Zoom lens and imaging apparatus

Abstract

To provide a zoom lens advantageous in terms of its small size, high zoom ratio, and high optical performance.SOLUTION: A zoom lens has a positive first lens group L1, a negative second lens group L2, a positive third lens group L3, and a positive fourth lens group L4. The first lens group does not move for zooming, and the second lens group and third lens group move for zooming. The third lens group is composed of five or less lenses. When the distances from a surface on the most image side of the third lens group to a surface on the most object side of the fourth lens group at a telephoto end and a wide angle end are defined as D34t and D34w, respectively, the amounts of movement of the second and third lens groups in zooming from the wide angle end to the telephoto end as M2 and M3, respectively, and the focal lengths of the zoom lens at the telephoto end and the wide angle end as ft and fw, respectively, conditions of 2.0<D34t / D34w<20.0, -25.0<M2 / M3<-5.1, and 11<ft / fw are satisfied.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Documents 1 and 2 disclose zoom lenses that are small and have a high zoom ratio, and have lens groups with positive, negative, positive, and positive refractive powers arranged in that order from the object side to the image side, in which the first lens group does not move during zooming, but the second and third lens groups move during zooming. The zoom lenses disclosed in these patent documents have a zoom ratio of about 11 to 12. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-148447 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-187640 Summary of the Invention [Problem to be solved by the invention]

[0004] SUMMARY OF THE INVENTION It is an object of the present invention to provide a zoom lens that is advantageous in terms of, for example, compactness, a high zoom ratio, and high optical performance. [Means for solving the problem]

[0005] One aspect of the present invention is a zoom lens having multiple lens groups, with the spacing between adjacent lens groups all changing during zooming. The multiple lens groups are arranged in order from the object side to the image side: a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, and a fourth lens group with positive refractive power. The first lens group does not move during zooming, while the second and third lens groups move during zooming. The third lens group consists of five or fewer lenses. Let D34t and D34w be the optical axial distances from the surface of the third lens group closest to the image at the telephoto end and the wide-angle end to the surface of the fourth lens group closest to the object, respectively; M2 and M3 be the amounts of movement of the second and third lens groups during zooming from the wide-angle end to the telephoto end; and ft and fw be the focal lengths of the zoom lens at the telephoto end and the wide-angle end, respectively. 2.0 <D34t / D34w<20.0 -25.0 <M2 / M3<-5.1 11 <ft / fw The present invention is characterized in that the following conditions are satisfied: An imaging device including the zoom lens described above also constitutes another aspect of the present invention. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide a zoom lens that is advantageous in terms of, for example, compact size, high zoom ratio, and high optical performance. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view of a zoom lens according to a first embodiment (first numerical example). [Figure 2] 10A and 10B are aberration diagrams at the wide-angle end of Numerical Example 1. [Figure 3] 10A and 10B are aberration diagrams at an intermediate zoom position in Numerical Example 1. [Figure 4] 10A and 10B are aberration diagrams at the telephoto end of Numerical Example 1. [Figure 5] FIG. 10 is a cross-sectional view of a zoom lens according to a second embodiment (Numerical Example 2). [Figure 6] 10A and 10B are aberration diagrams at the wide-angle end of Numerical Example 2. [Figure 7]10A and 10B are aberration diagrams at an intermediate zoom position in Numerical Example 2. [Figure 8] 10A and 10B are aberration diagrams at the telephoto end of Numerical Example 2. [Figure 9] FIG. 10 is a cross-sectional view of a zoom lens according to a third embodiment (Numerical Example 3). [Figure 10] 10A and 10B are aberration diagrams at the wide-angle end of Numerical Example 3. [Figure 11] 10A and 10B are aberration diagrams at an intermediate zoom position in Numerical Example 3. [Figure 12] 10A and 10B are aberration diagrams at the telephoto end of Numerical Example 3. [Figure 13] FIG. 10 is a cross-sectional view of a zoom lens according to a fourth embodiment (Numerical Example 1). [Figure 14] 10A and 10B are aberration diagrams at the wide-angle end of Numerical Example 4. [Figure 15] 10A and 10B are aberration diagrams at an intermediate zoom position in Numerical Example 4. [Figure 16] 10A and 10B are aberration diagrams at the telephoto end of Numerical Example 4. [Figure 17] FIG. 10 is a cross-sectional view of a zoom lens according to a fifth embodiment (Numerical Example 5). [Figure 18] 10A and 10B are aberration diagrams at the wide-angle end of Numerical Example 5. [Figure 19] 10A and 10B are aberration diagrams at an intermediate zoom position in Numerical Example 5. [Figure 20] 10A and 10B are aberration diagrams at the telephoto end of Numerical Example 5. [Figure 21] FIG. 1 is a diagram showing an imaging device equipped with a zoom lens according to any one of Examples 1 to 5. [Figure 22] FIG. 1 is a diagram showing a surveillance camera equipped with a zoom lens according to one of Examples 1 to 5. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, prior to describing specific embodiments 1 to 5, matters common to all embodiments will be described.

[0009] The zoom lens of each embodiment is used in various imaging devices such as digital still cameras, video cameras, broadcast cameras, surveillance cameras, cameras for silver halide film, etc. The zoom lens of each embodiment can also be used as a projection optical system for an image projection device (projector).

[0010] The zoom lens of each embodiment, as exemplified by Example 1 shown in FIG. 1, has multiple lens groups. The multiple lens groups are arranged in order from the object side to the image side: a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power, and a fourth lens group L4 with positive refractive power. The first lens group L1 does not move during zooming, while the second lens group L2 and the third lens group L3 move during zooming. The third lens group L3 is composed of five or fewer lenses. Regarding the number of lenses in a lens group, a single lens is counted as one, and for a cemented lens, each cemented lens is counted as one. The zoom lens of each embodiment achieves a high zoom ratio while being compact and efficient thanks to the configuration described above.

[0011] A lens group is a group of one or more lenses that move together during zooming between the wide-angle end and the telephoto end. That is, the spacing between adjacent lens groups among the multiple lens groups changes during zooming. Zooming is a concept that includes both variable magnification (changing focal length) and compensation for image plane movement. A zoom lens may include an aperture diaphragm. If a zoom lens includes an aperture diaphragm, the aperture diaphragm may not move during zooming, or may move along with one of the lens groups. The wide-angle end and telephoto end refer to the zoom states with the maximum angle of view (shortest focal length) and the minimum angle of view (maximum focal length), respectively, when the lens group that moves during zooming is located at the ends of its mechanically or controllably movable range on the optical axis. The zoom lens of each embodiment further satisfies the following conditions (1) to (3). 2.0 <D34t / D34w<20.0 (1) -25.0 <M2 / M3<-5.1 (2) 11 <ft / fw (3) In equations (1) to (3), D34t and D34w represent the axial distances from the surface of the third lens group closest to the image to the surface of the fourth lens group closest to the object at the telephoto and wide-angle ends, respectively. M2 and M3 represent the movement amounts of the second and third lens groups, respectively, when zooming from the wide-angle end to the telephoto end. The movement amounts referred to here are considered positive when the lens groups are positioned closer to the image at the telephoto end than at the wide-angle end. ft and fw represent the focal lengths of the zoom lens at the telephoto and wide-angle ends, respectively.

[0012] Equation (1) defines the condition for the relationship between the spacing between the third and fourth lens groups at the telephoto and wide-angle ends. If D34t / D34w exceeds the upper limit of equation (1), the range of movement of the third and fourth lens groups during zooming from the wide-angle end to the telephoto end becomes large, which undesirably increases the overall lens length. If D34t / D34w falls below the lower limit of equation (1), the range of movement of the third and fourth lens groups during zooming from the wide-angle end to the telephoto end becomes small, which undesirably makes it difficult to achieve a high zoom ratio.

[0013] Equation (2) defines the condition for the relationship between the amount of movement of the second lens group and the amount of movement of the third lens group during zooming from the wide-angle end to the telephoto end. If M2 / M3 exceeds the upper limit of equation (2), the zoom burden on the third lens group increases. However, the third lens group's contribution to zooming is smaller than that of the second lens group, making it difficult to achieve high zoom levels, which is undesirable. If M2 / M3 falls below the lower limit of equation (2), the change in focal length during zooming becomes gradual, increasing the angle of view at intermediate zoom positions, and the diameter of the first lens group, which is determined at intermediate zoom positions, also increases, which is undesirable.

[0014] Equation (3) shows the condition regarding the zoom ratio. If ft / fw falls below the lower limit of equation (3), the desired high zoom ratio cannot be obtained, which is not preferable.

[0015] It is more preferable that the numerical ranges of the formulas (1) to (3) are as follows: 2.0 <D34t / D34w<15.0 (1a) -25.00 <M2 / M3<-5.12 (2a) 15 <ft / fw<50 (3a) Furthermore, it is more preferable that the numerical ranges of the formulas (1) to (3) are as follows. 2.0 <D34t / D34w<11.0 (1b) -25.00 <M2 / M3<-5.15 (2b) twenty three <ft / fw<50 (3b) According to each embodiment, by having the above-described configuration and satisfying the conditions of expressions (1) to (3), it is possible to realize a compact zoom lens that has a simple configuration but also has a high zoom ratio and good optical performance.

[0016] It is preferable that the zoom lens of each embodiment satisfies at least one of the conditions of the following expressions (4) to (8). -4.9 <M2 / f2<-3.1 (4) -2.0 <f2 / fw<-1.2 (5) 0.00 <D12w / M2<0.10 (6) 1.00 <D12t / M2<1.10 (7) 50<νd1pave<102 (8) In equations (4) to (8), f2 is the focal length of the second lens group. D12w and D12t are the distances on the optical axis from the surface in the first lens group closest to the image to the surface in the second lens group closest to the object at the wide-angle end and the telephoto end, respectively. νd1pave is the average Abbe number (average Abbe number) of the Abbe numbers of multiple positive lenses in the first lens group, when the first lens group includes multiple positive lenses and the d-line of the multiple positive lenses is used as the reference.

[0017] Equation (4) shows the condition regarding the relationship between the focal length of the second lens group and the amount of movement of the second lens group from the wide-angle end to the telephoto end. If M2 / f2 exceeds the upper limit of equation (4), it becomes difficult to ensure the desired zoom ratio, which is undesirable. If M2 / f2 falls below the lower limit of equation (4), the overall lens length becomes too long, which is undesirable.

[0018] Equation (5) defines the condition for the relationship between the focal length of the second lens group and the focal length of the zoom lens at the wide-angle end. If f2 / fw exceeds the upper limit of equation (5), it becomes difficult to correct the fluctuation in field curvature that occurs with zooming, which is undesirable. If f2 / fw falls below the lower limit of equation (5), the overall lens length becomes too long to achieve the desired zoom ratio, which is undesirable.

[0019] Equation (6) expresses the condition regarding the relationship between the distance between the first and second lens groups at the wide-angle end and the amount of movement of the second lens group during zooming from the wide-angle end to the telephoto end. It is undesirable for D12w / M2 to exceed the upper limit of equation (6), as it becomes difficult to efficiently obtain the zoom ratio. It is also undesirable for D12w / M2 to fall below the lower limit of equation (6), as it becomes difficult to construct a lens barrel to hold the zoom lens.

[0020] Equation (7) expresses the condition regarding the relationship between the distance between the first and second lens groups at the telephoto end and the amount of movement of the second lens group during zooming from the wide-angle end to the telephoto end. It is undesirable for D12t / M2 to exceed the upper limit of equation (7), as it becomes difficult to efficiently obtain the zoom ratio. It is also undesirable for D12t / M2 to fall below the lower limit of equation (7), as it becomes difficult to construct a lens barrel to hold the zoom lens.

[0021] Expression (8) shows a condition regarding the average Abbe number of the plurality of positive lenses in the first lens group. When νd1pave exceeds the upper limit of expression (8), As a material for positive lenses Glass materials with low refractive indexes are increasingly being used, resulting in Positive lens This is undesirable because the curvature of the lens surface becomes large, resulting in significant spherical aberration and coma at the telephoto end. If νd1pave falls below the lower limit of equation (8), it becomes difficult to correct chromatic aberration at the telephoto end, which is also undesirable.

[0022] It is more preferable to specify the numerical ranges of the formulas (4) to (8) as follows: -4.9 <M2 / f2<-3.2 (4a) -2.0 <f2 / fw<-1.3 (5a) 0.00 <D12w / M2<0.05 (6a) 1.00 <D12t / M2<1.05 (7a) 50<νd1pave<99 (8a) It is more preferable to specify the numerical ranges of the formulas (4) to (8) as follows: -4.9 <M2 / f2<-3.3 (4b) -2.0 <f2 / fw<-1.4 (5b) 0.00 <D12w / M2<0.03 (6b) 1.00 <D12t / M2<1.03 (7b) 70<νd1pave<99 (8b) In the zoom lens of each embodiment, it is preferable to move the fourth lens group during zooming. By moving the fourth lens group during zooming, it is possible to both suppress changes in optical performance that occur with zooming and correct image plane movement.

[0023] In the zoom lens of each embodiment, it is preferable that the first lens group be composed of four or five lenses, including one negative lens. This configuration makes it possible to correct spherical aberration and coma, which are particularly noticeable at the telephoto end, as well as chromatic aberration, while preventing the first lens group and the overall lens length from increasing in size.

[0024] In the zoom lens of each embodiment, it is preferable that the second lens group be composed of a negative lens, a negative lens, a negative lens, and a positive lens arranged in that order from the object side to the image side. With this configuration, the principal point position of the second lens group is closer to the object side, making it possible to prevent the first lens group from becoming larger when the angle of view is widened.

[0025] Furthermore, in the zoom lens of each embodiment, it is preferable that the third lens group be composed of three or more lenses. This configuration makes it possible to effectively correct spherical aberration and coma, which are particularly noticeable at the wide-angle end.

[0026] Specific examples 1 to 5 will be described below. After the description of example 5, numerical examples 1 to 5 corresponding to examples 1 to 5, respectively, will be shown.

[0027] FIGS. 1, 5, 9, 13, and 17 each show a cross section of a zoom lens according to Examples 1 to 5 (Numerical Examples). As described above, the zoom lenses according to Examples 1 to 5 include, in order from the object side to the image side, a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power, and a fourth lens group L4 with positive refractive power. The first lens group L1 remains stationary during zooming, while the second lens group L2 and the third lens group L3 move during zooming. In each Example, the fourth lens group L4 also moves during zooming. Below the lens groups that move during zooming, arrows indicate the path of movement of each lens group during zooming from the wide-angle end to the telephoto end. The solid and dashed arrows below the fourth lens group L4 indicate the path of movement of the fourth lens group L4 during zooming when focused on an object at infinity and a close object, respectively.

[0028] SP denotes an aperture stop, which in all embodiments is located between the second lens group L2 and the third lens group L3. I denotes an image plane. The imaging surface of an imaging element such as a CMOS sensor or the film surface (photosensitive surface) of a silver halide film is located on image plane I. P denotes a glass block such as the faceplate of the imaging element or a low-pass filter.

[0029] In the zoom lenses of Examples 1 to 3, the first lens group L1 is composed of four lenses including one negative lens and three positive lenses, and in the zoom lenses of Examples 4 and 5, the first lens group L1 is composed of five lenses including one negative lens and four positive lenses.

[0030] In the zoom lens of each embodiment, the second lens unit L3 is composed of a negative lens, a negative lens, a negative lens and a positive lens arranged in this order from the object side to the image side.

[0031] Furthermore, the third lens unit L3 of the zoom lenses of Examples 1 to 3 is made up of three lenses, and the third lens unit L3 of the zoom lenses of Examples 4 and 5 is made up of five lenses.

[0032] In the numerical examples, surface number i indicates the order of the surface when counted from the object side. r is the radius of curvature (mm) of the ith surface from the object side, di is the lens thickness or air gap (mm) on the optical axis between the ith and (i+1)th surfaces, and ndi is the refractive index at the d-line of the optical material between the ith and (i+1)th surfaces. νd is the Abbe number based on the d-line of the optical material between the ith and (i+1)th surfaces. When the refractive indices at the d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) are Nd, NF, and NC, respectively, the Abbe number νd is given by νd=(Nd-1) / (NF-NC) It is expressed as:

[0033] The half angle of view (°) is a value determined by ray tracing. BF represents the back focus (mm). The back focus is the distance on the optical axis from the final surface of the zoom lens (the surface closest to the image) to the paraxial image plane, expressed as an air-equivalent length, and is the value when the glass block P is not included. The total lens length is the distance on the optical axis from the front surface of the zoom lens (the surface closest to the object) to the final surface plus the back focus.

[0034] An * next to a surface number indicates that the surface is aspherical. The aspherical shape is expressed by the following formula, where X is the displacement from the vertex of the surface in the optical axis direction, h is the height from the optical axis in a direction perpendicular to the optical axis, the direction of light travel is positive, R is the paraxial radius of curvature, k is the conic constant, and A3 to A11 are aspherical coefficients. The "e±XX" in the conic constant and aspherical coefficients is "×10± XX " Aspherical coefficients not listed in the numerical examples are 0. X=(h 2 / R) / [1+{1-(1+k)(h / R) 2} 1 / 2 +A4×h 4 +A6×h 6 +A8×h8 +A10×h 10 +A3×h 3 +A5×h 5 +A7×h 7 +A9×h 11 +A11×h 11 Table 1 shows the values ​​corresponding to the above-mentioned conditional expressions (1) to (8) in Numerical Examples 1 to 5.

[0035] 2, 6, 10, 14, and 18 respectively show longitudinal aberrations (spherical aberration, astigmatism, distortion, and chromatic aberration) at the wide-angle end for Numerical Examples 1 to 5, and FIGS. 3, 7, 11, 15, and 19 respectively show longitudinal aberrations at the intermediate zoom positions for Numerical Examples 1 to 5. FIGS. 4, 8, 12, 16, and 20 respectively show longitudinal aberrations at the telephoto end.

[0036] In the spherical aberration diagram, Fno is the F-number, the solid line shows spherical aberration at the d-line, and the two-dot chain line shows spherical aberration at the g-line (wavelength 435.8 nm). In the astigmatism diagram, the dashed line shows the meridional image plane at the d-line, and the solid line shows the sagittal image plane at the d-line. The distortion diagram shows distortion at the d-line. The chromatic aberration diagram shows lateral chromatic aberration at the g-line. ω is the half angle of view (°). (Numerical example 1) Unit: mm Surface Data Surface number rd nd νd 1 68.936 1.47 1.90366 31.3 2 32.464 6.16 1.49700 81.5 3 14111.814 0.17 4 47.209 2.42 1.49700 81.5 5 107.163 0.17 6 31.290 4.23 1.62299 58.2 7 202.191 (variable) 8 239.821 0.65 1.91082 35.3 9 7.682 3.43 10 -44.359 0.60 1.83481 42.7 11 29.633 1.35 12 -21.965 0.60 1.83481 42.7 13 -469.092 0.19 14 28.135 1.95 1.95906 17.5 15 -43.912 (variable) 16 (Aperture) ∞ (Variable) 17* 9.809 3.32 1.58313 59.4 18 -208.884 4.19 19 31.601 0.60 2.00100 29.1 20 8.807 0.42 21* 11.803 2.32 1.55332 71.7 22 -151.122 (variable) 23 13.449 3.00 1.63854 55.4 24 -18.116 0.60 1.84666 23.8 25 -62.104 (variable) 26 ∞ 1.16 1.51633 64.1 27∞1.00 Image plane ∞ Aspheric data Page 17 K =-1.14368e+000 A 4= 6.05819e-005 A 6= 4.00465e-008 Page 21 K=-8.02475e-001 A 4= 4.39512e-006 A 6= 1.10573e-006 Various data Zoom ratio 23.70 Wide-angle Mid-range Telephoto Focal length 3.73 29.48 88.37 F-number 1.85 2.76 2.99 Half angle of view (°) 37.50 5.13 1.70 Image height 2.64 2.64 2.64 Lens total length 91.60 91.60 91.60 BF 9.32 14.92 7.90 d 7 0.79 24.08 29.91 d15 30.76 7.47 1.64 d16 7.91 3.11 3.11 d22 4.96 4.16 11.18 d25 7.55 13.15 6.14 Lens group data Group starting plane focal length 1 1 43.36 2 8 -7.30 3 17 22.97 4 23 20.30 (Numerical example 2) Unit: mm Surface Data Surface number rd nd νd 1 83.879 2.12 1.91650 31.6 2 52.519 7.67 1.43700 95.1 3 -516.419 0.17 4 49.448 4.42 1.43700 95.1 5 294.840 0.17 6 38.291 3.85 1.43700 95.1 7 110.439 (variable) 8 212.178 0.87 1.89190 37.1 9 9.959 4.18 10 243.262 0.64 1.89190 37.1 11 31.422 2.23 12 -25.536 0.64 1.72916 54.7 13 70.823 0.17 14 28.819 2.60 1.92286 18.9 15 -66.873 (variable) 16 (Aperture) ∞ (Variable) 17* 11.575 5.63 1.58313 59.4 18* -77.205 2.72 19 43.686 0.60 1.85025 30.1 20 10.562 1.37 21 21.954 2.03 1.43700 95.1 22 -191.888 (variable) 23 17.137 4.42 1.43700 95.1 24 -14.515 0.60 1.74320 49.3 25 -24.766 (variable) 26 ∞ 0.81 1.51633 64.1 27∞1.00 Image plane ∞ Aspheric data Page 17 K =-7.17242e-001 A 4= 7.65652e-006 A 6= 7.21125e-008 Side 18 K =-2.50394e+001 A 4= 2.00371e-005 A 6=-4.81794e-008 Various data Zoom ratio 29.80 Wide-angle Mid-range Telephoto Focal length 6.01 53.44 179.04 F-number 1.85 3.83 4.94 Half angle of view (°) 37.30 4.71 1.39 Image height 4.41 4.41 4.41 Lens length 119.77 119.77 119.77 BF 14.82 25.47 5.34 d 7 1.02 31.96 39.69 d15 39.71 8.78 1.04 d16 8.78 1.96 1.96 d22 8.36 4.53 24.66 d25 13.29 23.94 3.81 Lens group data Group starting plane focal length 1 1 58.12 2 8 -9.81 3 17 31.91 4 23 29.72 (Numerical example 3) Unit: mm Surface Data Surface number rd nd νd 1 80.338 1.69 1.91650 31.6 2 50.812 5.50 1.43700 95.1 3 -416.630 0.17 4 45.582 4.01 1.43700 95.1 5 275.647 0.17 6 38.100 3.22 1.43700 95.1 7 88.116 (variable) 8 74.082 0.80 1.89190 37.1 9 9.109 3.71 10 55.310 0.61 1.89190 37.1 11 28.247 2.19 12 -23.535 0.61 1.72916 54.7 13 48.109 0.17 14 23.999 2.45 1.92286 18.9 15 -117.001 (variable) 16 (Aperture) ∞ (Variable) 17* 12.656 5.78 1.58313 59.4 18* -60.881 2.44 19 47.683 0.63 1.85025 30.1 20 12.093 1.76 21 39.966 1.71 1.43700 95.1 22 -97.594 (variable) 23 19.667 5.55 1.43700 95.1 24 -13.382 0.62 1.74320 49.3 25 -21.696 (variable) 26 ∞ 0.81 1.51633 64.1 27∞1.00 Image plane ∞ Aspheric data Page 17 K =-1.80143e+000 A 4= 6.96605e-005 A 6=-3.84045e-008 Side 18 K = 1.56377e+001 A 4= 3.64366e-005 A 6=-3.40734e-008 Various data Zoom ratio 29.80 Wide-angle Mid-range Telephoto Focal length 6.66 58.21 198.54 F-number 1.85 4.16 5.46 Half angle of view (°) 34.10 4.32 1.26 Image height 4.41 4.41 4.41 Lens total length 119.93 119.93 119.93 BF 16.86 29.04 5.28 d 7 0.71 31.91 39.71 d15 40.05 8.85 1.05 d16 7.16 1.95 1.95 d22 11.37 4.40 28.16 d25 15.33 27.51 3.75 Lens group data Group starting plane focal length 1 1 57.47 2 8 -9.83 3 17 34.86 4 23 30.67 (Numerical example 4) Unit: mm Surface Data Surface number rd nd νd 1 131.700 2.74 1.90525 35.0 2 69.597 6.68 1.43700 95.1 3 3369.268 0.17 4 72.744 4.02 1.43700 95.1 5 323.203 0.17 6 68.316 3.31 1.43700 95.1 7 183.508 0.17 8 63.201 3.37 1.43700 95.1 9 185.645 (variable) 10 799.809 1.03 1.88300 40.8 11 12.492 4.55 12 200.201 0.78 1.88300 40.8 13 46.993 2.56 14 -28.984 0.77 1.77250 49.6 15 100.837 0.17 16 36.376 4.02 1.95906 17.5 17 -130.187 (variable) 18 (Aperture) ∞ (Variable) 19* 15.227 5.81 1.58313 59.4 20* 348.863 0.71 21 30.108 1.65 1.43700 95.1 22 111.114 0.17 23 16.874 1.87 1.43700 95.1 24 40.340 0.79 1.90525 35.0 25 11.594 4.92 26 -33.890 2.35 1.43700 95.1 27 -24.913 (variable) 28 20.375 4.57 1.43700 95.1 29 -53.498 1.06 30 -41.606 1.05 2.00100 29.1 31 -70.932 0.17 32 57.260 2.68 1.48749 70.2 33 -348.810 (variable) 34 ∞ 0.81 1.51633 64.1 35∞1.00 Image plane ∞ Aspheric data Page 19 K=-4.92234e-001 A 4=-2.16872e-006 A 6=-6.87031e-010 Page 20 K = 7.53515e+002 A 4= 1.13528e-005 A 6=-3.22475e-008 Various data Zoom ratio 39.78 Wide-angle Mid-range Telephoto Focal length 5.83 59.85 231.92 F-number 2.06 5.03 5.77 Half angle of view (°) 40.00 4.22 1.08 Image height 4.41 4.41 4.41 Lens length 155.11 155.11 155.11 BF 14.59 28.51 6.00 d 9 1.10 44.58 55.45 d17 55.40 11.92 1.05 d18 14.86 4.34 4.34 d27 6.85 3.45 25.96 d33 13.06 26.97 4.47 Lens group data Group starting plane focal length 1 1 76.54 2 10 -11.62 3 19 40.29 4 28 34.69 (Numerical example 5) Unit: mm Surface Data Surface number rd nd νd 1 106.916 2.40 1.88300 40.8 2 51.610 8.11 1.43700 95.1 3 312.411 0.17 4 57.770 6.50 1.43700 95.1 5 450.194 0.17 6 62.704 4.76 1.43700 95.1 7 332.796 0.17 8 49.761 3.67 1.43700 95.1 9 104.116 (variable) 10 76.214 0.97 1.89190 37.1 11 11.467 5.21 12 -145.609 0.74 1.90525 35.0 13 31.377 1.83 14 -85.420 0.73 1.83400 37.2 15 146.285 0.17 16 30.024 2.78 1.95906 17.5 17 -132.712 (variable) 18 (Aperture) ∞ (Variable) 19* 24.330 1.47 1.43425 95.0 20* 36.181 0.43 21 130.704 1.14 1.89286 20.4 22 -43.588 2.68 23 -25.044 0.60 1.91650 31.6 24 10.545 1.05 1.95906 17.5 25 13.673 0.18 26* 19.023 2.89 1.69350 53.2 27* -25.503 (variable) 28 34.172 1.76 1.60738 56.8 29 -135.611 0.74 30 -28.910 0.76 1.92286 18.9 31 -266.155 0.38 32* 41.011 3.29 1.72903 54.0 33* -21.467 (variable) 34 ∞ 0.81 1.51633 64.1 35∞1.00 Image plane ∞ Aspheric data Page 19 K =-1.68693e+000 A 4=-3.42519e-004 Page 20 K =-2.69347e+001 A 4=-2.43876e-004 Page 26 K =-1.02910e+000 A 4= 1.85856e-004 Page 27 K = 1.31959e-001 A 4= 3.98928e-005 Page 32 K = 9.47339e-001 A 4=-4.36505e-006 A 6= 1.16031e-007 Page 33 K =-1.96310e+000 A 4=-6.78701e-008 A 6= 1.67118e-007 Various data Zoom ratio 39.80 Wide-angle Mid-range Telephoto Focal length 7.02 58.27 279.52 F-number 2.88 5.19 5.77 Half angle of view (°) 32.20 4.35 0.90 Image height 4.41 4.41 4.41 Lens length 141.93 141.93 141.93 BF 29.61 32.28 5.20 d 9 0.50 37.99 47.36 d17 47.91 10.42 1.04 d18 5.08 1.96 1.96 d27 3.06 3.51 30.59 d33 28.08 30.75 3.67 Lens group data Group starting plane focal length 1 1 67.46 2 10 -13.79 3 19 437499.60 4 28 22.66

[0037] [Table 1]

[0038] Fig. 21 shows a video camera as an imaging device equipped with a zoom lens according to any one of Examples 1 to 5 as an imaging optical system. In Fig. 21, 10 denotes the video camera body, and 11 denotes an imaging optical system constituted by a zoom lens according to any one of Examples 1 to 5. 12 denotes an imaging element such as a CCD sensor or CMOS sensor that photoelectrically converts (captures) the subject image formed by imaging optical system 11. 13 denotes a recording medium that records image data generated using an output signal from imaging element 12, and 14 denotes a finder through which a user can observe image data (subject image) displayed on a display element such as a liquid crystal panel (not shown).

[0039] Fig. 22 shows a surveillance camera as an imaging device that uses a zoom lens according to any one of Examples 1 to 5 as an imaging optical system. In Fig. 22, 16 is an imaging optical system configured with a zoom lens according to any one of Examples 1 to 5. 17 is a surveillance camera body, and 18 is an imaging element that captures an image of a subject formed by imaging optical system 16. 19 is a recording medium that records image data generated from an output signal from imaging element 18. 20 is a cable that serves as transfer means for transferring image data to the outside.

[0040] By using the zoom lenses of Examples 1 to 5 in an imaging device such as a video camera or a surveillance camera, a small-sized imaging device with high optical performance can be realized. Note that electronic aberration correction may be performed on the image data to output high-quality image data.

[0041] The embodiments described above are merely representative examples, and various modifications and alterations are possible to each embodiment when implementing the present invention. [Explanation of symbols]

[0042] L1 First lens group L2 Second lens group L3: Third lens group L4 4th lens group

Claims

1. A zoom lens comprising, arranged in order from the object side to the image side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having positive refractive power, wherein the spacing between adjacent lens groups changes during zooming, During zooming, the first lens group is stationary, and the second lens group and the third lens group are moved, the third lens group consists of five or fewer lenses, Let D34t and D34w be the distances on the optical axis from the surface of the third lens group closest to the image side to the surface of the fourth lens group closest to the object side at the telephoto end and the wide-angle end, respectively, M2 and M3 be the amounts of movement of the second lens group and the third lens group during zooming from the wide-angle end to the telephoto end, respectively, and ft and fw be the focal lengths of the zoom lens at the telephoto end and the wide-angle end, respectively. 2.0<D34t / D34w<20.0 -25.0<M2 / M3<-5.1 11<ft / fw A zoom lens characterized by satisfying the following conditions.

2. When the focal length of the second lens group is f2, -4.9<M2 / f2<-3.1 2. The zoom lens according to claim 1, which satisfies the following condition:

3. When the focal length of the second lens group is f2, -2.0<f2 / fw<-1.2 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

4. A zoom lens as described in any one of claims 1 to 3, characterized in that the fourth lens group moves during zooming.

5. 5. The zoom lens according to claim 1, wherein the first lens group is made up of four or five lenses, including a negative lens.

6. 6. The zoom lens according to claim 1, wherein the second lens group consists of a negative lens, a negative lens, a negative lens and a positive lens arranged in this order from the object side to the image side.

7. Let D12w and D12t be the distances on the optical axis from the surface of the first lens group closest to the image side to the surface of the second lens group closest to the object side at the wide-angle end and the telephoto end, respectively. 0.00<D12w / M2<0.10 1.00<D12t / M2<1.10 7. The zoom lens according to claim 1, which satisfies the following condition:

8. the first lens group includes a plurality of positive lenses, When the average Abbe number of the plurality of positive lenses based on the d-line is νd1pave, 50<νd1pave<102 8. The zoom lens according to claim 1, which satisfies the following condition:

9. 9. The zoom lens according to claim 1, wherein the third lens group includes three or more lenses.

10. A zoom lens according to any one of claims 1 to 9; and an image sensor for capturing an image formed through the zoom lens.

Images