Zoom lens and imaging apparatus and imaging system equipped with the same

Abstract

To provide a zoom lens that has a large aperture and high optical performance despite its small size and wide angle.SOLUTION: A zoom lens has a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a rear group, which are arranged in order from an object side to an image side, and an interval between the adjacent lens groups changes in zooming. The first lens group includes at least one resin lens having a negative refractive power, and at least one of the second lens group and the rear group includes at least one resin lens having a positive refractive power. A focal length of the first lens group, a focal length of the second lens group, an average of the focal lengths of the resin lenses having a negative refractive power included in the first lens group, and an average of the focal lengths of the resin lenses having a positive refractive power included in at least one of the second lens group and the rear group are each appropriately set.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, there has been a demand for zoom lenses with high optical performance that can accommodate the increasing resolution of imaging devices. Furthermore, there is a growing demand for compact zoom lenses used in surveillance cameras in terms of ease of installation and inconspicuousness. In addition, there is a strong demand for zoom lenses that can capture a wide range at the wide-angle end and have a large aperture because they are expected to capture images in dark places. To achieve such a zoom lens, one method is to use aspherical lenses (resin lenses) made of an easily manufactured resin material instead of aspherical lenses made of glass. Patent Documents 1 and 2 disclose negative-lead zoom lenses that use resin lenses with aspherical lens surfaces and have, 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, and a rear lens group. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-009113 [Patent Document 2] Japanese Patent Application Laid-Open No. 1988-292106 Summary of the Invention [Problem to be solved by the invention]

[0004] Resin materials generally have a greater change in refractive index with temperature changes than glass materials. In the zoom lens of Patent Document 1, the refractive power of the resin lenses with positive refractive power in the second lens group and the rear lens group is strong, which results in large fluctuations in focus and spherical aberration with temperature changes, leaving issues in terms of increasing the aperture. In addition, in the zoom lens of Patent Document 2, the refractive power of the resin lenses with negative refractive power in the first lens group is strong, which results in large fluctuations in field curvature with temperature changes, leaving issues in terms of further widening the angle of view.

[0005] SUMMARY OF THE INVENTION An object of the present invention is to provide a zoom lens that is small, has a wide angle, has a large aperture, and has high optical performance. [Means for solving the problem]

[0006] A zoom lens according to one aspect of the present invention 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, and a subsequent lens group, and the distance between adjacent lens groups changes during zooming. The first lens group includes at least one plastic lens with negative refractive power, and at least one of the second lens group and the subsequent lens group includes at least one plastic lens with positive refractive power. When the focal length of the first lens group is f1, the focal length of the second lens group is f2, the average focal length of the plastic lenses with negative refractive power included in the first lens group is fnpa, and the average focal length of the plastic lenses with positive refractive power included in at least one of the second lens group and the subsequent lens group is fppa, then: 0.01<|f1 / f2|<1.00 10.0<|fnpa / f1|<20.0 0.15<|fppa / fnpa|<1.00 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 zoom lens that is small, has a wide angle, has a large aperture, and has high optical performance. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view of a zoom lens at the wide-angle end of Example 1. [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 at the wide-angle end of Example 2. [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 at the wide-angle end according to a third embodiment. [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 at the wide-angle end according to a fourth embodiment. [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. 10 is a cross-sectional view of a zoom lens at the wide-angle end of Example 5. [Figure 10] 10A, 10B, and 10C are aberration diagrams of Example 5 at the wide-angle end, at the intermediate zoom position, and at the telephoto end. [Figure 11] FIG. 1 is a schematic diagram of an imaging device. [Figure 12] FIG. 1 is a schematic diagram of an imaging device. [Figure 13] 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, 7, and 9 are cross-sectional views of zoom lenses at the wide-angle end according to Examples 1 to 5. The zoom lenses according to each Example are used in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, cameras for 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 distance between adjacent lens groups changes during zooming. Note that a lens group may be configured with a single lens, or may be configured with multiple lenses. The lens group may also include an aperture stop.

[0012] In each cross-sectional view, Li denotes the i-th lens group (i is a natural number) counting from the object side. SP denotes an aperture stop, located between the first lens group L1 and the second lens group L2 or within the second lens group L2. The aperture diameter of the aperture stop SP can be constant or variable during zooming. By varying the aperture diameter of the aperture stop SP, it is possible to reduce the underline coma flare caused by off-axial light beams that occurs significantly at the telephoto end, thereby achieving better optical performance. P denotes an optical block equivalent to an optical filter, faceplate, low-pass filter, infrared cut filter, etc. I denotes the image plane, on which the imaging surface of an imaging element (photoelectric conversion element) such as a CCD sensor or CMOS sensor is located 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 located on the image plane I.

[0013] In each cross-sectional view, arrows indicate the movement locus of each lens group during zooming from the wide-angle end to the telephoto end. Focusing is performed by moving the first lens group L1 or the third lens group L3 along the optical axis. Of the movement loci of the first lens group L1 or the third lens group L3, the solid curves indicate the movement loci for correcting image plane fluctuations that occur when zooming from the wide-angle end to the telephoto end while focusing on an object at infinity. Furthermore, the dotted curves indicate the movement loci for correcting image plane fluctuations that occur when zooming from the wide-angle end to the telephoto end while focusing on a close-up object. Note that focusing may be performed by moving the second lens group L2 or the fourth lens group L4 along the optical axis instead of the first lens group L1 or the third lens group L3.

[0014] 2, 4, 6, 8, and 10 are aberration diagrams of the zoom lenses of Examples 1 to 5, respectively. In each aberration diagram, (A) is an aberration diagram at the wide-angle end, (B) is an aberration diagram at the intermediate zoom position, and (C) is an aberration diagram at the telephoto end.

[0015] 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, S shows the amount of astigmatism on the sagittal image plane, and M 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 (°).

[0016] Next, the characteristic configuration of the zoom lens of each embodiment will be described.

[0017] The zoom lens of each embodiment has, arranged in order from the object side to the image side, a first lens unit L1 with negative refractive power, a second lens unit L2 with positive refractive power, and a subsequent lens unit L3. This configuration makes it possible to obtain a compact, wide-angle, large-aperture zoom lens.

[0018] The first lens group L1 includes at least one resin lens having a negative refractive power, and at least one of the second lens group L2 and the subsequent group includes at least one resin lens having a positive refractive power. With this configuration, fluctuations in focus and curvature of field can be suppressed even when the temperature changes, and high optical performance can be maintained.

[0019] The zoom lens of each embodiment satisfies the following conditional expressions (1) to (3).

[0020] 0.01<|f1 / f2|<1.00 (1) 10.0<|fnpa / f1|<20.0 (2) 0.15<|fppa / fnpa|<1.00 (3) Here, f1 is the focal length of the first lens group L1, f2 is the focal length of the second lens group L2, fnpa is the average focal length (mean focal length) of the resin lenses with negative refractive power that are provided in the first lens group L1, and fppa is the average focal length (mean focal length) of the resin lenses with positive refractive power that are provided in at least one of the second lens group L2 and the subsequent group.

[0021] Conditional formula (1) defines the relationship between the focal length f1 of the first lens group L1 and the focal length f2 of the second lens group L2. If the lower limit of conditional formula (1) is not met, the refractive power of the first lens group L1 becomes too strong relative to the refractive power of the second lens group L2, which undesirably worsens field curvature, particularly at the wide-angle end. If the upper limit of conditional formula (1) is exceeded, the refractive power of the first lens group L1 becomes too weak relative to the refractive power of the second lens group L2, which undesirably makes it difficult to achieve a wide angle.

[0022] Conditional expression (2) defines the relationship between the average focal length of the negative refractive power resin lenses in the first lens group L1 and the focal length of the first lens group L1. Below the lower limit of conditional expression (2), fluctuations in focus and curvature of field due to temperature changes become large, which is undesirable. Above the upper limit of conditional expression (2), correction of distortion and curvature of field at the wide-angle end becomes insufficient, which is undesirable.

[0023] Conditional expression (3) defines the relationship between the average focal length of the resin lenses with positive refractive power in the second lens group L2 or the subsequent group and the average focal length of the resin lenses with negative refractive power in the first lens group L1. If the upper limit of conditional expression (3) is exceeded or the lower limit is exceeded, fluctuations in focus and field curvature due to temperature changes cannot be offset, which is undesirable.

[0024] With the above-described configuration, the zoom lens of each embodiment can have a large aperture and high optical performance while being small and having a wide angle.

[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] 0.32<|f1 / f2|<0.97 (1a) 10.5<|fnpa / f1|<17.5 (2a) 0.15<|fppa / fnpa|<0.76 (3a) It is more preferable that the numerical ranges of the conditional expressions (1) to (3) be the numerical ranges of the following conditional expressions (1b) to (3b).

[0027] 0.64<|f1 / f2|<0.93 (1b) 10.9<|fnpa / f1|<15.1 (2b) 0.15<|fppa / fnpa|<0.52 (3b) Next, the configurations that are preferably satisfied in the zoom lens of each embodiment will be described.

[0028] During zooming from the wide-angle end to the telephoto end, it is preferable that the first lens unit L1 move along a locus convex toward the image side, and the second lens unit L2 move monotonically toward the object side, which is preferable because this enables efficient zooming while keeping the overall system compact.

[0029] The resin lens included in the zoom lens is preferably aspherical, which is preferable because it allows for suitable correction of various aberrations such as spherical aberration and coma aberration.

[0030] Next, conditions that the zoom lens of each embodiment should preferably satisfy will be described. The zoom lens of each embodiment should preferably satisfy one or more of the following conditional expressions (4) to (11).

[0031] 0.20<|f2 / M2wt|<1.00 (4) Nd<0.00015×(νd-50) 2 +1.56 (5) 0.10<|M2wt / TLw|<0.70 (6) 0.05 <BFw / f2<0.60 (7) 0.50 <f2p / f2<1.50 (8) 0.05 <D2p / D2<0.50 (9) 0.50<|f3p / f3|<3.00 (10) 0.50 <f4p / f4<1.00 (11) Here, M2wt is the maximum movement amount of the second lens group L2 during zooming. Nd is the refractive index of the plastic lens included in the zoom lens. νd is the Abbe number of the plastic lens included in the zoom lens. TLw is the total lens length at the wide-angle end (the distance on the optical axis from the front surface (the surface closest to the object) of the zoom lens to the image plane). BFw is the back focus at the wide-angle end (the distance on the optical axis from the final lens surface (the lens surface closest to the image) of the zoom lens to the image plane). f2p is the average focal length (mean focal length) of the plastic lenses with positive refractive power included in the second lens group L2. D2 is the total thickness of the second lens group L2 (the distance on the optical axis from the surface closest to the object to the surface closest to the image). D2p is the total thickness of the plastic lenses with positive refractive power included in the second lens group L2 (the distance on the optical axis from the lens surface closest to the object to the lens surface closest to the image). f3 is the focal length of the third lens group L3. f3p is the average focal length (mean focal length) of the resin lenses with positive refractive power included in the third lens group L3. f4 is the focal length of the fourth lens group L4. f4p is the average focal length (mean focal length) of the resin lenses with positive refractive power included in the fourth lens group L4.

[0032] Conditional expression (4) defines the relationship between the focal length of the second lens unit L2 and the maximum amount of movement of the second lens unit L2 during zooming. Below the lower limit of conditional expression (4), the refractive power of the second lens unit L2 becomes stronger relative to the maximum amount of movement of the second lens unit L2, undesirably increasing the fluctuations in spherical aberration and coma during zooming. Above the upper limit of conditional expression (4), the refractive power of the second lens unit L2 becomes weaker relative to the maximum amount of movement of the second lens unit L2, undesirably increasing the lens diameter of the subsequent lens group and making it difficult to reduce the size of the zoom lens.

[0033] Conditional expression (5) defines the ranges that the refractive index and Abbe number, which are the optical characteristics of the resin lens element included in the zoom lens, should fall within. If the range of conditional expression (5) is not satisfied, there will be no material that can be selected for the resin lens element, and fluctuations in focus and field curvature due to temperature changes will not be able to be offset, which is undesirable.

[0034] Conditional expression (6) defines the relationship between the maximum amount of movement of the second lens unit L2 during zooming and the overall lens length at the wide-angle end. Below the lower limit of conditional expression (6), the refractive power of the second lens unit L2 becomes large, which is undesirable because it increases the fluctuations in spherical aberration and coma when the aperture is increased. Above the upper limit of conditional expression (6), it becomes difficult to reduce the size of the zoom lens, which is undesirable.

[0035] Conditional expression (7) defines the relationship between the back focal length at the wide-angle end and the focal length of the second lens unit L2. If the lower limit of conditional expression (7) is exceeded, the refractive power of the first lens unit L1 becomes excessively weak, making it difficult to achieve a wide angle, which is undesirable. If the upper limit of conditional expression (7) is exceeded, it becomes difficult to reduce the size of the zoom lens, which is undesirable.

[0036] Conditional expression (8) defines the relationship between the average focal length of the resin lenses with positive refractive power in the second lens group L2 and the focal length f2 of the second lens group L2. Below the lower limit of conditional expression (8), defocusing increases with temperature changes, which is undesirable. Above the upper limit of conditional expression (8), spherical aberration correction becomes insufficient when the aperture is increased, which is undesirable.

[0037] Conditional expression (9) defines the relationship between the sum of the thicknesses of the resin lenses with positive refractive power included in the second lens group L2 and the total thickness of the second lens group L2. If the lower limit of conditional expression (9) is exceeded, it is not preferable because focus fluctuations caused by temperature changes cannot be offset. If the upper limit of conditional expression (9) is exceeded, it is not preferable because it becomes difficult to reduce the size of the zoom lens.

[0038] Conditional expression (10) defines the relationship between the average focal length of the resin lenses with positive refractive power included in the third lens group L3 and the focal length of the third lens group L3. If the lower limit of conditional expression (10) is not met, focus shifts due to temperature changes become significant, which is undesirable. If the upper limit of conditional expression (10) is exceeded, correction of coma aberration will be insufficient when the aperture is increased, which is undesirable.

[0039] Conditional expression (11) defines the relationship between the average focal length of the resin lenses with positive refractive power included in the fourth lens group L4 and the focal length of the fourth lens group L4. If the lower limit of conditional expression (11) is exceeded, the focus will become larger due to temperature changes, which is undesirable. If the upper limit of conditional expression (11) is exceeded, the correction of field curvature will be insufficient, which is undesirable.

[0040] It is preferable that the numerical ranges of the conditional expressions (4) to (11) be the numerical ranges of the following conditional expressions (4a) to (11a).

[0041] 0.36<|f2 / M2wt|<0.83 (4a) Nd<0.00015×(νd-50) 2 +1.55 (5a) 0.22<|M2wt / TLw|<0.55 (6a) 0.12 <BFw / f2<0.48 (7a) 0.72 <f2p / f2<1.35 (8a) 0.11 <D2p / D2<0.40 (9a) 0.62<|f3p / f3|<2.82 (10a) 0.63 <f4p / f4<0.89 (11a) It is more preferable that the numerical ranges of the conditional expressions (4) to (11) be the numerical ranges of the following conditional expressions (4b) to (11b).

[0042] 0.53<|f2 / M2wt|<0.66 (4b) Nd<0.00015×(νd-50)^2+1.545 (5b) 0.35<|M2wt / TLw|<0.41 (6b) 0.19 <BFw / f2<0.36 (7b) 0.93 <f2p / f2<1.20 (8b) 0.17 <D2p / D2<0.30 (9b) 0.74<|f3p / f3|<2.63 (10b) 0.76 <f4p / f4<0.77 (11b) Next, the zoom lens of each embodiment will be described in detail.

[0043] The zoom lens of Example 1 includes 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, arranged in this order from the object side to the image side. The first lens group L1 includes, arranged in this order from the object side to the image side, a spherical lens with negative refractive power, a spherical lens with negative refractive power, a resin lens with negative refractive power, and a spherical lens with positive refractive power. The second lens group L2 includes, arranged in this order from the object side to the image side, an aspherical lens with positive refractive power, a cemented lens consisting of a spherical lens with positive refractive power and a spherical lens with negative refractive power, an aperture stop SP, and a spherical lens with positive refractive power. The third lens group L3 includes, arranged in this order from the object side to the image side, a spherical lens with negative refractive power and a resin lens with positive refractive power. The fourth lens group L4 includes a positive lens.

[0044] The zoom lens of Example 2 includes multiple lens groups 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. The first lens group L1 includes, arranged in order from the object side to the image side, a spherical lens with negative refractive power, a spherical lens with negative refractive power, a resin lens with negative refractive power, and a spherical lens with positive refractive power. The second lens group L2 includes, arranged in order from the object side to the image side, an aspherical lens with positive refractive power, an aperture stop SP, a cemented lens consisting of a spherical lens with positive refractive power and a spherical lens with negative refractive power, and a spherical lens with positive refractive power. The third lens group L3 includes, arranged in order from the object side to the image side, a cemented lens consisting of a spherical lens with negative refractive power and a spherical lens with positive refractive power. The fourth lens group L4 is composed of a spherical lens with negative refractive power and a resin lens with positive refractive power, arranged in this order from the object side to the image side.

[0045] The zoom lens of Example 3 includes 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, arranged in this order from the object side to the image side. The first lens group L1 includes, arranged in this order from the object side to the image side, a spherical lens with negative refractive power, a spherical lens with negative refractive power, a resin lens with negative refractive power, and a spherical lens with positive refractive power. The second lens group L2 includes, arranged in this order from the object side to the image side, an aperture stop SP, a resin lens with positive refractive power, a cemented lens consisting of a spherical lens with positive refractive power and a negative spherical lens, and a spherical lens with positive refractive power. The third lens group L3 includes, arranged in this order from the object side to the image side, a spherical lens with negative refractive power and a resin lens with positive refractive power. The fourth lens group L4 includes a spherical lens with positive refractive power.

[0046] The zoom lens of Example 4 includes multiple lens groups 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, and a third lens group L3 with positive refractive power. The first lens group L1 includes, arranged in order from the object side to the image side, a spherical lens with negative refractive power, a spherical lens with negative refractive power, a resin lens with negative refractive power, and a spherical lens with positive refractive power. The second lens group L2 includes, arranged in order from the object side to the image side, an aperture stop SP, an aspherical lens with positive refractive power, a cemented lens consisting of a spherical lens with positive refractive power and a spherical lens with negative refractive power, a spherical lens with positive refractive power, and a spherical lens with negative refractive power. The third lens group L3 includes a resin lens with positive refractive power.

[0047] The zoom lens of Example 5 includes a first lens group L1 with negative refractive power, a second lens group L2 with positive refractive power, and a third lens group L3 with positive refractive power, arranged in this order from the object side to the image side. The first lens group L1 includes a spherical lens with negative refractive power, a resin lens with negative refractive power, a resin lens with negative refractive power, and a spherical lens with positive refractive power, arranged in this order from the object side to the image side. The second lens group L2 includes an aperture stop SP, an aspherical lens with positive refractive power, a cemented lens consisting of a spherical lens with positive refractive power and a spherical lens with negative refractive power, a resin lens with positive refractive power, and a spherical lens with negative refractive power, arranged in this order from the object side to the image side. The third lens group L3 includes a resin lens with positive refractive power.

[0048] In the zoom lens of each embodiment, further aberration correction may be performed by dividing the cemented lens and providing an air gap between the lenses, or by replacing the spherical lens with an aspherical lens.

[0049] Furthermore, in each embodiment, the temperature change is assumed to be from -20°C to +70°C, with the ambient temperature reference being centered at +25°C, but it is also possible to accommodate temperature changes beyond this range by changing the number of resin lenses, the focal length, the arrangement of each group, etc.

[0050] Numerical Examples 1 to 5 corresponding to Examples 1 to 5, respectively, are shown below.

[0051] 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. Also, 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 when 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 are Nd, NF, and NC, respectively: νd=(Nd-1) / (NF-NC) It is expressed as:

[0052] In each numerical example, d, focal length (mm), F-number, and half angle of view (°) 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 length on the optical axis from the front surface (the surface closest to the object) of the zoom lens to the final lens surface (the surface closest to the image) plus the back focus.

[0053] 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.

[0054] <Numerical Example 1> Unit: mm Surface Data Surface number rd nd νd 1 ∞ 0.62 1.88300 40.8 2 7.705 4.38 3 -13.994 0.57 1.59522 67.7 4 -65.089 0.42 5* -50.255 0.59 1.53500 55.7 6* 2780.252 0.17 7 246.797 1.55 1.95906 17.5 8 -40.214 (variable) 9* 10.532 3.78 1.58313 59.4 10* -23.163 0.20 11 7.810 2.71 1.49700 81.5 12 21.771 0.56 1.85478 24.8 13 6.310 2.79 14 (Aperture) ∞ 1.04 15 11.944 2.23 1.88300 40.8 16 -63.086 (variable) 17 -88.272 0.58 2.05090 26.9 18 16.201 0.21 19* 25.859 1.29 1.53500 55.7 20* -1286.962 (variable) 21 38.435 1.65 1.49700 81.5 22 -14.856 (variable) 23 ∞ 0.80 1.51633 64.1 24 ∞ (variable) Image plane ∞ Aspheric data 5th page K = 6.47832e+01 A 4=-2.16571e-04 A 6= 2.39689e-06 Page 6 K =-6.36912e+22 A 4=-3.19923e-04 A 6= 1.40168e-06 A 8= 5.76572e-09 A10=-6.86490e-10 9th page K =-1.50213e-01 A 4=-1.04423e-04 A 6=-8.48732e-07 A 8= 2.53664e-08 A10=-1.00066e-09 Side 10 K =-1.60873e+01 A 4=-6.96346e-05 A 6= 6.41692e-07 A 8= 1.35366e-08 A10=-9.76832e-10 Page 19 K =-4.74262e+01 A 4= 5.23678e-04 A 6=-5.18130e-05 A 8= 1.74555e-06 Page 20 K =-6.61729e+19 A 4= 4.67813e-04 A 6=-1.46760e-05 Various data Zoom ratio 4.90 Wide-angle Mid-range Telephoto Focal length 3.44 9.91 16.88 F-number 1.44 2.46 3.60 Half angle of view (°) 62.2 18.5 10.9 Image height 3.20 3.20 3.20 Lens length 50.77 45.25 51.99 BF 3.60 3.60 3.60 d 8 19.69 4.00 0.57 d16 0.89 2.81 4.03 d20 1.27 9.51 18.47 d22 2.07 2.07 2.07 d24 1.00 1.00 1.00 Zoom lens group data Group starting plane focal length 1 1 -7.67 2 9 10.95 3 17 -18.04 4 21 21.78 5 23 ∞ <Numerical Example 2> Unit: mm Surface Data Surface number rd nd νd 1 -75.298 0.63 1.88300 40.8 2 8.787 2.83 3 -155.918 0.60 1.53775 74.7 4 21.713 1.62 5* -54.603 0.87 1.53500 55.7 6* -38799.299 0.23 7 32.506 1.37 1.95906 17.5 8 -367.230 (variable) 9* 10.450 3.40 1.58313 59.4 10* -27.805 1.32 11 (Aperture) ∞ 0.10 12 8.368 2.74 1.49700 81.5 13 59.461 0.60 1.85478 24.8 14 6.705 1.10 15 20.632 1.76 1.77250 49.6 16 -21.636 (variable) 17 -16.510 0.60 1.58144 40.8 18 25.906 0.96 1.88300 40.8 19 3060.488 (variable) 20 382.328 0.60 1.64769 33.8 21 37.627 0.18 22* 14.532 2.64 1.53500 55.7 23* -19.715 (variable) 24 ∞ 0.80 1.51633 64.1 25 ∞ (variable) Image plane ∞ Aspheric data 5th page K = 6.40470e+01 A 4=-3.38164e-04 A 6= 3.30958e-06 Page 6 K =-6.36912e+22 A 4=-4.04399e-04 A 6= 2.70582e-06 A 8= 5.76572e-09 A10=-6.86490e-10 9th page K =-1.12727e+00 A 4=-1.05065e-05 A 6= 1.59209e-08 A 8= 1.98133e-08 A10=-1.00066e-09 Side 10 K = 6.91227e+00 A 4= 1.00548e-04 A 6=-3.67346e-09 A 8= 1.35366e-08 A10=-9.76832e-10 Page 22 K =-1.17527e+01 A 4= 4.60854e-04 A 6=-1.08543e-05 Page 23 K = 2.14874e+00 A 4= 7.90531e-05 A 6=-5.93053e-06 Various data Zoom ratio 4.77 Wide-angle Mid-range Telephoto Focal length 3.50 9.99 16.68 F-number 1.44 2.52 3.61 Half angle of view (°) 66.3 18.6 11.1 Image height 3.20 3.20 3.20 Lens length 51.23 44.66 51.24 BF 3.96 3.96 3.96 d 8 20.98 4.30 0.77 d16 1.20 3.51 4.90 d19 0.93 8.72 17.45 d23 2.43 2.43 2.43 d25 1.00 1.00 1.00 Zoom lens group data Group starting plane focal length 1 1 -9.04 2 9 11.32 3 17 -42.16 4 20 21.01 5 24 ∞ <Numerical Example 3> Unit: mm Surface Data Surface number rd nd νd 1 123.641 0.66 1.88300 40.8 2 7.858 6.04 3 -9.816 0.60 1.80400 46.6 4 -33.910 0.17 5* -58.831 0.91 1.53500 55.7 6* 19817.132 0.17 7 -47.134 1.25 1.95906 17.5 8 -17.113 (variable) 9 (Aperture) ∞ 0.10 10* 9.332 3.33 1.53500 55.7 11* -27.801 0.17 12 8.569 1.83 1.49700 81.5 13 16.101 0.60 1.85478 24.8 14 6.764 3.04 15 14.458 2.31 1.71300 53.9 16 -32.513 (variable) 17 28.551 0.90 2.05090 26.9 18 9.600 0.52 19* 13.368 3.72 1.53500 55.7 20* -17191.284 (variable) 21 21.300 1.45 1.49700 81.5 22 -52.720 (variable) 23 ∞ 0.80 1.51633 64.1 24 ∞ (variable) Image plane ∞ Aspheric data 5th page K = 8.66914e+01 A 4= 2.47670e-05 A 6=-1.19261e-06 Page 6 K =-6.36912e+22 A 4=-1.28371e-04 A 6=-8.27771e-07 A 8= 5.76572e-09 A10=-6.86490e-10 Side 10 K =-9.01441e-01 A 4=-1.89289e-05 A 6= 8.03051e-08 A 8= 2.85385e-08 A10=-1.00066e-09 Page 11 K =-1.85210e+01 A 4= 5.65520e-06 A 6= 4.62581e-07 A 8= 1.35366e-08 A10=-9.76832e-10 Page 19 K =-1.32931e+01 A 4= 3.37309e-04 A 6=-2.51519e-05 A 8= 2.42695e-07 Page 20 K =-6.61729e+19 A 4=-3.27574e-04 A 6=-8.48404e-06 Various data Zoom ratio 4.47 Wide-angle Mid-range Telephoto Focal length 3.19 8.64 14.24 F-number 1.65 2.81 4.12 Half angle of view (°) 72.8 21.5 12.9 Image height 3.20 3.20 3.20 Lens length 54.13 48.32 54.66 BF 3.84 3.84 3.84 d 8 20.55 4.80 1.20 d16 1.10 2.35 3.14 d20 0.87 9.56 18.70 d22 2.31 2.31 2.31 d24 1.00 1.00 1.00 Zoom lens group data Group starting plane focal length 1 1 -7.31 2 9 11.26 3 17 -33.34 4 21 30.72 5 23 ∞ <Numerical Example 4> Unit: mm Surface Data Surface number rd nd νd 1 -77.119 0.67 1.77250 49.6 2 9.414 4.17 3 -18.931 0.60 1.53775 74.7 4 -602.098 0.17 5* 1092.137 0.92 1.53110 55.9 6* 57.408 0.17 7 87.635 1.46 1.95906 17.5 8 -52.052 (variable) 9 (Aperture) ∞ 0.00 10* 10.248 3.22 1.55332 71.7 11* -23.975 0.17 12 9.473 3.71 1.49700 81.5 13 137.307 0.60 1.85478 24.8 14 7.176 3.66 15 15.410 2.38 1.88300 40.8 16 -15.451 2.37 17 -10.290 0.60 1.68893 31.1 18 42.114 (variable) 19* 9.599 2.11 1.53110 55.9 20* -3669.299 (variable) 21 ∞ 0.80 1.51633 64.1 22 ∞ (variable) Image plane ∞ Aspheric data 5th page K = 1.11537e+03 A 4=-7.17236e-05 A 6=-8.43960e-07 Page 6 K =-8.45357e+01 A 4=-1.10581e-04 A 6=-1.25902e-06 Side 10 K = 4.22186e-01 A 4=-1.92465e-04 A 6=-3.44325e-07 A 8=-1.81069e-08 Page 11 K =-5.00617e-01 A 4= 1.03770e-04 A 6= 3.59572e-07 Page 19 K =-6.77685e+00 A 4= 8.21887e-04 A 6=-1.86867e-05 Page 20 K =-4.76325e+18 A 4= 1.20936e-04 A 6=-8.83516e-06 Various data Zoom ratio 4.91 Wide-angle Mid-range Telephoto Focal length 3.76 8.47 18.46 F-number 1.44 2.13 3.61 Half angle of view (°) 55.1 21.6 9.67 Image height 3.20 3.20 3.20 Lens length 50.21 42.74 50.29 BF 2.20 2.20 2.20 d 8 20.57 6.73 0.74 d18 0.45 6.82 20.36 d20 0.68 0.68 0.68 d22 1.00 1.00 1.00 Zoom lens group data Group starting plane focal length 1 1 -10.38 2 9 11.26 3 19 18.03 4 21 ∞ <Numerical Example 5> Unit: mm Surface Data Surface number rd nd νd 1 -53.258 0.64 1.80400 46.6 2 8.606 4.41 3* -18.517 0.77 1.53110 55.9 4* 124.153 0.17 5* 30.752 0.60 1.53110 55.9 6* 22.918 0.30 7 222.326 2.49 1.95906 17.5 8 -33.605 (variable) 9 (Aperture) ∞ -0.22 10* 9.763 3.62 1.55332 71.7 11* -22.694 0.96 12 8.919 2.19 1.53775 74.7 13 25.706 0.60 1.85478 24.8 14 6.738 4.14 15* 11.221 2.95 1.53110 55.9 16* -10.869 2.33 17 -8.878 0.60 1.58144 40.8 18 122.613 (variable) 19* 11.061 1.85 1.53110 55.9 20* -2544.228 (variable) 21 ∞ 0.80 1.51000 60.0 22 ∞ (variable) Image plane ∞ Aspheric data 3rd page K =-2.15075e+00 A 4=-1.79633e-04 A 6=-4.52201e-09 Side 4 K =-7.57533e+01 A 4=-5.32581e-04 A 6=-2.55729e-06 5th page K = 1.65922e+01 A 4=-7.17077e-04 A 6=-1.35298e-06 A 8=-5.75713e-08 Page 6 K =-2.21999e+01 A 4=-1.83385e-04 A 6=-1.80857e-06 Side 10 K = 9.14728e-02 A 4=-1.79236e-04 A 6=-6.17464e-07 A 8=-1.81069e-08 Page 11 K =-7.14555e+00 A 4= 4.38360e-05 A 6=-3.65722e-07 Page 15 K =-4.17997e+00 A 4= 4.18841e-04 A 6=-7.14560e-06 Page 16 K =-4.36963e+00 A 4=-3.13482e-04 A 6=-1.65206e-06 Page 19 K =-8.75822e+00 A 4= 8.25445e-04 A 6=-2.22444e-05 Page 20 K =-4.76325e+18 A 4= 4.43267e-04 A 6=-1.41270e-05 Various data Zoom ratio 4.11 Wide-angle Mid-range Telephoto Focal length 3.76 7.49 15.43 F-number 1.44 2.13 3.61 Half angle of view (°) 55.5 24.5 11.5 Image height 3.20 3.20 3.20 Lens length 50.16 44.16 50.22 BF 2.59 2.59 2.59 d 8 18.74 7.04 0.98 d18 0.45 6.16 18.28 d20 1.06 1.06 1.06 d22 1.00 1.00 1.00 Zoom lens group data Group starting plane focal length 1 1 -9.30 2 9 11.61 3 19 20.74 4 21 ∞ The various values ​​in each numerical example are summarized in Table 1 below.

[0055] [Table 1]

[0056] [Imaging device] Hereinafter, an embodiment of an imaging device using the zoom lens of each embodiment as a photographing optical system will be described with reference to Figures 11 to 13. Figures 11 to 13 are schematic diagrams of the imaging device.

[0057] 11 to 13, 16 denotes an imaging optical system constituted by the zoom lens of any one of Examples 1 to 5. In FIGS. 11 and 13, 15 denotes a cover that protects the imaging optical system 16. In FIG. 12, 17 denotes a cover that protects the imaging optical system 16. In FIG. 13, 11 denotes a surveillance camera body, and 12 denotes an imaging element (photoelectric conversion element) such as a CCD sensor or CMOS sensor that is built into the surveillance camera body 11 and receives a subject image formed by the imaging optical system 16. 13 denotes a memory that records information corresponding to the subject image photoelectrically converted by the imaging element 12. 14 denotes a network cable for transferring the subject image photoelectrically converted by the imaging element 12. Note that the imaging device is not limited to a surveillance camera, and can also be used in video cameras, digital cameras, etc.

[0058] The imaging device of the present invention may include a circuit for electrically correcting at least one of distortion and lateral chromatic aberration, along with the zoom lens of any of Examples 1 to 5. By adopting a configuration that can tolerate distortion and other aberrations of the zoom lens in this way, the number of lenses in the entire zoom lens can be reduced, facilitating miniaturization. Furthermore, electrically correcting lateral chromatic aberration reduces color bleeding in captured images, making it easier to improve resolution. [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 and focusing. 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.

[0059] 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. In this case, the control unit may be configured to 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.

[0060] 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 includes, for example, the zoom magnification (zoom state) and the amount of movement (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 the operation unit may be integrated by using, for example, a touch panel.

[0061] The disclosure of this embodiment includes the following configuration. (Configuration 1) A zoom lens having a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a subsequent lens group arranged in this order from the object side to the image side, in which the spacing between adjacent lens groups changes during zooming, the first lens group includes at least one resin lens having a negative refractive power, at least one of the second lens group and the subsequent lens group includes at least one resin lens having a positive refractive power; When the focal length of the first lens group is f1, the focal length of the second lens group is f2, the average focal length of the resin lenses with negative refractive power provided in the first lens group is fnpa, and the average focal length of the resin lenses with positive refractive power provided in at least one of the second lens group and the subsequent lens group is fppa, 0.01<|f1 / f2|<1.00 10.0<|fnpa / f1|<20.0 0.15<|fppa / fnpa|<1.00 A zoom lens characterized by satisfying the following conditional expressions: (Configuration 2) When the maximum movement amount of the second lens group during zooming is M2wt, 0.20<|f2 / M2wt|<1.00 2. The zoom lens according to claim 1, wherein the following condition is satisfied: (Configuration 3) 3. The zoom lens according to configuration 1 or 2, wherein, during zooming from the wide-angle end to the telephoto end, the first lens group moves along a convex locus toward the image side, and the second lens group moves monotonically toward the object side. (Configuration 4) 4. The zoom lens according to any one of configurations 1 to 3, wherein the resin lens included in the zoom lens has an aspherical shape. (Configuration 5) When the refractive index of the resin lens included in the zoom lens is Nd and the Abbe number of the resin lens included in the zoom lens is νd, Nd<0.00015×(νd-50) 2 +1.56 5. A zoom lens according to any one of configurations 1 to 4, characterized in that the following condition is satisfied: (Configuration 6) When the maximum movement amount of the second lens group during zooming is M2wt and the total lens length at the wide-angle end is TLw, 0.10<|M2wt / TLw|<0.70 6. A zoom lens according to any one of configurations 1 to 5, characterized in that the following condition is satisfied: (Configuration 7) When the back focal length at the wide-angle end is BFw, 0.05 <BFw / f2<0.60 7. A zoom lens according to any one of configurations 1 to 6, characterized in that the following condition is satisfied: (Configuration 8) the second lens group includes at least one resin lens having a positive refractive power, When the average focal length of the resin lenses with positive refractive power included in the second lens group is f2p, 0.50 <f2p / f2<1.50 8. A zoom lens according to any one of configurations 1 to 7, characterized in that the following condition is satisfied: (Configuration 9) the second lens group includes at least one resin lens having a positive refractive power, When the total thickness of the second lens group is D2 and the total thickness of the resin lenses with positive refractive power included in the second lens group is D2p, 0.05 <D2p / D2<0.50 10. The zoom lens according to configuration 2 of any one of configurations 1 to 8, wherein the following condition is satisfied: (Configuration 10) 10. A zoom lens according to any one of configurations 1 to 9, wherein the subsequent group is a third lens group having a positive refractive power. (Configuration 11) The zoom lens according to any one of configurations 1 to 9, wherein the subsequent lens group comprises a third lens group with negative refractive power and a fourth lens group with positive refractive power, arranged in this order from the object side to the image side. (Configuration 12) the third lens group includes at least one resin lens having a positive refractive power, When the focal length of the third lens group is f3 and the average focal length of the resin lenses with positive refractive power included in the third lens group is f3p, 0.50<|f3p / f3|<3.00 12. The zoom lens according to configuration 11, wherein the following condition is satisfied: (Configuration 13) the fourth lens group includes at least one resin lens having a positive refractive power, When the focal length of the fourth lens group is f4 and the average focal length of the resin lenses with positive refractive power included in the fourth lens group is f4p, 0.50 <f4p / f4<1.00 13. The zoom lens according to configuration 11 or 12, wherein the following condition is satisfied: (Configuration 14) 14. An imaging device comprising: the zoom lens according to any one of configurations 1 to 13; and an imaging element that receives an image formed by the zoom lens. (Configuration 15) 14. An imaging system comprising: a zoom lens according to any one of configurations 1 to 13; and a control unit that controls the zoom lens during zooming. (Configuration 16) 16. The imaging system according to claim 15, wherein the control unit is configured as a separate unit from the zoom lens and includes a transmission unit that transmits a control signal for controlling the zoom lens. (Configuration 17) 17. The imaging system according to configuration 15 or 16, wherein the control unit is configured as a separate unit from the zoom lens and has an operation unit for operating the zoom lens. (Configuration 18) 18. The imaging system according to any one of configurations 15 to 17, further comprising a display unit that displays information related to the zoom of the zoom lens.

[0062] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0063] L1 First lens group L2 Second lens group

Claims

1. A zoom lens having a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a subsequent lens group, which are arranged in this order from the object side to the image side, and in which the spacing between adjacent lens groups changes during zooming, the first lens group includes at least one resin lens having a negative refractive power, at least one of the second lens group and the subsequent lens group includes at least one resin lens having a positive refractive power; When the focal length of the first lens group is f1, the focal length of the second lens group is f2, the average focal length of the resin lenses with negative refractive power provided in the first lens group is fnpa, and the average focal length of the resin lenses with positive refractive power provided in at least one of the second lens group and the subsequent lens group is fppa, 0.01<|f1 / f2|<1.00 10.0<|fnpa / f1|<20.0 0.15<|fppa / fnpa|<1.00 A zoom lens characterized by satisfying the following conditional expressions:

2. When the maximum movement amount of the second lens group during zooming is M2wt, 0.20<|f2 / M2wt|<1.00 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

3. 3. The zoom lens according to claim 1, wherein, during zooming from the wide-angle end to the telephoto end, the first lens group moves along a locus convex toward the image side, and the second lens group moves monotonically toward the object side.

4. 3. The zoom lens according to claim 1, wherein the resin lens included in the zoom lens has an aspherical shape.

5. When the refractive index of the resin lens included in the zoom lens is Nd and the Abbe number of the resin lens included in the zoom lens is νd, Nd<0.00015×(νd-50) ２ +1.56 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

6. When the maximum movement amount of the second lens group during zooming is M2wt and the total lens length at the wide-angle end is TLw, 0.10<|M2wt / TLw|<0.70 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

7. When the back focus at the wide-angle end is BFw, 0.05<BFw / f2<0.60 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

8. the second lens group includes at least one resin lens having a positive refractive power, When the average focal length of the resin lenses with positive refractive power included in the second lens group is f2p, 0.50<f2p / f2<1.50 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

9. the second lens group includes at least one resin lens having a positive refractive power, When the total thickness of the second lens group is D2 and the total thickness of the resin lenses with positive refractive power included in the second lens group is D2p, 0.05<D2p / D2<0.50 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

10. 3. A zoom lens according to claim 1, wherein the subsequent lens group comprises a third lens group having a positive refractive power.

11. 3. The zoom lens according to claim 1, wherein the subsequent lens group comprises, in order from the object side to the image side, a third lens group having a negative refractive power and a fourth lens group having a positive refractive power.

12. the third lens group includes at least one resin lens having a positive refractive power, When the focal length of the third lens group is f3 and the average focal length of the resin lenses with positive refractive power included in the third lens group is f3p, 0.50<|f3p / f3|<3.00 12. The zoom lens according to claim 11, wherein the following condition is satisfied:

13. the fourth lens group includes at least one resin lens having a positive refractive power, When the focal length of the fourth lens group is f4 and the average focal length of the resin lenses with positive refractive power included in the fourth lens group is f4p, 0.50<f4p / f4<1.00 12. The zoom lens according to claim 11, wherein the following condition is satisfied:

14. 3. An imaging device comprising: the zoom lens according to claim 1; and an imaging element that receives an image formed by the zoom lens.

15. 3. An imaging system comprising: the zoom lens according to claim 1; and a control unit that controls the zoom lens during zooming.

16. 16. The imaging system according to claim 15, wherein the control unit is configured as a separate unit from the zoom lens and includes a transmission unit that transmits a control signal for controlling the zoom lens.

17. 16. The imaging system according to claim 15, wherein the control unit is configured as a separate unit from the zoom lens and has an operation unit for operating the zoom lens.

18. 16. The imaging system according to claim 15, further comprising a display unit that displays information related to the zoom of the zoom lens.

Images