Zoom lens and imaging device

Abstract

To realize a small, light, and low-priced imaging device with a wide angle of view.SOLUTION: A zoom lens has a first lens group with a negative refractive power, a second lens group with a positive refractive power, and a third lens group, which are sequentially arranged in a direction from an object to an image surface. The second lens group has a plastic lens with the negative refractive power and presents a specific optical characteristic represented by a specific formula.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Imaging measures equipped with solid-state imaging devices such as CCDs and COMSs have been rapidly spreading in a wide range of fields such as single-lens reflex cameras, digital still cameras, video cameras, and surveillance cameras. Along with this, the demand for lenses compatible with solid-state imaging devices is expanding.

[0003] In recent years, the number of pixels and sensitivity of solid-state imaging devices have been increasing, and high-resolution lenses are required. In addition, the spread of small imaging devices is progressing, and in addition to further miniaturization of the imaging device, it is also desired to make the imaging device wide-angle, lightweight, and low-cost. Under such circumstances, a zoom lens using a plastic lens in the second lens group is known (for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the prior art as described above, in order to achieve a wide angle, lightweight, and high optical performance, it is necessary to strongly design the refractive power of the plastic lens in the second lens group. Therefore, it may be difficult to achieve both cost reduction and weight reduction, which are advantages of using a plastic lens, and the expression of high optical performance at a wide angle. Thus, conventionally, there has been room for consideration from the viewpoint of realizing an imaging device with a wide angle of view, small size, lightweight, and low cost.

[0006] One aspect of the present invention aims to realize an imaging device with a wide angle of view, small size, light weight, and low cost.

Means for Solving the Problems

[0007] To solve the above problems, a zoom lens according to one aspect of the present invention includes: a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group, which are arranged in order from the object side to the image plane side; during zooming, the first lens group and the second lens group move so that the interval between adjacent lens groups changes; the first lens group includes at least two lenses having a negative refractive power and at least one lens having a positive refractive power; the second lens group includes a plastic lens having a negative refractive power; and satisfies the following formulas (1) to (3). 1.55 < Nd < 1.90 ··· (1) 18.0 < νd < 40.0 ··· (2) 1.5 < |fp / f2| < 3.0 ··· (3) However, Nd: refractive index of the plastic lens with respect to the d-line νd: Abbe number of the plastic lens based on the d-line fp: focal length of the plastic lens f2: focal length of the second lens group

[0008] In addition, to solve the above problems, an imaging device according to one aspect of the present invention includes the above zoom lens and a solid-state imaging device that converts an optical image formed by the zoom lens into an electrical signal on the image plane side of the zoom lens.

Effects of the Invention

[0009] According to one aspect of the present invention, an imaging device with a wide angle of view, small size, light weight, and low cost can be realized.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

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Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Embodiments for Carrying Out the Invention

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

[0012] In this specification, the "zoom lens" is a general term for those including the optical characteristics specified in the present invention, and means one or both of the optical system itself that exhibits the optical characteristics and an article including the optical system.

[0013] 1. Zoom Lens 1-1. Configuration Hereinafter, an embodiment of the present invention will be described in detail.

[0014] The zoom lens according to this embodiment has a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group, which are arranged in order from the object side to the image plane side. From the viewpoint of realizing desired optical characteristics, the zoom lens may have additional lens groups in addition to the first lens group, the second lens group, and the third lens group. On the other hand, from the viewpoint of downsizing the zoom lens, it is preferably composed of only the first lens group, the second lens group, and the third lens group.

[0015] In this specification, the "lens group" means a set of one or more lenses that interlock in the zooming operation. The lenses in the lens group move while maintaining their relative positional relationship in the zooming operation. The zooming operation is performed by changing the distance between the lens groups, and the distance between the lenses belonging to the same lens group does not change in the zooming operation.

[0016] Unless otherwise specified, the lenses included in each lens group may be glass lenses or plastic lenses. For example, from the perspective of achieving good optical characteristics, except for the plastic lenses with negative refractive power within the second lens group, the lens group may be composed of glass lenses.

[0017] (1) The first lens group The first lens group is the lens group arranged closest to the object side in the zoom lens according to the present embodiment. The first lens group has a negative refractive power. Also, the first lens group has at least two negative lenses and one positive lens.

[0018] From the perspective of miniaturization and weight reduction, the first lens group is preferably composed of only at least two lenses with negative refractive power and at least one lens with positive refractive power. On the other hand, from the perspective of realizing desired optical characteristics, the first lens group may have additional lenses in addition to at least two lenses with negative refractive power and at least one lens with positive refractive power.

[0019] The order in which at least two lenses with negative refractive power and at least one lens with positive refractive power included in the first lens group are arranged is not particularly limited. For example, these lenses may be arranged in order from the object side as a lens with negative refractive power, a lens with negative refractive power, and a lens with positive refractive power. This configuration is preferable from the perspective that it can have a wide angle of view at the wide-angle end, can correct the field curvature and distortion aberration well in the wide-angle end region, and can correct the axial chromatic aberration and lateral chromatic aberration within the first lens group well.

[0020] (2) The second lens group The second lens group is a lens group that is disposed closer to the image plane side than the first lens group and closer to the object side than the third lens group. The second lens group has a positive refractive power. The second lens group includes a plastic lens having a negative refractive power. The number of plastic lenses having a negative refractive power included in the second lens group may be one or more than one. At least one of the plastic lenses having a negative refractive power preferably has physical properties described later by the "1-3 formula".

[0021] The second lens group preferably has two or more lenses having a positive refractive power. This configuration is preferable from the viewpoint of favorably correcting spherical aberration and chromatic aberration. From the viewpoint of miniaturization, the number of lenses having a positive refractive power in the second lens group may be four or less, and preferably three or less.

[0022] The order in which each lens is disposed in the second lens group is not particularly limited.

[0023] (3) The third lens group The third lens group is a lens group that is disposed closer to the image plane side than the second lens group. The third lens group may have a positive refractive power or a negative refractive power. For example, from the viewpoint of favorably correcting image plane distortion and chromatic aberration, it is preferable that the third lens group has a positive refractive power.

[0024] The third lens group has one or more lenses having a negative refractive power, and may have one or more lenses having a positive refractive power. This configuration is preferable from the viewpoint of favorably correcting field curvature and chromatic aberration throughout the zoom range. From the viewpoint of miniaturization of the zoom lens, the number of lenses having a negative refractive power in the third lens group may be three or less, or two or less. Also, from the same viewpoint, the number of lenses having a positive refractive power in the third lens group may be three or less, or two or less. From the viewpoint of miniaturization of the zoom lens, the third lens group may have one lens having a negative refractive power and one lens having a positive refractive power.

[0025] The order in which each lens is arranged and included in the third lens group is not particularly limited. For example, these lenses may be arranged in order from the object side as a lens having a negative refractive power and a lens having a positive refractive power. This configuration is preferable from the viewpoint of favorably correcting field curvature and chromatic aberration of magnification.

[0026] (4) Aperture The zoom lens according to the present embodiment may have an aperture. In this specification, the "aperture" is an aperture that defines the light beam diameter of the zoom lens, that is, an aperture that defines the F-number of the zoom lens. The arrangement of the aperture in the zoom lens is not limited. For example, it may be arranged inside the second lens group or adjacent to the object side.

[0027] 1-2. Operation (1) Operation during zooming Both the first lens group and the second lens group move so that the distance between them changes during zooming. Also, it is preferable that the first lens group and the second lens group move along different trajectories.

[0028] When the first lens group moves from the wide-angle end to the telephoto end, it is preferably first moved toward the image plane side and then toward the object side. The position of the first lens group at the telephoto end is preferably on the image plane side with respect to the position at the wide-angle end.

[0029] When the second lens group moves from the wide-angle end to the telephoto end, it gradually moves toward the object side. Note that in this specification, "gradually moving" refers to the manner in which the lens group moves in one direction. Gradual movement is also referred to as monotonic movement in the art.

[0030] It is preferable that the third lens group does not move with respect to the image plane. By fixing the third lens group with respect to the image plane during zooming, the number of lens groups to be moved during zooming can be reduced, the zoom mechanism can be simplified, and at the same time, it is possible to make it difficult to generate manufacturing errors.

[0031] (2) Operation during focusing When focusing, it is preferable to move the first lens group in the optical axis direction.

[0032] Equation 1-3 The zoom lens preferably adopts the above-described configuration and satisfies at least one of the following equations.

[0033] 1-3-1. Equation (1) 1.55 < Nd < 1.90 ··· (1) However, Nd: Refractive index of the plastic lens with respect to the d-line

[0034] Equation (1) is an equation for appropriately setting the refractive index of the plastic lens having a negative refractive power included in the second lens group with respect to the d-line. By satisfying Equation (1), the refractive power of the plastic lens with respect to the d-line is in a good range, and the spherical aberration and field curvature generated in the second lens group can be appropriately corrected.

[0035] When Nd is lower than the lower limit value, the refractive power of the plastic lens may be too weak, and the spherical aberration and field curvature generated in the second lens group may be insufficiently corrected.

[0036] When Nd exceeds the upper limit value, the refractive power of the plastic lens may be too strong, and the spherical aberration and field curvature generated in the second lens group may increase.

[0037] From the viewpoint of sufficiently correcting various aberrations and realizing miniaturization of the zoom lens, Nd is preferably greater than 1.57, more preferably greater than 1.60. From the viewpoint of realizing good optical performance by suppressing the correction of various aberrations within an appropriate range, Nd is preferably less than 1.80, more preferably less than 1.75, and even more preferably less than 1.70.

[0038] 1-3-2. Equation (2) 10.0 < νd < 40.0 ··· (2) However, νd: Abbe number based on the d-line of the plastic lens

[0039] Equation (2) is an equation for appropriately setting the Abbe number with respect to the d-line of the plastic lens having a negative refractive power included in the second lens group. By satisfying Equation (2), the axial chromatic aberration generated in the second lens group can be appropriately corrected.

[0040] When νd is less than the lower limit value, the axial chromatic aberration generated within the second lens group may increase.

[0041] When νd exceeds the upper limit value, the axial chromatic aberration generated within the second lens group may be undercorrected.

[0042] From the viewpoint of appropriately suppressing the axial chromatic aberration within the second lens group and preferably performing chromatic aberration correction over the entire zoom region, νd is preferably greater than 13.0, more preferably greater than 15.0, and even more preferably greater than 18.0. From the viewpoint of sufficiently correcting the axial chromatic aberration generated within the second lens group and performing chromatic aberration correction over the entire zoom region, νd is preferably less than 38.0, more preferably less than 33.0, and even more preferably less than 30.0.

[0043] 1-3-3. Equation (3) 1.0 < |fp / f2| < 5.0 ··· (3) However, fp: Focal length of the plastic lens f2: Focal length of the second lens group

[0044] Equation (3) is an equation for appropriately setting the ratio between the focal length of the second lens group and the focal length of the plastic lens having a negative refractive power included in the second lens group. By satisfying Equation (3), the focal length of the plastic lens included in the second lens group can be appropriately set, and the spherical aberration and field curvature generated within the second lens group can be appropriately corrected.

[0045] When |fp / f2| is below the lower limit value, the refractive power of the plastic lens becomes too strong, and the spherical aberration and field curvature generated within the second lens group may increase. Further, if the refractive power of the plastic lens becomes too high, the sensitivity to manufacturing errors of the plastic lens may increase and the manufacturability may deteriorate.

[0046] When |fp / f2| exceeds the upper limit value, the refractive power of the plastic lens becomes too weak, and the correction of spherical aberration and field curvature generated within the second lens group may become insufficient.

[0047] From the viewpoint of realizing good optical performance and improving the manufacturability of the plastic lens, |fp / f2| is preferably greater than 1.2, and more preferably greater than 1.5. From the viewpoint of appropriately correcting various aberrations generated within the second lens group and realizing good optical performance, |fp / f2| is preferably less than 4.5, more preferably less than 4.0, and even more preferably less than 3.5.

[0048] 1-3-4. Equation (4) 1.5 < |f1 / fw| < 2.75 ··· (4) However, f1: Focal length of the first lens group fw: Focal length at the wide-angle end when the zoom lens is focused at infinity

[0049] Equation (4) is an equation for appropriately setting the ratio between the focal length of the first lens group and the focal length of the entire system at the wide-angle end when the zoom lens is focused at infinity. By satisfying Equation (4), the focal length of the first lens group can be appropriately set, so that the zooming and miniaturization of the zoom lens can be realized, and coma aberration and field curvature can be appropriately corrected.

[0050] When below the lower limit value of |f1 / fw|, the refractive power of the first lens group becomes too strong, and it may become difficult to correct coma aberration and field curvature.

[0051] When the upper limit value of |f1 / fw| is exceeded, the refractive power of the first lens group becomes too weak, and it may become difficult to widen the angle of view and miniaturize the zoom lens.

[0052] From the viewpoint of realizing good optical performance by setting the refractive power of the first lens group within an appropriate range, |f1 / fw| is preferably greater than 1.65, more preferably greater than 1.80, and even more preferably greater than 1.90. From the viewpoint of realizing wide-angle and miniaturization of the zoom lens by setting the refractive power of the first lens group within an appropriate range, |f1 / fw| is preferably less than 2.60, more preferably less than 2.40, and even more preferably less than 2.20.

[0053] 1-3-5. Equation (5) 0.80 < |f1 / f2| < 1.20 ··· (5)

[0054] Equation (5) is an equation for appropriately setting the ratio between the focal length of the first lens group and the focal length of the second lens group. By satisfying Equation (5), miniaturization and wide-angleization of the zoom lens can be realized, and further, aberration variation during zooming can be appropriately corrected.

[0055] When the lower limit value of Equation (5) is exceeded, the refractive power of the first lens group becomes too strong, and it may become difficult to correct coma aberration and field curvature at the wide-angle end.

[0056] When the upper limit of Equation (5) is exceeded, the refractive power of the second lens becomes too strong, the aberration variation during zooming becomes large, and it may become difficult to obtain high optical performance.

[0057] |f1 / f2| is preferably greater than 0.82, more preferably greater than 0.84, and even more preferably greater than 0.86, from the viewpoint of achieving good optical performance by setting the refractive powers of the first lens group and the second lens group within an appropriate range. |f1 / f2| is preferably less than 1.10, more preferably less than 1.00, and even more preferably less than 0.95, from the viewpoint of achieving good optical performance by setting the refractive powers of the first lens group and the second lens group within an appropriate range.

[0058] 1-3-6. Equation (6) 1.5 < β2t / β2w < 4.0 ··· (6) However, β2t: Lateral magnification at the telephoto end when the second lens group is focused at infinity β2w: Lateral magnification at the wide-angle end when the second lens group is focused at infinity

[0059] Equation (6) is an equation for appropriately setting the ratio between the lateral magnification of the second lens group at the wide-angle end and the lateral magnification of the second lens group at the telephoto end when focused at infinity. By satisfying Equation (6), the zoom ratio from the wide-angle end to the telephoto end can be realized, and miniaturization of the zoom lens and appropriate correction of aberration variation during zooming can be achieved.

[0060] If it is below the lower limit value of β2t / β2w, the zoom ratio obtained by moving the second lens group may become too small.

[0061] If it exceeds the upper limit value of β2t / β2w, the aberration variation during zooming may increase too much.

[0062] β2t / β2w is preferably greater than 1.8, more preferably greater than 2.0, and even more preferably greater than 2.2, from the viewpoint of miniaturizing the zoom lens. β2t / β2w is preferably less than 3.5, more preferably less than 3.0, and even more preferably less than 2.7, from the viewpoint of achieving high optical performance over the entire zoom range.

[0063] 1-3-7. Equation (7) 1.50 < |f2 / fw| < 3.50 ··· (7)

[0064] Equation (7) is an equation for appropriately setting the ratio between the focal length of the second lens group and the focal length at the wide-angle end when the zoom lens is focused at infinity. By satisfying Equation (7), the focal length of the second lens group can be appropriately set, and spherical aberration, astigmatism, and axial chromatic aberration generated in the second lens group can be appropriately corrected.

[0065] If it is less than the lower limit value of |f2 / fw|, the refractive power of the second lens group becomes too high, and spherical aberration, astigmatism, and axial chromatic aberration generated in the second lens group may increase.

[0066] If it exceeds the upper limit value of |f2 / fw|, the refractive power of the second lens group becomes too small, and the overall length of the zoom lens may become long.

[0067] |f2 / fw| preferably has a refractive power of the second lens group within an appropriate range, and from the viewpoint of realizing good optical performance by suppressing various aberrations generated in the second lens group, it is preferably greater than 1.75, more preferably greater than 2.00, and even more preferably greater than 2.30. |f2 / fw| preferably has a refractive power of the second lens group within an appropriate range, and from the viewpoint of realizing miniaturization of the zoom lens, it is preferably less than 3.25, more preferably less than 2.75, and even more preferably less than 2.50.

[0068] 1-3-8. Equation (8) 65.0 < νd_ave < 90.0 ··· (8) However, νd_ave: Average value of Abbe numbers based on the d-line of the lenses having positive refractive power within the second lens group

[0069] Equation (8) is an equation for appropriately setting the material of the lens having a positive refractive power within the second lens group. By satisfying Equation (8), the axial chromatic aberration generated within the second lens group can be appropriately corrected.

[0070] When νd_ave is below the lower limit value, the axial chromatic aberration generated within the second lens group may be insufficiently corrected.

[0071] When νd_ave exceeds the upper limit value, the axial chromatic aberration generated within the second lens group may be overcorrected.

[0072] From the viewpoint of realizing good optical performance by appropriately correcting the axial chromatic aberration generated within the second lens group and well-balancing the chromatic aberration over the entire zoom region, νd_ave is preferably greater than 67.0, more preferably greater than 70.0, and even more preferably greater than 72.0. From the viewpoint of realizing good optical performance by appropriately correcting the axial chromatic aberration generated within the second lens group and well-balancing the chromatic aberration over the entire zoom lens region, νd_ave is preferably less than 85.0, and more preferably less than 80.0.

[0073] 1-3-9. Equation (9) 0.4 < BFw / f2 < 0.8 ··· (9) However, BFw: The back focus of the zoom lens at the wide-angle end when focused at infinity

[0074] Equation (9) is an equation for appropriately setting the ratio between the focal length of the second lens group and the back focus at the wide-angle end. By satisfying Equation (9), miniaturization of the zoom lens can be achieved. In this specification, "back focus" refers to the distance from the image-side surface vertex of the lens closest to the image plane at the wide-angle end when focused at infinity to the image plane.

[0075] When below the lower limit value of BFw / f2, the back focus may become long.

[0076] If it exceeds the upper limit of BFw / f2, the refractive power of the second lens group becomes too weak, and the moving distance for zooming of the second lens group may become large.

[0077] From the viewpoint of shortening the back focus and realizing miniaturization of the zoom lens, BFw / f2 is preferably greater than 0.45, more preferably greater than 0.50, and even more preferably greater than 0.52. From the viewpoint of making the refractive power of the second lens group within an appropriate range and shortening the moving distance during variable magnification of the second lens group to realize miniaturization of the zoom lens, BFw / f2 is preferably less than 0.75, more preferably less than 0.68, and even more preferably less than 0.60.

[0078] 1-3-10. Equation (10) 0.8 < G01R2 / fw < 5.0 ··· (10) However, G01R2: The radius of curvature of the image-side surface of the lens closest to the object side

[0079] Equation (10) is an equation for appropriately setting the ratio between the radius of curvature of the image-side surface of the lens closest to the object side and the focal length at the wide-angle end when the zoom lens is focused at infinity. By satisfying Equation (10), the depth of the image-side surface of the lens closest to the object side becomes within a suitable range.

[0080] If G01R2 is below the lower limit, the radius of curvature of the image-side surface of the lens closest to the object side becomes too small, and the surface may become too steep.

[0081] If G01R2 exceeds the upper limit, the refractive power of the lens closest to the object side may become too weak.

[0082] G01R2 / fw is preferably greater than 1.0, more preferably greater than 1.3, and even more preferably greater than 1.5, from the viewpoint of improving the manufacturability of the most object-side lens, by setting the depth of the image-side surface of the most object-side lens within an appropriate range. G01R2 / fw is preferably less than 4.0, more preferably less than 3.0, and even more preferably less than 2.0, from the viewpoint of strengthening the refractive power of the most object-side lens and realizing wide-angle and miniaturization of the zoom lens.

[0083] 1-3-11. Equation (11) PdC - 0.0008 × νd < 0.2652 ··· (11) However, PdC is the partial dispersion ratio defined by PdC = (Nd - NC) / (NF - NC), Here, Nd: Refractive power of the plastic lens with respect to the d-line NF: Refractive power of the plastic lens with respect to the F-line NC: Refractive power of the plastic lens with respect to the C-line

[0084] Equation (11) represents the relationship between the Abbe number with respect to the d-line of the plastic lens having a negative refractive power within the second lens group and the partial dispersion ratio defined by PdC = (Nd - NC) / (NF - NC).

[0085] By satisfying Equation (11), chromatic aberration generated within the second lens group can be corrected well, and high performance across the entire zoom region can be realized.

[0086] When PdC - 0.0008 × νd exceeds the upper limit, the partial dispersion ratio of the plastic lens having a negative refractive power within the second lens group becomes too large, and chromatic aberration may be overcorrected.

[0087] PdC - 0.0008 × νd is preferably less than 0.2647, more preferably less than 0.2644, and even more preferably less than 0.2637, from the viewpoint of chromatic aberration correction.

[0088] 2. Imaging device Next, an imaging device according to an embodiment of the present invention will be described. The imaging device includes the zoom lens according to the above-described embodiment and an imaging element provided on the image plane side of the zoom lens that converts the optical image formed by the zoom lens into an electrical signal.

[0089] Here, there is no limitation on the imaging element, and solid-state imaging elements such as a CCD (Charge Coupled Device) sensor and a CMOS (Complementary Metal Oxide Semiconductor) sensor can be used for the imaging element, and a silver halide film, an infrared cut filter (IRCF), etc. can also be used. The imaging device according to the present embodiment is suitable for imaging devices using the above solid-state imaging elements such as digital cameras and video cameras. Further, the imaging device may be a lens-fixed imaging device in which the lens is fixed to the housing, or may be an interchangeable-lens imaging device such as a single-lens reflex camera and a mirrorless single-lens camera. In particular, the zoom lens according to the present embodiment can secure a back focus suitable for an interchangeable lens system. Therefore, it is suitable for imaging devices such as a single-lens reflex camera equipped with an optical viewfinder, a phase difference sensor, and a reflex mirror for branching light thereto.

[0090] FIG. 13 is a diagram schematically showing an example of the configuration of the imaging device according to the present embodiment. As shown in FIG. 13, the mirrorless single-lens camera 1 has a main body 2 and a lens barrel 3 detachable from the main body 2. The lens barrel 3 includes a zoom lens therein, and the zoom lens is configured by the lens barrel 3 and the zoom lens. The mirrorless single-lens camera 1 is an aspect of the imaging device.

[0091] The zoom lens includes a first lens group G1 to a third lens group G3. The zoom lens is configured to satisfy, for example, the above-described formulas (1) to (3). Note that an aperture S is disposed on the object side of the lens L4 included in the second lens group G2.

[0092] The first lens group G1 has a negative refractive power as a whole and is composed of lenses L1 to L3. The second lens group G2 has a positive refractive power as a whole and is composed of lenses L4 to L7. The third lens group G3 has a positive refractive power as a whole and is composed of lenses L8 and L9.

[0093] The main body 2 has a CCD sensor I as an imaging element and a cover glass CG. The CCD sensor I is arranged at a position in the main body 2 where the optical axis OA of the zoom lens in the lens barrel 3 attached to the main body 2 serves as the central axis. The main body 2 may have a parallel plane plate having no substantial refractive power, such as an infrared cut filter (IRCF), instead of the cover glass CG.

[0094] Since the mirrorless single-lens camera 1 includes a zoom lens, high optical performance and miniaturization of the product can be achieved simultaneously.

[0095] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0096] (Summary) The zoom lens according to Aspect 1 of the present invention has a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group, which are arranged in order from the object side to the image plane side. During zooming, the first lens group and the second lens group move so that the interval between adjacent lens groups changes. The first lens group has at least two lenses having a negative refractive power and at least one lens having a positive refractive power. The second lens group has a plastic lens having a negative refractive power. The following formulas (1) to (3) are satisfied. 1.55 < Nd < 1.90 ··· (1) 10.0 < νd < 40.0 ··· (2) 1.0 < |fp / f2| < 5.0 ··· (3) However, Nd: Refractive index of the Nd: plastic lens with respect to the d-line νd: Abbe number of the plastic lens based on the d-line fp: Focal length of the plastic lens f2: Focal length of the second lens group

[0097] The zoom lens according to Embodiment 2 of the present invention satisfies the following formula (4) in Embodiment 1. 1.5 < |f1 / fw| < 2.75 ··· (4) However, f1: Focal length of the first lens group fw: Focal length at the wide-angle end when the zoom lens is focused at infinity

[0098] The zoom lens according to Embodiment 3 of the present invention satisfies the following formula (5) in Embodiment 1 or 2. 0.80 < |f1 / f2| < 1.20 ··· (5)

[0099] The zoom lens according to Embodiment 4 of the present invention satisfies the following formula (6) in any one of Embodiments 1 to 3. 1.5 < β2t / β2w < 4.0 ··· (6) However, β2t: Lateral magnification at the telephoto end when the second lens group is focused at infinity β2w: Lateral magnification at the wide-angle end when the second lens group is focused at infinity

[0100] The zoom lens according to Embodiment 5 of the present invention satisfies the following formula (7) in any one of Embodiments 1 to 4. 1.50 < |f2 / fw| < 3.50 ··· (7)

[0101] The zoom lens according to Embodiment 6 of the present invention has at least one lens having a positive refractive power in the second lens group in any one of Embodiments 1 to 5, and satisfies the following formula (8). 65.0 < νd_ave < 90 ··· (8) However, νd_ave: Average value of Abbe number based on the d-line of the lens having positive refractive power within the second lens group

[0102] The zoom lens according to aspect 7 of the present invention satisfies the following formula (9) in any of aspects 1 to 6. 0.4 < BFw / f2 < 0.8 ··· (9) However,[[]] BFw: Back focus of the zoom lens at the wide-angle end when focused at infinity

[0103] The zoom lens according to aspect 8 of the present invention satisfies the following formula (10) in any of aspects 1 to 7. 0.8 < G01R2 / fw < 5.0 ··· (10) However,[[]] G01R2: Radius of curvature of the surface on the image plane side of the lens closest to the object side

[0104] The zoom lens according to aspect 9 of the present invention satisfies the following formula (11) in any of aspects 1 to 8. PdC - 0.0008×νd < 0.2652 ··· (11) However,[[]] PdC is the partial dispersion ratio defined by PdC = (Nd - NC) / (NF - NC), Here,[[]] Nd: Refractive power of the plastic lens with respect to the d-line NF: Refractive power of the plastic lens with respect to the F-line NC: Refractive power of the plastic lens with respect to the C-line

[0105] The imaging device according to aspect 10 of the present invention includes any one of the zoom lenses according to aspects 1 to 9, and a solid-state imaging device that converts the optical image formed by the zoom lens into an electrical signal.

Example

[0106] One embodiment of the present invention will be described below. In each of the following tables, unless otherwise specified, all units of length are "mm", all units of the angle of view are "°", and "E+a" means "×10a indicates ".

[0107] [Example 1] (1) Configuration of the optical system FIG. 1 is a diagram schematically showing the optical configuration at infinity focus at the wide-angle end in the zoom lens of Example 1. The zoom lens according to Example 1 is composed of, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. The lens L7 corresponds to a plastic lens having a negative refractive power included in the second lens group G2.

[0108] The first lens group G1 is composed of, in order from the object side, a concave meniscus lens L1, a biconcave lens L2, and a convex meniscus lens L3.

[0109] The second lens group G2 is composed of, in order from the object side, a biconvex lens L4, a cemented lens of a concave meniscus lens L5 and a biconvex lens L6, and a biconcave lens L7.

[0110] The third lens group G3 is composed of, in order from the object side, a biconcave lens L8 and a biconvex lens L9.

[0111] The aperture stop S is disposed on the object side of the second lens group G2. "CG" is a cover glass, and "I" is an image plane. Since these points are the same in the diagrams schematically showing the optical configurations shown in other embodiments, the description will be omitted below.

[0112] When focusing from an infinite object to a close object, the first lens group G1 is moved toward the object side. Since this point is the same in the diagrams schematically showing the optical configurations shown in other embodiments, the description will be omitted below.

[0113] In Example 1, the zoom lens performs zooming by changing the air interval on the optical axis between adjacent lens groups. The arrows in FIG. 1 indicate the moving direction and moving pattern of each lens group when zooming from the wide-angle end to the telephoto end. When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image plane side and then moves toward the object side. Here, the position of the first lens group G1 at the telephoto end is on the image plane side with respect to the position at the wide-angle end. When zooming from the wide-angle end to the telephoto end, the second lens group G2 gradually moves toward the object side. The third lens group G3 is fixed in the optical axis direction with respect to the image plane.

[0114] (2) Numerical Example Next, a numerical example applying the specific numerical values of the zoom lens will be described. Table 1 shows the data of each surface included in the zoom lens of Example 1.

[0115] In the table, "r" represents the radius of curvature, and "d" represents the lens thickness or the lens interval. Also, "Nd" represents the refractive index with respect to the d-line (wavelength λ = 587.56 nm), and "νd" represents the Abbe number with respect to the d-line. "PdC" represents the partial dispersion ratio defined by (Nd - NC) / (NF - NC). Also, the mark "*" in the table indicates that it is an aspherical lens, and "S" represents the aperture stop. "INF" means infinity. The display such as "D(6)" in the column of "d" indicates that it is a variable interval in which the interval on the optical axis of the lens surface changes during zooming or focusing.

[0116] In Table 1, surface numbers 1 to 6 are the surface numbers of the lenses of the lens group G1, and surface numbers 7 to 14 are the surface numbers of the second lens group G2. Surface number 7 represents the aperture stop. Surface numbers 15 to 18 are the surface numbers of the third lens group G3. Surface numbers 19 and 20 represent the cover glass (CG), and surface number 21 represents the image plane.

[0117] [Table 1] Surface number r d Nd νd PdC 1 -2952.9222 0.6500 1.65844 50.85 2 5.7134 3.5629 3 -15.6893 0.5000 1.49700 81.61 4 11.2672 0.4093 5 10.6957 1.7299 2.00069 25.46 6 29.7877 D(6) 7S INF 0.0000 8* 6.4416 3.3784 1.55332 71.68 9* -9.0174 0.1846 10 -59.7677 0.5000 1.54072 47.20 11 4.1426 3.1100 1.49700 81.61 12 -10.0621 0.2633 13* -31.9345 0.6000 1.61609 25.79 0.2832 14* 17.3627 D(14) 15* -12.0965 0.6000 1.61609 25.79 16* 30.4657 0.2285 17 31.2547 2.1436 1.95375 32.32 18 -11.1534 3.1500 19 INF 0.8000 1.51680 64.20 20 INF 0.5000 21 INF

[0118] Table 2 shows the specifications of the zoom lens of Example 1.

[0119] [Table 2] Wide-angle end Telephoto end Focal length (mm) 3.5000 9.1008 FNo 1.86 2.94 Angle of view (°) 132.3 42.8 Image height (mm) 3.4000 3.4000 D6 10.7622 1.5032 D14 1.7071 8.8533

[0120] Table 3 shows the aspherical coefficients of the aspherical surfaces of the zoom lens of Example 1. The aspherical coefficients in this table are expressed by the following formula (I), where the height perpendicular to the optical axis is H, the displacement amount in the optical axis direction at the height H with the vertex of the surface as the origin is X(H), the paraxial curvature radius is R, the conic coefficient is k, and the aspherical coefficients of the 4th, 6th, 8th, and 10th orders are A, B, C, D, and E, respectively.

[0121]

Equation

[0122] [Table 3] K A B C D 8 0 -7.46722e-04 -2.89526e-05 -6.38892e-08 -2.29655e-07 9 0 5.29980e-04 -5.49446e-05 -8.48467e-07 -5.73084e-08 13 0 -1.06226e-05 -2.82312e-04 1.53417e-05 -2.39972e-07 14 0 5.63300e-04 -1.37995e-04 -9.67704e-07 1.06315e-06 15 0 -9.68417e-05 2.69780e-05 3.24663e-06 -3.47181e-07 16 0 2.11252e-04 8.64453e-06 2.89835e-06 -2.54274e-07

[0123] Table 4 shows the focal lengths of the respective lens groups of the zoom lens of Example 1.

[0124] [Table 4] Group number Start surface - End surface Group focal length G1 1-6 -7.48 G2 7-14 8.20 G3 15-18 19.11

[0125] Fig. 2 shows the longitudinal aberration diagram at infinity focus at the wide-angle end of the zoom lens of Example 1. Fig. 3 shows the longitudinal aberration at infinity focus at the telephoto end of the zoom lens of Example 1. In each drawing, from the left side toward the drawing, they are spherical aberration (mm), astigmatism (mm), and distortion (%) respectively.

[0126] In the diagram representing spherical aberration, the vertical axis is the ratio to the open F value, and the horizontal axis is defocus. In each figure, the dotted line indicates the g line (wavelength λ = 435.84 nm), the solid line indicates the d line (wavelength λ = 587.56 nm), and the dashed line indicates the C line (wavelength λ = 656.27 nm) respectively.

[0127] In the diagram showing astigmatism, the vertical axis is the image height (mm), and the horizontal axis is defocus. In each figure, the solid line indicates the sagittal image plane (S) for the d line, and the dotted line indicates the meridional image plane (T) for the d line respectively.

[0128] In the diagram representing distortion, the vertical axis is the image height (mm), and the horizontal axis is %.

[0129] [Example 2] (1) Configuration of the optical system Fig. 4 is a diagram schematically showing the optical configuration at infinity focus at the wide-angle end in the zoom lens of Example 2. The zoom lens according to Example 2 is composed of a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power in order from the object side. The lens L7 corresponds to a plastic lens having a negative refractive power included in the second lens group G2.

[0130] The first lens group G1 is composed of a concave meniscus lens L1, a biconcave lens L2, and a convex meniscus lens L3 in order from the object side.

[0131] The second lens group G2 is composed of a biconvex lens L4, a cemented lens of a concave meniscus lens L5 and a biconvex lens L6, and a biconcave lens L7 in order from the object side.

[0132] The third lens group G3 is composed of, in order from the object side, a concave meniscus lens L8 and a biconvex lens L9.

[0133] In Embodiment 2, the zoom lens performs zooming by changing the air interval on the optical axis between adjacent lens groups. The arrows in Fig. 4 indicate the moving direction and moving pattern of each lens group during zooming from the wide-angle end to the telephoto end. When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image plane side and then moves toward the object side. Here, the position of the first lens group G1 at the telephoto end is on the image plane side with respect to the position at the wide-angle end. When zooming from the wide-angle end to the telephoto end, the second lens group G2 gradually moves toward the object side. The third lens group G3 is fixed in the optical axis direction with respect to the image plane.

[0134] (2) Numerical Example Table 5 shows the data of each surface included in the zoom lens of Embodiment 2.

[0135] [Table 5] Surface number r d Nd νd PdC 1 195.7958 0.7000 1.65843 50.85 2 5.6547 3.0902 3 -21.0507 0.6000 1.49700 81.61 4 11.5685 1.7756 5 12.5205 1.3210 2.00271 19.32 6 22.8170 D(6) 7S INF 0.0000 8* 6.2809 3.2066 1.53504 55.71 9* -12.9216 0.2079 10 27.0906 0.5999 1.60342 38.01 11 4.4426 2.8880 1.49700 81.61 12 -7.6097 0.3004 13* -12.8330 0.5998 1.61609 25.79 0.2832 14* 25.3110 D(14) 15* -4.5832 0.6000 1.61609 25.79 16* -8.2215 0.1478 17 119.0765 2.0838 1.91082 35.25 18 -9.5715 2.8975 19 INF 0.8000 1.51680 64.20 20 INF 1.0000 21 INF

[0136] Table 6 shows the specifications of the zoom lens of Example 2.

[0137] [Table 6] Wide-angle end Telephoto end Focal length (mm) 3.519 8.2514 FNo 1.86 2.83 Angle of view (°) 124.8 47.6 Image height (mm) 3.4000 3.4000 D6 9.5920 1.5207 D14 2.3227 8.9707

[0138] Table 7 shows the aspherical coefficients of the aspherical surfaces of the zoom lens of Example 2.

[0139] [Table 7] K A B C D 8 0 -2.64532e-04 1.50521e-05 -5.68206e-07 6.28915e-08 9 0 1.50480e-03 5.15519e-06 2.96993e-07 1.08639e-07 13 0 6.80443e-03 -7.91122e-04 5.17900e-05 -1.39325e-06 14 0 7.32599e-03 -7.10174e-04 4.49526e-05 -1.03409e-06 15 0 4.78701e-03 -2.35635e-04 1.89638e-05 -5.62812e-07 16 0 3.75235e-03 -1.90459e-04 9.85725e-06 -2.61553e-07

[0140] Table 8 shows the focal lengths of the respective lens groups of the zoom lens of Example 2.

[0141] [Table 8] Group number Starting surface - Ending surface Group focal length G1 1-6 -6.99 G2 8-14 8.34 G3 15-18 17.25

[0142] Fig. 5 shows a longitudinal aberration diagram at infinity focus at the wide-angle end of the zoom lens of Example 1. Fig. 6 shows the longitudinal aberration at infinity focus at the telephoto end of the zoom lens of Example 1.

[0143] [Example 3] (1) Configuration of the optical system Fig. 7 is a diagram schematically showing the optical configuration at infinity focus in the zoom lens of Example 3. The zoom lens according to Example 3 is composed of, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. The lens L7 corresponds to a plastic lens having a negative refractive power included in the second lens group G2.

[0144] The first lens group G1 is composed of, in order from the object side, a biconcave lens L1, a biconcave lens L2, and a convex meniscus lens L3.

[0145] The second lens group G2 is composed of, in order from the object side, a biconvex lens L4, a cemented lens of a concave meniscus lens L5 and a biconvex lens L6, and a biconcave lens L7.

[0146] The third lens group G3 is composed of, in order from the object side, a concave meniscus lens L8 and a biconvex lens L9.

[0147] In Example 3, the zoom lens performs zooming by changing the air interval on the optical axis between adjacent lens groups. The arrows in FIG. 7 indicate the moving direction and moving pattern of each lens group during zooming from the wide-angle end to the telephoto end. When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image plane side and then moves toward the object side. Here, the position of the first lens group G1 at the telephoto end is on the image plane side relative to its position at the wide-angle end. When zooming from the wide-angle end to the telephoto end, the second lens group G2 gradually moves toward the object side. The third lens group G3 is fixed in the optical axis direction with respect to the image plane.

[0148] (2) Numerical Example Table 9 shows the data of each surface included in the zoom lens of Example 3.

[0149] [Table 9] Surface number r d Nd νd PdC 1 -128.4331 0.6500 1.65844 50.85 2 5.6874 3.6304 3 -17.0051 0.5000 1.49700 81.61 4 10.6205 0.4513 5 10.5369 1.9161 2.00069 25.46 6 28.8278 D(6) 7S INF 0.0000 8* 6.4576 3.3800 1.55332 71.68 9* -10.5891 0.3098 10 -74.8717 0.5000 1.53172 48.84 11 4.5776 2.8081 1.49700 81.61 12 -12.4134 0.2650 13* -83.0957 0.6500 1.68103 18.15 0.2741 14* 22.8784 D(14) 15* -5.4816 0.6300 1.61609 25.79 16* -5.7964 0.1789 17 35.0000 1.6704 1.80610 40.73 18 -69.0307 2.6500 19 INF 0.8000 1.51680 64.20 20 INF 1.0000 21 INF

[0150] Table 10 shows the specifications of the zoom lens of Example 3.

[0151] [Table 10] Wide-angle end Telephoto end Focal length (mm) 3.5036 8.2673 FNo 1.91 2.83 Angle of view (°) 143.8 48.0 Image height (mm) 3.4000 3.4000 D6 10.4921 1.9432 D14 2.0420 8.2938

[0152] Table 11 shows the aspherical coefficients of the aspherical lenses of Example 3.

[0153] [Table 11] K A B C D 8 0 -6.74497e-04 -2.99262e-05 3.25966e-07 -2.40740e-07 9 0 2.29759e-04 -3.49864e-05 -3.06885e-06 2.73024e-08 13 0 -3.33390e-04 -8.17724e-05 -1.92271e-05 1.53808e-06 14 0 4.73062e-04 -3.30684e-05 -1.96155e-05 1.80914e-06 15 0 5.84331e-04 -2.42950e-04 4.51268e-05 -2.27647e-06 16 0 5.01107e-04 -2.30373e-04 3.54345e-05 -1.58956e-06

[0154] Table 12 shows the focal lengths of the respective lens groups of the zoom lens of Example 3.

[0155] [Table 12] Group number Start surface - End surface Group focal length G1 1 - 6 -7.17 G2 7 - 14 8.26 G3 15 - 18 28.95

[0156] Fig. 8 shows the longitudinal aberration diagram at infinity focus at the wide - angle end of the zoom lens of Example 3. Fig. 9 shows the longitudinal aberration at infinity focus at the telephoto end of the zoom lens of Example 3.

[0157] [Example 4] (1) Configuration of the optical system Fig. 10 is a diagram schematically showing the optical configuration at infinity focus in the zoom lens of Example 4. The zoom lens according to Example 4 is composed of, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. The lens L7 corresponds to a plastic lens having a negative refractive power included in the second lens group G2.

[0158] The first lens group G1 is composed of, in order from the object side, a biconcave lens L1, a biconcave lens L2, and a convex meniscus lens L3.

[0159] The second lens group G2 is composed of, in order from the object side, a biconvex lens L4, a cemented lens of a concave meniscus lens L5 and a biconvex lens L6, and a biconcave lens L7.

[0160] The third lens group G3 is composed of, in order from the object side, a concave meniscus lens L8 and a biconvex lens L9.

[0161] In Example 4, the zoom lens performs zooming by changing the air interval on the optical axis between adjacent lens groups. The arrows in FIG. 10 indicate the moving directions and moving patterns of the respective lens groups during zooming from the wide-angle end to the telephoto end. When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image plane side and then moves toward the object side. Here, the position of the first lens group G1 at the telephoto end is on the image plane side with respect to the position at the wide-angle end. When zooming from the wide-angle end to the telephoto end, the second lens group G2 gradually moves toward the object side. The third lens group G3 is fixed in the optical axis direction with respect to the image plane.

[0162] (2) Numerical Example Table 13 shows the data of each surface included in the zoom lens of Example 4. [Table 13] Surface number r d Nd νd PdC 1 -121.6952 0.6500 1.65844 50.85 2 5.6967 3.6612 3 -15.6899 0.5000 1.49700 81.61 4 11.2020 0.4642 5 11.0263 1.9287 2.00069 25.46 6 33.0051 D(6) 7S INF 0.0000 8* 6.7519 3.3800 1.55332 71.68 9* -10.5119 0.2235 10 -75.1341 0.5000 1.53172 48.84 11 4.6107 2.8173 1.55032 75.50 12 -13.1145 0.2943 13* -32.8784 0.6500 1.65605 21.26 0.2795 14 * 20.2791 D(14) 15 * -5.4541 0.6300 1.63975 23.50 16 * -6.0576 0.3702 17 35.0000 1.5420 1.80610 40.73 18 -39.1530 2.6500 19 INF 0.8000 1.51680 64.20 20 INF 1.0000 21 INF

[0163] Table 14 shows the specifications of the zoom lens of Example 4.

[0164] [Table 14] Wide-angle end Telephoto end Focal length (mm) 3.5056 8.2682 FNo 1.91 2.86 Angle of view (°) 143.9 48.1 Image height (mm) 3.4000 3.4000 D6 10.4891 1.9754 D14 2.0665 8.3420

[0165] Table 15 shows the aspherical coefficients of the aspherical lenses of Example 4.

[0166] [Table 15] K A B C D 8 0 -6.78651e-04 -2.93119e-05 3.45833e-08 -2.11825e-07 9 0 1.49552e-04 -3.40856e-05 -2.79308e-06 2.98571e-08 13 0 6.55202e-04 -1.28381e-04 -1.37735e-05 1.49035e-06 14 0 1.70916e-03 -6.24622e-05 -1.62553e-05 1.91219e-06 15 0 5.47337e-04 6.63884e-08 9.30278e-06 -3.14562e-07 16 0 3.22840e-04 -2.75321e-05 8.37328e-06 -2.78953e-07

[0167] Table 16 shows the focal lengths of the respective lens groups of the zoom lens of Example 4.

[0168] [Table 16] Group number Start surface - End surface Group focal length G1 1 - 6 -7.20 G2 7 - 14 8.26 G3 15 - 18 26.00

[0169] Fig. 11 shows the longitudinal aberration diagram at infinity focus at the wide-angle end of the zoom lens of Example 4. Fig. 12 shows the longitudinal aberration at infinity focus at the telephoto end of the zoom lens of Example 4.

[0170] The calculated values according to the above-mentioned various formulas in Examples 1 to 4 are shown in Table 17.

[0171] [Table 17] Example 1 Example 2 Example 3 Example 4 Formula (1) 1.61609 1.61609 1.65605 1.68103 Formula (2) 25.79 25.79 21.26 18.15 Formula (3) 2.20 1.65 3.18 2.30 Formula (4) 2.14 1.99 2.05 2.05 Formula (5) 0.91 0.84 0.87 0.87 Formula (6) 2.6 2.34 2.36 2.36 Formula (7) 2.34 2.37 2.36 2.36 Formula (8) 76.65 76.65 76.65 73.59 Formula (9) 0.54 0.56 0.54 0.54 Formula (10) 1.63 1.61 1.62 1.63 Formula (11) 0.2625 0.2625 0.2596 0.2625

Explanation of Symbols

[0172] 1 Mirrorless Single-lens Camera (Imaging Device) 2 Body 3 Lens Barrel

Claims

1. A zoom lens having, in order from the object side to the image plane side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group, wherein, during zooming, the first lens group and the second lens group move so that the distance between adjacent lens groups changes, the first lens group having at least two lenses having a negative refractive power and at least one lens having a positive refractive power, the second lens group having a plastic lens having a negative refractive power, and satisfying the following formulas (1) to (3). 1.55 < Nd < 1.90... (1) 10.0 < νd < 40.0... (2) 1.0 < |fp / f2| < 5.0... (3) However, Nd: refractive index of the plastic lens with respect to the d-line νd: Abbe number of the plastic lens based on the d-line fp: focal length of the plastic lens f2: focal length of the second lens group

2. The zoom lens according to claim 1, satisfying the following formula (4). 1.5 < |f1 / fw| < 2.75... (4) However, f1: focal length of the first lens group fw: focal length at the wide-angle end when the zoom lens is focused at infinity

3. The zoom lens according to claim 1, satisfying the following formula (5). 0.80 < |f1 / f2| < 1.20... (5)

4. The zoom lens according to claim 1, satisfying the following formula (6). 1.5 < β2t / β2w < 4.0... (6) However, β2t: lateral magnification at the telephoto end when the second lens group is focused at infinity β2w: lateral magnification at the wide-angle end when the second lens group is focused at infinity

5. The zoom lens according to claim 1, satisfying the following formula (7). 1.50 < |f2 / fw| < 3.50... (7)

6. The second lens group having at least one lens having a positive refractive power, The zoom lens according to claim 1, satisfying the following formula (8). 65.0 < νd_ave < 90... (8) However, νd_ave: average value of the Abbe numbers of the lenses having a positive refractive power within the second lens group based on the d-line

7. The zoom lens according to claim 1, satisfying the following formula (9). 0.4 < BFw / f2 < 0.8... (9) However, BFw: back focus of the zoom lens at the wide-angle end when focused at infinity

8. The zoom lens according to claim 1, satisfying the following formula (10). 0.8 < G01R2 / fw < 5.0... (10) However, G01R2: The radius of curvature of the surface on the image plane side of the lens closest to the object

9. The zoom lens according to claim 1, satisfying the following formula (11). PdC - 0.0008 × νd < 0.2652... (11) However, PdC is the partial dispersion ratio defined by (Nd - NC) / (NF - NC), Here, Nd: The refractive power of the plastic lens with respect to the d-line NF: The refractive power of the plastic lens with respect to the F-line NC: The refractive power of the plastic lens with respect to the C-line

10. An imaging device comprising: the zoom lens according to any one of claims 1 to 9, and a solid-state imaging device that converts an optical image formed by the zoom lens into an electrical signal.

Images