Zoom lens, imaging device having the same, and imaging system

Abstract

To provide a compact and wide-angle zoom lens having high optical performance in the entire zoom range, and an imaging device having the zoom lens, and an imaging system.SOLUTION: Provided is a zoom lens comprising a first lens group of negative refractive power, a second lens group of positive refractive power, an n-1'th lens group of negative refractive power and an n'th lens group of positive refractive power, arranged in order from the object side to the image side. The n-1'th and the n'th lens groups move on the occasion of zooming. The n'th lens group is arranged on the most image side, and the n-1'th lens group is arranged adjacent to the object side of the n'th lens group. An aperture diaphragm is arranged between the most image-side lens face of the first lens group and the most image-side lens face of the second lens group. The focal distance of the n'th lens group, the focal distance of the n-1'th lens group, the distance on an optical path from the most image-side lens face at a wide angle end to the paraxial image face position, the movement amounts of the n'th and the n-1'th lens groups on the occasion of zooming from the wide angle end to the telephoto end are appropriately set, respectively.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a zoom lens, and is suitable for digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, surveillance cameras, and the like.

Background Art

[0002] In recent years, zoom lenses used in imaging devices have been required to have high optical performance over the entire zoom range, be small in size, and have a wide angle of view as the imaging devices become more highly functional. As a zoom lens that is small in size and relatively easy to widen the angle of view, a negative-lead type zoom lens in which a lens group with negative refractive power precedes (is located closest to the object side) is known. As a negative-lead type zoom lens, Patent Document 1 discloses a zoom lens including first to fourth lens groups with negative, positive, negative, and positive refractive powers arranged in order from the object side to the image side. Further, Patent Document 2 discloses a zoom lens including first to fifth lens groups with negative, positive, positive, negative, and positive refractive powers arranged in order from the object side to the image side.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Disclosure of the Invention

Problems to be Solved by the Invention

[0004] In a negative rear-focus type zoom lens, since the lens configuration is asymmetric, it is difficult to correct various aberrations, and it is difficult to obtain high optical performance while achieving miniaturization. For example, in order to achieve a wide-angle conversion in a negative rear-focus type zoom lens, it is necessary to increase the power of the first lens group with negative refractive power. In this case, significant barrel distortion will occur. In order to obtain high optical performance throughout the entire zoom range while achieving miniaturization and wide-angle conversion, it is important to appropriately set the refractive power and the arrangement position of the lens group arranged near the image plane.

[0005] An object of the present invention is to provide a zoom lens having high optical performance throughout the entire zoom range, a compact and wide-angle zoom lens, an imaging device having the same, and an imaging system.

Means for Solving the Problems

[0006] The 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, an (n-1)th lens group having a negative refractive power, and an nth lens group having a positive refractive power, which are arranged in order from the object side to the image side. During zooming, the interval between adjacent lens groups changes, and the (n-1)th lens group and the nth lens group move during zooming. The nth lens group is arranged closest to the image side, the (n-1)th lens group is arranged adjacent to the object side of the nth lens group, the first lens group has a negative meniscus lens with a convex surface facing the object side, the aperture stop is arranged between the most image-side lens surface of the first lens group and the most image-side lens surface of the second lens group. Let the focal length of the nth lens group be fn, the focal length of the (n-1)th lens group be fn1, the distance on the optical axis from the most image-side lens surface at the wide-angle end to the paraxial image plane position be bfw, the movement amount of the nth lens group during zooming from the wide-angle end to the telephoto end be Mn, and the movement amount of the (n-1)th lens group during zooming from the wide-angle end to the telephoto end be Mn1. When the moving direction of the lens group toward the object side is defined as the positive direction Let the focal length of the first lens group be f1 and then, -0.50 < fn1 / fn < -0.20 4.00 < fn / bfw < 8.00 0.20 < Mn / Mn1 < 0.60 0.80 < fn1 / f1 < 1.50 A zoom lens characterized by satisfying the following conditional expression.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a zoom lens having high optical performance in the entire zoom range, being small-sized and having a wide angle of view, and an imaging device and an imaging system having the same.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Modes for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same members are denoted by the same reference numerals, and duplicate descriptions are omitted.

[0010] Figs. 1, 3, 5, and 7 are cross-sectional views of the wide-angle ends of the zoom lenses of Embodiments 1 to 4, respectively. The zoom lenses of each embodiment are used in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, and surveillance cameras.

[0011] In each cross-sectional view, the left side is the object side and the right side is the image side. The zoom lens of each embodiment is configured to have a plurality of lens groups. In the present specification, a lens group is a collection of lenses that move or remain stationary integrally during zooming. That is, in the zoom lens of each embodiment, the distance between adjacent lens groups changes during zooming. The arrows shown in each cross-sectional view represent the moving directions of the lens groups during zooming. Note that a lens group may be composed of one lens or a plurality of lenses. Further, a lens group may include an aperture stop.

[0012] The zoom lens of each embodiment has a first lens group with negative refractive power, a second lens group with positive refractive power, an (n - 1)th lens group with negative refractive power, and an nth lens group with positive refractive power, which are arranged in order from the object side to the image side. The nth lens group is arranged on the most image side, and the (n - 1)th lens group is adjacent to the nth lens group. The aperture stop is arranged between the most image-side lens surface of the first lens group and the most image-side lens surface of the second lens group. At least the (n - 1)th lens group and the nth lens group move during zooming.

[0013] In each cross-sectional view, Li (i is a natural number) represents the i-th lens group counted from the object side among the lens groups included in the zoom lens.

[0014] Also, SP is the aperture stop. IP is the image plane. When the zoom lens of each embodiment is used as the imaging optical system of a digital still camera or a digital video camera, the imaging surface of a solid-state imaging device (photoelectric conversion element) such as a CCD sensor or a CMOS sensor is arranged. When the zoom lens of each embodiment is used as the imaging optical system of a silver halide film camera, a photosensitive surface corresponding to the film surface is placed on the image plane IP.

[0015] Figs. 2(A), 4(A), 6(A), and 8(A) are aberration diagrams at the wide-angle end of the zoom lenses of Examples 1 to 4, respectively. Figs. 2(B), 4(B), 6(B), and 8(B) are aberration diagrams at the intermediate zoom positions of the zoom lenses of Examples 1 to 4, respectively. Figs. 2(C), 4(C), 6(C), and 8(C) are aberration diagrams at the telephoto end of the zoom lenses of Examples 1 to 4, respectively.

[0016] In the spherical aberration diagram, Fno is the F-number, showing the spherical aberration amounts for the d-line (wavelength 587.6 nm) and g-line (wavelength 435.8 nm). In the astigmatism diagram, ΔS shows the astigmatism amount on the sagittal image plane, and ΔM shows the astigmatism amount on the meridional image plane. The distortion aberration diagram shows the distortion aberration amount for the d-line. The chromatic aberration diagram shows the chromatic aberration amount for the g-line. ω is the imaging semi-field angle (°).

[0017] Next, the characteristic configurations of the zoom lenses of each example will be described.

[0018] When the focal length of the n-th lens group Ln is fn and the focal length of the (n - 1)-th lens group Ln-1 is fn1, the zoom lenses of each example satisfy the following conditional expression (1).

[0019] -0.50 < fn1 / fn < -0.20 (1) Conditional expression (1) defines the ratio of the focal length of the n-th lens group to the focal length of the (n - 1)-th lens group in order to achieve both off-axis aberration correction such as field curvature and miniaturization of the zoom lens. If the focal length of the (n - 1)-th lens group becomes shorter exceeding the upper limit value of conditional expression (1), it becomes difficult to correct off-axis aberrations such as field curvature, which is not preferable. If the focal length of the (n - 1)-th lens group becomes longer falling below the lower limit value of the conditional expression (1), the distance from the front lens to the entrance pupil position becomes too long. In that case, in order to sufficiently secure the light amount at the peripheral part of the image at the wide-angle end, the front lens diameter becomes too large, which is not preferable.

[0020] Also, when the distance on the optical axis from the most image-side lens surface at the wide-angle end to the paraxial image plane position is defined as bfw, the zoom lens of each embodiment satisfies the following conditional expression (2).

[0021] 4.00 < fn / bfw < 8.00 (2) The conditional expression (2) defines the ratio of the focal length of the n-th lens group to the distance from the most image-side lens surface at the wide-angle end to the image plane in order to achieve both off-axis aberration correction such as field curvature and shortening of the overall length of the zoom lens. If the focal length of the n-th lens group becomes longer beyond the upper limit value of the conditional expression (2), it becomes difficult to shorten the overall length of the zoom lens and to reduce the diameter of the lens disposed on the object side of the n-th lens group, which is not preferable. If the focal length of the n-th lens group becomes shorter below the lower limit value of the conditional expression (2), it becomes difficult to correct off-axis aberrations such as field curvature, which is not preferable.

[0022] Also, when zooming from the wide-angle end to the telephoto end, the zoom lens of each embodiment satisfies the following conditional expression (3) when the movement amount of the n-th lens group Ln is Mn and the movement amount of the (n - 1)-th lens group Ln-1 is Mn1. Note that the positive direction of the movement of the lens group is the direction toward the object side.

[0023] 0.20 < Mn / Mn1 < 0.60 (3) The conditional expression (3) defines the ratio of the movement amounts of the n-th lens group Ln and the (n - 1)-th lens group Ln-1 when zooming from the wide-angle end to the telephoto end in order to obtain a sufficient zoom ratio while satisfactorily correcting off-axis aberrations such as coma and field curvature. If the movement amount of the n-th lens group Ln becomes larger than the movement amount of the (n - 1)-th lens group Ln-1 beyond the upper limit value of the conditional expression (3), it becomes difficult to correct coma and field curvature at the telephoto end, which is not preferable. If the movement amount of the n-th lens group Ln becomes smaller than the movement amount of the (n - 1)-th lens group Ln-1 below the lower limit value of the conditional expression (3), it becomes difficult to obtain a sufficient zoom ratio, which is not preferable.

[0024] By having the above-described configuration, it is possible to realize a zoom lens having high optical performance throughout the entire zoom range and being small-sized and wide-angle.

[0025] It is preferable that the numerical ranges of the conditional expressions (1) to (3) be the numerical ranges of the following conditional expressions (1a) to (3a).

[0026] -0.45 < fn1 / fn < -0.23 (1a) 4.30 < fn / bfw < 7.00 (2a) 0.26 < Mn / Mn1 < 0.58 (3a) Furthermore, it is more preferable that the numerical ranges of the conditional expressions (2) to (3) be the numerical ranges of the following conditional expressions (1b) to (3b).

[0027] -0.40 < fn1 / fn < -0.26 (1b) 4.60 < fn / bfw < 6.50 (2b) 0.32 < Mn / Mn1 < 0.56 (3b) When the focal length of the first lens group L1 is f1, it is desirable that the zoom lens of each example satisfy the following conditional expression (4).

[0028] 0.80 < fn1 / f1 < 1.50 (4) The conditional expression (4) defines the ratio of the focal lengths of the first lens group L1 and the (n - 1)-th lens group Ln-1 in order to realize miniaturization and wide-angle conversion of the zoom lens while satisfactorily correcting off-axis aberrations at the wide-angle end. If the focal length of the first lens group L1 becomes shorter than the upper limit value of the conditional expression (4), it becomes difficult to correct coma aberration and field curvature at the wide-angle end, which is not preferable. If the focal length of the first lens group L1 becomes longer than the lower limit value of the conditional expression (4), the front lens diameter becomes too large to sufficiently secure the amount of light in the peripheral part of the image at the wide-angle end, which is not preferable.

[0029] When the distance on the optical axis from the most image-side lens surface of the (n - 1)-th lens group Ln-1 to the image plane at the wide-angle end is bfwn-1, it is desirable that the zoom lens of each example satisfy the following conditional expression (5).

[0030] -1.30 < fn1 / bfwn-1 < -0.80 (5) Conditional expression (5) defines the ratio of the focal length of the (n - 1)-th lens group Ln-1 to the distance on the optical axis from the most image-side lens surface to the image plane in order to achieve both miniaturization of the zoom lens and good correction of off-axis aberrations while ensuring image-side telecentricity at the wide-angle end. If the focal length of the (n - 1)-th lens group Ln-1 becomes shorter than the upper limit value of conditional expression (5), it becomes difficult to correct coma aberration and field curvature while ensuring image-side telecentricity at the wide-angle end, which is not preferable. If the focal length of the (n - 1)-th lens group Ln-1 becomes longer than the lower limit value of conditional expression (5), it becomes difficult to miniaturize the zoom lens, which is not preferable.

[0031] For the zoom lens of each embodiment, when the distance on the optical axis from the most object-side lens surface to the aperture stop at the wide-angle end is LDwfs and the distance from the aperture stop to the image plane at the wide-angle end is LDwsi, it is desirable to satisfy the following conditional expression (6).

[0032] 0.50 < LDwfs / LDwsi < 1.00 (6) Conditional expression (6) defines the position of the aperture stop for miniaturization of the lens diameter. If the distance from the aperture stop to the most object-side lens surface becomes longer than the upper limit value of conditional expression (6), the front lens diameter becomes too large to sufficiently ensure the light amount at the image periphery at the wide-angle end, which is not preferable. If the distance from the aperture stop to the image plane becomes longer than the lower limit value of conditional expression (6), the rear lens diameter becomes too large to sufficiently ensure the light amount at the image periphery at the wide-angle end, which is not preferable.

[0033] For the zoom lens of each embodiment, when the focal length of the group adjacent to the object side of the (n - 1)-th lens group Ln-1 is fn2, it is desirable to satisfy the following conditional expression (7).

[0034] -1.40 < fn2 / fn1 < -0.70 (7) Conditional expression (7) defines the ratio of the focal length of the (n - 1)-th lens group Ln-1 to the focal length of the (n - 2)-th lens group Ln-2 for miniaturizing the lens diameter near the aperture stop. If the focal length of the (n - 2)-th lens group Ln-2 becomes shorter than the upper limit value of conditional expression (7), it becomes difficult to correct spherical aberration and coma aberration over the entire zoom range, which is not preferable. If the focal length of the (n - 2)-th lens group Ln-2 becomes longer than the lower limit value of conditional expression (7), it becomes difficult to miniaturize the lens diameter near the aperture stop, which is not preferable.

[0035] When the focal length of the zoom lens at the wide-angle end is fw, it is desirable for the zoom lens of each embodiment to satisfy the following conditional expression (8).

[0036] -1.60 < f1 / fw < -1.00 (8) Conditional expression (8) defines the ratio of the focal length of the first lens group L1 to the focal length of the zoom lens at the wide-angle end in order to realize miniaturization and wide-angleization of the zoom lens while correcting off-axis aberrations well at the wide-angle end. If the focal length of the first lens group L1 becomes shorter than the upper limit value of conditional expression (8) with respect to the focal length of the zoom lens at the wide-angle end, it becomes difficult to correct coma aberration and field curvature at the wide-angle end, which is not preferable. If the focal length of the first lens group L1 becomes longer than the lower limit value of conditional expression (8) with respect to the focal length of the zoom lens at the wide-angle end, the front lens diameter becomes too large to sufficiently secure the amount of light in the peripheral part of the image at the wide-angle end, which is not preferable.

[0037] When the focal length of the lens disposed most on the object side of the first lens group L1 is f11, it is desirable for the zoom lens of each embodiment to satisfy the following conditional expression (9).

[0038] 1.50 < f11 / f1 < 3.00 (9) In order to achieve miniaturization and wide-angle conversion of the zoom lens while satisfactorily correcting off-axis aberrations at the wide-angle end, conditional expression (9) defines the ratio of the focal length of the first lens group L1 to the focal length of the lens disposed closest to the object side of the first lens group L1. If the focal length of the lens disposed closest to the object side of the first lens group L1 becomes longer exceeding the upper limit value of conditional expression (9), the diameter of the lens disposed closest to the object side of the first lens group L1 becomes too large in order to sufficiently secure the amount of light in the peripheral part of the image at the wide-angle end, which is not preferable. If the focal length of the lens disposed closest to the object side of the first lens group L1 becomes shorter falling below the lower limit value of conditional expression (9), it becomes difficult to correct field curvature and distortion aberration at the wide-angle end, which is not preferable.

[0039] Note that it is preferable that the numerical ranges of conditional expressions (4) to (9) be the numerical ranges of conditional expressions (4a) to (9a) below.

[0040] 0.90 < fn1 / f1 < 1.47 (4a) -1.25 < fn1 / bfwn-1 < -0.86 (5a) 0.57 < LDwfs / LDwsi < 0.93 (6a) -1.30 < fn2 / fn1 < -0.73 (7a) -1.55 < f1 / fw < -1.06 (8a) 1.70 < f11 / f1 < 2.75 (9a) Furthermore, it is more preferable that the numerical ranges of conditional expressions (4) to (9) be the numerical ranges of conditional expressions (4b) to (9b) below.

[0041] 1.00 < fn1 / f1 < 1.43 (4b) -1.20 < fn1 / bfwn-1 < -0.92 (5b) 0.64 < LDwfs / LDwsi < 0.85 (6b) -1.20 < fn2 / fn1 < -0.76 (7b) -1.50 < f1 / fw < -1.12 (8b) 1.90 < f11 / f1 < 2.50 (9b) Further, the first lens group L1 preferably consists of a first lens with negative refractive power, a second lens with negative refractive power, a third lens with negative refractive power, and a fourth lens with positive refractive power, which are arranged in order from the object side to the image side. By arranging a plurality of negative lenses, the refractive power of each negative lens can be appropriately dispersed, so that coma aberration, field curvature, and distortion aberration at the wide-angle end can be corrected well.

[0042] Also, as in Embodiments 1 to 3, the second lens group L2 preferably consists of a first lens with positive refractive power, a cemented lens of a second lens with negative refractive power and a third lens with positive refractive power, which are arranged in order from the object side to the image side. Further, as in Embodiment 4, the second lens group L2 preferably consists of a first lens with positive refractive power, a cemented lens of a second lens with negative refractive power and a third lens with positive refractive power, and a fourth lens with positive refractive power, which are arranged in order from the object side to the image side. With such a configuration, spherical aberration and coma aberration can be corrected well over the entire zoom range.

[0043] Also, the (n - 1)-th lens group Ln-1 preferably consists of two or fewer negative lenses. With such a configuration, coma aberration and field curvature can be corrected well over the entire zoom range.

[0044] Also, the n-th lens group Ln preferably consists of one lens with positive refractive power. With such a configuration, while being small-sized, telecentricity on the image side can be ensured well over the entire zoom range.

[0045] Next, the zoom lenses of each embodiment will be described in detail.

[0046] The zoom lens of Embodiment 1 is a five-group zoom lens consisting of a first lens group L1 with negative refractive power, a second lens group L2 with positive refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with negative refractive power, and a fifth lens group L5 with positive refractive power, which are arranged in order from the object side to the image side. The aperture stop SP is arranged within the second lens group L2.

[0047] The zoom lens of Example 2 is a six-group zoom lens including, in order from the object side to the image side, a first lens group L1 with negative refractive power, a second lens group L2 with positive refractive power, a third lens group L3 with negative refractive power, a fourth lens group L4 with positive refractive power, a fifth lens group L5 with negative refractive power, and a sixth lens group L6 with positive refractive power. The aperture stop SP is disposed between the first lens group L1 and the second lens group L2.

[0048] The zoom lens of Example 3 is a five-group zoom lens including, in order from the object side to the image side, a first lens group L1 with negative refractive power, a second lens group L2 with positive refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with negative refractive power, and a fifth lens group L5 with positive refractive power. The aperture stop SP is disposed between the first lens group L1 and the second lens group L2.

[0049] The zoom lens of Example 4 is a four-group zoom lens including, in order from the object side to the image side, a first lens group L1 with negative refractive power, a second lens group L2 with positive refractive power, a third lens group L3 with negative refractive power, and a fourth lens group L4 with positive refractive power. The aperture stop SP is disposed within the second lens group L2.

[0050] In Examples 1 to 4, when zooming from the wide-angle end to the telephoto end, the first lens group L1 moves along a locus convex toward the image side. Specifically, after moving toward the image side, the first lens group L1 moves toward the object side. By moving in this way, it is possible to satisfactorily correct the field curvature in the intermediate zoom region while ensuring a sufficient zoom ratio. Further, when zooming from the wide-angle end to the telephoto end, the second lens group L2 moves toward the object side integrally with the aperture stop SP, the third lens group L3 moves toward the object side, and the fourth lens group L4 moves toward the object side.

[0051] In Examples 1 to 3, when zooming from the wide-angle end to the telephoto end, the fifth lens group L5 moves toward the object side. In Example 2, when zooming from the wide-angle end to the telephoto end, the sixth lens group L6 moves toward the object side.

[0052] In Example 1, focusing from an infinite object to a near-distance object is performed by extending the third lens group L3 forward as indicated by the dotted arrow in FIG. 1. In Example 2, focusing from an infinite object to a near-distance object is performed by extending the fourth lens group L4 forward as indicated by the dotted arrow in FIG. 3. In Example 3, focusing from an infinite object to a near-distance object is performed by extending a part of the third lens group L3 forward as indicated by the dotted arrow in FIG. 5. In Example 4, focusing from an infinite object to a near-distance object is performed by extending a part of the second lens group L2 forward as indicated by the dotted arrow in FIG. 7.

[0053] Numerical Examples 1 to 4 corresponding to Examples 1 to 4 are shown below.

[0054] In the surface data of each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the on-axis distance (distance on the optical axis) between the m-th surface and the (m + 1)-th surface. However, m is the surface number counted from the light incident side. Also, nd represents the refractive index with respect to the d-line of each optical member, and νd represents the Abbe number of the optical member. The Abbe number νd of a certain material is given by νd=(Nd - 1) / (NF - NC) and is represented by.

[0055] Note that in each numerical example, d, focal length (mm), F-number, and half field angle (degrees) are all the values when the zoom lens of each example is focused on an infinite object. "Back focus" is the distance on the optical axis from the last lens surface (the lens surface closest to the image side) to the paraxial image plane, expressed in terms of the air equivalent length. "Overall lens length" is the length obtained by adding the back focus to the distance on the optical axis from the frontmost lens surface (the lens surface closest to the object side) to the last surface of the zoom lens. "Lens group" includes not only cases composed of a plurality of lenses but also cases composed of a single lens.

[0056] When the optical surface is an aspherical surface, an asterisk (*) is attached to the right side of the surface number. The aspherical shape is defined as follows, where X is the displacement amount from the surface vertex in the optical axis direction, h is the height from the optical axis in the direction perpendicular to the optical axis, R is the paraxial curvature radius, K is the conic constant, and A4, A6, A8, and A10 are the aspherical coefficients of each order: X = (h 2 / R) / [1 + {1 - (1 + K)(h / R) 2} 1 / 2 + A4 × h 4 + A6 × h 6 + A8 × h 8 + A10 × h 10 This is expressed as such. Note that "e±XX" in each aspherical coefficient means "×10± XX ".

[0057] [Numerical Example 1] Unit: mm Surface Data Surface Number r d nd νd 1 45.834 1.70 1.60311 60.6 2 16.312 3.91 3* 29.906 2.00 1.53110 55.9 4* 14.939 8.54 5 -168.841 1.50 1.49700 81.5 6 19.984 2.16 7 22.940 3.28 1.72047 34.7 8 68.566 (Variable) 9 27.988 2.00 1.91082 35.3 10 101.185 3.32 11 (Aperture Stop) ∞ 1.00 12 28.303 1.10 1.85026 32.3 13 10.418 4.66 1.48749 70.2 14 -53.373 (Variable) 15 30.850 6.50 1.48749 70.2 16 - 17.744 (variable) 17 - 49.984 1.20 1.83481 42.7 18 40.590 2.60 19* - 109.881 1.50 1.53110 55.9 20* - 258.089 (variable) 21 79.577 4.92 1.49700 81.5 22 - 98.520 (variable) Image plane ∞ Aspherical data The 3rd surface K = 0.00000e+000 A4 = 1.36686e - 004 A6 = - 9.36712e - 007 A8 = 5.46779e - 009 A10 = - 2.19182e - 011 A12 = 4.70614e - 014 A14 = - 4.08928e - 017 The 4th surface K = 0.00000e+000 A4 = 1.50400e - 004 A6 = - 1.12618e - 006 A8 = 6.22546e - 009 A10 = - 2.84544e - 011 A12 = 3.02968e - 014 The 19th surface K = 0.00000e+000 A4 = - 1.53736e - 004 A6 = 7.11077e - 007 A8 = - 4.77310e - 009 A10 = 1.17652e - 011 The 20th surface K = 0.00000e+000 A4 = - 8.44793e - 005 A6 = 8.13825e - 007 A8 = - 2.48598e - 009 A10 = 8.88608e - 012 Various data Zoom ratio 1.79 Wide - angle Middle Telephoto Focal length 16.48 22.05 29.50 F number 4.12 4.79 5.61 Half field angle (degrees) 55.80 44.90 35.80 Image height 21.64 21.64 21.64 Overall lens length 100.88 99.27 100.51 BF 14.00 16.25 19.80 d 8 16.88 8.41 1.50 d14 7.77 7.16 6.16 d16 3.16 3.78 4.78 d20 7.17 11.77 16.38 d22 14.00 16.25 19.80 Zoom lens group data Group Starting surface Focal length 1 1 -20.13 2 9 36.01 3 15 24.17 4 17 -24.70 5 21 89.39 Single lens data Lens Starting surface Focal length 1 1 -42.92 2 3 -58.94 3 5 -35.86 4 7 46.45 5 9 41.93 6 12 -19.95 7 13 18.32 8 15 24.17 9 17 -26.67 10 19 -361.55 11 21 89.39 [Numerical Example 2] Unit mm Surface data Surface number r d nd νd 1 46.467 1.50 1.60311 60.6 2 17.216 3.00 3* 18.369 1.80 1.58313 59.4 4* 10.817 8.72 5 815.959 1.30 1.49700 81.5 6 18.205 1.81 7 20.515 4.24 1.72047 34.7 8 63.312 (Variable) 9 (Aperture) ∞ 0.30 10 21.271 1.91 1.91082 35.3 11 106.046 0.20 12 34.731 1.10 1.91082 35.3 13 9.656 3.28 1.48749 70.2 14 -81.148 (Variable) 15 -51.179 1.00 2.45820 43.8 16 -72.593 (Variable) 17 27.274 1.30 1.54628 42.9 18 14.936 8.49 1.48749 70.2 19 -16.607 (Variable) 20* -18.350 1.40 1.85400 40.4 21* -112.273 (Variable) 22 49.800 4.80 1.59282 68.6 23 -585.286 (Variable) Image plane ∞ Aspherical data The third surface K = 0.00000e+000 A 4= 1.89421e-005 A 6=-2.19943e-007 A 8= 1.91474e-010 A10= 4.46130e-013 A12=-2.49243e-015 The fourth surface K = -5.13629e-001, A4 = 2.30727e-005, A6 = -1.91602e-007 A8 = -2.36992e-009, A10 = 1.17112e-011, A12 = -3.54845e-014 The 20th surface K = 0.00000e+000, A4 = -6.14106e-005, A6 = -1.11079e-007 A8 = -2.86339e-009, A10 = 6.30218e-012 The 21st surface K = 0.00000e+000, A4 = -6.24674e-006, A6 = 2.90640e-008 A8 = -1.68972e-010, A10 = 1.41164e-012 Various data Zoom ratio 1.79 Wide angle, intermediate, telephoto Focal length 16.48, 22.05, 29.50 F-number 4.12, 4.76, 5.58 Half field angle (degrees) 55.20, 45.10, 36.40 Image height 21.64, 21.64, 21.64 Overall lens length 97.90, 95.92, 97.50 BF 13.25, 16.64, 20.63 d8 17.38, 9.17, 2.80 d14 4.73, 4.29, 3.50 d16 3.06, 3.06, 3.06 d19 9.68, 10.11, 10.90 d21 3.64, 6.48, 10.44 d23 13.25, 16.64, 20.63 Zoom lens group data Group, starting surface, focal length 1, 1, -21.86 2940.64 315 - 122.37 41723.63 520 - 25.86 62277.64 Single - lens data Lens starting surface focal length 11 - 46.24 23 - 49.46 35 - 37.49 4740.44 51028.90 612 - 15.00 71317.91 815 - 122.37 917 - 62.78 101817.69 1120 - 25.86 122277.64 [Numerical Example 3] Unit: mm Surface data Surface number r d nd νd 150.4511.501.7130053.9 220.0063.00 3*23.1811.801.5831359.4 4*10.97510.47 5 - 176.0921.301.4970081.5 628.4160.20 723.9515.001.7204734.7 8161.523 (Variable) 9(Diaphragm) ∞0.30 1034.4922.181.5174252.4 11 - 786.0630.20 1228.6251.201.9537532.3 1311.0134.791.5814440.8 14 -117.410 (Variable) 15 -24.537 1.00 1.72916 54.7 16 72.485 3.79 1.49700 81.5 17 -22.006 2.40 18 27.274 1.30 1.51742 52.4 19 14.600 8.50 1.49700 81.5 20 -21.740 (Variable) 21* -23.675 1.40 1.85400 40.4 22* 172.434 (Variable) 23 84.478 5.75 1.59282 68.6 24 -62.297 (Variable) Image plane ∞ Aspherical data The 3rd surface K = 0.00000e+000 A 4= 1.15568e-005 A 6=-1.69310e-007 A 8= 6.26704e-010 A10=-1.55731e-012 A12= 1.63967e-015 The 4th surface K =-5.13629e-001 A 4= 1.37630e-005 A 6=-1.99486e-007 A 8=-3.16951e-010 A10= 2.59034e-012 A12=-1.51843e-014 The 21st surface K = 0.00000e+000 A 4=-6.36973e-005 A 6=-8.28985e-009 A 8=-1.72974e-009 A10= 7.56727e-013 The 22nd surface K = 0.00000e+000 A 4=-1.61980e-005 A 6= 1.36614e-007 A 8 = -7.95104e-010 A10 = 2.49773e-012 Various data Zoom ratio 1.79 Wide angle, medium, telephoto Focal length 16.48, 22.05, 29.50 F number 4.12, 4.12, 4.12 Half field angle (degrees) 55.20, 45.00, 36.20 Image height 21.64, 21.64, 21.64 Overall lens length 110.07, 105.92, 108.00 BF 12.80, 17.50, 21.37 d 8 20.76, 10.32, 3.12 d14 2.54, 2.19, 1.65 d20 13.07, 13.42, 13.96 d22 4.80, 6.41, 11.82 d24 12.80, 17.50, 21.37 Zoom lens group data Group, starting surface, focal length 1 1 -24.13 2 9 48.52 3 15 28.22 4 21 -24.30 5 23 61.38 Single lens data Lens, starting surface, focal length 1 1 -47.47 2 3 -37.80 3 5 -49.13 4 7 38.45 5 10 63.92 6 12 -19.41 7 13 17.56 8 15 -25.03 9 16 34.43 10 18 -62.92 11 19 19.05 12 21 -24.30 13 23 61.38 [Numerical Example 4] Unit: mm Surface data Surface number r d nd νd 1 42.899 1.70 1.60311 60.6 2 16.486 3.48 3* 29.906 2.00 1.53110 55.9 4* 15.229 7.69 5 1201.766 1.50 1.49700 81.5 6 14.526 1.91 7 16.813 3.50 1.72047 34.7 8 35.622 (Variable) 9 29.099 2.00 1.91082 35.3 10 67.009 2.51 11 (Aperture) ∞ 2.63 12 21.932 1.10 1.85026 32.3 13 10.165 4.49 1.48749 70.2 14 -58.666 7.16 15 35.589 6.45 1.48749 70.2 16 -17.143 (Variable) 17 -34.675 1.20 1.83481 42.7 18 81.524 2.60 19* -109.881 1.50 1.53110 55.9 20* -258.089 (Variable) 21 -155.132 6.00 1.49700 81.5 22 -33.886 (Variable) Image plane ∞ Aspherical data The third surface K = 0.00000e+000 A 4= 1.36686e-004 A 6=-9.36712e-007 A 8= 5.46779e-009 A10=-2.19182e-011 A12= 4.70614e-014 A14=-4.08928e-017 The 4th side K = 0.00000e+000 A 4= 1.50400e-004 A 6=-1.12618e-006 A 8= 6.22546e-009 A10=-2.84544e-011 A12= 3.02968e-014 The 19th side K = 0.00000e+000 A 4=-1.71744e-004 A 6= 5.08427e-007 A 8=-3.37254e-009 A10= 2.39721e-011 The 20th side K = 0.00000e+000 A 4=-9.54197e-005 A 6= 5.24837e-007 A 8= 4.24234e-010 A10= 1.41039e-012 Various data Zoom ratio 1.79 Wide angle, medium, telephoto Focal length 16.48 22.03 29.50 F-number 4.12 4.78 5.70 Half angle of view (degrees) 55.90 45.00 36.00 Image height 21.64 21.64 21.64 Overall lens length 100.00 99.71 104.31 BF 14.62 18.14 20.32 d 8 15.88 8.01 2.35 d16 3.90 4.51 5.33 d20 6.18 9.63 16.88 d22 14.62 18.14 20.32 Zoom lens group data Group starting surface Focal length 1 1 -18.82 2 9 20.79 3 17 -26.69 4 21 85.83 Single lens data Lens starting surface Focal length 1 1 -45.50 2 3 -61.33 3 5 -29.60 4 7 41.00 5 9 55.09 6 12 -23.28 7 13 18.16 8 15 24.72 9 17 -29.01 10 19 -361.55 11 21 85.83 The various values in each numerical example are summarized in Table 1 below.

[0058]

Table 1

[0059] [Imaging device] Next, an example of a digital still camera (imaging device) using the optical system of the present invention as an imaging optical system will be described with reference to FIG. 9. In FIG. 9, 10 is a camera body, and 11 is a photographing optical system constituted by any one of the zoom lenses described in Examples 1 to 4. 12 is a solid-state imaging device (photoelectric conversion element) such as a CCD sensor or a CMOS sensor that is built in the camera body and receives the optical image formed by the photographing optical system 11 and performs photoelectric conversion. The camera body 10 may be a so-called single-lens reflex camera having a quick-turn mirror, or a so-called mirrorless camera not having a quick-turn mirror.

[0060] By applying the zoom lens of the present invention to an imaging device such as a digital still camera, an imaging device with a small lens can be obtained. [Imaging System] In addition, an imaging system (surveillance camera system) including the zoom lens of each embodiment and a control unit for controlling the zoom lens may be configured. In this case, the control unit can control the zoom lens so that each lens group moves as described above during zooming, focusing, and image blur correction. At this time, it is not necessary for the control unit to be integrally configured with the zoom lens, and the control unit may be configured separately from the zoom lens. For example, a configuration may be adopted in which a control unit (control device) disposed remotely from a driving unit that drives each lens of the zoom lens includes a transmission unit that sends a control signal (command) for controlling the zoom lens. According to such a control unit, the zoom lens can be remotely operated.

[0061] Further, a configuration may be adopted in which an operation unit such as a controller and buttons for remotely operating the zoom lens is provided in the control unit, and the zoom lens is controlled in response to an input to the operation unit by the user. For example, an enlargement button and a reduction button are provided as the operation unit, and a signal is sent from the control unit to the driving unit of the zoom lens so that the magnification of the zoom lens increases when the user presses the enlargement button and the magnification of the zoom lens decreases when the user presses the reduction button.

[0062] In addition, the imaging system may have a display unit such as a liquid crystal panel that displays information (movement state) related to the zoom of the zoom lens. Information related to the zoom of the zoom lens is, for example, the zoom magnification (zoom state) and the movement amount (movement state) of each lens group. In this case, the user can remotely operate the zoom lens via the operation unit while viewing the information related to the zoom of the zoom lens shown on the display unit. At this time, the display unit and the operation unit may be integrated by adopting, for example, a touch panel.

[0063] As described above, the preferred embodiments and examples of the present invention have been explained. However, the present invention is not limited to these embodiments and examples, and various combinations, modifications, and changes are possible within the scope of the gist thereof.

Explanation of Reference Numerals

[0064] L1 First lens group L2 Second lens group L3 Third lens group L4 Fourth lens group L5 Fifth lens group SP Aperture stop

Claims

1. A zoom lens having, in order from an object side to an image side, a first lens group having negative refractive power, a second lens group having positive refractive power, an (n-1)th lens group having negative refractive power, and an nth lens group having positive refractive power, wherein an interval between adjacent lens groups changes during zooming, and the (n-1)th lens group and the nth lens group move during zooming, the nth lens group is disposed closest to the image side, the (n-1)th lens group is disposed adjacent to the nth lens group on the object side, the first lens group has a negative meniscus lens having a convex surface facing an object side, an aperture stop is disposed between a lens surface of the first lens group closest to the image side and a lens surface of the second lens group closest to the image side; Let fn be the focal length of the nth lens group, fn1 be the focal length of the n-1th lens group, bfw be the distance on the optical axis from the lens surface closest to the image side at the wide-angle end to the paraxial image plane position, Mn be the movement amount of the nth lens group during zooming from the wide-angle end to the telephoto end, Mn be the movement amount of the n-1th lens group during zooming from the wide-angle end to the telephoto end, Mn1 be the movement amount of the n-1th lens group during zooming from the wide-angle end to the telephoto end, the movement direction of the lens groups toward the object side be the positive direction, and f1 be the focal length of the first lens group. -0.50<fn1 / fn<-0.20 4.00<fn / bfw<8.00 0.20<Mn / Mn1<0.60 0.80<fn1 / f1<1.50 A zoom lens characterized by satisfying the following conditional expressions:

2. When the distance on the optical axis from the lens surface closest to the image side in the n-1 lens group at the wide-angle end to the image plane is bfwn-1, -1.30<fn1 / bfwn-1<-0.80 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

3. When the distance on the optical axis from the lens surface closest to the object side at the wide-angle end to the aperture stop is LDwfs, and the distance from the aperture stop to the image plane at the wide-angle end is LDwsi, 0.50<LDwfs / LDwsi<1.00 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

4. Further comprising an (n-2)th lens group arranged adjacent to the (n-1)th lens group on the object side, When the focal length of the n-2 lens group is fn2, -1.40<fn2 / fn1<-0.70 4. The zoom lens according to claim 1, which satisfies the following condition:

5. When the focal length of the zoom lens at the wide-angle end is fw, -1.60<f1 / fw<-1.00 5. The zoom lens according to claim 1, which satisfies the following condition:

6. 6. The zoom lens according to claim 1, wherein, during zooming from the wide-angle end to the telephoto end, the first lens group moves toward the image side and then moves toward the object side.

7. the first lens group, the second lens group, a third lens group having a positive refractive power, a fourth lens group as the (n-1)th lens group, and a fifth lens group as the nth lens group, which are arranged in this order from the object side to the image side; 7. The zoom lens according to claim 1, wherein the aperture stop is disposed within the second lens group.

8. A zoom lens comprising, arranged in order from the object side to the image side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having positive refractive power, an (n-1)th lens group having negative refractive power, and an nth lens group having positive refractive power, wherein the spacing between adjacent lens groups changes during zooming, and the (n-1)th lens group and the nth lens group move during zooming, the first lens group has a negative meniscus lens having a convex surface facing an object side, an aperture stop is disposed within the second lens group; The focal length of the nth lens group is fn, the focal length of the n-1th lens group is fn1, the distance on the optical axis from the lens surface closest to the image side at the wide-angle end to the paraxial image plane position is bfw, the amount of movement of the nth lens group during zooming from the wide-angle end to the telephoto end is Mn, the amount of movement of the n-1th lens group during zooming from the wide-angle end to the telephoto end is Mn1, and the direction of movement of the lens groups toward the object side is the positive direction. -0.50<fn1 / fn<-0.20 4.00<fn / bfw<8.00 0.20<Mn / Mn1<0.60 A zoom lens characterized by satisfying the following conditional expressions:

9. the first lens group, the second lens group, a third lens group having negative refractive power, a fourth lens group having positive refractive power, a fifth lens group as the (n-1)th lens group, and a sixth lens group as the nth lens group, arranged in this order from the object side to the image side; 8. The zoom lens according to claim 1, wherein the aperture diaphragm is disposed between the first lens group and the second lens group.

10. A zoom lens comprising, arranged in order from the object side to the image side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, a fourth lens group having positive refractive power, an (n-1)th lens group having negative refractive power, and an nth lens group having positive refractive power, wherein the spacing between adjacent lens groups changes during zooming, and the (n-1)th lens group and the nth lens group move during zooming, the first lens group has a negative meniscus lens having a convex surface facing an object side, an aperture stop is disposed between the first lens group and the second lens group; The focal length of the nth lens group is fn, the focal length of the n-1th lens group is fn1, the distance on the optical axis from the lens surface closest to the image side at the wide-angle end to the paraxial image plane position is bfw, the amount of movement of the nth lens group during zooming from the wide-angle end to the telephoto end is Mn, the amount of movement of the n-1th lens group during zooming from the wide-angle end to the telephoto end is Mn1, and the direction of movement of the lens groups toward the object side is the positive direction. -0.50<fn1 / fn<-0.20 4.00<fn / bfw<8.00 0.20<Mn / Mn1<0.60 A zoom lens characterized by satisfying the following conditional expressions:

11. the first lens group, the second lens group, a third lens group having a positive refractive power, a fourth lens group as the (n-1)th lens group, and a fifth lens group as the nth lens group, which are arranged in this order from the object side to the image side; 7. The zoom lens according to claim 1, wherein the aperture diaphragm is disposed between the first lens group and the second lens group.

12. A zoom lens comprising, arranged in order from the object side to the image side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having positive refractive power, an (n-1)th lens group having negative refractive power, and an nth lens group having positive refractive power, wherein the spacing between adjacent lens groups changes during zooming, and the (n-1)th lens group and the nth lens group move during zooming, the first lens group has a negative meniscus lens having a convex surface facing an object side, an aperture stop is disposed between the first lens group and the second lens group; The focal length of the nth lens group is fn, the focal length of the n-1th lens group is fn1, the distance on the optical axis from the lens surface closest to the image side at the wide-angle end to the paraxial image plane position is bfw, the amount of movement of the nth lens group during zooming from the wide-angle end to the telephoto end is Mn, the amount of movement of the n-1th lens group during zooming from the wide-angle end to the telephoto end is Mn1, and the direction of movement of the lens groups toward the object side is the positive direction. -0.50<fn1 / fn<-0.20 4.00<fn / bfw<8.00 0.20<Mn / Mn1<0.60 A zoom lens characterized by satisfying the following conditional expressions:

13. the first lens group, the second lens group, a third lens group as the (n-1)th lens group, and a fourth lens group as the nth lens group, which are arranged in this order from the object side to the image side, 7. The zoom lens according to claim 1, wherein the aperture stop is disposed within the second lens group.

14. A zoom lens according to any one of claims 1 to 13; and an image sensor that receives an image formed by the zoom lens.

Images