Zoom lens and imaging device

Abstract

To provide a compact and high-performance zoom lens and imaging device.SOLUTION: There is provided a zoom lens which comprises a first lens group having positive refractive power arranged in order from an object side, and a rear group comprising multiple lens groups, in which an interval between adjacent lens groups varies during zooming, and which has a lens A having negative refractive power on the most image side in the rear group, and satisfies the following conditional expressions: (1) 1.83<Nd2<2.50, (2) 0.20<TLt / ft<0.96, and (3) 1.16<βLt, where Nd2 is the refractive index on the d-line of the lens on the most object side in the rear group; TLt is the distance from the most object side surface to the image surface at the telephoto end of the zoom lens; ft is the focal length at the telephoto end of the zoom lens; and βLt is the lateral magnification at the telephoto end of the lens group on the most image side in the rear group.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Conventionally, imaging devices using solid-state imaging devices such as digital still cameras and digital video cameras have become widespread. With the increase in the number of pixels of the solid-state imaging devices used in these imaging devices, the optical system is required to maintain high resolution performance while maintaining small size and light weight.

[0003] To satisfy these requirements, for example, a small zoom lens having a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, a fourth lens group having a positive refractive power, and a fifth lens group, and suppressing various aberrations has been proposed (see "Patent Document 1").

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] For miniaturization of a zoom lens, it is effective to adopt a telephoto-type power arrangement having a positive refractive power on the object side and a negative refractive power on the image side. However, if the power arrangement is strengthened, it becomes difficult to correct various aberrations well with a small number of lens elements. Therefore, in order to achieve both miniaturization and high performance of the zoom lens, it is necessary to optimize the refractive power and lens configuration of each lens group.

[0006] An object of the present invention is to provide a small and high-performance zoom lens and an imaging device.

Means for Solving the Problem

[0007] In order to solve the above problems, the zoom lens according to the present invention is composed of a first lens group having a positive refractive power in order from the object side and a rear group having a plurality of lens groups. The distance between adjacent lens groups changes during zooming, and it has a lens A having a negative refractive power on the most image side of the rear group, and is characterized by satisfying the following conditional expressions. 1.83 < Nd2 < 2.50 ···(1) 0.20 < TLt / ft < 0.96 ···(2) 1.16 < βLt ···(3) However, Nd2: Refractive index of the lens on the most object side of the rear group at the d line TLt: Distance from the most object side surface to the image surface at the telephoto end of the zoom lens ft: Focal length at the telephoto end of the zoom lens βLt: Lateral magnification at the telephoto end of the lens group on the most image side of the rear group

[0008] Also, in order to solve the above problems, the zoom lens according to the present invention is composed of a first lens group having a positive refractive power in order from the object side and a rear group having a plurality of lens groups. The distance between adjacent lens groups changes during zooming, and it has a lens A having a negative refractive power on the most image side of the rear group, and has a focus group that moves in the optical axis direction during focusing in the rear group, and satisfies the following conditional expressions. 1.83 < Nd2 < 2.50 ···(1) 0.20 < TLt / ft < 0.96 ···(2) 7.1 < |(1 - βFt 2 )×βrt 2 | < 20.0 ···(14) However, Nd2: Refractive index of the lens on the most object side of the rear group at the d line TLt: Distance from the most object side surface to the image surface at the telephoto end of the zoom lens βFt: Lateral magnification at the telephoto end of the focus group βrt: The composite lateral magnification at the telephoto end of all lens groups on the image side from the focus group

[0009] Also, in order to solve the above problems, the zoom lens according to the present invention is composed of a first lens group having a positive refractive power in order from the object side and a rear group having a plurality of lens groups. The distance between adjacent lens groups changes during zooming. A group including a lens group N having the most negative refractive power on the object side in the rear group is defined as an FR group, and a group from a lens group P having the most positive refractive power on the image side and the most object side from the lens group N to the most image-side lens group is defined as an RR group. The rear group is composed of the FR group and the RR group, and has a lens A having a negative refractive power on the most image side of the rear group, and satisfies the following conditional expressions. 1.83 < Nd2 < 2.70 ···(1) 0.20 < TLt / ft < 0.96 ···(2) 2.70 < βCt ···(4) However, Nd2: The refractive index of the lens on the most object side of the rear group at the d line TLt: The distance from the most object side surface to the image surface at the telephoto end of the zoom lens ft: The focal length at the telephoto end of the zoom lens βCt: The composite lateral magnification at the telephoto end of the most image-side lens group from the most object-side negative lens group in the RR group

[0010] Also, in order to solve the above problems, the imaging device according to the present invention is characterized by including the above-described optical system and an imaging element that receives the optical image formed by the optical system and converts it into an electrical image signal.

Effect of the Invention

[0011] According to the present invention, a small and high-performance zoom lens and an imaging device can be provided.

Brief Description of the Drawings

[0012]

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Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the zoom lens and the imaging device according to the present invention will be described.

[0014] 1. Zoom lens 1-1. Optical configuration of the zoom lens First, the optical configuration of the zoom lens according to the present invention will be described. The zoom lens of the present embodiment is composed of a first lens group having a positive refractive power and a rear group having a plurality of lens groups. In this zoom lens, zooming is performed from the wide-angle end to the telephoto end by changing the distance between the lens groups. A "lens group" has one or more lenses. A "lens group" is a set of one lens or two or more lenses in which the distance between adjacent lens groups changes during zooming between the wide-angle end and the telephoto end. When a lens group has a plurality of lenses, the plurality of lenses maintain a relative positional relationship during zooming between the wide-angle end and the telephoto end. The lens group may be configured to be movable on the optical axis or may be fixed.

[0015] In this zoom lens, the lens group with the positive refractive power is located on the object side most. By arranging the lens group having a condensing action on the object side most, it becomes easy to adopt a telephoto-type power arrangement, so it becomes easy to reduce the overall optical length at the telephoto end. Further, since it has a condensing action on the object side most, it becomes easy to reduce the diameter of the rear group arranged on the image side thereof.

[0016] In this zoom lens, it has a lens A having a negative refractive power on the image side most of the rear group. By having a negative refractive power on the image side most, it becomes easy to adopt a telephoto-type power arrangement, so it becomes easy to reduce the overall optical length at the telephoto end. Further, since it has a diverging action on the image side most, it becomes easy to reduce the diameter of the lens on the image side most. Lens A is a single lens and may be either a spherical lens or an aspherical lens. Further, the aspherical lens shall include what is called a composite aspherical lens with an aspherical film attached to the surface.

[0017] Hereinafter, the optical configuration of the zoom lens will be described in more detail.

[0018] (1) First group lens group The first lens group is a lens group having a positive refractive power and being arranged on the object side most among the plurality of lens groups constituting the zoom lens. However, an optical element having no refractive power or an extremely small refractive power may be arranged on the object side of the first lens group. Examples of such an optical element include a prism that reflects and bends the optical axis of a lens, a protective filter for protecting the lens from dirt and scratches, an ND filter used to reduce the incident light amount, and various filters such as a PL filter for adjusting colors.

[0019] As long as the first lens group has a positive refractive power, its specific lens configuration is not particularly limited. Since the first lens group has a positive refractive power as a whole, the first lens group may have at least one lens having a positive refractive power. If the first lens group is configured using a plurality of lenses having a positive refractive power, it is preferable because it facilitates correction of chromatic aberration and spherical aberration at the telephoto end.

[0020] The number of lenses constituting the first lens group is not particularly limited. However, in order to achieve high optical performance while reducing the size and weight and cost of the zoom lens, it is more preferable that the lenses having a positive refractive power in the first lens group be configured with 2 or less lenses.

[0021] (2) Rear group The rear group is a general term for a plurality of lens groups arranged on the image side of the first lens group having a positive refractive power. As long as it has a plurality of lens groups and the lens on the most image side has a negative refractive power, the configuration of the lens groups and the configuration of the lenses are not particularly limited.

[0022] A combined group composed of one or more lens groups including a lens group N having the most negative refractive power on the object side of the rear group is defined as an FR group, and a combined group composed of one or more lens groups from a lens group P having the most positive refractive power on the image side and closer to the object side than the FR group to the most image-side lens group is defined as an RR group. In this case, it is preferable that the rear group is composed of two combined groups, namely the FR group and the RR group. As a result, a telephoto arrangement is formed between the first lens group and the lens group N having a negative refractive power, and furthermore, a telephoto arrangement is formed between the lens group P having a positive refractive power and the lens A having the most negative refractive power on the image side of the rear group. As a result, miniaturization in the overall length direction and the radial direction at the telephoto end becomes easy.

[0023] It is preferable that 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 lens group N having a negative refractive power included in the FR group has a large varifocal effect, a large varifocal effect will be achieved 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 having a positive refractive power are large. Therefore, it is preferable to widen the air gap between the FR group and the RR group at the wide-angle end for high magnification.

[0024] The most image-side lens group of the rear group preferably has a negative refractive power. By having a negative refractive power on the most image side, it becomes easier to adopt a telephoto power arrangement, making it easy to miniaturize the overall optical length at the telephoto end. Also, since it has a diverging effect on the most image side, it becomes easy to miniaturize the diameter of the most image-side lens group. In addition, it is preferable in terms of cost reduction that the most image-side lens group of the rear group is composed of 4 or fewer lens elements.

[0025] The number of lens groups constituting the rear group is not particularly limited, but it is preferable that the number of lens groups constituting the rear group is larger because aberration correction can be better performed over the entire zoom range. From this perspective, 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, field curvature can be well corrected at the intermediate focal length, so a zoom lens with higher optical performance can be obtained over the entire zoom range, which is preferable. Also, 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, it is even more preferable that the RR group is composed of a lens group having one or more positive refractive powers and a lens group having two or more negative refractive powers.

[0026] (3) FR group The FR group is disposed between the first lens group and the RR group, and the refractive power of the entire FR group may be positive or negative. When the entire FR group has a positive refractive power, it has a condensing action, so it is easy to increase the aperture. When the entire FR group has a negative refractive power, it has a telephoto type configuration with the first lens group and the FR group, and it is more preferable in that it is easy to reduce the overall optical length.

[0027] The configuration within the FR group is not limited as long as it includes the lens group N having the most negative refractive power on the object side of the rear group. When there is a lens group having a positive refractive power on the object side of the lens group N within the FR group, it is effective for correcting spherical aberration and is preferable in terms of improving performance. Also, when there is a lens group having a negative refractive power on the image side of the lens group N within the FR group, it is effective for correcting field curvature and is preferable in terms of improving performance.

[0028] Also, it is preferable for the FR group to have at least one lens with positive refractive power in terms of correcting chromatic aberration. At this time, arranging a lens with negative refractive power on the image side of the lens with positive refractive power is preferable because chromatic aberration can be corrected better at the telephoto end. Also, it is preferable for the lens group N with negative refractive power to have at least one lens with positive refractive power in terms of correcting chromatic aberration. It is more preferable that the Abbe number of the lens with positive refractive power included in the lens group N at the d-line is less than 45 because chromatic aberration can be corrected better. Further, in order to perform chromatic aberration correction even better, it is even more preferable that the Abbe number of at least one lens with positive refractive power included in the lens group N at the d-line is less than 40, and it is even more preferable that the Abbe number of at least one lens with positive refractive power included in the lens group N at the d-line is less than 35.

[0029] Also, 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, it is preferable in terms of cost reduction because the number of mechanical members holding the lens group can be reduced. When the number of lens groups constituting the FR group is larger, it is preferable in terms of high performance because aberration correction can be performed well throughout the zoom range.

[0030] (4) RR group The RR group is arranged on the image side of the FR group and is the general term for the combined group composed of the lens group P with the most positive refractive power on the object side and the most image-side lens group on the image side of the FR group. The refractive power of the entire RR group may be positive or negative. When the entire RR group has negative refractive power, it is preferable in terms of easily reducing the overall optical length as it forms a telephoto type configuration with the first lens group. When the entire RR group has positive refractive power, it has a condensing effect and can cancel out the diverging effect of the lens group N, so it is more preferable in terms of easily achieving high performance.

[0031] The configuration within the RR group is not limited as long as it includes, on the object side of the image side of the FR group, the lens group P having the most positive refractive power on the most object side. It is preferable that the lens group on the most image side of the RR group has a negative refractive power. By having a negative refractive power on the most image side, it becomes easier to adopt a telephoto-type power arrangement, and thus it becomes easier to reduce the overall optical length at the telephoto end. Also, since it has a diverging effect on the most image side, it becomes easier to reduce the diameter of the lens group on the most image side. Further, it is more preferable that there are two or more lens groups having a negative refractive power on the image side of the lens group P. In this case, it is easier to adopt a telephoto-type power arrangement and correct the field curvature, so it is more preferable in terms of achieving both miniaturization and high performance.

[0032] Also, it is preferable that the RR group has at least one lens having a negative refractive power from the viewpoint of correcting field curvature. It is more preferable that the refractive index of at least one lens having a negative refractive power included in the RR group at the d-line is greater than 1.86 because the field curvature can be better corrected. Further, in order to correct the field curvature even better, it is even more preferable that the refractive index of at least one lens having a negative refractive power included in the RR group at the d-line is greater than 1.88, and it is even more preferable that the refractive index of at least one lens having a negative refractive power included in the RR group at the d-line is greater than 1.90.

[0033] The number of lens groups constituting the RR group is not particularly limited, but it is preferable that the number of lens groups constituting the RR group is larger because aberration correction can be better performed over the entire zoom range. From this viewpoint, the number of lens groups constituting the RR group is preferably 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 it is preferable to obtain a zoom lens with higher optical performance over the entire zoom range.

[0034] (5) Focus group In this zoom lens, the presence or absence of a focus group is not particularly limited. When a focus group is provided, at least one of the lenses constituting the zoom lens is used as the focus group, and when focusing, the focus group can be moved in the optical axis direction to focus on the subject. The position and refractive power of the lens used as the focus group in the zoom lens are not particularly limited.

[0035] When a focus group is provided in the zoom lens, 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 a plurality. However, in order to suppress aberration variation that occurs when focusing on a nearby subject, the focus group is preferably composed of a plurality of lenses.

[0036] Also, in order to reduce the size and weight of the focus group, it is preferable to configure the focus group from a single lens unit. Here, the single lens unit refers to a lens unit such as a single lens or a cemented lens in which a plurality of single lenses are integrated without an air gap. That is, the single lens unit means that even if it has a plurality of optical surfaces, only its outermost object side surface and outermost image side surface are in contact with air, and the other surfaces are not in contact with air. Also, in this specification, the single lens may be either a spherical lens or an aspherical lens. Also, the aspherical lens includes a so-called composite aspherical lens in which an aspherical film is attached to the surface. In particular, from the viewpoint of suppressing aberration variation that occurs when focusing on the nearby subject and reducing the size and weight of the focus group, the focus group is more preferably composed of a cemented lens in which a plurality of single lenses are integrated without an air gap.

[0037] When the focus group is composed of the above single lens unit, the focus group does not include an air gap. Therefore, compared with the configuration in which a plurality of single lenses are arranged with an air gap therebetween, the focus group can be miniaturized and lightened. As a result, the mechanical member (hereinafter referred to as "focus drive mechanism") for moving the focus group in the optical axis direction during focusing can be miniaturized and lightened, and the entire zoom lens unit can be miniaturized and lightened. Note that the zoom lens unit includes, in addition to the zoom lens, a drive mechanism for relatively moving each lens group during zooming, the above focus drive mechanism, and a lens barrel for housing these.

[0038] When providing a focus group in the zoom lens, the arrangement of the focus group is not particularly limited, but it is preferable to use, as the focus group, any one of the lens groups constituting the rear group or a part thereof. Since the first lens group is composed of lenses with a relatively large diameter, miniaturization and weight reduction of the focus group are facilitated by arranging the focus group in the lens group of the rear group or a part thereof.

[0039] In particular, it is preferable to use, as the focus group, any one of the lens groups constituting the RR group or a part thereof. By adopting the above power arrangement, the diameter of the incident light beam with respect to the RR group can be made smaller than the diameter of the incident light beam with respect to the first lens group and the FR group. Therefore, by using, as the focus group, any one of the lens groups constituting the RR group or a part thereof, miniaturization and weight reduction of the focus group can be achieved as compared with the case where the focus group is arranged in the first lens group or the FR group. Further, it is more preferable to use, as the focus group, any one of the lens groups on the image side of the lens group P having a positive refractive power included in the RR group or a part thereof. The lens group P having a condensing action can further reduce the diameter of the incident light beam. Therefore, miniaturization and weight reduction of the focus group are more easily achieved.

[0040] The refractive power of the focus group may be positive or negative. When the refractive power of the focus group is positive, it is preferable that the lens group on the object side has a negative refractive power. When the refractive power of the focus group is negative, it is preferable that the lens group on the object side has a positive refractive power. Thereby, it becomes easy to increase the lateral magnification of the focus group and to increase the focus sensitivity of the focus group. As a result, it becomes possible to focus with a small movement amount, which is preferable in terms of miniaturization.

[0041] The lens configuration of the focus group is not limited, but it is preferable in terms of chromatic aberration correction to have a lens with a positive refractive power. It is more preferable that the Abbe number at the d-line of the lens having a positive refractive power included in the focus group is less than 35, because chromatic aberration correction can be better corrected. Further, in order to perform chromatic aberration correction even better, it is more preferable that the Abbe number at the d-line of at least one lens having a positive refractive power included in the focus group is less than 32, and it is even more preferable that the Abbe number at the d-line of at least one lens having a positive refractive power included in the focus group is less than 29.

[0042] Note that the focus group included in the zoom lens is not limited to one, and a plurality of lens groups or a part of a plurality of lens groups may be used as the focus group. That is, focusing may be performed by a floating method. By adopting the floating method, it is possible to improve spherical aberration and image plane property at closer focusing, so that it is possible to realize a zoom lens with higher optical performance, which is preferable.

[0043] (6) Anti-vibration group In the zoom lens, the presence or absence of the anti-vibration group is not particularly limited. In order to correct image blur caused by vibration being transmitted to the imaging device during shooting, it can be performed by electrically correcting the image or moving the imaging element. When the zoom lens is not provided with an anti-vibration group, image blur can be corrected by these methods.

[0044] When an anti-vibration group is provided in the zoom lens, image shift may be achieved by decentering at least one lens among the lenses constituting the zoom lens, and the method is not particularly limited.

[0045] For example, among the lenses constituting the zoom lens, when at least one lens is used as the anti-vibration group and the anti-vibration group is moved in a direction substantially orthogonal to the optical axis to cause image shift, the entire zoom lens unit including the lens barrel can be downsized, which is preferable for downsizing.

[0046] When an anti-vibration group is provided in the zoom lens, the arrangement of the anti-vibration group is not particularly limited, but it is more preferable to provide the anti-vibration group within the rear group. By adopting the above power arrangement for the zoom lens, the diameter of the incident light beam with respect to the rear group can be made smaller than the diameter of the incident light beam with respect to the first lens group. Therefore, by arranging the anti-vibration group in the rear group, miniaturization and weight reduction of the anti-vibration group can be achieved as compared with the case where the anti-vibration group is arranged in the first lens group.

[0047] When an anti-vibration group is provided in the zoom lens, the number of lenses constituting the anti-vibration group is not particularly limited. If the anti-vibration group is composed of a plurality of lenses, it is preferable because aberration variation during anti-vibration can be suppressed. At this time, the anti-vibration group preferably has at least one lens with negative refractive power and at least one lens with positive refractive power respectively. When the anti-vibration group has at least one lens with negative refractive power and at least one lens with positive refractive power respectively, the occurrence of chromatic aberration during anti-vibration can be suppressed, and a zoom lens with higher optical performance can be realized.

[0048] (6) Aperture stop In the zoom lens, the arrangement of the aperture stop is not particularly limited. However, the aperture stop referred to here is the aperture stop that defines the light beam diameter of the zoom lens, that is, the aperture stop that defines the Fno of the zoom lens.

[0049] In this zoom lens, arranging the aperture stop in the rear group is preferable in terms of reducing the aperture diameter and miniaturizing the aperture unit. Arranging the aperture stop in the rear group means that the aperture stop is arranged on the object side or the image side of each lens group constituting the rear group, or within each lens group constituting the rear group. In this zoom lens, since the first lens group having the converging action on the object side is arranged, the incident light beam on the rear group becomes smaller. Therefore, the aperture diameter of the aperture stop can be made smaller, which is preferable in terms of miniaturization. As described above, in this zoom lens, since the zooming action by the lens group N is relatively large, the variation in the diameter of the incident light beam on the RR group is small. Therefore, the aperture diameter of the aperture stop can be made smaller, and in order to suppress the variation in the aperture diameter, it is more preferable in terms of miniaturization to arrange the aperture stop on the object side of the RR group or within the lens group arranged most on the object side among the lens groups constituting the RR group.

[0050] 1-2. Operation (1) Operation during zooming In this zoom lens, zooming from the wide-angle end to the telephoto end is performed by changing the interval on the optical axis between adjacent lens groups. As long as the interval on the optical axis between adjacent lens groups changes, the increase or decrease in the interval between each lens group is not particularly limited. For example, when zooming from the wide-angle end to the telephoto end, if the first lens group and the second lens group are relatively moved so that the interval on the optical axis between the first lens group and the rear group increases, it is preferable to obtain a small-sized and high-zoom-ratio zoom lens. At this time, it is more preferable to obtain a small-sized and high-zoom-ratio zoom lens by relatively moving the most image-side lens group of the FR group and the most object-side lens group of the RR group so that the interval on the optical axis between the FR group and the RR group in the rear group decreases. Note that relatively moving the lens groups includes not only moving two adjacent lens groups through an air interval respectively, but also moving either one of the two adjacent lens groups through an air interval.

[0051] When zooming, as long as the distance on the optical axis between each lens group changes, the increase or decrease in the distance between each lens group is not particularly limited. Also, when zooming, each lens group may move relatively so that the distance on the optical axis between each lens group changes. All lens groups may move along the optical axis, or one or more of the lens groups may be fixed with respect to the image plane and the other lens groups may move along the optical axis.

[0052] (2) Operation at focusing In the case where a focus group is provided in the zoom lens, as described above, the position, refractive power, etc. of the focus group are not particularly limited. Also, when focusing from infinity to a nearby object, the direction of movement of the focus group, etc. is not particularly limited. It is preferable to move the focus group from the object side to the image side when focusing from infinity to a nearby object. For example, when the lateral magnification of the focus group is βN and the combined lateral magnification of all the lens groups on the image side of the focus group is βR, the focus sensitivity of the focus group can be expressed as (1 - βN 2 ) × βR 2 When the lateral magnification of the focus group is greater than 1, it means that the focus group moves to the image side when focusing from an infinite object to a finite-distance object. Also, by having a lateral magnification greater than 1, it is possible to increase the focal length and shorten the overall length. For miniaturization of the overall optical length, it is preferable to arrange a lens group with a lateral magnification greater than 1 as the focus group.

[0053] 1 - 3. Conditional expression In the optical system, it is preferable to adopt the above-described configuration and satisfy the conditional expressions described below.

[0054] 1 - 3 - 1. Conditional expression (1) The zoom lens preferably satisfies the following conditional expression. 1.83 < Nd2 < 2.50 ···(1) However, Nd2: Refractive index of the most object-side lens of the rear group at the d-line

[0055] The above conditional expression (1) is an expression that defines the refractive index of the most object-side lens of the rear group of the zoom lens in the d-line. For the light rays incident from the first lens group having a converging action to the rear group, it is important from the viewpoints of performance and manufacturability to suppress the radius of curvature of the most object-side surface of the rear group within an appropriate range. Since the refractive power of the most object-side surface of the rear group is determined by the radius of curvature of the surface and the refractive index of the optical material, when the refractive index is defined within a certain range, it becomes easier to suppress the refractive power of the surface within an appropriate range. Here, when the conditional expression (1) is satisfied, a zoom lens with high off-axis performance can be achieved while suppressing costs. Further, in the case of a so-called composite aspherical lens in which an aspherical film is attached to the object-side surface of the most object-side lens of the rear group, Nd2 is the refractive index of the base lens, not the refractive index of the aspherical film.

[0056] On the other hand, when the value of the above conditional expression (1) exceeds the upper limit, the cost of the material becomes too high, which is not preferable in terms of cost reduction. When the value of the above conditional expression (1) is below the lower limit, it becomes difficult to correct field curvature, and it becomes difficult to suppress the radius of curvature within an appropriate range, resulting in deteriorated manufacturability. Therefore, it is not preferable from the viewpoints of off-axis performance and manufacturability.

[0057] In order to obtain the above effects, the upper limit values of the above conditional expression (1) are preferably 2.30, 2.15, and 2.12 in this order. Further, the lower limit values of the above conditional expression (1) are preferably 1.84 and 1.85 in this order.

[0058] 1-3-2. Conditional Expression (2) The zoom lens preferably satisfies the following conditional expression. 20 < TLt / ft < 0.96 ···(2) However, TLt: The distance from the most object-side surface to the image plane at the telephoto end of the zoom lens ft: The focal length at the telephoto end of the zoom lens

[0059] The above conditional expression (2) is an expression that defines the ratio of the overall optical length at the telephoto end of the zoom lens to the focal length at the telephoto end. To make the overall optical length smaller than the focal length, aberration correction becomes difficult and the error sensitivity deteriorates. On the other hand, if the overall optical length is made too large relative to the focal length, the weight including the mechanical structure increases, so there is an appropriate range for the ratio of the overall length to the focal length. Here, when the conditional expression (2) is satisfied, both miniaturization and high performance of the optical system can be achieved.

[0060] On the contrary, when the numerical value of the above conditional expression (2) exceeds the upper limit, the overall optical length becomes too large relative to the focal length, and the weight including the mechanical structure increases, which is not preferable in terms of weight reduction. When the numerical value of the above conditional expression (2) is below the lower limit, the overall optical length becomes too small relative to the focal length, and many lens elements are required for aberration correction, which is not preferable in terms of cost. Furthermore, it causes deterioration in manufacturability and is not preferable in terms of high performance.

[0061] In order to obtain the above effects, 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 in that order. Also, the lower limit value of the above conditional expression (2) is preferably 0.25, 0.30, 0.35 in that order.

[0062] 1-3-3. Conditional Expression (3) The zoom lens preferably satisfies the following conditional expression. 1.16 < βLt ···(3) However, βLt: Lateral magnification at the telephoto end of the most image-side lens group of the rear group

[0063] The above conditional expression (3) is an expression that defines the lateral magnification at the telephoto end of the most image-side lens group of the rear group. Increasing the lateral magnification of the most image-side lens group makes it easier to adopt a telephoto type power arrangement, thus facilitating miniaturization of the overall optical length at the telephoto end. Also, since the most image-side lens group has a magnifying effect, it is effective in reducing the diameter of the most image-side lens. Therefore, when the conditional expression (3) is satisfied, miniaturization can be achieved.

[0064] When the numerical value of the above conditional expression (3) is below the lower limit, the telephoto type power arrangement becomes weak, leading to an increase in the overall optical length and the diameter of the lens, which is not preferable in terms of miniaturization. Also, if the lateral magnification of the most image-side lens group is increased too much, the error sensitivity increases, so it is preferable to define an upper limit value from the perspective of manufacturability. It is more preferable that the upper limit value of the above conditional expression (3) is less than 5.0.

[0065] In order to obtain the above effects, the lower limit value of the above conditional expression (3) is preferably 1.18, 1.19, 1.20, 1.21 in that order. Also, the upper limit value of the above conditional expression (3) is preferably 4.80, 4.50, 4.20, 3.90, 3.60 in that order.

[0066] 1-3-4. Conditional Expression (4) The zoom lens preferably satisfies the following conditional expression. 2.70 < βCt ···(4) However, βCt: The combined lateral magnification from the most object-side negative lens group to the telephoto end of the most image-side lens group among the RR groups

[0067] The above conditional expression (4) is an expression that defines the combined lateral magnification at the telephoto end of the most image-side lens group from the most object-side negative lens group among the RR groups. Here, as described above, the zoom lens is composed of a first lens group, an FR group, and an RR group in order from the object side. By arranging an enlargement system on the image side of the zoom lens, a telephoto type power arrangement is achieved, and miniaturization is achieved. Therefore, it is important for miniaturization to set the lateral magnification on the image side within the RR group within an appropriate range. By satisfying the conditional expression (4), miniaturization is achieved.

[0068] When the numerical value of the above conditional expression (4) is below the lower limit, the telephoto type power arrangement becomes weak, leading to an increase in the overall optical length and the diameter of the lens, which is not preferable in terms of miniaturization. Also, if the lateral magnification of the most image-side lens group is made too large, the error sensitivity increases, so it is preferable to define an upper limit value from the perspective of manufacturability. It is more preferable that the above conditional expression (4) sets the upper limit value to less than 9.0.

[0069] In order to obtain the above effects, the lower limit values of the above conditional expression (4) are preferably 2.80, 2.85, 2.90, 2.95, 3.00, 3.05, 3.10, 3.12, 3.14 in order. Also, the upper limit values of the above conditional expression (4) are 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 in order.

[0070] 1-3-5. Conditional Expression (5) The zoom lens preferably satisfies the following conditional expression. 1.73 < NdA < 2.50 ···(5) However, NdA: Refractive index of the lens A at the d line

[0071] The above conditional expression (5) is an expression that defines the refractive index of the d-line of the lens A having a negative refractive power disposed on the most image side of the zoom lens. Since the zoom lens has a positive refractive power as a whole, in order to reduce the Petzval sum, it is necessary to increase the refractive index of the lens having a negative refractive power. However, optical materials with a high refractive index are costly. Therefore, in order to achieve both high performance and low cost, it is important to define the refractive index within an appropriate range. Here, when the conditional expression (5) is satisfied, a zoom lens with high off-axis performance can be achieved while suppressing costs. Also, in the case of a so-called compound aspherical lens in which an aspherical film is attached to the image side surface of the lens A having a negative refractive power disposed on the most image side, NdA is the refractive index of the base lens, not the refractive index of the aspherical film.

[0072] On the other hand, when the numerical value of the above conditional expression (5) exceeds the upper limit, the cost of the optical material becomes too high, which is not preferable in terms of cost reduction. When the numerical value of the above conditional expression (5) is below the lower limit, it becomes difficult to correct the field curvature, which is not preferable in terms of high performance.

[0073] In order to obtain the above effects, the upper limit values of the above conditional expression (5) are preferably 2.30, 2.15, 2.12, 2.06, 2.01, 2.00, 1.99, 1.97, 1.96, 1.95, 1.93 in order. Also, the lower limit values of the above conditional expression (5) are preferably 1.74, 1.75 in order.

[0074] 1-3-6. Conditional Expression (6) The zoom lens preferably satisfies the following conditional expression. (CrAf + CrAr) / (CrAf - CrAr) < 0.30 ···(6) However, CrAf: The radius of curvature of the object side surface of the lens A CrAr: The radius of curvature of the image side surface of the lens A

[0075] The above conditional expression (6) is an expression for defining the shape of the lens A having a negative refractive power disposed on the most image side of the zoom lens. By setting the shape of the lens A on the most image side to the shape defined by the above conditional expression (6), it becomes possible to perform good correction of coma, and a zoom lens with high off-axis performance can be realized. Further, in the case of a so-called compound aspherical lens in which an aspherical film is attached to the lens A having a negative refractive power disposed on the most image side, CrAf and CrAr are the curvature radii of the base lens, not the curvature radii of the aspherical film.

[0076] On the other hand, when the numerical value of the above conditional expression (6) exceeds the upper limit, the curvature radius of the image side surface becomes too small with respect to the curvature radius of the object side surface, so that it becomes difficult to correct coma aberration, which is not preferable in terms of high performance. Further, in the case of the shape of the lens A on the most image side, if the curvature radius on the object side becomes too small with respect to the curvature radius on the image side, the error sensitivity increases, so it is preferable to define a lower limit value from the viewpoint of manufacturability. It is more preferable that the lower limit value of the above conditional expression (6) is greater than -30.0.

[0077] In order to obtain the above effects, the upper limit values of the above conditional expression (6) are 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 order. Further, the lower limit values of the above conditional expression (6) are preferably -20.00, -10.00, -9.00, -7.90, -6.80 in order.

[0078] 1-3-7. Conditional Expression (7) The zoom lens preferably satisfies the following conditional expression. 0.02 < BFw / fw < 0.98 ···(7) However, BFw: The distance from the most image side surface to the image plane at the wide-angle end of the zoom lens fw: The focal length at the wide-angle end of the zoom lens

[0079] The above conditional expression (7) is an expression that defines the ratio between the value obtained by air-converting the distance on the optical axis from the most image-side surface to the image plane at the wide-angle end of the zoom lens and the focal length at the wide-angle end of the zoom lens. It is necessary to arrange an optical element such as a low-pass filter between the most image-side surface and the image plane at the wide-angle end. Therefore, it is important to optimize the back of the wide-angle end in order to arrange the optical element while achieving miniaturization. When the conditional expression (7) is satisfied, it becomes easy to realize a small-sized zoom lens because the back of the wide-angle end is within an optimal range.

[0080] On the other hand, when the numerical value of the above conditional expression (7) exceeds the upper limit, the overall optical length at the wide angle increases and the weight including the mechanism becomes heavy. Therefore, it is not preferable in terms of miniaturization and weight reduction. On the other hand, when the numerical value of the above conditional expression (7) is below the lower limit, it becomes difficult to arrange an optical element such as a low-pass filter, which is not preferable. Also, it leads to an increase in the diameter of the final lens, which is not preferable.

[0081] In order to obtain the above effects, the upper limit values of the above conditional expression (7) are preferably 0.93, 0.91, 0.84, 0.78, 0.75, 0.70, 0.68, 0.66, 0.64 in this order. Also, the lower limit values of the above conditional expression (7) are preferably 0.04, 0.06, 0.07, 0.10, 0.13, 0.16 in this order.

[0082] 1-3-8. Conditional Expression (8) The zoom lens preferably satisfies the following conditional expression. 0.15 < f1 / ft < 0.70 ···(8) However, f1: Focal length of the first lens group ft: Focal length at the telephoto end of the zoom lens

[0083] The above conditional expression (8) is an expression that defines the ratio of the focal length of the first lens group to the focal length of the optical system. By satisfying the conditional expression (8), it is possible to reduce fluctuations in spherical aberration and field curvature during zooming, achieving high performance. Also, when the conditional expression (8) is satisfied, it becomes easier to adopt a telephoto-type power arrangement, so the optical system can be miniaturized in the optical overall length direction.

[0084] On the other hand, when the numerical value of the above conditional expression (8) exceeds the upper limit, the refractive power of the first lens group becomes weak. As a result, the telephoto-type power arrangement becomes weak, making it difficult to miniaturize the zoom lens, which is not preferable. On the other hand, when the numerical value of the above conditional expression (8) is below the lower limit, the refractive power of the first lens group becomes too strong, making it difficult to reduce fluctuations in spherical aberration and field curvature during zooming, which is not preferable in terms of high performance.

[0085] In order to obtain the above effects, the upper limit value of the above conditional expression (8) is preferably 0.68, 0.66, 0.64, 0.63, 0.61, 0.60 in order. Also, 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 in order.

[0086] 1-3-9. Conditional Expression (9) The zoom lens preferably satisfies the following conditional expression. 0.10 < Lnsr / Lnall < 0.74 ···(9) However, Lnsr: The total number of lenses on the image side of the aperture stop Lnall: The total number of lenses of the zoom lens

[0087] The above conditional expression (9) is an expression that defines the ratio of the total number of lenses on the image side of the aperture stop to the total number of lenses of the zoom lens. As the number of lenses increases, aberration correction becomes easier. Also, for off-axis rays, when the chief ray passes below the optical axis on the object side of the aperture stop, it passes above the optical axis on the image side of the aperture stop. Therefore, if off-axis coma aberration and magnification chromatic aberration cancel each other out on the object side and the image side of the aperture stop, it becomes easier to improve the off-axis performance. From these facts, there is an appropriate range for the ratio of the number of lenses out of the total number of lenses on the image side of the aperture stop. By satisfying the conditional expression (9), the number of lenses falls within an optimal range, making it easy to achieve both high performance and low cost. The number of lenses represents the number of lenses, excluding those without power such as cover glass, IR cut filter, and prism. Also, for the number of lenses, a compound aspherical lens is counted as 1, and a cemented lens in which two lenses are cemented is counted as 2.

[0088] On the other hand, when the value of the above conditional expression (9) exceeds 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 ability on the object side of the aperture stop becomes insufficient, which is not preferable in terms of high performance. On the other hand, when the value of the above conditional expression (9) is 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 ability on the image side of the aperture stop becomes insufficient, which is not preferable in terms of high performance.

[0089] In order to obtain the above effects, the upper limit values of the above conditional expression (9) are preferably 0.71, 0.69, 0.66, 0.65, 0.64, 0.63, 0.62 in this order. Also, the lower limit values of the above conditional expression (9) are 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 in this order.

[0090] 1-3-10. Conditional Expression (10) It is preferable that the zoom lens satisfies the following conditional expression. 1.20 < TLsrw / BFw < 6.95 ···(10) However, TLsrw: Distance from the aperture stop at the wide-angle end to the image-side surface of lens A BFw: Distance from the most image-side surface to the image plane at the wide-angle end of the zoom lens

[0091] The above conditional expression (10) is an expression that defines the ratio of the distance from the aperture stop at the wide-angle end of the zoom lens to the image-side surface of lens A to the value obtained by air-converting the distance on the optical axis from the most image-side surface to the image plane at the wide-angle end of the zoom lens. The lens A having a negative refractive power is disposed on the most image side of the zoom lens. By disposing the lens A within an appropriate range between the aperture stop and the image plane, the off-axis aberration correction ability of the lens A is optimized. By satisfying the conditional expression (10), the distance from the aperture stop of the lens A and the distance from the lens A to the image plane are within an optimal range, and it becomes easy to achieve high performance of the zoom lens.

[0092] On the other hand, when the numerical value of the above conditional expression (10) exceeds the upper limit, that is, the lens A approaches the image plane side between the aperture stop and the image plane. In that case, the height of the off-axis light beam passing through the lens A becomes too high, and the aberration correction ability of the lens A becomes weak. Or the refractive power of the lens A becomes too strong, making it difficult to correct field curvature and coma aberration. Therefore, it is not preferable in terms of achieving high performance. When the numerical value of the above conditional expression (10) is below the lower limit, that is, the lens A moves away from the image plane side between the aperture stop and the image plane. In that case, the height of the off-axis light beam 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 aberration, and it is not preferable in terms of achieving high performance.

[0093] In order to obtain the above effects, the upper limit values of the above conditional expression (10) are preferably 6.50, 6.20, 5.90, 5.60, 5.40, 5.10, 4.90, 4.60, 4.35, 4.10, 4.00 in order. Also, the lower limit values of the above conditional expression (10) are preferably 1.30, 1.40, 1.50, 1.60, 1.70 in order.

[0094] 1-3-11. Conditional expression (11) It is preferable that the zoom lens satisfies the following conditional expression. 0.06 < BFt / TLt < 0.32 ···(11) However, BFt: Distance from the most image-side surface to the image plane at the telephoto end of the zoom lens TLt: Distance from the most object-side surface to the image plane at the telephoto end of the zoom lens

[0095] The above conditional expression (11) is an expression that defines the ratio of the value obtained by converting the distance on the optical axis from the most image-side surface to the image plane at the telephoto end of the zoom lens to the air equivalent value, and the distance from the most object-side surface to the image plane at the telephoto end of the zoom lens (the distance from the most image-side surface to the image plane is converted to the air equivalent value). To increase the back length with respect to the overall optical length at the telephoto end, it is necessary to increase the positive refractive power on the object side. If the positive refractive power on the object side is too strong, it becomes difficult to correct spherical aberration and field curvature. Also, if the back length is shortened at the telephoto end, it leads to an increase in the diameter of the lens on the image side. Therefore, it is important to set the back length and the overall length at the telephoto end to an appropriate ratio. By satisfying the conditional expression (11), the value of the back length with respect to the overall optical length at the telephoto end becomes appropriate, and it becomes easier to achieve both high performance and miniaturization.

[0096] On the other hand, when the numerical value of the above conditional expression (11) exceeds the upper limit, the length of the back with respect to the overall optical length becomes longer. As a result, the converging power on the object side of the zoom lens becomes stronger, and it becomes difficult to correct spherical aberration and field curvature. On the other hand, when the numerical value of the above conditional expression (11) is below the lower limit, the length of the back with respect to the overall optical length becomes shorter. As a result, as the lens on the image side approaches the image plane, it leads to an increase in the diameter of the lens on the image side, which is not preferable in terms of miniaturization.

[0097] In order to obtain the above effects, the upper limit values of the above conditional expression (11) are preferably 0.31, 0.30, 0.29, 0.28, 0.27, 0.26, 0.25, 0.24 in that order. Also, the lower limit values of the above conditional expression (11) are preferably 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16 in that order.

[0098] 1-3-12. Conditional expression (12) It is preferable that the zoom lens satisfies the following conditional expression. 2.90 < f1 / |fFRt| < 8.00 ···(12) However, f1: Focal length of the first lens group fFRt: Focal length at the telephoto end of the FR group

[0099] The above conditional expression (12) is an expression that defines the ratio of the focal length of the first lens group to the focal length at the telephoto end of the FR group. By satisfying the conditional expression (12), it is possible to reduce the variations in spherical aberration and field curvature during zooming, and high performance can be achieved. Also, when the conditional expression (12) is satisfied, it becomes easier to adopt a telephoto-type power arrangement, so the miniaturization of the optical system in the optical overall length direction can be achieved.

[0100] On the other hand, when the numerical value of the above conditional expression (12) exceeds the upper limit, the focal length of the first lens group becomes too large with respect to the focal length at the telephoto end of the FR group. Therefore, the telephoto-type power arrangement becomes weak, and miniaturization becomes difficult and is not preferable. On the other hand, when the numerical value of the above conditional expression (12) is below the lower limit, the focal length of the first lens group becomes too small with respect to the focal length at the telephoto end of the FR group. The refractive power of the first lens group becomes too strong, and it becomes difficult to reduce the variations in spherical aberration and field curvature during zooming, so it is not preferable in terms of high performance.

[0101] In order to obtain the above effects, the upper limit values of the above conditional expression (12) are preferably 7.70, 7.40, 7.20, 7.00, 6.90, 6.80, 6.70, 6.60, 6.50, 6.40 in order. Also, the lower limit values of the above conditional expression (12) are preferably 2.95, 3.00, 3.05, 3.10 in order.

[0102] 1-3-13. Conditional expression (13) It is preferable that the zoom lens satisfies the following conditional expression. -2.50 < βRRw < -0.50 ···(13) However, βRRw: Lateral magnification at the wide-angle end of the RR group

[0103] The above conditional expression (13) is an expression that defines the lateral magnification at the wide-angle end of the RR group. By satisfying the conditional expression (13), the lateral magnification at the wide-angle end of the RR group becomes optimal, and the back at the wide-angle end falls within an appropriate range. Thereby, miniaturization is achieved.

[0104] On the other hand, when the numerical value of the above conditional expression (13) exceeds the upper limit, that is, when the lateral magnification at the wide-angle end of the RR group becomes too large. As a result, the back at the wide-angle end becomes short, making it difficult to arrange optical elements such as a low-pass filter, which is not preferable. In addition, it leads to an increase in the diameter of the final lens, which is not preferable. When the numerical value of the above conditional expression (13) is below the lower limit, the back at the wide-angle end becomes long, so the overall optical length at the wide-angle becomes large and the weight including the mechanism becomes heavy. Therefore, it is not preferable in terms of miniaturization and weight reduction.

[0105] In order to obtain the above effects, the upper limit values of the above conditional expression (13) are preferably -0.55, -0.60, -0.65, -0.70, -0.75, -0.80, -0.85, -0.90, -0.95, -1.00 in order. Also, the lower limit values of the above conditional expression (13) are preferably -2.20, -2.00, -1.90, -1.80, -1.70, -1.60 in order.

[0106] 1-3-14. Conditional Expression (14) It is preferable that the zoom lens satisfies the following conditional expression. 7.1 < |(1-βFt 2 )×βrt 2 | < 20.0 ···(14) However, βFt: Lateral magnification at the telephoto end of the focus group βrt: The combined lateral magnification at the telephoto end of all lens groups on the image side from the focus group

[0107] The above conditional expression (14) is an expression that defines the focus sensitivity at the telephoto end of the focus group. The focus sensitivity of the focus group is a value indicating the ratio of how much the focus position moves on the image plane when the focus group moves by one unit. Here, the combined lateral magnification βrt at the telephoto end of all lens groups on the image side from the focus group is the combined lateral magnification at the telephoto end of the lens groups and lenses on the image side from the focus group. When there are no lens groups or lenses on the image side from the focus group, the value of βrt is 1. By satisfying the conditional expression (14), the focus sensitivity at the telephoto end of the focus group becomes optimal, it becomes easy to reduce the movement amount during focusing, and miniaturization is achieved. Also, since the stop accuracy during driving of the focus group does not become higher than necessary, a zoom lens with high imaging performance can be achieved even if the control of the focus group does not have high stop accuracy.

[0108] On the other hand, when the numerical value of the above conditional expression (14) exceeds the upper limit, that is, when the focus sensitivity at the telephoto end of the focus group becomes too large, a large deviation in the focus position due to the stop position error during driving of the focus group is caused, making it difficult to improve performance. When the numerical value of the above conditional expression (14) is below the lower limit, the focus sensitivity at the telephoto end of the focus group becomes too small. As a result, the movement amount during focusing from an infinite-distance object to a finite-distance object becomes large, making it difficult to miniaturize the overall optical length, which is not preferable.

[0109] In obtaining the above effects, the upper limit values of the above conditional expression (14) are preferably 19.0, 18.0, 17.0, 16.0 in order. Also, the lower limit values of the above conditional expression (14) are preferably 7.20, 7.30, 7.40, 7.50, 7.60, 7.80, 8.00 in order.

[0110] 2. Imaging device Next, the imaging device according to the present invention will be described. The imaging device according to the present invention is characterized by comprising the optical system according to the present invention and an imaging element that receives the optical image formed by the zoom lens and converts it into an electrical image signal.

[0111] Here, there is no particular limitation on the imaging element or the like, and solid-state imaging elements such as a CCD sensor (Charge Coupled Device) and a CMOS sensor (Complementary Metal Oxide Semiconductor) can also be used. The imaging device according to the present invention is suitable for imaging devices using these solid-state imaging elements such as digital cameras, video cameras, surveillance cameras, in-vehicle cameras, drone cameras, and medical cameras. Further, the imaging device may be a lens-fixed imaging device in which the lens is fixed to the housing, or of course, may be an interchangeable-lens imaging device such as a single-lens reflex camera or a mirrorless single-lens camera.

[0112] FIG. 21 is a diagram schematically showing an example of the configuration of the imaging device according to the present embodiment. As shown in FIG. 21, the imaging device 1 has a camera 2 and a lens 3 that is detachable from the camera 2. The imaging device 1 is one aspect of the imaging device. The camera 2 has a CCD sensor 21 as an imaging element and a cover glass 22. The CCD sensor 21 is disposed at a position in the camera 2 where the optical axis of the zoom lens in the lens 3 attached to the camera 2 is the central axis. The camera 2 may have an IR cut filter or the like instead of the cover glass 22.

[0113] Next, the present invention will be specifically described by showing examples. However, the present invention is not limited to the following examples. Also, in each lens cross-sectional view, the left side toward the drawing is the object side, and the right side is the image side.

Examples

[0114] FIG. 1 is a lens cross-sectional view at the wide-angle end showing the configuration of the zoom lens according to Embodiment 1 of the present invention. The zoom lens includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a negative refractive power, and a fifth lens group G5 having a negative refractive power. The rear group GR is composed of, in order from the object side, the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5. The second lens group G2 corresponds to the lens group N having the most negative refractive power on the object side among the rear group GR. The third lens group G3 corresponds to the lens group P having a positive refractive power on the image side and the most object side among 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 most object side of the RR group as a lens group having a positive refractive power, it is possible to suppress the spherical aberration variation during zooming. Here, the fourth lens group G4 corresponds to the lens group having the most negative refractive power on the object side among the RR group. Also, the fifth lens group G5 corresponds to the most image-side lens group.

[0115] In order from the object side, the first lens group G1 is composed of a cemented lens including a meniscus-shaped first lens L1 having a negative refractive power and a convex object-side surface, and a biconvex-shaped second lens L2 having a positive refractive power and convex object-side and image-side surfaces.

[0116] In order from the object side, the second lens group G2 is composed of a cemented lens including a biconcave-shaped third lens L3 having a negative refractive power and concave object-side and image-side surfaces, a biconcave-shaped fourth lens L4 having a negative refractive power and concave object-side and image-side surfaces, and a meniscus-shaped fifth lens L5 having a positive refractive power and a convex object-side surface. Here, the third lens L3 corresponds to the most object-side lens of the rear group.

[0117] In order from the object side, the third lens group G3 is composed of a double-convex sixth lens L6 having a positive refractive power with both the object-side surface and the image-side surface being convex, a double-convex seventh lens L7 having a positive refractive power with both the object-side surface and the image-side surface being convex, a cemented lens of an eighth lens L8 having a negative refractive power with both the object-side surface and the image-side surface being concave, a diaphragm S, a cemented lens of a meniscus-shaped ninth lens L9 having a negative refractive power with the object-side surface being convex on the object side and a double-convex tenth lens L10 having a positive refractive power with both the object-side surface and the image-side surface being convex, and an eleventh lens L11 having a negative refractive power with the object-side surface being concave on the object side. By making the most object-side surface of the third lens group convex on the object side, the correction of spherical aberration becomes good.

[0118] In order from the object side, the fourth lens group G4 is composed of a cemented lens of a double-convex twelfth lens L12 having a positive refractive power with both the object-side surface and the image-side surface being convex and a double-concave thirteenth lens L13 having a negative refractive power with both the object-side surface and the image-side surface being concave.

[0119] The fifth lens group G5 is composed of a meniscus-shaped fourteenth lens L14 having an aspherical layer on the object side and a negative refractive power with the object-side surface being concave on the object side. Here, the fourteenth lens L14 corresponds to the lens A having the most negative refractive power on the image side of the rear group.

[0120] 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 becomes easy to increase the focal length at the telephoto end, and the variation of spherical aberration during zooming can be suppressed. Also, 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 variation of field curvature during zooming can be suppressed.

[0121] 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 with respect 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 locus during zooming. Thereby, the mechanical mechanism can be simplified, which is effective for cost reduction and miniaturization. If the third lens group G3 and the fifth lens group G5 are mechanically integrated, the error amount will be subordinate during decentration, so the amount of aberration generated during decentration will be small, and high performance can be achieved.

[0122] Here, the fourth lens group G4 corresponds to a focus group that performs focusing from an infinite-distance object to a finite-distance object by moving toward the image side. Also, here, the second lens group G2 corresponds to an anti-shake group that corrects the image position by moving in a direction substantially perpendicular to the optical axis when camera shake occurs.

[0123] Note that "IMG" in the figure indicates the image plane. It is the imaging plane of a solid-state imaging device such as a CCD sensor or a CMOS sensor. The light incident from the object side of the optical system forms an image on the image plane. The solid-state imaging device converts the received optical image into an electrical image signal. Based on the electrical image signal output from the imaging device, a digital image corresponding to the image of the subject is generated by an image processing unit (such as an image processing processor) provided in the imaging device or the like. The digital image can be recorded on a recording medium such as an HDD (Hard Disk Device), a memory card, an optical disk, or a magnetic tape. Note that the image plane may be the film surface of a silver halide film.

[0124] Also, "CG" in the figure indicates the image plane. It is an optical block. The optical block CG corresponds to an optical filter, a cover glass, a crystal low-pass filter, an infrared cut filter, etc. These symbols (IMG, CG) indicate the same things in the respective figures shown in other embodiments, so the description will be omitted below.

Embodiment

[0125] FIG. 5 is a lens cross-sectional view at the wide-angle end showing the configuration of the zoom lens according to Embodiment 2 of the present invention. The zoom lens includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a positive refractive power, a fifth lens group G5 having a negative refractive power, and a sixth lens group G6 having a negative refractive power. The rear group GR is composed of, in order from the object side, the second lens group G2, the third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6. The second lens group G2 corresponds to the lens group N having the most negative refractive power on the object side among the rear group GR. The third lens group G3 corresponds to the lens group P having the most positive refractive power on the object side and on the image side with respect to 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 most object-side lens of the RR group as a lens group having a positive refractive power, it is possible to suppress the spherical aberration variation during zooming. Here, the fifth lens group G5 corresponds to the lens group having the most negative refractive power on the object side among the RR group. Also, the sixth lens group G6 corresponds to the most image-side lens group.

[0126] The first lens group G1, in order from the object side, is a cemented lens including a meniscus-shaped first lens L1 having a negative refractive power and a convex object-side surface and a biconvex-shaped second lens L2 having a positive refractive power and convex object-side and image-side surfaces, and a biconvex-shaped third lens L3 having a positive refractive power and convex object-side and image-side surfaces.

[0127] The second lens group G2, in order from the object side, is a cemented lens including a meniscus-shaped fourth lens L4 having a positive refractive power and a concave object-side surface and a biconcave-shaped fifth lens L5 having a negative refractive power and concave object-side and image-side surfaces, and a biconcave-shaped sixth lens L6 having a negative refractive power and concave object-side and image-side surfaces. Here, the fourth lens L4 corresponds to the most object-side lens of the rear group.

[0128] From the object side, the third lens group G3 is composed of a cemented lens including a biconvex seventh lens L7 having a positive refractive power with both the object-side surface and the image-side surface being convex, an eighth lens L8 having a positive refractive power with both the object-side surface and the image-side surface being convex, and a ninth lens L9 having a negative refractive power with both the object-side surface and the image-side surface being concave. Here, by making the object-side surface of the third lens group convex toward the object side, the correction of spherical aberration becomes good.

[0129] From the object side, the fourth lens group G4 is composed of a cemented lens including a stop S, a meniscus-shaped tenth lens L10 having a negative refractive power with the object-side surface being convex toward the object side, and an eleventh lens L11 having a positive refractive power with the object-side surface being convex, a cemented lens including a meniscus-shaped twelfth lens L12 having a positive refractive power with the object-side surface being concave toward the object side and a thirteenth lens L13 having a negative refractive power with both the object-side surface and the image-side surface being concave, and a fourteenth lens L14 having an aspherical layer on the object side and having a positive refractive power with both the object-side surface and the image-side surface being convex.

[0130] From the object side, the fifth lens group G5 is composed of a cemented lens including a meniscus-shaped fifteenth lens L15 having a positive refractive power with the object-side surface being concave toward the object side and a sixteenth lens L16 having a negative refractive power with both the object-side surface and the image-side surface being concave.

[0131] The sixth lens group G6 is composed of a meniscus-shaped seventeenth lens L17 having a negative refractive power with the object-side surface being concave toward the object side. Here, the seventeenth lens L17 corresponds to the lens A having the most negative refractive power on the image side of the rear group.

[0132] When zooming from the wide-angle end to the telephoto end, the distance between adjacent lens groups changes. When zooming from the wide-angle end to the telephoto end, the distance between the first lens group G1 and the second lens group G2 increases, and the distance between the second lens group G2 and the third lens group G3 decreases. By changing the distance in this way, it becomes easy to increase the focal length at the telephoto end, and it is possible to suppress fluctuations in spherical aberration during zooming. Also, when zooming from the wide-angle end to the telephoto end, the distance between the third lens group G3 and the fourth lens group G4 increases, and the distance between the fourth lens group G4 and the fifth lens group G5 first decreases and then increases. By changing the distance in this way, it is possible to suppress fluctuations in field curvature during zooming.

[0133] When zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed with respect 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 with respect 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 with respect to the image plane. By having a group that is fixed with respect to the image plane during zooming, it is possible to simplify the mechanical mechanism, which is effective for cost reduction and miniaturization.

[0134] Here, the fifth lens group G5 corresponds to a focus group that performs focusing from an infinite-distance object to a finite-distance object by moving toward the image side. Also, here, the cemented lens of L12 and L13 in the fourth lens group G4 corresponds to an anti-shake group that corrects the image position by moving in a direction substantially perpendicular to the optical axis when camera shake occurs.

Example

[0135] FIG. 9 is a lens cross-sectional view at the wide-angle end showing the configuration of the zoom lens according to Embodiment 3 of the present invention. The zoom lens includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a positive refractive power, a fifth lens group G5 having a negative refractive power, and a sixth lens group G6 having a negative refractive power. The rear group GR is composed of, in order from the object side, the second lens group G2, the third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6. The second lens group G2 corresponds to the lens group N having the most negative refractive power on the object side among the rear group GR. The third lens group G3 corresponds to the lens group P having the most positive refractive power on the object side and on the image side with respect to 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 most object-side lens of the RR group as a lens group having a positive refractive power, it is possible to suppress the spherical aberration variation during zooming. Here, the fifth lens group G5 corresponds to the lens group having the most negative refractive power on the object side among the RR group. Also, the sixth lens group G6 corresponds to the most image-side lens group.

[0136] In order from the object side, the first lens group G1 is composed of a cemented lens of a meniscus-shaped first lens L1 having a negative refractive power and a convex object-side surface, and a biconvex-shaped second lens L2 having a positive refractive power and both convex object-side and image-side surfaces, and a meniscus-shaped third lens L3 having a positive refractive power and a convex object-side surface.

[0137] In order from the object side, the second lens group G2 is composed of a meniscus-shaped fourth lens L4 having an aspherical layer on the object side and a negative refractive power and a convex object-side surface, a cemented lens of a biconcave-shaped fifth lens L5 having a negative refractive power and both concave object-side and image-side surfaces, and a biconvex-shaped sixth lens L6 having a positive refractive power and both convex object-side and image-side surfaces, and a meniscus-shaped seventh lens L7 having an aspherical shape on both the object side and the image side and a negative refractive power and a concave object-side surface. Here, the fourth lens L4 corresponds to the most object-side lens of the rear group.

[0138] From the object side in order, the third lens group G3 is composed of a diaphragm S, an eighth lens L8 with a positive refractive power and both a convex object-side surface and a convex image-side surface (a biconvex shape), a ninth lens L9 with a positive refractive power and both a convex object-side surface and a convex image-side surface (a biconvex shape), and a tenth lens L10 with an aspherical shape on the image-side surface and a negative refractive power and both a concave object-side surface and a concave image-side surface (a biconcave shape). Here, by making the most object-side surface of the third lens group convex toward the object side, the correction of spherical aberration becomes good.

[0139] From the object side in order, the fourth lens group G4 is composed of a joined lens of an eleventh lens L11 with a positive refractive power and both a convex object-side surface and a convex image-side surface (a biconvex shape), a twelfth lens L12 with a negative refractive power and a meniscus shape with a convex object-side surface toward the object side, and a thirteenth lens L13 with a positive refractive power and both a convex object-side surface and a convex image-side surface (a biconvex shape), and a fourteenth lens L14 with an aspherical shape on both the object-side and image-side surfaces and a positive refractive power and a meniscus shape with a concave object-side surface toward the object side.

[0140] From the object side in order, the fifth lens group G5 is composed of a joined lens of a fifteenth lens L15 with a positive refractive power and both a convex object-side surface and a convex image-side surface (a biconvex shape) and a sixteenth lens L16 with an aspherical shape on the image-side surface and a negative refractive power and both a concave object-side surface and a concave image-side surface (a biconcave shape).

[0141] From the object side in order, the sixth lens group G6 is composed of a seventeenth lens L17 with a positive refractive power and a meniscus shape with a convex object-side surface toward the object side, and an eighteenth lens L18 with a negative refractive power and a meniscus shape with a concave object-side surface toward the object side. Here, the eighteenth lens L18 corresponds to the lens A with the most negative refractive power on the image side of the rear group.

[0142] When zooming from the wide-angle end to the telephoto end, the distance between adjacent lens groups changes. When zooming from the wide-angle end to the telephoto end, the distance between the first lens group G1 and the second lens group G2 increases, and the distance between the second lens group G2 and the third lens group G3 decreases. By changing the distance in this way, it becomes easy to increase the focal length at the telephoto end and suppress fluctuations in spherical aberration during zooming. Also, when zooming from the wide-angle end to the telephoto end, the distance between the third lens group G3 and the fourth lens group G4 decreases, and the distance between the fourth lens group G4 and the fifth lens group G5 first increases and then decreases. By changing the distance in this way, fluctuations in field curvature during zooming can be suppressed.

[0143] 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 moves along an S-shaped trajectory moving toward the image side again, 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.

[0144] Here, the fifth lens group G5 corresponds to a focus group that performs focusing from an infinite-distance object to a finite-distance object by moving toward the image side. Also here, the cemented lens of L12 and L13 in the fourth lens group G4 corresponds to an anti-shake group that corrects the image position by moving in a direction substantially perpendicular to the optical axis when camera shake occurs.

Example

[0145] FIG. 13 is a lens cross-sectional view at the wide-angle end showing the configuration of the zoom lens according to Embodiment 4 of the present invention. The zoom lens includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a negative refractive power, a fourth lens group G4 having a positive refractive power, a fifth lens group G5 having a negative refractive power, a sixth lens group G6 having a positive refractive power, and a seventh lens group G7 having a negative refractive power. The rear group GR is composed of, in order from the object side, the second lens group G2, the third lens group G3, the fourth lens group G4, the fifth lens group G5, the sixth lens group G6, and the seventh lens group G7. The second lens group G2 corresponds to the lens group N having the most negative refractive power on the object side among the rear group GR. The fourth lens group G4 corresponds to the lens group P having the most positive refractive power on the object side and on the image side with respect to 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 with the most positive refractive power on the object side in the RR group, it is possible to suppress the variation in spherical aberration during zooming. Here, the fifth lens group G5 corresponds to the lens group having the most negative refractive power on the object side among the RR group. Also, the seventh lens group G7 corresponds to the lens group on the most image side.

[0146] In order from the object side, the first lens group G1 is composed of a cemented lens of a meniscus-shaped first lens L1 having a negative refractive power and a convex object-side surface, and a biconvex-shaped second lens L2 having a positive refractive power and convex both on the object-side surface and the image-side surface, and a meniscus-shaped third lens L3 having a positive refractive power and a convex object-side surface.

[0147] In order from the object side, the second lens group G2 is composed of a meniscus-shaped fourth lens L4 having a positive refractive power and a concave object-side surface, and a meniscus-shaped fifth lens L5 having a negative refractive power and a convex object-side surface. Here, the fourth lens L4 corresponds to the most object-side lens of the rear group.

[0148] From the object side in order, the third lens group G3 is composed of a biconcave-shaped sixth lens L6 having a negative refractive power and both the object-side surface and the image-side surface being concave, a meniscus-shaped seventh lens L7 having a positive refractive power and the object-side surface being convex on the object side, and a meniscus-shaped eighth lens L8 having a negative refractive power and the object-side surface being concave on the object side.

[0149] From the object side in order, the fourth lens group G4 is composed of a meniscus-shaped ninth lens L9 having a positive refractive power and the object-side surface being convex on the object side, a meniscus-shaped tenth lens L10 having a positive refractive power and the object-side surface being convex on the object side, a cemented lens of a biconvex-shaped eleventh lens L11 having a positive refractive power and both the object-side surface and the image-side surface being convex and a biconcave-shaped twelfth lens L12 having a negative refractive power and both the object-side surface and the image-side surface being concave, an aperture stop S, a cemented lens of a biconcave-shaped thirteenth lens L13 having a negative refractive power and both the object-side surface and the image-side surface being concave and a meniscus-shaped fourteenth lens L14 having a positive refractive power and the object-side surface being convex on the object side, a biconvex-shaped fifteenth lens L15 having a positive refractive power and both the object-side surface and the image-side surface being convex, and a cemented lens of a meniscus-shaped sixteenth lens L16 having a negative refractive power and the object-side surface being convex on the object side and a biconvex-shaped seventeenth lens L17 having an aspherical shape on the image-side surface and having a positive refractive power and both the object-side surface and the image-side surface being convex. Here, by making the object-side surface of the fourth lens group convex on the object side, the correction of spherical aberration becomes good.

[0150] From the object side in order, the fifth lens group G5 is composed of a cemented lens of a meniscus-shaped eighteenth lens L18 having a positive refractive power and the object-side surface being concave on the object side and a biconcave-shaped nineteenth lens L19 having a negative refractive power and both the object-side surface and the image-side surface being concave.

[0151] From the object side in order, the sixth lens group G6 is composed of a cemented lens of a meniscus-shaped twentieth lens L20 having a negative refractive power and the object-side surface being convex on the object side and a biconvex-shaped twenty-first lens L21 having a positive refractive power and both the object-side surface and the image-side surface being convex.

[0152] From the object side, the seventh lens group G7 is composed of a double-convex lens 22nd lens L22 having a positive refractive power and both the object-side surface and the image-side surface being convex, a double-concave lens 23rd lens L23 having a negative refractive power and both the object-side surface and the image-side surface being concave, and a meniscus lens 24th lens L24 having a negative refractive power and the object-side surface being concave on the object side. Here, the 24th lens L24 corresponds to the lens A having the most negative refractive power on the image side in the rear group.

[0153] When zooming from the wide-angle end to the telephoto end, the distance between adjacent lens groups changes. When zooming from the wide-angle end to the telephoto end, the distance between the first lens group G1 and the second lens group G2 increases, the distance between the second lens group G2 and the third lens group G3 increases, and the distance between the third lens group G3 and the fourth lens group G4 decreases. By changing the distance in this way, it becomes easy to increase the focal length at the telephoto end, and it is possible to suppress the fluctuations in spherical aberration and field curvature during zooming. Also, when zooming from the wide-angle end to the telephoto end, the distance between the fourth lens group G4 and the fifth lens group G5 first increases and then decreases, and the distance between the fifth lens group G5 and the sixth lens group G6 first decreases and then increases. By changing the distance in this way, it is possible to suppress the fluctuations in field curvature during zooming.

[0154] 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 locus during zooming. Thereby, the mechanical mechanism can be simplified, which is effective for cost reduction and miniaturization. If the fourth lens group G4 and the seventh lens group G7 are mechanically integrated, the error amount will be subordinate during decentration, so the amount of aberration generated during decentration will be small, and high performance can be achieved.

[0155] Here, the fourth lens group G4 corresponds to a focus group that performs focusing from an infinite object to a finite-distance object by moving the focus toward the image side. Also, here, the cemented lens of L13 and L14 in the fourth lens group G4 corresponds to an anti-shake group that corrects the image position by moving it in a direction substantially perpendicular to the optical axis when camera shake occurs.

[0156] Here, by making the air interval between the fourth lens L4 and the fifth lens L5 that constitute the second lens group G2 a variable interval during zooming, it is conceivable as an application example to have a lens group with positive refractive power and a lens group with negative positive refractive power. Embodiment 4 has a lens group power arrangement of positive, negative, negative, positive, negative, positive, negative, but this application example can be applied to a lens group power arrangement of positive, positive, negative, negative, positive, negative, positive, negative. Thus, by configuring the FR group with three lens groups of positive, negative, and negative, correction of spherical aberration and field curvature becomes easier, which is more preferable in terms of high performance.

Embodiment

[0157] FIG. 17 is a lens cross-sectional view at the wide-angle end showing the configuration of the zoom lens according to Embodiment 5 of the present invention. The zoom lens includes, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative 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 the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 in order from the object side. The third lens group G3 corresponds to the lens group N having the most negative refractive power on the object side among the rear group GR. The fourth lens group G4 corresponds to the lens group P having the most positive refractive power on the object side and on the image side of 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 making the lens group with the most positive refractive power on the object side of the RR group, it is possible to suppress the variation of spherical aberration during zooming. Here, the fifth lens group G5 corresponds to the lens group having the most negative refractive power on the object side among the RR group. Also, the sixth lens group G6 corresponds to the lens group on the most image side.

[0158] The first lens group G1 is composed of a cemented lens including a meniscus-shaped first lens L1 having a negative refractive power and a convex object-side surface and a biconvex-shaped second lens L2 having a positive refractive power and convex object-side and image-side surfaces, in order from the object side.

[0159] The second lens group G2 is composed of a biconvex-shaped third lens L3 having a positive refractive power and convex object-side and image-side surfaces. Here, the third lens L3 corresponds to the most object-side lens of the rear group.

[0160] The third lens group G3 is composed of a cemented lens including a biconcave-shaped fourth lens L4 having a negative refractive power and concave object-side and image-side surfaces, a biconcave-shaped fifth lens L5 having a negative refractive power and concave object-side and image-side surfaces, and a meniscus-shaped sixth lens L6 having a positive refractive power and a convex object-side surface, in order from the object side.

[0161] The fourth lens group G4 is composed of a cemented lens including a biconvex-shaped seventh lens L7 having a positive refractive power and convex object-side and image-side surfaces, a biconvex-shaped eighth lens L8 having a positive refractive power and convex object-side and image-side surfaces, and a biconcave-shaped ninth lens L9 having a negative refractive power and concave object-side and image-side surfaces, an aperture stop S, a cemented lens including a meniscus-shaped tenth lens L10 having a negative refractive power and a convex object-side surface and a biconvex-shaped eleventh lens L11 having a positive refractive power and convex object-side and image-side surfaces, and a meniscus-shaped twelfth lens L12 having a negative refractive power and a concave object-side surface, in order from the object side. By making the most object-side surface of the fourth lens group convex toward the object side, the correction of spherical aberration becomes good.

[0162] The fifth lens group G5 is composed of a cemented lens including a biconvex-shaped thirteenth lens L13 having a positive refractive power and convex object-side and image-side surfaces and a biconcave-shaped fourteenth lens L14 having a negative refractive power and concave object-side and image-side surfaces, in order from the object side.

[0163] The sixth lens group G6 is composed of the 15th lens L15 having an aspherical layer on the object side and having a negative refractive power and having a meniscus shape with the object side surface being concave on the object side. Here, the 15th lens L14 corresponds to the lens A having the most negative refractive power on the image side in the rear group.

[0164] 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 becomes easy to increase the focal length at the telephoto end, and it is possible to suppress fluctuations in spherical aberration during zooming. Also, 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, it is possible to suppress fluctuations in field curvature during zooming.

[0165] 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 with respect 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 locus during zooming. Thereby, the mechanical mechanism can be simplified, which is effective for cost reduction and miniaturization. If the fourth lens group G4 and the sixth lens group G6 are mechanically integrated, the error amount will be subordinate during decentration, so the amount of aberration generated during decentration will be small, and high performance can be achieved.

[0166] Here, the fifth lens group G5 corresponds to the focus group that performs focusing by moving toward the image side when focusing from an infinite-distance object to a finite-distance object. Also here, the third lens group G3 corresponds to the anti-shake group that corrects the image position by moving in a direction substantially perpendicular to the optical axis when camera shake occurs.

[0167] The figure showing the longitudinal aberration when the zoom lens is focused at infinity is presented. The longitudinal aberration figure shows, in order from the left side towards the drawing, spherical aberration (mm), astigmatism (mm), and distortion (%) respectively. In the figure representing spherical aberration, the vertical axis represents the open F-number (Fno). The solid line indicates the spherical aberration at the d-line (wavelength 587.56 nm), the dotted line indicates the spherical aberration at the C-line (wavelength 656.27 nm), and the dashed-dotted line indicates the spherical aberration at the g-line (wavelength 435.84 nm). In the figure representing astigmatism, the vertical axis represents the image height (mm). The solid line indicates the sagittal direction at the d-line (wavelength 587.56 nm), and the dotted line indicates the meridional direction at the d-line. In the figure representing distortion, the vertical axis takes the image height (mm) and shows the distortion (%) at the d-line (wavelength 587.56 nm).

[0168] Numerical Examples 1 to 5 corresponding to Examples 1 to 5 are shown below. In the surface data of each numerical example, "surface number" is the number of the lens surface counted from the object side, "r" is the radius of curvature of the lens surface (mm) (however, a surface with an r value of 0.000 indicates that the surface is a plane), "d" is the distance on the optical axis between the i-th (i is a natural number) lens surface from the object side and the (i + 1)-th lens surface (mm), "Nd" is the refractive index with respect to the d-line (wavelength λ = 587.56 nm), "νd" is the Abbe number with respect to the d-line, and "h" is the effective radius (mm).

[0169] In addition, in each numerical example, the focal length (mm), F-number (F value), semi-field angle (°), image height (mm), overall lens length (mm), and back focus (BF(in air)) (mm) of the imaging lens are shown. Here, the overall lens length is the distance on the optical axis from the object side surface of the first lens to the image plane, and it is the value obtained by air-converting the distance on the optical axis from the image side surface of the n-th lens, which is arranged on the most image side, to the image plane. Also, the back focus is the value obtained by air-converting the distance on the optical axis from the image side surface of the n-th lens, which is arranged on the most image side, to the image plane.

[0170] When the optical surface is an aspherical surface, an asterisk (*) is attached to the right side of the surface number. The aspherical shape, and the aspherical coefficient, can be expressed by the following aspherical formula for the displacement amount Z in the optical axis direction at the position of the height h from the optical axis with respect to the surface vertex reference. Z = ch 2 / [1 + {1 - (1 + k)c 2 h 2} 1 / 2 + A4h 4 + A6h 6 + A8h 8 + A10h 10 + ··· However, c is the curvature (1 / r), h is the height from the optical axis, k is the conic coefficient (conic constant), A4, A6, A8, A10, ··· are the aspherical coefficients of each order. Also, the notation "E±m" (where m represents an integer) in the numerical values of the aspherical coefficient and the conic constant means "×10±m".

[0171] The aperture stop has an S attached to the right side of the surface number.

[0172] The interval that changes during zooming has a D attached to the left side of the interval number. The interval data indicates the variable interval of the zoom lens.

[0173] Also, the lens focal length indicates the focal length of each lens that makes up the zoom lens.

[0174] Also, the lens group focal length indicates the focal length of each lens group that makes up the zoom lens. Here, the FR group and the RR group indicate the focal length at the telephoto end.

[0175] [Numerical Example 1] Surface Data Surface Number r d Nd vd h 1 104.5322 1.100 1.91082 35.25 24.000 2 73.2142 7.160 1.49700 81.61 23.739 3 -392.1577 D3 23.606 4 -121.7472 0.900 1.83481 42.72 13.280 5 146.6443 1.625 13.270 6 -199.6215 0.800 1.75500 52.32 13.309 7 43.0030 3.400 1.85478 24.80 13.540 8 328.1949 D8 13.608 9 93.8755 4.040 1.59349 67.00 13.820 10 -67.4866 3.302 13.890 11 39.7554 5.594 1.51680 64.20 13.185 12 -50.5657 0.800 1.90366 31.31 12.887 13 185.4547 23.241 12.644 14S 0.0000 2.000 10.310 15 41.3694 0.800 1.91082 35.25 10.229 16 22.9137 6.324 1.54814 45.82 9.964 17 -30.6441 1.119 9.790 18 -30.2984 1.000 1.87070 40.73 9.387 19 -51.9396 D19 9.300 20 58.0943 2.230 1.77047 29.74 8.375 21 -67.2810 0.800 1.72916 54.67 8.192 22 23.2914 10.000 7.747 23 0.0000 D23 7.400 24* -43.2104 0.200 1.53610 41.21 13.127 25 -44.6776 1.000 1.75500 52.32 13.170 26 -196.6548 D26 13.803 27 0.0000 2.500 1.51680 64.20 21.078 28 0.0000 1.000 21.425 29 0.0000 0.000 21.650 Aspherical data Surface 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 Wide angle, intermediate, telephoto Focal length 102.949 199.916 387.364 F-number 5.525 6.362 8.330 Half field angle 11.682 6.039 3.143 Image height 21.633 21.633 21.633 Overall length 179.158 233.595 259.101 BF 18.913 32.058 54.384 Variable interval data Wide angle, intermediate, 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 Lens focal length Lens surface number, focal length L1 1-2 -272.866 L2 2-3 124.775 L3 4-5 -79.562 L4 6-7 -46.796 L5 7-8 57.578 L6 9 - 10 66.776 L7 11 - 12 43.995 L8 12 - 13 -43.898 L9 15 - 16 -57.581 L10 16 - 17 24.962 L11 18 - 19 -85.351 L12 20 - 21 40.779 L13 21 - 22 -23.640 L14 24 - 26 -74.455 Lens group focal length Group, surface 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 [Numerical Example 2] Surface data Surface number, r, d, Nd, vd, h 1 201.6962 1.200 1.88547 40.23 26.550 2 75.5879 7.430 1.49700 81.61 26.290 3 -464.6252 0.150 26.324 4 77.4883 7.308 1.49700 81.61 26.309 5 -451.7481 D5 26.074 6 -310.4473 2.911 1.84666 23.78 13.800 7 -52.2883 1.200 1.52176 76.02 13.661 8 68.1960 2.959 12.882 9 -54.6757 1.000 1.77311 49.21 12.846 10 127.9522 D10 12.895 11 48.8360 6.037 1.59402 65.14 16.500 12 -102.1451 0.150 16.401 13 33.5267 7.392 1.50021 81.17 15.416 14 -79.9512 1.000 1.90355 33.53 14.752 15 116.6714 D15 14.164 16S 0.0000 2.000 11.700 17 53.7749 0.800 1.91082 35.25 10.976 18 17.2565 4.979 1.54829 52.62 10.298 19 245.1068 2.485 10.104 20 -234.6815 3.257 1.87037 29.10 10.029 21 -24.0776 0.700 1.84347 43.24 9.949 22 60.6347 2.000 9.698 23* 25.3029 0.200 1.53610 41.21 9.528 24 27.8613 4.351 1.52436 62.43 9.517 25 -56.8203 D25 9.300 26 -281.1120 3.070 1.62660 37.51 8.054 27 -18.6657 0.700 1.59913 64.57 7.822 28 27.2739 3.500 7.246 29 0.0000 D29 6.975 30 -37.6558 1.200 1.87378 41.33 12.41 31 -50.8002 33.758 12.82 32 0.0000 2.500 1.51680 64.20 21.05 33 0.0000 1.000 21.43 34 0.0000 0.000 21.73 Aspherical data 23 k 0.00000E+00 A4 -1.02709E-05 A6 -8.24691E-10 A8 0.00000E+00 A10 0.00000E+00 Wide-angle Middle Telephoto Focal length 103.026 199.961 387.962 F-number 5.769 6.684 7.312 Half field angle 11.737 5.962 3.053 Image height 21.633 21.633 21.633 Overall length 215.148 215.148 215.148 BF 36.406 36.406 36.406 Variable interval data 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 Lens focal length Lens surface 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 Lens group focal length Focal length Group surface 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 [Numerical Example 3] Surface data Surface number r d Nd vd h 1 184.2714 1.200 1.88100 40.14 30.000 2 81.2480 9.560 1.49700 81.61 29.606 3 -455.2915 0.150 29.559 4 76.6478 6.882 1.49700 81.61 29.200 5 1085.1547 D5 28.963 6* 44.8010 0.200 1.51460 49.96 14.857 7 67.3993 1.000 1.85150 40.78 14.652 8 15.2147 5.850 11.779 9 -2416.3697 1.000 1.88100 40.14 11.738 10 26.1934 7.580 1.76182 26.61 11.415 11 -29.0415 0.427 11.246 12* -24.1294 0.740 1.76802 49.24 11.244 13* -143.8885 D13 11.200 14S 0.0000 1.500 10.705 15 22.5036 5.500 1.56732 42.82 11.661 16 -62.6638 0.120 11.532 17 74.8708 3.180 1.49700 81.61 10.944 18 -41.3544 0.767 10.708 19 -30.5488 1.070 1.90366 31.34 10.523 20* 26.8685 D20 10.300 21 24.3104 3.790 1.62280 57.05 10.581 22 -1822.9087 0.300 10.562 23 29.7787 0.700 1.71300 53.87 10.502 24 16.1378 4.810 1.49700 81.61 10.105 25 -116.0517 1.130 10.034 26* -62.7977 3.430 1.62263 58.16 10.040 27* -22.3738 D27 10.100 28 101.8009 2.500 1.84666 23.78 9.716 29 -45.6206 0.700 1.80400 46.53 9.623 30* 21.5837 D30 9.248 31 48.0697 6.190 1.56732 42.84 13.015 32 122.2989 4.670 13.103 33 -24.3914 2.000 1.88100 40.14 13.116 34 -55.9823 D34 14.422 35 0.0000 2.500 1.5168 64.20 21.110 36 0.0000 1.000 21.440 37 0.0000 0.000 21.656 Aspherical data 6 12 13 20 k 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A4 -1.85400E-05 6.48777E-06 -1.88129E-05 1.22253E-05 A6 -1.13368E-09 -1.83439E-08 -5.14847E-08 6.77969E-10 A8 -1.98529E-10 3.45260E-10 2.74951E-10 1.01193E-10 A10 1.01259E-12 -1.75144E-12 -2.29160E-12 -1.27586E-12 A12 -1.47224E-15 -1.96502E-15 0.00000E+00 2.84547E-15 26 27 30 k 0.00000E+00 0.00000E+00 0.00000E+00 A4 -5.76825E-05 -2.40681E-05 -6.05312E-06 A6 -1.56137E-07 -1.35230E-07 4.24081E-08 A8 -5.27964E-10 1.57303E-11 -7.77128E-10 A10 5.21323E-12 1.19861E-12 3.97614E-12 A12 -4.37017E-14 -2.11754E-14 0.00000E+00 Wide angle, Medium, Telephoto Focal length 28.864 99.989 388.242 F-number 3.591 5.823 6.547 Half field angle 38.152 11.622 3.061 Image height 21.633 21.633 21.633 Overall length 154.886 184.556 243.546 BF 16.648 39.7515 56.1239 Variable interval data Wide angle, Medium, 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 Lens focal length Lens surface number, Focal length L1 1-2 -165.857 L2 2-3 139.548 L3 4-5 165.568 L4 6-8 -25.704 L5 9-10 -29.407 L6 10-11 19.218 L7 12-13 -37.850 L8 15-16 29.884 L9 17-18 54.093 L10 19-20 -15.681 L11 21-22 38.551 L12 23-24 -50.489 L13 24-25 28.855 L14 26 - 27 54.064 L15 28 - 29 37.500 L16 29 - 30 - 18.139 L17 31 - 32 135.512 L18 33 - 34 - 50.562 Lens group focal length Group surface 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 [Numerical Example 4] Surface data Surface number r d Nd vd h 1 186.5293 1.800 1.83481 42.72 33.200 2 90.1226 8.350 1.43700 95.10 32.770 3 - 595.4609 0.200 32.766 4 83.6867 7.030 1.43700 95.10 32.600 5 1305.1393 D5 32.422 6 - 1266.8375 3.010 1.85883 30.00 20.423 7 - 165.6515 0.200 19.866 8 55.3969 1.200 1.59282 68.62 16.681 9 23.4034 D9 14.507 10 - 237.8404 0.900 1.75700 47.82 13.842 11 45.4511 0.373 13.102 12 35.8624 3.200 1.85478 24.80 12.950 13 161.6916 3.080 12.625 14 -34.2103 1.200 1.80420 46.50 12.543 15 -120.0115 D15 12.500 16 57.1309 3.200 1.60738 56.82 11.800 17 3125.0000 0.200 11.799 18 39.7989 3.150 1.60342 38.03 11.702 19 4571.7071 0.500 11.506 20 29.6958 4.100 1.49700 81.61 10.954 21 -92.1797 1.000 2.00100 29.13 10.593 22 31.4265 2.556 10.084 23S 0.0000 1.600 10.000 24 -126.5689 1.000 1.80420 46.50 10.500 25 43.1479 2.750 1.90366 31.31 10.613 26 252.6904 1.900 10.655 27 34.4452 3.340 1.68893 31.07 10.929 28 -207.0512 0.200 10.874 29 42.8161 1.000 1.91082 35.25 10.671 30 17.2634 5.250 1.59201 67.02 10.142 31* -79.1192 D31 9.980 32 -103.0333 2.590 1.68893 31.07 8.700 33 -24.8379 0.800 1.61800 63.39 8.656 34 35.9276 D34 8.400 35 88.5153 0.900 1.92286 20.88 10.845 36 28.8363 4.960 1.59551 39.24 10.821 37 -50.4147 D37 11.033 38 102.6694 5.720 1.72825 28.46 12.967 39 -36.4904 0.200 12.968 40 -47.6273 1.300 1.80420 46.50 12.706 41 61.6829 6.920 12.566 42 -23.4206 1.100 1.75500 52.32 12.770 43 -52.2833 D43 13.770 44 0.0000 2.500 1.51680 64.20 21.112 45 0.0000 1.000 21.423 46 0.0000 0.000 21.676 Aspherical data 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 Wide-angle Medium Telephoto Focal length 51.525 199.275 491.282 F-number 4.546 6.419 7.832 Half field angle 21.749 5.880 2.430 Image height 21.633 21.633 21.633 Overall length 197.927 241.121 288.927 BF 19.305 34.762 56.866 Variable interval data Wide angle, medium, 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 Lens focal length Lens surface 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 Lens group focal length Group surface number Focal length G1 1 - 5 175.950 G2 6 - 9 -101.735 G3 10 - 15 -55.881 G4 16 - 31 35.120 G5 32 - 34 -47.145 G6 35 - 37 91.610 G7 38 - 43 -51.222 FR 6 - 15 -33.533 RR 16 - 43 37.143 [Numerical Example 5] Surface data Surface number r d Nd vd h 1 108.8912 1.100 1.91082 35.25 25.000 2 75.5744 7.170 1.49700 81.61 24.714 3 -363.1458 D3 24.580 4 1075.2688 3.000 1.85883 30.00 14.662 5 -432.9004 D5 14.230 6 -164.4929 0.900 1.82002 43.17 13.450 7 157.7151 1.809 13.363 8 -99.4994 0.800 1.75500 52.32 13.360 9 45.3038 3.310 1.85478 24.80 13.561 10 221.2092 D10 13.616 11 96.9428 4.040 1.59349 67.00 13.880 12 -65.4872 3.180 13.904 13 40.0553 5.570 1.51680 64.20 13.171 14 -49.8172 0.800 1.90366 31.31 12.863 15 195.5718 22.940 12.604 16S 0.0000 2.000 10.280 17 40.4445 0.800 1.91082 35.25 10.008 18 23.0511 6.323 1.54814 45.82 9.754 19 -30.4077 1.086 9.551 20 -29.9298 1.000 1.87070 40.73 9.154 21 -51.5976 D21 9.300 22 66.1480 2.226 1.77047 29.74 8.366 23 -57.3795 0.800 1.72916 54.67 8.190 24 23.7151 10.000 7.743 25 0.0000 D25 7.400 26* -37.0118 0.200 1.53610 41.21 12.827 27 -37.7523 1.000 1.75500 52.32 12.855 28 -100.4555 D28 13.513 29 0.0000 2.500 1.51680 64.20 21.079 30 0.0000 1.000 21.418 31 0.0000 0.000 21.647 Aspherical data 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 Wide-angle Middle Telephoto Focal length 103.480 201.399 393.048 F value 5.474 6.326 8.228 Half field angle 11.539 5.960 3.086 Image height 21.633 21.633 21.633 Overall length 182.163 235.250 262.122 BF 19.494 32.897 55.171 Variable interval data Wide angle Medium 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 Lens focal length Lens surface number Focal length L1 1-2 -275.523 L2 2-3 126.554 L3 4-5 359.704 L4 6-7 -98.065 L5 8-9 -41.134 L6 9-10 66.078 L7 11-12 66.471 L8 13-14 43.889 L9 14-15 -43.869 L10 17-18 -60.167 L11 18-19 24.966 L12 20-21 -83.652 L13 22-23 40.195 L14 23-24 -22.917 L15 26-28 -78.883 Lens group focal length Group surface 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

[0176] The corresponding values and various numerical values of the conditional expressions (1) to (14) in Examples 1 to 5 are listed in Table 1 below. [Table 1] (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) |(1 - βFt2)× βrt2| Example 1 Example 2 Example 3 Example 4 Example 5 (1) 1.835 1.847 1.852 1.859 1.859 (2) 0.669 0.555 0.627 0.588 0.667 (3) 1.743 1.223 1.560 2.110 1.712 (4) 3.746 3.178 4.262 3.746 3.792 (5) 1.755 1.874 1.881 1.755 1.755 (6) -1.588 -6.730 -2.544 -2.623 -2.204 (7) 0.184 0.353 0.577 0.375 0.188 (8) 0.596 0.330 0.359 0.358 0.598 (9) 0.429 0.471 0.611 0.500 0.400 (10) 3.000 1.872 3.867 3.851 2.841 (11) 0.210 0.169 0.230 0.197 0.211 (12) 3.879 3.155 6.315 5.247 3.918 (13) -1.129 -1.520 -1.022 -1.064 -1.116 (14) 10.993 8.671 15.744 12.682 11.449 TLt 259.101 215.148 243.546 288.927 262.122 ft 387.364 387.962 388.242 491.282 393.048 CrAf -44.678 -37.656 -24.391 -23.421 -37.752 CrAr -196.655 -50.800 -55.982 -52.283 -100.456 BFw 18.913 36.406 16.648 19.305 19.494 fw 102.949 103.026 28.864 51.525 103.480 f1 230.858 127.886 139.334 175.950 234.850 Lnsr 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 BFt 54.384 36.406 56.124 56.866 55.171 fFRt -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

[0177] The preferred embodiments of the present invention have been described above. However, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist thereof. In addition, the following can be considered as another invention applying the present invention. To solve the above problems, the zoom lens according to the present invention is composed of a positive first lens group and a rear group having a plurality of lens groups in order from the object side, and has a focus group having a negative refractive power that moves in the optical axis direction at the time of focusing in the rear group, and satisfies the following conditional expressions.

[0178] 0.10 < Lnsr / Lnall < 0.74 ···(9) 1.20 < TLsrw / BFw < 6.95 ···(10) 7.1 < |(1 - βFt 2 ) × βrt 2 2 | < 20.0 ···(14) However, Lnsr: The total number of lenses on the image side of the aperture stop Lnall: The total number of lenses of the zoom lens TLsrw: The distance from the aperture stop at the wide-angle end to the image side surface of lens A BFw: The distance from the most image side surface to the image plane at the wide-angle end of the zoom lens βFt: The lateral magnification at the telephoto end of the focus group βrt: The combined lateral magnification at the telephoto end of all lens groups on the image side of the focus group

[0179] (Summary) The zoom lens according to the first aspect of the present invention is It is composed of a first lens group having a positive refractive power in order from the object side and a rear group having a plurality of lens groups. The distance between adjacent lens groups changes during zooming, and it has a lens A having a negative refractive power on the most image side of the rear group, and may satisfy the following conditional expressions. 1.83 < Nd2 < 2.50 ···(1) 0.20 < TLt / ft < 0.96 ···(2) 1.16 < βLt ···(3) However, Nd2: Refractive index of the lens on the most object side of the rear group at the d line TLt: Distance from the most object side surface to the image surface at the telephoto end of the zoom lens ft: Focal length at the telephoto end of the zoom lens βLt: Lateral magnification at the telephoto end of the lens group on the most image side of the rear group

[0180] The zoom lens according to the second aspect of the present invention is It is composed of a first lens group having a positive refractive power in order from the object side and a rear group having a plurality of lens groups. The distance between adjacent lens groups changes during zooming, and it has a lens A having a negative refractive power on the most image side of the rear group. The rear group has a focus group that moves in the optical axis direction during focusing, and may satisfy the following conditional expressions. 1.83 < Nd2 < 2.50 ···(1) 0.20 < TLt / ft < 0.96 ···(2) 7.1 < |(1 - βFt2)×βrt2| < 20.0 ···(14) However, Nd2: Refractive index of the lens on the most object side of the rear group at the d line TLt: Distance from the most object side surface to the image surface at the telephoto end of the zoom lens βFt: Lateral magnification at the telephoto end of the focus group βrt: Combined lateral magnification at the telephoto end of all lens groups on the image side of the focus group

[0181] The zoom lens according to the third aspect of the present invention is It is composed of a first lens group having a positive refractive power in order from the object side and a rear group having a plurality of lens groups. The interval between adjacent lens groups changes during zooming. A group including a lens group N having the most negative refractive power on the object side in the rear group is defined as an FR group, and a group from a lens group P having the most positive refractive power on the image side and closest to the object side than the lens group N to the most image-side lens group is defined as an RR group. The rear group is composed of the FR group and the RR group. It may have a lens A having a negative refractive power on the most image side of the rear group and may satisfy the following conditional expressions. 1.83 < Nd2 < 2.50 ···(1) 0.20 < TLt / ft < 0.96 ···(2) 2.70 < βCt ···(4) However, Nd2: Refractive index of the most object-side lens in the rear group at the d line TLt: Distance from the most object side surface to the image surface at the telephoto end of the zoom lens ft: Focal length at the telephoto end of the zoom lens βCt: Composite lateral magnification at the telephoto end from the most object-side negative lens group to the most image-side lens group in the RR group

[0182] The zoom lens according to the fourth aspect of the present invention is, in the first aspect or the second aspect, An FR group including a lens group N having the most negative refractive power on the object side in the rear group, and an RR group from a lens group P having the most positive refractive power on the image side and closest to the object side than the lens group N to the most image-side lens group. The rear group may be composed of the FR group and the RR group.

[0183] The zoom lens according to the fifth aspect of the present invention is, in the third aspect to the fourth aspect, The FR group may have a negative refractive power as a whole, and the RR group may have a positive refractive power as a whole.

[0184] The zoom lens according to the sixth aspect of the present invention is, in the first aspect to the fifth aspect, It may satisfy the following conditional expressions. 1.73 < NdA < 2.50 ···(5) However, NdA: Refractive index of the lens A at the d-line

[0185] The zoom lens according to the seventh aspect of the present invention may satisfy the following conditional expression in the first to sixth aspects. The following conditional expression may be satisfied. (CrAf + CrAr) / (CrAf - CrAr) < 0.30 ···(6) However, CrAf: Radius of curvature of the object side surface of the lens A CrAr: Radius of curvature of the image side surface of the lens A

[0186] The zoom lens according to the eighth aspect of the present invention may satisfy the following conditional expression in the first to seventh aspects. The following conditional expression may be satisfied. 0.02 < BFw / fw < 0.98 ···(7) However, BFw: Distance from the most image side surface 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

[0187] The zoom lens according to the ninth aspect of the present invention may be configured such that the most image-side lens group of the rear group has 4 or fewer lens elements in the first to eighth aspects. The most image-side lens group of the rear group may be composed of 4 or fewer lens elements.

[0188] The zoom lens according to the tenth aspect of the present invention may have 2 or fewer positive refractive power lenses included in the first lens group in the first to ninth aspects. The number of positive refractive power lenses included in the first lens group may be 2 or fewer.

[0189] The zoom lens according to the eleventh aspect of the present invention may satisfy the following conditional expression in the first to tenth aspects. The following conditional expression may be satisfied. 0.15 < f1 / ft < 0.70 ···(8) However, f1: Focal length of the first lens group

[0190] In the twelfth aspect of the present invention, the zoom lens in the first aspect to the eleventh aspect The rear group has an aperture stop that determines the effective diameter of the axial light beam, and may satisfy the following conditional expression. 0.10 < Lnsr / Lnall < 0.74 ···(9) However, Lnsr: The total number of lenses on the image side of the aperture stop Lnall: The total number of lenses of the zoom lens

[0191] In the thirteenth aspect of the present invention, the zoom lens in the first aspect to the twelfth aspect The rear group has an aperture stop that determines the effective diameter of the axial light beam, and may satisfy the following conditional expression. 1.20 < TLsrw / BFw < 6.95 ···(10) However, TLsrw: The distance from the aperture stop at the wide-angle end to the image side surface of the lens A BFw: The distance from the most image side surface to the image plane at the wide-angle end of the zoom lens

[0192] In the fourteenth aspect of the present invention, the zoom lens in the first aspect to the thirteenth aspect May satisfy the following conditional expression. 0.06 < BFt / TLt < 0.32 ···(11) However, BFt: The distance from the most image side surface to the image plane at the telephoto end of the zoom lens

[0193] In the fifteenth aspect of the present invention, the zoom lens in the third aspect to the fourteenth aspect A group including the lens group N having the most negative refractive power on the object side in the rear group is defined as the FR group, and the lens group from the lens group P having the most positive refractive power on the image side and the most object side than the lens group N to the most image side lens group is defined as the RR group. The rear group is composed of the FR group and the RR group, May satisfy the following conditional expression. 2.90 < f1 / |fFRt| < 8.00 ···(12) However, f1: Focal length of the first lens group fFRt: Focal length at the telephoto end of the FR group

[0194] In the sixteenth aspect of the present invention, the zoom lens, in the second aspect to the tenth aspect, A group including a lens group N having the most negative refractive power on the object side in the rear group is defined as the FR group, and the lens group from the lens group P having the most positive refractive power on the image side and closest to the object side than the lens group N to the most image-side lens group is defined as the RR group. The rear group is composed of the FR group and the RR group, The following conditional expression may be satisfied. -2.50 < βRRw < -0.50 ···(13) However, βRRw: Lateral magnification at the wide-angle end of the RR group

[0195] The imaging device according to the seventeenth aspect of the present invention may include the zoom lens according to the first aspect to the sixteenth aspect, and an imaging element provided on the image side of the zoom lens that receives the optical image formed by the zoom lens and converts it into an electrical signal.

[0196] The optical systems and imaging devices described in the above embodiments and examples are one aspect of the zoom lens and imaging device according to the present invention, and correspond to the optical systems according to the first aspect to the sixteenth aspect and the imaging device according to the seventeenth aspect. According to the zoom lens and imaging device of each of the above aspects, the same effects as those described in the above embodiments and examples are achieved. The zoom lens and imaging device according to the present invention are not limited to the zoom lens and imaging device described in the embodiments and examples, and can be appropriately changed within the scope of the zoom lens and imaging device of each of the above aspects.

Industrial Applicability

[0197] According to the present invention, a small and high-performance zoom lens and imaging device can be provided.

Explanation of Reference Numerals

[0198] GR ··· Rear group FR ··· FR group RR ··· RR group G1 ··· First lens group G2 ··· Second lens group G3 ··· Third lens group G4 ··· Fourth lens group G5 ··· Fifth lens group G6 ··· Sixth lens group G7 ··· Seventh lens group L1 ··· First lens L2 ··· Second lens L3 ··· Third lens L4 ··· Fourth lens L5 ··· Fifth lens L6 ··· Sixth lens L7 ··· Seventh lens L8 ··· Eighth lens L9 ··· Ninth lens L10 ··· Tenth lens L11 ··· Eleventh lens L12 ··· Twelfth lens L13 ··· Thirteenth lens L14 ··· Fourteenth lens L15 ··· Fifteenth lens L16 ··· Sixteenth lens L17 ··· Seventeenth lens L18 ··· Eighteenth lens L19 ··· Nineteenth lens L20 ··· Twentieth lens L21 ··· Twenty - first lens L22 ··· Twenty - second lens L23 ··· Twenty - third lens L24 ··· Twenty - fourth lens S ··· Aperture stop F ··· Focus group CG ··· Optical block IMG ··· Image plane 1 ··· Imaging device 2 ··· Camera 3 ··· Lens 21 ··· CCD sensor 22 ··· Optical filter

Claims

1. A zoom lens comprising, in order from the object side, a first lens group having positive refractive power and a rear group having a plurality of lens groups, the spacing between adjacent lens groups changing during zooming, lens A having negative refractive power located closest to the image side of the rear group, and satisfying the following conditional expression: 1.83 < Nd2 < 2.50...(1) 0.20 < TLt / ft < 0.96 (2) 1.16 < βLt (3) however, Nd2: the refractive index at the d line of the lens closest to the object in the rear group TLt: the distance from the most object-side surface to the image plane at the telephoto end of the zoom lens ft: focal length at the telephoto end of the zoom lens βLt: lateral magnification at the telephoto end of the lens unit closest to the image side of the rear group

2. A zoom lens comprising, in order from the object side, a first lens group having positive refractive power and a rear group having a plurality of lens groups, the spacing between adjacent lens groups changing during zooming, lens A having negative refractive power located closest to the image side of the rear group, the rear group having a focus group that moves in the optical axis direction during focusing, and satisfying the following conditional expression: 1.83 < Nd2 < 2.50...(1) 0.20 < TLt / ft < 0.96 (2) 7.1 < |(1-βFt ２ )×βrt ２ | < 20.0 ・・・(14) however, Nd2: the refractive index at the d line of the lens closest to the object in the rear group TLt: the distance from the most object-side surface to the image plane at the telephoto end of the zoom lens ft: focal length at the telephoto end of the zoom lens βFt: lateral magnification at the telephoto end of the focus group βrt: composite lateral magnification at the telephoto end of all lens groups on the image side of the focus group

3. a first lens group having positive refractive power and a rear group having a plurality of lens groups, the distance between adjacent lens groups changing during zooming, a group including a lens group N having negative refractive power closest to the object in the rear group being defined as an FR group, a lens group P having positive refractive power closest to the image side and closest to the object side than lens group N being defined as an RR group, the rear group being composed of the FR group and the RR group, a lens A having negative refractive power closest to the image side of the rear group, and satisfying the following conditional expression: 1.83 < Nd2 < 2.50...(1) 0.20 < TLt / ft < 0.96 (2) 2.70 < βCt (4) however, Nd2: the refractive index at the d line of the lens closest to the object in the rear group TLt: the distance from the most object-side surface to the image plane at the telephoto end of the zoom lens ft: focal length at the telephoto end of the zoom lens βCt: 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

4. 2. The zoom lens according to claim 1, wherein an FR group includes a lens group N having negative refractive power and closest to the object in the rear group, and an RR group is a lens group closest to the image side from a lens group P having positive refractive power, which is closest to the image side of the lens group N and closest to the object, and the rear group is composed of the FR group and the RR group.

5. 3. The zoom lens according to claim 2, wherein an FR group includes a lens group N having negative refractive power and closest to the object in the rear group, and an RR group is a lens group closest to the image side from a lens group P having positive refractive power, which is closest to the image side of the lens group N and closest to the object, and the rear group is composed of the FR group and the RR group.

6. 6. The zoom lens according to claim 3, wherein the FR group has a negative refractive power as a whole, and the RR group has a positive refractive power as a whole.

7. 4. The zoom lens according to claim 1, wherein the following condition is satisfied: 1.73 < NdA < 2.50 (5) however, NdA: refractive index of the lens A at the d line

8. 4. The zoom lens according to claim 1, wherein the following condition is satisfied: (CrAf+CrAr) / (CrAf-CrAr)<0.30...(6) however, CrAf: radius of curvature of the object side surface of the lens A CrAr: radius of curvature of the image side surface of the lens A

9. 4. The zoom lens according to claim 1, wherein the following condition is satisfied: 0.02 < BFw / fw < 0.98...(7) however, 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 of the zoom lens at the wide-angle end

10. 4. The zoom lens according to claim 1, wherein the lens group in the rear group closest to the image side is composed of four or less lenses.

11. 4. The zoom lens according to claim 1, wherein the first lens group includes two or less lenses having positive refractive power.

12. 4. The zoom lens according to claim 1, wherein the following condition is satisfied: 0.15 < f1 / ft < 0.70 (8) however, f1: focal length of the first lens group

13. 4. The zoom lens according to claim 1, wherein the rear group has an aperture stop which determines an effective diameter of an axial light beam, and the following condition is satisfied: 0.10<Lnsr / Lnall<0.74...(9) however, Lnsr: the total number of lenses located on the image side of the aperture stop Lnall: the total number of lenses in the zoom lens

14. 4. The zoom lens according to claim 1, wherein the rear group has an aperture stop which determines an effective diameter of an axial light beam, and the following condition is satisfied: 1.20 < TLsrw / BFw < 6.95 (10) however, 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. 4. The zoom lens according to claim 1, wherein the following condition is satisfied: 0.06 < BFt / TLt < 0.32 (11) however, BFt: the distance from the most image-side surface to the image plane at the telephoto end of the zoom lens

16. 6. The zoom lens according to claim 3, wherein the following condition is satisfied: 2.90 < f1 / | fFRt | < 8.00 (12) however, f1: focal length of the first lens group fFRt: focal length at the telephoto end of the FR group

17. 6. The zoom lens according to claim 3, wherein the following condition is satisfied: -2.50 < βRRw < -0.50 (13) however, βRRw: lateral magnification of the RR group at the wide-angle end

18. 4. An imaging apparatus comprising: the zoom lens according to claim 1; and an imaging element that receives an optical image formed by the zoom lens and converts the optical image into an electrical image signal.

Images