reaches or exceeds the lower limit, the focal length of the first lens group becomes too small relative to the focal length at the telephoto end of the FR group. The optical focal length of the first lens group becomes too strong, and it is difficult to reduce the change of spherical aberration or field curvature when changing magnification, so it is not preferred from the perspective of high performance.

[0220] In order to obtain the above effect, the upper limit of the above conditional expression (12) is preferably 7.70, 7.40, 7.20, 7.00, 6.90, 6.80, 6.70, 6.60, 6.50, 6.40, and the lower limit of the above conditional expression (12) is preferably 2.95, 3.00, 3.05, 3.10, respectively.

[0221] 1-3-13.Conditional expression (13)

[0222] Preferably, the zoom lens satisfies the following conditional expression.

[0223] -2.50<βRRw<-0.50…(13)

[0224] in,

[0225] βRRw: lateral magnification of the RR group at the wide angle end

[0226] The above conditional expression (13) is a formula for defining the lateral magnification of the RR group at the wide angle end. By satisfying conditional expression (13), the lateral magnification of the RR group at the wide angle end becomes optimal, and the back focus at the wide angle end is within an appropriate range. Thus, miniaturization is achieved.

[0227] In contrast, when the value of the above conditional formula (13) reaches above the upper limit, the lateral magnification at the wide-angle end of the RR group becomes too large. As a result, the back intercept at the wide-angle end becomes shorter, making it difficult to configure optical elements such as low-pass filters, and is therefore not preferred. In addition, this causes the diameter of the final lens to be enlarged, and is therefore not preferred. If the value of the above conditional formula (13) reaches below the lower limit, the back intercept at the wide-angle end becomes longer, and therefore, the total optical length at wide angle becomes longer and the weight including the machinery becomes heavier. Therefore, from the perspective of miniaturization and lightness, it is not preferred.

[0228] In order to obtain the above effect, the upper limit of the above conditional expression (13) is preferably -0.55, -0.60, -0.65, -0.70, -0.75, -0.80, -0.85, -0.90, -0.95, -1.00, and the lower limit of the above conditional expression (13) is preferably -2.20, -2.00, -1.90, -1.80, -1.70, -1.60, respectively.

[0229] 1-3-14.Conditional expression (14)

[0230] Preferably, the zoom lens satisfies the following conditional expression.

[0231] 7.1<|(1-βFt 2 )×βrt 2 |<20.0…(14)

[0232] in,

[0233] βFt: lateral magnification of the focusing group at the telephoto end

[0234] βrt: The combined lateral magnification at the telephoto end of all lens groups closer to the image side than the focusing group

[0235] The above-mentioned conditional expression (14) is a formula that specifies the focus sensitivity at the telephoto end of the focusing group. The focus sensitivity of the focusing group is a value that represents the ratio of the focus position movement on the image plane when the focusing group moves 1 unit. In addition, here, βrt, which is the composite lateral magnification at the telephoto end of all lens groups closer to the image side than the focusing group, refers to the composite lateral magnification at the telephoto end of the lens group and lens closer to the image side than the focusing group. When there is no lens group or lens closer to the image side than the focusing group, the value of βrt is 1. By satisfying conditional expression (14), the focus sensitivity at the telephoto end of the focusing group is optimized, and it is easy to reduce the amount of movement during focusing, thereby achieving miniaturization. In addition, even if the control of the focusing group is not high in stopping accuracy in order to avoid excessively high stopping accuracy when driving the focusing group, a zoom lens with high imaging performance can be achieved.

[0236] In contrast, when the value of the above conditional expression (14) reaches or exceeds the upper limit, the focus sensitivity at the telephoto end of the focus group becomes too large. As a result, the focus position is greatly offset due to the stop position error when driving the focus group, and high performance becomes difficult. If the value of the above conditional expression (14) reaches or falls below the lower limit, the focus sensitivity at the telephoto end of the focus group becomes too small. As a result, the amount of movement when focusing from an object at infinity to an object at a finite distance becomes large, and miniaturization of the total optical length becomes difficult, which is not preferred.

[0237] In order to obtain the above effect, the upper limit value of the above conditional expression (14) is preferably 19.0, 18.0, 17.0, 16.0, and the lower limit value of the above conditional expression (14) is preferably 7.20, 7.30, 7.40, 7.50, 7.60, 7.80, 8.00, respectively.

[0238] 2. Camera device

[0239] Next, an imaging device according to the present invention is described. The imaging device according to the present invention includes the optical system according to the present invention described above, and an imaging element that receives an optical image formed by the zoom lens and converts the optical image into an electrical image signal.

[0240] Here, the imaging element is not particularly limited, and solid-state imaging elements such as CCD sensors (charge coupled devices) or CMOS sensors (complementary metal oxide semiconductors) can be used. The imaging device involved in the present invention is suitable for imaging devices using these solid-state imaging elements, such as digital cameras or video cameras, surveillance cameras, vehicle-mounted cameras, drone cameras, medical cameras, etc. In addition, the imaging device can be a fixed-lens imaging device in which the lens is fixed to the housing, or of course, a replaceable lens imaging device such as a SLR camera or a mirrorless single-lens camera.

[0241] Fig.21 Schematically shows an example of the configuration of the imaging device according to the present embodiment. Fig.21 As shown, the imaging device 1 includes a camera 2 and a lens barrel 3 that can be attached to and detached from the camera 2. The imaging device 1 is one form of an imaging device. The camera 2 includes a CCD sensor 21 as an imaging element and a protective glass 22. The CCD sensor 21 is arranged at a position in the camera 2 where the optical axis of the zoom lens installed in the lens barrel 3 of the camera 2 becomes its central axis. The camera 2 may also include an IR cut filter or the like instead of the protective glass 22.

[0242] Next, the present invention will be specifically described by showing an embodiment. However, the present invention is not limited to the following embodiment. In each lens cross-sectional view, the left side is the object side and the right side is the image side when facing the drawing.

[0243] [Example 1]

[0244] Figure 1 : This is a lens cross-sectional view at the wide-angle end showing the configuration of the zoom lens of Example 1 involved in the present invention. The zoom lens is composed of, from the object side, a first lens group G1 having positive power, a second lens group G2 having negative power, a third lens group G3 having positive power, a fourth lens group G4 having negative power, and a fifth lens group G5 having negative power. The rear group GR is composed of, from the object side, a second lens group G2, a third lens group G3, a fourth lens group G4, and a fifth lens group G5. The second lens group G2 corresponds to the lens group N having negative power closest to the object side in the rear group GR. The third lens group G3 corresponds to the lens group P having positive power closer to the image side and closest to the object side than the lens group N. The FR group is composed of the second lens group G2. The RR group is composed of the third lens group G3, the fourth lens group G4, and the fifth lens group G5. By setting the lens group closest to the object side of the RR group to a positive optical power lens group, it is possible to suppress the spherical aberration variation during zooming. Here, the fourth lens group G4 is equivalent to the lens group with negative optical power closest to the object side of the RR group. In addition, the fifth lens group G5 is equivalent to the lens group closest to the image side.

[0245] The first lens group G1 is composed, in order from the object side, of a cemented lens of a meniscus-shaped first lens L1 having negative refractive power and a convex object-side surface facing the object side, and a biconvex second lens L2 having positive refractive power and a convex object-side surface and an image-side surface.

[0246] The second lens group G2 is composed of, from the object side, a biconcave third lens L3 having negative power and a concave object side and image side, and a cemented lens, which is composed of a biconcave fourth lens L4 having negative power and a concave object side and image side, and a meniscus fifth lens L5 having positive power and a convex object side facing the object side. Here, the third lens L3 is equivalent to the lens closest to the object side in the rear group.

[0247] The third lens group G3 includes, in order from the object side, a biconvex sixth lens L6 having positive power and convex surfaces on both the object side and the image side; a cemented lens consisting of a biconvex seventh lens L7 having positive power and convex surfaces on both the object side and the image side and a biconcave eighth lens L8 having negative power and concave surfaces on both the object side and the image side; an aperture stop S; a cemented lens consisting of a meniscus ninth lens L9 having negative power and convex surface on the object side facing the object side and a biconvex tenth lens L10 having positive power and convex surface on both the object side and the image side; and a meniscus eleventh lens L11 having negative power and concave surface on the object side. By making the side closest to the object of the third lens group convex toward the object side, spherical aberration can be corrected well.

[0248] The fourth lens group G4 is composed, in order from the object side, of a cemented lens of a biconvex 12th lens L12 having positive refractive power and having convex object-side and image-side surfaces, and a biconcave 13th lens L13 having negative refractive power and having concave object-side and image-side surfaces.

[0249] The fifth lens group G5 is composed of a fourteenth lens L14 having an aspherical layer on the object side and having negative refractive power, and a meniscus shape with a concave object side surface facing the object side. Here, the fourteenth lens L14 corresponds to the lens A with negative refractive power closest to the image side in the rear group.

[0250] When zooming from the wide-angle end to the telephoto end, the interval between adjacent lens groups changes. When zooming from the wide-angle end to the telephoto end, the interval between the first lens group G1 and the second lens group G2 increases, and the interval between the second lens group G2 and the third lens group G3 decreases. By changing the interval in this way, it is easy to lengthen the focal length at the telephoto end, and the change of spherical aberration during zooming can be suppressed. In addition, when zooming from the wide-angle end to the telephoto end, the interval between the third lens group G3 and the fourth lens group G4 first decreases and then increases. By changing the interval in this way, the change of field curvature during zooming can be suppressed.

[0251] When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the object side, the second lens group G2 is fixed relative to the image plane, the third lens group G3 moves toward the object side, the fourth lens group G4 moves toward the object side, and the fifth lens group G5 moves toward the object side. The third lens group G3 and the fifth lens group G5 move along the same trajectory when changing magnification. As a result, the mechanical structure can be simplified, which is effective for low cost and miniaturization. If the third lens group G3 and the fifth lens group G5 are designed as a mechanically integrated structure, the error amount will affect each other when decentered, so the amount of aberration generated when decentered will be reduced, and high performance can be achieved.

[0252] Here, the fourth lens group G4 corresponds to a focusing group that focuses from an infinitely distant object to a finitely distant object by moving toward the image side. Also, here, the second lens group G2 corresponds to an anti-vibration group that corrects the image position by moving in a direction substantially orthogonal to the optical axis when hand shake occurs.

[0253] In addition, "IMG" in the figure represents an image plane. "IMG" is an imaging surface of a solid-state imaging element such as the CCD sensor or CMOS sensor mentioned above. Light incident from the object side of the optical system forms an image on the image plane. The solid-state imaging element converts the received optical image into an electrical image signal. The image processing unit (image processing processor, etc.) possessed by the imaging device, etc., generates a digital image corresponding to the image of the subject based on the electrical image signal output from the imaging element. For example, the digital image can be recorded on a recording medium such as a hard disk device (HDD) or a memory card, a CD, or a magnetic tape. In addition, the image plane can be a film surface of a silver halide film.

[0254] In addition, "CG" in the figure represents an image plane. "CG" is an optical block. The optical block CG is equivalent to a filter, a protective glass, a crystal low-pass filter, or an infrared cutoff filter, etc. These reference numerals (IMG, CG) also represent the same objects in the figures shown in other embodiments, so their description is omitted below.

[0255] [Example 2]

[0256] Figure 5: This is a lens cross-sectional view at the wide-angle end showing the configuration of the zoom lens of Example 2 involved in the present invention. The zoom lens is composed of, from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, and a sixth lens group G6 having negative refractive power. The rear group GR is composed of, from the object side, a second lens group G2, a third lens group G3, a fourth lens group G4, a fifth lens group G5, and a sixth lens group G6. The second lens group G2 corresponds to the lens group N having negative refractive power closest to the object side in the rear group GR. The third lens group G3 corresponds to the lens group P having positive refractive power closer to the image side and closest to the object side than the lens group N. The FR group is composed of the second lens group G2. The RR group is composed of the third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6. By setting the lens group closest to the object side of the RR group to have positive focal length, the spherical aberration variation during zooming can be suppressed. Here, the fifth lens group G5 is equivalent to the lens group with negative focal length closest to the object side of the RR group. In addition, the sixth lens group G6 is equivalent to the lens group closest to the image side.

[0257] The first lens group G1 is composed of a cemented lens and a third lens L3 in sequence from the object side, wherein the cemented lens is composed of the first lens L1 having a negative optical focal length and a meniscus shape with the object side surface being convex toward the object side, and the second lens L2 having a positive optical focal length and a biconvex shape with both the object side surface and the image side surface being convex; the third lens L3 has a positive optical focal length and a biconvex shape with both the object side surface and the image side surface being convex.

[0258] The second lens group G2 is composed of a cemented lens and a sixth lens L6 in order from the object side, wherein the cemented lens is composed of a fourth lens L4 having a positive focal power and a meniscus shape with a concave surface on the object side and a fifth lens L5 having a negative focal power and a biconcave shape with concave surfaces on both the object side and the image side; the sixth lens L6 has a negative focal power and a biconcave shape with concave surfaces on both the object side and the image side. Here, the fourth lens L4 is equivalent to the lens closest to the object side in the rear group.

[0259] The third lens group G3 is composed of the seventh lens L7 and a cemented lens in order from the object side, wherein the seventh lens L7 has positive power and has a biconvex shape with both the object side and the image side being convex; the cemented lens is composed of the eighth lens L8 with positive power and a biconvex shape with both the object side and the image side being convex, and the ninth lens L9 with negative power and a biconcave shape with both the object side and the image side being concave. Here, by making the side closest to the object of the third lens group convex toward the object side, spherical aberration can be well corrected.

[0260] The 4th lens group G4 includes, in order from the object side: an aperture stop S; a cemented lens consisting of a 10th lens L10 having a negative optical power and a meniscus shape with the object side surface being convex toward the object side, and an 11th lens L11 having a positive optical power and a meniscus shape with the object side surface being convex toward the object side; a cemented lens consisting of a 12th lens L12 having a positive optical power and a meniscus shape with the object side surface being concave toward the object side, and a 13th lens L13 having a negative optical power and a biconcave shape with both the object side surface and the image side surface being concave; and a 14th lens L14 having an aspherical layer on the object side and having positive optical power and a biconvex shape with both the object side surface and the image side surface being convex.

[0261] The fifth lens group G5 includes, in order from the object side, a cemented lens of a meniscus-shaped 15th lens L15 having positive refractive power and a concave object side surface facing the object side, and a biconcave 16th lens L16 having negative refractive power and a concave object side surface and an image side surface.

[0262] The sixth lens group G6 is composed of a seventeenth lens L17 having negative refractive power and a meniscus shape with a concave object side surface on the object side. Here, the seventeenth lens L17 corresponds to the lens A having negative refractive power closest to the image side in the rear group.

[0263] When zooming from the wide-angle end to the telephoto end, the interval between adjacent lens groups changes. When zooming from the wide-angle end to the telephoto end, the interval between the first lens group G1 and the second lens group G2 increases, and the interval between the second lens group G2 and the third lens group G3 decreases. By changing the interval in this way, it is easy to lengthen the focal length at the telephoto end, and the change in spherical aberration during zooming can be suppressed. In addition, when zooming from the wide-angle end to the telephoto end, the interval between the third lens group G3 and the fourth lens group G4 increases, and the interval between the fourth lens group G4 and the fifth lens group G5 first decreases and then increases. By changing the interval in this way, the change in field curvature during zooming can be suppressed.

[0264] When zooming from the wide angle end to the telephoto end, the first lens group G1 is fixed relative to the image plane, the second lens group G2 moves toward the image side, the third lens group G3 moves toward the object side, the fourth lens group G4 is fixed relative to the image plane, the fifth lens group G5 moves along a convex trajectory toward the image side, and the sixth lens group G6 is fixed relative to the image plane. By having a group that is fixed relative to the image plane when zooming, the mechanical mechanism can be simplified, which is effective in reducing costs and miniaturization.

[0265] Here, the fifth lens group G5 is equivalent to a focusing group that focuses from an infinitely distant object to an object at a finite distance by moving toward the image side. In addition, the cemented lens formed by L12 and L13 in the fourth lens group G4 is equivalent to an anti-vibration group that corrects the image position by moving in a direction substantially orthogonal to the optical axis when hand shake occurs.

[0266] [Example 3]

[0267] Fig. 9 : This is a lens cross-sectional view at the wide-angle end showing the configuration of the zoom lens of Example 3 involved in the present invention. The zoom lens is composed of, from the object side, a first lens group G1 having positive power, a second lens group G2 having negative power, a third lens group G3 having positive power, a fourth lens group G4 having positive power, a fifth lens group G5 having negative power, and a sixth lens group G6 having negative power. The rear group GR is composed of, from the object side, a second lens group G2, a third lens group G3, a fourth lens group G4, a fifth lens group G5, and a sixth lens group G6. The second lens group G2 corresponds to the lens group N having negative power which is closest to the object side in the rear group GR. The third lens group G3 corresponds to the lens group P having positive power which is closer to the image side and closest to the object side than the lens group N. The FR group is composed of the second lens group G2. The RR group is composed of the third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6. By setting the lens group closest to the object side of the RR group to have positive focal length, the spherical aberration variation during zooming can be suppressed. Here, the fifth lens group G5 is equivalent to the lens group with negative focal length closest to the object side in the RR group. In addition, the sixth lens group G6 is equivalent to the lens group closest to the image side.

[0268] The first lens group G1 includes, from the object side, a cemented lens consisting of a meniscus-shaped first lens L1 having negative optical power and an object side surface that is convex toward the object side, and a biconvex second lens L2 having positive optical power and a convex surface on both the object side and the image side surfaces; and a meniscus-shaped third lens L3 having positive optical power and an object side surface that is convex toward the object side.

[0269] The second lens group G2 includes, in order from the object side, a meniscus-shaped fourth lens L4 having an aspherical layer on the object side and having negative power, and an object side surface that is convex and faces the object side; a cemented lens consisting of a biconcave fifth lens L5 having negative power, and both the object side and the image side surfaces are concave, and a biconvex sixth lens L6 having positive power, and both the object side and the image side surfaces are convex; and a meniscus-shaped seventh lens L7 having an aspherical shape on both the object side and the image side surfaces and having negative power, and an object side surface that is concave and faces the object side. Here, the fourth lens L4 corresponds to the lens closest to the object side in the rear group.

[0270] The third lens group G3 is composed of, in order from the object side, an aperture stop S, an eighth lens L8 having positive power and a biconvex shape with both the object side and the image side being convex, a ninth lens L9 having positive power and a biconvex shape with both the object side and the image side being convex, and a tenth lens L10 having a biconcave shape with an aspherical shape on the image side and negative power and both the object side and the image side being concave. Here, by making the side closest to the object of the third lens group convex toward the object side, spherical aberration can be well corrected.

[0271] The 4th lens group G4 includes, in order from the object side: an 11th lens L11 having positive optical power and a biconvex shape with both the object side and the image side being convex; a cemented lens consisting of a 12th lens L12 having negative optical power and a meniscus shape with the object side being convex facing the object side, and a 13th lens L13 having positive optical power and a biconvex shape with both the object side and the image side being convex; and a meniscus-shaped 14th lens L14, both surfaces of which on the object side and the image side are aspherical shapes and have positive optical power and the object side is concave facing the object side.

[0272] The 5th lens group G5 is composed, from the object side, in sequence: a cemented lens of the 15th lens L15 which has a positive refractive power and a biconvex shape with both the object side and the image side being convex, and the 16th lens L16 which has a biconcave shape with an aspherical shape on the image side and negative refractive power and both the object side and the image side being concave.

[0273] The sixth lens group G6 is composed of, from the object side, a 17th lens L17 having positive power and a meniscus shape with a convex object side facing the object side, and an 18th lens L18 having negative power and a meniscus shape with a concave object side facing the object side. Here, the 18th lens L18 is equivalent to the lens A having negative power closest to the image side in the rear group.

[0274] When zooming from the wide-angle end to the telephoto end, the interval between adjacent lens groups changes. When zooming from the wide-angle end to the telephoto end, the interval between the first lens group G1 and the second lens group G2 increases, and the interval between the second lens group G2 and the third lens group G3 decreases. By changing the interval in this way, it is easy to lengthen the focal length at the telephoto end, and the change in spherical aberration during zooming can be suppressed. In addition, when zooming from the wide-angle end to the telephoto end, the interval between the third lens group G3 and the fourth lens group G4 decreases, and the interval between the fourth lens group G4 and the fifth lens group G5 first increases and then decreases. By changing the interval in this way, the change in field curvature during zooming can be suppressed.

[0275] When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the object side, the second lens group G2 moves toward the image side, then moves toward the object side, and then moves toward the image side again, moving in an S-shaped trajectory. The third lens group G3 moves toward the object side, the fourth lens group G4 moves toward the object side, the fifth lens group G5 moves toward the object side, and the sixth lens group G6 moves toward the object side.

[0276] Here, the fifth lens group G5 is equivalent to a focusing group that focuses from an infinitely distant object to an object at a finite distance by moving toward the image side. In addition, the cemented lens formed by L12 and L13 in the fourth lens group G4 is equivalent to an anti-vibration group that corrects the image position by moving in a direction substantially orthogonal to the optical axis when hand shake occurs.

[0277] [Example 4]

[0278] Fig.13 : This is a lens cross-sectional view at the wide-angle end showing the configuration of the zoom lens of Example 4 involved in the present invention. The zoom lens is composed of, from the object side, a first lens group G1 having positive power, a second lens group G2 having negative power, a third lens group G3 having negative power, a fourth lens group G4 having positive power, a fifth lens group G5 having negative power, a sixth lens group G6 having positive power, and a seventh lens group G7 having negative power. The rear group GR is composed of, from the object side, a second lens group G2, a third lens group G3, a fourth lens group G4, a fifth lens group G5, a sixth lens group G6, and a seventh lens group G7. The second lens group G2 corresponds to the lens group N having negative power which is closest to the object side in the rear group GR. The fourth lens group G4 corresponds to the lens group P having positive power which is closer to the image side and closest to the object side than the lens group N. The FR group is composed of the second lens group G2 and the third lens group G3. The RR group is composed of the fourth lens group G4, the fifth lens group G5, the sixth lens group G6, and the seventh lens group G7. By setting the lens group closest to the object side of the RR group to have positive focal length, the spherical aberration variation during zooming can be suppressed. Here, the fifth lens group G5 is equivalent to the lens group with negative focal length closest to the object side in the RR group. In addition, the seventh lens group G7 is equivalent to the lens group closest to the image side.

[0279] The first lens group G1 includes, from the object side, a cemented lens consisting of a meniscus-shaped first lens L1 having negative optical power and an object side surface that is convex toward the object side, and a biconvex second lens L2 having positive optical power and a convex surface on both the object side and the image side surfaces; and a meniscus-shaped third lens L3 having positive optical power and an object side surface that is convex toward the object side.

[0280] The second lens group G2 is composed of, from the object side, a fourth lens L4 having positive power and a meniscus shape with the object side surface being concave toward the object side, and a fifth lens L5 having negative power and a meniscus shape with the object side surface being convex toward the object side. Here, the fourth lens L4 is equivalent to the lens closest to the object side in the rear group.

[0281] The third lens group G3 is composed, from the object side, in sequence: a biconcave 6th lens L6 having negative optical power and with both the object side and the image side being concave, a meniscus 7th lens L7 having positive optical power and with the object side being convex toward the object side, and a meniscus 8th lens L8 having negative optical power and with the object side being concave toward the object side.

[0282] The fourth lens group G4 includes, in order from the object side, a meniscus-shaped ninth lens L9 having positive power and an object-side surface that is convex toward the object side; a meniscus-shaped tenth lens L10 having positive power and an object-side surface that is convex toward the object side; a cemented lens consisting of a biconvex eleventh lens L11 having positive power and a convex surface on both the object-side and image-side surfaces and a biconcave twelfth lens L12 having negative power and a concave surface on both the object-side and image-side surfaces; an aperture stop S; a cemented lens consisting of a biconvex eleventh lens L11 having positive power and a convex surface on both the object-side and image-side surfaces; and a concave twelfth lens L12 having negative power and a concave surface on both the object-side and image-side surfaces. The 13th lens L13 is a biconcave lens having a concave surface on both the object side and the image side, and the 14th lens L14 is a meniscus lens having positive power and a convex object side facing the object side; the 15th lens L15 is a biconvex lens having positive power and a convex object side and image side; and the cemented lens is a meniscus lens L16 having negative power and a convex object side facing the object side, and the 17th lens L17 is a biconvex lens having an aspherical image side and positive power and a convex object side and image side. Here, by making the side closest to the object side of the 4th lens group convex toward the object side, spherical aberration can be well corrected.

[0283] The fifth lens group G5 includes, in order from the object side, a cemented lens of a meniscus-shaped 18th lens L18 having positive refractive power and whose object side surface is concave toward the object side, and a biconcave 19th lens L19 having negative refractive power and whose object side surface and image side surface are both concave.

[0284] The sixth lens group G6 is composed, in order from the object side, of a cemented lens of a meniscus-shaped 20th lens L20 having negative refractive power and whose object side surface is convex toward the object side, and a biconvex 21st lens L21 having positive refractive power and whose object side surface and image side surface are both convex.

[0285] The seventh lens group G7 is composed, in order from the object side, of a biconvex 22nd lens L22 having positive power and a convex surface on both the object side and the image side, a biconcave 23rd lens L23 having negative power and a concave surface on both the object side and the image side, and a meniscus 24th lens L24 having negative power and a concave surface on the object side. Here, the 24th lens L24 is equivalent to the lens A having negative power closest to the image side in the rear group.

[0286] When zooming from the wide-angle end to the telephoto end, the interval between adjacent lens groups changes. When zooming from the wide-angle end to the telephoto end, the interval between the first lens group G1 and the second lens group G2 increases, the interval between the second lens group G2 and the third lens group G3 increases, and the interval between the third lens group G3 and the fourth lens group G4 decreases. By changing the interval in this way, it is easy to lengthen the focal length at the telephoto end, and the changes in spherical aberration and field curvature during zooming can be suppressed. In addition, when zooming from the wide-angle end to the telephoto end, the interval between the fourth lens group G4 and the fifth lens group G5 first increases and then decreases, and the interval between the fifth lens group G5 and the sixth lens group G6 first decreases and then increases. By changing the interval in this way, the changes in field curvature during zooming can be suppressed.

[0287] When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the object side, the second lens group G2 moves toward the image side and then moves toward the object side, the third lens group G3 moves toward the image side and then moves toward the object side, the fourth lens group G4 moves toward the object side, the fifth lens group G5 moves toward the object side, the sixth lens group G6 moves toward the object side, and the seventh lens group G7 moves toward the object side. The fourth lens group G4 and the seventh lens group G7 move along the same trajectory when changing magnification. As a result, the mechanical structure can be simplified, which is effective for low cost and miniaturization. If the fourth lens group G4 and the seventh lens group G7 are designed as a mechanically integrated structure, the error amount will affect each other when decentered, so the amount of aberration generated when decentered will be reduced, and high performance can be achieved.

[0288] Here, the fourth lens group G4 is equivalent to a focusing group that focuses from an infinitely distant object to a finitely distant object by moving toward the image side. In addition, the cemented lens composed of L13 and L14 in the fourth lens group G4 is equivalent to an anti-vibration group that corrects the image position by moving in a direction substantially orthogonal to the optical axis when hand shake occurs.

[0289] Here, by setting the air interval between the 4th lens L4 and the 5th lens L5 constituting the 2nd lens group G2 as a variable interval during zooming, as an application example, it can be considered to set a lens group with positive focal power and a lens group with negative positive focal power. Example 4 is a positive-negative-negative-positive-negative lens group focal power configuration, but in this application example, it can be applied to a positive-positive-negative-negative-positive-negative lens group focal power configuration. In this way, by constituting the FR group with three positive-negative-negative lens groups, it is easier to correct spherical aberration and field curvature, which is more preferable from the perspective of high performance.

[0290] [Example 5]

[0291] Fig.17 This is a lens cross-sectional view at the wide-angle end showing the configuration of the zoom lens of Example 5 involved in the present invention. The zoom lens is composed of, from the object side, a first lens group G1 having positive power, a second lens group G2 having positive power, a third lens group G3 having negative power, a fourth lens group G4 having positive power, a fifth lens group G5 having negative power, and a sixth lens group G6 having negative power. The rear group GR is composed of, from the object side, a second lens group G2, a third lens group G3, a fourth lens group G4, and a fifth lens group G5. The third lens group G3 corresponds to the lens group N having negative power which is closest to the object side in the rear group GR. The fourth lens group G4 corresponds to the lens group P having positive power which is closer to the image side and closest to the object side than the lens group N. The FR group is composed of the second lens group G2. The RR group is composed of the third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6. By setting the lens group closest to the object side of the RR group to have positive focal length, the spherical aberration variation during zooming can be suppressed. Here, the fifth lens group G5 is equivalent to the lens group with negative focal length closest to the object side in the RR group. In addition, the sixth lens group G6 is equivalent to the lens group closest to the image side.

[0292] The first lens group G1 is composed, in order from the object side, of a cemented lens of a meniscus-shaped first lens L1 having negative refractive power and a convex object-side surface facing the object side, and a biconvex second lens L2 having positive refractive power and a convex object-side surface and an image-side surface.

[0293] The second lens group G2 is composed of a biconvex third lens L3 having positive refractive power and convex surfaces on both the object side and the image side. Here, the third lens L3 corresponds to the lens closest to the object side in the rear group.

[0294] The third lens group G3 is composed, from the object side, in sequence: a fourth lens L4 having a negative optical focal length and a biconcave shape with both the object side and the image side being concave, and a cemented lens, which is composed of a fifth lens L5 having a negative optical focal length and a biconcave shape with both the object side and the image side being concave, and a sixth lens L6 having a positive optical focal length and a meniscus shape with the object side being convex toward the object side.

[0295] The fourth lens group G4 includes, in order from the object side, a biconvex seventh lens L7 having positive power and having convex surfaces on both the object side and the image side; a cemented lens consisting of a biconvex eighth lens L8 having positive power and having convex surfaces on both the object side and the image side and a biconcave ninth lens L9 having negative power and having concave surfaces on both the object side and the image side; an aperture stop S; a cemented lens consisting of a meniscus-shaped tenth lens L10 having negative power and having a convex object side facing the object side and an eleventh lens L11 having positive power and having a convex object side and the image side; and a meniscus-shaped twelfth lens L12 having negative power and having a concave object side facing the object side. By making the side closest to the object of the fourth lens group convex toward the object side, spherical aberration can be corrected well.

[0296] The fifth lens group G5 is composed, in order from the object side, of a cemented lens of a biconvex 13th lens L13 having positive refractive power and having convex surfaces on both the object side and the image side, and a biconcave 14th lens L14 having negative refractive power and having concave surfaces on both the object side and the image side.

[0297] The sixth lens group G6 is composed of the fifteenth lens L15 having an aspherical layer on the object side and having negative refractive power, and a meniscus shape with a concave object side surface facing the object side. Here, the fifteenth lens L14 corresponds to the lens A with negative refractive power closest to the image side in the rear group.

[0298] When zooming from the wide-angle end to the telephoto end, the interval between adjacent lens groups changes. When zooming from the wide-angle end to the telephoto end, the interval between the first lens group G1 and the second lens group G2 increases, the interval between the second lens group G2 and the third lens group G3 increases, and the interval between the third lens group G3 and the fourth lens group G4 decreases. By changing the interval in this way, it is easy to lengthen the focal length at the telephoto end, and the change of spherical aberration during zooming can be suppressed. In addition, when zooming from the wide-angle end to the telephoto end, the interval between the fourth lens group G4 and the fifth lens group G5 first decreases and then increases. By changing the interval in this way, the change of field curvature during zooming can be suppressed.

[0299] When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the object side, the second lens group G2 is fixed relative to the image plane, the third lens group G3 moves toward the image side, the fourth lens group G4 moves toward the object side, the fifth lens group G5 moves toward the object side, and the sixth lens group G6 moves toward the object side. The fourth lens group G4 and the sixth lens group G6 move along the same trajectory when changing magnification. As a result, the mechanical structure can be simplified, which is effective for low cost and miniaturization. If the fourth lens group G4 and the sixth lens group G6 are designed as a mechanically integrated structure, the error amount will affect each other when eccentricity occurs, so the amount of aberration generated when eccentricity occurs will be reduced, and high performance can be achieved.

[0300] Here, the fifth lens group G5 corresponds to a focusing group that focuses from an infinitely distant object to a finitely distant object by moving toward the image side. Also, the third lens group G3 corresponds to an anti-vibration group that corrects the image position by moving in a direction substantially orthogonal to the optical axis when hand shake occurs.

[0301] The longitudinal aberration diagram of the zoom lens when focusing at infinity is shown. The longitudinal aberration diagram, from the left side of the figure, is spherical aberration (mm), astigmatism (mm), and distortion aberration (%). In the diagram showing spherical aberration, the vertical axis represents the open F value (Fno). The solid line shows the spherical aberration at the d-line (wavelength 587.56nm), the dotted line shows the spherical aberration at the C-line (wavelength 656.27nm), and the single-point dashed line shows the spherical aberration at the g-line (wavelength 435.84nm). In the diagram showing astigmatism, the vertical axis represents the image height (mm). The solid line represents the sagittal direction at the d-line (wavelength 587.56nm), and the dotted line represents the meridional direction at the d-line. In the diagram showing distortion aberration, the vertical axis is the image height (mm), and the distortion aberration (%) at the d-line (wavelength 587.56nm) is shown.

[0302] The following shows numerical examples 1 to 5 corresponding to examples 1 to 5, respectively. In the surface data of each numerical example, "surface number" shows the order of the lens surface from the object side, "r" shows the radius of curvature of the lens surface (mm) (wherein, a surface with an r value of 0.000 indicates that the surface is a flat surface), "d" shows the interval (mm) between the lens surface of the i-th (i is a natural number) lens surface and the i+1-th lens surface on the optical axis from the object side, "Nd" shows the refractive index corresponding to the d-line (wavelength λ = 587.56nm), "νd" shows the Abbe number corresponding to the d-line, and "h" shows the effective radius (mm).

[0303] In addition, each numerical embodiment shows the focal length (mm), F number (F value), half field of view (°), image height (mm), total lens length (mm), and back focal length (BF (in air)) (mm) of the imaging lens. Here, the total lens length is the distance from the object side of the first lens to the optical axis of the image plane, and is the value obtained by converting the distance from the image side of the nth lens closest to the image side to the optical axis of the image plane in air. In addition, the back focal length is the value obtained by converting the distance from the image side of the nth lens closest to the image side to the optical axis of the image plane in air.

[0304] When the optical surface is an aspherical surface, the right side of the surface number is marked with a *. In addition, in an aspherical shape, the aspherical coefficient can be expressed by the following aspherical formula using the displacement Z in the optical axis direction at a position h from the optical axis as the surface vertex reference.

[0305] Z=ch 2 / [1+{1-(1+k)c 2 h 2} 1 / 2 ]+A4h 4 +A6h 6 +A8h 8 +A10h 10 +…

[0306] Among them, c is the curvature (1 / r), h is the height from the optical axis, k is the cone coefficient (cone constant), and A4, A6, A8, A10, ... are aspheric coefficients of each order. In addition, "E±m" (m represents an integer) in the numerical values ​​of aspheric coefficients and cone constants means "×10±m".

[0307] The aperture stop is marked with an S to the right of the face number.

[0308] The intervals that change during zooming are marked with a D on the left side of the interval number. The interval data shows the variable intervals of the zoom lens.

[0309] In addition, the lens focal length indicates the focal length of each lens constituting the zoom lens.

[0310] In addition, the lens group focal length indicates the focal length of each lens group constituting the zoom lens. Here, the FR group and the RR group indicate the focal length at the telephoto end.

[0311] [Numerical Example 1]

[0312] Area data

[0313]

[0314]

[0315] Aspheric surface data

[0316] Face number 24 k 0.00000E+00 A4 5.93279E-06 A6 -1.14548E-08 A8 1.02291E-10 A10 -2.59090E-13 A12 1.28403E-16

[0317] Wide Angle middle Telephoto focal length 102.949 199.916 387.364 F-number 5.525 6.362 8.330 Half field of view 11.682 6.039 3.143 Image height 21.633 21.633 21.633 full length 179.158 233.595 259.101 BF 18.913 32.058 54.384

[0318] Variable interval data

[0319] Wide Angle middle Telephoto D3 15.080 69.517 95.023 D8 36.477 23.332 1.006 D19 4.942 2.230 2.609 D23 26.313 29.025 28.646 D26 16.264 29.410 51.735

[0320] Lens focal length

[0321]

[0322]

[0323] Lens focal length

[0324] Group Face number focal length G1 1-3 230.858 G2 4-8 -59.520 G3 9-19 46.673 G4 20-23 -59.822 G5 24-26 -74.455 FR 4-8 -59.520 RR 9-26 38.145

[0325] [Numerical Example 2] Surface Data

[0326]

[0327]

[0328] Aspheric surface data

[0329] 23 k 0.00000E+00 A4 -1.02709E-05 A6 -8.24691E-10 A8 0.00000E+00 A10 0.00000E+00

[0330] Wide Angle middle Telephoto focal length 103.026 199.961 387.962 F-number 5.769 6.684 7.312 Half field of view 11.737 5.962 3.053 Image height 21.633 21.633 21.633 full length 215.148 215.148 215.148 BF 36.406 36.406 36.406

[0331] Variable interval data

[0332] Wide Angle middle Telephoto D5 1.937 32.303 57.676 D10 58.535 27.443 1.000 D15 11.395 12.120 13.191 D25 3.673 8.922 2.301 D29 35.224 29.976 36.596

[0333] Lens focal length

[0334] lens Face number focal length L1 1-2 -137.145 L2 2-3 131.408 L3 4-5 133.698 L4 6-7 73.885 L5 7-8 -56.530 L6 9-10 -49.431 L7 11-12 56.461 L8 13-14 48.272 L9 14-15 -52.379 L10 17-18 -28.193 L11 18-19 33.597 L12 20-21 30.606 L13 21-22 -20.356 L14 23-25 33.987 L15 26-27 31.764 L16 27-28 -18.391 L17 30-31 -173.959

[0335] Lens focal length

[0336] focal length

[0337] Group Face number focal length G1 1-5 127.886 G2 6-10 -40.530 G3 11-15 45.742 G4 16-25 106.722 G5 26-29 -43.825 G6 30-31 -173.959 FR 6-10 -40.530 RR 11-31 43.050

[0338] [Numerical Example 3] Surface Data

[0339]

[0340]

[0341] Aspheric surface data

[0342]

[0343]

[0344] Wide Angle middle Telephoto focal length 28.864 99.989 388.242 F-number 3.591 5.823 6.547 Half field of view 38.152 11.622 3.061 Image height 21.633 21.633 21.633 full length 154.886 184.556 243.546 BF 16.648 39.7515 56.1239

[0345] Variable interval data

[0346] Wide Angle middle Telephoto D5 1.200 37.568 92.088 D13 38.078 9.741 1.069 D20 1.486 1.339 1.022 D27 1.027 7.064 1.381 D30 19.501 12.146 14.916 D34 14.000 37.103 53.476

[0347] Lens focal length

[0348]

[0349]

[0350] Lens focal length

[0351] Group Face number focal length G1 1-5 139.334 G2 6-13 -22.066 G3 14-20 4761.983 G4 21-27 19.587 G5 28-30 -36.422 G6 31-34 -91.588 FR 6-13 -22.066 RR 14-34 28.938

[0352] [Numerical Example 4] Surface Data

[0353]

[0354]

[0355] Aspheric surface data

[0356] 31 k 0.00000E+00 A4 5.22606E-06 A6 -7.23861E-09 A8 1.87062E-11 A10 -1.17724E-13 A12 0.00000E+00

[0357]

[0358]

[0359] Variable interval data

[0360] Wide Angle middle Telephoto D5 3.192 66.976 101.489 D9 6.800 7.106 7.960 D15 49.047 12.694 3.030 D31 2.892 12.813 4.869 D34 11.480 9.884 26.136 D37 18.432 10.108 1.800 D43 16.657 32.114 54.218

[0361] Lens focal length

[0362] lens Face number focal length L1 1-2 -210.665 L2 2-3 179.786 L3 4-5 204.266 L4 6-7 221.615 L5 8-9 -69.324 L6 10-11 -50.339 L7 12-13 53.288 L8 14-15 -59.874 L9 16-17 95.775 L10 18-19 66.517 L11 20-21 45.702 L12 21-22 -23.319 L13 24-25 -39.908 L14 25-26 57.224 L15 27-28 43.110 L16 29-30 -32.362 L17 30-31 24.432 L18 32-33 46.871 L19 33-34 -23.644 L20 35-36 -46.683 L21 36-37 31.541 L22 38-39 37.620 L23 40-41 -33.243 L24 42-43 -57.129

[0363] Lens focal length

[0364]

[0365]

[0366] [Numerical Example 5] Surface Data

[0367]

[0368]

[0369] Aspheric surface data

[0370] 26 k 0.00000E+00 A4 5.33813E-06 A6 -1.92603E-08 A8 1.86912E-10 A10 -5.88673E-13 A12 4.80636E-16

[0371] Wide Angle middle Telephoto focal length 103.480 201.399 393.048 F-number 5.474 6.326 8.228 Half field of view 11.539 5.960 3.086 Image height 21.633 21.633 21.633 full length 182.163 235.250 262.122 BF 19.494 32.897 55.171

[0372] Variable interval data

[0373] Wide Angle middle Telephoto D3 12.593 65.680 92.552 D5 2.579 3.207 3.398 D10 37.503 23.471 1.006 D21 5.191 2.835 2.871 D25 24.750 27.106 27.070 D28 16.845 30.249 52.523

[0374] Lens focal length

[0375]

[0376]

[0377] Lens focal length

[0378] Group Face number focal length G1 1-3 234.850 G2 4-8 359.704 G3 9-19 -50.602 G4 20-23 45.912 G5 24-26 -56.295 G6 24-27 -78.883 FR 4-8 -59.520 RR 9-26 38.983

[0379] The following Table 1 lists the corresponding values ​​and numerical values ​​of conditional expressions (1) to (14) in Examples 1 to 5.

[0380] [Table 1]

[0381] (1) Nd2 (2) TLt / ft (3) βLt (4) βCt (5) NdA (6) (CrAf+CrAr) / (CrAf-CrAr) (7) BFw / fw (8) f1 / ft (9) Lnsr / Lnall (10) TLsrw / BFw (11) BFt / TLt (12) f1 / |fFRt| (13) βRRw (14) <![CDATA[|(1-βFt 2 )×βrt 2 |]]>

[0382]

[0383]

[0384] TTL 259.101 215.148 243.546 288.927 262.122 ft 387.364 387.962 388.242 491.282 393.048 Cf -44.678 -37.656 -24.391 -23.421 -37.752 Cr -196.655 -50.800 -55.982 -52.283 -100.456 Bf 18.913 36.406 16.648 19.305 19.494 f 102.949 103.026 28.864 51.525 103.480 f1 230.858 127.886 139.334 175.950 234.850 LnS 6.000 8.000 11.000 12.000 6.000 Lnall 14.000 17.000 18.000 24.000 15.000 TLsrw 56.727 68.139 64.371 74.334 55.376 BF 54.384 36.406 56.124 56.866 55.171 f -59.520 -40.530 -22.066 -33.533 -59.946 βFt 2.150 2.599 2.733 3.226 2.215 βrt 1.742 1.223 1.560 1.161 1.712

[0385] As mentioned above, although the preferred embodiment of the present invention was described, the present invention is not limited to the embodiment, and various modifications and changes can be made within the scope of the gist of the present invention.

[0386] In addition, as other inventions to which the present invention is applied, the following invention can be considered. In order to solve the above-mentioned problem, the zoom lens involved in the present invention is composed of, from the object side, a positive first lens group and a rear group having a plurality of lens groups, wherein the rear group has a focus adjustment group having negative optical power that moves along the optical axis direction when focusing, and satisfies the following conditional expression:

[0387] 0.10 <Lnsr / Lnall<0.74…(9)

[0388] 1.20 <TLsrw / BFw<6.95…(10)

[0389] 7.1<|(1-βFt 2 )×βrt 2 |<20.0…(14)

[0390] in,

[0391] Lnsr: The total number of lenses on the image side of the aperture stop

[0392] Lnall: The total number of lenses in this zoom lens

[0393] TLsrw: The distance from the aperture stop to the image side of lens A at the wide angle end

[0394] BFw: The distance from the side closest to the image to the image plane at the wide-angle end of the zoom lens

[0395] βFt: lateral magnification of the focusing group at the telephoto end

[0396] βrt: The combined lateral magnification at the telephoto end of all lens groups closer to the image side than the focusing group.

[0397] (Summary)

[0398] Zoom lens according to the first aspect of the present invention

[0399] It can also be composed of a first lens group having positive refractive power and a rear group having multiple lens groups in order from the object side, the intervals between adjacent lens groups change when the magnification is changed, and the rear group closest to the image side has a lens A having negative refractive power, and the zoom lens satisfies the following conditional formula:

[0400] 1.83 <Nd2<2.50…(1)

[0401] 0.20 <TLt / ft<0.96…(2)

[0402] 1.16<βLt…(3)

[0403] in,

[0404] Nd2: The d-line refractive index of the lens closest to the object side in the rear group

[0405] TLt: The distance from the side closest to the object to the image plane at the telephoto end of the zoom lens

[0406] ft: focal length at the telephoto end of the zoom lens

[0407] βLt: lateral magnification of the lens group closest to the image side in the rear group at the telephoto end

[0408] Zoom lens according to the second aspect of the present invention

[0409] It can also be composed of a first lens group having positive refractive power and a rear group having multiple lens groups in order from the object side, the intervals between adjacent lens groups change when the magnification is changed, the rear group closest to the image side has a lens A having negative refractive power, the rear group has a focusing group that moves along the optical axis direction when focusing, and the zoom lens satisfies the following conditional formula:

[0410] 1.83 <Nd2<2.50…(1)

[0411] 0.20 <TLt / ft<0.96…(2)

[0412] 7.1<|(1-βFt2)×βrt2|<20.0…(14)

[0413] in,

[0414] Nd2: The d-line refractive index of the lens closest to the object side in the rear group

[0415] TLt: The distance from the side closest to the object to the image plane at the telephoto end of the zoom lens

[0416] βFt: lateral magnification of the focusing group at the telephoto end

[0417] βrt: The combined lateral magnification at the telephoto end of all lens groups closer to the image side than the focusing group.

[0418] Zoom lens according to the third aspect of the present invention

[0419] It can also be composed of a first lens group with positive focal length and a rear group with multiple lens groups in order from the object side, and the intervals between adjacent lens groups change when the magnification is changed, and the group including the lens group N with negative focal length closest to the object side in the rear group is referred to as the FR group, and the lens group from the lens group P with positive focal length closer to the image side and closest to the object side than the lens group N to the lens group closest to the image side is referred to as the RR group, the rear group is composed of the FR group and the RR group, and a lens A with negative focal length is provided on the image side of the rear group, and the zoom lens satisfies the following conditional formula:

[0420] 1.83 <Nd2<2.50…(1)

[0421] 0.20 <TLt / ft<0.96…(2)

[0422] 2.70<βCt…(4)

[0423] in,

[0424] Nd2: The d-line refractive index of the lens closest to the object side in the rear group

[0425] TLt: The distance from the side closest to the object to the image plane at the telephoto end of the zoom lens

[0426] ft: focal length at the telephoto end of the zoom lens

[0427] βCt: The combined lateral magnification at the telephoto end of the RR group from the negative lens group closest to the object side to the lens group closest to the image side

[0428] A zoom lens according to a fourth aspect of the present invention is, in the first aspect or the second aspect,

[0429] The group including the lens group N with negative optical focal length closest to the object side in the rear group is called the FR group, and the lens group P with positive optical focal length closer to the image side and closest to the object side than the lens group N to the lens group closest to the image side is called the RR group. The rear group can also be composed of the FR group and the RR group.

[0430] A zoom lens according to a fifth aspect of the present invention is, in any one of the third and fourth aspects,

[0431] The FR group as a whole has negative optical power, and the RR group as a whole has positive optical power.

[0432] A zoom lens according to a sixth aspect of the present invention is, in any one of the first to fifth aspects,

[0433] The following conditions can also be met:

[0434] 1.73 <NdA<2.50…(5)

[0435] in,

[0436] NdA: d-line refractive index of the lens A.

[0437] A zoom lens according to a seventh aspect of the present invention is, in any one of the first to sixth aspects,

[0438] The following conditions can also be met:

[0439] (CrAf+CrAr) / (CrAf-CrAr)<0.30…(6)

[0440] in,

[0441] CrAf: The radius of curvature of the object side of the lens A

[0442] CrAr: The radius of curvature of the image side surface of the lens A.

[0443] The zoom lens according to an eighth aspect of the present invention is, in the first to seventh aspects,

[0444] The following conditions can also be met:

[0445] 0.02 <BFw / fw<0.98…(7)

[0446] in,

[0447] BFw: The distance from the side closest to the image to the image plane at the wide-angle end of the zoom lens

[0448] fw: Focal length at the wide-angle end of the zoom lens.

[0449] A zoom lens according to a ninth aspect of the present invention is, in any one of the first to eighth aspects,

[0450] The lens group closest to the image side in the rear group may be composed of four or less lenses.

[0451] A zoom lens according to a tenth aspect of the present invention is, in any one of the first to ninth aspects,

[0452] The first lens group may include two or less lenses having positive refractive power.

[0453] The zoom lens according to the eleventh aspect of the present invention is, in the first aspect to the tenth aspect,

[0454] The following conditions can also be met:

[0455] 0.15 <f1 / ft<0.70…(8)

[0456] in,

[0457] f1: focal length of the first lens group.

[0458] In the zoom lens according to the twelfth aspect of the present invention, based on the first aspect to the eleventh aspect,

[0459] The rear group may also have an aperture stop that determines the effective diameter of the on-axis light beam, and the zoom lens satisfies the following conditional expression:

[0460] 0.10 <Lnsr / Lnall<0.74…(9)

[0461] in,

[0462] Lnsr: The total number of lenses on the image side of the aperture stop

[0463] Lnall: The total number of lenses in this zoom lens

[0464] In the zoom lens according to the 13th aspect of the present invention, based on the 1st aspect to the 12th aspect,

[0465] The rear group may also have an aperture stop that determines the effective diameter of the on-axis light beam, and the zoom lens satisfies the following conditional expression:

[0466] 1.20 <TLsrw / BFw<6.95…(10)

[0467] in,

[0468] TLsrw: The distance from the aperture stop to the image side of the lens A at the wide angle end

[0469] BFw: The distance from the side closest to the image to the image plane at the wide-angle end of the zoom lens.

[0470] A zoom lens according to a fourteenth aspect of the present invention is, in any one of the first to thirteenth aspects,

[0471] The following conditions can also be met:

[0472] 0.06 <BFt / TLt<0.32…(11)

[0473] in,

[0474] BFt: The distance from the side closest to the image to the image plane at the telephoto end of the zoom lens

[0475] A zoom lens according to a fifteenth aspect of the present invention is, in any one of the third to fourteenth aspects,

[0476] The group including the lens group N with negative power closest to the object side in the rear group is referred to as the FR group, and the lens group P with positive power closer to the image side and closest to the object side than the lens group N to the lens group closest to the image side is referred to as the RR group. The rear group may also be composed of the FR group and the RR group.

[0477] The zoom lens may also satisfy the following conditional formula:

[0478] 2.90 <f1 / |fFRt|<8.00…(12)

[0479] in,

[0480] f1: focal length of the first lens group

[0481] fFRt: focal length at the telephoto end of the FR group.

[0482] A zoom lens according to a sixteenth aspect of the present invention is, in any one of the second to fifteenth aspects,

[0483] The group including the lens group N with negative power closest to the object side in the rear group is referred to as the FR group, and the lens group P with positive power closer to the image side and closest to the object side than the lens group N to the lens group closest to the image side is referred to as the RR group. The rear group may also be composed of the FR group and the RR group.

[0484] The zoom lens may also satisfy the following conditional formula:

[0485] -2.50<βRRw<-0.50…(13)

[0486] in,

[0487] βRRw: lateral magnification of the RR group at the wide angle end

[0488] The imaging device according to the seventeenth aspect of the present invention may include a zoom lens according to any of the first to sixteenth aspects, and an imaging element which is arranged on the image side of the zoom lens and receives an optical image formed by the zoom lens and converts the image into an electrical signal.

[0489] The optical system and the imaging device described in the above-mentioned embodiments and examples are one mode of the zoom lens and the imaging device involved in the present invention, and correspond to the optical system involved in the above-mentioned first to sixteenth modes and the imaging device involved in the seventeenth mode. The zoom lens and the imaging device according to the above-mentioned modes have the same effects as those described in the above-mentioned embodiments and examples. The zoom lens and the imaging device involved in the present invention are not limited to the zoom lens and the imaging device described in the above-mentioned embodiments and examples, and can be appropriately changed within the scope of the zoom lens and the imaging device of the above-mentioned modes.

[0490] Industrial Applicability

[0491] According to the present invention, it is possible to provide a compact and high-performance zoom lens and an imaging device.

[0492] Description of Reference Numerals

[0493] GR group

[0494] FR FR group

[0495] RR RR group

[0496] G1 Lens Group 1

[0497] G2 2nd lens group

[0498] G3 third lens group

[0499] G4 4th lens group

[0500] G5 5th lens group

[0501] G6 lens group 6

[0502] G7 7th lens group

[0503] L1 1st lens

[0504] L2 2nd lens

[0505] L3 3rd lens

[0506] L4 4th lens

[0507] L5 5th lens

[0508] L6 6th lens

[0509] L7 7th lens

[0510] L8 8th lens

[0511] L9 9th lens

[0512] L10 10th lens

[0513] L11 11th lens

[0514] L12 12th lens

[0515] L13 13th lens

[0516] L14 14th lens

[0517] L15 15th lens

[0518] L16 16th lens

[0519] L17 17th lens

[0520] L18 18th lens

[0521] L19 19th lens

[0522] L20 20th lens

[0523] L21 21st lens

[0524] L22 22nd lens

[0525] L23 23rd lens

[0526] L24 24th lens

[0527] S aperture

[0528] F Focus Group

[0529] CG optical block

[0530] IMG Image

[0531] 1 Camera device

[0532] 2 Camera

[0533] 3 lenses

[0534] 21CCD sensor

[0535] 22 filters

Claims

1. A zoom lens, characterized in that: The zoom lens comprises, from the object side, a first lens group having positive refractive power; and The rear group, which has multiple lens groups, When the zoom is changed, the interval between adjacent lens groups changes, the rear group closest to the image side has a lens A with negative optical power, and the zoom lens satisfies the following conditional formula: 1.83 <Nd2<2.50…(1) 0.20 <TLt / ft<0.96…(2) 1.16<βLt…(3) in, Nd2: the d-line refractive index of the lens closest to the object side in the rear group, TLt: The distance from the side closest to the object to the image plane at the telephoto end of the zoom lens. ft: focal length of the zoom lens at the telephoto end, βLt: lateral magnification at the telephoto end of the lens group closest to the image side in the rear group.

2. A zoom lens, characterized in that: The zoom lens comprises, from the object side, a first lens group having positive refractive power; and The rear group, which has multiple lens groups, The intervals between adjacent lens groups change when the zoom is changed, the rear group closest to the image side has a lens A with negative optical power, the rear group has a focus group that moves along the optical axis when focusing, and the zoom lens satisfies the following conditional formula: 1.83 <Nd2<2.50…(1) 0.20 <TLt / ft<0.96…(2) 7.1<|(1-βFt 2 )×βrt 2 |<20.0…(14) in, Nd2: the d-line refractive index of the lens closest to the object side in the rear group, TLt: The distance from the side closest to the object to the image plane at the telephoto end of the zoom lens. ft: focal length of the zoom lens at the telephoto end, βFt: lateral magnification of the focusing group at the telephoto end, βrt: The combined lateral magnification at the telephoto end of all lens groups closer to the image side than the focusing group.

3. A zoom lens, characterized in that: The zoom lens comprises, from the object side, a first lens group having positive refractive power; and The rear group, which has multiple lens groups, When the zoom is changed, the interval between adjacent lens groups changes, and the group including the lens group N with negative focal length closest to the object side in the rear group is referred to as the FR group, and the lens group from the lens group P with positive focal length closer to the image side and closest to the object side than the lens group N to the lens group closest to the image side is referred to as the RR group, the rear group is composed of the FR group and the RR group, and the rear group has a lens A with negative focal length closest to the image side, and the zoom lens satisfies the following conditional formula: 1.83 <Nd2<2.50…(1) 0.20 <TLt / ft<0.96…(2) 2.70<βCt…(4) in, Nd2: the d-line refractive index of the lens closest to the object side in the rear group, TLt: The distance from the side closest to the object to the image plane at the telephoto end of the zoom lens. ft: focal length of the zoom lens at the telephoto end, βCt: The combined lateral magnification at the telephoto end from the negative lens group closest to the object side to the lens group closest to the image side in the RR group.

4. The zoom lens according to claim 1, wherein: The group including the lens group N having negative refractive power closest to the object side in the rear group is referred to as the FR group. The lens group P having positive refractive power which is closer to the image side than the lens group N and closest to the object side to the lens group closest to the image side is referred to as the RR group. The latter group is composed of the FR group and the RR group.

5. The zoom lens according to claim 2, wherein: The group including the lens group N having negative refractive power closest to the object side in the rear group is referred to as the FR group. The lens group P having positive refractive power which is closer to the image side than the lens group N and closest to the object side to the lens group closest to the image side is referred to as the RR group. The latter group is composed of the FR group and the RR group.

6. The zoom lens according to any one of claims 3 to 5, characterized in that: The FR group as a whole has negative optical power, and the RR group as a whole has positive optical power.

7. The zoom lens according to any one of claims 1 to 3, wherein: The zoom lens satisfies the following conditional formula: 1.73 <NdA<2.50…(5) in, NdA: d-line refractive index of the lens A.

8. The zoom lens according to any one of claims 1 to 3, wherein: The zoom lens satisfies the following conditional formula: (CrAf+CrAr) / (CrAf-CrAr)<0.30…(6) in, CrAf: the radius of curvature of the object side of the lens A, CrAr: The radius of curvature of the image side surface of the lens A.

9. The zoom lens according to any one of claims 1 to 3, wherein: The zoom lens satisfies the following conditional formula: 0.02 <BFw / fw<0.98…(7) in, BFw: The distance from the side closest to the image to the image plane at the wide-angle end of the zoom lens. fw: Focal length at the wide-angle end of the zoom lens.

10. The zoom lens according to any one of claims 1 to 3, wherein: The lens group closest to the image side in the rear group is composed of four or less lenses.

11. The zoom lens according to any one of claims 1 to 3, wherein: The first lens group includes two or less lenses having positive refractive power.

12. The zoom lens according to any one of claims 1 to 3, wherein: The zoom lens satisfies the following conditional formula: 0.15 <f1 / ft<0.70…(8) in, f1: focal length of the first lens group.

13. The zoom lens according to any one of claims 1 to 3, wherein: The rear group has an aperture stop that determines the effective diameter of the on-axis light beam, and the zoom lens satisfies the following conditional formula: 0.10 <Lnsr / Lnall<0.74…(9) in, Lnsr: The total number of lenses on the image side of the aperture stop, Lnall: The total number of lenses in this zoom lens.

14. The zoom lens according to any one of claims 1 to 3, wherein: The rear group has an aperture stop that determines the effective diameter of the on-axis light beam, and the zoom lens satisfies the following conditional formula: 1.20 <TLsrw / BFw<6.95…(10) in, TLsrw: the distance from the aperture stop to the image side of the lens A at the wide angle end, BFw: The distance from the side closest to the image to the image plane at the wide-angle end of the zoom lens.

15. The zoom lens according to any one of claims 1 to 3, wherein: The zoom lens satisfies the following conditional formula: 0.06 <BFt / TLt<0.32…(11) in, BFt: The distance from the side closest to the image to the image plane at the telephoto end of the zoom lens.

16. The zoom lens according to any one of claims 3 to 5, wherein: The zoom lens satisfies the following conditional formula: 2.90 <f1 / |fFRt|<8.00…(12) in, f1: focal length of the first lens group, fFRt: focal length at the telephoto end of the FR group.

17. The zoom lens according to any one of claims 3 to 5, wherein: The zoom lens satisfies the following conditional formula: -2.50<βRRw<-0.50…(13) in, βRRw: lateral magnification of the RR group at the wide angle end.

18. A camera device, characterized in that: have: The zoom lens according to any one of claims 1 to 3; and The imaging element receives the optical image formed by the zoom lens and converts the optical image into an electrical image signal.

Images