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

Abstract

To provide a zoom lens that has a small size, good optical performance, and a wide angle.SOLUTION: A zoom lens has a plurality of lens groups. The plurality of lens groups consist of a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a fourth lens group having a positive refractive power, which are arranged in order from an object side to an image side. In zooming, the interval between the adjacent lens groups changes. The second lens group includes at least one negative lens. The minimum value of the Abbe number of the negative lens, the focal length of the second lens group, the focal length of the fourth lens group, the entire optical length at a wide angle end, and the focal length at the wide angle end of the zoom lens 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] Conventionally, there is known a zoom lens that has a first to fourth lens group with negative, positive, negative, and positive refractive powers arranged in order from the object side to the image side, and that is small and can efficiently secure a variable magnification ratio. Patent Document 1 discloses a zoom lens that has a first to fourth lens group with negative, positive, negative, and positive refractive powers arranged in order from the object side to the image side, in which all the lens groups move during zooming, and has a variable magnification ratio of about 5 and a half angle of view of about 39°. Patent Document 2 discloses a zoom lens that has a first to fourth lens group with negative, positive, negative, and positive refractive powers arranged in order from the object side to the image side, in which the first to third lens groups move during zooming, in which the first lens group is composed of five lenses, has a variable magnification ratio of about 2, and a half angle of view of about 63°. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-283648 A [Patent Document 2] JP 2019-174711 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the zoom lens of Patent Document 1, if the lens arrangement at the wide-angle end disclosed in the patent document is used to widen the angle, the shape of the first lens group becomes unsatisfactory as the front lens becomes larger, and it becomes necessary to increase the number of lenses in the first lens group, which results in an increase in diameter, overall length, and weight.

[0005] In the zoom lens of Patent Document 2, the first lens group has a large number of constituent lenses, which is undesirable in terms of diameter, overall length, and weight. In addition, since the zoom ratio is about 2x, further increasing the magnification would result in further increases in diameter, overall length, and weight.

[0006] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a wide-angle zoom lens which is small in size and has good optical performance. [Means for solving the problem]

[0007] A zoom lens according to one aspect of the present invention is a zoom lens having a plurality of lens groups, the plurality of lens groups being arranged in order from the object side to the image side: a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, and a fourth lens group having positive refractive power, wherein a distance between adjacent lens groups changes during zooming, the second lens group having at least one negative lens, and wherein the minimum Abbe number of the negative lenses is v2n, the focal length of the second lens group is f2, the focal length of the fourth lens group is f4, the total lens length at the wide-angle end is Lw, and the focal length of the zoom lens at the wide-angle end is fw, 20<ν2n<28 0.00 <f2 / f4<0.40 12 <Lw / fw<55 The present invention is characterized in that the following conditional expression is satisfied: Effect of the Invention

[0008] According to the present invention, it is possible to provide a wide-angle zoom lens that is small in size and has good optical performance. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of a zoom lens according to a first embodiment. [Diagram 2] 3A, 3B, and 3C are aberration diagrams of the zoom lens of Example 1 at the wide-angle end, at the intermediate focal length, and at the telephoto end. [Diagram 3] FIG. 11 is a cross-sectional view of a zoom lens according to a second embodiment. [Figure 4]5A, 5B, and 5C are aberration diagrams of the zoom lens of Example 2 at the wide-angle end, at the intermediate focal length, and at the telephoto end. [Diagram 5] FIG. 11 is a cross-sectional view of a zoom lens according to a third embodiment. [Figure 6] 13A, 13B, and 13C are aberration diagrams of the zoom lens of Example 3 at the wide-angle end, at the intermediate focal length, and at the telephoto end. [Figure 7] FIG. 11 is a cross-sectional view of a zoom lens according to a fourth embodiment. [Figure 8] 13A, 13B, and 13C are aberration diagrams of the zoom lens of Example 4 at the wide-angle end, at the intermediate focal length, and at the telephoto end. [Figure 9] FIG. 11 is a cross-sectional view of a zoom lens according to a fifth embodiment. [Figure 10] 13A, 13B, and 13C are aberration diagrams of the zoom lens of Example 5 at the wide-angle end, at the intermediate focal length, 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. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In each drawing, the same reference numerals are given to the same members, and duplicated explanations will be omitted.

[0011] 1, 3, 5, 7, and 9 are cross-sectional views of zoom lenses according to Examples 1 to 5. The zoom lenses according to the respective Examples are optical systems used in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, cameras for silver halide film, and surveillance cameras.

[0012] In each cross-sectional view, the left side is the object side and the right side is the image side. The zoom lens of each embodiment is configured to have multiple lens groups. In this specification, a lens group is a group of lenses that move or stand still 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 the lens group may be composed of one lens or multiple lenses. The lens group may also include an aperture stop.

[0013] As described above, the zoom lens of each embodiment has a plurality of lens groups, which are arranged in order from the object side to the image side, including a first lens group L1 with negative refractive power, a second lens group L2 with positive refractive power, a first lens group L3 with negative refractive power, and a second lens group L4 with positive refractive power.

[0014] SP is an aperture stop. P is a glass block such as a face plate of a CCD sensor or a low-pass filter. I is an image plane, on which the imaging surface of a solid-state imaging element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor is disposed when the zoom lens of each embodiment is used as the photographing optical system of a digital still camera or a digital video camera. When the zoom lens of each embodiment is used as the photographing optical system of a silver halide film camera, a photosensitive surface equivalent to the film surface is disposed on the image plane I.

[0015] In the zoom lens of each embodiment, when zooming from the wide-angle end to the telephoto end, each lens group moves in the direction of the arrow. The solid line and the dotted line respectively indicate the movement locus when focusing on an object at infinity and a close distance object. In each embodiment, the second lens group L2 at the telephoto end is located closer to the object side than the second lens group L2 at the wide-angle end.

[0016] In the zoom lenses of Examples 1 to 4, the third lens group L3 functions as a focus group, and in the zoom lens of Example 5, the fourth lens group L4 functions as a focus group. Note that the first lens group L1 may function as a focus group, or the first lens group L1 and the second lens group L2 may function as a focus group together.

[0017] Fig. 2(A), Fig. 4(A), Fig. 6(A), Fig. 8(A), and Fig. 10(A) are aberration diagrams at the wide-angle ends of the zoom lenses of Examples 1 to 5, respectively. Fig. 2(B), Fig. 4(B), Fig. 6(B), Fig. 8(B), and Fig. 10(B) are aberration diagrams at the intermediate focal lengths of the zoom lenses of Examples 1 to 5, respectively. Fig. 2(C), Fig. 4(C), Fig. 6(C), Fig. 8(C), and Fig. 10(C) are aberration diagrams at the telephoto ends of the zoom lenses of Examples 1 to 5, respectively.

[0018] 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 (°).

[0019] Next, the characteristic configuration of the zoom lens of each embodiment will be described.

[0020] The second lens group L2 includes at least one negative lens, which allows correction of axial chromatic aberration.

[0021] The zoom lens of each embodiment satisfies the following conditional expressions (1) to (3).

[0022] 20<ν2n<28 (1) 0.00 <f2 / f4<0.40 (2) 12 <Lw / fw<55 (3) Here, ν2n is the minimum value of the Abbe number of the negative lens in the second lens group L2. f2 is the focal length of the second lens group L2. f4 is the focal length of the fourth lens group L4. Lw is the total optical length at the wide-angle end. fw is the focal length of the zoom lens at the wide-angle end. In this specification, the Abbe number is a value based on the d-line. The total optical length is the distance on the optical axis from the lens surface on the object side of the first lens group L1 to the lens surface on the image side of the fourth lens group L4, plus the back focus. If a glass block or the like is placed in the back focus, the extension due to the glass block or the like is also added to the back focus.

[0023] Conditional formula (1) specifies the minimum value of the Abbe number of the negative lens in the second lens group L2. If the lower limit of conditional formula (1) is exceeded, it is undesirable because axial chromatic aberration is easily overcorrected, particularly on the short wavelength side. If the upper limit of conditional formula (1) is exceeded, it is undesirable because it becomes difficult to correct axial chromatic aberration.

[0024] Conditional expression (2) defines the value of the ratio of the focal length of the second lens group L2 to the focal length of the fourth lens group L4. The lower limit of conditional expression (2) must not be exceeded. Exceeding the upper limit of conditional expression (2) makes it difficult to perform efficient zooming, and the overall length becomes too long to ensure a desired zoom ratio, which is undesirable.

[0025] Conditional formula (3) specifies the ratio of the total optical length at the wide-angle end to the focal length at the wide-angle end of the zoom lens. If the lower limit of conditional formula (3) is exceeded, it is not preferable because a wide angle cannot be obtained. Alternatively, it is not preferable because it becomes more necessary to increase the refractive power of the first lens group L1 to widen the angle, making it difficult to correct curvature of field and chromatic aberration of magnification. If the upper limit of conditional formula (3) is exceeded, the total length becomes too long, which is not preferable.

[0026] It is preferable that the numerical ranges of the conditional expressions (1) to (3) are set to the numerical ranges of the following conditional expressions (1a) to (3a).

[0027] 20.2<ν2n<27.7 (1a) 0.120 <f2 / f4<0.395 (2a) 13 <Lw / fw<26 (3a) It is further preferable that the numerical ranges of the conditional expressions (1) to (3) be the numerical ranges of the following conditional expressions (1b) to (3b).

[0028] 20.3<ν2n<27.6 (1b) 0.130 <f2 / f4<0.393 (2b) 13.5 <Lw / fw<25.5 (3b) Next, a description will be given of configurations that are preferably satisfied in the zoom lens of each embodiment.

[0029] The number of lenses included in the first lens group L1 is preferably 3 or less. If the number of lenses is large, it is advantageous for correcting aberrations, but it is not preferable since it tends to increase the front lens diameter, the overall length, and the weight.

[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 (10).

[0031] 0.00 <f1 / f3<0.41 (4) -0.95 <f1 / f2<-0.55 (5) -0.48 <f2 / f3<-0.12 (6) -1.43 <f3 / f4<-0.63 (7) -1.51 <D1 / f1<-0.81 (8) 0.00 <D34w / Lw<0.03 (9) 3.4 <z<9.0 (10) Here, f1 is the focal length of the first lens group L1. f3 is the focal length of the third lens group L3. D1 is the distance on the optical axis from the lens surface of the first lens group L1 closest to the object to the lens surface of the first lens group L1 closest to the image. D34w is the distance on the optical axis from the lens surface of the third lens group L3 closest to the image to the lens surface of the fourth lens group L4 closest to the object at the wide-angle end. z is the zoom ratio.

[0032] Conditional expression (4) defines the value of the ratio of the focal length of the first lens group L1 to the focal length of the third lens group L3. The lower limit of conditional expression (4) must not be exceeded. Exceeding the upper limit of conditional expression (4) is not preferable because it weakens the refractive power of the first lens group L1 and makes it difficult to achieve a wide angle.

[0033] Conditional formula (5) defines the value of the ratio of the focal length of the first lens group L1 to the focal length of the second lens group L2. If the lower limit of conditional formula (5) is exceeded, it becomes difficult to achieve a wide angle, which is undesirable. If the upper limit of conditional formula (5) is exceeded, it becomes difficult to correct curvature of field and chromatic aberration of magnification, which is undesirable. Alternatively, it becomes difficult to perform efficient zooming, and the overall length becomes too long to ensure a desired zoom ratio, which is undesirable.

[0034] Conditional expression (6) defines the value of the ratio of the focal length of the second lens group L2 to the focal length of the third lens group L3. If the lower limit of conditional expression (6) is exceeded, it becomes difficult to perform efficient zooming, and the overall length becomes too long to ensure a desired zoom ratio, which is undesirable. If the upper limit of conditional expression (6) is exceeded, it becomes difficult to correct spherical aberration and coma aberration, which is undesirable.

[0035] Conditional expression (7) defines the value of the ratio of the focal length of the third lens group L3 to the focal length of the fourth lens group L4. If the lower limit of conditional expression (7) is exceeded, it is undesirable because it becomes difficult to suppress the fluctuation of the field curvature during zooming. If the upper limit of conditional expression (7) is exceeded, it is undesirable because it becomes difficult to suppress the fluctuation of the spherical aberration during zooming.

[0036] Conditional expression (8) defines the ratio of the distance on the optical axis from the lens surface of the first lens group L1 closest to the object to the lens surface of the first lens group L1 closest to the image to the focal length of the first lens group L1. If the lower limit of conditional expression (8) is not satisfied, the front lens diameter, overall length, and weight tend to increase, which is undesirable. If the upper limit of conditional expression (8) is exceeded, it becomes difficult to achieve both a wide angle and aberration correction, which is undesirable.

[0037] Conditional expression (9) prescribes the value of the ratio of the distance on the optical axis from the lens surface of the third lens group L3 closest to the image side to the lens surface of the fourth lens group L4 closest to the object side at the wide-angle end to the total optical length at the wide-angle end. The lower limit of conditional expression (9) cannot be exceeded. Conditional expression (9) is not preferable because it makes it difficult to suppress fluctuations in spherical aberration during zooming.

[0038] Condition (10) defines the zoom ratio. If the lower limit of condition (10) is exceeded, the necessity of the present invention decreases, which is not preferable. If the upper limit of condition (10) is exceeded, the front lens diameter, overall length, and weight tend to increase, which is not preferable.

[0039] It is preferable that the numerical ranges of the conditional expressions (4) to (10) be the numerical ranges of the following conditional expressions (4a) to (10a).

[0040] 0.10 <f1 / f3<0.39 (4a) -0.90 <f1 / f2<-0.58 (5a) -0.46 <f2 / f3<-0.13 (6a) -1.37 <f3 / f4<-0.66 (7a) -1.44 <D1 / f1<-0.85 (8a) 0.010 <D34w / Lw<0.025 (9a) 3.6 <z<8.5 (10a) It is even more preferable that the numerical ranges of the conditional expressions (4) to (10) be the numerical ranges of the following conditional expressions (4b) to (10b).

[0041] 0.11 <f1 / f3<0.38 (4b) -0.88 <f1 / f2<-0.60 (5b) -0.45 <f2 / f3<-0.14 (6b) -1.30 <f3 / f4<-0.68 (7b) -1.40 <D1 / f1<-0.90 (8b) 0.010 <D34w / Lw<0.020 (9b) 3.7 <z<8.0 (10b) Numerical examples 1 to 5 corresponding to the first to fifth embodiments, respectively, are given below.

[0042] 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. Additionally, nd represents the refractive index of each optical member with respect to the d-line, and νd represents the Abbe number of the optical member. The Abbe number νd 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:

[0043] 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. The half angle of view is a value obtained by ray tracing. "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 surface expressed as an air-equivalent length, and is the value when the glass block is not included. "Total lens length" is the length obtained by adding the back focus to the distance on the optical axis from the frontmost lens surface (the lens surface closest to the object) to the final surface of the zoom lens not including the glass block.

[0044] If the optical surface is aspheric, a * symbol is added to the right of the surface number. The aspheric shape is expressed as follows, where X is the displacement from the apex 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 aspheric 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 aspheric coefficient is "×10±XX In addition, coefficients not described in the numerical examples are zero.

[0045] [Numerical Example 1] Unit: mm Surface Data Surface number rd nd νd 1 72.527 0.93 1.59522 67.7 2 11.379 5.79 3 -27.255 0.67 1.72916 54.7 4 13.849 0.20 5 14.878 2.22 1.95906 17.5 6 34.667 (variable) 7(Aperture) ∞ 0.10 8* 13.773 5.10 1.55332 71.7 9* -36.742 0.17 10 16.256 3.33 1.95375 32.3 11 -26.737 0.60 1.85478 24.8 12 9.491 4.20 13 15.713 0.60 1.85478 24.8 14 12.031 4.66 1.59522 67.7 15 -17.062 (variable) 16 -17.547 0.82 1.95906 17.5 17 -13.209 1.16 18 -10.722 0.60 1.67270 32.1 19 -29.412 (variable) 20 9.948 0.88 1.89190 37.1 21 12.792 2.61 22 ∞ 0.80 1.51633 64.1 23∞1.00 Image plane ∞ Aspheric Data Side 8 K =-1.57466e+00 9th page K = 0.00000e+00 A 4= 5.62163e-05 Various data Zoom ratio 4.92 Wide Angle Mid-Telephoto Focal length 3.62 9.96 17.81 F-number 1.44 2.19 2.58 Half angle of view (°) 56.26 18.60 10.30 Image height 3.20 3.20 3.20 Lens length 68.73 56.09 59.31 BF 4.14 4.14 4.14 d 6 30.63 8.04 1.31 d15 0.96 2.18 8.90 d19 0.98 9.71 12.94 Zoom lens group data Group starting plane focal length 1 1 -10.17 2 7 14.01 3 16 -50.21 4 20 43.78 [Numerical Example 2] Unit: mm Surface Data Surface number rd nd νd 1 56.058 0.98 1.69680 55.5 2 9.735 7.38 3* -24.519 0.68 1.76802 49.2 4 27.444 2.10 1.95906 17.5 5 1715.781 (variable) 6 (Aperture) ∞ 0.08 7* 11.055 3.68 1.59201 67.0 8* -39.998 0.87 9 23.181 3.61 2.00100 29.1 10 -14.983 0.60 1.85478 24.8 11 8.242 2.91 12 13.110 3.96 1.49700 81.5 13 -15.918 (variable) 14 -20.364 0.91 1.49710 81.6 15* -36.032 (variable) 16 10.707 1.59 1.69680 55.5 17 11.851 2.61 18 ∞ 0.80 1.51633 64.1 19∞1.00 Image plane ∞ Aspheric Data 3rd page K = 1.28585e+00 A 4= 2.45808e-05 Side 7 K =-1.93828e+00 A 4= 7.55192e-05 Side 8 K =-9.08920e-01 A 4= 9.41364e-05 Page 15 K =-1.09444e+00 A 4= 4.35236e-05 Various data Zoom ratio 4.92 Wide Angle Mid-Telephoto Focal length 3.48 9.74 17.13 F-number 1.44 2.23 2.58 Half angle of view (°) 57.33 19.00 10.73 Image height 3.20 3.20 3.20 Lens length 69.04 52.98 55.37 BF 4.14 4.14 4.14 d 5 32.71 7.52 0.78 d13 1.78 2.53 10.59 d15 1.07 9.45 10.51 Zoom lens group data Group starting plane focal length 1 1 -10.64 2 6 13.73 3 14 -96.06 4 16 101.38 [Numerical Example 3] Unit: mm Surface Data Surface number rd nd νd 1 43.824 0.66 1.80400 46.5 2 9.455 4.24 3 -16.906 0.60 1.69930 51.1 4 12.794 0.26 5 15.208 1.89 1.95906 17.5 6 83.820 (variable) 7(Aperture) ∞ 0.18 8* 10.864 2.35 1.59201 67.0 9* -26.966 1.88 10 14.568 1.98 1.95375 32.3 11 -15.399 0.87 1.85478 24.8 12 7.401 3.30 13 11.993 2.10 1.49700 81.5 14 -12.195 (variable) 15 -26.067 1.12 1.92286 18.9 16 -13.596 0.99 17 -9.228 0.60 2.00100 29.1 18 -25.318 (variable) 19 12.116 0.86 1.85150 40.8 20 17.551 2.61 21 ∞ 0.80 1.51633 64.1 22∞1.00 Image plane ∞ Aspheric Data Side 8 K =-1.73438e+00 A 4=-9.56202e-06 9th page K =-1.01922e+00 A 4= 8.83438e-05 Various data Zoom ratio 4.90 Wide Angle Mid-Telephoto Focal length 3.64 10.16 17.85 F-number 1.96 3.41 5.05 Half angle of view (°) 56.24 18.20 10.26 Image height 3.20 3.20 3.20 Lens length 49.93 44.39 49.92 BF 4.13 4.13 4.13 d 6 20.17 4.99 0.89 d14 0.81 2.38 5.54 d18 0.92 8.98 15.45 Zoom lens group data Group starting plane focal length 1 1 -8.24 2 7 11.23 3 15 -30.04 4 19 42.82 [Numerical Example 4] Unit: mm Surface Data Surface number rd nd νd 1 71.188 1.29 1.49700 81.5 2 14.006 8.00 3 -35.563 0.86 1.77250 49.6 4 16.513 0.17 5 17.223 2.79 1.95906 17.5 6 39.260 (variable) 7(Aperture) ∞ 0.09 8* 12.544 3.78 1.59201 67.0 9* -98.106 0.17 10 14.787 3.12 1.71300 53.9 11 -345.490 0.60 1.72825 28.5 12 9.231 4.68 13 -17.632 0.72 1.69680 55.5 14 -16.355 0.17 15 15.660 0.60 1.89286 20.4 16 13.461 3.97 1.59522 67.7 17 -36.323 (variable) 18 -39.722 1.17 1.95906 17.5 19 -16.902 1.13 20 -12.305 0.60 1.78880 28.4 21 -533.810 (variable) 22 11.894 0.92 1.88300 40.8 23 17.308 2.60 24 ∞ 0.80 1.51633 64.1 25∞1.00 Image plane ∞ Aspheric Data Side 8 K =-3.20404e-01 A 4=-2.55905e-05 9th page K = 2.83697e+00 A 4= 4.40781e-05 Various data Zoom ratio 7.95 Wide Angle Mid-Telephoto Focal length 3.65 14.34 28.98 F-number 1.44 2.58 3.30 Half angle of view (°) 55.62 12.80 6.30 Image height 3.20 3.20 3.20 Lens length 89.00 65.07 70.70 BF 4.13 4.13 4.13 d 6 48.00 9.90 1.34 d17 1.09 2.36 10.54 d21 0.96 13.87 19.86 Zoom lens group data Group starting plane focal length 1 1 -13.33 2 7 15.58 3 18 -36.06 4 22 39.87 [Numerical Example 5] Unit: mm Surface Data Surface number rd nd νd 1 38.799 0.71 1.83481 42.7 2 9.795 6.07 3 -14.573 0.60 1.77250 49.6 4 13.140 0.72 5 15.290 1.94 1.95906 17.5 6 104.715 (variable) 7(Aperture) ∞ 0.14 8* 9.539 4.38 1.58313 59.4 9* -45.724 1.07 10 23.764 1.48 1.69680 55.5 11 -30.067 0.60 1.75520 27.5 12 8.475 1.67 13 13.371 2.39 1.55200 70.7 14 -11.277 (variable) 15 -33.738 0.83 1.95906 17.5 16 -14.786 1.50 17 -12.441 0.60 2.05090 26.9 18 -115.470 (variable) 19 15.567 1.20 1.55200 70.7 20 184.405 2.60 21 ∞ 0.80 1.51633 64.1 22∞1.00 Image plane ∞ Aspheric Data Side 8 K =-1.97205e+00 A 4= 1.86383e-04 9th page K =-8.69262e-01 A 4= 3.02826e-04 Various data Zoom ratio 3.80 Wide Angle Mid-Telephoto Focal length 3.69 7.24 14.02 F-number 1.96 3.95 4.73 Half angle of view (°) 55.88 25.74 13.07 Image height 3.20 3.20 3.20 Lens length 53.23 53.23 53.23 BF 4.12 4.12 4.12 d 6 18.55 10.50 2.44 d14 3.71 1.05 10.63 d18 0.95 11.66 10.13 Zoom lens group data Group starting plane focal length 1 1 -7.36 2 7 11.98 3 15 -28.79 4 19 30.72 The various values ​​in each numerical example are summarized in Table 1 below.

[0046] [Table 1]

[0047] [Imaging device] Next, an embodiment of a digital still camera (imaging device) using the zoom lens of each embodiment as an imaging optical system will be described with reference to Fig. 11. In Fig. 11, 10 denotes a camera body, and 11 denotes an imaging optical system constituted by any of the zoom lenses described in the first to fifth embodiments. 12 denotes a solid-state imaging element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor that is built into the camera body and receives an optical image formed by the imaging optical system 11 and photoelectrically converts it. 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.

[0048] In this way, by applying the zoom lens of each embodiment to an imaging device such as a digital still camera, it is possible to obtain an imaging device with a small lens. [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 blur correction. In this case, the control unit does not need to be configured integrally with the zoom lens, and the control unit may be configured separately from the zoom lens. For example, a configuration may be adopted in which a control unit (control device) that is disposed far away from a drive unit that drives each lens of the zoom lens includes a transmission unit that sends a control signal (command) for controlling the zoom lens. With such a control unit, the zoom lens can be remotely operated.

[0049] In addition, the control unit may be provided with an operation unit such as a controller or buttons for remotely operating the zoom lens, so that the zoom lens is controlled in response to a user's input to the operation unit. For example, a zoom-in button and a zoom-out button may be provided as the operation unit. In this case, the control unit may be configured to send a signal to a drive unit for the zoom lens so that the magnification of the zoom lens increases when the user presses the zoom-in button, and decreases when the user presses the zoom-out button.

[0050] 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 is, for example, the zoom magnification (zoom state) and the movement amount (movement state) of each lens group. In this case, the user can remotely operate the zoom lens via the operation unit while viewing the information related to the zoom of the zoom lens displayed on the display unit. In this case, the display unit and the operation unit may be integrated by adopting, for example, a touch panel.

[0051] FIG. 12 is a schematic diagram of an imaging device (monitoring camera) that uses the zoom lens of each embodiment as a photographing optical system.

[0052] 12(A), reference numeral 21 denotes a surveillance camera body, and 22 denotes a solid-state imaging element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor that is built into the camera body and receives a subject image formed by a lens unit 26. Reference numeral 23 denotes a memory unit that records information corresponding to the subject image photoelectrically converted by the solid-state imaging element 22. Reference numeral 24 denotes a network cable for transferring the subject image photoelectrically converted by the solid-state imaging element 22.

[0053] 12B shows an example of an imaging device that is attached to a ceiling with a dome-shaped cover 25 attached thereto. 20 denotes a portion that is not covered by the dome-shaped cover 25.

[0054] In this way, by applying the imaging device of the present invention to optical equipment such as a surveillance camera, it is possible to realize an optical equipment that is small in size and has high optical performance.

[0055] The imaging device is not limited to a surveillance camera, but may also be a video camera, a digital camera, or the like.

[0056] Furthermore, if an electronic imaging element such as a CCD is used as the imaging element, the image quality of the output image can be further improved by electronically correcting aberrations.

[0057] The disclosure of this embodiment includes the following configuration. (Configuration 1) A zoom lens having a plurality of lens groups, the plurality of lens groups are arranged in order from the object side to the image side, comprising a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, and a fourth lens group having positive refractive power; When zooming, the spacing between adjacent lens groups changes, the second lens group includes at least one negative lens, Let v2n be the minimum Abbe number of the negative lens, f2 be the focal length of the second lens group, f4 be the focal length of the fourth lens group, Lw be the total optical length at the wide-angle end, and fw be the focal length of the zoom lens at the wide-angle end. 20<ν2n<28 0.00 <f2 / f4<0.40 12 <Lw / fw<55 A zoom lens characterized by satisfying the following conditional expressions: (Configuration 2) When the focal length of the first lens group is f1 and the focal length of the third lens group is f3, 0.00 <f1 / f3<0.41 2. The zoom lens according to claim 1, wherein the following condition is satisfied: (Configuration 3) When the focal length of the first lens group is f1, 0.95 <f1 / f2<-0.55 3. The zoom lens according to claim 1, wherein the following condition is satisfied: (Configuration 4) When the focal length of the third lens group is f3, -0.48 <f2 / f3<-0.12 4. The zoom lens according to any one of configurations 1 to 3, wherein the following condition is satisfied: (Configuration 5) When the focal length of the third lens group is f3, -1.43 <f3 / f4<-0.63 5. The zoom lens according to any one of configurations 1 to 4, wherein the following condition is satisfied: (Configuration 6) 6. The zoom lens according to any one of configurations 1 to 5, wherein the number of lenses included in the first lens group is three or less. (Configuration 7) When the distance on the optical axis from the lens surface of the first lens group closest to the object side to the lens surface of the first lens group closest to the image side is D1, -1.51 <D1 / f1<-0.81 7. The zoom lens according to any one of configurations 1 to 6, wherein the following condition is satisfied: (Configuration 8) When the distance on the optical axis from the lens surface of the third lens group closest to the image side to the lens surface of the fourth lens group closest to the object side at the wide-angle end is D34w, 0.00 <D34w / Lw<0.03 8. The zoom lens according to any one of configurations 1 to 7, wherein the following condition is satisfied: (Configuration 9) When the zoom ratio is z, 3.4 <z<9.0 9. The zoom lens according to 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 second lens group at the telephoto end is located closer to the object side than the second lens group at the wide-angle end. (Configuration 11) A zoom lens according to any one of configurations 1 to 10; and an image sensor that receives an image formed by the zoom lens. (Configuration 12) 11. An imaging system comprising: a zoom lens according to any one of configurations 1 to 10; and a control unit that controls the zoom lens during zooming. (Configuration 13) 13. The imaging system according to claim 12, wherein the control unit is configured separately from the zoom lens and has a transmission unit that transmits a control signal for controlling the zoom lens. (Configuration 14) 14. The imaging system according to configuration 12 or 13, wherein the control unit is configured separately from the zoom lens and has an operation unit for operating the zoom lens. (Configuration 15) 15. The imaging system according to any one of configurations 12 to 14, further comprising a display unit that displays information related to the zoom of the zoom lens.

[0058] 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]

[0059] L1 First lens group L2 Second lens group L3: Third lens group L4 4th lens group

Claims

1. A zoom lens having a plurality of lens groups, the plurality of lens groups are arranged in order from the object side to the image side, comprising a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a fourth lens group having a positive refractive power; When zooming, the spacing between adjacent lens groups changes, the second lens group includes at least one negative lens, Let v2n be the minimum Abbe number of the negative lens, f2 be the focal length of the second lens group, f4 be the focal length of the fourth lens group, Lw be the total optical length at the wide-angle end, and fw be the focal length of the zoom lens at the wide-angle end. 20<ν2n<28 0.00<f2 / f4<0.40 12<Lw / fw<55 A zoom lens characterized by satisfying the following conditional expressions:

2. When the focal length of the first lens group is f1 and the focal length of the third lens group is f3, 0.00<f1 / f3<0.41 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

3. When the focal length of the first lens group is f1, 0.95<f1 / f2<-0.55 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

4. When the focal length of the third lens group is f3, -0.48<f2 / f3<-0.12 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

5. When the focal length of the third lens group is f3, -1.43<f3 / f4<-0.63 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

6. 3. The zoom lens according to claim 1, wherein the number of lenses included in the first lens group is three or less.

7. When the distance on the optical axis from the lens surface of the first lens group closest to the object side to the lens surface of the first lens group closest to the image side is D1, -1.51<D1 / f1<-0.81 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

8. When the distance on the optical axis from the lens surface of the third lens group closest to the image side to the lens surface of the fourth lens group closest to the object side at the wide-angle end is D34w, 0.00<D34w / Lw<0.03 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

9. When the zoom ratio is z, 3.4<z<9.0 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

10. 3. The zoom lens according to claim 1, wherein the second lens group at the telephoto end is located closer to the object side than the second lens group at the wide-angle end.

11. The zoom lens according to claim 1 or 2, and an image sensor that receives an image formed by the zoom lens.

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

13. 13. The imaging system according to claim 12, 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.

14. 13. The imaging system according to claim 12, wherein the control unit is configured as a separate unit from the zoom lens, and has an operation unit for operating the zoom lens.

15. 13. The imaging system according to claim 12, further comprising a display unit that displays information related to the zoom of the zoom lens.

Images