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

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, which is suitable for digital video cameras, digital still cameras, broadcast cameras, cameras for silver halide film, surveillance cameras, and the like. [Background technology]

[0002] In recent years, as imaging devices have become more sophisticated, zoom lenses used in imaging devices are required to have high optical performance throughout the entire zoom range, be compact, and have a wide angle of view. Negative-lead zoom lenses, in which a lens group with negative refractive power is positioned at the front (closest to the object), are known as zoom lenses that are compact and relatively easy to achieve a wide angle of view. Patent Document 1 discloses a negative-lead zoom lens consisting of first to fourth lens groups with negative, positive, negative, and positive refractive powers, arranged in this order from the object side to the image side. Patent Document 2 also discloses a zoom lens consisting of first to fifth lens groups with negative, positive, positive, negative, and positive refractive powers, arranged in this order from the object side to the image side. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-34892 [Patent Document 2] Japanese Patent Application Publication No. 2019-8031 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0004] Negative-lead zoom lenses have an asymmetrical lens configuration, making it difficult to correct various aberrations and achieve high optical performance while miniaturizing the lens. For example, to achieve a wide angle of view in a negative-lead zoom lens, the power of the first lens group, which has negative refractive power, must be increased. This results in significant barrel distortion. To achieve high optical performance across the entire zoom range while miniaturizing the lens and achieving a wide angle of view, it is important to appropriately set the refractive power and position of the lens groups located near the image plane.

[0005] An object of the present invention is to provide a compact, wide-angle zoom lens that has high optical performance over the entire zoom range, and an imaging device and imaging system that include the same. [Means for solving the problem]

[0006] A zoom lens according to one aspect of the present invention comprises, 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, an (n-1)th lens group having negative refractive power, and an (n-1)th 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 (n-1)th lens group move during zooming, and the zoom lens further comprises a focus group having positive refractive power that moves toward the object side during focusing from an object at infinity to an object at a close distance, the (n-1)th lens group being arranged closest to the image side, and the (n-1)th lens group being arranged adjacent to the (n-1)th lens group on the object side, The aperture stop is disposed between the lens surface of the first lens group closest to the image and the lens surface of the second lens group closest to the image, and when the focal length of the nth lens group is fn, the focal length of the (n-1)th lens group is fn1, the focal length of the first lens group is f1, the distance on the optical axis from the lens surface closest to the image to the paraxial image plane position at the wide-angle end is bfw, the amount of movement of the nth lens group during zooming from the wide-angle end to the telephoto end is Mn, and the amount of movement of the (n-1)th 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 defined as the positive direction, -0.50 <fn1 / fn<-0.20 4.00 <fn / bfw<8.00 0.20 <Mn / Mn1<0.60 The present invention is characterized in that the following conditional expression is satisfied: [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a small-sized zoom lens with a wide angle of view that has high optical performance over the entire zoom range, as well as an imaging device and an imaging system that include the same. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of a zoom lens of Example 1 at a wide-angle end. [Figure 2] 1A, 1B, and 1C are aberration diagrams of Example 1 at the wide-angle end, at the intermediate zoom position, and at the telephoto end. [Figure 3] FIG. 10 is a cross-sectional view of a zoom lens of a second embodiment at the wide-angle end. [Figure 4] 10A, 10B, and 10C are aberration diagrams of Example 2 at the wide-angle end, at the intermediate zoom position, and at the telephoto end. [Figure 5] FIG. 10 is a cross-sectional view of a zoom lens of Example 3 at the wide-angle end. [Figure 6] 10A, 10B, and 10C are aberration diagrams of Example 3 at the wide-angle end, at the intermediate zoom position, and at the telephoto end. [Figure 7] FIG. 10 is a cross-sectional view of a zoom lens of Example 4 at the wide-angle end. [Figure 8] 10A, 10B, and 10C are aberration diagrams of Example 4 at the wide-angle end, at the intermediate zoom position, and at the telephoto end. [Figure 9] FIG. 1 is a schematic diagram of an imaging device. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to designate the same components, and redundant explanations will be omitted.

[0010] 1, 3, 5, and 7 are cross-sectional views at the wide-angle end of the zoom lenses of Examples 1 to 4. The zoom lenses of the respective Examples are used in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, cameras using silver halide film, 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 with multiple lens groups. In this specification, a lens group refers to a group of lenses that move or remain stationary as a unit during zooming. That is, in the zoom lens of each embodiment, the spacing between adjacent lens groups changes during zooming. The arrows shown in each cross-sectional view indicate the direction of movement of the lens group during zooming. Note that a lens group may be composed of a single lens or multiple lenses. The lens group may also include an aperture stop.

[0012] The zoom lens of each embodiment has, arranged in order from the object side to the image side, 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. The nth lens group is arranged closest to the image, and the (n-1)th lens group is adjacent to the nth lens group. An aperture stop is arranged between the lens surface of the first lens group closest to the image and the lens surface of the second lens group closest to the image. 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] Additionally, SP denotes an aperture stop. IP denotes an image plane, on which the imaging surface of a solid-state imaging element (photoelectric conversion element) such as a CCD sensor or CMOS sensor is placed when the zoom lens of each embodiment is used as the imaging optical system of a digital still camera or digital video camera. When the zoom lens of each embodiment is used as the imaging optical system of a silver halide film camera, a photosensitive surface equivalent to the film surface is placed on the image plane IP.

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

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

[0017] Next, the characteristic configuration of the zoom lens of each embodiment will be described.

[0018] The zoom lens of each embodiment satisfies the following conditional expression (1), where the focal length of the n-th lens unit Ln is fn and the focal length of the (n-1)th lens unit Ln-1 is fn1.

[0019] -0.50 <fn1 / fn<-0.20 (1) Conditional expression (1) defines the ratio between the focal length of the nth lens group and the focal length of the (n-1)th lens group in order to achieve both the correction of off-axial aberrations such as field curvature and the compactness of the zoom lens. If the upper limit of conditional expression (1) is exceeded and the focal length of the (n-1)th lens group becomes short, it becomes difficult to correct off-axial aberrations such as field curvature, which is undesirable. If the focal length of the (n-1)th lens group becomes long and falls below the lower limit of conditional expression (1), the distance from the front lens to the entrance pupil becomes too long. In that case, the diameter of the front lens becomes too large to ensure a sufficient amount of light in the peripheral areas of the image at the wide-angle end, which is undesirable.

[0020] Furthermore, the zoom lens of each embodiment satisfies the following conditional expression (2), where bfw is 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.

[0021] 4.00 <fn / bfw<8.00 (2) Conditional expression (2) defines the ratio between the focal length of the nth lens group and the distance from the lens surface closest to the image at the wide-angle end to the image plane in order to achieve both correction of off-axial aberrations such as field curvature and a reduction in the overall length of the zoom lens. If the focal length of the nth lens group becomes longer by exceeding the upper limit of conditional expression (2), it becomes difficult to reduce the overall length of the zoom lens and the diameter of the lens located on the object side of the nth lens group, which is undesirable. If the focal length of the nth lens group becomes shorter by falling below the lower limit of conditional expression (2), it becomes difficult to correct off-axial aberrations such as field curvature, which is undesirable.

[0022] Furthermore, when zooming from the wide-angle end to the telephoto end, the zoom lens of each embodiment satisfies the following conditional expression (3), where Mn is the amount of movement of the n-th lens unit Ln and Mn1 is the amount of movement of the (n-1)th lens unit Ln-1: The direction of movement of the lens units toward the object side is defined as the positive direction.

[0023] 0.20 <Mn / Mn1<0.60 (3) Conditional expression (3) defines the ratio of the movement amounts of the nth lens unit Ln and the (n-1)th lens unit Ln-1 during zooming from the wide-angle end to the telephoto end, so as to obtain a sufficient zoom ratio while favorably correcting off-axial aberrations such as coma and field curvature. If the upper limit of conditional expression (3) is exceeded, and the movement amount of the nth lens unit Ln becomes larger relative to the movement amount of the (n-1)th lens unit Ln-1, it becomes difficult to correct coma and field curvature at the telephoto end, which is undesirable. If the lower limit of conditional expression (3) is exceeded, and the movement amount of the nth lens unit Ln becomes smaller relative to the movement amount of the (n-1)th lens unit Ln-1, it becomes difficult to obtain a sufficient zoom ratio, which is undesirable.

[0024] With the above-described configuration, it is possible to realize a compact, wide-angle zoom lens that has high optical performance over the entire zoom range.

[0025] It is preferable that the numerical ranges of the conditional expressions (1) to (3) be set to 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) It is more preferable that the numerical ranges of the conditional expressions (2) to (3) be set to 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) It is desirable that the zoom lens of each embodiment satisfies the following conditional expression (4), where f1 is the focal length of the first lens unit L1.

[0028] 0.80 <fn1 / f1<1.50 (4) Conditional expression (4) specifies the ratio of the focal lengths of the first lens unit L1 and the (n-1)th lens unit Ln-1 in order to achieve a compact zoom lens and a wide angle of view while effectively correcting off-axis aberrations at the wide-angle end. If the upper limit of conditional expression (4) is exceeded and the focal length of the first lens unit L1 becomes short, it becomes difficult to correct coma and curvature of field at the wide-angle end, which is undesirable. If the focal length of the first lens unit L1 becomes long and falls below the lower limit of conditional expression (4), the diameter of the front lens element becomes too large to ensure a sufficient amount of light at the periphery of the image at the wide-angle end, which is undesirable.

[0029] It is desirable that the zoom lens of each embodiment satisfy the following conditional expression (5), where bfwn-1 is the distance on the optical axis from the lens surface closest to the image in the (n-1)th lens unit Ln-1 at the wide-angle end to the image plane:

[0030] -1.30 <fn1 / bfwn-1<-0.80 (5) Conditional expression (5) defines the ratio between the focal length of the (n-1)th lens unit Ln-1 and the axial distance from the lens surface closest to the image plane to the image plane in order to achieve both compactness of the zoom lens and good correction of off-axis aberrations while ensuring telecentricity on the image side at the wide-angle end. If the focal length of the (n-1)th lens unit Ln-1 becomes too short, exceeding the upper limit of conditional expression (5), it becomes difficult to correct coma and field curvature while ensuring telecentricity on the image side at the wide-angle end, which is undesirable. If the focal length of the (n-1)th lens unit Ln-1 becomes too long, falling below the lower limit of conditional expression (5), it becomes difficult to achieve compactness of the zoom lens, which is undesirable.

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

[0032] 0.50 <LDwfs / LDwsi<1.00 (6) Conditional expression (6) defines the position of the aperture stop in order to reduce the lens diameter. If the upper limit of conditional expression (6) is exceeded and the distance from the aperture stop to the lens surface closest to the object becomes long, the diameter of the front lens element becomes too large to ensure a sufficient amount of light in the peripheral areas of the image at the wide-angle end, which is undesirable. If the lower limit of conditional expression (6) is exceeded and the distance from the aperture stop to the image plane becomes long, the diameter of the rear lens element becomes too large to ensure a sufficient amount of light in the peripheral areas of the image at the wide-angle end, which is undesirable.

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

[0034] -1.40 <fn2 / fn1<-0.70 (7) Conditional expression (7) defines the ratio between the focal length of the (n-1)th lens group Ln-1 and the focal length of the (n-2)th lens group Ln-2 in order to reduce the lens diameter near the aperture stop. If the upper limit of conditional expression (7) is exceeded and the focal length of the (n-2)th lens group Ln-2 becomes short, it becomes difficult to correct spherical aberration and coma aberration over the entire zoom range, which is undesirable. If the lower limit of conditional expression (7) is exceeded and the focal length of the (n-2)th lens group Ln-2 becomes long, it becomes difficult to reduce the lens diameter near the aperture stop, which is undesirable.

[0035] It is desirable that the zoom lens of each embodiment satisfies the following conditional expression (8), where fw is the focal length of the zoom lens at the wide-angle end.

[0036] -1.60 <f1 / fw<-1.00 (8) Conditional expression (8) specifies the ratio between the focal length of the first lens group L1 and the focal length of the zoom lens at the wide-angle end in order to achieve a compact zoom lens and a wide angle of view while effectively correcting off-axial aberrations at the wide-angle end. If the upper limit of conditional expression (8) is exceeded and the focal length of the first lens group L1 becomes shorter than the focal length of the zoom lens at the wide-angle end, it becomes difficult to correct coma and curvature of field at the wide-angle end, which is undesirable. If the lower limit of conditional expression (8) is exceeded and the focal length of the first lens group L1 becomes longer than the focal length of the zoom lens at the wide-angle end, the diameter of the front lens element becomes too large to ensure a sufficient amount of light at the periphery of the image at the wide-angle end, which is undesirable.

[0037] It is desirable that the zoom lens of each embodiment satisfies the following conditional expression (9), where f11 is the focal length of the lens in the first lens unit L1 that is located closest to the object side.

[0038] 1.50 <f11 / f1<3.00 (9) Conditional expression (9) specifies the ratio between the focal length of the first lens group L1 and the focal length of the lens located closest to the object in the first lens group L1 in order to achieve a compact zoom lens with a wide angle of view while effectively correcting off-axis aberrations at the wide-angle end. If the focal length of the lens located closest to the object in the first lens group L1 becomes longer by exceeding the upper limit of conditional expression (9), the diameter of the lens located closest to the object in the first lens group L1 becomes too large to ensure a sufficient amount of light in the peripheral areas of the image at the wide-angle end, which is undesirable. If the focal length of the lens located closest to the object in the first lens group L1 becomes shorter by falling below the lower limit of conditional expression (9), it becomes difficult to correct field curvature and distortion at the wide-angle end, which is undesirable.

[0039] It is preferable that the numerical ranges of the conditional expressions (4) to (9) be set to the numerical ranges of the following conditional expressions (4a) to (9a).

[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) It is more preferable that the numerical ranges of the conditional expressions (4) to (9) be the numerical ranges of the following conditional expressions (4b) to (9b).

[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) Preferably, the first lens group L1 comprises, in order from the object side to the image side, a first lens having negative refractive power, a second lens having negative refractive power, a third lens having negative refractive power, and a fourth lens having positive refractive power. By arranging multiple negative lenses, the refractive power of each negative lens can be appropriately distributed, thereby enabling excellent correction of coma, field curvature, and distortion at the wide-angle end.

[0042] As in Examples 1 to 3, it is preferable that the second lens group L2 be composed of, arranged in order from the object side to the image side, a first lens having positive refractive power, a cemented lens consisting of a second lens having negative refractive power and a third lens having positive refractive power. As in Example 4, it is preferable that the second lens group L2 be composed of, arranged in order from the object side to the image side, a first lens having positive refractive power, a cemented lens consisting of a second lens having negative refractive power and a third lens having positive refractive power, and a fourth lens having positive refractive power. With this configuration, spherical aberration and coma can be effectively corrected throughout the entire zoom range.

[0043] It is also preferable that the (n-1)th lens unit Ln-1 is made up of two or less negative lenses. With this configuration, coma and curvature of field can be effectively corrected over the entire zoom range.

[0044] It is also preferable that the n-th lens unit Ln is made up of one lens with positive refractive power. With this configuration, it is possible to ensure good telecentricity on the image side over the entire zoom range while maintaining a compact size.

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

[0046] The zoom lens of Example 1 is a five-group zoom lens consisting of, arranged 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. An aperture stop SP is located within the second lens group L2.

[0047] The zoom lens of Example 2 is a six-group zoom lens consisting of, arranged 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. An 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 consisting of, arranged 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. An 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 consisting of, arranged 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. An aperture stop SP is located within the second lens group L2.

[0050] In Examples 1 to 4, during zooming from the wide-angle end to the telephoto end, the first lens unit L1 moves along a convex path toward the image side. Specifically, the first lens unit L1 moves toward the image side and then moves toward the object side. This movement ensures a sufficient zoom ratio while effectively correcting field curvature in the intermediate zoom range. Furthermore, during zooming from the wide-angle end to the telephoto end, the second lens unit L2 moves toward the object side together with the aperture stop SP, the third lens unit L3 moves toward the object side, and the fourth lens unit L4 moves toward the object side.

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

[0052] In Example 1, focusing from an object at infinity to a close object is performed by moving the third lens group L3 forward, as shown by the dotted arrow in Fig. 1. In Example 2, focusing from an object at infinity to a close object is performed by moving the fourth lens group L4 forward, as shown by the dotted arrow in Fig. 3. In Example 3, focusing from an object at infinity to a close object is performed by moving a portion of the third lens group L3 forward, as shown by the dotted arrow in Fig. 5. In Example 4, focusing from an object at infinity to a close object is performed by moving a portion of the second lens group L2 forward, as shown by the dotted arrow in Fig. 7.

[0053] Numerical Examples 1 to 4 corresponding to Examples 1 to 4, respectively, 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 axial spacing (distance on the optical axis) between the mth surface and the (m+1)th surface. Here, m is the surface number counted from the light incident side. Furthermore, nd represents the refractive index of each optical element with respect to the d-line, and vd represents the Abbe number of the optical element. Note that the Abbe number vd of a certain material is given by the following equation, where Nd, NF, and NC are the refractive indices at the d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) of the Fraunhofer lines: νd=(Nd-1) / (NF-NC) It is expressed as:

[0055] In each numerical example, d, focal length (mm), F-number, and half angle of view (degrees) are all values ​​when the zoom lens of each example is focused on an object at infinity. "Back focus" is the distance on the optical axis from the final lens surface (the lens surface closest to the image) to the paraxial image plane, expressed as an air-equivalent length. "Total lens length" is the distance on the optical axis from the frontmost lens surface (the lens surface closest to the object) to the final lens surface plus the back focus. "Lens group" is not limited to cases where it is composed of multiple lenses, but also includes cases where it is composed of a single lens.

[0056] If the optical surface is aspherical, an asterisk (*) is added to the right of the surface number. The aspherical shape is expressed as follows: X is the displacement from the vertex of the surface 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 radius of curvature, 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 In addition, "e±XX" in each aspherical coefficient is "×10± XX " means.

[0057] [Numerical Example 1] Unit: mm Surface Data Surface number rd 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) ∞ 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 ∞ Aspheric data 3rd page K = 0.00000e+000 A 4= 1.36686e-004 A 6=-9.36712e-007 A8= 5.46779e-009 A10=-2.19182e-011 A12= 4.70614e-014 A14=-4.08928e-017 Side 4 K = 0.00000e+000 A 4= 1.50400e-004 A 6=-1.12618e-006 A8= 6.22546e-009 A10=-2.84544e-011 A12= 3.02968e-014 Page 19 K = 0.00000e+000 A 4=-1.53736e-004 A 6= 7.11077e-007 A8=-4.77310e-009 A10=1.17652e-011 Page 20 K = 0.00000e+000 A 4=-8.44793e-005 A 6= 8.13825e-007 A8=-2.48598e-009 A10=8.88608e-012 Various data Zoom ratio 1.79 Wide-angle Mid-range Telephoto Focal length 16.48 22.05 29.50 F-number 4.12 4.79 5.61 Half angle of view (degrees) 55.80 44.90 35.80 Image height 21.64 21.64 21.64 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 plane 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 rd 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 ∞ Aspheric data 3rd page K = 0.00000e+000 A 4= 1.89421e-005 A 6=-2.19943e-007 A8= 1.91474e-010 A10= 4.46130e-013 A12=-2.49243e-015 Side 4 K=-5.13629e-001 A 4= 2.30727e-005 A 6=-1.91602e-007 A 8=-2.36992e-009 A10= 1.17112e-011 A12=-3.54845e-014 Page 20 K = 0.00000e+000 A 4=-6.14106e-005 A 6=-1.11079e-007 A8=-2.86339e-009 A10=6.30218e-012 Page 21 K = 0.00000e+000 A 4=-6.24674e-006 A 6= 2.90640e-008 A8=-1.68972e-010 A10=1.41164e-012 Various data Zoom ratio 1.79 Wide-angle Mid-range Telephoto Focal length 16.48 22.05 29.50 F-number 4.12 4.76 5.58 Half angle of view (degrees) 55.20 45.10 36.40 Image height 21.64 21.64 21.64 Lens length 97.90 95.92 97.50 BF 13.25 16.64 20.63 d 8 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 plane focal length 1 1 -21.86 2 9 40.64 3 15 -122.37 4 17 23.63 5 20 -25.86 6 22 77.64 Single lens data Lens starting surface focal length 1 1 -46.24 2 3 -49.46 3 5 -37.49 4 7 40.44 5 10 28.90 6 12 -15.00 7 13 17.91 8 15 -122.37 9 17 -62.78 10 18 17.69 11 20 -25.86 12 22 77.64 [Numerical Example 3] Unit: mm Surface Data Surface number rd nd νd 1 50.451 1.50 1.71300 53.9 2 20.006 3.00 3* 23.181 1.80 1.58313 59.4 4* 10.975 10.47 5 -176.092 1.30 1.49700 81.5 6 28.416 0.20 7 23.951 5.00 1.72047 34.7 8 161.523 (variable) 9 (Aperture) ∞ 0.30 10 34.492 2.18 1.51742 52.4 11 -786.063 0.20 12 28.625 1.20 1.95375 32.3 13 11.013 4.79 1.58144 40.8 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 ∞ Aspheric data 3rd page K = 0.00000e+000 A 4= 1.15568e-005 A 6=-1.69310e-007 A8= 6.26704e-010 A10=-1.55731e-012 A12= 1.63967e-015 Side 4 K=-5.13629e-001 A 4= 1.37630e-005 A 6=-1.99486e-007 A8=-3.16951e-010 A10=2.59034e-012 A12=-1.51843e-014 Page 21 K = 0.00000e+000 A 4=-6.36973e-005 A 6=-8.28985e-009 A8=-1.72974e-009 A10=7.56727e-013 Page 22 K = 0.00000e+000 A 4=-1.61980e-005 A 6= 1.36614e-007 A8=-7.95104e-010 A10=2.49773e-012 Various data Zoom ratio 1.79 Wide-angle Mid-range Telephoto Focal length 16.48 22.05 29.50 F-number 4.12 4.12 4.12 Half angle of view (degrees) 55.20 45.00 36.20 Image height 21.64 21.64 21.64 Lens total 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 plane 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 rd 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 ∞ Aspheric data 3rd page K = 0.00000e+000 A 4= 1.36686e-004 A 6=-9.36712e-007 A8= 5.46779e-009 A10=-2.19182e-011 A12= 4.70614e-014 A14=-4.08928e-017 Side 4 K = 0.00000e+000 A 4= 1.50400e-004 A 6=-1.12618e-006 A8= 6.22546e-009 A10=-2.84544e-011 A12= 3.02968e-014 Page 19 K = 0.00000e+000 A 4=-1.71744e-004 A 6= 5.08427e-007 A8=-3.37254e-009 A10=2.39721e-011 Page 20 K = 0.00000e+000 A 4=-9.54197e-005 A 6= 5.24837e-007 A8= 4.24234e-010 A10= 1.41039e-012 Various data Zoom ratio 1.79 Wide-angle Mid-range 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 Lens total 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 plane 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 embodiment 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 denotes a camera body, and 11 denotes an imaging optical system constituted by any of the zoom lenses described in Examples 1 to 4. 12 denotes a solid-state imaging element (photoelectric conversion element) such as a CCD sensor or CMOS sensor that is built into the camera body and receives and photoelectrically converts an optical image formed by the imaging optical system 11. The camera body 10 may be a so-called single-lens reflex camera having a quick-turn mirror, or a so-called mirrorless camera having no quick-turn mirror.

[0060] In this way, by applying the zoom lens of the present invention to an imaging device such as a digital still camera, an imaging device with a compact lens can be obtained. [Imaging system] An imaging system (surveillance camera system) may be configured that includes the zoom lens of each embodiment and a control unit that controls the zoom lens. 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 stabilization. In this case, the control unit does not need to be configured integrally with the zoom lens; the control unit may be configured separately from the zoom lens. For example, a control unit (control device) located far from the drive units that drive each lens of the zoom lens may include a transmission unit that sends control signals (commands) to control the zoom lens. Such a control unit allows the zoom lens to be remotely controlled.

[0061] Alternatively, the control unit may be provided with an operation unit such as a controller or buttons for remotely operating the zoom lens, thereby controlling the zoom lens in response to user input to the operation unit. For example, the operation unit may be provided with a zoom-in button and a zoom-out button, and the control unit may send a signal to a zoom lens driver so that the zoom magnification increases when the user presses the zoom-in button, and decreases when the user presses the zoom-out button.

[0062] The imaging system may also 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 may be, for example, the zoom magnification (zoom state) or 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 displayed on the display unit. In this case, the display unit and operation unit may be integrated by using, for example, a touch panel.

[0063] Although the preferred embodiments and examples of the present invention have been described above, 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 of the present invention. [Explanation of symbols]

[0064] L1 First lens group L2 Second lens group L3: Third lens group L4 4th lens group L5 Fifth lens group SP aperture stop

Claims

1. A zoom lens having, 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, 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 zoom lens includes a focus group that moves toward the object side during focusing from an object at infinity to an object at a close distance and has positive refractive power; 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, an aperture stop is disposed between the lens surface of the first lens group closest to the image side and the 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-1)th lens group, f1 be the focal length of the first 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 amount of movement of the nth lens group during zooming from the wide-angle end to the telephoto end, and Mn1 be the amount of movement of the (n-1)th lens group during zooming from the wide-angle end to the telephoto end, and the direction of movement of the lens groups toward the object side be 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:

2. When the focal length of the first lens group is f1, 0.80<fn1 / f1<1.50 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 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 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

4. When the distance on the optical axis from the lens surface closest to the object 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 4. The zoom lens according to claim 1, wherein the following condition is satisfied:

5. 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)th lens group is fn2, -1.40<fn2 / fn1<-0.70 5. The zoom lens according to claim 1, wherein the following condition is satisfied:

6. When the focal length of the first lens group is f1 and the focal length of the zoom lens at the wide-angle end is fw, -1.60<f1 / fw<-1.00 6. The zoom lens according to claim 1, wherein the following condition is satisfied:

7. 7. 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.

8. the first lens group, the second lens group, a third lens group having positive refractive power, a fourth lens group as the (n-1)th lens group, and a fifth 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 stop is disposed within the second lens group.

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 stop is disposed between the first lens group and the second lens group.

10. the first lens group, the second lens group, a third lens group having positive refractive power, a fourth lens group as the (n-1)th lens group, and a fifth 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 stop is disposed between the first lens group and the second lens group.

11. 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, arranged in this order from the object side to the image side, 8. The zoom lens according to claim 1, wherein the aperture stop is disposed within the second lens group.

12. A zoom lens according to any one of claims 1 to 11; and an image sensor that receives an image formed by the zoom lens.

Images